JP2005300573A - Heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material which is unlikely to be charged and is superior in adhesiveness. <P>SOLUTION: The heat developable photosensitive material has a photosensitive layer, containing photosensitive silver halide, an organic silver salt and a reducing agent on one surface of a support and has a backing layer, whose surface resistivity in an environment of 23°C and 55% and RH is ≤1×10<SP>13</SP>Ω/cm<SP>2</SP>on the surface of the support opposite to the photosensitive layer, wherein the backing layer comprises two or more layers, a compound represented by Formula (1): M<SB>1</SB>O<SB>3</SB>S-(CF<SB>2</SB>)<SB>m</SB>-SO<SB>3</SB>M<SB>1</SB>is contained in the uppermost layer but substantially is not contained in layers other than the uppermost layer; a polyester resin is contained in the layer closest to the support; and a fluoropolymer, having a constitutional unit of a structure represented by Formula (2) in its constitutional unit, is contained in at least one of the backing layers. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photothermographic material.

Conventionally, in the field of printing plate making and medical treatment, waste liquids resulting from wet processing of image forming materials have been a problem in terms of workability. In recent years, reduction of processing waste liquids is strongly desired from the viewpoint of environmental conservation and space saving. It is rare. Therefore, there is a need for a technique relating to photothermographic materials for photographic applications that can be efficiently exposed by a laser image setter or a laser imager and can form a clear black image with high resolution. As this technique, a photothermographic material containing an organic silver salt, photosensitive silver halide grains, a reducing agent and a binder on a support is known. (For example, see Patent Document 1, Patent Document 2, and Non-Patent Document 1)
These photothermographic materials form photographic images by heat development processing, and reducible silver sources (organic silver salts), photosensitive silver halides, reducing agents and, if necessary, suppress the color tone of silver. Is usually contained in a dispersed state in an (organic) binder matrix. The photothermographic material is stable at room temperature, but is developed by heating to a high temperature (for example, 80 ° C. to 140 ° C.) after exposure. By heating, silver is generated through an oxidation-reduction reaction between an organic silver salt (functioning as an oxidizing agent) and a reducing agent. This redox reaction is promoted by the catalytic action of the latent image generated on the photosensitive silver halide upon exposure. The silver produced by the reaction of the organic silver salt in the exposed areas provides a black image that contrasts with the unexposed areas and forms an image. This reaction process proceeds without supplying a treatment liquid such as water from the outside.

  Since many of the materials used for manufacturing a base layer or a support layer for a photothermographic material are electrically insulating, an electrostatic charge often accumulates on the surface of the photosensitive material during their production and processing. . In addition, since these photothermographic materials do not form an image alone, but images are recorded by passing through an image recording apparatus, the image recording material is stably conveyed in various situations. In addition, the accumulated electrostatic charge can cause various problems. For example, the discharge of the accumulated electrostatic charge before development of the photothermographic material generates light that the photosensitive silver halide feels. When the photothermographic material (film) exposed to such electrostatic discharge is developed, undesirable spot-like marks (called positive electrostatic charge marks) and branch-like marks (negative electrostatic charge marks) appear. . This is a problem, especially in the medical field, because such traces of developed photothermographic material can induce dangerous misreading. Furthermore, the accumulated electrostatic charge on the support layer attracts and attaches dirt or other particles onto the support or substrate layer. These particles can adversely affect the quality of the coating layer applied to the support layer or substrate layer during the manufacturing process. For this reason, antistatic performance is a very important function. For example, in a photothermographic material, an image is formed by being exposed to a laser and processed by a heat developing machine, so that it must be able to pass through a printer without any problem.

  Of particular concern is the problem of static electricity. Static electricity is more likely to occur due to a decrease in the external environment, especially humidity, but this changes depending on seasonal fluctuations, the weather of the day, the environment where the device is placed, and the environment where the image recording material is placed. Control (so-called antistatic) technology has been demanded. As the electrostatic control technique, there is a so-called charge train adjustment technique for reducing the amount of charge to be peeled off when contacting and peeling a certain substance.

  Here, a fluorine compound is added as an antistatic agent in order to improve the charging characteristics, but most of the conventionally used fluorine compounds have a perfluorinated octyl group (for example, non-patent documents). 2). Many of them are perfluorooctyl sulfonates or have structures that can be decomposed into perfluorooctyl sulfonates, and recent reports point to environmental problems. Accordingly, a surfactant that cannot be decomposed into perfluorooctyl sulfonate or perfluorooctyl sulfonate is desirable. However, when such a surfactant is aligned with the layer in contact with it, there arises a problem that the adhesiveness deteriorates.

Although it is not a technique for reducing the peel charge amount, a technique for improving the coating surface state by increasing the molecular weight of the fluorosurfactant has been proposed, but with this technique, the peel charge amount can also be lowered, There was a problem that dust would adhere due to stickiness. (For example, refer to Patent Document 3). That is, since the difference in perfluoroalkyl of the fluorine-containing polymer used is long, it is sticky at high temperature, and stickiness under high humidity due to the polyoxyalkylene group of the side chain is generated, so that there is a problem that dust adheres. there were.
U.S. Pat. No. 3,152,904 US Pat. No. 3,487,075 JP 09-281636 A D. “Dry Silver Photographic Materials” by Morgan (Handbook of Imaging Materials, Marcel Dekker, Inc. 48, 1991) Applied Surface Chemistry (Asakura Shoten, Toshio Sakurai, Yasukatsu Tamai), p. 120, 1967

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a photothermographic material that is less likely to be charged with static electricity and excellent in adhesiveness.

  The above object of the present invention can be achieved by the following constitution.

(Claim 1)
A photosensitive layer containing a photosensitive silver halide, an organic silver salt and a reducing agent is provided on one surface of the support, and the surface opposite to the support is opposite to the support in an environment of 23 ° C. and 55% RH. A photothermographic material having a backing layer having a surface specific resistance value of 1 × 10 ¹³ Ω / cm ² or less, wherein the backing layer comprises two or more layers, and is a compound represented by the following general formula (1) Is contained in the uppermost layer and is not substantially contained in layers other than the uppermost layer, the polyester resin is contained in the layer closest to the support, and a structural unit represented by the following general formula (2) A photothermographic material comprising a fluorine-containing polymer having a structural unit in at least one of the backing layers.

Formula _{(1) M 1 O 3 S-} (CF 2) m -SO 3 M 1
(In the formula, M ₁ represents H, Li, Na, K, or an ammonium group, and m represents an integer of 1 to 8. However, when M ₁ represents Li, m represents an integer of 1 to 4. , When M ₁ represents H, m represents an integer of 1 to 6 or 8, when M ₁ represents Na, m represents an integer of 3 or 4, and when M ₁ represents K, m is 1 Represents an integer of ˜6, and when M ₁ represents an ammonium group, m represents an integer of 1 to 8.)

Wherein R ₁ represents a hydrogen atom, a fluorine atom or a methyl group, R ₂ represents a methylene group, an ethylene group or a 2-hydroxypropylene group, X represents a hydrogen atom or a fluorine atom, and n represents 1 to 1 Represents an integer of 4.)

  According to the present invention, it is possible to provide a photothermographic material that is hardly charged with static electricity and has excellent adhesiveness.

  Hereinafter, although the best mode for carrying out the present invention will be described, the present invention is not limited to these.

The photothermographic material of the present invention has a photosensitive layer containing a photosensitive silver halide, an organic silver salt and a reducing agent on one side of a support, and the photosensitive layer is on the side opposite to the support. A photothermographic material having a backing layer having a surface resistivity of 1 × 10 ¹³ Ω / cm ² or less in an environment of 23 ° C. and 55% RH, wherein the backing layer comprises two or more layers, The compound represented by the formula (1) is contained in the uppermost layer and is not substantially contained in layers other than the uppermost layer, the polyester resin is contained in the layer closest to the support, and the general formula (2) ) Is contained in at least one layer of the backing layer.

  Hereinafter, each requirement constituting the present invention will be sequentially described.

  The configuration of the backing layer of the present invention will be described.

  In the present invention, the backing layer has two or more layers, preferably two layers. When the backing layer is composed of two layers, it is preferable that the thickness of the lower layer (lower h) is larger than the thickness of the upper layer (upper h).

  The compound represented by the general formula (1) of the present invention will be described.

Formula _{(1) M 1 O 3 S-} (CF 2) m -SO 3 M 1
(In the formula, M ₁ represents H, Li, Na, K, or an ammonium group, and m represents an integer of 1 to 8. However, when M ₁ represents Li, m represents an integer of 1 to 4. , When M ₁ represents H, m represents an integer of 1 to 6 or 8, when M ₁ represents Na, m represents an integer of 3 or 4, and when M ₁ represents K, m is 1 Represents an integer of ˜6, and when M ₁ represents an ammonium group, m represents an integer of 1 to 8.)
When M ₁ represents an ammonium group, in addition to NH ₄ , known 1-4 quaternary organic ammonium groups (methylammonium, dibutylammonium, triethylammonium, tetra Decyl ammonium and the like).

  Although the specific example of a compound represented by General formula (1) below is shown, this invention is not limited to these.

  The compound represented by the general formula (1) can be synthesized with reference to known synthesis methods described in JOURNAL OF FLUORINE CHEMISTRY, 79 (1996), pp. 33-38.

  The compound represented by General formula (1) may use only 1 type, or may use 2 or more types together.

  The compound represented by the general formula (1) is preferably used in the backing layer among the constituent layers of the photothermographic material of the invention. Moreover, it is preferable that it is used for the uppermost layer among backing layers, and is not contained substantially in layers other than this uppermost layer. Here, the term “substantially not contained in the layers other than the uppermost layer” means that, in the present invention, “the compound represented by the general formula (1) is contained in the uppermost layer and the layers other than the uppermost layer are included. "Substantially does not contain" means "the amount of the compound represented by the general formula (1) contained in all layers other than the uppermost layer is 5% or less with respect to the amount contained in all layers" Means.

The addition amount of the compound represented by the general formula (1) is preferably in the range of 5 to 500 mg per 1 m ² of the backing layer of the photothermographic material, and more preferably 20 to 300 mg.

  The polyester resin of the present invention will be described.

The polyester resin of the present invention is preferably used for improving the adhesiveness of the photothermographic material of the present invention by using it in the backing layer of the photothermographic material. Although the specific example of the polyester resin of this invention is shown below, this invention is not limited to these.
H-1 VitelPE2200B (manufactured by Boston)
H-2 VitelPE2700B (manufactured by Boston)
H-3 VitelPE3200B (manufactured by Boston)
H-4 VitelPE3300B (manufactured by Boston)
H-5 VitelPE3550B (manufactured by Boston)
The addition amount of the polyester resin of the present invention is preferably in the range of 1 to 40%, more preferably 1 to 10% per mass in the backing layer of the photothermographic material. Moreover, it is preferable that it is used for the lowest layer among backing layers, and it is not contained substantially in layers other than this lowest layer. Here, “substantially not contained in layers other than the lowermost layer” means that the amount of the polyester resin of the present invention contained in all layers other than the lowermost layer is 5 with respect to the amount contained in all layers. % Or less.

  A fluoropolymer having a structural unit represented by the general formula (2) of the present invention in the structural unit will be described.

[Wherein, R ₁ represents a hydrogen atom, a fluorine atom or a methyl group, R ₂ represents a methylene group, an ethylene group or a 2-hydroxypropylene group, X represents a hydrogen atom or a fluorine atom, and n represents 1 to Represents an integer of 4. ]
Among the structural units of the structure represented by the general formula (2), the most important point is that n in the formula is 1 to 4.

  From the viewpoint of water repellency etc., it is generally considered that the number of carbons in the perfluoro group (n in the general formula (2)) of perfluoroacrylate or perfluoromethacrylate is preferably 8 or more. As a result of investigations, it was found that when n is in the range of 1 to 4, a polymer having all the desired performance can be obtained. The desired performance is that it first has a charge train adjustment function, further has blocking resistance when heat or pressure is applied, has good compatibility with the polymer binder constituting the existing layer, and It is the performance that solvent solubility is good.

  The structural unit represented by the general formula (2) can be introduced by using a monomer such as the corresponding fluoroalkyl acrylate, fluoroalkyl methacrylate, fluoroalkyl α-fluoro acrylate (used for polymerization).

  In particular, fluoroalkyl acrylate and fluoroalkyl methacrylate are commercially available from Daikin Chemicals under the following trade names. Commercially available products include M-1110 (2,2,2-trifluoroethyl methacrylate), M-1210 (2,2,3,3,3-pentafluoropropyl methacrylate), M-1420 (2- (perfluoro Butyl) ethyl methacrylate), M-1433 (3- (pentafluorobutyl) -2-hydroxypropyl), M-5210 (1H, 1H, 3H-tetrafluoropropyl methacrylate), M-5410 (1H, 1H, 5H- Octafluoropropyl methacrylate), M-7210 (1H-1- (trifluoromethyl) trifluoroethyl methacrylate), M-7310 (1H, 1H, 3H-hexafluorobutyl methacrylate), R-1420 (3,3,4) , 4,5,5,6,6,6-nonafluorohexyl acrylate) A-1110 (2,2,2-trifluoroethyl acrylate), A-1210 (2,2,3,3,3-pentafluoropropyl acrylate), A-1420 (2- (perfluorobutyl) ethyl acrylate) , A-1433 (3- (pentafluorobutyl) -2-hydroxypropyl), A-5210 (1H, 1H, 3H-tetrafluoropropyl acrylate), A-5410 (1H, 1H, 5H-octafluoropropyl acrylate) Octafluoropropyl acrylate), A-7210 (1H-1- (trifluoromethyl) trifluoroethyl acrylate), A-7310 (1H, 1H, 3H-hexafluorobutyl acrylate), and the like are listed in the catalog.

  As the structural unit of the fluoropolymer having the structural unit represented by the general formula (2) of the present invention as the structural unit, the structural unit represented by the following general formula (3) is also a structural unit. And can be introduced by copolymerizing the corresponding acrylate or methacrylate.

In the formula, R ₃ represents a hydrogen atom or a methyl group, and Y represents an alkyl group, an alicyclic group or an aromatic ring group.

  Specifically, alkyl acrylate (for example, methyl acrylate, ethyl acrylate, butyl acrylate, propyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, iso-nonyl acrylate, n-dodecyl acrylate, stearyl acrylate, etc.), benzyl acrylate, Cyclohexyl acrylate, alkyl methacrylate (eg, methyl methacrylate (MMA), ethyl methacrylate, propyl methacrylate, butyl methacrylate, hexyl methacrylate, 2-ethylhexyl methacrylate, iso-nonyl methacrylate, dodecyl methacrylate, stearyl methacrylate, etc.), benzyl methacrylate, cyclohexyl methacrylate ( CHMA), etc. It can be, but are not these limitations.

  Subsequently, as a structural unit having an epoxy unit that can be further introduced into these structural units, glycidyl methacrylate (GMA), glycidyl acrylate, vinylcyclohexene monooxide and the like can be introduced by copolymerization.

  Although the specific example of the fluorine-type polymer which has the structural unit of the structure represented by General formula (2) of this invention in the structural unit below is shown, this invention is not limited to these.

2-1 M-1210 / M-5210 / MMA = 1/1/1 (molar ratio)
2-2 M-1210 / M-5210 / MMA = 48/17/35 (molar ratio)
2-3 R-1420 / CHMA = 20/80 (molar ratio)
2-4 R-1420 / CHMA = 50/50 (molar ratio)
Next, the nonionic fluorine surfactant represented by the following general formula (4) that can be used in combination with the compound represented by the general formula (1) in the present invention will be described.

In the formula, Rf ₃ and Rf ₄ each represents a fluorine-containing aliphatic group. AO represents a group having at least one alkyleneoxy group, and n represents an integer of 1 to 50.

In the general formula (4), examples of the fluorine-containing aliphatic group represented by Rf ₃ and Rf ₄ include an aliphatic group composed of a straight chain, a branched chain, a cyclic group, or a combination thereof. Preferred fluorine-containing aliphatic groups are each a fluoroalkyl group having 1 to 20 carbon atoms (such as —C ₄ F ₉ and —C ₈ F ₁₇ ), a fluoroalkenyl group (such as —C ₉ F ₁₇ ), and a sulfofluoroalkyl group. _{(-C 7 F 14 SO 3,} -C 8 F 16 SO 3 , _{etc.), C n F 2n + 1} SO 2 n (R 9) R 10 - group (R ₉ is a hydrogen atom, C 1-20 carbon respectively Represents an alkyl group, an alkoxy group, a carboxyalkyl group or an aryl group, R ₁₀ represents an alkylene group having 1 to 20 carbon atoms and a carboxyalkylene group, and n represents an integer of 1 to 20. For example, C ₇ F ₁₅ SO ₂ N (C ₂ H ₅ ) CH ₂ —, C ₈ F ₁₇ SO ₂ N (CH ₂ COOH) CH ₂ CH ₂ CH ₂ —, etc.), and the like. Good.

  AO is a group having an alkyleneoxy group such as ethyleneoxy, propyleneoxy, i-propyleneoxy, and may have a substituent such as an amino group at the terminal.

  Although the specific example of the nonionic fluorine surfactant represented by General formula (4) below is shown, this invention is not limited to these.

  The photothermographic material of the present invention can contain compounds represented by the following general formulas (3 ′), (4 ′), and (5 ′). These will be described sequentially.

In the formula, R represents a monovalent substituent, m represents an integer of 0 to 4, and when m ≧ 2, a plurality of R may be the same or different. Further, adjacent Rs may be bonded to form an aliphatic ring, aromatic ring or heterocyclic ring. R ₁ and R ₂ each represent a hydrogen atom or a monovalent substituent.

In the general formula (3 ′), R represents a monovalent substituent, and examples of a preferable alkyl group represented by R have 1 to 8 carbon atoms, and more preferably 1 to 5 carbon atoms. Examples include methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, t-amyl, octyl and the like. m represents an integer of 0 to 4. When m ≧ 2, a plurality of R may be the same or different. Further, when a plurality of R are adjacent to each other, an aliphatic ring, an aromatic ring or a heterocyclic ring may be formed. R ₁ and R ₂ each represent a hydrogen atom or a monovalent substituent.

  Examples of the compound represented by the general formula (3 ′) are given below, but the present invention is not limited to these.

  These compounds are described, for example, in R.A. G. By Elder Field: Heterocyclic Compounds, John Wiley and Sons, Vol. 1-9, 1950-1967 and A.I. R. It can be synthesized by a known method described by Katritzky: Comprehensive Heterocyclic Chemistry, Pergamon Press, 1984 and the like.

In the formula, Z represents a nonmetallic atom group necessary for forming a heteroaromatic 5-membered ring, and R ₁ and R ₂ each represent a hydrogen atom or a monovalent substituent.

In the general formula (4 ′), the heteroaromatic 5-membered ring formed by Z is preferably a thiophene ring or the like, and may further have a substituent. The definition of aromatic here is, for example, J. Wiley & Sons, J. By March: Advanced Organic Chemistry, Chapter 2. R ₁ and R ₂ represent a hydrogen atom or a monovalent substituent. The substituents on the sulfur-containing aromatic 5-membered ring formed by R ₁ , R ₂ and Z may be bonded to each other to form a ring. In addition, the compound of the general formula (4 ′) may be protonated to form a salt.

The monovalent substituent represented by R ₁ and R ₂ and the substituent on the heteroaromatic 5-membered ring formed by Z may be the same or different, for example, an alkyl group (preferably having a carbon number of 1 to 20, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, octyl, decyl, hexadecyl, cyclopropyl , Cyclopentyl, cyclohexyl, etc.), alkenyl groups (preferably having 2-20 carbon atoms, more preferably 2-12 carbon atoms, particularly preferably 2-8 carbon atoms, vinyl, allyl, 2-butenyl, 3-pentenyl, etc. ), An alkynyl group (preferably having 2 to 20 carbon atoms, more preferably 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms such as propargyl, 3-pentynyl, etc.), An aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenyl, p-methylphenyl, naphthyl, etc.), an amino group (preferably having 0 carbon atoms). -20, more preferably 0-10 carbon atoms, particularly preferably 0-6 carbon atoms, such as amino, methylamino, dimethylamino, diethylamino, dibenzylamino, etc.), alkoxy groups (preferably 1-20 carbon atoms). More preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms, methoxy, ethoxy, butoxy and the like), an aryloxy group (preferably 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, Particularly preferably, it has 6 to 12 carbon atoms, such as phenyloxy, 2-naphthyloxy), an acyl group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, acetyl, benzoyl, formyl, pivaloyl, etc.), an alkoxycarbonyl group (preferably 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably Has 2 to 12 carbon atoms, such as methoxycarbonyl, ethoxycarbonyl, cyclohexyloxycarbonyl, etc.), an aryloxycarbonyl group (preferably 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 7 carbon atoms). 10 and phenyloxycarbonyl etc.), acyloxy group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 10 carbon atoms, acetoxy, benzoyloxy etc.), acylamino group (Preferably 2-20 carbon atoms, more preferably 2-16 carbon atoms, particularly preferred. Or acetylamino, benzoylamino, etc.), an alkoxycarbonylamino group (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, and particularly preferably 2 to 12 carbon atoms). , Methoxycarbonylamino and the like), aryloxycarbonylamino group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, phenyloxycarbonylamino etc.), sulfonylamino A group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methanesulfonylamino, benzenesulfonylamino), a sulfamoyl group (preferably having 0 to 20 carbon atoms). More preferably 0 to 16 carbon atoms, particularly preferably 0 to 12 carbon atoms, , Methylsulfamoyl, dimethylsulfamoyl, phenylsulfamoyl, etc.), a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, Carbamoyl, methylcarbamoyl, ethylcarbamoyl, diethylcarbamoyl, phenylcarbamoyl, etc.), alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, methylthio, ethylthio Etc.), an arylthio group (preferably having 6 to 20 carbon atoms, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio), a sulfonyl group (preferably having 1 to 20 carbon atoms, and more). Preferably it has 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms. Sulfinyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms such as methanesulfinyl and benzenesulfinyl), ureido group (preferably carbon number) 1-20, more preferably 1-16 carbon atoms, particularly preferably 1-12 carbon atoms, ureido, methylureido, butylureido, phenylureido, etc.), phosphoric acid amide group (preferably having 1-20 carbon atoms) Preferably having 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as diethyl phosphoric acid amide and phenylphosphoric acid amide), hydroxyl group, mercapto group, halogen atom (fluorine, chlorine, bromine, iodine), cyano group, Sulfo group, carboxyl group, nitro group, hydroxamic acid group, sulfino group, hydrazino group, heterocyclic group (imidazolyl) Pyridyl, furyl, thienyl, piperidyl, and morpholino) and the like. These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different.

