JP2005241959A - Heat developable photosensitive material and image forming method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material having high sensitivity, a high Dmax and high contrast, ensuring the occurrence of few black spots, and good in image preservability after development, as a material for a scanner or an image setter particularly for printing plate making, and to provide an image forming method for the same. <P>SOLUTION: The heat developable photosensitive material has: on a support at least one image forming layer containing a non-photosensitive organic silver salt, a reducing agent for the organic silver salt, a photosensitive silver halide, a contrast enhancer and a binder; and at least one non-photosensitive layer for protecting the image forming layer, wherein the contrast enhancer is a compound selected from the formulae (1), (2) and (3) and an intensity of odor emitted from the heat developable photosensitive material is -3 to 1 at 120°C. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a photothermographic material and an image forming method thereof, and more particularly to a photothermographic material and an image forming method suitable for printing plate making. More specifically, the present invention relates to a photothermographic material excellent in sensitivity, maximum density (Dmax), high contrast, black spots, and image storability, and an image forming method thereof.

  Conventionally, in the fields of printing plate making and medical treatment, waste liquids resulting from wet processing of image forming materials have been a problem in terms of workability. In recent years, reduction of processing waste liquids has been strongly desired from the viewpoint of environmental conservation and space saving. ing. Therefore, there is a need for a technique related to photothermographic materials for photographic applications that can be used for efficient exposure and can form a clear black image with high resolution using a laser image setter, a laser imager, or the like. . Examples of this technique include U.S. Pat. Nos. 3,152,904, 3,487,075 and D.I. “Silver Photographic Materials” by Morgan (Handbook of Imaging Materials, Marcel Dekker, Inc., p. 48, 1991), etc. A photothermographic material containing photosensitive silver halide grains, a reducing agent and a binder is known.

  These heat-developable photosensitive materials form photographic images by heat-development processing, and the reducible silver source (organic silver salt), photosensitive silver halide, reducing agent, and the color tone of silver are adjusted as necessary. Toning agents and the like are usually contained in a dispersed state in an (organic) binder matrix. The photothermographic material is stable at normal temperature, but is developed by heating to a high temperature (for example, 80 ° C. to 140 ° C.) after exposure. That is, by heating, silver is generated through an oxidation-reduction reaction between an organic silver salt (functioning as an oxidizing agent) and a reducing agent. This redox reaction is promoted by the catalytic action of the latent image generated in the silver halide upon exposure. The silver produced by the reaction of the organic silver salt in the exposed areas provides a black image that contrasts with the unexposed areas and forms an image. This reaction process proceeds without supplying a treatment liquid such as water from the outside.

  Such photothermographic materials have been widely used for microfilms and X-ray photosensitive materials, but are only partially used as printing photosensitive materials.

  One reason for the lack of widespread use of heat-developable photosensitive materials in the field of printing photosensitive materials is that the maximum density of images obtained for printing photosensitive materials is low, and the gradation is soft. Low image quality is a major obstacle.

  On the other hand, due to the rapid progress of lasers and light emitting diodes in recent years, suitability for scanners having an oscillation wavelength of 700 to 1000 nm, or development of photosensitive materials having high sensitivity and maximum density (Dmax) and high gradation are strongly desired. It was rare. In addition to that, there is a growing demand for simple processing and drying.

  In response to the above situation, US Pat. No. 3,667,958 discloses that a photothermographic material using a combination of polyhydroxybenzenes and hydroxylamines, reductones or hydrazines has high image quality discrimination and resolution. However, it has been clarified that the combination of these reducing agents tends to cause an increase in fog.

  In addition, each specification of US Pat. Nos. 5,464,738 and 5,496,695 includes a heat containing an organic silver salt, photosensitive silver halide, hindered phenols and certain hydrazine derivatives. A development photosensitive material is disclosed. However, when these hydrazine derivatives are used, sufficient Dmax or the hard gradation required for printing photosensitive materials cannot be obtained, and in addition to this, a black spot failure occurs and the image quality deteriorates. It turns out that there is a problem of inviting.

  On the other hand, hydrazine derivatives with improved black pots are disclosed in JP-A-9-292671, JP-A-9-304870, JP-A-9-304871, JP-A-9-304872, and JP-A-10-31282. ing. Furthermore, Patent Document 1 discloses hydrazine derivatives with improved image reproducibility, all satisfying all of the obtained Dmax density, high gradation, black spot failure resistance, and high image reproducibility. It has not reached.

  Furthermore, Patent Document 2 or Patent Document 3 discloses examples using acrylonitriles, but with these compounds, a high gradation is not obtained, and the occurrence of black spots is suppressed. Not in.

In addition, as a method for producing these photothermographic materials, a method of applying and drying a coating solution containing a solvent such as an organic solvent is generally performed. However, a solvent remaining in the produced photothermographic material. Depending on the amount of the toner, not only problems in photographic performance such as sensitivity and fog and image storage stability are caused, but also smell is generated from the photothermographic material, which is not preferable in the working environment.
Japanese Patent Laid-Open No. 10-62898 US Pat. No. 5,545,515 US Pat. No. 5,635,339

  The present invention has been made in view of the above circumstances, and particularly for printing plate making scanners and image setters, high sensitivity, high Dmax, high contrast, little black spots are generated, and image storability after development processing is provided. An object of the present invention is to provide a photothermographic material having good image quality and to provide an image forming method thereof.

  The object of the present invention has been achieved by the following photothermographic material and image forming method.

(Claim 1)
An image forming layer containing a non-photosensitive organic silver salt, an organic silver salt reducing agent, a photosensitive silver halide, a contrast increasing agent and a binder on the support, and at least a non-photosensitive layer protecting the image forming layer, respectively In the photothermographic material having one layer, the high contrast agent is a compound selected from general formulas (1) to (3), and the odor intensity generated from the photothermographic material is −3 to 1 at 120 ° C. A photothermographic material, characterized in that it is present.

[Wherein R ₁₁ , R ₁₂ and R ₁₃ each represent a hydrogen atom or a monovalent substituent, and X ₁₁ represents an electron-donating heterocyclic group, cycloalkyloxy group, cycloalkylthio group, cycloalkylamino group or Represents a cycloalkenyl group. ]

[Wherein R ₂₁ represents an alkyl group, R ₂₂ and R ₂₃ each represents a hydrogen atom or a monovalent substituent, X ₂₁ represents an electron-withdrawing group, and L ₂₁ represents an aromatic carbocyclic group. , N2 represents 0 or 1. ]

[Wherein, X ₃₁ represents an electron-withdrawing heterocyclic group, a halogen atom or a haloalkyl group, and either R ₃₁ or R ₃₂ represents a hydrogen atom, and the other represents a hydroxyl group. ]
(Claim 2)
The photothermographic material according to claim 1, wherein the photothermographic material has a preheating part in front of the heat developing part of the heat developing machine, and the temperature of the preheating part is 80 to 120 ° C. An image forming method characterized by processing.

  The present invention provides a photothermographic material having high sensitivity, high Dmax, high contrast, little black spots, and good image storability after development processing, particularly for printing plate making scanners and imagesetters. And an image forming method thereof.

  Hereinafter, the photothermographic material and the image forming method of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

  The photographic light-sensitive material in the present invention is a black-and-white light-sensitive material represented by a printing light-sensitive material, an X-ray light-sensitive material, a microfilm, a general black-and-white film, a color negative film, a color reversal film, a color paper represented by a color paper, or the like. Any photosensitive material may be used, but a photosensitive material for printing plate making is preferred, and a photothermographic material for printing plate making is particularly preferred.

  The photothermographic material preferably used in the invention contains at least one compound represented by the general formulas (1) to (3). By incorporating the compound according to the present invention, it is possible to obtain a photothermographic material having high sensitivity, high Dmax and high gradation, and having black spot resistance and excellent storage stability.

  The compounds represented by the general formulas (1) to (3) will be described in detail below. First, the electron donating group and the electron withdrawing group in the present invention will be described.

  The electron donating group in the present invention is a substituent having a negative Hammett substituent constant σp. Examples of the electron donating group include a hydroxyl group (or a salt thereof), an alkoxy group, An aryloxy group, a heterocyclic oxy group, an amino group, an alkylamino group, an arylamino group, a heterocyclic amino group, a heterocyclic group in which σp takes a negative value, or a phenyl group substituted with these electron donating groups, etc. Can be mentioned. The electron-withdrawing group in the present invention is a substituent having a positive Hammett substituent constant σp. Examples of the electron-withdrawing group include a halogen atom, a cyano group, a nitro group, and an alkenyl group. Alkynyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, alkylsulfonyl group, arylsulfonyl group, carbamoyl group, carbonamido group, sulfamoyl group, sulfonamido group, trifluoromethyl group, trichloromethyl group, phosphoryl group, Examples thereof include a carboxy group (or a salt thereof), a sulfo group (or a salt thereof), an imino group, a heterocyclic group in which σp has a positive value, or a phenyl group substituted with these electron-withdrawing groups. Hammett's law was introduced in 1935 by L. L. to quantitatively discuss the effect of substituents on the reaction or equilibrium of benzene derivatives. P. A rule of thumb proposed by Hammett, which is widely accepted today. Substituent constants obtained by Hammett's rule include a σp value and a σm value, and these values are described in many general books, “Lange's Handbook of Chemistry” (JA Dean). ) "12th sale, 1979 (Mc Graw-Hill) and" Chemical domain special issue ", No. 122, 96-103, 1979 (Nankodo), Chemical Reviews, Vol. 91, 165-195 Page, 1991. The electron-withdrawing group and the electron-donating group in the present invention are defined by the σp value, but are not limited to substituents having known values described in the above-mentioned books.

The compound represented by the general formula (1) will be described. In the formula, X ₁₁ represents an electron-donating heterocyclic group, a cycloalkyloxy group, a cycloalkylthio group, a cycloalkylamino group, or a cycloalkenyl group. As typical examples of the electron-donating heterocycle, σp described in pages 66 to 339 of “Substituent Constants for Correlation Analysis in Chemistry and Biology” (Corwin Hansch and Albert Leo) is negative, and σp is negative. Specific examples of the ring include piperidinyl group, pyrrolidinyl group, morpholino group, piperazinyl group, 3-thienyl group, 2-furyl group, 3-furyl group and 2-pyrrolo group. A 3-thienyl group, a 2-furyl group or a 3-furyl group is preferred. These heterocycles may have an arbitrary substituent as long as σp is 0 or not positive.

  Specific examples of the cycloalkyloxy group, cycloalkylthio group or cycloalkylamino group include a cyclopropyloxy group, a cyclopentyloxy group, a cyclohexyloxy group, a cycloheptyloxy group, a cyclopropylthio group, a cyclopentylthio group, Examples include cyclohexylthio group, cycloheptylthio group, cyclopropylmethylamino group, cyclopentylmethylamino group, cyclohexylmethylamino group, cycloheptylmethylamino group, and the like. A cyclopentyloxy group, a cyclohexyloxy group, a cyclopentylthio group and a cyclohexylthio group are preferred. Specific examples of the cycloalkenyl group include a cyclopropenyl group, a cyclobutenyl group, a cyclopentenyl group, a cyclohexenyl group, and a cycloheptenyl group. A cyclopentenyl group or a cyclohexenyl group is preferable.

R ₁₁ , R ₁₂ and R ₁₃ each represent a hydrogen atom or a monovalent substituent. Examples of the monovalent substituent include an alkyl group, an alkenyl group, an alkynyl group, an aryl group, a heterocyclic group, a heterocyclic group containing a quaternized nitrogen atom (for example, a pyridinium group), a hydroxy group, and an alkoxy group (for example, Including a group repeatedly containing ethyleneoxy group or propyleneoxy group unit), aryloxy group, acyloxy group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, urethane group, carboxyl group, imide group, amino group, Carboxamide group, sulfonamide group, ureido group, thioureido group, sulfamoylamino group, semicarbazide group, thiosemicarbazide group, hydrazino group, quaternary ammonio group, (alkyl, aryl, or heterocyclic) thio group, mercapto group , (Alkyl or aryl) sulfur Nyl group, (alkyl or aryl) sulfinyl group, sulfo group, sulfamoyl group, acylsulfamoyl group, (alkyl or aryl) sulfonylureido group, (alkyl or aryl) sulfonylcarbamoyl group, halogen atom, cyano group, nitro group, Examples thereof include a phosphoric acid amide group.

R ₁₁ is preferably an electron withdrawing group, more preferably a cyano group. R ₁₂ is preferably a hydrogen atom and R ₁₃ is preferably an electron donating group. Most preferably, R ₁₁ is a cyano group, R ₁₂ is a hydrogen atom, and R ₁₃ is a hydroxyl group.

  Hereinafter, although the specific example of a compound represented by General formula (1) is given, this invention is not limited to these. In addition, in the compounds listed below, when keto-enol tautomers or cis-trans geometric isomers are present, both are meant.

Next, the compound represented by the general formula (2) will be described. In the formula, R ₂₁ represents an alkyl group, R ₂₂ and R ₂₃ represent a hydrogen atom or a monovalent substituent, X ₂₁ represents an electron-withdrawing group, L ₂₁ represents a carbon aromatic ring group, n 2 Represents 0 or 1. Specific examples of the alkyl group represented by R ₂₁ include methyl group, ethyl group, propyl group, isopropyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group and the like. A methyl group, an ethyl group or a propyl group is preferred. When R ₂₂ and R ₂₃ are monovalent substituents, specific examples include the same substituents as R ₁₁ , R ₁₂ and R ₁₃ in the general formula (1). Examples of the electron withdrawing group represented by X ₂₁ formula (1) include the same electron withdrawing group as X ₁₁ in, preferably a cyano group. Specific examples of the carbon aromatic ring residue represented by L ₂₁ include a phenylene group and a naphthylene group. The phenylene group and naphthylene group may be further substituted with an alkyl group. Further, R ₂₂ is preferably a hydrogen atom and R ₂₃ is an electron donating group. Most preferably, X ₂₁ is a cyano group, R ₂₂ is a hydrogen atom, and R ₂₃ is a hydroxyl group.

  Although the specific example of a compound represented by General formula (2) below is given, this invention is not limited to these. In addition, in the compounds listed below, when keto-enol tautomers or cis-trans geometric isomers are present, both are meant.

Next, the compound represented by the general formula (3) will be described. In the formula, X ₃₁ represents an electron-withdrawing heterocyclic group, a halogen atom or a haloalkyl group. As a representative example of the electron-withdrawing heterocyclic group, the σp described in pages 66 to 339 of “Substituent Constants for Correlation Analysis in Chemistry and Biology” (Corwin Hansch and Albert Leo) is a positive group. Specific examples include 2-pyridyl group, 2-pyrimidyl group, 2-pyrazyl group, 2-quinazolyl group, 2-benzothiazolyl group, 2-benzoxazolyl group and the like. These electron-withdrawing heterocyclic groups may have an arbitrary substituent as long as σp is not 0 or negative. A preferred example of the electron-withdrawing heterocyclic group is a 2-pyridyl group, a 2-pyrimidyl group or a 2-pyrazyl group. Specific examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Preferred examples of the halogen atom are a chlorine atom or a bromine atom. Examples of the haloalkyl group include a monochloromethyl group, a dichloromethyl group, a trichloromethyl group, a tribromomethyl group, a trifluoromethyl group, a 1,2-dichloroethyl group, and a pentafluoroethyl group. The haloalkyl group is preferably a trichloromethyl group, a tribromomethyl group, or a trifluoromethyl group.

  Although the specific example of a compound represented by General formula (3) below is given, this invention is not limited to these. In addition, in the compounds listed below, when keto-enol tautomers or cis-trans geometric isomers are present, both are meant.

  In the present invention, the “odor intensity” generated from the photothermographic material is a value measured by the following method.

<Preparation of sample>
Take out the photothermographic material from the hermetically sealed packaging at room temperature (25 ° C), immediately cut it into 4cm x 4cm, fill it in a sample bag (polyethylene terephthalate: 2 liters) and fill it with nitrogen gas To do. In the measurement at 120 ° C., the sample bag filled with nitrogen gas is heated on a hot plate at 120 ° C. for 4 minutes.

<Measurement of odor intensity>
Odor identification device FF-1 (manufactured by Shimadzu Corporation: temperature-enhanced thermal desorption concentration method using carbon-based collection tube, oxide semiconductor sensor, 6 sensors) collects odors in the sample bag, and smell strength SC1 (SC1 axis ). The measurement conditions are as follows.

Thermostatic bath temperature: 60 ° C
Steady gas flow rate: 40 ml / min
Sampling flow rate: 165 ml / min
Sampling time: 18 s (collection tube temperature 40 ° C.)
Dry purge flow rate: 500 ml / min
Dry purge time: 90s (collection tube temperature 40 ° C)
Desorption flow rate: 20 ml / min
Desorption time: 120 s (collection tube temperature 220 ° C.)
Cleaning flow rate: 150ml / min
Cleaning time: 60s (collection tube temperature 250 ° C)
<Calibration of odor intensity>
The odor intensity SC1 obtained under the above measurement conditions is calibrated by the following method. Thereby, it is possible to always compare with the same ruler. For standard data, 5 ppm of toluene is used, and the sampling time is 3 seconds, 12 seconds, 48 seconds, and the concentration is changed to 3 points. These SC1 values are set to -1.0, 0.0, and 1.8, respectively, and FF-1 is calibrated. A commercially available 5 ppm toluene can be used. Each time a film sample is measured, the above-described method is used to calibrate to obtain highly reproducible data in which the sensor deterioration with time is corrected. This measurement can be automatically calculated by selecting an automatic measurement mode called FF-1 calibration sequence and starting up the software incorporated in FF-1.

  In the present invention, the method for controlling the odor intensity generated from the photothermographic material is not particularly limited. For example, (1) the organic solvent and the odor generating compound are not used as much as possible, and (2) the organic solvent is used. Use a low boiling point organic solvent, (3) enhance the drying ability during coating and drying of the photothermographic material (e.g., increase the drying temperature, lengthen the drying time, etc.), (4) apply the photothermographic material Examples of the method include further heating after drying. These methods may be used alone or in appropriate combination. Sources of odor strength include not only organic solvents but also volatile components from other additives other than organic solvents, and the amount of organic solvent does not necessarily correspond to odor strength. The components that increase the odor strength include many mercapto compounds, relatively high molecular compounds, and the like, and also include substances generated by reaction of several components at high temperatures during heat development. These components different from the organic solvent and detected by the sensor of the odor discriminating device are within a certain range, and the odor intensity as the photothermographic material is -3 to 1 as described above. It was unexpected that photographic performance was good in terms of photographic performance.

  The compounds represented by the general formulas (1) to (3) according to the present invention can be easily synthesized by known methods, and there are also compounds that can be purchased directly from drug manufacturers.

The compound-added layer represented by the general formulas (1) to (3) is preferably a photosensitive layer containing a silver halide emulsion and / or a layer adjacent to the photosensitive layer. Further, the amount of the compound according to the present invention varies depending on the grain size of the silver halide grains, the halogen composition, the degree of chemical sensitization, the type of the inhibitor, etc. A range of about 10 ⁻⁶ mol to 10 ⁻¹ mol, particularly 10 ⁻⁵ mol to 10 ⁻² mol per mol is preferable.

  The compounds represented by the general formulas (1) to (3) according to the present invention are suitable organic solvents such as alcohols (methanol, ethanol, propanol, fluorinated alcohol), ketones (acetone, methyl ethyl ketone), dimethylformamide. , Dimethyl sulfoxide, methyl cellosolve and the like. It can also be incorporated by the well-known emulsion dispersion method. For example, a high-boiling organic solvent such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate and an auxiliary solvent such as ethyl acetate or cyclohexanone are dissolved and mechanically emulsified to prepare an emulsified dispersion. It can be added to a desired constituent layer. Further, a method known as a solid dispersion method, for example, a powder of the compound represented by the general formulas (1) to (3) of the present invention is dispersed in, for example, a ball mill, a colloid mill, or an ultrasonic disperser. Can be optionally added as a water-based fine particle dispersion.

  In addition to the above compounds, the photothermographic material of the invention includes hydroxylamine compounds, alkanolamine compounds and ammonium phthalate compounds described in US Pat. No. 5,545,505, and US Pat. No. 5,545,507. Hydroxamic acid compounds described in US Pat. No. 5,558,983, N-acyl-hydrazine compounds described in US Pat. No. 5,937,449, benzhydrol, diphenylphosphine, dialkylpiperidine, alkyl- A hydrogen atom donor compound such as β-ketoester can be appropriately added. By containing these compounds, it is possible to further improve Dmax and to suppress the occurrence of black spots that tend to occur in an image formed using a hydrazine derivative, and as a result, it is possible to achieve a marked improvement in image quality. .

  Further, the photothermographic material of the present invention has, for example, US Pat. Nos. 3,874,946, 4,756,999, 5,340,712, and European patents for the purpose of reducing fog. Nos. 605, 981 A1, 622,666 A1, 631,176 A1, JP-B 54-165, JP-A-7-2781, JP-A-9-160164, JP-A-9-244178, JP-A-9-258367 Nos. 9-265150, 9-281640, 9-319022 and the like can be preferably used. Among these, it is particularly preferable to use a compound represented by the following general formula (B) together with the compound according to the present invention.

In the formula, Q represents an aliphatic hydrocarbon group, an aromatic carbocyclic group or a heterocyclic group. X ₁ and X ₂ each represent a halogen atom. Y represents a carbonyl group or a sulfonyl group. A represents a hydrogen atom, a halogen atom or an electron-withdrawing group. n represents 0 or 1.

  Specific examples of the compound represented by the general formula (B) are given below, but the present invention is not limited thereto.

  The compound represented by the general formula (B) can be synthesized by an ordinary method well known to those skilled in the art.

There is no particular limitation on the addition amount of the compounds represented by these in the general formula (B), preferably 10 ^-4 to 1 mol / Ag mol, in particular 10 ^-3 to 0.3 mol / Ag mol are preferred.

  Next, the photothermographic material of the present invention will be described.

  The non-photosensitive organic silver salt used in the image forming layer (photosensitive layer) of the photothermographic material of the present invention is a reducible silver source, and includes organic acids and heteroorganic acids containing a reducible silver ion source. Among them, silver salts, particularly long-chain (10 to 30 carbon atoms, preferably 15 to 25) aliphatic carboxylic acids and nitrogen-containing heterocyclic rings are particularly preferable. An organic or inorganic silver complex in which the ligand has a value of 4.0 to 10.0 as a total stability constant with respect to silver ions is also useful in the present invention. Examples of suitable silver salts include Research Disclosure (hereinafter also simply referred to as RD) No. 17029 and 29963, and may include the following: silver salts of organic acids (eg, silver such as gallic acid, oxalic acid, behenic acid, arachidic acid, stearic acid, palmitic acid, lauric acid, etc. Salt); silver carboxyalkylthiourea salt (for example, 1- (3-carboxypropyl) thiourea, 1- (3-carboxypropyl) -3,3-dimethylthiourea, etc.); aldehyde and hydroxy-substituted aromatic carboxylic acid Silver complex of polymer reaction product of (for example, aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) and hydroxy-substituted acids (for example, salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, 5,5-thiodisalicylic acid) A silver complex of a polymer reaction product with a silver salt or complex of a thione (for example, 3- 2-carboxyethyl) -4-hydroxymethyl-4- (thiazoline-2-thione, and 3-carboxymethyl-4-thiazoline-2-thione)); imidazole, pyrazole, urazole, 1,2,4-thiazole and A complex or salt of nitrogen acid and silver selected from 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; silver salts such as saccharin and 5-chlorosalicylaldoxime; and Silver salts of mercaptides. Preferred silver sources are silver behenate, silver arachidate, silver stearate and mixtures thereof.

  The organic silver salt compound can be obtained by mixing a water-soluble silver compound and a compound that forms a complex with silver. As described in Japanese Patent Application Laid-Open No. 9-127643, a normal mixing method, a reverse mixing method, and a simultaneous mixing method are used. A controlled double jet method or the like is preferably used. For example, an alkali metal salt (for example, sodium hydroxide, potassium hydroxide, etc.) is added to an organic acid to produce an organic acid alkali metal salt soap (for example, sodium behenate, sodium arachidate, etc.). The soap and silver nitrate are added by a jet method to produce an organic silver salt crystal. In that case, photosensitive silver halide grains described below (hereinafter, simply referred to as silver halide grains) may be mixed.

  The silver halide grains in the present invention function as an optical sensor. In the present invention, the average particle size is preferably small, and the average particle size is preferably 0.1 μm or less, more preferably 0.01 to 0 in order to suppress white turbidity of the photosensitive material after image formation and to obtain good image quality. 0.1 μm, particularly preferably 0.0 to 0.08 μm. The grain size (particle diameter) as used herein refers to the length of the edge of a silver halide grain when the silver halide grain is a so-called normal crystal of a cube or octahedron. In the case of non-normal crystals, for example, in the case of spherical, rod-like, or tabular grains, it means the diameter of the sphere assuming a sphere equivalent to the volume of the silver halide grains. The silver halide grains are preferably monodispersed. The monodispersion here means that the monodispersity obtained by the following formula is 40% or less. The particles are more preferably 30% or less, particularly preferably 0.1% or more and 20% or less.

Monodispersity = (standard deviation of particle size) / (average value of particle size) × 100
In the present invention, the silver halide grains are preferably monodisperse grains having an average grain size of 0.1 μm or less, and the graininess of the image is improved by setting the grain size within this range.

  The shape of the silver halide grains is not particularly limited, but the ratio occupied by the Miller index [100] plane is preferably high, and this ratio is 50% or more, further 70% or more, particularly 80% or more. It is preferable. The ratio of the Miller index [100] plane is calculated by using the adsorption dependency between the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani, J .; Imaging Sci. 29, 165 (1985).

  In addition, another preferable silver halide grain shape in the present invention is a tabular grain. The term “tabular grains” as used herein refers to those having an aspect ratio = r / h of 3 or more when the square root of the projected area is the grain size r μm and the thickness in the vertical direction is h μm. Among them, the aspect ratio is preferably 3 to 50. The particle size of the tabular grains is preferably 0.1 μm or less, and more preferably 0.01 μm to 0.08 μm. These tabular grains can be easily obtained by the method described in US Pat. Nos. 5,264,337, 5,314,798, 5,320,958 and the like. In the present invention, the sharpness of the image can be further improved by using the tabular grains.

  The halogen composition of the silver halide grains is not particularly limited and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide. The photographic emulsion used in the present invention is P.I. Chifie et Physique Photographic (published by Paul Montel, 1967) by Glafkides. F. Duffin's Photographic Emission Chemistry (published by The Focal Press, 1966), V.C. L. It can be prepared using a method described in Making and Coating Photographic Emulsion (published by The Focal Press, 1964) by Zelikman et al.

