JPH08197764A - Thermal transfer printer - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a thermal transfer printer which is capable of high-quality printing with no wrinkles on the ink ribbon and has high color reproducibility in color printing. [Structure] The control circuit 19 includes electrodes 16-k and 17-k arranged in a row or a plurality of rows in the width direction of the ink ribbon 2.
And a dielectric layer that covers the electrode 16-k,
An electrostatic brake 15 that individually applies a tension in the direction opposite to the traveling direction of the ink ribbon 2 to each portion in the width direction of the ink ribbon 2 by the electrostatic attraction force generated by the voltage Vk applied to each of 17-k, Electrodes 16-k and 17-k at the positions corresponding to the positions where the ink is transferred to the printing paper with respect to the width direction of the ink ribbon 2 do not generate electrostatic attraction force, so that the ink is not transferred to the printing paper at the positions. Corresponding position electrode 16
-k and 17-k are controlled so as to generate an electrostatic attraction force, thereby controlling the tension in accordance with the printing state of the ink ribbon 2 in the width direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printer capable of high-speed and high-quality printing.

[0002]

2. Description of the Related Art A so-called thermal transfer printer is a printer in which a predetermined portion of an ink ribbon coated with ink is heated by a print head to thermally transfer the ink onto a printing paper for printing. More specifically, the ink is applied to one surface of the thin film-shaped ink ribbon, and the ink surface of the ink ribbon and the printing paper are brought into pressure contact with each other. Then, by heating a predetermined portion of the surface of the ink ribbon on which the ink is not applied by the print head, the ink is transferred to the printing paper.

FIG. 7 is a side sectional view showing an example of the structure of a conventional monochromatic thermal transfer printer. FIG. 8 is a side sectional view showing a detailed structure within a broken line range in FIG. Figure 7
Ink ribbon 2 wound around feed roller 1
Is taken up by the take-up roller 3. Ink is applied to the lower surface (ink surface 2a) of the ink ribbon 2. Further, 4 is a guide roller and 5 is a brake. The brake 5 is rotatable around a support point 6, and one end of the brake 5 is urged toward the feed roller 1 by the force of the pulling spring 7. These guide rollers 4 and brakes 5
This prevents the slack of the ink ribbon 2. One printing paper 8 is conveyed by being sandwiched between a platen roller 9 and pinch rollers 10a and 10b which are pressed against the platen roller 9. During printing, the print head 11 moves to the platen roller 9
The ink ribbon 2 and the printing paper 8 are sandwiched between the platen roller 9 and the print head 11. When not printing, the print head 11 separates from the platen roller 9 and releases the ink ribbon 2 from pressure contact.

The print head 11 of this embodiment is generally called a line type thermal head, and has a plurality of heating elements 12-1 and 12 along the longitudinal direction of the platen roller 9 on the surface pressed against the platen roller 9 side. -2 ... 12-n (hereafter 12-k
(Referred to as) is arranged. When a current is applied to the heating element 12-k, the ink applied to the ink surface 2a of the ink ribbon 2 is heated by Joule heat, and this ink is transferred to the printing paper 8.

The heating element 12-k has a structure in which the flowing current can be independently controlled by a control unit (not shown), and the surface temperature of the heating element 12-k is determined by the flowing current. On the other hand, the degree to which the ink applied to the ink surface 2a of the ink ribbon 2 is transferred to the printing paper 5 depends on the surface temperature of the heating element 12-k. Therefore, the printing paper 8 and the ink ribbon 2 are conveyed at the same speed in the directions of the arrow A and the arrow B, respectively, and the current flowing through each heating element 12-k is controlled at a predetermined timing, so that the printing paper 8 can be changed in density. You can draw certain characters and pictures.

During printing, the ink ribbon 2 is pulled by the take-up roller 3 with a take-up force Tm in the direction of arrow B shown in FIG. FIG. 9A is a plan view of the ink ribbon 2 at this time as viewed from above. Tb is a pulling force generated from the brake 5. The relationship between Tm and Tb is T
m> Tb. Ink ribbon 2 is print head 1
Since the pressure contact resistance is Tf, the relationship with Tm is Tf> Tm.

[0007]

Ink ribbon 2 is generally used.
Has a structure in which ink is applied on a PET (polyethylene terephthalate) base film, and the ink ribbon 2 has a surface not coated with ink (heating surface).
The ink is heated from the above to be transferred onto the printing paper 8. The ink ribbon 2 has a base film having a thin thickness of 3 to 6 μm in order to improve its heat transfer property. Therefore, the base film is easily deformed by being heated by the heating element 12-k.

At the current-carrying portion of the blank portion 13 shown in FIG. 9, the base film of the ink ribbon 2 is thermally deformed and welded to the heating resistor of the print head 11. Further, the ink melted for printing and the paper are adhered to each other. Now, if the resistance due to welding is Tr1 and the resistance due to adhesion is Tr2,
For the energized part of each heating element, (Tr1 + T
The resistance of r2) is added. This is the printing resistance Tt
And Since the pressure contact resistance force Tf acts on the non-energized portion, the relationship with the winding force Tm is as follows. Non-energized part Tf + Tb> Tm, energized part Tf + Tb +
Tr1 + Tr2> Tm That is, the tension balance between the non-printing portion and the printing portion is lost, and as a result, wrinkles of the ink ribbon 2 occur at the boundary between the non-printing portion and the printing portion. Then, printing defects occur in the wrinkled portion. By the way, in order to improve the printing speed,
The ink of the ink ribbon 2 needs to be heated in a short time, but for this purpose, the temperature of the heating element 12-k must be raised. Further, when the gradation difference in printing is increased during gradation printing, the maximum temperature of the heating element 12-k increases. Therefore, in these cases, wrinkles are more likely to occur.

Further, in the case of color printing, the above-mentioned ink ribbon 2 is, as shown in FIG. 10 (a) or (b),
Y (yellow), M (magenta), C (cyan) or Y, M, C, K (pure black) for each fixed length L according to the printing paper 8.
Ink of the color is applied. Then, the ink ribbon 2 is conveyed in the direction of arrow B, and the printing paper 8 is reciprocated in the directions of arrows A and D shown in FIG. Therefore, when wrinkles occur, color spots are generated or color reproducibility is significantly reduced. The present invention has been made under such a background, and since a wrinkle does not occur on the ink ribbon, high-quality printing without printing spots is possible, and a thermal transfer printer having high color reproducibility in color printing. Is intended to provide.

[0010]

In order to solve the above-mentioned problems, in the invention described in claim 1, there is provided a winding means for winding the ink ribbon coated with the ink with a predetermined winding force. A thermal transfer printer including a printing unit configured to transfer the ink to a printing sheet by heating the ink ribbon to print a predetermined character or the like, the thermal transfer printer being provided behind the printing unit, and a traveling direction of the ink ribbon. Braking means for individually applying a tension in the opposite direction to each portion of the ink ribbon in the width direction, and control means for controlling the braking means in response to the printing state of the ink ribbon in the width direction by the printing means. Is provided.

According to a second aspect of the invention, in the thermal transfer printer according to the first aspect, the braking means is
A high voltage applied to each of the bipolar electrodes, which is composed of one or more rows of bipolar electrode groups in the width direction of the ink ribbon, and a dielectric layer that covers the plurality of bipolar electrode groups. A tension is applied to the ink ribbon by an electrostatic attraction force generated by the above.

According to a third aspect of the invention, in the thermal transfer printer according to the second aspect, the control means is
In the width direction of the ink ribbon, the bipolar electrode at a position corresponding to the position where the ink is transferred to the printing paper does not generate an electrostatic attraction force, and the position where the ink is not transferred to the printing paper is set. The bipolar electrodes at corresponding positions control the braking means so as to generate an electrostatic attraction force.

[0013]

According to the present invention, the control means is composed of a bipolar electrode group arranged in a row or a plurality of rows in the width direction of the ink ribbon, and a dielectric layer covering the bipolar electrode group. A braking means for individually applying a tension in a direction opposite to the traveling direction of the ink ribbon to each portion in the width direction of the ink ribbon by an electrostatic attraction force generated by a high voltage applied to each of the Therefore, the bipolar electrode at the position corresponding to the position where the ink is transferred to the printing paper does not generate the electrostatic attraction force, and the bipolar electrode at the position corresponding to the position where the ink is not transferred to the printing paper does the electrostatic attraction force. By controlling so as to generate, the tension is controlled corresponding to the printing state of the ink ribbon in the width direction.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal transfer printer according to an embodiment of the present invention will be described below. In the present embodiment, an example applied to a single color thermal transfer printer will be described. FIG. 1 is a side sectional view showing a schematic configuration of a thermal transfer printer according to an embodiment of the present invention. In the figure, those parts corresponding to the parts shown in FIG. 7 are designated by the same reference numerals, and a description thereof will be omitted. An electrostatic brake 15 is provided between the guide roller 4 and the print head 11 of the thermal transfer printer shown in FIG.

FIG. 2 is a sectional view showing a schematic structure of the electrostatic brake 15 in FIG. The electrostatic brake 15 includes positive electrodes 16-1, 16-2, ... 16 in an insulator having a high dielectric constant.
-n (hereinafter referred to as 16-k) and negative electrodes 17-1 and 17-2
... 17-n (hereinafter referred to as 17-k). The electrodes 16-k and 17-k are paired, and a high voltage is applied from the high voltage generating circuit 18 between them. The high voltage generation circuit 18 generates high voltages V1, V2 ... Vn (hereinafter referred to as Vk) based on the control signals S1, S2 ... Sn (hereinafter referred to as Sk) output from the control circuit 19, It is applied between the corresponding electrodes 16-k to 17-k. When the print data D is input from a computer (not shown) or the like, the control circuit 19 outputs a current signal (current flowing in the heating element 12-k) based on the print data D to the print head 11. At the same time, the control signal Sk corresponding to the current signal output to the print head 11 is output.

FIG. 3 is a sectional view showing the detailed construction of the electrostatic brake 15. The electrostatic brake 15 includes electrodes 16-k, 17 made of a copper foil pattern on one surface of an insulating base 15-1.
-k is formed, and the upper surface of this is an insulator 15-2 such as epoxy resin
And a flat dielectric 15-3 is fixed to the upper part of the structure. When a voltage is applied between the electrodes 16-k to 17-k, the electrodes 16-k to 17-k inside the electrostatic brake 15
Charge is applied according to the voltage and polarity applied between them (Fig. 2
reference). On the other hand, the electrostatic brake 1 on the ink ribbon 2
The non-contact surface (ink surface) with 5 has an electric charge opposite to that of the electrodes 16-k and 17-k. Therefore, electrostatic attraction force F is generated between the electrostatic brake 15 and the ink ribbon 2.

The electrostatic attraction force F generated between the electrostatic brake 15 and the ink ribbon 2 is obtained by F = ε / 2 · (V / d) ² (1) Here, ε is the dielectric constant of the dielectric 15-3, V is the voltage applied between the electrodes 16-k to 17-k, and d is the thickness of the dielectric 15-3. In this way, the electrostatic attraction force F generated by the electrostatic brake is applied to each of the electrodes 16-k to 17-k.
It is determined by the voltage Vk applied in between. Therefore, the control circuit 19 applies the voltage Vk to the electrodes 16-k to 17-k at the positions corresponding to the non-printing heating elements 12-k, and the electrodes 16-k at the positions corresponding to the printing heating elements 12-k. No voltage Vk is applied to .about.17-k. Further, the voltage Vk corresponding to the value of the current flowing through the heating element 12-k is set to the corresponding electrodes 16-k to 17-k.
Apply to. That is, the darker the part is printed, the electrostatic attraction force F
Is small, and the electrostatic attraction force F is controlled to be maximum in a portion where printing is not performed.

A. First Configuration Example FIG. 4 is a perspective view showing the overall configuration of the electrostatic brake 15 and the positional relationship with the ink ribbon 2. Electrodes 16-k are provided in the electrostatic brake 15 in the width direction of the ink ribbon 2.
And 17-k are arranged alternately and in one row. Further, in this embodiment, in order to effectively utilize the electrostatic attraction force F generated by the electrodes 16-k and 17-k, the electrodes 16-k and 17-k are used.
-k has a long shape in the transport direction of the ribbon 2 (direction of arrow B).

FIG. 5 shows the electrostatic attraction force F of the electrostatic brake 15.
It is the figure which showed the mode of the effect by. The print head 11 shown in FIG. 5 is shown as an example having the heating elements 12-1 to 12-8, and the electrostatic brake 15 is the heating element 12-1.
Electrodes 16-1 to 16-8 and 1 at positions corresponding to ~ 12-8
An explanation will be given by showing an example having 7-1 to 17-8.

(1) First Example In the example shown in FIG. 5 (a), the heating elements 12-6, 12-7, 12
As a result of the current flowing at -8, a blank portion 13 having a corresponding shape was formed. At this time, the heating elements 12-6, 12-7,
Printing resistance Tt is generated at the position 12-8. Therefore, the control circuit 19 controls the heating elements 12-1, 12-2, 1 and 1 through which no current flows.
A voltage Vk is applied between the electrodes 16-k to 17-k at the positions corresponding to 2-3, 12-4 and 12-5. As a result, from the positions of the electrodes 16-1 and 17-1 to the positions of the electrodes 16-5 and 17-5, the electrostatic braking force Ts due to the electrostatic attraction force F of each electrode.
Occurs.

The relationship between the current value flowing in each of the heating elements 12-1 to 12-8 and the printing resistance Tt generated at this time can be experimentally obtained in advance. Therefore, the control circuit 19
The voltage Vk is controlled so that s = Tt. By doing so, tension is uniformly applied in the width direction of the ink ribbon 2, and wrinkles do not occur around the blank portion 13.

(2) Second Example In the example shown in FIG. 5B, the heating elements 12-3, 12-4, 12 are used.
As a result of the current flowing through -5 and 12-6, a blank portion 13 having a corresponding shape was formed. At this time, the heating element 12
Print resistance Tt at positions -3, 12-4, 12-5 and 12-6
Occurs. Therefore, the control circuit 19 applies the voltage Vk between the electrodes 16-k to 17-k at the positions corresponding to the heating elements 12-1, 12-2, 12-7 and 12-8 to which no current flows. . This allows electrodes 16-7, 17-7 and electrode 16
-8, 17-8, the electrostatic braking force Ts1 by the electrostatic attraction force F of each electrode, the electrodes 16-1, 17-1 and the electrode 16-
An electrostatic braking force Ts2 is generated by the electrostatic attraction force F of each electrode at the positions 2 and 17-2. At this time, the control circuit 19 sets the voltage Vk so that Ts1 and Ts2 of each electrode become equal to Tt.
By controlling the tension, tension is uniformly applied in the width direction of the ink ribbon 2, and wrinkles do not occur around the blank portion 13.

(3) Third Example In the example shown in FIG. 5 (c), as a result of the current flowing through the heating elements 12-7, 12-8 and 12-1 and 12-2, Blank areas 13-1 and 13-2 were formed, respectively. At this time, the printing resistance Tt1 is generated at the positions of the heating elements 12-7 and 12-8, and the printing resistance Tt2 is generated at the positions of the heating elements 12-1 and 12-2. Therefore, the control circuit 19 controls the heating elements 12-3, 12-4, 12-5 and 12 to which no current flows.
The voltage Vk is applied between the electrodes 16-k to 17-k at the positions corresponding to -6. As a result, an electrostatic braking force Ts due to the electrostatic attraction force F of each electrode is generated from the position of the electrodes 16-3, 17-3 to the position of the electrodes 16-6, 17-6. At this time, the control circuit 19 controls the voltage Vk of each electrode so that Ts1 and Ts2 of each electrode become equal to Tt, so that tension is uniformly applied in the width direction of the ink ribbon 2 and the blank portion 13- Wrinkles do not occur around 1 and 13-2.

B. Second Configuration Example FIG. 6 is a perspective view showing the overall configuration of an electrostatic brake 15a, which is a second configuration example of the electrostatic brake, and the positional relationship with the ink ribbon 2. In the electrostatic brake 15a,
Similar to the electrostatic brake 15, in the width direction of the ink ribbon 2,
The electrodes 16a-k and 17a-k are arranged alternately. Further, these electrodes are divided into a first electrode group 20-1 and a second electrode group 20-2 in the longitudinal direction of the ink ribbon 2. Further, an independent voltage Vk can be applied to each of the first electrode group 20-1 and the second electrode group 20-2 divided into two. As a result, the electrostatic braking force Ts
Can be controlled more finely. The detailed operation according to this configuration example is the same as that shown in the first configuration example, and therefore its description is omitted.

