Heat-developable photosensitive material and compound

Abstract

Provided are: a heat-developable photosensitive material having, on one surface of a support, an image-forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, and a development accelerator represented by general formula (1); and a compound represented by general formula (2). R1, R3 and R4 are each independently H, Cl, F, an alkyl group, an alkoxy group, an amide group, an ester group or a sulfonyl group, and R5 is an alkyl group or a phenyl group. At least one among R1, R3, and R4 is F.

Description

Photothermographic materials and compounds

[0001] The present disclosure relates to photothermographic materials and compounds.

[0002] In recent years, in the medical field, there has been a strong demand for a reduction in the amount of wastewater produced from processing from the viewpoints of environmental conservation and space saving, and there is a need for a technology relating to a photosensitive heat-developable photographic material for medical diagnosis and photography that can be efficiently exposed by a laser image setter or laser imager and can form black images with good resolution and clarity. Such a heat-developable photosensitive material can provide a simpler and more environmentally friendly thermal development processing system that does not require the use of solution-based processing chemicals.

[0003] Known examples of heat-developable color photosensitive materials include those capable of obtaining good images in a short development time, which use a color former made of a phthalonitrile derivative as a reducing agent that reacts with a specific compound to form an image (Patent Document 1).

[0004] Patent Document 1: U.S. Patent No. 6,251,576

[0005] In photothermographic materials for dry imaging systems using silver halide, images are formed by exposure and development, but no fixing process is performed, and reactive materials remain in the material. Therefore, there is a demand for photothermographic materials that can simultaneously improve the color density (sensitivity) of exposed areas and suppress color development (fogging suppression) in unexposed areas.

[0006] The present disclosure has been made in view of the above-mentioned problems, and an object of one embodiment of the present disclosure is to provide a photothermographic material and a compound that can achieve both an improvement in color density in exposed areas and suppression of color development in unexposed areas.

[0007] Specific means for solving the problems include the following embodiments: <1> A photothermographic material having, on one surface of a support, an image-forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, and a development accelerator represented by the following general formula (1):

[0008]

[0009] (R １ ~R ４ are each independently H, Cl, F, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an alkylamide group, an alkylthioamide group, an alkylester group, an alkylsulfonyl group, an alkylsulfinyl group, an alkylamino group, an acyl group, a phenoxy group, a thiophenoxy group, a benzyl group, a hydrazino group, a nitro group, or a cyano group. １ ~R ４ At least one of R is a hydrazino group; １ ~R ４ At least one of these is F.) <2> R ２ is a hydrazino group, and R １ , R ３ , and R ４ <3> The photothermographic material according to <1>, wherein any one of R ２ is a hydrazino group, and R ３ is an alkylthio group, an alkylsulfonyl group, or an alkylsulfinyl group, and R １ and R ４ <4> The photothermographic material according to <1> or <2>, wherein at least one of R ２ is a hydrazino group, and R ３ is an alkylsulfonyl group or F, and R １ and R ４ <5> The photothermographic material according to any one of <1> to <4>, wherein at least one of the above is F. <6> The photothermographic material according to any one of <1> to <4>, wherein the binder is an aqueous latex. <7> A compound represented by the following general formula (2):

[0010]

[0011] (R １ , R ３ , and R ４ are each independently H, Cl, F, an alkyl group, an alkylthio group, an alkoxy group, an amide group, an ester group, or a sulfonyl group, and R ５ is an alkyl group or a phenyl group.１ , R ３ , and R ４ At least one of is F.)

[0012] According to one embodiment of the present disclosure, there is provided a photothermographic material and a compound that can achieve both improved color density in exposed areas and suppressed color development in unexposed areas.

[0013] Embodiments of the present disclosure are described below. The present disclosure is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the present disclosure. In the present disclosure, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the upper and lower limits. In the numerical ranges described in stages in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with the upper or lower limit of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit described in a certain numerical range may be replaced with a value shown in the Examples. In the present disclosure, when multiple substances corresponding to each component are present in the composition, the amount of each component in the composition refers to the total amount of the multiple substances present in the composition, unless otherwise specified. In the present disclosure, a combination of two or more preferred aspects or forms is a more preferred aspect or form. The photothermographic materials and compounds according to the present disclosure are described in detail below.

[0014] (Hydromic Photosensitive Material) A thermally developable photosensitive material (hereinafter also referred to as "thermally developable photosensitive material") according to one embodiment of the present disclosure has an image forming layer on one surface of a support, the image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, and a development accelerator represented by the general formula (1) above.

[0015] As described above, photothermographic materials for use in dry imaging systems using silver halide are required to achieve both high color density (sensitivity) in exposed areas and low color density (fogging suppression) in unexposed areas. The present inventors conducted detailed studies on the various components contained in photothermographic materials and discovered that the use of a novel phthalonitrile derivative as a development accelerator can achieve both high sensitivity and low fogging. The phthalonitrile derivative is a compound represented by the general formula (1) above, specifically, a compound having a phthalonitrile skeleton with a substituent having one hydrazino group and at least one fluorine atom (hereinafter sometimes abbreviated as "F" or "F atom" in this specification). Although the detailed mechanism is unclear, the present inventors speculate that when a phthalonitrile compound is used as a development accelerator, the electron-withdrawing effect of the F atom in the phthalonitrile compound facilitates the dissociation of protons from the hydrazine moiety, thereby enhancing the reducing ability of silver halide during thermal development, thereby increasing the sensitivity of the photothermographic material. It is also speculated that the effect of F atoms reduces the compatibility of the phthalonitrile compound in the film of the development accelerator, reducing the amount of silver halide that comes into contact with the phthalonitrile compound, and therefore reducing the reactivity with silver halide in the unexposed state, thereby suppressing the occurrence of fogging in the photothermographic material.

[0016] <Image Forming Layer> The photothermographic material has an image forming layer on one surface of a support, the image forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, and a development accelerator represented by the above general formula (1). The image forming layer is at least one photosensitive layer provided on the support, and a typical example is a photosensitive layer formed from a silver halide emulsion containing a photosensitive silver halide provided on the support.

[0017] <<Development Accelerator>> The image forming layer in the photothermographic material contains a development accelerator represented by the following general formula (1).

[0018]

[0019] In the above general formula (1), R １ ~R４ are each independently H, Cl, F, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an alkylamide group, an alkylthioamide group, an alkylester group, an alkylsulfonyl group, an alkylsulfinyl group, an alkylamino group, an acyl group, a phenoxy group, a thiophenoxy group, a benzyl group, a hydrazino group, a nitro group, or a cyano group. １ ~R ４ At least one of R is a hydrazino group; １ ~R ４ At least one of R is F. １ ~R ４ In the above, each of the alkyl group, alkenyl group, alkynyl group, alkoxy group, alkylthio group, alkylamide group, alkylthioamide group, alkyl ester group, alkylsulfonyl group, alkylsulfinyl group, alkylamino group, acyl group, phenoxy group, thiophenoxy group, benzyl group, and hydrazino group may be unsubstituted or substituted with a substituent.

[0020] The alkyl group may be cyclic. The chain alkyl group may be branched. The number of carbon atoms in the alkyl group is preferably 1 to 20, more preferably 1 to 12, and particularly preferably 1 to 8. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an s-butyl group, an isobutyl group, a t-butyl group, a cyclopropyl group, a cyclohexyl group, and a 2-ethylhexyl group.

[0021] The alkyl group includes a substituted alkyl group. The alkyl portion of the substituted alkyl group is the same as the alkyl group described above. Examples of the substituent of the substituted alkyl group include a halogen atom, a cyano group, a nitro group, a hydroxyl group, a carboxyl group, an amino group, a formyl group, a carbamoyl group, a ureido group, a urethane group, a mercapto group, a sulfo group, a sulfamoyl group, an aliphatic group, an aromatic group, a heterocyclic group, -O-R, -CO-R, -CO-O-R, -O-CO-R, -NH-R, and -N(R) ２ , -NH-CO-R, -CO-NH-R, -CO-N(R) ２ , -NH-CO-NH-R, -NH-CO-N(R) ２, -NH-CO-OR, -SR, -SO ２ -R, -SO ２ -OR, -NH-SO ２ -R, -SO ２ -NH-R, and -SO ２ -N(R) ２ Each R independently represents an aliphatic group, an aromatic group, or a heterocyclic group. The carboxyl group and the sulfo group may have a dissociated hydrogen atom or may be in the form of a salt. These substituents may be further substituted. Examples of the substituted alkyl group include a 2-hydroxyethyl group, a 2-carboxyethyl group, a 2-methoxyethyl group, a 2-diethylaminoethyl group, a 3-sulfopropyl group, a 4-sulfobutyl group, a benzyl group, and a phenethyl group.

[0022] The alkenyl group may be cyclic. The chain alkenyl group may be branched. The number of carbon atoms in the alkenyl group is preferably 2 to 20, more preferably 2 to 12, and particularly preferably 2 to 8. Examples of the alkenyl group include a vinyl group, an allyl group, a 1-propenyl group, a 2-butenyl group, a 2-pentenyl group, and a 2-hexenyl group. The alkenyl group includes a substituted alkenyl group. The alkenyl moiety of the substituted alkenyl group is the same as the alkenyl group described above. The substituents of the substituted alkenyl group are the same as the substituents of the alkyl group.

[0023] The alkynyl group may be cyclic. The chain alkynyl group may be branched. The alkynyl group preferably has 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, and particularly preferably 2 to 8 carbon atoms. Examples of the alkynyl group include an ethynyl group and a 2-propynyl group.

