JP2007161594A - Method for producing organic silver salt dispersion and heat-developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an organic silver salt dispersion, having high productivity, and to provide a heat-developable photosensitive material by using the dispersion. <P>SOLUTION: The method for producing the organic silver salt dispersion comprises forming the organic silver salt by mixing a water-soluble silver salt solution with an alkali metal salt solution of an organic acid in the presence of a compound represented by general formula (DF-1) (wherein R<SB>1</SB>and R<SB>2</SB>are each independently an alkyl group, an aryl group or a heterocyclic group and R<SB>1</SB>and R<SB>2</SB>each has at least one hydroxy group as a substituent) or a compound represented by general formula (DF-2) (wherein n is an integer of 1-3; m is an integer of 0-2; R is an alkyl group or an allyl group). The heat-developable photosensitive material comprises an organic silver salt produced by the production method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing an organic silver salt dispersion and a photothermographic material, and more particularly relates to a method for producing an organic silver salt dispersion having improved raw storability and image storability, and a photothermographic material. .

  In recent years, in the medical diagnostic film field and the photoengraving film field, it is strongly desired to reduce the amount of processing waste liquid from the viewpoint of environmental protection and space saving. Therefore, thermal development as a medical diagnostic film and a photoengraving film that can be efficiently exposed by a laser image setter or a laser imager and can form a clear black image having high resolution and sharpness. There is a need for techniques relating to photosensitive materials. According to these photothermographic materials, it is possible to supply a customer with a photothermographic processing system that does not require solution processing chemicals and that is simpler and does not impair the environment.

  There are similar requirements in the field of general image forming materials, but medical diagnostic images in particular require fine depiction, so they require high image quality with excellent sharpness and graininess, and ease of diagnosis. From the viewpoint, a cool black image is preferred. At present, various hard copy systems using pigments and dyes such as inkjet printers and electrophotography are distributed as general image forming systems. However, there is no satisfactory output system for medical images.

  On the other hand, thermal imaging systems using organic silver salts are disclosed in, for example, US Pat. Nos. 3,152,904 and 3,457,075, and D.C. Klosterboer, “Thermally Processed Silver Systems” (Imaging Processes and Materials), 8th edition, J. Sturge. (Walworth, A. Shepp, Chapter 9, 279, 1989). In particular, the photothermographic material generally contains a catalytically active amount of a photocatalyst (for example, silver halide), a reducing agent, a reducible silver salt (for example, an organic silver salt), and, if necessary, a toning agent that controls the color tone of silver. And an image forming layer dispersed in a binder matrix. The photothermographic material is heated to a high temperature (for example, 80 ° C. or higher) after image exposure, and a black silver image is formed by a redox reaction between a reducible silver salt (functioning as an oxidizing agent) and a reducing agent. Form. The oxidation-reduction reaction is promoted by the catalytic action of the latent image of silver halide generated by exposure. Therefore, a black silver image is formed in the exposure area. It is disclosed in many documents including US Pat. No. 2,910,377 and Japanese Patent Publication No. 43-4924.

  The photothermographic material using an organic silver salt contains all the chemicals for image formation in the film in advance, so that the sensitivity decreases during use until image formation and fogging increases. It had a problem of deteriorating image quality. In addition, unreacted chemicals remain after image formation, and reaction products of the reacted chemicals remain in the film. Therefore, the storage stability of the image is not unique to conventional wet development type silver halide light-sensitive materials. Had problems. In order to solve this problem, many studies on the activity of developing agents and studies on additives based on polyhalogen compounds have been conducted so far (for example, see Patent Documents 1 to 3). I couldn't say that further improvements were required.

In addition, the organic silver salt is usually mixed with a water-soluble silver salt solution and an alkali metal salt solution of an organic acid to form an organic silver salt crystal precipitate or suspension, which is then converted into a fine dispersion by a disperser. Prepared and used. This method for producing an organic silver salt dispersion has a relatively small bulk specific gravity, so that it separates above the aqueous phase and causes a creaming phenomenon when it is stirred at a high speed. It was an obstacle to efficiently produce organic silver salt dispersion by stirring at high speed. As the use of photothermographic materials has expanded in many fields, increasing the productivity of organic silver salts has become a major issue.
Japanese Patent Laid-Open No. 11-271920 JP 2002-287291 A Japanese Patent Laid-Open No. 2003-307808

  An object of the present invention is to provide a method for producing an organic silver salt dispersion with high productivity, and a photothermographic material having little fogging and excellent in raw storability and image storability.

The problems of the present invention have been solved by the following means.
<1> Production of an organic silver salt dispersion comprising mixing an aqueous silver salt solution and an alkali metal salt solution of an organic acid to form an organic silver salt, and a step of dispersing the organic silver salt It is a method, Comprising: The said organic silver salt formation process is performed in presence of an antifoamer, The manufacturing method of the organic silver salt dispersion characterized by the above-mentioned.
<2> The method for producing an organic silver salt dispersion according to <1>, wherein the antifoaming agent is a compound represented by the following general formula (DF-1) or an ethoxylated derivative thereof:

(Wherein R ₁ and R ₂ are each independently an alkyl group, an aryl group, or a heterocyclic group, each having at least one hydroxyl group as a substituent).
<3> The method for producing an organic silver salt dispersion according to <1>, wherein the antifoaming agent is a compound represented by the following general formula (DF-2):

(In the formula, n represents an integer of 1 to 3, m is a value of 0, 1 or 2. R represents a hydrogen atom, an alkyl group, or an allyl group).
<4> In the presence of an antifoaming agent in the organic silver salt formation step, the maximum peripheral speed of the stirring blade rotation in the entire organic silver salt formation step is at least 260 m / min. 3> The manufacturing method of the organic silver salt dispersion of any one of 3>.
<5> In the organic silver salt forming step, in the presence of an antifoaming agent, the maximum peripheral speed of the stirring blade rotation in the entire organic silver salt forming step is at least 320 m / min or more. A method for producing an organic silver salt dispersion.
<6> The method for producing an organic silver salt dispersion according to any one of <1> to <5>, wherein the organic silver salt is a silver salt of a fatty acid.
<7> The method for producing an organic silver salt dispersion according to <6>, wherein the silver salt of the fatty acid is a silver salt of a higher fatty acid having 16 or more carbon atoms.
<8> The method for producing an organic silver salt dispersion according to any one of <1> to <7>, further comprising a desalting step between the organic silver salt forming step and the dispersing step of the organic silver salt.
<9> On at least one surface of the support, at least photosensitive silver halide, an organic silver salt dispersion produced by the production method according to any one of <1> to <8>, silver ions A photothermographic material containing a reducing agent and a binder.
<10> The photothermographic material according to <9>, wherein the silver coating amount is 0.5 g / m ² or more and 1.9 g / m ² or less.

  According to the present invention, a method for producing an organic silver salt dispersion with high productivity is provided, and a photothermographic material having little fogging and excellent in raw storability and image storability is provided.

The present invention is described in detail below.
1. Method for Producing Organic Silver Salt 1) Composition An organic silver salt that can be used in the present invention (hereinafter sometimes simply referred to as “organic silver salt”) is relatively stable to light, but is exposed to light. A silver salt that forms a silver image when heated to 80 ° C. or higher in the presence of a photocatalyst (such as a latent image of photosensitive silver halide) and a reducing agent. The organic silver salt may be any organic material containing a source capable of reducing silver ions. With respect to such organic silver salts, paragraph numbers 0048 to 0049 of JP-A Nos. 06-130543, 08-314078, 09-127643, and 10-62899, JP-A Nos. 10-94074 and 10- No. 94075, European Patent Publication No. 0803764A1, page 18, line 24 to page 19, line 37, European Patent Publication No. Nos. 2000-72711, 2000-112057, 2000-155383, and the like.

As the organic silver salt, a silver salt of a long-chain aliphatic carboxylic acid having 10 to 30 carbon atoms, preferably 15 to 28 carbon atoms is particularly preferable. Preferable examples of the organic silver salt include silver behenate, silver arachidate, silver stearate, lignoceric acid, and a mixture thereof. In the present invention, the silver behenate content is 50 mol% or more. 70 mol% or more is more preferable, 88 mol% or more is further more preferable, and 95 mol% or more is particularly preferable.
By setting it as such a content rate, the silver salt of the organic acid which is excellent in the fog over time at the time of raw preservation | save, and was excellent also in image preservability is obtained. The silver arachidate is preferably 30 mol% or less in terms of obtaining a low Dmin and obtaining a silver salt of an organic acid having excellent image storage stability, more preferably 9 mol% or less, and 3 mol%. It is particularly preferred that Moreover, it is preferable that silver stearate is 10 mol% or less, and it is still more preferable that it is 1 mol% or less. It is especially preferable that it is 0.1 mol% or less.

2) Shape The shape of the organic silver salt that can be used in the present invention is characterized by scaly particles having an aspect ratio of 1 to 9. It is preferable for the aspect ratio to be in the range of 1 or more and 9 or less because the particles are not crushed and, as a result, the image storage stability is improved.
In the present specification, the scale-like organic silver salt and the aspect ratio are defined as follows. The organic silver salt is observed with an electron microscope, the shape of the organic silver salt particle is approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped are defined as a, b, and c from the shortest side (even though c is the same as b) It is good to calculate x and y in the following way.
x = b / a
y = c / b

  In this way, x and y are obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of 30 ≧ X (average) ≧ 1.5 are formed into flakes. Preferably, 30 ≧ X (average) ≧ 1.5, more preferably 20 ≧ x (average) ≧ 2.0. Incidentally, the needle shape is 1 ≦ X (average) <1.5. The average value y (average) is defined as the aspect ratio.

  In the flake shaped particle, a can be regarded as a thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 μm or more and 0.23 μm or less, and more preferably 0.1 μm or more and 0.20 μm or less.

In flake shaped particles, the equivalent spherical diameter / a of the particles is defined as the aspect ratio. The aspect ratio of the flake shaped particles in the present invention is preferably 1.1 or more and 30 or less. By setting the aspect ratio in such a range, aggregation is hardly caused in the photosensitive material, and image storability is good. It becomes. The aspect ratio is more preferably 1.1 or more and 15 or less.
In addition, the sphere-equivalent diameter of the scaly particles in the present invention is preferably 0.05 μm or more and 1 μm or less, which makes it difficult for aggregation to occur in the photosensitive material and improves image storage stability. More preferably, it is 0.1 μm or more and 1 μm or less. In the present invention, the method for measuring the equivalent sphere diameter is obtained by directly photographing a sample using an electron microscope and then image-processing the negative.

  The particle size distribution of the organic silver salt is preferably monodispersed. Monodispersion is a method of obtaining the standard deviation of the volume weighted average diameter of the organic silver salt, and the percentage (coefficient of variation) of the value divided by the volume weighted average diameter is preferably 100% or less, more preferably 80% or less, and further Preferably it is 50% or less. The measurement can be performed with a commercially available laser light scattering type particle size assumption apparatus.

3) Method for Producing Organic Silver Salt Dispersion The organic silver salt dispersion in the present invention comprises an organic silver salt forming step of forming an organic silver salt by mixing a water-soluble silver salt solution and an alkali metal salt solution of an organic acid, and It is produced by a step of dispersing the organic silver salt. The present invention is characterized in that the organic silver salt forming step is carried out in the presence of a compound represented by the general formula (DF-1) or an ethoxylated derivative thereof, or a compound represented by (DF-2).

In the formula, R ₁ and R ₂ are each independently an alkyl group, an aryl group, or a heterocyclic group, each having at least one hydroxyl group as a substituent.

In the formula, n represents an integer of 1 to 3, and m is a value of 0, 1 or 2. R represents a hydrogen atom, an alkyl group, or an allyl group.
Specific examples of the compound represented by the general formula (DF-1) or an ethoxylated derivative thereof are shown below.

  Examples of the compound represented by the general formula (DF-1) include 2,5,8,11-tetramethyl-6-dodecin-5,8-diol and 5,8-dimethyl-6-dodecin-5,8. -Diol, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 4,7-dimethyl-5-decyne-4,7-diol, 2,3,6,7-tetramethyl -4-octyne-3,6-diol, 3,6-dimethyl-4-octyne-3,6-diol, 2,5-dimethyl-3-hexyne-2,5-diol, and the like. Examples of the ethoxylated derivative of the above compound include ethoxylated derivatives of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (ethylene oxide addition mole number: 1.3), 2,4 , 7,9-Tetramethyl-5-decyne 4,7-diol ethoxylate (ethylene oxide addition moles: 4), 3,6-dimethyl-4-octyne-3,6-diol ethoxylate (ethylene oxide addition moles: 4), and 2 , 5,8,11-tetramethyl-6-dodecine-5,8-diol, ethoxylated product (ethylene oxide addition mole number: 6), and the like. When the total number of moles of ethylene oxide added is 10 moles or more, the solubility in water is increased and the foaming property is further improved, so that the defoaming effect is lowered.

These compounds represented by the general formula (DF-1) or ethoxylated derivatives thereof can be used alone or in admixture of two or more to prepare the antifoam composition of the present invention. The amount used in the process is from 5% to 80% by weight, preferably from 10% to 75% by weight, based on the entire composition. When the content exceeds 80% by mass, the solubility decreases, and when a ceramic molded sheet is produced, repellent (recessed spheres) are generated. When the content is less than 5% by mass, the defoaming effect is reduced and pinholes due to bubbles are generated. To do.
The compound represented by the general formula (DF-1) can be prepared by the method described in JP-A-2003-038906, and can be obtained as Surfinol 104 manufactured by Nissin Chemical.

  The HLB of the compound represented by the general formula (DF-1) or an ethoxylated derivative thereof is 10 to 18, preferably 14 to 17. When the HLB exceeds 18, the solubilizing ability of the component (A) is improved. The foaming property is also improved, and pinholes are inevitably generated due to the generation of bubbles. If the HLB is less than 10, the solubility in water is lowered and aggregates are generated in the slurry.

  The total number of moles of ethylene oxide units added is 10 to 40 moles, preferably 10 to 30 moles. When the total number of moles of ethylene oxide exceeds 40 moles, the solubilization performance is improved. The foaming property is also improved, foaming occurs at the time of ceramic molding, causing pinholes, and if it is less than 10 mol, the solubilization performance is lost and the solubility in water itself is lost. Dissolution performance is remarkably lowered, and repellency accompanying the generation of aggregates occurs.

  An ethoxylated derivative of the compound represented by the general formula (DF-1) can be prepared by the method described in JP-A-2003-038906, and is available as Surfinol 400 manufactured by Nisshin Chemical Co., Ltd.

In General Formula (DF-2), examples of R include a hydrogen atom, an alkyl group such as a methyl group, an ethyl group, a propyl group, and an octyl group, and an allyl group such as an ethylene group, and a hydrogen atom is preferable.
As specific examples of the compound represented by the general formula (DF-2), for example, triethoxysilane and trimethoxysilane are preferably used.
These alkoxysilane compounds can be prepared by the method described in JP-A-8-208663.

  The addition amount of the antifoaming agent to be used is preferably 0.001% by mass to 5% by mass, more preferably 0.005% by mass to 1% by mass, and 0.01% by mass to 0.5% by mass with respect to the organic silver. Is most preferred.

<Organic silver salt formation process>
In the present invention, the organic silver salt is prepared by reacting a solution containing silver ions such as silver nitrate with an organic acid alkali metal salt solution or suspension, but the addition of 50% or more of the total added silver amount Is preferably performed simultaneously with the addition of the organic acid alkali metal salt solution or suspension in the presence of the compound represented by the general formula (DF-1) or (DF-2). Examples of the addition method include a method of adding to the liquid surface of the reaction bath, a method of adding to the solution, and a method of adding to the closed mixing means described later, and any method may be used.
In order to increase productivity, it is preferable to stir at a high speed, and the maximum peripheral speed of the stirring blade rotation is preferably at least 200 m / min to 1000 m / min, and 260 m / min to 800 m / min. It is preferable that it is 320 m / min or more and 600 m / min or less.
In the presence of the compound of the above general formula (DF-1) or (DF-2) in the present invention, foaming is small even when stirring at such a high speed, and the creaming phenomenon is suppressed, so that the fluidity is not lost. , Can be stirred efficiently.

  The pH of the silver ion-containing solution (for example, silver nitrate aqueous solution) used in the present invention is preferably pH 1 or more and 6 or less, more preferably pH 1.5 or more and 4 or less. Furthermore, acids and alkalis can be added for pH adjustment. The type of acid and alkali is not particularly limited.

  In the preparation of the organic silver salt in the present invention, the addition of the organic acid alkali metal salt solution may be carried out by dividing it by 2 to 6 times. By adding in a divided manner here, various functions can be imparted to the particles, such as addition for improving photographic performance and addition for changing the hydrophilicity of the surface. The number of divided additions is preferably 2 or more and 4 or less. Here, since the organic acid salt is solidified unless the temperature is high, it is necessary to take into account, for example, having a plurality of addition lines for dividing, or devising a circulation method or the like.

  The silver ion concentration of the silver ion-containing solution (for example, silver nitrate aqueous solution) used in the present invention is arbitrarily determined, but the molar concentration is preferably 0.03 mol / L or more and 6.5 mol / L or less, more preferably 0. It is 1 mol / L or more and 5 mol / L or less.

In the practice of the present invention, in order to form organic acid particles, at least one of a silver ion-containing solution, an organic acid alkali metal salt solution or suspension, and a solution prepared in advance in the reaction field, It is preferable that the alkali metal salt contains an organic solvent in an amount capable of forming a substantially transparent solution, not a string-like aggregate or micelle. The solution may be an organic solvent alone, but is preferably a mixed solution with water.
The organic solvent used in the present invention is not particularly limited as long as it is water-soluble and has the above-mentioned properties. However, those that impede photographic performance are not preferred, preferably alcohol that can be mixed with water, acetone, A tertiary alcohol having 4 to 6 carbon atoms is preferred.

Specifically, the alkali metal of the alkali metal salt of the fatty acid used in the present invention is preferably Na or K. The alkali metal salt of a fatty acid is prepared by adding NaOH or KOH to the fatty acid.
At this time, it is preferable that the amount of alkali is equal to or less than that of fatty acid to leave a small amount of unreacted fatty acid. In this case, the amount of residual fatty acid is 7 mol% or less, preferably 4 mol% or less, more preferably 3 mol% or less, based on the total fatty acids. Moreover, after adding an alkali more than desired amount, you may prepare by adding acids, such as nitric acid and a sulfuric acid, and neutralizing an excess alkali content.
In the present invention, the excess fatty acid and / or fatty acid salt (excluding Ag) with respect to the silver ion to be added is preferably 7.0 mol% or less, and more preferably 3.0 mol% or less. .

  Furthermore, the silver ion-containing solution and the organic acid alkali metal salt solution used in the present invention, or the liquid in the closed mixing vessel to which both liquids are added, are represented by, for example, general formula (1) in JP-A-62-65035. A water-soluble group-containing N heterocyclic compound as described in JP-A No. 62-150240, and an inorganic peroxide as described in JP-A No. 50-101019. A sulfur compound as described in JP-A-51-78319, a disulfide compound as described in JP-A-57-643, hydrogen peroxide, and the like can be added.

