JPH0768818A - Thermal head - Google Patents

Abstract

PURPOSE:To form a high-temperature part which is wide in not only a main scanning direction but also an auxiliary direction and is more close to a rectangle in a region where a difference in temperatures in a heating unit is little and improve a printing efficiency. CONSTITUTION:Two pieces or two sets of holes 10 are provided in a heating unit 7 by keeping intervals in an auxiliary direction, and 1/3<j/a<4/5, 1/12<e/a<1/3 are set up by taking respectively a width of an auxiliary direction of the heating unit 7, an interval of the auxiliary direction of the holes 10 each and an interval among the holes 10 each and lead electrodes 4, 5 of both the ends of the heating unit 7 as a, j and e. Then 1<g/f<4 is set up by taking respectively dimensions of the main scanning direction of the hole 10 and a distance of the hole 10 up to the hole from both end parts of the main scanning direction as f and g.

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 for heat-sensitive recording or thermal transfer recording, and more specifically, a high temperature region having a small temperature difference is formed in a wide area within a heating element forming one dot. Regarding the shape of the heating element.

[0002]

2. Description of the Related Art A thermal head in which a large number of heating elements are arranged in a direction perpendicular to the feeding direction of a printing medium such as thermal paper is generally shown in FIG.
As shown in the plan view of the plan view of (A), the partially enlarged view of (B) and the sectional view of (C), a glaze layer 2 made of glass (illustrated example) is formed on a substrate 1 made of ceramic or the like. Shows a case of a partial glaze layer), a heating resistor layer 3 made of, for example, molybdenum silicide is formed by a thin film, and a common side lead electrode 4 and an individual lead electrode 5 made of a metal thin film are formed thereon. It is covered with an electrically insulating heat-resistant and wear-resistant layer 6, and at the time of driving,
The heating resistor layer 3 between the electrodes 4 and 5 functions as the heating element 7 by causing a current to flow through the heating resistor layer 3 at the break of the conductor between the common side lead electrode 4 and the individual lead electrode 5. is there.

In such a heating element shape, as shown in FIG.
As shown by the curves shown in FIGS. 4A and 4B in FIGS. 4A and 4B, the high temperature portion is concentrated in the central portion in the main scanning direction (X direction) and the sub scanning direction (Y direction). For this reason, the portion of the heat-sensitive recording paper or the like corresponding to the region other than the central portion of the heating element does not develop color, the size of the dot becomes small and the white portion becomes large, and the print quality deteriorates. Further, as the color direct thermal paper, for example, as disclosed in Japanese Patent Laid-Open No. 1-267055, there is a multi-layered structure in which different color forming layers are laminated. When applied, when a certain layer is heated by a thermal head to develop color, if there is a local high temperature area as described above, the next layer develops color, and conversely the next layer does not develop color at low temperature. When the head is heated, this causes a problem that the coloring area becomes smaller. Under such circumstances, there has been a demand for a heating element shape that does not generate a local high-temperature region in the heating element and can form a wide region with a small temperature difference.

On the other hand, with the intention of forming a high temperature region with a small temperature difference in a wide region of the heating element, FIG.
As shown in FIG. 6, a slit 8 in which the heating resistor layer 3 is omitted is provided in the heating element 7 in the sub-scanning direction.
As shown by the curve shown in FIG. 5 (A) in (A), there are those in which the high temperature portion is dispersed in the main scanning direction (Japanese Patent Laid-Open Nos. 61-262142 and 63-63142).
25058, JP-A-2-130342). But,
According to the shape of the heating element provided with this slit 8, FIG.
As represented by the curve shown in FIG. 5A with FIG. 5B, the high temperature portion is long in the sub-scanning direction and is formed up to the vicinity of the lead electrodes 4 and 5. There is a problem in that it easily escapes to the lead electrodes 4 and 5 having a high rate, and the printing efficiency (optical density / power consumption) deteriorates.

Another conventional heating element shape is shown in FIG.
As shown in (B), a heating element 7 provided with a hole 9 in the central portion has been proposed (JP-A-63-25058, JP-A-2-147352, JP-A-2-274565, and JP-A-2-274565).
JP-A-4-126261). According to such a heating element shape, the current flow in the heating element 7 is as shown by the arrow i, and the current density on both sides of the hole 9 is high, so that the temperature on both sides of the hole 9 is high, As shown by the curve in FIG. 5A in FIG. 6A, the temperature distribution can be averaged due to the dispersion of the high temperature portion in the main scanning direction, and the printing efficiency is improved, but in the sub scanning direction. As shown by the curve in FIG. 5B in FIG. 6B, the temperature is projected at the central portion, and when this thermal head is used for the direct thermal paper of the multilayer structure, the next layer is the sub-scanning direction. Color develops in the central part of.

FIG. 5 shows another conventional heating element shape.
As a modified example of (A), as shown in FIG. 5C, there is one in which slits 8a to 8f are formed dispersed in the main scanning direction and the sub scanning direction (Japanese Patent Laid-Open No. 61-262143).
issue). However, these slits 8a to 8f are set such that the ratio h / w of the width h in the sub-scanning direction and the width w in the main scanning direction is set to 3 or more. The distance u between the electrodes 4 and 5 and the dimension a of the heating element 7 in the sub-scanning direction
Since the ratio u / a is set to about 1/7, the high temperature portion generated near the ends of the slits 8a to 8f comes close to the lead electrodes 4 and 5, and as a result, as shown in FIG. As shown in, the temperature near the lead electrodes 4 and 5 increases,
As in the example of FIG. 5A, the generated heat easily escapes to the lead electrodes 4 and 5, and the printing efficiency (optical density / power consumption) deteriorates. Also, the interval t between the slits in the sub-scanning direction
Since the ratio t / a of the dimension a of the heating element 7 in the sub scanning direction is also set to about 1/7, the slit 8 in the central portion
There is a problem that the objects of a to 8f are close to each other, the high temperature portions are overlapped with each other, and the purpose of preventing the high temperature portions from protruding in the central portion cannot be sufficiently achieved.

In view of the above problems, the present invention has an area where the temperature difference is small in the heating element is wide not only in the main scanning direction but also in the sub scanning direction, and a high temperature portion closer to a rectangle is formed and the printing efficiency is improved. It is an object of the present invention to provide a thermal head having a shape of a heating element capable of improving the temperature.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to a thermal head having a large number of heating elements arranged in a direction perpendicular to the paper feeding direction. Two or two sets of holes are provided with a space between them, the width of the heating element in the sub-scanning direction is a, the interval of each hole in the sub-scanning direction is j, and each hole and the lead electrodes at both ends of the heating element are The interval is set to e, and 1/3 <j / a <4/5 and 1/12 <e / a <1/3 are set. In the present invention, it is more preferable to set 1 <g / f <4, where f is the dimension of the hole in the main scanning direction and g is the distance from both ends of the hole in the main scanning direction to the hole.

[0009]

According to the present invention, as described above, two or two holes are provided in the heating element in the sub-scanning direction, and the distance in the sub-scanning direction and the distance to the lead electrode are set as described above. This prevents concentration of the high temperature region in the central portion due to the holes being too close, and reduces the amount of heat escaping from the high temperature region around the hole to the lead electrode.

[0010]

1 is a plan view showing an example of the shape of a heating element of a thermal head according to the present invention. Heating element 7 of this embodiment
Has a width c in the sub-scanning direction Y at the center in the main scanning direction X,
Two holes 10 each having a rectangular shape with a width f in the main scanning direction X are separated from each other by a distance j in the sub scanning direction Y, a distance d between the centers of the holes, and a distance e from the lead electrodes 4 and 5. It is provided. The position of the hole 10 and the dimension in the sub-scanning direction (Y direction) are: 1/3 <j / a <4/5, 1/12 <e / a <, where a is the width of the heating element 7 in the sub-scanning direction. Set to 1/3. Further, in order to suppress the heat propagation to the adjacent heating element, the dimension of the hole 10 in the main scanning direction (X direction) is f, and the distance from both ends of the heating element 7 in the main scanning direction to the hole 10 is g.
Is set to 1 <g / f <4.

As the heating element 7, the width a in the main scanning direction X =
260 μm, width b in sub-scanning direction b = 155 μm, j / a
= 1/2, e / a = 1/7, g / f = 2, the temperature distribution during driving by numerical analysis using a computer in the main scanning direction in the central portion of the heating element 7 is shown in FIG.
As indicated by the broken line in (A), a high temperature region was formed in a wide region. Further, by setting the distance j between the two holes 10 to the above value, an excessive temperature rise due to the overlap of the high temperature portions generated on both sides of the holes 10 is eliminated, and as shown by the broken line in FIG. 6 (B). The high temperature region can be widened also in the sub-scanning direction, and the high temperature region can be formed in a rectangular shape. Further, by setting the distance e between the hole 10 and the lead electrodes 4, 5 to the above value, the heat escaping to the lead electrodes 4, 5 having good thermal conductivity is reduced, and the printing efficiency can be improved. Became. In addition, by setting the relationship between the width f of the hole 10 in the main scanning direction and the distance g between the hole 10 and the end portion in the main scanning direction to the above value, the adjacent heating elements 7 are formed.
It is possible to suppress the transfer of heat between each other and maintain the printing quality.

FIG. 2 is a plan view showing another example of the heating element according to the present invention. Two holes 11 are provided in the main scanning direction, and two holes 11 are provided in the sub scanning direction. Is provided. In the present example, the relationship among the dimensions a to g, j is set in the same manner as in the case of FIG. By providing a plurality of holes 11 in the main scanning direction as in this example, the temperature distribution in the main scanning direction is further flattened.

FIG. 3 shows an example in which the shape of the hole 12 is circular. Such a shape of the hole 12 can be applied to the case of the hole arrangement of FIG. 1 and the same effect can be obtained. Other,
It is also possible to change such that three or more holes are arranged in the main scanning direction for one set.

[0014]

According to the first aspect of the present invention, the temperature distribution in the main scanning direction in the central portion of the heat generating element is, of course, such that a high temperature area is formed in a wide area. By setting the distance between the holes in the above range to be within the above range, excessive temperature rise due to the overlapping of the high temperature portions occurring on both sides of the holes can be eliminated, and the high temperature region can be widened also in the sub-scanning direction. It can be formed in a rectangular shape. Further, by setting the distance between the hole and the lead electrode in the above range, the heat escaping to the lead electrode having good thermal conductivity is reduced, and the printing efficiency can be improved.

According to the second aspect, the relationship between the width of the hole in the main scanning direction and the distance between the hole and the end portion in the main scanning direction is set within the above range, so that the heat transfer between the adjacent heating elements. The print quality can be suppressed and the print quality can be maintained.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a heating element of a thermal head according to the present invention.

FIG. 2 is a plan view showing another example of the heating element of the thermal head according to the present invention.

FIG. 3 is a plan view showing another example of the heating element of the thermal head according to the present invention.

4A is a plan view showing the arrangement of heating elements of a conventional thermal head, FIG. 4B is a partially enlarged view of FIG. 4A, and FIG.

5A to 5C are plan views showing another example of the shape of the heating element of the conventional thermal head.

6A and 6B are diagrams showing temperature distributions in the main scanning direction and the sub-scanning direction of heating elements of various thermal heads.

[Explanation of symbols]

 1 Substrate 2 Glaze Layer 3 Heating Resistor 4 Common Side Lead Electrode 5 Individual Lead Electrode 7 Heating Element 10-12 Holes

Claims (2)

[Claims] 1. A thermal head comprising a large number of heating elements arranged in a direction perpendicular to the paper feeding direction, wherein the heating elements are provided with two or two holes at intervals in the sub-scanning direction. 1/3 <j / a <, where a is the width of the heating element in the sub-scanning direction, j is the distance between the holes in the sub-scanning direction, and e is the distance between each hole and the lead electrodes at both ends of the heating element. A thermal head characterized by being set to 4/5 and 1/12 <e / a <1/3. 2. The method according to claim 1, wherein the dimension of the hole in the main scanning direction is f, and the distance from both ends of the hole in the main scanning direction to the hole is g, and 1 <g / f <4 is set. And thermal head.