JPH1142802A - Manufacture of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance corrosion resistance while preventing a protective film from being peeled off by etching the circumferential fringe part of a wiring electrode in a protective film region in the vicinity of a heating resistor repeatedly a specified number of times and forming a tapered cross-section. SOLUTION: A wiring electrode 4 is formed to have tapered circumferential cross-section in order to eliminate a step due to the wiring electrode 4 at the time of forming a protective film 9 and the difference in the growing process of the protective film 9 on a heating resistor 3 and the wiring electrode 4 thus preventing formation of dislocation. More specifically, a glaze 2 and a heating resistor 3 are formed on an insulating substrate 1 followed by formation of a wiring electrode 4 and a resist 8. Subsequently, etching is performed once using a mixed acid aqueous solution, e.g. phosphoric acid solution. Etching progresses simultaneously on the interface between the resist 8 and the wiring electrode 4 in the plane direction and a tapered face 5 is formed at the circumferential part of the electrode. According to the method, level difference is eliminated from the surface of the protective film 9 resulting in the enhancement of abrasion resistance, and the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a thermal head used for thermal recording of a facsimile, a printer or the like.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 10 (a) and 10 (b), a glaze layer 2 is provided as a heat storage layer on an insulating substrate 1 made of ceramic or the like to form a Ta-based, silicide-based, Ni--Cr
A heating resistor material such as a system and an electrode material such as Al, Cr-Cu, Au, etc. are formed by sputtering or vapor deposition, and the heating resistor 3 and the wiring electrodes 12 of the common electrode and the individual electrode are formed by patterning in a photolithography process. Forming
Thereafter, in order to prevent oxidation and abrasion resistance of the heating resistor 3, SiO ₂ , Ta ₂ O ₅ , SiAlON, Si ₃ N ₄ , SiC
A thermal head is manufactured by forming a protective film 9 such as by sputtering, ion plating, or CVD.

However, in the conventional method for manufacturing a thermal head, since the cross-sectional shape of the peripheral portion of the wiring electrode 12 of the common electrode and the individual electrode is substantially perpendicular, a similar step occurs on the surface of the protective film 9. Further, the heating resistor 3 and the wiring electrode 12
Due to the difference in the growth process at the time of forming the protective film, a fault 10 in which the continuity in the surface direction of the film is broken occurs in the protective film layer.

For this reason, the resistance value of such a thermal head increases at an early stage, and when printing is performed using this thermal head, dot missing is caused and the printing running life of the thermal head is reduced. In addition, due to the tomographic portion 10 of the protective film, penetration of ions of the thermal paper, moisture in the atmosphere, Na ⁺ , Cl ⁻ ions, and the like during printing traveling can be considered. As a result, the heating resistor 3, the wiring electrode 12 corroded, and there was a subject that corrosion resistance was inferior.

As a conventional example for solving these problems, as a conventional method, a tip of a wiring electrode 12 connected to a heating resistor 3 is formed in a tapered shape to reduce a tomographic layer and a step of a protective film (for example, Japanese Patent Application Laid-Open No. 129184) or a manufacturing method for reducing the step by making the tip of the wiring electrode 12 connected to the heating resistor 3 into a two-step shape by performing a photo and etching process twice (for example, Japanese Patent Publication No. 55-3046).
No. 8) or a manufacturing method for preventing cracks and cracks by applying high-frequency bias sputtering at the time of forming a protective film (for example, JP-A-63-135261).

[0006]

However, in the thermal head manufactured by the conventional manufacturing method, the wiring electrode has a special shape only at the tip connected to the heating resistor. The effect of improving reliability was not sufficient. That is, the fault and the step of the protective film due to the step of the electrode occur in at least all parts of the electrode peripheral portion in the protective film region except for the tip connected to the heating resistor.

On the other hand, if there is the step, mechanical stress on the step of the protective film due to sliding of the thermal paper and pressing pressure by the platen roller, or heat due to the difference in thermal expansion coefficient between the heating resistor and the electrode. Chipping and peeling of the protective film 9 from the protective film tomographic portion 10 easily occur due to stress. Therefore, the influence of the sliding of the thermal paper and the pressing pressure by the platen roller affects not only on the heating resistor but also on the peripheral portion thereof, and even when a peripheral portion other than the tip of the wiring electrode is triggered, the protective film is not affected. Chipping easily occurs. Further, the foreign matter may be caught by the stepped portion of the wiring electrode due to the scratch caused by the foreign matter or the like attached to the recording paper, and the protective film may easily be peeled off at a portion other than the electrode tip as described above.

[0008] As described above, the protective film is chipped and peeled not only from the tip of the electrode but also from the periphery of the wiring electrode, thereby reducing the printing running life of the thermal head. In recent years, materials having high hardness of the protective film have been used for the purpose of improving abrasion resistance, but the above-mentioned problems have been emphasized. In particular, when coated with a hard protective film, there is a problem that phenomena such as peeling of the protective film are likely to be remarkable because external force cannot be flexibly received and stress is not easily relieved.

Conversely, when the hardness of the protective film is low, the abrasion resistance is inferior, and the heating resistor is destroyed due to the abrasion of the protective film. In addition, due to the steps of the electrode peripheral portion, the ions of the thermal paper, moisture in the atmosphere, N
The intrusion of a ⁺ , Cl ^- ions and the like causes corrosion of the heating resistor and the electrode, and there is a problem that the corrosion resistance is particularly poor at the time of printing standby.

Accordingly, an object of the present invention is to provide a thermal head having a wear-resistant, fault-free thermal head having a tapered edge portion to reduce steps on the surface of a protective film in order to solve the conventional problems. It is to get.

[0011]

In order to solve the above-mentioned problems, the present invention provides at least a heating resistor, a wiring electrode for supplying power to the heating resistor, and a heating resistor on an insulating substrate. In a thermal head having a protective film covering the peripheral wiring electrodes, at least a section of the peripheral portion of the wiring electrode in the protective film region in the vicinity of the heating resistor has a tapered shape, so as to reduce a step of the wiring electrode with respect to the substrate surface, Further, the hardness of the protective film to be coated is set to Vv1200 hardness of Hv1200 or more.

[0012]

In the thermal head constructed as described above, the step between the insulating substrate surface and the peripheral edge of the wiring electrode is gently tapered, so that the coverage of the protective film is enhanced, and thus the peripheral edge of the wiring electrode is improved. The fault which is likely to occur in the portion is eliminated, and the protective film becomes a film having continuous connection in the plane direction. Even if the protective film has a hardness of Vv 1200 or higher in terms of Vickers hardness, failure due to peeling of the peripheral portion of the wiring electrode from the protective film fault, which is easily caused conventionally, can be suppressed, and corrosive ions and the like from the protective film fault portion can be suppressed. As a result, the printing running durability is improved, and at the same time, the environmental reliability is improved.

[0013]

【Example】

[Embodiment 1] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1A is an enlarged cross-sectional view of a heat-generating portion around a heat-generating resistor of a thermal head according to the present invention, and FIG. 1B is a cross-sectional view of a peripheral portion of the same electrode.

In these drawings, a glaze 2 is formed on the surface of an insulating substrate 1, and a wiring electrode 4 is formed so as to be electrically connected to a heating resistor 3. 5
Is a tapered portion of the wiring electrode 4, which is formed around the heating resistor 3 and at the periphery of the entire wiring electrode 4. Reference numeral 9 denotes a protective film which is formed so as to cover the heating resistor 3 and the wiring electrode 4 at the periphery thereof. Since the cross section of the peripheral edge of the wiring electrode 4 has a tapered shape, a step due to the wiring electrode 4 and a difference in a growth process on the heating resistor 3 and the wiring electrode 4 are eliminated when the protective film 9 is formed. Is configured to disappear.

2 (a) and 2 (b), a glaze 2 is formed on the surface of the insulating substrate 1, and a heating resistor 3 is further formed on the surface thereof. A wiring electrode 4 is formed so as to be electrically connected to the body 3. Reference numeral 6 denotes a multi-stage portion, which is formed on the periphery facing the heating resistor 3 and on the periphery of all the wiring electrodes 4. Reference numeral 9 denotes a protective film formed so as to cover all of them.

Since the entire periphery of the wiring electrode 4 has a multi-stage shape, when the protective film 9 is formed, the wiring electrode 4
, And the difference in the growth process on the heating resistor 3 and the wiring electrode 4 is eliminated, and the fault is eliminated. The manufacturing process of the present application will be described in order. As shown in FIG. 3A, a glaze 2 is formed on an insulating substrate 1 made of, for example, alumina ceramics for heat storage. Next, Ta-N, T containing Ta as a main component as a heating resistor material
a-SiO ₂ film etc. about 0.1 μm by sputtering
After the formation, the heating resistor 3 is formed by photolithography. Next, as an electrode material for supplying electric power to the heating resistor 3, Al containing Al as a main component, Al-S
i, an Al-Si-Cu film or the like is formed to a thickness of about 1 to 2 [mu] m by sputtering or the like, and then a photoresist is applied and exposed and developed using a photomask to form a resist 8 having a wiring electrode shape.

Next, in FIG. 3 (b), a mixed acidic aqueous solution composed of phosphoric acid, acetic acid, nitric acid, pure water and the like is used to adjust the viscosity according to the mixing ratio. Is etched, the etching solution is simultaneously etched with the resist 8 and the Al
At the interface, the etching proceeds in the plane direction of the conductor layer, and if the relationship between the etching direction in the plane direction and the film thickness direction is made appropriate, the electrode peripheral portion can have a tapered surface 5 at the end of the etching.

Thereafter, in FIG. 3C, the resist 8 is removed with a stripping solution such as an organic solvent to form a wiring electrode and a tapered portion 5. Next, as shown in FIG.
In order to prevent oxidation and abrasion resistance of the heating resistor 3 and the wiring electrode 4, a protective film 9 is formed by covering a mixed film of Si ₃ N ₄ and SiO ₂ by about 3 to 6 μm by sputtering or the like so as to cover them. I do.

In the thermal head obtained by the above-described steps, the peripheral edge of the wiring electrode is not cliff-shaped and has an appropriate tapered slope. Therefore, the protective film covering the tapered surface 5 of this wiring electrode has The fault is hardly generated in the peripheral part. In particular, sputtering has poor step coverage, and therefore, there is a remarkable difference in the coverage of the protective film between the thermal head of the present invention in which the protective film is formed by sputtering and the conventional thermal head. This effect will be described later together with the evaluation results.

[Embodiment 2] Next, as shown in FIG.
A manufacturing method for forming an electrode peripheral portion in a tapered shape by forming an electrode material having as a main component a multilayer will be described. In FIG. 4A, a glaze 2 is formed on an insulating substrate 1 made of alumina ceramic or the like and a heating resistor 3 is formed as in the first embodiment. Next, as an electrode material for supplying electric power to the heating resistor 3, a first layer of an Al electrode 4b mainly composed of Al is formed to a thickness of about 0.3 to 0.8 μm by sputtering.
The second layer contains Al, as a main component, Si, Cu, T
An Al alloy electrode 4c film to which i or the like is added is formed to a thickness of about 0.3 to 0.6 μm by sputtering or the like, and a total of about 1 to 2 μm is formed.
m electrode films are formed. Thereafter, in the same manner as in Example 1,
A resist 8 is formed.

Next, in FIG. 4B, the first layer and the second layer are etched using an etching solution composed of an acidic mixed aqueous solution of phosphoric acid, acetic acid, nitric acid and pure water. Compared to the Al electrode 4b film containing Al as the main component, a second layer Al alloy electrode 4 in which Si, Cu, Ti, etc. are added to Al.
Since the c film has a fine crystal grain size, the etching rate is high. For this reason, the etching in the plane and in the film thickness direction proceeds, and at the end of the etching, the peripheral portion of the electrode has a tapered shape. Thereafter, in FIG. 4C, the resist 8 is removed by a stripping solution such as an organic solvent to form a wiring electrode and a tapered portion 5. Then, as in the previous embodiment, FIG.
In (d), a protective film 9 is formed.

[Embodiment 3] Next, a method of changing the crystal grain size of an electrode in the film thickness direction to form a tapered shape as shown in FIG. 5 will be described. In FIG. 5A, a glaze 2 is formed on an insulating substrate 1 made of alumina ceramic or the like, and a heating resistor 3 is formed on the upper surface thereof, as in the first embodiment. Further, a film mainly containing Al is formed as an electrode material for supplying electric power to the heating resistor 3 on the upper surface thereof by sputtering to a thickness of 1 to 2 μm. At this time, the crystal grain size of Al changes depending on sputter DC power, substrate temperature, sputter pressure, and the like. The crystal grain size of a normal Al sputtered film is 2 to 4 μm
m. In this embodiment, the Al electrode 4d having a different grain size was formed by changing the crystal grain size by controlling the sputtering DC power and the substrate temperature. In the initial stage of film formation, film formation was performed under normal conditions, and the film was formed by gradually lowering the DC power of sputtering with the passage of time. At the same time, when the sputtering power is reduced, the substrate temperature is reduced because the film forming speed is reduced. The crystal grain size at this time was about 0.5 μm near the Al surface, whereas it was about 2 μm near the lower layer. Then, a resist 8 is formed on the upper surface.

Next, in FIG. 5B, when Al is etched in an etching solution composed of a mixture of phosphoric acid, acetic acid, nitric acid and pure water, the etching rate changes because the crystal grain size differs in the film thickness direction. . That is, the finer the crystal grain size, the faster the etching rate. For this reason, etching is performed in the plane and in the film thickness direction, and at the end of the etching, the peripheral portion of the electrode has a tapered shape. Thereafter, in FIG. 5C, the resist 8 is removed with a stripping solution such as an organic solvent, and the wiring electrode and the tapered portion 5 are removed.
To form Then, a protective film 9 is formed in FIG.

[Embodiment 4] Next, as shown in FIG. 6, a manufacturing method will be described in which the resist electrode forming and etching steps are used a plurality of times to make the peripheral portion of the wiring electrode multi-step and the same effect as the tapered electrode is obtained. .

FIG. 6A shows that a glaze 2 is formed on an insulating substrate 1 made of alumina ceramic or the like as in the first embodiment.
The heating resistor 3 is formed on the glaze 2. Further, a film containing Al as a main component as an electrode material for supplying electric power to the heating resistor 3 is formed on the upper surface by sputtering.
μm is formed. Thereafter, after forming the resist 8-1, in FIG. 6B, normal etching is performed using an etching solution composed of a mixed acidic aqueous solution composed of phosphoric acid, acetic acid, nitric acid, pure water and the like. Further, in FIG. 6C, the resist 8a is removed by a stripping solution such as an organic solvent to form the wiring electrode 4a.
Is the first stage. Next, in FIG.
After the photoresist is applied again to form the second step of a, a photomask in which the contour of the exposure pattern is reduced by 5 μm or more with respect to the contour of the wiring electrode 4a formed in the first step of the wiring electrode 4a is used. By exposure and development, a resist 8-2 having the shape of the second-stage wiring electrode is formed. Next, FIG.
In (a), etching is performed using an etching solution composed of a mixed acidic aqueous solution containing phosphoric acid, acetic acid, nitric acid, pure water, and the like. The step 6 can be attached. Thereafter, in FIG. 7B, the resist 8-2 is removed with a stripping solution such as an organic solvent to form a two-stage wiring electrode 4a. Further, by repeating these steps, 3
It is also possible to form the wiring electrodes 4a of a level or more. Finally, a protective film 9 is formed. FIG. 7C shows the result of forming the protective film 9 on the wiring electrode 4a obtained in the present embodiment. It was confirmed that the step of the protective film 9 was smaller than in the conventional case. It has been confirmed that the level difference of the wiring electrode 4a is smaller in three stages than in two stages. That is,
By providing the wiring electrodes 4a in two or three stages, the same effect as that of the electrode taper can be obtained.