[0024] The alkynyl group includes a substituted alkynyl group. The alkynyl moiety of the substituted alkynyl group is the same as the above-mentioned alkynyl group. The substituents of the substituted alkynyl group are the same as the substituents of the alkyl group.

[0025] The aliphatic group means an alkyl group, a substituted alkyl group, an alkenyl group, a substituted alkenyl group, an alkynyl group, or a substituted alkynyl group. The alkyl group, the substituted alkyl group, the alkenyl group, the substituted alkenyl group, the alkynyl group, or the substituted alkynyl group is the same as defined above.

[0026] The aromatic group refers to an aryl group or a substituted aryl group. The number of carbon atoms in the aryl group is preferably 6 to 25, more preferably 6 to 15, and particularly preferably 6 to 10. Examples of the aryl group include a phenyl group and a naphthyl group. The aryl moiety of the substituted aryl group is the same as the aryl group described above. Examples of the substituents of the substituted aryl group include the substituents described above. Examples of the substituted aryl group include a 4-carboxyphenyl group, a 4-acetamidophenyl group, a 3-methanesulfonamidophenyl group, a 4-methoxyphenyl group, a 3-carboxyphenyl group, a 3,5-dicarboxyphenyl group, a 4-methanesulfonamidophenyl group, and a 4-butanesulfonamidophenyl group.

[0027] The heterocyclic group refers to an unsubstituted heterocyclic group or a substituted heterocyclic group. The heterocyclic ring of the heterocyclic group is preferably a 5- or 6-membered ring. The heterocyclic ring may be fused with an aliphatic ring, an aromatic ring, or another heterocyclic ring. Examples of heterocyclic rings (including fused rings) include a pyridine ring, a piperidine ring, a furan ring, a furan ring, a thiophene ring, a pyrrole ring, a quinoline ring, a morpholine ring, an indole ring, an imidazole ring, an oxazole ring, a pyrazole ring, a carbazole ring, a phenothiazine ring, a phenoxazine ring, an indoline ring, a thiazole ring, a pyrazine ring, a thiadiazine ring, a benzoquinoline ring, and a thiadiazole ring. The substituents of the substituted heterocyclic group are the same as those of the substituted aryl group.

[0028] The development accelerator represented by the above general formula (1) is, from the viewpoint of achieving both sensitivity and fogging suppression in the photothermographic material, R ２ is a hydrazino group, and R １ , R ３ , and R ４ Preferably, any one of R is a F atom. １ , R ３ , and R４ More preferably, two of the above are F atoms, and all of them may be F atoms. Further preferred are development accelerators represented by the following general formula (2).

[0029]

[0030] In the above general formula (2), R １ , R ３ , and R ４ are each independently H, Cl, F, an alkyl group, an alkylthio group, an alkoxy group, an amide group, an ester group, or a sulfonyl group, and R ５ is an alkyl group or a phenyl group. １ , R ３ , and R ４ At least one of R is a F atom. １ , R ３ , and R ４ Each of the alkyl group, alkoxy group, amide group, ester group, and sulfonyl group in R may be unsubstituted or substituted with a substituent. ５ The alkyl group or phenyl group in the formula (I) may be unsubstituted or substituted with a substituent.

[0031] R １ , R ３ , and R ４ The same applies to R. ５ The same applies to the alkyl group as described above, and the same applies to the substituent in the case of substitution as described above.

[0032] In the development accelerator, the hydrazino group is -CO-, -COCO-, -CONR- or -SO ２ It is preferable that the alkyl group has either one of the following structures: -CONR- or -SO-. ２ -, more preferably -CONR-, where R represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom. Specific examples include the compounds shown below.

[0033]

[0034] The development accelerator represented by the above general formula (1) is, from the viewpoint of achieving both sensitivity and fogging suppression in the photothermographic material, R ２ is a hydrazino group, and R ３ is an alkylthio group, an alkylsulfonyl group, or an alkylsulfinyl group, and R １ and R ４ At least one of R is preferably a F atom. １ and R ４ It is more preferable that all of the groups are F atoms.

[0035] The development accelerator represented by the general formula (1) is preferably R ２ is a hydrazino group, and R ３ is an alkylsulfonyl group or an F atom, and R １ and R ４ At least one of R is preferably a F atom. １ and R ４ It is more preferable that all of the groups are F atoms.

[0036] Specific examples include the compounds shown below.

[0037]

[0038]

[0039]

[0040] The development accelerator represented by the general formula (1) is preferably R ４ is a hydrazino group, and R １ ~R ３ Preferably, any one of R is a F atom. １ ~R ３ More preferably, two of R are F atoms, １ ~R ３ may all be F atoms. As the development accelerator, a compound having a structure represented by the following general formula (3) may be used.

[0041]

[0042] In the above general formula (3), R １ ~R ３ are each independently H, Cl, F, an alkyl group, an alkoxy group, an amide group, an ester group, or a sulfonyl group, and R ６ is an alkyl group or a phenyl group. １ ~R ３ At least one of R is a F atom. １ ~R ３ Each of the alkyl group, alkoxy group, amide group, ester group, and sulfonyl group in R may be unsubstituted or substituted with a substituent. ５ The alkyl group or phenyl group in the formula (I) may be unsubstituted or substituted with a substituent.

[0043] R １ ~R ３ The details of each group in R are the same as those described above. ６ The same applies to the alkyl group as described above, and the same applies to the substituent in the case of substitution. Specific examples include the compounds shown below.

[0044]

[0045] The development accelerator may be used alone or in combination of two or more different types.

[0046] <<Photosensitive Silver Halide>> The image-forming layer contains a photosensitive silver halide.

[0047] 1) Halogen composition The photosensitive silver halide used in the image forming layer is not particularly limited in terms of halogen composition, and silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide and silver iodide can be suitably used, and silver bromide, silver iodobromide and silver iodide are more preferred.Details of the halogen composition can be as described in WO 2018 / 074430.

[0048] 2) Grain Formation Method Methods for forming photosensitive silver halide grains are well known in the art, and can be, for example, those described in Research Disclosure No. 17029, June 1978, and U.S. Pat. No. 3,700,458. Specifically, a method is used in which a photosensitive silver halide grain is prepared by adding a silver donor compound and a halogen donor compound to a gelatin or other polymer solution, and then mixed with an organic silver salt. Also preferred are the methods described in paragraphs

[0217] to

[0224] of JP-A No. 11-119374, JP-A No. 11-352627, and JP-A No. 2000-347335.

[0049] 3) Grain Size The grain size of the photosensitive silver halide is preferably small in order to suppress cloudiness after image formation, and specifically, is preferably 0.20 μm or less, more preferably 0.01 μm to 0.15 μm, and even more preferably 0.02 μm to 0.12 μm. The grain size referred to here means the diameter of a circle having the same area as the projected area of ​​the silver halide grain (the projected area of ​​the major plane in the case of tabular grains).

[0050] 4) Particle Shape The shape of the photosensitive silver halide grains may be cubic, octahedral, tabular, spherical, rod-like, potato-like, etc., with cubic grains being particularly preferred. Silver halide grains with rounded corners are also preferred. Details of the shape of the photosensitive silver halide grains can be found in the specification of International Publication No. 2018 / 074430.

[0051] 5) Heavy Metals The photosensitive silver halide grains may contain a metal or metal complex of Groups 6 to 13 of the periodic table (showing Groups 1 to 18). Preferably, a metal or metal complex of Groups 6 to 10 of the periodic table is contained. Preferred central metals of metals or metal complexes of Groups 6 to 10 of the periodic table include iron, rhodium, ruthenium, and iridium. One type of these metal complexes may be used, or two or more types of complexes of the same metal or different metals may be used in combination. A preferred content is 1 x 10 per mole of silver. －９ moles ~ 1 x 10－３ These heavy metals and metal complexes and methods for adding them are described in JP-A Nos. 7-225449, 11-65021, paragraphs 0018 to 0024, and 11-119374, paragraphs 0227 to 0240.

[0052] As the photosensitive silver halide, silver halide grains having a hexacyanometallic complex present on the outermost surface of the grain are preferred. The hexacyanometallic complex, the amount of the hexacyanometallic complex to be added, and the like can be as described in WO 2018 / 074430.

[0053] Furthermore, metal atoms that can be contained in silver halide grains (e.g., [Fe(CN) ６ ] ４－ ), desalting methods and chemical sensitization methods for silver halide emulsions are described in paragraphs 0046 to 0050 of JP-A No. 11-84574, paragraphs 0025 to 0031 of JP-A No. 11-65021, and paragraphs 0242 to 0250 of JP-A No. 11-119374.

[0054] 6) Gelatin The photosensitive silver halide emulsion used in one embodiment of the present disclosure may contain gelatin. Various gelatins can be used as the gelatin. It is necessary to maintain a good dispersion state of the photosensitive silver halide emulsion in a coating solution containing an organic silver salt, and it is preferable to use gelatin with a molecular weight (Mw) of 10,000 to 1,000,000. It is also preferable to phthalate the substituents of the gelatin. These gelatins may be used during grain formation or during dispersion after desalting, but are preferably used during grain formation.

[0055] 7) Sensitizing dyes Sensitizing dyes that can be used in the image-forming layer are those that can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed to the silver halide grains, and can advantageously be selected from sensitizing dyes that have spectral sensitivity suited to the spectral characteristics of the exposure light source. Sensitizing dyes and methods of addition are described in paragraphs

[0103] to

[0109] of JP-A-11-65021, the compounds represented by formula (II) in JP-A-10-186572, the dyes represented by formula (I) and paragraph

[0106] in JP-A-11-119374, the dyes described in U.S. Pat. Nos. 5,510,236 and Example 5 of U.S. Pat. No. 3,871,887, dyes disclosed in JP-A-2-96131 and JP-A-59-48753, page 19, line 38 to page 20, line 35 of European Patent Publication No. 0803764A1, JP-A-2001-272747, JP-A-2001-290238, JP-A-2002-23306, etc. These sensitizing dyes may be used alone or in combination of two or more.

[0056] The timing of adding the sensitizing dye to the silver halide emulsion is preferably after the desalting step and before coating, more preferably after the desalting step and before chemical ripening is completed. The amount of the sensitizing dye to be added can be determined as desired depending on the sensitivity and fog performance. －６ mol to 1 mol is preferred, and 10 －４ moles to 10 －１ It is a mole.

[0057] In order to improve the spectral sensitization efficiency, a supersensitizer can be used in the image forming layer. Examples of the supersensitizer include the compounds described in European Patent Publication No. 587,338, U.S. Pat. Nos. 3,877,943 and 4,873,184, JP-A Nos. 5-341432, 11-109547, and 10-111543.

[0058] 8) Chemical Sensitization Photosensitive silver halide grains are preferably chemically sensitized by a chalcogen sensitization method such as sulfur sensitization, selenium sensitization, or tellurium sensitization. Compounds preferably used in sulfur sensitization, selenium sensitization, or tellurium sensitization can be known compounds, such as those described in JP-A-7-128768. Tellurium sensitization is particularly preferred, and the compounds described in paragraph 0030 of JP-A-11-65021 and the compounds represented by formulas (II), (III), and (IV) in JP-A-5-313284 are more preferred.

[0059] The photosensitive silver halide grains are preferably chemically sensitized by gold sensitization alone or in combination with the chalcogen sensitization method. The gold sensitizer preferably has a gold valence of +1 or +3, and commonly used gold compounds are preferred. Typical examples include chloroauric acid, bromoauric acid, potassium chloroaurate, potassium bromoaurate, auric trichloride, potassium auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium auric thiocyanate, and pyridyl trichlorogold. Gold sensitizers described in U.S. Pat. No. 5,858,637 and JP-A-2002-278016 are also preferably used.

[0060] Chemical sensitization can be carried out at any time after grain formation and before coating, and can be carried out after desalting, (1) before spectral sensitization, (2) simultaneously with spectral sensitization, (3) after spectral sensitization, or (4) immediately before coating. The amount of sulfur, selenium, or tellurium sensitizer used varies depending on the silver halide grains used, chemical ripening conditions, etc., but is generally 10 moles per mole of silver halide contained in the image-forming layer. －８ moles to 10 －２ It is preferred to use 10 moles, more preferably 10 －７ moles to 10 －３ The amount of gold sensitizer added varies depending on various conditions, but as a guideline, it is about 10 moles per mole of silver halide contained in the image forming layer. －７ moles to 10 －３ moles, more preferably 10 －６ moles ~ 5 x 10 －４The conditions for chemical sensitization are not particularly limited, but the pH is preferably 5 to 8, the pAg is 6 to 11, and the temperature is preferably about 40°C to 95°C. Here, the pH is a value measured at 40°C. A thiosulfonic acid compound may be added to the silver halide emulsion by the method disclosed in European Patent Publication No. 293,917.

[0061] The amount of photosensitive silver halide added is 1 / 100 of the above image forming layer. ２ The amount of silver applied per unit area (elemental silver amount) is 0.03 g / m ２ 0.6g / m or more ２ It is preferable that the content is 0.05 g / m or less. ２ 0.5g / m or more ２ More preferably, it is 0.07 g / m or less. ２ 0.4g / m or more ２ The amount of the photosensitive silver halide added is preferably from 0.01 mol to 0.5 mol, more preferably from 0.02 mol to 0.3 mol, and even more preferably from 0.03 mol to 0.2 mol, per mol of the non-photosensitive organic silver salt.

[0062] The method and conditions for mixing the separately prepared photosensitive silver halide and the non-photosensitive organic silver salt described below include a method of mixing the prepared silver halide particles and the organic silver salt using a high-speed stirrer, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc., or a method of mixing the prepared photosensitive silver halide at any timing during the preparation of the organic silver salt to prepare the organic silver salt, but are not particularly limited as long as the effects of one embodiment of the present disclosure are sufficiently exhibited. Furthermore, mixing two or more aqueous dispersions of organic silver salts with two or more aqueous dispersions of photosensitive silver salts when mixing is a preferred method for adjusting photographic properties.

[0063] The preferred time for adding the photosensitive silver halide to the coating solution for the image-forming layer is between 180 minutes and immediately before coating, preferably between 60 minutes and 10 seconds before coating, but there are no particular limitations on the mixing method and conditions as long as the effects of one embodiment of the present disclosure are sufficiently exhibited.Specific mixing methods include a method of mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid sent to the coater is set to a desired time, and a method using a static mixer, etc., as described in Chapter 8 of "Liquid Mixing Technology" by N. Harnby, M. F. Edwards, and A. W. Nienow, translated by Takahashi Koji (published by Nikkan Kogyo Shimbun, Ltd., 1989).

[0064] <<Non-photosensitive organic silver salt>> The image-forming layer contains a non-photosensitive organic silver salt.

[0065] 1) Composition: The non-photosensitive organic silver salt that can be used in the image-forming layer is a silver salt that is relatively stable to light, but functions as a silver ion donor when heated to 80°C or higher in the presence of exposed photosensitive silver halide and a reducing agent, thereby forming a silver image. The organic silver salt may be any organic substance that can donate silver ions that can be reduced by a reducing agent. Such non-photosensitive organic silver salts are described in paragraphs

[0048] to

[0049] of JP-A-10-62899, EP-A-0803764-A1, p. 18, line 24 to p. 19, line 37, EP-A-0962812-A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, and the like. Silver salts of organic acids are preferred, particularly silver salts of long-chain aliphatic carboxylic acids (having 10 to 30 carbon atoms, preferably 15 to 28 carbon atoms). Preferred examples of fatty acid silver salts include silver lignocerate, silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, silver erucate, and mixtures thereof. Among these fatty acid silver salts, fatty acid silver salts having a silver behenate content of preferably 50 mol% to 100 mol%, more preferably 85 mol% to 100 mol%, and even more preferably 95 mol% to 100 mol% are preferred. Furthermore, fatty acid silver salts having a silver erucate content of 2 mol% or less, more preferably 1 mol% or less, and even more preferably 0.1 mol% or less are preferred. The composition of the non-photosensitive organic silver salt may be as described in WO 2018 / 074430.

[0066] 2) Shape The shape of the non-photosensitive organic silver salt is not particularly limited, and may be any of needle-like, rod-like, tabular, and scaly shapes, with scaly organic silver salts being preferred. Also preferred are irregular particles in the shape of short needles, rectangular parallelepipeds, cubes, or potatoes, with a ratio of the length of their major axis to their minor axis of 5 or less. These organic silver particles have less fogging during thermal development than long needle-like particles with a ratio of the length of their major axis to their minor axis of 5 or more. The shape of the non-photosensitive organic silver salt may be as described in International Publication No. WO 2018 / 074430.

[0067] 3) Preparation Known methods can be applied to the production and dispersion of non-photosensitive organic acid silver salt. For example, the above-mentioned JP-A-10-62899, EP 0803763A1, EP 0962812A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, JP-A-2001-163889, JP-A-2001-163890, JP-A-2001-163827, JP-A-2001-33907, JP-A-2001-188313, JP-A-2001-83652, JP-A-2002-6442, JP-A-2002-49117, JP-A-2002-31870, JP-A-2002-107868, and the like can be referenced.

[0068] In addition, if a photosensitive silver salt is present when dispersing a non-photosensitive organic silver salt, fog increases and sensitivity significantly decreases, so it is more preferable that the non-photosensitive organic silver salt is substantially free of the photosensitive silver salt when dispersed. The amount of the photosensitive silver salt in the dispersed aqueous dispersion is preferably 1 mol% or less, more preferably 0.1 mol% or less, per mol of the organic silver salt in the dispersion, and even more preferably no photosensitive silver salt is actively added. The production and dispersion method of the non-photosensitive organic silver salt can be as described in WO 2018 / 074430.

[0069] 4) Amount Added The non-photosensitive organic silver salt can be used in any desired amount, but the image-forming layer should contain at least 0.1 g / m2 of total coated silver (elemental silver amount) including silver halide from the viewpoints of sensitivity and image preservability. ２ ~1.5g / m ２ is preferred, and 0.3 g / m ２ ~1.5g / m ２ More preferably, 0.3 g / m ２ ~1.4g / m ２ , particularly preferably 0.5 g / m ２ ~1.3g / m ２ In particular, in order to improve image storage stability, the total coated silver amount is 1.5 g / m ２ Preferably, the content is 0.8 g / m or less. ２ ~1.3g / m ２By using a preferable reducing agent described later, it is possible to obtain a sufficient image density even with such a low amount of silver.

[0070] <<Reducing Agent>> The image forming layer contains a reducing agent for silver ions.

[0071] The photothermographic material according to an embodiment of the present disclosure preferably contains a reducing agent for silver ions (hereinafter also referred to as a reducing agent). The reducing agent may be any substance (preferably an organic substance) that reduces silver ions to metallic silver. Examples of such reducing agents are described in paragraphs

[0043] to

[0045] of JP-A-11-65021 and in EP-A-0803764-A1, page 7, line 34 to page 18, line 12. The reducing agent is preferably a so-called hindered phenol reducing agent or a bisphenol reducing agent having a substituent at the ortho position of the phenolic hydroxyl group. The reducing agent may be as described in WO 2018 / 074430.

[0072] The amount of reducing agent added was 0.1 g / m ２ ~3.0g / m ２ is preferably 0.2 g / m ２ ~2.0 g / m ２ and more preferably 0.3 g / m ２ ~1.0 g / m ２ The reducing agent is preferably contained in an amount of 5 mol % to 50 mol %, more preferably 8 mol % to 30 mol %, and even more preferably 10 mol % to 20 mol %, per mol of silver on the side having the image-forming layer. The reducing agent is preferably contained in the image-forming layer and its adjacent layer.

[0073] The reducing agent may be incorporated into the photothermographic material by any method, such as in the form of a solution, an emulsion dispersion, or a solid particle dispersion, into the coating solution. Well-known emulsion dispersion methods include dissolving the reducing agent in an oil such as dibutyl phthalate, tricresyl phosphate, dioctyl sebacate, or tri(2-ethylhexyl)phosphate, or in an auxiliary solvent such as ethyl acetate or cyclohexanone, and then adding a surfactant such as sodium dodecylbenzenesulfonate, sodium oleoyl-N-methyltaurate, or sodium di(2-ethylhexyl)sulfosuccinate to mechanically prepare an emulsion dispersion. In this case, it is also preferable to add a polymer such as α-methylstyrene oligomer or poly(t-butylacrylamide) to adjust the viscosity and refractive index of the oil droplets.

[0074] Solid particle dispersion methods include dispersing a reducing agent powder in a suitable solvent such as water using a ball mill, colloid mill, vibrating ball mill, sand mill, jet mill, roller mill, or ultrasonic waves to prepare a solid dispersion. Protective colloids (e.g., polyvinyl alcohol) and surfactants (e.g., anionic surfactants such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups substituted at different positions)) may also be used. Zirconium beads, such as zirconia, are typically used as the dispersion medium in these mills, and zirconium (Zr) may leach from these beads and become mixed into the dispersion. While this varies depending on the dispersion conditions, the preferred range is 1 ppm to 1000 ppm. The Zr content in the photothermographic material is preferably 0.5 mg or less per gram of silver. The aqueous dispersion preferably contains a preservative (e.g., benzoisothiazolinone sodium salt). It is particularly preferred to add the reducing agent in the form of particles formed by a solid particle dispersion method, with the average particle size of the particles being preferably 0.01 μm to 10 μm, more preferably 0.05 μm to 5 μm, and even more preferably 0.1 μm to 2 μm. It is also preferred to disperse other solid dispersions to particle sizes within this range before use.

[0075] <<Binder>> The image forming layer contains a binder.

[0076] The binder (i.e., binder polymer) used in the image-forming layer may be any polymer, and suitable binders are transparent or translucent, generally colorless, and include natural resins, polymers, and copolymers, synthetic resins, polymers, and copolymers, and other film-forming media, such as gelatins, rubbers, poly(vinyl alcohols), hydroxyethyl celluloses, cellulose acetates, cellulose acetate butyrates, poly(vinylpyrrolidones), casein, starch, poly(acrylic acids), poly(methyl methacrylate ... Examples of binders include poly(acrylic acid), poly(vinyl chloride), poly(methacrylic acid), styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, poly(vinyl acetals) (e.g., poly(vinyl formal) and poly(vinyl butyral)), poly(esters), poly(urethanes), phenoxy resins, poly(vinylidene chloride), poly(epoxides), poly(carbonates), poly(vinyl acetate), poly(olefins), cellulose esters, and poly(amides). The binder may be coated from water, an organic solvent, or an emulsion. In this disclosure, "transparent" in a binder refers to a visible light (400 to 700 nm) transmittance of 80% or more, and "semitransparent" refers to a visible light (400 to 700 nm) transmittance of 10% or more but less than 80%.

[0077] The glass transition temperature (Tg) of the binder is preferably 0°C or higher and 80°C or lower (hereinafter, sometimes referred to as a high Tg binder), more preferably 10°C or higher and 70°C or lower, and even more preferably 15°C or higher and 60°C or lower.

[0078] In this specification, Tg was calculated using the following formula.

[0079]

[0080] Here, the polymer is a copolymer of n monomer components, i=1 to n. X ｉ is the mass fraction of the i-th monomer (ΣX ｉ = 1), Tg ｉis the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer, where Σ is the sum from i=1 to i=n. The glass transition temperature (Tgi) of the homopolymer of each monomer was taken from Polymer Handbook (3rd Edition) (by J. Brandrup and E. H. Immergut (Wiley-Interscience, 1989)).

[0081] Two or more binders may be used in combination as needed. Also, a binder having a glass transition temperature of 20° C. or higher may be used in combination with a binder having a glass transition temperature of less than 20° C. When two or more polymers having different Tg's are blended, it is preferable that the weight average Tg be within the above range.

[0082] The image-forming layer is preferably formed by coating and drying a coating solution containing 30% by mass or more of water based on the total mass of the solvent. When the image-forming layer is formed by coating and drying a coating solution containing 30% by mass or more of water based on the total mass of the solvent, and when the binder of the image-forming layer is soluble or dispersible in an aqueous solvent (water solvent), performance is improved, particularly when the binder is made of a polymer latex whose equilibrium water content at 25°C and 60% RH is 2% by mass or less. The most preferred form is one prepared so that the ionic conductivity is 2.5 mS / cm or less, and an example of such a preparation method is a method in which the polymer is synthesized and then purified using a separation membrane.

[0083] The aqueous solvent in which the polymer is soluble or dispersible herein refers to water or a mixture of water and 70% by mass or less of a water-miscible organic solvent. Examples of the water-miscible organic solvent include alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, ethyl acetate, and dimethylformamide.

[0084] The term "aqueous solvent" is also used herein in the case of a system in which the polymer is not thermodynamically dissolved but exists in a dispersed state.

[0085] The "equilibrium moisture content at 25°C and 60% RH" refers to the mass W of the polymer in a moisture-controlled equilibrium state in an atmosphere of 25°C and 60% RH. １ and the mass W of the polymer in an absolute dry condition at 25°C. ０ can be expressed as follows using

[0086]

[0087] For the definition and measurement method of equilibrium water content, reference can be made to, for example, Polymer Engineering Lectures 14, Polymer Material Testing Methods (edited by the Society of Polymer Science, Chijin Shokan).

[0088] The equilibrium moisture content of the binder polymer at 25° C. and 60% RH is preferably 2% by mass or less, more preferably 0.01% by mass to 1.5% by mass, and even more preferably 0.02% by mass to 1% by mass.

[0089] As the polymer, a polymer dispersible in an aqueous solvent is particularly preferred. Examples of the dispersed state include latex in which particles of a water-insoluble hydrophobic polymer are dispersed, and polymer molecules are dispersed in a molecular state or in the form of micelles, but latex-dispersed particles are more preferred. The average particle size of the dispersed particles is 1 nm to 50,000 nm, preferably 5 nm to 1,000 nm, more preferably 10 nm to 500 nm, and even more preferably 50 nm to 200 nm. The particle size distribution of the dispersed particles is not particularly limited, and they may have either a wide particle size distribution or a monodisperse particle size distribution. Mixing two or more particles with a monodisperse particle size distribution is also preferred for controlling the physical properties of the coating solution.

[0090] Preferred examples of the polymer dispersible in an aqueous solvent include hydrophobic polymers such as acrylic polymers, poly(esters), rubbers (e.g., styrene butadiene rubber (SBR resin)), poly(urethanes), poly(vinyl chlorides), poly(vinyl acetates), poly(vinylidene chloride), and poly(olefins). These polymers may be linear, branched, or crosslinked polymers, and may be homopolymers formed by polymerizing a single monomer or copolymers formed by polymerizing two or more monomers. In the case of copolymers, they may be random or block copolymers. The molecular weight of these polymers, in number average molecular weight, is preferably 5,000 to 1,000,000, more preferably 10,000 to 200,000. Within the above range, the image-forming layer has sufficient mechanical strength and excellent film-forming properties. Crosslinkable polymer latexes are particularly preferred.

[0091] Specific examples of the latex and preferred latexes may be those described in WO 2018 / 074430.

[0092] The image-forming layer of the photothermographic material may contain, as needed, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, etc. The amount of such a hydrophilic polymer added is preferably 30% by weight or less, more preferably 20% by weight or less, of the total binder in the image-forming layer.

[0093] The image-forming layer (non-photosensitive organic silver salt-containing layer) is preferably formed using a polymer latex. The binder is more preferably an aqueous latex. The amount of binder in the image-forming layer is such that the mass ratio of total binder / non-photosensitive organic silver salt is 1 / 10 to 10 / 1, more preferably 1 / 3 to 5 / 1, and even more preferably 1 / 1 to 3 / 1.

[0094] Furthermore, such an organic silver salt-containing layer is usually also a photosensitive layer (image-forming layer) containing a photosensitive silver halide, which is a photosensitive silver salt, and in such a case, the total binder / silver halide mass ratio is in the range of 400 to 5, more preferably 200 to 10.

[0095] The total amount of binder in the image forming layer is preferably 0.2 g / m ２ 30g / m or more ２ Less than 1 g / m, more preferably ２ 15g / m or more ２ More preferably, 2 g / m or less ２ 10g / m or more ２ The range is as follows: A crosslinking agent for crosslinking, a surfactant for improving coating properties, etc. may be added to the image forming layer.

[0096] <<Other Components>> The image forming layer preferably contains other components. Examples of the other components include a sensitizing compound, a development accelerator, a hydrogen-bonding compound, a compound capable of releasing one or more electrons from a one-electron oxidized product produced by one-electron oxidation, a compound having an adsorptive group and a reducing group (adsorbable redox compound), an antifogging agent, etc. The contents of these may be as described in WO 2018 / 074430.

[0097] <Support> Photothermographic materials have a support. A transparent support is preferred. Resin is also preferred as the support material. In this disclosure, "transparent" refers to a film having a visible light (400 nm to 700 nm) transmittance of 80% or more. The support is preferably a polyester, particularly polyethylene terephthalate, heat-treated at a temperature range of 130°C to 185°C to relieve internal strain remaining in the film during biaxial stretching and eliminate thermal shrinkage strain that occurs during thermal development. In the case of photothermographic materials for medical use, the transparent support may be colored with a blue dye (e.g., Dye-1 described in the examples of JP-A No. 8-240877), or may be uncolored. As the support, it is preferred to use a water-soluble polyester described in JP-A No. 11-84574, a styrene-butadiene copolymer described in JP-A No. 10-186565, a vinylidene chloride copolymer described in JP-A No. 2000-39684, or the like. The water content of the support is preferably 0.5% by mass or less. The thickness of the support is not particularly limited, but is preferably 10 μm or more and 500 μm or less, more preferably 100 μm or more and 300 μm or less, and even more preferably 150 μm or more and 190 μm or less.

[0098] <Other Layer Structures> The photothermographic material preferably has an image-forming layer and a non-photosensitive layer in this order on at least one side of the support. The non-photosensitive layer is preferably the outermost layer, and a non-photosensitive intermediate layer is preferably provided between the image-forming layer and the non-photosensitive layer. In addition, an antihalation layer may be provided. Furthermore, a non-photosensitive back layer may be provided on the other side of the support (the side opposite to the side on which the image-forming layer is formed). Other layer structures including these may be as described in WO 2018 / 074430.

[0099] <Surface pH> The surface pH of the image-forming layer of the photothermographic material prior to thermal development is preferably 7.0 or less, more preferably 6.6 or less. While there is no particular lower limit, it is generally around 3. A particularly preferred pH range is 4 to 6.2. Adjusting the surface pH using an organic acid such as a phthalic acid derivative, a non-volatile acid such as sulfuric acid, or a volatile base such as ammonia is preferred from the perspective of reducing the surface pH. Ammonia, in particular, is preferred for achieving a low surface pH because it is easily volatile and can be removed before coating or thermal development. It is also preferred to use ammonia in combination with a non-volatile base such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. The method for measuring surface pH is described in paragraph 0123 of JP-A 2000-284399. The pH values ​​measured here are measured at 25°C.

[0100] <Hardening Agent> Each layer of the photothermographic material, such as the image forming layer and the protective layer, may contain a hardening agent. The hardening agent may be the one described in WO 2018 / 074430.

[0101] <Surfactants> Surfactants that can be used in photothermographic materials are described in paragraph 0132 of JP-A-11-65021, solvents in paragraph 0133 of the same publication, supports in paragraph 0134 of the same publication, antistatic or conductive layers in paragraph 0135 of the same publication, methods for obtaining color images in paragraph 0136 of the same publication, and lubricants in paragraphs 0061 to 0064 of JP-A-11-84573. The surfactants may be those described in the specification of WO 2018 / 074430.

[0102] <Antistatic Agent> The photothermographic material preferably has a conductive layer containing a metal oxide or a conductive polymer. The antistatic layer may also be used as an undercoat layer or as a layer separate from these layers. The antistatic agent may be the same as that described in WO 2018 / 074430.

[0103] <Packaging Material> The photothermographic material is preferably packaged in at least one of a packaging material having low oxygen permeability and low moisture permeability in order to suppress fluctuations in photographic performance during raw storage or to suppress curling, rolling, etc. The packaging material may be the same as that described in WO 2018 / 074430.

[0104] <Other Usable Techniques> Techniques that can be used for heat-developable photosensitive materials include those described in European Patent Application Publication No. 803764A1, European Patent Application Publication No. 883022A1, International Publication No. WO 98 / 36322, JP-A Nos. 56-62648, 58-62644, JP-A Nos. 9-43766 and 9-281637. No. 9-297367, No. 9-304869, No. 9-311405, No. 9-329865, No. 10-10669, No. 1 No. 0-62899, No. 10-69023, No. 10-186568, No. 10-90823, No. 10-171063, No. 10-1 No. 86565, No. 10-186567, No. 10-186569 to No. 10-186572, No. 10-197974, No. 10- No. 197982, No. 10-197983, No. 10-197985 to No. 10-197987, No. 10-207001, No. 10- No. 207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10 -307365 Publication, Publication No. 10-312038, Publication No. 10-339934, Publication No. 11-7100, Publication No. 11-15105, Publication No. 11-24No. 200, No. 11-24201, No. 11-30832, No. 11-84574, No. 11-65021, No. 11- No. 109547, No. 11-125880, No. 11-129629, No. 11-133536 to No. 11-133539 Publications, No. 11-133542, No. 11-133543, No. 11-223898, No. 11-352627, No. 11- No. 305377, No. 11-305378, No. 11-305384, No. 11-305380, No. 11-316435 Publication Nos. 11-327076, 11-338096, 11-338098, 11-338099, 11-343420, JP 2000-187298, 2000-10229, 2000-47345, 2000- Also mentioned are Patent Publication Nos. 206642, 2000-98530, 2000-98531, 2000-112059, 2000-112060, 2000-112104, 2000-112064, and 2000-171936.

[0105] (Method for producing a photothermographic material) The method for producing a photothermographic material is not particularly limited, but preferably includes a step of forming the image-forming layer by aqueous coating, from the viewpoint of easily adjusting the pH and facilitating the introduction of mechanisms such as chemical sensitization and color sensitization of silver halide. Furthermore, the method for producing a photothermographic material preferably includes a step of forming a non-photosensitive layer by aqueous coating. Each layer, such as the image-forming layer in the photothermographic material, may be coated by any method, but dry coating is preferably used. The coating method may be as described in International Publication No. WO 2018 / 074430.

[0106] The image forming layer coating liquid is preferably a thixotropic fluid. For details of thixotropic fluids, reference can be made to JP-A-11-52509. The image forming layer coating liquid, which is an organic silver salt-containing layer coating liquid, is preferably a thixotropic fluid having a shear rate of 0.1 S. －１The viscosity of the coating liquid for the image forming layer is preferably 400 mPa·s or more and 100,000 mPa·s or less, and more preferably 500 mPa·s or more and 20,000 mPa·s or less, at a shear rate of 1,000 S. －１ The viscosity at 1 mPa·s or more and 200 mPa·s or less is preferably 5 mPa·s or more and 80 mPa·s or less.

[0107] The solvent for the coating solution for the image-forming layer of the photothermographic material (here, for simplicity, the solvent and dispersion medium are collectively referred to as the solvent) is preferably an aqueous solvent containing 30% by weight or more of water. As a component other than water, any water-miscible organic solvent such as methyl alcohol, ethyl alcohol, isopropyl alcohol, methyl cellosolve, ethyl cellosolve, dimethylformamide, or ethyl acetate may be used. The water content of the solvent for the coating solution is preferably 50% by weight or more, more preferably 70% by weight or more. Examples of preferred solvent compositions include water, water / methyl alcohol = 90 / 10, water / methyl alcohol = 70 / 30, water / methyl alcohol / dimethylformamide = 80 / 15 / 5, water / methyl alcohol / ethyl cellosolve = 85 / 10 / 5, and water / methyl alcohol / isopropyl alcohol = 85 / 10 / 5 (values ​​are by weight %).

[0108] When preparing a coating solution, it is preferable to use a known in-line mixer or implant mixer when mixing two types of solution. Examples of preferred in-line mixers include those described in JP-A No. 2002-85948, and examples of preferred implant mixers include those described in JP-A No. 2002-90940. It is preferable to degas the coating solution to maintain good coating surface condition. Examples of preferred degassing methods include the method described in JP-A No. 2002-66431. When applying the coating solution, it is preferable to perform static elimination to prevent adhesion of dust, dirt, etc. due to the static resistance of the support. Examples of preferred static elimination methods include the method described in JP-A No. 2002-143747. It is important to precisely control the drying air and drying temperature to dry a non-setting image-forming layer coating solution. Examples of preferred drying methods are described in detail in JP-A Nos. 2001-194749 and 2002-139814. In order to improve film-forming properties, the photothermographic material is preferably heat-treated immediately after coating and drying. The heat treatment temperature is preferably in the range of 60°C to 100°C, more preferably 70°C to 90°C, as film surface temperature. The heating time is preferably in the range of 1 second to 60 seconds, more preferably 2 seconds to 10 seconds. Preferred heat treatment methods include those described in JP-A No. 2002-107872. Furthermore, for stable and continuous production of photothermographic materials, the manufacturing methods described in JP-A Nos. 2002-156728 and 2002-182333 are preferably used.

[0109] The photothermographic material is preferably a mono-sheet type (a type in which an image can be formed on the photothermographic material without using another sheet such as an image-receiving material).

[0110] (Image Forming Method) 1) Exposure The photothermographic material may be exposed by any method. As the exposure light source, scanning exposure with laser light is preferably used. As the laser, a red to infrared He—Ne laser, a red semiconductor laser, a blue to green emitting argon laser, a blue to green emitting He—Ne laser, a blue to green emitting He—Cd laser, or a blue semiconductor laser can be used. The exposure can be as described in WO 2018 / 074430.

[0111] 2) Thermal Development The photothermographic material may be developed by any method, but typically the photothermographic material is developed by heating after imagewise exposure. The development temperature is preferably 80°C to 250°C, more preferably 100°C to 140°C, and even more preferably 110°C to 130°C. The development time is preferably 1 second to 60 seconds, more preferably 3 seconds to 30 seconds, even more preferably 5 seconds to 25 seconds, and particularly preferably 7 seconds to 15 seconds.

[0112] As a thermal development method, either a drum type heater or a plate type heater may be used, but a plate type heater method is more preferred. The thermal development method may be the same as that described in WO 2018 / 074430.

[0113] 3) System The photothermographic material can be used in a system such as a medical laser imager equipped with an exposure section and a heat development section. Conventionally known systems can be used as such systems.

[0114] (Uses) The photothermographic material forms a black-and-white image containing silver, and can be used as a photothermographic material for medical diagnosis, a photothermographic material for industrial photography, a photothermographic material for printing, or a photothermographic material for computer output microfilm (COM).

[0115] (Compound) A compound according to one embodiment of the present disclosure is a compound represented by the following general formula (2).

[0116]

[0117] In the above general formula (2), R１ , R ３ , and R ４ are each independently H, Cl, F, an alkyl group, an alkylthio group, an alkoxy group, an amide group, an ester group, or a sulfonyl group, and R ５ is an alkyl group or a phenyl group. １ , R ３ , and R ４ At least one of R is a F atom. １ , R ３ and R ４ The alkyl group, alkoxy group, amide group, ester group, and sulfonyl group in R may be unsubstituted or substituted with a substituent. ５ The alkyl group and phenyl group in the formula (I) may be unsubstituted or substituted with a substituent.

[0118] R １ , R ３ , and R ４ Regarding R in the above general formula (1), １ , R ３ , and R ４ It is the same as R ５ The same applies to the alkyl group and phenyl group as described above, and the same applies to the substituent in the case of substitution. In the compound, the hydrazino group is -CO-, -COCO-, -CONR- or -SO ２ It is preferable that the alkyl group has either one of the following structures: -CONR- or -SO-. ２ -, more preferably -CONR-, where R represents a hydrogen atom or an alkyl group, and is preferably a hydrogen atom. The hydrazino group is -COCO-, -CON-, or -SO ２ The compound represented by the general formula (2) is the same compound as the development accelerator represented by the general formula (2) explained in the development accelerator section above, and specific examples are also as mentioned above.

[0119] The compound according to an embodiment of the present disclosure is a novel compound, and is preferably used as a development accelerator in a photothermographic material, because the use of this compound as a development accelerator can particularly achieve both an improvement in color density in exposed areas and suppression of color development in unexposed areas in the photothermographic material.

[0120] The present disclosure will be described in more detail below based on examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present disclosure. Therefore, the scope of the present disclosure should not be interpreted as being limited by the examples shown below. In the examples, "%" and "parts" regarding concentration, content, etc. mean "% by mass" and "parts by mass," respectively, unless otherwise specified.

[0121] (Synthesis of Development Accelerator) Development accelerators 1 to 5 were synthesized by the following synthesis method. [Example 1: Synthesis of Development Accelerator 1 (Compound (1))] 25 ml of DMAc and 5.01 g of 3,4,5,6-tetrafluorophthalonitrile (Tokyo Chemical Industry Co., Ltd.) were added to a 100 mL recovery flask and stirred under ice cooling. 2.53 g of sodium bicarbonate (Fujifilm Wako Pure Chemical Industries, Ltd.) was added, and then 4.73 g of N-(2,4,4-trimethylpentan-2-yl)hydrazinecarboxamide was added in portions while maintaining the temperature at 10°C or below. The ice bath was removed and the mixture was stirred at room temperature for 2 hours. The reaction solution was poured into 75 mL of distilled water and stirred at room temperature. The mixture was decanted into a separatory funnel, and 100 mL of ethyl acetate was added. The aqueous layer was discarded, and 100 mL of dilute hydrochloric acid was added, followed by separation, and the aqueous layer was removed. 100 mL of saturated saline was further added, followed by separation, and the aqueous layer was removed. The organic layer was dried over magnesium sulfate, filtered, and concentrated. 30 mL of chloroform was added, and the precipitated solid was filtered. The mixture was dissolved in 25 mL of ethyl acetate by heating, and 38 mL of hexane was added and stirred at room temperature. The mixture was suction filtered and dried at room temperature to obtain compound (1). Compound (1) was purified by deuterated dimethyl sulfoxide (DMSO-d ６ ) as a solvent １ H-NMR spectrum analysis was performed, and the obtained chemical shift values ​​are shown below. 1H-NMR (DMSO-d) δ = 0.95 (s, 9H), 1.28 (s, 6H), 1.65 (s, 2H), 5.09 (s, 2H), 5.98 (s, 1H), 7.99 (s, 1H), 9.01 (s, 1H). Compound (1) was the compound shown below.

[0122]

[0123] Example 2: Synthesis of development accelerator 2 (compound (2)) Compound (2) was synthesized according to the following route.

[0124]

[0125] 2-1) Synthesis of Intermediate (2)-1 To a 200 ml three-neck flask, 100 mL of N,N-dimethylformamide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 50.0 g of 3,4,5,6-tetrafluorophthalonitrile were added. After ice-cooling, 38.0 g of potassium carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added, and 50.6 g of 1-dodecanethiol (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added dropwise while maintaining the internal temperature at 10°C or below. The mixture was stirred for 2 hours under ice-cooling. The mixture was subjected to suction filtration, and the filtrate was decanted into a separatory funnel, to which 300 mL of ethyl acetate was added. The organic layer was washed three times with 250 mL of 5% aqueous ammonium chloride solution. The mixture was dried over magnesium sulfate and then concentrated. Column purification was performed to obtain 51.9 g of Intermediate (2)-1 (yield: 54%). Intermediate (2)-1 was prepared by deuterated chloroform (CDCl ３ ) as a solvent １ H-NMR spectrum analysis was performed, and the obtained chemical shift values ​​are shown below. 1 H-NMR(CDCl3) δ = 0.86-0.90(t, 3H), 1.25-1.31(m, 16H), 1.39-1.42(m, 2H), 1.60-1.64(m, 2H), 3.10-3.14(t, 2H)

[0126] 2-2) Synthesis of Intermediate (2)-2 A 300 mL three-neck flask was charged with 260 mL of acetic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 53.2 g of intermediate (2)-1, and 4.3 g of sodium tungstate dihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.). While immersed in a 45°C water bath and stirring, 43.1 g of 35% aqueous hydrogen peroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added dropwise over 1 hour. After the dropwise addition, the water bath was heated to 60°C and stirred for 1 hour. The temperature was lowered to room temperature, and 470 mL of water was added dropwise. The mixture was stirred at room temperature for 1 hour, and the precipitated solid was filtered. The solid was then spray-washed with water. The filtered solid was added to 500 g of a 1% aqueous sodium sulfite solution and stirred at room temperature for 1 hour. The mixture was then suction-filtered and spray-washed with water. After drying at 50°C, 43 g (75% yield) of intermediate (2)-2 was obtained. Intermediate (2)-2 was purified by deuterated chloroform (CDCl ３ ) as a solvent １ H-NMR spectrum analysis was performed, and the obtained chemical shift values ​​are shown below. 1 H-NMR(CDCl3) δ = 0.86-0.89(t, 3H), 1.25-1.33(m, 16H), 1.44-1.48(m, 2H), 1.82-1.86(m, 2H), 3.37-3.41(m, 2H)

[0127] 2-3) Synthesis of Intermediate (2) To a 1 L (liter) three-neck flask were added 160 mL of N,N-dimethylformamide (Fujifilm Wako Pure Chemical Industries, Ltd.) and 33.1 g of Intermediate (2)-2. Under ice cooling, 15.0 g of N-(2,4,4-trimethylpentan-2-yl)hydrazinecarboxamide was added in portions while maintaining the temperature below 10°C. After stirring at 10°C or below for 1 hour, a mixed solution of 160 mL of 0.5 mol / L aqueous sodium bicarbonate solution and 160 mL of methanol was added dropwise while maintaining the internal temperature below 10°C. The mixture was stirred at 10°C or below for 15 minutes, and the precipitated solid was filtered. The mixture was dried overnight at 50°C to obtain a crude product. The obtained crude product was added to 250 mL of acetonitrile, stirred at 40°C for 30 minutes, and hot-filtered. The filtrate was decanted into a recovery flask, and 130 mL of acetonitrile was added. After stirring at room temperature for 15 minutes, 190 mL of water was added dropwise and stirred at room temperature for 1 hour. The mixture was washed three times with a mixed solvent of 30 mL of acetonitrile and 30 mL of water. After drying at 50°C with a blower, 30 g (yield 60%) of compound (2) was obtained as a yellow solid. Compound (2) was purified by deuterated dimethyl sulfoxide (DMSO-d ６ ) as a solvent １ H-NMR spectrum analysis was performed, and the obtained chemical shift values ​​are shown below. 1 H-NMR (DMSO-d) δ = 0.83-0.86 (s, 3H), 0.94 (s, 9H), 1.22-1.26 (m, 20H), 1.34-1.36 (m, 2H), 1.63 (s, 2H), 1.70-1.74 (m, 2H), 3.63-3.67 (t, 2H), 5.09 (s, 2H), 6.23 (s, 1H), 8.14 (s, 1H), 8.92 (s, 1H). Compound (2) was the compound shown below.

