JPS5983682A - Ceramic thermal head - Google Patents

Abstract

PURPOSE:To provide a ceramic thermal head for heat-sensitive recording which is small in size, inexpensive, excellent in resolution and high in reliability, obtained by integrating an insulator material, a heating resistor material, a conductor material, a high thermal conductor material or the like with each other, followed by sintering. CONSTITUTION:Raw material powders such as high-purity alumina or lead borosilicate base crystallized glass are mixed with each other, the resultant mixture is dispersed into an organic vehicle, and a green sheet of an insulator is produced therefrom by a casting method or the like. A gold paste or the like is printed on the green sheet of the insulator to form a conductor layer, on which a ruthenium oxide base resistor paste or the like is printed to form resistor layers 2. Then a silver paste or the like is printed on the green sheet to form high thermal conductor layers 3. A plurality of the green sheets of the insulator thus provided with the layers thereon are laminated with each other, and are pressed to produce a laminate body, which is cut to a predetermined size, and after sintering, external connecting terminals 4 and the like are fitted to obtain the objective thermal head.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of a ceramic thermal head, and particularly to an insulating material, a heating element material, and a conductive material.

This invention relates to a ceramic thermal head in which a heat sink material is integrated and sintered.

Traditionally, thermal heads for heat-sensitive recording use the thick film method.

It is formed on a ceramic substrate by a thin film method or a mixed thin film/thick film method, and is put into practical use.

The conventionally used thermal head is a thick film type.

Each thin film type had advantages and disadvantages. In other words, in the case of a thick film type, a large size product can be produced relatively inexpensively, but since the electrode 2 heating element is formed by a thick film printing method, the resolution is limited, and the limit is 8 dots/area. Furthermore, when trying 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 the thick film type, the resistance variation of the heating element becomes large because it is difficult to control the printing thickness, and even a very good one has a resistance variation of about ±20%, which causes problems with the recording quality when used as a head. Ah, again.

Thermal heads using the thin film method can form fine patterns, so the resolution is low, but it is possible to
Large dimensions are difficult to produce and the manufacturing process is difficult. U5+
This increases the cost, and the formed surface layer is rough, so there are problems with wear resistance. In addition, it is difficult to conduct multilayer wiring with the thermal head using the thin film method, and the occurrence of bottle balls in the multilayer wiring layer causes a reduction in the wiring resistance and increases the wiring resistance of the multilayer wiring, resulting in heat generation of the element and time required for driving one circuit. There was a problem.

The present invention (which solves all the problems between r and i,
Small and low cost, lIi'i! It provides highly reliable thermal imaging with excellent image resolution.

Saalhenod has a uniform shape and resistance value -) 1tl
(More than 1,000 antibodies must be lined up horizontally at minute intervals, and the same number of lead wires as resistors must be wired at the same density. Moreover, the number of resistors and lead wires If any one of them is defective, the head and the other head cannot be used.

Furthermore, with conventional thermal heads using the thick film method, thin film method, or a combination of these methods, the printing resolution is at most about 10 dots/WIM. At this level of resolution, the distance between the heating elements is relatively long, so there was 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/town or more, which poses a problem of deterioration of resolution due to heat diffusion between the heating elements.

The present invention solves this problem and provides an FF two-layer 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,
Further, a conductor is formed on another surface of the ceramic body or on the other surface and inside the ceramic body, and the heating resistor and the conductor are connected on the surface or inside the ceramic body. The ceramic thermal head has a structure in which high heat is generated at the surface portion of the ceramic body where the heating resistor is exposed and at a position sandwiched between the heating resistors inside the ceramic body near the surface portion and in the vicinity thereof. This is a ceramic thermal head characterized by forming a conductor. 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 9. This achieves a resolution approximately equal to the interval.

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 multilayer 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. It is something that

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.

FIG. 2 shows a cross section of the thermal head shown in FIG. 1(a), where (a) shows the cross section taken at points 1 to 9 indicated by the dotted line in FIG. 1 shows a cross section cut along the dashed-dotted line in FIG. In FIG. 2, 1 is a heating resistor, 2 is an insulating ceramic, 3 is a high heat conductor, a 5-layer conductor, and 5' is a through-hole portion filled with a 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 the wear of the resistor is protected by the insulator. The structure is sufficiently wear-resistant even without a wear-resistant layer on the surface. Since most of the leaked 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, with conventional thermal heads, when current flows inside the resistor and generates heat, the amount of heat generated changes depending on the location due to the width of the resistor and variations in the thickness of the resistor within that width, and the recorded image However, according to the structure of the present invention, since the thickness direction of the resistor is exposed to the surface, the heat within the same dome becomes uniform, and density unevenness is reduced. Furthermore, the resistor of the present invention is formed by pasting a resistor raw sheet or screen printing method to form a uniform resistor on a uniform raw insulator sheet, and the thickness of the resistor is from several microns to several micrometers. The thickness of the resistor and the pitch of the resistor can be made very fine. The recording resolution can be dramatically improved from the conventional 6 to 8 dots/distance to several tens of dots/mt.

Figure 3 shows an example of the cross section of the thermal conductor shown in Figure 1 (b), where (a) shows the cross section of the dotted line in Figure 1 (b), and b) also shows the cross section of the thermal conductor shown in Figure 1 (b). The cross section of xlfl(b) is shown along the dashed dotted line. In FIG. 3, 1 is an insulating seven-lamic 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.

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 within 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.

1.1 as a method for manufacturing a thermal head having the structure of the embodiment shown in FIG. An alumina-crystalline glass mixture was used as the insulator material. Alumina 56 wt% with purity of 99.9% or more and lead borosilicate crystallized glass 44
wt% was 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 thus formed insulator G-1 by screen printing using gold paste. Further, a rutinium oxide resistor paste was printed on the insulator green sheet on which conductors were formed using the same screen printing method to form a resistor layer. In addition, the silver base is printed on a raw insulator sheet, and this is used as a highly thermally conductive layer. These insulator raw sheets were laminated and pressed together to form a laminate, which was cut into predetermined dimensions, and after removing the binder, was sintered at a temperature of 800°C to 1000°C. After sintering, the thermal paper (c) was polished to a mirror surface with the dark contact side, attached with external electrodes, and the lead wires were attached to the thermal head [7]. Using the thermal head made in this way,
The results of printing on thermal paper show an excellent relationship between print quality and good resolution. FIG. 2(a) shows the humidity distribution of a laminated ceramic thermal head without a high thermal conductor layer, where 1 indicates an insulator and 2 indicates a heat generating layer. From the temperature distribution graph, it can be seen that the temperature between the heat generating layers is significantly higher. FIG. 2(b) 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 humidity distribution diagram that the temperature between the heat generating layers is lower.

As described above, in the laminated ceramic head of the present invention, the temperature distribution of the dots is very sharp, so that the resolution when printing is approximately the size of a dot, and printing 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 and silver were used as the metals.

Single elements such as platinum, palladium, @, nickel, etc., or alloys of two or more of these; beryllium oxide as gold monoride; silicon carbide as metal carbide; silicon nitride and boron nitride as metal nitride.

particularly good results were obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing an embodiment of the thermal head of the present invention. 2 is a sectional view of the thermal head shown in FIG. 1(a), and FIG. 3 is a sectional view of the thermal head shown in FIG. 1(b). 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,
5' is a through hole. Part 1 (d) (b) Part 2

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 on a part of the surface of the ceramic body, and furthermore, a part of each heat generating resistor is exposed on a part of the surface of the ceramic body, and another surface of the ceramic body is exposed. A ceramic thermal head having a structure in which a conductor is formed within the ceramic body and the other surface portion, and the heating resistor and the conductor are connected on the surface or inside the ceramic body, A ceramic thermal conductor characterized in that a high heat 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. head.