JP2008009461A - Image forming method using heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming method using a heat developable photosensitive material, giving an image that is free of density unevenness due to interference fringes and has superior image quality by laser exposure, in a mode in which the laser spectral number is single. <P>SOLUTION: The image forming method is for forming a visible image by heat development, while imagewise exposing the heat developable photosensitive material having photosensitive silver halide grains, an organic silver salt, a reducing agent and a binder on a support with laser light in a mode in which the laser spectral number is single, wherein the photosensitive silver halide grains have an average grain diameter of 0.0001-0.2 μm and contain, at least two kinds of photosensitive silver halide grains which are different in sensitivity by 0.2-1.0 at a ratio that is effective for controlling the gamma values; and in the method the applied quantity of silver by the photosensitive silver halide is 0.01-1 g per 1 m<SP>2</SP>of the support, and the visible image having the gamma value of 2.0-3.7 is formed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming method using a photothermographic material for laser beam exposure, and there is no density unevenness due to interference fringes even when exposed to a laser beam having a mode with a single laser beam spectrum. It is an object of the present invention to provide an image forming method using a photothermographic material excellent in laser light exposure.

  In recent years, in the medical field, reduction of waste processing liquid has been strongly desired from the viewpoint of environmental protection and space saving. Therefore, a developer for medical diagnosis and photographic technology that can be efficiently exposed by a laser image setter or a laser imager, and can form a clear black image having high resolution and sharpness. There is a need for techniques relating to photosensitive materials that do not require processing. These photosensitive material systems that do not require processing such as a developing solution can eliminate the use of solution processing chemicals and supply a simpler processing system that does not damage the environment to customers.

  Although there is a similar requirement in the field of general image forming materials, medical images are required to have high image quality with excellent sharpness and graininess because they are required to be finely drawn, and are cooled from the viewpoint of ease of diagnosis. There is a feature that a black tone image is preferred. At present, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed as general image forming systems. However, there is no satisfactory output system for medical images.

  On the other hand, thermal image forming systems using organic silver salts are known (for example, see Non-Patent Document 1, Patent Documents 1 and 2). In particular, the photothermographic material generally contains a catalytically active amount of a photocatalyst (eg, silver halide), a reducing agent, a reducible silver salt (eg, an organic silver salt), and a color tone that controls the color tone of silver if necessary. And a photosensitive layer dispersed in a binder matrix. The photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, and is blackened by an oxidation-reduction reaction between silver halide or a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form a silver image. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure. Therefore, a black silver image is formed in the exposure region (see, for example, Patent Documents 3 and 4). Various studies have been made on thermal image forming systems using these organic silver salts in order to achieve image quality and color tone that are satisfactory as medical images.

When an image is formed from an image forming material by laser exposure, there is a problem of so-called interference fringes caused by laser light exposure. As a method for improving the interference fringes in a photothermographic material exposed using laser light, a method of exposing by vertical multimode laser exposure has been disclosed (for example, see Patent Document 5). However, vertical multimode laser exposure has problems such as difficulty in control and reduced output, and means for solving interference fringes without using vertical multimode laser exposure as much as possible has been demanded.
B. “Thermal Processed Silver Systems” (Imaging Processes and Materials), 8th edition, Sturge, V., by Shely, “Thermally Processed Silver Systems”. (Walworth), edited by A. Shepp, page 2, 1996) U.S. Pat. No. 3,152,904 U.S. Pat. No. 3,457,075 US Patent No. 2910377 US Patent Publication No. 43-4924 U.S. Pat. No. 8,211,521

  An object of the present invention is an image forming method in which exposure is performed with laser light in a mode having a single laser light spectrum and heat development, and there is no density unevenness due to interference fringes, and heat development capable of obtaining an image with excellent image quality An object of the present invention is to provide an image forming method using a photosensitive material.

The above-described problems of the present invention have been solved by the following means. That is, the present invention is as follows.
<1> A photothermographic material having photosensitive silver halide grains, an organic silver salt, a reducing agent and a binder on a support is imagewise exposed with a laser beam having a single laser beam spectrum number, An image forming method for forming a visible image by development, wherein the photosensitive silver halide grains have an average particle diameter of 0.0001 μm to 0.2 μm, and a sensitivity expressed by a LogE value of a characteristic curve is 0.2 or more and 1 And containing at least two kinds of photosensitive silver halide grains different from each other in an amount effective for controlling the gamma value, and the coated silver amount of the photosensitive silver halide is 0.01 g to 1 g per 1 m ^{2 of the} support. And an image forming method for forming the visible image having a gamma value represented by a slope of a tangent at a minimum density (Dmin) +1.0 of the characteristic curve of 2.0 to 3.7.
<2> The image forming method according to <1>, wherein the laser beam is a red to infrared laser having a maximum wavelength of 600 nm to 900 nm.
<3> The image forming method according to <1> or <2>, wherein the laser beam is a semiconductor laser.
<4> The image forming method according to any one of <1> to <3>, wherein a coated silver amount of the photosensitive silver halide is 0.01 g to 0.4 g per 1 m ^{2 of the} support.
<5> The image forming method according to <4>, wherein the coated silver amount of the photosensitive silver halide is 0.01 g to 0.2 g per 1 m ^{2 of the} support.
<6> The image forming method according to any one of <1> to <5>, wherein the layer containing the photosensitive silver halide grains contains an irradiation dye or pigment.
<7> An antihalation layer is provided on the surface opposite to the surface of the photosensitive layer containing the photosensitive silver halide grains relative to the support, or between the photosensitive layer and the support < The image forming method according to any one of 1> to <6>.
<8> The image forming method according to any one of <1> to <7>, wherein the photosensitive silver halide grains or the layer containing the photosensitive silver halide grains contains water-soluble iridium.

  According to the present invention, generation of interference fringes can be suppressed even when exposure is performed with a longitudinal single mode laser beam.

  The present invention is described in detail below. In the present invention, a longitudinal single mode laser beam is an example of a laser beam having a single laser beam spectrum number.

  Such vertical single-mode laser light is superior in operability compared to vertical multi-mode lasers and does not have a decrease in output. However, the photothermographic material as in the present invention has a low haze during exposure, and therefore interference fringes. Tend to occur.

  As the laser light, a gas laser (Ar +, He—Ne), a YAG laser, a dye laser, a semiconductor laser, or the like is preferable. A semiconductor laser and a second harmonic generation element can also be used. A gas or semiconductor laser of red to infrared emission (maximum wavelength 600 nm to 900 nm) is preferable. Most preferred is a semiconductor laser.

  For exposing the photothermographic material used in the present invention, SPIE vol. 169 Laser Printing, pages 116-128 (1979), JP-A-4-51043, WO95 / 31754, etc., so that the laser beams are overlapped so that the scanning lines cannot be seen. preferable.

  In the present invention, a technique of making laser light incident on the photosensitive material obliquely as disclosed in JP-A-5-113548 and the like can also be applied.

The laser output is preferably 1 mW or more, more preferably 10 mW or more, and even more preferably 40 mW or more. There is no particular limitation on the upper limit, but it is usually about 5 W due to device restrictions. At that time, a plurality of lasers may be combined. The diameter of the laser light can be about 30 μm to 200 μm with a 1 / e ² spot size of a Gaussian beam.

  In the present invention, the gamma value refers to the slope of a tangent at a density Dmin + 1.0 in a photographic characteristic curve based on the density / logE (E is an exposure amount) of a visualized image. Since the photothermographic material used in the present invention is preferably used for medical diagnosis, the gamma value of the visible image is 2.0 to 3.7. If the gamma value is less than 2.0, it is difficult to diagnose. On the other hand, the upper limit of the gamma value is not particularly limited. However, in the exposure with the single mode laser light as described above, if the gamma value exceeds 3.7, the generation of interference fringes can no longer be prevented. It is intended as a range. More preferably, it is 2.0-3.4.

  In the present invention, the size of the photosensitive silver halide grains is 0.0001 μm to 0.2 μm, more preferably 0.0001 μm to 0.1 μm, and still more preferably 0.001 μm to 0.1 μm in terms of average particle diameter. The average particle diameter here means the volume of the silver halide grains in the case where the silver halide grains are so-called normal crystals such as cubes and octahedrons, other than normal crystals, for example, spherical particles, rod-like grains, etc. The diameter when considering a sphere equivalent to the so-called sphere equivalent diameter. In the case where the silver halide grains are tabular grains, the diameter is the diameter when converted into a circular image having the same area as the projected area of the main surface.

The addition amount of the photosensitive silver halide, when expressed by the amount of coated silver per photosensitive material 1 m ^2, is preferably from ^{0.01g / m 2 ~1g / m 2} , 0.01g / m 2 ~0.4g further preferably / ^{m 2,} and most preferably ^{0.01g / m 2 ~0.2g / m 2} .

The reason why the photosensitive silver halide grain size and addition amount are set as described above is to improve the photographic performance, reduce haze (turbidity), and do not affect diagnosis. If it is less than 0.0001 μm, the sensitivity is remarkably lowered, and if it exceeds 0.2 μm, haze (turbidity) becomes a problem. On the other hand, when the coated silver amount is less than 0.01 g / m ² , the function as a light-sensitive material is deteriorated and sufficient photographic performance cannot be obtained, and when it exceeds 1 g / m ² , haze (turbidity) becomes a problem.

  The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide can be used. The distribution of the halogen composition in the grains may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Further, silver halide grains having a core / shell structure can be preferably used. A preferable structure is a 2- to 5-fold structure, and more preferably 2- to 4-fold core / shell particles can be used. A technique of localizing silver bromide on the surface of silver chloride or silver chlorobromide grains can also be preferably used.

  Methods for forming photosensitive silver halide are well known in the art, for example using the methods described in Research Disclosure No. 17029 of June 1978 and US Pat. No. 3,700,458. Specifically, a method in which a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound to gelatin or another polymer solution and then mixed with an organic silver salt is used.

  Examples of the shape of the silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-shaped grains, and potato grains. In the present invention, cubic grains and tabular grains are particularly preferred. A preferable value as an average aspect ratio in the case of using tabular silver halide grains is 100: 1 to 2: 1, more preferably 50: 1 to 3: 1. Further, grains having rounded corners of silver halide grains can be preferably used. The surface index (Miller index) of the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the [100] plane having high spectral sensitization efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The ratio is preferably 50% or more, more preferably 65% or more, and still more preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of a sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

  As the water-soluble iridium compound used in the present invention, various compounds can be used. For example, iridium (III) halide compounds, iridium (IV) halide compounds, iridium complex salts as ligands, halogens, amines, oxalato Such as hexachloroiridium (III) or (IV) complex salt, hexaammineiridium (III) or (IV) complex salt, trioxalatoiridium (III) or (IV) complex salt, hexacyanoiridium, pentachloronitrosyliridium, etc. Is mentioned. In the present invention, among these compounds, a valence of III and a valence of IV can be used in any combination. These iridium compounds are used by dissolving in water or an appropriate solvent, and are generally used in order to stabilize a solution of the iridium compound, that is, an aqueous hydrogen halide solution (for example, hydrochloric acid, odorous acid, hydrofluoric acid). Or a method of adding an alkali halide (for example, KCl, NaCl, KBr, NaBr, etc.) can be used. Instead of using water-soluble iridium, it is also possible to add another silver halide grain previously doped with iridium and dissolve it at the time of silver halide preparation.

  In the present invention, the addition of the water-soluble iridium compound can be appropriately carried out at the time of production of the silver halide emulsion grains and at each stage before coating the emulsion, but it is particularly added at the time of forming the emulsion and incorporated into the silver halide grains. It is preferable that

The addition amount of these water-soluble iridium compounds is preferably in the range of 1 × 10 ⁻⁸ mol to 1 × 10 ⁻³ mol per mol of silver halide, more preferably in the range of 1 × 10 ⁻⁸ mol to 5 × 10 ⁻⁵ mol. The range of 5 × 10 ⁻⁸ mol to 5 × 10 ⁻⁶ mol is particularly preferable.

In addition to iridium, the photosensitive silver halide grains of the present invention may contain other group VII or group VIII (groups 7 to 10) metals or metal complexes. Preferred examples of such a central metal include rhodium, rhenium, ruthenium and osmium. One kind of these metal complexes may be used, or two or more kinds of complexes of the same metal and different metals may be used in combination. The preferable content is in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol, and more preferably in the range of 1 × 10 ⁻⁸ mol to 1 × 10 ⁻⁴ mol with ^respect to 1 mol of silver. As a specific metal complex structure, a metal complex having a structure described in JP-A-7-225449 can be used.

  As the rhodium compound used in the present invention, a water-soluble rhodium compound can be used. For example, a rhodium (III) halide compound or a rhodium complex salt having halogen, amines, oxalato, etc. as a ligand, for example, hexachlororhodium (III) complex salt, pentachloroacorodium (III) complex salt, tetrachlorodia Examples thereof include a corodium (III) complex salt, a hexabromorhodium (III) complex salt, a hexaammine rhodium (III) complex salt, and a trizaratrodium (III) complex salt. These rhodium compounds are used by dissolving in water or an appropriate solvent, and are generally used in order to stabilize the rhodium compound solution, that is, an aqueous hydrogen halide solution (for example, hydrochloric acid, odorous acid, hydrofluoric acid). Or a method of adding an alkali halide (for example, KCl, NaCl, KBr, NaBr, etc.) can be used. Instead of using water-soluble rhodium, it is also possible to add another silver halide grain previously doped with rhodium and dissolve it at the time of silver halide preparation.

The addition amount of these rhodium compounds is preferably in the range of 1 × 10 ⁻⁸ mol to 5 × 10 ⁻⁶ mol per mol of silver halide, particularly preferably 5 × 10 ⁻⁸ mol to 1 × 10 ⁻⁶ mol. .

  The addition of these compounds can be appropriately carried out at the time of production of the silver halide emulsion grains and at each stage before coating the emulsion, but it is particularly preferred that they are added during the formation of the emulsion and incorporated into the silver halide grains. .

Rhenium, ruthenium and osmium used in the present invention are added in the form of water-soluble complex salts described in JP-A-63-2042, JP-A-1-2855941, JP-A-2-20852, JP-A-2-20855 and the like. The Particularly preferred is a hexacoordination complex represented by the following formula. [ML ₆ ] ^n— where M represents Ru, Re or Os, L represents a ligand, and n represents 0, 1, 2, 3 or 4.

  In this case, the counter ion has no significance and ammonium or alkali metal ions are used.

  Preferable ligands include a halide ligand, a cyanide ligand, a cyan oxide ligand, a nitrosyl ligand, a thionitrosyl ligand, and the like. Although the example of the specific complex used for this invention below is shown, this invention is not limited to this.

[ReCl ₆ ] ³⁻ , [ReBr ₆ ] ³⁻ , [ReCl ₅ (NO)] ²⁻ , [Re (NS) Br ₅ ] ²⁻ , [Re (NO) (CN) ₅ ] ²⁻ , [Re (O) ₂ (CN) ₄ ] ³⁻ , [RuCl ₆ ] ³⁻ , [RuCl ₄ (H ₂ O) ₂ ] ⁻ , [RuCl ₅ (H ₂ O)] ²⁻ , [RuCl ₅ (NO)] ^{_{2-, [RuBr 5 (NS)}} ] 2-, [Ru (CO) 3 Cl 3] 2-, [Ru (CO) Cl 5] 2-, [Ru (CO) Br 5] 2-, [OsCl 6 ^{_{] 3-, [OsCl 5 (NO}} )] 2-, [Os (NO) (CN) 5] 2-, [Os (NS) Br 5] 2-, and _{[Os (O) 2 (CN} ) 4] ^4-

The addition amount of these compounds is preferably in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻⁵ mol, and more preferably 1 × 10 ⁻⁸ mol to 1 × 10 ⁻⁶ mol, per mol of silver halide.

  The addition of these compounds can be appropriately carried out at the time of production of the silver halide emulsion grains and at each stage before coating the emulsion, but it is particularly preferred that they are added during the formation of the emulsion and incorporated into the silver halide grains. .

  In order to add these compounds during silver halide grain formation and incorporate them into silver halide grains, a metal complex powder or an aqueous solution dissolved together with NaCl and KCl is used as a water-soluble salt or water-soluble solution during grain formation. A method of adding silver halide solution to a silver halide solution, or a method of preparing silver halide grains by a method of three-liquid simultaneous mixing when silver salt and halide solution are mixed at the same time, or grain formation There is a method in which a required amount of an aqueous solution of a metal complex is put into a reaction vessel. In particular, a method of adding a powder or an aqueous solution dissolved together with NaCl and KCl to the water-soluble halide solution is preferable.

  In order to add to the particle surface, a necessary amount of an aqueous solution of a metal complex can be added to the reaction vessel immediately after the formation of the particle, during or after the physical ripening, or at the chemical ripening.

  Furthermore, the silver halide grains used in the present invention may contain metal atoms such as cobalt, iron, nickel, chromium, palladium, platinum, gold, thallium, copper and lead. For cobalt, iron, chromium and ruthenium compounds, hexacyano metal complexes can be preferably used. Specific examples include, but are not limited to, ferricyanate ions, ferrocyanate ions, hexacyanocobaltate ions, hexacyanochromate ions, and hexacyanoruthenate ions. The metal complex in the silver halide may be contained uniformly, may be contained in the core part at a high concentration, or may be contained in the shell part at a high concentration, and there is no particular limitation.

The metal is preferably 1 × 10 ⁻⁹ to 1 × 10 ⁻⁴ mol per mol of silver halide. In order to contain the above metal, it can be added in the form of a metal salt in the form of a single salt, a double salt or a complex salt at the time of preparing the particles.

  The photosensitive silver halide grains can be desalted by washing with water known in the art, such as a noodle method or a flocculation method, but in the present invention, it may or may not be desalted.

  The silver halide emulsion of the present invention is preferably subjected to chemical sensitization. As chemical sensitization, known methods such as sulfur sensitization, gold sensitization, selenium sensitization, tellurium sensitization, and noble metal sensitization can be used.

The sulfur sensitization preferably used in the present invention is usually performed by adding a sulfur sensitizer and stirring the emulsion at a high temperature of 40 ° C. or higher for a predetermined time. Known compounds can be used as the sulfur sensitizer, for example, various sulfur compounds such as thiosulfate, thioureas, thiazoles, rhodanines, etc. in addition to sulfur compounds contained in gelatin. be able to. Preferred sulfur compounds are thiosulfate and thiourea compounds. The addition amount of the sulfur sensitizer, pH during the chemical ripening, the temperature will vary with various conditions such as the size of the silver halide grains, silver halide per mole ¹ × 10 -7 ~1 × 10 ^{- 2} mol, more preferably 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol.

  A known selenium compound can be used as the selenium sensitizer used in the present invention. That is, it is usually carried out by adding unstable and / or non-labile selenium compounds and stirring the emulsion at a high temperature of 40 ° C. or higher for a predetermined time. As the unstable selenium compound, compounds described in JP-B Nos. 44-15748, 43-13489, JP-A-4-25832, JP-A-4-109240, JP-A-4-324855 and the like can be used. In particular, it is preferable to use compounds represented by general formulas (VIII) and (IX) in JP-A-4-324855.

  The tellurium sensitizer used in the present invention is a compound that forms silver telluride presumed to be a sensitization nucleus on the surface or inside of a silver halide grain. The silver telluride formation rate in the silver halide emulsion can be tested by the method described in JP-A-5-313284. Examples of tellurium sensitizers include diacyl tellurides, bis (oxycarbonyl) tellurides, bis (carbamoyl) tellurides, diacyl tellurides, bis (oxycarbonyl) ditellurides, bis (carbamoyl) ditellurides, P = Te. Compounds having a bond, tellurocarboxylates, Te-organyltellurocarboxylic acid esters, di (poly) tellurides, tellurides, tellurols, telluroacetals, tellurosulfonates, compounds having a P-Te bond, Te heterocycles, tellurocarbonyl compounds, inorganic tellurium compounds, colloidal tellurium and the like can be used. Specifically, U.S. Patent Nos. 1,623,499, 3,320,069, 3,772,031, British Patent Nos. 235,211, 1,121,496, 1,295,462, 1,396,696, Canadian Patent 800,958, JP-A-4-204640, Patents 2654722, 2699029, 2811257, Journal of Chemical Society Chemical Communication (J. Chem. Soc. Chem. Commun.), P. 635 (1980), ibid, 1102 (1979), ibid, p. 645 (1979), Journal of Chemical Society Parkin Transaction 1 (J. Chem. Soc. Perkin. Trans. 1), p. 2191 (1980), S.A. Edited by S. Patai, The Chemistry of Organic Selenium and Tellurium Compounds, Vol., The Chemistry of Organic Serenium and Tellunium Compounds. 1 (1986), Vol. 2 (1987) can be used. Particularly preferred are compounds represented by the general formulas (II), (III) and (IV) in JP-A-5-313284.

The amount of selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but generally 1 × 10 ⁻⁸ to 1 × 10 ⁻² mol per mol of silver halide. Preferably, about 1 × 10 ⁻⁷ to 1 × 10 ⁻³ mol is used. The conditions for chemical sensitization in the present invention are not particularly limited, but the pH is 5 to 8, the pAg is 6 to 11, preferably 7 to 10, and the temperature is 40 ° C to 95 ° C, preferably 45. ~ 85 ° C.

  As a gold sensitizer used for gold sensitization of the silver halide emulsion of the present invention, the oxidation number of gold may be +1 or +3, and a gold compound usually used as a gold sensitizer is used. Can do. Typical examples include chloroauric acid, potassium chloroaurate, auric trichloride, potassium auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, pyridyltrichlorogold, and the like.

The amount of the gold sensitizer added varies depending on various conditions, but as a guide, it is 1 × 10 ⁻⁷ mol or more and 1 × 10 ⁻³ mol or less, more preferably 1 × 10 ⁻⁶ mol or more and 5 or more per mol of silver halide. × 10 ⁻⁴ mol or less.

  The silver halide emulsion of the present invention can be used in combination with gold sensitization and other chemical sensitization. When used in combination with gold sensitization, for example, sulfur sensitization and gold sensitization, Selenium sensitizing method and gold sensitizing method, sulfur sensitizing method and selenium sensitizing method and gold sensitizing method, sulfur sensitizing method and tellurium sensitizing method and gold sensitizing method, sulfur sensitizing method and selenium sensitizing method Tellurium sensitization and gold sensitization are preferred.

  In the silver halide emulsion used in the present invention, a cadmium salt, a sulfite salt, a lead salt, a thallium salt or the like may coexist in the process of silver halide grain formation or physical ripening.

  In the present invention, reduction sensitization can be used. As specific compounds of the reduction sensitization method, for example, stannous chloride, aminoiminomethanesulfinic acid, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds, etc. can be used in addition to ascorbic acid and thiourea dioxide. . Further, reduction sensitization can be performed by ripening the emulsion while maintaining the pH at 7 or higher or the pAg at 8.3 or lower. Further, reduction sensitization can be performed by introducing a single addition portion of silver ions during grain formation.

  A thiosulfonic acid compound may be added to the silver halide emulsion of the present invention by the method shown in European Patent Publication 293,917.

  Two or more types of silver halide emulsions in the light-sensitive material used in the present invention (for example, those having different average grain sizes, different halogen compositions, different crystal habits, and different chemical sensitization conditions) are used in combination. Used.

  In the present invention, a plurality of photosensitive silver halide emulsions are used to control gamma. Preferably, multiple types of photosensitive silver halide emulsions can be obtained by controlling the grain size, shape, halogen composition, sensitizing dye adsorption amount, and amount of chemical sensitizer so that each has a different sensitivity. Become. As emulsion types to be used, it is preferable to use 2 to 4 types, preferably 2 to 3 types, as mixed or separate layers. The sensitivity difference between the at least two types of photosensitive silver halide has a difference of 0.2 logE or more and 1.0 logE or less, and preferably has a difference of at least 0.3 logE. Examples of these technologies include JP-A-57-119341, 53-106125, 47-3929, 48-55730, 46-5187, 50-73627, and 57-150841. It is done. At least two light sensitive silver halides are mixed in a ratio effective to control gamma. The mixing ratio varies depending on the sensitivity of each silver halide and the difference between them, but examples thereof include 20:80, 30:70, 30:40, and 50:50 by mass ratio.

  The organic silver salt that can be used in the present invention is relatively stable to light, but is 80 ° C. or higher in the presence of an exposed photocatalyst (such as a latent image of photosensitive silver halide) and a reducing agent. It is a silver salt that forms a silver image when heated above. The organic silver salt may be any organic material containing a source capable of reducing silver ions. Such a non-photosensitive organic silver salt is described in paragraph Nos. 0048 to 0049 of JP-A-10-62899, page 18, line 24 to page 19, line 37 of European Patent Publication No. 0803763A1. Yes. Silver salts of organic acids, particularly silver salts of long-chain fatty carboxylic acids (particularly fatty acids) (having 10 to 30, preferably 15 to 28 carbon atoms) are preferred. The organic silver salt can preferably constitute about 5 to 70% by weight of the image forming layer. Preferred organic silver salts include silver salts of organic compounds having a carboxyl group. Examples of these include, but are not limited to, silver salts of aliphatic carboxylic acids and silver salts of aromatic carboxylic acids. Preferred examples of the aliphatic carboxylic acid silver salt include silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver maleate and fumarate. Silver acid, silver tartrate, silver linoleate, silver butyrate and silver camphorate, mixtures thereof, and the like.

Although there is no restriction | limiting in particular as a shape of the organic silver salt which can be used for this invention, In the present invention, scaly organic silver salt is preferable. In the present invention, the scaly organic silver salt is defined as follows. The organic acid silver salt was observed with an electron microscope, the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped were designated a, b, and c from the shortest side (c was the same as b). Then, the shorter numerical values a and b are calculated, and x is obtained as follows.
x = b / a

  In this way, x is obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of x (average) ≧ 1.5 are defined as flakes. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 20 ≧ x (average) ≧ 2.0. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

  In the flake shaped particle, a can be regarded as a thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 μm or more and 0.23 μm, more preferably 0.1 μm or more and 0.20 μm or less. The average of c / b is preferably 1 or more and 6 or less, more preferably 1.05 or more and 4 or less, further preferably 1.1 or more and 3 or less, and particularly preferably 1.1 or more and 2 or less.

  The particle size distribution of the organic silver salt is preferably monodispersed. Monodispersion is preferably 100% or less, more preferably 80% or less, and even more preferably 50% of the value obtained by dividing the standard deviation of the lengths of the short and long axes by the short and long axes. It is as follows. The method for measuring the shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion. As another method for measuring monodispersity, there is a method for obtaining the standard deviation of the volume weighted average diameter of the organic silver salt, and the percentage (variation coefficient) of the value divided by the volume weighted average diameter is preferably 100% or less, more Preferably it is 80% or less, More preferably, it is 50% or less. As a measuring method, for example, it is obtained from the particle size (volume weighted average diameter) obtained by irradiating an organic silver salt dispersed in a liquid with laser light and obtaining an autocorrelation function with respect to the temporal change of the fluctuation of the scattered light. Can do.

  The organic acid silver used in the present invention is prepared by reacting silver nitrate with a solution or suspension of an alkali metal salt (including Na salt, K salt, Li salt, etc.) of the organic acid shown above. The organic acid alkali metal salt of the present invention is obtained by subjecting the organic acid to an alkali treatment. The organic acid silver of the present invention can be run batchwise or continuously in any suitable container. Stirring in the reaction vessel can be performed by any stirring method depending on the required properties of the particles. The organic acid silver can be prepared by adding a silver nitrate aqueous solution gradually or rapidly to a reaction vessel containing an organic acid alkali metal salt solution or suspension, or an organic acid prepared in advance in a reaction vessel containing a silver nitrate aqueous solution. Any of the method of adding an alkali metal salt solution or suspension gradually or rapidly, and the method of simultaneously adding an aqueous silver nitrate solution and an organic acid alkali metal salt solution or suspension to a reaction vessel are preferably used. Can do.

  The silver nitrate aqueous solution and the organic acid alkali metal salt solution or suspension can be used at any concentration for controlling the particle size of the organic acid silver to be prepared, and can be added at any addition rate. As a method for adding the silver nitrate aqueous solution and the organic acid alkali metal salt solution or suspension, it can be added by a method of adding at a constant addition rate, an accelerated addition method or a slow addition method by an arbitrary time function. Moreover, you may add to a liquid level with respect to a reaction liquid, and may add in a liquid. In the case of a method in which a silver nitrate aqueous solution and an organic acid alkali metal salt solution or suspension prepared in advance are simultaneously added to the reaction vessel, either the silver nitrate aqueous solution or the organic acid alkali metal salt solution or suspension is preceded. Although it can be added, it is preferable to add the silver nitrate aqueous solution in advance. The leading degree is preferably 0 to 50% by volume, particularly preferably 0 to 25% by volume of the total amount added. Further, as described in JP-A-9-127643, etc., a method of adding while controlling the pH or silver potential of the reaction solution during the reaction can be preferably used.

  The pH of the aqueous silver nitrate solution or organic acid alkali metal salt solution or suspension added can be adjusted according to the required properties of the particles. Arbitrary acids and alkalis can be added for pH adjustment. Depending on the required properties of the grains, for example, the temperature in the reaction vessel can be arbitrarily set to control the grain size of the organic acid silver to be adjusted. Alternatively, the suspension can be adjusted to an arbitrary temperature. The organic acid alkali metal salt solution or suspension is preferably heated and kept at 50 ° C. or higher in order to ensure fluidity of the liquid.

  The organic acid silver used in the present invention is preferably prepared in the presence of a tertiary alcohol. The tertiary alcohol used in the present invention preferably has a total carbon number of 15 or less, particularly preferably 10 or less. Examples of preferred tertiary alcohols include tert-butanol, but the present invention is not limited thereto.

The tertiary alcohol used in the present invention may be added at any time during the preparation of the organic acid silver, but it may be added during the preparation of the organic acid alkali metal salt to dissolve and use the organic acid alkali metal salt. preferable. Further, the amount of the tertiary alcohol of the present invention can be arbitrarily used within a range of 0.01 to 10 by mass ratio with respect to H ₂ O as a solvent at the time of preparing the organic acid silver. A range of 03 to 1 is preferred.

  In the present invention, a preferred scaly organic acid silver salt is prepared by reacting an aqueous solution containing a water-soluble silver salt with an aqueous tertiary alcohol solution containing an organic acid alkali metal salt in a reaction vessel (the organic solution is added to the solution in the reaction vessel). A step of adding a tertiary alcohol aqueous solution containing an acid-alkali metal salt.) (Preferably an aqueous solution containing a water-soluble silver salt previously introduced, or a water-soluble silver salt) When an aqueous solution containing a tertiary alcohol aqueous solution containing an organic acid alkali metal salt is added at the same time from the beginning without being preceded, water or a mixed solvent of water and a tertiary alcohol, as described later, is water-soluble. Even when an aqueous solution containing a silver salt is added in advance, water or a mixed solvent of water and a tertiary alcohol may be added in advance.) And a tertiary containing an organic acid alkali metal salt to be added The temperature difference between the alcohol aqueous solution are preferably prepared in a way that the 20 ° C. or higher 85 ° C. or less.

  By maintaining such a temperature difference during the addition of the tertiary alcohol aqueous solution containing the organic acid alkali metal salt, the crystal form or the like of the organic acid silver salt is preferably controlled.

  The water-soluble silver salt is preferably silver nitrate, and the water-soluble silver salt concentration in the aqueous solution is preferably 0.03 mol / l or more and 6.5 mol / l or less, more preferably 0.1 mol / l or more and 5 mol / l or less. The pH of this aqueous solution is preferably 2 or more and 6 or less, more preferably pH 3.5 or more and 6 or less.

  Further, a tertiary alcohol having 4 to 6 carbon atoms may be contained. In that case, the volume is 70% or less, preferably 50% or less, with respect to the total volume of the aqueous solution of the water-soluble silver salt. . The temperature of the aqueous solution is preferably 0 ° C. or higher and 50 ° C. or lower, more preferably 5 ° C. or higher and 30 ° C. or lower. As described later, an aqueous solution containing a water-soluble silver salt and a tertiary alcohol of an organic acid alkali metal salt When adding aqueous solution simultaneously, 5 to 15 degreeC is the most preferable.

  The alkali metal of the organic acid alkali metal salt is specifically Na or K. The organic acid alkali metal salt is prepared by adding NaOH or KOH to the organic acid. At this time, it is preferable that the amount of alkali is equal to or less than the amount of organic acid to leave unreacted organic acid. In this case, the amount of residual organic acid is 3 mol% or more and 50 mol% or less, preferably 3 mol% or more and 30 mol% or less with respect to 1 mol of all organic acids. Moreover, after adding an alkali more than desired amount, you may prepare by adding acids, such as nitric acid and a sulfuric acid, and neutralizing an excess alkali content.

  Further, the pH can be adjusted according to the required properties of the organic acid silver salt. For adjusting the pH, any acid or alkali can be used.

  Further, the aqueous solution containing a water-soluble silver salt used in the present invention, the tertiary alcohol aqueous solution of an organic acid alkali metal salt, or the liquid in a reaction vessel is represented by, for example, the general formula (1) of JP-A-62-65035. A water-soluble group-containing N heterocyclic compound as described in JP-A No. 62-150240, an inorganic peroxide as described in JP-A No. 50-101019, A sulfur compound as described in 78319, a disulfide compound as described in JP-A-57-643, hydrogen peroxide, and the like can be added.

  The tertiary alcohol aqueous solution of the organic acid alkali metal salt of the present invention is preferably a mixed solvent of a tertiary alcohol having 4 to 6 carbon atoms and water in order to obtain liquid uniformity. If the carbon number exceeds this, there is no compatibility with water, which is not preferable. Among tertiary alcohols having 4 to 6 carbon atoms, tert-butanol, which is most compatible with water, is most preferable. Alcohols other than tertiary alcohols are not preferred as described above because they have reducibility and cause harmful effects when forming organic acid silver salts. The amount of the tertiary alcohol used in the tertiary alcohol aqueous solution of the organic acid alkali metal salt is 3% or more and 70% or less as a solvent volume with respect to the volume of water in the tertiary alcohol aqueous solution, preferably 5% or more and 50% or less.

  The concentration of the organic acid alkali metal salt in the tertiary alcohol aqueous solution of the organic acid alkali metal salt used in the present invention is 7% by mass to 50% by mass, preferably 7% by mass to 45% by mass. Or less, and more preferably 10 mass% or more and 40 mass% or less.

  The temperature of the tertiary alcohol aqueous solution of the organic acid alkali metal salt added to the reaction vessel of the present invention is 50 ° C. for the purpose of keeping the temperature necessary for avoiding the crystallization and solidification of the organic acid alkali metal salt. The temperature is preferably 90 ° C. or lower, more preferably 60 ° C. or higher and 85 ° C. or lower, and most preferably 65 ° C. or higher and 85 ° C. or lower. Further, in order to control the temperature of the reaction to be constant, it is preferably controlled to be constant at a certain temperature selected from the above range.

  The organic acid silver salt of the present invention is obtained by i) adding a single aqueous solution of a tertiary alcohol of an organic acid alkali metal salt to an aqueous solution in which an aqueous solution containing a water-soluble silver salt is present in the reaction vessel first, or ii ) A water-soluble silver salt aqueous solution and an organic acid alkali metal salt tertiary alcohol aqueous solution are produced by a method (simultaneous addition method) in which there is a time when they are simultaneously added to the reaction vessel. In the present invention, the latter method in which the average grain size of the organic acid silver salt is controlled and the distribution is narrowed is preferred in view of narrowing the distribution. In that case, 30 vol% or more of the total addition amount is preferably added simultaneously, more preferably 50 vol% to 75 vol% is added simultaneously. When adding any of these in advance, it is preferable to precede the solution of the water-soluble silver salt.

  In either case, if the liquid in the reaction vessel (the aqueous solution of the water-soluble silver salt added previously as described above or the aqueous solution of the water-soluble silver salt is not added previously, as described later, The temperature of the solvent in the reaction vessel is preferably 5 ° C. or higher and 75 ° C. or lower, more preferably 5 ° C. or higher and 60 ° C. or lower, and most preferably 10 ° C. or higher and 50 ° C. or lower. The temperature is preferably controlled to a certain temperature selected from the above temperatures throughout the entire reaction process, but it is also preferable to control with several temperature patterns within the above temperature range.

  In the present invention, the temperature difference between the tertiary alcohol aqueous solution of the organic acid alkali metal salt and the liquid in the reaction vessel is preferably 20 ° C. or higher and 85 ° C. or lower, more preferably 30 ° C. or higher and 80 ° C. or lower. In this case, it is preferable that the temperature of the tertiary alcohol aqueous solution of the organic acid alkali metal salt is higher.

  As a result, the rate at which the aqueous tertiary alcohol solution of the high-temperature organic acid alkali metal salt is quenched in the reaction vessel and precipitated into a fine crystal and the rate at which the organic acid silver salt is chlorinated by the reaction with the water-soluble silver salt are preferably controlled. The crystal form, crystal size, and crystal size distribution of the organic acid silver salt can be preferably controlled. At the same time, the performance as a photothermographic material can be further improved.

  The reaction vessel may contain a solvent in advance, and water is preferably used as the solvent put in advance, but a mixed solvent with the tertiary alcohol is also preferably used.

  A dispersion aid that is soluble in an aqueous medium can be added to the aqueous solution of a tertiary alcohol of an alkali metal organic acid, an aqueous solution of a water-soluble silver salt, or a reaction solution of the present invention. Any dispersing aid may be used as long as it can disperse the formed organic acid silver salt. Specific examples conform to the description of the organic acid silver salt dispersion aid described below.

  In the method for preparing an organic acid silver salt of the present invention, it is preferable to perform a desalting / dehydrating step after the formation of the silver salt. The method is not particularly limited, and well-known and conventional means can be used. For example, known filtration methods such as centrifugal filtration, suction filtration, ultrafiltration, and flock-forming water washing by a coagulation method, and supernatant removal by centrifugal sedimentation are preferably used. Desalting / dehydration may be performed once or a plurality of times. Water may be added and removed continuously or separately. The desalting / dehydration is performed so that the conductivity of the finally dehydrated water is preferably 300 μS / cm or less, more preferably 100 μS / cm or less, and most preferably 60 μS / cm or less. The lower limit of conductivity in this case is not particularly limited, but is usually about 5 μS / cm.

  Furthermore, in order to improve the coated surface shape of the photothermographic material, an aqueous dispersion of an organic acid silver salt is obtained, converted into a high-speed flow at high pressure, and then redispersed by dropping the pressure to obtain a fine dispersion. An aqueous dispersion is preferred. The dispersion medium in this case is preferably only water, but may contain an organic solvent as long as it is 20% by mass or less.

  The method for finely dispersing the organic acid silver salt is known in the presence of a dispersing aid, such as known finer means (for example, a high speed mixer, a homogenizer, a high speed impact mill, a Banbury mixer, a homomixer, a kneader, a ball mill, a vibrating ball mill, a planetary planet. A ball mill, an attritor, a sand mill, a bead mill, a colloid mill, a jet mill, a roller mill, a tron mill, and a high-speed stone mill) can be used for mechanical dispersion.

  When a photosensitive silver salt is allowed to coexist at the time of dispersion, the fog rises and the sensitivity is remarkably lowered. Therefore, it is more preferable that the photosensitive silver salt is not substantially contained at the time of dispersion. In the present invention, the amount of the photosensitive silver salt in the aqueous dispersion to be dispersed is 0.1 mol% or less with respect to 1 mol of the organic acid silver salt in the liquid, and positive addition of the photosensitive silver salt is performed. There is nothing.

  In the present invention, in order to obtain a uniform organic silver salt solid dispersion having a high S / N, a small particle size, and no agglomeration, the organic silver salt particles as an image forming medium are not damaged or heated at high temperatures. It is preferable to apply a large force uniformly. For this purpose, a dispersion method is preferred in which an aqueous dispersion composed of an organic silver salt and an aqueous dispersant is converted into a high-speed flow and then the pressure is dropped.

  In the present invention, for example, “dispersion rheology and dispersion technology” (Toshio Kajiuchi, Hiroki Arai, 1991, Shinyamasha) Publishing Co., Ltd., p357 to p403), “Progress of Chemical Engineering, Vol. 24” (Chemical Engineering Society, Tokai Branch, 1990, Sakai Shoten, p184 to p185), JP 59-49832 A, US Pat. No. 4,533,254 However, the redispersion method in the present invention contains at least an organic acid silver salt, as described in JP-A-8-137004, JP-A-8-238848, JP-A-2-261525, and JP-A-1-94933. After the aqueous dispersion is pressurized with a high-pressure pump or the like and fed into the pipe, it is passed through a narrow slit provided in the pipe, and then a sudden pressure drop is caused in the dispersion. It is a method of performing fine Do not distributed.

As for the high-pressure homogenizer to which the present invention relates, in general, (a) “shearing force” generated when the dispersoid passes through a narrow gap (about 75 μm to 350 μm) at high pressure and high speed, and (b) in a narrow space where the pressure is increased. It is considered that the impact force generated when the liquid-liquid collision or the wall collision occurs is not changed, and the cavitation force due to the subsequent pressure drop is further increased, and uniform and efficient dispersion is performed. In the old days, this type of dispersing device includes a gorin homogenizer. In this device, the liquid to be dispersed sent at a high pressure is converted into a high-speed flow in a narrow gap on the cylindrical surface, and this force is applied to the surrounding wall surface. Colliding and emulsifying / dispersing by the impact force. Examples of the liquid-liquid collision include a Y-type chamber of a microfluidizer, a spherical chamber using a spherical check valve as described in JP-A-8-103642, which will be described later, and the like. Includes a Z-type chamber of a microfluidizer. Operating pressure is generally ^{100kg / cm 2 ~600kg / cm 2} , the flow rate is in the range of a few M～30m / sec, contrivance such as increasing the number collision with the fast flow portion in a saw blade shape in order to improve the dispersion efficiency The thing which gave is devised. Typical examples of such devices include Gorin homogenizers, microfluidizers manufactured by Microfluidics International Corporation, microfluidizers manufactured by Mizuho Industry Co., Ltd., and nanomizers manufactured by Special Machine Industries Co., Ltd. . Also described in JP-A-8-238848, JP-A-8-103642 and USP4533254.

In the organic acid silver salt of the present invention, it can be dispersed to a desired particle size by adjusting the flow rate, the differential pressure at the time of pressure drop and the number of treatments, but from the viewpoint of photographic characteristics and particle size, the flow rate is 200 m / sec ～600M / sec, preferably in the range differential pressure of 900kg ^/ cm ² ~3000kg ^/ cm 2 during the pressure drop, further flow rate 300 meters / sec ～600M / sec, the pressure difference at the pressure drop 1500 kg / ^cm 2 ~ More preferably, it is in the range of 3000 kg / cm ² . The number of distributed processes can be selected as necessary. Usually, a range of 1 to 10 times is selected, but about 1 to 3 times is selected from the viewpoint of productivity. Increasing the temperature of such an aqueous dispersion under high pressure is not preferable from the viewpoint of dispersibility and photographic properties, and at temperatures exceeding 90 ° C, the particle size tends to increase and the fog tends to increase. is there. Accordingly, the present invention includes a cooling device in the process before the conversion to the high pressure and high speed flow, the process after the pressure drop, or both of these processes, and the temperature of such water dispersion is 5 by the cooling process. It is preferable that the temperature is maintained in the range of from 0C to 90C, more preferably in the range of from 5C to 80C, and particularly preferably in the range of from 5C to 65C. In ^particular, at the time of 1500kg / cm ² ~3000kg / cm 2 in the range of high pressure dispersion, it is effective to install the cooling step. Depending on the required heat exchange amount, a cooling device using a static mixer in a double tube or triple tube, a multi-tube heat exchanger, a serpentine heat exchanger, or the like can be appropriately selected. In addition, in order to increase the efficiency of heat exchange, a suitable tube thickness, wall thickness, material, or the like may be selected in consideration of the operating pressure. The refrigerant used for the cooler is a refrigerant such as 20 ° C. well water, 5 ° C. to 10 ° C. cold water treated with a refrigerator, or −30 ° C. ethylene glycol / water, etc., if necessary. Can be used.

  When organic acid silver salt is made into solid fine particles using a dispersant, for example, polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, maleic acid monoester copolymer, acryloylmethylpropanesulfone Synthetic anionic polymers such as acid copolymers, semi-synthetic anionic polymers such as carboxymethyl starch and carboxymethyl cellulose, anionic polymers such as alginic acid and pectinic acid, and the like described in JP-A-52-92716, WO88 / 04794, etc. Anionic surfactants, compounds described in JP-A-9-179243, or known anionic, nonionic, cationic surfactants, other polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl Known polymers Le cellulose, or a polymer compound existing in nature such as gelatin can be suitably selected and used.

