JPH10305604A - Thermal head and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermal head of a long print life, by forming a protecting layer of a material mainly consisting of AlN and an insulating oxide ceramics formed with the use of at least one of SiO2 , etc. SOLUTION: A material essentially consisting of AlN and an insulating oxide ceramics such as SiO2 or the like is sputtered to a formation area for a protecting layer 15 with the use of Ar gas, whereby the protecting layer 15 is formed. In this case, an addition ratio of the insulating oxide ceramics is approximately 20-50 mol.%. As the insulating oxide ceramics, other than SiO2 , CeO2 , Y2 O3 , Al2 O3 , ZrO2 , CrO3 , Ta2 O5 , etc., can be used singly or mixed. Since the insulating oxide ceramics can be selected from a plurality of kinds, abrasion resistance and crack resistance can be balanced well, and adhesion of the protecting layer is enhanced, so that insulation performance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a thermal head used in a thermal printer, in which a protective layer of a thermal head has improved adhesion, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, a thermal head used in a thermal printer has a plurality of heating resistors linearly arranged on a substrate made of alumina or silicon.
By selectively sequentially energizing desired heating resistors based on print information and heating the heating resistors, a thermal printer causes the recording paper to develop color and prints, and a thermal transfer printer performs ink printing. It is formed so that printing is performed by partially melting the ink of the ribbon and transferring it to recording paper or the like.

In this type of conventional thermal head, as shown in FIG. 6, a ridge 1b is formed near an end 1a of a substrate 1 made of silicon or the like by a photolithographic technique, and a sputtering technique is formed on the upper surface of the substrate 1. As a result, a heat insulating layer 2 made of silicon, a transition metal, and oxygen is formed. Also,
A heating resistor 3 made of Ta—SiO ₂ or the like is laminated on the upper surface of the heat insulating layer 2 by sputtering or the like, and a pattern of the heating resistor 3 is formed by a photolithography technique. The heat generating portion 3a is formed.

In order to generate heat from the heat generating portion 3a,
Electrode 4 for supplying electric energy to heating resistor 3
Are laminated by a photolithography technique using Al or the like to form a pair of common electrodes 4a and individual electrodes 4b. Further, the heating resistor 3 and the common electrode 4a / individual electrode 4
A conventional thermal head is formed by forming a protective layer 5 made of hard sialon or SiC or the like on the respective surfaces b by sputtering in order to prevent oxidation or wear.

[0005] As shown in FIG. 7, the conventional thermal head manufacturing method as described above employs a heat insulating layer 2 on the upper surface of the substrate 1.
Forming a plurality of heating resistors 3 on the upper surface of the heat insulating layer 2, and forming an electrode 4 including a common electrode 4a and an individual electrode 4b connected to the plurality of heating resistors 3. And a step of forming a protective layer 5 covering the exposed upper surfaces of the heat insulating layer 2, the heating resistor 3, and the electrode 4. Although not shown here, as a conventional first manufacturing method, the step of forming the protective layer 5 first removes organic contaminants on the heat insulating layer 2, the heating resistor 3, and the exposed surface of the electrode 4. In the first step, a pretreatment for performing sputter etching using Ar gas is performed, and after the sputter etching, the second process is performed.
In the step (3), a sputtering target made of a material such as hard sialon or SiC is sputtered using Ar gas to form a protective layer 5 on which a conventional thermal head is manufactured. However, when the sputter etching in the first step is performed using Ar gas, light element components such as oxygen in the surface composition of the heating resistor 3 jump out from the surface, and oxygen deficiency occurs in the outermost surface composition. for that reason,
A low resistance layer having a low specific resistance is formed on the outermost surface of the heating resistor 3.

A conventional thermal head in which a protective layer 5 is formed on the surface of the low resistance layer of the heat generating resistor 3 by sputtering a material such as Sialon or SiC using Ar gas in the second step, There is a problem that the dot resistance value of the portion 3a is reduced, for example, by about 20% with respect to a desired dot resistance value required for printing. Further, using a thermal head manufactured by the above-mentioned conventional manufacturing method, a step stress test (S
ST), the dot resistance value of the heat generating portion 3a decreases with the increase of the heat generating temperature of the heat generating portion 3a, and even at a constant current value, the temperature of the heat generating portion 3a rises above the proper printing temperature, and the thermal head Has a problem that the thermal characteristics of the ink are deteriorated and the printing quality is deteriorated.

To reduce the occurrence of the low resistance layer,
There is also a method of finely controlling the power of the sputter etching or the pressure of the Ar gas in the first step of the protective layer 5 forming step. However, according to this method, the sputter etching power or the gas pressure varies and the sputter etching is performed. The removal of the original surface contaminants varies. As a result, the adhesion between the heating resistor 3 and the protective layer 5 is reduced, and the control of the resistance value of the heating portion 3a is varied, thereby deteriorating the print life, manufacturing quality, manufacturing yield, and the like. was there.

As a second manufacturing method for solving the problem of the first manufacturing method of the conventional thermal head as described above, as shown in the process diagram of FIG. The sputter etching of the step is performed not by the Ar gas but by the O.
Sputter etching is performed using _two gases or a mixed gas of Ar + O ₂ . Then, the organic contaminants on the surface of the heating resistor 3 and the like are ashed and removed, and then, in a second step, a sputtering target made of a material such as hard sialon or SiC is sputtered using Ar gas. Thus, the protective layer 5 is laminated to form a thermal head according to the second manufacturing method.

[0009]

However, in the case of the thermal head manufactured by the above-described second manufacturing method, the O ₂ gas used for the sputter etching in the first step of the protective layer 5 forming step is not required. However, even if organic contaminants can be completely removed by incineration, the exposed surface of the heating resistor 3 becomes an inactive oxide, and the exposed surface of the inert heating resistor 3 has the second surface. By sputtering the protective layer 5 made of sialon or SiC with Ar gas in the step, even if active Si is generated due to the deficiency of nitrogen or oxygen, the free oxide generation energy of Si is, for example, Al _2.
O ₃ is −400 kcal / mol, whereas SiO ₂ is −
Since it is as small as 205 kcal / mol, Si is hard to be oxidized, and even if active Si metal is interposed at the close interface between the surface of the heating resistor 3 and the like, oxygen of oxide on the surface of the heating resistor is deprived of chemicals. Bonding was not possible, resulting in only physical bonding, and the adhesion between the heating resistor 3 and the protective layer 5 was weak.

The above-mentioned conventional thermal head is
When printing is performed by repeatedly rubbing the thermal paper or the ink ribbon to generate heat in the heating portion 3a in a state of being pressed against a platen (not shown), particularly, the protective layer 5 on the heating portion 3a
There has been a problem that a large shearing force is repeatedly applied to cause peeling (poor adhesion) in a fatigue fracture mode. The protective layer 5, once peeled off at the boundary surface between the heating resistor 3 is generated, the heating resistor 3 poor oxidation resistance consisting of Ta-SiO ₂ or the like, the dot resistance value is easily oxidized Get higher,
There has been a problem that the temperature of the heat generating portion 3a does not rise to a desired temperature, the ink on the ink ribbon is not transferred at the time of printing, dot missing occurs, printing becomes defective, and the life of the thermal head is reduced.

