JPS5863473A - thermal head - Google Patents

Abstract

PURPOSE:To minimize the thermal warping of a substrate carrying heat generating elements by sticking it on a mount plate with a hardening type adhesive adapted to be rubber-elastic when hardened. CONSTITUTION:A ceramic substrate 1 carrying trains of heat generating elements 7 is stuck on a mount plate 2 with an adhesive 11 adapted to be elastic like rubber when hardened. For example, a silicone adhesive can be used for the adhesive providing a rubber-like elastisity when hardened. If the adhesive became hard when hardened, the substrate 1 would bend due to a sort of bimetal effect developed by a difference in the coefficient of thermal expansion between the substrate 1 and the mount plate 2, which eventually will causes a change in the printing density. It is preferable that a concave groove is provided longitudinally on the mating surface of the mount plate 2 so that the substrate 1 will be applied thereon with the adhesive 11 filling the groove 12.

Description

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

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, in which 1 is a ceramic substrate, 2 is a mounting plate, 3 is a thermal head, 4 is a thermosensitive recording paper, 5 is a roller platen, 6 is a pressing spring, and 7 is a heating element array. The thermal 5 board 3 is composed of a ceramic substrate 1, a mounting plate 2, and a heating element row 7. The heating element row 7 has a plurality of heating elements arranged on the ceramic substrate 1 in a line in the longitudinal direction of the contact surface of the roller platen 5. They are arranged in a row. The thermal head 3 is pressed against the roller silane 5 via the thermal recording paper 4 by a spring 6, and the ceramic substrate is pressed! Recording is performed on the thermosensitive recording paper 4 by the upper heating element row 2. In this case, the ceramic substrate 1 may warp due to the heat generated by the heating element array 70, and the pressing 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, where 10 is an adhesive, h is anti-DJit of the ceramic substrate 1, and other symbols are the same as in FIG. 1. In the figure, a thermal head 3 is constructed by adhering a ceramic substrate 1 to a mounting plate 2 with an adhesive lO, 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 the difference in thermal expansion coefficients between the ceramic substrate 1 and the mounting plate 2 causes a shibaimetal effect, causing a reaction in the entire thermal head 3. Bh is generated.

In this case, in the thermal head 3, the ceramic substrate 1
and mounting plate 2, use adhesive 1 that hardens after curing.
For example, the dimensions are 220 meters long and 25 meters wide.
When a ceramic substrate 1 with a thickness of 1.2 m and a thickness of 1.2 m is attached to a mounting plate 2 made of iron having a cross section of 10 m in thickness and 60 cm in width,
It is clear from experiments that the warpage h is within a range of about 0.1 m in the operating temperature range of 65°C.

(This amount of warpage almost matches the calculated value of the Guimetal 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 substrate 1 Changes in printing density occur in the longitudinal direction, which poses a practical problem.

In order to solve the above-mentioned problem, the present invention aims to extremely reduce the size of a heat generating element mounting substrate which is subject to temperature changes during use, and will be described in detail below.

FIG. 3 is an explanatory diagram showing the first embodiment of the present invention, 1
1 indicates an adhesive having rubber elasticity after curing, and other symbols indicate the same as in FIG. 2. In this embodiment, the ceramic substrate 1 and the mounting plate 2 have rubber elasticity after being cured. It is attached with adhesive 11. The temperature of the ceramic substrate 1 and the mounting plate 2 rises as heat is generated when the heat generating resistor element array 7 is used. Since the ceramic base 1 and the mounting plate 2 each have a different coefficient 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 the adhesive 11 having rubber elasticity, the bimetal effect is absorbed by the layer of the adhesive 11. Unlike the conventional embodiment described above, the amount by which the entire thermal head 9 is warped is extremely small, and no change in printing density occurs in practical use.

In the case of this embodiment, for example, the length is 276 cm, the width is 2511 I+
I+, a ceramic substrate 1 with a thickness of 1 or 2 mm and a mounting plate 2 made of iron with a cross-sectional dimension of 10 mm in thickness and 60 mm in width were heated to a temperature using a silicone adhesive as an adhesive having rubber elasticity. 120℃, heating time 1 hour, pressure 0.7
When a thermal head manufactured by bonding under the conditions of 5 kg/crIL2 is used in the same operating temperature range of 65° C. as described above, the change in longitudinal direction is 0.03 mm or less. Therefore, the warpage of the thermal head due to temperature changes is greatly improved compared to the conventional embodiment.

As explained above, in the first embodiment, the amount of change in anti-reflection due to the bimetallic effect of the thermal head, which occurred in the conventional embodiment, can be absorbed by the adhesive 11 having rubber elasticity to a practically negligible extent. When printing on the thermal recording paper 4, there is an advantage that clear surface printing without density unevenness can always be obtained.

In the first embodiment, the attachment surface of the mounting plate 2 is smooth, but as shown in the fourth example, a concave groove is provided in the longitudinal direction on the flat attachment surface of the mounting plate 2, and a single adhesive layer is applied. A similar effect can also be obtained by filling the groove 12 and attaching the ceramic substrate 1. In this case, since the layer of the adhesive 11 becomes thicker, the amount of absorption of the bimetal effect is reduced, and therefore, the amount of change in anti-ph when the thermal head is used can be reduced. .

Further, as shown in FIG. 5, a similar effect can be obtained when two concave grooves 12 are provided in the longitudinal direction on the attachment surface of the mounting plate 2 and the ceramic substrate 1 is attached as described above.

[Brief explanation of the drawing]

Fig. 1 is a side view of the printing section of a thermal printing device, Fig. 2 is an explanatory diagram showing a method of attaching a thermal head in a conventional embodiment, and Fig. 3 is an explanation of a thermal head in a first embodiment of the present invention. 4 are explanatory diagrams of a thermal head in a second embodiment of the present invention, and FIG. 5 is an explanatory diagram of a thermal head in a third embodiment of the present invention. V...Ceramic board, 2...Mounting plate, 3...
Thermal head, 7... Heating element row, 9... Thermal head, 0.11... Adhesive, 12... Concave groove,
h...Amount 4.1 Figure 71 Figure 2 Procedural Amendment (Mutsu) 1. Indication of the case 1982 Patent application No. 162079 2 Name of the invention Thermal head 3 Person making the amendment Relationship to the case Patent application Person Address (105) 1-7-12 Toranomon, Minato-ku, Tokyo Name 'Name (029) Oki Electric Works li! Co., Ltd. Representative
Director and President Masao Miyake, 1 Agent Address (105) 1-7-1, Toranomon, Minato-ku, Tokyo
No. 2 No. 6, on page 6, lines 9 to 10 of the statement of contents of the amendment, the phrase "Substrate 1 is produced as described above" has been replaced with "a structure in which the substrate I is attached as described above." By doing so, the adhesive layer under the heating element becomes thinner, which improves the heat dissipation efficiency when the heating element generates heat, and at the same time improves the thermal head.''

Claims (2)

[Claims] (1) A board on which a heating element is mounted and a mounting plate to which the board is attached are attached using an adhesive that has rubber elasticity when cured, and bimetallic particles are generated between the board and the mounting plate due to the heat generated by the heating element. A thermal head whose one feature is that the effect is absorbed by the adhesive layer. (2) One or more concave grooves are provided in the longitudinal direction of the adhesive portion of the mounting plate, and the heat generating element mounting board is attached by filling the concave grooves with an adhesive that has rubber elasticity when cured. A thermal head according to claim 1.