JPS62261458A - Thermal head - Google Patents

Abstract

PURPOSE:To enable the high resistance value of heating elements to be maintained and their long life to be realized by constituting a plurality of stages of partly glazed protrusions at the uppermost stage with an electrode provided at a part other than the uppermost stage. CONSTITUTION:A partly glazed layer 21 consists of two stages, one being a part glaze 21b forming a bottom protrusion and the part glaze 21a forming an upper stage protrusion. Electrodes 23, 24 at the end of a heating element 22 do not contact paper 9 because of the arrangement of electrodes 23, 24 at the end of the heating element 22 on the part glaze 21b. If stationary printing is performed, transfer dots are tapered in an electrode direction. For this reason, in ordinary printing, the dots are prolonged in a thermal head 4 movement direction, enabling appropriate recording dots 27 to be obtained. A contact part between the heating element and recording paper has the same vertical size as the heating element and the same short lateral size as the center of the heating element. Therefore, recording dots tend to become long laterally by the movement of the thermal head. Considering this, arrangement of the recording dots is appropriate. In addition, somewhat low heating temperatures of the electrode at both ends of the heating element disable thermal recording, so incomplete thermal recording is prevented at the external edge of recording dots, making sharp recording dots.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head for a thermal printer, and particularly to a thermal head suitable for obtaining high print quality.

[Conventional technology]

In a conventional thermal head, as described in Japanese Patent Laid-Open No. 56-150574, the partial glaze from which the heating element is projected from the substrate has a simple cylindrical shape. The partial glaze was designed to cause the heating element array to protrude as a whole, so that the contact surface pressure of the heating element portion with the recording paper during recording was approximately uniform. Therefore, the shape of the recording dot should approximately reproduce the shape of the heating element. However, since recording is normally performed while the thermal head is continuously running, the shape of the recording dot is longer in the direction of movement of the thermal head than the shape of the heating element. Therefore, as the recording speed increases, the recording dot shape becomes laterally elongated (with the direction of movement of the thermal head being horizontal), which deteriorates the print quality. In this way, no consideration was given to devices capable of high speed and high print quality.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional apparatus, the recording dots are horizontally long.

Incidentally, in order to reduce the size and cost of the thermal head driving IC, it is necessary to increase the resistance value of the first heating element and drive it at a high voltage and low current in order to suppress the current loss of the power source for driving the heating element. Here, the resistance value of the heating element depends on the material, dimensions, and film thickness of the resistor. The horizontal length of the recording dot can be corrected by the dimensions of the heating element by shortening the distance between the electrodes since the electrodes are drawn out laterally as shown in FIG. However, if the horizontal dimension of the heating element is shortened, the resistance value of the heating element will be low, the amount of current will increase when energized, the IC for driving the thermal head will be large, 1 heat generation will be concentrated in the heating element with short horizontal dimension, and the life of the heating element will be shortened. becomes shorter.

Although the resistance value can be increased by reducing the film thickness of the heat generating element, heat generation is concentrated in the thin film and the life of the heat generating element is shortened as described above.

The purpose of the present invention is to increase the resistance value of the heating element, maintain its lifespan, and achieve high printing quality. A thermal head that makes it possible? It is about providing.

[Means for solving problems]

The above object is achieved by processing the partial glaze from which the heating element protrudes, so that the projections of the partial glaze are formed in multiple stages as shown in Fig. This is achieved by installing the electrodes at both ends of the heating element in a portion other than the top of the protrusion of the partial glaze. This is because the heating element has the same dimensions and film thickness as conventional ones, but the part of the heating element that comes into contact with the recording paper during recording is the narrow part in the center, and the horizontal length of the recording dots mentioned above is corrected. .

[Effect]

As mentioned above, the central part of the heating element is placed on the top protrusion of the partial glaze, and the electrodes at both ends of the heating element are placed outside the top part, so during operation, the part that directly contributes to heat recording is the part of the heating element. Since this is the part that is in contact with the recording paper, the horizontal dimension of the central part of the heating element is shorter than the dimension of the heating element. When the effect of movement of the thermal head is added to this, the recording dots extend in the lateral direction and become correction dots.

〔Example〕

The following is an example of the present invention? explain.

Figure 2 is a perspective view of the external appearance of a thermal transfer printer. show.

A carriage 2 is slidably disposed within the frame 1,
A ribbon cassette 3 and a thermal head 4 are mounted on the carriage 2, and an ink ribbon 5 is stored in the ribbon cassette 3.

The carriage 2 is configured to be movable in the left and right directions in the figure by means of a carriage motor 6 and a timing belt 7. In this printer, a thermal head 4 is supported by a platen 8, and an ink ribbon 5? Printing is possible only when the paper 9 is moved while being pressed through the paper 9. Further, when thermal paper is used as the paper 9, printing can be performed by removing the ribbon cassette 3. The thermal head 4 is connected to a main control board 11 along with a carriage motor 6 and the like via a flexible A/-'P handle 10, and is energized and controlled.

FIG. 3 shows the configuration of the thermal head 4. A partial glaze 21 is provided on a ceramic substrate 20, and a heating element array 22 is provided on the glaze 21 in the portion. Figure 4 shows the wiring near the heating element. Each heating element 22
The electrodes are drawn out in a direction perpendicular to the columns a, 22b, . . .
It consists of control electrodes 24a, 24b, . The print movement direction of the thermal head 4 is a direction perpendicular to the heating element row 22.

FIG. 5 is a cross section of the thermal head 4 during printing using the conventional partial glaze 21. As shown in FIG. The ink ribbon 5 is omitted. A resistor film 25, two electrodes 23, 24, and a protective film 26 are sequentially coated on the partial glaze 21. As shown in the figure, the entire surface of the heating element 22 is in contact with the paper 9. Therefore, if only one dot is transferred without moving the thermal head ``4'', a recorded dot with approximately the same size as the heating element 22 should be obtained.

However, in normal printing, the thermal head 4 prints while moving, so the power supply time of the heating element 22 and the protective film 2
6-Heating element 2 depending on the time of heat transfer of the ink ribbon 5
The recording dot 27 becomes longer in the moving direction in proportion to the amount by which the dot 2 moves (FIG. 7).

FIG. 6 is a cross section of the thermal head 4 having the heating element 22 and the partial glaze 21 according to the present invention during printing.

The partial glaze 21 is processed into two stages, and consists of a partial glaze B21b forming a bottom protrusion and a partial glaze A21a forming an upper protrusion. The resistor film 25, the two electrodes 23 and 24, and the protective film 26 are formed in the same manner as in the prior art. The processing of the partial glaze 21 is originally intended to improve the contact with the rough-surfaced paper, so that the contact of parts other than the heating element 22 that do not contribute to printing is reduced, and the contact pressure is concentrated on the heating element 22. In the present invention, the electrode 23 at the end of the heating element 22
, 24° are also arranged on the partial glaze 821b, the electrode end of the heating element 22 does not come into contact with the paper 9, and if stationary printing is performed, the transfer dot should become narrower in the direction of the electrode. For this reason, in normal printing, the thermal head 4 is long in the moving direction.
Appropriate recording dots 27 can be obtained. The same effect as that of the present invention can be obtained even in the conventional method by using the distance between the electrodes 23 and 24 in FIG. It is also possible to make it shorter. But % electrode 2
3.If the distance between 24 and 24 is shortened, the heating element resistance value will be lower.
If the power is constant, the heating element driving current will be large, and the IC for driving the thermal head will have a large current capacity and be expensive. Further, by making the resistor film 25 thinner, the resistance value of the heat generating element can be increased, but when heat is generated, heat is concentrated on the thin resistor film 25, and the life of each heat generating element 22 is shortened.

According to one aspect of the present invention, the electrode portions at both ends of the heating element 22 are connected to the sixth electrode portion.
Since it does not come into contact with the paper 9 as shown in Figure (b), the M retaining film 26
Is the fault part of etc. mechanically abraded? This also has the effect of extending the wear life of the thermal head 4.

〔Effect of the invention〕

According to the present invention, the contact portion between the heating element and the recording paper is vertically equivalent to the heating element, and horizontally shorter at the center of the heating element, taking into consideration the horizontal elongation of recording dots due to movement of the thermal head. Then, the recorded dots become correct.

In addition, since there is no heat recording due to the electrode portions at both ends of the heating element and the low heat generation temperature, incomplete heat recording at the outer edge of the recording dot is prevented, and the recording dot becomes sharp.

In addition, the mechanical strength of the electrodes at both ends of the heating element was low due to distortion of the protective film, etc., which was a bottleneck in wear life, but since there is almost no contact between the ends of the heating element and the recording paper, the wear resistance has been improved. is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the vicinity of a heat generating part of a thermal head according to the present invention, FIG. 2 is an external perspective view of a thermal transfer printer, and FIG.
The figure is an external perspective view of the thermal head, FIG. 4 is a pattern diagram of the vicinity of the heat generating element of the thermal head, and FIG. 5 is a front view and a sectional view of the vicinity of the heat generating element of a conventional thermal head.
6 is a front view and a sectional view of the vicinity of the heating element of the thermal head according to the present invention, FIG. 7 is a print recording dot with the thermal head of FIG. 5, and FIG. 8 is a print with the thermal head of FIG. 6. It is a recording dot. DESCRIPTION OF SYMBOLS 1... Frame, 2... Carriage, 3... Ribbon cassette, 4... Thermal head, 5... Ink ribbon, 6... Carriage motor, 7... Timing belt, 8...・Platen, 9...Paper, 10...
・Flexible switchboard, 11... Main control board, 18.
...Driver IC119...Touching part, 20...Ceramic substrate, 21...Partial glaze, 21a...Partial glaze A, 21b...Partial glaze B, 22...
- Heat generating element (row), 22a.

Claims (1)

[Claims] 1. A thermal head having a partial glaze on a substrate and a plurality of heating elements arranged on the partial glaze,
The cross section of the partial glaze having a heat generating element is formed to have a plurality of stages of protrusions, the heat generating elements are arranged in a plurality of stages including at least the top stage of the projections, and the electrode portions at both ends of the heat generating element are arranged in a section other than the top stage of the projections. A thermal head characterized by being placed in the glaze part of. 2. A thermal head according to claim 1, characterized in that the width of the uppermost protrusion of the partial glaze is 0.4 to 0.8 times the pitch between the electrodes of the heating element with respect to the electrode direction of the heating element.