Printer and printing method

Abstract: Printing on a tape is carried out using an ink ribbon having yellow, magenta, cyan and overprinting ink arranged thereon. First, the ink position of the ink ribbon is aligned with the print position of the tape, and one ink is transferred on the tape. This transfer is repeated for the yellow, magenta and cyan colors at the same print position to accomplish color printing. When color printing is completed, the position of the overprinting ink is aligned with the position of the tape, and the overprinting ink is overprinted on the color-printed area line by line. When the cut position of the tape reaches the position of a cutter, printing with the overprinting ink and feeding of the tape stop. In this state, the tape is cut. Then, the tape is cut when printing with the overprinting ink is carried out to the trailing edge of the color-printed area.

Description: The present invention relates to a printer and a printing method, and, more particularly, to a printer which thermally transfers ink on an elongated recording medium. There are tape printers known as apparatus for preparing labels, such as index labels for audio tapes or the like or name labels for personal goods. An ordinary tape printer prints characters input through a keyboard or an image, scanned by an image reader, by heating up its thermal print head to thermally transfer ink coated on an ink ribbon onto a tape. Every time one line printing is performed, the tape is sequentially fed out and is discharged out of the tape printer through a tape discharge port. The tape printer cuts the tape in the desired position by activating a cutter provided at the tape discharge port. There is a given distance between the thermal print head and the cutter, so that during printing and tape feeding, the tape cutting position may become where the cutter is positioned. In this case, the tape printer should temporarily stop printing and tape feeding in order to cut the tape at the desired position. The thermal print head however discharges heat while printing is stopped to cut the tape. Therefore, the temperature of the thermal print head after the tape is cut becomes lower immediately than the temperature before the cutting of the tape. The amount of ink to be transferred on a tape is affected by the temperature of the thermal print head. The conventional tape printer therefore suffers an uneven print density as a tape is cut. There is a color tape printer which has an ink ribbon holding ink of yellow (Y), magenta (M) and cyan (C) and can print a color image by overprinting the ink Y, M and C. In order to cut the tape at the desired position, this color tape printer should temporarily stop printing and tape feeding while printing with one of the color ink is in progress. Naturally, an uneven print density occurs on what is printed with one of the yellow, magenta and cyan ink. That is, the color tape printer also inevitably suffers the occurrence of an uneven print density. EP-A-0 641 663 introduces a printer where the print medium is fed to a cutter such that the desired leading edge and trailing edge margins can be obtained and where the cutting operation is carried out when printing is stopped. In such a printer, before printing starts, the front end of a print tape is positioned at a cutting mechanism. Then, the print tape is rewound a distance in order to shorten the front end margin of the print tape. Next, rewinding stops in order to execute the print operation, e. g. of an image. During the print operation, the print tape will be fed in forward direction, and when printing is finished, the end of the printed image on the print tape is forwarded to the cutting mechanism, while printing is stopped, and than cut. After cutting, the above described procedure restarts. A major inconvenience of such a printer is, that the print tape is immediately cut after printing of an image on the trailing edge of said image, so that the tape must first be fed in forward direction until the cut position, while printing is stopped. Then, the tape must be cut and lastly, it must be rewound before printing can be restarted. Thus, such a printing method is always very time expensive. Accordingly, it is an object of the present invention to provide a printer, having an optimized time performance while avoiding the occurrence of an uneven print density. To achieve the above object, a printer according to the invention is provided as defined in claim 1 and a method as defined in claim 8. It is preferable that the print means transfer the ink on the recording medium by a thermal transfer method, particularly, by a sublimination type thermal transfer method. In this printer, the print control means causes the first and second feed means to continuously feed the ink ribbon and the recording medium until the print means finishes printing over a predetermined range of the recording medium. Further, the second feed means may operate in responsive to the operation of the first feed means. With this structure, the printer does not interrupt printing and the feeding of the recording medium even when the cut position of the leading edge portion of the recording medium reaches the position of the cut means during printing. After the entire printing is completed, the cut position of the leading edge portion of the recording medium is moved again to the position of the cut means. Therefore, the print means does not discharge heat during printing and can thus avoid a variation in its temperature, thus preventing an uneven ink density from occurring. In this printer, the recording medium may have position marks; and the printer may further comprise: detection means for detecting the position marks; and position determination means for determining the position of the recording medium from the position marks detected by the detection means. In this case, for example, said position marks may be provided at equal intervals along the feeding direction of the recording medium; and the position determination means may have counter means for counting the number of the position marks. The cut control means may include: determination means for determining if the cut position of the recording medium comes to the position of the cut means; and means for activating the cut means when the determination means determines that the cut position of the recording medium has come to the position of the cut means. The cut control means may include: determination means for determining if the cut position of the recording medium comes to the position of the cut means; and means for determining if the cut means is activated, whereby when the determination means determines that the cut position of the recording medium has come to the position of the cut means, the operation of the second feed means is stopped until the activation of the cut means is determined. In this printer, the color ink means colored ink including black, gray and white ink. The invention can be more fully understood from the following detailed description when take in conjunction with the accompanying drawings, in which: Fig. 1 is a block diagram illustrating the structure of an electronic circuit of a color tape printer according to one embodiment of this invention; Fig. 2 is a diagram showing the structure of a cassette retainer provided in the main body of the color tape printer according to this embodiment; Fig. 3 is a diagram depicting the internal structure of an ink tape cassette which is to be loaded into the cassette retainer of the color tape printer according to this embodiment; Fig. 4 is a diagram showing the structure of a color ink ribbon to be installed in the ink tape cassette of the color tape printer according to this embodiment; Fig. 5 is a flowchart illustrating a color printing process which is executed by the color tape printer according to this embodiment; and Fig. 6 is a diagram exemplifying the state of image data printed by the color tape printer according to this embodiment. A preferred embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 presents a block diagram illustrating the structure of an electronic circuit of a sublimination-oriented thermal transfer type color tape printer according to one embodiment of this invention. The electronic circuit of this color tape printer has a control unit 11 constituted of a CPU (Central Processing Unit). When the color tape printer is powered on, the control unit 11 invokes a system program which has previously been stored in a ROM (Read Only Memory) 13. The control unit 11 controls the operation of the color tape printer in accordance with the system program. Connected to this control unit 11 are a key input section 12, the ROM 13, a RAM (Random Access Memory) 14, a CGROM (Character Generator ROM) 15, a printer controller 16, an image reader 27, a display device 28, a mark counter 30 and an ink position detector 32. The key input section 12 has character input keys, an execution key, a print key, and function keys. The character input keys include character keys, numeral keys and symbol keys. A string of characters which is text data is input using the character input keys. The settlement of various kinds of input data, the settlement of selection data and the initiation of any set function are instructed by the depression of the execution key. The setting of the lengths of the leading margin and the trailing margin, which will be discussed later, is accomplished by operating one of the function keys and numeral keys. Stored previously in the ROM 13 the system program which is executed by the control unit 11 and which includes a program for controlling the entry of text data and image data, a program for controlling the printing operation, and a program for controlling the feeding of a tape and an ink ribbon. The RAM 14 includes an input buffer, an image memory and a print buffer. The input buffer stores text data input through the key input section 12. The image memory stores image data input from the image reader 27. The dot pattern of text data is developed in the print buffer based on the image data stored in the image memory or data from the CGROM 15. The RAM 14 also serves as a work area for the control unit 11. For example, data on the lengths of the leading margin and the trailing margin, which will be discussed later, and the position of a tape are temporarily stored in this work area. The CGROM 15 has previously stored pattern data corresponding to all the character codes, numeral codes and symbol codes which can be entered using the key input section 12. Connected to the printer controller 16 are a head driver 17 for energizing and heating the thermal print head 18, a head-drive-motor driver 19 for driving a thermal-print-head drive motor 20, a rewind-shaft-drive-motor driver 21 for driving a platen/ink-ribbon-rewind-shaft drive motor 22, a feed-shaft-drive-motor driver 23 for driving a tape-feed-shaft drive motor 24, and a cutter-drive-motor driver 25 for driving a tape-cutter drive motor 26. The control unit 11 controls the individual drivers 17, 19, 21, 23 and 25 through the printer controller 16. Accordingly, the operations of the thermal print head 18, the thermal-print-head drive motor 20, the platen/ink-ribbon-rewind-shaft drive motor 22, the tape-feed-shaft drive motor 24 and the tape-cuter drive motor 26 are controlled. The image reader 27 acquires an image, scanned by a scanner, as image data. The display device 28 displays characters and/or symbols entered through the key input section 12 or displays an image to be printed based on a dot pattern developed in the print buffer. A recording sheet sensor 29 is connected to the mark counter 30. The recording sheet sensor 29 is of a reflection type photosensor which detects each position mark on a tape and outputs a position detection signal. The mark counter 30 is comprised of a counter which counts up the count every time the position detection signal is input. The count of the mark counter 30 is cleared when the tape changes its feeding direction. The number of the position detection signals counted by the mark counter 30 is input to the control unit 11 as tape position data and is stored as such in the RAM 14. The position marks are put on a breakaway sheet at the back of the tape along the feeding direction of the tape (the direction in which the tape is fed at the time of printing, i.e., the direction toward outside of the color tape printer from inside). An ink ribbon sensor 31 is connected to the ink position detector 32. The ink ribbon sensor 31 optically detects boundary marks put on the ink ribbon and outputs an ink position detection signal. The ink position detection signal output from the ink ribbon sensor 31 is input to the ink position detector 32. The ink position detector 32 detects the position of each ink on the ink ribbon in accordance with the ink position detection signal. An ink position signal output