JPH03143685A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To enable dye to be transferred to a transfer medium easily and obtain high density, excellent durability and preservability by providing a base sheet and a dye carrying layer formed on one surface of the base sheet, and using a dye of specific structure on the dye carrying layer. CONSTITUTION:The subject thermal transfer sheet consists of a base sheet and a dye carrying layer contains the dye shown by the formula. In the formula, R1 is a substituted or non-substituted alkyl group, cycloalkyl group, aralkyl group or an aryl group; R2 is a substituted or non-substituted alkyl group, cycloalkyl group, aralkyl group or aryl group. In addition, R1 and R2 can form a 5-member ring or a 6-member ring which can contain an oxygen atom, a nitrogen atom or a sulfur atom. X, R3, R4 are a hydrogen atom, a halogen atom, a cyano group, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an acylamino group, a ureido group, an acyl group or an amino group; R5 is a hydrogen atom, a halogen atom, a cyano group or an alkyl group; Y is an atom or atomic group which forms a 5-member ring or a 6-member ring with R1 and n is 1 or 2.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a thermal transfer sheet, and more specifically, to color density,
The purpose of the present invention is to provide a thermal transfer sheet capable of forming recorded images with excellent clarity and various fastness properties, especially storage stability.

(Prior Art) Various thermal transfer methods have been known in the past, but among them, a sublimation dye is used as a recording agent, this is carried on a base sheet such as paper to form a thermal transfer sheet, and the dye is dyed with a sublimation dye. The thermal transfer sheet is layered on a transferable material such as polyester woven cloth, and thermal energy is applied in a pattern from the back side of the thermal transfer sheet.
A sublimation transfer method is used in which a sublimable dye is transferred to a transfer material.

Also, recently, using the above-mentioned sublimation type thermal transfer method,
Various methods have been proposed for forming full-color images on paper and plastic films.

In this case, the printer's thermal head is used as a heating means, and by heating in an extremely short time, three or four colors can be printed.
A large number of colored dots are transferred to a transfer material, and a full-color image of an original is reproduced using the multicolored colored dots.

The images formed in this way are very clear because the coloring material used is dye, and they have excellent transparency, so the images obtained have excellent intermediate color reproducibility and gradation, and are It is possible to form high-quality images that are similar to images produced by offset printing or gravure printing, and comparable to full-color photographic images.

(The problem that the invention is trying to solve) However,
The most important problems in the above-mentioned thermal transfer method include the color density of the formed image, storage stability, and one-color fading.

In other words, in the case of high-speed recording, the application of thermal energy is required to be extremely short, on the order of seconds or less. , it is not possible to form an image with sufficient density.

Therefore, in order to cope with such high-speed recording, sublimable dyes with excellent sublimation properties were developed, but dyes with excellent sublimation properties generally have small molecular weights, so they do not dissolve in the transferred material after transfer. However, storage problems arise in that the dye migrates over time or bleeds onto the surface, causing the image formed to be distorted or unclear, or contaminating surrounding articles.

If a sublimable dye with a relatively large molecular weight is used to avoid such problems, the sublimation speed will be poor in the high-speed recording method described above, so it will not be possible to form an image with a satisfactory density as described above. there were.

Therefore, an object of the present invention is to provide a thermal transfer sheet that provides a clear image with sufficient density in a thermal transfer method using a sublimable dye, and that also exhibits excellent fastness properties, particularly excellent storage stability. The goal is to provide the following.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention comprises a base sheet and a dye-carrying layer formed on one side of the base sheet, and the dye contained in the dye-carrying layer is a dye represented by the following formula (I). This is a thermal transfer sheet characterized by the following.

(R5 in the above formula represents a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, aryl group, or an atom or atomic group that forms a 5-membered ring or 6-membered ring together with Y,
R2 represents a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, or aryl group, and R1 and R3 may contain an oxygen atom, a nitrogen atom, or a sulfur atom.
A membered ring or a 6-membered ring may be formed, and X is a hydrogen atom, a halogen atom, a cyano group, an alkyl group that may have a substituent, a cycloalkyl group, an alkoxy group, an aryl group, an aralkyl group, an acylamino group , a sulfonylamino group, a ureido group, a carbamoyl group, a sulfamoyl group, an acyl group, an amino group, and R1 is a hydrogen atom, a halogen atom, a cyano group, an alkyl group that may have a substituent, a cycloalkyl group, an aryl group , aralkyl group, alkoxy group, alkylthio group, aryloxy group, arylthio group, acylamino group, sulfonylamino group, ureido group, carbamoyl group, sulfamoyl group, acyl group, amino group, and R4 is a hydrogen atom, a halogen atom, or a cyano group. group, nitro group, alkyl group, alkoxy group, aryl group, aralkyl group, acylamino group, ureido group, acyl group, or amino group, R6 represents a hydrogen atom, a halogen atom, a cyano group, or an alkyl group, and Y represents Represents a hydrogen atom or an atom or atomic group that forms a 5-membered ring or 6-membered ring together with R1, and n
(represents 1 or 2) (Function) By using a dye with a specific structure, even when thermal energy is applied for an extremely short period of time, the used dye easily transfers to the transfer material, resulting in a high transfer rate. A thermal transfer sheet is provided that provides recorded images with density and excellent fastness properties, particularly excellent storage stability.

(Preferred Embodiments) Next, the present invention will be described in more detail by citing preferred embodiments.

The dye of the general formula (1) used in the present invention can be obtained by a known method, for example, by combining a pyrazolopyrimidine derivative represented by the following general formula (a) and a nitroso compound represented by the following general formula (b). It can be easily produced by dehydration reaction in the presence of an acid or a base.

(R1 to R, , X, Y and n in the formula are as defined above.) The pyrazolopyrimidine derivative of the general formula (a) is described, for example, in Pharmaceutical Journal Vol. 85.442-448 (1965
It can be easily synthesized by the method described in ).

Preferred examples of substituents represented by R3 to R and groups, ethoxyethyl groups, etc.; hydroxyalkyl groups include hydroxyethyl groups, β-hydroxypropyl groups, etc.; halogenoalkyl groups include chloroethyl groups; cyanoalkyl groups include cyanomethyl groups, cyanoethyl groups, etc.; cycloalkyl groups Examples of the aralkyl group include a benzyl group and a phenethyl group; examples of the aryl group include a phenyl group, tolyl group, halogenophenyl group, and an alkoxyphenyl group; examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, Iodine atom, etc.; Alkoxy groups include methoxy, ethoxy, propoxy, butoxy groups; acylamino groups include acetylamino, benzoylamino, etc.; sulfonylamino groups include methanesulfonylamino and ethanesulfonylamino groups. , benzenesulfonylamino group, etc.; as a ureido group, methylureido group, 1.3-methylureido group, ethylureido group, etc.; as a carbamoyl group, methylcarbamoyl group, ethylcarbamoyl group, phenylcarbamoyl group, etc.; as a sulfamoyl group is a methylsulfamoyl group, an ethylsulfamoyl group, a phenylsulfamoyl group; an acyl group is an acetyl group, a propanoyl group, a benzoyl group; an amino group is a methylamino group, an ethylamino group, a propylamino group , dimethylamine group, diethylamino group, etc.; As an alkylthio group, methylthio group, ethylthio group, propylthio group, etc.; as an aryloxy group, phenoxy group, p-methylphenoxy group, etc.; as an arylthio group, phenylthio group, p- Examples include tolylthio group.

Further, preferred dyes in the present invention have a molecular weight in the range of 300 to 600.

Specific examples of dyes suitable for the present invention are listed in Table 1 below. Table 1 below shows the substituents R+ to Rs, X, n, and molecular weights in general formula (I).

In addition, Y is a hydrogen atom.

(Hereinafter, blank spaces) Week U The thermal transfer sheet of the present invention is characterized by using the above-mentioned specific dye, and other than that, the structure may be the same as that of a conventionally known thermal transfer sheet.

The base sheet used in the thermal transfer sheet of the present invention containing the above-mentioned dye may be any conventionally known material having a certain degree of heat resistance and strength.
．． Particularly preferred are paper with a thickness of about 5 to 50 μm, preferably 3 to 10 μm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, aramid film, polyvinyl alcohol film, cellophane, etc. is a polyester film.

The dye-carrying layer provided on the surface of the base sheet as described above is a layer in which the dye of formula (I) is supported by an arbitrary binder resin.

As the binder resin for supporting the dye, any conventionally known binder resin can be used, and preferred examples include ethyl cellulose, hydroxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methyl cellulose, cellulose acetate, and butyric acid acetate. Examples include cellulose resins such as cellulose, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinylpyrrolidone, and polyacrylamide. Among these, polyvinyl butyral and polyvinyl acetal are particularly heat-resistant. , is preferable from the viewpoint of dye migration.

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

Preferably, such a dye-supporting layer is prepared by adding the dye, binder resin, and other optional components in a suitable solvent, dissolving or dispersing each component, and preparing a coating solution or ink for forming the dye-supporting layer. It is formed by coating and drying on the above base sheet.

The supporting layer formed in this way has a thickness of 0.2 to 5.0 μm.
The thickness is preferably on the order of 0.4 to 2.0 μm, and the dye in the carrier layer is present in an amount of 5 to 70% by weight, preferably 10 to 60% by weight of the weight of the carrier layer. is suitable.

The thermal transfer sheet of the present invention as described above is sufficiently useful for thermal transfer as it is, but an anti-adhesive layer, that is, a release layer may be further provided on the surface of the dye-carrying layer, and such a layer may be provided. This prevents adhesion between the thermal transfer sheet and the transferred material during thermal transfer, and uses a higher thermal transfer temperature.
-1 An image with excellent density can be formed.

As this mold release layer, even if an inorganic powder with anti-adhesive properties is simply attached, it has a considerable effect. It can be formed by providing a release layer of 0.01 to 5 μm, preferably 0.05 to 2 μm.

Incidentally, the above-mentioned inorganic powder or mold-releasing polymer exhibits a sufficient effect even when included in the dye-carrying layer.

Furthermore, a heat-resistant layer may be provided on the back surface of such a thermal transfer sheet in order to prevent the adverse effects of the heat of the thermal head.

The transfer material used to form an image using the thermal transfer sheet as described above may be any material as long as its recording surface has dye receptivity to the above-mentioned dyes. If the material is paper, metal, glass, synthetic resin, etc. that does not have any properties, a dye-receiving layer may be formed on at least one surface thereof.

As the means for applying thermal energy used when performing thermal transfer using the thermal transfer sheet of the present invention as described above and the recording material as described above, any conventionally known applying means can be used.
For example, by controlling the recording time using a recording device such as a thermal printer (for example, Video Printer VY-Zoo manufactured by Hitachi), it is possible to
The intended purpose can be fully achieved by applying thermal energy of about J/mrd.

In particular, the thermal transfer sheet of the present invention can form a cyan image, and when used in combination with yellow and magenta thermal transfer sheets, can provide a full-color image with excellent color reproducibility. The dye for the yellow thermal transfer sheet used in combination is:
Yellow dyes of the following structural formula are particularly suitable.

Further, as a dye for a magenta thermal transfer sheet used in combination with the thermal transfer sheet of the present invention, a magenta dye having the following structural formula is particularly suitable.

(Effects) According to the present invention as described above, the dye used in the composition of the thermal transfer sheet of the present invention is a sublimable dye (molecular weight of about 150 to 250) that was used in the conventional thermal transfer sheet.
Despite having a significantly higher molecular weight than
Because it has a specific structure and a substituent at a specific position, it exhibits excellent heat migration properties, dyeing properties and coloring properties on the transferred material, and it does not migrate in the transferred material after transfer. or bleed out onto the surface.

Furthermore, although the resulting images are formed from dyes, the problem of discoloration due to indoor light and discoloration when exposed to direct light, such as inside albums, cases, books, etc., has not been sufficiently resolved. There is.

Therefore, images formed using the thermal transfer sheet of the present invention have excellent fastness, especially migration resistance and stain resistance, and excellent fading resistance, so they can be stored for a long time. The various problems of the prior art are solved without any loss of sharpness of the image formed, contamination of other articles, or loss of sharpness.

(Example) Next, the present invention will be described in more detail with reference to reference examples, examples, and comparative examples. In the text, parts or percentages are based on weight unless otherwise specified.

Reference Example 1 2.54 parts of a pyrazolopyrimidine derivative represented by the following structural formula (a) and 2.0 g of a nitroso compound represented by the following structural formula (b) were dissolved in 20 mj2 of ethyl acetate, and 150 mff of acetic anhydride was dissolved therein. 1.0 mff of pyridine was added, and the mixture was reacted at 50°C for 2 hours. After the reaction is complete, add ethyl acetate 2
00 mA and 100 mβ of water were added, and the ethyl acetate layer was separated and concentrated. This was purified by a column using a mixed solvent of ethyl acetate/n-hexane, and the dye No. 1 in Table 1 (0.8 g, yield 24%) represented by the following structural formula (c) was used for reference. Examples 2 to 26 The dyes listed in Table 1 Nos. 2 to 26 were obtained in the same manner as in Reference Example 1 except that the raw materials corresponding to the dyes Nos. 12 to 26 in Table 1 were used.

Example An ink composition for forming a dye-carrying layer having the following composition was prepared, and a dry coating amount of 1.0 g/n? The thermal transfer sheet of the present invention was obtained by coating and drying to give a heat transfer sheet of the present invention.

Dyes of Table 1 3 parts Polyvinyl butyral resin 4.5 parts Methyl ethyl ketone 46.25 parts Toluene
46.25 parts However, when the dye was insoluble in the above composition, DMF, dioxane, chloroform, etc. were appropriately used as a solvent.

Next, synthetic paper (Yubo FP manufactured by Tamago Yuka Co., Ltd.) was used as a base sheet.
G#150), apply a coating liquid with the following composition to one side at a rate of 10.0g/ITr when dry,
The material to be transferred was obtained by drying at 00° C. for 30 minutes.

Polyester resin (Vylon200, manufactured by Toyobo) 11
．． 5 parts vinyl chloride/vinyl acetate copolymer (VY, ucg)
s, o parts Amino-modified silicone (KF-393, Shin-Etsu Chemical Co., Ltd.) 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 of the present invention and the transfer material described above were placed one on top of the other with their respective dye-carrying layers and dye-receiving surfaces facing each other, and a head was applied from the back side of the thermal transfer sheet. Voltage 10V, printing time 4,
Recording was performed with a thermal head under the conditions of 0 m5ec,
The results shown in Table 2 below were obtained.

Comparative Examples 1 to 5 The dyes shown in Table 3 below were used in place of the dyes in Example 1, and the results shown in Table 3 below were obtained in the same manner as in the Examples.

Also, if you rub the surface with white paper, the white paper will not become colored.
An image with a slight loss of sharpness and a slightly colored white paper is rated O, an image with a loss of sharpness and a colored white paper is △, and an image with blurred images and a markedly colored white paper is rated an ×. It was displayed in

Comparative example 1 = C, 1, Disbirds Blue 14 Comparative example 2 =
C,1, Disbirds Blue 134 Comparative Example 3=C,1,
Solvent Blue 63 Comparative Example 4 = C, 1, Disperse Blue 26 Comparative Example 5 = C, 1, Disperse Violet 4 The color density in the above is the value measured with a densitometer RD-918 manufactured by Macbeth Corporation in the United States. be.

Claims (2)

[Claims] (1) Consists of a base sheet and a dye-supporting layer formed on one side of the base sheet, and the dye included in the dye-supporting layer is a dye represented by the following general formula (I). A thermal transfer sheet featuring ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (R_1 in the above formula is a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, aryl group, or together with Y, a 5- or 6-membered ring. R_2 represents a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, or aryl group, and R_1 and R_2 contain an oxygen atom, nitrogen atom, or sulfur atom. X may form a 5- or 6-membered ring, and X is a hydrogen atom, a halogen atom, a cyano group, an alkyl group that may have a substituent, a cycloalkyl group, an alkoxy group, an aryl group, an aralkyl group. , acylamino group, sulfonylamino group, ureido group, carbamoyl group, sulfamoyl group,
Represents an acyl group, an amino group, and R_3 is a hydrogen atom, a halogen atom, a cyano group, an alkyl group that may have a substituent,
Cycloalkyl group, aryl group, aralkyl group, alkoxy group, alkylthio group, aryloxy group, arylthio group, acylamino group, sulfonylamino group, ureido group, carbamoyl group, sulfamoyl group, acyl group,
Represents an amino group, R_4 represents a hydrogen atom, a halogen atom, a cyano group, a nitro group, an alkyl group, an alkoxy group, an aryl group, an aralkyl group, an acylamino group, a ureido group, an acyl group, an amino group, and R_5 represents a hydrogen atom , represents a halogen atom, a cyano group, or an alkyl group, Y represents a hydrogen atom or an atom or atomic group forming a 5-membered ring or a 6-membered ring together with R_1, and n represents 1 or 2. ) (2) The thermal transfer sheet according to claim 1, wherein the molecular weight of the dye is in the range of 300 to 600.