JP2009069757A - Heat developable photosensitive sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive sheet comprising a heat developable photosensitive material superior in conveyance and silver color tone without generating inside contamination in a heat developing device even when quickly and thermally developing the heat developable photosensitive sheet comprising the heat developable photosensitive material by the compact and low cost developing device. <P>SOLUTION: Concerning the heat developable photosensitive sheet comprising the heat developable photosensitive material having a back coat layer on the face of the rear side of a support by having a photosensitive layer containing silver halide particles, organic silver salt, a reducer, and a binder on the support, and a non-photosensitive layer provided on the photosensitive layer, a fluctuation coefficient of center line average roughness (Ra(E)) of the photosensitive layer side uppermost surface of the heat developable photosensitive sheet is 7% or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photothermographic sheet comprising a photothermographic material containing an organic silver salt, silver halide grains, a binder and a reducing agent on a support.

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

  This photothermographic material is usually processed by a photothermographic processing apparatus (hereinafter also referred to as a thermal development apparatus) which forms an image by applying stable heat to the photothermographic material called a photothermographic processor. As described above, with the rapid spread in recent years, a large amount of this heat developing apparatus has been supplied to the market. In recent years, there has been a demand for a high-quality dry film with a high image density that can cope with downsizing and speeding up of a laser imager, and also with digital mammography.

  However, when rapid development is performed using a compact imager, it is difficult to obtain a sufficient image density, and there is also a problem in transportability during thermal development.

On the other hand, in conventional photothermographic materials, the friction coefficient is adjusted using a slip agent to improve transportability, and the surface roughness of the outermost surface of the photosensitive layer side and the outermost surface of the backcoat layer is adjusted. (For example, refer to Patent Documents 1, 2, and 3). It is also possible to adjust the surface glossiness and the coefficient of variation of the film thickness distribution of the image forming layer and intermediate layer in order to improve front / back discrimination after heat development, and to improve image density unevenness and image storage stability. It is known (see, for example, Patent Documents 4, 5, 6, and 7).
JP 2004-219794 A JP 2004-334077 A JP 2005-346026 A JP 2002-333686 A JP 2004-012579 A JP 2006-227599 A JP 2007-101733 A

  There is a need for a small, low-cost, fast-development thermal development device, and when these thermal development devices are used for rapid processing, improvement of image density, a problem during thermal development, which has been a problem in the past, is required. In addition to the improvement in transportability, a new problem has arisen that in-machine contamination of the thermal development apparatus during thermal development occurs. For mammography applications, an image density of 4.0 or higher is required. However, when the image density exceeds 4.0, a new problem arises in that the silver tone of the entire sheet deteriorates.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to develop a photothermographic sheet made of a photothermographic material quickly and thermally with a small and low-cost thermal development apparatus. An object of the present invention is to provide a photothermographic sheet made of a photothermographic material which is free from contamination in the heat developing apparatus and has excellent transportability and silver tone.

  In order to achieve the above object, the present inventor has studied the improvement of in-machine contamination, transportability, and silver tone of the heat development apparatus. By reducing and uniforming the variation in surface roughness and film thickness of the photosensitive layer, it has been found that the occurrence of in-machine contamination, transportability and silver tone in the heat developing device are greatly improved, and the present invention has been achieved. did.

  That is, the above object of the present invention is achieved by the following configuration.

  1. A photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on the support, a non-photosensitive layer provided on the photosensitive layer, and the opposite surface of the support In the photothermographic sheet comprising the photothermographic material having a back coat layer on the surface, the coefficient of variation of the center line average roughness (Ra (E)) of the outermost surface of the photothermographic sheet is 7% or less. A heat-developable photosensitive sheet, comprising:

  2. A photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on the support, a non-photosensitive layer provided on the photosensitive layer, and the opposite surface of the support A heat-developable photosensitive sheet comprising a heat-developable photosensitive material having a backcoat layer on the surface, wherein the coefficient of variation in surface glossiness of the outermost surface on the photosensitive layer side of the heat-developable photosensitive sheet is 7% or less. Photosensitive sheet.

  3. A photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on the support, a non-photosensitive layer provided on the photosensitive layer, and the opposite surface of the support In the photothermographic sheet made of the photothermographic material having a backcoat layer, the variation coefficient of the total film thickness of the photosensitive layer of the photothermographic sheet and the non-photosensitive layer provided thereon is 7% or less. A heat-developable photosensitive sheet.

  4). 4. The photothermographic sheet according to any one of 1 to 3, wherein the non-photosensitive layer or the back coat layer on the photosensitive layer contains a lubricant having a molecular weight of 550 to 10,000.

  5). 5. The photothermographic sheet according to any one of 1 to 4, wherein the maximum value of image density after heat development is 4.0 to 5.0.

  6). 6. The photothermographic sheet according to any one of 1 to 5, wherein a gradation (γ value) at an optical density of 1.2 of a photographic characteristic curve is 2.0 to 6.0.

  According to the present invention, it is possible to provide a photothermographic sheet made of a photothermographic material which is free from internal contamination in the thermal development apparatus and is excellent in transportability and silver tone.

  In particular, even when a photothermographic sheet made of a photothermographic material is rapidly heat-developed by a small and low-cost photothermographic apparatus, there is no occurrence of in-machine contamination in the photothermographic apparatus, and the transportability and silver tone are excellent. A photothermographic sheet made of a photothermographic material can be provided.

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

  The components of the present invention will be described sequentially.

(Coefficient of variation of surface roughness)
The coefficient of variation of the center line average roughness (Ra (E)) of the outermost surface of the photosensitive layer in the present invention is determined as follows. The heat-developable photosensitive sheet before heat development is divided into 5 squares with the transport direction at the time of heat development as vertical and the direction perpendicular to the transport direction as horizontal, and the whole is divided into 25 squares. At the center of each quadrangle (intersection of diagonal lines), the center line average roughness (Ra (E)) is measured by the method described later (unit of measurement is nm). The value obtained by multiplying the value obtained by dividing the standard deviation of Ra (E) obtained for the 25 measured points by the average value of Ra (E) by 100 is indicated as a coefficient of variation. In the present invention, the coefficient of variation of the center line average roughness (Ra (E)) on the outermost surface on the photosensitive layer side is preferably 5% or less, and more preferably 3% or less. Also, the variation coefficient of the ten-point average roughness (Rz (E)) of the outermost surface of the photosensitive layer side and the variation coefficient of the maximum roughness (Rt (E)) of the outermost surface of the photosensitive layer side are preferably 7% or less. 5% or less is more preferable, and 3% or less is particularly preferable.

(Coefficient of variation of surface gloss)
The coefficient of variation of the surface glossiness on the outermost surface of the photosensitive layer in the present invention is determined as follows. The heat-developable photosensitive sheet before heat development is divided into 5 squares with the transport direction at the time of heat development as vertical and the direction perpendicular to the transport direction as horizontal, and the whole is divided into 25 squares. At the center of each quadrangle (intersection of diagonal lines), the surface glossiness is measured by the method described later. The value obtained by multiplying the value obtained by dividing the standard deviation of the surface glossiness obtained for the 25 measured points by the average value of the surface glossiness by 100 is indicated as a coefficient of variation. In the present invention, the coefficient of variation of the surface glossiness on the outermost surface of the photosensitive layer is preferably 5% or less, and more preferably 3% or less.

(Coefficient of variation of the total film thickness of the photosensitive layer and the non-photosensitive layer thereon)
The coefficient of variation of the photosensitive layer thickness in the present invention and the total thickness of the non-photosensitive layer provided thereon is determined as follows. The heat-developable photosensitive sheet before heat development is divided into 5 squares with the transport direction at the time of heat development as vertical and the direction perpendicular to the transport direction as horizontal, and the whole is divided into 25 squares. At the center of each quadrangle (intersection of diagonal lines), a tomographic photograph using an electron microscope is taken, and the total film thickness of the photosensitive layer and the non-photosensitive layer provided thereon is measured (measurement unit is μm). The value obtained by dividing the standard deviation of the total film thickness of the photosensitive layer and the non-photosensitive layer determined for the 25 measured points by the average value of the total film thickness of the photosensitive layer and the non-photosensitive layer is multiplied by 100 to%. The displayed value is used as the coefficient of variation. In the present invention, the variation coefficient of the total film thickness of the photosensitive layer and the non-photosensitive layer is preferably 5% or less, and more preferably 3% or less.

Setting the coefficient of variation of the surface roughness, surface glossiness, and total film thickness of the photosensitive layer and the non-photosensitive layer to 7% or less means that the photosensitive layer and the non-photosensitive layer provided thereon are applied in the direction and width. This can be achieved by uniformly coating the support in the hand direction. As means for achieving uniform coating, for example, methods described below can be used in appropriate combination.
1) Polishing the slit portion of the extrusion coating device precisely to make the coating thickness distribution uniform in the width direction of the coating 2) Minimizing changes in the rheological characteristics of the coating solution over time. Minimize the time from application of the cross-linking agent to application. Also, do not use highly reactive crosslinking agents. 3) Improve the dispersibility and dispersion stability of the matting agent dispersion so that the unevenness of the matting agent does not occur during coating. 4) When calendering is performed after coating. The compliant roll and the heat roll are in uniform contact with each other, and the temperature distribution of the heat roll is made uniform.

  In the present invention, the center line average roughness of the outermost surface on the photosensitive layer side is better achieved in order to better achieve excellent in transportability and silver tone without occurrence of in-machine contamination in the thermal development apparatus which is the object of the present invention. It is preferable that the coefficient of variation (Ra (E)) is 7% or less, and the coefficient of variation of the surface glossiness on the outermost surface of the photosensitive layer is 7% or less. The coefficient of variation of the average roughness (Ra (E)) is 7% or less, the coefficient of variation of the surface glossiness on the outermost surface of the photosensitive layer is 7% or less, and is provided on the photosensitive layer of the photothermographic sheet and the photosensitive layer. The coefficient of variation of the total film thickness of the non-photosensitive layer is particularly preferably 7% or less.

(Surface layer)
In the present invention, the center line average roughness (Ra (E)) on the outermost surface on the side provided with the photosensitive layer is preferably 120 to 200 nm, more preferably 125 to 180 nm, and 130 to 170 nm is particularly preferable. By setting Ra (E) within this range, the effects of the present invention, in particular, transportability and in-machine contamination of the heat development apparatus can be improved.

  The ten-point average roughness Rz (E) of the outermost surface on the side where the photosensitive layer is provided is preferably 2.8 to 3.8 μm, and more preferably 3.0 to 3.6 μm. The maximum roughness Rt (E) of the outermost surface on the photosensitive layer side is preferably 4.2 to 5.8 μm, and particularly preferably 4.4 to 5.6 μm. By setting Rz (E) and Rt (E) on the outermost surface of the photosensitive layer in this range, the effects of the present invention, particularly the in-machine contamination of the heat development apparatus can be improved. In the present invention, (E) represents the outermost surface on the photosensitive layer side, and (B) represents the outermost surface on the backcoat layer side opposite to the photosensitive layer.

  The centerline average roughness (Ra (B)) on the outermost surface on the side where the backcoat layer is provided is preferably 70 to 150 nm, more preferably 80 to 130 nm, and particularly preferably 90 to 120 nm. By setting Ra (B) on the surface of the backcoat layer side in this range, the effects of the present invention, particularly the in-machine contamination of the thermal development apparatus can be improved. The ten-point average roughness Rz (B) of the outermost surface on the side where the backcoat layer is provided is preferably 4.0 to 6.0 μm, and particularly preferably 4.5 to 5.5 μm. The maximum roughness Rt (B) on the outermost surface on the side where the backcoat layer is provided is preferably 4.0 to 9.0 μm, and particularly preferably 5.0 to 8.0 μm. By setting Rz (B) and Rt (B) on the back coat layer side surface in this range, the effects of the present invention, particularly the in-machine contamination of the thermal development apparatus can be improved.

  The ten-point average roughness (Rz), maximum roughness (Rt), and centerline average roughness (Ra) in the present invention are defined by JIS surface roughness (B0601-1982) described below. The ten-point average roughness (Rz) is the peak from the highest to the fifth measured in the direction of the vertical magnification from the straight line that is parallel to the average line and does not cross the cross-sectional curve in the part extracted from the cross-sectional curve by the reference length. The difference between the average value of the altitude and the average value of the altitude of the valley bottom from the deepest to the fifth is expressed in μm.

  The maximum roughness (Rt) means that when the roughness curve is extracted by the reference length L and the extracted portion is sandwiched by two straight lines parallel to the center line, the interval between the two straight lines is in the direction of the vertical magnification of the roughness curve. Measured and refers to this value expressed in μm. The centerline average roughness (Ra) is a portion of the measured length L in the direction of the centerline from the roughness curve, the centerline of this extracted portion is the X axis, the direction of the vertical magnification is the Y axis, and the roughness When the curve is represented by y = f (x), the value obtained by the following equation is represented by μm.

  As a measuring method of the above Rz, Rt, and Ra, the humidity was measured for 24 hours under conditions of 25 ° C. and 65% RH (relative humidity) in which the measurement samples did not overlap with each other, and then measured in the environment. The non-overlapping conditions shown here include, for example, a method in which the edge of the photothermographic material is wound up, a method in which the paper is sandwiched between the photothermographic material and the photothermographic material, and a frame is formed using cardboard, etc. It is one of the methods of producing and fixing the four corners. Examples of the measuring apparatus that can be used include an RSTPLUS non-contact three-dimensional micro surface shape measuring system manufactured by WYKO.

Rz, Rt, and Ra on the front and back surfaces of the photothermographic material can be easily adjusted by appropriately combining the following technical means.
1) Type of matting agent (inorganic or organic powder) contained in the layer on the side having the photosensitive layer and the layer opposite to the side having the photosensitive layer, the average particle diameter, the added amount, the surface treatment method 2) The matting agent Dispersion conditions (type of disperser used, dispersion time, type of beads used for dispersion, average particle size, type and amount of dispersant used during dispersion, type of polar group of binder, polar group content)
3) Drying conditions at the time of coating (coating speed, distance to the coating surface of the hot air blowing nozzle, amount of dry air), amount of residual solvent 4) type of filter used for filtering the coating liquid, filtration time 5) calendaring after coating Are performed under the same conditions (for example, a calendar temperature of 40 to 80 ° C., a pressure of 4.53 × 10 ^{3 to} 2.72 × 10 ⁴ kPa, a line speed of 20 to 100 m / min, and a nip number of 2 to 6).

  The photothermographic material of the present invention preferably contains a matting agent having an average particle size of 4.0 to 10.0 μm on the outermost surface on the photosensitive layer side, and contains a matting agent of 4.5 to 8.0 μm. More preferably. A matting agent may be used in combination, but when used in combination, it may contain matting agent A having an average particle size of 0.3 to 2.0 μm and matting agent B having an average particle size of 4.0 to 10.0 μm. Preferably, it contains 0.5 to 1.5 μm matting agent A and 4.5 to 8.0 μm matting agent B. The mass ratio of the matting agent A and the matting agent B is preferably 99: 1 to 60:40, and more preferably 95: 5 to 70:30. The addition amount of the matting agent used in the outermost layer on the photosensitive layer side is usually 10.0 to 30% by mass with respect to the binder amount (including the crosslinking agent included in the binder amount) used in the outermost layer, preferably It is 12.0-27 mass%, More preferably, it is 15.0-25 mass%.

  The average particle diameter of the matting agent (preferably a crosslinked organic resin) contained in the outermost layer opposite to the photosensitive layer side across the support is preferably 5.0 to 15.0 μm. More preferably, it is 7.0-12.0 micrometers. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably 0.6% with respect to the binder amount (including the crosslinking agent included in the binder amount) used in the outermost layer. ˜5 mass%.

  Further, the coefficient of variation of the particle size distribution of the matting agent 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 addition method of the matting agent (organic or inorganic powder) may be a method in which it is dispersed in a coating solution in advance, or a method in which an organic or inorganic powder is sprayed after the coating solution has been applied and before drying is completed. Good. Moreover, when adding several types of powder, you may use both methods together.

  In the present invention, the value of Rz (E) / Rz (B) is preferably 0.1 to 0.7, particularly preferably 0.2 to 0.6, and 0.3 to 0.55. Is more preferable. By setting it within this range, the transportability of the photothermographic material is good, and the occurrence of density unevenness during heat development can be suppressed.

  The photothermographic material preferably has a constitutional layer containing a plurality of types of matting agents on both sides on the support from the viewpoint of improving the image quality of the image. The average particle size of the matting agent having the maximum average particle size contained in the layer containing the matting agent on the side having the photosensitive layer is Le (μm), and the side opposite to the side having the photosensitive layer across the support That is, when the average particle size of the matting agent having the maximum average particle size contained in the layer containing the matting agent on the side having the back coat layer is Lb (μm), Lb / Le is 2.0 to 10 It is preferable that it is 3.0, and 4.5 is more preferable. By setting Lb / Le within this range, density unevenness during heat development can be improved. In the image forming method of the present invention, the value of Rz (E) / Ra (E) is preferably 12 or more and 60 or less, more preferably 14 or more and 50 or less. By setting the value of Rz (E) / Ra (E) within this range, density unevenness during heat development and storage characteristics over time can be improved.

  In the present invention, the value of Rz (B) / Ra (B) is preferably 25 to 65, more preferably 30 to 60. By setting the value of Rz (B) / Ra (B) within this range, density unevenness during heat development and storage characteristics over time can be improved. About the above-mentioned surface roughness, it carried out with the following method.

(Evaluation of surface roughness)
About the sample before heat development processing, it measured by the method shown below using the non-contact three-dimensional surface analyzer (RST / PLUS by WYKO).

1) Objective lens: × 10.0 Intermediate lens: × 1.0
2) Measurement range: 463.4 μm × 623.9 μm
3) Pixel size: 368 × 238
4) Filter: Cylindrical correction and tilt correction 5) Smoothing: Medium smoothing 6) Scanning speed: Low
Ra, Rz, and Rt were defined according to JIS surface roughness (above: B0601-1982).

  In the measurement, each sample of 10 cm × 10 cm was divided into 100 in a grid pattern at intervals of 1 cm, the measurement was performed on the center of each square region, and the average value was obtained from 100 measurements.

  In the present invention, the case where the layer containing the matting agent is the outermost layer is one of the preferred embodiments. That is, even when a non-photosensitive layer is provided on the photosensitive layer side of the photothermographic material or on the opposite side of the photosensitive layer with the support interposed therebetween, for the purpose of controlling the surface roughness of the outermost layer, etc. It is preferable to use organic or inorganic powder as the matting agent.

The powder used in the present invention is preferably a powder having a Mohs hardness of 5 or more. As the powder, a known inorganic powder or organic powder can be appropriately selected and used. Examples of the inorganic powder include titanium oxide, boron nitride, SnO ₂ , SiO ₂ , Cr ₂ O ₃ , α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, SiC, cerium oxide, corundum, artificial diamond , Stone meteorite, garnet, mica, silica, silicon nitride, silicon carbide and the like. Examples of the organic powder include powders such as polymethyl methacrylate (PMMA), polystyrene, and Teflon (registered trademark).

  In the present invention, the back coat layer provided on the opposite side of the photosensitive layer with the support interposed therebetween is preferably an organic powder as a matting agent, more preferably an organic polymer particle, and three-dimensionally crosslinked. It is particularly preferable to use PMMA. The glass transition temperature (Tg) of the organic polymer particles is preferably 130 to 150 ° C. By setting Tg within this range, it is possible to suppress the occurrence of contamination in the heat developing apparatus.

On the other hand, it is preferable to use inorganic powder as a matting agent in the non-photosensitive layer on the photosensitive layer. Among the inorganic powders, preferred are inorganic powders such as SiO ₂ , titanium oxide, barium sulfate, α-Al ₂ O ₃ , α-Fe ₂ O ₃ , α-FeOOH, Cr ₂ O ₃ , and mica. , SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ (tin oxide) is particularly preferable.

  In the present invention, it is preferable to use the organic polymer particles and inorganic powder in combination as the matting agent. The combined ratio of the organic polymer particles and the inorganic powder in the layer containing these matting agents is preferably 10:90 to 90:10, more preferably 20:80 to 80:20, and 30 : 70 to 70:30 is particularly preferable.

In the present invention, the powder is preferably surface-treated, for example. The surface treatment layer is formed by dry pulverizing the inorganic powder material, adding water and a dispersing agent, and performing coarse particle classification by wet pulverization and centrifugal separation. Thereafter, the fine slurry is transferred to a surface treatment tank, where the surface of the metal hydroxide is coated. First, a predetermined amount of an aqueous salt solution such as Al, Si, Ti, Zr, Sb, Sn, Zn or the like is added, and the surface of the inorganic powder particles is coated with a hydrous oxide formed by adding an acid or an alkali that neutralizes the aqueous solution. Water-soluble salts produced as a by-product are removed by decantation, filtration, and washing. Finally, the slurry pH is adjusted, filtered, and washed with pure water. The washed cake is dried with a spray dryer or a band dryer. Finally, the dried product is pulverized by a jet mill into a product. In addition to the water system, AlCl ₃ and SiCl ₄ vapors can be passed through the non-magnetic inorganic powder, and then steam can be introduced to perform Al and Si surface treatment. For other surface treatment methods, “Characterization of Powder Surfaces”, Academic Press can be referred to.

  In the present invention, the powder is preferably surface-treated with a Si compound or an Al compound. Use of such a surface-treated powder can improve the dispersion state when the matting agent is dispersed. The content of Si or Al is preferably 0.1 to 10% by mass of Si and 0.1 to 10% by mass of Al with respect to the powder, and more preferably 0.1 to 5% of Si. Mass% and Al are 0.1 to 5 mass%, particularly preferably Si is 0.1 to 2 mass% and Al is 0.1 to 2 mass%. Further, Si / Al <1 (mass ratio) is preferable. The surface treatment can be performed by the method described in JP-A-2-83219.

  The average particle diameter of the powder in the present invention is the average diameter in the case of spherical powder, the average major axis length in the case of acicular powder, and the maximum diagonal line of the plate-like surface in the case of plate-like powder. Means the average value of each length, and can be easily obtained from measurement with an electron microscope.

