JPS61215067A - Preparation of thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head excellent in thermal response, by printing a pasty glass powder material containing a specific amount of a finely divided glass powder and having a softening point set to a specific range on a base material before baking. CONSTITUTION:A finely divided glass powder is contained in a glass paste used in the formation of a heat accumulator 2 in an amount of at least 20% or more by wt. of the total amount of a glass powder and the softening point of these glass powders is set to 650-850 deg.C. When the glass paste is printed on a base material 1 and baked, air bubbles generated at a baking time is extremely reduced because the moisture or gaseous component adsorbed by the finely divided glass powder is extremely little and, even if said air bubbles are issued to the surface, no adverse effect is exerted on printing quality. Because the glass softening point is specified as mentioned above, air bubble generating temp. almost coincides with necessary baking temp. and control for uniformizing the pore size or distribution of air bubbles is easily performed and, as a result, a desired thermal head is obtained with good efficiency.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for manufacturing a thermal head.

More specifically, the present invention relates to a manufacturing method for efficiently obtaining a thermal head with good thermal responsiveness.

(Conventional technology and its problems) Thermal recording method, which is a typical non-impact method, has been widely used because it has advantages such as no noise. Since the heat storage body located at the front has a great influence on printing efficiency and printing quality in particular, various measures have been taken 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. Although it is considered preferable to use a material with low conductivity, in practice the layer thickness of the heat storage material must be increased to a certain extent in order to provide the necessary and sufficient amount of heat during printing.

On the other hand, if the layer thickness is too large, the amount of heat stored will increase, and the amount of heat dissipated during de-energization, that is, during cooling, will be relatively insufficient, making it impossible to quickly cool down the temperature, resulting in unnecessary printing. 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 the 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 lower, and the amount of heat stored at a certain temperature is also lower. That is, 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 -! However, the amount of heat stored is small, and therefore, when power is applied, the printing temperature can be maintained and the speed of cooling down quickly.

The heat storage body is considered useful because it has such good thermal responsiveness.

However, various problems arise when actually obtaining a heat storage body for such a thermal head.

That is, in order to obtain glass having a large number of bubbles, generally, 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. It is conceivable that it could be obtained by using it, but it could also be used to manufacture heat storage bodies for thermal heads.

When controlling the firing process, for example, the firing temperature must be adjusted by ±2 to 3
It must be maintained within a range of ℃.

The problem arises that controlling the firing conditions is technically sophisticated and difficult, and if the appropriate firing conditions cannot be set, the bubbles generated from inside the glass powder will not stay only inside the heat storage body but will spread to its surface. This exposure causes the surface to exhibit unevenness, which adversely affects printing quality, resulting in the problem that a thermal head having good thermal responsiveness but having commercial value cannot be obtained.

(Means for Solving the Problems) The present invention has been 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. As a result of intensive research into a manufacturing method that can efficiently obtain this, it was finally completed.

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 on the lower part of two heat generating parts, in which the glass powder is finely pulverized. The gist of the present invention is a method for manufacturing a thermal head, characterized in that the glass powder contains at least 20% by weight of glass powder, 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. The softening point of these glass powders is 650℃~8.
It is at a point where the temperature is 50°C.

Due to this, in the present invention, even if the glass paste is printed on the substrate and fired, the moisture and gas components adsorbed to the finely ground glass powder are extremely small, so these moisture and gas components are removed during firing. Even if they turn into bubbles, the bubbles are extremely small, so even if the bubbles are exposed on the surface of the heat storage element, the roughness of the surface should be minimized to the extent that it does not adversely affect the printing quality. It is something that can be done. Furthermore, due to this.

It is believed that there is 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.

Furthermore, in the present invention, by specifying the glass material to be used according to its softening point as described above, the general bubble generation temperature in glass (800°C to 900°C) and the required temperature of the firing vessel are approximately the same. The bubble generation process progresses after the viscosity of the glass is maintained in an optimal state during firing, making it easier to control the bubble pore size and distribution to make it uniform, resulting in the desired thermal head. can be obtained efficiently. This is because when the softening point of the glass powder used is less than 650°C, a considerably high temperature is applied for firing it, and this causes an extreme drop in viscosity of the glass powder, which causes air bubbles to form in the glass. If the softening point of the glass powder used is higher than 850°C, it will be exposed during firing, making it difficult to obtain a smooth surface as a heat storage body. .

This is because moisture, gas components, etc. that are the source of bubbles evaporate before the viscosity of the glass decreases, and it becomes impossible to even obtain a heat storage body having a large number of bubbles.

Note 1: As mentioned above, it is essential that the proportion of finely ground glass powder used in the present invention is at least 20% by weight based on the total amount of glass powder, but this point is not satisfied. Because of that.

The finely ground glass powder used in the present invention is:

The average particle size is approximately 5 μm or less,
Considering the reduction of air bubbles exposed on the surface of the heat storage body during printing and firing, the size of the air bubbles (pore diameter), or the porosity of the air bubbles, the average particle size is particularly 05 μm to 1.0 μm.
It is preferable that This is because if the size of the resulting bubbles is too large or the porosity of the trenched bubbles is too high, there is a risk that the heat storage body will lack mechanical strength. Therefore, the average particle size is 05 μm.
If finely pulverized glass powder of ~10 μm is used, a heat storage body with the most preferable properties will 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. By printing on a substrate made of alumina or the like using a machine, after drying, it is fired at a temperature (bubble generation temperature) approximately 50°C to 150°C higher than the softening point of the glass used according to a conventional method, to create the desired number of bubbles. A heat storage body made of glass having the following properties can be easily obtained.

(Example) The present invention will be described in detail below with reference to the accompanying drawings. 3゜Example 1 Finely ground glass powder with a softening point of 730°C and an average particle size of 05 μm 5
A glass paste was prepared by mixing 50% by weight of glass powder with a softening point of 730 DEG C. and an average particle size of 10 .mu.m into 0% by weight of glass powder, and kneading this into a vehicle containing 5% of ethyl cellulose dissolved in alpha-terpineol. This glass paste was screen printed onto the alumina base material 1 to a width of 05 mm.

Length 10. Ou, printed with a thickness of 65μ,
1. After drying at 100°C, drying at 820°C for 25 minutes. ',,',
, (,), the aluminum alloy layers are sequentially stacked, and the
-10- After turning, 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 The same as 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.
Example 2 was prepared in the same manner as above.

Comparative Example 1 All the same procedures as in Example 1 except that in Example 1, finely pulverized glass powder was not used and only glass powder with an average particle size of 10 μm was used.
Comparative Example 1 was prepared in the same manner as above.

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 Except for Example 1, in which 10% by weight of finely ground glass powder with a softening point of 550°C and 90% by weight of other glass powder with a softening point of 550°C were used, and these glass powders were fired at 850°C for 25 minutes. All of the steps were performed in the same manner as in Example 1, and this was designated as Comparative Example 6.

(Effect of the invention) Examples 1 and 2 above. The following points were investigated regarding the heat storage bodies obtained in Comparative Examples 1 to 3 and thermal heads made based on these heat storage bodies. The results are shown in Table-1.

*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 description, 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 it was specified within the range, when printing and firing these glass pastes on the base material.

It does not require advanced technology or is accompanied by difficulties, and therefore, the generated air bubbles are exposed on the surface of the heat storage element, causing the surface to become uneven, which adversely affects the quality of subsequent printing. This is something that can be eliminated as much as possible.

Of course, regarding the thermal response of the thermal head obtained based on this heat storage body, it is possible to guarantee rapid temperature rise and temperature drop, and provide an excellent thermal head.

[Brief explanation of the drawing]

The drawing is a sectional view of a main part showing an embodiment of a thermal head obtained by the present invention. 1... Base material 2... Heat storage body 3
...Heating resistor 4...Electrode 5...
····Protective film

Claims (2)

[Claims] (1) In 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 on the lower part of a heat generating part, the glass powder is finely ground glass powder. is at least 2
A method for producing a thermal head, characterized in that the glass powder contains 0% by weight or more, and the softening point of the glass powder is 650°C to 850°C. (2) The average particle size of the finely pulverized glass powder is 0.5 μm to 1
．． Claim No. 1 (1) characterized in that the diameter is 0 μm.
) The method for manufacturing the thermal head described in item 2.