Light-and heat-sensitive recording material and recording method by use thereof

Abstract: A light- and heat-sensitive recording material is disclosed, comprising a support provided thereon a light- and heat-sensitive layer containing a photo-color-forming element comprising a photodecomposable compound and an element capable of forming a color upon reaction with a decomposition product of the photodecomposable compound, wherein the photo-color-forming element is imagewise heated so as to be mixed to thereby form a latent image and the latent image is further exposed to light to form a color; at least one of the photodecomposable compound and the element capable of forming a color upon reaction with the decomposition product of the photodecomposable compound being dispersed through solution in an organic solvent.

Description: Field of the Invention The present invention relates to a light- and heat-sensitive recording material which is subjected to heating, followed by exposure to light to form color images and a recording method by use thereof. Background of the Invention Thermal recording materials using a thermal print-head are broadly employed in a variety of fields such as facsimile machines and printers, because of such features as a simplified recording apparatus, no need of a development process, no noise during recording, no mechanical maintenance and inexpensive operating cost. Although conventional thermal recording materials have the above-described features, the color forming reaction occurs merely by application of heat, so that unwanted color-forming inevitably occurs during storage, in particular, when materials are allowed to stand at a high temperature and high humidity over a long time period. A photosensitive recording material which is imagewise exposed to light to form a color image has been known in so-called free radical photography. For instance, there is known a method of forming a color image by oxidation of a variety of leuco dyes by use of free radicals produced by exposure to UV light, or a method of obtaining a color image by reacting the photolytically produced free radicals with an aniline derivative to form a triarylmethane type dye, as disclosed in Phot. Sci. Eng., 5, 98-103 (1961); JP-B 43-29407 (herein, the term, "JP-B" is referred to as examined published Japanese Patent), JP-A 55-55335, 57-60329 and 62-66254 (herein, the term, "JP-A" is referred to as an unexamined published Japanese Patent Application). There is also disclosed an image forming material such as Dylux R , produced by du Pont, which involves image formation by exposure to UV light, followed by fixation by activating a photoreducible material with visible light. Image formation only by exposure to light through an original has the advantages that the apparatus and operation are quite simple; however, there are also the disadvantages that handling it is limited to darkroom conditions and its storage stability is poor. As an example of applying these color forming principles to thermal recording, a light- and heat-sensitive recording material containing a photolytical free radical producing compound and an oxidatively color-forming type leuco dye in a separated state at ordinary temperature is disclosed in JP-A 60-2393. In a thermal recording material of this type, the recording apparatus may be provided with at least a thermal print-head and light source necessary for overall light-exposure and recording can be made through simple operation, without compromising the advantages of conventional thermal recording. In order to produce a high color density image by use of the above-described light- and heat-sensitive recording material, however, it is required to dissolve and sufficiently mix a free radical producing compound and the leuco dye so that, during the period from heat-recording to light exposure, dissolved and mixed components cool and precipitate, resulting in deterioration of color forming potential. Further, a light- and heat-sensitive recording material (hereinafter, referred to merely as a recording material) having a coating containing a specific pyrazolone compound and a specific phenol compound and a salicylic acid derivative as color-forming aids is disclosed in JP-A 7-237354, in which these compounds are heated and mixed to form a latent image, followed by exposure to UV light to develop a color image. Although the color-forming mechanism of this recording material is not fully understood, it is believed that the pyrazolone compound is photolytically decomposed to form a color forming dye and the phenol compound and salicylic acid derivative accelerate the photolysis. Neither of these compounds above-described is photolyzable by itself. As described in the above disclosure, the pyrazolone compound is likely to decompose at high temperatures to form color, resulting in such disadvantages that fogging occurs during long-term storage and, in particular, at high temperature and high humidity and that the background portion tints after image recording. It was further found that a color density was lowered when dissolving and mixing by the thermal head was insufficient. As none of these compounds is photodecomposable before being heated and mixed, non-recording portions are not fixed and uncolored portions can be readily changed by reheating and exposing to light. Each of the above-described recording materials is concerned with monochromatic color image recording and there was no cited example in the references of its application to multicolor images. With regard to multicolor thermal recording materials which have so far been proposed, various methods, in which to form independently each color, it was necessary to fix an element recorded at a low temperature, so as to prevent color-forming when recording at a high temperature. As a fixable multicolor thermal recording material is cited a recording material containing a diazonium compound and a coupler, in which the diazonium compound is subjected to thermal recording to form a color image, followed by light exposure to decompose the compound and stop color-forming , and subsequently succesive recordings are made. Although the diazonium could be stabilized by varying its substituent or a counter salt, the diazonium is, however, basically an unstable compound, and particularly unstable in heat and poor in storage stability. Accordingly, there has been a strong desire for a thermal recording material which is stable to heat, and fixable. JP-A 1-129247, 1-143252 and 3-10252 and 3-1983 disclose a recording material in which a free radical photoproducing material and a leuco dye are enclosed on a microcapsule, and outside thereof, a reducing agent is present. There is also described an application of the recording material for multicolor recording, in which the reducing agent is present in the microcapsule and mixed with the free radical producing compound enclosed in the microcapsule during thermal recording, followed by cassation of colour-forming, and subsequent overall exposure to form a colour in the unheated portion. However, the above-described recording material has the disadvantage that the oxidative colour-forming type leuco dye is capable of reacting with the free radical producing compound to form a colour and on exposure to roomlight or sunlight during storage over a long period of time, the free radical producing compound is gradually decomposed and produces fog. Therefore, a light- and heat-sensitive recording material which can be easily manipulated and has excellent storage stability, has been strongly desired. JP 63-159845 discloses a free radical recording material comprising a recording layer containing a free radical generating compound and a colouring agent provided on the base. At least one of the free radical generating compound and the colouring agent is included in a microcapsule. The colouring agent is suitably an aromatic amine compound, an aromatic diamine compound or a leuco dye. Summary of the Invention Accordingly, an object of the present invention is to overcome the above described problems in the prior art and to provide a light- and heat-sensitive recording material, in which a recording image is formed by the use of two types of energies, heat and light, involving only steps of heating with a thermal head and simply exposing to light to obtain a multi-colour image excellent in colour formability without fogging during storage. Another object of the invention is to provide a light- and heat-sensitive recording material superior in fixability and a recording method by use thereof. The above-described objectives can be accomplished by the following constitution: (1) A light- and heat-sensitive recording material comprising a support having provided thereon a light- and heat-sensitive layer having therein a photo-colour-forming element comprising a photodecomposable compound and a component capable of forming a colour upon reaction with a decomposition product of the photodecomposable compound, wherein said photo-color-forming element can be imagewise heated so as to be mixed to thereby form a latent image and the latent image may be exposed to light to form a color; at least one of the photodecomposable compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound being present as a dispersion in an organic solvent, wherein at least one of the photodecomposable compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound is enclosed in microcapsules, and wherein the photodecomposable compound is a free radical producing compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound is a coupler and an aromatic primary amine compound, or the photodecomposable compound is an aromatic azide compound, and the component capable of reacting with the decomposition product is a coupler. (2) The recording material described in (1), wherein the organic solvent is a high boiling solvent having a boiling point of not less than 100°C. (3) The recording material described in (1), wherein at least one further photo-colour-forming element comprising a photodecomposable compound and a component capable of reacting with a decomposition product of the photodecomposable compound is provided and at least one of the photodecomposable compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound is present as a dispersion in an organic solvent. (4) The recording material described in (3), wherein the at least two photo-colour-forming elements form colours different in hue from each other. (5) The recording material described in (3) or (4), wherein the at least two photo-colour-forming elements form colours different in density from each other. (6) The recording material described in (3) to (5), wherein the at least two photo-colour-forming elements are separately contained in at least two different layers. (7) The recording material described in (3) to (5), wherein the at least two photo-colour-forming elements are provided in the same layer. (8) An image forming method by use of a light- and heat-sensitive recording material described in (1) to (7), which method comprises heating imagewise the photo-colour-forming element to mix the photodecomposable compound and the component capable of forming a colour, thereby forming a latent image and then exposing the formed latent image to light to develop the latent image, forming a colour image. (9) The image forming method described in (8), wherein two photo-colour-forming elements are provided on the support, and the two photo-colour-forming elements are respectively heated with different thermal energies to form a latent image. (10) The image forming method described in (8), wherein two photo-colour-forming elements are provided on the support, and the two photo-colour-forming elements are respectively exposed to light at different wavelengths to form a colour. (11) The image forming method described in (8) to (10), wherein the photo-colour-forming element which has not been heated is exposed to light so that colour formability of the non-heated photo-colour-forming element is inhibited. In the light- and heat-sensitive recording material of the invention and the image forming method by use thereof, the photo-colour-forming element provided on the support is heated so that the photodecomposable element and the component capable of forming a colour are thereby mixed, followed by light exposure to produce a dye, thereby forming a colour image. In a non-heated portion in which the photo-colour-forming element has not been mixed, when exposed to light, the dye forming reaction does not occur and only photolysis of the photodecomposable compound occurs. In such a light- and heat-sensitive recording material and a recording method by use thereof, the recording apparatus may be a conventional thermal recording apparatus provided with a light source, such as a fluorescent lamp and an excellent colour image can be obtained without jeopardizing the advantages of conventional thermal recording. The photodecomposable compound and that the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound are not mixed with each other before being subjected to heating, so that, even in cases where being exposed to a roomlight or allowed to stand for a long period of time, unwanted colour forming reaction does not occur and handling becomes easier. Detailed Description of the Invention In the invention, the photo-color-forming element comprises a photodecomposable compound and an element capable of forming a color upon reaction with a decomposition product of the photodecomposable compound. The photodecomposable compound is capable of being decomposed on exposure to light at particular wavelengths, such as UV light, visible light or infrared light, and is a free radical photolytically-producing compound (so-called free radical photo-generator), or an azide compound. As examples of the free radical producing compound are cited a 2,4,6-triarylimidazole dimer described in JP-B 62-39728 and 63-2099; 2-azidobenzooxadiazole, benzoylazide and 2-azidobenzimidazole, described in U.S. Patent 3,282,693; a pyridinium compound such as 3'-ethyl-1-methoxy-2-pyridothiacyanine perchlorate, l-methoxy-2-methylpyridinium-p-toluenesulfonate, described in U.S. Patent 3,615,568; an organic halogen compound such as N-bromosuccinimide, tribromomethylphenylsulfone, diphenyliodide, 2-trichloromethyl-5-(p-butoxystyryl)-1,3,4-oxadiazole and 2,6-bis (trichloromethyl)-4-(p-methoxyphenyl)-s-triazine; a carbonyl compound such as benzophenone, thioxanthone, anthraquinone and benzoin ether; an azo compound such as azobisisobutylonitrile; an organic sulfur compound such as an alkyldisulfide or mercaptan and phosphorus compound such as triphenylphosphine. The wavelength at which the photodecomposition of the compound takes place can be optionally selected by taking account of handleability as a recording material, availability of a light source to be used and cost. With regard to the handleability as a recording material, for example, if the material is highly sensitive to the wavelength region of such a roomlight, it has a problem in stability, so that the use thereof is limited to handling under darkroom light. To avoid such a limitation, it is preferred to employ the range of from UV region to a partial region of visible light and infrared light. Among these, the light within the range of 300 to 450 nm is preferred, taking account of strength of its energy and no need of using such an expensive material as quartz. The photodecomposable compound, after being decomposed, produces a dye, upon reaction of its decomposition product with an component capable of forming a color upon reaction with the decomposition product of the photodecomposable compound. The decomposition product may constitute a part of the dye produced or may concern only the dye producing reaction to change to another compound. It depends on a combination of the photodecomposable compound and the component capable of forming a color upon reaction with the decomposition product of the photodecomposable compound and can be selected by taking account of forming efficiency, hue, fastness and extinction coefficient of the dye produced upon the reaction. As the reaction with the decomposition product of the photodecomposable compound to produce a color forming dye, the following three modes of reaction are cited, though a variety of reactions can be employed. In the above, A represents a photodecomposable compound and A' represent its photodecomposition product. B, C and D represent compounds capable of reacting with A' to form a color. D', B-C and A-C represent formed coloring dyes. B' represents a modified form of B, resulted from the reaction with A'. The above described reaction equations represent schematically reactions of each type, which are useful to understand what each dye skeleton originates from. In the above reactions, an element capable of reacting with A' to form a color may be comprised of a single compound (corresponding to modes 1 and 3) or two kinds of compounds (corresponding to mode 2). It may be comprised of three or more kinds of compounds. An auxiliary component for accelerating dye forming reaction (e.g., base, acid, etc.) may be contained in the photo-color-forming element, though it is not described therein. In the case of mode 1, thus, the reaction of the photodecomposition product of A with D gives rise to a coloring dye through oxidation or decomposition, therefore, the basic skeleton of the coloring dye originates from D. In the case of mode 2, one of the color forming elements, B reacts with A', giving rise to an activated species (through a change such as oxidation or decomposition), which further reacts with another color forming element, C (through such as coupling reaction) to form a coloring dye. In this case, the basic skeleton of the formed dye originates from B and C. In the case of mode 3, A' reacts with C (through such as coupling reaction) to a dye. In this case, the basic skeleton of the dye originated from A and C, which is different from the case of mode 1. As examples of mode 1 (not used according to the invention), the photodecomposable compound is a free radical producing compound such as a 2,4,6-triarylimidazole dimer compound or an organic halogen compound; and the component capable of forming a color upon reaction with the decomposition product of the photodecomposable compound is a leuco dye. In this case, the decomposition product formed upon exposure to light is an imidazolyl free radical or halogen free radical, which have strong oxidizing ability. Using the strong oxidizing ability, for example, the leuco dye is oxidized to form a coloring dye. Of the leuco dyes (in other words, oxidative-color-forming type leuco dyes) are usable those described in U.S. Patent 3,445,234 and representative structures thereof are shown as below. 1) Aminotriarylmethane 2) Aminoxanthene 3) Aminothioxanthene 4) Amino-9.10-dihydroacridine 5) Aminophenoxazine 6) Aminophenothiazine 7) Aminodihydrophenazine 8) Aminodiphenylmethane 9) Leucoindamine 10) Aminohydrocinnamic acid 11) Hydrazine 12) Leucoindigoid dye 13) Aminodihydroanthraquinone 14) 4,4'-Biphenol 15) 2-(p-Hydroxyphenyl)-4,5-diphenylimidazole 16) Phenethylaniline Exemplary compounds include leucocrystal violet, tris(4-dimethylamino-o-tolyl)methane, bis(4-dimethylamino-o-tolyl)phenylmethane, bis(4-dimethylamino-o-tolyl)thienylmethane, 2-(2-chlorophenylamino-6-N,N-dibutylamino-9-(2-methoxycarbonyl)-phenylxanthene, 2-N,N-dibenzylamino-6-N,N-diethylamino-9-(2-methoxycarbonyl)phenylxanthene, benzo[a]-6-N,N-diethylamino-9-(2-methoxycarbonyl)phenylxanthene, benzoylleucomethylene blue, benzoyl-3,7-diethylaminophenoxazine, benzoyl-3,7-diethylamino-9-phenyldihydrophenazine, 6,6'-di-t-butyl-p,p'-bi-o-cresol. Of these, preferred leuco dyes include triarylmethane type leuco dyes such as tris(4-dimethylamino-o-tolyl)methane and acylated leucoazine type dyes such as benzoylleucomethylene blue, benzoyl-3,7-diethylaminophenoxazine and benzoyl-3,7-diethylamino-9-phenyldihydrophenazine. Examples of the free radical producing compound used in combination with the above-described leuco dye include a 2,4,6-triarylimidazole dimer compound and an organic halogen compound such as tribromomethylphenylsulfone and 2,6-bis(trichloromethyl)-4-(p-methoxyphenyl)-s-triazine. These free radical producing compounds are able to increase inherent sensitivity and spectral sensitivity in combined use of a variety of sensitizers. Exemplary sensitizers are referred to those described in K. Tokumaru and M. Ohgahara "Zohkanzai" (Sensitizers) Kodansha (1987) pp. 64-75. As examples of mode 2, the photodecomposable compound is a free radical producing compound, of which decomposition product has oxidizing ability similar to the case of mode 1 and the component capable of forming a color upon reaction with the decomposition product of the photodecomposable compound to form a color is a coupler and aromatic primary amine compound. As well known in the field of silver halide photographic light sensitive materials, aromatic primary amines such as N,N-diethyl-p-phenylenediamine and 4-aminoantipyrine undergo oxidative coupling reaction with phenols or active methylene compounds to form an azomethine dye. Accordingly, using the above-described free radicals, the oxidative coupling reaction is also caused to occur to form a dye. Usable aromatic primary amine compounds include, besides the above-described amines, p-aminophenol, N-ethyl--N-methanesulfonylaminoethyl-2-methyl-p-phenylenediamine and N,N-didodecyl-p-phenylenediamine. The aromatic primary amines may be optionally used in the form of hydrochloride, sulfate, tosylate or perfluoroalkylsulfonate. Acyl forms such as an acetyl, benzoyl, p-toluenesulfonyl, (2,4-di-t-pentylphenoxy)acetyl and p-dodecyloxyphenylsufonyl may be used. Of these, preferred aromatic primary amines include aminoantipyrine, perfluoroalkylsulfonates of N,N-dialkylaminop-phenylenediamine derivatives. As couplers capable of oxidative-coupling with the aromatic primary amine to form a dye are usable those known in the field of silver halide color photographic materials. Examples thereof are referred to U.S. Patents 2,772,162, 2,895,826, 3,002,836, 3,034,892, 2,474,293, 2,423,730, 2,367,531, 3,041,236, 4,333,999, 2,600,788, 2,369,869, 2,343,703, 2,311,082, 3,152,896, 3,519,429, 3,062,653, 2,908,573, 2,875,057, 2,470,210, 3,265,506, 2,298,443, 3,048,194 and 3,447,928; and Agfa Mitteilungen, Farbkupplereine Literraturueberesicht vol. III pp. 112-175 (1961). Of these, preferred couplers include phenols, naphthols, pyrazolones, pyrazolotriazoles and acylacetoanilides. Any two-equivalent coupler in which the coupling position is substituted by a leaving group and any four-equivalent coupler with no substituent on the active point may be usable. As the reaction with the coupler may be accelerated by the use of a base, the base may be optionally used in combination. Useful bases include organic bases such as triphenylguanidine, trihexylamine, pyridine and quinoline, inorganic bases such as sodium hydrogencarbonate, potassium carbonate, potassium hydroxide and salicylic acid metal salt and metal salts of organic acids. As an example of mode 3, in cases where the photodecomposable compound is an aromatic azide compound, the component capable of forming a color upon reaction with the decomposition product of the photodecomposable compound is a coupler. The aromatic azide compound is photolyzed to form a nitrene. The formed nitrene is reacted with the above-described coupler to form the azomethine dye. Usable aromatic azide compounds include 4-(N,N-diethylamino)phenylazide, 2,5-dibutoxy-4-morpholinophenylazide, 2,5-dibutoxy-4-phenylthiophenylazide, 4-(N-ethyl-N-methylsulfonylaminoethylamino)-2-methylphenylazide, 4-diethylamino-3-dodecyloxycarbonylphenylazide, 1-naphthylazide, 2-naphthylazide, anthranylazide, 3-quinolineazide and 9-acridineazide. Examples of preferred aromatic azides include p-dialkylaminophenylazides. As examples of couplers capable of coupling with the azides are cited the same ones as described above. The total number of carbon atoms of each components of the photodecomposable compound and the color forming element upon reaction