JPS6255649B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to silver halide compositions for photothermography. As is well known, silver halide compositions for photothermography are well known in the art. Such a composition can form a developed image by subjecting it to imagewise exposure and then heating it to a suitably elevated temperature. It is unnecessary to use a separate processing liquid or processing bath to obtain the desired image. Heat processing can be performed to form a developed silver image within such compositions. Typical photothermographic silver halide elements include (a) a hydrophilic silver halide emulsion containing a gelatin peptizer, (b) an organic solvent mixture, (c) a hydrophobic binder, and (d ) (i) silver salts of long-chain fatty acids, such as silver behenate or silver stearate; and (ii)
The present invention includes an oxidation-reduction imaging composition having an organic reducing agent, such as a phenolic reducing agent. It is advantageous to include hydrophilic silver halide light-sensitive emulsions containing gelatin peptizers in such photothermographic elements, since the silver halide emulsions possess high sensitivity. It is from. Furthermore, if the emulsion is prepared based on the commonly used aqueous silver halide gelatin emulsion method, it is very easy to control. However, one problem is unavoidable in the preparation of such photothermographic silver halide elements. That is, the problem is to mix a hydrophilic silver halide emulsion containing a gelatin peptizer with a composition containing a hydrophobic component. Hydrophobic components include hydrophobic binders, such as poly(vinyl butyral), and silver salts of long chain fatty acids, such as silver salts of behenic acid.
Generally, a photothermographic element is prepared by mixing a hydrophilic silver halide emulsion containing a gelatin peptizer with a hydrophobic component as described above and then coating it on a support. In this case, the resulting element provides less sensitivity, contrast, and maximum density than desired after exposure and heat treatment. The use of various organic solvents has been proposed to assist in the preparation of photothermographic silver halide compositions containing hydrophilic and hydrophobic components as described above. Organic solvents that have been proposed include isopropanol, acetone, toluene, methanol, 2-methoxyethanol, chlorinated solvents, acetone-toluene mixtures, and certain non-aqueous polar organic solvents. However, it is not possible to obtain improved desirable properties using these organic solvents. Accordingly, there is a long-standing need to provide improved relative sensitivity and contrast as well as desirable maximum image density in photothermographic compositions after exposure and processing. The present invention solves the problems of the prior art as described above by providing a silver halide composition for photothermography that can be coated onto a support. Can be done. The silver halide composition for photothermography of the present invention comprises a hydrophilic silver halide photosensitive emulsion containing a gelatin peptizer, an organic solvent mixture, a hydrophobic binder, and (i) a silver salt of a long-chain fatty acid and ( ii) an oxidation-reduction imaging composition comprising an organic reducing agent, wherein said solvent mixture comprises (A) a photographic speed enhancing solvent selected from benzyl alcohol and its derivatives and 2-phenoxyethanol; and (B) an aromatic hydrocarbon solvent that is miscible with the sensitivity-enhancing solvent. Benzyl alcohol may be substituted with methyl, trifluoromethyl, methoxy, ethoxy or phenoxy groups. Aromatic hydrocarbon solvents are miscible with this sensitivity enhancing solvent. Particularly useful organic solvent mixtures include up to 10% by weight (relative to the weight of the solvent mixture), preferably from 3 to 8% of a hydrophobic binder (C).
further includes. The photothermographic composition according to the invention is prepared by mixing a hydrophilic silver halide emulsion containing a gelatin peptizer very carefully with an organic solvent mixture, for example by ultrasonic mixing, and then An oxidation-reduction imaging composition (b) comprising a binder (a), a silver salt of a long-chain fatty acid (i), and an organic reducing agent (ii)
It can be prepared by mixing with a hydrophobic component containing. The solvent mixture used here is
(A) () Benzyl alcohol solvent optionally substituted with a methyl group, trifluoromethyl group, methoxy group, ethoxy group or phenoxy group or () 2-phenoxyethanol solvent: (B) The above solvent ( A) an aromatic hydrocarbon solvent that is miscible with the solvent; and (C) a hydrophobic binder, such as poly(vinyl butyral), in an amount of 0 to 10% by weight of said solvent mixture. A photothermographic composition according to the invention can be coated onto a support to form a photothermographic element. After exposure of a photothermographic element, the image can be developed by simply heating the element to a suitably elevated temperature. A variety of photographic speed enhancing alcohol solvents are useful in solvent mixtures such as those described above. The alcohol solvent used here needs to be sufficiently soluble in the aromatic hydrocarbon solvent and other components of the silver halide composition for photothermography.
