Photothermographic imaging material and method for forming image Number:7,144,694 from the United States Patent and Trademark Office (PTO) owispatent

Title: Photothermographic imaging material and method for forming image

Abstract: A photothermographic imaging material including a support; an image forming layer containing an organic silver salt, a photosensitive silver halide, a binder and a silver ion reducing agent, the image forming layer being provided on the support; and a cyan coloring leuco dye. The photosensitive silver halide contains silver halide grains having a mean particle size of 10 to 50 nm, and the silver ion reducing agent is a compound represented by the following Formula (A-3) ##STR00001##

Patent Number: 7,144,694 Issued on 12/05/2006 to Kashiwagi,   et al.

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Inventors:	Kashiwagi; Hiroshi (Hino, JP), Goto; Narito (Hino, JP)
Assignee:	Konica Minolta Holdings, Inc. (Tokyo, JP)
Appl. No.:	11/262,161
Filed:	October 28, 2005

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Foreign Application Priority Data

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Dec 09, 2002 [JP]			2002-356615
Jan 14, 2003 [JP]			2003-005526

Current U.S. Class:	430/617 ; 430/224; 430/336; 430/350; 430/551; 430/567; 430/598; 430/600; 430/618; 430/619; 430/620
Current International Class:	G03C 1/00 (20060101); G03C 1/005 (20060101); G03C 1/494 (20060101); G03C 5/16 (20060101); G03C 8/00 (20060101)
Field of Search:	430/617-620,336,224,350,567,551,598,600

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References Cited [Referenced By]

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U.S. Patent Documents

	5330864		July 1994		Biavasco et al.
	2003/0190565		October 2003		Fujiwara et al.

Primary Examiner: Letscher; Geraldine
Attorney, Agent or Firm: Lucas & Mercanti, LLP

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Parent Case Text

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CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Divisional of U.S. patent application Ser. No. 10/727,313 filed Dec. 2, 2003 which, in turn, claims the priority of Japanese Patent Application Nos. JP2002-356615 filed Dec. 9, 2002 and 2003-005526 filed Jan. 14, 2003, the priority of which are all claimed.

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Claims

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What is claimed is:

1. A silver salt photothermographic dry imaging material, comprising: a photosensitive layer having an organic silver salt, a photosensitive silver halide, a silver ion reducing agent and a binder, the organic silver salt containing aliphatic silver carboxylate; and a cyan coloring leuco dye, wherein 70 mol % or more and less than 100 mol % of the aliphatic silver carboxylate in the organic silver salt is silver behenate.

2. The material of claim 1, further comprising: at least one crosslinker selected from a group consisting of a vinylsulfone group, an isocyanate group and a carbodiimide group.

3. The material of claim 1, wherein coefficient of determination (multiple determination) R.sup.2 of a linear regression straight line is 0.998 or more and 1.000 or less, the R.sup.2 being made by measuring each density at optical density of 0.5, 1.0, 1.5 and minimum optical density on a silver image obtained after thermal development processing of the silver salt photothermographic dry imaging material and by disposing u* and v* at the above each optical density on two dimensional coordinates where a horizontal and vertical axes in CIE 1976 (L*u*v*) color space are made u* and v*, respectively; and v* value of an intersection point with the vertical axis of the linear regression straight line is -5 or more and 5 or less; and a slope (v*/u*) is 0.7 or more and 2.5 or less.

4. The method for recording an image on the material of claim 1, comprising: performing image exposure according to a vertical multiple mode laser scanning exposure apparatus when recording the image on the material.

5. A method for forming an image after performing image recording on the material of claim 1, comprising: thermal developing in a state containing 40 to 4500 ppm of organic solvent when forming the image on the material.

6. The material of claim 1, wherein 80 to 99.9 mol % of the aliphatic silver carboxylate in the organic silver salt is silver behenate.

7. The material of claim 1, wherein 90 to 99.9 mol % of the aliphatic silver carboxylate in the organic silver salt is silver behenate.

8. The material of claim 1, further comprising a compound represented by the following Formula (YB), ##STR00067## wherein Z represents --S-- group or --C(R.sub.91') (R.sub.91')-group, R.sub.91, R.sub.91', X.sub.94 and X.sub.94 each represent hydrogen atoms or substituents, and R.sub.92, R.sub.93, R.sub.92' and R.sub.93' each represent substituents.

9. The material of claim 8, wherein R.sub.91 and R.sub.91' each represent hydrogen atoms or alkyl groups, and R.sub.92, R.sub.93, R.sub.92' and R.sub.93' each represent alkyl groups.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photothermographic imaging material, and particularly to a photothermographic imaging material with high density which is excellent in light radiated image stability, silver color tone and the like, and to a method for forming an image by using the same.

2. Description of Related Art

Recently, in the fields of medical care and print plate making, waste solutions involved in wet processings of image formation materials have been problematic in terms of working property, and reduction of processing waste solutions has been strongly desired in the light of environmental preservation and saving space. Thus, technology concerning photothermal photographic materials for photographic technology use such as laser imagers and laser image setters where efficient exposure is possible and clear black images with high resolution can be formed has been required.

As the technology according to the above photothermal photographic materials, for example, known are silver salt photothermographic dry imaging materials (hereinafter, also referred to as photothermographic imaging materials or simply imaging materials) containing an organic silver salt, photosensitive silver halide and a reducing agent on a support (e.g., U.S. Pat. No. 3,152,904 specification, U.S. Pat. No. 3,487,075 specification, D. H. Klosterboer, "Dry Silver Photographic Materials", (Handbook of Imaging Materials, page 48, 1991, Marcel Dekker Inc.)). This silver salt photothermographic dry imaging material has an advantage capable of providing users with a system which is simpler and does not impair the environment because no solution type processing chemical is used at all.

This photothermographic material is processed by a thermal development apparatus which adds stable heat to the photothermographic material to form the image, typically called a thermal developing apparatus. As mentioned above, in conjunction with the recent rapid prevalence, this thermal developing apparatus has been supplied in the market in large quantities. In the meanwhile, there has been problematic in that slipping property between the imaging material and a transport roller or processing members of the thermal developing apparatus changes, and transport failure and density unevenness occur. Also there has been problematic in that the density of the photothermographic imaging material varies with time. It has been found that these phenomena noticeably occur in the photothermographic imaging materials where image exposure is performed by laser light and subsequently the image is formed by thermal development.

Also recently, downsizing of laser imagers and acceleration of processings have been required. Therefore property improvement of the photothermographic imaging materials becomes essential. For downsizing the thermal development processing apparatus, it is more advantageous to use a heat drum mode than to use a horizontal transport mode, but there has been problematic in that powder drop off, density unevenness and roller mark easily occur at the thermal development processing. Also, even when the rapid processing is carried out, to obtain sufficient density of the photothermographic imaging material, it is effective to enhance covering power by increasing coloring point numbers using silver halide with smaller average particle size as shown in JP-A-11-295844 and JP-A-11-352627, to use reducing agents with high activity having secondary or tertiary alkyl groups (see JP-A-2001-209145), and to use development accelerators such as hydrazine compounds and vinyl compounds.

However, when these technologies were used, there was problematic in that density changes (printout property) with time after the thermal development processing became large and the silver color tone became extremely different (took on a yellow tinge) compared to wet type-X-ray films in earlier technology. Additionally, a new problem where the color tone takes on a red tinge at high density areas with density of 2.0 or more has occurred when those with smaller average particle size are used as the silver halide.

On the other hand, in image diagnosis by imaging materials for the medical use, silver color tone formed by development is an important factor which determines good or poor image quality. A silver ion reducing agent, a compound which forms a complex with the silver ions, a compound which bleaches fine silver nuclei which become sources of photographic fog which produces on surfaces of silver halide grains, and the like are contained in the silver salt photothermographic dry imaging material, and thus it is not easy to control developed silver shapes and retain images after the thermal development. That is, color tone changes must be reduced not only immediately after the thermal development of the imaging material but also in a long term storage before the thermal development and in image storage after the development. For example, disclosed is the method for reducing the ingredient having reducibility contained in the silver salt photothermographic dry imaging material (e.g., see JP-A-2002-328442). However, the color tone in the image storage is improved, but the color tone immediately after the thermal development is not improved. In earlier technology, these improvements have been attempted by controlling developed silver shapes. For example, disclosed is the method where the "color tone" changes under an atmosphere with high moisture is reduced by reducing particle sizes of silver halide grains and fatty acid silver salt crystals and controlling a "potency range" at the thermal development to the certain range (e.g., see JP-A-10-282601). Also, proposed are the improvement methods by activating photothermographic property by contrivance of fatty acid silver salt crystal structures (e.g., see JP-A-2002-23303 and JP-A-2002-49119), but it can not help being said that all the methods are at insufficient levels in terms of realizing the stable silver color tone. Also disclosed is the method using leuco compounds which imagewisely produce yellow compounds by oxidation-reduction reaction at the thermal development, in combination with the certain silver ion reducing agent (e.g., see JP-A-2002-169249). However, the technology described in JP-A-2002-169249 is more excellent in improvement level of the color tone compared to the above technology which controls the developed silver shape, but has disadvantages that the photographic fog and deterioration of the color tone changes frequently occur in the long term storage and in the image storage probably because produced dyestuffs are unstable and further adversely affect the silver halide.

Also, in the light of effectively utilizing the silver which is a valuable resource, efforts to increase the maximum density on the imaging materials at an identical amount of the silver must be continued. A basic technical concept for this is to make individual developed silver small at the identical silver amount and make the particle sizes of photosensitive silver halide grains small. That is, the combination with so-called sensitization technology becomes essential. But when the individual developed silvers are made small, extents of optical scattering and absorption are changed and thus the silver color tone is changed. Further, when the chemical sensitization is given with a Te sensitizer and a gold sensitizer, the photographic fog is increased. Thus, a new technology where the increase of maximum density, sensitization, low photographic fog and color tone are compatible has been required.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above problems.

That is, an object of the present invention is to provide a photothermographic imaging material with high density which is excellent in light radiated image stability and silver color tone, and to a method for forming an image. Also, the object of the present invention is to further provide a photothermographic imaging material which is excellent in image storage stability in storage at high temperature or excellent in film transportability and environmental suitability if necessary.

Further, another object of the present invention is to provide a silver salt photothermographic dry imaging material with low photographic fog, high sensitivity and high maximum density, which is excellent in image color tone and excellent in rapid thermal development suitability, as well as to an image recording method and an image forming method using the same.

In order to achieve the above-described objects, according to a first aspect of the present invention, the photothermographic imaging material of the present invention comprises a support; an image forming layer containing an organic silver salt, a photosensitive silver halide, a binder and a silver ion reducing agent, the image forming layer being provided on the support; and a cyan coloring leuco dye, wherein the photosensitive silver halide contains silver halide grains having a mean particle size of 10 to 50 nm, and the silver ion reducing agent is a compound represented by the following Formula (A-3),

##STR00002##

wherein the X.sub.31 represents a chalcogen atom or a CHR, the R representing a hydrogen atom, a halogen atom, an alkyl group or an alkenyl group; each R.sub.33 represents an alkyl group, at least one R.sub.33 being a secondary or tertiary alkyl group; the each R.sub.34 represents a hydrogen atom or a group capable of being substituted on a benzene ring; each Q.sub.20 represents a group capable of being substituted on a benzene ring; and each of the m2 and the n2 represents an integer of 0 to 2.

Here, in the photothermographic imaging material, and the R.sub.33s may be the same or different.

Further, preferably, the compound represented by the Formula (A-3) comprises an alkyl group having a hydroxyl group or a precursor of the hydroxyl group.

Further, preferably, the material further comprises a compound represented by the following Formula (YA) on a side of a face having the image forming layer,

##STR00003##

wherein the R.sub.11 represents a substituted or non-substituted alkyl group; the R.sub.12 represents a hydrogen atom, a substituted or non-substituted alkyl group or a substituted or non-substituted acylamino group, the R.sub.11 and the R.sub.12 being substantially free from 2-hydroxyphenylmethyl group; the R.sub.13 represents a hydrogen atom or a substituted or non-substituted alkyl group; and the R.sub.14 represents a substituent capable of being substituted on a benzene ring.

Further, preferably, an average gradation is from 2.0 to 4.0 at an optical density of 0.25 to 2.5 in diffused light on a characteristic curve shown on rectangular coordinates where unit lengths of diffuse density (Y axis) and common logarithm exposure amount (X axis) are equal on an image obtained by thermally developing at a development temperature of 123.degree. C. for a development time of 13.5 sec.

Further, preferably, the material comprises at least one silver saving agent selected from a vinyl compound, a hydrazine derivative, a silane compound and a quaternary onium salt in a side of a face having the image forming layer.

Further, preferably, a glass transition temperature (Tg) of the binder is from 70.degree. C. to 150.degree. C.

Further, preferably, the material comprises a compound represented by the following Formula (SF), (Rf--(L.sub.5).sub.n1--).sub.p--(Y).sub.m1--(A).sub.q (SF)

wherein the Rf represents a substituent containing a fluorine atom; the L.sub.5 represents a bivalent linkage group substantially free from a fluorine atom; the Y represents a bivalent to quadrivalent linkage group substantially free from a fluorine atom; the A represents an anion group or a base of the anion group; each of the m1 and n1 represents an integer of 0 or 1; each of the p and the q represents an integer of 1 to 3; and when the q is 1, the n1 and m1 are not simultaneously 0.

Further, preferably, the photosensitive silver halide further contains silver halide grains having a means particle size of 55 to 100 nm.

Further, preferably, the photosensitive silver halide further contains silver halide grains which are chemically sensitized with a chalcogen compound.

Further, preferably, an amount of silver contained in the image forming layer is from 0.3 to 1.5 g/m.sup.2.

Further, according to a second aspect of the present invention, the method for forming an image of the present invention comprises thermally developing the material of the above-described first aspect by using a thermal development apparatus having a thermal development portion, an imaging material supplying portion and an image exposure section, wherein a transport velocity of the material at the thermal development portion is from 10 to 200 mm/sec, a transport velocity of the material between the imaging material supplying portion and the image exposure portion is from 10 to 200 mm/sec, and a transport velocity of the material at the image exposure portion is from 10 to 200 mm/sec.

According to a third aspect of the present invention, the silver salt photothermographic dry imaging material of the present invention comprises a photosensitive layer having an organic silver salt, a photosensitive silver halide, a silver ion reducing agent and a binder, the organic silver salt containing aliphatic silver carboxylate; and a cyan coloring leuco dye, wherein 50 mol % or more and less than 100 mol % of the aliphatic silver carboxylate in the organic silver salt is silver behenate.

According to a fourth aspect of the present invention, the silver salt photothermographic dry imaging material of the present invention comprises a photosensitive layer having an organic silver salt, a photosensitive silver halide, a silver ion reducing agent and a binder; and a cyan coloring leuco dye, wherein an average iodine content in the photosensitive silver halide is 2.0 mol % or more and 7.0 mol % or less.

In the silver salt photothermographic dry imaging material, preferably, the organic silver salt containing aliphatic silver carboxylate, and 70 mol % or more and less than 100 mol % of the aliphatic silver carboxylate in the organic silver salt is silver behenate.

Further, according to a fifth aspect of the present invention, the silver salt photothermographic dry imaging material of the present invention comprises a photosensitive layer having an organic silver salt, a photosensitive silver halide, a silver ion reducing agent and a binder; a cyan coloring leuco dye; and at least one crosslinker selected from a group consisting of a vinylsulfone group, an isocyanate group and a carbodiimide group.

Preferably, the silver salt photothermographic dry imaging material further comprises at least one crosslinker selected from a group consisting of a vinylsulfone group, an is cyanate group and a carbodiimide group.

Further, preferably, in the silver salt photothermographic dry imaging material, coefficient of determination (multiple determination) R.sup.2 of a linear regression straight line is 0.998 or more and 1.000 or less, the R.sup.2 being made by measuring each density at optical density of 0.5, 1.0, 1.5 and minimum optical density on a silver image obtained after thermal development processing of the silver salt photothermographic dry imaging material and by disposing u* and v* at the above each optical density on two dimensional coordinates where a horizontal and vertical axes in CIE 1976 (L*u*v*) color space are made u* and v*, respectively; and v* value of an intersection point with the vertical axis of the linear regression straight line is -5 or more and 5 or less; and a slope (v*/u*) is 0.7 or more and 2.5 or less.

According to a sixth aspect of the present invention, the method for recording an image on the materials of the above-described third to fifth aspects of the present invention comprises performing image exposure according to a vertical multiple mode laser scanning exposure apparatus when recording the image on the material.

According to a seventh aspect of the present invention, the method for forming an image after performing image recording on the materials of the above-described third to fifth aspects of the present invention comprises thermal developing in a state containing 40 to 4500 ppm of organic solvent when forming the image on the material.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given hereinbelow and the appended drawings which given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein;

FIG. 1 is a view showing an example of a thermal development apparatus for processing a photothermographic imaging material of the present invention.

PREFERRED EMBODIMENT OF THE INVENTION

Hereinafter, the present invention will be described in detail.

The photothermographic imaging material and silver salt photothermographic dry imaging material of the present invention comprises organic silver salt, photosensitive silver halide, binder, silver ion reducing agent, and further, cyan coloring leuco dye.

[Organic Silver Salts]

In the invention, as organic silver salts as silver ion supplying source for silver image formation, preferred are silver salts of organic acids and hetero organic acids, especially in these salts, silver salts of long chain (from 10 to 30, preferably from 15 to 25 carbons) aliphatic carboxylic acids, and silver salts of nitrogen-containing heterocyclic compounds. Also preferred are organic or inorganic complexes described in Research Disclosure (hereinafter, also referred to as RD) 17029 and 29963 such as those where ligands have values of 4.0 to 10.0 as a total stability constant for silver ions.

Examples of these suitable silver salts include the followings.

Silver salts of organic acids, e.g., silver salts of gallic acid, oxalic acid, behenic acid, stearic acid, arachidic acid, palmitic acid, lauric acid, etc.; carboxyalkylthio urea salts of silver, e.g., silver salts of 1-(3-carboxypropyl) thiourea, 1-(3-carboxypropyl)-3,3-dimethyl thiourea; silver salts or silver complexes of polymer reaction product of aldehyde with hydroxy-substituted aromatic carboxylic acid, e.g., silver salts or silver complexes of the reaction product of aldehydes (formaldehyde, acetaldehyde, butylaldehyde, etc.) with hydroxy-substituted acids (e.g., salicylic acid, benzoic acid, 3,5-hydroxybenzoic acid); silver salts or silver complexes of thiones, e.g., silver salts or silver complexes of 3(2-carboxyethyl)-4-hydroxymethyl-4-thiazoline-2-thione, and 3-carboxymethyl-4-thiazoline-2-thione, etc.; complexes or salts of silver with nitrogen acid selected from imidazole, pyrazole, urazole, 1,2,4-thiazole and 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole and benzotriazole; silver salts of saccharine, 5-chlorosalicylaldoxime, and the like; silver mercaptides and the like.

In the photothermographic imaging material of a first embodiment, especially preferable silver salts include the silver salts of long chain (from 10 to 30, preferably from 15 to 25 carbons) aliphatic carboxylic acids such as silver behenate, silver arachidate and silver stearate.

Also, in the embodiment, it is preferred that two or more organic silver salts are mixed in terms of increasing development performance and forming silver images with high density and high contrast, and for example, it is preferable to prepare by mixing a silver ion solution to a mixture of two or more organic acids.

An organic silver salt can be obtained by mixing a water soluble silver compound and a compound which forms complex with the silver, and preferably used are a normal mixing method, a reverse mixing method, a simultaneous mixing method, a controlled double jet method as described in JP-A-9-127643, and the like. For example, an alkali metallic salt (e.g., sodium hydroxide, potassium hydroxide, etc.) is added to an organic acid to make an organic acid alkali metallic salt soap (e.g., sodium behenate, sodium arachidate, etc.), and subsequently crystal of an organic silver salt is made by mixing silver nitrate with the soap. At that time, silver halide grains may be mixed.

It is possible to use various shapes of the above organic silver salt according to the present invention, but tabular particles are preferable. Especially, preferred are the particles which are tabular organic silver salt particles with an aspect ratio of 3 or more and where the average value of an acicular ratio of the tabular organic silver salt particles measured from a major plane direction is from 1.1 or more and less than 10.0 in order to increase a filling rate in a photosensitive layer by reducing shape anisotropy of nearly parallel opposed two faces (major planes) having maximum area. Besides, more preferable acicular ratio is from 1.1 or more and less than 5.0.

Also, tabular organic silver salt particles with the aspect ratio of 3 or more represents that the tabular organic silver salt particles occupy 50% or more of the number of whole organic silver salt particles. Further, in the organic silver salt according to the present invention, the tabular organic silver salt particles with the aspect ratio of 3 or more occupy preferably 60% or more, more preferably 70% or more (number), and especially preferably 80% or more (number) of the number of whole organic silver salt particles.

Tabular particles with the aspect ratio of 3 or more are the particles where a ratio of a particle size to a thickness, so-called the aspect ratio (abbreviated as AR) represented by the following formula is 3 or more. AR=Particle size (.mu.m)/Thickness (.mu.m)

The aspect ratio of the tabular organic silver salt particles is preferably from 3 to 20, and more preferably from 3 to 10. The reasons are that the organic silver salt particles are easily close-packed when the aspect ratio is too low whereas when the aspect ratio is too high, then the organic silver salt particles are easily overlapped and light scattering and the like easily occur because the particles are easily dispersed in a clung state, resulting in reduction of clear feeling of imaging materials. Thus, the range described above is preferable.

The average values of particle sizes, average thickness, and acicular rates can be obtained by the methods described in the paragraphs [0031] to [0047] of JP-A-2002-287299.

The method where the organic silver salt particles having the above shape are obtained is not especially limited, but effective are that a mixing state at the formation of the organic acid alkali metallic salt soap and/or a mixing state at the addition of silver nitrate to the soap are kept well and that a rate of silver nitrate which reacts with the soap is made optical.

It is preferred that the tabular organic silver salt particles according to the present invention are predispersed with a binder and surfactants if necessary and subsequently dispersed/pulverized by a media dispersing machine or a high pressure homogenizer. For the above predispersion, it is possible to use common mixers such as anchor type and propeller type, a high-speed rotation centrifuging radiation type mixer (dissolver) and a high-speed rotation shearing type mixer (homo mixer).

Also, as the above media dispersing machine, it is possible to use rolling mills such as a ball mill, planetary ball mill and vibrating ball mill, media mixing mills such as a bead mill and attritor, and the others such as a basket mill, and as high pressure homogenizers, it is possible to use various types such as a type of conflicting to walls and plugs, a type where a liquid is divided into two and then the liquids are crashed at a high-speed and a type of passing through thin orifices.

As ceramics used for ceramics beads used upon media dispersion, preferred are those described in the paragraph [0051] of the above JP-A-2002-287299. Yttrium stabilized zirconia and zirconia toughened alumina (hereinafter these zirconia-containing ceramics are abbreviated as zirconia) are especially preferably used from the reason that impurity production due to friction with beads and a dispersing machine upon the dispersion is low.

In the apparatuses used upon dispersing the tabular organic silver salt particles, as materials of members to which the organic silver salt particles contact, it is preferable to use ceramics such as zirconia, alumina, silicon nitride and boron nitride, or diamond, and among others it is preferable to use zirconia.

When the above dispersion is carried out, it is preferred that the binder is added at a concentration of 0.1 to 10% of the organic silver salt by mass, and it is preferred that liquid temperature is less than 45.degree. C. throughout from predispersion to main dispersion. A preferable operating condition of the main dispersion includes the condition of 29.42 MPa to 98.06 MPa and two times or more of operations when the high pressure homogenizer is used as the dispersion means as the preferable operating condition. Also when the media dispersing machine is used as the dispersing means, the condition where a peripheral velocity is from 6 m/second to 13 m/second is included as the preferable condition.

Also, the preferable mode in the photothermographic imaging materials in the embodiment is made by coating the organic silver salt having the characteristics that the rate of the organic silver salt particles which exhibit a projected area of less than 0.025 .mu.m.sup.2 when a sectional face perpendicular to the support face of the material is observed by the electron microscope is 70% or more of whole projected areas and the rate of the particles which exhibit the projected area of 0.2 .mu.m.sup.2 or more is 10% or less of whole projected areas of the organic silver salt particles, and further a photosensitive emulsion containing the photosensitive silver halide. In such a case, it is possible to obtain the state where agglomeration of the organic silver salt particles is low and the particles are distributed evenly in the photosensitive emulsion.

The conditions to make the photosensitive emulsion having such characteristics are not especially limited, but include that the mixing state at the formation of organic acid alkali metallic salt soap and/or the mixing state at the addition of silver nitrate to the soap are kept well, that the rate of silver nitrate which reacts to the soap is made optical, dispersing by the media dispersing machine or the high pressure homogenizer for dispersion/pulverization, that the use amount of binder (concentration) is made from 0.1 to 10% of the organic silver salt by mass at that time, agitating at the peripheral velocity of 2.0 m/second or more using the dissolver at the preparation of solution, in addition to that the temperature is less than 45.degree. C. throughout from dry to the termination of main dispersion as the preferable conditions.

For the projected area of the organic silver salt particle having the certain projected area value as the above and a percentage thereof occupying in the whole projected area, as is described in the description to obtain the average thickness of the tabular particles described above, places corresponding to the organic silver salt particles are extracted by the method using TEM (transmission electron microscope). Specifically, they can be obtained by the method described in the paragraphs of [0057] to [0059] of JP-A2002-287299.

It is preferred that the organic silver salt particles used in the embodiment are monodisperse particles, preferable monodisperse degree is from 1 to 30%, and the image with high density is obtained by making the monodisperse particles in this range. The monodisperse degree herein is defined by the following formula. Monodisperse degree={(Standard deviation of particle sizes)/(Mean value of particle sizes)}.times.100

The mean particle size (circle corresponding diameter) of the organic silver salt described above is preferably from 0.01 to 0.3 .mu.m, and more preferably from 0.02 to 0.2 .mu.m. Besides, the mean particle size (diameter of corresponding circle) represents the diameter of a circle which has the same area as each particle image observed by the electron microscope.

To prevent devitrification of the imaging materials in the present invention, it is preferred that the total amount of silver halide and organic silver salt is from 0.3 g to 1.5 g per 1 m.sup.2 in terms of the silver amount. The preferable images are obtained when used as medical images by making this range. When it is less than 0.3 g per 1 m.sup.2, the image density is reduced in some cases. Also when it is more than 1.5 g per 1 m.sup.2, sensitivity reduction occurs at printing to PS plates in some cases.

On the other hand, in the silver salt photothermographic dry imaging material of a second embodiment, the higher the percentage of behenic acid is, moist storage fog and image storage fog are further improved. The percentage of silver behenate occupying in the organic silver salt is 50 mol % or more and less than 100 mol %, preferably, 70 mol % or more and less than 100 mol %, more preferably, 80 mol % or more and 99.9 mol % or less, and further preferably, 90 mol % or more and 99.9 mol % or less. On the other hand, when the percentage of the silver behenate becomes high, the melting point becomes high and it becomes difficult that silver ions are released, and thus the photothermographic property is deteriorated. As a means to improve this, it is preferable to combine a reducing agent described below. The other examples include the organic silver salts described in the paragraph number [0193] of JP-A-2001-83659. Also, concerning the methods for manufacturing the organic silver salts and the particle sizes of the organic silver salts, it i possible to refer to the description in the paragraph numbers of [0194] to [0197] of the same patent. Also, as the organic silver salts according to the invention, it is possible to use the technologies described in the paragraph numbers of [0028] to [0033] of JP-A-2001-48902 and in the paragraph numbers of [0025] to [0041] of JP-A-2000-72777. Also in the invention, it is desirable to manufacture silver salt particles under the condition where the compound which works as a crystal growth inhibitor or a dispersant for the silver salt particles is made coexist, in a process for manufacturing the silver salt particles. Such compounds are referred to the compounds having functions or effects to make the particle sizes smaller and/or to make more monodisperse compared to when manufactured under the condition where such a compound does not coexist. Specific examples include tertiary alcohols with 10 or less carbons, and are especially preferably tert-butanol. The preferable addition amount is from 10 to 200% by mass based on the aliphatic silver carboxylate.

[Silver Halide]

Described is photosensitive silver halide according to the present invention (hereinafter also referred to as silver halide, photosensitive silver halide grains or silver halide grains). Besides, the silver halide according to the present invention is referred to the silver halide crystalline particles treated and manufactured to be capable of originally absorbing light as an inherent nature of the silver halide crystal or capable of absorbing visual light or infrared light by artificial physicochemical methods, and such that physicochemical changes occur in the silver halide crystal or on the surface of the crystal when light is absorbed in any area of the light wavelength range from the ultraviolet light area to the infrared light area.

The silver halide grains per se used for the present invention can be prepared as the silver halide particle emulsion (also referred to as silver halide emulsion) using the well-known methods. For example, the photosensitive silver halide can be prepared as the silver halide particle emulsion using the methods described in P. Glafkides, Chimie et Physique Photographique (published by Paul Montel, 1967); G. F. Duffin, Photographic Emulsion Chemistry (published by The Focal Press, 1966); and V. L. Zelikman et al., Making and Coating Photographic Emulsion (published by The Focal Press, 1964).

That is, any of an acid method, neutral method, ammonia method and the like may be used, and also as the method to react a soluble silver salt with a soluble halogen salt, any of an one side mixing method, a simultaneous mixing method and the combination thereof may be used, but among the above methods, so-called controlled double jet method is preferable where the silver halide grains are prepared with controlling the formation condition.

A halogen composition of the photosensitive silver halide used in the first embodiment is not especially limited, and may be any of silver chloride, silver chloride bromide, silver chloride iodide bromide, silver bromide, silver iodide bromide and silver iodide.

On the other hand, the halogen composition of the photosensitive silver halide use in the second embodiment may be any of silver chloride iodide bromide, silver iodide bromide and silver iodide. In the embodiment, the iodine content is 2.0 mol % or more and 7.0 mol % or less, preferably, 2.5 mol % or more and 7.0 mol % or less, further preferably, 2.0 mol % or more and 6.0 mol % or less, more preferably, 2.5 mol % or more and 6.0 mol % or less, furthermore preferably, 2.5 mol % or more and 5.0 mol % or less, and most preferably, 3.0 mol % or more and 5.0 mol % or less. Physical phenomena are substantially given to the silver salt photothermographic dry imaging material of the invention, and within the iodine content of the invention, development fog can be reduced as desensitization is minimally inhibited. Also, the other effect can include accomplishment of high covering power. That is, when the particle sizes of the photosensitive silver halide which can become development initiation points are reduced to accomplish the high covering power, the particles are easily agglomerated, but when the appropriate iodine content of the invention is present, this agglomeration can be reduced.

