JPH0464864B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method of manufacturing a thermal head, and more particularly to a method of manufacturing a thermal head with good thermal responsiveness. Thermal recording method, which is a typical non-impact method, has become widely used because it has advantages such as no noise, but the heat storage body located below the heat generating part of the thermal head used for this method Since this has a great impact on printing efficiency and printing quality, various efforts have been made in the past. In general, the heat storage element in a thermal head is used to efficiently secure the amount of heat necessary for printing by reducing the amount of heat that escapes to the base material when power is applied to the heat generating part of the resistor through the electrode. It is considered preferable to use a material with low conductivity, but in practice, in order to provide the necessary and sufficient amount of heat for printing, the layer thickness of the heat storage material must be increased to a certain extent; If is too large, the amount of heat storage will increase, so when the power is not energized,
In other words, the amount of heat dissipated during cooling becomes relatively insufficient, making it impossible to quickly lower the temperature, resulting in unnecessary printing, which causes the heat storage body in the thermal head to have contradictory characteristics. It is hoped that In recent years, in order to meet such demands, it has become known that the heat storage body below the heat generating part of a thermal head is made of glass having a large number of bubbles. This type uses glass with low thermal conductivity as the heat storage body, and there are many pores (bubbles) inside the heat storage body, so the number of pores is larger than that of a type without pores. However, the overall thermal conductivity is decreasing, and the amount of heat stored at a certain temperature is also decreasing. In other words, if heat storage bodies with holes and those without holes are formed with the same appearance, those with holes have lower thermal conductivity than those without holes, and the amount of heat storage is smaller than that of conventional heat storage bodies. Then,
When power is applied, the printing temperature can be maintained and the temperature can be lowered quickly.The heat storage body is considered to be useful because it has such good thermal response. However, various problems arise when actually obtaining a heat storage body for such a thermal head. That is, in general, when obtaining glass with a large number of bubbles, a paste of glass powder with an average particle size of about 10 μm to 50 μm is fired under certain conditions to prevent the generation of bubbles from inside the glass powder. However, if this is to be used in the production of heat storage bodies for thermal heads, the firing temperature must be maintained within a range of ±2 to 3°C, for example. The problem arises that controlling the firing conditions becomes technically sophisticated and difficult.
In addition, if accurate firing conditions cannot be set, air bubbles generated from inside the glass powder will not only be exposed inside the heat storage body but also on its surface, creating an uneven surface that will adversely affect print quality and cause thermal damage. Although the responsiveness is good, the problem arises that it is virtually impossible to obtain a thermal head that has commercial value. The present invention was made in view of these circumstances, and was finally completed as a result of intensive research into a manufacturing method for efficiently obtaining a thermal head with good thermal response. In the method for manufacturing a thermal head, the average particle size of the glass powder is The method of producing a thermal head is characterized in that the glass powder has a particle diameter of 10 μm to 50 μm, and contains at least 20% by weight of finely ground glass powder with an average particle size of 5 μm or less. What is particularly important in the present invention is that the glass paste from which the heat storage body is formed contains at least 20% by weight of finely ground glass powder based on the total amount of glass powder, specifically, the average particle size thereof is about 5 μm or less. In this invention, even if the glass paste is printed and fired, the moisture and gas components adsorbed to the finely ground glass powder are extremely small. Even if these moisture and glass components form bubbles during firing, the bubbles will be small, so even if the bubbles are exposed to the surface of the heat storage element, the roughness of the surface will adversely affect printing quality. Furthermore, due to this, there is flexibility in various controls for regulating the generation of air bubbles during firing and the exposure of air bubbles to the surface, resulting in improved efficiency. It is believed that a thermal head with good thermal responsiveness can be obtained. In addition, the content of the finely ground glass powder is based on the total amount of glass powder.
When the amount is less than 20% by weight, the surface of the heat storage body becomes uneven, making it difficult to obtain the desired smoothness of the surface of the heat storage body, which is not preferable. The finely pulverized glass powder used in the present invention has an average particle size of approximately 5 μm or less. ) or the porosity of the bubbles, it is particularly preferable that the average particle diameter is 0.5 μm to 1.0 μm. This is because if the size of the resulting bubbles is too large or the porosity of the bubbles is too high, there is a risk that the heat storage body will lack mechanical strength. Therefore, if a finely pulverized glass powder having an average particle size of 0.5 μm to 1.0 μm is used, a heat storage body having the most preferable characteristics can be obtained. Incidentally, according to experiments conducted by the present inventors, it is particularly preferable that the pore diameter of the bubbles is 10% or less of the layer thickness of the heat storage body, and that the porosity of the bubbles is particularly preferably within the range of 10% to 30%. It has been found that. The finely pulverized glass powder described above is added to a solution of ethyl cellulose, nitrocellulose, etc. dissolved in a solvent such as terpineol and kneaded to form a glass paste. It is printed on a base material such as alumina using a machine, and after drying, the temperature is 50℃ to 150℃ higher than the softening point of the glass used.
By firing at a moderately high temperature, a heat storage body made of glass having a desired number of bubbles can be easily obtained. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 50% by weight of finely ground glass powder with a softening point of 630°C and an average particle size of 0.5 μm was mixed with 50% by weight of glass powder with a softening point of 630°C and an average particle size of 10 μm, and this was mixed with α-terpionelle and ethyl cellulose. A glass paste was prepared by kneading it in a 5% dissolved vehicle. This glass paste was printed on the alumina base material 1 by screen printing in a size of 0.5 mm in width, 10.0 mm in length, and 65 μ in thickness, dried at 100°C, fired at 740°C for 15 minutes, and cooled. A heat storage body 2 was obtained on the base material 1. Si-
An O ₂ film, _two TiSi layers as the heating resistor 3, and an aluminum alloy layer as the electrode 4 were successively laminated, and after patterning, a silicon layer doped with nitrogen was formed as the protective film 5 to obtain a thermal head. (See attached drawings) Example 2 Example 2 was prepared in the same manner as in Example 1 except that the finely ground glass powder in Example 1 was 22% by weight and the other glass powders were 78% by weight. did. Example 3 Example 3 was prepared in the same manner as in Example 1 except that the finely ground glass powder in Example 1 was 80% by weight and the other glass powders were 20% by weight. Example 4 The average particle size of the finely ground glass powder in Example 1 was
Example 4 was prepared in the same manner as in Example 1 except that the average particle size of the other glass powder was 0.4 μm and 20 μm. Example 5 The average particle size of the finely ground glass powder in Example 1 was
Example 5 was prepared in the same manner as in Example 1 except that the thickness was 1.5 μm. Comparative Example 1 Everything was the same as in Example 1, except that finely pulverized glass powder was not used, only glass powder with an average particle size of 10 μm was used, and the firing conditions were set at 740°C for 40 minutes. This was designated as Comparative Example 1. Comparative Example 2 Comparative Example 2 was prepared in the same manner as in Example 1 except that 10% by weight of finely ground glass powder and 90% by weight of other glass powders were used. The following points were investigated regarding the heat storage bodies obtained in Examples 1 to 5 and Comparative Examples 1 and 2, and the thermal head made based on these heat storage bodies.
The results are shown in Table-1.