R ₁ and R ₂ are preferably a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group, a cyano group, a halogen atom, a nitro group, or a heterocyclic group, more preferably a hydrogen atom, an alkyl group, An aryl group, an alkoxy group, an aryloxy group, a halogen atom, and a heterocyclic group, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, and a thienyl group, and particularly preferably a hydrogen atom and an alkyl group. .

  The group bonded to the heteroaromatic 5-membered ring formed by Z is preferably a hydrogen atom, alkyl group, aryl group, alkoxy group, aryloxy group, cyano group, halogen atom, nitro group, carboxyl group, amino group. An acyl group, more preferably a hydrogen atom, an alkyl group, an aryl group, an alkoxy group, an aryloxy group or a halogen atom, still more preferably a hydrogen atom, an alkyl group, an aryl group or an alkoxy group, particularly Preferably they are a hydrogen atom, an alkyl group, and an aryl group.

  Although the example of a compound represented by general formula (4 ') below is given, this invention is not limited to these.

  These compounds are described in, for example, Tetrahedron Letters, 1981, Vol. 22, 345-349, J. Am. Heterocycl. Chem, 1980, 17, 1019-1023, Bull. Soc. Chim. Fr. 1967, 4220-4235, Bull. Soc. Chim. Fr. 1967, pages 2495-2507, French Patent No. 1453897, etc., can be easily synthesized by those skilled in the art.

  In the formula, R ′ is a monovalent substituent, k represents an integer of 0 to 4, and when k ≧ 2, a plurality of R ′ may be the same or different.

  In the general formula (5 ′), examples of the monovalent substituent represented by R ′ include an alkyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 1 carbon atoms). 8, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, octyl, decyl, hexadecyl, cyclopropyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 20 carbon atoms, More preferably, it has 2 to 12 carbon atoms, particularly preferably 2 to 8 carbon atoms, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an alkynyl group (preferably 2 to 20 carbon atoms, more preferably 2 to 2 carbon atoms). 12, particularly preferably 2 to 8, such as propargyl and 3-pentynyl), an aryl group (preferably having 6 to 30 carbon atoms, more preferably 6 to 6 carbon atoms). 0, particularly preferably 6 to 12 carbon atoms, phenyl, p-methylphenyl, naphthyl, etc.), amino group (preferably 0 to 20 carbon atoms, more preferably 0 to 10 carbon atoms, particularly preferably 0 carbon atoms). -6, amino, methylamino, dimethylamino, diethylamino, dibenzylamino, etc.), an alkoxy group (preferably having 1 to 20 carbon atoms, more preferably 1 to 12 carbon atoms, particularly preferably 1 to 8 carbon atoms). Yes, methoxy, ethoxy, butoxy, etc.), aryloxy group (preferably having 6-20 carbon atoms, more preferably 6-16 carbon atoms, particularly preferably 6-12 carbon atoms, phenyloxy, 2-naphthyloxy, etc. ), An acyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms). Yl, formyl, pivaloyl, etc.), an alkoxycarbonyl group (preferably having 2-20 carbon atoms, more preferably 2-16 carbon atoms, particularly preferably 2-12 carbon atoms, methoxycarbonyl, ethoxycarbonyl, tetradecyloxycarbonyl) Etc.), an aryloxycarbonyl group (preferably having 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 10 carbon atoms such as phenyloxycarbonyl), an acyloxy group (preferably having a carbon number) 2-20, more preferably 2-16 carbon atoms, particularly preferably 2-10 carbon atoms, acetoxy, benzoyloxy, etc.), acylamino group (preferably 2-20 carbon atoms, more preferably 2-16 carbon atoms). Particularly preferably, it has 2 to 10 carbon atoms, and acetylamino, propionylamino, Nzoylamino, etc.), alkoxycarbonylamino groups (preferably having 2-20 carbon atoms, more preferably 2-16 carbon atoms, particularly preferably having 2-12 carbon atoms, such as methoxycarbonylamino), aryloxycarbonylamino groups (preferably Has 7 to 20 carbon atoms, more preferably 7 to 16 carbon atoms, particularly preferably 7 to 12 carbon atoms, such as phenyloxycarbonylamino), a sulfonylamino group (preferably 1 to 20 carbon atoms, more preferably carbon atoms). 1 to 16, particularly preferably 1 to 12, and methanesulfonylamino, octanesulfonylamino, benzenesulfonylamino, etc.), a sulfamoyl group (preferably having 0 to 20 carbon atoms, more preferably 0 to 16 carbon atoms, Particularly preferably, it has 0 to 12 carbon atoms, and sulfamoyl, methylsulfa Yl, dimethylsulfamoyl, phenylsulfamoyl, etc.), a carbamoyl group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as carbamoyl, methylcarbamoyl) , Diethylcarbamoyl, phenylcarbamoyl and the like. ), An alkylthio group (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms, such as methylthio, ethylthio, etc.), an arylthio group (preferably carbon). 6 to 20, more preferably 6 to 16 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio), a sulfonyl group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, especially Preferably it has 1 to 12 carbon atoms, mesyl, tosyl, etc.), sulfinyl group (preferably 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, particularly preferably 1 to 12 carbon atoms, methanesulfinyl, Benzenesulfinyl and the like) and ureido groups (preferably having 1 to 20 carbon atoms, more preferably 1 to 16 carbon atoms, and particularly preferably 1 to 12 carbon atoms). Ureido, methylureido, phenylureido, etc.), phosphoric acid amide groups (preferably having 1-20 carbon atoms, more preferably 1-16 carbon atoms, particularly preferably 1-12 carbon atoms, diethylphosphoric acid amide, phenyl phosphorus Acid amide, etc.), hydroxyl group, carboxyl group, sulfo group, sulfino group (sulfinic acid group), mercapto group, halogen atom (fluorine, chlorine, bromine, iodine), cyano group, nitro group, hydroxamic acid group Hydrazino group, heterocyclic group (imidazolyl, pyridyl, furyl, piperidyl, morpholino, etc.) and the like. A substituent capable of forming a salt with an alkali metal or the like may form a salt. These substituents may be further substituted. Moreover, when there are two or more substituents, they may be the same or different.

  Specific examples of the compound represented by the general formula (5 ′) are shown below, but the present invention is not limited thereto.

  These compounds are synthesized by known methods described in, for example, New Experimental Chemistry Course (Maruzen) 14-III, Chapter 5-1, Organic Functional Group Preparations (Academic Press New York and London) Chapter I-9. can do. Various commercially available reagents can also be used.

  The compounds represented by the above general formulas (3 ′), (4 ′) and (5 ′) are preferably added to the photosensitive layer of the photothermographic material, but are further added to a non-photosensitive layer such as a protective layer. It may be added.

The addition amount of the compounds represented by the general formulas (3 ′), (4 ′) and (5 ′) is 10 ⁻⁴ to 1 mol, preferably 10 ^{−3 to} 0.3 mol, per mol of silver, Preferably 10 < ^-3 > -0.1 mol is preferable. In addition, the compounds of the general formulas (3 ′), (4 ′) and (5 ′) may be used alone or in combination of two or more.

  The compounds represented by the general formulas (3 ′), (4 ′) and (5 ′) may be added by any method such as a solution, a powder, or a solid fine particle dispersion. The solid fine particle dispersion is performed by a known finer means (ball mill, vibrating ball mill, side mill, colloid mill, jet mill, roller mill, etc.). A dispersion aid may be used when dispersing the solid fine particles.

  Subsequently, organic silver salts, photosensitive silver halides, reducing agents, binders, supports and various additives that are preferably used as essential materials for the photothermographic material of the invention will be described in order.

(Organic silver salt)
Organic silver salts as silver ion sources for silver image formation are silver salts of organic acids and heteroorganic acids, especially long chain (C10-30, preferably 15-25) aliphatic carboxylic acids. And silver salts of nitrogen-containing heterocyclic compounds are preferred. Also preferred are organic or inorganic complexes described in Research Disclosure (RD) 17029 and 29963 such that the ligand has a value of 4.0 to 10.0 as the total stability constant for silver ions. Examples of these suitable silver salts include the following.

  Silver salts of organic acids, such as gallic acid, succinic acid, behenic acid, stearic acid, arachidic acid, palmitic acid, lauric acid and the like. Silver carboxyalkylthiourea salts such as 1- (3-carboxypropyl) thiourea, 1- (3-carboxypropyl) -3,3-dimethylthiourea and the like. Silver salt or complex of polymer reaction product of aldehyde and hydroxy-substituted aromatic carboxylic acid, such as aldehydes (formaldehyde, acetaldehyde, butyraldehyde, etc.) and hydroxy-substituted acids (salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid) A silver salt or complex of the reaction product of Silver salts or complexes of thiones, such as silver salts or complexes such as 3- (2-carboxyethyl) -4-hydroxymethyl-4-thiazoline-2-thione and 3-carboxymethyl-4-thiazoline-2-thione. A complex or salt of nitrogen acid and silver selected from imidazole, pyrazole, urazole, 1,2,4-thiazole and 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benztriazole. Silver salts such as saccharin and 5-chlorosalicylaldoxime, and silver salts of mercaptides.

  Among these, particularly preferred silver salts include silver salts of long-chain aliphatic carboxylic acids such as silver behenate, silver arachidate, and silver stearate.

  It is preferable that two or more organic silver salts are mixed in order to improve developability and form a high-concentration and high-contrast silver image. For example, a silver ion solution is mixed with two or more organic acid mixtures. It is preferable to prepare them.

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

(Organic silver salt crystal growth inhibitor / dispersant)
It is preferable to produce silver aliphatic carboxylate under conditions where a compound that functions as a crystal growth inhibitor or dispersant for the aliphatic carboxylate particles is coexisted in the production process of the silver carboxylate particles.

  In addition, the organic silver salt crystal growth inhibitor or dispersant is a silver carboxylate particle production process, when silver carboxylate is produced under the condition of coexisting the compound, and when it is produced under the condition of not coexisting. A compound having the function and effect of reducing the particle size and monodispersing. Specific examples include monohydric alcohols having 10 or less carbon atoms, preferably secondary alcohols, tertiary alcohols, glycols such as ethylene glycol and propylene glycol, polyethers such as polyethylene glycol, and glycerin. . A preferable addition amount is 10 to 200% by mass with respect to silver carboxylate.

  On the other hand, branched aliphatic carboxylic acids containing isomers such as isoheptanoic acid, isodecanoic acid, isotridecanoic acid, isomyristic acid, isopalmitic acid, isostearic acid, isoarachidic acid, isobehenic acid and isohexaconic acid are also preferred. In this case, a preferable side chain includes an alkyl group or alkenyl group having 4 or less carbon atoms. Also, aliphatic unsaturated carboxylic acids such as palmitoleic acid, oleic acid, linoleic acid, linolenic acid, morotic acid, eicosenoic acid, arachidonic acid, eicosapentaenoic acid, erucic acid, docosapentaenoic acid, docosahexaenoic acid, ceracolonic acid It is done. A preferable addition amount is 0.5 to 10 mol% of the aliphatic carboxylate silver.

  Glycosides such as glucoside, galactoside and fructoside, trehalose type disaccharides such as trehalose and sucrose, polysaccharides such as glycogen, dextrin, dextran and alginic acid, cellosolves such as methyl cellosolve and ethyl cellosolve, sorbitan, sorbit, ethyl acetate and acetic acid Water-soluble organic solvents such as methyl and dimethylformamide, water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, acrylic acid copolymer, maleic acid copolymer, carboxymethylcellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, polyvinylpyrrolidone and gelatin Are also preferred compounds. A preferable addition amount is 0.1 to 20% by mass with respect to the aliphatic carboxylate silver.

  Alcohols having 10 or less carbon atoms, preferably secondary alcohols and tertiary alcohols are reduced in viscosity by increasing the solubility of sodium aliphatic carboxylate in the preparation step, and monodispersed and small by increasing the stirring efficiency. Grain size. Branched aliphatic carboxylic acids and aliphatic unsaturated carboxylic acids have higher steric hindrance than the main component linear aliphatic carboxylic acid silver when crystallization of the aliphatic carboxylic acid silver, and the disorder of the crystal lattice is large. Therefore, large crystals are not generated, and as a result, the particle size is reduced.

  The organic silver salt can be used in various shapes, but tabular grains, particularly tabular organic silver salt grains having an aspect ratio of 3 or more are preferred.

  In the present invention, a flat organic silver salt particle having an aspect ratio of 3 or more means that the flat organic silver salt particle accounts for 50% or more of the total number of organic silver salt particles. Further, in the organic silver salt according to the present invention, it is preferable that tabular organic silver salt particles having an aspect ratio of 3 or more occupy 60% or more of the total number of organic silver salt particles, and more preferably 70% or more (number). Yes, particularly preferably 80% or more (number).

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

AR = particle diameter (μm) / thickness (μm)
The aspect ratio of the tabular organic silver salt particles is preferably 3 to 20, and more preferably 3 to 10. The reason is that if the aspect ratio is too low, the organic silver salt particles are likely to be close-packed, and if the aspect ratio is too high, the organic silver salt particles are likely to overlap with each other, and are easily dispersed in an attached state. Therefore, light scattering or the like is likely to occur, and as a result, the transparency of the photosensitive material is lowered. Therefore, the above range is considered to be a preferable range.

  The method for obtaining the organic silver salt particles having the above-mentioned shape is not particularly limited. However, the mixed state at the time of forming the organic acid alkali metal salt soap and / or the mixed state at the time of adding silver nitrate to the soap is preferably maintained. It is also effective to optimize the ratio of silver nitrate that reacts with soap.

  The tabular organic silver salt particles are preferably preliminarily dispersed together with a binder or a surfactant as necessary, and then dispersed and pulverized with a media disperser or a high-pressure homogenizer. For the preliminary dispersion, a general stirrer such as an anchor type or a propeller type, a high-speed rotating centrifugal radiation type stirrer (dissolver), or a high-speed rotating shear type stirrer (homomixer) can be used.

  In addition, as the media dispersing machine, a rolling mill such as a ball mill, a planetary ball mill, a vibrating ball mill, a bead mill that is a medium stirring mill, an attritor, other basket mills, and the like can be used, and as a high-pressure homogenizer, Various types can be used, such as a type that collides with a wall, a plug, etc., a type in which liquids are collided at a high speed after dividing the liquid, and a type that passes through a thin orifice.

Examples of ceramics used for the ceramic beads used when dispersing the media include Al ₂ O ₃ , BaTiO ₃ , SrTiO ₃ , MgO, ZrO, BeO, Cr ₂ O ₃ , SiO ₂ , SiO ₂ —Al ₂ O ₃ , Cr. ₂ O ₃ —MgO, MgO—CaO, MgO—C, MgO—Al ₂ O ₃ (spinel), SiC, TiO ₂ , K ₂ O, Na ₂ O, BaO, PbO, B ₂ O ₃ , Sr ₂ TiO ₃ (strontium _{titanate), BeAl 2 O 4, Y} 3 Al 5 O 12, ZrO 2 -Y 2 O 3 ( cubic _{zirconia), 3BeO-Al 2 O 3} -6SiO 2 ( synthesis emerald), C (diamond) , SiO ₂ -nH ₂ O, nitrogenated silicon, yttrium stabilized zirconia, zirconia toughened alumina, and the like are preferable. Yttrium-stabilized zirconia and zirconia-reinforced alumina (ceramics containing these zirconia are hereinafter abbreviated as zirconia) are particularly preferably used because of the low generation of impurities due to friction with beads and dispersers during dispersion.

  In the apparatus used when dispersing the flat organic silver salt particles, it is preferable to use ceramics such as zirconia, alumina, silicon nitride, boron nitride or diamond as the material of the member in contact with the organic silver salt particles, Among these, it is preferable to use zirconia.

  When the above dispersion is performed, the binder concentration is preferably added in an amount of 0.1 to 10% of the mass of the organic silver, and it is preferable that the liquid temperature does not exceed 45 ° C. from the preliminary dispersion through the main dispersion. As preferable operating conditions for the present dispersion, for example, when a high-pressure homogenizer is used as the dispersing means, preferable operating conditions are 29.42 to 98.06 MPa, and the number of operations is preferably 2 times or more. Moreover, when using a media disperser as a dispersion | distribution means, 6-13 m / sec of peripheral speed is mentioned as preferable conditions.

Further, a preferred embodiment of the photothermographic material of the present invention is such that the proportion of organic silver salt particles exhibiting a projected area of less than 0.025 μm ² when the cross section perpendicular to the support surface of the material is observed with an organic silver salt An organic silver salt having a characteristic that the ratio of the particles showing 70% or more of the total projected area of the grains and the projected area of 0.2 μm ² or more is 10% or less of the total projected area of the organic silver salt grains; A photosensitive emulsion containing a photosensitive silver halide is coated. In such a case, it is possible to obtain a uniformly distributed state with little aggregation of organic silver salt particles in the photosensitive emulsion.

  The conditions for producing the photosensitive emulsion having such characteristics are not particularly limited. However, the mixed state at the time of forming the organic acid alkali metal salt soap and / or the mixed state at the time of adding silver nitrate to the soap is kept good. In addition, the ratio of silver nitrate that reacts with the soap is optimized, the dispersion is pulverized with a media disperser or a high-pressure homogenizer, and the binder concentration is 0.1 to 10% of the mass of organic silver. In addition to the fact that the temperature from drying to the end of the main dispersion does not exceed 45 ° C., it is preferable to use a dissolver at the time of liquid preparation and stir at a peripheral speed of 2.0 m / second or more.

The method using the TEM is the same as described in the section for obtaining the average thickness of the tabular grains, such as the ratio of the projected area of the organic silver particles having the specific projected area value as described above to the total projected area. To extract a portion corresponding to organic silver. At this time, the agglomerated organic silver is treated as one particle, and the area (AREA) of each particle is obtained. Similarly, at least 1,000, preferably obtains the area about 2,000 particles, each, A: 0.025 .mu.m less than ^2, B: 0.025 .mu.m ² or 0.2μm below ^2, C: 0 Classify into 3 groups of ² μm ² or more.

  The photothermographic material of the present invention is 70% or more of the total area of particles measured for the total area of particles belonging to Group A, and the total area of particles for the group C is measured. It is preferable to satisfy 10% or less of the area.

  In order to perform measurement according to the above procedure, it is preferable to sufficiently perform length correction (scale correction) per pixel and correction of two-dimensional distortion of the measurement system using a standard sample in advance. Uniform latex particles (DULP) commercially available from Dow Chemical Company, USA are suitable as the standard sample, and polystyrene particles having a coefficient of variation of less than 10% for a particle size of 0.1 to 0.3 μm. Specifically, a lot having a particle size of 0.212 μm and a standard deviation of 0.0029 μm is available.

  The details of the image processing technology can be referred to “Hiroshi Tanaka: Image processing application technology (Industry Research Committee)” as described above, and the image processing program or apparatus is particularly limited as long as the above operation is possible. Although it is not done, as an example of the arrow, Luzex-III manufactured by Nireco is mentioned as above.

  The organic silver salt particles are preferably monodisperse particles, and the preferred monodispersity is 1 to 30%. By using monodisperse particles in this range, an image having a high density can be obtained. The monodispersity mentioned here is defined by the following formula.

Monodispersity = (standard deviation of particle size / average value of particle size) × 100
The average particle diameter (equivalent circle diameter) of the organic silver salt is preferably 0.01 to 0.2 μm, more preferably 0.02 to 0.15 μm. The average particle diameter (equivalent circle diameter) represents the diameter of a circle having the same area as each particle image observed with an electron microscope.

In order to prevent devitrification of the photothermographic material, the total amount of silver halide and organic silver salt is preferably 0.5 to 2.2 g per m ² in terms of silver amount. By setting this range, an image preferable as a medical image can be obtained.

(Photosensitive silver halide)
The photosensitive silver halide grains in the present invention can inherently absorb light as an inherent property of silver halide crystals, or artificially absorb visible light or infrared light by a physicochemical method. So that physicochemical changes can occur in the silver halide crystal and / or on the crystal surface when light in any region within the light wavelength range from the ultraviolet light region to the infrared light region is absorbed. This refers to processed and produced silver halide crystal grains.

  The silver halide grains themselves are P.I. By Glafkides: Chimie et Physique Photographic (published by Paul Montel, 1967), G. F. By Duffin: Photographic Emulsion Chemistry (published by The Focal Press, 1966), V.C. L. It can be prepared as a silver halide grain emulsion by a method described in Zelikman et al: Making and Coating Photographic Emulsion (published by The Focal Press, 1964). That is, any method such as an acidic method, a neutral method, and an ammonia method may be used, and the formation of a reaction between a soluble silver salt and a soluble halogen salt may be any one of a one-side mixing method, a simultaneous mixing method, and a combination thereof. Of these methods, the so-called controlled double jet method, in which silver halide grains are prepared while controlling the formation conditions, is preferred. The halogen composition is not particularly limited, and may be any of silver chloride, silver chlorobromide, silver chloroiodobromide, silver bromide, silver iodobromide, and silver iodide.

  Grain formation is usually divided into two stages: silver halide seed grain (nucleus) generation and grain growth, and these may be performed continuously at once, or the nucleus (seed grain) formation and grain growth are separated. It is also possible to do this. The controlled double jet method in which the particle formation is controlled by controlling the pAg, pH, etc., which are particle formation conditions, is preferable because the particle shape and size can be controlled. For example, when nucleation and grain growth are performed separately, first, soluble silver salt and soluble halogen salt are uniformly and rapidly mixed in an aqueous gelatin solution to produce nuclei (seed particles) (nucleation process). Silver halide grains are prepared by a grain growth process in which grains are grown while supplying a soluble silver salt and a soluble halogen salt under controlled pAg, pH, and the like. After the formation of the grains, the desired salt halide emulsion is obtained by removing unnecessary salts by a known desalting method such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. I can do it.

  In order to keep the white turbidity after image formation low and to obtain good image quality, the silver halide preferably has a small average grain size, and the average grain size is 0.2 μm or less, more preferably 0.01 to 0.00. It is preferably 17 μm, particularly 0.02 to 0.14 μm. The grain size referred to here means the length of the edge of the silver halide grain when the silver halide grain is a so-called normal crystal of a cube or octahedron. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface.

  The grain size of the silver halide grains is preferably monodispersed. The term “monodispersion” used herein refers to a particle size variation coefficient of 30% or less obtained by the following formula. Preferably it is 20% or less, More preferably, it is 15% or less.

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

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

  There is no particular limitation on the crystal habit on the outer surface of the silver halide grain, but when using a spectral sensitizing dye having crystal habit (plane) selectivity in the adsorption reaction of the silver sensitizing dye on the surface of the silver halide grain It is preferable to use silver halide grains having a relatively high proportion of crystal habits adapted to the selectivity. For example, when using a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100], the proportion of the [100] face on the outer surface of the silver halide grain is preferably high, and this ratio is 50 % Or more, more preferably 70% or more, and particularly preferably 80% or more. The ratio of the Miller index [100] plane is a T.K. based on the adsorption dependency of the [111] plane and the [100] plane in the adsorption of the sensitizing dye. Tani, J .; Imaging Sci. 29, 165 (1985).

  The silver halide grains are preferably prepared using low molecular weight gelatin having an average molecular weight of 50,000 or less at the time of forming the grains, and particularly preferably used at the time of nucleation of silver halide grains. The low molecular weight gelatin has an average molecular weight of 50,000 or less, preferably 2000 to 40000, more preferably 5000 to 25000. The average molecular weight of gelatin can be measured by gel filtration chromatography.

  Low molecular weight gelatin can be decomposed by adding gelatin-degrading enzyme to a commonly used gelatin aqueous solution with an average molecular weight of about 100,000, hydrolyzing by adding acid or alkali, and heating under atmospheric pressure or pressure. Can be obtained by thermal decomposition, decomposition by ultrasonic irradiation, or a combination of these methods.

  The concentration of the dispersion medium during nucleation is preferably 5% by mass or less, and it is effective to carry out at a low concentration of 0.05 to 3.0% by mass.

  The photosensitive silver halide grains may be added to the photosensitive layer (image forming layer) by any method, and at this time, the silver halide grains are arranged close to a reducible silver source (organic silver salt). Is preferred.

  The silver halide is prepared in advance and added to the solution for preparing the organic silver salt grains, so that the silver halide preparation process and the organic silver salt grain preparation process can be handled separately. Although preferable, as described in British Patent 1,447,454, when preparing organic silver salt particles, a halogen component such as a halide ion is allowed to coexist with an organic silver salt forming component, and silver ions are injected into this. Thus, the organic silver salt particles can be produced almost simultaneously. It is also possible to prepare silver halide grains by converting a halogen-containing compound to an organic silver salt and converting the organic silver salt. That is, a silver halide forming component is allowed to act on a solution or dispersion of an organic silver salt prepared in advance or a sheet material containing the organic silver salt to convert a part of the organic silver salt into photosensitive silver halide. You can also.

  Examples of the silver halide forming component include inorganic halogen compounds, onium halides, halogenated hydrocarbons, N-halogen compounds, and other halogen-containing compounds. Specific examples thereof are described in US Pat. No. 4,009,039. 3,457,075, 4,003,749, British Patent 1,498,956 and JP-A-53-27027, 53-25420, etc. Inorganic halides such as trimethylphenylammonium bromide, cetylethyldimethylammonium bromide, onium halides such as trimethylbenzylammonium bromide; halogenated carbonization such as iodoform, bromoform, carbon tetrachloride, 2-bromo-2-methylpropane Hydrogens: N-bromo珀酸 imide, N- bromo phthalimide, N- halogen compounds such as N- bromoacetamide; others such as triphenylmethyl chloride, bromide triphenylmethyl, 2-bromoacetic acid, 2-bromo ethanol, dichloro benzophenone. Thus, silver halide can also be prepared by converting a part or all of silver in the organic acid silver salt into silver halide by the reaction between the organic acid silver and the halogen ion. Moreover, you may use together the silver halide grain manufactured by converting a part of organic silver salt into the silver halide prepared separately.

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

The silver halide used in the present invention preferably contains transition metal ions belonging to groups 6 to 11 of the periodic table. As the metal, W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt, and Au are preferable. These may be used alone or in combination of two or more of the same or different metal complexes. For these metal ions, the metal salt may be introduced as it is into the silver halide, but it can be introduced into the silver halide in the form of a metal complex or complex ion. The preferred content is in the range of 1 × 10 ⁻⁹ to 1 × 10 ⁻² mol, and more preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻⁴ mol, per mol of silver. The transition metal complex or complex ion is preferably represented by the following general formula.

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

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

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

  Separately prepared photosensitive silver halide grains can be desalted by known desalting methods such as noodle method, flocculation method, ultrafiltration method, electrodialysis method, etc. It can also be used without.

(Reducing agent)
Examples of suitable reducing agents incorporated in the photothermographic material of the present invention are described in U.S. Pat. Nos. 3,770,448, 3,773,512, 3,593,863, RD17029 and 29963, and the like. Can be used by appropriately selecting from known reducing agents, but when using an aliphatic carboxylic acid silver salt as the organic silver salt, two or more phenol skeletons are alkylene groups or sulfur. Substituted with an alkyl group (methyl, ethyl, propyl, t-butyl, cyclohexyl, etc.) or acyl group (acetyl, propionyl, etc.) at least one of the positions adjacent to the hydroxy substitution position of the phenol skeleton. Bisphenols in which two or more of the phenol skeletons are connected by an alkylene group or sulfur, for example, the following general formula (A) The compound represented are preferred.

In the formula, X represents a chalcogen atom or CHR ₁₀ , and R ₁₀ represents a hydrogen atom, a halogen atom, an aliphatic group having 7 or less carbon atoms or a cyclic group having 6 or less members. R ₁₁ and R ₁₂ each represent a hydrogen atom or a substituent.

The chalcogen atom represented by X is sulfur, selenium or tellurium, preferably a sulfur atom. The halogen atom represented by R ₁₀ is a fluorine, chlorine, bromine atom or the like, and the aliphatic group having 7 or less carbon atoms is methyl, ethyl, propyl, butyl, hexyl, heptyl, vinyl, allyl, butenyl. , Hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, and the like. A carbocyclic group is preferably a 4- to 6-membered ring such as cyclobutene, cyclopentyl, cyclopentenyl, cyclohexyl, cyclohexenyl, cyclohexadienyl, phenyl group, etc. , Pyrrole, pyrrolidine, pyrimidine, pyrazine, pyridine, triazine, thiazole, furan, pyran, etc. It is preferred, particularly preferably a hydrogen atom or a cycloalkyl group, a cycloalkenyl group, a group having a cyclic structure such as a phenyl group.

  These groups may further have a substituent, such as a halogen atom (fluorine, chlorine, bromine, etc.), a cycloalkyl group (cyclohexyl, cycloheptyl, etc.), a cycloalkenyl group (1-cycloalkenyl). 2-cycloalkenyl etc.), alkoxy groups (methoxy, ethoxy, propoxy etc.), alkylcarbonyloxy groups (acetyloxy etc.), alkylthio groups (methylthio, trifluoromethylthio etc.), carboxyl groups, alkylcarbonylamino groups (acetylamino) ), Ureido group (such as methylaminocarbonylamino), alkylsulfonylamino group (such as methanesulfonylamino group), alkylsulfonyl group (such as methanesulfonyl group, trifluoromethanesulfonyl group), carbamoyl group (carbamoyl, N, N-dimethyl) Carba Yl, N-morpholinocarbonyl, etc.), sulfamoyl groups (sulfamoyl, N, N-dimethylsulfamoyl, morpholinosulfamoyl etc.), trifluoromethyl groups, hydroxyl groups, nitro groups, cyano groups, alkylsulfonamide groups (methane) Sulfonamides, butanesulfonamides, etc.), alkylamino groups (amino, N, N-dimethylamino, N, N-diethylamino, etc.), sulfo groups, phosphono groups, sulfite groups, sulfino groups, alkylsulfonylaminocarbonyl groups (methane) Sulfonylaminocarbonyl, ethanesulfonylaminocarbonyl, etc.), alkylcarbonylaminosulfonyl groups (acetamidosulfonyl, methoxyacetamidosulfonyl, etc.), alkynylaminocarbonyl groups (acetamidocarbonyl, methoxy) Seto amide carbonyl, etc.), alkylsulfinyl aminocarbonyl group (methanesulfinyl aminocarbonyl include ethanesulfinyl aminocarbonyl, etc.) and the like. Moreover, when there are two or more substituents, they may be the same or different.

Examples of the halogen atom represented by R ₁₁ and R ₁₂ include a fluorine, chlorine, bromine atom, etc. Examples of the substituent represented by R ₁₁ and R ₁₂ include an alkyl group, an aryl group, a cycloalkyl group, an alkenyl group, Cycloalkenyl group, alkynyl group, amino group, acyl group, acyloxy group, acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, heterocyclic group, etc. Can be mentioned. A plurality of R ₁₁ and R ₁₂ may be the same or different.

R ₁₁ preferably has 2 or more carbon atoms. R ₁₂ preferably has 1 to 5 carbon atoms, and more preferably 1 carbon atom. These groups may further have a substituent, such as a halogen atom (fluorine, chlorine, bromine, etc.), an alkyl group (methyl, ethyl, propyl, butyl, pentyl, i-pentyl, 2-ethylhexyl). , Octyl, decyl, etc.), cycloalkyl groups (cyclohexyl, cycloheptyl, etc.), alkenyl groups (ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl) Etc.), cycloalkenyl groups (1-cycloalkenyl, 2-cycloalkenyl etc.), alkynyl groups (ethynyl, 1-propynyl etc.), alkoxy groups (methoxy, ethoxy, propoxy etc.), alkylcarbonyloxy groups (acetyloxy etc.) , Alkylthio groups (methylthio, trifluoromethylthio, etc.), carboxyl groups Alkylcarbonylamino groups (such as acetylamino), ureido groups (such as methylaminocarbonylamino), alkylsulfonylamino groups (such as methanesulfonylamino), alkylsulfonyl groups (such as methanesulfonyl and trifluoromethanesulfonyl), carbamoyl groups (carbamoyl, N N-dimethylcarbamoyl, N-morpholinocarbonyl, etc.), sulfamoyl groups (sulfamoyl, N, N-dimethylsulfamoyl, morpholinosulfamoyl etc.), trifluoromethyl groups, hydroxyl groups, nitro groups, cyano groups, alkylsulfones. Amide groups (methanesulfonamide, butanesulfonamide, etc.), alkylamino groups (amino, N, N-dimethylamino, N, N-diethylamino, etc.), sulfo groups, phosphono groups, sulfite groups, sulfo groups Inino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl, etc.), alkylcarbonylaminosulfonyl group (acetamidosulfonyl, methoxyacetamidosulfonyl, etc.), alkynylaminocarbonyl group (acetamidocarbonyl, methoxyacetamidocarbonyl, etc.) And alkylsulfinylaminocarbonyl groups (methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.) and the like.

  Specific examples of the compound represented by the general formula (A) include the following compounds.

  In addition, U.S. Pat. Nos. 3,589,903, 4,021,249, or British Patent 1,486,148 and JP-A-51-51933, 50-36110, 50-11603, 52 Polyphenol compounds described in JP-A-84727 or JP-B-51-35727, such as 2,2'-dihydroxy-1,1'-binaphthyl, 6,6'-dibromo-2,2'-dihydroxy-1,1 Bisnaphthols described in U.S. Pat. No. 3,672,904 such as' -binaphthyl and the like, and further, for example, 4-benzenesulfonamidophenol, 2-benzenesulfonamidophenol, 2,6-dichloro-4-benzenesulfonamidophenol As described in US Pat. No. 3,801,321, such as 4-benzenesulfonamidonaphthol Sulfonamide phenol or sulfonamide naphthols can also be cited.

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

  The amount of the reducing agent used in the photothermographic material varies depending on the type of organic silver salt and reducing agent and other additives, but generally 0.05 to 10 mol per mol of organic silver salt, 0.1 to 3 mol is preferable. Within the range of this amount, two or more reducing agents may be used in combination.

  In the present invention, it may be preferable to apply the reducing agent to a photosensitive emulsion solution composed of photosensitive silver halide and organic silver salt grains and a solvent immediately before coating, since the variation in photographic performance due to stagnation time is small. is there.

  In addition, it is also preferable to use together the compound which can form a hydrogen bond with the hydrogen of the hydroxyl group of a reducing agent like triphenylphosphine oxide etc. which are described in EP1096310 as an adjuvant of a reducing agent.

(Chemical sensitization)
The silver halide grains can be chemically sensitized. For example, according to the method disclosed in Japanese Patent Application Nos. 2000-57004 and 2000-61942, a chemical sensitization center (chemical sensitization) is obtained by using a compound that releases chalcogen such as sulfur or a noble metal compound that releases noble metal ions such as gold ions. Nuclei) can be formed.

  In the present invention, it is preferably chemically sensitized with an organic sensitizer containing chalcogen atoms such as sulfur, selenium, tellurium and the like described below. These organic sensitizers containing chalcogen atoms are preferably compounds having groups capable of adsorbing to silver halide and unstable chalcogen atom sites.

  As these organic sensitizers, organic sensitizers having various structures disclosed in JP-A-60-150046, JP-A-4-109240, JP-A-11-218874, and the like can be used. Among them, the chalcogen atom is preferably at least one of compounds having a structure in which a carbon atom or a phosphorus atom is linked with a double bond.

The amount of chalcogen compound used as the organic sensitizer varies depending on the type of chalcogen compound, silver halide grains, reaction environment for chemical sensitization, and the like, but it is 10 ⁻⁸ to 10 ⁻² per mole of silver halide. Moles are preferred, more preferably 10 ⁻⁷ to 10 ⁻³ moles.

  The chemical sensitization environment is not particularly limited, but it is preferable to chemically sensitize the silver halide grains under the condition that no organic acid silver salt such as silver behenate is present, and it is formed on the silver halide grains. An organic sensitizer containing a chalcogen atom in the presence of an oxidized oxidant capable of annihilating or reducing the size of the generated chalcogenide or silver nucleus, particularly in the presence of an oxidizing agent capable of oxidizing the silver nucleus It is also preferable to perform chalcogen sensitization, and the sensitizing conditions in this case are preferably 6 to 11, more preferably 7 to 10 as pAg, and more preferably 7 to 10, and more preferably 5 to 10. -8, and the temperature is preferably 30 [deg.] C. or lower.

  Accordingly, in the photothermographic material of the present invention, the photosensitive silver halide is heated at a temperature of 30 using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei on the grain. It is preferable to use a light-sensitive emulsion that has been chemically sensitized at a temperature of 0 ° C. or lower, mixed with an organic silver salt, dispersed, dehydrated and dried.

  Further, chemical sensitization using these organic sensitizers is also preferably performed in the presence of a heteroatom-containing compound having adsorptivity to spectral sensitizing dyes or silver halide grains. By performing chemical sensitization in the presence of a compound having an adsorptivity to silver halide, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved.

  Although the spectral sensitizing dye used in the present invention will be described later, the heteroatom-containing compound having adsorptivity to silver halide is preferably a nitrogen-containing heterocyclic compound described in JP-A-3-24537. Can be mentioned. Examples of the heterocyclic ring of the nitrogen-containing heterocyclic compound include pyrazole, pyrimidine, 1,2,4-triazole, 1,2,3-triazole, 1,3,4-thiadiazole, 1,2,3-thiadiazole, 1, Each ring of 2,4-thiadiazole, 1,2,5-thiadiazole, 1,2,3,4-tetrazole, pyridazine, 1,2,3-triazine, a ring in which 2 to 3 of these rings are bonded, Mention may be made of rings such as triazolotriazole, diazaindene, triazaindene, pentaazaindene and the like. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, a ring such as phthalazine, benzimidazole, indazole, and benzothiazole can also be used.

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

  These heterocyclic rings may have a substituent other than the hydroxyl group. Examples of the substituent include (substituted) alkyl groups, alkylthio groups, amino groups, hydroxyamino groups, alkylamino groups, dialkylamino groups, arylamino groups, carboxyl groups, alkoxycarbonyl groups, halogen atoms, cyano groups, and the like. .

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

  As described above, the silver halide grains can be subjected to noble metal sensitization using a compound that releases noble metal ions such as gold ions. For example, chloroaurate and organic gold compounds can be used as the gold sensitizer.

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

  The silver halide subjected to chemical sensitization may be formed in the presence of an organic silver salt, formed in the absence of an organic silver salt, or a mixture of both. .

(Spectral sensitization)
Spectral sensitizing dyes are preferably adsorbed on the photosensitive silver halide grains for spectral sensitization. As the spectral sensitizing dye, dyes such as cyanine, merocyanine, complex cyanine, complex merocyanine, holopolar cyanine, styryl, hemicyanine, oxonol, hemioxonol and the like can be used. For example, JP-A Nos. 63-159841, 60-140335, 63-231437, 63-259651, 63-304242, 63-15245, U.S. Pat. Nos. 4,639,414, 4 , 740,455, 4,741,966, 4,751,175, 4,835,096 and the like. Useful sensitizing dyes are described in, for example, documents described or cited in RD 17643, page 23, section IV-A (December 1978), page 18431, page 437, section X (August 1978). . In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of various laser imagers and scanner light sources. For example, dyes described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

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

  In the present invention, it is particularly preferable to use a sensitizing dye having spectral sensitivity in the infrared. Examples of infrared spectral sensitizing dyes preferably used include infrared spectral sensitizing dyes disclosed in U.S. Pat. Nos. 4,536,473, 4,515,888, and 4,959,294. It is done. Among them, a long-chain polymethine dye characterized in that a sulfinyl group is substituted on a benzene ring of a benzoazole ring is particularly preferable. The above-mentioned infrared sensitizing dyes are described in, for example, HM Hammer: The Chemistry of Heterocyclic Compounds, Vol. 18, The Cyanine Dies and Related Compounds, published by A. Weissberger ed. It can be easily synthesized by the method described.

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

  Spectral sensitizing dyes may be used alone or in combination, and sensitizing dye combinations are often used for the purpose of supersensitization.

(Strong color sensitization)
Emulsions containing silver halide grains and organic silver salt grains used in photothermographic materials are sensitizing dyes, dyes that themselves do not have spectral sensitization, or substances that do not substantially absorb visible light. The emulsion may contain a substance exhibiting a supersensitization effect, whereby the silver halide grains may be supersensitized.

  Useful sensitizing dyes, combinations of dyes exhibiting supersensitization, and substances exhibiting supersensitization are described in RD17643 (issued in December 1978), page IV-J, or Japanese Patent Publication No. 9-25500, 43. No.-4933, JP-A-59-19032, JP-A-59-192242, JP-A-5-341432, and the like. In the present invention, the complex fragrance represented by the following general formula (7) is used. A group mercapto compound or a mercapto derivative compound is preferred.

Formula (7) Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic ring or condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium or tellurium atoms. Preferably, benzoimidazole, naphthimidazole, benzothiazole, naphthothiazole, benzoxazole, naphthoxazole, benzoselenazole, benzotelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine as a heteroaromatic ring , Purine, quinoline or quinazoline. However, other heteroaromatic rings are also included.

  In addition, a mercapto derivative compound which substantially forms the above mercapto compound when included in a dispersion of an organic acid silver salt and / or a silver halide grain emulsion is also included. Particularly preferred examples include mercapto derivative compounds represented by the following general formula (7a).

General formula (7a) Ar-SS-Ar
Ar in the formula has the same meaning as in the case of the mercapto compound represented by the general formula (7).

  The heteroaromatic ring includes, for example, a halogen atom (chlorine, bromine, iodine), a hydroxyl group, an amino group, a carboxyl group, an alkyl group (preferably having 1 to 4 carbon atoms) and an alkoxy group (preferably, One having 1 to 4 carbon atoms) and the like.

  As described above, the biggest difference in the composition of the photothermographic material as compared with the conventional silver salt photographic material is that the latter photosensitive material is fogged and printed regardless of before and after the development processing. That is, it contains a large amount of photosensitive silver halide, silver carboxylate and developer (reducing agent) that can cause out silver (baked out silver). For this reason, the photothermographic material is required to have a high antifogging and image stabilization technique for maintaining the storage stability not only before development but also after development. In addition to aromatic heterocyclic compounds that suppress oxidization, mercury compounds such as mercury acetate, which have the function of oxidizing and extinguishing fog nuclei, have been used as highly effective storage stabilizers. However, it was a safety / environmental problem.

(Anti-fogging agent, image stabilizer)
The antifogging and image stabilizer used for the photothermographic material will be described below.

  As mentioned above, reducing agents with protons such as bisphenols and sulfonamidophenols are mainly used as reducing agents in the sensitive materials, so these active species that can extract hydrogen are generated. It is preferable that the compound which can inactivate a reducing agent by containing is contained. Preferably, it is a compound capable of generating free radicals as reactive species upon exposure as a colorless photo-oxidizing substance.

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

  In addition, as a compound that generates free radicals, a carbocyclic or heterocyclic ring is used so that the generated free radicals are stable enough to be in contact with the reducing agent for a sufficient period of time to be inactivated. Those having an aromatic group of the formula are preferred.

  Representative examples of these compounds include biimidazolyl compounds represented by general formula [1] and iodonium compounds represented by general formula [2] in Japanese Patent Application No. 2000-57004.

  In addition, as a compound that inactivates the reducing agent and prevents the reducing agent from reducing the organic silver salt to silver, a compound in which the reactive species is not a halogen atom is preferable. It can be used in combination with a compound that releases an active species that is not an atom. Many compounds capable of releasing a halogen atom as an active species are known, and a good effect can be obtained by the combined use.

  Specific examples of these compounds that generate active halogen atoms include the following compounds represented by the general formula [4] in the Japanese Patent Application No. 2000-57004.

Q-Y-C (X ₁ ) (X ₂ ) (X ₃ )
In the formula, Q represents an aryl group or a heterocyclic group. X ₁ , X ₂ and X ₃ each represent a hydrogen atom, a halogen atom, an acyl group, an alkoxycarbonyl group, an aryloxycarbonyl group, a sulfonyl group or an aryl group, at least one of which is a halogen atom. Y represents —C (═O) —, —SO— or —SO ₂ —.

  Detailed explanation of each group is described in paragraphs “0088” to “0093”, and specific compound examples are described in paragraphs “0095” to “0102” as 4-1 to 4-64.

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

(Silver saving agent)
A silver saving agent is preferably used in the photothermographic material of the present invention. A silver saving agent refers to a compound that can reduce the amount of silver necessary to obtain a certain silver image density. Various action mechanisms of the function of decreasing can be considered, but a compound having a function of improving the covering power of developed silver is preferable. Here, the covering power of developed silver refers to the optical density per unit amount of silver.

  Examples of the silver saving agent include a hydrazine derivative compound represented by the general formula [H] described in Japanese Patent Application No. 2001-192698, a vinyl compound represented by the general formula (G), and a general formula (P). Preferred examples include quaternary onium compounds, and alkoxysilane compounds having two or more primary or secondary amino groups and salts thereof.

  Here, having two or more primary or secondary amino groups means that only two or more primary amino groups, two or more secondary amino groups, and further primary amino groups and secondary amino groups. The term “alkoxysilane compound salt” refers to an adduct of an inorganic acid or an organic acid and an alkoxysilane compound capable of forming an onium salt with an amino group.

(binder)
Binders suitable for the photothermographic material of the present invention are transparent or translucent and generally colorless, and are natural polymer synthetic resins, polymers and copolymers, and other media for forming films such as gelatin, gum arabic, polyvinyl alcohol, Hydroxyethyl cellulose, cellulose acetate, cellulose acetate butyrate, polyvinyl pyrrolidone, casein, starch, poly (meth) acrylic acid, polymethyl methacrylate, polyvinyl chloride, copoly (styrene-maleic anhydride), copoly (styrene-acrylonitrile), copoly (Styrene-butadiene), polyvinyl acetals (polyvinyl formal, polyvinyl butyral, etc.), polyesters, polyurethanes, phenoxy resins, polyvinylidene chloride, polyepoxides, poly Boneto, polyvinyl acetates, cellulose esters, and polyamides. These may be hydrophilic or non-hydrophilic.

  Preferred binders for the photosensitive layer of the photothermographic material are polyvinyl acetals, and a particularly preferred binder is polyvinyl butyral. Details will be described later. For non-photosensitive layers such as overcoat layers and undercoat layers, especially protective layers and backcoat layers, cellulose esters which are polymers with higher softening temperatures, especially polymers such as triacetyl cellulose and cellulose acetate butyrate preferable. In addition, as needed, said binder can be used in combination of 2 or more type.

Such a binder is used in an effective range to function as a binder. The effective range can be easily determined by one skilled in the art. For example, as an index for holding at least the organic silver salt in the photosensitive layer, the ratio of the binder to the organic silver salt is preferably in the range of 15: 1 to 1: 2, particularly 8: 1 to 1: 1. That is, it is preferable amount of the binder in the photosensitive layer is a 1.5~6g / m ^2. More preferably, it is 1.7-5 g / m < ² >. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.

  The glass transition temperature (Tg) of the binder used for the photosensitive layer of the photothermographic material is particularly preferably 70 to 105 ° C. By using a binder having such characteristics, the film can be prevented from being softened by an organic acid, the temperature of the heat transition point can be increased, and a remarkable effect can be exhibited for preventing scratches. On the other hand, when a binder having a Tg of less than 70 ° C. is used, the thermal transition point temperature is lowered and a desired value cannot be obtained as a physical property value such as scratch resistance. On the other hand, using a binder having a Tg of more than 105 ° C. is not preferable because it results in a significant decrease in physical properties.

  As a preferred binder, a conventionally known polymer compound can be used, and Tg is 70 to 105 ° C., number average molecular weight is 1,000 to 1,000,000, preferably 10,000 to 500,000, polymerization degree. Is about 50-1000. Examples of such include vinyl chloride, vinyl acetate, vinyl alcohol, maleic acid, acrylic acid, acrylic ester, vinylidene chloride, acrylonitrile, methacrylic acid, methacrylic ester, styrene, butadiene, ethylene, vinyl butyral, vinyl acetal, There are compounds comprising a polymer or copolymer containing an ethylenically unsaturated monomer such as vinyl ether as a structural unit, polyurethane resins, and various rubber resins. Moreover, phenol resin, epoxy resin, polyurethane curable resin, urea resin, melamine resin, alkyd resin, formaldehyde resin, silicone resin, epoxy-polyamide resin, polyester resin and the like can be mentioned. These resins are described in detail in “Plastic Handbook” issued by Asakura Shoten. These polymer compounds are not particularly limited, and may be either a homopolymer or a copolymer as long as the glass transition temperature (Tg) of the derived polymer is within the above range.

  Polymers or copolymers containing such ethylenically unsaturated monomers as structural units include (meth) acrylic acid alkyl esters, (meth) acrylic acid aryl esters, cyanoacrylic acid alkyl esters, cyanoacrylic acid. Aryl esters and the like, and the alkyl group and aryl group thereof may or may not be substituted. Specifically, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, sec -Butyl, t-butyl, amyl, hexyl, cyclohexyl, benzyl, chlorobenzyl, octyl, stearyl, sulfopropyl, N-ethyl-phenylaminoethyl, 2- (3-phenylpropyloxy) ethyl, dimethylaminophenoxyethyl, furfuryl , Tetrahydrofurfuryl, phenyl, Resil, naphthyl, 2-hydroxyethyl, 4-hydroxybutyl, triethylene glycol, dipropylene glycol, 2-methoxyethyl, 3-methoxybutyl, 2-acetoxyethyl, 2-acetoacetoxyethyl, 2-ethoxyethyl, 2- i-propoxyethyl, 2-butoxyethyl, 2- (2-methoxyethoxy) ethyl, 2- (2-ethoxyethoxy) ethyl, 2- (2-butoxyethoxy) ethyl, 2-diphenylphosphorylethyl, ω-methoxypolyethylene Examples include glycol (addition mole number n = 6), allyl, dimethylaminoethylmethyl chloride salt and the like.

  In addition, the following monomers can be used. Specific examples of vinyl esters include vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl chloroacetate, vinyl methoxyacetate, vinyl phenyl acetate, vinyl benzoate, vinyl salicylate. N-substituted acrylamides, N-substituted methacrylamides and acrylamides, methacrylamides: N-substituents include methyl, ethyl, propyl, butyl, t-butyl, cyclohexyl, benzyl, hydroxymethyl, methoxyethyl, dimethyl Aminoethyl, phenyl, dimethyl, diethyl, β-cyanoethyl, N- (2-acetoacetoxyethyl), diacetone and the like; olefins: for example, dicyclopentadiene, ethylene, propylene, 1-butene, -Pentene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, 2,3-dimethylbutadiene, etc .; styrenes: for example methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, tert-butylstyrene, chloromethylstyrene , Methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester, etc .; vinyl ethers: eg methyl vinyl ether, butyl vinyl ether, hexyl vinyl ether, methoxyethyl vinyl ether, dimethylaminoethyl vinyl ether, etc .; N-substituted Maleimides: As N-substituent, methyl, ethyl, propyl, butyl, t-butyl, cyclohexyl, benzyl, dode Those having silyl, phenyl, 2-methylphenyl, 2,6-diethylphenyl, 2-chlorophenyl, etc .; others include butyl crotonate, hexyl crotonate, dimethyl itaconate, dibutyl itaconate, diethyl maleate, maleate Dimethyl acid, Dibutyl maleate, Diethyl fumarate, Dimethyl fumarate, Dibutyl fumarate, Methyl vinyl ketone, Phenyl vinyl ketone, Methoxyethyl vinyl ketone, Glycidyl acrylate, Glycidyl methacrylate, N-vinyl oxazolidone, N-vinyl pyrrolidone, Acrylonitrile, Examples thereof include methacrylonitrile, methylenemalonnitrile, and vinylidene chloride.

  Among these, particularly preferred examples include methacrylic acid alkyl esters, methacrylic acid aryl esters, styrenes, and the like. Among such polymer compounds, it is preferable to use a polymer compound having an acetal group. A polymer compound having an acetal group is preferable because it is excellent in compatibility with the organic acid to be produced and has a great effect of preventing the film from being softened.

  In the present invention, the binder is preferably polyvinyl acetal having a substantially acetoacetal structure. Examples thereof include polyvinyl acetals shown in U.S. Pat. Nos. 2,358,836, 3,003,879, 2,828,204, and British Patent 771,155.

  As the polymer compound having an acetal group, a compound described as the general formula (V) in Japanese Patent Application No. 2000-380225 is particularly preferable.

(Crosslinking agent)
It is known that the use of a cross-linking agent with the above binder improves filming and reduces development unevenness, but also has an effect of suppressing fog during storage and suppressing generation of printout silver after development. .

  As the crosslinking agent, various crosslinking agents conventionally used for photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based, sulfonic acid described in JP-A-50-96216 are used. Ester-based, acryloyl-based, carbodiimide-based, and silane compound-based crosslinking agents may be used, but preferred are isocyanate-based compounds, silane compounds, epoxy compounds, and acid anhydrides. These three compounds are described in detail in Japanese Patent Application No. 2000-57004.

(Matting agent)
In the present invention, the surface layer of the photothermographic material (when the photosensitive layer side or a non-photosensitive layer is provided on the opposite side of the photosensitive layer with the support interposed) is treated before development or after thermal development. It is preferable to contain a matting agent for preventing the image from being scratched, and it is preferably contained in an amount of 0.1 to 30% by mass with respect to the binder.

  The material of the matting agent used may be either organic or inorganic. Examples of inorganic substances include silica described in Swiss Patent 330,158, glass powder described in French Patent 1,296,995, alkaline earth metal or cadmium described in British Patent 1,173,181, and the like. Further, carbonates such as zinc can be used as the matting agent. Examples of organic substances include starch described in U.S. Pat. No. 2,322,037, starch derivatives described in Belgian Patent 625,451 and British Patent 981,198, and polyvinyls described in Japanese Patent Publication No. 44-3643. Such as alcohol, polystyrene or polymethacrylate described in Swiss Patent 330,158, polyacrylonitrile described in US Pat. No. 3,079,257, and polycarbonate described in US Pat. No. 3,022,169 An organic matting agent can be used.

  The matting agent preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm. The coefficient of variation of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less.

  Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

(Standard deviation of particle size / average value of particle size) × 100
The method of adding the matting agent may be a method in which the matting agent is dispersed in the coating solution in advance, or a method of spraying the matting agent after the coating solution is applied and before drying is completed. In addition, when a plurality of types of matting agents are added, both methods may be used in combination.

(Support)
Examples of the material for the support of the photothermographic material of the present invention include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (aluminum, etc.), etc. A material that can be processed into a flexible sheet or roll is preferred. Therefore, as a suitable support, plastic films (films of cellulose acetate, polyester, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyimide, cellulose triacetate, polycarbonate, etc.) are preferable, and among them, biaxially stretched polyethylene terephthalate (PET) ) Film is particularly preferred. The thickness of the support is about 50 to 300 μm, preferably 70 to 180 μm.

(Coloring agent)
In the photothermographic material according to the present invention, it is preferable to use a color toning agent. Examples of suitable color toning agents are RD17029, U.S. Pat. Nos. 4,123,282, 3,994,732, and 3,846,136. And No. 4,021,249, for example.

  Imides (succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide, etc.); mercaptans (3-mercapto-1,2,4-triazole, etc.); phthalazinone derivatives or metal salts of these derivatives (phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); phthalazine and phthalic acids (phthalic acid, 4 -A combination of methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid; phthalazine and maleic anhydride, and phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylene acid derivative and its anhydride (phthalic acid, 4 -Methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid The combination and the like with at least one compound selected from the anhydride and the like). Particularly preferred color tones are phthalazinone or a combination of phthalazine and phthalic acids and phthalic anhydrides.

  Conventionally, regarding the color tone of an output image for medical diagnosis, it is said that a cold tone image tone is more likely to provide a more accurate diagnostic observation result of a recorded image for an X-ray photograph reader. Here, the cool image tone is a pure black tone or a bluish black tone with a black image, and the warm image tone is a warm black tone with a brown image on a black image. Say.

(Layer structure)
For gradation adjustment or the like, two or more photosensitive layers may be provided on one side of the support or one or more layers on both sides of the support.

(Filter dye)
In the photothermographic material, a filter layer is formed on the same side as or opposite to the photosensitive layer in order to control the amount of light transmitted through the photosensitive layer or the wavelength distribution, or a dye or pigment is contained in the photosensitive layer. Is preferred.

  As the dye used, known compounds that absorb light in various wavelength regions can be used depending on the color sensitivity of the photothermographic material. For example, when the photothermographic material according to the present invention is an image recording material using infrared light, a squarylium dye having a thiopyrylium nucleus as disclosed in Japanese Patent Application No. 11-255557 (thiopyrylium squarylium dye and And a squarylium dye having a pyrylium nucleus (referred to as a pyrylium squarylium dye), or a thiopyrylium croconium dye similar to a squarylium dye, or a pyrylium croconium dye.

