JPH09267570A - Heat transfer sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide printing with excellent heat resistance and durability such as abrasion resistance by constituting a release layer and/or a protective layer with a compsn. contg. a heat-unfusible resin. SOLUTION: A heat transfer sheet 1 is constituted of at least a base material sheet 2, a release layer 3, a protective layer 6 and a hot-melt ink layer 4 and in this case, the release layer 3 and/or the protective layer 6 are constituted of a compsn. contg. a heat-unfusible resin. The heat-unfusible resin is dissolved in a solvent or emulsified to form a film but after the film is formed, it is not melted by heat and chlorinated polypropylene is used. When the release layer 3 is formed of the heat-unfusible resin, it is obtd. by coating the base material sheet 2 with a coating contg. the heat-unfusible resin by means of a gravure coating, etc., and by heating and drying it. In addition, it is pref. that as the hot-melt ink layer 4, a polyester resin with a glass transition temp. Tg of at least 60 deg.C is used as a binder.

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 suitable for bar code printing.

[0002]

2. Description of the Related Art Conventionally, when an output print of a computer, a word processor or the like is printed by a thermal transfer method, a thermal transfer sheet having a heat-fusible ink layer provided on one side of a substrate sheet is often used. These conventional thermal transfer sheets are used as base material sheets such as condenser paper or paraffin paper having a thickness of about 10 to 20 μm or a thickness of 3 to 3 μm.
A plastic film such as polyester or cellophane having a thickness of about 20 μm is used, and a hot-melt ink containing a colorant such as a pigment or a dye mixed with wax is applied on the base sheet to form a hot-melt ink layer. . Then, from the back side of the base material sheet, a predetermined position is heated and pressed by a thermal head, and the heat-meltable ink layer at the position corresponding to the printed portion of the heat-meltable ink layer is transferred to the transfer material to perform printing. Be seen.

These known thermal transfer sheets are image-wise heated from the back side by a thermal head to melt the transfer ink layer and form an image on a transfer material by the adhesiveness of the ink layer generated at that time. Therefore, the ink layer is naturally formed of a material having a low melting point. Therefore, the transferred image has low abrasion resistance, solvent resistance, heat resistance, etc., and the image easily wears, peels off, or draws lines due to friction to contaminate the white background around the printed area. There's a problem.

Such a problem is a serious problem in a field requiring excellent durability such as abrasion resistance, solvent resistance and heat resistance such as a tag label such as a price tag and a size and a bar code label. . For example, conventional bar codes by thermal transfer cannot be used in places where there are many opportunities for products to come into contact with each other, mechanical oil is present, or high temperatures are likely to occur, such as in automobile factories and other mechanical parts manufacturing plants. Therefore, it is an object of the present invention to provide a thermal transfer sheet which solves the problems of the prior art as described above and provides printing having excellent durability such as heat resistance and abrasion resistance.

[0005]

The above objects are achieved by the present invention described below. That is, the present invention is a thermal transfer sheet in which a release layer, a protective layer and a heat transferable ink layer are sequentially provided on at least one side of a base material sheet, and the release layer and / or the protective layer are composed of a composition containing a resin that is not melted by heat. The thermal transfer sheet is characterized in that

By providing the release layer and / or the protective layer of the thermal transfer sheet with a composition containing a resin which is not melted by heat, a thermal transfer sheet which provides printing having excellent durability such as heat resistance and abrasion resistance is provided. You can

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to the preferred embodiments shown in the drawings. FIG. 1 is a view showing a vertical section of a thermal transfer sheet according to an embodiment of the present invention. The thermal transfer sheet 1 of the present invention is characterized by comprising at least a base sheet 2, a release layer 3, and a heat-meltable ink layer 4, and the release layer is made of a composition containing a resin that is not melted by heat. In this case, the ink layer 4 has a Tg of 60 ° C.
It is preferable for the purpose of the present invention to form the above polyester resin as a binder. FIG. 2 is a view showing a vertical section of a thermal transfer sheet according to another embodiment of the present invention,
The thermal transfer sheet 1 is composed of at least a base sheet 2, a release layer 3, a heat-fusible ink layer 4, and a back layer 5 formed on the back side of the base sheet 2. The formation of the release layer and the ink layer in this case is the same as in the case of FIG.

FIG. 3 is a view showing a longitudinal section of a thermal transfer sheet according to another embodiment of the present invention. This thermal transfer sheet 1 includes at least a base sheet 2, a release layer 3, a protective layer 6, and a heat-meltable ink layer. 4 and. In this case, the peeling layer and / or the protective layer are formed of a composition containing a resin that is not melted by heat. In this case, it is preferable that the ink layer 4 is formed by using a polyester resin having Tg of 60 ° C. or more as a binder. However, since the protective layer has a function of protecting the ink layer after transfer, the ink layer is formed of a usual wax or thermoplastic resin. Alternatively, a mixture thereof may be formed as a binder. The back layer 5 may be formed as in the case of FIG.

As the base material sheet 2 of the thermal transfer sheet 1 of the present invention, the same base material sheet as that used in the conventionally known thermal transfer sheet can be used as it is, and other materials can also be used. , Not particularly limited. Specific examples of the preferable substrate sheet include, for example,
Polyester, polypropylene, cellophane, cellulose acetate, polycarbonate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesins, chlorinated rubber, plastic films such as ionomers, condenser paper, paraffin paper, etc. There are papers, non-woven fabrics, etc.
Further, it may be a base sheet which is a composite of any of these. The thickness of the base sheet 2 may be appropriately selected depending on the material used so that the strength and thermal conductivity are appropriate, and for example, a thickness of about 2 to 25 μm is preferable.

Further, as illustrated in FIG. 2, a back layer 5 may be provided on the back surface of the base material sheet 2 for the purpose of improving sliding with the thermal head and preventing thermal fusion of the thermal head. Is. The back surface layer 5 has a heat-resistant resin such as a conventionally known melamine resin, a heat release agent such as a silicone resin and a fluororesin, a substance acting as a lubricant, and the like as basic constituent components. By providing such a back layer, it becomes possible to use a resin film which is relatively weak against heat as a base sheet.

The resin that does not melt by the heat of forming the peeling layer 3 and / or the protective layer 4 can be dissolved in a solvent or emulsified to form a film, but after the film is formed, heat is applied. Resins that do not melt in, and specific materials include chlorinated polypropylene, acrylic resin, and the like, and thermosetting resins, resins that are crosslinked and cured by a crosslinking agent, such as acrylic polyol and phenolic resin. To be It is particularly effective to use chlorinated polypropylene for the release layer. These resins which are not melted by heat may be used alone, but for the purpose of improving the adhesiveness to polyethylene terephthalate film, adjusting the coating property of the print, etc., such as ethylene / vinyl acetate copolymer, etc. Thermoplastic resins and waxes can be used together.

Further, the release layer 3 is provided with a carbonaceous substance such as carbon black, a heat conducting substance such as a metal powder, a conductive substance, or a heat melting substance in order to provide good heat conducting property and antistatic property. The colorant to be incorporated in the volatile ink layer can be incorporated in the release layer 3. The thickness of the peeling layer 3 is preferably about 0.2 to 2 μm, and if the thickness is less than 0.2 μm, the performance as the peeling layer cannot be sufficiently obtained. On the other hand, if it exceeds 2 μm, the thermal head and the heat-fusible ink layer are formed during printing. Is too large, and a large amount of printing energy is required, which is not preferable.

When such a peeling layer 3 is formed from a resin which is not melted by heat, a coating solution containing a resin which is not melted by heat is applied to a base sheet by a known coating method such as gravure coating or gravure coating. Apply by a method such as reverse coating,
Obtained by heating and drying. When a thermoplastic resin or wax is used as a component of the release layer 3, the release layer 3 can be formed as a uniform coating film by drying at a temperature equal to or higher than the melting point of the thermoplastic resin or wax. .

Further, as shown in FIG. 3, a layer 6 serving as a protective layer for a printed image after transfer is provided between the release layer 3 and the ink layer 4.
Can be provided. The protective layer 6 is transferred together with the ink layer 4 during thermal transfer and covers the surface of the transferred image. This protective layer 6 is made of acrylic resin, polyurethane resin, copolymer resin of acrylic monomer and other monomer,
Heat resistance, such as polyester resin and polyamide resin,
It can be formed of a resin that forms a tough coating such as abrasion resistance, but if the release layer 3 is not formed of a resin that does not melt by heat, it may be formed of a resin that does not melt by heat as described above. preferable. The protective layer 6 made of a composition containing these resins naturally does not have good film breakage during printing. Therefore, a thin layer, such as
It is desirable to form it to a thickness of about 0.1 to 1.5 μm. Further, in order to improve film breakage, it is preferable to form a protective layer 6 by adding a fine extender pigment such as silica, alumina, clay or calcium carbonate.

When the heat-fusible ink layer 4 is not provided with a protective layer as shown in FIG. 1, a polyester resin having a Tg of 60 ° C. or more is used as a binder in order to secure various durability of the printed matter. It is preferable. As such a polyester resin, for example, one obtained from Toyobo Co. under the trade name Byron 200 is preferably used.
Of course, when a protective layer is provided as shown in FIG. 3, by using the polyester resin as a binder for the ink layer as described above, it is possible to perform printing with further excellent durability. However, when the protective layer is provided, usual waxes, thermoplastic resins, or a mixture thereof can also be used as the binder of the ink layer.

Examples of the wax component used as the binder include waxes such as carnauba wax, paraffin wax, microcrystalline wax, rice wax, and polyethylene wax.
In particular, a wax having a melting point of 60 to 90 ° C. is preferably used. Further, if necessary, the waxes may be added with resins such as acrylic resin, styrene-acrylic resin, and various additives. Acrylic resins and styrene-acrylic resins can impart excellent scratch resistance to printed matter.

The colorant may be appropriately selected from known organic or inorganic pigments or dyes. For example, in the case of bar code printing, the colorant has a sufficient black density, Those that do not discolor or fade due to heat or the like are preferable.
Examples of such a colorant include carbon black such as lamp black, graphite, and nigrosine dye. When color printing is required, other chromatic dyes or pigments are required. Further, a carbonaceous substance such as carbon black or a heat conductive or conductive substance such as metal powder may be blended in order to provide good heat conductivity and antistatic property in a range where the melt viscosity is not significantly increased.

When waxes are used as a binder when forming the heat-meltable ink layer 4, first, a coloring agent is added to the wax emulsion, and if necessary, a resin emulsion or resin such as acrylic resin, styrene-acrylic resin, or the like. Add an additive to the dispersion, to obtain a coating liquid for hot-melt ink, and apply the coating liquid by a known method such as gravure coating or gravure reverse coating on the release layer previously provided on the base material sheet, It is carried out by drying at a temperature below the melting point of the wax. Thus, by using the wax emulsion as the wax component and setting the drying temperature of the coating film to a temperature equal to or lower than the melting point of the wax, the wax particles dispersed in the wax emulsion in the formed hot-melt ink layer are removed. It becomes possible to exist while maintaining the state of fine particles. Therefore, during printing, film breakage occurs between the fine particles relatively easily, which contributes to improving the foil cutting property of the heat-meltable ink layer.

When the above polyester resin is used as the binder, an emulsion of the polyester resin can be prepared in the same manner as above, and the ink layer can be formed in the same manner. Further, a polyester resin, a colorant and other components are dissolved / dispersed in an appropriate solvent to prepare a coating liquid, and an ink layer can be similarly formed.
The thickness of the heat-meltable ink layer 4 is preferably about 0.5 to 4 μm. If it is less than 0.5 μm, the printing density is low, and if it exceeds 4 μm, a large amount of printing energy is required, which is not preferable.

In another embodiment of the present invention, a heat-sensitive adhesive layer (negative shown) can be formed on the surface of the ink layer 2. By forming the adhesive layer on the surface of the ink layer in advance, good transferability can be obtained with respect to any transfer material having low adhesiveness. The heat-sensitive adhesive layer is a thermoplastic resin that softens and exhibits adhesiveness at a temperature of about 50 to 200 ° C., for example, ethylene-vinyl acetate copolymer (EVA), ethylene-acrylic acid ester copolymer ( EEA), polyester resin and the like. The layer composed of these heat-sensitive adhesives can be formed by hot-melt coating the above-mentioned adhesive resin or by coating and drying a coating solution prepared by dissolving or dispersing it in a suitable organic solvent or water, and a preferable thickness is 1 It is about 20 μm. These heat-sensitive adhesive layers may be transparent or colored.

Further, while the thermal transfer image is generally glossy and beautiful in printing, it may make the document difficult to read, so that matte printing may be desirable. In such a case, for example, the release layer is coated with an inorganic pigment such as silica or calcium carbonate dispersed in an appropriate solvent to form a mat layer (not shown), and then the ink layer is formed. Can also be formed.

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. The transfer material to be printed by the thermal transfer sheet of the present invention may be any of ordinary paper, bar code label paper, synthetic paper, plastic film, sheet, metal, wood, glass, resin molded product, etc. Although not provided, the thermal transfer sheet of the present invention is particularly suitable for barcode printing on barcode label paper.

[0023]

EXAMPLES Next, the thermal transfer sheet of the present invention will be described more specifically with reference to Examples and Comparative Examples. In the text, part or%
Unless otherwise specified, the weight is based on the weight. Example 1 A polyethylene terephthalate film having a thickness of 4.5 μm was used as a base sheet, and a release layer coating solution having the following composition was applied to one side of the base sheet by gravure reverse and dried at a temperature of 80 ° C. to 0.3 g / The release layer had a thickness of m ² (when dried). Then, a protective layer coating solution having the following composition was applied onto the release layer by gravure reverse and dried at a temperature of 80 ° C. to form a protective layer having a thickness of 0.3 g / m ² (dry). did. Further, the following ink layer coating liquid was applied to the surface of the protective layer by gravure reverse and dried at a temperature of 80 ° C.
A thermal transfer sheet of the present invention was obtained as an ink layer having a thickness of 9 g / m ² (when dried).

Coating liquid for release layer Chlorinated polypropylene (manufactured by Nippon Paper Industries) 81 parts Ethylene / vinyl acetate copolymer 13 parts Polyethylene wax 6 parts Toluene 200 parts Coating liquid for protective layer Polymethylmethacrylate (manufactured by Mitsubishi Rayon, Trade name B-80) 77 parts Vinyl chloride / vinyl acetate copolymer 19 parts Polyethylene resin 3.5 parts Polyester tel 0.5 parts Toluene 100 parts Methyl ethyl ketone 100 parts Heat-fusible ink layer coating liquid Polyester tel (manufactured by Unitika) , Trade name UE-3200) 29.9 parts Blue pigment 53.9 parts Dispersant 16.2 parts Toluene 100 parts Methyl ethyl ketone 100 parts

Example 2 A release layer identical to the release layer in Example 1 was formed, and the same composition as in Example 1 was formed thereon, but the coating amount was 0.5 g / m ^2.
And a solid content of 1.2 g / m ^{2 by} a gravure reverse coating method using a coating liquid having the following composition.
A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the ink layer was formed in. Coating liquid polyester for hot-melt ink layer (manufactured by Toyobo, trade name Bayronal MD-1200, Tg67 ° C) 15.8 parts Water-dispersed red pigment 72.2 parts Water 200 parts

Example 3 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the peeling layer and the protective layer were the same as those in Example 1, the ink layers were the following coating solutions. Coating liquid for hot-melt ink layer (coating amount 1.2 g / m ² ) Polyester Tell (Toyobo, trade name Byron 200, Tg 67 ° C.) 29.9 parts Solvent-dispersed carbon black (Mikuni dye, MHI # 201) ) 58.1 parts Dispersion solvent (toluene / methyl ethyl ketone = 1/1) 200 parts

Comparative Example 1 Example 3 except that the composition of the release layer coating liquid was changed to the following composition
A thermal transfer sheet was obtained in the same manner as described above. 100 parts of coating liquid carnauba wax emulsion for release layer (WE-95 made by Konishi, solid content 40%)

Comparative Example 2 Example 3 except that the composition of the protective layer coating liquid was changed to the following composition:
A thermal transfer sheet was obtained in the same manner as described above. Coating liquid for protective layer Ethylene / vinyl acetate copolymer 100 parts Toluene 100 parts Comparative Example 3 A thermal transfer sheet was obtained in the same manner as in Example 3 except that the release layer was not formed.

Using the thermal transfer sheets of the above-mentioned Examples and Comparative Examples, a printing test was carried out under the following conditions with BC8MKII manufactured by Autonics as a printer for bar code printing, and the foil holding property, foil breaking property and scratch resistance were evaluated. It evaluated and obtained the result of Table 1. Printing conditions Printing speed: 67 mm / sec Printing energy: 0.5 mJ / dot Transferred paper: Treated PET film Evaluation method Foil holding: Cellophane tape 90 ° peeling. Foil break: Visually judge the sharpness of the edge when printing horizontal bars. Scratch resistance: Toyo Seiki rotary abrasion tester 1 kg load 60 r. p. m. , Wear resistant wheel CS-10
50 times Sensitivity: Bar code was read and evaluated by AUTO SCAN700.

Table 1

[0031]

As described above, according to the present invention, by forming the release layer and / or the protective layer in the thermal transfer sheet with a composition containing a resin that is not melted by heat, excellent durability such as heat resistance and abrasion resistance can be obtained. It is possible to provide a thermal transfer sheet which gives printing having properties.

[0032]

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a thermal transfer sheet of the present invention.

FIG. 2 is a longitudinal sectional view showing another embodiment of the thermal transfer sheet of the present invention.

FIG. 3 is a longitudinal sectional view showing another embodiment of the thermal transfer sheet of the present invention.

[Explanation of Reference Signs] 1: Thermal transfer sheet 2: Base material sheet 3: Release layer 4: Thermal melting ink layer 5: Back surface layer 6: Protective layer

Claims (3)

[Claims] 1. A release layer on at least one side of a substrate sheet,
A thermal transfer sheet having a protective layer and a thermal transferable ink layer sequentially provided, wherein the release layer and / or the protective layer is composed of a composition containing a resin that is not melted by heat. 1. The thermal transfer sheet according to 1. 2. The thermal transfer sheet according to claim 1, wherein the resin that does not melt by heat is a chlorinated polypropylene resin. 3. The thermal transfer sheet according to claim 1, wherein the binder of the ink layer contains a polyester resin having a Tg of 60 ° C. or higher.