JPS63154371A - Manufacture of thermal head - Google Patents

Abstract

PURPOSE:To favorably bond an electrode conductor onto a recessed hole generated through polishing of an underglaze layer, by additionally providing a step of blankly baking a polished underglaze layer at a temperature near the baking temperature for the underglaze layer, between a polishing step and a step of providing an electrode pattern. CONSTITUTION:A thermal head 21 comprises two kinds of electrode conductors 4, 5 alternately arranged on an underglaze layer 3, with a single heat generating resistor 6 disposed in electrical connection with the conductors. In manufacturing the thermal head, the underglaze layer 3 is provided and polished, in the same manner as in the prior art. The underglaze layer is blankly baking at a temperature near the baking temperature for the underglaze layer. In the blank baking, an aluminum ceramic substrate is gradually superheated so that a temperature near the baking temperature for the underglaze layer 3, namely, a temperature of + or -20 deg.C relative to the baking tempertaure is reached after the lapse of at least 5 min from the start of superheating.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for manufacturing a thick film thermal head used in a recording section of a thermal recording type facsimile machine, printer, or the like.

"Prior Art" In recording apparatuses that record image information using a thermal transfer recording method or a thermosensitive coloring method, a thermal head is often used as a recording head.

FIG. 4 illustrates the structure of a thick film thermal head (hereinafter simply referred to as a thermal head). An underglaze layer 3 is formed on the alumina ceramic substrate 2 of the thermal head 1. Underglaze layer 3
Two types of electrode conductive materials 4.5 are formed on the electrodes 4.5 at a predetermined interval and are not in contact with each other. A heating resistor 6 is formed at a location where these electrode conductive materials 4.5 are intricately arranged so as to be in electrical contact with them. On the surface of the heating resistor 6, etc.,
Although not shown, an overglaze layer is formed to protect these. Note that the underglaze layer 3 is also called a heat storage layer, and is provided to store heat generated by the heating resistor 6.

Recently, there has been a strong demand for thermal heads that are (1) capable of high-speed recording and (11) capable of high-density printing. In order to satisfy such requirements, there is a demand for an underglaze layer that has a higher heat storage effect.

However, there is a limit to the heat storage or thermal conductivity of the underglaze layer itself due to its material properties. Therefore, it has recently been proposed to make the glass material constituting the underglaze layer porous.

"Problems to be Solved by the Invention" When the underglaze layer is made porous, a high heat storage effect can be obtained due to the presence of air bubbles. However, in the underglaze layer using such materials, the presence of microscopic air bubbles causes countless unevenness of 10 to 20 μm on the surface of the layer, and on top of this, there is a layer with a thickness of only 0.5 μm.
．． It becomes impossible to form an electrode conductive material with a thickness of 5 to 3.0 μm.

Therefore, in order to reduce the unevenness on the surface of the underglaze layer, it has been proposed to perform a polishing treatment on this surface. When the polishing treatment is performed, the protrusions on the surface of the underglaze layer are removed, but since the underglaze layer is porous, undefeated pits (concave holes) are formed on the surface after the polishing treatment. The depth of this recessed hole is approximately 5 to 40 μm, but the edges are sharply cut due to polishing. Therefore, if the electrode conductive material 4 or 5 is formed on this, a phenomenon occurs in which the electrode conductive material 4 or 5 does not adhere well to the edge portion 11 of the recessed hole 10, as shown in FIG. Therefore, if a concave hole 10 that is larger than the width of the electrode conductive material 4 or 5 completely crosses the electrode conductive material 4 or 5 as shown in FIG. ) occurs. In such a thermal head, it becomes impossible to control the energization of the heat generating resistor 6 at a portion corresponding to the cut point of the electrode, and the thermal head cannot function as a normal thermal head.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a method for manufacturing a thermal head that allows an electrode conductive material to be satisfactorily adhered to the recesses generated by polishing the underglaze layer.

"Problems to be Solved by the Invention" In the method for manufacturing a thermal head of the present invention, between the step of polishing the surface of the underglaze layer and the step of forming an electrode pattern on this underglaze layer, An additional step is added to dry-fire the underglaze layer at a temperature close to that of the underglaze layer. That is, the edge portions of the recessed holes existing in the underglaze layer are made "sloping" by the step of blank firing the underglaze layer at a temperature close to the firing temperature thereof, thereby making it possible to improve the adhesion of the electrode conductive material.

To give a specific example of the step of empty firing the underglaze layer after polishing at a temperature close to its firing temperature, the temperature range is raised to ±20 degrees Celsius of the firing temperature of the underglaze layer over a period of 5 minutes or more from the ambient temperature, The process involves empty firing in this temperature range for 5 minutes to 20 minutes, and then returning to the ambient temperature over a period of 5 minutes or more.

"Example" The present invention will be described in detail below with reference to Examples.

FIG. 2 shows the main parts of a thermal nozzle used in one embodiment of the present invention. This thermal hept 21
Two types of electrode conductive materials 4.5 are placed on the underglaze layer 3.
A large number of these are arranged alternately in parallel.

A heating resistor 6 is formed at a location where these electrode conductive materials 4.5 are intricately arranged so as to be in electrical contact with them.

Although not shown in this figure, the first electrode conductive materials 4 are commonly connected to each other, and are connected to a power source (not shown) as a common electrode. The second electrode conductive materials 5 are each independently connected to the output terminals of a shift register (not shown) mounted on the thermal head 21, and are selectively grounded according to the image signal. ing. That is, a pulse voltage is applied between the second electrode conductive material 5 and the first electrode conductive material 4 which are in a grounded state, and the current is applied to that part, which generates heat.

The length a of the heating resistor 6 of the thermal head 210 varies depending on the size of the recording paper, and is approximately equal to the width of an A4 size paper, for example. Further, as shown in FIG. 3, the width of each electrode conductive material 4.50 is, for example, about 20 μm, although it differs depending on the recording density, and the arrangement interval C of these electrode conductive materials 4.5 is, for example, about 60 μm. ing.

By the way, in the thermal head 21 of this embodiment, (i) the underglaze layer 3 is formed in the same manner as in the conventional thermal head, and (11) this underglaze layer 3 is then polished. (iii) After this polishing, the underglaze layer 3 is dry-fired at around the firing temperature. (iv) After this, an electrode pattern is formed on the underglaze layer 3.

In this example, as the glass material constituting the underglaze layer 3, a glass paste with product number 4608H manufactured by Electronic Science Laboratories 17 was used. This glass paste has a softening point of 820 degrees Celsius. The glass paste is fired at a temperature that is typically 50 to 100 degrees Celsius higher than the softening temperature of the glass material. In this example, after printing a glass paste on a 96% alumina ceramic substrate, it was fired at 930 degrees Celsius. As a result, an underglaze layer 3 is formed. During this firing process, the glass material becomes porous and has a thermal conductivity of 2.5X1.
0-3caj! /cm-sec ・Celsius, resulting in an underglaze layer with excellent heat storage properties.

The formed underglaze layer 3 is porous, as described above, and therefore has an uneven surface.

Therefore, the surface of the underglaze layer 3 is polished by about 20 μm. As a result, the underglaze layer 3 after surface polishing has a maximum diameter of 40 μm and a maximum depth of 10 μm.
There are recessed holes on the order of μm. If such recessed holes exist, it is difficult to form a pattern of electrode conductive material with a width of about 20 μm using thick film printing and photolithography techniques to construct a thermal head with a resolution of about 8 lines/mm. It becomes difficult. Therefore, in this embodiment, the underglaze layer 3 after surface polishing is blank fired.

FIG. 1 shows the state of blank firing in this example.

In this dry firing, the alumina ceramic substrate is gradually heated (Fig. 1 ■), and reaches a temperature close to the firing temperature of the underglaze layer 3, that is, ±20 degrees Celsius, after 5 minutes or more from the start of heating. let In this example, the firing temperature of the underglaze layer 3 is 930 degrees Celsius, so the temperature is 910 to 950 degrees Celsius.

Then, it is left in this temperature range for 10 minutes (■ in the figure).

At this time, the glass material generally does not lose its shape so much. However, at the edge of the recessed hole, the surface of the glass material is rounded and rounded. Therefore, even if a pattern of electrode conductive material is formed in the recessed hole, the electrode is less likely to break at this portion. After leaving for 10 minutes in the above temperature range, cooling is performed for 5 minutes or more (■ in the figure).

Incidentally, such blank firing has the effect of removing impurities such as dust and oil adhering to the underglaze layer 3 and the alumina ceramic substrate, and is also effective as a pretreatment for forming the electrode layer. However, if the temperature of this blank firing is low, even if it is effective in removing these impurities, the edges of the recessed holes cannot be made "smooth". Furthermore, if the temperature of the blank firing is too high, the glass material will become extremely soft and return to the surface state before surface polishing. That is, the underglaze layer 3 becomes extremely uneven, making it difficult to form an electrode layer. Therefore, the blank firing temperature of the underglaze layer 3 is preferably approximately ±20 degrees Celsius of the firing temperature of the glass material.

After dry firing the alumina ceramic substrate, a thick film gold paste is printed and fired at 870 degrees Celsius in the conventional manner. The subsequent steps are also the same as conventional ones.

In the case of the thermal head 21 manufactured by the method of the present embodiment described above, which had a length for A4 size paper, one out of ten thermal heads had electrode breakage. On the other hand, when alumina ceramic substrates were blank-fired at 870 degrees Celsius as a conventional method for comparison, electrode breaks occurred at 10 locations per 10 A4 size thermal hept sheets.

"Effects of the Invention" As explained above, according to the present invention, after polishing a porous underglaze layer, dry firing is performed at a temperature of approximately ±20 degrees Celsius of the firing temperature of the glass material forming this underglaze layer. Therefore, the adhesion of the electrodes becomes good, making it possible to form electrodes with a shorter width, and making it possible to manufacture a thermal head that enables high-density recording.

[Brief explanation of the drawing]

Figures 1 to 3 are for explaining one embodiment of the present invention, of which Figure 1 is a temperature characteristic diagram showing the state of dry firing of the underglaze layer, and Figure 2 is a diagram showing the main points of the thermal head. Figure 3 is an enlarged view of the main part of the thermal head, Figure 4 is a structural diagram of the thick film type thermal head, Figure 5 is a diagram showing the structure of the thick film type thermal head, and Figure 5 is a diagram showing the structure of the thermal head. FIG. 6 is a cross-sectional view of a main part showing the adhesion state of the recessed hole and the electrode conductive material, and a plan view showing an example of the surface state of the underglaze layer when a recessed hole larger than the width of the electrode conductive material is formed. 2...Alumina ceramic substrate, 3...
- Underglaze layer, 4.5...Electrode conductive material, 6...Heating resistor, 10...Recessed hole. Applicant: Fuji Xerox Co., Ltd. Agent

Claims (1)

[Claims] 1. A step of forming an underglaze layer on an alumina ceramic substrate, a step of polishing the surface of this underglaze layer, and an empty firing of the underglaze layer after polishing at a temperature near the firing temperature. a step of forming an electrode pattern on the blank-fired underglaze layer; and a step of forming a heating resistor on the underglaze layer on which the electrode pattern is formed. manufacturing method. 2. The step of dry firing the underglaze layer after polishing at a temperature close to its firing temperature is a step of dry firing for 5 to 20 minutes at a temperature range of ±20 degrees Celsius of the firing temperature of the underglaze layer. 2. The method of manufacturing a thermal head according to claim 1, wherein a time of 5 minutes or more is required for rising to the temperature range and falling from the temperature range to the environmental temperature.