JPS5814781A - Thermal head - Google Patents

Abstract

PURPOSE:To eliminate irregularity of color density according to the printing direction of a both-direction printing head, by a method wherein a common electrode is provided on the center line of heating elements which are placed on the outside peripheral surface of a cylindrical head made of glass or the like, and heat is generated by passing an electric current through the element on either side of the center line. CONSTITUTION:A common electrode element 5 is provided on the center line of the heating elements 21-2n, provided on the outside peripheral surface of a cylindrical head 1 made of glass or the like, and individual electrodes 611-61n, 621-62n are provided in correspondence to the heating elements 21-2n to constitute the head 1. When the center line of the head 1 is maintained to the orthogonal to a thermal printing paper 3 and a platen 4, printing in a printing direction (+) is performed by the electrode provided at the position corresponding to a head inclination angle of +theta0 (curve E), while the printing in the opposite printing direction (-) is performed by the electrode provided at the position corresponding to a heat inclination angle of -theta0 (curve F). In both cases of printing, the maximum color density Dmax is obtained. When there is a stagger of an angle DELTAtheta to the direction (+), the printing in the direction (+) is performed in the condition corresponding to a point R, while the printing in the direction (-) is performed in the condition corresponding to a point S, and the difference in color density is extremely little.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head, and particularly to a thermal head that does not cause color density unevenness depending on the printing direction when performing bidirectional printing.

A conventional thermal head is, for example, disclosed in Japanese Utility Model Application No. 52-6566.
Glass, as disclosed in Publication No. 0.

A large number of heating elements are arranged in a row on the outer peripheral surface of a cylindrical base made of a ceramic hemorrhoid insulator.

In thermal printing in which recording is performed on thermal paper using the thermal head configured as described above, the heating element on the thermal head and the thermal head A/Heeha J-
There is a certain relationship between the contact pressure of the thermal paper and the color density of the thermal paper, and if the driving conditions of the thermal head and the ambient temperature are constant, the color density increases as the contact pressure increases.

When using a thermal head (hereinafter simply referred to as "head") 1 having a heat generating element 2 arranged on a cylindrical base as described above, the heat generating element 2 and thermal paper 3 are usually used as shown in FIG. The heating element 2 is placed on the center line of the curved surface of the head 1 so that the surface of the Yohi platen 4 is parallel to the surface, and the center is set perpendicular to the thermal paper 3 and the platen 4. With this ε, □Platen 4
improves the adhesion between the head 1 and the thermal paper 3:
It is common to use elastic materials such as rubber for this purpose.
Further, when recording and printing is performed using the bed having the dot array in vertical 1° rows, it is customary to energize the heating element 2 while moving the heating element 1. However, as mentioned above, the head 1 is covered with thermal paper 3. When the platen is pressed against the hand, the thermal paper 3 and the platen 4 are deformed, so when the head 1 is moved in this state, the point where the contact pressure between the head 1 and the thermal paper 3 is highest will be at the point where the contact pressure between the head 1 and the thermal paper 3 is highest. The position is slightly tilted in the direction of movement of the head 1 with respect to the center line (the position tilted by θ shown in FIG. 1).

Figure 2 is a plot of the relationship between the tilt angle and the color density when the center line of the head is tilted as described above, in both printing directions (directions (G) and (C) shown in Figure 1). Curve A is for (g) direction printing, and curve B is for (g) direction printing.
The cases of directional printing are shown respectively.

As is clear from Figure 2, (g) the printing direction (direction in which the head moves to the right) is 10. , (to) In the case of the printing direction (direction in which the head moves to the left), the center line of the head is tilted by 1 θ0, that is, the center line is θ in the direction of head movement. Maximum color density Dm & 8 when tilted by
is obtained.

Therefore, the center line of the head 1 and the thermal head 3.

Assuming that the platen 4 is kept perpendicular to the platen 4, the color density will be high regardless of whether the printing direction is (G) or (F). Therefore, there is no difference in color density depending on the printing direction, but the maximum color density is lower than D□A. This results in poor thermal efficiency.

Also, the center line is +θ. When tilted, (g) the maximum color density D□d is obtained in the printing direction, but (c) the color density becomes Dl in the printing direction, resulting in a difference in color density depending on the printing direction.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems of conventional heads, and to eliminate uneven color density depending on the printing direction when performing bidirectional printing. Another object of the present invention is to provide a head having extremely high thermal efficiency (coloring efficiency).

The above object of the present invention is to provide a head in which heating elements are arranged in a row on the outer peripheral surface of a cylindrical base formed of an insulator such as glass or ceramic, and a common electrode element is arranged on the center line of the row of heating elements. This is achieved by a head configured so that the heat generating element can individually generate heat using 3RF electric current 2 on both sides of the center line of the heating element.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

3rd ffj is a perspective view of a head showing one embodiment of the present invention, and FIG. 4 is a sectional view thereof.

In the figure, 21+21+...21.・・2n is a heating element, 5 is a common electrode, en, aiat'・61i,
I...6h1゜611' 61g+...61.・・６
．． 7 indicates an individual electrode, and 7 indicates a retentive layer.

Further, in FIG. 5(4), @ indicates a state in which electricity is applied between the common electrode and either one of the side electrodes 6□1t or 6,1 connected to the heating element 21, Heating element 2□
The shaded area represents the area that is energized and generates heat, and the white area represents the non-energized and non-heated area. The distance between the two heat generating parts of the heat generating element 21 shown in FIG. 6 is the angle θ shown in FIG. 2 above. The decision should be made accordingly. In addition, the above θ. The size of I see θ. needs to get bigger.

FIG. 6 shows a connection diagram of the device of this embodiment. Resistance elements R&□ and Rb□ in this figure correspond to the heating element 21.

Hereinafter, the operation when printing and recording is performed using the head of this embodiment will be explained based on FIG. 7.

First, if the pressure contact angle of the head is correct, that is,
When the center line of the head 1 and the thermal paper 3 and platen 4 are kept perpendicular, (g) printing in the printing direction is +θ. (c) Printing angle θ in the printing direction due to the part of the electrode located at a tilted position (coloring density characteristics are shown by curve I). The part of the electrode that is tilted by
Color density characteristics are curved! ◎Here, considering the case where there is a deviation of △θ in the (G) direction, (G) printing For direction printing, point RXH
In printing in the printing direction, the point S1, that is, the degree of color development is D and R, respectively, but the difference y (is extremely small and is practically acceptable).

On the other hand, when using a conventional head, as long as the pressure contact angle is correct, the color density η regardless of the printing direction as described above.
. However, if the pressure contact angle deviates, the difference is extremely large, with point T1 in the case of printing in the direction, and point U1 in the case of printing in the (toward) direction, that is, the color density becoming D'2゜R', respectively. It was something like that.

As described above, when the head of this embodiment is used, heat conduction efficiency (coloring efficiency) is good during bidirectional printing, and furthermore, stable coloring density can be obtained with respect to changes in the contact angle of the head.

FIGS. 8 and 9 show the drive circuit and timing circuit 10 of the head of this embodiment, and in the figures, AND represents an AND circuit, and D represents a driver.

As shown in FIG. 8, the signal input corresponding to each dot and the print timing signals (a) and (b) are ANDed,
This output drives the driver D to generate heat generating elements Ra1 in the head 1. Apply voltage to Hori, Ran, and TL. As shown in Figure 9, the details of the timing circuit 10 are as follows: A series of pulse trains are created by a delay circuit that adjusts the timing of heat generation and a pulse width control circuit that determines the energization time. The signal is generated by switching to the output terminal t or (b). It goes without saying that the delay circuit and the pulse width adjustment circuit can be configured to be controlled by external signals, and that dot displacement and density can be adjusted in combination with a sensor.

As described above, according to the present invention, one layer is placed on the outer peripheral surface of a cylindrical base made of an insulator such as glass or ceramic.
In the head in which heat generating elements are arranged in a row, a common electrode element is provided on the center line of the heat generating element row, and parts of the heat generating elements on both sides of the center line as boundaries can be individually energized. This has an excellent effect in that it is possible to realize a head having high thermal efficiency (coloring efficiency) without causing color density unevenness depending on the printing direction when performing bidirectional printing.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing the pressure contact situation between a conventional head, a thermal paver, and a platen, Fig. 2 is a diagram showing color density characteristics of the conventional head, and Fig. 3 is a perspective view of a head showing an embodiment of the present invention. Figure 4 is a cross-sectional view of the same, Figure 5 is a diagram showing the heat generation situation, Figure 6 is a connection diagram of the example device, Figure 7 is a diagram showing its color density characteristics, Figures 8 and 9 are FIG. 3 is a diagram showing a drive circuit of the example device. 1: Head, 2, 2□, 2. ...2n: heating element, δ:
Thermal paper, 4 nib platen, δ: common electrode, 6.6
,...6. 6, 6,...6. □: Individual electrode, 11 12 111
111 217: Film-retaining layer. Figure 1 θ Team 2 [Teichi θ Oθ. ←) -Head inclination angle -〇〇Fig. 3 □ l Fig. 5 470 - Fig. 6 5 Mark Fig. 7 Ritoichi θ. O ten θ. (→- Head inclination angle - (G) Figures 8 and 9

Claims (1)

[Claims] In a thermal head in which heating elements are arranged in a row on the outer peripheral surface of a cylindrical base formed of an insulator such as glass or ceramic, a common electrode element is provided on the center line of the row of heating elements. , individually energizing portions of the heat generating element on both sides of the center line. A thermal head characterized in that it is configured to generate heat.