JPH09300680A - Manufacture of thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the photolitho accuracy, decrease the unevenness of resistance value of heat resistors and realize the real edge of a thermal head. SOLUTION: Patterns of heat resistors 4 and patterns of respective electrodes 5a and 5b are formed on a lagging layer 2 laminated on a base 1 on which a plurality of projected line sections 1a and recessed line sections 1b are formed by the photolitho processing, in which high voltage is applied to photoresists formed into ultrafine particles and a resist film formed on the surface of a base 2 placed on a grouding electrode by static coating is used as an etching mask.

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 used in a thermal printer, and more particularly, to a thermal head capable of reducing variations in resistance values of heating resistors and achieving a real edge. It relates to a manufacturing method.

[0002]

2. Description of the Related Art A thermal head mounted on a thermal printer has a plurality of heating resistors linearly arranged on a substrate and selectively energizes one of the heating resistors selectively in accordance with desired print information. By heating the heating resistor, the thermal recording paper is colored in the thermal printer, and in the thermal transfer printer, the ink of the ink ribbon is partially melted and transferred to plain paper to perform dot printing. The thermal head is constructed by forming a heating resistor on a substrate made of an insulating material such as ceramic or silicon via a heat insulating layer and an electrode pattern for energizing the heating resistor. are doing.

FIGS. 6 and 7 are sectional views showing the structure of a conventional thermal head. The thermal head shown in FIG. 6 has a plurality of projections formed by partial glazes on a substrate 1 made of an insulating material such as alumina. A heat insulating layer 2 is formed, a plurality of concave grooves 3 including a part of the convex heat insulating layer 2 are formed on one side of the convex heat insulating layer 2, and Ta-SiO ₂ or the like is formed thereon. The heating resistor 4 is formed, the common electrode 5a and the individual electrode 5b made of Al, Cu or the like are formed so as to supply electric power to the heating resistor 4, and finally the heating resistor 4 and each electrode 5a, 5b. It is formed by laminating a protective layer 6 made of sialon or the like for preventing the oxidation and wear.

Further, FIG. 7 shows that a single crystal substrate 1 made of silicon or the like is subjected to anisotropic etching and isotropic etching.
A plurality of high ridges 1a and deep ridges 1b are formed on a substrate 1, and a heat insulating layer 2 containing silicon oxide as a main component is laminated thereon by sputtering or the like, and Ta is formed on top of this.
A heating resistor 4 made of —SiO ₂ or the like is formed, and then A
The common electrode 5a and the individual electrode 5b made of Cu, Cu, etc. are formed, and finally the protective layer 6 made of sialon or the like is laminated.

[0005]

[Problems that the Invention is to Solve In the production method of such a conventional thermal head, the heating resistor 4 and the electrodes 5a, 5b are patterned, this heating resistor 3, the Ta-SiO ₂ or the like After applying the material of the heating resistor 3 to the surface of the heat retaining layer 2 by sputtering or the like,
It is formed by etching with a photolithography technique. If an attempt is made to apply the photoresist of this photolithography technique using a general spin coat or roll coat, the unevenness of the substrate 1 causes large unevenness of the coating, and the variation of the resist film thickness within the surface of the substrate 1 becomes large. . Therefore, there is a problem that the finished dimensional accuracy of the heating resistor 4 and each of the electrode patterns 5a and 5b is reduced, the resistance value of the thermal head is varied, the manufacturing specifications cannot be satisfied, and the manufacturing yield is significantly reduced.

FIG. 8 schematically shows the uneven coating of photoresist, in which the resist applied to the shoulders of the ridges of the substrate 1 is thin, and the hem and recess of the ridges are thick. .

Therefore, if the concave stripes and convex stripes of the substrate 1 are eliminated or reduced, the manufacturing yield is improved, but the printing quality of thermal transfer using the ink ribbon is remarkably deteriorated and the product of the thermal transfer printer is manufactured. There was a big problem that impaired sex. Further, in the manufacture of such a thermal head, since edge polishing of the diced end surface is indispensable, there is a problem that the manufacturing yield of the real edge thermal head and the accuracy of the edge distance are reduced, and the substrate with large unevenness is present. It has been desired to improve the accuracy of photoresist coating.

The present invention has been made in view of the above-mentioned points, and by forming a photoresist film on the surface of a substrate having a convex portion and a concave portion to have a substantially uniform thickness, the photolithographic accuracy is improved and the heating resistor is formed. It is an object of the present invention to provide a method of manufacturing a thermal head, which can reduce the variation in the resistance value of the thermal head and can achieve a real edge of the thermal head.

[0009]

In order to achieve the above object, the method of manufacturing a thermal head according to claim 1 of the present invention is formed by laminating on a substrate on which a plurality of convex stripes and concave stripes are formed. A resist formed by applying a high voltage to a photoresist made of ultrafine particles, and electrostatically applying the pattern of the heating resistor and the pattern of each electrode on the heat insulating layer to the surface of the substrate placed on the ground electrode. The thermal head manufacturing method according to claim 2, wherein the film is formed by photolithography using the film as an etching mask. The thermal head manufacturing method according to claim 1, wherein Is characterized as being submicron.

In the method of manufacturing a thermal head according to a third aspect of the present invention, a heat retaining layer is formed on a substrate on which a plurality of convex stripes and concave stripes are formed, and a photomicrograph of ultrafine particles is formed on the heat insulating layer. Apply a high voltage to the resist and electrostatically apply it to the surface of the substrate placed on the ground electrode to form a pattern of the heating resistor using the photoresist film formed as an etching mask. , A plurality of thermal head chips are obtained by forming a pattern of electrodes by using a photoresist film formed in the same manner as an etching mask, forming a protective layer on the upper surface thereof, and then dicing the groove bottoms of the recessed portions. It is characterized by that.

According to the method of manufacturing a thermal head of the present invention, a solvent-containing resist is used by using a method of electrostatically coating a photoresist in which submicron ultrafine particles are applied to a substrate having a large variation in unevenness. It is possible to form a resist film in which fine particles are almost uniformly attached to the substrate and the film thickness unevenness is small. By using this resist film as an etching mask, a heating resistor can be formed with high photolithographic accuracy, Variations in the resistance value of the heating resistor can be significantly reduced, and a deep groove is formed in advance on the substrate surface close to the high ridge, and finally the groove bottom of the deep groove is formed. By dicing, it becomes possible to easily and highly accurately form a real edge thermal head that separates the ink ribbon in the vicinity of the heat generating portion.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to FIGS. In addition, the portions denoted by the same reference numerals as those in the conventional FIG. 6, FIG. 7 and FIG. 8 indicate the same or corresponding portions.

FIG. 1 shows that a single crystal substrate 1 made of silicon or the like is formed on the substrate 1 by anisotropic etching and isotropic etching.
The ridge 1a having a height of about 10 to 20 μm and the ridge 1 having a depth of about 30 to 100 μm near the ridge 1a.
b is formed. A heat insulating layer 2 is laminated on the substrate 1. A plurality of heating resistors 4 are formed on the upper surface of the ridge 1a on the heat retaining layer 2. The heating resistors 4 are made of Ta-SiO ₂ or the like by sputtering or the like. After being deposited on the surface of the heat insulating layer 2 by means of, a photolithographic technique is used for etching.

A common electrode 5a connected to each heating resistor 4 is laminated on one side of the surface of each heating resistor 4, and the other side of each heating resistor 4 and the substrate 1 ( On the wall surface of the recessed portion 1b of the substrate 1 in FIG. 1, individual electrodes 5 for independently energizing each heating resistor 4 are provided.
b is formed. In the present embodiment, the common electrode 5a and the individual electrode 5b are made of, for example, Al, Cu, etc., and are deposited in the same shape as the heating resistor 4 by sputtering or the like and then formed into a pattern of a desired shape by etching. Has been done.

Also, the heating resistor 4 and the common electrode 5 are provided.
a, the individual electrode 5b, and the exposed surface of the heat retaining layer 2,
A protective layer 6 made of sialon or the like and having a thickness of about 5 μm is formed to protect them.

Next, a method of manufacturing the thermal head according to this embodiment will be described with reference to the flow charts shown in FIGS.