  Dispersing aid is generally mixed with organic acid silver salt powder or wet cake organic acid silver salt before dispersion, and sent to the disperser as a slurry. It is good also as an organic acid silver salt powder or a wet cake by giving the heat processing and the process by a solvent in the combined state. The pH may be controlled with an appropriate pH adjuster before, during or after dispersion.

  In addition to mechanical dispersion, it may be coarsely dispersed in a solvent by controlling the pH, and then finely divided by changing the pH in the presence of a dispersion aid. At this time, an organic acid solvent may be used as a solvent used for rough dispersion, and the organic solvent is usually removed after the formation of fine particles.

  The prepared dispersion is stored with stirring for the purpose of suppressing sedimentation of fine particles during storage, or stored in a highly viscous state (for example, in a jelly state using gelatin) by a hydrophilic colloid. You can also. In addition, a preservative can be added for the purpose of preventing the propagation of various bacteria during storage.

  The organic acid silver salt prepared by the method for preparing an organic acid silver salt of the present invention is dispersed in an aqueous solvent, mixed with a photosensitive silver salt aqueous solution, and supplied as a photosensitive image forming medium coating solution. It is preferable.

  Prior to the dispersion operation, the raw material liquid is roughly dispersed (preliminary dispersion). As a means for rough dispersion, known dispersion means (for example, high speed mixer, homogenizer, high speed impact mill, Banbury mixer, homomixer, kneader, ball mill, vibration ball mill, planetary ball mill, attritor, sand mill, bead mill, colloid mill, jet mill) , Roller mill, tron mill, high-speed stone mill). In addition to mechanical dispersion, it may be coarsely dispersed in a solvent by controlling the pH, and then finely divided by changing the pH in the presence of a dispersion aid. At this time, an organic solvent may be used as a solvent used for the coarse dispersion, and the organic solvent is usually removed after the formation of fine particles.

  The photosensitive silver salt aqueous solution is finely dispersed and then mixed to produce a photosensitive image forming medium coating solution. When a photothermographic material is produced using such a coating solution, a photothermographic material having a low haze and high sensitivity can be obtained with a low fog. On the other hand, when the photosensitive silver salt is coexisted when converted to a high pressure and high speed flow, the fog increases and the sensitivity is remarkably lowered. In addition, when an organic solvent is used as the dispersion medium instead of water, haze increases, fogging increases, and sensitivity tends to decrease. On the other hand, if the conversion method in which a part of the organic silver salt in the dispersion is converted into a photosensitive silver salt is used instead of the method of mixing the aqueous photosensitive silver salt solution, the sensitivity is lowered.

  In the above, the aqueous dispersion dispersed by converting to high pressure and high speed is substantially free of photosensitive silver salt, and its content is 0.1% with respect to the non-photosensitive organic silver salt. It is less than mol%, and no positive photosensitive silver salt is added.

  The particle size (volume weighted average diameter) of the organic silver salt solid fine particle dispersion of the present invention is such that, for example, a solid fine particle dispersion dispersed in a liquid is irradiated with laser light, and the autocorrelation function with respect to the time variation of the fluctuation of the scattered light. Can be determined from the particle size (volume weighted average diameter) obtained. A solid fine particle dispersion having an average particle size of 0.05 μm to 10.0 μm is preferable. More preferably, the average particle size is 0.1 μm or more and 5.0 μm or less, and still more preferably the average particle size is 0.1 μm or more and 2.0 μm or less.

  The organic silver salt solid fine particle dispersion used in the present invention comprises at least an organic silver salt and water. The ratio of the organic silver salt to water is not particularly limited, but the ratio of the organic silver salt to the whole is preferably 5% by mass to 50% by mass, particularly in the range of 10% by mass to 30% by mass. Is preferred. It is preferable to use the above-mentioned dispersion aid, but it is preferable to use the minimum amount in a range suitable for minimizing the particle size #, and 1 to 30% by weight, particularly 3% by weight based on the organic silver salt. The range of% -15 mass% is preferable.

  In the present invention, it is possible to produce a photosensitive material by mixing an organic silver salt aqueous dispersion and a photosensitive silver salt aqueous dispersion, but the mixing ratio of the organic silver salt and the photosensitive silver salt can be selected according to the purpose. The ratio of the photosensitive silver salt to the organic silver salt is preferably in the range of 1 mol% to 30 mol%, more preferably 3 mol% to 20 mol%, and particularly preferably in the range of 5 mol% to 15 mol%. Mixing two or more organic silver salt aqueous dispersions and two or more photosensitive silver salt aqueous dispersions when mixing is a method preferably used for adjusting photographic characteristics.

The organic silver salt of the present invention can be used in a desired amount, preferably 0.1g ^{/ m 2} ~5g ^/ m 2 as silver amount, more preferably from ^{1g / m 2 ~3g / m 2} .

  The photothermographic material used in the present invention contains a reducing agent for organic silver salt. The reducing agent for the organic silver salt may be any substance, preferably an organic substance, that reduces silver ions to metallic silver. Conventional photographic developers such as phenidone, hydroquinone and catechol are useful, but hindered phenol reducing agents such as bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane, 2,2-bis (4-hydroxy-3-methylphenyl) propane, 4,4-ethylidene-bis (2-tert-butyl-6-methylphenol), 1,1-bis (2-hydroxy-3,5-dimethylphenyl)- 3,5,5-trimethylhexane, 2,2-bis (3,5-dimethyl-4-hydroxyphenyl) propane) are preferred. Such reducing agents are described in paragraph Nos. 0052 to 0053 of JP-A-10-62899 and page 7 line 34 to page 18 line 12 of European Patent Publication No. 0803764A1.

The addition amount of the reducing agent is preferably from ^{0.01g / m 2 ~5.0g / m 2} , more preferably from ^{0.1g / m 2 ~3.0g / m 2} , having an image forming layer 5 mol% to 50% (mol) is preferably contained with respect to 1 mol of silver on the surface, and more preferably 10 mol% to 40 mol%. The addition layer of the reducing agent may be any layer on the surface having the image forming layer. When it is added to a layer other than the image forming layer, it is preferably used in an amount of 10 mol% to 50 mol% with respect to 1 mol of silver. The reducing agent may be a so-called precursor that is derivatized so as to have an effective function only during development.

  The reducing agent of the present invention may be added by any method such as a solution, a powder, or a solid fine particle dispersion. The solid fine particle dispersion is performed by a known finer means (for example, ball mill, vibration ball mill, sand mill, colloid mill, jet mill, roller mill, etc.). A dispersion aid may be used when dispersing the solid fine particles.

  Regarding the mixing method and mixing conditions of the photosensitive silver halide and organic silver salt prepared separately, the silver halide grains and organic silver salt that were prepared separately were mixed with a high-speed stirrer, ball mill, sand mill, colloid mill, vibration mill, homogenizer, respectively. Etc., or a method of preparing an organic silver salt by mixing photosensitive silver halide that has been prepared at any timing during the preparation of the organic silver salt, etc., but the effect of the present invention is sufficient As long as it appears in, there is no particular limitation.

  The preferred addition time of the photosensitive silver halide of the present invention to the image-forming layer coating solution is from 180 minutes before coating to immediately before, preferably from 60 minutes to 10 seconds before. As long as the effects of the present invention are sufficiently exhibited, there is no particular limitation. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is a desired time, and N.I. Harnby, M.M. F. Edwards, A.D. W. There is a method using a static mixer described in Chapter 8 of Nienow's Koji Takahashi "Liquid Mixing Technology" (published by Nikkan Kogyo Shimbun, 1989).

  In the present invention, when the organic silver salt-containing layer (that is, the image forming layer) is formed using a coating solution in which 30% by mass or more of the solvent is water and dried, the organic silver salt-containing layer is further formed. This binder is soluble or dispersible in an aqueous solvent (aqueous solvent), and is improved particularly when it is composed of a latex of a polymer having an equilibrium water content at 25 ° C. and 60% RH of 2% by mass or less. The most preferable form is one prepared so that the ionic conductivity is 2.5 mS / cm or less, and as such a preparation method, there is a method of performing purification treatment using a separation functional membrane after polymer synthesis.

  The aqueous solvent in which the polymer is soluble or dispersible here is a mixture of water or water with 70% by mass or less of a water-miscible organic solvent. Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol, cellosolvs such as methyl cellosolve, ethyl cellosolve and butyl cellosolve, ethyl acetate and dimethylformamide.

  In the case of a system in which the polymer is not dissolved thermodynamically and exists in a so-called dispersed state, the term aqueous solvent is used here.

  The “equilibrium moisture content at 25 ° C. and 60% RH” is the following using the mass W1 of the polymer in a humidity-controlled equilibrium under an atmosphere of 25 ° C. and 60% RH and the mass W0 of the polymer in an absolutely dry state at 25 ° C. It can be expressed as Equilibrium water content at 25 ° C. and 60% RH = [(W1-W0) / W0] × 100 (mass%)

  For the definition and measurement method of moisture content, for example, Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Society of Polymer Sciences, Jinshokan) can be referred to.

  The equilibrium moisture content at 25 ° C. and 60% RH of the binder polymer of the present invention is preferably 2% by mass or less, more preferably 0.01% by mass or more and 1.5% by mass or less, and further preferably 0.02% by mass. % To 1% by mass is desirable.

  In the present invention, a polymer dispersible in an aqueous solvent is particularly preferred.

  Examples of the dispersed state include latex in which fine particles of solid polymer are dispersed and polymer molecules dispersed in a molecular state or forming micelles, and all are preferable.

  In the present invention, it is preferable to use a hydrophobic polymer such as an acrylic resin, a polyester resin, a rubber-based resin (for example, SBR resin), a polyurethane resin, a vinyl chloride resin, a vinyl acetate resin, a vinylidene chloride resin, and a polyolefin resin. it can. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer obtained by polymerizing a single monomer, or a copolymer obtained by polymerizing two or more monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is 5,000 to 1,000,000, preferably 10,000 to 200,000 in terms of number average molecular weight. When the molecular weight is too small, the mechanical strength of the emulsion layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable.

  The “aqueous solvent” refers to a dispersion medium in which 30% by mass or more of the composition is water. The dispersion state may be any one such as an emulsified dispersion, a micelle-dispersed, or a polymer having a hydrophilic portion in the molecule dispersed in the molecular state, and among these, latex is particularly preferable. .

  Specific examples of preferable polymer latex include the following. Below, it represents using a raw material monomer, the numerical value in a parenthesis is the mass%, and molecular weight is a number average molecular weight.

Latex (molecular weight 37000) of P-1; -MMA (70) -EA (27) -MAA (3)-
Latex of P-2; -MMA (70) -2EHA (20) -St (5) -AA (5)-(molecular weight 40000)
Latex of P-3; -St (50) -Bu (47) -MAA (3)-(molecular weight 45000)
Latex of P-4; -St (68) -Bu (29) -AA (3)-(molecular weight 60000)
P-5; Latex (molecular weight 120,000) of -St (70) -Bu (27) -IA (3)-
Latex of P-6; -St (75) -Bu (24) -AA (1)-(molecular weight 108000)
P-7; Latex (molecular weight: 150,000) of -St (60) -Bu (35) -DVB (3) -MAA (2)-
P-8; Latex (molecular weight 280000) of -St (70) -Bu (25) -DVB (2) -AA (3)-
Latex (molecular weight 80000) of P-9; -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-
P-10; latex of VDC (85) -MMA (5) -EA (5) -MAA (5)-(molecular weight 67000)
Latex of P-11; -Et (90) -MAA (10)-(molecular weight 12000)
-St (70) -2EHA (27) -AA (3) latex (molecular weight 130,000) P-13; -MMA (63) -EA (35) -AA (2) latex (molecular weight 33000)

  The abbreviations for the above structures represent the following monomers. MMA; Methyl methacrylate, EA; Ethyl acrylate, MAA; Methacrylic acid, 2EHA; 2-Ethylhexyl acrylate, St; Styrene, Bu; Butadiene, AA; Acrylic acid, DVB; Divinylbenzene, VC; Vinyl chloride, AN; Acrylonitrile, VDC Vinylidene chloride, Et; ethylene, IA; itaconic acid.

  The polymer latex described above is also commercially available, and the following polymers can be used. Examples of acrylic resins include polyester resins such as Ceviane A-4635, 46583, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.). Examples include polyurethane resins such as FINITEX ES650, 611, 675, and 850 (manufactured by Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (manufactured by Eastman Chemical), and HYDRAN AP10, 20, Examples of rubber-based resins such as 30, 40 (manufactured by Dainippon Ink Chemical Co., Ltd.) include LACSTAR 7310K, 3307B, 4700H, 7132C (manufactured by Dainippon Ink Chemical Co., Ltd.), Nipol Lx416, 410, 438C. , 2507 (made by Nippon Zeon Co., Ltd.) Examples of vinyl chloride resins include G351 and G576 (manufactured by Nippon Zeon Co., Ltd.), examples of vinylidene chloride resins include L502 and L513 (manufactured by Asahi Kasei Kogyo Co., Ltd.), and examples of olefin resins. Chemipearl S120, SA100 (manufactured by Mitsui Petrochemical Co., Ltd.) and the like.

  These polymer latexes may be used alone or in combination of two or more as required.

  As the polymer latex used in the present invention, a styrene-butadiene copolymer latex is particularly preferable. The mass ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably 40:60 to 95: 5. The proportion of the styrene monomer unit and the butadiene monomer unit in the copolymer is preferably 60% by mass to 99% by mass. The preferred molecular weight range is the same as described above.

  Examples of the latex of styrene-butadiene copolymer that is preferably used in the present invention include the above-mentioned P-3 to P-8, commercially available products LACSTAR-3307B, 7132C, Nipol Lx416, and the like.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, or hydroxypropylcellulose may be added to the organic silver salt-containing layer of the light-sensitive material of the present invention. The amount of these hydrophilic polymers added is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total binder of the organic silver salt-containing layer.

  The organic silver salt-containing layer of the present invention is formed using a polymer latex, and the amount of the binder in the organic silver salt-containing layer is such that the total binder / organic silver salt mass ratio is 1/10 to 10. / 1, more preferably in the range of 1/5 to 4/1.

  In addition, such an organic silver salt-containing layer (that is, an image forming layer) is usually a photosensitive layer (emulsion layer) containing a photosensitive silver halide that is a photosensitive silver salt. The mass ratio of the total binder / silver halide is preferably 400 to 5, more preferably 200 to 10.

The total amount of binder in the image forming layer of the present invention is ^{0.2g / m 2 ~30g / m 2} , more preferably from ^1g / ^{m 2 ~15g} / m 2 is preferred. The image forming layer of the present invention may contain a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like.

  In the present invention, the solvent of the coating solution for the organic silver salt-containing layer of the light-sensitive material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is an aqueous solvent containing 30% by mass or more of water. As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, and ethyl acetate may be used. The water content of the solvent of the coating solution is preferably 50% by mass or more, more preferably 70% by mass or more. Examples of preferred solvent compositions include water, water / methyl alcohol = 90/10, water / methyl alcohol = 70/30, water / methyl alcohol / dimethylformamide = 80/15/5, water / methyl alcohol / Ethyl cellosolve = 85/10/5, water / methyl alcohol / isopropyl alcohol = 85/10/5, etc. (numerical values are mass%).

  As the sensitizing dye in the present invention, any sensitizing dye may be used as long as it can spectrally sensitize the silver halide grains in a desired wavelength region when adsorbed on the silver halide grains. As the sensitizing dye, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes, and the like can be used. Useful sensitizing dyes used in the present invention are described in, for example, documents described or cited in RESEARCH DISCLOSURE Item 17643IV-A (December 1978, p.23) and Item 1831X (August 1979, p.437). Has been. In particular, a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light sources of various laser imagers, scanners, image setters and plate-making cameras can be advantageously selected.

  Sensitizing dyes include compounds represented by paragraphs 0056 to 0066 of JP-A-10-62899, general formula (II) of JP-A-10-186572, page 19, line 38 to EP-A-0803762A1. 20 pages, line 35. Examples of the sensitizing dye include dyes having a carboxylic acid group (for example, dyes described in JP-A-3-163440, 6-301141, US Pat. No. 5,441,899), merocyanine dyes, polynuclear merocyanine dyes, Multinuclear cyanine dyes (JP-A-47-6329, 49-105524, 51-127719, 52-80829, 54-61517, 59-214846, 60-6750, 63) No. 159841, JP-A-6-35109, JP-A-6-59381, JP-A-7-146537, JP-A-7-146537, JP-T-5-550111, British Patent 1,467,638, US Pat. And dyes forming J-band (US Pat. Nos. 5,510,236 and 3,871,887). Described in Example 5 of the dye, JP-A-2-96131, JP-59-48753) can be preferably used in the present invention.

  These sensitizing dyes may be used alone or in combination of two or more. A combination of sensitizing dyes is often used for the purpose of supersensitization. Along with the sensitizing dye, the emulsion itself may contain a dye having no spectral sensitizing action or a substance that does not substantially absorb visible light and exhibits supersensitization. Useful sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in Research Disclosure 176, 17643 (issued in December, 1978), page 23, Section J, or Japanese Patent Publication No. 49-25500. 43-4933, JP-A-59-19032, 59-192242 and the like.

  In order to add the sensitizing dye into the silver halide emulsion, they may be dispersed directly in the emulsion, or water, methanol, ethanol, propanol, acetone, methyl cellosolve, 2,2,3,3- Solvents such as tetrafluoropropanol, 2,2,2-trifluoroethanol, 3-methoxy-1-propanol, 3-methoxy-1-butanol, 1-methoxy-2-propanol, N, N-dimethylformamide alone or It may be dissolved in a mixed solvent and added to the emulsion.

  Further, as disclosed in US Pat. No. 3,469,987, etc., a dye is dissolved in a volatile organic solvent, and this solution is dispersed in water or a hydrophilic colloid. As disclosed in Japanese Patent Publication Nos. 44-23389, 44-27555, and 57-22091, the dye is dissolved in an acid, and this solution is added to the emulsion. A method of adding an acid or base to the emulsion in the presence of an aqueous solution, as disclosed in US Pat. Nos. 3,822,135 and 4,006,025, etc. Alternatively, a method in which a colloidal dispersion is added to the emulsion, as disclosed in JP-A-53-102733 and 58-105141, a dye is directly dispersed in a hydrophilic colloid, and the dispersion is obtained. A method of adding in the dosage, as disclosed in JP-51-74624, with a compound capable of red shift to dissolve the dye, the solution can also be used a method of adding to the emulsion. In addition, ultrasonic waves can be used for dissolution.

  The time when the sensitizing dye used in the present invention is added to the silver halide emulsion of the present invention may be during any step of emulsion preparation that has been found useful. For example, U.S. Pat. Nos. 2,735,766, 3,628,960, 4,183,756, 4,225,666, JP-A-58-184142, 60-19649, etc. As disclosed in Japanese Patent Application Laid-Open No. Sho-58, the silver halide grain formation step or / and the time before desalting, the time during the desalting step and / or after the desalting to the start of chemical ripening, As disclosed in the specification such as No. 113920, it may be added in any process at any time immediately before or during chemical ripening, or after chemical ripening and before coating. Good. Further, as disclosed in the specifications of US Pat. No. 4,225,666 and JP-A-58-7629, the same compound may be used alone or in combination with a compound having a different structure, for example, during the particle formation process. May be added separately during the chemical ripening step or after completion of chemical ripening, or may be added separately before or during chemical ripening or after completion of the chemical ripening, or the compounds and combinations of compounds added in divided portions You may add and change the kind of. Preferably, it is the time from the desalting step to application, more preferably the time from desalting to before the start of chemical ripening.

It may be desired amount depending on the performance such as sensitivity and fog as the use amount of the sensitizing dye in the present invention, preferably 1 mol of silver halide per 10 ^-6 to 1 mol of the photosensitive layer, ^10-4 More preferably, mol to 10 ⁻¹ mol.

In the photosensitive layer of the present invention, it is preferable to use an irradiation-preventing dye or pigment in order to more effectively exhibit the effect of reducing the occurrence of interference fringes. Examples of the irradiation prevention dye or pigment that can be applied to the present invention include those described in detail in WO 98/36322. Preferred dyes and pigments for use in the photosensitive layer of the present invention include anthraquinone dyes, azomethine dyes, indoaniline dyes, azo dyes, anthraquinone-based indanthrone pigments (such as CI Pigment Blue 60), and phthalocyanine pigments (C.I. Pigment Blue 15 and other copper phthalocyanines, CI Pigment Blue 16 and other metal-free phthalocyanines), dyed lake pigment triarylcarbonyl pigments, indigo, and inorganic pigments (ultraviolet, cobalt blue, etc.). As a method for adding these dyes and pigments, any method such as a solution, an emulsion, a solid fine particle dispersion, or a state mordanted in a polymer mordant may be used. Absorption purposes the amount of these compounds (preferably absorbance of 0.06 to 1.0 at the exposure wavelength, and more preferably 0.1 to 0.5), but is determined by the generally sensitive material 1 m ² It is preferably used in the range of 1 μg to 3 g, more preferably in the range of 1 mg to 1 g.

  The silver halide emulsions and / or organic silver salts in the present invention are further protected against the formation of additional fog by antifoggants, stabilizers and stabilizer precursors, and against reduced sensitivity during inventory storage. Can be stabilized. Suitable antifogging agents, stabilizers and stabilizer precursors which can be used alone or in combination are disclosed in paragraph No. 0070 of JP-A-10-62899, page 20 lines 57 to 57 of EP-A-0803764. Patents described on page 21, line 7 can be mentioned.

  The antifoggant preferably used in the present invention is an organic halide, such as JP-A-50-119624, JP-A-50-120328, JP-A-51-121332, JP-A-54-58022, JP-A-56-70543, 56-99335, 59-90842, 61-129642, 62-129845, JP-A-6-208191, 7-5621, 7-27881, 8-15809, USA Examples thereof include compounds disclosed in Japanese Patent Nos. 5340712, 5369000, and 5464737. In particular, compounds of the general formula (II) of JP-A-10-339934 (specifically tribromomethylnaphthylsulfone, tribromomethyl (4- (2,4,6-trimethylsulfonyl) phenyl) sulfone, tribromomethylphenyl) Sulfone and the like) are preferred.

  The antifoggant of the present invention may be added by any method such as a solution, powder, solid fine particle dispersion and the like. The solid fine particle dispersion is performed by a known finer means (for example, ball mill, vibration ball mill, sand mill, colloid mill, jet mill, roller mill, etc.). Further, a dispersion aid such as an anionic surfactant (for example, sodium triisopropyl naphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used when dispersing the solid fine particles.

Although not necessary to practice the present invention, it may be advantageous to add mercury (II) salts to the emulsion layers as antifoggants. Preferred mercury (II) salts for this purpose are mercury acetate and mercury bromide. The amount of mercury used in the present invention is preferably 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol, more preferably 1 × 10 ⁻⁹ mol to 1 × 10 ⁻⁴ mol per mol of applied silver. The range of moles.

The photothermographic material of the present invention may contain an azolium salt or benzoic acid for the purpose of increasing sensitivity and preventing fogging. Examples of the azolium salt include compounds represented by general formula (XI) described in JP-A-59-193447, compounds described in JP-B-55-12581, and general formula (II) described in JP-A-60-153039. And the compounds represented. The benzoic acid compound may be any benzoic acid derivative. Examples of preferable structures include US Pat. Nos. 4,784,939, 4,152,160, JP-A-9-329865, JP-A-9-329864, Examples thereof include compounds described in Kaihei 9-281737. An azolium salt or benzoic acid may be added to any part of the photosensitive material, but the additive layer is preferably added to the layer having the photosensitive layer, and more preferably added to the organic silver salt-containing layer. . The azolium salt and benzoic acid may be added at any step in the coating solution preparation. When added to the organic silver salt-containing layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. It is preferable that the salt is prepared and immediately before coating. The azolium salt or benzoic acid may be added by any method such as powder, solution, or fine particle dispersion. Moreover, you may add as a solution mixed with other additives, such as a sensitizing dye, a reducing agent, and a color toning agent. In the present invention, the azolium salt or benzoic acid may be added in any amount, but preferably 1 × 10 ⁻⁶ mol to 2 mol, and more preferably 1 × 10 ⁻³ mol to 0.5 mol, per mol of silver. preferable.

  In the present invention, a mercapto compound, a disulfide compound, and a thione compound can be contained in order to suppress or promote development and control development, to improve spectral sensitization efficiency, and to improve storage stability before and after development. .

  Examples of such mercapto compounds, disulfide compounds, and thione compounds include paragraph numbers 0067 to 0069 of JP-A No. 10-62899, compounds represented by the general formula (I) of JP-A No. 10-186572, and paragraph numbers as specific examples thereof. 0033-0052, European Patent Publication No. 0803764A1, page 20, lines 36-56. Among them, mercapto-substituted heteroaromatic compounds are preferable, and 2-mercaptobenzimidazole, 2-mercapto-5-methylbenzimidazole, 2-mercaptobenzoxazole, 2-mercaptobenzothiazole, 2-mercapto-5-methylbenzimidazole, 6- Ethoxy-2-mercaptobenzothiazole, 2,2′-dithiobis- (benzothiazole, 3-mercapto-1,2,4-triazole, 4,5-diphenyl-2-imidazolethiol, 2-mercaptoimidazole, 1-ethyl 2-mercaptobenzimidazole, 2-mercaptoquinoline, 8-mercaptopurine, 2-mercapto-4 (3H) -quinazolinone, 7-trifluoromethyl-4-quinolinethiol, 2,3,5,6-tetrachloro- 4-pyridine All, 4-amino-6-hydroxy-2-mercaptopyrimidine monohydrate, 2-amino-5-mercapto-1,3,4-thiadiazole, 3-amino-5-mercapto-1,2,4-triazole, 4-hydroxy-2-mercaptopyrimidine, 2-mercaptopyrimidine, 4,6-diamino-2-mercaptopyrimidine, 2-mercapto-4-methylpyrimidine hydrochloride, 3-mercapto-5-phenyl-1,2,4- Examples include triazole, 2-mercapto-4-phenyloxazole, 3-mercapto-4-phenyl-5-heptyl-1,2-4-triazole.

  The addition amount of these mercapto compounds is preferably in the range of 0.001 mol to 1.0 mol per mol of silver in the emulsion layer, more preferably 0.01 mol to 0.3 mol per mol of silver. Amount.

  When an additive known as a “toning agent” for improving an image is included, the optical density may be increased, and in the present invention, the addition of a toning agent is preferable. The toning agent may also be advantageous in forming a black silver image. The toning agent is preferably contained in the surface having the image forming layer in an amount of 0.1 mol% to 50 mol% per mol of silver, more preferably 0.5 mol% to 20 mol%. The toning agent may be a so-called precursor that is derivatized so as to have an effective function only during development.

  Such a color toning agent includes phthalazinone, a phthalazinone derivative or a color toning agent described in paragraph Nos. 0054 to 0055 of JP-A No. 10-62899, page 21, lines 23 to 48 of European Patent Publication No. 0803764A1. Metal salts, or derivatives such as 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione; phthalazinone and phthalic acid derivatives (For example, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, tetrachlorophthalic anhydride, etc.); phthalazines (phthalazine, phthalazine derivatives or metal salts, or 4- (1-naphthyl) phthalazine, 6- Isopropyl phthalazine, 6-t-butyl phthalazine, 6-chloro Derivatives such as tarazine, 5,7-dimethoxyphthalazine and 2,3-dihydrophthalazine); phthalazines and phthalic acid derivatives (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic anhydride, etc.) ), And a combination of phthalazines and phthalic acid derivatives is particularly preferable.

  The toning agent of the present invention may be added by any method such as a solution, a powder, or a solid fine particle dispersion. The solid fine particle dispersion is performed by a known finer means (for example, ball mill, vibration ball mill, sand mill, colloid mill, jet mill, roller mill, etc.). A dispersion aid may be used when dispersing the solid fine particles.

  In the photosensitive layer in the present invention, a polyhydric alcohol (for example, glycerol and diol of the kind described in US Pat. No. 2,960,404), US Pat. No. 2,588,765 is used as a plasticizer and a lubricant. And fatty acids or esters described in US Pat. No. 3,121,060, silicone resins described in British Patent No. 955,061, and the like.

  In the photothermographic material of the invention, a surface protective layer can be provided for the purpose of preventing adhesion of the image forming layer.

The binder for the surface protective layer of the present invention may be any polymer, but preferably contains a polymer having a carboxylic acid residue in an amount of 100 mg / m ^{2 to} 5 g / m ² . Examples of the polymer having a carboxyl residue are natural polymers (gelatin, alginic acid, etc.), modified natural polymers (carboxymethylcellulose, phthalated gelatin, etc.), synthetic polymers (polymethacrylate, polyacrylate, polyalkylmethacrylate / acrylate). Copolymer, polystyrene / polymethacrylate copolymer, etc.). The content of carboxy residues in such a polymer is preferably 1 × 10 ⁻² mol or more and 1.4 mol or less per 100 g of the polymer. In addition, the carboxylic acid residue may form a salt with an alkali metal ion, an alkaline earth metal ion, an organic cation or the like.

  In addition, it is also preferable to use polyvinyl alcohol (PVA) as a binder for the surface protective layer. PVA-105 of a fully saponified product [polyvinyl alcohol (PVA) content of 94.0% by mass or more, saponification degree 98.5 ± 0 0.5 mol%, sodium acetate content 1.5 mass% or less, volatile content 5.0 mass% or less, viscosity (4 mass%, 20 ° C.) 5.6 ± 0.4 CPS], partially saponified PVA-205 [PVA content 94.0% by mass, saponification degree 88.0 ± 1.5 mol%, sodium acetate content 1.0% by mass, volatile matter 5.0% by mass, viscosity (4% by mass, 20 ° C.) 5 0.0 ± 0.4 CPS], and modified polyvinyl alcohols such as MP-102, MP-202, MP-203, R-1130, and R-2105 (trade names manufactured by Kuraray Co., Ltd.).

