JPS61267328A - Wear-resisting protective film - Google Patents

Abstract

PURPOSE:To obtain a protective film having a superior wear resistance, heat resistance and cracking resistance by a method wherein a compound having a composition of SiNxBy [the ratio of the (x) to be within an extent of 0.1-10 and the ratio of the (x): the (y) to be within an extent of 0.1-10] is used as the material for the protective film. CONSTITUTION:The heating unit part of the thermal head is constituted of an alumina substrate 1 having its surface whereon a grease layer is provided, a resistor layer 2 consisting of a thin film to be made of a ternary compound of polycrystalline Si, Au electrodes 3 and 3' and a protective film 4. The protective film is a film to be made of a compound, which is represented by a composition of SiNxBy. It is desirable that the ratio of the (x) is within an extent of 0.1-10 and when the ratio of the (x) is smaller than an extent of 0.1 or less, than is, when the ratio of the N is too low compared with that of the Si, the insulating properties of the protective film lowers. Even though the N is big in quantitative fluctuations, the N has the advantage of mitigating fluctuations in the insulating properties and other characteristic of the protective film and of facilitating control of the manufacturing process of the protective film. Moreover, it is desirable that the ratio of the (x): the (y) is adopted within an extent of 0.1-10. When this ratio is lower than an extent of 0.1 or less, the electrical insulating property of the protective film lowers, so the ratio lower than the extent of 0.1 or less is not desirable, while when this ratio is larger than an extent of 10 or more, the strength of the protective film to cracking and the wear resistance thereof are decreased, so the ratio larger than the extent of 10 or more is not desirable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a wear-resistant protective film, and particularly to a wear-resistant protective film for a thermal head.

[Prior art]

The thermal head of a thermal printer, which is conventionally used as an output method for facsimiles, computer terminals, word processors, recorders, etc., basically has a heat storage glaze layer on its surface, as shown in Figure 1. A resistive heating element layer 2 is formed on the surface of the ceramic substrate 1, and lead layers 5.5' for conducting electricity are provided at both ends of the resistive heating element layer 2, and as the top layer, a heating element layer 2 and Lead layer 3
．． 3', a protective layer 4 is provided to prevent wear and damage. In use, when electricity is applied between the lead layers 3 and 3', the resistance heating layer 2 generates heat, and this heat is applied to the thermal paper via the protective layer 4, thereby performing thermal recording.

The protective layer for the thermal head is required to have high hardness, wear resistance, and heat resistance, and as a result, to be able to fully perform its functions against long-term sliding contact and long-term heat generation. Ru.

There is no material that is fully satisfactory as a protective layer material that can cope with such severe conditions.Those conventionally used are Ta2O, SiC, etc., but Ta and O are inferior in terms of hardness and wear resistance. . Although SiC has high hardness,
It has no toughness and low crack resistance. Sio has also been considered, but has not been used because it reacts with thermal paper and has a high coefficient of friction with photosensitive paper, causing problems such as sticking.

[Purpose of the invention]

An object of the present invention is to provide a protective film with excellent wear resistance, heat resistance, and crack resistance. Another object of the present invention is to provide a protective film having the above-mentioned excellent properties, especially for thermal heads.

[Summary of the invention]

The protective film of the present invention has a composition of 5iNxBy (where Vcx is α
1 to 10, x/y consists of a compound having [1, 1 to 10), or a compound represented by the above formula f containing up to 5N (atomic ratio) of O to the total amount of Si, N, and H.

The protective film of the present invention has high heat resistance and excellent abrasion resistance, and has sufficiently high abrasion resistance compared to conventional TatOs, and has no reactivity with paper such as 5tO2. , cracks do not occur even under thermal stress caused by repeated pulse-like energization. The protective film of the present invention can be provided with sufficient insulation properties by containing the element.

Although the amount of nitrogen varies over a wide range (x = 0.1-10
), it has the advantage that the insulation properties etc. do not vary greatly and are easy to control.

The use of oxygen also provides the benefit of increased gas efficiency and increased crack strength.

[Detailed description of the invention]

The present invention will be explained in detail below. FIG. 1 shows a heating element part of a thermal head according to an embodiment of the present invention.
1 is an alumina substrate with a glaze layer, 2 is 0.2 μm
Thick poly-Si ternary compound thin film resistor layer, 3.3
' is a 2 μm thick Au electrode, 4 is a 3 μm thick 5iNxBy
(However, X = α1 ~ i0 ° x/y - α1 ~ 10)
It is a thin film.

The protective film of the present invention is a compound represented by 5iNxBy, where X preferably ranges from +1.1 to 10. X is 0.1
If it is smaller, that is, if there is too little N with respect to SN, the insulation properties will deteriorate. N has the advantage that even if the quantitative variation is large, the insulating properties and other properties of the protective film vary slowly, making it easy to control the manufacturing process. Also, x/y is 0.1
It is preferable to use it in the range of 10 to 10. This ratio is 111
If it is lower than , the electrical insulation properties will be low, which is not desirable.

On the other hand, if this ratio is greater than 10, it is undesirable because crack strength and wear resistance decrease.

Oxygen may be further added to the above compound.

Oxygen can be used in an amount up to 5N (atomic ratio) based on the total amount of the above compound. The use of oxygen not only improves insulation but also improves gas efficiency. When the amount of oxygen exceeds 5X, the wear resistance of the protective film decreases. However, an improvement effect on crack strength can be seen. From above, substitute k for N.

Although it is possible to use oxygen, it becomes difficult to control the conditions when oxygen is used. Therefore, in the present invention, O is used auxiliary.

Examples of the present invention will be described in detail below. The protective film of the present invention can be formed by vapor phase epitaxy (plasma CVD), sputtering, etc., but preferably the former is used.

1007s10 by parallel plate plasma CVD method
A film was formed on a base device (see FIG. 1) with a thickness of 0.07 μm. That is, using H2 as a carrier and 500 SCCM of 20% SiH4/H2 as a source, 5
%B2H6/H2 5~j SCCM (variable) and NH
, was flowed at a flow rate of 20 SCCM to so SCCM (variable), and film formation was performed under conditions of a temperature of 300° C., a pressure of 1 Torr, and an input of 200 W.

Tests were conducted on printing elements (dots) for thermal heads having protective films of various compositions thus obtained.

-J1[-! A simple way to determine the crack resistance of an l--maru head is a step stress test. In this method, the resistance change of the heat generating resistor is measured while gradually increasing the voltage applied to the heat generating resistor for a certain period of time. Evaluate crackability. The method used in the test is as follows.

That is, the scanning line printing time is 10 m, 88C or more, the number of scanning line divisions is B48, and the data transfer frequency is IMHz.

Data transfer amount 24B (84M8), print voltage 1&0~2
The printing rate is 2ON and the mileage is 30Aa+. The dimensions of the heating resistor are 160 μm in width and 280 μm in length.

In the step stress test, the electric power (watts/dot) applied per heating resistor where a crack has occurred is defined as the crack strength. Further, when the recording paper is run with the applied power at the maximum print density, the wear rate is defined as the value (μm/Ax) obtained by dividing the abrasion depth of the abrasion-resistant protective film by the running distance of the recording paper.

FIG. 2 shows the dependence of the wear rate and crack strength on the composition ratio x/y of the thermal head shown in FIG. 1 using 5iNxBy as the wear-resistant protective film. x
The crack strength and wear rate decrease with the value of /y. However, if this value is less than 10, the conventional Ta, 0. Since the wear rate is lower than that of SiC, there is no practical problem, and the crack strength is far superior to that of conventional SiC. On the other hand, if x/y is smaller than (Ll) and X is smaller than al, conductivity occurs1.In addition, in the above example, when CO3 was used to dope O to 5%, the gas efficiency was improved by about 20X. , the crack strength was improved, and it had the same effect as N in terms of wear rate and insulation properties.At 5% or more, the wear rate increased.

As described above, the protective film of the present invention can improve electrical insulation without substantially reducing wear resistance and crack resistance. Therefore, the protective film of the present invention can increase the lifespan and reliability of the thermal head.

[Brief explanation of drawings]

Figure 1 is a sectional view showing the structure of the thermal head, and
The figure is a graph showing the influence of the component ratio of an impulsion scar on its characteristics.

Claims (1)

[Claims] 1. Composition SiN_xB_y (where x is 0.1 to 10,
A protective film made of a compound where x/y is 0.1 to 10). 2. The protective film according to item 1, which contains up to 5% (atomic ratio) of O based on the total amount of Si, N, and B.