JPH03297691A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer sheet forming a recording image having excellent developed color density, sharpness and various fastnesses and especially excellent in preservability by using a specific dye as the dye contained in the dye support layer formed to at least one surface of a base sheet. CONSTITUTION:A thermal transfer sheet consists of a base sheet and the dye support layer formed to at lease one surface of the base sheet and the dye contained in the dye support layer is represented by formula (I) or (II). The MW of a pref. dye is within the range of 300-700. The base sheet to be used has a thickness of 0.5-50mum, pref., about 3-10mum and, for example, there are various papers, a polyester film and a polystyrene film and the polyethylene film is especially pref. By using a dye having a specific structure, a used dye is easily transferred to a transfer material even when heat energy is applied for an extremely short time and the thermal transfer sheet forming a recording image having high density and various excellent fastnesses and especially excellent in preservability is obtained.

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 thermal transfer method include the color density, storage stability, and resistance to fading of the formed image.

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 included in the dye-carrying layer has the following general formula (I) or (I[). This is a thermal transfer sheet characterized by being a dye represented by:

R1 and R2 in the above formula may be the same or different and represent a hydrogen atom, a substituted or unsubstituted alkyl group, a cycloalkyl group, an aralkyl group, or an aryl group, and R1 and R2 are an oxygen atom, a nitrogen atom, A 5-membered ring or a 6-membered ring which may contain an atom or a sulfur atom may be formed, and R3 may be the same or different (represents an electron-withdrawing group, and Y represents a divalent linking group). , X represents a hydrogen atom or an atom or atomic group that forms a 5-membered ring or a 6-membered ring together with R. A thermal transfer sheet is provided in which the dye used easily transfers to the transfer material even when energy is applied, and provides a recorded image having high density, excellent fastness properties, and especially 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 (I) used in the present invention can be obtained by a known method, for example, by combining an aldehyde compound acid represented by the following general formula (a) and an active methylene compound represented by the general formula (b) with an acid. Alternatively, it can be easily produced by dehydration condensation in the presence of a base or an acid-base catalyst.

Moreover, the dye of the general formula (I[) used in the present invention can also be prepared by a known method, for example, a nitroso compound acid represented by the following general formula (c) and an active methylene compound represented by the general formula (b). It can be easily produced by dehydration condensation of and in the presence of an acid, a base, or an acid-base catalyst.

(R1 to R, , Y and X in the formula are as defined above.) Preferred examples of substituents represented by R3 to R2 in the above general formula (I) or (II) include methyl group, ethyl alkyl groups such as methoxyethyl and ethoxyethyl groups; hydroxyalkyl groups such as hydroxyethyl and β-hydroxypropyl groups; halogenoalkyl groups such as chloroethyl groups; cyanomethyl groups R3 is an atom that forms a 5-membered ring or a 6-membered ring together with X. Note that R3 and R2 may form a 5-membered ring or a 6-membered ring that may contain an oxygen atom, nitrogen atom, or sulfur atom.

Examples of the electron-withdrawing group R3 include a cyano group; a carboxyl group; an acyl group such as an acetyl group, a propanoyl group, and a benzoyl group; an alkylsulfonyl group such as a methanesulfonyl group and an ethanesulfonyl group; a phenylsulfonyl group, and a p-
Arylsulfonyl groups such as chlorophenylsulfonyl groups; Carbamoyl groups such as methylcarbamoyl, ethylcarbamoyl, and phenylcarbamoyl groups; Sulfamoyl groups such as methylsulfamoyl, ethylsulfamoyl, and phenylsulfamoyl groups; methoxycarbonyl groups , ethoxycarbonyl group, alkoxycarbonyl group such as propoxycarbonyl group, phenoxycarbonyl group,
Examples include aryloxycarbonyl groups such as p-methylphenoxycarbonyl group.

Y, which is a divalent linking group, includes an oxygen atom, a methylene group,
Unsubstituted or substituted alkylene groups such as ethylene group, propylene group, butylene group, isopropylene group, bromoethylene group, 2-hydroxypropylene group, alkenylene group such as vinylene group, propenylene group, butenylene group, phenylene group, hydroxyphenylene group , unsubstituted or substituted arylene groups such as naphthylene groups, and the following functional groups (ether groups, thioether groups, carbonyl groups, amino groups, amide groups, imido groups, ureido groups, carbonyloxy groups,
sulfonyl group, sulfonylamino group, vinyl group, etc.), alkenylene groups, and arylene groups.

-C) 1.0CH2-1-CI(,CH,5CHtCH
t-1-CH, N(R,)-(R4 is a hydrogen atom or an alkyl group).

