DE69029783T2 - Material for fixing dyes - Google Patents

Description

This invention relates to a dye fixing material for use in a method of forming an image by heat development. Photography using silver halide photographic materials is widely used because it is superior in photographic properties such as sensitivity and gradation controllability to other photographic processes such as electrophotography and diazo process.

Many methods for producing a color image by heat development have been proposed. For example, methods for producing a color image by coupling between an oxidation product of a developing agent and a coupler are described, for example, in US-A-3,531,286, 3,761,270 and 4,021,240, in BE-A-802,519 and in "Research Disclosure", September 1975, pp. 31-32.

In these conventional heat development systems, after heat development, a reduced silver image and a color image are simultaneously produced on the exposed area, resulting in the formation of an impure color image.

In order to eliminate the above-mentioned disadvantage, various improved methods have been proposed: for example, a method in which a light-sensitive Material is imagewise heated to produce or release a mobile (diffusible) dye which is transferred to an image-receiving element containing a mordant by means of a solvent such as water; a process in which the mobile dye is transferred to a dye fixing element by means of a high boiling organic solvent; a process in which the mobile dye is transferred to a dye fixing element by means of a hydrophilic thermal solvent which is incorporated in the dye fixing element; and a process in which the mobile dye is a heat-diffusible or sublimating dye and is transferred to a dye-receiving element, for example a support. These processes are described in US-A-4 463 079, 4474 867, 4478 927, 4 507 380, 4 500 626 and 4 483 914, JP-A-58-149046, JP-A- 58-149047, JP-A-59-152440, JP-A-154445, JP-A-59-165054, JP-A-59- 180548, JP-A-59-168439, JP-A-59-174832, JP-A-59-174833, JP-A-59-174834 and JP-A-59-174835 (the term used here "JP-A" stands for "unexamined published Japanese patent application").

The color image obtained by the image forming methods described above generally has a high fog density and suffers from the occurrence of color stains on the white background or unevenness in development. In addition, when the image is stored for a long period of time, it is subject to a change in density or an increase in discoloration on the white background.

In order to solve the above problem, it has been proposed to incorporate a fluorescent brightener into a dye fixing element as described in JP-A-61-143 752. Although this method brings about an improvement in the background color immediately after image formation, the effects obtained are not stable, so that the image suffers from considerable unevenness and the like. For example, when the image is kept under light for a long period of time, the Density of the white background increases noticeably, while the density of the image decreases sharply.

JP-A-61-159644 describes a method of incorporating a hydroquinone derivative and the like into a dye fixing material to improve dye image stability to light. Although the image obtained by this method has improved stability to light, a large increase in background density occurs when it is kept in the dark for a long period of time.

On the other hand, JP-A-1-159655 discloses an image forming method using a fluorescent brightener without causing unevenness in development, which provides an image free from changes in image density or unevenness even when stored for a long period of time. It is stated therein that a water-soluble fluorescent brightener is preferred from the standpoint of production. However, studies by the present inventors have shown that an oil-soluble fluorescent brightener is preferred from the standpoint of light stability of the image. It has also been found, however, that the use of an oil-soluble fluorescent brightener in a dye fixing material results in deterioration of the surface finish with the passage of time.

There was therefore a need to develop a dye fixing material that produces an image with satisfactory light and darkness stability while simultaneously maintaining its properties (surface gloss) during storage.

EP-A-386761 describes a heat-developable colour photographic material comprising a support on which there are at least one light-sensitive silver halide, a binder and a dye-providing compound which reacts correspondingly or inversely to the reduction of the silver halide to silver, said heat-developable photographic material further comprising a compound of the formula (C6n(H₂O)5n+1) wherein n is an integer of 1 or more.

EP-A-411 466 describes a heat-developable color photographic light-sensitive material comprising at least one light-sensitive silver halide, a binder, a dye-forming non-diffusible compound capable of releasing a diffusible dye upon reduction, and a reducing agent, the light-sensitive material further comprising at least one ester or amide derivative of oxalic acid, malonic acid, substituted malonic acid, α-keto acid, β-keto acid, substituted α-keto acid or substituted β-keto acid.

An object of this invention is to provide a dye fixing material which provides an image with satisfactory light and dark stability while maintaining its properties (surface gloss) during preservation (storage).

The above object of the invention is achieved by a dye fixing material comprising a support and a dye fixing layer capable of receiving a diffusible dye formed in a heat-developable photosensitive material by heat development, said dye fixing material containing, on the side of the support on which the dye fixing layer is provided, an oil-soluble fluorescent brightener and at least one anionic surface active agent (surfactant), the total amount of the anionic surface active agent (surfactant) in the layers on the side of the support on which the dye fixing layer is provided being in the range of 25 to 150 mg/m².

An anionic surface-active agent (surfactant) is used essentially to stabilize an emulsion, to improve the coating properties and used to improve the support properties or the release properties of the materials. In studies, the present inventors have found that an anionic surface-active agent (surfactant) in a hydrophilic binder is highly diffusible and diffuses and migrates to the surface during storage, thereby causing a decrease in surface gloss.

It has also been found that an anionic surface active agent (surfactant) has the effect of accelerating the diffusion of an oil-soluble substance in a hydrophilic binder, and a decrease in surface gloss is also caused by the migration of such an oil-soluble substance to the surface.

Therefore, when using an oil-soluble substance such as an oil-soluble fluorescent brightener as used in the present invention, it has been found that the amount of the anionic surface active agent (surfactant) should not exceed 200 mg/m² from the viewpoint of surface gloss. However, as stated in JP-A-62-173463, the anionic surface active agent (surfactant) should be present in an amount of at least 20 mg/m² in order to ensure releasability between a dye fixing material and a photosensitive material. In the present invention, the total amount of the anionic surface active agent or agents in the layers on the side of the support on which the dye fixing layer is provided is in the range of 25 to 150 mg/m².

Anionic surface active agents (surfactants) that can be used in the present invention are surface active agents having an anionic group, excluding the betaine type surface active agents. The anionic group referred to here includes those capable of forming an anion, for example, a carboxyl group, a sulfo group, a sulfinic acid group, a phospho group, a boric acid group and a hydroxyl group, and salts thereof.

The anionic surfactant can be used in any layer of a dye fixing material. It can be added directly in the form of an aqueous solution or in the form of a dispersion in a high boiling organic solvent, in the form of an oil-soluble compound or in the form of a polymer. Preferred methods for adding relatively oil-soluble surfactants include methods in which these oil-soluble surfactants are dissolved and added to a high boiling or low boiling solvent, or in which these oil-soluble surfactants are dissolved in a solvent mixture comprising a water-soluble organic solvent (e.g., methanol) and water. Preferred methods for adding relatively water-soluble surfactants include methods in which these water-soluble surfactants are added as such or in the form of an aqueous solution.

The anionic surfactant may be used either singly or, usually, in combinations of two or more of them, as desired.

Anionic surface-active agents which can preferably be used according to the invention are those of the formulas (I) to (IX) given below:

where:

R¹ is a fluorine-substituted or unsubstituted saturated or unsaturated hydrocarbon group having 3 to 20 carbon atoms;

R² is a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms;

n is an integer from 1 to 20; and

M is a monovalent alkali metal.

In the formula (I), examples of R¹ include propyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, octadecyl, pentadecafluoroheptyl, heptadecafluorooctyl, heptacosafluorotridecyl and tritriacontafluoroheptadecyl groups. Examples of the hydrocarbon groups represented by R² include methyl, ethyl, n-propyl and iso-propyl groups. n preferably represents an integer of 1 to 8. M preferably represents Na or K;

wherein R¹, M and n are as defined above; a is 0, 1 or 2; and m is an integer from 1 to 6, preferably from 2 to 4;

wherein R¹, M, m and a are as defined above;

wherein R¹ and M are as defined above and the two R¹ groups may be the same or different;

wherein R¹ and M are as defined above;

wherein R¹ and M are as defined above;

where R², M and m are as defined above;

wherein R², M and m are as defined above; and R³ represents a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms which may be partially or fully fluorinated;

where R², R³ and m are as defined above.

In formulas (VIII) and (IX), R³ preferably contains 7 to 18 carbon atoms and includes, for example, pentadecanefluoroheptyl, heptadecafluorooctyl, heptacosafluorotridecyl and tritriacontafluoroheptadecyl groups.

Specific examples of the anionic surface active agents (surfactants) preferably used in the present invention are given below.

Fluorescent brighteners that can be used in the present invention include those described in K. Veenkataraman (ed.), "The Chemistry of Synthetic Dyes", Volume V, Chapter 8. Examples of the fluorescent brighteners include stilbene compounds, coumarin compounds, biphenyl compounds, benzoxazolyl compounds, naphthalimide compounds, pyrazoline compounds and carbostyryl compounds.

The fluorescent brighteners used in the present invention are oil-soluble. The term "oil-soluble" as used herein means that they are substantially water-insoluble. In particular, they have a water solubility of not more than 100 mg in 100 g of water at 20°C. Specific examples of suitable fluorescent brighteners are given below.

Preferred examples include those of the benzoxazole type such as F-10, F-15, F-28, F-29, F-30, F-31 and F-32.

These fluorescent brighteners can be used either individually or in combinations of two or more of them.

The fluorescent brightener is incorporated into any of the layers in a dye-fixing material, for example, a protective layer, a dye-fixing layer and an adhesive layer (subbing layer), preferably a dye-fixing layer. When a dye-fixing layer contains a mordant, the fluorescent brightener can be mordanted with the mordant.

The fluorescent brightener is preferably present in a dye fixing material in an amount of 0.1 to 200 mg/m², in particular 5 to 100 mg/m².

The incorporation of the oil-soluble fluorescent brightener into a dye fixing material can be carried out using a dispersion method using a polymer, using a method of finely dispersing in a binder or, preferably, using an oil-protection method.

Specifically, the method described in US-A-2 322 027 can be used. In this method, the fluorescent brightener is dissolved in a high boiling organic solvent, e.g., a phthalic acid ester (such as dibutyl phthalate, dioctyl phthalate), a phosphoric acid ester (such as tricresyl phosphate, dioctyl butyl phosphate), a citric acid ester (such as acetyl tributyl citrate), a benzoic acid ester (such as octyl benzoate), an alkylamide (such as diethyl laurylamide), a fatty acid ester (such as dibutoxyethyl succinate), a trimesic acid ester (such as tributyl trimesate) and a chlorinated paraffin (such as "Empara 40" manufactured by Ajinomoto Co., Inc.) with or without a low boiling organic solvent having a boiling point of 30 to 150°C, e.g., a lower alkyl acetate (such as Ethyl acetate, butyl acetate), ethyl propionate, sec-butyl alcohol, methyl isobutyl ketone, cyclohexanone and methyl cellosolve acetate. The solution is then dispersed in a hydrophilic colloid to prepare a dispersion of the oil-soluble fluorescent brightener.

In a preferred embodiment of the present invention, the dispersion of the fluorescent brightener is prepared using a phthalic acid ester or a chlorinated paraffin or a combination of two or more of them and the high boiling organic solvents described above.

The terminology "a combination of two or more high-boiling organic solvents" used here means a combination of two or more kinds of high-boiling organic solvents, e.g. those enumerated above (including two or more isomers thereof). The two or more kinds of solvents combined may be completely different from each other in structure, but it is more effective to use a mixture of alkyl phosphates, alkyl phthalates, alkyl carboxylates or alkyl oxalates differing in alkyl chain length, a mixture of aryl phosphates differing in the position of the substituent, a mixture of halogenated paraffins differing in the position of the halogen atom, or a similar mixture.

Isomers of the high boiling organic solvents listed above include those having a double bond in their alkyl chain, which form cis-trans isomers, and substituted cyclohexyl phosphates, which form structural isomers.

Examples of the combination of solvents include a mixture of the above-mentioned high boiling organic solvents and a mixture containing isomers.

The inventors have found through investigation that the use of a phthalic acid ester, a chlorinated paraffin or a combination of two or more high boiling point organic solvents as a dispersing medium for the oil-soluble fluorescent brightener brings about an excellent surface gloss, although the reason for this has not yet been clarified. In many cases, these dispersing media are superior to other media in terms of the ability to dissolve an oil-soluble fluorescent brightener and are therefore considered to be effective in suppressing the diffusion of an oil-soluble fluorescent brightener. It is therefore appropriate to consider that these dispersing media prevent the decrease in surface gloss as a result of the diffusion of the fluorescent brightener to the surface.

The dye fixing material of the present invention and a light-sensitive material to be combined therewith may be applied to the same support or to separate supports. Regarding the mutual relationship between the light-sensitive material and the dye fixing material, the relationship between these materials and a support and the relationship between these materials and a white reflecting layer, reference may be made to US-A-4 500 626, column 57. According to the present invention, the dye fixing material is preferably applied to a support which is separate from the support for a light-sensitive material.

The dye fixing material comprises a support having applied thereto a dye fixing layer and optionally auxiliary layers, e.g. a protective layer, a release layer, an anti-curling layer and a backing layer. A protective layer and a backing layer are particularly useful. One or more of these layers may contain, in addition to the fluorescent brightener, a hydrophilic thermal solvent, a plasticizer, a discoloration inhibitor, a UV absorbent, a lubricant, a matting agent, an antioxidant and a dispersed vinyl compound as a dimensional stabilizer.

The dye fixing layer preferably contains a polymer mordant which can fix a mobile dye released during development.

The polymer mordant includes polymers containing a tertiary amino group, a nitrogen-containing heterocyclic radical or a quaternized cationic group derived therefrom. These polymer mordants are preferably used in a mixture with other hydrophilic polymers (such as gelatin).

Polymers containing a vinyl monomer bearing a tertiary amino group are described in JP-A-60-60643 and JP-A-60-57836. Polymers containing a vinyl monomer bearing a tertiary imidazole group are described in JP-A-60-118834, JP-A-60-122941, Japanese Patent Application Nos. 61-87180 and 61-87181, and US-A-4282305, 4,115,124, and 3,148,061.

Examples of suitable polymers containing a vinyl monomer having a quaternary imidazolium salt are described in GB-A-2 056 101, 2 093 041 and 1 594 961, in US-A-4 124 386, 4 115 124, 4 273 853 and 4 450 224 and in JP-A-48-28225.

Examples of suitable polymers containing a vinyl monomer with a quaternary ammonium salt are described in US-A-3,709,690, 3,898,088 and 3,958,995, in JP-A-60-57836, JP-A-60-60643, JP-A-60-122940, JP-A-60-122942 and JP-A-60-235134.

The polymer mordant which can be used according to the invention has preferably a molecular weight of 1,000 to 1,000,000, in particular of 10,000 to 200,000.

The polymer mordant is used in a mordant layer of the dye fixing element in combination with a hydrophilic colloid serving as a binder, as described below.

The mixing ratio of polymer mordant to hydrophilic colloid and the amount of polymer mordant to be applied in the form of a layer can be easily determined by one skilled in the art depending on the amount of dye to be mordant, the type and composition of the polymer mordant and the image forming system used. Typically, the mixing ratio of mordant to hydrophilic colloid is in the weight range of 20/80 to 80/20 and the amount of mordant to be applied in the form of a layer is in the range of 0.2 to 15 g/m², preferably 0.5 to 8 g/m².

By combined use of the polymer mordant with a metalon in the dye fixing element, the transferred dye density is increased. The metal ion can be added to a mordant layer containing a mordant or to a layer adjacent thereto (on the side either closer to or further from a support having a mordant layer applied thereto, etc.). The metal ion usable is suitably colorless and stable to heat and light and preferably comprises polyvalent ions of transition metals such as Cu²⁺, Zn²⁺, Ni²⁺, Pt²⁺, Pd²⁺ and Co³⁺, with Zn²⁺ being particularly preferred. These metal ions are typically in the form of a water-soluble compound such as ZnSO₄. and Zn(CH₃CO₂)₂, in an amount of 0.01 to 5 g/m², preferably 0.1 to 1.5 g/m².

In the layer containing the metal ion, a hydrophilic polymer can be used as a binder. The hydrophilic colloids described below can be used as a hydrophilic binder for the layer containing the metal ion.

The mordant layer containing the polymer mordant may contain various surface active agents for different purposes, for example to improve the coating properties.

The dye fixing material according to the invention may contain a base and/or a precursor thereof.

Examples of suitable bases include inorganic bases such as a hydroxide, a carbonate, a bicarbonate, a borate, a secondary or tertiary phosphate or a metaborate of an alkali metal or a quaternary alkyl ammonium; and organic bases such as aliphatic amines, aromatic amines, heterocyclic amines, amidines, cyclic amidines, guanidines and cyclic guanidines and their carbonates, bicarbonates, borates and secondary or tertiary phosphates.

Suitable base precursors include the precursors of the above-mentioned organic bases. The term "base precursor" as used herein means a compound capable of releasing a basic component upon thermal decomposition or electrolysis. Examples of such base precursors include the salts of a thermally decomposable organic acid such as trichloroacetic acid, cyanoacetic acid, acetoacetic acid and α-sulfonylacetic acid, and the above-mentioned organic base or 2-carboxycarboxamide as described in US-A-4 088496. In addition, the base precursors as described in GB-A-998 945, in US-A-3 220 846 and in JP-A-50-22625 are also usable.

Examples of compounds capable of forming a base upon electrolysis include those capable of forming a base upon electrolytic oxidation with high efficiency, e.g. various fatty acid salts which are electrolytically decomposed with high efficiency to form a carbonate of an alkali metal, a guanidine and an amidine; and those which can form a base on electrolytic reduction, e.g. nitro or nitroso compounds which are reduced to form an amine, nitriles which are reduced to form an amine, and nitro, azo or azoxy compounds which are reduced to form a p-aminophenol, a p-phenylenediamine or a hydrazine. p-Aminophenols, p-phenylenediamines and hydrazines can be used not only as a base but also as a dye image-forming substance. It is also advantageous to electrolytically decompose water in the presence of various inorganic salts to form an alkali component.

Specific examples of suitable bases or precursors thereof which can be used in the invention are given below.

Lithium hydroxide, sodium hydroxide, sodium carbonate, cesium carbonate, sodium hydrogen carbonate, potassium carbonate, potassium hydrogen carbonate, sodium quinolinate, sodium sec-phosphate, potassium sec-phosphate, sodium tert-phosphate, potassium tert-phosphate, potassium pyrophosphate, sodium metaborate, borax, aqueous ammonia, tetramethylammonium hydroxide, tetraethylammonium hydroxide, (CH₃)₂NH, (C₂H₅)₂NH, C₃H�7;NH₂, HOC₂H�4;NH₂, (HOC₂H�4;)₂NH, (HOC₂H�4;)�3;N, H₂NC₂H�4;NH₂, H₂NC₄H�8;NH₂, CH₃NHC₂H₄NHCH₃, (CH₃)₂NC₃H�6N(CH₃)₂,

Guanidinotrichloroacetic acid, piperidinotrichloroacetic acid, morpholinotrichloroacetic acid, p-toluidinotrichloroacetic acid, 2-picolinotrichloroacetic acid, guanidine carbonate, piperidine carbonate, morpholine carbonate and tetramethylammonium trichloroacetate.

In addition, a method may also be used in which a sparingly soluble metal salt (such as zinc oxide, basic zinc carbonate, calcium carbonate) and a complexing compound capable of forming a complex with a metal ion constituting the metal salt (such as a picolinic acid salt) are reacted with each other in the presence of water as a medium to form a water-soluble base. In this method, a dispersion of the sparingly soluble metal salt is incorporated into a photosensitive material while a water-soluble compound capable of forming a complex with the metal ion is incorporated into a dye fixing material as a base precursor, and they are reacted with each other in the presence of water upon intimate contact with heating to form a base. This method is therefore particularly effective from the viewpoint of the storage stability of a photosensitive material and a dye fixing material.

The above-mentioned bases and/or base precursors may be used either individually or in combination of two or more of them .

The base and/or its precursor is used in an amount of from 5 x 10⁻⁴ to 5 x 10⁻¹ mol/m², preferably from 2.5 x 10⁻³ to 2.5 x 10⁻² mol/m².

The heat-developable light-sensitive material which can be used in combination with the dye fixing material of the present invention essentially comprises a support having applied thereto a light-sensitive silver halide, a binder and a dye-providing compound which, upon heat development, forms a diffusible can release or form a dye (the dye-providing compound sometimes serves as a reducing agent, as described below). If desired, the light-sensitive material may contain, for example, an organic metal salt oxidizing agent and a reducing agent. These components are usually incorporated in the same layer, but they may be incorporated separately in different layers as long as they are in a reactive state. For example, the presence of a colored dye-providing compound in a layer beneath a silver halide emulsion layer prevents a decrease in sensitivity. A reducing agent is preferably incorporated in a heat-developable light-sensitive material. It may also be supplied from the outside, for example by diffusion from a dye fixing material, as described below.

To obtain colors with a wide range of the chromaticity diagram using the three primary colors yellow, magenta and cyan, at least three silver halide emulsion layers having a different spectral sensitivity should be used in combination. For example, a blue-sensitive layer, a green-sensitive layer and a red-sensitive layer are combined; or a green-sensitive layer, a red-sensitive layer and an infrared-sensitive layer are combined. The order of application of these layers is arbitrarily selected from those known for general color photosensitive materials. If desired, each photosensitive layer may consist of two or more sublayers.

The heat-developable photosensitive material may further contain auxiliary layers such as a protective layer, a subbing layer (adhesive layer), an interlayer, a yellow filter layer, an antihalation layer (antihalation layer) and a backing layer.

Silver halide grains which can be used in the present invention may, for example, be those of silver chloride, silver bromide, silver iodobromide, silver chlorobromide, silver chloroiodide and silver chloroiodobromide.

The silver halide emulsions may be either a latent surface image type emulsion or an internal latent image type emulsion. The internal latent image type emulsion is used as a direct reversal emulsion in combination with a nucleating agent or with a light veil. The emulsion may be a so-called core/shell emulsion with different phases between the interior of the grains and the surface layer thereof. The silver halide emulsions may be either mono-disperse or polydisperse. A mixture of mono-disperse emulsions may also be used.

The silver halide grains have an average grain size of 0.1 to 2 µm, preferably 0.2 to 1.5 µm. The grains may have a regular crystal form, such as a cubic form, an octahedral form and a tetradecahedral form, or an irregular crystal form, such as a tabular form having a high aspect ratio.

Specific examples of suitable silver halide emulsions are described in US-A-4 500 626 (column 50) and 4 628 021, in "Research Disclosure" 17029 (1978) and in JP-A-62-253 159.

The silver halide emulsions may be used in the primitive (unripened) state, but are usually used after being chemically sensitized using known methods such as sulfur sensitization, reduction sensitization and noble metal sensitization, either individually or in combination thereof. The chemical sensitization may be carried out in the presence of a nitrogen-containing heterocyclic compound as proposed in JP-A-62-253159.

The light-sensitive silver halide emulsion is usually applied in the form of a layer on a support up to a silver coating amount of 1 mg to 10 g/m².

As stated above, an organic metal salt can be used as an oxidizing agent in combination with light-sensitive silver halide emulsions. Among the organic metal salts, organic silver salts are particularly preferred.

Organic compounds that form organic silver salt oxidizing agents include benzotriazoles, fatty acids and other compounds as described in US-A-4 500626, columns 52-53. In addition, silver salts of alkynyl-containing carboxylic acids such as silver phenylpropiolate as described in JP-A-60-113235 and acetylene silver as described in JP-A-61-249044 can also be used. These organic silver salts can be used either individually or in the form of a combination of two or more of them.

The organic silver salt is usually used in an amount of 0.01 to 10 mol, preferably 0.01 to 1 mol, per mol of photosensitive silver halide. The total silver coating amount of photosensitive silver halide and organic silver salt is suitably in the range of 50 mg to 10 g/m².

In the heat-developable photosensitive material, various antifogging agents or stabilizers can be used. Examples of this compound include azoles or azaindenes as described in "Research Disclosure", 17643, pp. 24-25 (1978), nitrogen-containing carboxylic acids or phosphoric acids as described in JP-A-59-168442, mercapto compounds and metal salts thereof as described in JP-A-59-111636, and acetylene compounds as described in JP-A-62-87957.

Silver halides which can be used in the present invention can be spectrally sensitized with methine dyes or other sensitizing dyes. Suitable sensitizing dyes include cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, hemicyanine dyes, styryl dyes and hemioxonol dyes. Specific examples of these sensitizing dyes are described in US-A-4,617,257, JP-A-59-180550, JP-A-60-140335 and in "Research Disclosure", 17029 (1978), pp. 12-13.

The sensitizing dyes can be used either individually or in a combination of them. Combinations of sensitizing dyes are often used for the purpose of supersensitization.

The photographic emulsions may contain a compound which itself has no spectral sensitization effect or does not absorb substantially any visible light, but which in combination with the sensitizing dye produces a supersensitization effect. Examples of such a compound are described, for example, in US-A-2 615641 and in JP-A-63-23145.

The sensitizing dyes can be added during, before or after the chemical ripening of an emulsion. They can also be added before or after the nucleation of the silver halide grains as described in US-A-4,183,756 and 4,225,666. The amount in which the sensitizing dye can be added is generally in the range of 1 x 10-8 to 1 x 10-2 mole per mole of silver halide.

The binders to be used in the layers constituting the light-sensitive material and the dye-fixing material are preferably hydrophilic. Examples of suitable hydrophilic binders are described in JP-A-62-253159, pp. 26-28. Transparent or simitransparent binders are particularly preferred. These hydrophilic binders also include naturally occurring compounds such as proteins (e.g. gelatin and derivatives thereof), cellulose derivatives and polysaccharides (e.g. starch, gum arabic, dextran and pullulan); and synthetic high polymers such as polyvinyl alcohol, polyvinylpyrrolidone and acrylamide polymers. Also usable as the binder are highly water-absorbent polymers as described in JP-A-62-245260, e.g., homo- or copolymers of one or more vinyl monomers having -COOM or -SO₃M (wherein M represents a hydrogen atom or an alkali metal), and copolymers of such a vinyl monomer with one or more other vinyl monomers (e.g., sodium methacrylate, ammonium methacrylate, and Sumikagel L-5H (manufactured by Sumitomo Chemical Co., Ltd.)). These binders may be used in the form of combinations of two or more of them.

In a system in which heat development is carried out by supplying a small amount of water, the use of the highly water-absorbent polymer described above promotes the absorption of water. In addition, the use of the highly water-absorbent polymer in a dye-fixing layer or in a protective layer thereof is effective in preventing the retransfer of the transferred dye from the dye-fixing material to other materials. In the present invention, the binder is preferably coated in an amount of not more than 20 g/m², more preferably not more than 10 g/m², and most preferably not more than 7 g/m².

The layers constituting the photosensitive material or the dye fixing material, including the undercoat layer (back layer), may contain various polymer latexes for improving film properties, such as improving dimensional stability, preventing curling, blocking or cracking, and preventing pressure sensitization or desensitization. For this purpose, any of the polymer latexes described in JP-A-62-245258, JP-A-62-136648 and JP-A-62-110066 can be used. In particular, the incorporation of a polymer latex with a low glass transition point (for example 40ºC or below) into a mordant layer is effective in preventing cracking of the mordant layer, while the incorporation of a polymer latex with a high glass transition point into a base layer (back layer) achieves anti-curling effects.

The reducing agents which can be used in the heat-developable photosensitive material of the present invention are selected from those which are conventionally used in the field of heat-developable photosensitive materials. Reducing dye-providing compounds as described below also belong to the reducing agents. The reducing dye-providing compound can be used in combination with other reducing agents. In addition, reducing agent precursors which do not have a reducing effect by themselves but can exhibit a reducing effect when reacted with a nucleophilic reagent or when heated at the time of development can also be used.

Specific examples of suitable reducing agents including their precursors which can be used in the present invention are described in US-A-4 500 626 (columns 49-50), 4 483 914 (columns 30-31), 4 330 617 and 4 590 152, JP-A-60-140335 (pages 17-18), JP-A-57-40245, JP-A-56-138736, JP-A- 59-175458, JP-A-59-53831, JP-A-59-182449, JP-A-59-182450, JP-A-60- 1195553 JP-A-60-128436 to 128439, JP-A-60-198540, JP-A-60-181742, JP-A-61-259253, JP-A-62-244044, JP-A-62-131253 to 131256 and EP-A-220746 (pp. 78-96).

Combinations of different reducing agents as described in US-A-3 039 869 can also be used.

If desired, where a non-diffusible reducing agent is used, an electron transfer agent and/or a precursor thereof may be used in combination therewith to thereby accelerate the electron transfer between the non-diffusible reducing agent and the developable silver halide.

Such an electron transfer agent or a precursor thereof can be selected from the above-mentioned reducing agents or their precursors. It is desirable that the electron transfer agent or its precursor has a higher mobility than the non-diffusible reducing agent (i.e. an electron donor). Particularly suitable electron transfer agents are 1-phenyl-3-pyrazolidones or aminophenols.

The non-diffusible reducing agent (electron donor) to be combined with the electron transfer agent is selected from the above-mentioned reducing agents as long as it is substantially immobile in the layer to which it belongs. Suitable examples of such a non-diffusible reducing agent include hydroquinones, sulfonamidophenols, sulfonamidonaphthols, compounds described in JP-A-53-110827 as electron donors, and non-diffusible reducing dye-providing compounds as described below.

The amount in which the reducing agent is to be used according to the invention is generally in the range from 0.001 to 20 mol, preferably from 0.01 to 10 mol, per mol of silver.

Typical examples of the dye-providing compounds that can be used in the present invention include 2-equivalent couplers that have a non-diffusible group as a releasable group and can form a diffusible dye upon coupling reaction with the oxidation product of a color developing agent. The non-diffusible group may have a polymer chain. Specific examples of color developing agents and couplers are given in T.H. James, "The Theory of the Photographic Process" (4th edition), pp. 291-334 and 354-361, in JP-A-58-123533, JP-A-58-149046, JP-A-58-149047, JP-A-59-111148, JP-A- 59-124399, JP-A-59-174835, JP-A-59-231 539, JP-A-59-231540, JP-A-60- 2950, JP-A-60-2951, JP-A-60-14242, JP-A-60-23474 and JP-A-60-66249.

Dye-providing compounds also include compounds that have the function of releasing or diffusing a diffusible dye in an image-wise manner. These compounds can be represented by the formula (LI):

(Dye-Y)n-Z (LI)

where:

Dye a dye group, a dye group that has been temporarily shifted to a shorter wavelength range, or a dye precursor group;

Y is a bond or a connecting group;

Z is a group which imparts a difference in the diffusivity of the compound of the formula (Dye-Y)n-Z or releases dye to create a difference in the diffusivity between the dye thus released and (Dye-Y)n-Z corresponding or counter-corresponding to the photosensitive silver salts which have an image-wise distributed latent image; and

n is the number 1 or 2,

where, if n = 2, the two Dye-Y residues can be the same or different.

Specific examples of the dye-providing compounds of the formula (LI) include the following compounds (i) to (v). The compounds (i) to (iii) form a diffusible dye image in response to the development of the silver halide, while the compounds (iv) and (v) form a diffusible dye image (negative dye image) in response to the development of the silver halide.

(i) dye developing agents comprising a hydroquinone developing agent bound to a dye component as described in US-A-3,134,764, 3,362,819, 3,597,300, 3,544,545 and 3,482,972. The compounds of this type are diffusible under alkaline conditions, but become non-diffusible upon reaction with silver halide;

(ii) non-diffusible compounds which release a diffusible dye under alkaline conditions but lose their function upon reaction with silver halide, as described in US-A-4 503 137. Examples of these compounds include compounds which undergo intramolecular nucleophilic substitution to release a diffusible dye, as described in US-A-3 980479, and compounds which undergo intramolecular rearrangement of the isooxazolone ring. releasing a diffusible dye as described in US-A-4 199 354;

(iii) Non-diffusible compounds which react with a reducing agent which remains unoxidized after development to release a diffusible dye, as described in US-A-4 559 290, EP-A-220 746, US-A-4 783 396 and in "Technical Disclosure Bulletin", 87-6199. Examples of these compounds include compounds which, after reduction, undergo intramolecular nucleophilic substitution to release a diffusible dye, as described in US-A-4,139,389 and 4,139,379, in JP-A-59-185333 and JP-A-57-84453, compounds which, after reduction, undergo intramolecular electron transfer to release a diffusible dye, as described in US-A-4-232,107, JP-A-59-101649, JP-A-61-88257 and in "Research Disclosure", 24025 (1984), compounds whose single bond is cleaved (dissolved) after reduction to release a diffusible dye, as described in DE-A-3 008 588, JP-A-56-142530 and US-A-4 343 893 and 4 619 884, nitro compounds which accept electrons to release a diffusible dye as described in US-A-4 450 223, and compounds which accept electrons to release a diffusible dye as described in US-A-4 609 610.

Preferred examples of compounds of this type include compounds having an NX bond (wherein X is an oxygen, sulfur or nitrogen atom) and one electrophilic group per molecule as described in EP-A-220 746, in "Technical Disclosure Bulletin", 87-6199, in US-A-4 783 396, JP-A-63-201653 and JP-A-63-201654, compounds having an SO₂-X group (wherein X is as defined above) and one electrophilic group per molecule as described in US-A-4 840 887 (corresponding to Japanese Patent Application No. 62-106885), compounds having a PO-X bond (wherein X is as defined above) and one electrophilic group per molecule as described in JP-A-63-271344, and compounds which a C-X' bond (wherein X' has the same meaning as X or represents -SO₂-) and one electrophilic group per molecule, as described in JP-A-63-271341.

In addition, compounds in which a single bond is cleaved after reduction by a π-bond in conjugation to an electron acceptor group to release a diffusible dye as described in JP-A-1-161237 and JP-A-1-161342 can also be used.

Particularly preferred among these compounds are the compounds having one N-X bond and one electrophilic group per molecule. Specific examples of the compounds are Compound Nos. (1) to (3), (7) to (10), (12), (13), (15), (23) to (26), (31), (32), (35), (36), (40), (41), (44), (53) to (59), (64) and (70) as described in EP-A-220 746 or US-A-4 783 396, and Compound Nos. (11) to (23) as described in "Technical Disclosure Bulletin" 87-6199;

(iv) compounds having a diffusible dye as a releasable group, capable of releasing a diffusible dye upon reaction with the oxidation product of a releasing agent (DRR couplers). Specific examples of the DRR couplers are described in GB-A-1 330 524, JP-B-48-39165 (the term "JP-B" as used herein means an "examined published Japanese patent application") and US-A-3 443 940, 4 474 867 and 4 483 914;

(v) Compounds having a reducing effect on a silver halide or an organic silver salt, which release a diffusible dye upon exerting the reducing effect (DRR compounds). Since the compounds of this type do not require other reducing agents, image discoloration due to the oxidative decomposition products of the reducing agents can be eliminated. Typical examples of these compounds are described in US-A-3 928 312, 4 053 312, 4 055 428 and 4 336 322, in JP-A-59-65839, JP-A-59-69839, JP-A-53-381 9, JP-A-51 -104343, in "Research Disclosure" 17465, in US-A-3 725 062, 3 728 113 and 3 443 939, in JP-A-58-116537, JP-A-57-179840 and in US-A-4 500626. Specific examples of the DRR compounds include the compounds of columns 22 to 44 of US-A-4 500626 supra. Among them, particularly preferred are compound Nos. (1) to (3), (10) to (13), (16) to (19), (28) to (30), (33) to (35), (38) to (40) and (42) to (64). The compounds described in US-A-4 639408, columns 37 to 39 are also usable.

In addition to the above-mentioned coppers and compounds of formula (LI), dye-providing compounds which can be used in the present invention include silver dye compounds consisting of an organic silver salt bound to a dye as described in Research Disclosure, May 1978 issue, pp. 54-58; azo dyes for use in heat development in a silver dye bleaching process as described in US-A-4,235,957 and in Research Disclosure, April 1976 issue, pp. 30-32; and leuco dyes as described in US-A-3,985,565 and 4,022,617.

Hydrophobic additives, e.g. dye-forming compounds and non-diffusible reducing agents, can be incorporated into the layers of the photosensitive materials by known methods, as described in US-A-2 322 027. In this case, high-boiling organic solvents, e.g. those described in JP-A-59-83154, JP-A-59-178451 to 178455 and JP-A-59-178457, can be used either alone or, if desired, in combination with low-boiling organic solvents having a boiling point of 50 to 160°C.

The high boiling organic solvent is generally used in an amount of not more than 10 g, preferably not more than 5 g, per gram of the dye-providing compound and in an amount of not more than 1 ml, preferably not more than 0.5 ml and particularly preferably not more than 0.3 ml, per gram of binder.

The dispersion method using polymerization products, as described in JP-B-51-39853 and JP-A-51-59943, is also used for incorporating the hydrophobic additives.

If the additive to be introduced is essentially water-insoluble, it can also be incorporated into the binder in the form of a finely divided dispersion.

In order to disperse hydrophobic additives in a hydrophilic colloid, various surface-active agents can be used. For example, the surface-active agents as described in JP-A-59-157636, pp. 37-38, as well as the above-mentioned ionic surface-active agents are suitably used.

According to the invention, the light-sensitive material may contain a compound which serves both to accelerate development and to stabilize the image. Examples of such a compound which can preferably be used are given in US-A-4 500 626, columns 51-52.

Layers constituting the photosensitive material and the dye fixing material may contain a high boiling organic solvent as a plasticizer, a lubricant or an agent for improving the separability between the photosensitive material and the dye fixing material. Specific examples of suitable high boiling organic solvents are described in JP-A-62-253159 (p. 25) and JP-A-62-245253. Various kinds of silicone oils (including those from dimethyl silicone oil to modified silicone oils comprising dimethylsiloxane into which various organic groups have been introduced) can also be used for the same purposes. Examples of effective silicone oils are modified silicone oils of various kinds, and in particular, carboxyl-modified silicone oil ("X-22-3710", manufactured by Shin-Etsu Silicone Co., Ltd.) described on pages 6-8 of "Modified Silicone Oil" of the technical data report of Shin-Etsu Silicone Co., Ltd. Silicone oils as described in JP-A-62-215953 and JP-A-63-46449 are also effective.

The photosensitive material and the dye fixing material may also contain a discoloration inhibitor, such as antioxidants, ultraviolet absorbers and a certain type of metal complexes.

Examples of suitable antioxidants include chroman compounds, coumaran compounds, phenol compounds (e.g. hindered phenols), hydroquinone derivatives, hindered amine derivatives and spiroindane compounds. Compounds as described in JP-A-61-159644 are also effective.

Examples of suitable ultraviolet absorbers include benzotriazole compounds (e.g., those described in US-A-3,533,794), 4-thiazolidone compounds (e.g., those described in US-A-3,352,681), benzophenone compounds (e.g., those described in JP-A-46-2784), and compounds described in JP-A-54-48535, JP-A-62-136641, and JP-A-61-88256. Also effective are ultraviolet absorbing polymers described in JP-A-62-260152.

Examples of metal complexes useful as discoloration inhibitors include compounds as described in US-A-4 241155, 4245 018 (columns 3-36) and 4 254 195 (columns 3-8), JP-A-62-1 74741, JP-A-61 -88256 (pages 27-29), JP-A-63-1 99248, JP-A-1 -75568 and JP-A-1-74272.

Examples of suitable discoloration inhibitors are described in JP-A-62-215272, pp. 125-137.

The discoloration inhibitor which prevents the discoloration of the dye transferred to a dye fixing material may be previously incorporated into the dye fixing material or may be supplied to the dye fixing material from the outside, for example, a light-sensitive material.

The above-mentioned antioxidants, ultraviolet absorbents and metal complexes may be used in the form of a combination thereof.

Hardeners that can be used in the layers constituting the photosensitive material or the dye fixing material include those described in US-A-4 678 739 (column 41), JP-A-59-1 16655, JP-A-62-245261 and JP-A-61-18942. Specific examples of suitable hardeners are aldehyde hardeners (e.g. formaldehyde), aziridine hardeners, epoxy hardeners (e.g.

Vinylsulfone hardeners (e.g. N,N'-ethylenebis(vinylsulfonylacetamido)ethane), N-methylol hardeners (e.g. dimethylol urea) and high molecular weight hardeners (e.g. the compounds described in JP-A-62-234157).

The layers constituting the light-sensitive material or the dye-fixing material may contain various surface active agents as a coating aid, for improving separation, for improving slip properties, for preventing electrostatic charge, and for accelerating development. However, the amount of the anionic surface active agent is adjusted based on the above description according to the present invention.

The layers constituting the photosensitive material or the dye fixing material may further contain organofluorine compounds to improve the slip properties, to prevent electrostatic charging and to improve the separation. Typical examples of organofluorine Compounds are fluorine-containing surface active agents as described in JP-B-57-9053 (columns 8-17), JP-A-61-20944 and JP-A-62-135826, and hydrophobic fluorine compounds, e.g., oily fluorine compounds (such as fluorine oil) and solid fluorine compound resins (e.g., tetrafluoroethylene resin). However, the amount of the organofluoro compounds having an anionic group and surface activity is adjusted based on the above definition according to the invention.

The photosensitive material or the dye fixing material may further contain a matting agent, for example, the compounds described in JP-A-61-88256 (p. 29) (e.g., silicon dioxide, polyolefins and polymethacrylates) and the compounds described in JP-A-63-274944 and JP-A-63-274952 (e.g., benzoguanamine resin beads, polycarbonate resin beads and AS resin beads).

The layers constituting the photosensitive material or the dye fixing material may further contain other additives, e.g. thermal solvents, defoaming agents, antiseptic biocides and colloidal silica. Specific examples of these additives are described in JP-A-61-88256, pp. 26-32.

The photosensitive material or dye fixing material may further contain image formation accelerators. Image formation accelerators have the function of accelerating the reduction-oxidation reaction between a silver salt oxidizing agent and a reducing agent to accelerate dye formation, dye decomposition or release of a diffusible dye from a dye-providing compound and also to accelerate transfer of a dye from a photosensitive layer to a dye fixing layer. From the standpoint of physicochemical functions, the image formation accelerators are divided into bases or base precursors, nucleophilic compounds, high-boiling organic solvents (oils), thermal solvents, surface active agents and compounds which react with silver or silver ions. It should be noted that these groups of substances generally have composite functions so that they exhibit some of the acceleration effects described above in combination. For details, see US-A-4 678 739, columns 38-40.

The light-sensitive material and/or the dye fixing material may contain various development stopping agents to obtain images with a constant quality regardless of variations in temperature and development time. The term "development stopping agent" as used herein means a compound which, after sufficient development, rapidly neutralizes a base or reacts with a base to lower the base concentration in the film to thereby stop development, or a compound which, after sufficient development, reacts with silver or a silver salt to inhibit development. Examples of such a development stopping agent include acid precursors which release an acid when heated, electrophilic compounds which undergo a substitution reaction with a coexisting base when heated, and nitrogen-containing heterocyclic compounds, mercapto compounds and precursors thereof. For details, see JP-A-62-2531 59, pp.31-32.

The supports which can be used in the light-sensitive material and/or the dye fixing material should be stable at the processing temperature and generally include paper and synthetic resin films. Specific examples of suitable supports are films of polyethylene terephthalate, polycarbonate, polyvinyl chloride, polystyrene, polypropylene, polyimide and cellulose derivatives (such as triacetyl cellulose), films of these synthetic resins with incorporated pigments, e.g. titanium oxide, synthetic paper films of, for example, polypropylene, mixed paper made from a synthetic resin pulp (e.g. polyethylene) and a natural Pulp, Yankee paper, baryta paper, coated paper (especially cast coated paper), metals, fabrics and glass.

These supports can be used either alone or in the form of a film coated with a synthetic high polymer such as polyethylene on one or both sides.

In addition, the supports described in JP-A-62-253159 (pp. 29-31) can also be used.

The surfaces of the carrier can be coated with a hydrophilic binder and a semiconducting metal oxide (e.g. aluminum sol and tin oxide), carbon black or other antistatic agents.

The image formation or image recording on the photosensitive material by exposure is carried out using a method which comprises directly photographing a scene or persons with a camera and the like, a method which comprises exposing the photosensitive material to light through a reversal film or a negative film using a printer or an enlarger, a method which comprises exposing an original by scanning through a slit using an exposure device of a copying machine and the like, a method which comprises exposing the photosensitive material to light emitted from a light emitting diode (LED) or a laser by electrical signals converted from the image information, and a method which comprises inputting image information to an image display device such as a CRT, a liquid crystal display, an electroluminescent display and a plasma display and exposing the photosensitive material to light emitted directly or through a optical system has been emitted from it.

Light sources for recording images on the photosensitive material include natural light, a tungsten lamp, an LED, a laser light source, and a CRT light source as described in US-A-4 500 626, column 56.

The imagewise exposure can also be carried out using a wave conversion element comprising a combination of a non-linear optical material and a coherent light source, for example a laser. The term "non-linear optical material" as used herein means a material that can exhibit non-linearity between polarization and an electric field when a strong optical-electric field, for example a laser beam, is applied thereto. Suitable examples of such a material include inorganic compounds such as lithium niobate, potassium dihydrogen phosphate (KDP), lithium iodate and BaB₂O₄; urea derivatives; nitroaniline derivatives; Nitropyridine N-oxide derivatives, for example 3-methyl-4-nitropyridine N-oxide (POM) and compounds as described in JP-A-61-53462 and JP-A-62-21 0432. Known wavelength conversion elements include a single crystal optical waveguide mode and a fiber mode, both of which can be used in the present invention.

The image information that can be recorded on the photosensitive material includes image signals obtained from a video camera, an electronic still camera and the like, TV signals according to the Nippon Television Signal Code (NTSC), image signals obtained by dividing an original into many pixels, and image signals generated by a computer represented by CG or CAD.

The photosensitive material and/or the dye fixing material may have an electrically conductive heating element layer as a heating means for heat development or for dye diffusion transfer. In this case, transparent or opaque heating elements as described in JP-A-61- 145544. The electrically conductive layer can also serve as an antistatic layer.

The heating temperature for heat development is 50 to 250°C, and preferably 80 to 180°C. The dye diffusion transfer process may be carried out simultaneously with or after heat development. In the latter case, the transfer may be carried out at a temperature from room temperature to the heat development temperature, particularly from 50°C to a temperature lower than the heat development temperature by about 10°C.

Migration of a dye can only be effected by the application of heat. A solvent can be used to accelerate migration of a dye. In a preferred embodiment of an image forming system, the photosensitive material is heated either after or simultaneously with imagewise exposure in the presence of a small amount of water as a solvent and a base and/or a base precursor to thereby carry out development and, simultaneously or subsequently, transfer of a diffusible dye formed on the surface corresponding to or opposite to a developed silver image to the dye fixing layer. In this image forming system, a high density dye image can be obtained within a short period of time because the formation or release of a diffusible dye proceeds very rapidly and the transfer of the formed or released diffusible dye to a dye fixing layer also proceeds rapidly.

The amount of water to be used in the above-described embodiment is at least 1/10 of the weight of the total amount of the coating films of the photosensitive material and the dye fixing material, and is preferably so small that it is not more than the weight of water corresponding to the maximum swelling volume of the total amount of the coating films, in particular it does not exceed the amount obtained by subtracting the weight of the total amount of the coating films from the weight of the water corresponding to the maximum swollen volume of the total amount of the coating films.

The applied films become very unstable when swollen and tend to cause local smearing under certain conditions. To avoid this, the amount of water added is preferably not more than the weight corresponding to the water volume of the total applied films of both the photosensitive material and the dye fixing material swollen to the maximum degree. The water is particularly preferably used in an amount of 1 to 50 g, more preferably 2 to 35 g and most preferably 3 to 25 g, per m² of the total area of the photosensitive material and the dye fixing material.

The base and/or base precursor that can be used in this embodiment can be incorporated into both the light-sensitive material and the dye fixing material. They can also be supplied in a form dissolved in water.

In the embodiment described above, it is preferable that a combination of a basic metal compound which is sparingly soluble in water and a compound which can form a complex with a metal ion constituting the metal compound is present in a water medium in the image forming reaction system as a base precursor. These two compounds are allowed to react with each other upon heating to increase the pH of the system. The term "image forming reaction system" as used herein means an area in which an image forming reaction takes place and includes the layers which are both the photosensitive material and the dye fixing material. If there are two or more layers, each of these layers can be referred to as an "image forming reaction system".

In order to prevent a reaction between the sparingly soluble metal compound and the complexing compound prior to development treatment, it is necessary to incorporate these compounds into at least separate layers. For example, in the case of monolayer materials comprising a photosensitive material and dye fixing material on the same support, these two compounds should be added to different layers, preferably with at least one layer interposed therebetween. In a particularly preferred embodiment, the two compounds are added to different layers, each provided separately on the respective support. For example, it is desirable to add a sparingly soluble metal compound to a photosensitive material, while a complexing compound is added to a dye fixing element having its own support. The complexing compound can be added dissolved in water, which is added as a solvent for image formation. The sparingly soluble metal compound is preferably added in the form of a finely divided dispersion prepared by the method described in JP-A-56-174830 and JP-A-53-102733. The dispersion preferably has an average particle size of 50 µm or less, and particularly 5 µm or less. The sparingly soluble metal compound may be added to one or more layers of the photosensitive material, for example, a photosensitive layer, an intermediate layer and a protective layer.

The amount in which the sparingly soluble metal compound and the complex-forming compound should be added depends on the type of compound, the particle size of the sparingly soluble metal compound, the complex formation rate, etc. As a rule, it is not more than 50% by weight, preferably 0.01 to 40% by weight, based on the Weight of the coating. If the complexing compound is added dissolved in water, a preferred concentration range is 0.005 to 5 mol/l and especially 0.05 to 2 mol/l. The molar ratio between complexing compound and sparingly soluble metal compound in the reaction system is generally in the range from 1/100 to 100, preferably from 1/10 to 20.

According to the method described in JP-A-61-147244, water can be supplied to a light-sensitive layer or a dye-fixing layer.

The heating for development and/or dye transfer can be carried out using a heating means such as a heated block or plate, a hot plate, a hot press or a heating roller as described in JP-A-61-147244. The photosensitive member and/or the dye fixing member can be directly heated by providing an electrically conductive layer made of an electrically conductive material such as graphite, carbon black and a metal and allowing electricity to flow through the electrically conductive layer.

Regarding the printing conditions and pressurizing methods for bringing the photosensitive material and the dye fixing material into intimate contact with each other, reference is made to JP-A-61-147244.

Any of various heat developing devices can be used for the photographic processing of the photographic element of the present invention. Examples of suitable devices are described in JP-A-59-75247, JP-A-59-177547, JP-A-59-181353, JP-A- 60-18951 and JP-A-U-62-25944 (the term "JP-A-U" as used herein means an "unexamined published Japanese utility model application").

The present invention is further illustrated by the following examples. In the examples, all parts, percentages and ratios are by weight unless otherwise indicated.

example 1 Production of dye fixing materials Preparation of the dye fixing material (4)

A dye fixing material (4) with the following layer structure was produced:

3 layer:

Gelatin 0.05 g/m²

Silicone oil (1) 0.04 g/m²

surfactant (2) 0.03 g/m²

surfactant (3) 0.10 g/m²

surfactant (4) 0.08 g/m²

Matting agent (1) 0.02 g/m²

Guanidine picolinate 0.45 g/m²

water soluble polymer (1) 0.24 g/m²

2 layer:

Mordant (1) 2.35 g/m²

water soluble polymer (1) 0.20 g/m²

Gelatine 1.40 g/m²

water soluble polymer (2) 0.60 g/m²

high boiling solvent (2) 1.40 g/m²

Guanidine picolinate 2.2591m²

Fluorescent brightener F-30 0.05 g/m²

surfactant (1) 0.10 g/m²

surfactant (5) 0.01 g/m²

1st layer:

Gelatin 0.45 g/m²

surfactant (3) 0.01 g/m²

water soluble polymer (1) 0.04 g/m²

Hardener (1) 0.30 g/m²

Carrier (1):

As shown in Table 1 below.

1. Back layer:

Gelatin 3.25 g/m²

Hardener (1) 0.25 g/m²

2. Back layer:

Gelatin 0.44 g/m²

Silicone oil (1) 0.08 g/m²

surfactant (4) 0.04 g/m²

surfactant (5) 0.01 g/m²

Matting agent (2) 0.03 g/m² Table 1 Structure of the carrier (1):

The physical properties of the support (1) are given in Table 2 below. Table 2

The compounds used in the preparation of the sample were as follows: Silicone oil (1): surfactant (1): surfactant (2): surfactant (3): surfactant (4): surfactant (5):

Fluorescent brightener F-30:

2,5-bis(5-t-butylbenzoxazole(2)thiophene

Water-soluble polymer (1):

Sumikagel L5-H (manufactured by Sumitomo Chemical Co., Ltd.)

Water-soluble polymer (2):

Dextran (molecular weight: 70 000) Mordants (1): High boiling solvent (1): surfactant (6): Hardener (1):

Matting agents (1)

Silicon dioxide

Matting agents (2):

Benzoguanamine resin (average particle size: 15 µm)

The fluorescent brightener was used in the form of a gelatin dispersion, which was prepared as follows:

5 g of fluorescent brightener (1) was dissolved in 140 g of high boiling organic solvent (2) and 50 ml of ethyl acetate with heating to prepare a uniform solution. The resulting solution was mixed with 300 g of 20% aqueous solution of lime-treated gelatin and 10.0 g of surfactant (1) with stirring and the mixture was dispersed with an ultrasonic disperser.

Dye fixing materials (1) to (3) and (5) to (32) were prepared in the same manner as dye fixing material (4) except that the gelatin dispersion of fluorescent brightener F-30 was replaced by a dispersion prepared in the same manner as described above using each of the fluorescent brighteners and high boiling organic solvents shown in Table 3 below and the surface active agent (1), (4) or (6) for the second layer in the amount shown in Table 3. Table 3 Table 3 (continued) Table 3 (continued)

The compounds used in the preparation of dye fixing materials (1) to (3) and (5) to (32) were as follows: High boiling organic solvent (2): High boiling organic solvent (3): High boiling organic solvent (4): High boiling organic solvent (5): High boiling organic solvent (6): High boiling organic solvent (7): High boiling organic solvent (8): High boiling organic solvent (9):

Ratio of position isomers (o:m:p) = 40:12:48 High boiling organic solvent (10):

Ratio of alkyl chain lengths (n=10:n=12:n=14:n=16) = 0.4:5:17:78

High boiling organic solvent (11):

(CnH2n+1O)P=O

Ratio of alkyl chain lengths (n=6:n=8:n=9) = 2:11:87 High boiling organic solvent (12):

Ratio of alkyl chain lengths (n=10:n=12) = 5:95 High boiling organic solvent (13):

High boiling organic solvent (14):

C₂₆H43.5Cl6.5 (Cl content: about 41%)

High boiling organic solvent (15):

C₁₄H25.9Cl4.1 (Cl content: about 43%)

The multilayer photosensitive material prepared in the reference example (comparative example) was exposed to the light of a tungsten lamp (5000 lux) through a gray filter with continuously changing density.

The exposed photosensitive material was placed on a belt (web) at a linear speed of 20 mm/s while water was supplied to the emulsion surface of the same at a rate of 15 ml/m2 with a wire rod, and immediately thereafter each of the dye fixing materials (1) to (32) was brought into intimate contact with the photosensitive material in such a manner that the coated surfaces were opposed to each other.

The film unit was heated for 15 seconds by means of a heating roller set at a temperature such that the film which had absorbed water was heated to 80°C. The light-sensitive material was then peeled off from the dye-fixing material to obtain a gray image on the dye-fixing material.

The specular gloss of the dye fixing material was measured at an angle of incidence of 200 using a gloss meter manufactured by Nihon Densoku Kogyo K.K. Then, the dye fixing material was left at 50ºC and 80% relative humidity (RH) for 40 hours and the specular gloss was measured again.

The maximum density Dmax of the image formed on the dye fixing material was measured with a densitometer ("FCD-3", manufactured by Fuji Photo Film Co., Ltd.). Then, the dye fixing material was left under a fluorescent lamp (15,000 lux) for 4 weeks and the maximum density D'max was measured again. A ratio D'max/Dmax was obtained.

The separability (peelability) between the photosensitive material and the dye fixing material was systematically evaluated by the force required for peeling, regardless of whether or not the surface of the dye fixing material suffered from peeling during peeling or regardless of whether the film of the light-sensitive material remained on the dye fixing material after peeling off or not.

The results of these measurements and evaluations are given in Table 4 below. Table 4 Table 4 (continued) Table 4 (continued)

As is clear from Tables 3 and 4, the dye fixing materials of the present invention in which the total amount of anionic surface active agents is within a specific range have satisfactory releasability (peelability) and surface gloss. On the other hand, when the total amount of surface active agents is below the specified range (Sample Nos. 1 and 20), the dye fixing materials have deteriorated releasability, although the initial surface gloss is satisfactory. In addition, the surface gloss of these samples decreases with the passage of time. The reason for these results is not yet clear, but it is considered that the stability of the fluorescent brightener dispersion is thereby reduced, thereby accelerating the precipitation of oil-soluble components.

When the total amount of surfactants is above the specified range, the surface gloss is poor and it also becomes poorer with the passage of time. In addition, the dye image has a slightly deteriorated light stability. It is believed, although not yet clear, that the anionic surfactants interact with a cationic mordant, thereby decreasing the image stability.

In addition, when a phthalic acid ester (Sample Nos. 9 to 11) or a combination of two or more kinds of high boiling point organic solvents (Sample Nos. 16 and 19 to 22) is used in the preparation of a fluorescent brightener dispersion, a satisfactory surface gloss can be obtained and changes during storage can be reduced. The dye images formed on the dye fixing materials of the present invention have a satisfactory stability.

From all these considerations, the effects of the invention are obvious.

The structure of the photosensitive material (1) used in the examples of the invention is explained below.

The preparation of the light-sensitive silver halide emulsion in each layer is described below.

Preparation of the emulsion (1)

An aqueous gelatin solution was prepared from 800 ml of water, 20 g of gelatin, 3 g of potassium bromide and 0.3 g of HO(CH2)2S(CH2)2S(CH2)2OH and the solution was kept at 55°C with stirring. The below-mentioned solutions (I) and (II) were simultaneously added to the aqueous gelatin solution over a period of 30 min. Then, the below-mentioned solutions (III) and (IV) were added over a period of 20 min. 5 min after the start of the addition of the solutions (III) and (IV), a dye solution prepared by dissolving 0.12 g of each of the below-mentioned dyes (a) and (b) in 160 ml of methanol was added over a period of 18 min.

After washing with water and desalting, 20 g of lime-treated bone gelatin was added and the emulsion was adjusted to pH 6.2 and pAg 8.5. To the emulsion, sodium thiosulfate, 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene and chloroauric acid (III) were added to carry out optimal chemical sensitization to obtain 600 g of a monodisperse tetradecahedral silver iodobromide emulsion having an average grain size of 0.40 µm. The resulting emulsion was designated as Emulsion (I). Dye (a): Dye (b):

Preparation of the emulsion (II):

An aqueous gelatin solution was prepared from 730 ml of water, 20 g of gelatin, 0.30 g of potassium bromide, 6 g of sodium chloride and 0.015 g of the compound (A) shown below, and the solution was kept at 60.0°C with stirring. To the aqueous gelatin solution were simultaneously added the solutions (I) and (II) shown below over a period of 60 minutes at constant flow rates. After the addition of the solutions (I) and (II), 77 ml of a methanol solution containing 0.23 g of the sensitizing dye (c) shown below was added to obtain a monodisperse emulsion containing cubic grains having an average grain size of 0.45 µm.

After washing with water and desalting, 20 g of gelatin was added to the emulsion and the emulsion was adjusted to pH 6.4 and pAg 7.8. Then, the emulsion was chemically sensitized with 1.6 mg of triethylthiourea and 100 mg of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene at 60.0°C for 55 minutes to obtain 635 g of an emulsion designated as Emulsion (II). Connection (A): Dye (c):

Preparation of the emulsion (III):

An aqueous gelatin solution was prepared from 800 ml of water, 20 g of gelatin, 1 g of potassium bromide and 0.5 g of OH(CH2)2S(CH2)2OH and the solution was kept at 50°C with stirring. To the aqueous gelatin solution were simultaneously added the solutions (I), (II) and (III) given below over a period of 30 minutes at constant feed rates to prepare a monodisperse emulsion of silver bromide grains having an average grain size of 0.42 µm with dyes adsorbed thereon.

After washing with water and desalting, 20 g of lime-treated bone gelatin was added to the emulsion, and the emulsion was adjusted to pH 6.4 and pAg 8.2. To the emulsion kept at 60°C, 9 mg of sodium thiosulfate, 190 mg of 4-hydroxy-6-methyl-1,3,3a,7-tetraazaindene and 6 ml of a 0.01% aqueous solution of chloroauric acid (III) were added to conduct chemical sensitization for 45 min. The yield of the emulsion was 635 g. The resulting emulsion is hereinafter referred to as Emulsion (III). Dye (d): Colorant(s):

Preparation of a dispersion of a dye-providing substance:

A mixture of a yellow, a magenta or a blue-green dye-forming compound, an electron donor, a high boiling organic solvent and an electron transfer agent precursor having the formulation given below was dissolved in 50 ml Ethyl acetate with heating at about 60°C to form a uniform solution. The resulting solution was mixed with 100 g of a 10% aqueous solution of lime-treated gelatin, 50 ml of water and 0.6 g of sodium dodecylbenzenesulfonate with stirring, and the mixture was dispersed in a homogenizer at 10,000 rpm for 10 minutes to prepare a gelatin dispersion of the respective dye-providing compound. Dye-providing compound (1): Dye-providing compound (2): Dye-providing compound (3): Electron donor (1): High boiling solvent (2): Electron transfer agent precursors (3):

Preparation of a gelatin dispersion of the electron donor (4):

To 30 ml of ethyl acetate were added 23.6 g of the electron donor (4) shown below and 8.5 g of the high boiling point solvent (2) shown below to form a uniform solution. The resulting solution was mixed with 100 g of a 10% aqueous solution of lime-treated gelatin, 0.25 g of sodium hydrogen sulfite, 0.3 g of sodium dodecylbenzenesulfonate and 30 ml of water with stirring, and the mixture was dispersed in a homogenizer at 100,000 rpm for 10 minutes. Electron donor (4):

Preparation of a zinc hydroxide dispersion:

To 100 ml of a 4% aqueous gelatin solution were added 12.5 g of zinc hydroxide with an average particle size of 0.2 µm, 1 g of carboxymethyl cellulose as a dispersant and 0.1 g of sodium polyacrylate, and the mixture was ground in a mill using glass beads with a diameter of 0.75 mm as a grinding medium for 30 min. The glass beads were separated to obtain a dispersion of zinc hydroxide.

Preparation of an activated carbon dispersion:

To 100 ml of a 5% aqueous gelatin solution were added 2.5 g of activated carbon powder (guaranteed reagent manufactured by Wako Pure Chemical Industries, Ltd.), 1 g of Demol N (a dispersant manufactured by Kao Soap Co., Ltd.) and 0.25 g of polyethylene glycol nonylphenyl ether, and the mixture was ground in a mill using glass beads having an average particle size of 0.75 mm for 120 minutes. The glass beads were separated to obtain a dispersion of activated carbon having an average particle size of 0.5 µm.

Preparation of a dispersion of the electron transfer agent (8):

To a 5% aqueous gelatin solution were added 10 g of the electron transfer agent (8) shown below, 0.5 g of polyethylene glycol nonylphenyl ether as a dispersant and 0.5 g of the anionic surfactant (6) shown below, and the mixture was milled in a mill using glass beads having a diameter of 0.75 mm for 60 minutes. The glass beads were separated to obtain a dispersion of the electron transfer agent having an average particle size of 0.3 µm. Electron transfer agents (8): Anionic surfactant (6):

A heat-developable color light-sensitive material having the layer structure shown below was prepared using the silver halide emulsions and dispersions of various additives prepared above.

Layer structure: Sixth layer (protective layer):

Gelatin 900 mg/m²

Silicon dioxide (particle size: 4 µm) 40 mg/m²

Zinc hydroxide 600 mg/m²

surfactant (5) 130 mg/m²

surfactant (6) 26 mg/m²

water soluble polymer 8 mg/m²

Fifth layer (blue-sensitive layer):

Emulsion (I) 380 mg Ag/m²

yellow dye-producing compound (1) 400 mg/m²

Gelatin 600 mg/m²

Electron donor (1) 308 mg/m²

high boiling solvent (2) 200 mg/m²

Electron transfer agent precursor (3) 15 mg/m²

Zinc hydroxide 330 mg/m²

Antifoggant (6) 0.6 mg/m²

surfactant (7) 18 mg/m²

water soluble polymer 13 mg/m²

Fourth layer (intermediate layer):

Gelatin 700 mg/m²

Electron donor (4) 130 mg/m²

high boiling solvent (2) 48 mg/m²

surfactant (6) 15 mg/m²

surfactant (8) 61 mg/m²

surfactant (7) 2 mg/m²

Electron transfer agent (8) 27 mg/m²

Electron transfer agent (9) 36 mg/m²

water soluble polymer 19 mg/m²

Hardener (10) 37 mg/m²

Third layer (green sensitive layer):

Emulsion (II) 220 mg Ag/m²

substance providing a purple-red dye (2) 365 mg/m²

Gelatin 310 mg/m²

Electron donor (1) 158 mg/m²

high boiling solvent (2) 183 mg/m²

Electron transfer agent precursor (3) 15 mg/m²

Electron transfer agent (8) 27 mg/m²

surfactant (7) 13 mg/m²

water soluble polymer 11 mg/m²

Antifoggant (6) 0.8 mg/m²

Second layer (intermediate layer):

Gelatin 790 mg/m²

Zinc hydroxide 300 mg/m²

Electron donor (4) 130 mg/m²

high boiling solvent (2) 73 mg/m²

surfactant (7) 2 mg/m²

surfactant (8) 100 mg/m²

surfactant (6) 11 mg/m²

water soluble polymer 12 mg/m²

Activated carbon 25 mg/m²

First layer (red-sensitive layer):

Emulsion (III) 230 mg Ag/m²

blue-green dye-producing compound (3) 343 mg/m²

Gelatin 330 mg/m²

Electron donor (1) 163 mg/m²

high boiling solvent (2) 172 mg/m²

Electron transfer agent precursor (3) 17 mg/m²

Electron transfer agent (8) 28 mg/m²

surfactant (7) 10 mg/m²

water soluble polymer 5 mg/m²

Antifoggant (11) 0.7 mg/m²

Carrier:

96 µm thick polyethylene terephthalate film with carbon black on its back.

The compounds used in the preparation of the light-sensitive material are shown below. Surfactant (5): Surfactant (6): water-soluble polymer Anti-staining agents (6): Surfactant (7): Surfactant (8): Electron transfer agents (8): Electron transfer agents (9):

Hardener (10):

1,2-bis(vinylsulfonylacetamido)ethane Antifoggants (11):

Example 2

The dye fixing materials obtained in Example 1 were tested in the same manner as in Example 1 except that the photosensitive material of the reference example was replaced with the photosensitive material of Example 1 of JP-A-63-316848. As a result, substantially the same results as in Example 1 were obtained.

Claims (7)

1. A dye fixing material comprising a support and a dye fixing layer capable of receiving a diffusible dye formed by heat development in a heat-developable photosensitive material, the dye fixing material containing, on the side of the support on which the dye fixing layer is applied, an oil-soluble fluorescent brightener and at least one anionic surfactant, the total amount of the anionic surfactant in the layers on the side of the support on which the dye fixing layer is applied being in the range of 25 to 150 mg/m². 2. A dye fixing material according to claim 1, wherein the oil-soluble fluorescent brightener is in the form of a dispersion in a dispersion medium comprising a high-boiling organic solvent. 3. A dye fixing material according to claim 2, wherein the dispersion medium comprises two or more high boiling point organic solvents. 4. A dye fixing material according to claim 2, wherein the high boiling organic solvent comprises phthalic acid esters or chlorinated paraffins. 5. The dye fixing material according to claim 1, wherein the fluorescent brightener is present in the dye fixing material in an amount of 0.1 to 200 mg/m². 6. A dye fixing material according to claim 1, wherein the fluorescent brightener is selected from the group consisting of stilbene compounds, coumarin compounds, biphenyl compounds, benzoxazolyl compounds, naphthalimide compounds, pyrazoline compounds and carbostyril compounds. 7. A dye fixing material according to claim 1, wherein the anionic surfactant(s) is/are represented by at least one of the formulas (I) to (IX): wherein R¹ represents a fluorine-substituted or unsubstituted saturated or unsaturated hydrocarbon group having 3 to 20 carbon atoms; R represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms; n represents an integer of 1 to 20; M represents a monovalent alkali metal; wherein R¹, M and n have the same meaning as above; a represents 0, 1 or 2; and m represents an integer from 1 to 6; wherein R¹, M, m and a have the same meaning as above; where R¹ and M have the same meaning as above and the two groups R¹ can be the same or different; R¹ -O-SO₃M (V) wherein R¹ and M have the same meaning as above; wherein R¹ and M have the same meaning as above; wherein R², M and m have the same meaning as above; wherein R², M and m have the same meaning as above; R³ represents a saturated or unsaturated hydrocarbon group having 3 to 22 carbon atoms which may be partially or fully fluorinated; where R², R³ and m have the same meaning as above.