JPS62164560A - Thermal head for printer - Google Patents

Abstract

PURPOSE:To favorably print even when heat generating dots are driven divisionally on a group basis, by a construction wherein of a plurality of heat generating dots constituting a group, the one located at a boundary of the group is provided with a notched part at a side opposite to the boundary. CONSTITUTION:A heat generating dot 1a is provided with a notched part 11a at the right side thereof, whereas a heat generating dot 1b is provided with a notched part 11b at the left side thereof. with the notched parts provided at the sides of the dots opposite to the boundary between a group A and a group B, the paths of electric current supplied through an electrode layer 9 are concentrated on the side of the boundary, as indicated by arrows. Accordingly, electric power density on the boundary side is enhanced, whereby temperature can be prevented from being lowered, and it is possible to solve the problem that a needless line is formed at the boundary of the groups, which problem occurs in the case of a conventional thermal head. The notched parts can be provided by for example, trimming using a laser light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a thermal head for a printer, and particularly to a thermal head for a printer of a type in which heat-generating dots are divided into groups and each group is driven to generate heat.

[Technical background of the invention]

Thermal printers have advantages over dot impact printers, such as less noise, and are now widely used. The thermal head used in this thermal printer is composed of a large number of heating dots 1, as shown in FIG. The heating dots 1 are arranged in a row in the main scanning direction X in the figure, and one row of dots can be printed on paper in one scan. The paper is in the sub-scanning direction Y in the figure.
As a result, two-dimensional planar pudding 1 can be performed. Each heating dot 1 is connected to an electrode layer (not shown) for power supply. fever dot 1
FIG. 3 shows a cross-sectional view taken along cutting line zz' in the figure. A heat resistance layer 3 made of glass or the like is formed on a heat dissipation substrate 2 made of ceramic or the like, and a heating resistor 4 made of Ta2N or the like is formed thereon. A pair of lead electrode layers 5 made of aluminum or the like formed on the heating resistor 4 are provided with a gap between them on the left and right sides of the figure, and in this gap, current flows through the heating resistor 4 and generates heat. On top of these are an oxidation-resistant layer 6 made of 8102 or the like and a wear-resistant layer 7 made of Ta205 or the like.
is formed.

In this way, a typical thermal head is driven by supplying power to the heat-generating paper/antibodies. By supplying power to the heating dots that perform printing and not supplying power to the heating dots that do not perform scanning, an image can be printed as a collection of each printing dot.

Therefore, if all the heating dots arranged as shown in FIG. 2 are simultaneously driven and the paper is fed in the Y direction, an image print on a two-dimensional plane can be obtained. However, the electric power machine that supplies the heating resistor is quite large, and a fairly large-scale power supply device is required to drive all the heating dots arranged in a row at the same time. Therefore, each heating dot is usually divided into several adjacent dots, and each of the eight divided dots is driven in a time-division manner. For example, in the example shown in FIG. 2, four groups are formed from groups A to D, and first each heating dot in group A is driven, and then B1! I': There is C, which drives the 0 group and the D group at different times. Like this 4
If the power supply is divided into two groups, the power consumed at one time will be reduced to 1/4, and the scale of the power supply device can be reduced accordingly.

For convenience of explanation, only a small number of heating dots are shown in one group in Fig. 2, but in reality, for example, when driving a total of 512 heating dots divided into four groups of 128 each, Split drive is being performed.

(Problems with the Background Art) When the above-described time-division driving is performed, the conventional head has a problem in that an unnecessary line is inserted between the boundaries of each group. FIG. 4 shows a print result with such unnecessary lines. Here, areas a and b.

c and d are A group, B group, respectively, of the head shown in FIG.
This is an image printed by the 0 group and the D group. Unnecessary lines 8 are included at the boundaries of each area. In reality, this unnecessary line 8 is a line that occurs because the driver which should be printed is not printed, so it appears as a white line on the printed image.

The reason why such unnecessary lines are formed is the heating dots 1a, 1b, and 1c located at the boundaries of each group.

This is because the temperature when the dot 1d generates heat is lower than the temperature when the other heat generating dots generate heat. For example, in Figure 2, while group B is being driven, the temperature of the area where group B is placed increases overall, but since the adjacent groups A and 0 are not being driven, group B The temperature of the heating dot 1b located at the boundary between the two ends up becoming low. In general, the relationship between the temperature of the heating dot and the print density is as shown in Figure 5, and at a temperature T2 printing is possible, but when the temperature drops to temperature 1, the dot is no longer printed. This phenomenon is particularly noticeable in sublimation transfer type thermal printers, and is a major problem that deteriorates image quality.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a thermal head for a printer that can perform good printing even when the heating dots are divided into groups and driven.

[Summary of the invention]

The feature of the present invention is that n heat generating drivers are arranged in the main scanning direction.
- and a driving means for grouping m adjacent heat generating dots among the n heat generating dots and driving them to generate heat in a time-division manner for each group. A notch is provided on the side opposite to the boundary of the heating driver 1- located at the boundary among the m heating dots,
The current is concentrated on the boundary side so that good printing can be achieved even when the heating dots are driven in groups.

[Embodiments of the Invention] The present invention will be described below based on illustrated embodiments. 1st
The figure is a partially enlarged view of an embodiment of a thermal head according to the present invention. Lightning bolts N1H9 and 10 are connected to each heating dot 1, and power is supplied thereto.

Heat-generating dots ia located at the border even if they receive the same power supply
, 1b decreases in temperature during heat generation, as described above. In particular, the temperature drop will be severe in areas that are in contact with the boundary. Therefore, the present invention aims to prevent the temperature drop by providing a large portion on the side opposite to this boundary. That is, as shown in FIG. 1, a notch 11a is provided on the left side of the heating dot 1a, and a notch 11b is provided on the right side of the heating dot 1b. By providing a notch on the side opposite to the boundary between Group A and Group 8 in this way, the flow path of the current supplied from the electrode layer 9 will be concentrated on the boundary side as shown by the arrow in the figure. . Therefore, the power density on this boundary side is increased, a temperature drop can be prevented, and the problem of unnecessary lines being inserted at the boundaries of each group as in conventional thermal heads can be solved.

This notch can be formed by trimming using a laser beam, for example. The present invention can be realized by using the same driving means as in the conventional thermal head for supplying power to each electrode layer, and by simply adding a laser trimming step to the manufacturing process of the heating dot array. Note that although the heating resistor 4 is not present in the cutout portion, there is no fear that the temperature of this portion will drop to the extent that it will adversely affect the print result due to the influence of the heat generated by the adjacent heating dots.

(Effects of the Invention) As described above, according to the present invention, in a thermal head for a printer of a type in which heat-generating dots are divided into groups and each group is driven to generate heat, the boundary between heat-generating dots located at the boundary of one group and By providing a notch on the opposite side and concentrating the current on the boundary side, even if the heating dots are divided into groups and driven, there will be no unnecessary lines at the boundaries of each group. It becomes possible to perform good printing.

[Brief explanation of drawings]

Fig. 1 is a partially enlarged view of an embodiment of a thermal head according to the present invention, Fig. 2 is a schematic diagram of a conventional general thermal head, and Fig. 3 is a cross section showing an example of a heat generating dot constituting the thermal head. 4 is a diagram showing an example of the results of printing using a conventional thermal head, and FIG. 5 is a graph showing the general relationship between the temperature of the heating dot and the print density. DESCRIPTION OF SYMBOLS 1... Heat generating dot, 1a-1d... Heat generating dot located at the boundary, 2... Heat dissipation board, 3... Heat resistance layer, 4
... Heating resistor, 5... Lead electrode layer, 6... Oxidation-resistant layer, 7... Wear-resistant layer, 8... Unnecessary wire, 9.1
0... Electrode layer, 11a, 11b... Notch, A-D
...Each heating dot group. Applicant's agent Mr. Sato - Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. n heating dots arranged in the main scanning direction;
a driving means for time-divisionally driving each group to generate heat by forming one group of m adjacent heat generating dots among the number of heat generating dots;
A thermal head for a printer, characterized in that a notch is provided on the side opposite to the boundary of a heat-generating dot located at a boundary among the m heat-generating dots constituting one group. . 2. The thermal head for a printer according to claim 1, wherein the notch is a notch formed by laser trimming.