[0128]

[0129] Comparative Example 1: Synthesis of Development Accelerator 3 (Compound (3)) Compound (3) is Compound (6) described in paragraph

[0032] of JP-A-10-254111, and was synthesized by the method described therein. Compound (3) was the compound shown below.

[0130]

[0131] Reference Example 2 Development Accelerator 4 (Compound (4)) Compound (4) was synthesized. The compound was described in WO2018 / 074430 and was the compound shown below.

[0132]

[0133] Example 3: Synthesis of development accelerator 5 (compound (5)) Compound (5) was synthesized according to the following route.

[0134]

[0135] 5-1) Synthesis of Intermediate (5)-1 To a 200 ml three-neck flask were added 40 mL of N,N-dimethylacetamide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 4.97 g of benzyl mercaptan (manufactured by Tokyo Chemical Industry Co., Ltd.). 8.81 g of 3,4,5,6-tetrafluorophthalonitrile was added with stirring at room temperature. The mixture was cooled with ice, and 6.71 g of potassium carbonate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added in portions while maintaining the internal temperature at around 10°C. The mixture was stirred at room temperature for 2 hours, and then 120 mL of water was added and stirred for 1 hour. The precipitated solid was filtered, washed with water, and dried at room temperature to obtain 12.2 g of a crude product containing Intermediate (5)-1.

[0136] 5-2) Synthesis of Intermediate (5)-2 To a 200 mL three-neck flask were added 60 mL of acetic acid (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), 1.3 g of sodium tungstate dihydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.), and the obtained crude product 12.2. While immersed in a 45°C water bath and stirring, 12.3 g of 35% aqueous hydrogen peroxide (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was added dropwise over 30 minutes. After the dropwise addition, the water bath was heated to 60°C and stirred for 1 hour. The temperature was lowered to room temperature, and 120 mL of water was added dropwise. After stirring at room temperature for 1 hour, the precipitated solid was filtered and washed with water. Drying at room temperature yielded 10.0 g of a crude product containing intermediate (5)-2.

[0137] 5-3) Synthesis of Compound (5) To a 200 mL recovery flask were added 15 mL of N,N-dimethylacetamide (Fujifilm Wako Pure Chemical Industries, Ltd.), 5.04 g of intermediate (5)-2, and 1.31 g of sodium bicarbonate (Fujifilm Wako Pure Chemical Industries, Ltd.). Under ice cooling, 2.81 g of N-(2,4,4-trimethylpentan-2-yl)hydrazinecarboxamide was added in portions while maintaining the temperature at 10°C or below. The mixture was stirred under ice cooling for 1 hour, decanted into a separatory funnel with 90 mL of ethyl acetate, and 75 mL of water was added to separate the layers. After removing the aqueous layer, 60 mL of dilute hydrochloric acid was added, followed by separation, and the aqueous layer was removed. 60 mL of water was added, followed by separation, and the aqueous layer was removed. 60 mL of saturated saline was added, followed by separation, and the aqueous layer was removed. The mixture was dried over magnesium sulfate and concentrated. After column purification, the mixture was dissolved in ethyl acetate, hexane was added, and the precipitated solid was filtered. The compound (5) was dried at 50°C to obtain 3.59 g of compound (5). ６ ) as a solvent １ H-NMR spectrum analysis was performed, and the obtained chemical shift values ​​are shown below. 1 H-NMR (DMSO-d) δ = 0.95 (s, 9H), 1.28 (s, 6H), 1.66 (s, 2H), 5.09 (s, 2H), 6.30 (s, 1H), 7.33-7.43 (m, 5H), 8.20 (s, 1H), 8.84 (s, 1H). Compound (5) was the compound shown below.

[0138]

[0139] Example 4: Synthesis of development accelerator 6 (compound (6)) Compound (6) was synthesized according to the following route.

[0140]

[0141] 30 mL of N,N-dimethylformamide (FUJIFILM Wako Pure Chemical Industries, Ltd.) and 5.73 g of intermediate (2)-1 were added to a 200 mL recovery flask and cooled in an ice bath. 2.81 g of N-(2,4,4-trimethylpentan-2-yl)hydrazinecarboxamide was added in portions while maintaining the temperature at 5°C or below. The ice bath was removed, and the mixture was stirred at room temperature for 1 hour. 1.26 g of sodium bicarbonate (FUJIFILM Wako Pure Chemical Industries, Ltd.) was added and stirred for 15 minutes. The mixture was filtered under suction to remove solids, and then spray-washed with 50 mL of ethyl acetate. The filtrate was decanted into a separatory funnel, and the organic layer was washed three times with 50 mL of 5% aqueous ammonium chloride solution. The organic layer was then concentrated. Column purification was performed, and the column filtrate was concentrated to obtain a solid. Drying at 50°C yielded 2.4 g of compound (6) (yield: 26%). Compound (6) was subjected to 1H-NMR spectrum analysis using deuterated dimethyl sulfoxide (CDCl3) as a solvent, and the obtained chemical shift values ​​are shown below. 1 H-NMR (CDCl) δ = 0.89 (t, 3H), 0.99 (s, 9H), 1.25-1.43 (m, 18H), 1.55-1.62 (m, 8H), 1.69 (s, 2H), 2.91 (t, 2H), 4.84 (s, 1H), 6.40 (d, 1H), 7.36 (s, 1H). Compound (6) was the compound shown below.

[0142]

[0143] [Example 5: Synthesis of development accelerator 7 (compound (7))] Compound (7) was synthesized in the same manner as compound (6), except that 1-hexanethiol was used instead of 1-dodecanethiol. Compound (7) was synthesized by the same method as compound (6). ３ ) as a solvent, and the resulting chemical shift values ​​are shown below. 1H-NMR (CDCl) δ = 0.89 (t, 3H), 0.99 (s, 9H), 1.25-1.43 (m, 6H), 1.55-1.62 (m, 8H), 1.69 (s, 2H), 2.91 (t, 2H), 4.84 (s, 1H), 6.40 (d, 1H), 7.36 (s, 1H). Compound (7) was the compound shown below.

[0144]

[0145] [Examples 6 to 10 and Comparative Example 2: Preparation of Photothermographic Materials] (Preparation of Undercoat Layer-Containing PET Support) A 175 μm-thick PET (polyethylene terephthalate) support was prepared according to the procedure described in paragraphs

[0319] to

[0325] of JP-A No. 2006-91780. The support had an undercoat layer on the image-forming surface and two undercoat layers on the back surface opposite the image-forming surface.

[0146] (Preparation of Back Surface Coating Liquid) A back surface coating liquid was prepared according to the procedure described in paragraph

[0326] of JP-A No. 2006-91780.

[0147] (Preparation of Back Surface Protective Layer Coating Solution) A container was maintained at 40°C, and 40 g of gelatin, 35 mg of benzoisothiazolinone, and 840 ml of water were added to dissolve the gelatin. Furthermore, 5.8 ml of a 1 mol / L aqueous solution of sodium hydroxide, a 6.7% by weight aqueous dispersion of carnauba wax, 10 ml of a 5% by weight aqueous solution of di(2-ethylhexyl)sulfosuccinate sodium salt, 20 ml of a 3% by weight aqueous solution of polystyrenesulfonate, 4.5 ml of a 1% by weight solution of fluorine compound F-29 (shown below) in a 1:1 water:methanol solvent, and 32 g of a 19% by weight solution of methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization weight ratio: 57 / 8 / 28 / 5 / 2) latex were mixed. Just before coating, 25 ml of a 4% by weight aqueous solution of N,N-ethylenebis(vinylsulfoneacetamide) was added to prepare a back surface protective layer coating solution.

[0148]

[0149] (Coating of Back Surface Coating Layer) A back surface coating solution was applied to the back surface of the above-mentioned undercoated support in a gelatin coating amount of 1.04 g / m ２ and the coating amount of the back surface protective layer was adjusted to 1.7 g / m ２ The layers were then dried to form a backing layer.

[0150] (Formation of image-forming layer, intermediate layer, and surface protective layer) 1. Preparation of coating materials 1) Preparation of mixed emulsion A for coating solution having silver halide emulsion A mixed emulsion A for coating solution, which is a mixture of silver halide emulsions, was prepared according to the procedure described in paragraphs

[0332] to

[0337] of JP-A No. 2006-91780.

[0151] 2) Preparation of Fatty Acid Silver Dispersion A silver behenate dispersion, which is a fatty acid silver dispersion, was obtained according to the procedure described in paragraphs

[0338] to

[0342] of JP-A No. 2006-91780.

[0152] 3) Preparation of Reducing Agent Dispersion The following Reducing Agent-1 Dispersion and Reducing Agent-2 Dispersion were obtained according to the procedure described in paragraphs

[0343] to

[0344] of JP-A No. 2006-91780.