First, referring to FIG. 2, the single crystal silicon substrate 1 is subjected to anisotropic etching and isotropic etching.
The ridge portion 1a having a height of about 10 to 20 μm and the ridge portion 1
A groove portion 1b, which is a groove having a depth of approximately 30 to 100 μm, is formed close to a (step ST1).

A heat insulating layer 2 containing silicon oxide as a main component is laminated on the surface of the substrate 1 by sputtering (step ST2), and Ta is formed on the surface of the heat insulating layer 2.
A heating resistor layer made of —SiO ₂ or the like is sputtered to form a laminate (step ST3).

Then, in order to form the pattern of the heating resistor 4, a resist film is formed in the photolithography process (step ST4).

This resist film is formed as shown in the flow chart of FIG.

That is, the ultrafine particle generator 13 shown in FIG.
In the photoresist fine particle generator 6 of FIG.
Fine particles 7a (less than μm) (hereinafter referred to as resist fine particles) are formed (step ST21).

Then, the resist fine particles 7a are carried to the nozzle 9 of the coating chamber 8 by air or a carrier gas of an inert gas such as N ₂ (step ST22).

A negative high pressure (30
(KV to 100 KV) The electrode 10 is arranged so that the resist fine particles 7a are negatively charged (step ST23).

On the other hand, the substrate 1 is placed on the positive electrode 11 having the ground potential so as to face the nozzle 9, and the negatively charged resist fine particles 7b are made to fly toward the substrate 1 having the ground potential. To efficiently and evenly adhere to the surface of the substrate 1 (step ST24).

By doing so, as shown in the schematic view of FIG. 5, the resist fine particles 7b are applied to the surface of the substrate 1 (correctly, the upper surface of the heat insulating layer 2) to have a uniform thickness. The film 12 can be formed.

In this embodiment, as the ultrafine particle generator 13, an aero coat system manufactured by Nordson Co., Ltd. is used. Further, the high voltage applied to the resist particles 7a is not limited to the negative high voltage, and may be the positive high voltage.

Then, returning to the flowchart of FIG.
Using this resist film 12 as an etching mask, wet etching is carried out with phosphoric acid or the like by a photolithography technique to form a pattern of the heating resistor 4 in a substantially uniform size (step ST5).

Next, an electrode layer made of aluminum or the like is laminated on the heating resistor 4 by sputtering (step ST6).

Then, in the photolithography process, a resist film 12 is formed in the same manner as the heating resistor 4 (step ST7), and a pattern of the common electrode 5a and the individual electrode 5b is formed by using this resist film 12 as an etching mask (step ST7). ST8).

Finally, a protective layer 6 such as sialon having oxidation resistance and wear resistance is laminated on the upper surface of these (step ST9), and external connection terminals (not shown) are solder-plated. To form a plurality of thermal heads on the substrate (step ST10), and dicing the groove bottom portion of the deep groove portion 1b provided in advance on the substrate 1,
Obtain a desired thermal head chip (step ST1
1).

As described above, according to the method of manufacturing a thermal head according to the present invention, the solvent is contained by applying the photoresist 7 to the substrate 1 having a large variation in unevenness by the electrostatic application method. The resist fine particles 7a adhere to the substrate 1 almost uniformly, and the resist film 1 having a small thickness unevenness is formed.
2 can be formed. In particular, by using the photoresist 7 as submicron ultrafine particles, the resist film 12
Can have a more uniform thickness.

The etching mask formed by exposing, developing, and fixing the resist film 12 has small dimensional variation, and the heating resistor 4 and each electrode 5a, 5b formed by etching using this etching mask have ,
Variations in finished dimensions are also small. Therefore, even if the substrate 1 has large irregularities, it is possible to reduce the variation in the resistance values of the heating resistors 4 of the plurality of thermal head chips formed in the same substrate 1 surface, and significantly improve the manufacturing yield. be able to.

Further, by forming the resist film 12 by the electrostatic coating method, it becomes possible to arbitrarily design the unevenness of the surface of the substrate 1, and the groove is processed in advance on the substrate 1 to form the edge first. Since the thermal head can be manufactured by dicing after that, it is not necessary to polish the edge portion of the substrate, and the real-edge thermal head that peels the ink ribbon close to the heat generating portion can be formed with high accuracy. Therefore, in particular, it is possible to remarkably improve the printing quality of the rough paper of the thermal transfer printer using the ink ribbon.

The present invention is not limited to the above embodiment, but can be variously modified as needed.

[0035]

As described above, in the method of manufacturing the thermal head according to the present invention, the method of forming the resist film, which is particularly important in forming the pattern of the resistor and each electrode with high precision, is a submicron ultrafine particle. By using the resist electrostatic coating method described above, even if there are large irregularities on the surface of the substrate and the protective layer, the resist film can be applied almost uniformly, so the photolithography accuracy is improved and the heat is generated with high accuracy. The resistor can be formed, and the variation in the resistance value of the heating resistor can be significantly reduced, and the resistor can be manufactured with a high yield.

Since large irregularities can be arbitrarily provided on the substrate and the heat retaining layer, a deep groove portion is formed in advance on the surface of the substrate in the vicinity of the high protrusion portion, and finally the deep groove portion is formed. Since the bottom of the groove can be diced into a thermal head chip, the substrate edge does not need to be polished, the number of manufacturing steps can be reduced, and the real edge that peels the ink ribbon close to the heat generating part The thermal head can be formed easily and with high accuracy, and the production yield can be improved, and the printing quality of the thermal transfer printer can be significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view of a thermal head manufactured by an embodiment of a method of manufacturing a thermal head according to the present invention.

FIG. 2 is a flowchart showing an embodiment of a method of manufacturing a thermal head according to the present invention.

FIG. 3 is a flowchart showing a resist film manufacturing process, which is one process of the thermal head manufacturing method of the present invention.

FIG. 4 is an explanatory view showing a simple structure of an ultrafine particle generator used for manufacturing a resist film which is one step of the method for manufacturing a thermal head of the present invention.

FIG. 5 is a schematic diagram of a resist film formed in a manufacturing process of a thermal head according to the present invention.

FIG. 6 is a sectional view showing the structure of a conventional thermal head.

FIG. 7 is a sectional view showing another structure of a conventional thermal head.

FIG. 8 is a schematic diagram of a resist film formed in a conventional thermal head manufacturing process.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 1a Convex ridge 1b Recessed ridge 2 Thermal insulation layer 3 Recessed groove 4 Heating resistor 5 Electrode 5a Common electrode 5b Individual electrode 6 Protective layer 7 Photoresist 7a Resist fine particle 7b Negatively charged resist fine particle 8 Coating chamber 9 Nozzle 10 Negative electrode 11 Positive electrode 12 Resist film 13 Ultrafine particle generator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Noboru Tsushima 1-7 Yukiya Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd.

Claims (3)

[Claims] 1. A heat retaining layer is formed on a substrate on which convex ridges and concave ridges are formed, a heating resistor is laminated on the heat retaining layer, and a common electrode and a heating electrode are formed on the heating resistor and the heat retaining layer. A method of manufacturing a thermal head, in which individual electrodes are formed and a protective layer is formed on the upper surface thereof, in which a high voltage is applied to a photoresist of ultrafine particles, and a photoresist film is formed on the surface of a substrate placed on a ground electrode. Is electrostatically applied, and the pattern of the heating resistor and the electrode is formed by performing photolithography using the formed photoresist film as an etching mask. 2. The method of manufacturing a thermal head according to claim 1, wherein the particle size of the ultrafine particles is submicron. 3. A heat insulating layer is formed on a substrate on which a plurality of convex stripes and concave stripes are formed, and a high voltage is applied to the ultrafine particle photoresist on the heat insulating layer to mount it on a ground electrode. The pattern of the heating resistor is formed by performing photolithography using the photoresist film formed by electrostatic coating on the surface of the placed substrate as an etching mask, and the photo resist formed in the same manner on the pattern of the heating resistor. A plurality of thermal head chips are obtained by forming a pattern of electrodes by performing photolithography using a resist film as an etching mask, forming a protective layer on the upper surface of the electrodes, and then dicing the groove bottoms of the recesses. A method of manufacturing a thermal head, comprising: