JP2006133365A - Heat developable photosensitive material and image forming method for heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material maintaining high image density and high sensitivity, also free from the occurrence of unevenness in the density in heat development, and having excellent image preservability in light irradiation, and to provide an image forming method for the heat developable photosensitive material. <P>SOLUTION: The heat developable photosensitive material has, on one side of a support, a photosensitive layer containing an organic silver salt, silver halide, a binder, and a reducing agent, and on the other side, a back coat layer, wherein the back coat layer is a layer formed using modified gelatin soluble in both of water and an organic solvent, and polymer latex. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention provides a photosensitive material for heat development, in which a photosensitive layer containing an organic silver salt, silver halide, a binder and a reducing agent is provided on one side of a support, and a backcoat layer is provided on the other side, and The present invention relates to an image forming method.

  Conventionally, in the medical and printing plate making fields, waste liquid treatment associated with wet processing of image forming materials has been a problem in terms of workability, and in recent years, reduction of waste processing liquid is strongly desired from the viewpoint of environmental conservation and space saving. It is rare. Therefore, photothermographic materials capable of forming an image only by applying heat have been put into practical use and are rapidly spreading in the above fields.

  A photothermographic material (hereinafter also simply referred to as a photothermographic material or a photosensitive material) has been proposed for a long time. For example, US Pat. Nos. 3,152,904 and 3,457,075 It is described in.

  This heat-developable material is usually processed and image-formed by a heat-development processing apparatus called a heat-development processor that forms an image by applying stable heat to the heat-developable material.

  As described above, with the rapid spread in recent years, a large amount of this heat development processing apparatus has been supplied to the market. In recent years, there has been a demand for compact laser imagers and rapid processing.

  For this purpose, it is necessary to improve the characteristics of the photothermographic material. In order to obtain a sufficient density of the photothermographic material even if rapid processing is performed, a silver halide having a small average grain size as disclosed in JP-A-11-295844 and JP-A-11-352627 To increase the covering power by increasing the number of coloring points, or to use a highly active reducing agent having a secondary or tertiary alkyl group as disclosed in JP-A-2001-209145, It is effective to use development accelerators such as hydrazine compounds, vinyl compounds, phenol derivatives, and naphthol derivatives as described in Japanese Patent No. 278017 and Japanese Patent Application Laid-Open No. 2003-066558.

Further, in the photothermographic material using photosensitive silver halide, since silver halide remains in the emulsion layer even after heat development, there is a problem that light irradiation image storage stability deteriorates.
As described in JP-A-2003-270755 and JP-A-2004-004522, attempts have been made to improve the emulsion layer to solve these problems.

  Further, as a response from the apparatus side to the rapid processing, a technique of performing thermal development while transporting at 23 mm / second or more, or performing thermal development simultaneously with exposure is disclosed (see Patent Documents 1 and 2).

  However, when thermal development is performed at the same time as exposure, the exposure section and the thermal development section are close to each other, so vibration in the exposure section is easily transmitted to the thermal development section, and the time from exposure to thermal development. There is a problem that a time difference occurs between the front and rear ends of the photosensitive material, and density unevenness occurs during thermal development (see Patent Document 3).

  On the other hand, a technique is known in which polymer latex is used as 50% by mass or more of the total binder of the backcoat layer for the purpose of preventing sticking between sensitive materials even when stored in a high humidity atmosphere (Patent Literature). 4).

However, even in the photosensitive material as described above, when thermal development is performed while conveying the photosensitive material at a high speed, density unevenness occurs more significantly than when the thermal development is performed at a low speed, and the humidity during the thermal development fluctuates. In some cases, the image density may fluctuate greatly, the image storability during light irradiation is insufficient, and the sensitivity and the maximum density of the image are also insufficient.
US Patent Application Publication No. 2004/0058281 JP 2004-087563 A (Claims) JP 2004-138724 A (conventional technology) JP-A-10-069023 (Claims)

  An object of the present invention is to provide a photothermographic material and an image forming method for the photothermographic material that maintain high image density and high sensitivity, have no uneven density during heat development, and have excellent image storability during light irradiation. It is to provide.

  The above object of the present invention is achieved by the following means.

(Claim 1)
In a photothermographic material having a photosensitive layer containing an organic silver salt, silver halide, a binder and a reducing agent on one side of a support and a backcoat layer on the other side, the backcoat layer is A photothermographic material characterized by being a layer formed using a modified gelatin and polymer latex soluble in both water and an organic solvent.

(Claim 2)
2. The photothermographic material according to claim 1, wherein 95% or more of the amino groups in the molecule of the modified gelatin are substituted with hydrophobic groups.

(Claim 3)
3. The photothermographic material according to claim 1, wherein in the modified gelatin, 50% or more of the carboxyl groups in the molecule are substituted with hydrophobic groups.

(Claim 4)
The photothermographic material according to claim 1, wherein the polymer latex has a polymer amount of 15 to 45% by mass with respect to the backcoat layer.

(Claim 5)
The said photosensitive layer is a layer formed using the coating liquid for photosensitive layers whose 60 mass% or more of a solvent is an organic solvent, The any one of Claims 1-4 characterized by the above-mentioned. Photothermographic material.

(Claim 6)
A photothermographic development process comprising: an image forming process comprising: an exposure process for exposing an image of the photothermographic material according to any one of claims 1 to 5; and a development process for thermally developing the photothermographic material subjected to image exposure. An image forming method of a photosensitive material, wherein the image forming step includes a step in which the exposure step and the development step are performed simultaneously.

(Claim 7)
7. The image forming method of a photothermographic material according to claim 6, wherein the photothermographic treatment is performed while conveying the photothermographic material at a speed of 20 to 200 mm / sec.

(Claim 8)
The photothermographic material according to claim 6, wherein the photothermographic material according to any one of claims 1 to 5 is subjected to heat development while being conveyed at a speed of 20 to 200 mm / sec. Image forming method.

  With the above-described configuration of the present invention, a photothermographic material that maintains high image density and high sensitivity, does not cause density unevenness due to conveyance during heat development, and does not generate density unevenness due to humidity fluctuation, and is excellent in image storability during light irradiation. And an image forming method of the photothermographic material.

  The present invention relates to a photothermographic material having a photosensitive layer containing an organic silver salt, silver halide, a binder and a reducing agent on one side of a support and a backcoat layer on the other side. The backcoat layer is a layer formed using a modified gelatin and a polymer latex that are soluble in both water and an organic solvent as a binder.

  In the present invention, a modified gelatin and a polymer latex that are soluble in both water and an organic solvent are used as a binder for the backcoat layer in particular, so that high image density and high sensitivity can be maintained, and at the time of heat development. A photothermographic material having no density unevenness and excellent image storability upon light irradiation can be provided.

  The backcoat layer according to the present invention refers to a substantial outermost layer among the layers provided on the surface opposite to the surface having the photosensitive layer of the support, and is used for both water and organic solvents. It is a layer formed using soluble modified gelatin and polymer latex. The substantially outermost layer means a case where the other layer is not formed on this layer (on the side opposite to the support) or the film thickness is 0.1 μm or less even if there is a layer. Say.

  Between the backcoat layer according to the present invention and the support, an intermediate layer containing gelatin and polymer latex similar to the backcoat layer according to the present invention may be provided.

  The layer formed using modified gelatin and polymer latex soluble in both water and organic solvent refers to a layer formed by applying and drying a coating solution containing the modified gelatin and polymer latex. The backcoat layer contains the modified gelatin and polymer latex polymer.

The amount attached on the support of the back coat layer, it is preferably ^{1.0g / m 2 ~4.0g / m 2} , a further 1.5g / m ² ~3.0g / m ² preferable.

(Modified gelatin)
The modified gelatin soluble in both water and organic solvent according to the present invention will be described.

  Soluble in both water and organic solvent means that the solubility in water (g dissolved in 100 ml of water at 25 ° C.) is 3 g or more and the solubility in tetrahydrofuran (THF) (g dissolved in 100 ml of THF at 25 ° C. This refers to a modified gelatin having a (number) of 2.4 g or more.

  The modified gelatin referred to in the present invention is one in which a part of the amino group and / or carboxyl group in the molecule of natural gelatin is substituted with a hydrophobic group (hereinafter, substitution with a hydrophobic group is simply abbreviated as substitution) A hydrophobic group is a group whose solubility in water is reduced by substitution.

  Examples of the hydrophobic group include, but are not limited to, alkyl groups, phenylcarbamoyl groups, phthalic acid residues, succinic acid residues, acetyl groups, benzoyl groups, and nitrophenyl groups.

  As the modified gelatin according to the present invention, any one in which only an amino group is substituted and one in which only a carboxyl group is substituted can be used, but a modified gelatin having at least an amino group substituted is preferably used.

  In the modified gelatin having at least an amino group substituted, the substitution ratio of the amino group with a hydrophobic group is preferably 95% or more, and more preferably 99% or more.

  As the modified gelatin according to the present invention, those having an amino group substituted and a carboxyl group substituted can also be preferably used.

  Further, the substitution ratio of the carboxyl group with the hydrophobic group is preferably 50 to 90%, more preferably 70 to 90%.

  The ratio of substitution of the amino group by the hydrophobic group is the ratio of the amino group substituted by the hydrophobic group to the amount of the amino group of the natural gelatin of the raw material, the amount of the amino group of the natural gelatin before the substitution and the amino group after the substitution It can be calculated by measuring the amount of.

  The substitution ratio of the carboxyl group can be similarly determined.

  The molecular weight of the modified gelatin according to the present invention is preferably 10,000 to 1,000,000. The molecular weight here refers to the number average molecular weight calculated by gel permeation chromatography (GPC) in terms of styrene.

  Examples of the method for producing the modified gelatin include the method described in “The Macromolecular Chemistry of Gelatin” written by Arthur Weiss (Academic Press, 1964).

  The content of the modified gelatin is preferably 55% by mass to 85% by mass and particularly preferably 60% by mass to 80% by mass with respect to the back coat layer from the viewpoint of coating suitability and scratch resistance.

(Polymer latex)
The polymer latex according to the present invention is obtained by dispersing particles made of a polymer in a solvent.

  The dispersed dispersed particles have an average particle size of 1 to 50000 nm, preferably 5 to 1000 nm, more preferably 10 to 500 nm, and still more preferably 50 to 200 nm.

  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.

  The polymer used in the polymer latex according to the present invention is preferably a polymer dispersible in an aqueous solvent. For example, acrylic polymers, poly (esters), rubbers (for example, SBR resin), poly (urethanes), poly (urethanes) Hydrophobic polymers such as vinyl chlorides), poly (vinyl acetate) s, poly (vinylidene chloride) s, poly (olefins) and the like.

  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. These polymers have a number average molecular weight of 5,000 to 1,000,000, preferably 10,000 to 200,000.

  A polymer latex containing a crosslinkable polymer is particularly preferably used.

  The glass transition temperature (hereinafter sometimes abbreviated as Tg) of these polymers is preferably −10 ° C. or higher and 120 ° C. or lower, and more preferably 0 ° C. or higher and 90 ° C. or lower. The polymer is preferably transparent or translucent and generally colorless.

  In the present invention, Tg is 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. The homopolymer glass transition temperature value (Tgi) of each monomer is the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)).

  Specific examples of preferred polymers 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 crosslinkable and the molecular weight description was omitted.
B-1; -MMA (70) -EA (27) -MAA (3)-(molecular weight 37000, Tg 61 ° C.)
B-2; -MMA (70) -2EHA (20) -St (5) -AA (5)-(molecular weight 40000, Tg 59 ° C.)
B-3; -MMA (63) -EA (35) -AA (2)-(molecular weight 33000, Tg 47 ° C.)
B-4; -St (67) -Bu (30) -DVB (0.5) -HEMA (2.5)-(crosslinkability, Tg 14 ° C.)
B-5; -St (75) -Bu (24) -AA (1)-(crosslinkability, Tg 29 ° C.)
B-6; -St (68) -Bu (29) -AA (3)-(crosslinkability, Tg 18 ° C.)
B-7; -St (71) -Bu (26) -AA (3)-(Crosslinkability, Tg 24 ° C.)
B-8; -St (74) -Bu (23) -AA (3)-(crosslinkability, Tg 31 ° C.)
B-9; -St (77.5) -Bu (19.5) -AA (3)-(crosslinkability, Tg 40 ° C.)
B-10; -St (81.3) -Bu (15.7) -AA (3)-(crosslinkability, Tg 50 ° C.)
B-11; -St (84.8) -Bu (12.2) -AA (3)-(crosslinkability, Tg 60 ° C.)
B-12; -St (88) -Bu (9) -AA (3)-(crosslinkability, Tg 70 ° C.)
B-13; -St (70) -2EHA (27) -AA (3)-(molecular weight 130000, Tg 43 ° C)
B-14; -St (57) -MMA (9) -BA (28) -HEHA (4) -AA (2) (Tg 50 ° C.)
The abbreviations for the above structures represent the following monomers. MMA; methyl methacrylate, EA; ethyl acrylate, BA; butyl acrylate, MAA; methacrylic acid, 2EHA; 2-ethylhexyl acrylate, St; styrene, Bu; butadiene, AA; acrylic acid, DVB; divinylbenzene, VC; AN; acrylonitrile, VDC; vinylidene chloride, HEMA; hydroxyethyl methacrylate, Et; ethylene, IA; itaconic acid.

  Latexes containing the polymers described above are also commercially available, and the following polymers can be used.

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

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

  As the polymer latex used in the backcoat layer according to the present invention, a latex containing an acrylic copolymer is preferable.

  The mass ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably 40:60 to 95: 5.

  The proportion of the styrene monomer unit and the butadiene monomer unit in the copolymer is preferably 60 to 99% by mass.

  In the present invention, the polymer latex polymer preferably contains 1 to 15% by mass of a monomer having a hydrophilic group such as acrylic acid or methacrylic acid based on the sum of styrene and butadiene, more preferably 2 to 10%. Contains by mass%.

  Examples of latexes of styrene-butadiene acid copolymer that are preferably used in the present invention include B-4 to B-13, LACSTAR-3307B, 7132C, and NipolLx416, which are commercially available products.

  In addition, the polymer latex polymer according to the present invention is a polymer having an equilibrium water content of 2% by mass or less at 25 ° C. and 60% (relative humidity). Yes, it is preferable.

  The equilibrium moisture content is more preferably 0.01% by mass to 1.5% by mass, and further preferably 0.02% by mass to 1% by mass.

  The equilibrium water content at 60 ° C. (relative humidity) at 25 ° C. means the mass W1 of the polymer in a humidity-controlled equilibrium under an atmosphere of 25 ° C. and 60% (relative humidity) and the mass of the polymer in an absolutely dry state at 25 ° C. It can be expressed as follows using W0.

  Equilibrium water content at 25 ° C. and 60% (relative humidity) = [(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.

In the present invention, the amount per polymer mer latex polymer is preferably 0.15~1.8g / m ^2, and more preferably from 0.2~1.4g / m ^2.

  The content of the polymer latex in the polymer back coat layer is preferably 15% by mass to 45% by mass, and particularly preferably 20% by mass to 40% by mass.

(Organic silver salt)
The photosensitive layer according to the present invention contains an organic silver salt, silver halide, a binder and a reducing agent.

  The organic silver salt according to the present invention is relatively stable to light, but is heated to 80 ° C. or higher in the presence of an exposed photocatalyst (such as a latent image of photosensitive silver halide) and a reducing agent. Silver salt that forms a silver image when applied.

  As for such a non-photosensitive organic silver salt, paragraphs “0048” to “0049” of JP-A No. 10-62899, page 18, line 24 to No. 803 of European Patent Application Publication No. 803,764A1. 19th page, 37th line, European Patent Application Publication No. 962,812A1, Japanese Patent Application Laid-Open No. 11-349591, Japanese Patent Application Laid-Open No. 2000-7683, Japanese Patent Application Laid-Open No. 2000-72711, Japanese Patent Application Laid-Open No. 2002-23301, 2002. No. 23303, No. 2002-49119, No. 196446, European Patent Application Publication No. 1246001A1, European Patent Application Publication No. 1258775A1, Japanese Patent Application Laid-Open No. 2003-140290, Japanese Patent Application Laid-Open No. 2003-195445. Gazette, 2003-295378, 2003-295379, ibid. 003-295380, JP disclosed in this 2003-295381 Patent Publication.

  In the present invention, a silver salt of an aliphatic carboxylic acid, particularly (a silver salt of a long-chain aliphatic carboxylic acid having 10 to 30, preferably 15 to 28 carbon atoms) is used in combination with the organic silver salt. The molecular weight of the aliphatic carboxylic acid for producing the silver salt is preferably 200 to 500, more preferably 250 to 400. Preferred examples of the fatty acid silver salt include silver behenate and silver arachidate. Silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, and mixtures thereof.

  In the present invention, among these fatty acid silvers, the silver behenate content is preferably 50 mol% or more, more preferably 80 mol% or more and 99.9 mol% or less, still more preferably 90 mol% or more and 99.9 mol%. The following fatty acid silver is preferably used.

  As organic silver other than the above, a core-shell organic silver salt (Japanese Patent Laid-Open No. 2002-23303), a silver salt of a polyvalent carboxylic acid (EP1246001 and Japanese Patent Laid-Open No. 2004-061948), and a polymer silver salt (Japanese Patent Laid-Open No. 2000) No. -292881, Japanese Patent Laid-Open No. 2003-295378 to 2003-29581) can also be used.

  There is no restriction | limiting in particular as a shape of the organic silver salt which can be used for this invention, Any of needle shape, rod shape, flat plate shape, and flake shape may be sufficient. 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 salt particles are characterized by less fogging during thermal development than long needle-like particles having a major axis / uniaxial length ratio of 5 or more. The scaly organic silver salt is defined as follows. The organic acid silver salt was observed with an electron microscope, the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped were designated a, b, and c from the shortest side (c was the same as b). Then, the shorter numerical values a and b are calculated, and x is obtained as follows.

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

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

  The particle size distribution of the organic silver salt is preferably monodispersed. Monodispersion is preferably 100% or less, more preferably 80% or less, and even more preferably 50% of the value obtained by dividing the standard deviation of the lengths of the short and long axes by the short and long axes. It is as follows.

  The method for measuring the shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion. As another method for measuring monodispersity, there is a method for obtaining the standard deviation of the volume weighted average diameter of the organic silver salt, and the percentage (variation coefficient) of the value divided by the volume weighted average diameter is preferably 100% or less, more Preferably it is 80% or less, More preferably, it is 50% or less.

  As a measuring method, for example, 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 temporal change of fluctuation of the scattered light. Can be sought.

  Known methods and the like can be applied to the production of the organic acid silver that can be used in the present invention and the dispersion method thereof. For example, Japanese Patent Application Laid-Open No. 10-62899, European Patent Application Publication No. 803,763A1, European Patent Application Publication No. 962,812A1, Japanese Patent Application Laid-Open No. 2001-167022, and Japanese Patent Application Laid-Open No. 2000-7683. No. 2000-72711, No. 2001-163889, No. 2001-163890, No. 2001-163828, No. 2001-33907, No. 2001-188313, No. 2001-83651, Reference can be made to JP-A Nos. 2002-6442, 2002-31870, and 2003-280135.

  In addition, when the photosensitive silver salt is allowed to coexist at the time of dispersion of the organic silver salt, the fog is increased 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.

  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% or less, based on 1 mol of the organic acid silver salt in the solution, More preferably, no positive photosensitive silver salt is added.

  It is possible to produce a photosensitive material by mixing an organic silver salt aqueous dispersion and a photosensitive silver salt aqueous dispersion, but the mixing ratio of the organic silver salt and the photosensitive silver salt can be selected according to the purpose. The ratio of the photosensitive silver salt to 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.

The organic silver salt according to the present invention can be used in a desired amount, but the silver amount is preferably 0.1 to 5 g / m ² , more preferably 0.3 to 3 g / m ² , still more preferably 0.5 to ² g. / M ² .

(Silver halide)
The silver halide according to the present invention (hereinafter also referred to as photosensitive silver halide grains or silver halide grains) will be described. The silver halide according to the present invention can inherently absorb light as an intrinsic property of a silver halide crystal, or can absorb visible light or infrared light by an artificial physicochemical method, In addition, it is processed and manufactured so that physicochemical changes can occur in the silver halide crystal and / or on the crystal surface when light in any region within the light wavelength range from the ultraviolet light region to the infrared light region is absorbed. Silver halide crystal grains.

  The silver halide grains themselves used in the present invention can be prepared as a silver halide grain emulsion (also referred to as a silver halide emulsion) using a known method.

  That is, any of an acidic method, a neutral method, an ammonia method, etc. may be used, and a method of reacting a soluble silver salt and a soluble halogen salt may be any one of a one-side mixing method, a simultaneous mixing method, a combination thereof, and the like. Of these methods, the so-called controlled double jet method, in which silver halide grains are prepared while controlling the formation conditions, is preferred.

  Grain formation is usually divided into two stages: silver halide seed grain (nucleus) generation and grain growth, and these may be performed continuously at once, or the formation of nucleus (seed grain) and grain growth is separated. The method of performing may be used. The controlled double jet method in which the particle formation is controlled by controlling the pAg, pH, etc., which are particle formation conditions, is preferable because the particle shape and size can be controlled.

  For example, when performing a method in which nucleation and particle growth are performed separately, first, an aqueous silver salt solution and an aqueous halide solution are uniformly and rapidly mixed in an aqueous gelatin solution to produce nuclei (seed particles) (nucleation process). Then, silver halide grains are prepared by a grain growth process in which grains are grown while supplying an aqueous silver salt solution and an aqueous halide solution under controlled pAg, pH, and the like.

  After the formation of grains, a desired silver halide emulsion can be obtained by removing unnecessary salts and the like by a desalting step by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, or an electrodialysis method. .

  The grain size of the silver halide grains is preferably monodispersed. The monodispersion here means that the coefficient of variation of the particle size determined by the following formula is 30% or less. Preferably it is 20% or less, More preferably, it is 15% or less.

Coefficient of variation of particle size% = (standard deviation of particle size / average value of particle size) × 100
Examples of the shape of the silver halide grains include cubes, octahedrons, tetrahedron grains, tabular grains, spherical grains, rod-like grains, potato-like grains, etc. Among these, cubic, octahedral, 14 Planar and tabular silver halide grains are preferred.

  The average aspect ratio when using tabular silver halide grains is preferably 1.5 or more and 100 or less, more preferably 2 or more and 50 or less. These are described in US Pat. Nos. 5,264,337, 5,314,798 and 5,320,958, and the desired tabular grains can be easily obtained. . Further, grains having rounded corners of silver halide grains can be preferably used.

  There is no particular limitation on the crystal habit on the outer surface of the silver halide grain, but when using a sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the sensitizing dye on the surface of the silver halide grain. It is preferable to use silver halide grains having a relatively high proportion of crystal habits adapted to the selectivity. For example, when using a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100], the proportion of the [100] face on the outer surface of the silver halide grain is preferably high, and this ratio is 50 % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani, J .; ImagingSci. 29, 165 (1985).

  The silver halide grains used in the present invention are preferably prepared using low molecular weight gelatin having an average molecular weight of 50,000 or less at the time of forming the grains, but particularly preferably used at the time of nucleation of silver halide grains.

  In the present invention, the low molecular weight gelatin preferably has an average molecular weight of 50,000 or less, more preferably 2,000 to 40,000, and particularly preferably 5,000 to 25,000. The average molecular weight of gelatin can be measured by gel filtration chromatography. Low molecular weight gelatin can be hydrolyzed by adding gelatin-degrading enzyme to a commonly used gelatin aqueous solution with an average molecular weight of about 100,000, heating by adding acid or alkali, and heating under atmospheric pressure or pressure. Can be obtained by thermal decomposition, decomposition by ultrasonic irradiation, or a combination of these methods.

  The concentration of the dispersion medium at the time of nucleation is preferably 5% by mass or less, and more preferably 0.05 to 3.0% by mass.

  As the silver halide grains used in the present invention, it is preferable to use a compound represented by the following general formula when forming the grains.

YO (CH ₂ CH ₂ O) _m (CH (CH ₃ ) CH ₂ O) _p (CH ₂ CH ₂ O) _n Y
In the formula, Y represents a hydrogen atom, —SO ₃ M, or —CO—B—COOM, and M represents an ammonium group substituted with a hydrogen atom, an alkali metal atom, an ammonium group, or an alkyl group having 5 or less carbon atoms. And B represents a chain or cyclic group forming an organic dibasic acid. m and n each represents 0 to 50, and p represents 1 to 100.

  The polyethylene oxide compound represented by the above general formula comprises a step of producing a gelatin aqueous solution, a step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, and an emulsion. It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved, such as a step of coating on a support. This is described in Japanese Patent Publication No. 44-9497. The polyethylene oxide compound represented by the above general formula also functions as an antifoaming agent during nucleation. The compound represented by the above general formula is preferably used at 1% by mass or less, more preferably 0.01 to 0.1% by mass with respect to silver.

  The polyethylene oxide compound represented by the above general formula may be present at the time of nucleation and is preferably added in advance to the dispersion medium before nucleation, but may be added during nucleation or You may add and use for the silver salt aqueous solution and halide aqueous solution which are used at the time of formation.

  Preferably, it is used by adding 0.01 to 2.0% by mass to the halide aqueous solution or both aqueous solutions. Further, the compound represented by the above general formula is preferably present for a time of at least 50% of the nucleation step, and more preferably for a time of 70% or more. The compound represented by the above general formula may be added as a powder or dissolved in a solvent such as methanol.

  The temperature at the time of nucleation is usually 5 to 60 ° C., preferably 15 to 50 ° C. Even if the temperature is constant, the temperature rising pattern (for example, the temperature at the start of nucleation is 25 ° C. It is preferable to control the temperature within the above temperature range even when the temperature is gradually increased and the temperature at the end of nucleation is 40 ° C.) and vice versa.

The concentration of the aqueous silver salt solution and aqueous halide solution used for nucleation is preferably 3.5 mol / L or less, and more preferably used in a low concentration range of 0.01 to 2.5 mol / L. The addition rate of silver ions during nucleation is preferably 1.5 × 10 ^{−3 to} 3.0 × 10 ⁻¹ mol / min, more preferably 3.0 × 10 ^{−3 to} 8.0, per liter of the reaction solution. × 10 ^-2 mol / min.

  The pH at the time of nucleation can usually be set in the range of 1.7 to 10, but the pH on the alkali side broadens the particle size distribution of the nuclei to be formed, and is preferably pH 2 to 6. Moreover, pBr at the time of nucleation is 0.05-3.0 normally, Preferably it is 1.0-2.5, More preferably, it is 1.5-2.0.

  In the present invention, the average grain size of silver halide is usually from 10 to 50 nm, preferably from 10 to 40 nm, more preferably from 10 to 35 nm, from the viewpoint of image density and light irradiation image storage stability.

  The average grain size refers to the length of the edge of silver halide grains when the silver halide grains are cubic or octahedral so-called normal crystals. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface. In addition, in the case of non-normal crystals, for example, in the case of spherical particles, rod-like particles, etc., the diameter when considering a sphere equivalent to the volume of silver halide grains is calculated as the grain size. The measurement is performed using an electron microscope, and the average particle size is obtained by averaging the measured values of 300 particle sizes.

  By using silver halide grains having an average grain size of 55 to 100 nm and silver halide grains having an average grain size of 10 to 50 nm in combination, the image density can be improved or the image density deterioration with time can be improved ( Small).

  The ratio (mass ratio) of silver halide grains having an average grain size of 10 to 50 nm and silver halide grains having an average grain size of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90. : 10-60: 40.

(Silver halide having a silver iodide content of 5 mol% to 100 mol%)
As the halogen composition of silver halide, the silver iodide content is preferably 5 mol% or more and 100 mol% or less.

  If the silver iodide content is in this range, the intragranular halogen composition distribution may be uniform, may change stepwise, or may change continuously.

  Further, silver halide grains having a core / shell structure having a high silver iodide content inside and / or on the surface can also be preferably used. A preferable structure is a 2- to 5-fold structure, more preferably 2- to 4-fold core / shell particles.

  A preferable silver iodide content of halogen or silver is 10 mol% or more and 100 mol% or less with respect to the amount of silver halide.

  More preferably, they are 40 mol% or more and 100 mol% or less, More preferably, they are 70 mol% or more and 100 mol% or less, Especially preferably, they are 90 mol% or more and 100 mol% or less.

  The silver halide according to the present invention preferably exhibits direct transition absorption derived from the silver iodide crystal structure at a wavelength between 350 nm and 440 nm. Whether these silver halides have light absorption of direct transition can be easily distinguished by the fact that exciton absorption due to direct transition is observed in the vicinity of 400 nm to 430 nm. As a method for introducing silver iodide into the silver halide grains, a method of adding an alkali iodide aqueous solution during grain formation, fine grain silver iodide, fine grain silver iodobromide, fine grain silver iodochloride, fine grain silver iodochlorobromide Among them, the method of adding at least one fine particle, the method of using an iodide ion releasing agent described in JP-A-5-323487 and JP-A-6-11780 are preferable.

(Inner latent type silver halide grains after heat development)
The silver halide according to the present invention is preferably a silver halide grain whose surface sensitivity is lowered by converting from a surface latent image type to an internal latent image type by heat development.

  That is, in the exposure before thermal development, a latent image that can function as a catalyst for a development reaction (reduction reaction of silver ions by a silver ion reducing agent) is formed on the surface of the silver halide grains, and the exposure after the thermal development process has passed. Then, since many latent images are formed inside the surface of the silver halide grains, the silver halide grains are characterized in that the formation of latent images on the surface is suppressed.

  In the present invention, it is preferable to use silver halide grains whose latent image forming function greatly changes before and after heat development.

  In general, when photosensitive silver halide grains are exposed, the silver halide grains themselves or spectral sensitizing dyes adsorbed on the surface of the photosensitive silver halide grains are photoexcited to freely move electrons. Although generated, these electrons are competitively trapped (captured) by an electron trap (photosensitive center) existing on the surface of the silver halide grain or an electron trap inside the grain.

  Therefore, if there are more chemical sensitization centers (chemical sensitization nuclei) and dopants effective as electron traps on the surface than the inside of the silver halide grains, a latent image is preferentially formed on the surface and development is possible. It becomes.

  On the contrary, when there are more chemical sensitization centers (chemical sensitization nuclei) and dopants effective as electron traps in the inside than the silver halide grain surface, a latent image is preferentially formed inside, and the surface Development becomes difficult.

  In other words, in the former case, it can be said that the surface sensitivity is higher than in the interior, and in the latter case, the surface sensitivity is lower than in the interior (reference: (1) edited by TH James “The Theory of the Photographic Process”. 4th edition, McCillan Publishing Co., Ltd., 1977, (2) Japan Photographic Society edited “Basics of Revised Photo Engineering (Silver Salt Photography)”, Corona, 1998).

  In the silver halide grains according to the present invention, it is preferable from the viewpoint of sensitivity and image storability that a dopant functioning as an electron trapping dopant is contained inside the silver halide grains at least during exposure after heat development.

  In addition, a dopant that functions as a hole trap during the exposure for image formation before heat development, changes in the heat development process, and functions as an electron trap after heat development, Particularly preferred.

  The electron trapping dopant used here is an element or compound other than silver and halogen constituting silver halide grains, and the dopant itself has a property of trapping (capturing) free electrons, or the dopant is halogen. It is the one in which a site such as an electron trapping lattice defect is generated by being contained in a silver halide grain.

  For example, a metal ion other than silver or a salt or complex thereof, a chalcogen (oxygen group element) such as sulfur, selenium or tellurium, or an inorganic compound or organic compound containing a nitrogen atom or a metal complex thereof, a rare earth ion or a complex thereof, etc. Can be mentioned.

  Examples of metal ions or salts or complexes thereof include lead ions, bismuth ions, gold ions, etc., or lead bromide, lead nitrate, lead carbonate, lead sulfate, bismuth nitrate, bismuth chloride, bismuth trichloride, bismuth carbonate, sodium bismutate, Examples thereof include chloroauric acid, lead acetate, lead stearate, bismuth acetate and the like.

  As the compound containing chalcogen such as sulfur, selenium, and tellurium, various chalcogen-releasing compounds generally known as chalcogen sensitizers in the photographic industry can be used.

  Moreover, as an organic substance containing chalcogen or nitrogen, a heterocyclic compound is preferable.

  For example, imidazole, pyrazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, indazole, purine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, Tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzthiazole, indolenine, tetrazaindene, preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, thiadiazole, oxadiazole, quinoline, phthalazine, Naphthyridine, quinoxaline, quinazoline, cinnoline, tetrazole, thiazole, o Sasol, benzimidazole, benzoxazole, benzthiazole, a tetrazaindene.

  The above heterocyclic compound may have a substituent, and the alkyl group, alkenyl group, aryl group, alkoxy group, aryloxy group, acyloxy group, acyl group, alkoxycarbonyl group are preferable as the substituent. Aryloxycarbonyl group, acyloxy group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, sulfonyl group, ureido group, phosphoric acid amide group, halogen atom, cyano group, Sulfo group, carboxyl group, nitro group and heterocyclic group, more preferably alkyl group, aryl group, alkoxy group, aryloxy group, acyl group, acylamino group, alkoxycarbonylamino group, aryloxycarbonylamino group, sulfonyl group Amino group, sulfamoyl group, carbamoyl group, ureido group, phosphoric acid amide group, halogen atom, cyano group, nitro group, heterocyclic group, more preferably alkyl group, aryl group, alkoxy group, aryloxy group, acyl group An acylamino group, a sulfonylamino group, a sulfamoyl group, a carbamoyl group, a halogen atom, a cyano group, a nitro group, or a heterocyclic group.

  The silver halide grains used in the present invention include groups 6 to 11 in the periodic table so that they function as electron trapping dopants as described above or as hole trapping dopants. Transition metal ions belonging to the above may be contained by chemically adjusting the oxidation state of the metal with a ligand or the like.

  As the transition metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, and Pt are preferable.

  About said various dopants, you may use together 2 or more types of the same kind or a different kind of compound or complex. However, at least one kind needs to function as an electron trapping dopant at the time of exposure after thermal development. These dopants may be introduced into the silver halide grains in any chemical form.

The preferable content of the dopant is preferably in the range of 1 × 10 ⁻⁹ to 1 × 10 mol and more preferably in the range of 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol with ^respect to 1 mol of silver. Furthermore, 1 * 10 ^{< -6} > ^-1 * 10 ^<-2> mol is preferable.

  However, since the optimum amount depends on the kind of dopant, the grain size and shape of the silver halide grains, and other environmental conditions, it is preferable to examine optimization of the dopant addition conditions according to these conditions.

  In the present invention, the transition metal complex or complex ion is preferably represented by the following general formula.

General formula [ML ₆ ] ^m
In the formula, M represents a transition metal selected from Group 6 to 11 elements in the periodic table, L represents a ligand, and m represents 0,-, 2-, 3-, or 4-.

  Specific examples of the ligand represented by L include halogen ions (for example, fluorine ion, chlorine ion, bromine ion, iodine ion), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aquo. Each ligand includes nitrosyl, thionitrosyl, and the like, preferably aco, nitrosyl, thionitrosyl, and the like.

  When an acoligand is present, it preferably occupies one or two of the ligands. L may be the same or different.

  The compounds providing these metal ions or complex ions are preferably added at the time of silver halide grain formation and incorporated into the silver halide grains. Preparation of silver halide grains, that is, nucleation, growth, physical ripening In addition, it may be added at any stage before or after chemical sensitization, but it is particularly preferably added at the stage of nucleation, growth and physical ripening, and more preferably at the stage of nucleation and growth, Most preferably, it is added at the stage of nucleation. In addition, it may be divided and added several times, and can be uniformly contained in the silver halide grains. For example, JP-A-63-29603, JP-A-2-306236, 3 As described in JP-A Nos. 167545, 4-76534, 6-110146, 5-273683, etc., the particles can be contained with a distribution.

  These metal-containing compounds (metal compounds) can be added by dissolving in water or an appropriate organic solvent (for example, alcohols, ethers, glycols, ketones, esters, amides). For example, a method in which an aqueous solution of a metal compound powder or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to a water-soluble silver salt solution or a water-soluble halide solution during particle formation, or a silver salt solution Is added as a third aqueous solution when the solution and the halide solution are mixed at the same time, a method of preparing silver halide grains by the method of simultaneous mixing of the three solutions, and a required amount of the aqueous solution of the metal compound is charged into the reaction vessel during grain formation Or a method of adding another silver halide grain previously doped with a metal ion or complex ion and dissolving it at the time of silver halide preparation. In particular, a method of adding an aqueous solution of a metal compound powder or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to the water-soluble halide solution.

  When added to the particle surface, a required amount of an aqueous solution of a metal compound can be charged into the reaction vessel immediately after the formation of the particle, during or after physical ripening, or at the time of chemical ripening.

  In addition, a nonmetallic dopant can also be introduce | transduced inside a silver halide by the method similar to said metallic dopant.

  Whether or not the dopant has an electron trapping property can be evaluated by a method generally used in the photographic industry as follows. That is, a silver halide emulsion comprising silver halide grains doped with the above-mentioned dopant or a decomposition product thereof in silver halide grains is subjected to a photoconductivity measurement by a microwave photoconductivity measurement method or the like, and the halogenation does not contain a dopant. It can be evaluated by measuring the degree of decrease in photoconduction with a silver grain emulsion as a reference. In addition, the method for evaluating the effect of the electron trapping dopant after making a photothermographic dry imaging material can also be performed by a comparative experiment of the internal sensitivity and surface sensitivity of the silver halide grains. And heating under the same conditions as normal practical heat development conditions, followed by a certain period of time (for example, 30 seconds), white light or light in a specific spectral sensitization region (spectral sensitization to laser light in a specific wavelength region). In the case of giving a sensation, light in the wavelength region, for example, in the case of spectral sensitization to infrared light, infrared light) is exposed through an optical wedge, and further heated under the same heat development conditions. The sensitivity obtained on the basis of the characteristic curve (sensitometry curve) obtained by development is compared with the sensitivity of the imaging material using the silver halide grain emulsion not containing the electron trapping dopant. It can be evaluated by compare.

  The photothermographic material of the present invention is exposed to white light or light in a specific spectrally sensitized region (for example, infrared light) through an optical wedge for a certain time (for example, 30 seconds), and then subjected to normal heat development. For the sensitivity of the sample obtained based on the characteristic curve obtained when heat development is performed under the conditions, the sample is heated under the same conditions as normal heat development conditions before exposure, and then the same constant time as above, and The sensitivity obtained on the basis of the characteristic curve obtained by performing constant exposure and further heat development under normal heat development conditions is 1/10 or less, preferably 1/20 or less, and further chemically sensitizing the silver halide emulsion. When applied, the sensitivity is preferably 1/50 or less.

  The silver halide grains according to the present invention may be added to the photosensitive layer by any method, and at this time, the silver halide grains are arranged so as to be close to a reducible silver source (aliphatic carboxylic acid silver salt). This is preferable in order to obtain an imaging material with high sensitivity and high covering power (CP).

  The silver halide grains according to the present invention are prepared in advance and added to a solution for preparing the aliphatic carboxylate silver salt grains. The preparation process can be handled separately, and is most preferable in terms of production control. However, as described in British Patent No. 1,447,454, when preparing aliphatic carboxylic acid silver salt particles, halide ions, etc. It is also possible to use silver halide grains formed at almost the same time as the formation of the aliphatic carboxylate silver salt grains by injecting silver ions into the aliphatic carboxylate silver salt-forming ingredient. it can.

  It is also possible to prepare a silver halide grain by allowing a halogen-containing compound to act on an aliphatic carboxylic acid silver salt and converting the aliphatic carboxylic acid silver salt, and use the grain together. That is, a silver halide-forming component is allowed to act on a solution or dispersion of an aliphatic carboxylic acid silver salt prepared in advance, or a sheet material containing the aliphatic carboxylic acid silver salt, so that a part of the aliphatic carboxylic acid silver salt is removed. It can also be converted to photosensitive silver halide.

  Examples of the silver halide grain forming component include inorganic halogen compounds, onium halides, halogenated hydrocarbons, N-halogen compounds, and other halogen-containing compounds. Specific examples thereof are US Pat. No. 4,009,039. No. 3,457,075, No. 4,003,749, British Patent No. 1,498,956 and JP-A-53-27027, No. 53-25420.

  You may use together the silver halide grain manufactured by converting a part of aliphatic carboxylic acid silver salt into the silver halide grain separately prepared as mentioned above.

  These silver halide grains are separately prepared silver halide grains, 0.001 to 0.7 mol per 1 mol of aliphatic carboxylic acid silver salt, and silver halide grains obtained by conversion of aliphatic carboxylic acid silver salt. Preferably it is used at 0.03-0.5 mol.

  Separately prepared photosensitive silver halide grains are desalted by a known desalting method such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. However, it can be used without desalting.

(Chemical sensitization)
The silver halide grains according to the present invention can be chemically sensitized. For example, use of compounds that release chalcogens such as sulfur, selenium, and tellurium and noble metal ions that release noble metal ions such as gold ions by the methods described in JP-A Nos. 2001-249428 and 2001-249426 Thus, it is possible to form and impart a chemical sensitization center (chemical sensitization nucleus) capable of capturing electrons or holes generated by photoexcitation of photosensitive silver halide grains or spectral sensitizing dyes on the grains. In particular, it is preferably chemically sensitized with an organic sensitizer containing a chalcogen atom.

  These organic sensitizers containing chalcogen atoms are preferably compounds having groups capable of adsorbing to silver halide and unstable chalcogen atom sites.

  These organic sensitizers are disclosed in JP-A-60-150046, JP-A-4-109240, JP-A-11-218874, JP-A-11-218875, JP-A-11-218876, JP-A-11-194447, etc. Organic sensitizers having various structures can be used, and among them, at least one compound having a structure in which a chalcogen atom is bonded to a carbon atom or a phosphorus atom by a double bond It is preferable.

  In particular, a thiourea derivative having a heterocyclic group and a triphenylphosphine sulfide derivative are preferred.

  As a method for chemical sensitization, techniques according to various chemical sensitization techniques conventionally used in the production of conventional silver halide light-sensitive materials for wet processing can be used (reference: (1) T Edited by H. James “The Theory of the Photographic Process” 4th edition, McMillan Publishing Co., Ltd., (2) edited by the Japan Photographic Society, “Basics of Photographic Engineering (Silver Salt Photography), Corona, 1979) .

  In particular, when the silver halide grain emulsion is previously chemically sensitized and then mixed with non-photosensitive organic silver salt grains, it can be chemically sensitized by a conventional method.

The amount of the chalcogen compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, etc., but is 10 ⁻⁸ to 10 ⁻ per mol of silver halide. ² mol is preferred, more preferably 10 ⁻⁷ to 10 ⁻³ mol.

  The environmental conditions for chemical sensitization are not particularly limited, but in the presence of a compound capable of eliminating or reducing the size of silver chalcogenide or silver nuclei on the photosensitive silver halide grains. In particular, it may be preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei.

