JP2004240404A - Heat developable photosensitive material and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material having high density and excellent in image preservability under photoirradiation and in silver tone; and an image forming method, and to provide a heat developable photosensitive material excellent further in image preservability in high temperature storage if necessary or excellent in film conveyability and environmental suitability; and an image forming method. <P>SOLUTION: In the heat developable photosensitive material including an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, the silver halide comprises silver halide particles having an average particle size of 10-50 nm, the reducing agent is a bisphenol compound represented by formula (1), and a cyan developing leuco dye is further contained. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a photothermographic material, and more particularly, to a photothermographic material having high density, excellent light-irradiation image preservability, excellent silver tone and the like, and an image forming method using the same.

  Conventionally, in the fields of medical treatment and printing plate making, waste liquids caused by wet processing of image forming materials have been a problem in terms of workability.In recent years, it has been strongly desired to reduce the amount of treated waste liquids from the viewpoint of environmental conservation and space saving. It is rare. Therefore, a photothermographic material capable of forming an image only by applying heat has been put to practical use, and has rapidly spread in the above-mentioned fields.

  A heat-developable photosensitive material (hereinafter, also simply referred to as a heat-developable material or a light-sensitive material) itself has been proposed for a long time, and is described in, for example, U.S. Patent Nos. 3,152,904 and 3,457,075.

  The heat development material is usually processed by a heat development processing apparatus called a heat development processor, which applies stable heat to the heat development material to form an image. As described above, with the rapid spread in recent years, a large amount of this thermal development processing apparatus has been supplied to the market. However, depending on the temperature and humidity conditions at the time of the thermal development processing, there is a problem that the slipperiness between the photosensitive material and the transport roller or the processing member of the thermal development processing apparatus changes, resulting in poor transport and uneven density. Was. Another problem is that the density of the photothermographic material fluctuates over time. It has been found that these phenomena occur remarkably in a photothermographic material which forms an image by thermal development after image exposure with a laser beam.

  In recent years, there has been a demand for a laser imager to be more compact and to have faster processing. For that purpose, it is essential to improve the characteristics of the photothermographic material. Although it is more advantageous to use a heat drum method than a horizontal transfer method in order to reduce the size of the heat development processing apparatus, there is a problem that powder dropout, density unevenness, and roller marks tend to occur during the heat development processing. Was. In order to obtain a sufficient density of the photothermographic material even after rapid processing, silver halides having a small average grain size as disclosed in JP-A-11-295844 and JP-A-11-352627 are required. The covering power can be increased by increasing the number of coloring points by using, a highly active reducing agent having a secondary or tertiary alkyl group (see Patent Document 3), or a development accelerator such as a hydrazine compound or a vinyl compound. It is effective to use.

  However, when these techniques are used, the change in density (printout characteristics) over time after the heat development processing becomes large, or the silver tone is greatly different from that of a conventional wet X-ray film (the yellow tint is reduced). Problem). Further, when a silver halide having a small average grain size is used, a new problem occurs that the color tone becomes reddish in a high density portion having a density of 2.0 or more.

Japanese Patent Application Laid-Open No. 2001-133925 discloses a technique for improving printout characteristics, and a technique for adjusting silver tone is disclosed (for example, see Patent Documents 1 and 2). Was not enough.
JP-A-11-231460 JP 2002-169249 A JP 2001-209145 A

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photothermographic material and an image forming method which have a high density, a light-irradiated image storage property, and an excellent silver tone. is there. Another object of the present invention is to provide a photothermographic material and an image forming method which are further excellent in image storability during high-temperature storage, or excellent in film transportability and environmental suitability, if necessary.

  The above object of the present invention has been achieved by the following configurations.

(Claim 1)
In a photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, the silver halide contains silver halide grains having an average grain size of 10 to 50 nm. And a photothermographic material, wherein the reducing agent is a compound represented by the following general formula (1), and further contains a cyan coloring leuco dye.

[In the formula, X represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group. R ₂ represents an alkyl group, which may be the same or different, at least one of which is a secondary or tertiary alkyl group. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a group that can be substituted on the benzene ring, and m and n each represent an integer of 0 to 2. ]
(Claim 2)
2. The photothermographic material according to claim 1, wherein the compound represented by the general formula (1) has a hydroxyl group or an alkyl group having a precursor group thereof.

(Claim 3)
3. The photothermographic material according to claim 1, wherein the surface having the image forming layer contains a compound represented by the following general formula (YA).

[Wherein, 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 represent a 2-hydroxyphenylmethyl group. Never be. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on a benzene ring. ]
(Claim 4)
An image obtained by thermal development at a development temperature of 123 ° C. and a development time of 13.5 seconds has a characteristic curve shown on orthogonal coordinates where the diffusion density (Y axis) and the unit length of the common logarithmic exposure (X axis) are equal. The heat development according to any one of claims 1 to 3, wherein an average gradation in a range of 0.25 to 2.5 in optical density with diffused light is 2.0 to 4.0. Photosensitive material.

(Claim 5)
The surface having the image forming layer contains at least one silver-saving agent selected from a vinyl compound, a hydrazine derivative, a silane compound and a quaternary onium salt. Item 2. The photothermographic material according to item 1.

(Claim 6)
The photothermographic material according to any one of claims 1 to 5, wherein the binder has a glass transition temperature (Tg) of 70 to 150 ° C.

(Claim 7)
The photothermographic material according to any one of claims 1 to 6, further comprising a compound represented by the following general formula (SF).

Formula (SF) (Rf- (L) n1 -) p - (Y) m1 - (A) q
[Wherein, Rf represents a substituent having a fluorine atom, L represents a divalent linking group having no fluorine atom, Y represents a divalent to tetravalent linking group having no fluorine atom, and A represents an anion. Represents a group or its base. m1 and n1 each represent an integer of 0 or 1, and p and q each represent an integer of 1 to 3. However, when q is 1, n1 and m1 do not become 0 at the same time. ]
(Claim 8)
The photothermographic material according to any one of claims 1 to 7, wherein the silver halide further contains silver halide grains having an average grain size of 55 to 100 nm.

(Claim 9)
9. The photothermographic material according to claim 1, wherein the silver halide contains silver halide grains chemically sensitized with a chalcogen compound.

(Claim 10)
The photothermographic material of any one of claims 1 to 9, wherein the amount of silver contained in the image forming layer is 0.3 to 1.5 g / m ^2.

(Claim 11)
The heat-developable photosensitive material according to any one of claims 1 to 10, wherein the heat-development unit is used to transport the heat-developable photosensitive material at a speed of 10 to 200 mm / sec between the photosensitive material supply unit and the image exposure unit. An image forming method, wherein heat development is performed at a transport speed of 10 to 200 mm / sec and at a transport speed of 10 to 200 mm / sec in an image exposure unit.

  According to the present invention, it is possible to provide a photothermographic material having high density, excellent light-storing image preservability, and excellent silver tone. Further, if necessary, a photothermographic material having further excellent image storability during high-temperature storage, or excellent film transportability and environmental suitability can be provided.

  By adopting the constitutions of (Claim 1) to (Claim 5), it is possible to obtain a photothermographic material having a high density, excellent storage stability of light-irradiated image and improved silver tone.

  Further, by adopting the configuration of (claim 2), the image density can be remarkably improved.

  With the configuration of (Claim 6), the image storability during high-temperature storage can be further improved.

  With the configuration of (Claim 7), it is possible to further improve film transportability and environmental suitability (reduced accumulation in a living body).

  In (Claim 1), the average grain size of the silver halide needs to be 10 to 50 nm, but is preferably 10 to 35 nm. If the average grain size of the silver halide is smaller than 10 nm, the image density may be reduced, or the light irradiation image storage stability may be deteriorated. If it exceeds 50 nm, the image density may be reduced.

  The term "average grain size" as used herein refers to the length of the edge of a silver halide grain when the silver halide grain is a cubic or octahedral so-called normal crystal. In the case where the silver halide grains are tabular grains, the diameter refers to a diameter when converted into a circular image having the same area as the projected area of the main surface. In addition, when the crystal is not a normal crystal, for example, in the case of a spherical particle, a rod-like particle, or the like, the diameter of a sphere equivalent to the volume of the silver halide particle is calculated as the particle size. The measurement was performed using an electron microscope, and the average particle size was obtained by averaging the measured values of 300 particle sizes.

  (Claim 8) The image density can be improved or the aging can be improved by using a combination of 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. Can be reduced (smaller). The ratio (mass ratio) of silver halide grains having an average grain size of 10 to 50 nm to silver halide grains having an average grain size of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90:50. : 10 to 60:40.

  Hereinafter, the components of the present invention will be sequentially described.

(Organic silver salt)
Examples of the organic silver salt as a silver ion supply source for forming a silver image include silver salts of organic acids and heteroorganic acids, and particularly, long-chain (10 to 30, preferably 15 to 25) fatty acids. Silver salts of aromatic carboxylic acids and silver salts of nitrogen-containing heterocyclic compounds are preferred. Organic or inorganic complexes described in Research Disclosure (hereinafter simply referred to as RD) 17029 and 29963 in which the ligand has a value of 4.0 to 10.0 as a total stability constant for silver ions are also preferable. . Examples of these suitable silver salts include the following.

  Silver salts of organic acids such as gallic acid, oxalic acid, behenic acid, stearic acid, arachidic acid, palmitic acid and lauric acid; silver carboxyalkylthiourea salts such as 1- (3-carboxypropyl) thiourea; Silver salts such as 1- (3-carboxypropyl) -3,3-dimethylthiourea; silver salts or complexes of polymer reaction products of aldehydes with hydroxy-substituted aromatic carboxylic acids, for example, aldehydes (formaldehyde, acetaldehyde, butyraldehyde) Etc.) and a hydroxy-substituted acid (e.g., salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid); a silver salt or complex; a thione silver salt or complex such as 3- (2-carboxyethyl)- 4-hydroxymethyl-4-thiazoline-2-thione and 3-carboxymethyl-4-thiazo Silver salts or complexes such as 2-thione; selected from imidazole, pyrazole, urazole, 1,2,4-thiazole and 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole Complex or salt of nitrogen acid and silver; silver salt such as saccharin and 5-chlorosalicylaldoxime; silver mercaptides.

  Among these, particularly preferred silver salts include silver salts of long-chain (10 to 30, preferably 15 to 25 carbon atoms) aliphatic carboxylic acids such as silver behenate, silver arachidate and silver stearate. .

  In the present invention, it is preferable that two or more kinds of organic silver salts are mixed in order to enhance developability and to form a high-density, high-contrast silver image. It is preferable to prepare by mixing the solutions.

  The organic silver salt can be obtained by mixing a water-soluble silver compound and a compound which forms a complex with silver. The mixed silver salt can be prepared by a normal mixing method, a reverse mixing method, a double-mixing method, or a controlled mixing method described in JP-A No. 9-127643. A double jet method or the like is preferably used. For example, an organic acid alkali metal salt soap (sodium behenate, sodium arachidate, etc.) is prepared by adding an alkali metal salt (sodium hydroxide, potassium hydroxide, etc.) to an organic acid, and then controlled by a controlled double jet method. A soap and silver nitrate are mixed to produce an organic silver salt crystal. At that time, silver halide grains may be mixed.

  Although the above-mentioned organic silver salt can be used in various shapes, tabular grains are preferred. In particular, it is a tabular organic silver salt particle having an aspect ratio of 3 or more, and is filled in the photosensitive layer by reducing the shape anisotropy of two substantially parallel surfaces (principal planes) having the largest area. In order to increase the ratio, particles having an average needle-like ratio of the tabular organic silver salt particles measured from the main plane direction of 1.1 to less than 10.0 are preferable. A more preferred needle ratio is 1.1 or more and less than 5.0.

  The phrase "tabular organic silver salt particles having an aspect ratio of 3 or more" means that the tabular organic silver salt particles occupy 50% or more of the total number of organic silver salt particles. Further, in the organic silver salt according to the invention, tabular organic silver salt particles having an aspect ratio of 3 or more preferably account for 60% or more of the total number of organic silver salt particles, and more preferably 70% or more (number). It is particularly preferably at least 80% (number).

  The tabular particles having an aspect ratio of 3 or more are particles having a so-called aspect ratio (abbreviated as AR) of 3 or more expressed by the following formula, which is a ratio of particle diameter to thickness.

AR = particle size (μm) / thickness (μm)
The aspect ratio of the tabular organic silver salt grains is preferably from 3 to 20, and more preferably from 3 to 10. The reason for this is that if the aspect ratio is too low, the organic silver salt particles are likely to be most densely packed, and if the aspect ratio is too high, the organic silver salt particles are likely to overlap with each other and disperse in a stuck state. As a result, light scattering and the like are likely to occur, and as a result, the transparency of the photosensitive material is reduced.

  The average value of the particle size, average thickness and needle ratio of the organic silver salt particles can be determined by the method described in paragraphs “0031” to “0047” of JP-A-2002-287299.

  The method for obtaining the organic silver salt particles having the above-mentioned shape is not particularly limited, and it is possible to favorably maintain a mixed state when forming an organic acid alkali metal salt soap or a mixed state when adding silver nitrate to the soap, It is effective to optimize the ratio of silver nitrate that reacts with soap.

  It is preferable that the tabular organic silver salt particles according to the invention are preliminarily dispersed together with a binder, a surfactant and the like, if necessary, and then dispersed and pulverized with a media disperser or a high-pressure homogenizer. For the preliminary dispersion, a general stirrer such as an anchor type or a propeller type, a high-speed rotary centrifugal radiation type stirrer (dissolver), and a high-speed rotary shear type stirrer (homomixer) can be used.

  Further, as the media dispersing machine, a rolling mill such as a ball mill, a planetary ball mill, and a vibrating ball mill, and a bead mill, an attritor, and a basket mill as a medium stirring mill can be used. As the high-pressure homogenizer, a wall mill can be used. Various types can be used, such as a type that collides with a plug or the like, a type in which liquids are divided into a plurality of parts and then collides with each other at a high speed, and a type that passes through a thin orifice.

  As the ceramic used for the ceramic beads used at the time of media dispersion, for example, those described in paragraph “0051” of JP-A-2002-287299 described above are preferable. Yttrium-stabilized zirconia and zirconia reinforced alumina (ceramics containing these zirconia, hereinafter abbreviated as zirconia) are particularly preferably used because the generation of impurities due to friction with beads and a disperser during dispersion is small.

  In devices used when dispersing the tabular organic silver salt particles, it is preferable to use ceramics or diamond such as zirconia, alumina, silicon nitride, and boron nitride as a material of a member with which the organic silver salt particles are in contact, Among them, zirconia is preferably used.

  When performing the above dispersion, the binder concentration is preferably 0.1 to 10% of the mass of the organic silver salt, and it is preferable that the liquid temperature does not exceed 45 ° C. from the preliminary dispersion to the main dispersion. As preferable operating conditions of the main dispersion, for example, when a high-pressure homogenizer is used as the dispersing means, preferable conditions include 29.42 to 98.06 MPa and the number of operations is two or more. When a media dispersing machine is used as the dispersing means, a preferable condition is a peripheral speed of 6 to 13 m / sec.

Further, a preferred embodiment of the photothermographic material of the present invention, when the support surface and the cross section perpendicular of the material observed with an electron microscope, the ratio organic silver salt of an organic silver salt particles exhibiting a projection area of less than 0.025 .mu.m ² An organic silver salt having a feature that the ratio of particles exhibiting 70% or more of the total projected area of the grains and exhibiting a projected area of 0.2 μm ² or more is 10% or less of the total projected area of the organic silver salt particles; It is formed by coating a photosensitive emulsion containing photosensitive silver halide. In such a case, it is possible to obtain a state in which the organic silver salt particles are less aggregated and uniformly distributed in the photosensitive emulsion.

  The conditions for producing a photosensitive emulsion having such characteristics are not particularly limited, and the mixed state at the time of forming the organic acid alkali metal salt soap or the mixed state at the time of adding silver nitrate to the soap can be favorably maintained. , To optimize the ratio of silver nitrate reacting with soap, to disperse and pulverize with a media disperser or a high-pressure homogenizer or the like. In addition to the fact that the temperature from drying to the end of the main dispersion does not exceed 45 ° C., it is preferable to use a dissolver at the time of liquid preparation and to stir at a peripheral speed of 2.0 m / sec or more. As

  The projected area of the organic silver salt grains having the specific projected area value as described above, the ratio of the organic silver salt grains to the total projected area, and the like are determined in the same manner as described in the above-described section for calculating the average thickness of the tabular grains. A portion corresponding to organic silver salt particles is extracted by a method using a transmission electron microscope). Specifically, it can be determined by the method described in paragraphs “0057” to “0059” of JP-A-2002-287299.

