JPS60245566A - Thermal printer - Google Patents

Abstract

PURPOSE:To uniformize heating under the compensation of a gap effect between a cylindrical platen and a flat thermal head and eliminate the irregularity in density of printing by giving heating elements in the middle the highest resistance and those at the external side a low resistance among a plurality of heating elements. CONSTITUTION:In order to eliminate the gap effect between both external sides when a flat thermal head is pressed onto a cylindrical platen 4, the resistance value of heating elements is highest in the middle and gradually smaller toward both external sides in accordance with said gap. Consequently, the heating is almost equalized and the print density is nearly constant, and when printing is performed on a cylindrical platen under the pressure of a flat thermal head consisting of plural heating elements, the shade irregularity does not occur in the middle and at both external sides of the thermal head.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field The present invention relates to thermal printers, and in particular to thermal printers that print by pressing a flat thermal head consisting of a plurality of heating elements onto a cylindrical platen surface. It is related to.

(2) Prior Art and Problems Conventionally, thermal dot printers have been used in which a flat thermal head consisting of a plurality of heating elements is pressed against a cylindrical platen surface. In this case, as shown in FIG. 2 (5), a thermal head in which, for example, 16 heating elements 10 are arranged in a vertical row in correspondence with dots on the surface of a cylindrical platen 40 via a plastic ribbon 2 and paper 5. 1, the ribbon ink is melted by heat generation and printed in one column according to the character pattern, and one character is printed by shifting one dot in 16 columns in the direction perpendicular to the paper surface. When one line of printing is completed in this way, the paper on the platen 4 is fed by one line, and the next line is printed. The problem in this case is that while the platen 4 has a curvature, the lower heating surface of the thermal head 1 is flat, so as shown in the same figure (cL), strong contact is made at the center. On the other hand, since the contact is weak and creates a gap 5 at the front and back in the paper feeding direction, and the heat dissipation characteristics of the thermal head 1 are better at the edges, the print pattern at the center as shown in FIG. This causes uneven shading at both ends, and when characters are printed with this, there are unclear areas at the top and bottom, which is a drawback.

(3) Purpose of the Invention The purpose of the present invention is that when printing is performed by pressing a flat thermal head composed of a plurality of heating elements onto a cylindrical platen surface, uneven shading occurs at the center and both outer sides of the thermal head. It is an object of the present invention to provide a thermal printer that avoids the need for

(4) Structure of the Invention In order to achieve the above-mentioned object, the thermal printer of the present invention uses a flat thermal head consisting of a plurality of vertical heating elements corresponding to a plurality of dots to press a sheet of paper in contact with a cylindrical platen surface. , a thermal printer that prints by shifting one dot horizontally, characterized in that among the plurality of vertical heating elements of the thermal head, the resistance of the central part is set to be large and the resistance of the outer part is set to be small. Chiru.

(5) Embodiment of the invention FIGS. 1(cL) and (6) are diagrams explaining the principle of the present invention.

As described above in FIG. 2 (α), in order to eliminate the effect of the gap between the two outer sides when the flat thermal head 1 is pressed against the cylindrical platen 4, the heating circuit 10 shown in FIG. According to this gap, the resistance value of the heating element is increased at the center and decreased toward both outer sides.

As a result, heat is generated almost evenly and the printing density is kept constant. In the heat generating circuit 10' shown in FIG. 6(b), normal uniform heat generating elements are used, and predetermined resistances are added to only the central elements to obtain uniform density.

FIGS. 3(α) and 3(b) are detailed illustrations of the present invention according to the above-mentioned principle. 0) is a top view of the thermal head, and FIG. 6(6) is a sectional view thereof.

As shown in the same figure ((Z), Cb), a gas (8i02) layer 15 is provided on the alumina substrate 14, a metal resistance layer 11 such as N5Or is placed on it, and this resistance value is set. Therefore, the distance between lead wires 12.15 using gold etc.
In the case of the heating circuit shown in FIG. 1 (α), the spacing is wide in the center and narrowed toward both outer sides. Note that 12 is a selection side, and 13 is a common side.

Note that it is also possible to make the thickness small in the center and thicken it toward both outer sides so that the spacing is the same.

Further, the upper layer is covered with a protective layer (Ta205) to protect against damage caused by pressing.

In the case of the heating circuit shown in FIG. 1(b), a small resistance element is connected to the B1 (II lead wire) of each heating element in the center.

(6) Effect of emitted j As explained above, according to the present invention, by setting the resistance of the central part of the plurality of vertical heating elements of the thermal head to be large and the resistance of the outer part to be small, the cylindrical platen It is possible to equalize heat generation by compensating for the effect of the gap between the flat thermal head and the flat thermal head, thereby eliminating uneven printing shading.

[Brief explanation of drawings]

Figures 1 (G) and (b) are diagrams explaining the principle of the present invention;
Figure (cL). (6) is an explanatory diagram of the structure and problems of the thermal head;
Figures (α) and (6) are configuration explanatory diagrams of embodiments of the present invention, in which 1 is a thermal head, 2 is a ribbon, 6 is Kawakaze, and 4
is a platen, '5 is a gap, 10 is a heating circuit, 11 is a resistance layer, 12.15 is a lead wire, 14 is an alumina substrate, 1
5 shows an enlarged 8i02 layer, and 16 shows a protective layer. Patent applicant: Fujitsu Limited, sub-agent patent attorney 1) Yoshishige Saka Figure 1 Figure 3 (a)

Claims (1)

[Claims] A plurality of sheets of paper are placed in contact with a cylindrical platen surface. In a thermal printer that prints by pressing a flat thermal head consisting of a plurality of vertical heating elements corresponding to each dot and shifting the dot horizontally by one dot, the central part of the plurality of vertical heating elements of the thermal head is used. A thermal printer characterized in that the resistance value and the outer resistance value are set to different resistance values.