JPH0457508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a ceramic thermal head, and particularly relates to the structure of a ceramic thermal head, and particularly to the structure of a ceramic thermal head.
This invention relates to a ceramic thermal head in which a heat sink material is integrated and fired.

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 has 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, when attempting 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 and have good resolution, but they are difficult to make with large dimensions.
The manufacturing process was complicated, resulting in high costs, and the thin surface layer formed caused problems in wear resistance. In addition, multilayer wiring is difficult for thermal heads made using the thin film method, and there are problems such as the generation of pinholes in the multilayer wiring layers, resulting in poor performance and high wiring resistance in the multilayer wiring, resulting in heat generation in the elements, and problems with drive circuits.

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

A thermal head must have at least 1,000 resistors with uniform shapes and resistance values lined up in a horizontal row at minute intervals, and it must also have the same number of lead wires as resistors wired at the same density. . Moreover, if any one of these resistors and lead wires becomes defective, it becomes unusable as a head.

In addition, with conventional thermal heads using the thick film method, thin film method, or a combination of these methods, the printing resolution is about 10 dots/mm at most. At this level of resolution, the distance between the heating elements is relatively long, so there is relatively little reduction in resolution due to heat diffusion.
However, in a laminated ceramic thermal head having a laminated structure, the spacing between the heating elements is 10 dots/mm or more, so deterioration of resolution due to heat diffusion between the heating elements becomes a problem.

The present invention solves this problem and provides a laminated ceramic thermal head with excellent resolution.

That is, in the present invention, a plurality of heating resistors are formed inside an insulating ceramic body, and a part of each heating resistor is exposed to a part of the surface of the ceramic body, and furthermore, a part of each heating resistor is exposed to a part of the surface of the ceramic body. A ceramic thermal head having a structure in which a conductor is formed on the surface portion or the other surface portion and inside the ceramic body, and the heating resistor and the conductor are connected on the surface or inside the ceramic body. , a ceramic body characterized in that a high thermal conductor is formed at a surface portion of the ceramic body where a heating resistor is exposed and at a position sandwiched between each heating resistor inside the ceramic body near the surface portion and in the vicinity thereof. It is a thermal head. By forming a layer of metal, oxide, semiconductor, etc. with good thermal conductivity between the heating element layers adjacent to each other, a structure is created in which heat from the heating element is quickly released from the head surface, and the size of the heating element is reduced. This achieves a resolution that is approximately equal to the spacing.

Next, the structure of the present invention will be explained with reference to the drawings. FIG. 1 shows an external view of an embodiment of a laminated ceramic thermal head having the structure of the present invention, in which (a) the heat generating layers are arranged in a straight line, and (b) the heat generating layers are arranged in a matrix.

In these figures, 1 is an insulator, 2 is a heat generating layer, 3 is a layer with high thermal conductivity, and 4 is an external electrode.

Figure 2 shows a cross section of the thermal head shown in Figure 1 a, where a represents the cross section taken along the dotted line in Figure 1, and b represents the cross section taken along the dashed line in Figure 1. A cross section is shown. In FIG. 2, 1 is a heating resistor, 2 is an insulating ceramic, 3 is a high heat conductor, 5 is a conductor, and 5' is a through-hole portion filled with the conductor.

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, so wear of the resistor is caused by the insulator. It is protected and has a structure that is sufficiently wear-resistant even without abrasion-resistant surfaces. Furthermore, since most of the resistor is embedded within the insulating ceramic, the structure is such that the resistor never becomes disconnected. Therefore, unlike in conventional heads, heat does not diffuse into the wear-resistant layer, and since a high thermal conductor layer is placed between each heating resistor, a resolution approximately equal to the thickness of the resistor can be obtained. Furthermore, in conventional thermal heads, when current 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, the heat within the same dot becomes uniform and density unevenness is reduced. Furthermore, in the thermal head of the present invention, a uniform resistor is formed on a uniform raw insulator sheet by pasting a raw resistor sheet or by screen printing, so the thickness of the resistor can range from several microns to several hundreds of microns. It can be formed uniformly down to a thickness of microns, and raw insulator sheets can be uniformly formed from tens of microns to hundreds of microns, so the thickness of the resistor and the pitch of the resistor can be made extremely fine, making it possible to The resolution can be dramatically improved from the conventional 6 to 8 dots/mm to several tens of dots/mm.

