JPH03184877A - Line-type thermal print head - Google Patents

Abstract

PURPOSE:To make a common electrode wide by a method wherein the common electrode and an electrode/a driver IC are formed across a glazed glass respectively on the lower side and upper side of the glazed glass. CONSTITUTION:On a heat-resistant insulating substrate 1, a metal paste of Au or Pt series is screen-printed, whereby a common electrode 5 and a connecting lead 6 are formed. On the upper surface of the common electrode 5, a glazed glass 2 is printed, whereby an electrically insulating layer is formed. A glazed glass 3 is partially printed so as to be positioned under a required heating element 4 and baked. After a heating element layer 4 and an electrode layer 7 are formed on this substrate by sputtering or the like using a vacuum film forming device, an heating element is formed, and an electrode pattern is formed. An insulating heat-resistant protective film 8 is formed by the vacuum film forming device, and a driver IC 9 is mounted. In this manner, the common electrode can be made wide, a head size in the main scanning direction can be reduced, and a low-cost head can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a line-type thermal print head used in thermal printers and facsimiles.

[Prior art] The structure of a conventional line-type thermal print head is
As shown in Figures (a) and (b), the electrode was formed in a single layer on a heat-resistant insulating substrate.

[Problems to be Solved by the Invention] However, in the head having the structure as shown in FIG. 5(a),
When the head size is increased in the main scanning direction to meet the recent trend of printers increasing print size, the current capacity of the common electrode becomes smaller and when multiple dots are energized at the same time, a voltage drop phenomenon occurs and the printing concentration decreases.

In particular, when the size of the head in the main scanning direction is 8 inches or more, the effect of voltage drop cannot be ignored. In addition, one or more must be provided inside. However, this structure also has the following drawbacks because the common electrode connection lead is formed between the driver ICs.

1) The head size increases in the main scanning direction, leading to an increase in cost.

2) The distance between the driver ICs in the area where the common electrode is formed is widened, and the length of the electrode in this area becomes longer, leading to higher lead resistance and a difference in density during printing.

[Means for Solving the Problems 1] In order to solve the above-mentioned problems, the line-type thermal printhead of the present invention has a connection point between the common electrode under the partial glaze and the power supply line, other than at both ends of the heat-resistant insulating substrate. It is characterized by having a structure in which one or more are provided inside, then a glaze glass is formed on the entire or part of the upper surface, desired electrodes are formed on the upper surface, and a driver IC is mounted.

Furthermore, the common electrode under the partial glaze is formed by thick film printing and firing.

[Example 1] FIG. 1 shows an example of a cross-sectional view taken along line A-A of the thermal print head according to the present invention shown in FIG. In Figure 1, 1 is a heat-resistant insulating substrate, 2 is the first layer glaze glass, and 3 is the second layer glaze glass.
The heating element 4 is formed on the second layer of glazed glass.

The common electrode 5 is formed under the first layer glaze, and is connected to the upper thin film common electrode at part A.

Further, a top view of the structure of the thermal print head according to the present invention is shown in FIG. In FIG. 2, the connection lead 6 between the common electrode and the power supply line is connected to the heat-resistant insulating substrate 1.
There are three in total, one at each end and one in the center.

This thermal print head is manufactured through the following steps.

First, as shown in FIG. 3(a), an Au or PT metal paste is printed on a heat-resistant insulating substrate 1 made of alumina or the like by screen printing to form a common electrode 5 and a connection lead 6. It is better for this metal paste to have a firing temperature as high as possible. In the present invention, the firing temperature is 8700C to 8800C.
Au paste of C was used. Here, the same effect can be obtained even if the common electrode and the connection lead are formed by a thin film manufacturing method such as a sputtering method or a CVD method. Furthermore, the width and thickness of the common electrode and the connection lead must be designed to vary depending on the dot density and number of dots in the thermal head.

Next, as shown in FIG. 3(b), a glaze glass 2 is printed on the upper surface of the common electrode 5 to form an electrically insulating layer. Here, the same effect can be obtained even if the glaze glass 2 is formed by a thin film manufacturing method such as a sputtering method or a CVD method.

Next, as shown in FIG. 3(C), glaze glass 3 is partially printed under the desired position of the heating element 4 and fired. The firing temperature at this time is slightly lower than the firing temperature of the metal paste.

A heating element layer 4 and an electrode layer 7 are formed on the substrate completed as described above using a vacuum thin film apparatus such as sputtering. After that, a heating element and an electrode shape are formed using an in-shell photolithography technique, and finally an insulating heat-resistant protective film 8 is formed using a vacuum thin film apparatus. Next, the driver IC 9 is mounted. The mounting method here may be a flip chip method, a wire bonding method, or a TAB method.

In this embodiment, the case where there are three connection leads has been described, but the number of connection leads needs to be set to an appropriate value depending on the size of the head in the main scanning direction. Fourth
The figure shows an example.

[Effects of the Invention] As explained above, by using a simple two-layer electrode structure in which the common electrode is formed on the lower part and the electrode and driver IC are formed on the upper part with glaze glass in between, the common electrode can be formed widely and the main Since the size of the head in the scanning direction can be reduced, it is possible to supply an inexpensive multi-head, and it is expected that the printing quality will be improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram showing a cross-sectional structure of a line type thermal print head of the present invention. FIG. 2 is a diagram showing the top structure of the line type thermal print head of the present invention. FIGS. 3(a) to 3(c) are diagrams showing the manufacturing process of the line type thermal print head of the present invention. FIG. 4 is a diagram showing an embodiment of the present invention. FIGS. 5(a) and 5(b) are diagrams showing the structure of a conventional line type thermal print head.・Heat-resistant insulating substrate ・1st layer glaze glass ・2nd layer glaze glass ・Heating element layer ・Common electrode ・Connection lead ・Electrode ・Protective film ・Driver IC ・External connection terminal and above

Claims (1)

[Scope of Claims] 1) In a thermal print head having a partially glazed glass on a heat-resistant insulating substrate, and having at least a heating element, an electrode, a common electrode, and a driver IC, the common glass is placed on the heat-resistant insulating substrate. A line-type thermal device comprising an electrode layer, a glaze layer that electrically insulates the common electrode on a part or the entire surface of the common electrode layer, and further has an electrode layer and a driver IC on top of the glaze layer. print head. 2) The line type thermal print head according to claim 1, wherein the common electrode is formed by thick film printing and firing.