JP6552982B2 - Printing apparatus and printing method - Google Patents

Description

  The present invention relates to a printing apparatus and a printing method.

  BACKGROUND Conventionally, an inkjet printer that performs printing by an inkjet method is widely used. In an inkjet printer, printing is usually performed using an inkjet head (recording head) having a plurality of nozzles. In addition, in the ink jet head, a part of the nozzles may be abnormal and may become a non-ejection nozzle. On the other hand, the structure which performs the alternative process (alternative recording) which prints using another normal nozzle instead of a non-ejection nozzle is conventionally known (for example, refer patent documents 1-3).

  Patent Document 1 discloses a configuration using a recording head in which nozzles are arranged in two rows in the main scanning direction, and in the case where a non-ejection nozzle is generated, a dot is alternately ejected by an adjacent nozzle. In Patent Document 2, when one nozzle used for dot formation in an overlapping area with an adjacent print area fails to discharge, another nozzle used for dot formation in the overlapping area is used as an alternative nozzle. A configuration to determine is disclosed. Patent Document 3 discloses a method of alternative processing in the case where recording is performed in which the recording order is defined by limiting the nozzles used for each ink color.

JP 2005-67049 A JP 2012-125957 A JP 2011-156732 A

  When an alternative process is performed on a non-ejection nozzle, the print quality may be affected by the change in the position of the nozzle, the timing of ejection, and the like. For this reason, there are cases where the quality of printing cannot be improved appropriately by simply using other nozzles instead of non-ejection nozzles.

  On the other hand, for example, Patent Document 2 discloses that the occurrence of a new streak or the like is prevented by determining the size or density of dots to be formed in the alternative nozzle based on the dot distribution. Yes. Further, Patent Document 3 discloses, for substitution processing performed when a non-ejection nozzle is detected, assigning recording data corresponding to the non-ejection nozzle to a nozzle whose ink recording order does not change depending on whether or not substitution printing is performed. ing.

  However, in order to perform printing with higher quality, it is desirable to cope with nozzle abnormalities by a more appropriate method. Accordingly, an object of the present invention is to provide a printing apparatus and a printing method that can solve the above-described problems.

  As the abnormality of the discharge characteristic of the nozzle, for example, a non-discharge state can be considered as described above. Further, as the abnormality of the ejection characteristics other than the non-ejection, for example, an abnormality of the ejection speed or the ejection direction (bending angle), an abnormality of the amount of ink droplets (volume), etc. can be considered.

  In addition, when performing substitution processing with the conventional configuration, it is common to perform substitution processing by regarding discharge characteristic abnormalities other than complete non-ejection as non-ejection in a broad sense. That is, when performing the substitution process with the conventional configuration, the abnormal nozzle is set to a non-ejection nozzle that does not eject ink droplets even if it is not completely non-ejection, and the substitution process is performed.

  However, when the substitution process is performed by such a method, there is a case where a difference in state is conspicuous between the ink dots formed by the substitution process and the surrounding dots, and the print quality may be deteriorated. More specifically, for example, the dots of ink formed in the alternative process are normally formed in a pass different from the original pass in the multi-pass operation. Then, in this case, for example, the dots formed by the alternative process may be more noticeable due to the influence of the timing of forming the dots. In addition, for example, due to the influence of an error in the feed amount in the sub-scanning operation performed between passes, the shift of the position of the dot formed in the alternative process may be noticeable. In addition, due to these effects, the continuity of the arrangement of the ink dots may be reduced, and the print quality may be reduced.

  In addition, when many abnormal nozzles exist near the end of the nozzle row in which the plurality of nozzles are arranged in the inkjet head, if all the abnormal nozzles are not ejected, the area where the ink droplets can be ejected in the nozzle row is significantly reduced. It will be done. As a result, it is conceivable that printing productivity decreases.

  In contrast, the inventor of the present application, based on earnest research, causes ink droplets to be ejected to a part of ejection positions, rather than setting abnormal nozzles that can eject ink droplets to non-ejection nozzles completely. Thought. Further, in this case, it has been found that by making the ratio of the discharge position for discharging the ink droplet smaller than that at the normal time, the influence of the abnormality of the discharge characteristic can be suppressed and the print quality can be enhanced. Furthermore, it has been found that by replacing ink droplets at some discharge positions with an abnormal nozzle, the dots formed at the same timing as in the normal state remain to some extent, and a substitute process can be performed with a more natural impression. .

  That is, in order to solve the above-described problems, the present invention is a printing apparatus that performs printing on a medium by an ink jet method, in which a plurality of nozzles that respectively eject ink droplets by an ink jet method are arranged in a predetermined direction. An ink jet head having a row and a control unit for controlling the discharge of ink droplets from each of the nozzles in the ink jet head, wherein the nozzles having discharge characteristics within a preset normal range are defined as normal nozzles The nozzles whose ejection characteristics deviate from the normal range are defined as abnormal nozzles, and for each of the nozzles in the nozzle row, the ejection position for ejecting ink droplets when the nozzle is the normal nozzle is normal. When the discharge target position is further defined, any one of the nozzles in the nozzle row is When the nozzle is an abnormal nozzle, the control unit applies an ink droplet to the abnormal nozzle with respect to a part of the normal ejection target positions set when the abnormal nozzle is the normal nozzle. Discharge the

  When configured in this way, for example, by reducing the number of ejection positions at which ink droplets are ejected by an abnormal nozzle, it is possible to appropriately suppress the influence of abnormal ejection characteristics. In this case, the abnormal nozzles are not completely set as non-ejection nozzles, but are caused to eject ink droplets to a part of the ejection positions, for example, the arrangement of ink dots formed on the medium. In order to improve the continuity of the nozzle, the influence of the nozzle at the position of the abnormal nozzle can be left to some extent. Also, this makes it possible, for example, to carry out substitution processing with a more natural impression than when performing substitution processing completely as in the conventional configuration, for example. Therefore, if configured in this way, for example, the influence of the abnormal nozzle can be appropriately suppressed, and high-quality printing can be appropriately performed. In addition, for example, it is possible to cope with a nozzle abnormality by a more appropriate method and form a high-quality image.

  In addition, in this configuration, when any nozzle in the nozzle row is an abnormal nozzle, the control unit causes ink to be ejected to nozzles other than the abnormal nozzle for ejection positions other than a part of the ejection positions at the normal ejection target position. It is preferable to eject droplets. According to this configuration, for example, an alternative process using a normal nozzle instead of the abnormal nozzle can be appropriately performed on the discharge positions other than the partial discharge position at the normal discharge target position. Moreover, thereby, for example, high quality printing can be performed more appropriately.

  Further, it is preferable that this printing apparatus perform printing in a multipass method, for example. In this case, the control unit causes the ink jet head to perform the main scanning operation a plurality of times with the sub scanning operation interposed between each position of the medium. The main scanning operation is, for example, an operation of ejecting ink droplets while moving in a preset main scanning direction. Further, the sub scanning operation is, for example, an operation in which the inkjet head moves relative to the medium in the sub scanning direction orthogonal to the main scanning direction.

In this case, in each main scanning operation, each nozzle in the inkjet head ejects ink droplets to a part of ejection positions selected according to a preset duty. In addition, when all the nozzles in the nozzle row are normal nozzles, the duty set for each nozzle is set as a normal duty, and when any nozzle is an abnormal nozzle, the duty is set for each nozzle. When the abnormal duty is the abnormal duty, the control unit sets a value larger than 0 and smaller than the normal duty as the abnormal duty for the abnormal nozzle. In this case, the duty of other nozzles is increased in accordance with the duty lowered with respect to the abnormal nozzle. With this configuration, for example, the abnormal nozzle replacement process can be appropriately performed while causing the abnormal nozzle to eject ink droplets to a part of the ejection positions.

  In this case, it is preferable to perform the substitution process similar to the abnormal nozzle for a plurality of nozzles including the nozzles around the abnormal nozzle, instead of selecting the abnormal nozzle alone and performing the substitution process. With this configuration, for example, the replacement process can be performed more appropriately while further improving the continuity with the surroundings. Also, in this case, for example, by performing replacement processing in units of nozzle groups including a plurality of nozzles, for example, even if the position of the abnormal nozzle is not completely specified, if the group including the abnormal nozzle is known, the replacement processing You can do it properly. Therefore, if constituted in this way, substitution processing can be performed more simply and appropriately, for example.

  Moreover, it is preferable that the selection ratio for selecting the ejection position for ejecting ink droplets to the abnormal nozzle can be changed in a plurality of stages. In this case, for example, for an abnormal nozzle, it may be possible to determine the selection ratio according to the degree of abnormality in the ejection characteristics. More specifically, for example, when the ejection characteristics are closer to the normal range, it is conceivable to use a selection ratio for selecting more ejection positions. In addition, it is conceivable to use a selection ratio for selecting a smaller number of discharge positions when the discharge characteristics are further away from the normal range.

  In addition, if the ejection characteristics of the abnormal nozzle deviate from the normal range beyond the predetermined allowable range, ink droplets are not ejected even at some ejection positions, and the nozzles are completely non-ejection. It may be set. If comprised in this way, even when a nozzle with a large abnormality degree exists, for example, a substitute process can be performed more appropriately.

  Moreover, it is also considered to use the printing method which has the characteristic similar to the above as a structure of this invention. Also in this case, for example, the same effect as described above can be obtained.

  According to the present invention, for example, nozzle abnormalities can be dealt with in a more appropriate manner.

FIG. 1 is a diagram showing an example of a printing apparatus 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the main part of the printing apparatus 10. FIG. 1B illustrates an example of the configuration of the head unit 12 in the printing apparatus 10. FIG. 1C illustrates an example of the configuration of the inkjet head 102 in the head unit 12. It is a figure which shows an example of the operation | movement of the multipath system performed in this example. FIG. 2A is a diagram schematically showing the operation of the multipath method. FIGS. 2B and 2C are diagrams showing an example of the arrangement of ink dots 302 formed on the medium 50 by the operation of the multipass method. FIG. 7 is a diagram illustrating an example of a main scanning operation capable of ejecting an ink droplet to the position of one dot 302. FIG. 3A shows an example of a pass that can eject an ink droplet to the position of each dot 302. FIG. 3B shows an example of a pass which can eject an ink droplet to the position of each dot 302 when the number of passes which can form the dot 302 in principle is larger. It is a figure explaining an example of the operation | movement of correction | amendment performed in this example. FIG. 4A is a view showing an example of the arrangement of the dots 302 when there is no abnormal nozzle. FIG. 4B shows an example of the case where the abnormal nozzle is set as a non-ejection nozzle and the substitution process is performed. FIG. 4C is a diagram showing an example of the correction operation performed in this example. FIGS. 4D and 4E show another example of the discharge position for causing the abnormal nozzle to discharge the ink droplet. FIG. 4F shows another example of the correction operation performed in this example. It is a figure explaining the operation | movement which correct | amends a duty. FIG. 5A is a diagram showing an example of the operation of correcting the duty. FIG. 5B is a diagram showing another example of the operation of correcting the duty. It is a figure which shows an example of the structure which correct | amends a duty by a preset group unit. It is a figure which shows the various examples of the setting of a duty, and the method of correction | amendment. FIGS. 7A and 7B show examples of setting and correction of duty. It is a figure which shows the various examples of the setting of a duty, and the method of correction | amendment. 8A, 8B, and 8C show examples of duty setting and correction. It is a figure which shows the various examples of the setting of a duty, and the method of correction | amendment. FIGS. 9A and 9B show examples of duty setting and correction.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of a printing apparatus 10 according to an embodiment of the present invention. FIG. 1A shows an example of the configuration of the main part of the printing apparatus 10. FIG. 1B illustrates an example of the configuration of the head unit 12 in the printing apparatus 10. FIG. 1C illustrates an example of the configuration of the inkjet head 102 in the head unit 12.

  Note that, except for the points described below, the printing apparatus 10 of this example may have the same or similar configuration as a known inkjet printer. For example, the printing apparatus 10 may further have various known configurations necessary for the printing operation, in addition to the illustrated configuration.

  The printing apparatus 10 is an inkjet printer that performs printing on a medium 50 to be printed using an inkjet method, and includes the head unit 12, the platen 14, the heater 16, the main scanning drive unit 18, the sub scanning drive unit 20, and a multi A path control information storage unit 22 and a control unit 24 are provided. Further, in this example, the printing apparatus 10 performs printing on the medium 50 using the evaporation-drying type ink that fixes the medium 50 by volatilizing and removing the solvent in the ink. As the evaporation drying ink, for example, a solvent ink using an organic solvent as a solvent can be suitably used. Further, it is also conceivable to use various aqueous inks as the evaporation-drying type ink. Further, in a modification of the configuration of the printing apparatus 10, the printing apparatus 10 may perform printing using an ink other than the evaporation drying type, such as an ultraviolet curing ink, for example. In this case, it is preferable that the specific configuration of the printing apparatus 10 is appropriately changed according to the ink to be used.

  The head unit 12 is a part that ejects ink droplets onto the medium 50. In the present example, the head unit 12 includes a plurality of inkjet heads 102. The plurality of ink-jet heads are print heads that eject ink droplets by an ink-jet method. For example, as shown in FIG. 1B, the plurality of ink-jet heads are arranged side by side in a preset main scanning direction (Y direction and scanning direction in the figure). Established. Further, in the present embodiment, the plurality of inkjet heads eject ink droplets of different colors. More specifically, each of the plurality of inkjet heads 102 ejects ink droplets of each color for color printing, such as each color of yellow (Y), magenta (M), cyan (C), and black (K). To do.

  Further, as shown in FIG. 1C, for example, each inkjet head 102 has a nozzle row 204 in which a plurality of nozzles 202 for respectively discharging ink droplets are arranged in a predetermined direction. More specifically, in the nozzle row 204 of the inkjet head 102, the plurality of nozzles 202 are arranged at a constant nozzle interval (nozzle pitch) in the sub-scanning direction (X direction and feed direction in the drawing) orthogonal to the main scanning direction. Lined with). In the printing operation, the inkjet head 102 discharges ink droplets from the respective nozzles 202 to the respective positions on the medium 50 by performing a main scanning operation of discharging ink droplets while moving in the main scanning direction. .

  The platen 14 is a trapezoidal member that holds the medium 50, and holds the medium 50 facing the head portion 12 by placing the medium 50 on the upper surface at a position facing the head portion 12. Further, in the present embodiment, the platen 14 accommodates the heater 16 therein.

  The heater 16 is a heater that heats the medium 50. In the present embodiment, the heater 16 heats the medium 50 at a position facing the head unit 12 with the medium 50 in the platen 14. Also, the ink on the medium 50 is dried and the ink is fixed on the medium 50.

  The heater 16 is an example of a fixing unit that fixes the ink on the medium 50. In the modification of the printing apparatus 10, when ink other than the evaporation drying type is used, it is preferable to use a fixing unit corresponding to the type of ink instead of the heater 16. For example, when an ultraviolet curable ink is used, it is conceivable to use an ultraviolet light source as the fixing means.

  The main scanning driving unit 18 is a driving unit that causes the inkjet head 102 in the head unit 12 to perform a main scanning operation. In the present example, the main scanning drive unit 18 causes each of the moving inkjet heads 102 to eject ink droplets from the nozzles 202 while moving the plurality of inkjet heads 102 in the head unit 12 in the main scanning direction, for example. The main scanning operation is performed on each of the inkjet heads 102.

  The sub scanning drive unit 20 is a driving unit that causes the inkjet head 102 to perform a sub scanning operation that moves relative to the medium 50 in the sub scanning direction. In this example, the sub scanning drive unit 20 moves the inkjet head 102 relative to the medium 50 by transporting the medium 50 in the transport direction parallel to the sub scanning direction. Further, the sub scanning drive unit 20 transports the medium 50 between main scanning operations. As a result, the sub scanning drive unit 20 shifts the position of the medium 50 facing the ink jet head 102, and changes the area on the medium 50 that is the target of the next main scanning operation. In a modification of the configuration of the printing apparatus 10, for example, the position of the medium 50 may be fixed, and the sub scanning operation may be performed by moving the head unit 12.

  The multi-pass control information storage unit 22 is a storage unit that stores (stores) information used for controlling the printing operation in the multi-pass method. In this case, the multi-pass method also means, for example, a method (multi-pass recording method) in which printing is performed by performing a plurality of main scanning operations on each position on the medium 50. The multi-pass control information storage unit 22 stores, for example, a preset mask (mask data) as information used to control the printing operation in the multi-pass method. In this case, the mask is, for example, data that designates an ink droplet ejection target in each main scanning operation.

  More specifically, for example, from among the ejection positions that can be ejected in principle in the main scanning operation of each time, the mask, according to the number of passes in the multipass method, ink droplets in the main scanning operation of each time. Specify the discharge position to be discharged. In this case, the ejection positions that can be ejected in principle in each main scanning operation are, for example, that ink droplets are ejected when the main scanning operation is performed so as to eject as many ink droplets as possible without using a mask. Discharge position. Further, the ejection position may be a target position for ejecting ink droplets.

