PRINTING PROCESS FOR A THERMAL TRANSFER TYPE MULTICOLOR PRINTER

Abstract: A printing process for a thermal transfer type multicolor printer repeatedly transfer a plurality of color ink, such as yellow, magenta and cyan color ink, in turn on a printing paper (1) so as to obtain a multicolor printed paper (1c). After every time when one color ink is transferred to the printing paper (1), the printing paper (1) lapped with a multicolor ink film (2) is fed forward to a predetermined separation position at a predetermined printing speed under a pressure applied between a thermal head (7) and a platen roller (6). Thereafter, the thermal head (7) is separated from the platen roller (6) so as to prevent the remaining heat of the thermal head (7) from affecting to the multicolor ink film (2), so that the ink wax of the multicolor ink film (2) is prevented from being melted and working as an adhesive agent for the printing paper (1) and the multicolor ink film (2). Hence, the printing paper (1) can be separated from the multicolor ink film (2) with ease. Then the feeding speed of the printing paper (1) is made slower than that of the multicolor ink film (2) so as to prevent the multicolor ink film (2) from slackening. Thereafter, the printing paper (1) is completely separated from the multicolor ink film (2) and the transferred ink quantity is not changed in this separation process (S5, S10 and S15; S6, S11 and S16), thus, the multicolor dot printing can be performed with accuracy.

Description: The present invention generally relates to printing processes for thermal transfer type multicolor printers, and more particularly to a printing process for a thermal transfer type multicolor printer in which a printing paper is repeatedly feeding forward and backward so as to perform a multicolor printing with a multicolor ink film. Fig. 1 is a diagrammatic side view showing a conventional thermal transfer type multicolor printer. In Fig. 1, 1 designates a printing paper and 2 designates a color ink film on which a color ink group including yellow(Y) ink, magenta (M) ink and cyan (C) ink is repeatedly painted as shown in Fig. 2. In addition, 3 designates a feeding reel for feeding the color ink film 2 forward, 4 designates a rewinding reel for rewinding the printing paper 1, 4a represents a sprocket pin, a plurality of sprocket pins 4a are mounted around the rewinding reel 4 by a predetermined distance, and 5 designates a roller. Furthermore, 6 designates a platen roller, 7 designates a thermal head, 8 and 9 designate rollers, 10 designates a take-up reel for taking up the color ink film 2, and 11 designates a cutter having a sharp cutting edge. Next, description will be given with respect to a diagrammatic printing process for the conventional thermal transfer type multicolor printer shown in Fig. 1 in conjunction with Fig. 6. First, the printing paper 1 is fed forward in a direction A by a distance corresponding to a predetermined number of steps in step SP1. The distance corresponding one step is set identical to the distance between two adjacent dot lines. Next, the printing paper 1 is rewound back in a direction B to a predetermined printing position, so that the printing paper 1 is lapped over a yellow color region of the color ink film 2 in a step SP2. Thereafter, a dummy printing is performed in a step SP3. More specifically, the thermal head 7 is not driven, and the printing paper 1 lapped with the color ink film 2 is fed forward by a distance corresponding to a predetermined number of steps. In a next step SP4, a yellow color dot printing corresponding to one page is performed by driving the thermal head 7 while the printing paper 1 and the color ink film 2 are continuously fed forward by one step distance. The printing paper 1 and the color ink film 2 is lapped (or slightly adhered) together when the printing paper 1 and the color ink film 2 is fed forward between the thermal head 7 and the roller 8 after the above yellow color dot printing is completed. In a next step SP5, the printing paper 1 and the color ink film 2 are further fed forward, so that these printing paper 1 and the color ink film 2 are separated. At this time, a tip edge portion of a magenta color region of the color ink film 2 is located at a mark sensor position which is located just above the thermal head 7. The printing paper 1 is fed backward (or rewound back) to the mark sensor position, so that a tip edge portion of a yellow color printed region of the printing paper 1 coincides with the tip edge portion of the magenta color region of the color ink film 2, and the printing paper 1 and the color ink film 2 is lapped together again in a step SP6. Same as the step SP3, the dummy printing is performed in a step SP7. Thereafter, similar to the steps SP4 to SP6, a magenta color dot printing is performed in a step SP8, the printing paper 1 is separated from the color ink film 2 in a step SP9, and the printing paper is rewound back in a step SP10. Similarly, the dummy printing is performed in a step SP11, and a cyan color dot printing is performed in a step SP12, and then the printing paper 1 is separated from the color ink film 2 in a step SP13. In the above steps SP1 to SP13, the