In the organic acid alkali metal salt solution used in the present invention, the amount of the organic solvent is preferably 3% or more and 70% or less, more preferably 5% or more and 50% or less as the solvent volume with respect to the water volume. At this time, since the optimum solvent volume varies depending on the reaction temperature, the optimum amount can be determined by trial and error.
The concentration of the alkali metal salt of the organic acid used in the present invention is 5 to 50% by mass, preferably 7 to 45% by mass, more preferably 10 to 40% by mass. It is below mass%.

  The temperature of the third alcohol aqueous solution of the organic acid alkali metal salt added in the closed mixing means or in the reaction vessel is 50 for the purpose of maintaining the temperature necessary to avoid the crystallization and solidification of the organic acid alkali metal salt. The temperature is preferably from 90 ° C to 90 ° C, more preferably from 60 ° C to 85 ° C, and most preferably from 65 ° C to 85 ° C. Further, in order to control the temperature of the reaction to be constant, it is preferably controlled to be constant at a certain temperature selected from the above range.

  As a result, the rate at which the third alcohol aqueous solution of the high-temperature organic acid alkali metal salt is rapidly cooled in the closed mixing means to precipitate in the form of fine crystals and the rate at which the organic silver salt is chlorinated by reaction with the silver ion-containing solution are preferably controlled The crystal form, crystal size, and crystal size distribution of the organic silver salt can be preferably controlled. At the same time, the performance can be further improved as a heat-developable material, particularly as a heat-developable photosensitive material.

  The reaction vessel may contain a solvent in advance, and water is preferably used as the solvent put in advance, but a mixed solvent with the third alcohol is also preferably used.

<Desalting step>
The organic silver salt in the present invention is preferably a dispersion that has undergone a desalting step. More preferred is a non-photosensitive organic silver salt that has undergone a desalting step by electrodialysis.
Preferably, the electrodialysis method is an ultrafiltration method using ultrafiltration in combination, and is a non-photosensitive organic silver salt that has undergone a desalting step at a pressure of 0.5 kg / cm ² or more and 10 kg / cm ² or less. is there.
Preferably, the non-photosensitive organic silver salt is a non-photosensitive organic silver salt prepared with a water content of 65% or more in all steps from the crystal formation step to the dispersion preparation step.
-Measurement method of moisture content-
About 2 g of organic dispersion is weighed and its mass is precisely weighed (T). Then the sample to evaporate the water contained was allowed to stand for about 16 hours under reduced pressure in a vacuum pump, to precisely weighed residue mass (and T _0). The water content is calculated by the following formula to define the water content (referred to as R) of the present invention.
R (%) = 100 × (T−T ₀ ) / T
-Electrodialysis-
There are various electrodialysis methods, and any method can be used as long as it can remove K ⁺ ions and NO ₃ ⁻ ions. For example, a desktop electrodialysis desalination apparatus ME-O (tank capacity 1 L) manufactured by Asahi Glass Co., Ltd. It is possible to obtain a desired desalted dispersion by stacking several pairs of ion exchange membrane selemions DSV, circulating the test solution and the electrode solution and applying a voltage at both ends until the electrical conductivity of the test solution reaches the target. I can do it.
Only one set of ion exchange membranes may be used, but it is efficient to use two or more sets in a permissible name range of two or more sets. Any electrode solution may be used as long as it is a conductive ionic solution, but it is preferable to use a medium that does not affect the photographic properties and physical properties of the test solution. For example, KNO ₃ , KCl, NaNO ₃ , NaCl, LiNO ₃ , or LiCl can be used. The applied voltage is variously selected depending on the necessity of the desalting speed, but the applied voltage per set is preferably 0.1 V or more and 20 V or less, more preferably 0.2 V or more and 10 V or less.
The circulation flow rate of the test solution and the electrode solution can also be arbitrarily selected according to the necessity.
This liquid can be kept at 25 ° C., and reduced in pressure with a decompression device, and concentrated by evaporation to obtain a dispersion having a desired water content.

<Dispersing process>
The obtained dispersion may be used for coating as it is, but may also be used as an ultrafine dispersion after high-pressure dispersion.

  The production of the organic silver salt and the dispersion method thereof include known methods. For example, the above-mentioned JP-A-8-234358, JP-A-10-62899, European Patent Publication No. 0803763A1, European Patent Publication No. 0968212A1, JP-A-11-349591, JP-A-2000-7683, 2000-72711, 2000-53682, 2000-75437, 2000-86669, 2000-143578, 2000-178278, 2000-256254, JP-A-2001-163890, 2001-163890, 2001-163827, 2001-33907, 2000-305214, 2001-11081, Japanese Patent Application No. 11-297964, Japanese Patent Application Laid-Open No. 2000-344710, Japanese Patent Application No. 11-202081, Japanese Patent Application Laid-Open No. 2001-2001. 188313, 200 No. -83652, same 2002-006442 JP, same 2002-31870 JP, same 2000-214155 Patent, or the like can be referred to.

  The method of dispersing fine particles of organic silver salt is known in the presence of a dispersing aid, such as known finer means (eg, high speed mixer, homogenizer, high speed impact mill, Banbury mixer, homomixer, kneader, ball mill, vibrating ball mill, planetary ball mill). , An attritor, a sand mill, a bead mill, a colloid mill, a jet mill, a roller mill, a tron mill, or a high-speed stone mill).

  In order to obtain a uniform fatty silver salt solid dispersion having a high S / N, a small particle size, and no agglomeration, a large force is used as long as the organic silver salt particles as an image forming medium are not damaged or heated. It is preferable to give uniformly. For this purpose, a dispersion method is preferred in which a dispersion comprising an organic silver salt and a dispersant solution is converted into a high-speed flow and then the pressure is dropped. The dispersion medium in this case may be any solvent as long as the dispersion aid functions, but is preferably only water, and may contain an organic solvent as long as it is 20% by mass or less. Further, when a photosensitive silver salt is allowed to coexist at the time of dispersion, the fog rises and the sensitivity is remarkably lowered. Therefore, it is more preferable that the photosensitive silver salt is not substantially contained at the time of dispersion. In the present invention, the amount of the photosensitive silver salt in the dispersion to be dispersed is 0.1 mol% or less with respect to 1 mol of the organic silver salt in the liquid, and it is preferable not to add the photosensitive silver salt. .

  For example, “dispersion system rheology and dispersion technology” (Toshio Kajiuchi, Hiroki Arai, 1991, Shinyamasha Publishing Co., Ltd.) , P357-p403), “Progress of Chemical Engineering, Vol. 24” (Chemical Engineering Society Tokai Branch, 1990, Tsuji Shoten, p184-185), JP 59-49832 A, US Pat. No. 4,533,254, JP As described in detail in Japanese Patent Laid-Open Nos. 8-137044, 8-238848, 2-261525, and 1-94933, the redispersion method of the present invention uses a high-pressure pump to disperse a dispersion containing at least an organic silver salt. In such a method that fine pressure dispersion is performed by passing through a narrow slit provided in the pipe after the pressure is applied in the pipe, and then causing a rapid pressure drop in the dispersion liquid. is there.

  For high-pressure homogenizers, in general, (a) “shearing force” generated when the dispersoid passes through a narrow gap (about 75 μm to 350 μm) at high pressure and high speed, (b) liquid-liquid collision in a narrow space of high pressure, Alternatively, it is considered that the impact force generated when colliding with the wall surface is not changed, and the cavitation force due to the subsequent pressure drop is further increased, and uniform and efficient dispersion is performed. In the old days, this type of dispersing device includes a gorin homogenizer. In this device, the liquid to be dispersed sent at a high pressure is converted into a high-speed flow in a narrow gap on the cylindrical surface, and this force is applied to the surrounding wall surface. Colliding and emulsifying / dispersing by the impact force.

Examples of the liquid-liquid collision include a Y-type chamber of a microfluidizer, a spherical chamber using a spherical check valve as described in JP-A-8-103642, which will be described later, and the like. Includes a Z-type chamber of a microfluidizer.
The operating pressure is generally ^{100kg / cm 2 ~600kg / cm 2} (1MPa~6MPa), flow rate is in the range of a few M～30m / sec, the number of collisions with the high-speed flow portion in a saw blade shape in order to increase the dispersion efficiency Something that has been devised such as increasing the number has been devised. Representative examples of such devices include Gorin homogenizers, microfluidizers manufactured by Microfluidics International Corporation, microfluidizers manufactured by Mizuho Industry Co., Ltd., and nanomizers manufactured by Tokushu Kika Kogyo Co., Ltd. . Also described in JP-A-8-238848, JP-A-8-103642 and USP4533254.

The organic silver salt can be dispersed to a desired particle size by adjusting the flow rate, the differential pressure at the time of pressure drop, and the number of treatments. However, from the viewpoint of photographic characteristics and particle size, the flow rate is 200 m / second to 600 m / second. is preferably in the range of pressure drop differential pressure during the ^{900kg / cm 2 ~3000kg / cm 2} (9MPa~30MPa), further the flow rate is 300 meters / sec ～600M / sec, the pressure difference at the pressure drop 1500 kg / ^cm 2 ~ More preferably, it is in the range of 3000 kg / cm ² (15 MPa to 30 MPa). The number of distributed processes can be selected as necessary. Usually, a range of 1 to 10 times is selected, but about 1 to 3 times is selected from the viewpoint of productivity. Increasing the temperature of such a dispersion under high pressure is not preferable from the viewpoint of dispersibility and photographic properties, and at a temperature exceeding 90 ° C., the particle size tends to increase and the fog tends to increase. .

Therefore, a cooling device is included in the process before the conversion to the high-pressure and high-speed flow, the process after the pressure drop, or both of these processes, and the temperature of such dispersion is 5 ° C. to 90 ° C. depending on the cooling process. It is preferable to be kept within the range, more preferably within the range of 5 ° C to 80 ° C, and particularly preferably within the range of 5 ° C to 65 ° C. In ^particular, when high-pressure dispersion range of ^{1500kg / cm 2 ~3000kg / cm 2} (15MPa~30MPa), it is effective to install the cooling device. Depending on the required heat exchange amount, a cooling device using a static mixer in a double tube or triple tube, a multi-tube heat exchanger, a serpentine heat exchanger, or the like can be appropriately selected.
In addition, in order to increase the efficiency of heat exchange, a suitable tube thickness, wall thickness, material, or the like may be selected in consideration of the operating pressure. The refrigerant used for the cooler is a refrigerant such as 20 ° C. well water, 5 ° C. to 10 ° C. cold water treated with a refrigerator, or −30 ° C. ethylene glycol / water, etc., if necessary. Can be used.

When organic silver salt is made into solid fine particles using a dispersant, for example, polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, maleic acid monoester copolymer, acryloylmethylpropane sulfonic acid Synthetic anionic polymers such as copolymers, semi-synthetic anionic polymers such as carboxymethyl starch and carboxymethyl cellulose, anionic polymers such as alginic acid and pectic acid, anions described in JP-A-52-92716, WO88 / 04794, etc. Surfactants, compounds described in JP-A-9-179243, or known anionic, nonionic, cationic surfactants, other polyvinyl alcohol, polyvinylpyrrolidone, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethy Known polymers such as cellulose, or a polymer compound existing in nature such as gelatin can be suitably selected and used.
When a solvent is used as the dispersion medium, polyvinyl butyral, butyl ethyl cellulose, methacrylate copolymer, maleic anhydride ester copolymer, polystyrene and butadiene-styrene copolymer are preferably used.

  Dispersing aid is generally mixed with organic silver salt powder or wet cake organic silver salt before dispersion, and sent to the disperser as a slurry. The organic silver salt powder or wet cake may be obtained by heat treatment or treatment with a solvent. The pH may be controlled with an appropriate pH adjusting agent before or during dispersion.

  In addition to mechanical dispersion, it may be coarsely dispersed in a solvent by controlling the pH, and then finely divided by changing the pH in the presence of a dispersion aid. At this time, you may use a fatty acid solvent as a solvent used for rough dispersion.

2. Photothermographic material The photothermographic material of the invention has an image forming layer containing at least a photosensitive silver halide, an organic silver salt, a reducing agent, and a binder on at least one surface of a support. Preferably, an intermediate layer and a surface protective layer may be provided on the image forming layer, or a non-image forming layer such as a back layer and a back protective layer may be provided on the opposite surface.

(Organic silver salt)
The photothermographic material of the present invention contains an organic silver salt produced by the above-described production method as an organic silver salt.
In the present invention, the total coating silver amount including the organic silver salt and the photosensitive silver halide salt is preferably 1.9 g / m ² or less and 0.5 g / m ² or more, more preferably 1.4 g / m ² or less 0. 0.8 g / m ² or more.

(Reducing agent)
The photothermographic material of the present invention preferably contains a reducing agent for organic silver salt. The reducing agent for the organic silver salt may be any substance (preferably an organic substance) that reduces silver ions to metallic silver. Such reducing agents are described in JP-A No. 11-65021, paragraph numbers 0043 to 0045, and European Patent Publication No. 0803764A1, page 7, line 34 to page 18, line 12.
In the present invention, the reducing agent is preferably a hindered phenol reducing agent or a bisphenol reducing agent, and more preferably a compound represented by the following general formula (I).

In the general formula (I), R ¹¹ and R ¹¹ ′ each independently represents an alkyl group having 1 to 20 carbon atoms. R ¹² and R ¹² ′ each independently represent a hydrogen atom or a substituent that can be substituted on the benzene ring. L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. X ¹ and X ¹ ′ each independently represent a hydrogen atom or a group that can be substituted on a benzene ring.

The general formula (I) will be described in detail.
R ¹¹ and R ¹¹ ′ are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and the substituent of the alkyl group is not particularly limited, but is preferably an aryl group, hydroxy group Group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group, ester group, halogen atom and the like.

R ¹² and R ¹² ′ are each independently a substituent that can be substituted on a hydrogen atom or a benzene ring, and X ¹ and X ¹ ′ each independently represent a group that can be substituted on a hydrogen atom or a benzene ring. Preferred examples of each group that can be substituted on the benzene ring include an alkyl group, an aryl group, a halogen atom, an alkoxy group, and an acylamino group.

L represents an —S— group or a —CHR ¹³ — group. R ¹³ represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms, and the alkyl group may have a substituent. Specific examples of the unsubstituted alkyl group represented by R ¹³ include methyl, ethyl, propyl, butyl, heptyl, undecyl, isopropyl, 1-ethylpentyl, and 2,4,4. -A trimethylpentyl group etc. are mentioned. Examples of the substituent of the alkyl group are the same as the substituent of R ¹¹ , and are a halogen atom, alkoxy group, alkylthio group, aryloxy group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, oxycarbonyl group, A carbamoyl group, a sulfamoyl group, etc. are mentioned.

R ¹¹ and R ¹¹ ′ are preferably a secondary or tertiary alkyl group having 3 to 15 carbon atoms, specifically, an isopropyl group, an isobutyl group, a t-butyl group, a t-amyl group, or a t-octyl group. Group, cyclohexyl group, cyclopentyl group, 1-methylcyclohexyl group, 1-methylcyclopropyl group and the like. R ¹¹ and R ¹¹ ′ are more preferably a tertiary alkyl group having 4 to 12 carbon atoms, and among them, a t-butyl group, a t-amyl group, or a 1-methylcyclohexyl group is more preferable, and a t-butyl group is more preferable. Most preferred.

R ¹² and R ¹² ′ are preferably an alkyl group having 1 to 20 carbon atoms, specifically a methyl group, an ethyl group, a propyl group, a butyl group, an isopropyl group, a t-butyl group, a t-amyl group, Examples include cyclohexyl group, 1-methylcyclohexyl group, benzyl group, methoxymethyl group, and methoxyethyl group. More preferably, they are a methyl group, an ethyl group, a propyl group, an isopropyl group, or a t-butyl group.
X ¹ and X ¹ ′ are preferably a hydrogen atom, a halogen atom, or an alkyl group, and more preferably a hydrogen atom.

L is preferably a —CHR ¹³ — group.
R ¹³ is preferably a hydrogen atom or an alkyl group having 1 to 15 carbon atoms, and the alkyl group is preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, or a 2,4,4-trimethylpentyl group. Particularly preferred as R ¹³ is a hydrogen atom, a methyl group, a propyl group or an isopropyl group.

When R ¹³ is a hydrogen atom, R ¹² and R ¹² ′ are preferably an alkyl group having 2 to 5 carbon atoms, more preferably an ethyl group or a propyl group, and most preferably an ethyl group.
When R ¹³ is a primary or secondary alkyl group having 1 to 8 carbon atoms, R ¹² and R ¹² ′ are preferably methyl groups. As the primary or secondary alkyl group having 1 to 8 carbon atoms represented by R ¹³ , a methyl group, an ethyl group, a propyl group, or an isopropyl group is more preferable, and a methyl group, an ethyl group, or a propyl group is further included. preferable.
When all of R ¹¹ , R ¹¹ ′, R ¹² and R ¹² ′ are methyl groups, R ¹³ is preferably a secondary alkyl group. In this case, the secondary alkyl group represented by R ¹³ is preferably an isopropyl group, an isobutyl group, or a 1-ethylpentyl group, and more preferably an isopropyl group.

  Although the specific example of the reducing agent used for this invention including the compound represented with the said general formula (I) below is shown, this invention is not limited to these.

The addition amount of the reducing agent is preferably a ^{0.01g / m 2 ~5.0g / m 2} , more preferably from ^{0.1g / m 2 ~3.0g / m 2} , the image forming It is preferably contained in an amount of 5 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, based on 1 mol of silver on the surface having the layer. The reducing agent is preferably contained in the image forming layer.

The reducing agent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form, and may be contained in the photosensitive material.
Well-known emulsifying dispersion methods include dissolving oil using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, or an auxiliary solvent such as ethyl acetate or cyclohexanone, and mechanically dispersing the emulsified dispersion. The method of producing is mentioned.

  Further, as a solid fine particle dispersion method, a reducing agent powder is dispersed in an appropriate solvent such as water by a ball mill, a colloid mill, a vibration ball mill, a sand mill, a jet mill, a roller mill, or an ultrasonic wave to produce a solid dispersion. A method is mentioned. In this case, a protective colloid (for example, polyvinyl alcohol) or a surfactant (for example, an anionic surfactant such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used. Good. The aqueous dispersion can contain a preservative (eg, benzoisothiazolinone sodium salt).

(Photosensitive silver halide)
1) Halogen composition The photosensitive silver halide used in the present invention is not particularly limited as a halogen composition. Silver chloride, silver chlorobromide, silver bromide, silver iodobromide, silver iodochlorobromide, silver iodide Can be used. Of these, silver bromide, silver iodobromide and silver iodide are preferred. The distribution of the halogen composition in the grain may be uniform, the halogen composition may be changed stepwise, or may be continuously changed. Further, silver halide grains having a core / shell structure can be preferably used. A preferable structure is a 2- to 5-fold structure, and more preferably 2- to 4-fold core / shell particles can be used. A technique for localizing silver bromide or silver iodide on the surface of silver chloride, silver bromide or silver chlorobromide grains can also be preferably used.

2) Grain Forming Methods Methods for forming photosensitive silver halide are well known in the art and are described, for example, in Research Disclosure No. 17029, June 1978, and US Pat. No. 3,700,458. In particular, a photosensitive silver halide is prepared by adding a silver supply compound and a halogen supply compound into gelatin or another polymer solution, and then mixed with an organic silver salt. Use the method. In addition, the method described in paragraph Nos. 0217 to 0224 of JP-A No. 11-119374, and the methods described in JP-A Nos. 11-352627 and 2000-347335 are also preferable.

3) Grain size The grain size of the photosensitive silver halide is preferably small for the purpose of keeping the cloudiness after image formation low, specifically 0.20 μm or less, more preferably 0.01 μm or more and 0.15 μm or less. More preferably, it is 0.02 μm or more and 0.12 μm or less. The grain size here means the diameter when converted into a circular image having the same area as the projected area of silver halide grains (in the case of tabular grains, the projected area of the main plane).

4) Grain shape Examples of the shape of silver halide grains include cubes, octahedrons, tabular grains, spherical grains, rod-like grains, and potato grains. In the present invention, cubic grains are particularly preferred. Grains with rounded corners of silver halide grains can also be preferably used. The surface index (Miller index) of the outer surface of the photosensitive silver halide grain is not particularly limited, but the ratio of the {100} plane having high spectral sensitization efficiency when the spectral sensitizing dye is adsorbed is high. preferable. The ratio is preferably 50% or more, more preferably 65% or more, and still more preferably 80% or more. The ratio of the Miller index {100} plane is a T.K. based on the adsorption dependency of {111} plane and {100} plane in the adsorption of sensitizing dye. Tani; Imaging Sci. 29, 165 (1985).

5) Heavy Metal The photosensitive silver halide grain in the invention may contain a metal or metal complex of Group 6 to Group 13 of the Periodic Table (showing Groups 1 to 18). More preferably, it can contain a metal or metal complex of Group 6 to Group 10 of the Periodic Table. Preferable specific examples of the group 6 to group 10 metal or metal complex of the periodic table are rhodium, ruthenium, iridium, and iron. One kind of these metal complexes may be used, or two or more kinds of complexes of the same metal and different metals may be used in combination. The preferred content is in the range of 1 × 10 ⁻⁹ mol to 1 × 10 ⁻³ mol with respect to 1 mol of silver. These heavy metals and metal complexes and methods of adding them are described in JP-A-7-225449, JP-A-11-65021, paragraphs 0018 to 0024, and JP-A-11-119374, paragraphs 0227 to 0240.

In the present invention, silver halide grains in which a hexacyano metal complex is present on the outermost surface of the grains are preferred. Examples of the hexacyano metal complex include [Fe (CN) ₆ ] ⁴⁻ , [Fe (CN) ₆ ] ³⁻ , [Ru (CN) ₆ ] ⁴⁻ , [Os (CN) ₆ ] ⁴⁻ , [Co ( CN) ₆ ] ³⁻ , [Rh (CN) ₆ ] ³⁻ , [Ir (CN) ₆ ] ³⁻ , [Cr (CN) ₆ ] ³⁻ , [Re (CN) ₆ ] ^{3− and the} like. .
In the present invention, a hexacyano Fe complex is preferred.

  The hexacyano metal complex is present in the form of ions in aqueous solution, so the counter cation is not important, but it is easy to mix with water and is suitable for precipitation of silver halide emulsions. Sodium ion, potassium ion, rubidium It is preferable to use alkali metal ions such as ions, cesium ions, and lithium ions, ammonium ions, and alkylammonium ions (for example, tetramethylammonium ions, tetraethylammonium ions, tetrapropylammonium ions, tetra (n-butyl) ammonium ions).

  In addition to water, the hexacyano metal complex is miscible with a mixed solvent or gelatin with an appropriate organic solvent miscible with water (for example, alcohols, ethers, glycols, ketones, esters, or amides). Can be added.

The addition amount of the hexacyano metal complex is preferably 1 × 10 ⁻⁵ mol or more and 1 × 10 ⁻² mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻³ mol or less per mol of silver.

  In order for the hexacyano metal complex to be present on the outermost surface of the silver halide grain, the chalcogen sensitization of sulfur sensitization, selenium sensitization and tellurium sensitization is completed after the addition of the silver nitrate aqueous solution used for grain formation. It is added directly before the completion of the preparation step before the chemical sensitization step for performing noble metal sensitization such as sensitization and gold sensitization, during the washing step, during the dispersion step, or before the chemical sensitization step. In order to prevent the silver halide fine grains from growing, it is preferable to add the hexacyano metal complex immediately after the grain formation, and it is preferable to add it before the completion of the preparation step.

  The addition of the hexacyano metal complex may be started after adding 96% by mass of the total amount of silver nitrate to be added to form grains, more preferably starting after adding 98% by mass, The addition of 99% by mass is particularly preferable.

  When these hexacyanometal complexes are added after the addition of the aqueous silver nitrate solution just before the completion of grain formation, they can be adsorbed on the outermost surface of the silver halide grains, and most of them form slightly soluble salts with silver ions on the grain surface. To do. Since this silver salt of hexacyanoiron (II) is a less soluble salt than AgI, it is possible to prevent re-dissolution by fine particles and to produce silver halide fine particles having a small particle size. .

Further, regarding a metal atom (for example, [Fe (CN) ₆ ] ⁴⁻ ), a silver salt emulsion desalting method and a chemical sensitization method which can be contained in the silver halide grains used in the present invention, JP-A-11- No. 84574, paragraph numbers 0046 to 0050, JP-A No. 11-65021, paragraph numbers 0025 to 0031, and JP-A No. 11-119374, paragraph numbers 0242 to 0250.

6) Gelatin As the gelatin contained in the photosensitive silver halide emulsion used in the present invention, various gelatins can be used. It is necessary to maintain a good dispersion state of the photosensitive silver halide emulsion in the coating solution containing an organic silver salt, and gelatin having a molecular weight of 10,000 to 1,000,000 is preferably used. It is also preferable to phthalate the gelatin substituent. These gelatins may be used at the time of grain formation or at the time of dispersion after desalting, but are preferably used at the time of grain formation.

7) Sensitizing Dye Sensitizing dyes applicable to the present invention are those that can spectrally sensitize silver halide grains in a desired wavelength region when adsorbed on silver halide grains, and are suitable for the spectral characteristics of the exposure light source. Sensitizing dyes with sensitivity can be advantageously selected. Regarding the sensitizing dye and the addition method, paragraphs 0103 to 0109 of JP-A-11-65021, compounds represented by the general formula (II) of JP-A-10-186572, and general formulas (I) of JP-A-11-119374 ) And the dye described in Example 5 of U.S. Pat. Nos. 5,510,236 and 3,871,887, JP-A-2-96131, JP-A-59-48753. No. 19, line 38 to page 20, line 35 of JP-A-0803764A1, JP-A No. 2001-272747, JP-A No. 2001-290238, JP-A No. 2002-23306, etc. It is described in.
These sensitizing dyes may be used alone or in combination of two or more. In the present invention, the time when the sensitizing dye is added to the silver halide emulsion is preferably the time from the desalting step to the coating, and more preferably the time from desalting to the end of chemical ripening.
The addition amount of the sensitizing dye in the present invention can be set to a desired amount in accordance with sensitivity and fogging performance, but is preferably 10 ⁻⁶ mol to 1 mol per mol of silver halide in the image forming layer, and Preferably it is 10 ^<-4> mol-10 < ^{-1 >} mol.

  In the present invention, a supersensitizer can be used to improve spectral sensitization efficiency. As the supersensitizer used in the present invention, European Patent Publication No. 587,338, US Pat. Nos. 3,877,943, 4,873,184, JP-A-5-341432, 11- 109547, 10-111543, etc. are mentioned.

8) Chemical Sensitization The photosensitive silver halide grain in the invention is preferably chemically sensitized by sulfur sensitizing method, selenium sensitizing method or tellurium sensitizing method. As the compound preferably used in the sulfur sensitization method, selenium sensitization method, and tellurium sensitization method, known compounds such as compounds described in JP-A-7-128768 can be used.
In the present invention, tellurium sensitization is particularly preferred. The compounds described in the literature described in paragraph No. 0030 of JP-A-11-65021, and the general formulas (II), (III), (IV) described in JP-A-5-313284 The compound shown by is more preferable.

  The photosensitive silver halide grains in the present invention are preferably chemically sensitized by gold sensitization alone or in combination with the chalcogen sensitization described above. As the gold sensitizer, the valence of gold is preferably +1 or +3, and the gold sensitizer is preferably a commonly used gold compound. Typical examples are chloroauric acid, bromoauric acid, potassium chloroaurate, potassium bromoaurate, auric trichloride, potassium auric thiocyanate, potassium iodoaurate, tetracyanoauric acid, ammonium aurothiocyanate, pyridyltrichlorogold. Etc. are preferable. Further, gold sensitizers described in US Pat. No. 5,858,637 and JP-A No. 2002-278016 are also preferably used.

In the present invention, chemical sensitization can be performed at any time after particle formation and before coating. After desalting, (1) before spectral sensitization, (2) simultaneously with spectral sensitization, (3) spectral After sensitization, there may be (4) immediately before application.
The amount of sulfur, selenium and tellurium sensitizers used in the present invention varies depending on the silver halide grains used, chemical ripening conditions, etc., but from 10 ⁻⁸ mol to 10 ⁻² mol per mol of silver halide Preferably, about 10 ⁻⁷ mol or more and 10 ⁻³ mol or less is used.
The amount of the gold sensitizer added varies depending on various conditions, but as a guideline, it is 10 ⁻⁷ mol or more and 10 ⁻³ mol or less, more preferably 10 ⁻⁶ mol or more and 5 × 10 ⁻⁴ mol or less per mol of silver halide. It is.
The conditions for chemical sensitization in the present invention are not particularly limited, but the pH is 5 to 8, the pAg is 6 to 11, and the temperature is about 40 ° C to 95 ° C.
A thiosulfonic acid compound may be added to the silver halide emulsion used in the present invention by the method described in European Patent Publication No. 293,917.

A reducing agent is preferably used for the photosensitive silver halide grains in the present invention. As specific compounds for the reduction sensitization, ascorbic acid and aminoiminomethanesulfinic acid are preferable, and in addition, it is preferable to use stannous chloride, hydrazine derivatives, borane compounds, silane compounds, polyamine compounds, and the like. The reduction sensitizer may be added at any stage in the photosensitive emulsion production process from crystal growth to the preparation process immediately before coating.
Further, reduction sensitization is preferable by ripening while maintaining the pH of the emulsion at 7 or more or pAg at 8.3 or less, and reduction sensitization is achieved by introducing a single addition portion of silver ions during grain formation. It is also preferable to do.

9) Compound in which 1-electron oxidant produced by 1-electron oxidation can emit 1 electron or more electrons In the photothermographic material of the present invention, 1-electron oxidant produced by 1-electron oxidation is 1 electron or 1 electron or more. It is preferable to contain a compound capable of emitting more electrons. The compound can be used alone or in combination with the above-described various chemical sensitizers, and can increase the sensitivity of silver halide.

The one-electron oxidant produced by one-electron oxidation contained in the light-sensitive material of the present invention is a compound selected from the following types 1 and 2 that can emit one or more electrons.
(Type 1)
A compound in which a one-electron oxidant produced by one-electron oxidation can further emit one or more electrons with a subsequent bond cleavage reaction.
(Type 2)
A compound capable of emitting one or more electrons after a one-electron oxidant produced by one-electron oxidation undergoes a subsequent bond formation reaction.

First, the compound of type 1 will be described.
JP-A-9-211769 (specific examples: 28 to 15) is a compound that can emit one electron with a one-electron oxidant produced by one-electron oxidation of a type 1 compound, followed by a bond cleavage reaction. Compounds PMT-1 to S-37 described in Table E and Table F on page 32), JP-A-9-211774, JP-A-11-95355 (specific examples: compounds INV1-36), JP-T 2001-500996 (Specific examples: Compounds 1-74, 80-87, 92-122), US Pat. No. 5,747,235, US Pat. No. 5,747,236, European Patent 786692A1 (Specific examples: Compounds INV 1-35), "One-photon two-electron sensitizer" or "deprotonated electron donation" described in patents such as European Patent No. 893732A1, US Patent No. 6,054,260 and US Patent No. 5,994,051 Compound called sensitive agent "and the like. The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In addition, as a compound of type 1 that can be emitted by one-electron oxidant produced by one-electron oxidation and further releasing one electron or more with a subsequent bond cleavage reaction, a compound represented by the general formula (1) ( General formula (1) described in JP-A-2003-114487), general formula (2) (synonymous with general formula (2) described in JP-A-2003-114487), general formula (3) General formula (1) described in 2003-114488), general formula (4) (synonymous with general formula (2) described in Japanese Patent Application Laid-Open No. 2003-114488), general formula (5) (Japanese Patent Application Laid-Open No. 2003-114488). 114488 (synonymous with general formula (3)), general formula (6) (synonymous with general formula (1) described in JP-A-2003-75950), and general formula (7) (JP-A-2003-75950). Synonymous with general formula (2) described in , General formula (8) (synonymous with general formula (1) described in JP-A-2004-239934), or chemical reaction formula (1) (synonymous with chemical reaction formula (1) described in JP-A-2004-245929) Among the compounds capable of causing the reaction represented by (), a compound represented by the general formula (9) (synonymous with the general formula (3) described in JP-A-2004-245929) can be given.
The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the formula, RED ₁ and RED ₂ represent a reducing group. R ₁ represents a non-metallic atomic group capable of forming a cyclic structure corresponding to a tetrahydro form of a 5-membered or 6-membered aromatic ring (including an aromatic heterocycle) or an octahydro form together with the carbon atom (C) and RED _1. To express. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. L ₁ represents a leaving group. ED represents an electron donating group. Z ₁ represents an atomic group capable of forming a 6-membered ring with a nitrogen atom and two carbon atoms of a benzene ring. X ₁ represents a substituent, and m 1 represents an integer of 0 to 3. Z ₂ represents —CR ₁₁ R ₁₂ —, —NR ₁₃ —, or —O—.
R ₁₁ and R ₁₂ each independently represents a hydrogen atom or a substituent. R ₁₃ represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. X ₁ represents an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, a heterocyclic thio group, an alkylamino group, an arylamino group, or a heterocyclic amino group. L ₂ represents a carboxy group or a salt thereof, or a hydrogen atom. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

Next, the type 2 compound will be described.
A compound that can be emitted by one-electron oxidant produced by one-electron oxidation with a type 2 compound and further generating one or more electrons with a subsequent bond formation reaction is represented by general formula (10) A compound capable of causing a reaction represented by the general formula (1) described in 2003-140287) and the chemical reaction formula (1) (synonymous with the chemical reaction formula (1) described in JP-A-2004-245929). And a compound represented by the general formula (11) (synonymous with the general formula (2) described in JP-A No. 2004-245929). The preferred ranges of these compounds are the same as the preferred ranges described in the cited patent specifications.

In the formula, X represents a reducing group that is oxidized by one electron. Y reacts with a one-electron oxidant produced by one-electron oxidation of X to form a new bond, a carbon-carbon double bond site, a carbon-carbon triple bond site, an aromatic group site, or a benzo The reactive group containing the non-aromatic heterocyclic part of a condensed ring is represented. L ₂ represents a linking group for linking X and Y. R ₂ represents a hydrogen atom or a substituent. When a plurality of R ₂ are present in the same molecule, these may be the same or different. X ₂ represents a group which forms a 5-membered heterocycle with C═C. Y ₂ represents a group which forms a 5- or 6-membered aryl group or heterocyclic group with C═C. M represents a radical, a radical cation, or a cation.

Of the compounds of types 1 and 2, “a compound having an adsorptive group to silver halide in the molecule” or “a compound having a partial structure of a spectral sensitizing dye in the molecule” is preferable.
Typical examples of the adsorptive group to silver halide are groups described in JP-A No. 2003-156823, page 16, right line 1 to page 17, right line 12. The partial structure of the spectral sensitizing dye is a structure described on page 17, right line 34 to page 18, left line 6 of the same specification.

  More preferably, the compound of type 1 or 2 is “a compound having at least one adsorptive group to silver halide in the molecule”. More preferred is “a compound having two or more adsorptive groups to silver halide in the same molecule”. When two or more adsorptive groups are present in a single molecule, these adsorptive groups may be the same or different.

  The adsorptive group is preferably a mercapto-substituted nitrogen-containing heterocyclic group (for example, 2-mercaptothiadiazole group, 3-mercapto-1,2,4-triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4). -Oxadiazole group, 2-mercaptobenzoxazole group, 2-mercaptobenzthiazole group, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group, etc.) or imino silver (> NAg) And a nitrogen-containing heterocyclic group having a —NH— group as a heterocyclic partial structure (for example, a benzotriazole group, a benzimidazole group, an indazole group, etc.). Particularly preferred are a 5-mercaptotetrazole group, a 3-mercapto-1,2,4-triazole group, and a benzotriazole group, and most preferred are a 3-mercapto-1,2,4-triazole group, and 5 -Mercaptotetrazole group.

  It is also particularly preferred that the adsorptive group has two or more mercapto groups as a partial structure in the molecule. Here, the mercapto group (—SH) may be a thione group if it can be tautomerized. Preferred examples of the adsorptive group having two or more mercapto groups as a partial structure (such as a dimercapto-substituted nitrogen-containing heterocyclic group) include 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, 3, A 5-dimercapto-1,2,4-triazole group may be mentioned.

  A quaternary salt structure of nitrogen or phosphorus is also preferably used as the adsorptive group. Specific examples of the quaternary salt structure of nitrogen include an ammonio group (such as a trialkylammonio group, a dialkylaryl (or heteroaryl) ammonio group, an alkyldiaryl (or heteroaryl) ammonio group) or a quaternized nitrogen atom. A group containing a nitrogen-containing heterocyclic group containing The quaternary salt structure of phosphorus includes a phosphonio group (trialkyl phosphonio group, dialkylaryl (or heteroaryl) phosphonio group, alkyldiaryl (or heteroaryl) phosphonio group, triaryl (or heteroaryl) phosphonio group, etc.) Is mentioned. More preferably, a quaternary salt structure of nitrogen is used, and more preferably a 5-membered or 6-membered nitrogen-containing aromatic heterocyclic group containing a quaternized nitrogen atom is used. Particularly preferably, a pyridinio group, a quinolinio group, or an isoquinolinio group is used. These nitrogen-containing heterocyclic groups containing a quaternized nitrogen atom may have an arbitrary substituent.

Examples of quaternary salt counter anions include halogen ions, carboxylate ions, sulfonate ions, sulfate ions, perchlorate ions, carbonate ions, nitrate ions, BF ₄ ⁻ , PF ₆ ⁻ , Ph ₄ B ^{− and the} like. It is done. When a group having a negative charge in a carboxylate group or the like is present in the molecule, an inner salt may be formed together with the group. As a counter anion not present in the molecule, a chlorine ion, a bromo ion or a methanesulfonate ion is particularly preferable.

  A preferred structure of the compound represented by types 1 and 2 having a quaternary salt structure of nitrogen or phosphorus as the adsorptive group is represented by the general formula (X).

Formula _{(X) (P-Q 1} -) i -R (-Q 2 -S) j

In the general formula (X), P and R each independently represent a quaternary salt structure of nitrogen or phosphorus that is not a partial structure of a sensitizing dye. Q ₁ and Q ₂ each independently represent a linking group. Specifically, a single bond, an alkylene group, an arylene group, a heterocyclic group, —O—, —S—, —NR _N —, —C (= O) —, —SO ₂ —, —SO—, —P (═O) — represents a group consisting of a single group or a combination of these groups. Here, _RN represents a hydrogen atom, an alkyl group, an aryl group, or a heterocyclic group. S is a residue obtained by removing one atom from a compound represented by type (1) or (2). i and j are integers of 1 or more, and i + j is selected from the range of 2-6. Preferably, i is 1 to 3, and j is 1 to 2, more preferably i is 1 or 2, and j is 1, and particularly preferably i is 1 and j is 1. The compound represented by the general formula (X) preferably has a total carbon number of 10 to 100. More preferably, it is 10-70, More preferably, it is 11-60, Most preferably, it is 12-50.

  The compounds of type 1 and type 2 in the present invention may be used at any time during the preparation of the photosensitive silver halide emulsion and during the process of producing the photothermographic material. For example, at the time of photosensitive silver halide grain formation, desalting step, chemical sensitization, before coating. Moreover, it can also add in several steps in these processes. The addition position is preferably from the end of formation of the photosensitive silver halide grains to before the desalting step, at the time of chemical sensitization (immediately after the start of chemical sensitization to immediately after completion), and before application, more preferably from the time of chemical sensitization. Until before mixing with the non-photosensitive organic silver salt.

  The compounds of type 1 and type 2 in the present invention are preferably added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. When the compound is dissolved in water, the compound having higher solubility when the pH is raised or lowered may be dissolved at a higher or lower pH and added.

The compounds of type 1 and type 2 in the present invention are preferably used in an image forming layer containing a photosensitive silver halide and a non-photosensitive organic silver salt, but the photosensitive silver halide and the non-photosensitive organic silver salt are used. It may be added to the protective layer or intermediate layer together with the image forming layer containing, and diffused during coating. The timing of addition of these compounds is preferably 1 × 10 ⁻⁹ mol to 5 × 10 ⁻¹ mol, more preferably 1 × 10 ⁻⁸ mol, per mol of silver halide, regardless of before and after the sensitizing dye. It is contained in a silver halide emulsion layer (image forming layer) at a ratio of ˜5 × 10 ⁻² mol.

10) Adsorbing redox compound having an adsorbing group and a reducing group In the present invention, it is preferable to contain an adsorbing redox compound having an adsorbing group and a reducing group for silver halide in the molecule. The adsorptive redox compound is preferably a compound represented by the following formula (I).

Formula (I) A- (W) n-B
In the formula (I), A represents a group capable of adsorbing to silver halide (hereinafter referred to as an adsorbing group), W represents a divalent linking group, n represents 0 or 1, and B represents a reducing group. To express.

  In the formula (I), the adsorption group represented by A is a group that directly adsorbs to silver halide, or a group that promotes adsorption to silver halide, and specifically, a mercapto group (or a salt thereof). , A thione group (—C (═S) —), a heterocyclic group, a sulfide group, a disulfide group, a cationic group, or an ethynyl group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom, and a tellurium atom Etc.

The mercapto group (or salt thereof) as the adsorptive group means the mercapto group (or salt thereof) itself, and more preferably, a heterocyclic group or aryl group substituted with at least one mercapto group (or salt thereof) or Represents an alkyl group. Here, the heterocyclic group is at least a 5- to 7-membered monocyclic or condensed aromatic or non-aromatic heterocyclic group such as an imidazole ring group, a thiazole ring group, an oxazole ring group, or a benzimidazole ring. Group, benzothiazole ring group, benzoxazole ring group, triazole ring group, thiadiazole ring group, oxadiazole ring group, tetrazole ring group, purine ring group, pyridine ring group, quinoline ring group, isoquinoline ring group, pyrimidine ring group, And triazine ring group.
Further, it may be a heterocyclic group containing a quaternized nitrogen atom. In this case, the substituted mercapto group may be dissociated to form a meso ion. When the mercapto group forms a salt, the counter ion includes a cation such as alkali metal, alkaline earth metal, heavy metal (Li ⁺ , Na ⁺ , K ⁺ , Mg ²⁺ , Ag ⁺ , or Zn ²⁺ ), ammonium ion, Examples thereof include a heterocyclic group containing a quaternized nitrogen atom, and a phosphonium ion.

Further, the mercapto group as the adsorptive group may be tautomerized into a thione group.
The thione group as an adsorbing group also includes a chain or cyclic thioamide group, thioureido group, thiourethane group, or dithiocarbamate group.
A heterocyclic group containing at least one atom selected from a nitrogen atom, a sulfur atom, a selenium atom and a tellurium atom as the adsorptive group is a -NH- group capable of forming imino silver (> NAg) as a partial structure of the heterocyclic ring. A nitrogen-containing heterocyclic group, or a “—S—” group, a “—Se—” group, a “—Te—” group, or a “═N—” group that can be coordinated to a silver ion by a coordination bond. A heterocyclic group having a partial structure of benzotriazole group, triazole group, indazole group, pyrazole group, tetrazole group, benzimidazole group, imidazole group, purine group, etc. , Thiazole group, oxazole group, benzothiophene group, benzothiazole group, benzoxazole group, thiadiazole group, oxadiazole group, tri Jin group, seleno azole group, benzoselenazole group, tellurium azole group, and the like benzo tellurium azole group.

Examples of the sulfide group or disulfide group as the adsorptive group include all groups having a partial structure of -S- or -SS-.
The cationic group as the adsorptive group means a group containing a quaternized nitrogen atom, specifically, an ammonio group or a group containing a nitrogen-containing heterocyclic group containing a quaternized nitrogen atom. Examples of the nitrogen-containing heterocyclic group containing a quaternized nitrogen atom include a pyridinio group, a quinolinio group, an isoquinolinio group, an imidazolio group, and the like.
An ethynyl group as an adsorptive group means a —C≡CH group, and the hydrogen atom may be substituted.
The adsorbing group may have an arbitrary substituent.

  Further, specific examples of the adsorbing group include those described in the specifications p4 to p7 of JP-A No. 11-95355.

  In the formula (I), preferred as the adsorptive group represented by A is a mercapto-substituted heterocyclic group (for example, 2-mercaptothiadiazole group, 2-mercapto-5-aminothiadiazole group, 3-mercapto-1,2,4). -Triazole group, 5-mercaptotetrazole group, 2-mercapto-1,3,4-oxadiazole group, 2-mercaptobenzimidazole group, 1,5-dimethyl-1,2,4-triazolium-3-thiolate group 2,4-dimercaptopyrimidine group, 2,4-dimercaptotriazine group, 3,5-dimercapto-1,2,4-triazole group, 2,5-dimercapto-1,3-thiazole group), or Nitrogen-containing heterocyclic group having —NH— group capable of forming imino silver (> NAg) as a partial structure of heterocyclic ring (for example, benzotriazo Group, benzimidazole group, an indazole group), more preferable as an adsorptive group is a 2-mercaptobenzimidazole group, a 3,5-dimercapto-1,2,4-triazole group.

In formula (I), W represents a divalent linking group. Any linking group may be used as long as it does not adversely affect photographic properties. For example, a divalent linking group composed of a carbon atom, a hydrogen atom, an oxygen atom, a nitrogen atom, or a sulfur atom can be used. Specifically, an alkylene group having 1 to 20 carbon atoms (for example, a methylene group, an ethylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, etc.), an alkenylene group having 2 to 20 carbon atoms, and an alkynylene group having 2 to 20 carbon atoms. , An arylene group having 6 to 20 carbon atoms (eg, phenylene group, naphthylene group, etc.), —CO—, —SO ₂ —, —O—, —S—, —NR ₁ —, combinations of these linking groups, and the like. It is done. Here, R ₁ represents a hydrogen atom, an alkyl group, a heterocyclic group, or an aryl group.
The linking group represented by W may have an arbitrary substituent.

  In formula (I), the reducing group represented by B represents a group capable of reducing silver ions. For example, a triple bond group such as formyl group, amino group, acetylene group or propargyl group, mercapto group, hydroxylamines. Hydroxamic acids, hydroxyureas, hydroxyurethanes, hydroxysemicarbazides, reductones (including reductone derivatives), anilines, phenols (chroman-6-ols, 2,3-dihydrobenzofuran-5-ols, (Including aminophenols, sulfonamidophenols, and hydroquinones, catechols, resorcinols, polyphenols such as benzenetriols, bisphenols), acylhydrazines, carbamoylhydrazines, 3-pyrazolidones, etc. Residue with one removed And the like. Of course, these may have an arbitrary substituent.

In the formula (I), the reducing group represented by B shows its oxidation potential by Akira Fujishima “Electrochemical measurement method” (pages 150-208, published by Gihodo) or “The Experimental Chemistry Course” edited by the Chemical Society of Japan, 4th edition ( 9 pages 282-344, Maruzen). For example, by a rotating disk voltammetry technique, specifically, a sample is dissolved in a solution of methanol: pH 6.5 Briton-Robinson buffer (10%: 90% (volume%)) and nitrogen gas is used for 10 minutes. , A glassy rotating disk electrode (RDE) is used as a working electrode, a platinum wire is used as a counter electrode, a saturated calomel electrode is used as a reference electrode, 25 ° C., 1000 rev / min, 20 mV / sec. Can be measured at sweep speed. A half-wave potential (E1 / 2) can be obtained from the obtained voltammogram.
In the present invention, the reducing group represented by B preferably has an oxidation potential in the range of about -0.3 V to about 1.0 V when measured by the above measurement method. More preferably, it is in the range of about -0.1V to about 0.8V, and particularly preferably in the range of about 0V to about 0.7V.

  In the formula (I), the reducing group represented by B is preferably hydroxylamines, hydroxamic acids, hydroxyureas, hydroxysemicarbazides, reductones, phenols, acylhydrazines, carbamoylhydrazines, or 3-pyrazolidones. Is a residue obtained by removing one hydrogen atom from

  The compound of the formula (I) in the present invention may be one in which a ballast group or polymer chain commonly used in an immobile photographic additive such as a coupler is incorporated. Examples of the polymer include those described in JP-A-1-100530.

  The compound of the formula (I) in the present invention may be a bis form or a tris form. The molecular weight of the compound of formula (I) in the present invention is preferably between 100 and 10000, more preferably between 120 and 1000, particularly preferably between 150 and 500.

  Examples of the compound of formula (I) in the present invention are shown below, but the present invention is not limited thereto.

  Furthermore, specific compounds 1 to 30 and 1 ″ -1 to 1 ″ -77 described in European Patent No. 1308776A2 p73 to p87 are also preferable examples of the compound having an adsorbing group and a reducing group in the present invention.

  These compounds can be easily synthesized according to known methods. As the compound of the formula (I) in the present invention, one kind of compound may be used alone, but it is also preferred to use two or more kinds of compounds at the same time. When two or more kinds of compounds are used, they may be added in the same layer or in different layers, and the addition method may be different.

The compound of formula (I) in the present invention is preferably added to the silver halide image forming layer, and more preferably added during the preparation of the emulsion. When added at the time of emulsion preparation, it can be added at any time during the process. For example, silver halide grain formation process, before desalting process start, desalting process, chemical ripening Examples include a step before starting, a chemical ripening step, and a step before preparing a finished emulsion. Moreover, it can also add in several steps in these processes. Although it is preferably used for the image forming layer, it may be added to the adjacent protective layer or intermediate layer together with the image forming layer and diffused during coating.
The preferred addition amount largely depends on the above-mentioned addition method and the kind of compound to be added, but generally 1 × 10 ⁻⁶ mol to 1 mol, preferably 1 × 10 ⁻⁵ mol per mol of photosensitive silver halide. The amount is 5 × 10 ⁻¹ mol or less, more preferably 1 × 10 ⁻⁴ mol or more and 1 × 10 ⁻¹ mol or less.

  The compound of the formula (I) in the present invention can be added after being dissolved in water, a water-soluble solvent such as methanol or ethanol, or a mixed solvent thereof. At this time, the pH may be appropriately adjusted with an acid or a base, and a surfactant may be allowed to coexist. Furthermore, it can also be dissolved in a high boiling point organic solvent and added as an emulsified dispersion. It can also be added as a solid dispersion.

11) Multiple silver halides in combination The photosensitive silver halide emulsion in the light-sensitive material used in the present invention may be only one kind, or two or more kinds (for example, those having different average grain sizes, those having different halogen compositions, Those having different crystal habits and different chemical sensitization conditions may be used in combination. The gradation can be adjusted by using a plurality of types of photosensitive silver halides having different sensitivities. As techniques relating to these, there are JP-A-57-119341, 53-106125, 47-3929, 48-55730, 46-5187, 50-73627, 57-150841, and the like. Can be mentioned. The sensitivity difference is preferably 0.2 log E or more for each emulsion.

12) Application amount The addition amount of the photosensitive silver halide is preferably 0.03 g / m ² or more and 0.6 g / m ² or less, expressed as the amount of silver applied per 1 m ² of the light-sensitive material. / M ² or more and 0.4 g / m ² or less is more preferable, and 0.07 g / m ² or more and 0.3 g / m ² or less is most preferable. The functional silver halide is preferably from 0.01 mol to 0.5 mol, more preferably from 0.02 mol to 0.3 mol, and still more preferably from 0.03 mol to 0.2 mol.

13) Mixing of photosensitive silver halide and organic silver salt Regarding the mixing method and mixing conditions of separately prepared photosensitive silver halide and organic silver salt, the silver halide grains and the organic silver salt that were prepared are respectively stirred at high speed. Prepare an organic silver salt by mixing with a machine, ball mill, sand mill, colloid mill, vibration mill, homogenizer, etc., or by mixing photosensitive silver halide that has been prepared at any time during the preparation of the organic silver salt However, there is no particular limitation as long as the effects of the present invention are sufficiently exhibited. In addition, mixing two or more organic silver salt aqueous dispersions and two or more photosensitive silver salt aqueous dispersions when mixing is a preferred method for adjusting photographic characteristics.

14) Mixing of silver halide into coating solution The preferred addition time of silver halide into the image forming layer coating solution is from 180 minutes before application, preferably from 60 minutes to 10 seconds before application. The method and mixing conditions are not particularly limited as long as the effects of the present invention are sufficiently exhibited. Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is a desired time. Harnby, M.M. F. Edwards, A.D. W. There is a method of using a static mixer described in Chapter 8 of Nienow's Koji Takahashi's “Liquid mixing technology” (published by Nikkan Kogyo Shimbun, 1989).

(Description of development accelerator)
In the photothermographic material of the present invention, a sulfonamide phenol compound represented by the general formula (A) described in JP-A-2000-267222, JP-A-2000-330234, or the like is used as a development accelerator. Hindered phenol compounds represented by general formula (II) described in No. 92075, general formula (I) described in JP-A Nos. 10-62895 and 11-15116, and JP-A No. 2002-278017 A hydrazine-based compound represented by the general formula (1) described above and a phenol-based or naphthol-based compound represented by the general formula (2) described in JP-A No. 2001-264929 are preferably used. These development accelerators are used in the range of 0.1 mol% to 20 mol% with respect to the reducing agent, preferably in the range of 0.5 mol% to 10 mol%, more preferably 1 mol% to 5 mol. % Range.
The introduction method to the light-sensitive material includes the same method as the reducing agent, but it is particularly preferable to add as a solid dispersion or an emulsified dispersion. When added as an emulsified dispersion, it is added as an emulsified dispersion dispersed using a high-boiling solvent and a low-boiling auxiliary solvent that are solid at room temperature, or as a so-called oilless emulsified dispersion that does not use a high-boiling solvent. It is preferable to add.

  In the present invention, among the above development accelerators, a hydrazine-based compound represented by the general formula (1) described in JP-A No. 2002-278017 and a general formula (2) described in JP-A No. 2001-264929 A phenolic or naphtholic compound represented by the formula is particularly preferred.

  Hereinafter, although the preferable specific example of the development accelerator of this invention is given, this invention is not limited to these.

(Description of hydrogen bonding compound)
In the present invention, it is preferable to use an aromatic hydroxyl group (—OH) of the reducing agent, or, in the case of having an amino group, a non-reducing compound having a group capable of forming a hydrogen bond with the amino group. .

  Examples of the group capable of forming a hydrogen bond include a phosphoryl group, a sulfoxide group, a sulfonyl group, a carbonyl group, an amide group, an ester group, a urethane group, a ureido group, a tertiary amino group, and a nitrogen-containing aromatic group. Among them, preferred are a phosphoryl group, a sulfoxide group, an amide group (however, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a urethane group. (However, it has no> N—H group and is blocked like> N—Ra (Ra is a substituent other than H)), a ureido group (however, it has no> N—H group,> N-Ra (Ra is a substituent other than H).)

  In the present invention, particularly preferred hydrogen bonding compounds are compounds represented by the following general formula (D).

In the general formula (D), R ²¹ to R ²³ each independently represents an alkyl group, an aryl group, an alkoxy group, an aryloxy group, an amino group or a heterocyclic group, and these groups may be substituted even if they are unsubstituted. You may have.

When R ²¹ to R ²³ have a substituent, the substituent is a halogen atom, alkyl group, aryl group, alkoxy group, amino group, acyl group, acylamino group, alkylthio group, arylthio group, sulfonamide group, acyloxy group, Examples thereof include an oxycarbonyl group, a carbamoyl group, a sulfamoyl group, a sulfonyl group, and a phosphoryl group. Preferred examples of the substituent include an alkyl group or an aryl group such as a methyl group, an ethyl group, an isopropyl group, a t-butyl group, a t-butyl group. Examples include an octyl group, a phenyl group, a 4-alkoxyphenyl group, and a 4-acyloxyphenyl group.

Specific examples of the alkyl group of R ²¹ to R ²³ include a methyl group, an ethyl group, a butyl group, an octyl group, a dodecyl group, an isopropyl group, a t-butyl group, a t-amyl group, a t-octyl group, a cyclohexyl group, Examples thereof include 1-methylcyclohexyl group, benzyl group, phenethyl group, and 2-phenoxypropyl group.

  Examples of the aryl group include a phenyl group, a cresyl group, a xylyl group, a naphthyl group, a 4-t-butylphenyl group, a 4-t-octylphenyl group, a 4-anisidyl group, and a 3,5-dichlorophenyl group.

  Alkoxy groups include methoxy, ethoxy, butoxy, octyloxy, 2-ethylhexyloxy, 3,5,5-trimethylhexyloxy, dodecyloxy, cyclohexyloxy, 4-methylcyclohexyloxy, and A benzyloxy group etc. are mentioned.

  Examples of the aryloxy group include a phenoxy group, a cresyloxy group, an isopropylphenoxy group, a 4-t-butylphenoxy group, a naphthoxy group, and a biphenyloxy group.

  Examples of the amino group include a dimethylamino group, a diethylamino group, a dibutylamino group, a dioctylamino group, an N-methyl-N-hexylamino group, a dicyclohexylamino group, a diphenylamino group, and an N-methyl-N-phenylamino group. It is done.

R ²¹ to R ²³ are preferably an alkyl group, an aryl group, an alkoxy group, or an aryloxy group. From the viewpoint of the effect of the present invention, at least one of R ²¹ to R ²³ is preferably an alkyl group or an aryl group, and more preferably two or more are an alkyl group or an aryl group. Further, it is preferable that R ²¹ to R ²³ are the same group in that they can be obtained at low cost.

