JPH08288611A - Manufacture of thermal head - Google Patents

Abstract

PURPOSE: To make the reflectivity of a glazed layer equivalent to that of individual electrodes by lowering the surface roughness of an insulating substrate underlying a photoresist or of the one having higher reflectivity against the light used for exposing a photoresist of the metal films formed on the insulating substrate. CONSTITUTION: A glazed layer 2 is formed on an insulating substrate 1 and baked. The surface roughness of an area 10 on the surface of the glazed layer 2 having high reflectivity is lowered by roughening the surface of the area 10 by lapping. The reflectivity of the area 10 can be lowered to 40% by increasing the surface lapping amount of the layer 2. The reflectivity of the metallic films of an individual electrode 3 and common electrode 4, on the other hand, is about 50% when the film is composed of one metallo-gold film and about 10% when the film is composed of three metallo-gold films. Although the reflectivity drops as the number of metallo-films increases, the reflectivity does not drop much and falls within the range of 10-50% even when the number of metallo-gold films increases from three. The reflectivity of the surface of the glazed layer 2 can be made equivalent to that of the electrodes 3 and 4 by changing the surface lapping amount of the the layer 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention In the present invention, a metal film is formed on a part of an insulating substrate, the same photoresist is applied on the insulating substrate and the metal film, and the photoresist is subjected to pattern exposure and development. The present invention relates to a method for forming a pattern conductive film on an insulating substrate and a metal film by using a resist pattern formed by the above method, and more particularly to a method for forming a heating resistor of a thermal head in a uniform rectangular shape.

[0002]

2. Description of the Related Art Conventionally, a thick film type thermal head used in a recording section of a facsimile, a printer or the like has an insulating substrate as shown in FIGS. 5 (a), 5 (b) and 5 (c). 1 further forms a glaze layer 2 which is an insulating substrate,
A plurality of individual electrodes 3 and a common electrode 4 made of a metal film are alternately formed on the upper portion of the common electrode 4 at predetermined intervals, and the common electrodes 4 are connected by a common electrode body portion 6. A band-shaped heating resistor 5'is formed so as to cover the portion, and the whole is covered with an insulating overglaze layer 7. In addition, FIG. 5A shows the overglaze layer 7
It is a plane explanatory view showing a part of thick film type thermal head in the state where it omitted. (B) is an AA 'cross section explanatory view of (a), and (c) is BB of (a). ′ It is a cross-sectional explanatory diagram.

The glaze layer 2 is made of a material that does not dissipate the heat generated by the heating resistor 5'to the side of the insulating substrate 1 on the lower surface, and is an indispensable structure in a thermal head for printing by heat. . Each individual electrode 3 is connected to a driving IC (not shown), and each common electrode 4 is connected to an electrode (not shown) through a common electrode body 6 reinforced with a material having a small resistance value to have the same potential. Is kept.
When a signal is applied from the driving IC to each individual electrode 3, 1
Between the individual electrodes 3 and the two common electrodes 4 arranged on both sides thereof, electricity is selectively applied to generate heat in a corresponding area (corresponding to one dot) of the heating resistor 5 ', and the heating portion is shown in the figure. The printing is performed by melting the heat-sensitive recording paper or the ink film which comes into contact with the printing roller by pressing force.

In order to obtain a high quality image using this thick film type thermal head, it is necessary to form the heating resistor 5'in a uniform rectangular shape in order to make the dot sizes uniform. Furthermore, the heating resistor 5'is formed so that the width in the sub-scanning direction is a fraction of the conventional width, one pixel is composed of a plurality of dots in the sub-scanning direction, and the sum of the areas of the plurality of dots in the pixel is used. In order to perform halftone recording with a large number of gradations by adopting the sub-scanning division method for reproducing gradations, it is necessary to narrow the width of the heating resistor 5'in the sub-scanning direction and subdivide one pixel. is there.
In this case, the influence on the print quality due to the variation in the resistance value of the heating resistor 5'becomes more serious, so that it is necessary to form a more accurate and uniform rectangular heating resistor 5 '.

