JP2003237123A - Cooling device for thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device for a thermal head which is small and has a high cooling performance. <P>SOLUTION: The cooling device 31 has end parts of a graphite sheet 33 held between a head substrate 21 and a heat sink 32 of the thermal head 19 and between the heat sink 32 and a pressure welding plate 34 respectively. The graphite sheet 33 has a flexibility and a high thermal conductivity in a plane direction. Heat generated at the thermal head 19 is conducted from the head substrate 21 through a lower spread 38 of the heat sink 32 to a plurality of fins 40 from below. Moreover, heat of the thermal head 19 is conducted through the graphite sheet 33 and an upper spread 39 of the heat sink 32 to the fins 40 from above. The heat conducted to the fins 40 is emitted by a blast from fans 35 and 36. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling device that effectively cools a thermal head that heats a heating element to perform thermal recording.

[0002]

2. Description of the Related Art In a color thermal printer, a plurality of heating elements mounted on a thermal head are brought into pressure contact with a color thermal recording paper, and each heating element is heated according to print data to generate multi-gradation and multi-color. I am printing. In order to obtain a print with appropriate density and gray balance, it is necessary to heat the heating element to a specified temperature. However, if printing is continuously performed, the thermal head accumulates heat and the temperature of the heating element rises.

In order to prevent heat accumulation in the thermal head,
A heat sink for heat dissipation is attached to the thermal head. The heat sink is composed of a plate-shaped spread that comes into contact with the thermal head and a plurality of fins that are provided upright integrally with the spread, and is made of a material having high thermal conductivity such as aluminum.

[0004]

Since the fins of the heat sink have poor heat dissipation efficiency, the spread must be increased to increase the number of fins in order to cool the thermal head. However, this increases the size of the color thermal printer. In order to solve this, it is conceivable to form the heat sink with a material having high thermal conductivity such as graphite, but it is expensive, and the cost of the color thermal printer increases.

As a relatively inexpensive product using graphite, the graphite sheet described in JP-A-8-23183 is used for heat dissipation. This graphite sheet has high thermal conductivity in the plane direction, and as shown in FIG. 4, one end of the graphite sheet 2 is attached to the thermal head 3 and a heat sink 4 is attached to the other end, so that heat can be efficiently radiated. . However, it requires a space for installing the graphite sheet 2, and is not suitable for downsizing a color thermal printer.

SUMMARY OF THE INVENTION The present invention is intended to solve the above problems, and an object of the present invention is to provide a cooling device for a thermal head that is small and has high cooling performance.

[0007]

In order to solve the above problems, in the cooling device of the present invention, a plurality of fins and a pair of spreads sandwiching these fins are integrally made of a material having a high thermal conductivity. A heat sink formed so that one spread is attached to a thermal head, and a flexible heat conductive sheet that is sandwiched between the thermal head and one spread at one end and abuts the other spread at the other end. And a pressing plate that is made of a material having high thermal conductivity and presses the other spread to sandwich the other end of the thermally conductive sheet, and a fan that blows air along the surface direction of the fins. .

A graphite sheet can be used as the heat conductive sheet.

[0009]

FIG. 1 is a schematic diagram showing the structure of a color thermal printer embodying the present invention. In this color thermal printer, a long color thermal recording paper 10 is used as a recording medium. The color thermosensitive recording paper 10 is set in the color thermosensitive printer in the form of a recording paper roll 11 wound in a roll shape. The recording paper roll 11 is rotated by the paper feed roller 12 that is in contact with the outer circumference, and the color thermosensitive recording paper 10 is fed and rewound.

In the vicinity of the recording paper roll 11, a pair of conveying rollers 14 for sandwiching and conveying the color thermosensitive recording paper 10 is arranged. The conveyance roller pair 14 is composed of a capstan roller 16 which is rotationally driven by a conveyance motor 15 and a pinch roller 17 which is in pressure contact with the capstan roller 16. And reciprocally convey in the printing direction on the right side in the figure.

As is well known, the color thermosensitive recording paper 10 has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer and a yellow thermosensitive coloring layer which are sequentially laminated on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest heat sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with a large amount of heat energy. The yellow thermosensitive coloring layer has a thickness of 420 nm.
When it is irradiated with the near-ultraviolet rays, the coloring ability disappears. The magenta thermosensitive coloring layer, which is the second thermosensitive coloring layer, develops magenta with heat energy in the middle of those of the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer, and loses its coloring ability when irradiated with ultraviolet rays of 365 nm. .

A thermal head 19 and a platen roller 20 are arranged downstream of the conveying roller pair 14 in the fixing direction so as to sandwich the conveying path of the color thermosensitive recording paper 10. The thermal head 19 is made of a material having good thermal conductivity,
For example, the head substrate 21 made of aluminum and the alumina substrate 22 attached to the lower surface of the head substrate 21. On the alumina substrate 22, there is formed a heating element array 23 in which a large number of heating elements are provided in a line in a direction orthogonal to the transport direction of the color thermosensitive recording paper 10.

The platen roller 20 is a heating element array 2
It is arranged below the conveyance path at a position facing the sheet No. 3.
The platen roller 20 is movable in the vertical direction, and the thermal head 19 is moved by a spring (not shown).
It is urged in the direction of pressure contact with.

The thermal head 20 includes a pair of transport rollers 14.
Is pressed against the color thermosensitive recording paper 10 conveyed in the printing direction, and the heating element array 23 is heated to a predetermined temperature to develop each thermosensitive coloring layer. The platen roller 20 is driven to rotate in response to the conveyance of the color thermosensitive recording paper 10 to facilitate the sliding contact between the color thermosensitive recording paper 10 and the heating element array 23.

On the downstream side of the thermal head 19 in the fixing direction, a yellow fixing lamp 25 constituting an optical fixing device,
A magenta fixing lamp 26 is arranged. The yellow fixing lamp 25 radiates near-ultraviolet rays having an emission peak of 420 nm to fix the yellow thermosensitive coloring layer of the color thermosensitive recording paper 10. The fixing lamp 26 for magenta is 365
The thermosensitive coloring layer of magenta is fixed by emitting ultraviolet rays of nm.

At the downstream side of the fixing lamp 25 for yellow in the fixing direction, a cutter 28 for cutting the long color thermosensitive recording paper 10 into recording areas is provided. A discharge port 29 for discharging the cut sheet-shaped color thermosensitive recording paper 10 is disposed on the downstream side of the cutter 28.

As shown in FIG. 2, the cooling device 31 of the present invention is attached to the upper surface of the head substrate 21 of the thermal head 19. As shown in FIG. 3, which is an exploded perspective view of the cooling device 31, the cooling device 31 includes a heat sink 32.
, A graphite sheet 33, a pressure contact plate 34, and fans 35 and 36.

The heat sink 32 is made of a material having high thermal conductivity such as aluminum, and has a lower spread 38 attached to the head substrate 21, an upper spread 39 provided in parallel with the lower spread 38, and lower parts thereof. A plurality of fins 40 are provided upright between the spread 38 and the upper spread 39. A pressure contact plate 34, which is also made of aluminum, is attached to the upper surface of the upper spread 39 with four screws 41.

The graphite sheet 33 is made of highly oriented graphite in the form of a flexible sheet, and has a higher thermal conductivity in the plane direction than copper. The graphite sheet 33 is formed in a strip shape and has one end 33
a is sandwiched between the head substrate 21 and the heat sink 32, and the bent other end 33b is sandwiched between the upper spread 39 of the heat sink 32 and the pressure contact plate 34. The fans 35 and 36 are attached to the side surfaces of the heat sink 32 with screws 43, and blow air between the fins 40.

When the temperature of the head substrate 21 of the thermal head 32 rises during printing on the color thermosensitive recording paper 10, the heat is transferred to the lower spread 38 of the heat sink 32. The heat transferred to the lower spread 38 is applied to each fin 4
The heat transmitted from the fins 40 is radiated from the fins 40 by the wind transmitted from the fans 35 and 36.

The heat of the head substrate 21 is also transferred to the graphite sheet 33. Graphite sheet 33
Transfers heat to the upper spread 39 and the pressure plate 34. The heat transferred to the upper spread 39 is applied to each fin 4
It is dissipated by the wind which is transmitted to 0 and sent from the fans 35 and 36. As a result, the fin 40 having a poor heat dissipation effect
Since heat can be simultaneously transferred from above and below to radiate heat, the same heat radiating effect as when the number of fins that is twice the actual number is provided can be obtained, and the heat sink can be downsized.

In the above embodiment, the graphite sheet is used as the heat conductive sheet, but other heat conductive sheets may be used.

Although the graphite sheet is provided only on one side surface of the heat sink, the graphite sheet may be provided on the other side surface. Although two fans are attached to the heat sink, one large fan may be attached. Further, the fan need not be attached to the heat sink and may be located remote from the heat sink.

Although the color thermal printer has been described as an example, it can also be used for heat dissipation from the thermal head of a thermal printer of another recording type such as a thermal transfer type or a thermal sublimation type. Further, it can be used for cooling a heating element other than the thermal head.

[0025]

As described above, the cooling device of the present invention uses a thermally conductive sheet such as a graphite sheet.
Since the fins are used efficiently to dissipate heat, it is possible to obtain high cooling performance despite its small size.
This can contribute to downsizing of the printer.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of a color thermal printer embodying the present invention.

FIG. 2 is an external perspective view of a thermal head with a cooling device attached.

FIG. 3 is an exploded perspective view showing a configuration of a cooling device.

FIG. 4 is an explanatory diagram showing a conventional example of a cooling device using a graphite sheet.

[Explanation of symbols]

19 thermal head 21 head substrate 31 Cooling device 32 heat sink 33 Graphite sheet 34 Pressure plate 35,36 fans 38,39 Spread 40 fins

Claims (2)

[Claims] 1. In a cooling device of a thermal head for performing thermal recording by heating a heating element pressed against a recording paper, a plurality of fins and a pair of spreads sandwiching these fins are made of a material having high thermal conductivity. A heat sink with one spread attached to the thermal head, and one end sandwiched between the thermal head and one spread, and the other end abuts the other spread. Consists of a heat conductive sheet, a pressure contact plate that is made of a material with high heat conductivity and that presses against the other spread to sandwich the other end of the heat conductive sheet, and a fan that blows air along the surface direction of the fins. A cooling device for a thermal head characterized in that 2. The cooling device for a thermal head according to claim 1, wherein the heat conductive sheet is a graphite sheet.