JP3017550B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used for a printing device such as a facsimile, a printer, a word processor and the like.

[0002]

2. Description of the Related Art A thermal head used in a printing apparatus such as a thermal or thermal transfer printer generally has a structure shown in FIGS. The thermal head shown here is a thick film type, in which a glaze layer 11, a common electrode 12, an individual electrode 13, and a heating resistor 14 are formed on an insulating substrate 10 made of alumina or the like, and the whole is covered with a protective glass layer 15. It was done.

As can be seen from FIG. 5, the common electrode 12 and the individual electrode 13 have a bar shape that alternately crosses below a heating resistor 14 arranged in the print scanning direction. When a current is applied between the common electrode 12 and an arbitrary individual electrode 13, the heating resistor between the common electrode 12 and the individual electrode 13 generates heat, and printing is performed.

[0004]

In such a thermal head, one of the thermal heads divided by a common electrode 12 and an individual electrode 13 is used.
When microscopically viewing the flow of current through the two heating resistors, the current flows under the resistor (on the glaze layer 11 side), so that the current density under the resistor is high and the thermal stress due to heat generation is low. It will concentrate on the lower side of the resistor. In particular, when printing paper such as low-sensitivity thermal paper is used, it is necessary to increase the power. However, due to the concentration of the thermal stress, there is a limit to the withstand voltage of the heating resistor. Therefore, it cannot sufficiently cope with low-sensitivity paper.

The heat generated below the heating resistor is transmitted to the upper side of the resistor and reaches the printing paper through the protective glass layer 15. However, since the resistor is a thick film resistor, the heat transfer path is long. Become. Poor heat transfer efficiency, poor thermal response,
The printing quality also decreases. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal head in which the heat resistance of the heating resistor is improved so as to sufficiently cope with low-sensitivity printing paper, and the thermal response and printing quality are improved.

[0006]

According to a first aspect of the present invention, there is provided a thermal head, wherein a common electrode is formed below a heating resistor, and an individual electrode is formed above or across a width of the heating resistor. The common electrode and the individual electrode are alternately crossed with the heat generating resistor.
In the thermal head according to the second aspect, the common electrode is formed on the heating resistor, the individual electrode is formed below or around the width direction of the heating resistor, and the common electrode and the individual electrode are alternately arranged with the heating resistor. It is characterized by crossing. In the thermal head according to the third aspect, the common electrode is formed around the heating resistor in the width direction, the individual electrode is formed below, above or around the heating resistor, and the common electrode and the individual electrode are heated. It is characterized by being alternately crossed with a resistor.

The thermal head according to the present invention is characterized in that:
There are a total of seven modes as described below depending on each combination in the above configuration. Aspect: Common electrode formed below heating resistor, individual electrode formed above heating resistor Aspect: Common electrode formed below heating resistor, individual electrode in width direction of heating resistor Formed around: Aspect: Common electrode formed on heating resistor, individual electrode formed below heating resistor Aspect: Common electrode formed on heating resistor, and individual electrode formed as heating resistor Formed around the body in the width direction Aspect: Common electrode formed around the width direction of the heating resistor, and individual electrode formed below the heating resistor Aspect: Common electrode formed in the width direction of the heating resistor And the individual electrodes are formed on the heating resistor. Aspect: The common electrode is formed around the heating resistor in the width direction, and the individual electrode is formed around the heating resistor in the width direction. In any of the thermal heads of the above-described embodiments, the current is Does not flow biased only to the lower side of the resistor, but flows obliquely up and down the resistor, and the current density on the lower side of the resistor is reduced. In addition, since the heat generating portion is distributed not only on the lower portion of the resistor but also on the upper portion, the heat transfer distance from the resistor to the surface of the protective glass layer coated on the resistor is reduced.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal head according to the present invention will be described below with reference to embodiments. FIG. 1 shows an embodiment according to the above aspect. The thermal head of this embodiment is provided with a common electrode 2, an individual electrode 3, and a heating resistor 4 arranged in a print scanning direction on a glaze layer 1 formed on an insulating substrate (not shown) made of alumina or the like. is there. The common electrode 2 has a bar-shaped electrode 21 extending at a certain interval in a direction crossing the heating resistor 4. The rod-shaped electrode 21 exists around the resistor 4 in the width direction, and at a peripheral portion of the resistor 4, an arc-shaped electrode 21 a passing above the resistor 4 and a straight electrode passing below the resistor 4. Branch to 21b. Individual electrode 3 is common electrode 2
The portion extending below the resistor 4 between the rod-shaped electrodes 21 and the lower portion of the resistor 4 becomes the straight electrode 3b. The upper portions of the common electrode 2, the individual electrode 3, and the heating resistor 4 are covered with a protective glass layer, but are omitted in the drawing.

In such a thermal head, the common electrode 2 is provided on a portion of the heating resistor 4 corresponding to one print dot.
When the current is passed through the rod-shaped electrode 21 and the individual electrode 3, the current flows through the resistor 4 connecting the straight electrode 21 b and the straight electrode 3 b.
Not only the lower region but also the arc-shaped electrode 21a and the straight electrode 3
b also flows to the region connecting diagonally. Thereby, the resistor 4
As a result, the current density in the lower region of the resistor 4 is reduced, and the power durability of the resistor 4 is improved. Therefore, low-sensitivity printing paper can be used.

Further, since the heat generating area of the resistor 4 is expanded, and especially in addition to the heat generating area above the lower part in addition to the lower part of the resistor 4, the protective glass passes through the resistor 4. The heat transfer path reaching the surface of the layer is shortened, and the heat transfer efficiency is improved. Therefore, the thermal responsiveness is improved, and the printing quality is also improved. An example according to the above embodiment is shown in FIG. The thermal head of this embodiment is different from the head of FIG. 1 in that the individual electrode 3 crosses the upper side of the resistor 4, and all other configurations are the same. The individual electrode 3 has a portion above the resistor 4 serving as an arc-shaped electrode 3a. Also in this head, since the current flows in the region extending to the arc-shaped electrode 21a and the arc-shaped electrode 3a, and to the straight electrode 21b and the region extending to the arc-shaped electrode 3a, the same operation and effect as in the above embodiment can be obtained.

FIG. 3 shows an embodiment in which the individual electrodes 3 are present around the resistor 4 in the width direction. The individual electrode 3 has an arc-shaped electrode 3a on the upper side of the resistor 4 and a straight electrode 3b on the lower side. In this embodiment, since the current flows in the region around the resistor 4, the same operation and effect as in the above embodiment can be obtained.
FIGS. 4 (a) to 4 (c) show various aspects of FIG.
(A) to (d) schematically show cross sections of the heating resistor 4 in the printing scanning direction in each of the embodiments. The arrows shown in the resistor 4 indicate the current paths. The current path seen in each embodiment is in a direction obliquely crossing the resistor 4 vertically in the vertical direction as compared with the conventional path (only the lower side of the resistor 4), the current flow area is expanded, and the heating area is also the resistor. 4 above.

[0012]

As described above, the thermal head of the present invention has the following effects because the common electrode and the individual electrode are formed on the heating resistor in any one of the above-described embodiments. (1) The current density is reduced because the current flow area in the heating resistor is increased. For this reason, the entire heating resistor generates heat, the power resistance of the heating resistor is improved, and it is possible to sufficiently cope with low-sensitivity printing paper. (2) Since the heat-generating portion exists not only in the lower portion of the heat-generating resistor but also in the upper portion, the heat transfer distance from the resistor to the surface of the protective glass layer on the resistor is shortened. For this reason,
Heat transfer efficiency is improved, and thermal responsiveness and printing quality are improved. (3) Since the common electrode and the individual electrode alternately intersect the heating resistor, the current injection efficiency is improved, and wasteful power consumption can be prevented. (4) According to the above items (1) to (3), high-quality printing on low-sensitivity printing paper can be performed at high speed.

[Brief description of the drawings]

FIG. 1 is a partially omitted plan view according to an embodiment of a thermal head of the present invention.

FIG. 2 is a partially omitted plan view according to an embodiment of the thermal head of the present invention.

FIG. 3 is a partially omitted plan view according to an aspect of the thermal head of the present invention.

FIG. 4 is a view schematically showing a current path in a heating resistor in each of the embodiments to of the thermal head of the present invention.

FIG. 5 is a diagram schematically showing a current path in a heating resistor in each of the embodiments to of the thermal head of the present invention.

FIG. 6 is a partially omitted plan view of an example of a conventional thermal head.

7 is a cross-sectional view of the head shown in FIG. 6, taken along line AA.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Glaze layer 2 Common electrode 3 Individual electrode 3a Arc electrode of individual electrode 3b Straight electrode of individual electrode 21 Rod electrode of common electrode 21a Arc electrode of rod electrode 21b Straight electrode of rod electrode

Claims (3)

(57) [Claims] A common electrode is formed below the heating resistor, an individual electrode is formed on the heating resistor or around the width , and
Cross the common electrode and individual electrodes alternately with the heating resistor.
A thermal head characterized by having 2. A common electrode is formed on the heating resistor, an individual electrode is formed below or around the width of the heating resistor , and
Cross the common electrode and individual electrodes alternately with the heating resistor.
A thermal head characterized by having 3. A common electrode is formed around the heating resistor in the width direction, an individual electrode is formed below, above, or around the heating resistor, and the common electrode and the individual electrode are formed together with the heating resistor. Mutual
A thermal head characterized by crossing at different angles. [0001]