JP2008180863A - Heat developable photosensitive material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat developable photosensitive material which can be rapidly heat-developed with a small low-cost heat developing apparatus while substantially avoiding the internal contamination of the heat developing apparatus and film scratching, and which is excellent in transportability at low humidity, density variation due to humidity change, and image density. <P>SOLUTION: The heat developable photosensitive material has a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on one surface of a support and a back coat layer on the other surface of the support, wherein the photosensitive layer has a dry film thickness of 9-16 μm; the outermost surface on the back coat layer side has a center line average roughness (Ra) of 100-150 nm, and the back coat layer contains a lubricant having a molecular weight of 550-10,000. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to 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 are rapidly spreading in the above fields.

  This photothermographic material is usually processed by a photothermographic processor called a photothermographic processor that applies stable heat to the photothermographic material to form an image. As described above, with the rapid spread in recent years, a large amount of this heat development processing apparatus has been supplied to the market. In recent years, there has been a demand for a compact laser imager and quick processing.

On the other hand, it is known that in a photothermographic material, a friction coefficient is adjusted by using a slip agent in order to improve transportability (see, for example, Patent Documents 1 and 2).
JP 2004-219794 A (Claims) JP 2004-334077 A (Claims)

  There is a need for a thermal development apparatus that is small, low-cost, and has a fast first print. When rapid processing is performed using these thermal development apparatuses, internal contamination of the thermal development apparatus and film scratches occur during thermal development. A new problem occurred. In addition, it is difficult to obtain a sufficient image density that can also be used for mammography, and it is necessary to improve transportability under low humidity and density fluctuation accompanying humidity change.

  The present invention has been made in view of the above background circumstances. The object of the present invention is to reduce the occurrence of in-machine contamination and film scratches in the heat developing device even when the photothermographic material is rapidly heat-developed by a small and low-cost heat developing device, and transportability under low humidity. Another object of the present invention is to provide a photothermographic material that is excellent in density fluctuations and image density accompanying changes in humidity.

  In order to achieve the above-mentioned object, the phenomenon of in-machine contamination of the heat developing apparatus, the occurrence of film scratches, the transportability under low humidity, and the density fluctuation accompanying the humidity change was examined. As a result, depending on the type of lubricant used, the dry thickness of the photosensitive layer, and the surface roughness of the outermost surface of the backcoat layer, it causes contamination in the machine, film scratches, transportability under low humidity, and changes in humidity. The present inventors have found that the concentration fluctuation is greatly affected and have reached the present invention. In addition, it has also been found that the adhesion promoting binder used in the backcoat layer to improve the adhesive layer with the support affects on-machine contamination during heat development. As a result of investigations based on these findings, the amount of the adhesion promoting binder existing on the surface of the backcoat layer in contact with the heat development apparatus was reduced as much as possible. The occurrence of in-machine contamination in the developing device has been improved. And it has been found that the object of the present invention is achieved at a higher level.

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

  1. A photothermographic material having a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on a support, and a backcoat layer on the opposite side of the support. Lubricant having a dry film thickness of 9 to 16 μm, a center line average roughness (Ra) of the outermost surface on the back coat layer side of 100 to 150 nm, and the back coat layer having a molecular weight of 550 to 10,000 A photothermographic material comprising a photothermographic material.

  2. A photothermographic material having a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on a support, and a backcoat layer on the opposite side of the support. The dry film thickness of the layer is 9 to 16 μm, the center line average roughness (Ra) on the outermost surface on the back coat layer side is 100 to 150 nm, and the back coat layer contains a fatty acid ester of a polyhydric alcohol A photothermographic material characterized in that:

  3. 3. The photothermographic material according to item 1 or 2, wherein the center line average roughness (Ra) of the outermost surface on the backcoat layer side is 110 to 140 nm.

  4). 4. The photothermographic material according to any one of items 1 to 3, wherein the photosensitive layer contains a silver saving agent.

  5. 5. The photothermographic material according to 4 above, wherein the silver saving agent is at least one selected from hydrazine derivatives, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds.

  6). 6. The photothermographic material according to any one of 1 to 5, wherein the maximum value of image density after heat development is 4.0 or more and 5.0 or less.

  7. 7. The thermal development according to any one of 1 to 6 above, wherein an average gradation (Ga value) at an optical density of 0.25 to 2.5 in a photographic characteristic curve is 2.0 to 6.0. Photosensitive material.

  8). A photothermographic material having a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on a support, and a backcoat layer on the opposite side of the support. An undercoat layer containing a binder is provided between the backcoat layers, the backcoat layer and the undercoat layer contain at least one of a polyester resin, an acrylic resin, or a polyurethane resin, and the polyester in the backcoat layer The mass ratio of the total amount of resin, acrylic resin and polyurethane resin to the binder amount of the backcoat layer is A, and the total amount of polyester resin, acrylic resin and polyurethane resin in the undercoat layer to the binder amount of the undercoat layer A photothermographic material, wherein B> A, where B is a mass ratio.

  According to the present invention, it is possible to provide a photothermographic material having a high image density and excellent in in-machine contamination of the heat developing apparatus, film scratches, transportability under low humidity, and density fluctuation accompanying humidity change.

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

  Hereinafter, the constituent elements of the present invention will be sequentially described.

(lubricant)
In the present invention, a lubricant having a molecular weight of 550 or more or a fatty acid ester of a polyhydric alcohol is used as the lubricant. In particular, it is 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 heat developing apparatus can be remarkably improved. The structure of the lubricant of the present invention is not particularly limited as long as the molecular weight is 550 or more, but paraffin, liquid paraffin, fatty acid ester, and silicon-containing comb graft polymer are more preferable. As the silicon-containing comb-shaped graft polymer, the compounds described in paragraph number “0018” of JP-A No. 2003-15259 can be used. Of these, fatty acid esters are particularly preferred, and fatty acid esters of polyhydric alcohols are more preferred.

  Moreover, when using the fatty acid ester of a polyhydric alcohol, even if all are esterified, some alcohol groups may remain | survive. 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 (glycerin trioleate), glycerin trilaurate, glycerin tripalmitate, glycerin tristearate, glycerin tribehenate, isotridecyl laurate, isotridecyl myristate, and palmitic acid. Isotridecyl, isotridecyl stearate, isotridecyl arachidate, isotridecyl erucate, isotridecyl behenate, trimethylolpropane triisolaurate, trimethylolpropane triisomyristate, trimethylolpropane triisopalmitate, trimethylolpropane triisostearate, triisoeruca Acid trimethylolpropane, triisoarachidic acid trimethylolpropane, triisooleic acid trimethylolpropane Bread, trimethylolpropane triisobehenate, dipentaerythrityl hexaisostearate, dipentaerythrityl hexaisopalmitate, dipentaerythrityl hexaisomyristate, dipentaerythrityl hexaisobehenate, compounds described in Table 1, Table 2 and Table 3 of JP-A No. 2004-334077 However, it is not limited to these compounds.

  The lubricant of the present invention is contained in the backcoat layer. In the present invention, the back coat layer 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. The lubricant of the present invention is more preferably contained in the backcoat protective layer among the backcoat layers. The addition amount of the lubricant of the present invention to the backcoat layer is 0.1 to 20% by mass with respect to the mass 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). Preferably, it is 0.5-10 mass%. The lubricant of the present invention may be added to any layer other than the back coat layer, but is preferably added to the surface protective layer on the photosensitive layer side. The amount of addition of the lubricant of the present invention to the layers other than the backcoat layer is the same as that of the backcoat layer, with respect to the mass of the binder contained in the layer used (when the curing agent is included, the curing agent is also included in the binder), 0.1-20 mass% is preferable, and it is more preferable that it is 0.5-10 mass%.

(Gamma value)
Photographic Characteristic Curve In the present invention, the photographic characteristic curve represents the relationship between the optical density, that is, the scattered light photographic density (D), on the horizontal axis and the common logarithm (logE) of the exposure amount, which is exposure energy, on the horizontal axis. The D-log E curve. The gamma (γ) value is the average gradation (Ga value) at the optical density 0.25 to 2.5 on the characteristic curve (the angle formed by the straight line connecting the optical density 0.25 and 2.5 and the horizontal axis). tan θ when θ is set.

  The average gradation (Ga value) at an optical density of 0.25 to 2.5 in the photographic characteristic curve is preferably 2.0 to 6.0, and particularly preferably 3.5 to 5.5. By setting the average gradation (Ga value) at an optical density of 0.25 to 2.5 to 2.0 to 6.0, it is possible to maintain a good level of development unevenness even if thermal development is performed while transporting at high speed. In addition, it is possible to obtain an image with high diagnostic recognizability even if the amount of silver is small.

In the present invention, in order to adjust the average gradation (Ga value) in the range of 0.25 to 2.5 to 2.0 to 6.0, it can be easily adjusted by appropriately combining the following techniques.
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 grains 4) Spectral increase to be adsorbed on silver halide grains 5) Change the type and amount of sensitization of silver halide grains.

  The dry film thickness of the photosensitive layer is from 9.0 μm to 16.0 μm, preferably from 9.5 μm to 14.0 μm, particularly preferably from 10.0 μm to 13.0 μm. preferable. This is preferable because the maximum density is high and the effect of excellent image storability can be obtained. 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 μm or more and 19.0 μm or less, more preferably 14.0 μm or more, 18 It is particularly preferable that the thickness is 0.0 μm or less. 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 or more and 5.0 or less, but 4.0 or more and 4.8 or less. It is more preferable that it is 4.2 or more and 4.6 or less.

(Surface layer)
In the present invention, the center line average roughness (Ra (B)) on the outermost surface on the side where the back coat layer is provided is 100 to 150 nm. More preferably, it is 110-140 nm, and it is especially preferable that it is 115-135 nm. By setting Ra (B) on the surface of the back coat layer side in this range, the effects of the present invention, in particular, the in-machine contamination and scratch characteristics of the heat developing apparatus can be improved. Here, (B) represents the outermost surface on the back coat layer side opposite to the photosensitive layer. The ten-point average roughness (Rz) of the outermost surface on the side where the back coat layer is provided is preferably 4.0 to 8.0 μm, and particularly preferably 4.0 to 7.0 μm. The maximum roughness (Rt) of the outermost surface on the side where the back coat layer is provided is preferably 5.0 to 12.0 μm, and particularly preferably 5.5 to 10.0 μm. By setting Rz (B) and Rt (B) on the back coat layer side surface in this range, the effects of the present invention, in particular, the in-machine contamination and scratch characteristics 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 the following JIS surface roughness (B0601-1994). The 10-point average roughness (Rz) is the reference length extracted from the cross-sectional curve. The average value of the top to fifth peak elevations and the average of the bottom to fifth peak elevations, measured in the direction of the vertical magnification from the straight line that does not cross the cross-section curve, and the extracted part. The difference between the two is expressed in micrometers (μm) and is called Rz. The maximum roughness (Rt) is the roughness curve extracted by the reference length L, and when the extracted part is sandwiched between two straight lines parallel to the center line, the distance between the two straight lines is measured in the direction of the vertical magnification of the roughness curve. Then, this value is expressed in micrometers (μm). With the centerline average roughness (Ra), a portion of the measurement length L is extracted from the roughness curve in the direction of the centerline. When the center line of this extracted portion is represented by the X axis, the direction of the vertical magnification is represented by the Y axis, and the roughness curve is represented by y = f (x), the value obtained by the following formula is represented by micrometers (μm). Say.

  As a method for measuring Rz, Rt, and Ra, the humidity was adjusted for 24 hours under the condition that the measurement samples were not overlapped in an environment of 25 ° C. and 65% RH, 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 rolled up, a method in which paper is stacked between the photothermographic material and the photothermographic material, and a frame such as cardboard Is one of the methods of manufacturing and fixing the four corners. Examples of the measuring apparatus that can be used include a 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 amount added, and the surface treatment method 2) 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 application (application speed, distance from the application 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) Calendar treatment after application Conditions (for example, calendar temperature 40-80 ° C, pressure 50-300 kg / cm, line speed 20-100 m / min, nip number 2-6)
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 70 to 140 nm, more preferably 80 to 135 nm, 90 It is particularly preferable that the thickness is ˜130 nm. The ten-point average roughness of the outermost surface on the side where the photosensitive layer is provided is preferably 1.5 to 4.0 μm, and more preferably 2.0 to 3.5 μm. In the present invention, the value of Rz (E) / Rz (B) is preferably 0.1 or more and 0.7 or less, and more preferably 0.2 or more and 0.6 or less.

  Here, (E) represents the outermost surface on the photosensitive layer side, and (B) represents the outermost surface on the back coat layer side opposite to the photosensitive layer. By setting (Rz (E)) to 1.5 to 4.0 μm, it is possible to improve in-machine contamination and film transportability of the thermal development apparatus.

  In the present invention, the value of Ra (E) / Ra (B) is preferably 0.6 or more and 1.5 or less, and particularly the value of Ra (E) / Ra (B) is 0.6 or more. 1.3 or less. By setting it within this range, the increase in fog over time is small, the transportability of the film is good, and the occurrence of uneven density during heat development can be further improved.

  The photothermographic material of the present invention contains a matting agent A having an average particle size of 0.3 to 2.0 μm and a matting agent B having an average particle size of 2.5 to 7.0 μm on the outermost surface on the photosensitive layer side. It is preferable. The average particle size of the matting agent A is more preferably 0.5 to 1.5 μm, and the average particle size of the matting agent B is more preferably 3.0 to 6.0 μm. 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 1.0 to 20% by mass with respect to the binder amount used in the outermost layer (including the crosslinking agent in the binder amount), preferably It is 2.0-15 mass%, More preferably, it is 3.0-10 mass%.

  The average particle size of the matting agent (preferably a cross-linked organic resin) contained in the outermost layer opposite to the photosensitive layer side across the support is preferably 8.5 to 15.0 μm. Yes, more preferably from 9.0 to 12.0 μm.

  The addition amount of the matting agent is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably 0.4 to 7% by mass with respect to the binder amount used for the outermost layer (including the crosslinking agent in the binder amount). Preferably it is 0.6-5 mass%.

