Color printer

Abstract: Of a plurality of page memories (23 to 26) for storing printing data corresponding to the printing heads (1 to 4), at least the page memory (26) is associated with an auxiliary memory (27) for storing at least two continuous pages of printing data for at least one printing head (32), wherein a printing data write unit (21, 33) executes a process for writing the next page of printing data in one of the page memory (26) and the auxiliary memory (27) while the printing data stored in the other one of the page memory (26) and the auxiliary memory (27) is being printed, and the image processing unit (21) supplies printing data continuously and alternately from the page memory (26) and the auxiliary memory (27) to each corresponding printing head (32).

Description: The present invention relates to a printer comprising a plurality of printing heads arranged sequentially along the direction in which long printing paper is fed and a plurality of page memories each for storing a page of image data corresponding to each of the printing heads, wherein color components of an image are printed in superposed relation on the printing paper on the basis of each page of image date supplied from the page memory corresponding to each printing head in the order in which the printing paper is fed thereby to perform the desired color printing. The present invention also relates to a method of printing an image on a printing medium. Fig. 1 shows an example of a set of labels 100, 200, 300, 400 printed by print units having four printing heads such as thermal line heads not shown of yellow, magenta, cyan and black arranged sequentially along the direction in which the printing paper P is fed. These labels 100, 200, 300, 400 are printed in the manner described below. The four print units are located in such relative positions that when the leading portion of an area on the printing paper P to be printed with label 400 is transported to the position of the black print unit, the leading portion of label 300 is located at the position of the cyan print unit, the leading portion of label 200 at the position of the magenta print unit, and the leading portion of label 100 at the position of the yellow print unit. Labels 100 to 400 have hatched outer frames 101a, 101b, 101c, 101d respectively of the same shape. Amount frames 102a to 102d and item frames 103a to 103d inside the outer frames 101a to 101d, respectively, have also the same shape. When labels 100, 200, 300, 400 are printed, label image data stored in each page memory connected with each print unit corresponding to each label position is read out and supplied to the thermal line head of the print unit. In the case where the outer frames 101c, 101b, 101a of labels 300, 200, 100 are to be printed sequentially in superposed colors, for example, the print units corresponding to yellow, magenta and cyan are supplied with the image data of the outer frames 101a, 101b, 101c from the corresponding memories, respectively. The outer frames 101a, 101b, 101c, therefore, are printed yellow by the print unit at the position of label 100 when arriving at the position of label 100, printed magenta by the print unit at the position of label 200 when arriving at the position of label 200, and printed cyan by the print unit at the position of label 300 when arriving at the position of label 300. In this way, each color is printed in superposed relation in synchronism when the portion to be printed in color arrives at the heat generating surface of the head of each print unit. In the process, inks of different colors are superposed and mixed thereby to print with a predetermined hue. The outer frames 101a, 101b, 101c, which have the same size and shape, can be printed without rewriting the image data stored in each page memory. The amount frames 102a to 102d and the item frames 103a to 103d, which also have the same size and shape, respectively, can be printed in color in similar fashion without rewriting the image data stored in each page memory. In a thermal transfer color recording method having a plurality of thermal line heads each for one color described above, the paper P is not reciprocated for each color unlike in the single-head system, and therefore high-speed printing is made possible. The amounts and names of commodities are printed black in the amount frames 102a to 102d and the item frames 103a to 103d in the outer frames 101a to 101d. As seen from FIG. 1, however, the contents to be printed, i.e., the amounts and the names of commodities are different for different labels 100 to 400. When labels 100 to 400 are printed continuously, therefore, the printing data are required to be changed with labels. In the case of FIG. 1, for example, the thermal line head for printing black is arranged at the position of label 400. After label 400 is printed black, the black printing data for label 300 is required to be fetched and stored in the corresponding page memory before the next label 300 is