JPH11321054A - Thermal transfer recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal transfer recording apparatus which prevents a next color from being blanked out due to fold wrinkles of an ink sheet when an energy of a thermal head is increased to improve an image density, and less generates a color shift of color images. SOLUTION: This apparatus has motors 23, 33 for driving a delivery roll 2 and a take-up roll 3 for an ink sheet 1, a thermal head 4 for thermally transferring an ink of the ink sheet 1 to a print paper 9, and a driving control means 11 for controlling the motors 23, 33 in driving so as to apply a front tension at the side of the take-up roll of the ink sheet 1 and a back tension at the side of the delivery roll of the ink sheet 1 at a print position of the thermal head 4. The driving control means 11 controls the motors 23, 33 to make the front tension of the ink sheet 1 smaller than the front tension during printing of a previous color if a print ratio of the previous color to the print paper 9 exceeds a reference value when the ink sheet is taken up from a print end of the previous color to a start of a next color ink.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a thermal transfer printer,
Regarding the control of the tension of the ink sheet during printing of a thermal transfer recording device such as a thermal transfer copying machine or a thermal transfer scanner, the purpose is to improve the image quality, and in particular, to improve the color loss due to wrinkling of the ink sheet and the positional deviation between the colors to be overprinted in the color print. It is assumed that.

[0002]

2. Description of the Related Art FIG.
And FIG. 10 is a perspective view showing a main part of a conventional thermal transfer printer. In the figure, reference numeral 1 denotes an ink sheet, and yellow (Y color) and magenta (M
Color), cyan (C color), and black (K color) inks are arranged in a plane-sequential manner. Reference numeral 2 denotes a supply roll for supplying the ink sheet 1, and reference numeral 3 denotes a take-up roll for winding the ink sheet 1 from which ink after thermal transfer has been removed. 4 is a thermal head, 5 is a heating element of the thermal head 4, 6 is a peeling member provided on the downstream side of the thermal head 4 in the conveying direction of the ink sheet 1, 7 is an ink sheet roller, 8 is a platen,
9 is a printing paper.

In the above-described conventional thermal transfer printer, the platen 8 is rotated while holding the ink sheet 1 and the printing paper 9 between the thermal head 4 and the platen 8 in a state where the ink sheet 1 and the printing paper 9 are overlapped. It is transported in the direction of arrow F by frictional force with the platen 8. At the same time, by selectively applying an electric signal to the heating element 5 of the thermal head 4, the heating element 5 heats the ink sheet 1 and thermally transfers the ink to the printing paper 9 in correspondence with a print image. The fed ink sheet 1 is bent by the peeling member 6, separated from the printing paper 9, and then wound up on the winding roll 3 via the ink sheet roller 7.

[0004] At this time, by selectively heating the thermal head 4 corresponding to printing, as shown in FIG. 10, a heated extension portion B of the base film 1 a which is heated and extended occurs in a part of the ink sheet 1. I do. This heating extension B is
The material of the base film 1a of the ink sheet 1 is partially elongated by heating, and is in a slack state compared to the non-heated portion of the ink sheet 1. In FIG. 10, E is a weak tension generated in the ink sheet heating extension,
F is the normal tension generated in the heat unaffected area of the ink sheet,
G is the slack of the heat-affected zone of the ink sheet, HS is the folding wrinkle generated after the slack of the heat-affected zone of the ink sheet, H
Y indicates the ink generated after the slack of the heat affected zone of the ink sheet, and arrow J indicates the ink sheet 1 on the supply roll 2 side.
Shows the tension (back tension).

FIG. 11 is an explanatory view showing a state in which a trailing edge wrinkle reaching the ink surface of the next color has occurred on the ink sheet. In FIG. 11, an arrow E indicates a weak tension of the ink sheet 1 generated at the heat extension portion B (broken line portion in FIG. 11) of the ink sheet 1. An arrow F indicates the winding tension of the ink sheet 1 generated in the unstretched (unheated) portion of the ink sheet 1 (solid line in FIG. 11). G is a slack portion generated at the boundary between the heated extension portion B and the unheated portion. As described above, in thermal transfer printing, the ink sheet 1 is loosened due to heating and elongation depending on the degree of heating during thermal transfer. Then, at the boundary between the heated portion and the unheated portion, the ink slack portion G
Is inflated. This phenomenon occurs remarkably when the printing heating temperature of the thermal head 4 is increased in order to improve the printing density, and when half of the printing is performed in the scanning direction and the remaining portion is unprinted.

To start printing of the next color, the thermal head 4 is once separated from the platen 8, the printing paper 9 is returned to a predetermined printing position, and the ink sheet 1 is set to the head of the next color ink surface. Send. Then, when the thermal head 4 is again brought into contact with the platen 8 at the start of the next color printing,
The ink twist HY that has continued from the ink slack portion G is folded between the thermal head 4 and the platen 8, and a folding wrinkle HS occurs. As a result, there occurs a problem that a portion K on which an image is not transferred occurs due to the folding wrinkles HS of the ink sheet 1 as shown in FIG. In FIG. 12, the color of the ink on the ink sheet 1 is magenta (M
This shows an example in which a portion K in which the color of the next ink is not transferred to the head of cyan (C color) appears after printing (color).

[0007]

In such a conventional thermal transfer printer as described above, the front tension on the take-up roll 3 side during printing is increased so that the slack portion G, which becomes a folding wrinkle, is stretched to reduce the bulge. I have to.
However, when the front tension (tension: F + E) on the take-up roll 3 side is increased, the swelling of the slack portion G is reduced, but the weak tension E of the heating extension portion B of the ink sheet 1 and the unstretched (non-extended) The difference from the normal tension F caused by the winding of the ink sheet 1 generated in the (heating) portion increases. For this reason, the higher the tension (front tension) at the time of winding up to the next color, the smaller the folding wrinkles during printing, but the longer the HY of the ink becomes, the easier it is to extend to the printing screen of the next color, and the negative becomes negative. Occurred. Also, if the winding tension (front tension) at the time of cueing the next color of the ink sheet 1 is always weakened, the ink sheet 1 is wound while being stretched, and the ink winding diameter on the winding side becomes large. There is a problem that the winding may become thick and the outer shape of the printer becomes large.

For the above-mentioned reason, when the printing of the next color is started, the ink sheet 1 and the printing paper 9 are sandwiched between the platen 8 and the thermal head 4 is brought into contact with the thermal head 4 to start printing by applying the front tension. Extended YY
Is not only a folding wrinkle pressed by the head, but also the difference between the tension F and the tension E of the front tension becomes a skew force S that generates skew, and this skew force S is applied to the printing paper 9 via the ink sheet 1. Join
The printing paper 9 is slightly twisted. This moving position is the leading part of the print, but the trailing end of the print is shown in FIG.
As shown in FIG. 3, the amount of twisting movement is enlarged, which also causes a color shift (FIG. 13 shows an example in which the next color C after the M color is printed has shifted).

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. In the case where the energy of the thermal head is increased (to improve the print density), the ink sheet is heated. It is an object of the present invention to provide a thermal transfer recording apparatus which can prevent the next color printing from being lost due to expansion and wrinkling of an ink sheet. Also,
An object of the present invention is to provide a thermal transfer recording apparatus in which color misregistration of color printing is small.

[0010]

According to the present invention, there is provided a thermal transfer recording apparatus comprising: an ink sheet on which ink is applied or printed in a face-sequential manner; a motor for driving a supply roll and a take-up roll of the ink sheet; A thermal head for thermally transferring the ink of the sheet onto the printing paper; and a drive control means for driving and controlling the motor so that a front tension on the winding side of the ink sheet and a back tension on the supply roll side at the printing position of the thermal head are applied. The front-tension tension applying means, during winding from the end of printing of the previous color to the next color ink cueing, the front tension of the ink sheet based on the printing ratio of the front color to the printing paper of the previous color. Is designed to be weaker than the front tension during printing.

[0011] The drive control means may control the printing rate according to the printing ratio.
The motor is controlled so as to adjust the front tension. The drive control means controls the motor so as to gradually increase the front tension to a predetermined tension at the start of next color printing.

Further, the motor for driving the take-up roll of the ink sheet is a DC motor, and the drive control means changes the voltage applied to the DC motor to carry the ink sheet and adjust the tension. It controls a DC motor.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, Embodiment 1 of the present invention will be described. FIG. 1 is a configuration diagram showing a main part of a thermal transfer printer according to Embodiment 1 of the present invention. In the drawing, reference numerals 1 to 9 are the same as those of the above-mentioned conventional device, and the description thereof will be omitted. Reference numeral 10 denotes a CPU for controlling the thermal transfer printer, and reference numeral 11 denotes drive control means for controlling the drive motors 21 and 31 of the supply roll 2 and the take-up roll 3. Reference numerals 22 and 32 denote torque limiters provided between the drive motors 21 and 31 and the supply rolls 2 and 3, respectively, which are capable of switching transmission torque. 11 and the like are controlled based on print data sent from a host computer (not shown), and print rate data is transferred to the drive control means 11 as drive reference data. Here, the printing rate is the ratio of the total energy required for the printing to the energy required for printing the entire surface of the printing paper 9 at the highest density, in other words, the printing paper 9
Is a ratio of a value obtained by multiplying the print screen area in the print by the print density to a value obtained by multiplying the printable area by the highest density.

Next, the operation will be described. FIG. 2 is a diagram showing the front tension of the ink sheet according to the first embodiment of the present invention. The vertical axis represents the tension of the front tension (winding), and the horizontal axis represents the printing operation from during printing to the next color printing. FIG. 3 is a flowchart showing the printing operation. When a printing command is output from a host computer (not shown), the thermal transfer printer starts printing (S3).
0). That is, the CPU 10 controls the thermal head 4, the platen 8, the drive control means 11 and the like based on the printing data, and starts printing. During printing, the front tension of the ink sheet 1 is maintained at a large tension T1, and the printing rate of the printing data is counted simultaneously with the start of the printing operation (S31). When printing of one color is completed (S3
2) The print ratio of the print (print of the previous color) is set to S31.
The printing rate is determined based on the count value in the above, and the printing rate is compared with a reference value (for example, 30%) to determine the printing rate (S33). Although the example in which the reference value is 30% has been described, it is preferable that this value is appropriately determined according to the type and use of the thermal transfer printer.

In step S33, when the printing ratio of the preceding color exceeds 30% at the time of cueing the next color of the ink sheet 1, it is determined that the tension is weakened, and a signal is sent from the printing control means 12 to the torque limiter 32. The tension T1 is changed to the tension T2, and the ink sheet 1 is wound (S34). Then
The cue of the next color ink sheet 1 and the printing paper 9 is performed (S
36) At the start of printing of the next color, a signal is sent from the printing control means 12 to the torque limiter 32 to change the tension T2 to the tension T1, that is, return to the tension T1 during printing, and printing of the next color is started (S37). On the other hand, in S33, when the printing ratio of the previous color does not exceed 30% at the time of cueing the next color of the ink sheet 1, it is determined that the tension is maintained, and a signal is sent from the printing control means 12 to the torque limiter 32 to transmit the tension T
While holding the ink sheet 1 (S3)
5). Next, the cueing of the next color ink sheet 1 and the printing paper 9 is performed (S36). At the start of the next color printing, a signal is sent from the printing control means 12 to the torque limiter 32, and the tension T is set.
1 is held, that is, printing of the next color is started with the tension T1 during printing (S37).

As described above, when the printing ratio of the previous color exceeds the reference value, the front tension of the ink sheet 1 is reduced during cueing of the next color after printing.
Ink sheet 1 that was printed immediately before (the previous color was printed)
Heated and stretched region B and unheated unstretched region E
Skew force S due to the tension difference (| E-F |) applied to the printing paper, the twist of the printing paper 9 via the ink sheet 1 at the start of printing of the next color is reduced, and Color shift can be suppressed. In addition, since the front tension of the ink sheet 1 is reduced during cueing of the next color after printing, the ink sheet 1 extending from the slack portion G generated by heating and stretching during printing of the previous color is formed. HY can be shortened, and the occurrence of non-transfer of an image due to folding wrinkles HS caused by entering between the thermal head 4 and the platen 8 can be reduced.

Embodiment 2 FIG. Hereinafter, a second embodiment of the present invention will be described. FIG. 4 is a diagram illustrating a change in the tension of the ink sheet 1 according to the second embodiment of the present invention. The vertical axis indicates the tension of the front tension (winding), and the horizontal axis indicates the printing operation from during printing to the next color printing. is there. FIG. 5 is a flowchart showing the operation of the second embodiment. In the drawing, Ta, Tb, Tc, Td, and Te are ink winding tensions (front tensions) corresponding to the respective printing rates a, b, c, d, and e. Then, as shown in the correlation diagram of the winding tension with respect to the printing ratio shown in S53 of FIG. 5, after the printing of one color is completed, the set tension table at the time of starting one head of the next color ink sheet is held in the drive control means 11. The control is performed steplessly according to the printing ratio. The other configuration is the same as that of the first embodiment, and a description thereof will be omitted.

Next, the operation will be described. When a print command is output from a host computer (not shown), the thermal transfer printer starts printing (S50). That is, the CPU 10 controls the thermal head 4, the platen 8, the drive control means 11 and the like based on the printing data, and starts printing. During printing, the front tension of the ink sheet 1 is maintained at a large tension Ta, and the printing rate of the printing data is counted simultaneously with the start of the printing operation (S5).
1). When the printing of one color is completed (S52), the printing rate b in the printing (printing of the previous color) is determined based on the count value in S51, and the ink sheet 1 is wound with the winding tension Tb corresponding to the printing rate b. Winding, ie, S53 in FIG.
The winding tension is selected with reference to the correlation diagram of the winding tension with respect to the printing ratio shown in (5) (S53). In the second embodiment, the case where the printing rate is b is described. Next, cueing of the next color ink sheet 1 and the printing paper 9 is performed (S56). At the start of the next color printing, a signal is sent from the printing control means 12 to the torque limiter 32 to increase the tension Tb to the tension T.
a, ie, return to the tension Ta during printing, and printing of the next color is started (S57).

In the first embodiment, the winding tension at the next color cueing feed portion after printing is determined based on the printing rate reference value and the winding tension is switched. The difference from the tension value of the winding is large, and a good result can be obtained with the ordinary ink sheet 1. However, when the ink sheet 1 with a thin base film is used for higher definition printing, the folding wrinkles HS Was easy to occur. On the other hand, in the second embodiment, since the ink sheet 1 is wound with the winding tension corresponding to the printing ratio, the folding wrinkle HS does not occur even in high-definition printing, so that the printing accuracy is further improved.

Embodiment 3 Hereinafter, a third embodiment of the present invention will be described. FIG. 6 is a structural diagram showing a main part of a thermal transfer printer according to Embodiment 3 of the present invention, and FIG. 7 is a diagram showing a smooth incremental drive of the front tension of the ink sheet in Embodiment 3 of the present invention. FIG. 8 is a characteristic diagram of the DC motor according to Embodiment 3 of the present invention, in which the horizontal axis represents torque, and the vertical axis represents rotation speed (rotation speed). In FIG. 6, reference numeral 23 denotes a winding motor composed of a DC motor for driving and rotating the winding roll 3, and a DC motor of a shunt or permanent magnet field is used. In FIG. 8, with respect to a to b in the area, the DC motor rotates at a speed corresponding to the load from point a at a speed of 0 to point b at a no-load rotation speed.
In the third embodiment, by utilizing this characteristic, the applied voltage of the winding motors 23 and 33 is changed, that is, the torque is changed in the range of the torques a and b, and the rotation speed (the predetermined conveying speed of the ink sheet 1) is changed. ) To control the winding of the ink sheet 1 and the tension. Other configurations are the same as those of the first and second embodiments, and thus description thereof will be omitted.

Next, the operation will be described. The ink sheet 1 and the printing paper 9 during printing are conveyed by a frictional force with the platen 8. The printing mechanism rotates the platen 8 at a predetermined rotation speed, and conveys the ink sheet 1 and the printing paper 9 at a predetermined conveyance speed V. When the take-up motor 33 is driven to take up the ink sheet 1 at a speed V or higher with respect to the ink sheet 1 conveyed at the speed V, the difference between the take-up speed and the speed V becomes smaller on the winding side of the ink sheet 1. Front tension. The rotation speed of the winding motor 33, which is a DC motor, can be easily changed by changing the applied voltage by the drive control unit 11.

The winding tension (front tension) of the ink sheet 1 caused by the winding of the winding motor 33.
As shown in FIG. 7, the tension T is applied during the printing of the previous color, and the printing rate of the previous color exceeds the reference value during the cueing of the next color. Similarly, the ink sheet 1 and the printing paper 9 of the next color have a weak tension T2.
Is completed and the next color print command is output,
The drive control means 11 gradually increases the applied voltage of the winding motor 33, and gradually increases the tension from the tension T2 to the tension T1.

As described above, the drive source of the take-up roll 3 of the ink sheet 1 is constituted by the DC motor 33, and the drive and tension control of the take-up roll 3 are performed by the drive control means 11 utilizing the characteristics of the DC motor 33. By doing so, the torque limiter 32 described in the first embodiment becomes unnecessary, and the configuration of the device can be simple and inexpensive. Further, since the strength of the front tension of the ink sheet 1 can be controlled by controlling the applied voltage, it is possible to easily realize a smooth switching configuration by gradually increasing and decreasing. Further, since the driving source of the winding roll 3 of the ink sheet 1 is constituted by the DC motor 33, the tension is changed smoothly and gradually, so that the effect of further reducing wrinkles and the effect of suppressing color misregistration can be exhibited. As in the first and second embodiments, the switching of the front tension during printing may be performed by the torque limiter 32, or may be performed by an electromagnetic clutch or the like. It gets complicated. Furthermore, it is more difficult to achieve a smooth gradual increase and decrease as compared with control of the applied voltage of the DC motor.

In the above-described first to third embodiments, the ink sheet 1 is set at a small front tension during the cueing of the next color based on the printing ratio for the entire printing area of the printing paper 9.
Has been described, but not only the print ratio for the entire print area of the print paper 9 but also the print distribution for the entire print area of the print paper 9 is taken into consideration, and the front tension of the ink sheet 1 during the cueing of the next color is considered. May be determined, and in this case, printing can be performed with higher precision. Also, a thermal transfer printer has been described as the thermal transfer recording device, but the thermal transfer recording device may be a thermal transfer copying machine, a thermal transfer scanner, or the like.

[0025]

According to the thermal transfer recording apparatus of the present invention, there is provided an ink sheet on which ink is applied or printed in a plane-sequential manner, a motor for driving a supply roll and a take-up roll for the ink sheet, and an ink for the ink sheet. A thermal head for performing thermal transfer to printing paper, and drive control means for controlling the drive of the motor so that a front tension on the winding side of the ink sheet and a back tension on the supply roll side at the printing position of the thermal head are applied; The tension applying means of the front tension, at the time of winding from the end of printing of the previous color to the next color ink cue,
The front tension of the ink sheet is configured to be weaker than the front tension during printing of the previous color based on the printing rate for the printing paper of the previous color, so that the ink sheet is heated and stretched, and the ink sheet is folded. It is possible to prevent the omission of a next color image based on the image. In addition, color misregistration of color printing is small and high-precision printing can be performed.

Further, the drive control means may control the printing
Since the motor is controlled so as to adjust the front tension, printing with high accuracy can be performed with less color shift in color printing.

Further, the drive control means can control the motor so that the front tension is gradually increased to a predetermined tension when the next color printing is started.

Further, the motor for driving the take-up roll of the ink sheet is a DC motor, and the drive control means changes the voltage applied to the DC motor to carry the ink sheet and adjust the tension. Since the DC motor is controlled, the configuration of the apparatus can be simple and inexpensive.
When the front tension is gradually increased, the effect is particularly excellent.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a main part of a thermal transfer printer according to Embodiment 1 of the present invention;

FIG. 2 is a diagram illustrating a change in front tension (ink winding tension) of the ink sheet according to the first embodiment of the present invention.

FIG. 3 is a flowchart illustrating tension control of the ink sheet according to the first embodiment of the present invention.

FIG. 4 is a diagram showing a change in front tension (ink winding tension) of an ink sheet according to Embodiment 2 of the present invention.

FIG. 5 is a flowchart illustrating tension control of an ink sheet according to Embodiment 2 of the present invention.

FIG. 6 is a structural diagram showing a main part of a thermal transfer printer according to Embodiment 3 of the present invention.

FIG. 7 is a diagram illustrating a change in front tension (ink winding tension) of an ink sheet according to Embodiment 3 of the present invention.

FIG. 8 is a characteristic diagram of a DC motor according to Embodiment 3 of the present invention.

FIG. 9 is a configuration diagram illustrating a main part of a conventional thermal transfer printer.

FIG. 10 is a perspective view showing a main part of a conventional thermal transfer printer.

FIG. 11 is an explanatory diagram of a state in which folding wrinkles have occurred in the ink sheet.

FIG. 12 is an explanatory diagram showing a state in which print color omission has occurred due to folding and wrinkling of an ink sheet.

FIG. 13 is an explanatory diagram showing a state in which the printing paper is misaligned in printing.

[Description of Signs] 1 ink sheet, 2 supply roll, 3 take-up roll 4 thermal head, 8 platen, 9 printing paper 10 CPU, 11 drive control means, 12 print control means 21, 31 drive motor, 22, 32 torque limiter 23, 33 DC motor B Color loss occurring in printing paper E Weak tension generated in slack portion of ink sheet F Normal tension generated in heat unaffected portion of ink sheet G Looseness of heat affected portion of ink sheet HY Ink sheet Distortion of ink generated after slack of heat-affected zone HS Inset wrinkle generated after slack of heat-affected zone of ink sheet T1, T2, Ta, Tb, Tc, Td, Te Tension

Claims (4)

[Claims] 1. An ink sheet on which ink is applied or printed in a plane-sequential manner, a motor for driving a supply roll and a take-up roll of the ink sheet, a thermal head for thermally transferring the ink of the ink sheet to printing paper, A drive control means for driving and controlling the motor so as to apply a front tension on the winding side of the ink sheet and a back tension on the supply roll side at the printing position of the thermal head. When winding from the end of printing of the previous color to the cueing of the next color ink, the front tension of the ink sheet is made weaker than the front tension during printing of the previous color based on the printing rate for the printing paper of the previous color. A thermal transfer recording apparatus, wherein the motor is controlled. 2. The thermal transfer recording apparatus according to claim 1, wherein the drive control means controls the motor so as to adjust the front tension according to the printing ratio. 3. The thermal transfer recording apparatus according to claim 1, wherein the drive control means controls the motor so as to gradually increase the front tension to a predetermined tension at the start of next color printing. 4. A motor for driving a take-up roll of the ink sheet is a DC motor, and the drive control means changes the voltage applied to the DC motor to transport the ink sheet.
The thermal transfer recording apparatus according to any one of claims 1 to 3, wherein the DC motor is controlled so as to adjust the tension.