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

  The photothermographic material according to the invention preferably has constituent layers containing a plurality of types of matting agents on both sides of 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 defined as Le (μm). The average particle diameter of the matting agent having the largest average particle diameter of the matting agent contained in the layer containing the matting agent on the side opposite to the side having the photosensitive layer across the support, that is, the side having the backcoat layer is Lb. (Μm). At this time, Lb / Le is preferably 2.0 to 10, and more preferably 3.0 to 4.5.

  By setting Lb / Le within this range, density unevenness during heat development can be improved. In the image forming method according to 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 thermal development and storage characteristics over time can be improved.

  In the image forming method according to the present invention, the value of Rz (B) / Ra (B) is preferably 25 or more and 65 or less, more preferably 30 or more and 60 or less. 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 the process of heat development, it measured by the method shown below using the non-contact three-dimensional surface analyzer (WYKO company 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 are defined according to JIS surface roughness (B0601-1994). 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.

  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 of the present invention, or on the opposite side of the photosensitive layer with the support interposed, the surface roughness is controlled on the outermost layer, etc. Therefore, it is preferable to use organic or inorganic powder as a matting agent.

As the powder used in the present invention, a powder having a Mohs hardness of 5 or more is preferably used. 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 Examples thereof include diamond, garnet, garnet, mica, silica, silicon nitride, silicon carbide and the like. Examples of the organic powder include powders such as polymethyl methacrylate, polystyrene, and Teflon (registered trademark). Among these, 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 , mica, etc. are preferable. SiO ₂ and α-Al ₂ O ₃ are preferable, and SiO ₂ 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 surface coating of metal hydroxide is performed. First, a predetermined amount of an aqueous salt solution such as Al, Si, Ti, Zr, Sb, Sn, and Zn is added, and an acid or alkali that neutralizes the solution is added, and the surface of the inorganic powder particles is coated with the resulting hydrous oxide. To do. 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 to become a product. In addition to the aqueous 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, it is preferable that the surface treatment is performed with an Si compound or an Al compound. When such a surface-treated powder is used, the dispersion state when the matting agent is dispersed can be improved. 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. More preferably, Si is 0.1 to 5% by mass, Al is 0.1 to 5% by mass, Si is 0.1 to 2% by mass, and Al is particularly preferably 0.1 to 2% by mass. . The mass ratio of Si and Al is preferably Si <Al. 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 length of the plate-like surface in the case of plate-like powder. Mean values can be easily obtained from measurement with an electron microscope.

  The organic or inorganic powder preferably has an average particle size of 0.5 to 10 μm, more preferably 1.0 to 8.0 μm.

  The average particle diameter of the organic or inorganic powder contained in the outermost layer on the photosensitive layer side is usually 0.5 to 8.0 μm, preferably 1.0 to 6.0 μm, more preferably 2.0 to 5.0 μm. It is.

  The addition amount is usually 1.0 to 20% by mass, preferably 2.0 to 15% by mass, more preferably 3 with respect to the amount of binder used in the outermost layer (including the crosslinking agent in the binder amount). 0.0 to 10% by mass.

  The average particle size of the organic or inorganic powder contained in the outermost layer opposite to the photosensitive layer side across the support is usually 2.0 to 15.0 μm, preferably 3.0 to 12.0 μm. More preferably, it is 4.0-10.0 micrometers. The addition amount is usually 0.2 to 10% by mass, preferably 0.4 to 7% by mass, and more preferably 0 to the amount of binder used in the outermost layer (including the crosslinking agent in the binder amount). .6 to 5% by mass.

  The variation coefficient of the particle size distribution is preferably 50% or less, more preferably 40% or less, and particularly preferably 30% or less. Here, the variation coefficient of the particle size distribution is a value represented by the following equation.

{(Standard deviation of particle size) / (Average value of particle size)} × 100
The method of adding the organic or inorganic powder may be a method in which the organic or inorganic powder is previously dispersed in the coating solution, or a method of spraying the organic or inorganic powder after the coating solution is applied and before the drying is completed. May be. Moreover, when adding several types of powder, you may use both methods together.

(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, the organic silver salt according to the present invention is 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. Heat developed. In this thermal development process, the organic silver salt according to the present invention can function as a silver ion supply source to supply silver ions and contribute to silver image formation.

  As such a non-photosensitive organic silver salt, conventionally, silver salts of organic compounds having various chemical structures are known. For example, paragraphs “0048” to “0049” of JP-A-10-62899, European Patent Application Publication No. 803,764A1, page 18, line 24 to page 19, line 37, European Patent Application Publication No. 962,812A1, Japanese Patent Application Laid-Open No. 11-349591, Japanese Patent Application Laid-Open No. 2000- 7683, 2000-72711, 2002-23301, 2002-23303, 2002-49119, 196446, European Patent Application No. 1246001A1, European Patent Application Publication No. 1258775A1, JP 2003-140290 A, JP 2003-195445 A, 2003-295378, JP same 2003-295379, JP same 2003-295380, JP same 2003-295381 JP, described in JP-A No. 2003-270755 Publication.

  In the present invention, a silver salt of an aliphatic carboxylic acid, particularly, having 10 to 30 carbon atoms, preferably in combination with or without using various organic silver salts disclosed in the above-mentioned patent publications, etc. A silver salt of 15 to 28 long chain aliphatic carboxylic acid 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 carboxylates, the silver behenate content is preferably 50 mol% or more, more preferably 80 mol% or more and 100 mol% or less, based on the total aliphatic carboxylate silver. Preferably they are 90 mol% or more and 99.99 mol% or less. Further, the silver erucate content is 2 mol% or less, more preferably 1 mol% or less, still more preferably 0.1 mol% or less.

  Prior to the preparation of the aliphatic carboxylic acid silver salt, it is necessary to prepare an alkali metal salt of an aliphatic carboxylic acid. In this case, examples of the types of alkali metal salts that can be used include sodium hydroxide. Potassium hydroxide and lithium hydroxide. Among these, it is preferable to use one kind of alkali metal salt, for example, potassium hydroxide, but it is also preferable to use sodium hydroxide and potassium hydroxide in combination. The combined ratio is preferably such that the molar ratio of both of the above-mentioned hydroxide salts is in the range of 10:90 to 75:25. When used in the above range when reacted with an aliphatic carboxylic acid to form an alkali metal salt of an aliphatic carboxylic acid, the viscosity of the reaction solution can be controlled in a good state.

  In addition, 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 is preferably a halide having a higher potassium ratio. It is preferable because dissolution of silver particles and Ostwald ripening are prevented. Furthermore, the higher the potassium salt ratio, the smaller the size of the fatty acid silver salt particles. A preferable ratio of the potassium salt is 50 to 100% based on the total alkali metal salt used in the step of producing the aliphatic carboxylate. The concentration of the alkali metal salt is preferably 0.1 to 0.3 mol / 1000 ml.

  The average sphere equivalent diameter of the aliphatic carboxylic acid silver salt means the diameter of a sphere having the same volume as the volume of one particle of the aliphatic carboxylic acid silver salt. The measuring method can be obtained by obtaining the particle volume from the projected area and thickness of the particle observed by a transmission electron microscope of the coated sample, and averaging the diameter when converted to a sphere having the same volume. . In order to control the average sphere equivalent diameter of the aliphatic carboxylic acid silver salt, the ratio of the potassium salt is increased and adjusted during the preparation of the aliphatic carboxylic acid silver salt as described above. Or it can carry out easily by adjusting suitably the particle size of a zirconia bead used at the time of dispersion | distribution of a photosensitive emulsion dispersion liquid, a mill peripheral speed, and dispersion time. In the present invention, the average equivalent sphere diameter of the aliphatic carboxylic acid silver salt is preferably 0.05 to 0.50 μm, more preferably 0.10 to 0 in order to obtain a sufficient density after heat development. .45 μm, particularly preferably 0.15 to 0.40 μm.

  Examples of the organic silver salt that may be used in addition to the aliphatic carboxylic acid silver salt used in the present invention include an organic silver salt having a core-shell structure (Japanese Patent Laid-Open No. 2002-23303), a polyvalent carboxylic acid Silver salts (EP1246001 and JP2004-061948) and polymer silver salts (JP2000-292881 and JP2003-295378 to 2003-29581) can also be used.

  The shape of the aliphatic carboxylic acid silver salt that can be used in the present invention is not particularly limited, and may be any of a needle shape, a rod shape, a flat plate shape, and a flake shape. In the present invention, flake-shaped 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 the present 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) Good)), and calculate with the shorter numbers a and b, and find x as follows.

x = b / a
In this way, x is obtained for about 200 particles, and when the average value x (average) is obtained, particles satisfying the relationship of x (average) ≧ 1.5 are defined as flakes. Preferably, 30 ≧ x (average) ≧ 1.5, more preferably 20 ≧ x (average) ≧ 2.0. Incidentally, the needle shape is 1 ≦ x (average) <1.5.

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

  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, from the particle size (volume weighted average diameter) obtained by irradiating an organic silver salt dispersed in a liquid with laser light and obtaining an autocorrelation function with respect to temporal change of fluctuation of the scattered light. Can be sought.

  Known methods and the like can be applied to the production and dispersion method of the organic silver salt used in the present invention. 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 preferably an aqueous solution or an aqueous dispersion. The addition and mixing are preferably performed at the same time, and the method may be performed by any method such as a method of adding to the liquid surface of the reaction bath or a method of adding to the liquid. A method of adding and mixing is preferable. Mixing in the transfer means means line mixing. That is, the solution containing silver ions and the aliphatic carboxylic acid alkali metal salt solution or suspension are mixed before entering the batch for storing the mixed solution containing the reactant. As the stirring means in the mixing section, any means such as mechanical stirring such as a homomixer, static mixer, turbulent flow effect or the like may be used, 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 Japanese Patent Application Laid-Open No. 10-62899, European Patent Application Publication No. 803,763A1, European Patent Application Publication No. 962,812A1, Japanese Patent Application Laid-Open No. 2001-167022, and Japanese Patent Application Laid-Open No. 2000-16722. 7683, 2000-72711, 2001-163889, 2001-163890, 2001-163827, 2001-33907, 2001-188313, 2001-83652. No. 2002, No. 2002-6442, No. 2002-31870, No. 2003-280135, No. 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 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. Yes, and more preferred is the addition of no silver halide grains.

  In the present invention, a photothermographic material can be produced by mixing an organic silver salt water dispersion and a photosensitive silver halide grain dispersion. The mixing ratio of the organic silver salt and the photosensitive silver salt can be selected according to the purpose, but 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%, especially The range of 3-15 mol% is preferable. 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 grains according to the present invention (hereinafter also referred to as photosensitive silver halide grains) are photosensitive silver halide grains. The silver halide grains inherently absorb light as an intrinsic property of silver halide crystals, or absorb visible light or infrared light by an artificial physicochemical method, or red from the ultraviolet region. Absorbs light in any region within the light wavelength range of the outside light region. The silver halide crystal grains are processed and manufactured so that physicochemical changes can occur in the silver halide crystal and / or on the crystal surface when the light is absorbed.

  The silver halide grains themselves according to the present invention 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 an acidic method, a neutral method, an ammonia method, etc. may be used, and a method of reacting a soluble silver salt and a soluble halogen salt may be any one of a one-side mixing method, a simultaneous mixing method, a combination thereof, and the like. Good. Among the above methods, the so-called controlled double jet method in which silver halide grains are prepared while controlling the formation conditions is preferable.

  Usually, silver halide seed grains are divided into two stages: grain nucleation and grain growth, and these may be performed continuously at a time, 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 separated, 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 step). Thereafter, 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 formation of grains, a desired silver halide emulsion can be obtained by removing unnecessary salts and the like by a desalting step by a known desalting method such as a noodle method, a flocculation method, an ultrafiltration method, or an electrodialysis method. .

  In the present invention, the grain size distribution of silver halide grains is preferably monodispersed. The term “monodispersed” as used herein 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, tetrahedron grains, tabular grains, spherical grains, rod-like grains, potato-like grains, etc. Among these, cubic, octahedral, 14 Planar and tabular silver halide grains are preferred.

  The average aspect ratio when using tabular silver halide grains is preferably 1.5 or more and 100 or less, more preferably 2 or more and 50 or less. 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 grains. However, when using a sensitizing dye having crystal habit (plane) selectivity, it is preferable to use silver halide grains having a relatively high proportion of crystal habit that is suitable for the selectivity. For example, when a sensitizing dye that is selectively adsorbed on the crystal face of the Miller index [100] is used, the proportion of the [100] face in the outer surface of the silver halide grain is preferably high. And this ratio is preferably 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, and particularly preferably used at the time of nucleation of silver halide grains.

  In the present invention, the low molecular weight gelatin preferably has an average molecular weight of 50,000 or less, more preferably 2,000 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 is produced from gelatin that is generally used and has an average molecular weight of about 100,000. For example, an gelatin-degrading enzyme is added to the gelatin aqueous solution for enzymatic decomposition, acid or alkali is added for heating to hydrolyze, thermal decomposition is performed by heating at atmospheric pressure or under pressure, and decomposition is performed by ultrasonic irradiation. Alternatively, these methods can be used in combination.

  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 an ammonium group substituted with a hydrogen atom, an alkali metal atom, an ammonium group, or an alkyl group having 5 or less carbon atoms. And B represents a chain or cyclic group forming 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 comprises a step of producing a gelatin aqueous solution, a step of adding a water-soluble halide and a water-soluble silver salt to the gelatin solution, and an emulsion. It is used in the step of coating on a support. These steps have been preferably used as an antifoaming agent for significant foaming when the emulsion raw material is stirred or moved. A technique used as an antifoaming agent is described, for example, in JP-A No. 44-9497. The polyethylene oxide compound represented by the above general formula 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 represented by the above general formula may be present at the time of nucleation and is preferably added in advance to the dispersion medium before nucleation, but may be added during nucleation or You may add and use for the silver salt aqueous solution and halide aqueous solution which are used at the time of formation. Preferably, it is used by adding 0.01 to 2.0% by mass to the halide aqueous solution or both aqueous solutions. Further, the compound represented by the above general formula is preferably present for a time of at least 50% of the nucleation step, and more preferably for a time of 70% or more. The compound represented by the above general formula 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 rising pattern (for example, 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 increased 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 at the time of 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 the nuclei to be formed, and is preferably pH 2 to 6. Moreover, pBr at the time of nucleation is 0.05-3.0 normally, Preferably it is 1.0-2.5, More preferably, it is 1.5-2.0.

  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. If the average grain size of the silver halide grains is smaller than 10 nm, the image density decreases, or the light irradiation image storage stability (the image obtained by heat development is used for diagnosis in a bright room or stored in a bright room) Storage stability) may be deteriorated. On the other hand, if it exceeds 50 nm, the image density may decrease.

  The average grain diameter referred to here is the length of the edge of the silver halide grains when the silver halide grains contained in the silver halide grain emulsion are cubic or octahedral so-called normal crystals. 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, when it is not a normal crystal, 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 preferable that the photosensitive layer is composed of two or more layers, and the silver halide grain emulsions having the two average grain sizes are separately contained in each layer.

(Silver halide grains having a silver iodide content of 5 mol% to 100 mol%)
As the silver halide grains according to the present invention, silver halide grains containing silver iodide can be preferably used. As the halogen composition, the silver iodide content is preferably 5 mol% or more and 100 mol% or less. More preferably, they are 40 mol% or more and 100 mol% or less, More preferably, they are 70 mol% or more and 100 mol% or less, Especially preferably, they are 90 mol% or more and 100 mol% or less. 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 with a high silver iodide content inside and / or on the surface can also be preferably used. A preferable structure is a 2- to 5-fold structure, more preferably 2- to 4-fold core / shell particles.

  Examples of the method for introducing silver iodide into the silver halide grains according to the present invention include 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 iodine. There is a method of adding at least one fine grain of silver chlorobromide. In addition, there is a method using an iodide ion releasing agent described in JP-A-5-323487 and JP-A-6-11780.

  The silver halide grains according to the present invention preferably exhibit direct transition absorption derived from the silver iodide crystal structure at a wavelength between 350 nm and 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 nm to 430 nm.

(Heat conversion internal latent image type silver halide grains)
The photosensitive silver halide grain according to the present invention is a heat-converted internal latent image type (post-thermal development internal latent image type) silver halide grain disclosed in JP2003-270755A and JP2005-106927A. It is preferable. That is, silver halide grains whose surface sensitivity is lowered by converting from a surface latent image type to an internal latent image type by heat development. 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 the exposure after the thermal development process, a larger number of latent images are formed inside the surface of the silver halide grains, so that the silver halide grains that suppress the formation of latent images on the surface are sensitive. And preferred in view of image storage stability.

  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. In addition, 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.

  It is also preferable depending on the purpose that the silver halide grain emulsion is 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 the 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 temperature. For example, although a polymer having an acidic group such as a carboxyl group becomes hydrophilic in a dissociated state depending on the type, it becomes 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. Polymers such as poly-N-i-propylacrylamide and copolymers thereof as well-known thermosensitive polymers are also included in the present invention. It is sufficient that micelles are formed and uniformly emulsified even if they are not completely dissolved.

  In the present invention, since various monomers are combined, it is not generally stated which monomer should be used and how much, but a desired polymer can be obtained by combining a hydrophilic monomer and a hydrophobic monomer in an appropriate ratio. Is easily understood.

  The polymer that dissolves in both the water and the organic solvent may be adjusted by adjusting the conditions such as pH as described above, or may not be adjusted. However, those having a solubility of at least 1% by mass (25 ° C.) in water and an organic solvent having a solubility of 5% by mass (25 ° C.) in methyl ethyl ketone are preferred. 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 Paragraph "0025" of Unexamined-Japanese-Patent No. 2005-316054 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 Science 2, Synthesis and Reaction of Polymers” edited by the Society of Polymer Science, Kyoritsu Shuppansha, 1995. It is also described in detail in Yuza 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. When the molecular weight is less than 10,000, the effect cannot be exhibited, and when it exceeds 100,000, the polymerizability with the copolymerization monomer forming the main chain is deteriorated. Specifically, Toagosei Co., Ltd. product: AA-6, AS-6S, AN-6S etc. can be 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 thereof 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, etc. 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 according to the present invention can be chemically sensitized. For example, use of compounds that release chalcogens such as sulfur, selenium, and tellurium and noble metal ions that release noble metal ions such as gold ions by the methods described in JP-A Nos. 2001-249428 and 2001-249426 To do. Then, it is possible to form and impart a chemical sensitization center (chemical sensitization nucleus) capable of capturing electrons or holes generated by photoexcitation of photosensitive silver halide grains or spectral sensitizing dyes on the grains. In particular, it is preferably chemically sensitized with an organic sensitizer containing a chalcogen atom.

  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. Among them, it is preferable that the chalcogen atom is at least one compound having a structure in which a carbon atom or a phosphorus atom is linked with a double bond. In particular, a thiourea derivative having a heterocyclic group and a triphenylphosphine sulfide derivative are preferred.

  As a method for chemical sensitization, techniques according to various chemical sensitization techniques conventionally used in the production of conventional silver halide light-sensitive materials for wet processing can be used (reference: (1) T Edited by H. James “The Theory of the Photographic Process”, 4th Edition, McMillan Publishing Co., Ltd., (2) edited by the Japan Photographic Society, “Basics of Photographic Engineering (Silver Salt Photography), Corona, 1979) 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, etc., but is 10 ⁻⁸ to 10 ⁻ per mol of silver halide. ² mol is preferred, more preferably 10 ⁻⁷ to 10 ⁻³ mol.

  There are no particular restrictions on the environmental conditions for chemical sensitization. Contains chalcogen atoms in the presence of silver chalcogenide or silver nuclei on photosensitive silver halide grains or compounds that can annihilate or reduce their size, or in the presence of an oxidant that can specifically oxidize silver nuclei It may be preferable to perform chalcogen sensitization using an organic sensitizer. The sensitizing conditions in this case are preferably 6 to 11 as pAg, more preferably 7 to 10, pH 4 to 10, more preferably 5 to 8, and the temperature increases at 30 ° C. or lower. It is preferable to give a feeling.

  In addition, chemical sensitization using these organic sensitizers is preferably performed in the presence of a heteroatom-containing compound having adsorptivity to spectral sensitizing dyes or silver halide grains. By performing chemical sensitization in the presence of a compound having an adsorptivity to silver halide, dispersion of the chemical sensitization central core can be prevented, and high sensitivity and low fog can be achieved. Although the spectral sensitizing dye 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. In the nitrogen-containing heterocyclic compound, examples of the heterocyclic ring include pyrazole ring, pyrimidine ring, 1,2,4-triazole ring, 1,2,3-triazole ring, 1,3,4-thiadiazole ring, 1,2 , 3-thiadiazole ring, 1,2,4-thiadiazole ring, 1,2,5-thiadiazole ring, 1,2,3,4-tetrazole ring, pyridazine ring, 1,2,3-triazine ring, these rings Can be mentioned, for example, a triazolotriazole ring, a diazaindene ring, a triazaindene ring, a pentaazaindene ring, and the like. A heterocyclic ring in which a monocyclic heterocyclic ring and an aromatic ring are condensed, for example, a phthalazine ring, a benzimidazole ring, an indazole ring, a benzthiazole ring, or the like can also be applied.

  Of these, an azaindene ring is preferable, and an azaindene compound having a hydroxyl group as a substituent, for example, a hydroxytriazaindene, tetrahydroxyazaindene, hydroxypentaazaindene compound, or the like is 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 amount of these heterocyclic compounds added 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 per mole of silver halide. It is in the range of ˜1 mol, preferably in the range of 10 ⁻⁴ to 10 ⁻¹ mol.

  The photosensitive silver halide according to the present invention 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-described 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, A borane 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.

  In the present invention, when chemical sensitization is performed on the surface of the photosensitive silver halide grains, it is necessary that the chemical sensitization effect substantially disappears after the thermal development process. Here, the chemical sensitization effect substantially disappears when the sensitivity of the imaging material obtained by the chemical sensitization technique is 1.1 when the chemical sensitization is not performed after the thermal development process. Say to decrease to less than double. 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 is included during thermal development. For example, it is necessary to contain an appropriate amount of the above-mentioned halogen radical releasing compound or the like in the emulsion layer or / and the non-photosensitive layer of the imaging 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 in the present invention is preferably subjected to spectral sensitization by adsorbing a spectral sensitizing dye. As spectral sensitizing dyes, cyanine dyes, merocyanine dyes, complex cyanine dyes, complex merocyanine dyes, holopolar cyanine dyes, styryl dyes, hemicyanine dyes, oxonol dyes, hemioxonol dyes, and the like can be used. For example, JP-A-63-159841, JP-A-60-140335, JP-A-63-231437, JP-A-63-259651, JP-A-63-304242, JP-A-63-15245, US Pat. No. 4,639,414, No. 4,740,455, No. 4,741,966, No. 4,751,175, No. 4,835,096 can be used.

  Useful sensitizing dyes used in the present invention include, for example, Research Disclosure (hereinafter abbreviated as RD) 17643IV-A (December 1978 p.23), RD18431X (August 1978 p.437). It is described in the literature described or cited. In particular, it is preferable to use a sensitizing dye having a spectral sensitivity suitable for the spectral characteristics of the light sources of various laser imagers and scanners. For example, compounds described in JP-A Nos. 9-34078, 9-54409, and 9-80679 are preferably used.

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

  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 sensitization disclosed in US Pat. Nos. 4,536,473, 4,515,888, 4,959,294, and the like. Examples include dyes.

  In the photothermographic material used in the thermal development method of the present invention, the sensitizing dye represented by the general formula (1) and the general formula (2) described in US Patent Publication No. 2004-0224266 are used. It is preferable to contain at least one of the represented sensitizing dyes. It is more preferable to contain at least one of a sensitizing dye represented by the general formula (5) and a sensitizing dye represented by the general formula (6) of the US Patent Publication. It is particularly preferable to use the sensitizing dye represented by the general formula (5) and the sensitizing dye represented by the general formula (6) in combination for improving the exposure wavelength dependency at the time of exposure.

  The above-mentioned infrared sensitizing dyes are described in, for example, The Chemistry of Heterocyclic Compounds, Volume 18 by The FM Hammer, The Cyanine Dies and Related Compounds (A. Weissberger ed. It can be easily synthesized by this method.

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

  In the present invention, one kind of spectral sensitizing dye may be used alone, but as described above, it is preferable to use a combination of plural kinds of spectral sensitizing dyes. The combination is often used for the purpose of supersensitization and enlargement or adjustment of the photosensitive wavelength region.

  The emulsion used in the photothermographic material of the present invention is a dye having no spectral sensitizing action or a substance that does not substantially absorb visible light together with a sensitizing dye, and exhibits a supersensitizing effect. Such a substance may be contained 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. Examples of supersensitizers include heteroaromatic mercapto represented by the following. A compound or a mercapto derivative compound is preferred.

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

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

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

  In addition to the supersensitizer described above, macrocycles having heteroatoms disclosed in JP-A No. 2001-330918 can also be used as the supersensitizer.

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

  In the present invention, it is necessary that the spectral sensitizing dye is adsorbed on the surface of the photosensitive silver halide grain to effect spectral sensitization, and that the spectral sensitizing effect should substantially disappear after the thermal development process. It is. 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 sensitization effect in the thermal development process, use a spectral sensitizing dye that is easily detached from the silver halide grains by heat during thermal development or / and destroy the spectral sensitizing dye by an oxidation reaction. Use an oxidizing agent that can. For example, an appropriate amount of the above-mentioned halogen radical releasing compound or the like needs to be contained in the emulsion layer and / or the non-photosensitive layer of the imaging 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 according to the present invention can reduce silver ions in the photosensitive layer and is also referred to as 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 of reducing agents. 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 may be the same or different represent a group capable of substituting a hydrogen atom or a benzene ring. 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, the compound of (RD1) and the compound of the following general formula (RD2) can be used in combination in order to control the heat development characteristics.

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 combined ratio, [the mass of the compound of (RD1)]: [the mass of the compound of general formula (RD2)] is preferably 5:95 to 45:55, more preferably 10:90 to 40: 60.

In the general formula (RD1), X ₁ represents a chalcogen atom or CHR ₁ . The chalcogen atom is sulfur, selenium or tellurium, preferably a sulfur atom. R ₁ in CHR 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 atom, a chlorine atom, a 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, and hexyl. Alkenyl groups such as vinyl, allyl, butenyl, hexenyl, hexadienyl, ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl, Examples of the aryl group include a benzene ring and a naphthalene ring, and examples of the heterocyclic group include thiophene, furan, imidazole, pyrazole, and pyrrole.

  These groups may further have a substituent. Specific examples of the substituent include 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 groups (methylthio, trifluoromethylthio, etc.), Sil group (acetyl group, benzoyl group), carboxyl group, alkylcarbonylamino group (acetylamino etc.), ureido group (methylaminocarbonylamino etc.), alkylsulfonylamino group (methanesulfonylamino etc.), alkylsulfonyl group (methanesulfonyl) , Trifluoromethanesulfonyl, etc.), 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 group, phosphono group, sulfite group, sulfino group, alkylsulfonylaminocarbonyl group (methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl etc.), alkylcarbonylaminosulfonyl group (acetamidesulfonyl, methoxyacetamidosulfonyl etc.), alkynyl Examples thereof include aminocarbonyl groups (acetamidocarbonyl, 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.

R ₂ represents an alkyl group, at least one of which 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, sulfonamide group, sulfonyl group, phosphoryl group, acyl group, carbamoyl group , Ester groups, halogen atoms and the like. 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.

R ₃ 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 such as fluorine, chlorine, bromine, 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. 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 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. preferable. More preferably, R ₃ is an alkyl group having 3 to 10 carbon atoms having a hydroxyl group as a substituent, or an alkyl group having 3 to 10 carbon atoms having a group that can be deprotected to form a hydroxyl group as a substituent. It is. When the carbon number of the alkyl group is in this range, it is preferable in that an image suitable for diagnosis within an average gradation range of 2.0 to 6.0 can be obtained without causing the image to be hardened. R ₃ is particularly preferably an alkyl group having 3 to 5 carbon atoms having a hydroxyl group as a substituent. Examples of R ₃ 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 forms a hydroxyl group by deprotection by the action of an acid and / or heat.

  Specifically, ether groups (methoxy groups, tert-butoxy groups, allyloxy groups, benzyloxy groups, triphenylmethoxy groups, trimethylsilyloxy groups, etc.), hemiacetal groups (tetrahydropyranyloxy groups, etc.), ester groups (acetyl) Oxy group, benzoyloxy group, p-nitrobenzoyloxy group, formyloxy group, trifluoroacetyloxy group, pivaloyloxy group, etc.), carbonate group (ethoxycarbonyloxy group, phenoxycarbonyloxy group, tert-butyloxycarbonyloxy group, etc.) ), Sulfonate groups (p-toluenesulfonyloxy group, benzenesulfonyloxy group etc.), carbamoyloxy groups (phenylcarbamoyloxy group etc.), thiocarbonyloxy groups (benzylthiocarbonyloxy group etc.), Ester group, sulfenates group (2,4-dinitrobenzene sulfenyl group and the like).

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 3-hydroxypropyl. 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 Ethoxy, 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-pi Lysylaminosulfonyl, 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 general formula (RD2), R ₅ is the same group as R _1, and R ₈ is the same group as R ₄ . 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 a benzene ring. Examples of groups that can be substituted on the benzene ring include halogen atoms such as fluorine, chlorine, bromine, 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 include groups such as methyl, ethyl, propyl, and butyl.

  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 , Ester groups, halogen atoms and the like.

R ₆ may form a saturated ring with (R ₈ ) _n and (R ₈ ) _m . R ₆ is preferably methyl. 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 EP 1,278,101, Specific examples include compounds (1-24), (1-28) to (1-54), and (1-56) to (1-75) described in p21 to p28.

  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.

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

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 diagnostic 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 color coordinates a ^* and b ^* of the color space L ^* a ^* b ^* color space, which is a color space having a perceptually uniform rate recommended by the International Commission on Illumination (CIE) in 1976. Using the following formula.

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 invention is preferably such that the range of the hue angle hab is 180 degrees <hab <270 degrees. More preferably, it was found that 200 degrees <hab <270 degrees, and most preferably 220 degrees <hab <260 degrees. This is disclosed in Japanese Patent 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 by adjusting to a numerical value, it is possible to obtain a diagnostic image with a preferable visual color tone. For example, it describes in Unexamined-Japanese-Patent No. 2000-29164.

However, as a result of further intensive studies on the photothermographic material of the present invention, the horizontal axis is u ^* or a ^* , in the CIE 1976 (L ^* u ^* v ^* ) color space or (L ^* a ^* b ^* ) color space. U ^* , v ^* or a ^* , b ^* at various photographic densities were plotted on a graph with the axis as v ^* or b ^* . From this, it was found that when a linear regression line was created, the linear regression line was adjusted to a specific range so that the diagnostic performance was 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 the photothermographic treatment of the photothermographic material is measured at 0.5, 1.0, 1.5 and the lowest optical density. CIE 1976 (L ^* u ^* v ^* ) Linear regression line created by arranging u ^* and v ^* at the above optical densities on two-dimensional coordinates where the horizontal axis of the color space is u ^* and the vertical axis is v ^*. It is preferable that the determination coefficient (heavy determination) R ² is 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) Further, the optical densities of the photothermographic material are measured at 0.5, 1.0, 1.5 and the lowest optical density. CIE 1976 (L ^* a ^* b ^* ) linear regression line created by arranging a ^* and b ^* at each optical density in two-dimensional coordinates where the horizontal axis of the color space is a ^* and the vertical axis is b ^*. It is preferable that the determination coefficient (heavy determination) R ² is 0.998 to 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.

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

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 part thus produced is measured with a spectral colorimeter (manufactured by 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 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 becomes a bluish direction, and when it is a filament shape, it becomes a yellowish direction. That is, it can be adjusted in consideration of the tendency of the developed silver shape.

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

  When rapid processing is performed using a compact laser imager with a short cooling section length, there may be a problem that the silver tone is greatly deviated from the neutral preferable tone as compared with the normal processing. In order to solve these problems, a compound (such as a leuco dye or a coupler compound) that forms an imagewise color image during heat development to form a dye image is used in addition to the above-mentioned toning agent such as a phthalazine compound. It is preferable to do. As these compounds, a compound that develops color during thermal development and forms a dye image having a maximum absorption wavelength of 360 to 450 nm, or a color that forms color during thermal development and forms a dye image that has a maximum absorption wavelength of 600 to 700 nm or less. Compounds are preferred. The case where both compounds are contained is particularly preferable for obtaining a good silver tone. As these compounds, it is preferable to use couplers disclosed in JP-A No. 11-288057, European Patent No. 1,134,611A2, etc., or leuco dyes described in detail below.

(Leuco dye)
As described above, the photothermographic material according to the invention can also be adjusted in color tone using a leuco dye. The 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 the body 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. For example, biphenol leuco dyes, phenol leuco dyes, indoaniline leuco dyes, acrylated azine leuco dyes, phenoxazine leuco dyes, phenodiazine leuco dyes. And phenothiazine leuco dye. Also useful are US Pat. Nos. 3,445,234, 3,846,136, 3,994,732, 4,021,249, 4,021,250, 4,022,617, 4,123,282, 4,368,247, 4,461,681, and JP-A-50-36110, 59-26831, These are leuco dyes disclosed in JP-A-5-204087, JP-A-11-231460, JP-A-2002-169249, and JP-A-2002-236334.

  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. Further, the use of a highly active reducing agent for rapid processing changes the color tone (especially yellowishness) depending on the amount and ratio of use. Further, by using fine silver halide grains or by reducing the particle size of developed silver, the image becomes excessively reddish particularly at a high density portion having a density of 2.0 or more. In order to prevent this, it is preferable to use a leuco dye that develops yellow and cyan colors 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 a dye image formed with a leuco dye is preferably 0.01 or more and 0.50 or less, more preferably 0.02 or more and 0.30 or less, and particularly preferably 0.8. It is preferable that the color is developed so as to have 03 or more and 0.10 or less. 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 the present invention, a color image forming agent whose absorbance at 360 to 450 nm is increased by oxidation is particularly preferably used as a yellow color-forming leuco dye. These color image forming agents are particularly preferably color image forming agents represented by the following general formula (YA).

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, and steric rather than i-propyl. Are preferably large groups (i-propyl, i-nonyl, t-butyl, t-amyl, t-octyl, cyclohexyl, 1-methyl-cyclohexyl, adamantyl, etc.), among which secondary or tertiary alkyl Group is preferable, and tertiary alkyl groups such as t-butyl, t-octyl, and t-pentyl are particularly preferable. 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. The alkyl group represented by R ₁₂ 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 an acetylamino group, an alkoxyacetylamino group, and an aryloxyacetylamino group. 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 ₁₁ and R ₁₂ are not 2-hydroxyphenylmethyl groups.

R ₁₃ represents a hydrogen atom or a substituted or unsubstituted alkyl group. 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 that for R ₁₁ . 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 represents a group substitutable on the benzene ring, and is, for example, the same group as described for the substituent R ₄ in the general 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), the 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, but an alkyl group is more preferable. 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, Examples thereof include compounds (ITS-1) to (ITS-12) described in paragraph “0026” of EP 1,211,093.

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

  The addition amount of the compound of the general formula (YA) (including hindered phenol compounds and compounds of the general formula (YB)) is usually 0.00001 to 0.01 mol, preferably 0. 0005 to 0.01 mol, more preferably 0.001 to 0.008 mol.

  Moreover, it is preferable that the addition amount ratio with respect to the sum total of the reducing agent represented by general formula (RD1) and (RD2) of yellow coloring leuco dye is 0.001-0.2 in molar ratio, 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 yellow color-forming leuco dye is preferably 0.01 or more and 0.50 or less. More preferably, the color is developed so as to have 0.02 or more and 0.30 or less, particularly 0.03 or more and 0.10 or less.

(Cyan coloring leuco dye)
The photothermographic material according to the invention preferably adjusts 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 is 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 the present invention, a color image forming agent whose absorbance at 600 to 700 nm is increased by oxidation is particularly preferably used as a cyan color-forming leuco dye. Examples of these compounds include compounds of general formula (I) to general formula (IV) described in JP-A-59-206831 (particularly compounds having λmax in the range of 600 to 700 nm) and JP-A-5-204087. Specifically, the compounds of (1) to (18) described in paragraphs “0032” to “0037”) and compounds of general formulas 4 to 7 in JP-A No. 11-231460 (specifically, paragraph “0105”). No. 1 to No. 79 compounds).

  Next, specific examples of the cyan color-forming leuco dye will be shown, but the present 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 or more and 0.50 or less. More preferably, the color is developed so as to have 0.02 or more and 0.30 or less, particularly 0.03 or more and 0.10 or less.

  In the present invention, a subtle color tone can be adjusted by using a magenta color developing leuco dye or a yellow color developing leuco dye in addition to the cyan color developing leuco dye.

  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). . For example, it may be contained in the coating solution by any method such as a solution form, an emulsified dispersion form, a solid fine particle dispersion form, etc., and may be 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. Good. 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 present invention, the photosensitive layer and the non-photosensitive layer according to the present invention can contain a binder for various purposes.

  The binder contained in the photosensitive layer according to the present invention can carry an organic silver salt, silver halide grains, a reducing agent, and other components. Suitable binders are transparent or translucent and generally colorless. is there. Examples thereof include natural polymers, synthetic polymers, 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, as needed, said binder can be used in combination of 2 or more type.

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), and at least one polar group selected from an epoxy group, —SH, —CN, etc. is introduced by copolymerization or addition reaction. In particular, —SO ₃ M and —OSO ₃ M are 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 (image forming layer), the ratio of the binder to the organic silver salt is preferably 15: 1 to 1: 2 (mass ratio), and particularly 8: A range of 1-1: 1 is preferred. 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. If it is less than 1.5 g / m ² , the density of the unexposed area is significantly increased and may not be used.

  The glass transition temperature (Tg) of the binder used in the present invention 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.) = V ₁ Tg ₁ + v ₂ Tg ₂ +... + V _n Tg _{n
Wherein, v 1, v 2 ··· v} n represents the mass fraction of the monomer in the _{copolymer, Tg 1, Tg 2 ··· Tg} n from each monomer in the copolymer Tg (° C.) of the obtained single polymer is represented. 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 according to 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.

  Of these, particularly preferred examples include methacrylic acid alkyl esters, methacrylic acid aryl esters, and styrenes. Among such polymer compounds, a polymer compound having an acetal group is preferably used. Even a polymer 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 2000%, and stress at break 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. Further, when a polymer latex is used in 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, and 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 these 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 according to the invention 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 according to 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 Polymer 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 too small, the mechanical strength of the photosensitive layer is insufficient, and when the molecular weight is too large, the film forming property is poor and both are not preferable.

  The polymer latex preferably has an equilibrium water 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 each latex 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 the photosensitive layer coating solution, it is preferable to use a coating solution that has been mixed for 30 minutes to 24 hours after mixing the organic silver salt and the aqueous-dispersed polymer latex. More preferably, after mixing, 60 minutes to 12 hours are allowed to pass, and particularly preferably, a coating liquid having passed 120 minutes to 10 hours is used.

  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 according to the present invention may contain a cross-linking agent capable of connecting the binders according to the present invention by cross-linking. By using a crosslinking agent for the binder, it is known that filming is improved and development unevenness is reduced, but there is also an effect of suppressing fogging during storage and suppressing generation of printout silver after development. is there.

  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, and the following isocyanate-based, silane compound-based, epoxy-based compounds, and acid anhydrides are preferable.

  Isocyanate-based crosslinking agents are isocyanates having at least two isocyanate groups and adducts thereof (adducts). More specifically, aliphatic diisocyanates, aliphatic diisocyanates having a cyclic group, benzene Diisocyanates, naphthalene diisocyanates, biphenyl isocyanates, diphenylmethane diisocyanates, triphenylmethane diisocyanates, triisocyanates, tetraisocyanates, adducts of these isocyanates and divalent or trivalent polyalcohols with these isocyanates Adducts and the like. 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.

  Moreover, as an epoxy compound which can be used as a crosslinking agent, what is necessary is just to have one or more epoxy groups, and there is no restriction | limiting in the number of epoxy groups, molecular weight, and others. 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, molecular weight, and the like are not particularly limited as long as they have one or more acid anhydride groups.

-CO-O-CO-
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)
The photosensitive layer or the non-photosensitive layer according to the present invention may contain a silver saving agent. As used herein, the silver saving agent 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 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 both. Preferred examples of the silver saving agent include hydrazine derivative compounds, 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, US Pat. No. 5,464,738, columns 9 to 11. 1 to 12 described in JP-A-2001-27790, compounds H-1-1 to H-1-28 described in paragraphs “0042” to “0052”, and H-2-1 to H-2- 9, H-3-1 to H-3-12, H-4-1 to H-4-21, H-5-1 to H-5-5.

  Specific examples of the vinyl compound include compounds CN-01 to CN-13 described in columns 13 to 14 of US Pat. No. 5,545,515 and column 10 of US Pat. No. 5,635,339. Compounds HET-01 to HET-02 described in US Pat. No. 5,654,130, columns MA-10 to compounds MA-01 to MA-07, US Pat. No. 5,705,324 Compounds IS-01 to IS-04 described in columns 9 to 10 of the specification, 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 A-89 described in paragraphs “0075” to “0078” of JP 2000-267222 A, and paragraph “0025” of JP 2003-66558 A. ”To“ 0045 ”. Examples thereof include compounds A-1 to A-258.

  Specific examples of the quaternary onium compound include triphenyltetrazolium.

  Specific examples of the silane compound include alkoxysilane compounds 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 The salt is mentioned.

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

  Hereafter, the preferable specific example of the silver saving agent of this invention is given. The present invention is not limited to these.

(Thermal solvent)
The photothermographic material according to the invention preferably contains a thermal solvent. Here, the thermal solvent is defined as a material capable of lowering the thermal development temperature by 1 ° C. or more compared to the thermal development photosensitive material containing no thermal solvent with respect to the thermal solvent-containing thermal development photosensitive material. More preferred are materials that can lower the heat development temperature by 2 ° C. or more, and particularly preferred are materials that can be lowered by 3 ° C. or more. For example, for the photothermographic material A containing the material A, a photothermographic material B not containing the material A is prepared from the photothermographic material A. The photothermographic temperature for obtaining the density obtained by exposing the photothermographic material B to the photothermographic material A at a heat development temperature of 120 ° C. and a heat development time of 20 seconds with the same exposure amount and heat development time is 119. When the temperature is not higher than ° C., the material A added to the photothermographic material A is a thermal solvent.

  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) _n Z
In General Formula (TS), Y represents an alkyl group, an alkenyl group, an alkynyl group, an aryl group, or a heterocyclic group. Z represents a group selected from a hydroxy group, carboxy group, amino group, amide group, sulfonamide group, phosphoric acid amide group, cyano group, imide, ureido, sulfoxide, sulfone, phosphine, phosphine oxide or nitrogen-containing heterocyclic group. . n represents an integer of 1 to 3, which is 1 when Z is a monovalent group, and is the same as the valence of Z when Z is a divalent or higher group. 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. In general formula (TS), Y is a linear, branched or cyclic alkyl group (preferably having 1 to 40 carbon atoms, more preferably 1 to 30 carbon atoms, particularly preferably 1 to 25 carbon atoms such as methyl, ethyl, n -Propyl, iso-propyl, sec-butyl, t-butyl, t-octyl, n-amyl, t-amyl, n-dodecyl, n-tridecyl, octadecyl, icosyl, docosyl, cyclopentyl, cyclohexyl and the like. An alkenyl group (preferably having 2 to 40 carbon atoms, more preferably 2 to 30 carbon atoms, particularly preferably 2 to 25 carbon atoms such as vinyl, allyl, 2-butenyl, 3-pentenyl, etc.), an aryl group (Preferably having 6 to 40 carbon atoms, more preferably 6 to 30 carbon atoms, particularly preferably 6 to 25 carbon atoms such as phenyl and p-methyl. Phenyl, naphthyl, etc.), heterocyclic groups (preferably having 2 to 20 carbon atoms, more preferably 2 to 16 carbon atoms, particularly preferably 2 to 12 carbon atoms such as pyridyl, pyrazyl, imidazolyl, pyrrolidyl, etc. Represents.). These substituents may be further substituted with other substituents. These substituents may be bonded to each other to form a ring.

  Y may further have a substituent, and examples of the substituent include those described in “0015” of JP-A No. 2004-21068. The reason why development activity is achieved by using a thermal solvent is that the thermal solvent melts near the development temperature, so that it is compatible with substances involved in development, and a reaction at a lower temperature than when no thermal solvent is added. This is thought to be possible. 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 ° C. or more and 200 ° C. or less, more preferably 60 ° C. or more and 150 ° C. or less. 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 heat solvent having a melting point of 100 ° C. or higher and 150 ° C. or lower is preferable.

  Specific examples of the thermal solvent include compounds described in “0017” of JP-A No. 2004-21068, compounds described in “0027” of US 2002/0025498, MF-1 to MF-3, and MF6. MF-7, MF-9 to MF-12, MF-15 to MF-22.

Preferably the added amount of thermal solvent is 0.01~5.0g / m ² in the present invention, more preferably 0.05~2.5g / m ^2, more preferably 0.1~1.5g / M ² . The thermal solvent is preferably contained in the photosensitive layer. Moreover, although the said thermal solvent may be used independently, you may use it in combination of 2 or more type. In the present invention, 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 may be contained in the photothermographic material.

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

  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 vibration ball mill, a sand mill, a jet mill, a roller mill or ultrasonic waves. Is mentioned. In this case, a protective colloid (for example, polyvinyl alcohol) or a surfactant (for example, an anionic surfactant such as sodium triisopropylnaphthalenesulfonate (a mixture of three isopropyl groups having different substitution positions)) may be used. Good. 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 ppm to 1000 ppm. If the Zr content in the light-sensitive material is 0.5 mg or less per 1 g of silver, there is no practical problem. The aqueous dispersion preferably contains a preservative (for example, benzoisothiazolinone sodium salt).

(Anti-fogging and image stabilizer)
In any of the constituent layers of the photothermographic material according to the present invention, an antifoggant for preventing fogging during storage before thermal development, and image stabilization for preventing image deterioration after thermal development are provided. It is preferable to contain an agent.

  The antifogging and image stabilizer that can be used in the photothermographic material according to 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 the compound which can prevent reaction to contain is contained. Further, it is preferable that the photothermographic material or a compound capable of oxidatively bleaching silver atoms or metallic silver (silver clusters) generated during storage of the obtained image is contained. Specific examples of compounds having these functions include biimidazolyl compounds and iodonium compounds. The amount of the biimidazolyl compound and iodonium compound added 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 is used. It is preferable to use together. Specific examples of particularly preferred hydrogen bonding compounds in the present invention include, for example, compounds (II-1) to (II-40) described in paragraphs [0061] to [0064] of JP-A-2002-90937. Is mentioned.

  On the other hand, many compounds that can release halogen atoms as active species are known as antifogging and image stabilizers. Specific examples of the compound that generates these active halogen atoms include compounds represented by general formula (9) described in paragraphs [0264] to [0271] of JP-A No. 2002-287299.

  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-mentioned publications, compounds (III-1) to 3 described in paragraphs “0086” to “0087” of JP-A No. 2002-169249. (III-23), compounds 1-1a to 1-1o and 1-2a to 1-2o described in paragraphs “0031” to “0034” of JP-A-2003-50441, and paragraphs “0050” to “0056” Compounds 2a to 2z, 2aa to 2ll, 2-1a to 2-1f, Compounds 4-1 to 4-32 described in paragraphs “0055” to “0058” of JP-A No. 2003-91054, paragraphs “0069” to Examples thereof include compounds 5-1 to 5-10 described in “0072”.

  Antifoggants preferably used in the present invention include, for example, compound examples a to j described in paragraph “0012” of JP-A-8-314059 and paragraph “0028” of JP-A-7-209797. Thiosulfonate esters A to K, compound examples (1) to (44) described from p14 of JP-A No. 55-140833, compounds described in paragraph “0063” of JP-A No. 2001-13627 (I-1 ) To (I-6), (C-1) to (C-3) described in paragraph “0066”, and compounds (III-1) to (III-) described in paragraph “0027” of JP-A-2002-90937. 108), compounds VS-1 to VS-7 and compounds HS-1 to HS-5 described in paragraph “0013” of JP-A-6-208192 as compounds of vinyl sulfones and / or β-halo sulfones. KS-1 to KS-8 compounds described in JP 2000-330235 A as sulfonylbenzotriazole compounds, PR-01 to PR-08 described in JP-T 2000-515995 as substituted propene nitrile compounds, Examples thereof include compounds (1) -1 to (1) -132 described in paragraphs “0042” to “0051” of JP-A-2002-207273.

  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 of the compound relative to the moles of silver, preferably 0.02 to 0.6 moles of the compound relative to the moles of silver.

  In addition to the above compounds, the photothermographic material according to the present invention may contain various compounds conventionally known as antifoggants, but the reactive species similar to the above compounds are included. Even if it is a compound which can be produced | generated, the compound from which an antifogging mechanism differs may be sufficient. 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. Examples thereof include compounds described in the specification, JP 4,756,999, JP-A-9-288328, and JP-A-9-90550. Further, as other antifoggants, compounds disclosed in US Pat. No. 5,028,523 and European Patent Nos. 600,587, 605,981 and 631,176 are exemplified. Can be mentioned.

(Toning agent)
The photothermographic material according to the present invention forms a photographic image by heat development, and a toning agent (toner) for adjusting the color tone of silver is dispersed in a normal (organic) binder matrix as necessary. It is preferable to contain in the state.

  Examples of suitable toning agents used in the present invention include Research Disclosure (RD) 17029, U.S. Pat. Nos. 4,123,282, 3,994,732, 3,846,136, and the like. For example, the following are disclosed.

  Imides (for example, succinimide, phthalimide, naphthalimide, N-hydroxy-1,8-naphthalimide); mercaptans (for example, 3-mercapto-1,2,4-triazole); phthalazinone derivatives or metal salts of these derivatives ( For example, phthalazinone, 4- (1-naphthyl) phthalazinone, 6-chlorophthalazinone, 5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione); phthalazine and phthalic acids ( For example, combinations of phthalic acid, 4-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 Products (eg, phthalic acid, 4-methylphthalic acid, 4 The combination and the like with at least one compound selected from nitrophthalic acid and tetrachlorophthalic anhydride). Particularly preferred toning agents are combinations of phthalazinone or phthalazine with phthalic acids and phthalic anhydrides. In the present invention, phthalazine and its derivatives and phthalazinone and its derivatives are preferably used in a molar ratio of 0.1 to 2.0 with respect to the reducing agent, more preferably 0.2 to 1.5, Preferably it is the range of 0.3-1.0. The phthalic acid and derivatives thereof, and phthalic anhydride and derivatives thereof in the present invention are preferably used in the range of 0.0001 mol to 1 mol, more preferably 0.001 to 1 mol per mol of silver applied. 0.5 mol, more preferably 0.002 to 0.2 mol.

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

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

In the general formula (SF), R _f 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 (for example, trifluoromethyl). Group, trifluoroethyl group, perfluoroethyl group, perfluorobutyl group, perfluorooctyl group, perfluorododecyl group and perfluorooctadecyl group) or fluorinated alkenyl group (for example, perfluoropropenyl group, perfluorobutenyl group) Perfluorononenyl group, perfluorododecenyl group, etc.). R _f preferably has 2 to 8 carbon atoms, more preferably 2 to 6 carbon atoms. R _f 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 divalent linking group having no fluorine atom include an alkylene group (for example, a methylene group, an ethylene group, a butylene group, etc.), Alkyleneoxy group (methyleneoxy group, ethyleneoxy group, butyleneoxy group, etc.), oxyalkylene group (for example, oxymethylene group, oxyethylene group, oxybutylene group, etc.), oxyalkyleneoxy group (for example, oxymethyleneoxy group, Oxyethyleneoxy group, oxyethyleneoxyethyleneoxy group, etc.), phenylene group, oxyphenylene group, phenyloxy group, oxyphenyloxy group, or a combination of these groups.

  A represents an anionic group or a salt thereof. For example, carboxylic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfonic acid group or a salt thereof (sodium salt, potassium salt and lithium salt), sulfuric acid half ester Group or a salt thereof (sodium salt, potassium salt and lithium salt), a phosphoric acid group or a salt thereof (sodium salt, potassium salt and the like) and the like.

  Y represents a (p + q) -valent linking group having no fluorine atom. For example, the trivalent or tetravalent linking group having no fluorine atom is composed mainly of a nitrogen atom or a carbon atom. An atomic group is mentioned. 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 (for example, trifluoromethyl group, pentafluoroethyl group, perfluorobutyl group, perfluorooctyl). Group and a compound having a perfluorooctadecyl group) and an alkenyl compound (for example, a perfluorohexenyl group and a perfluorononenyl group), a trivalent to hexavalent alkanol compound in which no fluorine atom is introduced, and a hydroxyl group, respectively. aromatic compound or a compound obtained by addition reaction and condensation reaction between the hetero compound having 3 or 4 (part R _f of alkanols compounds), further for example, introducing an anionic group (a) with sulfuric acid esterification, etc. Can be obtained.

  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 above-described fluorosurfactants include compounds (FS-1) to (FS-66) described in paragraphs “0029” to “0040” of JP-A No. 2003-149766, JP-A No. 2004-021084. Compound 1-1 to 1-4 described in paragraph “0014” of compound No., compounds 2-1 to 2-10 described in paragraph “0019”, and paragraph “0025” of Japanese Patent Application Laid-Open No. 2004-077772. Examples thereof include compounds described in paragraph “0030”.

  Below, the preferable specific compound of the fluorine-type surfactant represented by general formula (SF) is shown.

  Further, as fluorine surfactants other than those described above, compounds described in paragraph “0035” of JP-A No. 2004-117505, JP-A No. 2000-214554, JP-A No. 2003-156819, JP-A No. 2003-177494 are disclosed. The compounds described in JP-A No. 2003-114504, JP-A 2003-270754, and JP-A 2003-270760 may be used. In the present invention, it is particularly preferable to use a combination of an anionic fluorine-containing surfactant represented by the general formula (SF) and a known nonionic fluorine-containing surfactant from the viewpoint of improving charging characteristics and coating properties.

  As a method for 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 having a size of 1 μm or less can be added after being dispersed in water or an organic solvent by sand mill dispersion, jet mill dispersion, ultrasonic dispersion or homogenizer dispersion. 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 amount of the fluorosurfactant 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. If the range is less than the former range, the charging characteristics may not be obtained. If the range exceeds the former range, the humidity dependency is large and the storage stability under high humidity may be deteriorated.

(Layer containing radiation absorbing compound)
The layer on the side where the photosensitive layer is provided on the support of the photothermographic material according to the present invention and the layer provided on the side opposite to the side where the photosensitive layer is provided across the support Various known dyes and pigments can be used as the radiation-absorbing compound used in the above. Any of these dyes and pigments may be used. 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 (for example, compounds 1 to 9 described in JP-A-5-341441, compounds 3-6 to 18 and 3-23 to 38 described in JP-A-5-165147), azomethine Dyes (compounds 17 to 47 described in JP-A-5-341441), indoaniline dyes (for example, compounds 11 to 19 described in JP-A-5-289227, compound 47 described in JP-A-5-341441, And compounds 2-10 to 11 described in JP-A No. 165147) and azo dyes (compounds 10 to 16 described in JP-A-5-341441). For example, when the photothermographic material according to the present invention is used as an image recording material by infrared light, a squarylium dye having a thiopyrylium nucleus and a squarylium having a pyrylium nucleus as disclosed in JP-A-2001-83655. It is preferred to use dyes, or thiopyrylium croconium dyes similar to squarylium dyes, or pyrylium croconium dyes. 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. Examples of the dye include compounds described in JP-A-8-201959, compounds described in JP-T-9-509503, and compounds AD-1 to AD-55 described in JP-A-2003-195450. Is also preferable. When the photothermographic material according to the present invention is used as an image recording material by blue light, the compound No. described in JP-A-2003-215751 is used. 1-No. 93, and Dye-1 to Dye-51 described in JP-A-2005-157245 are preferably used. Further, these dyes may be added by any method such as a solution, an emulsion, a solid fine particle dispersion, or a mordanted state in a polymer mordant. 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. And a radiation absorbing compound (dye or pigment). The absorbance at the exposure wavelength in all the layers is set to 0.30 to 1.00. Further, radiation is applied to the layer opposite to the side where the photosensitive layer is provided across the support, specifically to the antistatic undercoat layer, antihalation layer and protective layer, more preferably to the antihalation layer. An absorptive compound (dye or pigment) is contained. And it is preferable to set the light absorbency in the exposure wavelength in all the layers of these layers in the range of 0.20-1.50. Moreover, it is preferable that the light absorbency in the exposure wavelength in the total layer of the layer by which the photosensitive layer on a support | substrate is provided is 0.40-0.90, Most preferably, it is 0.50-0.80. . Further, the absorbance at the exposure wavelength in the total 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 the density fluctuation accompanying the image product room and humidity change.

(Support)
Examples of the support material used in the photothermographic material according to the present invention include various polymer materials, glass, wool cloth, cotton cloth, paper, metal (aluminum, etc.), etc. A material that can be processed into a flexible sheet or roll is suitable. Therefore, as a support in the photothermographic material according to the present invention, cellulose acetate film, polyester film, polyethylene terephthalate (PET) film, polyethylene naphthalate (PEN) film, polyamide film, polyimide film, cellulose triacetate film (TAC) Alternatively, 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. Among these, 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. It is particularly preferable because of its high conductivity. 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%, but 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. Furthermore, 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. .

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 a transparent photothermographic material can be formed. 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. The thickness / 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))
In the present invention, when coating is performed using a slide coater, a thin undercoat layer (slip layer) is formed on the support, and on the photosensitive layer side, a slip layer, a photosensitive layer, and a protective layer on the photosensitive layer are formed. It is preferable to provide by simultaneous multilayer coating. 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 very thin by a layer containing an organic silver salt and a binder or a layer containing a binder. When the dry film thickness SA of the slip layer on the photosensitive layer side and the dry film thickness SB of the photosensitive layer are set, SA / SB is preferably 0.005 to 0.10. The SA / SB is preferably 0.01 to 0.07, more preferably 0.02 to 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 Sc of the slip layer on the back coat layer side and the dry film thickness Sd of the back coat layer are used, Sc / Sd is preferably 0.01 to 0.30. The Sc / Sd is preferably 0.05 to 0.25, more preferably 0.08 to 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 made 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. And homopolymers and copolymers. Among these, polymethyl methacrylate 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 preferably contain a polyester resin, an acrylic resin or a polyurethane resin. Let A be the mass ratio of the total amount of the polyester resin, acrylic resin or polyurethane resin in the backcoat layer to the total binder amount of the backcoat layer. When the mass ratio of the total amount of the polyester resin, acrylic resin or polyurethane resin in the undercoat layer on the backcoat layer side to the total binder amount in the undercoat layer is B, it is preferable that B> A. Here, the crosslinking agent is included in the binder. Polyester resin, acrylic resin or polyurethane resin is used as an adhesion promoting binder on the backcoat layer side in order to improve the adhesive layer with the support. However, it has been found that these adhesion promoting binders affect in-machine contamination during heat development. Therefore, the amount of the adhesion promoting binder existing on the surface of the back coat layer that contacts the heat development apparatus is reduced as much as possible, and the adhesion promoting binder is contained in the undercoat layer, so that the adhesion to the support is maintained. The occurrence of in-machine contamination in the heat developing apparatus has been improved. Here, the value of (B-A) is preferably 0.02 to 0.3, more preferably 0.05 to 0.2. A is preferably 0 or more and 0.01 or less, and 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 or more. The degree of improvement increases as the coating speed increases. A higher coating speed is preferable from the viewpoint of productivity, but 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. However, if the photosensitive layer is water-based, the water-based layer is used. 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 above-described constituent materials are dissolved or dispersed in a solvent, applying a plurality of these coating solutions simultaneously, and then performing a heat treatment. Is preferred. Here, "multiple simultaneous multi-layer coating" means that a coating solution for each constituent layer (for example, a photosensitive layer, a protective layer) is prepared, and each layer is repeatedly coated and dried when it is coated on a support. Instead, it means that each constituent layer can be formed in such a state that a multilayer coating and drying process can be performed simultaneously. 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 simultaneously to each constituent layer, for example, bar coater method, curtain coating method, dipping method, air knife method, hopper coating method, reverse roll coating method, gravure coating method, and extrusion. A known method such as a coating 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 undercoating when the back layer is provided. Regarding the simultaneous multilayer coating method in the photothermographic material, there is a detailed description in JP-A No. 2000-15173.

In the present invention, the silver coating amount is preferably selected in accordance with the purpose of the photothermographic material. However, for the purpose of medical images, 0.3 g / m ² or more, 1.5 g / m. m ² or less is preferable. 0.5 g / m ² or more and 1.4 g / m ² or less are more preferable, and 0.7 g / m ² or more and 1.2 g / m ² or less are particularly preferable. Among the applied silver amounts, those derived from silver halide preferably account for 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 particle diameter equivalent to a sphere) is preferably 1 × 10 ¹⁴ particles / m ² or more and 1 × 10 ¹⁸ particles / m ² or less. Furthermore, 1 × 10 ¹⁵ pieces / m ² or more and 1 × 10 ¹⁷ pieces / m ² or less are preferable.

Furthermore, the coating density of the non-photosensitive long-chain aliphatic carboxylate is 1 × 10 ⁻¹⁷ g or more, 1 × 10 1 per silver halide grain of 0.01 μm or more (equivalent particle diameter equivalent to sphere). ^-14 g or less is preferable, and 1 x 10 ^-16 g or more and 1 x 10 ^-15 g or less are more preferable.

  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.

In the present invention, 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 those described in paragraph “0030” of JP-A No. 2001-264930. However, it is not limited to these. 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 a temperature condition in a drying process after the coating process. The content of the solvent can be measured by gas chromatography under conditions suitable for detecting the contained solvent.

(Packaging body)
Hereinafter, the sheet-shaped recording material packaging method and the sheet-shaped recording material package preferably used in the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

  In the present invention, it is preferable that the cutting process and / or the packaging process be performed in an environment having a cleanliness of US Federal Standard 209d class 10,000 or less. By performing the cleaning in an environment of US Federal Standard 209d class 10,000 or less, the degree of in-machine contamination of the heat developing apparatus during heat development can be remarkably improved. Although the cause of the improvement of in-machine contamination of the heat developing apparatus by performing the cutting process and / or the packaging process in an environment having a cleanness of US Federal Standard 209d class 10,000 or less is unclear, 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 photothermographic material adhere to transport members such as rollers in the heat development apparatus, which is the cause of heat development. In-machine contamination occurs when chips dropped from the cut surface of the photosensitive material accumulate there.

The US federal standard 209d class 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-like recording material in a clean room. For example, a mechanism for applying an air flow to the sheet-like recording material is provided in the apparatus from cutting to packaging so that the sheet-like recording material is maintained in an environment of US Federal Standard 209d class 10,000 or less. Can also be processed.

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

  In the present specification, the packaging process means a process including at least a step of packaging the sheet-shaped recording material when the sheet-shaped recording material itself is attached to the image recording apparatus. When the load loaded with the sheet-like recording material is mounted on the image recording apparatus, it means a process including at least a step of packaging the sheet-like recording material load. That is, it means a step 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 cleanliness level does not necessarily need to be US federal standard 209d class 10,000 or less, but it is preferable to maintain an environment of US federal standard 209d class 10,000 or less. The same applies to the time until the manufactured sheet-like recording material is cut. The degree of cleanliness in the cutting process is preferably class 7,000 or less by a measuring method according to the US Federal Standard 209d. It is more preferably 4,000 or less, even more preferably 1,000 or less, and particularly preferably 500 or less. The degree of cleanliness in the packaging process is preferably a 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.

  In the present invention, the packaging material used for packaging the sheet-like 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 the photothermographic material according to the present invention is stored, the oxygen permeability and / or moisture permeability is low in order to prevent density change and fog generation with time, or to improve curling and curling. It is preferable to package with a packaging material. The oxygen permeability is preferably 50 ml / atm · m ² · day or less at 25 ° C. (where 1 atm is 1.01325 × 10 ⁵ Pa), more preferably 10 ml / atm · m ² · day or less, More preferably, it 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, JP 2003-057990 A, JP 2003-084397 A, JP 2003-098648 A, JP 2003-098635 A, JP 2003-107635 A, JP 2003-131337 A, JP 2003-146330 A, Special It is a packaging material described in Japanese Patent Application Laid-Open No. 2003-226439 and Japanese Patent Application Laid-Open No. 2003-228152. The void ratio 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 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 nm to 900 nm, preferably 620 nm to 850 nm.

  On the other hand, in recent years, in particular, a module in which an SHG (Second Harmonic Generator) element and a semiconductor laser are integrated and a blue semiconductor laser have been developed, and a laser output device in a short wavelength region has been closed up. The blue semiconductor laser is expected to increase in demand in the future because 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 nm to 500 nm, particularly preferably 400 nm 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 unit and the second heating unit has a higher heating temperature at the carry-in entrance side of the photothermographic material than at the exit 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 means is 1.2 times or more larger than the coil density of the second heating means. Preferably, the heating member is a heat plate.

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

  Also, 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, it is heated at the conveyance inlet side of the heat plate. The required temperature can be secured by keeping the temperature high. As a result, it is possible to prevent the heat plate that performs 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 high. It is preferable to arrange so as to be. 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 wire 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. If it carries out like this, it can be extended without making a linear heat ray intermittent in the inside of a heat plate. And, if the heat rays are generated at the time of heat development, the heating temperature on the conveyance inlet side where the heat rays are densely arranged becomes high without requiring a complicated configuration of controlling the temperature for each predetermined part of the heat plate. The entire heat plate can be heated while maintaining the above.

  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 formed. In addition, the heating temperature on the upstream side in the developing unit can be made higher than the heating temperature on the downstream side. 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 development process can be performed with a single heat plate, and there is no need to provide another heat plate in the heat development section, so the structure can be simplified and miniaturized, and the cost can be reduced. You can also

  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. The thermal development apparatus 10 uses a sheet-like photothermographic material F that does not require a wet development process as an image recording material. After the latent image is formed by irradiating the laser beam L modulated based on the image signal inputted to the photothermographic material F, the photothermographic material F is thermally developed to allow the surface of the photothermographic material to be developed. This is a configuration for obtaining a visual image. The present invention is not limited to such a configuration, and is applied to a configuration in which a sheet-shaped photothermographic material is exposed in advance by a laser beam L to form an image, and only the photothermographic material is subjected to thermal development. Can do.

  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. In addition, a transport unit for transporting the photothermographic material F provided at a key point between the units and a power supply / control unit E for driving and controlling the units 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 one photothermographic material F on the same transport path. Further, by performing the exposure process and the heat development process within a short transport distance, the transport 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 mm 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. A plurality (two in the present embodiment) of loading units 11a and 11b, a pair of supply rollers 13a and 13b respectively disposed in the loading units 11a and 11b, and a conveyance roller and a conveyance guide (not shown) are included. Composed. 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 according to 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. (I.e., transport direction). As a result, a latent image corresponding to the 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 includes a main body 65 that is attachable to and detachable from the heat developing apparatus 10 and a plurality of carry-out rollers 66a, 66b, and 66c provided on the main body 65. In order to hold the photothermographic material F carried out of the main body 65 by the plurality of carry-out rollers 66a, 66b, 66c, 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 and carries 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 development apparatus, and may be omitted as necessary, and the heat development photosensitive material F may be carried out 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 device 40 includes a sub-scanning conveyance unit 18 having a flutter prevention mechanism that conveys the photothermographic material F from the conveyance surface while preventing flapping, and a scanning exposure unit 19. 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 driving rollers (conveying means) 21 and 22 each having a rotation axis disposed substantially parallel to the scanning line with the main scanning line of the laser beam L to be scanned interposed therebetween. ing. A guide plate 24 that is disposed to face the drive rollers 21 and 22 and supports the photothermographic material F is provided. 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. It is bent along the part. Due to the elastic repulsive force of the photothermographic material F generated as a result, it is brought into contact with the portion between the drive rollers 21 and 22 and supported.

  Thus, 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, so that the photothermographic material F is reliably transferred from the driving rollers 21 and 22 to the photothermographic material F. The conveyance driving force is transmitted, and the photothermographic material F is conveyed. The driving rollers 21 and 22 are configured to rotate in the clockwise direction in FIG. 1 by receiving the driving force of driving means such as a motor (not shown) via transmission means such as a gear and a belt.

