JPH08324013A - Thick film type thermal head - Google Patents

Abstract

PURPOSE: To provide a low-cost thick film type thermal head of improving the printing quality level by reducing the thickness of a reinforcing silver film. CONSTITUTION: A common electrode 4 provided on a board is integrally coupled by a strip-like coupling part 4c, so disposed that the end 4a of the common electrode and the ends 6a of individual electrodes are alternately engaged, strip-like heating resistors 7 are formed on the ends 4a, 6a, silver films 5 are formed along the board edges 2a, 2b, further a plurality of branches 4b are branched from the part 4c in the direction perpendicular to the lengthwise direction of the resistor 7, and the films 5 are superposed on the branches 4b.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thick film type thermal head in which a common electrode is reinforced with a silver film.

[0002]

2. Description of the Related Art The structure of a conventional thick film type thermal head will be described below with reference to FIG. The substrate 12 is made of a material such as alumina ceramic, and a glass glaze layer 13 as a heat storage layer is formed on the surface thereof. [See (a) of FIG. 5]. A common electrode 14 and an individual electrode 16 made of a gold film are formed on the glass glaze layer 13,
These tip portions 14a, 16a are arranged so as to mesh with each other in a comb-like shape (see FIG. 5B). This gold film is formed by printing and firing a gold paste, and contains not only gold (Au) but also glass components and the like. On the common electrode tip portions 14a, ..., Individual electrode tip portions 16a ,.
A band-shaped heating resistor 17 is formed.

As shown in FIG. 5, when the heating resistor 17 is formed along the edge of the substrate 12, that is, in the case of an edge type, since the width of the common electrode 14 cannot be wide, its resistance value is And the voltage drop becomes large. Therefore, a reinforcing silver film 15 is formed on the common electrode 14. The silver film 15 is also formed by printing and firing a silver paste, and is composed of silver (Ag), a glass component and the like.

The common electrode 14, the silver film 15, the individual electrodes 16 and the heating resistor 17 are covered with a wear resistant layer 18 and are protected from wear with the thermal recording paper.

[0005]

The silver film is formed by printing a silver paste and firing it at a high temperature. At that time, the gold in the gold film causes an alloying layer to be formed. The resistance increases. As shown in FIG. 4A, when the common electrode is composed of only the silver film S on the glaze layer 13, the resistance value of the common electrode is about 0.7Ω in an 8-inch thermal head. However, as shown in FIG. 4B, when the silver film S is overlaid on the gold film G to form a common electrode, the resistance value increases to 1.8Ω with an 8-inch size thermal head, This is more than double the case of using only the silver film S.

Therefore, conventionally, it has been practiced to reduce the resistance value by stacking two or more silver films, and in FIG. 5, two layers of silver films 15a and 15b are laminated (for example, both film thicknesses are 10
μm), and the common electrode 14 is reinforced. However, if silver films are formed by stacking and the film thickness is increased, a large amount of silver (paste) is required, which causes a problem of cost increase. Also, the silver film 15 and the heating resistor 17
The platen (not shown) hits the heating resistor 17 weakly, the printing density is lowered, and the printing quality is impaired. Therefore, 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,
It is an object of the present invention to provide a thick film type thermal head capable of reducing the thickness of the reinforcing silver film to reduce the cost and improve the printing quality.

[0008]

In order to achieve the above object, the thick film type thermal head according to claim 1 of the present invention is provided with a strip-shaped heating resistor on a substrate, and the heating resistor and the substrate edge. In a thermal head in which a strip-shaped gold common electrode is provided between the common electrode and a silver film (silver film) on a part of the common electrode, the common electrode and the silver film are formed from the common electrode to the heating resistor. It is characterized in that a plurality of branching portions that branch in a direction orthogonal to the longitudinal direction of are overlapped.

In this thermal head, structurally, it is possible to efficiently reduce the overlapping area of the common electrode (gold film) and the silver film. That is, it is easy to minimize the overlapping portion between the branch portion of the common electrode and the silver film, thereby suppressing the generation of the alloy layer and preventing the specific resistance of the silver film from increasing. In the thick-film thermal head according to claim 2, a glaze layer is interposed between the substrate, the common electrode and the heating resistor that does not overlap the common electrode, and
On the substrate including the common electrode and the heating resistor, a plurality of branches of the common electrode partially overlap with the silver film to form a blank portion where the glaze layer is exposed between the adjacent branches and the silver film. It is characterized in that a wear-resistant layer made of glass is provided on.

In this thermal head, since a blank portion where the glaze layer is exposed is formed between the adjacent branch portion and the silver film, a glaze layer below the common electrode and a wear resistant layer made of glass above the common electrode are formed. Are in direct contact with each other, the upper and lower layers sandwiching the common electrode can be firmly adhered to each other, and the peeling problem of the common electrode having a thin pattern such as a branch portion can be prevented.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on embodiments. FIG. 1 is a plan view of a main part of the thick film thermal head according to the embodiment, in which an abrasion resistant layer is omitted, and FIGS. 3A and 3B are lines IIa-IIa in FIG. 1, respectively.
It is a principal part sectional drawing in the IIb-IIb line.

The substrate 2 is made of a material such as alumina ceramic. A glass glaze layer 3 functioning as a heat storage layer is formed on the substrate 2 ((a) of FIG. 3,
(B)]. The glass glaze layer 3 is formed by printing an amorphous glass paste on the surface of the substrate 2 and firing the paste. On the glass glaze layer 3, the common electrodes 4, ... 4, The individual electrodes 6 ,. First,
Gold paste is printed on the glass glaze layer 3 and baked to form a gold film. Further, this gold film is patterned by applying photolithography to form common electrodes 4, ... 4, Individual electrodes 6 ,.

The common electrodes 4, ... 4 have a fine linear pattern, are integrally connected to a strip-shaped connecting portion 4c extending along the edge 2a of the substrate 2, and are alternately connected to the tip portions 4a ,. The tips 6 of the individual electrodes 6, ..., 6 so as to mesh with each other
, a, 6a are arranged. Also, the common electrode connecting portion 4
From c, a plurality of branch portions (rear end portion 4) extending toward the substrate edge 2a in the direction orthogonal to the longitudinal direction of the heating resistor 7 are formed.
b, ..., 4b) are branched.

A reinforcing silver film 5 is formed on the glass glaze layer 3. This silver film 5 is formed on the substrate edge 2a,
It is a strip-shaped member extending along the side edges 2b, 2b, and is a single layer formed by firing a silver paste printed on the glass glaze layer 3. The silver film 5 is overlapped on the common electrode branch portions 4b, ..., 4b, and each overlap area is set to x = 0.1 mm and y = 0.05 mm, for example. By overlapping the silver film 5 and the branching portion 4b, the rectangular portion surrounded by the silver film 5 and the branching portions 4b and 4b of the adjacent common electrode does not have the silver film or the common electrode, and thus the glass glaze layer is not present. 3 becomes the exposed blank portion 9. Further, the lead-out portions 5b, 5b of the silver film 5 are the end portions 4 of the common electrode connecting portion 4c.
d and 4d, respectively.

Common electrode tip 4a and individual electrode tip 6
A strip-shaped heating resistor 7 is formed on a. The heating resistor 7 is formed by screen-printing a resistor paste containing a resistance component such as ruthenium oxide on the glass glaze layer 3 and firing the paste. In the adjacent common electrode tips 4a, 4a, The sandwiched resistor portion corresponds to one dot. The heating resistor 7 has a width of about 200 μm, and a distance d between the center of the heating resistor 7 and the substrate edge 2a is 2.2 mm. In this case, the widths of the silver film 5 and the connecting portion 4c can be about 1 mm and 0.5 mm, respectively.

A wear resistant layer 8 is further formed on the substrate 2, and the common electrodes 4, ..., 4, the silver film 5, the individual electrodes 6 ,.
6. The heating resistor 7 is coated to insulate them, and at the same time, they are protected from abrasion with thermal recording paper and the like. The abrasion resistant layer 8 is also formed by printing an amorphous glass paste and firing it. In the thick film type thermal head of this embodiment, the branch portion 4b branched from the common electrode connecting portion 4c.
Since the silver film 5 and the silver film 5 overlap each other, the overlapping region between the common electrodes 4, ..., 4 made of a gold film and the silver film 5 can be made as small as possible, and the alloy produced by the interaction between the gold film and the silver film. The number of layers is reduced, and an increase in the specific resistance of the silver film 5 can be prevented.
Therefore, the thickness of the silver film 5 can be reduced to about 1/2 of the conventional thickness, and the amount of silver (paste) used can be reduced by about 50% as compared with the conventional one. Further, the height difference between the silver film 5 and the heating resistor 7 becomes small, and the contact of the platen with the heating resistor 7 is improved.

Further, since the common electrode has a plurality of branch portions 4b and the strip-shaped silver film 5 overlaps the branch portions 4b, as described above, the branch portion of the common electrode adjacent to the silver film 5 is formed. A quadrangle portion surrounded by 4b and 4b becomes a blank portion 9 where the glass glaze layer 3 is exposed. Therefore, the blank part 9
The abrasion resistant layer 8 made of glass and the glass glaze layer 3 exposed in the blank portion 9 are in direct contact with each other, and the substrate 2 including the silver film 5, the common electrode 4, the heating resistor 7, etc. The abrasion resistant layer 8 can be provided on the top with a stronger adhesive force.

That is, in general, a common electrode having a low glass component content has poor adhesion between the lower glass glaze layer 3 and the upper abrasion resistant layer 8 which are mainly composed of glass, but the glass glaze layer 3 By providing a plurality of exposed blank portions 9 alternately with the branch portions 4b, the number of adhesive portions between the glass glaze layer 3 and the abrasion resistant layer 8 that strongly adhere to each other increases, and the glass glaze layer 3 and the abrasion resistant layer 8 are increased. It is possible to prevent the problem that the common electrode having a low adhesiveness with is separated from both layers 3 and 8.

By the way, in the thick film type thermal head of this embodiment, since the common electrodes 4, ..., 4 have a fine linear pattern, there is a high risk that some of them will be lost.
FIG. 2 shows a case where one of the common electrode branches 4b is missing (4
bx) is shown, but in this case, the common electrode 4
Is connected to the adjacent common electrode 4 by the connecting portion 4c, so that printing is not hindered. Thus, the connecting portion 4c
Plays a role of ensuring that printing can be performed even if a defect occurs in the common electrode branch portion 4b.

[0020]

According to the thick film type thermal head of claim 1 of the present invention, since it is configured as described above, it has the following effects (1) to (3). (1) Since the silver film overlaps a plurality of branch portions branched from the common electrode, it is possible to efficiently reduce the overlapping area with both (gold film and silver film). (2) It is possible to reduce the thickness of the silver film and reduce the amount of silver (paste) used to reduce the cost, and increase the print density to improve the print quality and save energy during driving. . (3) Since the branch portion of the common electrode extends in the direction orthogonal to the longitudinal direction of the heating resistor, that is, in the direction in which the thermal recording paper or the platen abuts, the thermal recording paper or the platen can be satisfactorily contacted with the thermal head. .

According to the thick film type thermal head of the second aspect, the following effect (4) is obtained. (4) Since a blank portion where the glaze layer is exposed is formed between the adjacent branch portion and the silver film, the glaze layer below the common electrode and the abrasion resistant layer made of glass above the common electrode should be in direct contact with each other. Therefore, the upper and lower layers sandwiching the common electrode can be firmly adhered to each other, and the problem of peeling of the common electrode having a thin pattern such as a branch portion can be prevented.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing a wear resistant layer of a thick film type thermal head according to an embodiment of the present invention.

FIG. 2 is a plan view of relevant parts for explaining a case where a defect occurs in a common electrode of the thick film type thermal head.

3 is a thick film type thermal head of FIG. 1 IIa-II.
It is the principal part sectional view in the a line, and the principal part sectional view in the IIb-IIb line.

FIG. 4 is a cross-sectional view for explaining the behavior of the resistance value in a silver film single layer.

FIG. 5 is a cross-sectional view (a) of a main part of a conventional thick film thermal head, and a plan view (b) of a main part of the conventional thick film thermal head with an abrasion resistant layer omitted.

[Explanation of symbols]

 2 substrate 3 glass glaze layer 4, ..., 4 common electrode 4c common electrode connection part 4a, ..., 4a common electrode tip part 4b, ..., 4b common electrode branch part 5 silver film 6, ..., 6 individual electrode 6a ,. 6a Tip of individual electrode 7 Heating resistor 9 Blank part

Claims (2)

[Claims] 1. A strip-shaped heating resistor is provided on a substrate, a strip-shaped common electrode made of gold is provided between the heating resistor and the substrate edge, and a silver film (silver film) is formed on a part of the common electrode. In the thermal head, the common electrode and the silver film are configured so that the common electrode and the silver film are overlapped by a plurality of branch portions that branch from the common electrode in a direction orthogonal to the longitudinal direction of the heating resistor. Membrane type thermal head. 2. A glaze layer is interposed between the substrate, a common electrode, and a heating resistor that does not overlap the common electrode, and a plurality of branch portions of the common electrode and a silver film are partially formed. A blank part where the glaze layer is exposed is formed between the overlapping and adjacent branch parts and the silver film, and a wear resistant layer made of glass is provided on the substrate including the common electrode and the heating resistor. The thick film thermal head according to claim 1, which is characterized in that: