JP2937660B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head for use in a thermal printer or the like, and more particularly to a thermal head capable of realizing a longer life by improving durability against abrasion.

[0002]

2. Description of the Related Art In a thermal head mounted on a thermal printer, for example, a plurality of heating elements are linearly arranged on the same substrate, and the heating elements are selectively energized and heated according to desired print information. It is used for color recording of a thermosensitive recording paper or transfer recording to plain paper via an ink ribbon.

FIG. 4 shows an outline of a general thermal head. In a thermal head 1, a heat generating portion 3 which selectively generates heat by energization is provided on an insulating substrate 2 made of ceramic such as alumina. It is configured to be formed on a straight line.

The heat generating portion 3 includes a glaze layer (not shown) made of glass or the like functioning as a heat storage layer formed on the substrate 2, and a plurality of heat generating layers made of Ta ₂ N or the like formed on the glaze layer. And a protective layer (not shown) such as an abrasion-resistant layer formed on the uppermost portion.

FIG. 5 is a plan view showing a main part of the heat generating portion 3 of the conventional thermal head 1, in which a plurality of heat generating members 4, 4 that generate heat when energized are linearly arranged. .

One end of each heating element 4 has all the heating elements 4
The common electrode 5 is connected to the heating element 4 and the other end is connected to an individual electrode 6 independent of each heating element 4. These electrodes are connected to a thermal head drive circuit (not shown). The heating element 4 is selectively energized by a signal from the drive circuit to perform desired printing.

[0007]

However, such a conventional thermal head has the following disadvantages, and it is difficult to extend the life of the thermal head itself.

That is, in a thermal printer,
As shown in FIG. 6, a thermal head 1 in which a glaze layer 7, a plurality of heating elements 4, 4 and a protective layer 8 are laminated on a substrate 2 in this order is pressed against a platen 10 via a recording medium 9 such as thermal recording paper. Printing is performed by selectively heating the heating elements 4 and 4 of the thermal head 1. At this time, it is difficult to press the heating section 3 of the thermal head 1 uniformly over the entire surface of the heating section 3 against the platen 10. And FIG.
As shown in FIG. 6, one end of the heat generating portion 3 is pressed against the platen 10 more strongly than the other portion, that is, a so-called one-sided contact state (in FIG. 6, the lower portion of the heat generating portion is pressed more strongly. , A “low hit state” is shown) in many cases.

If the printing operation is performed in such a one-sided contact state, the one-sided part of the heat generating portion 3 of the thermal head 1 is rapidly worn.

FIG. 7 shows the progress of the wear of the heat generating portion 3 as described above. The wear portion 11 is in a side contact state of the heat generating portion 3 as indicated by an arrow A in the figure. Starting from the end, gradually progressing toward the center, and in a much shorter time than in the case of the unbalanced state, the heating section 3
The heating element 4 closest to the end is destroyed by abrasion.

If at least one of the heating elements 4 constituting the heating section 3 is destroyed, it is impossible to perform complete printing as a thermal printer. There is a problem that the life of the thermal head is significantly shortened, and there is also a problem that the life of the thermal head greatly varies because the state of the one-side contact itself also varies.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and realizes high-quality printing for a long period of time even if the heat generating portion comes into contact with the platen or its pressing state varies. It is an object of the present invention to provide a thermal head that can perform the thermal head.

[0013]

In order to achieve the above object, a thermal head according to claim 1 of the present invention is provided on a substrate.
In a thermal head having a heating element array in which a plurality of heating elements are linearly arranged, a platen of the heating element array
A pseudo heating element that is not electrically connected to the drive circuit of the thermal head is connected to the end of the side that is strongly pressed in contact with the common head.
It is characterized in that it is arranged so as to be connected to the poles and the individual electrodes formed halfway .

[0014]

[0015]

According to the thermal head of the present invention having the above-described structure, a pseudo heating element which is not electrically connected to the driving circuit of the thermal head is arranged at the end of the row of heating elements formed on the substrate. In addition, even if the heat generating portion hits against the platen, the heat generating member at the end of the heat generating row is not destroyed in a short time.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the description of the embodiments described below, the same parts as those in the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a plan view showing a main part of a heat generating portion in an embodiment of the thermal head of the present invention.

In this embodiment, a plurality of heating elements 4 which generate heat when energized are arranged in a straight line, and a common electrode 5 is provided at one end of each heating element 4 and the other end thereof. The point that the individual electrodes 6 and 6 are connected to the portion is the same as the conventional one, however, the point that the pseudo heating element 12 is further formed at the end of the heating element 4 is different from the conventional one. Is different.

That is, as shown in FIG. 1, outside the heating element 4a located at the end in the arrangement direction of the heating elements 4, 4 arranged in a straight line, the heating elements 4 are connected to the heating element 4a. 3 of substantially the same shape made of the same material as the heating element 4a.
The pseudo heating elements 12, 12 are formed.

One end of the pseudo heating element 12 is connected to the common electrode 5 similarly to the heating element 4, and the other end is connected to the electrode pattern 13 similar to the individual electrode 6.
The electrode pattern 13 is formed only halfway as shown in FIG. 1, and the pseudo heating element 12 supplies electric power to a driving circuit (not shown) that supplies power to the heating element 4 to generate heat. It is configured so that it is not electrically connected.

The pseudo heating elements 12, taking into account the degree per the platen head in a thermal printer or the like to apply the thermal head may be formed at one end either of the heating element row.

For example, as shown in FIG.
If the lower side is more strongly pressed against the platen 10, the pseudo heating element 12 is formed at the lower end side in FIG. 2, and as shown in FIG. If the upper side is more strongly pressed against the platen 10, the pseudo heating element 12 is formed on the upper end side in FIG.

Next, the operation of this embodiment will be described.
The formation of the pseudo heating element 12 is performed in the same step as the formation of the heating element 4. The electrode pattern 13 connected to the pseudo heating element 12 is formed at the same time when the individual electrode 6 is formed, and the electrode pattern 13 is shaped such that the pattern is interrupted on the way.

When printing is performed using such a thermal head 1, if the heating portion 3 has a partial contact with the platen, the region of the end portion on the side that is strongly pressed against the platen 10 is the other portion. However, since the heating element 4 actually used for printing does not exist in this area, even if this area is worn,
It does not affect the function of the thermal head 1 itself.

Further, even if the contact position of the thermal head 1 varies and the wear position changes slightly, the heating element 4 does not exist in the early wear region as described above. There is no variation in the service life.

Furthermore, if the heating element 4 and the pseudo heating element 12 are made to have substantially the same shape, the pressure applied to each heating element becomes almost uniform near the end of the row of heating elements, and particularly, thermal transfer using an ink ribbon. When printing is performed by the method, the load applied to the ink ribbon is made uniform, and the ink ribbon can be stably driven.

Next, examples of the results of the wear test of the thermal head of the present invention and the conventional thermal head are shown below.

As the thermal head of the present invention, a heater in which four pseudo heating elements are formed at the upper and lower ends of 56 heating elements, respectively, is used.
One having only 56 heating elements was used.

In the abrasion test, printing was performed at a printing speed of 250 mm / sec in each of three types of printing: thermal transfer printing using an ink ribbon, printing using thermal recording paper, and printing using FAX paper. The evaluation was made by measuring the sliding distance up to the point where the head was worn and the dot missing occurred.

The results are as shown in the following table.

[0031]

[Table 1]

As described above, it was found that when the thermal head of the present invention was used, the durability against abrasion was greatly improved in any of the printing methods.

Also, in the case of printing using the ink ribbon, the running state of the ink ribbon was good.

The number of the pseudo heating elements in the present invention is as follows:
Needless to say, one, two, five or more may be set as appropriate according to the characteristics of the thermal head and the applied thermal printer.

Further, the present invention is not limited to the above-described embodiment, and can be changed as needed.

[0036]

As described above, according to the thermal head of the present invention, the heating element array is strongly pressed against the platen.
A pseudo heating element that is not electrically connected to the drive circuit of the thermal head is connected to the common electrode and the
In this configuration, high-quality printing can be achieved over a long period of time even if the thermal head has a partial contact with the platen. Even if it happens,
This has a remarkable effect that the life of the thermal head does not vary.

[Brief description of the drawings]

FIG. 1 is a plan view showing a main part of a heat generating portion in one embodiment of a thermal head of the present invention.

FIG. 2 is a schematic diagram showing an example of a main part of a heat generating portion of the thermal head of the present invention and a state where the thermal head is pressed against a platen.

FIG. 3 is a schematic diagram showing an example of a main part of a heat generating portion of the thermal head of the present invention and a state where the thermal head is pressed against a platen.

FIG. 4 is a perspective view showing an outline of a general thermal head.

FIG. 5 is a plan view showing a main part of a heat generating portion of a conventional thermal head.

FIG. 6 is a schematic diagram showing a state where a conventional thermal head is pressed against a platen.

FIG. 7 is a schematic plan view for explaining how wear progresses in a conventional thermal head.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Thermal head 2 Substrate 3 Heating part 4, 4a Heating element 5 Common electrode 6 Individual electrode 7 Glaze layer 8 Protective layer 9 Recording medium 10 Platen 11 Abrasion part 12 Pseudo heating element 13 Electrode pattern

Continuation of the front page (56) References JP-A-2-26760 (JP, A) JP-A-61-146567 (JP, A) JP-A-4-94453 (JP, U) (58) Fields investigated (Int) .Cl. ⁶ , DB name) B41J 2/345 B41J 2/335

Claims (1)

(57) [Claims] 1. A thermal head having a heating element row in which a plurality of heating elements are linearly arranged on a substrate, wherein the end of the heating element row on the side which is strongly pressed against a platen is provided. A thermal head, wherein a pseudo heating element that is not electrically connected to a drive circuit of the thermal head is connected to a common electrode and an individual electrode formed halfway, and is arranged.