with the decomposition product is preferably 10 or more so as to enhance the solubility in organic solvent. In cases where the molecular weight becomes too high, a color density per unit weight tends to decrease, so that the total number of carbon atoms is more preferably from 15 to 40. In the invention at least two kinds of photo-color-forming elements are usable optionally in various forms. For example, images with two colors can be formed by the use of two kinds of the photo-color-forming elements forming colors different in hue from each other. In this case it is possible to record with the appearance of one color by forming simultaneously two colors upon thermal recording and one light-exposure and it is also possible to separately record two colors. Separate recording of two colors can be achieved by causing two kinds of photo-color-forming elements to form colors, using lights having different wavelengths from each other. Thus, after each of the photo-color-forming elements is mixed by thermal recording to form a latent image, it is possible to cause the two photo-color-forming elements to form independently two colors by exposure of a specific portion to light with wavelengths, at which a first color forming element is capable of color-forming and a second color forming element is not, to form a first color, followed by exposure of another portion to light with wavelengths at which the second element is capable of color-forming. Alternatively, it is possible to form a mixture of two colors by exposing to light with wavelengths at which both color-forming elements are capable of forming colors. In this case, the extent of color-forming of the two elements can be controlled by the wavelength of light to be exposed. It is also possible to record separately two colors by causing the two elements to form latent images by different thermal energies. Thus, exposure to a first thermal energy causes only one photo-color-forming element to form a latent image, followed by exposure to a second thermal energy causing the other element to form a latent image. Thereafter, exposure to light with wavelengths at which the first and second elements are capable of color-forming enables separate recording of two colors. In this case, when recorded with the second thermal energy, latent image formation occurs also in the first element, so that one of the resulting color recording images arises from color-forming of the first element and the other one arises from the first and second elements. Further, before recording with the second thermal energy, latent image formation of the first element is caused by the first thermal energy, followed by exposure to light with the wavelength at which only the first element is capable of color-forming, causing the first element to form a color and after causing color formability of a nonrecorded portion of the first element to stop, latent image formation of the second element is caused by a second thermal energy, followed by exposure to light to form a color. Thus, a color image produced by the first photo-color-forming element and a color image produced by the second element can be separately formed. Furthermore, it is possible to cause two photo-color-forming elements to form a color in the same hue. For example, if a shade of the image to be recorded can be finely reflected on a color density through a difference of thermal energy to be applied, a recording image excellent in reproduction is obtained. However, it is limitative to provide a shade of color using a single color-forming element and a wide range of temperature. Instead thereof, it is possible to obtain a finer color image by providing plural photo-color-forming elements such as to form colors with an identical hue and higher density at a higher temperature. In the invention, two kinds of the photo-color-forming elements may be optionally contained together in the same layer or separately in at least two layers. In cases where color formation of the two elements are allowed to proceed at the same time to obtain a mixed color, color formation of the two elements containing a component in common with each other is allowed to proceed separately by heat and/or light, or the two elements forming a color with substantially the same hue and different in density are employed, for example, the two elements can be contained in the same layer. Two kinds of the photo-color-forming elements may be individually contained in separate layers. In cases where contained in separated layers, component(s) of each element can be readily separated because of the layers being different and heat conduction can be varied by controlling the layer, so that, when the two elements are mixed up by thermal recording to form two colors, separation of the two colors can be easily made. In the invention, all components contained in the photo-color-forming element are not to be homogeneously mixed up before being heated. At least one component of the element needs to be separated from other component(s) by any means, before being heated. When heated by a thermal print head, it is promptly mixed, causing color forming reaction to occur only in the mixing portion, upon exposure to light. If the photo-color-forming element is promptly melted and thereby mixed and each component is able to be maintained in the molten state until being subjected to exposure, a high color density can be obtained. At least one component of the photo-color-forming element is dispersed through solution in an organic solvent. Thus, it is preferred that at least one component of the photo-color -forming element is incorporated in a layer, in the form of a dispersion, which is prepared by dissolving it in an organic solvent and then dispersing the resulting solution in an aqueous medium containing a protective colloid. Of the organic solvents usable in the invention, those having a high boiling point are preferred. Examples of the high boiling solvents include phosphates, phthalates, acrylates, methacrylates or other carboxylic esters, fatty acid amide, alkylated biphenyls, alkylated terphenyls, chlorinated paraffins, alkylated naphthalenes, diarylethanes and dialkylphenols. Specifically those described in JP-A 60-242094 and 62-75409 are usable. Of the boiling point of the organic solvent to be used, it is desired to be nonvolatile at an ordinary temperature and solvents having a boiling point of 100 °C or higher are preferred. In case of the boiling point being too high, viscosity tends to be increased so that ones having a boiling point of from 120 to 500 ° C are more preferable. In addition to the above-described high boiling solvents, a low boiling solvent such as ethyl acetate or methylene chloride, as a dissolution-aid, may be used in combination. At least one of the photodecomposable compound and the element capable of forming a colour upon reaction with the decomposition product of the photodecompsable compound is enclosed in microcapsules. Microcapsules preferably used in the invention have a microcapsule wall of such property as to prevent contact between substances present inside and outside the microcapsule at ordinary temperature through its insulating function, and to increase permeability of the substances only while it is heated to a temperature higher than a prescribed temperature. Permeability variable with temperature can be freely controlled by optimally selecting a capsule wall, a capsule core material, and additives. Examples of microcapsule wall materials usable in the invention include a polyurethane, polyurea, polyamide, polyester, polycarbonate, polyether, polycarbonate, ureaformaldehyde resin, melamine-formaldehyde resin, polystyrene, styrene-methacrylate copolymer, gelatin, poly(vinylpyrrolidone), and poly(vinyl alcohol). These materials can be used in combination. Among the above-described wall materials, a polyurethane, polyurea, polyamide, polyester, and polycarbonate are preferred, and polyurea and polyurethane are more preferred. Microcapsules preferably used in the invention are described in detail in U.S. Patent 3,796,696. The microcapsules suitable for use in the invention are preferably manufactured in a method by interfacial polymerization in which a core material containing a substance to be microcapsulated is emulsified to form an emulsion in the form of oil drops dispersed in a medium and then a wall of a macromolecular substance is formed around the oil drops to form microcapsules. In this case, to form emulsified oil drops, an organic solvent is preferably employed and in general, organic solvents to be employed are optimally selected from high boiling organic solvents. Examples thereof include a phosphate, phthalate, fatty acid amide, alkylated biphenyl, alkylated terphenyl, chlorinated parafin, alkylated naphthalene and diarylethane. Suitable examples are described in JP-A 60-24209 and 62-75409. In addition to the above-described high boiling solvents, low boiling solvents such as ethyl acetate or methylene chloride, as a dissolution-aid, may be used in combination. On the other hand, in a water phase to be mixed with an oil phase may be contained a water-soluble polymer, as a protective colloid, such as poly(vinyl alcohol), gelatin and cellulose derivatives.A surfactant selected from ones known in the art can be used in emulsion-dispersing so as to prevent precipitation and coagulation. Other color forming element(s) present outside the microcapsules may be dispersed in either the form of an emulsified dispersion or solid particle dispersion, preferably, in the form of an emulsified dispersion. In the solid particle dispersion, emulsified dispersion or a dispersion used in the microcapsules, the particle size of a dispersed phase is preferably within the range of from 0.1 to 20 µm, more preferably, from 0.5 to 10 µm, from the standpoint of image quality and color density. According to the present invention, color forming reaction occurs at a portion in which, on being heated, a photodecomposable compound is mixed with an element capable of forming a color upon reaction with the decomposition product of the photodecomposable compound. On the other hand, at a non-heated portion, i.e., a portion separated from the element capable of forming a color upon reaction with the decomposition product of the photodecomposable compound, no color forming reaction occurs even when exposed to light. Preferably, when the nonheated portion is exposed to light, the photodecomposable compound is photolyzed, changing to a substantially inert compound as a result of reaction with surrounding materials, without participating in color forming reaction. In the invention, the amount of the photodecomposable compound or the element capable of forming a color upon reaction with the decomposition product of the photodecomposable compound is not limitative and is chosen taking account of the thickness of a layer coated on a support, color-forming efficiency, color density, etc. Either of them is preferably used in an amount of from 4x10 -4 mol to 2x10 -2 mol/m 2 . Of the layer thickness to be coated on the support, it is not limitative, but taking account of heat-sensitivity and image sharpness, dry layer thickness is preferably within the range of from 0.5 to 50 µm, more preferably, from 1 to 20 µm. The light- and heat-sensitive recording material of the invention can be manufactured by coating, on a support, the photodecomposable compound and the element capable of forming a color upon reaction with the decomposition product of the photodecomposable compound. In this case, as a binder of the above-described dispersion are usable various emulsions of poly(vinyl alcohol), gelatin, styrene-butadiene latex, carboxymethyl cellulose, arabic gum, poly(vinyl pyrrolidone, and a polyacrylate. The amount to be used is preferably from 0.5 to 5 g/m 2 , in terms of a solid component. In the recording material of the invention, taking account of image protection, prevention of adhesion of recording materials, prevention of adhesion to a thermal head, writability, and surface roughness, a protective layer is preferably provided. As binders of the protective layer, those known in the art are usable. Examples thereof include polymers, such as methyl cellulose, carboxymethyl cellulose, hydroxymethyl cellulose, starches, gelatin, arabic gum, casein, hydrolytic product of styrene-maleic acid copolymer, poly(vinyl alcohol), carboxy-modified poly(vinyl alcohol), polyacrylamide derivatives, poly(vinyl pyrrolidone), sodium poly(styrenesulfonate), sodium alginate, styrene-butadiene latex, acrylonitrile-butadiene rubber latex, and poly(vinyl acetate) emulsion; silicone resin, melamine resin, phenol resin, acryl resin, polyester resin, epoxy resin, fluororesin, nitrocellulose, cellulose acetatepropionate, cellulose acetate, fluoronated vinylidene resin, and chlorinated rubber. As a filler of the protective layer, inorganic pigments, such as zinc oxide, calcium carbonate, barium sulfate, titanium oxide, litbon, talc, agalmatolite, kaolin, aluminum hydroxide, amorphous silica, colloidal silica; organic pigments, such as polystyrene, poly(methyl methacrylate), polyethylene, vinyl acetate resin, vinyl sulfide resin, vinylidene sulfide resin, styrene-methacrylate copolymer, chlorovinylidene, polyurea, and melamine-formaldehyde; and waxes, such as paraffin wax, microcrystalline wax, carnauba wax, methylol steariloamide, polyethylene wax, and silicone. These fillers may be used alone or in combination. The light- and heat-sensitive recording material of the invention is coated on a support such as paper or synthetic resin film in any well-known manner, such as a dip coating method, air-knife coating method, curtain coating method, roller coating method, doctor blade coating method, wire-bar coating method, slide coating method, gravure coating method, spin coating method and extrusion coating method. As supports usable in the light- and heat-sensitive recording material of the invention mention may be made of papers; films such as regenerated cellulose, cellulose acetate, cellulose nitrate, poly(ethylene terephthalate), polyethylene, poly(vinyl acetate), and poly(ethylene naphthalate); glass; wood; and metals. Light sources usable in the invention are any of those capable of photolyzing the photodecomposable compound, including fluorescent lamps, high pressure mercury lamp, xenon lamp, tungsten lamp and solar light. Examples Examples of embodiments of the present invention will be shown below, but the invention should not be construed as being limited to these examples. Hereinafter, the word, "part(s)" refers to part(s) by weight. Comparative Example 1 Preparation of capsule solution A: Leuco dye; benzoylleucomethylene blue 1 part Wall material; Xylylenediisocyanate/trimethylolpropane adduct 15 parts Additive; Dodecylbenzenesulfonic acid 0.4 part Dissolution-aid; Methylene chloride 5 parts High boiling solvent; 1-Phenylene-1-xylylethane (b.p. 312°C) 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 54 parts of 6% poly(vinyl alcohol) aqueous solution and the mixture was dispersed at 20° C using a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 60 parts of water and stirring was further continued at 40° C for 3 hrs. Thereafter, the solution was returned to room temperature to obtain a capsule solution A. The glass transition temperature of the capsule wall was 80° C. Preparation of dispersion of free radical producing compound: Tribromomethylphenylsulfone of 30 parts was added to 150 parts of 4% poly(vinyl alcohol) aqueous solution and the mixture was dispersed by a sand mill to obtain a dispersion of tribromomethylphenylsulfone having an average oil-drop size of 1µm. A coating solution having the following composition was prepared. Capsule solution A 12 parts Dispersion of free radical producing compound 3 parts The coating solution was coated on wood free paper by a wire-bar so as to have a coating amount of the leuco dye of 0.5 g/m 2 and dried at 50°C to obtain a light- and heat-sensitive recording material of the invention. Comparative Example 2 A light- and heat-sensitive recording material of the invention was prepared in the same manner as in Comparative Example 1, except that the leuco dye was replaced by an equimolar amount of leucocrystal violet. Example 3 Coupler; 2,4-Dichloro-3-ethyl-6-[2-(2,4-di-t-pentylphenyloxy])butanoylamino]phenol 1.5 parts Additive; Dodecylbenzenesulfonic acid 0.4 parts Wall material; Xylylenediisocyanate/trimethylol propane adduct 15 parts Dissolution-aid; Ethyl acetate 5 parts High boiling solvent; Isopropylbiphenyl (b.p. 295° C) 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 54 parts of 6% poly(vinyl alcohol) aqueous solution and the mixture was dispersed at 20° C using a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 60 parts of water and stirring was further continued at 40° C for 3 hrs. Thereafter, the solution was returned to room temperature to obtain a capsule solution B. Preparation of free radical producing compound/amine dispersion: 2,2'-Bis-(o-chlorophenyl)-4,4',5,5'-tetraphenylbisimidazole 5 parts N,N-Dioctylamino-p-phenylenediamine 10 parts Triphenylguanidine 5 parts Methylene chloride 30 parts Tricresyl phosphate (b.p. 265° C/10 mmHg) 30 parts The above composition was added to 200 parts of 4% poly(vinyl alcohol) aqueous solution and the mixture was dispersed by a ultrasonic homogenizer to obtain a dispersion. A solution having the following composition was prepared Capsule solution B 10 parts Free radical producing compound/amine dispersion 20 parts The coating solution was coated on wood free paper by a wire-bar so as to have a coating amount of the coupler of 0.35 g/m 2 and dried at 50°C to obtain a light- and heat-sensitive recording material of the invention. Preparation of capsule solution C: Azide; 4-Morpholino-2, 5-dibutoxyphenylazide 3 parts High boiling solvent; Diisopropylnaphthalene (b.p. 318° C) 10 parts Wall material; Xylylenediisocyanate/trimethylolpropane adduct 8 parts Dissolution-aid; Ethyl acetate 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 46 parts of 8% phthalated gelatin aqueous solution and 18 parts of water and 2 parts of 10% sodium dodecylbenzenesulfonate aqueous solution were added thereto. The mixture was dispersed at 20° C by a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 20 parts of water and the emulsion was further stirred at 40° C for 3 hrs. and returned to room temperature to obtain capsule solution C. Preparation of coupler dispersion: 7-Chloro-6-tert-butyl-3-(3-dodecylsulfonyl propyl)pyrazolo[3,2-c]triazole 4 parts Triphenylguanidine 2 parts Tricresylphosphate 1 part The above composition was homogeneously mixed and 32 parts of gelatin (15% aqueous solution), 5 parts of dodecylbenzenesulfonic acid (10% aqueous solution) and 30 parts of water were added thereto. The mixture was emulsified at 20° C for 10 min. to obtain an emulsion. The emulsion was further stirred at 40° C to remove ethyl acetate and then water was added in an amount equivalent to the ethyl acetate removed to obtain a coupler dispersion. A coating solution of the following composition was prepared: Capsule solution C 6 parts Coupler dispersion 8 parts Gelatin (15% aqueous solution) 2 parts Water 4.5 parts The coating solution was coated on wood free paper by a wire-bar so as to have a coating amount of the azide of 0.2 g/m 2 and dried at 50°C to obtain a light- and heat-sensitive recording material of the invention. Comparative Example 3 A comparative sample (Comparison 1) was prepared in the same manner as Comparative Example 1, except that, in the capsule solution, 1-phenyl-1-xylylethane was not added. Comparative Example 4 A comparative sample (Comparison 2) was prepared in accordance with Comparative Example 1 of JP-A 3-1983, as follows: Leuco dye; Leucocrystal violet 1.5 parts Photooxidizing agent; 2,2'-Bis-(o-chlorophenyl)-4,4'5,5'-tetraphenylbisimidazole 3.0 parts Wall material; Xylylenediisocyanate/trimethylolpropane adduct 24 parts Dissolution-aid; Methylene chloride 5 parts High boiling solvent; Tricresylphosphate 24 parts The above composition was homogeneously mixed and the solution was added to a mixture of 63 parts of 8% poly(vinyl alcohol) aqueous solution and 100 parts of distilled water. The mixed solution was emulsified at 20° C by a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. The emulsion was further stirred at 40° C for 3 hrs. and returned to room temperature to obtain a capsule solution. Next, 42g of phenidone A (1-phenylpyrazolidinedione-3-one) was dissolved in 8g of diethyl maleate and 30g of ethyl acetate. The resulting solution was mixed with 100g of 8% poly(vinyl alcohol) aqueous solution and 0.5g of sodium dodecylbenzenesulfonate aqueous solution and the mixture was emulsified by a homogenizer to obtain an emulsified dispersion containing phenidone A. A mixture of 9 parts of the above-described capsule solution and phenidone A containing emulsion was coated on a wood free paper by a wire-bar so as to have the same coating amount of the leuco dye as in Example 1 and dried at 50° C to obtain comparative sample-2. Contrary to light-and heat-sensitive recording materials of the invention, no color forming occurred in a portion which had been heated and exposed, and in a portion which had been only exposed, color formation was observed. Color formation/Row stock stability test: Thus-obtained light-and heat-sensitive recording materials were subjected to heating at 120° C for 5 sec. (0.5 kg/m 2 ), using a heat-gradient tester (produced by Toyo Seiki) and then exposed overall for 30 sec. using a high pressure mercury lamp. Prior to recording, the light-and heat-sensitive materials were allowed to stand at high temperature and high humidity (50° C and 80% R.H.) for 3 days and thereafter, the recording materials were subjected to heating and exposure to light in the same manner as above to measure densities of the background and color forming portion. Color Before aging After aging Heated portion Non-heated portion Heated portion Non-heated portion comparative Example 1 Blue 1.26 0.07 1.22 0.10 Comparative Example 2 Blue 1.30 0.08 1.26 0.12 Example 3 Cyan 1.38 0.06 1.30 0.08 Example 4 Magenta 1.45 0.05 1.40 0.07 Comparative Ex. 3 Blue 0.50 0.07 0.46 0.20 Comparative Ex. 4 Blue 0.12 1.16 0.35 1.06 As can be seen from the above results, it was proved that inventive light- and heat-sensitive recording materials and recording methods by use thereof were excellent in color formation in the heat-recording portion and low in fogging at the nonheated portion even after being allowed to stand at high temperature and high humidity. Samples obtained in Comparative Examples 1 and 2 and Examples 3 and 4 were exposed overall to a high pressure mercury lamp for 1 min. and then heating and exposure were repeated. As a result, comparing to samples before heating and exposure, no significant difference in color formation was observed. Thus, it was confirmed that color formability of a portion in which no latent image was formed by heating was stopped. Comparative Example 5 Preparation of capsule solution A: Leuco dye; Leucocrystal violet 1 part Wall material; Xylylenediisocyanate/trimethylolpropane adduct 20 parts Additive; Dodecylbenzenesulfonic acid 0.4 part Dissolution-aid; Ethyl acetate 16 parts High boiling solvent; Isopropylnaphthalene 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 54 parts of 6% poly(vinyl alcohol) aqueous solution and the mixture was dispersed at 20° C using a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 60 parts of water and stirring was further continued at 40° C for 3 hrs. Thereafter, the solution was returned to room temperature to obtain a capsule solution A. The glass transition temperature of the capsule wall was 80° C. Preparation of capsule solution B: Leuco dye; 3,6-Dimethoxy-9-(2-methoxycarbonyl)phenyl xanthene 1.5 part Wall material; Tolylenediisocyanate/trimethylol -propane adduct (75% ethyl acetate solution) 20 parts Dissolution-aid; Ethyl acetate 5 parts High boiling solvent; Diisopropylnaphthalene 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 54 parts of 6% poly(vinyl alcohol) aqueous solution and the mixture was dispersed at 20° C using a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 60 parts of water and stirring was further continued at 40° C for 3 hrs. Thereafter, the solution was returned to room temperature to obtain a capsule solution A. The glass transition temperature of the capsule wall was 100° C. Preparation of dispersion of free radical producing compound: Five parts of tribromomethylphenylsulfone and 25 parts of 2,2'-bis-(o-chlorophenyl)-4,4',5,5'-tetraphenylbisimidazole were added to 150 parts of 4% poly(vinyl alcohol) aqueous solution and the mixture was dispersed by a sand mill to obtain a dispersion of tribromomethylphenylsulfone having an average oil-drop size of 1µm. A coating solution having the following composition was prepared: Capsule solution A 12 parts Capsule solution B 12 parts Dispersion of free radical photoproducing compound 5 parts The coating solution was coated on wood free paper by a wire-bar so as to have a coating amount of the leuco dye (capsule B) of 0.5 g/m 2 and dried at 50°C to obtain a light-and heat-sensitive recording material of the invention. The resulting light- and heat-sensitive recording material was subjected to heating at 90° C and 110° C (0.5 kg/m 2 ) for 5 sec. and exposed to a high pressure mercury lamp for 30 sec. As a result, a portion heated at 90° C exhibited vivid yellow color formation and the other portion heated at 110° C exhibited black color formation. Further, the nonheated portion was not colored. After overall exposure as above-described, a nonheated portion of the recording material was again subjected to heating and exposure, but no significant color formation was observed. The hue obtained by causing the leuco dye used in capsule A to form a color was yellow and that of capsule B was blue. It is anticipated that the portion heated at 90° C resulted color formation from the leuco dye of capsule A on exposure, exhibiting blue colour and, on the other hand, the portion heated at 110° C resulted in simultaneous color formation of the leuco dyes of capsule A and B, exhibiting black color. Example 6 Preparation of capsule C: Coupler; 2,4-Dichloro-3-ethyl-6-[2-(2,4-di-t-pentylphenyloxy])butanoylamino]phenol 1.5 parts Additive; Dodecylbenzenesulfonic acid 0.4 parts Wall material; Xylylenediisocyanate/trimethylol propane adduct 20 parts Dissolution-aid; Ethyl acetate 5 parts High boiling solvent; Isopropylbiphenyl (b.p. 295° C) 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 54 parts of 6% poly(vinyl alcohol) aqueous solution and the mixture was dispersed at 20° C using a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 60 parts of water and stirring was further continued at 40° C for 3 hrs. Thereafter, the solution was returned to room temperature to obtain a capsule solution C. Preparation of free radical producing compound/amine dispersion: 2,2'-Bis-(o-chlorophenyl)-4,4',5,5'-tetraphenylbisimidazole 4 parts 2,6-Bistrichloromethyl-4-methoxyphenyl-s-triazine 2 parts N,N-Dioctylamino-p-phenylenediamine-perfluorobutanesulfonate 10 parts Triphenylguanidine 5 parts Methylene chloride 30 parts Tricresyl phosphate 30 parts The above composition was added to 200 parts of 4% poly(vinyl alcohol) aqueous solution and the mixture was dispersed by an ultrasonic homogenizer to obtain an emulsified dispersion. A coating solution of the following composition was prepared: Upper layer coating solution: Above-described capsule solution C 10 parts Above-described dispersion of free radical photoproducing compound 20 parts Lower layer coating solution: Capsule solution prepared in Comparative Example 5 10 parts Dispersion of free radical photoproducing compound, prepared in Comparative Example 5 3 parts These coating solutions were coated on wood free paper by a wire-bar so as to have a coupler coating amount of 0.5 g/m 2 and dried at 50°C to obtain a light- and heat-sensitive recording material of the invention. Thus prepared light- and heat-sensitive recording material was partially heated at 90° C, using a heat-gradient tester (produced by Toyo Seiki) and then exposed, for 30 sec., to high pressure mercury lamp, in which light at the wavelengths of 400 nm or less was cut off with a filter. A heated portion exhibited a vivid cyan color. On the other hand, no color formation was observed in a non-heated portion. Thereafter, the non-heated portion was further heated at 110° C for 5 sec. (0.5 kg/m 2 ) and exposed overall to a high pressure mercury lamp. As a result, the re-heated portion exhibited a vivid yellow color and the non-heated portion formed no color. It is understood that the dispersion of free radical producing compound contained in the upper layer responded to light with a wavelength of more than 400 nm and heatedly mixed with the amine and coupler to form a cyan color; on the other hand, the dispersion of free radical producing compound of the lower layer responded to light with a wavelength of 400 nm or less and formed a yellow color upon reaction with the leuco dye. Furthermore, from the fact that no cyan color formation of the upper layer was observed even when exposed to light with a wavelength of 400 nm or more and then subjected to heating and exposure, it is apparent that upon exposure, color formation of the heated portion and prevention of color formation of the non-heated portion occurred. Example 7 Preparation of capsule solution D: Azide; 4-Morpholino-2,5-dibutoxyphenylazide 3 parts High boiling solvent; Diisopropylnaphthalene 10 parts Wall material; Xylylenediisocyanate/trimethylol -propane adduct (75% ethyl acetate solution) 20 parts Dissolution-aid; Ethyl acetate 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 46 parts of 8% phthalated gelatin aqueous solution and 18 parts of water and 2 parts of 10% sodium dodecylbenzenesulfonate aqueous solution were added thereto. The mixture was dispersed at 20° C by a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 20 parts of water and the emulsion was further stirred at 40° C for 3 hrs. and returned to room temperature to obtain capsule solution D. Preparation of capsule solution E: Azide; 4-Morpholino-2,5-dibutoxyphenylazide 6 parts High boiling solvent; Diisopropylnaphthalene 10 parts Wall material; Tolylenediisocyanate/trimethylolpropane adduct (75% ethyl acetate solution) 20 parts Dissolution-aid; Ethyl acetate 5 parts The above composition was homogeneously dissolved. The resulting solution was added to 46 parts of 8% phthalated gelatin aqueous solution and 18 parts of water and 2 parts of 10% sodium dodecylbenzenesulfonate aqueous solution were added thereto. The mixture was dispersed at 20° C by a homogenizer to obtain an emulsion having an average oil-drop size of 1 µm. To the emulsion was added 20 parts of water and the emulsion was further stirred at 40° C for 3 hrs. and returned to room temperature to obtain the capsule solution. Preparation of coupler dispersion: 7-Chloro-6-tert-butyl-3-(3-dodecylsulfonyl propyl)pyrazolo[3,2-c]triazole 4 parts Tricresylphosphate 1 part The above composition was homogeneously mixed and 32 parts of gelatin (15% aqueous solution), 5 parts of dodecylbenzenesulfonic acid (10% aqueous solution) and 90 parts of water were added thereto. The mixture was emulsified at 20° C for 10 min. to obtain an emulsion. The emulsion was further stirred at 40° C for to remove ethyl acetate and then water was added in an amount equivalent to the ethyl acetate removed to obtain a coupler dispersion. A coating solution of the following composition was prepared: Capsule solution D 3 parts Capsule solution E 3 parts Coupler dispersion 8 parts Gelatin (15% aqueous solution) 2 parts Water 4.5 parts The coating solution was coated on wood free paper by a wire-bar so as to have a coating amount of the azide of 0.5 g/m 2 and dried at 50°C to obtain a light- and heat-sensitive recording material of the invention. Example 8 An inventive light- and heat-sensitive recording material was prepared in the same manner as in Example 7, except that capsule solution D was replaced by an equivalent amount of capsule solution E. Light- and heat-sensitive recording materials obtained in Examples 7 and 8 were each subjected to heating at a temperature of 90, 100, 110 or 120° C for 5 sec. (0.5 kg/m 2 ), using a heat-gradient tester (produced by Toyo Seiki) and then exposed for 30 min., using a high pressure mercury lamp. As a result, heated portions each exhibited a magenta color and densities thereof are shown as below. Heating Temp. 90° C 100° C 110° C 120° C Example 7 0.22 0.50 0.73 1.20 Example 8 0.49 1.19 1.21 1.22 As can be seen from the above results, density tone reproduction can be made over a wider range of thermal energy by mixing two kinds of photo-color-forming elements different in color forming-initiating temperature and color forming density. This is advantageous for recording in a delicate shade of color. Comparative Example 6 Preparation of capsule solution A: Leucocrystal violet 1 part 2,2'-Bis-(o-chlorophenyl)-4,4',5,5'-tetraphenylbisimidazole 2 parts Tribromomethylphenylsulfone 0.4 parts 2,5-Di-tert-octylhydroquinone 0.6 part p-Toluenesulfonamide 0.2 part Xylylenediisocyanate/trimethylol-propane adduct (75 wt.