[Embodiment 5] Next, as shown in FIG. 8, a plurality of steps of photoresist development and etching are used to make the peripheral portion of the wiring electrode multi-step, so that the peripheral shape of the wiring electrode is tapered. A manufacturing method for obtaining the effect described above will be described.

FIG. 8A shows that a glaze 2 is formed on an insulating substrate 1 made of alumina ceramic or the like as in the first embodiment.
The heating resistor 3 is formed. As an electrode material for supplying electric power to the heating resistor 3, a film mainly composed of Al is formed to a thickness of 1 to 2 μm by sputtering. Thereafter, a resist 8a is formed, and in FIG. 8B, etching is performed by etching 10 to 90% of the film thickness with an etching solution including a mixed acidic aqueous solution including phosphoric acid, acetic acid, nitric acid, and pure water. To end.

After that, the resist 8 is formed by the conventional method.
Is removed in a stripping solution such as an organic solvent to form the wiring electrode 4a. However, since the developing solution has the characteristic of causing the film to decrease with respect to the resist 8, in this embodiment, as shown in FIG. After the etching, the resist 8 is immersed again in the developing solution to perform the second development for forcibly causing the film to be reduced, and the resist 8 is retreated by 5 μm or more. Next, in FIG. 8D, etching is performed using an etching solution composed of a mixed acidic aqueous solution composed of phosphoric acid, acetic acid, nitric acid, pure water, and the like, and the etching is completed to form the multi-step portion 6 on the wiring electrode. . Thereafter, in FIG. 9A, the resist 8 is removed with a stripping solution such as an organic solvent to form a two-stage wiring electrode 4a.

Further, by repeating these steps, it is possible to form three or more stages of wiring electrodes 4a.
Finally, a protective film 9 is formed. FIG. 9B shows the result of forming the protective film 9 on the wiring electrode 4a obtained in the present embodiment. Since the step at the periphery of the wiring electrode is stepped, the step of the protective film becomes gentler than in the related art, and the fault of the protection film at the periphery of the wiring electrode is suppressed. It should be noted that the step of the wiring electrode 4a in each step is more improved in the coverability of the protective film in three steps than in two steps. In an experiment by the inventors, when a protective film is formed by a normal sputtering method, the step is 0.2 to 0.1.
At about 3 μm, the step coverage was remarkably changed, that is, the occurrence or non-occurrence of the fault of the protective film at the step was changed. Therefore, it is desirable that each step is suppressed to 0.3 μm or less.

[Evaluation of Each Embodiment] Evaluation results of the above-described embodiments will be described below. Table 17 shows the evaluation results of this example when the taper angle 7 in FIG. 1 was changed.

In Table 17, the pulse resistance is an evaluation based on the magnitude of a change in the resistance value of the heating resistor with respect to the number of applied pulses when a voltage pulse is applied to the heating resistor. The corrosion resistance is an evaluation of the presence or absence of corrosion of the electrode and peeling of the protective film by contact with a thermal paper or a chemical under high temperature and high humidity. The scratch resistance is obtained by scuffing a protective film including a wiring electrode around the heating resistor with sandpaper or the like to evaluate the peeling of the protective film. The printing durability was evaluated by a failure occurrence rate when continuous printing was performed using poor thermal paper having high abrasion and containing many corrosive impurities.