  The silver halide used in the present invention preferably contains a metal ion or complex ion belonging to Group 6 to Group 10 of the periodic table of elements in order to improve reciprocity failure characteristics and to adjust the gradation. . As the metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, and Au are preferable.

  Silver halide grains can remove (desalinate) unnecessary salts by methods known in the art such as noodle method, flocculation method, etc., but in the present invention, desalting is performed even if performed. It does not matter either.

  The silver halide grains in the present invention are preferably chemically sensitized. Preferred chemical sensitization methods include sulfur sensitization methods, selenium sensitization methods, tellurium sensitization methods, noble metal sensitization methods such as gold compounds, platinum, palladium, and iridium compounds, as well known in the art. A sensitization method or the like can be used.

In the present invention, in order to prevent devitrification of the photosensitive material, the total amount of silver halide and organic silver salt is preferably 0.5 g or more and 2.2 g or less per 1 m ² in terms of silver amount. By setting the silver amount within this range, a high-contrast image can be obtained. Further, the ratio of the amount of silver halide to the total amount of silver is 50% or less, preferably 25% or less, more preferably 0.1 to 15% by mass ratio.

  Examples of the reducing agent used in the photothermographic material of the invention include generally known reducing agents such as phenols, polyphenols having two or more phenol groups, naphthols, bisnaphthols, and two. Polyhydroxybenzenes having the above hydroxyl groups, polyhydroxynaphthalenes having two or more hydroxyl groups, ascorbic acids, 3-pyrazolidones, pyrazolin-5-ones, pyrazolines, phenylenediamines, hydroxylamines, hydroquinone mono Ethers, hydroxamic acids, hydrazides, amide oximes, N-hydroxyureas and the like, and more specifically, for example, U.S. Pat. Nos. 3,615,533, 3,679,426, 3,672,904, 3,751,252, 3,78 No. 949, No. 3,801,321 No. 3,794,488 No. 3,893,863 No. 3,887,376 No. 3,770,448 3,819,382, 3,773,512, 3,839,048, 3,887,378, 4,009,039, 4,021, No. 240, British Patent No. 1,486,148 or Belgian Patent No. 786,086, and Japanese Patent Application Laid-Open Nos. 50-36143, 50-36110, 50-11603, and 50-99719. 50-140113, 51-51933, 51-23721, 52-84727, or JP-B 51-35851, and the like. The present invention is as described above. Can be used appropriately selected from among the known reducing agent. As the selection method, the most efficient method is to confirm the suitability of the reducing agent by actually producing a photothermographic material containing the reducing agent and directly evaluating the photographic performance.

  Among the reducing agents described above, preferred reducing agents when using an aliphatic carboxylic acid silver salt as the organic silver salt include polyphenols in which two or more phenol groups are linked by an alkylene group or sulfur, particularly a phenol group. Phenol in which an alkyl group (for example, a methyl group, an ethyl group, a propyl group, a t-butyl group, a cyclohexyl group, or the like) or an acyl group (for example, an acetyl group, a propionyl group, or the like) is substituted on at least one position adjacent to the hydroxy substitution position Polyphenols in which two or more of the groups are linked by an alkylene group or sulfur, such as 1,1-bis (2-hydroxy-3,5-dimethylphenyl) -3,5,5-trimethylhexane, 1,1-bis (2-hydroxy-3-tert-butyl-5-methylphenyl) methane, 1,1-bis (2-hydroxy-3) 5-di-t-butylphenyl) methane, (2-hydroxy-3-t-butyl-5-methylphenyl)-(2-hydroxy-5-methylphenyl) methane, 6,6′-benzylidene-bis (2 , 4-di-tert-butylphenol), 6,6′-benzylidene-bis (2-tert-butyl-4-methylphenol), 6,6′-benzylidene-bis (2,4-dimethylphenol), 1, 1-bis (2-hydroxy-3,5-dimethylphenyl) -2-methylpropane, 1,1,5,5-tetrakis (2-hydroxy-3,5-dimethylphenyl) -2,4-ethylpentane, US Pat. Nos. 3,5 such as 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane and 2,2-bis (4-hydroxy-3,5-di-t-butylphenyl) propane No. 9,903, No. 4,021,249 or British Patent No. 1,486,148, and JP-A Nos. 51-51933, 50-36110, 50-116023, 52- Polyphenol compounds described in Japanese Patent No. 84727 or Japanese Patent Publication No. 51-35727, bisnaphthols described in US Pat. No. 3,672,904, for example, 2,2′-dihydroxy-1,1′- Binaphthyl, 6,6'-dibromo-2,2'-dihydroxy-1,1'-binaphthyl, 6,6'-dinitro-2,2'-dihydroxy-1,1'-binaphthyl, bis (2-hydroxy- 1-naphthyl) methane, 4,4′-dimethoxy-1,1′-dihydroxy-2,2′-binaphthyl and the like, and further described in US Pat. No. 3,801,321. Sulfonamidophenols or sulfonamidonaphthols such as 4-benzenesulfonamidophenol, 2-benzenesulfonamidophenol, 2,6-dichloro-4-benzenesulfonamidophenol, 4-benzenesulfonamidonaphthol and the like. I can list them.

  The appropriate amount of the reducing agent used in the photothermographic material of the present invention is not uniform depending on the type of organic silver salt used, the type of reducing agent, and other additives, but is generally 0 per mole of organic silver salt. A range of 0.05 to 10 mol, preferably 0.1 to 3 mol is appropriate. Within this range, two or more reducing agents described above may be used in combination. In the present invention, it is preferable to add and apply the reducing agent to the photosensitive layer coating solution immediately before coating in order to reduce the photographic performance fluctuation due to the stagnation time of the photosensitive layer coating solution.

  Suitable binders for the photothermographic material of the present invention are transparent or translucent and generally colorless, natural polymer synthetic resins, polymers and copolymers, and other media forming films such as gelatin, gum arabic, poly (vinyl) Alcohol), hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, poly (vinyl pyrrolidone), casein, starch, poly (acrylic acid), poly (methyl methacrylic acid), poly (vinyl chloride), poly (methacrylic acid), copoly (Styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (styrene-butadiene), poly (vinyl acetal) s (eg, poly (vinyl formal) and poly (vinyl butyral)), poly (esters), Poly (urethane) , Phenoxy resins, poly (vinylidene chloride), poly (epoxides), poly (carbonates), poly (vinyl acetate), cellulose esters, and polyamides. The binder may be hydrophilic or hydrophobic, but in the present invention, it is preferable to use a hydrophobic transparent binder in order to reduce fogging after heat development. Preferable binders include, for example, polyvinyl butyral, cellulose acetate, cellulose acetate butyrate, polyester, polycarbonate, polyacrylic acid, and polyurethane. Among these, polyvinyl butyral, cellulose acetate, cellulose acetate butyrate and polyester are particularly preferably used.

  In order to protect the surface of the photosensitive material and prevent scratches, a non-photosensitive layer is coated on the outside of the photosensitive layer. The binder used for these non-photosensitive layers may be the same as or different from the binder used for the photosensitive layer.

In the present invention, the binder amount of the photosensitive layer is preferably 1.5 to 10 g / m ² in order to increase the heat development speed. More preferably 1.7~8g / m ^2. If it is less than 1.5 g / m ² , the density (Dmin) of the unexposed area is significantly increased, which may cause a practical problem.

  In the present invention, it is preferable to include a matting agent on the photosensitive layer side. In order to prevent damage to the image after heat development, the amount of the matting agent disposed on the surface of the photosensitive material is based on the total binder on the photosensitive layer side. It is preferable to contain 0.5-30% by mass ratio. Further, when a non-photosensitive layer is provided on the opposite side of the photosensitive layer with the support sandwiched, it is preferable to contain a matting agent in at least one layer on the non-photosensitive layer side in order to prevent slippage and fingerprint adhesion. The amount of the matting agent is preferably 0.5 to 40% by mass with respect to the total binder of the non-photosensitive layer. The shape of the matting agent may be either a regular shape or an irregular shape, but is preferably a regular shape, particularly a spherical shape.

  The photothermographic material of the present invention has at least one photosensitive layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer. Further, in order to control the amount of light passing through the photosensitive layer or the wavelength distribution, a filter dye layer and / or an antihalation dye layer, a so-called backing layer, may be formed on the same side as the photosensitive layer, or A dye or pigment may be directly contained in the photosensitive layer.

  These non-photosensitive layers may contain a sliding agent such as a polysiloxane compound, waxes or liquid paraffin in addition to the binder and matting agent.

  In the photothermographic material of the invention, various surfactants can be used as coating aids. Among these, fluorine surfactants are particularly preferably used for improving charging characteristics and preventing spotted coating failures.

  The photosensitive layer may be a plurality of layers, or may have a plurality of layer configurations such as a high sensitivity layer / low sensitivity layer or a low sensitivity layer / high sensitivity layer in order to adjust the gradation.

  Examples of suitable toning agents for use in the present invention are disclosed in RD17029.

  The photothermographic material of the present invention includes a mercapto compound, a disulfide compound, in order to suppress or promote development and control development intensity, to improve spectral sensitization efficiency or to improve storage stability before and after development processing, An inhibitor such as a thione compound can be contained.

  In the photothermographic material of the present invention, for example, surfactants, antioxidants, stabilizers, plasticizers, ultraviolet absorbers, coating aids and the like may be used. As these additives and the other additives described above, compounds described in RD17029 (June 1978, p.9-15) can be preferably used.

  The various additives described above may be added to any of the photosensitive layer, the non-photosensitive layer, and other forming layers.

  The support used in the present invention is a plastic film (for example, polyethylene terephthalate, polycarbonate, polyimide, nylon, cellulose triacetate, polyethylene naphthalate) in order to obtain a predetermined optical density after development processing and to prevent deformation of the image after development processing. Phthalate).

  Among them, preferable supports include polyethylene terephthalate (hereinafter abbreviated as PET) and a plastic (hereinafter abbreviated as SPS) support including a styrene polymer having a syndiotactic structure. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

  A heat-treated plastic support can also be used. Examples of the plastic to be used include the above-described plastics. The heat treatment of the support is a temperature that is 30 ° C. or more higher than the glass transition point of the support, preferably 35 ° C. or more, and more preferably after the support is formed and before the photosensitive layer is applied. It refers to heating at a temperature of 40 ° C. or higher.

  In the present invention, a conductive compound such as a metal oxide and / or a conductive polymer can be included in the constituent layers in order to improve the chargeability. These may be contained in any layer, but are preferably an undercoat layer, a backing layer, a layer between the photosensitive layer and the undercoat.

  Examples of the photothermographic material of the present invention include 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 The sensitizing dyes described in Patents 4,639,414, 4,740,455, 4,741,966, 4,751,175, and 4,835,096 can be used.

  Specific examples of useful sensitizing dyes used in the present invention include, for example, documents described or cited in Section RD17643IV-A (December 1978, p.23) and Section 18431X (August 1979, p.437). It is described in.

  In the present invention, a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various scanner light sources can be advantageously selected. For example, for A) an argon laser light source, JP-A-60-162247, JP-A-2-48653, US Pat. No. 2,161,331, West German Patent 936,071, and Japanese Patent Application No. 3-189532. Simple merocyanines described in No. 50, etc., and B) helium-neon laser light sources, trinuclear cyanine dyes described in JP-A Nos. 50-62425, 54-18726, 59-102229, Japanese Patent Application Nos. 48-42172, 51-9609, 55-39818, and Japanese Patent Application Laid-Open No. 62-284343 for merocyanines described in Japanese Patent Application No. 6-103272, C) LED light sources and red semiconductor lasers. JP-A-59-191032 for thiacarbocyanines described in JP-A-2-105135 and D) infrared semiconductor laser light source Contains tricarbocyanines described in JP-A-60-80841, 4-quinoline nuclei described in general formula (IIIa) and general formula (IIIb) in JP-A-59-192242 and JP-A-3-67242 Dicarbocyanines to be selected are advantageously selected.

  These sensitizing dyes may be used alone or in combination. The combination of sensitizing dyes is often used for the purpose of supersensitization. In addition to the sensitizing dye, the silver halide emulsion may contain a dye that itself does not have spectral sensitizing action or a substance that does not substantially absorb visible light and exhibits supersensitization.

  The photothermographic material of the present invention is exposed using a laser light source such as an Ar laser (488 nm), a He—Ne laser (633 nm), a red semiconductor laser (670 nm), or an infrared semiconductor laser (780 nm, 830 nm). However, this is one feature, and an infrared semiconductor laser having a wavelength of 700 to 1000 nm is particularly preferable.

  In the photothermographic material of the invention, a layer containing a dye can be provided as an antihalation layer. For Ar laser, He-Ne laser, and red semiconductor laser, it is preferable to add a dye so that absorption is at least 0.3 or more, preferably 0.8 or more at the exposure wavelength in the range of 400 nm to 750 nm. For infrared semiconductor lasers, it is preferable to add a dye in the range of 750 nm to 1500 nm so as to absorb at least 0.3 or more, preferably 0.8 or more at the exposure wavelength. One kind or a combination of several kinds of dyes may be used. The dye can be added to the dye layer close to the support on the same side as the photosensitive layer or to the dye layer on the opposite side of the photosensitive layer.

  The photothermographic material of the present invention may be developed by any method. In the present invention, the temperature of the photothermographic material exposed imagewise is increased, and the heat development is performed at 80 to 250 ° C. This is one characteristic, and preferably 100 to 140 ° C. The development time is preferably 1 to 180 seconds, more preferably 10 to 90 seconds.

  Hereinafter, the present invention will be described in detail with reference to examples, but the embodiments of the present invention are not limited thereto.

<Example 1>
(Preparation of undercoated PET support)
A commercially available biaxially stretched heat-fixed PET film with a thickness of 100 μm is subjected to a corona discharge treatment of 8 w / m ² · min, and the following undercoat coating liquid a-1 is applied to one side with a dry film thickness of 0.8 μm. The undercoat layer A-1 is coated and dried to form an undercoat layer A-1, and the opposite surface of the undercoat coating solution b-1 for antistatic processing is coated to a dry film thickness of 0.8 μm on the opposite surface. Then, it was dried to obtain an antistatic processed undercoat layer B-1.

<< Undercoat coating liquid a-1 >>
Butyl acrylate (30% by mass), t-butyl acrylate (20% by mass)
, Styrene (25% by mass), 2-hydroxyethyl acrylate (25% by mass) copolymer latex liquid (solid content 30%) 270 g
(C-1) 0.6g
Hexamethylene-1,6-bis (ethylene urea) 0.8g
Polystyrene fine particles (average particle size 3 μm) 0.05 g
Colloidal silica (average particle size 90μm) 0.1g
Finish to 1 liter with water.

<< Undercoating liquid b-1 >>
SnO ₂ / Sb (mass ratio 9/1, average particle size 0.18 μm)
Amount to be 200 mg / m ² Copolymer latex liquid of butyl acrylate (30% by mass), styrene (20% by mass), glycidyl acrylate (40% by mass) (solid content 30%) 270 g
(C-1) 0.6g
Hexamethylene-1,6-bis (ethylene urea) 0.8g
Finish to 1 liter with water.

Subsequently, a corona discharge of 8 w / m ² · min is applied to the upper surfaces of the undercoat layer A-1 and the undercoat layer B-1, and the following undercoat upper layer coating solution a is applied on the undercoat layer A-1. -2 was coated to a dry film thickness of 0.1 μm to form an undercoat upper layer A-2, and the following undercoat upper layer coating solution b-2 was applied on the undercoat layer B-1 to a dry film thickness of 0. It was coated as an undercoat upper layer B-2 having an antistatic function so as to be 8 μm.

<< Undercoating upper layer coating liquid a-2 >>
Mass to become gelatin 0.4g / m ² (C-1) 0.2g
(C-2) 0.2g
(C-3) 0.1 g
Silica particles (average particle size 3μm) 0.1g
Finish to 1 liter with water.

<< Undercoating Upper Layer Coating Liquid b-2 >>
(C-4) 60g
Latex liquid containing 20% of (C-5) (solid content 20%) 80g
Ammonium sulfate 0.5g
(C-6) 12g
Polyethylene glycol (weight average molecular weight 600) 6g
Finish to 1 liter with water.

(Heat treatment of support)
In the undercoating drying process of the above-described undercoated support, the support was heated at 140 ° C. and then gradually cooled.

(Preparation of silver halide emulsion A)
After dissolving 7.5 g of inert gelatin and 10 mg of potassium bromide in 900 ml of water and adjusting the temperature to 35 ° C. and pH to 3.0, 370 ml of an aqueous solution containing 74 g of silver nitrate and a molar ratio of (60/38/2) An aqueous solution containing sodium chloride, potassium bromide, potassium iodide and [Ir (NO) Cl ₅ ] salt at 1 × 10 ⁻⁶ mole per mole of silver and rhodium chloride salt at 1 × 10 ⁻⁶ mole per mole of silver 370 ml was added by the controlled double jet method while maintaining pAg 7.7. Thereafter, 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene was added and reduction sensitization was carried out by adjusting the pH to 8 and pAg 6.5 with NaOH. The average particle size was 0.06 μm. Cubic silver halide grains having a monodispersity of 10% and a projected diameter area variation coefficient of 8% and a [100] face ratio of 87% were obtained. This halogenated emulsion was coagulated and settled using a gelatin flocculant and desalted to obtain silver halide emulsion A.

(Preparation of Na behenate solution)
In 945 ml of pure water, 32.4 g of behenic acid, 9.9 g of arachidic acid, and 5.6 g of stearic acid were dissolved at 90 ° C. Next, 98 ml of a 1.5 mol / L aqueous sodium hydroxide solution was added while stirring at high speed. Next, after adding 0.93 ml of concentrated nitric acid, the mixture was cooled to 55 ° C. and stirred for 30 minutes to obtain a sodium behenate solution.

(Preparation of preform emulsion of silver behenate and silver halide emulsion A)
15.1 g of the above silver halide emulsion A is added to the sodium behenate solution, adjusted to pH 8.1 with a sodium hydroxide solution, 147 ml of a 1 mol / L silver nitrate solution is added over 7 minutes, and the mixture is further stirred for 20 minutes. Water-soluble salts were removed by ultrafiltration. The silver behenate produced as described above was an average grain size of 0.8 μm and a monodispersity of 8%. After the flocs of the dispersion were formed, water was removed, followed by washing with water 6 times and removing water, followed by drying to prepare a preform emulsion of silver behenate and silver halide emulsion A.

(Preparation of photosensitive emulsion)
The preform emulsion was divided into two parts, and 544 g of a methyl ethyl ketone solution (17% by mass) of polyvinyl butyral (average molecular weight 3000) and 107 g of toluene were gradually added and mixed, and then a 0.5 mm size ZrO ₂ bead mill was added. A photosensitive emulsion was prepared by carrying out dispersion at 30 ° C. for 10 minutes at 27.5 MPa with the media disperser used.

  The following layers were simultaneously coated on the undercoated support to prepare Sample 1-1 which is a photothermographic material. The drying was performed at 60 ° C. for 15 minutes.

(Back side application)
Back surface layer 1: A liquid having the following composition was applied on the B-2 layer of the support.

Cellulose acetate butyrate (10% methyl ethyl ketone solution)
15 ml / m ²
Dye A 37 mg / m ²
Matting agent: Monodispersity 15% Average particle size 8 μm Monodispersed silica
90 mg / m ²
C ₈ F ₁₇ (CH ₂ CH ₂ O) ₁₂ C ₈ F ₁₇ 50 mg / m ²
_{C 9 F 19 -C 6 H 4} -SO 3 Na 10mg / m 2
(Photosensitive layer side coating)
Photosensitive layer 1: A solution having the following composition was coated on the A-2 layer of the support so that the amount of coated silver was 2.4 g / m ² .

240g photosensitive emulsion
Sensitizing dye A (0.1% methanol solution) 1.7 ml
Pyridinium promide perbromide (6% methanol solution) 3 ml
Calcium bromide (0.1% methanol solution) 1.7ml
Antifoggant B-54 (10% methanol solution) 1.2 ml
2- (4-Chlorobenzoyl) benzoic acid (12% methanol solution)
9.2ml
11 ml of 2-mercaptobenzimidazole (1% methanol solution)
Comparative compound 1 0.3 g
Phthalazine 0.6g
4-methylphthalic acid 0.25g
Tetrachlorophthalic acid 0.2g
0.1 g of calcium carbonate with an average particle size of 3 μm
1,1- (2-hydroxy-3, -5-dimethylphenyl) -2-methylpropan (20% methanol solution) 20.5 ml
Isocyanate compound (Desmodur N3300, manufactured by Mobay)
0.5g
Surface protective layer 1: A solution having the following composition was simultaneously coated on the photosensitive layer 1.

Acetone 5ml / m ²
Methyl ethyl ketone 21ml / m ²
Cellulose acetate butyrate 2.3 g / m ²
Methanol 7ml / m ²
Phthalazine 250mg / m ²
1,1- (2-hydroxy-3, -5-dimethylphenyl) -2-methylpropan (20% methanol solution) 10 ml / m ²
Matting agent: 10% monodispersion average particle size 4 μm monodispersed silica
5 mg / m ²
CH ₂ = CHSO ₂ CH ₂ CH ₂ OCH ₂ CH ₂ SO ₂ CH = CH ₂
35 mg / m ²
C ₁₂ F ₂₅ (CH ₂ CH ₂ O) ₁₀ C ₁₂ F ₂₅ 10 mg / m ²
_{C 8 F 17 -C 6 H 4} -SO 3 Na 10mg / m 2

  Subsequently, Samples 1-2 to 1-18 were prepared in the same manner except that Comparative Compound 1 in the photosensitive layer 1 of Sample 1-1 was changed as shown in Table 1. In addition, each compound was added in the same mass as Comparative Compound 1.

  Samples 1-1 to 1-18 obtained as described above were subjected to the following heat development treatment and performance evaluation.

(Exposure and heat development processing)
Each sample was subjected to halftone dot exposure using a Dotex 2dry manufactured by Cytex Co., Ltd., which is an image setter equipped with a 780 nm semiconductor laser. For 25 seconds. At that time, exposure and development were all performed in a room temperature-controlled and humidity controlled at 23 ° C. and 50% RH.

(Evaluation of photographic performance)
The density of the obtained heat-developed sample was measured with an optical densitometer (manufactured by Konica: PDA-65) to prepare a characteristic curve of density D-exposure amount LogE. From the characteristic curve, the maximum density (Dmax) and sensitivity (the reciprocal of the exposure amount giving a density 1.5 higher than Dmin) were determined. The sensitivity was expressed as a relative sensitivity when that of Sample 1-1 was taken as 100. In addition, the slope (tan θ) of the straight line connecting the points of density 0.3 and 3.0 in the characteristic curve was measured as the gradation γ.

(Evaluation of black pot)
About each unexposed sample, after performing the heat development process similar to the above, each heat-developed sample was visually evaluated using a 100 times magnifier, and was ranked into the following five stages.

5: Black spots are not generated at all. 4: Black spots are generated slightly, but there are no practical problems. 3: Practical lower limit level 2: Practical impossibility 1: Black spots are generated in the entire field of view and cannot be used. The ranks 3 to 5 were determined to be practically usable levels.

(Evaluation of storage stability)
Two parts of a sealed container in which each sample was placed in a container maintained at 25 ° C. and a relative humidity of 55% were prepared, and one of them was stored for 7 days under the condition of 50 ° C. (this is referred to as a forced degradation treated sample). The other was also stored for 7 days under the condition of 25 ° C. for comparison (this is referred to as a comparative sample). Next, each sample was subjected to the same exposure and heat development processing as described above, the minimum density (Dmin) of each processed sample was measured, and the Dmin increase value of the forced degradation treated sample relative to the comparative sample was calculated. A measure of storage stability.

(Evaluation of image preservation)
A sample heat-developed for the purpose of sensitivity measurement was evaluated for image density after being stored under a 1000 Lux fluorescent lamp for 24 hours in an environment of 30 ° C. and a relative humidity of 70%. Evaluation was based on the increase in concentration in the Dmin part.

(Evaluation of odor intensity)
Using the aforementioned odor identification device FF-1 (manufactured by Shimadzu Corp .: heated thermal desorption concentration method using carbon-based collection tube, oxide semiconductor sensor, 6 sensors), the odor in the sample bag at 120 ° C. is collected. The odor intensity SC1 (SC1-axis numerical value) was measured. The SC1 axis value is a value calibrated by the method described above. Evaluation was based on the value of the SC1 axis.

  As is clear from the results in Table 1, sample No. It can be seen that 1-5 to 1-18 are excellent in sensitivity, Dmax, gradation, black spot, and image storability, and have excellent performance.

<Example 2>
Sample No. 1 prepared in Example 1 was used. Evaluation similar to Example 1 except that 1-1 to 1-18 are heat-developed using a heat-developing machine having a pre-heating part in front of the heat-developing part and setting the temperature of the pre-heating part to 100 ° C. Went.

  As a result, similar to the result of Example 1, the present sample No. 1-5 to 1-18 obtained good results.

Claims (2)

An image forming layer containing a non-photosensitive organic silver salt, an organic silver salt reducing agent, a photosensitive silver halide, a contrast increasing agent and a binder on the support, and at least a non-photosensitive layer protecting the image forming layer, respectively In the photothermographic material having one layer, the high contrast agent is a compound selected from general formulas (1) to (3), and the odor intensity generated from the photothermographic material is −3 to 1 at 120 ° C. A photothermographic material, characterized in that it is present.

[Wherein R ₁₁ , R ₁₂ and R ₁₃ each represent a hydrogen atom or a monovalent substituent, and X ₁₁ represents an electron-donating heterocyclic group, cycloalkyloxy group, cycloalkylthio group, cycloalkylamino group or Represents a cycloalkenyl group. ]

[Wherein R ₂₁ represents an alkyl group, R ₂₂ and R ₂₃ each represents a hydrogen atom or a monovalent substituent, X ₂₁ represents an electron-withdrawing group, and L ₂₁ represents an aromatic carbocyclic group. , N2 represents 0 or 1. ]

[Wherein, X ₃₁ represents an electron-withdrawing heterocyclic group, a halogen atom or a haloalkyl group, and either R ₃₁ or R ₃₂ represents a hydrogen atom, and the other represents a hydroxyl group. ] The photothermographic material according to claim 1, wherein the photothermographic material has a preheating part in front of the heat developing part of the heat developing machine, and the temperature of the preheating part is 80 to 120 ° C. An image forming method characterized by processing.