JPH05246148A - Heat transfer sheet and method for forming image - Google Patents

Abstract

PURPOSE:To provide a heat transfer sheet which can form an image with excellent adhesiveness to an object for transfer, wear resistance, heat resistance etc., and furthermore, with excellent quality of printing and a method for forming the image. CONSTITUTION:A heat transfer sheet characterized by a sheet wherein a transfer ink layer 4 is formed on one face of a base film 1 and an acrylic resin with a Tg of 50-105 deg.C and a mol.wt. of at least 60,000 is incorporated in a binder of the ink layer 4 and a method for forming of an image characterized by a method wherein a heat transfer sheet is laminated on an objective material to be transferred and transfer is performed by applying heat from the rear face of the heat transfer sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer sheet, and more particularly to a thermal transfer sheet and an image forming method capable of forming an image having excellent adhesion to a transfer material, abrasion resistance and heat resistance.

[0002]

2. Description of the Related Art Conventionally, when printing an output print of a computer or a word processor by a thermal transfer method, a thermal transfer sheet having a thermal transfer ink layer provided on one surface of a base film is used. The above-mentioned conventional thermal transfer sheet is a substrate film having a thickness of 10 to 20 μm, such as condenser paper or paraffin paper, or a thickness of 3 to 20 μm.
It is manufactured by coating a thermal transfer ink layer in which a colorant such as a pigment or a dye is mixed with wax by using a plastic film such as polyester or cellophane of m.

[0003]

One of the drawbacks of the above thermal transfer sheet is that the transfer ink layer has a low softening point and is formed of a relatively soft wax, so that the transferred image has abrasion resistance and heat resistance. Inferior properties and the like, rubbing against other objects deteriorates the image and deteriorates the printing quality, and also contaminates the blank area and other objects.
Such a drawback is that when the thermal transfer method is used for printing a barcode label or a tag label, the product is exposed to a relatively high temperature, the surface of the product is touched, and particularly the product is rubbed by a barcode scanner or the like. And the print is easily broken,
In addition, it causes a serious problem of contaminating the blank area and making it unreadable. Such a problem occurs not only when printing a barcode label or a tag label but also when it is used for printing a prepaid card, a boarding ticket, a commuter ticket, various admission tickets, or the like. Such a problem can be easily solved by laminating a transparent plastic film on the printing surface, but such laminating is complicated and costly, and cannot be adopted at all for simple applications. Therefore, the object of the present invention is to solve the above-mentioned drawbacks, and to improve the adhesion to a transfer material,
An object of the present invention is to provide a thermal transfer sheet and an image forming method capable of forming an image having excellent abrasion resistance, heat resistance, and the like, and also excellent printing quality.

[0004]

The above object can be achieved by the present invention described below. That is, the present invention is a thermal transfer sheet characterized in that a transfer ink layer is formed on one surface of a substrate film, and the binder of the ink layer contains an acrylic resin having a Tg of 50 to 105 ° C. and a molecular weight of 60,000 or more. ,
Also, the image forming method is characterized in that the heat transfer sheet is superposed on the transfer material, and heat is applied from the back surface of the heat transfer sheet.

[0005]

By using a specific acrylic resin as at least a part of the binder of the ink layer and, if necessary, further providing a peeling layer between the base film and the ink layer, the transfer material Printing that is excellent in adhesion, abrasion resistance, heat resistance, etc. becomes possible. Further, by forming an acrylic resin layer of the same kind as described above on the image forming surface of the transfer material, it becomes possible to perform printing with further excellent adhesion to the transfer material, abrasion resistance, heat resistance and the like.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail with reference to the preferred embodiments. The thermal transfer sheet of the present invention is the first
As shown in the drawing, a release layer 2, a protective layer 3 and a transfer ink layer 4 are sequentially formed on one surface of a substrate film 1 if necessary, and a heat resistant slipping layer is further formed on the back surface thereof as needed. 5 is provided. Base film 1 used in the present invention
As, the same base film 1 as that used in the conventional thermal transfer sheet can be used as it is,
Others can be used and are not particularly limited. Specific examples of the preferable base film 1 include polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, ionomer. Such as plastic film, condenser paper, paper such as paraffin paper, non-woven fabric, etc.
Further, it may be a base film in which these are combined. The thickness of the base film 1 can be appropriately changed according to the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably 2 to 25 μm, for example.

In the present invention, first, a release layer 2 is formed on the surface of the base film 1 as needed. The release layer 2 is made of, for example, acrylic resin, silicone resin,
Fluorine resin, silicone, or various resins modified with fluorine can be used, and particularly preferable ones are various waxes which exhibit releasability by melting during printing. Suitable waxes include, for example, microcrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsch wax, oxidized polyethylene wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ivowa wax, wool wax, shellac wax. , Candelilla wax, petrolactam, partially modified wax, fatty acid ester, fatty acid amide and the like. The release layer 2 is a thin layer, such as 0.1, so as not to reduce the sensitivity of the thermal transfer sheet.
The thickness is preferably about 2 μm. Such a peeling layer 2 peels at the interface with the base film 1 or breaks in its own layer and is transferred onto the protective layer 3 to impart slipperiness to the protective layer. A material having slipperiness and a certain degree of hardness, for example, a needle penetration of 20 to 150 ° C is 1
It is preferably formed from a material of 0 or less.

The protective layer 3, which is formed on the peeling layer 2 if necessary, is transferred together with the ink layer 4 at the time of thermal transfer and covers the surface of the transferred image, and this layer itself serves as the base film 1. When the peelability is good, the protective layer 3
May also serve as the release layer 2. The protective layer 3 is formed of a resin that forms a tough coating such as heat resistance and abrasion resistance, such as acrylic resin, polyurethane resin, copolymer resin of acrylic monomer and other monomer, polyester resin, polyamide resin, and the like. However, the film made of these resins naturally does not have good film breakage during printing. Therefore, according to the present invention, a thin layer such as 0.1
It is desirable to form it to a thickness of about 1.5 μm. Furthermore, in order to improve film cutting, silica, alumina, clay,
It is preferable to form a protective layer by adding a fine extender pigment such as calcium carbonate. The release layer and the protective layer as described above are not essential requirements of the present invention. For example, when the release property of the base film is good, or when a relatively large amount of the specific acrylic resin is used for forming the ink layer. In some cases it is not absolutely necessary.

An ink layer 4 is formed on the above-mentioned substrate film 1 directly or through a peeling layer 2 or a protective layer 3 from an ink containing necessary materials. The thermal transfer ink layer 4 in the thermal transfer sheet of the present invention comprises a colorant and a binder, and may further contain various additives if necessary. As the colorant, an organic or inorganic pigment or dye having good characteristics as a recording material,
For example, those having a sufficient coloring density and not discolored by light, heat, temperature, etc. are preferable. Black pigments are preferred, but pigments such as cyan, magenta and yellow can also be used. As a binder, Tg50 to 105
Other resins or waxes can be used in combination as long as the acrylic resin having a molecular weight of 60,000 or more and a content of 30% by weight or more is contained. If the amount used is less than 30% by weight, various printing durability is insufficient, and if the Tg is less than 50 ° C, various printing durability is insufficient. On the other hand, if the temperature exceeds 105 ° C, the cuttability of the foil deteriorates. If the molecular weight is less than 60,000, the printing durability is similarly insufficient.

The above-mentioned wax may be used as the binder which may be used in combination, but the preferred one is a thermoplastic resin having a relatively low softening point. Preferable thermoplastic resins include ethylene-vinyl acetate copolymer, ethylene-acrylic acid ester copolymer, polybutene, petroleum resin, vinyl chloride-vinyl acetate copolymer, polyester resin, polyvinyl acetate and the like. It is preferable that these binders have a softening point in the range of 100 ° C. to 200 ° C. If the softening point is less than 100 ° C., stains are not sufficient, while if it exceeds 200 ° C., the printing sensitivity decreases. The thickness of the ink layer 4 to be formed should be determined so that the required density and thermal sensitivity can be balanced, for example, 0.5 to 5 μm.
A thickness of about m is common. Release layer 2 and protective layer 3
As a method for forming the ink layer 4, in addition to hot melt coating, hot lacquer coating, gravure coating,
Gravure reverse coating, roll coating and many other means can be mentioned. In particular, the ink layer is preferably formed by an emulsion method. In the present invention, a sealing layer (not shown) may be further formed on the surface of the ink layer 4 so that the transfer material having a rough surface can be printed.

When a material weak to heat is used as the base film 1, a heat resistant slipping layer 5 is provided on the surface in contact with the thermal head to improve the slipperiness of the thermal head and prevent sticking. preferable. The heat resistant slipping layer 5 contains a heat resistant resin and a substance acting as a thermal release agent or a lubricant as basic constituent components. By providing such a heat resistant slipping layer 5, thermal printing can be performed without sticking on a thermal transfer sheet using a plastic film, which is weak against heat, as a base material. The advantages such as ease of use can be used. Needless to say, the present invention can be applied to a thermal transfer sheet for color printing, so that a multicolor thermal transfer sheet is also included in the scope of the present invention. Further, the thermal transfer printer can be applied to either a line type or a serial type. The thermal transfer sheet of the present invention as described above can give good printing to any transfer material.

The image forming method of the present invention is an image forming method in which the thermal transfer sheet of the present invention is superposed on a transfer material and heat is applied from the back surface of the thermal transfer sheet. A transfer material having at least an image forming surface on which a layer containing an acrylic resin having a Tg of 50 to 105 ° C. and a molecular weight of 60,000 or more is formed as a transfer material, for example, various cards such as a prepaid card are used as the transfer material. I am trying. The transferred material itself may be formed of the above specific acrylic resin, or other transferred material such as paper, synthetic paper, other synthetic resin film, sheet, card or the like may have the above specific acrylic resin on its surface. An ink receiving layer made of resin may be provided. As the image forming method itself, an ordinary thermal printer or bar code printer is optionally used.