Next, a method of forming the heating resistor 5'of this thick film type thermal head will be described with reference to FIGS. FIG. 6A and FIG. 7A are plan explanatory views showing the manufacturing process of the conventional thick film type thermal head.
(B) and FIG. 7 (b) are respectively FIG. 6 (a) and FIG. 7 (a).
7A is a cross-sectional view taken along the line AA ′ of FIG. 7B, and FIG.
It is a B'cross section explanatory drawing.

First, as shown in FIG. 6A, a glaze layer 2 of an insulating substrate is further formed on an insulating substrate 1, and an individual electrode 3, a common electrode 4 and a common electrode body 6 are formed on the glaze layer 2.
Are simultaneously formed of a metal film, and then a photoresist 8 is entirely applied on the insulating substrate 1. Next, the heating resistor 5 '
The photoresist 8 is exposed by using a mask pattern 11 that masks the portion where the film is to be formed.

Next, the photoresist 8 is developed to form an opening 12 'in the photoresist 8 as shown in FIG. The opening 12 'does not have a rectangular shape like the mask pattern 11 and has an opening width on the surface of the glaze layer 2 (see FIG. 7).
Compared to (c)), on the individual electrode 3 and the common electrode 4 (see FIG. 7).
In (b)), it opens wide. Generally, when exposing a photoresist, if the surface roughness of the film on the lower surface is low, the light passing through the unmasked portion of the photoresist will be diffusely reflected due to the unevenness of the film surface. ,
A phenomenon occurs in which the photoresist is penetrated again and the photoresist portion to be masked is also exposed. The reason why the shape of the opening 12 'is not rectangular is that the metal film of the individual electrode 3 or the common electrode 4 having a low surface roughness and a low reflectance and the glaze layer 2 having a high surface roughness and a high reflectance are reflected. It can be inferred that this is because the diffused reflection due to the surface roughness does not occur uniformly because the difference in the rates is large. Next, a heating resistor paste is embedded in the opening 12 'of the photoresist 8 and the excess heating resistor paste other than the opening 12' of the photoresist 8 is removed, followed by firing, as shown in FIG. As shown in a), a heating resistor 5'having the same shape as the opening 12 'is obtained.

When the ceramic layer 2'is used instead of the glaze layer 2, the reflectance of the surface of the ceramic layer 2'is lower than that of the metal film. As a result, a wide opening is formed on the surface of the ceramic layer 2 '.

As described above, the opening 1 of the photoresist 8 is formed.
Since 2'is not formed in a shape reflecting the shape of the mask pattern 11, the heating resistor 5'formed in the opening 12 'also reflects the shape of the opening 12'.
There is a problem in that a desired uniform rectangular heating resistor cannot be obtained, the heating portion area (resistance value) of each dot varies, and a high-quality image cannot be obtained. In particular, when halftone recording is performed by using the sub-scanning division method, it is difficult to obtain a high number of gradations, the dot shape is disturbed, and uneven printing occurs, and lines and figures become unclear. There was a problem.

[0010]

As a case similar to the above problem, conventionally, in order to pattern a metal film, a photoresist is directly coated on the metal film to form a desired mask pattern. Diffuse reflection on the metal film surface when the resist pattern is exposed and developed to form a resist pattern, and the metal film is selectively etched by an etching method using this resist pattern as a mask to form a wiring pattern. As a result, the pattern transferred to the photoresist becomes distorted compared to the mask pattern, and this distortion is reflected in the metal film, which not only lowers the accuracy and reliability of the metal film patterning. However, there is a case where the yield of the product is reduced.

As a solution to this problem, a method disclosed heretofore will be described below. FIG. 8 shows
It is a cross-sectional explanatory drawing of the patterning process of the metal film disclosed by the Unexamined-Japanese-Patent No. 35239. According to this method, the metal film 2
By forming the antireflection film 24 between the photoresist 3 and the photoresist 25, the light rays that have passed through the photoresist 25 when the photoresist 25 is exposed are weakened in the antireflection film 24, and diffuse reflection on the surface of the metal film 23 is prevented. It is to suppress. However, according to this method, the antireflection film 2
4 is newly applied and dried, which causes a problem that the process is complicated.

FIG. 9 is a cross-sectional explanatory view of a method for manufacturing a thick film wiring substrate disclosed in Japanese Patent Laid-Open No. 5-211382. According to this method, a dye-doped photoresist 24 'is formed between the metal film 23' and the photoresist film 25 'by doping a dye having an absorption wavelength region of a specific light beam, thereby forming a photoresist. The light rays which have passed through the photoresist 25 'when the resist 25' is exposed are absorbed in the dye-doped photoresist 24 'to prevent irregular reflection on the surface of the metal film 23'. However, the range of the wavelength range of light rays that can be absorbed by the dye is short, and it is necessary to select and use a dye that matches the wavelength to be used. Also, do not add dye in the photoresist.
Even if the light is reflected, the reflection of light rays cannot be sufficiently absorbed, the diffuse reflection is large and the pattern of the photoresist 25 'is disturbed, and the dye-doped photoresist 24' is easily melted during the development of the photoresist 25 '. However, there is a problem that the reliability of the resist pattern is low.

Both methods are intended to prevent the irregular reflection of light on the metal film, and a plurality of different films, such as the problem at the time of forming the heating resistor 5'of the thick film type thermal head described above. No problems have been considered when forming patterns simultaneously on top.

The present invention has been made in view of the above circumstances, and is a photoresist pattern formed on a photoresist.
In a method of manufacturing a thermal head using a photoresist to form a heating resistor, even if a plurality of films having different reflectances are present on the lower surface of the photoresist, a mask pattern shape used for exposing the photoresist is used after development. To a desired mask pattern by making the degree of reflection on the photoresist pattern uniform.
It is an object of the present invention to provide a method for easily forming a heating resistor that accurately reflects the shape of a heating element.

[0015]

In order to achieve the above object, the invention according to claim 1 is characterized by including the following steps in forming a thermal head. As a first step, a treatment for reducing the surface roughness is applied to a partial range (region A) on the insulating substrate. As a second step, a metal film having a reflectance lower than that of the insulating substrate is formed in a part of the region A on the insulating substrate. As a third step, a photoresist is applied so as to cover the entire insulating substrate. In the fourth step, a mask pattern (or a mask pattern obtained by inverting the mask pattern) that covers a part of each of the insulating substrate and the metal film and covers an area narrower than the area A is used to perform the photo. Expose the resist. As a fifth step, the photoresist is developed to form an opening. As a sixth step, a heating resistor is embedded in the opening formed in the photoresist.

The invention of claim 2 is characterized by including the following steps in forming the thermal head. As a first step, a metal film having a higher reflectance than that of the insulating substrate is formed on a part of the insulating substrate. Second
In the step (2), a process of reducing the surface roughness is performed on a region (region B) that partially covers the insulating substrate and the metal film. As a third step, a photoresist is applied so as to cover the entire insulating substrate. In the fourth step, a mask pattern (or a mask pattern obtained by inverting the mask pattern) that covers a part of each of the insulating substrate and the metal film and covers a region narrower than the region B is used. Expose the resist. As a fifth step, the photoresist is developed to form an opening.
As a sixth step, a heating resistor is embedded in the opening formed in the photoresist.

