JP2571864B2 - Thick film type thermal head - Google Patents

Description

The present invention relates to a thick-film type thermal head in which a common electrode is reinforced with a silver film.

(B) Conventional technology The configuration of a conventional thick film type thermal head will be described below with reference to FIG. Reference numeral 12 denotes a substrate made of a material such as alumina ceramic, on the surface of which a glass glaze layer 13 as a heat storage layer is formed [see FIG. 3 (a)].

A common electrode 14 made of a gold film is formed on the glass glaze layer 13.
And the individual electrodes 16 are formed.
The a and 16a are arranged so as to be alternately meshed in a comb shape (see FIG. 3 (b)). The gold film is formed by printing and firing a gold paste, and includes not only gold (Au) but also a glass component and the like. A strip-shaped heating resistor 17 is formed on the common electrode tips 14a,..., The individual electrode tips 16a,.

As shown in FIG. 3, when the heating resistor 17 is formed along the edge of the substrate 12, that is, in the case of the edge type, the width of the common electrode 14 cannot be made large, so that the resistance value increases. , The voltage drop becomes large. Therefore, a reinforcing silver film 15 is formed on the common electrode 14. The silver film 15 is formed by printing and baking a silver paste, and is made of silver (Ag), a glass component, or the like.

Common electrode 14, silver film 15, individual electrode 16, and heating resistor 17
Is covered with a wear-resistant layer 18 and protected from abrasion with the thermal recording paper.

(C) Problems to be Solved by the Invention The silver film is formed by printing a silver paste and baking it at a high temperature. At that time, the gold in the gold film forms an alloy layer, and The resistance increases. Fig. 2 (a)
As shown in the figure, when the common electrode is formed only of the silver film S on the glaze layer 13, the resistance value of the common electrode is about 0.7Ω in an 8-inch size thermal head. However, the second
As shown in FIG. 5B, when a silver film S is superimposed on a gold film G to form a common electrode, the resistance increases to 1.8Ω with an 8-inch size thermal head, and only the silver film S is used. It is more than twice as large as the case.

In view of this, conventionally, two or more silver films are formed to be stacked. In FIG. 3, two silver films 15a and 15b are stacked (for example, both have a film thickness of 10 μm) and a common electrode is formed. 14 are reinforced.

However, when a silver film is formed by lamination and the film thickness is increased, a large amount of silver (paste) is required and the cost is increased. In addition, the height difference between the silver film 15 and the heating resistor 17 becomes large, and the contact of the platen (not shown) to the heating resistor 17 becomes weak, so that the print density is reduced and the print quality is impaired. For this reason, there is a problem that the applied energy must be increased in order to increase the print density.

The present invention has been made in view of the above, and an object of the present invention is to provide a thick-film type thermal head capable of reducing the thickness of a reinforcing silver film, reducing costs and improving printing quality.

(D) Means and Action for Solving the Problems To solve the above problems, a thick film type thermal head according to the present invention forms a glaze layer on a substrate, and a common electrode made of a gold film on the glaze layer. And forming individual electrodes,
A common electrode tip and an individual electrode tip are arranged so as to alternately mesh with each other, and a strip-shaped heating resistor is formed on the common electrode tip and the individual electrode tip, and at least two heating resistors are formed on the common electrode. In the case where a reinforcing silver film in which at least two silver films are laminated is formed, the thickness of the silver film in contact with the common electrode is smaller than the thickness of the other silver films. It is a feature.

In the thick film type thermal head according to the present invention, the silver film in contact with the common electrode is for reducing the film thickness and terminating alloying, and the common electrode is reinforced by another silver film laminated on the silver film. To carry. Therefore, with the same resistance value, the thickness of the entire silver film can be reduced, and the amount of silver paste used can be reduced, and the difference in height between the silver film and the heating resistor can be reduced.

(E) Embodiment One embodiment of the present invention will be described below with reference to FIG.

FIG. 1A is a cross-sectional view of a main part of the thick-film type thermal head of the embodiment. Reference numeral 2 denotes a substrate made of a material such as alumina ceramic, on the surface of which a glass glaze layer 3 functioning as a heat storage layer is formed. The glass glaze layer 3 is formed by printing and firing an amorphous glass paste on the surface of the substrate 2.

A common electrode 4 and individual electrodes 6,..., 6 are formed on the glass glaze layer 3 (see also FIG. 1 (b)). When forming the common electrode 4 and the individual electrodes 6,..., 6 first, a gold paste is printed on the glass glaze layer 3, and the gold paste is fired to form a gold film. Then, this gold film is patterned by applying photolithography to form a common electrode 4 and individual electrodes 6,.

The common electrode 4 extends along the edge of the substrate 2, and has a plurality of comb-like tips 4a,..., 4a. The individual electrode tips 6a,..., 6a are arranged so as to alternately mesh with the tips 4a,.

On the common electrode 4, a silver film 5 for reinforcement is formed. The silver film 5 is formed by stacking a lower silver film 5a and an upper silver film 5b. For example, the lower silver film 5a has a thickness of 2 μm,
The film thickness of 5b is 10 μm. Of course, the film thickness of both is not limited to this, and is appropriately changed according to the film thickness of the gold film constituting the common electrode 4 and the content of gold, but the film thickness of the lower silver film 5a is other than that. Silver film (in this case, upper silver film 5b)
Always set smaller.

To form the silver film 5, first, a silver paste for the lower silver film 5a is printed and baked. During this firing, an alloy layer of gold in the gold film is formed, and the lower silver film 5a is in a state of high specific resistance.

Next, a silver paste for the upper silver film 5b is printed on the lower silver film 5a, and is fired. During this firing, the upper silver film
It has been experimentally confirmed that almost no alloy layer is formed in 5b. Therefore, the alloying reaction ends at the lower silver film 5a, and the specific resistance of the upper silver film 5b is almost the same as when the silver film is directly formed on the glass glaze layer.

On the other hand, a strip-shaped heating resistor 7 is formed on both electrode tips 4a, 6a,. The heating resistor 7 is screen-printed with a resistor paste containing a resistance component such as ruthenium oxide,
This is fired. The portion of the heating resistor 7 sandwiched between the adjacent common electrode tips 4a, 4a corresponds to one dot.

An abrasion-resistant layer 8 is further formed on the substrate 2 to cover and insulate the common electrode 4, the silver film 5, the individual electrodes 6, and the heating resistor 7, thereby protecting the recording medium from abrasion with the thermal recording paper. The wear-resistant layer 8 is formed by printing and firing an amorphous glass paste.

In the thick-film type thermal head of this embodiment, since the thickness of the silver film S as a whole can be reduced to about 2/3 of the conventional thickness, the amount of silver (paste) used is smaller than in the conventional case, and the cost is reduced. Can be. In addition, the height difference between the silver film 5 and the heating resistor 7 is reduced, and the contact of the platen to the heating resistor 7 is improved. For this reason, the print density is increased, the print quality is improved, the applied energy is reduced, and energy saving can be achieved.

(F) Effect of the Invention As described above, the thick-film type thermal head of the present invention has the thickness of the silver film in contact with the common electrode among the reinforcing silver films in which two or more silver films are laminated. It is characterized by being smaller than the thickness of the silver film other than that, while maintaining the reinforcing effect of the common electrode, the thickness of the entire silver film can be reduced,
It has the advantages of reducing costs, improving printing quality, and saving energy during driving.

[Brief description of the drawings]

FIG. 1A is a sectional view of a principal part of a thick-film type thermal head according to an embodiment of the present invention, and FIG. 1B is a diagram showing the arrangement of electrodes and heating resistors of the thick-film type thermal head. FIGS. 2 (a) and 2 (b) are cross-sectional views for explaining the behavior of the resistance value of a single silver film, and FIG. 3 (a) is a conventional thick film type thermal head. FIG. 3 (b) is a sectional view of a main part of FIG.
FIG. 4 is a diagram illustrating the arrangement of electrodes and heating resistors of the conventional thick film type thermal head. 2: substrate, 3: glass glaze layer, 4: common electrode, 5: silver film, 5a: lower silver film, 5b: upper silver film, 6... 6: individual electrode, 7: heating resistor.

Claims (1)

(57) [Claims] 1. A glaze layer is formed on a substrate, and a common electrode and an individual electrode made of a gold film are formed on the glaze layer, and the common electrode tips and the individual electrode tips are arranged so as to alternately mesh with each other. A strip-shaped heating resistor is formed on the common electrode tip and the individual electrode tip, and a reinforcing silver film formed by stacking at least two or more silver films is formed on the common electrode. A thick-film type thermal head according to claim 1, wherein the thickness of the silver film in contact with the common electrode is smaller than the thickness of the other silver films.