JPH02166451A - Photopolymerizable resin composition and recording medium - Google Patents

Abstract

PURPOSE:To obtain high sensitivity without producing Bronsted acid by incorporating a specified onium salt as a photopolymn. initiator. CONSTITUTION:A slightly water-soluble onium salt represented by formula I is incorporated as a photopolymn. initiator. In the formula I, each of R<1>-R<3> is aryl such as phenyl, naphthyl, substd. phenyl or substd. naphthyl and the substituent may be alkyl, alkoxy, nitro or halogen. Since the compd. represented by the formula I has no effective absorption band in a wavelength range of >=300nm, it is not used alone but can enhance the sensitivity of a generally used photopolymn. initiator by combination with the initiator. High sensitivity is obtd. without producing Bronsted acid.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to photopolymerizable compositions suitable for UV inks, U adhesives, photosensitive planographic printing plates, etc. that utilize photopolymerization reactions, and recording media used in recording devices such as printers, copiers, facsimile machines, etc. In particular, the present invention relates to a recording medium used in a recording method suitable for one-shot color recording.

[Conventional technology 1 Conventionally, fp4. Aromatic iodonium salts with counter anions such as AHFa and l'Fa are used as initiators for photocationic polymerization because they release strong Brønsted acids when irradiated with light (AnnualRev
iew Mater, Sci., 173-190
．． (13), 1983, etc.). Furthermore, in recent years, the application of aromatic iodonium salts having these counter anions to radical polymerization systems has been studied. For example, Fiber and Polymer Materials Research Institute Research Report No. 155 (1
(987), p. 87, describes a combination of diphenyliodonium hexafluorophosphate and p-dimethylaminobenzylidene derivatives as a highly sensitive photopolymerization initiator. Furthermore, in JP-A-61-24495, the sensitivity of photosensitive microcapsules is improved by adding diphenyliodonium hexafluorophosphate to the inner phase of the photosensitive microcapsules. However, these aromatic iodonium salts were developed as photoinitiators for cationic polymerization as described above, and have the undesirable property of releasing strong Brønsted acids upon decomposition. Furthermore, these aromatic iodonium salts are soluble in water and may have disadvantages in producing photopolymerizable compositions and recording media.
In No. 495, when diphenyliodonium hexafluorophosphate is added to the oil phase (microcapsule internal phase) during microcapsule production, propylene carbonate is used in combination. This is because diphenyliodonium hexafluorophosphate is soluble in water, and if encapsulated as it is, it will elute in water. Therefore, an aprotic solvent such as propylene carbonate is used in combination to suppress elution from the oil phase to the water phase. It is thought that there are. In this way, when the photopolymerization initiator is water-soluble, it may be necessary to use additional additives depending on the purpose of use. [Problems to be Solved by the Invention] An object of the present invention is to provide a radically polymerizable photopolymerizable composition and a composition useful for improving the sensitivity of a recording medium, without producing a strong Brønsted acid, and having almost no resistance to water. An object of the present invention is to provide a highly sensitive photopolymerizable composition containing an insoluble onium salt and a recording medium using the composition. [Means for Solving the Problems 1] The present invention provides a photopolymerizable composition comprising a compound having an ethylenically unsaturated double bond capable of radical addition polymerization and a photopolymerization initiator as essential components. A photopolymerizable composition comprising an onium salt represented by the following general formula (1) % formula % () [wherein Ht, Ht, and R3 each independently represent an aryl group], and a recording medium to which the composition is applied. First, the photopolymerization initiator of general formula (I) will be explained. Diphenyliodonium salts having the above-mentioned counter anions have been actively applied to radical polymerization systems in recent years, but the present inventors found that when diphenyliodonium salts are applied to radical polymerization systems, depending on the type of counter anion It was found that the sensitivity hardly changed. Therefore, by using a (R") 4 as a counter anion, the sensitivity in the radical polymerization system is not impaired, and
The present invention was completed by discovering an onium salt that does not generate strong Brønsted acids upon decomposition and is almost insoluble in water. In formula 11. R2,1! Examples of the aryl group corresponding to the above include phenyl group, naphthyl group, substituted phenyl group, and substituted naphthyl group. Furthermore, examples of the substituent include an alkyl group, an alkoxy group, a nitro group, and a halogen atom. Specific examples of the compound of general formula (I) include the following, but the present invention is not limited thereto. Since the compound of general formula (1) does not have an effective absorption band above 300 nm, it is not used alone, but is used in combination with a commonly used photoinitiator to improve the sensitivity of the photoinitiator. It has the effect of Photopolymerization initiators that can be used in combination include benzyl derivatives, α-diketones such as camphorquinone, benzophenone derivatives, benzoin derivatives, xanthone derivatives, thioxanthone derivatives, coumarin derivatives, chalcone rust conductors,
Examples include ketones such as styryl styryl ketone derivatives. Furthermore, the compound of general formula (I) can interact with various dyes or sensitizers to become a highly sensitive photopolymerization initiator. Such dyes or sensitizers include coumarin dyes,
merocyanine dye, xanthine dye, acridine dye,
Examples include thiazine dyes, oxazine dyes, indoline dyes, triarylmethane dyes, and tetrabenzoporphyrins. It is unclear why sensitivity increases when the compound of general formula (I) is used in combination with a photopolymerization initiator, dye, or sensitizer, but as mentioned above, sensitivity depends on the type of counter anion. Therefore, it is considered that the aryl radicals and iodized aryl cation radicals generated during the decomposition process contribute in some way to the radical polymerization reaction. Further, the compound of general formula (I) is a photopolymerization initiator used in combination,
About 1:10 to about 10:1 to dyes, sensitizers, etc.
It is preferable to use it in a ratio of (weight ratio). Furthermore, the addition-polymerizable compound having an ethylenically unsaturated double bond, which is an essential component of the photopolymerizable composition of the present invention, refers to a compound having at least one ethylenically unsaturated double bond in its chemical structure. It has chemical forms such as monomer, oligomer, and polymer. Examples include monomers such as methyl acrylate, methyl methacrylate, acrylonitrile, and acrylamide; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid, isocrotonic acid, and maleic acid; and ethylene glycol and triethylene glycol. , esters with aliphatic polyhydric polyol compounds such as tetraethylene glycol, trimethylolpropane, 1,3-butanediol, pentaerythritol, dipentaerythritol, and polyisocyanates (reacted with polyols as necessary). urethane acrylates, urethane methacrylates, and epoxy resins synthesized by the polyaddition reaction of alcohols and amines containing unsaturated double bonds, and urethane acrylates and urethane methacrylates, which are synthesized by the addition reaction of epoxy resins and acrylic acid or methacrylic acid. Examples include epoxy acrylates, polyester acrylates, spin acrylates, polyether acrylates, etc., but the present invention is not limited thereto. In addition, as a polymer, the main chain has a skeleton such as polyalkyl, polyether, polyester, polyurethane, etc.
Examples include those in which a polymerizable reactive group such as an acrylic group, a methacrylic group, a cinnamoyl group, a cinnamylidene acetyl group, and a furyl acryloyl group are introduced into the side chain, but the present invention is not limited thereto. . In addition, the photopolymerizable composition containing the above-mentioned photopolymerization initiator and a compound having an ethylenically unsaturated double bond as essential components may further contain known binders, colorants, etc. according to the purpose of use. It can be included. As the binder, any organic polymer may be used. Examples of such organic polymers include polyacrylic acid alkyl esters such as polymethyl acrylate and polyethyl acrylate; Polymethacrylic acid alkyl esters such as polymethyl methacrylate and polyethyl methacrylate, methacrylic acid copolymers, acrylic acid copolymers, maleic acid copolymers, or chlorinated polyolefins such as chlorinated polyethylene and chlorinated polypropylene, poly Examples include vinyl chloride, polyvinylidene chloride, polyacrylonitrile, or copolymers thereof, as well as polyvinyl alkyl ether, polyethylene, polypropylene, polystyrene polyamide, polyurethane, chlorinated rubber, cellulose derivatives, polyvinyl alcohol, polyvinylpyrrolidone, etc., but the present invention is not limited to these. These polymers may be used alone or in a mixture of two or more in an appropriate ratio, and may be used as binders, such as compatible or
Waxes are not limited to incompatible waxes and may be used. Any amount of these polymers can be mixed into the total composition. The colorant is a component contained in order to form an optically recognizable image, and various pigments and dyes are used as appropriate. Examples of such pigments and dyes include inorganic pigments such as carbon black, yellow lead, molybdenum red, and red iron.
