JPS62158064A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain an equal heating value in respective heating resistors without difficulty and eliminate irregularities in coloring density to enhance a printing quality, by providing correction resistors between the heating resistors and feeding electrodes. CONSTITUTION:On an insulating base material 1 of a high resistant substrate of material such as ceramic, a plurality of heating resistors 2, 2...2 of the same width are arranged at a fixed interval. On one side of the heating resistors 2, a common electrode 3 is so formed as to commonly conduct through the heating resistors 2, and on the other side, separate electrodes 4, 4...4 are formed. In addition, each of the separate electrodes 4 has a disconnecting portion 4a of distance (l) disposed in position and correction resistors 2a, 2a...2a of respectively a required value of resistance are made with the parameter of the distance (l) of the disconnecting portions 4a. In this manner, the same voltage is applied between the common electrode 3 and each of the separate electrodes 4, but the demand P can be equal in all the heating resistors 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal head used as a print head of a thermal transfer recording device, for example.

[Technical background of the invention and its problems] In recent years, thermal transfer recording devices that use a thermal head as a print head have a simple mechanism, high reliability, can be made at low cost, and have low noise, etc. Because of these advantages, it has come to be widely used in facsimiles and various printers.

The thermal head in such a thermal transfer recording device has a plurality of heat generating resistors arranged on an insulating substrate, a common electrode is formed on one side of these heat generating resistors, and a common electrode is formed on one side of each heat generating resistor. Individual electrodes are formed on each of the other sides, and a wear-resistant film is formed at least on the heating resistor.

For example, when performing thermal printing, the thermal paper is moved close to the heating resistors in a direction perpendicular to the arrangement direction of the heating resistors, and voltage is selectively applied to the heating resistors to generate heat. Thermal printing is performed on this thermal paper.

By the way, when the voltage applied to the heating resistor is ■, and the resistance value of this heating resistor is R, the power P consumed by this heating resistor is P=V2/R... (1), and the relationship between this electric power P and the coloring density of the thermal paper is almost directly proportional, as shown in FIG.

However, conventionally, there has been variation in the resistance value of each heating resistor, and on the other hand, the same voltage is applied to each heating resistor.

For this reason, for example, the resistance values of the two heating resistors are set as R1 and R2, respectively, and the color density of the thermal paper is set as Dl and D, respectively.
2, then R1 > R2 (2>), then D2 > DI...
・(3) becomes.

Therefore, when printing on thermal paper, there is a problem in that the color density varies and the print quality deteriorates.

[Object of the Invention] The present invention was made in response to the above-mentioned circumstances, and an object of the present invention is to provide a thermal head with no variation in color density and good print quality.

[Summary of the Invention] That is, the thermal head of the present invention includes a high-resistance base, a plurality of heat-generating resistors arranged on the high-resistance base, and a power feeding electrode connected to these heat-generating resistors. In the head, a correction resistor is inserted between each of the heat generating resistors and the power supply electrode, so that there is no variation in color density and print quality is good.

[Embodiments of the Invention] Hereinafter, details of embodiments of the present invention will be described based on the drawings.

FIG. 1 is a schematic partial plan view of a thermal head according to an embodiment of the present invention, and FIG. 2 is a schematic partial longitudinal sectional front view of this thermal head.

As shown in FIGS. 1 and 2, this thermal head consists of a plurality of heat generating resistors 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, and 2 being of the same width, mounted on an insulating substrate 1 made of a material such as a high-resistance substrate such as ceramic.
are arranged at predetermined intervals.

A common electrode 3 is formed on one side of these heating resistors 2, and a common electrode 3 is formed on the other side of the heating resistors 2, and the heating resistors 2 are electrically connected to each other. Individual electrodes 4.4, . . . 4, each of which is electrically conductive, are formed.

Furthermore, these individual electrodes 4 are provided with disconnected portions 4a each having an independent interval β at a predetermined position. Each of them is designed to be electrically conductive.

A wear-resistant film (not shown) is formed on the insulating substrate 1 so as to cover at least the heating resistor 2.

Due to the distance between the disconnected portions 4a provided in each of the individual electrodes 4 described above, a resistance (correction resistance>2a, 2a...2a) with this distance β as a parameter of resistance value is formed in this portion, and this correction resistance By setting 2a to a desired resistance value, the same voltage is applied between the common electrode 3 and each individual electrode 4, but the power P consumed by each heating resistor 2 can be made the same. I can do it.

That is, as shown in FIG. 3, two heating resistors 5.
Let the resistance values of 6 be R3 and R4, respectively, and R3>R
4, the resistance value of the correction resistor 7 provided in the heating resistor 6 is r, and a voltage of Va is applied to both ends of the heating resistor 5.6.

At this time, the power P1 consumed by the heating resistor 5 is calculated by the formula (1
), P+ = Va 2/R3...=(4).

The applied power P1 of the same value also applies to the heating resistor 6.
is consumed, and if the current flowing through this heating resistor 6 is i, then 1=Va/JFh ・R4=・= (5>).

Furthermore, since the same current i as that of the heating resistor 6 flows through the correction resistor 7, the resistance value r of the correction resistor 7 is r=JR3・P
+ R:1 -*・+-...(e>).

In an actual thermal head, as shown in FIG. 4, n heat generating resistors are lined up, so the resistance values of each heat generating resistor are R' + , R' 2 . . . R'. The maximum value among them is set as Rmax, and this value Rmax is used as R3 in the case described above, and each resistance value r1, R2...
・The value of r can be found.

Further, as a method for forming the heating resistors of the thermal head of this embodiment, as shown in FIGS. 5 and 6, each heating resistor 8.
8...8 are measured, and the resistance value r' of the correction resistor of each heating resistor 8 is determined by the method described above.

Then, a resist film is formed on the entire surface of the common electrode 9, the individual electrodes 10, and the heating resistor 8, and a resist film is formed at a predetermined position on the individual electrode 10 in the width direction at a position where a correction resistor is to be formed, as shown in FIG. A laser beam or spot light in the ultraviolet region is scanned under the following conditions.

That is, the line width of the individual electrode 10 is W, and the heating resistor 8 is
When the sheet resistance value of is R, the interval of the correction resistance (
The bale width)2 is β=r'・W/mouth R (7).

Furthermore, if the total number of laser beams or spot beams hitting the resist film is a, the number of scans n is n=r' ・W/
a. Mouth R......(8).

After such exposure, the conductor layer of the individual electrode 10 is removed by etching to form a correction resistor having a desired resistance value r'.

Furthermore, since the heat generated by this correction resistor is much smaller than the heat generated by the heating resistor, it hardly affects printing.

[Effects of the Invention] As explained above, according to the thermal head of the present invention,
Since a correction resistor is inserted between the heating resistor and the power supply electrode, the amount of heat generated by each heating resistor can be easily set to the same value, and as a result, there is no variation in color density. , the print quality is good.

[Brief explanation of drawings]

FIG. 1 is a schematic partial plan view of a thermal head according to an embodiment of the present invention, FIG. 2 is a schematic partial longitudinal sectional front view of this thermal head, and FIGS. 3 and 4 are corrections in this embodiment. An equivalent circuit diagram of a thermal head for explaining the principle for determining the resistance value of a resistor; FIGS. 5 to 7 are diagrams for explaining a method of forming a heating resistor of the thermal head of this embodiment; FIG. 8 is a diagram showing the relationship between electric power and color density in the thermal head. 1......Insulating substrate 2.2...2...Heating resistor 3...
・・・・・・・・・・・・・・・・・・Common electrode 4.
4...4......Individual electrodes 2a, 2a...
・2a...Correction resistor 4a......Disconnected portion Applicant: Higashi Corporation 2 Applicant: Toshiba Electronic Device Engineering Co., Ltd. Agent Patent Attorney Su Yamasa - Figure 1 2G

Claims (1)

[Claims] In a thermal head comprising a high resistance base, a plurality of heat generating resistors arranged on the high resistance base, and a power supply electrode connected to these heat generating resistors, each of the heat generating resistors and the power supply A thermal head characterized in that a correction resistor is inserted between the electrodes.