Some of these alcoholic solvents are not sufficiently soluble in compositions such as those mentioned above to be useful. These solvents include chloro-, hydroxy- and nitro-substituted benzyl alcohols. Selection of the optimal alcohol solvent depends on, for example, the characteristics of the components constituting the photothermographic composition, the desired image, coating conditions, the characteristics of the aromatic hydrocarbon solvent, the characteristics of the silver halide photographic emulsion, and the characteristics of the photothermographic composition. It will depend on various factors, such as the concentrations of the various components that make up the thermographic composition. It is also useful, if desired, to use mixtures of compatible alcoholic solvents. Selection of the optimum alcohol solvent can be carried out by a simple test (substituting an alcohol solvent for benzyl alcohol as described in Example 1 below). If the test results of the selected alcoholic solvent are the same as those of Example 1 below, the alcoholic solvent can be considered to be at least a satisfactory solvent. The term "sensitivity enhancement", when used herein in reference to a sensitivity (speed sensitivity) increasing solvent, refers to a photothermographic composition containing an alcoholic solvent as well as a photothermographic composition that does not contain an alcoholic solvent. The intention is to explain that it provides a higher relative sensitivity compared to other compositions. The benzyl alcohol solvent as described above may be unsubstituted benzyl alcohol or benzyl alcohol substituted with substituents that do not adversely affect the desired solvent or sensitometric properties. It may be hot. Substituents that do not adversely affect the desired properties are, for example, methyl, phenoxy, trifluoromethyl, methoxy and ethoxy. Unsubstituted benzyl alcohol is preferred. A variety of aromatic hydrocarbon solvents are useful in solvent mixtures such as those described above. The aromatic hydrocarbon solvent used herein must be compatible with the photographic sensitivity enhancing solvent and other components of the photothermographic composition, and must also be compatible with the desired solvent and sensitometric properties. It must not have a negative effect on the characteristics. The suitable aromatic hydrocarbon solvent will depend on various factors such as, for example, the nature of the components making up the photothermographic composition (including the nature of the alcoholic solvent) or the nature of the photosensitive silver halide emulsion or the nature of the photothermographic composition. The selection can be made based on the application conditions of the e-composition. It is also useful, if desired, to use mixtures of aromatic hydrocarbon solvents. Useful aromatic hydrocarbon solvents are, for example, toluene, xylene and benzene. Toluene is advantageously used as a solvent in combination with benzyl alcohol. Photographic speed-enhancing alcohol solvents are useful in photothermographic silver halide compositions such as those described above over a wide range of concentrations. The alcohol solvent is the photosensitive silver halide 1 contained in the emulsion.
It is preferred to use a concentration of 0.25 to 2.0 moles per mole. Generally, alcohol solvents are
It is useful at concentrations such that photothermographic elements containing 0.50 to 2.80 g/m ² of alcohol solvent are produced. Particularly useful concentrations of alcoholic solvents, such as benzyl alcohol, are in the range such that the amount of alcoholic solvent ^per square meter of photothermographic element support is from 0.8 to 1.35 grams. Additionally, the optimum concentration of alcoholic solvent will depend, for example, on the nature of the components of the photothermographic composition, the conditions of application, the desired image, the nature of the aromatic hydrocarbon solvent, or the nature of the alcoholic solvent. Additionally, aromatic hydrocarbon solvents are also useful in photothermographic silver halide compositions such as those described above over a wide range of concentrations. The concentration of aromatic hydrocarbon solvent is generally within the range of 30-80% by weight of the total photothermographic composition. A preferred concentration of aromatic hydrocarbon solvent, such as toluene, is within the range of 70-80% by weight of the total photothermographic composition. The optimal concentration of aromatic hydrocarbon solvent will also depend on various factors, such as those discussed above in connection with selecting the optimal concentration of alcoholic solvent. The ratio of the alcohol solvent to the aromatic hydrocarbon solvent contained in the solvent mixture as described above is determined at the time when the solvent mixture is mixed with silver halide.
Useful over a wide ratio range. Generally, the ratio of alcoholic solvent to aromatic hydrocarbon solvent is within the range of 1:10 to 1:30 at such times. The preferred ratio of alcohol solvent to aromatic hydrocarbon solvent is within the range of 1:15 to 1:25. The optimal ratio of alcohol solvent to aromatic hydrocarbon solvent depends on, for example, the characteristics of the solvent, the characteristics of the components of the silver halide composition for photothermography,
It will depend on various factors such as the coating conditions, the desired image and the nature of the silver halide emulsion. Generally, in a photothermographic composition as described above before coating on a support, the ratio of alcohol solvent to aromatic hydrocarbon solvent is:
It is within the range of 1:50 to 1:200, preferably 1:75 to 1:150. When applying photothermographic silver halide compositions, the concentration of water in the composition should be less than that which can be controlled by the sensitivity-enhancing alcohol solvent. The concentration of water in photothermographic compositions is usually less than about 3% by weight of the composition. It is desirable to concentrate the photothermographic composition prior to its application to achieve the desired application properties. The photosensitive silver halide useful in the compositions of this invention is in the form of a hydrophilic silver halide emulsion containing a gelatin peptizer. A typical concentration of a hydrophilic silver halide photosensitive emulsion containing a gelatin peptizer is such that the amount of photosensitive silver halide is 0.2 to 1.0 mole per mole of silver salt of long chain fatty acid. Within range. If necessary, other photosensitive materials can also be advantageously used in combination with the photosensitive silver halide as described above. Preferred photosensitive silver halides are silver chloride, silver bromoiodide, silver bromide, silver chlorobromoiodide or mixtures thereof. For purposes of this invention, silver iodide is also considered to be a photosensitive silver halide. The grain size of the photosensitive silver halide is useful in a wide range from very coarse grains to very fine grains. In general, ultrafine grained silver halides are preferred. Hydrophilic silver halide emulsions containing gelatin peptizers can be prepared according to any technique known in the photographic art. Useful preparation methods and forms of photosensitive silver halide gelatin emulsions are described, for example, in the Product Licensing Index,
Vol.92, December 1971, Publication9232, page 107 (Publisher: Industrial Opportunities Limited,
Homewell, Havant Hampshire, PO9 1EF,
UK). The gelatin peptizer can include a variety of peptizers known in the photographic art, including, for example, phthalated gelatin or non-phthalated gelatin. Other gelatin peptizers include gelatin hydrolyzed with acids or bases. Non-phthalated gelatin peptizers can be used particularly advantageously with light-sensitive silver halide emulsions such as those described above. Hydrophilic silver halide emulsions can contain gelatin peptizers in various concentrations.
Generally, the concentration range is such that the amount of gelatin peptizer is from 5 to 20 grams per mole of silver contained in the silver halide emulsion. Particularly useful low gelatin concentrations are in the range such that the amount of gelatin per mole of silver contained in the silver halide emulsion is from 9 to 15 grams. The optimum concentration of gelatin peptizer depends, for example, on the characteristics of the photosensitive silver halide, the desired image, the characteristics of the components of the photothermographic composition, the coating conditions, the characteristics of the benzyl alcohol solvent, and the aromatic hydrocarbon solvent. will depend on various factors such as the nature of the The term "hydrophilic" is used herein to describe that a light-sensitive silver halide emulsion containing a gelatin peptizer is compatible with an aqueous solvent. There is. The pH value of the silver halide emulsion is determined during the emulsion precipitation process.
The pH value can be maintained within the range of about 5.0 to about 6.2. A relatively low PH value of an emulsion can cause undesirable coagulation, and a relatively high PH value can cause undesirable grain growth. The temperature of the reaction vessel (in which the silver halide emulsion is prepared) is generally about 35°C during the preparation of the composition.
