JPH0428596A - thermal transfer sheet - Google Patents

Abstract

PURPOSE:To eliminate scumming, greasing, etc., at the time of printing even in the case of an N-fold mode method and to improve density, resolution of printing by providing finely inclined line uneven shape at an angle to a conveying direction on a surface layer. CONSTITUTION:A low melting viscosity sensitizing layer is formed between an ink layer of a heat transfer sheet and a base material film, and a colorless surface layer is formed on the ink layer to obtain a heat transfer sheet having no scumming, greasing, etc., at the time of printing even in the case of an N-fold mode method and improving density, resolution of printing. Finely inclined line uneven shape having an angle to a conveying direction of the sheet is formed on the surface layer to prevent adherence of the transfer sheet to a material to be transferred at the time of printing and to further effectively prevent scumming, greasing, etc. Since the N-fold printing is performed on the ink layer having a relatively small area, the colorant density of the ink layer is necessarily set to relatively high density.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a thermal transfer sheet, and more specifically to a thermal transfer method (hereinafter simply referred to as N-time mode) in which the conveyance speed of the transfer material is higher than the conveyance speed of the thermal transfer sheet. (referred to as law),
The present invention relates to a thermal transfer sheet that is free from scumming, trailing, etc. during printing, and has improved print density, resolution, etc.

(Prior art and its problems) Conventionally, when printing output prints from computers or word processors using a thermal transfer method, a thermal transfer sheet with a heat-melting ink layer provided on one side of a base film has been used. .

The above conventional thermal transfer sheet has a thickness of l as a base film.
Using paper such as O~2OLLm capacitor paper or paraffin paper, or plastic film such as polyester or cellophane with a thickness of 3~20μm, a layer of heat-melting ink made by mixing wax with coloring agents such as pigments and dyes is applied. It is manufactured by coating.

One problem with the thermal transfer sheet described above is the economical problem in that printing can be performed only once at the same location, and therefore a thermal transfer sheet of the same width as the printing width is consumed.

A known method to solve this problem is to use a thermal transfer sheet for multiple printing, which can print multiple times at the same location, but with this method, the print density decreases with the number of times it is used. There is a problem in that it is difficult to print with uniform density.

Another method is an N-times mode method in which the conveying speed of the transfer material is made higher than the conveying speed of the thermal transfer sheet (both conveying methods may be in the same direction or in opposite directions).

In this method, if the conveying speed of the transfer material is N, and the conveying speed of the thermal transfer sheet is N, and NUN', the printing distance is N, but the consumption amount of the thermal transfer sheet is N'.
For example, when N=5 and N'=1, the amount of thermal transfer sheets consumed is 115, which is very economical.

However, in this method, the transfer material and the thermal transfer sheet move while being subjected to relative friction, which causes background smudges and trailing of the print on the transfer material, making it difficult to print with clear and high resolution. There's a problem.

One way to solve the problem of scumming is to form a colorless wax layer on the surface of the ink layer, but this surface layer is easily removed by friction and is not a sufficient solution. On the other hand, one way to solve the problem of trailing is to form the ink layer with a wax that has a relatively high melt viscosity. In the case of a rough transfer material, voids (white spots) occur, making it difficult to print with high density and high resolution.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks, and to eliminate background smudges, trailing, etc. during printing even in the N-times mode method.
Another object of the present invention is to provide a thermal transfer sheet with improved print density, resolution, and the like.

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

That is, the present invention provides a sensitizing layer on one side of the base film,
A thermal transfer sheet comprising a transfer ink layer and an uncolored surface layer formed in the order described above, wherein the surface layer has diagonal fine unevenness having an angle with respect to the conveying direction.

(Function) By forming a sensitized layer with a low melt viscosity between the ink layer of the thermal transfer sheet and the base film, and by forming an uncolored surface layer on the ink layer, N (also in the sound mode method) ,
Provided is a thermal transfer sheet that is free from background smearing, trailing, etc. during printing, and has improved printing density, resolution, etc.

Moreover, the surface of the surface layer has 14I! which has an angle with respect to the conveyance direction of the thermal transfer sheet! By forming the fine irregularities, it is possible to prevent the thermal transfer sheet from sticking to the transfer material during printing, and also to more effectively prevent scumming, trailing, etc.

(Preferred Embodiments) Next, the present invention will be explained in more detail with reference to preferred embodiments.

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

Specific examples of preferred base films include polyester, polypropylene, and cellophane.

Polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride, polystyrene, nylon.

There are plastic films such as polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, and ionomer, papers such as condenser paper and paraffin paper, nonwoven fabrics, etc., and base films made of composites of these may also be used. - The thickness of this base film can be changed as appropriate depending on the material so that its strength and thermal conductivity are appropriate, but the thickness is preferably, for example,
It is 2 to 25 μm.

In the present invention, a heat-melting ink layer is formed on the surface of the base film via a sensitizing layer using an ink containing necessary materials.

The sensitizing layer is mainly formed from wax, but this wax layer may be colored with a coloring agent like the ink layer described later, or it may be colorless.

Representative examples of wax include microcrystalline wax, carnauba wax, paraffin wax, and the like. In addition, various waxes such as Fischer-Tropsch wax, various low molecular weight polyethylenes, wood wax, beeswax, spermaceti wax, privet wax, wool wax, shellac wax, candelilla wax, petrolactam, assorted waxes, fatty acid esters, fatty acid amides, etc. However, in the present invention, among the above-mentioned waxes, those having a melt viscosity at 100° C. of t 0 Ocps or less, preferably 50 cps or less are used. If the melt viscosity is too high, it will become similar to an ink layer, resulting in insufficient sensitization and voids. Such a sensitized layer has a thickness of 0.1 to 2 μm, preferably 0.5 to 1.0 μm.
It may be provided to have a thickness of about 5 am. If the sensitizing layer is too thin, the sensitizing effect will be insufficient, and if it is too thick, the sensitivity will decrease.

The ink layer provided on the sensitized layer comprises a colorant and a vehicle, and may further contain various additives as required. The colorant is preferably an organic or inorganic pigment or dye that has good properties as a recording material, for example, one that has sufficient color density and does not discolor due to light, heat, temperature, etc. Of course, colorants of various colors other than black, such as cyan, magenta, and yellow, can also be used.

In the present invention, in order to print N times as many characters using a relatively small area of the ink layer, it is necessary to set the colorant concentration of the ink layer to a relatively high concentration, and depending on the thickness of the ink layer,
In the preferred range of the ink layer from 3 to 204 zm,
The preferred concentration is 20-70% by weight, more preferably 30% by weight.
The range is from 50% to 50%, and if the density is too low, the printing density will be insufficient, and if it is too high, the ink will not adapt well to the paper and voids will easily occur, which is not preferable.

The vehicle used includes the above-mentioned wax as a main component, and mixtures of wax with drying oil, TI4 fat, mineral oil, cellulose, rubber derivatives, and the like.

The ink consisting of the above colorant and vehicle is preferably blended so that the melt viscosity at 100°C is 300 cps or more, and wax alone has a melt viscosity of 300 cps or more.
If it is not possible to make the melt viscosity higher than ps, it is possible to use various thermoplastic resins such as vinyl resins in combination to increase the cohesive force and improve the melt viscosity. Usually, the melt viscosity can be increased to 300c by using vinyl resin at 7% by weight or more of the wax.
It can be set to p3 or higher. The preferred melt viscosity is 10
It is 300-1.000 cps at 0°C, and if the melt viscosity is too low, the problems of scumming and trailing become noticeable, and if the melt viscosity is too high, voids are likely to occur. Furthermore, when a lubricant as described below is included in the ink layer, scumming and trailing can be improved.

The sensitized layer and the ink layer can be formed on the base film by hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many other methods. Examples include a method of coating.

In the present invention, an uncolored surface layer is formed on the surface of the ink layer. This surface layer may be formed, for example, from a wax as described above, or from a vehicle (medium) for the ink layer, and more preferably from a slippery wax, a silicone wax, a fluorine resin, or a silicone. It is preferable to form the film from a lubricant such as a resin, a higher fatty acid amide, an ester, or a surfactant, or to use a thermoplastic resin in combination with these lubricants to improve the film strength. It is also possible to close the surface layer of a two-layer structure.

On the surface layer, a linear fine unevenness shape having an angle of, for example, 15 to 60'' with respect to the conveyance direction of the thermal transfer sheet is formed.This fine unevenness shape is formed at an angle of 15 to 60 inches when forming the surface layer. It can be easily formed by using a gravure plate having lI.In particular, by forming these surface layers by coating an aqueous dispersion of a lubricant or vehicle and drying at a low temperature, fine particles that remain in the particle shape can be formed. Since the uneven surface is formed, the thermal transfer sheet is prevented from sticking to the transfer material during printing, and the thermal transfer sheet has excellent layer stain prevention properties.

It goes without saying that a layer for preventing sticking of the thermal head may be provided on the back surface of the thermal transfer sheet of the present invention.

It goes without saying that the present invention can be applied to thermal transfer sheets for color printing, so multi-colored thermal transfer sheets in which two or more colors are applied to the same base material are also included within the scope of the present invention.

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

Example 1 A slip layer was formed on the back surface using a coating liquid with the following composition, and the thickness was 6.
．． 0 μm polyester film (product name: Lumirror)
The amount of coating on the surface of the product (manufactured by Toshiku Kikki) is 1.0 g/
rrr (1.0 g/rd corresponds to 1 μm. The same applies hereinafter), and coated with a sensitized layer (100°C melt viscosity 28
cps) was formed.

Carnauba wax 30 parts nonionic surfactant 1 part isopropanol 100 parts water
30 parts Next, a composition having the following composition was heated at a temperature of 100°C, and applied to the surface of the sensitized layer at a coating amount of 8 g/rrr using a hot melt roll coating method to form a thermal transfer ink layer (100°C). Melt viscosity 50
0 cps).

Ink Ink Carnauba wax 20 parts Ethylene/vinyl acetate copolymer (Sumitate KC-10, manufactured by Sumitomo Chemical) 13 parts 150"F paraffin wax 45 parts Carbon black
35 parts Next, the following composition was heated at a temperature of 60°C, and applied at a rate of 2.0 g/d by a hot lacquer gravure coating method having diagonal grooves at an angle of 45° and dried to form a surface layer. A thermal transfer sheet of the present invention was obtained.

Higaki m white synthetic ethylene/vinyl acetate copolymer (Sumitate KC-10
(manufactured by Sumitomo Chemical) 40 parts carnauba wax 20 parts 150°F paraffin wax 50 parts xylene
100 parts isopropanol 1
0 parts Example 2 A sensitized layer was prepared using 150°F paraffin wax (100°C melt viscosity 5 cps). Qg/rr? A thermal transfer sheet of the present invention was prepared in the same manner as in Example 1, except that the surface layer was formed with a gravure plate having an angle of 30° with respect to the transport direction.

Example 3 The sensitized layer was made of the following wax composition (melt viscosity at 100°C: 80c).
A thermal transfer sheet of the present invention was prepared in the same manner as in Example 1, except that the surface layer was formed using a gravure plate having an angle of 60° with respect to the transport direction. It was created.

Dan Tamakiri Ee Kairi Aka Carnauba Wax 19 parts Vinyl chloride/vinyl acetate copolymer (Evaflex 210, manufactured by Mitsui Polychemicals) 1 part Isopropanol
60 parts water
ioo part Example 4 The sensitized layer was made of the following wax composition (melt viscosity at 100°C: 50c)
A thermal transfer sheet of the present invention was prepared in the same manner as in Example 1, except that the sheet was formed to have a thickness of 1.0 g/rrr using a heat transfer sheet (PS).

151 Rie Kaijioku Mei Carnauba Wax 19 parts Vinyl chloride/vinyl acetate copolymer (Evaflex 21O1 manufactured by Mitsui Polychemicals) 0.5 part Isopropanol
60 parts water
100 parts Example 5 The sensitizing layer was made of the following wax composition (melt viscosity at 100°C: 16c).
A thermal transfer sheet of the present invention was prepared in the same manner as in Example I, except that the sheet was formed to have a thickness of 1.5 g/I using .PS).

1 ink 1" LL shiitake or candelilla wax 30 parts Emulsion forming surfactant 1 part isopropanol 50 parts water
50 parts Example 6 A composition having the following composition was heated at a temperature of 100°C and applied to the surface of the sensitized layer of Example 1 using a hot melt roll coating method at a coating amount of 8 g/rrl to form a thermal transfer ink. A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that a layer (melt viscosity at 100° C. of 800 cps) was formed.

Ink Ink Carnauba wax 20 parts Ethylene/vinyl acetate copolymer (Sumitate KC-10, manufactured by Sumitomo Chemical) 20 parts 150°F Paraffin wax 45 parts Carbon black
35 parts Example 7 A composition having the following composition was heated at a temperature of 100°C and applied to the surface of the sensitized layer of Example 1 at a coating amount of 8 g/d using a hot melt roll coating method to form a thermal transfer ink. Layer (1
00°C melt viscosity 400 cps), and the others were as in Example 1.
A thermal transfer sheet of the present invention was obtained in the same manner as described above.

Ink Ink Carnauba wax 20 parts Ethylene/vinyl acetate copolymer (Sumitate KC-10, manufactured by Sumitomo Chemical) 10 parts 150°F Paraffin wax 45 parts Carbon black
25 parts Comparative Example 1 A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that the sensitized layer and surface layer in Example 1 were not formed.

Comparative Example 2 A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that the sensitized layer was not formed in Example 1.

Comparative Example 3 A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 3 except that 1 part of the vinyl chloride/vinyl acetate copolymer in Example 3 was changed to 5 parts to give a melt viscosity of 300 cps at 100°C.

Usage Example 1 The thermal transfer sheets of the above Example and Comparative Example were printed and compared at Nx mode (N=61), and the results are shown in Table 1 below. TRWI
(manufactured by Juyaku Paper) was used.

○: Good △: Slightly poor ×・Poor (Effect) As explained above, according to the present invention, a sensitized layer with a low melt viscosity is formed between the ink layer of the thermal transfer sheet and the base film, and By forming an uncolored surface layer on the ink layer, there is no scumming or trailing during printing even in the N-times mode method (and the thermal transfer sheet has improved printing density and resolution). provided.

Furthermore, by forming diagonal fine irregularities on the surface of the surface layer at an angle with respect to the conveying direction of the thermal transfer sheet, it is possible to prevent the thermal transfer sheet from sticking to the transfer material during printing, and also to prevent background smudges and Trailing etc. are more effectively prevented.

Claims (7)

[Claims] (1) A thermal transfer sheet in which a sensitized layer, a transfer ink layer, and an uncolored surface layer are formed on one side of a base film in the order described above, in which the surface layer has an angle with respect to the transport direction. A thermal transfer sheet characterized by having a diagonally lined fine unevenness shape. (2) The melt viscosity of the ink layer is 300c at 100℃
The thermal transfer sheet according to claim 1, wherein the sensitized layer has a melt viscosity of 100 cps or less at 100°C. (3) The thermal transfer sheet according to claim 1, wherein the ink layer has a pigment concentration of 20 to 70% by weight. (4) The thermal transfer sheet according to claim 1, wherein the thickness of the ink layer is in the range of 3 to 20 μm. (5) The thermal transfer sheet according to claim 1, wherein the ink layer is formed using wax and a thermoplastic resin as a vehicle. (6) The thermal transfer sheet according to claim 1, wherein the surface layer is formed of a gravure plate having diagonal grooves. (7) The thermal transfer sheet according to any one of claims 1 to 6, which is for N times mode.