JP2005250451A - Heat-developable photosensitive material and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat-developable photosensitive material having high density, free of faulty conveyance and occurrence of density unevenness during heat development, excellent in prevention of rise of fog with time, excellent in image preservability during hot holding, and excellent also in film conveyability and environmental suitability, and to provide an image forming method. <P>SOLUTION: The heat-developable photosensitive material has on a support an image forming layer containing an organic silver salt, silver halide, a binder and a reducing agent, wherein when the ten-point average roughness of the outermost surface of the image forming layer side is represented by Rz(E) and the ten-point average roughness of the outermost surface of the side of the support opposite to the side of the image forming layer by Rz(B), a value of Rz(E)/Rz(B) is 0.1-0.7. The heat-developable photosensitive material is exposed with a laser having a luminescence peak intensity at 350-450 nm as an exposure light source to form an image. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photothermographic material, and more particularly, to a photothermographic material having a high density, excellent silver tone, and the like, preserving light-irradiated images and preventing fogging with time, and an image forming method using the same.

  Conventionally, in the medical and printing plate making fields, waste liquids resulting from wet processing of image forming materials have been a problem in terms of workability. In recent years, reduction of waste processing liquids has been strongly desired from the viewpoint of environmental conservation and space saving. It is rare. Therefore, photothermographic materials capable of forming an image only by applying heat have been put into practical use and are rapidly spreading in the above fields.

  A photothermographic material (hereinafter also simply referred to as a photothermographic material or a photosensitive material) has been proposed for a long time (see, for example, Patent Documents 1 and 2).

  This heat-developable material is usually processed by a heat-development processing apparatus called a heat-development processor that applies stable heat to the heat-developable material to form an image. As described above, with the rapid spread in recent years, a large amount of this heat development processing apparatus has been supplied to the market. However, depending on the temperature and humidity conditions during the heat development processing, the slipping property between the photosensitive material and the transport roller or processing member of the heat development processing device changes, resulting in the problem of poor transport and uneven density. It was. Another problem is that the density of the photothermographic material varies with time. It has been found that these phenomena occur remarkably in a photothermographic material that forms an image by thermal development after image exposure with a laser beam.

  In recent years, there has been a demand for a compact laser imager and quick processing. In order to obtain a sufficient density of the photothermographic material even if rapid processing is performed, the covering power can be increased by increasing the number of color development points by using a silver halide having a small average grain size, second grade, third grade. It is effective to use a highly active reducing agent having an alkyl group, or to use a development accelerator such as a phenol compound, a hydrazine compound, or a vinyl compound (see, for example, Patent Documents 3 and 4).

In recent years, there has been a demand for a compact laser imager, a high-definition image, and prevention of fogging over time. In order to prevent fogging with time, a technique of performing exposure with an ultraviolet to blue laser without using a spectral sensitizing dye has been disclosed (for example, see Patent Document 5). In order to further reduce the size of the apparatus, a technique for exposing from a laser beam having an emission peak at 350 to 450 nm has been disclosed (for example, see Patent Document 6). However, even if these techniques are used, there is a problem that density unevenness occurs due to poor transport during thermal development when the apparatus is downsized and rapid processing is performed. Also, the improvement of fog rise with time was not sufficient.
US Pat. No. 3,152,904 (Claims) US Pat. No. 3,457,075 (Claims) JP-A-11-295844 (Claims) JP-A-11-352627 (Claims) JP 2000-305213 A (Claims) JP 2003-91053 A (Claims)

  The present invention has been made in view of the above problems, and an object of the present invention is a high density image that is free from poor conveyance and uneven density during heat development, and excellent in preventing fog rise over time. It is to provide a forming method. It is another object of the present invention to provide an image forming method that is further excellent in image storability during high-temperature storage or excellent in film transportability and environmental suitability.

  As a result of diligent studies to solve the above problems, the image forming layer side and the back coat are formed even when the exposure light source is downsized using a laser having an emission peak intensity at 350 nm to 450 nm and further rapid development is performed. The inventors have found that the above object can be achieved by setting the surface roughness on the layer side within a specific range, and have reached the present invention.

  The above object of the present invention can be achieved by the following configuration.

(Claim 1)
In a photothermographic material having an image forming layer containing an organic silver salt, silver halide, a binder and a reducing agent on a support, a ten-point average roughness of the outermost surface on the image forming layer side with the support interposed therebetween. Rz (E) / Rz (B) where (Rz (E)) is the ten-point average roughness of the outermost surface on the opposite side of the image forming layer across the support (Rz (B)) The photothermographic material is characterized by having a value of 0.1 or more and 0.7 or less.

(Claim 2)
Furthermore, the average particle size of the largest average particle size of the matting agent contained in the layer on the image forming layer side across the support is Le (μm), and the layer on the side opposite to the image forming layer across the support 2. The photothermographic material according to claim 1, wherein Lb / Le is 2.0 or more and 10 or less, where Lb (μm) is the average particle size of the matting agent having the largest average particle size. material.

(Claim 3)
When the center line average surface roughness of the surface on the image forming layer side is Ra (E) and the center line average surface roughness of the surface opposite to the image forming layer across the support is Ra (B), 3. The photothermographic material according to claim 1, wherein the value of Ra (E) / Ra (B) is from 0.5 to 1.5.

(Claim 4)
4. The photothermographic material according to claim 1, wherein the value of Rz (E) / Ra (E) is 10 or more and 70 or less.

(Claim 5)
5. The photothermographic material according to claim 1, wherein the silver halide contains silver iodide in a proportion of 5 mol% to 100 mol%.

(Claim 6)
6. The photothermographic material according to claim 1, wherein the silver halide contains silver iodide in a proportion of 40 mol% to 100 mol%.

(Claim 7)
2. A silver saving agent selected from a vinyl compound, a hydrazine derivative, a phenol derivative, a naphthol derivative, a silane compound, and a quaternary onium salt is contained on the side having an image forming layer. The photothermographic material according to claim 1.

(Claim 8)
The photothermographic material according to claim 1, wherein the binder has a glass transition temperature (Tg) of 70 to 150 ° C.

(Claim 9)
The photothermographic material according to claim 1, comprising a compound represented by the following general formula (SF).

Formula (SF) (Rf (L) _n1 ) _p (Y) _m1 (A) _q
Wherein Rf represents a substituent having a fluorine atom, L represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, and A represents an anion M1 and n1 each represents an integer of 0 or 1, and p and q each represent an integer of 1 to 5. However, when q is 1, n1 and m1 are not 0 at the same time. .)
(Claim 10)
10. The photothermographic material according to claim 1, further comprising silver halide grains having an average grain size of 10 to 50 nm.

(Claim 11)
11. The photothermographic material according to claim 1, wherein the silver halide further contains silver halide grains having an average grain size of 55 to 100 nm.

(Claim 12)
The photothermographic material according to claim 1, wherein the silver halide contains silver halide grains chemically sensitized with a chalcogen compound.

(Claim 13)
13. The photothermographic material according to claim 1, wherein the amount of silver contained in the image forming layer is from 0.3 to 1.5 g / m < ² >.

(Claim 14)
An image forming method comprising: exposing the photothermographic material according to claim 1 with a laser having an exposure light source having an emission peak intensity at 350 nm to 450 nm to form an image.

(Claim 15)
Regarding the characteristic curve shown on the orthogonal coordinate where the unit length of the diffusion density (Y axis) and the common logarithmic exposure (X axis) is equal, the image obtained by thermal development at a development temperature of 123 ° C. and a development time of 13.5 seconds The image forming method according to claim 14, wherein the average gradation in the range of 0.25 to 2.5 in terms of optical density with diffused light is 2.0 to 4.0.

(Claim 16)
Using a heat development processing apparatus, the conveyance speed of the heat development unit is 10 to 200 mm / sec, the conveyance speed between the photosensitive material supply unit and the image exposure unit is 10 to 200 mm / sec, and the conveyance speed of the image exposure unit is 10 The image forming method according to claim 14, wherein the image is thermally developed at a speed of ˜200 mm / sec.

(Claim 17)
The image forming method according to claim 14, 15 or 16, wherein the image is exposed to light having an illuminance of 1 mW / mm ² or more and then thermally developed.

  According to the present invention, it is possible to provide an image forming method that is high in density, does not cause conveyance failure or density unevenness during thermal development, and is excellent in preventing fog rise with time. Further, if necessary, it is possible to provide an image forming method which is further excellent in image storability at high temperature storage, or excellent in film transportability and environmental suitability.

  The present invention will be described in more detail. The image forming method according to claim 14 using the photothermographic material according to claim 1, wherein an image excellent in prevention of fog rise with time is obtained at high density, without occurrence of conveyance failure or density unevenness during heat development. Can be obtained.

  Further, by using the photothermographic material of claim 7, the image density can be remarkably improved.

  Further, by using the photothermographic material of claim 8, the image storability during high temperature storage can be further improved.

  By using the photothermographic material according to the ninth aspect, it is possible to further improve the film transportability and environmental suitability (decrease in accumulation in vivo).

  In claim 10, the average grain size of the silver halide is preferably 10 to 40 nm, more preferably 10 to 35 nm. If the average grain size of the silver halide is smaller than 10 nm, the image density may be lowered, or the light irradiation image storage stability may be deteriorated. On the other hand, if it exceeds 50 nm, the image density may decrease.

  The average grain size referred to here means the length of the edge of the silver halide grain when the silver halide grain is a cubic or octahedral so-called normal crystal. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface. In addition, in the case of non-normal crystals, for example, in the case of spherical particles, rod-shaped particles, etc., the diameter when considering a sphere equivalent to the volume of silver halide grains is calculated as the particle size. The measurement was performed using an electron microscope, and the average particle size was determined by averaging the measured values of 300 particle sizes.

  12. The gradation adjustment or the image density is improved by using silver halide grains having an average grain size of 55 to 100 nm and silver halide grains having an average grain size of 10 to 50 nm in combination according to claim 11. It is possible to improve (reduce) the decrease in image density over time. The ratio (mass ratio) of silver halide grains having an average grain size of 10 to 50 nm and silver halide grains having an average grain size of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90. : 10-60: 40.

  Hereinafter, the constituent elements of the present invention will be sequentially described.

(Organic silver salt)
Organic silver salts as silver ion sources for silver image formation include silver salts of organic acids and heteroorganic acids, especially long chain (C10-30, preferably 15-25) fats. A silver salt of a group carboxylic acid and a silver salt of a nitrogen-containing heterocyclic compound are preferred. Organic or inorganic complexes described in Research Disclosure (hereinafter also simply referred to as RD) 17029 and 29963 in which the ligand has a value of 4.0 to 10.0 as a total stability constant with respect to silver ions are also preferable. . Examples of these suitable silver salts include:

  Silver salts of organic acids such as gallic acid, succinic acid, behenic acid, stearic acid, arachidic acid, palmitic acid, lauric acid, etc .; silver carboxyalkylthiourea salts such as 1- (3-carboxypropyl) thiourea, Silver salts such as 1- (3-carboxypropyl) -3,3-dimethylthiourea; silver salts or complexes of polymer reaction products of aldehydes and hydroxy-substituted aromatic carboxylic acids, such as aldehydes (formaldehyde, acetaldehyde, butyraldehyde) Etc.) and hydroxy-substituted acids (for example, salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid) silver salts or complexes of reaction products; silver salts or complexes of thiones, such as 3- (2-carboxyethyl)- 4-hydroxymethyl-4-thiazoline-2-thione, and 3-carboxymethyl-4-thiazo Silver salt or complex such as N-2-thione; selected from imidazole, pyrazole, urazole, 1,2,4-thiazole and 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benztriazole Nitrogen acid and silver complexes or salts; silver salts such as saccharin and 5-chlorosalicylaldoxime; silver mercaptides and the like.

  Among these, particularly preferable silver salts include silver salts of long-chain (10 to 30 carbon atoms, preferably 15 to 25) aliphatic carboxylic acids such as silver behenate, silver arachidate, and silver stearate. .

  In the present invention, it is preferable that two or more kinds of organic silver salts are mixed in order to improve developability and form a silver image having a high density and a high contrast. For example, silver ions are mixed into two or more kinds of organic acid mixtures. It is preferable to prepare by mixing the solutions.

  The organic silver salt can be obtained by mixing a water-soluble silver compound and a compound that forms a complex with silver. The organic silver salt is controlled by a normal mixing method, a reverse mixing method, a simultaneous mixing method, or a controlled compound as described in JP-A-9-127643. A double jet method or the like is preferably used. For example, an alkali metal salt (sodium hydroxide, potassium hydroxide, etc.) is added to an organic acid to produce an organic acid alkali metal salt soap (sodium behenate, sodium arachidate, etc.). A soap and silver nitrate are mixed to produce an organic silver salt crystal. At that time, silver halide grains may be mixed.

  The organic silver salt can be used in various shapes, but tabular grains are preferred. In particular, it is a flat organic silver salt particle having an aspect ratio of 3 or more, and the filling in the photosensitive layer is made by reducing the shape anisotropy of two substantially parallel faces (main planes) having the largest area. In order to increase the rate, particles having an average needle-like ratio of the tabular organic silver salt particles measured from the main plane direction of 1.1 or more and less than 10.0 are preferable. A more preferable acicular ratio is 1.1 or more and less than 5.0.

  The term “tabular organic silver salt particles having an aspect ratio of 3 or more” means that the tabular organic silver salt particles occupy 50% or more of the total number of organic silver salt particles. Furthermore, in the organic silver salt in the present invention, it is preferable that tabular organic silver salt particles having an aspect ratio of 3 or more occupy 60% or more of the total number of organic silver salt particles, and more preferably 70% or more (number). Particularly preferably, it is 80% or more (number).

  The tabular grains having an aspect ratio of 3 or more are grains having a ratio of particle diameter to thickness, a so-called aspect ratio (abbreviated as AR) represented by the following formula of 3 or more.

AR = particle diameter (μm) / thickness (μm)
The aspect ratio of the tabular organic silver salt particles is preferably 3 to 20, and more preferably 3 to 10. The reason is that if the aspect ratio is too low, the organic silver salt particles are likely to be close-packed, and if the aspect ratio is too high, the organic silver salt particles are likely to overlap with each other and are dispersed in a stuck state. Therefore, light scattering or the like is likely to occur, and as a result, the transparency of the photosensitive material is lowered.

  The average value of the particle diameter, average thickness and acicular ratio of the organic silver salt particles can be determined by the method described in paragraphs “0031” to “0047” of JP-A-2002-287299.

  The method for obtaining the organic silver salt particles having the above-mentioned shape is not particularly limited, and it is preferable to maintain a mixed state when forming an organic acid alkali metal salt soap or a mixed state when adding silver nitrate to the soap, It is effective to optimize the ratio of silver nitrate that reacts with soap.

  The tabular organic silver salt particles according to the present invention are preferably pre-dispersed with a binder, a surfactant or the like, if necessary, and then dispersed and pulverized with a media disperser or a high-pressure homogenizer. For the preliminary dispersion, a general stirrer such as an anchor type or a propeller type, a high speed rotating centrifugal radiation type stirrer (dissolver), or a high speed rotating shear type stirrer (homomixer) can be used.

  As the media dispersing machine, a rolling mill such as a ball mill, a planetary ball mill or a vibrating ball mill, a bead mill which is a medium stirring mill, an attritor or other basket mill can be used, and a wall as a high-pressure homogenizer can be used. Various types such as a type that collides with a plug or the like, a type that collides liquids at a high speed after dividing the liquid into a plurality of types, and a type that passes through a thin orifice can be used.

  As the ceramic used for the ceramic beads used at the time of media dispersion, for example, those described in paragraph “0051” of the above-mentioned JP-A No. 2002-287299 are preferable. Yttrium-stabilized zirconia and zirconia reinforced alumina (hereinafter, these ceramics containing zirconia are hereinafter abbreviated as zirconia) are particularly preferably used because of the low generation of impurities due to friction with beads and dispersers during dispersion.

  In the apparatus used when dispersing the flat organic silver salt particles, it is preferable to use ceramics such as zirconia, alumina, silicon nitride, boron nitride or diamond as the material of the member in contact with the organic silver salt particles, Among these, it is preferable to use zirconia.

  When the dispersion is performed, the binder concentration is preferably 0.1 to 10% of the mass of the organic silver salt, and it is preferable that the liquid temperature does not exceed 45 ° C. from the preliminary dispersion through the main dispersion. Further, as preferable operating conditions for the present dispersion, for example, when a high-pressure homogenizer is used as the dispersing means, preferable conditions are 29.42 to 98.06 MPa, and the number of operations is preferably 2 times or more. Moreover, when using a media disperser as a dispersion | distribution means, 6-13 m / sec of peripheral speed is mentioned as preferable conditions.

Further, in a preferred embodiment of the photothermographic material of the present invention, when the cross section perpendicular to the support surface of the material is observed with an electron microscope, the proportion of organic silver salt particles exhibiting a projected area of less than 0.025 μm ² is an organic silver salt. An organic silver salt having a characteristic that the ratio of the particles showing 70% or more of the total projected area of the grains and the projected area of 0.2 μm ² or more is 10% or less of the total projected area of the organic silver salt particles; A photosensitive emulsion containing photosensitive silver halide is coated. In such a case, it is possible to obtain a uniformly distributed state in which the organic silver salt particles are less aggregated in the photosensitive emulsion.

  The conditions for producing the photosensitive emulsion having such characteristics are not particularly limited, but the mixed state at the time of forming the organic acid alkali metal salt soap, or the mixed state at the time of adding silver nitrate to the soap, etc. can be kept good. Optimize the ratio of silver nitrate that reacts with soap, disperse and grind with a media disperser or a high-pressure homogenizer, and the amount of binder used (concentration) is 0.1 to 0.1% of the organic silver salt mass. Preferred conditions are 10%, and that the temperature from drying to the end of the dispersion does not exceed 45 ° C., and that a dissolver is used during preparation and stirring is performed at a peripheral speed of 2.0 m / sec or more. As mentioned.

  The ratio of the projected area and the total projected area of the organic silver salt particles having a specific projected area value as described above is the same as that described in the section for obtaining the average thickness of the tabular grains described above. A portion corresponding to the organic silver salt particles is extracted by a method using a transmission electron microscope. Specifically, it can be determined by the method described in paragraphs “0057” to “0059” of JP-A No. 2002-287299.

  The organic silver salt particles used in the present invention are preferably monodisperse particles, and the preferred monodispersity is 1 to 30%. By making monodisperse particles in this range, an image with a high density can be obtained. The monodispersity mentioned here is defined by the following formula.

Monodispersity = {(standard deviation of particle size) / (average value of particle size)} × 100
The average particle diameter (equivalent circle diameter) of the organic silver salt is preferably 0.01 to 0.3 μm, more preferably 0.02 to 0.2 μm. The average particle diameter (equivalent circle diameter) represents the diameter of a circle having the same area as each particle image observed with an electron microscope.

In order to prevent devitrification of the photosensitive material, the total amount of silver halide and organic silver salt is preferably 0.3 to 1.5 g per 1 m ² in terms of silver amount. By using this range, a preferable image can be obtained when used as a medical image. If it is less than 0.3 g per m ² , the image density may decrease. Further, if the amount exceeds 1.5 g per 1 m ² , the fog may increase or the sensitivity may be lowered when printing on the PS plate.

(Silver halide)
The silver halide used in the present invention (hereinafter also referred to as photosensitive silver halide grains or silver halide grains) will be described. In the present invention, silver halide can inherently absorb light as an intrinsic property of a silver halide crystal, or can artificially absorb visible light or infrared light by a physicochemical method. In addition, when light in any region within the light wavelength range from the ultraviolet light region to the infrared light region is absorbed, a physicochemical change can occur in the silver halide crystal and / or on the crystal surface. This refers to the silver halide crystal grains produced.

  The silver halide grains themselves can be prepared as a silver halide grain emulsion (also referred to as a silver halide emulsion) using a known method. That is, any of acid method, neutral method, ammonia method, etc. may be used, and as a method of reacting soluble silver salt and soluble halogen salt, any one of one-side mixing method, simultaneous mixing method, combination thereof, etc. may be used. Of these methods, the so-called controlled double jet method of preparing silver halide grains while controlling formation conditions is preferable.

  As for the halogen composition, the silver halide content of the present invention preferably has a silver iodide content of 5 mol% or more and 100 mol% or less. If the silver iodide content is in this range, the intragranular halogen composition distribution may be uniform, may change stepwise, or may change continuously. Further, silver halide grains having a core / shell structure having a high silver iodide content inside and / or on the surface can also be preferably used. A preferable structure is a 2- to 5-fold structure, more preferably 2- to 4-fold core / shell particles. The preferred silver iodide content of the emulsion used in the present invention is 10 mol% or more and 100 mol% or less with respect to the amount of silver halide. More preferably, they are 40 mol% or more and 100 mol% or less, More preferably, they are 70 mol% or more and 100 mol% or less, Especially preferably, they are 90 mol% or more and 100 mol% or less. The silver halide of the present invention preferably exhibits direct transition absorption derived from the silver iodide crystal structure at a wavelength between 350 nm and 440 nm. Whether these silver halides have light absorption of direct transition can be easily distinguished by the fact that exciton absorption due to direct transition is observed in the vicinity of 400 nm to 430 nm. As a method for introducing silver iodide into the silver halide grains, a method of adding an alkali iodide aqueous solution during grain formation, fine grain silver iodide, fine grain silver iodobromide, fine grain silver iodochloride, fine grain silver iodochlorobromide Among them, the method of adding at least one fine particle, the method of using an iodide ion releasing agent described in JP-A-5-323487 and JP-A-6-11780 are preferable.

  Grain formation is usually divided into two stages: silver halide seed grain (nucleus) generation and grain growth, and these may be performed continuously at once, or the nucleus (seed grain) formation and grain growth are separated. It is also possible to do this. The controlled double jet method in which the particle formation is controlled by controlling the pAg, pH, etc., which are particle formation conditions, is preferable because the particle shape and size can be controlled. For example, when performing a method in which nucleation and particle growth are performed separately, first, an aqueous silver salt solution and an aqueous halide solution are uniformly and rapidly mixed in an aqueous gelatin solution to produce nuclei (seed particles) (nucleation process). Then, silver halide grains are prepared by a grain growth process in which grains are grown while supplying an aqueous silver salt solution and an aqueous halide solution under controlled pAg, pH, and the like. After the formation of grains, a desired silver halide emulsion can be obtained by removing unnecessary salts and the like by a desalting step by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, or an electrodialysis method. .

  The grain size of the silver halide grains is preferably monodispersed. The monodispersion mentioned here means that the variation coefficient of the particle size obtained by the following formula is 30% or less. Preferably it is 20% or less, More preferably, it is 15% or less.

Coefficient of variation of particle size% = (standard deviation of particle size / average value of particle size) × 100
Examples of the shape of the silver halide grains include cubes, octahedrons, tetrahedron grains, tabular grains, spherical grains, rod-like grains, and potato grains. Among these, cubes, octahedrons, 14 Planar and tabular silver halide grains are preferred.

  The average aspect ratio when using tabular silver halide grains is preferably 1.5 to 100, more preferably 2 to 50. These are described in US Pat. Nos. 5,264,337, 5,314,798, 5,320,958, etc., and the desired tabular grains can be easily obtained. Further, grains having rounded corners of silver halide grains can be preferably used.

  There is no particular limitation on the crystal habit on the outer surface of the silver halide grain, but when using a sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the sensitizing dye on the surface of the silver halide grain. It is preferable to use silver halide grains having a relatively high proportion of crystal habits adapted to the selectivity. For example, when using a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100], the proportion of the [100] face on the outer surface of the silver halide grain is preferably high, and this ratio is 50 % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

  The silver halide grains used in the present invention are preferably prepared using low molecular weight gelatin having an average molecular weight of 50,000 or less at the time of forming the grains, and particularly preferably used at the time of nucleation of silver halide grains. The low molecular weight gelatin preferably has an average molecular weight of 50,000 or less, more preferably 2,000 to 40,000, and particularly preferably 5,000 to 25,000. The average molecular weight of gelatin can be measured by gel filtration chromatography. Low molecular weight gelatin can be decomposed by adding gelatin-degrading enzyme to a commonly used gelatin aqueous solution with an average molecular weight of about 100,000, hydrolyzing by adding acid or alkali, and heating under atmospheric pressure or pressure. Can be obtained by thermal decomposition, decomposition by ultrasonic irradiation, or a combination of these methods.

  The concentration of the dispersion medium at the time of nucleation is preferably 5% by mass or less, and more preferably 0.05 to 3.0% by mass.

  For the silver halide grains used in the present invention, it is preferable to use a compound represented by the following general formula when the grains are formed.

Y ¹ O (CH ₂ CH ₂ O) _m2 [CH (CH ₃ ) CH ₂ O] _p2 (CH ₂ CH ₂ O) _n2 Y ¹
In the formula, Y ¹ represents a hydrogen atom, —SO ₃ M ¹ or —CO—B ¹ —COOM ¹ , and M ¹ is substituted with a hydrogen atom, an alkali metal atom, an ammonium group or an alkyl group having 5 or less carbon atoms. B ¹ represents a chain or cyclic group forming an organic dibasic acid. m ² and n2 each represents 0 to 50, p2 represents 1 to 100.

  The polyethylene oxide compound represented by the above general formula supports the step of producing an aqueous gelatin solution, the step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, and the emulsion when producing a silver halide photographic light-sensitive material. It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved, such as a step of coating on the body. 44-9497. This polyethylene oxide compound also functions as an antifoaming agent during nucleation.

  The compound represented by the above general formula is preferably used at 1% by mass or less, more preferably 0.01 to 0.1% by mass with respect to silver.

Regarding the conditions at the time of nucleation, the method described in paragraphs “0079” to “0082” of JP-A-2002-287299 can also be referred to.
Further, as photosensitive silver halide grains that can be used in the present invention, a halogen described in JP-A No. 2003-270755, whose surface sensitivity is lowered by conversion from a surface latent image type to an internal latent image type by thermal development. Examples include silver halide grains. That is, in the exposure before thermal development, a latent image that can function as a catalyst for a development reaction (reduction reaction of silver ions by a silver ion reducing agent) is formed on the surface of the silver halide grains, and the exposure after the thermal development process has passed. Then, since a larger number of latent images are formed inside the surface of the silver halide grains, the silver halide grains can suppress the formation of latent images on the surface.

  The silver halide grains may be added to the image forming layer by any method. At this time, the silver halide grains are preferably arranged so as to be close to a reducible silver source (organic silver salt).

  Silver halide grains are prepared in advance and added to the solution for preparing organic silver salt grains, so that the silver halide preparation process and the organic silver salt grain preparation process can be handled separately, so production control Although it is also preferable, as described in British Patent 1,447,454, when preparing organic silver salt particles, a halogen component such as a halide ion is allowed to coexist with an organic silver salt forming component, and silver ion is added thereto. By injecting, the organic silver salt particles can be generated almost simultaneously.

  It is also possible to prepare silver halide grains by converting a halogen-containing compound to an organic silver salt and converting the organic silver salt. That is, a silver halide forming component is allowed to act on a solution or dispersion of an organic silver salt prepared in advance or a sheet material containing the organic silver salt to convert a part of the organic silver salt into photosensitive silver halide. You can also.

  Examples of the silver halide forming component include inorganic halogen compounds, onium halides, halogenated hydrocarbons, N-halogen compounds, and other halogen-containing compounds. Specific examples thereof are described in paragraphs of JP-A-2002-287299. It is described in “0086”.

  Thus, silver halide can also be prepared by converting a part or all of silver in the organic acid silver salt into silver halide by the reaction of the organic acid silver salt with a halogen ion. Moreover, you may use together the silver halide grain manufactured by converting a part of these organic silver salt into the silver halide prepared separately.

  These silver halide grains are preferably used in an amount of 0.001 to 0.7 moles per mole of the organic silver salt, both separately prepared silver halide grains and silver halide grains obtained by conversion of the organic silver salt. It is more preferable to use 0.03 to 0.5 mol.

The silver halide preferably contains transition metal ions belonging to Groups 6 to 11 of the periodic table. As said metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, and Au are preferable. These may be used alone or in combination of two or more of the same or different metal complexes. Although these metal ions may introduce a metal salt into silver halide as it is, they can be introduced into silver halide in the form of a metal complex or complex ion. The content is preferably in the range of 1 × 10 ⁻⁹ to 1 × 10 ⁻² mol, and more preferably in the range of 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ mol, with ^respect to 1 mol of silver. In the present invention, the transition metal complex or complex ion is preferably represented by the following general formula.

General formula [ML ₆ ] ^m
In the formula, M represents a transition metal selected from Group 6 to 11 elements in the periodic table, L represents a ligand, and m represents 0,-, 2-, 3-, or 4-. Specific examples of the ligand represented by L include halogen ion (fluorine ion, chlorine ion, bromine ion, iodine ion), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide, and aco. A ligand, nitrosyl, thionitrosyl and the like can be mentioned, and ako, nitrosyl, thionitrosyl and the like are preferable. When an acoligand is present, it preferably occupies one or two of the ligands. L may be the same or different.

  The compounds providing these metal ions or complex ions are preferably added at the time of silver halide grain formation and incorporated into the silver halide grains. Preparation of silver halide grains, that is, nucleation, growth, physical ripening It may be added at any stage before or after chemical sensitization, but is preferably added at the stage of nucleation, growth and physical ripening, more preferably at the stage of nucleation and growth, particularly preferably. Add at the nucleation stage. In addition, it may be divided and added several times, or it can be uniformly contained in the silver halide grains. JP-A-63-29603, JP-A-2-306236, 3 As described in JP-A Nos. 167545, 4-76534, 6-110146, 5-273683, etc., the particles can be contained with a distribution.

  These metal compounds can be added by dissolving in water or an appropriate organic solvent (alcohols, ethers, glycols, ketones, esters, amides, etc.). For example, an aqueous solution of a metal compound powder Alternatively, an aqueous solution in which a metal compound and sodium chloride and potassium chloride are dissolved together is added to the water-soluble silver salt solution or water-soluble halide solution during particle formation, or the silver salt aqueous solution and the halide aqueous solution are mixed simultaneously. When adding, as a third aqueous solution, a method of preparing silver halide grains by a method of simultaneous mixing of three liquids, a method of charging a required amount of an aqueous solution of a metal compound into the reaction vessel during grain formation, or halogenation There is a method of adding another silver halide grain previously doped with a metal ion or complex ion and dissolving it at the time of silver preparation. In particular, a method in which an aqueous solution of a metal compound powder or an aqueous solution in which a metal compound and sodium chloride and potassium chloride are dissolved together is added to the halide aqueous solution. When added to the particle surface, a necessary amount of an aqueous solution of a metal compound can be charged into the reaction vessel immediately after the formation of the particle, during or after the physical ripening, or at the chemical ripening.

  Separately prepared photosensitive silver halide grains can be desalted by known desalting methods such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. It can also be used without salting.

  The silver halide grains can be chemically sensitized. For example, by a method disclosed in JP-A Nos. 2001-249428 and 2001-249426, a compound having a chalcogen atom such as sulfur or a noble metal compound that releases noble metal ions such as gold ions is used as a chemical sensitization center ( Chemical sensitization nuclei). In the present invention, it is particularly preferable to combine the chemical sensitization using the above-mentioned compound having a chalcogen atom and the chemical sensitization using a noble metal compound.

  In the present invention, it is preferably chemically sensitized by the following compound containing a chalcogen atom. The compound containing a chalcogen atom useful as an organic sensitizer is preferably a compound having a group capable of adsorbing to silver halide and an unstable chalcogen atom site.

  As these organic sensitizers, organic sensitizers having various structures disclosed in JP-A-60-150046, JP-A-4-109240, JP-A-11-218874, and the like can be used. Of these, at least one compound having a structure in which a chalcogen atom is bonded to a carbon atom or a phosphorus atom by a double bond is preferable. Particularly preferred are compounds of general formula (1-1) and general formula (1-2) disclosed in JP-A No. 2002-250984.

The amount of the compound containing a chalcogen atom as an organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, etc., but 1 × per 1 mol of silver halide. 10 ⁻⁸ to 1 × 10 ⁻² mol is preferable, and 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol is more preferable. The chemical sensitization environment is not particularly limited, but in the presence of a compound capable of annihilating or reducing the size of silver chalcogenide or silver nuclei on the photosensitive silver halide grains, and in particular silver nuclei. It is preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent that can be oxidized. As the sensitization condition, pAg is preferably 6 to 11 (more preferably 7 to 10) The pH is preferably 4 to 10 (more preferably 5 to 8), and the temperature is preferably 30 ° C. or lower for sensitization.

  Therefore, in the photothermographic material of the present invention, the photosensitive silver halide is heated at a temperature of 30 using an organic sensitizer containing chalcogen atoms in the presence of an oxidizing agent capable of oxidizing silver nuclei on the grains. It is preferable to use a light-sensitive silver halide emulsion that has been chemically sensitized at a temperature of 0 ° C. or lower, mixed with an organic silver salt, dispersed, dehydrated and dried.

  Further, chemical sensitization using these organic sensitizers is preferably performed in the presence of a heteroatom-containing compound having adsorptivity to silver halide grains. By performing chemical sensitization in the presence of a compound having an adsorptivity to silver halide, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved. Although the spectral sensitizing dye used in the present invention will be described later, the heteroatom-containing compound having adsorptivity to silver halide is preferably a nitrogen-containing heterocyclic compound described in JP-A-3-24537. It is done.

  In the nitrogen-containing heterocyclic compound, the heterocyclic ring includes pyrazole ring, pyrimidine ring, 1,2,4-triazole ring, 1,2,3-triazole ring, 1,3,4-thiadiazole ring, 1,2,3- Thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,2,3,4-tetrazole ring, pyridazine ring, 1,2,3-triazine ring, Examples thereof include three bonded rings such as a triazolotriazole ring, a diazaindene ring, a triazaindene ring, and a pentaazaindene ring. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, a phthalazine ring, a benzimidazole ring, an indazole ring, a benzothiazole ring, or the like can also be applied. Among these, an azaindene ring is preferable, and an azaindene compound having a hydroxyl group as a substituent, for example, a hydroxytriazaindene, hydroxytetraazaindene, hydroxypentaazaindene compound or the like is more preferable.

  The heterocyclic ring may have a substituent other than the hydroxyl group. Examples of the substituent include an alkyl group, a substituted alkyl group, an alkylthio group, an amino group, a hydroxyamino group, an alkylamino group, a dialkylamino group, an arylamino group, a carboxyl group, an alkoxycarbonyl group, a halogen atom, and a cyano group. May be.

The addition amount of these heterocyclic compounds varies over a wide range depending on the size, composition and other conditions of the silver halide grains, but the approximate amount is 1 × 10 5 per mole of silver halide. ^-6 to 1 mol, preferably 1 × 10 ⁻⁴ to 1 × 10 ⁻¹ mol.

  As described above, the silver halide grains can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, a chloroaurate or an organic gold compound can be used as a gold sensitizer.

  In addition to the above-described sensitization methods, reduction sensitization methods and the like can also be used. As the reduction-sensitized shell-like compounds, ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, borane compounds A silane compound, a polyamine compound, or the like can be used. Further, reduction sensitization can be performed by ripening the emulsion while maintaining the pH at 7 or higher or the pAg at 8.3 or lower.

  The silver halide subjected to chemical sensitization according to the present invention may be formed in the presence of an organic silver salt, formed in the absence of an organic silver salt, or a mixture of both. May be good.

  The silver halide grains may be spectrally sensitized by adsorbing spectral sensitizing dyes. A known spectral sensitizing dye can be appropriately used as the spectral sensitizing dye. In the present application, it is preferable to use direct transition absorption of silver halide, in which case no spectral sensitizing dye is used.

