JPH03230963A - Thermal head - Google Patents

Abstract

PURPOSE:To restrain warpage of a thermal head by a method wherein a radiator having a radiation fin is installed parallel to a longitudinal direction of a heating element in the thermal head where the heating element is formed on a substrate. CONSTITUTION:A radiator 4 having a radiation fin 5 parallel to a longitudinal direction of a heating element 1 is fixed to an opposite side surface of an aluminum plate 3 bonded to a ceramic substrate 2 with screws 6. This radiator 4 radiates heat to be generated in the heating element 1 and besides, is used for preventing this thermal head from warpage. Therefor, a direction of the fin 5 of the radiator 4 is parallel to the longitudinal direction of the heating element 1 and strength effective for prevention of warpage is provided to the radiator fin. That is, when total thickness TF of the radiator 4 is sufficiently larger than total thickness TM of the thermal head, warpage of the thermal head follows warpage of the radiator 4. Therefore, the total thickness TF of the radiator 4 is made sufficiently large. Flatness of a surface of the radiator 4 (the surface coming in contact with the aluminum plate 3) is made sufficiently uniform by machining or the like, and said surface of the radiator 4 is screwed to the aluminum plate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a thermal head having a heat radiator, and more particularly to a thermal head in which warping of the thermal head that occurs during the manufacturing process can be suppressed by the heat radiator.

[Conventional technology]

For example, a thermal head used in a color video image output device generally has a structure as shown in FIG.

That is, the ceramic substrate 32 (Δnzo3) is bonded to the aluminum plate 33J- using a thermosetting adhesive, and the heating element 31 is provided on the ceramic substrate 32-1- in a direction perpendicular to this cross-sectional view. Immediately below this heating element 31, a partial glaze is applied at least to increase the contact pressure with the photographic paper.

Note that other elements, such as the IC element 34, are mounted on a printed circuit board 35 bonded onto the aluminum plate 33. Here, the IC element 34 is protectively coated with a silicone sealing resin 36 and covered with an IC cover 37 fixed to the printed circuit board 35 with screws 38. 39 is a connector.

[Problem to be solved by the invention]

However, the thermal spatula of the conventional structure as shown in Figure 3
Now, the aluminum plate 33 and the ceramic substrate 32
Since the coefficient of thermal expansion is different from that of the two, for example, the completed thermal head will warp due to the bimetallic effect at a manufacturing process temperature of approximately 150° C. when the two materials are bonded together using a thermosetting adhesive. The direction of warpage is perpendicular to the cross-sectional view of FIG. 3, that is, the longitudinal direction along the row of heating elements of the thermal head.

This warping is considered to have a large effect on color density in thermal heads used in color video image output devices and the like.

Figure 4 shows the distribution of warpage (flatness) of the thermal head in the case of A6 size (95 mm long row) with conventional structure.
The figure shows the color density distribution of an image output using the same thermal head, and the relationship between warpage and color density is shown in FIG. 6 based on FIGS. 4 and 5.

It is desirable that the color density distribution be uniform throughout the output image. However, with the conventional structure of the thermal head, the fourth
As is clear from Figures 6 to 6, the color density distribution is not uniform.2 The distribution is similar to that of a warped distribution.

This eliminates the warpage of the thermal head,
It is expected that the color density distribution will also be uniform.

Therefore, an object of the present invention is to prevent the thermal head from warping and provide a thermal head having a uniform color density distribution.

[Failure to solve the problem]

In order to achieve the above object, the present inventor has conducted extensive research, and as a result,
It has been found that warping of the thermal head can be prevented by fixing a heat radiator that acts to suppress the warping to the side of the aluminum plate of the thermal head opposite to the ceramic substrate.

According to the present invention, a heat sink having heat sinks extending parallel to the longitudinal direction of the heating element of the thermal head is provided on an aluminum plate that supports the substrate of the thermal head.

With this structure, the heat generated in the direction along the row of heating elements is radiated from the heat sink, and the heat sink, whose surface has been processed to be sufficiently flat, is fixed to the aluminum plate, allowing the thermal head to Warpage is suppressed by this heat sink.

〔Example〕

An embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

FIG. 1 is a sectional view of the structure of the thermal head, and FIG. 2 is an exploded perspective view of the thermal head.

In the figure, reference numeral 1 denotes a heating element, which, as shown in FIG. 2, is formed in a direction perpendicular to the cross-sectional view of FIG. 1. Further, the heating element 1 is provided with a partial glaze in order to strengthen the contact pressure between the photographic paper and the heating element. 2 is a ceramic substrate, and 3 is an aluminum plate, both of which are bonded with, for example, a thermosetting adhesive.

Reference numeral 4 denotes a heat radiator which is characteristic of the present invention, and is made of aluminum, for example, 5 is a heat radiator fin which is a part of the heat radiator 4, and 6 is a screw.

7 is an IC element, 8 is a printed circuit board, 9 is an IC sealing resin,
10 is an IC cover, and 11 is a connector.

In the thermal head of this embodiment, a heat radiator 4 having heat radiating fins 5 extending parallel to the longitudinal direction of the heat generating element 1 is fixed to the opposite surface of an aluminum plate 3 bonded to a ceramic substrate 2 with screws 6.

The heat sink 4 radiates the heat generated in the heat generating body 1 and is also used to prevent the thermal head from warping. Therefore, the direction of the fins 5 of the heat dissipating body 4 is parallel to the longitudinal direction of the heat generating body 1, as shown in FIGS. 1 and 2, to provide strength effective for preventing warping.

That is, as shown in FIG. 1, the total thickness T of the heat sink 4.

When T is sufficiently larger than the total thickness T of the thermal head, the warpage of the thermal head follows the warpage of the heat sink 40.

Therefore, the total thickness TF of the heat sink 4 is made sufficiently large, and the heat sink 4
The flatness of the surface (the surface in contact with the aluminum plate 3, hereinafter referred to as surface A) is made sufficiently uniform by machining, etc., and then screwed to the aluminum plate 3.

For example, when we measured the warpage of a thermal head with a conventional structure of 34 size (peak row length 256 mm, 512 tons) with a thickness of 1's-8 mm, we found that the warp was the largest in a convex shape on the ceramic substrate side. - There was a warpage of 80 μm.

This thermal head has a heat dissipation fin 5 having a thickness of i-F-40 mm, the flatness of the A side being (0±10) μm, and extending parallel to the longitudinal direction of the heating element 1. The heat dissipating body 4 was screwed to the aluminum plate 3, and when the warpage was measured, the warpage was repaired to 25 μm.

Note that a heat dissipating body with heat dissipating fins is used in the thermal head. It has a structure in which a cavity 75 is provided between the substrate 72 and the radiation fins 74, and a heat exchange fluid is contained therein.The area of the radiation fins 7 is small, and the effective strength for preventing warping of the thermal head is I can't get it.

-1-1 In this structure, the direction of the radiation fins 74 is perpendicular to the longitudinal direction of the heating element 7I, so the effective thickness F, which provides strength to prevent warping, is the radiation fins 74.
The thickness will be the part that does not include 4. As a result, the effective total thickness TF of the heat sink cannot be made sufficiently larger than F,4.
It is almost ineffective in suppressing warpage.

In the above embodiment, the shape of the heat dissipation fins of the heat dissipation body 4 has been described as an example in which the heat dissipation fins have a substantially ■-shaped shape, but in the present invention, the shape and number of the heat dissipation fins are not particularly limited. For example, rectangular heat dissipation fins may be used. The number of fins may also be one.

In the above embodiment, an example was explained in which the heat sink 4 was attached to the aluminum plate of the thermal head, but the present invention is not limited to this fixing method, and any other method may be used as long as it is effective for suppressing and repairing warpage. For example, adhesives can also be used.

Furthermore, in the embodiment described in -, an example was described in which the heat sink 4 was made of aluminum, which is the same material as the aluminum plate 1 for mounting, but the heat sink is not necessarily limited to aluminum, and may be any material that has a heat dissipation effect. You can use it if you have it. In this case, it goes without saying that if the heat sink material has sufficient mechanical strength, the thickness of the heat sink including the heat sink fins does not need to be thicker than the thickness of the thermal head.

[Effects of the Invention] With the configuration of the present invention, the warpage of the thermal head can be suppressed without using any special device for suppressing warpage.
This can be suppressed only by installing a heat sink. By suppressing this warping, the color density distribution of a thermal head used in, for example, a color video image output device can be made uniform.

Furthermore, according to the present invention, since the warpage of the thermal head almost follows the warpage of the heat sink, the warpage of the thermal head can be changed by controlling the warpage of the heat sink. For example, by replacing the heat sink, Fine adjustment of the flatness of the thermal head is possible.

[Brief explanation of drawings]

FIG. 1 is a structural sectional view of a thermal head according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a thermal head according to an embodiment of the present invention, and FIG. 3 is a structural sectional view of a conventional thermal head. Fig. 4 is a warpage distribution diagram of a conventional thermal head, Fig. 5 is a color density distribution diagram of a conventional thermal head, Fig. 6 is a relation between warpage and color density of a conventional thermal head, and Fig. 7 is a structural cross-sectional view of another conventional thermal head. 1 - heating element, 2 - ceramic substrate, 3 - aluminum plate, 4 - heat sink, 5 - heat radiation fin, 6 screw, 6' screw (.

Claims (3)

[Claims] (1) A thermal head in which a heating element is formed on a substrate, characterized in that a heat radiating element having radiation fins is provided in parallel to the longitudinal direction of the heating element to suppress warping of the thermal head. . (2) The thermal head according to claim (1), wherein the heat radiator has a surface in contact with the thermal head whose flatness is in the range of (0±10) μm. (3) The thermal head according to claim (1), wherein the thickness of the radiation fin is thicker than the thickness of the thermal head.