JP2003341112A - Thermal printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To add a preheating performance in the case of a small thermal head without sacrifice of the cooling performance of the thermal head. <P>SOLUTION: A cut 36 is made in the fins 35 of a heat sink 31 and a heater 33 is set therein. The heater 33 is arranged such that the planar direction thereof is substantially identical to the axial direction of an axial fan 32. When heat is accumulated in a thermal head 17 during print operation to cause temperature rise of a head substrate 19, that heat is transmitted to the spread 34 of the heat sink 31. Heat transmitted to the spread 34 is then transmitted to each fin 35 and dissipated from the fins 35 by air supplied from the axial fan 32. When printing is started, the heater 33 operates to preheat the thermal head 17. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer having a thermal head equipped with a heat sink.

[0002]

2. Description of the Related Art In a thermal printer, for example, a color thermal printer, a plurality of heating elements attached to a thermal head are brought into pressure contact with a color thermal recording paper, and each heating element is heated in accordance with print data to produce multi-gradation. And multi-colored printing. In order to obtain a print with proper density and color balance, it is necessary to heat the heating element to a specified temperature. However, if printing is performed continuously, the thermal head accumulates heat,
The temperature of the heating element rises, the density and color balance deteriorate, and so-called thermal roughness occurs on the surface of the color thermosensitive recording paper, which significantly deteriorates the print image quality.

In order to solve the above problems, in a conventional color thermal printer, a heat sink for heat dissipation is attached to a 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 stand upright with respect to the spread, and is made of a material having high thermal conductivity such as aluminum. Further, since the heat dissipation efficiency is poor only with the fins of the heat sink, a fan is provided to blow air to the heat sink.

On the other hand, in the conventional color thermal printer, a preheating heater for preheating the thermal head before thermal recording is provided to prevent a decrease in density at the initial stage of printing and also to start printing quickly. I try not to consume extra energy at the start of printing. This preheating heater is directly installed on the thermal head as described in, for example, Japanese Patent Application Laid-Open Nos. 5-220990 and 11-1010.

[0005]

When the preheating heater is installed so as to be sandwiched between the thermal head and the heat sink, the direct contact area between the heat sink and the thermal head cannot be sufficiently secured, and the heat dissipation efficiency is deteriorated. As a result, there arises a problem that the thermal head cannot be cooled smoothly. In particular, when the thermal head is small, the contact area between the heat sink and the thermal head is limited, and this problem becomes more serious.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal printer which can add preheating performance without sacrificing the cooling performance of the thermal head even when the thermal head is small.

[0007]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a thermal head for performing thermal recording by heating a heating element pressed against a recording paper, and thermal recording by contacting the thermal head. In a thermal printer including a heat sink for radiating the accumulated heat of a thermal head generated therein, and a blowing unit for cooling the thermal head by blowing air to the heat sink, a heating unit for preheating the thermal head before thermal recording Is installed on the heat sink so as not to contact the thermal head.

It is preferable that the heating means is composed of a plate-shaped heater and the blowing means is composed of an axial fan. Further, it is preferable that the heater is arranged such that a surface direction of the heater and an axial direction of the axial fan, or a surface direction of the heater and a streamline direction of an air flow by the axial fan are substantially the same. .

[0009]

FIG. 1 is a schematic diagram showing the structure of a color thermal printer embodying the present invention. In this color thermal printer 2, 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 2 in the form of a recording paper roll 11 wound in a roll. The recording paper roll 11 is rotated by a paper feed roller 12 that is in contact with the outer periphery of the recording paper roll 11, whereby the color thermosensitive recording paper 10 is fed and rewound.

In the vicinity of the recording paper roll 11, a pair of carrying rollers 13 for sandwiching and carrying the color thermosensitive recording paper 10 are arranged. The conveying roller pair 13 is composed of a capstan roller 15 which is rotationally driven by a conveying motor 14 and a pinch roller 16 which is in pressure contact with the capstan roller 15, and fixes the color thermosensitive recording paper 10 in the fixing direction A and the printing direction. Reciprocate to B.

As is well known, the color thermosensitive recording paper 10 comprises 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 loses its coloring ability when irradiated with near-ultraviolet rays of 420 nm. The magenta thermosensitive coloring layer develops magenta with heat energy which is intermediate between those of the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer.
When it is irradiated with 5 nm ultraviolet light, the coloring ability disappears.

A thermal head 17 and a platen roller 18 are arranged downstream of the conveying roller pair 13 in the fixing direction so as to sandwich the conveying path of the color thermosensitive recording paper 10. The thermal head 17 has a head substrate 19 made of a material having high thermal conductivity, for example, aluminum.
And an alumina substrate 20 attached to the lower surface of the head substrate 19. The alumina substrate 20 is provided with a heating element array 21 in which a large number of heating elements are formed in a line in a direction orthogonal to the transport direction of the color thermosensitive recording paper 10.

The platen roller 18 is the heating element array 2
1 is located below the transport path.
The platen roller 18 is movable in the vertical direction, and is biased by a spring (not shown) in a direction of being pressed against the thermal head 17.

The thermal head 17 has a pair of conveying rollers 13.
Is pressed against the color thermosensitive recording paper 10 conveyed in the printing direction to heat the heating element array 21 to a predetermined temperature to develop each thermosensitive coloring layer. The platen roller 18 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 21.

On the downstream side of the thermal head 17 in the fixing direction, a yellow fixing lamp 22 constituting an optical fixing device,
A magenta fixing lamp 23 is arranged. The yellow fixing lamp 22 emits 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 23 for magenta is 365
The magenta thermosensitive coloring layer is fixed by radiating ultraviolet rays of nm. Behind these yellow fixing lamp 22 and magenta fixing lamp 23, there is provided a reflection plate 24 for condensing the emitted ultraviolet rays toward the color thermosensitive recording paper 10.

On the downstream side of the fixing lamp 22 for yellow in the fixing direction, a cutter 25 for cutting the long color thermosensitive recording paper 10 into recording areas is provided. On the downstream side of the cutter 25, a paper discharge port 26 for discharging the cut sheet-shaped color thermosensitive recording paper 10 is provided.

A heat sink 31 is attached to the head substrate 19 of the thermal head 17. The heat sink 31 is made of a material having high thermal conductivity such as aluminum, and has an axial fan 32 as a blower,
A plate-shaped heater 33 as a heating means is attached. As shown in FIG. 2, the heat sink 31 includes a spread 34 that contacts the head substrate 19 and a plurality of fins 35 that are erected on the spread 34.
The fin 35 is provided with a notch 36 for mounting the heater 33. The axial fan 32 is attached to the side surface of the heat sink 31 with screws or the like, and blows air to the fins 35. Although two axial fans 32 are used here, one large fan may be used.
Also, there is no need to attach the fan to the heat sink,
It may be provided at a position apart from the heat sink.

As the heater 33, for example, a silicon rubber heater or a stainless edge heater is used, and the heater 33 is arranged so that its surface direction is substantially the same as the axial direction of the axial fan 32. With such a configuration, the axial fan 3
Since the heater 33 does not hinder the blowing of the second fin 35, the thermal head 17 can be cooled more efficiently.

When the thermal head 17 accumulates heat during printing on the color thermosensitive recording paper 10 and the temperature of the head substrate 19 rises, the heat is transferred to the spread 34 of the heat sink 31. The heat transferred to the spread 34 is applied to each fin 3
5, and the heat is radiated from the fins 35 by the blown air from the axial fan 32. At this time, since the spread 34 is in contact with the entire surface of the head substrate 19, sufficient cooling performance can be secured even if the thermal head 17 is small.

When printing on the color thermosensitive recording paper 10, the heater 33 is operated to preheat the thermal head 17. As described above, even when the thermal head 17 is small, the preheating performance can be added without sacrificing the cooling performance of the thermal head 17.

The heaters may be arranged so that the surface direction thereof is orthogonal to the transport direction of the color thermosensitive recording paper 10 as shown in FIG. Further, as shown in FIG. 4, the heat sink 53 is housed in the duct 54, the axial fan 55 is installed in one opening of the duct 54, and the heater 56 is arranged such that the surface direction of the heater 56 is equal to that of the air flow by the axial fan 55. The same effect as that of the above-described embodiment can be obtained also in the case of arranging so as to be substantially the same as the streamline (shown by the two-dot chain line in the figure) direction.

In the above embodiment, the color thermal printer has been described as an example, but the present invention can be applied to other recording type thermal printers such as a thermal transfer type and a thermal sublimation type.

[0023]

As described above, according to the thermal printer of the present invention, the heating means for preheating the thermal head before the thermal recording is installed on the heat sink so as not to contact the thermal head. Even in such a case, the preheating performance can be added without sacrificing the cooling performance of the thermal head.

[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 exploded perspective view of a heat sink, an axial fan, and a heater.

FIG. 3 is a diagram showing another embodiment of the present invention.

FIG. 4 is a diagram showing still another embodiment of the present invention.

[Explanation of symbols]

2 color thermal printer (thermal printer) 10 color thermal recording paper 17 Thermal head 19 head substrate 31 heat sink 32 Axial fan (Blower) 33 Heater (heating means)

Claims (3)

[Claims] 1. A thermal head for performing thermal recording by heating a heating element pressed against a recording sheet, a heat sink for contacting the thermal head to radiate the accumulated heat of the thermal head generated during thermal recording, and a heat sink for the heat sink. In a thermal printer including a blowing unit that cools the thermal head by blowing air, a heating unit that preheats the thermal head before thermal recording is installed on the heat sink so as not to contact the thermal head. Characteristic thermal printer. 2. The thermal printer according to claim 1, wherein the heating means is composed of a plate-shaped heater, and the air blowing means is composed of an axial fan. 3. The heater is arranged such that the surface direction of the heater and the axial direction of the axial fan are substantially the same, or the surface direction of the heater and the streamline direction of the air flow by the axial fan are substantially the same. The thermal printer according to claim 2, wherein: