JPS5938077A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a high print quality at a low cost by connecting one terminal of heat generating resistor elements to a common electrode in parallel with an auxiliary electrode formed on a substrate after they are arranged on the substrate in numerous trains. CONSTITUTION:An auxiliary electrode substrate 11 is made thinner than the part at the center of a substrate 1 for a thermal head while a slant surface 3a is formed on the section intended for a common electrode 3 on the substrate 1 so that the common electrode 3 on the substrate 1 and an auxiliary electrode 10 on the auxiliary electrode substrate 11 contact each other at the position lower than the top of the substrate 1. Both the electrodes 3 and 10 are connected together electrically with a solder 12 along the entire length of the common electrode at the joint thereof 3 and 10. The lowered position of the auxiliary electrode 10 makes the top of the welded section so lower than that of the thermal head to prevent the projection of the welded section from the top of the thermal head even when the solder 12 swells.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention is used in printers, facsimile machines, etc. to convert information sent as electrical signals into letters and letters on thermal recording paper.
This invention relates to a thermal head for converting symbols or images.

FIG. 1 shows an example of a thermal head, in which 1 is a glazed ceramic substrate, and a large number of heating resistor elements 2 are arranged on the ceramic substrate 1. One end of the heating resistor element 2 is connected to a common electrode 3, and an electric current or applied voltage is applied to the common electrode 3. Further, the other end of the heating resistor element 2 is bonded to one end of the tape carrier 4, and an IC (SS l, h
4s I, integrated circuit such as LSI) connected to 5, lc
5 is connected to the wiring on the printed wiring board 6 through bonding at the other end of the tape carrier, and is connected to an external terminal. Reference numeral 7 denotes a metal support plate that adheres and supports the ceramic substrate 1 and the printed wiring board 6 and is also used as a heat sink for the heating resistor element 6.

This type of conventional thermal head is connected in parallel to a single common electrode 3 like a double series, and because an expensive metal such as Au is used due to the manufacturing process, the common electrode 3
cannot be made thick enough.

On the other hand, when the thermal head becomes longer and all dots are printed at once for high-speed printing, the current flowing through the common electrode 3 increases, causing a voltage drop at the center of the common electrode 3. , which has the disadvantage of causing a decrease in print density.

For example, when printing one line of A4 size paper thermally with 4 dots per line, a current of about 30A flows through the common electrode.
At the center of the common electrode, a voltage drop of several tens of percent occurs compared to both ends, resulting in insufficient concentration.

In order to avoid this, if the power applied to all the heating resistor elements is increased, the power will be excessive at both ends, which will shorten the life of the heating resistor elements.

In order to solve the above-mentioned problems, increasing the thickness and width of the common electrode is economically inappropriate as described above.

This invention was made in order to solve the above-mentioned problem, and by installing auxiliary electrodes in parallel in a thermal head in which one terminal of the heating resistor elements is commonly connected, it is possible to print long lengths and at high speed. Even in the thermal head of
It is an object of the present invention to provide a thermal head that can obtain high printing quality at low cost.

Examples of the present invention will be described below with reference to the drawings. In each figure, parts that are equivalent to those in Figure 1 are given the same reference numerals.

In FIGS. 2 and 3, 10 is an auxiliary electrode provided parallel to the common electrode 3. In FIG. This auxiliary electrode 1° uses, for example, a printed circuit board in which a Cu foil is formed in a band shape on an auxiliary electrode substrate 11 made of glass epoxy resin that is separate from the substrate 1 of the thermal head. The thickness of this Cu foil is preferably 10 times or more than the thickness of the Au film of the common electrode 3, for example, about 35 pm or more.

The auxiliary electrode substrate 11 has a thickness smaller than that of the central part of the substrate 1 of the thermal head, and the portion of the substrate 1 where the common electrode 3 is provided forms a slope 3a, so that the common electrode 3 on the substrate 1
The auxiliary electrode 10 of the auxiliary electrode substrate 111- is the substrate 1
The electrodes 3 and 10 are configured so that they touch each other at a position lower than the top surface, and the electrodes 3 and 10 are electrically connected to each other by solder 12 along the entire length of the common electrode at the joint between the electrodes 3 and 10. is connected to.

As described above, by lowering the position of the auxiliary electrode IO, even if the solder 12 bulges up, the upper surface of the solder part is lower than the thermal spatula F, 1 + T+i J, the remote is low, and the solder part is the thermal spatula l' 1tIn. It can prevent it from protruding further.

As the auxiliary electrode 10, instead of a printed circuit board type one, a normal metal wire may be bonded in parallel to the common electrode.

Further, the auxiliary electrode 10 is not limited to Cu, and other inexpensive materials with relatively high conductivity may be used.

Further, the auxiliary electrode 1o and the common electrode 3 may be electrically connected by any method.

By connecting the auxiliary electrode 10 to the common electrode 3 in parallel as described above, the voltage drop on the common electrode side is reduced.
Even when the thermal head is made longer, or when each heating resistor element is driven simultaneously to increase the printing speed, it is possible to perform printing that is consistent with each heating resistor element.

FIG. 4 shows the present invention in a so-called distribution type in which LC5 as a drive circuit is provided on both sides of a heating resistor element of a thermal head, and auxiliary electrodes 10a and 10b are provided on common electrodes 3a and 3b, respectively. An example of parallel arrangement is shown.

The other configurations are the same as those in FIG.

As detailed above, this invention provides a thermal head in which one terminal of a heating resistor element is connected to a common electrode, and since an auxiliary electrode is provided in parallel to the common electrode, the voltage drop within the common electrode is reduced, and a long Even when each heating resistor element is driven simultaneously, printing with uniform image density can be obtained. Furthermore, since an inexpensive conductor can be used for the auxiliary electrode, an increase in the cost of the thermal head can be suppressed.

[Brief Description of the Drawings] Fig. 1 is a plan view showing an example of a conventional thermal head, Fig. 2 is a plan view of SI showing an embodiment of the present invention, 1. Substrate, 3. Common electrode, 10.. Auxiliary. Electrode, 12...Solder. Patent applicant Ricoh Co., Ltd. − Attorney attorney Aoyama Hougai (2)

Claims (1)

[Claims] (1) In a thermal head in which heating resistor elements are arranged in multiple rows on a substrate, and one terminal of each heating resistor element is connected to a common electrode formed on the substrate, the heating resistor elements are arranged in parallel to the common electrode. A thermal head characterized by connecting an auxiliary electrode.