JPH0767814B2 - Thermal recording device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a thermal recording apparatus.

[Prior Art] In a thermal recording apparatus, a thermal head is used to heat a thermal recording paper or a thermal paper such as a heat-fusible carbon film.

FIG. 4 is a schematic explanatory view of such a thermal recording apparatus. The thermal recording paper 3 is sandwiched between the platen roller 1 and the thermal head 2 which are in pressure contact with each other, and the heat generating portion 2a on the thermal head 2 is imaged. The heat-sensitive recording paper 3 is caused to develop color by recording heat to generate characters and images.

Usually, the platen roller is formed of an elastic resin material such as silicon rubber or chloroprene rubber. On the other hand, in the heat generating portion 2a, heat generating elements for one line are arranged on the substrate of the thermal head 2 and the surface thereof is covered with a protective film.

By the way, in order to record a good image on the heat-sensitive recording paper 3, the heat-sensitive recording paper 3 is strongly adhered to the heat-generating portion 2a, and the heat-generating portion is so arranged that the heat-sensitive recording paper 3 develops a color at a predetermined density.
It is necessary to heat 2a to a predetermined temperature.

Therefore, conventionally, the platen shaft 1a of the platen roller 1 is mounted on the center line C of the heat generating portion 2a, the platen roller 1 is slightly deformed, and the pressing force is applied so as to contact the surface of the thermal head 2 with the nip width D. I was trying to add it.

However, this tends to cause a so-called stick phenomenon in which the thermal recording paper 3 sticks to the heat generating portion 2a during image recording. When this sticking phenomenon occurs, there is a problem in that the conveyance speed of the thermosensitive recording paper 3 becomes uneven, and noise is generated due to a sticking sound that occurs when the thermosensitive recording paper 3 clinging away from the heat generating portion 2a.

Further, when the nip width D is increased, the heat radiation of the heat generating portion 2a is deteriorated. Therefore, particularly in the case of an image having many black dots, the temperature of the heat generating portion 2a rises more than necessary, and the thermal recording paper 3
However, there is a problem that the black dots in the image become large and the image quality deteriorates.

For this reason, in order to prevent an abnormal temperature rise when there are many black dots, a control circuit for suppressing the current flowing to the thermal head 2 has also been provided.

[Object] In view of the above problems, it is an object of the present invention to provide a thermal recording apparatus in which the stick phenomenon is reduced and the quality of a recorded image is improved.

[Structure] Therefore, in the present invention, the platen roller is formed to have a hardness of 40 ± 10 degrees, and the recording line position of the heat generating portion is displaced from the axial center position of the platen roller by 0.2 to 0.8 mm in the thermal recording paper conveyance direction. This is set.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view of a thermal recording apparatus according to an embodiment of the present invention, and FIG. 2 is an exploded perspective view of a thermal head unit. In these figures, a cut-and-raised portion 4b having a hole 4a and a cut-and-raised portion 4d having a notch 4c are formed on one side of the heat dissipation base 4. A cut-and-raised portion 4f having a hole 4e and a cut-and-raised portion 4h having a notch 4g are formed on the other side portion. Such cuts 4d, 4
Reference numeral h is a support mechanism for the platen roller 1.

Pins 4i to 4k are planted on the upper surface of the heat dissipation base 4, and screw holes 4m to 4p are drilled on one side.

The thermal head substrate 5 is arranged on this surface.
The thermal head substrate 5 has a heating portion 5a which is an image recording layer formed on one side thereof and a terminal portion 5b for signal input / output on the other side thereof. The thermal head substrate 5 has its long side one side portion locked to the pins 4j and 4k, and its short side one side portion locked to the pin 4i and fixed at a fixed position.

A flexible substrate 6 is provided on the thermal head substrate 5.
Is provided. The flexible substrate 6 is a printed wiring board having flexibility, and a terminal portion 6a corresponding to the terminal portion 5b is formed on the lower surface of the front end portion of the flexible printed circuit board, and at the rear end portion of the flexible substrate 6, A terminal portion 6b is formed which is connected to the terminal portion 6a in a pattern. Further, holes 6c to 6f through which screws are passed are formed at the central positions of both of them.

The flexible substrate 6 is arranged on the thermal head substrate 5 so that the terminal portion 6a and the terminal portion 5b are in contact with each other.

A head cover 7 is provided on the flexible substrate 6. The head cover 7 has a hole 7a through which a screw passes.
7d are formed at positions corresponding to the holes 6c to 6f. The head cover 7 utilizes these holes 7a to 7d and 6c to 6f and is screwed onto the heat dissipation base 4 by screws 8a to 8d. As a result, both the thermal head substrate 5 and the flexible substrate 6 are fixed.

A pressure contact rubber 7e is fixed to the lower surface of the head cover 7. The pressure contact rubber 7e presses the terminal portion 6a from above, so that the terminal portion 6a and the terminal portion 5b are surely brought into contact with each other.

In this way, the thermal radiation base 4, the thermal head substrate 5, the flexible substrate 6, and the head cover 7 constitute the thermal head unit 9.

On the other hand, bearings 1b are attached to both ends of the platen shaft 1a of the platen roller 1. This bearing 1b is provided with notches 4c, 4
The platen roller 1 is set and positioned in the thermal head unit 9 so as to fit into g.