  In this example, the multi-pass control information storage unit 22 further stores correction data, which is data used for correction performed when there is an abnormal nozzle. In this case, the abnormal nozzle is the nozzle 202 whose ejection characteristic is out of the normal range set in advance. Further, in this case, the nozzles 202 other than the abnormal nozzles in the nozzle row 204 are treated as normal nozzles. In this case, a normal nozzle is a nozzle whose discharge characteristic is in a normal range. Further, the correction operation performed when there is an abnormal nozzle will be described in more detail later.

  The control unit 24 is, for example, a CPU of the printing apparatus 10 and controls the operation of each unit of the printing apparatus 10. More specifically, the control unit 24 controls the operation of the main scanning drive unit 18 and the sub-scanning drive unit 20 based on image data indicating an image to be printed, for example, on the medium 50. The desired image is printed on the inkjet head 102.

  In this example, the control unit 24 further controls the operations of the main scanning drive unit 18 and the sub-scanning drive unit 20 to cause the inkjet head 102 to perform multi-pass printing. In this case, in each main scanning operation, the control unit 24 causes the ink jet head 102 to eject ink droplets to the ejection position specified by the mask based on the mask stored in the multipass control information storage unit 22. Further, as a result, the control unit 24 controls the discharge of ink droplets from the respective nozzles 202 in the ink jet head 102 in each main scanning operation.

  Further, more specifically, in the main scanning operation of each time, the control unit 24 causes, for example, each nozzle 202 of the nozzle row in the inkjet head 102 to discharge the ink droplet in accordance with the pattern of the mask. To cause the ink jet head 102 to discharge ink droplets according to a mask means, for example, setting the discharge position at which each nozzle 202 discharges ink droplets to the discharge position designated by the mask. Further, in this case, the ejection position is, for example, the position on the medium 50 to be ejected with the ink droplet from the nozzle 202 of the inkjet head 102. In addition, this ejection position is a position corresponding to any of a plurality of pixels constituting an image to be printed. According to this embodiment, for example, printing can be appropriately performed on the medium 50 by the printing operation in the multipass method.

  Further, as described above, in the printing apparatus 10 of this example, when the nozzle row 204 includes an abnormal nozzle, a correction operation is performed. In this case, the control unit 24 performs a correction operation based on the correction data stored in the multipath control information storage unit 22. Hereinafter, the correction operation performed when there is an abnormal nozzle will be described in more detail.

  The operation of the multi-pass method performed in this example is the same as or similar to the operation of the known multi-pass method except for the correction operation performed when there is an abnormal nozzle. That is, it can be said that the operation of the multipass system performed in the case where there is no abnormal nozzle is the same as or similar to the operation of the known multipass system. Therefore, first, the operation of the multi-pass method performed in the case where there is no abnormal nozzle will be described.

  FIG. 2 shows an example of the multipath operation performed in this example. FIG. 2A is a diagram schematically showing the operation of the multi-pass method. Regarding the main scanning operation for the number of printing passes, the position of the position in the sub-scanning direction of the inkjet head 102 during each main scanning operation is shown. An example is shown.

  When printing by the multi-pass method, the main scanning driving unit 18 and the sub scanning driving unit 20 (see FIG. 1) cause the inkjet head 102 to repeatedly perform the main scanning operation and the sub scanning operation. In this case, the positional relationship between each position of the medium 50 (see FIG. 1) and the nozzle array of the inkjet head 102 is equal to the pass width by setting the feed amount in each sub-scanning operation to a preset pass width. Shift only one by one. The feed amount in the sub scanning operation is, for example, a movement amount for moving the inkjet head 102 relative to the medium 50 at the time of the sub scanning operation. This also sequentially changes the nozzles that eject ink droplets to each position of the medium 50 in each main scanning operation. More specifically, in FIG. 2A, regarding the case where the number of printing passes is eight, the sub-scanning direction for the inkjet head 102 at the time of the first to eighth main scanning operations (first to eighth passes) Indicates the position in

  FIGS. 2B and 2C are diagrams showing an example of the arrangement of ink dots 302 formed on the medium 50 by the operation of the multipass method, where the number of printing passes is 8 (eight passes). An example of an ink dot array formed by one inkjet head 102 will be described. FIG. 2B is a diagram showing each dot 302 with a different pattern for each time of the main scanning operation with respect to the arrangement of the ink dots 302 formed in each main scanning operation (first to eighth passes). . FIG. 2C is a view extracting and showing the dots 302 in the area 310 indicated by a broken line in FIG. 2B.

  In FIG. 2B, for convenience of explanation, the arrangement of the dots 302 in the case where the dots 302 are formed at the positions of all the pixels arranged at the printing resolution is illustrated. At the time of actual printing, the dots 302 are not necessarily formed at the positions of all the pixels, but for example, dots 302 are formed at positions selected according to the image to be printed.

  When printing is performed by a multipass method, for example, as shown in FIG. 2B, ink dots 302 are formed at different positions in each main scanning operation. Further, thereby, the plurality of dots 302 are formed side by side so that the ink dots 302 are arranged at intervals corresponding to the printing resolution.

  In this case, more specifically, for example, when attention is paid to the dots 302 in a predetermined unit area such as the eight dots 302 in the area 310 in FIG. One dot 302 is formed in each of the eighth pass). For example, in the first main scanning operation (first pass) performed on the area 310, the dots 302 indicated by adding a numeral 1 in FIG. 2C are formed. Further, in each of the second to eighth main scanning operations (second to eighth passes), dots 302 indicated by numerals 2 to 8 in FIG. With this configuration, for example, the operation in the multipal system can be appropriately performed.

  Here, the effects and the like obtained by performing printing by the multipass method will be described. When printing is performed by a multipass method, for example, printing with high resolution, reducing the influence of the discharge characteristics of individual nozzles, and the like can be performed.

  More specifically, when only one main scanning operation is performed for each position of the medium 50, the resolution of printing is limited by the configuration of the inkjet head 102 and the like. For example, when the nozzle spacing in the sub scanning direction in the nozzle row of the inkjet head 102 is Lx0, the minimum spacing in the sub scanning direction of the dots 302 formed in one main scanning operation is Lx0.

  Further, during the main scanning operation, each nozzle of the inkjet head 102 ejects ink droplets according to the ejection signal. Therefore, the ejection time interval when ejecting ink droplets continuously becomes equal to the cycle of the drive signal. Further, as a result, when the distance obtained by the product of the moving speed of the inkjet head 102 at the time of main scanning operation and the period of the drive signal is Ly0, in the main scanning direction of the dots 302 formed in one main scanning operation. The minimum interval is Ly0. That is, when only one main scanning operation is performed for each position of medium 50, the distance between dots 302 in the sub scanning direction is Lx0 or more, and the distance between dots 302 in the main scanning direction is Ly0 or more .

  On the other hand, when printing by the multi-pass method, by shifting the positions where the dots 302 are formed in each main scanning operation (pass) from each other, the interval between the dots 302 in the finally obtained dot 302 arrangement can be changed. It can be made smaller. For example, in the case shown in FIG. 2B, the multi-pass method is performed by forming the dots 302 by another main scanning operation between the arrangements of the dots 302 that can be formed by one main scanning operation. The distance Lxp between the dots 302 in the sub-scanning direction in the case of printing in is set smaller than Lx0. Further, the distance Lyp between the dots 302 in the main scanning direction when printing by the multi-pass method is made smaller than Ly0. More specifically, in the illustrated case, Lxp is 1/2 of Lx0. Also, Lyp is 1/2 of Ly0. As described above, by performing printing in a multipass method, high printing resolution can be appropriately realized.

  In this case, as is apparent from the figure, the dots 302 formed by different main scanning operations are mixedly arranged in the row of dots 302 arranged in the main scanning direction. That is, in this case, a row of dots 302 aligned in the main scanning direction is formed using a plurality of nozzles. In this case, compared to the case where all the dots 302 in one row are formed by using only one nozzle, it is possible to average the discharge characteristics of the nozzles and suppress the influence of the discharge characteristics of the individual nozzles. Therefore, by performing printing in a multipass method, it is also possible to suppress the influence of the ejection characteristics of the individual nozzles. This also makes it possible to perform high-quality printing more appropriately.

  Here, in the case illustrated, the interval in the main scanning direction of the dots 302 actually formed in one main scanning operation is larger than the minimum interval Ly0 that can be formed. In this case, for example, the row of dots 302 aligned in the main scanning direction can be divided into more main scanning operations. In addition, this makes it possible to more appropriately suppress the influence of the ejection characteristics of individual nozzles and more appropriately perform high quality printing. More specifically, in the illustrated case, the interval in the main scanning direction of the dots 302 actually formed by one main scanning operation is twice as large as Ly0. That is, in this case, in principle, it can be said that the dots 302 that can be formed by one main scanning operation are formed separately in two main scanning operations.

  In this case, if attention is paid to the position of each dot 302, it can be said that there are a plurality of main scanning operations (passes) capable of ejecting ink droplets to the position of one dot 302 in principle. More specifically, for example, in the case shown in FIG. 2, the number of main scanning operations that can eject ink droplets to the positions of the respective dots 302 is two.

  FIG. 3 shows an example of a main scanning operation (pass) capable of ejecting an ink droplet to the position of one dot 302. FIG. 3A shows an example of a pass that can eject ink droplets to the positions of the respective dots 302 in the case of performing the operation of the multi-pass method shown in FIG.

  In the drawing, each of the eight squares indicates the position of each of the eight dots 302 shown in FIG. 2C. Also, in each square, numbers shown without parentheses indicate paths forming dots 302 at the positions during normal operation. In this case, the normal operation time is, for example, the operation time in the case shown in FIG. Also, numbers shown in parentheses indicate paths in which the dots 302 can be formed at the positions in principle, other than the paths that form the dots 302 in normal operation.

  Further, in this case, as described above, the number of passes through which the ink droplet can be discharged to the position of each dot 302 is two. Therefore, at each dot 302 position, the number of passes in which the dot 302 can be formed is 1 except during normal operation. More specifically, for example, in the case of the leftmost square position in the upper row, the dot 302 is formed in the first pass during normal operation. In addition, in principle, the dot 302 can be formed even in the third pass. In addition, also at the positions of the other squares, similarly, paths in which the dots 302 can be formed in principle are shown.

  Here, with respect to the position of each dot 302, a path that can form the dot 302 in principle other than a path that forms the dot 302 during a normal operation can be considered as a path that can be used in an alternative process. Also in the present example, such a relationship is used to perform correction when there is an abnormal nozzle, as will be described in detail later.

  Further, as is clear from the above description, the number of passes in which the dots 302 can be formed in principle at the positions of the respective dots 302 is the number of passes 302 actually formed in one main scanning operation in the main scanning direction. It depends on the relationship between the interval and the minimum interval Ly0 described above. For this reason, when the interval in the main scanning direction of the dots 302 that are actually formed in one main scanning operation is larger, the number of passes in which the dots 302 can be formed in principle increases.

  FIG. 3B shows an example of a pass which can eject an ink droplet to the position of each dot 302 when the number of passes which can form the dot 302 in principle is larger. More specifically, in the illustrated case, the interval in the main scanning direction of the dots 302 actually formed in one main scanning operation is four times Ly0.

  In this case, the number of passes in which the dot 302 can be formed is three at the position of each dot 302 except during normal operation. More specifically, for example, in the case of the leftmost square position in the upper row, the dot 302 is formed in the first pass during normal operation. In addition, in principle, the dots 302 can be formed in the third, fifth, and seventh passes. In addition, also at the positions of the other squares, similarly, paths in which the dots 302 can be formed in principle are shown.

  When the interval in the main scanning direction of the dots 302 formed in one main scanning operation is larger than the minimum interval Ly0, the number of necessary main scanning operations (the number of passes) increases accordingly. Also, as a result, the printing speed will be reduced. That is, it can be said that there is a trade-off between the printing quality and the printing speed. For this reason, the number of printing passes is preferably determined according to the required printing quality, the required printing speed, and the like.

  Subsequently, the correction operation performed when there is an abnormal nozzle will be described. FIG. 4 is a diagram for explaining an example of the correction operation performed in this example. FIG. 4A is a diagram illustrating an example of the arrangement of dots 302 when there is no abnormal nozzle, and illustrates an example of the arrangement of a plurality of dots 302 arranged in the main scanning direction at intervals according to the printing resolution. The arrangement of the dots 302 shown in FIG. 4A is an extraction of the arrangement of the dots 302 in the main scanning direction from the arrangement of the dots 302 shown in FIG. 2B. Also in FIG. 4A, as in FIG. 2B, dots 302 formed in each main scanning operation are shown with different patterns.

  As described with reference to FIG. 2, in this example, the inkjet head 102 (see FIG. 1) is configured to perform a plurality of main scanning operations (passes) in the multi-pass method by arranging the dots 302 in the main scanning direction. ). As a result, as shown in FIG. 4A, in the arrangement of the dots 302 in the main scanning direction, the dots 302 formed by different main scanning operations are mixedly arranged.

  Further, in the operation in the multipass method, the dots 302 having the same pattern in FIG. 4A are formed by the same nozzles in the nozzle row. Also, the dots 302 having different patterns are formed by different nozzles. Therefore, when any of the nozzles used for forming the dots 302 shown in FIG. 4A is an abnormal nozzle, the plurality of dots 302 shown in the same pattern are affected. More specifically, for example, in the case where the nozzle that forms the dot 302 at the position indicated by the symbol A in FIG. 4A is an abnormal nozzle, it is indicated by the symbols A, B, C, and D. In the case of the dots 302 having the same pattern, the influence of the abnormality of the ejection characteristics is generated. In this case, if the nozzles that form the other dots 302 are normal nozzles, the other dots 302 are formed normally.

  On the other hand, in order to suppress the influence of abnormal nozzles, for example, it is conceivable that abnormal nozzles are set as non-ejection nozzles so that ink droplets are not ejected. In this case, for example, as in the configuration of a conventional printing apparatus, it is conceivable to perform an alternative process (recovery) in which ink droplets are ejected from another normal nozzle instead of an abnormal nozzle.

  FIG. 4B shows an example of the case where the abnormal nozzle is set as a non-ejection nozzle and the substitution process is performed. Like the multi-pass method described with reference to FIGS. 2 and 3, the interval in the main scanning direction of the dots 302 that are actually formed in one main scanning operation is larger than the minimum interval that can be formed. In this case, the number of main scanning operations (passes) that can eject ink droplets to the positions of the respective dots 302 is a plurality of times. More specifically, when the pattern of the dots 302 formed in each main scanning operation (1st to 8th passes) is shown as in FIG. 2C, reference numerals A, B, C, The dot 302 with D is formed in the first pass. Further, as described with reference to FIG. 3A, in principle of operation, the dots 302 at these positions can be formed also in the third pass other than the first pass.

  Therefore, when the abnormal nozzle is completely set as a non-ejection nozzle and the substitution process is performed, for example, if the nozzle that forms the dots 302 with the symbols A, B, C, and D in the first pass is an abnormal nozzle, It is conceivable that the dots 302 at these positions are formed in the third pass. Further, in FIG. 4B, when such an alternative process is performed, only the dots 302 at the positions of the symbols A, B, C, and D are extracted from the arrangement of the dots 302 shown in FIG. Is shown.

  According to this configuration, it is possible to appropriately suppress the influence of the abnormal nozzle by not forming the dot 302 on the abnormal nozzle. In addition, by forming the dots 302 with other normal nozzles instead of the abnormal nozzles, it is possible to prevent the dots 302 from being missed.

  However, when the alternative process is performed in this manner, as described above, the difference in state is noticeable between the ink dots formed by the alternative process and the surrounding dots, and the printing quality is improved. May decrease. More specifically, for example, the dot formed by the alternative process may be more noticeable due to the influence of the timing of forming the dot. In addition, for example, due to the influence of an error in the feed amount in the sub-scanning operation performed between passes, the shift may be noticeable at the position of the dot formed in the alternative process. In addition, due to these influences, the continuity of the states of the pixels constituting the image may be reduced, and the print quality may be reduced.

  Further, dots formed by the alternative processing are particularly noticeable when printing with high accuracy (high resolution), for example. In addition, for example, when the printing surface is mat-like as in the case of using an ultraviolet curable ink, the change in appearance depending on the surface state becomes remarkable, and the dots formed by the alternative process are easily noticeable. . Therefore, in these cases, it is considered that the print quality is particularly likely to be degraded.

  For example, when there are many abnormal nozzles near the end of the nozzle row, if all the abnormal nozzles are not ejected, the area in which ink droplets can be ejected in the nozzle row is greatly reduced. Moreover, as a result, it is possible that the productivity of printing falls.

  On the other hand, in this example, as will be described in detail below, the ratio of the dots 302 to be formed while forming some of the dots 302 even with the abnormal nozzles, rather than causing the abnormal nozzles to completely fail to discharge. Reduce. According to this structure, for example, the influence of the abnormal nozzle can be suppressed while suppressing the problem caused by the substitution process. This also makes it possible to more appropriately suppress the influence of abnormal nozzles even when, for example, high-precision printing is performed or when the change in appearance due to the surface state becomes significant. In addition, even in the case where many abnormal nozzles exist near the end of the nozzle row, for example, it is possible to secure more regions where the ink droplets can be discharged in the nozzle row. Also, this can appropriately suppress the decrease in printing productivity caused by the alternative process.

