JPS61290067A - Thermal head - Google Patents

Abstract

PURPOSE:To contrive inexpensively a higher printing quality, by a method wherein a polyimide film is provided on an insulating substrate at a position corresponding to a heating part, and a resistor layer, an electrode wiring and a protective layer are sequentially provided thereon. CONSTITUTION:The polyimide film 5 trapezoid in cross section is formed on the insulating substrate 1, and the resistor layer 2 having a predetermined film thickness is formed on the substrate 1 and the film 5. Further, the electrode wiring 3 is formed on the resistor layer 2 except the part corresponding to the polyimide film 5, and the protective layer 4 is formed on the wiring 3 and the layer 2. Since the surface of the resistor layer 2 between the wirings 3 is slightly protruded upward from the level of the surfaces of the wirings 3 due to the presence of the polyimide film 5, the surface of the protective layer 4 is protuberant, so that a thermal recording paper can be thereby pressed against the thermal head while exerting a relatively low pressure. In addition, since the polyimide film can be easily patterned and has a favorable heat- accumulating effect, favorable printing quality can be obtained inexpensively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a thermal head used in facsimiles, printers, and the like.

[Background of the invention]

FIG. 2 is an explanatory diagram showing a conventional example of a thermal head, and FIG. 2 (α) is a plan view of the thermal head, and FIG.
is a cross-sectional view of the thermal head, 1 is an abrasive substrate, 2 is
3 is a resistance layer, 3 is an electrode wiring, and 4 is a protective layer.

In the figure, a resistive layer 2 having a predetermined thickness is formed on an insulating substrate 1, and an electrode wiring 3 is formed on the resistive layer 2, facing a part of the resistive layer 2. This electrode arrangement! The resistance layer 2 facing between 13 and 13 is a heat generating part, and a protective layer 4 for transmitting heat from the heat generating part by means of thermal paper (not shown) is provided on the entire surface of the electrode wiring 3 and a part of the resistance layer 20. It is formed to a nearly uniform thickness.

Therefore, the protective layer 4 on the heat generating part is
It is formed in a concave shape.

However, in the conventional thermal head configured as described above, since the heat conductive portion 1iJi4 has a concave shape, the contact between the protective layer 4 and the thermal paper pressed against it is unstable. However, there was a drawback that the print quality deteriorated. Possible countermeasures to this problem include supplying a large amount of power to the heat generating part, or strongly pressing thermal paper against the thermal head, but the former has the problem of increased power consumption, while the latter requires a protective layer. No. 4 had the problem of abnormal wear, and neither method was a good idea. Therefore, with the aim of solving such problems,
As shown in FIG. 3, there is a thermal head with a flat surface of the protective layer 40, and a thermal head with a partially convex insulating substrate 1 under the heat generation as shown in FIG. It has been proposed (% Kaisho 59 = Publication No. 191'78,
(Japanese Unexamined Patent Publication No. 87974).

However, in the thermal head having the structure shown in FIG. 3, after the protective layer 4 is formed relatively thick.

It is necessary to remove the protective layer 4' located on the electrode wiring 3 by etching as shown by the broken line in the figure.In addition, in the thermal head having the structure shown in FIG. The formation of the layer requires a step of partially making it convex, and in either case there is a problem in that a complicated processing step is required.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a thermal head that is inexpensive and has good print quality.

[Summary of the invention]

In order to achieve this object, the present invention is configured such that a polyimide film is formed at a position corresponding to a heat generating part on an insulating substrate, and a resistive layer, an electrode wiring, and a protective layer are sequentially formed thereon. There are characteristics.

[Embodiments of the invention]

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

FIG. 1 is a sectional view of a thermal head according to an embodiment of the present invention, in which 5 is a polyimide film, and parts corresponding to FIGS. 2 to 4 are given the same reference numerals.

In the figure, a polyimide film 5 having a trapezoidal cross section is formed on an insulating substrate 1, and a resistive layer 2 having a predetermined thickness is formed on the insulating substrate 1 and the polyimide film 5. Furthermore, an electrode wiring 3 is formed on this resistance layer 2 except above the polyimide film 5, and the electrode wiring 3 and the resistance layer 2 are
A protective layer 4 is formed thereon. The surface of this protective layer 40 has a convex shape because the electrode wiring 3 and the surface of the resistance layer 20 facing between the electrode wirings 3 are formed in a slightly protruding state from the surface of the electrode wiring 3 due to the presence of the polyimide film 5. is formed.

In the thermal head configured in this way, since the surface of the protection 40 is formed in a convex shape, the thermal paper can be pressed against the thermal head with relatively weak pressure, and the print quality can be improved. It becomes possible to do so.

Next, the manufacturing process of the above embodiment will be briefly explained.

First, a polyimide film with a thickness of 0.5 to 30 μm is uniformly formed on an insulating substrate 1, and this is removed using a normal photoetching technique (leaving only a part) to form a polyimide film 5 with a trapezoidal cross section. Form. The polyimide film 5 to be left may be formed individually in a convex shape corresponding to each heat generating portion, or may be formed continuously in a band shape.

Next, on the insulating substrate 1 and the polyimide film, a Cr-Si-0 series resistor, which will become the resistive layer 2, is formed by sputtering. A 15 to 2 μm thick layer of aluminum is formed using a sputtering method.

Next, the resistive layer 2 is separated into several parts by photoetching, and the electrode wiring 3 is partially removed so that the resistive layer 2, which will become a heat generating part, is exposed. lastly,
When the protective layer 4 is formed on this, the protective layer 4 above the polyimide film 5 partially protrudes, forming a thermal head having a convex structure as shown in FIG.

As shown in the above embodiment, forming the polyimide film 5 partially on the insulating substrate 1 simplifies the manufacturing process compared to the conventional technique in which the insulating substrate is shaped like a glaze layer. Thermal conductivity is 2 to 3.6X10-Ca17cm-E than that of conventional glazed glass.
The polyimide of the present invention is 0.8 x 10-'
Since it is a material as small as Ca cm-5C, it has a large heat storage effect, and has the advantage that a thin film is required to obtain the same heat storage effect.

In the above embodiment, the polyimide film 5 is formed partially on the insulating substrate 1, so that the polyimide film 5 has a thickness of several tens of μm in order to have a heat storage effect.
However, since only a convex effect is expected, it is necessary to have a film thickness of several tens of microns over the entire surface of the insulating substrate.
Even if the polyimide film 11 is formed and a polyimide film similar to that in the embodiment described above is partially formed on the polyimide film, the density is high. In this case, by forming a polyimide film that is 0.1 to several tens of microns thicker than the electrode wiring 3, the protective layer 4 formed thereon has a convex shape.

Further, the insulating conductive plate 1 used in the present invention is not limited to the above embodiment, and an insulating substrate having a thicker glaze layer formed on its surface may also be used.

〔Effect of the invention〕

As explained above, according to the present invention, a polyimide film that is easy to form a pattern and has a good heat storage effect is formed under the resistive layer that constitutes the estrous area, so that a thermal head that is inexpensive and has good printing quality can be realized. Can be provided.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a main part of an embodiment of the length-round head according to the present invention, Fig. 2 shows a conventional thermal head, Fig. 2 (α) is a plan view thereof, and Fig. 2 [bl is 3 and 4 are cross-sectional views showing other conventional examples of thermal heads. 1... Insulating substrate 2... Resistance layer 3...
Electrode wiring 4-layer protective layer 5...Polyimide film 1 Figure 2 (σ) (Me) Figure 3 Figure 4

Claims (1)

[Claims] In a thermal head formed by sequentially laminating a resistive layer, electrode wiring, and a protective layer on an insulating substrate, a polyimide film is interposed between the insulating substrate and the resistive layer, and the resistive layer is covered by the polyimide film. A thermal head characterized by a partially convex shape.