multicolor dot printing of one page is completely performed. Thereafter, the color printed paper 1 is fed forward by a predetermined distance in a step SP14, and the printing process is ended. In the conventional printing process, the thermal head 7 is separated from the platen roller 6, and the printing paper 1 and the color ink film 2 are fed forward in the case where the printing paper 1 is separated from the color ink film 2 in the steps SP5, SP9 and SP13 shown in Fig. 3. In this case, the color ink film 2 is taken up by the take-up reel 10 rotated by a take-up apparatus (not shown), however, the take-up speed of the color ink film 2 is slightly larger than the feeding speed of the printing paper 1 so that the feeding speed of the printing paper 1 becomes slightly different from that of the color ink film 2 and necessary amount of ink transferred on the printing paper 1 is rendered to be take-off. Hence, the conventional thermal transfer type multicolor printer is disadvantageous in that whole amount of ink transferred on the printing paper 1 is not remained accurately. In order to eliminate the above disadvantage, another conventional thermal transfer type multicolor printer employs a method in which the printing paper 1 lapped with the color ink film 2 is fed forward under a pressure applied between the thermal head 7 and the platen roller 6 in a separating process in the steps SP5, SP9 and SP13 shown in Fig. 3. In this printer, the printing paper 1 and the color ink film 2 is fed forward with a constant speed under the pressure applied between the thermal head 7 and the platen roller 6 so that a transfer operation will be performed with accuracy. However, due to the remaining heat of the thermal head 7, the ink wax of the ink film 2 is melted so that the color ink film 2 is slightly adhered to the unprinted region of the printing paper 1. Therefore, this conventional printer is disadvantageous in that the color ink film 2 is forced to feed backward by the printing paper 1 when the printing paper 1 is fed backward in the steps SP2, SP6 and SP10. It is therefore a primary object of the invention to provide a printing process for a thermal transfer type multicolor printer in which the multicolor ink is transferred on the printing paper with accuracy. It is another object of the invention to provide a printing process for a thermal transfer type multicolor printer in which a color ink film is not forced to feed backward by the printing paper when the printing paper is fed backward after one color dot printing is performed. According to the present invention there is provided a printing process for a thermal transfer type multicolor printer, said thermal transfer type multicolor printer comprising at least a thermal head, a platen roller, a feeding reel, a take-up reel, a rewinding reel, a printing paper and a multicolor ink film, said multicolor ink film being repeatedly painted with a plurality of color inks, said multicolor ink film being fed forward by said feeding reel and being taken up by said take-up reel, said printing paper and said multicolor ink film being put and lapped between said thermal head and said platen roller under a pressure applied between said thermal head and said platen roller so as to repeatedly transfer one color ink within said plurality of color ink to said printing paper when a multicolor printing is performed, and said thermal head being separated from said platen roller and thereafter said printing paper being fed backward by said rewinding reel at every time when one different color ink is to be transferred to said printing paper and at a time when said multicolor printing is completed and a multicolor printed paper is obtained, characterised by the provision of: (a) a first step for separating the printed portion of the printing paper from said multicolor ink film at every time when one different ink is to be transferred to said printing paper, said printing paper being fed forward to a separation position at a predetermined printing speed under the pressure applied between said thermal head and said platen roller so as to separate said printing paper from said multicolor ink film; and (b) a second step for completely separating said printing paper from said multicolor ink film after said first step is performed, said thermal head being separated from said platen roller so as to prevent remaining heat of said thermal head from affecting to said multicolor ink film, thereafter said printing paper being fed forward at a speed slower than that of said multicolor ink film so as not to slacken said multicolor ink film, thus said printing paper being completely separated from said multicolor ink film, regardless of a state in which said printing paper is slightly adhered to said multicolor ink film because of ink wax of said multicolor ink film. Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown. In the drawings: Fig. 1 is a diagrammatic side view showing an example of the conventional thermal transfer type multicolor printer; Fig. 2 is a perspective side view showing an example of the color ink film; Fig. 3 is a flow chart showing a conventional printing process; Fig. 4 is a block diagram showing a constitution of an embodiment of the present invention; Fig. 5 is a flow chart showing a printing process according to the present invention; and Figs. 6A and 6B are diagrams showing relations between the printing paper, the thermal head and the cutter. Referring now to the drawings, Fig. 4 shows a constitution of a control circuit for the thermal transfer type multicolor printer according to an embodiment of the invention. In Fig. 4, the printing unit of the present invention is identical to that shown in Fig. 1. In Fig. 4, 15 designates a central processing unit (CPU), 16 designates a read only memory (ROM) in which several kinds of programs are stored, 17 designates a random access memory (RAM) for storing a plurality of printing data groups, and 18 designates an interface circuit. The interface circuit 18 employs a CENTRONICS STANDARD, and an external device (not shown) supplies image data group D of one byte and a strobe signal STB to the interface circuit 18 wherein the image data group D is stored therein and is outputted to a bus line 19 when the interface circuit 18 outputs a ready signal READY to the external device. At this time, the interface circuit 18 outputs an acknowledge signal ACK to the external device. The above image data groups D include yellow image data groups D Y , magenta image data groups D M and cyan image data groups D C therein. 20 designates a parallel-to-serial converter (P/S converter) in which parallel data of eight bits from the bus line 19 is converted into serial data of eight bits and this serial data is supplied to a head drive circuit 21. The head drive circuit 21 includes shift registers and gates for controlling the shift registers. The number the shift registers is identical to that of heating elements within the thermal head 7, and the serial data from the P/S converter 20 is converted into parallel data in the shift registers. The output signals of the gates are supplied to respective heating elements within the thermal head 7. 23 designates a mechanism control circuit for controlling the printing unit shown in Fig. 1. The mechanism control circuit 23 is connected to a pulse motor 25 for driving the platen roller 6 and the rewinding reel 4 so as to feed the printing paper 1, a motor for driving the take-up reel 10 so as to take up the color ink film 2, a solenoid 28 for separating the thermal head 7 from the platen roller 6, and a color detection sensor 30 for detecting the length of each color region of the color ink film 2. Next, description will be given with respect to a printing process according to the present invention in conjunction with Figs. 4, 5, 6A and 6B. When an operator depresses a printing command button switch (not shown), the CPU 15 outputs the ready signal READY to the external device via the interface circuit 18. The external device sequentially supplies the image data groups D of some bytes corresponding to yellow, magenta and cyan colors to the interface circuit 18. The image data groups D are sequentially stored in the RAM 17. Next, the CPU 15 performs a pre-feeding process in a step S1 shown in Fig. 5. More specifically, the CPU 15 first supplies a paper set command signal to the mechanism control circuit 23, whereby the pulse motor 25 is driven and the platen roller 6 is rotated so that the printing paper 1 is pre-fed forward by a predetermined step distance. In the step S1, the printing paper 1 is pre-fed forward as shown in Fig. 6A(a) and Fig. 6A(b). In Figs. 6A and 6B, a full line represents a position of the thermal head 7 with respect to the printing paper 1, and a dotted line represents a position of the cutter 11 with respect to the printing paper 1. Next, the CPU 15 drives the pulse motor 25 so as to feed the printing position backward to an initial position as shown in Fig. 6A(c). Thereafter, the CPU 15 outputs a film set command to the mechanism control circuit 23, whereby the motor 27 is driven based on a detection signal outputted from the color detection sensor 30 so that the yellow color region of the color ink film 2 is fed forward and arranged just below the printing region of the printing paper 1. In a next step S3, the CPU 15 performs the dummy printing. More specifically, the CPU 15 drives the pulse motor 25 and the motor 27 so as to feed the printing paper 1 and the color ink film 2 forward by a distance corresponding to some steps at a predetermined printing speed, as shown in Fig. 6A(d). Next, the CPU 15 performs the yellow color dot printing in a step S4 shown in Fig. 5. In this case, the parallel yellow image data groups D Y are sequentially read out from the RAM 17 and are sequentially supplied to the P/S converter 20 wherein the parallel yellow image data groups D Y are converted into serial yellow image data groups D Y . This serial yellow image data groups D Y are supplied to the head drive circuit 21 wherein the serial yellow image data groups D Y are sequentially stored in the shift registers. When the serial yellow image data groups D Y of first line are stored in the shift registers, the CPU 15 outputs a printing command PR to the head drive circuit 21, whereby the gates within the head drive circuit 21 are opened. Hence, the yellow image data groups D Y are outputted from the shift registers in parallel and the parallel yellow image data groups D Y are supplied to the thermal head 7, so that the yellow image of first line is printed on the printing paper 1. Similarly, the parallel yellow image data groups D Y of second line are read out from the RAM 17, whereby the yellow image of second line is printed on the printing paper 1. By repeatedly performing the above processes, the yellow image of one page is finally printed on the printing paper 1. As a result, the yellow color printed paper 1a is fed forward as shown in Fig. 6A(e). Due to the printing process in the step S4, the yellow color printed paper 1a is lapped with and slightly adhered with the yellow color region of the color ink film 2 under the pressure applied between the thermal head 7 and the platen roller 6. In a next step S5 shown in Fig. 5, the CPU 15 outputs a command for first separation to the mechanism control circuit 23. At this time, the mechanism control circuit 23 drives the pulse motor 25 and the motor 27 so that the yellow color printed paper 1a lapped with the color ink film 2 is fed forward by a predetermined step distance. As a result, the yellow color printed paper 1a lapped with the color ink film 2 is fed forward as shown in Fig. 6A(f), thereafter, the yellow color printed paper 1a is separated from the color ink film. 2, regardless of the pressure applied between the thermal head 7 and the platen roller 6. In a next step S6, the CPU 15 outputs a command for second separation to the mechanism control circuit 23. At this time, the mechanism control circuit 23 drives the solenoid 28 so as to separate the thermal head 7 and the platen roller 6. Thereafter, the mechanism control circuit 23 drives the pulse motor 25 and the motor 27, so that the yellow color printed paper 1a is further fed forward as shown in Fig. 6A(g). Before this step S6, the yellow color printed paper 1a is slightly adhered to the color ink film 2 by the remaining heat of the thermal head 7. However, in this step S6, the yellow color printed paper 1a is completely separated from the color ink film 2. In a next step S7, the yellow color printed paper 1a is fed backward as shown in Fig. 6A(h). Thereafter, same as the step S3, the dummy printing is performed in a step S8. Hence, the yellow color printed paper 1a is slightly fed forward as shown in Fig. 6A(i). Next, similar to the step S4, the magenta color dot printing of one page is performed on the yellow color printed paper 1a in a step S9, so that the yellow and magenta color printed paper 1b will be obtained as shown in Fig. 6A(j). Same as the step S5, the printed paper 1b lapped with the magenta color region of the color ink film 2 is fed forward as shown in Fig. 6B(a), and the printed paper 1b is separated from the color ink film 2 in a step S10. Same as the step S6, the printed paper 1b is further fed forward as shown in Fig. 6B(b), and the printed paper 1b is completely separated from the color ink film 2 in a step 11. Same as the step S7, in a next step S12, the printed paper 1b is fed backward as shown in Fig. 6B(c). Thereafter same as the step S3, the dummy printing is performed so that the printed paper 1b is slightly fed forward as shown in Fig. 6B(d). Similar to the steps S4 and S9, the cyan color dot printing of one page is performed on the printed paper 1b as shown in Fig. 6B(e), hence, the yellow, magenta and cyan colors printed paper 1c can be obtained. Next, similar to the steps S5, S6, S10 and S11, the first and second separations are performed so that the printed paper 1c is completely separated from the color ink film 2 in steps S15 and S16. Thus, the the printed paper 1c is further fed forward as shown in Figs. 6B(f) and 6B(g). After the multicolor printing is performed in the steps S1 to S16, a step S17 judges whether any image data groups D are remained not to be printed on the printing paper 1 or not. When the judgment result of the step S17 is "NO", the printed paper 1c is fed forward by a predetermined distance as shown in Fig. 6B(h) in a step S18, and the multicolor printing is ended. On the other hand, when the judgment result of the step S17 is "YES", the CPU 15 outputs a command for rewinding the printed paper 1c to the mechanism control circuit 23 in a step S19, whereby the printed paper 1c is fed backward by a predetermined distance. Thus, a first line of second page of the printing paper 1 is located just before the thermal head 7. Thereafter, the multicolor dot printing of the second page will be performed in steps S1 to S16. Above is the description of the present embodiment. This invention may be practised or embodied in other ways, for instance, any colors other than the yellow, magenta and cyan colors can be applied to the present invention, and the constitution of the thermal transfer type multicolor printer is not limited to that shown in Fig. 1 and other constitution can be applied to the present invention. The preferred embodiment described herein is therefore illustrative and not restrictive, the scope of the invention being indicated by the appended claims and all variations which come within the meaning of the claims are intended to be embraced therein.

Claims: A printing process for a thermal transfer type multicolor printer, said thermal transfer type multicolor printer comprising at least a thermal head, a platen roller, a feeding reel, a take-up reel, a rewinding reel, a printing paper and a multicolor ink film, said multicolor ink film being repeatedly painted with a plurality of color inks, said multicolor ink film being fed forward by said feeding reel and being taken up by said take-up reel, said printing paper and said multicolor ink film being put and lapped between said thermal head and said platen roller under a pressure applied between said thermal head and said platen roller so as to repeatedly transfer one color ink within said plurality of color ink to said printing paper when a multicolor printing is performed, and said thermal head being separated from said platen roller and thereafter said printing paper being fed backward by said rewinding reel at every time when one different color ink is to be transferred to said printing paper and at a time when said multicolor printing is completed and a multicolor printed paper is obtained, characterised by the provision of: (a) a first step (S5,S10 and S15) for separating the printed portion of the printing paper (1) from said multicolor ink film (2) at every time when one different ink is to be transferred to said printing paper (1), said printing paper being fed forward to a separation position at a predetermined printing speed under the pressure applied between said thermal head (7) and said platen roller (6) so as to separate said printing paper (1) from said multicolor ink film (2); and (b) a second step (S6,S11 and S16) for completely separating said printing paper (1) from said multicolor ink film (2) after said first step (S5,S10 and S15) is performed, said thermal head (7) being separated from said platen roller (6) so as to prevent remaining heat of said thermal head (7) from affecting to said multicolor ink film (2), thereafter said printing paper (1) being fed forward at a speed slower than that of said multicolor ink film (2) so as not to slacken said multicolor ink film (2), thus said printing paper (1) being completely separated from said multicolor ink film (2), regardless of a state in which said printing paper(1) is slightly adhered to said multicolor ink film (2) because of ink wax of said multicolor ink film (2). A printing process according to claim 1, wherein multicolor ink film (2) is repeatedly painted by a color ink group including yellow color ink, magenta color ink and cyan color ink. A printing process according to claim 1 further comprising a third step (S3,S8 and S13) for performing a dummy printing, said printing paper (1) and said multicolor ink film (2) being lapped together between said platen roller (6) and said thermal head (7) which is not driven and said printing paper (1) lapped with said multicolor ink film (2) being fed forward by a predetermined distance without being printed just before a time when one color ink among said plurality of color ink is transferred to said printing paper (1). A printing process according to claim 2, wherein one color dot printing is repeatedly performed at three times and said printing paper (1) is printed by said yellow color ink, said magenta color ink and said cyan color ink in turn so that said multicolor printed paper (1c) is obtained.

Inventors: MITSUSHIMA, SUSUMU C/O SHINKO ELECTRIC CO. LTD., TOIDA, AKIKAZU C/O SHINKO ELECTRIC CO. LTD.
Applicants: SHINKO ELECTRIC CO. LTD.
Application year: 1987
Main classification: B41J35
IPC codes: B41J2, B41J11, B41J35, B41J17