(Surface gloss)
In this invention, it is preferable that the surface glossiness of the outermost surface in the side in which the photosensitive layer was provided is 40-70, More preferably, it is 43-67, Most preferably, it is 45-65. Further, the surface glossiness of the outermost surface of the backcoat side is larger than the surface glossiness of the outermost surface of the photosensitive layer, and the difference is preferably 25 to 45, more preferably the difference is 27 to 43, particularly preferably. Is 30-40. By adjusting the surface glossiness within this range, it is effective to prevent the occurrence of contamination in the heat developing apparatus and transportability during heat development, which is an effect of the present invention. The glossiness and the glossiness measurement method in the present invention mean the glossiness defined in JIS K 7105 and the measurement method thereof. In the present invention, 20 degree specular gloss was used. The surface glossiness on the outermost surface on the photosensitive layer side and the outermost surface on the backcoat layer side can be adjusted by using known means. For example, the following technical means can be used in appropriate combination.
1) Type of matting agent (inorganic or organic powder) contained in the layer on the side having the photosensitive layer and the layer opposite to the side having the photosensitive layer, the average particle diameter, the added amount, the surface treatment method 2) The matting agent Dispersion conditions (type of disperser used, dispersion time, type of beads used for dispersion, average particle size, type and amount of dispersant used during dispersion, type of polar group of binder, polar group content)
3) Re-dispersion by sonication or the like before adding the matting agent dispersion to the photosensitive emulsion solution 4) From the time when the matting agent dispersion solution is added to the photosensitive emulsion solution to the actual coating 5) Type of filter used for filtration of coating solution, filtration time 6) Drying conditions during coating (coating speed, distance to application surface of hot air blowing nozzle, amount of drying air), amount of residual solvent 7) When calendering is performed after coating, the conditions (for example, calendar temperature 40 to 80 ° C., pressure 4.53 × 10 ^{3 to} 2.72 × 10 ⁴ kPa, line speed 20 to 100 m / min, nip number 2 to 6 and the like) ).

(lubricant)
In the present invention, it is preferable to use a lubricant having a molecular weight of 550 or more as the lubricant in order to improve transportability and eliminate the occurrence of in-machine contamination in the thermal development apparatus. A fatty acid ester of a polyhydric alcohol is preferably used as the lubricant, and it is particularly preferable to use a fatty acid ester of a polyhydric alcohol having a molecular weight of 550 or more. The molecular weight is preferably 700 or more, more preferably 800 or more. The upper limit of the molecular weight is not particularly limited as long as the object of the present application can be achieved, but is usually 10,000 or less, preferably 7,000 or less, more preferably 5,000 or less. By setting the molecular weight to 550 or more, among the effects of the present invention, in-machine contamination in the thermal development apparatus can be remarkably improved. Here, in the case of a polymer type lubricant, the molecular weight refers to a mass average molecular weight. The mass average molecular weight can be determined by a light scattering method.

  The structure of the lubricant is not particularly limited as long as the molecular weight is 550 or more, but paraffin, liquid paraffin, fatty acid ester, and silicon-containing polymer are more preferable. As the silicon-containing polymer, a silicon-containing acrylic graft polymer is preferable. For example, a compound described in paragraph “0018” of JP-A No. 2003-15259 can be used. Among these, fatty acid esters are particularly preferable, and fatty acid esters of polyhydric alcohols are more preferable.

  Moreover, when using the fatty acid ester of a polyhydric alcohol, even if all are esterified, a hydroxyl group may remain partially. A fatty acid ester containing two or more ester groups in one molecule is preferred, and a fatty acid ester containing three or more ester groups is more preferred.

  Examples of the lubricant used in the present invention include triolein (glycerol trioleate), glycerol trilaurate, glycerol tripalmitate, glycerol tristearate, glycerol tribehenate, lauric acid-i-tridecyl, myristic acid- i-tridecyl, palmitic acid-i-tridecyl, stearic acid-i-tridecyl, arachidic acid-i-tridecyl, erucic acid-i-tridecyl, behenic acid-i-tridecyl, tri-i-lauric acid trimethylolpropane, tri -Trimethylolpropane i-myristic acid, trimethylolpropane tri-i-palmitate, trimethylolpropane tri-i-stearate, trimethylolpropane tri-erucate, trimethylolpropane tri-i-arachidate, tri -I Trimethylolpropane oleate, trimethylolpropane tri-i-behenate, dipentaerythrityl hexa-i-stearate, dipentaerythrityl hexa-i-palmitate, dipentaerythrityl hexa-i-myristate, dipentaerythrityl hexa-i-behenate, JP Although the compound etc. of Table 1-Table 3 of 2004-334077 are mentioned, It is not limited to these.

  The lubricant is contained in the non-photosensitive layer or the backcoat layer on the photosensitive layer, and more preferably contained in both the non-photosensitive layer and the backcoat layer on the photosensitive layer. The back coat layer in the present invention means a layer provided on the opposite side of the support on the side where the photosensitive layer is provided, and the back coat side undercoat layer and the back coat layer protective layer are also included in the back coat layer. Shall be. In the non-photosensitive layer on the photosensitive layer, the lubricant is more preferably contained in the backcoat protective layer among the backcoat layers.

  The addition amount of the lubricant to the non-photosensitive layer and the back coat layer on the photosensitive layer is 0.1 to 20 of the binder contained in the layer to be used (when the curing agent is contained, the curing agent is also included in the binder). % By mass is preferable, 0.2 to 10% by mass is more preferable, and 0.5 to 5% by mass is particularly preferable.

(Photo characteristic curve)
In the present invention, the photographic characteristic curve is D-logE that represents the relationship between the logarithm of logarithm (log E) of the exposure amount, which is exposure energy, on the horizontal axis, and the optical density, that is, the scattered light photographic density (D) on the horizontal axis. Say the curve. The gamma (γ) value is the slope of the tangent line at the optical density D = 1.2 on the characteristic curve (tan θ when the angle between the tangent line and the horizontal axis is θ).

  The gamma value at an optical density of 1.2 in the photographic characteristic curve is preferably 2.0 to 6.0, particularly preferably 3.5 to 5.5. By setting the gamma value at an optical density of 1.2 within this range, it is possible to maintain a good level of development unevenness even if heat development is carried out while transporting at high speed, and diagnostic recognition is possible even if the amount of silver is small. High image quality can be obtained.

In the present invention, in order to adjust the gamma value to 2.0 to 6.0, it is easy to use the following techniques in combination.
1) Change the type and addition amount of developer 2) Change the type and addition amount of silver saving agent 3) Change the addition amount and average grain size of silver halide 4) Spectral sensitizing dye to be adsorbed on silver halide 5) The method of chemical sensitization of silver halide and the degree of ripening are changed.

  The dry film thickness of the photosensitive layer is preferably 9.0 to 16.0 μm, more preferably 9.5 to 14.0 μm, and particularly preferably 10.0 to 13.0 μm. Thereby, the highest density is high, and an effect of excellent image storability can be obtained, which is preferable. The total dry film thickness of the photosensitive layer and the non-photosensitive layer provided on at least one surface of the support of the photothermographic material is preferably 12.0 to 19.0 [mu] m, and 14.0 to 18.0 [mu] m. It is particularly preferred that In order to improve image density unevenness and sharpness after heat development, the maximum value of image density after heat development is preferably 4.0 to 5.0, more preferably 4.0 to 4.8. Preferred is 4.2 to 4.6.

(Organic silver salt)
The organic silver salt according to the present invention is a non-photosensitive organic silver salt that can function as a supply source for supplying silver ions for forming a silver image in the photosensitive layer of the photothermographic material. That is, as a silver ion source in a heat development process heated to 80 ° C. or higher in the presence of photosensitive silver halide grains (photocatalyst) having a latent image formed by exposure on the grain surface and a reducing agent. A silver salt that functions to supply silver ions and contribute to silver image formation.

  As such non-photosensitive organic silver salts, silver salts of organic compounds having various chemical structures are conventionally known. For example, paragraphs “0048” to “0049” of JP-A-10-62899, European Patents Application Publication No. 803,764A1, page 18, line 24 to page 19, line 37, JP 962,812A1, JP-A-11-349591, JP-A-2000-7683, JP-A-2000-72711, JP-A-2002-23301, 2002-23303, 2002-49119, 196446, European Patent Application Publication Nos. 1246001A1, 12587775A1, JP-A-2003-140290, 2003-195445, 2003-295378, 2003-295379, JP 2003-295380 A, JP 2003-295382 A, JP 20 It is described in 3-270755 Patent like.

  In the present invention, a silver salt of an aliphatic carboxylic acid, particularly having 10 to 30 carbon atoms, preferably 15 to 15 carbon atoms, with or without various organic silver salts disclosed in the above-mentioned patent publications. 28 long chain aliphatic carboxylic acid silver salts can be used. The molecular weight of the aliphatic carboxylic acid for producing the silver salt is preferably 200 to 500, more preferably 250 to 400. Preferred examples of the aliphatic carboxylic acid silver salt include silver behenate, silver arachidate, silver stearate, silver oleate, silver laurate, silver caproate, silver myristate, silver palmitate, and a mixture thereof. Including.

  In the present invention, among these aliphatic carboxylic acid silvers, the silver behenate content is preferably 50 mol% or more, more preferably 80 to 100 mol%, still more preferably 90 to 90%, based on the total aliphatic carboxylic acid silver. It is preferable to use 99.99 mol% of fatty acid silver. In addition, it is preferable to use an aliphatic carboxylic acid silver salt having a silver erucate content of 2 mol% or less, more preferably 1 mol% or less, and still more preferably 0.1 mol% or less.

  Prior to preparing the aliphatic carboxylic acid silver salt, it is necessary to prepare an alkali metal salt of an aliphatic carboxylic acid. Examples of alkali metal salts that can be used in this case include sodium hydroxide, potassium hydroxide, Examples include lithium hydroxide. Among these, it is preferable to use one kind of alkali metal salt such as potassium hydroxide, but it is also preferable to use sodium hydroxide and potassium hydroxide in combination. As a combined ratio, it is preferable that the molar ratio of both of the above hydroxide salts is in the range of 10:90 to 75:25. When it reacts with an aliphatic carboxylic acid to become an alkali metal salt of an aliphatic carboxylic acid, the viscosity of the reaction solution can be controlled to a good state by using it within the above range.

  When preparing an aliphatic carboxylate silver salt in the presence of silver halide grains having an average particle diameter of 0.050 μm or less, the alkali metal of the alkali metal salt has a higher potassium ratio. This is preferable because dissolution of particles and Ostwald ripening are prevented. Moreover, the size of fatty acid silver salt particle | grains can be made small, so that the ratio of potassium salt is high. The ratio of a preferable potassium salt is 50-100 mass% with respect to the total alkali metal salt used at the process of manufacturing aliphatic silver carboxylate. The concentration of the alkali metal salt is preferably 0.1 to 0.3 mol / L.

  The average sphere equivalent diameter of the non-photosensitive aliphatic carboxylic acid silver salt means the diameter of the sphere having the same volume as the volume of one particle of the non-photosensitive aliphatic carboxylic acid silver salt. The particle volume can be obtained from the projected area and thickness of the particles observed by the above, and the diameter when converted to a sphere having the same volume as that volume can be obtained by averaging. In order to control the average sphere equivalent diameter of the non-photosensitive aliphatic carboxylic acid silver salt, it can be prepared by increasing the ratio of the potassium salt during preparation of the aliphatic carboxylic acid silver salt as described above, or a photosensitive emulsion. This can be easily performed by appropriately adjusting the particle diameter, mill peripheral speed, and dispersion time of the zirconia beads used at the time of dispersion of the dispersion.

  The average equivalent sphere diameter of the non-photosensitive aliphatic carboxylic acid silver salt is preferably 0.05 to 0.50 μm, more preferably 0.10 to 0.45 μm in order to obtain a sufficient density after heat development. Particularly preferably, it is 0.15 to 0.40 μm.

  Examples of the organic silver salt that may be used in addition to the non-photosensitive aliphatic carboxylic acid silver salt include an organic silver salt having a core / shell structure (Japanese Patent Laid-Open No. 2002-23303), a silver salt of a polyvalent carboxylic acid ( EP1246001, JP2004-061948), and polymer silver salts (JP2000-292881, JP2003-295378-2003-295811).

  The shape of the aliphatic carboxylic acid silver salt is not particularly limited, and may be any of a needle shape, a rod shape, a flat plate shape, and a scale shape. In the present invention, scale-like aliphatic carboxylic acid silver salts and short needle-shaped or rectangular parallelepiped-shaped aliphatic carboxylic acid silver salts having a major axis / minor axis length ratio of 5 or less are preferably used.

  In this specification, the scaly organic silver salt is defined as follows. The organic silver salt is observed with an electron microscope, the shape of the organic silver salt particle is approximated to a rectangular parallelepiped, and the sides of the rectangular parallelepiped are defined as a, b, and c from the shortest side (even though c is the same as b) When it is good), the shorter numerical value a, b is used to calculate x as follows.

x = b / a
Thus, x is calculated | required about about 200 particle | grains, and when it is set as the average value x (average), what satisfy | fills the relationship of x (average)> = 1.5 is made into a scale shape. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 20 ≧ x (average) ≧ 2.0. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

  In scaly particles, a can be regarded as the thickness of a tabular particle having a main plane with b and c as sides. The average of a is preferably 0.01 to 0.23 μm, and more preferably 0.1 to 0.20 μm. The average of c / b is preferably 1 to 6, more preferably 1.05 to 4, still more preferably 1.1 to 3, and particularly preferably 1.1 to 2.

  The particle size distribution of the organic silver salt is preferably monodispersed. Monodispersion is preferably 100% or less, more preferably 80% or less, and even more preferably 50% of the value obtained by dividing the standard deviation of the lengths of the short and long axes by the short and long axes. It is as follows. The method for measuring the shape of the organic silver salt can be determined from a transmission electron microscope image of the organic silver salt dispersion. As another method for measuring monodispersity, there is a method for obtaining the standard deviation of the volume weighted average diameter of the organic silver salt, and the percentage (variation coefficient) of the value divided by the volume weighted average diameter is preferably 100% or less, more Preferably it is 80% or less, More preferably, it is 50% or less. As a measuring method, for example, the organic silver salt dispersed in the liquid is irradiated with laser light, and the particle size (volume weighted average diameter) obtained by obtaining the autocorrelation function with respect to the temporal change of the fluctuation of the scattered light is obtained. be able to.

  Known methods and the like can be applied to the production of organic silver used in the present invention and the dispersion method thereof. For example, aliphatic carboxylic acid silver salt particles are prepared by reacting a solution containing silver ions with an aliphatic metal carboxylate salt solution or suspension. The solution containing silver ions is preferably an aqueous silver nitrate solution, and the aliphatic carboxylic acid metal salt solution or suspension is an aqueous solution or an aqueous dispersion, and the addition and mixing are preferably performed simultaneously. Any method such as a method of adding to the liquid surface or a method of adding to the liquid may be used, but a method of adding and mixing in the transfer means is preferred. Mixing in the transfer means means line mixing, and before the mixture of the solution containing silver ions and the aliphatic metal carboxylic acid alkali metal salt solution or suspension enters the batch storing the mixture containing the reactants. It is performed. Any mixing means such as a mechanical mixer such as a homomixer, a static mixer, or a turbulent flow effect may be used as the stirring means in the mixing section, but it is preferable not to use mechanical stirring. In addition, the mixing in the transfer means includes a solution containing silver ions, an alkali metal salt of an aliphatic carboxylic acid salt or a suspension, water, a circulated liquid of a mixed liquid stored in a batch after mixing, and the like. Liquids or suspensions may be mixed. In addition, for example, the above-mentioned JP-A-10-62899, European Patent Application Publication Nos. 803,763A1, 962,812A1, JP-A-2001-167022, 2000-7683, 2000-72711, 2001- No. 163889, No. 2001-163890, No. 2001-163825, No. 2001-33907, No. 2001-188313, No. 2001-83652, No. 2002-6442, No. 2002-31870, No. 2003-280135 2005-157190, etc. can be referred to.

  A photosensitive silver salt such as photosensitive silver halide grains can coexist when the organic silver salt is dispersed. However, when silver halide grains are allowed to coexist at the time of dispersion of the organic silver salt, fog is increased and sensitivity is remarkably lowered. Therefore, it is more preferable that silver halide grains are not substantially contained at the time of dispersion. In the present invention, the amount of silver halide grains in the aqueous dispersion to be dispersed is preferably 1 mol% or less, more preferably 0.1 mol% or less with respect to 1 mol of the organic silver salt in the liquid. More preferably, the active addition of silver halide grains is not performed.

  In the present invention, it is possible to produce a photothermographic material by mixing an organic silver salt aqueous dispersion and a photosensitive silver halide particle dispersion, but the mixing ratio of the organic silver salt and the photosensitive silver salt is intended. The ratio of the photosensitive silver halide grains to the organic silver salt is preferably in the range of 1 to 30 mol%, more preferably 2 to 20 mol%, and particularly preferably 3 to 15 mol%. Mixing two or more kinds of organic silver salt dispersions and two or more kinds of silver halide grain dispersions when mixing is a method preferably used for adjusting photographic characteristics.

The organic silver salt of the present invention can be used in a desired amount, but the silver amount is preferably 0.1 to 5 g / m ² , more preferably 0.3 to 3 g / m ² , still more preferably 0.5 to ² g / m ² . m ² .

(Silver halide grains)
The silver halide grain according to the present invention is a photosensitive silver halide grain, and can inherently absorb light as an intrinsic property of a silver halide crystal, or can be visible light or artificially by a physicochemical method. Physicochemical changes in the silver halide crystal and / or on the crystal surface when it can absorb infrared light and absorb light in any region within the light wavelength range of ultraviolet to infrared light Refers to silver halide crystal grains that have been processed and produced so that can occur.

  The silver halide grains themselves can be prepared as a silver halide grain emulsion (also referred to as a silver halide emulsion) using a known method. That is, any of acid method, neutral method, ammonia method, etc. may be used, and as a method of reacting soluble silver salt and soluble halogen salt, any one of one-side mixing method, simultaneous mixing method, combination thereof, etc. may be used. Of these methods, the so-called controlled double jet method in which silver halide grains are prepared while controlling the formation conditions is preferred.

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

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

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

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

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

  The silver halide grains used in the present invention are preferably prepared using low molecular weight gelatin having an average molecular weight of 50,000 or less at the time of forming the grains, but particularly preferably used at the time of nucleation of silver halide grains. The low molecular weight gelatin preferably has an average molecular weight of 50,000 or less, more preferably 20,000 to 40,000, and particularly preferably 5,000 to 25,000. The average molecular weight of gelatin can be measured by gel filtration chromatography. Low molecular weight gelatin can be 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 at the time of nucleation is preferably 5% by mass or less, and more preferably 0.05 to 3.0% by mass.

  As the silver halide grains used in the present invention, it is preferable to use a compound represented by the following general formula when forming the grains.

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

  The polyethylene oxide compound represented by the above general formula supports the step of producing an aqueous gelatin solution, the step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, and the emulsion when producing a silver halide photographic light-sensitive material. It has been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved, such as a step of coating on the body. 44-9497. The polyethylene oxide compound also functions as an antifoaming agent during nucleation. The compound represented by the above general formula is preferably used at 1% by mass or less, more preferably 0.01 to 0.1% by mass with respect to silver.

  The polyethylene oxide compound only needs to be present at the time of nucleation, and is preferably added in advance to the dispersion medium before nucleation, but it may be added during nucleation or a silver salt used at the time of nucleation. You may add and use for aqueous solution or halide aqueous solution. Preferably, it is used by adding 0.01 to 2.0% by mass to the aqueous halide solution or both aqueous solutions. The polyethylene oxide compound is preferably present for at least 50% of the nucleation step, more preferably 70% or more. The polyethylene oxide compound may be added as a powder or dissolved in a solvent such as methanol.

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

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

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

  In the present invention, the average grain size of the silver halide grains is usually 10 to 50 nm, preferably 10 to 40 nm, and more preferably 10 to 35 nm. By making the average grain size of silver halide grains within this range, image density can be reduced, light irradiation image storability (images obtained by thermal development can be used for diagnosis, etc. in a bright room, Deterioration of storage stability when stored in the storage medium can be suppressed.

  The average grain size referred to here means the length of the edge of the silver halide grain when the silver halide grain contained in the silver halide grain emulsion is a so-called normal crystal of a cube or octahedron. To tell. Further, when the silver halide grain is a tabular grain, it means the diameter when converted into a circular image having the same area as the projected area of the main surface. In addition, in the case of non-normal crystals, for example, in the case of spherical particles, rod-shaped particles, etc., the diameter when considering a sphere equivalent to the volume of the silver halide grains is calculated as the particle size. The measurement was performed using an electron micrograph, and the average particle size was determined by averaging the measured values of the particle size of 300 particles.

  In the present invention, the gradation of the image density can be adjusted by using silver halide grains having an average particle diameter of 55 to 100 nm and silver halide grains having an average particle diameter of 10 to 50 nm in combination. In addition, the image density can be improved, and the decrease in image density over time can be improved (smaller). The ratio (mass ratio) of silver halide grains having an average particle diameter of 10 to 50 nm and silver halide grains having an average particle diameter of 55 to 100 nm is preferably 95: 5 to 50:50, more preferably 90. : 10-60: 40.

  As described above, when two types of silver halide grain emulsions having an average particle diameter are used, the two types of silver halide emulsions may be mixed and contained in the photosensitive layer. In order to adjust the gradation, it is also preferred that the photosensitive layer is composed of two or more layers, and each layer contains the silver halide grain emulsions having the two average grain sizes separately.

(Silver halide grains having a silver iodide content of 5 to 100 mol%)
As the silver halide grains according to the present invention, silver halide grains containing silver iodide are preferably used. As the halogen composition, the silver iodide content is preferably 5 to 100 mol%. More preferably, it is 40-100 mol%, More preferably, it is 70-100 mol%, Most preferably, it is 90-100 mol%. If the silver iodide content is in this range, the intra-grain halogen composition distribution may be uniform, may be changed stepwise, or may be continuously changed.

  Further, silver halide grains having a core / shell structure having a high silver iodide content inside and / or on the surface can also be preferably used. A preferred structure is a 2- to 5-fold structure, more preferably 2- to 4-fold core / shell particles.

  As a method for introducing silver iodide into the silver halide grains, a method of adding an alkali iodide aqueous solution during grain formation, fine grain silver iodide, fine grain silver iodobromide, fine grain silver iodochloride, fine grain silver iodochlorobromide Of these, the method of adding at least one fine particle, the method of using an iodide ion releasing agent described in JP-A-5-323487 and JP-A-6-11780 are preferred.

  The silver halide grains according to the present invention preferably exhibit direct transition absorption derived from the silver iodide crystal structure at a wavelength in the range of 350 to 440 nm. Whether these silver halides have light absorption of direct transition can be easily distinguished by the fact that exciton absorption due to direct transition is observed in the vicinity of 400 to 430 nm.

(Heat conversion internal latent image type silver halide grains)
The photosensitive silver halide grains according to the present invention are heat-converted internal latent image type silver halide grains disclosed in JP-A Nos. 2003-270755 and 2005-106927, that is, from surface latent image type to internal latent image by thermal development. Silver halide grains whose surface sensitivity is lowered by conversion to an image type are preferred. In other words, in exposure before heat development, a latent image that can function as a catalyst for a development reaction (reduction reaction of silver ions by a silver ion reducing agent) is formed on the surface of the silver halide grains, In exposure, since many latent images are formed inside the surface of the silver halide grains, it is a silver halide grain that suppresses the formation of latent images on the surface. preferable.

  The heat-converted internal latent image type silver halide grains are 0.001 to 0.001 mol per mol of an aliphatic carboxylic acid silver salt that can function as a silver ion source, as in the case of ordinary surface latent image type silver halide grains. It is preferably used in the range of 7 mol, preferably 0.03 to 0.5 mol.

(Amphiphilic dispersion of silver halide grains)
In the process of manufacturing a photothermographic material, from the viewpoint of improving photographic performance and color tone, aggregation of silver halide grains is prevented, silver halide grains are dispersed relatively uniformly, and finally developed silver is desired. It is preferable that the shape can be controlled.

  In order to prevent aggregation, to uniformly disperse, etc., the gelatin used is preferably one in which hydrophilic properties such as amino groups and carboxyl groups of gelatin are chemically modified to modify the properties of gelatin according to the conditions of use. For example, examples of the hydrophobic modification of the amino group in the gelatin molecule include phenylcarbamoylation, phthalation, hatching, acetylation, benzoylation, and nitrophenylation, but are not particularly limited thereto. Further, the substitution rate is preferably 95% or more, more preferably 99% or more. Further, hydrophobic modification of the carboxyl group may be combined, and examples thereof include methyl esterification and amidation, but are not particularly limited thereto. The substitution rate of the carboxyl group is preferably 50 to 90%, more preferably 70 to 90%. Here, the hydrophobic group in the above-mentioned hydrophobization modification refers to a group whose hydrophobicity is increased by substituting the amino group and / or carboxyl group of gelatin.

  Further, depending on the purpose, the silver halide grain emulsion is preferably prepared by using a polymer that dissolves in both water and an organic solvent as described below, instead of gelatin or in combination with gelatin. For example, it is particularly preferred when the silver halide grain emulsion is coated with being uniformly dispersed in an organic solvent system. Examples of the organic solvent include alcohol-based, ester-based, and ketone-based compounds. In particular, ketone organic solvents such as methanol, acetone, methyl ethyl ketone, diethyl ketone and the like are preferable.

  The polymer that is soluble in both the water and the organic solvent may be a natural polymer, a synthetic polymer, or a copolymer. For example, gelatins, rubbers and the like that have been modified to belong to the category of the present invention can be used. Alternatively, polymers belonging to the following classifications can be used by introducing functional groups suitable for the purpose of preventing aggregation and uniform dispersion. Examples of the polymer include polymers described in paragraph “0018” of JP-A-2005-316054.

  The polymer may be a polymer that dissolves in both water and an organic solvent in the same state, but includes a polymer that can be dissolved or insolubilized in water or an organic solvent by controlling pH or controlling temperature. For example, a polymer having an acidic group such as a carboxyl group becomes hydrophilic in a dissociated state depending on the type, but can be made oleophilic and soluble in a solvent when the pH is lowered to a non-dissociated state. Conversely, a polymer having an amino group becomes lipophilic when the pH is raised, and becomes ionized and water-soluble when the pH is lowered. Nonionic activators are well known for the cloud point phenomenon, but they become lipophilic and soluble in organic solvents when the temperature rises, and they are hydrophilic, that is, soluble in water when the temperature is lowered. Included in the present invention is a water-soluble polymer (such as poly-N-i-propylacrylamide and copolymers thereof as well-known thermosensitive polymers). It is sufficient that micelles are formed and uniformly emulsified even if they are not completely dissolved.

  Since various monomers are combined, it is generally not stated which monomer should be used and how much, but the desired polymer can be obtained by combining hydrophilic monomers and hydrophobic monomers in an appropriate ratio. Is easy to understand.

  The polymer that dissolves in both the water and the organic solvent may have a solubility of at least 1% by mass (25 ° C.) with respect to water, although it may be adjusted by adjusting the conditions such as pH as described above or not adjusted. The organic solvent preferably has a solubility of 5% by mass or more (25 ° C.) in methyl ethyl ketone.

  From the viewpoint of solubility, so-called block polymers, graft polymers, comb polymers, and the like are more suitable as polymers that are soluble in both water and organic solvents used in the present invention. Comb polymers are particularly preferred. The isoelectric point of the polymer is preferably pH 6 or less.

  When manufacturing a comb polymer, various methods can be used, but it is desirable to use a monomer capable of introducing a side chain having a molecular weight of 200 or more into the comb part (side chain). In particular, it is preferable to use a polyoxyalkylene group-containing ethylenically unsaturated monomer such as ethylene oxide or propylene oxide. As the polyoxyalkylene group-containing ethylenically unsaturated monomer, those having a polyoxyalkylene group described in paragraphs “0022” to “0024” of JP-A-2005-316054 are particularly preferable.

  Moreover, as a monomer of a commercial item, the monomer etc. which were described in the paragraph "0025" of the said patent are mentioned.

  As the polymer, a graft polymer using a so-called macromer can also be used. For example, it is described in “New Polymer Experimental Studies 2, Synthesis and Reaction of Polymers” edited by the Society of Polymer Science, Kyoritsu Shuppansha, 1995. It is also described in detail in Yuya Yamashita's “Chemical Monomer Chemistry and Industry” published by IPC, 1989. Among the macromers, the useful molecular weight is in the range of 10,000 to 100,000, the preferred range is 10,000 to 50,000, and the particularly preferred range is in the range of 10,000 to 20,000. The above range is preferable from the viewpoints of exerting good effects and polymerizability with the copolymerization monomer forming the main chain. Specifically, AA-6, AS-6S, AN-6S, etc. manufactured by Toagosei Co., Ltd. are used.

  Needless to say, the present invention is not limited to the above specific examples. The polyoxyalkylene group-containing ethylenically unsaturated monomer may be used alone or in combination of two or more.

  Other monomers specifically reacted with the above monomers include (meth) acrylic acid esters, (meth) acrylamides, allyl esters, allyloxyethanols, vinyl ethers, vinyl esters, dialkyl itaconate, fumaric acid And other mono (or di) alkyl esters, crotonic acid, itaconic acid, (meth) acrylonitrile, maleronitrile, styrene, and the like. Specific examples include compounds described in paragraphs “0029” and “0030” of JP-A-2005-316054. The polymerization initiator, the polymerization inhibitor, the isoelectric point of the polymer, the kind of the solvent used in the polymerization, the molecular weight of the polymer, and the like are described in paragraphs “0031” to “0039” of JP-A-2005-316054.

  Although the specific example of an amphiphilic polymer is shown below, it is not limited to these.

(Chemical sensitization)
The photosensitive silver halide grains can be chemically sensitized. For example, by using methods such as those described in JP-A Nos. 2001-249428 and 2001-249426, compounds that release chalcogens such as sulfur, selenium, and tellurium and noble metal compounds that release noble metal ions such as gold ions can be used for photosensitivity. It is possible to form and impart a chemical sensitization center (chemical sensitization nucleus) capable of capturing electrons or holes generated by photoexcitation of the light-sensitive silver halide grains or the spectral sensitizing dye on the grains. In particular, chemical sensitization with an organic sensitizer containing a chalcogen atom is preferred. These organic sensitizers containing chalcogen atoms are preferably compounds having groups capable of adsorbing to silver halide and unstable chalcogen atom sites.

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

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

The amount of the chalcogen compound used as the organic sensitizer varies depending on the chalcogen compound used, silver halide grains, reaction environment for chemical sensitization, 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.

  There are no particular restrictions on the environmental conditions for the chemical sensitization, but in the presence of a compound capable of annihilating or reducing the size of silver chalcogenide or silver nuclei on the photosensitive silver halide grains, In particular, it may be preferable to perform chalcogen sensitization using an organic sensitizer containing a chalcogen atom in the presence of an oxidizing agent capable of oxidizing silver nuclei. The sensitizing conditions in this case are preferably 6 to 11 as pAg, more preferably 7 to 10, pH 4 to 10 is more preferable, 5 to 8 is more preferable, and temperature is 30 ° C. or less. It is preferable to perform sensitization.

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

  Examples of the heterocyclic ring in 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, Triazolotriazole, diazaindene, triazaindene, pentaazaindene ring and the like can be mentioned. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, phthalazine, benzimidazole, indazole, benzthiazole ring and the like can also be applied. 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.

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

The 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 10 ⁻⁶ to 1 per mole of silver halide. The molar range is preferably 10 ⁻⁴ to 10 ⁻¹ mol.

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

  In addition to the above sensitization methods, reduction sensitization methods and the like can also be used. Examples of reduction sensitization shell-like compounds include ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, 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.

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

  When the surface of the photosensitive silver halide grain is chemically sensitized, it is preferable that the effect of the chemical sensitization substantially disappears after the thermal development process. Here, the effect of chemical sensitization substantially disappears is the sensitivity 1 when the sensitivity of the photothermographic material obtained by the chemical sensitization technique is not chemically sensitized after the thermal development process. It means to decrease to 1 times or less. In order to eliminate the chemical sensitization effect in the thermal development process, an oxidant capable of destroying the chemical sensitization center (chemical sensitization nucleus) by an oxidation reaction at the time of thermal development, such as the above-mentioned halogen radical releasing compound, etc. It is necessary to put an appropriate amount in the emulsion layer and / or non-photosensitive layer of the photothermographic material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the chemical sensitization effect, and the like.

(Spectral sensitization)
The photosensitive silver halide is preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. 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, and 4,835,096.

  Useful sensitizing dyes used in the present invention are described in, for example, Research Disclosure (hereinafter abbreviated as RD) 17643IV-A (December 23, 1978), RD18431X (August 1978, 437) or It is described in the cited literature. 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, the compounds 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, a sensitizing dye having spectral sensitivity particularly in the infrared can also be used. Examples of infrared spectral sensitizing dyes preferably used include infrared spectral sensitizing dyes disclosed in U.S. Pat. Nos. 4,536,473, 4,515,888, and 4,959,294. It is done.

  The photothermographic material of the present invention contains at least one selected from the sensitizing dyes represented by the general formula (1) and the general formula (2) described in US Published Patent Application No. 2004-0224266. It is preferable that at least one sensitizing dye represented by the general formula (5) and the general formula (6) is selected and contained. It is particularly preferable to use the sensitizing dyes represented by the general formula (5) and the general formula (6) together in order to improve the exposure wavelength dependency at the time of exposure.

  The above-mentioned infrared sensitizing dyes are described in, for example, F. M. 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.

  These infrared sensitizing dyes may be added at any time after the preparation of the silver halide. For example, it is added to a solvent or dispersed in the form of fine particles, so-called silver halide grains or silver halides in a solid dispersion state. It can be added to a light-sensitive emulsion containing grains / silver aliphatic carboxylate 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.

  The above spectral sensitizing dyes may be used alone, but it is preferable to use a combination of plural kinds of spectral sensitizing dyes as described above. Often used for purposes such as supersensitization and expansion or adjustment of the photosensitive wavelength region.

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

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

Ar-SM
In the formula, M is a hydrogen atom or an alkali metal atom, and Ar is an aromatic ring or condensed aromatic ring having one or more nitrogen, sulfur, oxygen, selenium, or tellurium atoms.

  Preferably, the heteroaromatic ring is benzimidazole, naphthimidazole, benzthiazole, naphthothiazole, benzoxazole, naphthoxazole, benzselenazole, benztelrazole, imidazole, oxazole, pyrazole, triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine , Purine, quinoline, or quinazoline. However, other heteroaromatic rings are also included.

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

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

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

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

  The supersensitizer according to the present invention is preferably used in a photosensitive layer containing an organic silver salt and silver halide grains in an amount of 0.001 to 1.0 mol, particularly preferably silver 1 per mol of silver. 0.01 to 0.5 mole per mole.

  In the present invention, it is preferable that the spectral sensitizing dye is adsorbed on the surface of the photosensitive silver halide grains to effect spectral sensitization, and that the spectral sensitizing effect substantially disappears after the thermal development process. . Here, the spectral sensitization effect substantially disappears when the sensitivity of the imaging material obtained by a sensitizing dye, supersensitizer, etc. is the sensitivity when spectral sensitization is not performed after the thermal development process. It means to decrease to 1.1 times or less.

  In order to eliminate the spectral sensitizing effect in the thermal development process, a spectral sensitizing dye that is easily detached from the silver halide grains by heat is used during thermal development, or / and the spectral sensitizing dye is oxidized by an oxidation reaction. It is necessary to put an appropriate amount of an oxidizing agent that can be destroyed, such as the above-mentioned halogen radical releasing compound, in the emulsion layer and / or non-photosensitive layer of the photothermographic material. The content of the oxidizing agent is preferably adjusted in consideration of the oxidizing power of the oxidizing agent, the reduction range of the spectral sensitization effect, and the like.

(Reducing agent)
The reducing agent is capable of reducing silver ions in the photosensitive layer and is also called a developer. In the present invention, it is preferable to use a compound represented by the following general formula (RD1) as a silver ion reducing agent. The reducing agent represented by the general formula (RD1) may be one type or two or more types. Moreover, you may use together with the reducing agent which has another different chemical structure.

In the formula, X ₁ represents a chalcogen atom or CHR ₁ , and R ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. R ₂ represents an alkyl group, which may be the same or different, but at least one is a secondary or tertiary alkyl group. R ₃ represents a hydrogen atom or a group that can be substituted on the benzene ring, and may be the same or different. R ₄ represents a substitutable group on the benzene ring, and m and n each represents an integer of 0 to 2.

  In the present invention, in order to control heat development characteristics, a compound of the general formula (RD1) and a compound of the following general formula (RD2) can be used in combination.

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

  As the ratio of the combined use, [the mass of the compound of (RD1)]: [the mass of the compound of (RD2)] is preferably 5:95 to 85:15, more preferably 15:85 to 75:25. Yes, particularly preferably 25:75 to 65:35.

In the general formula (RD1), the chalcogen atom represented by X ₁ is sulfur, selenium or tellurium, preferably a sulfur atom. R ₁ in CHR ₁ where X ₁ represents a hydrogen atom, a halogen atom, an alkyl group, an alkenyl group, an aryl group or a heterocyclic group. The halogen atom is a fluorine, chlorine, bromine atom or the like, and the alkyl group is preferably a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. Specific examples include methyl, ethyl, propyl, butyl, hexyl, heptyl and the like. As an alkenyl group, an aryl group such as vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, etc. Are phenyl, naphthyl and the like, and examples of the heterocyclic group are thienyl, furyl, imidazolyl, pyrazolyl, pyrrolyl and the like.

  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 groups, etc.), alkynyl groups (ethynyl, 1-propynyl, etc.), alkoxy groups (methoxy, ethoxy, propoxy, etc.), alkylcarbonyloxy groups (acetyloxy) Etc.), alkylthio group (methylthio, trifluoromethylthio, etc.), acyl group (a) Til, benzoyl etc.), carboxyl group, alkylcarbonylamino group (acetylamino etc.), ureido group (methylaminocarbonylamino etc.), alkylsulfonylamino group (methanesulfonylamino etc.), alkylsulfonyl group (methanesulfonyl, trifluoromethanesulfonyl) ), Carbamoyl group (carbamoyl, N, N-dimethylcarbamoyl, N-morpholinocarbonyl, etc.), sulfamoyl group (sulfamoyl, N, N-dimethylsulfamoyl, morpholinosulfamoyl etc.), trifluoromethyl group, hydroxyl group Nitro group, cyano group, alkylsulfonamide group (methanesulfonamide, butanesulfonamide, etc.), alkylamino group (amino, N, N-dimethylamino, N, N-diethylamino, etc.), sulfo , Phosphono group, sulfite group, sulfino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl, etc.), alkylcarbonylaminosulfonyl group (acetamidosulfonyl, methoxyacetamidosulfonyl, etc.), alkynylaminocarbonyl group (acetamido) Carbonyl, methoxyacetamidocarbonyl, etc.), alkylsulfinylaminocarbonyl groups (methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.) and the like. Moreover, when there are two or more substituents, they may be the same or different. A particularly preferred substituent is an alkyl group.

At least one of the alkyl groups represented by R ₂ is a secondary or tertiary alkyl group. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, specifically, methyl, ethyl, propyl, i-propyl, butyl, i-butyl, t-butyl, t-pentyl, t-amyl. , T-octyl, cyclohexyl, cyclopentyl, 1-methylcyclohexyl, 1-methylcyclopropyl and the like.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group, An ester group, a halogen atom, etc. are mentioned. Or it may form a saturated ring with (R _{4) n} and (R _{4) m.}

R ₂ is preferably a secondary or tertiary alkyl group, and preferably has 2 to 20 carbon atoms. A tertiary alkyl group is more preferable, t-butyl, t-amyl, t-pentyl and 1-methylcyclohexyl are more preferable, and t-butyl and t-amyl are most preferable.

Examples of the group that can be substituted on the benzene ring represented by R ₃ include halogen atoms (fluorine, chlorine, bromine, etc.), alkyl groups, aryl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, amino groups. , Acyl group, acyloxy group, acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, heterocyclic group and the like. Specific examples of R ₃ include methyl, ethyl, i-propyl, t-butyl, cyclohexyl, 1-methylcyclohexyl, 2-hydroxyethyl, 3-hydroxypropyl, and the like. These groups may further have a substituent, and the substituents mentioned in the above R ₁ can be used as the substituent.

R ₃ is preferably an alkyl group having 2 to 20 carbon atoms, more preferably an alkyl group having 2 to 10 carbon atoms, and particularly preferably an alkyl group having 2 to 5 carbon atoms. R ₃ is an alkyl group having 1 to 20 carbon atoms having a hydroxyl group as a substituent, or an alkyl group having 1 to 20 carbon atoms having a group capable of forming a hydroxyl group by being deprotected as a substituent. Preferably, it is an alkyl group having 3 to 10 carbon atoms having a hydroxyl group as a substituent, or an alkyl group having 2 to 10 carbon atoms having a group capable of forming a hydroxyl group by being deprotected as a substituent. . When the carbon number of the alkyl group is within this range, it is preferable in that the image does not become hard and an image suitable for diagnosis within a gradation range of 2.0 to 6.0 is obtained. R ₃ is particularly preferably an alkyl group having 3 to 5 carbon atoms having a hydroxyl group as a substituent. Specific examples include 3-hydroxypropyl, 4-hydroxybutyl, 5-hydroxypentyl and the like. These groups may further have a substituent, and the substituents mentioned in the above R ₁ can be used as the substituent.

  The group that can be deprotected to form a hydroxyl group is preferably a group that is deprotected by the action of an acid and / or heat to form a hydroxyl group. Specifically, ether groups (methoxy, t-butoxy, allyloxy, benzyloxy, triphenylmethoxy, trimethylsilyloxy, etc.), hemiacetal groups (tetrahydropyranyloxy, etc.), ester groups (acetyloxy, benzoyloxy, p- Nitrobenzoyloxy, formyloxy, trifluoroacetyloxy, pivaloyloxy, etc.), carbonate groups (ethoxycarbonyloxy, phenoxycarbonyloxy, t-butyloxycarbonyloxy, etc.), sulfonate groups (p-toluenesulfonyloxy, benzenesulfonyloxy, etc.) Carbamoyloxy group (phenylcarbamoyloxy etc.), thiocarbonyloxy group (benzylthiocarbonyloxy etc.), nitrate ester group, sulfenato group (2,4-dinitrobenze) Sulfenyl oxy, etc.).

R ₃ is most preferably a primary alkyl group having 3 to 5 carbon atoms having a hydroxyl group or a precursor group thereof, such as a 3-hydroxypropyl group. In the most preferred combination of R ₂ and R ₃ , R ₂ is a tertiary alkyl group (t-butyl, t-amyl, t-pentyl, 1-methylcyclohexyl, etc.), and R ₃ is a hydroxyl group or a precursor group thereof. And a primary alkyl group having 3 to 10 carbon atoms (3-hydroxypropyl, 4-hydroxybutyl, etc.). A plurality of R ₂ and R ₃ may be the same or different.

R ₄ represents a hydrogen atom or a group that can be substituted on the benzene ring, and specifically, an alkyl group having 1 to 25 carbon atoms (methyl, ethyl, propyl, i-propyl, t-butyl, pentyl, hexyl, cyclohexyl). Etc.), halogenated alkyl groups (trifluoromethyl, perfluorooctyl etc.), cycloalkyl groups (cyclohexyl, cyclopentyl etc.), alkynyl groups (propargyl etc.), glycidyl groups, acrylate groups, methacrylate groups, aryl groups (phenyl etc.) , Heterocyclic groups (pyridyl, thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl, pyrimidinyl, pyridazinyl, selenazolyl, sriphoranyl, piperidinyl, pyrazolyl, tetrazolyl, etc.), halogen atoms (chlorine, bromine, iodine, fluorine), alkoxy groups ( Methoxy, Toxyl, propyloxy, pentyloxy, cyclopentyloxy, hexyloxy, cyclohexyloxy, etc.), aryloxy groups (phenoxy, etc.), alkoxycarbonyl groups (methyloxycarbonyl, ethyloxycarbonyl, butyloxycarbonyl, etc.), aryloxycarbonyl groups ( Phenyloxycarbonyl, etc.), sulfonamide groups (methanesulfonamide, ethanesulfonamide, butanesulfonamide, hexanesulfonamide group, cyclohexanesulfonamide, benzenesulfonamide, etc.), sulfamoyl groups (aminosulfonyl, methylaminosulfonyl, dimethylaminosulfonyl) Butylaminosulfonyl, hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl, 2-pyri Diylaminosulfonyl, etc.), urethane groups (methylureido, ethylureido, pentylureido, cyclohexylureido, phenylureido, 2-pyridylureido, etc.), acyl groups (acetyl, propionyl, butanoyl, hexanoyl, cyclohexanoyl, benzoyl, pyridinoyl, etc.) ), Carbamoyl group (aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl, propylaminocarbonyl, pentylaminocarbonyl group, cyclohexylaminocarbonyl, phenylaminocarbonyl, 2-pyridylaminocarbonyl), amide group (acetamide, propionamide, butanamide, hexane Amide, benzamide, etc.), sulfonyl group (methylsulfonyl, ethylsulfonyl, butylsulfonyl, cyclohexyl) Sulfonyl, phenylsulfonyl, 2-pyridylsulfonyl, etc.), amino group (amino, ethylamino, dimethylamino, butylamino, cyclopentylamino, anilino, 2-pyridylamino, etc.), cyano group, nitro group, sulfo group, carboxyl group, hydroxyl group Group, oxamoyl group and the like. These groups may be further substituted with these groups.

  n and m represent an integer of 0 to 2, and most preferably n and m are 0.

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

In the general formula (RD2), R ₅ is the same group as R _1, and R ₈ is the same group as R ₄ . The alkyl groups represented by R ₆ may be the same or different, but are not secondary or tertiary alkyl groups. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, and more preferably one having 1 to 10 carbon atoms. Particularly preferred is a primary alkyl group having 1 to 5 carbon atoms, and specific examples include groups such as methyl, ethyl, propyl, and butyl. R ₆ is most preferably methyl.

Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group, An ester group, a halogen atom, etc. are mentioned. R ₆ may form a saturated ring with (R ₈ ) _n and (R ₈ ) _m .

R ₇ represents a hydrogen atom or a group that can be substituted on a benzene ring. Examples of groups that can be substituted on the benzene ring include halogen atoms (fluorine, chlorine, bromine, etc.), alkyl groups, aryl groups, cycloalkyl groups, alkenyl groups, cycloalkenyl groups, alkynyl groups, amino groups, acyl groups, and acyloxy groups. , Acylamino group, sulfonylamino group, sulfamoyl group, carbamoyl group, alkylthio group, sulfonyl group, alkylsulfonyl group, sulfinyl group, cyano group, heterocyclic group and the like.

R ₇ is preferably methyl, ethyl, i-propyl, t-butyl, cyclohexyl, 1-methylcyclohexyl, 2-hydroxyethyl, 3-hydroxypropyl and the like. More preferred are methyl and 3-hydroxypropyl. The alkyl group is preferably a substituted or unsubstituted one having 1 to 20 carbon atoms, and specific examples thereof include methyl, ethyl, propyl, butyl and the like.

  Although the substituent of the alkyl group is not particularly limited, for example, aryl group, hydroxyl group, alkoxy group, aryloxy group, alkylthio group, arylthio group, acylamino group, sulfonamido group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group, An ester group, a halogen atom, etc. are mentioned.

  Among the compounds represented by the general formula (RD2), compounds preferably used are compounds satisfying the general formula (S) and the general formula (T) described in European Patent No. 1,278,101, specifically Include the compounds (1-24), (1-28) to (1-54), and (1-56) to (1-75) described on page 21-2.

  Specific examples of the compounds represented by general formula (RD1) and general formula (RD2) are shown below, but the present invention is not limited to these.

  These bisphenol compounds represented by the general formula (RD1) and general formula (RD2) can be easily synthesized by a conventionally known method.

  Examples of the reducing agent that can be used in the present invention include US Pat. Nos. 3,770,448, 3,773,512, 3,593,863, RD17029 and 29963, and JP-A-11- 119372, JP-A-2002-62616, and the like.

The amount of the reducing agent including the compound represented by the general formula (RD1) is preferably 1 × 10 ⁻² to 10 mol, particularly preferably 1 × 10 ^{−2 to} 1.5 mol, per mol of silver. It is.

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

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

The terms “more cold” and “more warm” regarding the color tone can be expressed by the hue angle hab at the minimum density Dmin and the optical density D = 1.0. That is, the hue angle hab is expressed by the following equation using the color coordinates a ^* and b ^* of the L ^* a ^* b ^* color space which is a color space recommended by the CIE in 1976 and having a substantially perceptual rate. Ask for.

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

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

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

(1) The optical density of the silver image obtained after heat development processing of the photothermographic material was measured at 0.5, 1.0, 1.5 and the lowest optical density, and CIE 1976 (L ^* u ^* v ^*) the horizontal axis of the color space u ^*, the vertical axis to the two-dimensional coordinates to v ^*, the u ^* at each optical density, v ^* was placed, the linear coefficient of determination of the regression line (multiple determination created) R ₂ is preferably 0.998 to 1.000. Furthermore, it is preferable that the v ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (v ^* / u ^* ) is 0.7 to 2.5.

(2) The optical density of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density, and the horizontal axis of the CIE 1976 (L ^* a ^* b ^* ) color space. Is a ^* , and the vertical axis is b ^*. The a ^* and b ^* at each optical density are arranged in two-dimensional coordinates, and the determination coefficient (multiple determination) R _{2 of} the created linear regression line is 0.998 to It is preferable that it is 1.000. Furthermore, it is preferable that the b ^* value of the intersection with the vertical axis of the linear regression line is −5 to 5 and the slope (b ^* / a ^* ) is 0.7 to 2.5.

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

A four-stage wedge sample including an unexposed portion and optical densities of 0.5, 1.0, and 1.5 is prepared using a heat development apparatus. Each wedge density portion is measured with a spectral colorimeter (Minolta (former name): CM-3600d, etc.) to calculate u ^* , v ^* or a ^* , b ^* . The measurement conditions at that time are F7 light source as the light source, the viewing angle is 10 degrees, and the measurement is performed in the transmission measurement mode. Plot u ^* , v ^* or a ^* , b ^* measured on a graph with u ^* or a ^{* on} the horizontal axis and v ^* or b ^{* on the} vertical axis to obtain a linear regression line, and the coefficient of determination (multiple determination) Find R ₂ , intercept and slope.

  Next, a specific method for obtaining a linear regression line having the above characteristics will be described.

  In the present invention, adjustment of the addition amount of a compound or the like directly or indirectly involved in the development reaction process of a reducing agent (developer), silver halide grains, aliphatic silver carboxylate and the following toning agent, etc. Thus, the developed silver shape can be optimized to obtain a preferable color tone. For example, when the developed silver shape is dendritic, it tends to be bluish, and when it is made filamentous, it tends to be yellowish. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

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

  When performing rapid processing using a compact laser imager with a short cooling section length, there may be a problem that the silver color tone is greatly collapsed from the neutral preferred color tone compared to the normal processing. In order to solve the problem, it is preferable to use a compound (such as a leuco dye or a coupler compound) that develops an imagewise color image during heat development to form a dye image in addition to the toning agent such as the phthalazine compound. These compounds include compounds that form a dye image that develops a color upon thermal development and has a maximum absorption wavelength of 360 to 450 nm, or compounds that develop a color and develop a dye image that exhibits a maximum absorption wavelength of 600 to 700 nm upon thermal development. However, the case where both compounds are included is particularly preferable for obtaining a good silver tone.

  As these compounds, it is preferable to use couplers disclosed in JP-A-11-288057, European Patent 1,134,611A2, etc., or leuco dyes described in detail below.

(Leuco dye)
The photothermographic material of the present invention can also be adjusted in color tone using a leuco dye as described above. Preferably, the leuco dye may be any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80 to 200 ° C. for about 0.5 to 30 seconds. Any leuco dye that oxidizes to form a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  Representative leuco dyes suitable for use in the present invention are not particularly limited, such as biphenol leuco dyes, phenol leuco dyes, indoaniline leuco dyes, acrylated azine leuco dyes, phenoxazine leuco dyes, phenodiazine leuco dyes and And phenothiazine leuco dye. US Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4 No. 4,022,617, No. 4,123,282, No. 4,368,247, No. 4,461,681, and JP-A-50-36110, No. 59-206931, JP-A-5-204087. No. 11-231460, JP-A Nos. 2002-169249, 2002-236334, and the like.

  In order to adjust to a predetermined color tone, it is preferable to use leuco dyes of various colors singly or in combination of a plurality of types. Furthermore, with the use of a highly active reducing agent for rapid processing, the color tone (especially yellow) changes depending on the amount and ratio of use, and fine silver halide grains are used for development. In order to prevent the image from becoming excessively reddish, particularly in the high density part where the density is 2.0 or more, the leuco dye that develops yellow and cyan colors is used in combination with the reduction of the silver particle size. It is preferable to adjust the amount used.

  The color density is preferably adjusted appropriately in relation to the color tone of the developed silver itself. In the present invention, the color tone is adjusted so as to have an image in the above preferable color tone range by developing the color so as to have a reflection optical density of 0.01 to 0.05 or a transmission optical density of 0.005 to 0.50. preferable. In the present invention, the sum of the maximum densities at the maximum absorption wavelength of the dye image formed with the leuco dye is preferably 0.01 to 0.50, more preferably 0.02 to 0.30, and particularly preferably 0.0. It is preferable to develop the color so as to have 03 to 0.10. The maximum absorption wavelength of the dye image can be obtained by measuring the spectral absorption spectrum of the photothermographic material after heat development.

(Yellow coloring leuco dye)
As described above, the photothermographic material according to the invention preferably adjusts the color tone using a leuco dye. In particular, a color image forming agent whose absorbance at 360 to 450 nm increases when oxidized is preferably used as a yellow coloring leuco dye. Among these, a color image forming agent represented by the following general formula (YA) is particularly preferable.

In the formula, R ₁₁ represents a substituted or unsubstituted alkyl group, R ₁₂ represents a hydrogen atom, a substituted or unsubstituted alkyl group or an acylamino group, and R ₁₁ and R ₁₂ are 2-hydroxyphenylmethyl groups. There is nothing. R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group, and R ₁₄ represents a substituent that can be substituted on the benzene ring.

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

In General Formula (YA), R ₁₁ represents a substituted or unsubstituted alkyl group. When R ₁₂ is a substituent other than a hydrogen atom, R ₁₁ represents an alkyl group. The alkyl group is preferably an alkyl group having 1 to 30 carbon atoms and may have a substituent. Specifically, methyl, ethyl, butyl, octyl, i-propyl, t-butyl, t-octyl, t-pentyl, sec-butyl, cyclohexyl, 1-methyl-cyclohexyl and the like are preferable. It is preferably a group sterically larger than i-propyl (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl, etc.). Secondary or tertiary alkyl groups are preferred, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferred.

Examples of the substituent that R ₁₁ may have include a halogen atom, an aryl group, an alkoxy group, an amino group, an acyl group, an acylamino group, an alkylthio group, an arylthio group, a sulfonamido group, an acyloxy group, an oxycarbonyl group, and a carbamoyl group. , Sulfamoyl group, sulfonyl group, phosphoryl group and the like.

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

The acylamino group represented by R ₁₂ may be unsubstituted or substituted, and specific examples include acetylamino, alkoxyacetylamino, and aryloxyacetylamino groups. R ₁₂ is preferably a hydrogen atom or an unsubstituted alkyl group having 1 to 24 carbon atoms, and specific examples include methyl, i-propyl, and t-butyl.

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

R ₁₄ is a group capable of substituting on the benzene ring, and is, for example, the same group as described for the substituent R ₄ in formula (RD1). R ₁₄ is preferably a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms or an oxycarbonyl group having 2 to 30 carbon atoms, and more preferably an alkyl group having 1 to 24 carbon atoms. Examples of the substituent of the alkyl group include an aryl group, an amino group, an alkoxy group, an oxycarbonyl group, an acylamino group, an acyloxy group, an imide group, and a ureido group, and more preferable examples include an aryl group, an amino group, an oxycarbonyl group, and an alkoxy group. preferable. These alkyl group substituents may be further substituted with these substituents.

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

In the formula, Z represents —S— or —C (R ₂₁ ) (R ₂₁ ′) —, and R ₂₁ and R ₂₁ ′ each represents a hydrogen atom or a substituent.

Examples of the substituent represented by R ₂₁ and R ₂₁ ′ include the same groups as the substituents exemplified in the description of R _{1 in} the general formula (RD1). R ₂₁ and R ₂₁ ′ are preferably a hydrogen atom or an alkyl group.

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ each represent a substituent, and examples of the substituent include the same groups as those described for R ₂ and R ₃ in the general formula (RD1).

R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are preferably an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group, with an alkyl group being more preferred. Examples of the substituent on the alkyl group include the same groups as those described in the description of the substituent in the general formula (RD1). R ₂₂ , R ₂₃ , R ₂₂ ′ and R ₂₃ ′ are more preferably tertiary alkyl groups such as t-butyl, t-pentyl, t-octyl and 1-methyl-cyclohexyl.

R ₂₄ and R ₂₄ ′ each represent a hydrogen atom or a substituent, and examples of the substituent include the same groups as the substituents described in the description of R ₄ in formula (RD1).

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

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

  The addition amount of the compound of the general formula (YA) (including the hindered phenol compound and the compound of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0.0005, per mol of silver. It is -0.01 mol, More preferably, it is 0.001-0.008 mol.

  The addition ratio of the yellow coloring leuco dye to the total sum of the reducing agents represented by the general formulas (RD1) and (RD2) is preferably 0.001 to 0.2 in terms of molar ratio, More preferably, it is -0.1.

  In the photothermographic material of the invention, the sum of the maximum densities at the maximum absorption wavelength of a dye image formed with a yellow color-forming leuco dye is preferably 0.01 to 0.50, more preferably 0.02 to 0.02. It is preferable to cause the color to be 0.30, particularly preferably 0.03 to 0.10.

(Cyan coloring leuco dye)
In the photothermographic material of the invention, it is preferable to adjust the color tone by using a cyan coloring leuco dye in addition to the yellow coloring leuco dye.

  The cyan color-forming leuco dye is preferably any colorless or slightly colored compound that is oxidized to a colored form when heated at a temperature of about 80-200 ° C. for about 0.5-30 seconds, Any leuco dye that can be oxidized by an oxidant of a reducing agent to form a pigment can be used. Compounds that are pH sensitive and can be oxidized to a colored state are useful.

  In particular, a color image forming agent whose absorbance at 600 to 700 nm increases when oxidized is preferably used as a cyan color-forming leuco dye. Examples of these compounds include compounds of general formulas (I) to (IV) disclosed in JP-A-59-206831 (particularly compounds having λmax in the range of 600 to 700 nm) and JP-A-5-204087 (specific examples). Are described in paragraphs “0032” to “0037” (1) to (18)) and compounds of general formulas 4 to 7 in JP-A No. 11-231460 (specifically, in paragraph “0105”). No. 1-79 compounds).

  Next, specific examples of the cyan chromogenic leuco dye will be shown, but the invention is not limited thereto.

  The addition amount of the cyan coloring leuco dye is usually 0.00001 to 0.05 mol / Ag1 mol, preferably 0.0005 to 0.02 mol / Ag1 mol, more preferably 0.001 to 0.01 mol. / Ag1 mol. The addition ratio of the cyan coloring leuco dye to the sum of the reducing agents represented by the general formulas (RD1) and (RD2) is preferably 0.001 to 0.2 in terms of molar ratio, and 0.005. More preferably, it is -0.1.

  In the photothermographic material according to the invention, the sum of the maximum densities at the maximum absorption wavelength of a dye image formed with a cyan leuco dye is preferably 0.01 to 0.50, more preferably 0.02 to 0.00. It is preferable to develop the color so that it is 30, particularly preferably 0.03 to 0.10.

  In the present invention, by using a magenta color-forming leuco dye in combination with the yellow color-forming leuco dye and the cyan color-forming leuco dye, it is possible to further adjust the color tone.

  As a method for adding the compounds represented by the general formulas (YA) and (YB) and the cyan color-forming leuco dye, they can be added in the same manner as the method for adding the reducing agent represented by the general formula (RD1). , Solution form, emulsified dispersion form, solid fine particle dispersion form, etc. may be contained in the coating solution by any method and contained in the photothermographic material.

  The compounds of the general formulas (RD1), (RD2), general formulas (YA) and (YB) and the cyan color-forming leuco dye are preferably contained in a photosensitive layer (image forming layer) containing an organic silver salt. One may be contained in the photosensitive layer and the other may be contained in the non-photosensitive layer adjacent to the photosensitive layer, or both may be contained in the non-photosensitive layer. When the photosensitive layer is composed of a plurality of layers, they may be contained in separate layers.

(binder)
In the photothermographic material according to the invention, the photosensitive layer and the non-photosensitive layer can contain a binder for various purposes. The binder contained in the photosensitive layer is capable of carrying an organic silver salt, silver halide grains, a reducing agent, and other components, and is preferably transparent or translucent and generally colorless, and is a natural polymer or synthetic polymer. , And copolymers and other media for forming a film, for example, those described in paragraph “0069” of JP-A No. 2001-330918. Among these, preferred binders for the photosensitive layer are polyvinyl acetals, and particularly preferred is polyvinyl butyral. These will be described in detail later.

  In addition, for non-photosensitive layers such as overcoat layers and undercoat layers, especially protective layers and backcoat layers, cellulose esters which are polymers having a higher softening temperature, particularly polymers such as triacetyl cellulose and cellulose acetate butyrate. Is preferred. In addition, a binder can be used in combination of 2 or more types as needed.

The _{binder, -COOM, -SO 3 M, -OSO} 3 M, -P = O (OM) 2, -O-P = O (OM) 2, -N (R) 2, -N + (R) ₃ (M represents a hydrogen atom or an alkali metal base, R represents a hydrocarbon group), an epoxy group, —SH, —CN, and the like introduced by copolymerization or addition reaction. It is preferable to use, and —SO ₃ M and —OSO ₃ M are particularly preferable. The amount of such a polar group is 1 × 10 ⁻¹ to 1 × 10 ⁻⁸ mol / g, preferably 1 × 10 ⁻² to 1 × 10 ⁻⁶ mol / g.

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 15: 1 to 1: 2 (mass ratio), and particularly 8: 1 to 1: 1. The range of is preferable. That is, it is preferable that the binder amount of the photosensitive layer is a 1.5~6g / m ^2, more preferably from 1.7~5g / m ^2. By making the amount of the binder within this range, the increase in the density of the unexposed area is reduced, which is preferable.

  The glass transition temperature (Tg) of the binder is preferably 70 to 105 ° C. Tg can be obtained by measuring with a differential scanning calorimeter, and the intersection of the baseline and the endothermic peak slope is defined as Tg. Tg in the present invention is determined by the method described in “Polymer Handbook” III-139-179 (1966, Wiley and Sun, Inc.) by Brand Wrap et al.

  Tg when the binder is a copolymer resin is obtained by the following formula.

Tg (copolymer) (° C.) = V1Tg1 + v2Tg2 +... + VnTgn
In the formula, v1, v2,... Vn represent mass fractions of monomers in the copolymer, and Tg1, Tg2,... Tgn are single polymers obtained from the respective monomers in the copolymer. Represents Tg (° C). The accuracy of Tg calculated according to the above equation is ± 5 ° C.

  Use of a binder having a Tg of 70 to 105 ° C. is preferable because a sufficient maximum density can be obtained in image formation.

  The binder used in the present invention has a Tg of 70 to 105 ° C., a number average molecular weight of 1,000 to 1,000,000, preferably 10,000 to 500,000, and a degree of polymerization of about 50 to 1,000. Is. Examples of the polymer or copolymer containing an ethylenically unsaturated monomer as a constituent unit include those described in paragraph No. “0069” of JP-A No. 2001-330918. Among these, methacrylic acid alkyl esters, methacrylic acid aryl esters, styrenes and the like are particularly preferred examples. Among such polymer compounds, a polymer compound having an acetal group is preferably used. Even a high molecular compound having an acetal group is more preferably a polyvinyl acetal having an acetoacetal structure, for example, U.S. Pat. Nos. 2,358,836, 3,003,879, 2,828,204, UK The polyvinyl acetal shown by patent 771,155 etc. can be mentioned.

  As the polymer compound having an acetal group, a compound represented by the general formula (V) described in “150” of JP-A No. 2002-287299 is particularly preferable.

As the polyurethane resin that can be used in the present invention, known resins such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, polyester polycarbonate polyurethane, and polycaprolactone polyurethane can be used. Moreover, it is preferable to have a total of 2 or more hydroxyl groups, at least one at each polyurethane molecule end. Since hydroxyl groups are cross-linked with polyisocyanate which is a curing agent to form a three-dimensional network structure, it is more preferable that the hydroxyl groups are contained in the molecule. In particular, it is preferable that the hydroxyl group is at the molecular end because the reactivity with the curing agent is high. The polyurethane preferably has 3 or more hydroxyl groups at the molecular terminals, and particularly preferably 4 or more. In the present invention, when polyurethane is used, Tg is preferably 70 to 105 ° C., elongation at break is 100 to 2,000%, and break stress is preferably 0.5 to 100 N / mm ² .

  These polymer compounds (polymers) may be used alone or in a blend of two or more.

  In the photosensitive layer according to the present invention, the above polymer is preferably used as a main binder. The main binder mentioned here means “a state in which the polymer occupies 50% by mass or more of the total binder of the photosensitive layer”. Therefore, other polymers may be blended and used within a range of less than 50% by weight of the total binder. These polymers are not particularly limited as long as they can be arbitrarily mixed with the polymer according to the present invention. More preferably, a polyvinyl acetate, a polyacryl resin, a urethane resin, etc. are mentioned.

  An organic gelling agent may be contained in the photosensitive layer. Incidentally, the organic gelling agent referred to here has a function of giving a yield value to the system by adding it to an organic liquid, such as polyhydric alcohols, and eliminating or reducing the fluidity of the system. The compound which has.

  It is also a preferred embodiment that the photosensitive layer coating solution contains an aqueous dispersed polymer latex. In this case, a polymer latex in which 50% by mass or more of the total binder in the coating solution for the photosensitive layer is dispersed in water is preferable. When a polymer latex is used for the preparation of the photosensitive layer, 50% by mass or more of the total binder in the photosensitive layer is preferably a polymer latex-derived polymer, more preferably 70% by mass or more.

  Here, the polymer latex is a water-insoluble hydrophobic polymer dispersed as fine particles in a water-soluble dispersion medium. As the dispersion state, the polymer is emulsified in a dispersion medium, the emulsion is polymerized, the micelle is dispersed, or the polymer molecule has a partially hydrophilic structure and the molecular chain itself is molecularly dispersed. Any of them may be used. The average particle diameter of the dispersed particles is preferably 1 to 50,000 nm, more preferably in the range of about 5 to 1,000 nm. The particle size distribution of the dispersed particles is not particularly limited, and may have a wide particle size distribution or a monodispersed particle size distribution.

  The polymer latex that can be used in the photothermographic material may be a so-called core / shell type latex in addition to a normal polymer latex having a uniform structure. In this case, it may be preferable to change the Tg of the core and the shell. The minimum film-forming temperature (MFT) of the polymer latex used in the present invention is preferably -30 to 90 ° C, more preferably about 0 to 70 ° C. In addition, a film-forming auxiliary may be added to control the minimum film-forming temperature. The film-forming aid, also called a plasticizer, is an organic compound (usually an organic solvent) that lowers the minimum film-forming temperature of polymer latex. For example, “Synthetic Latex Chemistry (Souichi Muroi, published by Kobunshi Publishing Co., Ltd.) , 1970).

  Examples of the polymer species used for the polymer latex include acrylic resins, vinyl acetate resins, polyester resins, polyurethane resins, rubber resins, vinyl chloride resins, vinylidene chloride resins, polyolefin resins, and copolymers thereof. The polymer may be a linear polymer, a branched polymer, or a crosslinked polymer. The polymer may be a so-called homopolymer in which a single monomer is polymerized or a copolymer in which two or more monomers are polymerized. In the case of a copolymer, it may be a random copolymer or a block copolymer. The molecular weight of the polymer is a number average molecular weight and is usually about 5,000 to 1,000,000, preferably about 10,000 to 100,000. When the molecular weight is within this range, both the mechanical strength and film-forming property of the photosensitive layer are satisfied.

  The polymer latex preferably has an equilibrium moisture content of 0.01 to 2% by mass or less, more preferably 0.01 to 1% by mass at 25 ° C. and 60% RH (relative humidity). For the definition and measurement method of the equilibrium moisture content, for example, “Polymer Engineering Course 14, Polymer Material Testing Method (Edited by Polymer Society, Jinshokan)” can be referred to.

  Specific examples of the polymer latex include latexes described in “0173” of JP-A No. 2002-287299. These polymers may be used alone or in combination of two or more as required. As a polymer seed | species of a polymer latex, what contains about 0.1-10 mass% of carboxylic acid components, such as an acrylate or a methacrylate component, is preferable. Furthermore, if necessary, a hydrophilic polymer such as gelatin, polyvinyl alcohol, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose or the like may be added within a range of 50% by mass or less of the total binder. The addition amount of these hydrophilic polymers is preferably 30% by mass or less based on the total binder of the photosensitive layer.

  Regarding the order of addition of the organic silver salt and the aqueous dispersed polymer latex in the preparation of the coating solution for the photosensitive layer, any of them may be added first or simultaneously, but preferably the polymer latex is used. Later.

  Furthermore, it is preferable that an organic silver salt and further a reducing agent are mixed before adding the polymer latex. In addition, after mixing the organic silver salt and the polymer latex, if the temperature to be aged is too low, the coated surface shape is impaired, and if it is too high, there is a problem that fog increases, so the coating solution after mixing is 30 to 65 ° C. It is preferable that the above time is elapsed. Furthermore, it is preferable to be aged at 35 to 60 ° C, and a time at 35 to 55 ° C is particularly preferable. In order to maintain the temperature in this way, it is sufficient to keep the temperature of the coating solution preparation tank or the like.

  For coating of the coating solution for the photosensitive layer, it is preferable to use a coating solution that has passed 30 minutes to 24 hours after mixing the organic silver salt and the aqueous polymer latex, and more preferably, 60 minutes after mixing. It is to make -12 hours pass, and it is especially preferable to use the coating liquid which passed 120 minutes-10 hours.

  Here, “after mixing” means after the organic silver salt and the aqueous polymer latex are added and the additive material is uniformly dispersed.

(Crosslinking agent)
The photosensitive layer can contain a cross-linking agent that can link the binders together by bridging bonds. This is known to improve filming and reduce development unevenness, but also has an effect of suppressing fogging during storage and generation of printout silver after development.

  Examples of the crosslinking agent to be used include various crosslinking agents conventionally used for photographic light-sensitive materials, for example, aldehyde-based, epoxy-based, ethyleneimine-based, vinylsulfone-based, sulfone described in JP-A-50-96216. Acid ester-based, acryloyl-based, carbodiimide-based, and silane compound-based crosslinking agents are used. Preferred are isocyanate-based, silane-based, epoxy-based compounds, and acid anhydrides shown below.

  Isocyanate-based crosslinking agents are isocyanates having at least two isocyanate groups and adducts thereof (adducts), specifically, aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, and benzene diisocyanate. , Naphthalene diisocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates and divalent or trivalent polyalcohols with these isocyanates And adducts. As specific examples, isocyanate compounds described on pages 10 to 12 of JP-A-56-5535 can be used.

  In addition, the adduct of isocyanate and polyalcohol has particularly high ability to improve interlayer adhesion and prevent layer peeling, image shift and bubble generation. Such isocyanate may be placed in any part of the photothermographic material. For example, the photosensitive layer of the support such as a photosensitive layer, a surface protective layer, an intermediate layer, an antihalation layer, an undercoat layer in the support (especially when the support is paper, it can be included in the size composition) It can be added to any layer on the side and can be added to one or more of these layers.

  As the thioisocyanate-based crosslinking agent that can be used in the present invention, compounds having a thioisocyanate structure corresponding to the above-mentioned isocyanates are also useful.

  The amount of the crosslinking agent used is usually in the range of 0.001 to 2 mol, preferably 0.005 to 0.5 mol, with respect to 1 mol of silver.

  The isocyanate compound and thioisocyanate compound that can be contained in the present invention are preferably compounds that function as the above-mentioned crosslinking agent, but a good result can be obtained even if the compound has only one functional group.

  Examples of the silane compound include compounds represented by general formulas (1) to (3) disclosed in JP-A No. 2001-264930.

  The epoxy compound that can be used is not limited as long as it has one or more epoxy groups and the number of epoxy groups, molecular weight, and the like. The epoxy group is preferably contained in the molecule as a glycidyl group via an ether bond or an imino bond. The epoxy compound may be any of a monomer, an oligomer, a polymer, etc., and the number of epoxy groups present in the molecule is usually about 1 to 10, preferably 2 to 4. When the epoxy compound is a polymer, it may be either a homopolymer or a copolymer, and the number average molecular weight Mn is particularly preferably in the range of about 2,000 to 20,000.

  The acid anhydride used in the present invention is a compound having at least one acid anhydride group represented by the following structural formula. The number of acid anhydride groups, the molecular weight, and the like are not particularly limited as long as they have one or more acid anhydride groups.

-CO-O-CO-
The said epoxy compound and acid anhydride may use only 1 type, or may use 2 or more types together. The addition amount is not particularly limited, but is preferably in the range of 1 × 10 ⁻⁶ to 1 × 10 ⁻² mol / m ² , more preferably in the range of 1 × 10 ⁻⁵ to 1 × 10 ⁻³ mol / m ² . It is. This epoxy compound or acid anhydride can be added to any layer on the photosensitive layer side of the support, such as the photosensitive layer, surface protective layer, intermediate layer, antihalation layer, subbing layer, etc. It can be added to one layer or two or more layers.

(Silver saving agent)
A silver saving agent can be contained in the photosensitive layer or the non-photosensitive layer. The silver saving agent as used herein refers to a compound that can reduce the amount of silver necessary to obtain a certain silver image density.

  Although various mechanisms for the function of reducing the required silver amount are conceivable, a compound having a function of improving the covering power of developed silver is preferred. Here, the covering power (CP: covering power) of developed silver refers to the optical density per unit amount of silver. This silver saving agent can be present in the photosensitive layer, the non-photosensitive layer, or any of them. Preferred examples of the silver saving agent include hydrazine derivatives, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds.

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

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

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

  Specific examples of the quaternary onium compound include triphenyltetrazolium.

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

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

  Examples of preferable silver saving agents are listed below. The present invention is not limited to these.

(Thermal solvent)
The photothermographic material of the present invention preferably contains a thermal solvent. Here, the thermal solvent is defined as a material capable of lowering the heat development temperature by 1 ° C. or more as compared with a photothermographic material not containing a thermal solvent by containing a thermal solvent. More preferably, the material can lower the heat development temperature by 2 ° C. or more, and particularly preferably the material that can lower the temperature by 3 ° C. or more. For example, with respect to the photothermographic material A containing a thermal solvent, when the photothermographic material containing no thermal solvent from the photothermographic material A is B, the photothermographic material B is exposed to a thermal development temperature of 120 ° C. A thermal solvent is used when the heat development temperature is 119 ° C. or less to obtain the density obtained by processing with a heat development time of 20 seconds with the same exposure amount and heat development time for the photothermographic material A.

  The thermal solvent has a polar group as a substituent and is preferably represented by the general formula (TS), but is not limited thereto.

General formula (TS) (Y) nZ
In the formula, Y represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group or a heterocyclic group. Z is hydroxyl group, carboxyl group, amino group, amide group, sulfonamide group, phosphoric acid amide group, cyano group, imide group, ureido group, sulfoxide group, sulfone group, phosphine group, phosphine oxide group, or nitrogen-containing heterocyclic group Represents. n represents an integer of 1 to 3, and corresponds to the valence of Z. When n is 2 or more, the plurality of Y may be the same or different. Y may further have a substituent, and may have a group represented by Z as a substituent.

  Y will be described in more detail. Y is a linear, branched or cyclic alkyl group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30, particularly preferably 1 to 25, methyl, ethyl, propyl, i-propyl, sec-butyl, t-butyl, t-octyl, amyl, t-amyl, dodecyl, tridecyl, octadecyl, eicosyl, docosyl, cyclopentyl, cyclohexyl, etc.), an alkenyl group (preferably having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, particularly preferably Is 2 to 25, vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an aryl group (preferably 6 to 40, more preferably 6 to 30, particularly preferably 6 to 25, phenyl, p-methylphenyl, naphthyl, etc.), heterocyclic groups (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably It is 12, representing pyridyl, pyrazinyl, imidazolyl, pyrrolidyl, etc.). These substituents may be further substituted with other substituents, or may be bonded to each other to form a ring. Examples of the substituent that Y may further include include a substituent described in “0015” of JP-A No. 2004-21068.

  The reason why development activity is achieved by using a hot solvent is that the hot solvent melts near the development temperature and is compatible with substances involved in development, allowing reaction at a lower temperature than when no hot solvent is added. It is thought to be because. Since heat development is a reduction reaction involving a carboxylic acid having a relatively high polarity or a silver ion transporter, it is preferable to form a reaction field having an appropriate polarity with a thermal solvent having a polar group. .

  The melting point of the thermal solvent preferably used in the present invention is 50 to 200 ° C, more preferably 60 to 150 ° C. In particular, in a photothermographic material that emphasizes stability to an external environment such as image storage stability, which is the object of the present invention, a thermal solvent having a melting point of 100 to 150 ° C. is preferable.

  Specific examples of the hot solvent include a compound described in “0017” of JP-A No. 2004-21068, a compound described in “0027” of US 2002/0025498, MF-1 to 3, 6, 7, 912, 15-22 can be mentioned.

Preferably the added amount of thermal solvent is 0.01~5.0g / m ^2, more preferably 0.05~2.5g / m ^2, more preferably at 0.1 to 1.5 g / m ² is there.

  The thermal solvent is preferably contained in the photosensitive layer. Moreover, the said thermal solvent may be used independently and may be used in combination of 2 or more type. The thermal solvent may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, or a solid fine particle dispersion form and added to the photothermographic material.

  Well-known emulsification dispersion methods include dissolving oil using an oil such as dibutyl phthalate, tricresyl phosphate, glyceryl triacetate or diethyl phthalate, or an auxiliary solvent such as ethyl acetate or cyclohexanone, and mechanically producing an emulsified dispersion. The method of doing is mentioned.

  The solid fine particle dispersion method is a method of producing a solid dispersion by dispersing a hot solvent powder in a suitable solvent such as water by a ball mill, a colloid mill, a vibrating ball mill, a sand mill, a jet mill, a roller mill or ultrasonic waves. Is mentioned. At that time, protective colloid (eg, polyvinyl alcohol), surfactant (eg, anionic surfactant such as sodium tri-i-propylnaphthalenesulfonate (a mixture of three i-propyl groups with different substitution positions)) May be used. In the mills, beads such as zirconia are usually used as a dispersion medium, and Zr and the like eluted from these beads may be mixed in the dispersion. Although it depends on the dispersion conditions, it is usually in the range of 1 to 1,000 ppm. If the content of Zr in the photothermographic material is 0.5 mg or less per 1 g of silver, there is no practical problem. The aqueous dispersion preferably contains a preservative (benzoisothiazolinone sodium salt).

(Anti-fogging agent, image stabilizer)
Any constituent layer of the photothermographic material contains an antifoggant for preventing fogging during storage before thermal development and an image stabilizer for preventing image deterioration after thermal development. It is preferable.

  Hereinafter, the antifoggant and the image stabilizer that can be used in the photothermographic material of the invention will be described.

As reducing agents according to the present invention, reducing agents having protons such as bisphenols and sulfonamidophenols are mainly used, so that these hydrogens are stabilized, the reducing agents are deactivated, and silver ions are reduced. It is preferable that a compound capable of preventing the reaction is contained. Further, it is preferable to contain a compound capable of oxidatively bleaching silver atoms or silver metal (silver clusters) generated during storage of raw photosensitive materials and images. Specific examples of compounds having these functions include biimidazole compounds and iodonium compounds. The addition amount of the biimidazole compound and iodonium compound is in the range of 0.001 to 0.1 mol / m ² , preferably 0.005 to 0.05 mol / m ² .

  When the reducing agent used in the present invention has an aromatic hydroxyl group (—OH), particularly in the case of bisphenols, a non-reducing compound having a group capable of forming a hydrogen bond with these groups It is preferable to use together. Specific examples of particularly preferred hydrogen bonding compounds include compounds (II-1) to (II-40) described in [0061] to [0064] of JP-A-2002-90937.

  Many compounds capable of releasing halogen atoms as active species are known as antifogging and image stabilizers. Specific examples of these active halogen atom releasing compounds include compounds represented by general formula (9) described in JP-A No. 2002-287299 [0264] to [0271].

  The addition amount of these compounds is preferably within a range in which the increase in printout silver due to the formation of silver halide due to the reaction between the halogen released from the compound and silver ions does not become a problem. Specific examples of the compound that generates these active halogen atoms include, in addition to the above patents, compounds (III-1 to 23) described in “0086” to “0087” of JP-A No. 2002-169249, Compounds 1-1a to 1o and 1-2a to 2o described in "0031" to "0034" of 2003-50441, Compounds 2a to 2z, 2aa to 2ll, 2-1a to 1f described in "0050" to "0056" And compounds 5-1 to 32 described in “0055” to “0058” of JP-A No. 2003-91054 and compounds 5-1 to 10 described in paragraphs “0069” to “0072”.

  Antifoggants preferably used include, for example, compound examples a to j described in “0012” of JP-A-8-314059, thiosulfonate esters A to K described in “0028” of JP-A-7-209797, Compound examples (1) to (44) described on page 14 of JP-A No. 55-140833, compounds (I-1 to 6) described in “0063” of JP-A No. 2001-13627, (0066) C-1 to 3), compounds (III-1 to 108) described in “0027” of JP-A-2002-90937, compounds of vinyl sulfones and / or β-halosulfones, “0013” of JP-A-6-208192 VS-1-7, Compounds HS-1-5, and sulfonylbenzotriazole compounds described in JP-A-2000-330235. Products, substituted propene nitrile compounds, PR-01 to 08 described in JP-T 2000-515995, compounds (1) to 132 described in JP-A-2002-207273, "0042" to "0051", and the like Can be mentioned.

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

  In addition to the above compounds, the photothermographic material may contain various compounds conventionally known as antifoggants, but may generate reactive species similar to the above compounds. Even a compound that can be used may be a compound that has a different antifogging mechanism. For example, U.S. Pat. Nos. 3,589,903, 4,546,075, 4,452,885, JP-A-59-57234, U.S. Pat. No. 3,874,946, 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, and 631,176.

(Toning agent)
The photothermographic material preferably contains a toning agent (toner) that adjusts the color tone of silver as required in a dispersed state in a normal (organic) binder matrix.

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

  Imides (succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide, etc.); mercaptans (3-mercapto-1,2,4-triazole); 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 derivatives and anhydrides thereof (phthalic acid, 4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalic acid The combination and the like with at least one compound selected from the anhydrous and the like).

  Particularly preferred toning agents are combinations of phthalazinone or phthalazine with phthalic acids and phthalic anhydrides. Phthalazine and its derivatives and phthalazinone and its derivatives are preferably used in a molar ratio of 0.1 to 2.0, more preferably 0.2 to 1.5, and still more preferably 0, with respect to the reducing agent. .3 to 1.0. In addition, phthalic acid and its derivatives, phthalic anhydride and its derivatives are preferably used in the range of 0.0001 mol to 1 mol, more preferably 0.001 to 0.5 mol per mol of silver applied. Mol, more preferably 0.002 to 0.2 mol.

(Fluorine surfactant)
In the present invention, a fluorine-based interface represented by the following general formula (SF) is used in order to improve transportability and environmental suitability (accumulation in a living body) of a photothermographic material in a laser imager (thermal development processing apparatus). An activator is preferably used.

Formula (SF) (Rf− (L ₁ ) _n1 −) _p − (Y) _m1 − (A) _q
In the formula, Rf represents a substituent containing a fluorine atom, L1 represents a divalent linking group having no fluorine atom, Y represents a (p + q) -valent linking group having no fluorine atom, and A is An anion group or a salt thereof is represented, n1 and m1 each represent an integer of 0 or 1, and p and q each represent an integer of 1 to 3. However, when q is 1, n1 and m1 are not 0 at the same time.

  Rf represents a substituent containing a fluorine atom. Examples of the substituent containing the fluorine atom include a fluorinated alkyl group having 1 to 25 carbon atoms (trifluoromethyl, trifluoroethyl, perfluoroethyl, perfluoro Butyl, perfluorooctyl, perfluorododecyl, perfluorooctadecyl, etc.) or alkenyl fluoride groups (perfluoropropenyl, perfluorobutenyl, perfluorononenyl, perfluorododecenyl, etc.). Rf preferably has 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms. Rf preferably has 2 to 12 fluorine atoms, more preferably 3 to 12 fluorine atoms.

L ₁ represents a divalent linking group having no fluorine atom. Examples of the linking group include an alkylene group (methylene, ethylene, butylene, etc.) and an alkyleneoxy group (methyleneoxy, ethyleneoxy, butyleneoxy, etc.). , Oxyalkylene groups (oxymethylene, oxyethylene, oxybutylene, etc.), oxyalkyleneoxy groups (oxymethyleneoxy, oxyethyleneoxy, oxyethyleneoxyethyleneoxy, etc.), phenylene groups, oxyphenylene groups, phenyloxy groups, oxyphenyl Examples thereof include an oxy group or a group obtained by combining these groups.

  A represents an anionic group or a salt thereof. For example, a carboxylic acid group or a salt thereof (sodium, potassium and lithium salts), a sulfonic acid group or a salt thereof (sodium, potassium and lithium salts), a sulfuric acid half ester group or a salt thereof ( Sodium, potassium and lithium salts), and phosphoric acid groups or salts thereof (such as sodium and potassium salts).

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

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

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

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

  Specific examples of the fluorine-based surfactant include compounds (FS-1 to 66) described in “0029” to “0040” of JP-A No. 2003-149766, and “0014” of JP-A No. 2004-021084. Compounds 1-1 to 4, compounds 2-1 to 10 described in “0019”, compounds described in “0025” of Japanese Patent Application Laid-Open No. 2004-077772, and compounds described in “0030”.

  The preferred specific compounds of the fluorine-based surfactant represented by the general formula (SF) are shown below.

  Further, as fluorine-based surfactants other than those described above, compounds described in “0035” of JP-A No. 2004-117505, JP-A Nos. 2000-214554, 2003-156819, 2003-177494, 2003-2003 114504, 2003-270754, and JP-A-2003-270760 may be used.

  In the present invention, the anionic fluorine-containing surfactant represented by the general formula (SF) and a known nonionic fluorine-containing surfactant are used in combination from the viewpoint of improving charging characteristics and coating properties. Particularly preferred.

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

The addition amount of the fluorine-based surfactant represented by the general formula (SF) is preferably 1 × 10 ⁻⁸ to 1 × 10 ⁻¹ mol per 1 m ² , particularly 1 × 10 ⁻⁵ to 1 × 10 ⁻² mol. preferable. By being in this range, improvement in desired charging characteristics and humidity dependence (deterioration of storage stability under high humidity) can be seen.

(Layer containing radiation absorbing compound)
Radiation absorption used for the layer provided on the side opposite to the photosensitive layer across the support and the layer on the side where the photosensitive layer is provided on the support of the photothermographic material according to the present invention Various known dyes and pigments can be used as the compound. These dyes and pigments may be any kind, for example, there are pigments and dyes described in the color index, specifically pyrazoloazole dyes, anthraquinone dyes, azo dyes, azomethine dyes, oxonol dyes, carbocyanine dyes, styryl dyes. , Triphenylmethane dyes, indoaniline dyes, indophenol dyes, organic pigments such as phthalocyanine, and inorganic pigments.

  Preferred dyes used in the present invention include anthraquinone dyes (compounds 1-9 described in JP-A-5-341441, compounds 3-6-18 and 3-23-38 described in JP-A-5-165147, etc.), azomethine dyes (Compounds 17 to 47 described in JP-A-5-341441), indoaniline dyes (compounds 11 to 19 described in JP-A-5-289227, compound 47 described in JP-A-5-341441, and JP-A-5-165147) Compounds 2-10 to 11) and azo dyes (compounds 10 to 16 described in JP-A No. 5-341441).

  For example, when the photothermographic material is an image recording material using infrared light, a squarylium dye having a thiopyrylium nucleus and a squarylium dye having a pyrylium nucleus as disclosed in JP-A-2001-83655, or a squarylium dye. It is preferred to use a thiopyrylium croconium dye or a pyrylium croconium dye similar to The compound having a squarylium nucleus is a compound having 1-cyclobutene-2-hydroxy-4-one in the molecular structure, and the compound having a croconium nucleus is 1-cyclopentene-2-hydroxy- in the molecular structure. It is a compound having 4,5-dione. Here, the hydroxyl group may be dissociated. As the dye, the compounds described in JP-A-8-201959, the compounds described in JP-A-9-509503, and the compounds AD-1 to 55 described in JP-A-2003-195450 are also preferable.

  When the photothermographic material is an image recording material using blue light, compound No. 2003-215751 described in JP-A-2003-215751 is used. 1 to 93 and Dye-1 to 51 described in JP-A No. 2005-157245 are preferably used.

As a method for adding these dyes, any method such as a solution, an emulsion, a solid fine particle dispersion, or a state mordanted in a polymer mordant may be used. The amount of these compounds to be used is determined by the target absorption amount, but generally it is preferably used in the range of 1 μg to 1 g per 1 m ^{2 of the} light-sensitive material.

  In the photothermographic material according to the present invention, the layer on the side on which the photosensitive layer is provided, specifically the undercoat layer, the photosensitive layer, the intermediate layer, and the protective layer, more preferably the photosensitive layer. A radiation-absorbing compound (dye or pigment) is contained in the photosensitive layer, the absorbance at the exposure wavelength in all layers of these layers is set to 0.30 to 1.00, and the support is sandwiched between the photosensitive layers. The layer on the side opposite to the side provided with the above, specifically, an antistatic undercoat layer, an antihalation layer, a protective layer, more preferably an antihalation layer containing a dye or a pigment, The absorbance at the exposure wavelength in the layer is preferably set in the range of 0.20 to 1.50. Further, the absorbance at the exposure wavelength in the total of the layers on the side on which the photosensitive layer on the support is provided is preferably 0.40 to 0.90, particularly preferably 0.50 to 0. .80. In addition, the absorbance at the exposure wavelength of the total layer of the layers provided on the side opposite to the side where the photosensitive layer is provided across the support is preferably 0.30 to 1.20, more preferably 0. .40 to 1.00. By setting it within this range, even when a resin lens is used in the exposure system, it is possible to greatly improve density fluctuations accompanying changes in image quality and humidity.

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

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

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

The metal oxide fine particles used in the present invention have electrical conductivity, and the volume resistivity is 10 ⁷ Ω · cm or less, particularly 10 ⁵ Ω · cm or less. These oxides are described in JP-A Nos. 56-143431, 56-120519, 58-62647 and the like. Further, as described in Japanese Examined Patent Publication No. 59-6235, a conductive material in which the above metal oxide is attached to other crystalline metal oxide particles or fibrous materials (such as titanium oxide) may be used. Good.

The particle size that can be used is preferably 1 μm or less, but if it is 0.5 μm or less, the stability after dispersion is good and it is easy to use. In order to make the light scattering property as small as possible, it is very preferable to use conductive particles of 0.3 μm or less because it is possible to form a transparent photothermographic material. Further, when the conductive metal oxide is needle-like or fibrous, the length is preferably 30 μm or less and the diameter is preferably 1 μm or less, particularly preferably the length is 10 μm or less and the diameter is 0.3 μm or less. / Diameter ratio is 3 or more. As the SnO _2, are commercially available from Ishihara Sangyo Kaisha, it can be used SNS10M, SN-100P, SN- 100D, the FSS10M like.

(Component layer)
The photothermographic material according to the invention has at least one photosensitive layer which is an image forming layer on a support. Although only the photosensitive layer may be formed on the support, it is preferable to form at least one non-photosensitive layer on the photosensitive layer. For example, a protective layer is preferably provided on the photosensitive layer for the purpose of protecting the photosensitive layer, and the opposite surface of the support is between the photothermographic materials or between the photothermographic materials. A backcoat layer is provided to prevent “sticking” on the roll.

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

  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.

(Undercoat layer (slip layer))
When applying using a slide coater, apply a thin undercoat layer (slip layer) on the support, and on the photosensitive layer side, apply a slip layer, a photosensitive layer, and a protective layer on the photosensitive layer simultaneously. Is preferably provided. When used on the back coat layer (BC layer) side, it is preferable to provide a slip layer and a BC layer by simultaneous multilayer coating. Here, the photosensitive layer, the protective layer on the photosensitive layer, and the BC layer may be composed of a plurality of layers. The slip layer is usually formed much thinner than a layer containing an organic silver salt and a binder or a layer containing a binder. When the dry film thickness of the slip layer on the photosensitive layer side is SA and the dry film thickness of the photosensitive layer is SB, SA / SB is preferably 0.005 to 0.10. More preferably, it is 0.01-0.07, More preferably, it is 0.02-0.06. The dry film thickness SA of the slip layer on the photosensitive layer side is preferably 0.1 to 1.0 μm, more preferably 0.2 to 0.7 μm, and particularly preferably 0.3 to 0.6 μm.

  When the dry film thickness of the slip layer on the backcoat layer side is Sc and the dry film thickness of the backcoat layer is Sd, Sc / Sd is preferably 0.01 to 0.30. More preferably, it is 0.05-0.25, More preferably, it is 0.08-0.20. The dry film thickness Sc of the slip layer on the backcoat layer side is preferably 0.1 to 0.8 μm, more preferably 0.15 to 0.7 μm, and particularly preferably 0.2 to 0.5 μm.

  As the binder for the slip layer, polyvinyl acetal resin, acrylic resin, polyester resin, polyurethane, or cellulose ester is preferably used. Polyurethane is obtained from the reaction of a polyol and a polyisocyanate.

  As the polyol, a polyester polyol obtained by a reaction between a polyol and a polybasic acid is generally used. Therefore, if a polyester polyol having a polar group is used as a raw material, a polyurethane having a polar group can be synthesized. In the present invention, it is preferable to use an aliphatic or aromatic polyester polyurethane produced using a polyester polyol having an aliphatic or aromatic ring and / or a polyester polyol containing a cyclic hydrocarbon residue.

  Examples of polyisocyanates include diphenylmethane-4,4'-diisocyanate (MDI), hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TDI), 1,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine An isocyanate methyl ester (LDI) etc. are mentioned. Examples of the monomer component constituting the acrylic resin include acrylonitrile, acrylate, methacrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxyethyl methacrylate, 3-cyanophenyl methacrylamide, 4-cyanophenyl methacrylate, 4-hydroxyphenyl methacrylamide, and the like. Homopolymers and copolymers consisting of Among these, polymethyl methacrylate (PMMA) is preferable.

  The content of the polyester resin, acrylic resin or polyurethane contained in the slip layer is 10 to 90%, preferably 20 to 80%, more preferably 30 to 70% by mass ratio with respect to the total binder contained in the slip layer. is there. The crosslinking agent is included in the binder. By making the addition amount of the polyester resin, the acrylic resin and the polyurethane within this range, the adhesion to the support can be remarkably improved.

  In the present invention, the backcoat layer and the undercoat layer (slip layer) on the backcoat layer side contain a polyester resin, an acrylic resin or a polyurethane resin, and the total amount of the polyester resin, acrylic resin or polyurethane resin in the backcoat layer is When the mass ratio of the backcoat layer to the binder amount is A, and the total amount of the polyester resin, acrylic resin or polyurethane resin in the undercoat layer on the backcoat layer side is B, the mass ratio to the binder amount of the undercoat layer is B> A is preferred. Here, the crosslinking agent is included in the binder. The polyester resin, acrylic resin or polyurethane resin is used as an adhesion promoting binder on the back coat layer side in order to improve the adhesive layer with the support. However, since these adhesion promoting binders were found to affect in-machine contamination during heat development, the amount of adhesion promoting binder present on the backcoat layer surface in contact with the heat developing device was reduced as much as possible, and the adhesion promoting binder was In the undercoat layer, the occurrence of in-machine contamination in the thermal development apparatus was improved while maintaining the adhesion to the support. Here, the value of (B-A) is preferably 0.02 to 0.3, more preferably 0.05 to 0.2. A is preferably from 0 to 0.01, particularly preferably 0. B is preferably 0.02 to 0.5, particularly preferably 0.05 to 0.3.

  Further, the effect of improving the coating unevenness when the slip layer and the photosensitive layer are applied simultaneously is remarkable when the coating speed of the photosensitive layer is 25 m / min or more, particularly 30 m / min or more, and further 35 m / min. As described above, the degree of improvement increases as the coating speed increases. A higher coating speed is preferable from the viewpoint of productivity, but it is usually 300 m / min or less, and 200 m / min or less is preferable from the viewpoint of maintaining coatability. The slip layer may be water-based or solvent-based using an organic solvent, but if the photosensitive layer is water-based, it is water-based, and if the photosensitive layer is organic-solvent-based, the organic solvent system is more suitable for simultaneous multi-layer coating. It is preferable in carrying out. When the acrylic resin or polyurethane is used in an aqueous system, it is preferable to use a water-soluble acrylic resin or polyurethane, or a water-dispersible latex.

(Application of component layers)
The photothermographic material according to the present invention is formed by preparing a coating solution in which the material of each constituent layer described above is dissolved or dispersed in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment. Is preferred. Here, “multiple simultaneous multi-layer coating” means that a coating solution for each constituent layer (photosensitive layer, protective layer, etc.) is prepared, and each layer is repeatedly coated and dried when it is coated on a support. Rather, it means that each constituent layer can be formed in a state in which multiple layers can be simultaneously applied and dried. That is, the upper layer is provided before the remaining amount of all the solvents in the lower layer reaches 70% by mass or less (more preferably 90% by mass or less).

  There are no particular restrictions on the method of applying multiple layers of each constituent layer simultaneously, for example, bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, reverse roll coating method, gravure coating method, extrusion coating. A known method such as a method can be used.

  Of the various methods described above, the slide coating method and the extrusion coating method are more preferable. These coating methods have been described on the side having the photosensitive layer, but the same applies to the case of coating with the undercoat layer when providing the back layer. Japanese Unexamined Patent Publication No. 2000-15173 has a detailed description on the simultaneous multilayer coating method in the photothermographic material.

In the present invention, the coated silver amount is preferably selected in accordance with the purpose of the photothermographic material, but is preferably 0.3 to 1.5 g / m ² for the purpose of medical images. 0.5 to 1.4 g / m ² is more preferable, and 0.7 to 1.2 g / m ² is particularly preferable. 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.

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

Furthermore, the coating density of the non-photosensitive long-chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ to 1 × 10 ⁻¹⁴ g per silver halide grain of 0.01 μm or more (equivalent particle diameter in terms of sphere). Is preferably 1 × 10 ⁻¹⁶ to 1 × 10 ⁻¹⁵ g.

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

The photothermographic material preferably contains a solvent in the range of 5 to 1,000 mg / m ² during development. It is more preferable to adjust so that it may be 10-150 mg / m < ² >. As a result, the photothermographic material has high sensitivity, low fog, and high maximum density. Examples of the solvent include, but are not limited to, those described in “0030” of JP-A No. 2001-264930. These solvents can be used alone or in combination of several kinds. The content of the solvent in the photothermographic material can be adjusted by changing conditions such as temperature conditions in the drying step after the coating step. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

(Packaging body)
Hereinafter, a method for packaging a sheet-shaped recording material and a sheet-shaped recording material package that are preferably used in the present invention will be described in detail.

  In the present invention, it is preferable that the cutting process and / or the packaging process be performed in an environment where the cleanliness is US Federal Standard 209d class 10,000 or less. When the cleanness is performed in this environment, the degree of in-machine contamination of the heat development apparatus during heat development can be remarkably improved. Although the cause of the improvement of the in-machine contamination of the heat developing apparatus by performing the cutting process and / or the packaging process in the environment is unknown, for example, the following reasons can be considered.

  Chips and dust brought in from the cutting process and / or packaging process during heat development and adhering to the photosensitive material adhere to the conveying member such as a roller in the heat developing apparatus, which is a trigger, and the cut surface of the photosensitive material In-flight contamination occurs as chips that fall off accumulate from there.

The US federal standard 209d class referred to here indicates a clean room standard. The U.S. Standard 209d class 10,000 environment below 10,000 cumulative number particle size 0.5μm or more particles / ft ³ (1ft ³ is 28,320cm ³⁾ or less, the particle size An environment in which the cumulative number of particles of 5.0 μm or more is 65 particles / ft ³ or less.

  An environment satisfying such conditions can be formed in a clean room, but the method of the present invention is not necessarily limited to the case where the method is performed in a clean room. That is, it is not always necessary to process the entire apparatus for cutting and packaging the sheet-shaped recording material in a clean room.For example, a mechanism for applying an air current to the sheet-shaped recording material in the apparatus from cutting to packaging. It is also possible to process the sheet-like recording material so that the cleanness of the sheet-like recording material is maintained in an environment of US Federal Standard 209d class 10,000 or less.

  It is at least one of the cutting process and the packaging process that the degree of cleanliness needs to be maintained in an environment of US standard 209d class 10,000 or less. Preferably, the cutting process environment is US Federal Standard 209d class 10,000 or less, and more preferably, both the cutting process and the packaging process are US Federal Standard 209d class 10,000 or less.

  The cutting step referred to in this specification means a step of cutting a sheet-shaped recording material into a predetermined size, and usually refers to a step of cutting into a size at the time of use (A4, half cut, etc.). The number of times of cutting is not particularly limited, and may be one or more times. Alternatively, the recording material may be cut together in the vertical direction, and a striped recording material is once formed and placed, and then cut in the horizontal direction to a predetermined size. Further, the cutting means and the cutting device used at the time of cutting are not particularly limited.

  The packaging process referred to in this specification means a process including at least a step of packaging the sheet-like recording material when the sheet-like recording material itself is mounted on the image recording apparatus. When the loaded material is mounted on the image recording apparatus, it means a process including at least a step of packaging the sheet-shaped recording material loaded material. That is, it means a process of packaging a sheet-like recording material or a sheet-like recording material load to be mounted on the image recording apparatus. The packaging means and the packaging device are not particularly limited.

  During the process from the cutting process to the packaging process, the degree of cleanness does not necessarily have to be US Federal Standard 209d class 10,000 or less, but it is preferable to maintain this environment. The same applies to the time until the sheet-shaped recording material after production is cut. The degree of cleanliness in the cutting process is preferably class 7,000 or less, more preferably 4,000 or less, even more preferably 1,000 or less, by a measurement method according to the US Federal Standard 209d. Particularly preferably, it is 500 or less. The degree of cleanliness in the packaging process is preferably class 7,000 or less, more preferably 4,000 or less, even more preferably 1,000 or less, by a measurement method according to the US Federal Standard 209d. Particularly preferably, it is 500 or less.

  The packaging material used for packaging the sheet-shaped recording material is preferably selected from those that do not easily generate dust. In particular, it is preferable not to select such a packaging material when the dust derived from the packaging material makes it impossible to maintain an environment with a cleanness of US Federal Standard 209d class 10,000 or less.

When storing the photothermographic material of the present invention, a package having a low oxygen permeability and / or moisture permeability in order to prevent density changes and fogging with time, or to improve curling, curling, etc. It is preferable to package with materials. The oxygen transmission rate is preferably 50 ml / atm · m ² · day or less (1 atm is 1.01325 × 10 ⁵ Pa) at 25 ° C., more preferably 10 ml / atm · m ² · day or less, and still more preferably Is 1.0 ml / atm · m ² · day or less. The moisture permeability is preferably 0.01 g / m ² · 40 ° C · 90% RH · day or less (according to JIS Z0208 cup method), more preferably 0.005 g / m ² · 40 ° C. · 90% RH · Day or less, more preferably 0.001 g / m ² · 40 ° C · 90% RH · day or less.

  Specific examples of the packaging material for the photothermographic material include, for example, JP-A-8-254793, JP-A-2000-206653, JP-A-2000-235241, JP-A-2002-062625, JP-A-2003-015261, and 2003-2003. No. 057790, No. 2003-084397, No. 2003-098648, No. 2003-098635, No. 2003-107635, No. 2003-131337, No. 2003-146330, No. 2003-226439, No. 2003-228152 The packaging material to be described.

  Further, the porosity in the package is 0.01 to 10%, preferably 0.02 to 5%. Nitrogen sealing is performed so that the nitrogen partial pressure in the package is 80% or more, preferably 90% or more. It is good to do. The relative humidity (RH) in the package is 10 to 60%, preferably 40 to 55%.

(Heat development device)
The thermal development apparatus that can be used in the present invention preferably has an image exposure unit and a thermal development unit. Each will be described.

(Image exposure part)
Image exposure may be performed by any conventionally known method. A preferred image exposure is scanning exposure with a laser. Any laser can be used as the laser. Preferred are a red to infrared emitting He—Ne laser, a red semiconductor laser, or a blue to green emitting Ar ⁺ , He—Ne, He—Cd laser, and a blue semiconductor laser. Preferably, it is a red to infrared semiconductor laser, and the peak wavelength of the laser beam is 600 to 900 nm, preferably 620 to 850 nm.

  On the other hand, in particular, a module in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated and a blue semiconductor laser have been developed, and a laser output device in a short wavelength region has been closed up. The blue semiconductor laser is expected to increase in demand in the future because it is capable of high-definition image recording, an increase in recording density, and a stable output with a long lifetime. The peak wavelength of the blue laser light is preferably 300 to 500 nm, particularly preferably 400 to 500 nm. It is also preferable that the laser light is oscillated in a vertical multi by a method such as high frequency superposition.

(Heat development part)
The heat developing section has a heating means for heating the photothermographic material to a heat developing temperature. The heating means preferably has two heating portions arranged so as to heat one surface of the photothermographic material along the conveyance path of the photothermographic material. More preferably, the heating means is disposed so as to be thermally developed by passing through the second heating means after passing through the first heating means, and the heat capacity of the first heating means is the second heating means. It is 1.2 times or more larger than the heat capacity of the heating means. Preferably, it is 1.3 times or more larger, more preferably 1.5 times or more larger.

  Particularly preferably, each of the first heating means and the second heating means has a higher heating temperature at the inlet side of the photothermographic material than at the outlet side.

  Preferably, each of the first heating unit and the second heating unit includes a heating member and a member that presses the photothermographic material against the heating member. More preferably, the heating member uses an electric resistor coil as a heat source, and the coil density of the first heating unit is 1.2 times or more larger than the coil density of the second heating unit. Preferably, the heating member is a heat plate.

  The heat development apparatus that can be used in the present invention is preferably configured such that the heating temperature of the heat plate of the heat development unit is higher on the conveyance inlet side than the conveyance direction of the photothermographic material. When a photothermographic material less than the heat development temperature is carried in from the upstream side, the time for heating the photothermographic material to a predetermined heat development temperature can be shortened, and sufficient heat development time is secured. be able to. Accordingly, it is possible to prevent the image density of the heat-developable photosensitive material from being lowered.

  In addition, when a photothermographic material less than the photothermographic temperature is carried into a heat plate for heat development, even if heat is absorbed by contact with the photothermographic material, heating is performed on the conveyance inlet side of the heat plate. Since the necessary temperature can be ensured by keeping the temperature high, it is possible to prevent the heat plate for heat development from becoming lower than the heat development temperature.

  In the heat developing apparatus, the heat plate is provided with a heat generating member, the heat generating member changes the heater watt density of the heat plate with respect to the transport direction of the photothermographic material, and the heater watt density on the transport inlet side is increased. It is preferable that they are arranged as described above. In this way, a controllable heat supply means is connected to the heat generating member of the heat plate, and the electric capacity is changed by controlling the heat supply means, so that the heat plate is maintained at a high temperature while maintaining the high temperature on the conveyance inlet side. The heating temperature can be set.

  The heat development apparatus is a linear heat ray in which the heat generating member is folded back in a direction orthogonal to the conveyance direction of the photothermographic material on the heat plate, and is on the conveyance inlet side in the conveyance direction of the photothermographic material It is preferable that the distance between the heat rays is narrow. In this way, it is possible to extend the inside of the heat plate without intermittently forming a linear heat wire, and if the heat wire is heated during heat development, the temperature is controlled for each predetermined part of the heat plate. Without requiring a configuration, the entire heat plate can be heated while maintaining a state in which the heating temperature on the conveyance inlet side where the heat rays are densely arranged is increased.

  According to this thermal development apparatus, the pre-heating unit and the development unit are formed on a single heat plate, and the photothermographic material is preheated to a temperature near the thermal development temperature in the heating region, and then in the development unit. A photothermographic material can be produced, and the upstream heating temperature in the developing section can be made higher than the downstream heating temperature. In this way, the photothermographic material can be heated to a sufficient heat development temperature in the developing unit, and a reduction in image density can be prevented.

  In addition, the heating process and the developing process can be performed with a single heat plate, and it is not necessary to provide another heat plate in the heat developing section, so the structure can be simplified and miniaturized, and the cost can be reduced. It can also be reduced.

  Hereinafter, a thermal development apparatus that can be used in the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram showing a heat development apparatus that can be used in the present invention. As shown in FIG. 1, the thermal development apparatus 10 uses a sheet-like photothermographic material F that does not require wet development processing as an image recording material, and is based on an image signal input to the photothermographic material F. After forming a latent image by irradiating the modulated laser beam L, the photothermographic material F is thermally developed to obtain a visible image on the surface of the photothermographic material. The present invention is not limited to such a configuration, and is applied to a configuration in which a sheet-shaped photothermographic material is preliminarily exposed with a laser beam L to form an image and only the photothermographic material is subjected to thermal development. I can do it.

  The thermal development apparatus 10 is generally configured by a thermal development photosensitive material supply unit A, an image exposure unit B, a thermal development unit C, and a cooling unit D in the order of conveyance of the thermal development photosensitive material F. Further, a transport means for transporting the photothermographic material F, which is provided at an important point between the respective sections, and a power source / control section E for driving and controlling the respective sections are provided.

  In the thermal development apparatus 10, the power supply / control unit E is disposed at the bottom, the photothermographic material supply unit A is disposed at the top, and the image exposure unit B, the thermal development unit C, and the cooling unit D are disposed at the top. In addition, the image exposure unit B and the heat development unit C are arranged adjacent to each other. According to this configuration, both the exposure process and the heat development process can be performed on the same photothermographic material F on the same transport path, and the exposure process and the heat development process are performed at a short transport distance. In this case, the conveyance path length of the photothermographic material F can be minimized, and the output time of one sheet can be shortened.

  As the photothermographic material F, a photothermographic material having a thickness of about 0.2 mm (0.1 to 0.3 mm) can be used. As the photothermographic material, an image is recorded (exposed) with a laser beam L, and then heat developed to develop a color.

  The photothermographic material supply unit A is a part that takes out the photothermographic material F one by one and supplies it to the image exposure unit B located downstream in the transport direction of the photothermographic material F. In FIG. 2, the apparatus includes two loading units 11a and 11b, a pair of supply rollers 13a and 13b disposed in each loading unit 11a and 11b, and a conveyance roller and a conveyance guide (not shown). Further, magazines 15a and 15b in which photothermographic materials F of different sizes are accommodated are inserted into the loading sections 11a and 11b having a two-stage configuration, and the magazines 15a and 15b loaded in the respective stages. Is selectively used depending on the size and orientation of the photothermographic material F. Note that the loading unit is not limited to a two-stage configuration, and may have a three-stage configuration or a single configuration.

  The image exposure unit B scans and exposes the laser beam L in the main scanning direction to the photothermographic material F conveyed from the photothermographic material supply unit A, and also performs a sub-scanning direction substantially orthogonal to the main scanning direction. By transporting in the transport direction (that is, the transport direction), a latent image corresponding to a desired image is formed on the image forming layer on the surface of the photothermographic material F.

  In the conveyance path between the photothermographic material supply unit A and the image exposure unit B, a width adjusting mechanism 17 is provided, and the photothermographic material F carried in from the photothermographic material supply unit A is The image is supplied to the image exposure unit B with the end portions in the width direction aligned.

  The thermal development unit C performs thermal development by performing a temperature rise process while conveying the photothermographic material F after scanning exposure. Then, the photothermographic material F after the development processing is cooled in the cooling unit D and carried out to the discharge tray 16.

  As shown in FIG. 1, the discharge tray 16 may be provided with a sorter S that holds the photothermographic material F carried out. The sorter S is unloaded from the main body 65 by a main body 65 that can be attached to and detached from the heat development apparatus 10, a plurality of unloading rollers 66a, 66b, and 66c provided on the main body 65, and a plurality of unloading rollers 66a, 66b, and 66c. In order to hold the photothermographic material F, a plurality of supply portions 67a, 67b, 67c partitioned in the vertical direction of the main body 65 are provided. The sorter S selects any one of the carry-out rollers 66a, 66b, and 66c to carry out the photothermographic material F, whereby each of the supply units 67a, 67b, and 67c corresponding to the carry-out rollers 66a, 66b, and 66c. It is the structure which can be classified and hold | maintained suitably. The sorter S may be configured to be detachable from the upper portion of the heat developing apparatus, and may be omitted as necessary, and the heat developing photosensitive material F may be transported only to the discharge tray 16.

  The image exposure unit B includes a scanning exposure device 40 that exposes the photothermographic material F by scanning exposure with laser light. The scanning exposure apparatus 40 includes a sub-scanning conveyance unit 18 having a “flapping prevention mechanism” that conveys the photothermographic material F from the conveyance surface while preventing “flapping”, and a scanning exposure unit 19. Yes. The scanning exposure unit 19 scans (main scans) the laser light L while controlling the laser output in accordance with separately prepared image data. At this time, the photothermographic material F is moved in the sub scanning direction by the sub scanning conveyance unit 18.

  The sub-scanning conveyance unit 18 includes two drive rollers (conveying means) 21 and 22 each having a rotation axis arranged substantially parallel to the scanning line with the main scanning line of the laser beam L to be scanned in between. And a guide plate 24 that is disposed to face the drive rollers 21 and 22 and supports the photothermographic material F. The guide plate 24 is configured to place the photothermographic material F inserted between the drive rollers 21 and 22 on one side of the peripheral surface of the drive rollers 21 and 22 outside the drive rollers 21 and 22 arranged in parallel. The photothermographic material F, which is generated by being bent along the portion, is supported by being brought into contact with the portion between the drive rollers 21 and 22 by the elastic repulsive force of the photothermographic material F.

  As described above, an appropriate frictional force is generated between the photothermographic material F and the driving rollers 21 and 22 by the elastic repulsive force of the photothermographic material F itself. Then, the conveyance driving force is transmitted to the photothermographic material F. The drive rollers 21 and 22 are configured to rotate clockwise in FIG. 1 by receiving a driving force of a driving unit such as a motor (not shown) via a transmission unit such as a gear or a belt.

  Further, the photothermographic material F is pressed on the upper surface of the guide plate 24 by its own elastic repulsive force, and “flapping” from the conveying surface of the photothermographic material F, that is, “flapping” in the vertical direction in the figure is suppressed. Is done. By irradiating the photothermographic material F between the drive rollers 21 and 22 with the laser light L, good recording without exposure position deviation can be performed.

  The heat developing section C is provided with a plurality of (two in this embodiment) heat plates 51a and 51b as heating members for heat-treating the heat developable photosensitive material F, and these heat plates 51a and 51b are provided with the heat developable photosensitive material F. Are arranged in an arc shape along the transfer path. The heat plates 51a and 51b function as heating means for performing heat development by contacting the photothermographic material F being conveyed.

  In the cooling unit D, a plurality of flocking rollers 57 for transferring the heat-developable photothermographic material F further downstream in the transport direction are disposed immediately downstream of the heat development unit C in the transport direction. The plurality of flocking rollers 57 are arranged in a staggered manner with respect to the conveyance path of the photothermographic material. The photothermographic material F discharged from the heat developing section C is gradually cooled to a temperature below the glass transition point (Tg) while being conveyed by the flocking roller 57. The reason for gently cooling the photothermographic material F is that if the photothermographic material F is cooled rapidly immediately after the heat development, the degree of cooling differs between the central portion and the end of the photothermographic material F in the transport direction. This is because, since the photothermographic material F is hardened in a deformed state, for example, in a corrugated form, it is necessary to provide a heat retaining part immediately after the thermal development to lower the cooling efficiency and moderate the progress of the cooling. .

  After the photothermographic material F is gently cooled by the flocking roller 57, the photothermographic material F is conveyed so as to come into contact with the planes of the pair of metal plates 61 having opposed planes through the conveyance path of the photothermographic material F. . The heat of the photothermographic material F is absorbed by the metal plate 61, and is cooled appropriately so as not to cause wrinkles and to avoid curved wrinkles. The photothermographic material F discharged from the cooling unit D is transported from the transport roller 64 to the downstream transport roller 63, and supplied from the transport roller 63 (or 66a, 66b, 66c) to the discharge tray 16 (or each sorter S). Parts 67a, 67b, 67c).

  The photothermographic material F is subjected to a heat development process that is heated to a predetermined heat development temperature (about 120 ° C.) in the heat development part C at the time of heat development, and an image is formed. Shrinkage occurs when heated to temperature. Therefore, in the heat development apparatus 10 of the present embodiment, the heat plate 50 is heated to about 110 ° C. in advance by the heat plate 50 on the upstream side in the conveyance direction of the photothermographic material F (heating process), and then the remaining heat arranged on the downstream side. Thermal development is performed at the thermal development temperature by the plates 51 and 52 (development process). Further, the number of heat plates formed in the heat developing portion C is not limited to three, and may be two or four or more. When a plurality of heat plates are provided, the heating step can be performed with an arbitrary number of heat plates on the upstream side in the transport direction, and the developing step can be performed with the remaining heat plates on the downstream side.

  FIG. 2 is a diagram schematically showing the configuration of the heat plate of the present embodiment. As shown in FIG. 2, the heat plate 51 has a configuration in which a heat ray H that is a heat generating member is folded and arranged. The interval between the heat rays is characterized in that the photothermographic material is dense on the carry-in entrance side.

  The heat plate 51 of the present embodiment is arranged with the heat ray H folded back over the entire heating member made of a silicon rubber heater or the like in a direction orthogonal to the conveyance direction of the photothermographic material. Further, the heat rays H are arranged so that the interval on the conveyance inlet side 51f is narrower than the interval on the conveyance outlet side 51r in the conveyance direction of the photothermographic material. As a result, the heat ray H on the conveyance inlet side 51f of the heat plate 51 is arranged. High heater watt density. Further, a part of the heat wire H may be led out of the heat plate 51 and connected to the heat supply means 70 for controlling the heating temperature.

  According to the present embodiment, it is particularly desirable to use the heat plate with the heat ray arrangement as the heat plate 51a. Accordingly, even when the photothermographic material F that is less than the heat development temperature is carried into the heat plate 51a during heat development, the heat development temperature is prevented from becoming lower than the heat development temperature that the heat plate 51a should maintain. be able to. Further, the photothermographic material F immediately before being transported to the heat plate 51a can quickly reach the heat development temperature. Therefore, according to this embodiment, it is possible to prevent the image density of the heat-developable photosensitive material F from being lowered.

  In the present invention, the heat plate 51b is also preferably arranged as described above.

  In the laser imager preferably used in the present invention, the ratio of the path length of the cooling section to the path length of the heat developing section is 1.5 or less, more preferably 0.1 to 1.2, and more preferably 0.2 to 1.0. Is particularly preferred. Here, the path length of the heat developing unit is a transport path length in which the photothermographic material F is heated to the developing temperature in the heat developing apparatus. Further, the path length of the cooling unit means that the photothermographic material F is discharged from the region where the photothermographic material F is shielded by the laser imager to the room light where the laser imager is installed. Say the path length until.

  In addition, the cooling speed of the surface (hereinafter referred to as a non-photosensitive surface) on the side where the laser imager does not have the photosensitive layer with the support of the photothermographic material F interposed therebetween is set to the surface (hereinafter referred to as the photosensitive layer). It is preferable to have a function that can be larger than the cooling rate of the photosensitive surface.

  The ratio of the cooling rate of the non-photosensitive surface to the cooling rate of the photosensitive surface is preferably 1.1 or more. More preferably, it is 1.1-5.0, Most preferably, it is 1.5-3.0. The means for increasing the cooling rate of the non-photosensitive surface is not particularly limited, but it is a preferred embodiment that the non-photosensitive surface is directly brought into contact with a metal plate, a metal roller, a non-woven fabric, or a flocked roller. More preferably, it is also desirable to use a heat sink or a heat pipe together in order to positively discharge the heat accumulated in these members to the outside.

  A laser imager having a small processing speed and a high processing speed can be provided by a laser imager in which the ratio of the path length of the cooling unit to the path length of the heat developing unit is 1.5 or less and the path length of the cooling unit is short.

  The cooling time from the exit from the heat developing section to the ejection is arbitrary, but it is preferably 0 to 25 seconds. More preferably, it is 0 to 15 seconds, and particularly preferably 5 to 15 seconds.

  The path length through which the photothermographic material passes after leaving the heat developing portion and before discharging is arbitrary, but it is preferably 1 to 60 cm. More preferably, it is 5-50 cm, More preferably, it is 5-40 cm.

  The photothermographic material of the present invention may be developed by any method. Usually, the photothermographic material exposed imagewise is heated and developed. A preferred development temperature is 80 to 250 ° C, preferably 100 to 140 ° C, more preferably 110 to 130 ° C. The development time is preferably 1 to 10 seconds, more preferably 2 to 10 seconds, and further preferably 3 to 10 seconds. If the heating temperature is within this range, a sufficient image density can be obtained in a short time, the binder can be melted, and transfer effects to the roller, such as transfer to a roller, and adverse effects on the developing machine can be reduced.

  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 time required for the heat development processing (the time required for the photothermographic material to be picked up and discharged from the tray portion) is preferably 60 seconds or less, and 10 to 50 seconds is preferable for emergency diagnosis. Is also preferable.

  As a thermal development method, either a drum type heater or a plate type heater may be used, but a plate heater method is more preferable. As a heat development method using a plate heater method, a method described in JP-A-11-133572, that is, a photothermographic material in which a latent image is formed on silver halide grains by exposure is brought into contact with a heating means in a heat developing unit. A laser imager for obtaining a visible image, wherein the heating means is composed of a plate heater, and a plurality of pressing rollers are arranged to face each other along one surface of the plate heater; A development method using a laser imager that performs thermal development by passing the photothermographic material between the plate heater and the plate heater is preferable.

  In order to perform the exposure process and the thermal development process at the same time, that is, to start development on a part of the sheet photosensitive material that has already been exposed while exposing a part of the sheet photosensitive material, an exposure unit and a development unit that perform the exposure process The distance between the two is preferably 0 to 50 cm, and this makes the series of processing time for exposure and development extremely short. A preferable range of this distance is 3 to 40 cm, and more preferably 5 to 30 cm. Here, the exposure part refers to a position where light from an exposure light source is irradiated to the photothermographic material, and the development part refers to a position where the photothermographic material is heated for the first time for heat development. In FIG. 1, the position (the tip of the arrow) where the laser beam indicated by L hits the photothermographic material is the exposure part, and the photothermographic material F conveyed from 15 in FIG. The part is the developing part.

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

  The linear velocity of the photothermographic material in the exposure unit, the thermal development unit, and the cooling unit is arbitrary, but a higher speed is preferable for rapid processing and improvement in throughput. A preferable linear velocity is 20 mm / second or more and 150 mm / second or less, more preferably 25 mm / second or more and 120 mm / second or less, and further preferably 30 mm / second or more and 100 mm / second or less. By setting the conveyance speed within this range, it is preferable because it is possible to improve in-machine contamination in the heat developing apparatus during heat development and the conveyance property, and to shorten the processing time, and thus it is possible to cope with an emergency diagnosis.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “part” in the examples represents “part by mass” and “%” represents “% by mass”.

Example 1
[Preparation of undercoated photographic support]
Corona discharge of 8 W · min / m ² on both sides of a biaxially stretched heat-fixed polyethylene terephthalate film of 175 μm thickness colored with the following blue dye at an optical density of 0.150 (measured with a Densitometer PDA-65 manufactured by Konica Minolta) The processed photographic support was subjected to a subbing process. That is, the undercoat coating solution a-1 was applied to one surface of this photographic support so that the dry film thickness was 0.2 μm at 22 ° C. and 100 m / min, and dried at 140 ° C. for photosensitivity. A layer (image forming layer) side undercoat layer was formed (referred to as undercoat underlayer A-1). Also, on the opposite side, as the backing layer undercoat layer, the following undercoat coating solution b-1 was applied at 22 ° C. and 100 m / min so that the dry film thickness was 0.12 μm, and dried at 140 ° C. Then, an undercoat conductive layer having an antistatic function (referred to as undercoat underlayer B-1) was coated on the backing layer side. A corona discharge of 8 W · min / m ² is applied to the upper surfaces of the subbing lower layer A-1 and the subbing lower layer B-1, and the following subbing coating solution a-2 is dried on the lower subbing layer A-1. The film was coated at 33 ° C. and 100 m / min so as to have a film thickness of 0.03 μm, and dried at 140 ° C. to form an undercoat upper layer A-2. -2 was coated at 33 ° C. and 100 m / min to a dry film thickness of 0.2 μm, dried at 140 ° C. to form an undercoating upper layer B-2, and the support was further heat treated at 123 ° C. for 2 minutes. The sample was wound up under the conditions of 50 ° C. and 50% RH (relative humidity) to produce a sample that had been subtracted.

<Preparation of aqueous polyester A-1 solution>
35.4 parts dimethyl terephthalate, 33.63 parts dimethyl isophthalate, 17.92 parts dimethyl sodium 5-sulfoisophthalate, 62 parts ethylene glycol, 0.065 parts calcium acetate monohydrate, manganese acetate tetrahydrate After transesterifying 0.022 parts in a nitrogen stream while distilling methanol at 170 to 220 ° C., 0.04 parts of trimethyl phosphate, 0.04 parts of antimony trioxide as a polycondensation catalyst, and 1 , 4-cyclohexanedicarboxylic acid (6.8 parts) was added, and an esterification was carried out by distilling off a theoretical amount of water at a reaction temperature of 220 to 235 ° C. Thereafter, the inside of the reaction system was further depressurized and heated over about 1 hour, and finally subjected to polycondensation at 280 ° C. and 133 Pa or less for about 1 hour to synthesize aqueous polyester A-1. The obtained aqueous polyester A-1 had an intrinsic viscosity of 0.33, an average particle size of 40 nm, and a mass average molecular weight (Mw) of 80,000 to 10,000.

  Next, 850 ml of pure water was placed in a 2 L three-necked flask equipped with a stirring blade, a reflux condenser, and a thermometer, and 150 g of the aqueous polyester A-1 was gradually added while rotating the stirring blade. After stirring for 30 minutes at room temperature, the mixture was heated to an internal temperature of 98 ° C. over 1.5 hours and dissolved at this temperature for 3 hours. After dissolution, the mixture was cooled to room temperature over 1 hour and allowed to stand overnight to prepare a 15% aqueous polyester A-1 solution.

<Preparation of modified aqueous polyester B-1, B-2 solution>
The 1,900 ml of the 15% aqueous polyester A-1 solution was placed in a 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer, and a dropping funnel, and the internal temperature was adjusted to 80 ° C. while rotating the stirring blade. Until heated. Into this, 6.52 ml of a 24% aqueous solution of ammonium peroxide was added, and a monomer mixture (28.5 g of glycidyl methacrylate, 21.4 g of ethyl acrylate, 21.4 g of methyl methacrylate) was dropped over 30 minutes, The reaction is continued for another 3 hours. Then, it cooled and filtered to 30 degrees C or less, and prepared the modified aqueous polyester B-1 solution (vinyl component modification ratio 20%) whose solid content concentration is 18%.

  The solid content concentration was 18% in the same manner except that the vinyl modification ratio was 36% and the modified component was styrene / glycidyl methacrylate / acetoacetoxyethyl methacrylate / butyl acrylate = 39.5 / 40/20 / 0.5. A modified aqueous polyester B-2 solution (vinyl component modification ratio 20%) was prepared.

<Preparation of acrylic polymer latex C-1 to C-3>
Acrylic polymer latexes C-1 to C-3 having the monomer composition shown in Table 1 were synthesized by emulsion polymerization. The solid content concentration was 30% by mass.

(Photosensitive layer side undercoat underlayer coating solution a-1)
Acrylic polymer latex C-3 (solid content 30%) 70.0 g
Water dispersion of ethoxylated alcohol and ethylene homopolymer (10% solids)
5.0g
Surfactant (A) 0.1g
Distilled water was added to make 1,000 ml, and a coating solution was obtained.

(Photosensitive layer side undercoat upper layer coating solution a-2)
Modified aqueous polyester B-2 (18%) 30.0 g
Surfactant (A) 0.1g
True spherical silica matting agent (Nippon Shokubai Co., Ltd .: Seahoster KE-P50) 0.04g
Distilled water was added to make 1 L to obtain a coating solution.

(Coating liquid b-1 for backing layer side undercoat layer)
Acrylic polymer latex C-1 (solid content 30%) 30.0 g
Acrylic polymer latex C-2 (solid content 30%) 7.6 g
Tin oxide sol (SnO ₂ sol synthesized by the method described in Example 1 of Japanese Examined Patent Publication No. 35-6616 was heated and concentrated to a solid content of 10%, and then adjusted to pH = 10 with ammonia water. 180g
Surfactant (A) 0.5g
PVA-613 (Kuraray PVA) 5% aqueous solution 0.4g
Distilled water was added to make 1 L to obtain a coating solution.

(Backing layer side undercoat upper layer coating solution b-2)
Modified aqueous polyester B-1 (18%) 145.0 g
True spherical silica matting agent (supra: Seahoster KE-P50) 0.2g
Surfactant (A) 0.1g
Distilled water was added to make 1 L to obtain a coating solution.

  A backcoat layer and a backcoat layer protective layer having the following composition were coated on the undercoat layer B-2 on which the undercoat layer was applied.

<Preparation of backcoat layer coating solution>
While stirring 830 g of methyl ethyl ketone (MEK), 84.2 g of cellulose acetate propionate (manufactured by Eastman Chemical: CAP482-20) was added and dissolved. Next, 0.30 g of the following infrared dye 1 is added to the dissolved liquid, and 4.5 g of a fluorine-based surfactant (manufactured by Asahi Glass Co., Ltd .: Surflon KH40) dissolved in 43.2 g of methanol and a fluorine-based surfactant. (Dainippon Ink Co., Ltd .: MegaFag F120K) 2.3 g was added and stirred well until dissolved to obtain a backcoat layer coating solution.

<Preparation of backcoat layer protective layer (surface protective layer) coating solution>
The backcoat layer protective layer was also prepared in the same manner as the backcoat layer coating solution at the following composition ratio. The crosslinked PMMA was dispersed in MEK at a concentration of 1% using a dissolver type homogenizer, and finally added.

Cellulose acetate propionate (supra: CAP482-20) 10% MEK solution
15g
Three-dimensionally crosslinked spherical PMMA with a monodispersity of 15% (polymethyl methacrylate, average particle size 8.0 μm) 0.030 g
C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₂ C ₉ F ₁₇ 0.075 g
Fluorine-based surfactant (SF-17) 0.01g
Fluorine polymer (FM-1) 0.05g
Lubricant (type listed in Table 2) 0.1g

<Preparation of photosensitive silver halide grain emulsion A1>
(A1)
Phenylcarbamoylated gelatin 88.3g
10% aqueous methanol solution of compound (AO-1) 10ml
Potassium bromide 0.32g
Finish to 5,429 ml with water (B1)
0.67 mol / L silver nitrate aqueous solution 2635 ml
(C1)
Potassium bromide 50.69g
Potassium iodide 2.66g
Finish to 660ml with water (D1)
Potassium bromide 151.6g
Potassium iodide 7.67g
0.93ml potassium hexachloroiridium (IV) (1% aqueous solution)
Potassium hexacyanoferrate (II) 0.004g
Hexachloroosmium (IV) potassium salt 0.004g
Finish to 1,982 ml with water (E1)
0.4 mol / L potassium bromide aqueous solution The following silver potential control amount (F1)
Potassium hydroxide 0.71g
Finish to 20ml with water (G1)
56% acetic acid aqueous solution 18.0 ml
(H1)
Anhydrous sodium carbonate 1.72 g
Finish to 151 ml with water.

_{AO-1: HO (CH 2} CH 2 O) n [CH (CH ₃₎ CH ₂ O] _{17 (CH 2 CH 2 O)} m H
(M + n = 5-7)
Using the mixing stirrer shown in Japanese Patent Publication No. 58-58288, while controlling 1/4 of the solution (B1) in the solution (A1) and the total amount of the solution (C1) to 20 ° C. and pAg 8.09, the simultaneous mixing method Was added for 4 minutes and 45 seconds to nucleate. After 1 minute, the entire amount of solution (F1) was added. During this time, pAg was adjusted as appropriate using (E1). After 6 minutes, 3/4 amount of the solution (B1) and the total amount of the solution (D1) were added by a simultaneous mixing method over 14 minutes and 15 seconds while controlling at 20 ° C. and pAg 8.09. After stirring for 5 minutes, the temperature was lowered to 40 ° C., the whole amount of the solution (G1) was added, and the silver halide emulsion was allowed to settle. The supernatant was removed leaving 2 L of the sedimented portion, 10 L of water was added and stirred, and then the silver halide emulsion was precipitated again. The remaining portion of 1,500 ml was left, the supernatant was removed, 10 L of water was further added and stirred, and then the silver halide grain emulsion was precipitated. After leaving 1,500 ml of the sedimented portion and removing the supernatant, the solution (H1) was added, the temperature was raised to 60 ° C., and the mixture was further stirred for 120 minutes. Finally, the pH was adjusted to 5.8, and water was added so that the amount of silver was 1,161 g per mole of silver to obtain photosensitive silver halide grain emulsion A1.

  This emulsion was monodisperse cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%).

<Preparation of photosensitive silver halide grain emulsion A2>
In the preparation of the above photosensitive silver halide emulsion A1, after adding all of the solution (F1) after nucleation, a 5% aqueous solution of 4-hydroxy-6-methyl-1,3,3a, 7-tetrazaindene was added. A photosensitive silver halide emulsion A2 was prepared in the same manner except that 40 ml was added. The grains in the emulsion were monodisperse cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol). %).

<Preparation of photosensitive silver halide grain emulsion A3>
Photosensitive silver halide emulsion A1 was prepared in the same manner except that 4 ml of a 0.1% ethanol solution of the following compound (TPPS) was added after the addition of the entire amount of solution (F1) after nucleation. Silver halide grain emulsion A3 was prepared.

  The grains in the emulsion were monodisperse cubic silver iodobromide grains having an average grain size of 25 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol). %).

<Preparation of photosensitive silver halide grain emulsion B1>
The procedure was the same as the preparation of the photosensitive silver halide grain emulsion A1, except that the temperature at the time of addition by the simultaneous mixing method was changed to 45 ° C. The grains in this emulsion were monodisperse cubic silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%). .

<Preparation of photosensitive silver halide grain emulsion B2>
Photosensitive silver halide grain emulsion B1 was prepared in the same manner except that 4 ml of a 0.1% ethanol solution of the compound (TPPS) was added after the addition of the whole amount of the solution (F1) after nucleation. Silver halide grain emulsion B2 was prepared. The grains in this emulsion were monodisperse cubic silver iodobromide grains having an average grain size of 55 nm, a grain size variation coefficient of 12%, and a [100] face ratio of 92% (AgI content is 3.5 mol%). .

<Preparation of powdered organic silver salt>
In 4,720 ml of pure water, 130.8 g of behenic acid, 67.7 g of arachidic acid, 43.6 g of stearic acid, and 2.3 g of palmitic acid were dissolved at 80 ° C. Next, 540.2 ml of a 1.5 mol / L potassium hydroxide aqueous solution was added, and 6.9 ml of concentrated nitric acid was added, followed by cooling to 55 ° C. to obtain a fatty acid potassium solution. While maintaining the temperature of this potassium fatty acid solution at 55 ° C., the above-described photosensitive silver halide grain emulsions A1 to B2 (types and addition amounts are listed in Table 2) and 450 ml of pure water were added and stirred for 5 minutes. Next, 468.4 ml of 1 mol / L silver nitrate solution was added over 2 minutes and stirred for 10 minutes to obtain an organic silver salt dispersion.

  Thereafter, the obtained organic silver salt dispersion was transferred to a water-washing container, deionized water was added and stirred, and then allowed to stand to float and separate the organic silver salt dispersion, thereby removing the lower water-soluble salts. Thereafter, washing with deionized water and drainage were repeated until the electrical conductivity of the drainage reached 2 μS / cm, and centrifugal dehydration was carried out. Then, the obtained cake-like organic silver salt was converted into an air-flow dryer Flashjet dryer (Seishin). A powder organic silver salt that has been dried and dried to a moisture content of 0.1% under the operating conditions (inlet 65 ° C., outlet 40 ° C.) of nitrogen gas atmosphere and dryer hot air temperature Obtained. In addition, the infrared moisture meter was used for the moisture content measurement of an organic silver salt composition.

<Preparation of preliminary dispersion>
As a binder for the photosensitive layer, 14.57 g of SO ₃ K group-containing polyvinyl butyral (Tg 62 ° C., containing 0.2 mmol / g of —SO ₃ K group) was dissolved in 1,457 g of MEK, and dissolver DISPERMAT CA-40M type ( While stirring with VMA-GETZMANN), 500 g of the powdered organic silver salt was gradually added and mixed well to prepare a preliminary dispersion.

<Preparation of photosensitive emulsion dispersion>
Media type disperser DISPERMAT SL filled with 80% of the internal volume of 0.5 mm zirconia beads (Toray Industries, Inc .: Treceram) so that the residence time in the mill is 1.5 minutes using a pump. A photosensitive emulsion dispersion was obtained by supplying to -C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 8 m / sec.

<Preparation of stabilizer solution>
1.0 g of Stabilizer 1 and 0.31 g of potassium acetate were dissolved in 4.97 g of methanol to prepare a stabilizer solution.

<Preparation of infrared sensitizing dye liquid A>
9.6 mg of infrared sensitizing dye 1, 9.6 mg of infrared sensitizing dye 2, 1.488 g of 2-chlorobenzoic acid, 2.779 g of stabilizer 2 and 365 mg of 5-methyl-2-mercaptobenz Imidazole was dissolved in 31.3 ml of MEK in the dark to obtain infrared sensitizing dye liquid A.

<Preparation of additive solution a>
Reducing agent (compounds and amounts described in Table 2), 0.159 g of yellow chromophoric leuco dye (YA-1) of general formula (YB), 0.159 g of cyan chromogenic leuco dye (CLA-4), 1 .54 g of 4-methylphthalic acid and 0.48 g of the infrared dye 1 were dissolved in 110.0 g of MEK to obtain an additive solution a.

<Preparation of additive liquid b>
1.56 g antifoggant 2, 0.5 g antifoggant 3, 0.5 g antifoggant 4, 0.5 g antifoggant 5, 3.43 g phthalazine dissolved in 40.9 g MEK and added It was set as the liquid b.

<Preparation of additive liquid c>
Silver saving agent (SE1-3) 0.05g was melt | dissolved in MEK39.95g, and it was set as the addition liquid c.

<Preparation of additive liquid d>
0.1 g of supersensitizer 1 was dissolved in 9.9 g of MEK to obtain additive solution d.

<Preparation of additive liquid e>
0.5 g of potassium p-toluenethiosulfonate and 0.5 g of antifoggant 6 were dissolved in 9.0 g of MEK to obtain an additive solution e.

<Preparation of additive liquid f>
An antifoggant containing 1.0 g of vinyl sulfone [(CH ₂ ═CH—SO ₂ CH ₂ ) ₂ CHOH] was dissolved in 9.0 g of MEK to obtain an additive solution f.

<Preparation of photosensitive layer coating solution>
In an inert gas atmosphere (nitrogen 97%), 50 g of the photosensitive emulsion dispersion and 15.11 g of MEK were kept at 21 ° C. with stirring, and the chemical sensitizer S-5 (0.5% methanol solution) 1 2 minutes later, 390 μl of antifoggant 1 (10% methanol solution) was added and stirred for 1 hour. Further, 494 μl of calcium bromide (10% methanol solution) was added and stirred for 10 minutes, and then gold sensitizer Au-5 corresponding to 1/20 mole of the chemical sensitizer was added, and further stirred for 20 minutes. Subsequently, 167 μl of a stabilizer solution was added and stirred for 10 minutes, and then 1.32 g of the infrared sensitizing dye solution A was added and stirred for 1 hour. Thereafter, the temperature was lowered to 13 ° C. and further stirred for 30 minutes. While keeping the temperature at 13 ° C., 0.5 g of additive d, 0.5 g of additive e, 0.5 g of additive f, SO ₃ K group-containing polyvinyl butyral (Tg 62 ° C., -SO ₃ K group of 0.1%). After adding 13.31 g (containing 2 mmol / g) and stirring for 30 minutes, 1.084 g of tetrachlorophthalic acid (9.4% MEK solution) was added and stirred for 15 minutes. While further stirring, 12.43 g of additive liquid a, 1.6 ml of Desmodur N3300: Moby's aliphatic isocyanate (10% MEK solution), 4.27 g of additive liquid b, 4.0 g of additive liquid c By sequentially adding and stirring, a photosensitive layer coating solution was obtained. The chemical structures of the additives used for the preparation of each coating solution including the stabilizer solution and the photosensitive layer coating solution are shown below.

<Preparation of photosensitive layer protective layer lower layer (surface protective layer lower layer) coating solution>
Acetone 5g
MEK 21g
Cellulose acetate propionate (manufactured by Eastman Chemical: CAP-141-20, Tg = 190 ° C.) 2.3 g
7g of methanol
Phthalazine 0.25g
(CH ₂ = CHSO ₂ CH ₂ CH ₂ ) ₂ O 0.035 g
<Preparation of coating solution for photosensitive layer protective layer upper layer (surface protective layer upper layer)>
Acetone 5g
21g of methyl ethyl ketone
Cellulose acetate propionate (supra: CAP-141-20) 2.3 g
Paraloid A-21 (Rohm and Haas) 0.08g
Benzotriazole 0.03g
7g of methanol
Phthalazine 0.25g
Monodispersed 15% spherical three-dimensional crosslinked PMMA (average particle size 1.0 μm) 0.10 g
Monodispersed 15% spherical three-dimensional crosslinked PMMA (average particle size 4.3 μm) 0.40 g
(CH ₂ = CHSO ₂ CH ₂ CH ₂ ) ₂ O 0.035 g
C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₂ C ₉ F ₁₇ 0.01 g
Fluorine-based surfactant (SF-17) 0.005g
Fluorine polymer (FM-1: supra) 0.01g
Lubricant (type listed in Table 2) 0.1g
In addition, about the photosensitive layer protective layer upper layer coating liquid and the photosensitive layer protective layer lower layer coating liquid, it carried out by the method similar to preparation of a backcoat layer coating liquid by said composition ratio. The crosslinked PMMA is dispersed in MEK with a dissolver type homogenizer at a concentration of 1% in the same manner as in the backcoat layer protective layer coating solution, and finally added and stirred, whereby the photosensitive layer protective layer upper layer coating solution. A photosensitive layer protective layer lower layer coating solution was obtained.

[Preparation of photothermographic material]
The prepared backcoat layer coating solution and backcoat layer protective layer coating solution were extruded onto the undercoating upper layer B-2 so that the dry film thicknesses were 1.1 μm and 1.0 μm, respectively, and the coating speed was 50 m / Application was performed in min. The drying was performed for 5 minutes using a drying air having a drying temperature of 100 ° C. and a dew point temperature of 10 ° C.

  By coating the photosensitive layer coating solution and the photosensitive layer protective layer (surface protective layer) coating solution simultaneously on the subbing upper layer A-2 at a coating speed of 50 m / min using an extrusion coater, Table 2, The photothermographic material samples 101 to 131 shown in FIG. Coating has a dry thickness of 13.5 μm of the photosensitive layer, and the photosensitive layer protective layer (surface protective layer) has a dry film thickness of 3.0 μm (surface protective layer upper layer 1.5 μm, surface protective layer lower layer 1.5 μm). Then, drying was performed for 10 minutes using a drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

 In Samples 101 to 131, an absorption peak at a maximum absorption wavelength of 420 nm due to the yellow coloring leuco dye was observed. In Samples 101 to 131, an absorption peak at a maximum absorption wavelength of 620 nm due to the cyan color-forming leuco dye was observed.

  Variation coefficient of centerline average roughness (Ra (E)) of the outermost surface of the photosensitive layer, variation coefficient of surface glossiness of the outermost surface of the photosensitive layer, photosensitive layer and non-photosensitive layer provided thereon Regarding the variation coefficient of the total film thickness, samples were prepared so that each variation coefficient became as shown in Table 2 by changing the polishing method of the slit portion of the extrusion coater used for coating. Specifically, as the extrusion coater used in the samples 101 to 122, one that precisely grinds the slit portion and has a uniform thickness distribution in the width direction of the coating was used. As the sample 131, a sample having a more uniform thickness distribution in the width direction of coating by further precisely polishing the slit portion of the extrusion coater used in the samples 101 to 122 was used. For samples 123, 128, 124, 125, 129, 126, and 130, the polishing method of the slit portion was changed, and an extrusion coater that gave a concave film thickness profile that increased the film thickness at both ends of the extrusion coater in this order. Using. Further, for the sample 127, an extrusion coater that changes the polishing method of the slit portion and gives a convex film thickness profile that increases the film thickness at the center of the extrusion coater was used.

<Measurement of surface roughness>
About the sample before the process of heat development, it measured by the method shown below using the non-contact three-dimensional surface-analysis apparatus (The product made by WYKO: RST / PLUS).

1) Objective lens: × 10.0 Intermediate lens: × 1.0
2) Measurement range: 463.4 μm × 623.9 μm
3) Pixel size: 368 × 238
4) Filter: Cylindrical correction and tilt correction 5) Smoothing: Medium smoothing 6) Scanning speed: Low
Ra, Rz, and Rt were defined according to JIS surface roughness (above B0601-1982). For each sample of 10 cm × 10 cm, the sample was divided into 100 in a grid pattern at 1 cm intervals, the center of each square region was measured, and the average value was obtained from 100 measurements.

  Table 2 shows Ra (nm) on the photosensitive layer side surface and Ra (nm) on the back coating side surface.

<Exposure and development processing>
The photothermographic material samples 101 to 131 produced as described above were processed into half-cut sizes (34.5 cm × 43.0 cm), and then packaged in the following packaging materials in an environment of 25 ° C. and 50% RH. After storing at room temperature for a week, the following evaluation was performed.

(Packaging material)
PET 10 μm / PE 12 μm / Aluminum foil 9 μm / Ny 15 μm / PE 50 μm containing 3% carbon, oxygen permeability: 0.02 ml / m ² per day at 25 ° C. and 1.013 × 10 ⁵ Pa, moisture permeability: 0.001 g / m ^{2 · 40 ℃ · 90% RH} · day barrier bags (by JIS Z0208 cup method). Use paper tray.

<Exposure and development processing>
The photothermographic material samples 101 to 131 produced as described above were subjected to thermal development simultaneously with exposure in the thermal development apparatus shown in FIG. 1 (equipped with a 810 nm semiconductor laser with a maximum output of 50 mW, installation area 0.35 m ² ) (FIG. 1 is set to 125 ° C. and the set temperature of 51b (length in the transport direction 175 mm) is set to 129 ° C., for a total of 6 in 2 seconds and 4.5 seconds, respectively. The heat plates 51a and 51b were set so that the heating temperature was higher on the conveyance entrance side with respect to the conveyance direction of the photosensitive material. “Developing” means that one sheet of photosensitive material composed of a heat-developable photosensitive material is partially exposed, and at the same time, development is started on a part of the sheet that has already been exposed. The distance between the photosensitive section and the developing section was 12 cm, and the transport speed from the photosensitive material supply apparatus section to the image exposure apparatus section, the transport speed in the image exposure section, and the transport speed in the thermal development section were 40 mm each. The bottom of the photosensitive material stock tray located at the bottom was 45 cm high from the floor, and the time required for the heat development process (the photosensitive material was picked up at the tray portion). The time taken for the discharge to be discharged) was 40 seconds (in the case of continuous processing, the interval time of thermal development was 4 seconds). I went down the steps step by step.

<Evaluation of sample>
The following evaluation was performed for each sample.
<< Image density Dmax >>
The value of the highest density portion of the image obtained under the above conditions was measured with a densitometer and indicated as the image density.

《Gamma value》
The optical density of the obtained photothermographic material was measured, and the gamma value was calculated. The gamma value is represented by gamma at an optical density of 1.2 in a characteristic curve when the photothermographic material is heated and developed. The photographic characteristic curve is a D-logE curve representing the relationship between the logarithm of logarithm (log E) of exposure dose as exposure energy on the horizontal axis and the optical density, that is, scattered light photo density (D) on the horizontal axis. Say. The gamma (γ) value is the slope of the tangent line at the optical density D = 1.2 on the characteristic curve (tan θ when the angle between the tangent line and the horizontal axis is θ).

<In-machine contamination of thermal development equipment>
After heat developing 5,000 photothermographic materials (sheet films) in an environment of 25 ° C. and RH 65% using the heat developing apparatus shown in FIG. Visually evaluated. The best level with no contamination on the roller surface was set to 5, and the worst level (contamination occurred on the entire surface of the roller) was set to 1, and the evaluation was performed in 0.5 increments.

<Film transportability>
100 times each of the photothermographic material (sheet film) is processed in an environment of 20 ° C. and RH 50% using the heat developing apparatus shown in FIG. Count).

《Silver tone》
The photothermographic material (sheet film) was processed in an environment of 20 ° C. and RH 50% using the heat developing apparatus shown in FIG. 1, and the silver color tone was visually determined. The color tone equivalent to that of a wet conventional film was set to the best level 5, and the worst level (color tone unevenness occurred on the entire surface of the sheet) was set to 1, and the evaluation was performed in 0.5 increments.

  The results are shown in Table 3.

* 1): (1-47) / (2-6) = 4.20 / 23.78
* 2): (1-47) / (2-6) = 1.11.19 / 16.79
* 3): (1-47) / (2-6) = 16.79 / 11.19
LB-1: Stearic acid-i-tridecyl LB-2: Palmitic acid-i-tridecyl LB-3: Glycerol trioleate LB-4: Glycerin trimyristate LB-5: Glycerin trilaurate LB-6: Tri-i -Trimethylolpropane stearate LB-7: Dipentaerythritol hexa-i-stearate LB-8: Silicon-containing comb-shaped graft polymer (hydroxyl group-containing copolymer having a weight average molecular weight of 5,000 consisting of a silicon-containing macromonomer and methyl methacrylate) polymer)
LB-9: Silicon-containing comb-shaped graft polymer (hydroxyl group-containing copolymer having a weight average molecular weight of 10,000 consisting of a silicon-containing macromonomer and methyl methacrylate)
A: Butyl stearate B: Oleyl oleate

  As is clear from Tables 2 and 3, in the case of the photothermographic material (photothermographic photosensitive sheet) of the present invention, there is no occurrence of in-machine contamination in the heat developing apparatus, and it is excellent in transportability and silver tone. Recognize.

  In particular, according to the present invention, even when a heat-developable photosensitive sheet made of a heat-developable photosensitive material is rapidly heat-developed by a small and low-cost heat-development apparatus, there is no occurrence of internal contamination in the heat-development apparatus, It can be seen that a photothermographic sheet comprising a photothermographic material excellent in silver tone can be provided.

  In Sample 102, a paper tray with a raised paper tray and a silica gel sealed in the space formed at the bottom of the tray was used. As a result, the concentration fluctuation with humidity fluctuation was improved, and an improvement effect was recognized. .

  The best mode for carrying out the present invention has been described above, but the present invention is not limited to these, and various modifications can be made within the scope of the technical idea of the present invention. For example, the image forming apparatus 10 in FIG. 1 can be configured as a medical laser imager capable of forming and outputting a medical image on a film by inputting medical image data.

  The image forming apparatus 10 of FIG. 1 has a relatively compact configuration of a desktop type as a whole. However, the photothermographic material (sheet film) conveying apparatus of the present invention is an example of such a desktop type image forming apparatus. Needless to say, the present invention can be applied to a relatively large heat developing type image forming apparatus such as a stand-alone type (self-standing type).

It is the schematic which shows an example of embodiment of the heat development apparatus which can be used for this invention. It is the figure which showed typically an example of the structure of the heat plate in a heat developing apparatus.

Explanation of symbols

10: Thermal development apparatus 11a, 11b: Loading unit 51a, 51b: Heat plate A: Photothermographic material supply unit B: Image exposure unit C: Thermal development unit D: Cooling unit F: Photothermographic material H: Heat ray (heat generation) Element)

Claims (6)

A photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on the support, a non-photosensitive layer provided on the photosensitive layer, and the opposite surface of the support In the photothermographic sheet comprising the photothermographic material having a back coat layer on the surface, the coefficient of variation of the center line average roughness (Ra (E)) of the outermost surface of the photothermographic sheet is 7% or less. A heat-developable photosensitive sheet, comprising: A photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on the support, a non-photosensitive layer provided on the photosensitive layer, and the opposite surface of the support A heat-developable photosensitive sheet comprising a heat-developable photosensitive material having a backcoat layer on the surface, wherein the coefficient of variation in surface glossiness of the outermost surface on the photosensitive layer side of the heat-developable photosensitive sheet is 7% or less. Photosensitive sheet. A photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on the support, a non-photosensitive layer provided on the photosensitive layer, and the opposite surface of the support In the photothermographic sheet made of the photothermographic material having a backcoat layer, the variation coefficient of the total film thickness of the photosensitive layer of the photothermographic sheet and the non-photosensitive layer provided thereon is 7% or less. A heat-developable photosensitive sheet. The photothermographic sheet according to any one of claims 1 to 3, wherein the non-photosensitive layer or the backcoat layer on the photosensitive layer contains a lubricant having a molecular weight of 550 to 10,000. . 5. The photothermographic sheet according to claim 1, wherein the maximum image density after heat development is 4.0 to 5.0. 6. The photothermographic sheet according to claim 1, wherein a gradation (γ value) at an optical density of 1.2 of a photographic characteristic curve is 2.0 to 6.0.

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