Maintain within a temperature range of ~75°C. The temperature range and time during preparation can be varied to obtain the desired emulsion grain size and desired composition properties. Silver halide emulsions can be prepared using a variety of emulsion preparation methods and equipment known in the photographic art. A particularly useful method for preparing photothermographic compositions involves adding in parallel the aforementioned components () and () to a jacket containing ultrasonic means for exposing the composition to radiofrequency waves. This is a method (double jet emulsion method). After the mixing in the jacket and thorough mixing by ultrasonic waves are completed, the resulting mixture is taken out, and
For additional mixing, the resulting mixture can be recirculated in the jacket containing the ultrasonic means or removed immediately and easily combined with other additives, thus forming the desired phototherm. Graphite compositions can be prepared. A variety of hydrophobic binders are useful in photothermographic materials such as those described above. Binders useful herein include a variety of colloids alone or in combination with vehicles and/or binders. Suitable hydrophobic binders include transparent or translucent materials. Useful binders include, for example, polymers of alkyl acrylates and -methacrylates, acrylic acid, sulfoalkyl acrylates or -methacrylates, and those having crosslinking sites to promote curing or curing. . Other useful hydrophobic binders include, for example, high molecular weight materials and resins such as poly(vinyl butyral), cellulose acetate butyrate, poly(methyl methacrylate), poly(styrene), poly(vinyl chloride), and chlorinated rubbers. , poly(isobutylene), butadiene-
These include styrene copolymers, vinyl chloride-vinyl acetate copolymers, vinyl acetate, vinyl chloride and maleic anhydride copolymers, and others. here,
It is important that the hydrophobic binder does not adversely affect the photothermographic properties or other desired properties of the photothermographic material as described above. Poly(vinyl butyral), such as “BUTVAR” from Monsanto in the United States
Particularly useful is the one commercially available under the trade name . The hydrophobic binder to be included in the photothermographic silver halide material according to the invention is useful in various concentrations. Generally, the concentration of hydrophobic binder included in photothermographic silver halide compositions according to the present invention is within the range of about 20 to about 65 mg/dm ² . The optimum concentration of a hydrophobic binder as described above depends on various factors such as, for example, the nature of the binder, other components of the photothermographic material, application conditions, and the desired image or processing temperature and conditions. can be changed. If desired, a portion of the photographic silver halide contained in the photothermographic composition according to the invention can be prepared in situ within the photothermographic material. The photothermographic composition can be prepared, for example, independently of a portion of the photographic silver halide, i.e., one or more of the other components that make up the photothermographic material, and then their It can include those that are not mixed with other ingredients, but that are prepared within or on top of those other ingredients. Such a method for preparing silver halide in situ is described, for example, in US Pat. No. 3,457,075. Photothermographic compositions as described above include an oxidation-reduction imaging mixture containing a silver salt of a long chain fatty acid and a suitable reducing agent.
Oxidation derived from this mixture by heating -
The reduction reaction is catalyzed by a latent silver image from photosensitive silver halide formed by imagewise exposure of the photothermographic material and subsequent general heating of the material. Believable. However, the exact mechanism of such image formation is currently not fully understood. Silver salts of various long chain fatty acids are useful in photothermographic materials according to the present invention. “long chain”
The term, as it is used herein, refers to such fatty acids that contain 12 to 30 carbon atoms and are generally resistant to darkening after exposure to light. Useful silver salts of long chain fatty acids are, for example, silver stearate, silver behenate, silver caprate, silver hydroxystearate, silver myristate and silver palmitate. If desired, it is also possible to advantageously use small amounts of other silver salt oxidizing agents (not silver salts of long chain fatty acids) in combination with the silver salts of long chain fatty acids. Silver salts which can be advantageously used in combination with the silver salts of long chain fatty acids as mentioned above are, for example, silver benzotriazole, silver imidazole, silver benzoate, and others. If desired, it is also possible to advantageously use mixtures of silver salts of long-chain fatty acids in photothermographic materials as described above. A variety of organic reducing agents are useful in the photothermographic silver halide materials of the present invention.
These reducing agents are generally silver halide developers that cause the desired oxidation-reduction image forming reaction after exposure and heating of the photothermographic silver halide material. Useful organic reducing agents include, for example, polyhydroxybenzene,
For example hydroquinone and alkyl-substituted hydroquinone; catechol and pyrogallol;
phenylenediamine developers; aminophenol developers; ascorbic acid developers, such as ascorbic acid, ascorbic acid ketals and other ascorbic acid derivatives; hydroxylamine developers;
3-pyrazolidone developers, e.g. 1-phenyl-
3-pyrazolidone and 4-methyl-4-hydroxymethyl-1-phenyl-3-pyrazolidone; hydroxytetronic acid and hydroxytetronamide developer; reductone developer; bis-β-naphthol reducing agent; sulfonamide phenol reducing agent;
Others. In the photothermographic silver halide materials as described, it is also possible to advantageously use mixtures of organic reducing agents. In silver halide compositions for photothermography, sulfonamidophenol developers can be used with particular advantage, for example as described in Belgian Patent No. 802,519 (published January 18, 1974). Various concentrations of organic reducing agents can be advantageously used in photothermographic silver halide materials such as those described above. The concentration of organic reducing agent generally ranges from about 5 to about 20 mg/dm ² , such as from about 10 to about 20 mg/dm 2 .
It is within the range of about 17 mg/dm ² . The optimum concentration of organic reducing agent will depend on various factors such as the nature of the long chain fatty acids, the desired image, processing conditions, the nature of the solvent mixture, application conditions, etc. Prior to coating the photothermographic composition on a suitable support, the composition is prepared in such a way that the order in which the listed components are added is determined to achieve optimum photographic sensitivity, contrast and maximum density. It is very important to obtain In a particularly useful method according to the invention, a low gelatin silver halide emulsion is added to the ultrasonic mixing means through one charge thereof, and toluene, up to about 4% by weight of poly(vinyl butyral) and A solvent mixture containing benzyl alcohol is added through the other charge. Under this environment, the low gelatin silver halide is thoroughly dispersed by ultrasound. The resulting product is then mixed with the remaining ingredients of the desired photothermographic composition. If the low-gelatin silver halide is not dispersed as described above before adding other ingredients, the silver halide grains in the resulting composition will coagulate (clamp) together and the resulting clumps will be used for mixing the composition. There is a tendency to settle at the bottom of the container. A variety of mixing means are useful for preparing compositions such as those described above. However, the mixing means here should be those which allow very careful mixing, for example ultrasonic mixing means. Other mixing means other than ultrasonic mixing means which can be used advantageously are commercially available colloid mill mixing means and disperzeter mixing means known in the field of photography. Blenders, such as those known under the trade name "Waring" blender, do not allow for the very thorough mixing that is considered desirable in most cases. In some cases, it is called a toning agent and an activator -
It is desirable to include what are also known as toning agents in the photothermographic materials according to the invention. Mixtures of toning agents are also often useful.
Common toning agents are, for example, phthalimide, succinimide, N-hydroxyphthalimide, N-
They are hydroxy-1,8-naphthalimide, N-hydroxysuccinimide, 1-(2H)-phthalazinone and phthalazinone derivatives. Photothermographic compositions according to the invention can contain other additives useful in imaging. Suitable additives include development regulators, hardeners, which act as sensitivity-enhancing compounds;
Antistatic layers, plasticizers and lubricants, coating aids, brighteners, spectral sensitizers, light absorbing and photodyes, matting agents, etc. In certain cases, it is useful to include stabilizers in photothermographic materials such as those described above. Stabilizers have the function of helping to stabilize images that have been developed. If desired, it is also possible to advantageously use mixtures of stabilizers. Common stabilizers or stabilizer precursors include certain halogen compounds, such as tetrabromobutane and 2-
(tribromomethylsulfonyl), benzothiazole (provides improved post-processing stability),
and includes azothioether and blocked azolinthion stabilizer precursors. Photothermographic elements containing compositions according to the invention can have a variety of supports that can withstand the processing temperatures useful for developing the image. Common supports include cellulose ester, poly(vinyl acetal), poly(ethylene terephthalate), polycarbonate and polyester film supports.
Additionally, related film and resinous support materials and supports such as paper, glass, metal, etc. that can withstand processing temperatures are also useful.
Generally, flexible supports are most useful. Photothermographic compositions can be applied by dip application,
It can be coated onto a suitable support using coating techniques known in the photographic art including air knife coating, curtain coating or extrusion coating using a hopper. If desired, two or more layers can be applied simultaneously. Silver halide and oxidation-reduction imaging mixtures as described above can be present at any suitable location in the photothermographic element according to the invention to obtain the desired image. In some cases, specific proportions of reducing agents, silver salt oxidizing agents, and/or other additives as described above may be added to a protective layer or overcoat layer (containing other components of the elements as described above). It is also desirable to include the However, these components must be located in a position that allows for the desired interaction of the components after processing. To obtain the desired image, it is necessary that the photosensitive silver halide and the other components of the imaging combination, as described above, be "reactively associated" with each other. “Reactively combined”
As the term is used herein, the term refers to a specific location in which the photosensitive silver halide and the image-forming combination are relative to each other, i.e., to permit the desired processing and to provide a useful image. It means existing in such a position. One useful embodiment of the present invention is a silver halide composition for photothermography which can be coated onto a support and comprises the following (a) to (d): . (a) an aqueous silver halide emulsion containing a gelatin peptizer; (b) a benzyl alcohol photographic speed-enhancing solvent, such as a mixture of benzyl alcohol with toluene and up to 4% by weight of poly(vinyl butyral); (c) a hydrophobic polymeric binder consisting essentially of poly(vinyl butyral), and (d) (i) a silver salt of a long chain fatty acid consisting essentially of silver behenate; ) an organic reducing agent consisting essentially of a sulfonamidophenol. Photothermographic elements according to the invention can be prepared by coating this composition on a suitable support. Representing another aspect of the invention, it comprises preparing a desired photothermographic element by coating a composition as described above on a suitable support. This is the preparation method. A variety of imagewise exposure means are useful in photothermographic materials according to the present invention. The imaging means according to the invention can be any suitable radiation source that typically emits radiation to which the photothermographic material is sensitive. Imaging materials according to the invention have a general sensitivity to the ultraviolet and blue parts of the spectrum, and therefore exposure means that provide such radiation are useful. Generally, however, when a spectral sensitizing dye or a mixture of such dyes is present in the photothermographic material,
It is advantageous to use exposure means using another region of the electromagnetic spectrum. Typically, a visible light source, such as a tungsten lamp, is used to imagewise expose the photothermographic material according to the invention. Other radiation sources may also be used to advantage, including, for example, lasers, electron beams, x-ray sources, and the like. Generally, photothermographic materials can be subjected to imagewise exposure to form a developable latent image. In the photothermographic material according to the invention, a visible image can be developed in a short time (for example within a few seconds) simply by heating the material to a suitably elevated temperature. For example, the exposed photothermographic material may be heated to a temperature of about 100 to about 200°C, such as about 110 to about 140°C.
can be heated to a temperature of Heating is generally carried out for about 2 to about 30 seconds, such as about 2 to about 10 seconds, until the desired image is developed. Selection of optimal processing times and temperatures will depend on various factors, such as the desired image, the nature of the components of the photothermographic element, the nature of the latent image, etc. to subject the described photothermographic material to the heat necessary to develop the desired image;
Various means can be used to advantage. The heating means can be, for example, a simple hot plate, an iron, a roller, an infrared heating means, a hot air heating means, or the like. Processing according to the invention is generally carried out under ambient pressure and humidity conditions. Pressures and humidity other than standard atmospheric conditions can be used if desired. However, it is advantageous to use standard atmospheric conditions. Next, the present invention will be explained in more detail with reference to the following examples. Example 1 This example is an implementation of the invention. A silver behenate/behenic acid dispersion (c) was prepared by mixing the following ingredients: Acetone 250ml Toluene 250ml Poly(vinyl butyral) 30.3g Behenic acid 16.0g Silver behenate 42.0g as follows: A silver halide gelatin photosensitive dispersion (Z) was prepared. 10 ^-3 mol of lithium bromide in water with 0.02 mol of
400 Å silver bromoiodide (6 mole % bromide) was added to a gelatin emulsion (40 g of non-phthalated gelatin per mole of silver) to give a total amount of 200 mg. The resulting mixture 40
Heated for 15 minutes at °C and PH = 6.1 and pAg = 8.4. The emulsion was centrifuged at 3000 rpm for 20 minutes. Sample 100 of silver halide emulsion after wet centrifugation
mg was treated with ultrasound for 30 seconds (during treatment, 87
g of toluene, 4 g of benzyl alcohol and 4
% of poly(vinyl butyral) was present). The silver halide dispersion (Z) prepared as described above was combined with the following ingredients: acetone/toluene containing 0.01% by weight of 3-ethyl-2-thio-2,4-oxazolidinedione ( 1:9 parts by volume) solution (sensitivity enhancing additive) 0.15ml Contains 0.01% by weight of 3-ethyl-5-(3-ethyl-2-benzoxazolylideneethylidene)-1-phenyl-2-thiohydantoin. acetone/toluene (1:9 parts by volume) solution (sensitizing agent) 0.50 ml Silver behenate dispersion C (as above) (oxidizing agent) 3.6 ml By shaking the resulting composition for several minutes, and mixed. The dispersion was combined with the solution described below and coated onto an unsubbed poly(ethylene terephthalate) film support to a wet film thickness of 8 mils. Acetone/toluene (1:1 parts by volume) solution containing 2.5% by weight of 2,6-dichloro-4-benzenesulfonamidophenol (reducing agent) 0.50ml Siloxane surfactant, 2% by weight of Silicone AF- 2 drops of a toluene solution containing 70 (trade name of GE) 0.30 ml of an acetone solution containing 5% by weight of 2-(tribromomethylsulfonyl)benzothiazole (stabilizer) Resulting coating film was dried at 48.9°C for 5 minutes. What is thus obtained is a photothermographic element according to the invention. The resulting photothermographic element was subjected to imagewise exposure through a 1.0 neutral density and stepped density step wedge, resulting in a developable latent image in the element. The previously obtained latent image was developed by heating the photothermographic element at a temperature of 140°C for 5 seconds. A developed image with high contrast was obtained. The resulting image had a maximum density of over 3.8 and a minimum density of 0.12. The photothermographic element obtained as described above was free of mottles and had a smooth surface. The resulting photothermographic element and its sensitometric properties may be compared with another photothermographic element (containing silver halide having a similar grain size as the previous element) prepared similarly to that element. However, it was prepared in the absence of gelatin (prepared in poly(vinyl butyral) using an acetone solvent instead of a mixture of benzyl alcohol and toluene). Favorable results were obtained. Example 2 This example illustrates the use of a silver halide emulsion decomposed with phthalated gelatin (using up to 9 g of phthalated gelatin per mole of silver) in a non-aqueous photothermographic material according to the invention. do. A gelatin silver halide emulsion was prepared by adding solutions B and C to solution A simultaneously at an addition rate of 6.3 ml/min. Solution A: Phthalated gelatin 9g Distilled water 783ml Temperature 35℃ PH 5.0 VAg + 60mV Solution B: NaBr 133.9g KI 4.6g Distilled water 152ml Room temperature (about 20℃) Total volume 186ml Solution C: AgNO ₃ 170g Distilled water 109 ml Room temperature (approx. 20°C) Total volume 143 ml After 50 seconds, bromide ion solution was added to solution A to adjust its VAg value to +110 mV. total precipitation time,
That is, it took about 22 minutes to completely add Solution C. Addition of solution B was then discontinued. The final composition has a PH value of 5.50 and
It had a pAg value of 8.41. Increase the temperature of the reaction vessel to 40
℃ and its pH value was adjusted to 3.5 by adding 1.5N nitric acid. The supernatant was decanted and the coagulum was redispersed by adding 10 ^-3 M lithium bromide solution, thus giving a final weight of 1300 g (pAg = 7.70) and 2.0 M Its pH value was adjusted to 6.50 by adding lithium hydroxide to the composition. This procedure was repeated twice and, after removal of the final supernatant, the concentrated coagulum (1 mol of silver Approximately 500g per portion)
By stirring vigorously for 30 minutes at a temperature of 40°C, its pH value was reduced to 6.5, and its pAg
Adjusted the value to 8.3. The obtained silver halide emulsion (40°C) was mixed with 87 g of toluene, 4 g of benzyl alcohol and 4% by weight of poly(vinyl butyral).
using ultrasonic mixing means. The resulting composition was then combined with other ingredients as described in Example 1 above to obtain a photothermographic element according to the invention. Imagewise exposure of the resulting photothermographic element resulted in a developable latent image in the element. photothermography elements
The image was developed by heating at a temperature of 125°C for 5 seconds. The developed image has a maximum density of 1.64 and
It had a minimum concentration of 0.26. Example 3 The procedure described in Example 2 above was repeated. However, in this example, one of the following compounds A to G was used as a solvent at a concentration of 0.90 mol/silver halide 1 mol.

TABLE Photothermographic elements containing the above compounds were prepared using silver halide as described in Example 2 above. Imagewise exposure (1/8 second) of each of the resulting photothermographic elements to a mercury light source via a step density step wedge resulted in a developable latent image in the element. For each element, 5 at a temperature of 125℃
The heating was carried out for a period of seconds and the image was developed. The table below summarizes the sensitometric measurements obtained for each of the compounds mentioned above.

【table】

[Table] The data listed in the table above show that compounds B, C and D give similar results to compound A (benzyl alcohol). That is, these compounds can provide improved relative sensitivity and maximum concentration compared to photothermographic elements that do not contain benzyl alcohol. Compounds E, F and G gave undesirable relative sensitivity results. Compound B
Enhanced contrast was observed in photothermographic elements containing C and C. Example 4 The procedure described in Example 2 above was repeated. However, in this example, instead of benzyl alcohol at the stated concentration, one of the following compounds 4A, 4H, 4I and 4J was used as a solvent at a concentration of 0.90 mol/mol silver halide. Compound name 4A Benzyl alcohol 4H p-Methylbenzyl alcohol 4I p-methoxybenzyl alcohol 4J 2-phenoxyethanol The resulting coating film was imagewise exposed to a tungsten light source for 10 ^-3 seconds via a step density step wedge. A developable latent image was then obtained in the exposed photothermographic element.
The image-wise exposed photothermographic element
The treatment was carried out by heating at a temperature of 125° C. for 5 seconds. A developed image was obtained for each element. The table below summarizes the sensitometric measurement results obtained.

TABLE Comparing the results of compounds 4A, 4H, 4I and 4J with the control, improvements in photographic speed, contrast and maximum density and reduced minimum density are observed. The use of benzyl alcohol and its derivatives in photothermographic materials as described can also reduce haze in the photothermographic layer in the element. In each case, there was no haze present in the photothermographic elements after processing. Example 5 A photothermographic film containing no sensitizer was prepared as follows: A. Preparation of silver behenate dispersion: The following ingredients were combined in the order listed using a commercially available homogenizer. , and blended.

[Table] B Preparation of silver halide emulsion: A silver bromoiodide gelatin emulsion with pH=6.5 and pAg=8.3 was melted at 50°C. The emulsion was chemically sensitized with sulfur and gold compound sensitizers and then held at 50°C for 10 minutes. C Preparation of silver halide/polymer dispersion: In a 100 ml beaker, add 52.8 g of silver halide in toluene.
55 grams of 4% by weight poly(vinyl butyral) ("B-76" above) and 2.5 grams of benzyl alcohol were added. 13.1g (0.02g) of this polymer solution
mol) of chemically sensitized silver halide gelatin emulsion and was carefully mixed using ultrasonic mixing means at a temperature of 50°C. D. Preparation of Photothermographic Compositions and Elements: The following ingredients were mixed.

Table: The ingredients were stirred for 1 minute.
30ml (27g) of silver behenate/polymer dispersion (as in C above) was added. The resulting composition was stirred and then the following ingredients were added: 1 2,6-dichloro-4-benzenesulfonamidophenol (5 g dissolved in 4.3 g acetone, total amount 18.5 g (20 ml) 9.2g of toluene was added to make it) (reducing agent)
10ml (9.6g) 2 2-(Tribromomethylsulfonyl)benzothiazole (1.0g to 7.8g of acetone and
Dissolve in 8.6g of toluene to make the total amount 17.4g
(20ml)) (stabilizer precursor)
6 ml (5.2 g) of the resulting composition in the form of a melt was deposited on a poly(ethylene terephthalate) film support.
It was applied at 12.0ml/929cm ² (approximately 0.0129ml/cm ² ). The film support contained a blue antihalation dye. E Overcoat Preparation: An overcoat composition was prepared by mixing the following ingredients:

[Table] After mixing, this composition was applied onto the silver bromoiodide-containing layer of the film from D above at 3.7 ml/929 cm ² (approximately 0.004
ml/cm ² ). The photothermographic film obtained was found to be useful as an aviation print film. Imagewise exposure provided a developable latent image and heat treatment provided a developed image. Example 6 A photothermographic film similar to that described in Example 5 above was prepared. However, in the case of this example, the following two types of sensitizing dyes were further included in the silver bromoiodide-containing layer. 3-ethyl-5-(3-ethyl-2-benzoxazolylidene)-1-phenyl-2-thiohydantoin (0.05 wt. of 0.50 ml containing 1.36 mg dye in 1:9 volume of acetone:toluene) % solution was added to the composition prior to application) anhydro-3-ethyl-9-methyl-3'-
(3-Sulfobutyl)-thiacarbocyanine hydroxide (0.01% by weight of 3 ml containing 5 mg dye/3 ml solution in 1:1 volume methanol:toluene)
The resulting photothermographic film was exposed to light to provide a developable latent image, which was then heat treated to provide a developed image.

Claims (1)

[Scope of Claims] 1. A hydrophilic silver halide photosensitive emulsion containing a gelatin peptizer, an organic solvent mixture, a hydrophobic binder, and an oxidizing agent comprising (i) a silver salt of a long-chain fatty acid and (ii) an organic reducing agent. - A silver halide composition for photothermography comprising a reduced image forming composition, wherein the solvent mixture comprises (A) benzyl alcohol and a methyl group, a phenoxy group, a trifluoromethyl group, a methoxy group or an ethoxy group; A phototherm comprising: a photographic sensitivity increasing solvent selected from substituted benzyl alcohol and 2-phenoxyethanol; and (B) an aromatic hydrocarbon solvent miscible with the sensitivity increasing solvent. Silver halide composition for graphics.