JPH06127007A - Thermal head - Google Patents

Abstract

PURPOSE:To realize a high-quality printing for a long term even if a heating part comes into ununiform contact with a platen or has variation in its pressure contact state. CONSTITUTION:Dummy heating elements 12 that are not electrically connected to a drive circuit of a thermal head 1 are disposed on the end of a heating part 3 made of a plurality of heating elements 4 and provided on a substrate 2. In this manner, the heating elements on the end of the heating part 3 are not broken in a short time even if the heating part 3 comes into ununiform contact with a platen 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a thermal printer or the like, and more particularly to a thermal head which can be extended in life by improving its durability against abrasion.

[0002]

2. Description of the Related Art A thermal head mounted on a thermal printer, for example, has a plurality of heating elements arranged linearly on the same substrate and selectively energizes and heats the heating elements according to desired print information. It is used for color recording of heat-sensitive recording paper or transfer recording onto plain paper via an ink ribbon.

FIG. 4 shows an outline of a general thermal head. In the thermal head 1, a heat generating portion 3 which selectively generates heat when energized 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 has a plurality of heat generations such as a glaze layer (not shown) made of glass or the like which functions as a heat storage layer formed on the substrate 2 and Ta ₂ N etc. formed on the glaze layer. It comprises a body (not shown), an electrode layer for energizing the heating element, and a protective layer (not shown) such as a wear-resistant layer formed on the uppermost portion.

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

All the heating elements 4 are attached to one end of each heating element 4.
Is connected to the common electrode 5, and the other end is connected to the individual electrodes 6 which are independent for each heating element 4, and these electrodes are connected to a thermal head drive circuit (not shown). The heating element 4 is connected to the heating element 4 by a signal from the driving circuit, and the desired printing is performed.

[0007]

However, such a conventional thermal head has the following drawbacks, which makes it difficult to prolong the life of the thermal head itself.

That is, in the 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 in this order on a substrate 2 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, however, it is difficult to press the heating section 3 of the thermal head 1 to the platen 10 uniformly over the entire surface. And FIG.
As shown in Fig. 6, one end of the heat generating part 3 is pressed against the platen 10 more strongly than the other part, that is, a so-called one-side contact state (in Fig. 6, the lower part of the heat generating part is pressed more strongly). In some cases, the "under-approach condition" is shown).

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

FIG. 7 shows the state of progress of wear of the heat generating part 3 as described above. The wear part 11 is a side where the heat generating part 3 is in one-side contact as shown by an arrow A in the figure. Starting from the edge of the heating element, gradually progressing toward the center of the heating element, it takes much less time than in the unattended state.
The heat generating element 4 located closest to the end of the is destroyed due to wear.

If even one of the heating elements 4 constituting the heating section 3 is destroyed in this manner, complete printing cannot be performed as a thermal printer, so in the conventional thermal head, the head itself is caused by this one-sided contact. There is also 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 one-side contact state itself also varies.

The present invention has been made in order to solve the above-mentioned problems, and realizes high-quality printing for a long period of time even if uneven contact of the heat generating portion with respect to the platen or variation in the pressure contact state occurs. It is an object of the present invention to provide a thermal head that can be used.

[0013]

In order to achieve the above-mentioned object, the thermal head according to claim 1 of the present invention comprises:
In a thermal head having a heating element array in which a plurality of heating elements are linearly arranged, a pseudo heating element that is not electrically connected to a drive circuit of the thermal head is arranged at at least one end of the heating element array. It is characterized by

A thermal head according to a second aspect of the present invention is the thermal head according to the first aspect, wherein the pseudo heating element is formed in the same shape as the heating element.

[0015]

According to the thermal head of the present invention having the above-described structure, the pseudo heating element which is not electrically connected to the driving circuit of the thermal head is arranged at the end of the heating element array formed on the substrate. Even if the heat generating portion is partially contacted with the platen, the heat generating element at the end of the heat generating element array is not destroyed in a short time.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. In the following description of the embodiments, the same parts as those of the conventional one are designated 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 the present embodiment, a plurality of heating elements 4, 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 individual electrodes 6 and 6 are connected to the respective portions in the same manner as the conventional one, but the conventional one is that a pseudo heating element 12 is further formed at the end of the heating element 4. Is different.

That is, as shown in FIG. 1, in the arrangement direction of the heating elements 4 and 4 which are linearly arranged, the heating element 4a is arranged outside the outermost end of the heating element 4a. , Made of the same material as the heating element 4a and having substantially the same shape 3
The individual pseudo heating elements 12, 12 are formed.

One end of the pseudo heating element 12 is connected to the common electrode 5 like 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 part way as shown in FIG. 1, and the pseudo heat generating element 12 is electrically connected to a drive circuit (not shown) that supplies electric power to the heat generating element 4 to generate heat. It is configured so that it is not physically connected.

The pseudo heating element 12 is formed at one end or both ends of the heating element row in consideration of how the head contacts the platen in the thermal printer to which the thermal head is applied. Good.

For example, as shown in FIG. 2, the thermal head 1
If the lower side is pressed against the platen 10 more strongly, the pseudo heating element 12 is formed on the lower end side in FIG. 2, and as shown in FIG. If the upper side is pressed against the platen 10 more strongly, 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 process as the formation of the heating element 4. Further, the electrode pattern 13 connected to the pseudo heating element 12 is formed at the same time when the individual electrode 6 is formed, but the electrode pattern 13 is formed such that the pattern is interrupted midway.

When printing is performed using the thermal head 1 as described above, if the heat generating portion 3 is unevenly contacted with the platen, the region of the end portion that is strongly pressed against the platen 10 is the other portion. However, since there is no heating element 4 actually used for printing in this area, even if this area is worn,
It does not affect the function of the thermal head 1 itself.

Even if the contacting position of the thermal head 1 varies and the wear position changes a little, the heating element 4 does not exist in the early wear region as described above. There is no variation in 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 substantially uniform near the end of the heating element row, and thermal transfer is performed especially using an ink ribbon. When the printing is performed by the method, the load applied to the ink ribbon is made uniform, and the running of the ink ribbon can be performed stably.

Next, an example of the results of the wear tests of the thermal head of the present invention and the conventional thermal head is shown below.

As the thermal head of the present invention, one in which four pseudo heating elements are formed on each of the upper and lower ends of 56 heating elements is used. As a conventional thermal head,
The one in which only 56 heating elements were formed was used.

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

The results are shown in the table below.

[0031]

[Table 1]

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

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

In the present invention, the number of pseudo heating elements in
Needless to say, it may be appropriately set according to the characteristics of the thermal head and the applied thermal printer, and the number may be one, two, or five or more.

Further, the present invention is not limited to the above-mentioned embodiment, but can be modified as necessary.

[0036]

As described above, according to the thermal head of the present invention, the pseudo heating element which is not electrically connected to the drive circuit of the thermal head is arranged at at least one end of the heating element array. As a result, high-quality printing can be achieved for a long period of time even if the thermal head is partially hit against the platen, and even if the pressure contact state varies, the thermal head life varies. There is a remarkable effect that there is no.

[Brief description of drawings]

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

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

FIG. 7 is a schematic plan view for explaining the progress of wear 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 worn part 12 pseudo heating element 13 electrode pattern

Claims (2)

[Claims] 1. A thermal head having a heating element array in which a plurality of heating elements are linearly arranged on a substrate, wherein at least one end of the heating element array is electrically connected to a drive circuit of the thermal head. The thermal head is characterized by arranging a pseudo heating element that is not connected to. 2. The thermal head according to claim 1, wherein the pseudo heating element is formed in the same shape as the heating element.