JPS61291176A - Thermal transfer type copying method - Google Patents

Abstract

PURPOSE:To provide a novel color copying method, by using an aqueous solution of polyvinyl alcohol converted into a urethane as a binder, in a method wherein a transferred image consisting of azo dyes is formed on a receiving sheet by thermal transfer. CONSTITUTION:An aqueous solution of a polyvinul alcohol converted into an urethane is used as a binder for a silver halide emulsion containing azo dyes. By this, sublimability or evaporability of the azo dyes in thermal transfer can be markedly enhanced. The receiving sheet 2 is placed on a color master sheet A, and the laminate is heated by applying thermal energy H, whereby the azo dye present on the sheet A are sublimed or evaporated, and are transferred onto the receiving sheet 2. The thermal transfer copy thus obtained has a color image corresponding to a color original. In the figure, symbols BR, R, G, BL and W denote the transferred images formed on the receiving sheet 2 in correspondence with the color master sheet which are respectively black, red, green, blue and white in color.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal transfer type copying method using a heat sublimable or heat vaporizable azo dye as a transfer dye.

[Prior art]

Traditionally, there has been a strong demand for color copying, and much research has been devoted to the development of color copying methods. However, in the case of conventional color copying methods, (1) it takes a long time to copy and is not suitable for making large numbers of copies; They have common drawbacks such as 2) rough images and poor gradation, and (3) complicated and high cost equipment, as well as high cost per copy, and there is a strong desire to improve these drawbacks. has been done.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide a new color copying method that overcomes the drawbacks of the conventional color copying method based on a principle different from that of the conventional color copying method.

〔composition〕

According to the present invention, a photosensitive material in which a plurality of azo dye layers each consisting of a heat sublimable or heat vaporizable azo dye, silver halide, and a binder are laminated on a support is subjected to a series of image hazing, development, and dye bleaching processes. A color master sheet for thermal transfer having a positive image made of an azo dye is created by applying the above treatment, and a receiving sheet is placed on top of the positive image of the color master sheet for thermal transfer, and thermal transfer is performed to form a receiving sheet. There is provided a thermal transfer copying method characterized in that a urethanized polyvinyl alcohol aqueous solution is used as the binder.

As mentioned above, the present invention is characterized in that an aqueous solution of mononotanated polyvinyl alcohol is used as a binder for a silver halide emulsion containing an azo dye, which improves the sublimation of the azo dye in the thermal transfer process described later. Alternatively, vaporization can be significantly improved. The content of urethanized polyvinyl alcohol in the aqueous solution of urethanized polyvinyl alcohol used as a binder in the present invention is usually in the range of 1 to 20% by weight, preferably 4 to 7% by weight. Furthermore, according to the present invention, there is provided a thermal transfer copying method characterized in that the emulsion comprising the azo dye, silver halide, and aqueous urethanized polyvinyl alcohol solution contains a chromium compound as a hardening agent. .

In this way, by including a chromium compound as a hardening agent in the light-sensitive material, it is possible to prevent image destruction caused by the use of strong acid (0.8±0.05) in the dye bleaching process described later. I can do it. Examples of such ROM compounds include chromium potassium sulfate (chromium alum)
Examples include various chromium-based compounds such as.

Simply put, the principle of the color copying method of the present invention is a combination of the principle of producing color photographs using a silver dye bleaching method and the principle of thermal transfer copying using an azo dye as a transfer dye. Next, the principle of the thermal transfer type color copying method of the present invention will be explained.

(a) Color master sheet (Figure 1) In the color copying method of the present invention, a color master sheet is a sheet having at least one layer of a photosensitive material containing a heat-sublimable or heat-vaporizable azo dye to which silver halide is added. Used as Sea 1. FIG. 1 shows an example of the layer structure of this color master sheet in the case of a three-layer structure of a yellow dye layer, a magenta dye layer, and a cyan dye layer. In Figure 1, ■
indicates a yellow dye layer and a blue photosensitive layer, a magenta dye layer and a green photosensitive layer, C indicates a cyan dye layer and a red photosensitive layer, and each of these layers y, M and C are laminated on the support 1. to form a photosensitive layer X.

(b) Exposure step (Figure 2) This step is a step in which the color master sheet is exposed to direct imaging light or reflected imaging light from the original to form a latent image in the photosensitive layer X. . An explanatory diagram of the cod light principle in this case is shown in FIG. In FIG. 2, V indicates white, BL indicates blue, G indicates green, R indicates red, and BR indicates black light. The position of the latent image formed in the photosensitive layer is determined by the tone of the exposed color.
), are formed in each layer of the green photosensitive layer (M) and red photosensitive layer (C), in the case of blue (Bl, ), it is formed in the blue photosensitive layer (V), and in the case of green (G), the green photosensitive layer (M), and in the case of red (R), it is formed in the red photosensitive layer (C), while in the case of black, no latent image is formed on the photosensitive layer.

(C) Black-and-white development step (Figure 3) This step is a step in which the exposed color master sheet obtained in the exposure step is subjected to black-and-white development, and the latent image formed in the photosensitive layer Developed as an image. FIG. 3 shows an explanatory diagram of the principle of black development. In FIG. 3, the X mark indicates the developed blackened silver image. The reaction formula for this black and white development is as follows.

Ag"X +DP-+, Ag+X-10XIDP:
Developer OXI: Oxidized product of the developer (d) Dye bleaching step (Figure 4) This step uses the blackened silver obtained in the black developing step as a catalyst, and reduces the amount of blackened silver with a strongly acidic solution. In this process, the azo dye in the area where blackened silver is present is decomposed and reductively bleached. FIG. 4 shows a diagram explaining the principle of dye bleaching. In FIG. 4, the white area including the X mark without diagonal lines indicates the dye bleached area.

The reaction formula for this dye bleaching is as follows.

4AV, +RN=NR' +411+ →4Hg+ +RNII 2+R' N112RN=N
I'<': Azo dye (e) fixing step (Figure 5) In this step, the decomposed dye obtained in the dye bleaching step is treated with a fixing solution, unnecessary silver halide is removed, and the azo dye is This is the process of obtaining a positive image.

FIG. 5 shows an explanatory diagram of the principle of the fixing process. In FIG. 5, the completely white area without diagonal lines indicates the bleached area of the dye that has been fixed. The color master sheet obtained in this way is a color positive image (
However, as shown in Fig. 5, depending on the exposure to the light of the color tone shown in Fig. 2, white (11), blue (Ill), green, etc. (G), red (R) and black (BR) tones.

(1) Thermal transfer step (FIG. 6) This step is a step in which the azo dye image formed on the color master sheet I- of the positive image obtained in the fixing step is transferred onto the receiving sheets 1 to 1. FIG. 6 shows a diagram explaining the principle of this thermal transfer process. In FIG. 6, A indicates the color master sheet 1, and 2 indicates the receiving sheet. In this step, the receptor sheet (2) is placed on the color master sheet (A)J-, and the azo dye present on the color master sheet is sublimated or vaporized by applying thermal energy (11) and heating it. Transfer onto a receiving sheet (2). Thermal transfer copies obtained in this way
has a color image corresponding to a color original,
FIG. 7 shows a cross-sectional view of the color copy. In this FIG. 7, transfer images formed on the receiving sheet-1- corresponding to the color master sheet (A) are shown for BR, R, G, BL and the old color master sheet (A), respectively. Shows blue and white transferred images. That is, the color of the image formed on the receiving sheet consists of a mixture of azo dyes transferred from the color master sheet.

In the present invention, the structure of the color master sheet shown in FIG. 1, the exposure process, black development process, dye bleaching process, and fixing process of the color master sheet shown in FIG. sjlver dy
It is possible to apply color photography techniques based on the basic principle of ``e bleach process''. For example, the color master sheet can be used for yellow, magenta,
It can be created by coating and drying a silver bromide emulsion containing an azo dye showing each color of cyan to form each dye layer. layers can be provided. Further, if necessary, an intermediate layer may be provided between the dye layers to separate each emulsion layer from other emulsion layers, and these intermediate layers may also contain a filter dye and an oxidizing agent.

Further, it is preferable to add additives to each layer as necessary, and thiazoline, benzotriazole, acrylonitrile, and benzophenone compounds can be used as ultraviolet absorbers, and azaindenes, triazoles, tetrazoles, and stabilizers can be used as stabilizers. Imidazolium salts, tetrazolium salts, polyhydroxy compounds, etc. are used.

Further, development accelerators such as benzyl alcohol and polyoxyethylene compounds, and image stabilizers such as chroman, coumaran, bisphenol and phosphite esters can be used.

In addition, sensitizers include noble metal sensitizers such as water-soluble gold salts, water-soluble platinum salts, water-soluble palladium salts, water-soluble rhodium salts, and water-soluble iridium salts, sulfur sensitizers, selenium sensitizers, boramine, and dichloromethane. A reduction sensitizer such as tin can be used, and furthermore, as an optical sensitizer, a cyanine dye such as a zeromethine dye, a monomethine dye, a dimethine dye, a trimethine dye, or a merocyanine dye can be used in combination with the dye.

A suitable pyrazine, quinoxaline or phenazine (e.g. 2,3
-dimethylquinoxaline, 2,3-diaminophenazine, 2-hydroxy-3-aminophenazine, etc.), anthraquinone sulfonic acid, pyrazine-2,3-dicarboxylic acid, pyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine , diphenylpyrazine, acylaminopyrazine, etc. are also preferably used. Further, the photosensitive layer may be of a dye laminated type or a dye mixed type. Regarding photosensitive materials in such a silver dye bleaching method and the formation of positive images using the same, there are conventionally known documents, such as Makoto Kikuchi's "Photo Chemistry" (published by Kyoritsu Shuppan KK, Kyoritsu Zensho 21, 1968). (Edition) Paragraphs 292-293, Akira Sasai, “
"Chemistry of Photography" (Shashin Kogyo Publishing Co., Ltd. 1978 edition) 293
Item -297; A, Meyer+ J, Phot
, Scj, 20.81 (1972) i 1. ,F
, A. Mason, Photography, c Pr.
occessjngchemistry, Focal
Press, London, +966, P, 2
75 etc., as well as Japanese Patent Publication No. 43-24743, Japanese Patent Application Laid-Open No. 47-8979, and Japanese Patent Application Laid-open No. 46-68.
It is described in Japanese Patent Publication No. 808, Japanese Patent Publication No. 43-16185, and many other patent documents.

In the present invention, a receiving sheet is placed over a color master sheet having a positive image that is a mirror image of a color original, and the azo dye image on the color master sheet is transferred to the receiving sheet. It is characterized by
In this case, in order to make this thermal transfer process practical, the selection of the azo dye is important, and in the case of the present invention, the heating temperature is 8.
It is advantageous to use azo dyes which exhibit thermal sublimation or thermal vaporizability at 0 to 250°C, preferably from 120 to 180°C.

In the case of the present invention, it is preferable to use an azo dye having a structure represented by the following general formula.

In the general formula, x, ■ and Z represent the following substituents.

(In the above formula, A, I( are 11.01(, CQ, Br
, NO2, CN, 5O2CH3, Cnt12n+ s
(n = 1-5), D indicates 11, cI+3, etc.) [In the formula, R1 and R2 are ■1, CnH2n+1 (n is 1
~5 integer), (CI+2)null' (n is 1
Z; H1014, CQ, Br
, NO2, CN, SO2CH3C02CII3, CN
H2n+1 (n is an integer of 1 to 5) Examples of the above dyes include the following compounds.

-12= Also, the dye may be mixed with a surfactant or a dispersant at a rate of 0.0% relative to the dye. It can be added in a weight range of 1.0 to 1.0% by weight and sufficiently mixed and dispersed in water. In this case, the particle size of the disperse dye is about 0.1 to 6.0 μm, preferably 0.1 to 1.0 μm.
0 μm is good.

Plain paper can be used as the receiving sheet used in the present invention. In this case, the plain paper has a smooth surface, for example, a smoothness of 20 to 150, preferably
The use of between 50 and 150 is advantageous. It is also preferable to use a surface-treated sheet as the receptor sheet, for example, a sheet having a receptor layer made of a mixture of a heat-softening meltable resin and an organic filler that is dyeable with an azo dye. In this case, the resin used to form the receptor layer may be any heat softening and melting resin that can be easily dyed with sublimation or vaporizable dyes, and is well known in the field of sublimation printing. A variety of polymers are used. For example, such things include:
Examples include amino alkyd resin, polyamide, polyurethane, polyvinyl chloride, polyvinyl acetate, polyester, acrylic resin, acetal resin, polyvinyl alcohol, polyvinylidene chloride, polyvinyl acetal, polystyrene, polycarbonate, and epoxy resin.

In the case of the present invention, it is preferable to use a resin having a softening point of 60 to 120°C. Various fine polymer particles can be used as the organic filler, but the particle diameter is preferably 10 μm or less. Examples of polymers constituting the organic filler include methylcellulose, ethylcellulose, polystyrene, polyurethane, urea/polymarine resin, melamine resin, phenol resin, iso(or diiso)butylene/
Maleic anhydride copolymer, styrene/maleic anhydride copolymer, polyvinyl acetate, polyvinyl chloride, vinyl chloride/vinyl acetate copolymer, polyester, polyacrylic ester, polymethacrylic ester, styrene/butadiene/acrylic Examples include copolymers and the like. Further, as the base sheet, paper, synthetic paper, plastic film, metal foil, etc. can be used. When thermal transfer is performed using such a receptor sheet, the surface of the resin forming the receptor layer of the receptor sheet is softened and melted, and the vaporized dye enters the molten resin and is dyed. Therefore, after the transfer is completed, the dye molecules are incorporated into the resin, so the fading resistance and storage stability of the resulting dye image are significantly improved, and a large amount of dye is adsorbed, resulting in extremely high image density and sharpness. Excellent. The dyeable resin is usually applied to the base sheet 2 in the form of an aqueous emulsion containing an organic filler, but of course it can also be applied to the hot melt 1 in some cases. The ratio of resin and organic filler used is preferably 1/9 to 9/I in terms of weight ratio. In this receiving sheet, the organic filler mixed with the resin of the receiving layer exhibits the effect of facilitating peeling of the receiving sheet from the transfer sheet after completion of transfer. The lower the softening point of the resin in the receiving layer, the better the pigmented image.On the other hand, the lower the softening point of the resin, the stronger the adhesion between the transfer layer and the receiving layer, and the more difficult it is to peel off the receiving sheet from the transfer sheet. make it difficult The use of organic fillers solves severe delamination problems. In addition, the organic filler prevents the heat transferred from the transfer layer to the receptor layer from escaping toward the substrate, and has the effect of increasing the effective utilization rate of heat that is effectively used for softening and melting the resin. show. The dye image formed on such a receiving sheet has excellent fading resistance and storage stability, and is extremely excellent in density and sharpness. Other surface-treated sheets used as receiving sheets in the present invention include those in which a resin layer containing fillers such as calcium carbonate, silica, and kaolin is provided on a base sheet. As the resin in this case, various resins as mentioned above can be used.

Further, as the receiving sheet in the present invention, it is preferable to use a dyeable film having a heat-sensitive adhesive surface on one side in combination with a support sheet.

In this case, the dyeable film may be any film as long as it has dyeability to sublimed or vaporized dyes, and plastic films are generally preferred. In the case of the present invention, those having a softening point in the temperature range of 100 to 200°C are particularly preferable, such as polyester films, polysulfones, polyvinyl chloride films, polyamide films, etc., and the thickness thereof is usually 20 to 150 μm. ,
Preferably it is 30 to 80 μm. In the present invention,
A heat-sensitive adhesive layer is formed on one side of this dyeable film, and the film is processed into a heat-sensitive adhesive surface. The heat-sensitive adhesive layer in this case can be formed by a conventionally known method, for example, by applying a coating agent commonly used as a hot-melt adhesive. Examples of such coating agents include those based on ethylene/vinyl acetate copolymer, polyvinyl acetate, polyvinyl butyral, polyethylene, and polyamide, and those based on ionomer resins are also used. be done. The heat-sensitive adhesion temperature of these coating agents is generally 60 to 120°C, but any coating agent may be used as long as it produces adhesive properties when heated below the melting point of the dyeable film. Further, the heat-sensitive adhesive layer can be formed not only by using the above-mentioned coating agent but also by dry laminating a film of the above-mentioned coating resin, such as a polyethylene film. This heat-sensitive adhesive layer can be formed on a part or the entire surface of the dyeable film. The type of support sheet used in combination with the dyeable film is not limited and any type can be used. For example, various types such as paper 1 synthetic paper, plastic film, metal foil, etc. can be used.

When thermal transfer is performed using a receiving sheet in which a dyeable film as described above is combined with a support sheet, the dyeable film and the support sheet 1- & Heat transfer is performed in this order by overlapping the dyeable film so that the heat-sensitive adhesive surface provided on the dyeable film is in contact with the support sheet. Through such thermal transfer, the azo dye that is thermally sublimated or thermally vaporized from the surface of the color master sheet is dyed onto the dyeable film to form an image, and at the same time, the dyeable film is thermally bonded to the support sheet and copied. As a result, it is integrated with the support sheet and dyeable film,
A sheet having an azo dye image on the surface (dyeable film surface) is obtained.

In the present invention, when thermal transfer is performed by overlapping a color master sheet having a positive image made of an azo dye and a receiving sheet, a transfer mechanism consisting of a pair of heating rolls and a color master sheet support drum is used. The sheet is wound and fixed on the surface of the support drum, and the receiving sheet is continuously fed from one direction between the support drum and the heated roll. When the receiving sheet is supplied in this manner, the receiving sheet is overlapped with the color master sheet wound around the supporting drum between the supporting drum and the heating roll, and is simultaneously thermo-pressed and bonded to the positive image on the color master sheet. When the image is transferred onto a receiving sheet, successive color copies thereof are obtained. That is, similar to a normal copying machine, by using one color master sheet, a large number of color copies can be obtained in succession. In this case, the number of color copies that can be obtained is
It is proportional to the amount of azo dye formed as a positive image on the color master sheet used. That is, in the color master sheet shown in FIG.

By increasing the layer thickness of the azo dye layer indicated by H and C, a larger number of color copies can be obtained. The thickness of each azo dye layer V, M and C is generally 0.
．． It is about 5 to 3.0 μm, preferably about 0.5 to 2.0 μm.

Next, FIG. 8 shows the basic mechanism of a copying apparatus for carrying out color copying according to the present invention.

In FIG. 8, 1 is a color original, 2 is a glass substrate, and the image of the color original placed on the glass substrate is transmitted through a lens 3 onto a color master sheet 4 supported by an S color master sheet cartridge 5. exposed to light. This exposed color master sheet 4 is loaded into the developing and fixing section 6 together with the cartridge 5, and subjected to the above-described development (black development 1 dye bleaching) and fixing processing, so that the surface has a mirror image relation to the color original. A color master sheet 4 having a positive image is obtained. This color master sheet is supported and fixed on the surface of the support drum 7 via the biting portion 8.

On the other hand, a receiving sheet 10 as a copy paper is placed on a conveyor belt 2'' by a feed roller 11, and is fed between a color master sheet support drum 7 and a heating roll 13. The heating roll 13 includes an infrared lamp 14 for heating the color master sheet inside thereof. Between the support drum 7 and the heating roll 13, the receiving sheet is overlapped with the color master sheet supported by the support drum 7, and heated at the same time.
A second positive image is thermally transferred onto the receiver sheet. and,
A color copy 20 having a transferred image in a normal image relationship with respect to the color original is taken out from the copy takeout port 15 .

Although the color copying principle of the present invention has been described above, various modifications can be made to the present invention. For example, although multicolor color copying has been described above, in the case of the present invention, monochrome color copying can be performed based on the same principle. In this case, in the color master sheet shown in FIG. 1, a pasted azo dye layer having a desired color tone is formed on the base sheet. Furthermore, the color master sheet shown in FIG. 1 has three color azo dye layers Y, M, and C laminated on a base material sheet, but these three color azo dyes are used as a mixture on the base material sheet. It can also be supported on a sheet.

〔effect〕

The color copying principle of the present invention is as described above, and compared to conventional color copying, color copies can be obtained with high resolution, high gradation, high sensitivity, and at high speed using a copying machine with a simpler structure. . According to the invention, therefore, the color copies obtained have the advantage of being low cost.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples.

23-Example I A: Formulation of urethanized polyvinyl alcohol emulsion Urethaneized polyvinyl alcohol (Neelamine XP-66,
Solution (I-) was obtained by adding 25 g of water to 72 g of 10% aqueous solution (manufactured by Mitsui Toatsu Co., Ltd.), and adding NH3 to 60 g of silver nitrate.
[Add and dissolve 5% aqueous solution to bring the total volume to 100 cc, and use it as [11] liquid, and then add water to 42 g of potassium bromide and dissolve it, bringing the total volume to 1.0 Occ (m).
It was made into a liquid. Next, add (IT) solution 25. to the above [1] solution.
'1 lcc and 25.4 cc of [m'-] liquid were added to prepare a urethanized polyvinyl alcohol emulsion.

B: Preparation of color master sheet (1) Preparation of photosensitive material Using baryta paper (manufactured by Mitsubishi Paper Industries, Ltd.) with a thickness of 165 μm as a support, the azo dye is contained in the urethanized polyvinyl alcohol emulsion on it. Apply a coating liquid to form each layer shown below in sequence.

A photosensitive material having three color azo dye layers was prepared.

1st layer (lowest layer): Odor in a red sensitized urethanized polyvinyl alcohol aqueous solution containing a cyan azo dye of Sumika'ron B'lue '5E-RF (manufactured by Sumika Chemical Industry Co., Ltd.) Silver oxide emulsion 2nd layer: Urethane polyvinyl alcohol intermediate layer 3rd layer: Green sensitized urethane polyvinyl alcohol aqueous solution containing magenta azo dye of Sumikaron Red E-3BR (manufactured by Sumikagaku Co., Ltd.) 4th layer of silver bromide emulsion inside: urethanized polyvinyl alcohol intermediate layer 5th layer: yellow filter layer containing dye represented by Cθ 6th layer: TS-Yell, ow 115 (manufactured by Sumitomo Chemical Co., Ltd.)
A silver bromide emulsion in an aqueous solution of urethanized polyvinyl alcohol containing a yellow azo dye of 0.5 dye per rrr.
g and an amount of silver bromide corresponding to 5.0 to 5.2 g of silver.

(2) Exposure, development, bleaching, and fixing After exposing the photosensitive material to white light through a transparent original having each color of red, green, and blue, add a developing stock solution of 1:4 with water as shown below. 20℃ with diluted solution.
Developed for 4 minutes.

<Developer> Water
750cc Sulfuric acid-P-methylaminophenol (Eron) 1g Hydroquinone 9N Anhydrous sodium sulfite 7511 Potassium bromide
5n sodium carbonate monohydrate
3QnWater was added to the above product to make the total amount IQ.

