JPH048590A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer sheet, which gives a distinct picture image with a sufficient density and in which the formed picture image shows various excellent fastnesses, especially excellent keeping quality, by adding a specific dye in a dye-carrying layer. CONSTITUTION:The title sheet is composed of a backing sheet and a dye- carrying layer formed on one side of said backing sheet and a dye included in the dye-carrying layer is a dye represented by general formula (I). When the dye of formula (I) is used, the used dye moves easily to a transferred material even in the case of giving thermal energy in a very short time so that it is possible to obtain a thermal transfer sheet giving a high density and various excellent fastnesses, especially excellent keeping quality.

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 a 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 4-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.

In order to avoid such problems, if a sublimable dye with a relatively high molecular weight is used, the sublimation speed will be inferior in the high-speed recording method described above, Met.

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 also includes a base sheet and a dye-supporting layer formed on one surface of the base sheet, and the dye included in the dye-supporting layer is a dye represented by the following general formula (I). This is a thermal transfer sheet characterized by the following.

(R1 or R2 in the above formula may be the same or different (,
It represents a substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, or aryl group, and R and R2 may form a 5-membered ring or a 6-membered ring that may contain an oxygen atom or a nitrogen atom, R3 is a hydrogen atom, a halogen atom, a cyano group,
Alkyl group, cycloalkyl group, which may have a substituent,
Alkoxy group, aralkyl group, aryl group, acyl group,
Represents an acylamino group, sulfonylamino group, ureido group, carbamoyl group, sulfamoyl group or amino group,
R4 represents a hydrogen atom, an alkyl group that may have a substituent, a cycloalkyl group, an alkoxy group, an aralkyl group, an aryl group, a heterocyclic group, an acylamino group, a sulfonylamine group, or an amino group, and X is a hydrogen atom. Y represents an oxygen atom or a sulfur atom, Z represents a nitrogen atom or a methine group, and m represents 1 or 2. By using a dye with a specific structure, the dye used can easily transfer to the transfer material even when thermal energy is applied for an extremely short period of time, resulting in high concentration and excellent fastness. A thermal transfer sheet is provided which provides a recorded image with excellent storage properties.

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

The dye of the general formula (I) used in the present invention can be obtained by a known method, for example, by combining a heteroazole compound represented by the following general formula (a) and a nitroso compound represented by the general formula (b), or a general formula ( It can be easily produced by dehydration condensation with the aldehyde compound represented by C) in the presence of an acid, base or hydrochloric acid group catalyst. The heteroazole compound represented by -6 formula (a) can be prepared by a known method, for example, Bul
l.

Chem, soc, Jap, 42(2) 16
17 (1969) and U, S, P.

It can be easily synthesized by the method described in No. 4,371.734.

(a) (b) (a) (c) (R1 to R, , X, Y and m in the formula are as defined above.) Preferred represented by R1 to R4 in the above general formula (I) Examples of substituents include alkyl groups such as methyl, ethyl, propyl, and butyl groups; alkoxyalkyl groups such as methoxyethyl and ethoxyethyl groups; hydroxyalkyl groups such as hydroxyethyl and β-hydroxypropyl groups: Halogenoalkyl groups such as chloroethyl groups; cyanoalkyl groups such as cyanomethyl and cyanethyl groups; cycloalkyl groups such as cycloalkyl groups; aralkyl groups such as benzyl and phenethyl groups; phenyl groups; tolyl groups; halogenophenyl groups; alkoxy Aryl groups such as phenyl groups;
Alkoxy groups such as methoxy, ethoxy, propoxy and butoxy groups; hydrogen atoms, halogen atoms such as chlorine, bromine and iodine; carboxyl groups; acyl groups such as acetyl, propanoyl and benzoyl groups; niacetylamino groups , acylamino groups such as benzoylamino groups, sulfonylamino groups such as methanesulfonylamino groups, ethanesulfonylamino groups, benzenesulfonylamino groups:
Ureido groups such as methylureido group, 1,3-dimethylureido group, ethylureido group: methylcarbamoyl group,
Carbamoyl groups such as ethylcarbamoyl group and phenylcarbamoyl group: sulfamoyl groups such as methylsulfamoyl group, ethylsulfamoyl group, phenylsulfamoyl group; methylamino group, ethylamino group, propylamino group, dimethylamine group, Dimethylamine group, pyrazolyl group, imidazolyl group, pyridyl group, thiazolyl group,
Examples include heterocyclic groups such as an oxacylyl group.

In addition, preferred dyes in the present invention have a molecular weight of 300 to 5.
00 range.

Preferred specific examples of dyes of general formula (I) suitable for the present invention are shown in Table 1 below.

(Left below) Amino groups such as mino groups, furyl groups, thienyl groups, bi(1)
--j! The thermal transfer sheet of the present invention is characterized by the use of the above-mentioned specific dye, and the other structure may be the same as that of conventionally known thermal transfer sheets.

The base sheet used in the thermal transfer sheet of the present invention containing the above-mentioned dye may be any conventionally known base sheet as long as it has a certain degree of heat resistance and strength (for example,
Paper with a thickness of about 5 to 50 μm, preferably about 3 to 10 μm, various processed papers, polyester film, polystyrene film, polypropylene film, polysulfone film, polycarbonate film, aramid film, polyvinyl alcohol film, cellophane, etc. are particularly preferred. 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 the general 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. This is preferable from the viewpoints of properties, dye migration properties, etc.

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 thus formed has a thickness of about 02 to 50 μm, preferably 0.4 to 20 μm, and the dye in the supporting layer is preferably 5% to 0% by weight of the weight of the supporting layer. Preferably it is present in an amount of 10-60% by weight.

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 (such a layer may be provided). By providing this, it is possible to prevent adhesion between the thermal transfer sheet and the transferred material during thermal transfer, and to use a higher thermal transfer temperature.
- Images with excellent layer 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., which does not have any properties, a dye-receiving layer may be formed on one surface of the material.

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-100 manufactured by Hitachi), it is possible to
J/mrr? In particular, the thermal transfer sheet of the present invention can form a cyan image and can be used in combination with yellow and magenta thermal transfer sheets. , it is possible to provide full-color images with excellent color reproducibility. As a dye for a yellow thermal transfer sheet used in combination with the thermal transfer sheet of the present invention, a yellow dye having the following structural formula is 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.

(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-dicyanomethyl-4-phenylthiazole 1.0g
and 1.2 g of 2-ethoxy-4-diethylaminonitrone benzene were dissolved in 60 mβ of toluene and heated to 50-55°C.
The mixture was heated and reacted for 2 hours.

After the reaction was completed, it was cooled, the precipitated crystals were filtered, and the obtained crude crystals were purified by column chromatography to obtain 1.6 g of the dye No. 1 in Table 1 (yield 84%, melting point 248-249°C).
I got it.

Reference Example 2 The dyes listed in Table 1 were obtained in the same manner as in Reference Example 1 except that the raw materials corresponding to the dyes in Table 1 were used.

Example An ink composition for forming a dye-carrying layer having the following composition was prepared, and it was coated and dried on a 6 μm thick polyethylene terephthalate film whose back side had been heat-resistant treated so that the dry coating amount was 1.0 g/ni'. A thermal transfer sheet of the present invention was obtained.

Dyes listed in Table 1 1 part Polyvinyl butyral resin 4.5 parts Methyl ethyl ketone 47.25 parts Toluene
47.25 parts However, when the dye was insoluble in the above composition, DMF, dioxane, chloroform, etc. were appropriately used as a solvent. In addition, when sufficient dissolution was not achieved even after using the above-mentioned solvent, the '6i solution was used.

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 on one side at a rate of 10.0g/rrl' when dry,
The material to be transferred was obtained by drying at 100° C. for 30 minutes.

Polyester resin (Vylon200, manufactured by Toyobo) 11
．． 5 parts Vinyl chloride/vinyl acetate copolymer (manufactured by VYHH1UCC) 50 parts amine-modified silicone (KF-393, manufactured by Shin-Etsu Chemical) 1.2 parts Kiboxy-modified silicone (X-22-343, manufactured by Shin-Etsu Chemical) 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 are placed so that the respective dye-carrying layers and dye-receiving surfaces face each other. Apply a head voltage of 10 V from the back side of the thermal transfer sheet, 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.

(The following is a margin) Table 2 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 Example 1 except that the dyes shown in Table 3 below were used.

Comparative example 1 = C, 1, Disbirds Blue 14 Comparative example 2 =
C,1, Disperse Blue 134 Comparative Example 3 = C,I 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 US. This is a value measured with a densitometer RD-918 manufactured by Macbeth.

Storage stability is defined as 0 if the sharpness of the image does not change after the recorded image is left in an atmosphere at 70°C for 48 hours, and the white paper does not become colored even when the surface is rubbed with white paper. When the sharpness was lost and the white paper was slightly colored, it was marked as ○, when the sharpness was lost and the white paper was colored, it was marked as △, and when the image became unclear and the white paper was markedly colored, it was marked as ×.

(Effects) According to the present invention as described above, the dye used in the composition of the thermal transfer sheet of the present invention has a higher molecular weight than the sublimable dye (molecular weight approximately 150 to 250) used in the thermal transfer sheet of the prior art. Although it has a significantly high molecular weight, it has a specific structure and a substituent at a specific position, so
It exhibits excellent heat transferability, dyeability and coloring properties on the transfer material, and does not migrate into the transfer material or bleed out onto the surface of the transfer material after transfer.

In addition, although the resulting images are formed from dyes, the problem of discoloration due to indoor light and discoloration when exposed to no direct light, such as the contents of albums, cases, books, etc., has not been sufficiently solved. 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. Otherwise, the sharpness of the image formed may be lost, or it may contaminate other objects or lose sharpness.
However, various problems of the prior art have been solved.

Patent applicant: Inu Nippon Printing Co., Ltd. (1 other person)

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 or R_2 in the above formula may be the same or different, and may be a substituted or unsubstituted alkyl group, a cycloalkyl group,
It represents an aralkyl group or an aryl group, R_1 and R_2 may form a 5- or 6-membered ring that may contain an oxygen atom or a nitrogen atom, and R_3 is a hydrogen atom, a halogen atom, a cyano group, or a substituted Represents an alkyl group, cycloalkyl group, alkoxy group, aralkyl group, aryl group, acyl group, acylamino group, sulfonylamino group, ureido group, carbamoyl group, sulfamoyl group, or amino group that may have a group, and R_4 is hydrogen represents an atom, an alkyl group, a cycloalkyl group, an alkoxy group, an aralkyl group, an aryl group, a heterocyclic group, an acylamino group, a sulfonylamino group, or an amino group which may have a substituent, and X is a hydrogen atom or Represents an atom or atomic group that forms a 5-membered ring or 6-membered ring together with R_1, Y represents an oxygen atom or a sulfur atom, Z represents a nitrogen atom or a methine group, m 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 500.