-C1(,CH,C0CH,CH,-1-CH2CHt
OCOCH2CH, -1-CHaCH-CONHCOC
H2CHg-1-CHICHtNHCONHCH,CH
2-2-CH*C0NHCH2-1-CH2SO□NH
CHa-1-CHiCH2SOtCHzGHz-1-C
HiCHiC=CCH*CHa-1-〇GHz-1-C
H20- Also, preferred dyes in the present invention have a molecular weight of 300 to 7.
00 range.

Specific examples of dyes of general formula (I) suitable for the present invention are listed in Table 1 below, and specific examples of dyes of general formula (IT) suitable for the present invention are listed in Table 2 below. Tables 1 and 2 below show substituents R1 to R, Y and molecular weights in general formulas (I) and (II).

(Hereinafter in the margin) Hair styling - U 2 The thermal transfer sheet of the present invention is characterized by using the above-mentioned specific dye, and the other configurations may be the same as those 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 material having a certain degree of heat resistance and strength.
．． 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.
Particularly preferred is 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) or (n) 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 thickness of the support layer formed in this manner is about 0.2 to 5.0 μm, preferably 0.4 to 2.0 μm, and the above-mentioned dye in the support layer is about 5 to 5.0 μm thick by weight of the support layer. 70% by weight,
Preferably it is present in an amount of 10 to 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. , 01 to 5 μm, preferably 0.05 to 2 μm, by providing a release layer.

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

Furthermore, a heat-resistant layer may be provided on the back side 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-100 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 yellow image, and when used in combination with magenta and cyan thermal transfer sheets, can form a full-color image with excellent color reproducibility.

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.

Furthermore, as a dye for a cyan thermal transfer sheet to be used in combination with the thermal transfer sheet of the present invention, a cyan 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 9.4 g of 3.3'-diethylamino-6,6'-diformyldiphenylmethane and 5.1 g of malononitrile were dissolved in 96 mρ of ethanol, 0.4 g of piperidine was added thereto, and the mixture was reacted under reflux for 1 hour. After the reaction is completed, cool
The precipitated crystals were filtered.

The obtained crude crystals were purified by column chromatography,
4.2 g of dye No. 1 in Table 1 (yield 35%)
, melting point 213-214°C).

Reference Examples 2 to 26 Raw materials corresponding to the dyes in Table 1 Nos. 2 to 21 and PkL 1 to 15 in Table 2 were used, and the other conditions were the same as in Reference Example 1 to produce Nos. 32 to 21 and 2 of Table 1. The dyes described in Tables 1 to 15 were obtained.

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

Dyes from Table 1 or Table 2 above 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. In addition, when sufficient dissolution was not achieved even when using the above-mentioned solvent, the filtrate 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/rrr 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 (VYHI(, UCC)
) 5.0 parts 9 Amino-modified silicone (KF-393, manufactured by Shin-Etsu Chemical) 1.2 parts Epoxy-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 described above are stacked on top of each other with their respective dye-carrying layers and dye-receiving surfaces facing each other, and the back side of the thermal transfer sheet is From head applied voltage 10■, printing time 4,
Recording was performed with a thermal head under the conditions of 0 m5ec,
The results shown in Table 3 below were obtained.

0 Comparative Examples 1 to 4 The dyes shown in Table 4 below were used in place of the dyes in Example 1, and the other conditions were the same as in Example 1 to obtain the results shown in Table 4 below.

Comparative Example 1 = C, 1, Solvent Yellow-56 Comparative Example 2 =
C,1, Solvent Yellow-14 Comparative Example 3 = C,1, Disbird's Yellow-3 Comparative Example 4 = C,1, Disbird's Yellow 54 The color density in the above was measured using a densitometer RD- manufactured by Macbeth Corporation in the United States. This is the value measured at 918.

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. An image in which sharpness was lost and the white paper was slightly colored was rated O, an image in which sharpness was lost and the white paper was colored was rated Δ, and an image became unclear and the white paper was markedly colored was rated X.

(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
3 4 It exhibits excellent transferability, dyeability and coloring properties to the transfer material, and does not migrate into the transfer material or bleed out onto the surface of the transfer material after transfer.

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 have been solved without any loss of sharpness of the image formed or contamination of other articles or loss of sharpness.

(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 represented by the following general formula (I) or (II). A thermal transfer sheet characterized by being a dye. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (I) (II) (R_1 to R_2 in the above formula may be the same or different, and are hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, aralkyl groups, Represents an aryl group, R_1 and R
_2 may form a 5-membered or 6-membered ring that may contain an oxygen atom, nitrogen atom or sulfur atom, R_3 may be the same or different and represents an electron-withdrawing group, and Y is a divalent represents a linking group, and X represents a hydrogen atom or an atom or atomic group forming a 5-membered ring or a 6-membered ring together with R_1. ) (2) The thermal transfer sheet according to claim 1, wherein the molecular weight of the dye is in the range of 300 to 700.