  When the direct transition absorption of the above silver halide is not used, it is preferable to perform spectral sensitization by adsorbing a spectral sensitizing dye to the silver halide grains. As spectral sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes and the like can be used. For example, JP-A Nos. 63-159841, 60-140335, 63-231437, 63-259651, 63-304242, 63-15245, U.S. Pat. Nos. 4,639,414, 4 , 740,455, 4,741,966, 4,751,175, 4,835,096 and the like. Useful sensitizing dyes are described in, for example, documents described or cited in Section RD17643-A (December 1978, page 23) and Section 18431X (August 1978, page 437). In particular, it is preferable to use a sensitizing dye having spectral sensitivity suitable for spectral characteristics of various laser imagers and scanner light sources. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

(Reducing agent)
In the present invention, as the reducing agent (silver ion reducing agent), in particular, at least one of the reducing agents is a compound represented by the following general formula (1) alone or in combination with a reducing agent having another different chemical structure. It is preferable to use it. By using these highly active reducing agents, it is possible to obtain a photothermographic material having a high concentration and excellent light irradiation image storage stability.

[Wherein, X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₂ represents an alkyl group, which may be the same or different, but at least one is a secondary or tertiary alkyl group. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2. ]
In the present invention, it is preferable to use a compound of the general formula (1) and a compound of the following general formula (2) together in order to obtain a desirable color tone.

[Wherein, X ₂ represents a chalcogen atom or CHR ₅ , and R ₅ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₆ represents an alkyl group, which may be the same or different, but is not a secondary or tertiary alkyl group. R ₇ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₈ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2. ]
As the ratio of the combined use, [mass of compound of general formula (1)]: [mass of compound of general formula (2)] is preferably 5:95 to 45:55, more preferably 10:90 to 40:60.

In the general formula (1), X ₁ represents a chalcogen atom or CHR ₁ . The chalcogen atom is sulfur, selenium or tellurium, preferably a sulfur atom. CHR R ₁ in ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group, a halogen atom, a fluorine atom, a chlorine atom, a bromine atom, the alkyl group substituted or An unsubstituted alkyl group having 1 to 20 carbon atoms is preferred. Specific examples include methyl, ethyl, propyl, butyl, hexyl, cyclohexyl, heptyl and the like, and examples of the alkenyl group include vinyl, allyl, butenyl, hexenyl, cyclohexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1- Methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, etc., aryl groups are benzene rings, naphthalene rings, etc., and heterocyclic groups are thiophene, furan, imidazole, pyrazole, pyrrole, etc. .

These groups may further have a substituent, and examples of the substituent include a substituent in R ₁₄ of the general formula (YA). Moreover, when there are two or more substituents, they may be the same or different. A particularly preferred substituent is an alkyl group.

R ₂ represents an alkyl group, which may be the same or different, but at least one is a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, specifically, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, t-pentyl, t-octyl. , Cyclohexyl, cyclopentyl, 1-methylcyclohexyl, 1-methylcyclopropyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group, An ester group, a halogen atom, etc. are mentioned. Or it may form a saturated ring with (R _{4) n} and (R _{4) m.} R ₂ is preferably a secondary or tertiary alkyl group, and preferably has 2 to 20 carbon atoms. A tertiary alkyl group is more preferred, t-butyl, t-pentyl and 1-methylcyclohexyl are more preferred, and t-butyl is most preferred.

R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. Examples of the group that can be substituted on the benzene ring include halogen atoms such as fluorine, chlorine, bromine, alkyl groups, aryl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, amino groups, acyl groups, acyloxy groups, Examples include acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, and heterocyclic group.

R ₃ is preferably methyl, ethyl, i-propyl, t-butyl, cyclohexyl, 1-methylcyclohexyl, 2-hydroxyethyl and the like. More preferred are methyl and 2-hydroxyethyl.

These groups may further have a substituent, and the substituents exemplified in the above R ₁ can be used as the substituent. R ₃ is preferably a C 1-20 alkyl group having a hydroxyl group or a precursor group thereof, and more preferably a C 1-5 alkyl group. Most preferred is 2-hydroxyethyl. In the most preferred combination of R ₂ and R ₃ , R ₂ is a tertiary alkyl group (t-butyl, 1-methylcyclohexyl, etc.), and R ₃ is a primary alkyl group having a hydroxyl group or a precursor group thereof ( 2-hydroxyethyl and the like). A plurality of R ₂ and R ₃ may be the same or different.

R ₄ represents a substitutable group on the benzene ring, specifically, an alkyl group having 1 to 25 carbon atoms (methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl, etc.), Halogenated alkyl group (trifluoromethyl, perfluorooctyl etc.), cycloalkyl group (cyclohexyl, cyclopentyl etc.), alkynyl group (propargyl etc.), glycidyl group, acrylate group, methacrylate group, aryl group (phenyl etc.), heterocyclic ring Groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups (methoxy, ethoxy) , Pyroxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc.), aryloxy groups (phenoxy, etc.), alkoxycarbonyl groups (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl groups (phenyloxycarbonyl) ), Sulfonamide groups (methanesulfonamide, ethanesulfonamide, butanesulfonamide, hexanesulfonamide group, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl groups (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl, butylamino) Sulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyridylaminos Sulfonyl, etc.), urethane groups (methylureido, ethylureido, pentylureido, cyclohexylureido, phenylureido, 2-pyridylureido, etc.), acyl groups (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.), Carbamoyl group (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, pentylaminocarbonyl group, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl), amide group (acetamide, propionamide, butanamide, hexaneamide, Benzamide etc.), sulfonyl group (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexylsulfonyl, Phenylsulfonyl, 2-pyridylsulfonyl, etc.), amino group (amino, ethylamino, dimethylamino, butylamino, cyclopentylamino, anilino, 2-pyridylamino, etc.), cyano group, nitro group, sulfo group, carboxyl group, hydroxyl group, An oxamoyl group can be exemplified. These groups may be further substituted with these groups. n and m represent an integer of 0 to 2, and most preferably n and m are 0.

R ₄ may form a saturated ring with R ₂ and R ₃ . R ₄ is preferably a hydrogen atom, a halogen atom or an alkyl group, more preferably a hydrogen atom. A plurality of R ₄ may be the same or different.

In general formula (2), R ₅ is the same group as R ₁ , but is more preferably a cyclic group such as cyclohexyl or cyclohexenyl. R ₇ is the same group as R _3, and R ₈ is the same group as R ₄ . R ₆ represents an alkyl group, which may be the same or different, but is not a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, and specific examples thereof include methyl, ethyl, propyl, butyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group, An ester group, a halogen atom, etc. are mentioned. Further, a saturated ring may be formed with (R ₈ ) _n and (R ₈ ) _m . R ₆ is preferably methyl.

  Among the compounds represented by the general formula (2), compounds that are preferably used are compounds satisfying the general formula (S) and general formula (T) described in European Patent No. 1,278,101. Include the compounds (1-24), (1-28) to (1-54), and (1-56) to (1-75) described in p21 to p28.

  Specific examples of the compounds represented by general formula (1) and general formula (2) are shown below, but the present invention is not limited to these.

  These bisphenol compounds represented by the general formulas (1) and (2) can be easily synthesized by a conventionally known method.

  The reducing agent contained in the photothermographic material is for reducing the organic silver salt to form a silver image. Examples of the reducing agent that can be used in combination with the reducing agent of the present invention include US Pat. Nos. 3,770,448, 3,773,512, 3,593,863, RD17029 and 29963, 11-119372 and JP-A-2002-62616.

The amount of the reducing agent including the compound represented by the general formula (1) is preferably 1 × 10 ⁻² to 10 mol, particularly preferably 1 × 10 ^{−2 to} 1.5 mol, per mol of silver. It is.

  In the photothermographic material preferably used in the present invention, the general formulas (1) to (4) and JP-A-2003-66559 described in JP-A No. 2003-43614 are used as development accelerators used in combination with the reducing agent. Hydrazine derivatives, phenol derivatives and naphthol derivatives represented by the general formulas (1) to (3) described in No. 1 are preferably used.

(Image tone)
Next, the color tone of an image obtained by thermally developing a photothermographic material will be described.

  Regarding the color tone of an output image for medical diagnosis such as a conventional X-ray photographic film, it is said that a cold tone image tone is easier for a reader to obtain a more accurate diagnosis observation result. Here, the cool image tone means a pure black tone or a bluish black tone of a black image. On the other hand, the warm image tone is said to be a warm black tone in which the black image is tinged with brown. However, in order to allow a more precise quantitative discussion, the International Lighting Commission (CIE) ), Based on the recommended expression.

The terms “more cold” and “more warm” regarding the color tone can be expressed by the hue angle hab at the minimum density Dmin and the optical density D = 1.0. That is, the hue angle hab is expressed by the color coordinates a ^* and b ^* of the color space L ^* a ^* b ^* color space, which is a color space having a perceptually uniform rate recommended by the International Commission on Illumination (CIE) in 1976. Using the following formula.

hab = tan ⁻¹ (b ^* / a ^* )
As a result of the examination based on the expression method based on the hue angle, the color tone after development of the photothermographic material of the present invention is preferably such that the hue angle hab is in the range of 180 ° <hab <270 °, more preferably 200 °. It was found that <hab <270 degrees, most preferably 220 degrees <hab <260 degrees. This is disclosed in Japanese Patent Application Laid-Open No. 2002-6463.

Conventionally, the CIE 1976 (L ^* u ^* v ^* ) color space or the (L ^* a ^* b ^* ) color space near the optical density of 1.0 is specified as u ^* , v ^* or a ^* , b ^* . It is known that a diagnostic image having a favorable color tone can be obtained by adjusting the numerical value, and is described in, for example, Japanese Patent Application Laid-Open No. 2000-29164.

However, as a result of further intensive studies on the photothermographic material of the present invention, the horizontal axis is u ^* or a ^* , in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space. When plotting u ^* , v ^* or a ^* , b ^* at various photographic densities on a graph with the axis as v ^* or b ^* and creating a linear regression line, the linear regression line is specified. By adjusting the range, it was found that it has a diagnostic ability equal to or higher than that of conventional wet silver salt photosensitive materials. A preferable range of conditions is described below.

1. The CIE 1976 (L ^* u ^* v ^* ) color was measured by measuring the optical densities of 0.5, 1.0, 1.5 and the lowest optical density of the silver image obtained after heat development processing of the photothermographic material. The coefficient of determination (multiple determination) R ^{2 of} the linear regression line created by arranging u ^* and v ^* at the respective optical densities on two-dimensional coordinates with the horizontal axis u ^* and the vertical axis v ^* is 0. It is preferable that it is .998 to 1.000.

Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (v ^* / u ^* ) is 0.7 to 2.5.

2. In addition, the optical density of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density, and the horizontal axis of the CIE 1976 (L ^* a ^* b ^* ) color space is plotted as a ^*. , vertical axis in the two-dimensional coordinates to b ^*, a ^* in the above each optical density, coefficient of determination of the linear regression line that created arranged b ^* (multiple determination) R ² is at 0.998 to 1.000 Preferably there is.

Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (b ^* / a ^* ) is 0.7 to 2.5.

An example of a method for creating the above-described linear regression line, that is, a method for measuring u ^* , v ^*, a ^* , and b ^{* in} the CIE 1976 color space will be described next.

A four-stage wedge sample including an unexposed portion and optical densities of 0.5, 1.0, and 1.5 is prepared using a heat development apparatus. Each wedge density part thus produced is measured with a spectrocolorimeter (Minolta Co., Ltd .: CM-3600d or the like), and u ^* , v ^* or a ^* , b ^* are calculated. The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 degrees, and measurement is performed in the transmission measurement mode. Plot u ^* , v ^* or a ^* , b ^* measured on a graph with u ^* or a ^{* on} the horizontal axis and v ^* or b ^{* on the} vertical axis to obtain a linear regression line, and the coefficient of determination (multiple determination) Find R ² , intercept and slope.

  Next, a specific method for obtaining a linear regression line having the above characteristics will be described.

  In the present invention, the developed silver can be adjusted by adjusting the addition amount of a compound or the like directly or indirectly involved in the development reaction process of the following toning agent, developer, silver halide grains and aliphatic carboxylate. The shape can be optimized to obtain a preferable color tone. For example, when the developed silver shape is dendritic, it becomes a bluish direction, and when it is a filament shape, it becomes a yellowish direction. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

  Conventionally, phthalazinone or phthalazine and phthalic acids and phthalic anhydrides are generally used as toning agents. Examples of suitable toning agents are disclosed in RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, 4,021,249 and the like. .

  In the present invention, it is preferable to use a compound that forms a dye image in a wavelength range of 360 nm to 700 nm during heat development. From the viewpoint of freedom of design and color tone adjustment, it is preferable to use a colorless leuco dye or coupler before heat development, but it is a colored dye, and the maximum absorption wavelength changes during heat development. In addition, a compound capable of forming a dye image in a wavelength range of 360 nm to 700 nm can also be used.

  The leuco dye and coupler preferably used in the present invention will be described below.

(Cyan coloring leuco dye)
The cyan color-forming leuco dye preferably used in the present invention will be described. The leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds, and is oxidized by silver ions. Any leuco dye that forms a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  In the present invention, a color image forming agent that increases its absorbance at 600 to 700 nm when oxidized is particularly used as a cyan color-forming leuco dye. JP-A-59-206831 (in particular, λmax is 600 to 600). Compounds within the range of 700 nm), compounds of general formula (I) to general formula (IV) of JP-A-5-204087 (specifically, (1) to (1) described in paragraphs “0032” to “0037”) 18) and compounds of general formula 4 to general formula 7 of JP-A No. 11-231460 (specifically, compounds of No. 1 to No. 79 described in paragraph “0105”).

  A cyan color-forming leuco dye particularly preferably used in the present invention is represented by the following general formula (CL).

In the formula, R ₈₁ and R ₈₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, —NHCO—R ₁₀ group (R ₁₀ is an alkyl group, aryl group, heterocyclic group) Or R ₈₁ and R ₈₂ are groups which are linked to each other to form an aliphatic hydrocarbon ring, an aromatic hydrocarbon ring or a heterocyclic ring. A ₈ represents a —NHCO— group, a —CONH— group or a —NHCONH— group, and R ₈₃ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group. In addition, —A ₈ —R ₈₃ may be a hydrogen atom. W ₈ is a hydrogen atom or —CONH—R ₈₅ group, —CO—R ₈₅ group or —CO—O—R ₈₅ group (R ₈₅ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). R ₈₄ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, carbamoyl group, or nitrile group. R ₈₆ represents a —CONH—R ₈₇ group, a —CO—R ₈₇ group or a —CO—O—R ₈₇ group (R ₈₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). . X ₈ represents a substituted or unsubstituted aryl group or heterocyclic group.

In the general formula (CL), examples of the halogen atom represented by R ₈₁ and R ₈₂ include a fluorine atom, a bromine atom, and a chlorine atom, and the alkyl group includes an alkyl group having up to 20 carbon atoms (for example, Methyl group, ethyl group, butyl group, dodecyl group, etc.). Examples of the alkenyl group include alkenyl groups having up to 20 carbon atoms (for example, vinyl group, allyl group, butenyl group, hexenyl group, hexadienyl group, ethenyl-2-ethyl group). A propenyl group, a 3-butenyl group, a 1-methyl-3-propenyl group, a 3-pentenyl group, a 1-methyl-3-butenyl group, and the like. As the alkoxy group, an alkoxy group having up to 20 carbon atoms (for example, methoxy) Group, ethoxy and the like). Examples of the alkyl group represented by R ₁₀ in the —NHCO—R ₁₀ group include alkyl groups having up to 20 carbon atoms (for example, a methyl group, an ethyl group, a butyl group, a dodecyl group, etc.), and an aryl group. Examples thereof include a group having 6 to 20 carbon atoms such as a phenyl group and a naphthyl group, and examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group. Alkyl group represented by R ₈₃ is preferably an alkyl group having up to 20 carbon atoms, such as methyl group, ethyl group, butyl group, dodecyl group and the like, the aryl group preferably having 6 to 20 carbon atoms Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group. In the —CONH—R ₈₅ group, —CO—R ₈₅ group or —CO—O—R ₈₅ group represented by W ₈ , the alkyl group represented by R ₈₅ is preferably an alkyl group having up to 20 carbon atoms. Examples thereof include a methyl group, an ethyl group, a butyl group, and a dodecyl group. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, and examples thereof include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.

Examples of the halogen atom represented by R ₈₄ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a chain or cyclic alkyl group such as a methyl group, a butyl group, and dodecyl. Group, cyclohexyl group and the like. Examples of the alkenyl group include alkenyl groups having up to 20 carbon atoms (for example, vinyl group, allyl group, butenyl group, hexenyl group, hexadienyl group, ethenyl-2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl, etc.), and alkoxy groups include, for example, methoxy group, butoxy group, tetradecyloxy group, etc., and carbamoyl Examples of the group include a diethylcarbamoyl group and a phenylcarbamoyl group. Nitrile groups are also preferred. Among these, a hydrogen atom and an alkyl group are more preferable. R ₈₃ and R ₈₄ may be connected to each other to form a ring structure.
The above groups can further have a single substituent or multiple substituents. Typical substituents include halogen atoms (eg, fluorine atom, chlorine atom, bromine atom), alkyl groups (eg, methyl group, ethyl group, propyl group, butyl group, dodecyl group), hydroxyl group, cyano group , Nitro group, alkoxy group (for example, methoxy group, ethoxy group, etc.), alkylsulfonamide group (for example, methylsulfonamide group, octylsulfonamide group, etc.), arylsulfonamide group (for example, phenylsulfonamide group, naphthylsulfone) Amide group etc.), alkylsulfamoyl group (eg butylsulfamoyl group etc.), arylsulfamoyl (eg phenylsulfamoyl group etc.), alkyloxycarbonyl group (eg methoxycarbonyl group etc.), aryl Oxycarbonyl group (for example, phenyloxycarbonyl group, etc.) , Amino sulfonamido group, an acylamino group, a carbamoyl group, a sulfonyl group, a sulfinyl group, a sulfoxy group, a sulfo group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, arylcarbonyl group, and an amino carbonyl group.

R ₁₀ or R ₈₅ is preferably a phenyl group, and more preferably a phenyl group having a plurality of halogen atoms and cyano groups as substituents.
-CONH-R ₈₇ group represented by R _86, in -CO-R ₈₇ group, or -CO-O-R ₈₇ group, the alkyl group represented by R ₈₇ is preferably an alkyl group having up to 20 carbon atoms Yes, for example, a methyl group, an ethyl group, a butyl group, a dodecyl group, and the like. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, a thienyl group, and the like. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.
As the substituent that the group represented by R ₈₇ can have, the same substituents as those described in the description of R _{81 to} R _{84 in} formula (CL) can be used.

Examples of the aryl group represented by X ₈ include aryl groups having 6 to 20 carbon atoms such as phenyl group, naphthyl group, and thienyl group. Examples of the heterocyclic group include thiophene group, furan group, and imidazole. Group, pyrazole group, pyrrole group and the like.

Examples of the substituent that the group represented by X ₈ can have include the same substituents as those described in the description of R _{81 to} R _{84 in} formula (CL).
The group represented by X ₈ is preferably an aryl group or heterocyclic group having an alkylamino group (such as a diethylamino group) at the para position.

  These groups may include photographically useful groups.

  Specific examples of the cyan coloring leuco dye (CL) are shown below, but the cyan coloring leuco dye used in the present invention is not limited thereto.

  The addition amount of the cyan coloring leuco dye is usually 0.00001 to 0.05 mol / Ag1 mol, preferably 0.0005 to 0.02 mol / Ag1 mol, more preferably 0.001 to 0.01 mol. / Ag1 mol. The addition ratio of the cyan color-forming leuco dye to the total sum of the reducing agents represented by the general formulas (1) and (2) is preferably 0.001 to 0.2 in terms of molar ratio. More preferably, it is -0.1. In the present invention, the sum of the maximum densities at the maximum absorption wavelength of the dye image formed with the cyan leuco dye is preferably 0.01 or more and 0.50 or less, more preferably 0.02 or more and 0.30 or less, particularly preferably. Is preferably colored so as to have 0.03 or more and 0.10 or less.

  In the present invention, a subtle color tone can be adjusted by using a magenta chromogenic leuco dye or a yellow chromogenic leuco dye in addition to the cyan chromogenic leuco dye.

(Yellow coloring leuco dye)
In the present invention, in addition to the above-described cyan color developing leuco dye and magenta color forming leuco dye, a yellow color forming leuco dye can be used for the purpose of finely adjusting the color tone. A color image forming agent whose absorbance at 360 to 480 nm increases when oxidized is preferably used as the yellow color-forming leuco dye, and is represented by the compound represented by the general formula (YA) or the general formula (YL). In particular, a color image forming agent represented by the general formula (YA) is preferable.

In the formula, R ₁₁ represents a substituted or unsubstituted alkyl group, R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively, and R ₁₁ and R ₁₂ are 2-hydroxyphenylmethyl groups. There is never. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on the benzene ring.

  Hereinafter, the compound of the general formula (YA) will be described in detail.

  As an alkyl group in general formula (YA), a C1-C30 alkyl group is preferable and may have a substituent.

Specifically, methyl, ethyl, butyl, octyl, i-propyl, t-butyl, t-octyl, t-pentyl, sec-butyl, cyclohexyl, 1-methyl-cyclohexyl and the like are preferable, and steric rather than i-propyl. Are preferably large groups (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl, etc.), among which secondary or tertiary alkyl Group is preferable, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferable. Examples of the substituent that R ₁₁ may have include a halogen atom, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamide group, an acyloxy group, an oxycarbonyl group, and a carbamoyl group. , Sulfamoyl group, sulfonyl group, phosphoryl group and the like.

R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively. The alkyl group represented by R ₁₂ is preferably an alkyl group having 1 to 30 carbon atoms, and the acylamino group is preferably an acylamino group having 1 to 30 carbon atoms. Among these, the description of the alkyl group is the same as R ₁₁ described above.

The acylamino group represented by R ₁₂ may be unsubstituted or substituted, and specific examples include an acetylamino group, an alkoxyacetylamino group, and an aryloxyacetylamino group. R ₁₂ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, and t-butyl. R ₁₁ and R ₁₂ are not 2-hydroxyphenylmethyl groups.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, and the description of the alkyl group is the same as that for R ₁₁ . R ₁₃ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, t-butyl and the like. Further, it is preferable either R _12, R ₁₃ is a hydrogen atom.

R ₁₄ represents a group capable of substituting on the benzene ring. For example, specific examples include halogen atoms (fluorine, chlorine, bromine, etc.), alkyl groups (methyl, ethyl, propyl, butyl, pentyl, i-pentyl, 2-ethylhexyl). , Octyl, decyl, etc.), cycloalkyl groups (cyclohexyl, cycloheptyl, etc.), alkenyl groups (ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl) Etc.), cycloalkenyl groups (1-cycloalkenyl, 2-cycloalkenyl groups, etc.), alkynyl groups (ethynyl, 1-propynyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, etc.), alkylcarbonyloxy groups (acetyloxy, etc.) ), Alkylthio group (methylthio, trifluoromethylthio, etc.), carboxyl , Alkylcarbonylamino groups (such as acetylamino), ureido groups (such as methylaminocarbonylamino), alkylsulfonylamino groups (such as methanesulfonylamino), alkylsulfonyl groups (such as methanesulfonyl and trifluoromethanesulfonyl), carbamoyl groups (carbamoyl, N, N-dimethylcarbamoyl, N-morpholinocarbonyl, etc.), sulfamoyl group (sulfamoyl, N, N-dimethylsulfamoyl, morpholinosulfamoyl etc.), trifluoromethyl group, hydroxyl group, nitro group, cyano group, alkyl Sulfonamide groups (methanesulfonamide, butanesulfonamide, etc.), alkylamino groups (amino, N, N-dimethylamino, N, N-diethylamino, etc.), sulfo groups, phosphono groups, sulfite groups, sulfo groups Inino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl, etc.), alkylcarbonylaminosulfonyl group (acetamidosulfonyl, methoxyacetamidosulfonyl, etc.), alkynylaminocarbonyl group (acetamidocarbonyl, methoxyacetamidocarbonyl, etc.) And alkylsulfinylaminocarbonyl groups (methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.) and the like. R ₁₄ is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or an oxycarbonyl group having 2 to 30 carbon atoms, and more preferably an alkyl group having 1 to 24 carbon atoms. Examples of the substituent of the alkyl group include an aryl group, an amino group, an alkoxy group, an oxycarbonyl group, an acylamino group, an acyloxy group, an imide group, and a ureido group, and more preferable examples include an aryl group, an amino group, an oxycarbonyl group, and an alkoxy group. preferable. These alkyl group substituents may be further substituted with these substituents.

  Next, among the compounds represented by the general formula (YA), a bisphenol compound represented by the following general formula (YB), which is particularly preferably used in the present invention, will be described.

In the formula, Z represents —S— or —C (R ₂₁ ) (R ₂₁ ′) —, and R ₂₁ and R ₂₁ ′ each represents a hydrogen atom or a substituent. Examples of the substituent represented by R ₂₁ and R ₂₁ ′ include the substituent in R ₁₄ of the general formula (YA). R ₂₁ and R ₂₁ ′ are preferably a hydrogen atom or an alkyl group.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ each represent a substituent, and examples of the substituent include the same groups as the substituents represented by R ₂₁ and R ₂₁ ′.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, with an alkyl group being more preferred. Examples of the substituent on the alkyl group include the same groups as those described in the description of the substituents represented by R ₂₁ and R ₂₁ ′.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are more preferably tertiary alkyl groups such as t-butyl, t-pentyl, t-octyl and 1-methyl-cyclohexyl.

R ₂₄ and R ₂₄ ′ each represent a hydrogen atom or a substituent, and examples of the substituent include the same groups as the substituents represented by R ₂₁ and R ₂₁ ′.

  Examples of the compounds represented by the general formulas (YA) and (YB) include compounds (II-1) to (II-40) described in paragraphs “0032” to “0038” of JP-A No. 2002-169249, EP1, And compounds (ITS-1) to (ITS-12) described in paragraph “0026” of No. 211,093.

  Although the specific example of the bisphenol compound represented by general formula (YA) and (YB) below is shown, this invention is not limited to these.

  The addition amount of the compound of the general formula (YA) (including hindered phenol compounds and compounds of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0. 0005 to 0.01 mol, more preferably 0.001 to 0.008 mol. In addition, the ratio of the amount of the compound of the general formula (YA) (including the hindered phenol compound and the compound of the general formula (YB)) to the sum of the reducing agents represented by the general formula (1) and the general formula (2) is The molar ratio is preferably 0.001 to 0.2, and more preferably 0.005 to 0.1.

  In the present invention, the sum of the maximum densities at the maximum absorption wavelength of a dye image formed with a yellow color-forming leuco dye is preferably 0.01 or more and 0.50 or less, more preferably 0.01 or more and 0.30 or less. In particular, it is preferable to make the color develop so as to have 0.02 to 0.10.

  Representative leuco dyes suitable for use in the present invention in addition to the yellow color-forming leuco dyes described above are not particularly limited. Examples include sazine leuco dyes, phenodiazine leuco dyes, and phenothiazine leuco dyes. Also useful are U.S. Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4 No. 4,022,617, No. 4,123,282, No. 4,368,247, No. 4,461,681, and JP-A-50-36110, No. 59-206931, JP-A-5-204087. No. 11-231460, JP-A Nos. 2002-169249, 2002-236334, and the like.

  In the present invention, with the use of a highly active reducing agent, the amount used varies in color tone (especially yellowishness) depending on the use ratio, or the concentration is particularly 2.0 by using fine grain silver halide. In order to prevent the image from becoming excessively reddish in the above high density area, in addition to the yellow color-forming leuco dye described above, a cyan color-forming leuco dye is used in combination, and the amount and ratio of use are adjusted. Is preferred.

(binder)
A binder suitable for the photothermographic material is transparent or translucent and generally colorless, and is a natural polymer synthetic resin, polymer and copolymer, or other medium for forming a film, for example, paragraph “0069” of JP-A No. 2001-330918. The thing of description is mentioned. Among these, preferred binders for the photosensitive layer of the photothermographic material of the invention are polyvinyl acetals, and particularly preferred is polyvinyl butyral. These will be described in detail later.

  For non-photosensitive layers such as overcoat layers and undercoat layers, especially protective layers and backcoat layers, cellulose esters which are polymers with higher softening temperatures, especially polymers such as triacetyl cellulose and cellulose acetate butyrate preferable. In addition, as needed, said binder can be used in combination of 2 or more type.

The binder includes —COOM, —SO ₃ M, —OSO ₃ M, —P═O (OM) ₂ , —O—P═O (OM) ₂ , —N (R) ₂ , —N ⁺ (R) _3. (M represents a hydrogen atom or an alkali metal base, R represents a hydrocarbon group), a group in which at least one polar group selected from an epoxy group, —SH, —CN and the like is introduced by copolymerization or addition reaction It is preferable to use, and —SO ₃ M and —OSO ₃ M are particularly preferable. The amount of such a polar group is 1 × 10 ⁻¹ to 1 × 10 ⁻⁸ mol / g, preferably 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / g.

Such a binder is used in an effective range to function as a binder. The effective range can be easily determined by one skilled in the art. For example, as an index for holding at least the organic silver salt in the image forming layer, the ratio of the binder to the organic silver salt is preferably 15: 1 to 1: 2 (mass ratio), and particularly 8: 1 to 1: 1. The range of is preferable. That is, it is preferable that the binder amount of the image forming layer is 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.

  The glass transition temperature (Tg) of the binder used in the present invention is preferably 70 to 105 ° C. Tg can be obtained by measuring with a differential scanning calorimeter, and the intersection of the baseline and the endothermic peak slope is defined as Tg. Tg in the present invention is determined by the method described in “Polymer Handbook” III-139-179 (1966, Wiley and Sun, Inc.) by Brand Wrap et al.

  Tg when the binder is a copolymer resin is obtained by the following formula.

Tg (copolymer) (° C.) = V ₁ Tg ₁ + v ₂ Tg ₂ +... + V _n Tg _{n
Wherein, v 1, v 2 ··· v} n represents the mass fraction of the monomer in the _{copolymer, Tg 1, Tg 2 ··· Tg} n from each monomer in the copolymer Tg (° C.) of the obtained single polymer is represented. The accuracy of Tg calculated according to the above equation is ± 5 ° C.

  Use of a binder having a Tg of 70 to 105 ° C. is preferable because a sufficient maximum density can be obtained in image formation.

  The binder of the present invention has a Tg of 70 to 105 ° C., a number average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 500,000, and a degree of polymerization of about 50 to 1,000. It is. Examples of the polymer or copolymer containing an ethylenically unsaturated monomer as a constituent unit include those described in paragraph No. “0069” of JP-A No. 2001-330918.

  Of these, particularly preferred examples include methacrylic acid alkyl esters, methacrylic acid aryl esters, and styrenes. Among such polymer compounds, a polymer compound having an acetal group is preferably used. Even a polymer compound having an acetal group is more preferably a polyvinyl acetal having an acetoacetal structure, for example, U.S. Pat. Nos. 2,358,836, 3,003,879, 2,828,204, UK The polyvinyl acetal shown by patent 771,155 etc. can be mentioned.

  As the polymer compound having an acetal group, a compound represented by the general formula (V) described in “150” of JP-A No. 2002-287299 is particularly preferable.

As the polyurethane resin that can be used in the present invention, known resins such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. Moreover, it is preferable to have a total of 2 or more hydroxyl groups, at least one at each polyurethane molecule end. Since hydroxyl groups are cross-linked with polyisocyanate which is a curing agent to form a three-dimensional network structure, it is more preferable that the hydroxyl groups are contained in the molecule. In particular, it is preferable that the hydroxyl group is at the molecular end because the reactivity with the curing agent is high. The polyurethane preferably has 3 or more hydroxyl groups at the molecular terminals, and particularly preferably 4 or more. In the present invention, when polyurethane is used, Tg is preferably 70 to 105 ° C., elongation at break is 100 to 2000%, and stress at break is preferably 0.5 to 100 N / mm ² .

  These polymer compounds (polymers) may be used alone or in a blend of two or more.

  In the image forming layer of the present invention, the above polymer is preferably used as a main binder. The main binder here refers to “a state in which the polymer occupies 50% by mass or more of the total binder in the image forming layer”. Therefore, other polymers may be blended and used within a range of less than 50% by weight of the total binder. These polymers are not particularly limited as long as the polymers preferably used in the present invention are soluble. More preferably, a polyvinyl acetate, a polyacryl resin, a urethane resin, etc. are mentioned.

  An organic gelling agent may be contained in the image forming layer. The organic gelling agent referred to here has a function of giving a yield value to the system by adding to an organic liquid, such as polyhydric alcohols, and eliminating or reducing the fluidity of the system. The compound which has.

  It is also a preferred embodiment that the image forming layer coating solution contains an aqueous dispersed polymer latex. In this case, a polymer latex in which 50% by mass or more of the total binder in the coating solution for the image forming layer is dispersed in water is preferable. When the image forming layer contains a polymer latex, 50% by mass or more of the total binder in the image forming layer is preferably polymer latex, and more preferably 70% by mass or more.

  The polymer latex is a water-insoluble hydrophobic polymer dispersed as fine particles in a water-soluble dispersion medium. As the dispersion state, the polymer is emulsified in a dispersion medium, the emulsion is polymerized, the micelle is dispersed, or the polymer molecule has a partially hydrophilic structure, and the molecular chain itself is molecularly dispersed. Any of these may be used. The average particle diameter of the dispersed particles is preferably 1 to 50,000 nm, more preferably in the range of about 5 to 1,000 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution.

  The polymer latex preferably used in the present invention may be a so-called core / shell type latex other than a normal polymer latex having a uniform structure. In this case, it may be preferable to change the Tg of the core and the shell. The minimum film-forming temperature (MFT) of the polymer latex according to the present invention is preferably -30 to 90 ° C, more preferably about 0 to 70 ° C. In addition, a film-forming auxiliary may be added to control the minimum film-forming temperature.

  The film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of polymer latex. For example, “Synthetic Latex Chemistry (Souichi Muroi, published by Polymer Publishing Co., Ltd.) , 1970).

  Examples of the polymer species used for the polymer latex include acrylic resins, vinyl acetate resins, polyester resins, polyurethane resins, rubber resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, and copolymers thereof. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is a number average molecular weight and is usually about 5,000 to 1,000,000, preferably about 10,000 to 100,000. When the molecular weight is too small, the mechanical strength of the photosensitive layer is insufficient.

  The polymer latex preferably has an equilibrium water content of 0.01 to 2% by mass or less, more preferably 0.01 to 1% by mass at 25 ° C. and 60% RH (relative humidity). For the definition and measurement method of the equilibrium moisture content, for example, “Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Polymer Society, Jinshokan)” can be referred to.

  Specific examples of the polymer latex include latexes described in “0173” of JP-A No. 2002-287299. These polymers may be used alone or in combination of two or more as required. As a polymer seed | species of a polymer latex, what contains about 0.1-10 mass% of carboxylic acid components, such as an acrylate or a methacrylate component, is preferable.

  Furthermore, if necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose or the like may be added within a range of 50% by mass or less of the total binder. The addition amount of these hydrophilic polymers is preferably 30% by mass or less based on the total binder of the photosensitive layer.

  In the preparation of the coating solution for the image forming layer, the order of the addition of the organic silver salt and the aqueous-dispersed polymer latex may be added first or at the same time, but preferably the polymer latex There will be later.

  Furthermore, it is preferable that an organic silver salt and further a reducing agent are mixed before adding the polymer latex. In addition, after mixing the organic silver salt and the polymer latex, if the temperature to be aged is too low, the coated surface shape is impaired, and if it is too high, there is a problem that fog increases, so the coating solution after mixing is 30 to 65 ° C. It is preferable that the above time is elapsed. Furthermore, it is preferable to be aged at 35 to 60 ° C, and a time at 35 to 55 ° C is particularly preferable. In order to maintain the temperature in this way, it is sufficient to keep the temperature of the coating solution preparation tank or the like.

  For coating of the image forming layer coating solution, it is preferable to use a coating solution that has been mixed for 30 minutes to 24 hours after mixing the organic silver salt and the aqueous dispersed polymer latex, and more preferably, 60 minutes after mixing. It is to make -12 hours pass, and it is especially preferable to use the coating liquid which passed 120 minutes-10 hours.

  Here, “after mixing” means after the organic silver salt and the aqueous polymer latex are added and the additive material is uniformly dispersed.

  By using a crosslinking agent for the binder, it is known that filming is improved and development unevenness is reduced, but there is also an effect of suppressing fogging during storage and suppressing generation of printout silver after development. is there.

  Examples of the crosslinking agent to be used include various crosslinking agents conventionally used for photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based, sulfone described in JP-A-50-96216. Acid ester-based, acryloyl-based, carbodiimide-based, and silane compound-based crosslinking agents are used, and the following isocyanate-based, silane compound-based, epoxy-based compounds, and acid anhydrides are preferable.

  Isocyanate-based crosslinking agents are isocyanates having at least two isocyanate groups and adducts thereof (adducts). More specifically, aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, benzene Diisocyanates, naphthalene diisocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates and divalent or trivalent polyalcohols with these isocyanates Adducts and the like. As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used.

  In addition, the adduct of isocyanate and polyalcohol has particularly high ability to improve interlayer adhesion and prevent layer peeling, image shift and bubble generation. Such isocyanate may be placed in any part of the photothermographic material. For example, in the support (especially when the support is paper, it can be included in the size composition) photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc. It can be added to any layer and can be added to one or more of these layers.

  As the thioisocyanate-based crosslinking agent that can be used in the present invention, compounds having a thioisocyanate structure corresponding to the above-mentioned isocyanates are also useful.

  The amount of the crosslinking agent used is usually in the range of 0.001 to 2 mol, preferably 0.005 to 0.5 mol, with respect to 1 mol of silver.

  The isocyanate compound and thioisocyanate compound that can be contained in the present invention are preferably compounds that function as the above-mentioned crosslinking agent, but a good result can be obtained even if the compound has only one functional group.

  Examples of the silane compound include compounds represented by general formulas (1) to (3) disclosed in JP-A No. 2001-264930.

  Moreover, as an epoxy compound which can be used as a crosslinking agent, what is necessary is just to have one or more epoxy groups, and there is no restriction | limiting in the number of epoxy groups, molecular weight, and others. The epoxy group is preferably contained in the molecule as a glycidyl group via an ether bond or an imino bond. The epoxy compound may be any of a monomer, an oligomer, a polymer, etc., and the number of epoxy groups present in the molecule is usually about 1 to 10, preferably 2 to 4. When the epoxy compound is a polymer, it may be either a homopolymer or a copolymer, and the number average molecular weight Mn is particularly preferably in the range of about 2,000 to 20,000.

  The acid anhydride used in the present invention is a compound having at least one acid anhydride group represented by the following structural formula. The number of acid anhydride groups, molecular weight, and the like are not particularly limited as long as they have one or more acid anhydride groups.

-CO-O-CO-
Said epoxy compound and acid anhydride may use only 1 type, or may use 2 or more types together. The addition amount is not particularly limited, but is preferably in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / m ² , more preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / m ² . It is. This epoxy compound or acid anhydride can be added to any layer on the photosensitive layer side of the support, such as the photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc., and one of these layers Or it can add to two or more layers.

(Silver saving agent)
In the present invention, the effect of the present invention can be further enhanced by using a silver saving agent. The silver saving agent used in the present invention refers to a compound that can reduce the amount of silver necessary to obtain a certain silver image density. Various action mechanisms of the function of decreasing can be considered, but a compound having a function of improving the covering power of developed silver is preferable. Here, the covering power of developed silver refers to the optical density per unit amount of silver.
Preferred examples of the silver saving agent include hydrazine derivative compounds, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds.

  Specific examples of the hydrazine derivative include compounds H-1 to H-29 described in US Pat. No. 5,545,505, columns 11 to 20, US Pat. No. 5,464,738, columns 9 to 11. 1 to 12 described in JP-A-2001-27790, compounds H-1-1 to H-1-28 described in paragraphs “0042” to “0052”, and H-2-1 to H-2- 9, H-3-1 to H-3-12, H-4-1 to H-4-21, H-5-1 to H-5-5.

  Specific examples of the vinyl compound include compounds CN-01 to CN-13 described in columns 13 to 14 of US Pat. No. 5,545,515 and column 10 of US Pat. No. 5,635,339. Compounds HET-01 to HET-02 described in US Pat. No. 5,654,130, columns MA-10 to compounds MA-01 to MA-07, US Pat. No. 5,705,324 Compounds IS-01 to IS-04 described in columns 9 to 10 of the specification, and compounds 1-1 to 218-2 described in paragraphs “0043” to “0088” of JP-A-2001-125224.

  Specific examples of the phenol derivative and the naphthol derivative include compounds A-1 to A-89 described in paragraphs “0075” to “0078” of JP 2000-267222 A, and paragraph “0025” of JP 2003-66558 A. ”To“ 0045 ”. Examples thereof include compounds A-1 to A-258.

  Specific examples of the quaternary onium compound include triphenyltetrazolium.

  Specific examples of the silane compound include alkoxysilane compounds having two or more primary or secondary amino groups as shown in compounds A1 to A33 described in paragraphs “0027” to “0029” of JP-A No. 2003-5324 or The salt is mentioned.

The amount of the silver saving agent added is in the range of 1 × 10 ⁻⁵ to 1 mol, preferably 1 × 10 ^{−4 to} 5 × 10 ⁻¹ mol, per mol of the organic silver salt.

(Anti-fogging and image stabilizer)
The antifogging and image stabilizer used in the photothermographic material of the present invention will be described.

  Since reducing agents with protons such as bisphenols and sulfonamidophenols are mainly used as reducing agents, these reducing agents are deactivated by generating active species that can extract hydrogen. It is preferable that the compound which can be converted is contained. Preferably, the colorless photo-oxidizing substance is preferably a compound capable of generating free radicals as reactive active species during exposure.

  Accordingly, any compound having these functions may be used, but an organic free radical composed of a plurality of atoms is preferred. A compound having any structure may be used as long as it has such a function and does not cause any particular adverse effect on the photothermographic material.

  In addition, as a compound that generates these free radicals, the generated free radicals are carbocyclic or complex in order to have a stability that allows contact with the reducing agent for a time sufficient to react with the reducing agent and inactivate it. Those having a cyclic aromatic group are preferred. Representative examples of these compounds include biimidazolyl compounds and iodonium compounds.

The amount of the biimidazolyl compound and iodonium compound added is in the range of 0.001 to 0.1 mol / m ² , preferably 0.005 to 0.05 mol / m ² . The compound can be contained in any constituent layer in the light-sensitive material of the present invention, but is preferably contained in the vicinity of the reducing agent.

  Many compounds capable of releasing halogen atoms as active species are known as antifogging and image stabilizers. Specific examples of the compound that generates these active halogen atoms include compounds represented by general formula (9) described in “0264” to “0271” of JP-A-2002-287299.

  The amount of these compounds added is preferably within a range in which the increase in printout silver due to the formation of silver halide is not a problem, and is a maximum of 150% or less, more preferably 100% in terms of the ratio to the compound that does not generate active halogen radicals. % Or less is preferable. Specific examples of compounds that generate these active halogen atoms include compounds (III-1) to (III-23) described in paragraphs “0086” to “0087” of JP-A No. 2002-169249, Compounds 1-1a to 1-1o and 1-2a to 1-2o described in paragraphs “0031” to “0034” of JP-A-2003-50441, and compounds 2a to 2z and 2aa described in paragraphs “0050” to “0056” To 2ll, 2-1a to 2-1f, compounds 4-1 to 4-32 described in paragraphs “0055” to “0058” of JP-A No. 2003-91054, and compounds 5 described in paragraphs “0069” to “0072” -1 to 5-10.

  Next, antifoggants other than those described above that are preferably used in the present invention will be described. Antifoggants preferably used in the present invention include, for example, compound examples a to j described in paragraph “0012” of JP-A-8-314059 and paragraph “0028” of JP-A-7-209797. Thiosulfonate esters A to K, compound examples (1) to (44) described from p14 of JP-A No. 55-140833, compounds described in paragraph “0063” of JP-A No. 2001-13627 (I-1 ) To (I-6), (C-1) to (C-3) described in paragraph “0066”, and compounds (III-1) to (III-) described in paragraph “0027” of JP-A-2002-90937. 108), compounds VS-1 to VS-7 and compounds HS-1 to HS-5 described in paragraph “0013” of JP-A-6-208192 as compounds of vinyl sulfones and / or β-halo sulfones. KS-1 to KS-8 compounds described in JP-A No. 2000-330235 as sulfonylbenzotriazole compounds, PR-01 to PR-08 described in JP-T-2000-515995 as substituted propene nitrile compounds, Examples thereof include compounds (1) -1 to (1) -132 described in paragraphs “0042” to “0051” of JP-A-2002-207273.

  The antifoggant is generally used in an amount of at least 0.001 mole per mole of silver. Usually, the range is 0.01 to 5 moles of the compound relative to the moles of silver, preferably 0.02 to 0.6 moles of the compound relative to the moles of silver.

  In addition to the above compounds, the photothermographic material of the present invention may contain a compound conventionally known as an antifoggant, but generates a reactive species similar to the above compound. Even a compound that can be used may be a compound having a different antifogging mechanism. For example, U.S. Pat. Nos. 3,589,903, 4,546,075, 4,452,885, JP-A-59-57234, U.S. Pat. No. 3,874,946. Examples thereof include compounds described in the specification, JP 4,756,999, JP-A-9-288328, and JP-A-9-90550. Further, as other antifoggants, compounds disclosed in US Pat. No. 5,028,523 and European Patent Nos. 600,587, 605,981 and 631,176 are exemplified. Can be mentioned.

  When the reducing agent used in the present invention has an aromatic hydroxyl group (—OH), particularly in the case of bisphenols, a non-reducing compound having a group capable of forming a hydrogen bond with these groups is used. It is preferable to use together.

  Specific examples of particularly preferred hydrogen bonding compounds in the present invention include, for example, compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937. Is mentioned.

(Coloring agent)
The photothermographic material of the present invention forms a photographic image by heat development processing, and contains a toning agent that adjusts the color tone of silver as necessary dispersed in an ordinary (organic) binder matrix. Preferably it is.

  Examples of suitable toning agents for use in the present invention include those of RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. For example, the following are disclosed.

  Imides (eg, succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide); mercaptans (eg, 3-mercapto-1,2,4-triazole); phthalazinone derivatives or metal salts of these derivatives ( For example, phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); phthalazine and phthalic acids ( For example, combinations of phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid; phthalazine and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivatives and anhydrides thereof Products (eg, phthalic acid, 4-methylphthalic acid, 4 The combination and the like with at least one compound selected from nitrophthalic acid and tetrachlorophthalic anhydride). A particularly preferred colorant is a combination of phthalazinone or phthalazine with phthalic acids and phthalic anhydrides.

  When the reducing agent used in the present invention has an aromatic hydroxyl group (—OH), particularly in the case of bisphenols, a non-reducing compound having a group capable of forming a hydrogen bond with these groups is used. It is preferable to use together. Specific examples of particularly preferable hydrogen bonding compounds include compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937.

  The photothermographic material forms a photographic image by heat development processing, and may contain a toning agent that adjusts the color tone of silver as necessary, usually dispersed in an (organic) binder matrix. preferable.

  Examples of suitable toning agents for use in the present invention are disclosed in RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. For example, there are the following.

  Imides (succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide, etc.); mercaptans (3-mercapto-1,2,4-triazole, etc.); phthalazinone derivatives or metal salts of these derivatives (phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, 2,3-dihydro-1,4-phthalazinedione, etc .; phthalazine and phthalic acids (phthalic acid, 4 -A combination of methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid; phthalazine and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivative and its anhydride (phthalic acid, 4 -No methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid Combination of at least one compound selected from the object).

  A particularly preferable colorant is a combination of phthalazinone or phthalazine with phthalic acids and phthalic anhydrides.

(Fluorine surfactant)
In the present invention, a fluorosurfactant represented by the following general formula (SF) is preferably used in order to improve film transportability and environmental suitability (accumulation in vivo) in a heat development processing apparatus.

General formula (SF)
(Rf (L ₁ ) _n1 ) _p (Y) _m1 (A) _q
In the formula, Rf represents a substituent containing a fluorine atom, L ₁ represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, A Represents an anionic group or a salt thereof, n1 and m1 each represents an integer of 0 or 1, p represents an integer of 1 to 3, and q represents an integer of 1 to 3. However, when q is 1, n1 and m1 are not 0 at the same time.

  In the general formula (SF), Rf represents a substituent containing a fluorine atom. Examples of the substituent containing a fluorine atom include a fluorinated alkyl group having 1 to 25 carbon atoms (for example, a trifluoromethyl group). Trifluoroethyl group, perfluoroethyl group, perfluorobutyl group, perfluorooctyl group, perfluorododecyl group and perfluorooctadecyl group) or fluorinated alkenyl group (for example, perfluoropropenyl group, perfluorobutenyl group, Perfluorononenyl group, perfluorododecenyl group, etc.). Rf preferably has 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms. Rf preferably has 2 to 12 fluorine atoms, and more preferably 3 to 12 fluorine atoms.

L ₁ represents a divalent linking group having no fluorine atom. Examples of the divalent linking group having no fluorine atom include an alkylene group (for example, a methylene group, an ethylene group, a butylene group, etc.), Alkyleneoxy group (methyleneoxy group, ethyleneoxy group, butyleneoxy group, etc.), oxyalkylene group (for example, oxymethylene group, oxyethylene group, oxybutylene group, etc.), oxyalkyleneoxy group (for example, oxymethyleneoxy group, Oxyethyleneoxy group, oxyethyleneoxyethyleneoxy group, etc.), phenylene group, oxyphenylene group, phenyloxy group, oxyphenyloxy group, or a combination of these groups.

  A represents an anionic group or a salt thereof. For example, carboxylic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfonic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfuric acid half ester Group or a salt thereof (sodium salt, potassium salt and lithium salt), a phosphoric acid group or a salt thereof (sodium salt, potassium salt and the like) and the like.

  Y represents a (p + q) -valent linking group having no fluorine atom. For example, the trivalent or tetravalent linking group having no fluorine atom is composed mainly of a nitrogen atom or a carbon atom. An atomic group is mentioned. n1 represents 0 or an integer of 1, and is preferably 1.

  The fluorine-based surfactant represented by the general formula (SF) is an alkyl compound having 1 to 25 carbon atoms into which a fluorine atom is introduced (for example, trifluoromethyl group, pentafluoroethyl group, perfluorobutyl group, perfluorooctyl). Group and a compound having a perfluorooctadecyl group) and an alkenyl compound (for example, a perfluorohexenyl group and a perfluorononenyl group), a trivalent to hexavalent alkanol compound in which no fluorine atom is introduced, and a hydroxyl group, respectively. An anionic group (A) is further introduced into the compound (partially Rf-modified alkanol compound) obtained by addition reaction or condensation reaction with 3 to 4 aromatic compounds or hetero compounds by, for example, sulfate esterification. Can be obtained.

  Examples of the trivalent to hexavalent alkanol compound include glycerin, pentaerythritol, 2-methyl-2-hydroxymethyl 1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentene, and 1,2,6-hexane. Examples include triol, 1,1,1-tris (hydroxymethyl) propane, 2,2-bis (butanol) -3, aliphatic triol, tetramethylolmethane, D-sorbitol, xylitol, D-mannitol and the like.

  Examples of the aromatic compound and hetero compound having 3 to 4 hydroxyl groups include 1,3,5-trihydroxybenzene and 2,4,6-trihydroxypyridine.

  Below, the preferable specific compound of the fluorine-type surfactant represented by general formula (SF) is shown.

  As a method for adding the fluorosurfactant represented by the general formula (SF) of the present invention to the coating solution, it can be added according to a known addition method. That is, it can be dissolved and added in alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone and acetone, polar solvents such as dimethyl sulfoxide and dimethylformamide. Further, fine particles having a size of 1 μm or less can be added after being dispersed in water or an organic solvent by sand mill dispersion, jet mill dispersion, ultrasonic dispersion or homogenizer dispersion. Many techniques for fine particle dispersion are disclosed, but they can be dispersed according to these techniques. The fluorine-based surfactant represented by the general formula (SF) is preferably added to the outermost protective layer.

The amount of the fluorosurfactant represented by the general formula (SF) of the present invention is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ² , and 1 × 10 ⁻⁵ to 1 × 10 ^−2. Mole is particularly preferred. If it is less than the former range, charging characteristics cannot be obtained, and if it exceeds the former range, the humidity dependence is large and the storage stability under high humidity deteriorates.

(Surface layer)
The ten-point average roughness (Rz), maximum roughness (Rt), and centerline average roughness (Ra) in the present invention are defined by the following JIS surface roughness (B0601). Ten-point average roughness (Rz) is the peak from the highest to the fifth measured in the direction of the vertical magnification from the straight line that is parallel to the average line and does not cross the cross-sectional curve, in the portion that has been cut by the reference length from the cross-sectional curve. The difference between the average value of the altitude and the average value of the altitude at the bottom of the valley from the deepest to the fifth is expressed in micrometers (μm). The maximum roughness (Rt) is the roughness curve extracted by the reference length L, and when the extracted part is sandwiched between two straight lines parallel to the center line, the distance between the two straight lines is measured in the direction of the vertical magnification of the roughness curve. Then, this value is expressed in micrometers (μm). The centerline average roughness (Ra) is a portion of the measured length L extracted from the roughness curve in the direction of the centerline, the centerline of this extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve Is represented by y = f (x), the value obtained by the following equation is expressed in micrometers (μm).

  As a method for measuring Rz, Rt, and Ra, the humidity was adjusted for 24 hours under the condition that the measurement samples were not overlapped in an environment of 25 ° C. and 65% RH, and then measured in the environment. The non-overlapping conditions shown here are, for example, a method of winding with the film edge portion raised, a method of stacking paper between the films, a method of making a frame with cardboard and fixing the four corners, etc. One of them. Examples of the measuring apparatus that can be used include a RSTPLUS non-contact three-dimensional micro surface shape measuring system manufactured by WYKO.