The thermal head positioning device of the present embodiment has the above-described configuration, and the thermal head unit 9 is attached to the main body frame side (not shown) of, for example, a facsimile device. In this case, the pin 1 formed on the body frame side
0 and 11 are fitted in the holes 4a and 4e, respectively, and the thermal head unit 9 is supported rotatably about the pins 10 and 11 thereof.

In this case, as shown in FIG. 3, the platen shaft 1a is formed so as to be displaced toward the fulcrum side of the heat dissipation base 4 by the distance L with respect to the center line C of the heat generating portion 5a. Also, at this time,
The platen roller 1 and the heating portion 5a are held in pressure contact by a pressure contact mechanism (not shown), and the surface of the platen roller 1 and the surface of the thermal head substrate 5 are in pressure contact with a nip width D.

On the other hand, the connector 12 is coupled to the terminal portion 6b,
It is connected via 13 to a control circuit (not shown). When recording is performed, the thermosensitive recording paper 3 is conveyed from the fulcrum side of the heat dissipation base 4 toward the end thereof. At this time, the heat generating portion 5a is energized and generates heat according to the image information, whereby an image is recorded on the thermal recording paper 3.

In this case, since the center line C of the heat generating portion 5a is displaced from the center of pressure contact of the platen roller 1 by the distance L in the conveying direction of the thermal recording paper 3, the thermal recording paper is compared with the case of FIG. 3 is in contact with the heat generating portion 5a and is heated, and then the platen roller 1
It will be released soon after being pressed for a short time. As a result, the stick phenomenon in which the thermal recording paper 3 sticks to the thermal head substrate 5 is less likely to occur.

Therefore, the thermal recording paper 3 is smoothly conveyed, and the unevenness of the speed is reduced. In addition, noise, which is a stick sound generated when the thermal recording paper 3 separates from the heat generating portion 2a, is also reduced.

Further, since the heat generating portion 5a is located away from the center position of the nip width D, the heat generating portion 5a easily radiates heat. As a result, even when recording images with many black dots,
The heat storage is reduced, and the temperature of the heat generating part 5a is prevented from rising more than necessary. Therefore, the thermal recording paper 3 is not heated more than necessary, and the quality of the recorded image is improved.

Further, the pressure of the platen roller 1 applied to the surface of the heat generating portion 5a is reduced as compared with the case of FIG.
5a The surface is less worn, and the damage caused by adhesion of dust is also reduced.

The applicant found that the platen roller 1
The rubber hardness is 40 ± 10 degrees, and when the distance L is adjusted in the range of 0.2 to 0.8 mm, the stick phenomenon is reduced and the image quality is improved.

As described above, in the present embodiment, since the center line C of the heat generating portion 5a is arranged so as to be displaced by the distance L in the transport direction of the thermal recording paper 3 with respect to the mounting position of the platen shaft 1a, the stick phenomenon may occur. The amount of the heat-sensitive recording paper 3 is reduced, and the unevenness of the conveyance speed of the thermosensitive recording paper 3 and the noise are eliminated.

Further, since the heat storage is reduced and the temperature is prevented from rising more than necessary, the image quality is improved. Further, in order to prevent an abnormal temperature rise when there are many black dots, a conventional control circuit for suppressing a current flowing to the thermal head substrate 5 is unnecessary.

Furthermore, since the pressure applied to the surface of the heat generating portion 5a is reduced, the wear and damage thereof are reduced.

In the above-described embodiment, the thermal head substrate 5 has a flat surface, and the example in which the thermal recording paper is heated has been described. However, in the case of using a partial glaze type thermal head in which the heating portion 5a is raised. In particular, the effect is particularly high with respect to wear and damage of the heat generating portion or adhesion of dust. Further, when a heat-meltable carbon film or a copy facsimile paper is heated, the melt tends to adhere to the heat-generating portion, but this case also has the same effect.

[Effects] As described above, according to the present invention, the heat generating portion of the thermal head is displaced with respect to the axial center position of the platen roller in the conveyance direction of the recording paper, so that the stick phenomenon can be reduced. Since the heat storage is reduced and the temperature rise is suppressed, the image quality of the recorded image is improved.

[Brief description of drawings]

FIG. 1 is an exploded perspective view of a thermal recording apparatus according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a thermal head unit,
FIG. 3 is an explanatory diagram showing the positional relationship between the thermal head and the platen roller, and FIG. 4 is an explanatory diagram showing the positional relationship between the conventional thermal head and the platen roller. 1 ... Platen roller, 1a ... Platen shaft, 1b, 1c ...
Bearing, 2 ... Thermal head, 2a, 5a ... Heat generating part, 3 ...
… Thermal recording paper, 4… Heat dissipation base, 4a, 4e… Hole, 4b, 4
f, 4d, 4h ... cut-up portion, 4d, 4g ... cut-up portion, 5 ... thermal head substrate, 9 ... thermal head unit, 10,11 ...
…pin.

Claims (1)

[Claims] 1. A platen roller which is rotatably supported by a fixed position, a heat-sensitive recording paper which is conveyed in contact with the platen roller, and a heat generating portion which is at a recording line position with the heat-sensitive recording paper sandwiched therebetween. In a thermal recording apparatus having a thermal head that presses against the side and records an image line by line, the platen roller is formed to have a hardness of 40 ± 10 degrees, and
A heat-sensitive recording apparatus, wherein the recording line position of the heat generating portion is set to a position displaced from the axial center position of the platen roller by 0.2 to 0.8 mm in the heat-sensitive recording paper conveyance direction.