JPH07180031A - Wear resistant protective film for thermal head - Google Patents

Abstract

PURPOSE:To obtain a protective film for a thermal head having high hardness and a long service life by forming a film having a prescribed compsn. contg. C, Si, O and N as essential components by sputtering using an SiC-Si3N4-SiO2 mixed sintered compact as a target. CONSTITUTION:Sputtering is carried out using an SiC-Si3N4-SiO2 mixed sintered compact as a target or sputtering is carried out using an SiC-Si3N4 mixed sintered compact as the target in an atmosphere contg. gaseous oxygen to obtain the objective wear-resistant protective film for a thermal head having a compsn. represented by SiCxOyNz (where 0.01<=x<=1, 0<=y<=2 and 0.01<=z<=1.4).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wear-resistant protective film for a thermal head which has Si, C, O and N as essential constituent components and has a high hardness and a long life.

[0002]

2. Description of the Related Art In general, thermal transfer recording (thermal printing) can be used for facsimiles, ticket vending machines, word processors, etc. because it can record with higher recording density and contrast with almost the same recording energy as thermal recording. It's being used.

The thermal recording head of these thermal printers is composed of a thermal head, a platen roll, an ink ribbon, and a transfer paper. By selectively energizing each minute dot of a resistance heating element of the thermal head, a melting type thermal transfer or a sublimation dye thermal transfer is carried out. It is what is printed.

FIG. 1 shows an example of the structure of a thermal head. In order from the bottom, a substrate 1 made of alumina, a glaze layer 2 for heat storage, a resistance heating element layer 3 made of tantalum nitride, electrodes 4 made of aluminum, and protection. It consists of layer 6. Since such a thermal head is brought into direct contact with the transferred paper while being loaded with an appropriate static pressure by a platen roll (not shown), it is necessary to protect the resistance heating element with a protective film having high abrasion resistance. Therefore, the protective layer 6 is required to have characteristics such as high hardness, resistance to abrasion, and resistance to thermal shock, and various materials have been proposed.

The wear-resistant protective film that has been conventionally used includes
Although there are Ta ₂ O ₅ , SiC, Si—O—N, etc., these wear-resistant protective films have advantages and disadvantages, respectively. That is, the Ta ₂ O ₅ film has an advantage of high toughness, but has a low hardness, for example, Vickers hardness Hv = 700 k.
It is about g / cm ² . Therefore, there is a problem of poor wear resistance. Further, since it is difficult to obtain a dense film, it is necessary to protect the resistance heating element film by interposing a dense film such as SiO _{2 under the} abrasion-resistant protective film, which complicates the head structure. It also has the problem.

The SiC film has an Hv of 4000 kg / cm ²
Although it has the advantages of high degree and hardness and excellent wear resistance, it has a problem that cracks easily occur in the film and peeling easily occurs because the internal stress of the film is large. Also,
The Si-O-N film has a Hv of about 1000 kg / cm ² , and since it does not require a base film, it has been widely used as a substitute material for Ta ₂ O ₅ recently. The demand for longer life has not been met.

An object of the present invention is to provide a wear resistant protective film for a thermal head which has sufficient wear resistance and solves the problems caused by the internal stress of the film such as cracks and peeling. Is.

[0008]

The wear-resistant protective film for a thermal head of the present invention contains Si, C, O and N as essential constituent components, and more specifically, SiCxOyN.
z (where 0.01 ≦ x <1.0, 0 <y <2.0,
It has a composition represented by 0.01 ≦ z <1.4). These wear-resistant protective films for thermal heads are made of SiC-Si ₃ N ₄
Si—C—O formed by a sputtering method using a —SiO ₂ mixed sintered body as a target, or by sputtering in an atmosphere containing oxygen gas using a SiC—Si ₃ N ₄ mixed sintered body as a target. −
It consists of N film.

Among the constituent elements of the present invention, C and N have the effect of increasing the hardness of the film and increasing the wear resistance, but if they are too large, the internal stress of the film increases and cracks and peeling occur in the film. It will be easier. O has the effect of ensuring the adhesion strength of the film and improving the toughness of the film, but if it is too large, the film becomes soft and wear resistance decreases. Therefore, the composition ratio of each of these elements is preferably within the above range.

Printing methods, vacuum deposition methods, CVD methods, sputtering methods and the like are conceivable as methods for forming the wear-resistant protective film of the present invention, but since the composition control is simple, etc.
It is desirable to use the sputtering method. Moreover, as a starting material (target) when forming a Si—C—O—N film by a sputtering method, SiC, SiC—SiO ₂
Mixed Sintered Body, SiC-Si ₃ N ₄ Mixed Sintered Body, SiC
A mixed sintered body of —SiO ₂ —Si ₃ N ₄ or the like is considered. Of these, when SiC is used as a target, O ₂
Gas and N ₂ gas, when using a mixed sintered body of SiC-SiO ₂ as a target, N ₂ gas is changed to SiC-Si ₃
When using a mixed sintered body of N ₄ as a target, O ₂
It is necessary to perform sputtering in an atmosphere containing gas. However, since it is difficult to manufacture a sintered body of SiC or SiC-SiO ₂ having sufficient mechanical strength to be used as a target, it is more preferable to use the latter two targets.

Depending on the required characteristics of the film, it is possible to change the film quality by further introducing O ₂ or N ₂ gas during the sputtering. In addition, the material of the present invention may contain Si, C,
It is also possible to add elements or compounds other than O and N within a range that does not impair the above characteristics. For example, when imparting conductivity to the film for the purpose of preventing static electricity, Ta, Al
This object is achieved by adding a metal element such as or a compound such as TaC or TiC.

[0012]

According to the present invention as described above, Hv is large, and cracks and peeling due to internal stress can be prevented,
An abrasion-resistant protective film for a thermal head that can significantly extend its life is obtained.

[0013]

Example 1 A sintered body obtained by pressing and firing powder mixed with a molar ratio of SiC: Si ₃ N ₄ = 10: 90 was used as a target, and an Ar gas pressure containing an appropriate amount of O ₂ was 3 m.
An RF power of 6 W / cm ² was applied in a Torr atmosphere to form a 4 μm thick Si—C—O—N abrasion resistant protective film on the Al ₂ O ₃ substrate. SiCxO thus obtained
yNz (0.01 ≦ x <1.0, 0 <y <2.0, 0.
01 ≦ z <1.4) The Vickers hardness of the film and the crack generation state were visually evaluated. The results are shown below together with those of the conventional example. In addition, the conventional SiC film, Ta ₂
The O ₅ film and the Si—O—N film were both formed with Ar gas pressure 3
RF power 6 W / cm in an argon atmosphere of mmTorr
² was added to each to give a film thickness of 4 μm.

[0014]

Further, the wear loss of the above-mentioned SiCxOyNz film is extremely small at 0.1 micron / km or less, compared with 0.3 micron / km of Ta ₂ O ₅ when the load is 2.5 kg / cm ^2. Met.

[0016]

Example 2 SiC: Si ₃ N ₄ : SiO ₂ = 50: 4
A powder obtained by mixing powders having a molar ratio of 0:10 was pressed and fired, and a sintered body obtained as a target was used, and an Ar gas pressure was 3 mTorr.
In the atmosphere of r, RF power of 6 W / cm ² was applied to Al ₂
A Si-C-O-N abrasion-resistant protective film having a film thickness of 4 µm was formed on the O ₃ substrate. SiCxOyNz thus obtained
(0.01 ≦ x <1.0, 0 <y <2.0, 0.01 ≦
The z <1.4) film had a Vickers hardness of 1 as in Example 1.
It was as high as 200 kg / cm ^2, and no cracks were observed on the surface.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a basic structure of a thermal head.

[Explanation of symbols]

 1 substrate 2 glaze layer 3 resistance heating element layer 4 electrode 5 electrode 6 protective layer

Claims (4)

[Claims] 1. A wear-resistant protective film for a thermal head, which contains Si, C, O and N as essential constituent components. 2. SiCxOyNz (where 0.01 ≦ x <1.0, 0 <y <2.0, 0.
The abrasion-resistant protective film for a thermal head according to claim 1, having a composition represented by 01 ≦ z <1.4). 3. The thermal head resistance according to claim 1, comprising a Si—C—O—N film formed by a sputtering method using a SiC—Si ₃ N ₄ —SiO ₂ mixed sintered body as a target. Abrasive protective film. 4. A Si—C—O—N film formed by sputtering using an SiC—Si ₃ N ₄ mixed sintered body as a target in an atmosphere containing oxygen gas. A wear-resistant protective film for a thermal head as described above.