  Further, the photothermographic material F is pressed against the upper surface of the guide plate 24 by its own elastic repulsive force, and fluttering from the transport surface of the photothermographic material F, that is, fluttering in the vertical direction in the figure is suppressed. 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 portion C is gradually cooled to a temperature below the glass transition point while being conveyed by the flocking roller 57. The reason for slowly cooling the photothermographic material F is that if the photothermographic material is rapidly cooled immediately after the heat development, the degree of cooling at the center and the end in the transport direction of the photothermographic material F is different. The developed photosensitive material is hardened in a state of being deformed into, for example, a waveform. For this reason, immediately after the heat development, it is necessary to provide a heat retaining portion or the like to lower the cooling efficiency and to 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. . Then, 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 bend. The photothermographic material F discharged from the cooling unit D is transported from the transport roller 64 to the transport roller 63 on the downstream side, and is transported from the transport roller 63 (or 66a, 66b, 66c) to the discharge tray 16 (or each sorter S). It is carried out to supply part 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 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 ray 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 a 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. Can do. Further, the photothermographic material F immediately before being conveyed to the heat plate 51a can be quickly brought to 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 or more and 1.2 or less. It is especially preferable that it is 2 or more and 1.0 or less. Here, the path length of the heat developing unit is a transport path length in which the photothermographic material is heated to the developing temperature in the heat developing apparatus. Further, the path length of the cooling unit means that the photothermographic material is discharged from the area where the photothermographic material is shielded by the laser imager to the room light where the laser imager is installed. The path length until.

  Further, the cooling speed of the surface on which the laser imager does not have the photosensitive layer (hereinafter referred to as “non-photosensitive surface”) across the support of the photothermographic material is adjusted to the surface on the side having the photosensitive layer. It is preferable that it has a function capable of being larger than the cooling rate (hereinafter referred to as “photosensitive surface”).

  In the present invention, 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.

  It is possible to provide a small-sized laser imager with a high processing speed by using a laser imager with a short path length of the cooling unit whose ratio of the path length of the cooling unit to the path length of the heat developing unit is 1.5 or less. .

  The cooling time from the exit from the heat development portion to the discharge is arbitrary, but it is preferably from 0 second to 25 seconds. More preferably, it is 0 second or more and 15 seconds or less, and particularly preferably 5 seconds or more and 15 seconds or less.

  The path length through which the photothermographic material passes after leaving the heat developing portion and before discharging is arbitrary, but is preferably 1 cm or more and 60 cm or less. More preferably, they are 5 cm or more and 50 cm or less, More preferably, they are 5 cm or more and 40 cm or less.

  The photothermographic material of the present invention may be developed by any method, but is usually developed by raising the temperature of the photothermographic material exposed imagewise. The preferred development temperature is 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 less than 80 ° C., sufficient image density cannot be obtained in a short time. If the heating temperature exceeds 200 ° C., the binder melts, and not only the image itself such as transfer to a roller but also transportability and developing machine etc. Adversely affect. 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 process (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 seconds or more and 50 seconds or less is an emergency. It is more preferable that it can cope with the diagnosis.

  Either a drum type heater or a plate type heater may be used as the thermal development method, but the plate heater method is more preferable. The heat development method using a plate heater method is a method described in JP-A-11-133572, in which 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 development unit. It is a laser imager that obtains a visible image. The heating means comprises a plate heater, and a plurality of pressing rollers are disposed to face each other along one surface of the plate heater, and the photothermographic material is passed between the pressing roller and the plate heater. Heat development.

  The linear velocity of the photothermographic material in the exposure unit, the thermal development unit, and the cooling unit is arbitrary, but higher ones are preferable for rapid processing and improvement in throughput. The linear velocity is preferably 20 mm / second or more and 100 mm / second or less, more preferably 25 mm / second or more and 80 mm / second or less, and further preferably 25 mm / second or more and 60 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, so that it can cope with an emergency diagnosis.

  An exposure process and a heat development process are performed at the same time, that is, in order to start development on a part of the sheet-like photothermographic material that has already been exposed while exposing a part of the sheet-like photothermographic material, the exposure process It is preferable that the distance between the exposed portion and the developing portion to be 0 cm or more and 50 cm or less. As a result, a series of processing time for exposure and development becomes extremely short. A preferable range of this distance is 3 cm or more and 40 cm or less, and more preferably 5 cm or more and 30 cm or less. 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 (tip of the arrow) where the laser beam indicated by L hits the photothermographic material is the exposure part, and the part where the photothermographic material conveyed from 15 in FIG. Is the developing section.

  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. This method is preferable from the viewpoint of uniform heating and from the viewpoints of thermal efficiency, workability, and the like. It is preferable that the surface having the protective layer is conveyed while being in contact with the heat roller, and is developed by heat treatment. .

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

Example 1
<< Preparation of undercoated photographic support >>
A corona of 8 W · min / m ² on both sides of a biaxially stretched heat-fixed polyethylene terephthalate film having an optical density of 0.150 (measured with a Densitometer PDA-65 manufactured by Konica Corporation) and colored with the following blue dye. The photographic support subjected to the discharge treatment was subjected to subbing. 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. to be photosensitive. A layer (image forming layer) side undercoat layer was formed (referred to as an undercoat underlayer A-1). Moreover, the following undercoat coating liquid b-1 was applied to the opposite surface as a backing layer undercoat layer at 22 ° C. and 100 m / min so that the dry film thickness was 0.12 μm, and dried at 140 ° C. An undercoat conductive layer having an antistatic function (referred to as undercoat underlayer B-1) was applied 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. It was applied at 33 ° C. and 100 m / min so as to have a film thickness of 0.03 μm, and dried at 140 ° C. to obtain an undercoat upper layer A-2. On the undercoat layer B-1, the following undercoat coating solution b-2 is applied at 33 ° C. and 100 m / min so as to have a dry film thickness of 0.2 μm, and dried at 140 ° C. -2. Further, the support was heat-treated at 123 ° C. for 2 minutes and wound up under the conditions of 25 ° C. and 50% RH to prepare a sample with an underdrawn.

[Preparation of aqueous polyester A-1 solution]
Dimethyl terephthalate 35.4 parts by weight Dimethyl isophthalate 33.63 parts by weight 5-Sulfoisophthalic acid dimethyl sodium salt 17.92 parts by weight Ethylene glycol 62 parts by weight Calcium acetate / monohydrate 0.065 parts by weight Manganese acetate tetrahydrate 0.022 parts by mass The above was subjected to a transesterification reaction while distilling off methanol at 170 to 220 ° C. in a nitrogen stream. Next, 0.04 parts by mass of trimethyl phosphate, 0.04 parts by mass of antimony trioxide as a polycondensation catalyst and 6.8 parts by mass of 1,4-cyclohexanedicarboxylic acid were added, and the reaction temperature was 220 to 235 ° C. An amount of water was distilled off for esterification.

  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 Mw = 80000 to 100,000.

  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 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 completion of the heating, the mixture was cooled to room temperature over 1 hour and allowed to stand overnight to prepare a 15% by mass aqueous polyester A-1 solution.

[Preparation of Modified Aqueous Polyester B-1-2 Solution]
Into a 3 L four-necked flask equipped with a stirring blade, a reflux condenser, a thermometer and a dropping funnel, 1900 ml of the 15% by mass aqueous polyester A-1 solution was placed, and the internal temperature was adjusted to 80 ° C. while rotating the stirring blade. Until heated. Into this, 6.52 ml of a 24 mass% 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-type component modification | denaturation ratio 20 mass%) whose solid content concentration is 18 mass%.

  The solid content concentration was the same except that the vinyl modification ratio was 36% by mass and the modified components were styrene: glycidyl methacrylate: acetoacetoxyethyl methacrylate: n-butyl acrylate = 39.5: 40: 20: 0.5. An 18% by mass modified aqueous polyester B-2 solution (vinyl component modification ratio 20% by mass) was prepared.

[Production 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.

[Coating liquid a-1 for photosensitive layer side undercoat layer]
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 1000 ml, and a coating solution was obtained.

<< Coating liquid a-2 for photosensitive layer side undercoat upper layer >>
Modified aqueous polyester B-2 (18% by mass) 30.0 g
Surfactant (A) 0.1g
Spherical silica matting agent (Nippon Shokubai Co., Ltd. Sea Hoster KE-P50)
0.04g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Backing layer side undercoat coating solution b-1]
Acrylic polymer latex C-1 (solid content 30%) 30.0 g
Acrylic polymer latex C-2 (solid content 30%) 7.6 g
SnO ₂ sol 180g
(SnO ₂ sol synthesized by the method described in Example 1 of Japanese Patent Publication No. 35-6616 was heated and concentrated so that the solid content concentration was 10% by mass, and then adjusted to pH = 10 with ammonia water)
Surfactant (A) 0.5g
PVA-613 (PVA manufactured by Kuraray Co., Ltd.) 5% by weight aqueous solution 0.4 g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

[Backing layer side undercoat upper layer coating solution b-2]
Modified aqueous polyester B-1 (18% by mass) 145.0 g
True spherical silica matting agent (Nippon Shokubai Co., Ltd. Sea Hoster KE-P50) 0.2g
Surfactant (A) 0.1g
Distilled water was added to make 1000 ml, and a coating solution was obtained.

  A backcoat layer and a backcoat layer protective layer having the following composition were coated on the undercoat layer B-2 of the support on which the undercoat layer had been 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 was added to the dissolved solution, and 4.5 g of a fluorosurfactant (manufactured by Asahi Glass Co., Ltd .: Surflon KH40) and a fluorosurfactant dissolved in 43.2 g of methanol. (Dainippon Ink Co., Ltd .: MegaFag F120K) 2.3 g was added and stirred well until dissolved to prepare 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 cross-linked PMMA (matting agent) was dispersed in MEK at a concentration of 1% using a dissolver type homogenizer, and finally added.

Cellulose acetate propionate (10% MEK solution) 15g
(Manufactured by Eastman Chemical: CAP482-20)
Monodisperse three-dimensionally crosslinked spherical PMMA (polymethyl methacrylate) with a monodispersity of 15%
(Average particle size and amount are listed in Tables 2 and 3)
C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₂ C ₉ F ₁₇ 0.075 g
Fluorine-based surfactant (described in Tables 2 and 3) 0.01 g
Fluoropolymer (FM-1) 0.05g
Lubricant (described in Tables 2 and 3) 0.1 g
α-Alumina (Mohs hardness 9) 0.1g
<Preparation of backcoat layer side slip layer coating solution>
The back coat layer side slip layer was also prepared in the same manner as the back coat layer coating solution at the following composition ratio.

Cellulose acetate propionate (10% MEK solution) 15g
(Manufactured by Eastman Chemical: CAP482-20)
0.15 g of polyester resin (Bostic: VitelPE2200B)

<Preparation of photosensitive silver halide grain emulsion A1>
(A1)
Phenylcarbamoylated gelatin 88.3g
10% aqueous methanol solution of compound (AO-1) 10 ml
Potassium bromide 0.32g
Finish to 5429 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 660 ml with water.

(D1)
Potassium bromide 151.6g
Potassium iodide 7.67g
Hexachloroiridium (IV) acid potassium: K ₂ (IrCl ₆ ) (1% aqueous solution)
0.93ml
Potassium hexacyanoferrate (II) 0.004g
Hexachloroosmium (IV) potassium salt 0.004g
Finish to 1982 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 20 ml 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 2000 ml of the sedimented portion, 10 L of water was added, and after stirring, the silver halide emulsion was sedimented again. The remaining portion of 1500 ml was left, the supernatant was removed, 10 L of water was further added, and after stirring, the silver halide grain emulsion was allowed to settle. After leaving 1500 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 1161 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 light-sensitive silver halide emulsion A1, after adding the entire amount of the solution F1 after nucleation, 40 ml of a 5% aqueous solution of 4-hydroxy-6-methyl-1,3,3a, 7-tetraazaindene was added. A photosensitive silver halide emulsion A2 was prepared in the same manner as described above. The grains in this emulsion were monodispersed 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 was 3.5 mol). %).

[Preparation of photosensitive silver halide grain emulsion A3]
In the preparation of the photosensitive silver halide emulsion A1, the photosensitive halogenation was similarly carried out except that 4 ml of a 0.1% ethanol solution of the following compound (TPPS) was added after the whole amount of the solution F1 was added after nucleation. Silver grain emulsion A3 was prepared.

  The grains in this emulsion were monodispersed 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 was 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>
In the preparation of the photosensitive silver halide grain emulsion B1, the photosensitive halogen halide was similarly treated except that 4 ml of a 0.1% ethanol solution of the above compound (TPPS) was added after adding the whole amount of the solution F1 after nucleation. A 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>
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 in 4720 ml of pure water 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 the fatty acid potassium solution at 55 ° C., photosensitive silver halide grain emulsions A1, A2, A3, B1, B2 (types and addition amounts are listed in Tables 2 and 3) 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. 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 (image forming 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 1457 g of MEK, and VMA-GETZMANN While stirring with a dissolver DISPERMAT CA-40M type, 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 prepared by supplying to -C12EX type (manufactured by VMA-GETZMANN) and dispersing at a mill peripheral speed of 8 m / s.

<Preparation of stabilizer solution>
A stabilizer solution was prepared by dissolving 1.0 g of Stabilizer 1 and 0.31 g of potassium acetate in 4.97 g of methanol.

<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 Infrared sensitizing dye solution A was prepared by dissolving imidazole in 31.3 ml of MEK in the dark.

<Preparation of additive solution a>
Reducing agent (compounds and amounts described in Tables 2 and 3), 0.159 g of yellow chromophoric leuco dye (YA-1) of general formula (YB), 0.159 g of cyan chromophoric 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 b.

