JP2005300951A - Heat developable photosensitive material and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material excellent in silver tone, density unevenness and conveyability in heat development as well as in image preservability under photoirradiation, ensuring small fog even in storage at high temperature, and excellent also in image preservability in storage at high temperature or in film conveyability and environmental adaptation, and to provide an image forming method. <P>SOLUTION: In the heat developable photosensitive material having on a support an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent, ≥50 mass% of the binder in the image forming layer is a water-soluble binder and the silver halide is silver halide grains whose surface sensitivity lowers after heat development by conversion from surface latent image type grains to internal latent image type grains in a heat developing process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, and an image forming method.

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

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

  This heat-developable material is usually processed by a heat-development processing apparatus called a heat-development processor that applies stable heat to the heat-developable material to form an image. As described above, with the rapid spread in recent years, a large amount of this heat development processing apparatus has been supplied to the market. However, depending on the temperature and humidity conditions during the heat development processing, the slipping property between the photosensitive material and the transport roller or processing member of the heat development processing apparatus changes, resulting in the problem of poor transport and uneven density. It was. There is also a problem that the density of the photothermographic material varies with time. It has been found that these phenomena occur remarkably in a photothermographic material that forms an image by thermal development after image exposure with a laser beam. In recent years, there has been a demand for a compact laser imager and rapid processing.

For this purpose, it is essential to improve the characteristics of the photothermographic material. In order to obtain a sufficient density of the photothermographic material even if rapid processing is performed, a silver halide having a small average grain size as disclosed in JP-A-11-295844 and JP-A-11-352627 The covering power is increased by increasing the number of color development points using, a highly active reducing agent having a secondary or tertiary alkyl group as disclosed in JP-A-2001-209145, a hydrazine compound or a vinyl compound. It is effective to use a development accelerator such as a phenol derivative or a naphthol derivative. In recent years, attempts have been made to reduce the size of the apparatus using a blue laser in order to make the laser imager compact. (For example, see Patent Document 1)
On the other hand, in the photothermographic material using photosensitive silver halide, since silver halide remains in the emulsion layer even after heat development, there is a problem that the preservability of light-irradiated image is deteriorated. Has been tried. (For example, see Patent Documents 2 and 3)
European Patent No. 1276007 (Claims) JP 2003-270755 A (Claims) JP 2004-004522 A (Claims)

  However, when the apparatus is downsized, there is a problem that conveyance failure and density unevenness occur. Moreover, although the light irradiation image storability can be improved to some extent by the techniques of Patent Documents 1 to 3, there is a problem that the silver tone is deteriorated.

  The present invention has been made in view of the above problems, and the object of the present invention is excellent in light-irradiated image storage stability, and at the same time, excellent in silver tone, density unevenness during heat development and transportability, and stored at high temperature. An object of the present invention is to provide a photothermographic material and an image forming method having a small fog. It is another object of the present invention to provide an image forming method that is further excellent in image storability during high-temperature storage or excellent in film transportability and environmental suitability.

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

(Claim 1)
In the photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, 50 to 100% by mass of the binder of the image forming layer is a water-soluble binder, A photothermographic material, wherein the silver halide grains are silver halide grains whose surface sensitivity is lowered from that before heat development by converting the surface latent image type to the internal latent image type in the heat development process.

(Claim 2)
Sensitivity obtained based on a characteristic curve obtained when the photothermographic material is exposed to white light or light in a specific spectral sensitization region through an optical wedge for a certain period of time and then heat-developed under normal heat-development conditions. Is obtained on the basis of a characteristic curve obtained by heating under the same conditions as the heat development conditions before exposure, followed by exposure with white light or light in a specific spectral sensitization region for a certain period of time, and further heat development. 2. The photothermographic material according to claim 1, wherein the sensitivity is 1/10 or less.

(Claim 3)
3. The photothermographic material according to claim 1, wherein the silver halide grains contain therein a dopant that functions as an electron trap after at least thermal development.

(Claim 4)
The spectral sensitizing dye is adsorbed on the surface of the silver halide grains to be spectrally sensitized, and the effect of the spectral sensitization substantially disappears after the thermal development process. The photothermographic material according to any one of 1 to 3.

(Claim 5)
The surface of the silver halide grain is chemically sensitized, and the effect of the chemical sensitization substantially disappears after the thermal development process. The photothermographic material described in 1.

(Claim 6)
The surface of the silver halide grain is chemically sensitized, spectrally sensitized by adsorbing a spectral sensitizing dye, and the chemical sensitization and spectral sensitization after the thermal development process. The photothermographic material according to claim 1, wherein the effect is substantially lost.

(Claim 7)
In the photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, 50 to 100% by mass of the binder of the image forming layer is a water-soluble binder, A photothermographic material, wherein the silver halide contains 5 to 100 mol% of silver iodide.

(Claim 8)
8. The photothermographic material according to claim 7, wherein the silver halide contains 40 to 100 mol% of silver iodide.

(Claim 9)
The average particle size of the largest average particle size of the matting agent contained in the image forming layer side across the support is Le (μm), and is contained in the layer opposite to the image forming layer across the support. The average particle size of the matting agent having the largest average particle size is Lb (μm), and Lb / Le is 2.0 to 10.0. The photothermographic material according to claim 1.

(Claim 10)
When the ten-point average roughness of the outermost surface on the image forming layer side is Rz (E) and the ten-point average roughness of the outermost surface on the opposite side of the image forming layer across the support is Rz (B), 10. The photothermographic material according to claim 1, wherein the value of Rz (E) / Rz (B) is 0.10 to 0.70.

(Claim 11)
An image forming method comprising heat-developing the photothermographic material according to any one of claims 1 to 10 at a conveying speed of a heat developing unit of 20 to 200 mm / sec using a heat developing apparatus. .

(Claim 12)
An image forming method, wherein the photothermographic material according to claim 1 is exposed using a laser whose exposure light source has an emission peak intensity at 350 nm to 450 nm.

That is, when the present invention improves the storage stability of light-irradiated image, the deterioration of silver tone, the fog rise at high temperature storage, and the density unevenness at the time of thermal development, which becomes a problem when the apparatus is downsized, As a result of various studies to improve the conveyance failure,
1) 50% by mass or more of the binder of the image forming layer is a water-soluble binder, and the silver halide grains are converted from the surface latent image type to the internal latent image type in the heat development process, so that the surface sensitivity is higher than that before the heat development. The silver halide grains are lowered,
2) 50% by mass or more of the binder of the image forming layer is a water-soluble binder, and the silver halide contains 5 to 100 mol% of silver iodide,
Thus, the inventors have found that the above object of the present invention can be achieved, and have reached the present invention.

  Further, it has also been found that the transportability and density unevenness at the time of rapid thermal development processing can be improved by adopting the constitutions of claims 9 and 10.

  The photothermographic material and the image forming method according to the present invention are excellent in light-irradiated image storage stability, silver tone, excellent density unevenness during heat development and transportability, and have excellent effects with small fog even during high-temperature storage. Furthermore, it has excellent image storability during high-temperature storage, or has excellent effects in film transportability and environmental suitability.

  Hereinafter, the present invention will be described in more detail.

  The components of the present invention will be described sequentially.

(Organic silver salt)
The organic silver salt in the present invention is relatively stable to light, but when heated to 80 ° C. or higher in the presence of exposed photosensitive silver halide and a reducing agent, a silver ion supplier Function as a silver image.
In addition to silver behenate, any organic substance capable of supplying silver ions that can be reduced by a reducing agent may be included as an organic silver salt. As for such non-photosensitive organic silver salt, paragraph numbers 0048 to 0049 of JP-A-10-62899, page 18 line 24 to page 19 line 37 of European Patent Publication No. 0803764A1, European Patent Publication. No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, and the like. Of these, silver salts of organic acids, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30 carbon atoms, preferably 15 to 28 carbon atoms) are preferred. Preferred examples of the fatty acid silver salt include lignoceric acid, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver erucate and the like. Including mixtures.

  In the present invention, when an organic silver salt having a silver behenate content of 40 mol% or more and 99 mol% or less is used, the characteristics regarding image storability, heat development activity and rapidity are good. Preferably they are 50 mol% or more and 95 mol% or less, More preferably, they are 60 mol% or more and 90 mol% or less, More preferably, they are 65 mol% or more and 85 mol% or less. In particular, in a design that emphasizes image storability, the silver behenate content is preferably 70 mol% or more and 99 mol% or less, and more preferably 80 mol% or more and 99 mol% or less. In a design that emphasizes heat development activity and rapidity, the silver behenate content is preferably 50 mol% or more and 85 mol% or less, and more preferably 55 mol% or more and 80 mol% or less. Further, the silver erucate content is preferably 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0.1 mol% or less.

  There is no restriction | limiting in particular as a shape of the organic silver salt in this invention, Any of needle shape, rod shape, flat plate shape, and flake shape may be sufficient.

  In the present invention, scaly organic silver salts are preferred. Also, short needle-shaped, rectangular parallelepiped, cubic or potato-shaped amorphous particles having a major axis / uniaxial length ratio of 5 or less are preferably used. These organic silver particles have a feature that there is less fog at the time of thermal development than long needle-like particles having a ratio of the major axis to the uniaxial length of 5 or more. In particular, particles having a major axis / uniaxial ratio of 3 or less are preferable because the mechanical stability of the coating film is improved.

  In the present invention, the scaly organic silver salt is defined as follows. The organic acid silver salt was observed with an electron microscope, the shape of the organic acid silver salt particle was approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped were designated a, b, and c from the shortest side (c was the same as b). May be calculated with the shorter numerical values a and b, and x is obtained as follows.

x = b / a
In this way, x is obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of x (average) ≧ 1.5 are defined as flakes. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 15 ≧ x (average) ≧ 1.5. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

  In the flake shaped particle, a can be regarded as a thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 μm to 0.30 μm, more preferably 0.1 μm to 0.23 μm. The average of c / b is preferably 1 to 6, more preferably 1 to 4, still more preferably 1 to 3, and particularly preferably 1 to 2.

  The particle size distribution of the organic silver salt is preferably monodispersed. The monodispersion is preferably 100% or less, more preferably 80% or less, and still more preferably 50% of the value obtained by dividing the standard deviation of the lengths of the short axis and the long axis by the short axis and the long axis, respectively. % Or less. The method for measuring the shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion.

  As another method for measuring monodispersity, there is a method for obtaining the standard deviation of the volume weighted average diameter of the organic silver salt, and the percentage (variation coefficient) of the value divided by the volume weighted average diameter is preferably 100% or less, more Preferably it is 80% or less, More preferably, it is 50% or less. As a measuring method, a commercially available laser light scattering type particle size measuring device can be used. This measurement method can also be used for other particle size measurements described below.

  A known method or the like can be applied to the production of organic acid silver and the dispersion method thereof in the present invention. For example, Japanese Patent Application Laid-Open No. 10-62899, European Patent Publication No. 0803763A1, European Patent Publication No. 0968212A1, Japanese Patent Application Laid-Open No. 11-349591, Japanese Patent Application Laid-Open No. 2000-7683, Japanese Patent Application No. 2000-72711, Japanese Patent Application No. 11-348228. -30, 11-203413, Japanese Patent Application 2000-90093, 2000-195621, 2000-191226, 2000-213813, 2000-214155, 2000-191226, etc. can do.

The organic silver salt of the present invention can be used in a desired amount, preferably 0.1-5 g / m ² as silver amount, more preferably from 1 to 3 g / m ^2. Particularly preferred is 1.2 to 2.5 g / m ² .

