JP2001318195A - Radiation image conversion screen and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation image conversion screen, its production method and a radiation image detector having relatively easy productivity and giving a radiation image superior in image quality. SOLUTION: A radiation image conversion screen and a two-dimensional photodetector are used in combination for a method for radiation image formation. In the radiation image conversion screen, stripe fluorescent layers consisting of stripe partition walls finely partitioning along plane direction in one dimension and a fluorescent body charging region partitioned with the partition walls are piled and the stripe partition walls of adjacent fluorescent layers cross perpendicularly or with an angle of approximately 60 deg..

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation image conversion screen used in a radiation image forming method using a combination of a radiation image conversion screen and a two-dimensional photodetector,
The present invention relates to a method of manufacturing the same and a radiation image detecting apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, in radiography such as X-ray radiography used for medical diagnosis and nondestructive inspection of substances, a radiographic film forming method using a combination of a radiographic film and a radiographic intensifying screen (radiography) Photographic method). A radiographic intensifying screen absorbs radiation such as X-rays and emits light, and a radiographic film is exposed to the light together with the radiation to form a radiographic image on the film. An intensifying screen usually has a basic structure in which a support, a phosphor layer, and a protective film are laminated in this order, and the phosphor layer usually includes phosphor particles and a binder containing and supporting the phosphor particles in a dispersed state. . However, as the phosphor layer, there is a phosphor layer formed of an aggregate of a phosphor that does not contain a binder and is formed by an evaporation method, a sintering method, or the like. It is also known to provide the phosphor layer with light-reflective partitions that subdivide the phosphor layer along a planar direction in order to avoid diffusion of light emitted from the phosphor in the phosphor layer. .

[0003] In recent years, in the field of digital radiography and the like, a radiation image detecting apparatus using a radiation image detecting apparatus in which a pixelated radiation image converting screen (also referred to as a phosphor screen) and a two-dimensional photodetector are combined. A forming method has been proposed. In this method, radiation such as X-rays is converted to light by a radiation image conversion screen of an image detection device, and then the light is detected by a two-dimensional photodetector and converted into an electric signal having image information, and the obtained signal is obtained. A radiographic image is obtained by sending an electric signal having image information to an appropriate image reproducing means to form an image. As two-dimensional photodetectors, photodiodes,
A phototransistor, a photoconductive element, a charge transfer device (CCD), or the like is used.

[0004] For example, US Pat. No. 5,153,438 describes a configuration in which a pixelated phosphor screen and a photodetector array are combined, and the pixels of the screen are the same as the cells of the light receiving section of the detector array. The size and the shape are formed so as to correspond one-to-one. It is described that the pixelation of the screen is performed by vapor deposition, cutting, ablation, chemical etching, or the like, and the gap between each pixel may be filled with a light-reflective substance such as titanium dioxide.

Japanese Patent Application Laid-Open No. 7-198852 discloses that
A configuration is described in which a fiber optic plate is provided between the pixelated phosphor screen and the photodetector array, with one-to-one or more sized optical fibers and screen pixels relative to the size of the detector array. Has been stipulated. Note that the gap between each pixel may be filled with a material having a lower refractive index than the inside of the pixel (for example, a phosphor material having a composition different from that of the inside phosphor).
This describes that light is confined within a single pixel.

Even a pixelated radiation image conversion screen (phosphor screen) used in the above-described radiation image forming method has high image quality (especially high sharpness leading to high resolution) with a small amount of radiation irradiation. It is desirable to be able to provide a radiographic image.

[0007] Therefore, Japanese Patent Application No. 11-13 filed by the present applicant.
No. 4599, a radiation image detecting apparatus having a phosphor screen and a two-dimensional photodetector, wherein the phosphor screen is partitioned by a partition that subdivides the screen along a plane direction and the partition. And a scattering length of the phosphor-filled region and the partition walls with respect to light emitted from the phosphor is 20 to 200, respectively.
μm range and 0.05-20 μm range,
In addition, a radiation image detecting device that provides a high-quality radiation image, in which the ratio is 3.0 or more and the absorption length of emitted light is 1000 μm or more, is described. In this specification, as a method of manufacturing a phosphor screen, a laminate block is formed by laminating a plurality of films each substantially consisting of a phosphor and a film for forming a partition wall alternately to form a laminate block. A one-dimensional stripe-like phosphor film is obtained by slicing along the lamination surface, and then the stripe phosphor film and the partition wall forming film are again laminated alternately to form a laminate block, and then laminated. A method of slicing again along a plane (laminated slicing method) is described.

