JPS6034801B2 - Thermal head for thermal recording device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a substrate on which a heat generating resistor is formed and a thermal head in which a heat generating resistor is formed on the substrate when manufacturing a thermal head used in a thermal recording device.

The thermal recording method is noiseless, maintenance-free, low cost, and has excellent printing properties, so it has recently attracted attention from various quarters and has been researched and developed.

However, compared to methods such as electrostatic recording or current recording,
The recording speed is low, and further speeding up is required for use in facsimiles, computer printers, etc.

In order to increase the speed of thermal recording, it is necessary to improve the wiring method, electric circuit, etc., and to improve the durability of the heating resistor used in the thermal head when it is used at high temperatures.

Conventionally, the following requirements are required for a substrate for a thermal head (hereinafter referred to as a thin film thermal head) manufactured using thin film manufacturing technology. That is, 1. The surface must be extremely smooth. 2. The heat generated by the heating resistor can be efficiently transferred to the thermal paper, and the temperature of the board must not rise due to heat accumulation. 3.
There is no warping or twisting, and good flatness (because photo-etch technology is used to produce fine patterns for resistors and electrodes, etc.); 4) there are fewer alkali ions that can cause deterioration of heating resistors; and so on.

Due to these conditions, glazed ceramics, which are alumina ceramics coated with a glass layer, are generally preferred.

Additionally, the glass layer of glazed ceramics requires the following:

1. The coefficient of thermal expansion is similar to that of alumina (to achieve flatness). 2. Good adhesion to alumina. 3. A smooth glazed surface can be obtained. A glazed ceramic glaze that satisfies these conditions. Currently, it is difficult to obtain a layer with a high softening temperature, and the maximum use temperature is currently limited.

On the other hand, due to the demand for faster thermal recording, thermal head heating resistors are required to be more durable at high temperatures than ever before.

As a result of various studies regarding the above points, it has been found that in order to improve the durability of the thermal head at high temperatures, it is necessary to improve the heating resistor as well as the substrate on which the heating resistor is formed. .

The present invention has been made in view of these points,
By interposing a low-alkali glass layer with good heat resistance and low alkali content between the glass layer with a low softening point on the glazed substrate and the heating resistor, we can create glazed ceramics without sacrificing the characteristics of glazed ceramics. By improving the drawback of a low maximum operating temperature, the present invention provides a thermal head that can withstand use at high temperatures and is useful for speeding up thermal recording.

In the present invention, as a material having good thermal conductivity for the substrate to be glazed, a material obtained by sintering an oxide such as alumina, beryllia, or magnesia as a main component is used.

In addition, as a heating resistor, shelved zirconium or other shelved heating resistors are stable over time and the resistance value can be adjusted, especially since it is possible to set a high specific resistance value, so it is recommended to use a substrate with good heat resistance. It is used in conjunction with rope.

FIG. 1 shows an example of a conventional thermal head, in which a heating resistor 2 is mounted on a glazed ceramic substrate 1.
The lead-out conductors 3 and 4 are placed on top of that, and a protective layer 5 is placed on top of that.
, 6 are coated.

FIG. 2 is a sectional view of a main part of the thermal head according to the present invention, and is characterized in that a glass composition 7 is coated on glazed ceramics. The rest of the machine is the same as the conventional one shown in Figure 1. The embodiments of the present invention will be explained below using examples.

Example No. 1 having the composition shown in Table 1 was placed on glazed ceramics (manufactured by Kyoto Ceramics Co., Ltd., trade name GS-2), which was a glass-covered alumina sintered plate with a plate thickness of 0.63 ribs. 1~No. 7 glass target in argon,
It was deposited as a glass thin film of about 2 mm by radio frequency sputtering.

Table 1 (% by weight) The softening point (Ts°C) of the glass in the glaze layer is 6
20 o'clock C, and the sum of K20 and Na20 is 0.9
%Met.

Shelved zirconium was placed on the glass thin film by high-frequency sputtering in argon using a target of about 800△.
The resistor was formed as a thin film resistor, and furthermore, Ti and Au were deposited thereon by electron beam evaporation to a thickness of 50 Δ and 1.5 Δ, respectively.

Next, these were formed into a heating resistor and lead-out conductor pattern by etching, and silicon oxide and tantalum oxide were deposited thereon by high-speed sputtering, respectively, in 2 and 8 layers, respectively.

The resolution of the thermal head made in this way is 4 lines/
It was hot by my side. In addition, a rectangular electric pulse of 1 skin sec was applied to the thermal head made in the above process at a cycle of 50Hz.
Table 2 shows the change in resistance value of the heating resistor when a power of 2.4 W per heating resistor (power that allows practical printing density to be obtained with one pulse) was applied for one hour.

Table 2 The numbers in Table 2 correspond to the numbers in Table 1, respectively.

In Comparative Example 1 in Table 2, a side-cured zirconium heating resistor was directly adhered to the glazed ceramics, and the other conditions were the same. From Table 2, it can be seen that the deterioration of the resistance value is greatly affected by the underlying material in contact with the heating resistor.

That is, K20+Na20SI. 0% and softening point 74
Good results have been obtained at temperatures above 5°C. In addition, No. in Table 2.
When the No. 6 thermal head was tested for 500 hours, the resistance value change was 13.4%, and its lifespan was 500 hours.
It was found that the distance between the thighs and temples was more than that, and in Comparative Example 1, the wire broke after 5 field hours in the same long-term test.

From the above, it has become clear that the effects of the present invention are significant. Next, an example will be shown in which the lateralized zirconium heating resistor is replaced with another shelved heating resistor.

This thermal head is No. 1 in Table 1. The following heating resistor was provided on the glass layer of No. 4, and the other configurations were the same. In addition, various thermal heads were prepared on the substrate without a glass layer according to the present invention to prepare thermal heads for comparison. For these thermal heads, a 50Hz cycle,
Table 3 shows the resistance change rate after applying a rectangular wave electric pulse of 1 ms during the pulse and a power of 2.4 W per dot for 1 hour. The results confirmed the effectiveness of the glass layer according to the present invention. Table 3 Furthermore, the effects of the present invention were observed in tantalum nitride and nichrome heating resistors.

As described above, the thermal head substrate, which is made by adhering glass with a high softening point and low alkaline content on glazed ceramics, has the excellent flatness of glazed ceramics.
It is possible to improve the drawback of a low maximum operating temperature without impairing characteristics such as smoothness and thermal properties, and is useful for increasing the speed of thermal recording.

Note that the present invention is not limited to the above embodiments.

That is, 1. For the ceramic substrate used in the present invention, materials with good thermal conductivity such as beryllia, sapphire, metal, etc. can be used instead of alumina.

2. The means for forming the glass layer of the present invention is high-speed sputtering, ion plating, electron beam evaporation, CVD, etc., but any method provides good adhesion to the glazed layer.

3. If the thickness of the glass layer is too thin, it will be susceptible to the influence of the underlying material, and if it is too thick, heat will accumulate in the glass layer, which is not preferable for high-speed recording. Therefore, the preferred range of thickness is 0.2 to 50 mm, particularly preferably 1 to 10 mm. 4 The present invention can also be used for thick film thermal heads, substrates for hybrid integrated circuits, etc.

[Brief explanation of the drawing]

FIG. 1 shows a thermal head conventionally used in a thermal recording device, and FIG. 2 shows a thermal head according to the present invention.
Each is an enlarged cross-section of the main part. 1... Glazed ceramics substrate, 2...
... Heating resistor, 3, 4 ... Output conductor, 5
, 6... Protective layer, 7... Glass layer. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. A glazed substrate in which a glass layer is coated on a material with good thermal conductivity, and a compound of sodium oxide and potassium oxide that is coated on the glazed substrate and has a softening point of 745°C or higher, and contains sodium oxide and potassium oxide. 1. A thermal head for a thermal recording device, comprising a low alkali glass layer having an amount of 1.0% by weight or less, and a heating resistor disposed on the low alkali glass layer. 2. The thermal head according to claim 1, wherein the low alkali glass layer has a thickness of 0.2 to 50 μm. 3. The thermal head according to claims 1 and 2, wherein the heating resistor is zirconium boride.