After washing with water, it was treated with the following dye bleaching solution at 24°C for 5 minutes.

<Dye bleaching solution> Acid sulfonic acid 60g Ascorbic acid in Potassium iodide 25172-amino-3-
Hydroxyphenazine 3 mg Water was added to the above mixture to make the total amount JQ.

After washing with water, it was treated with the following silver bleaching solution at 24°C for 5 minutes.

<Silver bleaching solution> Red blood salt 60g phosphoric acid 2
Sodium hydrogen 1% 2QLJ phosphoric acid 2
Sodium hydrogen (71120) 10 '1
Potassium bromide 15! 1 glacial acetic acid] 0+nQ Water was added to the above mixture to make a total volume of 1Q.

After washing with water, the sample was treated with the following fixing solution at 24° C. for 5 minutes.

Fixer> Ammonium thiosulfate 120g Anhydrous sodium sulfite 1Qtt=27=isomeric potassium bisulfite ]Og Water was added to the mixture to make the total amount 1Q.

In this way, a color master sheet having red, green, and blue positive images on its surface was obtained.

C: Preparation of receiving sheet C-1 = Plain paper (high quality paper with smoothness of 70) is used as receiving sheet 1-.

C-2: Polyester resin emulsion 40 parts by weight (resin concentration 50%) Styrene resin fine particles 20 water
40″
The above composition was stirred and mixed for 1 hour, and then coated and dried on a high-quality paper with a basis weight of 50 g/rrf to a dry weight of 4 g1r& to prepare a receptor sheet C-2.

(2): Thermal transfer The receiving sheet was placed on the color master sheet obtained above, and this was passed between heated rolls to perform thermal transfer to obtain a color copy of Example 1 of the present invention.

Comparative Example ■ Comparative Example 1 was carried out in the same manner except that gelatin was used in place of the urethanized polyvinyl alcohol used in Example 1.
I got a color copy of it.

The density of the image area of the color copy thus obtained was measured. The results are shown in Table-1.

Table 1 Example 2 A color copy of Example 2 of the present invention was obtained in the same manner as Example 1 except that 4 cc of a 220% aqueous solution was added.

The color copy of Example 2 thus obtained has no image destruction, and is comparable to the one obtained in Example 1 in both the density of the image area and the whiteness of the background area. It turned out to be even better.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example of the layer structure of a color master sheet, Fig. 2 is an explanatory diagram of the exposure principle, Fig. 3 is an explanatory diagram of black development,
FIG. 4 is an explanatory diagram of the dye bleaching principle, FIG. 5 is an explanatory diagram of the fixing principle, FIG. 6 is an explanatory diagram of the thermal transfer principle, and FIG. 7 is a cross-sectional diagram of a color copy. FIG. 8 is an explanatory diagram showing the basic mechanism of a color copying machine for carrying out the method of the present invention. In FIG. 8, ■ is a color original, 4 is a color master sheet, 5 is a color master cartridge, 6 is a developing and fixing section, 7 is a color master sheet support drum, 10 is a receiving sheet, 13 is a heating roll 1.20 is A color copy of each is shown.

Claims (2)

[Claims] (1) A series of processing consisting of image exposure, development, and dye bleaching is applied to a photosensitive material in which multiple azo dye layers consisting of a heat sublimable or heat vaporizable azo dye, silver halide, and a binder are laminated on a support. to create a color master sheet for thermal transfer having a positive image made of an azo dye, a receiving sheet is placed on top of the positive image of the color master sheet for thermal transfer, and thermal transfer is performed to create a color master sheet for thermal transfer having a positive image made of an azo dye on the receiving sheet. A thermal transfer copying method characterized in that the method for forming a transferred image uses a urethanized polyvinyl alcohol aqueous solution as the binder. (2) The thermal transfer copying method according to claim 1, wherein the azo dye layer further contains a chromium compound as a hardening agent.