JPH02184458A - Production of thermal head - Google Patents

Abstract

PURPOSE:To enhance efficiency of heat transfer and contact of a head with a thermal recording paper by a method wherein a conductor pattern formed on an insulating substrate by use of a metal-organic paste is buried into the substrate through diffusion by a high-temperature heat treatment, and a heat generating resistor is formed on the conductor pattern by a thin film method. CONSTITUTION:Conductor patterns 31 are provided on an insulating substrate 11 by applying a metal-organic paste by printing and baking the applied paste. Then, a high-temperature heat treatment is conducted for interdiffusion of the materials of the substrate 11 and the conductor patterns 31, thereby burying the patterns 31 into the substrate 11. Thus, the upper surfaces of the substrate 11 and the conductor patterns 31 become substantially flush with each other, so that a heat generating resistor 2 formed thereon by a thin film method has a smooth upper surface, and a protective film 4 provided thereon has no recessed parts. Since the area of thermal contact of the resistor 2 with the conductor patterns 31 is small and the patterns 31 are small in thickness and heat capacity, the heat generated by the resistor 2 is mostly transferred to the protective film 4. The protective film 4, having no recessed parts, can transfer the heat effectively to a thermal recording paper 6. In addition, favorable contact between the protective film 4 and the paper 6 is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a thermal head, which is a printing device such as a facsimile or a printer.

[Conventional technology]

In general, a thermal head prints numbers, letters, etc. on thermal recording paper.
It is used to record symbols, etc., and usually consists of a pair of electrodes formed on an insulating substrate such as ceramic, and a resistor as a heating element electrically connected between the two electrodes. It is configured. When recording using a thermal head, a voltage is applied to the resistor between both electrodes to cause the resistor to generate heat, and the heat is applied to the thermal recording paper. Thermal recording is performed in response to the heat generated. As is well known, the heat-sensitive recording paper used here is one that has been treated to change color physically or chemically by applying heat.

As mentioned above, the basic elements of a thermal head are electrodes and heating resistors, and these are generally formed by printing and baking a paste, which is called the thick film method, or by sputtering or CVD, which is called the thin film method. is fabricated on an insulating substrate by Combining these methods results in the following four sets.

(a) Electrode; thick film method Resistor; thick film method (b) Electrode;
Thick film method Resistor; Thin film method (c) Electrode; Thin film method
Resistor: thick film method) Electrode: thin film method Resistor: thin film method Which of these combinations to use for manufacturing depends on the required thermal head performance, quality, equipment, production volume, cost, etc. Although it is determined by various factors, -
Although the thin film method can produce high quality and high performance inside the film, it is expensive.

Now, FIG. 5 is a sectional view showing a conventional thermal head in which the electrodes are made by the thick film method and the resistor is made by the thin film method, which generally corresponds to the above (2) shown in, for example, Japanese Unexamined Patent Publication No. 58-220769.
In the figure, ([) is an insulating substrate, (1) is a heating resistor formed by a thin film method, (3) is a conductor pattern formed by a thick film method, and (3a) is a conductor pattern step. (
4) is a protective film that protects the periphery of the heating resistor, and (4a) is a recess. (5) is a driving IC for driving the number heating resistor (2), and (6) is thermal paper that develops color due to the heat from the heating resistor (2).

The electrode-thick film method and resistor-thin film method shown in Figure 5 above have less variation in resistance and less power applied than the electrode-thick film method and resistor-thick film method. It also has a good thermal response, and has an advantageous structure in response to the demand for high-precision, high-speed thermal recording on thermal recording paper, as in recent thermal heads.

Current flows through the ring (3). This current is supplied to the heating resistor (2) through the thick film conductor pattern (3), and the heating resistor (2) generates heat. Protection to prevent oxidative deterioration of the heating resistor (2) when generating heat, and to protect the heating resistor (2) and conductor pattern (3) from friction with the thermal paper (6) during printing. A film (4) is formed. Also protective film (4)
The thermal paper (6) pressed against it reacts with the heat transferred from the heating resistor (2) through the protective film (4) and develops color.
Text and figures are displayed.

[Problem to be solved by the invention]

Conventional thermal heads are manufactured with the above-mentioned configuration and have the following problems.

Since the printed conductor pattern (3) is a thick-film conductor using a conductive paste containing a metal material such as Al or gold, the protective film (4) on the thick-film conductor pattern (3) covers the conductor pattern step ( 3i) cannot be filled, resulting in a depression (4a) as shown in FIG.

(Also, as shown in FIG. 7, a protective film (4b) with poor step coverage and an exposed conductor (3a) are generated at the step (3a) of the conductor pattern.

(c) Furthermore, as shown in FIG. 6, the heat generated in the heat generating portion (2a) of the heat generating resistor (2) is transmitted to the insulating substrate (1), the conductor pattern (3) and the protective film (4). Here, since the conductor pattern (3) has a thick film structure, it has a large heat capacity and therefore most of the heat flow (8) is transmitted to the conductor pattern (3). Of the remaining heat flow (9) αQ, (9) will be transmitted to the protective film (4), but the heat transmitted between the protective film (4) and the thermal paper (6) will be transmitted via the recess (4a). Therefore, the heat flow DI is extremely small, resulting in very poor thermal efficiency.

B) The adhesiveness between the protective film (4) and the thermal paper (6) is poor due to the presence of the recess (4a). There were problems such as.

As one way to solve these problems,
In this issue, an extremely thin conductor pattern was formed using a thick film method using metal organic paste as the conductor material.
It has been shown that a thick film heating resistor is formed on this conductor pattern, but even in this method, the heating resistor weighs 7 g.
Since it is a film, problems (6) and (c) above cannot be completely solved.

In addition, by making the conductor pattern thinner and the heating resistor thinner, it is possible to solve the problems (6) to (6) above, but it is not always possible to solve them completely from the viewpoint of cost and equipment. Not adopted.

This invention was made in order to solve all of the problems (a) to (b) above, and it forms an extremely thin conductor pattern using a thick film method and then heat-treats it at high temperature to diffuse it and spread it onto an insulating substrate. To provide a method for manufacturing a highly reliable thermal head with low cost, high thermal efficiency, no step coverage, and good adhesion to thermal paper by embedding it in the soil and forming a heating resistor using a thin film method in the soil. The purpose is to

[Means to solve the problem]

A method for manufacturing a thermal head according to the present invention is to form a conductor pattern on an insulating substrate using metal organic paste, diffuse it by high-temperature heat treatment, embed it in the insulating substrate, and apply a heating resistor using a thin film method on top of the conductor pattern. It is what formed the body.

[Effect]

The thermal head manufactured according to the present invention has a thin conductor pattern, is diffused into the insulating substrate through heat treatment, and is embedded in the surface of the insulating substrate, and a thin film heating resistor is formed on the top surface, so there is no dent on the surface of the protective film. The surface becomes smoother, improving heat transfer efficiency and increasing the adhesion between the protective film and the thermal paper.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings.

In Fig. 1, αη is formed by printing and firing a conductor pattern Cl force on an insulating substrate using metal organic paste, and then forming the conductor pattern Cl force on an insulating substrate Op and the above conductor pattern 0υ.
A high-temperature heat treatment is performed for the purpose of interdiffusion with the insulating substrate, and a conductive pattern is embedded into the insulating substrate. (2) is the conductor pattern 61 and the insulating substrate (b).
A heating resistor is formed on top by a thin film method, and (4) is a protective film. Compared to the conventional thick-film conductor pattern (3) shown in Fig. 5, the metal organic conductor pattern (b) has zero resistance by firing as shown in Japanese Patent Publication No. 62-30114. The pattern is extremely thin, about .3 μm, about 1/10 of the conventional pattern, and therefore the conductor pattern step (31 m) is extremely small.

Therefore, as can be seen from FIG. 1, the insulating substrate 0η and the upper surfaces of the six conductor patterns are almost flush with each other, and the upper surface of the heating resistor (2) formed thereon by the thin film method is smooth, and the protective film ( 4) has a dent (4a) on the surface like the conventional example.
does not occur.

Figure 3 shows data on the level difference between the conductor pattern and the insulating substrate depending on the heat treatment temperature. In this example, the level difference is 0 at 850° C., but it goes without saying that the degree of the level difference varies depending on the material of the insulating substrate and the processing temperature.

Next, the operation will be explained. A signal enters the driving IC (5) from the outside, and a current flows through the conductor pattern 6. This current is supplied to the heating resistor (2) through the conductor pattern 6p, and the heating resistor (2) generates heat. The protective film (4) protects the heating resistor (2) from oxidizing and deteriorating when it generates heat, and protects the heating resistor (2) from friction with thermal paper (6) during printing. Protect the conductor pattern (b).

Thermal paper (6) pressed against the protective film (4) develops color in response to heat transferred from the heating resistor (2) through the protective film (4) to display characters and figures.

Here, the heat generated by the heating resistor (2) has a small thermal contact surface with the conductor pattern 61) as shown in FIG.
Since the conductor pattern C(l) is extremely thin and has a small heat capacity, most of it is transferred to the protective film (4).

Since the protective film (4) does not have a recess (4a) unlike the conventional example, the entire heat is efficiently transferred to the thermal paper (6). Furthermore, the adhesion between the protective film (4) and the thermal paper (6) is improved.

FIG. 2 is a diagram showing heat propagation in the thermal head of the present invention. The heat generated in the heat generating part (2a) of the heat generating resistor (2) flows into a heat flow (8) to the conductor pattern cl), a heat flow (9) to the protective film (4), and a heat flow to the insulating substrate αp. α0, but as mentioned above, most of the generated heat is transferred to the protective film (4) because the thermal contact area between the heating resistor (2) and the conductor pattern 6p is small, and because the six conductor patterns are thin films and have a small heat capacity. (9). The heat transferred to the protective film (4) is efficiently transferred to the well-adhered thermal paper (6). In this way, an energy-saving thermal head with improved thermal efficiency can be obtained. Furthermore, as shown in Fig. 4, since there is no step between the conductor pattern 6η, the heating resistor (2), and the insulating substrate (b), there is no step coverage problem for the protective film (4), resulting in high reliability and long service life. It becomes a long thermal head.

In one embodiment of the present invention, an example was shown in which the entire thickness of the conductor pattern 6]) was embedded in the insulating substrate (b), but it is also possible to embed a part of the thickness of the conductor pattern (6) into the insulating substrate (b). You may

Furthermore, in the above embodiment, the conductor pattern cli metal
Although an example has been shown in which the organic paste is formed by printing and firing, the conductor pattern may be formed by photolithography or etching after printing and firing.

〔Effect of the invention〕

As described above, according to the present invention, a metal layer is formed on an insulating substrate.
A conductor pattern formed using organic paste was diffused through high-temperature heat treatment and embedded in an insulating substrate, and a heating resistor was formed on this conductor pattern using a thin film method.
An inexpensive thermal head with good heat transfer efficiency, energy saving, good adhesion to thermal paper, no step coverage, low printing variation, high reliability, and long life can be obtained.

[Brief explanation of the drawing]

Figure 1 is a sectional view showing a thermal head according to an embodiment of the present invention, Figure 2 is a diagram showing heat propagation in the thermal head shown in Figure 1, and Figure 3 is a diagram showing a conductor pattern and an insulating substrate depending on the heat treatment temperature. Figure 4 is an enlarged sectional view of the protective film portion, Figure 5 is a sectional view of a conventional thermal head, Figure 6 is a diagram showing heat propagation in a conventional thermal head, and Figure 4 is an enlarged sectional view of the protective film. FIG. 7 is an enlarged sectional view of a conventional protective film portion. In the figure, (1) and (b) are insulating substrates, (2) are heating resistors, (3) and (b) are conductive patterns, (4) are protective films, and (6) are
) is thermal paper. In addition, in the figures, the same reference numerals are the same.

Claims (1)

[Claims] A thermal device characterized in that a conductor pattern formed using metal organic paste on an insulating substrate is diffused by high-temperature heat treatment and embedded in the insulating substrate, and a heating resistor is formed on the conductor pattern by a thin film method. Head manufacturing method.