  The sensitizing conditions in this case are preferably 6 to 11 as pAg, more preferably 7 to 10, pH 4 to 10, more preferably 5 to 8, and the temperature increases at 30 ° C. or lower. It is preferable to give a feeling.

  In addition, chemical sensitization using these organic sensitizers is preferably performed in the presence of a heteroatom-containing compound having adsorptivity to spectral sensitizing dyes or silver halide grains.

  By performing chemical sensitization in the presence of a compound having an adsorptivity to silver halide, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved. Although the spectral sensitizing dye will be described later, preferred examples of the heteroatom-containing compound having adsorptivity to silver halide include nitrogen-containing heterocyclic compounds described in JP-A-3-24537.

  In the nitrogen-containing heterocyclic compound, examples of the heterocyclic ring include pyrazole ring, pyrimidine ring, 1,2,4-triazole ring, 1,2,3-triazole ring, 1,3,4-thiadiazole ring, 1,2 , 3-thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,2,3,4-tetrazole ring, pyridazine ring, 1,2,3-triazine ring, these rings Can be mentioned, for example, a triazolotriazole ring, a diazaindene ring, a triazaindene ring, a pentaazaindene ring, and the like. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, a phthalazine ring, a benzimidazole ring, an indazole ring, a benzthiazole ring, or the like can also be applied.

  Of these, an azaindene ring is preferable, and an azaindene compound having a hydroxyl group as a substituent, for example, a hydroxytriazaindene, tetrahydroxyazaindene, hydroxypentaazaindene compound, or the like is more preferable.

  The heterocyclic ring may have a substituent other than the hydroxyl group. Examples of the substituent include an alkyl group, a substituted alkyl group, an alkylthio group, an amino group, a hydroxyamino group, an alkylamino group, a dialkylamino group, an arylamino group, a carboxyl group, an alkoxycarbonyl group, a halogen atom, and a cyano group. You may have.

The amount of the heterocyclic compound added varies over a wide range depending on the size, composition, and other conditions of the silver halide grains, but the approximate amount is 10 ^-6 per mole of silver halide. It is in the range of ˜1 mol, preferably in the range of 10 ⁻⁴ to 10 ⁻¹ mol.

  The silver halide according to the present invention can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, a chloroaurate or an organic gold compound can be used as a gold sensitizer. The gold sensitization technique disclosed in JP-A-11-194447 is useful as a reference.

  In addition to the above-described sensitization methods, reduction sensitization methods and the like can also be used. Examples of reduction sensitization shell-like compounds include ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, A borane compound, a silane compound, a polyamine compound, or the like can be used. Further, reduction sensitization can be performed by ripening the emulsion while maintaining the pH at 7 or higher or the pAg at 8.3 or lower.

  In the present invention, the silver halide grains subjected to chemical sensitization may be formed in the presence of an aliphatic carboxylic acid silver salt, or in the absence of the organic silver salt, A mixture of the two may be used.

  In the present invention, when chemical sensitization is performed on the surface of the photosensitive silver halide grains, it is necessary that the chemical sensitization effect substantially disappears after the thermal development process.

  Here, the chemical sensitization effect substantially disappears when the sensitivity of the imaging material obtained by the chemical sensitization technique is 1.1 when the chemical sensitization is not performed after the thermal development process. Say to decrease below. In order to eliminate the chemical sensitization effect in the heat development process, an oxidant capable of destroying the chemical sensitization center (chemical sensitization nucleus) by an oxidation reaction at the time of heat development, for example, the above-mentioned halogen radical releasing compound, etc. It is necessary to contain an appropriate amount of the above in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the chemical sensitization effect, and the like.

(Spectral sensitization)
The silver halide according to the present invention is preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. As spectral sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes and the like can be used. For example, JP-A-63-159841, JP-A-60-140335, JP-A-63-231437, JP-A-63-259651, JP-A-63-304242, JP-A-63-15245, US Pat. No. 4,639,414, No. 4,740,455, No. 4,741,966, No. 4,751,175, No. 4,835,096 can be used.

  Useful sensitizing dyes that can be used in the present invention include, for example, Research Disclosure (hereinafter abbreviated as RD) 17643IV-A (December 1978 p.23), RD18431X (August 1978 p.23). 437) or described in the cited literature.

  In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various laser imagers and scanner light sources. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

  Useful cyanine dyes are, for example, cyanine dyes having basic nuclei such as thiazoline nucleus, oxazoline nucleus, pyrroline nucleus, pyridine nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus and imidazole nucleus.

  Useful merocyanine dyes are preferably acidic nuclei such as thiohydantoin nucleus, rhodanine nucleus, oxazolidinedione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus in addition to the above basic nucleus. Including.

  In the present invention, a sensitizing dye having spectral sensitivity particularly in the infrared can also be used. Examples of infrared spectral sensitizing dyes preferably used include infrared spectral sensitization disclosed in US Pat. Nos. 4,536,473, 4,515,888, 4,959,294, and the like. Examples include dyes.

  The photosensitive layer according to the present invention is represented by a sensitizing dye represented by the following general formula (SD-1) and the following general formula (SD-2) as described in Japanese Patent Application No. 2003-102726. It is preferable to contain at least one selected from the sensitizing dyes.

[Wherein, Y ¹¹ and Y ¹² each represent an oxygen atom, a sulfur atom, a selenium atom, or a —CH═CH— group, and L _{1 to} L ₉ each represent a methine group. R ¹¹ and R ¹² each represents an aliphatic group. R ¹³ , R ¹⁴ , R ²³ and R ²⁴ each represent a lower alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group. W ¹¹ , W ¹² , W ¹³ , and W ¹⁴ are each a hydrogen atom, a substituent, or a nonmetallic atom necessary for bonding between W ¹¹ and W ¹² , W ¹³ and W ¹⁴ to form a condensed ring. Group, or R ¹³ and W ¹¹ , R ¹³ and W ¹² , R ²³ and W ¹¹ , R ²³ and W ¹² , R ¹⁴ and W ¹³ , R ¹⁴ and W ¹⁴ , R ²⁴ and W ¹³ , R ²⁴ and W ¹⁴ Represents a group of non-metallic atoms necessary to form a 5-membered or 6-membered condensed ring by bonding between the two. X ¹¹ represents an ion necessary for canceling the charge in the molecule, and k 11 represents the number of ions necessary for canceling the charge in the molecule. m11 represents 0 or 1. n11 and n12 each represents 0, 1 or 2. However, n11 and n12 are not 0 at the same time. ]
The above-mentioned infrared sensitizing dyes are described in, for example, The Chemistry of Heterocyclic Compounds, Volume 18 by The FM Hammer, The Cyanine Dies and Related Compounds (A. Weissberger ed. It can be easily synthesized by this method.

  These infrared sensitizing dyes may be added at any time after the silver halide is prepared. For example, silver halide grains or halogens may be added in a so-called solid dispersion state added to a solvent or dispersed in a fine particle form. It can be added to a light-sensitive emulsion containing silver halide grains / aliphatic carboxylic acid silver salt grains.

  Similarly to the heteroatom-containing compound having adsorptivity to the silver halide grains, chemical sensitization can be performed after adding and adsorbing to the silver halide grains prior to chemical sensitization. Thus, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved.

  In the present invention, one kind of spectral sensitizing dye may be used alone, but as described above, it is preferable to use a combination of plural kinds of spectral sensitizing dyes. The combination is often used for the purpose of supersensitization and enlargement or adjustment of the photosensitive wavelength region.

  The emulsion containing silver halide according to the present invention is a dye having no spectral sensitizing action itself or a substance that does not substantially absorb visible light together with a sensitizing dye, and exhibits a supersensitizing effect. Such a substance may be contained in the emulsion, whereby the silver halide grains may be supersensitized.

  Useful sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in RD17643 (issued in December, 1978), page 23, Section J, or Japanese Patent Publication No. 9-25500, 43-4933, JP-A-59-19032, JP-A-59-192242, JP-A-5-341432, and the like. Examples of supersensitizers include heteroaromatic mercapto represented by the following. A compound or a mercapto derivative compound is preferred.

Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic ring or condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium, or tellurium atoms.

  Heteroaromatic rings include benzimidazole, naphthimidazole, benzthiazole, naphthothiazole, benzoxazole, naphthoxazole, benzselenazole, benztelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine, Purine, quinoline, or quinazoline is preferred.

  The heteroaromatic ring includes, for example, a halogen atom (for example, chlorine, bromine, iodine), a hydroxyl group, an amino group, a carboxyl group, and an alkyl group (for example, one or more carbon atoms, preferably 1 to 4 carbon atoms). It may have a substituent selected from the group consisting of those having a carbon atom) and alkoxy groups (for example, those having 1 or more carbon atoms, preferably 1 to 4 carbon atoms).

  In addition to the above supersensitizers, macrocycles having heteroatoms disclosed in JP-A-2001-330918 can also be used as supersensitizers.

  The supersensitizer is preferably used in a photosensitive layer containing an organic silver salt and silver halide grains in an amount of 0.001 to 1.0 mol per mol of silver. Particularly preferred is an amount of 0.01 to 0.5 mole per mole of silver.

  In the present invention, it is necessary that the spectral sensitizing dye is adsorbed on the surface of the photosensitive silver halide grain to effect spectral sensitization, and that the spectral sensitizing effect should substantially disappear after the thermal development process. It is.

  Here, the spectral sensitization effect substantially disappears when the sensitivity of the imaging material obtained by a sensitizing dye, supersensitizer, etc. is the sensitivity when spectral sensitization is not performed after the thermal development process. It means to decrease to 1.1 times or less.

  In order to eliminate the chemical sensitization effect in the thermal development process, a spectral sensitizing dye that is easily detached from the silver halide grains by heat is used during thermal development or / and the spectral sensitizing dye is destroyed by an oxidation reaction. It is necessary to contain an appropriate amount of an oxidizing agent that can be formed, for example, the above-mentioned halogen radical releasing compound in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the spectral sensitization effect, and the like.

(Reducing agent)
The reducing agent according to the present invention is a silver ion reducing agent, and as the reducing agent, at least one of them is preferably a compound represented by the following general formula (1).

In the formula, X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₂ represents an alkyl group and may be the same or different. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2.

Among the compounds represented by the general formula (1), a highly active reducing agent (hereinafter referred to as a compound of the general formula (1a)) in which at least one of R ₂ is a secondary or tertiary alkyl group is used. It is more preferable that a photothermographic material having a high density and excellent light-storing image storage stability can be obtained.

  In the present invention, it is preferable to use a compound of the general formula (1a) and a compound of the following general formula (2) in order to obtain a desirable color tone.

In the formula, X ₂ represents a chalcogen atom or CHR ₅ , and R ₅ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₆ represents an alkyl group, which may be the same or different, but is not a secondary or tertiary alkyl group. R ₇ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₈ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2.

  As the ratio of the combined use, [mass of compound of general formula (1a)]: [mass of compound of general formula (2)] is preferably 5:95 to 45:55, more preferably 10:90 to 40:60.

In the general formula (1), X ₁ represents a chalcogen atom or CHR ₁ . The chalcogen atom is sulfur selenium or tellurium, preferably a sulfur atom. R ₁ in CHR ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. The halogen atom is a fluorine atom, a chlorine atom, a bromine atom or the like, and the alkyl group is preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. Specific examples include methyl, ethyl, propyl, butyl, and hexyl. Alkenyl groups such as vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, Examples of the aryl group include a benzene ring and a naphthalene ring, and examples of the heterocyclic group include thiophene, furan, imidazole, pyrazole, and pyrrole.

  These groups may further have a substituent. Specific examples of the substituent include a halogen atom (fluorine, chlorine, bromine, etc.), an alkyl group (methyl, ethyl, propyl, butyl, pentyl, i-pentyl). , 2-ethylhexyl, octyl, decyl, etc.), cycloalkyl groups (cyclohexyl, cycloheptyl, etc.), alkenyl groups (ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl) -3-butenyl, etc.), cycloalkenyl groups (1-cycloalkenyl, 2-cycloalkenyl groups, etc.), alkynyl groups (ethynyl, 1-propynyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, etc.), alkylcarbonyloxy groups (Acetyloxy, etc.), alkylthio groups (methylthio, trifluoromethylthio, etc.), Sil group (acetyl group, benzoyl group), carboxyl group, alkylcarbonylamino group (acetylamino etc.), ureido group (methylaminocarbonylamino etc.), alkylsulfonylamino group (methanesulfonylamino etc.), alkylsulfonyl group (methanesulfonyl) , Trifluoromethanesulfonyl, etc.), carbamoyl group (carbamoyl, N, N-dimethylcarbamoyl, N-morpholinocarbonyl, etc.), sulfamoyl group (sulfamoyl, N, N-dimethylsulfamoyl, morpholinosulfamoyl etc.), trifluoromethyl Group, hydroxyl group, nitro group, cyano group, alkylsulfonamide group (methanesulfonamide, butanesulfonamide, etc.), alkylamino group (amino, N, N-dimethylamino, N, N-diethylamino) Etc.), sulfo group, phosphono group, sulfite group, sulfino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl etc.), alkylcarbonylaminosulfonyl group (acetamidesulfonyl, methoxyacetamidosulfonyl etc.), alkynyl Examples thereof include aminocarbonyl groups (acetamidocarbonyl, methoxyacetamidocarbonyl, etc.), alkylsulfinylaminocarbonyl groups (methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.) and the like. Moreover, when there are two or more substituents, they may be the same or different. Particularly preferred substituents are alkyl groups.

R ₂ represents an alkyl group, which may be the same or different, but at least one is preferably a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, specifically, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, t-pentyl, t-octyl. , Cyclohexyl, cyclopentyl, 1-methylcyclohexyl, 1-methylcyclopropyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group , Ester groups, halogen atoms and the like. Or it may form a saturated ring with (R _{4) n} and (R _{4) m.} R ₂ is preferably a secondary or tertiary alkyl group, and preferably has 2 to 20 carbon atoms. A tertiary alkyl group is more preferred, t-butyl, t-pentyl and 1-methylcyclohexyl are more preferred, and t-butyl is most preferred.

R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. Examples of groups that can be substituted on the benzene ring include halogen atoms such as fluorine, chlorine, bromine, alkyl groups, aryl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, amino groups, acyl groups, and acyloxy groups. , Acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, heterocyclic group and the like.

R ₃ is preferably methyl, ethyl, i-propyl, t-butyl, cyclohexyl, 1-methylcyclohexyl, 2-hydroxyethyl and the like. More preferred are methyl and 2-hydroxyethyl.

These groups may further have a substituent, and the substituents mentioned in the above R ₁ can be used as the substituent. R ₃ is preferably a C 1-20 alkyl group having a hydroxyl group or a precursor group thereof, and more preferably a C 1-5 alkyl group. Most preferred is 2-hydroxyethyl. In the most preferred combination of R ₂ and R ₃ , R ₂ is a tertiary alkyl group (t-butyl, 1-methylcyclohexyl, etc.), and R ₃ is a primary alkyl group having a hydroxyl group or a precursor group thereof ( 2-hydroxyethyl and the like). A plurality of R ₂ and R ₃ may be the same or different.

R ₄ represents a substitutable group on the benzene ring, specifically, an alkyl group having 1 to 25 carbon atoms (methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl, etc.), Halogenated alkyl group (trifluoromethyl, perfluorooctyl etc.), cycloalkyl group (cyclohexyl, cyclopentyl etc.), alkynyl group (propargyl etc.), glycidyl group, acrylate group, methacrylate group, aryl group (phenyl etc.), heterocyclic ring Groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups (methoxy, ethoxy) , Ropyloxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc.), aryloxy groups (phenoxy, etc.), alkoxycarbonyl groups (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl groups (phenyloxycarbonyl) ), Sulfonamide groups (methanesulfonamide, ethanesulfonamide, butanesulfonamide, hexanesulfonamide group, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl groups (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl, butylamino) Sulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyridylamino Sulfonyl, etc.), urethane groups (methylureido, ethylureido, pentylureido, cyclohexylureido, phenylureido, 2-pyridylureido, etc.), acyl groups (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.), Carbamoyl group (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, pentylaminocarbonyl group, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl), amide group (acetamide, propionamide, butanamide, hexaneamide, Benzamide, etc.), sulfonyl groups (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexylsulfonyl) Phenylsulfonyl, 2-pyridylsulfonyl, etc.), amino group (amino, ethylamino, dimethylamino, butylamino, cyclopentylamino, anilino, 2-pyridylamino, etc.), cyano group, nitro group, sulfo group, carboxyl group, hydroxyl group, An oxamoyl group can be exemplified. These groups may be further substituted with these groups. n and m represent an integer of 0 to 2, and most preferably n and m are 0.

R ₄ may form a saturated ring with R ₂ and R ₃ . R ₄ is preferably a hydrogen atom, a halogen atom or an alkyl group, more preferably a hydrogen atom. A plurality of R ₄ may be the same or different.

In general formula (2), R ₅ is the same group as R ₁ , R ₇ is the same group as R _3, and R ₈ is the same group as R ₄ . R ₆ represents an alkyl group, which may be the same or different, but is not a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, and specific examples thereof include methyl, ethyl, propyl, butyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group , Ester groups, halogen atoms and the like. R ₆ may form a saturated ring with (R ₈ ) _n or (R ₈ ) _m . R ₆ is preferably methyl. Among the compounds represented by the general formula (2), a compound that is preferably used is a compound that satisfies the general formula (S) and the general formula (T) described in European Patent No. 1,278,101, Specific examples include compounds (1-24), (1-28) to (1-54), and (1-56) to (1-75) described in p21 to p28.

  Specific examples of the compounds represented by general formula (1) and general formula (2) are shown below, but the present invention is not limited to these.

  These bisphenol compounds represented by the general formulas (1) and (2) can be easily synthesized by a conventionally known method.

  The reducing agent contained in the photothermographic material of the invention forms a silver image by reducing the organic silver salt. Examples of the reducing agent that can be used in combination with the reducing agent of the present invention include, for example, US Pat. Nos. 3,770,448, 3,773,512, and 3,593,863, RD17029 and No. 29963, JP-A-11-119372, JP-A-2002-62616, and the like.

The amount of the reducing agent including the compound represented by the general formula (1) is preferably 1 × 10 ⁻² to 10 mol, particularly preferably 1 × 10 ^{−2 to} 1.5 mol, per mol of silver. It is.

(Image tone)
Next, the color tone of an image obtained by thermally developing a photothermographic material will be described.

  Regarding the color tone of an output image for medical diagnosis such as a conventional X-ray photographic film, it is said that a cold tone image tone is easier for a reader to obtain a more accurate diagnostic observation result. Here, the cool image tone means a pure black tone or a bluish black tone of a black image. On the other hand, the warm image tone is said to be a warm black tone with a black image, but in order to allow a more precise quantitative discussion, the International Lighting Commission (CIE) ), Based on the recommended expression.

The terms “more cold” and “more warm” regarding the color tone can be expressed by the hue angle hab at the minimum density Dmin and the optical density D = 1.0. That is, the hue angle hab is expressed by the color coordinates a ^* and b ^* of the color space L ^* a ^* b ^* color space, which is a color space having a perceptually uniform rate recommended by the International Commission on Illumination (CIE) in 1976. Using the following formula.

hab = tan ⁻¹ (b ^* / a ^* )
The color tone after development of the photothermographic material of the present invention is preferably such that the hue angle hab is in the range of 180 degrees <hab <270 degrees, more preferably 200 degrees <hab <270 degrees, and most preferably 220 degrees <. hab <260 degrees.

Conventionally, u ^* , v ^* or a ^* , b ^* in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space near an optical density of 1.0 is a specific numerical value. It is known that a diagnostic image having a preferable appearance color tone can be obtained by adjusting the color tone, for example, as described in JP-A-2000-29164.

  A preferable range of conditions is described below.

(1) The optical density of the silver image obtained after heat development processing of the photothermographic material was measured at 0.5, 1.0, 1.5 and the lowest optical density, and CIE 1976 (L ^* u ^* v ^* ) Determination coefficient (multiple determination) R of linear regression line created by arranging u ^* and v ^* at the above optical densities in two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^{*. 2} is preferably 0.998 to 1.000.

Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (v ^* / u ^* ) is 0.7 to 2.5.

(2) The optical density of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density, and the horizontal axis of the CIE 1976 (L ^* a ^* b ^* ) color space. Is a determination coefficient (multiple determination) R ² of 0.998 to 1 for a linear regression line created by arranging a ^* and b ^* at each optical density in two-dimensional coordinates where a ^{* is} the vertical axis and b ^* is the vertical axis. .000 is preferred. Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (b ^* / a ^* ) is 0.7 to 2.5.

Next, an example of a method for creating the above-described linear regression line, that is, a method for measuring u ^* , v ^* and a ^* , b ^{* in} the CIE 1976 color space will be described.

A four-stage wedge sample including an unexposed portion and optical densities of 0.5, 1.0, and 1.5 is prepared using a heat development apparatus. Each wedge density part thus produced is measured with a spectrocolorimeter (Minolta Co., Ltd .: CM-3600d or the like), and u ^* , v ^* or a ^* , b ^* are calculated. The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 degrees, and the measurement is performed in the transmission measurement mode. Plot u ^* , v ^* or a ^* , b ^* measured on a graph with u ^* or a ^{* on} the horizontal axis and v ^* or b ^{* on the} vertical axis to obtain a linear regression line, and the coefficient of determination (multiple determination) Find R ² , intercept and slope.

  Next, a specific method for obtaining a linear regression line having the above characteristics will be described.

  In the present invention, the developed silver can be adjusted by adjusting the addition amount of a compound or the like directly or indirectly involved in the development reaction process of the following toning agent, developer, silver halide grains and aliphatic carboxylate. The shape can be optimized to obtain a preferable color tone.

  For example, when the developed silver shape is dendritic, it becomes a bluish direction, and when it is a filament shape, it becomes a yellowish direction. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

  Conventionally, phthalazinone or phthalazine and phthalic acids and phthalic anhydrides are generally used as toning agents. Examples of suitable toning agents include RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, and 4,021,249. Is disclosed.

  In addition to such toning agents, color tone using couplers disclosed in JP-A No. 11-288057, European Patent No. 1,134,611A2, etc. and leuco dyes described in detail below. Can also be adjusted. In particular, a coupler or leuco dye is preferably used for fine adjustment of the color tone.

(Leuco dye)
The leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds, and is oxidized by silver ions. Any leuco dye that forms a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  The leuco dye that can be used in the present invention is not particularly limited. Etc. Also useful are US Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4,022,617, 4,123,282, 4,368,247, 4,461,681, and JP-A-50-36110, 59-26831, These are leuco dyes disclosed in JP-A-5-204087, JP-A-11-231460, JP-A-2002-169249, and JP-A-2002-236334.

  In order to adjust to a predetermined color tone, it is preferable to use leuco dyes of various colors singly or in combination of a plurality of types. In the present invention, when a highly active reducing agent is used, the color tone (especially yellowishness) changes depending on the amount and ratio of use, or by using fine grain silver halide, the concentration is particularly 2.0. In order to prevent the image from being excessively reddish at the above high density portion, it is preferable to use a leuco dye that develops yellow and cyan colors and to adjust the amount of use.

  The color density is preferably adjusted appropriately in relation to the color tone of the developed silver itself. In the present invention, the color tone may be adjusted so as to have an image in the above-described preferable color tone range by developing the color so as to have a reflection optical density of 0.01 to 0.05 or a transmission optical density of 0.005 to 0.50. preferable. In the present invention, the sum of the maximum densities at the maximum absorption wavelength of the dye image formed by the leuco dye is preferably 0.01 or more and 0.50 or less, more preferably 0.02 or more and 0.30 or less, and particularly preferably It is preferable that the color is developed so as to have 0.03 to 0.10.

(Yellow coloring leuco dye)
In the present invention, a color image forming agent that increases the absorbance at 360 to 450 nm when oxidized is particularly preferably used as a yellow color-forming leuco dye. Color image formation represented by the following general formula (YA) It is preferable that it is an agent.

In the formula, R ₁₁ represents a substituted or unsubstituted alkyl group, R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively, and R ₁₁ and R ₁₂ are 2-hydroxyphenylmethyl groups. There is never.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on the benzene ring.

  Hereinafter, the compound of the general formula (YA) will be described in detail.

In General Formula (YA), R ₁₁ represents a substituted or unsubstituted alkyl group. When R ₁₂ is a substituent other than a hydrogen atom, R ₁₁ represents an alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms and may have a substituent.

Specifically, methyl, ethyl, butyl, octyl, i-propyl, t-butyl, t-octyl, t-pentyl, sec-butyl, cyclohexyl, 1-methyl-cyclohexyl and the like are preferable, and steric rather than i-propyl. Are preferably large groups (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl, etc.), among which secondary or tertiary alkyl Group is preferable, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferable. Examples of the substituent that R ₁₁ may have include a halogen atom, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamido group, an acyloxy group, an oxycarbonyl group, and a carbamoyl group. , Sulfamoyl group, sulfonyl group, phosphoryl group and the like.

R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively. The alkyl group represented by R ₁₂ is preferably an alkyl group having 1 to 30 carbon atoms, and the acylamino group is preferably an acylamino group having 1 to 30 carbon atoms. Among these, the description of the alkyl group is the same as R ₁₁ described above.

The acylamino group represented by R ₁₂ may be unsubstituted or substituted, and specific examples include an acetylamino group, an alkoxyacetylamino group, and an aryloxyacetylamino group. R ₁₂ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, and t-butyl. R ₁₁ and R ₁₂ are not 2-hydroxyphenylmethyl groups.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms, and the description of the alkyl group is the same as that for R ₁₁ . R ₁₃ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, t-butyl and the like. Further, it is preferable either R _12, R ₁₃ is a hydrogen atom.

R ₁₄ represents a group substitutable on the benzene ring, and is, for example, the same group as described for the substituent R ₄ in the general formula (1). R ₁₄ is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or an oxycarbonyl group having 2 to 30 carbon atoms, and more preferably an alkyl group having 1 to 24 carbon atoms. Examples of the substituent of the alkyl group include an aryl group, an amino group, an alkoxy group, an oxycarbonyl group, an acylamino group, an acyloxy group, an imide group, and a ureido group, and more preferable examples include an aryl group, an amino group, an oxycarbonyl group, and an alkoxy group. preferable. These alkyl group substituents may be further substituted with these substituents.

  Next, among the compounds represented by the general formula (YA), the bisphenol compound represented by the following general formula (YB), which is particularly preferably used in the present invention, will be described.

In the formula, Z represents —S— or —C (R ₂₁ ) (R ₂₁ ′) —, and R ₂₁ and R ₂₁ ′ each represents a hydrogen atom or a substituent.

Examples of the substituent represented by R ₂₁ and R ₂₁ ′ include the same groups as the substituents exemplified in the description of R _{1 in} the general formula (1). R ₂₁ and R ₂₁ ′ are preferably a hydrogen atom or an alkyl group.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ each represent a substituent, and examples of the substituent include the same groups as those described for R ₂ and R ₃ in the general formula (1).

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, but an alkyl group is more preferable. Examples of the substituent on the alkyl group include the same groups as those described in the description of the substituent in the general formula (1).

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are more preferably tertiary alkyl groups such as t-butyl, t-pentyl, t-octyl and 1-methyl-cyclohexyl.

R ₂₄ and R ₂₄ ′ each represent a hydrogen atom or a substituent, and examples of the substituent include the same groups as those described in the description of R ₄ in the general formula (1).

  Examples of the compounds represented by the general formulas (YA) and (YB) include compounds (II-1) to (II-40) described in paragraphs “0032” to “0038” of JP-A No. 2002-169249, Examples thereof include compounds (ITS-1) to (ITS-12) described in paragraph “0026” of EP 1,211,093.

  Although the specific example of the bisphenol compound represented by general formula (YA) and (YB) below is shown, this invention is not limited to these.

  The addition amount of the compound of the general formula (YA) (including hindered phenol compounds and compounds of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0. 0005 to 0.01 mol, more preferably 0.001 to 0.008 mol.

  Moreover, it is preferable that the addition amount ratio with respect to the sum total of the reducing agent represented by general formula (1), (2) of yellow coloring leuco dye is 0.001-0.2 by molar ratio, and 0.005- More preferably, it is 0.1.

(Cyan coloring leuco dye)
The cyan color-forming leuco dye preferably used in the present invention will be described. The leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds, and is oxidized by silver ions. Any leuco dye that forms a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  In the present invention, a color image forming agent that increases its absorbance at 600 to 700 nm when oxidized is particularly preferably used as a cyan color developing leuco dye. JP-A-59-206831 (in particular, λmax is 600 to 600 nm). Compounds within the range of 700 nm), compounds of general formula (I) to general formula (IV) of JP-A-5-204087 (specifically, (1) to (1) described in paragraphs “0032” to “0037”) 18) and compounds of general formula 4 to general formula 7 of JP-A No. 11-231460 (specifically, compounds of No. 1 to No. 79 described in paragraph “0105”).

  A cyan color-forming leuco dye particularly preferably used in the present invention is represented by the following general formula (CL).

[Wherein R ₈₁ and R ₈₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, —NHCO—R ₁₀ group (R ₁₀ is an alkyl group, aryl group, heterocyclic group) Or R ₈₁ and R ₈₂ are bonded to each other to form an aliphatic hydrocarbon ring, an aromatic hydrocarbon ring or a heterocyclic ring. The —A ₈ —R ₈₃ moiety represents a hydrogen atom, or A ₈ represents a —NHCO— group, —CONH— group or —NHCONH— group, and R ₈₃ represents a substituted or unsubstituted alkyl group, aryl Represents a group or a heterocyclic group.

W ₈ is a hydrogen atom or —CONH—R ₈₅ group, —CO—R ₈₅ group or —CO—O—R ₈₅ group (R ₈₅ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). R ₈₄ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, carbamoyl group, or nitrile group. R ₈₆ represents a —CONH—R ₈₇ group, a —CO—R ₈₇ group or a —CO—O—R ₈₇ group (R ₈₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). . X ₈ represents a substituted or unsubstituted aryl group or heterocyclic group. ]
In the general formula (CL), examples of the halogen atom represented by R ₈₁ and R ₈₂ include a fluorine atom, a bromine atom, and a chlorine atom, and the alkyl group includes an alkyl group having up to 20 carbon atoms (for example, Methyl group, ethyl group, butyl group, dodecyl group, etc.). Examples of the alkenyl group include alkenyl groups having up to 20 carbon atoms (for example, vinyl group, allyl group, butenyl group, hexenyl group, hexadienyl group, ethenyl-2-ethyl group). A propenyl group, a 3-butenyl group, a 1-methyl-3-propenyl group, a 3-pentenyl group, a 1-methyl-3-butenyl group, and the like. As the alkoxy group, an alkoxy group having up to 20 carbon atoms (for example, methoxy) Group, ethoxy and the like). Examples of the alkyl group represented by R ₁₀ in the —NHCO—R ₁₀ group include alkyl groups having up to 20 carbon atoms (for example, a methyl group, an ethyl group, a butyl group, a dodecyl group, etc.), and an aryl group. Examples thereof include a group having 6 to 20 carbon atoms such as a phenyl group and a naphthyl group, and examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group. Alkyl group represented by R ₈₃ is preferably an alkyl group having up to 20 carbon atoms, such as methyl group, ethyl group, butyl group, dodecyl group and the like, the aryl group preferably having 6 to 20 carbon atoms Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group. In the —CONH—R ₈₅ group, —CO—R ₈₅ group or —CO—O—R ₈₅ group represented by W ₈ , the alkyl group represented by R ₈₅ is preferably an alkyl group having up to 20 carbon atoms. Examples thereof include a methyl group, an ethyl group, a butyl group, and a dodecyl group. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, and examples thereof include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.

Examples of the halogen atom represented by R ₈₄ include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group include a chain or cyclic alkyl group such as a methyl group, a butyl group, and dodecyl. Group, cyclohexyl group and the like. Examples of the alkenyl group include alkenyl groups having up to 20 carbon atoms (for example, vinyl group, allyl group, butenyl group, hexenyl group, hexadienyl group, ethenyl-2-propenyl group, 3-butenyl group, 1-methyl-3-propenyl group, 3-pentenyl group, 1-methyl-3-butenyl, etc.), and alkoxy groups include, for example, methoxy group, butoxy group, tetradecyloxy group, etc., and carbamoyl Examples of the group include a diethylcarbamoyl group and a phenylcarbamoyl group. Nitrile groups are also preferred. Among these, a hydrogen atom and an alkyl group are more preferable. R ₈₃ and R ₈₄ may be connected to each other to form a ring structure.

  The above groups can further have a single substituent or multiple substituents. Typical substituents include halogen atoms (eg, fluorine atom, chlorine atom, bromine atom), alkyl groups (eg, methyl group, ethyl group, propyl group, butyl group, dodecyl group), hydroxyl group, cyano group , Nitro group, alkoxy group (for example, methoxy group, ethoxy group, etc.), alkylsulfonamide group (for example, methylsulfonamide group, octylsulfonamide group, etc.), arylsulfonamide group (for example, phenylsulfonamide group, naphthylsulfone) Amide group etc.), alkylsulfamoyl group (eg butylsulfamoyl group etc.), arylsulfamoyl (eg phenylsulfamoyl group etc.), alkyloxycarbonyl group (eg methoxycarbonyl group etc.), aryl Oxycarbonyl group (for example, phenyloxycarbonyl group, etc.) , Amino sulfonamido group, an acylamino group, a carbamoyl group, a sulfonyl group, a sulfinyl group, a sulfoxy group, a sulfo group, an aryloxy group, an alkoxy group, an alkylcarbonyl group, arylcarbonyl group, and an amino carbonyl group.

R ₁₀ or R ₈₅ is preferably a phenyl group, and more preferably a phenyl group having a plurality of halogen atoms and cyano groups as substituents.
-CONH-R ₈₇ group represented by R _86, in -CO-R ₈₇ group, or -CO-O-R ₈₇ group, the alkyl group represented by R ₈₇ is preferably an alkyl group having up to 20 carbon atoms Yes, for example, a methyl group, an ethyl group, a butyl group, a dodecyl group, and the like. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, a thienyl group, and the like. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.

As the substituent that the group represented by R ₈₇ can have, the same substituents as those described in the description of R _{81 to} R _{84 in} formula (CL) can be used.

Examples of the aryl group represented by X ₈ include aryl groups having 6 to 20 carbon atoms such as phenyl group, naphthyl group, and thienyl group. Examples of the heterocyclic group include thiophene group, furan group, and imidazole. Group, pyrazole group, pyrrole group and the like.

Examples of the substituent that the group represented by X ₈ can have include the same substituents as those described in the description of R _{81 to} R _{84 in} formula (CL).

The group represented by X ₈ is preferably an aryl group or heterocyclic group having an alkylamino group (such as a diethylamino group) at the para position.

  These groups may include photographically useful groups.

  Specific examples of the cyan coloring leuco dye (CL) are shown below, but are not limited thereto.

  The addition amount of the cyan coloring leuco dye is usually 0.00001 to 0.05 mol / Ag1 mol, preferably 0.0005 to 0.02 mol / Ag1 mol, more preferably 0.001 to 0.01 mol. / Ag1 mol. The addition ratio of the cyan color-forming leuco dye to the total sum of the reducing agents represented by the general formulas (1) and (2) is preferably 0.001 to 0.2 in terms of molar ratio. More preferably, it is -0.1. In the present invention, the sum of the maximum densities at the maximum absorption wavelength of the dye image formed with the cyan leuco dye is preferably 0.01 or more and 0.50 or less, more preferably 0.02 or more and 0.30 or less, particularly preferably. Is preferably colored so as to have 0.03 or more and 0.10 or less.

  In the present invention, a subtle color tone can be adjusted by using a magenta chromogenic leuco dye or a yellow chromogenic leuco dye in addition to the cyan chromogenic leuco dye.

  As a method for adding the compounds represented by the general formulas (YA) and (YB) and the cyan color-forming leuco dye, it can be added in the same manner as the method for adding the reducing agent represented by the general formula (1). , A solution form, an emulsified dispersion form, a solid fine particle dispersion form or the like may be contained in the coating solution by any method and contained in the photosensitive layer.

  The compounds of the general formulas (1), (2), general formulas (YA) and (YB) and the cyan color-forming leuco dye are preferably contained in a photosensitive layer containing an organic silver salt, but one of them is photosensitive. The other layer may be contained in a non-photosensitive layer adjacent to the photosensitive layer, or both may be contained in the non-photosensitive layer. When the photosensitive layer is composed of a plurality of layers, they may be contained in separate layers.

(binder)
The binder contained in the photosensitive layer according to the present invention is capable of supporting an organic silver salt, silver halide, a reducing agent, and other components, and the binder suitable for the photothermographic material of the present invention is transparent or Translucent, generally colorless, and natural polymer synthetic resins, polymers and copolymers, and other media for forming films, for example, those described in paragraph “0069” of JP-A No. 2001-330918.

  Among these, preferred binders for the photosensitive layer of the photothermographic material of the invention are polyvinyl acetals, and particularly preferred is polyvinyl butyral. These will be described in detail later.

  In addition, a binder can be used in combination of 2 or more types as needed.

The binder _{-COOM, -SO 3 M, -OSO 3} M, -P = O (OM) 2, -O-P = O (OM) 2, -N (R) 2, -N + (R) 3 ( M represents a hydrogen atom or an alkali metal base, R represents a hydrocarbon group), and at least one polar group selected from an epoxy group, —SH, —CN, etc. is introduced by copolymerization or addition reaction. In particular, —SO ₃ M and —OSO ₃ M are preferable. The amount of such a polar group is 1 × 10 ⁻¹ to 1 × 10 ⁻⁸ mol / g, preferably 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / g.

Such a binder is used in an effective range to function as a binder. The effective range can be easily determined by one skilled in the art. For example, as an index for holding at least the organic silver salt in the photosensitive layer, the ratio of the binder to the organic silver salt is preferably 15: 1 to 1: 2 (mass ratio), and particularly 8: 1 to 1: 1. The range of is preferable. That is, it is preferable that the binder amount of the photosensitive layer is a 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.

  The glass transition temperature (Tg) of the binder of the photosensitive layer is preferably 70 to 105 ° C. Tg can be obtained by measuring with a differential scanning calorimeter, and the intersection of the baseline and the endothermic peak slope is defined as Tg. Tg in the present invention is determined by the method described in “Polymer Handbook” III-139-179 (1966, Wiley and Sun, Inc.) by Brand Wrap et al.

  Use of a binder having a Tg of 70 to 105 ° C. is preferable because a sufficient maximum density can be obtained in image formation.

  The binder according to the present invention has a Tg of 70 to 105 ° C., a number average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 500,000, and a degree of polymerization of about 50 to 1,000. Is.

  Examples of the polymer or copolymer containing an ethylenically unsaturated monomer as a constituent unit include those described in paragraph No. “0069” of JP-A No. 2001-330918.

  Of these, particularly preferred examples include methacrylic acid alkyl esters, methacrylic acid aryl esters, and styrenes. Among such polymer compounds, a polymer compound having an acetal group is preferably used. Even a polymer compound having an acetal group is more preferably a polyvinyl acetal having an acetoacetal structure, for example, U.S. Pat. Nos. 2,358,836, 3,003,879, 2,828,204, UK The polyvinyl acetal shown by patent 771,155 etc. can be mentioned.

  As the polymer compound having an acetal group, a compound represented by the general formula (V) described in “150” of JP-A No. 2002-287299 is particularly preferable.

  A polyurethane resin can also be preferably used as the binder.

  As the polyurethane resin, those having a known structure such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. Moreover, it is preferable to have a total of 2 or more hydroxyl groups, at least one at each polyurethane molecule end.

Since hydroxyl groups are cross-linked with polyisocyanate which is a curing agent to form a three-dimensional network structure, it is more preferable that the hydroxyl groups are contained in the molecule. In particular, it is preferable that the hydroxyl group is at the molecular end because the reactivity with the curing agent is high. The polyurethane preferably has 3 or more hydroxyl groups at the molecular terminals, and particularly preferably 4 or more. In the present invention, when polyurethane is used, Tg is preferably 70 to 105 ° C., elongation at break is 100 to 2000%, and stress at break is preferably 0.5 to 100 N / mm ² .

  These polymer compounds (polymers) may be used alone or in a blend of two or more.

  The photosensitive layer according to the present invention may contain an organic gelling agent. Incidentally, the organic gelling agent referred to here has a function of giving a yield value to the system by adding it to an organic liquid, such as polyhydric alcohols, and eliminating or reducing the fluidity of the system. The compound which has.

  When a photosensitive layer coating solution is used when producing the photosensitive layer, it is also a preferred embodiment that the photosensitive layer coating solution contains a polymer latex in which the aqueous dispersion is dispersed.

  In this case, a polymer latex in which 50% by mass or more of the total binder in the coating solution for the photosensitive layer is dispersed in water is preferable.

  When the photosensitive layer contains a polymer latex, 50% by mass or more of the total binder in the photosensitive layer is preferably a polymer latex, and more preferably 70% by mass or more.

  The polymer latex referred to here is a polymer in which a water-insoluble hydrophobic polymer is dispersed as fine particles in a water-soluble dispersion medium.

  As the dispersion state, the polymer is emulsified in a dispersion medium, the emulsion is polymerized, the micelle is dispersed, or the polymer molecule has a partially hydrophilic structure, and the molecular chain itself is molecularly dispersed. Any of these may be used. The average particle diameter of the dispersed particles is preferably 1 to 50,000 nm, more preferably in the range of about 5 to 1,000 nm. 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.

  The polymer latex used in the photosensitive layer may be a so-called core / shell type latex in addition to a normal polymer latex having a uniform structure. In this case, it may be preferable to change the Tg of the core and the shell. The minimum film-forming temperature (MFT) of the polymer latex according to the present invention is preferably -30 to 90 ° C, more preferably about 0 to 70 ° C. In addition, a film-forming auxiliary may be added to control the minimum film-forming temperature.

  The film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of polymer latex. For example, “Synthetic Latex Chemistry (Souichi Muroi, published by Polymer Publishing Co., Ltd.) , 1970).

  Examples of the polymer species used for the polymer latex include acrylic resins, vinyl acetate resins, polyester resins, polyurethane resins, rubber resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, and copolymers thereof. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is a number average molecular weight and is usually about 5,000 to 1,000,000, preferably about 10,000 to 100,000. When the molecular weight is too small, the mechanical strength of the photosensitive layer is insufficient, and when the molecular weight is too large, the film forming property is poor and both are not preferable.

  The polymer latex preferably has an equilibrium water content of 0.01 to 2% by mass or less, more preferably 0.01 to 1% by mass at 25 ° C. and 60% RH (relative humidity). For the definition and measurement method of the equilibrium moisture content, for example, “Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Polymer Society, Jinshokan)” can be referred to.

  Specific examples of the polymer latex include each latex described in “0173” of JP-A No. 2002-287299. These polymers may be used alone or as a blend of two or more as necessary. As a polymer seed | species of a polymer latex, what contains about 0.1-10 mass% of carboxylic acid components, such as an acrylate or a methacrylate component, is preferable.

