JP3413472B2 - Thermal transfer sheet for color image formation - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet for forming a color image, and more specifically, it has a wide and excellent color reproducibility similar to various color prints and color photographs which have been widely used in the past. The present invention relates to a thermal transfer sheet for forming a color image.

[0002]

2. Description of the Related Art Conventionally, a large amount of color printing has been performed by offset printing, gravure printing and the like. In such color printing, the original document as it is or by combining it with other characters, symbols, etc. is color-separated to create a plate of the three primary colors of cyan, magenta, and yellow, and if necessary, add a black plate. Each printing ink reproduces the hue, pattern, etc. of the original. In most cases, pigments are used as color materials for the three primary color inks of cyan, magenta, and yellow in such a printing method, and these pigments widely reproduce not only the three primary colors but also their intermediate colors. As a matter of fact, the most preferable three primary color pigments have been selected from many past experiences. In the conventional printing method as described above, it is indispensable to make a plate of four colors, and thus there is a problem that a lot of equipment cost and space are required. For example, it is easy to perform color printing in a light industry or an office. There is a problem that you can not.

As one method for solving such a problem, a heat transfer sheet of three primary colors is prepared from a sublimable (or heat transferable) dye, and the heat transfer sheet is used to generate heat energy corresponding to image information. Transfer the dye by
A thermal transfer method for forming a color image has been proposed. Such a method does not require a large printing machine or other various auxiliary equipment, and can easily form a color image,
Future development is expected.

[0004]

In the thermal transfer method, the thermal transfer image-receiving sheet and the thermal transfer sheet are superposed on each other, and thermal energy is applied from either side by a recording means such as a thermal head or a laser, so that the dye on the thermal transfer sheet is transferred. This is a method of transferring onto the receiving layer of the image receiving sheet, and the size of the color dot formed by this transfer is very large compared to the dot (halftone dot) in conventional offset printing. In the case of printing ink, the color density of halftone dots can be freely changed mainly by the size of halftone dots, whereas in the case of the thermal transfer method, it is difficult to change the dot size. There is no choice but to change the difference by the thermal energy applied. Therefore, it is ideal that the density of dots can be proportionally controlled according to the amount of heat energy to be applied, but in the case of the conventional thermal transfer sheet, the migration of the dye especially when the heat energy to be applied is small. Is poor, the color density is poor, and it was almost impossible to adjust the transferability to the same level for all three primary colors.
There is a problem in that the color reproducibility of the relatively light-colored portion is insufficient, and an intermediate color with sufficient gradation cannot be formed.

Further, in the conventional dye, when a color image is formed by using the three primary colors of cyan, magenta and yellow, it is extremely difficult to reproduce an intermediate color of these three colors, and a color image close to a printed image is obtained. In order to obtain the heat transfer method, it is desired to develop a heat transfer sheet having a wide range of color reproducibility not only in the three primary colors but also in the intermediate colors. Further, in the case of a full-color image formed by the above-mentioned recording method, when a dye having poor weather resistance is used even in any one color, no matter how excellent the other dyes are in weather resistance, the entire full-color image is obtained. Inferior in weather resistance,
There was a problem that the color balance was lost. Thus, while most of the three primary colors of conventional offset printing inks are composed of pigments, the color materials used for the thermal transfer sheet are all sublimable (or heat transferable) dyes, Both of them have different color development mechanisms from each other, and it was very difficult to select a sublimable (heat transferable) dye that matches the three primary colors of the offset printing ink. As described above, from the difference between both methods, when forming a color image by the thermal transfer method, the range of color reproducibility is significantly inferior as compared with the color image by offset printing, etc. There is a demand for improvement in.

[0006]

In order to achieve the above object, in the present invention, a long base sheet and at least yellow, magenta, and cyan formed on one surface of the base sheet in a frame-sequential manner are used. In a thermal transfer sheet for forming a color image provided with dye layers of three colors, the yellow dye layer contains dyes of the following formulas (1), (2) and (5), and the magenta dye layer is The cyan dye layer contains dyes represented by the following formulas (3), (4), (5) and (1), and the cyan dye layer is represented by the following formulas (6), (7) and (8). A thermal transfer sheet for forming a color image, characterized by containing the dye of

[0007]

[Chemical 17] (In the formula (1), R ₁ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, and R ₂ is Represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted alkoxycarbonyl group.)

[Chemical 18] (In the formula (2), R ₃ and R ₄ each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, ₅ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, or a substituted or unsubstituted alkoxy group.)

[Chemical 19] (In the formula (3), R ₆ and R ₇ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, ₈ represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group,
R ₉ is a substituted or unsubstituted alkyl group or —NR
₂₂ R ₂₃ (wherein R ₂₂ and R ₂₃ represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group). )

[0008]

[Chemical 20] (In the formula (4), R ₁₀ and R ₁₁ each represent a hydrogen atom, a hydroxy group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group.)

[Chemical 21] (In the formula (5), R ₁₂ represents a hydrogen atom, a hydroxy group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group.)

[Chemical formula 22] (In the formula (6), R ₁₃ , R ₁₄ and R ₁₆ are each a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group. the stands, R ₁₅ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group,
It represents a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, or a substituted or unsubstituted alkoxy group. )

[0009]

[Chemical formula 23] (In the formula (7), R ₁₇ and R ₁₈ each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, R ₁₉ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, or a substituted or unsubstituted alkoxy group.)

[Chemical formula 24] (In the formula (8), R ₂₀ and R ₂₁ each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group. )

[Action]

Since the dye used in the present invention is in a dissolved state in the dye layer, the dye is precipitated from the resin binder during storage, which causes blocking with the back layer side when the transfer sheet is wound and stored. There is no such problem. Further, not only can a wide range of color reproducibility be realized by forming a dye layer of three colors of yellow, magenta, and cyan which are sequentially formed on the base material sheet in combination with a specific dye. , Known as the standard color of printing ink by setting a specific composition ratio,
SWOP (Specifications Web O)
It is possible to reproduce a hue close to that of a ffset Publications) color reference, EURO COLOR, etc., and is very suitable as a thermal transfer sheet for print proofing. Further, the dye used in the present invention, both yellow, magenta, and cyan are good without variations in weather resistance, and also in the formed image, fading due to interaction between the dyes,
There is no problem of discoloration. Further, among the dyes used in the thermal transfer sheet of the present invention, formulas (1), (3),
The dyes of (4), (5), (6) and (8) are excellent in light resistance, and the dyes of formulas (2), (3), (6) and (7) are excellent in heat transfer characteristics. Therefore, it has excellent light resistance,
A highly sensitive image can be obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments. The base sheet used in the thermal transfer sheet of the present invention may be any one as long as it has a conventionally known degree of heat resistance and strength,
For example, 0.5 to 50 μm, preferably 3 to 10 μm thick paper, various processed papers, polyester films including polyethylene terephthalate film, polystyrene films, polypropylene films, polysulfone films, polyphenylene sulfide films,
Polyethylene naphthalate film, 1,4-polycyclohexylene dimethyl terephthalate film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, etc., and polyester film is particularly preferable. These substrate sheets may be single-wafer type or continuous film and are not particularly limited. Among these, polyethylene terephthalate film is particularly preferable, and it is also preferable to provide an adhesive layer (primer layer) on one or both surfaces of the film, if necessary.

In the present invention, at least yellow, magenta, and cyan dye layers are formed on one surface of a long base material sheet made of the above-mentioned materials in a frame-sequential manner, and a black dye layer is further formed if necessary. A thermal transfer sheet for forming a color image, which is provided. Of course, the order of forming each dye layer is not limited to the above,
The object of the present invention can be achieved by using a plurality of thermal transfer sheets each having a dye layer of one color formed by using as many substrate sheets as there are dye layers. Each dye layer is characterized by containing a resin binder and a specific dye. That is, as the yellow dye layer , the above formulas (1), (2) and
And the dye of the formula (5), the magenta dye layer contains the dyes of the formulas (3), (4), (5) and (1), and the cyan dye layer contains the dye of the formula (5). 6), the formula (7) and the dye of the formula (8) are contained. The black dye used when the black dye layer is provided adjacent to the dye layer is selected from the dyes of the above formulas (1) to (8) of the present invention and used in combination. Alternatively, another dye may be used.

Among the dyes represented by the above general formula, those having the following structures are particularly preferable.

[Chemical 25]

[Chemical formula 26]

[Chemical 27]

[Chemical 28]

[0014]

[Chemical 29]

[Chemical 30]

[Chemical 31]

[Chemical 32]

In each dye layer, each dye to be used and its ratio can be appropriately selected and adjusted depending on what the intended reference color is, but especially the dye contained in the yellow dye layer. The ratio of the formula / formula / formula = 1 /
0.01 to 0.5 / 0.03 to 0.15,
Further, the ratio of the dyes contained in the magenta dye layer is calculated by the following formula / formula / formula / formula = 1 / 0.2 to 1.0 / 0.3 to 1.4 /
The ratio of the dyes contained in the cyan dye layer should be expressed by formula / formula / formula = 1 / 0.8
By adjusting the ratio (weight ratio) of 3.0 / 1.0 to 3.5, the light resistance is excellent and the storage stability is excellent (no blocking occurs when the thermal transfer sheet is wound and stored). SW, which is known as a process ink suitable not only for good color reproducibility but also for print proofing,
It is possible to obtain a thermal transfer sheet that can reproduce a hue close to that of an OP color reference or EUROCOLOR.

As the binder resin for carrying the dye as described above, known binder resins can be used. Examples thereof include cellulose resins such as ethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose and cellulose acetate, polyvinyl alcohol, Examples include vinyl resins such as polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, and polyvinylpyrrolidone, acrylic resins such as poly (meth) acrylate and poly (meth) acrylamide, polyurethane resins, polyamide resins, polyester resins, etc. Alternatively, they can be optionally used by mixing. Of these, cellulose-based, vinyl-based, acrylic-based, polyurethane-based, and polyester-based resins are preferable from the viewpoint of heat resistance and dye migration. The suitable amount of the dye in the dye layer is 5 to 300 parts by weight with respect to 100 parts by weight of the binder resin. Dyes and binder resins as described above, further added various additives if necessary dissolved in a suitable organic solvent, or a dispersion prepared by dispersing in an organic solvent or water gravure printing method, screen printing method, gravure It can be formed by applying and drying by a forming means such as a reverse roll coating method using a plate. The thickness of the dye layer is 0.2 to 5.0 μm, preferably 0.4 to 2.0 μm.

An anti-adhesion layer, that is, a release layer can be provided on the surface of the dye layer to prevent fusion of the material to be transferred and the thermal transfer sheet at the time of thermal transfer. It is possible to form a density image. The release layer is made of a resin having an excellent release property such as an anti-sticking inorganic powder, a silicone polymer, an acrylic polymer, or a fluorinated polymer, and has a thickness of 0.01 to 5 μm, preferably 0.05 to A 2 μm layer can be provided.
Further, a releasable binder obtained by grafting a releasable segment such as a silicone segment, a fluorocarbon segment, or a long chain alkyl segment on the binder resin forming the dye layer may be used.

The material to be transferred used in combination with the thermal transfer sheet as described above may be any material as long as its recording surface has dye receptivity, and paper, metal, glass, etc. which do not have dye receptivity. When it is a synthetic resin or the like, a dye receiving layer may be formed on at least one surface thereof and used. As the resin having a dye-receptive property, any of those conventionally used in this method can be used, and examples thereof include polyester resin, polycarbonate resin, acrylic resin, vinyl chloride / vinyl acetate copolymer, polyurethane resin and polyamide resin. can give. Further, a releasing agent such as a silicone compound may be added to these receiving layer resins, if necessary. The color image forming thermal transfer sheet of the present invention is very excellent for proofreading, and it is possible to use a proofing paper (texture, texture) like a proofing paper that has been conventionally used for printing as a material to be transferred. By carrying out the transfer, it is possible to exert a more excellent effect for proofreading. In order to give a texture like the above-mentioned proof paper, by adding an additive such as pigment or dye in the receiving layer, providing an intermediate layer, or using a paper base material such as coated paper as a base material. Can be adjusted.

[0019]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, parts and% are based on weight unless otherwise specified. [Example 1] A polyethylene terephthalate film (Lumirror made by Toray Co., Ltd.) having a thickness of 6 µm that had been subjected to an easy-adhesion treatment was used as a base sheet, and the following ink composition was applied to one side of
It was dried and further heat-aged in an oven at 60 ° C. for 5 days for curing treatment to form a heat resistant slipping layer. Ink for heat resistant slipping layer Polyvinyl butyral resin (S-REC BX-1 Sekisui Chemical Co., Ltd.) 3.6 parts Polyisocyanate (Bernock D750 manufactured by Dainippon Ink) 8.4 parts Phosphate ester surfactant (Prysurf A208S manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd.) 2.8 parts Talc (Microace P-3 made by Nippon Talc) 0.6 parts Toluene / methyl ethyl ketone 190 parts Next, prepare three color dye layer forming ink compositions of the following composition and dry each on the opposite surface of the heat resistant slipping layer. A full-color thermal transfer sheet of the present invention was obtained by applying a gravure coater so that the coating amount was 1.0 g / m ² and drying.

Ink type dye for yellow dye layer 3.0 parts Type dye 1.0 part Type dye 0.3 part Polyvinyl acetoacetal resin (KS-5 manufactured by Sekisui Chemical Co., Ltd.) 3.5 parts Methyl ethyl ketone 46. 2 parts Toluene 46.2 parts Polyethylene wax fine particles 0.05 parts Ink dye for magenta dye layer 4.0 parts Formula dye 1.0 parts Formula dye 2.0 parts Formula dye 0.5 parts Polyvinyl acetoacetal Resin (KS-5, manufactured by Sekisui Chemical Co., Ltd.) 3.5 parts Methyl ethyl ketone 44.2 parts Toluene 44.2 parts Polyethylene wax fine particles 0.07 parts Cyan dye layer ink type dye 1.3 parts Formula dye 1.2 Partial dye 3.0 parts Polyvinyl acetoacetal resin (KS-5 manufactured by Sekisui Chemical Co., Ltd.) 3.5 parts Methyl ethyl ketone 46.2 parts Toluene 46 2 parts 0.05 parts of polyethylene wax particles

Next, as a base material sheet, synthetic paper (YUPO-FPG # 1
50 Oji-Okaka Synthetic paper), one side of which is coated with an ink for forming a receptive layer having the following composition at a rate of 10.0 g / m ² when dried, and dried at 100 ° C for 30 minutes for thermal transfer. An image receiving sheet was obtained. Ink for forming receptor layer Polyester resin (Vylon 200 Toyobo) 11.5 parts Vinyl chloride / vinyl acetate copolymer 5.0 parts Amino-modified silicone (KF-393 Shin-Etsu Chemical) 1.2 parts Epoxy-modified silicone (X- 22-343 Shin-Etsu Chemical Co., Ltd.) 1.2 parts Methyl ethyl ketone / toluene / cyclohexanone (weight ratio = 4: 4: 2) 102.0 parts

The thermal transfer sheet and the image receiving sheet as described above are superposed so that the dye layer and the dye receiving layer face each other, and from the back side of the thermal transfer sheet, the head applied voltage is 17 V and the printing time is 8.0 msec / line. Then, recording was carried out with a thermal head, and solid printing was carried out for three colors of yellow, magenta and cyan. For this printed matter, L ^* a ^* b ^* based on CIE1976 is MINOLT
It was measured using ACR-221. (Light source: D65, viewing angle: 10 °) The results are shown in Table 1. L ^* a shown as a reference
^* b ^* values are SWOP color reference values measured in the same manner.

Example 2 A full color thermal transfer sheet of the present invention was formed in the same manner as in Example 1 except that the composition of the dye in the dye layer was changed as follows. Ink dye for yellow dye layer 3.0 parts Dye of formula 1.2 parts Dye of formula 0.2 parts Ink dye for magenta dye layer 3.0 parts Dye of formula 1.0 parts Dye of formula 2. 0 part Dye 0.6 part Cyan dye layer ink dye 0.7 part Dye 2.0 part Dye 2.0 part Same as Example 1 for the thermal transfer sheet obtained as described above. Solid printing was performed for the three colors of yellow, magenta, and cyan under the above conditions. The results are shown in Table 1. The L ^* a ^* b ^* values shown as a reference are the values of EURO COLOR measured in the same manner.

[0024]

[Table 1]

Comparative Example 1 A thermal transfer sheet was formed in the same manner as in Example 1 except that the composition of the dye and binder resin in each dye layer was changed as follows. Ink dye for yellow dye layer 3.0 parts Dye 0.7 part Polyvinyl acetoacetal resin (KS-5 manufactured by Sekisui Chemical Co., Ltd.) Magenta dye layer ink dye 4.0 parts Dye 2. 0 parts Type dye 2.0 parts Polyvinyl acetoacetal resin (KS-5 manufactured by Sekisui Chemical Co., Ltd.) Ink type dye for cyan dye layer 3.5 parts Type dye 1.0 part Polyvinyl acetoacetal resin (Sekisui Chemical Co., Ltd. KS-5) 3.5 parts Solid printing was performed on the thermal transfer sheet under the same conditions as in Example 1, and L ^* a ^* b ^* values were measured. The results are shown in Table 1.

[0026]

As described above, not only can a wide range of color reproducibility be realized by forming a dye layer by combining specific dyes, but also by setting a specific composition ratio, the standard of printing ink can be obtained. SWOP, known as color
(Specifications Web Offset Publications) It becomes possible to reproduce a color reference, a hue close to that of EURO COLOR, etc., and it is very suitable as a thermal transfer sheet for print proofing. Further, since the dye is precipitated from the resin binder during storage, there is no problem that blocking occurs with the back layer side when the transfer sheet is wound and stored. Further, the dye used in the present invention, yellow, magenta, and cyan are both good, without variations in light resistance, and also in the formed image, fading due to interaction between the dyes,
There is no problem of discoloration.

Continuation of the front page (56) Reference JP-A-5-262062 (JP, A) JP-A-6-155929 (JP, A) JP-A-5-262056 (JP, A) JP-A-7-257053 (JP , A) JP-A-6-328866 (JP, A) JP-A-7-96675 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B41M 5/38-5/40 CAPLUS (STN) REGISTRY (STN)

Claims (4)

(57) [Claims] 1. A color image forming apparatus comprising a long base sheet and a dye layer of at least three colors of yellow, magenta, and cyan formed on one surface of the base sheet in a frame-sequential manner. In the thermal transfer sheet, the yellow dye layer contains dyes represented by the following formulas (1), (2) and (5), and the magenta dye layer contains the following formulas (3), (4),
Said cyan dye containing dyes of formula (5) and formula (1)
A thermal transfer sheet for forming a color image, wherein the layer contains dyes represented by the following formulas (6), (7) and (8). [Chemical 1] (In the formula (1), R ₁ represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, and R ₂ is Represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, or a substituted or unsubstituted alkoxycarbonyl group.) (In the formula (2), R ₃ and R ₄ each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, ₅ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, or a substituted or unsubstituted alkoxy group.) (In the formula (3), R ₆ and R ₇ represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, ₈ represents a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group,
R ₉ is a substituted or unsubstituted alkyl group or —NR
₂₂ R ₂₃ (wherein R ₂₂ and R ₂₃ represent a hydrogen atom, a substituted or unsubstituted alkylcarbonyl group, or a substituted or unsubstituted arylcarbonyl group). ) [Chemical 4] (In the formula (4), R ₁₀ and R ₁₁ each represent a hydrogen atom, a hydroxy group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group.) (In the formula (5), R ₁₂ represents a hydrogen atom, a hydroxy group, a substituted or unsubstituted alkyl group, or a substituted or unsubstituted alkoxy group.) (In the formula (6), R ₁₃ , R ₁₄ and R ₁₆ are each a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group. the stands, R ₁₅ is a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group,
It represents a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, or a substituted or unsubstituted alkoxy group. ) [Chemical 7] (In the formula (7), R ₁₇ and R ₁₈ each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group, R ₁₉ represents a hydrogen atom, a halogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted acylamino group, a substituted or unsubstituted sulfonylamino group, or a substituted or unsubstituted alkoxy group.) ] (In the formula (8), R ₂₀ and R ₂₁ each represent a substituted or unsubstituted alkyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted allyl group, or a substituted or unsubstituted aralkyl group. ) 2. The thermal transfer sheet for forming a color image, wherein the yellow dye layer contains a dye of the following formula, formula and formula, and the magenta dye layer :
The thermal transfer sheet for forming a color image according to claim 1, characterized in that the cyan dye layer contains a dye of formula and formula, and the cyan dye layer contains a dye of formula and formula. [Chemical 9] [Chemical 10] [Chemical 11] [Chemical 12] [Chemical 13] [Chemical 14] [Chemical 15] [Chemical 16] 3. The thermal transfer sheet for color image formation according to claim 1, wherein the resin binder in each of the dye layers is made of polyvinyl acetoacetal resin. 4. The thermal transfer sheet for color image formation according to claim 1, further comprising a black dye layer adjacent to the dye layer.