JPH0768943A - Heat transfer sheet - Google Patents

Abstract

PURPOSE:To provide a heat transfer sheet which can reproduce required color and clarity without being influenced by the color even if a material to be transferred is colored with regard to the heat transfer sheet. CONSTITUTION:A heat transfer sheet has a constitution wherein a heat transferring ink layer 2 is provided on a base material 1 and in addition, an opacifying layer 3 with a transmittance in a visible light region (400nm-700nm) of at most 5% is provided thereon.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-melting type heat transfer sheet, and when an image such as a print is recorded on a transfer material facing the heat transfer sheet by a thermal head or the like, an ink layer to be transferred is It has excellent hiding power,
The image can be recorded clearly on a colored transfer material and can be widely used in various printers and the like.

[0002]

2. Description of the Related Art Conventionally, polyethylene terephthalate film (hereinafter PE
A heat-meltable ink layer made of a pigment and / or a dye and wax is provided on one surface of a base material such as T), and a heat-resistant release layer is provided on the other surface for the purpose of preventing sticking. Things are known. When performing thermal transfer recording using these thermal transfer sheets, an image is formed by heating the thermal transfer sheet into an image with a thermal head or the like from the surface opposite to the ink layer, and transferring the ink layer onto the opposite transfer material. To form.

[0003]

However, in such thermal transfer, the ink layer does not always have sufficient hiding power, and the transfer material is colored or a pattern is printed. In this case, the transferred image is affected by the color of the background, and there is a drawback that the desired color and sharpness cannot be obtained. The present invention solves such a problem and reproduces a desired color and sharpness regardless of what color the material to be transferred is colored or what color pattern is printed. An object is to provide a heat transfer sheet that can be obtained.

[0004]

Means for Solving the Problems The present invention has been intensively studied to solve the above problems, and as a result, a thermal transfer sheet was formed on a thermal transferable ink layer provided on a substrate, and further,
The object is achieved by providing a concealing layer having a transmittance of 5% or less in the visible light region (400 nm to 700 nm).

That is, the thermal transfer sheet of the present invention is provided with a thermal transferable ink layer on a substrate, and further has a transmittance of 5 at a wavelength in the visible light region (400 nm to 700 nm).
% Of the concealing layer is provided.

(Preferred Embodiment) Next, a preferred embodiment of the present invention will be described in more detail with reference to the drawings. Figure 1
2 and 2 are schematic cross-sectional views showing an embodiment of the thermal transfer sheet of the present invention. In the thermal transfer sheet of FIG. 1, a thermal transferable ink layer 2 is provided on a base material 1, and a concealing layer 3 having a transmittance of 5% or less at a wavelength in a visible light region (400 nm to 700 nm) is further provided thereon. It is a thermal transfer sheet having a configuration provided. In the thermal transfer sheet shown in FIG. 2, the mat layer 4, the thermal transfer ink layer 2, the above-mentioned concealing layer 3, and the surface layer 5 are sequentially provided on one surface of the base material 1 in this order, and the heat resistant release layer is provided on the other surface. The thermal transfer sheet has a configuration in which a mold layer 6 is provided.

(Substrate) As the substrate film used in the thermal transfer sheet of the present invention, the same substrate film as that used in the conventional thermal transfer sheet can be used as it is, and other substrates can also be used. It is possible,
There is no particular limitation. Specific examples of preferable substrate film include, for example, polyester, polypropylene, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol,
There are plastic films such as fluororesins, chlorinated rubbers and ionomers, papers such as condenser papers and paraffin papers, non-woven fabrics and the like, and a substrate film obtained by combining these may be used.

The thickness of the base film can be appropriately changed depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably, for example, 2 to 2.
It is 25 μm. It is also possible to provide a heat-resistant release layer on the back surface of the substrate film, which prevents adhesion with the thermal head and improves slipperiness.

(Ink Layer) As the binder of the ink layer used in the present invention, waxes are mainly used.
There are microcrystalline wax, carnauba wax, paraffin wax and the like. Furthermore, Fischer-Tropsch wax, various low molecular weight polyethylene, wood wax, beeswax, whale wax, ivowa wax, wool wax, shellac wax, candelilla wax, petrolactam, polyester wax, partially modified wax, fatty acid ester,
Fatty acid amides and the like are also used. Among these, especially, the freezing point is 50 to 70 ° C. and the melt viscosity at 100 ° C. is 1
Waxes in the range 0-200 mPas are preferred.

The colorant can be appropriately selected from known organic or inorganic pigments or dyes. For example, it has a sufficient coloring density and does not discolor or fade due to light, heat or the like. Is preferred. Further, it may be a substance that develops a color by heating or a substance that develops a color when it comes into contact with a component applied to the surface of the transfer target. The color of the colorant is not limited to cyan, magenta, yellow and black, and colorants of various colors can be used.

In addition to these, vegetable oil, animal oil, mineral oil and the like can be added as a softening agent or a dispersing agent, if necessary. As the ink itself, a known ink can be used, and it is usually prepared by melting and dispersing 5 to 30 parts by weight of a colorant in 100 parts by weight of a binder. The ink may be applied by either hot melt coating or solvent coating, but in either case, it is preferable to use the gravure method. In the case of solvent coating, of course, an ink of the type in which a solvent is added to the above composition to be dissolved and dispersed is used. The thickness of the ink layer is 1 to 10 μm.

(Hiding Layer) The hiding layer, which is also a feature of the thermal transfer sheet of the present invention, has a thermal transfer property and has a transmittance of 5% or less at a wavelength in the visible light region (400 to 700 nm) as described above. It is configured to become. Specifically, a colorant such as an inorganic pigment or an organic pigment having a hiding power and a binder are mainly used, and if necessary, an additive such as a softener or a dispersant is added thereto. Examples of the colorant include titanium oxide, zinc sulfide, calcium carbonate, silica, and the like.Titanium oxide is a chlorine method and a sulfuric acid method. The method is more preferable. Also, their particle size is 0.1
It is preferably not less than μm and not more than 10 μm.

Regarding the additives such as the binder and the softening agent, those mentioned in the above ink layer can be similarly used. For example, in the binder, in addition to microcrystalline wax, carnauba wax, paraffin wax, etc., Fischer-Tropsch wax, various low molecular weight polyethylene, wooden wax, beeswax, spermaceti wax, ivowa wax,
Wool wax, shellac wax, candelilla wax,
Petrolactam, polyester wax, partially modified wax, fatty acid ester, fatty acid amide, and the like, and among these, those having a freezing point of 50 to 70 ° C. and a melt viscosity at 100 ° C. of 10 to 200 mPas are preferable.

The coating of the hiding layer is usually carried out with the binder 100.
A coating agent mainly composed of a composition in which 10 to 250 parts of the colorant is dispersed can be applied by hot melt coating or solvent coating using a gravure cylinder, and the thickness of the coating film is 0.1. The range of 10 μm is preferable.

(Mat layer) In the thermal transfer sheet of the present invention,
When it is desired to deluster the surface of the transferred characters or patterns, a mat layer can be provided between the base material and the ink layer as shown in FIG. This matte layer is generally
For example, a liquid in which an inorganic pigment such as silica or calcium carbonate is dispersed in a wax-based binder using a solvent is applied onto a base film by gravure coating or the like. The matting agent is not limited to the above-mentioned inorganic pigments. For example, in the case of a thermal transfer sheet using black ink, carbon black can be used. In this case, by forming a matte layer, it is possible to make the printed surface matte and also have a function of preventing static electricity. The thickness of the mat layer is preferably about 0.1 to 4 μm.

(Surface Layer) The surface layer is generally formed on the ink layer of the transfer sheet, and serves to prevent the surface of the printed portion of the material to be transferred at the time of transfer and to prevent scumming. It is a thing. In another sense, it also has an effect of preventing winding of the transfer sheet from causing blocking (set-off) between the ink layer and the back surface of the substrate during storage. In this respect, in the transfer sheet of the present invention, the concealing layer is provided on the ink layer, and the concealing layer can also serve as a surface layer. Therefore, the surface layer may be provided only when necessary. For this surface layer, the same waxes as those listed as the binder for the ink layer can be used. From these, one type or a mixture type of two or more types is selected, and an aqueous emulsion or dispersion is used. it can.

For example, a dispersion prepared by using 4 to 6 parts by weight of microcrystalline wax and 50 to 70 parts by weight of water with respect to 35 parts by weight of carnauba wax can be used. As the method of applying the surface layer, gravure coating is preferable in terms of uniformity of the applied amount, and the surface layer can be formed by applying and drying so that the thickness is 0.5 to 4 μm.

(Heat-resistant release layer) In the thermal transfer sheet,
When the surface of the base material opposite to the surface provided with the ink layer is brought into contact with the thermal head of the printer and heated, it may soften depending on the material and may stick to the surface to make it difficult to move. Therefore, a heat-resistant release layer may be provided on this surface for the purpose of improving heat resistance, slipping property, and releasing property. The heat-resistant release layer is easily formed by applying a silicone resin by gravure coating or the like, but a fluororesin and various other thermosetting resins can also be used. The coating film may have a small thickness, and it is effective if it is 0.1 to 2 μm.

[0019]

In the thermal transfer sheet of the present invention, the visible light region (400 nm to 700 nm) is formed on the ink layer provided on the substrate.
A hiding layer having a transmittance of 5% or less at the wavelength m) is provided. Therefore, when thermally transferred to the transfer material, the hiding layer is laminated under the ink layer and transferred in an integrated state. Therefore, even if the material to be transferred is colored, the ink layer transferred thereon is not affected by the color of the material to be transferred, and the desired color and vividness can be reproduced.

[0020]

EXAMPLES The present invention will be described in more detail with reference to the following examples. (Example 1) PET having a thickness of 4.5 μm was used as a base material, and a silicone resin was applied to one surface of the base material by gravure coating so that the application amount was 1 g / m ² (solid content). A layer was provided, and on the other surface, an ink layer coating agent and a hiding layer coating agent having the following compositions were sequentially hot-melt coated by a gravure method so as to have thicknesses of 3 μm and 2 μm, respectively. A thermal transfer sheet of was obtained.

Composition of coating agent for ink layer Paraffin wax (HNP10 Nippon Seiro) 40 parts by weight Carnauba wax 20 parts by weight Ethylene-vinyl acetate copolymer (vinyl acetate content 25% by weight) 25 parts by weight Carbon black (carbon black # 25 Mitsubishi Kasei) 15 parts by weight Composition of coating agent for concealing layer Paraffin wax (HNP10 Nippon Seiro) 10 parts by weight Titanium oxide (CR-60 particle size 0.25 μm Ishihara Sangyo) 20 parts by weight

(Example 2) In the thermal transfer sheet having the structure of Example 1, a matte layer was provided between the base material and the ink layer, and the surface layer was provided on the concealing layer. The heat transfer sheet of Example 2 was used (see FIG. 2). That is, PET with a thickness of 4.5 μm is used as a base material, and one surface of the base material is coated with silicone resin by gravure coating to give a coating amount of 1 g.
/ M ² (solid content) to provide a heat-resistant release layer, and the other surface is coated with a mat layer coating solution having the following composition: 0.5 g / m ² (solid content) So that
It is dried to form a matte layer, an ink layer and a masking layer are successively applied and laminated thereon under the same conditions as in Example 1, and a surface layer coating solution having the following composition is further applied thereon at a coating amount of 1 g / m 2.
² (solid content) was applied and dried to form a surface layer to obtain a thermal transfer sheet of Example 2.

Composition of coating liquid for mat layer Carbon black (# 25 Mitsubishi Kasei) (as matting agent) 24 parts by weight Polyester wax 16 parts by weight Dispersant (vegetable oil plain act) 1.5 parts by weight Curing agent (Takenate A-) 10 Takeda Pharmaceutical Co., Ltd. 3.0 parts by weight Mixed solvent Methyl ethyl ketone / toluene (weight ratio 1: 1) 60 parts by weight

Composition of coating liquid for surface layer (wax dispersion) Carnauba wax 35 parts by weight Microcrystalline wax 5 parts by weight Water 60 parts by weight As mentioned above, two examples were given, but the thermal transfer sheet of the present invention is not limited thereto. It is not something that will be done.

(Comparative Example 1) In the constitution of Example 1, only the coating agent for the hiding layer was changed to the following composition and applied, and the other processing conditions were the same as in Example 1 and the same procedure as in Comparative Example 1 was performed. A thermal transfer sheet was obtained. Composition of coating agent for concealing layer Paraffin wax (HNP10 Nippon Seiro) 10 parts by weight Titanium oxide [TTO-55 (B) particle size 0.03 μm Ishihara Sangyo] 20 parts by weight

(Comparative Example 2) In the constitution of Example 2, only the coating agent for the hiding layer was changed to the following composition and applied, and the other processing conditions were the same as those of Example 2 and the same procedure as in Comparative Example 2 was performed. A thermal transfer sheet was obtained. Composition of coating agent for concealing layer Paraffin wax (HNP10 Nippon Seiro) 10 parts by weight Titanium oxide [TTO-55 (D) particle size 0.04 μm Ishihara Sangyo] 20 parts by weight

(Evaluation Test and Results) Using the thermal transfer sheets of Examples 1 and 2 and Comparative Examples 1 and 2 prepared as described above, a high-quality paper colored in yellow, red and indigo with a thermal printer was prepared. The print quality was evaluated by printing on uncolored (white) high-quality paper and comparing it with that printed on a white high-quality paper, such as hue, sharpness, and printing accuracy. Separately, the wavelength of each thermal transfer sheet is 450 nm and 70 nm.
The transmittance at 0 nm was measured, and the results are also shown in Table 1.
It was shown to. As the transmittance measuring device, a spectrophotometer UV-3100 manufactured by Shimadzu Corporation was used.

[0028]

[Table 1]

[0029]

INDUSTRIAL APPLICABILITY The thermal transfer sheet of the present invention is provided with a thermal transferable ink layer on a substrate, and a visible light region (400 to 400) is formed on the thermal transferable ink layer.
(700 nm), a masking layer having a transmittance of 5% or less is provided. By adopting such a configuration, even if the transferred material is colored or a pattern is printed, it is possible to reproduce the desired color and sharpness without being influenced by the color of the base. The effect that an excellent thermal transfer sheet can be obtained is exhibited.

[0030]

[Brief description of drawings]

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

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Base material 2 Ink layer 3 Concealment layer 4 Matt layer 5 Surface layer 6 Heat-resistant release layer

Claims (1)

[Claims] 1. A thermal transfer characterized in that a thermal transferable ink layer is provided on a base material, and a concealing layer having a transmittance of 5% or less at a wavelength in the visible light region (400 nm to 700 nm) is provided thereon. Sheet.