JPS63149165A - Thick-film thermal head - Google Patents

Abstract

PURPOSE:To enable uniform heat generation, by setting the width of a heat generating resistor provided on an insulating base to be sufficiently large, uniformizing the thickness of a central part of the resistor, opposing electrodes to each other over a length shorter than the width of the resistor, and determining the dot size of an energization region by the length of the opposed parts of the electrodes. CONSTITUTION:A thick film thermal bead, having a recording density of 8 dots/mm, comprises a glass heat-accumulating layer 2 on a ceramic substrate 1, and a common electrode 13 and discrete electrodes 14 provided on the layer 2, with an organogold paste being used as a material so as to ensure favorable contact of the head with a recording paper. The length l of opposed parts of the electrodes 13, 14 is set to be shorter than that in a conventional system so that the length coincides with the size of s print dot in an auxiliary scanning direction. A single heat generating resistor 15 is provided, with a central part of the resistor being located at the opposed parts of the electrodes and the width L of the resistor being sufficiently greater than the length l of the opposed parts of the electrodes, end an abrasion-resistant layer 16 is provided thereon by using a glass paste.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to 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. 3 shows the structure of a conventionally used thick film thermal head. In the thick film thermal head, a glass heat storage layer 2 is printed and fired on a ceramic substrate 1 for heat dissipation, and two types of electrodes 3.4 are further printed and fired on the glass heat storage layer 2, and then patterned by photolithography.

A heating resistor 5 is formed on the electrode 3.4 and extends perpendicularly to the plane of the drawing, and is covered with a wear-resistant layer 6. The heating resistor 5 is a ruthenium oxide thick film resistor, and is formed in a line shape by screen printing. The wear-resistant layer 6 is also printed and fired in the same manner as the heating resistor 5.

FIG. 4 shows the connection relationship between the two types of electrodes 3.4 and the heating resistor 5 in principle. A plurality of two types of electrodes 3.4 are alternately arranged on one heating resistor 5 at predetermined intervals. One of the electrodes 3.3, . . . is called a common electrode, and these electrodes are commonly connected to a power supply line (not shown). The other electrode 4.4,...
... are called individual electrodes, and when these are grounded or insulated from the ground depending on the image information, only desired portions of the heating resistor 5 are energized and generate heat.

Therefore, when a recording paper or a thermal transfer recording medium is brought into contact with the wear-resistant layer 6 of the thick-film thermal head shown in FIG. 3, thermal recording is performed by the thermal energy emitted from the heating resistor 5.

"Problems to be Solved by the Invention" Thick film thermal heads have advantages over thin film thermal heads, such as superior mass productivity and low cost since they do not require expensive manufacturing equipment. However, in the conventional thick film thermal head, the heating resistor 5 is formed as an m-line by screen printing. Therefore, the cross-sectional shape of the heating resistor thus formed is chevron-shaped or semi-circular as shown in FIG. 3, which causes the following problems.

That is, for example, when a positive voltage is applied to the common electrode 3 and the individual electrodes 4 are grounded, a current flows intensively to the center of the heat generating resistor 5 between them, and as a result, the peak-shaped heat generating resistor 5 An imbalance in temperature distribution occurs in which the temperature near the peak becomes higher. Therefore, when the amount of energization is small, there is a tendency for ink color development and ink transfer to occur only on the paper corresponding to the vicinity of this vertex, resulting in a problem that the dot size becomes smaller. Furthermore, in order to solve these problems, it is necessary to increase the power applied to the thick film thermal head, resulting in problems such as poor printing efficiency and an increase in the size of the power supply circuit.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thick film thermal head that can generate heat more uniformly in a portion corresponding to a required dot size.

"Means for Solving the Problems" In the present invention, the width of the heating resistor formed on the insulating substrate is made sufficiently wide, and the thickness at the central part thereof is made uniform.

Then, the electrodes are opposed to each other with a length shorter than the width of the heating resistor, and the length of this opposed portion defines the current-carrying area, that is, the dot size in the sub-scanning direction.

As described above, in the present invention, the thickness of the heating resistor in the current-carrying portion is substantially uniform, so that the temperature distribution during heating is good, and the above-mentioned disadvantages can be solved.

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

FIG. 1 shows a cross section of a thick film thermal head according to an embodiment of the present invention.

The thick film thermal head of this embodiment has a recording density of 8 dots) and 7 mm, and is the same as the conventional thick film thermal head in that a glass heat storage layer 2 is formed on a ceramic substrate 1.

On the glass heat storage layer 2, as shown in FIG. 2, common electrodes 13.13, . . . and individual electrodes 14.14, .
. . . is formed by the same process as the conventional method. Organic gold paste was used as the material for these electrodes 13 and 14 in order to make good contact with the recording paper (paper contact). In this example, the line width of each of these electrodes 13 and 14 was set to 20 μm, and the pitch of each of these electrodes was set to 125 μm.

The length l of the opposing portions of both electrodes 13 and 14 was set shorter than the conventional one so as to match the size of the printed dot in the sub-scanning direction. In this example, this length l was set to 150 μm. In conventional thick film thermal heads, this length l
corresponds to the width of the heating resistor. In this embodiment, since both electrodes 13 and 14 are formed by photolithography after thick film printing, the length l and both electrodes 13 and 14 are formed by photolithography after thick film printing.
14 can be set accurately.

Once both electrodes 13 and 14 are formed, one heat generating resistor 15 is formed with a width sufficiently wider than the length l of these parts centered on these opposing parts. Heat generating resistor 1
As No. 5, a ruthenium oxide-based resistance material was used. In this embodiment, the width of the heating resistor 15 is set to 450 μm, which is three times the length β. As a result, the upper surface of the heating resistor portion corresponding to the opposing portions of both electrodes 13 and 14 became flat with an accuracy of approximately 10±1 μm. After the heating resistor 15 was formed, a wear-resistant layer 16 was formed thereon using glass paste.

In the thick-film thermal head of this embodiment created as described above, when a voltage is applied between both electrodes 13 and 14, the heating resistor portions (represented by halftone dots in FIG. The portion 18 generates heat with a nearly uniform temperature distribution, and thermal energy is supplied to a sheet (not shown) to form printed dots. Since thermal energy is evenly supplied to the print area in this way, there is no need to waste power for recording, and it is possible to reduce power consumption and downsize the power supply circuit.

"Effects of the Invention" As explained above, according to the present invention, the heat generation of the heating resistor is made uniform, so if the opposing parts of the electrodes, that is, the part through which the current flows, are adjusted when designing the electrodes, the shape of the printed dots or The size can be set with high precision, and the quality of recorded images can be improved. In addition, since the portion that contacts the paper is flattened, the contact relationship with the paper becomes smoother during recording, and the positioning of the paper and the thermal head in the recording section becomes easier. Additionally, the length of the opposing portions of two types of electrodes that are arranged parallel to each other at high density can be reduced to, for example, one-fourth of that of the conventional method, which eliminates manufacturing defects in these portions. It is possible to significantly reduce the occurrence of , and improve product yield.

[Brief explanation of the drawing]

Figures 1 and 2 are for explaining one embodiment of the present invention, of which Figure 1 is a cross-sectional view of a thick film thermal head, and Figure 2 shows the arrangement of electrodes and heating resistors. FIG. 3 is a cross-sectional view showing the structure of a conventional thick film thermal head, and FIG. 4 is a layout explanatory view showing the electrode arrangement of a conventional thick film thermal head. DESCRIPTION OF SYMBOLS 1...Ceramic substrate, 2...Glass heat storage layer, 13...Common electrode, 14...Individual electrode, 15...Heating resistor body, L: Width (of the heating resistor), β: Length (of the heating part). Applicant Fuji Xerox Co., Ltd.

Claims (1)

[Scope of Claims] 1. An insulating substrate, a strip-shaped heating resistor of a predetermined width disposed on the insulating substrate, and a heating resistor disposed on the insulating substrate at a predetermined interval in the length direction of the heating resistor. A plurality of first electrodes are arranged one by one on the resistor, and these first electrodes are arranged at the predetermined intervals in the length direction and in a non-contact state with the first electrode. 1 on the heating resistor from the opposite direction.
a plurality of second electrodes arranged one by one;
A thick film thermal head characterized in that the length of the opposing portion of the electrode and the second electrode is set to be sufficiently shorter than the width of the heating resistor. 2. The length of the heating resistor corresponds to the maximum length in the main scanning direction during recording, and the length of the opposing portion of the first electrode and the second electrode corresponds to the recording section in the sub-scanning direction. A thick film thermal head according to claim 1, characterized in that: