JPH0410869B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal transfer type color printer that uses a recording head such as a thermal head to transfer and record ink on an ink sheet onto recording paper.

Conventional structure and its problems In thermal transfer printers that obtain color records by overlapping colors, in order to obtain good image quality without color shift, it is necessary to align the dot rows of each color at the beginning. Of course, it is necessary to do this reliably, but
It is even more important to wind up the ink sheet in a stable state so that the recording paper does not expand, contract, or skew while recording one color.

Figure 1 is a schematic configuration diagram of a conventional thermal transfer color printer. In Figure 1, 1 is an ink sheet, in which heat-melting or heat-sublimating ink is superimposed on a thin base material. The colors are applied sequentially (for example, yellow → magenta → cyan). A recording paper 2 is wound around the outer periphery of the platen 4 and is conveyed by rotation of the platen 4. 3
is a thermal head, which is supported so as to be movable in the vertical direction of the figure. 5 is a supply reel on which an unused ink sheet 1 is wound. Reference numeral 6 denotes a take-up reel for winding up the ink sheet 1 after transfer recording. Reference numeral 7 denotes a torque limiter for applying back tension and is provided coaxially with the supply reel 5. Reference numeral 8 denotes a torque limiter that supports the take-up tension, and is provided coaxially with the take-up reel 6.

The operation of the conventional thermal transfer color printer configured as described above will be described below. The platen 4 wraps and fixes the recording paper 2 around its outer periphery.
The recording paper 2 is rotated until the recording start position is at the position of the thermal head 3. Here, the recording paper 2 is overlapped with the ink sheet 1 and is pressed and held on the platen 4 by the thermal head 3. Thermal head 3
At the same time as adding the recording signal of the first color to
The recording paper 2 and ink sheet 1 are rotated in the direction of arrow A to run the recording paper 2 and ink sheet 1, thereby recording the first color.
After the recording of the first color is completed, the thermal head 3 is separated from the platen 4, the recording paper 2 is conveyed by the rotation of the platen 4 to the same recording start position as that of the first color, and the ink sheet 1 is idle-fed to locate the beginning of the second color. be done.
When the respective operations of the recording paper 2 and the ink sheet 1 are completed, the thermal head 3 presses the recording paper 2 and the ink sheet 1 again, and recording of the second color is started. Color recording is obtained by repeating the same operation for the first color for three colors.

Normally, a back tension F _B and a winding tension F _W are added to the ink sheet 1 so that the ink sheet 1 runs stably without skew both during recording and during air feeding. The back tension F _B and the take-up tension F _W are torque limiters 7 and 8 provided coaxially with the supply reel 5 and take-up reel 6 of the ink sheet 1, respectively (the respective torque capacities are F _B and F _W ). ) is given by By the way, as the ink sheet 1 travels, the winding radius of both the supply reel 5 and the take-up reel 6 changes, so the tension changes in inverse proportion to this.
F _B and F _W change. Figure 2 shows the changes in the tensions F _B and _{F W} from the beginning to the end of the _ink sheet 1 of a conventional thermal transfer color printer. The winding tension F _We and the back tension F _Be at the end of winding are set so that F _Be <F _We so that winding is always possible even during the first idle feed. Therefore, the winding tension F _Wi and the back tension F _Bi at the beginning of winding become F _Bi <<F _Wi . However, the above configuration has the following drawbacks. That is, the portions of the ink sheet 1 heated by the thermal head 3 are thermally deformed, so that wrinkles may occur between the portions of the ink sheet 1 and the unused portions, or one-sided elongation may occur depending on the recording pattern. If the ink sheet 1 deformed in this way is wound up with a large winding tension F _W , the recording quality will be degraded due to adverse effects such as uneven recording pitch and skew feeding on the recording paper 2 during recording. . Particularly in color printers, when colors are superimposed, color misregistration occurs, resulting in a significant drop in resolution. Furthermore, the larger the winding radius of the ink sheet 1 that is first loaded onto the supply reel 5, the greater the problem described above, so there is a limit to the number of ink sheets 1 that can be loaded at one time.

Purpose of the invention The present invention solves the above-mentioned conventional problems.
By setting the back tension of the ink sheet to a strong force during recording and a weak force during empty feeding, the ink sheet is always wound stably and high-quality color recording without misalignment can be obtained by thermal transfer type. The purpose is to provide a color printer.

Structure of the Invention The present invention includes an ink sheet coated with thermal transferable ink, a thermal head that selectively generates heat from a heating element, a platen that faces the thermal head and presses and holds a recording paper and an ink sheet, and a platen that connects the thermal head to the platen. A head driving device that presses or separates the ink sheet from the thermal head, a sheet supply device that applies back tension to the ink sheet, and a head position detection means to detect the ink sheet when the thermal head is separated from the platen. A back tension switching means is provided to make the back tension smaller than the back tension of the ink sheet when the thermal head is pressing against the platen. Since the ink sheet can be wound up stably even at times, it is possible to prevent color shift when superimposing colors.

DESCRIPTION OF EMBODIMENTS FIGS. 3 and 4 are schematic configuration diagrams of a thermal transfer color printer according to an embodiment of the present invention.
The same parts as those in the figure are given the same reference numerals. Third
4, reference numeral 1 is an ink sheet in which heat-melting or heat-sublimating ink is applied on a thin base material in the order of overlapping colors, and this ink sheet 1 is transferred from a supply reel 5 to a take-up reel 6. It is wound so that it runs to. 8 is a torque limiter installed coaxially with the take-up reel, and its torque capacity is
A winding tension F _W is applied to the ink sheet 1 by T _W . 9 is a torque limiter installed coaxially with the supply reel 5, and its torque capacity T _B is the same as that of the control circuit 1.
T _{BL and} T _BH (T _{BL <}
The back _tension F _B of the ink sheet 1 is also changed accordingly into two stages F _BL and F _BH (F _BL <F _BH ). 3 is a thermal head, and the thermal head 3 is driven by a head drive device (not shown) to the platen 4.
It is supported so as to be movable between a pressed state and a separated state. Reference numeral 10 denotes head position detection means constituted by an optical sensor or the like, and the thermal head 3
The detection signal is input to the control circuit 11, and the torque capacity of the torque controller 9 on the supply reel 5 side is set as T _BL in accordance with the detection signal. It is now possible to switch to T _BH .

The operation of the thermal transfer type color printer of this embodiment configured as described above will be explained below.

FIG. 3 is a diagram showing the recording state. In FIG. 3, when the ink sheet 1 and the recording paper 2 are pressed by the thermal head 3, and the platen 4 is rotated in the direction of arrow A while sending a recording signal to the thermal head 3. At the same time, the ink sheet 1 sent out by the rotation of the platen 4 is wound onto the take-up reel 6, thereby recording the first color. If the winding tension of the ink sheet 1 at this time is set to a light force F _W that does not loosen the ink sheet 1 after recording, which is sent out by the rotation of the platen 4, the recording paper 1
Since the ink sheet 1 is stably conveyed in synchronization with the rotation of the platen 4 without being affected by the winding tension of the deformed ink sheet 1 after recording, uneven recording pitch and skew do not occur. In addition, the back tension of the ink sheet 1 at this time is a somewhat strong force F _BH to prevent wrinkles and skew feeding of the ink sheet 1.
(acted by T _BH ). Here, even if F _W <F _BH , since the ink sheet 1 is being fed by the rotation of the platen 4, the ink sheet 1 will be fed out stably. Fourth
The figure shows a state in which the thermal head 3 is separated from the platen 4 by a head drive device (not shown) after the recording of the first color is completed. In FIG. 4, the head position detection means 10 detects that the thermal head 3 has moved away from the platen 4, and based on that signal, the back tension of the ink sheet 1 changes from F _BH to F _BL (acted by T _BL ). Switch to . The back tension F _BL at this time is set to a very light force that can sufficiently transport the ink sheet 1 by the winding tension F _W of the ink sheet 1 . In other words, when the thermal head 3 is separated from the start to the end of the take-up reel 6, F _BL <F _W always holds.
is set so that it holds true. In this state, the ink sheet 1 is continuously fed to the cue position for the second color. During this time, the recording paper 2 is also conveyed to the recording start position for the first color. When the respective cue operations for the recording paper 2 and the ink sheet 1 are completed, the thermal head 3 is again driven by a head drive device (not shown) to move the recording paper 2 and the ink sheet 1 to the platen 4.
Press against. At this time, the head position detection means 10 detects that the thermal head 3 is pressing the platen 4, so the back tension F _B of the ink sheet 1 is switched from F _BL to F _BH again.
From this state, the recording signal for the second color is applied to the thermal head 3, and the recording for the second color is performed in the same manner as for the first color. Color recording can be obtained by performing the same operation for recording the third color.

As described above, according to this embodiment, the back tension of the ink sheet when the thermal head 3 is separated is set to be smaller than the back tension of the ink sheet when the thermal head is press-recording, so that the ink sheet is always in contact with the ink sheet. Since it can be wound stably, color recording without color deviation can be obtained. Also, in conjunction with the head position detection means that detects the pressed state or separated state of the thermal head,
Since the back tension of the ink sheet is switched, the back tension of the ink sheet is reliably controlled.

In this embodiment, the switching of the back tension is performed by a switching circuit in the control circuit.
It goes without saying that the same effect can be obtained even if the back tension is changed mechanically using a plunger or the like.

Effects of the Invention The thermal transfer color printer of the present invention is configured so that the back tension of the ink sheet when the thermal head is separated can be made smaller than the back tension of the ink sheet when the thermal head is press-recording. This allows the ink sheet to be wound up stably with an appropriate force at all times, both during pressure recording with the thermal head and when the thermal head is separated. A stable pixel pitch can be obtained without being affected by uneven winding tension. Moreover, since the back tension of the ink sheet is changed according to the pressing state of the thermal head, its control is reliable. In other words, it is possible to realize a printer with a simple configuration that can produce high-quality color records with no color shift when colors are superimposed.
Its practical effects are great. In addition, regardless of the size of the winding radius of the ink sheet loaded on the supply reel, it is possible to always wind up the ink sheet in a stable state, so it is possible to increase the number of ink sheets that can be loaded at one time. , it is possible to realize a thermal transfer printer that requires less maintenance.

[Brief explanation of drawings]

Figure 1 is a schematic configuration diagram of a conventional thermal transfer color printer, and Figure 2 is a diagram showing the winding tension and back tension due to changes in the winding diameter of the ink sheet from the beginning to the end of the winding of the conventional thermal transfer color printer. FIGS. 3 and 4 are characteristic diagrams illustrating changes in the temperature, and are schematic configuration diagrams of a thermal transfer color printer according to an embodiment of the present invention. 1... Ink sheet, 2... Recording paper, 3... Thermal head, 4... Platen, 5... Supply reel, 6... Take-up reel, 8, 9... Torque limiter, 11... Control circuit .

Claims (1)

[Claims] 1. A thermal head that selectively generates heat from a heating element, a platen that faces the thermal head and presses and holds a recording paper and an ink sheet coated with thermal transfer ink, and a device that presses or separates the thermal head from the platen. a head driving device that applies back tension to the ink sheet; a head position detecting device that detects a state in which the thermal head is pressed against the platen and a state in which it is separated from the platen; The first back tension of the sheet feeding device when the separation state of the thermal head is detected is the second back tension of the sheet feeding device when the pressing state of the thermal head is detected by the head position detection means. A thermal transfer color printer equipped with a means for switching the back tension to be smaller than the back tension.