JPS61257475A - Protective film - Google Patents

Abstract

PURPOSE:To obtain a protective film having superior resistance to wear, moisture, heat and cracking by forming a film under specified conditions while feeding gaseous Si(CH3)4, N2 and NH3 each at a prescribed flow rate to a plasma CVD chamber. CONSTITUTION:A film is formed on a device by a plasma CVD method using flows of 10-100 SCCM gaseous Si(CH3)4, 50-500 SCCM gaseous N2 and 10-100 SCCM gaseous NH3 under the conditions of 0.5-1W/cm<2> power density, 0.5-1.5Torr pressure and 250-500 deg.C temp. The resulting protective film is made of an amorphous compound contg. Si, C, N and H as the principal components. In the composition, the atomic ratio of C/Si is 0.2-2.0, that of N/Si is 0.2-2.0, and the amount of H is 2-<22atom%. The protective film is suitably formed on the thermal head of a heat sensitive printer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a wear-resistant protective film, and more 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 3 and 3' are provided at both ends of the resistance heating element layer 2 for conducting electricity. Lead layer 3
．． A protective layer 4 is provided to prevent abrasion and damage to the part 3'. In use, when electricity is applied between the leads 1913.5', 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 satisfactory protective layer material that can meet such severe conditions. Conventionally used materials include Ta206 and SiC, but Ta20B is inferior in hardness and wear resistance. In addition, although SIC has high hardness,
It has no toughness and low crack resistance. 5102 has also been considered, but it 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.

Furthermore, in high-humidity environments such as summer or rainy seasons, alkali ions may enter the heat generating layer through the protective film, and SiC, which is considered to be one of the best protective films, cannot adequately deal with this problem. On the other hand, a 5l-O-B type protective film has also been proposed, but boron is a very expensive material.

[Purpose of the invention]

An object of the present invention is to provide a protective film with excellent wear resistance, moisture 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 present invention consists of an amorphous compound containing Si, C, N, and H as main components, and these components are expressed in atomic ratios such that 0.2≦C/Si≦2.0 0.2≦N/Si≦20 2 It is a wear-resistant protective film in the range of %≦H≦22%.

Furthermore, the present invention uses Si(CHg)4, N! as a raw material gas source!
The above-mentioned protective film is formed by a method characterized by forming a film by plasma CVD using , and NH3.

The protective film of the present invention has high hardness and wear resistance, and can withstand long-term use. This is thought to be mainly due to the effects of carbon and nitrogen. The protective film of the present invention has sufficient electrical insulation properties, which is probably due to the fact that it contains hydrogen in addition to carbon and nitrogen. Furthermore, the above-mentioned properties of the protective film of the present invention are not impaired even under high temperature and high humidity conditions, which is thought to be mainly due to the nitrogen content. In addition, 5t (CHs)4 is used as a gas source.
Although it is available at low cost, it serves as a source of Si, C, and H.
A film can be formed simply by adding a nitrogen source to this. Therefore, S
It is much cheaper than the 1-0-B series.

The protective film of the present invention has excellent wear resistance and insulation properties,
Furthermore, it was found that it has excellent moisture resistance and acts as an alkali ion barrier.

[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 provided with a glaze layer, 2 is a poly-Si ternary compound thin film resistor layer with a thickness of 12 μm, and 3.3'
is an Au electrode with a thickness of 2 μm, and 4 is a protective film with a thickness of S pm.

The protective film of the present invention is 81. It is an amorphous compound containing C, N, and H (minor impurities are allowed), as defined above. Within the composition range of the present invention,
It not only has high abrasion resistance, but also high heat resistance, moisture resistance, and crack resistance. In general, a large amount of Si increases the crank strength, but from the viewpoint of insulation, the amount should not be too large. On the other hand, from the viewpoint of wear resistance, it is good to have a high content of C and N. Therefore, C/81 and N/81 should be 0.2 or more. or,
If the hydrogen content is also at least 2%, the wear resistance will be improved. At the same time, the presence of nitrogen improves moisture resistance and increases resistance to alkali ions. On the other hand, C76i,
When N/S i exceeds 2.0, toughness is lost and cracks occur. Regarding hydrogen, the higher the hydrogen content, the greater the crack strength, but conversely the wear rate increases, so approximately 2
The limit is 2%.

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

100 μm x s by parallel plate plasma CVD method
A film was formed on an oo μm base device (see FIG. 1). The film forming conditions were as follows.

Gas flow 5L (CR3) 4 10~1008CCMN2
50-500 SCCMNHs 10
~100 SCCM power density 0.5~I W
/cm2 pressure [lL5~15
Torr temperature 250~50
Tests were conducted on printing elements (dots) for thermal heads having protective films of various compositions obtained by waving at 0°.

-S An easy way to check the crack resistance of a thermal head is to perform 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 for the test is as follows.

That is, the scanning line printing time is longer than jomBee, the number of scanning line divisions is B48, and the data transfer frequency is IMHz.

Data transfer amount 248 (B4M8), printing voltage 18.0~
210■ Printing rate is 20% and mileage is 50 Km.

The dimensions of the heating resistor are 130 μm in width and 280 μm in length.

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

Figure 2 shows the wear rate and crack strength of the thermal head shown in Figure 1 using Si CNT (x as a wear-resistant protective film) and hydrogen (expressed as x/(5+x)X100%).
This shows the dependence on Both the hydrogen value and the crack strength are rapidly improved.

This increases the wear rate, which is undesirable.

Next, using tungsten as an electrode and covering it with the protective film of the present invention to a thickness of 5 μm, a test was conducted at 60° C. and under the conditions of 90% RI. As a result, the atomic ratio of N to S11 was 0.2. In this case, neither corrosion of the electrode nor peeling of the protective film occurred for more than 250 hours.

Next, the wear rate and crack strength were examined by changing the C/N atomic ratio, and the results shown in FIG. 3 were obtained.

This revealed that changes in the C/N ratio did not affect the physical properties.

As described above, the present invention can provide an excellent protective film by controlling the composition of the amorphous alloy of Si, C, N, and H.

[Brief explanation of the drawings] Figure 1 is a cross-sectional view showing the structure of the thermal head, Figure 2 is a diagram showing the influence of hydrogen content on the protective film, and Figure 3 is a diagram showing the influence of hydrogen content on the protective film.
The figure shows the relationship between C/N ratio and physical properties. Figure 1

Claims (1)

[Claims] 1. Consisting of an amorphous compound mainly composed of Si, C, N and H, the atomic ratio of C and N to Si1 is in the range of 0.2 to 2.0, respectively. , H in an atomic ratio of 2 to 22% of the total amount of the compound. 2. Si(CH_3)_ in the plasma CVD chamber
4 from 10SCCM to 100SCCM, N_2 to 50SC
CM~500SCCM and NH_3 to 10SCCM~1
While flowing at a flow rate of 00 SCCM, the power density is 0.5 to 1.
W/cm^2, pressure 0.5-1.5 Torr and temperature 2
A method for producing a wear-resistant protective film formed under conditions of 50 to 500°C.