JPH0582824B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for manufacturing a thermal head, and more particularly to a method for efficiently obtaining a thermal head with good thermal response. (Conventional technology and its problems) Thermal recording method, which is a typical non-impact method, has come to be widely used because it has advantages such as no noise, but the heat generating part of the thermal head used in this method Since the heat storage body located at the bottom has a great influence on printing efficiency and printing quality in particular, various improvements 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 stored will increase, and the amount of heat dissipated when the power is off, that is, when cooling, will be relatively insufficient, making it impossible to cool down quickly, resulting in unnecessary printing, etc. Therefore, it is desired that the heat storage body in the thermal head has contradictory characteristics. 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 appropriate 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 printing quality. Although the thermal response is good, a problem arises in that a thermal head having commercial value cannot be obtained. (Means for Solving the Problems) The present invention was made in view of the above circumstances, and provides a thermal head comprising glass having a large number of bubbles as a heat storage body, and equipped with such a heat storage body. This was finally completed as a result of intensive research into a manufacturing method for efficiently obtaining . That is, the present invention provides 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. The particle size is 10 μm to 50 μm, and at least finely pulverized glass powder with an average particle size of 5 μm or less is added.
The gist of the present invention is a method for manufacturing a thermal head, characterized in that the glass powder contains 20% by weight or more and the softening point of the glass powder is 650°C to 850°C. 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. These glass powders contain glass powder, and the softening point of these glass powders is 650°C to 850°C. As a result, in the present invention, even if the glass paste is printed and fired on the base material, the moisture and gas components adsorbed to the finely ground glass powder are extremely small, so that these moisture and gas components are eliminated during firing. Even if the ingredients turn into bubbles, the bubbles are extremely small, so even if the bubbles are exposed to the surface of the heat storage element, the roughness of the surface is minimized to the extent that it does not adversely affect print quality. It is something that can be encouraged. Furthermore, this allows flexibility in various controls for controlling the generation of bubbles during firing and the exposure of bubbles to the surface, and as a result, a thermal head with good thermal responsiveness can be efficiently obtained. It seems to be. Furthermore, in the present invention, by specifying the glass material to be used with the softening point as described above, the general bubble generation temperature in glass (800
℃ to 900℃) and the required temperature for firing are almost the same, and the bubble generation process proceeds while the viscosity of the glass is maintained at the optimum state during firing, so the pore size and It becomes easier to control the distribution to make it uniform, and as a result, a desired thermal head can be obtained efficiently. This is because the softening point of the glass powder used is less than 650℃.
Quite high temperatures are applied for firing, which causes an extreme drop in the viscosity of the glass powder, causing the bubbles that are generated to be exposed to the surface instead of remaining inside the glass, resulting in heat accumulation. In addition, if the softening point of the glass powder used is higher than 850°C, moisture and gas, which cause bubbles, will form before the viscosity of the glass decreases during firing. This is because the components and the like will volatilize, making it impossible to even obtain a heat storage body having a large number of bubbles. As mentioned above, it is essential that the proportion of finely pulverized glass powder used in the present invention is at least 20% by weight based on the total amount of glass powder.
This is because if this point is not satisfied, the surface of the heat storage body will exhibit an uneven shape, making it difficult to obtain the desired smoothness, which is not preferable. The finely ground glass powder used in the present invention is
The average particle size is about 5 μm or less, but if you consider the reduction of air bubbles exposed on the surface of the heat storage element during printing and firing, the size of the air bubbles (pore diameter), and the porosity of the air bubbles, The average particle diameter is particularly preferably 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, the average particle size is 0.5 μm to 1.0 μm.
If a finely pulverized glass powder of m is used, a heat storage body having the most preferable characteristics can be obtained. Incidentally, according to experiments conducted by the present inventors, it has been found that the pore diameter of the bubbles is particularly preferably 10% or less of the layer thickness of the heat storage body. 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. Printed on a base material such as alumina using a machine, and after drying, the softening point was 50
By firing at a temperature approximately 150°C to 150°C higher (bubble generation temperature), a heat storage body made of glass having a desired number of bubbles can be easily obtained. (Examples) Hereinafter, the present invention will be explained in detail by examples together with the accompanying drawings. Example 1 50% by weight of finely ground glass powder with a softening point of 730°C and an average particle size of 0.5 μm was mixed with 50% by weight of glass powder with a softening point of 730°C and an average particle size of 10 μm, and this was mixed with α-terpineol and 5% of ethyl cellulose. % dissolved vehicle to prepare a glass paste. This glass paste was printed on the alumina base material 1 by screen printing in a size of 0.5 mm in width, 10 mm in length, and 65 μ in thickness, dried at 100°C, and then fired at 820°C for 25 minutes. , and cooled to obtain a heat storage body 2 on the base material 1. Si is deposited on this heat storage body 2 by sputtering.
A -O ₂ film, _two TiSi layers as the heating resistor 3, and an aluminum alloy layer as the electrode 4 were sequentially laminated and patterned, and then a silicon layer doped with nitrogen was formed as the protective film 5 to obtain a thermal head. (Refer to the 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 90% by weight and the other glass powders were 10% by weight. did. Comparative Example 1 Comparative Example 1 was prepared in the same manner as in Example 1 except that finely pulverized glass powder was not used and only glass powder with an average particle size of 10 μm was used. 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. Comparative Example 3 In Example 1, 10% by weight of finely ground glass powder with a softening point of 550°C and another glass powder with a softening point of 550°C were used.
Soft Example 3 was prepared in the same manner as in Example 1 except that 90% by weight of the glass powder was used and the glass powder was fired at 850° C. for 25 minutes. (Effects of the Invention) The following points were investigated regarding the heat storage bodies obtained in Examples 1 and 2 and Comparative Examples 1 to 3, and the thermal head made based on these heat storage bodies.
The results are shown in Table-1.

【table】

[Table] * Results of observation of the surface and cross section of the heat storage body using a scanning electron microscope.
As can be seen from the above explanation, according to the present invention,
In order to obtain a heat storage body made of glass having a large number of bubbles, the base glass powder is made to contain a specific amount of finely ground glass powder, and the softening point of the glass powder containing this finely ground glass powder is kept at a certain level. Because these glass pastes were specified within the range, printing and firing these glass pastes on the base material does not require advanced technology or is accompanied by difficulty, and therefore the bubbles generated do not accumulate heat. When exposed to the body surface, the surface becomes uneven,
This makes it possible to eliminate as much as possible any adverse effects on subsequent printing quality. Naturally, the thermal responsiveness of the thermal head obtained based on this heat storage body ensures rapid temperature rise and temperature drop, and provides an excellent thermal head.

[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, has an average particle size 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, and the softening point of these glass powders is 650°C.
A method for producing a thermal head characterized by a temperature of ~850°C. 2 The average particle size of the finely pulverized glass powder is 0.5 μm or more
The method for manufacturing a thermal head according to claim 1, wherein the thickness is 1.0 μm.