  The compound having a squarylium nucleus is a compound having 1-cyclobutene-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy- in the molecular structure. It is a compound having 4,5-dione. Here, the hydroxyl group may be dissociated.

  As the dye, a compound described in JP-A-8-201959 is also preferable.

(Application of component layers)
The photothermographic material is preferably formed by preparing a coating solution in which the above-described constituent materials are dissolved or dispersed in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment.

  There are no particular restrictions on the method of applying multiple layers of each constituent layer simultaneously, and for example, a known method such as a bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, or extrusion coating method may be used. Can do. Of these, a pre-weighing type coating method called an extrusion coating method is more preferable. The extrusion coating method is suitable for precision coating and organic solvent coating because there is no volatilization on the slide surface unlike the slide coating method. Although this coating method has been described on the side having the photosensitive layer, the same applies to the case of coating with undercoating when providing the backcoat layer.

The amount of coated silver is preferably selected in accordance with the purpose of the imaging material, but is preferably 0.6 to 2.5 g / m ² for medical purposes, and more preferably 0. 8-1.5 g / m ² is preferred. Of the amount of silver applied, those derived from silver halide preferably occupy 2 to 18%, more preferably 5 to 15%, based on the total silver amount.

(Development of imaging materials)
The development conditions of the photothermographic material of the present invention vary depending on the equipment, apparatus, or means used. Typically, the photothermographic material exposed imagewise at a suitable high temperature is heated. Accompanied by. The latent image obtained after exposure heats the photothermographic material at a moderately high temperature (about 80 to 200 ° C., preferably about 100 to 200 ° C.) for a sufficient time (generally about 1 second to about 2 minutes). It can develop by doing.

  If the heating temperature is less than 80 ° C, a sufficient image density cannot be obtained in a short time. If the heating temperature exceeds 200 ° C, the binder melts, and not only the image itself, such as transfer to a roller, but also to transportability and a developing machine. Also has an adverse effect. By heating, a silver image is generated by an oxidation-reduction reaction between an organic silver salt (which functions as an oxidizing agent) and a reducing agent. This reaction process proceeds without any supply of treatment liquid such as water from the outside.

  The heating device, apparatus, or means may be a heating means typical as a heat generator using a hot plate, iron, hot roller, carbon, white titanium or the like. More preferably, the photothermographic material provided with the protective layer is subjected to heat treatment by bringing the surface having the protective layer into contact with the heating means in order to perform uniform heating, thermal efficiency and workability. It is preferable from the point of view, and it is preferable that the surface is conveyed while being brought into contact with a heat roller, heated and developed.

(Exposure to sensitive material)
For exposure of the photothermographic material, it is desirable to use a light source suitable for the color sensitivity imparted to the photosensitive material. For example, if the sensitive material can be felt in infrared light, it can be applied to any light source in the infrared light range, but the laser power is high power, the photosensitive material can be made transparent, etc. From this point, an infrared semiconductor laser (780 nm, 820 nm) is more preferably used.

  The exposure is preferably performed by laser scanning exposure, but various methods can be adopted as the exposure method. For example, as a first preferable method, there is a method using a laser scanning exposure machine in which the angle formed by the scanning laser beam and the exposure surface of the photosensitive material is not substantially perpendicular.

  Here, “substantially not perpendicular” means that the angle that is closest to the vertical during laser scanning is preferably 55 to 88 degrees, more preferably 60 to 86 degrees, still more preferably 65 to 84 degrees, Most preferably, it is 70 to 82 degrees.

  The beam spot diameter on the photosensitive material exposure surface when the photosensitive material is scanned with the laser beam is preferably 200 μm or less, more preferably 100 μm or less. This is preferable in that a smaller spot diameter can reduce the angle of deviation of the laser incident angle from the vertical. The lower limit of the beam spot diameter is 10 μm. By performing such laser scanning exposure, it is possible to reduce image quality deterioration related to reflected light such as generation of interference fringe-like unevenness.

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

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

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

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

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

Example 1
[Preparation of underdrawn support]
The biaxially stretched polyethylene terephthalate film is subjected to corona discharge treatment on both sides under the condition of 10 W / m ² · min, and the following << backing layer side undercoat coating liquid >> is applied on one side to a dry film thickness of 0.12 μm After coating so that it was dried at 140 ° C., the following << backing layer side undercoat upper layer coating solution >> was coated to a dry film thickness of 0.3 μm and then dried at 140 ° C. Further, the following << image forming surface side undercoat lower layer coating solution >> is coated on the opposite surface so as to have a dry film thickness of 0.2 μm, and then the following image forming surface side undercoat upper layer coating solution >>. Was coated at a dry film thickness of 0.05 μm and dried at 140 ° C. These were heat-treated at 125 ° C. for 2 minutes to prepare an underdrawn support.

<Backing layer side undercoat coating solution>
Oxazoline group-containing latex polymer liquid (solid content 40%) 37.5 g
Dispersion of ethoxylated alcohol and ethylene homopolymer (solid content 10%) 5g
Surfactant (A) 6.5g
Ammonia (0.5% by mass) 1.1 g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

<< Backing layer side undercoat upper layer coating liquid >>
Surfactant (A) 31.0g
Co-polyester aqueous dispersion A 214.9 g
Distilled water was added to make 1000 ml, and the backcoat surface side undercoat upper layer coating solution 1 was obtained.

<< Coating liquid for underlayer on the image forming side >>
Copolymer of styrene / butyl acrylate / hydroxymethyl methacrylate (25/45/30) (solid content 30%)
70g
Unitox D-110 (Acre Peterlite, USA) 5.0g
Surfactant (A) 0.3g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

<Image forming surface side undercoat upper layer coating solution>
Polymer having vinyl alcohol unit (5% solid content) 80.0 g
3.0 g of polymer latex having a composition of styrene / butyl acrylate / hydroxymethyl methacrylate (= 25/45/30) (solid content 30%)
Surfactant (A) 0.4g
Spherical silica matting agent Seahoster KE-P50 (Nippon Shokubai Co., Ltd.) 0.3g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Coating of image forming layer and image forming surface protective layer]
The image forming layer and the image forming surface protective layer were applied by the method described in JP-A No. 2003-5322 (18 to 21).

(Preparation of photothermographic material sample 1)
The following layers were sequentially formed on the support to prepare a photothermographic material sample 1. The drying was performed at 60 ° C. for 15 minutes.
Coating of backing layer: The backing layer was composed of two layers, and a liquid having the following composition was applied.

<Coating liquid for backing layer upper layer>
Cellulose acetate propionate 0.37 g / m ²
Antistatic agent: compound represented by general formula (1) of the present invention (shown in Table 1)
(Amount shown in Table 1)
Polyester resin: polyester resin of the present invention (shown in Table 1)
(Amount shown in Table 1)
Fluoropolymer: Fluoropolymer having the structural unit represented by the general formula (2) of the present invention in its structural unit: (Exemplary Compound 2-1: M-1210 / M-5210 / MMA = 1 / 1/1 (molar ratio))
(Amount shown in Table 1)
Infrared dye 1 0.7mg / m ²
C ₉ F ₁₇ (CH ₂ CH ₂ O) ₂₃ C ₉ F ₁₇ 8 mg / m ²
Methyl ethyl ketone 3.8 g / m ²
<< Coating liquid for backing layer lower layer >>
Cellulose acetate propionate 3.30 g / m ²
Antistatic agent: compound represented by general formula (1) of the present invention (shown in Table 1)
(Amount shown in Table 1)
Polyester resin: polyester resin of the present invention (shown in Table 1)
(Amount shown in Table 1)
Fluoropolymer: Fluoropolymer having the structural unit represented by the general formula (2) of the present invention in its structural unit: (Exemplary Compound 2-1: M-1210 / M-5210 / MMA = 1 / 1/1 (molar ratio))
(Amount shown in Table 1)
Infrared dye 1 6.3 mg / m ²
Matting agent: monodispersed silica having a monodispersity of 15% and an average particle size of 10 μm
46 mg / m ²
C ₉ F ₁₇ (CH ₂ CH ₂ O) ₂₃ C ₉ F ₁₇ 72 mg / m ²
Methyl ethyl ketone 34.0 g / m ²

(Production of photothermographic material samples 2 to 8)
Photothermographic material samples 2 to 8 are the same as photothermographic material sample 1 except that the antistatic agent, polyester resin and fluoropolymer for the upper layer of the backing layer and lower layer of the backing layer are changed as shown in Table 1. Was made.

The photothermographic materials 1 to 8 were evaluated for conductivity and film attachment as follows.
〔Evaluation methods〕
(Conductivity)
A sample before heat development (123 ° C., 12.5 seconds) was conditioned at 23 ° C., 20% RH, 23 ° C., 55% RH for 24 hours, and a Terra Ohm Model VE-30 manufactured by Kawaguchi Electric Co., Ltd. was used. Then, the conductivity (surface specific resistance value) on the backing layer side of the sample was measured under the condition of an applied voltage of 100V.

(With membrane)
A cellophane adhesive tape was pressure-bonded to the side of the backing layer of the sample before and after heat development (123 ° C., 12.5 seconds), and peeled off rapidly to determine the peeling area of the backing layer, and evaluated according to the evaluation criteria shown below. .
Evaluation criteria 1: Adhesive strength is very weak and the backing layer is completely peeled 2: The peeled area is 50% or more and less than 100% 3: The peeled area is 20% or more and less than 50% 4: Adhesion The peel strength is 5% or more and less than 20%. 5: Adhesive strength is very strong, and the peel area is less than 5%. If the evaluation is 4 or more, it can be considered that the film is sufficiently strong for practical use.

  The results are also shown in Table 1.

* Fluoropolymer: Fluoropolymer having the structural unit represented by the general formula (2) of the present invention as its structural unit. From Table 1, the sample of the present invention is superior to the comparison. Understand. It can be seen that the present invention can provide a photothermographic material that is less likely to be charged with static electricity and has excellent adhesion.

  It was confirmed that the sample of the present invention had no stickiness under high temperature (heat development treatment (123 ° C.)) and no stickiness under high humidity (55% RH), and there was no dust adhesion.

Claims (1)

A photosensitive layer containing a photosensitive silver halide, an organic silver salt and a reducing agent is provided on one surface of the support, and the surface opposite to the support is opposite to the support in an environment of 23 ° C. and 55% RH. A photothermographic material having a backing layer having a surface specific resistance value of 1 × 10 ¹³ Ω / cm ² or less, wherein the backing layer comprises two or more layers, and is a compound represented by the following general formula (1) Is contained in the uppermost layer and is not substantially contained in layers other than the uppermost layer, the polyester resin is contained in the layer closest to the support, and a structural unit represented by the following general formula (2) A photothermographic material comprising a fluorine-containing polymer having a structural unit in at least one of the backing layers.
Formula _{(1) M 1 O 3 S-} (CF 2) m -SO 3 M 1
(In the formula, M ₁ represents H, Li, Na, K, or an ammonium group, and m represents an integer of 1 to 8. However, when M ₁ represents Li, m represents an integer of 1 to 4. , When M ₁ represents H, m represents an integer of 1 to 6 or 8, when M ₁ represents Na, m represents an integer of 3 or 4, and when M ₁ represents K, m is 1 Represents an integer of ˜6, and when M ₁ represents an ammonium group, m represents an integer of 1 to 8.)

Wherein R ₁ represents a hydrogen atom, a fluorine atom or a methyl group, R ₂ represents a methylene group, an ethylene group or a 2-hydroxypropylene group, X represents a hydrogen atom or a fluorine atom, and n represents 1 to 1 Represents an integer of 4.)