JPS6271665A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head for a thermal printer having excellent durability, by constituting a protective film of an ion-plated film of silicon monoxide, in a thermal head comprising a substrate provided with a glaze layer thereon, a heating resistor film, an electrode film and a protective film. CONSTITUTION:A thermal head comprises an insulating substrate 1 consisting of alumina or the like, a vitreous glaze layer 2, a heating resistor film 3 formed of Ta2N or the like, and electrode film 4 consisting of a Cr-Au film and a protective film 7, laminated in this order. The protective film 7 is a layer obtained by ion plating of silicon monoxide in a high vacuum. The protective film does not contain silicon dioxide or silicon nitride mixed therein, and has such a high hardness that it has a practically sufficient abrasion resistance without any abrasion-resistant layer. In addition, the protective film 7 has an excellent oxygen-shielding capability due to the sufficiently dense structure thereof, and since it has favorable adhesion to the substrate on which it is provided, there is no need to provide a vapor-deposited film of a metal fluoride compound or the like therebetween.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a head for a thermal printer, and particularly to a type of thermal head using an ion plating film of silicon monoxide as a protective film.

<Prior Art> Conventionally, as shown in FIG. 1, a thermal head for a thermal printer includes a substrate 1 having a glaze layer 2 for heat insulation, a resistor film 3 for heat generation, and the resistor. A thermal head having electrode films 4 arranged in a matrix for selectively heating the films with electricity, and a protective film 5 made of silicon dioxide for preventing oxidation of the resistor film 3 or the electrode film 4. It has been known. Further, since the surface of the protective film 5 is firmly attached to the ribbon or printing paper, a wear-resistant film 6 made of tantalum pentoxide or the like may be provided on the surface of the protective film.

However, during printing, the resistance of the resistor is momentarily 250 to 40
In order to heat the stomach to about 0°C, thermal stress is applied to each film, and oxygen in the atmosphere or in the protective film, glaze layer, etc. tends to diffuse and oxidize the resistor film, reducing the durability of the thermal head. It was a restriction on sexuality.

Therefore, Japanese Patent Application Laid-Open No. 52-89336 proposes the use of a vapor-deposited film of silicon monoxide, which is denser and has better hardness than silicon dioxide.

However, - the silicon oxide vapor deposited film is relatively brittle and has problems in terms of its ability to block the atmosphere due to the occurrence of cracks, etc. Therefore, - silicon dioxide or silicon nitride is mixed into the silicon oxide vapor deposited film to improve the air blocking ability. I try to do that. Therefore, there is a problem that the denseness or hardness of the protective film is impaired.

In addition, since the silicon oxide vapor deposited film does not have good adhesion to the base, a vapor deposited film of a metal fluoride compound such as magnesium fluoride is applied prior to the silicon monoxide film to improve the adhesion. However, the melting point of the metal fluoride compound is lower than that of silicon monoxide, and there is a problem in that the heat resistance of the thermal head is impaired.

<Problems to be Solved by the Invention> In view of these drawbacks of the prior art, the main object of the present invention is to provide a thermal head for a thermal printer with excellent durability.

<Means for Solving the Problems> According to the present invention, such an objective is to provide a thermal printer having a substrate having a glaze layer, a heating resistor film, an electrode film, and a protective film. This can be achieved by providing a thermal head characterized in that it is made of the above-mentioned protective film or a silicon oxide ion plating film.

<Function> Silicon monoxide ion plating film has superior hardness and density compared to silicon dioxide evaporation film or silicon monoxide evaporation film. Since there is no need to use a melting point substance, the durability of the thermal head can be significantly improved.

<Embodiment> FIG. 2 is a sectional view showing a main part of an embodiment of a thermal head based on the present invention. This thermal head includes an insulating substrate 1 made of a material such as alumina, a glaze layer 2 made of glass, a heating resistor film 3 made of Ta2N, etc., and an electrode film 4 made of Cr-AL. The protective film 7 is laminated in this order.

The protective film 7 is a layer formed by ion-plating silicon monoxide in a high vacuum, and since it is free of silicon dioxide or silicon nitride and has high hardness, it can be put to practical use even without a wear-resistant layer. Specifically, it has sufficient wear resistance, has a sufficiently dense structure, has excellent oxygen blocking ability, and has good adhesion to the base, so there is no need to interpose a vapor-deposited film of a metal fluoride compound.

FIG. 3 shows that between the heating resistor film 3 and the glaze layer 2, -
An undercoat film 8 formed by ion plating silicon oxide is provided. By providing such an undercoat film 8, oxidation of the resistor film 3 due to the diffusion of oxygen from the glaze layer 2 is prevented, and -M silica cable has better hydrofluoric acid resistance than silicon dioxide. Therefore, the formation of unevenness on the surface of the glaze layer 2 is avoided when forming the anti-reflection film 3 by etching.

Figure 4 shows the resistance of thermal heads with various structures when accelerated tests were performed with a pulse period of 3 m5 ec and a pulse width of 1.5 m5 ec, with the applied power increasing by 1 W/#2 every 10 minutes. Rate of change ΔR/RX100 (
%) measurement results are shown. However, R represents the resistance value before the test, and ΔR represents the amount of change in the resistance value.

Thermal head A has a structure in which only a resistor film and an electrode film are laminated on a glaze layer, and there is no protective film. Thermal head B, in contrast to the above-mentioned thermal head A, has a protective film formed by ion plating -silicon oxide under a pressure of 5.times.10@-5 Torr in an oxygen atmosphere. Thermal head C is 5
It has a structure formed by ion plating under a pressure of 10-Torr. Furthermore, the thermal head D prepared for comparison is different from the above thermal head A in that it uses electron beam heating using silicon dioxide as an evaporation source.
Thermal head E has a structure with a 2-micron thick protective film formed by 9 deposition under a pressure of 10-5 Torr. X 10'Torr
A protective film with a thickness of 2 microns is formed by high-frequency magnetron sputtering in an argon atmosphere.

From the graph of FIG. 4, it can be seen that the linear head based on the present invention,
In particular, the durability of one-dimensional head C, which is made by ion plating silicon monoxide under high vacuum, is excellent, and by introducing a small amount of oxygen, if silicon dioxide is mixed into silicon oxide, it can be easily removed. It can be seen that in the case of straw thermal head B, the durability is slightly inferior.

Figure 5 shows two types of thermal heads F and G.
At a pulse period of 3m5eC and a pulse width of 1.5m5eC,
The results of the resistance change rate with respect to the peak temperature of the heat generating resistor when an accelerated test was performed by increasing the temperature by 5 W/m2 every 10 minutes are shown. Here, the lower 9-maru head is made by laminating silicon monoxide as a protective film to the thermal head A with a thickness of 5 microns by ion plating, and the thermal head G is made by laminating the thermal head A with a thickness of 5 microns. Head F
It has a structure similar to that of the undercoat film 8, and is made by ion plating silicon monoxide with a thickness of about 1 micron on both the heating resistor film 3 and the glaze layer 2. .

From FIG. 5, by providing the undercoat film 8,
It can be seen that the durability of the thermal head is improved. Moreover, by providing such an undercoat film,
When etching the resistance heating element with hydrofluoric acid, it is possible to effectively prevent the glaze layer from being etched. Furthermore, such an undercoat film has the effect of preventing oxygen in the glaze layer from diffusing toward the heating resistor, so that it can further prevent deterioration of the heating element.

<Effects of the Invention> As described above, according to the present invention, with the extremely simple structure,
Ion plating is a method that can improve the durability of the thermal head and is relatively suitable for mass production.
Further, since a wear-resistant film on the surface or a film for improving the adhesion of the protective film can be omitted, the effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the structure of a thermal head based on the prior art. FIG. 2 is a longitudinal sectional view showing the structure of a thermal head based on the first embodiment of the present invention. FIG. 3 is a longitudinal sectional view showing the structure of a second embodiment of the thermal head according to the present invention. FIG. 4 is a graph showing the rate of change in resistance with respect to applied power in order to evaluate the durability of various thermal heads. FIG. 5 is a graph showing the rate of change in resistance with respect to temperature, which was measured for two types of thermal heads based on the present invention in order to evaluate the effects of the second embodiment of the present invention. 1...Substrate 2...Glaze layer 3...
Heating resistor film 4... Electrode film 5... Vapor deposited film of silicon dioxide 6... @ deposited film of tantalum pentoxide 7... - Ion plating film of silicon oxide 8...
undercoat film

Claims (2)

[Claims] (1) In a thermal head for a thermal printer having a substrate having a glaze layer, a heating resistor film, an electrode film, and a protective film, the protective film is made of an ion plating film of silicon monoxide. A thermal head featuring (2) The thermal head according to claim 1, wherein an undercoat film made of silicon monoxide is formed between the glaze layer and the heating resistor film.