JP2825282B2 - Thermal transfer sheet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a thermal transfer sheet using a sublimable dye (heat-migrating dye), and more particularly, to a transfer image excellent in sharpness and color reproducibility. The purpose is to provide a thermal transfer sheet.

(Prior Art) Conventionally, various thermal transfer methods are known. Among them, a sublimable dye is used as a recording agent, and this is carried on a base sheet such as a polyester film to form a thermal transfer sheet. There have been proposed methods of forming various full-color images on an image receiving sheet having a dye receiving layer formed on a transferable material, for example, paper or plastic film, which can be mounted. In this case, a thermal head of a printer is used as a heating means, and a large number of three or four color dots are transferred to a transfer material by heating for a very short time, and a full-color image of an original is formed by the multicolor dots. Is to reproduce.

The image formed in this way is very clear because the coloring material used is a dye, and is excellent in transparency, so that the obtained image is excellent in the reproducibility and gradation of intermediate colors. It is possible to form a high-quality image which is similar to an image by offset printing or gravure printing, and is comparable to a full-color photographic image.

(Problems to be Solved by the Invention) However, dyes that are generally excellent in sharpness are inferior in light resistance and bleeding resistance, and conversely, dyes that are excellent in light resistance and bleeding resistance are inferior in sharpness. In many cases, it is difficult to achieve a balance between clarity and other properties such as light fastness. or,
An image receiving sheet used as a material to be transferred often has a resin layer having excellent dye-attachability formed on the surface of a film or a sheet, but since these resin layers are generally slightly yellowish. However, there is a problem that the vividness of the transfer dye is reduced.

As a method of solving the above-mentioned drawbacks, a method of adding a fluorescent whitening agent to the dye receiving layer to eliminate the base of the receiving layer and improve the sharpness of the transferred dye can be considered.

However, since the fluorescent whitening agent is a compound that absorbs ultraviolet light and emits blue to violet light, it tends to inevitably discolor yellow, and the color transferability of yellow transferred to the image receiving sheet and There is a problem that the sharpness is reduced, and there is a problem that the color reproducibility and the yellow coloring of a full-color document are reduced.

Accordingly, an object of the present invention is to provide a thermal transfer sheet capable of forming a transfer image excellent in sharpness and color reproducibility in a thermal transfer method using a sublimable dye.

(Means for Solving the Problems) The above object is achieved by the present invention described below.

That is, the present invention relates to a heat transfer sheet having a magenta or cyan dye layer formed on the surface of a base film,
A thermal transfer sheet comprising a fluorescent whitening agent in the dye layer or on the surface of the dye layer.

(Function) A fluorescent whitening agent is included in the magenta or cyan dye layer of the thermal transfer sheet, or a layer containing the above fluorescent whitening agent is formed on the surface of the dye layer, and the fluorescent brightening agent is simultaneously transferred with the dye. By transferring the white agent to the image forming area, it is not necessary to use a fluorescent whitening agent in the dye receiving layer, and a color excellent in sharpness and color reproducibility without lowering the color development and sharpness of yellow color. An image is obtained.

(Preferred Embodiment) Next, the present invention will be described in more detail with reference to preferred embodiments.

The substrate film of the thermal transfer sheet of the present invention may be any one having a conventionally known degree of heat resistance and strength, for example, paper having a thickness of about 0.5 to 50 μm, preferably about 3 to 10 μm. , Various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, aramid film, polycarbonate film, polyvinyl alcohol film, cellophane, etc., and particularly preferred is polyester film.

When the substrate film as described above has poor adhesion to the dye layer formed on the surface, it is preferable to subject the surface to a primer treatment or a corona discharge treatment.

The sublimable (heat-migrating) dye layer formed on the base film as described above is a layer in which the dye is supported by an arbitrary binder resin.

As the dye to be used, any of magenta or cyan dyes used in conventionally known thermal transfer sheets can be effectively used in the present invention, and is not particularly limited.

Magenta or cyan dyes particularly useful in the present invention have low clarity but other properties, such as excellent heat transfer properties, light resistance, and bleed resistance, and specifically have the following structure: Dyes.

By using an appropriate fluorescent whitening agent in combination with these dyes, their sharpness after transfer is improved.

As the binder resin for supporting the heat transferable dye as described above, any of conventionally known binder resins can be used, and preferred examples thereof include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxycellulose, hydroxypropyl cellulose, methyl cellulose, and acetic acid. Cellulose, cellulose resins such as cellulose acetate butyrate, polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl pyrrolidone, vinyl resins such as polyacrylamide, polyester and the like, among these, cellulose,
Acetal, butyral, polyester and the like are particularly preferred.

One embodiment of the present invention is characterized in that when forming a dye receiving layer from the above-described material, a fluorescent whitening agent for improving the sharpness of the dye is included in the dye layer.

The fluorescent whitening agent used in the present invention is a substantially colorless compound that emits blue to violet light by absorbing ultraviolet light in daylight or illumination light, and conventionally, paper, fiber, and synthetic resin. It is used for brightening. Various types of fluorescent whitening agents are known, but the fluorescent whitening agent preferred for the purpose of the present invention is not a water-soluble whitening agent but a disperse dye type fluorescent whitening agent.

The above-described fluorescent whitening agent preferably has the same thermal transferability (thermal transferability) as the sublimable dye, and for example, does not contain a carboxyl group or a sulfonic acid group, and has a molecular weight of
Those having 500 or less are preferable. When the molecular weight exceeds 500, transferability may be insufficient.

Specific examples of the fluorescent brightening agent preferred for the purpose of the present invention include, for example, CI Fluorescent Brightening Agent 91 CI Fluorescent Brightening Agent 112 CI Fluorescent Brightening Agent 121 CI Fluorescent Brightening Agent 135 CI Fluorescent Brightening Agent 162 CI Fluorescent Brightening Agent 170 CI Fluorescent Brightening Agent 171 CI Fluorescent Brightening Agent 172 Mikawhite STN (Nippon Kayaku) Mikawhite GTN (Nippon Kayaku) Whitefluor PVG (Sumitomo Chemical) Whitex SNP (Sumitomo Chemical) Kaycoll E (Nippon Soda) and the like.

The above optical brighteners can be used alone or as a mixture,
The addition amount is preferably in the range of 0.01 to 10 parts by weight based on 100 parts by weight of the dye. If the amount is too small, the sharpening effect on the dye is insufficient. If the amount is too large, the so-called quenching effect loses the fluorescence and conversely impairs the coloring properties and sharpness of the dye.

The dye layer of the thermal transfer sheet of the present invention is basically formed from the above-mentioned materials, but may also include various additives as conventionally known, if necessary.

Such a dye layer is preferably prepared by adding the above-mentioned sublimable dye, fluorescent brightener, binder resin and other optional components in a suitable solvent and dissolving or dispersing each component to prepare a dye layer-forming paint or ink. Then, this is applied onto the above-mentioned base film and dried to form a film.

The dye layer thus formed has a thickness of about 0.2 to 5.0 μm, preferably about 0.4 to 2.0 μm, and the sublimable dye in the dye layer accounts for 5 to 90% by weight of the weight of the dye layer, preferably Is preferably present in an amount of 10 to 70% by weight.

In another embodiment of the present invention, the dye layer is formed without including the fluorescent whitening agent in the dye layer in the above embodiment, and the fluorescent whitening agent is formed as a thin film on the surface of the dye layer. .

The thin film of the fluorescent whitening agent may be formed by dissolving the above-described fluorescent whitening agent in a solvent and coating and drying the surface of the dye layer. At the same time, it is dissolved in a solvent, applied to the surface of the dye layer and dried to form a fluorescent whitening agent layer. The ratio of the fluorescent whitening agent to the binder is not particularly limited, but is generally about 1/10 to 10/1 by weight. The thickness of the layer to be formed is generally about 0.05 to 10 μm. If it is too thin, the effect of clearing the transfer dye is insufficient, and if it is too thick, the transferability of the dye is hindered.

The heat transfer sheet of the present invention as described above may be provided with a heat-resistant layer on the back surface thereof in order to prevent adverse effects due to the heat of the thermal head.

The image receiving sheet used to form an image using the thermal transfer sheet as described above may be any image-receiving sheet as long as its recording surface has a dye-accepting property with respect to the dye. In the case of paper, metal, glass, synthetic resin film, sheet or the like having no dye, a dye receiving layer may be formed on at least one surface from a resin having excellent dye receiving property. Such a dye-receiving layer may contain a solid wax such as polyethylene wax, amide wax, or Teflon powder, a fluorine-based or phosphate-based surfactant, silicone oil, or the like as a release agent. preferable.

As a means for applying thermal energy at the time of thermal transfer used in the method of the present invention, any conventionally known applying means can be used, for example, a thermal printer (for example, a video printer VY-100 manufactured by Hitachi, Ltd.) or the like. By controlling the recording time by the recording device, 5 to 10
By applying thermal energy of about 0 mJ / mm ² , the intended purpose can be sufficiently achieved.

(Effect) According to the present invention as described above, a magenta or cyan dye layer of a thermal transfer sheet contains a fluorescent whitening agent or a layer containing the above fluorescent whitening agent is formed on the surface of the dye layer,
By transferring these fluorescent brighteners to the image forming area simultaneously with the transfer of the dye, the necessity of using a fluorescent brightener in the dye receiving layer is eliminated, and the yellow color is sharpened without deteriorating the color developability and sharpness. A color image having excellent properties and color reproducibility can be obtained.

(Examples) Next, the present invention will be described more specifically with reference to examples, reference examples, comparative examples, and use examples. In the following description, parts and% are based on weight unless otherwise specified.

Example 1 An ink composition for forming a dye layer having the following composition was prepared, and was coated on a 4.5 μm-thick polyethylene terephthalate film (Lumirror 5AF53, manufactured by Toray Co., Ltd.) having a heat-resistant rear surface, and the dry coating amount was adjusted to 1.0 g / m ² . The resultant was coated and dried with a wire bar to obtain a thermal transfer sheet (1) of the present invention.

Sublimable dye (the above exemplified dye I) 5.5 parts Polyvinyl acetoacetal 4.0 parts CI Fluorescent Brightening Agent 162 0.05 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 89.0 parts Examples 2 to 6 Dyes and fluorescent brighteners in Example 1 Instead, the thermal transfer sheets (2) to (6) of the present invention were obtained in the same manner as in Example 1 except that the following dyes and fluorescent brighteners were used.

Example 2 Dye: Exemplified Dye II Fluorescent Brightener: CI Fluorescent Brightening Agent 162 Example 3 Dye: Exemplified Dye III Fluorescent Brightener: CI Fluorescent Brightening Agent 112 Example 4 Dye: Dye: Exemplified Dye VI Fluorescent Brightener: CIFluorescent Brightening Agent 91 Example 5 Dye: Exemplified Dye VII Fluorescent Brightener: CI Fluorescent Brightening Agent 164 Example 6 Dye: Exemplified Dye VIII Fluorescent Brightener: CI Fluorescent Brightening Agent 172 Example 7 For forming a dye layer having the following composition Ink composition A was prepared and applied to a 4.5 μm-thick polyethylene terephthalate film (Lumirror 5AF53, manufactured by Toray Co., Ltd.) with a heat-resistant treatment on the back side using a wire bar so that the dry application amount would be 1.0 g / m ^2. Then, the following composition B was further applied to the surface of the composition in the same manner at a rate of a dry coating amount of 1.0 g / m ² and dried to obtain a thermal transfer sheet (7) of the present invention.

Composition A Sublimable dye (Exemplary dye III) 5.5 parts Polyvinyl butyral resin (Eslec BX-1, manufactured by Sekisui Chemical) 4.5 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 90.0 parts Composition B Polyvinyl butyral resin (Eslec BX) 6.0 parts CI Fluorescent Brightening Agent 112 0.3 parts Methyl ethyl ketone / toluene (weight ratio 1/1) 90.0 parts Comparative Examples 1 to 3 Except that no optical brightener was used in Examples 1 to 3. Thermal transfer sheets (a) to (c) of comparative examples were obtained in the same manner as in Examples 1 to 3.

Reference Example 1 Synthetic paper (Yupo-FRG-150, thickness 15) was used as the base film.
0 μm, manufactured by Oji Oil Chemical Co., Ltd.), and applying and drying a coating solution having the following composition at a rate of 5.0 g / m ² when dried with a bar coater to obtain a thermal transfer image-receiving sheet (A) Was.

Polyester (Vylon 600, manufactured by Toyobo) 4.0 parts Vinyl chloride / vinyl acetate copolymer (# 1000A, manufactured by Denki Kagaku Kogyo Co., Ltd.) 6.0 parts Amino-modified silicone (X-22-3050C, manufactured by Shin-Etsu Chemical) 0.2 part Epoxy Modified silicone (X-22-300E, manufactured by Shin-Etsu Chemical) 0.2 part Methyl ethyl ketone / toluene (weight ratio 1/1) 89.6 parts Reference Example 2 Synthetic paper (Yupo-FRG-150, thickness 15 as base film)
0 μm, manufactured by Oji Oil Chemical Co., Ltd.), and applying and drying a coating solution having the following composition at a rate of 5.0 g / m ² when dried by a bar coater on one surface to obtain a thermal transfer image-receiving sheet (B). Was.

Polyester (Vylon 600, manufactured by Toyobo Co., Ltd.) 4.0 parts Vinyl chloride / vinyl acetate copolymer (# 1000A, manufactured by Denki Kagaku Kogyo Co., Ltd.) 6.0 parts Amino-modified silicone (X-22-3050C, manufactured by Shin-Etsu Chemical) 0.2 parts Epoxy Modified silicone (X-22-300E, manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2 parts Optical brightener (Ubitex OB, manufactured by Ciba Geigy) 0.005 parts Methyl ethyl ketone / toluene (1/1 by weight) 87.6 parts Reference Example 3 To the dye in Example 1 Instead, the yellow dye (Foron Br
illiant Yellow S-6GL, manufactured by Sandoz Co., Ltd.), and in the same manner as in Example 1, a thermal transfer sheet (Z) of Reference Example was obtained.

Usage Examples The thermal transfer sheets of Examples 1 to 7 and Comparative Examples 1 to 3 and the thermal transfer image receiving sheets of Reference Examples 1 and 2 are superposed with their respective dye layers and dye-receiving surfaces facing each other, and are subjected to thermal sublimation transfer. Using a printer (VY-50, manufactured by Hitachi, Ltd.), recording was performed with a thermal head from the back side of the thermal transfer sheet at a printing energy of 90 mJ / mm ² . Similarly, on the thermal transfer image-receiving sheets of Reference Examples 1 and 2 recorded using the thermal transfer sheet (Z), recording was performed by overlay recording using the thermal transfer sheets of Examples 1 to 7 and Comparative Examples 1 to 3. The results in Table 1 were obtained.

Continuation of the front page (56) References JP-A-2-219694 (JP, A) JP-A-5095012 (JP, A) JP-A-2-106395 (JP, A) JP-A-2-145389 (JP) , A) JP-A-2-120088 (JP, A) JP-A-2-190392 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/38 B41M 5/40

Claims (2)

(57) [Claims] 1. A thermal transfer sheet having a magenta or cyan dye layer formed on the surface of a substrate film, wherein a fluorescent whitening agent is contained in the dye layer or on the surface of the dye layer. Thermal transfer sheet. 2. The thermal transfer sheet according to claim 1, wherein the fluorescent whitening agent has a molecular weight of less than 500.