JPH0538857A - Thermosensitive image formation apparatus - Google Patents

Abstract

PURPOSE:To obtain a high-quality thermosensitive images by a method wherein a highly hard platen roller is made usable, highly accurate transfer of thermosensitive material is made available, and contact areas between each of heating elements and the thermosensitive material are reduced. CONSTITUTION:A reinforcing roller 9 is provided to a position facing a thermal head 5, positioned opposite to a platen roller 4, with the platen roller 4 interposed in between, and being in contact with and in parallel with the platen roller 4 in its axial direction. As platen pressure acting on the thermal head 5 is borne with the reinforcing roller 9 through the platen roller 4 and a thermosensitive material, the platen roller 4 does not yield to the pressure. Therefore, it becomes possible to apply bigger platen pressure without enlarging the diameter of the platen roller, and thereby thermosensitive efficiency can be improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a thermal image forming apparatus such as a thermal recording apparatus, a thermal plate making apparatus and a thermal transfer recording apparatus.

[0002]

2. Description of the Related Art Conventionally, a thermal image forming apparatus provided with a thermal head, a platen roll positioned so as to face the thermal head, and a heat-sensitive material conveying means has been widely practiced and is well known. Is. In the thermal image forming apparatus as described above, the platen roll is fixed to the base of the thermal image forming apparatus, and the thermal head is provided with a shaft of the platen roll according to supply of a thermal material, cleaning of a heating element of the thermal head, and the like. The thermal head is provided so as to be able to come into contact with and separate from the platen roll and the heat-sensitive material in a direction intersecting the direction, and when forming a heat-sensitive image on the heat-sensitive material, the thermal head is heated at two points at both ends by a coil spring, It is common to have a configuration in which pressure is applied while being divided into several points along the arrangement direction of the body, and the heating element of the thermal head and the heat-sensitive material are brought into pressure contact with each other.

The heat-sensitive characteristics of the heat-sensitive material depend on the sensitivity and surface smoothness of the heat-sensitive material, the pressure applied to the thermal head, and the accuracy of conveyance of the heat-sensitive material. Particularly, the pressure applied to the thermal head is called a platen pressure, and the more uniform the distribution is along the arrangement direction of the thermal head, the higher the quality of the heat-sensitive image, and the higher the pressure, the higher the heat-sensitive efficiency. Further, when the surface smoothness of the heat sensitive material is low, a larger platen pressure is required.

By the way, when the platen pressure is set to be large, the platen roll is required to have a mechanical strength that does not bend due to the platen pressure, and the platen roll has a large diameter. In particular, when the size of the heat-sensitive image is large in the direction intersecting the direction in which the heat-sensitive material is conveyed, the platen roll inevitably becomes long and a platen roll having a larger diameter is required. However, if the diameter of the platen roll is increased, the contact area between the heating element of the thermal head and the heat sensitive material sandwiched between the thermal head and the platen roll increases, and the heat-sensitive image is not detailed and of high quality. For this reason, the diameter of the thermal head is limited to a certain range, and the platen pressure that can be applied is necessarily limited to a certain range.

Further, the transport accuracy of the heat sensitive material depends on the hardness of the platen roll. The higher the hardness of the platen roll, the less elastic deformation of the platen roll surface and the smaller the contact area with the heat sensitive material. Then, the smaller the contact area between the platen roll and the heat-sensitive material, the smaller the adhesiveness between the platen roll and the heat-sensitive material, the less the deviation of conveyance, and the more the heat-sensitive material can be conveyed according to the rotation of the platen roll. However, on the other hand, due to the problem of bending of the thermal head and the platen roll, the platen roll contacts the heating element of the thermal head and the heat-sensitive material in order to make the distribution of the platen pressure uniform along the arrangement direction of the thermal head. Low hardness was selected within a range substantially unrelated to the problem of area, and the transport accuracy of the heat-sensitive material was also limited as with the platen pressure.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problem of platen roll deflection, and makes it possible to apply a large platen pressure with a simple mechanism without increasing the diameter of the platen roll. Another object of the present invention is to provide a thermal image forming apparatus having high efficiency and high quality by increasing the degree of freedom in selecting the platen roll hardness to improve the transport accuracy of the thermal material.

[0007]

In order to achieve the above-mentioned object, a thermal image forming apparatus according to the present invention comprises a thermal head, a platen roll positioned to face the thermal head, and a thermal material. In a heat-sensitive image forming apparatus having a conveying means, first, one or more reinforcing rolls are provided in a position facing the thermal head across the platen roll and in contact with the platen roll parallel to the axial direction of the platen roll. Secondly, two reinforcing rolls are provided so that the axis of the platen roll is located at the bottom of the triangle forming the triangle with the axis of the platen roll as the apex. The third feature is that the reinforcing roll is divided into a plurality of parts on the same axis, and the fourth feature is that one roll is provided in contact with the platen roll. And rolls, still other reinforcing rolls in contact rolls for supporting the platen roll 1
The present invention is characterized in that the reinforcing roll is a hollow or solid metal roll, a plastic roll made of engineering plastic or the like, or a roll having a plastic or rubber layer provided on a metal core. , Which has sufficient mechanical strength not to be deformed by the applied platen pressure, and a hollow metal roll is most suitable in terms of strength and weight of the apparatus. The reinforcing roll may be driven by either a system in which the reinforcing roll itself is rotatable and is driven by transmission from the platen roll, or a system in which the peripheral speed is the same as that of the platen roll.

[0008]

The thermal image forming apparatus according to the present invention comprises a thermal head in which a large number of heating elements are arranged in a row, and a platen roll positioned so as to face in parallel with the direction of arrangement of the heating elements in the thermal head. A heat-sensitive material conveying means, the heat-sensitive material being slidably conveyed in a direction intersecting with the arrangement direction of the heating elements of the thermal head, and at the same time, each heating element of the thermal head selectively generates heat. Characters and images are formed on the heat sensitive material. Then, the thermal head is divided into two points at both ends by a coil spring or the like or divided into several points along the arrangement direction of the heating element of the thermal head, and a platen pressure is applied in a direction of being pressed against the platen roll. And, one or more reinforcing rolls are provided in contact with the platen roll at a position facing the thermal head across the platen roll, and the axial direction of the platen roll and the axial direction of the reinforcing roll are parallel to each other. The reinforcing roll is in contact with the platen roll with a uniform contact pressure along the axial direction. In the heat-sensitive image forming apparatus having the above-described configuration, the platen pressure applied to the thermal head is supported by the above-mentioned reinforcing rolls via the heat-sensitive material and the platen roll, and the platen roll is acted on by the law of reaction. A force having a direction opposite to that of the platen pressure applied from the thermal head and having the same magnitude is applied from the reinforcing roll, and therefore the platen roll does not bend due to the platen pressure.

[0009]

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a side view showing a heat-sensitive image forming apparatus, and is illustrated with some omission for ease of understanding. In FIG. 1, 1
The reference numeral 2 denotes a main body of the apparatus, and 2 denotes a supply port of the heat sensitive material for supplying the heat sensitive material to the main body 1 of the apparatus. 5 and the platen roll 4 located opposite to each other. Reference numeral 6 is a coil spring, 7 is a cam mechanism for causing the tension of the coil spring 6 to act on the thermal head 5, 8 is an outlet of the heat sensitive material, and 9
Is a reinforcing roll that is in contact with the platen roll 4 described above, and the reinforcing roll 9 is provided in a position facing the thermal head 5 across the platen roll 4 and in parallel with the axial direction of the platen roll 4. ..

The above-mentioned heat-sensitive material can be supplied in the form of a roll, but in this embodiment, the heat-sensitive material is supplied as paper sheets to the above-mentioned supply port 2, and the tip of the heat-sensitive material is the photoelectric sensor 1
It is detected at 0, and is automatically conveyed by the conveyance driving roll 3 between the thermal head 5 and the platen roll 4.
After the heat sensitive material is conveyed by a predetermined amount, the platen pressure of the coil spring 6 is applied to the thermal head 5 via the cam mechanism 7, the heat sensitive material is brought into pressure contact with the heat sensitive body of the thermal head 5, and the transport drive roll 3 and the platen roll are pressed. The sheet is conveyed by the rotation of 4, and at the same time, the heating element of the thermal head 5 selectively generates heat, so that characters and images are formed on the heat-sensitive material. The heat-sensitive material is a paper or film whose surface is coated with a heat-sensitive layer, and a heat-sensitive image is formed according to characters and image information created or edited by a word processor, a personal computer, a DTP, etc. or read by a document. It is used as a medium or as a printing plate for stencil printing and lithographic printing.

FIG. 2 is a perspective view showing a thermal head portion of the heat-sensitive plate making apparatus. As mentioned above, 5 is a thermal head, 4 is a platen roll, and 9 is a platen roll 4 which faces the thermal head 5. At a position parallel to the axial direction of the platen roll 4
The platen pressure applied to the thermal head 5 is supported by the reinforcing roll 9 via the heat-sensitive material and the platen roll 4 by the reinforcing roll provided in contact with the platen roll 4 according to the law of action and reaction. A force having the same magnitude as the platen pressure applied by the thermal head 5 but in the opposite direction is applied by the reinforcing roll 9. Figure 3
An explanatory view showing a contact state of the platen roll 4, the thermal head 5, and the reinforcing roll 9 of the heat-sensitive part, in which 11 is a heat sink and 1
Reference numeral 2 is a heating element of the thermal head 5.

Table 1 shows the measurement of the flexure of the shaft of the platen roll according to this embodiment. The thermal image forming apparatus used for the measurement corresponds to a thermal material width dimension of 257 mm, and the dimensions of each unit are as follows. , Platen roll shaft length 344mm, light diameter 12mm, platen roll length 30
The platen roll had a diameter of 6 mm and a diameter of 24 mm, and the platen roll was made of silicon rubber and had a hardness of 60 degrees. Platen pressure is 4.5kg and 9.
Using 0kg, the length of the heating element of the thermal head is 274mm
Then, the platen roll and the thermal head were pressed uniformly along the length of the heating element. A laser sensor with a resolution of 0.001 mm was used to measure the deflection of the platen roll. As the reinforcing roll, a solid metal roll having a length of 344 mm and a diameter of 18 mm was used. The normal use condition of the thermal image forming apparatus is that a platen pressure of 4.5 kg is applied without a reinforcing roll. By using the reinforcing roll, the deflection of the platen roll shaft can be reduced even under normal use conditions, and the deflection of the platen roll shaft can be suppressed to be small even if a platen pressure that is twice the normal platen pressure is applied. I got the result.

[0013]

Table 2 shows the conveyance accuracy of the heat sensitive material depending on the hardness of the platen roll. The structure of the thermal image forming apparatus was in accordance with the above-described embodiment. Platen roll shaft has a length of 34
4mm, light diameter 12mm, platen roll length 306mm,
With a diameter of 24 mm, the heating element of the thermal head is 274 mm,
A platen pressure of 4.5 kg was applied, and the platen rolls made of silicone rubber having a hardness of 40 and 60 degrees were used for comparison. The evaluation method was carried out by measuring the rotation of the platen roll with a rotary encoder, and the accuracy was determined by the difference between the number of rotations and the rotation angle and the transport distance obtained from the diameter of the platen roll and the actual transport dimension of the heat-sensitive material. The smaller the accuracy, the more constant the distance between the dots formed on the heat-sensitive material corresponding to each heat-generating body of the thermal head, and the higher quality heat-sensitive image can be obtained. From the measurement of the transport accuracy of the heat-sensitive material with different platen roll hardness, it was found that the transport accuracy of the heat-sensitive material can be significantly improved by using the high hardness platen roll.

[0015]

FIG. 4, FIG. 5, and FIG.
The third and fourth embodiments are shown. In the second embodiment of FIG. 4, two reinforcing rolls are provided, a triangle having the axis of the platen roll 4 as the apex, and the axes of the reinforcing rolls 9A and 9B as the bases. The two reinforcing rolls 9A have a positional relationship such that they are formed.
9B is in contact with the platen roll 4. The reinforcing rolls 9A and 9B may have the same or different diameters, and the strengths should be the same.

In the third embodiment of FIG. 5, the reinforcing roll 9 is divided into a plurality of parts on the same axis. Further, it is preferable that the above-mentioned division is performed according to the point of action of the platen pressure applied to the thermal head 5 in a divided manner.

In FIG. 6, two reinforcing rolls are provided, the axes of the platen roll 4 and the reinforcing rolls 9a and 9b are aligned, and the reinforcing roll 9a is in contact with the platen roll 4.
The reinforcing roll 9b is in contact with the reinforcing roll 9a and supports the platen pressure.

[0019]

The heat-sensitive image forming apparatus according to the present invention comprises a thermal head for forming a heat-sensitive image on the heat-sensitive material, a platen roll positioned to face the thermal head, and a heat-sensitive material conveying means. In the thermal image forming apparatus, since one or more reinforcing rolls are provided in contact with the platen roll in parallel with the axial direction of the platen roll at a position facing the thermal head, the platen roll diameter is It is possible to reduce the deflection of the platen roll and apply a larger platen pressure without increasing the platen roll, and the heat-sensitive efficiency is improved. Further, it is possible to use a long-axis platen roll without increasing the diameter of the platen roll, and it is possible to realize a thermal image forming apparatus capable of obtaining a large thermal image.
Furthermore, since the deflection of the platen roll is reduced, the distribution of the platen pressure becomes more uniform, and a platen roll having a higher hardness can be used, which improves the transport accuracy of the heat-sensitive material and improves the thermal head. Since the contact area between the heating element and the heat-sensitive material is small, it is possible to obtain an extremely high-quality heat-sensitive image together with the increase of the platen pressure.

[Brief description of drawings]

FIG. 1 is a side view of a thermal image forming apparatus of the present invention.

FIG. 2 is a perspective view of a heat-sensitive part.

FIG. 3 is a cross-sectional view showing a contact state of each unit of the heat-sensitive section.

FIG. 4 is a sectional view showing a second embodiment of the reinforcing roll.

FIG. 5 is a perspective view showing a third embodiment of a reinforcing roll.

FIG. 6 is a perspective view showing a fourth embodiment of a reinforcing roll.

[Explanation of symbols]

 1 Device Main Body 2 Heat Sensitive Material Supply Port 3 Conveying Roll 4 Platen Roll 5 Thermal Head 9 Reinforcing Roll 10 Photoelectric Sensor 11 Heat Dissipation Section 12 Thermal Head Heating Element

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display part 8305-2H B41M 5/26 P

Claims (4)

[Claims] 1. A thermal image forming apparatus having a thermal head, a platen roll positioned to face the thermal head, and a heat-sensitive material transporting means, facing the thermal head across the platen roll. 1. A thermosensitive image forming apparatus, characterized in that at least one reinforcing roll is provided at a position parallel to the axial direction of the platen roll and in contact with the platen roll. 2. The two reinforcing rolls are provided so that the axis of the platen roll is located at the bottom of a triangle forming a triangle with the axis of the platen roll as the apex. Thermal image forming device. 3. The thermal image forming apparatus according to claim 1, wherein the reinforcing roll is formed by being divided into a plurality of parts on the same axis. 4. A reinforcing roll provided in contact with the platen roll, and another reinforcing roll provided in contact with one reinforcing roll supporting the platen roll. 1. The heat-sensitive image forming apparatus described in 1.