In order to set Rz, Rt, and Ra on the front and back surfaces of the photosensitive material within the scope of the present invention, it can be easily adjusted by appropriately combining the following technical means.
1. 1. Type of matting agent (inorganic or organic powder) contained in the layer having the image forming layer and the layer opposite to the side having the image forming layer, average particle diameter, amount added, surface treatment method Matting agent dispersion conditions (type of disperser used, dispersion time, type of beads used for dispersion, average particle size, type and amount of dispersant used during dispersion, type of polar group of binder, polar group content )
3. 3. Drying conditions during application (application speed, distance from the application surface of the hot air blowing nozzle, amount of dry air), residual solvent amount 4. Filter type used for filtration of coating solution, filtration time When the calendering is performed after coating, the conditions (for example, calendar temperature 40 to 80 ° C., pressure 50 to 300 kg / cm, line speed 20 to 100 m, nip number 2 to 6)
In the present invention, the value of Rz (E) / Rz (B) is particularly not less than 0.2 and not more than 0.6 in the range described in claim 1 (0.1 or more and 0.7 or less). It is preferable that it is 0.3 or more and 0.5 or less. By setting it within this range, among the effects of the present invention, the transportability of the film is particularly good, and the occurrence of uneven density during thermal development can be remarkably improved.

  In the present invention, the Ra (E) / Ra (B) value is 0.6 or more and 1.3 or less, particularly within the range described in claim 3 (0.6 or more and 1.5 or less). It is preferable that it is 0.7 or more and 1.1 or less. By setting it within this range, among the effects of the present invention, in particular, the increase in fog over time is small, the transportability of the film is good, and the occurrence of uneven density during thermal development can be further improved.

  In the image forming method of the present invention, the average particle size of the matting agent having the maximum average particle size contained in the surface on the side having the image forming layer is Le (μm), and is included in the surface on the side having the backcoat layer. Lb / Le is preferably 2.0 to 10 and more preferably 3.0 to 4.5 when the average particle size of the matting agent having the maximum average particle size is Lb (μm). . By setting Lb / Le within this range, among the effects of the present invention, density unevenness during thermal development can be improved. In the image forming method of the present invention, the value of Rz (E) / Ra (E) is preferably 12 or more and 60 or less, more preferably 14 or more and 50 or less. By setting the value of Rz (E) / Ra (E) within this range, among the effects of the present invention, density unevenness during heat development and storage characteristics over time can be improved. In the image forming method of the present invention, the value of Rz (B) / Ra (B) is preferably 25 or more and 65 or less, more preferably 30 or more and 60 or less. By setting the value of Rz (E) / Ra (E) within this range, among the effects of the present invention, density unevenness during heat development and storage characteristics over time can be improved.

In the present invention, the surface layer of the photothermographic material (when the image forming layer side or a non-image forming layer is provided on the opposite side of the image forming layer with the support interposed therebetween) It is preferable to use organic or inorganic powder as a matting agent in order to control roughness. As the powder used in the present invention, a powder having a Mohs hardness of 5 or more is preferably used. As the powder, a known inorganic powder or organic powder can be appropriately selected and used. Examples of the inorganic powder include titanium oxide, boron nitride, SnO ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, SiC, cerium oxide, corundum, artificial Examples thereof include diamond, garnet, garnet, mica, silica, silicon nitride, silicon carbide and the like. Examples of the organic powder include powders such as polymethyl methacrylate, polystyrene, and Teflon (registered trademark). Among these, inorganic powders such as SiO ₂ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃ , mica, etc. are preferable. SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ is particularly preferable.

In the present invention, the powder is preferably surface-treated, for example. The surface treatment layer is formed by dry pulverizing the inorganic powder material, adding water and a dispersing agent, and performing coarse particle classification by wet pulverization and centrifugal separation. Thereafter, the fine slurry is transferred to a surface treatment tank, where the surface of the metal hydroxide is coated. First, a predetermined amount of an aqueous salt solution such as Al, Si, Ti, Zr, Sb, Sn, and Zn is added, and an acid or alkali that neutralizes the solution is added, and the surface of the inorganic powder particles is coated with the resulting hydrous oxide. To do. Water-soluble salts produced as a by-product are removed by decantation, filtration, and washing. Finally, the slurry pH is adjusted, filtered, and washed with pure water. The washed cake is dried with a spray dryer or a band dryer. Finally, the dried product is pulverized by a jet mill to become a product. In addition to the aqueous system, AlCl ₃ and SiCl ₄ vapors can be passed through the non-magnetic inorganic powder, and then steam can be introduced to perform Al and Si surface treatment. For other surface treatment methods, “Characterization of Powder Surfaces”, Academic Press can be referred to.

  In the present invention, it is preferable that the surface treatment is performed with an Si compound or an Al compound. When such a surface-treated powder is used, the dispersion state when the matting agent is dispersed can be improved. The content of Si or Al is preferably 0.1 to 10% by mass of Si and 0.1 to 10% by mass of Al, more preferably 0.1 to 10% by mass with respect to the powder. It is particularly preferable that 5% by mass, Al is 0.1-5% by mass, Si is 0.1-2% by mass, and Al is 0.1-2% by mass. The mass ratio of Si and Al is preferably Si <Al. The surface treatment can be performed by the method described in JP-A-2-83219. The average particle diameter of the powder in the present invention is the average diameter in the case of spherical powder, the average major axis length in the case of acicular powder, and the maximum diagonal length of the plate-like surface in the case of plate-like powder. Mean values can be easily obtained from measurement with an electron microscope.

  The organic or inorganic powder preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm.

  The average particle size of the organic or inorganic powder contained in the outermost layer on the image forming layer side is usually 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm. It is. The addition amount is usually 1.0 to 20% by mass, preferably 2.0 to 15% by mass, more preferably 3 with respect to the amount of binder used in the outermost layer (including the crosslinking agent in the binder amount). 0.0 to 10% by mass. The average particle size of the organic or inorganic powder contained in the outermost layer on the opposite side of the image forming layer across the support is usually 2.0 to 15.0 μm, preferably 3.0 to 12.0 μm. More preferably, it is 4.0-10.0 micrometers. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably 0 to the amount of binder used in the outermost layer (including the crosslinking agent in the binder amount). .6 to 5% by mass.

  The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less. Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

{(Standard deviation of particle size) / (Average value of particle size)} × 100
The method of adding the organic or inorganic powder may be a method in which the organic or inorganic powder is previously dispersed in the coating solution, or a method of spraying the organic or inorganic powder after the coating solution is applied and before the drying is completed. May be. Moreover, when adding several types of powder, you may use both methods together.

(Support)
Examples of the support material used in the photothermographic material of the present invention include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (for example, aluminum), etc. Is preferably one that can be processed into a flexible sheet or roll.

  Therefore, as a support in the photothermographic material of the present invention, a plastic film (for example, cellulose acetate film, polyester film, polyethylene terephthalate film, polyethylene naphthalate film, polyamide film, polyimide film, cellulose triacetate film, or polycarbonate film). In the present invention, a biaxially stretched polyethylene terephthalate film is particularly preferable. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  In the present invention, a conductive compound such as a metal oxide and / or a conductive polymer can be included in the constituent layers in order to improve the chargeability. These may be contained in any layer, but are preferably contained in a surface protective layer, an undercoat layer or the like on the back layer or image forming layer side. In the present invention, conductive compounds described in U.S. Pat. No. 5,244,773, columns 14 to 20 are preferably used.

  Especially in this invention, it is preferable to contain a conductive metal oxide in the surface protective layer by the side of a back layer. This proved that the effects of the present invention (particularly the transportability during heat development) can be further enhanced. Here, the conductive metal oxide is a crystalline metal oxide particle, and those that contain oxygen defects and those that contain a small amount of hetero atoms that form donors with respect to the metal oxide used are generally referred to. In particular, the latter is particularly preferable because it has high conductivity, and the latter is particularly preferable because it does not give fog to the silver halide emulsion.

Examples of metal oxides include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O ₅ , or a composite oxide thereof. In particular, ZnO, TiO ₂ and SnO ₂ are preferable. As an example of containing a heteroatom, the addition Al, or In respect ZnO, Sb for SnO _2, Nb, P, the addition of such a halogen element, also Nb for TiO _2, Ta Etc. are effective. The amount of these different atoms added is preferably in the range of 0.01 to 30 mol%, but particularly preferably 0.1 to 10 mol%. Furthermore, a silicon compound may be added during the production of fine particles in order to improve fine particle dispersibility and transparency. The metal oxide fine particles used in the present invention have electrical conductivity, and the volume resistivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A Nos. 56-143431, 56-120519, and 58-62647. Furthermore, as described in Japanese Examined Patent Publication No. 59-6235, a conductive material in which the above metal oxide is adhered to other crystalline metal oxide particles or fibrous materials (for example, titanium oxide) is used. Also good.

The particle size that can be used is preferably 1 μm or less, but if it is 0.5 μm or less, the stability after dispersion is good and it is easy to use. In order to make the light scattering property as small as possible, it is very preferable to use conductive particles of 0.3 μm or less because a transparent photosensitive material can be formed. When the conductive metal oxide is needle-like or fibrous, the length is preferably 30 μm or less and the diameter is preferably 1 μm or less, and particularly preferably the length is 10 μm or less and the diameter is 0.3 μm or less. / Diameter ratio is 3 or more. As the SnO _2, are commercially available from Ishihara Sangyo Kaisha, it can be used SNS10M, SN-100P, SN- 100D, the FSS10M like.

  The photothermographic material of the invention has an image forming layer which is at least one image forming layer on a support. Although only the image forming layer may be formed on the support, it is preferable to form at least one non-image forming layer on the image forming layer. For example, a protective layer is preferably provided on the image forming layer for the purpose of protecting the image forming layer, and the opposite surface of the support is stuck between the heat developing materials or in the heat developing material roll. A back layer is provided to prevent this. As the binder used in these protective layers and back layers, a polymer having a glass transition point higher than that of the image forming layer and not easily scratched or deformed, for example, a polymer such as cellulose acetate or cellulose acetate butyrate is used. Chosen from the inside.

  For gradation adjustment or the like, two or more image forming layers may be provided on one side of the support or one or more layers on both sides of the support.

  As the powder used in the present invention, a powder having a Mohs hardness of 5 or more is preferably used. As the powder, a known inorganic powder or organic powder can be appropriately selected and used.

Examples of the inorganic powder include titanium oxide, boron nitride, SnO ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, SiC, cerium oxide, corundum, artificial Examples thereof include diamond, garnet, garnet, mica, silica, silicon nitride, silicon carbide and the like. Examples of the organic powder include powders such as polymethyl methacrylate, polystyrene, and Teflon (registered trademark). Among these, inorganic powders such as SiO ₂ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃ , mica, etc. are preferable. , SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ is particularly preferable.

  In the present invention, the powder is preferably surface-treated with a Si compound or an Al compound. By using such surface-treated powder, the surface state of the uppermost layer can be improved. The content of Si or Al is preferably 0.1 to 10% by mass of Si and 0.1 to 10% by mass of Al, more preferably 0.1 to 10% by mass with respect to the powder. It is particularly preferable that 5% by mass, Al is 0.1-5% by mass, Si is 0.1-2% by mass, and Al is 0.1-2% by mass. The mass ratio of Si and Al is preferably Si <Al.

  The surface treatment can be performed by the method described in JP-A-2-83219. The average particle diameter of the powder in the present invention is the average diameter in the case of spherical powder, the average major axis length in the case of acicular powder, and the maximum diagonal length of the plate-like surface in the case of plate-like powder. Mean values can be easily obtained from measurement with an electron microscope.

  The organic or inorganic powder preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm.

  The average particle size of the organic or inorganic powder contained in the outermost layer on the photosensitive layer side is usually 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm. is there. The addition amount is usually 1.0 to 20% by mass, preferably 2.0 to 15% by mass, and more preferably 3% with respect to the amount of binder used in the outermost layer (the curing agent includes the binder amount). 0.0 to 10% by mass. The average particle diameter of the organic or inorganic powder contained in the outermost layer opposite to the photosensitive layer side across the support is usually 2.0 to 15.0 μm, preferably 3.0 to 12.0 μm. More preferably, it is 4.0-10.0 micrometers. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably 0 to the amount of binder used in the outermost layer (the curing agent includes the binder amount). .6 to 5% by mass.

  The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less.

  Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

{(Standard deviation of particle size) / (Average value of particle size)} × 100
The method of adding the organic or inorganic powder may be a method in which the organic or inorganic powder is previously dispersed in the coating solution, or a method of spraying the organic or inorganic powder after the coating solution is applied and before the drying is completed. May be. Moreover, when adding several types of powder, you may use both methods together.

(dye)
In the photothermographic material of the present invention, a filter layer is formed on the same side as or opposite to the image forming layer in order to control the amount of light transmitted through the image forming layer or the wavelength distribution, or a dye is formed on the image forming layer. Or it is preferable to contain a pigment.

  As the dye used, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the heat developing material. For example, when the photothermographic material is an image recording material using infrared light, a squarylium dye having a thiopyrylium nucleus as disclosed in JP-A-2001-83655 (referred to as a thiopyrylium squarylium dye in the present invention). And a squarylium dye having a pyrylium nucleus (referred to as a pyrylium squarylium dye in the present invention), a thiopyrylium croconium dye similar to a squarylium dye, or a pyrylium croconium dye.

  The compound having a squarylium nucleus is a compound having 1-cyclobuten-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy in the molecular structure. It is a compound having -4,5-dione. Here, the hydroxyl group may be dissociated. Hereinafter, in the present specification, these pigments are collectively referred to as squarylium dyes for convenience. In addition, as a dye, the compound of Unexamined-Japanese-Patent No. 8-201959 is also preferable.

(Application of component layers)
The photothermographic material of the present invention is preferably formed by preparing a coating solution in which the materials of the above-described constituent layers are dissolved or dispersed in a solvent, applying a plurality of coating solutions simultaneously, and then performing a heat treatment. . Here, "multiple simultaneous multi-layer coating" means that a coating solution for each constituent layer (photosensitive layer, protective layer, etc.) is prepared, and when this is coated on a support, the coating and drying are repeated for each layer individually. Rather, it means that each constituent layer can be formed in a state in which multiple layers can be simultaneously applied and dried. That is, the upper layer is provided before the remaining amount of the total solvent in the lower layer reaches 70% by mass or less.

  There are no particular restrictions on the method of applying multiple layers of each constituent layer simultaneously, and for example, a known method such as a bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, or extrusion coating method may be used. Can do. Among these, a pre-weighing type coating method called an extrusion coating method is more preferable. The extrusion coating method is suitable for precision coating and organic solvent coating because there is no volatilization on the slide surface unlike the slide coating method. This coating method has been described on the side having the photosensitive layer, but the same applies to the case of coating with undercoating when providing the backcoat layer. Japanese Unexamined Patent Publication No. 2000-15173 has a detailed description on the simultaneous multilayer coating method in the photothermographic material.

In the present invention, the silver coating amount is preferably selected in accordance with the purpose of the photothermographic material, but is preferably 0.3 to 1.5 g / m ² for medical purposes. 5-1.5 g / m < ² > is more preferable. Among the amount of coated silver, those derived from silver halide preferably occupy 2 to 18%, more preferably 5 to 15%, based on the total silver amount.

In the present invention, the coating density of silver halide grains having a particle diameter of 0.01 μm or more (equivalent sphere equivalent diameter) is preferably 1 × 10 ¹⁴ to 1 × 10 ¹⁸ particles / m ² . Furthermore, 1 * 10 < ¹⁵ > -1 * 10 < ¹⁷ > piece / m < ² > is preferable.

Furthermore, the coating density of the non-photosensitive long-chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ to 1 × 10 ⁻¹⁴ g per silver halide grain of 0.01 μm or more (equivalent particle diameter in terms of sphere). Is preferably 1 × 10 ⁻¹⁶ to 1 × 10 ⁻¹⁵ g.

  In the case of coating under the conditions within the above range, a preferable result from the viewpoint of the optical maximum density of the silver image per fixed coating silver amount, that is, the silver coating amount (covering power) and the color tone of the silver image. Is obtained.

In the present invention, the photothermographic material preferably contains a solvent in the range of 5 to 1,000 mg / m ² during development. It is more preferable to adjust so that it may be 100-500 mg / m < ² >. As a result, the photothermographic material has high sensitivity, low fog and high maximum density.

  Examples of the solvent include those described in paragraph “0030” of JP-A No. 2001-264930. However, it is not limited to these. These solvents can be used alone or in combination of several kinds.

  The content of the solvent in the photothermographic material can be adjusted by changing conditions such as temperature conditions in the drying step after the coating step. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

(Packaging body)
When storing the photothermographic material of the present invention, a package having a low oxygen permeability and / or moisture permeability in order to prevent density changes and fogging over time, or to improve curling, curling, etc. It is preferable to package with materials. The oxygen permeability is preferably 50 ml / atm · m ² · day or less at 25 ° C. (where 1 atm is 1.01325 × 10 ⁵ Pa), more preferably 10 ml / atm · m ² · day or less, More preferably, it is 1.0 ml / atm · m ² · day or less. The moisture permeability is preferably 10 g / atm · m ² · day or less, more preferably 5 g / atm · m ² · day or less, and still more preferably 1 g / atm · m ² · day or less. Specific examples of the packaging material for the photothermographic material include, for example, JP-A-8-254793, JP-A-2000-206653, JP-A-2000-235241, JP-A-2002-062625, JP-A-2003-015261, JP 2003-057990 A, JP 2003-084397 A, JP 2003-098648 A, JP 2003-098635 A, JP 2003-107635 A, JP 2003-131337 A, JP 2003-146330 A, Special It is a packaging material described in Japanese Patent Application Laid-Open No. 2003-226439 and Japanese Patent Application Laid-Open No. 2003-228152. The void ratio in the package is 0.01 to 10%, preferably 0.02 to 5%. Nitrogen sealing is performed so that the nitrogen partial pressure in the package is 80% or more, preferably 90% or more. It is good to do. The relative humidity in the package is 10% to 60%, preferably 40% to 55%.