<Preparation of additive liquid c>
The 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 1000 μl of chemical sensitizer S-5 (0.5% methanol solution) was added. Was added. Two 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, then gold sensitizer Au-5 corresponding to 1/20 mole of the above organic 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 continuing to stir, 12.43 g of additive liquid a, 1.6 ml of Desmodur N3300 / Mobey 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 2.3g
(Manufactured by Eastman Chemical: CAP-141-20, glass transition temperature Tg = 190 ° C.)
7g of methanol
Phthalazine 0.25g
_{CH 2 = CHSO 2 CH 2 CH} 2 OCH 2 CH 2 SO 2 CH = CH 2 0.035g
<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 2.3g
(Manufactured by Eastman Chemical: CAP-141-20 glass transition temperature Tg = 190 ° C.)
Paraloid A-21 (Rohm and Haas) 0.08g
Benzotriazole 0.03g
7g of methanol
Phthalazine 0.25g
Monodispersed 15% monodispersed spherical three-dimensional crosslinked PMMA 0.40 g
(Polymethylmethacrylate average particle size 1.0μm)
Monodispersity 15% monodisperse spherical three-dimensional crosslinked PMMA 0.10 g
(Polymethylmethacrylate average particle size 4.5μm)
_{CH 2 = CHSO 2 CH 2 CH} 2 OCH 2 CH 2 SO 2 CH = CH 2 0.035g
C ₉ F ₁₇ O (CH ₂ CH ₂ O) ₂₂ C ₉ F ₁₇ 0.01 g
Fluorine-based surfactant (described in Tables 2 and 3) 0.005 g
Fluoropolymer (FM-1: supra) 0.01g
0.1 g isotridecyl stearate
Silicon-containing comb-shaped graft polymer 0.1 g
(Copolymer of weight-average molecular weight 5000 consisting of silicon-containing macromonomer and methyl methacrylate)
α-Alumina (Mohs hardness 9) 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% by mass in the same manner as in the case of 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 photosensitive layer side slip layer coating solution>
The photosensitive layer coating solution was diluted with MEK to a solid content concentration of 10.5% by mass using a dissolver type homogenizer. Then, after dissolving and adding 30% by mass of polymethyl methacrylate to the MEK solution with respect to the amount of binder in the coating solution, a dissolver type homogenizer is used so that the solid content concentration becomes 10.5% by mass using MEK. A photosensitive layer side slip layer coating solution was prepared.

<Preparation of photothermographic material>
Slip layer coating solution, back coating layer coating solution, and back coating layer protective layer coating solution prepared as described above are subbing upper layers so that the dry film thicknesses are 0.3 μm, 1.1 μm, and 1.0 μm, respectively. Coating was performed on B-2 at a coating speed of 50 m / min with a slide coater. 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.

  The slip layer coating solution, the photosensitive layer coating solution, and the photosensitive layer protective layer (surface protective layer) coating solution are simultaneously coated on the subbing upper layer A-2 at a coating speed of 50 m / min using a slide coater. Thus, photothermographic material samples 101 to 140 shown in Tables 2 and 3 were prepared. Coating is a dry film thickness of 0.3 μm of the slip layer, a dry film thickness of the photosensitive layer (described in Tables 2 and 3), and a protective layer of the photosensitive layer (surface protective layer) is 3.0 μm (surface protective) And then dried for 10 minutes using a drying air having a drying temperature of 75 ° C. and a dew point temperature of 10 ° C.

  For sample 123, behenic acid 259.4 g instead of 130.8 g behenic acid, 67.7 g arachidic acid, 43.6 g stearic acid, 2.3 g palmitic acid in the preparation of powdered organic silver salt A in sample 111, A sample was prepared in the same manner as Sample 111 except that 0.5 g of arachidic acid was used.

  For sample 132, the same amount of polymethyl methacrylate (Rohm and Haas, Paraloid A21) was used in place of the polyester resin (Bostic: VitelPE2200B) in the preparation of the backcoat layer side slip layer coating solution in sample 111. A sample was prepared in the same manner as Sample 111 except that. Note that B = 0.09 and A = 0 for the sample 111, and B = 0.09 and A = 0 for the sample 132 as well.

  For sample 133, in the preparation of the backcoat layer side slip layer coating solution in sample 111, polyurethane resin (UR8300 manufactured by Toyobo Co., Ltd.) was used in the same mass as the solid content instead of polyester resin (Bostic: VitelPE2200B). A sample was prepared in the same manner as Sample 111. For sample 133, B = 0.09 and A = 0.

  For sample 134, a sample was prepared in the same manner as sample 111, except that in the preparation of the backcoat layer side slip layer coating solution in sample 111, the polyester resin (Bostic: VitelPE2200B) was not used. For sample 134, B = 0 and A = 0.

  For sample 135, in the preparation of the backcoat layer protective layer coating solution in sample 111, in addition to 15 g of cellulose acetate propionate (10% MEK solution), 0.50 g of a polyester resin (Bostic: VitelPE2200B) was added. A sample was prepared in the same manner as Sample 111 except for the above. For sample 135, B = 0.09 and A = 0.125. In calculating A and B, the backcoat protective layer (surface protective layer) was calculated as being included in the backcoat layer.

  For sample 136, in the preparation of the backcoat layer protective layer coating solution in sample 111, in addition to 15 g of cellulose acetate propionate (10% MEK solution), 0.20 g of polyester resin (Bostic: VitelPE2200B), polymethyl methacrylate A sample was prepared in the same manner as Sample 111 except that 0.20 g (Rohm and Haas, Paraloid A21) was added. Regarding sample 136, B = 0.09 and A = 0.105. In calculating A and B, the backcoat protective layer (surface protective layer) was calculated as being included in the backcoat layer.

  For sample 137, in the preparation of the backcoat layer protective layer coating solution in sample 111, in addition to 15 g of cellulose acetate propionate (10% MEK solution), 0.10 g of polyester resin (Bostic: VitelPE2200B), polyurethane resin ( A sample was prepared in the same manner as Sample 111 except that 0.30 g of UR8300 (Toyobo 30% MEK solution) was added, and B = 0.09 and A = 0.105 for Sample 137. In calculating A and B, the backcoat protective layer (surface protective layer) was calculated as being included in the backcoat layer.

  Samples 138 and 139 were the same as Sample 111 except that two types of matting agents having different particle sizes shown in Table 3 were added as shown in Table 3 in the preparation of the backcoat layer protective layer coating solution in Sample 111. A sample was prepared.

  Moreover, when the surface roughness of the photosensitive layer side outermost surface was measured about the samples 101-140, it was Rz (E) = 2.9 micrometer. Ra (E) was 126 nm.

  With respect to Samples 101 to 140, an absorption peak at a maximum absorption wavelength of 420 nm due to the yellow coloring leuco dye was observed. Further, with respect to Samples 101 to 140, an absorption peak at a maximum absorption wavelength of 620 nm due to the cyan color-forming leuco dye was observed.

* 1): (RD1-47) / (RD2-6) = 4.20 / 23.78
LB-1 Isotridecyl stearate LB-2 Isotridecyl palmitate LB-3 Glycerol trioleate LB-4 Glycerol trimyristate LB-5 Glycerol trilaurate LB-6 Trimethylolpropane triisostearate LB-7 Dipentaerythritol hexaisostearate AC ₈ F ₁₇ SO ₃ Li
B butyl stearate C oleyl oleate D silicon-containing comb-shaped graft polymer (copolymer of weight-average molecular weight 5000 consisting of silicon-containing macromonomer and methyl methacrylate)
<Exposure and development processing>
The photothermographic material samples 101 to 140 prepared 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% for 2 weeks at room temperature. Following storage, the following evaluations were made.

(Packaging material)
PET 10 μm / PE 12 μm / Aluminum foil 9 μm / Ny 15 μm / polyethylene 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 / Barrier bag of m ² · 40 ° C · 90% RH · day (according to JIS Z0208 cup method). Use paper tray.

(Sample evaluation)
<Exposure and development processing>
The photothermographic material samples 101 to 140 produced as described above were subjected to thermal development simultaneously with exposure in the thermal development apparatus shown in FIG. 1 (mounted with an 810 nm semiconductor laser with a maximum output of 50 mW, installation area 0.35 m ² ) (FIG. 1 set the temperature of 51a (75 mm in the conveying direction) to 123 ° C. and the setting temperature of 51b (the length of 175 mm in the conveying direction) to 127 ° C., respectively, and contact each for 3 seconds and 7 seconds for a total of 10 seconds. Was conveyed). In each of the heat plates 51a and 51b, the heating temperature was set higher on the conveyance entrance side with respect to the conveyance direction of the photothermographic material. Here, “heat development at the same time as exposure” is a sheet of photothermographic material made of a photothermographic material, and a part of the sheet that has been exposed at the same time is developed while being partially exposed. Means to be started. The distance between the exposed part and the developing part was 12 cm. At this time, the conveyance speed from the photothermographic material supply apparatus section to the image exposure apparatus section, the conveyance speed at the image exposure section, and the conveyance speed at the heat development section were each 30 mm / second. Further, the position of the bottom surface of the photothermographic material stock tray located at the bottom was 45 cm high from the floor surface. Further, the time required for the heat development processing (the time taken for the photothermographic material to be picked up at the tray portion and discharged) was 45 seconds. (In the case of continuous processing, the interval time for heat development is 4 seconds.) The exposure was performed in a stepped manner while reducing the exposure energy amount by log E0.05 step by step from the maximum output.

<< Average gradation Ga value >>
The obtained sensitometric sample was subjected to concentration measurement using a PDM65 transmission densitometer (manufactured by Konica), and the measurement result was computer processed to obtain a characteristic curve. From this characteristic curve, an average gradation Ga value having an optical density of 0.25 to 2.5 was obtained.

<< Evaluation 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 analyzer (WYKO company 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 (B0601). 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.

<Film scratches>
The film is transported using the heat development apparatus shown in FIG. 1, and the occurrence of scratches on the outermost surface on the photosensitive layer side is visually observed, and the five-level evaluation is performed with the best level being 5 and the worst level being 1. (However, the evaluation was performed in increments of 0.5). Level 2.5 is not practical.

<In-machine contamination of thermal development equipment>
Using the thermal development apparatus shown in FIG. 1, after the thermal development of 5000 sheet films in an environment of 25 ° C. and a relative humidity of 65%, the dirt attached to the conveying roller in the thermal development apparatus was 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 increments of 0.5.

<Film transportability under low humidity>
Using the heat development apparatus shown in FIG. 1, 100 sheet films were processed each in an environment of 10 ° C. and 15% relative humidity to carry the film, and the number of occurrences of conveyance failure (times / 100 sheets) was counted. .

<Concentration fluctuation accompanying humidity fluctuation>
When heat development was performed under the same conditions as those used for image quality evaluation after conditioning for 24 hours in an environment of 25 ° C. and a relative humidity of 40% (ie, in an environment of 25 ° C. and a relative humidity of 40%) Under the same conditions as when the sample was conditioned for 24 hours under the conditions of the maximum density part (Dmax1) and 45 ° C. and 90% relative humidity (ie, at 45 ° C. and 90% relative humidity) The difference (Dmax1−Dmax2 = ΔDmax) between the maximum density part value (Dmax2) when heat development was performed was measured using a PDM65 transmission densitometer (manufactured by Konica Corporation).

"Adhesiveness"
Cellotape (registered trademark) was put on the sample, scratches were made in a grid pattern, and the area ratio of the part peeled off after the tape was peeled off was evaluated in 0.5 increments according to the following criteria.

5: When the peeled portion is 0% 4: When the peeled portion is 1 to 33% 3: When the peeled portion is 34 to 66% 2: When the peeled portion is 67% to 99% 1: The peeled portion is 100% in the case of.

  The results are shown in Table 4.

  Further, when a paper tray containing silica gel was used in which the paper tray was raised in the sample 102 and the silica gel was sealed in the space formed at the bottom of the tray, the concentration fluctuation due to humidity fluctuation was improved, and an improvement effect was recognized.

  As described above, the best mode for carrying out the present invention has been described. However, the present invention is not limited to these, and various modifications are possible 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.

  In addition, although the image forming apparatus 10 of FIG. 1 has a relatively compact configuration of a desktop type as a whole, the sheet film conveying apparatus of the present invention is not only applicable to such a desktop type image forming apparatus. For example, the present invention can be applied to a relatively large heat development 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 (8)

A photothermographic material having a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on a support, and a backcoat layer on the opposite side of the support. Lubricant having a dry film thickness of 9 to 16 μm, a center line average roughness (Ra) of the outermost surface on the back coat layer side of 100 to 150 nm, and the back coat layer having a molecular weight of 550 to 10,000 A photothermographic material comprising a photothermographic material. A photothermographic material having a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on a support, and a backcoat layer on the opposite side of the support. The dry film thickness of the layer is 9 to 16 μm, the center line average roughness (Ra) on the outermost surface on the back coat layer side is 100 to 150 nm, and the back coat layer contains a fatty acid ester of a polyhydric alcohol A photothermographic material characterized in that: 3. The photothermographic material according to claim 1, wherein a center line average roughness (Ra) of the outermost surface on the backcoat layer side is 110 to 140 nm. The photothermographic material according to claim 1, wherein the photosensitive layer contains a silver saving agent. 5. The photothermographic material according to claim 4, wherein the silver saving agent is at least one selected from hydrazine derivatives, vinyl compounds, phenol derivatives, naphthol derivatives, quaternary onium compounds, and silane compounds. 6. The photothermographic material according to claim 1, wherein the maximum value of image density after heat development is 4.0 or more and 5.0 or less. The heat according to any one of claims 1 to 6, wherein an average gradation (Ga value) of the photographic characteristic curve at an optical density of 0.25 to 2.5 is 2.0 to 6.0. Development photosensitive material. A photothermographic material having a photosensitive layer containing silver halide grains, an organic silver salt, a reducing agent and a binder on a support, and a backcoat layer on the opposite side of the support. An undercoat layer containing a binder is provided between the backcoat layers, the backcoat layer and the undercoat layer contain at least one of a polyester resin, an acrylic resin, or a polyurethane resin, and the polyester in the backcoat layer The mass ratio of the total amount of resin, acrylic resin and polyurethane resin to the binder amount of the backcoat layer is A, and the total amount of polyester resin, acrylic resin and polyurethane resin in the undercoat layer to the binder amount of the undercoat layer A photothermographic material, wherein B> A, where B is a mass ratio.

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