JPS6412234B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal head in which warping of a heating element mounting substrate that generates heat during use is reduced.

A conventional example of a method for attaching a heating element mounting board and the problems involved therein will first be described. FIG. 1 is a side view of a printing section of a thermal printing device using a thermal head in which a large number of heating elements are arranged in a straight line.
1 is a ceramic substrate, 2 is a mounting plate, 3 is a thermal head, 4 is a thermal recording paper, 5 is a roller platen,
Reference numeral 6 indicates a pressing spring, and reference numeral 7 indicates a heat generating element array. The thermal head 3 is composed of a ceramic substrate 1, a mounting plate 2, and a heating element row 7. The heating element row 7 is a plurality of heating elements arranged in a line in the longitudinal direction of the contact surface of the roller platen 5 on the ceramic substrate 1. It is something. The thermal head 3 is pressed against a roller platen 5 via a thermal recording paper 4 by a spring 6, and records on the thermal recording paper 4 by means of a heating element array 7 on a ceramic substrate 1. In this case, the ceramic substrate 1 may warp due to the heat generated by the heating element array 7, and the pressed state of the thermal recording paper 4 may become uneven, resulting in uneven printing. FIG. 2 shows an overall view of the thermal head 3, in which 10 is an adhesive;
h is the amount of warpage of the ceramic substrate 1, and the other symbols are the same as in FIG. In the figure, a thermal head 3 is constructed by adhering a ceramic substrate 1 to a mounting plate 2 with an adhesive 10, and a heating element array 7 is mounted on the ceramic substrate 1. During use, the temperature of the entire thermal head 3 rises due to the heat generated by the heating element array 7, and due to the difference in thermal expansion coefficients between the ceramic substrate 1 and the mounting plate 2, a bimetallic effect occurs, causing the entire thermal head 3 to warp. occurs. In this case, when attaching the ceramic substrate 1 and the mounting plate 2 in the thermal head 3,
An adhesive 10 that hardens after curing is used,
For example, when a ceramic substrate 1 with dimensions of 220 mm in length, 25 mm in width, and 1.2 mm in thickness is attached to a mounting plate 2 made of iron with a cross section of 10 mm in thickness and 60 mm in width, the operating temperature range
It is clear from experiments that warping occurs within a range of about 0.1 mm at 65°C. (This amount of warpage h almost matches the calculated value of the bimetal effect.) Therefore, the contact state between the thermal recording paper 4 and the heating element array 7 changes depending on the position of the heating element array 7, and the ceramic Changes in print density occur in the longitudinal direction of the substrate 1, which poses a practical problem.

In order to solve the above-mentioned problems, the present invention aims to minimize the warping of a heating element mounting substrate that is subject to temperature changes during use, and will be described in detail below.

FIG. 3 is an explanatory diagram showing an embodiment of the present invention,
This will be explained below with reference to the drawings. As shown in FIG. 3, in the thermal head 9, two concave grooves 12 are provided in the longitudinal direction on the attachment surface of the mounting plate 2, the grooves 12 are filled with adhesive 11, and the ceramic substrate 1 is attached. are doing. Reference numeral 11 indicates an adhesive having rubber elasticity after curing, and reference numeral 7 indicates a heat generating element, similar to the thermal head shown in FIG. 2 shows a row of heat generating elements arranged in multiple rows.

The temperature of the ceramic substrate 1 and the mounting plate 2 rises as heat is generated during use of the heat generating resistor element array 7. Since the ceramic substrate 1 and the mounting plate 2 each have different coefficients of thermal expansion, they expand and contract independently with changes in temperature. However, in the case of this embodiment, since the ceramic substrate 1 and the mounting plate 2, which have two different coefficients of thermal expansion, are bonded with a bonding agent 11 having rubber elasticity, the layer of the adhesive 11 absorbs the bimetallic effect. Therefore, the amount by which the entire thermal head 9 is warped as in the conventional embodiment is extremely small, and there is no change in printing density even in practical use. In the case of this embodiment, for example, the ceramic substrate 1 is 276 mm long, 25 mm wide, and 1.2 mm thick, and the cross-sectional dimensions are 10 mm thick and 60 mm wide.
A mounting plate 2 made of iron material is heated to a temperature using a silicone adhesive as an adhesive 11 having rubber elasticity.
When a thermal head manufactured by bonding at 120℃, heating time for 1 hour, and pressure of 0.75Kg/ ^cm2 is used in the same operating temperature range of 65℃ as above, the amount of change in warpage is less than 0.03mm. becomes. Therefore, the warpage of the thermal head due to temperature changes is greatly improved compared to the conventional embodiment.

Furthermore, a concave groove 12 is formed on the attachment surface of the mounting plate 2.
Since the structure is such that the ceramic substrate 1 is attached to the heat generating element row 7, the adhesive layer under the heat generating element array 7 becomes thinner, the heat dissipation efficiency when the heat generating elements generate heat can be improved, and the warpage of the thermal head can be improved.

As explained above, in the embodiment of the present invention, the amount of change in warpage due to the bimetallic effect of the thermal head, which occurred in the conventional embodiment, can be absorbed to a practically negligible extent by the adhesive 11 having rubber elasticity. Because it can improve heat dissipation efficiency when the element generates heat,
There is an advantage that clear printing without density unevenness can always be obtained when printing on the thermal recording paper 4.

[Brief explanation of drawings]

Figure 1 is a side view of the printing section of the thermal printing device;
The figure is an explanatory diagram showing a method of attaching a thermal head in a conventional embodiment, and FIG. 3 is an explanatory diagram of a thermal head in an embodiment of the present invention. 1...Ceramic board, 2...Mounting plate, 3...
Thermal head, 7... Heating element row, 9... Thermal head, 10, 11... Adhesive, 12... Concave groove, h... Warpage amount.

Claims (1)

[Claims] 1. A substrate, heating elements mounted in a row in the longitudinal direction at the center of the substrate in the lateral direction, a mounting plate to which the substrate is attached, and both ends of the bonded portion of the mounting plate in the lateral direction. It has two concave grooves provided in the longitudinal direction of the adhesive length, and an adhesive that has rubber elasticity when cured due to the concave groove, and the substrate and the mounting plate are attached with the adhesive. . A thermal head, wherein the adhesive layer absorbs a bimetal effect generated between the substrate and the mounting plate due to heat generated by the heating element.