JP2009080196A - Heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material of high image quality with excellent surface membrane characteristic. <P>SOLUTION: In the heat developable photosensitive material having an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt and a reducing agent and a binder on at least one face of a support, a non-photosensitive layer on the image forming layer surface side of the support, and a non-photosensitive back layer on the other surface thereof, the non-photosensitive back layer contains mat agent, and either layer on the image forming layer surface side contains a hollow particle. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photothermographic material.

  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, the photosensitive heat 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 developed photographic materials. These photosensitive photothermographic materials can eliminate the use of solution processing chemicals and supply customers with a simpler heat development processing system that does not damage the environment.

  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.

  A photothermographic material using an organic silver salt is known. The photothermographic material contains a catalytically active amount of a photocatalyst (eg, silver halide), a reducing agent, a reducible silver salt (eg, an organic silver salt), and, if necessary, a colorant that controls the color tone of silver, and a matrix of binder. It has an image forming layer dispersed therein. 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 area. Fuji Medical Dry Imager FM-DPL was released as a medical image forming system using a photothermographic material.

In photothermographic materials, surface film physical properties are important as well as photographic performance. For example, the photothermographic material is produced by coating and drying on a long roll, winding it, slitting, cutting, and processing into a roll or sheet. In that process, the roll is wound at a high speed. Alternatively, it is unwound and conveyed. Further, in the image forming process, the sheet is conveyed at a high speed or in a roll shape. In order for the photothermographic material to have such transportability, it has been conventionally performed in general for photothermographic materials to provide fine irregularities on the film surface and reduce the contact resistance by reducing the contact area. It was. For example, it is well known to add a matting agent as means for providing irregularities on the surface of the photothermographic material. It is known that polymethyl methacrylate particles are used as the organic polymer matting agent (for example, see Patent Document 1) or inorganic pigment particles such as silica and titanium oxide (for example, see Patent Documents 2 to 4). Yes.
Patent Documents 5 to 7 are known as hollow particles used for improving transportability.
JP 2000-194749 A JP 11-311849 A JP 2000-235242 A JP 2000-298326 A JP 2002-268179 A JP 2005-77794 A JP 2006-349870 A

In recent years, the performance of photothermographic materials has been improved and high-sensitivity and rapid image formation has become possible. In addition, the composition of the material has been able to exhibit a sufficient image density with a small amount of coated silver as compared with the prior art. Under such circumstances, it is still an effective means for improving the transportability of the photothermographic material to provide unevenness by the matting agent on the surface having the image forming layer of the photothermographic material and the back surface. However, it has become clear that it will cause unexpected harm.
Usually, in order to more effectively exhibit the unevenness effect by the matting agent, the amount of the binder in the layer containing the matting agent is used as small as possible with respect to the amount of the matting agent. This is because when the amount of the binder is increased, the matting agent is buried and unevenness is not generated. When the binder ratio is small, the matting agent is more exposed and the matting effect is more exerted. is there. As a result, where the matting agent is present in the coating layer, for example, a spherical polymer mat is functioning as a convex lens, and the matting agent may be detached from the layer during transportation. The part from which the agent is detached becomes the shape of the concave lens. When an image is exposed in such a situation, image unevenness is caused by a convex lens effect or a concave lens effect. Further, it has been found that this image unevenness occurs particularly in a photothermographic material having a reduced amount of coated silver. One reason is that the transparency of the coating film is improved when the amount of silver applied is reduced.
Furthermore, when the amount of coated silver is reduced and the transparency of the coating film is increased, the phenomenon that light reflected and scattered by the matting agent of the non-photosensitive back layer irradiates and irradiates the image forming layer, resulting in image unevenness. Or when a plurality of materials are stacked and applied with a load, the outermost layer on the image forming layer surface side where the matting agent on the non-photosensitive back layer surface side is in contact generates a recess, resulting in a stardust-like image. It was also found that unevenness occurred. These troubles are completely unexpected to be observed for the first time in a region where the coated silver amount is 1.5 g / m ² or less.
In view of the above circumstances, an object of the present invention is to provide a photothermographic material having improved overall performance by improving the above-mentioned adverse effects in a photothermographic material whose surface film properties such as transportability are improved by a matting agent. There is.

The object of the present invention has been achieved by the following photothermographic materials.
<1> An image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder on one surface of the support, and a non-photosensitive surface on the image forming layer side of the support A photothermographic material having a layer and a non-photosensitive back layer on the other side, wherein the non-photosensitive back layer contains a matting agent, and any one layer on the image-forming layer side has hollow particles. A photothermographic material comprising a photothermographic material.
<2> The non-photosensitive outermost layer containing a matting agent having an average particle size of 0.1 μm or more and 10 μm or less is provided on the image forming layer surface side, and the hollow particles are contained between the support and the non-photosensitive outermost layer. The photothermographic material according to <1>, wherein the photothermographic material has at least one layer.
<3> The layer containing the hollow particles is at least one layer selected from the image forming layer or a layer between the image forming layer and the non-photosensitive outermost layer. <1> or <1. 2> a photothermographic material.
<4> The heat development according to <2> or <3>, wherein the image forming layer, the layer containing the hollow particles, and the non-photosensitive outermost layer are formed by aqueous coating. Photosensitive material.
<5> The photothermographic material according to any one of <1> to <4>, wherein the hollow ratio of the hollow particles is 20% to 70%.
<6> The photothermographic material according to any one of <1> to <5>, wherein the hollow particles have a refractive index of 1.0 to 1.3.
<7> The photothermographic material according to any one of <1> to <6>, wherein the hollow particles have a glass transition temperature (Tg) of 30 ° C. or higher and 150 ° C. or lower.
<8> The photothermographic material according to any one of <1> to <7>, wherein the hollow particles are a hollow polymer latex.
<9> The photothermographic material according to any one of <1> to <8>, wherein the coated silver amount is from 0.3 g / m ^{2 to} 1.5 g / m ² .
<10> The photothermographic material according to <9>, wherein the coating silver amount is 0.7 g / m ² or more and 1.2 g / m ² or less.
<11> The photothermographic material according to any one of <1> to <10>, wherein the haze degree of the photothermographic material after heat development is less than 80% before heat development.
<12> The photothermographic material according to any one of <4> to <11>, wherein 50% by mass or more of the binder of the non-photosensitive outermost layer is gelatin.
<13> In any one of <4> to <12>, 50% by mass or more of the binder in the image forming layer is a polymer latex obtained by copolymerizing the monomer represented by the general formula (M). The photothermographic material described:
General formula (M)
CH ₂ = CR ⁰¹ -CR ⁰² = CH ₂
(In the formula, R ⁰¹ and R ⁰² are a group selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group).
<14> The photothermographic material according to <13>, wherein R ⁰¹ and R ⁰² are both hydrogen atoms, or one is a hydrogen atom and the other is a methyl group.

  The present invention can provide a high-quality photothermographic material excellent in surface film characteristics.

  The photothermographic material of the present invention comprises, on one side of a support, an image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder, and the image formation of the support. A photothermographic material having a non-photosensitive layer on the layer side and a non-photosensitive back layer on the other side, wherein the non-photosensitive back layer contains a matting agent having an average particle size of 3 μm or more and 15 μm or less. The non-photosensitive layer on the image forming layer surface side contains hollow particles having an average particle size of 0.1 μm or more and 10 μm or less. Preferably, the image forming layer surface side has a non-photosensitive outermost layer containing a matting agent having an average particle size of 0.1 μm or more and 10 μm or less, and the hollow particles are contained between the support and the non-photosensitive outermost layer. A non-photosensitive layer. The layer containing the hollow particles is at least one layer selected from the image forming layer or a layer between the image forming layer and the non-photosensitive outermost layer.

  The hollow particles in the present invention are present inside the layer and do not have a function as a matting agent. The hollow particles in the present invention function as a micro light scatterer inside the layer and have a function of eliminating exposure unevenness due to a convex or concave lens effect caused by a matting agent during exposure.

  Furthermore, it has a function to eliminate the exposure unevenness as a scatterer at the time of exposure, but has no effect as a scatterer when observing an image after heat development after exposure, and the haze degree of the image is lowered. It is preferable. That is, the haze degree after heat development of the photothermographic material of the present invention is reduced to less than 80% before heat development. The haze degree after heat development is preferably less than 75% before heat development, and more preferably less than 70%.

The hollow particles in the present invention have a unique effect of eliminating exposure unevenness (image unevenness caused thereby) without deteriorating the sharpness and resolution of the image.
In order to exhibit the above effect, the hollow ratio of the hollow particles is preferably 20% or more and 70% or less. Furthermore, it is preferable that the refractive index of a hollow particle is 1.0 or more and 1.3 or less at the point of the light scattering effect. Further, the hollow particles in the present invention do not need a function as a matting agent, and a hollow polymer latex is particularly preferable in terms of further expressing the function as a light scatterer.
In the present invention, the image forming layer, the non-photosensitive layer, and the non-photosensitive outermost layer are layers formed by aqueous coating, and the coating silver amount is 0.3 g / m ² or more and 1.5 g / m ² or less. Furthermore, the effect is particularly exhibited in the photothermographic material having a coated silver amount of 0.7 g / m ² or more and 1.2 g / m ² or less. Preferably, 50% by mass or more of the binder of the non-photosensitive outermost layer is gelatin. Preferably, 50% by mass or more of the binder in the image forming layer is a polymer latex obtained by copolymerizing the monomer represented by the general formula (M).

(Matting agent)
The matting agent used in the non-photosensitive back layer of the present invention preferably has an average particle size of 3 μm or more and 15 μm or less, more preferably 4 μm or more and 13 μm or less, and further preferably 5 μm or more and 10 μm or less.
The second matting agent used in the non-photosensitive outermost layer of the present invention preferably has an average particle size of 0.1 μm to 10 μm, more preferably 0.5 μm to 10 μm, still more preferably 1 μm to 8 μm. is there.
Preferably, the ratio (LB / LA) of the average particle size of the first matting agent (denoted as LA) to the average particle size of the second matting agent (denoted as LB) is 1.3 or more and 5.0. It is as follows. More preferably, the ratio (LB / LA) is 1.4 or more and 4.0 or less.

  The matting agent particles used in the present invention are preferably monodisperse particles, and the size distribution coefficient of variation is preferably 50% or less, more preferably 40% or less, and even more preferably 30% or less. Here, the coefficient of variation is a value represented by (standard deviation of particle size) / (average value of particle size) × 100. It is also preferable to use two types of matting agents having a small variation coefficient and having an average particle size ratio larger than 3.

  The matting agent particles used in the present invention are organic particles or inorganic particles, preferably organic particles, and more preferably a polymer matting agent.

  The matting agent particles used in the present invention are preferably dispersed in advance with a binder and used as a matting agent particle dispersion. Preferably, the binder is gelatin.

1) Polymer matting agent The polymer is preferably a vinyl polymer, for example, those mainly composed of polystyrene, polymethyl acrylate, polymethyl methacrylate, polyacrylonitrile, etc. Preferable examples include styrene-divinylbenzene copolymer and poly (ethylene glycol dimethacrylate co-methyl methacrylate).

These products are also commercially available, and commercially available products can be used.
・ M-1: Polyethylene particles, specific gravity 0.90 (flow beads LE-1080, manufactured by Sumitomo Seika Co., Ltd.)
M-2: Polyethylene particle specific gravity 0.93 (Flow Beads EA-209, manufactured by Sumitomo Seika Co., Ltd.)
・ M-3: Polyethylene particles, specific gravity 0.96 (Flow Beads HE-3040, manufactured by Sumitomo Seika Co., Ltd.)
M-4: Silicone particle specific gravity 0.97
・ M-5: Silicone particles, specific gravity 1.00 (E701, Toray Dow Silicone Co., Ltd.)
M-6: Silicone particle specific gravity 1.03
M-7: Polystyrene particles, specific gravity 1.05 (SB-6 Sekisui Plastics Co., Ltd.)
M-8: poly (St / MAA = 97/3) copolymer particles specific gravity 1.05
M-9: poly (St / MAA = 90/10) copolymer particles specific gravity 1.06
M-10: Poly (St / MMA / MAA = 50/40/10) copolymer particle specific gravity 1.09
M-11: Crosslinked polyethylene particles, specific gravity 0.92.
M-12: Cross-linked polyethylene particles, specific gravity 0.95
M-13: Cross-linked polyethylene particles, specific gravity 0.98
M-14: Cross-linked silicone particles, specific gravity 0.99
M-15: Cross-linked silicone particles, specific gravity 1.02
M-16: Cross-linked silicone particle specific gravity 1.04
M-17: poly (St / DVB = 90/10) particles specific gravity 1.06 (SX-713, manufactured by Soken Chemical Co., Ltd.)
M-18: Poly (St / DVB = 80/20) particle specific gravity 1.06 (SX-713, manufactured by Soken Chemical Co., Ltd.)
M-19: Poly (St / DVB = 70/30) particle specific gravity 1.07 (SX-713, manufactured by Soken Chemical Co., Ltd.)
M-20: Poly (St / MAA / DVB = 87/3/10) copolymer particle specific gravity 1.06 (SX-713α, manufactured by Soken Chemical Co., Ltd.)
M-21: poly (St / MAA / DVB = 80/10/10) copolymer particles specific gravity 1.07 (SX-713α, manufactured by Soken Chemical Co., Ltd.)
M-22: Poly (St / MMA / MAA / DVB = 40/40/10/10) copolymer particle specific gravity 1.10

2) Inorganic particles As examples of inorganic compounds, silicon dioxide, titanium dioxide, magnesium dioxide, aluminum oxide, barium sulfate, calcium carbonate, silver chloride desensitized by a known method, silver bromide, glass, diatomaceous earth, etc. are preferably used. be able to. Different types of substances can be mixed and used as required.

3) Coating amount of matting agent particles The coating amount of matting agent particles in the present invention varies depending on the particle size and size distribution, but is important in determining the surface convexity.
The addition amount of the matting agent particles to the non-photosensitive backing layer is approximately ^{3.0mg / m 2 ~400mg / m 2} , preferably from ^{5.0mg / m 2 ~300mg / m 2} .
The addition amount of the matting agent particles to the non-photosensitive outermost layer is approximately ^{3.0mg / m 2 ~400mg / m 2} , preferably from ^{10mg / m 2 ~200mg / m 2} .

  In the method of dispersing the matting agent particles, an aqueous medium containing a binder is previously present as a dispersion aid in an aqueous solvent, and known high-speed stirring means (for example, a disperser emulsifier, homomixer, turbine mixer, homogenizer). ) Or an ultrasonic emulsifier or the like. In dispersing, in order to suppress foaming, means for dispersing in a reduced pressure state rather than atmospheric pressure can be used in combination. The dispersion aid to be used is generally dissolved in an aqueous medium in advance and then the matting agent particles are generally added. However, in the case of an organic synthetic compound, the matting agent particles were previously obtained by polymerization. It may be added as an aqueous dispersion (without passing through a drying step). The dispersion aid can also be added to the dispersion during dispersion. Moreover, it can also add to a dispersion liquid for stabilization of the physical property after dispersion | distribution. In either case, it is common that a solvent (for example, water / alcohol) coexists. The pH may be controlled with an appropriate pH agent before or after dispersion.

In addition to the mechanical dispersion means, the stability of the dispersed matting agent particles may be increased by controlling the pH. In addition, an extremely small amount of a low boiling point organic solvent may be supplementarily used for 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 the matting agent particles during storage, or stored in a highly viscous state (for example, using gelatin to make a jelly state) with a hydrophilic colloid. You can also. Moreover, it is preferable to add a preservative for the purpose of preventing the propagation of various germs during storage.
The binder is preferably added and dispersed so as to be 5% by mass or more and 300% by mass or less with respect to the matting agent particles. More preferably, it adds so that it may become 10 mass% or more and 200 mass or less.

  Since the dispersion state of the matting agent particle dispersion in the present invention is stabilized when it contains a surfactant, it is preferable to add a surfactant. The surfactant used here is not particularly limited, but is preferably a fluorine compound. Among these, the following specific fluorine compounds are particularly preferable.

(Hollow particles)
The hollow particles used in the present invention will be described in detail.
The hollow particles in the present invention are polymer particles having independent pores inside the particles, preferably polymer latex, for example, 1) water or the like inside the partition formed by polystyrene, acrylic resin, styrene-acrylic resin or the like. Non-foamed hollow polymer particles in which the water inside the particles evaporates to the outside of the particles and the inside of the particles becomes hollow after coating and drying, and 2) a low boiling point liquid such as butane or pentane, Covered with a resin made of vinylidene chloride, polyacrylonitrile, polyacrylic acid, polyacrylic acid ester, or a mixture or polymer thereof, and after coating, the low-boiling liquid inside the particles expands by heating. Micro-balloon that becomes hollow, 3) Microphone made by heating and foaming the above 2) into a hollow polymer Such as a balloon, and the like.

  Among these, the non-foamed hollow polymer particles of 1) are preferable. In the microballoon of 2), it is necessary to foam the microballoon by a method such as heating after forming a heat insulating layer by a coating method, and it becomes difficult to form a smooth surface. 3) Since gas is contained inside the pre-heated and foamed microballoon, it is difficult to prepare a uniform coating solution when manufacturing by a coating method, and it is also difficult to form a smooth surface.

  The method for producing non-foamed hollow polymer particles is not particularly limited. For example, JP-A-56-32513, JP-A-63-213509, JP-A-64-1704, JP-A-3-26724. And the methods described in JP-A-5-279409, JP-A-6-248012, JP-A-10-182761, and the like.

The average particle size of the hollow particles used in the present invention is 0.1 μm to 10.0 μm, preferably 0.2 μm to 5 μm, more preferably 0.3 μm to 2 μm.
If this size is too small, the hollowness tends to decrease and the desired heat-insulating light scattering effect cannot be obtained.If the size is too large, the light scattering effect per unit weight of the hollow particles is reduced and the coating amount is increased in large amounts. Increasing it causes deterioration of film quality. Moreover, since the particle diameter is too large, it becomes difficult to obtain a smooth surface, and a coating failure due to coarse particles tends to occur, which is not preferable.

  The hollow particles preferably have a hollowness of about 20% to 70%, more preferably 20% to 60%. If the hollow ratio is too small, the desired light scattering effect cannot be obtained, and if it is too large, the physical strength of the hollow particles is reduced, and the ratio of fragile hollow particles and incomplete hollow particles increases, resulting in sufficient light scattering effect. Cannot be obtained, and sufficient film strength cannot be obtained.

  In the present invention, the size of the hollow polymer particles is calculated by measuring the equivalent-circle diameter of the outer diameter using a transmission electron microscope. The average particle diameter is obtained by observing at least 300 hollow polymer particles using a transmission electron microscope, calculating the circle equivalent diameter of the outer shape, and averaging.

In order to obtain an excellent light scattering effect, the hollow particles used in the present invention have an important refractive index, preferably 1.0 to 1.3, more preferably 1.0 to 1.25. The refractive index of the hollow particles is determined by the shell material forming the hollow particles, the thickness thereof, and the ratio of the gas components in the internal pores. The higher the hollow ratio, the smaller the refractive index of the hollow particles.
The difference between the refractive index of the hollow particles used in the present invention and the surrounding binder is important, and the larger the difference, the greater the light scattering effect. The hollow particles have a hollow structure, and the pores after coating and drying contain only air or a small amount of moisture, and have a lower refractive index than the polymer material that forms the shell of the intermediate particles. Assuming that the polymer material forming the shell has a refractive index equivalent to that of the surrounding binder, the hollow particles form a region having a lower refractive index than the surrounding. Accordingly, the hollow particles used in the present invention have a larger light scattering effect as the refractive index is smaller.

  The glass transition temperature of the hollow particles used in the present invention is not particularly limited. In some cases, it is preferable that the light scattering effect of the hollow particles disappear after the heat development to make it transparent. In this case, the glass transition temperature of the hollow particles is preferably equal to or lower than the heat development temperature. If the glass transition temperature is too low, hollow polymer particles having a sufficient porosity cannot be obtained after the coating / drying process in the production stage of the photothermographic material. More specifically, the glass transition temperature is preferably 30 ° C. or higher and 150 ° C. or lower, more preferably 30 ° C. or higher and 130 ° C. or lower.

  Two or more types of hollow polymers can be mixed and used as necessary. Specific examples of 1) include Low and Haas Ropaque 1055, Dainippon Ink Boncoat PP-1000, JSR SX866 (B), Nippon Zeon Nipol MH5055 (all trade names), and the like. . Specific examples of 2) include F-30 and F-50 (both trade names) manufactured by Matsumoto Yushi Seiyaku Co., Ltd. Specific examples of 3) include F-30E manufactured by Matsumoto Yushi Seiyaku Co., Ltd., EXPANSEL 461DE, 551DE, and 551DE20 (all trade names) manufactured by Nippon Ferrite Co., Ltd. The hollow polymer used for the heat insulating layer may be made into a latex.

The coating amount of in the hollow particles in the present invention is preferably more preferably ^{1mg / m 2 ~500mg / m 2} 50mg / m 2 ~300mg / m 2.

(Description of non-photosensitive organic silver salt)
1) Composition Non-photosensitive organic silver salt that can be used in the image-forming layer in the present invention (in order to be distinguished from the second non-photosensitive organic silver salt described later in the following description, the first non-photosensitive organic silver salt) Salt)) is relatively stable to light but is silver when heated to 80 ° C. or higher in the presence of exposed photosensitive silver halide and reducing agent. It is a silver salt that functions as an ion supplier and forms a silver image. The organic silver salt may be any organic substance that can supply silver ions that can be reduced by a reducing agent. Regarding such non-photosensitive organic silver salt, paragraph numbers 0048 to 0049 of JP-A-10-62899, page 18 line 24 to page 19 line 37 of European Patent Publication No. 0803764A1, European Patent Publication. No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, and the like. Silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30, preferably 15 to 28 carbon atoms) are preferred. Preferable examples of the fatty acid silver salt include silver lignocerate, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver erucate and the like. Including a mixture of In the present invention, among these fatty acid silvers, the silver behenate content is preferably 50 mol% to 100 mol%, more preferably 85 mol% to 100 mol%, still more preferably 95 mol% to 100 mol%. The following fatty acid silver is preferably used. Furthermore, it is preferable to use fatty acid silver having a silver erucate content of 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0.1 mol% or less.

  Moreover, it is preferable that silver stearate content rate is 1 mol% or less. By making the stearic acid content 1 mol% or less, a silver salt of an organic acid having a low Dmin, high sensitivity and excellent image storage stability can be obtained. As said stearic acid content rate, 0.5 mol% or less is preferable and it is especially preferable not to contain substantially.

  Furthermore, when silver arachidate is included as the silver salt of the organic acid, the silver arachidate content is 6 mol% or less to obtain a low Dmin and an organic acid silver salt excellent in image storability. It is preferable at a point and it is still more preferable that it is 3 mol% or less.

2) Shape The shape of the organic silver salt that can be used in the present invention is not particularly limited, and may be any of a needle shape, a rod shape, a flat plate shape, and a flake shape.
In the present invention, scaly organic silver salts are preferred. Also, short needle-shaped, rectangular parallelepiped, cubic or potato-shaped amorphous particles having a major axis / uniaxial length ratio of 5 or less are preferably used. These organic silver particles have a feature that the fog at the time of heat development is less than that of long needle-like particles in which the ratio of the length of the major axis to the uniaxial axis is 5 or more. In particular, particles having a major axis / uniaxial ratio of 3 or less are preferable because the mechanical stability of the coating film is improved. In the present specification, 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 15 ≧ x (average) ≧ 1.5. 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 0.3 μm or less, and more preferably 0.1 μm or more and 0.23 μm or less. The average c / b is preferably 1 or more and 9 or less, more preferably 1 or more and 6 or less, still more preferably 1 or more and 4 or less, and most preferably 1 or more and 3 or less.

By setting the equivalent sphere diameter to 0.05 μm or more and 1 μm or less, aggregation is hardly caused in the photothermographic material, and image storability is improved. The sphere equivalent diameter is preferably 0.1 μm or more and 1 μm or less. In the present invention, the method for measuring the equivalent sphere diameter is obtained by directly photographing a sample using an electron microscope and then image-processing the negative.
In the flake shaped particles, the spherical equivalent diameter / a of the particles is defined as the aspect ratio. The aspect ratio of the flake shaped particles is preferably 1.1 or more and 30 or less, and preferably 1.1 or more and 15 or less, from the viewpoint of preventing aggregation in the photothermographic material and improving the image storage stability. More preferred.

  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.

3) Preparation Known methods and the like can be applied to the production and dispersion method of the organic acid silver used in the present invention. For example, the above-mentioned JP-A-10-62899, European Patent Publication No. 0803763A1, European Patent Publication No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, JP-A-2001-163889, 2001-163890, 2001-163828, 2001-33907, 2001-188313, 2001-83651, 2002-6442, 2002-49117, 2002-31870, 2002-107868 You can refer to the issue.

  In addition, when the photosensitive silver salt is allowed to coexist at the time of dispersion of the organic silver salt, 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 preferably 1 mol% or less, more preferably 0.1 mol% relative to 1 mol of the organic acid silver salt in the liquid. The following is more preferable, and positive addition of photosensitive silver salt is not performed.

  In the present invention, a photothermographic material can be produced 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. However, the ratio of the photosensitive silver salt to the organic silver salt is preferably in the range of 1 to 30 mol%, more preferably 2 to 20 mol%, and particularly preferably 3 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.

4) Addition Amount organic silver salt in the invention can be used in a desired amount, preferably 0.1g ^{/ m 2} ~5.0g ^/ m 2 as the total amount of coated silver halide silver was also included, and more preferably 0 ^{.3g / m 2 ~3.0g / m 2} , more preferably from ^{0.5g / m 2 ~2.0g / m 2} . In particular, in order to improve image storability, the total coated silver amount is preferably 1.8 g / m ² or less, more preferably 1.6 g / m ² . If the preferred reducing agent of the present invention is used, it is possible to obtain a sufficient image density even with such a low silver amount.

(Second non-photosensitive organic silver salt contained in the non-photosensitive layer)
The second non-photosensitive organic silver salt contained in the non-photosensitive layer in the present invention is preferably a nitrogen-containing heterocyclic silver salt.
The non-photosensitive layer containing these organic silver salts has at least one non-photosensitive layer on the side opposite to the support with respect to the image forming layer. And an intermediate layer between the image forming layer and the like. Any one of these non-photosensitive layers preferably contains an organic silver salt.

The nitrogen-containing heterocyclic silver salt is a silver salt of a nitrogen-containing heterocyclic compound. Examples of the nitrogen-containing heterocyclic compound include azoles, oxazoles, thiazoles, thiazolines, imidazoles, diazoles, pyridines, and indolizines. And triazines, but are not limited thereto. More preferred are indolizines, imidazoles and azoles. Preferred as azoles are triazole, tetrazole, and derivatives thereof. More preferred are benzimidazole and derivatives thereof, and benzotriazole and derivatives thereof. As the indolizines, triazaindolizine derivatives are preferred.
Further, typical nitrogen-containing heterocyclic compounds are listed below, but are not limited to these compounds. For example, 1,2,4-triazole, or benzotriazole and derivatives thereof, benzotriazole, methylbenzotriazole, and 5-chlorobenzotriazole are preferable. Further, 1H-tetrazole compounds such as phenylmercaptotetrazole described in US Pat. No. 4,220,709 (de Mauriac), imidazoles and imidazoles described in US Pat. No. 4,260,677 (Windslow et al.) Derivatives and the like, and benzimidazole and nitrobenzimidazole are preferable. The triazaindolizine derivative is preferably 5-methyl-7-hydroxy-1,3,5-triazaindolizine, but is not limited thereto.

The second non-photosensitive organic silver salt in the present invention is characterized in that the average equivalent circle diameter is in the range of 0.03 μm to 0.5 μm. Preferably they are 0.05 micrometer or more and 0.4 micrometer or less, More preferably, they are 0.08 micrometer or more and 0.3 micrometer or less.
If the average equivalent circle diameter is smaller than 0.03 μm, dissolution and aggregation occur during storage of the dispersion, and coarse particles are formed, making the production unstable, and the desired performance cannot be obtained. On the other hand, if the average equivalent circle diameter is larger than 0.5 μm, the original expected effect of the second non-photosensitive organic silver salt cannot be obtained even if the particle size is stable within the range.

  The organic silver salt particle size can be determined by observing the organic silver salt particles with an electron microscope, converting the projected area into a circle, and determining the equivalent circle diameter.

As means for preparing the average equivalent circle diameter of the second non-photosensitive organic silver salt in the present invention within the scope of the present invention, the preparation conditions of organic silver salt crystals and the dispersion conditions thereof can be used.
<< Crystal Preparation Process of Second Non-Photosensitive Organic Silver Salt >>
The second non-photosensitive organic silver salt crystal in the present invention can be prepared by a usual synthesis method. For example, it is heated and melted in water to a melting point or higher (generally 10 ° C. to 90 ° C.) to prepare a sodium salt using sodium hydroxide, and an aqueous silver nitrate solution is added thereto to precipitate silver salt crystals. Alternatively, if the alkali metal salt has high water solubility, an aqueous solution of sodium salt, potassium salt or lithium salt is prepared using sodium hydroxide, potassium hydroxide or lithium hydroxide. A silver salt crystal may be precipitated by mixing. It is preferable to perform a desalting treatment step if necessary. When preparing crystals, hydrophilic colloids such as gelatin and modified polyvinyl alcohol may coexist. Preferably, it is desirable to adjust the concentration of each drug, the mixing temperature, and the mixing speed to prepare soft structure crystals so that they are finely dispersed in the next dispersion step.

  The particle size of the second non-photosensitive organic silver salt is preferably monodispersed, and in order to make the monodisperse, an alkali metal salt aqueous solution of an organic compound and an aqueous silver nitrate solution are mixed by a simultaneous addition method, and non-photosensitive It is preferable to prepare a functional organic silver salt.

  When adjusting by the simultaneous addition method, the reaction temperature at the time of addition is preferably 30 ° C. or higher and 95 ° C. or lower, more preferably 50 ° C. or higher and 90 ° C. or lower in order to obtain the particle size of the present invention. If the reaction temperature is too low, an organic silver salt having a small particle size is produced, and the stability during storage is impaired, which is not preferable. On the other hand, when the reaction temperature is too high, an organic silver salt having a large particle size is produced, and the expected effect of the present invention cannot be obtained, which is not preferable.

<< Dispersing process >>
In order to obtain a fine dispersion, it is preferable to disperse in a wet slurry state after the preparation of crystals. It is desirable to use an appropriate dispersant for dispersion. As the dispersing means, various dispersing methods described in the explanation of the reducing agent of the present application can be used, and a solid dispersing method is particularly preferable. A specific synthesis method is described in JP-A-1-100197.

The addition amount of the second non-photosensitive organic silver salt contained in the non-photosensitive layer in the present invention is 0.001g ^{/ m 2} ~3g ^/ m 2 as silver amount, preferably 0.005 g / ^{m 2} was ~ 1 g / ^{m 2,} more preferably from ^{0.01g / m 2 ~0.5g / m 2} .
The second non-photosensitive organic silver salt contained in the non-photosensitive layer in the invention is 0.5 mol% or more and 50 mol% with respect to the first non-photosensitive organic silver salt added to the image forming layer. Is more preferable, and more preferably 1 mol% or more and 20 mol%.

(Reducing agent)
The photothermographic material of the present invention preferably contains a heat developer which is a reducing agent for the 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. Examples of such reducing agents are described in JP-A No. 11-65021, paragraphs 0043 to 0045, and European Patent Publication No. 0803764A1, page 7, line 34 to page 18, line 12.
In the present invention, the reducing agent is preferably a so-called hindered phenol-based reducing agent or bisphenol-based reducing agent having a substituent at the ortho position of the phenolic hydroxyl group, and more preferably a compound represented by the following general formula (R).

In the general formula (R), R ¹¹ and R ¹¹ ′ each independently represents an alkyl group having 1 to 20 carbon atoms. R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent that can be substituted on the benzene ring. L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring.

The general formula (R) will be described in detail.
In the following, when referred to as an alkyl group, a cycloalkyl group is also included in this unless otherwise specified.
1) R ¹¹ and R ¹¹ '
R ¹¹ and R ¹¹ ′ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. The substituent of the alkyl group is not particularly limited, but preferably an aryl group, a hydroxy group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acylamino group, a sulfonamido group, a sulfonyl group, a phosphoryl group, Examples include an acyl group, a carbamoyl group, an ester group, a ureido group, a urethane group, and a halogen atom.

2) R ¹² and R ¹² ′, X ¹ and X ¹ ′
R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent capable of substituting for a benzene ring, and X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group capable of substituting for a benzene ring. Preferred examples of the group that can be substituted on the benzene ring include an alkyl group, an aryl group, a halogen atom, an alkoxy group, and an acylamino group.

3) L
L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and the alkyl group may have a substituent. Specific examples of the unsubstituted alkyl group for R ¹³ are methyl group, ethyl group, propyl group, butyl group, heptyl group, undecyl group, isopropyl group, 1-ethylpentyl group, 2,4,4-trimethylpentyl group, cyclohexyl. Group, 2,4-dimethyl-3-cyclohexenyl group, 3,5-dimethyl-3-cyclohexenyl group and the like. Examples of the substituent of the alkyl group are the same as the substituent of R ¹¹ , and are a halogen atom, alkoxy group, alkylthio group, aryloxy group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, oxycarbonyl group, A carbamoyl group, a sulfamoyl group, etc. are mentioned.

4) Preferred substituents R ¹¹ and R ¹¹ ′ are preferably primary, secondary or tertiary alkyl groups having 1 to 15 carbon atoms, specifically methyl, isopropyl, t-butyl, t -Amyl group, t-octyl group, cyclohexyl group, cyclopentyl group, 1-methylcyclohexyl group, 1-methylcyclopropyl group and the like. More preferable R ¹¹ and ^{R 11 'each} represent an alkyl group having 1 to 4 carbon atoms, a methyl group among them, t- butyl group, t-amyl group or 1-methylcyclohexyl group are further preferred, a methyl group, t- A butyl group is most preferred.

R ¹² and R ¹² ′ are preferably an alkyl group having 1 to 20 carbon atoms, specifically, a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a t-butyl group, a t-amyl group, a cyclohexyl group. Group, 1-methylcyclohexyl group, benzyl group, methoxymethyl group, methoxyethyl group and the like. More preferred are a methyl group, an ethyl group, a propyl group, an isopropyl group, or a t-butyl group, and particularly preferred are a methyl group and an ethyl group.
X ¹ and X ¹ ′ are preferably a hydrogen atom, a halogen atom, or an alkyl group, and more preferably a hydrogen atom.

L is preferably a —CHR ¹³ — group.
R ¹³ is preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, and a cyclic alkyl group as well as a chain alkyl group are preferably used as the alkyl group. Moreover, what has a C = C bond in these alkyl groups can also be used preferably. Examples of the alkyl group include a methyl group, ethyl group, propyl group, isopropyl group, 2,4,4-trimethylpentyl group, cyclohexyl group, 2,4-dimethyl-3-cyclohexenyl group, or 3,5-dimethyl-3. -A cyclohexenyl group and the like are preferable. R ¹³ is particularly preferably a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, or a 2,4-dimethyl-3-cyclohexenyl group.

When R ¹¹ and R ¹¹ ′ are tertiary alkyl groups and R ¹² and R ¹² ′ are methyl groups, R ¹³ is a primary or secondary alkyl group having 1 to 8 carbon atoms (methyl group, ethyl group, propyl group). Group, isopropyl group, or 2,4-dimethyl-3-cyclohexenyl group).
When R ¹¹ and R ¹¹ ′ are tertiary alkyl groups and R ¹² and R ¹² ′ are alkyl groups other than methyl groups, R ¹³ is preferably a hydrogen atom.
When R ¹¹ and R ¹¹ ′ are not a tertiary alkyl group, R ¹³ is preferably a hydrogen atom or a secondary alkyl group, and particularly preferably a secondary alkyl group. Preferred groups as the secondary alkyl group for R ¹³ are isopropyl group and 2,4-dimethyl-3-cyclohexenyl group.
The reducing agent has different heat developability, developed silver tone, and the like depending on the combination of R ¹¹ , R ¹¹ ′, R ¹² , R ¹² ′ and R ¹³ . Since these can be prepared by combining two or more reducing agents, it is preferable to use a combination of two or more depending on the purpose.

  Although the specific example of the reducing agent of this invention including the compound represented by general formula (R) of this invention below is shown, this invention is not limited to these.

Examples of preferable reducing agents of the present invention other than the above are the compounds described in JP-A Nos. 2001-188314, 2001-209145, 2001-350235, 2002-156727, and EP1278101A2.
The addition amount of the reducing agent is preferably a ^{0.1g / m 2 ~3.0g / m 2} , more preferably ^{0.2g / m 2 ~2.0g / m 2} , more preferably 0 .3 g / m ^{2 to} 1.0 g / m ² . It is preferably contained in an amount of 5 mol% to 50 mol%, more preferably 8 mol% to 30 mol%, and more preferably 10 mol% to 20 mol%, based on 1 mol of silver on the surface having the image forming layer. More preferably. The reducing agent is preferably contained in the image forming layer.

The reducing agent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form, and may be contained in the photothermographic material.
Well-known emulsification and dispersion methods include oils such as dibutyl phthalate, tricresyl phosphate, dioctyl sebacate or tri (2-ethylhexyl) phosphate, and an auxiliary solvent such as ethyl acetate and cyclohexanone, and dodecylbenzene. Examples thereof include a method of mechanically preparing an emulsified dispersion by adding a surfactant such as sodium sulfonate, oleoyl-N-methyl taurate, sodium di (2-ethylhexyl) sulfosuccinate. At this time, it is also preferable to add a polymer such as α-methylstyrene oligomer or poly (t-butylacrylamide) for the purpose of adjusting the viscosity and refractive index of the oil droplets.

Further, as a solid fine particle dispersion method, a reducing agent powder is dispersed in an appropriate solvent such as water by a ball mill, a colloid mill, a vibration ball mill, a sand mill, a jet mill, a roller mill, or an ultrasonic wave to produce a solid dispersion. A method is mentioned. In this case, a protective colloid (for example, polyvinyl alcohol) or a surfactant (for example, an anionic surfactant such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used. Good. In the mills, beads such as zirconia are usually used as a dispersion medium, and Zr and the like eluted from these beads may be mixed in the dispersion. Although it depends on the dispersion conditions, it is usually in the range of 1 ppm to 1000 ppm. If the Zr content in the light-sensitive material is 0.5 mg or less per 1 g of silver, there is no practical problem.
The aqueous dispersion preferably contains a preservative (for example, benzoisothiazolinone sodium salt).
Particularly preferred is a solid particle dispersion method of a reducing agent, and it is preferable to add fine particles having an average particle size of 0.01 μm to 10 μm, preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 2 μm. In the present application, it is preferable to use other solid dispersions dispersed in a particle size within this range.

(Development accelerator)
In the photothermographic material of the present invention, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, or the like as a development accelerator, Hindered phenol compounds represented by general formula (II) described in JP-A No. 2001-92075, general formula (I) described in JP-A Nos. 10-62895 and 11-15116, A hydrazine-based compound represented by the general formula (D) of JP-A No. 2002-156727 or the general formula (1) described in JP-A No. 2002-278017, and described in the specification of JP-A No. 2001-264929 A phenolic or naphtholic compound represented by the general formula (2) is preferably used. Moreover, the phenol type compound described in Unexamined-Japanese-Patent No. 2002-311533 and Unexamined-Japanese-Patent No. 2002-341484 is also preferable. In particular, naphthol compounds described in JP-A No. 2003-66558 are preferable. These development accelerators are used in the range of 0.1 mol% to 20 mol% with respect to the reducing agent, preferably in the range of 0.5 mol% to 10 mol%, more preferably 1 mol% to 5 mol. % Range. The introduction method to the light-sensitive material includes the same method as the reducing agent, but it is particularly preferable to add as a solid dispersion or an emulsified dispersion. When added as an emulsified dispersion, it is added as an emulsified dispersion dispersed using a high-boiling solvent and a low-boiling auxiliary solvent that are solid at room temperature, or as a so-called oilless emulsified dispersion that does not use a high-boiling solvent. It is preferable to add.
In the present invention, among the above development accelerators, hydrazine compounds described in JP-A Nos. 2002-156727 and 2002-278017 and naphthol-type compounds described in JP-A No. 2003-66558 are used. Is more preferable.

Particularly preferred development accelerators of the present invention are compounds represented by the following general formulas (A-1) and (A-2).
Formula (A-1)
Q ₁ -NHNH-Q ₂
In the formula, Q ₁ represents an aromatic group or a heterocyclic group bonded to —NHNH—Q ₂ at a carbon atom, and Q ₂ represents a carbamoyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group, or Represents a sulfamoyl group.

In the general formula (A-1), the aromatic group or heterocyclic group represented by Q ₁ is preferably a 5- to 7-membered unsaturated ring. Preferred examples include benzene ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, 1,2,4-triazine ring, 1,3,5-triazine ring, pyrrole ring, imidazole ring, pyrazole ring, 1,2 , 3-triazole ring, 1,2,4-triazole ring, tetrazole ring, 1,3,4-thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,3,4 -Oxadiazole ring, 1,2,4-oxadiazole ring, 1,2,5-oxadiazole ring, thiazole ring, oxazole ring, isothiazole ring, isoxazole ring, or thiophene ring are preferable, A condensed ring in which these rings are condensed with each other is also preferable.

  These rings may have a substituent, and when they have two or more substituents, these substituents may be the same or different. Examples of substituents include halogen atoms, alkyl groups, aryl groups, carbonamido groups, alkylsulfonamido groups, arylsulfonamido groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, carbamoyl groups, sulfamoyl groups, cyano Groups, alkylsulfonyl groups, arylsulfonyl groups, alkoxycarbonyl groups, aryloxycarbonyl groups, and acyl groups. When these substituents are substitutable groups, they may further have substituents. Examples of preferred substituents include halogen atoms, alkyl groups, aryl groups, carbonamido groups, alkylsulfonamido groups, aryls. Sulfonamide group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, cyano group, sulfamoyl group, alkylsulfonyl group, arylsulfonyl group, and acyloxy group Can be mentioned.

The carbamoyl group represented by Q ₂ is preferably a carbamoyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms. For example, unsubstituted carbamoyl, methylcarbamoyl, N-ethylcarbamoyl, N-propylcarbamoyl N-sec-butylcarbamoyl, N-octylcarbamoyl, N-cyclohexylcarbamoyl, N-tert-butylcarbamoyl, N-dodecylcarbamoyl, N- (3-dodecyloxypropyl) carbamoyl, N-octadecylcarbamoyl, N- {3 -(2,4-tert-pentylphenoxy) propyl} carbamoyl, N- (2-hexyldecyl) carbamoyl, N-phenylcarbamoyl, N- (4-dodecyloxyphenyl) carbamoyl, N- (2-chloro-5 Dodecyloxycarbo Nylphenyl) carbamoyl, N-naphthylcarbamoyl, N-3-pyridylcarbamoyl, and N-benzylcarbamoyl.

The acyl group represented by Q ₂ is preferably an acyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms. For example, formyl, acetyl, 2-methylpropanoyl, cyclohexylcarbonyl, octanoyl, 2 -Hexyldecanoyl, dodecanoyl, chloroacetyl, trifluoroacetyl, benzoyl, 4-dodecyloxybenzoyl, and 2-hydroxymethylbenzoyl. The alkoxycarbonyl group represented by Q ₂ is preferably an alkoxycarbonyl group having 2 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, isobutyloxycarbonyl, cyclohexyloxycarbonyl, Examples include dodecyloxycarbonyl and benzyloxycarbonyl.

The aryloxycarbonyl group represented by Q ₂ is preferably an aryloxycarbonyl group having 7 to 50 carbon atoms, more preferably 7 to 40 carbon atoms, such as phenoxycarbonyl, 4-octyloxyphenoxycarbonyl, 2-hydroxy Examples include methylphenoxycarbonyl and 4-dodecyloxyphenoxycarbonyl. The sulfonyl group represented by Q ₂ is preferably a sulfonyl group having 1 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as methylsulfonyl, butylsulfonyl, octylsulfonyl, 2-hexadecylsulfonyl, 3- Dodecyloxypropylsulfonyl, 2-octyloxy-5-tert-octylphenylsulfonyl, and 4-dodecyloxyphenylsulfonyl.

The sulfamoyl group represented by Q ₂ is preferably a sulfamoyl group having 0 to 50 carbon atoms, more preferably 6 to 40 carbon atoms, such as an unsubstituted sulfamoyl group, an N-ethylsulfamoyl group, N- (2- Ethylhexyl) sulfamoyl, N-decylsulfamoyl, N-hexadecylsulfamoyl, N- {3- (2-ethylhexyloxy) propyl} sulfamoyl, N- (2-chloro-5-dodecyloxycarbonylphenyl) sulfamoyl, N- (2-tetradecyloxyphenyl) sulfamoyl is mentioned. The group represented by Q ₂ may further have a group listed as an example of the substituent of the 5-membered to 7-membered unsaturated ring represented by Q ₁ at a substitutable position, When it has two or more substituents, these substituents may be the same or different.

Next, a preferable range of the compound represented by formula (A-1) is described. Q ₁ is preferably a 5- to 6-membered unsaturated ring, such as a benzene ring, pyrimidine ring, 1,2,3-triazole ring, 1,2,4-triazole ring, tetrazole ring, 1,3,4-thiadiazole. Ring, 1,2,4-thiadiazole ring, 1,3,4-oxadiazole ring, 1,2,4-oxadiazole ring, thiazole ring, oxazole ring, isothiazole ring, isoxazole ring, and these More preferred are rings in which the ring is fused with a benzene ring or an unsaturated heterocycle. Q ₂ is preferably a carbamoyl group, particularly preferably a carbamoyl group having a hydrogen atom on the nitrogen atom.

In General Formula (A-2), R ₁ represents an alkyl group, an acyl group, an acylamino group, a sulfonamide group, an alkoxycarbonyl group, or a carbamoyl group. R ₂ represents a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acyloxy group, or a carbonate group. R ₃ and R ₄ each represents a group that can be substituted on the benzene ring mentioned in the example of the substituent of formula (A-1). R ₃ and R ₄ may be connected to each other to form a condensed ring.
R ₁ is preferably an alkyl group having 1 to 20 carbon atoms (for example, a methyl group, an ethyl group, an isopropyl group, a butyl group, a tert-octyl group, or a cyclohexyl group), an acylamino group (for example, an acetylamino group, a benzoylamino group). , Methylureido group, 4-cyanophenylureido group, etc.), carbamoyl group (n-butylcarbamoyl group, N, N-diethylcarbamoyl group, phenylcarbamoyl group, 2-chlorophenylcarbamoyl group, 2,4-dichlorophenylcarbamoyl group, etc.) And an acylamino group (including a ureido group and a urethane group) is more preferable. R ₂ is preferably a halogen atom (more preferably a chlorine atom or a bromine atom), an alkoxy group (such as a methoxy group, a butoxy group, an n-hexyloxy group, an n-decyloxy group, a cyclohexyloxy group, or a benzyloxy group), An aryloxy group (such as a phenoxy group or a naphthoxy group);
R ₃ is preferably a hydrogen atom, a halogen atom, or an alkyl group having 1 to 20 carbon atoms, and most preferably a halogen atom. R ₄ is preferably a hydrogen atom, an alkyl group, or an acylamino group, and more preferably an alkyl group or an acylamino group. Examples of these preferable substituents are the same as those for R ₁ . When R ₄ is an acylamino group, R ₄ is preferably linked to R ₃ to form a carbostyryl ring.

In the general formula (A-2), when R ₃ and R ₄ are connected to each other to form a condensed ring, the condensed ring is particularly preferably a naphthalene ring. The same substituent as the example of a substituent quoted by general formula (A-1) may couple | bond with the naphthalene ring. When general formula (A-2) is a naphthol compound, R ₁ is preferably a carbamoyl group. Of these, a benzoyl group is particularly preferable. R ₂ is preferably an alkoxy group or an aryloxy group, and particularly preferably an alkoxy group.

  Hereinafter, preferred specific examples of the development accelerator of the present invention will be given. The present invention is not limited to these.

(Hydrogen bonding compound)
When the reducing agent in the present invention has an aromatic hydroxyl group (—OH) or an amino group (—NHR, R is a hydrogen atom or an alkyl group), particularly in the case of the aforementioned bisphenols, these groups and hydrogen bonds It is preferable to use together a non-reducing compound having a group capable of forming.
Examples of groups that form hydrogen bonds with hydroxyl groups or amino groups include phosphoryl groups, sulfoxide groups, sulfonyl groups, carbonyl groups, amide groups, ester groups, urethane groups, ureido groups, tertiary amino groups, and nitrogen-containing aromatic groups. Is mentioned. Among them, preferred are a phosphoryl group, a sulfoxide group, an amide group (however, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a urethane group. (However, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a ureido group (however, it has no> N—H group,> N-Ra (Ra is a substituent other than H).)
In the present invention, a particularly preferred hydrogen bonding compound is a compound represented by the following general formula (D).

In the general formula (D), R ²¹ to R ²³ each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group or a heterocyclic group, and these groups may be substituted even if they are unsubstituted. You may have.
When R ²¹ to R ²³ have a substituent, the substituent is a halogen atom, alkyl group, aryl group, alkoxy group, amino group, acyl group, acylamino group, alkylthio group, arylthio group, sulfonamide group, acyloxy group, Examples thereof include an oxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, and a phosphoryl group, and a preferable substituent is an alkyl group or an aryl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a t-butyl group. Examples include an octyl group, a phenyl group, a 4-alkoxyphenyl group, and a 4-acyloxyphenyl group.
Specific examples of the alkyl group for R ²¹ to R ²³ include a methyl group, an ethyl group, a butyl group, an octyl group, a dodecyl group, an isopropyl group, a t-butyl group, a t-amyl group, a t-octyl group, a cyclohexyl group, Examples include 1-methylcyclohexyl group, benzyl group, phenethyl group, and 2-phenoxypropyl group.
Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-t-butylphenyl group, a 4-t-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group.
Alkoxy groups include methoxy, ethoxy, butoxy, octyloxy, 2-ethylhexyloxy, 3,5,5-trimethylhexyloxy, dodecyloxy, cyclohexyloxy, 4-methylcyclohexyloxy, and A benzyloxy group etc. are mentioned.
Examples of the aryloxy group include a phenoxy group, a cresyloxy group, an isopropylphenoxy group, a 4-t-butylphenoxy group, a naphthoxy group, and a biphenyloxy group.
Examples of the amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, a dioctylamino group, an N-methyl-N-hexylamino group, a dicyclohexylamino group, a diphenylamino group, and an N-methyl-N-phenylamino group. It is done.

R ²¹ to R ²³ are preferably an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. From the viewpoint of the effect of the present invention, at least one of R ²¹ to R ²³ is preferably an alkyl group or an aryl group, and more preferably two or more are an alkyl group or an aryl group. In addition, it is preferable that R ²¹ to R ²³ are the same group in that they can be obtained at low cost.
Specific examples of the hydrogen bonding compound including the compound of the general formula (D) in the present invention are shown below, but the present invention is not limited thereto.

Specific examples of the hydrogen bonding compound include those described in European Patent No. 1096310, JP-A No. 2002-156727, and JP-A No. 2002-318431 in addition to the above.
The compound of the general formula (D) of the present invention can be used in a photothermographic material by being incorporated in a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersion fine particle dispersion in the same manner as the reducing agent. It is preferably used as a solid dispersion. The compound of the present invention forms a hydrogen-bonding complex with a compound having a phenolic hydroxyl group or an amino group in a solution state, and depending on the combination of the reducing agent and the compound of the general formula (D) of the present invention, It can be isolated in the crystalline state.
The use of the crystal powder isolated in this way as a solid dispersed fine particle dispersion is particularly preferable for obtaining stable performance. Further, a method in which the reducing agent and the compound of the general formula (D) of the present invention are mixed as a powder and complexed at the time of dispersion with a sand grinder mill or the like using an appropriate dispersant can be preferably used.
The compound of the general formula (D) of the present invention is preferably used in the range of 1 mol% to 200 mol%, more preferably in the range of 10 mol% to 150 mol%, still more preferably relative to the reducing agent. It is in the range of 20 mol% to 100 mol%.

(Photosensitive silver halide)
1) Halogen composition The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition, and is silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide, silver iodide. Can be used. Of these, silver bromide, silver iodobromide and silver iodide are preferred. 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, more preferably 2- to 4-fold core / shell particles. A technique for localizing silver bromide or silver iodide on the surface of silver chloride, silver bromide or silver chlorobromide grains can also be preferably used.

2) Grain Forming Methods Methods for forming photosensitive silver halide are well known in the art and are described, for example, in Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458. In particular, a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound into gelatin or another polymer solution, and then mixed with an organic silver salt. Use the method. In addition, the method described in paragraph Nos. 0217 to 0224 of JP-A No. 11-119374, and the methods described in JP-A Nos. 11-352627 and 2000-347335 are also preferable.

3) Grain size The grain size of the photosensitive silver halide is preferably small for the purpose of keeping the cloudiness after image formation low, specifically 0.20 μm or less, more preferably 0.01 μm or more and 0.15 μm or less. More preferably, it is 0.02 μm or more and 0.12 μm or less. The grain size here means the diameter when converted into a circular image having the same area as the projected area of silver halide grains (in the case of tabular grains, the projected area of the main plane).

4) Grain shape Examples of the shape of silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-like grains, and potato-like grains. In the present invention, cubic grains are particularly preferred. Grains with rounded corners of silver halide grains can also be preferably used.
The surface index (Miller index) on the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the {100} plane, which has high spectral sensitizing efficiency when adsorbed by the spectral sensitizing dye, 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 {111} plane and {100} plane in the adsorption of a sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

5) Heavy Metal The photosensitive silver halide grain in the invention may contain a metal or metal complex of Group 6 to Group 13 of the Periodic Table (showing Groups 1 to 18). Preferably it contains a metal or metal complex of Group 6 to Group 10. The metal of Group 6 to Group 10 of the periodic table or the central metal of the metal complex is preferably iron, rhodium, ruthenium, or iridium. 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 preferred content is in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol with respect to 1 mol of silver. These heavy metals and metal complexes and methods for adding them are described in JP-A-7-225449, JP-A-11-65021, paragraphs 0018 to 0024, and JP-A-11-119374, paragraphs 0227 to 0240.

In the present invention, silver halide grains in which a hexacyano metal complex is present on the outermost surface of the grains are preferred. Examples of the hexacyano metal complex include [Fe (CN) ₆ ] ⁴⁻ , [Fe (CN) ₆ ] ³⁻ , [Ru (CN) ₆ ] ⁴⁻ , [Os (CN) ₆ ] ⁴⁻ , [Co ( CN) ₆ ] ³⁻ , [Rh (CN) ₆ ] ³⁻ , [Ir (CN) ₆ ] ³⁻ , [Cr (CN) ₆ ] ³⁻ , and [Re (CN) ₆ ] ^3−. It is done. In the present invention, a hexacyano Fe complex is preferred.

  The hexacyano metal complex is present in the form of ions in aqueous solution, so the counter cation is not important, but it is easy to mix with water and is suitable for precipitation of silver halide emulsions. Sodium ion, potassium ion, rubidium It is preferable to use alkali metal ions such as ions, cesium ions and lithium ions, ammonium ions, alkylammonium ions (for example, tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, or tetra (n-butyl) ammonium ions). .

  In addition to water, the hexacyano metal complex is miscible with a mixed solvent or gelatin with an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters, or amides). Can be added.

The addition amount of the hexacyano metal complex is preferably 1 × 10 ⁻⁵ mol or more and 1 × 10 ⁻² mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻³ mol or less, per mol of silver.

  In order for the hexacyano metal complex to be present on the outermost surface of the silver halide grain, the chalcogen sensitization of sulfur sensitization, selenium sensitization and tellurium sensitization is completed after the addition of the silver nitrate aqueous solution used for grain formation. It is added directly before the completion of the preparation step before the chemical sensitization step for performing noble metal sensitization such as sensitization and gold sensitization, during the washing step, during the dispersion step, or before the chemical sensitization step. In order to prevent the silver halide fine grains from growing, it is preferable to add the hexacyano metal complex immediately after the grain formation, and it is preferable to add it before the completion of the preparation step.

  The addition of the hexacyano metal complex may be started after adding 96% by mass of the total amount of silver nitrate to be added to form grains, more preferably starting after adding 98% by mass, The addition of 99% by mass is particularly preferable.

  When these hexacyanometal complexes are added after the addition of the aqueous silver nitrate solution just before the completion of grain formation, they can be adsorbed on the outermost surface of the silver halide grains, and most of them form slightly soluble salts with silver ions on the grain surface. To do. Since this silver salt of hexacyanoiron (II) is a less soluble salt than AgI, it is possible to prevent re-dissolution by fine particles and to produce silver halide fine particles having a small particle size. .

Further, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a silver salt emulsion desalting method and a chemical sensitization method which can be contained in the silver halide grains used in the present invention, JP-A-11- No. 84574, paragraph numbers 0046 to 0050, JP-A No. 11-65021, paragraph numbers 0025 to 0031, and JP-A No. 11-119374, paragraph numbers 0242 to 0250.

6) Gelatin As the gelatin contained in the photosensitive silver halide emulsion used in the present invention, various gelatins can be used. It is necessary to maintain a good dispersion state of the photosensitive silver halide emulsion in the coating solution containing an organic silver salt, and gelatin having a molecular weight of 10,000 to 1,000,000 is preferably used. It is also preferable to phthalate the gelatin substituent. These gelatins may be used at the time of grain formation or at the time of dispersion after desalting, but are preferably used at the time of grain formation.

7) Sensitizing Dye Sensitizing dyes applicable to the present invention are those that can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed on silver halide grains, and are suitable for the spectral characteristics of the exposure light source. Sensitizing dyes with sensitivity can be advantageously selected. Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A No. 11-65021, compounds represented by formula (II) of JP-A No. 10-186572, and formulas (I of JP-A No. 11-119374) ) And the dye described in Example 5 of U.S. Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59-48753. No. 19, page 38 to line 20, page 35 of European Patent Publication No. 0803764A1, JP 2001-272747, JP 2001-290238, JP 2002-23306, etc. It is described in. These sensitizing dyes may be used alone or in combination of two or more. In the present invention, the time when the sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from desalting to the end of chemical ripening.
The addition amount of the sensitizing dye in the present invention can be set to a desired amount in accordance with sensitivity and fogging performance, but is preferably 10 ⁻⁶ mol to 1 mol per mol of silver halide in the image forming layer, and Preferably it is 10 ^<-4> mol-10 < ^{-1 >} mol.

  In the present invention, a supersensitizer can be used to improve spectral sensitization efficiency. As the supersensitizer used in the present invention, European Patent Publication No. 587,338, US Pat. Nos. 3,877,943, 4,873,184, JP-A-5-341432, 11- 109547, 10-111543, etc. are mentioned.

8) Chemical Sensitization The photosensitive silver halide grain in the present invention is prepared by the conventional sulfur sensitization method, selenium sensitization method or tellurium together with the chemical sensitization by the gold-chalcogen compound of the general formula (I). Chemical sensitization by a sensitization method may be used in combination. As the compound preferably used in the sulfur sensitization method, selenium sensitization method, and tellurium sensitization method, known compounds such as compounds described in JP-A-7-128768 can be used. In the present invention, tellurium sensitization is particularly preferred. The compounds described in the literature described in paragraph No. 0030 of JP-A-11-65021, and the general formulas (II), (III), (IV) described in JP-A-5-313284 The compound shown by is more preferable.

  Or you may use together the chemical sensitization by the gold sensitizing method known conventionally. As the gold sensitizer, the valence of gold is preferably +1 or +3, and the gold sensitizer is preferably a commonly used gold compound. Typical examples include chloroauric acid, bromoauric acid, potassium chloroaurate, potassium bromoaurate, auric trichloride, potassium auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, or pyridyltrichloro. Gold or the like is preferable. Further, gold sensitizers described in US Pat. No. 5,858,637 and JP-A No. 2002-278016 are also preferably used.

In the present invention, chemical sensitization can be performed at any time after particle formation and before coating. After desalting, (1) before spectral sensitization, (2) simultaneously with spectral sensitization, (3) spectral After sensitization, there may be (4) immediately before application.
The amount of sulfur, selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but from 10 ⁻⁸ mol to 10 ⁻² mol per mol of silver halide, Preferably, about 10 ⁻⁷ mol or more and 10 ⁻³ mol or less is used.
The amount of the gold sensitizer added varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol or more and 10 ⁻³ mol or less, more preferably 10 ⁻⁶ mol or more and 5 × 10 ⁻⁴ mol or less per mol of silver halide. It is.
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, and the temperature is about 40 ° C to 95 ° C.
A thiosulfonic acid compound may be added to the silver halide emulsion used in the present invention by the method described in European Patent Publication No. 293,917.

  In the present invention, a reduction sensitizer is preferably used for the photosensitive silver halide grains. As specific compounds for the reduction sensitization, ascorbic acid and aminoiminomethanesulfinic acid are preferable, and in addition, it is preferable to use stannous chloride, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds, and the like. The reduction sensitizer may be added at any stage in the photosensitive emulsion production process from crystal growth to the preparation process immediately before coating. Further, reduction sensitization is preferable by ripening while maintaining the pH of the emulsion at 7 or more or pAg at 8.3 or less, and reduction sensitization is achieved by introducing a single addition portion of silver ions during grain formation. It is also preferable to do.

9) Compound in which 1-electron oxidant produced by 1-electron oxidation can emit 1 electron or more electrons In the photothermographic material of the invention, 1-electron oxidant produced by 1-electron oxidation is 1 electron or It is preferable to contain a compound capable of emitting more electrons. The compound can be used alone or in combination with the above-described various chemical sensitizers, and can increase the sensitivity of silver halide.

The one-electron oxidant produced by one-electron oxidation contained in the photothermographic material of the present invention is a compound selected from the following types 1 and 2 that can emit one or more electrons.
(Type 1)
A compound in which a one-electron oxidant produced by one-electron oxidation can further emit one or more electrons with a subsequent bond cleavage reaction.
(Type 2)
A compound capable of emitting one or more electrons after a one-electron oxidant produced by one-electron oxidation undergoes a subsequent bond formation reaction.

First, the compound of type 1 will be described.
JP-A-9-211769 (specific example: page 28) is a compound of type 1 which can be further released by one-electron oxidant produced by one-electron oxidation with subsequent bond cleavage reaction. Compounds PMT-1 to S-37 described in Table E and Table F on page 32), JP-A-9-211774, JP-A-11-95355 (specific examples: compounds INV1-36), JP 2001-500996 No. (specific examples: compounds 1 to 74, 80 to 87, 92 to 122), US Pat. No. 5,747,235, US Pat. No. 5,747,236, European Patent No. 786692A1 (specific examples: compounds INV 1 to 35) European Patent 893732A1, US Pat. No. 6,054,260, US Pat. No. 5,994,051, etc. Compound called donor sensitizer "and the like. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

  Further, as a compound of type 1 that can be emitted by one-electron oxidant formed by one-electron oxidation and further undergoing bond cleavage reaction, one or more electrons can be emitted from the general formula (1) ( General formula (1) described in JP-A-2003-114487), general formula (2) (synonymous with general formula (2) described in JP-A-2003-114487), general formula (3) General formula (1) described in 2003-114488), general formula (4) (synonymous with general formula (2) described in Japanese Patent Application Laid-Open No. 2003-114488), general formula (5) (Japanese Patent Application Laid-Open No. 2003-114488). 114488 (synonymous with general formula (3)), general formula (6) (synonymous with general formula (1) described in JP-A-2003-75950), and general formula (7) (JP-A-2003-75950). Synonymous with general formula (2) described in , General formula (8) (synonymous with general formula (1) described in JP-A-2004-239934), or chemical reaction formula (1) (synonymous with chemical reaction formula (1) described in JP-A-2004-245929) Among the compounds capable of causing the reaction represented by (), a compound represented by the general formula (9) (synonymous with the general formula (3) described in JP-A-2004-245929) can be given. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the formula, RED ₁ and RED ₂ represent a reducing group. R ₁ represents a non-metallic atomic group capable of forming a cyclic structure corresponding to a tetrahydro form of a 5-membered or 6-membered aromatic ring (including an aromatic heterocycle) or an octahydro form together with the carbon atom (C) and RED _1. To express. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. L ₁ represents a leaving group. ED represents an electron donating group. Z ₁ represents an atomic group capable of forming a 6-membered ring with a nitrogen atom and two carbon atoms of a benzene ring. X ₁ represents a substituent, and m 1 represents an integer of 0 to 3. Z ₂ represents —CR ₁₁ R ₁₂ —, —NR ₁₃ —, or —O—. R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent. R ₁₃ represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. X ₁ represents an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylamino group, an arylamino group, or a heterocyclic amino group. L ₂ represents a carboxy group or a salt thereof, or a hydrogen atom. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

Next, the type 2 compound will be described.
As a compound that can be emitted by one-electron oxidant generated by one-electron oxidation with a type 2 compound and further undergoing a bond formation reaction, one or more electrons can be emitted from the general formula (10) A compound capable of causing a reaction represented by the general formula (1) described in 2003-140287) and the chemical reaction formula (1) (synonymous with the chemical reaction formula (1) described in JP-A-2004-245929). And a compound represented by the general formula (11) (synonymous with the general formula (2) described in JP-A No. 2004-245929). The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the above formula, X represents a reducing group that is one-electron oxidized. Y reacts with a one-electron oxidant produced by one-electron oxidation of X to form a new bond, a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site, or a benzo The reactive group containing the non-aromatic heterocyclic part of a condensed ring is represented. L ₂ represents a linking group for linking X and Y. R ₂ represents a hydrogen atom or a substituent.
When a plurality of R ₂ are present in the same molecule, these may be the same or different.
X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

  Of the compounds of types 1 and 2, “a compound having an adsorptive group to silver halide in the molecule” or “a compound having a partial structure of a spectral sensitizing dye in the molecule” is preferable. Typical examples of the adsorptive group to silver halide include those described in JP-A No. 2003-156823, page 16, right line 1 to page 17, right line 12. The partial structure of the spectral sensitizing dye is a structure described on page 17, right line 34 to page 18, left line 6 of the same specification.

  More preferably, the compound of type 1 or 2 is “a compound having at least one adsorptive group to silver halide in the molecule”. More preferred is “a compound having two or more adsorptive groups to silver halide in the same molecule”. When two or more adsorptive groups are present in a single molecule, these adsorptive groups may be the same or different.

  The adsorptive group is preferably a mercapto-substituted nitrogen-containing heterocyclic group (for example, 2-mercaptothiadiazole group, 3-mercapto-1,2,4-triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4). -Oxadiazole group, 2-mercaptobenzoxazole group, 2-mercaptobenzthiazole group, or 1,5-dimethyl-1,2,4-triazolium-3-thiolate group), or imino silver (> NAg) A nitrogen-containing heterocyclic group having a —NH— group that can be formed as a partial structure of the heterocyclic ring (for example, a benzotriazole group, a benzimidazole group, or an indazole group). Particularly preferred are a 5-mercaptotetrazole group, a 3-mercapto-1,2,4-triazole group, and a benzotriazole group, and most preferred is a 3-mercapto-1,2,4-triazole group, or 5 -Mercaptotetrazole group.

  It is also particularly preferred that the adsorptive group has two or more mercapto groups as a partial structure in the molecule. Here, the mercapto group (—SH) may be a thione group if it can be tautomerized. Preferred examples of the adsorptive group having two or more mercapto groups as a partial structure (such as a dimercapto-substituted nitrogen-containing heterocyclic group) include 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, and 3 , 5-dimercapto-1,2,4-triazole group.

A quaternary salt structure of nitrogen or phosphorus is also preferably used as the adsorptive group. The quaternary salt structure of nitrogen specifically includes an ammonio group (such as a trialkylammonio group, a dialkylaryl (or heteroaryl) ammonio group, an alkyldiaryl (or heteroaryl) ammonio group) or a quaternized nitrogen atom. A group containing a nitrogen-containing heterocyclic group containing The quaternary salt structure of phosphorus includes a phosphonio group (such as a trialkyl phosphonio group, dialkylaryl (or heteroaryl) phosphonio group, alkyldiaryl (or heteroaryl) phosphonio group, triaryl (or heteroaryl) phosphonio group). Is mentioned. More preferably, a quaternary salt structure of nitrogen is used, and more preferably a 5-membered or 6-membered nitrogen-containing aromatic heterocyclic group containing a quaternized nitrogen atom is used. Particularly preferably, a pyridinio group, a quinolinio group, or an isoquinolinio group is used.
These nitrogen-containing heterocyclic groups containing a quaternized nitrogen atom may have an arbitrary substituent.

Examples of quaternary salt counter anions include halogen ions, carboxylate ions, sulfonate ions, sulfate ions, perchlorate ions, carbonate ions, nitrate ions, BF ₄ ⁻ , PF ₆ ⁻ , and Ph ₄ B ^{− and the} like. Can be mentioned. When a group having a negative charge in a carboxylate group or the like is present in the molecule, an inner salt may be formed together with the group. As a counter anion that is not present in the molecule, a chlorine ion, a bromo ion, or a methanesulfonate ion is particularly preferable.

  A preferred structure of the compound represented by type 1 or 2 having a quaternary salt structure of nitrogen or phosphorus as the adsorptive group is represented by the general formula (X).

In general formula (X), P and R each independently represent a quaternary salt structure of nitrogen or phosphorus that is not a partial structure of a sensitizing dye. Q ₁ and Q ₂ each independently represent a linking group, specifically a single bond, an alkylene group, an arylene group, a heterocyclic group, —O—, —S—, —NR _N —, —C (═O ) —, —SO ₂ —, —SO—, —P (═O) — each independently or a combination of these groups. Here, _RN represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. S is a residue obtained by removing one atom from a compound represented by type (1) or (2). i and j are integers of 1 or more, and i + j is selected from the range of 2-6. Preferably, i is 1 to 3, and j is 1 to 2, more preferably i is 1 or 2, and j is 1, and particularly preferably i is 1 and j is 1. The compound represented by the general formula (X) preferably has a total carbon number of 10 to 100. More preferably, it is 10-70, More preferably, it is 11-60, Most preferably, it is 12-50.

  The type 1 and type 2 compounds of the present invention may be used at any time during the preparation of the photosensitive silver halide emulsion and during the process of producing the photothermographic material. For example, at the time of photosensitive silver halide grain formation, desalting step, chemical sensitization, before coating. Moreover, it can also add in several steps in these processes. The addition position is preferably from the end of formation of the photosensitive silver halide grains to before the desalting step, at the time of chemical sensitization (immediately after the start of chemical sensitization to immediately after completion), and before application, more preferably from the time of chemical sensitization. Until before mixing with the non-photosensitive organic silver salt.

  The compounds of type 1 and type 2 of the present invention are preferably added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. When the compound is dissolved in water, the compound having higher solubility when the pH is increased or decreased may be dissolved at a higher or lower pH and added.

The compounds of type 1 and type 2 of the present invention are preferably used in an image forming layer containing photosensitive silver halide and non-photosensitive organic silver salt, but photosensitive silver halide and non-photosensitive organic silver salt It may be added to the protective layer or intermediate layer together with the image forming layer containing, and diffused during coating.
The timing of addition of the compound of the present invention is preferably 1 × 10 ⁻⁹ mol to 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁸ mol, per mol of silver halide, regardless of before and after the sensitizing dye. It is contained in a silver halide emulsion layer (image forming layer) at a ratio of ˜5 × 10 ⁻² mol.

10) Compound having an adsorbing group and a reducing group In the present invention, an adsorbing redox compound having an adsorbing group and a reducing group for silver halide is preferably contained in the molecule. The adsorptive redox compound is preferably a compound represented by the following formula (Rd).

Formula (Rd) A- (W) n-B
In formula (Rd), A represents a group that can be adsorbed to silver halide (hereinafter referred to as an adsorbing group), W represents a divalent linking group, n represents 0 or 1, and B represents a reducing group. To express.

  In the formula (Rd), the adsorptive group represented by A is a group that directly adsorbs to silver halide or a group that promotes adsorption to silver halide. Specifically, a mercapto group (or a salt thereof) , A thione group (—C (═S) —), a heterocyclic group, a sulfide group, a disulfide group, a cationic group, or an ethynyl group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom, and a tellurium atom Etc.

The mercapto group (or salt thereof) as the adsorptive group means the mercapto group (or salt thereof) itself, and more preferably, a heterocyclic group or aryl group substituted with at least one mercapto group (or salt thereof) or Represents an alkyl group. Here, the heterocyclic group means at least a 5- to 7-membered monocyclic or condensed aromatic or non-aromatic heterocyclic group, such as an imidazole ring group, a thiazole ring group, an oxazole ring group, or a benzimidazole ring. Group, benzothiazole ring group, benzoxazole ring group, triazole ring group, thiadiazole ring group, oxadiazole ring group, tetrazole ring group, purine ring group, pyridine ring group, quinoline ring group, isoquinoline ring group, pyrimidine ring group, And triazine ring group. Moreover, the heterocyclic group containing the quaternized nitrogen atom may be sufficient, and in this case, the substituted mercapto group may dissociate and it may become a meso ion. When the mercapto group forms a salt, the counter ions include alkali metal, alkaline earth metal, heavy metal and other cations (such as Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ag ⁺ , or Zn ²⁺ ), ammonium ions, Examples thereof include a heterocyclic group containing a quaternized nitrogen atom, and a phosphonium ion.

Further, the mercapto group as the adsorptive group may be tautomerized into a thione group.
The thione group as an adsorptive group includes a chain or cyclic thioamide group, thioureido group, thiourethane group, or dithiocarbamate group.

  A heterocyclic group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom and a tellurium atom as an adsorptive group is a -NH- group capable of forming imino silver (> NAg) as a partial structure of the heterocyclic ring. A nitrogen-containing heterocyclic group having a heterocyclic ring, or a "-S-" group, a "-Se-" group, a "-Te-" group or a "= N-" group capable of coordinating to a silver ion by a coordination bond A heterocyclic group having a partial structure of benzotriazole group, triazole group, indazole group, pyrazole group, tetrazole group, benzimidazole group, imidazole group, purine group, etc. , Thiazole group, oxazole group, benzothiophene group, benzothiazole group, benzoxazole group, thiadiazole group, oxadiazo Group, a triazine group, seleno azole group, benzoselenazole group, tellurium azole group, and the like benzo tellurium azole group.

  Examples of the sulfide group or disulfide group as the adsorbing group include all groups having a partial structure of “—S—” or “—S—S—”.

The cationic group as the adsorptive group means a group containing a quaternized nitrogen atom, specifically, an ammonio group or a group containing a nitrogen-containing heterocyclic group containing a quaternized nitrogen atom. Examples of the nitrogen-containing heterocyclic group containing a quaternized nitrogen atom include a pyridinio group, a quinolinio group, an isoquinolinio group, and an imidazolio group.
An ethynyl group as an adsorbing group means a —C≡CH group, and the hydrogen atom may be substituted.
The adsorbing group may have an arbitrary substituent.

  Further, specific examples of the adsorbing group include those described in the specifications p4 to p7 of JP-A No. 11-95355.

  In the formula (Rd), preferred as the adsorptive group represented by A is a mercapto-substituted heterocyclic group (for example, 2-mercaptothiadiazole group, 2-mercapto-5-aminothiadiazole group, 3-mercapto-1,2,4). -Triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4-oxadiazole group, 2-mercaptobenzimidazole group, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, 3,5-dimercapto-1,2,4-triazole group, 2,5-dimercapto-1,3-thiazole group), or Nitrogen-containing heterocyclic groups having —NH— groups that can form imino silver (> NAg) as a partial structure of the heterocyclic ring (for example, benzotri A tetrazole group, a benzimidazole group, or an indazole group, etc.), more preferable as an adsorptive group is a 2-mercaptobenzimidazole group, a 3,5-dimercapto-1,2,4-triazole group.

In formula (Rd), W represents a divalent linking group. Any linking group may be used as long as it does not adversely affect photographic properties. For example, a divalent linking group composed of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom can be used. Specifically, an alkylene group having 1 to 20 carbon atoms (for example, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, or a hexamethylene group), an alkenylene group having 2 to 20 carbon atoms, and an alkynylene having 2 to 20 carbon atoms. Group, an arylene group having 6 to 20 carbon atoms (eg, phenylene group, naphthylene group, etc.), —CO—, —SO ₂ —, —O—, —S—, —NR ₁ —, a combination of these linking groups, and the like. can give.
Here, R ₁ represents a hydrogen atom, an alkyl group, a heterocyclic group, or an aryl group.
The linking group represented by W may have an arbitrary substituent.

  In the formula (Rd), the reducing group represented by B represents a group capable of reducing silver ions, for example, a triple bond group such as formyl group, amino group, acetylene group or propargyl group, mercapto group, hydroxylamines. Hydroxamic acids, hydroxyureas, hydroxyurethanes, hydroxysemicarbazides, reductones (including reductone derivatives), anilines, phenols (chroman-6-ols, 2,3-dihydrobenzofuran-5-ols, Aminophenols, sulfonamidophenols, and hydroquinones, catechols, resorcinols, benzenetriols, polyphenols such as bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. Removed one Group, and the like. Of course, these may have an arbitrary substituent.

  In the formula (Rd), the reducing group represented by B indicates its oxidation potential, Akira Fujishima “Electrochemical Measurement Method” (pages 150-208, published by Gihodo Publishing) and the Chemical Society of Japan, “Experimental Chemistry Course” 4th edition. It can be measured using the measurement method described in (Vol. 9, pages 282 to 344, Maruzen). For example, by rotating disk voltammetry, specifically, a sample is dissolved in a solution of methanol: pH 6.5, Briton-Robinson buffer (Britton-Robinson buffer) = 10%: 90% (volume%), and nitrogen is added for 10 minutes. After aeration of gas, a rotating disc electrode (RDE) made of glassy carbon is used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, 25 ° C., 1000 rev / min, 20 mV / sec. It can be measured at the sweep speed. A half-wave potential (E1 / 2) can be obtained from the obtained voltammogram.

  The reducing group represented by B of the present invention preferably has an oxidation potential in the range of about -0.3 V to about 1.0 V when measured by the above-described measurement method. More preferably, it is in the range of about -0.1V to about 0.8V, and particularly preferably in the range of about 0V to about 0.7V.

  In the formula (Rd), the reducing group represented by B is preferably selected from hydroxylamines, hydroxamic acids, hydroxyureas, hydroxysemicarbazides, reductones, phenols, acylhydrazines, carbamoylhydrazines, and 3-pyrazolidones. A residue obtained by removing one hydrogen atom.

  The compound of the formula (Rd) of the present invention may be one in which a ballast group or polymer chain commonly used in an immobile photographic additive such as a coupler is incorporated. Examples of the polymer include those described in JP-A-1-100530.

  The compound of the formula (Rd) of the present invention may be a bis form or a tris form. The molecular weight of the compound of formula (I) of the present invention is preferably between 100 and 10,000, more preferably between 120 and 1000, particularly preferably between 150 and 500.

  Examples of the compound of the formula (Rd) of the present invention are shown below, but the present invention is not limited thereto.

  Furthermore, specific compounds 1 to 30 and 1 ″ -1 to 1 ″ -77 described in European Patent No. 1308776A2 p73 to p87 are also preferable examples of the compound having an adsorbing group and a reducing group of the present invention.

  The compounds of the present invention can be easily synthesized according to known methods. As the compound of the formula (Rd) of the present invention, one kind of compound may be used alone, but it is also preferred to use two or more kinds of compounds at the same time. When two or more kinds of compounds are used, they may be added in the same layer or in different layers, and the addition method may be different.

The compound of the formula (Rd) of the present invention is preferably added to the silver halide emulsion layer (image forming layer), and more preferably added during preparation of the emulsion. When added at the time of emulsion preparation, it can be added at any time during the process. For example, silver halide grain formation process, before the start of desalting process, desalting process, chemical ripening Examples include a step before starting, a chemical ripening step, and a step before preparing a finished emulsion. Moreover, it can also be added in several steps in these processes. Although it is preferably used for the image forming layer, it may be added to the adjacent protective layer or intermediate layer together with the image forming layer and diffused during coating.
The preferred addition amount largely depends on the above-mentioned addition method and the kind of compound to be added, but generally 1 × 10 ⁻⁶ mol to 1 mol, preferably 1 × 10 ⁻⁵ mol to 1 mol of photosensitive silver halide. 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁴ mol to 1 × 10 ⁻¹ mol.

  The compound of the formula (Rd) of the present invention can be added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. At this time, the pH may be appropriately adjusted with an acid or a base, and a surfactant may be allowed to coexist. Furthermore, it can also be dissolved in a high boiling point organic solvent and added as an emulsified dispersion. It can also be added as a solid dispersion.

11) Two or more silver halides used in combination The photosensitive silver halide emulsion in the photothermographic material used in the invention may be only one type, or two or more types (for example, those having different average grain sizes or different halogen compositions). , Different crystal habits, and different chemical sensitization conditions) may be used in combination. The gradation can be adjusted by using a plurality of photosensitive silver halides having different sensitivities. Examples of these technologies include JP-A-57-119341, JP-A-53-106125, JP-A-47-3929, JP-A-48-55730, JP-A-46-5187, JP-A-50-73627, and JP-A-57-150841. Can be mentioned. The sensitivity difference is preferably 0.2 log E or more for each emulsion.

12) Coating amount The addition amount of the photosensitive silver halide is preferably 0.03 g / m ² or more and 0.6 g / m ² or less, expressed as the coating silver amount per 1 m ² of the light-sensitive material, and 0.05 g. / M ² or more and 0.4 g / m ² or less is more preferable, and 0.07 g / m ² or more and 0.3 g / m ² or less is most preferable. The functional silver halide is preferably from 0.01 mol to 0.5 mol, more preferably from 0.02 mol to 0.3 mol, and still more preferably from 0.03 mol to 0.2 mol.

13) Mixing of photosensitive silver halide and organic silver salt Regarding the mixing method and mixing conditions of separately prepared photosensitive silver halide and organic silver salt, the silver halide grains and the organic silver salt that were prepared are respectively stirred at high speed. Prepare an organic silver salt by mixing with a machine, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc., or mixing photosensitive silver halide that has been prepared at any time during the preparation of the organic silver salt However, there is no particular limitation as long as the effects of the present invention are sufficiently exhibited. In addition, mixing two or more organic silver salt aqueous dispersions and two or more photosensitive silver salt aqueous dispersions when mixing is a preferred method for adjusting photographic characteristics.

14) Mixing of silver halide into coating solution The preferred addition time of silver halide into the image forming layer coating solution is from 180 minutes before application, preferably from 60 minutes to 10 seconds before application. The method and mixing conditions are not particularly limited as long as the effects of the present invention are sufficiently exhibited. 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. Harnby, M.M. F. Edwards, A.D. W. There is a method of using a static mixer described in Chapter 8 of Nienow's Koji Takahashi's “Liquid mixing technology” (published by Nikkan Kogyo Shimbun, 1989).

(Binder for image forming layer)
As the binder for the image forming layer in the present invention, any polymer may be used. Suitable binders are transparent or translucent and generally colorless, and are natural resins, polymers and copolymers, synthetic resins, polymers and copolymers, and other films. Forming media such as gelatins, rubbers, poly (vinyl alcohol) s, hydroxyethyl celluloses, cellulose acetates, cellulose acetate butyrates, poly (vinyl pyrrolidone) s, casein, starch, poly (acrylic acid) , Poly (methyl methacrylic acid) s, poly (vinyl chloride) s, poly (methacrylic acid) s, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, Poly (vinyl acetal) s (for example, poly (vinyl acetal) (Formal) and poly (vinyl butyral)), poly (esters), poly (urethane) s, phenoxy resins, poly (vinylidene chloride) s, poly (epoxides), poly (carbonates), poly (vinyl acetate) s , Poly (olefin) s, cellulose esters, and poly (amides). The binder may be formed from water, an organic solvent or an emulsion.

  In the present invention, the glass transition temperature of the binder that can be used in combination with the layer containing the organic silver salt is preferably 0 ° C. or higher and 80 ° C. or lower (hereinafter sometimes referred to as a high Tg binder), and preferably 10 ° C. to 70 ° C. Is more preferable, and it is still more preferable that it is 15 to 60 degreeC.

In this specification, Tg was calculated by the following formula.
1 / Tg = Σ (Xi / Tgi)
Here, it is assumed that n monomer components from i = 1 to n are copolymerized in the polymer. Xi is the mass fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n. In addition, the value (Tgi) of the homopolymer glass transition temperature of each monomer employ | adopted the value of Polymer Handbook (3rd Edition) (J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

  Two or more binders may be used in combination as required. Further, a glass transition temperature of 20 ° C. or higher and a glass transition temperature of less than 20 ° C. may be used in combination. When two or more types of polymers having different Tg are blended, the mass average Tg is preferably within the above range.

In the present invention, it is preferable that the image forming layer is coated and dried using a coating solution in which 30% by mass or more of the solvent is water to form a film.
In the present invention, when 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 binder of the image forming layer is further added to an aqueous solvent (aqueous solvent). When it is soluble or dispersible, the performance is improved particularly when it is made of a latex of a polymer having an equilibrium water content of 2% by mass or less at 25 ° C. and 60% RH. 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 purifying 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 and 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 moisture 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 water content at 25 ° C. and 60% RH of the binder polymer in 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 still more preferably 0.02%. Desirably, the content is from 1% to 1% by mass.

  In the present invention, a polymer dispersible in an aqueous solvent is particularly preferred. Examples of the dispersed state may be either latex in which fine particles of water-insoluble hydrophobic polymer are dispersed or polymer molecules dispersed in a molecular state or forming micelles. preferable. The average particle size of the dispersed particles is 1 nm or more and 50000 nm or less, preferably 5 nm or more and 1000 nm or less, more preferably 10 nm or more and 500 nm or less, and further preferably 50 nm or more and 200 nm or less. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution. Mixing two or more types having a monodispersed particle size distribution is also a preferable method for controlling the physical properties of the coating solution.

  In the present invention, preferred embodiments of the polymer that can be dispersed in an aqueous solvent include acrylic polymers, poly (esters), rubbers (eg, SBR resin), poly (urethanes), poly (vinyl chloride) s, poly (acetic acid). Hydrophobic polymers such as vinyl), poly (vinylidene chloride) and poly (olefin) can be preferably used. These polymers may be linear polymers, branched polymers, crosslinked polymers, so-called homopolymers obtained by polymerizing a single monomer, or copolymers obtained by polymerizing two or more types of monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of these polymers 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 image forming layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable. A crosslinkable polymer latex is particularly preferably used.

<Specific examples of latex>
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. When a polyfunctional monomer was used, the concept of molecular weight was not applicable because a crosslinked structure was formed, so it was described as crosslinkability, and the description of molecular weight was omitted. Tg represents the glass transition temperature.

-P-1; latex of -MMA (70) -EA (27) -MAA (3)-(molecular weight 37000, Tg 61 ° C.)
-Latex of P-2; -MMA (70) -2EHA (20) -St (5) -AA (5)-(molecular weight 40000, Tg 59 ° C.)
-P-3; Latex of -St (50) -Bu (47) -MAA (3)-(crosslinkability, Tg-17 ° C)
-P-4; Latex of -St (68) -Bu (29) -AA (3)-(crosslinkability, Tg 17 ° C)
-P-5; Latex of -St (71) -Bu (26) -AA (3)-(crosslinkability, Tg 24 ° C)
-P-6; -St (70) -Bu (27) -IA (3)-latex (crosslinkable)
-P-7; Latex of -St (75) -Bu (24) -AA (1)-(crosslinkability, Tg 29 ° C.)
-P-8; Latex (crosslinkability) of -St (60) -Bu (35) -DVB (3) -MAA (2)-
-Latex (crosslinkable) of P-9; -St (70) -Bu (25) -DVB (2) -AA (3)-
-Latex (molecular weight 80000) of P-10; -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-
-Latex of P-11; -VDC (85) -MMA (5) -EA (5) -MAA (5)-(molecular weight 67000)
-P-12; -Et (90) -MAA (10)-latex (molecular weight 12000)
-P-13; -St (70) -2EHA (27) -AA (3) latex (molecular weight 130000, Tg 43 ° C)
-P-14; latex of MMA (63) -EA (35) -AA (2) (molecular weight 33000, Tg 47 ° C.)
-P-15; Latex of -St (70.5) -Bu (26.5) -AA (3)-(crosslinkability, Tg 23 ° C.)
-P-16; Latex of -St (69.5) -Bu (27.5) -AA (3)-(crosslinkability, Tg 20.5 ° C)
・ P-17; Latex of -St (61.3) -isoprene (35.5) -AA (3)-(crosslinkability, Tg17 ° C)
-P-18; Latex of -St (67) -isoprene (28) -Bu (2) -AA (3)-(crosslinkability, Tg 27 ° C.)

  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 the acrylic polymer include Sebian A-4635, 4718, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.), etc. Examples of poly (esters) include poly (urethane) such as FINETEX ES650, 611, 675, 850 (above, manufactured by Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (above, manufactured by Eastman Chemical). Examples of rubbers include HYDRAN AP10, 20, 30, 40 (manufactured by Dainippon Ink Chemical Co., Ltd.), and examples of rubbers include LACSTAR 7310K, 3307B, 4700H, 7132C (above, Dainippon Ink Chemical Co., Ltd.). (Made by Co., Ltd.), Nipol Lx416, 410, 438C, 2507 (above, Nippon Zeo) As examples of poly (vinyl chloride) such as G351 and G576 (above, manufactured by Nippon Zeon Co., Ltd.), examples of poly (vinylidene chloride) such as L502, L513 (above Examples of poly (olefin) s such as Asahi Kasei Kogyo Co., Ltd. include Chemipearl S120 and SA100 (above Mitsui Petrochemical Co., Ltd.).

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

<Preferred latex>
As the polymer latex used in the present invention, a polymer latex having a monomer component represented by the general formula (M) described as a binder for an intermediate layer described later is preferable, and a styrene-butadiene copolymer or styrene is particularly preferable. -Isoprene copolymer latex. 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. Moreover, it is preferable that the polymer latex in this invention contains acrylic acid or methacrylic acid 1-6 mass% with respect to the sum of styrene and butadiene, More preferably, it contains 2 mass%-5 mass%. The polymer latex in the present invention preferably contains acrylic acid. The preferable range of the monomer content is the same as described above. The copolymer ratio in the styrene-isoprene copolymer is the same as that in the styrene-butadiene copolymer.

  Examples of latexes of styrene-butadiene acid copolymer that are preferably used in the present invention include the aforementioned P-3 to P-9,15, commercially available products LACSTAR-3307B, 7132C, Nipol Lx416, and the like. Examples of the styrene-isoprene copolymer include the aforementioned P-16 and 17.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose may be added to the image forming layer of the photothermographic material of the 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 image forming layer.

  The organic silver salt-containing layer (that is, the image forming layer) in the present invention is preferably formed using a polymer latex. The amount of binder in the image forming layer is such that the total binder / organic silver salt mass ratio is 1/10 to 10/1, more preferably 1/3 to 5/1, and still more preferably 1/1 to 3/1. Range.

  Further, such an organic silver salt-containing layer is usually a photosensitive layer (image forming layer) containing a photosensitive silver halide that is a photosensitive silver salt. The mass ratio of silver halide is 400-5, more preferably 200-10.

The total binder amount of the image forming layer in the present invention is preferably 0.2 g / m ² or more and 30 g / m ² or less, more preferably 1 g / m ² or more and 15 g / m ² or less, and further preferably 2 g / m ² or more and 10 g. / M ² or less. In the image forming layer of the present invention, a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like may be added.

(Preferable solvent for coating solution)
In the present invention, the solvent of the image forming layer coating solution of the photothermographic material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is preferably 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%).

(Description of antifogging agent)
Antifogging agents, stabilizers and stabilizer precursors that can be used in the present invention are paragraph No. 0070 of JP-A No. 10-62899, European Patent Publication No. 0803764A, page 20, line 57 to page 21, line 7. And the compounds described in JP-A-9-281737 and JP-A-9-329864, and the compounds described in US Pat. No. 6,083,681 and European Patent 1048875.

1) Description of Organic Polyhalogen Compound Hereinafter, preferred organic polyhalogen compounds that can be used in the present invention will be specifically described. A preferred polyhalogen compound in the present invention is a compound represented by the following general formula (H).
General formula (H)
Q- (Y) n-C (Z ₁ ) (Z ₂ ) X
In general formula (H), Q represents an alkyl group, an aryl group, or a heterocyclic group, Y represents a divalent linking group, n represents 0 to ₁ , Z ₁ and Z ₂ represent a halogen atom, X represents a hydrogen atom or an electron withdrawing group.
In the general formula (H), Q is preferably an alkyl group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, or a heterocyclic group containing at least one nitrogen atom (pyridine, quinoline group, etc.).
In the general formula (H), when Q is an aryl group, Q preferably represents a phenyl group substituted with an electron-attracting group having a positive Hammett's substituent constant σp. For Hammett's substituent constants, see Journal of Medicinal Chemistry, 1973, Vol. 16, no. 11, 1207-1216 etc. can be referred to.
Examples of such an electron withdrawing group include a halogen atom, an alkyl group substituted with an electron withdrawing group, an aryl group substituted with an electron withdrawing group, a heterocyclic group, an alkyl or arylsulfonyl group, acyl Group, alkoxycarbonyl group, carbamoyl group, sulfamoyl group and the like. Particularly preferred as the electron withdrawing group are a halogen atom, a carbamoyl group and an arylsulfonyl group, and a carbamoyl group is particularly preferred.
X is preferably an electron withdrawing group. Preferred electron withdrawing groups are halogen atoms, aliphatic / aryl or heterocyclic sulfonyl groups, aliphatic / aryl or heterocyclic acyl groups, aliphatic / aryl or heterocyclic oxycarbonyl groups, carbamoyl groups, sulfamoyl groups, More preferred are a halogen atom and a carbamoyl group, and particularly preferred is a bromine atom.
Z ₁ and Z ₂ are preferably a bromine atom or an iodine atom, more preferably a bromine atom.
Y preferably represents _{-C (= O) -, -} SO -, - SO 2 -, - C (= O) N (R) -, - SO 2 N (R) - , more preferably -C ( ═O) —, —SO ₂ —, —C (═O) N (R) —, and particularly preferably —SO ₂ —, —C (═O) N (R) —. R here represents a hydrogen atom, an aryl group or an alkyl group, more preferably a hydrogen atom or an alkyl group, and particularly preferably a hydrogen atom.
n represents 0 or 1, and is preferably 1.
In general formula (H), when Q is an alkyl group, preferred Y is —C (═O) N (R) —, and when Q is an aryl group or a heterocyclic group, preferred Y is —SO ₂ —. is there.
In the general formula (H), a form in which residues obtained by removing a hydrogen atom from the compound are bonded to each other (generally referred to as bis type, tris type, tetrakis type) can also be preferably used.
In the general formula (H), a dissociable group (for example, a COOH group or a salt thereof, a SO ₃ H group or a salt thereof, a PO ₃ H group or a salt thereof), a group containing a quaternary nitrogen cation (for example, an ammonium group or a pyridinium group) Etc.), those having a polyethyleneoxy group, a hydroxyl group or the like as a substituent are also preferred.

  Specific examples of the compound represented by formula (H) in the present invention are shown below.

As polyhalogen compounds that can be used in the present invention other than those described above, US Pat. No. 3,874,946, US Pat. No. 4,756,999, US Pat. No. 5,340,712, US Pat. 119624, 59-57234, JP-A-7-2781, 7-5621, 9-160164, 9-244177, 9-244178, 9-160167, 9- 319022, 9-258367, 9-265150, 9-319022, 10-197988, 10-197989, 11-242304, JP-A 2000-2963, JP-A 2000-112070 , JP2000-284410, JP2 Although compounds described as exemplary compounds of the present invention in 00-284212, JP-A-2001-33911, JP-A-2001-31644, JP-A-2001-312027, and JP-A-2003-50441 are preferably used. In particular, compounds specifically exemplified in JP-A-7-2781, JP-A-2001-33911, and JP-A-2001-312027 are preferred.
The compound represented by formula (H) in the present invention is preferably used in the range of 10 ⁻⁴ mol to 1 mol, more preferably 10 ⁻³ , per mol of the non-photosensitive silver salt in the image forming layer. It is preferable to use in the range of not less than 0.5 mol and not more than 0.5 mol, more preferably not less than 1 × 10 ⁻² mol and not more than 0.2 mol.
In the present invention, examples of the method for incorporating the antifoggant into the photothermographic material include the methods described in the method for containing a reducing agent, and the organic polyhalogen compound is also preferably added as a solid fine particle dispersion.

2) Other antifoggants Other antifoggants include mercury (II) salts described in paragraph No. 0113 of JP-A No. 11-65021, benzoic acids described in paragraph No. 0114 of the same, salicylic acid derivatives of JP-A No. 2000-206642, A formalin scavenger compound represented by the formula (S) in JP-A-2000-221634, a triazine compound according to claim 9 in JP-A-11-352624, and a compound represented by the general formula (III) in JP-A-6-11791 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene and the like.

The photothermographic material in the invention may contain an azolium salt for the purpose of 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 azolium salt may be added to any part of the photothermographic material, but the addition layer is preferably added to the layer having the image forming layer, and more preferably to the image forming layer. The azolium salt may be added at any step during the preparation of the coating solution, and when added to the image forming layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. Immediately before is preferable. The azolium salt may be added by any method such as powder, solution, 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 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.

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used for the purpose of controlling development by suppressing or promoting development, improving spectral sensitization efficiency, and improving storage stability before and after development. And thione compounds, paragraphs 0067 to 0069 of JP-A-10-62899, compounds represented by formula (I) of JP-A-10-186572, and specific examples thereof include paragraph numbers 0033 to 0052. , European Patent Publication No. 0803764A1, page 20, lines 36-56. Of these, mercapto-substituted heteroaromatic compounds described in JP-A-9-297367, JP-A-9-304875, JP-A-2001-100388, JP-A-2002-303954, JP-A-2002-303951, and the like are preferable. .

2) Toning agent In the photothermographic material of the invention, it is preferable to add a toning agent. For the toning agent, paragraph numbers 0054 to 0055 of JP-A-10-62899, page 21 to 23 of European Patent Publication No. 0803764A1. Line 48, described in JP-A No. 2000-356317 and JP-A No. 2000-187298, and in particular, phthalazinones (phthalazinone, phthalazinone derivatives or metal salts; for example, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone. 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione); phthalazinones and phthalic acids (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, diammonium phthalate) , Sodium phthalate, potassium phthalate and tetrachlorophthalic anhydride) Combinations; phthalazines (phthalazine, phthalazine derivatives or metal salts; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6-t-butylphthalazine, 6-chlorophthalazine, 5,7-dimethoxyphthalazine And 2,3-dihydrophthalazine); a combination of phthalazines and phthalic acids is preferable, and a combination of phthalazines and phthalic acids is particularly preferable. Among them, a particularly preferable combination is a combination of 6-isopropylphthalazine and phthalic acid or 4-methylphthalic acid.

3) Plasticizers and lubricants In the present invention, known plasticizers and lubricants can be used to improve film physical properties. In particular, it is preferable to use a lubricant such as liquid paraffin, long chain fatty acid, fatty acid amide, fatty acid ester, etc., in order to improve handling at the time of manufacture and scratch resistance at the time of heat development.
In particular, liquid paraffin from which low-boiling components have been removed and fatty acid esters having a branched structure and having a molecular weight of 1000 or more are preferred.
Regarding the plasticizer and lubricant that can be used in the image forming layer and the non-photosensitive layer, JP-A No. 11-65021, paragraph No. 0117, JP-A No. 2000-5137, JP-A No. 2004-219794, JP-A No. 2004-219802, The compounds described in JP-A-2004-334077 are preferred.

4) Dye and Pigment In the image forming layer of the present invention, various dyes and pigments (for example, CI Pigment Blue 60, C.I. Pigment Blue 64, CI Pigment Blue 15: 6) can be used. These are described in detail in WO98 / 36322, JP-A-10-268465, JP-A-11-338098 and the like.

5) Nucleating Agent In the photothermographic material of the invention, it is preferable to add a nucleating agent to the image forming layer. Regarding the nucleating agent and the method and amount of addition thereof, JP-A No. 11-65021, paragraph No. 0118, JP-A No. 11-223898, paragraph Nos. 0136 to 0193, JP-A No. 2000-284399, the formula (H) , Compounds of formulas (1) to (3), formulas (A) and (B), compounds of general formulas (III) to (V) described in JP-A 2000-347345 (specific compounds: The nucleation promoter is described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

  In order to use formic acid or formate as a strong fogging substance, it is preferably contained in an amount of 5 mmol or less, more preferably 1 mmol or less per mol of silver on the side having an image forming layer containing photosensitive silver halide.

When a nucleating agent is used in the photothermographic material of the present invention, it is preferable to use an acid formed by hydrating diphosphorus pentoxide or a salt thereof in combination. Acids or salts thereof formed by hydration of diphosphorus pentoxide include metaphosphoric acid (salt), pyrophosphoric acid (salt), orthophosphoric acid (salt), triphosphoric acid (salt), tetraphosphoric acid (salt), hexametalin An acid (salt) etc. can be mentioned. Examples of the acid or salt thereof formed by hydrating diphosphorus pentoxide particularly preferably include orthophosphoric acid (salt) and hexametaphosphoric acid (salt). Specific examples of the salt include sodium orthophosphate, sodium dihydrogen orthophosphate, sodium hexametaphosphate, and ammonium hexametaphosphate.
The amount of acid or salt thereof formed by hydrating diphosphorus pentoxide (the coating amount per 1 m ^{2 of} photosensitive material) may be a desired amount according to the performance such as sensitivity and fogging, but is 0.1 mg / m ^2. It is preferably 500 mg / m ² or less, more preferably 0.5 mg / m ² or more and 100 mg / m ² or less.
The reducing agent, hydrogen bonding compound, development accelerator and polyhalogen compound in the present invention are preferably used as a solid dispersion, and a preferred method for producing these solid dispersions is described in JP-A-2002-55405. .

(Thickener)
The image forming layer coating solution of the photothermographic material of the present invention preferably contains a thickener.
The thickener used in the present invention is a compound that increases the viscosity of a coating solution containing a polymer latex as a binder, and is a compound represented by the following general formula (T).

In general formula (T), at least two of R ¹⁶ , R ¹³ and R ¹² are alkyl groups having 1 to 18 carbon atoms and hydroxyalkyl groups containing repeating units of ethylene oxide or propylene oxide, and n ¹ is The average degree of polymerization is 100 to 3000.
Preferably, one of R ¹⁶ , R ¹³ and R ¹² is the alkyl group having 1 to 18 carbon atoms, the other is a hydroxyalkyl group containing a repeating unit of ethylene oxide or propylene oxide, and One is a hydrogen atom, the alkyl group having 1 to 18 carbon atoms, or a hydroxyalkyl group containing a repeating unit of ethylene oxide or propylene oxide.
Preferably, the average degree of substitution of the alkyl group having 1 to 18 carbon atoms is 0.5 or more and 2.5 or less.
Preferably, the average number of units of ethylene oxide or propylene oxide is 0.01 or more and 10 or less.

The thickener of the present invention represented above will be described in more detail.
In the formula, the alkyl group having 1 to 18 carbon atoms is preferably an alkyl group having 1 to 12 carbon atoms, more preferably an alkyl group having 1 to 8 carbon atoms, and particularly preferably 1 carbon atom. It is an alkyl group of ~ 2.
In the formula, the alkyl group in the hydroxyalkyl group containing a repeating unit of ethylene oxide or propylene oxide has preferably 1 to 12 carbon atoms, more preferably 1 to 8 carbon atoms, and particularly preferably 1 to 2 carbon atoms.

In the above general formula, the average degree of substitution of the alkyl group having 1 to 18 carbon atoms is preferably 0.5 to 2.5, more preferably 0.7 to 2.2, and particularly preferably 0.9 to 2.0. . Here, the average degree of substitution represents the average number of cellulose per glucose ring unit. Moreover, the average number of units of the oxyethylene unit or oxypropylene unit of the hydroxyalkyl group containing a repeating unit of ethylene oxide or propylene oxide is preferably 0.01 to 10, more preferably 0.05 to 8. The average number of substituted units in the present invention represents the average number of oxyethylene units or oxypropylene units added per glucose ring unit of the cellulose. n ¹ represents an average degree of polymerization, preferably 100 to 3000, more preferably 200 to 2000, and particularly preferably 300 to 1000.

Specific examples of the present invention are given below, but the present invention is not limited thereto.

  In Table 1 above, PO represents a hydroxyalkyl group derived from propylene oxide, and EO represents a hydroxyalkyl group derived from ethylene oxide.

  The thickener of the present invention is made from cellulose, treated with a base such as sodium hydroxide, and reacted with an alkyl halide such as methyl chloride or ethyl chloride, and an etherifying agent such as ethylene oxide or propylene oxide. Can be synthesized.

  Further, as the thickener of the present invention, Metrows SH, SE manufactured by Shin-Etsu Chemical Co., Ltd., BERMOCOLL E, EBS, M, EHM, EHEC series manufactured by Akzo Nobel Co., etc. can also be suitably used.

  As for aqueous solution viscosity at the time of preparing 2% aqueous solution of the thickener of this invention, 10-1000 are preferable.

The thickener of the present invention may contain a cellulose derivative in which R ¹⁶ , R ¹³ and R ¹² described in the general formula (T) are hydrogen atoms. This is a derivative produced during the synthesis of the thickener of the present invention, and is preferably 30% by mass or less, more preferably 20% by mass or less of the thickener of the present invention, and 10% by mass or less. It is particularly preferred.

  In the present invention, the solid content concentration of the thickener in the image forming layer coating solution is preferably 0.005% by mass to 5% by mass, and 0.01% by mass in terms of the coatability and photographic properties of the photothermographic material. -1 mass% is more preferable.

The viscosity of the coating solution for the image forming layer in the present invention is preferably such that the viscosity at 40 ° C. with a B-type viscometer is 25 or more and the viscosity at high shear at 10,000 S ⁻¹ is 10 or less. Here, any apparatus may be used for measuring the viscosity at high shear, but an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd., a rheometer RS150 manufactured by Hake, etc. is preferably used.

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution in the invention is preferably from 30 ° C. to 65 ° C., more preferably from 35 ° C. to less than 60 ° C., and more preferably from 35 ° C. to 55 ° C. 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.

(Layer structure and components)
The photothermographic material of the present invention has an image forming layer and a non-photosensitive layer arranged in this order on at least one surface of the support in the order of proximity to the support. Preferably, the non-photosensitive layer is the outermost layer, and it is preferable to have a non-photosensitive intermediate layer between the image forming layer and the non-photosensitive layer. The image forming layer preferably contains a first non-photosensitive organic silver salt, and the intermediate layer preferably contains a second non-photosensitive organic silver salt.
Another non-photosensitive intermediate layer may be disposed between the image forming layer and the intermediate layer containing the second non-photosensitive organic silver salt. In the present invention, in the following description, for ease of understanding, the non-photosensitive intermediate layer is described as the intermediate layer B, and the non-photosensitive layer containing the second non-photosensitive organic silver salt is described as the intermediate layer A. There is.
The photothermographic material of the invention may further have an undercoat layer provided on the support and a back layer provided on the opposite side of the support from the image forming layer.

  When a layer that acts as an optical filter is provided, a light absorber (dye, pigment, etc.) is added to any non-photosensitive layer on the exposed surface side of the image forming layer. When a layer acting as an antihalation layer is provided, a light absorber (dye, pigment, etc.) is added to any non-photosensitive layer on the side opposite to the exposed surface of the image forming layer.

1) Binder of Intermediate Layer A and Intermediate Layer B In the present invention, at least 50% by mass or more of the binder of the intermediate layer B is preferably a polymer latex. As the remaining binder component, a hydrophilic polymer described later is preferably used. The binder of the intermediate layer A is preferably a hydrophilic binder and may contain additives such as a development accelerator or an antifogging agent, a dye or pigment, a plasticizer or a lubricant, a crosslinking agent, and a surfactant.

  A preferred polymer latex is a polymer latex having a monomer component represented by the following general formula (M) of 10% by mass or more and 70% by mass or less.

General formula (M)
CH ₂ = CR ⁰¹ -CR ⁰² = CH ₂
In the formula, R ⁰¹ and R ⁰² are groups selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, and a cyano group. More preferably, R ⁰¹ and R ⁰² are both hydrogen atoms, or one is a hydrogen atom and the other is a methyl group.

The preferred alkyl group for R ⁰¹ and R ^{02 is} an alkyl group having 1 to 4 carbon atoms, more preferably an alkyl group having 1 to 2 carbon atoms. The halogen atom for R ⁰¹ and R ⁰² is preferably a fluorine atom, a chlorine atom, or a bromine atom, and more preferably a chlorine atom.
R ⁰¹ and R ⁰² are preferably both hydrogen atoms, one is a hydrogen atom and the other is a methyl group or a chlorine atom, more preferably both are hydrogen atoms, or one is a hydrogen atom and the other is a methyl group.

  Specific examples of the monomer represented by the general formula (M) of the present invention include 2-ethyl-1,3-butadiene, 2-n-propyl-1,3-butadiene, and 2,3-dimethyl-1,3. -Butadiene, 2-methyl-1,3-butadiene, 2-chloro-1,3-butadiene, 1-bromo-1,3-butadiene, 2-fluoro-1,3-butadiene, 2,3-dichloro- Examples include 1,3-butadiene and 2-cyano-1,3-butadiene.

The copolymerization ratio of the monomer represented by the general formula (M) in the present invention is 10% by mass to 70% by mass, preferably 15% by mass to 65% by mass, and more preferably 20% by mass to 60% by mass. %. When the copolymerization ratio of the monomer represented by the general formula (M) is less than 10% by mass, the fusion component of the binder decreases, and the work brittleness deteriorates.
On the other hand, when the copolymerization ratio of the monomer represented by the general formula (M) exceeds 70% by mass, the fusion component of the binder increases and the mobility of the binder increases, so that the image storability deteriorates.

  As the acid group, carboxylic acid, sulfonic acid, and phosphoric acid are preferable, and carboxylic acid is particularly preferable. The copolymerization ratio of the acid group is preferably 1% by mass to 20% by mass, and more preferably 1% by mass to 10% by mass. Specific examples of the monomer having an acid group include acrylic acid, methacrylic acid, itaconic acid, p-styrenesulfonic acid sodium salt, isoprenesulfonic acid, and phosphorylethyl methacrylate, and acrylic acid and methacrylic acid are preferable. Acid is particularly preferred.

  The binder of the present invention preferably has a glass transition temperature (Tg) in the range of −30 ° C. to 70 ° C., more preferably in the range of −10 ° C. to 50 ° C., more preferably in terms of film formability and image storage stability. Is in the range of 0 ° C to 40 ° C. It is also possible to use a blend of two or more polymers as the binder, and in this case, it is preferable that the weighted average Tg in consideration of the composition falls within the above range. Moreover, when phase-separating or having a core-shell structure, the weighted average Tg is preferably within the above range.

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

The latex preferably has an equilibrium water content of 2% by mass or less at 25 ° C. and 60% RH. More preferably, the equilibrium water content is 0.01% by mass or more and 1.5% by mass or less, and further preferably 0.02% by mass or more and 1.0% by mass or less.

  A hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, or carboxymethyl cellulose may be added to the non-photosensitive intermediate layers A and B in the present invention as necessary. The amount of these hydrophilic polymers added is preferably 50% by mass or less, more preferably 20% by mass or less, based on the total binder of the non-photosensitive intermediate layer A.

Total binder coating amount of the non-photosensitive intermediate layer A of the present invention is preferably ^{0.5g / m 2 ~3.0g / m 2} , more preferably from 1.0g ^{/ m 2} ~2.0g ^/ m 2 It is.

Total binder coating amount of the non-photosensitive intermediate layer B in the present invention is preferably ^{0.3g / m 2 ~3.0g / m 2} , more preferably from 0.5g ^{/ m 2} ~1.5g ^/ m 2 It is.

2) Outermost layer It is preferable to contain 50% by mass or more of a hydrophilic polymer as the outermost layer binder in the present invention. A more preferable content of the hydrophilic polymer is 60% by mass or more.

The hydrophilic polymer in the present invention is preferably a hydrophilic polymer derived from animal protein. The hydrophilic polymer derived from animal protein refers to a water-soluble polymer that is naturally or chemically modified, such as glue, casein, gelatin, and egg white. Gelatin is preferred, and acid-treated gelatin and alkali-treated gelatin (such as lime treatment) are available depending on the synthesis method, and both can be preferably used. It is preferable to use gelatin having a molecular weight of 10,000 to 1,000,000. In addition, modified gelatin modified by utilizing the amino group or carboxyl group of gelatin can be used (for example, phthalated gelatin). As gelatin, inert gelatin (for example, Nitta gelatin 750), phthalated gelatin (for example, Nitta gelatin 801), or the like can be used.
The gelatin aqueous solution becomes sol when heated to a temperature of 30 ° C. or higher, and gels and loses fluidity when lowered to a temperature lower than 30 ° C. Since such a sol-gel change occurs reversibly with temperature, the gelatin aqueous solution which is a coating solution has a set property of losing fluidity when cooled to a temperature lower than 30 ° C.

3) Antihalation layer In the photothermographic material of the invention, the antihalation layer can be provided on the side farther from the light source than the image forming layer.

As for the antihalation layer, paragraph numbers 0123 to 0124 of JP-A No. 11-65021, JP-A Nos. 11-223898, 9-230531, 10-36695, 10-104779, 11-231457, 11 -352625, 11-352626 and the like.
The antihalation layer contains an antihalation dye having absorption at the exposure wavelength. When the exposure wavelength is in the infrared region, an infrared absorbing dye may be used, and in that case, a dye having no absorption in the visible region is preferable.
When antihalation is performed using a dye having absorption in the visible range, it is preferable that the dye color does not substantially remain after image formation, and a means for decoloring by the heat of heat development is used. In particular, it is preferable to add a thermally decolorable dye and a base precursor to the non-photosensitive layer to function as an antihalation layer. These techniques are described in JP-A-11-231457.

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 0.15 to 2, and more preferably 0.2 to 1. The amount of the dye for obtaining such an optical density is generally 0.001g ^{/ m 2} ~1g ^/ m 2 approximately.

If the dye is decolored in this way, the optical density after heat development 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.
In the thermal decolorization using such decoloring dye and base precursor, a substance (for example, diphenylsulfone, which lowers the melting point by 3 ° C. (deg) or more when mixed with a base precursor as described in JP-A No. 11-352626). 4-Chlorophenyl (phenyl) sulfone), 2-naphthyl benzoate and the like are preferably used in view of thermal decoloring properties and the like.

4) Back Layer Back layers that can be applied to the present invention are described in paragraph Nos. 0128 to 0130 of JP-A No. 11-65021.

In the present invention, a colorant having an absorption maximum at 300 to 450 nm can be added for the purpose of improving the silver color tone and the temporal change of the image. Such colorants are disclosed in JP-A-62-210458, JP-A-63-104046, JP-A-63-103235, JP-A-63-208846, JP-A-63-306436, JP-A-63-314535, and JP-A-01-61745. No. 1, Japanese Patent Laid-Open No. 2001-100363, and the like.
Such a colorant is usually added in the range of 0.1 mg / m ^{2 to 1} g / m ² , and the back layer provided on the opposite side of the image forming layer is preferable as the layer to be added.
In order to adjust the base color tone, it is preferable to use a dye having an absorption peak at 580 to 680 nm. Preferred dyes for this purpose are azomethine oil-soluble dyes described in JP-A-4-359967 and JP-A-4-359968, which have a low absorption intensity on the short wavelength side, and phthalocyanine-based water-soluble dyes described in JP-A-2003-295388. The target dye may be added to any layer, but is more preferably added to the non-photosensitive layer on the image forming layer surface side or the back surface side.

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

5) Membrane pH
The photothermographic material of the present invention preferably has a film surface pH of 7.0 or less, more preferably 6.6 or less before heat development. The lower limit is not particularly limited, but is about 3. The most preferred pH range is in the range of 4 to 6.2. For the adjustment of the film surface pH, it is preferable to use an organic acid such as a phthalic acid derivative, a non-volatile acid such as sulfuric acid, and a volatile base such as ammonia from the viewpoint of reducing the film surface pH. In particular, ammonia is volatile and is preferable for achieving a low film surface pH because it can be removed before the coating process or thermal development.
Further, it is also preferable to use ammonia and a non-volatile base such as sodium hydroxide, potassium hydroxide or lithium hydroxide in combination. In addition, the measuring method of film surface pH is described in paragraph number 0123 of Unexamined-Japanese-Patent No. 2000-284399.

6) Hardener A hardener may be used in each layer such as the image forming 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. In addition to hydroxy-s-triazine sodium salt, N, N-ethylenebis (vinylsulfoneacetamide), N, N-propylenebis (vinylsulfoneacetamide), polyvalent metal ions described on page 78 of the same document, 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-62-289048 are preferably used.

  The hardening agent is added as a solution, and the addition time of this solution into 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.

7) Surfactant As for the surfactant applicable to the present invention, paragraph No. 0132 of JP-A No. 11-65021, paragraph No. 0133 of the solvent, paragraph No. 0134 of the support, and antistatic or conductive layer Paragraph No. 0135 for the method of obtaining a color image, paragraph No. 0136 for JP-A No. 11-84573 and paragraph Nos. 0049 to 0062 of Japanese Patent Application No. 11-106881 for the slip agent. Has been.

  The photothermographic material of the invention preferably contains a fluorine compound having a fluorinated alkyl group having 2 or more carbon atoms and 12 or less fluorine atoms. The fluorine compound in the present invention can be used as a surfactant. Specific examples include compounds described in JP 2004-212903, page 10, line 1 to page 36, line 30.

  The fluorine compound used in the present invention is preferably used as a surfactant in a coating composition for forming any layer on the side provided with an image forming layer. Among these, it is particularly preferable to use it for forming the outermost layer of the photographic light-sensitive material because effective antistatic ability and coating uniformity can be obtained. The fluorine compound in the present invention is useful in that it exhibits antistatic ability and uniformity in coating, but is also effective for improving storage stability and use environment dependency.

There is no restriction | limiting in particular about the usage-amount of the fluorine compound in this invention, The usage-amount is arbitrarily determined according to the structure of the fluorine compound to be used, a place to use, and the kind and amount of other materials contained in the composition. be able to. For example, when used as an outermost layer coating solution for the heat-developable photosensitive material, the coating amount of the coating composition of the fluorine compound is ^{preferably 0.1mg / m 2 ~100mg / m 2} , 0.5mg / more preferably ^{m 2} ~20mg / m ^2.

  In the present invention, one fluorine compound may be used alone, or two or more fluorine compounds may be mixed and used. Further, a fluorine compound other than the fluorine compound in the present invention may be mixed and used. In addition, a surfactant other than the fluorine compound may be used in combination with the fluorine compound in the present invention.

8) Antistatic agent In this invention, it is preferable to have a conductive layer containing a metal oxide or a conductive polymer. The antistatic layer may serve as an undercoat layer, a back layer surface protective layer, or the like, or may be provided separately. As the conductive material for the antistatic layer, a metal oxide in which conductivity is improved by introducing oxygen defects or different metal atoms into the metal oxide is preferably used. Examples of metal oxides include ZnO, TiO ₂ and SnO _2. Addition of Al and In to ZnO, addition of Sb, Nb, P and halogen elements to SnO ₂ , and addition to TiO ₂ For example, addition of Nb, Ta or the like is preferable.
In particular, SnO ₂ added with Sb is preferable. The amount of different atoms added is preferably in the range of 0.01 mol% to 30 mol%, more preferably in the range of 0.1 mol% to 10 mol%. The shape of the metal oxide may be spherical, needle-like, or plate-like, but the long axis / uniaxial ratio is 2.0 or more, preferably 3.0 to 50 in terms of the effect of imparting conductivity. Good. Range amount preferably of ^1mg / ^{m 2 ~1000mg} / m 2 of metal oxide, more preferably 10mg ^{/ m 2} ~500mg ^/ m 2 range, more preferably at 20mg ^{/ m 2} ~200mg ^/ m 2 It is a range.
The antistatic layer of the present invention may be disposed on either the image forming layer surface side or the back surface side, but is preferably disposed between the support and the back layer. Specific examples of the antistatic layer of the present invention include paragraph No. 0135 of JP-A No. 11-65021, JP-A Nos. 56-143430, 56-143431, 58-62646, No. 56-120519, JP-A No. 11-120. No. 84573, paragraph numbers 0040 to 0051, US Pat. No. 5,575,957, and JP-A No. 11-223898, paragraph numbers 0078 to 0084.

9) Support The transparent support is subjected to heat treatment in a temperature range of 130 ° C. to 185 ° C. in order to alleviate internal strain remaining in the film during biaxial stretching and to eliminate heat shrinkage strain generated during heat development processing. Polyester, especially polyethylene terephthalate, is preferably used. In the case of a photothermographic material for medical use, the transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored. Examples of the support include water-soluble polyesters disclosed in JP-A-11-84574, styrene-butadiene copolymers described in JP-A-10-186565, and vinylidene chloride described in JP-A-2000-39684 and Japanese Patent Application No. 11-106881, paragraphs 0063 to 0080. It is preferable to apply an undercoating technique such as a copolymer. When the image forming layer or the back layer is applied to the support, the water content of the support is preferably 0.5% by mass or less.

10) Other additives Antioxidants, stabilizers, plasticizers, ultraviolet absorbers or coating aids may be further added to the photothermographic material. Various additives are added to either the image forming layer or the non-photosensitive layer. Regarding these, WO 98/36322, EP 803764A1, JP-A-10-186567, 10-18568 and the like can be referred to.

11) Coating method The photothermographic material in the invention may be coated 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. Extrusion coating or slide coating described in “LIQUID FILM COATING” by Schweizer (CHAPMAN & HALL, 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. . In the present invention, particularly preferred coating methods are those described in JP-A Nos. 2001-194748, 2002-153808, 2002-153803, and 2002-182333.

The organic silver salt-containing layer coating solution in the present invention is preferably a so-called thixotropic fluid. Regarding this technique, JP-A-11-52509 can be referred to. The organic silver salt-containing layer coating solution 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 20,000 mPa · s. is there. 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.

In the case of preparing the coating liquid of the present invention, a known in-line mixer or implant mixer is preferably used when mixing two kinds of liquids. A preferred in-line mixer of the present invention is described in JP-A No. 2002-85948, and an implant mixer is described in JP-A No. 2002-90940.
The coating solution in the present invention is preferably subjected to defoaming treatment in order to keep the coated surface state good. A preferable defoaming treatment method of the present invention is the method described in JP-A No. 2002-66431.
When applying the coating solution of the present invention, it is preferable to perform static elimination in order to prevent adhesion of dust, dust, and the like due to electric resistance of the support. An example of a preferable static elimination method in the present invention is described in JP-A No. 2002-143747.
In the present invention, it is important to precisely control the drying air and the drying temperature in order to dry the non-setting image forming layer coating solution. The preferred drying method of the present invention is described in detail in JP-A Nos. 2001-194749 and 2002-139814.
The photothermographic material of the present invention is preferably subjected to a heat treatment immediately after coating and drying in order to improve film formability. The temperature of the heat treatment is preferably in the range of 60 ° C. to 100 ° C. as the film surface temperature, and the heating time is preferably in the range of 1 second to 60 seconds. A more preferable range is a film surface temperature of 70 ° C. to 90 ° C. and a heating time of 2 seconds to 10 seconds. A preferable heat treatment method of the present invention is described in JP-A No. 2002-107872.
In order to stably and continuously produce the photothermographic material of the present invention, the production methods described in JP-A Nos. 2002-156728 and 2002-182333 are preferably used.

  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).

12) Packaging material The photothermographic material of the present invention is at least one of a packaging material having a low oxygen permeability and a low moisture permeability in order to suppress fluctuations in photographic performance during raw storage or to improve curling, curling, etc. It is preferable to package with. The oxygen permeability is preferably 50 mL / atm · m ² · day or less at 25 ° C., more preferably 10 mL / atm · m ² · day or less, more preferably 1.0 mL / atm · m ² · day or less. is there. The moisture permeability is preferably 10 g / atm · m ² · day or less, more preferably 5 g / atm · m ² · day or less, still more preferably 1 g / atm · m ² · day or less.
Specific examples of the packaging material having low oxygen permeability and / or moisture permeability are disclosed in, for example, JP-A-8-254793. This is a packaging material described in JP-A-2000-206653.

13) Other technologies that can be used Techniques that can be used in the photothermographic material of the present invention include EP80364A1, EP883022A1, WO98 / 36322, JP-A-56-62648, JP-A-58-62644, and JP-A-5-62644. 9-43766, 9-281737, 9-297367, 9-304869, 9-31405, 9-329865, 10-10669, 10-62899, 10-69023 10-186568, 10-90823, 10-171663, 10-186565, 10-186567, 10-186567 to 10-186572, 10-197974, Nos. 10-197982, 10-197983, 10-197985 to 1 No. 0-197987, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10-307365, No. 10- No. 312038, No. 10-339934, No. 11-7100, No. 11-15105, No. 11-24200, No. 11-24201, No. 11-30832, No. 11-84574, No. 11-65021 11-109547, 11-125880, 11-129629, 11-133536 to 11-133539, 11-133542, 11-133543, 11-223898, 11-352627, 11-305377, 11-305378, 11-305 84, 11-305380, 11-316435, 11-327076, 11-338096, 11-338098, 11-338099, 11-343420, JP 2000-187298 , 2000-10229, 2000-47345, 2000-206642, 2000-98530, 2000-98531, 2000-112059, 2000-112060, 2000-112104, Examples thereof include 2000-112064 and 2000-171936.

(Image forming method)
1) Exposure The photothermographic material of the invention may be exposed by any method, but scanning exposure with a laser beam is preferred as an exposure light source. As the laser, a red to infrared emission He—Ne laser, a red semiconductor laser, a blue to green emission Ar ⁺ , He—Ne, He—Cd laser, or a blue semiconductor laser can be used. Preferred is a red to infrared semiconductor laser, and the peak wavelength of the laser light is 600 nm to 900 nm, preferably 620 nm to 850 nm. On the other hand, in recent years, in particular, a module in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated and a blue semiconductor laser have been developed, and a laser output device in a short wavelength region has been closed up. The blue semiconductor laser is expected to increase in demand in the future because high-definition image recording is possible, the recording density is increased, and a stable output is obtained with a long lifetime. The peak wavelength of the blue laser light is preferably 300 nm to 500 nm, particularly preferably 400 nm to 500 nm.
It is also preferable that the laser light is oscillated in a vertical multi by a method such as high frequency superposition.

