JPH0768867A - Thermal transfer type color printer - Google Patents

Abstract

PURPOSE:To prevent the slack and tilt of a printing sheet during printing operation and improve the accuracy of superposing dots of each color to be printed on the printing sheet. CONSTITUTION:Gear rows 11 to 13 which transmit a rotational force of a roller 6 having microscopic protrusions, while reducing the number of rotations, are provided on a disc plate 14 rotatably mounted to a platen roller 4, and the' disc plate 14 and a disc plate 15 fixed to the platen roller 4 are allowed to abut against each other, thus it is so designed that braking is applied to the platen roller 4 by a frictional force caused on the abutting face of these disc plates 14, 15. According to these arrangements, a rotation speed of the platen roller 4 becomes slower than that of the roller 6 having microscopic protrusions during printing operation, and the slack and tilt of a printing sheet can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer type color printer which can improve dot overlay accuracy of each color printed on printing paper.

[0002]

2. Description of the Related Art FIG. 2 is a schematic diagram showing a configuration example of a conventional thermal transfer type color printer. In this figure, three colors (yellow, magenta, cyan) or four colors (yellow, magenta, cyan, black) of color ink are sequentially and repeatedly applied to the ink ribbon 1 in each predetermined region in the extension direction. Has been done.

The ink ribbon 1 is supplied from a ribbon supply roller (not shown), passes through the guide roller 2, and then the color ink is thermally transferred onto the printing paper 5 between the thermal head 3 and the platen roller 4, and the used ink is used. The ribbon 1 is wound up by a ribbon winding roller (not shown).

On the other hand, the printing paper 5 is conveyed on the platen roller 4 by the drive rollers 6 and 7 in the forward direction (direction m in the drawing) and in the reverse direction (direction n in the drawing). A drive roller (hereinafter referred to as a minute projection roller) 6 has innumerable minute projections formed on the outer peripheral surface thereof, holds the printing paper 5 together with the pinch roller 8 and conveys it in the m and n directions in the figure. Therefore, it is driven forward and backward. On the other hand, a drive roller (hereinafter referred to as a rubber roller) 7 is made of rubber or the like, and holds the printing paper 5 together with the pinch roller 9 and is reversely driven to convey the printing paper 5 in the n direction in the drawing. Further, the platen roller 4 is a roller that is not driven and is freely rotatable, and rotates normally or reversely as the printing paper 5 is conveyed.

In such a structure, when one color ink (for example, yellow) is thermally transferred, the fine protrusion roller 6 is driven to rotate normally, and the fine protrusion roller 6 and the pinch roller 8 are pressed against each other to form a printing paper. 5 is nipped and conveyed in the m direction in the figure, the ink ribbon 1 is supplied from a ribbon supply roller (not shown), and passes through the guide roller 2 and the thermal head 3 and the platen roller 4, and the ribbon is wound. It is wound by a roller (not shown).

During this time, the thermal head 3 is pressed in the direction p in the figure by a spring (not shown), and in synchronization with the speed at which the ink ribbon 1 and the printing paper 5 are conveyed, the head heating element of the thermal head 3 becomes a character. Heat is generated according to print data such as data and image data. As a result, one color ink (for example, yellow) is thermally transferred onto the printing paper 5 between the thermal head 3 and the platen roller 4 by heat and pressure. Printing paper 5
Of the rubber roller 7 at the rear end 5a during the thermal transfer.
When the thermal transfer is completed by moving away from the pinch roller 9 and the pinch roller 9, the rear end 5a is moved to the thermal head 3 and the platen roller 4.
It is conveyed in the direction m in the figure until it reaches the vicinity of the contact point with.

Next, in order to superimpose another color ink (for example, magenta) on the printing paper 5 for thermal transfer, as a preparatory step, the minute projection roller 6 is reversely driven and the printing paper 5 is moved in the n direction in the drawing. It is transported to, but at this time,
The thermal head 3 is rotated in the q direction in the figure and does not contact the ink ribbon 1 and the printing paper 5. Thus, while the printing paper 5 is conveyed in the direction n in the figure by the micro-projection roller 6, the trailing edge 5a is again caught between the rubber roller 7 and the pinch roller 9, and thereafter the micro-projection roller 6
And the rubber roller 7 that plays an auxiliary role of the roller 6 convey the sheet until the next printing start position is reached. When the operation described above is performed on the color inks of three colors or four colors, the trailing edge 5a of the printing paper 5 is separated from the ink ribbon 1 by the peeling plate 10 of the thermal head 3. In this way, color printing is completed on one sheet of printing paper 5.

[0008]

By the way, in the above-mentioned conventional thermal transfer type color printer, as described above, the fine protrusion roller 6 is normally driven during printing, but the platen roller 4 and the rubber roller 7 are driven. Instead, it freely rotates as the printing paper 5 is conveyed. Therefore, the printing paper 5 is moved by the minute protrusion rollers 6 during printing.
However, no tension is applied to the rear end 5a in the n direction in the figure. Therefore, at the time of printing, the printing paper 5 is likely to be loosened between the micro-projection roller 6 and the platen roller 4. on the other hand,
The conventional thermal transfer color printer structurally includes, for example, the following variable factors. That is, cylindricity imbalance of the rubber roller 7 and the platen roller 4. Unbalance of the pressing load of the pinch roller 9 against the rubber roller 7. Unbalance the pressing load of the thermal head 3 against the platen roller 4. Due to such a variation factor, in the conventional thermal transfer type color printer, the slack and the inclination with respect to the conveying direction described above occur in the printing paper 5, and thus the printing paper 5 is displaced and printed on the printing paper 5. There is a problem that the dot overlay accuracy for each color is reduced.

The present invention has been made under such a background, and it is possible to prevent the slack and inclination of the printing paper at the time of printing, and improve the dot overlay accuracy of each color printed on the printing paper. It is an object of the present invention to provide a thermal transfer type color printer.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a thermal head, a platen roller which is arranged so as to face the thermal head, and which freely rotates as the printing paper is conveyed. A driving roller which is installed in the traveling direction of the printing paper at the time of printing from the platen roller and is rotationally driven to convey the printing paper, and a plurality of rollers are provided between the thermal head and the platen roller. In a thermal transfer type color printer in which an ink ribbon coated with color inks is pressed against the printing paper to thermally transfer the color ink to the printing paper, a braking means for suppressing rotation of the platen roller is provided, and the printing is performed. The rotation speed of the platen roller at this time is lower than the rotation speed of the drive roller.

[0011]

According to the present invention, the braking means suppresses the rotation of the platen roller during printing, and makes the rotation speed of the platen roller smaller than the rotation speed of the drive roller. As a result, the printing paper does not become loose or tilted between the drive roller and the platen roller during printing.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view showing the configuration of the main part of one embodiment of the present invention. In this figure, parts common to the parts shown in FIG. 2 are assigned the same reference numerals and explanations thereof are omitted. In FIG. 1, 11 to 13 are gear trains that engage with each other. The gear 11 is rotatably attached to the platen roller 4 near its shaft end 4a.
On one side surface of the gear 11 on the shaft end 4a side, the disc plate 1
4 is fixed by fixing tools P1 and P2, and this disk plate 14 is rotatably attached to the platen roller 4 like the gear 11. A disc plate 15 is in contact with one side surface of the disc plate 14 on the side of the shaft end 4a.
It is attached to the roller 4 by a connecting member P3 so that it is not rotatable but is slidable in its axial direction. Further, the disc plate 15 is biased by the spring 16 from the side of the shaft end 4a, whereby the disc plate 15 is pressed against the disc plate 14 by a predetermined load.

Further, the gear 11 is engaged with the gear 12, and the gear 12 further has the shaft end 6a of the minute projection roller 6.
It engages with a gear 13 mounted in the vicinity. The gear 13 is fixed to the minute projection roller 6 by a fixing tool P4. The number of teeth of each of the gears 11 to 13 is determined so that the rotation speed N _{1 of the} gear 11 is smaller than the rotation speed N ₀ of the gear 13 (that is, the rotation speed of the minute protrusion roller 6). . The configuration of each of the other parts (not shown) is the same as that of the conventional example shown in FIG.

According to this structure, when the fine protrusion roller 6 is driven to rotate normally during printing, the printing paper 5 is pulled in the m direction in the figure. This pulling force acts as a torque on the platen roller 4, whereby the platen roller 4 tries to rotate at the same number of revolutions N _{0 as the} minute protrusion roller 6 (however, in this case, the platen roller 4 is rotated for simplicity). It is assumed that the shaft diameter and the shaft diameter of the minute protrusion roller 6 are equal.

On the other hand, the gear 11 rotates at a rotation speed N ₁ smaller than this, whereas the gear 13 rotates at a rotation speed N ₀ of the minute projection roller 6. As a result, the disc plate 1 that is about to rotate at the same rotation speed N _{0 as} the minute protrusion roller 6
5 (fixed to the platen roller 4) is braked in rotation by a frictional force with the disk plate 14 rotating at the same rotation speed N ₁ (N ₁ <N ₀ ) as the gear 11.

As a result, the rotation speed of the platen roller 4 is suppressed by the braking of the disk plate 15, and the predetermined rotation speed N ₂ (N ₁ <N ₂ smaller than the rotation speed N ₀ of the minute projection roller 6). It will rotate at <N ₀ ).

In this way, since the platen roller 4 always rotates at a rotation speed smaller than that of the minute protrusion roller 6 during printing, the printing paper 5 is prevented from being loosened or tilted between the minute protrusion roller 6 and the platen roller 4. The displacement of the printing paper 5 is prevented. As a result, the dot overlay accuracy of each color printed on the printing paper 5 is improved.

[0018]

As described above, according to the present invention, since the rotation speed of the platen roller during printing is lower than the rotation speed of the drive roller, slack in the printing paper between the drive roller and the platen roller occurs. The inclination does not occur, and the dot overlay accuracy of each color printed on the printing paper is improved.

[Brief description of drawings]

FIG. 1 is a plan view showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a configuration example of a conventional thermal transfer color printer.

[Explanation of symbols]

 1 Ink Ribbon 2 Guide Roller 3 Thermal Head 4 Platen Roller 5 Printing Paper 6 Micro Protrusion Roller 7 Rubber Roller 8, 9 Pinch Roller 10 Peeling Plate 11-13 Gear Train 14, 15 Disc Plate 16 Spring

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location B41J 13/02 13/076

Claims (1)

[Claims] 1. A thermal head, a platen roller that is disposed so as to face the thermal head and that freely rotates as the printing paper is conveyed, and is installed in the traveling direction of the printing paper when printing from the platen roller, A driving roller that is rotationally driven to convey the printing paper,
A thermal transfer type color printer for thermally transferring the color inks to the printing paper by press-contacting an ink ribbon coated with a plurality of color inks on the printing paper between the thermal head and the platen roller. Is provided with a braking means for suppressing the rotation of
A thermal transfer type color printer, wherein the rotational speed of the platen roller during the printing is set lower than the rotational speed of the drive roller.