Banza Yellow, Benzidine Yellow, Brilliant Carmine 6B. Examples include organic pigments such as Lake Red C1 Permanent Red F5R and Phthalocyanine Blue, leuco dyes, phthalocyanine dyes, and colorants such as Victoria Blue Lake and Fast Sky Blue. The photopolymerizable composition of the present invention is used by appropriately mixing the various components described above depending on the purpose of use. For example, for use in photosensitive lithographic printing plates, the mixture may be dissolved in a suitable solvent to
A photosensitive layer is formed by coating it on a support such as polypropylene, polystyrene (polypropylene, polystyrene, etc.) or metal plate (aluminum, zinc, etc.), imagewise exposed using a light source such as a high-pressure mercury lamp, fluorescent lamp, Xe lamp, etc., and then processed with a developer. The photopolymerizable composition of the present invention has high sensitivity and is effective in shortening the time required for plate production. In addition, as a coloring agent, a substantially colorless coloring agent may be used to develop the color by reacting with a coloring agent in a subsequent step.Such coloring agents include lactones and lactams in their partial skeletons. , sultone, spiropyran, a substantially colorless compound having an ester or amide structure, such as triarylmethane compounds, bisphenylmethane compounds, xanthine compounds, fluorans, thiazine compounds, and spiropyran compounds. Cyan, magenta and yellow precursors useful in the present invention may be selected from commercially available materials. Layout・
Yellow (Reakt Yellow) (186) (
BASF products), Copikem XI
and Cobichem XIV (a product of Hilton Davis Chemical Company) are useful yellow color formers. Cyan B-29663 (an experimental compound from Hilton Davis), Cobichem X (a product of Hilton Davis) and the color formers described in U.S. Pat. Yes, and Cobichem xx (a product of Hilton Davis) and Pergascript Red (Pergascript
Red (a Ciba-Geigy product) is useful as a magenta color former. Furthermore, as a color developer, for example, clay minerals such as acid clay, activated clay, and attapulgite, organic acids such as tannic acid, gallic acid, and propyl gallate, phenol-formaldehyde resins, phenolacetylene condensation resins, and at least one Acidic polymers such as condensates of formaldehyde and organic carboxylic acids having hydroxyl groups, zinc salicylate, tin salicylate, zinc 2-hydroxynaphthoate, zinc 3.5-di-t-butylsalicylate, 3-cyclohexyl -5-(α,α-dimethylbenzyl)zinc salicylate (U.S. Pat. No. 3.864.146)
and oil-soluble metal salts of phenol-formaldehyde novolac resins (see, e.g., U.S. Pat. No. 3,672,935). , 3rd, 7th
32.120, 3.737.410), zinc-modified oil-soluble phenol-formaldehyde resins, such as those disclosed in U.S. Pat. No. 3.732.120, zinc carbonate, and the like; It is a mixture of them. Furthermore, the photopolymerizable composition of the present invention can be used as a recording medium for an image forming system that utilizes a photopolymerization reaction. In particular, U.S. Patent No. 4,399,209, JP
It is suitable as a recording medium for the image forming method disclosed in Specification No. 1-24495 and Japanese Patent Application Laid-open No. 174195/1984. Here, the method described in Japanese Unexamined Patent Publication No. 174195/1988 will be briefly explained. JP-A-62-174195 discloses a method for recording at least one type of energy among the plurality of types of energy on a transfer recording medium having a transfer recording layer in which the physical properties governing transfer characteristics change when a plurality of types of energy are applied. This is an image forming method in which a transferred image is formed by applying the plurality of types of energy under conditions that correspond to information, and then transferred onto a recording medium. In the image forming method, a photopolymerization initiator and a compound having an ethylenic saturated double bond (hereinafter referred to as a polymerizable monomer) capable of addition polymerization are used, using light energy and thermal energy, and the thermal energy is made to correspond to recorded information. Also, a method of applying the coloring material to a transfer recording layer which is in a solid phase at room temperature and which includes a coloring material as an essential component will be explained. The transfer recording layer has a softening temperature Ts, and its viscosity decreases rapidly at temperatures above Ts. Here, the transfer recording layer is uniformly irradiated with light corresponding to the absorption wavelength of the photopolymerization initiator contained in the transfer recording layer, and at the same time, a heating means such as a thermal head is used to raise the transfer recording layer to a temperature of Ts or higher according to the recorded information. When partially heated, the viscosity of the portion heated above Ts rapidly decreases, the diffusion rate of the photopolymerization initiator and polymerizable polymer in the transfer recording layer increases, and the polymerization reaction rapidly progresses. On the other hand, in the non-heated area, the viscosity of the transfer recording layer does not decrease, so the photopolymerization initiator and polymerizable monomer do not diffuse sufficiently and the polymerization reaction occurs only partially. If the recording medium on which the transferred image has been formed is brought into pressure contact with the recording medium to be transferred and heated to a predetermined temperature necessary for transfer, for example, a temperature higher than Ts, the polymerization reaction will partially occur in the non-heated part of the thermal head. The areas where only a small amount of light has formed are transferred to the recording medium, and the heated part of the thermal head has sufficient polymerization, so the adhesion to the recording medium is weak and the area is not transferred.In this way, light energy and heat The energy forms an image. In addition, although the softening temperature Ts of the transfer recording layer has been explained as a physical property value that governs the transfer characteristics and polymerization reaction amount of the transfer recording layer, in addition to this, the glass transition point, melting temperature, etc. of the transfer recording layer can be used. I don't mind. In the present invention, the transfer recording layer may be a continuous layer coated on a support, or may be a layer coated with particulate bodies. Furthermore, the microcapsule may be composed of a core material containing a composition whose transfer characteristics change upon application of light and thermal energy. In addition, in order to form a multicolor image in the present invention, a transfer recording layer is formed of particulate bodies or microcapsules containing colorants exhibiting several different color tones, and a photopolymerization initiator contained therein is used. This can be done by changing the wavelength range to which the light is sensitive. That is, thermal energy modulated according to the recording signal is applied together with optical energy of a wavelength selected according to the color tone of the image forming element whose physical properties governing the transfer characteristics are desired to be changed. "Modulation" refers to changing the position where energy is applied according to the image signal, and "together" can mean applying light energy and thermal energy at the same time, or applying light energy and thermal energy separately. It is okay if you do. Next, a multicolor image forming method that can bring out the effects of the present invention most will be described. FIGS. 1A to 1C are partial views showing the relationship between the transfer recording medium and the thermal head of the present invention. The recording medium 1 of the present invention has a transfer recording layer 1a on a support ib.