transferred to the position of label 400 and begins to be printed by the black printing head. In other words, data on label 300 is required to have been fetched and stored during the period from the time when label 400 begins to be printed black to the time when the next single label 300 begins to be printed black. In the case where different printing data are printed in labels 400, 300, 200 and 100 in that order by the black printing head, as described above, a predetermined length of time is required for fetching and storing the next page of printing data during the period when the preceding label is actually printed, resulting in the problem of a limited printing speed. Suppose that the printing speed is increased without taking this fetch and storage period into consideration. When the next page data is to be printed black, for example, the problem is posed that the paper feed and the printing operation of the remaining color heads is required to be suspended until the next page data replacing the page data that has been printed is fetched and stored in the corresponding page memory. In the conventional color printer, as described above, a period of time is required for rewriting the next printing data in a memory in the presence of different printing data for different pages, and therefore it is difficult to increase the printing speed. The same is true with respect to the image processing apparatus and method as disclosed in EP 0 664 521 A2, where a page to be printed is stored in an image memory and is delivered via a direct memory access device to a printer engine. Accordingly, the object of the present invention is to provide a printer capable of continuous printing with a higher printing speed without any period for rewriting the printing data stored in a page memory even in the case where different pages have different printing data. This object is achieved by a printer and a method comprising the features of the independent claims. Further advantageous embodiments of the invention may be taken from the dependent claims. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: FIG. 1 is a plan view showing labels printed by a multi-head color printer having a plurality of printing heads arranged sequentially along the direction in which the printing paper is fed. FIG. 2 is a schematic diagram showing a configuration of the essential parts of a color printer according to an embodiment of the present invention. FIG. 3 is a block diagram showing a circuit configuration of the essential parts of a color printer according to the first embodiment. FIGS. 4A, 4B are diagrams showing the flow of the data transfer and the black-data plotting and storage process performed at regular intervals of time by an image processing unit of a color printer according to the first embodiment. FIGS. 5A to 5E are diagrams showing the printing timings of each head of a color printer according to the same embodiment. FIG. 6 is a block diagram showing a circuit configuration of the essential parts of a color printer according to a second embodiment of the present invention. FIG. 7 is a diagram showing the flow of data transfer performed by a CPU included in an image processing unit of a color printer according to the second embodiment. FIG. 8 is a block diagram showing a circuit configuration of the essential parts of a color printer according to a third embodiment of the invention. FIG. 9 is a diagram showing the flow of data transfer performed by an image processing unit of a color printer according to the same embodiment. A first embodiment of the invention will be described with reference to FIGS. 1 to 3, 4A, 4B and 5A to 5E. The first embodiment refers to the case in which the labels shown in FIG. 1 are printed in color. FIG. 2 is a schematic diagram showing a configuration of the essential parts of a color printer according to the first embodiment of the invention for printing the labels of FIG. 1 in four colors of yellow (Y), magenta (M), cyan (C) and black (K) in superposed relation or in one of the colors. Image printing heads including a yellow head 1, a magenta head 2, a cyan head 3 and a black head 4 (hereinafter referred to as the Y head 1, the M head 2, the C head 3 and the K head 4, respectively) are thermal line heads having a plurality of heating resistors with printing tips thereof aligned each at a 4-inch-long parallelopipedal printing end across the feeding direction of paper P. The heads are arranged at a predetermined spatial interval with each other sequentially on a transport path 5 along the main scanning direction in which the paper P is fed. This predetermined interval is so set, for example, that three heads coincide with a length of a label Lc as shown in FIG. 5A. The Y to K heads 1 to 4 have Y to K platens 6 to 9, respectively, arranged in opposed relation thereto. Also, ribbon magazines 10 to 13 are adapted to be removably set in the heads. The ribbon magazines 10 to 13 include supply rollers 10-1 to 13-1 having unused ink ribbons wound thereon and take-up rollers 10-2 to 13-2 for taking up the used ink ribbons, respectively. The ribbon magazines 10 to 13, in which a yellow ink ribbon, a magenta ink ribbon, a cyan ink ribbon and a black ink ribbon are set respectively, are adapted to supply these ribbons to each of the thermal heads 1 to 4. A paper feed roller 14 for controlling the feed rate of the paper P and an auxiliary roller 15 in opposed relation to the paper feed roller 14 are arranged on the paper supply side of the Y thermal head 1 on the paper feed path 5. A sensor unit 16 including a gap sensor for detecting a gap G between paper labels and a mark sensor for detecting a mark printed on the paper P is arranged on the transport path 5 between the paper feed roller 14 and the Y thermal head 1. Also, a paper end sensor unit 17 including an optical transmission sensor for detecting the trailing end of the paper P is arranged in the vicinity of a paper supply port 5-1 nearer to the paper supply side than the paper feed roller 14 on the transport path 5. A paper holder 18 is fixed outside of the paper supply port 5-1 of the transport path 5. The paper holder 18 has wound thereon the paper P as a long printing medium. The paper P includes a plurality of label sheets La to Ld adhered on a mount B at predetermined spatial intervals G as shown in FIG. 1. A paper discharge port 5-2 for delivering the printed paper P is provided on the side of the transport path 5 opposite to the paper supply port 5-1. The ink ribbons from the ribbon magazines 10 to 13 and the paper P from the paper holder 18 are fed substantially at equal speed between the thermal heads 1 to 4 and the platens 6 to 9. Desired images of yellow, magenta, cyan and black are thus formed in that order on labels 100, 200, and so on by this color printer. FIG. 3 is a block diagram showing a circuit configuration of the essential parts of this color printer. An image processing unit 21 includes a CPU (central processing unit), a ROM (read-only memory) and a RAM (random access memory) for producing, editing and storing printing data while at the same time controlling the transfer of the printing data among the units. Printing data of a label produced and edited by the image processing unit 21 are temporarily stored as bit map data in a Y-1 area 23, an M-1 area 24, a C-1 area 25 and a K-1 area 26 for storing the colors of yellow, magenta, cyan and black, respectively, and a K-2 area 27 used in association with the K-1 area 26, formed in the printing data storage unit 22. The Y-1 area 23, the M-1 area 24, the C-1 area 25 and the K-1 area 26 constitute a page memory, and the K-2 area 27, as described in detail later, is configured as an auxiliary memory of the K-1 area memory 26. The K-1 area 26 and the K-2 area 27 are both for storing bit map data plotted from the black printing data including different characters and numerical values for different labels. As described later, two alternate sets of labels of black printing data are temporarily stored in the K-1 area 26 and the K-2 area 27, respectively. According to this embodiment, first, third and other odd-numbered labels of image data are stored in the K-1 area 26, while second, fourth and other even-numbered labels of image data are stored in the K-2 area 27. The image processing unit 21 subjects each line of the image data stored in the areas 23 to 27 to parallel-serial conversion and other processes through a printing data converter 28. The data thus processed are supplied to the heads 1 to 4 and a Y head unit 29, an M head unit 30, a C head unit 31 and a K head unit 32 making up a circuit for driving the heads 1 to 4. A printer engine controller 33 is for controlling the print timing of the units 29 to 32 and performs the printing operation on the basis of the printing data supplied thereto through the printing data converter 28. The image processing unit 21 and the printer engine controller 33 are connected to the printing data storage unit 22 and the printing data converter 28 through a system bus 34. FIG. 4A is a diagram showing the flow of data transfer performed by the CPU of the image processing unit 21. First, step ST1 waits for a data transfer request from the printer engine controller 33. This waiting mode can be interrupted by other processes. Upon receipt of a data transfer request from the printer engine controller 33, a color is selected according to the data transfer request and whether the selected color is black or not is decided. When the decision is that the selected color is not black, the leading line of data being printed is transferred from the storage area of the printing data storage unit 22 corresponding to the particular color to the printing data converter 28, and the process proceeds to step ST2. In the case where the color is yellow, for example, the leading line of the data is transferred from the Y-1 area 23 to the printing data converter 28. When the decision is that the selected color is black, on the other hand, whether the page of the printing data being printed is an odd-numbered one (an odd-numbered label) or not. In the case where the printing data is for an odd-numbered page, the leading line of data being printed is transferred from the K-1 area 26 to the printing data converter 28, followed by the process proceeding to step ST2. In the case where the decision is that the printing data is not for an odd-numbered page but for an even-numbered page (for an even-numbered label), the leading line of the data is transferred from the K-2 area 27 to the printing data converter 28, followed by step ST2. Step ST2 decides whether the printing has ended or not. In the case where the decision is that the printing is not ended, the process returns to step ST1. In the case where the decision is that the printing has ended, on the other hand, the data transfer process is terminated. FIG. 4B is a chart showing the flow of the black data fetching and storing process performed at predetermined time intervals (by interrupt or the like) by the image processing unit 21. First, it is decided whether unprinted data is stored in the K-1 area 26. In the case where the decision is that unprinted data is not stored in the K-1 area 26, the black printing data of the next odd-numbered page to be printed, if any, is fetched and stored in the K-1 area 26 as bit map data, thereby terminating the black data storing process. In the case where the decision is that unprinted data is stored in the K-1 area 26, on the other hand, it is decided whether unprinted data is stored in the K-2 area or not. In the case where the decision is that unprinted data is not stored in the K-2 area 27, the black printing data of the next even-numbered page to be next printed, if any, is fetched and stored as bit map data. Upon termination of this storage process, the black data storage process is terminated. In the case where the decision is that unprinted data is stored in the K-2 area 27, the black data storing process is terminated. According to this embodiment having the above-mentioned configuration, the printing operation is performed at timings as shown in FIGS. 5A to 5E thereby to print labels 100, 200 and so on, as shown in FIG. 1. More specifically, the Y head 1, the M head 2 and the C head 3 perform the printing operation on the basis of the same printing data supplied from the Y-1 area 23, the M-1 area 24 and the C-1 area 25, respectively. The K-head 4 performs the printing operation, however, on the basis of the printing data which is different for each page supplied alternately from the K-1 area 26 and the K-2 area 27. In the case of FIG. 1, for example, the black printing data of the first label 300 is fetched and stored in the K-1 area 26. The black printing data of the second label 200 is then stored in the K-2 area 27. The printing operation is started. The image processing unit 21 transfers the printing data from the K-1 area 26 to the printing data converter 28 for each line. As a result, a black image including the commodity name of "apple" and the amount of "¥100" is printed black in the commodity frame 103c and the amount frame 102c, respectively, of the first label 300. Upon complete termination of the transfer of one-page printing data (a sheet of label 300) stored in the K-1 area 26, the printing data is transferred to the printing data converter 28 for each line from the K-2 area 27. As a result, a black image, i.e., the commodity name of "orange" and the amount of "¥50" are printed black in the commodity frame 103b and the amount frame 102b of the second label 200. On the other hand, the black printing data of the third label 100 is fetched and stored in the K-1 area 26. when a page of the printing data of label 200 stored in the K-2 area 27 is completely transferred, the printing data of label 100 is transferred from the K-1 area 26 to the printing data converter 28 for each line. As a result, a black image, i.e., the commodity name of "strawberry" and the amount of "Y300" are printed black in the commodity frame 103a and the amount frame 102a, respectively, of the third label 100. The black printing data of the fourth label not shown following label 100 is fetched and stored in the K-2 area 27. In similar fashion, the image data of odd-numbered and even-numbered labels are transferred and stored alternately in the K-1 area 26 and the K-2 area 27. As described above, according to the first embodiment, the K head 4 for printing different printing data for each page is associated with two storage areas of the K-1 area 26 and the K-2 area 27 each for storing a page of printing data as bit map data, so that the printing data of the next label can be started to be stored in the storage area before complete transfer of the printing data of a label to the K head 4 through the printing data converter 28. In the case where a page of black printing data can be stored during the one-page printing period of each head, the storage period following the printing period can be eliminated at the