JPH01310970A - Thermal head - Google Patents

Abstract

PURPOSE:To enhance durability by preventing the heat shock destruction of a protective layer at the time of high speed printing by a method wherein the constitutional material of the protective layer formed on a heat generating resistor consists of two kinds of materials and the component ratio of two kinds of materials is changed over three layers upwardly from the surface of a resistor. CONSTITUTION:A glaze layer 2 is formed on a ceramic substrate 1 and a heat generating resistor layer 3, an electric conductor layer 4 and protective layers 5-1, 5-2, 5-3 are successively laminated on the glaze layer 2. When the materials constituting the protective layers are Al2O3 and SiO2, each of the layers is set to a thickness of 5,000Angstrom or more and the composition ratios of the respective layers are set so that the first layer 5-1 in contact with the resistor layer consists of 10-30mol% of Al2O3 and 90-70mol% of SiO2, the intermediate layer 5-2 consists of 40-60mol% of Al2O3 and 60-40mol% of SiO2 and the uppermost layer 5-3 consists of 70-90mol% of Al2O3 and 30-10mol% of SiO2. By this method, the protective layers are not destructed by a heat shock even when high speed printing is performed and the life of a thermal head can be extended.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thermal head used for thermal print recording, and more particularly to an improvement of a protective layer.

(Prior Art) A thermal head has, for example, a plurality of heating resistors on a ceramic substrate treated with a glass glaze.

An electric conductor is provided to supply power to the heating resistor, and in order to obtain the necessary heat pattern according to the information to be recorded, a current is passed through the corresponding heating resistor through the electric conductor to generate heat and record the information. Recording is performed by touching the medium.

Conventionally, as a heating element, there is a so-called thick film type heating element in which RuO2 and glass are mixed, made into a paste, and then applied and baked. However, since the thick film method uses screen printing, it essentially cannot be processed finely and has the disadvantage that resolution is reduced. In order to eliminate this drawback, tantalum nitride, nickel chromium alloy, Cr-5
Thin films such as i-based thermets h and BaRu0J have been used.

On the other hand, when recording is performed by directly contacting the recording medium with the heating resistor,
In particular, thin film heating resistors wear out quickly and cannot withstand long-term use.

For this purpose, a protective layer is provided on the heating resistor to prevent wear of the heating resistor. Conventionally, this protective layer has been made relatively thick to provide sufficient resistance to wear. However, when such a thick i-retaining layer is provided, the thermal response deteriorates.
A serious disadvantage arises in that the printing record becomes slow. For this reason, hard materials have been used as the protective layer and the thickness has been reduced to solve the problem of ink spots, but when printing faster than before, it is necessary to instantly raise the temperature of the heating element and protective layer to a high temperature. However, a protective layer made of a hard material has the disadvantage that the protective layer itself is destroyed by the heat shock at this time.

(Problems to be Solved by the Invention) The present invention has been made in consideration of the above points, and is a thermal protection layer that can prevent the shin protection layer itself from being destroyed due to heat shock even when recording at extremely high speeds. The purpose is to provide the head.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the thermal head according to the present invention is characterized in that the protective layer is composed of two types of materials, and the ratio of the two types of components is different from the surface of the resistor. It changes over three layers upwards.

When the materials constituting the protective layer are Ag2O and Sin, the thickness of each layer is 5oooΔ or more, and the composition ratio of each layer is such that the first layer in contact with the resistor is Al220. ;
10-30 mol%, Sin: 90-70 mol%
, the middle layer is Al2,03; 40-60 mol%, S
in, ; 60 to 40 mol%, the top layer is AQ□O3
; 70 to 90 mol %; Sin; 30 to 10 mol %; Note that this thin film is formed, for example, by RF sputtering using the mixture as a target, but the method for forming the thin film is not limited to this.

(Function) The thermal head with the above configuration had a long lifespan, as the protective layer itself was not destroyed by heat shock even when printing was performed faster than before. The cause is unknown, but
Probably because there is a lot of Al2203 in the part that comes into contact with the paper, the protective layer does not wear out and has a long life.
It is thought that the structure in which there is a large amount of □ on the high-temperature side where it contacts the resistor and less on the low-temperature side effectively absorbs the heat stress caused by the instantaneous temperature rise, leading to the destruction of the protective layer itself.

(Example) The present invention will be described in detail below with reference to Examples.

FIG. 1 is a sectional view of a thermal head showing an embodiment of the present invention. This thermal head is mounted on a ceramic substrate.
A glaze layer 2 is formed thereon, followed by a heating resistor layer 3. Electrical conductor layer 4. A protective layer 5-1°5-2.5-3 is laminated. A BaRuO3 thin film was formed as the heating resistor layer, and Au was used as the electric core layer. The protective layer was formed by IF sputtering. Table 1 shows the target composition and whether or not the protective layer was destroyed. After printing on the paper at a high speed of 10 km, the presence or absence of damage was examined. Also, the thickness of each layer in Table 1 is 1.5
It was a cape.

As can be seen from Table 1, the thermal head of the present invention has a long life without destroying the protective layer even when printing at high speed.

Table 1 [Effects of the Invention] According to the thermal head of the present invention, even when printing is performed at high speed, the protective layer is not destroyed by heat shock, and a long-life thermal head can be provided.

[Brief explanation of the drawing]

FIG. 1 is a sectional view for explaining the present invention in detail. 1... Ceramic substrate, 2... Glaze layer,
3... Heat generating resistor, 4... Electric conductor, 5-
1.5-2.5-3...Protective layer. Figure 1

Claims (4)

[Claims] (1) In a thermal head consisting of a thin film heating resistor formed on a substrate and a protective layer formed on the resistor,
The protective layer is made of a thin film and the material constituting the protective layer is 2.
1. A thermal head characterized in that the ratio of the two types of components changes over three layers upward from the surface of the resistor. (2) The material constituting the protective layer is Al_2O_3, S
The thermal head according to claim 1, characterized in that it is iO_3. (3) The thermal head according to claim 1, wherein in the protective layer composed of three layers, each layer has a thickness of 5000A or more. (4) The layer in contact with the resistor has a composition ratio of the protective layer composed of the third layer: Al_2O_3; 10 to 30 mol%;
SiO_2: 90-70 mol%, middle layer is Al_2O
_3; 40 to 60 mol%, SiO_2; 60 to 40 mol%, the top layer is Al_2O_3; 70 to 90 mol%, S
The thermal head according to claim 1, characterized in that iO_2 is 30 to 10 mol%.