DE69400181T2 - Thermal transfer image recording method - Google Patents

Description

Field of the invention

This invention relates to a thermal transfer image recording method capable of providing high resolution recorded images.

Background of the invention

A thermal transfer recording method or image recording method by thermal transfer is usually a method in which a thermal transfer recording material or heat transfer recording material made of a base and a thermally fusible dye layer or a dye layer with a thermally sublimable dye thereon is placed opposite to an image receiving material and then a heat source controlled by an electric signal emitted from a thermal head or power supply head is brought into pressure contact from the side of the color layer, i.e. the recording material, so that an image can be transferred and then recorded. Thermal transfer recording has the advantage that it is noiseless, maintenance-free and inexpensive and enables color recording and digital recording in a simple manner. Thermal recording was therefore used in a wide variety of areas, e.g. in a variety of printers, recording devices, facsimile machines and computer terminals.

In the field of medicine and printing, on the other hand, there have recently been demands for a recording method with the ability to perform a so-called digital recording with high resolution, high recording speed and high image processing speed. However, in thermal transfer recording methods in which a conventional thermal head or current feed head was used as a heat source, an exothermic element could hardly have the ability to achieve high-density and high-resolution image recording because of the limits on the service life of the exothermic element of such a head.

To solve these problems, proposals have been made for a thermal recording technique using a laser beam as a heat source (see Japanese Patent Laid-Open Publications, hereinafter referred to as "JP-OPI Publications", Nos. 49-15437/1974, 49-17743/1974, 57-87399/1982 and 59-143659/1984). In a thermal recording technique using a laser beam as a heat source, the resolving power can be increased by reducing the size of the laser spot. However, when an image is recorded using a laser beam, the recording time cannot be shortened unless the dots of the recording medium are scanned at high speed. This is because it is common for recording to be carried out by scanning very small dots. In this case, it is disadvantageous to improve the recording speed in comparison with conducting floodlight exposure or using a line thermal head in general. It is also well known that the heating caused by light is relatively small in comparison with heating by means of an exothermic element, e.g. a thermal head. For this reason too, light/heat conversion type thermal recording using a laser beam and the like to improve the recording speed is disadvantageous in the current situation.

On the other hand, the JP-OPI publications describe Nos. 63-35 385/1988 and 63-35 387/1988 each use the following technique: a sublimable ink layer and a protective layer containing a thermoplastic resin as the main component are applied to a substrate, and the protective layer is removed image-wise by means of a laser beam. The surface of the protective layer is then brought into close contact with an image-receiving layer, and heat is applied from the side of the substrate containing the sublimable ink layer by means of a laser beam or thermal head. In this way, image information can be transferred thermally to an image-receiving layer. The advantages of this technique are that the laser beam emission is as low as possible, a protective layer containing a thermoplastic resin as the main component is melted, and holes formed by the melted areas are drawn into the surrounding areas by the surface tension of the melted thermoplastic resin.

JP-OPI Publication No. 4-201 486/1992 and EP-A-489 972/1992 each describe a technique in which a vacuum-deposited metal layer is applied to a dye barrier layer. This is equivalent to the protective layer mentioned.

With these techniques, there are relatively few limits to the heating required for image transfer, since the dye transfer itself takes place in a different way compared to a system in which the dye is transferred by heat from the laser beam mentioned. However, the patents mentioned in particular do not provide any clear information regarding the exposure intensity. In addition, there are no indications as to which layer, i.e. the color layer or the protective layer, can serve as a layer with the ability to absorb light rays.

Furthermore, in case of using a vapor-deposited Metal layer as a protective layer, the metal layer is vapor-deposited in a vacuum onto the dye barrier layer. The disadvantage of the vapor-deposition process is that the dye contained in the dye layer is sublimated during vapor-deposition.

However, US-A-5 156 938 and 5 171 650 describe the following technique as an alternative technique: By irradiating a layer of color or a layer lying between a layer carrier and a layer of color with a laser beam of extremely high power density, an explosion is caused. The color layer is blown onto an image receiving medium by the force of the explosion, so that an image can be transferred onto the image receiving material.

Summary of the invention

An object of the present invention is to provide an image recording method and a recording material for carrying out the same, whereby an image of high resolution can be recorded in a relatively simple manner and the process can be simplified.

The inventors of the present invention have developed the following technique: A dye barrier layer is exploded by irradiating it with (exposure) light of high power density in the order of 100,000 W/cm² or more in such a way that it is removed. The dye can then be transferred to an image receiving layer through the very small holes formed by applying heat or pressure. The inventors of the present invention have also found a component effective for such a dye barrier layer, so that the invention could ultimately be completed. More specifically, this problem underlying the invention can be solved as follows:

The thermal transfer image recording method according to the invention comprises the following steps:

(1) Image-correct exposure of a recording material comprising a support having thereon a colorant layer containing a colorant and a colorant barrier layer containing a substance absorbing in the infrared range as defined in claim 1 on the colorant layer with high intensity light for image-accurate removal of the colorant barrier layer;

(2) bringing the surface of the dye barrier layer into contact with the surface of an image-receiving layer of an image-receiving material and

(3) transferring the colorant of the colorant layer through the removed portion of the colorant barrier layer to the image-receiving layer by the action of heat or pressure.

The effects aimed at by the invention can be even more effectively achieved if, in a preferred embodiment of the thermal transfer recording method described, the following factors are met: the high-intensity exposure is carried out at a power density of not less than 100,000 W/cm²; the exposure speed is not slower than 1 ms⊃min;¹; the high-intensity exposure is carried out by means of a laser beam and the high-intensity exposure is carried out from the side of the dye barrier layer.

Short description of the drawing

Fig. 1 typically illustrates the chronologically successive stages of a recording process using a thermal transfer type recording material according to the invention. In the figure:

1 a substrate for a recording material;

2 a colorant layer;

3 a dye barrier layer;

4 a layer support for an image receiving material and

5 an image receiving layer.

Detailed description of the invention

As can be seen from Fig. 1, a thermal transfer recording material according to the invention (hereinafter sometimes simply referred to as "recording material") consists essentially of a layer support 1 and - in the order given - a colorant layer 2 and a colorant barrier layer 3 laminated thereon.

There are no particular limits on the layer supports, provided they are extremely dimensionally stable and resistant to a heat source, e.g. a laser. Usable layer supports include thin sheets of paper, such as capacitor paper and glassine paper, as well as heat-resistant plastic films, e.g. those made of polyethylene terephthalate, polyamide, polycarbonate, polysulfone, polyvinyl alcohol, cellophane and polystyrene.

The substrate thickness should typically be 2 to 200, preferably 25 to 100 µm.

The colorant layer contains a binder in addition to the colorant. If necessary, it can also contain any other component, e.g. an additive.

According to the invention, the colorant to be transferred to an image-receiving layer should preferably be a heat-diffusible dye. However, without being limited to this, the colorant can also consist of other dyes or pigments. For the transfer of the colorant, a so-called "heat-fusible transfer system" can also be used, in which a colorant and its binder component are transferred together.

There are no special restrictions on heat-diffusible dyes, provided they are thermally diffusible or sublimable. Thermally diffusible dyes include or heat-diffusible blue-green dyes include, for example, those from JP-OPI Publications Nos. 59-78 895/1984, 59-227 948/1984, 60-24 966/1985, 60-53 563/1985, 60-130 735/1985, 60-131 292/1985, 61-19 936/1986, 61-22 993/1986, 61-31 292/1986, 61-31 467/1986, 61- 35 994/1986, 61-49 893/1986, 61-148 269/1986, 62-191 191/1987, 63-91 287/1988, 63-91 288/1988 and 63-290 793/1988 known naphthoquinone, anthraquinone and azomethine dyes.

The thermally diffusible or heat-diffusible magenta dyes include, for example, the anthraquinone, azo and azomethine dyes known from JP-OPI publications Nos. 59-78 896/1984, 60-30 392/1985, 60-30 394/1985, 60-253 595/1985, 61-262 190/1986, 63-5 992/1988, 63-205 288/1988, 64-159/1989 and 64-63 194/1989.

The thermally diffusible or heat-diffusible yellow dyes include, for example, the methine, azo, quinophthalone and anthraisothiazole dyes known from JP-OPI publications Nos. 59-78 896/1984, 60-27 594/1985, 60-31 560/1985, 60-53 565/1985, 61-12 394/1986 and 63-122 594/1988.

Suitable for use as thermally diffusible dyes are azomethine dyes obtained by coupling a compound with an open- or closed-chain active methylene group with an oxidizing agent of a p-phenylenediamine or p-aminophenol derivative and indoaniline dyes obtained by reacting a phenol or naphthol derivative with an oxidation product of a p-phenylenediamine or p-aminophenol derivative.

Of these dyes, those with the ability to form a chelate compound with a metal ion are preferred.

Dyes with the ability to form a chelate compound are dyes which, after a chelation reaction, with a metal ion to form a chelate compound. In particular, these are dyes with at least two or more ligands or a group with the ability to form a chelate bond with a metal ion in their molecules, these ligands being in such a position that after the formation of a coordinate bond between the (respective) ligands and a metal ion, a cyclic structure, e.g. a 4-, 5-, 6- or 7-membered ring, can be formed. The groups mentioned with the respective ability to coordinate with a metal ion, ie the chelate-forming groups or ligands, are, for example, groups such as -OH, -COOH, -NH₂, -NH-, -N=, -CO-, -O-, -NHCO-, -S-, -SO-, -P=, -NO or -N=N-.

Preferred dyes having the ability to form a chelate compound are those of the following formula (I)

where:

X₁ represents a group of 5 to 7 atoms necessary to complete an aromatic carbon ring or an aromatic heterocyclic ring, wherein at least one atom adjacent to the carbon atom bonded to the nitrogen atom of the azo bond is a carbon atom having a substituent capable of forming a chelate bond with a metal ion or a nitrogen atom;

X₂ is a group of 5 to 7 atoms necessary to complete an aromatic carbon ring or an aromatic heterocyclic ring and

G is a hydrogen atom or a group to form a Chelating group with a metal ion capable of binding.

The dyes of the above formula (I) include those of the following formulae (2) to (8).

where:

Z₁ is a group of atoms which together with the two carbon atoms of the benzene ring and Q is necessary to form a 5- or 6-membered heterocyclic ring;

Q -O-, -S-, -N= or -N(R)- with R being a hydrogen atom or an alkyl group;

R₁ and R₂ each represent a hydrogen atom or a monovalent group and

su and w are each an integer from 1 to 5.

Examples of dyes of formula (2) are:

where:

L -CON(R')-, -COO- or SO₂ with R' being an alkyl group or a hydrogen atom;

X₃ is a nitrogen-containing heterocyclic ring or an aromatic carbon ring, wherein the atom adjacent to the carbon atom bonded to the azo group is a nitrogen atom or a carbon atom having a group having the ability to form a chelate bond with a metal ion, and

R₃ is a hydrogen atom, an aliphatic group or a heterocyclic group.

Examples of dyes of the above formula (3) are:

where:

R₄ is a substituent;

n is an integer from 0 to 3, where the majority of the R₄ radicals can be the same or different when n = 2 or 3, and

R�5 is a hydroxyl group or an amino group.

Examples of dyes of formula (4) are:

where:

R6 and R7 each represent a substituent of the benzene ring or the isoquinoline ring;

p and q are each an integer from 0 to 4, where in the case that p and q are each 2 or a larger number, the majority of the radicals R₆ and R₇ can each be the same or different and can be linked together to form a ring;

R�8 is a hydrogen atom, a halogen atom or a monovalent substituent and

G is a group with the ability to form a chelate bond with a metal ion.

Examples of dyes of formula (5) are:

where:

R�9 is an alkyl group or a cycloalkyl group, and

X₄ represents a group of atoms which, together with the carbon atom bonded to the azo group and the nitrogen atom bonded to the carbon atoms, is necessary to form a 5- or 6-membered nitrogen-containing heterocyclic ring, which heterocyclic ring may have a substituent capable of forming a 9- or 10-membered condensed ring.

Examples of dyes of formula (6) are:

where:

R₁₀ and R₁₁ are a hydrogen atom or a substituent, and

X₅ represents a group of atoms which, together with the carbon atom bonded to the azo group and the carbon group bonded to the hydroxyl group, is necessary to form a 6-membered nitrogen-containing heterocyclic ring, which heterocyclic ring may have a substituent capable of forming a condensed ring.

Examples of dyes of formula (7) are:

where:

R₁₂ is an alkyl group and

R₁₃ is a hydrogen atom or a substituent.

Examples of dyes of formula (8) are:

In addition to the dyes mentioned, the following thermally diffusible or heat-diffusible dyes can also be used according to the invention:

The thermally diffusible dyes can be used in an amount in the range of usually 0.1 to 20, preferably 0.2 to 5 g per m² of the layer support used. In the colorant layer, the content of the thermally diffusible dye is usually 5 to 70, preferably 30 to 70 wt.%.

All resins known in the field of thermal transfer recording are suitable as binders for the colorant layer. The binders used according to the invention preferably consist (but are not limited to) of the following resins of the polyvinyl acetal and cellulose type.

The polyvinyl acetal resins include a wide variety of types of compounds depending on the degree of acetalization and the content of acetyl groups and residual groups, e.g. hydroxyl groups. Typical examples of these can be polyvinyl acetoacetal and polyvinyl butyral.

The cellulose resins are, for example, nitrocellulose, ethylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, cellulose acetate and cellulose butyrate. Of these, nitrocellulose particularly preferred.

In addition to the resins mentioned, other resins known in the field of thermal transfer recording, e.g. acrylic and methacrylic resins, polycarbonate, polyvinyl alcohol, polyvinyl formal, polyvinyl ether, polyvinyl pyrrolidone, polystyrene, polystyrene copolymers and ionomer resins, can also be used.

The above-mentioned binders may be suitably selected for use alone or in combination of several. Preferably, the binder content is usually 30 to 70% by weight of the entire colorant layer. In the colorant layer, the weight ratio of binder to thermally diffusible dye is suitably 1/10 to 10/1, more preferably 2/8 to 8/2.

The colorant layer can have any thickness, provided that it can be peeled off from an image-receiving material in a controlled manner and the colorant contained therein can be transferred in a controlled manner by the action of thermal energy. The thickness of the colorant layer should suitably be in the range of 0.2 to 10, preferably 0.4 to 5 µm.

According to the invention, additives such as fluororesins, surfactants, waxes, higher aliphatic acids, higher aliphatic alcohols, higher aliphatic ethers, fine metal powders, silica gel, carbon black, organic fillers, inorganic fillers and curing agents reactive with a binder component such as radiation-active compounds such as isocyanate, acrylic acid and epoxy, and modified silicone resins can be added to the colorant layer. For the purpose of promoting transfer, a heat-meltable substance such as a higher aliphatic ester known from JP-OPI Publication No. 59-106997/1984 can also be used.

The amount of additives to be incorporated cannot be determined indiscriminately due to the different types of additives and the different additive purposes. Usually they are all preferably added in an amount of not more than 50% by weight of the binder used.

Typical examples of the modified silicone resins mentioned are polyester-modified silicone resins, acrylic-modified silicone resins, urethane-modified silicone resins, cellulose-modified silicone resins, alkyd-modified silicone resins and epoxy-modified silicone resins. These can be used alone or in combination.

The modified silicone resins mentioned can be added in an amount of usually 0.01 to 10, preferably 0.01 to 2.0 wt.%, based on the weight of the colorant layer.

The colorant layer can be formed as follows. The above thermally diffusible dye, the binder and, if necessary, the additive (as the case may be) are each dissolved or dispersed in a solvent to prepare a coating solution. The obtained coating solution is then applied to a substrate and dried.

The binders can not only be dissolved alone or in a mixture in a solvent, they can also be used in the form of a latex dispersion.

Examples of solvents include water, alcohols such as ethanol, propanol and butanol, cellosolve, esters such as ethyl acetate and butyl acetate, aromatic compounds such as toluene, xylene and chlorobenzene, ketones such as acetone and methyl ethyl ketone, ethers such as tetrahydrofuran and dioxane, and chlorinated solvents such as chloroform and trichloroethylene. These solvents can be used alone or in combination.

The coating solution can be applied by a conventional, known application method, e.g. a step-by-step application method using a gravure roller, an extrusion coating method, a coating method using a wire rail and a roller coating process.

The barrier layer must at least be given the property that it cannot be penetrated by the colorant or thermally diffusible dye of a colorant layer even under the action of heat or pressure. In addition, it must also be able to absorb any high intensity light used for exposure. In order to provide it with these properties, the colorant barrier layer should preferably contain a resin whose main component is (1) a water-soluble resin, (2) a resin with an ionic bond or (3) a resin with a Tg value (or glass transition temperature) not less than 120ºC, preferably not less than 150ºC and preferably not less than 200ºC.

The water-soluble resin usable in the present invention is a resin having the ability to dissolve in water at a concentration of not less than 1% by weight, preferably not less than 2% by weight. The solubility of the resin specified is not limited to that at ordinary temperature. The temperature for dissolving the resin can be changed as required. A resin soluble in water at a concentration of not less than 1% by weight at a temperature of 0 to 100°C can be used.

Examples of the water-soluble resins are gelatin, polyvinyl alcohol, water-soluble polyvinyl formal, water-soluble polyvinyl acetal, water-soluble polyvinyl butyral, polyvinylpyrrolidone, water-soluble polyesters, water-soluble nylon, polyacrylic acid, water-soluble polyurethane, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose and carboxyl cellulose. Copolymers of the monomer components constituting the resins mentioned above may also be used. At the time of preparing the coating solution, gelatin should preferably be heated at a temperature of not lower than 40ºC and methyl cellulose at a temperature of not higher than 10ºC. be dissolved.

The term "resin with an ionic bond" means a resin with an ionically bonded group, i.e. an acidic or basic group, in the main or side chain of a macromolecule.

Examples of acidic groups are -COO⊃min;, -SO₃⊃min; and -PO₃⊃min;. Examples of basic groups are -NH₂, - - and -N=.

Resins each having an ionic bond include, for example, those each having an acidic group and a basic group and those each having an acidic group with a divalent metal ion and crosslinking structure via the metal ion. Preferably, the resin having an ionic bond contemplated by the present invention should have at least one or more of the ionically bonded groups per 100 repeating monomer units. However, a resin which does not always have such a repeating monomer unit as mentioned above can be suitably used.

Resins having an ionic bond are, for example, resins containing styrene substituted with a sulfo group, acrylic acid, methacrylic acid, phthalic anhydride and the like, each with Na+, K+, Ca2+, NH4+ and the like as a counter ion, and ionomer resins and the like. Furthermore, gelatin and casein can also preferably be used.

Resins having a Tg value of not less than 120°C are, for example, polyvinyl chloride, polystyrene, polyaryl methacrylate, polybenzyl methacrylate, polycarbonate, nylon, polyphenylene oxide, polyphenylene sulfide, gelatin and polyparabanic acid. Another preferably used resin having a Tg value of not less than 120°C is a copolymer of a monomer component of styrene, vinyl chloride, methyl methacrylate, aryl methacrylate, acrylonitrile, ethylene oxide, benzyl methacrylate or cyclohexyl methacrylate. Furthermore, a thermosetting resin without any glass transition temperature is preferably used.

Of these resins usable for the dye barrier layer, the water-soluble resins are preferred. Particularly preferred water-soluble resins are gelatin, polyvinylpyrrolidone, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and carboxylcellulose. These water-soluble resins are thoroughly mixed with the water-soluble infrared-absorbing dyes mentioned later.

The proportion of the resin component in the colorant barrier layer is preferably in the range of 50 to 99% by weight of the colorant barrier layer. Among the resin components, the proportion of the above-mentioned resin components (1), (2) or (3) to the total resin component is generally not less than 50%, preferably not less than 70%, and most preferably not less than 90% by weight based on the total weight of the barrier layer.

The colorant barrier layer contains an infrared absorbing substance for absorbing high intensity light used for exposure and converting the absorbed light into heat. The infrared absorbing substances are preferably those that absorb infrared radiation of a wavelength of not shorter than 650 nm.

Suitable infrared-absorbing dyes are readily available dyes, provided that they can only absorb infrared radiation of not less than 700 nm. However, for an effective implementation of the invention, a dye with a molar extinction coefficient of not less than 50,000 and preferably not less than 100,000 in a wavelength range of the strongest absorption between 700 nm and 1200 nm should preferably be used.

Infrared-absorbing dyes that can be used according to the invention should preferably be well compatible with the binder for the dye barrier layer provided according to the invention. Furthermore, the inventive The infrared absorbing dyes which can be used are preferably dissolved in an amount of not less than 0.1% and preferably not less than 1% in at least water or an organic solvent. However, this is not intended to exclude infrared absorbing dyes which can be mixed with a binder for a dye barrier layer by dispersing them in at least water or an organic solvent.

Preferably, the infrared-absorbing dyes usable in the invention should also have the additional property that they are easily decomposable by the irradiation heat of a laser beam. For example, if the ambient temperature is increased under a nitrogen stream at a rate of 10°C/min, the temperature causing a 10% weight reduction should preferably not be higher than 500°C, preferably not higher than 400°C and especially not higher than 350°C. However, the heat decomposition properties mentioned are not essential for the success of the invention.

Suitable infrared-absorbing dyes are the infrared-absorbing dyes and carbon black known from JP application No. 4-334 584/1992, p. 7. Examples that can be used are the near infrared absorbing dyes disclosed in "Kinou Zairyo" (Functional Substances), June 1990 issue, pp. 64-68, the functional dyes for optical recording disclosed in "Shikizai" (Colorants), vol. 61 (1988), pp. 218-223, cyanine dyes, squarylium dyes, azulenium dyes, phthalocyanine dyes, naphthalocyanine dyes, anthraquinone dyes, dithiol metal complex salt dyes, indoaniline metal complex dyes, intermolecular CT complex dyes, transition metal chelate dyes and aluminum diimmonium dyes.

Preferably used infrared absorbing materials according to the invention Dyes for converting light into heat are those of the following formulae (I) to (XI) or (XII). Of the infrared-absorbing dyes of the formulae (I) to (XI) or (XII), the water-soluble ones are preferred. The water-soluble, infrared-absorbing dyes preferred according to the invention are those each having an acidic group, e.g. a sulfo, carboxyl or phosphono group, with those having a sulfo group being particularly preferred.

where:

Z₁ and Z₂ each independently represent a group of atoms necessary to form a substituted or unsubstituted pyridine ring, a substituted or unsubstituted quinoline ring or a substituted or unsubstituted benzene ring or a substituted or unsubstituted naphthalene ring, where Z₁ and Z₂ may comprise a =N⁺- or -N(R₆)- bond when they are a pyridine or quinoline ring;

Z₃ and Z₄ each independently represent a group of atoms necessary to form a substituted or unsubstituted pyridine ring or a substituted or unsubstituted quinoline ring, wherein Z₃ and Z₄ may comprise a = N⁺- or -N(R₆)- bond; Y₁ and Y₂ each independently represent a dialkyl-substituted carbon atom, a vinylene group, an oxygen atom, a sulfur atom, a selenium atom or a nitrogen atom bonded to a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group;

R₁ and R₆ each independently represents a substituted or unsubstituted alkyl group;

R₂, R₄ and R₅ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group, where R₂ may be linked to R₄ to form a ring;

R₃ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group or a nitrogen atom bonded to an alkyl group or an aryl group; wherein at least one of the groups represented by Z₁ to Z₄ and R₁ to R₆ has a sulfo, carboxyl or phosphono group;

X⊃min; is an anion;

m = 0 or 1 and

n = 1 or 2, where in the case that an intramolecular salt is formed, n = 1.

Of the dyes of the above formula (I), those in which at least one of the groups represented by R₁ to R₆ contains a sulfo, carboxyl or phosphono group, in particular a sulfo group, are preferred.

In the formula (II), Y₃ and Y₄ have the same meaning as Y₁ and Y₂ in the above formula (I). Z₃ and Z₄ have the same meaning as Z₁ and Z₂ in the formula (I). R₈, R₁₀, R₁₄ and R₁₆ independently represent a substituted or unsubstituted alkyl group, a halogen atom or a hydrogen atom. R₈ and R₁₀ and R₁₄ and R₁₆ may be may each be bonded to each other to form a ring. R�9;, R₁₁, R₁₂, R₁₃ and R₁₅ each independently represents a substituted or unsubstituted alkyl group, a halogen atom or a hydrogen atom. R₇ and R₁₇ each independently represents a substituted or unsubstituted alkyl group or a hydrogen atom. X⁻, m and n each have the same meaning as X⁻, m and n in formula (I). Of the dyes of the above formula, those in which at least one of the groups represented by R₇ to R₁₇ has a sulfo, carboxyl or phosphono group are preferred. Particularly preferred are those having a sulfo group.

In the formula (III), R 181 , R 19 and R 20 each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group, -N(R 23 )(R 24 ), =N + (R 23 )(R 24 ) or a sulfo group, wherein R 23 and R 24 independently represent a substituted or unsubstituted alkyl group. Y represents a carbon atom or a nitrogen atom. R 21 and R 22 independently represent a hydrogen atom or a substituted or unsubstituted alkyl group. X represents an anion. m = 0 to 5 and n = 1 or 2. Of the dyes of the formula (III), those in which at least one of the groups represented by R₁₈ to R₂₄ has a sulfo, carboxyl or phosphono group, in particular a sulfo group, are preferred.

In the formula (IV) given, R₂₅, R₂₆, R₂₇ and R₂₈ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group. Of the dyes of the formula (IV), those in which at least one of the groups represented by R₂₅ to R₂₈ contains a sulfo, carboxyl or phosphono group, especially a sulfo group, are preferred.

In the formula (V) given, R₂₉ and R₃₀ each independently represent a substituted or unsubstituted alkyl group. R₃₁ and R₃₂ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group. Of the dyes of the formula (V), those in which at least one of the groups represented by R₂₉ and R₃₀ contains a sulfo, carboxyl or phosphono group, in particular a sulfo group, are preferred. Furthermore, R₃₁ and R₃₂ can be substituted by a sulfo, carboxyl or phosphono group.

In formula (VI), R₃₃, R₃₄ and R₃₅ each independently represents a hydrogen atom or a substituted or unsubstituted alkyl group. X⁻ represents an anion. Of the dyes of formula (VI), those in which at least one of the groups represented by R₃₃ to R₃₅ contains a sulfo, carboxyl or phosphono group, in particular a sulfo group, are preferred.

In the formula (VII), R₃₆ and R₃₇ each independently represent a hydrogen atom, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. R' and R" each independently represent a hydrogen atom, a substituted or unsubstituted amino group or a substituted or unsubstituted alkyl group. The substituted alkyl groups represented by R₃₆ and R₃₇ are those which are substituted by a sulfo, carboxyl or phosphono group.

In formula (VIII), R₃₈ represents a hydrogen atom, a substituted or unsubstituted amino group, a substituted or unsubstituted amido group or a substituted or unsubstituted alkyl group. R₃₉ and R₄₀ each independently represent a hydrogen atom or a substituted or unsubstituted alkyl group. R₄₁ represents a hydrogen atom, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. M represents a metal atom. X⁻ represents an anion. As the substituted alkyl groups represented by R₃₈ to R₄₁, those substituted with a sulfo group, carboxyl group or phosphono group are preferred. As the metal M, Cu and Ni are preferred.

In formula (IX), R₄₂ represents a hydrogen atom or a substituted or unsubstituted alkyl group. R₄₃ represents a hydrogen atom, an amido group, a nitro group, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. R₄₄ represents a hydrogen atom, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. As the substituted alkyl groups represented by R₄₂ to R₄₄, alkyl groups substituted by a sulfo group, a carboxyl group or a phosphono group are preferred.

In the formula (X), R₄₄ and R₄₅ each independently represents a hydrogen atom, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. R₄₆, R₄₇, R₄₈ and R₄₇ each independently represents the same or different alkyl group. n = 0 to 4. As the substituted alkyl groups represented by R₄₄ and R₄₅, those substituted with a sulfo group, a carboxyl group or a phosphono group are preferred.

In formula (XI), R₅₁ and R₅₂ independently represent a hydrogen atom, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. M represents a divalent or trivalent metal atom. n = 2 or 3. As the substituted alkyl groups represented by R₅₁ and R₅₂, those substituted by a sulfo, carboxyl or phosphono group are preferred.

In formula (XII), R₅₃, R₅₄, R₅₅ and R₅₆ independently represent a hydrogen atom, a sulfo group, a carboxyl group, a phosphono group or a substituted or unsubstituted alkyl group. M represents a divalent metal atom. Preferred substituents of the alkyl groups represented by R₅₃ to R₅₆ are each a sulfo, carboxyl or phosphono group. Of the infrared absorbing dyes, the cyanine dyes of the formulas (I) or (II), the anthraquinone dyes of the formula (VII) and the chelate dyes of the formulas (VIII), (X), (XI) or (XII) are preferred. Cyanine dyes of the formulas (I) or (II) each with one sulfo group.

Of these infrared-absorbing dyes, the cyanine dyes of the formulas (I) or (II), the anthraquinone dyes of the formula (VII) and the chelate dyes of the formulas (VIII), (X), (XI) or (XII) are preferred. Cyanine dyes of the formulas (I) or (II) each with one sulfo group are particularly preferred.

Examples of water-soluble infrared absorbing dyes of the formulas (I) to (XI) or (XII) are:

Dyes of formulas (I) to (XII) without sulfo, carboxyl or phosphono groups can also be used.

When the colorant barrier layer contains a water-insoluble resin, the infrared absorbing dyes disclosed in JP-OPI publications 62-12345 (1987) and 3-146565 (1991) can be used.

When the wavelength of the light used for exposure is in the infrared range, the light-absorbing substance should preferably contain the said infrared-absorbing dyes in an amount in the range of 1 to 50% by weight in the dye barrier layer. If the infrared-absorbing substance does not impair the barrier function of the said infrared-absorbing dye of the dye barrier layer, the near infrared-absorbing dye can also be added in a larger amount.

In addition, the dye barrier layer mentioned can, if necessary, also contain additives, e.g. wetting agents to improve the applicability, conductive compounds as an antistatic agent and release agent to prevent blockage, as well as roughening agents.

The thickness of the dye barrier layer should be as thin as possible, provided that the barrier function is not impaired. More precisely, the thickness of the dye barrier layer should be in the range of 0.1 to 2.0, preferably 0.1 to 1.0 µm. However, the layer thickness is not limited to the specified ranges, since removal is also possible with a greater layer thickness if the intensity of the light used for exposure is satisfactorily high.

If necessary, the dye barrier layer can be formed in multiple layers, whereby the functions are separated. The functions to be separated are, for example, dye barrier property, conductivity, light absorption capacity and blocking resistance. These functions can be given to a plurality of layers separately.

The dye barrier layer can be applied in the same way as the dye layer described above.

According to the invention, if necessary, other layers can also be provided in addition to the colorant layer and the colorant barrier layer. For example, an underlayer can be inserted between the support and the colorant layer to improve adhesion and the like. An intermediate layer with a heat insulating or adhesive effect can be inserted between the colorant layer and the colorant barrier layer. Furthermore, a backing layer can be provided on the back of the support, i.e. the side opposite the colorant layer, in order to impart running stability, heat resistance and antistatic properties (to the recording material). The said backing layer preferably has a layer thickness in the range of 0.1 to 1 µm.

Furthermore, the recording material can be provided with a series of perforations, a detection mark for locating the positions of various areas of different color tones, and the like to enable convenient handling.

In the following, an image receiving material that can be used together with the recording material according to the invention is described in detail.

An image receiving material consists of a layer carrier and an image receiving layer. An image receiving material can, however, also consist only of a self-supporting image receiving layer.

Suitable substrates are, for example, those made of the following materials: paper, laminated paper, artificial paper, e.g. that made of polypropylene and polystyrene, or that made of mixed materials laminated to paper or a plastic film, that made of a white or transparent polyethylene terephthalate film, that made of a white or transparent polyvinyl chloride film and that made of Polyolefin laminated paper. The thickness of the substrate should normally be in the range of 20 to 300 and preferably 30 to 200 µm.

The image receiving layer consists of a binder for the image receiving layer and a wide variety of additives. Binders for the image receiving layer are, for example, polyvinyl chloride resins, copolymer resins made of vinyl chloride and another monomer, such as alkyl vinyl ether and vinyl acetate, polyester resins, polyacrylates, polyvinylpyrrolidone, polycarbonate, cellulose triacetate, styrene acrylate resins, vinyl toluene acrylate resins, polyurethane resins, polyamide resins, urea resins, polycaprolactone resins, styrene/maleic anhydride resins and polyacrylonitrile resins.

The resins mentioned can be freshly synthesized. However, commercially available resins can also be used. With regard to the physical properties, resins with a Tg value in the range of -20 to 15,000 and preferably 30 to 120°C are always used as binders for the image-receiving layers. Furthermore, resins with a weight-average molecular weight in the range of 2,000 to 100,000 are also preferred.

When forming an image-receiving layer, the various resins mentioned can also be crosslinked or cured by utilizing their reactive sites (if there is no reactive site, reactive sites are created) and then by irradiation, exposure to heat, exposure to moisture, with the aid of a catalyst, etc. If this is the case, epoxy and acrylic monomers and a crosslinking agent, e.g. isocyanate, can be used as radiation-active monomers.

Preferably, the image-receiving layer contains a metal ion-containing compound as a metal supplier for forming a chelate compound with a diffusible dye transferred from an image recording material. Suitable metal ion-containing compounds are all organic and inorganic compounds each with a metal ion bound to it by ionic bonding or coordination bonding. With regard to solubility and convenient handling, preference is given to salts or complexes of low molecular weight organic compounds - but this is not limited to them.

The metals mentioned are monovalent or polyvalent metals from groups I to VIII of the periodic table. Of these, Al, Co, Cu, Fe, Mg, Mn, Mo, Ni, Sn, Ti and Zn, in particular Cu, Cr, Co and Zn, are preferred. Examples of suitable metal ion-containing compounds are the salts of Ni²⁺, Cu²⁺, Cr²⁺, Co²⁺ or Zn²⁺ with an aliphatic acid, such as acetic acid and stearic acid, and the salts of these metal ions with an aromatic carboxylic acid, such as benzoic and salicylic acid.

Furthermore, complexes of the following formula C-1 are particularly preferred.

[M(Q₁)l(Q₂)m(Q₃)n]P+(Y⊃min;)P (C-1)

In the formula, M represents a metal ion, preferably Ni²⁺, Cu²⁺, Cr²⁺, Co²⁺ or Zn²⁺ and Q₁, Q₂ and Q₃, which may be the same or different, each independently represent a ligand compound capable of forming a coordinate bond with a same or different metal ion M. The above ligand compound represented by Q₁ to Q₃ may be selected from the ligand compounds described in "Chelate Chemistry (5)", pp. 1-372, Konando 1975. Y represents an anion, preferably an organic anion such as a tetraphenylborane anion and an alkylbenzenesulfonate anion. 1 = 1, 2 or 3. m = 1, 2 or 0 and n = 1 or 0. These numbers correspond to the number of ligands of the compounds represented by Q₁, Q₂ and Q₃ or to the coordination number, ie, for example, coordination number 4 or coordination number 6, of the complex. P = 0, 1 or 2. When the ligand compound represented by Q is an anionic compound and the cation of the metal ion M is neutralized by the anion of the compound Q, then P is 0. Preferably usable anionic compounds are those of the following formula C-2.

where:

R₅₇ and R₅₇, which may be the same or different, each represent a hydrogen atom, an alkyl group or an aryl group and

R₅₉ represents a hydrogen atom, an alkyl group, an alkoxyl group, a halogen atom or an alkoxycarbonyl group.

The metal source M²⁺ (X⁻)₂ is formed from the above-mentioned anionic compound X⁻ of formula C-2 and a metal ion M²⁺. Compounds having -COOCH₃ or -COOC₂H₅ as the group represented by R₄₆ are preferred. The metal represented by M is preferably Ni. The metal ion-containing compound is contained in the image-receiving layer in an amount of 0 to 80% by weight. The content may vary according to the type of the metal ion-containing compound and the thickness of the image-receiving layer.

Examples of the anionic compounds of formula C- 2 are:

A release agent, an antioxidant, an ultraviolet absorber, a light stabilizer, a filler and a pigment may be added to the image-receiving layer. Further, a plasticizer, a heat solvent and the like may be added as sensitizers.

A release agent can improve the release properties of the recording material. It includes, for example, silicone oils including so-called silicone resins, solid waxes, e.g. polyethylene wax, alkyd wax and Teflon powder, as well as fluorine type or phosphoric acid ester type wetting agents. Of these, silicone waxes are preferred.

The amounts of an easily added silicone oil as an additive cannot be determined uniformly, as there can be many different types. However, the amount added (of silicone oil) is 0.5 to 50, preferably 1 to 20, % by weight based on the weight of the binder to be used for the image-receiving layer.

Examples of reaction-curable silicone oils include silicone oils produced by reaction-curing an amino-denatured silicone oil with an epoxy-denatured silicone oil. Examples of catalyst-curable or light-curable silicone oils that are suitable are KS-705F-PS, KS-705F-PS-1 and KS-770-PL-3 as catalyst-curable silicone oils from Shinetsu Chemical Industrial Co. and KS-720 and KS-774-PL-3 as light-curable silicone oils from Shinetsu Chemical Industrial Co.

The light-curable silicone oils mentioned should preferably be added in an amount in the range of 0.5 to 30% by weight, based on the binder to be used for the image-receiving layer.

The above-mentioned release agent may further be dissolved or dispersed in a suitable solvent. The resulting solution or dispersion is then applied to a part of the surface of the image-receiving layer and dried to form a release layer.

Examples of the antioxidants mentioned are the compounds from JP-OPI publications Nos. 59-182 785/1984, 60-130 735/1985 and 1-127 387/1989. Also suitable are compounds which are known as compounds having the ability to improve the image durability of photographs or other image recording materials.

Examples of the UV absorbers and light stabilizers mentioned are the compounds from JP-OPI publications Nos. 59-158 287/1984, 59-196 292/1984, 61- 283 595/1986, 62-229 594/1987, 63-74 686/1988, 63-145 089/1988, 63-122 596/1988 and 1-204 788/1989. Also suitable are compounds which are known as compounds with the ability to improve the image durability of photographs or other image recording materials.

Suitable fillers include inorganic or organic fine particles. Examples of the inorganic particles are those of silica gel, calcium carbonate, titanium oxide, acid clay, active clay or alumina. Examples of the organic particles are resin particles, e.g. those of fluororesins, guanamine resins, acrylic resins and silicone resins.

These inorganic or organic fine particles are preferably added in an amount ranging from 0.1 to 70 wt%, but their amount may be varied according to their relative density.

Examples of suitable pigments include titanium white, calcium carbonate, zinc oxide, barium sulfate, silicon dioxide, talc, clay, kaolin, activated clay and acid clay.

Suitable plasticizers include, for example, phthalic acid esters, trimellitic acid esters, pyromellitic acid esters, adipic acid esters, other oleic acid esters, succinic acid esters, maleic acid esters, sebacic acid esters, citric acid esters, epoxidized soybean oil, epoxidized linseed oil, epoxystearic acid, ortho-phosphoric acid esters, phosphoric acid esters and glycol esters.

The total amount added must usually be in the range of 0.1 to 50% by weight of the binder used for the image-receiving layer.

The image recording layer can be prepared as follows. A coating solution is prepared by dispersing or dissolving the components of the image receiving layer in a solvent. The resulting coating solution is applied to the surface of a support and then dried. Alternatively, a mixture of the components of the image receiving layer can be melted for extrusion and the melt can then be laminated to the surface of a support by extrusion.

Solvents that can be used for the coating processes mentioned are, for example, tetrahydrofuran, methyl ethyl ketone, toluene, xylene, chloroform, dioxane, acetone, cyclohexane and butyl acetate.

If the laminating process described is used, in the case of a synthetic resin layer carrier, a coextrusion process can also be used.

The image-receiving layer may be formed on the entire surface of a support or on a part thereof.

The thickness of the image-receiving layer is in the order of general 1 to 50 and preferably 2 to 10 µm. On the other hand, when a self-supporting image-receiving layer forms the image-receiving material, its thickness may be in the range of general 60 to 200 and preferably 90 to 150 µm.

To prevent fusion, to improve image durability, and the like, a cover layer can also be laminated onto the surface of the image-receiving layer. The cover layer can be produced by gravure coating, billet coating, roller coating, by any other known coating method, or by laminating. The thickness of the cover layer is usually in the range of 0.05 to 3 µm.

When the image receiving material comprises a support and an image receiving layer, a cushion layer may be inserted between the support and the image receiving layer. This serves to reduce noise and to transfer and record an image with excellent image reproducibility corresponding to image information.

Materials for the cushioning layer can be, for example, urethane resins, acrylic resins, ethylene-type resins, epoxy resins and butadiene rubbers. The thickness of the cushioning layer is preferably in the range of 5 to 25 µm.

The thermal transfer image recording method according to the invention is explained in more detail below.

As shown in Fig. 1, the image forming process comprises a step in which a dye barrier layer is image-formed by high intensity exposure from the side of the recording material and preferably from a dye barrier layer, and a further step in which the recording material subjected to peeling and an image-receiving material are superimposed on one another in such a way that the dye barrier layer and an image-receiving layer lie face-to-face. Thereafter, heat or pressure is applied to their entire surfaces.

Examples of light sources for high-intensity exposure include xenon light, halogen light, semiconductor laser beams, He-Ne laser beams, Ar laser beams, YAG laser beams and carbon dioxide laser beams. For convenience, a semiconductor laser beam is preferred as the light source. However, the light sources are not limited to this.

The power density during exposure is practically not less than 100,000 W/cm² and preferably not less than 200,000 W/cm², in each case based on the image plane. The exposure speed is practically not less than 1 ms⁻¹ and preferably not less than 2 ms⁻¹.

The following is a preferable example of the exposure conditions, but the exposure conditions are not limited thereto.

The detachment 40 caused by high-intensity exposure can be in the form of raster dots or in the form of a continuous Replacement will take place.

If heat is applied to the entire surface of superimposed recording materials and image receiving materials, the heat energy can act from any side, namely from the side of the image receiving material and/or the recording material. Due to the described heat exposure, the thermally diffusible or heat-diffusible dye of the colorant layer is transferred by diffusion from the colorant layer through the previously removed dye barrier layer to the image receiving layer of the image receiving material, so that an image can be formed there. There are no particular restrictions on the heating temperature. However, it should be in the range of usually 60 to 200 and preferably 80 to 150°C.

Examples

In the following, the expressions "one part" or "parts" mean "one part by weight" or "parts by weight".

example 1 Production of a recording material

The following compositions were mixed and dispersed to prepare a coating solution for a colorant layer containing a thermally diffusible dye.

Coating solution for a colorant layer

Thermally diffusible dye (Kayaset Blue 714, manufactured by Nihon Kayaku Co.) 4 parts

Polyvinyl butyral resin (Eslec BX-1, manufactured by Sekisui Chemical Co.) 4 parts

Methyl ethyl ketone 90 parts

Cyclohexanone 10 parts

The resulting coating solution for a dye layer was applied to a 100 µm thick polyethylene terephthalate (PET) film and then dried to form a 4 µm thick colorant layer. On the back of the PET film, a nitrocellulose layer containing a silicone-denatured urethane resin (SP-2105, manufactured by Dai-Nichi Seika Co.) was formed.

Thereafter, a colorant barrier composition having the following composition was applied to the above-mentioned colorant layer by means of a stick and then dried, to obtain a recording material to form a 0.5 µm thick colorant barrier layer.

Composition of the dye barrier layer

Gelatine 3.5 parts

infrared absorbing dye (IR-1) 1.5 parts

pure water 95 parts

Production of an image receiving material

An image-receiving material was prepared as follows. On 150 µm thick art paper (Upo FPG-150, manufactured by Oji Yuka Synthetic Paper Co.) was coated with a coating solution using a wire bar or a billet to form an image-receiving layer having the following composition:

Coating solution for forming an image-receiving layer

Vinyl chloride/vinyl isobutyl ether copolymer (Laroflex MP25, manufactured by BASF) 9 parts

polyester denatured silicone resin (X-24-8300, manufactured by Shinetsu Silicone Co.) 1 part

Methyl ethyl ketone 40 parts

Cyclohexanone 10 parts

The resulting coated art paper was pre-dried using a dryer and then (finally) dried in an oven at 100ºC for 1 h to form a 5 µm thick image-receiving layer on the art paper.

Formation of an image Detachment of the dye barrier layer

The colorant barrier layer was peeled off as follows. A laser beam of a semiconductor laser LT090MD/MF having a wavelength of 830 nm and a maximum beam power of 100 mW (manufactured by Sharp Corp.) was concentrated into a beam having a diameter of about 6 µm. The resulting laser beam was irradiated onto the colorant barrier layer of the resulting recording material at a scanning speed of 2 ms⁻¹. At this time, the optical efficiency was 60%. The dot size at the points where point-by-point peeling occurred was 8 µm.

Transfer of the dye

As mentioned above, the recording material from which the colorant barrier layer was peeled off and the image-receiving material were superimposed in such a way that the colorant barrier layer and the image-receiving layer were allowed to come into contact with each other. Thereafter, only the colorant, which was the diffusible dye, in the peeled off part was transferred to the image-receiving layer by means of a heating roller capable of emitting heat at a temperature of 120°C and applying a pressure of 2 kg/cm².

A determination of the red reflection density in the entire solid transferred area or the total solid density resulted in a value of 2.3. If the reflection density in the non-detached area or the density of the white background measured, the result was 0.06. The reflection density mentioned also did not change compared to the reflection density of the image receiving material before passing through the heating roller.

Example 2

The manufacturing steps from the beginning to the formation of the colorant layer were practically the same as those of Example 1. However, by changing only the composition of the colorant barrier layers in the manner described below, three kinds of recording materials according to the present invention and a comparative recording material were prepared. The colorant barrier layers each had a thickness of 0.5 µm.

Recording material 2-1

Polycarbonate resin (w/Tg 140ºV) (IUPILON S2000, manufactured by Mitsubishi Gas-Chemical Co.) 4 parts

Near infrared absorbing dye (IR-2) 1 part

Methylene chloride 95 parts

Recording material 2-2

Water-soluble polyester resin (w/anionic property and pH value: 3 to 5), (Pesresin 200 in 20% aqueous solution, manufactured by Takamatsu Yushi Co.) 20 parts

Infrared absorbing dye (IR-3) 1 part

Pure water 79 parts

Recording material 2-3

Methyl cellulose resin (SM400, manufactured by Shinetsu Chemical Co.) 3 parts

Infrared absorbing dye (IR-4) 2 parts

Pure water 95 parts

Comparative recording material

Ethylene/vinyl acetate copolymer (w/Tg≤-20ºC), (EV40X, manufactured by Mitsui-Dupont Co.) 4 parts

Methyl ethyl ketone 96 parts

Using the above recording materials and the image receiving material of Example 1, the detachment of the colorant layers and the thermal transfer to the image receiving layers were each carried out approximately in accordance with Example 1. The results are shown below.

The control recording material did not contain any infrared absorbing substance. Consequently, no erosion was observed. There was no blocking effect in the dye barrier layer. Consequently, the dye was transferred to the image receiving layer at a significant density.

Example 3 Production of a recording material

A recording material was prepared according to Example 1.

An image-receiving material was prepared as follows. On a 150 µm thick art paper (Upo FPG-150, manufactured by Oji Yuka Synthetic Paper Co.) was coated with a coating solution using a wire bar to form an image-receiving layer having the following composition:

Coating solution for an image receiving layer

Vinyl chloride/vinyl isobutyl ether copolymer (Laroflex MP25, manufactured by BASF) 8.5 parts

Spherical fine particles of Polymethylmethacrylate (w/particle size of 12-15 µm) 0.5 parts

Polyester denatured silicone resin (X-24-8300, manufactured by Shinetsu Silicone Co.) 1 part

Methyl ethyl ketone 40 parts

Cyclohexanone 10 parts

The resulting coated art paper was pre-dried using a dryer and then (finally) dried in an oven at 100ºC for 1 h, whereby a 5 µm thick image-receiving layer was formed on the art paper.

The obtained recording material and the image-receiving material were brought into contact with each other at the colorant barrier layer surface and the image-receiving layer surface and combined into one body by means of a heating roller at 90°C under a pressure of 1 kg/cm2.

Image generation Detachment of the dye barrier layer

The colorant barrier layer was peeled off in the following manner. A laser beam from a semiconductor laser LT090MD/MF (a wavelength of 830 nm and a maximum beam power of 100 mW, manufactured by Sharp Corp.) was concentrated at maximum power on the colorant barrier layer into a beam of about 6 µm in diameter. The resulting laser beam was projected onto the colorant barrier layer of the resulting recording medium at a scanning line pitch of 10 µm and a scanning speed of 2 m/s. At this time, the optical efficiency was 60%.

Transfer of a dye

The elements combined to form a body from which the dye barrier layer had been removed were heated by a heating roller with the ability to emit heat at a temperature of 130ºC and applying a pressure of 3 kg/cm² so that only the colorants consisting of diffusible dyes in the ablated areas were transferred to the image-receiving layer.

The two combined materials were separated from each other.

A determination of the red reflection density in the transferred solid image area of 8 µm dots or the solid density gave a value of 3.1. If the reflection density in the non-transferred area or the density of the white background was determined, this determination gave a value of 0.06. It was also shown that the reflection density did not change compared to the reflection density of the image receiving material, which was measured before passing through the heating roller.

Example 4 Production of a recording material

By mixing and dispersing the following composition, a coating solution for a colorant layer containing a thermally diffusible dye was prepared.

Coating solution for the colorant layer

Thermally diffusible dye (D-1) 25 parts

Thermally diffusible dye (D-2) 15 parts

Thermally diffusible dye (D-3) 40 parts

Polyvinyl butyral resin (Eslec BX-1) 20 parts

Methyl ethyl ketone 700 parts

Cyclohexanone 200 parts

The above-mentioned coating solution for the colorant layer was applied to a 100 µm thick PET film using a wire bar or a stick and then dried to form a 4 µm thick colorant layer.

Afterwards, a recording material was created in the following way A coating solution for a dye barrier layer of the following composition was applied to the dye layer using a wire rail:

Coating solution for the dye barrier layer

Gelatine 2.5 parts

infrared absorbing dye (IR-3) 2.0 parts

colloidal silver 0.5 parts

pure water 95 parts

and then dried to obtain a 0.15 µm thick dye barrier layer to complete the recording material.

Production of an image receiving material

On a 100 µm thick PET film, the back of which had been antistatically treated and the surface resistance of which had been adjusted to 10¹⁹0; Ω, a coating solution for an image receiving layer of the following composition was applied using a wire bar to the surface of the PET film opposite the antistatically treated surface of the PET film:

Coating solution for an image receiving layer

Polyvinyl butyral (Eslec BL-1, manufactured by Sekisui Chemical Co.) 40 parts

Metal Supplier (D-4) 50 parts

Amino-modified silicone (KF-393, manufactured by Shinetsu Silicone Co.) 5 parts

Epoxy modified silicone (X-22-343, manufactured by Shinetsu Silicone Co.) 5 parts

Methyl ethyl ketone 300 parts

Cyclohexanone 100 parts

After drying for 30 minutes at 120ºC, a 4 µm thick image receiving layer was formed.