  Furthermore, if necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose or the like may be added within a range of 50% by mass or less of the total binder. The addition amount of these hydrophilic polymers is preferably 30% by mass or less based on the total binder of the photosensitive layer.

  In the preparation of the coating solution for the photosensitive layer, the order of addition of the organic silver salt and the aqueous-dispersed polymer latex may be added first or at the same time, but preferably the polymer latex There will be later.

  Furthermore, it is preferable that an organic silver salt and further a reducing agent are mixed before adding the polymer latex. In addition, after mixing the organic silver salt and the polymer latex, if the temperature to be aged is too low, the coated surface shape is impaired, and if it is too high, there is a problem that fog increases, so the coating solution after mixing is 30 to 65 ° C. It is preferable that the above time is elapsed. Furthermore, it is preferable to be aged at 35 to 60 ° C, and a time at 35 to 55 ° C is particularly preferable. In order to maintain the temperature in this way, it is sufficient to keep the temperature of the coating solution preparation tank or the like.

  For coating of the coating solution for the photosensitive layer, it is preferable to use a coating solution that has passed 30 minutes to 24 hours after mixing the organic silver salt and the aqueous polymer latex, and more preferably, 60 minutes after mixing. It is to make -12 hours pass, and it is especially preferable to use the coating liquid which passed 120 minutes-10 hours.

  Here, “after mixing” means after the organic silver salt and the aqueous polymer latex are added and the additive material is uniformly dispersed.

  By using a crosslinking agent for the binder, it is known that filming is improved and development unevenness is reduced, but there is also an effect of suppressing fogging during storage and suppressing generation of printout silver after development. is there.

  Examples of the crosslinking agent to be used include various crosslinking agents conventionally used for photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based, sulfone described in JP-A-50-96216. Acid ester-based, acryloyl-based, carbodiimide-based, and silane compound-based crosslinking agents are used, and the following isocyanate-based, silane compound-based, epoxy-based compounds, and acid anhydrides are preferable.

  Isocyanate-based crosslinking agents are isocyanates having at least two isocyanate groups and adducts thereof (adducts). More specifically, aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, benzene Diisocyanates, naphthalene diisocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates and divalent or trivalent polyalcohols with these isocyanates Adducts and the like. As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used.

  In addition, the adduct of isocyanate and polyalcohol has particularly high ability to improve interlayer adhesion and prevent layer peeling, image shift and bubble generation. Such isocyanate may be placed in any part of the photothermographic material. For example, the photosensitive layer of the support such as a photosensitive layer, a surface protective layer, an intermediate layer, an antihalation layer, an undercoat layer in the support (especially when the support is paper, it can be included in the size composition) It can be added to any layer on the side and can be added to one or more of these layers.

  Also useful as the isocyanate-based crosslinking agent are compounds having a thioisocyanate structure corresponding to the above-mentioned isocyanates.

  The amount of the crosslinking agent used is usually in the range of 0.001 to 2 mol, preferably 0.005 to 0.5 mol, with respect to 1 mol of silver.

  The isocyanate compound and thioisocyanate compound that can be used in the present invention are preferably compounds that function as the above-mentioned crosslinking agent, but a good result can be obtained even if the compound has only one functional group.

  Examples of the silane compound include compounds represented by general formulas (1) to (3) disclosed in JP-A No. 2001-264930.

  Moreover, as an epoxy compound which can be used as a crosslinking agent, what is necessary is just to have one or more epoxy groups, and there is no restriction | limiting in the number of epoxy groups, molecular weight, and others. The epoxy group is preferably contained in the molecule as a glycidyl group via an ether bond or an imino bond. The epoxy compound may be any of a monomer, an oligomer, a polymer, etc., and the number of epoxy groups present in the molecule is usually about 1 to 10, preferably 2 to 4. When the epoxy compound is a polymer, it may be either a homopolymer or a copolymer, and the number average molecular weight Mn is particularly preferably in the range of about 2,000 to 20,000.

  The acid anhydride that can be used in the present invention is a compound having at least one acid anhydride group represented by the following structural formula. The number of acid anhydride groups, molecular weight, and the like are not particularly limited as long as they have one or more acid anhydride groups.

-CO-O-CO-
Said epoxy compound and acid anhydride may use only 1 type, or may use 2 or more types together.

The addition amount is not particularly limited, but is preferably in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / m ² , more preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / m ² . It is.

  This epoxy compound or acid anhydride can be added to any layer on the photosensitive layer side of the support, such as the photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc., and one of these layers Or it can add to two or more layers.

(Silver saving agent)
The photosensitive layer according to the present invention may contain a silver saving agent. The silver saving agent refers to a compound that can reduce the amount of silver necessary to obtain a certain silver image density. Various action mechanisms of the function of decreasing can be considered, but a compound having a function of improving the covering power of developed silver is preferable. Here, the covering power of developed silver refers to the optical density per unit amount of silver.

  This silver saving agent can be present in the photosensitive layer, the non-photosensitive layer, or both. Preferred examples of the silver saving agent include hydrazine derivative compounds, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds.

  Specific examples of the hydrazine derivative include compounds H-1 to H-29 described in US Pat. No. 5,545,505, columns 11 to 20, US Pat. No. 5,464,738, columns 9 to 11. 1 to 12 described in JP-A-2001-27790, compounds H-1-1 to H-1-28 described in paragraphs “0042” to “0052”, and H-2-1 to H-2- 9, H-3-1 to H-3-12, H-4-1 to H-4-21, H-5-1 to H-5-5.

  Specific examples of the vinyl compound include compounds CN-01 to CN-13 described in columns 13 to 14 of US Pat. No. 5,545,515 and column 10 of US Pat. No. 5,635,339. Compounds HET-01 to HET-02 described in US Pat. No. 5,654,130, columns MA-10 to compounds MA-01 to MA-07, US Pat. No. 5,705,324 Compounds IS-01 to IS-04 described in columns 9 to 10 of the specification, and compounds 1-1 to 218-2 described in paragraphs “0043” to “0088” of JP-A-2001-125224.

  Specific examples of the phenol derivative and the naphthol derivative include compounds A-1 to A-89 described in paragraphs “0075” to “0078” of JP 2000-267222 A, and paragraph “0025” of JP 2003-66558 A. ”To“ 0045 ”. Examples thereof include compounds A-1 to A-258.

  Specific examples of the quaternary onium compound include triphenyltetrazolium.

  Specific examples of the silane compound include alkoxysilane compounds having two or more primary or secondary amino groups as shown in compounds A1 to A33 described in paragraphs “0027” to “0029” of JP-A No. 2003-5324 or The salt is mentioned.

The amount of the silver saving agent added is in the range of 1 × 10 ⁻⁵ to 1 mol, preferably 1 × 10 ^{−4 to} 5 × 10 ⁻¹ mol, per mol of the organic silver salt.

  Hereinafter, preferred specific examples of the silver saving agent are listed. The present invention is not limited to these.

(Anti-fogging and image stabilizer)
The photosensitive layer according to the present invention preferably contains an antifoggant and an image stabilizer.

  The antifogging and image stabilizer will be described.

  Since reducing agents with protons such as bisphenols and sulfonamidophenols are mainly used as reducing agents, these reducing agents are deactivated by generating active species that can extract hydrogen. It is preferable that the compound which can be converted is contained. Preferably, the colorless photo-oxidizing substance is preferably a compound capable of generating free radicals as reactive active species during exposure.

  Accordingly, any compound having these functions may be used, but an organic free radical composed of a plurality of atoms is preferred. A compound having any structure may be used as long as it has such a function and does not cause any particular adverse effect on the photothermographic material.

  In addition, as a compound that generates these free radicals, the generated free radicals are carbocyclic or complex in order to have a stability that allows contact with the reducing agent for a time sufficient to react with the reducing agent and inactivate it. Those having a cyclic aromatic group are preferred. Representative examples of these compounds include biimidazolyl compounds and iodonium compounds.

The amount of the biimidazolyl compound and iodonium compound added is in the range of 0.001 to 0.1 mol / m ² , preferably 0.005 to 0.05 mol / m ² . The compound can be contained in any constituent layer in the light-sensitive material of the present invention, but is preferably contained in the vicinity of the reducing agent.

  Many compounds capable of releasing halogen atoms as active species are known as antifogging and image stabilizers. Specific examples of the compound that generates these active halogen atoms include compounds represented by general formula (9) described in “0264” to “0271” of JP-A-2002-287299.

  The amount of these compounds added is preferably within a range in which the increase in printout silver due to the formation of silver halide is not a problem, and is a maximum of 150% or less, more preferably 100% in terms of the ratio to the compound that does not generate active halogen radicals. % Or less is preferable.

  Specific examples of compounds that generate these active halogen atoms include compounds (III-1) to (III-23) described in paragraphs “0086” to “0087” of JP-A No. 2002-169249, Compounds 1-1a to 1-1o and 1-2a to 1-2o described in paragraphs “0031” to “0034” of JP-A-2003-50441, and compounds 2a to 2z and 2aa described in paragraphs “0050” to “0056” To 2ll, 2-1a to 2-1f, compounds 4-1 to 4-32 described in paragraphs “0055” to “0058” of JP-A No. 2003-91054, and compounds 5 described in paragraphs “0069” to “0072” -1 to 5-10.

  Examples of the antifoggant preferably used in the present invention include compound examples a to j described in paragraph “0012” of JP-A-8-314059 and paragraph “0028” of JP-A-7-209797. Thiosulfonate esters A to K, compound examples (1) to (44) described from p14 of JP-A No. 55-140833, compounds described in paragraph “0063” of JP-A No. 2001-13627 (I-1 ) To (I-6), (C-1) to (C-3) described in paragraph “0066”, and compounds (III-1) to (III-) described in paragraph “0027” of JP-A-2002-90937. 108), compounds VS-1 to VS-7 and compounds HS-1 to HS-5 described in paragraph “0013” of JP-A-6-208192 as compounds of vinyl sulfones and / or β-halo sulfones. KS-1 to KS-8 compounds described in JP-A No. 2000-330235 as sulfonylbenzotriazole compounds, PR-01 to PR-08 described in JP-T-2000-515995 as substituted propene nitrile compounds, Examples thereof include compounds (1) -1 to (1) -132 described in paragraphs “0042” to “0051” of JP-A-2002-207273.

  The antifoggant is generally used in an amount of at least 0.001 mole per mole of silver. Usually, the range is 0.01 to 5 moles of the compound relative to the moles of silver, preferably 0.02 to 0.6 moles of the compound relative to the moles of silver.

  In addition to the above compound, the photosensitive layer of the present invention may contain a compound conventionally known as an antifoggant, but it generates a reactive species similar to the above compound. Even if it is a compound which can produce | generate, the compound from which an antifogging mechanism differs may be sufficient. For example, U.S. Pat. Nos. 3,589,903, 4,546,075, 4,452,885, JP-A-59-57234, U.S. Pat. No. 3,874,946. Examples thereof include compounds described in the specification, JP 4,756,999, JP-A-9-288328, and JP-A-9-90550. Further, as other antifoggants, compounds disclosed in US Pat. No. 5,028,523 and European Patent Nos. 600,587, 605,981 and 631,176 are exemplified. Can be mentioned.

  When the reducing agent used has an aromatic hydroxyl group (—OH), particularly in the case of bisphenols, a nonreducing compound having a group capable of forming a hydrogen bond with these groups should be used in combination. Is preferred.

  Specific examples of particularly preferred hydrogen bonding compounds include compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937.

  The photothermographic material of the present invention forms a photographic image by heat development processing, and has a color toning agent for adjusting the color tone of silver as needed dispersed in an ordinary (organic) binder. It is preferable.

  Examples of suitable toning agents for use in the present invention include those of RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136 and 4,021,249. For example, the following are disclosed.

  Imides (for example, succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide); mercaptans (for example, 3-mercapto-1,2,4-triazole); phthalazinone derivatives or metal salts of these derivatives ( For example, phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); phthalazine and phthalic acids ( For example, combinations of phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid; phthalazine and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivatives and anhydrides thereof Products (eg, phthalic acid, 4-methylphthalic acid, 4 The combination and the like with at least one compound selected from nitrophthalic acid and tetrachlorophthalic anhydride). A particularly preferred colorant is a combination of phthalazinone or phthalazine with phthalic acids and phthalic anhydrides.

(Fluorosurfactant)
In the present invention, in order to improve film transportability and environmental suitability (accumulation in a living body) in a thermal development processing apparatus, a fluorosurfactant represented by the following general formula (SF) is used as a photosensitive layer or thermal development. It is preferably contained in the constituent layer of the photosensitive material.

General formula (SF)
(Rf− (L1) _n1 −) _p − (Y) _m1 − (A) _q
In the formula, Rf represents a substituent containing a fluorine atom, L1 represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, and A represents Represents an anionic group or a salt thereof, n1 and m1 each represents an integer of 0 or 1, p represents an integer of 1 to 3, and q represents an integer of 1 to 3. However, when q is 1, n1 and m1 are not 0 at the same time.

  In the general formula (SF), Rf represents a substituent containing a fluorine atom. Examples of the substituent containing a fluorine atom include a fluorinated alkyl group having 1 to 25 carbon atoms (for example, a trifluoromethyl group). Trifluoroethyl group, perfluoroethyl group, perfluorobutyl group, perfluorooctyl group, perfluorododecyl group and perfluorooctadecyl group) or fluorinated alkenyl group (for example, perfluoropropenyl group, perfluorobutenyl group, Perfluorononenyl group, perfluorododecenyl group, etc.).

  L1 represents a divalent linking group having no fluorine atom. Examples of the divalent linking group having no fluorine atom include an alkylene group (eg, methylene group, ethylene group, butylene group), alkylene Oxy group (methyleneoxy group, ethyleneoxy group, butyleneoxy group, etc.), oxyalkylene group (for example, oxymethylene group, oxyethylene group, oxybutylene group, etc.), oxyalkyleneoxy group (for example, oxymethyleneoxy group, oxy Ethyleneoxy group, oxyethyleneoxyethyleneoxy group, etc.), phenylene group, oxyphenylene group, phenyloxy group, oxyphenyloxy group, or a combination of these groups.

  A represents an anionic group or a salt thereof. For example, carboxylic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfonic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfuric acid half ester Group or a salt thereof (sodium salt, potassium salt and lithium salt), a phosphoric acid group or a salt thereof (sodium salt, potassium salt and the like) and the like.

  Y represents a (p + q) -valent linking group having no fluorine atom. For example, the trivalent or tetravalent linking group having no fluorine atom is composed mainly of a nitrogen atom or a carbon atom. An atomic group is mentioned. n1 represents 0 or an integer of 1, and is preferably 1.

  The fluorine-based surfactant represented by the general formula (SF) is an alkyl compound having 1 to 25 carbon atoms into which a fluorine atom is introduced (for example, trifluoromethyl group, pentafluoroethyl group, perfluorobutyl group, perfluorooctyl). Group and a compound having a perfluorooctadecyl group) and an alkenyl compound (for example, a perfluorohexenyl group and a perfluorononenyl group), a trivalent to hexavalent alkanol compound in which no fluorine atom is introduced, and a hydroxyl group, respectively. An anionic group (A) is further introduced into the compound (partially Rf-modified alkanol compound) obtained by addition reaction or condensation reaction with 3 to 4 aromatic compounds or hetero compounds by, for example, sulfate esterification. Can be obtained.

  Examples of the trivalent to hexavalent alkanol compound include glycerin, pentaerythritol, 2-methyl-2-hydroxymethyl 1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentene, and 1,2,6-hexane. Examples include triol, 1,1,1-tris (hydroxymethyl) propane, 2,2-bis (butanol) -3, aliphatic triol, tetramethylolmethane, D-sorbitol, xylitol, D-mannitol and the like.

  Examples of the aromatic compound and hetero compound having 3 to 4 hydroxyl groups include 1,3,5-trihydroxybenzene and 2,4,6-trihydroxypyridine.

  Below, the preferable specific compound of the fluorine-type surfactant represented by general formula (SF) is shown.

  As a method for adding the fluorosurfactant represented by the general formula (SF) of the present invention to the coating solution, it can be added according to a known addition method. That is, it can be dissolved and added in alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone and acetone, polar solvents such as dimethyl sulfoxide and dimethylformamide. Further, fine particles having a size of 1 μm or less can be added after being dispersed in water or an organic solvent by sand mill dispersion, jet mill dispersion, ultrasonic dispersion or homogenizer dispersion. Many techniques for fine particle dispersion are disclosed, but they can be dispersed according to these techniques. The fluorine-based surfactant represented by the general formula (SF) is preferably added to the outermost protective layer.

The addition amount of the fluorosurfactant represented by the general formula (SF) is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per m ² from the viewpoint of charging characteristics and storage stability under high humidity. 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol is particularly preferable.

(Surface layer)
The surface layer on the photosensitive layer side (hereinafter represented by (E)) and the opposite side (hereinafter represented by (B)) of the photothermographic material of the present invention preferably has the following rough surface.

  In the present invention, the value of Rz (E) / Rz (B) is preferably 0.1 or more and 0.7 or less, particularly from the viewpoint of film transportability and prevention of density unevenness during thermal development. The value of Rz (E) / Rz (B) is preferably 0.2 or more and 0.6 or less, and more preferably 0.3 or more and 0.55 or less.

  In the present invention, the Ra (E) / Ra (B) value is 0.6 or more and 1.5 or less in terms of prevention of fog rise with time, transportability of the film, and prevention of uneven density during heat development. It is preferable that the value of Ra (E) / Ra (B) is preferably 0.6 or more and 1.3 or less, and more preferably 0.7 or more and 1.1 or less.

  The ten-point average roughness (Rz), maximum roughness (Rt), and centerline average roughness (Ra) in the present invention are defined by the following JIS surface roughness (B0601).

  Ten-point average roughness (Rz) is the peak from the highest to the fifth measured in the direction of the vertical magnification from the straight line that is parallel to the average line and does not cross the cross-sectional curve, in the portion that has been cut by the reference length from the cross-sectional curve. The difference between the average value of the altitude and the average value of the altitude at the bottom of the valley from the deepest to the fifth is expressed in micrometers (μm). The maximum roughness (Rt) is the roughness curve extracted by the reference length L, and when the extracted part is sandwiched between two straight lines parallel to the center line, the distance between the two straight lines is measured in the direction of the vertical magnification of the roughness curve. Then, this value is expressed in micrometers (μm). The centerline average roughness (Ra) is a portion of the measured length L extracted from the roughness curve in the direction of the centerline, the centerline of this extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness curve Is represented by y = f (x), the value obtained by the following equation is expressed in micrometers (μm).

  As a method for measuring Rz, Rt, and Ra, the humidity is adjusted for 24 hours in a 25 ° C. and 65% relative humidity environment in which the measurement samples are not overlapped with each other, and then measured in the environment.

  The non-overlapping conditions shown here are, for example, a method of winding with the film edge portion raised, a method of stacking paper between the films, a method of making a frame with cardboard and fixing the four corners, etc. One of them. Examples of the measuring apparatus that can be used include a RSTPLUS non-contact three-dimensional micro surface shape measuring system manufactured by WYKO.

  In order to set Rz, Rt, and Ra on the front and back surfaces of the photosensitive material within the scope of the present invention, it can be easily adjusted by appropriately combining the following technical means.

1) Adjustment of the type, average particle diameter, addition amount, and surface treatment method of the matting agent (inorganic or organic powder) contained in the layer having the image forming layer and the layer opposite to the side having the image forming layer 2) Matting agent dispersion conditions (type of disperser used, dispersion time, type of beads used for dispersion, average particle size, type and amount of dispersant used during dispersion, type of polar group of binder, polar group content ) Adjustment 3) Drying conditions during application (application speed, distance from the application surface of the hot air blowing nozzle, amount of drying air), adjustment of residual solvent amount 4) Type of filter used for filtration of coating liquid, filtration time Adjustment 5) When calendering is performed after coating, the conditions (for example, calendar temperature 40 to 80 ° C., pressure 50 to 300 kg / cm, line speed 20 to 100 m, nip number 2 to 6) are adjusted. Material composition Contain an organic or inorganic powder as a matting agent in the surface layer to be preferred.

As the powder used, it is preferable to use a powder having a Mohs hardness of 5 or more. As the powder, a known inorganic powder or organic powder can be appropriately selected and used. Examples of the inorganic powder include titanium oxide, boron nitride, SnO ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, SiC, cerium oxide, corundum, artificial Examples thereof include diamond, garnet, garnet, mica, silica, silicon nitride, silicon carbide and the like. Examples of the organic powder include powders such as polymethyl methacrylate, polystyrene, and Teflon (registered trademark). Among these, inorganic powders such as SiO ₂ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃ , mica, etc. are preferable. SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ is particularly preferable.

For example, the powder is preferably surface-treated. The surface layer is formed by dry pulverizing the inorganic powder material, adding water and a dispersing agent, and performing coarse particle classification by wet pulverization and centrifugation. Thereafter, the fine slurry is transferred to a surface treatment tank, where the surface of the metal hydroxide is coated. First, a predetermined amount of an aqueous salt solution such as Al, Si, Ti, Zr, Sb, Sn, and Zn is added, and an acid or alkali that neutralizes the solution is added, and the surface of the inorganic powder particles is coated with the resulting hydrous oxide. To do. Water-soluble salts produced as a by-product are removed by decantation, filtration, and washing. Finally, the slurry pH is adjusted, filtered, and washed with pure water. The washed cake is dried with a spray dryer or a band dryer. Finally, the dried product is pulverized by a jet mill to become a product. In addition to the aqueous system, AlCl ₃ and SiCl ₄ vapors can be passed through the non-magnetic inorganic powder, and then steam can be introduced to perform Al and Si surface treatment.

  For other surface treatment methods, “Characterization of Powder Surfaces”, Academic Press can be referred to.

  As the surface treatment, a surface treatment with a Si compound or an Al compound is preferable. When such a surface-treated powder is used, the dispersion state when the matting agent is dispersed can be improved. The content of Si or Al is preferably 0.1 to 10% by mass of Si and 0.1 to 10% by mass of Al, more preferably 0.1 to 10% by mass with respect to the powder. It is particularly preferable that 5% by mass, Al is 0.1-5% by mass, Si is 0.1-2% by mass, and Al is 0.1-2% by mass. The mass ratio of Si and Al is preferably Si <Al. The surface treatment can be performed by the method described in JP-A-2-83219. The average particle diameter of the powder is the average diameter of the spherical powder, the average major axis length of the needle-like powder, and the average value of the maximum diagonal length of the plate-like surface of the plate-like powder. And can be easily obtained from measurement by an electron microscope.

  The organic or inorganic powder preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm.

  The average particle diameter of the organic or inorganic powder contained in the outermost layer on the photosensitive layer side is usually 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm. It is. The addition amount is usually 1.0 to 20% by mass, preferably 2.0 to 15% by mass, more preferably 3 with respect to the amount of binder used in the outermost layer (including the crosslinking agent in the binder amount). 0.0 to 10% by mass. The average particle size of the organic or inorganic powder contained in the outermost layer on the opposite side of the image forming layer across the support is usually 2.0 to 15.0 μm, preferably 3.0 to 12.0 μm. More preferably, it is 4.0-10.0 micrometers. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably 0 to the amount of binder used in the outermost layer (including the crosslinking agent in the binder amount). .6 to 5% by mass.

  The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less. Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

{(Standard deviation of particle size) / (Average value of particle size)} × 100
The method of adding the organic or inorganic powder may be a method in which the organic or inorganic powder is previously dispersed in the coating solution, or a method of spraying the organic or inorganic powder after the coating solution is applied and before the drying is completed. May be. Moreover, when adding several types of powder, you may use both methods together.

(Support)
Examples of the material of the support according to the present invention include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (aluminum, etc.), etc. What can be processed into a certain sheet | seat or a roll is suitable.

  Accordingly, the support used in the photothermographic material of the present invention includes cellulose acetate film, polyester film, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyamide film, polyimide film, cellulose triacetate film (TAC). ) Or a plastic film such as a polycarbonate (PC) film is preferable, and a biaxially stretched PET film is particularly preferable.

  The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  The photothermographic material of the present invention preferably has a constituent layer containing a conductive compound such as a metal oxide and / or a conductive polymer in order to improve the chargeability.

  This constituent layer may be any layer constituting the photothermographic material, but is preferably a surface protective layer, an undercoat layer, a backcoat layer, or the like on the photosensitive layer side.

  As the conductive compound, conductive compounds described in columns 14 to 20 of US Pat. No. 5,244,773 are preferably used.

  In the present invention, the surface protective layer on the backing layer side preferably contains a conductive metal oxide. This further enhances the effects of the present invention (particularly the transportability during heat development).

  Here, the conductive metal oxide is crystalline metal oxide particles, and those containing oxygen defects and those containing a small amount of hetero atoms forming a donor with respect to the metal oxide used are generally used. In particular, it is particularly preferable because of its high conductivity, and the latter is particularly preferable because it does not give fog to the silver halide emulsion.

Examples of metal oxides are ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O _5, etc., or a composite oxide thereof, especially ZnO, TiO ₂ and SnO ₂ are preferred. Examples of containing different atoms include, for example, addition of Al, In, etc. to ZnO, addition of Sb, Nb, P, halogen elements, etc. to SnO ₂ , and Nb, Ta to TiO ₂ . Etc. are effective.

  The amount of these different atoms added is preferably in the range of 0.01 to 30 mol%, but particularly preferably 0.1 to 10 mol%. Furthermore, a silicon compound may be added during the production of fine particles in order to improve fine particle dispersibility and transparency.

The metal oxide fine particles used in the present invention have electrical conductivity, and the volume resistivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A Nos. 56-143431, 56-120519, 58-62647 and the like.

  Further, as described in JP-B-59-6235, a conductive material in which the above metal oxide is adhered to other crystalline metal oxide particles or fibrous materials (titanium oxide or the like) may be used.

  The particle size that can be used is preferably 1 μm or less, but if it is 0.5 μm or less, stability after dispersion is good and it is easy to use. In order to make the light scattering property as small as possible, it is very preferable to use conductive particles of 0.3 μm or less because a transparent photosensitive material can be formed.

Further, when the conductive metal oxide is needle-like or fibrous, the length is preferably 30 μm or less and the diameter is preferably 1 μm or less, particularly preferably the length is 10 μm or less and the diameter is 0.3 μm or less. The thickness / diameter ratio is 3 or more. As the SnO _2, are commercially available from Ishihara Sangyo Kaisha, it can be used SNS10M, SN-100P, SN- 100D, the FSS10M like.

  The photothermographic material of the present invention has at least one photosensitive layer layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer.

  For example, a protective layer is preferably provided on the photosensitive layer for the purpose of protecting the image forming layer.

  The binder used in these protective layers and the like is a polymer having a glass transition point (Tg) higher than that of the image forming layer and hardly causing scratches or deformation, such as cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate. Or the like is selected from the binders described above.

  There may be a plurality of photosensitive layers.

(Application of component layers)
The photothermographic material of the present invention is preferably formed by preparing a coating solution in which the material of each constituent layer is dissolved or dispersed in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment. Here, "multiple simultaneous multi-layer coating" means that a coating solution for each constituent layer (for example, a photosensitive layer, a protective layer) is prepared, and each layer is repeatedly coated and dried when it is coated on a support. Instead, it means that each constituent layer can be formed in such a state that a multilayer coating and drying process can be performed simultaneously. That is, the upper layer is provided before the remaining amount of all the solvents in the lower layer reaches 70% by mass or less (more preferably 90% by mass or less).

  There are no particular restrictions on the method of applying multiple layers simultaneously to each constituent layer, for example, bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, reverse roll coating method, gravure coating method, and extrusion. A known method such as a coating method can be used. Of these, the slide coating method and the extrusion coating method are more preferable.

  These coating methods have been described on the side having the photosensitive layer, but the same applies to the case of coating with undercoating when providing the backcoat layer. Japanese Unexamined Patent Publication No. 2000-15173 has a detailed description on the simultaneous multilayer coating method in the heat development material.

In the present invention, the silver coating amount is preferably selected in accordance with the purpose of the photothermographic material. However, for the purpose of medical images, 0.3 g / m ² or more, 1.5 g / m. m ² or less is preferable, and 0.5 g / m ² or more and 1.5 g / m ² or less are more preferable. Among the applied silver amounts, those derived from silver halide preferably account for 2 to 18%, more preferably 5 to 15%, based on the total silver amount.

In the present invention, the coating density of silver halide grains having a particle diameter of 0.01 μm or more (equivalent particle diameter equivalent to a sphere) is preferably 1 × 10 ¹⁴ particles / m ² or more and 1 × 10 ¹⁸ particles / m ² or less. Furthermore, 1 × 10 ¹⁵ pieces / m ² or more and 1 × 10 ¹⁷ pieces / m ² or less are preferable.

Further, the coating density of the non-photosensitive long chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ g or more and 1 × 10 ⁻¹⁴ per silver halide grain of 0.01 μm or more (equivalent particle diameter in terms of sphere). g is preferably 1 × 10 ⁻¹⁶ g or more and 1 × 10 ⁻¹⁵ g or less.

  In the case of coating under the conditions within the above range, preferable results are obtained from the viewpoint of the optical maximum density of the silver image per fixed coating silver amount, that is, the silver coating amount (covering power) and the color tone of the silver image. Is obtained.

In the present invention, the photothermographic material preferably contains a solvent in the range of 5 to 1,000 mg / m ² during development. It is more preferable to adjust so that it may be 100-500 mg / m < ² >. As a result, the photothermographic material has high sensitivity, low fog, and high maximum density.

  Examples of the solvent include those described in paragraph “0030” of JP-A No. 2001-264930. However, it is not limited to these. These solvents can be used alone or in combination of several kinds.

  The content of the solvent in the photothermographic material can be adjusted by changing conditions such as a temperature condition in a drying process after the coating process. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

(Packaging body)
When storing the photothermographic material of the present invention, a package having a low oxygen permeability and / or moisture permeability in order to prevent density changes and fogging over time, or to improve curling, curling, etc. It is preferable to package with materials. The oxygen permeability is preferably 5 × 10 ⁻⁴ ml / Pa · m ² · day or less at 25 ° C., more preferably 1 × 10 ⁻⁴ ml / Pa · m ² · day or less, and still more preferably 1. 0 × m10 ⁻⁵ ml / Pa · m ² · day or less. The moisture permeability is preferably 1 × 10 ⁻⁴ g / Pa · m ² · day or less, more preferably 5 × 10 ⁻⁵ g / Pa · m ² · day or less, and even more preferably 1 × 10 ^−5. g / Pa · m ² · day or less.

  Specific examples of the packaging material for the photothermographic material include, for example, JP-A-8-254793, JP-A-2000-206653, JP-A-2000-235241, JP-A-2002-062625, JP-A-2003-015261, JP 2003-057990 A, JP 2003-084397 A, JP 2003-098648 A, JP 2003-098635 A, JP 2003-107635 A, JP 2003-131337 A, JP 2003-146330 A, Special It is a packaging material described in Japanese Patent Application Laid-Open No. 2003-226439 and Japanese Patent Application Laid-Open No. 2003-228152. The void ratio in the package is 0.01 to 10%, preferably 0.02 to 5%. Nitrogen sealing is performed so that the nitrogen partial pressure in the package is 80% or more, preferably 90% or more. It is good to do. The relative humidity in the package is 10% to 60%, preferably 40% to 55%.

(Exposure of photothermographic material)
The image forming method according to the present invention includes an exposure process for image exposure and a development process for heat development.

  When the photothermographic material is image-exposed, it is preferable to use a laser beam.

  In the exposure according to the present invention, it is desirable to use a light source suitable for the color sensitivity imparted to the photosensitive material. For example, if the photosensitive material is sensitive to infrared light, it can be applied to any light source as long as it is in the infrared light range. However, the laser power is high, or the photothermographic material is made transparent. In view of being able to do so, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

In particular, the photothermographic material of the present invention preferably exhibits its characteristics when exposed to light of high illuminance with a light amount of 1 mW / mm ² or more for a short time.

The illuminance here refers to the illuminance when the photosensitive material after heat development has an optical density of 3.0. When exposure is performed at such high illuminance, the amount of light (= illuminance * exposure time) required to obtain a required optical density is reduced, and a high sensitivity system can be designed. More preferably, the amount of light is ² mW / mm ² or more and 50 W / mm ² or less, and more preferably 10 mW / mm ² or more and 50 W / mm ² or less.

Any light source may be used as long as it is such a light source, but it can be preferably achieved by using laser light. As the laser beam preferably used in the present invention, a gas laser (Ar ⁺ , Kr ⁺ , He—Ne) YAG laser, a dye laser, a semiconductor laser and the like are preferable. A semiconductor laser second harmonic generation element or the like can also be used. Further, a blue to violet light emitting semiconductor laser (such as one having a peak intensity at a wavelength of 350 nm to 440 nm) can be used. As a high-power semiconductor laser emitting blue to violet, Nichia's NLHV3000E semiconductor laser can be mentioned.

  In the present invention, the exposure is preferably performed by laser scanning exposure, but various methods can be adopted as the exposure method. For example, as a first preferred method, there is a method using a laser scanning exposure machine in which the angle formed by the scanning surface of the photosensitive material and the scanning laser beam is not substantially perpendicular.

  Here, “substantially not vertical” is preferably 55 to 88 degrees, more preferably 60 to 86 degrees, and still more preferably 65 to 84 degrees as the angle closest to the vertical during laser beam scanning. , Most preferably 70-82 degrees.

  When the laser light is scanned onto the photothermographic material, the beam spot diameter on the photosensitive material exposure surface is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the “shift angle” from the vertical of the laser beam incident angle. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

  Further, as a second method, it is also preferable to perform exposure using a laser scanning exposure machine that emits scanning laser light that is a vertical multi. Compared with a single longitudinal mode scanning laser beam, image quality degradation such as generation of interference fringe-like unevenness is reduced. In order to make a vertical multiplex, methods such as using return light by combining and applying high-frequency superposition are preferable. Note that the vertical multi means that the exposure wavelength is not single, and the distribution of the exposure wavelength is usually 5 nm or more, preferably 10 nm or more. The upper limit of the exposure wavelength distribution is not particularly limited, but is usually about 60 nm.

  Furthermore, as a third aspect, it is also preferable to form an image by scanning exposure using two or more laser beams. As such an image recording method using a plurality of laser beams, it is used in an image writing means of a laser printer or a digital copying machine for writing an image for each line by one scanning because of a demand for high resolution and high speed. For example, Japanese Patent Laid-Open No. 60-166916 is known. This is a method in which laser light emitted from a light source unit is deflected and scanned by a polygon mirror and imaged on a photoconductor via an fθ lens or the like. This is in principle the same laser scanning optics as a laser imager or the like. Device.

  The image formation of the laser beam on the photosensitive member in the image writing means of a laser printer or digital copying machine is shifted by one line from the image formation position of one laser because of the application of writing an image for each line by one scanning. The next laser beam is imaged. Specifically, the two light beams are close to each other on the image plane in the sub-scanning direction at an order of several tens of μm, and the print density is 400 dpi (dpi is the number of dots per inch = 2.54 cm). The sub-scanning direction pitch of the two beams is 63.5 μm, and 42.3 μm at 600 dpi. Unlike the method of shifting the resolution in the sub-scanning direction as described above, in the present invention, it is preferable to form an image by condensing two or more lasers on the same surface at different incident angles. In this case, the exposure energy on the exposure surface when writing with one ordinary laser beam (wavelength λ [nm]) is E, and N laser beams used for exposure have the same wavelength (wavelength λ [nm]). ), In the case of the same exposure energy (En), the range of 0.9 × E ≦ En × N ≦ 1.1 × E is preferable. By doing so, energy is secured on the exposure surface, but the reflection of each laser beam to the image forming layer is reduced because the exposure energy of the laser is low, and thus the occurrence of interference fringes is suppressed.

  In the above description, a plurality of laser beams having the same wavelength as λ are used. However, ones having different wavelengths may be used. In this case, it is preferable that (λ−30) <λ1, λ2,... Λn ≦ (λ + 30) with respect to λ [nm].

In the above-described image recording methods of the first, second, and third aspects, the laser used for scanning exposure is generally well-known solid laser such as ruby laser, YAG laser, glass laser; Ne laser, Ar ion laser, Kr ion laser, CO ₂ laser, CO laser, He—Cd laser, N ₂ laser, excimer laser and other gas lasers; InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP Semiconductor lasers such as ₂ lasers and GaSb lasers; chemical lasers, dye lasers, etc. can be selected and used in a timely manner, but among these, semiconductors with a wavelength of 600 to 1200 nm due to maintenance and light source size problems laser It preferred to use a laser beam with. In the laser beam used in a laser imager or a laser image setter, the beam spot diameter on the exposed surface of the material when scanned with a photothermographic material is generally 5 to 75 μm as the minor axis diameter, and the major axis. The diameter is in the range of 5 to 100 μm, and the laser beam scanning speed can be set to an optimum value for each photothermographic material depending on the sensitivity and laser power at the laser oscillation wavelength inherent to the photothermographic material.

(Image forming method-heat development processing (recording) apparatus)
The thermal development process according to the present invention is a process of developing by heating to form an image, and a thermal development processing apparatus is used for the development process.

  The thermal development processing apparatus is composed of a film supply unit represented by a film tray, a laser image recording unit, a thermal development unit for supplying uniform and stable heat to the entire surface of the photothermographic material, and a laser recording from the film supply unit. And a conveyance section until the photothermographic material image-formed by heat development is discharged out of the apparatus.

  Specific examples of the heat development processing (recording) apparatus of this aspect are shown in FIGS. 1 and 2, and this was used for the implementation.

  In the present invention, there is provided a photothermographic material having an image forming step including an exposure step for image exposure and a development step for heat development treatment of the photothermographic material according to any one of claims 1 to 5. The effect of the present invention is remarkable when the image forming process includes a process in which an exposure process and a development process are performed simultaneously.

  Including the step in which the exposure step and the development step are performed at the same time means that a portion of the sheet-shaped photosensitive material to be conveyed is exposed and development is started on a portion of the already exposed sheet. That means.

  In order to include a process in which the exposure process and the development process are performed simultaneously, it can be achieved by shortening the distance between the exposure part and the development part for performing the exposure process, and the distance is 0 cm or more and 50 cm or less. In this way, a series of processing time for exposure and development is extremely shortened.

  A preferable range of this distance is 3 cm or more and 40 cm or less, and more preferably 5 cm or more and 30 cm or less.

  Further, the conveyance speed of the photothermographic material in the photothermographic part is generally 20 to 200 mm / sec, preferably 25 to 200 mm / sec, particularly preferably 25 to 100 mm in terms of density unevenness and shortening of processing time. / Sec.

The conditions for the development processing of the photothermographic material vary depending on the equipment, apparatus, or means used. Typically, the development is performed by heating the photothermographic material exposed imagewise at a suitable high temperature. Is to do. The latent image obtained after exposure is moderately hot (about 80-200 ° C., preferably about 100-140 ° C., more preferably 110-130 ° C.) for a sufficient time (generally about 1 second to 2 minutes). , Preferably 3 to 30 seconds, more preferably 5 to 20 seconds.)
If the heating temperature is less than 80 ° C, a sufficient image density cannot be obtained in a short time. If the heating temperature exceeds 200 ° C, the binder melts, and not only the image itself such as transfer to a roller but also transportability and a developing machine. Adversely affect. By heating, a silver image is generated by an oxidation-reduction reaction between an organic silver salt (which functions as an oxidizing agent) and a reducing agent. This reaction process proceeds without any supply of treatment liquid such as water from the outside.

  The heating device, apparatus or means may be a heating means typical as a heat generator using, for example, a hot plate, iron, hot roller, carbon or white titanium. More preferably, the photothermographic material provided with the protective layer is subjected to heat treatment by bringing the surface having the protective layer into contact with the heating means, in order to perform uniform heating, thermal efficiency, workability, etc. In view of the above, it is preferable that the surface on the side having the protective layer is conveyed while being in contact with the heat roller, and is developed by heat treatment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, the embodiment of this invention is not limited to these. Unless otherwise specified, “%” in the examples represents “mass%”.

Example 1
<< Preparation of undercoated photographic support >>
On both sides of a biaxially stretched heat-fixed 175 μm thick polyethylene terephthalate film colored with the following blue dye at an optical density of 0.150 (measured with a Densitometer PDA-65 manufactured by Konica Minolta Photo Imaging Co., Ltd.), 8 W · min / The photographic support subjected to the corona discharge treatment of m ² was subjected to subbing.

  That is, the undercoat coating liquid a-1 was applied to one surface of this photographic support so that the dry film thickness was 0.2 μm at 22 ° C. and 100 m / min, and dried at 140 ° C. to form an image. A layer side undercoat layer was formed (referred to as undercoat underlayer A-1).

  Also, on the opposite surface, the following undercoat coating liquid b-1 as a backcoat layer undercoat layer was applied at 22 ° C. and 100 m / min so that the dry film thickness was 0.12 μm, and dried at 140 ° C. Then, an undercoat conductive layer having an antistatic function (referred to as undercoat lower layer B-1) was coated on the backcoat layer side.

A corona discharge of 8 W · min / m ² is applied to the upper surfaces of the subbing lower layer A-1 and the subbing lower layer B-1, and the following subbing coating solution a-2 is dried on the lower subbing layer A-1. The film was coated at 33 ° C. and 100 m / min so as to have a film thickness of 0.03 μm, and dried at 140 ° C. to form an undercoat upper layer A-2. -2 was coated at 33 ° C. and 100 m / min to a dry film thickness of 0.2 μm, dried at 140 ° C. to form an undercoating upper layer B-2, and the support was further heat treated at 123 ° C. for 2 minutes. The sample was wound up under the conditions of 50 ° C. and 50% RH to prepare a subtracted sample.

[Preparation of aqueous polyester A-1 solution]
35.4 parts by weight of dimethyl terephthalate, 33.63 parts by weight of dimethyl isophthalate, 17.92 parts by weight of dimethyl sodium 5-sulfoisophthalate, 62 parts by weight of ethylene glycol, 0.065 parts by weight of calcium acetate / monohydrate, After transesterification of 0.022 parts by mass of manganese acetate tetrahydrate under a nitrogen stream while distilling off methanol at 170 to 220 ° C., 0.04 parts by mass of trimethyl phosphate and a polycondensation catalyst were used. 0.04 parts by mass of antimony oxide and 6.8 parts by mass of 1,4-cyclohexanedicarboxylic acid were added, and at a reaction temperature of 220 to 235 ° C., a theoretical amount of water was distilled off for esterification.

  Thereafter, the inside of the reaction system was further depressurized and heated for about 1 hour, and finally subjected to polycondensation at 280 ° C. and 133 Pa or less for about 1 hour to synthesize aqueous polyester A-1. The obtained aqueous polyester A-1 had an intrinsic viscosity of 0.33, an average particle size of 40 nm, and Mw = 80000 to 100,000.

  Next, 850 ml of pure water was placed in a 2 L three-necked flask equipped with a stirring blade, a reflux condenser, and a thermometer, and 150 g of aqueous polyester A-1 was gradually added while rotating the stirring blade. After stirring for 30 minutes at room temperature, the mixture was heated to an internal temperature of 98 ° C. over 1.5 hours and dissolved at this temperature for 3 hours. After completion of the heating, the mixture was cooled to room temperature over 1 hour and allowed to stand overnight to prepare a 15% by mass aqueous polyester A-1 solution.

[Preparation of Modified Aqueous Polyester B-1-2 Solution]
Into a 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer and a dropping funnel, 1900 ml of the 15% by mass aqueous polyester A-1 solution was placed, and the internal temperature was adjusted to 80 ° C. while rotating the stirring blade. Until heated.

  Into this, 6.52 ml of a 24 mass% aqueous solution of ammonium peroxide was added, and a monomer mixture (28.5 g of glycidyl methacrylate, 21.4 g of ethyl acrylate, 21.4 g of methyl methacrylate) was dropped over 30 minutes. The reaction is continued for another 3 hours. Then, it cooled and filtered to 30 degrees C or less, and prepared the modified aqueous polyester B-1 solution (vinyl-type component modification | denaturation ratio 20 mass%) whose solid content concentration is 18 mass%.

  The solid content concentration was the same except that the vinyl modification ratio was 36% by mass and the modified components were styrene: glycidyl methacrylate: acetoacetoxyethyl methacrylate: n-butyl acrylate = 39.5: 40: 20: 0.5. An 18% by mass modified aqueous polyester B-2 solution (vinyl component modification ratio 20% by mass) was prepared.

[Production of Acrylic Polymer Latex C-1 to C-3]
Acrylic polymer latexes C-1 to C-3 having the monomer composition shown in Table 1 were synthesized by emulsion polymerization. The solid content concentration was 30% by mass.

[Undercoat coating liquid a-1]
Acrylic polymer latex C-3 (solid content 30%) 70.0 g
Water dispersion of ethoxylated alcohol and ethylene homopolymer (10% solids)
5.0g
Surfactant (A) 0.1g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Undercoat coating liquid a-2]
Modified aqueous polyester B-2 (18% by mass) 30.0 g
Surfactant (A) 0.1g
True spherical silica matting agent (Nippon Shokubai Co., Ltd. Sea Hoster KE-P50) 0.04g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Undercoat coating liquid b-1]
Acrylic polymer latex C-1 (solid content 30%) 30.0 g
Acrylic polymer latex C-2 (solid content 30%) 7.6 g
SnO ₂ sol 180g
(SnO ₂ sol synthesized by the method described in Example 1 of Japanese Patent Publication No. 35-6616 was heated and concentrated so that the solid content concentration was 10% by mass, and then adjusted to pH = 10 with ammonia water)
Surfactant (A) 0.5g
PVA-613 (Kuraray Co., Ltd. PVA) 5 mass% aqueous solution 0.4g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Undercoat coating liquid b-2]
Modified aqueous polyester B-1 (18% by mass) 145.0 g
Spherical silica matting agent (Nippon Shokubai Co., Ltd. Sea Hoster KE-P50) 0.2g
Surfactant (A) 0.1g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

  In addition, the intermediate | middle layer and the backcoat layer of the following composition were coated on undercoat layer A-2 of the support body which gave the said undercoat layer.

(Middle layer)
(Preparation of infrared dye 1 solid fine particle dispersion)
6.0 kg of the following infrared dye-1 and 3.0 kg of sodium p-dodecylbenzenesulfonate, 0.6 kg of surfactant Demol SNB manufactured by Kao Corporation, and antifoaming agent (trade name: Surfynol 104E, Nissin Chemical) 0.15 kg manufactured by Co., Ltd. was mixed with distilled water to make a total liquid volume of 60 kg. The mixed solution was dispersed with 0.5 mm zirconia beads using a horizontal sand mill (UVM-2: manufactured by Imex Corporation). The obtained dispersion was diluted with distilled water so that the concentration of the infrared dye was 6% by mass, and subjected to filter filtration (average pore diameter: 1 μm) for removing dust.

(Preparation of intermediate layer coating solution)
The container was kept at 40 ° C., and 32.2 g of gelatin (type is described in Table 2), 35 mg of benzoisothiazolinone and 840 ml of water were added to dissolve the gelatin. Furthermore, 5.8 ml of 1 mol / l sodium hydroxide aqueous solution, 2.6 g of solid dispersion of infrared dye-1, 0.3 g of C ₁₈ H ₃₇ CONHCH ₂ CH ₂ NHCOC ₁₈ H ₃₇ , and liquid paraffin emulsion were flowed 1.5 g as paraffin, 10 ml of 5% by weight aqueous solution of di (2-ethylhexyl) sodium sulfosuccinate, 20 ml of 3% by weight aqueous sodium polystyrene sulfonate, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer ( Copolymer mass ratio 57/8/28/5/2) 72.6 g of a 19% by weight latex solution was mixed to prepare an intermediate layer coating solution.

(Preparation of coating solution for backcoat layer) The container was kept at 40 ° C., and 32.2 g of gelatin (type is described in Table 2), 35 mg of benzoisothiazolinone and 840 ml of water were added to dissolve the gelatin. Further, 5.8 ml of 1 mol / l sodium hydroxide aqueous solution, 0.3 g of C ₁₈ H ₃₇ CONHCH ₂ CH ₂ NHCOC ₁₈ H ₃₇ , 1.5 g of liquid paraffin emulsion as liquid paraffin, di (2-ethylhexyl) sulfosuccinate Sodium salt 5% by weight aqueous solution 10 ml, polystyrene polystyrene sulfonate 3% by weight aqueous solution 20 ml, fluorinated surfactant (SF-19) 2% by weight solution 2.4 ml, fluorinated surfactant (SF-20) 2% by weight The solution was mixed with 2.4 ml of methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 57/8/28/5/2) and a latex 19 mass% liquid 72.6 g. Immediately before coating, 9.2 g of silica dispersion “monodispersed silica with a monodispersity of 15% (average particle diameter: surface treatment with 1% aluminum of 10 μm silica total mass) was added to water at a concentration of 1%, and the dissolver type Dispersed with a homogenizer "was added to obtain a backcoat layer coating solution.

<Preparation of photosensitive silver halide emulsion A1>
(A1)
Phenylcarbamoylated gelatin 88.3g
10% aqueous methanol solution of compound (AO-1) 10ml
Potassium bromide 0.32g
Finish to 5429 ml with water (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(C1)
Potassium bromide 50.69g
Potassium iodide 2.66g
Finish to 660ml with water (D1)
Potassium bromide 151.6g
Potassium iodide 7.67g
0.93 ml of potassium hexachloroiridium (IV) (1% aqueous solution)
K ₂ (IrCl ₆ )
0.004 g of potassium hexacyanoferrate (II)
0.004 g of potassium hexachloroosmium (IV)
Finish to 1982ml with water (E1)
0.4 mol / L potassium bromide aqueous solution Silver potential control amount (F1) shown below
Potassium hydroxide 0.71g
Finish to 20ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
(H1)
Anhydrous sodium carbonate 1.72 g
Water finish 151ml AO-1: HO (CH 2 CH 2 O) n [CH (CH ₃₎ CH ₂ O] _{17 (CH 2 CH 2 O)} m H (m + n = 5~7).

  Using the mixing stirrer shown in Japanese Patent Publication No. 58-58288, while controlling the 1/4 amount of the solution (B1) in the solution (A1) and the total amount of the solution (C1) to 20 ° C. and pAg 8.09, the simultaneous mixing method Was added for 4 minutes and 45 seconds to nucleate. After 1 minute, the entire amount of solution (F1) was added. During this time, pAg was adjusted as appropriate using (E1). After a lapse of 6 minutes, 3/4 amount of the solution (B1) and the whole amount of the solution (D1) were added by a simultaneous mixing method over 14 minutes and 15 seconds while controlling at 20 ° C. and pAg 8.09. After stirring for 5 minutes, the temperature was lowered to 40 ° C., the whole amount of the solution (G1) was added, and the silver halide emulsion was allowed to settle. The supernatant was removed leaving 2000 ml of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was sedimented again. The remaining portion of 1500 ml was left, the supernatant was removed, 10 L of water was further added, and after stirring, the silver halide emulsion was precipitated. After leaving 1500 ml of the sedimented portion and removing the supernatant, the solution (H1) was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount was 1161 g per mole of silver, to obtain a photosensitive silver halide emulsion A1.

  This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

[Preparation of photosensitive silver halide emulsion A2]
In the preparation of the above light-sensitive silver halide emulsion A1, after adding the entire amount of the solution F1 after nucleation, 40 ml of a 5% aqueous solution of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene was added. A photosensitive silver halide emulsion A2 was prepared in the same manner as described above.

  This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

[Preparation of photosensitive silver halide emulsion A3]
In the preparation of the above-described photosensitive silver halide emulsion A1, the same procedure was followed except that 4 ml of a 0.1% ethanol solution of the following compound (ETTU) was added after addition of the entire amount of solution F1 after nucleation. Silver emulsion A3 was prepared.

  This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of photosensitive silver halide emulsion B1>
The same procedure as in the preparation of the photosensitive silver halide emulsion A1 was conducted except that the temperature at the time of addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of photosensitive silver halide emulsion B2>
In the preparation of the photosensitive silver halide emulsion B1, the photosensitive halogenation was similarly performed except that 4 ml of a 0.1% ethanol solution of the above compound (ETTU) was added after adding the whole amount of the solution F1 after nucleation. Silver emulsion B2 was prepared. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of powdered organic silver salt A>
130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved in 4720 ml of pure water at 80 ° C. Next, 540.2 ml of a 1.5 mol / L sodium hydroxide aqueous solution was added and 6.9 ml of concentrated nitric acid was added, followed by cooling to 55 ° C. to obtain a fatty acid sodium solution. While maintaining the temperature of the fatty acid sodium solution at 55 ° C., a photosensitive silver halide emulsion (type and addition amount are listed in Table 2) and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 468.4 ml of 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an organic silver salt dispersion. Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 2 μS / cm, and centrifugal dehydration was carried out. Then, the obtained cake-like organic silver salt was converted into an air-flow dryer Flashjet dryer (Seishin). A powder organic silver salt A that has been dried and dried to a moisture content of 0.1% under the operating conditions (inlet 65 ° C., outlet 40 ° C.) of nitrogen gas atmosphere and dryer hot air temperature Got. The photothermographic material sample 17 (described later) prepared using this organic silver salt was analyzed using an electron microscope, and the average particle diameter (equivalent circle diameter) was 0.08 μm, the aspect ratio was 5, and the monodispersity was 10%. Tabular grains.

  In addition, the infrared moisture meter was used for the moisture content measurement of an organic silver salt composition.

<Preparation of preliminary dispersion A>
As an image-forming layer binder, 14.57 g of SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of —SO ₃ K group) is dissolved in 1457 g of MEK, and dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN While stirring in a mold, 500 g of the powdered organic silver salt A was gradually added and mixed thoroughly to prepare a preliminary dispersion A.

<Preparation of photosensitive emulsion dispersion A>
Media type disperser DISPERMAT filled with 80% of the internal volume of 0.5 mm zirconia beads (Toray Industries, Inc .: Treceram) so that the residence time in the mill is 1.5 minutes using a pump. A photosensitive emulsion dispersion A was prepared by supplying to SL-C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 8 m / s.

<Preparation of stabilizer solution>
A stabilizer solution was prepared by dissolving 1.0 g of Stabilizer 1 and 0.31 g of potassium acetate in 4.97 g of methanol.

<Preparation of infrared sensitizing dye liquid A>
9.6 mg of infrared sensitizing dye 1, 9.6 mg of infrared sensitizing dye 2, 1.488 g of 2-chlorobenzoic acid, 2.779 g of stabilizer 2 and 365 mg of 5-methyl-2-mercaptobenz Infrared sensitizing dye solution A was prepared by dissolving imidazole in 31.3 ml of MEK in the dark.

<Preparation of additive solution a>
Reducing agent (compounds and amounts listed in Table 2), 9.3 g of hot solvent (stearic acid amide melting point 100 ° C.), 0.159 g of compound of general formula (YB) (YA-1), 0.159 g of cyanide The chromogenic leuco dye CA-12, 1.54 g of 4-methylphthalic acid, and 0.48 g of the infrared dye 1 were dissolved in 100.7 g of MEK to obtain an additive solution a.

<Preparation of additive liquid b>
1.56 g antifoggant 2, 0.5 g antifoggant 3, 0.5 g antifoggant 4, 0.5 g antifoggant 5, 3.43 g phthalazine dissolved in 40.9 g MEK and added b.

<Preparation of additive liquid c>
The silver saving agent (A-7) 0.2g was melt | dissolved in MEK39.8g, and it was set as the addition liquid c.

<Preparation of additive liquid d>
0.1 g of supersensitizer 1 was dissolved in 9.9 g of MEK to obtain additive solution d.

<Preparation of additive liquid e>
0.5 g of potassium p-toluenethiosulfonate and 0.5 g of antifoggant 6 were dissolved in 9.0 g of MEK to obtain an additive solution e.

<Preparation of additive liquid f>
An antifoggant containing 1.0 g of vinyl sulfone [(CH ₂ ═CH—SO ₂ CH ₂ ) ₂ CHOH] was dissolved in 9.0 g of MEK to obtain an additive solution f.

<Preparation of photosensitive layer coating solution>
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion (described in Table 2) and 15.11 g of MEK were kept at 21 ° C. with stirring, and the chemical sensitizer S-5 (0. 5% methanol solution) 1000 μl was added, and after 2 minutes, 390 μl of antifoggant 1 (10% methanol solution) was added and stirred for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 10 minutes, then gold sensitizer Au-5 corresponding to 1/20 mole of the above organic chemical sensitizer was added, and further stirred for 20 minutes. . Subsequently, 167 μl of a stabilizer solution was added and stirred for 10 minutes, and then 1.32 g of the infrared sensitizing dye solution A was added and stirred for 1 hour.

  Thereafter, the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While maintaining the temperature at 13 ° C., 0.5 g of additive d, 0.5 g of additive e, 0.5 g of additive f, and 13.31 g of binder used in the preliminary dispersion A were added and stirred for 30 minutes. Thereafter, 1.084 g of tetrachlorophthalic acid (9.4% MEK solution) was added and stirred for 15 minutes. While continuing to stir, 12.43 g of additive a, 1.6 ml of Desmodur N3300 / Mobayic aliphatic isocyanate (10% MEK solution), 4.27 g of additive b, 4.0 g of additive c By sequentially adding and stirring, a photosensitive layer coating solution was obtained.

  The structures of the additives used for the preparation of each coating solution including the stabilizer solution and the photosensitive layer coating solution are shown below.

<Preparation of photosensitive layer protective layer lower layer (surface protective layer lower layer)>
Acetone 5g
MEK 21g
Cellulose acetate propionate 2.3g
(Manufactured by Eastman Chemical: CAP-141-20,
(Glass transition temperature Tg = 190 ° C)
7g of methanol
Phthalazine 0.25g
_{CH 2 = CHSO 2 CH 2 CH} 2 OCH 2 CH 2 SO 2 CH = CH 2 0.035g
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 0.01 g
Fluorine-based surfactant (SF-17: supra) 0.01g
Stearic acid 0.1g
C ₁₈ H ₃₇ CONHCH ₂ CH ₂ NHCOC ₁₈ H ₃₇ 0.1 g
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of photosensitive layer protective layer upper layer (surface protective layer upper layer)>
Acetone 5g
21g of methyl ethyl ketone
Cellulose acetate propionate 2.3g
(Manufactured by Eastman Chemical: CAP-141-20
(Glass transition temperature Tg = 190 ° C)
Paraloid A-21 (Rohm and Haas) 0.08g
Benzotriazole 0.03g
7g of methanol
Phthalazine 0.25g
Monodispersed 15% monodispersed silica (average particle size: 3 μm) 0.140 g
(Surface treatment with 1% by mass of aluminum based on the total mass of silica)
_{CH 2 = CHSO 2 CH 2 CH} 2 OCH 2 CH 2 SO 2 CH = CH 2 0.035g
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 0.01 g
Fluorine-based surfactant (SF-17: supra) 0.01g
Stearic acid 0.1g
C ₁₈ H ₃₇ CONHCH ₂ CH ₂ NHCOC ₁₈ H ₃₇ 0.1 g
α-Alumina (Mohs hardness 9) 0.1g
The upper layer and lower layer of the photosensitive layer protective layer were formed by the same method as the preparation of the intermediate layer coating solution at the above composition ratio. As for the silica, similarly to the backcoat layer, MEK was dispersed with a dissolver type homogenizer at a concentration of 1% by mass, and finally added and stirred to obtain a coating solution for the upper layer of the image forming layer and the lower layer.

<Preparation of photothermographic material>
The intermediate layer coating solution and the back coating layer coating solution prepared as described above are extruded onto the undercoating upper layer B-2 so as to have a dry film thickness of 3.5 μm, respectively, at a coating speed of 50 m / min. Application was performed. The drying was performed for 5 minutes using a drying air having a drying temperature of 100 ° C. and a dew point temperature of 10 ° C.

  The photosensitive layer coating solution and the photosensitive layer protective layer (surface protective layer) coating solution are simultaneously coated on the subbing upper layer A-2 at an application speed of 50 m / min using an extrusion coater. Thus, photosensitive material samples 1 to 19 shown in Table 2 were prepared.

  The photosensitive layer has a dry film thickness of 15.0 μm, and the photosensitive layer protective layer (surface protective layer) has a dry film thickness of 3.0 μm (surface protective layer upper layer 1.5 μm, surface protective layer lower layer 1.5 μm). Then, drying was performed for 10 minutes using a drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

  The surface roughness of samples 1 to 19 was measured and found to be Rz (E) / Rz (B) = 0.40 and Rz (E) = 1.4 μm.

  Rz (B) was 3.5 μm. Ra (E) was 0.09 μm. Ra (B) was 0.12 μm.

  For sample 11, the methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer mass ratio 57/8/28/5/2) in the intermediate layer and back coat layer in sample 5 was used. ) A sample was prepared in the same manner as Sample 5 except that 72.6 g of 19% by weight acrylic acid / ethyl acrylate copolymer latex (copolymerization ratio 5/95) was used instead of 72.6 g of 19% by weight latex. Produced.

  For sample 12, in the preparation of powdered organic silver salt A in sample 4, instead of 130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid, 259.9 g of behenic acid was used. A sample was prepared in the same manner as Sample 4 except that it was used.

  For sample 13, in the preparation of powdered organic silver salt A in sample 4, 540.2 ml of 1.5 mol / L potassium hydroxide aqueous solution was used instead of 540.2 ml of 1.5 mol / L sodium hydroxide aqueous solution. A sample was prepared in the same manner as Sample 4 except that it was used.

For Sample 14, Sample 4 except that the fluorine-based activator of the backcoat layer and the photosensitive layer protective layer (upper layer and lower layer) in Sample 4 was changed from SF-20, SF-17 to C ₈ F ₁₇ SO ₃ Li. A sample was prepared in the same manner as described above.

For sample 15, SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of SO ₃ K) was used as the photosensitive layer binder in the preparation of preliminary dispersion A in sample 4, instead of SO 3 _A sample was prepared in the same manner as Sample 4 except that ₃ K group-containing polyvinyl butyral (Tg 65 ° C., SO ₃ K contained 0.2 mmol / g) was used.

  Sample 17 was prepared in the same manner as Sample 16 except that the gelatin used in Sample 16 was insoluble in an organic solvent, and A-type gelatin having an amino group substitution rate of 90% was used.

  For sample 18, the latex used in sample 16 was replaced with the gelatin used in sample 16, and a sample was prepared using only gelatin as the binder.

  For sample 19, the gelatin used in sample 16 was replaced with the latex used in sample 16, and a sample was prepared using only latex as the binder.

<Exposure and development processing>
The photothermographic material samples 1 to 19 produced as described above were processed into half-cut size (34.5 cm × 43.0 cm), and then packaged in the following packaging materials in an environment of 25 ° C. and 50%, and kept at room temperature for 2 weeks. Following storage, the following evaluations were made.

(Packaging material)
PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% carbon, oxygen permeability: 0 ml / Pa · m ² · 25 ° C · day, moisture permeability: 0 g / Pa · m ² · 25 ° C · day Barrier bag. Use paper tray.

(Sample evaluation)
Evaluation is performed with the laser imager shown in FIGS. 1 and 2 (equipped with a 810 nm semiconductor laser with a maximum output of 50 mW) and thermal development simultaneously with three panel heaters set at 107 ° C.-123 ° C.-123 ° C. in total 13 5 seconds), and the obtained image was evaluated with a densitometer.

  Here, “thermal development at the same time as exposure” means a sheet of photosensitive material composed of a photothermographic material, and development is started on a part of the sheet that has already been exposed while part of the photosensitive material is exposed. Means that.

  The distance between the exposed part and the developing part was 12 cm. The linear velocity at this time was 25 mm / sec. At this time, the conveyance speed from the photosensitive material supply section to the image exposure section, the conveyance speed at the image exposure section, and the conveyance speed at the heat development section were each 25 mm / second.

  Further, the position of the bottom surface of the photosensitive material stock tray located at the bottom was 45 cm high from the floor surface. The exposure and development were performed in a room adjusted to 23 ° C. and 50% RH. The exposure was performed in a stepped manner while reducing the exposure energy amount by log E0.05 step by step from the maximum output.

<Performance evaluation>
The following performance was evaluated for each heat-developed image.

<Image density>
The value of the highest density portion of the image obtained under the above conditions was measured with a densitometer and indicated as the image density.

"sensitivity"
The image obtained under the above conditions was subjected to density measurement using a densitometer, and a characteristic curve comprising a horizontal axis—exposure amount and a vertical axis—density was created. In the characteristic curve, the sensitivity was defined by defining the reciprocal of the exposure amount giving a density 1.0 higher than that of the unexposed portion as sensitivity. The sensitivity is expressed as a relative value with Sample 1 as 100.

  (The values in parentheses in the Relative Sensitivity column indicate the case where the photosensitive material is heat-treated at the heat development temperature before the photosensitive material is exposed to white light, and then is exposed to white light through an optical wedge (4874K, 30 seconds) and thermally developed. The sensitivity relative value of the former when the sensitivity of the latter was set to 100 was shown in the comparison of the sensitivity of the above and the sensitivity when heat development was performed by exposure to white light under the same conditions as described above without heat treatment before exposure. .

  In this relative comparison, the main cause of the decrease in the relative sensitivity of the sample obtained by heat-treating the photosensitive material at the heat development temperature before exposing the photosensitive material to white light is the surface sensitivity of the silver halide grains due to the disappearance or reduction of the spectral sensitization effect. It was confirmed by observation / measurement of changes in the spectral sensitivity spectrum that the relative relationship between the internal sensitivity and the internal sensitivity was changed.

《Light irradiation image storage stability》
Each heat-developable photosensitive material sample was exposed and developed in the same manner as described above, and then the change in the image was visually observed after being stuck on a Schaukasten with a luminance of 1000 lux and left for 10 days. Evaluation was made. (If 0.5 is present, it represents the intermediate state between the following numbers)
5: Almost no change 4: Slight color change observed 3: Partial color change and fog increase observed 2: Color change and fog increase observed in considerable part 1: Color change and fog increase The increase is remarkable and strong density unevenness occurs on the entire surface.
The density unevenness after development was evaluated visually by 0.5 increments according to the following criteria.

5: Density unevenness is not observed 4: Slight density unevenness occurs 3: Some weak density unevenness occurs 2: Strong density unevenness occurs partly 1: Strong density unevenness occurs over the entire surface << Heat development Concentration fluctuation accompanying humidity fluctuation at the time >>
The absolute value of the difference between the image density at 25 ° C. and 55% humidity and the image density at 25 ° C. and 80% humidity was measured.

Example 2
《Preparation of undercoated support》
It was produced in the same manner as in Example 1.

(Middle layer)
(Preparation of infrared dye 1 solid fine particle dispersion)
It was produced in the same manner as in Example 1.

<Preparation of intermediate layer coating solution>
It was produced in the same manner as in Example 1.

<Preparation of backcoat layer coating solution>
It was produced in the same manner as in Example 1.

<Preparation of photosensitive silver halide emulsion A1>
Same as the preparation of photosensitive silver halide emulsion A1 in Example 1.

<Preparation of photosensitive silver halide emulsion B1>
Same as the preparation of photosensitive silver halide emulsion B1 in Example 1.

<Preparation of photosensitive silver halide emulsion C>
The procedure was the same as the preparation of the photosensitive silver halide emulsion A1, except that the potassium bromide used in the preparation of the photosensitive silver halide emulsion A1 was changed to potassium iodide. This emulsion was monodispersed pure silver iodide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<Preparation of photosensitive silver halide emulsion D>
Preparation of photosensitive silver halide emulsion A1 except that a portion of potassium bromide used in the preparation of photosensitive silver halide emulsion A1 was changed to potassium iodide so that the silver iodide content was 90 mol%. The same was done. This emulsion was monodispersed silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (silver iodide content was 90 mol%).

<Preparation of photosensitive silver halide emulsion E>
The same procedure as in the preparation of photosensitive silver halide emulsion C was carried out except that the temperature at the time of addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed pure silver iodide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<Preparation of photosensitive silver halide emulsion F>
The procedure was the same as the preparation of the photosensitive silver halide emulsion D except that the temperature at the time of addition by the simultaneous mixing method was changed to 45 ° C. This emulsion was monodispersed silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (silver iodide content was 90 mol%).

<Preparation of photosensitive silver halide emulsion G>
In the preparation of the photosensitive silver halide emulsion C, the photosensitive halogenation was similarly carried out except that 4 ml of a 0.1% ethanol solution of the above compound (ETTU) was added after the whole amount of the solution F1 was added after nucleation. Silver emulsion G was prepared.

  This emulsion was monodispersed pure silver iodide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<Preparation of photosensitive silver halide emulsion H>
In the preparation of the photosensitive silver halide emulsion E, the photosensitive halogenation was similarly carried out except that 4 ml of a 0.1% ethanol solution of the above compound (ETTU) was added after the entire amount of the solution F1 was added after nucleation. Silver emulsion H was prepared.

  This emulsion was monodispersed pure silver iodide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92%.

<Preparation of powdered organic silver salt A>
130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved in 4720 ml of pure water at 80 ° C. Next, 540.2 ml of a 1.5 mol / L sodium hydroxide aqueous solution was added and 6.9 ml of concentrated nitric acid was added, followed by cooling to 55 ° C. to obtain a fatty acid sodium solution.

  While maintaining the temperature of the fatty acid sodium solution at 55 ° C., a photosensitive silver halide emulsion (type and addition amount are listed in Table 3) and 450 ml of pure water were added and stirred for 5 minutes. Next, 468.4 ml of 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an organic silver salt dispersion. Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 2 μS / cm, and centrifugal dehydration was carried out. Then, the obtained cake-like organic silver salt was converted into an air-flow dryer Flashjet dryer (Seishin). A powder organic silver salt A that has been dried and dried to a moisture content of 0.1% under the operating conditions (inlet 65 ° C., outlet 40 ° C.) of nitrogen gas atmosphere and dryer hot air temperature Got.

<Preparation of preliminary dispersion A>
Same as Preliminary Dispersion A in Example 1.

<Preparation of photosensitive emulsion dispersion A>
Media type disperser DISPERMAT filled with 80% of the internal volume of 0.5 mm zirconia beads (Toray Industries, Inc .: Treceram) so that the residence time in the mill is 1.5 minutes using a pump. A photosensitive emulsion dispersion A was prepared by supplying to SL-C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 8 m / s.

<Preparation of stabilizer solution>
A stabilizer solution was prepared by dissolving 1.0 g of Stabilizer 1 and 0.31 g of potassium acetate in 4.97 g of methanol.

<Preparation of 2-chlorobenzoic acid solution>
1.488 g of 2-chlorobenzoic acid, 2.779 g of stabilizer 2 and 365 mg of 5-methyl-2-mercaptobenzimidazole are dissolved in 31.3 ml of MEK in the dark to prepare a 2-chlorobenzoic acid solution. did.

<Preparation of additive solution a>
Reducing agent (compound described in Table 3 (reducing agent) and amount), 9.3 g of hot solvent (ethyl p-hydroxybenzoate, melting point 116 ° C.), 0.159 g of yellow chromophoric leuco dye (YA-1), 0.159 g of cyan chromophoric leuco dye (CA-10) and 1.54 g of 4-methylphthalic acid were dissolved in 100.7 g of MEK to obtain additive solution a.

<Preparation of additive liquid b>
1.56 g of antifogging agent 2, 0.5 g of antifogging agent 3, 0.5 g of antifogging agent 4, 0.5 g of antifogging agent 5, 3.43 g of phthalazine are dissolved in 40.9 g of MEK and added. b.

<Preparation of additive liquid c>
0.2 g of silver saving agent A-7 was dissolved in 39.8 g of MEK to obtain an additive liquid c.

<Preparation of additive liquid d>
0.5 g of potassium p-toluenethiosulfonate and 0.5 g of antifogging agent 6 were dissolved in 9.0 g of MEK to obtain an additive solution d.

<Preparation of additive liquid e>
1.0 g of vinyl sulfone [(CH ₂ ═CH—SO ₂ CH ₂ ) ₂ CHOH] was dissolved in 9.0 g of MEK to obtain an additive solution e.

<Preparation of photosensitive layer coating solution>
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion A and 15.11 g of MEK were kept at 21 ° C. with stirring, and the chemical sensitizer S-5 (0.5% methanol solution) 1000 μl was added, and after 2 minutes, 390 μl of antifoggant 1 (10% methanol solution) was added and stirred for 1 hour.

  Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 10 minutes, then gold sensitizer Au-5 corresponding to 1/20 mole of the above organic chemical sensitizer was added, and further stirred for 20 minutes. . Subsequently, 167 μl of a stabilizer solution was added and stirred for 10 minutes, and then 1.32 g of the 2-chlorobenzoic acid solution was added and stirred for 1 hour. Thereafter, the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While maintaining the temperature at 13 ° C., 0.5 g of additive liquid d, 0.5 g of additive liquid e, and 13.31 g of binder used in the preliminary dispersion were added and stirred for 30 minutes, and then tetrachlorophthalic acid (9. (4% MEK solution) 1.084 g was added and stirred for 15 minutes. While further stirring, 12.43 g of additive liquid a, 1.6 ml of Desmodur N3300 / Movey aliphatic isocyanate (10% MEK solution), 4.27 g of additive liquid b, and 1.0 g of additive liquid c were added. By sequentially adding and stirring, a photosensitive layer coating solution was obtained.

<Preparation of photosensitive layer protective layer lower layer (surface protective layer lower layer)>
To 500 g of acetone, 2100 g of MEK and 700 g of methanol, 230 g of cellulose acetate butyrate (manufactured by Eastman Chemical: CAB-171-15S) was added, and the mixture was stirred and dissolved with a dissolver.

Then 25 g phthalazine, 3.5 g CH ₂ ═CHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH═CH ₂ , 1 g C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ , 1 g Compound SF-17 represented by the general formula (SF): 10 g of stearic acid, 10 g of C ₁₈ H ₃₇ CONHCH ₂ CH ₂ NHCOC ₁₈ H ₃₇ are added and dissolved with stirring, and a photosensitive layer protective layer undercoat The liquid was adjusted.

<Preparation of photosensitive layer protective layer upper layer (surface protective layer upper layer)>
To 500 g of acetone, 2100 g of MEK and 700 g of methanol, 230 g of cellulose acetate butyrate (manufactured by Eastman Chemical: CAB-171-15S) was added, and the mixture was stirred and dissolved with a dissolver.

Then 25 g phthalazine, 3.5 g CH ₂ ═CHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH═CH ₂ , 1 g C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ , 1 g Compound SF-17 represented by the general formula (SF): 10 g of stearic acid, 10 g of C ₁₈ H ₃₇ CONHCH ₂ CH ₂ NHCOC ₁₈ H ₃₇ were added with stirring and dissolved.

  Finally, 280 g of 15% monodispersed silica (average particle size 10.0 μm, surface treatment with 1% aluminum of the total mass of silica) dispersed in MEK with a dissolver type homogenizer at a concentration of 5% is added and stirred. Then, a photosensitive layer protective layer upper layer coating solution was prepared.

<Preparation of photothermographic material>
The intermediate layer coating solution and the back coating layer coating solution prepared as described above are extruded onto the undercoating upper layer B-2 so as to have a dry film thickness of 3.5 μm, respectively, at a coating speed of 50 m / min. Application was performed. The drying was performed for 5 minutes using a drying air having a drying temperature of 100 ° C. and a dew point temperature of 10 ° C.

  The photosensitive layer coating solution and the photosensitive layer protective layer (surface protective layer) coating solution are simultaneously coated on the subbing upper layer A-2 at an application speed of 50 m / min using an extrusion coater. Thus, photosensitive material samples 21 to 40 shown in Table 3 were prepared.

  Application is an image forming layer with a dry film thickness of 15.0 μm, and an image forming layer protective layer (surface protective layer) is a dry film thickness of 3.0 μm (surface protective layer upper layer 1.5 μm, surface protective layer lower layer 1.5 μm). Then, drying was performed for 10 minutes using a drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

  When surface roughness was measured about the samples 21-40, they were Rz (E) / Rz (B) = 0.40 and Rz (E) = 1.4 μm.

  Rz (B) was 3.5 μm. Ra (E) was 0.09 μm. Ra (B) was 0.12 μm.

  For sample 32, the methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer mass ratio 57/8/28/5/2) in the intermediate layer and back coat layer in sample 26 was used. ) A sample was prepared in the same manner as Sample 26 except that 72.6 g of 19% by weight acrylic acid / ethyl acrylate copolymer latex (copolymerization ratio 5/95) was used instead of 72.6 g of 19% by weight latex. Produced.

  For sample 33, 259.9 g of behenic acid was used instead of 130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid in the preparation of powdered organic silver salt A in sample 25. A sample was prepared in the same manner as Sample 25 except that it was used.

  For sample 34, in the preparation of powdered organic silver salt A in sample 25, 540.2 ml of 1.5 mol / L potassium hydroxide aqueous solution was used instead of 540.2 ml of 1.5 mol / L sodium hydroxide aqueous solution. A sample was prepared in the same manner as Sample 25 except that it was used.

For Sample 35, Sample 25 except that the fluorine-based activator of the backcoat layer and the image forming layer protective layer (upper layer and lower layer) in Sample 25 was changed from SF-20, SF-17 to C ₈ F ₁₇ SO ₃ Li. A sample was prepared in the same manner as described above.

For sample 36, SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing 0.2 mmol / g of SO ₃ K) was used as the image-forming layer binder in the preparation of preliminary dispersion A in sample 25. _A sample was prepared in the same manner as Sample 25 except that ₃ K group-containing polyvinyl butyral (Tg 65 ° C., containing 0.2 mmol / g SO ₃ K) was used.

  Sample 38 was prepared in the same manner as Sample 37, except that the gelatin used in Sample 37 was insoluble in an organic solvent, and A-type gelatin having an amino group substitution rate of 90% was used.

  For sample 39, the latex used in sample 37 was replaced with the gelatin used in sample 37, and a sample was prepared using only gelatin as the binder.

  For sample 40, the gelatin used in sample 37 was replaced with the latex used in sample 37, and a sample was prepared using only latex as the binder.

<Exposure and development processing>
After the photothermographic material samples 21 to 40 produced as described above were processed into half-cut size (34.5 cm × 43.0 cm), the evaluation was performed by the laser imager shown in FIG. 1 and FIG. Is changed from an 810 nm semiconductor laser to a semiconductor laser having a light emission wavelength of 405 nm (NLHV3000E manufactured by Nichia Corporation) and heat development simultaneously with three panel heaters set at 107 ° C.-123 ° C.-123 ° C. for a total of 13. 5 seconds), and the obtained image was evaluated with a densitometer.

  Here, “thermal development at the same time as exposure” means a sheet of photosensitive material composed of a photothermographic material, and development is started on a part of the sheet that has already been exposed while part of the photosensitive material is exposed. Means that.

  The distance between the exposed part and the developing part was 12 cm. At this time, the conveyance speed from the photosensitive material supply section to the image exposure section, the conveyance speed at the image exposure section, and the conveyance speed at the heat development section were each 25 mm / second.

  Further, the position of the bottom surface of the photosensitive material stock tray located at the bottom was 45 cm high from the floor surface. The exposure and development were performed in a room adjusted to 23 ° C. and 50% RH. The exposure was performed in a stepped manner while reducing the exposure energy amount by log E0.05 step by step from the maximum output.

<Packaging materials>
PET 10 μm / PE 12 μm / aluminum foil 9 μm / Ny 15 μm / polyethylene 50 μm containing 3% carbon, oxygen permeability: 0 ml / Pa · m ² · 25 ° C. · day, moisture permeability: 0 g / Pa · m ² · 25 ° C./day. Use paper tray.

<Performance evaluation>
The following performance was evaluated for each heat-developed image.

<Image density>
The value of the highest density portion of the image obtained under the above conditions was measured with a densitometer and indicated as the image density.

"sensitivity"
The image obtained under the above conditions was subjected to density measurement using a densitometer, and a characteristic curve comprising a horizontal axis—exposure amount and a vertical axis—density was created. In the characteristic curve, the sensitivity was defined by defining the reciprocal of the exposure amount giving a density 1.0 higher than that of the unexposed portion as sensitivity. The sensitivity is expressed as a relative value with Sample 1 as 100.

  (The values in parentheses in the Relative Sensitivity column indicate the case where the photosensitive material is heat-treated at the heat development temperature before the photosensitive material is exposed to white light, and then is exposed to white light through an optical wedge (4874K, 30 seconds) and thermally developed. The sensitivity relative value of the former when the sensitivity of the latter was set to 100 was shown in the comparison of the sensitivity of the above and the sensitivity when heat development was performed by exposure to white light under the same conditions as described above without heat treatment before exposure. .

  In this relative comparison, the main cause of the decrease in the relative sensitivity of the sample obtained by heat-treating the photosensitive material at the heat development temperature before exposing the photosensitive material to white light is the surface sensitivity of the silver halide grains due to the disappearance or reduction of the spectral sensitization effect. It was confirmed by observation / measurement of changes in the spectral sensitivity spectrum that the relative relationship between the internal sensitivity and the internal sensitivity was changed.

《Light irradiation image storage stability》
Each heat-developable photosensitive material sample was exposed and developed in the same manner as described above, and then the change in the image was visually observed after being stuck on a Schaukasten with a luminance of 1000 lux and left for 10 days. Evaluation was made. (If 0.5 is present, it represents the intermediate state between the following numbers)
5: Almost no change 4: Slight color change is observed 3: Color change and fog increase are observed in part 2: Color change and fog increase are observed in a considerable part 1: Color change and fog change The increase is remarkable and strong density unevenness occurs on the entire surface.
The density unevenness after development was evaluated visually by 0.5 increments according to the following criteria.

5: Density unevenness is not observed 4: Slight density unevenness occurs 3: Some weak density unevenness occurs 2: Strong density unevenness occurs partly 1: Strong density unevenness occurs over the entire surface << Heat development Concentration fluctuation accompanying humidity fluctuation at the time >>
The absolute value of the difference between the image density at 25 ° C. and 55% humidity and the image density at 25 ° C. and 80% humidity was measured.

<< Evaluation of surface roughness >>
About the sample before the process of heat development, it measured by the method shown below using the non-contact three-dimensional surface analyzer (WYKO company RST / PLUS).
1) Objective lens: × 10.0 Intermediate lens: × 1.0
2) Measurement range: 463.4 μm × 623.9 μm
3) Pixel size: 368 × 238
4) Filter: Cylindrical correction and tilt correction 5) Smoothing: Medium smoothing 6) Scanning speed: Low
Rz was defined according to JIS surface roughness (B0601). For each sample of 10 cm × 10 cm, the sample was divided into 100 in a grid pattern at 1 cm intervals, the center of each square region was measured, and the average value was obtained from 100 measurements.

  The results are also shown in Table 3.

  From Table 2 and Table 3, compared with the comparative sample, the sample of the present invention has high sensitivity and high density, is excellent in light-irradiated image storage stability, has no unevenness in density during thermal development, and is subjected to thermal development. It is clear that a stable image density can be obtained even when the humidity varies.

1 is a schematic configuration diagram of a heat development recording apparatus used in an embodiment of the present invention. It is a block diagram which shows schematic structure of the conveyance part for conveying the photothermographic material of the said heat development recording apparatus, and a scanning exposure part.

Explanation of symbols

3 Photothermographic recording materials 10a, 10b, 10c Photosensitive material trays 13a, 13b, 13c Single-wafer transport rollers 15a, 15b, 15c Photosensitive material 16 Upper light shielding cover 17 Sub-scan transport unit (sub-scanning means)
19 Scanning exposure unit (laser irradiation means)
21, 22 Driving roller 23 Guide plate 25, 26 Slope part 29 Pressing part 35 Semiconductor laser 37 Drive circuit 39 Intensity modulator 41 Polygon mirror 43 Condensing lens 45 Mirror 51a, 51b, 51c Heat developing plate 52 Driving roller 53 Reduction gear 55 Conveying roller 57 Cooling roller 59 Cooling roller 61 Cooling plate 63 Discharging roller 150 Thermal development recording apparatus

Claims (8)

In a photothermographic material having a photosensitive layer containing an organic silver salt, silver halide, a binder and a reducing agent on one side of a support and a backcoat layer on the other side, the backcoat layer is A photothermographic material characterized by being a layer formed using a modified gelatin and polymer latex soluble in both water and an organic solvent. 2. The photothermographic material according to claim 1, wherein 95% or more of the amino groups in the molecule of the modified gelatin are substituted with hydrophobic groups. 3. The photothermographic material according to claim 1, wherein in the modified gelatin, 50% or more of the carboxyl groups in the molecule are substituted with hydrophobic groups. The photothermographic material according to claim 1, wherein the polymer latex has a polymer amount of 15 to 45% by mass with respect to the backcoat layer. The said photosensitive layer is a layer formed using the coating liquid for photosensitive layers whose 60 mass% or more of a solvent is an organic solvent, The any one of Claims 1-4 characterized by the above-mentioned. Photothermographic material. A photothermographic development process comprising: an image forming process comprising: an exposure process for exposing an image of the photothermographic material according to any one of claims 1 to 5; and a development process for thermally developing the photothermographic material subjected to image exposure. An image forming method of a photosensitive material, wherein the image forming step includes a step in which the exposure step and the development step are performed simultaneously. 7. The image forming method of a photothermographic material according to claim 6, wherein the photothermographic treatment is performed while conveying the photothermographic material at a speed of 20 to 200 mm / sec. The photothermographic material according to claim 6, wherein the photothermographic material according to any one of claims 1 to 5 is subjected to heat development while being conveyed at a speed of 20 to 200 mm / sec. Image forming method.

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