JPH0435988A - Thermal transfer cover film - Google Patents

Abstract

PURPOSE:To form an image excellent in abrasion resistance, chemical resistance and solvent resistance by providing a transparent resin layer on a base material film in a releasable manner and further providing a thermal adhesive layer composed of a resin having specific glass transition temp. to the surface of the resin layer. CONSTITUTION:A thermal transfer cover film is formed by providing a transparent resin layer 2 on a base material film 1 in a releasable manner and further providing a thermal adhesive layer 5 thereon. The thermal adhesive layer 5 is formed in thickness of about 0.1 - 10mum by applying a solution of a thermoplastic resin with glass transition temp. Tg of 40 - 75 deg.C having good adhesiveness at the time of heating, for example, an acrylic resin, a polyvinyl chloride resin or a polyester resin and drying the formed coating layer. By this constitution, the transparent resin layer is easily transferred to an image by the heat of a thermal head and an image excellent in durability, especially, friction resistance, chemical resistance and solvent resistance can be obtained.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a thermal transfer cover film, and more specifically, it is capable of imparting durability such as excellent abrasion resistance, chemical resistance, solvent resistance, etc. to thermal transfer images, etc. Regarding the thermal transfer cover film that can be made.

(Prior Art and its Problems) Conventionally, thermal transfer methods have come to be widely used as a simple printing method. These thermal transfer methods allow various types of images to be easily formed, and are therefore being used to produce printed matter that requires a relatively small number of prints, for example, for the production of ID cards such as identification cards.

If a color image is preferred, such as a photograph of a face, a large number of colored thermal transfer layers of, for example, yellow, magenta, and cyan (and black if necessary) are repeatedly provided in sequence on a continuous base film. A thermal transfer method using a long thermal transfer film has been used.

These thermal transfer films can be roughly divided into so-called melt transfer type thermal transfer films, in which the thermal transfer layer is softened by heating and thermally transferred in image form to the thermal transfer material, and thermal transfer films in which the dye in the thermal transfer layer is sublimated by heating. It is broadly classified into so-called sublimation type thermal transfer film, in which only the dye is thermally transferred in the form of an image onto the thermal transfer material.

When creating ID cards such as identification cards using the above thermal transfer film, it is easy to form images such as letters and numbers with the melt transfer type thermal transfer film, but these images are not durable. In particular, it has the disadvantage of poor abrasion resistance.

On the other hand, in the case of a sublimation transfer type thermal transfer film, it is possible to form gradation images such as facial photographs, but unlike normal printing ink, the formed image has no vehicle, so it has poor abrasion resistance, etc. In addition, when it comes into contact with card cases, file sheets, plastic erasers, etc. that contain plasticizers, the dye may transfer to them or the image may bleed, resulting in poor chemical and solvent resistance. be.

A method to solve these problems is to laminate a transparent film on the formed image surface, but this method is complicated to operate, causes the image sheet to curl, and Due to the operation of lamination, it is not possible to use very thin films, and therefore there is a problem that the entire laminated image sheet becomes thick.

As a method to solve the above problem, the present inventor previously proposed a method of transferring a transparent resin layer only to the image surface. However, in this case, there is no problem when the transfer is performed using a hot stamper, but when the transfer is performed using a thermal head used for image formation, a problem arises in that sufficient transfer and foil cutting cannot be performed.

Therefore, an object of the present invention is to solve the above-mentioned problems of the prior art, and to produce images with excellent durability, especially abrasion resistance, chemical resistance, solvent resistance, etc., using only a thermal head without the need for a hot stamper. An object of the present invention is to provide a thermal transfer cover film that can be formed.

(Means for solving problems) The above objects are achieved by the present invention as described below.

That is, the present invention provides a thermal transfer cover film in which a transparent resin layer is releasably provided on a base film, and a heat-sensitive adhesive layer is further provided on the surface of the film, wherein the heat-sensitive adhesive layer has a glass transition temperature (Tg) of 40. This is a thermal transfer cover film characterized by being made of a resin having a temperature of ~75°C.

(Function) The heat-sensitive adhesive layer provided on the surface of the transparent resin layer has a Tg of 40 to
By forming the transparent resin layer from a resin heated to 75°C, the transparent resin layer can be easily transferred onto the image by the heat of the thermal head. Through these operations, it is possible to obtain images with excellent durability, especially abrasion resistance, chemical resistance, solvent resistance, etc.

(Preferred Embodiments) Next, the present invention will be described in more detail with reference to the accompanying drawings that schematically show preferred embodiments.

FIG. 1 is a diagram schematically showing a cross section of a thermal transfer cover film according to a preferred embodiment of the present invention. and a heat-sensitive adhesive layer 5 thereon.
is provided.

In addition, 3 in the figure is a peeling layer, which has the effect of lowering the adhesiveness between the transparent resin layer and the base film to facilitate transfer of the transparent resin layer. This layer 3 is unnecessary if the peelability between the base film and the transparent resin layer is excellent.

Further, 4 is a back layer, which has the function of preventing the thermal head of the printer from sticking. This layer 4 is also unnecessary if the base film has good heat resistance and slip properties.

Next, the thermal transfer cover film of the present invention will be explained in more detail using the materials used, the forming method, etc.

As the base film 1 used in the present invention, the same base film used in conventional thermal transfer films can be used as is, and other films can also be used, and there are no particular limitations.

As specific examples of preferable base film 1, thin paper such as glassine paper, capacitor paper, and paraffin paper is useful, and in addition, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, and polyvinyl chloride are useful. Examples include plastics such as polystyrene, nylon, polyimide, polyvinylidene chloride, and ionomer, and base films made of composites of these and the paper.

The thickness of the base film 1 can be changed as appropriate depending on the material so that its strength, heat resistance, etc. are appropriate, but the thickness is preferably 3 to 100 μm.

The transparent resin layer 2 provided on the base film is made of various resins having excellent abrasion resistance, chemical resistance, transparency, hardness, etc., such as polyester resin, polystyrene resin, acrylic resin, polyurethane resin, acrylic urethane resin. , silicone-modified resins of these resins, and mixtures of these resins. Although these resins have excellent transparency, they tend to form a relatively tough film, so it cannot be said that the film breaks sufficiently during transfer. Highly transparent fine particles such as plastic pigments, wax, etc. may be added to an extent that does not impair the transparency of the resin.

The method of forming the transparent resin layer 2 on the base film 1 or on the release layer 3 previously provided thereon includes applying an ink containing the resin by gravure coating, gravure reverse coating, roll coating, and many other means. Examples include a method of drying. The thickness of the transparent resin layer 2 is preferably 0.
It is about 1 to 20 μm.

Furthermore, when forming the transparent resin layer, additives such as a lubricant, an ultraviolet absorber, an antioxidant, and/or a fluorescent whitening agent may be added to the transparent resin layer to improve the durability of various images to be coated. Scratch resistance, gloss, light resistance, weather resistance, whiteness, etc. can be improved.

The release layer 3, which may be formed on the surface of the base film prior to the formation of the transparent resin layer, is formed from a release agent such as wax, silicone wax, silicone resin, fluororesin, acrylic resin, or the like. The formation method may be the same as the method for forming the transparent resin layer, and a thickness of about 0.05 to 5 μm is sufficient. If a matte protective layer is desired after transfer, the surface can be made matte by incorporating various particles into the release layer or by using a base film whose surface on the release layer side has been matt treated. You can also do it.

Furthermore, a heat-sensitive adhesive layer 5 is provided on the surface of the above-mentioned transparent resin layer in order to improve the transferability of these layers. These heat-sensitive adhesive layers are made of thermoplastic resins having a Tg of 40 to 75°C, more preferably Tg of 60 to 70°C, such as acrylic resins, polyvinyl chloride resins, polyvinyl acetate resins, and vinyl chloride/vinyl acetate resins. It is preferably formed to a thickness of about 0.1 to 10 um by applying and drying a solution of a resin such as a polymeric resin or a polyester resin (having good heat adhesion).

If the Tg of the heat-sensitive adhesive layer is less than 40°C, not only will the adhesion between the covered image and the transparent resin layer be insufficient (but also when the formed image is used at a relatively high temperature), When the adhesive layer softens, fine cracks occur in the transparent resin layer, resulting in poor chemical resistance, especially plasticizer resistance.On the other hand, when Tg exceeds 75°C, the thermal head When heated by heating, the transferability of the transparent protective layer is insufficient, and the foil tearability of the transparent resin layer decreases, making it difficult to transfer with good resolution.

Among the above heat-sensitive adhesives, particularly preferred are polyvinyl chloride resins, polyvinyl acetate resins, and vinyl chloride/vinyl acetate copolymer resins having a degree of polymerization of 50 to 300, more preferably 50 to 250. T whose degree is less than 50
The same disadvantages occur when g is low; on the other hand, when the degree of polymerization is 3
If it exceeds 00, the same disadvantages as when Tg is high will occur.

The above is the structure of the thermal transfer cover film of the present invention,
It goes without saying that the transparent resin layer of such a thermal transfer cover film may be provided alone on the base film, or may be provided surface-sequentially with the sublimation dye layer or wax ink layer.

The image to be protected using the thermal transfer cover film as described above is preferably an image formed by a sublimation type thermal transfer method and/or a wax type thermal transfer method, but is not limited to these images. In particular, when applying to a sublimation transfer image, A protective layer for the image is formed, and the dye forming the image is recolored by the heat during transfer, resulting in an effect that the image becomes even clearer.

Further, the sublimation transfer image and/or the melt transfer type transfer image may be formed on any transfer material, but in the present invention, particularly preferred is a card base material made of polyester resin, vinyl chloride resin, etc. This is an image formed in . Of course, these card base materials may be provided with embossments, signatures, IC memories, magnetic layers, other printing, etc., and it is also possible to provide embossments, signatures, magnetic layers, etc. after transfer of the cover film. be.

An example of manufacturing a card using the thermal transfer cover film of the present invention will be described with reference to FIG. 2.

First, a yellow dye layer of a sublimation type thermal transfer sheet is superimposed on the surface of the card base material 6, and a yellow image 7Y is transferred by a thermal printer operating according to color separation signals. Similarly, a magenta image 7M and a cyan image 7C are transferred to the same area to form a desired color image 7. Next, desired characters, symbols, etc. 8 are similarly printed using a wax ink type thermal transfer sheet. If the sublimation type thermal transfer area and the melting type thermal transfer area are different, the sublimation image may be formed after transferring the wax ink. Furthermore, a transparent resin layer is transferred onto the color image 7 and/or image 8 such as characters using the thermal transfer cover film of the present invention to form a protective layer 2. In this way, a desired card can be obtained.

For the above transfer, the thermal printer may be set separately (preferably consecutively) for sublimation transfer, wax ink transfer, and thermal transfer cover film, or these transfers may be performed using a common printer. The printing energy may be appropriately adjusted in each case. Incidentally, in the present invention, the heating means is not limited to a thermal printer, but it goes without saying that a geothermal plate, a hot roll, an iron, etc. may also be used.

(Example) Next, the present invention will be explained in more detail by giving reference examples, examples, and usage examples. In the text, parts or percentages are based on weight unless otherwise specified.

Reference example 1 An ink containing sublimable dyes of three colors having the following composition was prepared.

Yellow ink Disperse dye (Macrolex Yellow 6G, manufactured by Bayer) 5.5 parts Polyvinyl butyral resin (S-LEC BX-1, manufactured by Block Chemical) 4.5 parts Methyl ethyl ketone/toluene (weight ratio 1/1) 89.0 parts Magenta ink Magenta disperse dye (Disperse Re
Same as yellow ink except that d60) was used.

Cyan disperse dye (Solvent Blue) is used as cyan ink dye.
Same as yellow ink except that 63) was used.

A heat-resistant slip layer (thickness: 1 μm) was formed on the back surface using the above ink composition by gravure coating, and a brimer layer (thickness: 0.5 μm) made of polyurethane resin was formed on the surface.
Yellow, magenta and cyan were applied to the surface of a 6.0 μm thick polyester film (trade name "Lumirror" manufactured by Toshi) in the order of 3 g/rrr, respectively. Three color sublimable dye layers were formed by repeatedly applying and drying the dye in a width of 15 cm in order to form a sublimation type thermal transfer sheet.

Reference Example 2 The following wax ink composition was heated at a temperature of 100°C and coated on the same base film as in Example 1, but without a brimer layer, by a hot melt roll coating method to a coating amount of about 4. A melt-transfer type thermal transfer sheet was prepared by applying the resin to give a glrd.

Wax ink acrylic/vinyl chloride/vinyl acetate copolymer resin
20 parts carbon black
10 parts toluene
35 parts methyl ethyl ketone 35
Part Example 1 An ink having the following composition was applied to the same base film as in Reference Example 2 at a rate of 1 g/rr based on solid content and dried to form a transparent resin layer.

Acrylic silicone graft resin (XSA-1 (10,
(manufactured by Toagosei) 60 parts methyl ethyl ketone 20 parts toluene
20 parts Next, on the surface of the above resin layer, an ink having the following composition was applied at a rate of 0.7 g/rrr based on solid content and dried to form an adhesive layer to create a thermal transfer cover film of the present invention. did.

Send! Vinyl chloride/vinyl acetate copolymer (VYLF, UCC
(Tg=68℃, degree of polymerization 220) 30 parts microsilica 0.4 parts methyl ethyl ketone 35 parts toluene
35 parts Example 2 As the adhesive in Example 1, vinyl chloride/vinyl acetate copolymer (Denkarac #21zA, Denki Kagaku Kogyo ■
A thermal transfer cover film of the present invention was obtained in the same manner as in Example 1, except that a film manufactured by Co., Ltd., Tg=62° C., degree of polymerization 240) was used.

Example 3 The thermal transfer of the present invention was carried out in the same manner as in Example 1 except that vinyl chloride/vinyl acetate copolymer (VYHH, manufactured by UCC, Tg = 72°C, degree of polymerization 450) was used as the adhesive in Example 1. A cover film was obtained.

Use examples 1 to 3 Polyvinyl chloride containing about 10% of additives such as stabilizers (
100 parts of a compound (degree of polymerization: 800), 10 parts of a white pigment (titanium oxide), and a plasticizer (D).

P) The sublimable dye layer of the sublimation type thermal transfer film of Reference Example 1 is layered on the surface of the card base material consisting of 0.5 parts, and thermal energy is applied using a thermal head connected to electrical signals obtained by color-separating the facial photograph. was applied to form a full-color photographic image of the face, then letters and symbols were transferred and formed using the melt transfer type thermal transfer film of Reference Example 2, and furthermore, the thermal transfer cover film of the present invention of Examples 1 to 3 was applied. A transparent resin layer was transferred to each image portion using the same thermal head to obtain a card with a facial photograph and various necessary information.

Comparative Example 1 Acrylic resin (BR-
102, manufactured by Mitsubishi Rayon, Tg=20°C, degree of polymerization 5.0
A cover film was prepared in the same manner as in Example 1, except that 00) was used, and a card was prepared in the same manner as in Use Example 1.

Comparative Example 2 A cover film was created in the same manner as in Example 1, except that vinyl chloride/vinyl acetate copolymer (VAGH, manufactured by UCC, Tg = 79°C, degree of polymerization 450) was used as the adhesive in Example 1. A card was prepared in the same manner as in Use Example 1.

Comparative Example 3 As the adhesive in Example 1, vinyl chloride/vinyl acetate copolymer (VYNS, manufactured by LICC, Tg = 79°C,
A cover film was prepared in the same manner as in Example 1, except that a polymer with a degree of polymerization of 700) was used, and a card was prepared in the same manner as in Use Example 1.

Evaluation Example The cards obtained above were evaluated and the results shown in Table 1 below were obtained.

(Left below) Mino! FIG. 2 is a diagram schematically illustrating a cross section of a card made using the above-mentioned cover film.

1: Base film 3: Release layer 5: Adhesive layer 7: Color image 2: Transparent resin layer 4: Back layer 6: Card base material 8: Text, etc. (1 other person) ○: Good △: Slightly poor ×: Defects (Effects) According to the present invention as described above, by forming the heat-sensitive adhesive layer provided on the surface of the transparent resin layer from a resin having a Tg of 40 to 75°C, the transparent resin layer can be easily cut by a thermal head. It can be transferred well. Therefore, since the transparent resin layer is easily transferred onto the image by the heat of the thermal head, an image with excellent durability, particularly abrasion resistance, chemical resistance, solvent resistance, etc., can be obtained with a simple operation.

By forming the heat-sensitive adhesive layer provided on the film from a resin having a Tg of 40 to 75° C., the transparent resin layer can be transferred well with a thermal head, and the foil can be cut easily. Therefore, since the transparent resin layer is easily transferred onto the image by the heat of the thermal head, an image with excellent durability, particularly abrasion resistance, chemical resistance, solvent resistance, etc., can be obtained with a simple operation.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of the thermal transfer cover film of the present invention. Figure 2

Claims (4)

[Claims] (1) A transparent resin layer is releasably provided on the base film,
A thermal transfer cover film further comprising a heat-sensitive adhesive layer on its surface, wherein the heat-sensitive adhesive layer is made of a resin having a glass transition temperature of 40 to 75°C. (2) The thermal transfer cover film according to claim 1, wherein a release layer is provided between the base film and the transparent resin layer. (3) The thermal transfer cover film according to claim 1, wherein the thermal adhesive is selected from the group consisting of polyvinyl chloride, polyvinyl acetate, and vinyl chloride/vinyl acetate copolymers having an average degree of polymerization of 50 to 300. (4) The thermal transfer cover film according to claim 1, wherein the transparent resin layer contains a filler, a lubricant, an ultraviolet absorber, an antioxidant, and/or a fluorescent brightener.