Preferably 0.3g ^{/ m 2} ~4.0g ^/ m 2 as a polyvinyl alcohol coating amount (per support 1 m ²⁾ of the protective layer (per one ^{layer), 0.3g / m 2 ~2.0g /} m 2 Is more preferable.

  Any adhesion preventing material may be used as the surface protective layer of the present invention. Examples of anti-adhesive materials include wax, silica particles, styrene-containing elastomeric block copolymers (eg, styrene-butadiene-styrene, styrene-isoprene-styrene), cellulose acetate, cellulose acetate butyrate, cellulose propionate, and these There is a mixture. In addition, a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like may be added to the surface protective layer.

  In the present invention, the image forming layer or the protective layer of the image forming layer includes U.S. Pat. Nos. 3,253,921, 2,274,782, 2,527,583 and 2,956. Light absorbing materials and filter dyes such as described in 879 can be used. For example, a dye can be mordanted as described in US Pat. No. 3,282,699. The amount of filter dye used is preferably an absorbance at an exposure wavelength of 0.1 to 3.0, particularly preferably 0.2 to 1.5.

  In the image forming layer or the protective layer of the image forming layer in the present invention, a matting agent such as starch, titanium dioxide, zinc oxide, silica, U.S. Pat. Nos. 2,992,101 and 2,701,245 are used. Polymer beads including the types of beads described can be included.

  The preparation temperature of the image forming layer coating solution of the present invention is preferably 30 ° C. or more and 65 ° C. or less, and more preferably 35 ° C. or more and less than 60 ° C. (preferably 55 ° C. or less). Moreover, it is preferable that the temperature of the image forming layer coating liquid immediately after the addition of the polymer latex is maintained at 30 ° C. or higher and 65 ° C. or lower. Moreover, it is preferable that the reducing agent and the organic silver salt are mixed before adding the polymer latex.

  The organic silver salt-containing fluid or the thermal image forming layer coating solution in the present invention is preferably a so-called thixotropic fluid. Thixotropy refers to the property that the viscosity decreases as the shear rate increases. Although any apparatus may be used for the viscosity measurement of the present invention, an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd. is preferably used and measured at 25 ° C. Here, the organic silver salt-containing fluid or the thermal image forming layer coating liquid in the present invention preferably has a viscosity at a shear rate of 0.1 S-1 of 400 mPa · s to 100,000 mPa · s, more preferably 500 mPa · s to 20 1,000 mPa · s or less. Moreover, in shear rate 1000S-1, 1 mPa * s or more and 200 mPa * s or less are preferable, More preferably, they are 5 mPa * s or more and 80 mPa * s or less.

  Various systems that exhibit thixotropic properties are known, and are described in “Lectures / Rheology” edited by Polymer Publishing Co., “Polymer Latex” (published by Polymer Publishing Co., Ltd.) co-authored by Muroi and Morino. In order for the fluid to exhibit thixotropy, it is necessary to contain a large amount of solid fine particles. In order to enhance the thixotropy, it is effective to contain a thickening linear polymer, increase the aspect ratio in the anisotropic shape of the contained solid fine particles, increase the alkali viscosity, and use a surfactant.

  The heat-developable photographic emulsion of the present invention comprises one or more layers on a support. One layer composition must contain organic silver salts, silver halides, developers and binders, and optional additional materials such as toning agents, coating aids and other aids. The two-layer construction must include an organic silver salt and silver halide in the first emulsion layer (usually the layer adjacent to the support) and some other components in the second or both layers. Don't be. However, a two-layer configuration comprising a single emulsion layer containing all components and a protective topcoat is also conceivable. The construction of a multicolor photosensitive photothermographic material may include a combination of these two layers for each color and all components in a single layer as described in US Pat. No. 4,708,928. May be included. In the case of multi-dye multicolor photosensitive photothermographic materials, each emulsion layer is generally functionalized between each emulsion layer (photosensitive layer) as described in US Pat. No. 4,460,681. Alternatively, they can be kept separate from each other by using a non-functional barrier layer.

  The photothermographic material in the invention is a so-called single-sided photosensitive material having a photosensitive layer containing at least one silver halide emulsion on one side of a support and a back layer on the other side. preferable.

  The photothermographic material generally has a non-photosensitive layer in addition to the photosensitive layer. The non-photosensitive layer includes (1) a protective layer provided on the photosensitive layer (on the side farther from the support), and (2) a plurality of photosensitive layers or between the photosensitive layer and the protective layer. (3) an undercoat layer or an intermediate layer provided between the photosensitive layer and the support, and (4) a back layer provided on the opposite side of the photosensitive layer. The filter layer is provided on the photosensitive material as the layer (1) or (2). The antihalation layer is provided on the photosensitive material as the layer (3) or (4).

  In the present invention, the antihalation layer can be provided on the side far from the light source with respect to the photosensitive layer, that is, between the photosensitive layer and the support or on the surface opposite to the photosensitive layer of the support. The antihalation layer preferably has a maximum absorption in a desired wavelength range of 0.3 or more and 2 or less, more preferably an absorption of an exposure wavelength of 0.5 or more and 2 or less, and in the visible region after processing. Absorption is preferably 0.001 or more and less than 0.5, more preferably a layer having an optical density of 0.001 or more and less than 0.3.

  When antihalation dyes are used in the present invention, such dyes have the desired absorption in the wavelength range, and have a sufficiently low absorption in the visible region after processing, so that any desired absorbance spectrum shape of the antihalation layer can be obtained. It may be a compound. For example, the following is disclosed, but the present invention is not limited to this. As individual dyes, JP-A-59-56458, JP-A-2-216140, JP-A-7-13295, JP-A-7-11432, US Pat. No. 5,380,635, JP-A-2-68539 There are compounds described on page 13, lower left column, line 1 to page 14, lower left column, line 9 and JP-A-3-245539, page 14, lower left column to page 16, lower right column, and are dyes that can be erased by processing. JP-A-52-139136, 53-132334, 56-501480, 57-16060, 57-68831, 57-101835, 59-182436, JP-A-7-36145. No. 7-199409, No. 48-33692, No. 50-16648, No. 2-41734, US Pat. No. 4,088,497, No. 4,283,487, No. 4, No. 48,896, there is a Nos. 5,187,049.

  In the present invention, it is preferable to use a base precursor and a dye that can be bleached with a base (hereinafter referred to as a decoloring dye) as an antihalation layer of the photothermographic material.

  The decolorizing dye and the base precursor are preferably added to the same non-photosensitive layer. However, it may be added separately to two adjacent non-photosensitive layers. A barrier layer may be provided between the two non-photosensitive layers.

  As a method of adding the decoloring dye to the non-photosensitive layer, a method of adding a solution, an emulsion, a solid fine particle dispersion, or a polymer impregnated product to the coating solution for the non-photosensitive layer can be employed. Moreover, you may add dye to a non-photosensitive layer using a polymer mordant. These addition methods are the same as the method of adding a dye to a normal photothermographic material. The latex used for the polymer impregnation is described in U.S. Pat. No. 4,199,363, West German Patent Publication Nos. 25141274, 2541230, European Patent Publication No. 0291104, and Japanese Patent Publication No. 53-41091. An emulsification method in which a dye is added to a solution in which a polymer is dissolved is described in International Publication No. 88/00723.

The amount of decoloring dye added is determined by the use of the dye. In general, the optical density (absorbance) measured at the target wavelength is used in an amount exceeding 0.1. The optical density is preferably 0.2-2. The amount of the dye for obtaining such an optical density is generally 0.001g ^{/ m 2} ~1g ^/ m 2 approximately. ^Preferably, a 0.005g / ^{m 2} ~0.8g / m 2 about, particularly ^preferably 0.01g / ^{m 2} ~0.2g / m 2 approximately.

  If the dye is decolored in this way, the optical density can be reduced to 0.1 or less. Two or more kinds of decoloring dyes may be used in combination in a heat decoloring type recording material or a photothermographic material. Similarly, two or more kinds of base precursors may be used in combination.

  It is preferable to add a matting agent to the photothermographic material used in the present invention in order to improve the effects of the present invention and improve the transportability. The matting agent is generally fine particles of an organic or inorganic compound that is insoluble in water. Any matting agent can be used, for example, U.S. Pat. Nos. 1,939,213, 2,701,245, 2,322,037, 3,262,782, and 3,539. , 344, 3,767, 448, etc., the organic matting agents, 1,260,772, 2,192,241, 3,257,206, 3, Those well known in the art such as the inorganic matting agent described in each specification such as 370,951, 3,523,022, and 3,769,020 can be used. For example, specific examples of organic compounds that can be used as a matting agent include polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, acrylonitrile-α-methylstyrene copolymer, polystyrene as examples of water-dispersible vinyl polymers. , Styrene-divinylbenzene copolymer, polyvinyl acetate, polyethylene carbonate, polytetrafluoroethylene, etc. Examples of cellulose derivatives include methylcellulose, cellulose acetate, cellulose acetate propionate, etc. Examples of starch derivatives include carboxy starch, carboxynitrophenyl Preferred are gelatin hardened with known hardeners, such as starch, urea-formaldehyde-starch reactants, and hardened gelatin made into microcapsule hollow granules by coacervate hardening. It can be used properly. As examples of the inorganic compound, silicon dioxide, titanium dioxide, magnesium dioxide, aluminum oxide, barium sulfate, calcium carbonate, silver chloride desensitized by a known method, silver bromide, glass, diatomaceous earth, and the like can be preferably used. The above matting agents can be used by mixing different kinds of substances as required. The size and shape of the matting agent are not particularly limited, and those having an arbitrary particle size can be used. In the practice of the present invention, those having a particle diameter of 0.1 μm to 30 μm are preferably used, and those having an average particle diameter of 2 μm to 10 μm are more preferable. Further, the particle size distribution of the matting agent may be narrow or wide. On the other hand, since the matting agent greatly affects the haze and surface gloss of the light-sensitive material, the particle size, shape, and particle size distribution can be brought into a state as required by preparing the matting agent or mixing a plurality of matting agents. preferable.

When the matting agent is indicated by the coating amount per the photosensitive material 1 m ^2, preferably from ^{1mg / m 2 ~400mg / m 2} , more preferably ^{5mg / m 2 ~300mg / m 2} .

  The emulsion surface may have any matte degree as long as no stardust failure occurs, but the Beck smoothness is preferably 50 seconds or more and 10,000 seconds or less, particularly preferably 80 seconds or more and 10,000 seconds or less.

  In the present invention, the matte degree of the back layer is preferably Beck smoothness of 1200 seconds or less and 10 seconds or more, and more preferably 700 seconds or less and 50 seconds or more.

  In the present invention, the matting agent is preferably contained in the outermost surface layer of the photosensitive material, the layer functioning as the outermost surface layer, or a layer close to the outer surface, and is contained in a layer acting as a so-called protective layer. It is preferable.

  In the present invention, a suitable binder for the back layer is transparent or translucent and generally colorless, and is a natural polymer, synthetic resin, polymer and copolymer, or other medium for forming a film, such as: gelatin, gum arabic, poly (vinyl alcohol) , Hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (styrene -Maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), poly (esters) Ure Emissions), phenoxy resins, poly (vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, and polyamides. The binder may be formed from water or an organic solvent or emulsion.

  In the present invention, the back layer preferably has a maximum absorption in a desired wavelength range of 0.3 or more and 2 or less, more preferably 0.5 or more and 2 or less, and in the visible region after processing. Absorption is preferably 0.001 or more and less than 0.5, more preferably a layer having an optical density of 0.001 or more and less than 0.3. Examples of the antihalation dye used for the back layer are the same as those of the antihalation layer described above.

  A backside resistive heating layer as shown in U.S. Pat. Nos. 4,460,681 and 4,374,921 can also be used in photosensitive photothermographic systems.

  A hardener may be used for each layer such as the photosensitive layer, protective layer, and back layer of the present invention. Examples of hardeners include T.W. H. There are various methods described in “THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION” by James (published by Macmillan Publishing Co., Inc., published in 1977), pages 77 to 87. Polyisocyanates such as US Pat. No. 4,281,060 and JP-A-6-208193, epoxy compounds such as US Pat. No. 4,791,042, and vinyl sulfone compounds such as JP-A 62-89048 Preferably used.

  The hardener is added as a solution, and the addition time of this solution to the protective layer coating solution is from 180 minutes before to immediately before application, preferably from 60 minutes to 10 seconds before application. As long as the effects of the present invention are sufficiently exhibited, there is no particular limitation. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is a desired time, and N.I. Harnby, M.M. F. Edwards, A.D. W. There is a method using a static mixer described in Chapter 8 of Nienow's “Liquid Mixing Technology” (Nikkan Kogyo Shimbun, 1989), translated by Koji Takahashi.

  In the present invention, a surfactant may be used for the purpose of improving coating properties and charging. As an example of the surfactant, any nonionic, anionic, cationic, or fluorine-based one can be used as appropriate. Specific examples include fluoropolymer surfactants described in JP-A-62-170950, US Pat. No. 5,380,644, JP-A-60-244945, JP-A-63-188135, and the like. Fluorosurfactants described, polysiloxy acid surfactants described in US Pat. No. 3,885,965, polyalkylene oxides and anionic surfactants described in JP-A-6-301140, etc. .

  Examples of the solvent used in the present invention include New Edition Solvent Pocket Book (Ohm, published in 1994), but the present invention is not limited thereto. The boiling point of the solvent used in the present invention is preferably 40 ° C. or higher and 180 ° C. or lower.

  Examples of the solvent of the present invention include hexane, cyclohexane, toluene, methanol, ethanol, isopropanol, acetone, methyl ethyl ketone, ethyl acetate, 1,1,1-trichloroethane, tetrahydrofuran, triethylamine, thiophene, trifluoroethanol, perfluoropentane, xylene. , N-butanol, phenol, methyl isobutyl ketone, cyclohexanone, butyl acetate, diethyl carbonate, chlorobenzene, dibutyl ether, anisole, ethylene glycol diethyl ether, N, N-dimethylformamide, morpholine, propane sultone, perfluorotributylamine, water, etc. Is mentioned.

  The photographic emulsion for heat development in the present invention can be coated on various supports. Typical supports are polyester film, primed polyester film, poly (ethylene terephthalate) film, polyethylene naphthalate film, cellulose nitrate film, cellulose ester film, poly (vinyl acetal) film, polycarbonate film and related or resinous Including materials, as well as glass, paper, metal and the like. Coated with a flexible substrate, in particular a baryta and / or a partially acetylated α-olefin polymer, in particular an α-olefin polymer having 2 to 10 carbon atoms such as polyethylene, polypropylene, ethylene-butene copolymer. A paper support is typically used. Such a support may be transparent or opaque, but is preferably transparent.

  The light-sensitive material in the present invention is an antistatic or conductive layer such as a soluble salt (for example, chloride, nitrate, etc.), a vapor-deposited metal layer, U.S. Pat. Nos. 2,861,056 and 3,206,312. It may have a layer containing an ionic polymer as described or an insoluble inorganic salt as described in US Pat. No. 3,428,451.

  The photothermographic material is preferably a mono-sheet type (a type capable of forming an image on the photothermographic material without using another sheet such as an image receiving material).

  An antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber, or a coating aid may be further added to the photothermographic material. Various additives are added to either the photosensitive layer or the non-photosensitive layer. With respect to these, the respective specifications such as WO98 / 36322, EP803764A1, JP-A-10-186567, and 10-18568 can be referred to.

  In the photosensitive layer in the present invention, a polyhydric alcohol (for example, glycerol and diol of the kind described in US Pat. No. 2,960,404), US Pat. No. 2,588,765 is used as a plasticizer and a lubricant. And fatty acids or esters described in US Pat. No. 3,121,060, silicone resins described in British Patent No. 955,061, and the like.

  As a method for obtaining a color image using the photothermographic material in the invention, there is a method described in JP-A-7-13295, page 10, left column, line 43 to 11, left column, line 40. Examples of color dye image stabilizers include British Patent No. 1,326,889, US Pat. No. 3,432,300, US Pat. No. 3,698,909, US Pat. No. 3,574,627, US Pat. 3,573,050, 3,764,337 and 4,042,394.

  The photothermographic material in the invention may be applied by any method. Specifically, various coating operations including extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating, or extrusion coating using a hopper of the type described in US Pat. No. 2,681,294. And Stephen F. Kistler, Peter M. et al. The extrusion coating described in “LIQUID FILM COATING” (CHAPMAN & HALL, 1997) by Schweizer (1997), pages 399 to 536 is preferably used, and slide coating is particularly preferably used. An example of the shape of a slide coater used for slide coating is shown in FIG. 11b. 1 If desired, two or more layers can be simultaneously coated by the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761,791 and British Patent No. 837,095. .

  Additional layers in the photothermographic material of the present invention, such as a dye-receiving layer for receiving a moving dye image, an opacifying layer when reflective printing is desired, a protective topcoat layer, and a primer known in the photothermographic art Layers can be included. It is preferable that the photothermographic material used in the present invention can form an image with only one photosensitive material, and it is preferable that a functional layer necessary for image formation such as an image receiving layer does not become another photosensitive material.

  Techniques that can be used for the photothermographic material used in the present invention include EP80364A1, EP883022A1, WO98 / 36322, JP-A-9-281737, 9-297367, 9-304869, and 9-869. 311405, 9-329865, 10-10669, 10-62899, 10-69023, 10-186568, 10-90823, 10-171063, 10-186565 10-186567, 10-186568, 10-186570, 10-186571, 10-186572, 10-197974, 10-197982, 10-1977983, 10-197985, 10-197986, 10-1979 No. 7, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10-307365, No. 10-312038 No. 10-339934, No. 11-7100, No. 11-15105, No. 11-24200, No. 11-24201, No. 11-30832.

  The photothermographic material used in the present invention may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. The preferred development temperature is 80 ° C to 250 ° C, more preferably 100 ° C to 140 ° C. The development time is preferably 1 second to 180 seconds, more preferably 10 seconds to 90 seconds, and particularly preferably 10 seconds to 40 seconds.

  A plate heater method is preferred as the heat development method. The heat development method using the plate heater method is preferably a method described in Japanese Patent Application No. 9-229684 and Japanese Patent Application Laid-Open No. 11-133572. In this heat development apparatus for obtaining a visible image, the heating means is composed of a plate heater, and a plurality of press rollers are arranged to face each other along one surface of the plate heater, and the press roller and the The heat developing apparatus is characterized in that the heat development photosensitive material is passed between a plate heater and heat development is performed. It is preferable to divide the plate heater into two to six stages and lower the temperature at the tip by about 1 ° C. to 10 ° C. Such a method is also described in JP-A-54-30032, which can exclude moisture and organic solvents contained in the photothermographic material out of the system, and rapidly develop the photothermographic material. It is also possible to suppress the change in the shape of the support of the photothermographic material due to the heating of.

(Use of the present invention)
The image forming method using the photothermographic material used in the present invention preferably forms a black and white image by a silver image and is used as a photothermographic material for medical diagnosis. In these uses, it goes without saying that a duplicate image can be formed on a duplication film MI-Dup manufactured by Fuji Photo Film Co., Ltd. based on the formed black and white image.

Hereinafter, the present invention will be specifically described by way of examples.
Example 1
(Preparation of PET support)
Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured at 25 ° C. in phenol / tetrachloroethane = 6/4 (mass ratio)) was obtained according to a conventional method. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to produce an unstretched film having a thickness of 175 μm after heat setting.

This was longitudinally stretched 3.3 times using rolls with different peripheral speeds, and then stretched 4.5 times with a tenter. The temperatures at this time were 110 ° C. and 130 ° C., respectively. Thereafter, the film was heat-fixed at 240 ° C. for 20 seconds and relaxed by 4% in the lateral direction at the same temperature. Thereafter, the chuck portion of the tenter was slit and then knurled at both ends, and wound at 4 kg / cm ² to obtain a roll having a thickness of 175 μm.

(Surface corona treatment)
Using a solid state corona treatment machine 6KVA model manufactured by Pillar, both surfaces of the support were treated at room temperature at 20 m / min. From the current and voltage readings at this time, it was found that the support was processed at 0.375 kV · A · min / m ² . The treatment frequency at this time was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

(Preparation of undercoat support)
(1) Preparation of undercoat layer coating solution Formulation (for photosensitive layer side undercoat layer)
Takamatsu Oil & Fats Co., Ltd. Pes Resin A-515GB (30 mass% solution) 234g
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 10% solution 21.5 g
0.91 g of MP-1000 (polymer fine particles) manufactured by Soken Chemical Co., Ltd.
744 mL of distilled water
Formula (for back layer 1st layer)
Butadiene-styrene copolymer latex 131g
(Solid content 40% by mass, butadiene / styrene mass ratio = 32/68)
2,4-dichloro-6-hydroxy-S-triazine sodium salt 8 mass% aqueous solution
5.1g
Sodium laurylbenzenesulfonate-1 mass% aqueous solution 10mL
854 mL of distilled water
Formula (for back layer 2nd layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17% dispersion) 62 g
Gelatin (10% by weight aqueous solution) 65.7 g
METRONE TC-5 (2 mass% aqueous solution) 6.3g made by Shin-Etsu Chemical Co., Ltd.
MP-1000 (Polymer microparticles) manufactured by Soken Chemical Co., Ltd. 0.01g
Sodium dodecylbenzenesulfonate-1 mass% aqueous solution 10mL
856 mL of distilled water

(Preparation of undercoat support)
After the corona discharge treatment is performed on both sides of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm, the wet coating amount is 6.6 mL / m on one side (photosensitive layer surface) with a wire bar. ² (per side) and dry at 180 ° C. for 5 minutes, and then apply the undercoat coating liquid formulation to the back side (back side) with a wire bar so that the wet coating amount is 5.7 mL / m ^2. Apply and dry at 180 ° C for 5 minutes, then apply the undercoat coating formulation on the back (back surface) with a wire bar so that the wet coating amount is 5.7 mL / m ² and dry at 180 ° C for 6 minutes. An undercoat support was prepared.

(Preparation of back surface coating solution)
(Preparation of Base Precursor Solid Fine Particle Dispersion (a)) 64 g of the base precursor compound 11, 28 g of the diphenyl sulfone compound 12 and 10 g of the surfactant Demol N manufactured by Kao Corporation were mixed with 220 mL of distilled water, and the mixture was mixed. Was dispersed using a sand mill (1/4 Gallon sand grinder mill, manufactured by Imex Co., Ltd.) to obtain a solid fine particle dispersion (a) of a base precursor compound having an average particle size of 0.2 μm.

(Preparation of dye solid fine particle dispersion)
9.6 g of cyanine dye 13 and 5.8 g of sodium p-dodecylbenzenesulfonate are mixed with 305 mL of distilled water, and the mixture is dispersed in a bead using a sand mill (1/4 Gallon sand grinder mill, manufactured by IMEX Co., Ltd.). Thus, a dye solid fine particle dispersion having an average particle size of 0.2 μm was obtained.

(Preparation of antihalation layer coating solution)
Gelatin 17 g, polyacrylamide 9.6 g, solid fine particle dispersion (a) 70 g of the above-mentioned precursor precursor, 56 g of the above dye solid fine particle dispersion, 1.5 g of polymethyl methacrylate fine particles (average particle size 6.5 μm), sodium polyethylene sulfonate An antihalation layer coating solution was prepared by mixing 2.2 g, 0.2 g of blue dye 14 and 844 mL of H ₂ O.

(Preparation of back surface protective layer coating solution)
The container was kept at 40 ° C., 50 g of gelatin, 0.2 g of sodium polystyrenesulfonate, 2.4 g of N, N-ethylenebis (vinylsulfonacetamide), 1 g of sodium t-octylphenoxyethoxyethanesulfonate, 30 mg of compound 4, _{C 8 F 17 SO 3 K32mg,} C 8 F 17 SO 2 N (C 3 H 7) (CH 2 CH 2 O) 4 (CH 2) 4 -SO 3 Na 64mg, acrylic acid / ethyl acrylate copolymer ( Polymerization mass ratio 5/95) 8.8 g and 950 mL of H ₂ O were mixed to prepare a back surface protective layer coating solution.

<< Preparation of silver halide grains 1-A >>
While stirring 9.02 mL of 1% by weight potassium bromide solution in 1421 mL of distilled water and further adding 8.2 mL of 1N nitric acid and 20 g of phthalated gelatin, the mixture was stirred at 37 ° C. in a titanium-coated stainless steel reaction vessel. Maintaining the liquid temperature, prepare solution A in which distilled water was added to 37.04 g of silver nitrate and diluted to 159 mL, and solution B in which 32.6 g of potassium bromide was diluted with distilled water to a volume of 200 mL, and pAg was determined by the control double jet method. While maintaining 8.2, the whole amount of Solution A was added at a constant flow rate over 1 minute. Solution B was added by the controlled double jet method. Thereafter, 30 mL of a 3.5% by mass aqueous hydrogen peroxide solution was added, and 36 mL of a 3% by mass aqueous solution of Compound 1 was further added. Thereafter, Compound A is again diluted with distilled water to 317.5 mL, and Compound 2 is dissolved in Solution B so that the final amount is 1 × 10 ⁻⁴ mol per mol of silver. Using solution B2 diluted with distilled water to 400 mL, twice that of solution B, the total amount of solution A2 was maintained over 10 minutes at a constant flow rate while maintaining pAg at 8.1 by the controlled double jet method. Added. Solution B2 was added by the controlled double jet method. Thereafter, 50 mL of a 0.5 mass% methanol solution of Compound 3 was added, and after further increasing the pAg to 7.5 with silver nitrate, the pH was adjusted to 3.8 with 1N sulfuric acid, stirring was stopped, and sedimentation / desorption was performed. A salt / water washing step was performed, 3.5 g of deionized gelatin was added, and 1N sodium hydroxide was added to adjust the pH to 6.0 and pAg 8.2 to prepare a silver halide dispersion.

  Grains in the resulting silver halide emulsion were pure silver bromide grains having an average sphere equivalent diameter of 0.053 μm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope. The [100] face ratio of the particles was determined to be 85% using the Kubelka-Munk method.

While maintaining the above emulsion at 38 ° C. with stirring, 0.035 g of compound 4 (added in 3.5% by mass methanol solution) was added, and after 40 minutes, a solid dispersion of spectral sensitizing dye A (gelatin aqueous solution) was added to silver. 5 × 10 ⁻³ mol per mol was added, and after 1 minute, the temperature was raised to 47 ° C., 20 minutes later, 3 × 10 ⁻⁵ mol of compound 5 was added to 1 mol of silver, and another 2 minutes later, tellurium sensitizer B It was aged 5 × ^{10 -5} mol addition 90 minutes per 1 mol of silver. Ripening just before the end, 0.5 wt% methanol solution of Compound 6 to 5mL was added, the temperature was lowered to 31 ° C., 3.5 wt% methanol solution 5mL of Compound 7, Compound 3 per mole silver 7 × 10 ^{- 3} mol and Compound 8 were added in an amount of 6.4 × 10 ⁻³ mol per mol of silver to prepare silver halide emulsion 1-A.

<< Preparation of silver halide emulsion 1-B >>
In the preparation of silver halide emulsion 1-A, silver halide emulsion 1-A was similarly prepared except that the addition amount of spectral sensitizing dye A was changed to 50% of silver halide emulsion 1-A as sensitivity. B was obtained.

<< Preparation of silver halide emulsion 2-A >>
In the preparation of silver halide emulsion 1-A, silver halide emulsion 2 was prepared in the same manner except that the solution temperature at the time of grain formation was 37 ° C. so that the sensitivity was 200% of that of silver halide emulsion 1-A. -A was obtained. The average equivalent sphere diameter of the particles was 0.076 μm, and the variation coefficient of the equivalent sphere diameter was 18%.

<< Preparation of mixed emulsion A for coating solution >>
Silver halide emulsions 1-A, 1-B and 2-A were mixed in the ratios shown in Table 1, and Compound 9 was added in an amount of 7 × 10 ⁻³ mol per 1 mol of silver as a 1% by mass aqueous solution.

<< Preparation of flake fatty acid silver salt >>
Henkel behenic acid (product name Edenor C22-85R) 87.6 g, distilled water 423 mL, 5N NaOH aqueous solution 49.2 mL, tert-butanol 120 mL were mixed, stirred at 75 ° C. for 1 hour, reacted, sodium behenate A solution was obtained. Separately, 206.2 mL (pH 4.0) of an aqueous solution of 40.4 g of silver nitrate was prepared and kept warm at 10 ° C. A reaction vessel containing 635 mL of distilled water and 30 mL of tert-butanol was kept at 30 ° C., and while stirring, the total amount of the previous sodium behenate solution and the total amount of silver nitrate aqueous solution were 62 minutes, 10 seconds, and 60 minutes, respectively, at a constant flow rate. Added over time. At this time, only the silver nitrate aqueous solution was added for 7 minutes and 20 seconds after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution was started. After the addition of the aqueous silver nitrate solution was completed, only the sodium behenate solution was added for 9 minutes and 30 seconds. Was added. At this time, the temperature in the reaction vessel was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant. Further, the pipe of the addition system of the sodium behenate solution was kept warm by steam tracing, and the steam opening was adjusted so that the liquid temperature at the outlet of the addition nozzle tip was 75 ° C. Moreover, the piping of the addition system of the silver nitrate aqueous solution was kept warm by circulating cold water outside the double pipe. The addition position of the sodium behenate solution and the addition position of the silver nitrate aqueous solution were arranged symmetrically with respect to the stirring axis, and were adjusted to a height that did not contact the reaction solution.

  After completion of the addition of the sodium behenate solution, the mixture was left stirring for 20 minutes at the same temperature, and the temperature was lowered to 25 ° C. Thereafter, the solid content was separated by suction filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm. Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying.

