JPH01204763A - Thermal head - Google Patents

Abstract

PURPOSE:To achieve improvement of reliability by preventing corrosion of a conductor, by a method wherein a conductor layer which is an electrode, has a two layer structure of an upper layer having Al as a main constituent and a lower layer composed of good moisture resistant metals other than Al, and the conductor layer of an area protected by only a wear resistant layer is composed of only above-mentioned lower layer. CONSTITUTION:A thermal head has a driving IC10, a wear resistant layer 7, and protective resin 8a, 8b in a final process of manufacture. Common and discrete electrodes 5a, 5b and 4a, 4b composed of a two layer structure of Al and Ti or NiCr, of which a surface is protected by the protective resin 8a. Further, an area wherein an electrode edge part 4c on a projected part is protected by only the wear resistant layer 7, is of one layer structure of a Ti film or an NiCr film as the lower without an Al film as the upper layer. Then, since Al does not exist on an upper area of a heat reserving layer 2 protected by only the wear resistant layer 7, corrosion trouble of Al does not occur.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head, and particularly to a thermal head using a KE thin film as a conductor serving as an electrode.

[Conventional technology]

With the recent miniaturization of thermal heads, it has become important to improve the moisture resistance of the electrode parts.

FIG. 4 is a sectional view of an example of a conventional thermal head.

The thin film thermal head includes a convex heat storage layer 2, a heat generating resistor 3, and common and individual electrodes 5a and 5b formed on a part of an insulating substrate 1, and a surface of the heat generating resistor 3 in a central band 6 of the convex portion. The electrode end portion 5c is covered with a wear-resistant layer 7.

Common electrode5. The conductor material for the individual electrodes 5b is mainly a thin film metal mainly made of Aff for reasons such as ease of electrode pattern formation and wire bonding for connection to the drive ICl0, and for the wear-resistant layer 7, SiC, TazO9, 5iJ4, etc. with a thickness of several microns by sputtering is used.

[Problem to be solved by the invention]

The conventional thermal head described above is protected by covering it with a thin, pinhole-prone wear-resistant layer. When printing and recording on the electrode end, Na or CJ? Since the electrode is in contact with thermal paper containing ions, its moisture resistance is inferior to that of electronic devices sealed with resin such as ICs.

The reason for this is that the abrasion-resistant layer formed by sputtering or the like, which is several micrometers thick, has no protective effect against moisture or CE ions due to pinholes when a voltage is applied between the electrode and the thermal paper in a high-temperature, high-humidity environment. This is due to the fact that the electrodes may suffer corrosion due to insufficient corrosion.

To prevent this, the wear-resistant layer is made thicker, but forming a thin film of 10 μm or more using methods such as sputtering significantly increases production costs, and the wear-resistant layer is likely to peel off due to the internal stress of the thin film. However, there was a problem in that printing efficiency and thermal response characteristics deteriorated due to problems such as heat transfer to thermal paper.

An object of the present invention is to provide a thermal head having electrodes with good moisture resistance.

[Means to solve the problem]

The thermal head of the present invention includes a convex heat storage layer provided on a part of the surface of an insulating substrate, a heating resistor covering the heat storage layer and the surface of the insulating substrate, and a heating resistor sandwiching the heat storage layer. In a thermal head including a common electrode and a plurality of individual electrodes provided on a body, both electrode layers include a Ti or NiCr layer on the insulating substrate and a metal layer mainly composed of Ae covering the surface thereof. It has a two-layer structure, and the top of the heat storage layer is Ti or NiC except for the central zone of the convex part.
It is composed of one layer structure of r1.

〔Example〕

Next, the present invention will be explained using examples.

1(a) to 1(c) are plan views of a thermal head shown in order of manufacturing steps to explain one embodiment of the present invention;
Figures (a) to (c) are A in Figure 1 (a) to (c), respectively.
-A' line sectional view, BB' line sectional view, and c-c' line sectional view.

As shown in Figure 1 (a), each layer of the thermal head is
On an insulating substrate 1 having a heat storage layer 2, a Ta-8tN film with a thickness of 0.2 μm as a heating resistor 3, a lower JlTi film 4 with a thickness of 0.4 μm, and an upper layer Aff film 5 with a thickness of 0.7 μm are formed. Each layer is sequentially formed by a sputtering method.

Next, as shown in FIG. 1(b), the upper layer At? The diagonally dotted portion above the convex heat storage N1 of the film 5 is removed by etching to form a common electrode 5a and individual electrodes 5b separated into grooves S.

Next, as shown in FIG. 1(C), the lower Jli
The central band 6 of the convex portion of the Ti film 4 is selectively etched to form a pattern exposing the heating resistor 3.

The electrode pattern having the grooves S is formed by selective etching using photoresist, as in the production of ordinary thin film thermal heads.

The upper layer ^g film 5 is etched using phosphoric acid and acetic acid.

Etching of Ti and TaSi is carried out using a mixed solution of nitric acid.
It is carried out with a mixture of boiling acid, nitric acid, and acetic acid.

Dilute sulfuric acid was used as the Ti etching solution in this process in order to perform selective etching with TaSi, which is the heating resistor material.

FIG. 3 is a sectional view of one embodiment of the present invention.

The thermal head includes a drive ICl0, a wear-resistant layer 7, and protective resins 8a and 8b in the final process.

The common and individual electrodes 5a, 5b and 4-, '4b are At
? It has a two-layer structure of Ti and Ti, and the surface is covered with protective resin 8a
protected.

In addition, in the region where the electrode end 4° above the convex portion is protected only by the wear-resistant M7, there is no g film on the upper layer, and 1° of the lower Ti film is protected.
It has a layered structure.

Therefore, there is no A2 corrosion problem in the upper region of the heat storage layer 2, which is protected only by the wear-resistant layer 7.

A thermal paper is brought into contact with the abrasion resistant layer 7 of the Marsal head, and the top is pressed with a conductive rubber, so that two sheets are placed between the electrode and the conductive rubber.
The thermal head was left in an environment of 6°C and 90% relative humidity with a voltage of 4V applied, and the humidity resistance was compared with that of a conventional thermal head.
The results showed that the film had moisture resistance for 500 hours or more.

In the above embodiment, the upper M electrode and the lower layer electrode material are 8! However, even if NiCr is used as the lower layer electrode material, the same moisture resistance is not exhibited.

In this case, for etching NiCr, an aqueous solution of ceric ammonium nitrate and perchloric acid is used to perform selective etching between Al and TaSi, which is the heating resistor material.

Furthermore, similar effects were obtained using an alloy with 4% Cu or 1% St as the material for the upper g film.

〔Effect of the invention〕

As explained above, in the present invention, the conductor layer serving as the electrode is made of Ae.
The upper layer mainly consists of A! ! The conductor layer in the area protected only by the wear-resistant layer is formed of only the lower layer made of a metal with good moisture resistance, which prevents pinholes in the wear-resistant layer. This has the effect of increasing the reliability of the thermal head.

[Brief explanation of the drawing]

1(a) to 1(C) are plan views of a thermal head shown in order of manufacturing steps to explain one embodiment of the present invention;
Figures (a) to (C) are A in Figure 1 (a) to (c), respectively.
-A' line sectional view, B-B' line sectional view and c-c' line sectional view, FIG. 3 is a sectional view of an embodiment of the present invention, and FIG. 4 is a sectional view of an example of a conventional thermal head. It is. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Heat storage layer, 3... Heat generating resistor, 4... Lower layer Ti film, 5... Upper layer Aff film, 5
a...Common electrode, 5b...Individual electrode, 6...Convex central zone. Agent Patent Attorney Uchihara Onde 3rXJ Figure 4

Claims (1)

[Claims] a convex heat storage layer provided on a part of the surface of an insulating substrate; a heating resistor covering the heat storage layer and the surface of the insulating substrate; and a heating resistor provided on the heating resistor with the heat storage layer in between. In a thermal head including a common electrode and a plurality of individual electrodes, both electrode layers have Ti or N on the insulating substrate.
It has a two-layer structure with an iCr layer and a metal layer mainly composed of Al covering its surface, and above the heat storage layer has a single-layer structure of either a Ti or NiCr layer except for the central zone of the convex part. Features a thermal head.