JPH01232071A - Thermal head - Google Patents

Abstract

PURPOSE:To improve the printing quality and gradation recording property of a thermal head by dividing a section which comes into contact with the thermal resistors of discrete electrodes and forming each single display dot of the divided discrete electrode and a plurality of common electrodes. CONSTITUTION:A section which comes into contact with at least the thermal resistor 5 of a discrete electrode 4 of all the electrodes provided, is divided. A single display dot is formed using four heat-generating sections 8a-8d formed on the divisions, mutually opposed, which are sandwiched between a plurality of discrete electrodes 4a, 4b and a plurality of common electrodes 3. Thus the printing quality and gradation recording property of a thermal head can be increased, and electric power be saved very simply.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermal head used in a thermal recording device such as a printer or facsimile.

2. Description of the Related Art Conventional thermal recording devices such as printers and facsimile machines use thermal heads to perform thermal recording on thermal paper or plain paper overlaid with an ink sheet. The recording density during thermal recording is determined by the amount of heat generated per unit volume of the heating resistor of the thermal head, and if the resistance value or volume of the heating dots varies, the amount of heat generated by each dot will vary. ,
This causes uneven print density.

FIG. 5 is a cross-sectional configuration diagram of a conventional thick film type thermal head. A glass glaze layer 2 is formed on an alumina substrate 1, a common electrode 39 and individual electrodes 4 are formed on this substrate so as to be arranged alternately, and a common heating resistor 6 made of ruthenium oxide is formed on this electrode. , further forming a wear-resistant layer 6.

FIG. 6 is a plan view showing the electrode shape of the conventional thick-film thermal head shown in FIG. Since it is difficult to create heating resistors independently in a thick film type thermal head, a line-shaped common heating resistor 5 is provided, and the common heating resistors 5 are arranged alternately from both sides of the heating resistor as conductor electrodes for energization. Electrode 3
and individual electrodes 4 are introduced and arranged in a staggered manner. Furthermore, two heat generating parts 7a and 7b correspond to one individual electrode, forming one dot. Note that elements common to the embodiments of the present invention described later are given the same numbers.

When a voltage is applied in pulses to the conductive electrode, a current flows through the heating resistor, generating heat at a high temperature of 300 to 450°C, and as soon as the application of power is stopped, it cools down to around room temperature. By repeating this process, a thermal recording is made. It makes it possible. From the viewpoint of power saving, it is desirable to be able to generate heat to a higher temperature with the application of less electric power. In addition, in order to enable high-speed printing, the applied voltage must be turned on.

Thermal responsiveness is required to instantly generate heat and cool down when turned off.

Problems to be Solved by the Invention However, in conventional thick-film thermal heads, the volume of the heat-generating resistor is larger than in thin-film thermal heads, so the heat generation efficiency is lower, and it is difficult to obtain the same recording density. Yes, it required a lot of electricity. Furthermore, since the volume of the heating resistor is large, the heat capacity is also large, and high-speed printing cannot be performed because it cannot follow the input voltage with a short cycle.

In terms of printing quality, with conventional thick-film thermal heads having staggered electrode shapes, it is difficult to print the line width of the line-shaped common heating resistor 5 uniformly, resulting in variations of several percent. Because of this, the contact area between the conductive electrode and the heating resistor is different, and the resistance value of each dot basically varies widely, resulting in large print density unevenness. The resistance value of the dots can be trimmed to a uniform value of about ±1% using a method that utilizes the change in resistance value due to self-generated Joule heat generated when power is supplied to the body, but the shape of the resistor Due to the variation in the amount of heat generated per unit volume of the resistor, it was not possible to make the amount of heat generated per unit volume of the resistor uniform.

The present invention solves these problems by eliminating uneven printing density in the thermal head, improving heat generation efficiency, enabling power saving, and improving gradation recording performance, high printing quality, and high reliability. It is something that makes gender possible.

Means for Solving the Problems In order to solve the above-mentioned conventional problems, the present invention divides at least the portion of each individual electrode that contacts the heating resistor, and provides a plurality of common electrodes and a plurality of divided individual electrodes. One display dot is formed by In addition, the width of the heat generating resistor is made longer than the length in which the common electrode and the individual electrodes face each other. It is possible to provide a thermal head with excellent heat generation efficiency, thermal response, and high reliability.

Embodiment FIG. 1 is a cross-sectional configuration diagram of a thick film type thermal head according to an embodiment of the present invention. :lf Silasley XN2 is formed on an alumina substrate 1, and a gold conductor electrode (with a thickness of 0.5
Common electrodes 3 and individual electrodes 4 made of ruthenium oxide (~1.0 μm) were formed so as to be arranged alternately, a common heating resistor 5 made of ruthenium oxide was formed on these electrodes, and a wear-resistant layer 6 was further formed. 〇 Fig. 2 is a plan view showing the electrode shape of the thermal head according to the first embodiment of the present invention, in which common electrodes 39 and individual electrodes 4 are alternately introduced and arranged from both sides of the common heating resistor 6, and each individual The electrodes 4 are each divided into two at the portions that contact the common heating resistor 6. In this embodiment, one display dot is composed of four heat-generating portions 6a, 8b, 8c, and 8d formed between the common electrode 3 and the individual electrodes 4a and 4b. Furthermore, the width of the heating resistor 60 is also increased by the length of the wall where the common electrode group and the individual electrode group face each other. In this case, in order to print characters of the same size as the conventional one, the width of each electrode is made narrower than in the conventional one.

With this configuration, even if the area of the heat-generating portion of each dot is made smaller than that of the conventional staggered electrode type thermal head, the area of each display dot remains the same, so the heat generation will be lower than that of the conventional thermal head. The current density flowing through the resistor can be increased, and heat generation efficiency and thermal response can be improved.

In addition, as shown in the example of printing shown in Fig. 3, conventionally the heat generating parts were e and one display dot was made up of one display dot, but in this embodiment four of them make up one display dot, so the printing High density and extremely good gradation recording properties can be obtained.

Furthermore, in the case of the electrode shape shown in Figure 2, the resistance value of the heat generating part is mainly determined by the length of the portion where the individual electrodes and the common electrode face each other, so it is affected by the non-uniformity of the shape of the heat generating resistor. However, it is possible to suppress the variation in resistance value between one display dot to a small value.

In addition, in order to limit the size of the heat generating part and improve heat generation efficiency and thermal response, conventional methods have increased the area of the electrode by partially widening the electrode width, but Since the rate of heat generation is very large compared to that of the heating resistor, some of the Joule heat generated in the heating element is diffused by thermal conduction within the conductive electrode, which is a major cause of a decrease in thermal efficiency. In the example, as shown in Figure 2,
Since there are four heating elements, the thermal efficiency will not be impaired even if the width of the conductor electrode and the width of the heating resistor are made equal. The thermal head configured with a staggered electrode pattern and the thermal head of this example were
/dot, 1 /a duty, 16ms
/cycle, printed on thermal paper, and measured the density of the coloring point of each dot with a microdensitometer.
While the conventional thermal head had a variation in the density of the coloring point of ±6% or more, the thermal head of this embodiment was able to print with very high quality with a variation of within ±2%.

In addition, the thermal head with the electrode shape of the present invention is a head with excellent thermal response that prints 1.2 to 1.4 times higher printing density with the same human power than a conventional head with a simple staggered electrode pattern. I found out something.

Furthermore, as a result of measuring the temperature change of the heating dots using an infrared microscope, it was found that the head had an extremely excellent transient response and the time constant of temperature change was about 10 to 20 times smaller than that of a conventional simple staggered head.

FIG. 4 shows another embodiment of the present invention, which has an even higher density configuration than that shown in FIG. In this case, the portion of each individual electrode 4 that contacts the heating resistor 5 is divided into three parts, and high-density printing can be achieved as well as in the first embodiment.

As explained above, the feature of the present invention is that each individual electrode side of the electrodes alternately introduced into the heat generating resistor is divided into a plurality of parts, and these divided electrode parts and the corresponding plurality of common electrodes form one single electrode. The reason lies in the fact that each display dot is formed. By adopting this configuration, it is possible to reduce and suppress the resistance value variation of the heating resistor, which has been a problem in the past:
It is possible to improve high print quality without uneven print density and gradation recording performance, and it is also possible to improve thermal response and power saving at low cost.

Although the above embodiment describes a thick film type thermal head, the present invention is not limited to the above embodiment, and if the electrode shape is such that the effect of the present invention is achieved, a thin film type thermal head may be used. But it has the same effect. Moreover, the constituent material of the head is not particularly limited.

In addition, in the above embodiment, only the individual electrodes are divided, but
A portion of the common electrode corresponding to this divided portion can also be divided.

Effects of the Invention As is clear from the above explanation, according to the present invention, the portion of the individual electrode that contacts the heating resistor is divided, and each of the divided individual electrodes and a plurality of common electrodes form one display dot. In particular, the thermal head has excellent printing quality and 9-gradation recording performance, thermal responsiveness and power saving can be extremely easily realized, and a highly reliable thermal head can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a thermal head according to the present invention, FIG. 2 is a plan view showing the electrode structure of a thermal head according to a first embodiment of the present invention, and FIG. 3 is a cross-sectional view of a thermal head according to the present invention and a conventional staggered 4 is a plan view showing the electrode structure of a thermal head according to another embodiment of the present invention, and FIG. 6 is a sectional view of a conventional thermal head.
The figure is a plan view showing the electrode configuration of the thermal head. DESCRIPTION OF SYMBOLS 1...Alumina substrate, 2...Glass glaze layer, 3...Common electrode, 4...Individual electrode, 4a, 4b... Divided individual electrodes, 6... Heat generating resistor, 6... Wear resistant layer. Name of agent: Patent attorney Toshio Nakao and one other person
472.1Jb-Ha split Lλ pieces Otaki 1 3rd
Figure 4 Crab, Hei? J 5ne ζK) Mekashi IF
JFigure 4Figure 5Figure 6

Claims (2)

[Claims] (1) In a thermal head comprising a common electrode group that contacts a heating resistor formed on an insulating substrate and energizes the heating resistor, and an individual electrode group for energizing that faces the common electrode group, each A thermal head characterized in that at least a portion of the individual electrodes that contacts a heating resistor is divided, and one display dot is formed by a plurality of common electrodes and a plurality of divided individual electrodes. (2) The thermal head according to claim 1, wherein the width of the heating resistor is longer than the length of the common electrode group and the individual electrode group facing each other.