JP2002225325A - Method for manufacturing thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a thermal head in which productivity can be enhanced by simplifying the manufacturing process. SOLUTION: A thermal head is patterned through a step for forming a multilayer 6 of heaters 3a and a pair of electrodes 4a and 4b by laying a thin resistive film 3 and a thin metal film 4 on the upper surface of a ceramic substrate 1, a step for coating the upper surface of the multilayer 6 entirely with a photoresist 7a of positive photosensitive resin, exposing and developing the resist 7a in the inverted pattern of the heaters 3a and the electrodes 4a and 4b and removing the thin metal film 4 and the thin resistive film 3 by etching from a part where the photoresist 7a is not present, and a step for further exposing and developing the photoresist 7a in accordance with the pattern of the heaters 3a and removing the thin metal film 4 by etching from a part where the photoresist 7a' is not present.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for manufacturing a thermal head incorporated as a printer mechanism in a facsimile, word processor, video printer, or the like.

[0002]

2. Description of the Related Art A thermal recording type image recording apparatus has a simple structure, is advantageous in miniaturization, weight reduction and cost reduction, and has a quiet recording sound and low power consumption. Therefore, it is widely used for recording purposes such as various printers and facsimile machines.

As shown in FIG. 4, for example, a thermal head used in such a thermal recording system has a large number of heating elements 12 linearly arranged on an upper surface of a ceramic substrate 11.
A pair of electrodes 13 electrically connected to these heating elements 12
a and 13b are adhered in a predetermined pattern, and while the recording medium such as thermal paper is fed onto the heating element 12, these heating elements 12 are individually selected based on external image data. Joule heat is generated, and the generated heat is conducted to the recording medium to form a predetermined print on the recording medium, thereby functioning as a thermal head.

[0004] The heating element 12 of the thermal head described above.
And a pair of electrodes 13a and 13b are patterned by the following process.

[0005] First, a resistive thin film of TaSiO or the like forming the heating element 12 and a metal thin film of aluminum or the like forming the pair of electrodes 13a and 13b are formed on the upper surface of the ceramic substrate 11 by a conventionally known sputtering method or vacuum evaporation method. Process in which the obtained laminate is finely processed by two photo-etchings, specifically, a resistive thin film and a metal thin film are formed into a heating element 12 and a pair of electrodes 13a, 1
The first photo-etching for patterning the laminate into a predetermined shape by etching along the outer shape of 3b, and the second photo-etching for etching a part of the metal thin film to expose the lower resistive thin film As a result, the heating element 12 and the pair of electrodes 13a, 13
and b were pattern-formed in a predetermined shape.

[0006]

However, according to the above-described conventional method for manufacturing a thermal head, the heating element 1
Photo-etching is performed twice to pattern the electrodes 2 and the pair of electrodes 13a and 13b. Previously, a photoresist using a photosensitive resin was applied and formed as an etching mask. Therefore, after the first photo-etching is completed and before the second photo-etching is performed, the photoresist used in the first photo-etching is peeled off from the surface of the metal thin film using a solvent or the like. A photosensitive resin must be applied again to the exposed surface of the thin metal film or the like to newly apply and form a photoresist for the second photo-etching. The formation of the patterns of the body 12 and the electrodes 13a and 13b requires a great deal of trouble, and has the disadvantage of poor productivity.

The present invention has been made in view of the above-mentioned drawbacks, and an object of the present invention is to provide a method of manufacturing a thermal head capable of simplifying a manufacturing process and improving productivity.

[0008]

A method of manufacturing a thermal head according to the present invention comprises a heating element made of a resistive thin film and a metal thin film on the upper surface of a ceramic substrate, and is electrically connected to both ends of the heating element. A thermal head formed by applying and forming a pair of electrodes, wherein the heating element and the pair of electrodes are formed by sequentially applying an electric resistance material and a metal material on an upper surface of a ceramic substrate, thereby forming a resistance thin film and a metal. A step of forming a laminate made of a thin film, and applying and developing a photoresist made of a positive photosensitive resin over the entire upper surface of the laminate, exposing and developing the photoresist to a reverse pattern of a heating element and an electrode, Thereafter, a step of continuously etching and removing the metal thin film and the resistive thin film in a portion where the photoresist does not exist, and further exposing and / or exposing the photoresist according to the pattern of the heating element. Thereafter, the resistive thin film in the heating element forming portion is exposed by etching away the metal thin film in a portion where no photoresist is present to form a heating element, and the metal thin film is separated on both sides of the exposed portion to form a pair. And forming a pattern through the step of forming an electrode.

According to the present invention, when patterning a heating element and a pair of electrodes, a resistive thin film forming a heating element and a metal thin film forming a pair of electrodes are sequentially laminated and adhered to the surface thereof. By exposing and developing a single photosensitive resin (photoresist) in two steps, the heating element and a pair of electrodes are finely processed. And the process of forming the pattern of the heating element and the pair of electrodes can be simplified, and the productivity of the thermal head can be improved.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a plan view of a thermal head manufactured by the manufacturing method of the present invention, and FIG. 2 is a cross-sectional view of the thermal head of FIG. 1, where 1 is a ceramic substrate, 3a is a heating element made of a resistive thin film, and 4a and 4b are metal. It is a pair of electrodes formed of a thin film.

The ceramic substrate 1 is formed in a rectangular shape from a ceramic material such as alumina ceramics, and has a glaze layer 2 and a heating element 3 on its upper surface.
A pair of electrodes 4a, 4b and the like are attached and formed, and function as a supporting base material for supporting them.

When the ceramic substrate is made of alumina ceramic, a ceramic green sheet formed by using a ceramic material such as alumina, silica, magnesia or the like is punched into a predetermined shape and then fired at a high temperature. Is done.

A glaze layer 2 is provided on the entire upper surface of the ceramic substrate 1, and a plurality of heating elements 3a and a pair of electrodes 4a, 4b are further provided on the upper surface of the glaze layer 2. It is attached and formed on a pattern.

The glaze layer 2 is formed of a low thermal conductive material such as glass, and stores a part of the heat generated by the heating element 3a therein, so that the temperature of the heating element 3a is required for printing in a short time. It functions as a heat storage layer for maintaining the thermal response characteristics of the thermal head satisfactorily at a predetermined temperature.

When the glaze layer 2 is made of glass, a predetermined glass paste obtained by adding and mixing an appropriate organic solvent or the like to glass powder is applied over the entire upper surface of the ceramic substrate 1 by a conventionally known screen printing method or the like. It is formed by printing and coating and baking it at a high temperature.

The plurality of heating elements 3a provided on the upper surface of the glaze layer 2 are arranged linearly in the main scanning direction at a density of, for example, 600 dpi (dots per inch) along one side of the ceramic substrate 1. For example, TaSiO
Electric resistance material such as TiSiO, TaN, etc.
Since it is formed by the resistive thin film 3 applied to a thickness of about 0.2 μm, when power supply power is applied through a pair of electrodes 4 a and 4 b described below, Joule heat is generated,
A predetermined temperature required for forming a print is obtained.

On the other hand, the pair of electrodes 4a and 4b are used to supply power to the heating element 3 when a driver IC (not shown) is driven.
, And a separate electrode 4b individually connected to each heating element 3a. For example, a metal such as aluminum (Al) or copper (Cu) is made of 0.3 μm to 2.
It is formed of a metal thin film 4 having a thickness of 5 μm.

Further, such a pair of electrodes 4a, 4b
Are patterned so that the leading end members facing each other across the heating element 3a extend toward the heating element 3a by about 10 μm to 50 μm at the center in the main scanning direction. The shape is such that the central area in the main scanning direction is narrower than both end areas.

A protective film 5 is further applied to the surfaces of the heating element 3a and the pair of electrodes 4a and 4b, and the heating element 3a and the pair of electrodes 4a and 4b are covered with the protective film 5. .

The protective film 5 is made of silicon nitride (Si ₃ N ₄ ), silicon carbide (SiC), sialon (Si—Al—O—N).
The heating element 3a and the pair of electrodes 4a and 4b are made of an inorganic material having excellent abrasion resistance and corrosion resistance such as corrosion caused by contact of moisture or the like contained in the atmosphere and deterioration of the recording medium. It works well to protect against abrasion due to sliding contact.

The protective film 5 is formed, for example, by a conventionally known sputtering method, and the above-mentioned inorganic material is coated on the upper surface of the heating element 3a or the glaze layer 2 provided with the pair of electrodes 4a, 4b by 3 μm. It is formed by applying a thickness of 10 μm to 10 μm.

Thus, in the above-described thermal head, while a recording medium such as thermal paper is conveyed onto a plurality of heating elements 3a, these heating elements 3a are selectively selectively heated based on external image data. At the same time, the generated heat is conducted to the recording medium to form an image on the recording medium, thereby functioning as a thermal head.

In the thermal head having such a structure, the shape of each heating element 3a in a plan view is narrower in the central area in the main scanning direction than in both end areas as described above. The amount of paper waste generated can be reduced by reducing the friction between the paper waste and the print quality, and the deterioration of printing quality due to the adhesion of paper waste can be effectively prevented. There is an advantage that can be reduced.

Next, a method for forming a pattern of the heating element 3 and the pair of electrodes 4a and 4b of the thermal head on the ceramic substrate 1 will be described with reference to FIG.

(1) First, a ceramic substrate 1 on which a glaze layer 2 is adhered is prepared.
As shown in FIG. 1, a laminate 6 including the resistance thin film 3 and the metal thin film 4 is formed.

The resistive thin film 3 and the metal thin film 4 employ a conventionally known thin film forming technique such as sputtering or vacuum deposition, and are provided with a glaze layer 2 of an electric resistance material such as TaSiO and a metal material such as Al. Formed on the upper surface of the ceramic substrate 1 in order.

The thickness of the laminate 6 is set to, for example, 0.01 μm to 0.2 μm for the resistance thin film 3 and to 0.3 μm to 2.5 μm for the metal thin film 4.

(2) Next, as shown in FIG. 3 (b), a photoresist 7a made of a photosensitive resin is applied and formed on the entire upper surface of the above-mentioned laminated body 6 by employing a conventionally known photolithography technique. I do.

As the photosensitive resin, a positive type photosensitive resin is used in which a portion irradiated with ultraviolet light is denatured and removed in an exposure / development process, and a liquid photosensitive resin having such properties is used. A conductive resin is applied to the upper surface of the laminate 6 by a well-known spin coating method, roll coating method, or the like, and is dried. Thereafter, the resin is applied to the shape of the heating element 3a and the electrodes 4a, 4b shown in FIG. The photoresist 7a is formed by exposing and developing the photosensitive resin using the photomask having the predetermined pattern.

In this exposure process, the ultraviolet light applied to the photosensitive resin through the above-described photomask is:
The photoresist 7a is exposed by the reverse pattern of the heating element 3a and the electrodes 4a and 4b, and developed to have a shape corresponding to the pattern of the heating element 3a and the electrodes 4a and 4b.

(3) Next, as shown in FIG. 3C, the metal thin film 4 and the resistive thin film 3 where the photoresist 7a is not present are continuously removed by employing a conventionally known etching technique.

In this etching, the laminate 6 is immersed in a strong acid-based etchant capable of etching both the metal thin film 4 and the resistive thin film 3, and a photoresist 7 is formed.
The layered body 6 in a portion where a does not exist is eroded with an etching solution
By removing the laminate 6
Is patterned along the outer shape of the heating element 3 and the pair of electrodes 4a and 4b.

(4) Then, as shown in FIG. 3D, the photoresist 7a remaining on the laminated body 6 is further exposed and developed into a pattern of the heating element 3a.
As shown in (e), the metal thin film 4 at the portion where the photoresist 7a does not exist is etched away.

In this exposure process, a photomask corresponding to the pattern of the heating element 3a is used. In the subsequent etching process, the pattern of the photoresist 7a 'obtained by exposing and developing using the above-described photomask is used. Accordingly, a part of the metal thin film 4 is etched away. That is,
The surface of the metal thin film 4 exposed by the above-described exposure and development is brought into contact with a strong acid-based etchant different from the previous etchant to remove a part of the metal thin film 4, thereby forming a resistive thin film in the heating element forming portion. 3 is exposed to form a pattern of a plurality of heating elements 3a, and the metal thin film 4 is separated into a common electrode 4a and an individual electrode 4b on both sides of the exposed portion, thereby obtaining a desired thermal head pattern.

According to the manufacturing method of the present embodiment as described above,
When patterning the heating element 3a and the pair of electrodes 4a and 4b, the laminated body 6 composed of the resistive thin film 3 and the metal thin film 4 is exposed and developed with a single photosensitive resin 7 in two steps, thereby forming the heating element. Since the 3a and the pair of electrodes 4a and 4b are finely processed, there is no need to peel off the photoresist 7a on the way or apply a new photoresist, and the heating element 3a and the pair of electrodes 4a and 4b are not required. 4
The process of forming the pattern b can be simplified. Therefore, the productivity of the thermal head is greatly improved.

When the thermal head is manufactured by the above-described method, the shape of each heating element 3a in plan view becomes narrower in the central area in the main scanning direction than in both end areas. This is because the corners of the electrodes 4a and 4b are eroded (side-etched) from the side surfaces at the time of the second etching, whereby a simple-to-care thermal head with a reduced amount of paper residue can be obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the spirit of the present invention.

For example, in the above embodiment, the photoresist 7a may be baked before performing the second etching in order to suppress the side etching of the metal thin film 4.

[0039]

According to the present invention, when forming a pattern of a heating element and a pair of electrodes, a resistive thin film forming a heating element and a metal thin film forming a pair of electrodes are sequentially laminated and adhered to the surface thereof. A single photosensitive resin (photoresist)
By exposing and developing in stages, the heating element and the pair of electrodes are finely processed, so that there is no need to peel off the photoresist in the middle or to apply a new photoresist, and the heating element and The process of forming the pattern of the pair of electrodes can be simplified, and the productivity of the thermal head can be improved.

[Brief description of the drawings]

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

FIG. 2 is a cross-sectional view of the thermal head of FIG.

3 (a) to 3 (e) are perspective views for each step for explaining a manufacturing method of the present invention.

FIG. 4 is a plan view of a conventional thermal head.

[Explanation of symbols]

1 ... ceramic substrate, 3 ... resistive thin film, 3a ...
Heating element, 4 ... Metal thin film, 4a, 4b ... A pair of electrodes, 6 ... Laminated body, 7a, 7a '... Photoresist

Claims (1)

[Claims] A thermal head comprising: a heating element made of a resistive thin film; and a pair of electrodes made of a metal thin film and electrically connected to both ends of the heating element, formed on an upper surface of a ceramic substrate. A method of manufacturing a thermal head, wherein the heating element and the pair of electrodes are formed in a pattern through the following steps 1 to 3. Step 1: a step of forming a laminate comprising a resistance thin film and a metal thin film by sequentially applying an electric resistance material and a metal material on the upper surface of the ceramic substrate. Step 2: A photoresist made of a positive photosensitive resin is applied to the entire upper surface of the laminate, and the photoresist is exposed and developed to a reverse pattern of a heating element and an electrode. Thereafter, the photoresist is not present. A step of continuously removing the metal thin film and the resistive thin film at the site by etching; Step 3: The photoresist is further exposed and developed in accordance with the pattern of the heating element, and thereafter, the metal thin film in a portion where the photoresist does not exist is removed by etching, thereby exposing the resistance thin film of the heating element forming portion to generate heat. Forming a body and separating the metal thin film on both sides of the exposed portion to form a pair of electrodes.