JP2000246932A - Thermal head and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve product quality, thermal efficiency in the printing and printing quality by a method wherein lowering of the adhesion due to the membrane stress of a common conductive layer is eliminated, the electric resistance is lowered and the thermal loss is suppressed. SOLUTION: An interlayer insulation layer 5 having at least a heat insulation layer 2, a common conductive layer 4 and an aperture 5c, a plurality of heating resistors 9, individual electrodes 8 connected to the respective heating resistors 9 and a common conductive layer 7 that electrically connects the common conductive layer 4 and heating resistors 9 with the aperture 5c therebetween are laminated on a top face of a heat radiation substrate. The common conductive layer 4 is formed from four layers such that a first common conductive layer 4a made from a metallic cermet, a second common conductive layer 4b made from a metal, a third common conductive layer 4c made from a metal and a forth common conductive layer are laminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head mounted on a thermal printer or the like and a method of manufacturing the same, and more particularly, to a thermal head having a common electrode as a multilayer wiring and a method of manufacturing the same.

[0002]

2. Description of the Related Art In general, a thermal head as a recording head mounted on a thermal printer has a plurality of heating elements formed of heating resistors arranged in a line or a plurality of rows on a substrate, and each heating element is arranged in accordance with print information. Are selectively energized and heated to perform color recording on thermosensitive recording paper, or to transfer and record on plain paper or OHP paper by melting the ink of the ink ribbon.

FIG. 4 shows such a conventional thermal head. A heat insulating layer 12 made of a glaze such as glass is formed on the entire upper surface of a heat radiating substrate 11 made of an insulating ceramic such as alumina. The heat dissipation substrate 1
In the vicinity of one end 11a, a ridge 13 protruding from the heat insulating layer 12 is formed by means such as etching. On the entire upper surface of the heat insulation layer 12, a metal common conductive layer 14a made of a high melting point metal such as Cr having good adhesion to the heat insulation layer 12 and having excellent heat resistance and high hardness is formed to a thickness of about 1 μm by means such as sputtering. It is formed to a film thickness. The metal common conductive layer 14a is formed to have a large area and a thickness of 1 μm in order to reduce the resistance value. And
Ta-SiO is formed on the entire upper surface of the metal common conductive layer 14a.
₂ , a cermet common conductive layer 14b made of a metal cermet made of a mixture of a metal and an insulating ceramic (hereinafter referred to as Ta cermet when the metal is Ta) is laminated by sputtering or the like.

A strip-shaped oxidation-resistant mask layer adjacent to the ridge 13 is formed on the upper surface of the cermet common conductive layer 14b on the side of the end portion 11a of the heat dissipation substrate 11 rather than the ridge 13 of the heat insulating layer 12. I do. In this state, the cermet common conductive layer 14b is thermally oxidized at a temperature of about 700 ° C., so that the cermet common conductive layer 14b has a thickness of several thousand angstroms from the surface except for the portion covered with the oxidation-resistant mask layer. The first interlayer insulating layer 15 made of an insulating oxide ceramic which is oxidized to a depth and has very few formation defects.
a can be formed. After forming the first interlayer insulating layer 15a, the oxidation-resistant mask layer is peeled off. The portion protected by the oxidation resistant mask is the cermet common conductive layer 1
The conductive portion 16 protrudes from 4b to the surface of the first interlayer insulating layer 15a, and the conductive portion 16 is exposed on the surface of the first interlayer insulating layer 15a.

On the upper surface of the first interlayer insulating layer 15a, a second interlayer insulating layer 15b made of an insulating ceramic such as SiO ₂ is formed by sputtering or the like. An opening 15c is formed so that the conductive portion 16 is exposed from the second interlayer insulating layer 15b.

On the upper surface of the second interlayer insulating layer 15b, a lower common electrode 17a made of a high melting point metal such as Cr is provided.
6 is formed to cover the surface. On the upper surface of the second interlayer insulating layer 15b, a plurality of lower individual electrodes 18a made of a high melting point metal such as Cr are formed in a plurality of juxtaposed strips facing the lower common electrode 17a. In the upper part of 13, each lower-layer individual electrode 18a faces the lower-layer common electrode 17a at a fixed interval.

Heating resistor 19 made of Ta cermet or the like
Are a plurality of strips arranged side by side opposite to the end 11a of the heat dissipation board 11, each covering the lower individual electrode 18a, and connected by the lower common electrode 17a. A region of the heating resistor 19 sandwiched between the lower common electrode 17a and the lower individual electrode 18a is a heating region S1.

Further, the upper individual electrodes 18b made of Al, Cu or the like are connected to the respective heating resistors 19 so as to be opposed to the lower individual electrodes 18a via the heating resistors 19. The other end of the heat dissipation board 11 facing the end 11a is extended to a terminal for supplying power to the upper individual electrode 18b. The upper-layer common electrode 17b made of Al, Cu, or the like is arranged to face the lower-layer common electrode 17a with the heating resistor 19 interposed therebetween, and connects and connects the strip-shaped heating resistors 19 to each other.

Further, on the upper surface of the heating resistor 19, the upper common electrode 17b and the upper individual electrode 18b, except for the connection terminal portion of the external circuit, an acid-resistant material such as sialon is used to prevent oxidation and wear. A protective layer 20 made of a material having excellent chemical resistance and abrasion resistance and having a thickness of about 5 μm is laminated and coated by sputtering or the like.

The upper individual electrode 18b is energized based on desired print information. The current from the upper layer individual electrode 18b reaches the lower layer individual electrode 18a and the desired heating resistor 19, passes through the lower layer common electrode 17a and the upper layer common electrode 17b, and passes through each of the common conductive layers 14a, 14b via the conductive portion 16.
To an external circuit.

[0011]

In such a conventional thermal head, the thickness of the metal common conductive layer 14a made of Cr is increased, or the area of the metal common conductive layer 14a is increased to reduce the resistance value. It was necessary to reduce the voltage drop (common drop) generated at the portion 14a to prevent the print quality from being lowered.

However, when the thickness of the metal common conductive layer 14a made of a high melting point metal such as Cr is as thick as about 1 μm, the high melting point metal film formed by sputtering generally has a large tensile stress. The residual stress increases in proportion to the first interlayer insulating layer 15a in a later process.
To the thermal insulation layer 12 of the metal common conductive layer 14a against a thermal shock caused by a high-temperature thermal oxidation treatment for forming a layer, a high-temperature vacuum treatment for stabilizing the heating resistor 19, and a mechanical shock during the process. There is a problem that the interfacial adhesion decreases and the production quality and production yield of the thermal head decrease.

When the common conductive layers 14a and 14b are formed substantially over the entire surface of the heat dissipation substrate 11, if the interlayer insulating layers 15a and 15b are defective,
4a, 14b, the common conductive layers 14a, 1
There is a problem that the probability of occurrence of insulation failure between the upper electrode 4b and the upper-layer individual electrode 18b and the like increases, and the manufacturing quality and the manufacturing yield decrease.

Further, since the metal common conductive layer 14a made of Cr having good thermal conductivity exists with a thick film thickness of 1 μm below the heat generating region S1, the heat generated in the heat generating region S1 is not applied to the metal common conductive layer 14a. Then, the heat is radiated through the heater, and the rise in the heat generation temperature in the heat generation region S1 is slowed down, so that the print heat efficiency is reduced and the print quality is deteriorated.

Further, since the first common conductive layer 14a and the second common conductive layer 14b are formed on the entire surface of the heat dissipation substrate 11,
The common conductive layers 14a, 14
b is exposed, and there is a problem that leakage or short circuit to the outside occurs.

[0016]

Means for Solving the Problems As a first means for solving the above problems, a thermal head according to the present invention comprises a heat insulating layer made of glass, a heat insulating layer, a common conductive layer, A plurality of heating resistors formed on the interlayer insulation layer and provided in parallel with each other, and the heating resistor connected to one end of the heating resistor. And a plurality of individual electrodes connected to the other end of each of the heating resistors, wherein the common electrode projects from the common conductive layer and is exposed on a surface of the interlayer insulating layer. The common conductive layer is connected to the common conductive layer by a conductive portion, and the structure of the common conductive layer is formed by a first common conductive layer made of a metal cermet formed sequentially on an upper surface of the heat insulating layer, and a second common conductive layer made of a metal. A conductive layer;
A third common conductive layer made of metal covering the second common conductive layer on the upper surface of the first common conductive layer, and a fourth common conductive layer made of a metal cermet formed on the upper surface of the third common conductive layer. The laminated structure was adopted.