(Exposure of photothermographic material)
The photosensitive material of the present invention exhibits its characteristics by being exposed for a short time with light having a high illuminance of 1 mW / mm ² or more. The illuminance here refers to the illuminance when the photosensitive material after heat development has an optical density of 3.0. When exposure is performed at such high illuminance, the amount of light (= illuminance * exposure time) required to obtain a required optical density is reduced, and a high sensitivity system can be designed. More preferably, the amount of light is ² mW / mm ² or more and 50 W / mm ² or less, and more preferably 10 mW / mm ² or more and 50 W / mm ² or less. Any light source may be used as long as it is such a light source, but it can be preferably achieved by using laser light. As the laser beam preferably used in the present invention, a gas laser (Ar ⁺ , Kr ⁺ , He—Ne), a YAG laser, a dye laser, a semiconductor laser, and the like are preferable. In addition, a semiconductor laser and a second harmonic generation element can be used. More preferably, the semiconductor laser emits blue to violet light (such as one having a peak intensity at a wavelength of 350 nm to 440 nm). An example of a blue to purple light emitting high-power semiconductor laser is Nichia's NLHV 3000E semiconductor laser.

  In the present invention, the exposure is preferably performed by laser scanning exposure, but various methods can be adopted as the exposure method. For example, as a first preferred method, there is a method using a laser scanning exposure machine in which the angle formed by the scanning surface of the photosensitive material and the scanning laser beam is not substantially perpendicular.

  Here, “substantially not perpendicular” means that the angle closest to the vertical during laser beam scanning is preferably 55 to 88 degrees, more preferably 60 to 86 degrees, and still more preferably 65 to 84 degrees. , Most preferably 70-82 degrees.

  The beam spot diameter on the exposure surface of the photosensitive material when the laser beam is scanned onto the photosensitive material is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the “shift angle” from the vertical of the laser beam incident angle. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

  As a second method, it is also preferable to perform exposure using a laser scanning exposure machine that emits scanning laser light that is a vertical multi. Compared with a longitudinal single mode scanning laser beam, image quality degradation such as occurrence of interference fringe-like unevenness is reduced. In order to make a vertical multiplex, methods such as using return light by combining and applying high-frequency superposition are preferable. Note that the vertical multi means that the exposure wavelength is not single, and the distribution of the exposure wavelength is usually 5 nm or more, preferably 10 nm or more. The upper limit of the exposure wavelength distribution is not particularly limited, but is usually about 60 nm.

  Furthermore, as a third aspect, it is also preferable to form an image by scanning exposure using two or more laser beams. As such an image recording method using a plurality of laser beams, it is used in an image writing unit of a laser printer or a digital copying machine that writes an image line by line in one scan because of a demand for higher resolution and higher speed. For example, Japanese Patent Laid-Open No. 60-166916 is known. This is a method in which laser light emitted from a light source unit is deflected and scanned by a polygon mirror and imaged on a photoconductor via an fθ lens or the like. This is in principle the same laser scanning optics as a laser imager or the like. Device.

  The image formation of laser light on the photoconductor in the image writing means of a laser printer or digital copying machine is for one line from the image formation position of one laser light for the purpose of writing an image by a plurality of lines in one scan. The next laser beam is imaged by shifting. Specifically, the two light beams are close to each other on the image plane in the sub-scanning direction at an order of several tens of μm, and the print density is 400 dpi (dpi is the number of dots per inch = 2.54 cm). The sub-scanning direction pitch of the two beams is 63.5 μm, and 42.3 μm at 600 dpi. Unlike the method of shifting the resolution in the sub-scanning direction as described above, in the present invention, it is preferable to form an image by condensing two or more lasers at the same place on the exposure surface while changing the incident angle. At this time, the exposure energy on the exposure surface when writing with one normal laser beam (wavelength λ [nm]) is E, and N laser beams used for exposure have the same wavelength (wavelength λ [nm]). ), In the case of the same exposure energy (En), the range of 0.9 × E ≦ En × N ≦ 1.1 × E is preferable. By doing so, energy is secured on the exposure surface, but the reflection of each laser beam to the image forming layer is reduced because the exposure energy of the laser is low, and thus the occurrence of interference fringes is suppressed.

In the above description, the wavelengths of the plurality of laser beams are the same as λ, but those having different wavelengths may be used. In this case, it is preferable that (λ−30) <λ1, λ2,... Λn ≦ (λ + 30) with respect to λ [nm].
In the laser light used in a laser imager or a laser image setter, the beam spot diameter on the exposed surface of the material when scanned with the photothermographic material is generally 5 to 75 μm as the minor axis diameter, and the major axis. The diameter is in the range of 5 to 100 μm, and the laser beam scanning speed can be set to an optimum value for each photothermographic material depending on the sensitivity and laser power at the laser oscillation wavelength specific to the photothermographic material.

(Heat development processing equipment)
The heat development processing apparatus referred to in the present invention is composed of a film supply unit represented by a film tray, a laser image recording unit, a heat development unit for supplying uniform and stable heat to the entire surface of the photothermographic material, and a film supply. It is composed of a conveying section from the section through laser recording to the discharge of the photothermographic material image-formed by thermal development to the outside of the apparatus. A specific example of the heat development processing apparatus of this embodiment is shown in FIG.

  The heat development apparatus 100 includes a feeding unit 110 that feeds a sheet-like photothermographic material (photothermographic element or simply a film) one by one, an exposure unit 120 that exposes the fed film F, and an exposure. A developing unit 130 for developing the developed film F, a cooling unit 150 for stopping development, and a stacking unit 160, a supply roller pair 140 for supplying the film F from the feeding unit, and for feeding the film to the developing unit Supply roller pair 144, and a plurality of roller pairs such as transport roller pairs 141, 142, 143, and 145 for smoothly transferring the film F between the respective parts. The heat developing part is a heating means for developing the film F, and peeling the heat drum 1 having a plurality of opposed rollers 2 that can be heated while being held in close contact with the outer periphery, and the developed film F to be sent to the cooling part. It consists of nails 6 etc.

  The conveyance speed of the photothermographic material is preferably in the range of 10 to 200 mm / sec. In particular, the heat development is carried out at a conveyance speed of 10 to 200 mm / sec, a conveyance speed from the photosensitive material supply unit to the image exposure unit of 10 to 200 mm / sec, and a conveyance speed of the image exposure unit of 10 to 200 mm / sec. It is preferable that the conveying speed of the heat developing unit is 20 to 100 mm / sec. By setting it within this range, density unevenness during heat development can be improved, and processing time can be shortened.

  The development conditions of the photothermographic material vary depending on the equipment, apparatus, or means used. Typically, development is performed by heating the photothermographic material exposed imagewise at a suitable high temperature. Is. The latent image obtained after exposure is at moderately high temperatures (about 80 to 200 ° C., preferably about 100 to 200 ° C.) for a sufficient time (generally about 1 second to about 2 minutes, preferably 3 to 30 seconds). , More preferably for 5 to 20 seconds), the development is performed by heating the heat developing material.

  If the heating temperature is less than 80 ° C, a sufficient image density cannot be obtained in a short time. If the heating temperature exceeds 200 ° C, the binder melts, and not only the image itself such as transfer to a roller but also transportability and a developing machine. Adversely affect. By heating, a silver image is generated by an oxidation-reduction reaction between an organic silver salt (which functions as an oxidizing agent) and a reducing agent. This reaction process proceeds without any supply of treatment liquid such as water from the outside.

  The heating device, apparatus or means may be a heating means typical as a heat generator using, for example, a hot plate, iron, hot roller, carbon or white titanium. More preferably, the heat-developable material provided with the protective layer is subjected to heat treatment by bringing the surface having the protective layer into contact with the heating means. It is preferable from the viewpoint, and it is preferable that the surface on the side having the protective layer is conveyed while being in contact with the heat roller, and is developed by heat treatment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the embodiment of this invention is not limited to these. Unless otherwise specified, “%” in the examples represents “mass%”.

Example 1
<< Preparation of undercoated photographic support >>
Corona of 8 W · min / m ² on both sides of a 175 μm thick polyethylene terephthalate film with an optical density of 0.150 (measured with a Densitometer PDA-65 manufactured by Konica Corporation) colored with the following blue dye and heat-fixed biaxially. The photographic support subjected to the discharge treatment was subjected to subbing. That is, the undercoat coating liquid a-1 was applied to one surface of this photographic support so that the dry film thickness was 0.2 μm at 22 ° C. and 100 m / min, and dried at 140 ° C. to form an image. A layer side undercoat layer was formed (referred to as undercoat underlayer A-1). Moreover, the following undercoat coating liquid b-1 was applied to the opposite surface as a backing layer undercoat layer at 22 ° C. and 100 m / min so that the dry film thickness was 0.12 μm, and dried at 140 ° C. An undercoat conductive layer having an antistatic function (referred to as undercoat underlayer B-1) was applied on the backing layer side. A corona discharge of 8 W · min / m ² is applied to the upper surfaces of the subbing lower layer A-1 and the subbing lower layer B-1, and the following subbing coating solution a-2 is dried on the lower subbing layer A-1. The film was coated at 33 ° C. and 100 m / min so as to have a film thickness of 0.03 μm, and dried at 140 ° C. to form an undercoat upper layer A-2. -2 was coated at 33 ° C. and 100 m / min to a dry film thickness of 0.2 μm, dried at 140 ° C. to form an undercoating upper layer B-2, and the support was further heat treated at 123 ° C. for 2 minutes. The sample was wound up under the conditions of 50 ° C. and 50% RH to prepare a subtracted sample.

[Preparation of aqueous polyester A-1 solution]
35.4 parts by weight of dimethyl terephthalate, 33.63 parts by weight of dimethyl isophthalate, 17.92 parts by weight of dimethyl sodium 5-sulfoisophthalate, 62 parts by weight of ethylene glycol, 0.065 parts by weight of calcium acetate / monohydrate, After transesterification of 0.022 parts by mass of manganese acetate tetrahydrate under a nitrogen stream while distilling off methanol at 170 to 220 ° C., 0.04 parts by mass of trimethyl phosphate and a polycondensation catalyst were used. 0.04 parts by mass of antimony oxide and 6.8 parts by mass of 1,4-cyclohexanedicarboxylic acid were added, and at a reaction temperature of 220 to 235 ° C., a theoretical amount of water was distilled off for esterification.

  Thereafter, the inside of the reaction system was further depressurized and heated over about 1 hour, and finally subjected to polycondensation at 280 ° C. and 133 Pa or less for about 1 hour to synthesize aqueous polyester A-1. The obtained aqueous polyester A-1 had an intrinsic viscosity of 0.33, an average particle size of 40 nm, and Mw = 80000 to 100,000.

  Next, 850 ml of pure water was put into a 2 L three-necked flask equipped with a stirring blade, a reflux condenser, and a thermometer, and 150 g of aqueous polyester A-1 was gradually added while rotating the stirring blade. After stirring for 30 minutes at room temperature, the mixture was heated to an internal temperature of 98 ° C. over 1.5 hours and dissolved at this temperature for 3 hours. After completion of the heating, the mixture was cooled to room temperature over 1 hour and allowed to stand overnight to prepare a 15% by mass aqueous polyester A-1 solution.

[Preparation of Modified Aqueous Polyester B-1-2 Solution]
Into a 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer and a dropping funnel, 1900 ml of the 15% by mass aqueous polyester A-1 solution was placed, and the internal temperature was adjusted to 80 ° C. while rotating the stirring blade. Until heated. Into this, 6.52 ml of a 24 mass% aqueous solution of ammonium peroxide was added, and a monomer mixture (28.5 g of glycidyl methacrylate, 21.4 g of ethyl acrylate, 21.4 g of methyl methacrylate) was dropped over 30 minutes. The reaction is continued for another 3 hours. Then, it cooled and filtered to 30 degrees C or less, and prepared the modified aqueous polyester B-1 solution (vinyl-type component modification | denaturation ratio 20 mass%) whose solid content concentration is 18 mass%.

  The solid content concentration was the same except that the vinyl modification ratio was 36% by mass and the modified components were styrene: glycidyl methacrylate: acetoacetoxyethyl methacrylate: n-butyl acrylate = 39.5: 40: 20: 0.5. An 18% by mass modified aqueous polyester B-2 solution (vinyl component modification ratio 20% by mass) was prepared.

[Production of Acrylic Polymer Latex C-1 to C-3]
Acrylic polymer latexes C-1 to C-3 having the monomer composition shown in Table 1 were synthesized by emulsion polymerization. The solid content concentration was 30% by mass.

<< Aqueous polymer containing polyvinyl alcohol unit >>
D-1: PVA-617 (Kuraray Co., Ltd. aqueous dispersion (solid content 5%): degree of saponification 95)
[Image forming layer side undercoat coating solution a-1]
Acrylic polymer latex C-3 (solid content 30%) 70.0 g
Water dispersion of ethoxylated alcohol and ethylene homopolymer (10% solids)
5.0g
Surfactant (A) 0.1g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Image forming layer side undercoat layer coating solution a-2]
Modified aqueous polyester B-2 (18% by mass) 30.0 g
Surfactant (A) 0.1g
Spherical silica matting agent (Nippon Shokubai Co., Ltd. Sea Hoster KE-P50)
0.04g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Backing layer side undercoat coating solution b-1]
Acrylic polymer latex C-1 (solid content 30%) 30.0 g
Acrylic polymer latex C-2 (solid content 30%) 7.6 g
SnO ₂ sol 180g
(SnO ₂ sol synthesized by the method described in Example 1 of Japanese Patent Publication No. 35-6616 was heated and concentrated so that the solid content concentration was 10% by mass, and then adjusted to pH = 10 with ammonia water)
Surfactant (A) 0.5g
PVA-613 (PVA manufactured by Kuraray Co., Ltd.) 5% by weight aqueous solution 0.4 g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Backing layer side undercoat upper layer coating solution b-2]
Modified aqueous polyester B-1 (18% by mass) 145.0 g
True spherical silica matting agent (Nippon Shokubai Co., Ltd. Sea Hoster KE-P50) 0.2g
Surfactant (A) 0.1g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

  A backcoat layer and a backcoat layer protective layer having the following composition were coated on the undercoat layer B-2 of the support on which the undercoat layer had been applied.

<Preparation of backcoat layer coating solution>
While stirring 830 g of methyl ethyl ketone (MEK), 84.2 g of cellulose acetate propionate (manufactured by Eastman Chemical: CAP482-20) and 4.5 g of polyester resin (Bostic: VitelPE2200B) were added and dissolved. Next, 4.5 g of a fluorine-based surfactant (Asahi Glass Co., Ltd .: Surflon KH40) dissolved in 43.2 g of methanol and 2.3 g of a fluorine-based surfactant (Dainippon Ink Co., Ltd .: MegaFag F120K) were dissolved in the dissolved liquid. Add and stir well until dissolved. Next, 2.5 g of oleyl oleate was added. Finally, 75 g of silica dispersed in MEK with a dissolver type homogenizer at a concentration of 1% (average particle diameter is described in Table 2) was added and stirred to prepare a backcoat layer coating solution.

<Preparation of backcoat layer protective layer (surface protective layer) coating solution>
The following composition ratio was prepared in the same manner as the back coat layer coating solution. A dissolver type homogenizer was used for dispersion of silica.

Cellulose acetate propionate (10% MEK solution) 15g
(Manufactured by Eastman Chemical: CAP482-20)
Monodispersed silica with a monodispersity of 15% (average particle size: listed in Table 2)
(Surface treatment with 1% aluminum of the total mass of silica) 0.03 g
C ₈ F ₁₇ (CH ₂ CH ₂ O) ₁₂ C ₈ F ₁₇ 0.05 g
Fluorine-based surfactant (SF-17) 0.01g
Stearic acid 0.1g
Oleyl oleate 0.1g
α-Alumina (Mohs hardness 9) 0.1g

<Preparation of photosensitive silver halide emulsion A>
(A1)
Phenylcarbamoylated gelatin 88.3g
10% aqueous methanol solution of compound (AO-1) 10ml
Potassium bromide 0.32g
Finish to 5429 ml with water (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(C1)
Potassium bromide 50.69g
Potassium iodide 2.66g
Finish to 660ml with water (D1)
Potassium bromide 151.6g
Potassium iodide 7.67g
Potassium hexachloroiridium (IV) (1% aqueous solution of K ₂ (IrCl ₆ ))
0.93ml
Potassium hexacyanoferrate (II) 0.004g
Hexachloroosmium (IV) potassium salt 0.004g
Finish to 1982ml with water (E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount (F1)
Potassium hydroxide 0.71g
Finish to 20ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
(H1)
Anhydrous sodium carbonate 1.72 g
Water finish 151ml AO-1: HO (CH 2 CH 2 O) n [CH (CH ₃₎ CH ₂ O] _{17 (CH 2 CH 2 O)} m H (m + n = 5~7).

  Using the mixing stirrer shown in Japanese Patent Publication No. 58-58288, while controlling 1/4 of the solution (B1) and the total amount of the solution (C1) to 20 ° C. and pAg 8.09 using the mixing stirrer Was added for 4 minutes and 45 seconds to nucleate. After 1 minute, the entire amount of solution (F1) was added. During this time, pAg was adjusted as appropriate using (E1). After 6 minutes, 3/4 amount of the solution (B1) and the total amount of the solution (D1) were added by a simultaneous mixing method over 14 minutes and 15 seconds while controlling at 20 ° C. and pAg 8.09. After stirring for 5 minutes, the temperature was lowered to 40 ° C., the whole amount of the solution (G1) was added, and the silver halide emulsion was allowed to settle. The supernatant was removed leaving 2000 ml of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was sedimented again. The remaining portion of 1500 ml was left, the supernatant was removed, 10 L of water was further added, and after stirring, the silver halide emulsion was allowed to settle. After leaving 1500 ml of the sedimented portion and removing the supernatant, the solution (H1) was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount of silver was 1161 g per mole of silver, whereby photosensitive silver halide emulsion A was obtained.