print timing of the K head 4. Also, even in the case where a page of black printing data cannot be stored during the one-page printing period of each head, at least the above-mentioned storage period can be shortened at the print timing of the K head 4. As a consequence, the printing speed can be increased for continuous printing without being limited by the storage period for rewriting the printing data stored in the printing data storage unit 22. Although the fist embodiment refers to the case in which the two storage areas of K-1 area 26 and K-2 area 27 are provided for the black-printing K head 4, the invention is not limited to such a case, but two or more storage areas may be provided for at least one of the color heads 1-3. A second embodiment of the invention will be described with reference to FIGS. 6 and 7. The second embodiment has the same configuration of the essential parts of the color printer as the first embodiment shown in FIGS. 2 and 3. The same component parts of the second embodiment are therefore will be designated by the same reference numerals as the corresponding parts in FIGS. 2 and 3, respectively. FIG. 6 is a block diagram showing a circuit configuration of the essential parts of the color printer according to this embodiment. Printing data of one page is produced and edited by an image processing unit 41 and is stored temporarily as bit map data in the storage area formed in the printing data storage unit 42, i.e., in a Y-1 area 43-1, a Y-2 area 43-1, ···, a Y-n area 43-n for yellow, an M-1 area 44-1, an M-2 area 44-2, ···, an M-n area 44-n for magenta, a C-1 area 45-1, C-2 area 45-2, ···, a C-n area 45-n for cyan, and a K-1 area 46-1, a K-2 area 46-2, ···, a K-n area 46-n for black. The image processing unit 41 subjects the printing data stored in each area to parallel-serial conversion for each line through the printing data converter 28 and supplies the result to the units 29 to 32, respectively. The image processing unit 41 and the printer engine controller 33 are connected to the printing data storage unit 42 and the printing data converter 28 through the system bus 34. The embodiment shown in FIG. 6 is different from the embodiment of FIG. 3 in that the storage area in the image processing unit 41 is formed as a plurality of areas for each color other than black as well as for black. FIG. 7 is a diagram showing the flow of data transfer performed by the CPU of the image processing unit 41. First, step ST1 waits for a data transfer request from the printer engine controller 33. This waiting state can be interrupted by other processes. Upon receipt of a data transfer request from the printer engine controller 33, the color to be transferred is selected on the basis of the data transfer request and the printing page is confirmed. Then, an area to be read out is selected on the basis of the selected color and the confirmed printing page. In the case where the selected color is yellow and the printing page is the second page, for example, the Y-2 area 43-2 is selected as the area to be read out. The leading line of unprinted data is transferred from the read-out area thus selected to the printing data converter 28 thereby to decide whether the printing is complete or not. In the case where the decision is that the printing is not complete, the process is returned to step ST1. In the case where the decision is that the printing is complete, on the other hand, the data transfer process is terminated. The image processing unit 41 stores the printing data basically in the same manner as the image processing unit 21 according to the first embodiment. The printing data storage process of the image processing unit 41, therefore, will not be described below. In the case where it is confirmed that unprinted data is not stored in the Y-1 area 43-1, the Y-2 area 43-2, ···, the Y-n area 43-n sequentially, the printing data of the color (yellow) of the next label is stored in the corresponding area as bit map data. According to the second embodiment having this configuration, the printing data of yellow, magenta, cyan and black of the first label are sequentially stored in the Y-1 area 43-1, the M-1 area 44-1, the C-1 area 45-1 and the K-1 area 46-1. Then, the printing data of yellow, magenta, cyan and black of the second label are sequentially stored in the Y-1 area 43-2, the M-1 area 44-2, the C-1 area 45-2 and the K-1 area 46-2. In similar fashion, the printing data of each color of the third to n-th labels are stored sequentially in each area. Upon complete storage of the printing data, the printing operation is started. The printing operation may alternatively be started when the second printing data of black, the last printing color, is stored in the K-2 area 46-2. Description below will be made about the color of yellow. The other colors are processed concurrently in similar fashion. First, the image processing unit 41 transfers each line of the printing data from the Y-1 area 43-1 to the printing data converter 28. As a result, an yellow image is printed on the first label. Upon complete transfer of a page of printing data stored in the Y-1 area 43-1, each line of the printing data is transferred to the printing data converter 28 from the Y-2 area 43-2. An yellow image thus is printed on the second label. The yellow printing data of the (n+1)th label, on the other hand, is stored in the Y-1 area 43-1. Upon complete transfer of a page of printing data stored in the Y-2 area 43-2, each line of the printing data is transferred to the printing data converter 28 from the Y-3 area. As a consequence, a yellow image is printed on the third label. On the other hand, the yellow printing data of the (n+2)th label is stored in the Y-2 area 43-2. In similar fashion, the data transfer and storage are performed sequentially on rotation for each area. As described above, according to the second embodiment, since a plurality of storage areas are provided for storing a page of printing data as bit map data respectively, a similar effect to the first embodiment is obtained, while at the same time accommodating the case in which the printing data of each color are different for different pages. Now, a third embodiment of the invention will be described with reference to FIGS. 8 and 9. The configuration of the essential parts of the color printer according to the third embodiment is the same as that of the first embodiment shown in FIGS. 2 and 3, and therefore will be designated by the same reference numerals as the corresponding parts in FIGS. 2 and 3, respectively, and will not be described any further. FIG. 8 is a block diagram showing a circuit configuration of the essential parts of the color printer according to the third embodiment. In the embodiment of FIG. 8, an intermediate printing data storage unit 57 is added to the embodiment shown in FIG. 6, and the remaining parts are configured in the same way as the embodiment of FIG. 6. A page of printing data produced and edited by the image processing unit 51 is stored as bit map data temporarily in the storage areas formed in the printing data storage unit 52, including a Y-1 area 53-1, a Y-2 area 53-2, ···, a Y-n area 53-n for yellow, an M-1 area 54-1, an M-2 area 54-2, ···, an M-n area 54-n for magenta, a C-1 area 55-1, a C-2 area 55-2, ···, a C-n area 55-n for cyan, and a K-1 area 56-1, a K-2 area 56-2, ···, a K-n area 56n for black. The image processing unit 51, as described later, transfers a block of a plurality of lines of printing data stored in each area to the intermediate printing data storage unit 57. The intermediate printing data storage unit 57 has formed therein a Y2-1 area 58-1, a Y2-2 area 58-2, ···, a Y2-n area 58-n for yellow, an M2-1 area 59-1, an M2-2 area 59-2, ···, an M2-n area 59-n for magenta, a C2-1 area 60-1, a C2-2 area 60-2, ···, a C2-n area 60-n for cyan, and a K2-1 area 61-1, a K2-2 area 61-2, ···, a K2-n area 61-n for black, for storing a block of data including a plurality of lines, where n may be a numerical value constituting a sheet (page) of printing data or less than the particular numerical value according to the printing speed. The printer engine controller 62, as a printing control means, cooperates with the image processing unit 51 to subject each block of printing data stored in each area of the intermediate printing data storage unit 57 to parallel-serial conversion and other processes for each line and supply the result to the corresponding one of the units 29 to 32. Further, the printer engine controller 62 controls the print timing of the units 29 to 32 and executes the printing operation on the basis of the printing data supplied through the printing data converter 63. The image processing unit 51 and the printer engine controller 62 are connected through the first system bus 65 to the printing data storage unit 52 and the intermediate data storage unit 57 on the one hand, and to the intermediate printing data storage unit 57 and the printing data converter 63 through the second system bus 65. Further, the printing data is supplied for each line from the intermediate printing data storage unit 57 to the printing data converter 63. FIG. 9 is a diagram showing the flow of data transfer performed by the CPU of the image processing unit 51. First, step ST11 selects the color to be transferred on the basis of a predetermined sequence, searches the intermediate printing data storage unit 57 for an area corresponding to the selected color and thus decides whether there is any vacant area having no unprinted data. In the case where the decision is that no vacant area is available, the process returns to step ST11. In the case where the decision is that a vacant area is available, on the other hand, the page to be transferred is checked in the printing data storage unit 52 for the particular color, so that a block of unprinted data of the page to be transferred for which the selected color has been checked in the printing data storage unit 52 is transferred collectively to the vacant area. Upon complete transfer, the decision is made as to whether the printing is complete or not. If the printing is not yet complete, the process returns to step ST11. When the decision is that the printing is complete, on the other hand, the data transfer is completed. The printing data is printed and stored by the image processing unit 51 basically in the same manner as the black data are printed and stored by the image processing unit 21 according to the first embodiment. The printing and storage operation of the image processing unit 51, therefore, will not be described any more. According to the third embodiment of this configuration, the printing data are stored in each area of the printing data storage unit 52 in the same manner as in the second embodiment described above. Further, the printing data of the first block of the Y-1 area 53-1, the M-1 area 54-1, the C-1 area 55-1 and the K-1 area 56-1 storing the first page of printing data for each color is transferred sequentially to the Y2-1 area 58-1, the M2-1 area 59-1, the C2-1 area 60-1 and the K2-1 area 61-1 of the intermediate printing data storage unit 57. In similar fashion, the second block, the third block and so on, of the Y-1 area 53-1, the M-1 area 54-1, the C-1 area 55-1 and the K-1 area 56-1 are transferred sequentially to the corresponding areas of the intermediate printing data storage unit 57. The printing operation is started when all the first page of the printing data for each color has been transferred to the intermediate printing data storage unit 57, or as an alternative, when a predetermined number of blocks for each color has been transferred to the intermediate printing data storage unit 57 according to the printing speed. Explanation will be made with reference to the case of yellow. Other colors are also processed concurrently in similar fashion. To facilitate the understanding, one page of printing data is assumed to be configured of n blocks. First, the printer engine controller 62 transfers each line of the printing data from the Y2-1 area 58-1 of the intermediate printing data storage unit 57 to the printing data converter 63. As a result, an yellow image begins to be printed on the first label. Upon complete transfer of a block of printing data stored in the Y2-1 area 58-1, the printing data are transferred from the Y2-2 area 58-2 for each line to the printing data converter 63. When a block of the printing data stored in the Y2-1 area 58-1 is completely transferred to the printing data converter 63, the image processing unit 51 detects the Y2-1 area 58-1 as a vacant area in an area corresponding to yellow of the intermediate printing data storage unit 57, and transfers the leading block of printing data of the Y-2 area 53-2 of the printing data storage unit 52 collectively to the Y2-1 area 58-1. The above-mentioned basic process is repeated sequentially. Upon complete transfer of one block each of all the printing data stored in the Y2-n area 58-n, the printing data are transferred to the printing data converter 63 for each line from the Y2-1 area 58-1. As a result, the yellow image begins to be printed on the second label. At this time, the image processing unit 51 detects the Y2-n area 58-n as a vacant area in an area corresponding to yellow of the intermediate printing data storage unit 57, and transfers the last block of the printing data of the Y-2 area 53-2 of the printing data storage unit 52 collectively to the Y2-1 area 58-1. Upon complete transfer of the last block of printing data, the yellow printing data of the (n+2)th label is stored in the Y-2 area 53-2. In similar fashion, operations of transfer and storage are performed on rotation for each area of the intermediate printing data storage unit and each area of the printing data storage unit. As described above, according to the third embodiment comprising the intermediate printing data storage unit 57 divided into a plurality of areas each constituting a block including a plurality of lines of printing data (bit map data), the same effect is obtained as the second embodiment described above. At the same time, the image processing unit can transfer the printing data collectively in blocks but not for each line. A longer time is therefore allowed for other processes for an improved processing efficiency. The number of areas corresponding to each color of the printing data storage unit 52 and the intermediate printing data storage unit 57, which is explained above by the same constant n, may of course be different between the printing data storage unit 52 and the intermediate printing data storage unit 57. Instead, an appropriate number of areas may be set respectively according to the balance between the memory capacity and the printing speed. As described above, according to this invention, there is provided a color printer capable of increasing the printing speed in continuous printing without being limited by the storage period for rewriting the printing data stored in memory.