  The organic silver salt particles used in the present invention are preferably monodisperse particles, and the preferred degree of monodispersion is 1 to 30%. By using the monodisperse particles in this range, an image having a high density can be obtained. Here, the monodispersity is defined by the following equation.

Monodispersity = {(standard deviation of particle size) / (average value of particle size)} × 100
The average particle size (equivalent circle diameter) of the organic silver salt is preferably 0.01 to 0.3 μm, more preferably 0.02 to 0.2 μm. The average particle diameter (equivalent circle diameter) refers to the diameter of a circle having the same area as an individual particle image observed with an electron microscope.

To prevent devitrification of the photosensitive material, the total amount of silver halide and organic silver salt is preferably in terms of amount of silver 1 m ² per 0.3 to 1.5 g. By setting this range, a preferable image can be obtained when used as a medical image. If the amount is less than 0.3 g per 1 m ² , the image density may decrease. On the other hand, if the amount exceeds 1.5 g per 1 m ² , fog may increase or sensitivity may be reduced at the time of printing on a PS plate.

(Silver halide)
The silver halide (hereinafter also referred to as photosensitive silver halide grains or silver halide grains) used in the present invention will be described. In the present invention, the silver halide means that it can inherently absorb light as an intrinsic property of the silver halide crystal, or can absorb visible light or infrared light by an artificial physicochemical method. And, when the light in any region within the light wavelength range from the ultraviolet light region to the infrared light region is absorbed, the treatment is performed so that a physicochemical change may occur in the silver halide crystal and / or the crystal surface. It refers to the produced silver halide crystal grains.

  The silver halide grains themselves 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 and the like may be used, and a method of reacting a soluble silver salt with a soluble halide salt may be any one of a one-side mixing method, a double-mixing method, a combination thereof and the like. Of these methods, a so-called controlled double jet method for preparing silver halide grains while controlling the formation conditions is preferable among the above methods.

  The halogen composition is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide.

  Grain formation is usually divided into two stages of silver halide seed grain (nucleus) generation and grain growth, and these methods may be performed continuously at one time. Alternatively, nucleus (seed grain) formation and grain growth may be separated. It is also possible to use a method of performing this. The controlled double jet method for forming particles by controlling the pAg, pH and the like, which are the particle forming conditions, is preferable because the shape and size of the particles 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 generate nuclei (seed particles) (nucleation step). The silver halide grains are prepared by a grain growing step of growing grains while supplying an aqueous solution of silver salt and an aqueous solution of halide under controlled pAg, pH and the like. After forming the 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, flocculation method, ultrafiltration method, and electrodialysis method. .

  The silver halide grains preferably have a monodispersed grain size. The term “monodisperse” as used herein means that the coefficient of variation of the particle size determined by the following formula is 30% or less. It is preferably at most 20%, more preferably at most 15%.

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 cubic, octahedral, tetrahedral grains, tabular grains, spherical grains, rod-like grains, potato-like grains and the like. It is preferable to use a tabular or tabular silver halide grain.

  When tabular silver halide grains are used, the average aspect ratio is preferably from 1.5 to 100, more preferably from 2 to 50. These are described in U.S. 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 also be preferably used.

  The crystal habit on the outer surface of the silver halide grains is not particularly limited. However, in the case of using a sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the sensitizing dye on the surface of the silver halide grains. It is preferable to use silver halide grains having a relatively high proportion of crystal habit adapted to the selectivity. For example, when a sensitizing dye that selectively adsorbs to a crystal plane having a Miller index of [100] is used, the ratio of the [100] plane to the outer surface of the silver halide grain is preferably high, and this ratio is preferably 50%. % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is determined by the T.V. method using the dependence of the adsorption of the sensitizing dye on the [111] plane and the [100] plane. Tani; Imaging Sci. , 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, and particularly preferably used at the time of forming nuclei of the silver halide grains. 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 is generally used for enzymatic degradation by adding a gelatin-degrading enzyme to an aqueous gelatin solution having an average molecular weight of about 100,000, hydrolyzing by adding an acid or alkali, and heating under atmospheric pressure or under pressure. By thermal decomposition, decomposition by irradiation with ultrasonic waves, 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 a low concentration of 0.05 to 3.0% by mass.

  The silver halide grains used in the present invention preferably use a compound represented by the following general formula at the time of forming the grains.

YO (CH ₂ CH ₂ O) _m [CH (CH ₃ ) CH ₂ O] _p (CH ₂ CH ₂ O) _n Y
Wherein, Y is a hydrogen atom, a -SO ₃ M or -CO-B-COOM, M is a hydrogen atom, an alkali metal atom, ammonium group or substituted ammonium group at carbon atom number of 5 or less in the alkyl group And B represents a chain or cyclic group forming an organic dibasic acid. m and n each represent 0 to 50, and p represents 1 to 100.

  The polyethylene oxide compound represented by the above general formula is used for producing a silver halide photographic light-sensitive material, a step of producing an aqueous gelatin solution, a step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, and supporting an emulsion. It has been preferably used as an antifoaming agent against remarkable foaming when the emulsion raw material is stirred or moved, such as a step of coating on the body. No. 44-9497. This polyethylene oxide compound also functions as an antifoaming agent at the time of nucleation.

  The compound represented by the above general formula is preferably used in an amount of 1% by mass or less based on silver, and more preferably 0.01 to 0.1% by mass.

  Regarding the conditions at the time of nucleation, the method described in paragraphs “0079” to “0082” of JP-A-2002-287299 can also be referred to.

  The silver halide grains may be added to the image forming layer by any method. At this time, the silver halide grains are preferably arranged so as to be close to a reducible silver source (organic silver salt).

  Since silver halide grains are prepared in advance and added to a solution for preparing organic silver salt grains, since the silver halide preparation step and the organic silver salt grain preparation step can be handled separately, production control is performed. As described in British Patent No. 1,447,454, a halogen component such as a halide ion is allowed to coexist with an organic silver salt-forming component when preparing organic silver salt particles, and silver ion is added thereto. By injecting, it can be produced almost simultaneously with the production of the organic silver salt particles.

  It is also possible to prepare a silver halide grain by converting an organic silver salt with a halogen-containing compound and converting the organic silver salt. That is, a silver halide-forming component is applied to a solution or dispersion of an organic silver salt prepared in advance or a sheet material containing the organic silver salt to convert a part of the organic silver salt into photosensitive silver halide. You can also.

  Examples of the silver halide forming component include inorganic halogen compounds, onium halides, halogenated hydrocarbons, N-halogen compounds, and other halogen-containing compounds, and specific examples thereof are described in JP-A-2002-287299. "0086".

  Thus, the silver halide can be prepared by converting a part or all of the silver in the organic acid silver salt to silver halide by reacting the organic acid silver salt with the halogen ion. Further, silver halide grains produced by converting a part of these organic silver salts to separately prepared silver halide may be used in combination.

  These silver halide grains, both separately prepared silver halide grains and silver halide grains obtained by conversion of organic silver salt, are preferably used in an amount of 0.001 to 0.7 mol per 1 mol of organic silver salt. It is more preferable to use 0.03 to 0.5 mol.

The silver halide preferably contains ions of a transition metal belonging to Groups 6 to 11 of the periodic table. As the above metals, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt and Au are preferable. These may be used alone or in combination of two or more of the same or different metal complexes. These metal ions may be directly introduced into silver halide as a metal salt, but can be introduced into silver halide in the form of a metal complex or complex ion. The content is preferably in the range of 1 × 10 ⁻⁹ to 1 × 10 ⁻² mol per mol of silver, and more preferably in the range of 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ mol. 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 elements of Groups 6 to 11 of 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 ion (fluoride ion, chloride ion, bromine ion, iodine ion), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aquo. Ligand, nitrosyl, thionitrosyl and the like, and preferably aquo, nitrosyl and thionitrosyl. If an aquo ligand is present, it preferably occupies one or two of the ligands. L may be the same or different.

  The compound which provides the ion or complex ion of these metals is preferably added during silver halide grain formation and incorporated into silver halide grains. Preparation of silver halide grains, that is, nucleation, growth, and physical ripening , May be added at any stage before and after chemical sensitization, nucleation, growth, preferably added at the stage of physical ripening, nucleation, more preferably added at the stage of growth, particularly preferably It is added at the stage of nucleation. In the addition, it may be added in several portions, may be added uniformly in the silver halide grains, or may be added uniformly to the silver halide grains, as disclosed in JP-A-63-29603, JP-A-2-306236 and JP-A-2-306236. As described in JP-A-167545, JP-A-4-76534, JP-A-6-110146, JP-A-5-273683 and the like, the particles can be contained in the particles with a distribution.

  These metal compounds can be added by dissolving in water or a suitable organic solvent (alcohols, ethers, glycols, ketones, esters, amides, etc.). Alternatively, an aqueous solution in which a metal compound and sodium chloride and potassium chloride are dissolved together is added to a water-soluble silver salt solution or a water-soluble halide solution during grain formation, or a silver salt aqueous solution and a halide aqueous solution are mixed simultaneously. In this case, a method of preparing silver halide grains by a method of simultaneous mixing of three liquids, adding a required amount of an aqueous solution of a metal compound into a reaction vessel during grain formation, There is a method in which another silver halide grain doped with a metal ion or complex ion in advance during silver preparation is added and dissolved. In particular, a method of adding an aqueous solution of a powder of a metal compound or an aqueous solution in which a metal compound is dissolved together with sodium chloride and potassium chloride to an aqueous halide solution is preferable. When adding to the surface of the particles, a required amount of an aqueous solution of a metal compound can be charged into the reaction vessel immediately after the formation of the particles, during or at the end of physical ripening, or at the time of chemical ripening.

  The separately prepared photosensitive silver halide grains can be desalted by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, and an electrodialysis method. It can be used without salt.

  The silver halide grains can be subjected to chemical sensitization. For example, according to the methods disclosed in JP-A-2001-249428 and JP-A-2001-249426, a chemical sensitization center is prepared by using a compound having a chalcogen atom such as sulfur or a noble metal compound which releases a noble metal ion such as a gold ion ( A chemical sensitizing nucleus). In the present invention, it is particularly preferable to use both the chemical sensitization using the compound having a chalcogen atom and the chemical sensitization using a noble metal compound.

  In the present invention, it is preferable that the compound is chemically sensitized with a compound containing a chalcogen atom shown below. The compound containing a chalcogen atom useful as an organic sensitizer is preferably a compound having a group capable of adsorbing to silver halide and an unstable chalcogen atom site.

  As these organic sensitizers, organic sensitizers having various structures disclosed in JP-A-60-150046, JP-A-4-109240, and JP-A-11-218874 can be used. Of these, it is preferable that at least one compound having a structure in which a chalcogen atom is connected to a carbon atom or a phosphorus atom by a double bond is used. Particularly preferred are the compounds of the general formulas (1-1) and (1-2) disclosed in JP-A-2002-250984.

The amount of the chalcogen atom-containing compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, the reaction environment for chemical sensitization, and the like. It is preferably from 10 ^-8 to 1 × 10 ^-2 mol, more preferably from 1 × 10 ^-7 to 1 × 10 ^-3 mol. There is no particular limitation on the chemical sensitization environment, but in the presence of a compound capable of eliminating silver chalcogenide or silver nuclei on the photosensitive silver halide grains or reducing the size thereof, and particularly in the presence of silver nuclei. It is preferable to carry out chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent which can be oxidized. As the sensitization condition, the pAg is preferably 6 to 11 (more preferably 7 to 11). 10), the pH is preferably 4 to 10 (more preferably 5 to 8), and the sensitization is preferably performed at a temperature of 30 ° C or lower.

  Therefore, in the photothermographic material of the present invention, the photosensitive silver halide is heated to 30 ° C using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei on the grains. It is preferable to use a photosensitive silver halide emulsion which has been subjected to chemical sensitization at a temperature of not more than ℃, mixed with an organic silver salt, dispersed, dehydrated and dried.

  The chemical sensitization using these organic sensitizers is preferably performed in the presence of a spectral sensitizing dye or a heteroatom-containing compound having adsorptivity to silver halide grains. By performing chemical sensitization in the presence of a compound having an adsorptive property to silver halide, dispersion of the central core of the chemical sensitization can be prevented, and high sensitivity and low fog can be achieved. The spectral sensitizing dye used in the present invention will be described later, and the heteroatom-containing compound having adsorptivity to silver halide is preferably a nitrogen-containing heterocyclic compound described in JP-A-3-24537. Can be

  In the nitrogen-containing heterocyclic compound, the heterocyclic ring is a pyrazole ring, a pyrimidine ring, a 1,2,4-triazole ring, a 1,2,3-triazole ring, a 1,3,4-thiadiazole ring, a 1,2,3- A thiadiazole ring, a 1,2,4-thiadiazole ring, a 1,2,5-thiadiazole ring, a 1,2,3,4-tetrazole ring, a pyridazine ring, a 1,2,3-triazine ring; Examples of the ring include three bonded rings, for example, a triazolotriazole ring, a diazaindene ring, a triazaindene ring, and a pentaazaindene ring. A heterocyclic ring in which a monocyclic heterocycle and an aromatic ring are condensed, for example, a phthalazine ring, a benzimidazole ring, an indazole ring, a benzothiazole ring and the like can also be applied. Of these, azaindene rings are preferable, and azaindene compounds having a hydroxyl group as a substituent, such as hydroxytriazaindene, hydroxytetraazaindene, and hydroxypentaazaindene, are 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. May be.

The addition amount of these heterocyclic compounds varies over a wide range depending on the size, composition, and other conditions of silver halide grains, but the approximate amount is 1 × 10 5 per mole of silver halide. ^-6 to 1 mol, preferably 1 × 10 ^-4 to 1 × 10 ^-1 mol.

  As described above, silver halide grains can be sensitized with a noble metal using a compound that releases a noble metal ion such as a gold ion. For example, chloroaurate or an organic gold compound can be used as a gold sensitizer.

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

  The silver halide subjected to chemical sensitization according to the present invention may be one formed in the presence of an organic silver salt, one formed under the absence of an organic silver salt, or a mixture of both. May be used.

  The silver halide grains are preferably subjected to spectral sensitization by absorbing a spectral sensitizing dye. As the spectral sensitizing dye, a cyanine dye, a merocyanine dye, a complex cyanine dye, a complex merocyanine dye, a holopolar cyanine dye, a styryl dye, a hemicyanine dye, an oxonol dye, a hemioxonol dye, and the like can be used. For example, JP-A-63-159841, JP-A-60-140335, JP-A-63-231437, JP-A-63-259661, JP-A-63-304242, JP-A-63-15245, U.S. Pat. , 740,455, 4,741,966, 4,751,175, and 4,835,096. Useful sensitizing dyes are described, for example, in the documents described or cited in RD17643 IV-A (Dec. 1978, p. 23) and 18431X (August 1978, p. 437). 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-9-34078, JP-A-9-54409 and JP-A-9-80679 are preferably used.

  Useful cyanine dyes are cyanine dyes having a basic nucleus such as a thiazoline nucleus, an oxazoline nucleus, a pyrroline nucleus, a pyridine nucleus, an oxazole nucleus, a thiazole nucleus, a selenazole nucleus and an imidazole nucleus. Preferred useful merocyanine dyes include, in addition to the above basic nuclei, acidic nuclei such as thiohydantoin nucleus, rhodanine nucleus, oxazolidinedione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus. including.

  In the present invention, it is particularly preferable to use a sensitizing dye having spectral sensitivity in the infrared region. As the infrared spectral sensitizing dye preferably used, for example, infrared spectral sensitizing dyes disclosed in U.S. Pat. Nos. 4,536,473, 4,515,888, and 4,959,294 are exemplified. No.

  As the infrared spectral sensitizing dye used in the present invention, a long-chain polymethine dye characterized by having a sulfinyl group substituted on the benzene ring of a benzazole ring is particularly preferable. This infrared sensitizing dye is described in, for example, FM Hammer; The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dyes and Related Compounds (A. Weissberger ed., Inc., Y.N., N.I., 19th. It can be easily synthesized by the method.

  These infrared sensitizing dyes may be added at any time after the preparation of the silver halide, for example, by adding them to a solvent or dispersing them in fine particles, in a so-called solid dispersion state of silver halide grains or silver halide grains. / Can be added to a photosensitive emulsion containing organic silver salt particles. Also, like the heteroatom-containing compound having an adsorptivity to the silver halide grains, the chemical sensitization can be performed after adding and adsorbing the silver halide grains prior to the chemical sensitization. Thereby, the dispersion of the chemical sensitization center nucleus can be prevented, and high sensitivity and low fog can be achieved.

  The above-mentioned spectral sensitizing dyes may be used alone, or a combination thereof may be used, and a combination of sensitizing dyes is often used particularly for supersensitization.

  Emulsion containing silver halide grains or organic silver salt grains used in the present invention, together with a sensitizing dye, a dye having no spectral sensitizing effect itself, or a substance that does not substantially absorb visible light, A substance exhibiting a supersensitizing effect 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 (December, 1978), page 23, IV, J, or JP-B Nos. 9-25500 and 43-4933. And JP-A-59-19032, JP-A-59-192242, and JP-A-5-341432. In the present invention, a heteroaromatic compound represented by the following general formula is used as a supersensitizer. A group mercapto compound or a mercapto derivative compound is preferred.

General formula Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic heterocyclic or fused aromatic ring having one or more nitrogen, sulfur, oxygen, selenium, or tellurium atoms. Preferred aromatic heterocycles or aromatic condensed rings include benzimidazole, naphthoimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzotellurazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine. , Pyridazine, pyrazine, pyridine, purine, quinoline, quinazoline and the like. However, other aromatic heterocycles are also included.

  Incidentally, a mercapto derivative compound which substantially produces the above-mentioned mercapto compound when contained in a dispersion of an organic acid silver salt or a silver halide grain emulsion is also included in the present invention. Particularly, a mercapto derivative compound represented by the following general formula is mentioned as a preferable example.

General formula Ar-SS-Ar
Ar in the formula has the same meaning as in the case of the mercapto compound represented by the above general formula.

  The aromatic heterocyclic ring or aromatic condensed ring includes, for example, a halogen atom (chlorine, bromine, iodine, etc.), a hydroxyl group, an amino group, a carboxyl group, an alkyl group (one or more carbon atoms, preferably 1 to 4 carbon atoms). ) And an alkoxy group (having one or more carbon atoms, preferably having 1 to 4 carbon atoms).

  In the present invention, in addition to the above-described supersensitizer, a compound represented by the general formula (1) and a macrocyclic compound containing a hetero atom disclosed in JP-A-2001-330918 may be used as a supersensitizer. Can be used as

  The supersensitizer is preferably used in the emulsion layer containing the organic silver salt and the silver halide grains in a range of 0.001 to 1.0 mol per mol of silver, and 0.01 to 0.5 mol. It is particularly preferable to use in the range.

(Reducing agent)
In the present invention, as the reducing agent (silver ion reducing agent), in particular, at least one of the reducing agents may be a compound represented by the general formula (1) alone or in combination with another reducing agent having a different chemical structure. Used. By using these highly active reducing agents, it is possible to obtain a photothermographic material having a high density and excellent light-storing image preservability.

  In the present invention, it is preferable to use a compound of the general formula (1) in combination with an o-bisphenol compound other than the general formula (1). As the combination ratio, [mass of compound of general formula (1)]: [mass of o-bisphenol compound other than general formula (1)] is preferably from 5:95 to 45:55, and more preferably. 10:90 to 40:60.

In the general formula (1), X 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 or an alkenyl group, the halogen atom, fluorine atom, chlorine atom, bromine atom, a substituted or unsubstituted carbon atoms 1 as an alkyl group Twenty alkyl groups are preferred. Specific examples include methyl, ethyl, propyl, butyl, hexyl, heptyl and the like. Alkenyl groups include vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl , 3-pentenyl, 1-methyl-3-butenyl and the like. R ₁ is particularly preferably a cyclic group, for example, a cycloalkyl group or a cycloalkenyl group.

  These groups may further have a substituent, and specific examples of the substituent include a halogen atom (fluorine, chlorine, bromine, etc.) and an alkyl group (methyl, ethyl, propyl, butyl, pentyl, i-pentyl). , 2-ethylhexyl, octyl, decyl etc.), cycloalkyl group (cyclohexyl, cycloheptyl etc.), alkenyl group (ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl -3-butenyl, etc.), cycloalkenyl group (1-cycloalkenyl, 2-cycloalkenyl group, etc.), alkynyl group (ethynyl, 1-propynyl, etc.), alkoxy group (methoxy, ethoxy, propoxy, etc.), alkylcarbonyloxy group (Acetyloxy, etc.), alkylthio groups (methylthio, trifluoromethylthio, etc.), Boxyl 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 (acetamidosulfonyl, methoxyacetamidosulfonyl, etc.), alkynylaminocarbonyl group (acetamidocarbonyl, methoxyacetamidocarbonyl, etc.) ), Alkylsulfinylaminocarbonyl groups (methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.). 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, at least one of which is 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.

The substituent of the alkyl group is not particularly limited, for example, an aryl group, a hydroxyl group, an alkoxy group, an aryloxy group, an alkylthio group, an arylthio group, an acylamino group, a sulfonamide group, a sulfonyl group, a phosphoryl group, an acyl group, a carbamoyl group, Examples include an ester group and a halogen atom. In addition, (R ₄ ) _n and (R ₄ ) _m may form a saturated ring. R ₂ is preferably a secondary or tertiary alkyl group, and preferably has 2 to 20 carbon atoms. More preferred are tertiary alkyl groups, still more preferred are t-butyl, t-pentyl and 1-methylcyclohexyl, and most preferred is t-butyl.

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

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

These groups may further have a substituent, and as the substituent, the substituents described above for R ₁ can be used. R ₃ is preferably an alkyl group having 1 to 20 carbon atoms having a hydroxyl group or a precursor group thereof, and more preferably an alkyl group having 1 to 5 carbon atoms. Most preferably, it is 2-hydroxyethyl. The most preferred combination of R ₂ and R ₃ is that 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 its precursor group ( 2-hydroxyethyl). A plurality of R ₂ and R ₃ may be the same or different. Examples of the precursor group that generates a hydroxyl group in R ₃ include an acetyloxy group and a benzoyloxy group. By using a hydroxyl group or a primary alkyl group having a precursor group thereof as R ₃ , the image density can be remarkably improved.

R ₄ represents a group that can be substituted on the benzene ring, specifically, an alkyl group having 1 to 25 carbon atoms (eg, methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl), Halogenated alkyl groups (trifluoromethyl, perfluorooctyl, etc.), cycloalkyl groups (cyclohexyl, cyclopentyl, etc.), alkynyl groups (propargyl, etc.), glycidyl groups, acrylate groups, methacrylate groups, aryl groups (phenyl, etc.), heterocycles Groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, suliphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups (methoxy, ethoxy) , Pyroxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc., aryloxy group (phenoxy, etc.), alkoxycarbonyl group (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl group (phenyloxycarbonyl ), Sulfonamide group (methanesulfonamide, ethanesulfonamide, butanesulfonamide, hexanesulfonamide group, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl group (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl, butylamino) Sulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyridylaminos A urethane group (methylureide, ethylureide, pentylureide, cyclohexylureide, phenylureide, 2-pyridylureide, etc.), an acyl group (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 group (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, Oxamoyl groups and the like can be mentioned. These groups may be further substituted with these groups. n and m each represent an integer of 0 to 2, and most preferably n and m are both 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, and more preferably a hydrogen atom.

  Hereinafter, specific examples of the compound represented by the general formula (1) (the reducing agent of the present invention) will be described, but the present invention is not limited thereto.

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

  The reducing agent contained in the photothermographic material reduces an organic silver salt to form a silver image. Examples of the reducing agent which can be used in combination with the reducing agent of the present invention include, for example, U.S. Pat. Nos. 3,770,448, 3,773,512, 3,593,863, RD17029 and 29963, and No. 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.

(Color of the image)
Next, the color tone of an image obtained by subjecting the photothermographic material to heat development will be described.

  With respect to the color tone of an output image for medical diagnosis such as a conventional radiographic film, it is said that a cold tone of an image makes it easier for a reader to obtain more accurate diagnostic observation results. Here, the cool image tone means that a pure black tone or a black image has a bluish blue-black tone. On the other hand, it is said that a warm image tone is a warm black tone in which a black image has a brownish tint. However, in order to allow a more rigorous quantitative discussion, hereinafter, the International Commission on Illumination (CIE) will be described. ) Is explained based on the recommended expression method.

The terms “cooler” and “warmer” 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 obtained by calculating the color coordinates a ^* and b ^* of the 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. And is determined by the following equation.

hab = tan ^-1 (b ^* / a ^* )
As a result of examination by the expression method based on the above hue angle, the color tone of the photothermographic material of the present invention after development is preferably such that the range of the hue angle hab is 180 ° <hab <270 °, more preferably 200 °. <Hab <270 degrees, most preferably 220 degrees <hab <260 degrees. This is disclosed in JP-A-2002-6463.

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

However, as a result of further intensive studies on the photothermographic material of the present invention, in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space, the horizontal axis is u ^* or a ^* , and the vertical axis is When plotting u ^* , v ^* or a ^* , b ^* at various photographic densities on a graph with the axis being v ^* or b ^*, and creating a linear regression line, the linear regression line is specified. By adjusting the range, it has been found that the diagnostic performance is equal to or better than that of a conventional wet silver halide photosensitive material. The preferred condition range will be described below.

i) The optical densities 0.5, 1.0, 1.5 and the minimum optical density of the silver image obtained after the heat development of the photothermographic material were measured, and the CIE 1976 (L ^* u ^* v ^*) was measured ^. ) The determination coefficient (double determination) R2 of the linear regression line created by arranging u ^* and v ^* at each of the above optical densities in two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^*. It is preferably from 0.998 to 1.000.

Further, it is preferable that the v ^* value at 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.

ii) The optical density of the photothermographic material was 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 was measured. The coefficient of determination (multiple decision) R2 of the linear regression line created by arranging a ^* and b ^* at each of the above optical densities on two-dimensional coordinates where a ^* and the vertical axis is b ^* is 0.998 to 1.000. It is preferable that

Further, it is preferable that the b ^* value at 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 of preparing the above-described linear regression line, that is, an example of a method of 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 thermal developing apparatus. The wedge density parts thus produced are measured with a spectral colorimeter (manufactured by Minolta: CM-3600d or the like) to calculate u ^* , v ^* or a ^* , b ^* . The measurement is performed in a transmission measurement mode with an F7 light source as a light source and a viewing angle of 10 degrees. The horizontal axis u ^* or a ^*, vertical axis v ^* or b ^* are plotted on the graph u ^*, v ^* or a ^*, b ^* is used as the ordinate and a linear regression line is formed, (multiple determination) Find R2, intercept and slope.

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

  In the present invention, in the development reaction process of the following toning agent, developer, silver halide particles, silver aliphatic carboxylate and the like, the amount of a compound or the like that directly or indirectly participates in the development reaction process is adjusted so that the developed silver is adjusted. The shape can be optimized to achieve a favorable color tone. For example, when the developed silver shape is a dendrite shape, the direction becomes bluish, and when the developed silver shape is a filament shape, the direction becomes yellowish. That is, the adjustment can be made in consideration of such a tendency of the developed silver shape.

  Conventionally, phthalazinone or phthalazine, phthalic acids and phthalic anhydrides have been generally used as toning agents. Examples of suitable toning agents are disclosed in RD 17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, 4,021,249 and the like. .

  In addition to such a toning agent, the color tone can be adjusted using a coupler disclosed in JP-A-11-288057, EP1133461A2, or the like, and a leuco dye described in detail below. In particular, it is preferable to use a leuco dye for fine adjustment of color tone.

  Preferably, the leuco dye is 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 oxidized by silver ions. Any leuco dye that forms a dye can be used. Compounds that are pH sensitive and that can be oxidized to a colored state are useful.

  Representative leuco dyes suitable for use in the present invention are not particularly limited, but include, for example, biphenol leuco dyes, phenol leuco dyes, indoliniline leuco dyes, acrylated azine leuco dyes, phenoxazine leuco dyes, phenodiazine leuco dyes. And phenothiazine leuco dyes. Also useful are U.S. Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, and 4 Nos. 4,022,617, 4,123,282, 4,368,247, 4,461,681, JP-A-50-36110, JP-A-59-206831, and JP-A-5-204087. No. 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 alone or in combination of a plurality of types. In the present invention, the use of a highly active reducing agent causes the color tone to be excessively yellowish, and the use of fine silver halide particles results in an excessively high image density especially in a high density portion having a density of 2.0 or more. A leuco dye that develops a cyan color is used in order to prevent reddish coloration, but a leuco dye that develops a yellow color and a cyan color is preferably used in combination for fine adjustment of color tone.

  The color density is preferably adjusted appropriately in relation to the color tone of the developed silver itself. In the present invention, a color is formed so as to have a reflection optical density of 0.01 to 0.05 or a transmission optical density of 0.005 to 0.03, and the color tone is adjusted so as to obtain an image in a preferable color tone range described below. preferable.

  In the present invention, a color image forming agent represented by the formula (YA), which is particularly preferably used as a yellow-coloring leuco dye, whose extinction at 360 to 450 nm is increased by being oxidized. Hereinafter, the compound of the formula (YA) will be described in detail.

In the 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 are more steric than i-propyl. Is preferably a large group (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl and the like), and among them, secondary or tertiary alkyl Groups are preferred, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferred. 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 sulfonamide group, an acyloxy group, an oxycarbonyl group, and a carbamoyl group. , A sulfamoyl group, a sulfonyl group, a phosphoryl group and the like.

R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively. Alkyl group represented by R ₁₂ is preferably an alkyl group having 1 to 30 carbon atoms, an acylamino group is preferably an acylamino group having 1 to 30 carbon atoms. Of these, description for the alkyl group is the same as the R _11.

The acylamino group represented by R ₁₂ may be unsubstituted or have a substituent, 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. Further, R ₁₁ and R ₁₂ are not 2-hydroxyphenylmethyl groups.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group. Preferably an alkyl group having 1 to 30 carbon atoms as the alkyl group, the description of the alkyl groups is the same as R _11. R ₁₃ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, specifically, methyl, i-propyl, t-butyl and the like. Further, it is preferable that one of R ₁₂ and R ₁₃ is a hydrogen atom.

R ₁₄ represents a group that can be substituted on a benzene ring, and is, for example, the same group as described for the substituent R ₄ in the general formula (1). Preferred as R ₁₄ are a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms and an oxycarbonyl group having 2 to 30 carbon atoms, and an alkyl group having 1 to 24 carbon atoms is more preferred. 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 an aryl group, an amino group, an oxycarbonyl group, and an alkoxy group are more preferred. preferable. The substituents of these alkyl groups may be further substituted with these substituents.

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

Wherein, Z is -S- or _{-C (R 21) (R 21} ') - represent, R _21, R _21' each represent a hydrogen atom or a substituent. Examples of the substituent represented by R ₂₁ and R ₂₁ ′ include the same groups as the substituents described 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 formula (1).

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

More preferably the _{R 22, R 23, R 22} ' and R _23', t-butyl, t-pentyl, t-octyl, 1-methyl - a tertiary alkyl group such as 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 for R ₄ in Formula (1).

  Examples of the compounds represented by formulas (YA) and (YB) include compounds (II-1) to (II-40) described in paragraphs “0032” to “0038” of JP-A-2002-169249, EP1, Compounds (ITS-1) to (ITS-12) described in paragraph "0026" of 211,093 can be exemplified.

  Hereinafter, specific examples of the bisphenol compounds represented by formulas (YA) and (YB) are shown, but the present invention is not limited thereto.

  The amount of the compound of the general formula (YA) (including the hindered phenol compound and the compound of the general formula (YB)) is usually 0.00001 to 0.01 mol per mol of silver, preferably 0.1 to 0.1 mol. 0005 to 0.01 mol, more preferably 0.001 to 0.008 mol.

(Cyan coloring leuco dye)
Next, the cyan coloring leuco dye will be described. In the present invention, a color image-forming agent which is preferably used as a cyan color-forming dye is preferably a color image-forming agent whose absorbance at 600 to 700 nm is increased by being oxidized, and is disclosed in JP-A-59-206831 (particularly when λmax is 600 to 700 nm). And compounds of general formulas (I) to (IV) in JP-A-5-204087 (specifically, (1) to (18) described in paragraphs “0032” to “0037”). ) And the compounds of the general formulas 4 to 7 of JP-A-11-231460 (specifically, the compounds of Nos. 1 to 79 described in paragraph “0105”).

  In the present invention, a color image forming agent which is preferably used as a cyan-color-forming leuco dye, whose absorbance at 600 to 700 nm is increased by being oxidized, is disclosed in JP-A-59-206831 (particularly when λmax is 600 to 700 nm). Compounds within the range of 700 nm), and compounds of the general formulas (I) to (IV) of JP-A-5-204087 (specifically, (1) to (0037) described in paragraphs “0032” to “0037”). 18) and the compounds of the general formulas 4 to 7 in JP-A-11-231460 (specifically, the compounds of Nos. 1 to 79 described in paragraph “0105”).

  The cyan coloring leuco dye particularly preferably used in the invention is represented by the following general formula (CL).

In the formula, R ₈₁ and R ₈₂ represent a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, an alkenyl group, an alkoxy group, a —NHCO—R ₁₀ group (R ₁₀ is an alkyl group, an aryl group, a heterocyclic group, Or R ₈₁ and R ₈₂ are a group linked to each other to form an aliphatic hydrocarbon ring, an aromatic hydrocarbon ring or a heterocyclic ring. A ₈ represents a -NHCO- group, -CONH- group or a -NHCONH- group, R ₈₃ represents a substituted or unsubstituted alkyl group, an aryl group or a heterocyclic group. Further, -A ₈ -R ₈₃ may be a hydrogen atom. W ₈ represents a hydrogen atom or a —CONH—R ₈₅ group, a —CO—R ₈₅ group, or a —CO—O—R ₈₅ group (R ₈₅ represents a substituted or unsubstituted alkyl group, an aryl group, or a 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 atoms represented by R ₈₁ and R ₈₂ include fluorine, bromine, and chlorine atoms, and examples of the alkyl group include alkyl groups having up to 20 carbon atoms (eg, methyl and ethyl). , Butyl, dodecyl, etc.). Examples of the alkenyl group include alkenyl groups having up to 20 carbon atoms (vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl). , 3-pentenyl, 1-methyl-3-butenyl, etc.), and the alkoxy group includes an alkoxy group having up to 20 carbon atoms (methoxy, ethoxy, etc.). The alkyl group represented by R ₁₀ in the —NHCO—R ₁₀ group includes an alkyl group having up to 20 carbon atoms (eg, methyl, ethyl, butyl, dodecyl), and the aryl group includes phenyl and naphthyl. Examples of the heterocyclic group include groups such as thienyl, furyl, imidazolyl, pyrazolyl, and pyrrolyl. The alkyl group represented by R ₈₃ is preferably an alkyl group having up to 20 carbon atoms, for example, methyl, ethyl, butyl, dodecyl and the like. The aryl group is preferably an aryl group having 6 to 20 carbon atoms. There are, for example, phenyl, naphthyl and the like, and as the heterocyclic group, for example, thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like. -CONH-R ₈₅ groups represented by W _8, in -CO-R ₈₅ group or -CO-O-R ₈₅ group, the alkyl group represented by R ₈₅ is preferably an alkyl group having up to 20 carbon atoms For example, methyl, ethyl, butyl, dodecyl and the like are mentioned, and the aryl group is preferably an aryl group having 6 to 20 carbon atoms, for example, phenyl, naphthyl and the like, and the heterocyclic group is, for example, Thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like can be mentioned.

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

  The above groups can further have one or more substituents. Typical substituents include halogen atoms (fluorine, chlorine, bromine, etc.), alkyl groups (methyl, ethyl, propyl, butyl, dodecyl, etc.), hydroxyl groups, cyano groups, nitro groups, alkoxy groups (methoxy, ethoxy, etc.) ), Alkylsulfonamide groups (methylsulfonamide, octylsulfonamide, etc.), arylsulfonamide groups (phenylsulfonamide, naphthylsulfonamide, etc.), alkylsulfamoyl groups (butylsulfamoyl, etc.), arylsulfamoyl ( Phenylsulfamoyl, etc.), alkyloxycarbonyl group (such as methoxycarbonyl), aryloxycarbonyl group (such as phenyloxycarbonyl), aminosulfonamide group, acylamino group, carbamoyl group, sulfonyl group, sulfinyl group, sulfoxy group, sulfoxy group 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, 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 There are, for example, methyl, ethyl, butyl, dodecyl and the like, and the aryl group is preferably an aryl group having 6 to 20 carbon atoms, for example, phenyl, naphthyl and the like, and the heterocyclic group is, for example, thienyl, Ruffle, imidazolyl, pyrazolyl, pyrrolyl and the like can be mentioned.

As the substituent which 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.

The aryl group represented by X _8, phenyl, include an aryl group having 6 to 20 carbon atoms, such as naphthyl, examples of the heterocyclic group include such as thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl, etc. .

Examples of the substituent which 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).

As the group represented by X ₈ , an aryl group or a heterocyclic group having an alkylamino group (such as diethylamino) at the para position is preferable. These groups may include photographically useful groups.

  Specific examples of the cyan coloring leuco dye (CA) are shown below, but the invention is 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, and more preferably 0.001 to 0.01 mol. / Ag1 mol. Further, the molar ratio of the cyan coloring leuco dye to the total amount of the compound of the general formula (1) and the o-bisphenol compound other than the general formula (1) is 0.001 to 0.2. Is preferable, and 0.005 to 0.1 is more preferable.

  In the present invention, the sum of the maximum densities (Dmax) at the maximum absorption wavelength of the dye image formed by the cyan coloring leuco dye is preferably 0.01 to 0.5, more preferably 0.02 to 0.5. 3, it is particularly preferred to develop the color so as to have 0.03 to 0.1.

  The compounds represented by the general formulas (YA) and (YB) and the cyan-chromogenic leuco dye can be added in the same manner as the method for adding the reducing agent represented by the general formula (1). It may be contained in the coating liquid by any method such as a solution form, an emulsified dispersion form, a solid fine particle dispersion form, and may be contained in the photosensitive material.

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

  In the photothermographic material of the present invention, a phenol derivative represented by the formula (A) described in JP-A-2000-267222 is preferably used as a development accelerator.

(binder)
Binders suitable for photothermographic materials are transparent or translucent, generally colorless, and natural polymer synthetic resins, polymers and copolymers, and other film-forming media, for example, paragraph [0069] of JP-A-2001-330918. Described in (1). Among these, polyvinyl acetal is preferred as the binder for the photosensitive layer of the photothermographic material of the present invention, and polyvinyl butyral is particularly preferred. These will be described later in detail.

  Further, for non-photosensitive layers such as an overcoat layer and an undercoat layer, particularly a protective layer and a backcoat layer, polymers having a higher softening temperature, such as cellulose esters, especially triacetyl cellulose, and a polymer such as cellulose acetate butyrate. preferable. In addition, if necessary, the above binders may be used in combination of two or more.

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), an epoxy group, -SH, -CN, or the like, into which at least one or more polar groups are introduced by a copolymerization or addition reaction. it is preferable to use, in particular -SO ₃ M, -OSO ₃ M, is preferred. The amount of such a polar group is from 1 × 10 ^-1 to 1 × 10 ^-8 mol / g, preferably from 1 × 10 ^-2 to 1 × 10 ^-6 mol / g.

Such a binder is used in an effective range to function as a binder. Effective ranges can be readily determined by those skilled in the art. For example, as an index when at least the organic silver salt is retained in the image forming layer, the ratio of the binder to the organic silver salt is preferably from 15: 1 to 1: 2 (mass ratio), particularly preferably from 8: 1 to 1: 1. Is preferable. That is, it is preferable that the binder amount of the image forming layer is 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 portion will increase significantly and may not be usable.

  The glass transition temperature (Tg) of the binder used in the present invention is preferably from 70 to 105 ° C. Tg can be determined by measuring with a differential scanning calorimeter, and the intersection between the baseline and the slope of the endothermic peak is defined as Tg. Tg in the present invention is determined by the method described in "Polymer Handbook" by Brand Wrap and the like, pages III-139 to 179 (1966, Wiley & Sun).

  Tg when the binder is a copolymer resin is determined by the following equation.

Tg _{(copolymer) (℃) = v 1 Tg} 1 + v 2 Tg 2 + ··· + v n Tg n
_{Wherein, v 1, v 2 ··· v} n represents the mass fraction of the monomer in the _{copolymer, Tg 1, Tg 2 ··· Tg} n from each monomer in the copolymer It represents the Tg (° C.) of the obtained homopolymer. The accuracy of the Tg calculated according to the above equation is ± 5 ° C.

  It is preferable to use a binder having a Tg of from 70 to 105 [deg.] C., since a sufficient maximum density can be obtained in image formation.

  The binder of 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. It is. As the polymer or copolymer containing an ethylenically unsaturated monomer as a constituent unit, those described in paragraph [0069] of JP-A-2001-330918 can be mentioned.

  Of these, particularly preferred examples include alkyl methacrylates, aryl methacrylates, and styrenes. Among such polymer compounds, it is preferable to use a polymer compound having an acetal group. 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, and 2,828,204, United Kingdom Examples thereof include polyvinyl acetal disclosed in Japanese Patent No. 771,155.

  As the polymer compound having an acetal group, a compound represented by the following general formula (V) is particularly preferable.

In the formula, R ₃₁ represents a substituted or unsubstituted alkyl group or a substituted or unsubstituted aryl group, and is preferably a group other than an aryl group. R ₃₂ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, -COR ₃₃ or -CONHR _33. R ₃₃ has the same meaning as R ₃₁ .

The unsubstituted alkyl group represented by R ₃₁ , R ₃₂ and R ₃₃ preferably has 1 to 20 carbon atoms, and particularly preferably has 1 to 6 carbon atoms. These may be linear or branched, and are preferably linear alkyl groups. Examples of such unsubstituted alkyl groups include methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, amyl, t-pentyl, hexyl, cyclohexyl, hepsyl, octyl, t-octyl, -Ethylhexyl, nonyl, decyl, dodecyl, octadecyl and the like, and particularly preferably a methyl or propyl group.

  The unsubstituted aryl group preferably has 6 to 20 carbon atoms, and examples include phenyl and naphthyl groups.

  Examples of the group which can be substituted for the above-mentioned alkyl group and aryl group include an alkyl group (eg, methyl, propyl, t-amyl, t-octyl, nonyl, dodecyl), an aryl group (eg, phenyl), a nitro group, a hydroxyl group, and a cyano group. Group, sulfo group, alkoxy group (methoxy, ethoxy, etc.), aryloxy group (phenoxy, etc.), acyloxy group (acetoxy, etc.), acylamino group (acetylamino, etc.), sulfonamide group (methanesulfonamide, etc.), sulfamoyl group ( Methylsulfamoyl, etc.), a halogen atom (fluorine, chlorine, bromine, etc.), a carboxyl group, a carbamoyl group (methylcarbamoyl, etc.), an alkoxycarbonyl group (methoxycarbonyl, etc.), a sulfonyl group (methylsulfonyl, etc.) and the like. When there are two or more of these substituents, they may be the same or different. The total carbon number of the substituted alkyl group is preferably 1 to 20, and the total carbon number of the substituted aryl group is preferably 6 to 20.

The R _32, -COR ₃₃ (R ₃₃ is an alkyl group or an aryl group), - CONHR ₃₃ (R ₃₃ is an aryl group). a, b, and c are values in which the mass of the repeating unit is represented by mol%, a is 40 to 86 mol%, b is 0 to 30 mol%, c is 0 to 60 mol%, and a + b + c = 100 mol%, and particularly preferably, a is in the range of 50 to 86 mol%, b is in the range of 5 to 25 mol%, and c is in the range of 0 to 40 mol%. Each of the repeating units having the respective composition ratios of a, b, and c may be composed of only the same unit or different units.

  The polymer compound represented by the general formula (V) can be synthesized by a general synthesis method described in “Vinyl acetate resin” edited by Ichiro Sakurada (Polymer Chemistry Publishing Association, 1962).

As the polyurethane resin that can be used in the present invention, known resins such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. Further, it is preferable that the polyurethane molecule has at least one hydroxyl group at the terminal, and two or more hydroxyl groups in total. Since a hydroxyl group crosslinks with a polyisocyanate as a curing agent to form a three-dimensional network structure, it is preferable to include a large number of hydroxyl groups in a molecule. In particular, it is preferable that the hydroxyl group be located at the molecular terminal because the reactivity with the curing agent is high. The polyurethane preferably has three or more hydroxyl groups at the molecular terminals, and particularly preferably four or more hydroxyl groups. In the present invention, when polyurethane is used, the Tg is preferably 70 to 105 ° C., the elongation at break is 100 to 2000%, and the stress at break is preferably 0.5 to 100 N / mm ² .

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

  The above polymer is used as a main binder in the image forming layer of the present invention. The term "main binder" used herein means "a state in which the polymer accounts for 50% by mass or more of the total binder in the image forming layer". Therefore, other polymers may be blended and used in a range of less than 50% by mass of the total binder. These polymers are not particularly limited as long as they are solvents in which the polymer of the present invention is soluble. More preferably, polyvinyl acetate, polyacrylic resin, urethane resin and the like are mentioned.

  The image forming layer may contain an organic gelling agent. The organic gelling agent referred to herein is a function of imparting a yield value to the system by adding it to an organic liquid, such as a polyhydric alcohol, to eliminate or reduce the fluidity of the system. A compound having the following formula:

  It is also a preferred embodiment that the coating solution for the image forming layer contains a polymer latex dispersed in water. In this case, it is preferable that 50% by mass or more of the total binder in the coating solution for the image forming layer is a polymer latex dispersed in an aqueous solution. When the image forming layer contains a polymer latex, it is preferable that 50% by mass or more of all binders in the image forming layer is a polymer latex, and more preferably 70% by mass or more.

  The polymer latex is obtained by dispersing a water-insoluble hydrophobic polymer as fine particles in a water-soluble dispersion medium. The dispersion state is such that the polymer is emulsified in a dispersion medium, emulsion polymerized, micelle-dispersed, or has a partially hydrophilic structure in the polymer molecule, and the molecular chain itself is molecularly dispersed. Any of them may be used. The average particle size of the dispersed particles is preferably from 1 to 50,000 nm, more preferably from about 5 to 1,000 nm. There is no particular limitation on the particle size distribution of the dispersed particles, and they may have a wide particle size distribution or a monodispersed particle size distribution.

  The polymer latex used in the present invention may be a so-called core / shell type latex other than a polymer latex having a normal 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 from -30 to 90C, more preferably from about 0 to 70C. Further, a film-forming auxiliary may be added to control the minimum film-forming temperature.

  The film-forming aid is also called a plasticizer and is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of the polymer latex. For example, "Synthesis of synthetic latex (Souichi Muroi, published by Kobunshi Kankokai) , 1970) ".

  Examples of the polymer 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. Further, 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 generally about 5,000 to 1,000,000, preferably about 10,000 to 100,000, as a number average molecular weight. If the molecular weight is too small, the mechanical strength of the photosensitive layer is insufficient, and if it is too large, the film-forming properties are poor, and both are not preferred.

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

  Specific examples of the polymer latex include methyl methacrylate / ethyl acrylate / methacrylic acid copolymer, methyl methacrylate / 2-ethylhexyl acrylate / styrene / acrylic acid copolymer, styrene / butadiene / acrylic acid copolymer, styrene / butadiene / divinylbenzene / methacrylic acid copolymer And latexes such as methyl methacrylate / vinyl chloride / acrylic acid copolymer and vinylidene chloride / ethyl acrylate / acrylonitrile / methacrylic acid copolymer. These polymers may be used alone or as a blend of two or more as necessary. The polymer latex preferably contains a carboxylic acid component such as an acrylate or methacrylate component in an amount of about 0.1 to 10% by mass.

  Further, if necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, hydroxypropylcellulose, carboxymethylcellulose, or hydroxypropylmethylcellulose may be added in a range of 50% by mass or less of the whole binder. The addition amount of these hydrophilic polymers is preferably 30% by mass or less of the total binder in the photosensitive layer.

  In the preparation of the coating solution for the image forming layer, regarding the order of addition of the organic silver salt and the aqueous dispersion of the polymer latex, any of them may be added first, or they may be added at the same time. Is later.

  Further, it is preferable that an organic silver salt and further a reducing agent are mixed before the addition of the polymer latex. Also, after mixing the organic silver salt and the polymer latex, if the temperature for aging is too low, the coated surface state is damaged, and if it is too high, the fog rises. It is preferable that the above time is elapsed. Further, the aging is preferably performed at 35 to 60 ° C, and particularly preferably at 35 to 55 ° C. In order to maintain the temperature in this manner, it is only necessary to keep the temperature of the coating solution preparation tank or the like.

  The application of the coating solution for the image forming layer is preferably performed using a coating solution obtained by mixing the organic silver salt and the polymer latex dispersed in water, and then 30 minutes to 24 hours, more preferably 60 minutes after mixing. It is preferable to use a coating solution that has passed for 120 minutes to 10 hours.

  Here, "after mixing" refers to a state after the organic silver salt and the polymer latex dispersed in water are added, and the added materials are uniformly dispersed.

  It is known that the use of a crosslinking agent for the binder improves film formation and reduces development unevenness, but also has the effect of suppressing fogging during storage and suppressing the formation of printout silver after development. is there.

  Examples of the cross-linking agent used include various cross-linking agents conventionally used for photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based and sulfone-based compounds described in JP-A-50-96216. An acid ester-based, acryloyl-based, carbodiimide-based, or silane compound-based cross-linking agent is used, and is preferably an isocyanate-based, silane compound-based, epoxy-based compound, or an acid anhydride shown below.

  The isocyanate-based crosslinking agent is an isocyanate having at least two isocyanate groups and an adduct thereof (adduct), and more specifically, an aliphatic diisocyanate, an aliphatic diisocyanate having a cyclic group, and benzene. Diisocyanates, naphthalene diisocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates, and isocyanates and divalent or trivalent polyalcohols Adducts with the like. As a specific example, an isocyanate compound described on pages 10 to 12 of JP-A-56-5535 can be used.

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

  Further, as the thioisocyanate-based crosslinking agent usable in the present invention, a compound having a thioisocyanate structure corresponding to the above isocyanates is also useful.

  The amount of the crosslinking agent to be used is generally 0.001 to 2 mol, preferably 0.005 to 0.5 mol, per 1 mol of silver.

  The isocyanate compound and the thioisocyanate compound that can be contained in the present invention are preferably compounds that function as the above-mentioned cross-linking agent, but a compound having only one such functional group may provide good results.

  Examples of the silane compound include compounds represented by general formulas (1) to (3) disclosed in JP-A-2001-264930.

  The epoxy compound that can be used as a crosslinking agent may be any compound having at least one epoxy group, and there is no limitation on the number, molecular weight, and the like of the epoxy group. 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, oligomer, polymer and the like, 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 a homopolymer or a copolymer, and a particularly preferred range of the number average molecular weight Mn is about 2,000 to 20,000.

  The acid anhydride used in the present invention is a compound having at least one acid anhydride group represented by the following structural formula. What is necessary is just to have one or more such acid anhydride groups, and there is no restriction | limiting in the number, molecular weight, etc. of an acid anhydride group.

-CO-O-CO-
The above epoxy compounds and acid anhydrides may be used alone or in combination of two or more. 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 a photosensitive layer, a surface protective layer, an intermediate layer, an antihalation layer, and an undercoat layer. Alternatively, it can be added to two or more layers.

(Silver saving agent)
In the present invention, the effect of the present invention can be further enhanced by using a silver saving agent. The silver saving agent used in the present invention refers to a compound capable of reducing the amount of silver required for obtaining a constant silver image density. There are various possible mechanisms for the function of reducing silver, but a compound having a function of improving the covering power of developed silver is preferable. Here, the covering power of the developed silver means an optical density per unit amount of silver.

  Examples of the silver saving agent include a hydrazine derivative compound represented by the following general formula (H), a vinyl compound represented by the following general formula (G), and a quaternary onium compound represented by the following general formula (P); A silane compound is mentioned as a preferable example.

In the formula, A ₀ represents an aliphatic group, an aromatic group, a heterocyclic group or a -G ₀ -D ₀ group which may have a substituent, B ₀ represents a blocking group, and A ₁ and A ₂ Represents a hydrogen atom, or one represents a hydrogen atom and the other represents an acyl group, a sulfonyl group, or an oxalyl group. _Here, G 0 is -CO -, - COCO -, - CS -, - C (= NG 1 D 1) -, - SO -, - SO 2 - or _{-P (O) (G 1 D} 1) - Wherein G ₁ represents a mere bond, —O—, —S— or —N (D ₁ ) —; D ₁ represents an aliphatic group, an aromatic group, a heterocyclic group or a hydrogen atom; When a plurality of D ₁ are present, they may be the same or different. D ₀ represents a hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, an amino group, an alkoxy group, an aryloxy group, an alkylthio group or an arylthio group. Preferred examples of D ₀ include a hydrogen atom, an alkyl group, an alkoxy group, and an amino group.

The aliphatic group represented by A ₀ is preferably of 1 to 30 carbon atoms, particularly preferably a straight-chain, branched or cyclic alkyl group having 1 to 20 carbon atoms, such as methyl, ethyl, t- butyl And octyl, cyclohexyl and benzyl groups, which are further substituted with suitable substituents (aryl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, sulfoxy group, sulfonamide group, sulfamoyl group, acylamino group, ureido group). Etc.).

The aromatic group represented by A ₀ is an aryl group preferably a monocyclic or condensed, such as a benzene ring or a naphthalene ring, and examples of the heterocyclic group represented by A _0, a monocyclic or fused ring Nitrogen, sulfur, a heterocyclic ring containing at least one heteroatom selected from oxygen atoms is preferable, for example, a pyrrolidine ring, an imidazole ring, a tetrahydrofuran ring, a morpholine ring, a pyridine ring, a pyrimidine ring, a quinoline ring, a thiazole ring, a benzothiazole ring, A thiophene ring and a furan ring. Aromatic groups A _0, heterocyclic group or -G ₀ -D ₀ group may have a substituent. Particularly preferred as A ₀ are an aryl group and a —G ₀ -D ₀ group.

A ₀ preferably contains at least one diffusion-resistant group or silver halide-adsorbing group. As the diffusion-resistant group, a ballast group commonly used in immobile photographic additives such as couplers is preferable, and as the ballast group, a photographically inactive alkyl group, alkenyl group, alkynyl group, alkoxy group, Examples thereof include a phenyl group, a phenoxy group, and an alkylphenoxy group, and the total number of carbon atoms in the substituent is preferably 8 or more.

  Examples of the silver halide adsorption accelerating group include thiourea, thiourethane group, mercapto group, thioether group, thione group, heterocyclic group, thioamide heterocyclic group, mercapto heterocyclic group and the adsorption described in JP-A-64-90439. And the like.

B ₀ represents a blocking group, preferably a -G ₀ -D ₀ group, G ₀ is -CO -, - COCO -, - CS -, - C (= NG 1 D 1) -, - SO-, Represents —SO ₂ — or —P (O) (G ₁ D ₁ ) —. Preferable G ₀ includes -CO- and -COCO- groups, wherein G ₁ represents a simple bond, -O-, -S- or -N (D ₁ )-, and D ₁ is an aliphatic group or an aromatic group. Represents a group, a heterocyclic group or a hydrogen atom, and when a plurality of D ₁ are present in the molecule, they may be the same or different.

D ₀ represents a hydrogen atom, an aliphatic group, an aromatic group, a heterocyclic group, an amino group, an alkoxy group, an aryloxy group, an alkylthio group, or an arylthio group, and preferred D ₀ is a hydrogen atom, an alkyl group, an alkoxy group, And an amino group.

A ₁ and A ₂ are both a hydrogen atom, or one is a hydrogen atom and the other is an acyl group (acetyl, trifluoroacetyl, benzoyl, etc.), a sulfonyl group (methanesulfonyl, toluenesulfonyl, etc.), or an oxalyl group (ethoxalyl, etc.) Represents

  These compounds represented by the general formula (H) can be easily synthesized by a known method. For example, it can be synthesized with reference to U.S. Patent Nos. 5,464,738 and 5,496,695.

  Other hydrazine derivatives that can be preferably used include compounds H-1 to H-29 described in U.S. Pat. No. 5,545,505, columns 11 to 20, and U.S. Pat. No. 5,464,738. Compounds 1 to 12 described in 9 to 11, compounds H-1-1 to H-1-28 and H-2-1 to H-2-28 described in "0042" to "0052" of JP-A-2001-27790. 9, H-3-1 to H-3-12, H-4-1 to H-4-21, and H-5-1 to H-5-5. These hydrazine derivatives can be synthesized by a known method.

  Hereinafter, typical examples of the hydrazine derivative preferably used are shown, but the invention is not limited to these compounds.

The vinyl compound represented by the general formula (G) will be described. In the general formula (G), X ₄₁ and R ₄₁ are represented in a cis form, but the general formula (G) also includes a trans form of X ₄₁ and R ₄₁ . This is the same in the structural representation of the compound examples.

In the formula, X ₄₁ represents an electron-withdrawing group, W ₄₁ represents a hydrogen atom, an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, a halogen atom, an acyl group, a thioacyl group, an oxalyl group, an oxyoxalyl group. , Thiooxalyl, oxamoyl, oxycarbonyl, thiocarbonyl, carbamoyl, thiocarbamoyl, sulfonyl, sulfinyl, oxysulfinyl, thiosulfinyl, sulfamoyl, oxysulfinyl, thiosulfinyl, sulfinamoyl , A phosphoryl group, a nitro group, an imino group, an N-carbonylimino group, an N-sulfonylimino group, a dicyanoethylene group, an ammonium group, a sulfonium group, a phosphonium group, a pyrylium group, and an immonium group.

R ₄₁ is a halogen atom, a hydroxyl group, an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkenyloxy group, an acyloxy group, an alkoxycarbonyloxy group, an aminocarbonyloxy group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic thio group. Organic or inorganic salts (sodium salt, potassium salt, silver salt, etc.) of a group, alkenylthio group, acylthio group, alkoxycarbonylthio group, aminocarbonylthio group, hydroxyl group or mercapto group, amino group, alkylamino group, cyclic amino Group (e.g., pyrrolidino), acylamino group, oxycarbonylamino group, heterocyclic group (e.g., 5- to 6-membered nitrogen-containing heterocyclic ring such as benzotriazolyl, imidazolyl, triazolyl, tetrazolyl), ureido group, and sulfonamide group .

X ₄₁ and W ₄₁ , and X ₄₁ and R ₄₁ may be bonded to each other to form a ring. Examples of the ring formed by X ₄₁ and W ₄₁ include pyrazolone, pyrazolidinone, cyclopentanedione, β-ketolactone, β-ketolactam and the like.

The electron-withdrawing group represented by X ₄₁ is a substituent whose substituent constant σp can take a positive value. Specifically, a substituted alkyl group (eg, halogen-substituted alkyl), a substituted alkenyl group (eg, cyanovinyl), a substituted / unsubstituted alkynyl group (eg, trifluoromethylacetylenyl, cyanoacetylenyl), and a substituted aryl group (eg, cyanovinyl) Phenyl, etc.), substituted / unsubstituted heterocyclic groups (pyridyl, triazinyl, benzoxazolyl, etc.), halogen atoms, cyano groups, acyl groups (acetyl, trifluoroacetyl, formyl, etc.), thioacetyl groups (thioacetyl, thioformyl, etc.) ), An oxalyl group (such as methyloxalyl), an oxyoxalyl group (such as ethoxyl), a thiooxalyl group (such as ethylthiooxalyl), an oxamoyl group (such as methyloxamoyl), an oxycarbonyl group (such as ethoxycarbonyl), a carboxyl group, and a thiol group. Carbonyl group (ethylthiocarbonyl ), Carbamoyl, thiocarbamoyl, sulfonyl, sulfinyl, oxysulfonyl (such as ethoxysulfonyl), thiosulfonyl (such as ethylthiosulfonyl), sulfamoyl, oxysulfinyl (such as methoxysulfinyl), thiosulfinyl ( Methylthiosulfinyl, sulfinamoyl, phosphoryl, nitro, imino, N-carbonylimino (N-acetylimino), N-sulfonylimino (N-methanesulfonylimino), dicyanoethylene, ammonium , A sulfonium group, a phosphonium group, a pyrylium group, and an immonium group, and a heterocyclic group in which an ammonium group, a sulfonium group, a phosphonium group, an immonium group, and the like form a ring is also included. A substituent having a σp value of 0.30 or more is particularly preferred.

Examples of the alkyl group represented by W ₄₁ include methyl, ethyl, trifluoromethyl and the like, alkenyl groups such as vinyl, halogen-substituted vinyl and cyanovinyl, alkynyl groups such as acetylenyl and cyanoacetylenyl, and aryl groups such as Examples of the heterocyclic group include nitrophenyl, cyanophenyl, and pentafluorophenyl, and examples of the heterocyclic group include pyridyl, pyrimidyl, triazinyl, succinimide, tetrazolyl, triazolyl, imidazolyl, and benzoxazolyl. W ₄₁ is preferably an electron-withdrawing group having a positive σp value, and more preferably has a value of 0.30 or more.

Of the substituents of R ₄₁ , preferably a hydroxyl group, a mercapto group, an alkoxy group, an alkylthio group, a halogen atom, an organic or inorganic salt of a hydroxyl group or a mercapto group, a heterocyclic group, more preferably a hydroxyl group, Examples thereof include an organic or inorganic salt of an alkoxy group, a hydroxyl group or a mercapto group, and a heterocyclic group, and particularly preferably an organic or inorganic salt of a hydroxyl group or a mercapto group.

  Specific examples of the compound of the general formula (G) 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. Described compounds HET-01 to HET-02, compounds MA-01 to MA-07 described in columns 9 to 10 of U.S. Pat. No. 5,654,130, and columns 9 to of U.S. Pat. No. 5,705,324. Compounds IS-01 to IS-04 described in No. 10 and Compounds 1-1 to 218-2 described in paragraphs “0043” to “0088” of JP-A-2001-125224.

  Hereinafter, examples of the vinyl compound preferably used in the present invention will be shown, but the present invention is not limited to these compounds.

The onium compound represented by the general formula (P) will be described. Wherein, Q represents a nitrogen atom or phosphorus _{atom, R 51, R 52, R} 53 and R ₅₄ each represent a hydrogen atom or a substituent, X ₅₁ ^- represents an anion. Incidentally, R _{51 to} R ₅₄ may be connected to each other to form a ring.

Examples of the substituent represented by R _{51 to} R ₅₄ include an alkyl group (eg, methyl, ethyl, propyl, butyl, hexyl, cyclohexyl), an alkenyl group (eg, allyl, butenyl), an alkynyl group (eg, propargyl, butynyl), and an aryl group. Groups (phenyl, naphthyl, etc.), heterocyclic groups (piperidinyl, piperazinyl, morpholinyl, pyridyl, furyl, thienyl, tetrahydrofuryl, tetrahydrothienyl, sulfolanyl, etc.), amino groups and the like.

Examples of the ring which R _{51 to} R ₅₄ can form by linking each other include rings of piperidine, morpholine, piperazine, quinuclidine, pyridine, pyrrole, imidazole, triazole, tetrazole and the like.

The groups represented by R _{51 to} R ₅₄ may have a substituent such as a hydroxyl group, an alkoxy group, an aryloxy group, a carboxyl group, a sulfo group, an alkyl group, and an aryl group. As R ₅₁ , R ₅₂ , R ₅₃ and R ₅₄ , a hydrogen atom and an alkyl group are preferable.

X ₅₁ ^- The anion represented a halogen ion, sulfate ion, nitrate ion, acetate ion, and inorganic and organic anions, such as p- toluenesulfonic acid ion.

  The quaternary onium compound can be easily synthesized according to a known method. For example, a tetrazolium compound is described in Chemical Reviews vol. 55 pp. 335-483.

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

  In the present invention, it is preferable that at least one of the silver saving agents is a silane compound. The silane compound used as a silver saving agent is preferably an alkoxysilane compound having two or more primary or secondary amino groups or a salt thereof as described in Japanese Patent Application No. 2001-192698.

  Here, having two or more primary or secondary amino groups means that two or more primary amino groups only, two or more secondary amino groups only, and further, a primary amino group and a secondary amino group. And a salt of an alkoxysilane compound means an adduct of an inorganic or organic acid capable of forming an onium salt with an amino group and an alkoxysilane compound.

  Examples of such an alkoxysilane compound or a salt thereof include those described below. In the present invention, an alkoxysilane compound having two or more primary or secondary amino groups in the molecule or The salt is not limited to these compounds.

  In these compounds, the alkoxy group forming an alkoxysilyl is preferably an alkoxy group composed of a saturated hydrocarbon, and more preferably a methoxy group, an ethoxy group, or an i-propoxy group, because they have more excellent storage stability. Further, for the purpose of reducing sensitivity fluctuation due to storage conditions before thermal development, a compound having no unsaturated hydrocarbon group in the molecule is more preferable. These alkoxysilane compounds or salts thereof may be used alone or in combination of two or more.

  The image forming layer preferably contains a Schiff base formed by a dehydration condensation reaction between an alkoxysilane compound having at least one primary amino group and a ketone compound. By using such a Schiff base, silver can be saved, and an image having low fog, little sensitivity fluctuation, and extremely low gamma can be obtained regardless of storage conditions before thermal development. Further, since the primary amine portion is blocked in advance, when a ketone-based solvent is used when preparing a coating solution for forming an image forming layer described later, sensitivity fluctuation due to lapse of time after the preparation of the coating solution is suppressed. can do.

  The ketone compound used to form the above-mentioned alkoxysilane compound and the Schiff base can be used without any particular limitation. However, it has a boiling point of 150 due to the problem of odor generated when an image is formed by an image forming method described later. C. or less, more preferably 100.degree. C. or less.

  Examples of such a Schiff base include the following compounds, and any Schiff base formed by a dehydration condensation reaction between an alkoxysilane compound having one or more primary amino groups and a ketone compound may be used. It is not limited to.

  Of the above compounds, for the purpose of saving silver, a Schiff base having one or more secondary amino groups in the molecule is more preferable. These Schiff bases may be used alone or in combination of two or more.

  When an alkoxysilane compound or a salt thereof or a Schiff base is added to the image forming layer as a silver saving agent, it is preferably added in an amount of usually 0.00001 to 0.05 mol per 1 mol of silver. . The same applies to the case where both an alkoxysilane compound or a salt thereof and a Schiff base are added to the image forming layer.

  However, if the addition amount of the above-mentioned alkoxysilane compound or Schiff base to 1 mol of silver is slightly increased, the image density of an unexposed portion formed by an image forming method described later may be increased. In order to alleviate the dependence of the amount of the added alkoxysilane compound or Schiff base on 1 mol of silver, it is preferable to further add an isocyanate compound having two or more isocyanate groups in the molecule to the image forming layer. preferable. As the isocyanate compound, the isocyanate compound used as the above-mentioned crosslinking agent can be used.

  Next, the antifoggant and the image stabilizer used in the photothermographic material of the invention will be described.

  As a reducing agent for photothermographic materials, reducing agents having protons such as bisphenols and sulfonamidophenols are mainly used. By generating active species capable of extracting these hydrogens, reduction is performed. It preferably contains a compound capable of inactivating the agent. Preferably, it is a compound capable of generating free radicals as a reactive species upon exposure as a colorless photo-oxidizable substance.

  Accordingly, any compound having these functions may be used, but an organic free radical consisting of a plurality of atoms is preferable. 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, the compound generating these free radicals may be a carbocyclic or heterocyclic compound so that the generated free radicals are stable enough to allow contact with the reducing agent for a sufficient time to react with and inactivate the reducing agent. Those having a cyclic aromatic group are preferred.

  Representative examples of these compounds include a biimidazolyl compound and an iodonium compound.

The addition amount of the above biimidazolyl compound and iodonium compound 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 of the constituent layers of the light-sensitive material of the present invention, but is preferably contained near the reducing agent.

  Also, many compounds capable of releasing a halogen atom as an active species are known as antifoggants and image stabilizers.

  Specific examples of the compounds that generate these active halogen atoms include compounds of the following general formula (ST).

In the formula, Q ₆₁ represents an aryl group or a heterocyclic group. X ₆₁ , X ₆₂ and X ₆₃ each represent a hydrogen atom, a halogen atom, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group or an aryl group, at least one of which is a halogen atom. Y ₆₁ is -CO -, - SO- or -SO ₂ - represents a.

The aryl group represented by Q ₆₁ may have a single ring or condensed ring is preferably a monocyclic or bicyclic aryl group having 6 to 30 carbon atoms (phenyl, naphthyl, etc.), more preferably phenyl And a naphthyl group, and more preferably a phenyl group.

The heterocyclic group represented by Q ₆₁ is, N, a heterocyclic group of O or at least 3- to 10-membered containing one atom of a saturated or unsaturated S, which may be a single ring, Further, a condensed ring may be formed with another ring. The heterocyclic group is preferably a 5- to 6-membered unsaturated heterocyclic group which may have a condensed ring, and more preferably a 5- to 6-membered aromatic heterocyclic group which may have a condensed ring. It is. More preferably, it is a 5- to 6-membered aromatic heterocyclic group which may have a condensed ring containing a nitrogen atom, and particularly preferably 5 to 5 which may have a condensed ring containing 1 to 4 nitrogen atoms. It is a 6-membered aromatic heterocyclic group.

  Preferred examples of the heterocyclic group in such a heterocyclic group include those described in paragraph “0268” of JP-A-2002-287299, and more preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, Thiadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, tetrazole, thiazole, benzimidazole, benzothiazole, and particularly preferably pyridine, thiadiazole, quinoline and benzothiazole.

The aryl group and the heterocyclic group represented by Q ₅₁ may have a substituent in addition to —Y ₆₁ —C (X ₆₁ ) (X ₆₂ ) (X ₆₃ ). JP-A-2002-287299, paragraph [0269], more preferably, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an acyl group, an acylamino group, a sulfonylamino group, a sulfamoyl group, and a carbamoyl group , A halogen atom, a cyano group, a nitro group and a heterocyclic group, particularly preferably an alkyl group, an aryl group and a halogen atom.

X ₆₁ , X ₆₂ and X ₆₃ are preferably a halogen atom, a haloalkyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, and a heterocyclic group, and more preferably a halogen atom. , A haloalkyl group, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group and a sulfonyl group, particularly preferably a halogen atom. Among the halogen atoms, a chlorine atom, a bromine atom and an iodine atom are preferred, a chlorine atom and a bromine atom are more preferred, and a bromine atom is particularly preferred.

Y ₆₁ is -CO -, - SO -, - SO 2 - represents a, preferably -SO ₂ - is.

  The addition amount of these compounds is preferably within a range in which the increase in printout silver due to the formation of silver halide does not cause a problem, and the ratio (mass) to the compound that does not generate active halogen radicals is 150% or less at the maximum. Preferably, it is 100% or less. Specific examples of the compounds that generate these active halogen atoms include compounds (III-1) to (III-23) described in paragraphs “0086” to “0087” of JP-A-2002-169249. .

(Anti-fogging agent)
Next, the antifoggant preferably used in the present invention will be described. Such antifoggants include, for example, compound examples a to j described in paragraph “0012” of JP-A-8-314059 and thiosulfonate esters A to K described in paragraph “0028” of JP-A-7-209797. Compound Examples (1) to (44) described from page 14 of JP-A-55-140833, Compounds (I-1) to (I-6) described in paragraph "0063" of JP-A-2001-13627, (C-1) to (C-3) described in the above “0066”, Compounds (III-1) to (III-108) described in paragraph “0027” of JP-A-2002-90937, vinyl sulfones and / or As the β-halosulfone compounds, compounds VS-1 to VS-7, compounds HS-1 to HS-5, and sulfonylbenzotriazole compounds described in paragraph [0013] of JP-A-6-208192 are particularly useful. Compounds of KS-1~KS-8 described in JP 2000-330235, and the like can be given PR-01~PR-08 described in JP Table No. 2000-515995 as propenenitrile compounds substituted.

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

  In addition to the above compounds, the light-sensitive material may contain a compound conventionally known as an antifoggant, but it is a compound capable of generating the same reactive species as the above compound. Alternatively, compounds having different antifogging mechanisms may be used. For example, U.S. Pat. Nos. 3,589,903, 4,546,075, 4,452,885, JP-A-59-57234, U.S. Pat. Nos. 3,874,946, and 4,756,999. And compounds described in JP-A-9-288328 and JP-A-9-90550. Further, examples of other antifoggants include compounds disclosed in U.S. Pat. No. 5,028,523 and European Patents 600,587, 605,981 and 631,176.

  When the reducing agent used in the present invention has an aromatic hydroxyl group (-OH), particularly in the case of bisphenols, a non-reducing compound having a group capable of forming a hydrogen bond with these groups is used. It is preferable to use them in combination. Specific examples of particularly preferred hydrogen bonding compounds include, for example, compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937.

  The photothermographic material forms a photographic image by a heat development process, and may contain a toning agent for adjusting the color tone of silver, if necessary, usually in a state dispersed in an (organic) binder matrix. preferable.

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

  Imides (succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide, etc.); mercaptans (3-mercapto-1,2,4-triazole etc.); phthalazinone derivatives or metal salts of these derivatives (phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, 2,3-dihydro-1,4-phthalazinedione and the like; phthalazine and phthalic acids (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 derivative and its anhydride (phthalic acid, 4 -Without methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid Combination of at least one compound selected from the object).

  Particularly preferred toning agents are phthalazinone or a combination of phthalazine and phthalic acids and phthalic anhydrides.

(Fluorine surfactant)
In the present invention, the fluorine-based surfactant represented by the general formula (SF) is preferably used in order to improve film transportability and environmental suitability (accumulation in a living body) in a heat development processing apparatus.

  In the general formula (SF), examples of the substituent containing a fluorine atom represented by Rf include an alkyl group having 1 to 25 carbon atoms substituted with a fluorine atom (each of which is fluorine-substituted methyl, ethyl, butyl, octyl, dodecyl, Octadecyl or the like) or an alkenyl group substituted with a fluorine atom (such as fluorine-substituted propenyl, butenyl, nonenyl or dodecenyl).

Examples of the divalent linking group having no fluorine atom represented by L ₁ include an alkylene group (methylene, ethylene, butylene, etc.), an alkyleneoxy group (methyleneoxy, ethyleneoxy, butyleneoxy, etc.), an oxyalkylene group (oxymethylene , Oxyethylene, oxybutylene, etc.), oxyalkyleneoxy group (oxymethyleneoxy, oxyethyleneoxy, oxyethyleneoxyethyleneoxy, etc.), phenylene group, oxyphenylene group, phenyleneoxy group, oxyphenyleneoxy group, or these groups And the like.

  A represents an anion group or a base thereof, for example, a carboxylic acid group or a base thereof (sodium, potassium and lithium salt), a sulfonic acid group or a base thereof (sodium, potassium and lithium salt) and a phosphate group or a base thereof (sodium and potassium salt). Potassium salt) and the like.

  Examples of the trivalent or tetravalent linking group having no fluorine atom represented by Y include, for example, a group of atoms formed of a trivalent or tetravalent linking group having no fluorine atom and having a carbon atom or a nitrogen atom as a center. n1 represents an integer of 0 or 1, and is preferably 1.

  Fluorinated surfactants represented by the general formula (SF) include alkyl compounds having 1 to 25 carbon atoms into which a fluorine atom has been introduced (such as trifluoromethyl, pentafluoroethyl, perfluorobutyl, perfluorooctyl and perfluorooctadecyl). And an alkenyl compound (compound having perfluorohexenyl and perfluorononenyl), a tri- to hexa-valent alkanol compound to which no fluorine atom is introduced, an aromatic compound having 3 to 4 hydroxyl groups, or It is obtained by further introducing an anion group (A) into a compound (partially Rf-modified alkanol compound) obtained by an addition reaction or a condensation reaction with a hetero compound, by sulfate esterification or the like.

  Examples of the tri- to hexavalent alkanol compounds include glycerin, pentaerythritol, 2-methyl-2-hydroxymethyl-1,3-propanediol, 2,4-dihydroxy-3-hydroxymethylpentene, 1,2,6-hexane Triol, 1,1,1-tris (hydroxymethyl) propane, 2,2-bis (butanol) -3, aliphatic triol, tetramethylolmethane, D-sorbitol, xylitol, D-mannitol and the like can be mentioned. Examples of the aromatic compound and hetero compound having 3 to 4 hydroxyl groups include 1,3,5-trihydroxybenzene and 2,4,6-trihydroxypyridine.

  Preferred specific examples of the fluorine-based surfactant represented by the general formula (SF) are shown below.

  As a method for adding these fluorine-based surfactants to the coating solution, a known addition method can be used. That is, it can be added by dissolving in alcohols such as methanol and ethanol, ketones such as methyl ethyl ketone and acetone, and polar solvents such as dimethyl sulfoxide and dimethylformamide. Further, fine particles having a particle size of 1 μm or less can be formed by sand mill dispersion, jet mill dispersion, ultrasonic dispersion, or homogenizer dispersion, and dispersed in water or an organic solvent. Although many techniques have been disclosed as fine particle dispersion techniques, 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 is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ^{2, and} particularly preferably 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol. If it is less than the former range, the charging characteristics cannot be obtained, and if it exceeds the former range, the humidity dependency is large and the preservability under high humidity deteriorates.

  In the photothermographic material of the invention, the average particle size of the matting agent contained in the outermost surface on the side having the image forming layer is Le (μm), and the average particle size of the matting agent contained in the outermost surface on the side having the backcoat layer is provided. When the diameter is Lb (μm), Lb / Le is preferably from 1.5 to 10, and more preferably from 2.0 to 10. By controlling Lb / Le within this range, density unevenness during thermal development can be improved.

(Surface layer)
In the present invention, the object of the present invention is provided on the surface layer of the photothermographic material (even when a non-photosensitive layer is provided on the image forming layer side or on the opposite side of the image forming layer with the support interposed). In order to control the surface roughness, it is preferable to use an organic or inorganic powder as a matting agent. 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, cerium oxide, corundum, artificial diamond, and garnet. , Mica, silica, silicon nitride, silicon carbide, and the like. Examples of the organic powder include powders such as polymethyl methacrylate, polystyrene, and Teflon (R). Among these, preferred are 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. , SiO ₂ and α-Al ₂ O ₃ are preferred, and SiO ₂ is particularly preferred.

  In the present invention, the powder is preferably surface-treated with a Si compound or an Al compound. The use of such a surface-treated powder can improve the surface condition of the uppermost layer. 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 with respect to the powder, more preferably 0.1 to 5% by mass of Si. %, Al is 0.1 to 5% by mass, Si is preferably 0.1 to 2% by mass, and Al is preferably 0.1 to 2% by mass. Further, 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. In the present invention, the average particle size of the powder is the average diameter of the spherical powder, the average major axis length of the acicular powder, and the maximum diagonal length of the plate-like surface of the plate-like powder. Mean each value and can be easily obtained from measurement with 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 size of the organic or inorganic powder contained in the outermost layer on the photosensitive layer side is generally 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, and more preferably 2.0 to 5.0 μm. It is. The addition amount is usually from 1.0 to 20% by mass, preferably from 2.0 to 15% by mass, more preferably from 2.0 to 15% by mass, based on the binder amount (the curing agent is included in the binder amount) used in the outermost layer. Is 3.0 to 10% by mass.

  The average particle size of the organic or inorganic powder contained in the outermost layer on the side opposite to the photosensitive layer side with respect to the support is usually 2.0 to 15.0 μm, preferably 3.0 to 12.0 μm, Preferably it is 4.0 to 10.0 μm. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, more preferably 0.4 to 7% by mass, based on the amount of the binder used for the outermost layer (the curing agent is included in the amount of the binder). 0.6 to 5% by mass.

  The variation coefficient of the particle size distribution of the powder 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 dispersed in advance and applied, or a method in which the organic or inorganic powder is sprayed before the drying is completed after the application of the coating liquid. You may. When a plurality of types of powder are added, both methods may be used in combination.

(Supporting pair)
Examples of the material of the support used for the photothermographic material include various polymer materials, glass, wool cloth, cotton cloth, paper, and metal (aluminum, etc.). What can be processed into a sheet or a roll with a property is suitable. Accordingly, as the support in the photothermographic material of the present invention, a cellulose acetate film, a polyester film, a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polyamide film, a polyimide film, a cellulose triacetate film (TAC) or A plastic film such as a polycarbonate (PC) film is preferred, and a biaxially stretched PET film is particularly preferred. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  In order to improve the chargeability, a conductive compound such as a metal oxide and / or a conductive polymer can be included in the constituent layer. These may be contained in any layer, but are preferably contained in a backing layer, a surface protective layer on the photosensitive layer side, an undercoat layer and the like. Conductive compounds described in columns 14 to 20 of U.S. Pat. No. 5,244,773 are preferably used. In particular, in the present invention, the surface protective layer on the backing layer side preferably contains a conductive metal oxide. Thus, it was found that the effects of the present invention (particularly, transportability during thermal development processing) can be further improved.

Here, the conductive metal oxide is crystalline metal oxide particles, and those containing oxygen vacancies and those containing a small amount of heteroatoms forming a donor with respect to the metal oxide to be used are generally used. In particular, the latter is particularly preferable because it has high conductivity, and the latter is particularly preferable because it does not give fog to the silver halide emulsion. Examples of metal oxides include ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O _{5, and the} like, or a composite oxide thereof. ZnO, TiO ₂ and SnO ₂ are preferred. Examples of including heteroatoms include, for example, addition of Al and In to ZnO, addition of Sb, Nb, P, and a halogen element to SnO ₂ , and addition of Nb and Ta to TiO ₂ . Is effective. The addition amount of these different atoms is preferably in the range of 0.01 to 30 mol%, and particularly preferably 0.1 to 10 mol%. Further, a silicon compound may be added at the time of preparing the fine particles for improving the fine particle dispersibility and the transparency.

The metal oxide fine particles used in the present invention have conductivity, and have a volume resistivity of 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A-56-143431, JP-A-56-120519, and JP-A-58-62647. Furthermore, as described in JP-B-59-6235, a conductive material in which the above-mentioned metal oxide is adhered to other crystalline metal oxide particles or fibrous materials (such as titanium oxide) 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 easy to use. Use of conductive particles having a size of 0.3 μm or less to minimize the light scattering property is very preferable because a transparent photosensitive material can be formed. When the conductive metal oxide is acicular or fibrous, the length is preferably 30 μm or less and the diameter is preferably 1 μm or less, and particularly preferably the length is 10 μm or less and the diameter is 0.3 μm or less. The sa / 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 invention has at least one photosensitive layer as an image forming layer on a support. Although only the image forming layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the image forming layer. For example, a protective layer is preferably provided on the image forming layer for the purpose of protecting the image forming layer, and the opposite surface of the support is provided with a "sticking" between photosensitive materials or in a photosensitive material roll. Is provided with a back coat layer.

  As a binder used for the protective layer or the back coat layer, a polymer having a glass transition point (Tg) higher than that of the image forming layer and hardly causing abrasion and deformation, for example, a polymer such as cellulose acetate and cellulose acetate butyrate, It is selected from the above binders.

  In addition, two or more image forming layers may be provided on one side of the support, or one or more layers may be provided on both sides of the support, for gradation adjustment or the like.

(dye)
In the photothermographic material of the present invention, a filter layer is formed on the same side as or opposite to the image forming layer to control the amount or wavelength distribution of light transmitted through the image forming layer, or a dye is formed on the image forming layer. Alternatively, it is preferable to include a pigment.

  As the dye to be used, known compounds that absorb light in various wavelength regions according to the color sensitivity of the heat-developable material can be used. For example, when the photothermographic material is an image recording material using infrared light, a squarylium dye having a thiopyrylium nucleus as disclosed in JP-A-2001-83655 (referred to as a thiopyrylium squarylium dye in the present invention) And a squarylium dye having a pyrylium nucleus (hereinafter referred to as a pyrylium squarylium dye), or a thiopyrylium croconium dye similar to the squarylium dye or a pyrylium croconium dye.

  In addition, the compound having a squarylium nucleus is a compound having 1-cyclobuten-2-hydroxy-4-one in a molecular structure, and the compound having a croconium nucleus is a compound having 1-cyclopenten-2-hydroxy in a molecular structure. It is a compound having -4,5-dione. Here, the hydroxyl group may be dissociated. Hereinafter, in the present specification, these dyes are collectively referred to as squarylium dyes for convenience. As the dye, a compound described in JP-A-8-201959 is also preferable.

(Application of constituent layer)
The photothermographic material of the present invention is preferably formed by preparing a coating solution obtained by dissolving or dispersing the above-described constituent layer materials in a solvent, applying a plurality of these coating solutions simultaneously and then performing a heat treatment. . Here, the “multi-layer coating at the same time” means that a coating solution for each of the constituent layers (photosensitive layer, protective layer, etc.) is prepared, and when the coating solution is applied to the support, coating and drying are repeated for each layer individually. However, it does not mean that the respective constituent layers can be formed in a state where the steps of simultaneously performing the multi-layer coating and drying can be performed simultaneously. That is, the upper layer is provided before the remaining amount of all the solvents in the lower layer becomes 70% by mass or less.

  There is no particular limitation on the method of simultaneously applying a plurality of constituent layers in multiple layers, and for example, a known method such as a bar coater method, a curtain coat method, an immersion method, an air knife method, a hopper application method, or an extrusion application method may be used. Can be. Among them, a pre-metering type coating method called an extrusion coating method is more preferable. The extrusion coating method is suitable for precision coating and organic solvent coating since there is no volatilization on the slide surface unlike the slide coating method. Although this coating method has been described on the side having the photosensitive layer, the same applies to the case where the backcoat layer is provided and the coating is performed together with the undercoating. A detailed description of the simultaneous multilayer coating method for a photothermographic material is described in JP-A-2000-15173.

In the present invention, it is preferable to select an appropriate amount of silver according to the purpose of the photothermographic material. However, for the purpose of medical images, the amount is preferably 0.3 to 1.5 g / m ² . 5 to 1.5 g / m ² is more preferred. Of the coated silver amount, the amount derived from silver halide preferably accounts for 2 to 18% of the total silver amount, and more preferably 5 to 15%.

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

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

  When the coating is carried out under the above-mentioned conditions, a preferable result is obtained from the viewpoint of the optical maximum density of the silver image per a fixed amount of silver applied, 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 as to be 100 to 500 mg / m ² . As a result, a photothermographic material having high sensitivity, low fog, and high maximum density can be obtained.

  Examples of the solvent include those described in paragraph [0030] of JP-A-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 temperature conditions in a drying step or the like after the coating step. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

(Package)
When the photothermographic material is stored, it is preferable to store and store the photothermographic material in a package in order to prevent the density from changing over time and the occurrence of fogging. The porosity in the package is preferably from 0.01 to 10%, and more preferably from 0.02 to 5%. Nitrogen sealing is performed so that the partial pressure of nitrogen in the package is at least 80%, preferably at least 90%. Is good.

(Exposure of photothermographic material)
In the case of the photothermographic material, laser light is generally used when recording an image. In the present invention, it is desirable to use a light source appropriate for the color sensitivity imparted to the photosensitive material. For example, when the photosensitive material can be sensed by infrared light, the light-sensitive material can be applied to any light source in the infrared light range. From the standpoint of being able to do so, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

  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 laser beam and the exposure surface of the photosensitive material does not become substantially perpendicular.

  Here, "being substantially non-vertical" means that the angle is closest to vertical during laser beam scanning, preferably 55 to 88 degrees, more preferably 60 to 86 degrees, and still more preferably 65 to 84 degrees. , Most preferably 70-82 degrees.

  The beam spot diameter on the exposed surface of the photosensitive material when the laser beam is scanned on the photosensitive material is preferably 200 μm or less, more preferably 100 μm or less. It is preferable that the spot diameter is small in that the “shift angle” of the laser beam incident angle from the perpendicular can be reduced. Note that 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 occurrence of unevenness like interference fringes.

  Further, as a second method, it is preferable that the exposure is performed by using a laser scanning exposure machine that emits a scanning laser beam which is a vertical multi. Image quality deterioration such as generation of interference fringe-like unevenness is reduced as compared with the scanning laser beam in the longitudinal single mode. To achieve vertical multiplication, a method such as combining, using return light, or superimposing a high frequency is 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.

  Further, as a third aspect, it is preferable to form an image by scanning exposure using two or more laser beams. Such an image recording method using a plurality of laser beams is used in an image writing means of a laser printer or a digital copier which writes an image by a plurality of lines in one scan due to a demand for higher resolution and higher speed. This is known, for example, from Japanese Patent Application Laid-Open No. Sho 60-166916. This is a method in which laser light emitted from a light source unit is deflected and scanned by a polygon mirror, and an image is formed on a photoreceptor via an fθ lens or the like. Device.

  The image formation of the laser beam on the photoreceptor in the image writing means of the laser printer or the digital copier is performed by writing one image from a single laser beam for one line from the purpose of writing an image by a plurality of lines in one scan. The next laser light is imaged shifted. Specifically, the two light beams are close to each other at an interval of several tens of μm on the image plane in the sub-scanning direction, and have a print density of 400 dpi (dpi is the number of dots per inch = 2.54 cm). ), The pitch of the two beams in the sub-scanning direction is 63.5 μm, and 42.3 μm at 600 dpi. Unlike such a method in which the resolution is shifted in the sub-scanning direction, in the present invention, it is preferable to form an image by focusing two or more lasers at the same location on the exposure surface while changing the incident angle. At this time, the exposure energy on the exposure surface when writing with one ordinary laser beam (wavelength λ [nm]) is E, and the N laser beams used for exposure have the same wavelength (wavelength λ [nm]). ), When the exposure energy (En) is the same, the range is preferably 0.9 × E ≦ En × N ≦ 1.1 × E. By doing so, energy is secured on the exposed 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 generation of interference fringes is suppressed.

  In the above description, the wavelength of the plurality of laser beams is the same as that of λ, but those 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 image recording methods of the first, second and third aspects described above, as a laser used for scanning exposure, a well-known solid laser such as a ruby laser, a YAG laser, or a glass laser; Gas lasers such as Ne laser, Ar ion laser, Kr ion laser, CO2 laser, CO laser, He-Cd laser, N2 laser, excimer laser; InGaP laser, AlGaAs laser, GaAsP laser, InGaAs laser, InAsP laser, CdSnP2 laser, A semiconductor laser such as a GaSb laser; a chemical laser, a dye laser, or the like can be appropriately selected and used according to the intended use. Among them, a laser using a semiconductor laser having a wavelength of 600 to 1200 nm is used due to problems of maintenance and the size of a light source. Preferably, light is used. In the laser light used in a laser imager or a laser image setter, the beam spot diameter on the exposed surface of the photothermographic material when the material is scanned is generally 5 to 75 μm as a short axis diameter, and a long axis diameter. 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 by the sensitivity and laser power at the laser oscillation wavelength inherent to the photothermographic material.

(Heat development processing equipment)
The heat development processing apparatus according to the present invention includes a film supply unit represented by a film tray, a laser image recording unit, a heat development unit that supplies uniform and stable heat to the entire surface of the photothermographic material, and a film supply unit. And a transport section from the section through laser recording until the photothermographic material on which an image is formed by thermal development is discharged out of the apparatus. A specific example of the thermal development processing apparatus of this embodiment is shown in FIG.

  The thermal developing apparatus 100 includes a feeding unit 110 that feeds a sheet-like photothermographic material (also referred to as a photothermographic element or simply a film) one by one, an exposure unit 120 that exposes the fed film F, and an exposure unit. A developing unit 130 for developing the film F, a cooling unit 150 for stopping the development, and a stacking unit 160, a pair of supply rollers 140 for supplying the film F from a feeding unit, and for feeding the film to the developing unit. And a plurality of roller pairs, such as transport roller pairs 141, 142, 143, and 145, for smoothly transporting the film F between the respective units. The heat developing unit is a heating means for developing the film F. The heat drum 1 having a plurality of opposed rollers 2 that can be heated while being held almost in close contact with the outer periphery, and the peeling for peeling the developed film F and sending it to the cooling unit. It consists of nails 6 and the like.

  The transport speed of the photothermographic material is preferably in the range of 10 to 200 mm / sec.

  The development conditions of the photothermographic material vary depending on the equipment, apparatus, or means used, but typically, development is performed by heating the photothermographic material that has been imagewise exposed at a suitable high temperature. Things. The latent image obtained after exposure is heated at a moderately high temperature (about 80 to 200 ° C., preferably about 100 to 200 ° C.) for a sufficient time (generally about 1 second to about 2 minutes). Is developed.

  If the heating temperature is lower than 80 ° C., a sufficient image density cannot be obtained in a short time. Adversely affect. By heating, a silver image is generated by an oxidation-reduction reaction between an organic silver salt (functioning as an oxidizing agent) and a reducing agent. This reaction process proceeds without any supply of a processing liquid such as water from the outside.

  As a device, apparatus or means for heating, for example, a hot plate, an iron, a hot roller, a heating means typical of a heat generator using carbon or white titanium or the like may be used. More preferably, the heat-developable material provided with the protective layer may be subjected to a heat treatment by bringing the surface on the side having the protective layer into contact with a heating means, in order to perform uniform heating, and to improve heat efficiency and workability. From the viewpoint, it is preferable that the surface having the protective layer is conveyed while being brought into contact with a heat roller, subjected to heat treatment, and developed.

  Hereinafter, the present invention will be described in detail with reference to Examples, but embodiments of the present invention are not limited thereto. Unless otherwise specified, “%” in the examples represents “% by mass”.

Example 1
<Preparation of undercoated photographic support>
8 W / m ² · min on both sides of a commercially available biaxially stretched and heat-fixed PET film with a thickness of 175 μm and an optical density of 0.170 (measured with a Konica Densitometer PDA-65) with the following blue dye. On one side, the following undercoating coating solution a-1 is applied so as to have a dry film thickness of 0.8 μm, and dried to form an undercoating layer A-1. Then, the following undercoating coating solution b-1 was applied so as to have a dry film thickness of 0.8 μm and dried to obtain an undercoating layer B-1.

(Undercoating coating liquid a-1)
270 g of a copolymer latex solution of butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate (30/20/25/25% ratio) (solid content 30%)
(C-1) 0.6 g
Hexamethylene-1,6-bis (ethylene urea) 0.8 g
Finish to 1L with water (undercoating coating solution b-1)
Butyl acrylate / styrene / glycidyl acrylate (40/20 /
270 g of a copolymer latex liquid (solid content 30%) of 40%)
(C-1) 0.6 g
Hexamethylene-1,6-bis (ethylene urea) 0.8 g
Finish to 1L with water.

Subsequently, a corona discharge of 8 W / m ² · min. Was applied to the surface of the undercoat layer A-1 and the undercoat layer B-1, and the following undercoat upper layer coating solution a- 2 as an undercoating upper layer A-2 so as to have a dry film thickness of 0.1 μm, and the following undercoating upper layer coating solution b-2 on the undercoating layer B-1 so as to have a dry film thickness of 0.4 μm. Coating was performed as a lower drawing upper layer B-2 having an antistatic function.
(Undercoat upper layer coating solution a-2)
Gelatin 0.4 g / m ² (C-1) 0.2 g
(C-2) 0.2 g
(C-3) 0.1 g
Silica particles (average particle size 3 μm) 0.1 g
Finish to 1L with water (undercoating upper layer coating solution b-2)
60 g of Sb-doped SnO ₂ (SNS10M: manufactured by Ishihara Sangyo Co., Ltd.)
80 g of a latex liquid containing (C-4) as a component (solid content: 20%)
0.5 g of ammonium sulfate
(C-5) 12 g
6 g of polyethylene glycol (weight average molecular weight 600)
Finish to 1L with water.

<Preparation of coating liquid for back coat layer>
While stirring 830 g of methyl ethyl ketone (MEK), 84.2 g of cellulose acetate propionate (CAP482-20 manufactured by Eastman Chemical Company) and 4.5 g of a polyester resin (Bostic: VitelPE2200B) were added and dissolved. Next, 0.30 g of the following infrared dye 1 was added to the dissolved solution, and 4.5 g of a fluorine-based surfactant (Surflon KH40 manufactured by Asahi Glass Co., Ltd.) dissolved in 43.2 g of methanol and a fluorine-based surfactant were further added. 2.3 g (manufactured by Dainippon Ink and Chemicals, Inc .: Megafag F120K) was added, and the mixture was sufficiently stirred until dissolved. Next, 2.5 g of oleyl oleate was added. Lastly, 75 g of silica (manufactured by WR Grace: Syloid 64X6000) dispersed in MEK at a concentration of 1% with a dissolver-type homogenizer was added and stirred to prepare a backcoat layer coating solution.

<Preparation of backcoat layer protective layer (surface protective layer) coating solution>
Cellulose acetate propionate (10% MEK solution) 15 g
Monodisperse silica having a monodispersity of 15% (average particle size: 8 μm)
(Surface treatment with aluminum of 1% of the total mass of silica) 0.03 g
C ₈ F ₁₇ (CH ₂ CH ₂ O) ₁₂ C ₈ F ₁₇ 0.05 g
Fluorine surfactant (SF-17) 0.01g
0.1 g of stearic acid
Oleyl oleate 0.1g
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of photosensitive silver halide emulsion A>
(A1)
88.3 g of phenylcarbamoylated gelatin
10% methanol aqueous solution of compound (AO-1) 10 ml
Potassium bromide 0.32g
Finish to 5429 ml with water (B1)
0.67mol / L silver nitrate aqueous solution 2635ml
(C1)
Potassium bromide 51.55 g
1.47 g of potassium iodide
Finish to 660ml with water (D1)
Potassium bromide 151.6 g
7.67 g of potassium iodide
Potassium hexachloroiridate (IV) (1% aqueous solution) 0.93ml
K ₂ (IrCl ₆ )
Potassium hexacyanoferrate (II) 0.004g
Potassium hexachloroosmate (IV) 0.004g
Finish to 1982ml with water (E1)
0.4 mol / L aqueous potassium bromide solution Silver potential control amount below (F1)
Potassium hydroxide 0.71g
Finish to 20ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
(H1)
1.72 g of anhydrous sodium carbonate
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).