In any of the above-mentioned radiation image conversion screens (phosphor screens), the processing and manufacturing process for forming pixels tend to be complicated. For example, when a fine hole or a concave portion is filled with a fluorescent substance, there is a problem that the amount of the fluorescent substance to be filled is different for each hole or concave portion and is difficult to be constant. Further, when slicing a laminate block, complicated processing such as lamination and slicing of a thin film must be repeated twice, which is not desirable in terms of stability and cost.

The above-mentioned specification by the applicant also describes a method of manufacturing a phosphor screen provided with stripe-shaped partition walls by slicing the laminate block only once. Then, the difference in sharpness between the direction perpendicular to the stripe and the direction parallel to the stripe tends to increase.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a radiation image conversion screen which is relatively easy to manufacture and provides a radiation image of excellent image quality. Another object of the present invention is to provide a method for stably producing a high-quality radiation image conversion screen in a relatively simple process. Still another object of the present invention is to provide a radiation image detecting apparatus having a two-dimensional photodetector and a radiation image conversion screen which is relatively easy to produce and provides a radiographic image with excellent image quality.

[0011]

The inventor of the present invention has studied a method of manufacturing a radiation image conversion screen which is formed into pixels by providing partition walls. As a result, the laminated body is sliced once and the partition walls are provided in a stripe shape. It has been found that by obtaining a phosphor film and laminating two or more such films, a radiation image conversion screen in which partition walls are substantially provided in a two-dimensional direction can be obtained. That is, by laminating the stripes of the adjacent films so as to cross each other at an angle of about 60 ° or orthogonal to each other, both the direction perpendicular to the stripe of the stripe phosphor layer of the radiation image conversion screen and the direction parallel to the stripe are provided. It was found that a radiation image with good image quality was obtained.

According to the present invention, there is provided a method for forming a radiation image by combining a radiation image conversion screen for converting radiation having radiation image information into light and a two-dimensional photodetector for detecting light and converting it into an electric signal. A radiation image conversion screen used in the above, wherein at least two stripe phosphor layers each including a stripe-shaped partition wall subdivided in a one-dimensional direction along a plane direction and a phosphor-filled region partitioned by the partition wall are laminated. Wherein the striped partition walls of adjacent phosphor layers are orthogonal to each other.

The present invention also forms a radiation image by combining a radiation image conversion screen that converts radiation having radiation image information into light and a two-dimensional photodetector that detects light and converts it into an electric signal. A radiation image conversion screen used in the method, wherein at least two stripe phosphor layers each including a stripe-shaped partition wall subdivided in a one-dimensional direction along a plane direction and a phosphor-filled region partitioned by the partition wall are laminated. There is also a radiation image conversion screen wherein the stripe-shaped partition walls of adjacent phosphor layers cross each other at an angle of about 60 °.

The present invention further provides a method for producing the above radiation image conversion screen, comprising the following steps: 1) Forming a plurality of films A each substantially composed of a phosphor and a plurality of films B for forming partition walls. 2) a step of laminating a large number of phosphor films A and a plurality of films B for forming partition walls alternately and a step of heat-pressing to form a laminated block; 3) slicing the laminated block along the laminated surface Manufacturing a plurality of striped phosphor films having a configuration in which strips of the phosphor film A and strips of the partition wall forming film B are alternately arranged; and 4) a film in which a plurality of striped phosphor films are adjacent to each other. And laminating them so that the stripes intersect at right angles or intersect at an angle of about 60 °, and heat-press.

The present invention further provides a radiation image detecting apparatus having the above-mentioned radiation image conversion screen and a two-dimensional photodetector arranged on one surface of the radiation image conversion screen.

In the radiation image conversion screen of the present invention, each stripe phosphor layer has a thickness of 10 μm to 100 μm.
The number of phosphor layers is preferably in the range of 2 to 100 layers. The scattering length of each stripe phosphor layer for the emission light of the phosphor-filled region and the partition wall is in the range of 10 to 200 μm and 0.05 to 20 μm, respectively, and the scattering length of the phosphor-filled region is the scattering length of the partition wall. It is preferable that the length is longer than the length and the absorption length for the emitted light is 1000 μm or more.

It is desirable that the phosphor-filled region substantially comprises phosphor particles and a binder. The partition walls preferably contain at least low light-absorbing fine particles and a polymer substance. In addition, the partition wall may have its top exposed on the surface of each stripe phosphor layer, or the whole partition wall may be embedded inside the phosphor layer, but the height of each partition layer is It is desirable that the thickness be in the range of 1/3 to 1/1 of the thickness.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A radiation image conversion screen of the present invention is a radiation image conversion screen used in the above-described radiation image forming method, wherein a stripe-shaped partition wall which is subdivided in a one-dimensional direction along a plane direction is provided. The stripe phosphor layer composed of the phosphor-filled region partitioned by the partition
It is characterized by being stacked in layers.

The configuration of the radiation image conversion screen comprising the plurality of stripe phosphor layers will be described with reference to the accompanying drawings. FIG. 1 is a schematic perspective view of a stripe phosphor layer 1 according to the present invention. In FIG. 1, a hatched portion 2 is a partition, and a white portion 3 is a phosphor-filled region. In order to obtain suitable resolution characteristics and image quality, it is desirable that the width of the partition wall 2 (the average value of the width in the plane direction) is in the range of 0.5 μm to 50 μm, and the width of the phosphor-filled region 3 (the plane direction). (The average value of the widths) is preferably in the range of 5 μm to 300 μm. Then, the stripe phosphor layer 1
Is preferably in the range of 40 to 98%.

The partition 2 has a scattering length for light emitted from the phosphor in the range of 0.05 to 20 μm, and preferably has an absorption length of 1000 μm or more. The phosphor-filled region 3 has a scattering length for emitted light of 10 to 100 μm.
m, and the absorption length is desirably 1000 μm or more. Here, the scattering length of the emitted light means an average distance that the light travels straight before being scattered once, and the shorter the scattering length, the higher the light scattering property. Further, the absorption length for emitted light means an average free distance until light is absorbed, and the longer the absorption length, the lower the light absorption. The light scattering length and the light absorption length are, for example, as described in the above-mentioned Japanese Patent Application No. 11-134.
As described in detail in the specification of Japanese Patent No. 599, it is a value calculated from a measured value of transmittance by a calculation method based on Kubelka's theory.

As described above, regarding the partition walls, the scattering length of the phosphor with respect to the emitted light is shortened to increase the reflectance, and the absorption length is increased to decrease the absorption length, so that the emitted light is diffused in the plane direction. Can be effectively prevented to enhance the sharpness of the image, and the absorption of emitted light by the partition walls can be suppressed as much as possible to prevent a decrease in the amount of emitted light. On the other hand, for the phosphor-filled region, by increasing the scattering length for the emitted light to increase the transmittance, and increasing the absorption length for the emitted light to decrease the absorption rate, the radiation image conversion screen near the radiation irradiation side surface (That is, far from the photodetector) can be efficiently extracted. Thereby, a higher quality radiation image can be obtained.

In the striped phosphor layer of FIG. 1, both the top and bottom of the partition 2 are exposed on both surfaces of the phosphor layer, but both or one of the top and bottom is buried in the phosphor layer. May be. However, it is desirable that the height of the partition wall be in the range of 1/3 to 1/1 of the thickness of the phosphor layer.

FIG. 2 is an exploded schematic perspective view of one embodiment of the radiation image conversion screen of the present invention. In FIG. 2, the radiation image conversion screen is composed of the four stripe phosphor layers shown in FIG. 1, and adjacent phosphor layers have two stripes so that the stripes intersect each other at an angle of 90 °. Are stacked so as to make one rotation. Further, it is desirable that the width of the partition wall and the phosphor-filled region of each phosphor layer be the same, and every other phosphor layer having the same stripe direction is positioned so that the stripes completely coincide and overlap. It is desirable to match.

FIG. 3 is an exploded schematic perspective view of another embodiment of the radiation image conversion screen of the present invention. In FIG. 3, the radiation image conversion screen is composed of the four stripe phosphor layers shown in FIG. 1, and adjacent phosphor layers have their stripes crossing each other at an angle of about 60 ° (particularly, 60 ° ± 1 °). Then, the layers are stacked so as to make one rotation with three layers. Also, it is desirable that the width of the partition wall and the phosphor-filled region of each phosphor layer be the same, and every other phosphor layer having the same stripe direction is positioned so that the stripes completely coincide and overlap. It is desirable to match.

FIG. 2 shows the radiation image conversion screen of the present invention.
By the structure shown in the above, the emitted light first generated in the first layer of the uppermost layer by irradiation of the radiation, although slightly diffused in the direction parallel to the stripe, but not diffused by the partition in the vertical direction, In the second layer, the direction in which diffusion is suppressed is reversed. The cell shape seen through the screen from above is a square, resulting in a direction (main scanning direction) close to the conventional two-dimensional cell structure, perpendicular to the topmost stripe.
A radiation image with balanced image quality can be given in both directions (sub-scanning direction) parallel to the image. Further, even when the radiation image conversion screen has the structure shown in FIG. 3, a radiation image having a balanced image quality in both the main and sub scanning directions can be provided without significantly reducing the aperture ratio. However, in this case, the cell shape seen through the screen from above is a triangle.