Claims: A printer comprising: a plurality of printing heads (1 to 4) arranged sequentially along a direction in which long printing paper (P) is fed; a plurality of page memories (23 to 26) each for storing printing data of one page for a corresponding printing head; means (28, 29 to 32) for printing an image on the printing paper (P) on the basis of the printing data of one page supplied from the page memory corresponding to each printing head sequentially; characterised by further comprising: a main page memory (26) and an auxiliary memory (27) for storing at least two continuous pages of printing data for at least one corresponding printing head (32); printing data write means (21) for writing a next page of printing data in one of said main page memory (26) and said auxiliary memory (27) while the printing data stored in the other one of said main page memory (26) and said auxiliary memory (27) is being printed; and print control means (33) for supplying printing data to a printing head alternately and continuously from a corresponding main page memory and a corresponding auxiliary memory. A printer according to claim 1, characterized in that an auxiliary memory (43 - 2 to 46 - n) is provided for each printing head. A printer according to claim 1, characterized in that said plurality of printing heads (1 to 4) are arranged for printing images of different colors. A printer according to claim 1, characterized by an intermediate memory (57) divided by a predetermined number of lines for each printing head; and said printing control means (62) serving to transfer a predetermined number of lines of printing data from a corresponding main page memory and an auxiliary memory to the intermediate memory, and supplying the printing data sequentially to a corresponding printing head from the intermediate memory. A printer according to claim 4, characterized in that an auxiliary memory (43-2 to 46-n) is provided for each printing head. A printer according to claim 4, characterized in that said intermediate memory (57) is provided for each line block including a predetermined number of lines of the printing head. A printer according to claim 1, characterized in that said plurality of printing heads (1 to 4) are arranged for printing images of different colors. A printer according to one of the preceding claims, characterized by said printing means including first, second, third and fourth printing heads (1 to 4) for printing yellow, magenta, cyan and black images respectively. A method of printing an image on a printing medium, comprising the steps of: arranging a plurality of printing heads (1 to 4) sequentially along the direction in which long printing paper (P) is fed; supplying printing data of one page from a plurality of page memories (23 to 27) provided for the corresponding printing heads; and printing the image on the printing paper (P) based on the printing data of one page supplied to each printing head sequentially; wherein the method is characterised by further comprising the steps of: storing in a main page memory (26) and an auxiliary memory (27) at least two continuous pages of printing data corresponding to at least one corresponding printing head (32); writing a next page of printing data in one of said main page memory (26) and auxiliary memory (27) while the printing data stored in the other one of said main and auxiliary memories is being printed; and supplying printing data to the corresponding printing head alternately and continuously from a corresponding one of said main and auxiliary memories (26, 27).

Inventors: FUSHIMI KAZUHIRO, ICHIKAWA TAKASHI, IGA KANAME, MIHARA HIDEMI, FUSHIMI, KAZUHIRO, ICHIKAWA, TAKASHI, IGA, KANAME, MIHARA, HIDEMI
Applicants: TOSHIBA TEC KK, TOSHIBA TEC KABUSHIKI KAISHA
Application year: 1996
Main classification: G06K15
IPC codes: B41J2, G06F3, B41J5, B41J35, G06K15