  Specific examples of the hydrogen bonding compound including the compound of the general formula (D) in the present invention are shown below, but the present invention is not limited thereto.

  Specific examples of the hydrogen bonding compound include those described in JP-A Nos. 2001-281793 and 2002-014438 in addition to the above.

  The hydrogen bonding compound of the present invention can be used in a light-sensitive material after being contained in a coating solution in the form of a solution, an emulsified dispersion, or a solid dispersed fine particle dispersion in the same manner as the reducing agent. The compound of the present invention forms a complex by a hydrogen bond with a compound having a phenolic hydroxyl group in a solution state. Depending on the combination of the reducing agent and the compound of the general formula (A) of the present invention, the compound of the present invention Can be separated.

  The use of the crystal powder isolated in this way as a solid dispersed fine particle dispersion is particularly preferable for obtaining stable performance. Further, a method in which the reducing agent and the hydrogen bonding compound of the present invention are mixed as a powder and complexed at the time of dispersion with a sand grinder mill or the like using an appropriate dispersant can be preferably used.

  The hydrogen bonding compound of the present invention is preferably used in the range of 1 mol% to 200 mol%, more preferably in the range of 10 mol% to 150 mol%, still more preferably 30 mol%, based on the reducing agent. It is in the range of ˜100 mol%.

(Description of binder)
The binder of the organic silver salt-containing layer of the present invention may be any polymer, suitable binders are transparent or translucent and generally colorless, natural resins, polymers and copolymers, synthetic resins, polymers and copolymers, other films Forming media such as gelatins, rubbers, poly (vinyl alcohol) s, hydroxyethyl celluloses, cellulose acetates, cellulose acetate butyrates, poly (vinyl pyrrolidone) s, casein, starch, poly (acrylic acid) , Poly (methyl methacrylic acid) s, poly (vinyl chloride) s, poly (methacrylic acid) s, styrene-maleic anhydride copolymers, styrene-acrylonitrile copolymers, styrene-butadiene copolymers, Poly (vinyl acetal) s (eg, poly (vinyl acetal) Marl) and poly (vinyl butyral)), poly (esters), poly (urethane) s, phenoxy resins, poly (vinylidene chloride) s, poly (epoxides), poly (carbonates), poly (vinyl acetate) s , Poly (olefin) s, cellulose esters, and poly (amides). The binder may be coated from water or an organic solvent or emulsion.

  In the present invention, the glass transition temperature of the binder of the layer containing the organic silver salt is preferably 10 ° C. or higher and 80 ° C. or lower, more preferably 20 ° C. to 70 ° C., and 23 ° C. or higher and 65 ° C. or lower. More preferably.

In this specification, Tg is calculated by the following formula.
1 / Tg = Σ (Xi / Tgi)

Here, it is assumed that n monomer components from i = 1 to n are copolymerized in the polymer.
Xi is the mass fraction of the i-th monomer (ΣXi = 1), and Tgi is the glass transition temperature (absolute temperature) of the homopolymer of the i-th monomer. However, Σ is the sum from i = 1 to n.
As the transition temperature value (Tgi) of the homopolymer glass of each monomer, the value of Polymer Handbook (3rd Edition) (by J. Brandrup, EH Immergut (Wiley-Interscience, 1989)) was adopted.

  The polymer used as the binder may be used alone or in combination of two or more as required. Further, a glass transition temperature of 20 ° C. or higher and a glass transition temperature of less than 20 ° C. may be used in combination. When two or more types of polymers having different Tg are blended and used, the mass average Tg is preferably within the above range.

In the present invention, when the organic silver salt-containing layer is formed using a coating solution in which 30% by mass or more of the solvent is water and dried, the binder of the organic silver salt-containing layer is further an aqueous solvent ( When it is soluble or dispersible in an aqueous solvent), the performance is improved particularly when it is made of a latex of a polymer having an equilibrium moisture content of 2% by mass or less at 25 ° C. and 60% RH.
The most preferable form is one prepared so that the ionic conductivity is 2.5 mS / cm or less, and as such a preparation method, there is a method of purifying using a separation functional membrane after polymer synthesis.

The aqueous solvent in which the polymer is soluble or dispersible here is a mixture of water or water with 70% by mass or less of a water-miscible organic solvent.
Examples of water-miscible organic solvents include alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol, cellosolvs such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve, ethyl acetate, and dimethylformamide. .

The “equilibrium moisture content at 25 ° C. and 60% RH” is the following using the mass W1 of the polymer in a humidity-controlled equilibrium under an atmosphere of 25 ° C. and 60% RH and the mass W0 of the polymer in an absolutely dry state at 25 ° C. It can be expressed as
Equilibrium water content at 25 ° C. and 60% RH = [(W1-W0) / W0] × 100 (mass%)
For the definition and measurement method of moisture content, for example, Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Society of Polymer Sciences, Jinshokan) can be referred to.

  The equilibrium moisture content at 25 ° C. and 60% RH of the binder polymer of the present invention is preferably 2% by mass or less, more preferably 0.01% by mass or more and 1.5% by mass or less, and further preferably 0.02% by mass. % To 1% by mass is desirable.

  The binder of the present invention is particularly preferably a polymer that can be dispersed in an aqueous solvent. Examples of the dispersed state include latex in which fine particles of water-insoluble hydrophobic polymer are dispersed and polymer molecules dispersed in a molecular state or forming micelles, and all are preferable. The average particle size of the dispersed particles is preferably in the range of 1 nm to 50000 nm, more preferably about 5 nm to 1000 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution.

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

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

  Specific examples of preferable polymer latex include the following. Below, it represents using a raw material monomer, the numerical value in a parenthesis is the mass%, and molecular weight is a number average molecular weight. When a polyfunctional monomer was used, the concept of molecular weight was not applicable because a crosslinked structure was formed, so it was described as crosslinkability, and the description of molecular weight was omitted. Tg represents the glass transition temperature.

-P-1; latex of -MMA (70) -EA (27) -MAA (3)-(molecular weight 37000, Tg 61 ° C.)
-Latex of P-2; -MMA (70) -2EHA (20) -St (5) -AA (5)-(molecular weight 40000, Tg 59 ° C.)
-P-3; Latex of -St (50) -Bu (47) -MAA (3)-(crosslinkability, Tg-17 ° C)
-P-4; Latex of -St (68) -Bu (29) -AA (3)-(crosslinkability, Tg 17 ° C)
-P-5; Latex of -St (71) -Bu (26) -AA (3)-(crosslinkability, Tg 24 ° C)
-P-6; -St (70) -Bu (27) -IA (3)-latex (crosslinkable)
-P-7; Latex of -St (75) -Bu (24) -AA (1)-(crosslinkability, Tg 29 ° C.)
-P-8; Latex (crosslinkability) of -St (60) -Bu (35) -DVB (3) -MAA (2)-
-Latex (crosslinkable) of P-9; -St (70) -Bu (25) -DVB (2) -AA (3)-
-Latex (molecular weight 80000) of P-10; -VC (50) -MMA (20) -EA (20) -AN (5) -AA (5)-
-Latex of P-11; -VDC (85) -MMA (5) -EA (5) -MAA (5)-(molecular weight 67000)
-P-12; -Et (90) -MAA (10)-latex (molecular weight 12000)
-P-13; -St (70) -2EHA (27) -AA (3) latex (molecular weight 130000, Tg 43 ° C)
-P-14; -MMA (63) -EA (35) -AA (2) latex (molecular weight 33000, Tg 47 ° C.)
-P-15; Latex of -St (70.5) -Bu (26.5) -AA (3)-(crosslinkability, Tg 23 ° C.)
-P-16; Latex of -St (69.5) -Bu (27.5) -AA (3)-(crosslinkability, Tg 20.5 ° C)
・ P-17; Latex of -St (61.3) -isoprene (35.5) -AA (3)-(crosslinkability, Tg17 ° C)
・ P-18; -St (67) -Isoprene (28) -Bu (2) -AA (3)-

  The abbreviations for the above structures represent the following monomers. MMA; Methyl methacrylate, EA; Ethyl acrylate, MAA; Methacrylic acid, 2EHA; 2-Ethylhexyl acrylate, St; Styrene, Bu; Butadiene, AA; Acrylic acid, DVB; Divinylbenzene, VC; Vinyl chloride, AN; Acrylonitrile, VDC Vinylidene chloride, Et; ethylene, IA; itaconic acid.

The polymer latex described above is also commercially available, and the following polymers can be used. Examples of the acrylic polymer include Sebian A-4635, 4718, 4601 (manufactured by Daicel Chemical Industries, Ltd.), Nipol Lx811, 814, 821, 820, 857 (manufactured by Nippon Zeon Co., Ltd.), poly ( Examples of esters) include, for example, poly (urethanes) such as FINETEX ES650, 611, 675, 850 (above made by Dainippon Ink Chemical Co., Ltd.), WD-size, WMS (more made by Eastman Chemical). Examples of rubbers such as HYDRAN AP10, 20, 30, 40 (more from Dainippon Ink Chemical Co., Ltd.) include LACSTAR 7310K, 3307B, 4700H, 7132C (more from Dainippon Ink Chemical Co., Ltd.), Nipol Lx416, 410, 438C, 2507 (all manufactured by Nippon Zeon Co., Ltd.), etc. Examples of poly (vinyl chloride) s include G351 and G576 (manufactured by Nippon Zeon Co., Ltd.), and examples of poly (vinylidene chloride) include L502 and L513 (manufactured by Asahi Kasei Kogyo Co., Ltd.) Examples of poly (olefin) s include Chemipearl S120, SA100 (manufactured by Mitsui Petrochemical Co., Ltd.).
These polymer latexes may be used alone or in combination of two or more as required.

  As the polymer latex used in the present invention, a styrene-butadiene copolymer latex is particularly preferable. The mass ratio of the styrene monomer unit to the butadiene monomer unit in the styrene-butadiene copolymer is preferably 40:60 to 95: 5. The proportion of the styrene monomer unit and the butadiene monomer unit in the copolymer is preferably 60 to 99% by mass. The preferred molecular weight range is the same as described above.

  Examples of the latex of styrene-butadiene copolymer that is preferably used in the present invention include the aforementioned P-3 to P-8, 14, and 15, commercially available LACSTAR-3307B and 7132C, and Nipol Lx416.

  If necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methylcellulose, hydroxypropylcellulose, carboxymethylcellulose may be added to the organic silver salt-containing layer of the light-sensitive material of the present invention.

  The amount of these hydrophilic polymers added is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total binder of the organic silver salt-containing layer.

  The organic silver salt-containing layer (that is, the image forming layer) of the present invention is preferably formed using a polymer latex as a binder. The amount of the binder in the organic silver salt-containing layer is preferably such that the total binder / organic silver salt mass ratio is 1/10 to 10/1, more preferably 1/5 to 4/1.

  In addition, such an organic silver salt-containing layer is usually an image forming layer (image forming layer) containing a photosensitive silver halide that is a photosensitive silver salt. The mass ratio of silver halide is preferably 400 to 5, more preferably 200 to 10.

The total amount of binder in the image forming layer of the present invention is ^{0.2g / m 2 ~30g / m 2} , more preferably from ^1g / ^{m 2 ~15g} / m 2 is preferred. The image forming layer of the present invention may contain a crosslinking agent for crosslinking, a surfactant for improving coating properties, and the like.

  In the present invention, the solvent of the organic silver salt-containing layer coating solution of the light-sensitive material (here, for simplicity, the solvent and the dispersion medium are collectively referred to as a solvent) is preferably an aqueous solvent containing 30% by mass 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, and ethyl acetate may be used. The water content of the solvent is more preferably 50% by mass or more, and still more preferably 70% by mass or more.

  Specific examples of the preferred solvent composition include water 100, 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, water / methyl alcohol / isopropyl alcohol = 85/10/5, etc. (numerical values are mass%).

(Description of antifogging agent)
1) Organic polyhalogen compound The present invention preferably contains a compound represented by the following general formula (H) as an antifoggant.

Formula (H) Q- (Y) n-C (Z ₁ ) (Z ₂ ) X

In the general formula (H), Q represents an alkyl group, an aryl group or a heterocyclic group, Y represents a divalent linking group, n represents 0 or 1, Z ₁ and Z ₂ represent a halogen atom, X represents a hydrogen atom or an electron withdrawing group.

  Q preferably represents a phenyl group substituted with an electron-attracting group in which Hammett's substituent constant σp takes a positive value. For Hammett's substituent constants, see Journal of Medicinal Chemistry, 1973, Vol. 16, no. 11, 1207-1216 etc. can be referred to.

Examples of such an electron withdrawing group include a halogen atom (fluorine atom (σp value: 0.06), chlorine atom (σp value: 0.23), bromine atom (σp value: 0.23), iodine atom. (Σp value: 0.18)), trihalomethyl group (tribromomethyl (σp value: 0.29), trichloromethyl (σp value: 0.33), trifluoromethyl (σp value: 0.54)), Cyano group (σp value: 0.66), nitro group (σp value: 0.78), aliphatic aryl, or heterocyclic sulfonyl group (for example, methanesulfonyl (σp value: 0.72)), aliphatic aryl Or a heterocyclic acyl group (for example, acetyl (σp value: 0.50), benzoyl (σp value: 0.43)), alkynyl group (for example, C≡CH (σp value: 0.23)), aliphatic Aryl or heterocyclic oxycarbo Group (for example, methoxycarbonyl (σp value: 0.45), phenoxycarbonyl (σp value: 0.44)), carbamoyl group (σp value: 0.36), sulfamoyl group (σp value: 0.57), Examples thereof include a sulfoxide group, a heterocyclic group, and a phosphoryl group.
The σp value is preferably in the range of 0.2 to 2.0, more preferably in the range of 0.4 to 1.0.

  Preferred as the electron withdrawing group are a carbamoyl group, an alkoxycarbonyl group, an alkylsulfonyl group, an alkylphosphoryl group, a carboxyl group, an alkyl or arylcarbonyl group, and an arylsulfonyl group, and particularly preferably a carbamoyl group and an alkoxycarbonyl group. , An alkylsulfonyl group and an alkylphosphoryl group, and a carbamoyl group is most preferred.

X is preferably an electron-withdrawing group, more preferably a halogen atom, aliphatic / aryl or heterocyclic sulfonyl group, aliphatic / aryl or heterocyclic acyl group, aliphatic / aryl or heterocyclic oxycarbonyl group, A carbamoyl group and a sulfamoyl group, particularly preferably a halogen atom.
Among the halogen atoms, a chlorine atom, a bromine atom and an iodine atom are preferable, a chlorine atom and a bromine atom are more preferable, and a bromine atom is particularly preferable.

Y preferably represents -C (= O) -, - SO- or -SO ₂ -; more preferably, -C (= O) -, - SO 2 - , and particularly preferably -SO ₂ - is a . n represents 0 or 1, and is preferably 1.

  Although the specific example of the compound of general formula (H) of this invention is shown below, this invention is not limited to these.

The compound represented by the general formula (H) of the present invention is preferably used in the range of 10 ⁻⁴ mol to 0.8 mol, more preferably 10 ⁻ per mol of the non-photosensitive silver salt of the image forming layer. It is preferably used in the range of ³ mol to 0.1 mol, more preferably in the range of 5 × 10 ⁻³ mol to 0.05 mol.
In particular, when a silver halide having a high silver iodide content according to the present invention is used, the addition amount of the compound of the general formula (H) is important in order to obtain a sufficient antifogging effect. Most preferably, it is used in the range of 10 ⁻³ mol to 0.03 mol.

  In the present invention, examples of the method for incorporating the compound represented by the general formula (H) into the photosensitive material include the methods described in the method for containing a reducing agent.

  The melting point of the compound represented by the general formula (H) is preferably 200 ° C. or lower, more preferably 170 ° C. or lower.

  Other organic polyhalides used in the present invention include those disclosed in the patents described in paragraph Nos. 0111 to 0112 of JP-A No. 11-65021. In particular, an organic halogen compound represented by Formula (P) in JP-A No. 2000-284399, an organic polyhalogen compound represented by Formula (II) in JP-A No. 10-339934, and JP-A No. 2001-033911 Organic polyhalogen compounds are preferred.

2) Other antifoggants Other antifoggants include mercury (II) salts described in paragraph No. 0113 of JP-A No. 11-65021, benzoic acids described in paragraph No. 0114 of the same, salicylic acid derivatives of JP-A No. 2000-206642, A formalin scavenger compound represented by the formula (S) in JP-A-2000-221634, a triazine compound according to claim 9 in JP-A-11-352624, and a compound represented by the general formula (III) in JP-A-6-11791 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene and the like.

  Antifoggant, stabilizer and stabilizer precursor that can be used in the present invention described in paragraph No. 0070 of JP-A-10-62899, page 20, line 57 to page 21, line 7 of European Patent No. 0803764A1 Patented compounds and compounds described in JP-A Nos. 9-281737 and 9-329864 can be mentioned.

  The photothermographic material in the invention may contain an azolium salt for the purpose of preventing fogging. Examples of the azolium salt include compounds represented by general formula (XI) described in JP-A-59-193447, compounds described in JP-B-55-12581, and general formula (II) described in JP-A-60-153039. And the compounds represented. The azolium salt may be added to any part of the light-sensitive material, but the addition layer is preferably added to the layer having the image forming layer, and more preferably to the organic silver salt-containing layer.

  The azolium salt may be added at any step in the coating solution preparation. When added to the organic silver salt-containing layer, any step from the preparation of the organic silver salt to the preparation of the coating solution may be used. To immediately before coating. The azolium salt may be added by any method such as powder, solution, fine particle dispersion. Moreover, you may add as a solution mixed with other additives, such as a sensitizing dye, a reducing agent, and a color toning agent.

In the present invention, the azolium salt may be added in any amount, but preferably 1 × 10 ⁻⁶ mol to 2 mol, and more preferably 1 × 10 ⁻³ mol to 0.5 mol, per mol of silver.

(Other additives)
1) Mercapto, disulfide, and thiones In the present invention, mercapto compounds and disulfide compounds are used to control development by suppressing or accelerating development, to improve spectral sensitization efficiency, and to improve storage stability before and after development. And thione compounds, paragraphs 0067 to 0069 of JP-A-10-62899, compounds represented by formula (I) of JP-A-10-186572, and specific examples thereof include paragraph numbers 0033 to 0052. , European Patent Publication No. 0803764A1, page 20, lines 36 to 56, JP-A-2001-1003008 and the like. Of these, mercapto-substituted heteroaromatic compounds are preferred.

2) Toning agent In the photothermographic material of the invention, it is preferable to add a toning agent. For the toning agent, paragraphs 0054 to 0055 of JP-A No. 10-62899, p. Lines 21, 23 to 48, described in JP-A No. 2000-356317 and JP-A No. 2000-187298, and in particular, phthalazinones (phthalazinone, phthalazinone derivatives or metal salts; for example, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethoxyphthalazinone and 2,3-dihydro-1,4-phthalazinedione); phthalazinones and phthalic acids (eg, phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid, A combination of diammonium phthalate, sodium phthalate, potassium phthalate and tetrachlorophthalic anhydride); phthalazines (phthalazine, phthalazine derivatives or metal salts; for example, 4- (1-naphthyl) phthalazine, 6-isopropylphthalazine, 6 -T-butylphthalazine, 6-chloro (Talazine, 5.7-dimethoxyphthalazine, and 2,3-dihydrophthalazine) are preferable. In particular, in the combination with silver halide having a high silver iodide content, the combination of phthalazine and phthalic acid is preferable.

  The addition amount of phthalazines is preferably 0.01 mol to 0.3 mol, more preferably 0.02 mol to 0.2 mol, and particularly preferably 0.02 mol to 0.00 mol per mol of the organic silver salt. 1 mole. This addition amount is an important factor for promoting development, which is a problem in the silver halide emulsion having a high silver iodide content of the present invention. By selecting an appropriate addition amount, both sufficient developability and low fog are achieved. Is possible.

3) Plasticizers and lubricants The plasticizers and lubricants that can be used in the image forming layer of the invention are described in paragraph No. 0117 of JP-A No. 11-65021. The slip agent is described in JP-A No. 11-84573, paragraph numbers 0061 to 0064 and Japanese Patent Application No. 11-106881, paragraph numbers 0049 to 0062.

4) Dye and Pigment The image forming layer of the present invention has various dyes and pigments (for example, CI Pigment Blue 60, CI Pigment, etc.) from the viewpoints of color tone improvement, prevention of interference fringes during laser exposure, and prevention of irradiation. Blue 64, CI Pigment Blue 15: 6) can be used. These are described in detail in WO 98/36322, JP-A Nos. 10-268465 and 11-338098, and the like.

5) Nucleating Agent In the photothermographic material of the invention, it is preferable to add a nucleating agent to the image forming layer. Regarding the nucleating agent, the addition method and the addition amount thereof, paragraph No. 0118 of JP-A No. 11-65021, paragraph Nos. 0136 to 0193 of JP-A No. 11-223898, and formula (H) of JP-A No. 2000-284399. , Compounds of formulas (1) to (3), formulas (A) and (B), compounds of general formulas (III) to (V) described in Japanese Patent Application No. 11-91652 (specific compounds: The nucleation accelerators are described in paragraph No. 0102 of JP-A No. 11-65021 and paragraph Nos. 0194 to 0195 of JP-A No. 11-223898.

In order to use formic acid or formate as a strong fogging substance, it is preferable to contain 5 mmol or less, more preferably 1 mmol or less, per mol of silver on the side having the image forming layer containing photosensitive silver halide.
When a nucleating agent is used in the photothermographic material of the invention, it is preferable to use an acid formed by hydrating diphosphorus pentoxide or a salt thereof in combination. Acids or salts thereof formed by hydration of diphosphorus pentoxide include metaphosphoric acid (salt), pyrophosphoric acid (salt), orthophosphoric acid (salt), triphosphoric acid (salt), tetraphosphoric acid (salt), hexametalin An acid (salt) etc. can be mentioned. Examples of the acid or salt thereof formed by hydrating diphosphorus pentoxide particularly preferably include orthophosphoric acid (salt) and hexametaphosphoric acid (salt). Specific examples of the salt include sodium orthophosphate, sodium dihydrogen orthophosphate, sodium hexametaphosphate, ammonium hexametaphosphate and the like.
The amount of acid or salt thereof formed by hydrating diphosphorus pentoxide (the coating amount per 1 m ^{2 of the} photosensitive material) may be a desired amount according to the performance such as sensitivity and fogging, but is 0.1 mg / m ^2. preferably ^{~500mg / m 2, 0.5mg / m} 2 ~100mg / m 2 is more preferable.

(Preparation and application of coating solution)
The preparation temperature of the image forming layer coating solution of the present invention is preferably from 30 ° C. to 65 ° C., more preferably from 35 ° C. to less than 60 ° C., and more preferably from 35 ° C. to 55 ° C. Moreover, it is preferable that the temperature of the image forming layer coating liquid immediately after the addition of the polymer latex is maintained at 30 ° C. or higher and 65 ° C. or lower.

(Layer structure, other components)
The image forming layer in the invention is composed of one or more layers on a support. In the case of a single layer, it consists of an organic silver salt, a photosensitive silver halide, a reducing agent and a binder, and optionally contains additional materials such as toning agents, coating aids and other auxiliary agents. In the case of two or more layers, an organic silver salt and a light-sensitive silver halide are contained in the first image forming layer (usually a layer adjacent to the support), and some in the second image forming layer or both layers. Must contain other ingredients.
The photothermographic material of the present invention may be a “single-sided type” having an image forming layer only on one side of a support, or a double-sided type having image forming layers on both sides.

  The photothermographic material generally has a non-image forming layer in addition to the image forming layer. The non-image forming layer is composed of (1) a protective layer provided on the image forming layer (on the side farther from the support), and (2) a plurality of image forming layers or between the image forming layer and the protective layer. An intermediate layer provided between them, (3) an undercoat layer provided between the image forming layer and the support, and (4) a back layer provided on the opposite side of the image forming layer. The filter layer is provided on the photosensitive material as the layer (1) or (2). The antihalation layer is provided on the photosensitive material as the layer (3) or (4).

1) Surface protective layer The photothermographic material according to the invention may be provided with a surface protective layer for the purpose of preventing adhesion of the image forming layer. The surface protective layer may be a single layer or a plurality of layers. The surface protective layer is described in JP-A No. 11-65021, paragraph numbers 0119 to 0120 and JP-A No. 2001-348546.

  As the binder for the surface protective layer of the present invention, gelatin is preferable, but it is also preferable to use polyvinyl alcohol (PVA) or a combination thereof. As gelatin, inert gelatin (for example, Nitta gelatin 750), phthalated gelatin (for example, Nitta gelatin 801), and the like can be used.

  Examples of PVA include those described in paragraph Nos. 0009 to 0020 of JP-A No. 2000-171936. Completely saponified PVA-105, partially saponified PVA-205, PVA-335, and modified polyvinyl alcohol MP- Preferred is 203 (trade name, manufactured by Kuraray Co., Ltd.).

Preferably 0.3g ^{/ m 2} ~4.0g ^/ m 2 as a polyvinyl alcohol coating amount (per support 1 m ²⁾ of the protective layer (per one ^{layer), 0.3g / m 2 ~2.0g /} m 2 Is more preferable.

All (including water-soluble polymer and latex polymer) binder preferably 0.3g ^{/ m 2} ~5.0g ^/ m 2 as a coating amount (per support 1 m ²⁾ of the surface protective layer (per one layer), 0. 3g ^{/ m 2} ~2.0g ^/ m 2 is more preferable.

2) Antihalation layer In the photothermographic material of the invention, the antihalation layer can be provided on the side farther from the exposure light source than the image forming layer. As for the antihalation layer, paragraphs 0123 to 0124 of JP-A-11-65021, JP-A-11-223898, 9-230531, 10-36695, 10-104779, 11-231457, 11 -352625, 11-352626 and the like.

  The antihalation layer contains an antihalation dye having absorption at the exposure wavelength. When the exposure wavelength is in the infrared region, an infrared absorbing dye may be used, and in that case, a dye having no absorption in the visible region is preferable.

  When antihalation is performed using a dye having absorption in the visible range, it is preferable that substantially no dye color remains after image formation, and a means for decoloring by the heat of heat development is used. In particular, it is preferable to add a thermally decolorable dye and a base precursor to the non-photosensitive layer to function as an antihalation layer. These techniques are described in JP-A-11-231457 and the like.

The amount of decoloring dye added is determined by the use of the dye. In general, the optical density (absorbance) measured at the target wavelength is used in an amount exceeding 0.1. The optical density is preferably 0.2-2. The amount of the dye for obtaining such an optical density is generally 0.001g ^{/ m 2} ~1g ^/ m 2 approximately.

  When the dye is decolored in this way, the optical density after heat development can be reduced to 0.1 or less. Two or more kinds of decoloring dyes may be used in combination in a heat decoloring type recording material or a photothermographic material. Similarly, two or more kinds of base precursors may be used in combination.

  In thermal decoloration using such decoloring dyes and base precursors, substances that lower the melting point by 3 ° C. or more when mixed with a base precursor as described in JP-A No. 11-352626 (for example, diphenylsulfone, 4-chlorophenyl, etc.) (Phenyl) sulfone) is preferably used in view of thermal decoloring properties.

3) Back Layer Back layers that can be applied to the present invention are described in paragraph Nos. 0128 to 0130 of JP-A No. 11-65021.

In the present invention, a colorant having an absorption maximum at 300 nm to 450 nm can be added for the purpose of improving the silver tone and the temporal change of the image. Such colorants are disclosed in JP-A-62-210458, JP-A-63-104046, JP-A-63-103235, JP-A-63-208846, JP-A-63-306436, JP-A-63-141435, and JP-A-01-61745. And JP-A No. 2001-100363. Such a colorant is usually added in the range of 0.1 mg / m ^{2 to 1} g / m ² , and the back layer provided on the opposite side of the image forming layer is preferable as the layer to be added.

4) Matting agent In the present invention, it is preferable to add a matting agent to the surface protective layer and the back layer in order to improve transportability. Matting agents are described in JP-A No. 11-65021, paragraph numbers 0126 to 0127.
When the matting agent is indicated by the coating amount per the photosensitive material 1 m ^2, preferably from ^{1mg / m 2 ~400mg / m 2} , more preferably ^{5mg / m 2 ~300mg / m 2} .

  Further, the degree of matting of the image forming layer surface may be any as long as so-called stardust failure in which small white spots occur in the image portion and light leakage occurs, but the Beck smoothness is preferably 30 seconds or more and 2000 seconds or less, Particularly, it is preferably 40 seconds or more and 1500 seconds or less. The Beck smoothness can be easily obtained by Japanese Industrial Standard (JIS) P8119 “Smoothness test method using Beck tester for paper and paperboard” and TAPPI standard method T479.

  In the present invention, the matte degree of the back layer is preferably a Beck smoothness of 1200 seconds or less and 10 seconds or more, preferably 800 seconds or less and 20 seconds or more, and more preferably 500 seconds or less and 40 seconds or more.

  In the present invention, the matting agent is preferably contained in the outermost surface layer of the photosensitive material, the layer functioning as the outermost surface layer, or a layer close to the outer surface, and is contained in a layer acting as a so-called protective layer. It is preferable.

5) Polymer latex A polymer latex can be added to the surface protective layer or the back layer of the present invention.
For such polymer latex, “Synthetic resin emulsion (Hiraku Okuda, Hiroshi Inagaki, published by Kobunshi Publishing (1978))”, “Application of synthetic latex (Takaaki Sugimura, Ikuo Kataoka, Junichi Suzuki, Keiji Kasahara, Takashi "Molecular Publications (1993))" and "Synthetic Latex Chemistry (Muroichi Muroi, published by High Polymers Publication (1970))", specifically, methyl methacrylate (33.5% by mass) / Ethyl acrylate (50 wt%) / Methacrylic acid (16.5 wt%) copolymer latex, Methyl methacrylate (47.5 wt%) / Butadiene (47.5 wt%) / Itaconic acid (5 wt%) copolymer Latex, latex of ethyl acrylate / methacrylic acid copolymer, methyl methacrylate (58.9% by mass) / 2-ethyl Latex of xyl acrylate (25.4 mass%) / styrene (8.6 mass%) / 2-hydroxyethyl methacrylate (5.1 mass%) / acrylic acid (2.0 mass%) copolymer, methyl methacrylate (64. 0 mass%) / styrene (9.0 mass%) / butyl acrylate (20.0 mass%) / 2-hydroxyethyl methacrylate (5.0 mass%) / acrylic acid (2.0 mass%) copolymer latex, etc. Is mentioned.

  The polymer latex is preferably used in an amount of 10% by mass to 90% by mass, particularly preferably 20% by mass to 80% by mass, based on the total binder (including the water-soluble polymer and latex polymer) of the surface protective layer or the back layer.

6) Membrane pH
The photothermographic material of the present invention preferably has a film surface pH of 7.0 or less, more preferably 6.6 or less before heat development. The lower limit is not particularly limited, but is about 3. The most preferred pH range is in the range of 4 to 6.2.

The film surface pH is preferably adjusted 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 from the viewpoint of reducing the film surface pH. In particular, ammonia is volatile and is preferable for achieving a low film surface pH because it can be removed before the coating process or heat development.
In addition, it is also preferable to use ammonia in combination with a nonvolatile base such as sodium hydroxide, potassium hydroxide, or lithium hydroxide. A method for measuring the film surface pH is described in paragraph No. 0123 of JP-A No. 2000-284399.

7) Hardener A hardener may be used for each layer such as the image forming layer, protective layer, and back layer of the present invention.
Examples of hardeners include T.W. H. There are various methods described in "THE THEORY OF THE PHOTOGRAPHIC PROCESS FOURTH EDITION" by James (published by Macmillan Publishing Co., Inc., published in 1977), pages 77 to 87, Chrome Alum, 2,4-dichloro-6 In addition to hydroxy-s-triazine sodium salt, N, N-ethylenebis (vinylsulfonacetamide), N, N-propylenebis (vinylsulfonacetamide), polyvalent metal ions described on page 78 of the same document, US Pat. No. 4,281 , 060, and JP-A-6-208193, epoxy compounds such as US Pat. No. 4,791,042, and vinyl sulfone compounds such as JP-A-62-89048 are preferably used.

  The hardening agent is added as a solution, and the addition time of this solution into the protective layer coating solution is from 180 minutes before to immediately before application, preferably from 60 minutes to 10 seconds before application. As long as the effects of the present invention are sufficiently exhibited, there is no particular limitation.

  Specific mixing methods include mixing in a tank in which the average residence time calculated from the addition flow rate and the amount of liquid fed to the coater is a desired time, and N.I. Harnby, M.M. F. Edwards, A.D. W. There is a method using a static mixer described in Chapter 8 of Nienow's “Liquid Mixing Technology” (Nikkan Kogyo Shimbun, 1989), translated by Koji Takahashi.

8) Surfactant Surfactants applicable to the present invention are described in paragraph No. 0132 of JP-A No. 11-65021.
In the present invention, it is preferable to use a fluorochemical surfactant. Preferable specific examples of the fluorosurfactant include compounds described in JP-A Nos. 10-197985, 2000-19680, 2000-214554 and the like. Further, a polymeric fluorine-based surfactant described in JP-A-9-281636 is also preferably used. In the present invention, the use of a fluorosurfactant described in JP-A-2000-206560 is particularly preferred.

9) Antistatic agent In the present invention, an antistatic layer containing various known metal oxides or conductive polymers may be provided. The antistatic layer may also serve as the above-described undercoat layer, back layer surface protective layer, or the like, or may be provided separately. Regarding the antistatic layer, paragraph No. 0135 of JP-A No. 11-65021, paragraphs of JP-A Nos. 56-143430, 56-143431, 58-62646, No. 56-120519, and paragraphs of JP-A No. 11-84573. The techniques described in Paragraph Nos. 0078 to 0084 of Nos. 0040 to 0051, US Pat. No. 5,575,957 and JP-A-11-223898 can be applied.

10) Support The transparent support is subjected to heat treatment in a temperature range of 130 ° C to 185 ° C in order to relieve internal strain remaining in the film during biaxial stretching and to eliminate heat shrinkage strain generated during heat development processing. Polyester, especially polyethylene terephthalate, is preferably used.

  PEN can be preferably used as a support for a thermosensitive material used in combination with an ultraviolet light emitting screen. However, it is not limited to this. PEN is preferably polyethylene-2,6-naphthalate. The polyethylene-2,6-naphthalate referred to in the present invention is not limited as long as the repeating structural unit is substantially composed of an ethylene-2,6-naphthalenedicarboxylate unit. 6-naphthalene dicarboxylate as well as copolymers in which not more than 10%, preferably not more than 5% of the number of repeating structural units are modified with other components, and mixtures and compositions with other polymers. It is a waste.

Polyethylene-2,6-naphthalate is synthesized by combining naphthalene-2,6-dicarboxylic acid, or a functional derivative thereof, and ethylene glycol or a functional derivative thereof in the presence of a catalyst under suitable reaction conditions. However, one or more appropriate third components (modifiers) are added to the polyethylene-2,6-naphthalate referred to in the present invention before the completion of polymerization of the polyethylene-2,6-naphthalate. Copolymerized or mixed polyester may be used. Suitable third components include compounds having a divalent ester-forming functional group, such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalene-2,7-dicarboxylic acid, succinic acid, diphenyl ether dicarboxylic acid Dicarboxylic acids such as, lower alkyl esters thereof, oxycarboxylic acids such as p-oxybenzoic acid and p-oxyethoxybenzoic acid, or lower alkyl esters thereof, and dihydric alcohols such as propylene glycol and trimethylene glycol, etc. Compounds.
Polyethylene-2,6-naphthalate or a modified polymer thereof is obtained by blocking a terminal hydroxyl group and / or carboxyl group with a monofunctional compound such as benzoic acid, benzoylbenzoic acid, benzyloxybenzoic acid, and methoxypolyalkylene glycol. Alternatively, it may be modified with a very small amount of a trifunctional or tetrafunctional ester-forming compound such as glycerin or pentaerythritol so long as a substantially linear copolymer is obtained. "

In the case of a photothermographic material for medical use, the transparent support may be colored with a blue dye (for example, dye-1 described in Examples of JP-A-8-240877) or may be uncolored.
Specific examples of the support are described in paragraph No. 0134 of JP-A No. 11-65021.

  Examples of the support include water-soluble polyesters disclosed in JP-A-11-84574, styrene-butadiene copolymers described in JP-A-10-186565, and vinylidene chloride described in JP-A-2000-39684 and Japanese Patent Application No. 11-106881, paragraph numbers 0063 to 0080. It is preferable to apply an undercoating technique such as a copolymer.

11) Other additives An antioxidant, a stabilizer, a plasticizer, an ultraviolet absorber or a coating aid may be further added to the photothermographic material. A solvent described in paragraph No. 0133 of JP-A No. 11-65021 may be added. Various additives are added to either the image forming layer or the non-photosensitive layer. Regarding these, WO 98/36322, EP 803764A1, JP-A-10-186567, 10-18568 and the like can be referred to.

12) Coating method The photothermographic material in the invention may be coated by any method. Specifically, various coating operations including extrusion coating, slide coating, curtain coating, dip coating, knife coating, flow coating, or extrusion coating using a hopper of the type described in US Pat. No. 2,681,294. And Stephen F. Kistler, Peter M. et al. The extrusion coating described in “LIQUID FILM COATING” (CHAPMAN & HALL, 1997) by Schweizer (1997), pages 399 to 536 is preferably used, and slide coating is particularly preferably used.

  An example of the shape of a slide coater used for slide coating is shown in FIG. 11b. 1 If desired, two or more layers can be simultaneously coated by the method described on pages 399 to 536 of the same document, the method described in US Pat. No. 2,761,791 and British Patent No. 837,095. .

The organic silver salt-containing layer coating solution in the present invention is preferably a so-called thixotropic fluid. Regarding this technique, JP-A-11-52509 can be referred to.
The viscosity of the organic silver salt-containing layer coating solution in the present invention is preferably 400 mPa · s to 100,000 mPa · s, more preferably 500 mPa · s to 20,000 mPa · s, at a shear rate of 0.1S- ¹ .
Further, at a shear rate of 1000S- ^1, it is preferably 1 mPa · s or more and 200 mPa · s or less, more preferably 5 mPa · s or more and 80 mPa · s or less.

13) Packaging material The photothermographic material of the present invention is to prevent photographic performance from deteriorating during storage before use, or to prevent curling or curling in the case of a rolled product. It is preferable to hermetically package with a packaging material having low oxygen permeability and / or moisture permeability. The oxygen permeability is preferably 50 mL / atm / m ² · day or less at 25 ° C., more preferably 10 mL / atm / m ² · day or less, and even more preferably 1.0 mL / atm / m ² · day. day or less. The moisture permeability is preferably 10 g / atm / m ² · day or less, more preferably 5 g / atm / m ² · day or less, and further preferably 1 g / atm / m ² · day or less. As specific examples of at least one of the packaging materials having low oxygen permeability and moisture permeability, those described in, for example, JP-A-8-254793 and JP-A-2000-206653 can be used.

14) Other usable techniques The techniques that can be used in the photothermographic material of the present invention include EP80364A1, EP883022A1, WO98 / 36322, JP-A-56-62648, JP-A-58-62644, JP-A-5-62644. 9-43766, 9-281737, 9-297367, 9-304869, 9-31405, 9-329865, 10-10669, 10-62899, 10-69023 10-186568, 10-90823, 10-171663, 10-186565, 10-186567, 10-186567 to 10-186572, 10-197974, Nos. 10-197982, 10-197983, 10-197985 to 1 No. 0-197987, No. 10-207001, No. 10-207004, No. 10-221807, No. 10-282601, No. 10-288823, No. 10-288824, No. 10-307365, No. 10- No. 312038, No. 10-339934, No. 11-7100, No. 11-15105, No. 11-24200, No. 11-24201, No. 11-30832, No. 11-84574, No. 11-65021 11-109547, 11-125880, 11-129629, 11-133536 to 11-133539, 11-133542, 11-133543, 11-223898, 11-352627, 11-305377, 11-305378, 11-305 84, 11-305380, 11-316435, 11-327076, 11-338096, 11-338098, 11-338099, 11-343420, JP 2000-187298 2001-2004414, 2001-234635, 2002-020699, 2001-275471, 2001-275461, 2000-313204, 2001-292844, 2000-324888, JP-A-2001-293864 and JP-A-2001-348546 are also included.

(Image forming method)
1) Exposure The photosensitive material of the present invention may be exposed by any method, but a laser beam is preferable as an exposure light source. A silver halide emulsion having a high silver iodide content as in the present invention has been problematic because of its low sensitivity. However, it has been found that writing with high illuminance such as laser light eliminates the problem of low sensitivity and allows image recording with less energy. The target sensitivity can be achieved by writing with such strong light in a short time.

Especially when providing an exposure amount that gives a maximum density (Dmax), the preferred amount of the photosensitive material surface is ^{0.1W / mm 2 ~100W / mm 2} . More preferably ^{0.5W / mm 2 ~50W / mm 2} , and most preferably ^{1W / mm 2 ~50W / mm 2} .

As the laser beam according to the present invention, a gas laser (Ar ⁺ , He—Ne, He—Cd), a YAG laser, a dye laser, a semiconductor laser, and the like are preferable. A semiconductor laser and a second harmonic generation element can also be used. The laser preferably used is determined according to the light absorption peak wavelength of the photosensitizing material such as a spectral sensitizing dye, but it is a red to infrared emitting He-Ne laser, a red semiconductor laser, or a blue to green emitting Ar. ⁺ , He—Ne, He—Cd laser, blue semiconductor laser. In recent years, in particular, a module in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated and a blue semiconductor laser have been developed, and a laser output device in a short wavelength region has been closed up. The blue semiconductor laser is expected to increase in demand in the future because high-definition image recording is possible, the recording density is increased, and a stable output is obtained with a long lifetime. The peak wavelength of the laser light is 300 nm to 500 nm of blue, preferably 400 nm to 500 nm, and 600 nm to 900 nm of red to near infrared, preferably 620 nm to 850 nm.

  It is also preferable that the laser light is oscillated in a vertical multi by a method such as high frequency superposition.

2) Photothermographic development The photothermographic material of the present invention may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. The preferred development temperature is 100 ° C to 150 ° C, more preferably 110 ° C to 130 ° C.
The development time is preferably 5 to 15 seconds, more preferably 7 to 13 seconds.

  A plate heater method is preferred as the heat development method. The heat development method using the plate heater method is preferably the method described in JP-A-11-133572. The heat development photosensitive material having the latent image formed thereon is brought into contact with the heating means in the heat development section to obtain a visible image. In the developing device, the heating unit includes a plate heater, and a plurality of press rollers are disposed to face each other along one surface of the plate heater, and the heat is interposed between the press roller and the plate heater. A thermal development apparatus that performs thermal development by passing a development photosensitive material. It is preferable to divide the plate heater into two to six stages and lower the temperature at the tip by about 1 ° C. to 10 ° C.

  Such a method is also described in JP-A No. 54-30032, which can exclude moisture and organic solvents contained in the photothermographic material out of the system, and rapidly develop the photothermographic material. It is also possible to suppress changes in the shape of the support of the photothermographic material due to heating of the photothermographic material.

3) System Fuji Medical Dry Imager-FM-DPL and DRYPIX7000 can be given as medical laser imagers having an exposure unit and a thermal development unit. The system is described in Fuji Medical Review, No. 8, p. 39-55, and those techniques can be used. Further, it can also be applied as a photothermographic material for a laser imager in “AD network” proposed by Fuji Film Medical Co., Ltd. as a network system conforming to the DICOM standard.

(Use of the present invention)
The photothermographic material using the high silver iodide photographic emulsion of the present invention forms a black-and-white image with a silver image, and is a photothermographic material for medical diagnosis, a photothermographic material for industrial photography, and a photothermographic material for printing. It is preferably used as a photothermographic material for COM.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.

Example 1
1. 1. Production of PET support 1-1. Film formation PET having an intrinsic viscosity of IV = 0.66 (measured in phenol / tetrachloroethane = 6/4 (mass ratio) at 25 ° C.) was obtained using terephthalic acid and ethylene glycol according to a conventional method. This was pelletized, dried at 130 ° C. for 4 hours, melted at 300 ° C., extruded from a T-die, and rapidly cooled to produce an unstretched film having a thickness of 175 μm after heat setting.

This was longitudinally stretched 3.3 times using rolls having different peripheral speeds and then stretched 4.5 times with a tenter. The temperatures at this time were 110 ° C. and 130 ° C., respectively. Then, after heat setting at 240 ° C. for 20 seconds, the film was relaxed by 4% in the lateral direction at the same temperature. After that, after slitting the chuck portion of the tenter, knurl processing was performed at both ends, and the roll was wound at 4 kg / cm ² (4 × 10 ⁴ Pa) to obtain a roll having a thickness of 175 μm.

1-2. Surface Corona Discharge Treatment Using a solid state corona discharge treatment machine 6KVA model manufactured by Pillar, both surfaces of the support were treated at room temperature at 20 m / min. From the current and voltage readings at this time, it was found that the support was processed at 0.375 kV · A · min / m ² . The treatment frequency at this time was 9.6 kHz, and the gap clearance between the electrode and the dielectric roll was 1.6 mm.

1-3. Undercoat 1) Preparation formulation of undercoat layer coating solution (1) (for image forming layer side undercoat layer)
Takamatsu Oil & Fats Co., Ltd. Pes Resin A-515GB (30 mass% solution) 234g
Polyethylene glycol monononyl phenyl ether (average ethylene oxide number = 8.5) 10% by mass solution 21.5 g
MP-1000 (polymer fine particles, average particle size 0.4 μm) 0.91 g manufactured by Soken Chemical Co., Ltd.
744 mL of distilled water

Formula (2) (for back layer 1st layer)
Styrene-butadiene copolymer latex 158g
(Solid content 40% by mass, styrene / butadiene mass ratio = 68/32)
2,4-dichloro-6-hydroxy-S-triazine sodium salt (8% by mass aqueous solution)
20g
10 mL of 1% by weight aqueous solution of sodium laurylbenzenesulfonate
854 mL of distilled water

Formula (3) (for back side second layer)
SnO ₂ / SbO (9/1 mass ratio, average particle size 0.038 μm, 17 mass% dispersion)
84g
Gelatin (10 mass% aqueous solution) 89.2g
8.6 g of Metroise TC-5 (2% by mass aqueous solution) manufactured by Shin-Etsu Chemical Co., Ltd.
MP-1000 0.01g manufactured by Soken Chemical Co., Ltd.
10 mL of 1% by weight aqueous solution of sodium dodecylbenzenesulfonate
NaOH (1% by mass) 6 mL
Proxel (ICI) 1mL
805 mL of distilled water

2) Undercoat After the corona discharge treatment is performed on both surfaces of the biaxially stretched polyethylene terephthalate support having a thickness of 175 μm, the undercoat coating solution formulation (1) is wet coated with a wire bar on one surface (image forming layer surface). Apply to a volume of 6.6 mL / m ² (per side) and dry at 180 ° C. for 5 minutes, then wet coat the above-mentioned undercoat coating formulation (2) on the back (back side) with a wire bar Was applied at a temperature of 5.7 mL / m ² and dried at 180 ° C. for 5 minutes. The undercoat coating liquid formulation (3) was further applied to the back surface (back surface) with a wire bar so that the wet coating amount was 7.7 mL / m. ² and dried at 180 ° C. for 6 minutes to prepare an undercoat support.

2. Back layer 1) Preparation of back surface coating liquid (Preparation of solid fine particle dispersion (a) of base precursor)
64 g of the base precursor compound 1, 28 g of diphenylsulfone, and 10 g of surfactant demole N10 manufactured by Kao Co., Ltd. were mixed with 220 mL of distilled water, and the mixture was mixed with a sand mill (1/4 Gallon Sand Grinder Mill, manufactured by IMEX Co., Ltd.). Using the resulting solution, beads were dispersed to obtain a solid fine particle dispersion (a) of a base precursor compound having an average particle size of 0.2 μm.

(Preparation of dye solid fine particle dispersion)
9.6 g of cyanine dye compound 1 and 5.8 g of sodium p-dodecylbenzenesulfonate are mixed with 305 mL of distilled water, and the mixture is beads using a sand mill (1/4 Gallon sand grinder mill, manufactured by IMEX Co., Ltd.). Dispersion gave a dye solid fine particle dispersion having an average particle size of 0.2 μm.

(Preparation of antihalation layer coating solution)
Gelatin 17 g, polyacrylamide 9.6 g, solid fine particle dispersion (a) 70 g of the above-mentioned precursor precursor, 56 g of the above dye solid fine particle dispersion, monodisperse polymethyl methacrylate fine particles (average particle size 8 μm, particle size standard deviation 0.4) 1.5 g, benzoisothiazolinone 0.03 g, sodium polyethylenesulfonate 2.2 g, blue dye compound 1 0.2 g and water 844 mL were mixed to prepare an antihalation layer coating solution.

(Preparation of back surface protective layer coating solution)
The container was kept at 40 ° C., 50 g of gelatin, 0.2 g of sodium polystyrenesulfonate, 2.4 g of N, N-ethylenebis (vinylsulfonateacetamide), 1 g of sodium t-octylphenoxyethoxyethanesulfonate, 30 mg of benzoisothiazolinone , Fluorine-based surfactant (F-1: N-perfluorooctylsulfonyl-N-propylalanine potassium salt) 37 mg, fluorine-based surfactant (F-2: polyethylene glycol mono (N-perfluorooctylsulfonyl-N-) Propyl-2-aminoethyl) ether [ethylene oxide average polymerization degree 15]) 0.15 g, fluorosurfactant (F-3) 64 mg, fluorosurfactant (F-4) 32 mg, acrylic acid / ethyl acrylate Copolymer (copolymerization mass ratio 5/95 8.8 g, Aerosol OT (manufactured by American Cyanamid Co.) 0.6 g, and the back surface protective layer coating liquid was 950mL mixing 1.8g, water and liquid paraffin emulsion as liquid paraffin.

2) Application of back layer On the back surface side of the undercoat support, an antihalation layer coating solution is applied so that the solid content coating amount of the solid fine particle dye is 0.04 g / m ^2, and the back surface protective layer coating solution is applied. A multilayer coating was simultaneously applied so that the amount of gelatin applied was 1.7 g / m ² and dried to prepare a back layer.

3. 3. Image forming layer, intermediate layer, and surface protective layer 3-1. Preparation of coating solution preparation material 1) Photosensitive silver halide emulsion << Preparation of silver halide emulsion 1 >>
A solution containing 3.1 mL of 1% by mass potassium bromide solution in 1421 mL of distilled water, 3.5 mL of 0.5 mol / L sulfuric acid, and 31.7 g of phthalated gelatin was stirred in a stainless steel reaction vessel. While maintaining the liquid temperature at 30 ° C., a solution A in which distilled water was added to 22.22 g of silver nitrate and diluted to 95.4 mL, 15.3 g of potassium bromide and 0.8 g of potassium iodide in a distilled water volume of 97. Solution B diluted to 4 mL was added at a constant flow rate over 45 seconds. Thereafter, 10 mL of a 3.5% by mass aqueous hydrogen peroxide solution was added, and 10.8 mL of a 10% by mass aqueous solution of benzimidazole was further added.

Further, a solution C in which distilled water was added to 51.86 g of silver nitrate and diluted to 317.5 mL, and a solution D in which 44.2 g of potassium bromide and 2.2 g of potassium iodide were diluted with distilled water to a volume of 400 mL, Solution C was added at a constant flow rate over 20 minutes, and Solution D was added by the controlled double jet method while maintaining pAg at 8.1. The total amount of potassium hexachloroiridium (III) was added 10 minutes after the start of the addition of Solution C and Solution D so as to be 1 × 10 ⁻⁴ mol per mol of silver. In addition, 5 seconds after the completion of the addition of the solution C, a potassium iron (II) hexacyanide aqueous solution was added in an amount of 3 × 10 ⁻⁴ mol per mol of silver. The pH was adjusted to 3.8 using 0.5 mol / L sulfuric acid, stirring was stopped, and a precipitation / desalting / water washing step was performed. The pH was adjusted to 5.9 with 1 mol / L sodium hydroxide to prepare a silver halide dispersion having a pAg of 8.0.

While maintaining the silver halide dispersion at 38 ° C. while stirring, 5 mL of a methanol solution of 0.34% by mass of 1,2-benzisothiazolin-3-one was added, and after 40 minutes, spectral sensitizing dye A and the spectral solution were added. A methanol solution having a molar ratio of sensitizing dye B of 1: 1 was added in an amount of 1.2 × 10 ⁻³ mol as a total of spectral sensitizing dyes A and B per mol of silver, and the temperature was raised to 47 ° C. after 1 minute. Twenty minutes after the temperature increase, sodium benzenethiosulfonate was added in a methanol solution to 7.6 × 10 ⁻⁵ mol per 1 mol of silver, and further 5 minutes later, tellurium sensitizer C was added in methanol solution to 2 per 1 mol of silver. 9 × 10 ⁻⁴ mol was added and aged for 91 minutes. 1.3 mL of a 0.8 mass% methanol solution of N, N′-dihydroxy-N ″ -diethylmelamine was added, and after another 4 minutes, 5-methyl-2-mercaptoben ヅ imidazole was added with methanol solution to 4 per mol of silver. 5.4 × 10 ⁻³ mol and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole were added in a methanol solution to 5.4 × 10 ⁻³ mol with respect to 1 mol of silver. Silver halide emulsion 1 was prepared.

  The grains in the silver halide emulsion thus prepared were silver iodobromide grains containing 3.5 mol% of iodine with an average equivalent sphere diameter of 0.042 μm and a variation coefficient of 20% of the equivalent sphere diameter. The particle size and the like were determined from an average of 1000 particles using an electron microscope. The {100} face ratio of the particles was determined to be 80% using the Kubelka-Munk method.

<< Preparation of silver halide emulsion 2 >>
In the preparation of silver halide emulsion 1, the liquid temperature 30 ° C. at the time of grain formation was changed to 47 ° C., and solution B was changed to diluting 15.9 g of potassium bromide to a volume of 97.4 mL with distilled water, Solution D was changed to diluting 45.8 g of potassium bromide with distilled water to a volume of 400 mL, and the addition time of solution C was changed to 30 minutes to remove potassium hexacyanoiron (II) in the same manner. A silver halide emulsion 2 was prepared. Precipitation / desalting / washing / dispersion was carried out in the same manner as silver halide emulsion 1. Further 1 in a molar ratio of the spectral sensitizing dye B with a spectral sensitizing dye A: 1 methanol solution addition amount of spectral sensitizing dye per mole of silver A and spectral sensitizing dye B total as 7.5 × 10 in the ^{- 4} mol, the addition amount of tellurium sensitizer C is 1.1 × 10 ⁻⁴ mol per mol of silver, and 1-phenyl-2-heptyl-5-mercapto-1,3,4-triazole is added to 1 mol of silver. Except for changing to 3.3 × 10 ⁻³ mol, spectral sensitization, chemical sensitization and 5-methyl-2-mercaptoben ヅ imidazole, 1-phenyl-2-heptyl were performed in the same manner as silver halide emulsion 1. -5-mercapto-1,3,4-triazole was added to obtain a silver halide emulsion 2. The emulsion grains of the silver halide emulsion 2 were pure silver bromide cubic grains having an average sphere equivalent diameter of 0.080 μm and a sphere equivalent diameter variation coefficient of 20%.

<< Preparation of silver halide emulsion 3 >>
In the preparation of silver halide emulsion 1, silver halide emulsion 3 was prepared in the same manner except that the liquid temperature at the time of grain formation was changed from 30 ° C. to 27 ° C. Further, precipitation / desalting / washing / dispersion was performed in the same manner as silver halide emulsion 1. The addition amount of the solid dispersion (gelatin aqueous solution) having a molar ratio of the spectral sensitizing dye A and the spectral sensitizing dye B of 1: 1 is 6 × as the sum of the spectral sensitizing dye A and the spectral sensitizing dye B per mole of silver. Silver halide emulsion 3 was obtained in the same manner as silver halide emulsion 1 except that ^10-3 mol and the amount of tellurium sensitizer C added were changed to 5.2 × 10 ⁻⁴ mol per mol of silver. .
The emulsion grains of the silver halide emulsion 3 were silver iodobromide grains containing 3.5 mol% of iodine with an average equivalent sphere diameter of 0.034 μm and a sphere equivalent diameter variation coefficient of 20%.

<< Preparation of mixed emulsion A for coating solution >>
70% by weight of silver halide emulsion 1, 15% by weight of silver halide emulsion 2 and 15% by weight of silver halide emulsion 3 were dissolved, and 7% by mole of silver in a 1% by weight aqueous solution of benzothiazolium iodide. × 10 ⁻³ mol was added.
Further, the amount of the one-electron oxidant produced by one-electron oxidation is 2 × 10 ⁻³ moles per mole of silver halide of each of compounds 1, 2, and 3 capable of emitting one electron or more. Added.
The adsorbing redox compounds 1 and 2 having an adsorbing group and a reducing group were each added in an amount of 5 × 10 ⁻³ mol per mol of silver halide.
Further, water was added so that the content of silver halide per 1 kg of the mixed emulsion for coating solution was 38.2 g as silver. 1- (3-Methylureidophenyl) -5-mercaptotetrazole was added so as to give 0.34 g per kg of the mixed emulsion for coating solution.

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

<Preparation of organic silver salt particles>
88 kg of recrystallized behenic acid, 422 L of distilled water, 49.2 L of 5 mol / L NaOH aqueous solution, and 120 L of t-butyl alcohol were mixed and stirred at 75 ° C. for 1 hour to obtain a sodium behenate solution. Separately, 206.2 L (pH 4.0) of an aqueous solution containing 40.4 kg of silver nitrate was prepared and kept warm at 10 ° C. A reaction vessel containing 635 L of distilled water and 30 L of t-butyl alcohol was kept at 30 ° C., and with sufficient agitation, the total amount of the previous sodium behenate solution and the total amount of silver nitrate aqueous solution were kept at a constant flow rate of 93 minutes and 15 seconds, respectively. And added over 90 minutes. Stirring was performed at a peripheral speed of 260 m / min with a Faudler type stirring blade having a diameter of 840 mm.
At this time, only the aqueous silver nitrate solution is added for 11 minutes after the start of the addition of the aqueous silver nitrate solution, and then the addition of the sodium behenate solution is started. After the addition of the aqueous silver nitrate solution, only the sodium behenate solution is added for 14 minutes and 15 seconds. It was made to be. At this time, the temperature in the reaction vessel was 30 ° C., and the external temperature was controlled so that the liquid temperature was constant.
The pipe of the addition system for the sodium behenate solution was kept warm by circulating hot water outside the double pipe so that the liquid temperature at the outlet at the tip of the addition nozzle was 75 ° C.
Moreover, the piping of the addition system of the silver nitrate aqueous solution was kept warm by circulating cold water outside the double pipe. The addition position of the sodium behenate solution and the addition position of the aqueous silver nitrate solution were arranged symmetrically around the stirring axis, and were adjusted so as not to contact the reaction solution.

After completion of the addition of the sodium behenate solution, the mixture was left stirring for 20 minutes at the same temperature, heated to 35 ° C. over 30 minutes, and then aged for 210 minutes. Immediately after completion of aging, the solid content was separated by centrifugal filtration, and the solid content was washed with water until the conductivity of filtered water reached 30 μS / cm.
Thus, a fatty acid silver salt was obtained. The obtained solid content was stored as a wet cake without drying.
The water content was 60%.

  When the morphology of the obtained silver behenate particles was evaluated by electron microscope photography, the average values were a = 0.21 μm, b = 0.4 μm, c = 0.4 μm, average aspect ratio 2.1, sphere equivalent diameter. It was a crystal with a variation coefficient of 11% (a, b, and c are defined in the text).

<Dispersion of silver behenate particles>
19.3 kg of polyvinyl alcohol (trade name: PVA-217) and water are added to a wet cake corresponding to a dry solid content of 260 kg to make a total amount of 1000 kg, and then slurried with a dissolver blade, and a pipeline mixer (manufactured by Mizuho Kogyo Co., Ltd.). : PM-10 type).

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

  A silver behenate dispersion having an average particle size of 140 nm was obtained (3% by mass of solids).

<< Preparation of Organic Silver Salt Dispersions-1-6 >><Invention>
A reactor was charged with deionized water, 46.6 g of recrystallized organic acid, and a compound of the general formula (DF-1) or (DF-2) (shown in Table 1) in the present invention.
Organic silver salt particles were prepared under the same conditions as in the preparation of the organic silver salt dispersion A, and desalted and dispersed.

3) Preparation of reducing agent dispersion << Preparation of reducing agent-1 dispersion >>
16 kg of water was added to 10 kg of a reducing agent-1 and 10 kg of a 20% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the reducing agent to 25% by mass to obtain a reducing agent-1 dispersion. The reducing agent particles contained in the thus obtained reducing agent-1 dispersion had a median diameter of 0.42 μm and a maximum particle diameter of 2.0 μm or less.
The obtained reducing agent-1 dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of Reducing Agent-2 Dispersion >>
16 kg of water was added to 10 kg of a reducing agent-2 and 10 kg of a 20% by weight aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the reducing agent to 25% by mass to obtain a reducing agent-2 dispersion. The reducing agent particles contained in the thus obtained reducing agent-2 dispersion had a median diameter of 0.38 μm and a maximum particle diameter of 2.0 μm or less.
The obtained reducing agent-2 dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

4) Preparation of hydrogen bonding compound-1 dispersion 10 kg of hydrogen bonding compound-1 (tri (4-t-butylphenyl) phosphine oxide) and modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203) 10 kg of water was added to 20 kg of the aqueous solution and mixed well to obtain a slurry. This slurry was fed with a diaphragm pump and dispersed for 3 hours 30 minutes in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm, and then benzoisothiazolinone sodium salt 0.2 g and water were added to adjust the concentration of the hydrogen bonding compound to 22% by mass to obtain a hydrogen bonding compound-2 dispersion.
The hydrogen bonding compound particles contained in the thus obtained hydrogen bonding compound-2 dispersion had a median diameter of 0.35 μm and a maximum particle diameter of 1.5 μm or less. The obtained hydrogen bonding compound-1 dispersion was filtered through a polypropylene filter having a pore size of 3.0 μm to remove foreign substances such as dust and stored.

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

<< Preparation of Dispersion of Development Accelerator-2 and Color Adjusting Agent-1 >>
The solid dispersions of the development accelerator-2 and the color tone adjusting agent-1 were also dispersed by the same method as the development accelerator-1, and 20% by mass and 15% by mass of dispersions were obtained, respectively.

6) Preparation of organic polyhalogen compound dispersion << Preparation of organic polyhalogen compound-1 dispersion >>
10 kg of organic polyhalogen compound-1 and 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203), 0.4 kg of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, and 16 kg of water were added. Then, it was mixed well to make a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2g and water were added and it adjusted so that the density | concentration of an organic polyhalogen compound might be 23.5 mass%, and the organic polyhalogen compound-1 dispersion was obtained. The organic polyhalogen compound particles contained in the organic polyhalogen compound-1 dispersion thus obtained had a median diameter of 0.36 μm and a maximum particle diameter of 2.0 μm or less.
The obtained organic polyhalogen compound-1 dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

<< Preparation of organic polyhalogen compound-2 dispersion >>
10 kg of organic polyhalogen compound-2, 10 kg of 20 wt% aqueous solution of modified polyvinyl alcohol (Kuraray Co., Ltd., Poval MP203), 0.4 kg of 20 wt% aqueous solution of sodium triisopropylnaphthalenesulfonate, and 14 kg of water added Then, it was mixed well to make a slurry. This slurry was fed with a diaphragm pump and dispersed for 5 hours in a horizontal sand mill (UVM-2: manufactured by Imex Co., Ltd.) filled with zirconia beads having an average diameter of 0.5 mm. 2 g and water were added to adjust the concentration of the organic polyhalogen compound to 26% by mass to obtain an organic polyhalogen compound-2 dispersion. The organic polyhalogen compound particles contained in the organic polyhalogen compound-2 dispersion thus obtained had a median diameter of 0.41 μm and a maximum particle diameter of 2.0 μm or less.
The obtained organic polyhalogen compound-2 dispersion was filtered through a polypropylene filter having a pore size of 10.0 μm to remove foreign substances such as dust and stored.

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

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

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

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

10) Preparation of SBR latex liquid In a polymerization kettle of a gas monomer reactor (TAS-2J type manufactured by Pressure Glass Industrial Co., Ltd.), 287 g of distilled water and a surfactant (Pionin A-43-S (manufactured by Takemoto Yushi Co., Ltd.)) ): Solid content 48.5% by mass) 7.73 g, 1 mol / L, NaOH 14.06 mL, ethylenediaminetetraacetic acid tetrasodium salt 0.15 g, styrene 255 g, acrylic acid 11.25 g, and tert-dodecyl mercaptan 3.0 g The reaction vessel was sealed and stirred at a stirring speed of 200 rpm.
After degassing with a vacuum pump and repeating nitrogen gas replacement several times, 108.75 g of 1,3-butadiene was injected to raise the internal temperature to 60 ° C. A solution prepared by dissolving 1.875 g of ammonium persulfate in 50 mL of water was added thereto and stirred as it was for 5 hours. The temperature was further raised to 90 ° C. and stirred for 3 hours. After completion of the reaction, the internal temperature was lowered to room temperature, and then Na ⁺ ion: NH ₄ ⁺ ion = 1 using 1 mol / L NaOH and NH ₄ OH = 1. Addition treatment was performed so that the molar ratio was 5.3 (molar ratio), and the pH was adjusted to 8.4. Thereafter, the mixture was filtered through a polypropylene filter having a pore size of 1.0 μm to remove foreign substances such as dust and stored, and 774.7 g of SBR latex was obtained.
When the halogen ions were measured by ion chromatography, the chloride ion concentration was 3 ppm. As a result of measuring the concentration of the chelating agent by high performance liquid chromatography, it was 145 ppm.

  The latex has an average particle size of 90 nm, Tg = 17 ° C., solid content concentration of 44 mass%, equilibrium moisture content at 25 ° C. and 60% RH, 0.6 mass%, ion conductivity of 4.80 mS / cm (measurement of ion conductivity is A latex stock solution (44 mass%) was measured at 25 ° C. using a conductivity meter CM-30S manufactured by Toa Denpa Kogyo Co., Ltd.).

3-2. Preparation of coating solution 1) Preparation of coating solution for image forming layer 1000 g of the organic silver salt dispersion obtained above, water, reducing agent-1 dispersion, 91 g of reducing agent-2 dispersion, pigment-1 dispersion, organic poly Halogen compound-1 dispersion, organic polyhalogen compound-2 dispersion, phthalazine compound-1 solution g, development accelerator-1 dispersion, development accelerator-2 dispersion, color tone modifier-1 dispersion preparation, SBR latex Solution, mercapto compound-1 aqueous solution, and mercapto compound-2 aqueous solution are added in order, and silver halide mixed emulsion A for coating solution is added immediately before coating, and the well-mixed image forming layer coating solution is directly sent to the coating die. Liquid.

2) Preparation of intermediate layer coating solution 772 g of 10% by weight aqueous solution of polyvinyl alcohol PVA-205 (manufactured by Kuraray Co., Ltd.), 5.3 g of 20% by weight dispersion of pigment, methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / Acrylic acid copolymer (copolymerization mass ratio 64/9/20/5/2) 27.5 mass% aqueous solution of aerosol OT (manufactured by American Cyanamid Co., Ltd.) 226 g of latex 27.5 mass% liquid, phthalic acid Water is added to 10.5 mL of a 20% by mass aqueous solution of diammonium salt and a total amount of 880 g, and adjusted with NaOH to a pH of 7.5 to obtain an intermediate layer coating solution of 10 mL / m ² . The solution was fed to the coating die.
The viscosity of the coating solution was 21 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3) Preparation of surface protective layer first layer coating solution 64 g of inert gelatin was dissolved in water and methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5). / 2) 80 g of 27.5 wt% latex, 23 mL of 10 wt% methanol solution of phthalic acid, 23 mL of 10 wt% aqueous solution of 4-methylphthalic acid, 28 mL of 0.5 mol / L sulfuric acid, Aerosol OT (American 5 ml of a 5% by weight aqueous solution of Cyanamid), 0.5 g of phenoxyethanol, and 0.1 g of benzoisothiazolinone are added, and water is added so that the total amount becomes 750 g. the 26mL immediately before coating a mixture with a static mixer to 18.6 mL / ^{m 2} It was fed to a coating die to so that.
The viscosity of the coating solution was 17 [mPa · s] at 40 ° C. (No. 1 rotor, 60 rpm) B-type viscometer.

4) Preparation of surface protective layer second layer coating solution 80 g of inert gelatin was dissolved in water and a methyl methacrylate / styrene / butyl acrylate / hydroxyethyl methacrylate / acrylic acid copolymer (copolymerization mass ratio 64/9/20/5). / 2) 3.2 mL of 27.5% latex solution by weight, 102 mL of fluorine surfactant (F-1: N-perfluorooctylsulfonyl-N-propylalanine potassium salt), 3.2 mL, fluorine surfactant 32 mL of 2% by weight aqueous solution of the agent (F-2: polyethylene glycol mono (N-perfluorooctylsulfonyl-N-propyl-2-aminoethyl) ether [ethylene oxide average polymerization degree = 15]), Aerosol OT (American Cyt 23 ml of 5% by mass solution of Anamide), polymethyl methacrylate fine 4 g of particles (average particle size 0.7 μm), 21 g of polymethyl methacrylate fine particles (average particle size 4.5 μm), 1.6 g of 4-methylphthalic acid, 4.8 g of phthalic acid, 44 mL of 0.5 mol / L sulfuric acid, and Water is added to 10 mg of benzoisothiazolinone so that the total amount is 650 g, and 445 mL of an aqueous solution containing 4% by mass of chromium alum and 0.67% by mass of phthalic acid is mixed with a static mixer immediately before coating. The protective layer coating solution was supplied to the coating die so as to be 8.3 mL / m ² .
The viscosity of the coating solution was 9 [mPa · s] at a B-type viscometer of 40 ° C. (No. 1 rotor, 60 rpm).

3-3. Preparation of photothermographic material Simultaneously multilayer coating is applied by the slide bead coating method in the order of the image forming layer, intermediate layer, surface protective layer first layer, and surface protective layer second layer from the undercoat surface to the surface opposite to the back surface. Then, a sample of the photothermographic material was prepared. At this time, the image forming layer and the intermediate layer were adjusted to 31 ° C., the first surface protective layer was adjusted to 36 ° C., and the second surface protective layer was adjusted to 37 ° C.
The coating amount (g / m ² ) of each compound in the image forming layer is as follows.

Organic silver salt (shown in Table 1)
Pigment (CI Pigment Blue 60) 0.032
Polyhalogen compound-1 0.12
Polyhalogen compound-2 0.25
Phthalazine Compound-1 0.18
SBR latex 9.70
Reducing agent-1 0.40
Reducing agent-2 0.40
Hydrogen bonding compound-1 0.58
Development accelerator-2 0.02
Mercapto Compound-1 0.002
Mercapto compound-2 0.012
Silver halide (as Ag) 0.145

The coating and drying conditions are as follows.
The coating was performed at a speed of 160 m / min, the gap between the coating die tip and the support was set to 0.10 mm to 0.30 mm, and the pressure in the decompression chamber was set to be 196 Pa to 882 Pa lower than the atmospheric pressure. The support was neutralized with an ion wind before coating.
In the subsequent chilling zone, the coating liquid is cooled with a wind at a dry bulb temperature of 10 ° C. to 20 ° C., then transported in a non-contact manner, and dried at a dry bulb temperature of 23 ° C. to 45 ° C. It dried with the drying wind of 15 degreeC and the wet-bulb temperature of 15 to 21 degreeC.
After drying, the humidity was adjusted at 25 ° C. and humidity of 40% RH to 60% RH, and then the film surface was heated to 70 ° C. to 90 ° C. After heating, the film surface was cooled to 25 ° C.

  The photothermographic material thus prepared had a Beck smoothness of 550 seconds on the image forming layer surface side and 130 seconds on the back surface. Further, the pH of the film surface on the image forming layer surface side was measured and found to be 6.0.

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

4). Performance Evaluation 1) Exposure and Thermal Development Conditions Each sample was exposed with Fuji Medical Dry Laser Imager FM-DPL (mounted with a 660 nm semiconductor laser with a maximum output of 60 mW (IIIB)) and thermally developed (112 ° C.-119 ° C.-121 ° C. 4 panel heaters set at −121 ° C. for a total of 24 seconds).

2) Raw storage stability Each sample was conditioned at 25 ° C. and 40% RH for 16 hours immediately after application, and then exposed and thermally developed. The obtained image was measured with a densitometer. The minimum density at this time was set to Dmin ₁ .
Each sample was conditioned at 25 ° C. and 40% RH for 16 hours, sealed in a moisture-proof bag and stored at room temperature for 2 months, and similarly subjected to exposure heat development. The minimum density at this time was set to Dmin ₂ . The difference between Dmin ₂ and Dmin ₁ was defined as the fog increase (ΔDmin) during raw storage.
ΔDmin = Dmin ₂ −Dmin ₁

3) Results Table 1 shows the results obtained.

  From the results shown in Table 1, it can be seen that the sample of the present invention has little fogging and further little increase in fogging during raw storage.

Example 2
In order to increase productivity, high-speed stirring was performed to produce an organic silver salt.
The steps of preparing the silver behenate particles in the organic silver salt A of Example 1 and the organic silver salts 1 to 6 were performed at the stirring speed shown in Table 2, respectively. The normal stirring speed region in which the fluidity was maintained in each region and the creaming phenomenon occurred, and the region in which the fluidity was lost and preparation was impossible was examined.
As a result, as apparent from Table 2, the production method of the present invention was capable of high-speed stirring.

Claims (10)

  An organic silver salt forming step of forming an organic silver salt by mixing a water-soluble silver salt solution and an alkali metal salt solution of an organic acid, and a method for producing an organic silver salt dispersion comprising the step of dispersing the organic silver salt. A method for producing an organic silver salt dispersion, wherein the organic silver salt forming step is performed in the presence of an antifoaming agent. The method for producing an organic silver salt dispersion according to claim 1, wherein the antifoaming agent is a compound represented by the following general formula (DF-1) or an ethoxylated derivative thereof:

(Wherein R ₁ and R ₂ are each independently an alkyl group, an aryl group, or a heterocyclic group, each having at least one hydroxyl group as a substituent). The method for producing an organic silver salt dispersion according to claim 1, wherein the antifoaming agent is a compound represented by the following general formula (DF-2):

(In the formula, n represents an integer of 1 to 3, m is a value of 0, 1 or 2. R represents a hydrogen atom, an alkyl group, or an allyl group).   In the presence of an antifoaming agent in the organic silver salt forming step, the maximum peripheral speed of the stirring blade rotation in the entire organic silver salt forming step is at least 260 m / min or more. The manufacturing method of the organic silver salt dispersion of any one.   5. The organic silver salt according to claim 4, wherein in the organic silver salt forming step, in the presence of an antifoaming agent, the maximum peripheral speed of stirring blade rotation in all the steps of forming the organic silver salt is at least 320 m / min or more. A method for producing a salt dispersion.   The said organic silver salt is a silver salt of a fatty acid, The manufacturing method of the organic silver salt dispersion of any one of Claims 1-5 characterized by the above-mentioned.   The method for producing an organic silver salt dispersion according to claim 6, wherein the silver salt of the fatty acid is a silver salt of a higher fatty acid having 16 or more carbon atoms.   The method for producing an organic silver salt dispersion according to any one of claims 1 to 7, further comprising a desalting step between the organic silver salt forming step and the organic silver salt dispersing step.   At least photosensitive silver halide on at least one surface of the support, an organic silver salt dispersion produced by the production method according to any one of claims 1 to 8, for silver ions A photothermographic material containing a reducing agent and a binder. The photothermographic material according to claim 9, wherein the silver coating amount is 0.5 g / m ² or more and 1.9 g / m ² or less.