US 3552971 A
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Jan. 5, 197 1 HARUQ TAKENAKA ETAL 3,552,971
POSITIVE SHEET FOR DIFFUSION TRANSFER Filed Dec. 5, 1967 I 'I' -l-"rl 5 -3- I" FT- 55 if 3 R 2 V INVENTORS HARUO TAKENAKA AKIYASU SHIOZAWA TADAHIRO FUJIWARA BY M, WM M ATTORNEYS United States Patent 3,552,971 POSITIVE SHEET FOR DIFFUSION TRANSFER Haruo Takenaka, Akiyasu Shiozawa, and Tadahiro Fujiwara, Kanagawa, Japan, assiguors to Fuji Photo Film Co., Ltd., Kanagawa, Japan Filed Dec. 5, 1967, Ser. No. 688,029 Claims priority, application Japan, Dec. 5, 1966, 41/ 79,680 Int. Cl. G03c 1/48, /54
US. Cl. 96-76 2 Claims ABSTRACT OF THE DISCLOSURE A positive sheet for diffusion transfer comprising a support, a subbing layer, an image-receiving layer and. a surface layer, said surface layer comprising a polymer insoluble in water and soluble in an alkaline aqueous solution and an organic solvent.
BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to an image receiving paper or film (hereinafter, it is called positive sheet in this specification) for photographic silver halide transfer process (diffusion transfer process).
(2) Description of the prior art A conventional positive sheet for diffusion transfer is usually composed of, as shown in the accompanying drawing, a support 1 such as a film or a paper, a subbing layer 2 formed thereon, a diffusion transfer emulsion layer 3 or positive print layer (hereinafter the layer is simply called the image-receiving layer) and a surface layer 4 having the property of easily peeling an imagebearing silver halide photosensitive negative paper therefrom, after images are transferred from the negative paper to the positive sheet. The surface layer is usually formed by applying to the image-receiving layer a coating composition or an aqueous solution of a water-soluble polymer, such as carboxymethylcellulose, polyvinyl alcohol, hydroxyethylcellulose and the like. However, such a conventional surface layer has the disadvantages that the difiusion transfer nuclei are denatured and decomposed due to the hygroscopic property of the surface layer, whereby the color tone and the density of the transferred image are degraded and thus the transferred image becomes unstable. Also, since the main solvent for forming the surface layer on the positive film is water, it takes a very long period of time to dry the surface layer thus formed, which makes the production of the positive films inefficient.
Therefore, an object of this invention is to provide a positive sheet for diffusion transfer without having the aforesaid disadvantages and capable of providing stable and excellent images. Another object of this invention is to provide a positive sheet for diffusion transfer having an improved surface layer which can be formed on the image-receiving layer thereof in a short period of time. Still another object of this invention is to provide a method of preparing a positive sheet for diffusion transfer quickly and efficiently.
SUMMAJRY OF THE INVENTION These and other objects of this invention can be at tained by using a polymer or a copolymer insoluble in water but soluble in an alkaline solution and an organic solvent as a material for the surface layer of a positive sheet for diffusion transfer.
DETAILED DESCRIPTION OF THE INVENTION As the polymer or copolymer used in this invention as a material for the surface layer, there are illustrated a copolymer of vinyl acetate and maleic anhydride, a coice polymer of methyl methacrylate and acrylic acid, a copolymer of acrylic acid and styrene, a carboxyvinyl poly mer sold under the trade name of Carbopol (Goodrich-Gulf Chemicals Co.) which is understood to be a copolymer of carboxymethylcellulose and vinyl acetate, and the like. For forming the surface layer, at least one of these polymers or copolymers may be applied to the image-receiving layer as a solution thereof in an organic solvent, such as acetone, methanol, ethanol, or a mixture thereof by a conventional coating method. In this case, it is most preferable to employ as the aforesaid polymer or copolymer one having a viscosity of 0.5-1.0 when measured by dissolving about 0.5 g. of the polymer or copolymer in ml. of a solvent mixture of methanol and acetone (6:4) at 30 C. and testing by means of an Ostwald viscometer.
Since the surface layer of the positive sheet of this invention formed by using the aforesaid polymer or copolymer is insoluble in water and soluble in an aqueous alkaline solution and an organic solvent, the positive diffusion transfer sheet of this invention shows low hygroscopicity and hence provides stable and excellent images thereon transferred from a negative paper. Further, since the copolymer or polymer for the surface layer is soluble in an organic solvent, the copolymer or polymer is applied to the emulsion layer as a solution in an organic solvent in the case of preparing the positive sheet, which shortens the drying time for the surface layer. Moreover, the surface layer is easily swelled when the positive sheet is wetted with an alkaline developer (which is generally highly alkaline), which makes fast the transfer procedure of images from a negative paper. The reproductions obtained by using the positive dilfusion transfer sheet of this invention have a high transfer density as well as a high gradient.
The invention will be described by the following examples, in which part is part by weight.
EXAMPLE 1 Parts Maleic anhydride-vinyl acetate copolymer 3 Acetone v 60 Methanol 40 The drying time for the surface layer was about 5 of the drying time in a conventional case, where an aqueous solution was employed.
An image-bearing negative paper was superimposed on the positive diffusion transfer sheet thus prepared and they were processed in an alkaline developer to transfer images from the negative paper to the positive sheet. The transfer density of the image thus obtained was about 30% higher than that obtained by using a conventional positive diffusion transfer sheet. Also, the stability of the images thus transferred was about twice as high as that in a conventional case.
EXAMPLE 2 The same procedure as in Example 1 was repeated while using a coating liquid having the following composition, as a coating liquid for the surface layer:
- 4 v I The positive diffusion transfer sheet had the same efceiving layer is the dried residue from a solution of the fects as those'of the'positive sheet in'Example l. polymer in'an organic-solvent? l were? What is claimed is: 1. 'In a positive sheet for diffusion transfer compris- References Cited ing, in sequence, a support, a subbing layer, an image- 5 UNITED STATESPATENTS receiving layer and a surface layer, the improvement I 7 which comprises the surface layer consisting essentially 2719791 10/1955 Land of a polymer insoluble in Water and soluble in an akaline 3265505 8/1966 Yudelson T 9%7 aqueous solution and an organic solvent, said polymer WILLIAM M ARTIN, PrimaryEXaminer being selected from the group conslsting of a copolymer 1O 7 i of maleic anhydride and vinyl acetate and a copolymer HUSACK, ASSlStaIlt EXaIIllHer of methylmethacrylate and acrylic acid. r
2. The positive sheet for difiusion transfer according CL to claim 1 wherein said surface layer on said image-re-