% ethyl acetate solution) 20 parts The above composition was dissolved in a mixed solvent of 16 parts of ethyl acetate and 18 parts of diisopropylnaphthalene, The solution was added to 54 parts of an aqueous 6% by weight solution of carboxyl-modified poly(vinyl alcohol). The mixture was emulsified at 20° C to obtain an emulsified dispersion having an average oil-drop size of 1 µm. Adding thereto 68 parts of water, the emulsion was further stirred at 40° C for 3 hrs., returned to room temperature and filtered out to obtain capsule solution F. 3,6-Dimethoxy-9-(2-methoxycarbonyl)phenylxanthene 1.5 parts 2,2'-Bis-(o-chlorophenyl)-4,4',5,5'-tetraphenylbisimidazole 2 parts 2,6-ditrichloromethyl-4-(p-methoxyphenyl)triazine 0.8 part 2-(5'-methyl-2'-hydroxyphenyl)benzotriazole 4 parts Tolylenediisocyanate/trimethyolpropane adduct (75 wt.% ethyl acetate solution) 20 parts The above composition was dissolved in a mixed solvent of 16 parts of ethyl acetate and 18 parts of diisopropylnaphthalene. The solution was added to 54 parts of an aqueous 6% by weight solution of carboxyl-modified poly(vinyl alcohol). The mixture was emulsified at 20° C to obtain an emulsified dispersion having an average oil-drop size of 1 µm. Adding thereto 68 parts of water, the emulsion was further stirred at 40° C for 3 hrs., returned to room temperature and filtered out to obtain capsule solution G. Preparation of reducing agent dispersion: Thirty parts of 1-phenylpyrazolidine-3-one (Phenidone A) was added to 150 parts of 4% by weight aqueous solution of carboxyl-modified poly(vinyl alcohol) and the mixture was dispersed by a lateral type sand mill to obtain a Phenidone A dispersion having an average oil-drop size of 1 µm. A coating solution of the following composition was prepared: Capsule solution F 6.8 parts Capsule solution G 6.8 parts reducing agent dispersion 6.0 parts 30% epoxy-modified polyamide resin 0.4 part The coating solution was coated on wood free paper by a wire-bar so as to have a leuco dye coating amount of capsule solution G of 0.5 g/m 2 and dried at 50°C to obtain a light- and heat-sensitive recording material of the invention. Light- and heat-sensitive recording materials of Examples 6 to 8 and Comparative Examples 5 and 6 were allowed to stand under high temperature and high humidity (50° C and 80% R.H.) for 3 days and then subjected to thermal printing and exposure under such a condition as to give a highest color density to make measurements with respect to a maximum density (Dm') and background density (Dmin'). The maximum density (Dm) and background density (Dmin) of samples before being aged were also measured. Storage stability of each sample was shown in Table 2. Color Deterioration of color (Dm-Dm')/(Dm-Dmin) Stain of background (Dmin'-Dmin)/(Dm-Dmin) Comparative Example 5 Blue 0.02 0.10 Yellow 0.02 0.06 Example 6 Cyan 0.02 0.09 Yellow 0.01 0.05 Example 7 Magenta 0.03 0.04 Example 8 Magenta 0.03 0.07 Comparative Example 6 Blue 0.02 0.35 Yellow 0.01 0.23 As can be seen from the Table, it was proved that light-and heat-sensitive recording materials of the invention and a recording method by use thereof showed little deterioration in color formation and stain in the background, even when allowed to stand under high temperature and high humidity.

Claims: A light- and heat-sensitive recording material comprising a support having provided thereon a light- and heat-sensitive layer having therein a photo-colour-forming element comprising a photodecomposable compound and a component capable of forming a colour upon reaction with a decomposition product of the photodecomposable compound, wherein said photo-color-forming element can be imagewise heated so as to be mixed to thereby form a latent image and the latent image may be exposed to light to form a color; at least one of the photodecomposable compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound being present as a dispersion in an organic solvent, wherein at least one of the photodecomposable compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound is enclosed in microcapsules, and wherein the photodecomposable compound is a free radical producing compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound is a coupler and an aromatic primary amine compound, or the photodecomposable compound is an aromatic azide compound, and the component capable of reacting with the decomposition product is a coupler. The recording material of claim 1, wherein the organic solvent is a high boiling solvent having a boiling point of not less than 100° C. The recording material of any preceding claim, wherein at least one further photo-colour-forming element comprising a photodecomposable compound and a component capable of reacting with a decomposition product of the photodecomposable compound is provided and at least one of the photodecomposable compound and the component capable of forming a colour upon reaction with the decomposition product of the photodecomposable compound is present as a dispersion in an organic solvent. The recording material of claim 3, wherein the at least two photo-colour-forming elements form colours different in hue from each other. The recording material of claims 3 or 4, wherein the at least two photo-colour-forming elements form colours different in density from each other. The recording material of any of claims 3 to 5, wherein the at least two photo-colour-forming elements are separately contained in at least two different layers. The recording material of any of claims 3 to 5, wherein the at least two photo-colour-forming elements are provided in the same layer. An image forming method by use of a light- and heat-sensitive recording material according to any of claims 1 to 7, which method comprises heating imagewise the photo-colour-forming element to mix the photodecomposable compound and the component capable of forming a colour, thereby forming a latent image and then exposing the formed latent image to light to develop the latent image, forming a colour image. The image forming method of claim 8, wherein two photo-colour-forming elements are provided on the support, and the two photo-colour-forming elements are respectively heated with different thermal energies to form a latent image. The image forming method of claim 8, wherein two photo-colour-forming elements are provided on the support, and the two photo-colour-forming elements are respectively exposed to light at different wavelengths to form a colour. The image forming method of any of claims 8 to 10, wherein the photo-colour-forming element which has not been heated is exposed to light so that colour formability of the non-heated photo-colour-forming element is inhibited.

Inventors: HATANO OSAMU, KATOH EISAKU, KIDA SHUJI, NAKAZAWA KENZO, SHIBATA MANABU, YOSHIDA TETSUYA, HATANO, OSAMU, KATOH, EISAKU, KIDA, SHUJI, NAKAZAWA, KENZO, SHIBATA, MANABU, YOSHIDA, TETSUYA
Applicants: KONISHIROKU PHOTO IND, KONICA CORPORATION
Application year: 1996
Main classification: G03C1
IPC codes: B41M5, G03C1