In addition, there is a real edge type thermal head for printing on rough paper or the like having a large unevenness on the surface, and the real edge type thermal head is provided at a position close to the edge 1a of the substrate 1 so that the heat insulating layer 2 has a convex shape. The heat generating portion 3a is formed on the protruding portion 2a by forming the protruding portion 2a so as to protrude to about 10 μm or more. A rough paper compatible printer equipped with such a real edge type thermal head has a thermal head that is roughened with a strong pressing force enough to crush unevenness on the surface of the rough paper located on the platen (not shown) side. Printing is performed while pressing the paper, thereby improving the printing quality on the rough paper or the like. Therefore, the protective layer 5 of the real edge type thermal head, especially on the heat generating portion 3a,
Larger shear was being applied repeatedly. The protective layer 5 manufactured by the second manufacturing method includes a heating resistor 3
A short period of time, as shown in FIG. 8, is generated between the heat generating portion 3a and the heat generating portion 3a as shown by hatching.
As a result, a stress crack 5b occurred in the protective layer 5. Further, when the peeling portion 5a occurs locally, there is a problem that the peeling portion 5a propagates (expands the discoloration area).

Further, since the protective layer 5 is made of a material having a main composition of hard sialon or SiC or the like and having a thickness of several μm as a single layer in order to enhance the wear resistance,
The internal stress of the protective layer 5 is likely to be large, and if the protective layer 5 itself is separated from the surface of the protective layer 5 at the boundary surface with the heating resistor 3 or a foreign matter is present on the surface of the recording paper or the like during printing,
If the thermal head is pressed against the foreign matter during printing, a concentrated load is generated at the portion of the thermal head where the foreign matter is pressed, and there is a problem that cracks occur during the collection and the protective layer 5 is easily peeled off.

[0013]

Means for Solving the Problems As a first means for solving the above problems, a thermal head of the present invention comprises a substrate, a heat insulating layer formed on the upper surface of the substrate, and a heat insulating layer formed on the upper surface of the heat insulating layer. A plurality of heating resistors, individual electrodes and a common electrode connected to the plurality of heating resistors, the heat insulation layer,
A protective layer having a main composition of AlN and an insulating oxide ceramic formed by coating the surfaces of the heating resistor, the individual electrodes and the common electrode, wherein the insulating oxide ceramic of the protective layer is made of SiO ₂ , CeO ₂ , Y ₂ O ₃ , AI ₂ O ₃ , Zr
O ₂ , CrO ₃ , and Ta ₂ O ₅ were constituted by at least one kind or two or more kinds of components.

[0014] Further, a second aspect for solving the above-mentioned problem is as follows.
As a means of the above, the ratio of adding the insulating oxide ceramic of the material of the protective layer was set to 20 to 50 mol%.

[0015] A third aspect for solving the above-mentioned problem is as follows.
Forming a heat insulating layer on the upper surface of the substrate,
Forming a plurality of heating resistors on the upper surface of the heat insulating layer;
A step of forming an individual electrode and a common electrode connected to the plurality of heating resistors, and a step of forming a protective layer covering the surfaces of the heat insulating layer, the heating resistor, the individual electrodes and the common electrode. The step of forming the protective layer includes a first step of sputter-etching a region where the protective layer is formed using O ₂ gas, and a step of sputtering a material having a main composition of AlN and an insulating oxide ceramic. A second step of laminating and forming the protective layer by sputtering using an Ar gas in a region where the etched protective layer is to be formed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a thermal head according to the present invention is a method of manufacturing a thermal head by forming a heat insulating layer, a heating resistor, each electrode and a protective layer in this order. The step of forming a layer includes a first step and a second step. In the first step, the formation region of the protective layer is sputter-etched in an atmosphere containing O ₂ gas as in the related art, and the heat generation resistance is reduced. The organic contaminants on the surface of the body or the like are ashed and removed, and an inert oxide film is formed on the surface of the heating resistor or the like.

Next, in a second step of forming a protective layer on the surface of the inactive heating resistor or the like, a material having a main composition of AlN and an insulating oxide ceramic is used as a sputtering target and an Ar gas is used. Sputtering is performed in an atmosphere. Then, the main composition AlN becomes deficient in nitrogen and generates a large amount of active metal Al.
1 chemically reacts with oxygen of an inactive oxide film on the surface of the heating resistor or the like, and a boundary surface between the heating resistor or the like and the protective layer is chemically bonded to form a protective layer having strong adhesion strength. be able to.

In the present invention, when a protective layer is formed by sputtering a sputtering target composed of a material mainly composed of AlN and an insulating oxide ceramic, a film deficient in light elements such as oxygen and nitrogen is formed. AlN
The active metal Al liberated from the metal forms a brown, translucent insulating film. Further, since the active metal Al released from the AlN has a large oxide free generation energy, at the interface between the heating resistor and the protective layer,
Oxygen of the oxide film on the surface of the heating resistor or the like is deprived of oxygen to form an oxide of Al and chemically bonded by a chemical reaction. For example, the free generation energy of the Al oxide is SiO 2
₂ is −205 kcal / mol, whereas Al ₂ O ₃ is −
Since it is about twice as large as 400 kcal / mol, and Al has a property of easily becoming an oxide, Al that is active at the contact interface between the surface of the heat generating resistor and the like and the protective layer becomes Ta-
It is possible to obtain a protective layer in which the heat generating resistor made of SiO ₂ or the like is chemically bonded to the oxygen of SiO ₂ and the adhesion to the heat generating resistor or the like is remarkably improved.

Further, the protective layer is made of a hard AlN single material,
When sputtering is performed using Ar gas, an opaque conductive black film containing nitrogen and lacking Al is formed, and there is a problem that electric leakage occurs. Therefore, Ar
If an insulating film is to be formed by reactive sputtering using a mixed gas of Ar + N ₂ or Ar + O ₂ instead of a gas, the manufacturing variation of the protective layer becomes large due to the variation of the mixing ratio of the mixed gas and the like. There was a problem that manufacturing quality was not stable.

In order to solve this problem, the protective layer of the thermal head according to the present invention is formed by sputtering with a sputtering target composed of a material mainly composed of AlN and an insulating oxide ceramic, using only Ar gas. is there. And even if AlN becomes nitrogen deficient by this sputtering, it does not become a conductive film, but the excess metal Al released from oxygen and AlN of the insulating oxide ceramic.
Partially react to obtain an appropriately nitrogen-deficient insulating film. Further, in the manufacturing method of the present invention, since the protective layer made of the two materials of AlN and the insulating oxide ceramic can be formed as a single layer, the manufacturing efficiency and quality can be improved.

In the thermal printer for rough paper, printing is performed by strongly pressing the thermal head against the recording medium and the platen. Therefore, a protective layer having high abrasion resistance and high hardness is required. Is too high, on the contrary, it becomes brittle, and crack resistance becomes a problem. For example, when printing with a thermal printer compatible with the rough paper, if foreign matter or the like is attached to the printing portion and the thermal head bites the foreign material or the like during printing, a localized concentrated load is applied to the portion where the foreign matter is caught. Therefore, a protective layer having crack resistance enough to withstand the local concentrated load is required. For this purpose, the present invention provides a material for the protective layer, which is composed mainly of high-hardness AlN and an insulating oxide ceramic having excellent crack resistance in advance, and by adjusting the amount of the insulating oxide ceramic to be added. The crack resistance and the wear resistance can be balanced by appropriately adjusting the film hardness of the protective layer. Therefore, not only the adhesion of the protective layer of the thermal head can be improved, but also the film hardness of the protective layer can be appropriately adjusted according to the type of the thermal printer having a different pressure contact force of the thermal head.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal head manufactured by a method of manufacturing a thermal head according to the present invention will now be described with reference to FIG.
A trapezoidal ridge 11b is formed near the end 11a by photolithography, and a heat insulating layer 12 made of silicon, transition metal and oxygen is formed on the upper surface of the substrate 11 by sputtering. A heating resistor 13 made of Ta—SiO ₂ or the like is laminated on the upper surface of the heat insulating layer 12 by sputtering or the like, and the heating resistor 1 is formed by photolithography.
Pattern 3 is formed in a line at predetermined intervals,
The heat generating portion 13a is formed in a dot shape above the convex portion 12a of the heat insulating layer 12.

Further, in order to cause the heat generating portion 13a to generate heat, an electrode 14 made of Al or the like for supplying electric power energy to the heat generating resistor 13 is provided on one side of the heat generating resistor 13 by photolithography. The common electrode 14a is
Further, the individual electrode 1 is provided on the other slope side of the heating resistor 13.
4b are formed as a pair. Further, the heating resistor 13
In order to prevent oxidation or wear of the common electrode 14a and the individual electrode 14b, the heating resistor 13, the electrode 14,
In addition, the protective layer forming region on the exposed surface of the heat insulating layer 12 is made of a protective layer made of an insulating oxide ceramic material such as AlN and SiO _{2 having a} good balance of oxidation resistance, abrasion resistance and crack resistance. 15 is approximately 5 by sputtering
The thermal head of the present invention is formed by lamination with a thickness of μm.

In the method of manufacturing a thermal head according to the present invention, as shown in FIG. 2, a step of forming a heat insulating layer 12 on the upper surface of the substrate 11 and a step of forming a plurality of heating resistors on the upper surface of the heat insulating layer 12 are performed. Forming a common electrode 14a and individual electrodes 14b connected to the plurality of heating resistors 13;
Forming an electrode 14 consisting of:
Forming a protective layer 15 covering the exposed surface of each of the heating resistor 13 and the electrode 14. In the step of forming the protective layer 15, in order to remove organic contaminants on the exposed surface of the heating resistor 13, the area where the protective layer 15 is formed is made of O ₂ gas 100% or A ₂ gas.
a first step of performing sputter etching in an atmosphere containing oxygen such as an r + O ₂ mixed gas, and a formation region of the protective layer formed by sputter etching a material having a main composition of AlN and an insulating oxide ceramic such as SiO ₂ ; Ar inert to
A second step of laminating and forming the protective layer 15 by sputtering using a gas to form the protective layer 15 in the protective layer forming region on the exposed surface of the heating resistor 13, whereby the thermal head of the present invention is formed. Made.

The thermal head of the present invention, the protective layer 15 in the first step of the formation process, O ₂ gas or Ar + O ₂ heating resistors by sputter etching using a mixed gas such as body 13,
By removing organic contaminants on the exposed surface of the substrate and obtaining an inert oxide film on the surface of the heating resistor 13, the heating resistor 13 having a stable resistance value can be obtained. And the first
On the exposed surface of the inactive oxide film of the heat generating resistor 13 obtained in the step, a sputtering target mainly composed of an insulating oxide ceramic such as AlN and SiO ₂
By sputtering using a gas, the light elements of AlN and SiO _{2 such} as nitrogen and oxygen are depleted (Al
N) _1−x and (SiO ₂ ) _2−x films, and active Al or Si metal is generated in the protective layer 15, and the Al or Si metal is an oxide film of the heating resistor 13. Chemically bonding with the oxygen, thereby obtaining a protective layer 15 in which the adhesion to the heat generating resistor 13 and the like is remarkably improved.

Since the protective layer 15 mainly composed of the insulating oxide ceramics of AlN and SiO ₂ is formed as a brown semi-transparent film having an insulating property, the protective film 15 is formed by one sputtering. Even if the protective film 15 is formed as a single layer,
The pattern shape and the like of the internal heating resistor 13 can be confirmed from above, and when there is an abnormality in the pattern of the heating resistor 13 by an appearance inspection or the like, this abnormality can be found from above the protective layer 15. The ratio of the material for forming the protective layer 15 to which the insulating oxide ceramic is added is about 20 to 50 mol.
%, The result was that the adhesive strength, crack resistance, abrasion resistance, and insulation properties could be satisfied.