Figure 3 shows an example of the cross section of the thermal head shown in Figure 1b, where a represents the cross section taken along the dotted line in Figure 1b, and b also represents the cross section taken along the dashed dot line in Figure 1b. ing. In Figure 3, 1 is an insulating ceramic body, 2 is a heating resistor, 3 is a high heat conductor, and 4
5 indicates an external connection terminal, 5 a conductor, and 5' a through hole.

As shown in Figures 2 and 3, the resistor is embedded inside and directly connected to the internal conductor, and the internal conductor is three-dimensionally wired through a through hole and connected to the external electrode. Since it is compact and the resistor layer is embedded in the insulating layer, mechanical strength and wear resistance are greatly improved. Furthermore, by arranging a high heat conductor between each heat generating resistor, a resolution approximately equal to the thickness of the exposed portion of the heat generating resistor can be obtained.

Further, in the construction of the thermal head having the structure of the embodiment shown in FIG. 1, an alumina crystallized glass mixture was used as the insulating material. 56wt% of alumina with a purity of 99.9% or higher and 44wt% of lead borosilicate crystallized glass were weighed, wet mixed in a ball mill, and after over-drying, an insulator powder was obtained.

This insulating powder is dispersed in an organic vehicle, and a green insulating sheet is produced by a casting method using a doctor blade. The outer diameter and, if necessary, through-holes are simultaneously punched out from this insulating green sheet using a mold. A conductor layer was formed on the insulator raw sheet thus formed by screen printing using gold paste. Further, a rutinium oxide resistor paste was printed on the insulator raw sheet on which conductors were formed by the same screen printing method to form a resistor layer. In addition, silver paste was printed on a green insulator sheet, and this was used as a highly thermally conductive layer. These insulator raw sheets are laminated and crimped to form a laminate, which is cut into specified dimensions and heated to 800℃ after removing the binder.
Sintered at a temperature of 1000℃. After sintering, the surface in contact with the thermal paper was polished to a mirror finish, external electrodes were attached, and lead wires were attached to form a thermal head. As a result of printing on thermal paper using the thermal head made in this way, it was possible to record with good resolution and extremely good print quality.

Figure 4 shows a conventional laminated ceramic thermal head (Figure 4a) and a head portion of the present invention (Figure 4b).
This shows the relationship between the enlarged view of the surface temperature distribution and the surface temperature distribution. FIG. 2a shows the temperature distribution of a laminated ceramic thermal head without a high thermal conductor layer, where 1 is an insulator and 2 is a heat generating layer. From the temperature distribution graph, it can be seen that the temperature between the heat generating layers is quite high. FIG. 2b shows the temperature distribution of the laminated ceramic thermal head according to the structure of the present invention, where 1 is an insulator, 2 is a heat generating layer, and 3 is a high thermal conductor layer. It can be seen from the temperature distribution diagram that the temperature between the heat generating layers is lower.

In this way, in the laminated ceramic head of the present invention, the temperature distribution of the dots is very sharp, so the resolution when printing is approximately the size of a dot,
Print quality with extremely high resolution was obtained.

Although good results were obtained using any of metals, metal oxides, metal carbides, and metal nitrides as the high thermal conductivity material of the present invention, gold, silver,
Particularly suitable are platinum, palladium, copper, nickel, etc. alone or alloys of two or more of these, metal oxides such as beryllium oxide, metal carbides such as silicon carbide, and metal nitrides such as silicon nitride and boron nitride. Got the results.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the thermal head of the present invention, Fig. 2 is a sectional view of the thermal head shown in Fig. 1a, and Fig. 3 is a sectional view of the thermal head shown in Fig. 1(b). It is. FIG. 4 is a diagram showing the position of the heating resistor on the thermal head and the temperature distribution in the vicinity. In each figure, 1 is an insulating ceramic body, 2 is a heating resistor, 3 is a high heat conductor, 4 is an external connection terminal, 5 is a conductor, and 5' is a through hole.

Claims (1)

[Claims] 1 A plurality of heat generating resistors are formed inside an insulating ceramic body, and a part of each heat generating resistor is exposed to a part of the surface of the ceramic body, and furthermore, a part of each heat generating resistor is exposed to a part of the surface of the ceramic body or A ceramic thermal head has a structure in which a conductor is formed on the other surface portion and inside the ceramic body, and the heat generating resistor and the conductor are connected on the surface or inside the ceramic body, and the heat generating resistor 1. A ceramic thermal head characterized in that a high thermal conductor is formed at a surface portion of the ceramic body where the body is exposed and at a position sandwiched between the heating resistors inside the ceramic body near the surface portion and in the vicinity thereof.