In the radiation image conversion screens shown in FIGS. 2 and 3, the number of laminated stripe phosphor layers is four, but the number of laminated phosphor layers is not limited to four, and is generally two to 100. It can be selected from the range according to its purpose. Preferably, the number of layers is in the range of 2 to 10 layers. By setting the number of layers within these ranges, the image quality can be balanced in both the main and sub scanning directions, and the screen can be manufactured by simple processing.

The thickness of each stripe phosphor layer is generally 1
0 μm to 1000 μm, preferably 50 μm
It is in the range from μm to 200 μm. Each layer may be the same thickness or different. When the thicknesses are different, it is desirable that the lower layer be thicker than the upper layer on the radiation irradiation side in view of image quality. When the thickness of each layer is smaller than the above range, it is very difficult to control the film thickness when slicing, and it is necessary to stack 100 or more sheets to impart sufficient radiation absorption to the completed screen. Processing becomes complicated. Conversely, if the thickness is larger than the above range, the light diffusion in the direction parallel to the stripe is too large, particularly in the uppermost layer, and as a result, the image quality balance in the main and sub directions is impaired. In order to increase the absorption efficiency for radiation such as X-rays, the thickness of the entire radiation image conversion screen is generally in the range of 50 μm to 1500 μm.

The radiation image conversion screen of the present invention can be manufactured as follows, for example, by the method of the present invention shown in FIGS. 4 to 7 of the accompanying drawings. The case where the phosphor-filled region is made of phosphor particles and a binder and the partition walls are made of low light-absorbing fine particles and a polymer substance will be described as an example.

First, a film A consisting essentially of a phosphor
To form There is no particular limitation on the phosphor, and CaWO
₄ , YTaO ₄ , YTaO ₄ : Nb, LaOBr: Tm,
BaSO ₄ : Pb, ZnS: Ag, BaSO ₄ : Eu, Y
TaO ₄ : Tm, BaFCl: Eu, BaF (Br,
I): Eu, Gd ₂ O ₂ S: Tb, Y ₂ O ₂ S: Tb, La
₂ O ₂ S: Tb, (Y, Gd) ₂ O ₂ S: Tb or (Y, G
d) Known phosphors such as ₂ O ₂ S: Tb and Tm can be used alone or in combination.

Examples of the binder include proteins such as gelatin, polysaccharides such as dextran, and natural high molecular substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethyl cellulose, vinylidene chloride and vinyl chloride. Copolymer,
Synthetic polymer materials such as polyalkyl (meth) acrylate, vinyl chloride / vinyl acetate copolymer, polyurethane, cellulose acetate butyrate, polyvinyl alcohol, linear polyester, and thermoplastic elastomer can be used. In addition, these binders may be cross-linked by a cross-linking agent.

The phosphor particles and the binder are added to a solvent, and the mixture is sufficiently mixed to prepare a coating solution. Examples of the solvent for preparing the coating liquid include methanol, ethanol, and n.
Lower alcohols such as propanol, n-butanol;
Hydrocarbons containing chlorine atoms such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters of lower alcohols with lower fatty acids such as methyl acetate, ethyl acetate and butyl acetate; dioxane, ethylene glycol monoethyl ether , Ethylene glycol monomethyl ether,
Ethers such as tetrahydrofuran; and mixtures thereof.

The mixing ratio between the binder and the phosphor in the coating solution varies depending on the desired characteristics of the radiation image conversion screen, the kind of the phosphor, and the like, but is generally 1: 1 to 1: 100 (weight ratio). And particularly preferably from the range of 1: 8 to 1:40 (weight ratio). Various additives such as a dispersing agent for improving the dispersibility of the phosphor and a plasticizer for improving the bonding force between the binder and the phosphor after formation are mixed in the coating liquid. You may. The coating liquid is applied to a temporary support such as a glass plate, a metal plate, or a plastic sheet using a coating machine and dried to obtain a large number of phosphor films A as shown in FIG. In order to further increase the density of the phosphor, the obtained phosphor film may be heated and compressed by calendering.

The phosphor film may be formed by sintering or vapor deposition (evaporation) of the phosphor on a substrate such as a metal plate without using a binder.

On the other hand, a film B for forming a partition is formed in the same manner as described above. Examples of the low light-absorbing fine particles include inorganic white fine particles such as aluminum oxide (alumina), titanium dioxide, yttrium oxide, zircon oxide, gadolinium oxide, tellurium oxide, lutetium oxide, and lead oxide. Further, fine particles of the above phosphor can also be used. Of these, alumina and yttrium oxide are particularly preferred. Generally, the particle diameter of the low light-absorbing fine particles is preferably in the range of 0.01 to 5.0 μm.

The polymer substance (binder resin) is not particularly limited, and can be arbitrarily selected from those usable as the binder of the phosphor film. In order to shorten the light scattering length of the partition, the ratio of the refractive index of the low light-absorbing fine particles to the refractive index of the polymer substance is set to 1.
It is desirable to be in the range of 1 to 3.0, and examples of such a preferable polymer include polyurethane, polyacryl, polyethylene, polystyrene and fluorine-based resin.

The above-mentioned low light-absorbing fine particles and the polymer substance are added to an organic solvent, and they are sufficiently mixed to prepare a coating solution for forming partition walls. The solvent for preparing the coating liquid can be arbitrarily selected from the solvents used for the above-mentioned coating liquid for forming the phosphor film. Further, if desired, the partition wall material dispersion may contain a phosphor for the purpose of increasing the amount of emitted light, or may contain a substance that absorbs emitted light for the purpose of improving the sharpness of an image. . The mixing ratio between the polymer substance and the low light-absorbing fine particles varies depending on the desired characteristics of the radiation image conversion screen, the type of the low light-absorbing fine particles, and the like.
To 1: 3 (weight ratio), and particularly preferably in the range of 1:20 to 1:10 (weight ratio). This coating solution for forming a partition wall is applied and dried to obtain a coating solution shown in FIG.
A large number of thin film B for forming a partition as shown in FIG.

Next, as shown in FIG. 5, a plurality of phosphor films A and partition wall forming films B are alternately laminated to form a laminate. As shown in FIG. 6, the obtained laminated body is heated while applying pressure to bring the adjacent films into close contact to form a laminated block.

Next, as shown in FIG. 7, the laminate block is sliced along the lamination plane, whereby the strips of the phosphor film A and the strips of the partition wall forming film B are alternately arranged. To obtain a plurality of striped phosphor films.
This stripe phosphor film constitutes a stripe phosphor layer as shown in FIG.

Next, the obtained plurality of striped phosphor films were placed such that the stripes of adjacent films were orthogonal to each other or approximately 60 ° (particularly, 60 ° ± 1 °).
゜) The three layers intersect at an angle and make one rotation,
Thermocompression bonding (see FIGS. 2 and 3). At this time, every other or every other film having the same stripe direction may be aligned so that the partition walls of the stripe and the partition walls overlap each other and the phosphor-filled region overlaps the phosphor-filled region. preferable.

The radiation image conversion screen manufactured as described above does not need to be provided with a support or a protective film. However, the radiation image conversion screen is used for convenience in transporting and handling the radiation image conversion screen and avoiding a change in characteristics. May be provided with a support and / or a protective film. Further, in order to increase the sensitivity, a light reflection layer may be provided on one side of the screen (when a support is provided, between the screen and the support).

The support is usually made of a resin material and has a thickness of 5 mm.
It is a sheet or film of 0 μm to 1 mm. The support may be transparent, or may be filled with a light-reflective material (eg, titanium dioxide particles, barium sulfate particles), or may be provided with voids.
Alternatively, the support may be filled with a light absorbing material (eg, carbon black). As such a resin material,
Various resin materials such as polyethylene terephthalate, polyethylene naphthalate, aramid resin, and polyimide resin can be used. If necessary, the support may be
It may be a sheet-like material other than a resin material sheet such as a metal sheet, a ceramic sheet, and a glass sheet. On the lower surface of the support (the surface in contact with the screen), an auxiliary functional layer such as a light absorbing layer, an adhesive layer, or a conductive layer may be provided. Is also good.

The protective film is formed by bonding a separately formed plastic film to the surface of the radiation image conversion screen using an adhesive, or applying a protective film material solution to the screen surface and drying the screen. Can be attached above. In the protective film, light scattering fine particles having a high refractive index such as titanium oxide may be added to improve the image quality of the radiation image, or various known protective films such as an antistatic agent may be added. An agent may be added. Regarding the resin material used to form the protective film,
Although there is no particular limitation, polyester resins such as polyethylene terephthalate and polyethylene naphthalate, cellulose ester derivatives such as cellulose triacetate, polyolefin resins, polyamide resins, aramid resins, and fluororesins are preferably used. The thickness of the protective film is usually 30 μm or less, preferably 1 μm to 15 μm.
m, more preferably 5 μm to 12 μm.

As the light reflecting layer, for example, a layer formed by dispersing and supporting a white pigment such as alumina, titanium dioxide or barium sulfate with a binder can be used.

Examples of the two-dimensional photodetector used in combination with the above-mentioned radiation image conversion screen include a photodiode, a phototransistor, a photoconductive element, and a charge transfer device (CCD). Particularly preferred is a combination in which a photodiode and a thin film transistor are stacked. Materials for the photodetector include amorphous silicon, single crystal silicon, cadmium telluride,
And copper indium diselenide. Further, the size of the pixel of the photodetector and the size of the phosphor-filled area of the radiation image conversion screen are preferably in the range of 1: 1 to 10: 1 in terms of surface area ratio.

The radiation image detecting apparatus according to the present invention can have a configuration as shown in FIG. 8, for example. FIG. 8 is a cross-sectional view schematically showing a typical example of the radiation image detecting apparatus of the present invention. In FIG. 8, the radiation image detecting apparatus includes a radiation image conversion screen 10, a two-dimensional photodetector 11, a substrate 12, and a housing 13. A two-dimensional photodetector 11 and a radiation image conversion screen 1 are sequentially placed on a substrate 12.
0 are stacked and the stack is placed in the housing 13. When the radiation image conversion screen is provided with a support or a light reflection layer on one side, the screen side is laminated so that the screen side is in contact with the photodetector, and irradiation of radiation is performed from the opposite support or light reflection layer side. Done.

Examples of the material of the substrate 12 include various resins such as polyethylene terephthalate, polyethylene naphthalate, aramid resin, and polyimide resin, metal, ceramic, and glass.

The casing 13 shields radiation and light such as X-rays in order to prevent the radiation image conversion screen and the two-dimensional photodetector from generating noise in response to radiation and light outside the detection target. It is made of a sex material, for example lead. However, only the screen-side surface of the housing is made to be radiolucent so that radiation transmitted through the subject or emitted from the subject enters the radiation image conversion screen.

[0048]

EXAMPLES Example 1 1) Gd ₂ O ₂ S: Tb phosphor particles and a thermoplastic high molecular weight polyester resin are dispersed in an organic solvent at a weight ratio of 5: 1 to obtain a phosphor dispersion liquid. Was. This phosphor dispersion liquid is applied to the surface of the temporary support having a peelable surface by a coating machine,
After drying, peel off the temporary support to obtain a thickness of about 100μ.
m of phosphor film A was obtained. The transmittance at the emission wavelength (545 nm) of the phosphor film A was measured, and the scattering length and the absorption length were calculated. As a result, the scattering length at the emission wavelength is 55 μm, the absorption length is 1000 μm or more,
It had a long scattering length and a long absorption length.

2) Yttrium oxide particles having an average particle diameter of 0.6 μm and a high molecular weight acrylic resin were dispersed in an organic solvent at a weight ratio of 15: 1 to prepare a dispersion. This dispersion is applied to a temporary support having a peelable surface using a coating machine, dried, and then peeled off from the temporary support to have a thickness of about 30.
A film B for forming a partition wall having a thickness of μm was obtained. The transmittance at the emission wavelength of the partition wall forming film B was measured, and the scattering length and the absorption length were calculated. As a result, the scattering length at the emission wavelength was 3.5 μm, the absorption length was 1000 μm or more, and the short scattering length and the long absorption Was long.

3) The phosphor film A and the partition wall forming film B are alternately laminated in a total of 360 layers to obtain a laminate, and the laminate is subjected to a pressure of about 1 kg / cm ^{2 and} a pressure of 100 kg / cm ^2.
The laminate was placed at a temperature of 1 ° C. for 1 hour to perform a heat compression bonding process, thereby forming a laminate block.

4) The laminate block was sliced at a thickness of 100 μm along the lamination cross section using a wide microtome to obtain a stripe phosphor film having a one-dimensional stripe structure in a planar direction (width of partition: About 3
0 μm, width of phosphor-filled area: about 100 μm).

5) The obtained striped phosphor film 3
Sheets and six sheets are laminated so that the stripes of adjacent films are orthogonal to each other, and are heat-pressed to form two types of phosphor layers having a one-dimensional stripe structure in which the stripes are alternately orthogonal to each other. Radiation image conversion screen (see FIG. 2, thickness: about 300 μm, about 600 μm)
m).

[Comparative Example 1] The laminated block obtained in 3) of Example 1 was sliced along a laminated section at a thickness of 320 μm and 580 μm using a wide microtome, thereby forming a one-dimensional stripe in the plane direction. Two types of radiation image conversion screens having a structure were obtained.

Comparative Example 2 Gd ₂ O ₂ S: Tb phosphor particles and a thermoplastic high molecular weight polyester resin were dispersed in an organic solvent at a weight ratio of 20: 1 to obtain a phosphor dispersion liquid. This phosphor dispersion liquid is applied to the surface of a temporary support having a releasable surface by an applicator, dried, and then peeled off from the temporary support to obtain two types of radiation image conversion screens without partition walls ( Thickness: about 3
00 μm, about 610 μm). The transmittance at the emission wavelength of the radiation image conversion screen was measured, and the scattering length and the absorption length were calculated. As a result, the scattering length at the emission wavelength was 14 μm and the absorption length was 1000 μm or more.

[Evaluation of Performance of Radiation Image Conversion Screen]
The radiation image conversion screens obtained in Example 1 and Comparative Examples 1 and 2 were adhered to the photodiode-side surface of a two-dimensional photodetector composed of a laminate of a photodiode and a thin film transistor made of amorphous silicon. To form a radiation image detecting apparatus (see FIG. 8). A tube voltage of 80 kVp is provided on the screen side of the radiation image detecting device.
X-rays of 80 mA (dose of 10 mR) were irradiated, and the intensity of the signal obtained from the photodetector was defined as the amount of light emission (relative value). Further, a CTF chart was placed on the surface of the screen, X-ray photography was performed in the same manner as described above, and the sharpness (CTF at 1 lp) was obtained from the obtained image data, thereby evaluating the image quality. At that time, each case where the CTF chart was placed in a direction (sub-scanning direction) parallel to a direction (main scanning direction) perpendicular to the first stripe of the screen was evaluated. Table 1 summarizes the obtained results.

[0056]

[Table 1] Table 1 ──────────────────────────────────── Screen thickness 1 lp CTF (%) (Μm) Main scanning Sub scanning ──────────────────────────────────── Example 1 300 69 63 91 600 52 48 162 {Comparative Example 1 320 73 36 95 580 54 28 169 Comparative Example 2 300 72 71 100 610 48 46 121

From the results shown in Table 1, the radiation image conversion screen of the present invention (Example 1) is different from the radiation image conversion screen having the partition walls only in one-dimensional direction (Comparative Example 1) in the main scanning direction. And the difference in sharpness in the sub-scanning direction was clearly small. And the screen of the present invention (Example 1)
The thickness of the light-emitting device increases greatly as the thickness increases, while the sharpness does not decrease so much. Therefore, the thick screen (600 μm) has a larger thickness than the conventional radiation image conversion screen having no partition walls (Comparative Example 2). The overall image quality was excellent.

[Example 2] In Example 1, the dispersion for forming a partition wall according to 2) of Example 1 was applied to the surface of the obtained radiation image conversion screen having a thickness of about 600 µm, and dried to obtain a thickness of about 100 µm. A radiation image conversion screen with a light reflecting layer was obtained in the same manner as in Example 1 except that the light reflecting layer was formed.

Example 3 Example 5) was the same as Example 1 except that three and six stripe phosphor films were laminated by rotating the film stripes at an angle of 60 °. Two types of radiation image conversion screens (see FIG. 3, thickness: about 300 μm, about 600 μm) in which phosphor layers having a one-dimensional stripe structure are stacked such that the stripes cross each other at an angle of 60 °.
m).

Example 4 In Example 4), the laminated phosphor block was sliced by using a wide microtome with the thickness varied in the range of 50 to 600 μm along the lamination section to obtain stripe phosphors having different thicknesses. After getting the film,
In Example 1-5), a phosphor layer having a one-dimensional stripe structure was formed in the same manner as in Example 1 except that stripes of adjacent films were stacked so as to be orthogonal to each other in a configuration as shown in Table 2 below. Obtained four types of radiation image conversion screens having the stripes alternately perpendicular to each other.

[0061]

[Table 2] Table 2 ──────────────────────────────────── Layer thickness (μm) First layer 2nd layer 3rd layer 4th layer 5th layer 6th layer ─────────────────────────────────── Example 1 100 100 100 100 100 100 100 Example 4 50 550----100 500----100 100 400---100 100 100 300--- ───────────────────────

As a result of measuring the CTF and the amount of stimulated emission of the radiation image conversion screens of Examples 2 to 4 in the same manner as described above, any of the radiation image conversion screens according to the present invention gives a radiation image of good image quality. Was.

[0063]

According to the present invention, a radiographic image conversion screen can be stably manufactured in a relatively simple processing step, and a high image quality with excellent image quality balance in both the main scanning direction and the sub-scanning direction. Can be provided. Therefore, when used in a radiation image forming method for medical diagnosis, the radiation image conversion screen of the present invention and the radiation image detecting device using the same are particularly advantageous.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view of a stripe phosphor layer according to the present invention.

FIG. 2 is an exploded schematic perspective view of one embodiment of the radiation image conversion screen of the present invention.

FIG. 3 is an exploded schematic perspective view of another embodiment of the radiation image conversion screen of the present invention.

FIG. 4 is a diagram for explaining a method of manufacturing a radiation image conversion screen by the method of the present invention, and is a diagram illustrating a process for forming a phosphor film A and a film B for forming a partition wall, respectively.

FIG. 5 is a view showing a step of forming a laminate from films A and B in FIG. 4;

FIG. 6 is a view showing a step of processing the laminate of FIG. 5 into a laminate block.

7 is a view showing a slicing step of obtaining a striped phosphor film having a striped structure in a planar direction according to the present invention from the laminate block of FIG.

FIG. 8 is a cross-sectional view schematically showing the radiation image detecting device of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stripe phosphor layer 2 Partition wall 3 Phosphor filling area 10 Radiation image conversion screen 11 Two-dimensional photodetector 12 Substrate 13 Housing

Claims (15)

[Claims] 1. A method for forming a radiation image by combining a radiation image conversion screen that converts radiation having radiation image information into light and a two-dimensional photodetector that detects light and converts it into an electric signal. A radiation image conversion screen, wherein at least two stripe phosphor layers each including a stripe-shaped partition wall subdivided in a one-dimensional direction along a planar direction and a phosphor-filled region partitioned by the partition wall are laminated. A radiation image conversion screen, wherein stripe-shaped partitions of adjacent phosphor layers are orthogonal to each other. 2. The thickness of each stripe phosphor layer is 10 μm.
The radiation image conversion screen according to claim 1, wherein the radiation image conversion screen is in a range of 1 to 1,000 µm. 3. The radiation image conversion screen according to claim 1, wherein the number of stacked stripe phosphor layers is in the range of 2 to 100 layers. 4. The radiation image conversion screen according to claim 1, wherein the thickness of the stripe phosphor layer is larger in the lower layer than in the upper layer. 5. The scattering length of each of the stripe phosphor layers with respect to emission light of the phosphor-filled region and the partition wall is 10 to 2 respectively.
The scattering length of the phosphor-filled region is longer than the scattering length of the partition wall, and the absorption length of the phosphor-filled region and the partition wall for the emitted light is 1000 μm. Claim 1
5. The radiation image conversion screen according to any one of Items 4 to 4. 6. The radiation image conversion screen according to claim 1, wherein a light reflection layer is provided on the surface. 7. A radiation image detecting apparatus comprising: the radiation image converting screen according to claim 1; and a two-dimensional photodetector disposed on one surface of the radiation image converting screen. apparatus. 8. A method for forming a radiation image by combining a radiation image conversion screen that converts radiation having radiation image information into light and a two-dimensional photodetector that detects light and converts it into an electric signal. A radiation image conversion screen, in which at least two stripe phosphor layers each including a stripe-shaped partition wall subdivided in a one-dimensional direction along a planar direction and a phosphor-filled region partitioned by the partition wall are laminated. A radiation image conversion screen, wherein stripe-shaped partitions of adjacent phosphor layers cross each other at an angle of about 60 °. 9. The thickness of each stripe phosphor layer is 10 μm.
The radiation image conversion screen according to claim 8, wherein the radiation image conversion screen is in a range of from 1 to 1000 µm. 10. The radiation image conversion screen according to claim 8, wherein the number of stacked stripe phosphor layers is in the range of 2 to 100 layers. 11. The radiation image conversion screen according to claim 8, wherein the thickness of the stripe phosphor layer is larger in the lower layer than in the upper layer. 12. The phosphor-filled area of each stripe phosphor layer and the scattering length of emitted light from the partition walls are 10 to 10 respectively.
The scattering length of the phosphor-filled region is longer than the scattering length of the partition walls, and the absorption length of the phosphor-filled region and the partition walls for the emitted light is 1000 μm. The radiation image conversion screen according to any one of claims 8 to 11, which is as described above. 13. The radiation image conversion screen according to claim 8, wherein a light reflection layer is provided on the surface. 14. A radiation image detection apparatus comprising: the radiation image conversion screen according to claim 8; and a two-dimensional photodetector disposed on one surface of the radiation image conversion screen. apparatus. 15. The method according to claim 1, comprising the following steps:
Method for producing a radiation image conversion screen described in 1): 1) a step of forming a plurality of phosphor films substantially composed of a phosphor and a plurality of films for forming partition walls; 2) a phosphor film and a film for forming partition walls; 3) alternately laminating a large number of pieces, and heat-pressing to form a laminate block; 3) slicing the laminate block along the lamination surface to form a phosphor film strip and a partition formation film strip. Manufacturing a plurality of striped phosphor films having a configuration in which the stripes are alternately arranged; and 4) intersecting the plurality of striped phosphor films such that stripes of adjacent films are orthogonal to each other or at an angle of about 60 °. And laminating and thermocompression bonding.