JPH02225057A - Manufacture of thick film thermal head - Google Patents

Abstract

PURPOSE:To improve productivity of a thick film thermal head by enabling thick film paste to be simply flattened by a method wherein a knife edge is horizontally so transferred as to slide along a surface of a dry film. CONSTITUTION:Fluid thermal resistor paste 4 is buried in an opening formed selectively to a dry film 3. Further, the paste 4 is solidified by applying preliminary heating treatment. A knife edge 5 is horizontally moved along a surface of the dry film 3, and a dry paste 4 part protruded from the surface of the dry film 3 is cut. Horizontal transfer of the knife edge 5 is manually or automatically glindingly performed, and an inclination theta between the knife edge 5 and the dry film 3 is kept between 15 degree and 30 degree. The surface of the dry film 3 accords completely with a cut surface of the thermal resistor paste 4. Principal heating treatment is applied to the substrate, a thermal resistor thick film is burnt and at the same time, the dry film is thermally decomposed to be removed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thick film thermal head used for heat-sensitive recording in printers and facsimile machines, and more particularly, to a thick film thermal head for forming a flat heating resistor thick film. The present invention relates to a method for manufacturing a thick film thermal head.

[Conventional technology]

2. Description of the Related Art Conventionally, a method for manufacturing a thick film thermal head has been known in which a thick film of a heating resistor is fired into a substrate with electrodes in a desired shape. However, the core of the process of printing heat-generating resistor thick film paste is that the printed paste surface is not kept flat due to the inherent physical properties of the paste, such as surface tension and viscosity, and the cross-sectional shape of the fired thick film is chevron-shaped. Alternatively, it has a convex shape such as a circular arc shape. Since the thick film surface is not flat, the resistive heating distribution is not uniform over the entire thick film surface, and the thick film does not come into uniform contact with the recording medium, resulting in uneven heat-sensitive recording density, which has been a problem.

In order to eliminate this drawback, methods for flattening the surface of a thick film have been proposed. For example, JP-A-63-149167
The publication discloses a method for planarizing the surface of a thick film using polishing or lapping techniques. That is, according to this method, a plastic film layer having an opening of a desired planar shape and a predetermined thickness is formed on a substrate with electrodes, and then a heat generating resistor paste is embedded in the opening and dried. Next, the raised portion of the dried paste is wrapped using a wrapping sheet to flatten it until its thickness matches the thickness of the plastic film layer.

[Problem that the invention seeks to solve]

However, the above-described conventional planarization method by lapping has the following problems. In other words, the number of wrapping sheets to be used is 2000 depending on the remaining amount of paste that has risen above the top surface of the plastic film layer.
Not only does it have to be changed several times from No. 5000 to No. 5000, but if lapping is repeated using the same rough lapping sheet surface, the abrasive grains that have fallen off from the rough lapping sheet and the powder of the heating resistor paste that has been scraped off can be removed. Since scratches or streaks are formed on the rolled and wrapped resistive paste surface, the lamp surface that has been used several times cannot be reused, resulting in poor productivity. In addition, in lapping, not only the paste surface but also the surface of the plastic film layer is ground at the same time, which makes it impossible to accurately measure the thickness of the embedded heating resistor paste to match the initial thickness of the plastic film. was there.

The present invention aims to solve the problems of the above-described conventional method of flattening a thick film surface by lapping, and provides a novel method of manufacturing a thick film thermal head with excellent productivity.

c. Means for Solving Problems] In order to achieve the above object, according to the present invention, a novel method for manufacturing a thick film thermal head includes the steps of: arranging an electrode film on a substrate according to a predetermined pattern; A step of adhering a photosensitive dry film having a predetermined thickness onto a substrate, a step of exposing and developing the photosensitive dry film according to a predetermined pattern to form an opening, and burying a heating resistor paste in the opening and drying it. step, a step of horizontally moving a sharp blade along the surface of the photosensitive dry film to cut and flatten the surface of the dried heat-generating resistor paste, and a step of heating the substrate and sintering the heat-generating resistor paste. This process consists of the steps of forming a thick heating resistor film and thermally decomposing and removing the photosensitive dry film.

Preferably, the step of providing the openings is a step of exposing and developing the photosensitive dry film according to a plurality of separated opening patterns arranged in rows to form separate rows of openings, whereby the heat generating elements are It is possible to manufacture a separate heat generating resistor thick film thermal head that separates each printed dot.

[For production]

According to the method for manufacturing a thick film thermal head according to the present invention,
After embedding the heating resistor paste in the opening of the dry film and drying it, move a sharp knife horizontally along the surface of the dry film to cut and remove the part of the dry paste that has risen upward from the surface of the dry film. The surface of the dried paste is flattened prior to firing.

〔Example〕

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. FIGS. 1A to 1G are partial cross-sectional views showing steps of a method for manufacturing a thick film thermal head according to the present invention.

As shown in FIG. 1A, first, a group of electrodes 2 spaced apart according to a predetermined pattern is formed on a heat-resistant electrically insulating base Fil. The substrate 1 is made of ceramic such as alumina, and the electrode group 2 is obtained by etching a thin Au conductor film with a thickness of 0.5 μm to 3 μm into a predetermined pattern.

Next, as shown in FIG. 1B, a photosensitive dry film 3 is adhered to the entire surface of the substrate 1, and then exposed and developed by photolithography using a photomask having a predetermined pattern to form openings. The openings are selectively formed in relation to the pattern arrangement of the electrode group 2, and within the openings, ends of the electrodes facing and spaced apart from each other are exposed. In particular, dry film is used here because unlike liquid printing resist material, it has a fixed shape and is convenient to handle, and because it has a predetermined thickness, it is possible to accurately set the desired thickness. Another reason is that the entire surface of the substrate can be easily coated by thermocompression bonding.

In this example, a photosensitive resin dry film with a thickness of 25 μm (for example, manufactured by Dynachem) was used.

A product under the trade name LAMINARUF 1mtj was used. Note that a dry film having a thickness of 15 .mu.l to 30 .mu.m is usually used for forming a thick film of a heating resistor of a thermal head.

Furthermore, as shown in FIG. 1C, a fluid heating resistor paste 4 is embedded in the openings selectively formed in the dry film 3. The paste 4 may be a kneaded material containing, for example, ruthenium oxide, a binder, and a solvent, and is selectively supplied into the openings by printing using a screen mesh plate. However, due to factors such as the inherent surface tension and viscosity of the paste 4, the surface of the embedded paste 4 is not flat and bulges above the surface of the dry film 3.

Note that as a method for filling and supplying the paste 4, a drawing method can be used in addition to screen printing. That is, while extruding the heating resistor paste at a constant pressure using a fixed dispenser, the substrate 1 placed on the XY table is moved in a plane direction relative to the dispenser, and the paste is selectively applied to the openings of the dry film 3. supply.

Further, after the paste 4 is embedded in the opening, a preliminary heating treatment is applied to solidify the paste 4. The heating temperature is set at a temperature that volatilizes the solvent contained in the paste 4 and does not cause the dry film 3 to thermally decompose, for example, from 100°C to 150°C.

Next, as shown in the first diagram, a sharp cutting tool such as a knife 5 is moved horizontally along the surface of the dry film 30 to cut off the portion of the dry paste 4 protruding from the surface of the dry film 3. Since the dried paste 4 is in a brittle solid state, it can be cut easily and accurately. The horizontal movement of the knife 5 is carried out manually or automatically in a sliding manner, and the inclination angle θ between the knife 5 and the surface of the dry film 3 is adjusted so that the surface of the dry film 3 is not damaged and the surface of the dry film 3 is cut smoothly during the movement. It is preferable to maintain the temperature between 15 degrees and 30 degrees.

FIG. 1E shows the cross-sectional state after the cutting process. As is clear from the figure, the surface of the dry film 30 and the cut surface of the heat generating resistor paste 4 perfectly match, and a heat generating resistor paste that is flat and has the thickness as set, which is completely equal to the thickness of the dry film 3, is obtained.

Next, as shown in FIG. 1F, the substrate is subjected to main heat treatment to sinter the heating resistor paste 4 and fire the thick heating resistor film, and at the same time, the dry film is thermally decomposed and removed. The firing temperature depends on the composition of the paste, but for example 800°C to 900°C.
Set between.

At this temperature, ordinary resin dry films are completely thermally decomposed.

Finally, as shown in FIG. 1G, an overglaze layer 6 is formed on the thick film 4 by screen printing and baking to constitute a wear-resistant layer.

FIG. 2 is a plan view of a separate thick film thermal head manufactured by the method according to the present invention. This includes one common electrode 2a, a selection electrode group 2b arranged opposite to the common electrode, and a plurality of heat-generating resistor thick films arranged in a row and separated from each other between the common electrode 2a and the selection electrode group 2b. It is composed of a thick film group 4 consisting of elements. Separate type thermal heatherads have each heating resistor thick film element thermally separated, so
Even if electricity is selectively applied between the common electrode 2a and the selective electrode group 2b, each thick film element does not have a thermal effect on each other and a constant amount of resistance heat generation is always obtained. It has the advantage that it is uniform.

Conventionally, separate type thermal heads are known to use a thin heat-generating resistor film, but it has been difficult to realize a thick film due to issues such as printing accuracy.

However, by using the method according to the present invention, it is possible to fabricate a separate thick film thermal head with high precision. That is, first, using a photomask having a plurality of separated opening patterns arranged in rows, a photosensitive dry film bonded to a substrate under heat and pressure is exposed and developed to form separated rows of openings. The thick film paste is then printed onto the dry film using a screen printing plate. Since the purpose of this printing is simply to embed the thick film paste into the separation openings, no high printing precision is required. Finally, the knife is moved along the dry film surface to cut away the raised portions of the dry thick film paste and flatten the paste surface.

According to this method, the dimensional accuracy of the separated thick film element obtained is determined by that of the separation opening, so there is no practical problem.

By the way, the separate type thick film thermal head has an advantage over the separate type thin film thermal head in that the resistance value of each separate heat generating resistor thick film element can be finely adjusted by so-called voltage trimming. In other words, by applying a pulse of voltage (overvoltage) larger than the rated value to each thick film element, the resistance value can be changed by up to -40% depending on the magnitude of the overvoltage, and the resistance value of each thick film element can be changed by ±1. It is possible to make constant adjustments with an accuracy of %. On the other hand, with thin film elements, the change in resistance due to the application of overvoltage pulses is as small as about -5% and does not exceed the initial resistance variation range of ±5%, making effective resistance trimming impossible.

FIG. 3 is a plan view of an elongated or strip-shaped thick film thermal head manufactured by the method according to the present invention. This is composed of a common electrode 2a and a group of selective electrodes 2b which are arranged in a comb-tooth pattern, and a band-shaped heating resistor thick film 4 which is arranged transversely to the comb-tooth arrangement. This type of thick film thermal head has strip-shaped openings in the dry film that is thermocompressed to the substrate, prints thick film paste by screen printing, embeds it in the strip-shaped openings and dries, and then inserts a knife horizontally along the surface of the dry film. , and cut and flatten the raised part of the thick film paste.

Band-shaped or continuous thick-film thermal heads have the disadvantage that thermal isolation between heating elements is inferior to separate-type thick-film thermal heads, but according to the manufacturing method of the present invention, the strip-shaped thick film surface Since it is uniformly flattened, there is less unevenness in heat-sensitive recording density compared to conventional methods.

〔Effect of the invention〕

According to the present invention, by horizontally moving the knife so that it slides along the surface of the dry film, it is possible to flatten the thick film paste more easily than with the conventional lapping method, and the thick film thermal head productivity has improved. Furthermore, since the surface of the dry film is not scraped due to the smooth movement of the knife, there is no variation in the thickness of the thick film unlike in the conventional lapping method, and the thickness accuracy of the thick film can be improved. Further, according to the present invention, it is possible to manufacture a separate type thick film thermal head with high precision (and efficiency), which has been considered difficult in the past.

[Brief explanation of the drawing]

1A to 1G are partial sectional views for explaining the steps of the manufacturing method according to the present invention, and FIG. 2 is a plan view of a separate thick film thermal head manufactured by the manufacturing method according to the present invention. , and FIG. 3 are plan views of a band-shaped thick film thermal head manufactured by the manufacturing method according to the present invention. Regarding the reference numbers, 1 is the substrate, 2 is the electrode, 3 is the photosensitive dry film, 4 is the heating resistor paste and the heating resistor thick film, 5 is the knife, and 6 is the overglaze layer. Applicant shares

Claims (1)

[Claims] 1. A step of disposing an electrode film on a substrate according to a certain pattern, a step of adhering a photosensitive dry film having a predetermined thickness on the substrate, and a step of adhering a photosensitive dry film according to a predetermined pattern. A process of exposing and developing to form an opening, a process of embedding the heat generating resistor paste in the opening and drying it, and a process of moving a sharp blade horizontally along the surface of the photosensitive dry film to dry the dried heat generating resistor paste. A process of cutting and flattening the surface part, and a process of heating the substrate and sintering the heat generating resistor paste to form a thick heat generating resistor film, and thermally decomposing and removing the photosensitive dry film. Method for manufacturing a membrane thermal head. 2 The step of forming the openings is a step of exposing and developing the photosensitive dry film according to the long opening pattern to form long openings, thereby forming a continuous heat generating resistor thick film. 2. The method of manufacturing a thick film thermal head according to claim 1. 3 The step of providing the above openings is a step of exposing and developing the photosensitive dry film according to a plurality of separated opening patterns arranged in a row to form separate row-shaped openings, thereby forming a separate heating resistor. 2. The method of manufacturing a thick film thermal head according to claim 1, wherein a thick film is formed. 4. The method of manufacturing a thick film thermal head according to claim 1, wherein the step of embedding the heating resistor paste is a step of printing the heating resistor paste to match the opening by screen printing. 5. The method of manufacturing a thick film thermal head according to claim 1, wherein the step of embedding the heating resistor paste uses a drawing method. 6. Claim 6, wherein the flattening step involves cutting the surface of the dried heating resistor paste by moving a sharp cutting tool horizontally while maintaining an inclination angle of 15 degrees to 30 degrees with respect to a horizontal plane. 1. The method for manufacturing a thick film thermal head according to 1. 7. The method of manufacturing a thermal head according to claim 1, further comprising the step of forming a wear-resistant layer on the thick film after firing the thick film of the heating resistor.