from the ink position detector 32 is input to the control unit 11. The boundary marks are provided at the boundaries at the areas of the yellow ink, the magenta ink, the cyan ink and the overprinting ink. According to this color tape printer, margins of arbitrary lengths, which are called "leading margin" and "trailing margin" throughout the description of this embodiment, are provided on the front and back of an area where an image is to be printed. To set the margins, a user should operate one of the function keys on the key input section 12 to set a margin setting mode. In this mode, the display device 28 displays a message "length of leading margin?." Then, the user enters the desired length using the numeral keys and instructs the settlement of the entered length by using the execution key. As a result, the length of the leading margin is set. The length of the trailing margin is likewise set. When the lengths of the leading margin and trailing margin are set, the control unit 11 computes the number of position marks which can be fitted within the lengths of the leading margin and the trailing margin. The computation may be accomplished by multiplying the entered lengths by a predetermined coefficient. The computed number of position marks fittable within the lengths of the leading margin and the trailing margin is stored in the RAM 14. In this tape printer, the lengths of the leading margin and the trailing margin, if not set by the user, are automatically set to "0." Fig. 2 is a diagram showing the structure of a cassette retainer 41 provided in the main body 40 of the color tape printer. Referring to Fig. 2, the cassette retainer 41 comprises the thermal print head 18, a platen roller 22b provided to face the thermal print head 18, an ink ribbon rewind shaft 22a for feeding the ink ribbon, a tape feed shaft 24a for feeding the tape, the recording sheet sensor 29 for detecting a tape position, the ink ribbon sensor 31 for detecting the position of the color ink ribbon, a tape discharge portion 35 for discharging the tape out of the tape printer, and a cutter 26a provided at the tape discharge portion 35 to cut the tape at a predetermined position. As the drive mechanism (not shown) of the thermal-print-head drive motor 20 is driven, this head 18 is moved in the direction indicated by an arrow X in Fig. 2. As the control unit 11 controls the head-drive-motor driver 19 through the printer controller 16, the thermal print head 18 is pressed against the platen roller 22b or is separated therefrom as needed. The heating element (not shown) of the thermal print head 18, when heated, sublimates the ink on the ink ribbon and transfers it on the tape. This thermal print head 18 is controlled by the control unit 11 through the printer controller 16 and the head driver 17. As the transmission mechanism (not shown) of the platen/ink-ribbon-rewind-shaft drive motor 22 is driven, the ink ribbon rewind shaft 22a and the platen roller 22b are rotated in the feeding direction of the ink ribbon and tape. As the transmission mechanism (not shown) of the tape-feed-shaft drive motor 24 is driven, the tape feed shaft 24a rotates in the opposite direction to the feeding direction of the tape. As the drive mechanism (not shown) of the tape-cutter drive motor 26 is driven, the cutter 26a is actuated to cut the tape. As shown in Fig. 2, "L" denotes the distance between the ink transfer position of the thermal print head 18 and the position of the cutter 26a. Fig. 3 shows the structure of an ink tape cassette 42 which is to be loaded into the cassette retainer 41. Referring to Fig. 3, the ink tape cassette 42 has a head retainer 45 and a window 31a. The ink tape cassette 42 accommodates a tape feed reel 43, an ink ribbon feed reel 44, and an ink ribbon rewind reel 47. The tape feed reel 43, the ink ribbon feed reel 44 and the ink ribbon rewind reel 47 are designed to be rotatable. A tape T is wound around the tape feed reel 43. An ink ribbon R is wound around the ink ribbon reel 44. The tape feed reel 43 is fitted on the tape feed shaft 24a, and the ink ribbon rewind reel 47 is fitted on the ink ribbon rewind shaft 22a. The head retainer 45 is formed by cutting away a part of the main body of the cassette 42, and the thermal print head 18 is to be placed there. The tape T and ink ribbon R pass through the head retainer 45 while overlapping each other in such a way that the ink ribbon R faces the thermal print head 18. The ink ribbon sensor 31 optically detects the boundary marks on the ink ribbon R through the window 31a. The ink ribbon R has the yellow ink Y, magenta ink M, cyan ink C and overprinting ink OP repeatedly arranged along the feeding direction Q as shown in Fig. 4. The heat applied by the thermal print head 18 sublimates each of the yellow ink Y, magenta ink M and cyan ink C to be transferred on the tape T. The overprinting ink OP is made of a transparent thermally meltable resin. The heat generated by the thermal print head 18 melts the overprinting ink OP, thus forming a protection layer which protects the image that is printed with the yellow ink Y, magenta ink M and cyan ink C. Each of the ink Y, M, C and OP has the same lengths as the length of one print range d on the tape T. Boundary marks ml to m4 are provided at the boundaries between the each of the ink Y, M, C and OP to permit the ink ribbon sensor 31 to detect the positions of the color ink. A breakaway sheet is adhered to the back of the tape T by an adhesive applied to the back of the tape's recording surface. Position marks which are detected by the recording sheet sensor 29 are put on the back of this separate sheet. The position marks are formed by black lines put at equal distances along the feeding direction of the tape T. The recording sheet sensor 29 outputs a position detection signal when detecting that light is not reflected by such position marks. The operation of this color tape printer will now be described. Fig. 5 presents a flowchart illustrating a color printing process which is executed by the color tape printer. At the time this color tape printer starts printing, the leading edge of the tape T is located at the position of the cutter 26a or the position where the tape was cut in the previous printing. The user might have set the lengths of the leading margin and the trailing margin by using the key input section 12 before printing starts. The control unit 11 should have acquired the number of position marks