JPH02202490A - Thermal transfer medium - Google Patents

Abstract

PURPOSE:To provide the above transfer medium hard to melt by the heating due to a thermal head and prevented from the stickness to the thermal head by using a stretched film composed of aromatic component introduced polyamide having good heat resistance. CONSTITUTION:A heat-meltable or heat-sublimable ink layer is provided to the single surface of a polyamide stretched film having an m.p. of 270 deg.C or higher based on hexamethylenediamine (A) being a diamine component and adipic acid (B) and terephthalic acid (C) being dicarboxylic acid components or a composite stretched film containing at least one polyamide resin layer. Polyamide is called nylon 66-6T and obtained by usual known polycondensation, for example, the polycondensation of (A), (B) and (C) according to a melting method or the interface or solution polycondensation of acid halides (preferably acid chlorides) of (A), (B) and (C). The stretching magnification of the polyamide film is pref. stretched by 1.5 times or more at least uniaxially.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention is directed to the use of hexamethylene adipamide (hereinafter referred to as 66 components) and hexamethylene terephthalamide (hereinafter referred to as 6T component).
The present invention relates to a thermal transfer medium which uses a polyamide film as a support and which does not melt even when heated by a thermal head and is excellent in preventing sticking with the thermal head.

(Prior Art and Problems to be Solved by the Invention) Conventionally, for thermal transfer recording, a thermal transfer medium in which a heat-melting ink layer or a heat-sublimating ink layer is provided on one side of a polyester film or capacitor paper is used. In many cases, a method has been adopted in which the ink is transferred to paper by heating the support from the side opposite to the ink layer.

In this conventional method, especially when a polyester film is used, there is a problem in that it has low heat resistance and is partially melted by the heat of the thermal head, which instantaneously reaches about 400°C. This tendency was particularly strong when heat-sublimable ink was used, since the energy required for sublimation was large, making it necessary to increase the temperature of the thermal head and prolong the time. Further, even if the support is not melted, the contact surface of the support with the thermal head is partially softened, resulting in poor slip properties, and the so-called stick phenomenon is likely to occur.

In order to improve these problems, for example,
Although a heat-resistant slip coating is often applied to the thermal head side of the support as in Japanese Patent No. 13359, an increase in cost is unavoidable, and there are problems such as peeling between the heat-resistant coating layer and the support. There were many.

(Means for Solving the Problems) As a result of repeated studies on this problem, the inventors came up with the following thermal transfer medium.

That is, the present invention uses hexamethylene diamine (A) as the diamine component and adipic acid (A) as the dicarboxylic acid component.
B) and terephthalic acid (C) with a melting point of 270
Abstract: A heat-sensitive transfer medium characterized in that a heat-melting ink layer or a heat-sublimating ink layer is provided on one side of a polyamide-based stretched film or a composite stretched film containing at least one layer of the polyamide resin layer at a temperature of at least 10°C. shall be.

The polyamide used in the present invention is called nylon 66-6T, and 2 commonly known polycondensation methods 9 e.g. (A),
(B) and (C) are polycondensed by a melting method, or (A)
It can be obtained by interfacial or solution polycondensation of (B) and (C) acid halide (preferably acid chloride). In addition to components (A), (B), and (C), other polyamide-forming components may also be copolymerized as long as the melting point of the present invention is not less than 270°C. Copolymerization components include diamine components such as tetramethylenediamine, m-phenylenediamine, p-phenylenediamine, m-xylylenediamine, P-xylylenediamine, bis(P-aminocyclohexyl)methane, succinic acid, and glutaric acid. , dicarboxylic acid components such as sebacic acid, azelaic acid, isophthalic acid, naphthalene dicarboxylic acid, ε-aminocaproic acid, ω
Examples include aminocarboxylic acid components such as -aminododecanoic acid and aminobenzenecarboxylic acid.2 Copolymerization of aromatic group-containing components is particularly preferred in terms of dimensional stability of the resulting film. Copolyamide consisting of 66 components and 6T components shows so-called isomorphism, but it is judged comprehensively from mechanical properties, dimensional stability, melting point, heat resistance, ease of single polycondensation, processability into film, etc. Then, component (C) is preferably 15 to 70 mol%, more preferably 20 to 60 mol%, of the total amount of component (B) and component (C), and the melting point of the polyamide itself is 330 ° C or less. It is preferable that there be. The polyamide preferably has a high molecular weight and preferably has a relative viscosity of 2.5 or more, measured at 25°C at a concentration of 1 g/dj2 in 96% sulfuric acid. What should be noted here is the lower limit of the melting point of polyamide,
In order to achieve the objective of heat resistance, the polyamide must have a melting point of 270°C or higher. Note that the melting point is the melting peak temperature when the temperature is increased at a rate of 20° C./min using a differential scanning calorimeter (DSC).

The polyamide film in the present invention is a stretched film, and the stretching ratio is preferably 1.5 times or more in at least one axis from the viewpoint of mechanical properties and thermal properties. The manufacturing method will be described below.

(2) Preparation of unstretched film It can be produced by the commonly known melt T-die method or circular die method, but the melting temperature of the polymer is 10 to 50'C higher than the melting point of the polymer, that is, 290 to
The temperature is preferably about 350° C., and it is preferable to cool the film-like material discharged from the stick as much as possible to suppress crystallization. 6-row 67 polyamide is a polymer that crystallizes quickly.

For example, when a casting roller is used, its surface temperature is preferably 10°C or less.

(2) Production of uniaxially stretched film This can be obtained relatively easily by roll stretching the above-mentioned unstretched film. The stretching temperature is preferably 70 to 200°C, preferably 70 to 180°C.

■Manufacture of biaxially stretched film The best results can be obtained using the simultaneous biaxial stretching method.

This is because in the case of sequential biaxial stretching, the hydrogen bonds between polyamide molecular chains generated by uniaxial stretching inhibit the uniform stretching in the next step, whereas in the case of simultaneous biaxial stretching, this problem is avoided. This is because it can be avoided. The biaxial stretching method may be either the flat method or the tubular method, but the former is preferable from the viewpoint of film thickness accuracy. Then, the stretching temperature is the same as in the case of ■, and the flat method simultaneous 2
The stretching ratio in the axial stretching is 1.
5 to 5.0 times.

The area stretching ratio is preferably 2.0 to 4.0 times, and the area stretching ratio is 3 to 20 times, more preferably 4 to 15 times.

■Thermal fixation of the film The stretched film has two
The heat treatment is preferably carried out at 00 to 300°C, preferably 210 to 280°C.

The film in the present invention is generally used in the form of a single layer film of the above-mentioned polyamide, but may also be used in the form of a multilayer film containing at least one layer of the polyamide resin. In the case of multiple layers, it is effective to provide the polyamide resin layer on the surface that contacts the thermal head.

In the case of a thermal transfer medium, the thickness of the film is preferably 2 to 10 .mu.m, since the thinner the film, the better the sensitivity, but if it is too thin, problems will arise in terms of strength.

Coating an ink layer onto a film is mainly performed by hot melt coating, gravure coating, reverse coating, or the like. In the case of heat-melting type ink, a mixture of pigment and wax or polyester resin, ethylene, vinyl acetate resin, etc. is suitable; in the case of heat-sublimation type, a mixture of sublimable dye and polyolefin resin, polyester resin, etc. is suitable.
A mixture of low melting point or low softening point resins such as vinyl acetate resins is suitable, but is not particularly limited thereto.

(Example) The present invention will be explained in more detail below using Examples.

Examples 1-4. Comparative examples 1-2 First, three types of polyamides (■) shown in Table 1.

([) and (III) were prepared by melt polycondensation method. These polyamide pellets were fed into an extruder type melt extruder and extruded at 300°C with a lip width of 200mm.
, the extruded molten film was extruded through a T-die with a lip spacing of 0.6n+m, and the extruded molten film was cooled and solidified using a casting roller maintained at O'c to form a polyamide of 15μ for each polyamide.
A 50 μm unstretched film was obtained. A 15 μm unstretched film was stretched 1.8 times in the longitudinal direction using a roll-heating longitudinal stretching machine to produce a stretched film, which was heat-set at 240°C. The obtained 8μ film was hot-melt coated with a mixture consisting of 10 parts of paraffin wax, 30 parts of Carteba wax, 40 parts of ester wax and 20 parts of pigment to form an ink layer with a thickness of 4μ. The laminated film was microslit, and thermal transfer was performed using a thermal printer (Picoword, manufactured by Brother Industries, Ltd.).

During transfer, a sticking phenomenon occurred between the film and the thermal head in the case of polyamide (I) (Comparative Example 1), but this phenomenon occurred in the case of polyamide (1) and polyamide (II) (Examples 1 and 2). No such problems occur,
I was able to print well.

Next, the 50μ unstretched film was fed to a tenter-type simultaneous biaxial stretching machine, stretched at a temperature of 120°C and a longitudinal and horizontal stretching ratio of 3.0 times, and heat-set at 240°C. A stretched film with a thickness of 5 μm was made.

When this stretched film was subjected to a thermal transfer test under the same conditions as described above, a stick phenomenon was observed in the case of polyamide (r[[) (Comparative Example 2), but in the case of polyamide (
1) and polyamide (I[) (Examples 3 and 4), such problems did not occur.

Table 1 (Effects of the Invention) Since the heat-sensitive transfer medium of the present invention uses an aromatic component-introduced polyamide stretched film with good heat resistance as a support, it can withstand the force t12 exerted on the thermal head. It is also excellent in preventing stickiness with thermal heads, making it extremely useful industrially.

Claims (1)

[Claims] (1) Hexamethylenediamine (A
), on one side of a polyamide stretched film containing adipic acid (B) and terephthalic acid (C) as dicarboxylic acid components and having a melting point of 270° C. or higher, or a composite stretched film containing at least one polyamide resin layer. A heat-sensitive transfer medium characterized by being provided with a heat-fusible ink layer or a heat-sublimable ink layer.