2) Thermal development Although the photothermographic material of the present invention may be developed by any method, it is usually developed by raising the temperature of the photothermographic material exposed imagewise. A preferred development temperature is 80 ° C to 250 ° C, preferably 100 ° C to 140 ° C, and more preferably 110 ° C to 130 ° C. The development time is preferably 1 second to 60 seconds, more preferably 3 seconds to 30 seconds, still more preferably 5 seconds to 25 seconds, and particularly preferably 7 seconds to 15 seconds.

  Either a drum type heater or a plate type heater may be used as the thermal development method, but the plate type heater method is more preferable. The heat development method using the plate type heater method is preferably a method described in JP-A-11-133572, and a visible image is obtained by bringing a photothermographic material having a latent image formed thereon into contact with a heating means in a heat developing unit. In the heat development apparatus, the heating unit includes a plate heater, and a plurality of press rollers are disposed to face each other along one surface of the plate heater, and the press roller is disposed between the press roller and the plate heater. A heat development apparatus characterized in that heat development is performed by passing a photothermographic material. 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. For example, an example in which four sets of plate heaters capable of independent temperature control are used and the temperature is controlled to 112 ° C., 119 ° C., 121 ° C., and 120 ° C., respectively. 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 a change in the shape of the support of the photothermographic material due to the heating.

  In order to reduce the size of the heat developing machine and shorten the heat development time, it is preferable to be able to control the heater more stably. In addition, the exposure of one sheet of photosensitive material is started from the top and the exposure is finished to the rear end. It is desirable to start the heat development before the time. Imagers capable of rapid processing preferred in the present invention are described in, for example, JP-A Nos. 2002-289804 and -287668. If this imager is used, for example, heat development can be performed in 14 seconds with a three-stage plate heater controlled at 107 ° C.-121 ° C.-121 ° C., and the output time of the first sheet is reduced to about 60 seconds. be able to. For such rapid development processing, it is preferable to use the photothermographic material-2 of the present invention in combination with high sensitivity and less susceptible to environmental temperature.

3) System As a medical laser imager provided with an exposure part and a heat development part, Fuji Medical Dry Laser Imager FM-DPL can be mentioned. Regarding FM-DPL, Fuji Medical Review No. 8, pages 39 to 55, and it goes without saying that these techniques are applied as a laser imager of the photothermographic material of the present invention. Further, it can also be applied as a photothermographic material for a laser imager in “AD network” proposed by Fuji Film Medical Co., Ltd. as a network system adapted to the DICOM standard.

(Use of the present invention)
The photothermographic material of the present invention forms a black and white image by a silver image, and is used as a photothermographic material for medical diagnosis, a photothermographic material for industrial photography, a photothermographic material for printing, and a photothermographic material for COM. It is preferably used.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1
(Preparation of PET support)
1) Film formation Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured in phenol / tetrachloroethane = 6/4 (mass ratio) at 25 ° C.) is obtained. It was. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to prepare an unstretched film.

This was stretched 3.3 times longitudinally 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, after heat setting at 240 ° C. for 20 seconds, the film was 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.

2) Surface corona treatment Using a solid state corona treatment machine 6KVA model manufactured by Pillar, both surfaces of the support were treated at 20 m / min at room temperature. 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.

3) Undercoat <Preparation of undercoat layer coating solution>
Formula (1) (for image forming layer side undercoat layer)
46.8 g of pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Bailonal MD-1200 10.4g manufactured by Toyobo Co., Ltd.
Polyethylene glycol monononyl phenyl ether 11.0g
(Average ethylene oxide number = 8.5, 1% by mass solution)
MP-1000 (PMMA polymer fine particles, average particle size 0.4 μm) manufactured by Soken Chemical Co., Ltd.
0.91g
931 mL of distilled water

Formula (2) (for back layer 1st layer)
Styrene-butadiene copolymer latex 130.8 g
(Solid content 40% by mass, styrene / butadiene mass ratio = 68/32)
2,4-Dichloro-6-hydroxy-S-triazine sodium salt (8% by mass aqueous solution) 5.2 g
10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
Polystyrene particle dispersion (average particle size 2 μm, 20 mass%) 0.5 g
854 mL of distilled water

Formula (3) (for back side second layer)
84 g of SnO ₂ / SbO (9/1 mass ratio, average particle size 0.5 μm, 17 mass% dispersion)
Gelatin 7.9g
10g Metros TC-5 (2 mass% aqueous solution) manufactured by Shin-Etsu Chemical Co., Ltd.
10 mL of 1% aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 7g
Proxel (Abyssia) 0.5g
Distilled water 881mL

After both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm are subjected to the corona discharge treatment, the undercoat coating solution formulation (1) is applied on one side (image forming layer surface) with a wire bar with a wet coating amount of 6. .6mL / m 2 was applied ^(per one side) and dried for 5 minutes at 180 ° C., then the amount of wet coating the coating solution for the undercoat was coated (2) by a wire bar on the rear surface (back surface) 5. was applied so as to 7 mL / ^{m 2} and dried 5 minutes at 180 ° C., wet coating amount is 8.4 mL / ^{m 2} further backside (the back face) the coating solution for the undercoat was coated (3) with a wire bar It was applied as described above and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

(Back layer)
1) Preparation of Back Layer Coating Solution Keep the container at 40 ° C., gelatin 100 g, benzoisothiazolinone 400 mg, blue dye-2 5% by weight aqueous solution 45 mL, Clariant Blue dye FRL-SF 10% by weight aqueous solution 6 .1 mL and 1544 mL of water were added to dissolve the gelatin. Furthermore, 27 mL of a 20% by mass aqueous solution of diammonium phthalate, 25 mL of a 15% by mass methanol solution of phthalic acid, 72 mL of a 3% by mass aqueous sodium polystyrenesulfonate solution, and 200 g of a 10% by mass solution of isoprene latex (TP-1) were mixed. Immediately before coating, 52 mL of a 4% by mass aqueous solution of N, N-ethylenebis (vinylsulfone acetamide) was mixed. The viscosity of the coating solution was 32 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm). The pH of the coating solution was 5.15 at 40 ° C.

2) Preparation of back surface protective layer coating solution << Back surface protective layer coating solution-1 >>
The container was kept at 40 ° C., and gelatin was added by adding 100 g of gelatin, 5.7 g of monodispersed polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4), 637 mg of benzoisothiazolinone and 1645 mL of water as a matting agent. Was dissolved. Furthermore, 15.8 mL of a 30% by mass solution of carnauba wax (manufactured by Chukyo Yushi Co., Ltd., selezole 524), 5.7 mL of a 15% by mass methanol solution of phthalic acid, 24 mL of a 5% by mass aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate , 50 mL of a 3% by weight aqueous solution of sodium polystyrene sulfonate, 12 mL of a 1% by weight solution of a fluorosurfactant (F-1), 2.4 mL of a 2% by weight solution of a fluorosurfactant (F-2), ethyl acrylate / Acrylic acid copolymer (copolymerization mass ratio 64/4) latex 20 g liquid 72g was mixed. Immediately before coating, 90 mL of a 4% by weight aqueous solution of N, N-ethylenebis (vinylsulfone acetamide) was mixed to prepare a back surface protective layer coating solution. The viscosity of the coating solution was 28 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm). The pH of the coating solution was 5.5 at 40 ° C.

<< Back surface protective layer coating solution-2 >>
Back surface protective layer coating solution-2 was prepared in the same manner except that monodisperse polymethylmethacrylate fine particles were removed from back surface protective layer coating solution-1.

3) Application of Back Layer On the back surface side of the undercoat support, the back layer coating solution was applied in a gelatin coating amount of 1.5 g / m ^2, and the back surface protective layer coating solution was applied in a gelatin coating amount of 0.1%. A simultaneous multi-layer coating was applied so as to be 73 g / m ² , followed by drying to prepare a back layer.

(Image forming layer, intermediate layer, and surface protective layer)
1. Preparation of coating material 1) Silver halide emulsion <Preparation of silver halide emulsion 1>
To a solution of 1421 mL of distilled water, 3.1 mL of a 1% by mass potassium bromide solution was added, and a solution containing 3.5 mL of 0.5 mol / L sulfuric acid and 31.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 30 ° C., distilled water was added to 22.22 g of silver nitrate and diluted to 95.4 mL, solution A, 15.3 g of potassium bromide and 0.8 g of potassium iodide were added in distilled water to a volume of 97.4 mL. Solution B diluted in a total amount was added at a constant flow rate over 45 seconds. Thereafter, 10 mL of a 3.5% by mass aqueous hydrogen peroxide solution was added, and 10.8 mL of a 10% by mass aqueous solution of benzimidazole was further added. Further, a solution C in which distilled water was added to 51.86 g of silver nitrate and diluted to 317.5 mL, a solution D in which 44.2 g of potassium bromide and 2.2 g of potassium iodide were diluted with distilled water to a volume of 400 mL were added to solution C. Was added at a constant flow rate over 20 minutes, and solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so as to be 1 × 10 ⁻⁴ mol per mol of silver. Further, 5 seconds after the completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using sulfuric acid having a concentration of 0.5 mol / L, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

The silver halide dispersion was maintained at 38 ° C. with stirring, 5 mL of a 0.34 mass% 1,2-benzisothiazolin-3-one methanol solution was added, and the temperature was raised to 47 ° C. after 40 minutes. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per mol of silver, and further 5 minutes later, tellurium sensitizer C was added in a methanol solution to a ratio of 2. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes. Thereafter, a methanol solution having a molar ratio of the spectral sensitizing dye A and the sensitizing dye B of 3: 1 was added in an amount of 1.2 × 10 ⁻³ mol as the total of the sensitizing dyes A and B per mol of silver. , N′-dihydroxy-N ″ -diethylmelamine in 1.3 mL of a 0.8 wt% methanol solution was added, and after another 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the solution in methanol with a methanol solution of 4.8 per mol of silver. × 10 ⁻³ mol, 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in methanol solution is 5.4 × 10 ⁻³ mol and 1- (3-methyl with respect to 1 mol of silver A silver halide emulsion 1 was prepared by adding 8.5 × 10 ⁻³ mol of ureidophenyl) -5-mercaptotetrazole in an aqueous solution to 1 mol of silver.

  The grains in the prepared silver halide emulsion were silver iodobromide grains containing 3.5 mol% of iodine having an average sphere equivalent diameter of 0.042 μm and a sphere equivalent diameter variation coefficient of 20%. 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 80% using the Kubelka-Munk method.

<Preparation of silver halide emulsion 2>
In the preparation of silver halide emulsion 1, the liquid temperature 30 ° C. at the time of grain formation was changed to 47 ° C., and solution B was changed to diluting 15.9 g of potassium bromide to a volume of 97.4 mL with distilled water, Solution D was changed to diluting 45.8 g of potassium bromide with distilled water to a volume of 400 mL, and the addition time of solution C was changed to 30 minutes to remove potassium hexacyanoiron (II) in the same manner. A silver halide emulsion 2 was prepared. Precipitation / desalting / washing / dispersion was carried out in the same manner as silver halide emulsion 1. Further, the addition amount of tellurium sensitizer C is 1.1 × 10 ⁻⁴ mol per mol of silver, and the addition amount of methanol solution of 3: 1 in the molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is silver. The total of sensitizing dye A and sensitizing dye B per mole is 7.0 × 10 ⁻⁴ mole, and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole is added to 1 mole of silver. Same as Emulsion 1 except that 3.3 × 10 ⁻³ mol and 1- (3-methylureidophenyl) -5-mercaptotetrazole were changed to 4.7 × 10 ⁻³ mol added to 1 mol of silver. Spectral sensitization, chemical sensitization, and addition of 5-methyl-2-mercaptobenzimidazole and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole were carried out to obtain silver halide emulsion 2. . The emulsion grains of silver halide emulsion 2 were pure silver bromide cubic grains having an average sphere equivalent diameter of 0.080 μm and a sphere equivalent diameter variation coefficient of 20%.

<Preparation of silver halide emulsion 3>
In the preparation of silver halide emulsion 1, silver halide emulsion 3 was prepared in the same manner except that the liquid temperature at the time of grain formation was changed from 30 ° C. to 27 ° C. Further, precipitation / desalting / washing / dispersion was performed in the same manner as silver halide emulsion 1. The molar ratio of spectral sensitizing dye A and spectral sensitizing dye B is 1: 1 as a solid dispersion (gelatin aqueous solution), and the addition amount is 6 × 10 ⁻ as the total of sensitizing dye A and sensitizing dye B per mole of silver. ³ moles, the addition amount of tellurium sensitizer C was changed to 5.2 × 10 ⁻⁴ moles per mole of silver, and 3 minutes after the addition of tellurium sensitizers, bromoauric acid was 5 × 10 ⁻⁴ moles per silver mole. A silver halide emulsion 3 was obtained in the same manner as Emulsion 1 except that 2 × 10 ⁻³ mol of mol and potassium thiocyanate were added per mol of silver. The emulsion grains of the silver halide emulsion 3 were silver iodobromide grains containing 3.5 mol% of iodine having an average sphere equivalent diameter of 0.034 μm and a sphere equivalent diameter variation coefficient of 20%.

<Preparation of mixed emulsion A for coating solution>
70% by weight of silver halide emulsion 1, 15% by weight of silver halide emulsion 2 and 15% by weight of silver halide emulsion 3 were dissolved, and benzothiazolium iodide was dissolved in a 1% by weight aqueous solution of 7% per mole of silver. × 10 ⁻³ mol was added. Further, water is added so that the content of silver halide per 1 kg of the mixed emulsion for coating liquid is 38.2 g as silver, and 1- (3-methylureidophenyl) is adjusted to 0.34 g per 1 kg of the mixed emulsion for coating liquid. -5-mercaptotetrazole was added.

Further, as “a compound in which a one-electron oxidant produced by one-electron oxidation can emit one electron or more”, each of compounds 1, 20 and 26 is 2 × 10 ⁻³ per mole of silver halide. Molar amounts were added.

2) Preparation of fatty acid silver dispersion <Preparation of recrystallized behenic acid>
100 kg of behenic acid (product name Edenor C22-85R) manufactured by Henkel Corporation was mixed in 1200 kg of isopropyl alcohol, dissolved at 50 ° C., filtered through a 10 μm filter, cooled to 30 ° C., and recrystallized. The cooling speed during recrystallization was controlled at 3 ° C./hour. The obtained crystals were centrifugally filtered, washed with 100 kg of isopropyl alcohol, and then dried. When the obtained crystals were esterified and subjected to GC-FID measurement, the behenic acid content was 96 mol%, and in addition, lignoceric acid was 2 mol%, arachidic acid was 2 mol%, and erucic acid was 0.001 mol%. It was.

<Preparation of fatty acid silver dispersion>
88 kg of recrystallized behenic acid, 422 L of distilled water, 49.2 L of NaOH aqueous solution having a concentration of 5 mol / L, and 120 L of t-butyl alcohol were mixed and stirred at 75 ° C. for 1 hour to react to obtain a sodium behenate solution B. Separately, 206.2 L (pH 4.0) of an aqueous solution containing 40.4 kg of silver nitrate was prepared and kept warm at 10 ° C. A reaction vessel containing 635 L of distilled water and 30 L of t-butyl alcohol was kept at 30 ° C., and with sufficient stirring, the total amount of the previous sodium behenate solution B and the total amount of the aqueous silver nitrate solution were each maintained at a constant flow rate for 93 minutes 15 Added over seconds and 90 minutes.
At this time, only the silver nitrate aqueous solution is added for 11 minutes after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution B is started. After the addition of the aqueous silver nitrate solution is completed, only the sodium behenate solution B is added for 14 minutes and 15 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. The piping of the addition system of the sodium behenate solution B was prepared by keeping warm water by circulating hot water outside the double pipe 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 B and the addition position of the aqueous silver nitrate solution were arranged symmetrically with respect to the stirring axis, and were adjusted so as not to contact the reaction solution.

After completion of the addition of the sodium behenate solution B, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal 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 = 0.21 μm, b = 0.4 μm, c = 0.4 μm, average aspect ratio 2.1, sphere equivalent diameter. It was a crystal with a coefficient of variation of 11% (a, b, and c are defined in the text).

  19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to a wet cake corresponding to a dry solid content of 260 kg, and the whole amount is made 1000 kg, and then slurried with a dissolver blade, and further a pipeline mixer (manufactured by Mizuho Kogyo Co., Ltd.). : PM-10 type).

Next, the pre-dispersed stock solution is adjusted to a pressure of 1150 kg / cm ² in a disperser (trade name: Microfluidizer M-610, manufactured by Microfluidics International Corporation, using a Z-type interaction chamber) three times. Treatment gave a silver behenate dispersion. The cooling operation was set to a dispersion temperature of 18 ° C. by installing a serpentine heat exchanger before and after the interaction chamber and adjusting the temperature of the refrigerant.

3) Preparation of reducing agent dispersion <Preparation of reducing agent-1 dispersion>
10 masses of reducing agent-1 (6,6′-di-t-butyl-4,4′-dimethyl-2,2′-butylidenediphenol) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 16 kg of% aqueous solution and mixed well to obtain a slurry. This slurry was 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 30 minutes, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the reducing agent to 25% by mass. This dispersion was heated at 40 ° C. for 1 hour, and then further heated at 80 ° C. for 1 hour to obtain a reducing agent-12 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.50 μm and a maximum particle diameter of 1.6 μm or less.
The obtained reducing agent dispersion 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 reducing agent-2 dispersion>
10 kg of water was added to 10 kg of a reducing agent (PP-1) and 16 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and mixed well to obtain a slurry. This slurry was 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 30 minutes, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the reducing agent to 25% by mass. This dispersion was heated at 40 ° C. for 1 hour, and then further heated at 80 ° C. for 1 hour to obtain a reducing agent-2 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.35 μm and a maximum particle diameter of 1.6 μm or less.
The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

4) Preparation of Hydrogen Bonding Compound-1 Dispersion 10 kg of hydrogen bonding compound-1 (tri (4-t-butylphenyl) phosphine oxide) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 16 kg of the aqueous solution and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 4 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. 2 g and water were added to adjust the concentration of the hydrogen bonding compound to 25% by mass. This dispersion was heated at 40 ° C. for 1 hour and then further heated at 80 ° C. for 1 hour to obtain a hydrogen bonding compound-1 dispersion. The hydrogen bonding compound particles contained in the hydrogen bonding compound dispersion thus obtained had a median diameter of 0.45 μm and a maximum particle diameter of 1.3 μm or less. The obtained hydrogen bonding compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

5) Preparation of Development Accelerator-1 Dispersion 10 kg of Development Accelerator-1 and 20 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) were added with 10 kg of water and mixed well. To make a slurry. This slurry was 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 30 minutes, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the development accelerator to 20% by mass to obtain a development accelerator-1 dispersion. The development accelerator particles contained in the development accelerator dispersion thus obtained had a median diameter of 0.48 μm and a maximum particle diameter of 1.4 μm or less. The obtained development accelerator dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.
6) Dispersion Preparation of Development Accelerator-2 and Color Toner-1 The solid dispersion of Development Accelerator-2 and Color Toner-1 was also dispersed by the same method as Development Accelerator-1, and was 20% by mass. A dispersion was obtained.

7) Preparation of polyhalogen compound <Preparation of organic polyhalogen compound-1 dispersion>
10 kg of organic polyhalogen compound-1 (tribromomethanesulfonylbenzene), 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), 0.4 kg of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, Then, 14 kg of water was added and mixed well to obtain a slurry. This 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. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 26% by mass to obtain an organic polyhalogen compound-1 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less. The obtained organic polyhalogen compound 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 organic polyhalogen compound-2 dispersion>
10 kg of an organic polyhalogen compound-2 (N-butyl-3-tribromomethanesulfonylbenzoamide), 20 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and 20 of sodium triisopropylnaphthalenesulfonate 0.4 kg of a mass% aqueous solution was added and mixed well to obtain a slurry. This 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. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 30% by mass. This dispersion was heated at 40 ° C. for 5 hours to obtain an organic polyhalogen compound-2 dispersion. The organic polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.3 μm or less. The obtained organic polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

8) Preparation of phthalazine compound-1 solution 8 kg of modified polyvinyl alcohol MP203 manufactured by Kuraray Co., Ltd. was dissolved in 174.57 kg of water, and then 3.15 kg of a 20 mass% aqueous solution of sodium triisopropylnaphthalenesulfonate and phthalazine compound-1 ( 14.28 kg of a 70% by weight aqueous solution of 6-isopropylphthalazine) was added to prepare a 5% by weight solution of phthalazine compound-1.

9) Preparation of mercapto compound <Preparation of aqueous solution of mercapto compound-2>
20 g of mercapto compound-2 (1- (3-methylureidophenyl) -5-mercaptotetrazole) was dissolved in 980 g of water to obtain a 2.0 mass% aqueous solution.

10) Preparation of azomethine dye solid dispersion 1.0 kg of azomethine dye-A, 3.0 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., POVAL MP203), and surfactant (Pionin A-43-S) 42 g (48% by weight aqueous solution of Takemoto Yushi Co., Ltd.) and 3.0 g of antifoaming agent (Surfinol 104E (Shin-Etsu Chemical Co., Ltd.)) were added and mixed well to obtain a slurry.
This slurry was fed with a diaphragm pump and 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 5 hours. 0 g and water were added to adjust the concentration of the water-insoluble azomethine dye to 10% by mass. This dispersion was heated at 40 ° C. for 2 hours to obtain an azomethine-27 dispersion. The azomethine dye particles contained in the azomethine dye dispersion thus obtained had a median diameter of 0.49 μm and a maximum particle diameter of 2.6 μm or less. The obtained azomethine dye dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

11) Preparation of benzotriazole silver dispersion 1 kg of benzotriazole is added to a solution obtained by dissolving 360 g of sodium hydroxide in 9100 mL of water, and the mixture is stirred for 60 minutes, and the dissolved solution is used as a sodium benzotriazole solution BT.
A solution obtained by adding 55.9 g of alkali-treated deionized gelatin to 1400 mL of distilled water, stirring the solution in a stainless steel reaction vessel, maintaining the liquid temperature at 70 ° C., and adding distilled water to 54.0 g of silver nitrate and diluting to 400 mL A solution B is prepared by diluting A and benzotriazole sodium solution BT397mL with distilled water to a volume of 420mL, and by double jet method, solution B is added to a stainless steel reaction tank at a constant flow rate of 20mL / min over a period of 11 minutes. 1 minute after the start of addition of solution B, 200 ml of solution A was added to a stainless steel reaction vessel at a constant flow rate of 20 mL / min over 10 minutes. Thereafter, after 6 minutes, solutions A and B were added simultaneously at a constant flow rate of 33.34 mL / min in 200 mL portions over 6 minutes. After the temperature dropped to 45 ° C., 92 mL of Demol N (10% aqueous solution, manufactured by Kao Corporation) was added with stirring, the pH was adjusted to 4.1 with 1 mol / L sulfuric acid, and stirring was stopped. Then, precipitation / desalting / water washing steps were performed.
Then, after adjusting the temperature to 50 ° C. and adding 51 ml of 1 mol / L sodium hydroxide with stirring, 11 mL of a methanol solution of benzoisothiazolinone (3.5%), a methanol solution of sodium benzenethiosulfonate ( 1%) 7.7 mL was added, and after stirring for 80 minutes, the pH was adjusted to 7.8 using 1 mol / L sulfuric acid to prepare a benzotriazole silver dispersion.

  The particles of the prepared benzotriazole silver dispersion had an average equivalent circle diameter of 0.172 μm (variation coefficient of 18.5%), an average long side diameter of 0.32 μm, an average short side diameter of 0.09 μm, and an average long / short side ratio of 0.1. There were 298 particles. The particle size and the like were determined from the average of 300 particles using an electron microscope.

12) Preparation of SBR latex liquid SBR latex (TP-1) was prepared as follows.
In a polymerization kettle of a gas monomer reactor (TAS-2J type manufactured by Pressure Glass Industrial Co., Ltd.), 287 g of distilled water and a surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)): solid content 48.5 (Mass%) 7.73 g, 1 mol / L, NaOH 14.06 mL, ethylenediaminetetraacetic acid tetrasodium salt 0.15 g, styrene 255 g, acrylic acid 11.25 g, tert-dodecyl mercaptan 3.0 g were put, and the reaction vessel was sealed and stirred. Stir at a speed of 200 rpm. After degassing with a vacuum pump and repeating nitrogen gas replacement several times, 108.75 g of 1,3-butadiene was injected and the internal temperature was raised to 60 ° C. A solution prepared by dissolving 1.875 g of ammonium persulfate in 50 mL of water was added thereto and stirred as it was for 5 hours. The temperature was further raised to 90 ° C. and stirred for 3 hours. After completion of the reaction, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion = 1 using 1 mol / L NaOH and NH ₄ OH = 1. Addition treatment was performed so that the molar ratio was 5.3 (molar ratio), and the pH was adjusted to 8.4. Thereafter, the mixture was filtered with a polypropylene filter having a pore diameter of 1.0 μm to remove foreign substances such as dust and stored, and 774.7 g of SBR latex TP-1 was obtained. When halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. The concentration of the chelating agent measured by high performance liquid chromatography was 145 ppm.

  The latex has an average particle size of 90 nm, Tg = 17 ° C., solid content concentration of 44 mass%, equilibrium water content of 0.6 mass% at 25 ° C. and 60% RH, ion conductivity of 4.80 mS / cm (measurement of ion conductivity is The conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd. was used and measured at 25 ° C.).

13) Preparation of isoprene latex liquid Isoprene latex (TP-2) was prepared as follows.
Add 1500 g of distilled water to the polymerization kettle of the gas monomer reactor (Pressure Glass Industry Co., Ltd. TAS-2J type), heat at 90 ° C. for 3 hours, and passivate to the stainless steel surface of the polymerization kettle and members of the stainless steel stirring device A film is formed. In the polymerization kettle subjected to this treatment, 582.28 g of distilled water in which nitrogen gas was bubbled for 1 hour, 9.49 g of surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)), 1 mol / L NaOH Of ethylenediaminetetraacetic acid tetrasodium salt 0.20 g, styrene 314.99 g, isoprene 190.87 g, acrylic acid 10.43 g, tert-dodecyl mercaptan 2.09 g, and the reaction vessel was sealed and stirred at 225 rpm. The mixture was stirred and heated to an internal temperature of 65 ° C. A solution prepared by dissolving 2.61 g of ammonium persulfate in 40 mL of water was added thereto, and the mixture was stirred as it was for 6 hours. At this point, the polymerization conversion rate was 90% from the solid content measurement. Here, a solution in which 5.22 g of acrylic acid was dissolved in 46.98 g of water was added, 10 g of water was subsequently added, and a solution in which 1.30 g of ammonium persulfate was dissolved in 50.7 mL of water was further added. After the addition, the temperature was raised to 90 ° C. and stirred for 3 hours. After the reaction was completed, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion was used using 1 mol / L NaOH and NH ₄ OH. = 1: 5.3 (molar ratio) was added and adjusted to pH 8.4. Thereafter, the mixture was filtered with a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored, and 1248 g of isoprene latex TP-1 was obtained. When halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 142 ppm.

  The latex has an average particle size of 113 nm, Tg = 15 ° C., solid content concentration of 41.3 mass%, equilibrium water content at 25 ° C. and 60% RH of 0.4 mass%, ionic conductivity of 5.23 mS / cm (of ionic conductivity). Measurement was conducted at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.).

2. Preparation of coating solution 1) Preparation of coating solution for image forming layer 1000 g of fatty acid silver dispersion, 5% by weight aqueous solution of blue dye-2, azomethine dye solid dispersion, organic polyhalogen compound-1 dispersion, organic polyhalogen compound-2 Dispersion, phthalazine compound-1 solution, 2% by weight aqueous solution of Metroze 60SH50 manufactured by Shin-Etsu Chemical Co., Ltd., SBR latex (TP-1) solution, isoprene latex (TP-2) solution, reducing agent-1 as a thickener Dispersion, reducing agent-2 dispersion, hydrogen bonding compound-1 dispersion, development accelerator-1 dispersion, development accelerator-2 dispersion, color tone modifier-1 dispersion, mercapto compound-2 aqueous solution in this order Then, 140 g of silver halide mixed emulsion A was added immediately before coating, and the well-mixed image forming layer coating solution was fed to the coating die as it was and coated.

2) Preparation of intermediate layer coating solution << Intermediate layer coating solution-1 >>
Polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.) 1000 g, sulfosuccinic acid di (2-ethylhexyl) sodium salt 5% aqueous solution 37 mL, Clariant Blue dye FRL-SF 10 mass% aqueous solution 153 mL, methyl methacrylate / styrene / butyl Add 4632 mL of 19 mass% latex of acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2), reduce 565 mL of 20 mass% aqueous solution of diammonium phthalate. 1 dispersion to 2319G, the water to a total volume 13200ml added and adjusted with NaOH to pH 7.5 with an intermediate layer coating solution, a coating die so that 8.3 mL / ^{m 2} The solution was sent to.
The viscosity of the coating solution was 58 [mPa · s] at 40 ° C. (No. 1 rotor, 60 rpm) B-type viscometer.

<< Intermediate layer coating solution-2 to 10 >>
For intermediate layer coating solution-1, hollow polymer latex Nipol MH5055 (manufactured by Zeon Corporation, modified styrene / acrylic, particle size 0.5 μm, hollow ratio 55%, Tg 105 ° C.) as a solid content coating amount of 150 mg / was added such that the m ^2, and an intermediate layer coating solution 2. Furthermore, the hollow particles shown in Table 3 were added so as to have the coating amount shown in Table 2.

3) Preparation of surface protective layer first layer coating solution 1000 g of inert gelatin, 1 g of benzoisothiazolinone, 385 g of benzotriazole silver dispersion A, 543 mL of 15% by weight methanol solution of phthalic acid, 15% by weight of 4-methylphthalic acid Add 160 mL of aqueous solution, 58 mL of mixed aqueous solution of 17% by mass of homophthalic acid and 23% by mass of trishydroxyaminomethane, and 55.2 mL of 5% by mass aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate, and mix to a total amount of 9913 mL Water was added so that methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) latex 19% by weight 1788 mL immediately before coating, 4% by weight chromium alum A solution obtained by mixing 406 mL with a static mixer was fed to a coating die so that the amount of the coating solution was 25 mL / m ² .
The viscosity of the coating solution was 20 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

4) Preparation of surface protective layer second layer coating solution 1000 g of inert gelatin, 1 g of benzoisothiazolinone, 185 mL of 30% by mass solution of carnauba wax (manufactured by Chukyo Yushi Co., Ltd., SELESOL 524), methyl methacrylate / styrene / butyl acrylate / Hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) 1962% latex by weight 1762 mL, phthalic acid 15% by weight methanol solution 389 mL, fluorosurfactant (F- 129 mL of a 1% by mass solution of 1), 50 mL of a 1% by mass aqueous solution of a fluorosurfactant (F-2), 240 mL of a 10% by mass aqueous solution of a surfactant (F-3), disulfosuccinate (2- 244 mL of 5% by weight aqueous solution of ethylhexyl) sodium salt, polymethylmeta as a matting agent The surface protective layer coating solution is 8.3 mL, in which 31 g of acrylate fine particles (average particle size 0.7 μm) and 164 g of polymethyl methacrylate fine particles (average particle size 6.3 μm) are added and mixed so that the total amount is 13242 mL. / M ² to the coating die.
The viscosity of the coating solution was 24 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3. Preparation of photothermographic material Simultaneously multilayer coating by slide bead coating method in the order of image forming layer, intermediate layer, surface protective layer first layer, surface protective layer second layer from the undercoat surface to the surface opposite to the back surface, A sample of the photothermographic material was prepared. The coating amount of the intermediate layer coating solution 8.3 mL / ^{m 2,} the coating amount of the surface protective layer first layer coating solution is 25 mL / ^{m 2,} the coating amount of the surface protective layer and the second layer coating solution is 8.3 mL / ^{m 2} Met.
The coating amount (g / m ² ) of each compound in the image forming layer is as follows.

Fatty acid silver (as Ag) 0.958
Blue dye-2 0.006
Magenta dye 0.009
Polyhalogen compound-1 0.10
Polyhalogen compound-2 0.19
Phthalazine Compound-1 0.12
Thickener (60SH50) 0.10
SBR latex (TP-1) 1.78
Isoprene latex (TP-2) 4.17
Reducing agent-1 0.31
Reducing agent-2 0.32
Hydrogen bonding compound-1 0.05
Development accelerator-1 0.011
Development accelerator-2 0.016
Color tone adjusting agent-1 0.003
Mercapto compound-2 0.009
Silver halide (as Ag) 0.09

The coating and drying conditions are as follows.
Application was performed at a speed of 180 m / min, the gap between the coating die tip and the support was set to 0.10 mm to 0.30 mm, and the pressure in the decompression chamber was set to be 196 Pa to 882 Pa lower than the atmospheric pressure. The support was neutralized with an ion wind before coating.
In the subsequent chilling zone, the coating liquid is cooled with a wind at a dry bulb temperature of 10 ° C. to 20 ° C., then transported in a non-contact manner, and dried at a dry bulb non-contact dryer with a dry bulb temperature of 23 ° C. to 45 ° C. It dried with the dry wind of 15 degreeC and 21 degreeC wet bulb temperature.
After drying, the humidity was adjusted at 25 ° C. and humidity of 40% RH to 60% RH, and then the film surface was heated to 70 ° C. to 90 ° C. After heating, the film surface was cooled to 25 ° C.

  The chemical structures of the compounds used in the examples of the present invention are shown below.

4). Evaluation of photographic performance 1) Preparation The obtained samples were cut into half-cut sizes, packaged in the following packaging materials in an environment of 25 ° C. and 50% RH, stored at room temperature for 2 weeks, and then evaluated as follows. .
<Packaging materials>
Laminate film in which PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% by mass of carbon is laminated;
Oxygen permeability: 0.02 mL / atm · m ² · 25 ° C · day,
Moisture permeability: 0.10 g / atm · m ² · 25 ° C · day.

2) Image exposure and development of photothermographic material Each sample was image-exposed with a dry laser imager DRYPIX7000 (equipped with a 660 nm semiconductor laser with a maximum output of 50 mW (IIIB)) and heat development (107 ° C. − 3 panel heaters set at 121 ° C.-121 ° C. for a total of 14 seconds), and the obtained images were evaluated with a densitometer.

3) Evaluation method (transportability)
Using Fuji Medical's dry laser imager DRYPIX7000 (equipped with a 660 nm semiconductor laser with a maximum output of 50 mW (IIIB)), development processing was performed under forced conditions modified to cause conveyance failure, and the occurrence rate of conveyance failure was measured. did.

(Measure haze)
The degree of haze represents the degree to which the light beam incident on the photosensitive material diffuses, and represents the ratio between the diffuse transmitted light amount and the total transmitted light amount as a percentage. For the measurement of haze, a haze measuring device MODEL1001DP manufactured by NIPPON DENSHKU Co., Ltd. was used.
About each unexposed sample, the haze degree of the film | membrane before and after heat development processing was measured, and the ratio of the haze degree after heat development with respect to the haze degree before heat development processing was computed.

(Beck second measurement)
The smoothness of the surface of the photothermographic material was determined by measuring the time required for 10 mL of air to pass under the condition of JIS standard constant air pressure (370 mmHg).

(Photo performance)
The fog is indicated by the density of the unexposed portion of the sample exposed and developed with the photothermographic material.
Dmax is the same sample evaluated for fogging and represents the maximum density saturated with increasing exposure.

(Image unevenness test)
<Evaluation of Stardust>
Under the environment of 25 ° C. and 65 RH%, 10 photothermographic materials were prepared and stacked so that the non-photosensitive back surface and the image forming surface were in contact with each other. A stainless steel metal rod having a flat portion with a diameter of 1 cm was prepared, and a load of 10 kg / cm ² was applied for 30 minutes so that the flat portion was in contact with the upper side of the image forming surface of the stacked photothermographic material. Thereafter, an exposure heat development process was performed using the DRYPIX 7000 at an exposure amount giving a density of 3.0. In the photosensitive material having the image forming surface that was in contact with the non-photosensitive back surface, the density difference between the portion to which the load was applied and the portion to which the load was not applied was measured using a densitometer.

<Evaluation of interference fringes>
An exposure amount that gives a density of 2.0 in a situation where interference fringes are easily generated by replacing the 660 nm semiconductor laser of DRYPIX7000 with a semiconductor laser having excellent coherence (wavelength and phase are well aligned). After the exposure and heat development treatment, the level of occurrence of the wood-like interference fringes was visually evaluated using a shaucus ten.

4) Evaluation results The results obtained are shown in Table 4.
By adding hollow particles to the intermediate layer, image unevenness was remarkably improved. When the matting agent is not contained in the back layer, there is a problem that the transportability is lost and the image forming apparatus cannot be continuously processed, but image unevenness does not occur. By using hollow particles, the characteristics of transportability were maintained, and the occurrence of image unevenness was suppressed.
If the void ratio of the hollow particles is too high, the shape stability of the hollow particles is poor and the characteristics of the hollow particles are lost during the production process, so that the scattering effect cannot be obtained. On the other hand, if the size of the hollow particles is small, the porosity becomes low and a sufficient refractive index cannot be obtained, so that a scattering effect cannot be obtained.
If the Tg of the hollow particles is low, the shape stability against heat is poor, and the characteristics of the hollow particles are lost during the production process, so that the scattering effect cannot be obtained. If the Tg is too high, the haze does not decrease after the heat development process, so that the image quality is deteriorated. It has been found that when Tg is optimum, the form is stable in the production process to the exposure process, but the haze is lowered after heat development and a good image quality is obtained.

Example 2
1) Sample preparation Samples 13 to 24 in the same manner as in Example 1 except that the coated silver amount and the layer to which the hollow particles are added are changed as shown in Table 5 in Samples 2, 3 and 4 of Example 1. Was made.
2) Performance evaluation The obtained sample was evaluated in the same manner as in Example 1. The results are shown in Table 6.
From the results in Table 6, when the amount of applied silver was reduced to 1.5 g / m ² or less, star dust and interference fringe unevenness increased rapidly. The addition of the hollow particles was remarkable in improving the image unevenness in this region. Further, the matting agent for the back layer improves the transportability, but causes image unevenness in the region of a small amount of coated silver, but has been improved by using hollow particles. That is, it is possible to satisfy both transportability and image unevenness by including a matting agent in the back layer and incorporating hollow particles in the layer on the image forming layer surface. Further, it is unexpected that the hollow particles can be easily added to the intermediate layer and the light-sensitive emulsion layer, and further haze reduction after heat development can be greatly obtained, and the image quality is excellent. Among them, the addition to the intermediate layer is the best.

Example 3
1) Preparation of Samples Samples 25 and 30 were prepared in the same manner as in Example 1 except that the size of the matting agent on the non-photosensitive back surface side in Samples 3 and 4 of Example 1 was changed as shown in Table 7. .
2) Performance evaluation The obtained sample was evaluated in the same manner as in Example 1. The results are shown in Table 8.
From the results shown in Table 8, when the size of the non-photosensitive matting agent is reduced to less than 3 μm, the stardust is improved, but jamming occurs in the imager and the transportability is deteriorated. In order to ensure the transportability, the mat agent size needs to be 3 μm or more, but the star dust is deteriorated, but at this time, it was improved by using hollow particles.
That is, it is possible to satisfy both transportability and image unevenness by containing a matting agent having a particle diameter of 3 μm or more in the back layer and hollow particles in the image forming layer surface.

Claims (14)

  An image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent and a binder is provided on one side of the support, and a non-photosensitive layer is provided on the image forming layer side of the support. A photothermographic material having a non-photosensitive back layer on the other side, wherein the non-photosensitive back layer contains a matting agent, and any one layer on the image-forming layer side contains hollow particles. A photothermographic material characterized by the above.   A non-photosensitive outermost layer containing a matting agent having an average particle size of 0.1 μm or more and 10 μm or less is provided on the image forming layer surface side, and a layer containing the hollow particles is provided between the support and the non-photosensitive outermost layer. The photothermographic material according to claim 1, comprising at least one layer.   3. The layer containing the hollow particles is at least one layer selected from the image forming layer or a layer between the image forming layer and the non-photosensitive outermost layer. The photothermographic material according to the description.   4. The photothermographic material according to claim 2, wherein the image forming layer, the layer containing the hollow particles, and the non-photosensitive outermost layer are formed by aqueous coating.   5. The photothermographic material according to claim 1, wherein the hollow particles have a hollow ratio of 20% to 70%.   The photothermographic material according to claim 1, wherein the hollow particles have a refractive index of 1.0 to 1.3.   The photothermographic material according to claim 1, wherein the hollow particles have a glass transition temperature (Tg) of 30 ° C. or higher and 150 ° C. or lower.   8. The photothermographic material according to claim 1, wherein the hollow particles are a hollow polymer latex. The photothermographic material according to claim 1, wherein the silver coating amount is 0.3 g / m ² or more and 1.5 g / m ² or less. The photothermographic material according to claim 9, wherein the coated silver amount is 0.7 g / m ² or more and 1.2 g / m ² or less.   11. The photothermographic material according to claim 1, wherein the photothermographic material has a haze degree after heat development of less than 80% before heat development. 11.   12. The photothermographic material according to claim 4, wherein 50% by mass or more of the binder of the non-photosensitive outermost layer is gelatin. 13. The polymer latex according to claim 4, wherein 50% by mass or more of the binder in the image forming layer is a polymer latex obtained by copolymerizing the monomer represented by the general formula (M). Photothermographic material:
General formula (M)
CH ₂ = CR ⁰¹ -CR ⁰² = CH ₂
(In the formula, R ⁰¹ and R ⁰² are a group selected from a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a halogen atom, or a cyano group). 14. The photothermographic material according to claim 13, wherein R ⁰¹ and R ⁰² are both hydrogen atoms, or one is a hydrogen atom and the other is a methyl group.