From Table 17, it can be seen that the taper angle 7 is 60-3.
If it is less than 0 deg, it can be confirmed that each characteristic sharply improves. In the thermal head, especially during printing, heat generated from the heating resistor, the pressure of the platen roller, and the sliding of the thermal paper cause a large stress on the heating part and the periphery of the wiring electrode near the heating resistor. As can be clearly seen from Table 17, the overall printing durability including the above can be extremely good when the taper angle is 15 deg or less.

The above evaluation is an example in which the hardness of the protective film is about Hv of about 1500.
, Hv about 1200 and Hv about 1800 were also evaluated for scratch. Table 18 shows the results. From this result, it can be seen that in a conventional wiring electrode having a large step or taper angle and a large step, even if the hardness is increased, the printing durability is not so high when the scratch is involved. This is because a soft material such as Al is used for the wiring electrode, so that the harder the protective film is, the more the external force is applied by a foreign substance or the like, the more the force is transmitted in the surface direction of the film, and the fault portion of the protective film on the periphery of the wiring electrode It can be explained that it is because stress is gathered. Therefore, the effect of the present invention is Hv12
This is particularly noticeable in a thermal head having a protective film of 00 or more. The present invention provides an H film, because a protective film having high hardness is advantageous for abrasion resistance, and as long as the protective film has continuity in the surface direction, scratch resistance is also increased as a result.
The maximum effect can be exhibited by combining with a protective film of v1200 or more.

The evaluation results of this embodiment when the taper angle 7 is 15 deg will be described below in detail. FIG. 11 shows a print running durability test of the present invention. In the conventional example, when the printing travel distance is about 50 km, the step portion of the electrode triggers the peeling or chipping of the protective film from the tomographic portion of the protective film due to mechanical stress or scratch. As a result, the printing travel distance 100
At 10 km, the defective dot becomes 10%, whereas in the present embodiment, the protective film is peeled off even after printing at 100 km or more.
No phenomena such as chipping occurred. Further, by setting the hardness of the protective film to Hv1200 or more, the amount of wear of the protective film is reduced to two.
μm or less. In other words, in the present embodiment, various destructions can be suppressed by increasing the hardness of the protective film by tapering the electrode to remove the protective film, chipping, and abrasion of the protective film, which have been the causes of the conventional destruction, and printing. It can be confirmed that the durability is four times or more that of the conventional example, and the printing traveling property is improved.

FIG. 12 shows the results of a continuous pulse current test for evaluating the pulse resistance of the present invention. In the conventional example, the rise in resistance value is about 5% at 1 × 10 ⁸ pulses, and 6 × 10
^{With 8} pulses, it is 15% or more. However, in the present embodiment, the resistance value does not change even at 1 × 10 ⁸ pulses, and the resistance value increases at about 3% even at 6 × 10 ⁸ pulses, and the pulse resistance is improved. That is, in the present embodiment, although the heating resistor has been deteriorated due to oxidation or the like due to the protection film tomographic portion due to the electrode step, it is possible to prevent the heating resistor from being deteriorated by tapering the electrode. It was confirmed that the pulse resistance was improved.

FIG. 13 shows the results of an electrolytic corrosion test for evaluating the corrosion resistance of the present invention. In the test, a standing test was performed in a state where the temperature was 85 ° C., the humidity was 85%, the head voltage was 5 V, and the thermal paper was applied. In the conventional example, a large number of defective dots are generated from the initial stage, and are 5% or more in 48 hours, and about 15% in 96 hours.
At r, no defective dots were recognized, and only about 3% of defective dots were recognized at 96 hours. That is, in this example, it was confirmed that the electrode taper prevents moisture and ions of the thermal paper from easily penetrating, thereby preventing corrosion of the electrode and the like, and improving corrosion resistance.

In comparison with the conventional thermal head cross-sectional structure shown in FIG. 16, the taper of the electrode as shown in FIG.
The contact with a recording medium such as a platen roller is improved. FIG. 14 shows the results of the print density test of the present invention.

From the test results, it was confirmed that in this embodiment, even when the same print recording density as that of the related art was obtained, power saving of about 20% or more was possible, and the heat generation efficiency of printing was improved.

[0039]

According to the present invention, as described above, the step in the protective film is reduced by forming the electrode in the protective film region of the thermal head in a tapered shape, thereby suppressing the occurrence of a fault in the protective film. When the hardness is Vvickers hardness of Hv1200 or more, the abrasion resistance and the scratch resistance are remarkably improved, so that the printing durability is extremely increased, and the environmental reliability is also improved.

The manufacturing method of the present invention for tapering the cross-sectional shape of the peripheral portion of the wiring electrode can be performed without using a special apparatus such as a bias sputtering apparatus. By using the modified processing, the peripheral section of the electrode can be tapered without increasing the number of steps.

[Brief description of the drawings]

FIG. 1 is an enlarged sectional view of a heat generating portion and a sectional view of an electrode peripheral portion of a thermal head according to the present invention.

FIG. 2 is an enlarged sectional view of a heat generating portion of the thermal head of the present invention and a sectional view of an electrode peripheral portion.

FIG. 3 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 4 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 5 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 6 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 7 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 8 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 9 is an explanatory view showing a manufacturing process of the thermal head of the present invention.

FIG. 10 is an enlarged sectional view of a heat generating portion and a sectional view of an electrode peripheral portion of a conventional thermal head.

FIG. 11 is an explanatory diagram showing a print running test result of the thermal head of the present invention.

FIG. 12 is an explanatory diagram showing a result of a continuous pulse conduction test of the thermal head of the present invention.

FIG. 13 is an explanatory diagram showing the results of an electrolytic corrosion test of the thermal head of the present invention.

FIG. 14 is an explanatory diagram showing a print density test result of the thermal head of the present invention.

FIG. 15 is an explanatory diagram showing a contact portion between the thermal head of the present invention and a recording medium.

FIG. 16 is an explanatory diagram showing a contact portion between a conventional thermal head and a recording medium.

FIG. 17 is a chart showing evaluation results of the example.

FIG. 18 is a table showing evaluation results of the scratch test of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 Insulating substrate 2 Glaze 3 Heating resistor 4, 4 a, 12 Wiring electrode 4 b Al electrode 4 c Al alloy electrode 4 d Al electrode with different particle size 5 Tapered section 6 Multi-step section 7 Tapered angle 8, 8-1, 8-2 Resist 9 Protective film 10 Protective film fault section 11 Recording medium

Claims (3)

[Claims] A first step of forming a heating resistor on an insulating substrate; a second step of forming a wiring electrode electrically connected to the heating resistor; and a step of forming a heating resistor and the periphery of the heating resistor. A third step of forming a protective film covering the wiring electrode, wherein the second step forms a wiring electrode thin film composed of a material having a higher etching rate as the distance from the substrate increases. A film forming step, a step of forming a resist on the wiring electrode thin film, and a step of forming the wiring electrode by performing a single etching process on the wiring electrode thin film with one type of etchant. A method of manufacturing a thermal head, comprising forming a wiring electrode in which a cross-sectional shape of an electrode peripheral portion is tapered. 2. The film forming step includes: forming a first electrode film containing Al as a main component; and forming an Al alloy electrode film containing an additive on the first electrode film. The method for manufacturing a thermal head according to claim 1, wherein a thin film for a wiring electrode is formed by being provided. 3. The film forming step includes a step of forming a thin film for a wiring electrode by a sputtering method in which conditions are changed with the passage of time. The method according to claim 3, wherein the grain system is a small Al thin film.