USOO673047 OB2 (12) United States Patent (10) Patent No.: US 6,730,470 B2 Katoh (45) Date of Patent: May 4, 2004 (54) PHOTOTHERMOGRAPHIC MATERIAL 3,438,776 A 4/1969 Yudelson 3,666,477 A 5/1972 Goffe (75) Inventor: Kazunobu Katoh, Minami-ashigara 3,667,959 A 6/1972 Bojara et al. (JP) 4,948,698 A 8/1990 Komamura ................. 430/203 5.945,263 A * 8/1999 Deroover et al. ........... 430/350 (73) Assignee: Fuji Photo Film Co., Ltd., Kanagawa 6,280,923 B1 * 8/2001 Uytterhoeven et al. ..... 430/619 (JP) (*) Notice: Subject to any disclaimer, the term of this FOREIGN PATENT DOCUMENTS patent is extended or adjusted under 35 EP O8O3764 * 10/1997 ........... GO3C/1/498 U.S.C. 154(b) by 0 days. * cited by examiner (21) Appl. No.: 09/955,029 (22) Filed: Sep. 19, 2001 Primary Examiner Thorl Chea (65) Prior Publication Data (74) Attorney, Agent, or Firm-Birch, Stewart, Kolasch & US 2002/0086251A1 Jul. 4, 2002 Birch, LLP (30) Foreign Application Priority Data (57) ABSTRACT Sep. 19, 2000 (JP) ....................................... 2OOO-283731 A photothermographic material comprising at least (a) a photosensitive silver halide, (b) a silver Salt of an organic (51) Int. Cl. .......................... G03C 11498; G03C 1/31; acid, (c) a reducing agent and (d) a hydrophobic and GO3C 1/34 thermoplastic organic binder on a Support, which contains a (52) U.S. Cl. ....................... 430/619; 264/531; 264/607; heat-fusible Solvent that is Solid at an ordinary temperature 264/631 and can be fused at a heat development temperature. There (58) Field of Search ................................. 430/619,531, is provided a photothermographic material showing high 430/264, 607, 631 Sensitivity, high developing Speed and little performance (56) References Cited fluctuation due to variation of heat development tempera ture. U.S. PATENT DOCUMENTS 3,347,675 A 10/1967 Hennet al. 22 Claims, No Drawings US 6,730,470 B2 1 2 PHOTOTHERMOGRAPHIC MATERIAL Since use of Such a development enhancer in a larger amount relative to the main reducing agent causes problems. Such as fog, it can actually be used only in a limited amount. TECHNICAL FIELD Therefore, its effect is also limited. The present invention relates to a photothermographic Meanwhile, JP-A-58-198038 and JP-A-58-229556 dis material, in particular, a novel photothermographic material close photothermographic materials using a heat-fusible showing high Sensitivity, high developing Speed and little solvent with the aid of a hydrophilic binder Such as gelatin as a binder. AS the heat-fusible Solvent, these patent docu performance fluctuation due to variation of heat develop ments disclose urea derivatives, amide derivatives, polyeth ment temperature. ylene glycols and polyhydric alcohols. RELATED ART However, these photothermographic materials Suffer from A large number of photoSensitive materials are known bad storability before light exposure. Therefore, sensitivity which have a photosensitive layer on a Support and form is decreased and fog is increased during Storage. images by exposing imagewise. As an example of a System Furthermore, they also suffer from a problem of significant 15 fluctuation of developing Speed due to change of humidity in that contributes to environmental protection or enables Sim an environment for heat development. For example, under plification of image formation means, there is a technique of high humidity, the developing Speed becomes high, whereas forming an image by heat development. it will be lowered under low humidity. Methods for forming images by heat development are described in, for example, U.S. Pat. Nos. 3,152,904, 3,457, SUMMARY OF THE INVENTION 075 and D. Klosterboer, Imaging Processes and Materials, In view of the aforementioned problems of the prior art, “Thermally Processed Silver Systems' A, 8th ed., Chapter 9, an object of the present invention is to provide a photother page 279, compiled by J. Sturge, V. Walworth and A. Shepp, mographic material showing high Sensitivity, high develop Neblette (1989). Such a photothermographic material con ing Speed and little performance fluctuation due to variation tains a reducible non-photosensitive silver Source (e.g., 25 of heat development temperature. Silver Salt of an organic acid), a photocatalyst (e.g., Silver The inventors of the present invention assiduously Studied halide) in a catalytically active amount, and a reducing agent in order to achieve the aforementioned object. As a result, for Silver, which are usually dispersed in an organic binder they found that a photothermographic material providing the matrix. The photoSensitive material is stable at an ambient desired effects can be obtained by adding a heat-fusible temperature, but when the material is heated at a high Solvent that is Solid at an ordinary temperature and can be temperature (e.g., 80 C. or higher) after light exposure, fused at a heat development temperature to a photothermo Silver is produced through an oxidation-reduction reaction graphic material comprising at least (a) a photosensitive between the reducible silver source (which functions as an Silver halide, (b) a silver Salt of an organic acid, (c) a oxidizing agent) and the reducing agent. The oxidation reducing agent and (d) a hydrophobic and thermoplastic reduction reaction is accelerated by catalytic action of a 35 organic binder on a Support, and thus accomplished the latent image generated upon exposure. The Silver produced present invention. by the reaction of the reducible silver salt in the exposed The photothermographic material of the present invention region shows black color and this presents a contrast to the preferably further contains a halogen-releasing precursor non-exposed region to form an image. and/or an ultrahigh contrast agent. Further, the photother Density of images to be formed is controlled by heat 40 mographic material of the present invention is preferably development temperature and time. However, Since the produced through a step of coating and drying a coating image density is influenced by heating methods and means, Solution containing lateX dispersed in water as the organic development characteristics of photothermographic material binder. Furthermore, the photothermographic material of the and So forth, uniform images of a certain level are not always present invention is preferably produced through a step of obtained. For this reason, it has been one of major problems 45 coating and drying a coating Solution containing micropar of photothermographic materials that uneven density is more ticles of the reducing agent Solid-dispersed in water and/or likely to be caused compared with the case where a material microparticles of the halogen-releasing precursor Solid is immersed into a development Solution at a constant dispersed in water. temperature like in the wet type development. To Solve this The photothermographic material according to the present problem, it is effective to use a Sufficient development 50 invention is characterized by high Sensitivity, high develop temperature and take Sufficient time until the image forma ing Speed and little performance fluctuation due to variation tion is Saturated. However, when a Sufficient development of heat development temperature. temperature and Sufficient time are used, there is caused problems of degradation of quality Such as increase of fog PREFERRED EMBODIMENTS OF THE INVENTION and change of Silver color tone and reduction of productivity 55 Such as decrease of developing Speed. The photothermographic material of the present invention There has been proposed use of a highly active reducing will be explained in detail hereinafter. agent as a development enhancer in order to increase the The photothermographic material of the present invention Speed of the heat development treatment. For example, comprises at least (a) a photosensitive Silver halide, (b) a Japanese Patent Laid-open Publication (Kokai, hereinafter 60 Silver Salt of an organic acid, (c) a reducing agent and (d) a referred to as JP-A) 10-221806 discloses use of hindered hydrophobic and thermoplastic organic binder on a Support, phenol compounds and bisphenol compounds as a reducing and it is characterized by further containing a heat-fusible agent and use of Sulfonamidophenol compounds as a devel Solvent that is Solid at an ordinary temperature and can be opment enhancer. The development enhancer used in this fused at a heat development temperature. case is a reducing agent showing higher activity than the 65 Therefore, the heat-fusible solvent used for the photother main reducing agent, and it can accelerate advance of mographic material of the present invention will be development in an early Stage of development. However, explained first. US 6,730,470 B2 3 4 The heat-fusible solvent used for the photothermographic as is understandable from its characteristics, and the melted material of the present invention is an organic material that heat-fusible solvent can diffuse into all of layers to exert its is Solid at an ordinary temperature but melts or shows a effect during the heat development irrespective of the layer mixed melting point together with other components at a to which the heat-fusible solvent is added. Therefore, when heat development temperature to be used or a temperature the heat-fusible solvent may affect photosensitivity of the lower than that and is liquefied upon heat development to image-forming layer, in particular, when it may adversely accelerate the heat development. The Scope of the heat affect to promote fluctuation of performance during produc fusible Solvent includes compounds that can be a Solvent for tion and use of the photothermographic material, the heat a developing agent, compounds having a high dielectric fusible solvent is preferably added to a layer other than the constant and known to promote physical development of image-forming layer (e.g., protective layer, undercoat layer, silver Salt and so forth. intermediate layer) Preferred examples of the heat-fusible solvent include An ultrahigh contrast agent can be used for the photo ure a derivatives, amide derivatives, Sulfonamide thermographic material of the present invention.