JPH03203684A - Thermal transfer sheet and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a thermal transfer sheet capable of imparting printing excellent in dry cleaning properties or ironing properties by forming an ink layer from an emulsion containing polyethylene wax having a high m.p. and a colorant. CONSTITUTION:A thermal transfer ink layer is formed from ink consisting of polyethylene wax and a colorant. Polyethylene wax has a softening point of 100 deg.C or higher and, when the softening point is less than 100 deg.C, formed printing is insufficient in dry cleaning properties or ironing properties. As the colorant, org. or inorg pigment having good characteristics as a recording material, for example, carbon black is pref. The emulsion ink used in the formation of the ink layer is prepared by mixing a commercial polyethylene wax emulsion and a commercial pigment dispersion. The advantage due to the emulsion resides in such a point that the excellent transfer ink layer is formed even when polyethylene wax to be used has a relatively high softening point.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a thermal transfer sheet, and more particularly to a thermal transfer sheet capable of printing with excellent dry cleaning resistance, ironing resistance, etc.

(Prior Art and its Problems) Conventionally, when printing output prints from computers or word processors by a thermal transfer method, a thermal transfer sheet having a thermal transfer 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 a paper such as capacitor paper or paraffin paper with a thickness of 0 to 20 LLm, or a plastic film such as Bossester or cellophane with a thickness of 3 to 20 um, coat it with a thermal transfer ink layer made by mixing wax with a coloring agent such as pigment or dye. It was manufactured by the company.

The thermal transfer sheet mentioned above has been widely used for printing output of computers and word processors, but recently it has been used for printing barcode labels and tag labels attached to various products because of its simplicity and suitability for small lot printing. It became like that. One of these uses is customer management labels in dry cleaning, the quality of various clothing,
It is also beginning to be used for printing on cloth labels, etc. that display size, etc.

In the above-mentioned cleaning applications, customer management labels are cleaned while attached to clothing, and as a result, cloth labels are also subject to cleaning and ironing. There is a problem that it is easily dissolved by solvents such as Perkleen, making it unusable.Furthermore, various problems occur when ironing, such as the printed characters sometimes melting and becoming unclear, and conventional thermal transfer sheets can become dull. It was unusable for that purpose.

Of course, the above problems can be solved by forming the ink layer of the thermal transfer sheet from a resin with excellent solvent resistance and heat resistance, but conventionally known resins cannot print clearly with a simple thermal transfer printer. was not possible.

Therefore, an object of the present invention is to solve the above-mentioned drawbacks and provide a thermal transfer sheet capable of printing with excellent dry cleaning resistance, ironing resistance, etc.

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

That is, the present invention provides a dry cleaning resistant thermal transfer sheet comprising a transfer ink layer formed on one side of a base film, wherein the ink layer is made of a polyethylene wax with a high softening point and a colorant. In a method for producing a thermal transfer sheet and a thermal transfer sheet in which a transfer ink layer is formed on one side of a base film, the ink layer is formed from an emulsion containing a polyethylene wax with a high softening point and a colorant. This is a method for producing a dry cleaning resistant thermal transfer sheet.

(Function) By forming the ink layer from a high softening point polyethylene wax and a coloring agent, a thermal transfer sheet is provided that can print without dissolving or smearing even during dry cleaning and ironing.

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

The thermal transfer sheet of the present invention has a transfer ink layer formed on one side of a base film, and if necessary, an ink retaining layer between the base film and the transfer ink layer, and further an ink retaining layer on the back side of the base film. It has a structure in which a heat-resistant slipping layer is provided.

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,
There are plastic films such as polystyrene, nylon, polyimide, polyvinylidene chloride, polyvinyl alcohol, fluororesin, chlorinated rubber, and ionomers, papers such as condenser paper and paraffin paper, nonwoven fabrics, and base films that are composites of these. There may be.

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, it is preferable to form an ink retaining layer on the surface of the base film, but if the base film and the ink layer have appropriate adhesion and releasability, such an ink retaining layer may be formed. is not necessary.

However, when using a conventional polyester film as the base film, the adhesion between the base film and the ink layer described below is insufficient, and foil drop may occur, so an ink retaining layer is provided. It is preferable.

Such an ink-retaining layer needs to have appropriate adhesion and releasability, and for this purpose, a resin that has good adhesion to the base film, such as polyester resin, is used. Preferably, it is formed from a mixture to which is added a relatively low melting point wax that melts or softens by the process.

That is, when not printing, the thermoplastic resin sufficiently holds the ink layer on the base film and prevents the ink layer from falling off.On the other hand, when printing, the wax is softened by the heat of the thermal head, which is good for the ink layer. It becomes possible to impart excellent releasability. The wax having a relatively low melting point, preferably 100° C. or lower, contained in the ink retaining layer preferably accounts for 10 to 90% by weight of the ink retaining layer. The thickness of such an ink retaining layer is not particularly limited, but in order to have appropriate releasability, adhesion and heat sensitivity, a thickness of about 0.5 to 2 μm is preferably in the range.

Examples of the adhesive resin used above include acrylic resin, polyvinyl acetate resin, ethylene/vinyl acetate resin, vinyl chloride/vinyl acetate resin, polyethylene wax, polyurethane resin, and polyester resin. Examples include microcrystalline wax, carnauba wax, paraffin wax, and Fischer-Tropsch wax.

The thermal transfer ink layer formed on the surface of the ink holding layer is formed from an ink made of polyethylene wax and a colorant.

Various grades of the above-mentioned polyethylene waxes are readily available on the market and can be used, but preferred polyethylene waxes in the present invention have a softening point of 100°C or higher, more preferably 120°C to 160°C. If the softening point is less than 100° C., the printed characters formed will have insufficient dry cleaning resistance, ironing resistance, etc. On the other hand, if the softening point is 160° C. or higher, the transferability of the ink layer during printing will be insufficient.

The colorant to be used includes organic or inorganic pigments or dyes that have good properties as a recording material;
For example, it is preferable to have sufficient color density and not discolor or fade due to light, heat, temperature, etc. Carbon black pigments are preferred, but cyan, magenta, yellow, etc. pigments can also be used.

The thickness of the transfer ink layer to be formed should be determined in such a way as to balance the required density and thermal sensitivity, e.g.
．． The thickness is generally about 5 to 5 μm.

Examples of methods for forming the ink retaining layer and the transfer ink layer include hot melt coating, hot lacquer coating, gravure coating, gravure reverse coating, roll coating, and many other methods. is particularly preferably formed by an emulsion method.

That is, since the polyethylene wax is poorly soluble or insoluble in most organic solvents and has a relatively high softening point, hot melt coating is not easy. On the other hand, by using the emulsion method, such problems do not arise and the ink layer can be easily formed.

The emulsion ink used to form the ink layer may be manufactured by mixing a commercially available polyethylene wax emulsion and a commercially available pigment dispersion, or by melt-kneading polyethylene wax and pigment and emulsifying it in water. Good too. The latter method is more preferred since the pigment particles are completely encapsulated in the polyethylene wax.

Another advantage of the emulsion method is that an ink layer with excellent transferability is formed even though the polyethylene wax used has a relatively high softening point. That is, by applying a predetermined amount of emulsion ink to a base film or an ink retaining layer thereon, and heating and drying it at a temperature below the film formation temperature of polyethylene wax, for example, below the softening point of polyethylene wax, the ink layer is formed at least Since some of the particles retain their particle form, the foil cuts easily during printing, allowing for high-quality printing.

In particular, by combining it with the ink retaining layer, both excellent foil drop prevention properties and foil cutting properties can be achieved.

In the present invention, a sealing layer and an adhesive layer are further formed on the surface of the ink layer, so that it is possible to print even on a transfer material with a rough surface.

Further, when a heat-sensitive material is used as the base film, it is preferable to provide a heat-resistant slipping layer on the surface in contact with the thermal head to improve the slipperiness of the thermal head and prevent sticking. The basic components of the heat-resistant slipping layer are a heat-resistant resin and a substance that functions as a heat release agent or a lubricant. By providing such a heat-resistant slipping layer, thermal printing is possible without sticking even on thermal transfer sheets made of heat-sensitive plastic films as a base material. Benefits such as ease of use can be taken advantage of.

It goes without saying that the present invention can be applied to thermal transfer sheets for color printing, so multicolor thermal transfer sheets are also included within the scope of the present invention. Further, as a thermal transfer printer, it can be applied to either a line or serial type.

(Effects) According to the present invention as described above, by forming the ink layer from a polyethylene wax colorant having a high softening point,
A thermal transfer sheet capable of printing without dissolving or smearing even during dry cleaning and ironing is provided.

(Example) Next, 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 ink retaining layer coating solution was applied to the surface of a 6.0 μm thick polyester film (trade name "Lumirror", manufactured by Toshi ■) with a heat-resistant layer formed on the back surface in an amount of approximately 0.0 μm. 5g/r
An ink retaining layer was formed by coating and drying to give an ink retention layer of .

Ink E', Apolyester resin (manufactured by Toyobo ■, Tg 65℃) 50 parts Polyethylene wax 50 parts Isopropyl alcohol 50 parts Water
50 parts Next, transfer ink of the following composition was applied by gravure coating in an amount of 2.0 g/
rr? An ink layer was formed by coating and drying at a ratio of 100 to 100% to obtain a thermal transfer sheet of the present invention.

Rolling ink Ink.

Polyethylene wax (softening point 140°C) 20 parts Carbon black 2 parts Emulsifier 1 part Isopropyl alcohol 40 parts Water
40 parts Example 2 A thermal transfer sheet of the present invention was obtained in the same manner as in Example 1 except that the formation of the ink retaining layer in Example 1 was omitted.

Comparative Example 1 A thermal transfer sheet of a comparative example was obtained in the same manner as in Example 1 except that the ink layer was formed from the following ink.

Ink Ink thread Polyethylene wax (softening point 90°C) 20 parts Carbon black 2 parts Emulsifier
1 part isopropyl alcohol 40 parts water
40 copies Usage Example 1 Using the thermal transfer sheets of Examples 1 and 2 and Comparative Example 1, printing was carried out under the following printing conditions, and the solvent resistance, heat resistance, and printing quality were evaluated and the results were as shown in Table 1 below. Got the results.

Equipment used: Toshiba simulator equipped with a thin film thermal head Printing energy: 0.8 mJ/dot (constant) rotation
Photography: Coated paper (Beck smoothness: 1000 seconds) (1) Solvent resistance: Rubbed 5 times with trichlene-impregnated cloth.

○: No change.

×: Printing flows.

(2) Heat resistance: Rub 5 times with an iron at 120°C.

○: Page print does not collapse.

×: Printing is distorted.

(3) Print quality: Visually check for defects in the print.

○: No chipping is observed.

Δ: Some chipping is observed.

×: Chips are observed.

Claims (5)

[Claims] (1) A dry-cleaning-resistant thermal transfer sheet comprising a transfer ink layer formed on one side of a base film, wherein the ink layer is made of a polyethylene wax with a high softening point and a colorant. . (2) The thermal transfer sheet according to claim 1, wherein at least a portion of the ink layer is made of granular polyethylene wax. (3) The thermal transfer sheet according to claim 1, wherein an ink retaining layer is formed between the base film and the ink layer. (4) The thermal transfer sheet according to claim 3, wherein the ink retaining layer comprises a polyester resin and a low melting point wax. (5) A method for producing a thermal transfer sheet in which a transfer ink layer is formed on one side of a base film, characterized in that the ink layer is formed from an emulsion containing a polyethylene wax with a high softening point and a colorant. A method for producing a dry cleaning resistant thermal transfer sheet.