  Simultaneous mixing method using a mixing stirrer as disclosed in JP-B-58-58288, while controlling the 1/4 amount of the solution (B1) and the total amount of the solution (C1) in the solution (A1) at 20 ° C. and pAg 8.09. For 4 minutes 45 seconds to form nuclei. One minute later, the entire amount of the solution (F1) was added. During this time, pAg was adjusted appropriately using (E1). After a lapse of 6 minutes, a 3/4 amount of the solution (B1) and a total amount of the solution (D1) were added by a double jet method over 14 minutes and 15 seconds while controlling the pAg to 8.09 at 20 ° C. After stirring for 5 minutes, the temperature was lowered to 40 ° C., and the whole amount of the solution (G1) was added to precipitate a silver halide emulsion. The supernatant was removed except for 2000 ml of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was sedimented again. The supernatant was removed except for the sedimented portion of 1500 ml, and 10 L of water was further added. After stirring, the silver halide emulsion was sedimented. After removing the supernatant liquid leaving 1500 ml of the sedimented portion, 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 as to be 1161 g per 1 mol of silver, whereby photosensitive silver halide emulsion A was obtained.

  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: 3.5 mol%).

<Preparation of photosensitive silver halide emulsion B>
The preparation was performed in the same manner as in the preparation of the photosensitive silver halide emulsion A, except that the temperature at the time of addition by the double jet method was changed to 40 ° C. This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 50 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content: 3.5 mol%).

<Preparation of photosensitive silver halide emulsion C>
The preparation was performed in the same manner as in the preparation of the photosensitive silver halide emulsion A, except that the temperature at the time of addition by the double jet method was changed to 10 ° C. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 10 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content: 3.5 mol%).

<Preparation of photosensitive silver halide emulsion D>
The preparation was performed in the same manner as in the preparation of the photosensitive silver halide emulsion A, except that the temperature at the time of addition by the double jet method was changed to 5 ° C. This emulsion was monodispersed cubic silver iodobromide grains having an average grain size of 8 nm, a grain size variation coefficient of 12% and a [100] face ratio of 92% (AgI content: 3.5 mol%).

<Preparation of photosensitive silver halide emulsion E>
The preparation was performed in the same manner as in the preparation of the photosensitive silver halide emulsion A, except that the temperature at the time of addition by the double jet 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: 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 aqueous sodium hydroxide solution was added, 6.9 ml of concentrated nitric acid was added, and the mixture was cooled to 55 ° C. to obtain a fatty acid sodium solution. While maintaining the temperature of the above sodium fatty acid solution at 55 ° C., a photosensitive silver halide emulsion (types and addition amounts shown in Table 1) and 450 ml of pure water were added and stirred for 5 minutes.

  Next, 468.4 ml of a 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 thereto, and the mixture was stirred and allowed to stand. Then, the organic silver salt dispersion was floated and separated to remove lower water-soluble salts. After that, washing with deionized water and draining are repeated until the conductivity of the waste water becomes 2 μS / cm, and centrifugal dehydration is performed. The obtained organic silver salt in the form of a cake is then washed with a flash-type drier flash jet drier (Seishin). (Manufactured by a company) and dried under a nitrogen gas atmosphere and a hot air temperature at the dryer entrance until the water content became 0.1% to obtain a dried powdered organic silver salt A. Analysis of a photothermographic material sample 1 (described later) prepared using this organic silver salt using an electron microscope showed that the average particle size (equivalent diameter of circle) was 0.08 μm, the aspect ratio was 5, and the monodispersity was 10%. These were tabular grains.

  The moisture content of the organic silver salt composition was measured using an infrared moisture meter.

<Preparation of Preliminary Dispersion A>
As an image forming layer binder, 14.57 g of polyvinyl butyral containing SO ₃ K group (Tg 75 ° C., containing 0.2 mmol / g of —SO ₃ K group) was dissolved in 1457 g of MEK, and a dissolver DISPERMAT CA-40M manufactured by VMA-GETZMANN was used. Preliminary dispersion liquid A was prepared by gradually adding 500 g of the above-mentioned powdered organic silver salt A and stirring thoroughly while stirring with a mold.

<Preparation of photosensitive emulsion dispersion liquid 1>
Media type disperser DISPERMAT filled with 0.5 mm diameter zirconia beads (Toray Co., Ltd .: Treceram) so that the pre-dispersion liquid A has a residence time in a mill of 1.5 minutes using a pump so as to have an inner volume of 1.5 minutes. The emulsion was supplied to SL-C12EX type (manufactured by VMA-GETZMANN) and dispersed at a mill peripheral speed of 8 m / s to prepare a photosensitive emulsion dispersion liquid 1.

<Preparation of stabilizer liquid>
1.0 g of Stabilizer 1 and 0.31 g of potassium acetate were dissolved in 4.97 g of methanol to prepare a stabilizer solution.

<Preparation of infrared sensitizing dye solution A>
19.2 mg of infrared sensitizing dye, 1.488 g of 2-chlorobenzoic acid, 2.779 g of Stabilizer 2, and 365 mg of 5-methyl-2-mercaptobenzimidazole in 31.3 ml of MEK in the dark. After dissolution, an infrared sensitizing dye solution A was prepared.

<Preparation of additive liquid a>
A reducing agent (compounds and amounts shown in Table 1) and a compound represented by the general formula (YA) or a cyan chromogenic leuco dye (compounds and amounts shown in Table 1); 1.54 g of 4-methylphthalic acid; .48 g of the infrared dye 1 was dissolved in 110 g of MEK to prepare an additive liquid a.

<Preparation of additive liquid b>
1.56 g of an antifoggant 2, 0.5 g of an antifoggant 3, 0.5 g of an antifoggant 4, and 3.43 g of phthalazine were dissolved in 40.9 g of MEK to obtain an additive liquid b.

<Preparation of additive liquid c>
0.5 g of a silver saving agent (described in Table 1) was dissolved in 39.5 g of MEK to prepare an additive liquid c.

<Preparation of additive liquid d>
1 g of supersensitizer 1 was dissolved in 9 g of MEK to prepare an additive solution d.

<Preparation of additive liquid e>
1.0 g of potassium p-toluenethiosulfonate was dissolved in 9.0 g of MEK to prepare an additive solution e.

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

<Preparation of coating solution for image forming layer>
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion liquid 1 and 15.11 g of MEK were kept at 21 ° C. while stirring, and a chemical sensitizer S-5 (0.5% methanol solution) was added. 1000 μl was added, and 2 minutes later, 390 μl of antifoggant 1 (10% methanol solution) was added and the mixture was stirred for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added, and the mixture was stirred for 10 minutes. Then, a gold sensitizer Au-5 corresponding to 1/20 mol of the organic chemical sensitizer was added, and the mixture was further stirred for 20 minutes. . Subsequently, 167 ml 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 the mixture was further stirred for 30 minutes. While keeping the temperature at 13 ° C., 6.4 g of the additive solution d, 0.5 g of the additive solution e, 0.5 g of the additive solution f, and 13.31 g of the 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 the mixture was stirred for 15 minutes. While further stirring, 12.43 g of additive solution a, 1.6 ml of Desmodur N3300 / Mobay's aliphatic isocyanate (10% MEK solution), 4.27 g of additive solution b, and 4.0 g of additive solution c were added. The coating liquid for the image forming layer was obtained by sequentially adding and stirring.

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

<Preparation of image forming layer protective layer lower layer (surface protective layer lower layer)>
5 g of acetone
MEK 21g
2.3 g of cellulose acetate butyrate
7 g of methanol
Phthalazine 0.25g
Monodispersity 15% Monodisperse silica (average particle size: 3 μm) 0.140 g
(Surface treatment with aluminum of 1% of the total mass of silica)
CH ₂ ＣＨCHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH ＝ CH ₂ 0.035 g
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 0.01 g
Fluorine-based surfactant (SF-17: described above) 0.01 g
0.1 g of stearic acid
0.1 g of butyl stearate
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of upper layer of image forming layer protective layer (upper layer of surface protective layer)>
5 g of acetone
21 g of methyl ethyl ketone
2.3 g of cellulose acetate butyrate
7 g of methanol
Phthalazine 0.25g
Monodispersity 15% Monodisperse silica (average particle size: 3 μm) 0.140 g
(Surface treatment with aluminum of 1 mass% of the total mass of silica)
CH ₂ ＣＨCHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH ＝ CH ₂ 0.035 g
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 0.01 g
Fluorine-based surfactant (SF-17: described above) 0.01 g
0.1 g of stearic acid
0.1 g of butyl stearate
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of photothermographic material>
The backcoat layer coating solution and the backcoat layer protective layer coating solution prepared as described above were extruded onto the lower upper layer B-2 by a coater such that the dry film thickness became 3.5 μm, and the coating speed was 50 m / m. min. 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.

Simultaneous multilayer coating of the image forming layer coating solution and the image forming layer protective layer (surface protective layer) coating solution on an undercoating upper layer A-2 at an application speed of 50 m / min using an extrusion (extrusion) coater. As a result, photosensitive material samples 1 to 20 shown in Table 1 were produced. In the coating, the image forming layer had a coated silver amount of 1.2 g / m ² , and the image forming layer protective layer (surface protective layer) had a dry film thickness of 2.5 μm (the surface protective layer upper layer 1.3 μm, the surface protective layer lower layer 1. 2 μm), and then dried for 10 minutes using a drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

Sample 12 was the same as Sample 11 except that the fluorine-based activator of the protective layer for the back coat layer and the protective layer for the image forming layer (upper and lower layers) in Sample 11 was changed from SF-17 to C ₈ F ₁₇ SO ₃ Li. A sample was prepared in the same manner as described above.

As for Sample 13, SO ₃ K group-containing polyvinyl butyral (Tg 75 ° C., containing SO ₃ K at 0.2 mmol / g) was used as an image forming layer binder in the preparation of the preliminary dispersion A in Sample 11, instead of SO ₃ K. _A sample was prepared in the same manner as in Sample 11, except that polyvinyl butyral containing 3K group (Tg 65 ° C, containing 0.2 mmol / g of SO ₃ K) was used.

<Exposure and development processing>
The photothermographic material samples 1 to 21 produced as described above were processed into a half-cut size (34.5 cm × 43.0 cm), and then processed using the heat development processing apparatus shown in FIG. 1 in the following manner.

  After taking out the photothermographic material sample from the film tray and transporting it to the laser exposure section, from the image forming layer side, a vertical multi-mode semiconductor laser with a wavelength of 810 nm was superimposed by high-frequency superimposition (two lasers each having a maximum output of 35 mW per laser). (The combined output was set to a maximum output of 70 mW), and exposure was performed by laser scanning with an exposure machine using an exposure source. At this time, an image was formed at an angle of 75 degrees between the exposed surface of the photothermographic material and the exposed laser beam. Thereafter, the photothermographic material is conveyed to a photothermographic unit, and the heat drum is heated at 123 ° C. for 13.5 seconds so that the protective layer on the image forming layer side of the photothermographic material contacts the drum surface. After the processing, the photothermographic material was carried out of the apparatus. At this time, the conveying speed from the photosensitive material supply unit to the image exposing unit, the conveying speed in the image exposing unit, and the conveying speed in the heat developing unit were each set at 20 mm / sec. Exposure and development were performed in a room conditioned at 23 ° C. and 50% RH. Exposure was performed stepwise while decreasing the exposure energy by 0.05 logE for each step from the maximum output.

<Performance evaluation>
The following performance was evaluated for each of the thermally developed images.

《Image density》
The value of the highest density part of the image obtained under the above conditions was measured by a densitometer and indicated as image density.

《Average gradation》
The concentration of the obtained sensitometric sample was measured using a PDM65 transmission densitometer (manufactured by Konica Corporation), and the measurement result was processed by a computer to obtain a characteristic curve. The average gradation (Ga) value at an optical density of 0.25 to 2.5 was determined from this characteristic curve.

《Silver tone》
A chest X-ray image was printed on each photothermographic material sample, and the silver tone after processing was visually evaluated using a Shakasten. At this time, a wet-processed laser imager film manufactured by Konica Co., Ltd. was used as a standard sample, and the color tone relative to the standard sample was visually evaluated in 0.5 increments based on the following criteria.

5: Same color tone as the standard sample 4: Preferable color tone almost the same as the standard sample 3: Color tone slightly different from the standard sample but no practical problem 2: Color tone clearly different from the standard sample 1: Unpleasant color tone different from the standard sample << Light Irradiation Image Storage >>
After subjecting each photothermographic material sample to exposure and development in the same manner as described above, the sample was affixed on a sharksten having a luminance of 1000 lux and allowed to stand for 10 days. Was evaluated.

5: Almost no change 4: Slight change in color tone is observed 3: Partial change in color tone and increase in fog are observed 2: Part in color tone change and increase in fog are observed 1: Change in color tone and fog Table 1 also shows the results in which the density was significantly increased and strong density unevenness occurred on the entire surface.

TPT: triphenyltetrazolium *: 1-10 / b = 4.20 / 23.78
**: 1-10 / b / c = 4.20 / 11.89 / 11.89

  From Table 1, it is apparent that the photothermographic material of the present invention has a higher density, a better silver tone, and a better storage stability of light-irradiated images than the comparative photothermographic material.

  In addition, when comparing Samples 11 and 12, it was found that Sample 11 had more excellent transportability and environmental suitability (accumulation in vivo). Also, comparing Samples 11 and 13, it was found that Sample 11 had better characteristics with respect to image storability during high-temperature storage. Further, when comparing Samples 20 and 1, it was found that Sample 20 is superior in that an image having a more stable density can be obtained even when a temperature change occurs during thermal development.

FIG. 2 is a diagram illustrating an example of a heat development processing apparatus for processing the heat development photosensitive material of the present invention.

Explanation of reference numerals

REFERENCE SIGNS LIST 1 heat drum 2 opposed roller 6 peeling claw 100 thermal developing device 110 feed unit 120 exposure unit 130 developing unit 140 supply roller pair 141, 142, 143, 145 transport roller pair 144 supply roller pair 150 cooling unit 160 stacking unit F film C Film tray L Laser beam

Claims (11)

In a photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, the silver halide contains silver halide grains having an average grain size of 10 to 50 nm. And a photothermographic material, wherein the reducing agent is a compound represented by the following general formula (1), and further contains a cyan coloring leuco dye.

[In the formula, X represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group. R ₂ represents an alkyl group, which may be the same or different, at least one of which is a secondary or tertiary alkyl group. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a group that can be substituted on the benzene ring, and m and n each represent an integer of 0 to 2. ] 2. The photothermographic material according to claim 1, wherein the compound represented by the general formula (1) has a hydroxyl group or an alkyl group having a precursor group thereof. 3. The photothermographic material according to claim 1, wherein the surface having the image forming layer contains a compound represented by the following general formula (YA).

[Wherein, 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 represent a 2-hydroxyphenylmethyl group. Never be. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on a benzene ring. ] An image obtained by thermal development at a development temperature of 123 ° C. and a development time of 13.5 seconds has a characteristic curve shown on orthogonal coordinates where the diffusion density (Y axis) and the unit length of the common logarithmic exposure (X axis) are equal. The heat development according to any one of claims 1 to 3, wherein an average gradation in a range of 0.25 to 2.5 in optical density with diffused light is 2.0 to 4.0. Photosensitive material. The surface having the image forming layer contains at least one silver-saving agent selected from a vinyl compound, a hydrazine derivative, a silane compound and a quaternary onium salt. Item 2. The photothermographic material according to item 1. The photothermographic material according to any one of claims 1 to 5, wherein the binder has a glass transition temperature (Tg) of 70 to 150 ° C. The photothermographic material according to any one of claims 1 to 6, further comprising a compound represented by the following general formula (SF).
Formula (SF) (Rf- (L) n1 -) p - (Y) m1 - (A) q
[Wherein, Rf represents a substituent having a fluorine atom, L represents a divalent linking group having no fluorine atom, Y represents a divalent to tetravalent linking group having no fluorine atom, and A represents an anion. Represents a group or its base. m1 and n1 each represent an integer of 0 or 1, and p and q each represent an integer of 1 to 3. However, when q is 1, n1 and m1 do not become 0 at the same time. ] 8. The photothermographic material according to claim 1, wherein the silver halide further contains silver halide grains having an average grain size of 55 to 100 nm. 9. The photothermographic material according to claim 1, wherein the silver halide contains silver halide grains chemically sensitized with a chalcogen compound. The photothermographic material of any one of claims 1 to 9, wherein the amount of silver contained in the image forming layer is 0.3 to 1.5 g / m ^2. The heat-developable photosensitive material according to any one of claims 1 to 10, wherein the heat-development unit is used to transport the heat-developable photosensitive material at a transport speed of 10 to 200 mm / sec between the photosensitive material supply unit and the image exposure unit. An image forming method, wherein heat development is performed at a transport speed of 10 to 200 mm / sec and at a transport speed of 10 to 200 mm / sec in an image exposure unit.

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