JPH0543517B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an improved thermal transfer sheet that can be provided for recording using a printing means such as a thermal head that uses short-term high-temperature heating. (Prior Art) Conventionally, heat-sensitive transfer sheets are known in which a transfer layer is formed by blending a coloring agent into a binder such as wax on one side of a plastic film base material. In recent years, as the printing speed of such thermal transfer sheets has been increased, the back side of the thermal transfer sheet, that is, the exposed plastic film surface, is heated above its melting point, causing the plastic film to reach the thermal head. Fusing, the so-called "state king phenomenon", is more likely to occur. Several proposals have been made to try to eliminate this "statesking phenomenon." For example, it has been proposed to provide a heat-resistant protective layer made of one material selected from the group consisting of silicone resin, epoxy resin, melamine resin, phenol resin, fluororesin, polyimide resin, and nitrocellulose on the back surface of the heat-sensitive transfer sheet. (Tokuko Akira)
58-13359). However, in this proposed technology, most of the resins are thermosetting resins, and therefore a heating process is required for curing when forming the protective layer.Furthermore, although the protective layer has a high melting point, the film itself is brittle. There is a problem with smooth printing. Instead of using the above-mentioned resins, the applicant has already proposed the use of a protective layer made by adding isocyanate or the like to a thermoplastic resin containing an alcoholic OH group and curing it. 57−71035
(see specification). According to this method, since curing proceeds at approximately room temperature, there is no need to provide a special curing step, so although it has the advantage of facilitating the formation of a protective layer, it cannot be said that the slippage of the thermal head is sufficient. (Objective of the Invention) The present invention takes the above-mentioned conventional technology one step further, and aims to provide a thermal transfer sheet in which the step of forming a protective layer is simple and the slippage of a thermal head is significantly improved. (Structure of the Invention) The present invention provides a thermal transfer sheet having a transfer ink layer that melts when heated on one side of a plastic film base material, in which a thermoplastic resin having an alcoholic OH group is used on the other side of the base material. A heat-sensitive transfer sheet characterized by having a protective layer formed using a composition containing 100 parts by weight of a compound having two or more amino groups and a thermoplastic resin for forming the protective layer. Its main purpose is (Preferred Embodiment) Although any plastic film can be used as the base material, typical examples include polypropylene film, cellophane film, cellulose acetate film, etc. in addition to the above-mentioned polyester film. Appropriate thickness is around 10 μm, and for example, one as thin as 6 μm can also be used. The ink that is melted and transferred by heating uses a wax with an appropriate melting point, such as paraffin wax, microcrystalline wax, carnauba wax, etc., as a binder, and contains carbo black, various dyes, pigments, etc. It is made by adding a coloring agent. Its manufacture and application onto a base film can be carried out according to known techniques. Next, to explain the protective layer that mainly characterizes the invention, such a protective layer consists of alcoholic OH
It is constructed using a composition containing a thermoplastic resin having a group, a compound having two or more amino groups, and a thermoplastic resin for forming a protective layer. In the above, thermoplastic resins having alcoholic OH groups include polyester resins, saponified vinyl chloride/vinyl acetate copolymers, polyether resins, OH-modified polybutadiene resins, acrylic polyols, urethanes or epoxy resins having alcoholic OH groups. Prepolymers or nitrocellulose resins, cellulose acetate propionate resins, cellulose acetate butyrate resins, cellulose acetate resins, etc. are preferably selected. The above-mentioned resins may have alcoholic OH groups in their polymerized units or may have unreacted alcoholic OH groups at the terminals or side chains. A compound having two or more amino groups and a thermoplastic resin as a film-forming material are further added to the above thermoplastic resin having an alcoholic OH group. Examples of compounds having two or more amino groups include melamine, methylated melamine, methylated methylol melamine, butylated melamine, butylated methylol melamine, dicyandiamide, guanidine, biguanide, cyano melamine, guanyl melamine,
urea, biuret, ammeline, ammelide,
Butylated urea, methylated urea, etc., and guanamines such as formaguanamine, acetoguanamine, benzoguanamine, phenylacetoguanamine, methoxyguanamine, and N-methylolacrylamide copolymers can be used. When using a compound having two or more of the above amino groups, ammonium phosphate,
Triethanolamine, acetamide, urea, pyridine, para-toluenesulfonic acid, sulfanilic acid, guanidine stearate, guanidine carbonate, etc. are used in combination. The above-mentioned compound having two or more amino groups is preferably added at a ratio of 100 parts by weight to 100 parts by weight of the thermoplastic resin having an alcoholic OH group.
If it is less than 100 parts by weight, the degree of crosslinking and curing of the protective layer will be too low and no curing will occur, and if it exceeds 100 parts by weight, the anti-stinging performance will deteriorate, which is not preferable. Furthermore, by adding a compound having two or more of the above amino groups to a thermoplastic resin having an alcoholic OH group, the protective layer on the plastic film can be formed more easily than when a compound having two or more amino groups is not added. Adhesion strength increases. Furthermore, the thermoplastic resin used to form the protective layer can be selected from a wide range, but suitable examples include acrylic resin, polyester resin, vinylidene fluoride resin, and vinylidene fluoride/vinylidene fluoride resin.
Tetrafluoroethylene copolymer resin, polyfluorovinyl resin, acrylonitrile/styrene copolymer resin, acrylic/vinyl chloride copolymer resin, nitrile rubber, nylon, polyvinyl carbazole, chlorinated rubber, cyclized rubber, polyvinyl acetate resin ,
Examples include polyvinyl chloride resin and vinyl chloride/vinyl acetate copolymer resin. It has been empirically known that these resins preferably have a glass transition point of 60°C or higher. To construct a protective layer using each of the above compounds,
After each compound is dissolved in a suitable solvent and adjusted to a viscosity suitable for coating, it may be coated on one side of a plastic film base material by a known coating method. The heat-sensitive transfer sheet of the present invention basically has the above structure, but may be further modified as follows. First, a primer layer may be provided between the plastic film substrate and the protective layer to improve adhesion. The primer layer can be provided using a known primer paint, but for example, as a binder, acrylic resin, polyester resin, polyvinyl acetate resin, vinyl chloride/vinyl acetate resin, polyol and diisocyanate, polyol and melamine, epoxy resin. and diisocyanates, etc., and when a primer paint made with these binders is used, the adhesion strength is particularly improved when a polyester film is used as the base material. Second, in order to improve the slippage of the thermal head, it is recommended to add a lubricant or a heat release agent to the protective layer.
Waxes such as polyethylene wax and paraffin wax, higher fatty acid amides, higher fatty acid esters, higher fatty acid salts, higher alcohols, the first group such as phosphate esters such as lecithin, and powders of fluororesins such as polytetrafluoroethylene. Examples of the second group include powders of vinyl fluoride resin, powders of guanamine resin, boron nitride, silica, wood powder, talc, etc. The above-mentioned lubricants or thermal mold release agents can be used in any desired mixture, and it is desirable to add about 10 to 50% by weight to the protective layer. These lubricants or thermal mold release agents are added and kneaded when preparing the coating material for forming the protective layer. In the above, those belonging to the first group are melted by heating and exhibit the action of a lubricant or heat mold release agent, and those belonging to the second group are those that exhibit the action of a lubricant or heat mold release agent in the state of solid powder. It is. (Effects of the Invention) Since the thermal transfer sheet of the present invention has the above-described structure, thermal printing is possible without staking even on a thermal transfer sheet based on plastic film, and the plastic film has the ability to cut easily. Benefits such as resistance and ease of processing can be taken advantage of. Further, the protective layer in the present invention can be formed using a common coating device and does not require any special high heat treatment. Furthermore, in the protective layer of the present invention, the long-chain hydroxyl group-containing thermoplastic resin is loosely cross-linked with a compound having two or more amino groups, so it has excellent staking resistance and moderate softness. It has good thickness and cushioning properties, and has good contact with the thermal head despite the roughness of the surface of the paper that is the transfer material, and does not cause white spots or chips in printed characters. Further, by adding the thermoplastic resin used to form the above-mentioned protective layer, the sliding of the thermal head is improved and wear of the thermal head is significantly reduced. On the other hand, when the protective layer is formed of a thermosetting resin with a short distance between crosslinks, as in the prior art, it has excellent heat resistance, but the protective layer becomes very hard and lacks softness and cushioning properties. Therefore, the high quality printing effect and the thermal head wear prevention effect as described above cannot be expected by the present invention. (Examples) Examples and comparative examples are listed below to explain the present invention more specifically. In the following examples, the following materials were used as the base film and transfer ink layer. Base film: Polyethylene terephthalate film (manufactured by Toray) with a thickness of 6 μm or 12 μm is used. Transfer Ink Layer An ink composition having the following composition was kneaded using a blade kneader for 6 hours while heating to 90°C. Parafine wax 10 parts by weight Carnauba wax 10 parts by weight Polybdenum (manufactured by Nippon Oil Co., Ltd., HV-100)
1 part by weight carbon black (manufactured by Tokai Electrode Co., Ltd., Seast S)
2 parts by weight After forming the protective layer described below, the above ink composition was heated at a temperature of 100°C and applied to the surface of the above substrate film using a hot melt roll coating method to a coating thickness of 5 μm. , as a transfer ink layer. Example 1 The following ink (A) was prepared. Ink A Vinyl chloride/vinyl acetate copolymer resin (Union Carbide Co., Ltd., Vinyrite VYHH) 3 parts by weight Cellulose acetate propionate resin (Kodatsu Co., Ltd., CAP 482-05) 13 parts by weight hexamethoxymethylated melamine (Sanwa Chemical Co., Ltd.) 13 parts by weight Satucarose acetate isobenzoate (manufactured by Eastman Chemical Company) 3.6 parts by weight Methyl cellosolve 20 parts by weight Butyl acetate 20 parts by weight Methyl ethyl ketone 20 parts by weight For the above ink (A), A 40% IPA solution of toluenesulfonic acid was mixed at a ratio of 45:1 (weight ratio) by gravure printing on the side opposite to the side on which the transfer ink layer was to be provided, so that the coating thickness when dry was 1 μm. It was coated on the surface of the base film and dried at a temperature of 100°C to form a protective layer. Thermal transfer sheets obtained in the above Examples, Comparative Example 1 without a protective layer, and Comparative Example 2 with a protective layer formed from a phenol resin paint at 150°C.
The runnability of the head, the condition of the thermal transfer sheet, and the print quality were evaluated when printing was performed under the following conditions using a sheet cured at a temperature of By comparison, the results shown in Table 1 below were obtained. Head used: Thin-film thermal head Printing energy: 1 mJ dot (area per dot is 4 x 10 ^-4 cm ² ) Material to be transferred: High-quality paper (manufactured by Sanyo Kokusaku Pulp Co., Ltd., KYP)
46th edition 135Kg) [Table]

Claims (1)

[Scope of Claims] 1. In a thermal transfer sheet having a transfer ink layer that melts when heated on one side of a plastic film base material, 100% by weight of a thermoplastic resin having an alcoholic OH group on the other side of the base material. per part
1. A heat-sensitive transfer sheet comprising a protective layer formed using a composition containing 100 parts by weight of a compound having two or more amino groups and a thermoplastic resin for forming the protective layer. 2. The heat-sensitive transfer sheet according to claim 1, wherein a substance having the action of a lubricant or a heat release agent is added to the protective layer.