on the tape T which can be fitted in the lengths of the leading margin and the trailing margin and should have stored the information in the RAM 14. The control unit 11 should also have acquired the number of position marks on the tape T fittable within the length L from the transfer position of the thermal print head 18 to the position of the cutter 26a, and should have stored the information in the RAM 14. As the length L is fixed, the number of position marks fittable in the length L may be stored in the ROM. The process sequence of this flowchart starts when the initiation of printing is instructed by, for example, the operation of the print key on the key input section 12. When the process sequence starts, the ink ribbon R is fed in the feeding direction Q until the leading position of the yellow ink Y comes to the position corresponding to the transfer position of the thermal print head 18. The ink ribbon R is fed toward the ink ribbon rewind shaft 22a as the ink ribbon rewind shaft 22a rotates. The control unit 11 determines the position of the ink ribbon R based on the boundary mark m1 detected by the ink ribbon sensor 31. In this manner, the control unit 11 controls the feeding of the ink ribbon R. At this time, the platen roller 22b and the ink ribbon rewind shaft 22a rotate with the thermal print head 18 pressed against the platen roller 22b. Accordingly, the tape T is fed in the feeding direction by the same distance as the ink ribbon R. At this time, the mark counter 30 is counting the number of the position marks detected by the recording sheet sensor 29. The counted number of the position marks is temporarily stored in the associated register in the RAM 14 as feeding distance information of the tape T (step S1). Through the process in step S1, the leading edge of the tape T is located outward from the position of the cutter 26a by the positioning distance of the target ink of the ink ribbon R. Therefore, the leading edge of the tape T is fed to the initial position or the position of the cutter 26a to position the tape T. With the thermal print head 18 separated from the platen roller 22b and with the platen roller 22b and the ink ribbon rewind shaft 22a set still, the tape feed shaft 24a is rotated. As a result, the tape T is fed in the opposite direction to the feeding direction. The control unit 11 determines the position of the tape T and controls the feeding of the tape T. The position of the tape T is determined based on the number of the position marks on the tape T counted by the mark counter 30. When the number of the position marks counted becomes equal to the number of the position marks counted in step S1, the tape-feed-shaft drive motor 24 is stopped (step S2). While the processes in the steps S1 and S2 are being executed, the control unit 11 develops an image to be printed with the yellow ink Y into the print buffer in the RAM 14. When the process in step S2 is finished, the control unit 11 drives the thermal-print-head drive motor 20 through the printer controller 16 and the head-drive-motor driver 19 to press the thermal print head 18 against the platen roller 22b. Consequently, the ink ribbon R and the tape T are pressed against each other. Under this situation, the control unit 11 heats the thermal print head 18 through the printer controller 16 and the head driver 17 in accordance with image data which has been read from the print buffer in the RAM 14. At this time, the platen/ink-ribbon-rewind-shaft drive motor 22 is driven so that the ink ribbon R and the tape T are fed in the feeding direction Q. As a result, the image data for yellow which has been developed in the print buffer is transferred on the tape T. When the tape T is fed, the mark counter 30 counts the number of the position marks on the tape T detected by the recording sheet sensor 29. This number is stored in the RAM 14 as feeding distance information of the tape T (step S3). When printing with the yellow ink Y (first color) is completed in this manner, the ink ribbon R is fed in the feeding direction Q until the leading position of the magenta ink M comes to the position corresponding to the transfer position of the thermal print head 18. The ink ribbon R is fed toward the ink ribbon rewind shaft 22a as the ink ribbon rewind shaft 22a rotates. The control unit 11 determines the position of the ink ribbon R based on the boundary mark m2 detected by the ink ribbon sensor 31. In this manner, the control unit 11 controls the feeding of the ink ribbon R. At this time, the platen roller 22b and the ink ribbon rewind shaft 22a rotate with the thermal print head 18 pressed against the platen roller 22b. Accordingly, the tape T is fed in the feeding direction by the same distance as the ink ribbon R. At this time, the mark counter 30 is counting the number of the position marks detected by the recording sheet sensor 29. The counted number of the position marks is added to the number of position marks counted in step S3 and the accumulated number is temporarily stored in the associated register in the RAM 14 (step S4). Through the process in step S4, the leading edge of the tape T is located outward from the position of the cutter 26a by the positioning distance of the target ink of the ink ribbon R. Therefore, the leading edge of the tape T is fed to the initial position or the position of the cutter 26a to position the tape T. With the thermal print head 18 separated from the platen roller 22b and with the platen roller 22b and the ink ribbon rewind shaft 22a set still, the tape feed shaft 24a is rotated. As a result, the tape T is fed in the opposite direction to the feeding direction. The control unit 11 determines the position of the tape T and controls the feeding of the tape T. The position of the tape T is determined based on the number of the position marks on the tape T counted by the mark counter 30. When the number of the position marks counted becomes equal to the number of the position marks accumulated in steps S3 and S4, the tape-feed-shaft drive motor 24 is stopped (step S5). While the processes in the steps S4 and S5 are being executed, the control unit 11 develops an image to be printed with the magenta ink M into the print buffer in the RAM 14. When the process in step S5 is completed, the control unit 11 drives the thermal-print-head drive motor 20 through the printer controller 16 and the head-drive-motor driver 19 to press the thermal print head 18 against the platen