JPH0532073A - Thermal transfer sheet for multi-printing - Google Patents

Abstract

PURPOSE:To provide the above thermal transfer sheet capable of multi-printing. CONSTITUTION:The subject thermal transfer sheet for multi-printing is provided as follows; a first ink layer consisting of a binder having wax as a main component and a colorant is provided on one side surface of a base film: a second ink layer consisting of thermoplastic resin and the colorant is provided further thereon: a transfer control layer consisting of thermoplastic resin which does not contain the colorant is provided furthermore onto its surface.

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 capable of printing many times in the same area.

[0002]

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

[0003]

The greatest drawback of the above-mentioned thermal transfer sheet is that it can print only once in the same area of the thermal transfer sheet, which is very uneconomical. That is, in the case of a type ink ribbon in which a cloth tape which has been conventionally used is impregnated with ink, it is possible to perform printing more than once in the same area, whereas in the case of a thermal transfer sheet, it is possible to print once. Since the ink layer in the printed portion is entirely transferred by printing, printing cannot be performed twice or more at the same location, and the base material sheet used as the thermal transfer sheet becomes disposable once. In addition, the amount of ink actually transferred to the material to be transferred is a few% of the total amount of the thermal transfer sheet, and at most a dozen%.
Most other inks are discarded without being used. Therefore, an object of the present invention is to solve the above-mentioned drawbacks and to provide a thermal transfer sheet capable of printing many times.

[0004]

The above object can be achieved by the present invention described below. That is, the present invention provides a first ink layer composed of a binder composed mainly of wax and a colorant on one surface of a base film, and a second ink layer composed of a thermoplastic resin and a colorant formed on the first ink layer. A thermal transfer sheet for multi-use printing, comprising an ink layer and a transfer control layer made of a thermoplastic resin containing no colorant on the surface thereof.

[0005]

When the transferred layer has a three-layer structure and the outermost layer is the transfer control layer, printing can be performed many times. If the control layer does not exist, printing can be performed up to twice, but printing more than that will not result in practical density printing.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail with reference to the preferred embodiments. As the base film used in the present invention, the same base film as that used in the conventional thermal transfer sheet can be used as it is, and other films can also be used and are not particularly limited. Specific examples of the preferred base film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, ionomer and the like. , Such as plastic film, condenser paper, paraffin paper, non-woven fabric, etc.
Further, it may be a base film which is a composite of these. The thickness of the base film can be appropriately changed according to the material so that its strength and thermal conductivity are appropriate.
The thickness is preferably, for example, 2 to 25 μm.

In the present invention, when the adhesiveness between the substrate film and the first ink layer formed on the surface thereof is insufficient, it is preferable to form an adhesive layer (ink holding layer). When the material film and the first ink layer are well adhered to each other, the adhesive layer is not necessary. To form the adhesive layer, for example, polyvinyl acetate, ethylene-vinyl acetate copolymer, vinyl chloride-ethyl acetate copolymer, ethylene-acrylic acid ester copolymer, polybutene, petroleum resin, vinyl chloride resin, methacrylic resin Thermoplastic resins such as polyamide, polyamide, polyester, and high molecular weight polycaprolactone are used. The adhesive layer may have a small thickness, for example, 0.0
It may be about 5 to 5 μm. By providing this adhesive layer, the adhesiveness between the base film and the first ink layer is improved, and during printing, both the first ink layer and the second ink layer may be transferred in the first printing. Effectively prevented.

The first ink layer formed directly on the base film or on the adhesive layer contains a colorant and a vehicle as main components, and may further contain various additives as required. The colorant is preferably an organic or inorganic pigment or dye having good characteristics as a recording material, for example, a pigment having a sufficient coloring density and not fading due to light, heat, temperature or the like. Further, it may be a substance which is colorless when not heated but develops a color when heated, or a substance which develops a color when contacted with a substance applied to a transfer target. In addition to the colorants forming cyan, magenta, yellow and black, colorants of various other colors can be used. As the vehicle, a mixture containing wax as a main component and other wax and a drying oil, a resin, a mineral oil, a derivative of cellulose, a rubber or the like is used. Typical examples of waxes include microcrystalline wax, carnauba wax, and paraffin wax. In addition, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, spermaceti, squid wax,
Wool wax, shellac wax, candelilla wax,
Petrolactam, partially modified wax, fatty acid ester,
Various waxes such as fatty acid amides are used. Further, in order to impart good heat conductivity and melt transferability to the heat-meltable ink layer, a heat-conductive substance can be added to the heat-meltable ink. Such substances include carbonaceous substances such as carbon black, aluminum, copper, tin oxide, molybdenum disulfide and the like. The thickness of the first ink layer is preferably about 1 to 4 μm.

In the present invention, a second ink layer is further formed on the first ink layer made of the above material. This second ink layer is formed from a colorant and a thermoplastic resin. The colorant used is the same as that of the first ink layer. Examples of the thermoplastic resin include ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer (EEA), polyethylene, polystyrene, polypropylene, polybutene, petroleum resin, vinyl chloride resin, vinyl chloride. -Vinyl acetate copolymer, polyvinyl alcohol, vinylidene chloride resin, methacrylic resin, polyamide, polycarbonate, fluororesin, polyvinyl formal, polyvinyl butyral, acetyl cellulose, nitrocellulose, polyvinyl acetate, polyisobutylene, ethyl cellulose, polyacetal, polyester, Polycaprolactone or the like is used. Of these, a particularly preferable resin is polycaprolactone, and if the molecular weight is too high, foil breakage is insufficient, while if it is too low, transfer controllability is insufficient. A suitable molecular weight range is 6,000 to 20,0.
It is about 00. The thickness of the second ink layer is 2-10 μm
A degree is preferable.

In the present invention, a transfer control layer is provided on the surface of the second ink layer. This transfer control layer is formed from the same thermoplastic resin as that used for the second ink layer,
It is preferable to form the same thermoplastic resin as that used to form the second ink layer. In the most preferred embodiment, both the second ink layer and this transfer control layer have a molecular weight of 6,000.
It is formed from about 20,000 polycaprolactone. The thickness of the transfer control layer is preferably about 0.3 to 2.0 μm. As the method for forming each of the above layers, conventionally known hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating and many other known methods can be used, and also a method using an aqueous or non-aqueous emulsion can be adopted. Is. The total layer thickness is 10 to 20 μm, preferably 10 to 12 μm
Is.

When a material weak to heat is used for the base film, it is preferable to provide a layer for preventing sticking of the thermal head on the surface in contact with the thermal head. The sticking prevention layer contains a heat-resistant resin and a substance acting as a thermal release agent or a lubricant as basic constituent components. A resin having heat resistance has a glass transition point of 60.
Those obtained by adding a compound having two or more amino groups or a diisocyanate or triisocyanate to a synthetic resin having a temperature of not lower than ° C or a thermoplastic resin having an OH group or a COOH group to cause a slight crosslinking and curing are preferable. Thermal release agents or lubricants, such as amides, esters and salts of waxes and higher fatty acids, which act by melting by heating,
Some are useful as solids, such as powders of fluororesins and inorganic substances.

By providing such a sticking prevention layer, thermal printing can be performed without sticking even on a thermal transfer sheet having a plastic film, which is weak to heat, as a base material, and the plastic film has difficulty in cutting and processing. You can take advantage of ease of use.
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.

[0013]

EXAMPLES Next, the present invention will be described more specifically with reference to Examples and Comparative Examples. In addition, unless otherwise specified, "parts" and "%" in the text are based on weight. Example 1 A wax ink composition having the following composition was used in a sand mill,
It was prepared by mixing for 5 hours while heating to 100 ° C. Wax ink composition Carbon black (Dia Black, manufactured by Mitsubishi Kasei) 15 parts Ethylene / vinyl acetate copolymer (Evaflex 310, manufactured by Mitsui Polychemical) 8 parts Paraffin wax (paraffin 150 ° F, manufactured by Nippon Seiro Co., Ltd.) 50 parts Carnauba wax 25 parts The above ink composition was applied onto the surface of a polyethylene terephthalate film having a thickness of 6 μm by a hot melt roll coating method so that the dry weight was 4.5 g / m ² to form a first ink layer. Second ink composition Polycaprolactone H1 (manufactured by Daicel Chemical Industries) 25 parts Carbon black (Dia Black, manufactured by Mitsubishi Kasei) 5 parts Methyl ethyl ketone 70 parts The above composition is dried on the surface of the wax ink layer by a roll coating method to give a dry weight of 5 g / m. ^{A second} ink layer was formed by coating and drying so that the coating amount became ² . Next, a methyl ethyl ketone solution of polycaprolactone H1 (manufactured by Daicel Chemical Industries, Ltd.) was applied to the surface by a roll coating method in a dry coating amount of 1.0 g / m 2.
² is applied and dried to form a transfer control layer,
A thermal transfer sheet for multi-time printing of the present invention was obtained.

Example 2 A thermal transfer sheet for multi-printing of the present invention was obtained in the same manner as in Example 1 except that the second ink layer in Example 1 was formed from the following composition. Ink support layer : Polycaprolactone 240 (manufactured by Daicel Chemical Industries) 25 parts Carbon black (Diablack, manufactured by Mitsubishi Kasei) 5 parts Ethyl acetate 70 parts Example 3 In Example 1, between the base film and the first ink layer. High molecular weight polycaprolactone adhesive layer (thickness 0.5
The thermal transfer sheet for multi-printing of the present invention was obtained in the same manner as in Example 1 except that (1 μm) was provided. Comparative Example 1 A thermal transfer sheet of Comparative Example was obtained in the same manner as in Example 1 except that the formation of the second ink layer and the transfer control layer was omitted.

Example of Use Using the thermal transfer sheets of the above-mentioned Examples and Comparative Examples, printing was carried out a number of times at the same location under the following printing conditions, and the image density was measured to obtain the results shown in Table 1. Printing conditions Equipment used: Toshiba simulator equipped with a thin-film thermal head Printing energy: 0.4 mJ / dott (constant) Transfer material: Fine paper (made by Sanyo Kokusaku Pulp, KYP 46 edition 1)
25KG)

[Table 1]

[0016]

As described above, according to the present invention, there is provided a thermal transfer sheet for multi-use printing, which enables good printing with high density and small density difference.

Claims (4)

[Claims] 1. A first ink layer comprising a binder mainly containing wax and a colorant is provided on one surface of a base film, and a second ink comprising a thermoplastic resin and the colorant is further provided on the first ink layer. A thermal transfer sheet for multi-use printing, comprising a layer and a transfer control layer comprising a thermoplastic resin containing no colorant on the surface thereof. 2. The multi-use thermal transfer sheet according to claim 1, wherein the second ink layer and the control layer are made of the same thermoplastic resin. 3. The thermal transfer sheet for multi-printing according to claim 1, wherein the thermoplastic resin of the second ink layer and the thermoplastic resin of the transfer control layer are both polycaprolactone. 4. The thermal transfer sheet for multiple printing according to claim 1, wherein an adhesive layer is provided between the base film and the ink layer.