The particle formation is typically divided into two stages, silver halide seed particle (nucleus) generation and particle growth, may be performed by the method where they are performed simultaneously and continuously or the method where the nucleus (seed particle) formation and the particle growth are separated, and it is possible to use the technology described in the paragraph number [0063] of JP-A-2001-83659.

The controlled double jet method where the particle formation is carried out by controlling pAg, pH which are the particle formation condition is preferable because the particle shape and size can be controlled. For example, when the method where the nucleus generation and the particle growth are separately carried out is performed, first a silver salt aqueous solution and a halide aqueous solution are mixed evenly and rapidly in a gelatin aqueous solution to generate the nucleus (seed particle) (nucleus generation step), and subsequently the silver halide grains are prepared by a particle growth step where the particles are grown with supplying the silver salt aqueous solution and the halide aqueous solution under controlled pAg and pH. The desired silver halide photographic emulsion can be obtained by eliminating unnecessary salts by a desalting step such as the desalting method known in the art such as a noodle method, flocculation method, ultrafiltration method and electric dialysis method after the particle formation.

Here, in the embodiment as the photothermographic imaging material, it is necessary that the average particle size of the silver halide is from 10 to 50 nm, but preferably it is from 10 to 35 nm. When the average particle size of the silver halide is less than 10 nm, the image density is sometimes reduced and light radiated image stability is sometimes deteriorated. When it is more than 50 nm, the image density is sometimes reduced.

The average particle size in both embodiments is referred to a length of an arris of the silver halide particle when the silver halide particle is in normal crystal shape such as cubic or octahedral shape. Also, when the silver halide particle is a tabular particle, it is referred to a diameter at the time when the particle is converted into a circle with the same area as a projected area of a major surface of the particle. When the particle is in the other shape which is not the normal crystal, such as spherical particle and bar particle, the diameter at the time when a sphere with the same volume as that of the silver halide particle is thought is calculated as the particle size. The measurement was carried out using electron microscopy, and the average particle size was obtained by averaging the measured values of 300 particle sizes.

Further, by combining the silver halide with average particle size of 55 to 100 nm and the silver halide with average particle size of 10 to 50 nm, it is possible to enhance the image density and improve (reduce) the decrease of image density with time. A ratio (mass ratio) of the silver halide grains with the average particle size of 10 to 50 nm to the silver halide grains with the average particle size of 55 to 100 nm is preferably from 95:5 to 50:50, and more preferably from 90:10 to 60:40.

On the other hand, in the embodiment as the silver salt photothermographic dry imaging material, the photosensitive silver halide according to the invention preferably have the smaller mean particle size in order to keep white turbidity after the image formation low and obtain good image quality. The average particle size is 0.2 .mu.m or less, more preferably from 0.01 .mu.m to 0.17 .mu.m, and especially preferably from 0.02 .mu.m to 0.14 .mu.m.

It is preferred that particle sizes of the silver halide grains are monodisperse. The monodisperse herein is referred to those where a coefficient of variation of the particle sizes obtained by the following formula is 30% or less. Preferably it is 20% or less and more preferably 15% or less. Coefficient of variation of particle sizes %=(Standard deviation of particle sizes/Mean value of particle sizes).times.100

Shapes of the silver halide grains can include a regular hexahedron, octahedron, 14-hedron particles, tabular particles, spherical particles, stick particles, potato-shaped particles and the like, but in these, preferred are regular hexahedron, octahedron, 14-hedron, and tabular silver halide grains.

When the tabular silver halide grains are used, the average aspect ratio is preferably 1.5 to 100, and more preferably 2 to 50. These are described in U.S. Pat. Nos. 5,264,337, 5,314,798 and 5,320,958, and the target tabular particles can be readily obtained. Additionally, particles where corners of the silver halide grains uproll can be preferably used.

Crystal habits of external surfaces of the silver halide grains are not especially limited, but it is preferred to use the silver halide grains having the crystal habit compatible for the selectivity at a high rate when a sensitizing dye having the crystal habit (face) selectivity is used in absorption reaction of the sensitizing dye onto the surface of the silver halide grains. For example, when the sensitizing dye which is selectively absorbed to crystal face with mirror index [100] is used, it is preferred that a occupying rate of the [100] face is high on the external surface of the silver halide grains, and this rate is preferably 50% or more, more preferably 70% or more, and especially preferably 80% or more. Besides, the rate of mirror index [100] face can be obtained by T. Tani, J. Imaging Sci., 29, 165 (1985) where absorption dependency of [111] face and [100] face is utilized in the absorption of sensitizing dye.

It is preferred that the silver halide grains are prepared by using low molecular weight gelatin with the average molecular weight of 50,000 or less at the formation of the particles, and in particular it is preferable to use at the nucleus formation of the silver halide grains. The low molecular weight gelatin is preferably one with the average molecular weight of 50,000 or less, preferably from 2,000 to 40,000, and especially preferably from 5,000 to 25,000. The average molecular weight of gelatin can be measured by gel filtration chromatography. The low molecular weight gelatin can be obtained by enzymatically decomposing by adding gelatinase to an aqueous solution of gelatin with the average molecular weight of about 100,000 usually used, by hydrolyzing by adding an acid or an alkali to the solution, by thermally decomposing by heating in air or under pressure, by decomposing by sonication or by combining these methods.

A concentration of dispersion medium at the nucleus formation is preferably 5% by mass, and it is preferable to perform at the low concentration of 0.05 to 3.0% by mass.

Further, it is preferred that the compound represented by the following Formula is used for the silver halide grains at the particle formation. YO(CH.sub.2CH.sub.2O).sub.m(CH(CH.sub.3)CH.sub.2O).sub.p(CH.sub.2CH.sub.2- O).sub.nY

In the formula, Y represents a hydrogen atom, --SO.sub.3M or --CO--B--COOM, M represents a hydrogen atom, an alkali metal atom, an ammonium group or an ammonium group substituted with an alkyl group of 5 or less carbon atoms, B represents a chain or a cyclic group which forms an organic dibasic acid, m and n represent from 0 to 50, respectively, and p represents from 1 to 100.

The polyethyleneoxide compound represented by the above Formula is preferably used as a defoaming agent for remarkable effervescence when photographic emulsion raw materials are stirred and moved such as a step where a gelatin aqueous solution is produced, a step where a water soluble halide and a water soluble silver salt are added to the gelatin solution and a step where the photographic emulsion is coated on the support, upon producing the materials in both embodiments, and the technology using as the defoaming agent is described, for example, in JP-A-44-9497. The polyethyleneoxide compound represented by the above Formula also works as the defoaming agent at the nucleus formation.

The compound represented by the above Formula is preferably used at 1% or less by mass based on the silver, and more preferably is used at from 0.01 to 0.1% by mass.

For the condition at the nucleus formation, it is possible to refer to the method described in the paragraphs of [0079] to [0082] of JP-A-2002-287299.

The silver halide grains used for the present invention may be added to an image formation layer by any methods, and at that time, it is preferred that the silver halide grains are positioned to come close to reducible silver source (organic silver salt).

It is preferred that the silver halide grains are precedently prepared and added to a solution for the preparation of organic silver salt particles in terms of production control because the preparation step of silver halide and the preparation step of organic silver salt particles can be separately treated. But, as described in British Patent No. 1,447,454, the silver halide grains can be produced nearly simultaneously with the production of organic silver salt particles by coexisting a halogen ingredient such as halide ions with the organic silver salt formation ingredients and inpouring the silver ions thereto when the organic silver salt particles are prepared.

Also, it is possible to prepare the silver halide grains by making a halogen-containing compound act to the organic silver salt and by conversion of the organic silver salt. That is, it is possible to make the silver halide forming ingredients act to a solution or dispersion of precedently prepared organic silver salt or a sheet material comprising the organic silver salt and to convert a part of the organic silver salt into photosensitive silver halide.

As silver halide forming ingredients, there are inorganic halogen compounds, onium halides, halogenated hydrocarbons, N-halogen compounds and the other halogen-containing compounds, and specific examples thereof are described in the paragraph [0086] of JP-A-2002-287299.

This way, the silver halide can be also prepared by converting a part of or whole silver in the organic acid silver salt into the silver halide by the reaction of the organic acid silver salt with halogen ions. And, the silver halide grains manufactured by converting a part of these organic silver salts may be combined with the separately prepared silver halide.

For these silver halide grains, both the silver halide grains separately prepared and the silver halide grains by the conversion of organic silver salt are preferably used at from 0.001 to 0.7 mol for 1 mol of the organic silver salt, and more preferably used at from 0.03 to 0.5 mol.

It is preferred that the photosensitive silver halide contains ions of transition metal belonging to 6 to 11 Groups in the periodic table of elements for improving illuminance disobedience. As the above metals, preferred are W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt and Au. These may be used alone, or two or more of the same type or different type metallic complexes may be combined. These metallic ions may be obtained by introducing the metallic salt in the silver halide, and can be introduced into the silver halide in a metallic complex or complex ion form. A content is preferably in the range of 1.times.10.sup.-9 mol to 1.times.10.sup.-2 mol, and more preferably from 1.times.10.sup.-8 to 1.times.10.sup.-4. In the present invention, the transit metallic complex or complex ion is preferably one represented by the following Formula. [ML.sub.6].sup.m

In the formula, M represents a transit metal selected from the elements of Groups 6 to 11 in the periodic table of elements, L represents a ligand, and m represents 0, -, 2-, 3- or 4-. Specific examples of the ligand represented by L include halogen ion (fluorine ion, chlorine ion, bromine ion and iodine ion), cyanide, cyanate, thiocyanate, selenocyanate, tellurocyanate, ligands of azide and aquo, nitrosyl, thionitrosyl and the like, and preferably are aquo, nitrosyl and thionitrosyl. When the aquo ligand is present, it is preferable to occupy one or two of the ligands. L may be the same or different.

It is preferred that the compound which provides these metallic ions or complex ions is added at the silver halide particle formation and incorporated in the silver halide grains, and it may be added at any stage of the preparation of silver halide grains, i.e., before and after the nucleus formation, growth, physical maturation, and chemical sensitization, but it is preferable to add at the stage of nucleus formation, growth or physical maturation, it is more preferable to add at the stage of nucleus formation or growth, and in particular preferably it is added at the stage of nucleus formation. When added, the compound may be added by dividing in several times; can be evenly contained in the silver halide grains; and can be contained by possessing a distribution in the particle as described in JP-A-63-29603, JP-A-2-306236, JP-A-3-167545, JP-A-4-76534, JP-A-6-110146 and JP-A-5-273683.

These metallic compounds can be added by dissolving in water or an appropriate solvent (e.g., alcohols, ethers, glycols, ketones, esters, amides). For example, there are the method where an aqueous solution of powder of the metallic compound or an aqueous solution in which the metallic compound and sodium chloride, potassium chloride are dissolved together has been added in a water soluble silver salt solution during the particle formation or a water soluble halide solution, or the method where the metallic compound is added as the third aqueous solution when the silver salt aqueous solution and the halide aqueous solution are simultaneously mixed to prepare the silver halide particle by a three solution simultaneous mixing method, the method where an aqueous solution of a required amount of the metallic compound is put in a reactor during the particle formation, or the method where the other silver halide grains in which the metallic ions or complex ions have been precedently doped are added to dissolve at the preparation of the silver halide. Especially, the method where the aqueous solution of powder of the metallic compound or the aqueous solution in which the metallic compound and sodium chloride, potassium chloride are dissolved together is added to the halide aqueous solution is preferable. When added on the particle surface, the aqueous solution of the required amount of metallic compound can be put in the reactor immediately after the particle formation, during or at the end of the physical maturation, or at the chemical maturation.

Separately prepared photosensitive silver halide grains can be desalted by the desalting methods known in the art such as the noodle method, flocculation method, ultrafiltration method and electric dialysis method, but can be also used without desalting in the photothermographic imaging materials.

Chemical sensitization can be given to the silver halide grains. For example, by the methods disclosed in JP-A-2001-249428, JP-A-2001-249426 and JP-A-2000-112057, a chemical sensitization center (chemical sensitization nucleus) can be formed and imparted using the compound having chalcogen atoms such as sulfur or the noble metal compound which releases noble metal ions such as gold ions. In the present invention, it is especially preferred that the chemical sensitization by the above compound having the chalcogen atom and the chemical sensitization using the noble metal compound are combined.

Also, the photosensitive silver halide is preferred to be chemically sensitized by the compound having the chalcogen atom shown below. It is preferred that these compounds having the chalcogen atom useful as an organic sensitizer are the compounds having a group capable of being absorbed to the silver halide and an unstable chalcogen atomic site.

As these organic sensitizer, it is possible to use the organic sensitizers having various structures disclosed in JP-A-60-150046, JP-A-4-109240 and JP-A-11-218874, and among them, it is preferred that the sensitizer is at least one type of the compounds having the structure where the chalcogen atom is bound to a carbon atom or phosphorus atom by a double bond. Especially preferred are the compounds of the Formula (1-1) and the Formula (1-2) disclosed in JP-A-2002-250984.

An use amount of the chalcogen atom-containing compound as the organic sensitizer varies depending on the chalcogen compound used, the silver halide grains used and a reaction environment upon giving the chemical sensitization, is preferably from 1.times.10.sup.-8 to 1.times.10.sup.-2 mol, and more preferably from 1.times.10.sup.-7 to 1.times.10.sup.-3 mol. The chemical sensitization environment of the present invention is not especially limited, but it is preferred that chalcogen sensitization is given using the organic sensitizer having the chalcogen atom in the presence of the compound capable of vanishing or reducing in size chalcogenated silver or silver nucleus on the photosensitive silver halide grains, or in coexistence of an oxidizing agent capable of oxidizing the silver nucleus. As the sensitization condition, pAg is preferably from 6 to 11 (more preferably from 7 to 10), pH is preferably from 4 to 10 (more preferably from 5 to 8), and it is preferred that the sensitization is given at the temperature of 30.degree. C. or below.

Therefore, it is preferred that the chemical sensitization is given to the photosensitive silver halide at the temperature of 30.degree. C. or below using the chalcogen atom-containing organic sensitizer in the coexistence of the oxidizing agent capable of oxidizing silver nuclei on the particles, ant that used is a photosensitive silver halide emulsion which is mixed with the organic silver salt, dispersed, dehydrated and dried.

Also, it is preferred that the chemical sensitization using these organic sensitizers is carried out in the presence of a spectral sensitizing dye or a heteroatom-containing compound having absorbability to the silver halide grains. Dispersion of chemical sensitization center nuclei can be prevented, and high sensitivity and low photographic fog can be achieved by performing the chemical sensitization in the presence of the compound having the absorbability to the silver halide. The spectral sensitizing dye used in the present invention is described below, but the heteroatom-containing compounds having the absorbability to the silver halide include nitrogen-containing heterocyclic compounds described in JP-A-3-24537.

In the nitrogen-containing heterocyclic compounds used for the present invention, heterocyclic rings can include pyrazole ring, pyrimidine ring, 1,2,4-triazole ring, 1,2,3-triazole ring, 1,3,4-thiaziazole ring, 1,2,3-thiaziazole ring, 1,2,4-thiaziazole ring, 1,2,5-thiaziazole ring, 1,2,3,4-tetrazole ring, pyridazine ring, 1,2,3-triazine ring, rings where two to three of these rings are bound, e.g., triazolotriazole ring, diazaindene ring, triazaindene ring, pentaazaindene ring and the like. It is possible to apply the heterocyclic rings where a monocyclic heterocyclic ring and an aromatic ring is condensed, such as phthalazine ring, benzimidazole ring, indazole ring, and benzothiazole ring. Among them, preferred are azaindene rings, and more preferable are azaindene compounds having a hydroxyl group as a substituent, e.g., hydroxytriazaindene, hydroxytetraazaindene, hydroxypentaazaindene compounds and the like.

The heterocyclic ring may have substituents other than the hydroxyl group. It may have, for example, alkyl, alkylthio, amino, hydroxyamino, alkylamino, dialkylamino, arylamino, carboxyl, alkoxycarbonyl groups, halogen atoms, cyano group and the like as the substituents.

The addition amount of the heterocyclic compound containing them varies in the wide range depending on the sizes and composition of silver halide grains and the other conditions, and the approximate amount is in the range of 1.times.10.sup.-6 mol to 1 mol as the amount per mol of the silver halide, and preferably in the range of 1.times.10.sup.-4 mol to 1.times.10.sup.-1 mol.

The noble metal sensitization can be given to the silver halide grains by utilizing the compound which releases noble metal ions such as gold ions as described above. For example, as the gold sensitizer, it is possible to use aurichloride salts and organic gold compounds.

Also, reducing sensitization methods can be used in addition to the above sensitization methods. As specific compounds for the reducing sensitization, it is possible to use ascorbic acid, thiourea dioxide, stannous chloride, hydrazine derivatives, boron compounds, silane compounds, polyamine compounds and the like. Also, the reducing sensitization can be carried out by maturing with retaining pH of the photographic emulsion to 7 or more or pAg of the same to 8.2 or less, respectively.

The silver halide given the chemical sensitization in the embodiment may be those formed in the presence of the organic silver salt, those formed in the absence of the organic silver salt, or those where both are mixed.

It is preferred that the spectral sensitization is given to the photosensitive silver halide grains by making spectral sensitizing dye absorb. As the spectral sensitizing dye, it is possible to use cyanine dye, merocyanine dye, complex cyanine dye, complex-merocyanine dye, holopolar cyanine dye, styryl dye, hemicyanine dye, oxonol dye, hemioxonol dye and the like. For example, it is possible to use the sensitizing dyes described in JP-A-63-159841, JP-A-60-140335, JP-A-63-231437, JP-A-63-259651, JP-A-63-304242, JP-A-63-15245, U.S. Pat. Nos. 4,639,414, 4,740,455, 4,741,966, 4,751,175, 4,835,096 and JP-A-2001-83659. The useful sensitizing dyes used for the present invention are for example described in the references described or cited in RD17643IV-A section (December in 1978, page 23) and RD18431 X section (August in 1978, page 437). Especially it is preferable to use the sensitizing dye having spectral sensitivity suitable for spectral property of various laser imager and scanner light sources. For example, preferably used are the compounds described in JP-A-9-34078, JP-A-9-54409 and JP-A-9-80679.

Useful cyanine dyes are, for example, the cyanine dyes having basic nuclei such as thiazoline nucleus, oxazoline nu