JPS6290261A - Antiwear protective film for thermal head - Google Patents

Abstract

PURPOSE:To make it possible to enhance hardness and scratch strength, to impact excellent antiwear property and to enhance cracking resistance and heat conductivity, by providing an antiwear protective film for a thermal head containing Al, O and N as main elements. CONSTITUTION:An antiwear protective film for a thermal head is composed of an Al-O-N type substance, more concretely, a substance represented by AlNxO1-x(x=0.5-0.98). If x is smaller than 0.5, heat conductivity is lowered and said film becomes improper as one for a high speed printer and, if exceeds 0.98, the close adhesiveness of the film if lowered. If x is within a range of 0.5-0.98, heat conductivity is high, and so is the close adhesiveness of the film. The film can be formed using a sputtering method. When this method is employed, powdery aluminum nitride or oxide is mixed in a film composition as a film-forming stock in required ratio and the resulting mixture is pressed to form a target. By this method, the film has high hardness and relatively high heat conductivity and is suitable for a high-speed printer and also excellent i an antiwear property, chemical stability, scratch resistance, etc.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to a wear-resistant insulation film for a thermal head.

[Prior art and its problems]

Thermal head is computer, word processor, 7
It is widely used as a print head such as Aximil.

The thermal head is constructed by arranging a large number of dots of resistive heating elements such as amorphous silicon, and selectively energizing them to thermally transfer a printing ribbon onto a sheet of paper to print.

Since the paper is transferred while sliding against the surface of the thermal head, it is necessary to protect the surface of the resistance heating element with a protective film having high wear resistance.

As shown in FIG. 1, the dot-shaped printing elements in the thermal head include, in order from the bottom, a substrate 1 made of alumina or the like, a glazed glass layer 2 for heat storage, a heat generating layer 3 made of polysilicon, etc., an electrode 4.5, and a wear-resistant protective film 6. 7 in the figure is a heat generating part.

The protective film 6 is generally required to have high hardness, not to crack due to heat, to be resistant to wear, and to be stable against moisture, alkali, etc., and various materials have been researched in the past.

Conventionally used wear-resistant protective films include Ta20B and S.
10% A 120s, B4C% S i 0XN
y etc. are known. However, these protective films have advantages and disadvantages and are still not fully satisfactory. Ta205
has a slightly lower Vickers hardness (600 to 800 kg)
/mm”), has a problem with wear resistance and tends to oxidize the resistance heating element, so a layer of Sin must be interposed under the wear-resistant protective film, and it is easy to recrystallize at low temperatures and stress changes. Furthermore, SiC has a disadvantage that it is easily cracked due to the application of heat pulses due to its thermal expansion coefficient which is considerably smaller than that of the alumina substrate and glaze layer that are the base of the resistance heating element.On the other hand, SiC has low electrical resistance and As wear resistance decreases due to chemical reactions, it is necessary to form a film such as SiQ as a lower layer, and cracks are likely to occur.Also, AI, 0.84C, etc. have large internal stress and are prone to cracking. is likely to occur.Furthermore, S r Ox N
The coefficient of thermal expansion of y is considerably smaller than that of the base material, and there is a problem in that cracks occur when a heat pulse is applied. Accordingly, there is a need for an M that not only has high wear resistance but also excellent crack resistance and thermal fatigue resistance.

[Purpose of the invention]

An object of the present invention is to provide an S* wear-retaining material for a thermal head that has high crack resistance and excellent thermal fatigue resistance.

[Summary of the invention]

The wear-resistant maintenance film for thermal heads of the present invention contains A1.0 and N as main elements, and more specifically, A1.0 and N are the main elements.
It is a compound having a composition represented by lN0 (L5≦X≦x 1-x Cl2O).

The thermal head of the present invention has high hardness and relatively high thermal conductivity, and is suitable as a protective film for a thermal head for high-speed printers. It also has excellent wear resistance, chemical stability, scratch strength, etc.

[Details of the structure of the invention]

The wear-resistant MM for thermal heads of the present invention is Al-0
-N-based materials, more specifically AlNx0l-x (z=
0.5 to CL9B).

If X is smaller than α5, the heat transfer rate will decrease, making it unsuitable for high-speed printers. Moreover, when X exceeds α98, the adhesion of the film decreases. If X is in the range of 15 to α98, the thermal conductivity is high and the adhesiveness is good.As shown below, the protective film of the present invention is inferior to the conventional protective film in various other aspects as well. There is no.

The adhesive film of the present invention can be formed using, for example, a sputtering method. When this method is used, aluminum nitride or oxide powder, such as AIN, is used as a film forming raw material.
A Ivys is mixed in the required ratio corresponding to the film composition, pressed to make a target, and using Ar gas and N2.01 gas if necessary, Rpe force is applied and the target is ejected with Ar ions to perform sputtering. For example, by forming a glass glaze on an alumina substrate,
Furthermore, a heating element film is formed on the surface of the film. N,
When introducing O and/or gas, reactive sputtering film formation is possible, and the film composition can be adjusted.

Next, the present invention will be explained in detail.

Example AIN, AI, O, and powder were mixed at a molar ratio of 5:2 and pressed to form a target. Input power tsKW,
A film was formed by RF sputtering on a heating element at an Ar pressure of 3 Pa and a substrate temperature of 350''C. Various tests were conducted on this film, and the following results were obtained.

When a power of α7W was pulsed for 11 seconds per heating element dot and the change in surface temperature during that time was measured, the results shown in FIG. 2 were obtained. As a control, the same experiment was performed on 'ra, o, and protective films. hlo N tt is x 1
-x Heat is transferred to the surface immediately after the start of heat generation, and the temperature returns to a low temperature immediately after the heat generation stops, but the 'ra, o, and protective film's temperature rises and falls slowly. Therefore, it can be seen that the protective film of the present invention is suitable for high-speed printers.

Other characteristics were as follows.

The Vickers hardness is 1,800 to 2,000 cores/mm, which is harder than Ta!QB.

2 The scratch strength of the surface is 450 JF, and T a 2
It is larger than 2701 of Q5. This scratch strength was measured using a scratch tester (New Science) using a diamond needle.
It was measured using a HEIDON-14 model manufactured by Co., Ltd.

In a wear test using 61 balls with a diameter of 12 mm and diamond paste attached, the time was 35 seconds, and Ta! O,
longer than 7 seconds.

4. Even after repeated heating tests of 108 pulses with a pulse period of 7 msec and applied power of 12 W/dot, no crystallization occurred (no halo was observed in electron beam diffraction).

5. Stable against strong acids and strong alkalis.

B: It is electrically stable with a specific resistance of 10110 m or more.

[Effect]

As can be seen from the above, the Al-N-0-based protective film of the present invention has high hardness, high scratch strength, and excellent wear resistance.
Since crystallization does not occur, it has high crack resistance, and because of its high heat conductivity, it is suitable for high-speed printing, making it possible to provide an excellent wear-resistant protective film.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of the thermal head, and FIG. 2 is a graph showing the relationship between heat pulse application and protective film surface temperature.

Claims (1)

[Claims] 1. A wear-resistant protective film for a thermal head whose main constituent elements are Al, O, and N. 2, AlN_xO_1_-_x (0.5≦x≦0
．． 98) The wear-resistant protective film according to item 1 above, having a composition represented by: