JP2844345B2 - Thermal transfer sheet - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermal transfer sheet, and more specifically, to form a recorded image excellent in color density, sharpness, and various fastnesses, particularly, storage stability and resistance to discoloration. The purpose of the present invention is to provide a heat transfer sheet that can be used.

(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 paper to form a thermal transfer sheet, which is then dyed with a sublimable dye. A sublimation transfer method has been performed in which a sublimable dye is transferred to a transfer-receiving material by applying thermal energy in a pattern form from the back surface of a thermal transfer sheet to a transferable material such as a polyester woven cloth.

Recently, there has been proposed a method of forming various full-color images on paper or plastic film using the above-described sublimation type thermal transfer system. 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. 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, the most important problems in the above-described thermal transfer method include the problems of color density, storage stability, and discoloration resistance of the formed image.

That is, in the case of high-speed recording, the application of thermal energy is required to be performed in a very short time of less than seconds, and thus, in such a short time, the sublimable dye and the material to be transferred are not sufficiently heated. , An image having a sufficient density cannot be formed.

Therefore, in order to cope with such high-speed recording, a sublimable dye having excellent sublimability has been developed. In this case, the dye is transferred over time or bleeds on the surface, and the formed image is disturbed, becomes unclear, or contaminates the surrounding articles.

In order to avoid such a problem, when a sublimable dye having a relatively large molecular weight is used, the sublimation speed is inferior in the high-speed recording method as described above, so that an image having a satisfactory density cannot be formed as described above. Met.

Further, since the obtained image is formed from a dye, it generally has poor light fastness as compared with an image using a pigment, and there is a problem that the image is rapidly faded or discolored when exposed to direct sunlight. These problems of light resistance have been solved to some extent by adding an ultraviolet absorber or an antioxidant to the dye receiving layer of the material to be transferred.

However, the problem of discoloration occurs not only due to direct sunlight, but also, for example, discoloration due to room light and discoloration in a state where direct light does not shine such as the contents of albums, cases, books, etc. The problem of discoloration in a room or discoloration in a dark place cannot be solved by using a general ultraviolet absorber or antioxidant.

Therefore, an object of the present invention is to provide a clear image having a sufficient density in a thermal transfer method using a sublimable dye,
Moreover, it is an object of the present invention to provide a thermal transfer sheet in which a formed image shows excellent various fastnesses, particularly excellent storage stability and resistance to discoloration and fading.

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

That is, the present invention comprises a substrate sheet and a dye carrying layer formed on one surface of the substrate sheet, and the dye contained in the dye carrying layer is a dye represented by the following general formula (I) It is a thermal transfer sheet characterized by the following.

(R ₁ and R ₂ in the above formula are the same or different hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, aralkyl groups, aryl groups or R ₃ or R ₄ together with a 5-membered ring or 6
R ₃ and R ₄ are the same or different hydrogen atoms, halogen atoms, cyano groups, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkoxy groups, aryl groups, aralkyl groups, , an acylamino group, a sulfonylamino group, a ureido group, a carbamoyl group, a sulfamoyl group, an acyl group, an amino group, a ₁ and a ₂ represent the same or different electron-withdrawing groups, whereas one of a ¹ and a ₂ May be an aryl group. Z represents a methine group or a nitrogen atom, Y represents a divalent linking group, and m and n represent an integer of 1 to 3. (Action) By using a dye having a specific structure, even when heat energy is applied for a very short time, the dye used can easily transfer to the material to be transferred, and a high concentration and excellent various fastnesses can be obtained.
In particular, there is provided a thermal transfer sheet that provides a recorded image having storability and resistance to discoloration.

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

In the dye of the general formula (I) used in the present invention,
The dye wherein Z is a methine group is, for example, aniline which may have a substituent on the benzene ring, particularly preferably 1 mol of aliphatic, aliphatic aromatic or aromatic relative to 2 mol of N-monosubstituted aniline. A dimer is obtained by reacting a dihalide, and a Bilsmeier reagent is reacted with the dimer to prepare a bisformyl compound of the dimer. Further, these formyl groups are reacted with malononitrile or a derivative thereof. Obtained by:

In the above reaction, when a mixture is used as the aniline derivative, an asymmetric dye is obtained.

In the dye of the general formula (I) used in the present invention, the dye in which Z is a nitrogen atom is, for example, a dinitro-substituted derivative obtained by using a p-nitroaniline derivative instead of an aniline derivative in the above reaction. Nos. 2,3,4,6,6,7,8,1,1,1,1,1,1,1,1,1,1,1,1,1,1, 2, 1, 2, and 21, 2, 3, and 4, and can be obtained similarly by reducing the nitro group of the derivative to an amino group and reacting the amino group with malononitrile or a derivative thereof.

The production method as described above is merely an example, and the dye used in the present invention is, for example, first producing the left and right pigment portions,
Of course, it can also be prepared by other production methods such as a method of linking with an appropriate linking group.

The various substituted structures in the dye used in the present invention are as defined above. In particular, R ₁ and R _{2 each} have 1 to 6 carbon atoms.
R ₃ and R ₄ are a hydrogen atom or a carbon atom 1
And A ₁ and A ₂ are a cyano group or an alkoxycarbonyl group or an alkylaminocarbonyl group having 1 to 6 carbon atoms, and Y is a methylene group, an ethylene group, a propylene group, a butylene group, a pentylene group, Unsubstituted or substituted alkylene group such as hexelene group, heptylene group, octylene group, bromoethylene group, 2,3-dichloroethylene group, 2-hydroxypropylene group, 2,7-dihydroxyoctylene group, 2-cyanobutylene group, vinylene Group, propenylene group, butenylene group, unsubstituted or substituted arylene group such as alkenylene group like pentylene group, phenylene group, hydroxyphenylene group, methylphenylene group, naphthylene group, and the following functional groups (ether group, thioether group) , Carbonyl group, amino group, amide group, imide group, ureido group Carbonyl group, a sulfonyl group, a sulfonylamino group, an alkylene group containing a vinyl group, etc.), alkenylene groups and arylene groups are preferred.

−CH ₂ CH ₂ OCH ₂ CH ₂ − −CH ₂ CH ₂ SCH ₂ CH ₂ − −CH ₂ CH ₂ COCH ₂ CH ₂ − −−CH ₂ CH ₂ OCOCH ₂ CH ₂ − −CH ₂ CH ₂ CONHCOCH ₂ CH ₂ − −CH ₂ NHCONHCH ₂ − −CH ₂ CH ₂ CONHCH ₂ CH ₂ − −CH ₂ SO ₂ NHCH ₂ − −CH ₂ CH ₂ SO ₂ CH ₂ CH ₂ − −CH ₂ CH ₂ C = CCH ₂ CH ₂ − −CH = CHCH ₂ COCH ₂ CH ₂ --Ph-NHCO-Ph- -CH ₂ OCH ₂ -Ph-CH ₂ OCH ₂ -Particularly preferred linking groups have from 2 to 10 carbon atoms which may contain heteroatoms of oxygen, sulfur and nitrogen. Is preferably an alkylene group.

In the present invention, a preferred dye has a molecular weight of 400 or more.

Specific examples of suitable dyes in the present invention are shown in Table 1 below. Table 1 below shows the substituents R _{1 to} R ₁ in the general formula (I).
R ₄ , A ₁ , A ₂ , Z, Y, m, n and molecular weight are shown.

The thermal transfer sheet of the present invention is characterized by using the specific dyes as described above, and the other configuration may be the same as the configuration of a conventionally known thermal transfer sheet.

As the base sheet used in the thermal transfer sheet of the present invention containing the dye, any substrate may be used as long as it has 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, polycarbonate film, aramid film,
Polyvinyl alcohol film, cellophane, etc.,
Particularly preferred is a polyester film.

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

As a binder resin for supporting the dye,
Any of the conventionally known ones can be used, and preferred examples thereof include ethylcellulose, hydroxyethylcellulose, ethylhydroxycellulose, hydroxypropylcellulose, methylcellulose, cellulose acetate, cellulose resins such as cellulose acetate butyrate, polyvinyl alcohol, and polyvinyl acetate. And vinyl resins such as polyvinyl butyral, polyvinyl acetoacetal, polyvinyl pyrrolidone, and polyacrylamide. Of these, polyvinyl butyral and polyvinyl acetal are particularly preferable in terms of heat resistance, dye transferability, and the like. .

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

Such a dye-carrying layer is preferably prepared by adding the above-mentioned dye, binder resin and other optional components in a suitable solvent and dissolving or dispersing each component to prepare a coating solution or ink for forming a supporting layer. It is formed by coating and drying on the above substrate sheet.

The carrier layer thus formed has a thickness of about 0.2 to 5.0 μm, preferably about 0.4 to 2.0 μm, and the dye in the carrier layer is 5 to 70% by weight, preferably 5 to 70% by weight of the carrier layer. It is preferably present in an amount of 10 to 60% by weight.

Although the thermal transfer sheet of the present invention as described above is sufficiently useful as it is as a thermal transfer pattern, an anti-adhesion layer, that is, a release layer may be further provided on the surface of the dye-carrying layer, and such a layer is provided. Thereby, adhesion between the thermal transfer sheet and the material to be transferred at the time of thermal transfer can be prevented, and an image with a higher density can be formed by using a higher thermal transfer temperature.

As this release layer, even if only an anti-adhesive inorganic powder is simply attached, a considerable effect is exhibited.Moreover, for example, a silicone polymer, an acrylic polymer, a resin having excellent release properties such as a fluorinated polymer is 0.01% or less. To 5 μm, preferably 0.05 to 2 μm.

The inorganic powder or the releasable polymer as described above has sufficient effects even if it is included in the dye-carrying layer.

Further, a heat-resistant layer may be provided on the back surface of such a thermal transfer sheet in order to prevent adverse effects due to 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 a dye-accepting property for the dye. In the case of paper, metal, glass, synthetic resin or the like having no property, a dye-receiving layer may be formed on at least one surface thereof.

As a transfer material that does not need to form a dye receiving layer,
For example, polyolefin resins such as polypropylene, polyvinyl chloride, halogenated polymers such as polyvinylidene chloride, polyvinyl acetate, vinyl polymers such as polyacrylester, polyethylene terephthalate, polyester resins such as polybutylene terephthalate, polystyrene resins, Polyamide resin, copolymer resin of olefin such as ethylene and propylene and other vinyl monomers, ionomer, cellulose resin such as cellulose diacetate, fiber and woven fabric made of polycarbonate, etc.
Films, sheets, molded products and the like can be mentioned.

Particularly preferred is a sheet or film made of polyester or a processed paper provided with a polyester layer.
Further, even if paper, metal, glass or other non-dyeing non-transferring material is used, the recording surface is coated with a solution or dispersion of the above-described dyeing resin and dried, or the resin By laminating the film, a material to be transferred can be obtained.

Further, even in the case of the transfer material having dyeing properties, a dye-receiving layer may be formed on the surface thereof from a resin having better dyeing properties as in the case of the paper.

The dye receiving layer formed in this manner may be formed from a single material, or may be formed from a plurality of materials, and may further contain various additives as long as the intended purpose is not hindered. Is natural.

Such a dye-receiving layer may be of any thickness, but is generally between 3 and 50 .mu.m. Further, such a dye receiving layer is preferably a continuous coating, but may be formed as a discontinuous coating using a resin emulsion or a resin dispersion.

Such a material to be transferred is basically as described above and can be used satisfactorily as it is. However, the above-mentioned material to be transferred or its dye receiving layer contains an inorganic powder for preventing adhesion. In this way, even if the temperature at the time of thermal transfer is further increased, adhesion between the thermal transfer sheet and the material to be transferred can be prevented, and more excellent thermal transfer can be performed. Particularly preferred is finely divided silica.

Further, instead of or in combination with the above-mentioned inorganic powder such as silica, a resin as described above having good releasability may be added. A particularly preferred release polymer is a cured product of a silicone compound, for example, a cured product composed of an epoxy-modified silicone oil and an amino-modified silicone oil. Such a release agent is used in an amount of about 0.5 to 3% by weight of the dye receiving layer.
The proportion occupying 0% by weight is good.

The transfer material to be used is, on the surface of the dye receiving layer,
An inorganic powder as described above may be adhered to enhance the anti-adhesion effect, or a layer made of a release agent having excellent release properties as described above may be provided.

Such a release layer has a sufficient effect at a thickness of about 0.01 to 5 μm, and can further improve the dye receptivity while preventing adhesion to the dye receiving 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, a thermal printer (for example, The recording time is controlled by a recording device such as a video printer VY-100 (manufactured by Hitachi, Ltd.), and the
By applying thermal energy of about 0 mJ / mm ² , the intended purpose can be sufficiently achieved.

(Effects) According to the present invention as described above, the dye used in the construction of the thermal transfer sheet of the present invention is more sublimable than the sublimable dye (molecular weight of about 150 to 250) used in the thermal transfer sheet of the prior art. Despite having a remarkably high molecular weight, it has a specific structure and has a substituent at a specific position, so that it exhibits excellent heat transferability, dyeing property to a material to be transferred, and coloring property. In addition, after the transfer, the material does not migrate in the material to be transferred or bleed out to the surface.

Further, although the obtained image is formed from a dye, the problem of discoloration due to room light, and discoloration in a state where direct light does not shine, such as the contents of albums, cases, books, etc. are sufficiently solved. I have.

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

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

Reference Example 1 Nn-butylaniline (4 equivalents), pentamethylene dibromide (1 equivalent) and sodium carbonate (4 equivalents) were charged into a reactor and reacted at 100 to 140 ° C. for 4 hours. After the completion of the reaction, toluene is added to dissolve the organic substance, and the precipitated inorganic substance is removed. The obtained toluene solution was concentrated and purified by distillation to obtain bis (Nn-butylaniline) pentane.

A Vilsmeier reagent is prepared by dropwise addition of another dimethylformamide (15 eq) phosphorous oxychloride (4 eq).
The above bis (Nn-butylaniline) pentane (1 equivalent) dissolved in dimethylformamide was added dropwise at 85 ° C.
Incubate for 5 hours. After completion of the reaction, sodium acetate, water and ethyl acetate were added, the ethyl acetate layer was separated, and the solution was concentrated and purified by column to obtain a bisformyl compound.

The above bisformyl compound (1 equivalent), malononitrile (3 equivalents) and ethanol are charged into a reactor, and then piperidine (0.2 equivalent) is added dropwise, and the mixture is reacted under reflux for 1.5 hours. After completion of the reaction, the mixture was cooled, and the precipitated crystals were filtered and purified by column to obtain the dye (No. 9) shown in Table 1 above.

Reference Examples 2 to 32 The raw materials corresponding to the dyes of Tables Nos. 1 to 8 and 10 to 32 were used, and other than that of Table 1
The dyes described in o.1 to 8 and 10 to 32 were obtained.

Example To prepare an ink composition for forming a dye carrying layer having the following composition,
A 6 μm-thick polyethylene terephthalate film having a heat-treated rear surface was coated and dried so that the dry coating amount was 1.0 g / m ² , to obtain a thermal transfer sheet of the present invention.

Dye in 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 or the like was appropriately used as a solvent.

Next, as a base sheet, synthetic paper (Oji Yuka, YUPO FP
G♯150), a coating liquid having the following composition was applied to one surface of the coating at a rate of 10.0 g / m ² when dried, and dried at 100 ° C. for 30 minutes to obtain a transfer-receiving material.

Polyester resin (Vylon 200, manufactured by Toyobo) 11.5 parts Vinyl chloride / vinyl acetate copolymer (VYHH, manufactured by UCC) 5.0 parts Amino-modified silicone (KF-393, manufactured by Shin-Etsu Chemical) 1.2 parts Epoxy-modified series cone (X-22-) 343, manufactured by 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 are
The respective dye-carrying layers and the dye-receiving surface were superimposed on each other, and recording was performed with a thermal head from the back of the thermal transfer sheet under the conditions of a head applied voltage of 10 V and a printing time of 4.0 msec., And the results in Table 2 below were obtained. Was.

Comparative Examples 1 to 4 The dyes in Table 3 below were used in place of the dyes in Example 1, and the results in Table 3 below were obtained in the same manner as in Example 1 except for the following.

The color density described above is a value measured with a densitometer RD-918 manufactured by Macbeth Corporation in the United States.

The shelf life was slightly sharp when the recorded image was left in an atmosphere of 70 ° C for 48 hours and the sharpness of the image did not change and the white paper was not colored even if the surface was rubbed with white paper. When the white paper was lost and the white paper was slightly colored, the result was indicated by ○, when the sharpness was lost, and the white paper was colored was indicated by △, and when the image was unclear and the white paper was significantly colored, the result was indicated by ×.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-292371 (JP, A) JP-A-3-86591 (JP, A) JP-A-3-86592 (JP, A) JP-A-3-292 297691 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/38-5/40 CA (STN) REGISTRY (STN)

Claims (3)

(57) [Claims] 1. A dye comprising a substrate sheet and a dye-carrying layer formed on one surface of the substrate sheet, wherein the dye contained in the dye-carrying layer is a dye represented by the following general formula (I). A thermal transfer sheet, characterized in that: (R ₁ and R ₂ in the above formula are the same or different hydrogen atoms, substituted or unsubstituted alkyl groups, cycloalkyl groups, aralkyl groups, aryl groups or R ₃ or R ₄ together with a 5-membered ring or 6
R ₃ and R ₄ are the same or different hydrogen atoms, halogen atoms, cyano groups, substituted or unsubstituted alkyl groups, cycloalkyl groups, alkoxy groups, aryl groups, aralkyl groups, , an acylamino group, a sulfonylamino group, a ureido group, a carbamoyl group, a sulfamoyl group, an acyl group, an amino group, a ₁ and a ₂ represent the same or different electron-withdrawing groups, whereas one of a ¹ and a ₂ May be an aryl group. Z represents a methine group or a nitrogen atom, Y represents a divalent linking group, and m and n represent an integer of 1 to 3. ) 2. The thermal transfer sheet according to claim 1, wherein the dye has a molecular weight of 400 or more. 3. R ₁ and R ₂ are an alkyl group having 1 to 6 carbon atoms, R ₃ and R ₄ are a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and A ₁ and A ₂ are a cyano group. Or Y is an alkoxycarbonyl group or alkylaminocarbonyl group having 1 to 6 carbon atoms, and Y has 2 to 10 carbon atoms which may contain a different atom.
The thermal transfer sheet according to claim 1, which is an alkylene group of the formula (1).