[Table] * Results of observation of the surface and cross section of the heat storage body using a scanning electron microscope.
As described in detail above, according to the present invention, when obtaining a heat storage body made of glass having a large number of bubbles, the base glass powder contains a specific amount of finely pulverized glass powder. When printing and firing the glass paste base material, the control does not require advanced technology or is difficult, and therefore the bubbles generated are not exposed on the surface of the heat storage element. As a result, the surface will be uneven, which will have a negative effect on the quality of subsequent printing.Of course, the thermal response of the thermal head obtained based on this heat storage body will be evaluated as soon as possible. The temperature rise and fall are extremely excellent.

[Brief explanation of the drawing]

The drawing is a sectional view of a main part of an embodiment of a thermal head obtained according to the present invention. DESCRIPTION OF SYMBOLS 1... Base material, 2... Heat storage body, 3... Heat generating resistor, 4... Electrode, 5... Protective film.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a thermal head in which a heat storage body having a large number of bubbles is formed by printing and firing a glass paste made of glass powder in the lower part of a heat generating part, 1. A method for producing a thermal head, characterized in that the average particle size of the thermal head is 10 μm to 50 μm, and the glass powder contains at least 20% by weight of finely ground glass powder with an average particle size of 5 μm or less. 2 The average particle size of finely ground glass powder is 0.5 μm to 1.0 μm
A method for manufacturing a thermal head according to claim 1, characterized in that: