JPH01123760A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a uniform heat generating temperature distribution over a whole heat generating resistor even if counter electrodes are slightly displaced from the resistor by mask alignment or the like by increasing a width between the resistor and the electrodes in a scanning direction larger than that of the resistor. CONSTITUTION:When the width of a common electrode side discrete electrodes 2' is d2, the width of discrete electrodes 3 is d3 and the width of a heat generating resistor 4 is d4, they are so constructed as to satisfy d4<d2, d4<d3. That is, a conductive layer made of gold paste is formed by screen printing and baking on one side face of a glazed ceramic substrate 1, patterned by photolithography etching with a predetermined mask, thereby forming a common electrode 2 and discrete electrodes 3 of a facing structure. Then, the resistor 4 of the shape isolated at each one bit is formed on counter electrodes 2' and 3. In this case, since the width of the discrete electrodes is formed approx. 5-10mum wider than that of the resistor 4, they are not extended from the electrodes 2', 3 even if the resistor 4 is slightly displaced at is position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an individually facing thermal head, and particularly to the structure of a thermal head for improving printing quality.

[Conventional technology]

As a thermal head widely used in thermal printers, facsimile machines, etc., an individual facing thermal head is used, which has a structure in which each electrode faces individually, and each electrode is connected to a heating resistor by an overlapping part. It is being Conventionally, in this individually opposed thermal head, the width of each electrode and the width of the heating resistor are generally approximately the same.

An example is shown in FIG. In FIG. 3, 31 is a glazed ceramic substrate, 32 is a common electrode, 32' is an individual electrode on the common electrode side, 33 is an individual electrode, 34 is a heating resistor, and 35 is a superimposed portion of each electrode and the heating resistor. shows. In the figure, the width d32 of the opposing individual electrodes 32' and 33,
Since the width d33 and the width d34 of the heating resistor 34 are approximately the same, the width d35 of the overlapping portion 35 thereof is also formed to have approximately the same width. That is, d32! = id33 delivery d3
4#d35.

By the way, the thermal head prints using the heat generated in the heating resistor 34 by passing current between the opposing electric bridges 32' and 33, but each electrode has better thermal conductivity than the heating resistor. , a part of the heat generated by the heating resistor flows out to the electrode side through the overlapping portion 35 between the electrode and the heating resistor, and as a result, there is a problem that printing power becomes large in order to obtain printing quality. there were.

Therefore, in order to reduce the escape of heat generated from the heating resistor part to the electrodes when electricity is applied and to reduce the printing power consumption, the width of the overlapping part of the opposing electrode and the heating resistor is adjusted in the overlapping area. It has been proposed to make the width of the heating resistor narrower than the width in the main scanning direction (Japanese Patent Application No. 17777/1986).
(See No. 6).

For example, as shown in FIG.
This can be achieved by making the widths d42 and d43 of the heating resistor 44 narrower than the width d44 of the heating resistor 44 in the main scanning direction. .

[Problem that the invention seeks to solve]

However, in actual manufacturing of individual facing type thermal heads, the positional relationship between the heating resistor and each counter electrode varies from bit to bit due to variations. That is, it is thought that this is due to variations in mask precision when forming the heating resistor, variations in etching precision when forming electrodes, variations in alignment precision between the two, and the like.

In other words, as shown in FIG. 5(a), due to variations in alignment accuracy between the opposing electrode and the heat generating resistor, the positions of the two become misaligned and the current path in the heat generating resistor is biased to one side. figure(
As shown in b), the positions of the electrodes and the heating resistor are shifted for each bit due to variations in mask accuracy when forming the heating resistor and variations in etching accuracy when forming the electrode.
The resistance values of the heating resistors are different, and the current path is biased. As a result, the temperature distribution in the resistor is also biased, resulting in a problem that printing quality is degraded.

In addition, if the width of each counter electrode is made smaller than the width of the heating resistor in the main scanning direction, the printing power can be reduced, but the current path in the heating resistor is biased toward the center, resulting in a heating area. There is a problem in that the printed dot shape does not accurately reproduce the size of the heating resistor.

Furthermore, if the heat generating area of the heat generating resistor is uneven, the heat generating resistor is likely to be thermally destroyed, resulting in poor reliability.

Therefore, an object of the present invention is to provide a thermal head that improves printing quality and yield by reducing variations in resistance values of heating resistors and eliminating bias in temperature distribution.

[Means and effects for solving the problems] In order to achieve the above object, the present invention has a structure of individual facing electrodes, and in a thermal helad in which the facing electrodes are connected to a heat generating resistor through overlapped portions, the facing electrodes are connected to a heating resistor. The width in the main scanning direction at least in the overlapping portion is made wider than the width of the heating resistor.

By adopting this structure, even if a slight positional shift occurs between each opposing electrode and the heat generating resistor due to mask alignment, etc., there will be no part where the electrodes and the heat generating resistor are not overlapped, and the heat will be generated. The current path in the resistor is not biased toward one side or the center, and a uniform heat generation temperature distribution can be obtained over the entire area of the heat generating resistor.

[Example page] An embodiment of the present invention will be described with reference to FIG.

In Fig. 1, numeral 1 is a glazed ceramic substrate, 2 is a common electrode, 2' is an individual electrode on the common electrode side, 3 is an individual electrode, and 4 is an individual electrode.
indicates a heating resistor. In FIG. 1, if the width of the individual electrode 2' on the common electrode side is d2 - the width of the individual electrode 3 is d3, and the width of the heating resistor 4 is d-, the configuration is such that d4<d2, d4<d3 are satisfied. has been done.

In the manufacturing method of this embodiment, a conductive layer made of gold paste is formed on one surface of a glazed ceramic substrate 1 by screen printing and baking, and then patterned by photolithography using a predetermined mask to form a common electrode 2 with an opposing structure. , forming individual electrodes 3. Each opposing individual electrode 2'
, 3 is wider than the width of the heating resistor 4 to be formed next.
Design to be about 10 μm wide.

Next, heating resistors each having a shape separated for each bit are formed on each of the opposing electrodes 2' and 3. This is done by coating and baking a photoresist on each electrode in advance, creating an opening at the location where the heating resistor is to be provided, and filling the opening with, for example, ruthenium oxide (R).
A heating resistor 4 made of a mixture of u02) and glass frit is embedded.

Thereafter, the photoresist is removed to form heating resistors separated for each bit.

In the thermal head formed according to this embodiment, the width of the individual electrodes is formed in advance to be about 5 to 10 μm wider than the width of the heat generating resistor 4, so even if the heat generating resistor 4 is formed with some misalignment, It does not protrude from above the individual electrodes 2' and 3.

Finally, an overglaze layer (not shown) as a wear-resistant layer.
is formed on the heating resistor.

Another embodiment of the invention is shown in FIG. In Figure 2,
The same numbers as in FIG. 1 indicate the same parts, and 20 indicates a common electrode.

In this embodiment, no individual electrodes are formed on the common electrode 20, but a line-shaped common electrode is used, and a heating resistor is formed in a shape corresponding to the opposing individual electrode 3. The thermal head having such a configuration can also obtain the same effects as the first embodiment.

In addition to the method described in the above embodiments, the heating resistor may be formed by forming the resistor over a wider area than the desired shape of the heating resistor, and separating the resistor into bits by dry etching or wet etching. A method of forming a can be used.

Furthermore, although a thick film type heating resistor has been described, the present invention is not limited to this. After forming each electrode, a resistor layer is formed on the entire surface of the substrate, and then patterning is performed using photolithography technology to form a resistor. Needless to say, the present invention can also be applied to thin film type thermal heads. [Effects of the Invention] By employing the structure of the present invention, the resistance value of the heating resistor of the individually opposed thermal head can be reduced from variation for each bit because the contact between each electrode and the heating resistor is ensured. The current path during energization and heat generation is not biased to one side or the center, but is uniform over the entire resistor, and the heat generation temperature distribution is also uniform.

Therefore, the reproducibility of printed dots is improved, the quality thereof is also improved, and a thermal head with increased reliability and high yield can be formed.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of one embodiment of the thermal head of the present invention, FIG. 2 is a configuration diagram of another embodiment of the thermal head of the present invention, and FIGS. 3 to 5 are configuration diagrams of conventional thermal heads. It is an explanatory diagram. 1.--Glazed ceramic substrate, 2--Common electrode, 2'--Individual electrode on common electrode side, 3--Individual electrode, 4--Heating resistor.

Claims (1)

[Claims] In a thermal head in which electrodes are individually opposed to each other and each of the electrodes is connected to a resistor through an overlapping portion,
A thermal head characterized in that the width of the resistor at the overlapping portion is narrower than the width of the electrode.