JPH0353987A - Thermal transfer sheet - Google Patents

Abstract

PURPOSE:To obtain a recording image having high density and excellent in various fastnesses, especially, preservability and discoloration/fading resistance by the short-time application of heat energy by using a dye having a specific structure. CONSTITUTION:A thermal transfer sheet consists of a base material sheet and the dye supporting layer formed on one surface of said base material sheet and the dye contained in said dye supporting layer is represented by formula (I) wherein R1 and R2 are a 1-6C alkyl group which may has a substituent, X is a halogen atom, an alkyl group, an alkoxyalkyl group, a hydroxyalkyl group, a halogenoalkyl group, a cyanoalkyl group, a cycloalkyl group, an alkoxy group, an aryl group, an aralkyl group or amino group and Y is a non- substituted or substituted alkylene group and pref. an alkylene group containing an ether group, a thioether group or a vinyl group and especially pref. a 2-10C alkylene group which may contain a different kind of oxygen, sulfur and nitrogen atoms as couple groups. A pref. dye has an MW of 700 or less.

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 fastnesses, particularly in storage stability and resistance to change and fading.

(Prior art) Various thermal transfer methods have been known in the past. Among them, a sublimation dye is used as a recording agent, and this is supported on a base sheet such as paper to form a thermal transfer sheet. There is a sublimation transfer method in which the thermal transfer sheet is layered on a transfer material that can be dyed with Dye 4, such as polyester woven cloth, and heat energy is applied in a pattern from the back side of the thermal transfer sheet to transfer the sublimable dye to the transfer material. It is being done.

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

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 a document 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 transfer process are 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 have a molecular weight as small as 1M, so they cannot be easily transferred after transfer. The dye migrates in the material over time or bleeds onto the surface, causing storage problems such as disturbing or unclear images or contaminating surrounding articles.

In order to avoid such problems, if a sublimable dye with a relatively large molecular weight is used, the sublimation speed will be inferior in the high-speed recording method as described above, so it will not be possible to form an image with a satisfactory density as described above. Furthermore, since the resulting images are formed from dyes, they generally have inferior light fastness compared to images using pigments, and there is a problem in that the images fade or change color quickly when exposed to direct sunlight. These light fastness problems have been solved to some extent by adding ultraviolet absorbers and antioxidants to the dye-receiving layer of the transfer material.

However, the problem of discoloration and fading occurs not only due to direct sunlight; for example, discoloration due to indoor light, and discoloration of the contents of albums, cases, books, etc., which are not exposed to direct light, also occur. The problems of indoor discoloration and dark discoloration cannot be solved by using general ultraviolet absorbers and antioxidants.

Therefore, an object of the present invention is to provide a clear image with sufficient density in a thermal transfer method using a sublimable dye, and furthermore, the formed image has excellent fastness properties, particularly excellent storage stability, and resistance to change and fading. It is an object of the present invention to provide a thermal transfer sheet that exhibits no properties.

(Means for solving problems) ” The above object is achieved by the following present invention.

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 general formula (I). This is a thermal transfer sheet characterized by the following.

(R1 and R2 in the above formula represent the same or different hydrogen atoms, substituted or unsubstituted alkyl group, cycloalkyl group, aralkyl group, or aryl group, and R1 and R2 together represent a 5-membered ring or a 6-membered ring. A membered ring may be formed; group, sulfamoyl group, alkoxycarbonyl group, allyloxycarbonyl group, airyl group,
It represents an amino group, Y represents a divalent linking group, and n represents an integer of 1 or 2. ) (Function) By using a dye with a specific structure, the dye used can be easily transferred to the transfer material even when thermal energy is applied for an extremely short period of time, resulting in high concentration and excellent fastness. In particular, there is provided a thermal transfer sheet that provides recorded images with good storage stability and resistance to change and fading.

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

The dye of general formula (I) used in the present invention is, for example,
Diester of 2 moles of cyanacetic acid and 1 mole of glycol 1
It is obtained by reacting 2 moles of p-N monosubstituted benzaldehyde per mole, or by reacting 2 moles of the reaction product of 1 mole of cyanacetic acid and 1 mole of the above benzaldehyde with 1 mole of glycol. The left and right chromophores may be the same or different. These manufacturing methods are merely examples, and it goes without saying that other manufacturing methods can also be used.

In addition, various substitutional structures in the dye used in the present invention are as defined above, but in particular, R and R2 are cyano groups, chlorine atoms, hydroxyl groups, alkoxy groups, alkoxycarbonyl groups, phenyl groups, acyloxy groups, etc. It is an alkyl group having 1 to 6 carbon atoms which may have a substituent, and X is fluorine,
Halogen atoms such as chlorine, bromine, and iodine; Cyano group; Alkyl groups such as methyl, ethyl, probyl, and butyl groups; Alkoxyalkyl groups such as methoxyethyl and ethoxyethyl groups; hydroxyethyl group, β-hydroxy group; Hydroxyalkyl groups such as bil group: Halogenoalkyl groups such as chloroethyl group; Cyanoalkyl groups such as cyanomethyl group and cyanoethyl group; Cycloalkyl groups such as cyclohexane group, alkoxy groups such as methoxy group, propoxy group, butoxy group: phenyl group , tolyl group, halogenophenyl group, aryl group such as alkoxyphenyl group; aralkyl group such as pencil group, phenethyl group; acetylamino group,
Acylamino groups such as benzoylamino group: methanesulfonylamino group, ethanesulfonylamino group; sulfonylamino group such as benzenesulfonylamino group; ureido group such as methylureido group, 1,3-methylureido group, ethylureido group; methyl force Carbamoyl groups such as rubamoyl group, ethyl rubamoyl group, phenyl rubamoyl group; methylsulfamoyl group, ethylsulfamoyl group,
Sulfamoyl groups such as phenylsulfamoyl groups; acyl groups such as acetyl groups, propanoyl groups, benzoyl groups;
Methylamino group, ethylamino group, propylamino group,
is an amine group such as a dimethylamino group or a diethylamino group, and Y is an ethylene group, a propylene group, a butylene group, a pentylene group, a hexelene group, a hebutylene group, a cutylene group, a bromoethylene group, a 2,3 dichloroethylene group, 2
- Unsubstituted or substituted alkylene groups such as -hydroxypropylene group, 2,7-dihydroxyoctylene group, 2-cyanobutylene group, and further ether group, thioether group, carbonyl group, amino group, amide group, imide group, ureate group,
Preferred are the above alkylene groups containing a carbonyloxy group, a sulfonyl group, a sulfonylamino group, a vinyl group, and the like.

A particularly preferred linking group is an alkylene group having 2 to 10 carbon atoms which may contain heteroatoms of oxygen, sulfur and nitrogen.

Further, in the present invention, preferred dyes have a molecular weight of 700 or less.

Specific examples of dyes suitable for the present invention are listed in Table 1 below. Table 1 below shows substituents R+. in general formula (1). R
2. X. represents n and molecular weight.

(The following is a blank space) Table 1 Table 1 1 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 material 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 LLm, 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. Especially 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) 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 edyl cellulose, hydro-12-oxyethyl cellulose, ethyl hydroxy cellulose, hydroxypropyl cellulose, methylcellulose,
Examples include cellulose resins such as cellulose acetate and cellulose acetate, vinyl resins such as polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, polyvinyl acetoacetal, polyvinylpyrrolidone, and polyacrylamide, among which polyvinyl butyral and polyvinyl Acecool is preferred from the standpoint of heat resistance, dye migration, and the like.

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-mentioned base material sheet.

The support layer formed in this way has a thickness of 0.2 to 5.0 um.
The thickness is preferably about 0.4 to 2.0 LLm,
Further, the above-mentioned dye in the support layer accounts for 5 to 70% of the weight of the support layer.
It is suitably 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, 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.
Images with even better density can be formed.

As this mold release layer, even if an inorganic powder with anti-adhesive property is simply attached, it has a considerable effect, and in addition, resins with excellent mold release properties such as silicone polymers, acrylic polymers, and fluorinated polymers can be used. 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 dressing or mold-releasing polymer exhibits sufficient effects even when incorporated into 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.

Examples of transfer materials that do not require the formation of a dye-receiving layer include polyolefin resins such as polypropylene, halogenated polymers such as polyvinyl chloride and polyvinylidene chloride, vinyl polymers such as polyvinyl acetate and polyacrylic ester, and polyethylene. Polyester resins such as terephthalate and polybutylene terephthalate, polystyrene resins, polyamide resins, copolymers of olefins such as ethylene and propylene and other vinyl monomers■5 resins, ionomers, celluloses such as cellulose diacetate, etc. Examples include fibers, woven fabrics, films, sheets, and molded products made of resins, polycarbonates, and the like.

Particularly preferred are sheet or film made of polyester, or processed paper provided with a polyester layer. or,
Even if the transfer material is non-dyeable such as paper, metal, glass, etc., a dyeable resin solution or dispersion as mentioned above is applied and dried on the recording surface, or a resin film thereof is coated. By laminating, it can be used as a transfer material.

Furthermore, even if the transfer material has the dyeability described above, a dye-receiving layer may be formed on the surface thereof from a resin having better dyeability, as in the case of the paper described above.

The dye-receiving layer formed in this way may be formed from a single material or from a plurality of materials, and may also contain various additives as long as they do not interfere with the intended purpose. Of course.

1 6 Such a dye-receiving layer may have any thickness, but for grains it is
The thickness is between 50 μm and 50 μm. Although such a dye-receiving layer is preferably a continuous coating, it may also be formed as a discontinuous coating using a resin emulsion or resin dispersion.

This type of transfer material is basically as described above and can be used as is, but it is possible to incorporate an inorganic powder for preventing adhesion into the transfer material or its dye-receiving layer. In this way, even if the temperature during deep transfer is increased, adhesion between the thermal transfer sheet and the material to be transferred can be prevented, and even better thermal transfer can be performed. Particularly preferred is
It is finely powdered silica.

Further, in place of or in combination with the above-mentioned inorganic powder such as silica, the above-mentioned resin having good mold releasability may be added.

Particularly preferred release polymers include cured products of silicone compounds, such as cured products of epoxy-modified silicone oil and amine-modified silicone oil. Such a release agent may be used in an amount of about 0.5 to 30% of the weight of the dye-receiving layer.
The weight percentage is good.

In addition, the transfer material to be used may have an inorganic powder as described above adhered to the surface of the dye-receiving layer to enhance the anti-adhesion effect, or a mold release material having excellent mold release properties as described above may be used. A layer consisting of an agent may also be provided.

Such a release layer exhibits a sufficient effect at a thickness of about 0.01 to 5 μm, and can further improve dye receptivity while preventing adhesion to the dye receptive layer of the thermal transfer sheet.

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/mrn'.

(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.

In addition, since the resulting image is formed from dye, the problems of discoloration due to indoor light and discoloration when exposed to no direct light, such as the contents of albums, cases, books, etc., have been sufficiently resolved. .

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 in sharpness of the image formed or contamination of other articles or loss of sharpness.

l 9 (Example) Next, the present invention will be described in more detail with reference to Examples and Comparative Examples. In the text, parts or percentages are based on weight unless otherwise specified.

EXAMPLE An ink composition for forming a dye-carrying layer having the following composition was prepared, and applied onto 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/m and dried. A thermal transfer sheet of the present invention was obtained.

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 (Oji Yuka Co., Ltd., Yubo FP) was used as a base sheet.
G#I50), and a coating liquid having the following composition was applied to one side of the coating at a drying time of lo. It was coated at a ratio of 20 og/m' and dried at 100° C. for 30 minutes to obtain a transfer material.

Polyester resin (Vylon200, manufactured by Toyobo) l1
．． 5 parts vinyl chloride/vinyl acetate copolymer (VYHH. manufactured by UCC) 5.0 parts amine-modified silicone (KF-393. manufactured by Shin-Etsu Chemical) 1 2 parts epoxy-modified silicone (X-22-343, manufactured by Shin-Etsu Chemical) (manufactured by) 1 2
Methyl ethyl ketone/toluene/cyclohexanone (
Weight ratio 4:4:2) 102. 0 copies The thermal transfer sheet of the present invention and the transfer material described above were stacked with their respective dye-carrying layers and dye-receiving surfaces facing each other, and a head applied voltage of 10 V was applied from the back side of the thermal transfer sheet for a printing time of 4.
．． 0 msec. Recording was performed with a thermal head under the following conditions, and the results shown in Table 2 below were obtained.

Comparative Examples 1 to 4 The dyes shown in Table 3 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 3 below.

Table 3 Comparative Example 1=C. I Solvent Yellow 56 Comparative Example 2=C
．． I. Solvent Yellow 14 Comparative Example 3 = C.I. I Disperse Yellow 3 Comparative Example 4=C.I. I. Disperse Yellow 54 Note that the color density in the above is a value measured with a densitometer RD-918 manufactured by Macbeth Corporation in the United States.

Preservability is defined as 0 if the sharpness of the image does not change after the recorded image is left in an atmosphere of 70'C for 48 hours, and the white paper does not become colored even when the surface is rubbed with white paper. ○ If the sharpness is lost and the white paper is slightly colored.
△
The image was unclear and the white paper was markedly colored, which was marked with an "x".

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Claims (3)

[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 and R_2 in the above formula represent the same or different hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, aralkyl groups, aryl groups, and R_2 may form a 5-membered ring or a 6-membered ring together, and
are the same or different hydrogen atoms, halogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkoxy groups, aralkyl groups, acylamino groups, sulfonylamino groups, ureido groups, carbamoyl groups, sulfamoyl groups, alkoxycarbonyl groups, ali Roxycarbonyl group, airyl group, amino group, Y is a divalent linking group, n is 1
or represents an integer of 2. ) (2) The thermal transfer sheet according to claim 1, wherein the dye has a molecular weight of 700 or less. (3) The thermal transfer sheet according to claim 1, wherein Y is an alkylene group having 2 to 10 carbon atoms which may contain a different atom.