roller 22b. Consequently, the ink ribbon R and the tape T are pressed against each other. Under this situation, the control unit 11 heats the thermal print head 18 through the printer controller 16 and the head driver 17 in accordance with image data which has been read from the print buffer in the RAM 14. At this time, the platen/ink-ribbon-rewind-shaft drive motor 22 is driven so that the ink ribbon R and the tape T are fed in the feeding direction Q. As a result, the image data for magenta which has been developed in the print buffer is transferred on the tape T. When the tape T is fed, the mark counter 30 counts the number of the position marks on the tape T detected by the recording sheet sensor 29. This number is stored in the RAM 14 as feeding distance information of the tape T (step S6). When printing with the yellow ink Y and magenta ink M is completed in this manner, the ink ribbon R is fed in the feeding direction Q until the leading position of the cyan ink C comes to the position corresponding to the transfer position of the thermal print head 18. The ink ribbon R is fed toward the ink ribbon rewind shaft 22a as the ink ribbon rewind shaft 22a rotates. The control unit 11 determines the position of the ink ribbon R based on the boundary mark m3 detected by the ink ribbon sensor 31. In this manner, the control unit 11 controls the feeding of the ink ribbon R. At this time, the platen roller 22b and the ink ribbon rewind shaft 22a rotate with the thermal print head 18 pressed against the platen roller 22b. Accordingly, the tape T is fed in the feeding direction by the same distance as the ink ribbon R. At this time, the mark counter 30 is counting the number of the position marks detected by the recording sheet sensor 29. The counted number of the position marks is added to the number of position marks counted in step S6 and the accumulated number is temporarily stored in the associated register in the RAM 14 (step S7). Through the process in step S7, the leading edge of the tape T is located outward from the position of the cutter 26a by the positioning distance of the target ink of the ink ribbon R. Therefore, the leading edge of the tape T is fed to the initial position or the position of the cutter 26a to position the tape T. With the thermal print head 18 separated from the platen roller 22b and with the platen roller 22b and the ink ribbon rewind shaft 22a set still, the tape feed shaft 24a is rotated. As a result, the tape T is fed in the opposite direction to the feeding direction. The control unit 11 determines the position of the tape T and controls the feeding of the tape T. The position of the tape T is determined based on the number of the position marks on the tape T counted by the mark counter 30. When the number of the position marks counted becomes equal to the number of the position marks accumulated in steps S6 and S7, the tape-feed-shaft drive motor 24 is stopped (step S8). While the processes in the steps S7 and S8 are being executed, the control unit 11 develops an image to be printed with the cyan ink C into the print buffer in the RAM 14. When the process in step S8 is completed, the control unit 11 drives the thermal-print-head drive motor 20 through the printer controller 16 and the head-drive-motor driver 19 to press the thermal print head 18 against the platen roller 22b. Consequently, the ink ribbon R and the tape T are pressed against each other. Under this situation, the control unit 11 heats the thermal print head 18 through the printer controller 16 and the head driver 17 in accordance with image data which has been read from the print buffer in the RAM 14. At this time, the platen/ink-ribbon-rewind-shaft drive motor 22 is driven so that the ink ribbon R and the tape T are fed in the feeding direction Q. As a result, the image data for cyan which has been developed in the print buffer is transferred on the tape T. When the tape T is fed, the mark counter 30 counts the number of the position marks on the tape T detected by the recording sheet sensor 29. This number is stored in the RAM 14 as feeding distance information of the tape T (step S9). When printing with the yellow ink Y, magenta ink M and cyan ink C is completed in this manner, the ink ribbon R is fed in the feeding direction Q until the leading position of the overprinting ink OP comes to the position corresponding to the transfer position of the thermal print head 18. The ink ribbon R is fed toward the ink ribbon rewind shaft 22a as the ink ribbon rewind shaft 22a rotates. The control unit 11 determines the position of the ink ribbon R based on the boundary mark m4 detected by the ink ribbon sensor 31. In this manner, the control unit 11 controls the feeding of the ink ribbon R. At this time, the platen roller 22b and the ink ribbon rewind shaft 22a rotate with the thermal print head 18 pressed against the platen roller 22b. Accordingly, the tape T is fed in the feeding direction by the same distance as the ink ribbon R. At this time, the mark counter 30 is counting the number of the position marks detected by the recording sheet sensor 29. The counted number of the position marks is added to the number of position marks counted in step S9 and the accumulated number is temporarily stored in the associated register in the RAM 14 (step S10). Through the process in step S10, the leading edge of the tape T is located outward from the position of the cutter 26a by the positioning distance of the target ink of the ink ribbon R. Therefore, the leading edge of the tape T is fed to the initial position or the position of the cutter 26a to position the tape T. With the thermal print head 18 separated from the platen roller 22b and with the platen roller 22b and the ink ribbon rewind shaft 22a set still, the tape feed shaft 24a is rotated. As a result, the tape T is fed in the opposite direction to the feeding direction. The control unit 11 determines the position of the tape T and controls the feeding of the tape T. The position of the tape T is determined based on the number of the position marks on the tape T counted by the mark counter 30. When the number of the position marks counted becomes equal to the number of the position marks accumulated in steps S9 and S10, the tape-feed-shaft drive motor 24 is stopped (step S11). When the process in step S11 is completed, the control unit 11 drives the thermal-print-head drive motor 20 through the printer controller 16 and the head-drive-motor driver 19 to press the thermal print head 18 against the platen roller 22b. Consequently, the ink ribbon R and the tape T are pressed against each other. Under this situation, the control unit 11 heats the thermal print head 18 through the printer controller 16 and the head driver 17. At this time, the platen/ink-ribbon-rewind-shaft drive motor 22 is driven so that the ink ribbon R and the tape T are fed in the feeding direction Q. As a result, the overprinting ink OP is transferred over the yellow, magenta and cyan ink Y, M and C on the tape T. When the tape T is fed, the mark counter 30 counts the number of the position marks on the tape T detected by the recording sheet sensor 29 (step S12). Every time the transfer of the overprinting ink OP for one line is completed, the control unit 11 determines if the cut position of the leading edge portion of the tape T is at the position of the cutter 26a. This determination can be made by checking if the number of the position marks fittable in the distance L between the transfer position of the thermal print head 18 and the position of the cutter 26a, which is stored in the RAM 14, minus the number of the position marks fittable in the leading margin stored in the RAM 14 and the number of the position marks counted in step S12 becomes 0 (step S13). When the cut position of the leading edge portion of the tape T is not at the position of the cutter 26a in step S13, the flow returns to step S12 to execute printing of the next line. When it is determined in step S13 that the cut position of the leading edge portion of the tape T is at the position of the cutter 26a, the control unit 11 stops heating the thermal print head 18 through the printer controller 16 and the head driver 17. The control unit 11 also stops driving the platen/ink-ribbon-rewind-shaft drive motor 22 through the printer controller 16 and the rewind-shaft-drive-motor driver 21. Consequently, the transfer of the overprinting ink OP on the tape T and the feeding of the ink ribbon R and the tape T are stopped (step S14). Next, the control unit 11 drive the tape-cutter drive motor 26 to actuate the cutter 26a through the printer controller 16 and the cutter-drive-motor driver 25. As a result, the unnecessary leading portion of the tape T is cut away (step S15). When the unnecessary leading portion of the tape T is cut away in step S15, the control unit 11 heats the thermal print head 18 through the printer controller 16 and the head driver 17 to restart printing with the overprinting ink OP. The control unit 11 also drives the platen/ink-ribbon-rewind-shaft drive motor 22 through the printer controller 16 and the rewind-shaft-motor driver 21 to start feeding the color ink ribbon R and the tape T again. When the tape T is fed, the mark counter 30 counts the number of the position marks on the tape T detected by the recording sheet sensor 29 (step S16). Every time printing with the overprinting ink OP for one line is completed, the control unit 11 determines if the printing with the overprinting ink OP is for the last line (step S17). When it is determined in step S17 that the printing with the overprinting ink OP is not yet for the last line, the flow returns to step S16 to execute printing of the next line. When it is determined in step S17 that the printing is for the last line, the control unit 11 stops heating the thermal print head 18 through the printer controller 16 and the head driver 17. As a result, the printing with the overprinting ink OP is terminated (step S18). When the printing with the overprinting ink OP stops in step S18, the control unit 11 drives the platen/ink-ribbon-rewind-shaft drive motor 22 through the printer controller and the rewind-shaft-motor driver 21 to feed the tape T until the cut position of the trailing edge of the tape T comes to the position of the cutter 26a. This feeding distance can be discriminated as the mark counter 30 counts the value which is acquired by adding the number of the position marks fittable in the leading margin stored in the RAM 14 to the number of the position marks fittable in the distance L between the thermal print head 18 and the cutter 26a. When the cut position of the trailing edge of the tape T comes to the position of the cutter 26a, the control unit 11 stops driving the platen/ink-ribbon-rewind-shaft drive motor 22 through the yellow ink 16 and the rewind-shaft-motor driver 21. Then, the control unit 11 drives the tape-cutter drive motor 26 to actuate the cutter 26a through the printer controller 16 and the cutter-drive-motor driver 25. As a result, the printed portion of the tape T is cut away (step S19). The process of the color tape printer will be described specifically. Fig. 6 is a diagram exemplifying the state of image data printed by this color tape printer. This diagram shows an example of printing of an image, scanned by the image reader 27, on the tape T. In this example, the leading margin and trailing margin are not provided in the print area D. That is, the leading margin and trailing margin are both set to "0." The length of the unnecessary leading portion is equal to the distance L between the printing portion of the thermal print head 18 and the cutter 26a. In the example, after printing with the yellow, magenta and cyan ink Y, M and C is done through the aforementioned steps S1 to S9, the overprinting ink OP is aligned with the tape T in steps S10 and S11. Next, printing with the overprinting ink OP is carried out in steps S12 and S13. When the trailing edge P1 of the unnecessary leading portion of the tape T (the leading portion of the print range D) reaches the position of the cutter 26a, when the number of the position marks counted by the mark counter 30 becomes equal to the number of the position marks fittable in the distance L, printing and feeding are stopped in step S14. In the next step S15, the cutter 26a cuts away the unnecessary leading portion T1. When the unnecessary leading portion T1 is cut away, printing with the overprinting ink OP in steps S16 and S17 starts again. When printing with the overprinting ink OP till the trailing edge P2 of the print range D is completed, printing on the tape T is stopped in step S18. Even after printing is terminated, the tape T is kept being fed. In step S19, the cutter 26a cuts away the printed area T2 of the tape T. As described above, the color tape printer according to this embodiment cuts the tape at the time of printing with the overprinting ink OP so that printing with the yellow, magenta and cyan ink Y, M and C is not interrupted. Therefore, the thermal print head 18 does not discharge heat during printing with the yellow, magenta and cyan ink Y, M and C, thus preventing an uneven ink density from occurring. As the tape T is cut during printing with overprinting ink OP, fast printing is possible. According to this embodiment, color printing on the tape T is accomplished by the subtractive color mixture of the yellow ink Y, magenta ink M and cyan ink C which are arranged at the equal distances on the ink ribbon R. This invention is not however limited to this particular method. For instance, a 4-color ink ribbon having a black ink in addition to the yellow ink Y, magenta ink M and cyan ink C may also be used. It is also possible to use an ink ribbon which provides monochromatic printing using only a black ink. It is still possible to use an ink ribbon which retains ink of any single color. Although the overprinting ink OP is made of a transparent thermally meltable resin in this embodiment, the material is not limited to this type. For example, an ink base material which contains no pigment or dye may be used for the overprinting ink OP. In this embodiment, the ink ribbon R is provided with the area for the overprinting ink OP so that printing and feeding are stopped to cut the tape T at the time of performing printing with the overprinting ink OP. This invention can however be adapted for use with an ink ribbon which is not provided with the overprinting ink OP. For instance, an area which exposes the transparent film or the base material of the ink ribbon R may be provided instead of the area of the overprinting ink OP. Further, an ink ribbon which does not have such an area and has only the yellow, magenta and cyan ink Y, M and C arranged at the equal distances may be used as well. In this case, after printing with the yellow, magenta and cyan ink Y, M and C is completed, the tape T is temporarily returned to the initial position. Then, the tape T is fed until the cut position of the leading edge is aligned with the position of the cutter 26a. Thereafter, the tape T is fed again so that the cut position of the trailing edge is aligned with the position of the cutter 26a. In this embodiment, the leading positions of the yellow ink Y, magenta ink M, cyan ink C and overprinting ink OP are positioned by the detection of the boundary marks m1 to m4 provided on the color ink ribbon R by the ink ribbon sensor 32. The positioning of the leading positions of the individual ink is not however limited to this method. For example, position marks similar to those put on the tape T may be put at one edge of the ink ribbon R. To detect the position of the tape T, the mark counter 30 counts the number of position marks put on the tape T in the above-described embodiment. However, the feeding distance of the tape T may be acquired by other methods. For instance, the tape T may be held by a pair of pinch rollers so that the position of the tape T is obtained by the rotation of the pinch rollers. Although the count of the counter 30 is cleared when the feeding direction of the tape T is changed in this embodiment, the counter may be so designed as to count up the counter value when the tape T is fed in the feeding direction and to count down the value when the tape T is fed in the opposite direction to the feeding direction. In this case, it is possible to determine if the cut position of the tape T is at the position of the cutter 26a if the counter indicates a predetermined value. As the ink ribbon R is fed, the thermal print head 18 is pressed against the platen roller 22b in this embodiment. Therefore, the tape T is fed in responsive to the feeding of the ink ribbon R. When the ink ribbon R is fed for the position of ink at the other time than the printing time, the thermal print head 18 may be set free from the platen roller 22b. That is, the tape T may not be fed in responsive to the feeding of the ink ribbon R. In this embodiment, the cutter 26a is actuated by driving the tape-cutter drive motor 26. In other words, the tape cutter in this embodiment is an automatic cutter. This invention may however be adapted to a tape printer which is equipped with a manual cutter instead of an automatic cutter. In this case, printing and feeding are stopped when the tape cut position is aligned with the position of the manual cutter while printing with the overprinting ink OP is in progress. At this time, the display section 12 displays a message "cut the tape." When the user manipulates the operation lever of the manual cutter to cut the tape, printing with the overprinting ink OP and feeding of the tape T are restarted. This operation eliminates the need for the tape-cutter drive motor 26 and the cutter-drive-motor driver 25, which contributes to reducing the cost for the tape printer. The tape printer according to this embodiment prints an image by a sublimination-oriented thermal transfer system. This invention is not however limited to this particular system. For example, this invention may be adapted to a melt type thermal transfer printer. The invention may be adapted for every type of printer which is likely to cause an uneven density when printing is stopped. For instance, this invention can be adapted to the case where when the head temperature changes, the amount of ink injected by an ink jet printer varies, resulting in a probable occurrence of an uneven print density. When this invention is adapted to an ink jet printer, there is not ink ribbon used. Therefore, an ink jet printer embodying this invention operates in the following way. While the tape is being fed, ink is sprayed toward the tape from ink nozzles provided on the ink jet head to accomplish printing. The printing operation should not be stopped even when the cut position of the leading edge of the tape reaches the position of the cutter during printing. The tape is kept being fed until the cut position of the tape's leading edge comes to the position of the cutter again after the completion of the entire printing. Although the foregoing description of this embodiment has been given with reference to the tape printer which prints an image on an elongated recording medium (tape), this invention may be adapted to any printer which makes a print on any type of recording medium as long as the printer needs to stop printing in order to cut the recording medium.

Claims: A printer comprising: an ink ribbon (R) comprising a plurality of ink areas and a corresponding plurality of protective layer areas arranged regularly, each ink area retaining inks (Y, M, C) for printing an image on a recording medium (T), and each protective layer area retaining a protective agent (OP) which forms a protective layer for protecting a corresponding part of the printing surface of the recording medium (T) printed with the inks (Y, M, C); print means (18) for transferring the inks (Y,M,C) of the ink areas of the ink ribbon (R) and the the protective agent (OP) on the recording medium (T); first feed means (22, 22a, 22b) for feeding the ink ribbon (R) in one direction; second feed means (24, 24a) for feeding the recording medium (T) in the one direction and in a direction reverse to the one direction; cut means (26a) for cutting the recording medium (T); control means (11, 16, 17, 19, 21, 23) for controlling operations of the print means (18), the first and second feed means (22, 22a, 22b, 24, 24a) and the cut means (26a), characterized in that : the control means (11, 16, 17, 19, 21, 23) comprises: print control means for causing the print means (18) to transfer the inks (Y,M,C) to the recording medium (T) to thereby print the image on the recording medium (T) from a print start position while causing the first and second feed means (22, 22a, 22b, 24, 24a) to simultaneously feed in the one direction the ink ribbon (R) and the recording medium (T) with the ink areas overlapping on the recording medium (T), for causing the second feed means to feed back the recording medium (T) in the reverse direction to the print start position, and for causing the first and second feed means (22, 22a, 22b, 24, 24a) to simultaneously feed in the one direction the ink ribbon (R) and the recording medium (T) with the ink areas overlapping on the recording medium (T) while causing the print means to transfer the protective agent (OP) to the recording medium (T) on which the image was printed with inks (Y, M, C) to form a protective layer; stop control means, responsive to the second feed means (24, 24a) feeding the recording medium (T) until the cut position of the recording medium (T) before a leading end of the image printed on the recording medium (T) comes to the position of the cut means (26a) while the print control means is causing the print means to form the protective layer on the recording medium (T), for stopping the print means (18) and the first and second feed means (22, 22a, 22b, 24, 24a); and cut control means, responsive to the stop control means stopping the first and second feed means (22, 22a, 22b, 24, 24a), for activating the cut means (26a). The printer according to claim 1, wherein the print control means causes the first and second feed means (22, 22a, 22b, 24, 24a) to continuously feed the ink ribbon (R) and the recording medium (T) until the print means (18) finishes printing the image on the recording medium (T) in its predetermined range. The printer according to claim 1, wherein when the second feed means (24, 24a) feeds the recording medium (T) in the one direction, the second feed means (24, 24a) operates in conjunction with the first feed means (22, 22a, 22b), and wherein when the second feed means (24, 24a) feeds the recording medium (T) in the reverse direction, the second feed means (24, 24a) operates irrespective of the first feed means (22, 22a, 22b). The printer according to claim 1, wherein the recording medium (T) has position marks; and the printer further comprises: detection means (29) for detecting the position marks; and position determination means (30) for determining a position of the recording medium (T) from the position marks detected by the detection means (29). The printer according to claim 4, wherein the position marks are provided at equal intervals in a feeding direction of the recording medium (T); and wherein the position determination means (30) has counter means for counting the number of the position marks. The printer according to claim 1, wherein the stop control means comprises: determination means (11) for determining whether the cut position of the recording medium before the leading end of the image printed on the recording medium (T) has come to the position of the cut means (26a). The printer according to claim 1, wherein each of the ink areas retains a plurality of color inks (Y, M, C) arranged regularly on the ink ribbon (R). A printing method in which an ink ribbon (R) which retains inks (Y, M, C) and a protective agent (OP) is used to print an image on a recording medium (T) and to form a protective layer on the prinied image, and in which the recording medium (T) is then cut at a desired position before a leading end of the printed image on the recording medium (T), comprising the steps of: feeding the recording medium (T) and the ink ribbon (R) simultaneously in one direction; transferring the inks (Y, M, C) to the recording medium (T) to print an image on the recording medium (T) from a print start position; feeding back the recording medium (T) in a direction reverse to the one direction; simultaneously feeding the ink ribbon (R) and the recording medium (T) in the one direction to the print start position; transferring the protective agent (OP) to the recording medium (T) on which the image was printed to thereby form a protective layer; stopping the transfer of the protective agent (OP) and the feeding of the recording medium (1) in response to the desired position of the recording medium (T) before the leading end of the image printed on the recording medium (T) coming to the cutting position while the protective layer is being formed; and cutting the recording medium (T) at the desired position.

Inventors: MURAI YASUSHI, MURAI, YASUSHI, Murai, Yasushi, c/o Casio Computer Co., Ltd.
Applicants: CASIO COMPUTER CO LTD, CASIO COMPUTER CO., LTD.
Application year: 1996
Main classification: B41J3
IPC codes: B41J11, B41J2, B41J35, B41J29, B41J3, G06F3