JPH04369561A - Thermal head - Google Patents

Abstract

PURPOSE:To remove common irregularity by relaxing heat accumulation by enabling heat insulation to be realized to an extent that heat interference between heating elements can be neglected by a method wherein a groove for heat insulation is provided to a glazed glass layer between the adjacent heating elements and outside the heating elements of left and right both end parts. CONSTITUTION:A groove 20 is provided between mutual glazed glass layers 16 existing under each heating element 12 of an individual electrode 14 and further a groove 20a is provided to a mid way between an individual electrode 14a existing at left and right both ends and the glazed glass layer 16 existing under an extended part 13a of a common electrode 13 existing at left and right both ends. A width of the grooves 20 and 20a is as broad as possible within a gap of the individual electrodes 14 placed in an array, and its length is made slightly longer than a length L of a heating part of the heating element 12.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to the structure of a thermal head for a printer using thermal paper or ink film.

0002

2. Description of the Related Art A plan view of a thermal head used in a conventional printer is shown in FIG. 4, and FIG. 5 and FIG. A plurality of heating resistors 2 are arranged in a straight line, one end of which is connected to a common electrode 3, and the other end connected to a control IC 5 via an individual electrode 4. The individual electrodes 4 and the heating resistor 2 have the same width. 6 is a glaze glass layer, and 7 is a protective film, but illustration of the protective film 7 is omitted in FIGS. 4 and 6 for clarity.

[0003] When a signal is sent from the controller of the printer body to the control IC 5 of the thermal head and a current flows through the heating resistor 4, the heating resistor 4 generates heat, and this heat melts the ink on the ink ribbon to perform printing. .

0004

[Problems to be Solved by the Invention] Ideally, all of the thermal energy generated by the heating resistor 4 is used to melt the ink, but in reality, some of it is diffused to the surroundings and is used to melt the ink, for example. Heat is also conducted to adjacent heating resistors that are not generating heat.

FIG. 8 shows the thermal head shown in FIG.
, C are divided into three blocks and printed in block units. Figure 9 shows the density distribution with the Macbeth density as the vertical axis, and the heat generation occurs in the order of blocks A, B, and C. I'm printing it. Print density becomes non-uniform at the boundaries between blocks, resulting in so-called common unevenness. The cause of this common unevenness is that, for example, the light density part at the right end of block A causes heat to escape to the adjacent block B side during printing, and conversely, the heat conduction occurs when the left end of block B has a high density part when printing block A. Because the heat had been stored in advance, the heat from printing was added to this preheating, making it darker than other parts. As described above, in the conventional thermal head, thermal interference between adjacent heating resistors cannot be avoided.

[0006]

[Means for Solving the Problems] In the present invention, grooves for heat insulation are provided in the glazed glass layer between adjacent heating resistors and on the outside of the heating resistors at both left and right ends to provide insulation to the adjacent heating resistors. The above problem was solved by reducing heat conduction.

[0007]

[Operation] By providing a groove between adjacent heating resistors, the cross-sectional area of heat flow from a heated resistor to an unheated adjacent heating resistor becomes smaller, and the length of the heat conduction path becomes longer. This generally prevents heat conduction and eliminates common unevenness in printing.

[0008]

[Example] FIG. 1 is a plan view of a thermal head according to the present invention.
In addition, the II-II sectional view of FIG. 1 is shown in FIG.
An enlarged view of part II is shown in FIG. The structure is basically the same as that shown in FIG. Individual electrodes 14a at both left and right ends
and 13a, which is an extension of the common electrode 13 at both left and right ends.
A groove 20a is provided between the glaze glass layer 16 and the underlying glaze glass layer 16.
The only difference is that . In FIGS. 1 and 2, the protective film 17 shown in FIG. 3 is omitted to make the structure easier to understand.

The widths of the grooves 20 and 20a are as wide as possible within the distance between the individual electrodes 14 arranged in parallel, and the lengths are slightly longer than the length L of the heat generating part of the heat generating resistor 12 (see FIG. 1). Make it. The depth should be as deep as possible, but
In the case of wet etching, it is difficult to make the depth deeper than the distance between the individual electrodes, but in the case of dry etching, it is possible to achieve the full thickness of the glaze glass layer 16.

[0010] Heat diffusion by a thermal head is mostly due to thermal conduction, and FIG. 2 shows an embodiment of the present invention, FIG. 6 shows a conventional thermal head, and enlarged views of parts III and VII, respectively. This will be explained with reference to FIGS. 3 and 7. Reference symbols a1, a2, b1, and b2 in the figure are arrows indicating the direction of heat conduction to the right heat generating element when the heat generating elements 12 and 2 on the left side generate heat, respectively. As is clear from the figure, Fig. 3 has (i) a smaller heat flow area, and (ii)
The heat conduction path length is long, making it difficult to conduct heat.

On the other hand, wasted heat flow other than for thermal transfer such as ink melting is classified into the following three items. (a) Heat conduction to the heating resistors on both the left and right sides of the page. (b) Heat conduction in the direction of the electrode perpendicular to the plane of the paper. (c) Heat conduction from the board at the bottom of the paper toward the heat sink. Among these, in FIG. 3, the term (a) is smaller than in FIG. 7, so the amount of heat used for thermal transfer increases. Further, the amount of heat that causes heat storage in the heat generating resistor of the non-energized electrode portion is the above-mentioned (a) + (b), and as (a) becomes smaller, the amount of heat storage also becomes smaller.

0012

According to the present invention, as described above, thermal insulation can be achieved to the extent that thermal interference between adjacent heating resistors can be ignored, and heat accumulation is also alleviated, so that common unevenness can be eliminated and favorable printing can be performed.

[Brief explanation of drawings]

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

FIG. 2 is a sectional view taken along line II-II in FIG. 1;

FIG. 3 is an enlarged partial cross-sectional view of section III in FIG. 2;

FIG. 4 is a plan view of a conventional thermal head.

FIG. 5 is a sectional view taken along line V-V in FIG. 4;

FIG. 6 is a sectional view taken along VI-VI in FIG. 4;

7 is an enlarged partial sectional view of section VII in FIG. 6; FIG.

FIG. 8 is a diagram showing the shading when the thermal head generates heat for each block of A, B, and C shown in FIG. 6 and prints are performed in this order.

FIG. 9 is a graph diagram showing the shading situation of FIG. 8 in terms of Macbeth density.

[Explanation of symbols]

12 Heating resistor 13a Extensions on both left and right ends 14 Individual electrodes 14a Individual electrodes on both left and right ends 15 Control IC 20, 20a groove

Claims (1)

[Claims] 1. A substrate, a glazed glass layer on the substrate, and a plurality of heating resistors juxtaposed on the glazed glass layer in a direction transverse to the direction of print travel;
A common electrode connected to all of these heating resistors,
The heating resistor includes an individual electrode arranged above each of the heating resistors at a predetermined distance from the tip of the common electrode and connected to the heating resistor, and a control IC connected to the individual electrode. In the thermal head, there is a gap between the glazed glass layers at the bottom of each of the heat generating resistors, between the bottoms of the left and right outermost heat generating resistors in the heat generating resistors, and between the right and left outermost extensions of the common electrode. A thermal head characterized in that a groove of a predetermined size for conduction and diffusion of heat is formed in a glaze glass layer directly below the layer.