JPS62121068A - Thermal head - Google Patents

Abstract

PURPOSE:To enable a heat generated by a heat generating resistor to be efficiently transferred to a recording paper, by providing an air-containing heat- insulating layer on the surface of an insulating substrate. CONSTITUTION:For example, an alumina ceramic substrate 2 is heated, a glass 1 provided with air bubbles by blowing air into the glass in a molten state is cast on the substrate 2, then a plate 3 not wettable with the molten glass is placed thereon, and the molten glass is cooled while pressing the plate 3 against it with a fixed force. By this method, a glass layer having a flat surface and containing foams therein can be obtained. A protective layer 4, electrodes 5 and heat generating elements 6 are provided on the glass layer. Accordingly, since a heat-insulating layer having a low thermal conductivity, a low specific heat, excellent mechanical strength and favorable heat resistance is provided beneath a heat generating resistor, the heat generated by the heating elements can be prevented from escaping to the substrate side, and a thermal head having a high thermal efficiency can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thermal head for heat-sensitive recording, and particularly to a thermal head suitable for FAXs, printers, etc., which require miniaturization of the main body of the apparatus.

[Background of the invention]

Conventionally, it has been proposed to form a layer of various materials as a heat insulating layer under the heating resistor of a thermal head, and a proposal to provide a cavity as shown in Japanese Patent Application Laid-Open No. 11281/1983 is also known. There is. However, in this structure, the entire area under the heating resistor is hollow, and this hollow part is easily destroyed by the force of pressing the recording paper, and the method of forming the hollow part poses a major problem.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head that has a highly practical structure that efficiently transfers heat generated by a heating resistor to recording paper.

[Summary of the invention]

The thermal insulation layer directly under the heating element is thick (
It has long been known that the effects of
The results shown in the figure were obtained. During this study, it became clear that the physical properties that affect thermal efficiency are thermal conductivity and specific heat. The thermal conductivity and specific heat of each material are also shown in FIG. 1, and it is clear that materials with small values of these two physical properties exhibit better characteristics. However, from the results of this study, it has become clear that no glass or ceramic material has been found that has two orders of magnitude better physical property values, and that there is a limit in terms of materials. On the other hand, organic substances have good physical properties as shown in FIG. 1 and are highly effective. However, organic substances have problems in terms of heat resistance and are unsuitable for thermal heads because they are thermally decomposed with a relatively small amount of electric power.

In the present invention, the heat insulating layer is made of foamed ceramic material containing air, as seen in fire-resistant materials.

For example, the thermal conductivity and specific heat of a typical glazed glass are t05W/m-167J/, respectively, while for porous silica (5i0292+) each is 0.34
W/m-K, 0.90 J/g·K. Therefore, a heat insulating layer made of such a material is very effective.

[Embodiments of the invention]

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

[Example 1] As shown in Fig. 2, after heating an alumina ceramic substrate 2 and pouring glass 1 on which air was blown in a molten state to form air bubbles, the molten glass was wetted from above. A blank plate 3 is pressed against it and cooled while being pressed with a constant force. By such a method, a glass layer having a flat surface and containing air cells inside can be obtained. Each element 4, 5.6 of the thermal head is formed on this.

[Example 2] As shown in Fig. 3, thin hollow glass tubes 7 are arranged on an alumina ceramic substrate 2, and sheet glass 8 having a lower softening point than the glass is placed, and then only the sheet glass is melted. .

In this example, a cylindrical air layer is formed under the thin glass layer.

[Example 3] As shown in FIG. 4, ultrathin glass sheets 9 or glass fibers having a low softening point are arranged on an alumina ceramic substrate 2 at predetermined positions and at predetermined intervals. A glass sheet 8 having a high softening point is placed on top of this, and only the lower glass sheet is melted to form an air layer. In this case, instead of arranging glass sheets with a low softening point, grooves may be formed in advance on the surface of the alumina ceramic substrate, and the glass sheets may be placed on the grooves.

[Example 4] As shown in FIG. 5, a hollow or solid ceramic or glass sphere 10 is placed on the entire surface of an alumina ceramic substrate 2, a glass sheet is placed on top of this, and then the glass sheet is melted.

This allows a heat insulating layer containing air inside. In this case, it is desirable that the melting point of the glass sheet is lower than the melting point of the ceramic or glass sphere. On this, electrodes 59, heating resistors 6, etc., which are necessary components of the thermal head, are formed.

〔Effect of the invention〕

According to the present invention, a heat insulating layer with low thermal conductivity, low specific heat, excellent mechanical strength, and good heat resistance can be formed directly under the heating resistor, thereby preventing the heat generated from the heating element from escaping to the substrate side. It is possible to manufacture a thermal head with high thermal efficiency. This thermal head allows for the miniaturization of fax and printer devices.

Lower costs and lower power consumption can be achieved.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing the difference in power required for printing due to the difference in the characteristics of the heat insulating layer in the present invention, Fig. 2 is a structural diagram according to Embodiment 1 of the present invention, and Fig. 3 is a structural diagram according to Embodiment 2. , 4th
The figure is a structural diagram according to the third embodiment, and FIG. 5 is a structural diagram according to the fourth embodiment. 1... Foamed glass, 2... Ceramic substrate,
3... Pressing plate, 4... Protective layer, 5...
electrode, 6... heating element, 7... hollow tube,
8...Glass sheet, 9...Glass sheet. Representative Patent Attorney Katsoo Ogawa No. 1 Figure 0 20 4Q 60'm IQ
O seal Uden, power (W//71 prefecture 2nd mouth (b) (Cn (d-) Figure 3 (cL) (bn (C) Figure 4 (aan (b) (0n

Claims (1)

[Claims] 1. In a thermal head that is equipped with a heating resistor on an insulating substrate, wiring for supplying power to the heating resistor, and a protective layer that protects these from deterioration phenomena such as wear, a heat insulating layer containing air is placed on the surface of the insulating substrate. A thermal head characterized by a formed