[0153] 4) Preparation of Hydrogen-Bonding Compound-1 Dispersion The following hydrogen-bonding compound-1 dispersion was obtained according to the procedure described in paragraph

[0345] of JP-A No. 2006-91780.

[0154]

[0155] 5) Preparation of Development Accelerator-1 Dispersion 10 kg of any one of the comparative development accelerator compound (3), the compound (4) of Reference Example 2, and the development accelerator compounds (1), (2), (5), (6), and (7) of the present invention and 20 kg of a 10% by weight aqueous solution of modified polyvinyl alcohol (Poval MP203, manufactured by Kuraray Co., Ltd.) were added with 10 kg of water and thoroughly mixed to form a slurry. This slurry was pumped using a diaphragm pump and dispersed for 3 hours and 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. Thereafter, 0.2 g of benzoisothiazolinone sodium salt and water were added to adjust the development accelerator concentration to 20% by weight, thereby obtaining 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 resulting development accelerator dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign matter such as dust, and then stored.

[0156] 6) Preparation of Dispersions of Development Accelerator-101 and Tone Adjusting Agent-1 Solid dispersions of Development Accelerator-101 and Tone Adjusting Agent-1 were also dispersed in the same manner as for Development Accelerator-1 to obtain dispersions of 20% by mass and 15% by mass, respectively.

[0157]

[0158]

[0159] 7) Preparation of Various Dispersions An organic polyhalogen compound-1 dispersion, an organic polyhalogen compound-2 dispersion, a phthalazine compound-1 solution, a mercapto compound-1 aqueous solution, a mercapto compound-2 aqueous solution, and an SBR latex solution shown below were obtained according to the procedures described in paragraphs

[0348] to

[0354] of JP-A No. 2006-91780.

[0160]

[0161]

[0162] 2. Preparation of Coating Solution 1) Preparation of Image-Forming Layer Coating Solution 1000 g of fatty acid silver dispersion, 135 ml of water, 28.5 cc of a 2% by mass aqueous solution of metal phthalocyanine dye-1, 25 g of organic polyhalogen compound-1 dispersion, 39 g of organic polyhalogen compound-2 dispersion, 171 g of phthalazine compound-1 solution, 1060 g of SBR latex (Tg: 17°C) solution, 75 g of reducing agent-1 dispersion, 78 g of reducing agent-2 dispersion, 55 g of hydrogen-bonding compound-1 dispersion, 4.8 g of development accelerator-1 dispersion, 5.2 g of development accelerator-101 dispersion, 2.1 g of color tone adjuster-1 dispersion, 4 ml of a mercapto compound-1 aqueous solution, and 4 ml of a mercapto compound-2 aqueous solution were added in this order, and just before coating, 140 g of silver halide mixed emulsion A was added and mixed well. The image-forming layer coating solution was then sent directly to a coating die and coated. The viscosity of the image-forming layer coating solution was 40 mPa·s at 40° C. (No. 1 rotor, 60 rpm) as measured using a Tokyo Keiki Brookfield viscometer. The viscosities of the coating solution at 38° C. using a Haake RheoStress RS150 were 30, 43, 41, 28, and 20 mPa·s at shear rates of 0.1, 1, 10, 100, and 1,000 1 / sec, respectively.

[0163] The amount of zirconium in the coating solution was 0.30 mg per 1 g of silver.

[0164] An intermediate layer coating liquid, a first surface protective layer coating liquid, and a second surface protective layer coating liquid were obtained according to the procedures described in paragraphs

[0357] to

[0359] of JP-A No. 2006-91780.

[0165] 3. Preparation of Photothermographic Material A sample of a photothermographic material was prepared by simultaneously applying an image forming layer, an intermediate layer, a first surface protective layer, and a second surface protective layer to the surface opposite the back surface in the order of from the undercoat side by a slide bead coating method. At this time, the temperatures of the coating solutions for the image forming layer and intermediate layer were adjusted to 31°C, the coating solution for the first surface protective layer to 36°C, and the coating solution for the second surface protective layer to 37°C.

[0166] The coating and drying conditions were as follows: Coating was performed at a speed of 180 m / min, the gap between the tip of the coating die and the support was set to 0.10 mm to 0.30 mm, and the pressure in the vacuum chamber was set to 196 Pa to 882 Pa lower than atmospheric pressure. The support was neutralized with ionized air before coating. In the subsequent chilling zone, air with a dry-bulb temperature of 10°C to 20°C was blown in to cool the coating solution, and the film was then transported in a non-contact manner and dried in a spiral-type non-contact dryer by blowing dry air with a dry-bulb temperature of 23°C to 45°C and a wet-bulb temperature of 15°C to 21°C. After drying, the film surface was conditioned at 25°C and a humidity of 40% to 60% RH, and then heated to 70°C to 90°C. After heating, the film surface was cooled to 25°C.

[0167] (Evaluation of Photographic Performance) 1) Preparation The obtained photothermographic materials (photothermographic material for Example 6 (compound (1): development accelerator 1 used), photothermographic material for Example 7 (compound (2): development accelerator 2 used), photothermographic material for Example 8 (compound (5): development accelerator 5 used), photothermographic material for Example 9 (compound (6): development accelerator 6 used), photothermographic material for Example 10 (compound (7): development accelerator 7 used), photothermographic material for Comparative Example 2 (compound (3): comparative development accelerator 3 used), and Reference Example 2 as a reference photothermographic material (compound (4): development accelerator 4 used)) were each cut into halves, and one piece was packaged in the following packaging material in an environment of 25° C. and 50% RH and stored at room temperature for 2 weeks, and then the following evaluation was performed.

[0168] <Packaging material> Laminated film of polyethylene terephthalate 10 μm / polyethylene 12 μm / aluminum foil 9 μm / nylon 15 μm / polyethylene 50 μm containing 3% by mass of carbon; Oxygen permeability: 0.02 mL / atm m ２ ・25℃・day ・Moisture permeability: 0.10g / atm・m ２ ・25℃・day

[0169] 2) Exposure and Development of Photothermographic Material Each photothermographic material was thermally developed with a semiconductor laser using a Fuji Medical Co., Ltd. dry laser imager DRYPIX7000 (a total of 14 seconds using three panel heaters set at 107°C, 121°C, and 125°C), and the resulting images were evaluated using a densitometer (manufactured by Macbeth).

[0170] 3) Evaluation <Sensitivity> The maximum density (Dmax) was measured by increasing the exposure amount under the above-mentioned exposure and development conditions using each of the above-mentioned photothermographic materials as samples, and the saturated maximum density was measured. The range of decrease in sensitivity was calculated using the maximum density.

[0171] -Evaluation criteria- A: The sensitivity reduction is less than 2% compared to the value of the reference photothermographic material. B: The sensitivity reduction is 2% or more but less than 3% compared to the value of the reference photothermographic material.

[0172] <Density of Unexposed Area (Fog Density)> The density of the unexposed area (fogging density) was measured by processing each of the above photothermographic materials under the above developing conditions and measuring the density of the unexposed area of ​​the sample.

[0173] -Evaluation criteria- A: The increase in fog density is less than 4% relative to the value of the reference photothermographic material. B: The increase in fog density is 4% or more relative to the value of the reference photothermographic material.

[0174] The results of the above evaluations are shown in Table 1. In Table 1, "single amount" and "double amount" in the "amount added" column indicate the amount (% by mass) of each compound added in the development accelerator-1 dispersion, and "double amount" indicates that the amount added was twice the amount of "single amount."

[0175]

[0176] It has been demonstrated that the photothermographic material according to one embodiment of the present disclosure can simultaneously improve the color density (sensitivity) of exposed areas and suppress color development (suppression of fogging) in unexposed areas.

[0177] The disclosure of Japanese Patent Application No. 2024-109221, filed on July 5, 2024, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards mentioned herein are incorporated herein by reference to the same extent as if each individual document, patent application, and technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. A photothermographic material having, on one side of a support, an image-forming layer containing at least a photosensitive silver halide, a non-photosensitive organic silver salt, a reducing agent for silver ions, a binder, and a development accelerator represented by the following general formula (1): (R １ ~R ４ are each independently H, Cl, F, an alkyl group, an alkenyl group, an alkynyl group, an alkoxy group, an alkylthio group, an alkylamide group, an alkylthioamide group, an alkylester group, an alkylsulfonyl group, an alkylsulfinyl group, an alkylamino group, an acyl group, a phenoxy group, a thiophenoxy group, a benzyl group, a hydrazino group, a nitro group, or a cyano group. １ ~R ４ At least one of R is a hydrazino group; １ ~R ４ At least one of them is F.) 2. R ２ is a hydrazino group, and R １ , R ３ , and R ４ 2. The photothermographic material according to claim 1, wherein any one of the above is F.

3. R ２ is a hydrazino group, and R ３ is an alkylthio group, an alkylsulfonyl group, or an alkylsulfinyl group, and R １ and R ４ 2. The photothermographic material according to claim 1, wherein at least one of the above is F.

4. R ２ is a hydrazino group, and R ３ is an alkylsulfonyl group or F, and R １ and R ４ 2. The photothermographic material according to claim 1, wherein at least one of the above is F.

5. The photothermographic material according to any one of claims 1 to 4, wherein the binder is an aqueous latex.

6. A compound represented by the following general formula (2): (R １ , R ３ , and R ４ are each independently H, Cl, F, an alkyl group, an alkylthio group, an alkoxy group, an amide group, an ester group, or a sulfonyl group, and R ５ is an alkyl group or a phenyl group. １ , R ３ , and R ４ At least one of is F.)

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