JPS60171173A - Thermal head - Google Patents

Abstract

PURPOSE:To provide a thermal head of an output device for data and measuring equipment with a capability of uniformarizing a heating temperature distribution in a heating region and giving clear and high-quality printing data by forming a floating electrode between a common electrode and an individual lead electrode and covering said floating electrode with a heat generating resistor. CONSTITUTION:A floating electrode 19 or an island electrode which is electrically independent of a common electrode 4 connected to a heat generating resistor 6 and an individual lead electrode 5, is formed between both electrodes 4, 5. Then this floating electrode 19 is covered with the heat generating resistor 6. Thus a thermal head desired is constituted. EFFECT:Heat distribution is even and manufacture is simple. In addition, it is possible to manufacture the titled item by thick film technology.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a thermal head for a thermal printer, which is often used as an output device in various information devices, measuring devices, video processing devices, and the like.

(Prior art and its problems) A thermal head prints on thermal paper (or recording paper via a thermal transfer ink ribbon) by heating a heating resistor. It is necessary to generate heat. By the way, when one pixel (one dot) worth of heat generating area (heating resistor) is captured, the temperature tends to be high at the center and low at the periphery. Therefore,
When the entire area for one dot is heated to the temperature required for thermal recording, the center becomes an area with a higher temperature than necessary (hereinafter referred to as a heat spot), causing a so-called ``white spot'' in the center of the printed colored dot. In addition, the application of high-voltage pulses shortens the life of the thermal head. That is, as shown in FIG. 1, the heating resistor 3 between the common electrode 1 and the individual lead electrodes 2 is
In the configuration in which the heat generating area corresponds to a dot, the temperature distribution drops steeply from the center of the heat generating area, and one heat spot H5 shown by diagonal lines in the figure is generated. In addition, as shown in Fig. 2, one individual lead electrode 5 is arranged between adjacent common electrodes 4.40, and the part of the heating resistor 6 separated by the adjacent common electrodes 4.4 is divided into one dot. In the configuration where the heat generating area is used, the temperature drops sharply from two places in the center of the heat generating area to the periphery, and two heat spots H5 and H8 are generated.

[In addition, in Fig. 1.2, the closed curve in the heat generating region represents the heat distribution, with the center being a high temperature region and the peripheral region being a low temperature region. The bottom of both figures shows the cross-sectional state of heat distribution (heat distribution gradient), the shaded area corresponds to the heat spot H'S, and T is the exothermic temperature necessary for thermal recording. ] Therefore, various efforts have been made in the noodle industry to improve the above-mentioned heat distribution. For example, as shown in FIG. 3, there is a device in which the shape of the heat generating resistor 9 between the common electrode 7 and the individual lead electrodes 8 is meandered as shown in the figure to make the heat distribution uniform. L7
However, this configuration requires micro-machining of the heating resistor 9, and cannot be applied to a thermal head using thick film technology, which is easy to manufacture and inexpensive.

Further, as shown in FIG. 4, a metal layer 13 is formed on top of the heating resistor 11 formed on the substrate 10 with an insulating protective layer 12 interposed therebetween. There are also attempts to This configuration is also applicable, for example, to
As stated in Publication No. 0, it is formed using thin film technology.
If the thickness is not as thin as 300 m, the responsiveness of heat conduction will be poor. ) and planarization, and it is difficult to uniformly thicken and planarize the metal layer 13, so it cannot be applied to thermals formed by thick film technology. In addition, there are many manufacturing steps, which hinders cost reduction. In FIG. 4, 14 is a common electrode, 15 is an individual lead electrode, and 16 is an upper protective layer.

(Object of the Invention) The present invention has been made in view of the above circumstances, and its object is to provide a thermal head that has a uniform heat distribution, is easy to manufacture, and can also be manufactured using thick film technology. is to provide.

(Structure of the Invention) In order to achieve the above object, the thermal head of the present invention forms a floating electrode between a common electrode connected to a heating resistor and an individual lead electrode, and connects the floating electrode with the heating resistor. It is characterized by being covered.

(Embodiments of the invention).

Figures 5 to 8 relate to one embodiment of the present invention, where Figure 5 is a plan view of the main part with the upper protective layer* removed, Figure 6 is a sectional view of the main part, and Figure 7 is the heat distribution. It is an explanatory diagram of details.

This embodiment uses the same drive system as that shown in FIG. 2 described above, and the same reference numerals are given to the same components as in FIG. 2. In the figure, 17 is a substrate made of alumina ceramic, and a glaze layer 18 is adhered to the surface thereof. 4..., 5..., 19... are common electrodes, individual lead electrodes, and individual lead electrodes formed on the brain layer 18, respectively.
These three floating electrodes are simultaneously formed by a suitable method such as vapor deposition and photoetching process or screen printing, and in the embodiment, the gold electrodes are 2 to 5 pm thick. The common electrodes 4, . It is pulled out in the opposite direction to the pattern portion 4A and guided to the drive circuit. Furthermore, the floating electrode 19 located between each common electrode 4 and the individual lead electrode 5 is
．． It is an island electrode that is electrically independent from electrode 5. In the case shown in the figure, it has a rectangular shape and is slightly wider than both electrodes 4.5. It can be changed to an Ω shape as appropriate. (Preferably, a shape that is easy to process and relatively simple should be selected.) 6 is a band-shaped heating resistor, which includes the common electrode 4, individual lead electrodes 5,
. . , and is formed to have a thickness of 10 to 30 μm by screen printing or the like, and is made of an Ra02-based resistor in this embodiment. As described above, this heating resistor 6 is connected to the adjacent common electrode 4.
The area separated by 4 becomes the heating area for one dot, and the adjacent common electrode 4.4 and the individual REIT' electrode 5 between this
By controlling the current flow between the two dots, a heat generating area corresponding to one dot generates heat. 20 is an upper protective layer a having a thickness of 3 to 20 #In formed on the heating resistor 6, for example, 5i0
Consists of 2.

The configuration of the above embodiment and the conventional configuration shown in FIG. 2 were energized and heated under the same conditions (applied voltage 9.9 V, applied power A/sl tnsec, measuring device: Sanei Sokki ■ - Thermo Micro). Detailed measurements of the heat distribution are shown in Figs. 7 and 8. According to the measurement results of the example shown in Fig. 7, not only have the areas where H5 previously occurred disappeared, but the heat distribution is uniform throughout. It was confirmed that the temperature distribution was as follows. That is, compared to the steepness of the conventional temperature gradient in FIG. 8, it is clear that the temperature gradient is gentle and uniform, and the temperature gradient on line A-A in FIG. (see right side) is almost flat, and when looking at the temperature gradient perpendicular to the A-A line, it can be seen macroscopically that four small peaks are connected in succession, as shown in Figure 5. It was confirmed that it was the same.

The reason why the temperature distribution is uniform in this way is that the heat generated by the heating resistor 6 is temporarily stored in the floating electricity i@19, which has a much better thermal conductivity than the heating resistor 6, and this heat is transferred to the heating resistor. The presence of the floating electrode 19 causes the area between the floating electrode 19 and the other electrodes 4.5 to have a resistance effect (dispersed heat generation effect), etc. It is imagined that it is hanging. 7. Although the resistance value of the heating resistor 6 decreases somewhat due to the presence of the floating electrode 19, measurements have shown that this decrease is approximately 15%, which is acceptable for practical purposes.

(Effects of the Invention) As described above, according to the present invention, the heat generation temperature distribution in the heat generation region is made uniform with an extremely simple structure in which a floating electrode is formed between the common electrode and the individual and υ-doped electrodes. You can expect clear, high-quality print data.

Furthermore, since the temperature distribution in the heat generating area is made uniform, it is suitable for recording multiple gradations. In addition, floating electrodes can be formed at the same time as other electrodes, and the manufacturing process is very simple.Since the floating electrodes have a simple shape, they can be formed easily using thick film technology, making them highly productive and inexpensive. It has a very remarkable effect.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the main part of the first conventional example, Fig. 2 is a plan view of the main part of the second conventional example, Fig. 3 is a plan view of the main part of the third conventional example, and Fig. 4 is a plan view of the main part of the third conventional example. 4 shows a cross section of the main part of the conventional example, and FIGS. 5 to 7 show a thermal head according to an embodiment of the present invention,
Figure 5 is a plan view of the main part with the upper protective layer removed, -6
The figure is a sectional view of the main part, Figure -7 is an illustration of the thermal layer state,
FIG. 8 is an explanatory diagram of the state of heat distribution in the second conventional example of μ゛. In the figure, 4... is a common electrode, 5... is an individual lead electrode, patent applicant Copal Co., Ltd. Figure 3

Claims (1)

[Claims] A thermal head characterized in that a floating electrode is formed between a common electrode connected to a waste heat resistor and an individual lead electrode, and the floating electrode is covered with a heat generating resistor.