JPH0479315B2 - - Google Patents

Description

[Detailed description of the invention]

OBJECT OF THE INVENTION [Industrial Field of Application] The present invention relates to an improvement in a thermal transfer sheet, and more particularly to a thermal transfer sheet that provides matte printing. [Prior Art] When printing a computer or word processor using a thermal transfer method, a thermal transfer sheet is used, which has a base film and a heat-melting ink layer on one side. Conventional thermal transfer sheets use a 10 to 20 micron thick paper such as capacitor paper or paraffin paper, or a 3 to 20 micron thick plastic film such as polyester or cellophane as a base film, and add pigment to the wax. This product is manufactured by coating a layer of hot-melt ink containing a mixture of the following. However, prints or images recorded with a thermal printer are generally glossy. Although glossy printing is beautiful, it is not desirable in terms of readability, so it is desired to perform matte printing. If paper is used instead of plastic as the base film, the gloss of the print will be lower, but it is still insufficient, and plastics, especially polyester, can be made thinner (up to about 1.6μ).
Due to its high strength, it has recently become mainstream. For this reason, there is a strong demand for matte printing. However, the waxes commonly used in the past, especially paraffin waxes, are normal-type paraffin, and their crystal structure is plate-shaped, and hot-melt inks that contain a large amount of this have a high gloss level when transferred. is the current situation. [Problems to be Solved by the Invention] An object of the present invention is to meet this demand and provide a thermal transfer sheet that provides matte printing. This objective is achieved by causing the surface of the ink to be transferred to be diffusely reflective, forming a so-called matte surface. Structure of the Invention [Means for Solving the Problems] The heat-sensitive transfer sheet of the present invention that provides matte printing has a heat-meltable ink layer on one side of a base film. 1. A heat-sensitive transfer sheet that provides matte printing, characterized in that the ink layer is made of a binder containing wax having an acicular crystal structure. That is, it is a heat-melting ink that is characterized by changing the crystal structure of wax, one of its components, from the conventionally widely used disk-like structure to a needle-like structure. [Function] By making the crystalline structure of the wax contained in the heat-melting ink needle-like, even when transferred to smooth paper, the wax stands on the surface of the paper and appears as a diffused reflection. It looks like pine to the outside. [Embodiment] The heat-sensitive transfer sheet of the present invention has a heat-melting ink layer containing wax having an acicular crystal structure on one side of a base film, and a thermal head on the other side of the base film. It has a layer that prevents staking. The method for manufacturing the heat-sensitive transfer sheet of the present invention will be explained below. A heat-melt ink containing wax having an acicular crystal structure is coated on one side of the base film by a hot-melt method and a roll coating method to form a heat-sensitive transfer ink layer. Next, an anti-staking layer is applied to the other side of the base film by gravure printing. The thickness of the anti-staking layer is suitably 0.5 to 2μ. Any conventionally used base film can be used as desired. Examples include films made of plastic materials such as polypropylene, cellophane, cellulose acetate, and polycarbonate, in addition to the above-mentioned polyester. In this case, the appropriate thickness is 1 to 30 microns. Paper such as capacitor paper or paraffin paper may also be used. For paper, a thickness of 5 to 30μ is suitable. The hot-melt ink containing wax having an acicular crystal structure, which is a feature of the present invention, basically consists of the following components. (A) Colorant: Carbon black or various dyes and pigments are added depending on the color to be imparted to the ink. (B) Binder: A paraffin wax having an acicular crystal structure is mixed with conventionally used resins and waxes as necessary. The ratio of paraffin wax having needle-like crystals to the total wax in the hot-melt ink must be at least 20%, and if it is less than that, a sufficient matte feel cannot be obtained. The thermal transfer sheet of the present invention may include various modifications. For example, a layer is provided to prevent staking between the base film and the thermal head, which may occur depending on printing conditions. The anti-stacking layer basically includes a heat-resistant resin and a substance that functions as a heat release agent or a lubricant. Heat-resistant resins include synthetic resins with a glass transition point of 60°C or higher,
Alternatively, it is preferable to use a thermoplastic resin having an OH group or a COOH group to which a compound having two or more amino groups or a diisocyanate or triisocyanate is added to cause some crosslinking and curing.
Heat release agents or lubricants include those that melt when heated, such as waxes and amides, esters, and salts of higher fatty acids, and those that remain solid, such as fluororesin and inorganic substance powders. There are things that are helpful. [Examples and Comparative Examples] The following composition was prepared using a plaid kneader.
A hot melt ink was prepared by kneading at 100°C for 6 hours (generally 90°C to 120°C, 5 hours to 10 hours). (All parts are parts by weight) Comparative example (conventional product) Parafine wax (MP=155〓) 13 parts Carnauba wax 3 parts Ethylene/vinyl acetate copolymer 1 part (Sumitomo Chemical "Sumitate HC-10") ) Carbon black 2 parts (Tokai Electrode "Seest S") Example "Paraffin wax with an acicular crystal structure" applied to the entire wax in the ink of the above comparative example
(POPKO-600 "manufactured by Noda Waxus") were blended at the content rates shown in Table 1 below to obtain hot-melt inks. A heat-sensitive transfer ink layer was prepared by applying hot melt coating heated to 100° C. to a thickness of 5 μm using a roll coating method on a polyester film having a thickness of 6 μm as a base film. This was slit into a ribbon shape and used for thermal transfer under the following conditions. Thermal head Thin film type Printing energy 0.6 m J/dot (The area of 1 dot is 4 x 10 ^-4 cm ² ) Transferred material High quality paper (Mitsubishi Paper "Tokukobishi" 46 size/
72Kg) The glossiness of the printed area was measured at a measurement angle of 60° using a gloss meter (Murakami Color Research Institute "GM-3M").

〔Effect of the invention〕

By using the heat-sensitive transfer sheet of the present invention, it is possible to perform heat-sensitive transfer having functions of matte printing and prevention of staking. Table 1 shows the effect of matte printing using the thermal transfer sheet of the present invention. Generally, the matteness required for printing varies depending on the gloss level of the recording paper and the reading conditions, but if the gloss level is approximately 30 or less when measured with a gloss meter, it can be said that it is always at a sufficient level. . According to the present invention, this can be easily achieved.

Claims (1)

[Scope of Claims] 1. A heat-sensitive transfer sheet having a heat-fusible ink layer on one side of a base film, wherein the heat-fusible ink layer is made of a binder containing wax having an acicular crystal structure. A thermal transfer sheet that provides matte printing. 2. The thermal transfer sheet according to claim 1, wherein the base film is a plastic film and a layer for preventing sticking to a thermal head is provided on the other surface.