The invention of claim 3 is characterized in that the following steps are provided in forming the thermal head. As the first step, the amount of oxygen used for firing the insulating substrate is reduced and the insulating substrate is fired. As the second step,
A metal film having a reflectance lower than that of the insulating substrate is formed on a part of the insulating substrate. As a third step, a photoresist is applied so as to cover the entire insulating substrate. As a fourth step, the photoresist is exposed by using a mask pattern (or a mask pattern obtained by inverting the mask pattern) that covers a part of each of the insulating substrate and the metal film. As a fifth step, the photoresist is developed to form an opening. As a sixth step, a heating resistor is embedded in the opening formed in the photoresist.

The invention of claim 4 is characterized in that the following steps are provided in forming the thermal head. As a first step, a metal film having a higher reflectance than that of the insulating substrate is formed on a part of the insulating substrate. Second
In this step, the amount of oxygen used when firing the metal film is reduced and the metal film is fired. As a third step, a photoresist is applied so as to cover the entire insulating substrate.
As a fourth step, the photoresist is exposed by using a mask pattern (or a mask pattern obtained by inverting the mask pattern) that covers a part of each of the insulating substrate and the metal film. As a fifth step, the photoresist is developed to form an opening. As a sixth step, a heating resistor is embedded in the opening formed in the photoresist.

[0019]

According to the present invention, of the insulating substrate existing on the lower surface of the photoresist or the metal film formed on the upper surface of the insulating substrate, the surface roughness of the one having a higher reflectance for the light exposing the photoresist. By reducing the, it is possible to set the reflectance of both to a close value, to equalize the reflection of light when the same exposure is performed through the photoresist,
The degree of reflection of the mask pattern on the openings on the insulating substrate and the metal film can be made equal.

Further, in the insulating substrate or the metal film formed on the insulating substrate, one having a higher reflectance with respect to the light for exposing the photoresist is fired by reducing the amount of oxygen required for the firing. Therefore, the reflectance of both can be set to a close value, the reflection of light when the same exposure is performed through the photoresist is made equal, and the opening of the mask pattern on the insulating substrate and the metal film is made equal. The degree of reflection to can be made equal.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the thick film type thermal head according to the present invention will be described below with reference to FIG. FIG.
Is an explanatory view of a part of a thick film type thermal head,
5A is a plan explanatory view of the configuration excluding the overglaze layer 7, and FIG. 5B is a sectional view taken along the line AA ′ of FIG.
The same reference numerals are given to the parts having the same configuration as.

In the thick film type thermal head, a glaze layer 2 which is an insulating substrate is further formed on an insulating substrate 1, and a plurality of individual electrodes 3 and common electrodes 4 are alternately arranged at predetermined intervals on the glaze layer 2. Then, the common electrodes 4 are connected by the common electrode body 6, and the strip-shaped heating resistor 5 is formed so as to cover the individual electrodes 3 and a part of the common electrode 4. It is constituted by covering with a bar glaze layer 7.

Each individual electrode 3 is connected to a driving IC (not shown), and a signal is individually applied. Further, each common electrode 4 is connected to a common electrode body 6 respectively, and is connected to an electrode (not shown) via this common electrode body 6 to maintain the same potential. The common electrode body 6 is reinforced with a material having a small resistance value in order to suppress a voltage drop. Therefore, the heating resistor 5
Is connected to the plurality of individual electrodes 3 and the common electrode 4 which are alternately arranged at a predetermined interval on the lower surface thereof, and when a signal is applied to each individual electrode 3 from the driving IC, one individual electrode 3 is formed. Electrical conduction is selectively made between the electrode 3 and the two common electrodes 4 arranged on both sides thereof, and the heating resistor 5 in the corresponding region serves as a heating portion (corresponding to one dot) to generate heat. The thermal recording paper or the ink film which comes into contact with the printing roller (not shown) is melted for printing.

Next, a thick film type server according to an embodiment of the present invention.
A method of forming the heating resistor of the round head will be described with reference to FIGS. 2 (a) and 3 (a)
4A is a plan explanatory view of the manufacturing process of the thick film thermal head of the present invention, and FIG. 2B and FIG.
And FIG. 4 (b) are cross-sectional explanatory views of FIG. 2 (a), FIG. 3 (a) and FIG. 4 (a) taken along line AA ′, and FIG. 4 (c) is FIG. FIG.

First, as shown in FIG. 2, an insulating substrate 1 is prepared, and a glaze layer 2 which is an insulating substrate is further laminated thereon and fired. A metallo-gold film is used as the individual electrode 3 and the common electrode 4 formed on the glaze layer 2, but this metallo-gold film has a lower surface roughness than the glaze layer 2 and a light reflectance. Therefore, before forming the individual electrode 3 and the common electrode 4, the range of the region 10 on the surface of the glaze layer 2 having a high reflectance is rapped and roughened to lower the surface roughness. In the figure, the area 10 is wider than the area 9 where the heating resistor 5 is formed later.
The reflectivity of the surface of the glaze layer 2 before the lapping process is 90% or more, but it is 4% by increasing the lapping amount.
It can be reduced to 0% or less.

On the other hand, the reflectance of the metal film of the individual electrode 3 and the common electrode 4 is about 50% when the number of stacked metallogold films is one.
It is about 10% in three layers. The light ray reflectance decreases as the number of stacked metallogold films increases, but there is almost no difference in the light ray reflectance with three or more layers, and the light ray reflectance does not change even if the number of laminated layers increases. Further, although it depends on the gold content of the metallo-gold paste, the metal film of the individual electrode 3 and the common electrode 4 has a reflectance of 10 to 50% because it is rare that three or more layers are laminated. Therefore, by changing the amount of lapping on the surface of the glaze layer 2, the reflectivity of the glaze layer 2 can be made equal to the reflectivity of the individual electrode 3 or the common electrode 4. For example, when the reflectance of the glaze layer 2 is lowered to 40%, the difference in reflectance of light rays is 30% at the maximum. | Rg
−Rm | ≦ 30% (Rg: reflectivity of glaze layer 2, R
m: reflectance of metal film, metal compound film and conductive film of individual electrode 3 and common electrode 4, etc.), the same exposure was performed on the glaze layer 2 surface and the metal film surface through the photoresist. At this time, the reflection of light becomes almost the same, and the amount of light absorbed by the photoresist 8 can be made almost the same. Therefore, the photoresist 8 that almost reflects the mask pattern 11 on the glaze layer 2 and the metal film. The opening 12 can be formed.

Next, as shown in FIG. 3, after the individual electrode 3, the common electrode 4 and the common electrode body 6 are formed, a photoresist 8 is applied to the entire surface of the insulating substrate 1. Next, a mask pattern 11 for masking the portion where the heating resistor 5 is formed is set on the upper portion of the photoresist 8 and the photoresist 8 is exposed by an exposing means (not shown) on the upper portion. At this time, since the difference in reflectance between the surface of the glaze layer 2 and the surface of the metal film was within 30%, the reflection of light on both surfaces was almost the same, and the light rays absorbed by the photoresist were almost the same. The amount was almost the same.

Next, as shown in FIG.
Was developed to form the opening 12. The opening 12 of the photoresist 8 formed by the above method has a difference in opening width of 0.5 μm or less between the glaze layer 2 and the metal film of the individual electrode 3 and the common electrode 4, A good rectangular opening 12 was formed. Next, as shown in FIG.
A heating resistor paste was embedded in the opening 12 of the photoresist 8 and the excess heating resistor paste other than the opening 12 was removed, followed by firing to form the heating resistor 5. Since the heating resistor 5 reflects the shape of the rectangular opening 12 with high accuracy, it also has a rectangular shape with high accuracy.

Therefore, in the thick film type thermal head manufactured according to the present embodiment, the variation of the heating area between the dots is suppressed, so that the dot shape is stable and the printing unevenness is reduced, and the lines and figures are reduced. Becomes clearer and higher image quality is possible. In particular, when performing halftone recording using the sub-scanning division method, even if the sub-scanning width of the heating resistor is subdivided, the size of each dot becomes uniform, so high gradation recording can be performed.

Methods other than lapping to reduce the surface roughness of the glaze layer 2 include light etching, blasting and polishing. Light etching is gray
In this method, the surface roughness is lowered by immersing the copper layer 2 in hydrofluoric acid or an acid containing hydrofluoric acid. Light etching is for individual electrode 3
If it is performed before forming the common electrode 4, the metal film, the metal compound film and the conductive film to be used are not limited. For example, gold,
A transparent conductive film of silver, copper, nickel, chromium, ITO (indium tin oxide), or the like can be used as the electrode.

The blasting method is sand blasting,
There are shot blast, grit blast, wet blast and the like. The blasting method is a method in which hard particles are blown onto a metal surface at high pressure to remove scales, rusts, coating films, etc., but the surface roughness of the glaze layer 2 is lowered. For this, the hardness of the particles used for blasting and the spraying pressure are selected in relation to each other. The particles used for the blasting are preferably particles having a hardness higher than that of the glaze layer 2 and a small hardness difference, and the reflectance is gradually lowered when sprayed at a low pressure.

The individual electrode 3 and the common electrode 4 of the present invention are not limited to the metallogold film, and other metal films, metal compound films and conductive films may be used. When an aluminum film or a platinum film is used as a material for the individual electrodes 3 and the common electrode 4, the aluminum film or the platinum film has a reflectance of 95%.
% Or more, and the metal film has a higher glaze layer 2 (reflectance of 90%).
% Or more), and the glaze layer 2
Even if the treatment for lowering the surface roughness is not performed, the difference in the reflectance of the light rays is small, so that the opening shape of the photoresist 8 is not affected.

Next, a second embodiment of the present invention will be described. First, an insulating substrate 1 is prepared, a ceramic layer 2'of an insulating substrate is further formed on the insulating substrate 1, and a plurality of individual electrodes 3 and a common electrode 4 are alternately formed on the insulating substrate 1, and at the same time, the common electrodes 4 are formed. The common electrode body 6 is formed so as to be connected, and is reinforced with a material having a small resistance value in order to suppress a voltage drop. The reflectance of the ceramic layer 2'side is 5-10%
Is. The metal film of the individual electrode 3 and the common electrode 4 has a reflectance of 10 to 50% as described above when a metallogold film is used. Therefore, in the present embodiment, the metal film of the individual electrode 3 or the common electrode 4 having a high reflectance is used. Reduces surface roughness.

Next, the area 10 wider than that for forming the heating resistor is roughened by lapping it together with the ceramic layer 2'to prevent the individual electrodes 3 and the common electrode 4 from being broken. Lower. The reflectance of the surface of the ceramic layer 2'is almost unchanged even if lapping is performed. When a metallo-gold film is used as the individual electrode 3 and the common electrode 4, the reflectance is about the same as that of the ceramic layer 2 ′ surface when the number of laminated layers is 3 or more, and about 50% when the number of laminated metallo-gold films is 1 layer. The lapping treatment can reduce the amount to 35% or less. | Rm−Rc | ≦ 30% (Rm: reflectance of metal film, metal compound film and conductive film such as individual electrode 3 and common electrode 4, Rc: reflectance of ceramic layer 2 ′ surface)
In this case, when the same exposure is performed on the surface of the ceramic layer 2'and the surface of the metal film through the photoresist 8, the reflection of light is almost the same, and the amount of light absorbed by the photoresist 8 is also substantially the same. Therefore, it is possible to form the opening 12 of the photoresist 8 that substantially reflects the mask pattern 11 on the ceramic layer 2'and the metal film.
Thereafter, similarly to the first embodiment, the photoresist 8 is exposed and developed, and the heating resistor paste is embedded in the opening 12 formed in the photoresist 8 to obtain an accurate rectangular heating resistor 5. You can

Next, a third embodiment of the present invention will be described. Since the glaze of the insulating substrate is further laminated on the insulating substrate 1 and the reflectivity of the glaze is higher than the reflectivity of the metal film of the individual electrode 3 and the common electrode 4 or the like, it is suitable for firing the glaze. The amount of oxygen is 10% or less of the required amount of oxygen, and the firing is performed.
To form a protective layer 2. When the firing is performed while reducing the amount of oxygen in this way, the reflectance of the glaze layer 2 can be reduced to 40% or less as in the case of lapping. When a metallo gold film is used, the difference in reflectance is 30% at the maximum. Thereafter, similarly to the first embodiment, the photoresist 8 is exposed and developed, and the heating resistor paste is embedded in the opening 12 formed in the photoresist 8 to obtain a highly accurate rectangular heating resistor 5. be able to. Even after the glaze layer 2 is formed, even if various materials such as a metal film, a metal compound film, and a conductive film as the individual electrode 3 and the common electrode 4 are fired with a sufficient oxygen content, the firing temperature of the glaze layer 2 , The glaze layer 2 is not affected by the amount of oxygen and the reflectance does not change.

When an aluminum film or a platinum film is used as the material for the individual electrodes 3 and the common electrode 4,
Aluminum film and platinum film have a reflectance of 95% or more,
The reflectance of the metal film is higher than that of the glaze layer 2 (reflectance of 90% or more). Even if the amount of oxygen is not reduced during firing of the glaze layer 2, the difference in reflectance of light rays is obtained. Is small, it does not affect the opening shape of the photoresist 8.

Next, a fourth embodiment of the present invention will be described. A ceramic layer 2'of an insulating substrate is further laminated on the insulating substrate 1, and metal films of the individual electrodes 3 and the common electrode 4 are further deposited on the ceramic layer 2 '. Since the reflectance of this metal film is higher than that of the ceramics layer 2 ', the amount of oxygen required for firing the metal film of the individual electrode 3 or the common electrode 4 is 10%.
Baking is performed with an oxygen content of not more than%. When firing is performed while reducing the amount of oxygen in this way, similar to when lapping is performed,
The reflectance of the individual electrodes 3 and the common electrode 4 can be reduced to 35% or less, and when a metallo-gold film is used as the individual electrodes 3 and the common electrode 4, the difference from the reflectance of the ceramics layer 2'is at maximum. It will be 30%. Hereinafter, as in Example 2,
The photoresist 8 is exposed and developed, and the heating resistor paste is embedded in the opening 12 formed in the photoresist 8 to obtain the accurate rectangular heating resistor 5.

[0038]

According to the present invention, of the insulating substrate existing on the lower surface of the photoresist or the metal film formed on the insulating substrate, the surface having the higher reflectance for the light exposing the photoresist. By performing a treatment to reduce the roughness, or by performing the firing by reducing the amount of oxygen required at the time of firing the one having a higher reflectance, it is possible to set the reflectance of both to a close value, Through this, the difference in the amount of light absorbed by the photoresist when the same exposure is performed on both of them is reduced, and an opening is formed that uniformly reflects the mask pattern shape on the insulating substrate and the metal film. be able to. Therefore, by using the opening of the photoresist, it is possible to easily form the heating resistor having a shape that reflects the mask pattern with high accuracy.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a part of a thick film type thermal head according to an embodiment of the present invention, FIG.
(B) is AA 'cross section explanatory drawing of (a).

FIG. 2 is an explanatory diagram showing a manufacturing process of a thick film type thermal head according to an embodiment of the present invention, in which (a) is a plan explanatory diagram,
(B) is AA 'cross section explanatory drawing of (a).

FIG. 3 is an explanatory view showing a manufacturing process of a thick film type thermal head according to an embodiment of the present invention, in which (a) is a plan view.
(B) is AA 'cross section explanatory drawing of (a).

FIG. 4 is an explanatory view showing a manufacturing process of the thick film type thermal head according to the embodiment of the present invention, in which (a) is a plan view;
(B) is an AA 'cross section explanatory drawing of (a), (c) is (a).
FIG. 6 is a cross-sectional explanatory view taken along line BB ′ of FIG.

5A and 5B are explanatory views showing a part of a conventional thick film type thermal head, in which FIG. 5A is a plan explanatory view and FIG. 5B is an A- in FIG.
A'section explanatory drawing, (c) is BB 'sectional explanatory drawing of (a).

6A and 6B are explanatory views showing a manufacturing process of a conventional thick film type thermal head, in which FIG. 6A is a plan explanatory view, and FIG. 6B is an AA ′ sectional explanatory view in FIG.

7A and 7B are explanatory views showing a manufacturing process of a conventional thick film type thermal head, wherein FIG. 7A is a plan explanatory view, FIG. 7B is a sectional view taken along the line AA ′ of FIG. 7A, and FIG. It is a BB 'cross section explanatory drawing of (a).

FIG. 8 is a sectional explanatory view of a conventional patterning process of a metal film.

FIG. 9 is a cross-sectional explanatory view of a conventional method for manufacturing a thick film wiring substrate.

[Explanation of symbols]

1 ... Insulator substrate, 2 ... Glaze layer, 3 ... Individual electrode,
4 ... Common electrode, 5 ... Heating resistor, 6 ... Common electrode body, 7 ... Overglaze layer, 8 ... Photoresist, 9 ... Heating resistor forming region, 10 ... Surface roughness decreasing region, 11 ... mask pattern, 12 ... opening

Claims (4)

[Claims] 1. A step of subjecting a partial range (region A) on an insulating substrate to a treatment for reducing surface roughness, and a partial range of the region A on the insulating substrate, the insulating substrate Also forming a metal film having a low reflectance, applying a photoresist so as to cover the entire insulating substrate, covering each part of the insulating substrate and the metal film, and A step of exposing the photoresist using a mask pattern (or a mask pattern obtained by inverting the mask pattern) that covers a narrow area, a step of developing the photoresist to form an opening, and the photoresist And a step of embedding a heating resistor in the opening formed in the thermal head. 2. A step of forming a metal film having a reflectance higher than that of the insulating substrate in a partial area on the insulating substrate, and a region (region B) covering a part of each of the insulating substrate and the metal film. To reduce the surface roughness, a step of applying a photoresist so as to cover the entire insulating substrate, a part of each of the insulating substrate and the metal film, and A step of exposing the photoresist using a mask pattern (or a mask pattern obtained by inverting the mask pattern) that covers a narrow area, a step of developing the photoresist to form an opening, and the photoresist And a step of embedding a heating resistor in the opening formed in the thermal head. 3. A step of baking by reducing the amount of oxygen used when baking an insulating substrate, and a step of forming a metal film having a reflectance lower than that of the insulating substrate in a partial area on the insulating substrate. And a step of applying a photoresist so as to cover the whole of the insulating substrate, and a mask pattern (or an inverted mask pattern) for covering a part of each of the insulating substrate and the metal film.
Exposing the photoresist using a photoresist, forming an opening by developing the photoresist, and embedding a heating resistor in the opening formed in the photoresist. A method of manufacturing a characteristic thermal head. 4. A step of forming a metal film having a reflectance higher than that of the insulating substrate on a part of an insulating substrate, and a step of baking by reducing the amount of oxygen used when baking the metal film. And a step of applying a photoresist so as to cover the whole of the insulating substrate, and a mask pattern (or an inverted mask pattern) for covering a part of each of the insulating substrate and the metal film.
Exposing the photoresist using a photoresist, forming an opening by developing the photoresist, and embedding a heating resistor in the opening formed in the photoresist. A method of manufacturing a characteristic thermal head.