Although the present embodiment has been described with reference to an example applied to a single color thermal transfer printer, the present invention is also applicable to a color thermal transfer printer. Further, in the present embodiment, both the brake 5 and the electrostatic brake 15 are provided in order to prevent the slack of the ink ribbon 2, but the ink ribbon 2 is provided only by the electrostatic braking force of the electrostatic brake 15.
It may be configured to prevent the loosening of the. In this case, since a mechanical brake is not needed, it is possible to reduce the size and weight of the thermal transfer printer.

[0026]

As described above, according to the present invention,
The control means is composed of a bipolar electrode group arranged in one row or a plurality of rows in the width direction of the ink ribbon and a dielectric layer covering the bipolar electrode group, and is controlled by a high voltage applied to each of the bipolar electrodes. Ink is transferred onto the printing paper in the width direction of the ink ribbon by a braking means that individually applies tension in the direction opposite to the traveling direction of the ink ribbon to each portion in the width direction of the ink ribbon by the generated electrostatic attraction force. The position of the bipolar electrode at the position corresponding to the position where the ink is not transferred to the printing paper is controlled so that the bipolar electrode at the position corresponding to the position where the ink is not transferred to the printing paper generates the electrostatic attraction force. Since the ink ribbon is controlled according to the printing condition in the width direction of the ink ribbon, wrinkles do not occur on the ink ribbon, so high-quality printing without printing spots is possible, and high-quality color reproducibility is achieved during color printing. Turning Effect that the printer can be realized.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a schematic configuration of a thermal transfer printer according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a schematic configuration of an electrostatic brake 15 in the same embodiment.

FIG. 3 is a cross-sectional view showing a detailed configuration of an electrostatic brake 15 in the same embodiment.

FIG. 4 is a perspective view showing the overall configuration of the electrostatic brake 15 and the positional relationship with the ink ribbon 2 in the embodiment.

FIG. 5 is a diagram showing a state of an effect of electrostatic attraction force F in the example.

FIG. 6 is a perspective view showing an overall configuration of an electrostatic brake 15a, which is a second configuration example of the electrostatic brake of the present invention, and a positional relationship with the ink ribbon 2.

FIG. 7 is a side sectional view showing a schematic configuration example of a conventional thermal transfer printer.

8 is a side sectional view showing a detailed configuration within a broken line range in FIG.

FIG. 9 is a diagram showing a positional relationship between the ink ribbon 2 and the print head 11 and each force acting on the ink ribbon 2 in the conventional thermal transfer printer.

FIG. 10 is a diagram showing a color arrangement of Y, M, C or Y, M, C, K of the ink ribbon 2 in the color thermal transfer printer.

[Explanation of symbols]

 2 ink ribbon 8 printing paper 11 print head 12-k heating element 15 electrostatic brake 16-k electrode 17-k electrode 18 high voltage generation circuit 19 control circuit Sk control signal Vk voltage Tm winding force Tb reaction force Tt printing resistance Ts static Electric braking force

Claims (3)

[Claims] 1. A winding means for winding an ink ribbon coated with ink with a predetermined winding force, and heating the ink ribbon to transfer the ink onto a printing paper to print a predetermined character or the like. In a thermal transfer printer provided with a printing unit, a braking unit provided behind the printing unit, for individually applying a tension in a direction opposite to the traveling direction of the ink ribbon to each portion in the width direction of the ink ribbon, A thermal transfer printer comprising: a control unit that controls the braking unit in accordance with a printing state of the ink ribbon in the width direction by the printing unit. 2. The braking means includes a bipolar electrode group arranged in one row or a plurality of rows in a width direction of the ink ribbon, and a dielectric layer covering the plurality of bipolar electrode groups. The thermal transfer printer according to claim 1, wherein the ink ribbon is tensioned by an electrostatic attraction force generated by a high voltage applied to each of the bipolar electrodes. 3. The control means, in the width direction of the ink ribbon, the bipolar electrode at a position corresponding to a position at which the ink is transferred to the printing paper does not generate an electrostatic attraction force, and 3. The thermal transfer printer according to claim 2, wherein the bipolar electrode at a position corresponding to a position where ink is not transferred to the printing paper controls the braking means so as to generate an electrostatic attraction force.