JPH0419032B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ceramic thermal head, and more particularly to a method for manufacturing a ceramic thermal head in which an insulating material, a heating material, and a conductive material are integrated and sintered.

Traditionally, thermal heads for heat-sensitive recording have been produced using the thick film method.
By thin film method or thin film/thick film mixed method, etc.
It is formed on a ceramic substrate and has been put into practical use.

The thermal heads conventionally used are thick film type.
Each thin film type had advantages and disadvantages. In other words, in the case of the thick film type, large dimensions can be produced relatively inexpensively, but since the electrodes and heating elements are printed using a thick film printing method, the resolution is limited to 8 dots/mm. Furthermore, in order to increase the resolution using the thick film method, it is necessary to miniaturize the wiring pattern, which necessitates the use of gold as a conductor, which also has the disadvantage of extremely high costs.
Furthermore, the high density of multi-layer wiring leads to poor yields and increased costs.

Furthermore, with thick film types, the resistance variation of the heating element becomes large because it is difficult to control the printing thickness.
Resistance variation is ±20% even if it is very good.
There were also problems with recording quality when used as a head.

In addition, thermal heads using the thin film method can form fine patterns, which can improve resolution, but they are difficult to make in large dimensions and the manufacturing process is complicated, resulting in high costs and the surface area formed is small. There was a problem with wear resistance because it was thin.

In addition, multilayer wiring is difficult for thermal heads made using the thin film method, resulting in lower yields due to the occurrence of pinholes in the multilayer wiring, higher wiring resistance in the multilayer wiring, and problems with element heat generation and drive circuits.

The present invention solves all of these problems and provides a method for manufacturing a thermal head that is small in size, low in cost, has excellent resolution, and is highly reliable.

That is, the present invention comprises a process of forming a raw insulator sheet, a process of drilling holes in the raw insulator sheet, a process of filling the holes with a conductive material and at the same time forming a conductor layer on the raw insulator sheet, and a process of forming a conductive layer on the raw insulator sheet. A step of forming a resistor layer on a biosheet by printing, a raw insulator sheet with a resistor layer and a conductor layer formed thereon, a raw insulator sheet with only a conductor layer formed thereon, and a raw insulator sheet are laminated and crimped to form a laminate. cutting the laminate into predetermined dimensions and sintering the laminate, attaching external electrodes to the sintered laminate, and polishing a predetermined surface of the sintered body. This is a method for manufacturing a characteristic laminated ceramic thermal head. A thermal head must have more than 1,000 resistors of uniform shape and resistance value arranged in a horizontal row at minute intervals, and it must also have the same number of lead wires as resistors and wire them at the same density. Moreover, if any one of these resistors or lead wires becomes defective, the head cannot be used.

The present invention forms resistors and conductors on a raw insulator sheet, and uses through holes to wire each conductor three-dimensionally, thereby reducing the wiring density in a conventional plane. We were able to significantly improve the actual wiring density and the reliability of the wiring.

Furthermore, since the resistor is formed by thick film printing and the heat generating layer is formed by laminating in the thickness direction, the thickness of the resistor layer can be reduced to several tens of microns. As a result, it has become possible to achieve resolution as a thermal head equal to or higher than that of a thin film type head.

In addition, in conventional thermal heads, regardless of whether the thick film type or thin film type is used, the thickness of the resistor layer formed is from several thousand angstroms to several tens of microns, resulting in poor wear resistance and poor wear resistance. The resistor layer often wore out.

For this reason, in conventional thermal heads, a wear-resistant layer of abrasion-resistant glass, Ta ₂ O ₅ , or the like is formed on the surface to a thickness of several tens of microns.

However, when these wear-resistant layers are formed, when heat from the resistance heating element is conducted to the wear-resistant layers, heat diffusion in the lateral direction occurs simultaneously in the thickness direction, which causes resolution to deteriorate. Ta.

In this way, conventional thermal heads are thick film type,
Both the thin film method and the mixed method have their own problems.

The present invention solves these problems by using a structure completely different from conventional ones, and provides a high-performance, low-cost thermal head that can be mass-produced.

The details of the present invention will be explained below with reference to the drawings and examples.

FIG. 1 is a perspective view showing an example of the structure of a thermal head manufactured by the manufacturing method of the present invention, in which 1 is a resistor layer exposed on the surface, 2 is an insulator, and 3 is an externally connected It shows electrodes for external connection for inputting signals. In this figure, the resistor 1 and the insulator 2 are completely integrated into ceramic.

Figure 2 shows a cross section of the thermal head in Figure 1, where a represents the cross section of the portion indicated by the dotted line in Figure 1, and b represents the cross section of the portion indicated by the dashed-dotted line in Figure 1. . In FIG. 2a, 1 is a resistor, 2 is an insulator, and 4 in FIG. 2b is an internal conductor 4' is a through hole.

As is clear from FIGS. 1 and 2, in the thermal head according to the structure of the present invention, the heating resistor is embedded in the insulator.
The resistor is protected from wear by the insulator, and the structure is sufficiently wear-resistant even without a wear-resistant layer on the surface. Furthermore, since most of the resistor is embedded within the insulator, the structure is such that the resistor never becomes disconnected. Therefore, since there is no diffusion of heat through the wear-resistant layer, a resolution approximately equal to the thickness of the resistor can be obtained. Furthermore, in conventional thermal heads, when the electrode flows inside the resistor and generates heat, the amount of heat generated varies depending on the location due to the width of the resistor and variations in the thickness of the resistor within that width. Unevenness often occurred in the recorded images.

According to the structure of the present invention, since the thickness direction of the resistor is exposed at the surface, heat within the same dot becomes uniform and density unevenness is reduced. Furthermore, the thermal head of the present invention will be described in detail later in the manufacturing process of Examples, but since a uniform resistor is formed on a uniform insulating green sheet by screen printing, the thickness of the resistor is several microns. It is possible to uniformly form insulator sheets from tens of microns to hundreds of microns in thickness, so the thickness of the resistor and the pitch of the resistor can be made extremely fine. The recording resolution can be dramatically improved from the conventional 6 to 8 dots/mm to several tens of dots/mm.

Next, the manufacturing method of the present invention will be explained with reference to the drawings.
FIG. 3 shows a process diagram of the manufacturing process of the present invention.

The present manufacturing method will be explained with reference to FIG. 3. First, insulator powder is dispersed in an organic vehicle to form a slurry. This slurry is made into an insulating green sheet by a casting method using a doctor blade.

The insulator green sheet thus produced is punched out to a predetermined size, a conductor pattern is printed using conductor paste, and the through holes previously formed in the green sheet are filled with the conductor paste. A resistor layer is printed on the insulating green sheet on which the conductor is formed.

The required number of raw insulator sheets with through-holes and conductors formed in this way and printed with resistors, and raw insulator sheets with only conductors and through-holes formed, and raw insulator sheets with only conductors and through-holes formed. Each of them is laminated so as to form three-dimensional wiring, and pressed together by hot pressing to form a green laminate.

After the green laminate is cut into a predetermined shape, it is sintered through a binder removal process, and the external electrodes are baked to form a laminated ceramic thermal head.

Due to this manufacturing method, it is possible to form raw insulating sheets and resistor layers with a wide range of film thickness from several microns to several hundred microns, so the thickness of the resistor after sintering can be The distance between the resistor and the resistor can be freely selected from a wide range from several microns to several millimeters. In particular, by reducing the thickness of the resistor and insulator, a resolution of several tens of dots/mm or more can be achieved.

Additionally, with this manufacturing method, the wiring required to generate heat in the resistor can be formed three-dimensionally through through-holes, making it possible to create very advanced thick-film or thin-film wiring, unlike conventional wiring. A thermal head can be manufactured with high reliability, small size, and high yield without using any technology.

In addition, Figure 4 shows the raw sheets (I to O) that are laminated in the lamination step of the manufacturing process of the present invention in the order of lamination, where 1 is an insulator raw sheet, 2 is a conductor, and 3 is a resistor formed by printing. Body layer 4 indicates a through hole. In addition, the raw sheets I and O are layers with only through holes formed, the raw sheets TOL are layers with a conductor layer and through holes formed, and the raw sheets H~N are layers with all of the resistor layer, conductor layer, and through holes formed. This is a raw insulating sheet. Note that the number of layers of raw sheets can be increased or decreased as necessary.

Note that Fig. 4 shows the raw insulator sheet portion per element to make the diagram easier to understand, but in actual manufacturing, the pattern in Fig. 4 is repeated many times on a plane. Tens to hundreds of laminated ceramic thermal heads can be made by printing and laminating in one go.

When thermal heads are made using lamination technology in this way, a large number of thermal heads can be made in one lamination process, so the cost per unit becomes significantly cheaper than with conventional methods, making mass production possible. is also possible.

Next, the present invention will be explained in detail with reference to examples.

Example 1 An alumina-crystalline glass mixture was used as the insulator material. Powders of 50 wt% alumina and 50 wt% borosilicate lead crystallized glass were wet mixed in a ball mill, and then overdried to obtain insulating powder.

An insulator powder was dispersed in an organic vehicle to form a slurry, and a green insulator sheet having a thickness of 20 μm to 500 μm was produced by casting the slurry using a doctor blade. Note that polyvinyl butyral was used as the binder of the organic vehicle, and polyhydric alcohol ester was used as the solvent.

The outer shape and through holes were punched out of the insulating raw sheet using a mold, and a wiring pattern and a hole filling pattern for the through holes were printed thereon by screen printing using a silver-palladium alloy paste. Next, a resistor paste was printed by a screen printing method to form a resistor layer on the insulator raw sheet. Ruthenium oxide paste was used as the resistor paste.

A raw insulator sheet on which a conductor was formed by printing the resistor sheet made in this way, a raw insulator sheet on which only a conductor was formed, and a raw insulator sheet on which only through holes were formed if necessary, etc. A few pieces were placed in a mold, laminated, and bonded under heat.

After lamination, the green laminate was cut into a size of 5 mm x 10 mm, and after removing the binder at 500°C, it was sintered at a temperature of 800°C to 1000°C.

After baking an external electrode on the sintered laminate that had been fired, and polishing the exposed surface of the resistor in contact with the thermal paper to a mirror finish, a lead wire was attached to form a thermal head.

When the completed thermal head was set in a thermal printer and an operation test was performed, it produced 10 dots/print.
It was found that a resolution of mm to 50 dots/mm was obtained, which is sufficient for practical use, and also shows a significantly improved resolution compared to conventional thermal heads.

Example 2 An alumina-crystalline glass mixture was used as the insulator material. Alumina 56wt% with purity over 99.9%
Weighed 44wt% of lead borosilicate crystallized glass,
Wet mixing was performed in a ball mill, and after drying, an insulator powder was obtained.

This insulating powder was dispersed in an organic vehicle to form a slurry, and a green insulating sheet having a thickness of 20 μm to 500 μm was prepared by casting the slurry using a doctor blade. In addition, polyvinyl alcohol is used as the binder for the organic vehicle.
Water was used as the solvent.

The outer shape and through holes were punched out of the raw insulator sheet using a mold, and a wiring pattern and a through hole filling pattern were printed thereon using gold paste by screen printing.

Next, on the insulating green sheet on which the conductor was formed, a resistor layer was further formed at a predetermined position by screen printing using a ruthenium-based resistor paste. The thickness of the resistor layer is 6 μm to 100 μm,
When the resistor layer was thick, overprinting was performed.

A predetermined number of raw insulating sheets with resistor layers, conductor layers formed in this way, insulating raw sheets with only conductor formation, and insulating raw sheets with only through-holes formed if necessary. It was placed in a mold and laminated and thermocompressed.

After lamination, the raw laminate is cut into 5 mm x 10 mm dimensions, and the binder is removed at 500°C, followed by heating at 800°C.
Sintered at a temperature of 1000℃.

External electrodes were baked on the sintered laminate after firing, and the surface in contact with the thermal paper was polished to a mirror finish, and then lead wires were attached to form a thermal head.

When the completed thermal head was set in a thermal printer and an operation test was performed, a resolution of 10 dots/mm to 30 dots/mm was obtained, making it fully practical, and moreover, compared to conventional thermal heads. It was found to exhibit significantly improved resolution.

As described above, the laminated ceramic thermal head manufactured by the manufacturing method of the present invention has the advantage of achieving a resolution that cannot be achieved with conventional thermal heads, being compact and highly reliable, mass-produced, and reducing costs. It turned out to be a thermal head.

[Brief explanation of drawings]

FIG. 1 is a perspective view of an embodiment of a laminated ceramic thermal head manufactured by the manufacturing method of the present invention. FIG. 2 shows a cross-sectional view of the laminated ceramic thermal head of FIG. 1, where a shows the cross-section of the portion indicated by the broken line in FIG. FIG. 3 is a diagram showing the manufacturing process of the laminated ceramic thermal head of the present invention. FIG. 4 is a diagram showing the order of stacking green sheets in the stacking process of the laminated ceramic thermal head of the present invention. In each figure, 1 is a resistor, 2 is an insulator, 3 is an external lead electrode, 4 is an internal conductor, and 4' is a through hole.

Claims (1)

[Claims] 1. A step of forming a green insulator sheet, a step of drilling a hole in the green insulator sheet, a step of filling the hole with a conductive material and simultaneously forming a conductor layer on the green insulator sheet, and a step of forming a conductor layer on the green insulator sheet. A process of forming a resistor layer on a sheet by printing, and laminating and pressing a raw insulator sheet with a resistor layer and a conductor layer formed thereon, a raw insulator sheet with only a conductor layer formed thereon, and a raw insulator sheet to form a laminate. It is characterized by comprising the steps of: forming the laminate, cutting the laminate into predetermined dimensions and sintering it, attaching an external electrode to the sintered laminate, and polishing a predetermined surface of the sintered body. A method for manufacturing a laminated ceramic thermal head.