JPH07242011A - Thermal printing head - Google Patents

Abstract

PURPOSE:To uniformize the heat distribution of a heating resistor contributing to printing by constituting the embossed pattern composed of a conductive material provided between a common electrode and an individual electrode of the leading end part covered with the heating resistor and the exposed part exposed from the heating resistor. CONSTITUTION:Iindividual electrodes 2 and common electrodes 3 are formed on an insulating substrate l composed of ceramics having a glaze layer formed on the surface thereof and embossed patterns 5, 5 are formed between each of the individual electrodes 2 and each of the common electrodes 3 adjacent to each other and each of the patterns 5, 5 is constituted of the leading end part 5a covered with a heating resistor 4 and the exposed part 5b exposed from the heating resistor 4 and having width almost the same to that of the individual and common electrodes and formed in parallel to the electrodes. The embossed patterns 5, 5 can be simply formed from a conductive material such as gold paste in a process common to the common and/or individual electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head having a uniform heating distribution on a heating resistor.

[0002]

2. Description of the Related Art Conventionally, in general, an insulating substrate having a glaze layer formed on the upper surface thereof and a common electrode formed of a conductor so that the end portions thereof are alternately drawn out in a direction parallel to the short side of the insulating substrate. And an individual electrode, and a heating resistor formed in a direction parallel to the long side of the insulating substrate so as to traverse each end of the common electrode and the individual electrode, and between adjacent common electrodes. A thermal print head having a heat generating area is widely known. In this type of thermal print head, in use, with a required voltage applied to the common electrode side, a voltage is selectively applied to the individual electrode side to apply a resistor between the adjacent individual electrode and the common electrode. By energizing the heat generation area, heat is generated by the heat generation dots between the electrodes, and resistance heat is applied to the thermal paper, etc. as the printing medium that moves on the resistor, and the desired characters and figures are printed on the printing medium. I am able to do it.

On the other hand, with the recent improvement in the performance of office automation equipment, further improvement in the printing quality is required even in the above-mentioned type thermal print head. In order to improve the printing quality of this type of thermal print head, the dot density in the main scanning direction in which the heating resistor extends is increased, and the width of the heating resistor in the sub-scanning direction parallel to the moving direction of the printing medium is also increased. The print resolution must be improved by reducing the width.

[0004]

However, in the above-described conventional thermal print head, the heating resistor is formed by forming the individual and common electrodes formed on the glaze layer, and then forming the resistor paste so as to traverse these end portions. Is formed by applying and baking. Therefore, in the heating resistor, as shown in FIG. 5A, the portion that straddles the individual and common electrodes of the heating resistor is the other portion, that is, the portion where the heating resistor directly contacts the glaze. It is wider than the other and has a wavy shape as a whole (so-called "bleeding").
However, even if the heating resistor is thinned, its width dimension is limited, and it is difficult to reduce the dot size, and a high voltage pulse is applied between the adjacent common and individual electrodes. Even when the resistance value of the heating resistor is adjusted by pulse trimming, it is difficult to uniformly adjust the resistance value due to the above-mentioned waviness.

Further, as described above, the heating resistor generates heat between adjacent common and individual electrodes by selectively applying a signal voltage to the individual electrode side while a constant voltage is applied to the common electrode side. Although heat is generated in each heating dot by energizing the resistor, the generated heat is diffused inside the heating resistor by heat conduction, and at the same time, through the common and individual electrodes connected to the heating resistor. To be dissipated,
The heating area that can contribute to printing on the heating resistor has a large difference in the width direction of the heating resistor between the area on the individual electrode and the areas on both sides of the glaze. When thermal printing is performed under such a heat generation state, it is not possible to obtain good quality printing on the thermal paper due to the difference in the heat generation area. Figure 5
(B) schematically shows a heat generation area in a conventional thermal print head. In the same figure, in the heat generation area indicated by diagonal lines, there is a large difference in the width direction of the heat generating resistor between the area on the individual electrode 2'and the areas on both sides of the glaze.

Further, since the heating resistor of the conventional thermal print head described above has a semicircular cross section, the cross-sectional area per unit width in the width direction is maximum at the central portion. The resistance value decreases toward both sides, and the resistance value per unit width is minimum at the center and increases toward both sides. Therefore, in the heat generation distribution on the heat generating resistor, the heat generation temperature in the central portion becomes excessively high as compared with the both side portions in the cross section,
After all, good print quality could not be obtained.

SUMMARY OF THE INVENTION In order to solve the above problems, it is an object of the present invention to provide a thermal print head which improves the heat generation distribution on a heat generating resistor that contributes to printing, thereby improving the printing quality.

[0008]

To achieve the above object, according to the present invention, an insulating substrate, and a common electrode made of a conductive material and having a common connection portion on the insulating substrate,
An individual electrode made of a conductive material and formed corresponding to the common electrode, and a floating pattern provided between the adjacent electrodes of the common and individual electrodes made of a conductive material independently of the common and individual electrodes. And a heating resistor formed on the insulating substrate so as to traverse over the common electrode and the end of the individual electrode, and the floating pattern includes a tip covered with the heating resistor. And an exposed portion exposed from the heat generating resistor.

The floating pattern may be provided symmetrically with respect to the heating resistor, and the tip of the floating pattern may be formed in a substantially wedge shape in a plan view. The heating resistor may be an end portion in the width direction extending in the longitudinal direction and trimmed between adjacent floating patterns of the floating patterns.

[0010]

[Operation and effect] A floating pattern made of a conductive material is provided between the common electrode and the individual electrode adjacent to each other, and the floating pattern is exposed from the tip end covered with the heating resistor and the heating resistor. Since the heating resistors are formed so as to cross the common and individual electrode terminations and the floating pattern, the heating resistors are as if the pitch between the adjacent electrodes is large. Since the heating resistor is formed as if it is formed on the half electrode, the waviness in the width direction is reduced at both widthwise end edges extending in the longitudinal direction as compared with the conventional thermal print head. The contour shape is substantially closer to a straight line. Therefore, when using the thermal print head,
In the heat generating region, the waviness is reduced in the width direction of the heat generating resistor, and the heat generating region can have a contour shape approximate to a substantially rectangle.

Further, the floating pattern is provided symmetrically with respect to the heating resistor, and the tip of the floating pattern is formed in a substantially wedge shape in a plan view, so that the common electrode and the individual electrode are separated from each other. It can be considered that the combined resistance value of the heating resistor and the floating pattern per unit width is reduced by directing the resistance value of the heating resistor toward both sides in the width direction from the central part of the heating resistor. It can be understood that the heat distribution in the width direction of the heat generating resistor is substantially equalized in combination with the heat dissipation through the heat generating resistor. As a result, according to the thermal print head of the present invention, it is possible to effectively prevent the conventional problem that the heat generation temperature becomes excessively high at the central portion of the cross section of the heat generating resistor, which contributes to the improvement of print quality. obtain.

Further, a high voltage pulse is applied between adjacent floating patterns to pulse-trim both edges of the heating resistor, thereby destructively increasing the resistance value of both edges of the heating resistor to generate heat. The region can be limitedly defined in the central portion of the heating resistor in the width direction. Therefore, it is possible to easily reduce the size of the heating dot without thinning the heating resistor.

[0013]

Embodiments of the present invention will be described below in detail with reference to FIGS. FIG. 1 is a plan view of the main part of the thermal print head of the present invention, and FIG. 2 is A in FIG.
-Shows a cross-section along -A. In FIG. 1, an individual electrode 2 and a common electrode 3 are formed on an insulating substrate 1 made of ceramic or the like having a glaze layer formed on the surface thereof, as in the conventional thermal printhead. One end of each individual electrode 2 is an I (not shown) for supplying a signal voltage provided on the insulating substrate 1.
Each common electrode 3 is electrically connected to C and has a common wiring portion 3a commonly connected at one end. A heating resistor 4 is formed on the individual electrode 2 and the common electrode 3 so as to cross over the opposing end portions of the individual and common electrodes 2 and 3. In the figure, the contour of the heating resistor 4 is shown as a straight line for the sake of simplicity.

According to this embodiment, the floating patterns 5 and 5 are formed between the individual electrodes 2 and the common electrode 3 which are adjacent to each other so as to face each other. These floating patterns 5 are exposed from the extremity 5a and the exothermic resistor 4 which are respectively covered with the exothermic resistor 4, and the exposed portions 5b are formed in parallel with the individual and common electrodes 2 and 3 with substantially the same width. It consists of and.
The floating patterns 5 and 5 can be easily formed by using a conductive material such as gold paste in the same step as the common electrode and / or the individual electrode. However, a material different from these electrodes or a material having a different composition is used. You may form so that it may become a desired resistance value by meeting another process using. Since the thermal print head of this embodiment is provided with the floating patterns 5 and 5 having the tips 5a and the exposed portions 5b together with the common and individual electrodes 2 and 3, as shown in FIG. In addition, since the heating resistor 4 is formed as if it were formed on the electrodes in which the pitch between adjacent electrodes is half, the heating resistor 4 is formed on both sides extending in the longitudinal direction in the widthwise undulation. Is reduced, and the contour shape is substantially closer to a straight line.

When the thermal print head according to the present embodiment is used, a heat generating area on the heat generating resistor 4 (hereinafter simply referred to as "heat generating area") that can contribute to printing on the thermal paper.
As shown in FIG. 3B, the waviness in the width direction of the heating resistor is reduced as compared with the heating area of the conventional thermal print head shown in FIG. Since the area can be formed, good print quality can be obtained.

Next, another feature of the embodiment of the present invention will be described. As described above, in the conventional thermal print head, since the heating resistor is generally formed by linearly applying a resistor paste made of ruthenium oxide or the like and firing it, its cross section is a semicircle. It has an arc shape. Therefore, when electricity is applied to the portion between the individual and common electrodes of the heating resistor, the resistance value per unit width of the cross section is the highest at both sides and decreases toward the center. Therefore, when such a conventional thermal print head is used, the current density in the cross section is the lowest at both sides and increases toward the central portion, so that the heat generation distribution has the highest heat generation temperature in the central portion of the cross section. It exhibits a temperature characteristic that decreases toward both sides, and is non-uniform in the width direction of the heating resistor.

However, in the embodiment of the present invention, as shown in FIGS. 1 and 3A, the floating patterns 5 and 5 are provided symmetrically with respect to the heating resistor, and the floating patterns 5 and 5 are provided.
The tip of 5 is formed in a substantially wedge shape in a plan view, so that the resistance value of the heating resistor 4 between the common and individual electrodes 2 and 3 is directed from the central portion in the width direction of the heating resistor to both sides. ,
Since it can be considered that the combined resistance value of the heating resistor and the floating pattern per unit width is reduced, the heat distribution in the width direction of the heating resistor is substantially equalized together with the heat dissipation through the floating pattern. I understand that it will be done. As a result, in the thermal print head of this embodiment, it is possible to effectively prevent the conventional problem that the heat generation temperature becomes excessively high at the central portion of the cross section of the heat generating resistor, and the print quality is improved. . In this embodiment, the floating pattern 5,
The tip portion 5a of 5 is formed in a wedge shape in a plan view, but the shape is not limited to this, and the tip portion 5a may be formed in a symmetrical curve in the width direction or may be rounded at the tip. Any shape having a shape capable of equalizing the heat generation distribution in the width direction of is applicable.

Further, according to the modification of the present invention, both end edges 8, 8 along the longitudinal direction of the heating resistor 4 are used as trimming areas, and a high voltage, for example, several thousand volts is applied between adjacent floating patterns. By applying a pulse, the both ends 8 and 8 of the heat generating resistor are destructively increased in resistance, whereby the heat generating region can be limitedly defined in the widthwise central portion of the heat generating resistor 4. The heat generation distribution region on the heat generating resistor according to the present modification is schematically shown as a region 9 in FIG. As described above, conventionally, it is difficult to form the heating resistor to be thinner than a certain amount due to the waviness at the time of its formation, and a high voltage pulse is applied between the adjacent common and individual electrodes to generate heat by pulse trimming. Even if an attempt was made to adjust the resistance value of the resistor, the undulation caused variations in the resistance value after pulse trimming.However, according to this modification, the resistance value by pulse trimming can be adjusted uniformly and the heating resistor It is possible to easily reduce the size of the heat-generating dots as in the case of thinning without actually thinning.

The floating pattern of the present invention can be formed in a process that is almost common with the formation of a normal thermal print head. That is, when a gold paste is applied and fired on an insulating substrate having a glaze layer formed on the surface to form common and individual electrodes, a floating pattern can be formed together with these electrodes. When it is formed using a material different from the above, it may be formed in another step. After forming the common and individual electrodes and the floating pattern in this way, like the conventional thermal print head,
By forming the heating resistor, the thermal print head according to the present invention can be obtained. It goes without saying that mounting of the surface protection layer covering the heating resistors, the common and individual electrodes, the IC for driving the heat generation, the wiring thereof, and the like are appropriately performed.

[Brief description of drawings]

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

2 is a cross-sectional view of the thermal head of FIG. 1 taken along the line AA.

3A is a diagram showing a contour shape of a side portion in a width direction extending in a longitudinal direction of a heating resistor of the thermal head shown in FIG. 1, and FIG. 3B is a diagram showing a heating region of the thermal head. is there.

FIG. 4 is a diagram showing a trimming region of a heating resistor according to a modification of the present invention and a heating region of the heating resistor after trimming.

FIG. 5 is a plan view of a main part of a conventional thermal head.

[Explanation of symbols]

 1. ． ． 1. Insulating substrate having glaze layer ． ． Individual electrode 3. ． ． Common electrode 4. ． ． Heating resistor 5. ． ． Floating pattern 5a. ． ． Tip 5b. ． ． Exposed part 6. ． ． Protective layer 7. ． ． Heat generation area 8. ． ． Trimming area 9. ． ． Fever area

Claims (3)

[Claims] 1. An insulating substrate, a common electrode made of a conductive material and having a common connection portion on the insulating substrate, an individual electrode made of a conductive material corresponding to the common electrode, and a conductive material. Pattern formed of a conductive material between the adjacent electrodes of the common and individual electrodes independently of the common and individual electrodes, and the insulation so as to cross over the end portions of the common electrode and the individual electrodes. A heating resistor formed on a flexible substrate, and the floating pattern includes a tip end covered with the heating resistor and an exposed portion exposed from the heating resistor. Thermal print head. 2. The thermal structure according to claim 1, wherein the floating pattern is provided symmetrically with respect to the heating resistor, and the tip of the floating pattern is formed in a substantially wedge shape in a plan view. Print head. 3. The thermal print head according to claim 1, wherein the heating resistor is an edge portion in the width direction extending in the longitudinal direction, and trimming is performed between adjacent floating patterns of the floating patterns.