JPS6235915B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermal head used for printing on thermal recording paper.

In general, thermal heads apply voltage to a resistor connected between two electrodes formed on an insulating substrate, causing the resistor to generate heat to print numbers, letters, symbols, etc. on thermal recording paper. For printing, this thermal head reduces the applied power,
There is a strong demand for improved printing quality and higher density.

Figures 1 and 2 show a conventional thermal head, which consists of 1000 to 2000 electrode conductors arranged facing each other at a pitch of 125 to 250 μm on an insulating substrate 1 made of ceramic or the like. 2 and
It is composed of a pair of electrode conductors 2 and 1000 to 2000 resistors 3 electrically connected to the electrode conductors 2 so as to partially cover the electrode conductors 2. The electrode conductor 2 is formed using a method such as screen printing using a conductive paste containing a metal material such as gold or silver-palladium, while the resistor 3 is formed using a resistive paste made of ruthenium oxide or the like. It is formed by the same method as the electrode conductor 2.

When printing on thermal recording paper (not shown) using this thermal head, the thermal recording paper is placed in contact with the upper surface of the resistor 3, and the electrode conductor 2 is placed in contact with the upper surface of the resistor 3.
All you have to do is apply a pulse voltage to the resistor 3 to generate heat, and as a result, numbers, letters,
Symbols, etc. will be thermally printed.

However, in a conventional thermal head, the thickness of the electrode conductor 2 and the resistor 3 are required to be about 10 to 15 μm and 10 to 30 μm, respectively, from the viewpoint of current capacity, power resistance, etc., so the central part 3a of the resistor 3 is The upper surface of the resistor 3 is lower than the overlapping part 3b with the electrode conductor 2 and has a concave shape, and as a result, the center part 3a of the resistor 3 does not come into sufficient contact with the thermal recording paper, and a Since the generated heat is not efficiently transferred to the thermosensitive recording paper, there is a drawback that the electric power applied to the resistor 3 must be increased. Further, since the resistor 3 is formed by a method such as screen printing, its film thickness is not uniform, and as a result, the contact with the heat-sensitive recording paper is uneven, resulting in poor print quality. Furthermore, due to the limitations of screen printing technology for forming resistors 3 on insulating substrates 1 such as ceramics, it is extremely difficult to simultaneously form extremely large numbers of resistors 3 with widths and intervals of 100 μm or less with good productivity. Ta.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above.A conductor formed on an unfired insulating substrate (hereinafter referred to as a green sheet) is fired together with this green sheet. By oxidizing the center of the conductor to form a resistor, the power applied to the resistor can be reduced, good printing quality can be obtained, and the thermal head can be printed at high density. The purpose is to provide a manufacturing method.

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

FIG. 3 shows a thermal head manufactured according to an embodiment of the present invention. In the figure, 10 is an insulating substrate formed by firing an insulating material such as alumina, and 21 is an insulating substrate formed on this insulating substrate 10. An electrically conductive anti-oxidation film that covers both ends of a conductor 22 made of tungsten, molybdenum, etc., and the portions of the conductor 22 covered by the anti-oxidation film 21 form a pair of electrodes 20. . 30 is a resistor 30 formed by oxidizing the central part of the conductor 22.
It is.

Next, a method of manufacturing this thermal head will be explained.

When manufacturing this thermal head, first, a conductive pattern of a predetermined shape is formed on a green sheet made of an insulating material such as alumina by screen printing using a conductive paste made of a metal material such as tungsten or molybdenum. Then, heat this green sheet and conductor pattern to 1300~1800℃.
After baking in a reducing atmosphere to form the insulating substrate 10 and the conductor 22, an anti-oxidation coating 21 is applied to both ends of the conductor 22 using a conductive material such as gold by plating, vapor deposition, screen printing, or other methods.
, and finally, this conductor 22 is
Fired in an oxidizing atmosphere at 600℃. In this way, the center part of the conductor 22 is oxidized and transformed into the resistor 3.
0, and both ends of the conductor 22 are coated with an anti-oxidation coating 2.
1 prevents oxidation, and the pair of electrodes 2
It becomes 0.

In this embodiment as described above, the electrode 20 and the resistor 3
0 from one conductor 22, the upper surface of the resistor 30 does not become concave, and the oxidation-preventing coating 21 is provided simply to prevent the conductor 22 from oxidizing. The thickness may be about 1 μm. Therefore, the contact between the resistor 30 and the thermal recording paper becomes good, and the heat generated in the resistor 30 is efficiently transferred to the thermal recording paper.As a result, the power applied to the resistor 30 can be reduced, and the thermal response is improved. This improves performance and enables high-speed printing.

Further, since the resistor 30 is formed by oxidizing and modifying a part of the conductor 20, its surface smoothness is improved and the density of printing on the heat-sensitive recording paper becomes uniform. Furthermore, the conductor 22 is formed by screen-printing a conductive paste on a green sheet, which is an unfired ceramic product, and then firing it, so that the conductive paste is absorbed into the green sheet when screen-printed. As a result, conductors 22 having a width and spacing of about 50 μm can be easily formed without causing paste dripping or bleeding, and as a result, a high density thermal head can be achieved.

Furthermore, when the conductor 22 is partially oxidized, the conductive oxidation-preventing coating 21, which also serves as the lead electrode of the resistor 30, is used, so the manufacturing process is simplified.

As described above, according to the thermal head according to the present invention, a conductor pattern is formed on a green sheet, and then it is fired to form an insulating substrate and a conductor, and both ends of the conductor are coated with an antioxidant coating. In addition to forming a pair of electrodes by oxidizing the central part of the conductor to form a resistor, it is possible to reduce the power applied to the resistor, enable high-speed printing, and furthermore, the surface of the resistor can be This has the effect that a thermal head with good smoothness and high density can be manufactured by a simple method.

[Brief explanation of the drawing]

Figure 1 is a partial plan view of a conventional thermal head.
2 is a cross-sectional view taken along the line -- in FIG. 1, and FIG. 3 is a cross-sectional view of a thermal head manufactured according to an embodiment of the present invention. 10... Insulating substrate, 20... Electrode, 21...
Antioxidant coating, 22... conductor, 30... resistor.

Claims (1)

[Scope of Claims] 1. A step of depositing a conductor on an unfired insulating substrate, a step of simultaneously firing these substrates and the conductor, and a step of depositing a conductor on both sides of the conductor to serve as lead-out electrodes for electrodes to be described later. oxidizing the central part of the conductor part by coating it with a protective oxidation-preventing film, forming a pair of electrodes on both sides of the conductor part, and forming a resistor in the central part. Head manufacturing method.