JPH028977B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a glaze composition for glazing a ceramic substrate. BACKGROUND OF THE INVENTION In recent years, thermal heads, which print quietly and are easy to maintain, have become popular for use in printers such as facsimiles and microcomputer terminals. There are two methods for forming electrical circuits in thermal heads: thin-film and thick-film methods, but when high-speed, high-density printing is required, the thin-film method is common, and a glazed ceramic substrate is used as the substrate. used. Glazed ceramic substrates are created by applying a glaze composition to a ceramic substrate, and in order to form thin-film circuits and resistors with a thickness of less than several thousand angstroms with high precision on the ceramic substrate, it is necessary to have good surface smoothness and warpage. It is required that the electrical insulation properties of the circuit are not deteriorated during use, and that the electrical insulation properties of the circuit are not deteriorated during use. Furthermore, since the resistor is subject to thermal shock due to heat generation during use, it is necessary to have excellent heat resistance. Therefore, the glaze composition has good surface smoothness when fired at temperatures below about 1300°C, forms a highly heat-resistant glaze layer, is resistant to corrosion by fluoro-nitric acid mixed acids, and has a coefficient of thermal expansion that matches that of ceramic. must be maintained. If the difference in thermal expansion between the glaze composition and the ceramic is large, the warpage of the glazed ceramic substrate will become large, which not only significantly deteriorates dimensional accuracy but also generates excessive stress within the glaze layer, resulting in thermal shock when using a thermal head. Therefore, there is a problem in that microcracks are likely to occur in the glaze layer. Furthermore, as printing speeds have increased recently, thermal shocks have become more frequent.
As the temperature difference increases, there is an urgent need to develop a glaze composition with better heat resistance. Conventional glaze compositions have good matching with thermally expanding ceramics and good surface smoothness, but because they contain alkali or lead, they have low heat resistance and their electrical insulation properties deteriorate with repeated use. There is a drawback. For this reason, highly heat-resistant glaze compositions that do not contain alkali or lead have recently been developed, but these have the disadvantage of having a low coefficient of thermal expansion and an excessively large difference in thermal expansion from the ceramic substrate. Purpose of the Invention The present invention aims to provide a glaze composition for a ceramic substrate that maintains the smoothness of the glaze surface, has excellent heat resistance and acid resistance, has a small expansion difference with the ceramic substrate, and does not cause electrical insulation deterioration. This is the purpose. Structure of the Invention The glaze composition for ceramic substrates of the present invention includes:
In weight percentage, _SiO2 45-60%, _{Al2O3 7-17} %,
CaO10~25%, BaO1~15%, SrO0~15%,
It is characterized by consisting of 0.5 to 5% P ₂ O ₅ . The glaze composition for ceramic substrates of the present invention includes:
Preferably in weight percentage, SiO ₂ 49-56%,
_{Al2O3 9} ~15%, CaO13~22%, BaO3~13%,
It is characterized by consisting of 1 to 13% SrO and 1 to 3% P ₂ O ₅ . The reason why the content of each component constituting the glaze composition for ceramic substrates of the present invention is limited as described above will be explained below. SiO ₂ is the main component forming the glass structure,
Its content is 45-60%, preferably 49-56%. If it is less than 45%, the heat resistance of the glaze will be insufficient and at the same time it will tend to devitrify, making it difficult to form a good glaze. If it is more than 60%, the coefficient of thermal expansion will become too small. The content _{of Al2O3} is 7-17%, preferably 9-15
%. If it is less than 7%, the viscosity of the glaze will decrease, the yield point will drop, and sufficient heat resistance will not be obtained. If it is more than 17%, it will be difficult to melt the glass and the firing temperature of the glaze will rise, making it difficult to obtain a good result. It is difficult to obtain grace. CaO has the effect of making the glass easier to melt and increasing the thermal expansion coefficient of the glaze, and its content is 10 to 25%, preferably 13 to 22%.
If it is less than 10%, the above effect will not be obtained,
If it exceeds 25%, a tendency towards devitrification appears. BaO has the same effect as CaO, and by using both in combination, the tendency to devitrify is reduced, and its content is 1 to 15%, preferably 3 to 13%. 1
If it is less than 15%, the above effect will not be obtained and
%, a tendency toward devitrification appears and heat resistance also decreases. When SrO is used in combination with CaO and BaO, it has the effect of reducing the tendency to devitrify, and its content is 0.
-15%, preferably 1-13%. If it exceeds 15%, devitrification tends to occur. _P2O5 has the effect of increasing the thermal expansion coefficient without reducing heat resistance by replacing it with _SiO2 , and its content is 0.5 _to 5%, preferably 1 to 5%.
It is 3%. If it is less than 0.5%, the difference in expansion with the ceramic substrate becomes large, causing the substrate to warp or causing microcracks when using a thermal head. If it is more than 5%, a tendency of phase separation and devitrification will appear, making it impossible to obtain a good glaze. Examples Examples and comparative examples of the glaze composition for ceramic substrates of the present invention are shown below. The following table shows the compositions of Examples of the products of the present invention (Samples Nos. 1 to 5) and the compositions of Comparative Examples (Samples Nos. 6 and 7), as well as their thermal expansion coefficients, transition points, and yield points.

【table】

[Table] Samples No. 1 to 7 in the table were prepared as follows. Mix raw materials to have the oxide composition shown in the table,
Mix thoroughly. Each raw material may be an oxide, hydroxide, carbonate, or nitrate, but it is easier to melt if a fine powder raw material is used. After melting the mixed raw materials at 1500-1600℃ in a platinum crucible,
The glass obtained by rapid cooling is pulverized using an alumina ball mill. The glaze composition thus prepared was applied to a ceramic substrate by a spray method or screen printing method, and fired at 1200 to 1300°C to obtain a glaze substrate free of surface defects such as bubbles and devitrification. As is clear from the table, the product of the present invention does not contain alkali or lead oxide, has a transition point of 750°C or higher and a yield point of 800°C or higher, and has better heat resistance than Comparative Example No. 6. and has a coefficient of thermal expansion of 67.0 to 71.0,
Compared to Comparative Example No. 7, the coefficient of thermal expansion is similar to that of the ceramic substrate. Also, Example No. 4 and Comparative Example No. 4.
To compare the acid resistance of No. 6 and No. 7, HF:HNO ₃
When the glazed substrate was immersed in a mixed acid of =1:1 for 10 seconds and the etching depth was measured, No. 4 was
The diameter was 5.0 μm, which was extremely superior to No. 6's 7.5 μm and No.'s 8.0 μm. Effects of the Invention As described above, the glaze composition for ceramic substrates of the present invention has no surface defects such as bubbles and devitrification, has good surface smoothness, excellent acid resistance, and has a small expansion difference with respect to ceramic substrates. Its small size makes it particularly suitable for glazing ceramic substrates in thermal heads.

Claims (1)

[Claims] 1. In weight percentage, SiO ₂ 45-60%, Al ₂ O ₃ 7-17
%, CaO10~25%, BaO1~15%, SrO0~15%,
A glaze composition for ceramic substrates, characterized in that it consists of 0.5 to 5% P ₂ O ₅ . 2 In weight percentage, SiO ₂ 49-56%, Al ₂ O ₃ 9-15
%, CaO13~22%, BaO3~13%, SrO1~13%,
The glaze composition for ceramic substrates according to claim 1, characterized in that it consists of 1 to 3% P ₂ O ₅ . 3. The glaze composition for a ceramic substrate according to claim 1, wherein the ceramic substrate is an alumina substrate.