JPH03247490A - N-fold mode heat transfer sheet - Google Patents

Abstract

PURPOSE:To obtain an N-fold mode heat transfer sheet having excellent heat transfer sheet conveyance, no scumming, tailing at the time of printing, and improved printing density, resolution, etc., by providing a transfer ink layer to be melted by heating on one side surface of a base film, and adding lubricant to an ink phase. CONSTITUTION:An N-fold mold heat transfer sheet has a transfer ink layer to be melted by heating on one side surface of a base film, and lubricant to be added to the ink layer. The lubricant is added to an ink phase to continue N-fold mode printing for long time. Thus, even if the periphery of a thermal head stores heat, the melting of the film and a material to be transferred is prevented, thereby smoothing printing. A colorless adhesive layer is provided between the film and the layer, or a lubricating surface layer is provided on the ink layer to desirably solve problems of scumming, tailing due to friction between the sheet and the material to be transferred after printing.

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. The present invention relates to a thermal transfer sheet useful for a thermal transfer sheet.

(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 1 as a base film.
Using paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 μm, or plastic film such as polyester or cellophane with a thickness of 3 to 20 μm, a layer of heat-melting ink made by mixing coloring agents such as pigments and dyes with wax is applied. It is manufactured by coating.

One problem with the thermal transfer method using the above thermal transfer sheet is that
This is an economic problem because printing can be performed only once at the same location, and therefore a thermal transfer sheet with the same width as the printing 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 relatively higher than the conveying speed of the thermal transfer sheet (the conveying directions of both may be the same or opposite). In this method, when the conveyance speed of the transfer material is N, the conveyance speed of the thermal transfer sheet is N゛, and N>N',
Although the printing distance is N, the consumption of thermal transfer sheet is N.
For example, if N=5 and N°=1, the amount of thermal transfer sheet consumed is 115, which is very economical.

However, in this method, although the transfer speed of the transferred material is slower than in the normal thermal transfer method, the number of times of printing is the same, that is, the thermal energy applied per unit area is large. When printing continues for a long time, heat accumulates inside the printer, especially around the thermal head, and the thermal transfer sheet is heated, causing a problem in that the conveyance of the thermal transfer sheet is hindered. This problem was initially thought to be due to fusion between the thermal head and the back surface of the thermal transfer sheet, and although an excellent heat-resistant slipping layer was provided on the back surface, it was not completely solved.

In addition, in the N-time mode method, the transfer material and the thermal transfer sheet move while being rubbed against each other, which causes background smudges and trailing of print on the transfer material, making it difficult to print with clear and high resolution. There is a problem.

Therefore, the object of the present invention is to solve the above-mentioned drawbacks, to provide a thermal transfer sheet with excellent conveyance properties, free from scumming, trailing, etc. during printing, and with improved printing density, resolution, etc. An object of the present invention is to provide a thermal transfer sheet for double mode.

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

That is, the present invention is a thermal transfer sheet for N-fold mode, characterized in that a transfer ink layer that melts when heated is provided on one surface of a base film, and a lubricant is added to the ink layer.

(Function) In the N-time mode thermal transfer method, if continuous printing is performed for a long time, the conveyance performance of the thermal transfer sheet will deteriorate.

It has been found that this problem is largely related to not only the fusion between the thermal head and the thermal transfer sheet, but also the fusion between the surface of the thermal transfer sheet after the ink has been removed and the transfer material. This problem can be solved by subjecting the surface of the base film on which the ink layer is to be formed to be lubricated, but in this case, the durability of the ink layer is significantly impaired, making it impractical.

In the present invention, it has been discovered that by including a lubricant in the ink layer, the transportability of the thermal transfer sheet is not inhibited even if the printer accumulates heat.

In addition, by providing a substantially colorless adhesive layer between the base film and the ink layer, or by providing a slippery surface layer on the surface of the ink layer, it is possible to prevent friction between the thermal transfer sheet and the transfer material after printing. The problems of scumming and tailing are better solved.

(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, cellophane, polycarbonate, cellulose acetate, polyethylene, polyvinyl chloride,
polystyrene, nylon.

Plastic films such as polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, ionomer, etc., paper such as condenser paper, paraffin paper, etc.
There are non-woven 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, 2 to 25 μm.

In the present invention, a hot-melt ink layer is formed on the surface of the base film, preferably via a peelable adhesive layer, from an ink containing necessary materials.

The peelable adhesive layer is adhered to the base film, and
It has good adhesion to the ink layer (prevents the ink layer from peeling off all at once during printing, and after the last ink layer is transferred, it becomes a virtually colorless layer, causing background smudges and trailing of the print. In order to have this effect, the release adhesive layer is mainly composed of wax, which is used to form the ink layer described later, and is also made of a thermoplastic resin with adhesive properties. The thickness of the peelable adhesive layer is not particularly limited, but is preferably in the range of about 0.2 to 5 μm in order not to reduce the thermal sensitivity during thermal transfer.

The ink layer provided on the peelable adhesive layer comprises a colorant, a vehicle, and a lubricant, and may further contain various additives as necessary. 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, in addition to black, colorants of various colors 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 thickness of 3 to 20 um, the preferred concentration is 20 to 70% by weight, more preferably 30 to 70% by weight.
It is in the range of 50% by weight, and if the concentration is too low, the print density will be insufficient, and if it is too high, the ink will not wet the paper easily and voids will easily occur, which is not preferable.

The vehicle used includes wax as a main component, and mixtures of wax with drying oil, resin, mineral oil, cellulose, rubber derivatives, and the like.

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. used.

The lubricants added to the ink layer include lubricants such as waxes, silicone waxes, fluorine resins, silicone resins, higher fatty acid amides, higher fatty acid esters, and surfactants that have lubricity. It is preferably added in an amount of 0.2 to 5 parts by weight. If the amount added is less than the above range, the slip property between the base film and the transferred material due to heat accumulation during printing will be insufficient, while if it is too large, the adhesion between the ink layer and the base film will decrease. So I don't like it.

The ink consisting of the above colorant, vehicle, and lubricant is 1
It is preferable to blend so that the melt viscosity at 00°C is 30Ocps or more.If the melt viscosity cannot be increased to 30Ocps or more with wax alone, various thermoplastic resins such as vinyl resins are used in combination to increase the cohesive strength. can be used to improve melt viscosity. Usually, the melt viscosity can be increased to 30Ocps or more by using a vinyl resin in an amount of 7% by weight or more based on Fuchs. The preferred melt viscosity is 300 to 1,00 Ocps at 100°C.

Methods for forming the ink layer on the base film include hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many other methods of applying the respective coating liquids. can be mentioned.

It is preferable to form a surface layer with releasability and lubricity on the surface of the ink layer, and since such a surface layer is transferred to the transfer material together with the ink layer during thermal transfer, the release adhesive layer Similarly, it is preferable to use the above-mentioned wax as the main ingredient, and also to use various release agents and lubricants in combination.

Formation of the surface resin layer can be performed by various techniques similar to the formation of the ink layer. In the present invention, the thickness of the surface resin layer is preferably 0.1 μm or more and 5 μm or less so that sensitivity is not insufficient even when printing energy is low as in a high-speed printer.

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.

The thermal transfer sheet of the present invention described above is mainly used for black printing, but of course it also includes a thermal transfer sheet for color printing depending on the coloring agent in the ink layer.

The thermal transfer sheet of the present invention is useful in an N-times mode method in which the conveyance speed of the transfer material is relatively higher than the conveyance speed of the thermal transfer sheet (the conveyance directions of both may be the same or opposite directions). , the conveyance speed of the transfer material is N, the conveyance 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, N=5, When N°=1, the consumption of thermal transfer sheet is 115 compared to the conventional one, which is very economical.
Furthermore, background smudges and trailing of print do not occur, which were problems in the past.

(Effects) According to the present invention as described above, by adding a lubricant to the ink layer, even if Nx mode printing is continued for a long time and heat accumulates around the thermal head, the base film and the transfer material are This prevents fusion with the paper and enables smooth printing.

In addition, by providing a substantially colorless adhesive layer between the base film and the ink layer, or by providing a slippery surface layer on the surface of the ink layer, it is possible to prevent friction between the thermal transfer sheet and the transfer material after printing. The problems of scumming and tailing are better solved.

(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 The following coating solution was applied to the surface of a 6.0 μm thick polyester film with a slip layer formed on the back (product name: "Lumirror" manufactured by Toshi ■) in an amount of approximately 0.6 g/i. It was coated and dried at 80 to 90°C to form a peelable adhesive layer.

Nijishoen ttiue carnauba wax 30 parts nonionic surfactant 1 part isopropanol 100 parts water
30 parts Next, a transfer ink composition having the composition shown below was kneaded using an attritor for 6 hours while heating to 120°C.

Ink Ink Ethylene/vinyl acetate copolymer 13 parts Carnauba wax 20 parts Paraffin wax 45 parts Lubricant (silicon wax)
Part 2 carbon black
Heating 35 parts of the above ink composition at a temperature of 120°C,
A thermal transfer ink layer was formed by applying a coating amount of about 8 g/rrr to the surface of the above-mentioned release adhesive layer using a hot-melt roll coating method, and the following coating liquid was further applied to the surface of the above-mentioned ink layer. The thermal transfer sheet of the present invention was prepared by coating and drying at a rate of 2.0 g/g based on solid content to form a surface smooth layer.

Ink Carnauba wax 20 parts Ethylene/vinyl acetate copolymer 40 parts Paraffin wax 50 parts Isopropanol
10 parts xylene
100 parts Example 2 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 from the following coating solution.

Ink Poor Ink Ethylene/vinyl acetate copolymer 13 parts Carnauba wax 20 parts Paraffin wax 45 parts Lubricant (higher fatty acid amide)
5 parts carbon black
35 parts Example 3 The thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the ink layer was formed from the following coating solution. Wax 45 parts Lubricant (polyethylene glycol) 5 parts Carbon black
35 parts Comparative Example 1 A thermal transfer sheet of a comparative example was prepared in the same manner as in Example 1 except that no lubricant was added to the ink layer and no peelable adhesive layer or surface smooth layer was formed in Example 1. Obtained.

Use Example 1 The thermal transfer sheets of the above Example and Comparative Example were printed and compared using an N-time mode printing evaluation machine (N=6), and the results are shown in Table 1 below. Note that TRWI (manufactured by Jujo Paper Industries) was used as the recording paper.

Sudden I”-jku

Claims (3)

[Claims] (1) A thermal transfer sheet for N-fold mode, characterized in that a transfer ink layer that melts when heated is provided on one side of a base film, and a lubricant is added to the ink layer. (2) The thermal transfer sheet according to claim 1, further comprising a releasable adhesive layer between the base film and the ink layer. (3) The thermal transfer sheet according to claim 1, wherein a slippery surface layer is provided on the surface of the ink layer.