According to a second aspect of the present invention, there is provided a thermal head according to the present invention, wherein the second common conductive layer is formed from a heating area sandwiched between the individual electrode and the common electrode of the heating resistor. The structure was formed on the electrode side.

According to a third aspect of the present invention, there is provided a thermal head according to the present invention, wherein the second common conductive layer is adjacent to the heat generating region.

According to a fourth aspect of the present invention, there is provided a thermal head having a structure in which the interlayer insulating layer is formed on an upper surface of the heat insulating layer and covers an outer peripheral portion of the common conductive layer. .

According to a fifth aspect of the present invention, there is provided a thermal head according to the present invention, wherein the first common conductive layer is Ta cermet, the second common conductive layer is Cr, the third common conductive layer is Cr, and the third common conductive layer is Cr. The four common conductive layers had a structure made of Ta cermet.

According to a sixth aspect of the present invention, there is provided a thermal head according to the present invention, wherein the first common conductive layer has a thickness of about 0.1 μm and the second common conductive layer has a thickness of about 1 μm. The third common conductive layer has a thickness of about 0.2 μm, and the fourth common conductive layer has a thickness of about 1 μm.

According to a seventh aspect of the present invention, there is provided a thermal head manufacturing method according to the present invention, wherein a heat insulating layer made of glass and a common conductive layer are sequentially laminated on an upper surface of a heat radiating substrate. An interlayer insulating layer is formed so as to cover the common conductive layer, a heating resistor formed on the interlayer insulating layer, a common electrode connected to one end of the heating resistor, and a heating resistor on the other end. A connection area between the individual electrode and the common electrode of the heating resistor, and the common electrode is a conductive area protruding from the common conductive layer and exposed on a surface of the interlayer insulating layer. Forming a first common conductive layer made of Ta cermet on an upper surface of the thermal insulation layer, wherein the first conductive layer forming step comprises: Cr for conductive layer A second common conductive layer forming step of laminating a second common conductive layer, and a second conductive layer for patterning the second common conductive layer in a strip shape adjacent to the heat generating region on the individual electrode side of the heat generating region. A patterning step, a third conductive layer forming step of laminating a third common conductive layer made of Cr on the second common conductive layer, and extending the third common conductive layer from the individual electrode side to the common electrode side. A third conductive layer patterning step to form a pattern that has been issued,
A fourth common conductive layer forming step of forming a fourth common conductive layer made of Ta cermet so as to cover each of the common conductive layers, and an oxidation-resistant mask layer made of an oxidation-resistant material on an upper surface of the fourth common conductive layer. An oxidation-resistant mask forming step of stacking, an oxidation-resistant mask patterning step of forming a mask pattern of the oxidation-resistant mask layer at a position where the conductive portion of the fourth common conductive layer is arranged, and an outer periphery of the third common conductive layer A fourth common conductive layer processing step of processing the thickness of the fourth common conductive layer formed in the portion to be thin, and thermally oxidizing the entire surface of the fourth common conductive layer; A first interlayer insulating layer forming step of forming a first interlayer insulating layer consisting of: and an oxidation resistant mask that removes the oxidation resistant mask layer and exposes the conductive portion on the surface of the first interlayer insulating layer. Removing step, the first layer A second interlayer insulating layer forming step of laminating a second interlayer insulating layer made of an insulating ceramic on the insulating layer, and an opening forming step of forming an opening so that the conductive portion is exposed from the second interlayer insulating layer And a manufacturing method having the following steps.

[0023]

FIG. 1 is a sectional view of a principal part showing the structure of a thermal head of the present invention, and FIG. 2 is a plan view of the thermal head of the present invention as viewed from above.

The heat radiating substrate 1 has a rectangular shape made of an insulating ceramic such as alumina. As shown in FIG. 1, a heat insulating layer 2 made of a glaze such as glass is provided on the upper surface of the heat radiating substrate 1.
Are formed. In the region near the end 1a of the heat dissipation board 1, a ridge 3 projecting from the heat insulating layer 2 at a height of about 10 μm is formed.

The upper surface of the heat insulating layer 2 has a thickness of about 0.1 μm.
A first common conductive layer 4 a made of m Ta cermet is formed so as to cover the ridge 3 of the heat retaining layer 2. In addition,
The first common conductive layer 4 a is provided at the end 1 of the heat dissipation substrate 1 of the heat insulating layer 2.
a does not reach the upper surface and the upper surface of the other end of the heat radiation substrate 1.

A second common conductive layer 4b made of a high melting point metal such as Cr is provided on the upper surface of the first common conductive layer 4a on the other end side of the heat radiating substrate 1 with respect to the protrusion 3 of the heat insulating layer 2. 3 is formed in a belt shape. The film thickness of the second common conductive layer 4b is
The thickness is as thick as about 1 μm to reduce electric resistance.

On the upper surface of the first common conductive layer 4a, a third common conductive layer 4c made of Cr or the like having a thickness of about 0.2 μm is formed.
Are formed to cover the second common conductive layer 4b.

A fourth common conductive layer 4d made of Ta cermet or the like is formed on the upper surface of the third common conductive layer 4c. The conductive portion 6 protruding from the fourth common conductive layer 4d is formed in a band shape along the ridge 3 on the end 1a side of the heat radiation substrate 1 with respect to the ridge 3 of the heat insulating layer 2.

As described above, the second common conductive layer 4b made of Cr is formed thick to reduce electric resistance.
The first common conductive layer 4a made of a serves as an adhesive layer for stabilizing the adhesion between the heat insulating layer 2 and the second common conductive layer 4b, and the third common conductive layer is a thin Cr film having good adhesion. By forming 4c on the upper surface of the first common conductive layer 4a so as to cover the second common conductive layer 4b, the electric resistance of the second common conductive layer 4b is reduced and the adhesion to the heat insulating layer 2 is improved. .

The first interlayer insulating layer 5a made of an insulating ceramic is formed of a common conductive layer 4a obtained by removing the upper portion of the conductive portion 6 of the fourth common conductive layer 4d from the upper surface of the heat insulating layer 2 at the end 1a of the heat radiation substrate 1. , 4b, 4c, and 4d, are formed on substantially the entire surface of the heat radiation substrate 1 so as to cover the upper surfaces and the outer peripheral portions. The surface of the conductive portion 6 of the fourth common conductive layer 4d is in a state of being exposed on the surface of the first interlayer insulating layer 5a.

On the upper surface of the first interlayer insulating layer 5a, a second interlayer insulating layer 5b made of SiO ₂ or the like and having a thickness of about 2 μm is laminated. Second interlayer insulating layer 5b
Is formed so as to cover almost the entire surface of the heat radiating substrate 1, but has an opening 5c at the conductive portion 6 of the fourth common conductive layer 4d, and the upper surface of the conductive portion 6 extends from the opening 5c. It is in an exposed state.

The lower common electrode 7a made of a high melting point metal such as Mo, Cr, W, etc., covers the conductive portion 6 and the conductive portion 6 side of the ridge 3 of the heat insulating layer 2 on the upper surface of the second interlayer insulating layer 5b. It is strip-shaped. The lower-layer common electrode 7a includes a common conductive layer 4a,
4b, 4c, and 4d.

Lower individual electrode 8a made of high melting point metal such as Mo, Cr, W, etc., formed on the upper surface of second interlayer insulating layer 5b.
Is a plurality of strips arranged side by side as shown in FIG.
Each lower-layer individual electrode 8a faces the lower-layer common electrode 7a at a fixed interval with the protruding ridge portion 3 of the heat retaining layer 2 interposed therebetween.

As shown in FIG. 2, on the upper surface of the second interlayer insulating layer 5b, a plurality of strip-shaped heating resistors 9 made of Ta cermet or the like are arranged in parallel. One end 9a of each heating resistor 9 has a lower common electrode 7a.
The other end 9b of the heating resistor 9 is connected to the lower individual electrode 8a. An area of the heating resistor 9 between the lower common electrode 7a and the lower individual electrode 8a is a heating area S.

The upper layer common electrode 7b made of a good conductor such as Al or Cu is opposed to the lower layer common electrode 7a via the heating resistor 9, and like the lower layer common electrode 7a, the other end of the heating resistor 9 is provided. 9a, the heating resistor 9 is connected.
Further, the lower layer common electrode 7a extends on the side of the ridge 3 than the upper layer common electrode 7b.

The upper individual electrode 8b made of a good conductor such as Al or Cu is opposed to the lower individual electrode 8a via the heating resistor 9, and like the lower individual electrode 8a, each heating resistor 9b
Each is connected to the other end 9b of the heating resistor 9. The lower individual electrode 8a extends on the side of the ridge of the heat insulating layer 2 more than the upper individual electrode 8b. On the other hand, as shown in FIG. 2, the upper individual electrode 8b is extended to a terminal portion located on the other end side of the heat dissipation substrate 1.

Further, on the upper surface of the heating resistor 9, the upper common electrode 7b and the upper individual electrode 8b, except for the connection terminal portion of the external circuit, an acid-resistant material such as sialon is used to prevent oxidation and abrasion. A protective layer 10 made of a material having excellent chemical resistance and abrasion resistance and having a thickness of about 5 μm is laminated and coated by sputtering or the like.

Next, the method of manufacturing the thermal head according to the present invention will be described with particular reference to the common conductive layers 4a, 4b, 4c,
The process of forming the interlayer insulating layer 4d and the interlayer insulating layers 5a and 5b will be described with reference to the manufacturing process flowchart shown in FIG. First, in a heat insulating layer forming step, a heat insulating layer 2 made of glass glaze or the like is formed on the upper surface of a heat radiating substrate 1 made of an insulating ceramic such as alumina, and the heat insulating layer 2 is further etched to form an end portion 1a of the heat radiating substrate The ridge 3 is formed on the substrate.
(Step 1)

Subsequently, in the first common conductive layer forming step, the first common conductive layer 4a is formed by sputtering to a thickness of 0.1 μm on almost the entire surface of the heat dissipation substrate 1 on which the heat insulating layer 2 is formed. Then, in the second common conductive layer forming step, the second common conductive layer 4b having a film thickness of about 1 μm is formed by sputtering on the upper surface of the first common conductive layer 4a. (Step 2)

In the second common conductive layer patterning step, the second common conductive layer 4b is subjected to photolithography and etching to form a strip adjacent to the heat generating region S on the side of the individual electrodes 8a and 8b. (Step 3)

Next, in the third common conductive layer forming step,
On the upper surface of the second common conductive layer 4b, a third common conductive layer 4c made of Cr and having a thickness of about 0.2 μm is laminated. (Step 4) Then, in the third common conductive layer patterning step, the third common conductive layer 4c is subjected to photolithography and etching to cover the second common conductive layer 4b and extend to near the end 1a of the heat dissipation substrate 1. It is formed in a strip shape. (Step 5)

In the fourth common conductive layer forming step, the heat dissipation substrate 1
Over the entire surface of the first common conductive layer 4a formed over almost the entire surface of
A fourth common conductive layer 4d made of Ta cermet or the like and having a thickness of about 1 μm is laminated. Thereafter, in an oxidation-resistant mask layer forming step, an oxidation-resistant mask layer made of an oxidation-resistant ceramic or an oxidation-resistant alloy such as SiO ₂ or MoSi and having a thickness of about 0.2 μm is formed on the upper surface of the fourth common conductive layer 4d. Are laminated.
Then, in the oxidation-resistant mask layer patterning step, the oxidation-resistant mask layer is subjected to photolithography and etching so that the oxidation-resistant mask layer remains only at the position where the conductive portion 6 of the fourth common conductive layer 4d is formed. Next, in the fourth common conductive layer processing step, of the fourth common conductive layer 4d formed substantially over the entire surface of the heat dissipation substrate 1, the film thickness of the outer peripheral portion of the third common conductive layer 4c is reduced by about half. It is processed by means such as photolithography and etching so as to be thinner than the following. (Step 6)

Thereafter, in the first interlayer insulating layer forming step, the surface of the fourth common conductive layer 4d is subjected to a thermal oxidation treatment at a temperature of about 700.degree. By this thermal oxidation treatment, in the portion where the film thickness of the fourth common conductive layer 4d is reduced, the film thickness of the first and fourth common conductive layers 4a and 4d made of Ta cermet is oxidized, and the third common conductive layer 4d is formed. In the portion of the upper surface of the layer 4c where the thickness of the fourth common conductive layer 4d is kept at about 1 μm, about half the depth from the surface of the fourth common conductive layer surface 4d is oxidized, and the oxidized insulation of Ta cermet is obtained. The first interlayer insulating layer 5a made of conductive ceramic can be formed into a film having very few formation defects. Thus, the first, second, third, and fourth common conductive layers 4a, 4b, 4c, 4
A first interlayer insulating layer structure 5a is formed to cover the upper surface and the outer peripheral portion of the laminated structure d. (Step 7)

In the oxidation resistant mask removing step, the conductive part 6 projecting from the fourth common conductive layer 4d and exposed on the surface of the first interlayer insulating layer 5a is formed by removing the oxidation resistant mask layer by etching. . In the second interlayer insulating layer forming step, the upper surface of the first interlayer insulating layer 5a and the conductive portion 6 are formed.
A second interlayer insulating layer 5b made of SiO ₂ and having a thickness of about 2 μm. (Step 8)

In the opening forming step, the second interlayer insulating layer 5b is subjected to photolithography and etching to form the opening 5c so that the conductive portion 6 is exposed from the second interlayer insulating layer 5b. (Step 9)

In the present embodiment, the upper layer individual electrode 8b is selected based on desired print information and energization is performed. The current from the upper-layer individual electrode 8b reaches the lower-layer individual electrode 8a and a desired heating resistor 9, and causes the heating region S of the heating resistor 9 to generate heat. And the current from each heat generating area S is
It flows into the lower-layer common electrode 7a, passes through the lower-layer common electrode 7a (and the upper-layer common electrode 7b), and is led to the external circuit from each of the common conductive layers 4a, 4b, 4c, and 4d via the conductive portion 6. Has become. At this time, the upper common electrode 7b made of a good conductor such as Al or Cu plays a role of assisting the electrical conduction of the lower common electrode 7a made of high melting point metal such as Cr.

In this embodiment, the heating resistor 9 is formed on the upper surface of the lower common electrode 7a and the lower individual electrode 8a. However, on the upper surface of the heating resistor 9, the lower common electrode 7a, the upper common electrode 7b, Lower individual electrode 8a and upper individual electrode 8b
May be stacked. Further, since the lower-layer common electrode 7a is provided, the upper-layer common electrode 7b serving as an auxiliary role may not be formed.

【The invention's effect】

As described above, in the thermal head according to the present invention, the common conductive layer is formed by forming the first common conductive layer made of metal cermet and the second common conductive layer made of metal on the heat insulating layer made of glass or the like. And the third common conductive layer made of metal and the fourth common conductive layer made of Ta cermet are sequentially laminated, so that the first common conductive layer is formed of the second common conductive layer and the heat insulating layer. Adhesive layer, and
The third common conductive layer, which covers the second common conductive layer on the first common conductive layer upper surface, improves the adhesion of the second common conductive layer to the first common conductive layer, and The adhesion reliability between the layer and the heat insulating layer is high, and it is possible to eliminate the delamination of the laminate and the chipping of the substrate with respect to the thermal shock of the heat treatment step and the mechanical shock applied during the step. Stabilization can be achieved.

Further, the thermal head according to the present invention comprises:
A heating resistor formed on an upper surface of an interlayer insulating layer covering the common conductive layer, a common electrode connected to one end of the heating resistor, and an individual electrode connected to the other end of the heating resistor; Is connected to the common conductive layer by a conductive layer protruding from the common conductive layer and exposed on the surface of the interlayer insulating layer, and the second common conductive layer includes the individual electrode and the common electrode of the heating resistor. Since it is provided on the individual electrode side than the heating region sandwiched between the, the heat generated in the heating region is not radiated by the second common conductive layer,
The heat generation peak temperature in the heat generation region can be increased, and as a result, the printing thermal efficiency can be improved. Further, the third common conductive layer, which is a thin metal film, and the opaque first and fourth common conductive layers made of Ta cermet are interposed between the heat generating region and the heat retaining layer. Without the necessary heat being deprived by the thermal insulation layer,
The heat generation peak temperature in the heat generation region can be increased, and as a result, the printing thermal efficiency can be improved. ,

As described above, the adhesion reliability between the second common conductive layer and the heat insulating layer is improved by the first common conductive layer, and the second common conductive layer is located at a position outside the heat generating region. Since it is formed, it does not take away the heat of the heat generating region, so that the film thickness of the second common conductive layer can be increased, and the thick second common conductive layer is provided to the heat generating region. By being formed adjacent to each other, power can be supplied to the heating resistor by the second common conductive layer having a low resistance, a drop in the voltage applied to the heating resistor can be reduced, and high printing without printing variations can be achieved. Quality can be realized.

Further, since the second common conductive layer can be formed thick, the area of the second common conductive layer can be reduced while keeping the second common conductive layer at low resistance, and Even if there is a defect in the layer, the probability that the common conductive layer and the individual electrode are short-circuited is reduced, and the production quality and the production yield can be stabilized.

Further, since the outer periphery of the common conductive layer is covered with the interlayer insulating layer, the common conductive layer is not exposed at the end of the heat dissipation board. It is possible to reliably prevent the occurrence of insulation failure such as short-circuiting due to contact with the substrate.

The first common conductive layer is made of T having an excellent adhesive effect.
Since the a cermet and the second and third common conductive layers are made of a homogeneous Cr material having excellent adhesion, the reliability of the adhesion between the layers is high, and the production quality and the production yield can be stabilized.

In the method of manufacturing a thermal head according to the present invention, the first common conductive layer made of Ta cermet, the second common conductive layer made of Cr, and Cr are formed on the upper surface of the heat insulating layer formed on the heat radiation substrate. A step of sequentially stacking a third common conductive layer, a step of forming a fourth common conductive layer made of Ta cermet on the upper surface of the heat insulating layer so as to cover these common conductive layers, and a step of forming the fourth common conductive layer A step of thinning the outer peripheral portion of the three common conductive layers, and performing a thermal oxidation process on the fourth common conductive layer, and all the thicknesses of the thinned portions, and the first, second, and Forming a first interlayer insulating layer made of an insulating ceramic by oxidizing the surface from the surface on the three common conductive layers to about half the thickness, and forming a second interlayer made of SiO2 on the upper surface of the first interlayer insulating layer. Since it has a step of forming an insulating layer, Defects in the formation of the first interlayer insulating layer can be extremely reduced, and the reliability of the insulating layer is improved because of the two-layer structure with the second interlayer insulating layer.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a thermal head according to the present invention.

FIG. 2 is a plan view of the thermal head of the present invention as viewed from above.

FIG. 3 is a flowchart illustrating a method of manufacturing a thermal head according to the present invention.

FIG. 4 is a sectional view of a main part of a conventional thermal head.

[Explanation of symbols]

 S Heating area 1 Heat dissipation board 1a End 2 Heat insulation layer 3 Convex section 4a First common conductive layer 4b Second common conductive layer 4c Third common conductive layer 4d Fourth common conductive layer 5a First interlayer insulating layer 5b Second Interlayer insulating layer 5c Opening 6 Conductive part 7a Lower common electrode 7b Upper common electrode 8a Lower individual electrode 8b Upper individual electrode 9 Heating resistor 9a One end 9b Other end 10 Protective layer

Claims (7)

[Claims] 1. A heat insulating layer made of glass, a common conductive layer, and an interlayer insulating layer are sequentially laminated on an upper surface of a heat-dissipating substrate made of insulating ceramic, and a plurality of insulating layers are formed on the interlayer insulating layer. A plurality of heating resistors provided side by side; a common electrode connected to one end of the heating resistor to connect the heating resistor; and a plurality of electrodes connected to the other end of the heating resistor. And the common electrode is connected to the common conductive layer by a conductive portion projecting from the common conductive layer and exposed on the surface of the interlayer insulating layer, and the structure of the common conductive layer is A first common conductive layer made of a metal cermet sequentially formed on an upper surface of the heat insulating layer, a second common conductive layer made of a metal, and a metal covering the second common conductive layer on an upper surface of the first common conductive layer A third common conductive layer made of A thermal head having a four-layer structure in which a fourth common conductive layer made of a metal cermet formed on an upper surface of a conductive layer is sequentially laminated. 2. The device according to claim 1, wherein the second common conductive layer is formed on a side of the individual electrode from a heat generating region sandwiched between the individual electrode and the common electrode of the heating resistor. The described thermal head. 3. The thermal head according to claim 2, wherein the second common conductive layer is adjacent to the heat generating area. 4. The thermal head according to claim 1, wherein the interlayer insulating layer is formed on an upper surface of the heat insulating layer and covers an outer peripheral portion of the common conductive layer. . 5. The first common conductive layer is a Ta cermet,
The second common conductive layer is Cr, and the third common conductive layer is C
5. The thermal head according to claim 1, wherein the fourth common conductive layer is made of Ta cermet. 6. The first common conductive layer has a thickness of 0.1 μm.
m, the thickness of the second common conductive layer is about 1 μm, the thickness of the third common conductive layer is about 0.2 μm, and the thickness of the fourth common conductive layer is about 1 μm. Item 6. The thermal head according to Item 5. 7. A heat insulating layer made of glass and a common conductive layer are sequentially laminated on an upper surface of the heat dissipation substrate, and an interlayer insulating layer is formed on the upper surface of the heat insulating layer so as to cover the common conductive layer. A heating resistor formed on the interlayer insulating layer, a common electrode connected to one end of the heating resistor, and an individual electrode connected to the other end of the heating resistor; A method for manufacturing a thermal head, wherein a heat generating area is provided between the common electrodes, and the common electrode is connected to the common conductive layer by a conductive portion protruding from the common conductive layer and exposed on a surface of the interlayer insulating layer. A first conductive layer forming step of forming a first common conductive layer made of Ta cermet on the upper surface of the heat insulating layer, and a second common conductive layer of a second common conductive layer made of Cr on the first common conductive layer. A layer forming step and the second common A second conductive layer patterning step of patterning the conductive layer in a strip shape adjacent to the heat generating region on the individual electrode side of the heat generating region, and laminating a third common conductive layer made of Cr on the second common conductive layer A third conductive layer forming step of forming; a third conductive layer patterning step of forming the third common conductive layer in a pattern extending from the individual electrode side to the common electrode side; covering each of the common conductive layers A fourth common conductive layer forming step of forming a fourth common conductive layer made of Ta cermet, and an oxidation resistant mask forming step of stacking an oxidation resistant mask layer made of an oxidation resistant material on the upper surface of the fourth common conductive layer An oxidation-resistant mask patterning step of forming a mask pattern of the oxidation-resistant mask layer at an arrangement position of the conductive portion of the fourth common conductive layer; and forming an outer peripheral portion of the third common conductive layer. A fourth common conductive layer processing step of processing the formed fourth common conductive layer to have a reduced thickness, and a thermal oxidation treatment of the entire surface of the fourth common conductive layer, and the thermal oxidation treatment is performed to form a fourth layer made of an insulating ceramic. A first interlayer insulating layer forming step of forming one interlayer insulating layer, and an oxidation resistant mask removing step of removing the oxidation resistant mask layer and exposing the conductive portion on the surface of the first interlayer insulating layer. A second interlayer insulating layer forming step of laminating a second interlayer insulating layer made of an insulating ceramic on the first interlayer insulating layer; and an opening so that the conductive portion is exposed from the second interlayer insulating layer. And a step of forming an opening for forming a thermal head.