JPH0466348B2 - - Google Patents

Description

[Detailed description of the invention]

"Industrial Application Field" The present invention relates to photothermography, and particularly to a novel photothermography that uses a photopolymerization reaction to form a dye image. ``Prior Art'' Photothermography (a light- and heat-sensitive image recording method) involves developing images by uniformly heating them after exposing them to light, and has the advantage that images can be obtained using only dry processing. On the other hand, many image recording methods using photopolymerization are known and are applied to photoresists, printing plates, etc., but there are special cases (for example, N-vinylcarbazole-carbon tetrabromide-based photosensitive materials). It is difficult to directly form a visible image by photopolymerization using common monomers, except in cases where the monomer itself has a color-forming function. To visualize the image, either the exposed or unexposed areas are selectively colored with a dye solution or pigment powder depending on the difference in their permeability or tackiness, or the photosensitive layer is colored in advance and the image is exposed. After curing, the exposed area is separated from the exposed area by physical development operations such as liquid development or peeling development, taking advantage of the difference in physical properties such as solubility or adhesiveness between the cured and uncured areas. It is necessary to spatially separate the unexposed portions, and the processing is complicated. Several methods have been proposed for developing visible images in a dry process using photopolymerization, directly by chemical reaction. JP-A-52-89915 describes a method of forming a visible image by heat development using a photopolymerizable composition and a thermosensitive coloring material. This is because when the two components of a two-component heat-sensitive coloring material are placed separately inside and outside the photopolymerizable composition, or on both sides, when the material is exposed and heated, the heat-sensitive material does not move in the areas that are cured by exposure. Therefore, it does not develop color, but in unexposed areas it moves, reacts, and develops color to form an image, showing a positive-positive recording response. Furthermore, Japanese Patent Application Laid-open Nos. 57-179836 and 1987-197538, etc., describe a method of forming a visible image by using the same material as above and developing it under pressure. This is because one component of a two-component color-forming material is microencapsulated with a photopolymerizable composition, and the other component is placed outside the capsule. When the material is exposed to light and pressurized, the capsules hardened by exposure are not destroyed, so the color develops. However, in the unexposed area, the capsule wall is destroyed by pressure, and an image is formed by color development, indicating a positive-positive recording response. These photothermosensitive and photosensitive pressure-sensitive image recording methods using photopolymerization are all based on the principle of image-wise control of the coloring reaction by the difference in substance diffusivity between the polymer and the monomer. However, the degree of hardening due to photopolymerization, that is, the property as a barrier against diffusion of substances, is generally not proportional to the polymerization rate, and when the polymerization rate reaches a certain value (gel point), it hardens rapidly and acts as a barrier. Therefore, the image density is difficult to be proportional to the exposure amount, and therefore, there is a drawback that gradation reproducibility is poor. Furthermore, since it is generally difficult to completely prevent substance diffusion of polymers produced by photopolymerization, fogging is likely to occur, and fixation against heat is also insufficient. ``Problem to be solved by the invention'' Therefore, it is possible to convert (develop) a polymer image obtained by a photopolymerization system into a visible image by just dry processing, and it has excellent gradation reproducibility and little fog. It is desired to find a method for forming images (with a high signal-to-noise ratio), and this is the object of the present invention. "Means for Solving the Problems" The above problems can be solved by the following image forming method (1) and image forming material (2), resulting in the present invention. (1) A photopolymerizable composition consisting of a polymerizable vinyl monomer having at least one acidic group in the molecule (hereinafter simply referred to as "monomer") and a photopolymerization initiator is subjected to image exposure to photopolymerize the monomer. After that, it is uniformly heated in close proximity to a dye precursor capable of producing a dye with an acid, and a dye image is formed by reacting the unpolymerized remaining monomer with the dye precursor. An image forming method characterized by: (2) A layer consisting of a polymerizable vinyl monomer having at least one acidic group in the molecule, a photopolymerization initiator, a dye precursor capable of producing a dye with an acid, and a binder is provided on a support. An image forming material characterized by: "Operation" Image formation according to the present invention is a two-component heat-sensitive (pressure-sensitive)
The principle is to control the color-forming reaction of a color-forming material in an image-like manner through photopolymerization. This two-component thermosensitive coloring material generally consists of a dye precursor (leucobase) that forms a dye by the action of an acid, and a color developer that is an acid or a substance that can generate an acid, and at least one of them is melted by heating. However, the present invention uses an acidic monomer instead of a general acidic substance as a color developer, that is, the substance itself that directly participates in photoimage formation produces color. It is characterized by its functionality. As a result, when the monomer becomes a polymer through photopolymerization,
The color developer itself becomes immobile, does not diffuse even when heated, and does not produce dye, so there is no fog and high S/
An N-ratio image is obtained. Furthermore, since dyes are produced only by the reaction between unpolymerized monomers and leuco dyes, the dye image density is proportional to the amount of remaining monomer, while the amount of monomer consumption, that is, the polymerization rate, generally increases continuously with the exposure amount. Therefore, excellent gradation reproducibility can be obtained. In this regard, in the above-mentioned conventional technology (Japanese Patent Application Laid-open No. 52-89915), an acidic substance different from the monomer is used as the color developer, and the monomer is simply used as a medium to control the diffusion of the color developer through polymerization and curing. Therefore, as mentioned above, it has been difficult to obtain a high S/N ratio and gradation reproducibility. The imaging materials and methods of the present invention can take on a variety of different embodiments. FIG. 1 shows a case where an image is formed using two sheets, a photosensitive sheet and a coloring sheet. FIG. 1A shows a state in which a photosensitive layer 2 consisting of a monomer having an acidic group, a photopolymerization initiator, and a binder is image-exposed on a photosensitive sheet 1 provided on a support 3, and the exposed portions are exposed to light. Polymerization has occurred and a polymer image 4 is generated. FIG. 1B shows a state in which a coloring layer 6 made of a dye precursor (and generally a binder) is in close contact with a coloring sheet 5 provided on a support 7 and heated uniformly.
The unpolymerized monomer in the photosensitive layer diffuses into the coloring layer (or at the same time, the dye precursor in the coloring layer diffuses into the photosensitive layer), and a dye image 8 is formed by the reaction between the acidic monomer and the dye precursor. Both are fixed against heat. If necessary, more uniform exposure may be performed to polymerize unpolymerized monomers to achieve more complete fixing, but this is generally not necessary. (Fixing is the same in the cases of FIGS. 2 and 3.) FIG. 2 shows the case of an integrated image forming material (multilayer monosheet type). Figure 2 A shows the first
A support 1 includes a photosensitive layer 12 and a coloring layer 16 similar to those shown in the figure.
The image-forming material 11 laminated on the image-forming material 3 is image-exposed, and a polymer image 14 is generated in the exposed portion. FIG. 2B shows a state in which this is uniformly heated, and a dye image 18 is formed in the unexposed area in the same manner as in FIG. 1. Note that the stacking order of the two layers may be reversed from that shown in the figure. In addition, during the production and storage of image-forming materials, in order to prevent color development due to contact between monomers and dye precursors, a photosensitive layer or /
and the binder of the coloring layer can be hardened by known methods, or a barrier layer can be provided between the two layers, which is preferred. FIG. 3 shows a single-layer monosheet type of integrated image-forming material, which is different from that shown in FIG. FIG. 3A shows an imaging element 21 comprising a support 23 having a photosensitive layer 22 in which a monomer 29 and a leuco dye 26 are dispersed in particulate form in a binder continuous phase 30. Note that the photopolymerization initiator may be contained in either the monomer or the binder. FIG. 3B shows a polymer image 24 formed by imagewise exposure, and FIG. 3C shows a state in which a dye image 28 is formed by further uniform heating and the same mechanism as in FIGS. 1 and 2. It shows the condition. Note that for the same purpose as in the case of the image forming material of FIG. 2, the binder 30 can be hardened or the surfaces of the monomer particles and/or dye precursor particles can be wrapped with a barrier layer, which is preferred. The barrier layer can be provided by microencapsulating the particles using a barrier material as a wall material by a known method. The present invention can be used to form not only monochromatic dye images but also color images. In that case, three units of the layers shown in Figure 2A or Figure 3A are laminated as an image forming material, each containing a photopolymerization initiator sensitive to red light, a dye precursor that develops a cyan color, and an initiator sensitive to green light. A color image is formed by exposing a color light image to a dye precursor containing a dye precursor that develops a magenta color, an initiator that is sensitive to blue light, and a dye precursor that develops a yellow color, and then heating it uniformly. be done. Note that a barrier layer (intermediate layer) capable of preventing diffusion of monomers, photopolymerization initiators, or leuco dyes can be provided between each unit in order to prevent color mixing. When exposing a photosensitive sheet or image forming material to photopolymerization, if the polymerization is inhibited or slowed down by oxygen in the air, a plastic film or the like is tightly attached to the surface of the light-attenuating layer to block oxygen before exposure. You may. Alternatively, a layer that is difficult to transmit oxygen may be applied to the surface of the photosensitive layer and exposed in air. The image forming material of the present invention can be thermally printed first and then uniformly exposed to light over the entire surface to stop color development in areas other than the printed image. The monomer having an acidic group used in the present invention is
It is a compound that has at least one vinyl group or vinylidene group and contains a carboxyl group, a sulfonic acid group, a phosphoric acid group, a phenolic group, and a salt of these with a weak base in the molecule. −229376
The monomers described in 1 are substituted with the above-mentioned acidic groups. Specific examples include acrylic acid, methacrylic acid, and compounds that are condensates of acrylic acid and/or methacrylic acid, polyhydric alcohols, and polybasic acids, leaving unesterified acidic groups, such as (meth) Examples include acryloyloxyethyl phthalate and (meth)acryloyloxyethyl succinate. Note that other monomers can be used simultaneously with the above acidic monomers.
As other monomers, those described in Japanese Patent Application No. 58-229376 can be used. Examples of the photopolymerization initiator used in the present invention include "Chemical Review" by Oster et al., Vol. 68 (1968), pp. 125-151, and "Light-
Sensitive Systems” (John Wiley & Sons,
(1965), pp. 158-193,
Carbonyl compounds (e.g., acetophenone, benzoins, benzyl, diacetyl, ketones such as benzophenone, quinones such as anthraquinones, naphthoquinones, phenanthrenequinone),
Organic sulfur compounds, peroxides, halogen compounds,
optical semiconductors (e.g. zinc oxide, titanium dioxide, etc.),
Metal ions (eg iron() ions, metal carbonyls, metal complexes, uranyl salts, etc.), silver halides, azo and diazo compounds, photoreducible dyes are used. Among these, photoreducible dyes are particularly preferably used in the present invention in that they are capable of spectral sensitization of photopolymerization to any wavelength region in the visible light region and are useful for color image recording. A photoinitiator using a photoreducible dye generally includes a photoreducible dye and a reducing agent (or hydrogen-donating compound).
It is believed that the reaction between the photoexcited dye and the reducing agent generates radicals capable of initiating polymerization. Photoreducible dyes include methylene blue, thionine, rose bengal, erythrosin-B, eosin, rhodamine, and phloxine.
B, safranin, acriflavin, riboflavin, fluorescein, uranine, benzoflavin, N,N,N',N'-tetra-n-butylthionine, N,N,N',N'-tetramethyl-4'-dodecyl Examples include carbonyl compounds such as safranin, acridine orange, acridine yellow, and 9,10-phenanthrenequinone and benzanthrone. Examples of reducing agents include β-diketones such as dimedone and acetylacetone, amines such as triethanolamine, diethanolamine, monoethanolamine, dimethylamine, diethylamine, tetramethylethylenediamine, triethylamine, and phenylhydrazine, and p-toluenesulfin. acid, benzenesulfinic acid, p-
Examples include sulfinic acids such as (N-acetylamino)benzenesulfinic acid and salts thereof, N-phenylglycine, L-ascorbic acid, thiourea, allylthiourea, and the like. Among these, dimedone and N-phenylglycine are particularly preferred. The molar ratio of the photoreducible dye to the reducing agent varies depending on their solubility in the coating solvent, etc., but in general, the photoreducible dye is 0.005 to 3 moles per 1 mole of the reducing agent.
More preferably, it is in the range of 0.05 to 1 mol. Further, when a carbonyl compound such as 9,10-phenanthrenequinone is used as a photoreducible dye, a reducing agent does not necessarily need to be used since the binder acts as a hydrogen donating compound. The dye precursor used in the present invention is generally a compound that produces a dye by coloring under acidic conditions, and known coloring agents used in two-component heat-sensitive (pressure-sensitive) coloring materials can be suitably used. Specific examples of dye precursors; US patent
Triphenylmethane lactones (or triphenylmethane phthalide) described in 2548366, 2505472, and JP-A-53-56224, such as crystal violet lactone and malachite green lactone; 18727, same
45-4698, 45-4701, 46-29550, 48-
4051, 48-4052, 46-4614, 48-8725, 48-4052, 46-4614, 48-8725,
48-8726, 52-10871, 51-23203, 47-
29662, fluorans described in JP-A-52-82243, such as 3,6-dimethoxyfluorane, 2-methyl-6-isopropylaminofluorane, 2-bromo-3-chloro-6-n-propyl Amino-7-bromofluorane, 3-diethylamino-7-dibenzylaminofluorane, 3-
dimethylamino-7-methylaminofluorane,
4,5,6,7-tetrachloro-1',2',3'-trimethyl-6'-diethylaminofluorane, 3-
Diethylamino-5,6-benzfluorane, 3
-diethylamino-7,8-benzfluorane,
2-N-ethyl-N-phenylamino-6-diethylaminofluorane, 2-N-phenylamino-3-methyl-6-diethylaminofluorane,
2-N-phenylamino-3-methyl-6-N-
ethyl-N-(p-tolyl)aminofluorane,
3-diethylamino-7-phenylfluoran,
3',6'-bis(N-methyl-N-phenylamino)-4,5,6,7-tetrachlorofluorane,
2-ethoxyethylamino-3-chloro-6-diethylaminofluorane;
-8728, 48-8729, 48-8730 and 48-
18725, such as 3-(4'-diethylaminophenyl)-3-(4'-dimethylamino-2'-chlorophenyl)-7-azaphthalide, 3,3-bis(4 '-dimethylaminophenyl)-4,7-diazaphthalide; Japanese Patent Publication No. 47-29662, No. 49-103710
Fluoran-γ-lactams (rhodamine lactams) described in JP-A-48-45319, JP-A-48-47
- Phenothiazines described in 34427, such as benzoylleucomethylene blue; JP-A-47
−46010, indolyl phthalides described in British patent 1160940;
10783, spiropyrans described in JP-A-48-95420; JP-A-46-16052, JP-A-51-92207;
Triphenylmethanes described in JP-A-54-161637; chromenoindoles described in JP-A-52-148099 and JP-A-54-126114;
50-124930, 54-111528, 52-84238, 53
-90255, 46-29552, 51-121035, 51-
121035, Special Publication No. 46-12317, No. 46-2530, No. 55-
7473, 45-25654, 46-29552, 45-25654,
Compounds described in 49-5929, etc. Also PH
Indicators can also be used. Among these leuco dyes, those that provide a dye having a desired hue and weather resistance can be selected and used in the present invention. Moreover, two or more leuco dyes can be used at the same time. In the present invention, a thermal solvent can be included in the photosensitive layer and/or the coloring layer for the purpose of promoting diffusion of the monomer and/or dye precursor under heating and improving the rate of dye formation and image density. . Thermal solvent is a compound with a melting point in the range of 80°C to 200°C, more preferably 100°C to 150°C, which melts during heat development and dissolves the monomer or leuco dye. Among the compounds, those that are less likely to react with monomers and leuco dyes can be selected and used. Specific examples of hot solvents include sorbitol, dulcitol,
Examples include pentaerythritol, trimethylolpropane, trimethylolethane, acetamide, methylurea, dimethylurea, and the like. As binders, water-soluble polymers such as gelatin, polyvinyl alcohol, polyvinylpyrrolidone, carboxymethyl cellulose, gum arabic, and casein, as well as polymethyl methacrylate, polyvinyl chloride, vinylidene chloride-acrylonitrile copolymer, vinylidene chloride-vinyl chloride copolymer, and polyacetic acid. Polymers soluble in organic solvents such as vinyl, vinyl acetate-vinyl chloride copolymer, styrene-acrylonitrile copolymer, polyester, ABS resin, polyamide, chlorinated polyethylene, chlorinated polypropylene, polyvinyl butyral, polyvinyl formal, acetyl cellulose, etc. are used. . As the solvent, water, acetone, methanol, ethanol, methylene chloride, ethylene dichloride, chloroform, methyl ethyl ketone, methyl acetate, ethyl acetate, dimethylformamide, dimethyl sulfoxide, etc. are used. The monomer and dye precursor may be dispersed uniformly (molecularly) or as particles in the binder. In particular, in the case of monomers, it is more preferable to emulsion or microcapsule them and disperse them uniformly in the binder continuous phase as particles because they are less likely to be inhibited or slowed down by oxygen in the air. In this case, a water-insoluble monomer can be emulsified and dispersed in an aqueous solution of a water-soluble binder using a known emulsifier, and if necessary, it can be microencapsulated and applied by a known method. As the binder, polyvinyl alcohol and gelatin, which have low oxygen permeability, are particularly preferred. Moreover, since it can be applied using water as a solvent, it is inexpensive, odorless, safe, and easy to handle during application, which is preferable. The barrier layer (or capsule wall) can be selected from the polymers used in the binders mentioned above. In the case of a water-soluble polymer, it may be hardened by a known method. As the support, paper, polymer-coated waterproof paper, plastic film such as polyethylene terephthalate or triacetyl cellulose, metal plate, etc. can be used depending on the purpose of use. The oxygen permeation prevention layer provided on the photosensitive layer as necessary may include polyvinyl alcohol, gelatin,
Polymers with low oxygen permeability, such as vinylidene chloride copolymers, are used. In the present invention, various metal salts can be added to the photosensitive layer and/or coloring layer for the purpose of increasing image density. Specific examples of metal salts include zinc, copper, iron, nickel, cobalt, chromium, manganese, magnesium, calcium, styrontium, barium, aluminum, tin, lead, cadmium, silver, and inorganic acids (e.g., sulfuric acid, hydrochloric acid). ,
phosphoric acid, etc.) or organic acids (for example, acetic acid, citric acid, benzenesulfonic acid, etc.). The amount of the substance used in the present invention is as follows, but the amount is a preferable amount and is not necessarily limited to the following amount. The amount of monomer is 0.1 g/m 2 to 50 g/m ² , more preferably 0.5 to 10 g/m ² , and the amount of binder is 0.1 g/m 2 in the case of a photosensitive layer, a color forming layer or an integrated single layer image forming layer. g to 50 g/m ² , more preferably 0.5 to 10 g/m ² , the amount of dye precursor is
0.1g-50g/ ^m2 , more preferably 0.5-10g/ ^m2
It is. The amount of the photopolymerization initiator (when the photopolymerization initiator consists of a photoreducible dye and a reducing agent, the amount of the photoreducible dye) can vary widely depending on its molecular extinction coefficient and radical generation efficiency. Generally, a range of 0.0005 to 0.05 mole per mole of monomer is preferred. The amount of hot solvent ranges from 0g to 10g, more preferably from 0g to 3g, per gram of binder. The thickness of the layer is in the range of 0.5 .mu.m to 100 .mu.m, more preferably 1 .mu.m to 30 .mu.m in any case, whether it is a photosensitive layer, a coloring layer or an integrated single layer photosensitive layer. The thickness of the barrier layer (and microcapsule wall) is 0.1 μm ~
20 μm, more preferably in the range of 0.5 μm to 10 μm. The amount of metal salt is 0g to 5g per 1g of binder.
g, more preferably in the range of 0 g to 2 g. Image exposure can be carried out using any light source including the wavelength range to which the photopolymerization initiator is sensitive, such as a tungsten lamp, a xenon lamp, a mercury lamp, a laser, a light emitting diode, a CRT, etc., and is preferably carried out with ultraviolet rays or visible light. The exposure amount is 10 ² to 10 ⁶
It is in the range of ergs/ ^cm2 . Thermal development can be performed using a heat roller, hot plate, infrared heater, or the like. The heating temperature is in the range of 80°C to 200°C, more preferably 100°C to 150°C, and the heating time is in the range of 1 second to 100 seconds, more preferably 3 seconds to 30 seconds. Example 1 (Preparation of photosensitive sheet) Acryloyloxyethyl phthalate 1.5g Methylene blue (photoreducible dye) 0.007g Dimedone 0.2g Polyvinyl alcohol (average degree of polymerization approximately 500)
A mixed solution consisting of 10.0 g of a 10 wt% aqueous solution, 1.5 g of methylene chloride, 0.5 g of a 5 wt.% aqueous solution of sodium p-dodecylbenzenesulfonate, and 2.0 g of water was emulsified for 1 hour using an ultrasonic emulsifier.
This was applied onto a 100 μm thick polyethylene terephthalate film to a dry film thickness of about 5 μm and dried to produce a photosensitive sheet. (Preparation of coloring sheet) 2-ethoxyethylamino-3-chloro-6-
Diethylaminofluorane (dye precursor) 10g) 10% aqueous solution of gelatin 10g 5% aqueous solution of sodium p-dodecylbenzenesulfonate 0.2g A mixture of 40g water was dispersed with glass beads in a homogenizer for 1 hour. g, 10 of gelatin
After mixing 1.0 g of wt% aqueous solution and 1.0 g of water, and adding 0.3 g of sulfite to dissolve it, the thickness
A colored sheet was prepared by coating a 100 μm polyethylene terephthalate film to a dry film thickness of approximately 2 μm and drying. (Image formation) A polyethylene terephthalate film with a thickness of 100 μm is closely attached to the photosensitive layer of a photosensitive sheet, and a halogen lamp is used to pass the film through a black and white step wedge.
Image exposure was performed for 5 seconds at an illuminance of 10,000 lux. After peeling off the polyethylene terephthalate film, it adhered to the coloring sheet and was passed through a heat roller heated to 125°C (heating time was approximately 20°C).
sec), a positive black image with clear gradation reproducibility was formed on the original (wedge).
The gradation reproduction range was approximately 1.5 in Log (exposure amount). When the two sheets were peeled off, an image was formed on both sheet sides, and the maximum image density (Dmox) was 1.2 on the coloring sheet side and 1.2 on the photosensitive sheet side.
1.5, and the minimum image density (fog, D _nio ) is
It was 0.05 on the coloring sheet side and 0.15 on the photosensitive sheet side. (Fixability Test) The two peeled images were each divided into two parts, and the following tests were conducted on each part. (1) Uniform light irradiation for 5 minutes at 50,000 lux using the same light source used for image exposure
There was no change at all in D _nax or D _nio . (2) When the support side was placed in close contact with a hot plate heated to 150°C and heated for 10 minutes, D _nax and D _nio were observed.
There was almost no change. Examples 2 to 4 The dyes listed in Table 1 were used instead of methylene blue as the photoreducible dye in Example 1, and the dyes listed in Table 1 were used instead of 2-ethoxyethylamino-3-chloro-6-diethylaminofluorane as the dye precursor. Example 1 was carried out in exactly the same manner as in Example 1, except that the compound described in Example 1 was used and the image exposure was carried out through the filter described in Table 1.
The results described in were obtained. In addition, D _nax , D _nio ,
The gradation reproduction range and sensitivity were almost the same as in Example 1.

[Table] Example 5 A 5% by weight ethanol solution of polyvinyl butyral (molecular weight approximately 50,000) was applied onto the coloring sheet of Example 1 and dried to provide a barrier layer having a thickness of approximately 1 μm. The same coating liquid used for producing the photosensitive sheet in Example 1 was applied thereon to the same thickness.
It was dried to produce an integrated imaging material. This was subjected to image exposure in the same manner as in Example 1, and then passed through a heat roller, resulting in a black positive image similar to that in Example 1. D _nax is 2.3, D _nio is 0.23
It was hot.

[Brief explanation of the drawing]

FIG. 1A shows a state in which the photosensitive sheet has been imagewise exposed, and FIG. 1B shows a state in which it has been heated in close contact with a coloring sheet. FIG. 2A shows the integrated image forming material in a state where it has been image exposed, and FIG. 2B shows the state in which it has been further heated. FIG. 3A shows another type of integral imaging material; FIG. 3B shows it in an imagewise exposed state and FIG. 3C shows it in a further heated state. The numbers in each figure indicate the following. 1... Photosensitive sheet, 11, 21... Image forming material, 2, 12, 22... Photosensitive layer, 5... Color forming sheet, 6, 16... Color forming layer, 29... Monomer, 2
6...Dye precursor, 30...Binder,
3, 7, 13, 23...Support, 4, 14, 24
...Polymer image, 8,18,28...Dye image.

Claims (1)

[Scope of Claims] 1. A photopolymerizable composition comprising a polymerizable vinyl monomer having at least one acidic group in the molecule and a photopolymerization initiator is subjected to image exposure to photopolymerize the polymerizable vinyl monomer, and then an acid Forming a dye image by heating uniformly in a state close to a dye precursor capable of producing a dye by reacting the polymerizable vinyl monomer remaining unpolymerized with the dye precursor. An image forming method characterized by: 2. A layer consisting of a polymerizable vinyl monomer having at least one acidic group in the molecule, a photopolymerization initiator, a dye precursor capable of forming a dye with an acid, and a binder is provided on the support. Characteristic image forming materials. 3 In claim 2, the dye precursor capable of forming a dye with the acid is
An image forming material characterized by being encapsulated in microcapsules.