  FIG. 4C is a diagram showing an example of the correction operation performed in this example. In FIG. 4A, the nozzle that forms the dots 302 with the symbols A, B, C, and D in the first pass is shown. In the case of an abnormal nozzle, an example of a pass for forming dots 302 at each of positions A, B, C, and D will be shown. In the case shown in the figure, among the dots 302 at positions A, B, C, and D, dots 302 at positions B and D, which are some positions, are formed in the first pass, and at other positions. The dots 302 at positions A and C are formed in the third pass. Further, in this case, it can be said that the dots 302 at positions B and D are formed by abnormal nozzles, and the dots 302 at the positions A and C are formed by other normal nozzles.

  In such a configuration, a part of the dots 302 that should originally be formed by the abnormal nozzles are formed by other normal nozzles, thereby reducing the number of dots 302 formed by the abnormal nozzles, and appropriately affecting the influence of the abnormal nozzles. It can be suppressed. In this case, the dot 302 at the position that should normally be formed by the abnormal nozzle is the dot 302 at the position that should be formed by the nozzle when the abnormal nozzle is a normal nozzle.

  In this case, the abnormal nozzles are not completely ejected, but some of the dots 302 are formed as they are with the abnormal nozzles, so that some of the dots 302 that are formed in the original state in which the substitution process is not performed remain. be able to. Also, with this, for example, the influence of the dots 302 at the position of the abnormal nozzle can be left to a certain extent so as to enhance the continuity and the like of the arrangement of the ink dots formed on the medium. More specifically, it is possible to appropriately suppress the influence caused by the alternative processing, such as the influence of timing of forming dots, the influence of an error of the feed amount, and the like.

  Therefore, according to this example, for example, it is possible to appropriately suppress the influence of the abnormal nozzle while suppressing problems caused by the substitution process. In addition, for example, the replacement process can be performed with a more natural impression as compared with the case where the replacement process is performed with, for example, the abnormal nozzles being completely non-ejected.

  Further, when the correction operation performed in this example is considered in a more general manner, when any nozzle in the nozzle row is an abnormal nozzle, the control unit 24 (see FIG. 1) of the printing apparatus 10 (see FIG. 1). Thus, it can be considered that the abnormal nozzle ejects ink droplets to a part of the normal ejection target positions set when the abnormal nozzle is a normal nozzle. In this case, the normal discharge target position is a discharge position for discharging an ink droplet when each nozzle in the nozzle row is a normal nozzle. For example, in the case shown in FIG. 4A, the normal ejection target position corresponding to the nozzle that ejects ink droplets in the first pass is the position of the dot 302 indicated by reference signs A, B, C, and D. . Further, in this example, when any nozzle is an abnormal nozzle, the control unit 24 applies ink droplets to nozzles other than the abnormal nozzle with respect to ejection positions other than a part of the ejection positions in the normal ejection target position. Discharge.

  Further, in this example, the normal nozzles of the nozzle array form a plurality of dots 302 aligned in the main scanning direction in each main scanning operation. Therefore, the arrangement of a plurality of ejection positions at which ink droplets are ejected by one normal nozzle in one main scanning operation can be defined as one row of normal ejection target positions. In this case, a normal ejection target position in a row is a single main scanning operation by one normal nozzle, such as the plurality of dots 302 indicated by reference characters A, B, C, and D in FIG. It is a row of dots 302 formed. When one row of normal discharge target positions is defined as described above, when any nozzle in the nozzle row is an abnormal nozzle, the operation of the control unit 24 includes one row of main scanning operations. This can be considered as an operation of ejecting ink droplets to the abnormal nozzles with respect to a part of the ejection positions in the normal ejection target position. In this case, for example, in another main scanning operation, the control unit 24 sets the nozzles other than the abnormal nozzles to the ejection positions other than the partial ejection positions in the normal ejection target position of the row. Eject ink droplets.

  Further, as is apparent from the generalized concept as described above, in the case where some of the dots 302 are formed by abnormal nozzles, the ejection positions for ejecting ink droplets to the abnormal nozzles are shown in FIG. Not limited to the case, it can be changed variously. In this case, the ejection position for ejecting ink droplets to the abnormal nozzle is a position where the dot 302 is formed by the abnormal nozzle.

  FIGS. 4D and 4E show another example of the discharge position for causing the abnormal nozzle to discharge the ink droplet. In the case shown in FIG. 4D, among the dots 302 at positions A, B, C, and D, the dot 302 at the position C is formed by the abnormal nozzle in the first pass, and the other codes The dots 302 at positions A, B, and D are formed by the other normal nozzles in the third pass. In the case shown in FIG. 4E, of the dots 302 at each of the positions A, B, C, and D, the dots 302 at the positions A, C, and D are formed by the abnormal nozzle in the first pass. The dot 302 at the position of another code B is formed by the other normal nozzles in the third pass. Also in these cases, for example, the influence of the abnormal nozzle can be appropriately suppressed while suppressing the problem caused by the alternative processing.

  Moreover, it is preferable that the selection ratio for selecting the ejection position for ejecting ink droplets to the abnormal nozzle can be changed in a plurality of stages. In this case, the selection ratio for selecting the ejection position for ejecting ink droplets to the abnormal nozzle is, for example, without forming the dots 302 by other normal nozzles among the dots 302 at positions that should be originally formed by the abnormal nozzles. The ratio of dots 302 formed using the abnormal nozzle as it is.

  In this case, in the printing apparatus 10, for example, the control unit 24 has a configuration that can change the selection ratio in a plurality of steps. When any nozzle in the nozzle row of the inkjet head 102 is an abnormal nozzle, the control unit 24 sets the abnormal nozzle for the ejection position selected from the normal ejection target positions according to the selection ratio. To eject ink droplets.

  Further, in this case, for example, with regard to the abnormal nozzle, it is conceivable to determine the selection ratio in accordance with the degree of abnormality of the ejection characteristics. More specifically, for example, when the ejection characteristics are closer to the normal range, it is conceivable to use a selection ratio for selecting more ejection positions. In addition, it is conceivable to use a selection ratio for selecting a smaller number of discharge positions when the discharge characteristics are further away from the normal range.

  When the selection ratio can be changed in a plurality of stages, it is preferable to store information indicating the abnormal degree of the abnormal nozzle in the multi-pass control information storage unit 22 (see FIG. 1) in the printing apparatus 10. With this configuration, for example, the selection ratio can be set more appropriately according to the degree of abnormality of the abnormal nozzle.

  Here, in the above, as shown, for example to FIG.4 (b)-(e), the case where substitution of one abnormal nozzle was mainly performed by one normal nozzle was demonstrated. In this case, when any of the nozzles is an abnormal nozzle, the control unit 24 applies one of the nozzles other than the abnormal nozzle to a discharge position other than a part of the normal discharge target position corresponding to the abnormal nozzle. Ink droplets are ejected from the nozzles.

  However, the relationship between the abnormal nozzle and the normal nozzle to be used instead is not limited to one to one, and may be, for example, one to many (plural). More specifically, for example, when the number of passes in the multi-pass operation is larger, the number of main scanning operations (passes) that can eject ink droplets in principle at the same dot 302 position is three. In the case of the above, it is conceivable to use the above one-to-many relationship. In this case, when any of the nozzles is an abnormal nozzle, the control unit 24, for example, for a discharge position other than a part of the discharge positions at the normal discharge target position corresponding to the abnormal nozzle, other than the abnormal nozzle. The ink droplets are ejected to the plurality of nozzles.

  FIG. 4F is a diagram showing another example of the correction operation performed in the present example, and shows an example of the operation in the case of performing the alternative process with a plurality of normal nozzles for one abnormal nozzle. In this case, the relationship between the arrangement interval of the dots 302 that can be formed by one main scanning operation and the printing resolution is partially the same as the case described with reference to FIGS. It is different. More specifically, in the case shown in FIG. 4F, for example, as described with reference to FIG. 3B, the third pass with respect to the position of the dot 302 formed in the first pass. In addition to the above, it is configured to be able to eject ink droplets also in the fifth and seventh passes.

  Further, in the figure, the positions of the dots 302 indicated by reference signs A, B, C, and D are examples of normal ejection target positions corresponding to the abnormal nozzles. For example, they are originally formed with one nozzle in the first pass. The example of the position of the dot 302 to perform is shown. In the case shown in the figure, among the dots 302 at positions A, B, C, and D, only the dot 302 at the position C is formed by the abnormal nozzle in the first pass, and other codes A, B , D in the other round pass with other normal nozzles. In this case, more specifically, for example, with the different normal nozzles, the dot 302 at the code B position in the third pass, the dot 302 at the code A position in the fifth pass, and the dot at the code D position 302 is formed in the seventh pass. With this configuration, for example, the characteristics of the normal nozzles used for the alternative process can be averaged with a plurality of nozzles, as compared to the case where the alternative process is performed with only one normal nozzle. This also makes it possible to perform alternative processing with higher quality, for example.

  As described above, according to this example, for example, the influence of the abnormal nozzle can be appropriately suppressed, and high-quality printing can be appropriately performed. Also, this makes it possible, for example, to cope with nozzle abnormalities in a more appropriate manner.

  Next, a more specific method of the substitution process will be described regarding the correction operation performed when there is an abnormal nozzle. As described above, when printing by the multi-pass method, the control unit 24 determines a position at which the ink droplet is ejected in each main scanning operation based on a preset mask. For example, in this example, the control unit 24 causes the ink jet head 102 to eject ink droplets to the ejection position specified by the mask based on the mask stored in the multipass control information storage unit 22. Further, in the mask, in accordance with the pattern of the mask, a duty that is a ratio at which ink droplets are ejected in each main scanning operation is set to each nozzle in the nozzle row. The duty is a ratio set in advance according to, for example, the number of printing passes, and indicates the ratio of the discharge position at which the ink droplet is discharged by each nozzle in one main scanning operation.

  Further, in each main scanning operation in the multi-pass method, according to the control of the control unit 24, the main scanning driving unit 18 (see FIG. 1) has a plurality of nozzles arranged in the nozzle array in the main scanning direction. Ink droplets are ejected to a part of the ejection positions selected according to the duty. In this case, the plurality of ejection positions arranged in the main scanning direction are, for example, a plurality of ejection positions arranged in the main scanning direction at intervals corresponding to the printing resolution.

  Further, in this example, the control unit 24 performs the operation of the alternative process described above by correcting the duty according to the position of the abnormal nozzle. In this case, more specifically, the control unit 24 corrects the duty, for example, by correcting the mask. The control unit 24 also performs duty correction based on, for example, correction data stored in the multipath control information storage unit 22. In this case, the multi-pass control information storage unit 22 preferably stores, for example, the position of the abnormal nozzle in the nozzle array, the degree of abnormality (abnormality degree) of the abnormal nozzle, and the like as correction data.

  FIG. 5 is a diagram for explaining the operation for correcting the duty. In the following description, the duty set for each nozzle when all the nozzles in the nozzle row are normal nozzles is defined as the normal duty. This normal duty is, for example, the duty before correcting the duty when there is an abnormal nozzle. Further, when any nozzle is an abnormal nozzle, the duty set for each nozzle is defined as an abnormal duty. This abnormal duty is, for example, the duty after correcting the duty when there is an abnormal nozzle.

  FIG. 5A is a diagram illustrating an example of an operation for correcting the duty, and illustrates an example of a correction operation when a uniform duty is set as a normal duty for each nozzle in the nozzle row. In the drawing, regions 402a to 402h are regions obtained by dividing the nozzle array 204 according to the number of passes of the multi-pass method. In each pass, the inkjet head 102 (see FIG. 1) ejects ink droplets onto the medium by the nozzles included in each of the areas 402a-h. Further, in the figure, the arrows shown together with the characters “Error” indicate the positions of abnormal nozzles present in the nozzle row.

Further, in the case shown in FIG. 5A, the normal duty for each nozzle is set to a constant linear value. In contrast, if one of the nozzles is abnormal nozzle, by lowering the duty of the abnormal nozzle, reducing the proportion of dots formed by the abnormal nozzle. More specifically, in this case, the control unit 24 (see FIG. 1) in the printing apparatus 10 (see FIG. 1) has a value larger than 0 and smaller than the normal duty as an abnormal duty with respect to an abnormal nozzle. <Abnormal duty <Normal duty) is set.

  In this case, the duty of other nozzles is increased in accordance with the duty lowered with respect to the abnormal nozzle. More specifically, in this case, the control unit 24 sets an abnormal duty (normal duty <normal duty) larger than the normal duty for any normal nozzle other than the abnormal nozzle. Also, in this case, as a normal nozzle for increasing the duty, for example, a nozzle capable of forming a dot instead of an abnormal nozzle in another pass is selected. Also, in this way, in the other passes, ink droplets are ejected to the normal nozzles instead of the abnormal nozzles with respect to the positions of some dots.

  According to this structure, for example, it is possible to appropriately perform the substitution process of the abnormal nozzle while discharging the ink droplet to the partial ejection position to the abnormal nozzle. In addition, this makes it possible to appropriately suppress the influence of abnormal nozzles and appropriately perform high quality printing.

  Here, in order to perform the correction of the duty for an abnormal nozzle or the like in the simplest manner, correction is performed in units of one nozzle, and only one abnormal nozzle and one normal nozzle corresponding to the abnormal nozzle are corrected. It can be considered as a target. However, when the above duty correction is performed, for example, in units of one nozzle, for example, in the abnormal duty after correction for the entire nozzle array, the value largely changes only at the position of the abnormal nozzle, etc. As a result, there is a possibility that the location where the correction has been made may be noticeable.

Therefore, it is preferable that the correction of the duty for the abnormal nozzle is performed not for only the abnormal nozzle but for a plurality of nozzles including the abnormal nozzle and the surrounding normal nozzles. For example, when any nozzle is an abnormal nozzle, the control unit 24 sets a value larger than 0 and smaller than a normal duty as an abnormal duty for each of the plurality of nozzles including the abnormal nozzle. It is preferable to do. More specifically, in this example, for example, a plurality of nozzles arranged in succession in the nozzle row are selected as the plurality of nozzles arranged including the abnormal nozzles. In this case, selecting a plurality of nozzles arranged in series means, for example, selecting a plurality of nozzles arranged in a partial region in the nozzle row without pinching non-selected nozzles in between.

  Also, in this case, even for a normal nozzle that ejects an ink droplet instead of the abnormal nozzle in accordance with the correction amount on the abnormal nozzle side, for a plurality of nozzles including the normal nozzle and surrounding normal nozzles, Correct the duty.

  According to this structure, for example, the duty correction can be appropriately performed in units of a plurality of nozzles. In addition, this makes it possible to perform more natural correction than when changing the duty of only the abnormal nozzle, for example. Further, for example, it is possible to perform the substitute process more appropriately while further improving the continuity with the surroundings.

Further, when the duty correction is performed for a plurality of nozzles including the nozzles around the abnormal nozzle, the correction amount for each nozzle may be varied. In this case, it is preferable to set the correction amount for each nozzle so that the abnormal duty after correction changes more smoothly. An abnormal time duty is changed more smoothly, for example, is that the abnormal duty than when the correction amount of each nozzle in the same changes more smoothly.

  In addition, the width of the range to be corrected, that is, the width in the sub-scanning direction of the region in which a plurality of nozzles including abnormal nozzles are continuously arranged is visually inconspicuous and does not become too large. It is preferable to More specifically, for example, it is conceivable to make this width larger than twice the peak wavelength in the spatial frequency characteristic of visual sensitivity and smaller than the path width in the multipath system. Further, the width of the range to be corrected is preferably sufficiently larger (for example, five times or more of the peak wavelength) than the peak wavelength in the spatial frequency characteristic of the sensitivity of vision. With this configuration, for example, it is possible to more appropriately prevent the area where the correction has been made to stand out. In this case, by making the width of the correction target range smaller than the pass width, it is possible to easily and appropriately select a nozzle that increases the duty instead of the abnormal nozzle or the like.

  Moreover, about the width | variety of the range made into the object of correction | amendment practically, it is possible to make object about 3-20 nozzles arranged in a line continuously including an abnormal nozzle, for example. Moreover, as for this range, for example, it is more preferable to target about 5-10 nozzles arranged in a row.

  For example, as in the conventional configuration, when abnormal nozzles are completely non-ejection, when such correction is performed in units of a plurality of nozzles, a band-like region where the difference between the surroundings and the state is noticeable occurs, There is a possibility that the quality of printing may be greatly reduced. In addition, the load on the normal nozzles for ejecting ink droplets instead of the abnormal nozzles may be increased, and the life of the ink jet head may be shortened. On the other hand, in the present embodiment, these problems can be appropriately suppressed by not making the abnormal nozzle completely non-ejection. Also, this makes it possible to more appropriately perform correction in units of a plurality of nozzles.

  Further, the setting of the normal duty is not limited to the uniform case as described above, and may be variously changed. FIG. 5B is a diagram showing another example of the operation for correcting the duty, and shows an example of the correction operation when a duty other than uniform is set as the normal duty for each nozzle in the nozzle row.

  More specifically, in FIG. 5B, the duty at normal time is such that the usage rate of the nozzles at the end is lower than that at the center of the nozzle row. In addition, the nozzle usage rate at each position is highest at the center of the nozzle row and gradually lowered toward the end. When such a normal duty is used, for example, the printing result in each main scanning operation is made gradation, and the number of ink dots formed by the nozzles at the end of the nozzle row that easily affects the printing result can be reduced. . Thereby, for example, high-quality printing can be performed more appropriately.

  Also, when using such a normal duty setting, it is possible to perform duty correction as in the case described with reference to FIG. 5 (a). More specifically, in this case as well, the duty for the abnormal nozzle is reduced within a range that does not become zero, and the duty of the other nozzles is increased in accordance with the duty reduced for the abnormal nozzle. Also in this case, it is preferable that the correction of the duty is not performed on only the abnormal nozzle but on a plurality of nozzles including the abnormal nozzle and the normal nozzles around it. Also in this case, the influence of the abnormal nozzle can be appropriately suppressed, and high quality printing can be appropriately performed.

  Here, as described above, it is preferable that the change of the duty to the abnormal nozzle is performed to a plurality of nozzles including the abnormal nozzle and the normal nozzles around the abnormal nozzle. Also, in this case, for the plurality of nozzles, for example, it is conceivable to select a plurality of nozzles arranged around the abnormal nozzle. Moreover, in order to perform correction more simply, for example, it is conceivable to group the nozzles in the nozzle array in advance and perform correction on a group basis.

  FIG. 6 is a diagram illustrating an example of a configuration in which duty correction is performed in units of preset groups. In the case where a plurality of nozzles included in a region 402 for one pass in the nozzle row 204 are divided into a plurality of groups 404. An example of the configuration is shown. In FIG. 6, an area 402 is an area corresponding to any of the areas 402a to 402h shown in FIG.

In this case, the control unit 24 (see FIG. 1) in the printing apparatus 10 (see FIG. 1) divides the plurality of nozzles 202 in the nozzle row 204 into a plurality of groups 404 each including a plurality of nozzles 202 arranged consecutively. to manage. In addition, regarding the correction of the duty when there is an abnormal nozzle, the duty is changed on a group 404 basis. More specifically, for example, when any of the nozzles is an abnormal nozzle, the control unit 24 has an abnormality duty greater than 0 and is normal for each nozzle included in the group 404 including the abnormal nozzle. Set a value smaller than the hour duty. In addition, as an alternative process to the group 404 including the abnormal nozzle, for each nozzle included in the group 404 including the normal nozzle used instead of the abnormal nozzle, a value larger than the normal duty is set as the abnormality duty . If comprised in this way, the correction | amendment of a duty can be performed more simply and appropriately, for example.

  Further, in this case, even if it is not completely specified which nozzle in the nozzle row is the abnormal nozzle, for example, if it is known which group 404 includes the abnormal nozzle, the group 404 to be corrected is determined. can do. Therefore, also in this respect, it is possible to more simply and appropriately perform the alternative process for the abnormal nozzle.

  Here, the printing apparatus 10 may print a test pattern (test chart) for confirming the ejection characteristics of the respective nozzles. When such correction in units of groups is performed, for example, it is preferable to print a test pattern capable of confirming the ejection characteristics in units of groups 404. In this case, as a test pattern, for example, a pattern including a pattern associated with each group 404 in the nozzle row may be used.

  With this configuration, it can be more easily and appropriately confirmed as to which group 404 the malfunctioning nozzle is included. In addition, this makes it possible to more simply and appropriately perform the substitution process for the abnormal nozzle.

  Subsequently, supplementary explanation and the like will be given for the correction operation performed in this example. As described above, it is preferable that the selection ratio for selecting the ejection position for ejecting ink droplets to the abnormal nozzle can be changed in a plurality of stages. In this case, it is preferable that the duty change amount can be changed in a plurality of stages at the time of duty correction.

  Further, in this example, printing with higher quality is realized by not causing the abnormal nozzle to be completely non-ejection. However, depending on the state of the abnormal nozzle, the abnormal nozzle may be set to be non-ejection. For example, with regard to an abnormal nozzle, when the discharge characteristic of the abnormal nozzle deviates from the normal range beyond an allowable range set in advance, the abnormal nozzle may be completely set to the non-discharge. In this case, the control unit 24 does not cause the abnormal nozzle to eject ink droplets, and causes the nozzles other than the abnormal nozzles to eject ink droplets to all the normal ejection target positions corresponding to the abnormal nozzle.

  If comprised in this way, even when a nozzle with a large abnormality degree exists, for example, a substitute process can be performed more appropriately. Further, in this case, for example, even when a non-ejection nozzle occurs due to a nozzle clogging or the like, the alternative processing can be appropriately performed.

  Further, as an abnormality of each nozzle in the nozzle array, for example, an abnormality of an ejection speed or an ejection direction (bending angle), an abnormality of an ink droplet amount (volume), or the like can be considered. Further, as the abnormality of the amount of ink droplets, for example, in the case of volume shortage, in the case of volume excess, or in the case of complete non-ejection, etc. can be considered.

  On the other hand, as a method for confirming the abnormality of each nozzle, for example, a method using an NCU (nozzle check unit), a method using a test pattern (test chart), a method using head characteristic parameter data, and the like can be considered. The head property parameter is data indicating the property of the inkjet head, and is provided, for example, from the manufacturer of the inkjet head.

  Further, in this case, with the method using the NCU, for example, an abnormality in the discharge speed can be appropriately confirmed. Further, in the method of using a test pattern, for example, by confirming the deviation of the landing position, it is possible to confirm composite abnormalities and the like of the discharge speed and the discharge direction. Further, by confirming the dot diameter of the dots to be formed, it is possible to confirm an abnormality in the amount of ink droplets. Further, with the method of using the head characteristic parameter data, it is possible to confirm an abnormality in the ejection speed and the ejection direction, an abnormality in the amount of ink droplets, and the like.

  Further, the normal range of the ejection characteristics is set in advance according to, for example, a method for confirming abnormality of each nozzle. Further, for example, in the case where abnormalities in each nozzle are confirmed by a plurality of methods, it is preferable to set a normal range for each method. In this case, the fact that the discharge characteristic is out of the normal range may mean that the discharge characteristic is out of the normal range when abnormality of the nozzle is confirmed by any method.

  Further, in the present embodiment, the duty is corrected based on the abnormality of the nozzle confirmed by these various methods. Further, according to the state of the ink jet head, for example, the ratio of gradation designated by the duty, the number of nozzles used, etc. are changed. With this configuration, for example, the degree of use of the abnormal nozzles in the nozzle row can be appropriately adjusted. Moreover, thereby, the substitute process with respect to an abnormal nozzle can be performed appropriately, using an abnormal nozzle to some extent.

  Further, as described above, it is preferable to set the correction of the duty according to the degree of abnormality of the abnormal nozzle. In this case, the abnormal degree of the abnormal nozzle is, for example, a deviation amount from the normal range with respect to each of the discharge speed, the discharge direction, the ink droplet capacity, and the like.

  In addition, as described above, such correction of duty can be performed by correction of a mask used in the multipass method. Therefore, such correction of the duty can be considered, for example, as an operation using the setting of the mask corresponding to the abnormal nozzle.

  In the above description, as an alternative process for the abnormal nozzle, the case where the ink droplet is ejected by the normal nozzle to the same position as the original ejection position by the abnormal nozzle has been described. However, considering that the abnormal nozzle is used to some extent and the alternative processing to the abnormal nozzle is performed, the ejection position of the ink droplet in the normal nozzle used instead of the abnormal nozzle is the same position as the abnormal nozzle. Alternatively, it may be a position in the vicinity thereof. Also, in this case, as a substitute normal nozzle, not a nozzle that ejects an ink droplet in another main scanning operation but a nozzle that ejects an ink droplet in the same main scanning operation (in the same pass) May be That is, in the alternative process performed in the present embodiment, as a normal nozzle for substitution, not only other nozzles that come to the same position as the abnormal nozzle in other main scanning operations but also in the vicinity of the abnormal nozzle in the same pass. It is also conceivable to use surrounding nozzles that eject ink drops.

  Further, the method of setting the duty and correcting the duty is not limited to the form described above, and can be performed in various forms. 7-9 show various examples of how to set and correct the duty. FIGS. 7A, 7B, 8A, 8B, 9C, 9A, and 9B show examples of duty setting and correction.

  In each of these figures, the normal duty, which is the duty before correction, is shown as the normal duty. Further, the position of the abnormal nozzle is shown as the ejection characteristic. In the graph of the ejection characteristics, the position out of the line indicating 0 is the position of the abnormal nozzle. Further, in this case, the magnitude of the degree of abnormality is indicated by a distance away from zero. Further, the duty at the time of abnormality, which is the duty after correction according to the position of the abnormal nozzle, is shown as the duty after change (after).

  Further, among these figures, FIG. 7A shows the case where abnormal nozzles exist near both ends of the nozzle row when using the same or similar normal duty as the case shown in FIG. 5B. An example is shown. In this case, by lowering the duty at both ends of the nozzle array, the usage rate of the abnormal nozzle is reduced. In addition, according to this change, the duty in the vicinity of the center of the nozzle row is raised to perform the substitution process by the normal nozzle. According to this configuration, for example, the substitute process can be appropriately performed while using the abnormal nozzle.

