JPH0577466A - Production of thermal head - Google Patents

Abstract

PURPOSE:To reduce manufacturing cost and to easily align the pattern of a glaze layer with that of a heating resistor. CONSTITUTION:A polyimide resin is applied to an alumina ceramic substrate 11 and a photoresist is applied to the polyimide resin layer and, after a polyimide resin pattern is formed to the photoresist, the photoresist is exposed, developed and etched to form a strip like polyimide resin layer 17 extending in a main scanning direction. A metal is applied to the layer 17 by vapor deposition and the photoresist and the metal film on the photoresist are peeled off to expose the polyimide resin layer 17. Continuously, the photoresist is applied and, after a lead electrode pattern is formed to the photoresist, the photoresist is exposed, developed and etched to form lead electrodes 13. Next, the whole is subjected to sputtering to form the film of a heating resistor 18. Since a process applying etching to a glaze layer 12 becomes unnecessary, it becomes unnecessary to perform alignment when etching is performed in order to form the lead electrodes 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a thermal head.

[0002]

2. Description of the Related Art Conventionally, in a thermal printer, one or a plurality of heating resistors are provided on a substrate to form a thermal head, and a drive current is supplied to the heating resistors via lead electrodes to generate heat. Then, the heat is used to print on a thermal paper, or a thermal transfer film is used to perform thermal transfer for printing. A glaze layer is formed between the heating resistor and the substrate, and the heat generated by the heating resistor is stored in the glaze layer.

In this case, the glaze layer is etched to form a convex portion, or the glaze layer is projected in two steps by printing to form a convex portion, and the surface of the heating resistor of the convex portion is used as a lead electrode. It is higher than the surface (JP-A-57-4507).
See Japanese Patent Publication No. 3). 2 is a plan view of a conventional thermal head, and FIG. 3 is a sectional view of the conventional thermal head.

In the figure, 1 is a substrate and 2 is a glaze layer formed on the substrate 1. On the surface of the glaze layer 2, a convex portion 2a having a width of the sub-scanning length is formed by chemical etching, plasma etching, grinding, printing or the like. A heating resistor 3 is formed on the glaze layer 2. The heating resistor 3 is formed such that a large number of strips separated from each other are arranged in parallel as shown in FIG. 4,
Reference numeral 5 is a lead electrode formed on the heating resistor 3 other than the convex portion 2a, and 6 is a protective film formed so as to cover the entire surface of the laminated body having the above structure.

With the above-described structure, the surface of the heating resistor 3 projects above the lead electrodes 4 and 5,
Since the contact state with the thermal paper or the thermal transfer film is improved, the printing efficiency is improved. Further, when the above technique is applied to the partial glaze type thermal head in which the glaze layer 2 is formed in the portion where the heating resistor 3 is formed, the nip pressure between the platen roller and the heating resistor 3 is improved, and the smoothness is particularly low. The thermal transfer rate can be improved when thermal transfer recording is performed on a sheet.

[0006]

However, in the above-described conventional method of manufacturing a thermal head, the work of the manufacturing process becomes complicated and the manufacturing cost increases. That is, in the glaze layer 2, a step is formed by etching a required amount by etching other than a required portion by photolithography. Next, in order to prevent film breakage (step breakage) due to steps when forming the thin film of the heating resistor 3, reflow is performed at a high temperature of about 800 ° C. to make the steps curved. Therefore, the number of manufacturing steps is increased, yield loss is likely to occur, and the manufacturing cost is increased.

When the pattern of the heating resistor 3 is formed on the glaze layer 2, photolithography is similarly used, but between the pattern for etching the glaze layer 2 and the pattern of the heating resistor 3. It is necessary to perform highly accurate alignment. However, the surface reflowed after etching a part of the glaze layer 2 has a gradual step, which makes it impossible to optically detect an edge, which makes alignment difficult.

Also, when the glaze layer 2 is partially projected in two steps, not only the number of times of printing and baking increases but yield loss easily occurs, but also pattern alignment becomes difficult. I will end up. The present invention solves the problems of the conventional method of manufacturing the thermal head, reduces the manufacturing cost when the glaze layer below the heating resistor is partially convex, and reduces the pattern of the glaze layer and heat generation. It is an object of the present invention to provide a method of manufacturing a thermal head, which can be easily aligned with a resistor pattern.

[0009]

Therefore, in the method of manufacturing a thermal head of the present invention, a polyimide resin is applied on a substrate, a photoresist is applied on the polyimide resin, and the polyimide resin is applied to the photoresist. A pattern is formed, exposed, developed, and then etched to form a strip-shaped polyimide resin layer extending in the main scanning direction.

Then, a metal is vapor-deposited thereon, and the photoresist and the metal film on the photoresist are peeled off to expose the polyimide resin layer. Subsequently, a photoresist is applied, a lead electrode pattern is formed on the photoresist, exposed, developed, and etched to form a lead electrode. The lead electrodes are separated into individual electrodes and common electrodes by the strip-shaped polyimide resin layer.

Next, the whole is sputtered to form a film of a heating resistor.

[0012]

According to the present invention, the polyimide resin is coated on the substrate as described above, the photoresist is coated on the polyimide resin, and the polyimide resin pattern is formed on the photoresist, exposed and developed. After that, etching is performed to form a strip-shaped polyimide resin layer extending in the main scanning direction.

Then, a metal is vapor-deposited thereon, and the photoresist and the metal film on the photoresist are peeled off to expose the polyimide resin layer. A portion other than the polyimide resin layer has a metal film formed thereon.
Subsequently, a photoresist is applied, a lead electrode pattern is formed on the photoresist, exposed, developed, and etched to form a lead electrode. The lead electrodes are separated into individual electrodes and common electrodes by the strip-shaped polyimide resin layer.

Next, the whole is sputtered to form a film of a heating resistor. At this time, a step is formed between a portion where the polyimide resin layer and the lead electrode are formed and a portion where the lead electrode is not formed, and the portions are electrically separated. Therefore,
Since the step of etching the glaze layer is unnecessary,
It is not necessary to perform alignment when performing etching for forming the lead electrode.

[0015]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 is a perspective view of a thermal head manufactured by the manufacturing method of the present invention, FIG. 4 is a plan view of a thermal head manufactured by the manufacturing method of the present invention, and FIG.
FIG. 6 is a manufacturing process diagram of the thermal head manufacturing method of the present invention, and FIG. 6A shows the state of the photoresist coating and curing process, FIG. 6B shows the state of the conductive metal vapor deposition process, FIG. 6C shows the state of the heating resistor sputtering process, and FIG. 6D shows the protective film. The state of the sputtering process is shown.

In FIGS. 1 and 4, 11 is an alumina (Al ₂ O ₃ ) ceramic substrate, 12 is a glaze layer which is formed on the alumina ceramic substrate 11 to form a base material and which stores heat, and 13 is a glaze layer. It is a lead electrode formed on the glaze layer 12. The lead electrode 13 is composed of a common electrode 14 and an individual electrode 15, and a drive current corresponding to print data is passed.

Reference numeral 17 denotes a strip-shaped polyimide resin layer extending in the main scanning direction between the common electrode 14 and the individual electrode 15. Reference numeral 18 is a metal heating resistor that covers the entire surface. The heating resistor 18 is formed on the strip-shaped portion 18a formed on the surface of the polyimide resin layer 17, the electrode portion 18b formed on the surfaces of the common electrode 14 and the individual electrode 15, and the surface of the glaze layer 12. It consists of a glaze layer portion 18c. The strip portion 18a contributes to heat generation, but the electrode portion 18b and the glaze layer portion 18c do not contribute to heat generation. Reference numeral 19 is a protective film that covers the heating resistor 18.

Next, the manufacturing process of the method of manufacturing the thermal head of the present invention will be described with reference to FIGS.
First, a polyimide resin is applied to the alumina ceramic substrate 11 having the glaze layer 12 formed on the entire surface by, for example, spin coating so as to have a thickness of 1 μm, and is cured.
The conditions for curing are, for example, a temperature of 350 ° C. and a treatment time of 1 hour. A photoresist 21 is applied thereon so as to have a thickness of 3 μm or more and cured (see FIG. 6).
(See (a)). Conditions for curing include, for example, a temperature of 90
C. and processing time is about 30 minutes.

Next, a polyimide resin pattern having a width corresponding to the length of the heating resistor 18 in the sub-scanning direction is exposed on the photoresist 21 and developed, and then the polyimide resin is etched. For example, resolution 8 dots /
For a mm thermal head, the width is about 150 μm. In addition, hydrazine is used for the above etching.
After that, a conductor metal is vapor-deposited (see FIG. 6B). For example, Al is used as the metal, and the film thickness of Al is 1 μm.

Next, ultrasonic cleaning is performed in acetone to remove the photoresist 21 on the polyimide resin pattern portion.
Is melted and the Al film deposited thereon is peeled off. At this time, the polyimide resin under the portion of the polyimide resin pattern remains. Next, a photoresist is applied again, and the lead electrode pattern is exposed, developed, and cured. And
Using the lead electrode pattern as a mask, the Al film is etched with an etching solution of H ₃ PO ₄ : HNO ₃ : CH ₃ COOH: H ₂ O = 16: 1: 2: 1, for example.

Thereafter, a film of the heating resistor 18 made of a metal such as Ta ₂ N is formed by sputtering (FIG. 6C).
Then, as a protective film 19, for example, SiO ₂ and T
A film of a ₂ O ₅ is formed to a thickness of 2 μm by sputtering. At this time, the thickness of the heating resistor 18 is 1
If it is about 000Å, the lead electrode 13 and the glaze layer 1
When the step between the two is 1 μm, a step break occurs and the heating resistor 18
Is electrically separated into a strip portion 18a that contributes to heat generation, and an electrode portion 18b and a glaze layer portion 18c that do not contribute to heat generation.

The present invention is not limited to the above-mentioned embodiments, but various modifications can be made based on the spirit of the present invention, and they are not excluded from the scope of the present invention. For example, when the temperature for curing the polyimide resin is 140 ° C. and the treatment time is 30 minutes, the polyimide resin can be etched with a developing solution in the photoresist developing step. in this case,
The polyimide resin needs to be cured twice, and is treated at 350 ° C. for 1 hour after dissolving the photoresist.

[0023]

As described in detail above, according to the present invention, a polyimide resin is applied on a substrate, a photoresist is applied on the polyimide resin, and a polyimide resin pattern is formed on the photoresist. After exposure, development, and etching are performed to form a strip-shaped polyimide resin layer extending in the main scanning direction. Then, a metal is vapor-deposited thereon, and the photoresist and the metal film are peeled off to expose the polyimide resin layer. Then, a photoresist is applied again, a lead electrode pattern is formed on the photoresist, exposed, developed, and etched to form a lead electrode. Next, the whole is sputtered to form a film of a heating resistor.

Therefore, no metal is formed on the strip-shaped polyimide resin, and when a film of the heating resistor is formed on this, only this portion automatically becomes the heating element portion. In addition, the process for forming the protrusions is simplified, and the alignment of the protrusions with the lead electrode pattern or the heating resistor pattern becomes unnecessary (self-alignment). And
Since the polyimide resin has a low thermal conductivity and a low specific heat, it has a heat storage effect, and the thermal efficiency is improved as compared with the case where the convex portion is formed on the glaze layer.

Further, since the heating resistor is sputtered after forming the lead electrode, the lead electrode and the heating resistor are electrically connected only at the interface of the polyimide resin, and the individual terminals are separated from each other. It becomes unnecessary and the manufacturing process for forming the heating resistor is simplified.

[Brief description of drawings]

FIG. 1 is a perspective view of a thermal head manufactured by a manufacturing method of the present invention.

FIG. 2 is a plan view of a conventional thermal head.

FIG. 3 is a sectional view of a conventional thermal head.

FIG. 4 is a plan view of a thermal head manufactured by the manufacturing method of the present invention.

FIG. 5 is a manufacturing process diagram of the method for manufacturing the thermal head of the present invention.

FIG. 6 is a state diagram of a manufacturing process in a method of manufacturing a thermal head according to the present invention.

[Explanation of symbols]

 11 Alumina Ceramic Substrate 12 Glaze Layer 13 Lead Electrode 14 Common Electrode 15 Individual Electrode 17 Polyimide Resin Layer 18 Heating Resistor 19 Protective Film 21 Photoresist

Claims (1)

[Claims] 1. A method comprising: (a) applying a polyimide resin on a base material, applying a photoresist on the polyimide resin; and (b) forming a polyimide resin pattern on the photoresist, exposing it, developing it, and then etching. To form a strip-shaped polyimide resin layer extending in the main scanning direction, (c) metal is vapor-deposited thereon, and (d) next, the photoresist and the metal film on the photoresist are peeled off, and The polyimide resin layer is exposed, (e) a photoresist is subsequently applied, and (f) a lead electrode pattern is formed on the photoresist, exposed, and developed to form a lead electrode by etching, and (g) a next step. A method of manufacturing a thermal head, characterized in that a film of a heating resistor is formed by sputtering the whole on a substrate.