If the proportion of the insulating oxide ceramics is less than about 20 mol%, the protective layer becomes high in hardness and wear resistance is improved, but on the contrary, it becomes brittle and deteriorates crack resistance. In addition, the conductivity is increased and the insulating property is insufficient, resulting in a D0T leak failure. On the other hand, when the ratio of adding the insulating oxide ceramics is more than 50 mol%, the crack resistance is good, but the hardness of the protective layer is reduced and the wear resistance is deteriorated. Furthermore, the insulating oxide ceramics CeO ₂ in addition to _{SiO 2, Y 2 O 3,} Al 2 O 3, ZrO 2,
Cr ₂ O ₃ , Ta ₂ O ₅ or the like may be used, or a plurality of these insulating oxide ceramics may be mixed and used. As described above, the insulating oxide ceramics can be selected from a plurality of types and used, so that the balance between the wear resistance and the crack resistance is good, the adhesion of the protective layer is also increased, and the insulation performance can be improved. An optimum combination of thermal heads can be provided.

The graph shown in FIG. 3 shows the results of a step stress test (SST) for evaluating the thermal characteristics of the thermal head. The vertical axis represents the rate of change of the resistance value of the heating resistor, and the horizontal axis represents the heating portion 13a. 3 shows a change in temperature. The curve in the graph is an SST curve representing the rate of change of the resistance value with respect to this temperature change by increasing the temperature of the heat generating portion 13a by energizing until the thermal head is broken. First, Ta-SiO
When stable heat treatment temperature of the heating resistor 13 comprising _two like the (aging) eg, 700 ° C, this 700 ° C
In the above area, the protective layer 5 of the conventional thermal head
The SST curve indicates that when the temperature rises to the point A, the boundary between the surface of the heating resistor 13 and the protective layer 15 is peeled off, and the stress caused by the peeling causes cracks in the protective layer 15 to cause thermal stress. The head is broken, the temperature rise of the thermal head stops at point A, and the resistance value rises sharply. At this time, the drop rate of the resistance value at the point A is approximately 0 to 10%.
It is.

On the other hand, even if the SST curve of the protective layer 15 of the thermal head of the present invention rises to the point B where the temperature is higher than the point A, the protective layer 15 does not peel off. When the temperature of the heat generating portion 3a rises to the point B,
A portion of the heat generating portion 13a is melted at a high temperature, and a stress crack occurs in the protective layer 15 due to the stress caused by the melt, and the thermal head is broken. In this case, the rate of drop of the resistance value is about 15 to 20%, and the thermal head of the present invention has a protective layer above the heat generating portion 13a after the resistance value has dropped significantly compared to the conventional thermal head. No. 15 was broken by stress cracks. That is, the magnitude of the drop rate of the resistance value in the step stress test (SST) can be used as an evaluation index of the adhesion between the heating resistor 13 and the protective layer 15 and the crack resistance.

FIG. 4 is a schematic view of the thermal head according to the present invention when the thermal stress is increased to point B in the step stress test and a stress crack 15b is generated and destroyed in the protective layer 15 above the heat generating portion 13a. It is. Heating part 1
In the center of 3a, there is a melting mark 15a when the heating resistor 13 generated when the center is abnormally high in temperature is melted.
Then, a stress crack 15b is generated by the melting mark 15a. In addition, the thermal head of the present invention clearly shows that the adhesion of the protective layer 15 of the thermal head of the present invention is clear because there is no peeling propagation (expansion of the discoloration area) from the crack 15b unlike the conventional thermal head. Prove that it is excellent.

The graph shown in FIG. 5 is a result of a comparison test of printing life under predetermined printing conditions using the thermal head of the present invention and a conventional thermal head.
The horizontal axis indicates the number of characters to be printed when an abnormality occurs in the dot resistance value of the heating resistor 13. As a result, the conventional thermal head A prints 10 to 70 million characters, causes stress cracks due to delamination between the heating resistor 13 and the protective layer 15, and causes an abnormal dot resistance value of the heating resistor 13 to occur. did. However, in the thermal head B manufactured by the manufacturing method of the present invention, no abnormality occurs up to the printing of 80 to 120 million characters, and a remarkable difference in the printing life is clearly confirmed.
That the occurrence of delamination at the interface between the protective layer 15 and the protective layer 15 can be prevented. From this result, it became clear that the thermal head of the present invention had a long life.

[0032]

According to the thermal head of the present invention, the material of the protective layer is mainly composed of AlN and an insulating oxide ceramic, and the insulating oxide ceramic is made of SiO ₂ , CeO ₂ ,
Of Y ₂ O ₃ , Al ₂ O ₃ , ZrO ₂ , Cr ₂ O ₃ and Ta ₂ O ₅ ,
Since it is composed of at least one kind of component, the insulating oxide ceramics can be selected and used from a plurality of types depending on the type of the thermal printer having a different application, so that the abrasion resistance and the crack resistance are well balanced. In addition, it is possible to provide a thermal head having a long printing life and improved adhesion of the protective layer and improved insulation performance.

Further, since the ratio of adding the insulating oxide ceramic as the material of the protective layer is set to 20 to 50 mol%, the thermal resistance is excellent in a well-balanced abrasion resistance, crack resistance, adhesion and insulation. A head can be provided, and an optimal thermal head can be provided according to the type of thermal printer to be used.

Further, the step of forming the protective layer includes the first step of sputter etching the protective layer forming region using O ₂ gas, and the step of forming a material mainly composed of AlN and an insulating oxide ceramic. And a second step of laminating and forming the protective layer by sputtering using an Ar gas in a region where the protective layer is sputter-etched. In the head, the surface of the heating resistor or the like and the protective layer are chemically bonded to each other, and the adhesion strength is strengthened. A thermal head can be provided.

[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 schematic manufacturing process diagram of the thermal head of the present invention.

FIG. 3 is a graph comparing the SST curves of the present invention and a conventional thermal head.

FIG. 4 is a schematic diagram illustrating cracks generated in a step stress test (SST) of the thermal head of the present invention.

FIG. 5 shows a print life test result of the thermal head of the present invention.

FIG. 6 is a sectional view of a main part of a conventional thermal head.

FIG. 7 is a schematic manufacturing process diagram of a conventional thermal head.

FIG. 8 is a schematic diagram illustrating cracks generated in a step stress test (SST) of a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Heat insulating layer 3 Heating resistor 4 Electrode 4a Common electrode 4b Individual electrode 5 Protective layer 11 Substrate 12 Heat insulating layer 13 Heating resistor 14 Electrode 14a Common electrode 14b Individual electrode 15 Protective layer

Claims (3)

[Claims] 1. A substrate, a heat insulating layer formed on an upper surface of the substrate, a plurality of heat generating resistors formed on the upper surface of the heat insulating layer, and an individual electrode and a common electrode connected to the plurality of heat generating resistors. A protective layer having a main composition of AlN and an insulating oxide ceramic by forming and covering the respective surfaces of the heat insulating layer, the heating resistor, the individual electrode and the common electrode, wherein the insulating oxide of the protective layer is provided. Ceramics are SiO ₂ , CeO ₂ , Y ₂
A thermal head comprising at least one, or two or more, components of O ₃ , AI ₂ O ₃ , ZrO ₂ , CrO ₃ , and Ta ₂ O ₅ . 2. The thermal head according to claim 1, wherein a ratio of the insulating oxide ceramic to be added to the protective layer is 20 to 50 mol%. Forming a heat insulating layer on the upper surface of the substrate;
Forming a plurality of heating resistors on the upper surface of the heat insulating layer;
A step of forming an individual electrode and a common electrode connected to the plurality of heating resistors, and a step of forming a protective layer covering the surfaces of the heat insulating layer, the heating resistor, the individual electrodes and the common electrode. The step of forming the protective layer includes a first step of sputter-etching a region where the protective layer is formed using O ₂ gas, and a step of sputtering a material having a main composition of AlN and an insulating oxide ceramic. A second step of laminating and forming the protective layer by sputtering using an Ar gas in an area where the etched protective layer is to be formed.