It is configured with the following. The transfer recording layer 1a is a layer in which minute image forming elements 3 are distributed, and each image forming element 3 is
For example, in the embodiment shown in FIG. 1, each image forming element 3 contains colorants exhibiting different color tones.1 For example, in the embodiment shown in FIG. Contains colorants. Here, each of the Y, M, and C image forming elements contains a photopolymerization initiator having a different photosensitive wavelength range. Next, a specific example of the image forming method using the recording medium of the present invention will be shown. First, the transfer recording medium 1 is stacked on the thermal head 2, and light is irradiated so as to cover the entire heat generating part of the thermal head 2. The irradiated light is sequentially irradiated with wavelengths that the image forming element 3 reacts with. For example, if the image forming element 3 is colored cyan, magenta, or yellow, the wavelengths λ(C), λ (M) and λ(Y) are sequentially irradiated with light. That is, first, light of wavelength λ(Y) is irradiated from the transfer recording N1a side of the transfer recording medium 1, and the heating elements 2b, 2d, 2e, and 2f of the thermal head 2, for example, are caused to generate heat. Then, of the image forming element 3 containing the yellow coloring material, the image forming element 3 to which both heat and light of wavelength λ(Y) are applied (the hatched part in FIG. 1-a) (Hereinafter, the cured image forming element is indicated by hatching.)
hardens. Next, as shown in FIG.
When the light of (M) is irradiated and the heating elements 2a, 2e, and 2f generate heat, heat and light of wavelength λ(M) are added to the image forming element 3 containing the magenta coloring material. The image forming element 3 is cured. Furthermore, as shown in Figure 1-0, when light of wavelength λ(C) is irradiated and a desired heating element is heated, the image forming element 3 to which the light and heat have been applied is cured, and the final image is formed. A transferred image is formed on the transfer recording layer 1 by the image forming element 3 that has not been cured. The transfer image formed as described above is transferred to the transfer recording medium by pressing it against the transfer recording medium and heating it to a predetermined temperature (that is, the unhatched Y in FIG. 1C), M and C image forming elements 3 are transferred]. Here, by simultaneously using the photopolymerization initiator contained in the recording medium of the above-mentioned image forming method and the compound represented by general formula (1), high photosensitivity can be achieved, and the heating time of the recording medium can be shortened. Therefore, the recording speed is improved. Further, in the image forming method described in the specification of US Pat. No. 4,399,209, the image forming element (microcapsule) contains the above-mentioned photopolymerizable heptamer 1 photopolymerization initiator and a coloring agent ( (later developed by reacting with a color developer) as an essential component. Also in this image forming method, photosensitivity and recording speed can be improved by using the photopolymerization initiator and the compound of general formula (1) together. [Example] The present invention will be specifically explained below with reference to Examples. Synthesis example: Synthesis of diphenyliodonium tetraphenylborate> L KAgNOs
Dissolve 67.5 g of
mj) to precipitate Ag2O, this Agz
About 70 g (wet) of O and 24 g of diphenyliodonium chloride (1) are stirred in about 250 aj of ion-exchanged water for about 20 hours (under light shielding).Next, the reaction solution is filtered, and NaB (Q) a is added to the filtrate. Aqueous solution (NaB(QL3
4 g in LOcaloomj) is added and the precipitated crystals (z) are filtered out. The obtained crystal (z) was confirmed to be diphenyliodonium tetraphenylborate. Melting point: 195-198°C The IR spectrum of the obtained crystal (2) is shown in FIG. Step 1: As a compound having an ethylenically unsaturated double bond, 10 g% M of Aronix M-8030 manufactured by Toagosei Chemical Industry Co., Ltd.
10 g of -1100, 15 g of DuPont PMMA2041 as a binder, Ig of the compound shown in Table 1 as a photopolymerization initiator, 0.5 g of ethyl-p-dimethylaminobenzoate, and a compound represented by general formula (I). (
Using 0.8 g of (Table 1) and 0.3 g of Kayaset Blue 136 (manufactured by Nippon Kayaku Co., Ltd.) as a dye, dissolve it in about 200 dichloromethane, and spread it on an aluminum plate with a thickness of about 5 pm using a spinner. Approximately 30% of polyvinyl alcohol (PVA) is applied as an antioxidant layer on the coated photosensitive layer.
The sample was coated with a thickness of -. Place an optical wedge (optical density 0-10 steps) on top of this sample 4
After exposure with a 50W Xs lamp for 15 seconds, the PVA was removed by washing with water, and the photosensitive layer was further exposed to 1.1. The highest number of optical wedges corresponding to the image developed after treatment with i-trichloroethane for 30 seconds is shown in Table 1 as the sensitivity of the sample. The sensitivity in the case where the compound of general formula CI) is not added is also shown. As can be understood from the results in Table 1, sensitivity is increased by using the compound of general formula (I) in combination with a photopolymerization initiator. 9.10 1-3 In order to confirm that the compound of general formula (I) does not release Brønsted acid when photodecomposed, cationic polymerization was performed. 5 cationic polymerization monomer CY179 manufactured by Ciba Geigy
g, 0 2,4-diethylthioxanthone as a sensitizer
, 3g and 0.3g of the compound of general formula (1) were dissolved in about 10ml of dichloromethane and coated on an aluminum plate to a thickness of about 3μ. Next, a 450W Xe lamp was irradiated, and the time required for the surface to become tack-free was determined. At the same time, a similar test was conducted using a diphenyliodonium salt having BF, PF, 5bF4 as a counter anion in place of the compound of general formula (I) having the above composition. The results are shown in Table 2. As understood from Table 2, the compounds of Comparative Examples 1 to 3 release acid and cause cationic polymerization upon photolysis. On the other hand, in the compounds of Examples 9 and 10, cationic polymerization did not occur even after 60 seconds of light irradiation, indicating that no acidic substances were released. 11.12 4.5 Image formation using light and thermal energy was performed in the image forming method described in JP-A-62-174195. (Preparation of recording medium) Mix 100 g of water and 26 g of isobutylene-maleic anhydride copolymer (20.6%, manufactured by Kureha Chemical Co., Ltd.) from the microcapsules,
3.1g of pectin was added to this and stirred for 20 minutes.
The pH was then adjusted to 4.0 with a 20% sulfuric acid solution. 0.2 g of Quadrol (manufactured by BASF) was added. While stirring this with a homomixer at 3000 rpm,
A solution prepared by dissolving 20 g of the components shown in Table 3 in 30 g of chloroform was added over 10 to 15 seconds and emulsified for 10 minutes. The emulsion was transferred to a bead force of 500 mA and stirred with a stirring blade for 1 to 2 hours, and then the solvent was distilled off. Next, 8.3 g of urea solution (50 wt%), 0.4 g% of resorcinol dissolved in 5 g of water, 10.7 g of formalin (37%) and lOmj! 0.6 g of ammonium sulfate dissolved in water were added at 2 minute intervals. After raising the temperature to 60° C. and continuing stirring for 3 hours, the temperature was lowered and the pH was adjusted to 2.0 with a 20% caustic soda solution. After filtering this capsule liquid, 1000 mj twice!
This was washed with water and dried to obtain a microcapsule-shaped image forming element. As shown in FIG. 2, this image forming element is a microcapsule in which a core lc is covered with a shell 1d, and the particle size is 7 to 15.
The average particle size of the mucus was that of the θμ nail. Next, a polyester adhesive (LP-022, manufactured by Nippon Gosei Kagaku Kogyo ■) was applied as an adhesive layer 1e to a thickness of about 1 μm on the PET film lb as a support. An excess amount of the microcapsules was sprinkled onto the adhesive layer, and the excess image forming element not attached to the adhesive was brushed off. Next, the transfer recording media were pressed against each other at 1 kgf/cm'', and the speed was set at 300 mm/min between rollers each coated with 1 mm thick silicone rubber with a hardness of 70 degrees on an aluminum roller with a diameter of 40 mm. At this time, the surface temperature of each roller was maintained at 80° C. After passing between the rollers, the image forming element on the adhesive layer was firmly fixed to the PET film. A transfer recording medium l as shown in the schematic cross-sectional view of Fig. 2 was obtained by this method. (Sensitivity evaluation) Next, the recording medium l produced by the above method was wound into a roll and placed in the apparatus shown in Fig. 3. The thermal head 2 was an A4 size line type with 8 dots/mm and heat generating element arrays were arranged at the edges, and the heat generating elements were pressed against the heat generating elements by the tension of the recording medium l. Then, a chemical lamp 4 was placed at the opposite location.A lamp with a peak wavelength of 390 nm (manufactured by Toshiba, F10A70E39/33T15) was used as the chemical lamp 4, matching the sensitive wavelength range of the photopolymerization initiator.Next, The heat generation of the thermal head 2 is controlled according to the image signal. In this embodiment, a transfer recording layer whose softening temperature rises due to the application of light and heat and whose transfer start temperature also rises is used, so negative recording is performed. That is, the thermal head 2 is controlled such that it does not energize when there is a mark signal (magenta), but it energizes and generates heat when it is not a mark signal (white).The energizing energy at this time of heat generation is 0.8W/dotX
m5ec, the chemical lamp 4 synchronizes with the signal of the thermal head 2, uniformizes the X m5ec light irradiation, controls and drives the thermal head 2 according to the image signal as described above, and repeats 2 Xm5ec/1ine. The recording medium was conveyed synchronously with a stepping motor and a drive rubber roll, and then, as shown in FIG. and pinch rolls 9 and transported. The heat roll 8 has a 300W heater 7 inside, and the surface
The heater 7 was controlled to maintain the surface of the aluminum roll coated with mm-thick silicone rubber at an arbitrary temperature in the range of 50 to 150°C. The pinch roll 9 is a silicone rubber roll with a hardness of 50 degrees according to the JIS rubber hardness tester, and the pressure is IN1, 5k.
g/cm2. Controlling the heat roll 8 in the range of 110°C to 130°C,
After the plain paper was conveyed over the transfer recording layer, the support 1b was peeled off, and the minimum time X m5ec for obtaining an image was determined and defined as the sensitivity. That is, the smaller the value of X, the higher the sensitivity. Moreover, the obtained image was a high-quality image with good fixability. The results are shown in Table 4. Furthermore, the composition shown in Table 3 was dissolved in dichloromethane, and P
A recording medium was prepared by coating H7 with a thickness of 3 μm and a PVA layer of 3 μm thereon, and evaluating the sensitivity using the method described above (the PVA layer was removed by washing with water during the transfer process). Table 4 also shows the results when the compound of general formula (I) was excluded from the composition shown in Table 3, and when diphenyliodonium hexafluorophosphate was used in place of the compound of general formula (1). Table 4 1): Sensitivity A is in the microcapsule state. Sensitivity B is applied directly onto PH7. As can be seen from Table 4, by adding the compound of general formula (I), the sensitivity is significantly improved in both microcapsule form and direct application. In addition, as in Comparative Example 5, when diphenyliodonium hexafluorophosphate is used, it contributes to improved sensitivity when applied directly, similar to the compound of general formula (I), but when used in the form of microcapsules, the sensitivity improves. This is because during the microcapsule manufacturing process,
This is thought to be because diphenyliodonium hexafluorophosphate was eluted into the water. As is clear from the above, the compound of general formula (I) is effective in improving the sensitivity of a recording medium, and even if an aqueous substance is used during the manufacturing process of the recording medium, the sensitivity will not be adversely affected. Cold 1 Dish 1A Next, a method for forming a multicolor image using the image forming method described in JP-A-62-174195 will be described. First, in Table 3, the photopolymerization initiator 2-chlorothioxanthone is replaced with 4,4'-dimethoxybenzyl, and the compound of general formula (I) is 4.4°-di-t-butyldiphenyliodonium tetraphenyl. A borate composition and a composition shown in Table 5 below were each made into a microcapsule-shaped image forming element in the same manner as in Example 11. Next, the magenta and yellow hues obtained as described above were obtained. In the same manner as in Example 11, the same amount of microcapsules were fixed onto PET coated with an adhesive to prepare a recording medium. (See Figure 5) Here, 4.4°-dimethoxybenzyl and 3.3°-carbonylbis(7-dinithylaminocoumarin) have the absorption characteristics shown in Figures 6 and 7, respectively (in chloroform). . The transfer recording medium l produced by the above method was incorporated into the apparatus shown in FIG.
Toshiba, FIOA70ε35/33T15) and lamp B with a peak wavelength of 450 nm (Toshiba, F10A70B/
33T15) were placed. The transfer recording layer 1a has a property that when light and heat of a predetermined wavelength are applied, the softening point temperature increases and it is no longer transferred to the recording paper. When recording magenta color, power is not applied to the heating element corresponding to magenta of the image signal in the heating element array of the thermal head, but a current of 10 m5ec is applied to the part corresponding to the white of the image signal (the recording medium is white). At the same time, lamp A is uniformly irradiated for 12 m5ec. Next, when recording yellow, 8 m after the end of the lamp A irradiation.
After 5ec has passed, that is, 20m5e from the above energization time.
After c, a portion of the heating element of the thermal head corresponding to the yellow color of the image signal is energized for 12 m5 ec, and at the same time, lamp B is uniformly irradiated for 15 m5 ec. By controlling the thermal head according to the image signals of magenta, yellow, and white in the manner described above, a negative image is formed on the transfer recording layer, and is transferred onto plain paper in the same manner as in Example 11.
Color recording is done in one shot. [Effect of the invention] As explained above, as a photopolymerization initiator, general formula (I)
By containing the onium salt, it does not elute into water during microcapsule production, and since it does not release Brønsted acid during decomposition, there is no adverse effect during radical polymerization, and it can be used as a recording medium. This is intended to improve the sensitivity of the image.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of transfer recording using the recording medium of the present invention.
Figures 3 and 4 are schematic diagrams of an apparatus for performing transfer recording using the recording medium of the present invention, Figures 2 and 5 are configuration diagrams of the transfer recording medium, and Figures 6 and 7 are photopolymerization FIG. 8 is a UV chart showing the light absorption characteristics of the initiator, FIG. 8 is a timing chart, and FIG. 9 is an IR spectrum diagram of diphenyliodonium tetraphenylborate. 1...Recording medium la...Transfer recording layer tb...Support lc, I
g, fh...Core ld...Shell 1e...
Adhesive layer 2... Thermal head 4... Lamp 6... Supply roll 8... Heat roll IO... Plain paper 12... Recorded image 3... Image forming element 5... Control Circuit 7... Heater 9... Pinch roll II... Winding roll (a)

Claims (1)

[Scope of Claims] 1) In a photopolymerizable composition containing a compound having an ethylenically unsaturated double bond capable of radical addition polymerization and a photopolymerization initiator as essential components, the photopolymerization initiator is a compound having the following general formula ( I) ▲There are mathematical formulas, chemical formulas, tables, etc.▼・・・・・・( I
) [In the formula, R^1, R^2, and R^3 each independently represent an aryl group. ] A photopolymerizable composition comprising an onium salt represented by the following. 2) It has a transfer recording layer on a support whose physical properties governing the transfer characteristics change by applying light energy in correspondence with image recording information, and the transfer recording layer has at least a coloring material and light energy. A recording medium formed from an image-forming element that is solid at room temperature and comprising a sensitive component that becomes sensitive when the sensitive component is applied, and the sensitive component is the photopolymerizable composition according to claim 1. . 3) A transfer recording layer having a transfer recording layer on a support whose physical properties governing the transfer characteristics change by simultaneously applying at least one type of energy of light and thermal energy corresponding to image recording information; The recording layer is formed from an image forming element that is solid at room temperature and includes at least a coloring material and a sensitive component that becomes sensitive upon application of light energy and thermal energy, and the sensitive component is the photosensitive component according to claim 1. A recording medium characterized by being a polymerizable composition.