  This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of photosensitive silver halide emulsion B>
The same procedure as in the preparation of photosensitive silver halide emulsion A was carried out except that the temperature during addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of photosensitive silver halide emulsion C>
The procedure was the same as the preparation of the photosensitive silver halide emulsion A, except that the potassium bromide used in the preparation of the photosensitive silver halide emulsion A was changed to potassium iodide. This emulsion was monodispersed pure silver iodide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<Preparation of photosensitive silver halide emulsion D>
Preparation of photosensitive silver halide emulsion A, except that part of potassium bromide used in the preparation of photosensitive silver halide emulsion A was changed to potassium iodide so that the silver iodide content was 90 mol%. The same was done. This emulsion was monodispersed silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (silver iodide content was 90 mol%).

<Preparation of photosensitive silver halide emulsion E>
The same procedure as in the preparation of photosensitive silver halide emulsion C was carried out except that the temperature at the time of addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed pure silver iodide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<Preparation of photosensitive silver halide emulsion F>
The procedure was the same as the preparation of the photosensitive silver halide emulsion D except that the temperature at the time of addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (silver iodide content was 90 mol%).

<Preparation of powdered organic silver salt>
130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved in 4720 ml of pure water at 80 ° C. Next, 540.2 ml of a 1.5 mol / L sodium hydroxide aqueous solution was added and 6.9 ml of concentrated nitric acid was added, followed by cooling to 55 ° C. to obtain a fatty acid sodium solution. While maintaining the temperature of the fatty acid sodium solution at 55 ° C., a photosensitive silver halide emulsion (type and amount described in Table 2) and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 468.4 ml of 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an organic silver salt dispersion. Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 2 μS / cm, and centrifugal dehydration was carried out. Then, the obtained cake-like organic silver salt was converted into an airflow dryer Flashjet dryer (Seishin). Was used until the water content became 0.1% according to the operating conditions of the nitrogen gas atmosphere and the hot air temperature at the entrance of the dryer, to obtain a dried powdered organic silver salt. The photothermographic material sample 1 (described later) prepared using this organic silver salt was analyzed using an electron microscope. The average particle diameter (equivalent circle diameter) was 0.08 μm, the aspect ratio was 5, and the monodispersity was 10%. Tabular grains.

  In addition, the infrared moisture meter was used for the moisture content measurement of an organic silver salt composition.

<Preparation of preliminary dispersion>
As the image forming layer binder, 14.57 g of SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of —SO ₃ K group) was dissolved in 1457 g of MEK, and dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN While stirring with a mold, 500 g of the powdered organic silver salt was gradually added and mixed well to prepare a preliminary dispersion.

<Preparation of photosensitive emulsion dispersion>
Media type disperser DISPERMAT SL filled with 80% of the internal volume of 0.5 mm zirconia beads (Toray Industries, Inc .: Treceram) so that the residence time in the mill is 1.5 minutes using a pump. A photosensitive emulsion dispersion was prepared by supplying to -C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 8 m / s.

<Preparation of stabilizer solution>
A stabilizer solution was prepared by dissolving 1.0 g of Stabilizer 1 and 0.31 g of potassium acetate in 4.97 g of methanol.

<Preparation of 2-chlorobenzoic acid solution>
1.488 g of 2-chlorobenzoic acid, 2.779 g of stabilizer 2 and 365 mg of 5-methyl-2-mercaptobenzimidazole are dissolved in 31.3 ml of MEK in the dark to prepare a 2-chlorobenzoic acid solution. did.

<Preparation of additive solution a>
Reducing agent (compound described in Table 2 (reducing agent) and amount) and 0.159 g of yellow chromophoric leuco dye (YA-1), 0.159 g of cyan chromogenic leuco dye (CA-10), 1.54 g 4-methylphthalic acid was dissolved in 110 g of MEK to obtain an additive solution a.

<Preparation of additive liquid b>
1.56 g of antifogging agent 2, 0.5 g of antifogging agent 3, 0.5 g of antifogging agent 4, 0.5 g of antifogging agent 5, 3.43 g of phthalazine are dissolved in 40.9 g of MEK and added. b.

<Preparation of additive liquid c>
0.01 g of silver saving agent K was dissolved in 39.99 g of MEK to obtain additive liquid c.

<Preparation of additive liquid d>
0.5 g of potassium p-toluenethiosulfonate and 0.5 g of antifogging agent 6 were dissolved in 9.0 g of MEK to obtain an additive solution d.

<Preparation of additive liquid e>
1.0 g of vinyl sulfone [(CH ₂ ═CH—SO ₂ CH ₂ ) ₂ CHOH] was dissolved in 9.0 g of MEK to obtain an additive solution e.

<Preparation of image forming layer coating solution>
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion 1 and 15.11 g of MEK were kept at 21 ° C. with stirring, and the chemical sensitizer S-5 (0.5% methanol solution) 1000 μl was added, and after 2 minutes, 390 μl of antifoggant 1 (10% methanol solution) was added and stirred for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 10 minutes, then gold sensitizer Au-5 corresponding to 1/20 mole of the above organic chemical sensitizer was added, and further stirred for 20 minutes. . Subsequently, 167 ml of a stabilizer solution was added and stirred for 10 minutes, and then 1.32 g of the 2-chlorobenzoic acid solution was added and stirred for 1 hour. Thereafter, the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While maintaining the temperature at 13 ° C., 0.5 g of additive liquid d, 0.5 g of additive liquid e, and 13.31 g of binder used in the preliminary dispersion were added and stirred for 30 minutes, and then tetrachlorophthalic acid (9. (4% MEK solution) 1.084 g was added and stirred for 15 minutes. While further stirring, 12.43 g of additive liquid a, 1.6 ml of Desmodur N3300 / Movey aliphatic isocyanate (10% MEK solution), 4.27 g of additive liquid b, and 1.0 g of additive liquid c were added. By sequentially adding and stirring, an image forming layer coating solution was obtained.

  The structures of the additives used for the preparation of each coating solution including the stabilizer solution and the image forming layer coating solution are shown below.

<Preparation of image forming layer protective layer lower layer (surface protective layer lower layer)>
To 500 g of acetone, 2100 g of MEK, and 700 g of methanol, 230 g of cellulose acetate butyrate (manufactured by Eastman Chemical: CAB-171-15S) was added, and the mixture was stirred and dissolved with a dissolver. Then 25 g phthalazine, 3.5 g CH ₂ ═CHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH═CH ₂ , 1 g C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ , SF -17 g, 10 g stearic acid, 10 g butyl stearate were added with stirring and dissolved. Finally, 140 g of monodispersed 15% monodispersed silica (average particle size: described in Table 2. 1% of aluminum in the total mass of silica) dispersed in MEK with a dissolver type homogenizer at a concentration of 5% is added. Then, the mixture was stirred to prepare an image forming layer protective layer lower layer coating solution.

<Preparation of image forming layer protective layer upper layer (surface protective layer upper layer)>
To 500 g of acetone, 2100 g of MEK and 700 g of methanol, 230 g of cellulose acetate butyrate (manufactured by Eastman Chemical: CAB-171-15S) was added, and the mixture was stirred and dissolved with a dissolver. Then 25 g of phthalazine, 3.5 g of CH ₂ ═CHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH═CH ₂ , 1 g of C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ , SF -17 g, 10 g stearic acid, 10 g butyl stearate were added with stirring and dissolved. Finally, 280 g of monodispersed 15% monodispersed silica (average particle size: described in Table 2. 1% aluminum of the total mass of silica) dispersed in MEK with a dissolver type homogenizer at a concentration of 5% is added. Then, the mixture was stirred to prepare an image forming layer protective layer upper layer coating solution.

<Preparation of photothermographic material>
The backcoat layer coating solution and the backcoat layer protective layer coating solution prepared as described above were extruded onto the undercoating upper layer B-2 so that the dry film thickness was 3.5 μm, respectively, and the coating speed was 50 m / Application was performed in min. The drying was performed for 5 minutes using a drying air having a drying temperature of 100 ° C. and a dew point temperature of 10 ° C.

The image forming layer coating solution and the image forming layer protective layer (surface protective layer) coating solution are simultaneously coated on the subbing upper layer A-2 at an application speed of 50 m / min using an extrusion coater. Thus, photosensitive material samples 1 to 17 shown in Tables 2 and 3 were prepared. As for coating, the image forming layer has a coated silver amount of 1.2 g / m ² , and the image forming layer protective layer (surface protective layer) has a dry film thickness of 3.0 μm (surface protective layer upper layer 1.5 μm, surface protective layer lower layer 1. 5 μm), followed by drying for 10 minutes using drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

  The obtained photothermographic material had a film surface pH of 5.3 on the image forming layer side and a film surface pH of 5.5 on the backcoat layer side.

  For sample 9, in the preparation of powdered organic silver salt A in sample 1, behenic acid 259. instead of 130.8 g behenic acid, 67.7 g arachidic acid, 43.6 g stearic acid, and 2.3 g palmitic acid. A sample was prepared in the same manner as Sample 1 except that 9 g was used.

  For sample 10, in the preparation of powdered organic silver salt A in sample 1, 540.2 ml of 1.5 mol / L potassium hydroxide aqueous solution was used instead of 540.2 ml of 1.5 mol / L sodium hydroxide aqueous solution. A sample was prepared in the same manner as Sample 1 except that it was used.

Sample 11 was the same as Sample 1 except that the fluorine-based activator of the backcoat layer protective layer and the image forming layer protective layer (upper layer and lower layer) in Sample 1 was changed from SF-17 to C ₈ F ₁₇ SO ₃ Li. A sample was prepared.

Sample 12 was replaced with SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of SO ₃ K) as the image-forming layer binder in the preparation of preliminary dispersion A in Sample 1. _A sample was prepared in the same manner as Sample 1 except that ₃ K group-containing polyvinyl butyral (Tg 65 ° C., SO ₃ K was contained 0.2 mmol / g) was used.

<Exposure and development processing>
The photothermographic material samples 1 to 17 prepared as described above were processed into half-cut sizes (34.5 cm × 43.0 cm), and then processed in the following manner using the heat development processing apparatus shown in FIG.

After taking the photothermographic material sample from the film tray and transporting it to the laser exposure unit, from the image forming layer surface side, the laser beam is emitted by an exposure machine using a semiconductor laser having an emission wavelength of 405 nm (NLHV3000E from Nichia Corporation) as an exposure source. was exposed sensitive material of the light amount was varied between 0 and ^{1mW / mm 2 ~1000mW / mm 2} . Thereafter, the photothermographic material is conveyed to a heat developing unit, and the heat drum is heat-developed at 123 ° C. for 13.5 seconds so that the protective layer on the image forming layer side of the photothermographic material is in contact with the drum surface. After the processing, the photothermographic material was carried out of the apparatus. At this time, the conveyance speed from the photosensitive material supply section to the image exposure section, the conveyance speed at the image exposure section, and the conveyance speed at the heat development section were each 20 mm / sec. The exposure and development were performed in a room adjusted to 23 ° C. and 50% RH. The exposure was performed in a stepped manner while reducing the exposure energy amount by log E0.05 step by step from the maximum output.

<Packaging materials>
PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% carbon, oxygen transmission rate: 0 ml / atm · m ² · 25 ° C. · day, moisture transmission rate: 0 g / atm · m ² · 25 ° C./day. Use paper tray.

<Performance evaluation>
The following performance was evaluated for each heat-developed image.

<Image density>
The value of the highest density portion of the image obtained under the above conditions was measured with a densitometer and indicated as the image density.

《Average gradation》
The obtained sensitometric sample was subjected to concentration measurement using a PDM65 transmission densitometer (manufactured by Konica), and the measurement result was computer processed to obtain a characteristic curve. From this characteristic curve, an average gradation (Ga) value with an optical density of 0.25 to 2.5 was obtained.

<Transportability>
Development processing was performed 50 times using a heat development processing apparatus, and the number of times of occurrence of conveyance failure was measured.

《Density unevenness during heat development》
The density unevenness after development was visually evaluated based on the following criteria.

5: Concentration unevenness is not observed 4: Slight concentration unevenness occurs 3: Some weak density unevenness occurs 2: Strong concentration unevenness occurs partly 1: Strong density unevenness occurs over the entire surface Characteristic"
The produced photothermographic material was placed in a sealed container whose inside was kept at 25 ° C. and 55% humidity, and then stored at 55 ° C. for 7 days (forced aging). For comparison, the same photothermographic material was stored for 7 days in a light-shielding container at 25 ° C. and 55% humidity. These samples were subjected to the same treatment as that used for evaluation of sensitometry, and the density of the fogged part was measured.
ΔDmin (increased fog) = (fogging with forced aging) − (fogging with time for comparison) was calculated, and the aging characteristics of the photothermographic material were observed.

<< Rz (E) / Rz (B) >><< Ra (E) / Ra (B) >><< Rz (E) / Ra (E) >>
About the sample before the process of heat development, Rz and Ra were measured by the method shown below using the non-contact three-dimensional surface analyzer (WYKO company RST / PLUS).
1. Objective lens: × 10.0, Intermediate lens: × 1.0
2. Measurement range: 463.4 μm × 623.9 μm
3. Pixel size: 368 × 238
4). Filter: Cylindrical correction and tilt correction Smoothing: Medium smoothing6. Scan speed: Low
In addition, the definition of Rz and Ra followed JIS surface roughness (B0601). For each sample of 10 cm × 10 cm, the sample was divided into 100 in a grid pattern at 1 cm intervals, the center of each square region was measured, and the average value was obtained from 100 measurements. Thus, Rz (E), Rz (B), Ra (E), Ra (B) are obtained, and Rz (E) / Rz (B), Ra (E) / Ra (B), Rz (E) / Ra (E) was obtained.

  The results are also shown in Tables 2 and 3.

  From Tables 2 and 3, compared with the comparative image forming method, the image forming method of the present invention has a high density, no occurrence of conveyance failure or density unevenness at the time of heat development, and excellent prevention of fog rise with time. It is clear that

  Further, comparing Samples 11 and 1, it was found that Sample 1 has superior characteristics in terms of transportability and environmental suitability (accumulation in vivo). Further, comparing Samples 12 and 1, it was found that Sample 1 has superior characteristics with respect to image storage stability during high-temperature storage.

1 is a diagram showing an example of a heat development processing apparatus for processing a photothermographic material of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat drum 2 Opposed roller 6 Peeling nail | claw 100 Heat developing apparatus 110 Feeding part 120 Exposure part 130 Developing part 140 Supply roller pair 141,142,143,145 Transport roller pair 144 Supply roller pair 150 Cooling part 160 Accumulation part F Film C Film tray L Laser beam

Claims (17)

In a photothermographic material having an image forming layer containing an organic silver salt, silver halide, a binder and a reducing agent on a support, a ten-point average roughness of the outermost surface on the image forming layer side with the support interposed therebetween. Rz (E) / Rz (B) where (Rz (E)) is the ten-point average roughness of the outermost surface on the opposite side of the image forming layer across the support (Rz (B)) The photothermographic material is characterized by having a value of 0.1 to 0.7. Furthermore, the average particle size of the largest average particle size of the matting agent contained in the layer on the image forming layer side across the support is Le (μm), and the layer on the side opposite to the image forming layer across the support 2. The photothermographic material according to claim 1, wherein Lb / Le is 2.0 or more and 10 or less, where Lb (μm) is the average particle size of the matting agent having the largest average particle size. material. When the center line average surface roughness of the surface on the image forming layer side is Ra (E) and the center line average surface roughness of the surface opposite to the image forming layer across the support is Ra (B), 3. The photothermographic material according to claim 1, wherein the value of Ra (E) / Ra (B) is from 0.5 to 1.5. 4. The photothermographic material according to claim 1, wherein the value of Rz (E) / Ra (E) is 10 or more and 70 or less. 5. The photothermographic material according to claim 1, wherein the silver halide contains silver iodide in a proportion of 5 mol% to 100 mol%. 6. The photothermographic material according to claim 1, wherein the silver halide contains silver iodide in a proportion of 40 mol% to 100 mol%. 2. A silver saving agent selected from a vinyl compound, a hydrazine derivative, a phenol derivative, a naphthol derivative, a silane compound, and a quaternary onium salt is contained on the side having an image forming layer. The photothermographic material according to claim 1. The photothermographic material according to claim 1, wherein the binder has a glass transition temperature (Tg) of 70 to 150 ° C. The photothermographic material according to claim 1, comprising a compound represented by the following general formula (SF).
Formula (SF) (Rf (L) _n1 ) _p (Y) _m1 (A) _q
Wherein Rf represents a substituent having a fluorine atom, L represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, and A represents an anion M1 and n1 each represents an integer of 0 or 1, and p and q each represent an integer of 1 to 5. However, when q is 1, n1 and m1 are not 0 at the same time. .) 10. The photothermographic material according to claim 1, further comprising silver halide grains having an average grain size of 10 to 50 nm. 11. The photothermographic material according to claim 1, wherein the silver halide further contains silver halide grains having an average grain size of 55 to 100 nm. The photothermographic material according to claim 1, wherein the silver halide contains silver halide grains chemically sensitized with a chalcogen compound. 13. The photothermographic material according to claim 1, wherein the amount of silver contained in the image forming layer is from 0.3 to 1.5 g / m < ² >. An image forming method comprising: exposing the photothermographic material according to any one of claims 1 to 13 with a laser whose exposure light source has an emission peak intensity at 350 nm to 450 nm to form an image. Regarding the characteristic curve shown on the orthogonal coordinates where the unit length of the diffusion density (Y axis) and the common logarithmic exposure (X axis) is equal, the image obtained by thermal development at a development temperature of 123 ° C. and a development time of 13.5 seconds The image forming method according to claim 14, wherein the average gradation in the range of 0.25 to 2.5 in terms of optical density with diffused light is 2.0 to 4.0. Using a heat development processing apparatus, the conveyance speed of the heat development unit is 10 to 200 mm / sec, the conveyance speed between the photosensitive material supply unit and the image exposure unit is 10 to 200 mm / sec, and the conveyance speed of the image exposure unit is 10 The image forming method according to claim 14, wherein the image is thermally developed at a speed of ˜200 mm / sec. The image forming method according to claim 14, 15 or 16, wherein the image is exposed to light having an illuminance of 1 mW / mm ² or more and then thermally developed.

Images