Image generation Detachment of the dye barrier layer

The dye barrier layer of the above-mentioned recording material was exposed by concentrating a semiconductor laser beam having a wavelength of 810 nm and a maximum beam power of 150 mW so that the beam diameter of the half-band width at the time of the maximum output power was 5 µm, about 6 µm. The exposure was carried out using 16 semiconductor laser beams.

During exposure, the light output on the image plane was on average 101 mW per semiconductor laser. The exposure energy density calculated from the exposure light scanning speed was 150 mJ/cm2 for total solid exposure.

Dye transfer

As already mentioned, the colorant barrier layer of a recording material in which the colorant barrier layer had been peeled off and the image-receiving layer of an image-receiving material were superimposed on each other in such a way that the layers could come into contact with each other. Thereafter, only the colorants in the peeled off area were transferred to the image-receiving layer by means of a heating roller capable of emitting heat at a temperature of 180°C and applying a pressure of 2 kg/cm².

The transmittance density values were 0.02 for the PET film, 0.04 for the unexposed areas and 3.28 for the entire solid exposed areas. To confirm the durability of the obtained images, the images were further left at 50ºC for 1 month. Even when compared to a control image kept at room temperature, the durability was excellent with no image bleeding.

Example 5

A recording material was prepared on a 12 µm thick PET film in the same way as in Example 4, except that only the composition of the coating solution for the colorant layer was changed as follows.

Coating solution for the colorant layer

Thermally diffusible dye (D-1) 22 parts

Thermally diffusible dye (D-2) 13 parts

Thermally diffusible dye (D-3) 35 parts

Roughening agent (MR-20G of an average particle size of 17 µm, manufactured by Soken Chemical Co.) 10 parts

Polyvinyl butyral resin (Eslec BX-1) 20 parts

Methyl ethyl ketone 700 parts

Cyclohexanone 200 parts

Production of an image receiving material

An image receiving material was prepared as follows. A 175 µm thick PET film, the back side of which had been antistatically treated and the surface resistance of which had been adjusted to 5 x 10⁹ Ω, was coated, by means of a doctor blade, on the surface of the PET film opposite to the antistatically treated surface of the PET film, with a coating solution for a cushion layer having the following composition:

Coating solution for a cushion layer

Ethylene/vinyl acetate resin (Evaflex EV-40Y, manufactured by Mitsui-DuPont Polychemical Co.) 30 parts

Toluene 60 parts

Methyl ethyl ketone 10 parts

coated. After drying, a 10 µm thick cushioning layer was obtained.

In addition, a 25 µm thick PET film was made removable by applying a silicone surface treatment agent. coated surface of the film was coated with a coating solution for an image receiving layer of the following composition using a wire rail:

Coating solution for the image receiving layer

Vinyl chloride resin (TK-300, manufactured by Shinetsu Chemical Co.) 40 parts

Metal Supplier (D-4) 50 parts

Amino-modified silicone (KF-393, manufactured by Shinetsu Silicone Co.) 5 parts

Epoxy modified silicone (X-22-343, manufactured by Shinetsu Silicone Co.) 5 parts

Methyl ethyl ketone 300 parts

Cyclohexanone 100 parts

applied. After drying, a 3 µm thick image receiving layer was obtained.

The surface of the image-receiving layer formed on the 25 µm thick PET peelable film and the surface of the previously prepared cushion layer of the 175 µm thick PET film were placed on top of each other and the two layers were then bonded together using a laminating machine at room temperature under a pressure of 3 kg/cm². The PET peelable film was then peeled off so that an image-receiving material with a cushion layer and an image-receiving layer were formed on the 175 µm thick PET film in the order shown.

Unification procedure

Thereafter, the surface of the barrier layer of the recording material and the surface of the image-receiving layer of the image-receiving material were placed on top of each other and then subjected to a pressure of 0.5 kg/cm² at room temperature by means of a laminating device so that the recording material and the image-receiving material were combined into one body.

Image generation

The dye barrier layer was prepared according to example 4 was removed or detached. The material forming a unit was then exposed to a temperature of 180ºC and a pressure of 5 kg using a laminating device. The two materials were then separated from each other. The transmittance density values were 0.02 for the PET film, 0.04 for the unexposed areas and 3.14 for the entire solid exposed areas.

Comparison example 1

By mixing and dispersing the following compositions:

Coating solution for the colorant layer

Soot 7 parts

Phenolic resin (Tamanol 510, manufactured by Arakawa Chemical Co.) 3 parts

Methyl ethyl ketone 40 parts

A coating solution for a colorant layer of a recording material for explosively transferring a colorant layer was prepared. The resulting coating solution was applied to an aluminum-vaporized 100 µm thick polyester film in such a way that a transmission density of 50% was achieved.

An untreated polyester film was used as the image receiving material.

Image recording

The above recording material and the (obtained) image receiving material were placed on top of each other. Then, the remaining air in the space between the two sheet-like materials was sucked out under reduced pressure and in close contact so that the two materials came into close contact with each other. From the back of the recording material, the aluminum-deposited layer was irradiated with a semiconductor laser beam (a wavelength of 810 µm and a maximum beam power of 150 mW) which was concentrated so that the beam diameter of the half-band width to the At the time of maximum power, 16 x 16 dots (i.e., a total of 256 dots) each with a spot diameter of 5 µm served as a pixel unit in the exposure. An image was formed in 80 µm (large) square units. At this time, the exposure surface power was 101 mW. The total solid density values in the entire solid areas were found to be relatively high and were 2.85. However, there were numerous pinholes, so that the uniformity of the image was not satisfactory.

Claims (9)

1. Thermal transfer image recording process, comprising the following steps: Exposing a recording material comprising a layer support (1) with a colorant layer (2) thereon containing a colorant and a colorant barrier layer (3) provided on the colorant layer (2) and containing an infrared-absorbing substance and a resin in an amount of 50 to 99% by weight of their total weight with high-intensity light for image-accurate removal of the colorant barrier layer (3); Contacting the surface of the dye barrier layer (3) with the surface of an image receiving layer (5) of an image receiving material (4) and Transferring the colorant of the colorant layer (2) through the removed part of the colorant barrier layer (3) to the image receiving layer (5) by application of heat or pressure. 2. The method according to claim 1, wherein the colorant barrier layer (3) contains a water-soluble resin. 3. The method according to claim 2, wherein the water-soluble resin is selected from the group consisting of gelatin, polyvinyl alcohol, water-soluble polyvinyl formal, water-soluble polyvinyl acetal, water-soluble polyvinyl butyral, polyvinyl pyrrolidone, water-soluble Polyester, water-soluble nylon, polyacrylic acid, water-soluble polyurethane, methylcellulose, hydroxyethylcellulose, hydroxypropylcellulose and carboxylcellulose. 4. The method according to claim 1, wherein the colorant barrier layer (3) contains a resin having an acidic group selected from -COO⁻, -SO₃⁻ and -PO₃⁻, or a basic group selected from -NH₂, -NH- and -N=. 5. A method according to claim 1, wherein the colorant barrier layer (3) contains a resin having a glass transition temperature of not less than 120°C. 6. The method according to claim 1, wherein the colorant layer (2) contains a dye capable of forming a chelate compound. 7. The method according to claim 1, wherein the infrared absorbing substance consists of a dye having an absorption maximum within the range of 700 nm to 1200 nm and a molar extinction coefficient of 50,000 or more at the absorption maximum wavelength. 8. The method according to claim 1, wherein the image-receiving layer (5) contains a metal ion-containing compound. 9. The method according to claim 1, wherein the exposure is carried out with high intensity light of a power density of not less than 100,000 W/cm² at an exposure speed of not less than 1 ms⊃min;¹.