  When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average values were a = 0.14 μm, b = 0.4 μm, c = 0.6 μm, and the average sphere equivalent diameter variation coefficient was 15%. It was a flake crystal. (A, b, and c are defined in the text) 7.4 g of polyvinyl alcohol (trade name: PVA-205) and water are added to a wet cake equivalent to 100 g of dry solid content to make the total amount 385 g, and then into a homomixer. And pre-dispersed.

Next, the pre-dispersed undiluted solution was adjusted to a pressure of 1750 kg / cm ² of a disperser (trade name: Microfluidizer M-110S-EH, manufactured by Microfluidics International Corporation, using a G10Z interaction chamber). The silver behenate dispersion was obtained by repeated treatment. The cooling operation was carried out by installing a serpentine heat exchanger before and after the interaction chamber, and adjusting the temperature of the refrigerant to a dispersion temperature of 18 ° C.

<< Preparation of 25% by weight dispersion of reducing agent >>
To 10 kg of a 20 mass% aqueous solution of 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane 10 kg and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203), 16 kg of water was added and mixed well to make a slurry. The slurry is fed with a diaphragm pump, dispersed in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm for 3 hours and 30 minutes, and then added with water for reduction. The concentration of the agent was adjusted to 25% by mass to obtain a reducing agent dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.42 μm and a maximum particle diameter of 2.0 μm or less. The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of 10% by weight dispersion of mercapto compound >>
8.3 kg of water was added to 5 kg of the above-mentioned mercapto compound 4 and 5 kg of a 20% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and mixed well to form a slurry. The slurry was fed with a diaphragm pump and dispersed for 6 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. Then, water was added to add the mercapto compound 4 The concentration of was adjusted to 10% by mass to obtain a mercapto compound dispersion. The mercapto compound 4 particles contained in the dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 2.0 μm or less. The obtained dispersion of mercapto compound was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of Dispersion-1 of 20% by Mass of Organic Polyhalogen Compound >>
Add 5 kg of tribromomethylnaphthylsulfone, 2.5 kg of 20% aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203), 213 g of 20% aqueous solution of sodium triisopropylnaphthalenesulfonate, and 10 kg of water. And mixed well to obtain a slurry. The slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. The concentration of the compound was adjusted to 20% by mass to obtain a dispersion of an organic polyhalogen compound. The organic polyhalogen compound particles contained in the dispersion thus obtained had a median diameter of 0.36 μm and a maximum particle diameter of 2.0 μm or less. The obtained dispersion of organic polyhalogen compound was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

<< Preparation of Dispersion-2 of 20% by Mass of Organic Polyhalogen Compound >>
Similar to 20 mass% dispersion-1 of organic polyhalogen compound, except that 5 kg of tribromomethyl (4- (2,4,6-trimethylsulfonyl) phenyl) sulfone is used instead of 5 kg of tribromomethylnaphthyl sulfone. And filtered. The obtained organic polyhalogen compound particles had a median diameter of 0.38 μm and a maximum particle diameter of 2.0 μm or less.

<< Preparation of 20% by weight dispersion-3 of organic polyhalogen compound >>
Dispersion and filtration were carried out in the same manner as in the 20% by mass dispersion-1 of organic polyhalogen compound except that 5 kg of tribromomethylphenylsulfone was used instead of 5 kg of tribromomethylnaphthylsulfone. The obtained organic polyhalogen compound particles had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less.

<< Preparation of 10 mass% methanol solution of phthalazine compound >>
10 g of 6-isopropylphthalazine was dissolved in 90 g of methanol and used.

<< Preparation of 20% by weight dispersion of pigment >>
C. I. Pigment Blue 60 (64 g) and Kao Corp. Demol N (6.4 g) were added to 250 g of water and mixed well to prepare a slurry. 800 g of zirconia beads having an average diameter of 0.5 mm were prepared, put into a vessel together with the slurry, and dispersed for 25 hours with a disperser (1/4 G sand grinder mill: manufactured by IMEX Co., Ltd.) to obtain a pigment dispersion. The pigment particles contained in the pigment dispersion thus obtained had an average particle size of 0.21 μm.

<< Preparation of 40% by mass of SBR latex >>
The ultrafiltration (UF) purified SBR latex was obtained as follows. The following SBR latex diluted 10 times with distilled water is used until the ionic conductivity becomes 1.5 mS / cm using UF-purification module FS03-FC-FUY03A1 (Daisen Membrane System Co., Ltd.) Diluted and purified was used. The latex concentration at this time was 40% by mass. (SBR latex: Latex of -St (68) -Bu (29) -AA (3)-)

  Average particle size 0.1 μm, concentration 45%, equilibrium moisture content 0.6% by mass at 25 ° C. 60% RH, ion conductivity 4.2 mS / cm (measurement of ion conductivity is conducted by Toa Denpa Kogyo Co., Ltd.) Using a total CM-30S, latex stock solution (40 mass% measured at 25 ° C), pH 8.2

<< Preparation of emulsion layer (photosensitive layer) coating solution >>
1.1 g of the 20% by mass aqueous dispersion of the pigment obtained above, 103 g of the organic acid silver dispersion, 5 g of 20% by mass aqueous solution of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), and 25% by mass reducing agent dispersion 11.5 g of a mixture of 25 g of an organic polyhalogen compound, 20% by weight dispersion-1, -2, -3 of 5: 1: 3 (mass ratio), 3.1 g of a 20% by weight mercapto compound dispersion, 106 g of 40 wt% SBR latex purified by UF filtration and 16 mL of 10 wt% methanol solution of the phthalazine compound were added and 10 g of silver halide mixed emulsion A was mixed well to prepare an emulsion layer coating solution. The solution was fed to the coating die as it was to be 70 mL / m ² and applied.

  The viscosity of the emulsion layer coating solution was 85 [mPa · s] at 40 ° C. (No. 1 rotor) as measured with a B-type viscometer of Tokyo Keiki.

  The viscosity of the coating solution at 25 ° C. using an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd. is 1500, 220, and 70 at shear rates of 0.1, 1, 10, 100, and 1000 [1 / second], respectively. 40 and 20 [mPa · s].

<Preparation of emulsion surface intermediate layer coating solution>
772 g of 10% by weight aqueous solution of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), 0.7 g of 20% by weight dispersion of pigment, methyl methacrylate / styrene / 2-ethylhexyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer ( Copolymerization mass ratio 59/9/26/5/1) 2 mL of 5 wt% aqueous solution of aerosol OT (manufactured by American Cyanamid Co.) was added to 226 g of 27.5 wt% latex solution to make an intermediate layer coating solution. The solution was fed to the coating die so as to be 5 mL / m ² . The viscosity of the coating solution was 21 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor).

<< Preparation of emulsion surface protective layer first layer coating solution >>
64 g of inert gelatin is dissolved in water, 16 g of latex [methyl methacrylate / acrylic acid / N-methylolacrylamide copolymer, copolymer mass ratio 93/3/4], 64 mL of a 10 mass% methanol solution of phthalic acid, 4- 74 mL of a 10% by weight aqueous solution of methylphthalic acid, 28 mL of 1N sulfuric acid, 5 mL of a 5% by weight aqueous solution of aerosol OT (manufactured by American Cyanamid Co., Ltd.), 1 g of phenoxyethanol, and water added to a total amount of 1000 g. The solution was fed to the coating die so as to be 10 mL / m ² . The viscosity of the coating solution was 17 [mPa · s] at 40 ° C. (No. 1 rotor) with a B-type viscometer.

<< Preparation of emulsion surface protective layer second layer coating solution >>
80 g of inert gelatin is dissolved in water, latex [methyl methacrylate / acrylic acid / N-methylolacrylamide copolymer, copolymer mass ratio 93/3/4] 20 g, N-perfluorooctylsulfonyl-N-propylalanine potassium salt 20 mL of a 5% by weight solution of 50 ml of a 2% by weight aqueous solution of polyethylene glycol mono (N-perfluorooctylsulfonyl-N-propyl-2-aminoethyl) ether [ethylene oxide average polymerization degree = 15], Aerosol OT (American 16 mL of a 5% by mass solution of Cyanamide), 25 g of polymethyl methacrylate fine particles (average particle size 4.0 μm), 1.6 g of 4-methylphthalic acid, 8.1 g of phthalic acid, 44 mL of 1N sulfuric acid, benzoisothi The total amount is 1555g to 10mg of Azolinone Yo Water was added, a mixture of 4% by weight chrome alum and static mixer aqueous solution 445mL immediately before coating containing 0.67 wt% of phthalic acid and a surface protective layer coating solution, 10 mL / m ² Then, the solution was fed to the coating die. The viscosity of the coating solution was 9 [mPa · s] at 40 ° C. (No. 1 rotor) with a B-type viscometer.

<< Preparation of photothermographic material >>
On the back surface side of the undercoat support, the antihalation layer coating solution is applied so that the solid coating amount of the solid fine particle dye is 0.04 g / m ^2, and the back surface protection layer coating solution is applied with a gelatin coating amount of 1 g / m ^2. A multilayer was simultaneously applied so as to be m ² and dried to prepare an antihalation back layer.

Slide in order of emulsion layer (photosensitive silver halide coating amount (as silver) 0.15 g / m ² ), intermediate layer, protective layer first layer, protective layer second layer from the undercoat surface to the surface opposite to the back surface By simultaneous multilayer coating by the bead coating method, a medical photothermographic material sample was prepared.

  Coating is performed at a speed of 160 m / min, the distance between the coating die tip and the support is adjusted to 0.18 mm, and the coating width is adjusted so that the width of the coating is expanded by 0.5 mm on both the left and right sides of the coating liquid discharge slit. The chamber pressure was set to 392 Pa lower than the atmospheric pressure. At that time, handling and temperature / humidity were controlled so that the support was not charged. In the subsequent chilling zone, air with a dry bulb temperature of 18 ° C. and a wet bulb temperature of 12 ° C. is blown for 30 seconds to cool the coating solution. After spraying dry air of 30 ° C. and wet bulb temperature of 18 ° C. for 200 seconds, passing through a drying zone of 92 ° C. for 20 seconds (making the surface temperature of the film 85 ° C.), then cooling to 25 ° C. The solvent was volatilized. The average wind speed of the wind sprayed on the coating liquid film surface in the chilling zone and the drying zone was 7 m / sec.

(Evaluation of interference fringes)
After exposing the photosensitive material with a laser sensitometer (detailed below) equipped with a 660 nm diode of the vertical single mode below (exposure amount at which the obtained image density is 1.0), the photosensitive material is heated at 118 ° C. for 5 seconds. Subsequently, the film was processed (heat development) at 122 ° C. for 16 seconds.

Laser sensitometer: Two 660 nm diode lasers with 35 mW output are combined, vertical single mode, Gaussian beam spot 1 / e ² is sent in the sub-scanning direction at a pitch of 100 μm and 25 μm, and one pixel is drawn four times.

  Further, exposure was carried out in the same manner except that a vertical multimode was produced using the high-frequency superposition method described in JP-A-59-130494. The vertical multi-mode has a power of 60% compared to the vertical single mode.

Interference fringe evaluation level ×: Level at which interference fringes are clearly visible (problem).
(Triangle | delta): The level which can be seen lightly (it accepts practically).
○: Invisible level (no problem in practical use).
The evaluation of each sample is shown below.

  According to the present invention, the problem of interference fringes can be solved without performing vertical multimode laser exposure.

Example 2
As in Example 1, except that the emulsion layer was prepared using the following latexes Lb1 and Lc1 (both having an equilibrium water content of less than 2% by mass) instead of SBR latex. It was found that the same effect as Example 1 was obtained.

(Synthesis of Lb1) Glass autoclave (TEM-V1000 manufactured by Pressure Glass Industrial Co., Ltd.), styrene 140 g, distilled water 280 g, surfactant (Sandet BL (manufactured by Sanyo Chemical Co., Ltd.)) 4.44 g, acrylic acid 6 g And stirred for 1 hour under a nitrogen stream. Thereafter, 54 g of 2-ethylhexyl acrylate was added, and the temperature was raised to 70 ° C. Next, 20 g of an aqueous ammonium persulfate solution (5% by mass) was added and stirred as it was for 10 hours. Thereafter, the temperature of the reaction vessel was lowered to room temperature to obtain a styrene-acrylic latex. A 1N aqueous ammonia solution was added to the latex to adjust the pH to 7.5.

  Thus, latex (Lb1) having an average particle size of 98 nm and a concentration of 42% by mass was obtained. The equilibrium water content of the polymer at 25 ° C. and 60% RH was 0.7% by mass.

(Synthesis of Lc1)
A glass autoclave (TEM-V1000 manufactured by Pressure Glass Co., Ltd.) is charged with 126 g of methyl methacrylate, 280 g of distilled water, 8.2 g of a surfactant (Sandet BL (manufactured by Sanyo Chemical Co., Ltd.)), 4 g of acrylic acid, and nitrogen. Stir for 1 hour under air flow. Thereafter, 70 g of ethyl acrylate was added, and the temperature was raised to 60 ° C. Next, 20 g of an aqueous potassium persulfate solution (5% by mass) was added and stirred as it was for 10 hours. Thereafter, the temperature of the reaction vessel was lowered to room temperature to obtain an acrylic latex. A 1N aqueous ammonia solution was added to the latex to adjust the pH to 7.5.

  Thus, latex (Lc1) having an average particle diameter of 101 nm and a concentration of 44% by mass was obtained. The equilibrium water content of the polymer at 25 ° C. and 60% RH was 0.7% by mass.

Claims (8)

A photothermographic material having photosensitive silver halide grains, an organic silver salt, a reducing agent and a binder on a support is imagewise exposed with a laser beam having a single laser light spectrum number, and is visible by heat development. An image forming method for forming an image, wherein the photosensitive silver halide grains have an average particle diameter of 0.0001 μm to 0.2 μm, and a sensitivity expressed by a LogE value of a characteristic curve is 0.2 or more and 1.0 or less. Containing at least two different types of photosensitive silver halide grains in a ratio effective for controlling the gamma value, and the coated silver amount of the photosensitive silver halide is 0.01 g to 1 g per 1 m ^{2 of the} support; An image forming method for forming the visible image in which a gamma value represented by a slope of a tangent at a minimum density (Dmin) +1.0 of a characteristic curve is 2.0 to 3.7.   The image forming method according to claim 1, wherein the laser beam is a red to infrared laser having a maximum wavelength of 600 nm to 900 nm.   The image forming method according to claim 1, wherein the laser beam is a semiconductor laser. The image forming method according to any one of claims 1 to 3, wherein a coated silver amount of the photosensitive silver halide is 0.01 g to 0.4 g per 1 m ^{2 of the} support. 5. The image forming method according to claim 4, wherein the photosensitive silver halide is applied in an amount of 0.01 g to 0.2 g per 1 m ^{2 of the} support.   The image forming method according to any one of claims 1 to 5, wherein an irradiation dye or a pigment is contained in the layer containing the photosensitive silver halide grains.   An antihalation layer is provided on the surface opposite to the surface of the photosensitive layer containing the photosensitive silver halide grains with respect to the support or between the photosensitive layer and the support. The image forming method according to claim 6.   The image forming method according to any one of claims 1 to 7, wherein the photosensitive silver halide grains or the layer containing the photosensitive silver halide grains contains water-soluble iridium.