[0013]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, “part” or “%” is based on weight unless otherwise specified. Example 1 Carnauba wax was heated at a temperature of 100 ° C., and the surface of a 6.0 μm-thick polyester film (trade name “Lumirror” manufactured by Toray) having a heat resistant slipping layer formed on the back surface by a roll coating method using hot melt Coating amount is about 0.5g / m
^It was applied so that it would be ² to form a release layer. Next, an ink composition having the following composition was applied by emulsion coating at a coating amount of 0.7 g / m ² and dried to form an ink layer to obtain a thermal transfer sheet of the present invention. Ink composition for ink layer : Acrylic resin (BR-107, manufactured by Mitsubishi Rayon, Tg 50 ° C., molecular weight 60,000) 20 parts Carbon black 10 parts

Example 2 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the ink layer in Example 1 was formed from the following ink composition. Composition for transfer ink layer (coating amount 0.7 g / m ² ) Acrylic resin (BR-50, Tg 100 ° C., molecular weight 65,000) 20 parts Carbon black 10 parts Example 3 The ink layer in Example 1 was prepared using the following ink composition. A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the thermal transfer sheet was formed from. Composition for transfer ink layer (coating amount 0.7 g / m ² ) Acrylic resin (BR-95, Tg 80 ° C., molecular weight 320,000) 20 parts Carbon black 10 parts

Comparative Example 1 A thermal transfer sheet of Comparative Example was obtained in the same manner as in Example 1 except that the ink layer was formed from the following ink composition in Example 1. Composition for transfer ink layer (coating amount 0.7 g / m ² ) Polyester resin (MD-1200, Toyobo, softening point 165 ° C.) 20 parts Carnauba wax 10 parts Carbon black 15 parts Comparative Example 2 The ink layer was prepared in Example 1. A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that it was formed from the following ink composition. Composition for transfer ink layer (coating amount 0.7 g / m ² ) Polyester resin (MD-1200, manufactured by Toyobo, softening point 165 ° C.) 20 parts Oxidized polyethylene wax (melting point 110 ° C.) 10 parts Carbon black 15 parts Comparative Example 3 Implementation A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that the ink layer was formed from the following ink composition in Example 1. Transfer ink layer composition (coating amount 0.7 g / m ² ) acrylic resin (BR-113, Tg 75 ° C., molecular weight 30,000) 20 parts Carbon black 10 parts

Use Example 1 Using the thermal transfer sheets of Examples 1 to 3 and Comparative Examples 1 to 3 above, printing was carried out under the following printing conditions, and the adhesion to the material to be transferred, abrasion resistance and print quality were improved. Evaluation was made and the results shown in Table 1 below were obtained. Printing conditions Equipment: Simulator equipped with Mitsubishi thin-film thermal head Printing voltage: Constant (18V) Transfer material: (1) Back side of prepaid card (vinyl chloride / vinyl acetate copolymer silver ink coating and drying surface) ( 2) Acrylic resin (Tg50 ° C, molecular weight 60,000)
0) 10% methyl ethyl ketone / toluene (1: 1)
Polyvinyl chloride resin sheet coated with a solution and dried to provide an ink receiving layer

[0017]

[Table 1] Evaluation Criteria (1) Cellotape Peelability: Adhesion of print when a cellophane tape is attached to a printed matter and peeled off in the 180 ° direction. ◯: No change X: Printed matter peeled off (2) Friction resistance: ^{2 at} a load of 500 g / m ² and pencil height H
Rubbed 0 times. ◯: Good x: Bad (3) Print quality: Visually check for print defects. ◯: No chipping was observed ×: Chipping was observed

[0018]

According to the present invention as described above, at least a part of the binder of the ink layer is made of a specific acrylic resin, and if necessary, a release layer is further provided between the base film and the ink layer. By providing it, it becomes possible to perform printing with excellent adhesion to the material to be transferred, abrasion resistance, heat resistance and the like.
Further, by forming an acrylic resin layer of the same type as described above on the image forming surface of the transfer material, the adhesion to the transfer material,
Printing with more excellent abrasion resistance, heat resistance, etc. becomes possible.

[0019]

[Brief description of drawings]

FIG. 1 is a diagram schematically illustrating a cross section of a thermal transfer sheet of the present invention.

[Explanation of symbols]

 1: Base film 2: Release layer 3: Protective layer 4: Ink layer 5: Heat resistant slipping layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Keiji Hirose 1-1-1, Ichigayaka-cho, Shinjuku-ku, Tokyo Dai Nippon Printing Co., Ltd.

Claims (4)

[Claims] 1. A transfer ink layer is formed on one surface of a base film, and the binder of the ink layer is Tg50.
A thermal transfer sheet comprising an acrylic resin having a molecular weight of 60,000 or more at ˜105 ° C. 2. The thermal transfer sheet according to claim 1, wherein a release layer and / or a protective layer are provided between the base film and the ink layer. 3. An image forming method comprising: superposing the thermal transfer sheet according to claim 1 on a transfer target material and applying heat from the back surface of the thermal transfer sheet. 4. The Tg is formed on at least the image forming surface of the transfer material.
The image forming method according to claim 3, wherein a layer containing an acrylic resin having a molecular weight of 60,000 or more at 50 to 105 ° C. is formed.