JPH0532074A - Thermal transfer sheet for multiple printing - Google Patents

Abstract

(57) [Summary] [Purpose] To provide a thermal transfer sheet capable of printing many times. [Structure] An ink layer composed of a binder mainly composed of polycaprolactone and a coloring agent is provided on one surface of a base film, and a coloring material composed not of a thermoplastic resin mainly composed of polycaprolactone is further formed on the surface thereof. A thermal transfer sheet for multi-use printing, comprising a control layer.

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 an ink layer composed of a binder mainly composed of polycaprolactone and a colorant on one surface of a base film, and further, a colorant composed of a thermoplastic resin mainly composed of polycaprolactone is provided on the surface thereof. A thermal transfer sheet for multi-use printing, comprising a transfer control layer not containing it.

[0005]

By forming the ink layer and the transfer control layer mainly with polycaprolactone, printing can be performed many times. If the control layer is not present, most of the ink layer is transferred by one printing, and printing more than that number does not result in practical density printing. Also, when the binder of the ink layer and the resin of the transfer control layer are not the same resin, it is also difficult to perform good multi-time 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 base film and the ink layer formed on the surface is insufficient, it is preferable to form an adhesive layer (ink holding layer). The above-mentioned adhesive layer is not necessary when it adheres well to the ink layer. 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, polyester, and high molecular weight polycaprolactone are used. The thickness of the adhesive layer may be slight, for example, about 0.05 to 5 μm. By providing this adhesive layer, the adhesiveness between the base film and the ink layer is improved, and it is possible to effectively prevent the entire ink layer from being transferred by the first printing.

The ink layer formed directly on the base film or on the adhesive layer may contain a colorant and a binder 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. Cyan, magenta,
In addition to the colorants forming yellow and black, colorants of various other colors can also be used. As the binder, polycaprolactone is mainly used, and other resins for the adhesive layer can be mixed and used,
It is necessary that the amount of the other adhesive resin used in combination is equal to or less than that of the polycaprolactone, and if there are many other resins used in combination, it becomes difficult to print many times. A preferable combined ratio of this adhesive resin is about 0.3 to 5% by weight of polycaprolactone.
In addition, other binders, such as wax, may be contained as long as they do not interfere with the object of the present invention. The thickness of the ink layer is 8
It is preferably about 16 μm.

In the present invention, a transfer control layer is provided on the surface of the ink layer. This transfer control layer is preferably formed from a thermoplastic resin containing the same or the same composition as polycaprolactone used in the ink layer. In the most preferred embodiment, both the ink layer and this transfer control layer are formed from polycaprolactone having a molecular weight of about 6,000 to 20,000. The thickness of the transfer control layer is preferably about 0.3 to 2.0 μm. As a 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 1
2 μm.

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 a 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.

[0012]

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 polycaprolactone ink composition having the following composition was prepared by mixing with a sand mill while heating to 50 ° C. for 5 hours. Polycaprolactone ink : Polycaprolactone H1 (manufactured by Daicel Chemical Industries) 80 parts Polycaprolactone H4 (manufactured by Daicel Chemical Industries) 10 parts Carbon black 10 parts Methyl ethyl ketone 400 parts 12 g /
An ink layer was formed by coating so that the ink layer had a thickness of m ² . Next, a methyl ethyl ketone solution of polycaprolactone H1 (manufactured by Daicel Chemical Industries, Ltd.) is applied to the surface of the ink layer by a roll coating method so as to have a dry coating amount of 1.0 g / m ² 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 polycaprolactone ink composition having the following composition was prepared by mixing with a sand mill for 5 hours while heating at 50 ° C. Polycaprolactone ink : Polycaprolactone H1 (manufactured by Daicel Chemical) 60 parts Polycaprolactone 240 (manufactured by Daicel Chemical) 40 parts Ethylene / vinyl acetate copolymer 10 parts Carbon black 11 parts Methyl ethyl ketone 400 parts Thickness of the above composition is 6 μm by roll coating method 12 g / dry weight on the surface of polyethylene terephthalate film
An ink layer was formed by coating so that the ink layer had a thickness of m ² . Then, a methyl ethyl ketone solution of polycaprolactone H1 (manufactured by Daicel Chemical Industries, Ltd.) is applied to the surface of the ink layer by a roll coating method so as to have a dry coating amount of 0.7 g / m ² and dried to form a transfer control layer. A thermal transfer sheet for multi-time printing of the present invention was obtained.

Example 3 Multiple printing of the present invention was carried out in the same manner as in Example 1 except that a high molecular weight polycaprolactone adhesive layer (thickness 1 μm) was provided between the substrate film and the ink layer in Example 1. A thermal transfer sheet for use was obtained. 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 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: 0.8 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. An ink layer comprising a binder mainly composed of polycaprolactone and a colorant is provided on one surface of a base film, and the surface further comprises a colorant composed of a thermoplastic resin mainly composed of polycaprolactone. A thermal transfer sheet for multi-use printing, comprising a non-transfer control layer. 2. The thermal transfer sheet for multi-printing according to claim 1, wherein the binder of the ink layer and the resin of the control layer are the same. 3. The thermal transfer sheet for multi-printing according to claim 1, wherein an adhesive layer is provided between the base film and the ink layer. 4. The molecular weight of polycaprolactone is 6,000.
The thermal transfer sheet for multiple printing according to claim 1, wherein the thermal transfer sheet has a range of 0 to 20,000.