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

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

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

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

  For example, when performing a method in which nucleation and particle growth are performed separately, first, an aqueous silver salt solution and an aqueous halide solution are uniformly and rapidly mixed in an aqueous gelatin solution to produce nuclei (seed particles) (nucleation process). Then, silver halide grains are prepared by a grain growth process in which grains are grown while supplying an aqueous silver salt solution and an aqueous halide solution under controlled pAg, pH, and the like. After the formation of grains, a desired silver halide emulsion can be obtained by removing unnecessary salts and the like by a desalting step by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, or an electrodialysis method. .

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

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

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

  There is no particular limitation on the crystal habit on the outer surface of the silver halide grain, but when using a sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the sensitizing dye on the surface of the silver halide grain. It is preferable to use silver halide grains having a relatively high proportion of crystal habits adapted to the selectivity.

  For example, when using a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100], the proportion of the [100] face on the outer surface of the silver halide grain is preferably high, and this ratio is 50 % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani, J .; Imaging Sci. 29, 165 (1985).

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

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

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

  For the silver halide grains in the present invention, it is preferable to use a compound represented by the following general formula when the grains are formed.

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

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

  The polyethylene oxide compound represented by the above general formula may be present at the time of nucleation and is preferably added in advance to the dispersion medium before nucleation, but may be added during nucleation or You may add and use for the silver salt aqueous solution and halide aqueous solution which are used at the time of formation. Preferably, it is used by adding 0.01 to 2.0% by mass to the halide aqueous solution or both aqueous solutions.

  Further, the compound represented by the above general formula is preferably present for a time of at least 50% of the nucleation step, and more preferably for a time of 70% or more. The compound represented by the above general formula may be added as a powder or dissolved in a solvent such as methanol.

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

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

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

  In the present invention, the average grain size of silver halide is usually 10 to 50 nm, preferably 10 to 40 nm, and more preferably 10 to 35 nm. If the average grain size of the silver halide is smaller than 10 nm, the image density may be lowered, or the light irradiation image storage stability may be deteriorated. On the other hand, if it exceeds 50 nm, the image density may decrease.

  The average grain size referred to here means the length of the edge of the silver halide grain when the silver halide grain is a cubic or octahedral so-called normal crystal. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface. In addition, when it is not a normal crystal, for example, in the case of spherical particles, rod-like particles, etc., the diameter when considering a sphere equivalent to the volume of silver halide grains is calculated as the grain size. The measurement was performed using an electron microscope, and the average particle size was determined by averaging the measured values of 300 particle sizes.

  Further, in the present invention, by using silver halide grains having an average grain size of 55 to 100 nm and silver halide grains having an average grain size of 10 to 50 nm in combination, image density can be improved, or time-lapse image. The decrease in density can be improved (smaller). The ratio (mass ratio) of silver halide grains having an average grain size of 10 to 50 nm and silver halide grains having an average grain size of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90. : 10-60: 40.

(Silver halide having a silver iodide content of 5 to 00 mol%)
As for the halogen composition, the silver halide content of the present invention preferably has a silver iodide content of 5 mol% or more and 100 mol% or less. If the silver iodide content is in this range, the intragranular halogen composition distribution may be uniform, may change stepwise, or may change continuously.

  Further, silver halide grains having a core / shell structure having a high silver iodide content inside and / or on the surface can also be preferably used. A preferable structure is a 2- to 5-fold structure, more preferably 2- to 4-fold core / shell particles. The preferred silver iodide content of the emulsion used in the present invention is 10 to 100 mol% with respect to the amount of silver halide. More preferably, it is 40-100 mol%, More preferably, it is 70-100 mol%, Most preferably, it is 90-100 mol%.

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

(Inner latent type silver halide grains after heat development)
The photosensitive silver halide grain of the present invention is a silver halide grain whose surface sensitivity is lowered by converting from a surface latent image type to an internal latent image type by heat development. That is, in the exposure before thermal development, a latent image that can function as a catalyst for a development reaction (reduction reaction of silver ions by a silver ion reducing agent) is formed on the surface of the silver halide grains, and the exposure after the thermal development process has passed. Then, since many latent images are formed inside the surface of the silver halide grains, the silver halide grains are characterized in that the formation of latent images on the surface is suppressed. It has not been known in the past to use silver halide grains whose latent image forming function greatly changes before and after the heat development processing as a dry imaging material.

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

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

  On the contrary, when there are more chemical sensitization centers (chemical sensitization nuclei) and dopants effective as electron traps in the inside than the silver halide grain surface, a latent image is preferentially formed inside, and the surface Development becomes difficult. In other words, in the former case, the surface sensitivity is higher than in the interior, and in the latter case, it can be said that the surface sensitivity is lower than in the interior (reference: (1) edited by TH James, “The Theory of the Photographic Process”. “Fourth Edition, Macmillan Publishing Co., Ltd. 1977, (2) The Japan Photographic Society,“ Revised Photographic Engineering Basics (Silver Salt Photography) ”, Corona, 1998).

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

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

  The electron trapping dopant used here is an element or compound other than silver and halogen constituting silver halide grains, and the dopant itself has a property of trapping (capturing) free electrons, or the dopant is halogen. It is the one in which a site such as an electron trapping lattice defect is generated by being contained in a silver halide grain. For example, a metal ion other than silver or a salt or complex thereof, a chalcogen (oxygen group element) such as sulfur, selenium or tellurium, or an inorganic compound or organic compound containing a nitrogen atom or a metal complex thereof, a rare earth ion or a complex thereof, etc. Can be mentioned.

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

  As the compound containing chalcogen such as sulfur, selenium, and tellurium, various chalcogen-releasing compounds generally known as chalcogen sensitizers in the photographic industry can be used. Moreover, as an organic substance containing chalcogen or nitrogen, a heterocyclic compound is preferable. For example, imidazole, pyrazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, indazole, purine, thiadiazole, oxadiazole, quinoline, phthalazine, naphthyridine, quinoxaline, quinazoline, cinnoline, pteridine, acridine, phenanthroline, phenazine, Tetrazole, thiazole, oxazole, benzimidazole, benzoxazole, benzthiazole, indolenine, tetrazaindene, preferably imidazole, pyridine, pyrimidine, pyrazine, pyridazine, triazole, triazine, thiadiazole, oxadiazole, quinoline, phthalazine, Naphthyridine, quinoxaline, quinazoline, cinnoline, tetrazole, thiazole, o Sasol, benzimidazole, benzoxazole, benzthiazole, a tetrazaindene.

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

  The silver halide grains in the present invention belong to groups 6 to 11 of the periodic table so that they function as electron trapping dopants as in the above dopants or as hole trapping dopants. Transition metal ions may be contained by chemically adjusting the oxidation state of the metal with a ligand. As the transition metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, and Pt are preferable.

  In the present invention, the above various dopants may be used alone or in combination of two or more of the same or different compounds or complexes. However, at least one kind needs to function as an electron trapping dopant at the time of exposure after thermal development. These dopants may be introduced into the silver halide grains in any chemical form.

  In the present invention, an embodiment in which any one of Ir or Cu complex or salt is used alone is not preferable.

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

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

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

General formula [ML ₆ ] ^m
In the formula, M represents a transition metal selected from Group 6 to 11 elements in the periodic table, L represents a ligand, and m represents 0,-, 2-, 3-, or 4-. Specific examples of the ligand represented by L include halogen ions (for example, fluorine ion, chlorine ion, bromine ion, iodine ion), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, azide and aquo. Each ligand includes nitrosyl, thionitrosyl, and the like, preferably aco, nitrosyl, thionitrosyl, and the like. When an acoligand is present, it preferably occupies one or two of the ligands. L may be the same or different.

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

  These metal compounds can be added by dissolving in water or an appropriate organic solvent (for example, alcohols, ethers, glycols, ketones, esters, amides). A method in which an aqueous solution or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to a water-soluble silver salt solution or a water-soluble halide solution during particle formation, or the silver salt solution and the halide solution are mixed simultaneously. When adding a third aqueous solution, a method of preparing silver halide grains by a method of simultaneous mixing of three liquids, a method of introducing an aqueous solution of a required amount of a metal compound into a reaction vessel during grain formation, or a silver halide preparation There is a method of adding and dissolving another silver halide grain that has been previously doped with metal ions or complex ions. In particular, a method of adding an aqueous solution of a metal compound powder or an aqueous solution in which a metal compound and NaCl, KCl are dissolved together is added to the water-soluble halide solution. When added to the particle surface, a required amount of an aqueous solution of a metal compound can be charged into the reaction vessel immediately after the formation of the particle, during or after physical ripening, or at the time of chemical ripening.

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

  In the photothermographic material of the present invention, whether or not the above dopant has an electron trapping property can be evaluated by a method generally used in the photographic industry as follows.

  That is, a silver halide emulsion comprising silver halide grains doped with the above-mentioned dopant or a decomposition product thereof in silver halide grains is subjected to a photoconductivity measurement by a microwave photoconductivity measurement method or the like, and the halogenation does not contain a dopant. It can be evaluated by measuring the degree of decrease in photoconduction with a silver grain emulsion as a reference. Alternatively, it can be performed by a comparative experiment of the internal sensitivity and surface sensitivity of the silver halide grains.

  Alternatively, the method for evaluating the effect of the electron trapping dopant in the present invention after preparing a photothermographic material is, for example, heating the photothermographic material under the same conditions as normal practical heat development conditions before exposure. Then, for a certain period of time (for example, 30 seconds), white light or light in a specific spectral sensitization region (when spectral sensitization is performed on laser light in a specific wavelength region, When spectral sensitization is applied to infrared light, infrared light) is exposed through an optical wedge, and further subjected to thermal development under the same thermal development conditions, resulting in a characteristic curve (sensitometry curve). The sensitivity obtained based on this can be evaluated by comparing with the sensitivity of the imaging material using the silver halide grain emulsion not containing the electron trapping dopant.

  That is, it is necessary to confirm that the sensitivity of the former sample containing the silver halide grain emulsion containing the dopant in the present invention is lower than the sensitivity of the latter sample not containing the dopant.

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

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

  The silver halide grains of the present invention are prepared in advance and added to a solution for preparing aliphatic carboxylic acid silver salt grains to prepare a silver halide grain preparation step and aliphatic carboxylic acid silver salt grain preparations. Although the process can be handled separately and is most preferable in terms of production control, as described in British Patent No. 1,447,454, when preparing aliphatic carboxylic acid silver salt particles, such as halide ions By making a halogen component coexist with an aliphatic carboxylate silver salt-forming component and injecting silver ions into this, silver halide grains produced almost simultaneously with the production of aliphatic carboxylate silver salt particles can also be used in combination. .

  It is also possible to prepare silver halide grains by converting a halogen-containing compound to an aliphatic carboxylic acid silver salt and converting the aliphatic carboxylic acid silver salt, and use the silver halide grains in combination.

  That is, a silver halide-forming component is allowed to act on a solution or dispersion of an aliphatic carboxylic acid silver salt prepared in advance, or a sheet material containing the aliphatic carboxylic acid silver salt, so that a part of the aliphatic carboxylic acid silver salt is removed. It can also be converted to photosensitive silver halide.

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

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

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

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

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

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

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

  As a method for chemical sensitization, techniques according to various chemical sensitization techniques conventionally used in the production of conventional silver halide light-sensitive materials for wet processing can be used (reference: (1) T Edited by H. James “The Theory of the Photographic Process” 4th edition, Macmillan Publishing Co., Ltd., 1977, (2) The Japan Photographic Society, “Basics of Photographic Engineering (Silver Salt Photography), Corona, 1979) In particular, when the silver halide grain emulsion is previously chemically sensitized and then mixed with non-photosensitive organic silver salt grains, it can be chemically sensitized by a conventional method.

The amount of the chalcogen compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, etc., but is 10 ⁻⁸ to 10 ⁻ per mol of silver halide. ² mol is preferred, more preferably 10 ⁻⁷ to 10 ⁻³ mol. The environmental conditions for chemical sensitization are not particularly limited, but in the presence of a compound capable of annihilating or reducing the size of silver chalcogenide or silver nuclei on photosensitive silver halide grains. In particular, it may be preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei. The sensitizing conditions in this case are preferably 6 to 11 as pAg, more preferably 7 to 10, pH 4 to 10, more preferably 5 to 8, and the temperature increases at 30 ° C. or lower. It is preferable to give a feeling.

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

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

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

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

The amount of the heterocyclic ring containing compound will vary over a wide range depending on the size and composition of silver halide grains, the approximate amount 10 in an amount per mol of silver halide ^- The range is from ⁶ to 1 mol, and preferably from 10 ⁻⁴ to 10 ⁻¹ mol.

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

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

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

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

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

  Useful sensitizing dyes used in the present invention include, for example, Research Disclosure (hereinafter abbreviated as RD) 17643IV-A (December 1978 p.23), RD18431X (August 1978 p.437). It is described in the literature described or cited. In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light sources of various laser imagers and scanners. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

  Useful cyanine dyes are, for example, cyanine dyes having basic nuclei such as thiazoline nucleus, oxazoline nucleus, pyrroline nucleus, pyridine nucleus, oxazole nucleus, thiazole nucleus, selenazole nucleus and imidazole nucleus. Useful merocyanine dyes are preferably acidic nuclei such as thiohydantoin nucleus, rhodanine nucleus, oxazolidinedione nucleus, thiazolinedione nucleus, barbituric acid nucleus, thiazolinone nucleus, malononitrile nucleus and pyrazolone nucleus in addition to the basic nuclei described above. Including.

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

  In the photothermographic material of the present invention, the sensitizing dye represented by the following general formula (SD-1) and the following general formula (SD-2) as described in Japanese Patent Application No. 2003-102726 are used. It is preferable to select and contain at least one selected from the sensitizing dyes represented.

[Wherein, Y ₁ and Y ₂ each represent an oxygen atom, a sulfur atom, a selenium atom, or a —CH═CH— group, and L _{1 to} L ₉ each represent a methine group. R ₁ and R ₂ each represents an aliphatic group. R ₃ , R ₄ , R ₂₃ and R ₂₄ each represent a lower alkyl group, a cycloalkyl group, an alkenyl group, an aralkyl group, an aryl group, or a heterocyclic group. W ₁ , W ₂ , W ₃ , and W ₄ are each a hydrogen atom, a substituent, or a nonmetallic atom necessary for bonding between W ₁ and W ₂ , W ₃ and W ₄ to form a condensed ring. Represents a group. Or R ₃ and W ₁ , R ₃ and W ₂ , R ₂₃ and W ₁ , R ₂₃ and W ₂ , R ₄ and W ₃ , R ₄ and W ₄ , R ₂₄ and W ₃ , R ₂₄ and W ₄ Represents a group of non-metallic atoms necessary to form a 5-membered or 6-membered condensed ring by bonding. X ₁ represents an ion necessary for canceling the charge in the molecule, and k 1 represents the number of ions necessary for canceling the charge in the molecule. m1 represents 0 or 1. n1 and n2 each represents 0, 1 or 2. However, n1 and n2 are not 0 at the same time. ]
The above-mentioned infrared sensitizing dyes are described in, for example, HM Hammer, The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dies and Related Compounds, published by A. Weissberger ed. It can be easily synthesized by this method.

  These infrared sensitizing dyes may be added at any time after the silver halide is prepared. For example, silver halide grains or halogens may be added in a so-called solid dispersion state added to a solvent or dispersed in a fine particle form. It can be added to a light-sensitive emulsion containing silver halide grains / aliphatic carboxylic acid silver salt grains. Similarly to the heteroatom-containing compound having adsorptivity to the silver halide grains, chemical sensitization can be performed after adding and adsorbing to the silver halide grains prior to chemical sensitization. Thus, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved.

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

  The emulsion containing the photosensitive silver halide and the aliphatic carboxylic acid silver salt in the silver salt photothermographic dry imaging material of the present invention substantially contains a dye having no spectral sensitizing action or visible light itself, together with the sensitizing dye. In addition, a substance that does not absorb light and exhibits a supersensitization effect may be included in the emulsion, whereby the silver halide grains may be supersensitized.

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

Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic ring or condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium, or tellurium atoms. Preferably, the heteroaromatic ring is benzimidazole, naphthimidazole, benzthiazole, naphthothiazole, benzoxazole, naphthoxazole, benzselenazole, benztelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine , Purine, quinoline, or quinazoline. However, other heteroaromatic rings are also included.

  In addition, mercapto derivative compounds that substantially produce the above mercapto compounds when contained in a dispersion of an aliphatic carboxylic acid silver salt or silver halide grain emulsion are also included. In particular, mercapto derivative compounds represented below are preferred examples.

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

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

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

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

In the present invention, it is necessary that the spectral sensitizing dye is adsorbed on the surface of the photosensitive silver halide grain to effect spectral sensitization, and that the spectral sensitizing effect should substantially disappear after the thermal development process. It is. Here, the spectral sensitization effect substantially disappears when the sensitivity of the imaging material obtained by a sensitizing dye, supersensitizer, etc. is the sensitivity when spectral sensitization is not performed after the thermal development process. It means to decrease to 1.1 times or less.
In order to eliminate the chemical sensitization effect in the thermal development process, a spectral sensitizing dye that is easily detached from the silver halide grains by heat is used during thermal development or / and the spectral sensitizing dye is destroyed by an oxidation reaction. It is necessary to contain an appropriate amount of an oxidizing agent that can be formed, for example, the above-mentioned halogen radical releasing compound in the emulsion layer and / or the non-photosensitive layer of the imaging material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the spectral sensitization effect, and the like.

(Reducing agent)
In the present invention, as the reducing agent (silver ion reducing agent), in particular, at least one of the reducing agents is a compound represented by the following general formula (1) alone or in combination with a reducing agent having another different chemical structure. It is preferable to use it.

[Wherein, X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₂ represents an alkyl group and may be the same or different. R ₃ represents a hydrogen atom or a group that can be substituted on a benzene ring. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2. ]
Among the compounds represented by the general formula (1), a highly active reducing agent (hereinafter referred to as a compound of the general formula (1a)) in which at least one of R ₂ is a secondary or tertiary alkyl group is used. It is more preferable that a photothermographic material having a high density and excellent light-storing image storage stability can be obtained. In the present invention, it is preferable to use a compound of the general formula (1a) and a compound of the following general formula (2) in order to obtain a desirable color tone.

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

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

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

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

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

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

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

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

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

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

  These groups may be further substituted with these groups. n and m represent an integer of 0 to 2, and most preferably n and m are 0.

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

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

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

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

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

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

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

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

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

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

hab = tan ⁻¹ (b ^* / a ^* )
As a result of the examination based on the expression method based on the hue angle, the color tone after development of the photothermographic material of the present invention is preferably such that the hue angle hab is in the range of 180 ° <hab <270 °, more preferably 200 °. It was found that <hab <270 degrees, most preferably 220 degrees <hab <260 degrees. This is disclosed in Japanese Patent Laid-Open No. 2002-6463.

Conventionally, the CIE 1976 (L ^* u ^* v ^* ) color space or the (L ^* a ^* b ^* ) color space near the optical density of 1.0 is specified as u ^* , v ^* or a ^* , b ^* . It is known that a diagnostic image with a favorable color tone can be obtained by adjusting to a numerical value, and is described in, for example, Japanese Patent Application Laid-Open No. 2000-29164.

However, as a result of further intensive studies on the photothermographic material of the present invention, the horizontal axis is u ^* or a ^* , in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space. When plotting u ^* , v ^* or a ^* , b ^* at various photographic densities on a graph with the axis as v ^* or b ^*, and creating a linear regression line, the linear regression line is specified. By adjusting the range, it was found that it has a diagnostic ability equal to or higher than that of conventional wet silver salt photosensitive materials. A preferable range of conditions is described below.

a) The optical density of the silver image obtained after the photothermographic treatment of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density, and CIE 1976 (L ^* u ^* v ^*) is measured ^. ) The coefficient of determination (multiple determination) R2 of the linear regression line produced by arranging u ^* and v ^* at the respective optical densities on the two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^*. It is preferably 0.998 to 1.000. Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (v ^* / u ^* ) is 0.7 to 2.5.

b) In addition, the optical density of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density, and the horizontal axis of the CIE 1976 (L ^* a ^* b ^* ) color space is plotted. The coefficient of determination (multiple determination) R2 of the linear regression line prepared by arranging a ^* and b ^* at each optical density in two-dimensional coordinates with a ^* and b ^{* on} the vertical axis is 0.998 to 1.000. It is preferable that Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (b ^* / a ^* ) is 0.7 to 2.5.

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

A four-stage wedge sample including an unexposed portion and optical densities of 0.5, 1.0, and 1.5 is prepared using a heat development apparatus. Each wedge density part thus produced is measured with a spectrocolorimeter (Minolta Co., Ltd .: CM-3600d or the like), and u ^* , v ^* or a ^* , b ^* are calculated. The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 degrees, and measurement is performed in the transmission measurement mode. Plot u ^* , v ^* or a ^* , b ^* measured on a graph with u ^* or a ^{* on} the horizontal axis and v ^* or b ^{* on the} vertical axis to obtain a linear regression line, and the coefficient of determination (multiple determination) Find 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, the developed silver can be adjusted by adjusting the addition amount of a compound or the like directly or indirectly involved in the development reaction process of the following toning agent, developer, silver halide grains and aliphatic carboxylate. The shape can be optimized to obtain a preferable color tone. For example, when the developed silver shape is dendritic, it becomes a bluish direction, and when it is a filament shape, it becomes a yellowish direction. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

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

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

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

  Representative leuco dyes suitable for use in the present invention are not particularly limited. And phenothiazine leuco dye.

  Also useful are US Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4,022,617, 4,123,282, 4,368,247, 4,461,681, and JP-A-50-36110, 59-26831, These are leuco dyes disclosed in JP-A-5-204087, JP-A-11-231460, JP-A-2002-169249, and JP-A-2002-236334.

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

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

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

In the formula, R ₁₁ represents a substituted or unsubstituted alkyl group, R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, respectively, and R ₁₁ and R ₁₂ are 2-hydroxyphenylmethyl groups. There is never. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on the benzene ring.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

The addition amount of the compound of the general formula (YA) (including hindered phenol compounds and compounds of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0. 0005 to 0.01 mol, more preferably 0.001 to 0.008 mol.
Moreover, it is preferable that the addition amount ratio with respect to the sum total of the reducing agent represented by general formula (1), (2) of yellow coloring leuco dye is 0.001-0.2 by molar ratio, and 0.005- More preferably, it is 0.1.

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

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

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

[Wherein R ₈₁ and R ₈₂ are a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, —NHCO—R ₁₀ group (R ₁₀ is an alkyl group, aryl group, heterocyclic group) Or R ₈₁ and R ₈₂ are bonded to each other to form an aliphatic hydrocarbon ring, an aromatic hydrocarbon ring or a heterocyclic ring. A ₈ represents a —NHCO— group, a —CONH— group or a —NHCONH— group, and R ₈₃ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group. In addition, —A ₈ —R ₈₃ may be a hydrogen atom. W ₈ is a hydrogen atom or —CONH—R ₈₅ group, —CO—R ₈₅ group or —CO—O—R ₈₅ group (R ₈₅ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). R ₈₄ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, alkenyl group, alkoxy group, carbamoyl group, or nitrile group. R ₈₆ represents a —CONH—R ₈₇ group, a —CO—R ₈₇ group or a —CO—O—R ₈₇ group (R ₈₇ represents a substituted or unsubstituted alkyl group, aryl group or heterocyclic group). . X ₈ represents a substituted or unsubstituted aryl group or heterocyclic group. ]
In the general formula (CL), examples of the halogen atom represented by R ₈₁ and R ₈₂ include a fluorine atom, a bromine atom, and a chlorine atom, and the alkyl group includes an alkyl group having up to 20 carbon atoms (for example, Methyl group, ethyl group, butyl group, dodecyl group, etc.). Examples of the alkenyl group include alkenyl groups having up to 20 carbon atoms (for example, vinyl group, allyl group, butenyl group, hexenyl group, hexadienyl group, ethenyl-2-ethyl group). A propenyl group, a 3-butenyl group, a 1-methyl-3-propenyl group, a 3-pentenyl group, a 1-methyl-3-butenyl group, and the like. As the alkoxy group, an alkoxy group having up to 20 carbon atoms (for example, methoxy) Group, ethoxy and the like).

Examples of the alkyl group represented by R ₁₀ in the —NHCO—R ₁₀ group include alkyl groups having up to 20 carbon atoms (for example, a methyl group, an ethyl group, a butyl group, a dodecyl group, etc.), and an aryl group. Examples thereof include a group having 6 to 20 carbon atoms such as a phenyl group and a naphthyl group, and examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group. Alkyl group represented by R ₈₃ is preferably an alkyl group having up to 20 carbon atoms, such as methyl group, ethyl group, butyl group, dodecyl group and the like, the aryl group preferably having 6 to 20 carbon atoms Examples of the aryl group include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.

In the —CONH—R ₈₅ group, —CO—R ₈₅ group or —CO—O—R ₈₅ group represented by W ₈ , the alkyl group represented by R ₈₅ is preferably an alkyl group having up to 20 carbon atoms. Examples thereof include a methyl group, an ethyl group, a butyl group, and a dodecyl group. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, and examples thereof include a phenyl group and a naphthyl group. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.

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

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

R ₁₀ or R ₈₅ is preferably a phenyl group, and more preferably a phenyl group having a plurality of halogen atoms and cyano groups as substituents.

-CONH-R ₈₇ group represented by R _86, in -CO-R ₈₇ group, or -CO-O-R ₈₇ group, the alkyl group represented by R ₈₇ is preferably an alkyl group having up to 20 carbon atoms Yes, for example, a methyl group, an ethyl group, a butyl group, a dodecyl group, and the like. The aryl group is preferably an aryl group having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, a thienyl group, and the like. Examples of the heterocyclic group include a thiophene group, a furan group, an imidazole group, a pyrazole group, and a pyrrole group.
As the substituent that the group represented by R ₈₇ can have, the same substituents as those described in the description of R _{81 to} R _{84 in} formula (CL) can be used.

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

Examples of the substituent that the group represented by X ₈ can have include the same substituents as those described in the description of R _{81 to} R _{84 in} formula (CL).
The group represented by X ₈ is preferably an aryl group or heterocyclic group having an alkylamino group (such as a diethylamino group) at the para position.

  These groups may include photographically useful groups.

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

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

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

  The compounds of the general formulas (1), (2), general formulas (YA) and (YB) and the cyan chromophoric leuco dye are preferably contained in an image forming layer containing an organic silver salt, but one of them is image-forming. The other layer 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.

(binder)
1) Water-soluble binder of the present invention As a binder in the image forming layer of the present invention, a water-soluble binder is used for 50% by mass or more. The water-soluble binder is transparent or translucent and generally colorless, and natural resins, polymers and copolymers, synthetic resins, polymers and copolymers, and other film-forming polymers are preferred.
Specific examples of the water-soluble binder include synthetic anionic polymers such as polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, maleic acid monoester copolymer, and acrylomethylpropanesulfonic acid copolymer. , Semi-synthetic anionic polymers such as carboxymethyl starch and carboxymethyl cellulose, anionic polymers such as alginic acid and pectinic acid, compounds described in JP-A-7-350753, or known anionic, nonionic, and cationic surfactants And other known polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, carboxymethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, and naturally occurring polymer compounds such as gelatin. These water-soluble binders can be appropriately selected and used. A preferred water-soluble binder is a nonionic water-soluble polymer or an anionic water-soluble polymer.

  Examples of the nonionic water-soluble polymer include polyvinyl alcohol, modified polyvinyl alcohol, polyacrylamide, dextran, polyethylene glycol, and a block copolymer of polyethylene glycol and polypropylene glycol.

  As the natural polymer, gelatin is preferred. As the gelatin, alkali-treated gelatin, acid-treated gelatin, or carboxy-modified gelatin treated with phthalic acid or the like is preferably used.

  As the synthetic polymer, polyvinyl alcohols are preferable, and modified polyvinyl alcohol is particularly preferable. The polyvinyl alcohols preferably have a saponification degree of 80 to 99.9% and a polymerization degree of 300 to 2400, and the modified polyvinyl alcohols are copolymerized modified polyvinyl alcohol, terminal thiol modified polyvinyl alcohol, terminal alkyl modified polyvinyl. Alcohol and the like can be used, and it is particularly preferable to use alkyl-modified polyvinyl alcohol. Regarding modification of polyvinyl alcohol, C.I. A. It is described in detail on pages 77 to 156 of Polyvinyl Alcohol Developments (John. Wiley & Sons Ltd., 1992) edited by Finch. Copolymerization modification and chain transfer modification are mainly used. Particularly preferred is terminal alkyl-modified polyvinyl alcohol by chain transfer modification.

In addition, examples of the anionic water-soluble polymer include poly (meth) acrylic acid, a copolymer of (meth) acrylic acid and (meth) acrylic ester, carboxy-modified polyvinyl alcohol, and carboxymethyl cellulose.
As the water-soluble binder in the present invention, gelatin and polyvinyl alcohol are particularly preferable, and gelatin is most preferable.

  The water-soluble binder of the present invention is preferably used in an amount of 50% by mass or more of the binder of the image forming layer, more preferably 60% by mass or more, and most preferably 70% by mass or more.

  Two or more water-soluble binders of the present invention may be used in combination.

2) Polymer latex In the present invention, it is preferable to use a latex in combination with a water-soluble binder. Latex refers to a dispersion in which fine particles of a water-insoluble hydrophobic polymer are dispersed. The average particle diameter of the dispersed particles is 1 to 50000 nm, preferably 5 to 1000 nm, more preferably 10 to 500 nm, and still more preferably 50 to 200 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution. Mixing two or more types having a monodispersed particle size distribution is also a preferable method for controlling the physical properties of the coating solution.

  In the present invention, preferred embodiments of the latex include acrylic polymers, poly (esters), rubbers (for example, SBR resin), poly (urethanes), poly (vinyl chloride) s, poly (vinyl acetate) s, poly (vinyl Hydrophobic polymers such as vinylidene chloride) and poly (olefin) s can be preferably used. These polymers may be linear polymers, branched polymers, crosslinked polymers, so-called homopolymers obtained by polymerizing a single monomer, or copolymers obtained by polymerizing two or more types of monomers. In the case of a copolymer, it may be a random copolymer or a block copolymer.

  These polymers have a number average molecular weight of 5,000 to 1,000,000, preferably 10,000 to 200,000. When the molecular weight is too small, the mechanical strength of the emulsion layer is insufficient, and when the molecular weight is too large, the film formability is poor, which is not preferable. A crosslinkable polymer latex is particularly preferably used.

  Specific examples of the preferred polymer latex include the following latex.

  The latexes listed below are expressed using raw material monomers, the numerical values in parentheses are% by mass, and the molecular weight is the number average molecular weight. When a polyfunctional monomer was used, the concept of molecular weight was not applicable because a crosslinked structure was formed, so it was described as crosslinkability, and the description of molecular weight was omitted. Tg represents the glass transition temperature.

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

MMA; methyl methacrylate,
EA; ethyl acrylate,
MAA; methacrylic acid,
2EHA; 2-ethylhexyl acrylate,
St; styrene,
Bu; butadiene,
AA; acrylic acid,
DVB; divinylbenzene,
VC; vinyl chloride,
AN; acrylonitrile,
VDC; vinylidene chloride,
Et; ethylene,
IA; Itaconic acid.

  The polymer latex described above is also commercially available, and the following polymers can be used.

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

  The amount of the binder in the image forming layer of the present invention is such that the total binder / organic silver salt mass ratio is 1/10 to 10/1, more preferably 1/3 to 5/1, and still more preferably 1/1 to 1. The range is 3/1.

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

The total binder amount of the image forming layer of the present invention is preferably in the range of 0.2 to 30 g / m ² , more preferably 1 to 15 g / m ² , and still more preferably ² to 10 g / m ² . The image forming layer of the present invention may contain a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like.

(Thermal solvent)
A thermal solvent is preferably used for the image forming layer of the present invention.
The thermal solvent is a compound that has the effect of liquefying during thermal development and promoting thermal development, and is preferably in a solid state at room temperature.

  The photothermographic material of the invention preferably contains a thermal solvent having a melting point of 50 to 200 ° C.

  The thermal solvent of the present invention preferably has a polar group as a substituent. Examples of the substituent include a hydroxy group, a carboxy group, an amino group, an amide group, a sulfonamide group, a phosphoric acid amide group, a cyano group, an imide, and a ureido. It is preferable to have at least one group selected from sulfoxide, sulfone, phosphine, phosphine oxide or nitrogen-containing heterocyclic group.

  Since heat development is a reduction reaction involving a carboxylic acid having a relatively high polarity or a silver ion transporter, it is preferable to form a reaction field having an appropriate polarity with a thermal solvent having a polar group. . The melting point of the hot solvent is 50 ° C. or higher and 200 ° C. or lower, preferably 60 ° C. or higher and 150 ° C. or lower. Specific examples of the thermal solvent include compounds described in “0032” to “0039” of JP-A-2004-20645.

(Silver saving agent)
Preferred examples of the silver saving agent include hydrazine derivative compounds, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds.

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

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

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

  Specific examples of the quaternary onium compound include triphenyltetrazolium.

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

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

(Anti-fogging and image stabilizer)
The fog prevention and image stabilizer in the photothermographic material of the invention will be described.

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

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

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

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

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

  The amount of these compounds added is preferably within a range in which the increase in printout silver due to the formation of silver halide is not a problem, and is a maximum of 150% or less, more preferably 100% in terms of the ratio to the compound that does not generate active halogen radicals. % Or less is preferable. Specific examples of compounds that generate these active halogen atoms include compounds (III-1) to (III-23) described in paragraphs “0086” to “0087” of JP-A No. 2002-169249, Compounds 1-1a to 1-1o and 1-2a to 1-2o described in paragraphs “0031” to “0034” of JP-A-2003-50441, and compounds 2a to 2z and 2aa described in paragraphs “0050” to “0056” To 2ll, 2-1a to 2-1f, compounds 4-1 to 4-32 described in paragraphs “0055” to “0058” of JP-A No. 2003-91054, and compounds 5 described in paragraphs “0069” to “0072” -1 to 5-10.

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

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

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

  When the reducing agent 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 in combination. It is preferable to do.

  Specific examples of particularly preferred hydrogen bonding compounds in the present invention include, for example, compounds (II-1) to (II-40) described in paragraphs “0061” to “0064” of JP-A-2002-90937. Is mentioned.

  The photothermographic material of the present invention forms a photographic image by heat development processing, and contains a toning agent that adjusts the color tone of silver as necessary dispersed in an ordinary (organic) binder matrix. Preferably it is.

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

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

(Fluorosurfactant)
In the present invention, a fluorosurfactant represented by the following general formula (SF) is preferably used in order to improve film transportability and environmental suitability (accumulation in vivo) in a heat development processing apparatus.

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

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

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

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

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

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

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

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

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

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

The amount of the fluorosurfactant represented by the general formula (SF) of the present invention is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ² , and 1 × 10 ⁻⁵ to 1 × 10 ^−2. Mole is particularly preferred. If it is less than the former range, charging characteristics cannot be obtained, and if it exceeds the former range, the humidity dependence is large and the storage stability under high humidity deteriorates.

(Surface layer)
The photothermographic material used in the invention further has a ten-point average roughness (Rz (E)) of the outermost surface on the image forming layer side across the support and the opposite side of the image forming layer across the support. The value of Rz (E) / Rz (B) is preferably 0.10 to 0.70, and more preferably 0.10 to 0, when the ten-point average roughness (Rz (B)) of the outermost surface of 0.60, particularly preferably 0.10 to 0.50.

  By setting the value of Rz (E) / Rz (B) within this range, density unevenness during thermal development can be further improved. The average particle size of the matting agent having the maximum average particle size of the matting agent contained in the layer having the image forming layer is Le (μm), and the largest matting agent contained in the layer having the back coat layer is used. When the average particle diameter of the matting agent having an average particle diameter is Lb (μm), Lb / Le is preferably 2.0 or more and 10 or less, and more preferably 2.5 to 6.0.

  By setting Lb / Le within this range, density unevenness during thermal development can be further improved. The average particle size of the matting agent was determined as an average value for 100 matting agents observed in electron micrographs (tomographic photographs and surface photographs).

  The ten-point average roughness (Rz) is defined by the following JIS surface roughness (B0601). Ten-point average roughness (Rz) is the maximum to the fifth measured in the direction of the vertical magnification from the straight line that is parallel to the average line and does not cross the cross-sectional curve, in the portion that has been removed from the cross-sectional curve by the reference length. The difference between the average value of the altitude at the top of the mountain and the average value of the altitude at the bottom of the valley from the deepest to the fifth is expressed in micrometers (μm). As a measuring method of the ten-point average roughness (Rz), the humidity was adjusted for 24 hours in a 25 ° C., 65% RH environment in which the measurement samples were not overlapped with each other, and the measurement was performed in this environment. Examples of the non-overlapping condition shown here include any of a method of winding with the film edge portion raised, a method of stacking paper between films, and a method of producing a frame with cardboard and fixing its four corners. It is. Examples of the measuring apparatus that can be used include a RSTPLUS non-contact three-dimensional micro surface shape measuring system manufactured by WYKO.

  In order to make the ten-point average roughness of the front and back surfaces of the photosensitive material within the above-mentioned range, the type, average particle size and addition amount of the matting agent used, the matting agent dispersion conditions, and the drying conditions during coating are controlled. It can be adjusted easily. In the present invention, the surface layer of the photothermographic material (when the image forming layer side or a non-photosensitive layer is provided on the opposite side of the image forming layer across the support), the object of the present invention, In order to control the surface roughness, it is preferable to use organic or inorganic powder as the matting agent. As the powder used, it is preferable to use a powder having a Mohs hardness of 5 or more. Further, when the ten-point average roughness of the outermost surface on the image forming layer side across the support is Rz (E), Rz (E) is preferably 1.0 μm or more and 4.0 μm or less, more preferably. Is 1.2 μm or more and 3.8 μm or less, particularly preferably 1.4 μm or more and 3.6 μm or less. By setting Rz within this range, it is possible to improve density unevenness in heat development, transportability during heat development, and fog increase during development under high humidity conditions.

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, 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, inorganic powders such as SiO ₂ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃ , mica, etc. are preferable. , SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ is particularly preferable.

  In the present invention, the powder is preferably surface-treated with a Si compound or an Al compound. By using such a surface-treated powder, the surface state of the uppermost layer can be improved. The content of Si or Al is preferably 0.1 to 10% by mass of Si and 0.1 to 10% by mass of Al with respect to the powder, and more preferably 0.1 to 5% of Si. It is particularly preferable that the mass% is 0.1 to 5 mass%, Si is 0.1 to 2 mass%, and Al is 0.1 to 2 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.

  The average particle diameter of the powder in the present invention is the average diameter in the case of spherical powder, the average major axis length in the case of acicular powder, and the maximum diagonal length of the plate-like surface in the case of plate-like powder. Mean values can be easily determined 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 usually 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm. It is. The addition amount is usually 1.0 to 20% by mass, preferably 2.0 to 15% by mass, and more preferably based on the amount of binder used in the outermost layer (including the curing agent in the binder amount). Is 3.0-10 mass%.

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

  The coefficient of variation 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 previously dispersed in the coating solution, or a method of spraying the organic or inorganic powder after the coating solution is applied and before the drying is completed. May be. Moreover, when adding several types of powder, you may use both methods together.

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

  In order to improve the charging property, 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 the backing layer or the surface protective layer on the photosensitive layer side, the undercoat layer and the like. The conductive compounds described in columns 14 to 20 of US Pat. No. 5,244,773 are preferably used. Among these, in the present invention, the surface protective layer on the backing layer side preferably contains a conductive metal oxide. This proved that the effects of the present invention (particularly the transportability during heat development) can be further enhanced.

Here, the conductive metal oxide is crystalline metal oxide particles, and those containing oxygen defects and those containing a small amount of hetero atoms forming a donor with respect to the metal oxide used are generally used. In particular, it is particularly preferable because of its high conductivity, and the latter is particularly preferable because it does not give fog to the silver halide emulsion. Examples of metal oxides are ZnO, TiO ₂ , SnO ₂ , Al ₂ O ₃ , In ₂ O ₃ , SiO ₂ , MgO, BaO, MoO ₃ , V ₂ O _5, etc., or a composite oxide thereof, especially ZnO, TiO ₂ and SnO ₂ are preferred. As an example of containing a heteroatom, addition Al, or In to ZnO, addition Sb, Nb, P, such as a halogen element relative to SnO _2, In addition, Nb for TiO _2, Ta Etc. are effective. The amount of these different atoms added is preferably in the range of 0.01 to 30 mol%, but particularly preferably 0.1 to 10 mol%. Furthermore, a silicon compound may be added during the production of fine particles in order to improve fine particle dispersibility and transparency.

The metal oxide fine particles in the present invention have electrical conductivity, and their volume resistivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A Nos. 56-143431, 56-120519, 58-62647 and the like. Furthermore, as described in Japanese Examined Patent Publication No. 59-6235, a conductive material in which the above metal oxide is attached 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, the stability after dispersion is good and it is easy to use.

  In order to make the light scattering property as small as possible, it is very preferable to use conductive particles of 0.3 μm or less because a transparent photosensitive material can be formed.

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

  The photothermographic material of the present invention has an image forming layer which is at least one photosensitive 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 “sticking” between the photosensitive materials or in the photosensitive material roll. In order to prevent “,” a backcoat layer is provided.

  As a binder used in these protective layers and backcoat layers, a polymer having a glass transition point (Tg) higher than that of the image forming layer and hardly causing scratches or deformation, such as cellulose acetate, cellulose acetate butyrate, cellulose acetate propio. Polymers such as nates are selected from the binders described above.

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

(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 in order to control the amount of light transmitted through the image forming layer or the wavelength distribution, or a dye is formed on the image forming layer. Or it is preferable to contain a pigment.

  As the dye used in the present invention, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the heat developing material.

  For example, when the heat developing material of the present invention is used as an image recording material by infrared light, a squarylium dye having a thiopyrylium nucleus and a squarylium dye having a pyrylium nucleus as disclosed in JP-A-2001-83655, It is also preferable to use a thiopyrylium croconium dye similar to a squarylium dye or a pyrylium croconium dye.

  The compound having a squarylium nucleus is a compound having 1-cyclobutene-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy- in the molecular structure. It is a compound having 4,5-dione. Here, the hydroxyl group may be dissociated. As the dye, the compounds described in JP-A-8-201959 are also preferable.

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

  There are no particular restrictions on the method of applying multiple layers simultaneously to each constituent layer, for example, bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, reverse roll coating method, gravure coating method, and extrusion. A known method such as a coating method can be used. Of these, the slide coating method and the extrusion coating method are more preferable. These coating methods have been described on the side having the image forming layer, but the same applies to the case of coating with undercoating when the back layer is provided. Japanese Unexamined Patent Publication No. 2000-15173 has a detailed description on the simultaneous multilayer coating method in the heat development material.

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

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

Furthermore, the coating density of the non-photosensitive long-chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ g or more, 1 × 10 1 per silver halide grain of 0.01 μm or more (equivalent particle diameter equivalent to sphere). ^-14 g or less is preferable, and 1 x 10 ^-16 g or more and 1 x 10 ^-15 g or less are more preferable.

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

In the present invention, the photothermographic material preferably contains a solvent in the range of 5 to 1,000 mg / m ² during development. It is more preferable to adjust so that it may be 100-500 mg / m < ² >. As a result, the photothermographic material has high sensitivity, low fog, and high maximum density. Examples of the solvent include those described in paragraph “0030” of JP-A No. 2001-264930. However, it is not limited to these. These solvents can be used alone or in combination of several kinds.

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

(Packaging body)
When storing the photothermographic material of the present invention, a package having a low oxygen permeability and / or moisture permeability in order to prevent density changes and fogging over time, or to improve curling, curling, etc. It is preferable to package with materials. The oxygen permeability is preferably 50 ml / atm · m ² · day or less at 25 ° C., more preferably 10 ml / atm · m ² · day or less, more preferably 1.0 ml / atm · m ² · day or less. is there. The moisture permeability is preferably 10 g / atm · m ² · day or less, more preferably 5 g / atm · m ² · day or less, and still more preferably 1 g / atm · m ² · day or less.

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

(Exposure of photothermographic material)
The photothermographic material usually uses a laser beam when recording an image. In the present invention, it is desirable to use a light source suitable for the color sensitivity imparted to the photosensitive material. For example, if the photosensitive material is sensitive to infrared light, it can be applied to any light source as long as it is in the infrared light range, but the laser power is high or the photothermographic material is made transparent. From the viewpoint 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 surface of the photosensitive material and the scanning laser beam is not substantially perpendicular.

  Here, “substantially not perpendicular” means that the angle closest to the vertical during laser beam scanning is 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 exposure surface of the photosensitive material when the laser beam is scanned onto the photosensitive material is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the “shift angle” from the vertical of the laser beam incident angle. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

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

  Furthermore, as a third aspect, it is also preferable to form an image by scanning exposure using two or more laser beams.

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

  The image formation of laser light on the photoconductor in the image writing means of a laser printer or digital copying machine is for one line from the image formation position of one laser light for the purpose of writing an image by a plurality of lines in one scan. The next laser beam is imaged by shifting. Specifically, the two light beams are close to each other on the image plane in the sub-scanning direction at an order of several tens of μm, and the print density is 400 dpi (dpi is the number of dots per inch = 2.54 cm). The sub-scanning direction pitch of the two beams is 63.5 μm, and 42.3 μm at 600 dpi.

  Unlike the method of shifting the resolution in the sub-scanning direction as described above, in the present invention, it is preferable to form an image by condensing two or more lasers at the same place on the exposure surface while changing the incident angle. At this time, the exposure energy on the exposure surface when writing with one normal laser beam (wavelength λ [nm]) is E, and N laser beams used for exposure have the same wavelength (wavelength λ [nm]). ), In the case of the same exposure energy (En), the range of 0.9 × E ≦ En × N ≦ 1.1 × E is preferable. By doing so, energy is secured on the exposure surface, but the reflection of each laser beam to the image forming layer is reduced because the exposure energy of the laser is low, and thus the occurrence of interference fringes is suppressed.

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

(Heat development processing equipment)
The thermal development processing apparatus preferably used in the present invention has, as a configuration, a film supply unit represented by a film tray, a laser image recording unit, a thermal development unit that supplies uniform and stable heat to the entire surface of the photothermographic material, It is composed of a conveying section from the film supply section through laser recording until the heat-developable photosensitive material image-formed by heat development is discharged out of the apparatus. A specific example of the heat development processing apparatus of this embodiment is shown in FIG.

  The heat development apparatus 100 includes a feeding unit 110 that feeds a sheet-like photothermographic material (photothermographic element or simply a film) one by one, an exposure unit 120 that exposes the fed film F, and an exposure. A developing unit 130 for developing the developed film F, a cooling unit 150 for stopping development, and a stacking unit 160, a supply roller pair 140 for supplying the film F from the feeding unit, and for feeding the film to the developing unit Supply roller pair 144, and a plurality of roller pairs such as transport roller pairs 141, 142, 143, and 145 for smoothly transferring the film F between the respective parts. The heat developing part is a heating means for developing the film F, and peeling the heat drum 1 having a plurality of opposed rollers 2 that can be heated while being held in close contact with the outer periphery, and the developed film F to be sent to the cooling part. It consists of nails 6 etc.

  The transport speed of the photothermographic material in the heat developing section is preferably in the range of 10 to 200 mm / sec, more preferably 20 to 200 mm / sec. By setting the conveyance speed within this range, density unevenness during heat development can be improved and the processing time can be shortened.

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

  The heating device, apparatus or means may be a heating means typical as a heat generator using, for example, a hot plate, iron, hot roller, carbon or white titanium. More preferably, the heat-developable material provided with the protective layer is subjected to heat treatment by bringing the surface having the protective layer into contact with the heating means. It is preferable from the viewpoint, and it is preferable that the surface on the side having the protective layer is conveyed while being in contact with the heat roller, and is developed by heat treatment.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, the embodiment of this invention is not limited to these.

(Preparation of polyethylene terephthalate (PET) support)
Using terephthalic acid and ethylene glycol, PET having an intrinsic viscosity of IV = 0.66 (measured in phenol / tetrachloroethane = 6/4 (mass ratio) at 25 ° C.) was obtained according to a conventional method. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to produce an unstretched film having a thickness of 175 μm after heat setting.
This was longitudinally stretched 3.3 times using rolls having different peripheral speeds and then stretched 4.5 times with a tenter. The temperatures at this time were 110 ° C. and 130 ° C., respectively. Thereafter, the film was heat-fixed at 240 ° C. for 20 seconds and relaxed by 4% in the lateral direction at the same temperature. Thereafter, the chuck portion of the tenter was slit and then knurled at both ends, and wound at 4 kg / cm ² to obtain a roll having a thickness of 175 μm.

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

(Preparation of undercoat support)
(1) Preparation of undercoat layer coating solution Formulation (1) (for photosensitive layer side undercoat layer)
59 g of pesresin A-520 (30% by mass solution) manufactured by Takamatsu Yushi Co., Ltd.
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 10% by mass solution 5.4 g
MP-1000 (polymer fine particles, average particle size 0.4 μm) 0.91 g manufactured by Soken Chemical Co., Ltd.
935 ml of distilled water
Formula (2) (for back layer 1st layer)
Styrene-butadiene copolymer latex 158g
(Solid content 40% by mass, styrene / butadiene mass ratio = 68/32)
2,4-Dichloro-6-hydroxy-S-triazine sodium salt, 8% by mass aqueous solution
20g
10% 1% by weight aqueous solution of sodium laurylbenzenesulfonate
854 ml of distilled water
Formula (3) (for back side second layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion)
84g
Gelatin (10 mass% aqueous solution) 89.2g
8.6 g of Metroise TC-5 (2% by mass aqueous solution) manufactured by Shin-Etsu Chemical Co., Ltd.
MP-1000 0.01g manufactured by Soken Chemical Co., Ltd.
10% 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 6 ml
Proxel (ICI) 1ml
805 ml of distilled water
After both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm are subjected to the corona discharge treatment, the undercoat coating solution formulation (1) is applied on one side (photosensitive layer surface) with a wire bar with a wet coating amount of 6. .6ml / m ² was applied (per one side) and dried for 5 minutes at 180 ° C., then the amount of wet coating the coating solution for the undercoat was coated (2) by a wire bar on the rear surface (back surface) 5. Apply to 7 ml / m ² , dry at 180 ° C. for 5 minutes, and further wet coating amount of 7.7 ml / m ² with the above-mentioned undercoat coating liquid formulation (3) on the back surface (back surface) with a wire bar It was coated as described above and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

(Preparation of back surface coating solution)
(Preparation of antihalation layer coating solution)
60 g of gelatin, 24.5 g of polyacrylamide, 2.2 g of 1 mol / l sodium hydroxide, 0.08 g of benzoisothiazolinone, 0.3 g of sodium polystyrene sulfonate, 0.21 g of blue dye compound-1 and yellow dye compound- 0.15 g of 1 and 8.3 g of acrylic acid / ethyl acrylate copolymer latex (copolymerization ratio 5/95) were mixed, and the whole was made up to 818 ml with water to prepare an antihalation layer coating solution.

(Preparation of back surface protective layer coating solution)
The container was kept at 40 ° C., gelatin 40 g, liquid paraffin emulsion 1.5 g as liquid paraffin, benzoisothiazolinone 35 mg, 1 mol / l caustic 6.8 g, t-octylphenoxyethoxyethane sulfonate 0.5 g , 0.27 g of sodium polystyrene sulfonate, 5.4 mg of 2% aqueous solution of fluorosurfactant (FF-1), 100 mg of fluorosurfactant (SF-17), acrylic acid / ethyl acrylate copolymer (copolymerization) (Mass ratio 5/95) 6.0 g and N, N-ethylenebis (vinylsulfone acetamide) 2.0 g were mixed, stirred and dissolved with water to 1000 ml. Finally, monodispersed amorphous silica (average particle size: 9 μm, 1% of the total mass of silica) dispersed in water with dynomill (using 0.5 mm diameter ceramic beads) at a concentration of 5%. Surface treatment) 20.0 g, monodisperse spherical silica with a monodispersity of 15% dispersed in dynomill (using 0.5 mm diameter ceramic beads) at a concentration of 5% in water (average particle size: 12 μm, total silica 10.0 g of surface treatment with 1% by mass of aluminum was added to obtain a back surface protective layer coating solution.

(Preparation of silver halide emulsion)
<< Preparation of silver halide emulsion 1 >>
To a solution of 1420 ml of distilled water was added 4.3 ml of a 1% by weight potassium iodide solution, and a solution containing 3.5 ml of 0.5 mol / L sulfuric acid and 36.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 35 ° C., a solution B in which distilled water was diluted to 22.56 g of silver nitrate and diluted to 195.6 ml and solution B in which 21.8 g of potassium iodide was diluted to a volume of 218 ml with distilled water were added at a constant flow rate. The whole amount was added over 9 minutes. Thereafter, 10 ml of a 3.5% by mass aqueous hydrogen peroxide solution was added, and 10.8 ml of a 10% by mass aqueous solution of benzimidazole was further added.

Further, Solution C obtained by diluting 51.86 g of silver nitrate to 317.5 ml and diluting Solution I obtained by diluting 60 g of potassium iodide to a volume of 600 ml with distilled water was completely added over 120 minutes at a constant flow rate. Solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so that it would be 1 × 10 ⁻⁴ mole per mole of silver. Further, 5 seconds after the completion of the addition of the solution C, an aqueous solution of potassium iron (II) hexacyanide was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed.

  The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

While maintaining the silver halide dispersion at 38 ° C. with stirring, 5 ml of a 0.34 mass% 1,2-benzisothiazolin-3-one methanol solution was added, and the temperature was raised to 47 ° C. 20 minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per 1 mol of silver, and 5 minutes later, tellurium sensitizer B was added in a methanol solution to a ratio of 2. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes.

1.3 ml of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ -diethylmelamine was added, and after 4 minutes, 5-methyl-2-mercaptobenzimidazole was added to the methanol solution at a rate of 4. Halogenation by adding 8 × 10 ⁻³ mol and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole in a methanol solution to 5.4 × 10 ⁻³ mol with respect to 1 mol of silver Silver emulsion 1 was prepared.

  The grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 30 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 2 >>
The preparation of silver halide emulsion 1 was carried out in the same manner as the preparation of silver halide emulsion 1 except that the temperature of the solution at the time of addition was changed to 48 ° C. by the controlled double jet method. Grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 55 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 3 >>
Preparation of silver halide emulsion 1 was the same as the preparation of silver halide emulsion 1 except that 21.8 g of potassium iodide was changed to potassium bromide so that the silver iodide content was 90 mol%. It was. Grains in the prepared silver halide emulsion were silver iodobromide grains (silver iodide content of 90 mol%) having an average equivalent sphere diameter of 30 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 4 >>
Preparation of silver halide emulsion 2 was carried out in the same manner as in preparation of silver halide emulsion 2, except that a portion of 21.8 g of potassium iodide was changed to potassium bromide so that the silver iodide content was 90 mol%. It was. Grains in the prepared silver halide emulsion were silver iodobromide grains (silver iodide content of 90 mol%) having an average equivalent sphere diameter of 30 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 5 >>
Preparation of silver halide emulsion 1 Preparation of silver halide emulsion 1 except that 10 ml of a 3.5% by weight aqueous hydrogen peroxide solution was added followed by 4 ml of a 0.1% ethanol solution of the compound (ETTU). And adjusted in the same manner. The grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 30 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 6 >>
In the preparation of silver halide emulsion 2, 10 ml of a 3.5% by weight aqueous hydrogen peroxide solution was added, and then 4 ml of a 0.1% ethanol solution of the following compound (ETTU) was further added. It was prepared in the same manner as in the preparation of Grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 55 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 7 >>
In the preparation of silver halide emulsion 1, 10 ml of a 3.5% by weight aqueous hydrogen peroxide solution was added, and then a 5% aqueous solution of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene was further added. The same procedure as in the preparation of silver halide emulsion 1 was carried out except that 40 ml was added. The grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 30 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 8 >>
In the preparation of silver halide emulsion 2, 10 ml of a 3.5% by weight aqueous hydrogen peroxide solution was added, and then a 5% aqueous solution of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene was further added. Preparation was performed in the same manner as in the preparation of silver halide emulsion 2 except that 40 ml was added. Grains in the prepared silver halide emulsion were pure silver iodide grains having an average sphere equivalent diameter of 55 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

<< Preparation of silver halide emulsion 9 >>
Same as the preparation of silver halide emulsion 1 except that a part of 21.8 g of potassium iodide was changed to potassium bromide so that the silver iodide content was 3.5 mol% in the preparation of silver halide emulsion 1. Went to. Grains in the prepared silver halide emulsion were silver iodobromide grains (silver iodide content of 3.5 mol%) having an average sphere equivalent diameter of 30 nm and a sphere equivalent diameter variation coefficient of 18%. The particle size and the like were determined from an average of 1000 particles using an electron microscope.

(Preparation of silver halide mixed emulsion A for coating solution)
Silver halide emulsion 1 and silver halide emulsion 2 were dissolved at a mass ratio of 8: 2, and 7 × 10 ⁻³ mol of benzothiazolium iodide was added in a 1% by mass aqueous solution per mol of silver. . Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver.

(Preparation of silver halide mixed emulsion B for coating solution)
Silver halide emulsion 3 and silver halide emulsion 4 were dissolved at a mass ratio of 8: 2, and 7 × 10 ⁻³ mol of benzothiazolium iodide was added in a 1% by mass aqueous solution per mol of silver. . Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver.

(Preparation of silver halide mixed emulsion C for coating solution)
Silver halide emulsion 5 and silver halide emulsion 6 were dissolved at a mass ratio of 8: 2, and 7 × 10 ⁻³ mol of benzothiazolium iodide was added in a 1% by mass aqueous solution per mol of silver. . Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver.

(Preparation of silver halide mixed emulsion D for coating solution)
Silver halide emulsion 7 and silver halide emulsion 8 were dissolved at a mass ratio of 8: 2, and 7 × 10 ⁻³ mol of benzothiazolium iodide was added in a 1% by mass aqueous solution per mol of silver. . Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver.

(Preparation of silver halide mixed emulsion E for coating solution)
The silver halide emulsion 9 was dissolved, and benzothiazolium iodide was added in a 1% by mass aqueous solution at 7 × 10 ⁻³ mol per mol of silver. Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver.

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

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

After completion of the addition of the sodium behenate solution, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm. Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying.
When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average values were a = 0.21 μm, b = 0.4 μm, c = 0.4 μm, average aspect ratio 2.1, and equivalent sphere diameter. The crystal had a coefficient of variation of 11%. (A, b, and c are the text provisions)
19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to a wet cake corresponding to a dry solid content of 260 kg to make a total amount of 1000 kg, and then slurried with a dissolver blade. : PM-10 type).

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

(Preparation of reducing agent dispersion)
<< Preparation of Reducing Agent-1 Dispersion >>
10 kg of water was added to 16 kg of a 10 mass% aqueous solution of reducing agent-1 (1-10) and denatured polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump, dispersed for 3 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0. 2 g and water were added to prepare a reducing agent concentration of 25% by mass. This dispersion was heat-treated at 60 ° C. for 5 hours to obtain a reducing agent-1 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.4 μm or less. The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

<< Preparation of Reducing Agent-2 Dispersion >>
10 kg of water was added to 16 kg of a 10% by weight aqueous solution of reducing agent-2 (2-6) and modified polyvinyl alcohol (manufactured by Kuraray Co., Ltd., Poval MP203), and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to prepare a reducing agent concentration of 25% by mass. This dispersion was heated at 40 ° C. for 1 hour, and then further heated at 80 ° C. for 1 hour to obtain a reducing agent-2 dispersion. The reducing agent particles contained in the reducing agent dispersion thus obtained had a median diameter of 0.50 μm and a maximum particle diameter of 1.6 μm or less. The obtained reducing agent dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of hydrogen bonding compound-1 dispersion)
Add 10 kg of water to 10 kg of 10% aqueous solution of hydrogen bonding compound-1 (tri (4-t-butylphenyl) phosphine oxide) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203). Mix to make a slurry. This slurry was fed with a diaphragm pump, and dispersed for 4 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to prepare a hydrogen bonding compound concentration of 25% by mass. The dispersion was heated at 40 ° C. for 1 hour and then further heated at 80 ° C. for 1 hour to obtain a hydrogen bonding compound-1 dispersion. The hydrogen bonding compound particles contained in the hydrogen bonding compound dispersion thus obtained had a median diameter of 0.45 μm and a maximum particle diameter of 1.3 μm or less. The obtained hydrogen bonding compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

(Preparation of Development Accelerator-1 Dispersion)
10 kg of development accelerator-1 and 20 kg of 10% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) were added to 10 kg of water and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the development accelerator to 20% by mass to obtain a development accelerator-1 dispersion. The development accelerator particles contained in the development accelerator dispersion thus obtained had a median diameter of 0.48 μm and a maximum particle diameter of 1.4 μm or less. The obtained development accelerator dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

A solid dispersion of development accelerator-2 and color tone modifier-1 (yellow leuco dye, YA-1) and color tone modifier-2 (cyan leuco dye, CA-12) is also produced in the same manner as development accelerator-1. Dispersions were obtained to obtain dispersions of 20% by mass, 15% by mass, and 15% by mass, respectively.
(Preparation of additive S-1 aqueous solution)
Additive S-1 was added in a predetermined solid amount so as to be a 0.2% by mass aqueous solution.
An additive S-2 aqueous solution was prepared in the same manner except that the additive S-1 was changed to S-2.

(Preparation of polyhalogen compound)
<< Preparation of polyhalogen compound-1 dispersion >>
10 kg of polyhalogen compound-1 (tribromomethanesulfonylbenzene), 10 kg of a 20% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), 0.4 kg of a 20% by weight aqueous solution of sodium triisopropylnaphthalenesulfonate, 14 kg of water was added and mixed well to make a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to prepare a polyhalogen compound concentration of 30% by mass to obtain a polyhalogen compound-1 dispersion. The polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less. The obtained polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of polyhalogen compound-2 dispersion >>
10 kg of polyhalogen compound-2 (N-butyl-3-tribromomethanesulfonylbenzoamide), 20 kg of 10 wt% aqueous solution of modified polyvinyl alcohol (Poval MP203 manufactured by Kuraray Co., Ltd.), and 20 wt% of sodium triisopropylnaphthalenesulfonate A 0.4% aqueous solution was added and mixed well to form a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to prepare a polyhalogen compound concentration of 30% by mass. This dispersion was heated at 40 ° C. for 5 hours to obtain a polyhalogen compound-2 dispersion.

  The polyhalogen compound particles contained in the polyhalogen compound dispersion thus obtained had a median diameter of 0.40 μm and a maximum particle diameter of 1.3 μm or less. The obtained polyhalogen compound dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

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

(Preparation of mercapto compound)
<< Preparation of Mercapto Compound-1 Aqueous Solution >>
7 g of mercapto compound-1 (1- (3-sulfophenyl) -5-mercaptotetrazole sodium salt) was dissolved in 993 g of water to obtain a 0.7% by mass aqueous solution.

<< Preparation of Mercapto Compound-2 Aqueous Solution >>
20 g of mercapto compound-2 (1- (3-methylureido) -5-mercaptotetrazole sodium salt) was dissolved in 980 g of water to obtain a 2.0 mass% aqueous solution.

(Preparation of pigment-1 dispersion)
C. I. Pigment Blue 60 (64 g) and Kao Corp. Demol N (6.4 g) were added to 250 g of water and mixed well to obtain a slurry. Prepare 800 g of zirconia beads having an average diameter of 0.5 mm, put them in a vessel together with the slurry, and disperse with a disperser (1/4 G sand grinder mill: manufactured by IMEX Co., Ltd.) for 25 hours. A pigment-1 dispersion was obtained by adjusting the concentration to 5% by mass. The pigment particles contained in the pigment dispersion thus obtained had an average particle size of 0.21 μm.

(Preparation of SBR latex solution)
The SBR latex was prepared as follows.

In a polymerization kettle of a gas monomer reactor (TAS-2J type manufactured by Pressure Glass Industrial Co., Ltd.), 287 g of distilled water and a surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)): solid content 48.5 %) 7.73 g, 1 mol / liter NaOH 14.06 ml, ethylenediaminetetraacetic acid tetrasodium salt 0.15 g, styrene 255 g, acrylic acid 11.25 g, tert-dodecyl mercaptan 3.0 g, the reaction vessel was sealed and the stirring speed was 200 rpm. Stir with. After degassing with a vacuum pump and repeating nitrogen gas replacement several times, 108.75 g of 1,3-butadiene was injected and the internal temperature was raised to 60 ° C. A solution obtained by dissolving 1.875 g of ammonium persulfate in 50 ml of water was added thereto, and the mixture was stirred as it was for 5 hours. The temperature was further raised to 90 ° C. and stirred for 3 hours. After completion of the reaction, the internal temperature was lowered to room temperature, and then Na + ion: NH ₄ + ion = 1: 5 using 1 mol / liter NaOH and NH ₄ OH. To 3 (molar ratio) and adjusted to pH 8.4. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored to obtain 774.7 g of SBR latex.

  When the halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 145 ppm.

  The latex has an average particle size of 90 nm, Tg = 17 ° C., solid content concentration of 44 mass%, equilibrium moisture content at 25 ° C. and 60% RH, 0.6 mass%, ion conductivity of 4.80 mS / cm (measurement of ion conductivity is Toa Denki Kogyo Co., Ltd. conductivity meter CM-30S was used, latex stock solution (44% by mass) measured at 25 ° C), SBR latex with a different pH of 8.4Tg was changed by changing the ratio of styrene and butadiene as appropriate. It can be prepared by the method.

(Preparation of emulsion layer (photosensitive layer) coating solution-1)
1000 g of the fatty acid silver dispersion obtained above, 276 ml of water, pigment-1 dispersion, polyhalogen compound-1 dispersion, polyhalogen compound-2 dispersion, phthalazine compound-1 solution, binder solution (types listed in Table 1) ), Reducing agent-1 dispersion, hydrogen bonding compound-1 dispersion, development accelerator-1 dispersion, development accelerator-2 dispersion, color tone modifier-1 dispersion, mercapto compound-1 aqueous solution, mercapto compound -2 aqueous solution, additive S-1 aqueous solution, additive S-2 aqueous solution were added in order, and a silver halide mixed emulsion (types listed in Table 1) was added immediately before coating, and the emulsion layer coating solution was mixed well. The solution was fed directly to the coating die and applied.

The viscosity of the emulsion layer coating solution was 25 [mPa · s] at 40 ° C. (No. 1 rotor, 60 rpm) as measured with a B-type viscometer of Tokyo Keiki.
The viscosity of the coating solution at 25 ° C. using an RFS fluid spectrometer manufactured by Rheometrics Far East Co., Ltd. is 242, 65, 48 at shear rates of 0.1, 1, 10, 100, and 1000 [1 / second], respectively. 26 and 20 [mPa · s].
The amount of zirconium in the coating solution was 0.52 mg per 1 g of silver.

(Preparation of emulsion surface intermediate layer coating solution)
Polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.) 1000 g, pigment-1 dispersion 272 g, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymer mass ratio 64/9/20/5 / 2) 27200 ml of an aerosol OT (manufactured by American Cyanamid Co.) was added to 4200 ml of a latex 19 wt% solution, 135 ml of a 20 wt% aqueous solution of diammonium phthalate, and water was added to a total amount of 10,000 g In addition, the solution was adjusted with NaOH so that the pH was 7.5 to obtain an intermediate layer coating solution, and the solution was fed to the coating die so as to be 9.1 ml / m ² .
The viscosity of the coating solution was 58 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

(Preparation of emulsion surface protective layer first layer coating solution)
Inert gelatin (64 g) is dissolved in water, and methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5/2) 19.0% by weight of latex 112 g, 30 ml of 15% by weight methanol solution of phthalic acid, 23 ml of 10% by weight aqueous solution of 4-methylphthalic acid, 28 ml of sulfuric acid having a concentration of 0.5 mol / L, and 5% by weight aqueous solution of Aerosol OT (American Cyanamid Co., Ltd.) Add 5ml, 0.5g phenoxyethanol, 0.1g benzoisothiazolinone and add water to make a total amount of 750g. The solution was fed to the coating die so as to be 18.6 ml / m ² . The viscosity of the coating solution was 20 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

(Preparation of emulsion surface protective layer second layer coating solution)
80 g of inert gelatin is dissolved in water, and a methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5/2) latex 27.5% by mass solution 102 g, 9.6 ml of a 1% by weight solution of a fluorosurfactant (FF-1), 15 ml of a 5% by weight solution of a fluorosurfactant (SF-17), 1.6 g of 4-methylphthalic acid, 4. Water was added to 8 g, 44 ml of 0.5 mol / L sulfuric acid and 10 mg of benzoisothiazolinone so that the total amount was 650 g, and the mixture was stirred and dissolved with a dissolver. Thereafter, monodispersed amorphous silica (average particle size: 3 μm, 1% of the total mass of silica) dispersed in water with dynomill (using 0.5 mm diameter ceramic beads) at a concentration of 5%. Surface treatment) 132.0 g, monodispersed spherical silica with a monodispersity of 15% (average particle size: 5 μm, all silica dispersed in dynomill (using 0.5 mm diameter ceramic beads) at a concentration of 5% in water) (Surface treatment with 1% by mass of aluminum) 66.0 g was added, stirred and dissolved. A solution prepared by mixing 445 ml of an aqueous solution containing 4% by mass of chromium alum and 0.67% by mass of phthalic acid with a static mixer immediately before coating is used as the surface protective layer second layer coating solution, resulting in 8.3 ml / m ² . The solution was fed to the coating die.

  The viscosity of the coating solution was 19 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

(Preparation of photothermographic material- (1-1) to (1-18))
On the back surface side of the undercoat support, the gelatin coating amount of the antihalation layer coating solution is 0.88 g / m ^2, and the gelatin coating amount of the back surface protective layer coating solution is 1.2 g / m ² . A multi-layer coating was simultaneously applied and dried to prepare a back layer.

  A photothermographic material sample was prepared on the surface opposite to the back surface by simultaneous multi-layer coating using the slide bead coating method in the order of the emulsion layer, intermediate layer, protective layer first layer, and protective layer second layer from the undercoat surface. . At this time, the emulsion layer and the intermediate layer were adjusted to 31 ° C., the protective layer first layer was adjusted to 36 ° C., and the protective layer second layer was adjusted to 37 ° C.

The coating amount (g / m ² ) of each compound in the emulsion layer is as follows.

Silver behenate 5.27
Pigment (C.I. Pigment Blue 60) 0.036
Polyhalogen compound-1 0.09
Polyhalogen compound-2 0.14
Phthalazine Compound-1 0.18
Binder (type is listed in Table 1) Coating amount is listed in Table 1 Reducing agent-1 0.12
Reducing agent-2 0.65
Hydrogen bonding compound-1 0.28
Development accelerator-1 0.025
Development accelerator-2 0.020
Color tone adjusting agent-1 0.008
Color adjuster-2 0.008
Mercapto Compound-1 0.002
Mercapto compound-2 0.006
Additive S-1 0.001
Additive S-2 0.002
Silver halide (as Ag) 0.046
The coating and drying conditions are as follows.

  The support was neutralized with ion wind before coating, and coating was performed at a speed of 160 m / min. The coating and drying conditions were adjusted within the following ranges for each sample, and were set to conditions that would provide the most stable surface shape.

  The gap between the coating die tip and the support is 0.10 to 0.30 mm.

  The pressure in the decompression chamber is set to 196 to 882 Pa lower than the atmospheric pressure.

  In the subsequent chilling zone, the coating solution is cooled with air at a dry bulb temperature of 10 to 20 ° C.

  It is transported in a non-contact manner, and dried with a dry air having a dry bulb temperature of 23 to 45 ° C. and a wet bulb temperature of 15 to 21 ° C. in a helical contactless dryer.

After drying, the humidity is adjusted at 25 ° C. and humidity of 40-60% RH.
Subsequently, the film surface was heated to 70 to 90 ° C., and after the heating, the film surface was cooled to 25 ° C.

  The photothermographic material thus prepared had a Beck smoothness of 7000 seconds on the photosensitive layer surface side and 6000 seconds on the back surface. Further, the pH of the film surface on the photosensitive layer surface side was measured and found to be 6.0.

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

4). Evaluation of photographic performance (Evaluation of photographic performance)
The obtained samples were cut into half-cut sizes, packaged in the following packaging materials in an environment of 25 ° C. and 50%, stored at room temperature for 2 weeks, and then evaluated as follows.
The sample was mounted with an NLHV 3000E semiconductor laser manufactured by Nichia Corporation as a semiconductor laser light source at the exposure part of a medical dry laser imager, and the beam diameter was reduced to 100 μm. The illuminance on the photosensitive material surface of the laser light was exposed at 10 ^-6 seconds varied between 0 and ^{1mW / mm 2 ~1000mW / mm 2} . The oscillation wavelength of the laser beam was 405 nm. In the heat development, four panel heaters were set to 112 ° C.-118 ° C.-120 ° C.-120 ° C., and the development was carried out so that the conveyance speed was increased to a total of 14 seconds. The obtained image was evaluated with a densitometer.

<Exposure and development processing>
After processing the photothermographic material samples (1-1) to (1-18) produced as described above to a half-cut size (34.5 cm × 43.0 cm), the following packaging is performed in an environment of 25 ° C. and 50%. After packaging in materials and storing at room temperature for 2 weeks, the following evaluation was performed.

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

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

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

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

  Note: The values in parentheses in the relative sensitivity column indicate that the photosensitive material was heat-treated at the heat development temperature before the light-sensitive material was exposed to white light, and then exposed to white light through an optical wedge (4874K, 30 seconds) and heat-developed. The sensitivity relative value of the former when the sensitivity of the latter is assumed to be 100 is shown in the comparison between the sensitivity of the case and the sensitivity when heat development is performed by exposure to white light under the same conditions as above without heat treatment before exposure. It was. In this relative comparison, the main cause of the decrease in the relative sensitivity of the sample obtained by heat-treating the photosensitive material at the heat development temperature before exposing the photosensitive material to white light is the surface sensitivity of the silver halide grains due to the disappearance or reduction of the spectral sensitization effect. It was confirmed by observation / measurement of changes in the spectral sensitivity spectrum that the relative relationship between the internal sensitivity and the internal sensitivity was changed.

<Transportability>
Development processing was performed 50 times using a heat development processing apparatus, and the number of times of occurrence of conveyance failure was measured.

《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 Schaukasten. A wet processed laser imager film manufactured by Konica was used as a standard sample at this time, and the relative color tone with respect to the standard sample was evaluated visually by 0.5 increments according to the following criteria.

5: The same color tone as the standard sample 4: Almost the same preferred color tone as the standard sample 3: Level slightly different from the standard sample, but practically no problem 2: Color tone clearly different from the standard sample 1: Unpleasant color tone different from the standard sample << Light Irradiation Image Preservability >>
Each heat-developable photosensitive material sample was exposed and developed in the same manner as in the evaluation of silver tone, and then the change in the image was visually observed after being pasted on a Schaukasten with a luminance of 1000 lux and allowed to stand for 10 days. Evaluation was performed in 0.5 increments.

5: Almost no change 4: Slight color change is observed 3: Color change and fog increase are observed in part 2: Color change and fog increase are observed in a considerable part 1: Color change and fog The increase in density is remarkable and strong density unevenness occurs on the entire surface.
The produced photothermographic material was placed in a sealed container whose interior was kept at 25 ° C. and 55% humidity, and then stored at 55 ° C. for 7 days (forced aging). For comparison, the same photothermographic material was stored for 7 days in a light-shielding container at 25 ° C. and 55% humidity. These samples were subjected to the same treatment as that used for evaluation of sensitometry, and the density of the fog portion was measured. Over time fogging was observed as follows.

ΔDmin (Increase in fog) = (Fog in forced aging) − (Fog in comparison with time)
<< Evaluation of surface roughness >>
About the sample before the process of heat development, it measured by the method shown below using the non-contact three-dimensional surface analyzer (WYKO company RST / PLUS).

1) Objective lens: × 10.0, Intermediate lens: × 1.0
2) Measurement range: 463.4 μm × 623.9 μm
3) Pixel size: 368 × 238
4) Filter: Cylindrical correction and tilt correction 5) Smoothing: Medium smoothing 6) Scanning speed: Low
In addition, the definition of Rz, Rt, Ra followed JIS surface roughness (B0601). For each sample of 10 cm × 10 cm, the sample was divided into 100 in a grid pattern at 1 cm intervals, the center of each square region was measured, and the average value was obtained from 100 measurements.

<Evaluation of density unevenness after heat development>
The density unevenness after the heat development treatment is evaluated visually according to the following five-level rank, and the results are shown in Table 1.

Rank 1: Strong density unevenness occurs on the entire surface. Rank 2: Strong density unevenness occurs on a part. Rank 3: Some weak density unevenness occurs. Rank 4: Slight density unevenness occurs. Rank 5: Generation of density unevenness is observed. In the above evaluation, ranks 4 and 5 were judged to be practically acceptable levels.

  The results are shown in Table 1.

  From Table 1, compared with the comparative photothermographic material, the photothermographic material of the present invention has a high density, silver tone, light-irradiated image storability, fog characteristics over time, and density unevenness after heat development. It is clear that it is excellent.

  Moreover, when the centerline average roughness (Ra) of the outermost surface by the side of the image formation layer of a sample was measured about sample (1-1)-(1-18), all were 100 nm. Further, when the ten-point average roughness (Rz) of the outermost surface on the image forming layer side of the sample was measured, all were 1.5 μm. When the ten-point average roughness of the front and back surfaces was measured to determine Rz (E) / Rz (B), both were 0.48.

1 is a diagram showing an example of a heat development processing apparatus for processing a photothermographic material of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heat drum 2 Opposed roller 6 Peeling nail | claw 100 Heat developing apparatus 110 Feeding part 120 Exposure part 130 Developing part 140 Supply roller pair 141,142,143,145 Transport roller pair 144 Supply roller pair 150 Cooling part 160 Accumulation part F Film C Film tray L Laser beam

Claims (12)

In the photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, 50 to 100% by mass of the binder of the image forming layer is a water-soluble binder, A photothermographic material, wherein the silver halide grains are silver halide grains whose surface sensitivity is lowered from that before heat development by converting the surface latent image type to the internal latent image type in the heat development process. Sensitivity obtained based on a characteristic curve obtained when the photothermographic material is exposed to white light or light in a specific spectral sensitization region through an optical wedge for a certain period of time and then heat-developed under normal heat-development conditions. Is obtained on the basis of a characteristic curve obtained by heating under the same conditions as the heat development conditions before exposure, followed by exposure with white light or light in a specific spectral sensitization region for a certain period of time, and further heat development. 2. The photothermographic material according to claim 1, wherein the sensitivity is 1/10 or less. 3. The photothermographic material according to claim 1, wherein the silver halide grains contain therein a dopant that functions as an electron trap after at least thermal development. Spectral sensitization is performed by adsorbing a spectral sensitizing dye on the surface of the silver halide grain, and the effect of the spectral sensitization substantially disappears after the thermal development process. The photothermographic material according to any one of 1 to 3. The surface of the silver halide grain is chemically sensitized, and the effect of the chemical sensitization substantially disappears after the thermal development process. The photothermographic material described in 1. The surface of the silver halide grain is chemically sensitized, spectrally sensitized by adsorbing a spectral sensitizing dye, and the chemical sensitization and spectral sensitization after the thermal development process. The photothermographic material according to claim 1, wherein the effect is substantially lost. In the photothermographic material having an image forming layer containing an organic silver salt, a silver halide, a binder and a reducing agent on a support, 50 to 100% by mass of the binder of the image forming layer is a water-soluble binder, A photothermographic material, wherein the silver halide contains 5 to 100 mol% of silver iodide. 8. The photothermographic material according to claim 7, wherein the silver halide contains 40 to 100 mol% of silver iodide. The average particle size of the largest average particle size of the matting agent contained in the image forming layer side across the support is Le (μm), and is contained in the layer opposite to the image forming layer across the support. The average particle size of the matting agent having the largest average particle size is Lb (μm), and Lb / Le is 2.0 to 10.0. The photothermographic material according to any one of the above items. When the ten-point average roughness of the outermost surface on the image forming layer side is Rz (E) and the ten-point average roughness of the outermost surface on the opposite side of the image forming layer across the support is Rz (B), 10. The photothermographic material according to claim 1, wherein the value of Rz (E) / Rz (B) is 0.10 to 0.70. An image forming method comprising heat-developing the photothermographic material according to any one of claims 1 to 10 at a conveying speed of a heat developing unit of 20 to 200 mm / sec using a heat developing apparatus. . An image forming method, wherein the photothermographic material according to claim 1 is exposed using a laser whose exposure light source has an emission peak intensity at 350 nm to 450 nm.

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