  FIG. 7B shows an example in which an abnormal nozzle exists near one end of the nozzle row when the normal duty similar to that in FIG. 7A is used. In this case, by lowering the duty at one end of the nozzle row, the usage rate of abnormal nozzles is reduced. In addition, according to this change, the duty in the vicinity of the center of the nozzle row is raised to perform the substitution process by the normal nozzle. According to this configuration, for example, the substitute process can be appropriately performed while using the abnormal nozzle.

  In this case, as shown in the figure, the duty change at the center of the nozzle row is considered to be discontinuous in the abnormal duty after correction. Therefore, even when an abnormal nozzle is present only at one end of the nozzle row, the duty on both sides of the nozzle row may be reduced as in the case shown in FIG. According to this configuration, for example, the occurrence of a discontinuous portion in the abnormal time duty can be appropriately prevented.

  FIG. 8 shows an example in which an abnormal nozzle is present at a position other than the end of the nozzle row when the normal duty similar to that in FIG. 7A is used. FIG. 8A shows an example where an abnormal nozzle is present near the center of the nozzle row. In this case, by lowering the duty near the center of the nozzle array, the usage rate of abnormal nozzles is reduced. In addition, according to this change, the duty in the vicinity of both ends of the nozzle row is increased to perform the substitution process by the normal nozzle. According to this configuration, for example, the substitute process can be appropriately performed while using the abnormal nozzle.

  Moreover, FIG.8 (b), (c) shows the example in case the abnormal nozzle exists other than the edge and center vicinity of a nozzle row. Also in this case, the duty ratio at the position where the abnormal nozzle is present in the nozzle row is lowered to lower the usage rate of the abnormal nozzle. Also, by increasing the duty of the other corresponding portion of the nozzle row in accordance with this change, substitution processing by a normal nozzle is performed.

  More specifically, FIG. 8B shows an example in the case where correction is performed so that the change (inclination) of the duty at the position where the duty is changed at the abnormal time duty is not reversed with respect to the surroundings. . FIG. 8C shows an example in the case where the correction is performed by allowing the change (inclination) of the duty at the position where the duty is changed at the abnormal time duty to be reversed with respect to the surroundings. Also in these cases, for example, the substitution process can be appropriately performed while using the abnormal nozzle.

  FIG. 9 shows an example in the case of using a normal duty different from that of FIG. 7 (a). In FIGS. 9A and 9B, the usage rate of the end nozzles is lower than that of the central portion of the nozzle row, and the nozzle row usage rate is changed stepwise at a predetermined position in the nozzle row. An example is shown in the case where an abnormal nozzle is present near one end of the nozzle row when using the hour duty. Even when such a normal duty is used, the duty can be appropriately corrected by lowering the duty at the position of the abnormal nozzle and raising the duty of the nozzle at the corresponding other position.

  Further, more specifically, FIG. 9A shows an example in the case of changing the duty of the abnormal nozzle and the nozzles of the other corresponding positions while maintaining the inclination (incline) of the duty in the normal state. FIG. 9B shows an example of changing the duty of the abnormal nozzle and the nozzles at other corresponding positions while changing the duty gradient. Also in these cases, for example, the substitution process can be appropriately performed while using the abnormal nozzle.

  The present invention can be suitably used for a printing apparatus, for example.

DESCRIPTION OF SYMBOLS 10 ... Printing apparatus, 12 ... Head part, 14 ... Platen, 16 ... Heater, 18 ... Main scanning drive part, 20 ... Sub-scanning drive part, 22 ... Multipass Control information storage unit, 24 ... control unit, 50 ... medium, 102 ... ink jet head, 202 ... nozzle, 204 ... nozzle row, 302 ... dot, 310 ... region, 402 ... area, 404 ... group

Claims (12)

A printing apparatus that performs printing on a medium by an inkjet method,
An inkjet head having a nozzle row in which a plurality of nozzles each ejecting ink droplets in an inkjet system are arranged in a predetermined direction;
A control unit that controls ejection of ink droplets from each of the nozzles in the inkjet head ;
A main scanning drive unit that causes the inkjet head to perform a main scanning operation of ejecting ink droplets while moving relative to the medium in a preset main scanning direction;
A sub-scanning drive unit that causes the inkjet head to perform a sub-scanning operation that moves relative to the medium in a sub-scanning direction that is orthogonal to the main scanning direction ;
The control unit further controls the operations of the main scanning drive unit and the sub-scanning driving unit, thereby performing printing in a multi-pass method in which the main scanning operation is performed a plurality of times for each position on the medium. Let the inkjet head do,
Regarding the ejection characteristics of the individual nozzles, the nozzles whose ejection characteristics fall within a preset normal range are defined as normal nozzles, and the nozzles whose ejection characteristics fall outside the normal range are defined as abnormal nozzles, and the nozzles For each of the nozzles in the row, when the discharge position for discharging ink droplets when the nozzle is the normal nozzle is further defined as a normal discharge target position,
Ri Ah in the abnormal nozzle is one of the nozzles in the nozzle array, and, in the case where the ejection characteristics of the abnormal nozzle is out in the preset allowable range with respect to the normal range, the control unit The abnormal nozzle is caused to eject ink droplets to a part of the normal ejection target positions set when the abnormal nozzle is the normal nozzle, and the abnormal nozzle is In the main scanning operation different from the main scanning operation for ejecting ink droplets to the ejection position of the part, the abnormal nozzles for ejection positions other than the partial ejection positions at the normal ejection target position A printing apparatus that discharges ink droplets to nozzles other than the above . In the case where an arrangement of a plurality of ejection positions for ejecting ink droplets by one normal nozzle in one main scanning operation is defined as a normal ejection target position in a row ,
When any of the nozzles in the nozzle row is the abnormal nozzle, the control unit
In one main scanning operation, the abnormal nozzle is caused to eject ink droplets to a part of the normal ejection target positions in the one row,
In another main scanning operation, ink droplets are ejected to the nozzles other than the abnormal nozzles with respect to ejection positions other than the partial ejection positions in the normal ejection target positions of the row. The printing apparatus according to claim 1 . In the main scanning operation of each time, the main scanning driving unit is preset to each of the nozzles in the nozzle row among the plurality of ejection positions aligned in the main scanning direction at intervals corresponding to the resolution of printing Ink droplets are ejected to a part of the ejection positions selected according to the duty ratio.
When all the nozzles in the nozzle row are the normal nozzles, the duty set for each of the nozzles is a normal duty and each of the nozzles is the abnormal nozzle. When the duty set for the nozzle is an abnormal duty,
The printing apparatus according to claim 2 , wherein the control unit sets a value larger than 0 and smaller than the normal duty as the abnormal duty for the abnormal nozzle. When any of the nozzles is the abnormal nozzle, the control unit sets the abnormal duty with a value larger than the normal duty for any of the normal nozzles other than the abnormal nozzle. The printing apparatus according to claim 3 , wherein: When any of the nozzles is the abnormal nozzle, the control unit
As the abnormality duty for each of a plurality of said nozzles arranged include the abnormal nozzle, larger than 0, and, according to claim 3 or 4, characterized in that setting the value smaller than the normal time of duty Printing device. The plurality of nozzles arranged including the abnormal nozzles are the plurality of nozzles arranged continuously in the nozzle row,
The width in the sub-scanning direction of the region where the plurality of nozzles including the abnormal nozzle are continuously arranged is larger than twice the peak wavelength in the spatial frequency characteristic of visual sensitivity, and the path width in the multipass system The printing apparatus according to claim 5 , wherein the printing apparatus is smaller than the printing apparatus. The control unit, for a plurality of nozzles in the nozzle row, is managed by dividing into a plurality of groups each including a plurality of nozzles arranged continuously,
When any of the nozzles is the abnormal nozzle, a value larger than 0 and smaller than the normal duty is set as the abnormal duty for each of the nozzles included in the group including the abnormal nozzle. Set,
The printing apparatus is capable of printing a test pattern for confirming the ejection characteristics of each nozzle,
The printing apparatus according to claim 5 , wherein the test pattern includes a pattern associated with each group in the nozzle row. The control unit
The selection ratio for selecting an ejection position for ejecting ink droplets to the abnormal nozzle can be changed in a plurality of stages.
When any one of the nozzles is the abnormal nozzle, the abnormal nozzle is caused to eject ink droplets to a discharge position selected from the normal discharge target positions according to the selection ratio. the printing apparatus according to any one of claims 1 to 7 to be. When any one of the nozzles is the abnormal nozzle, the control unit applies ink droplets to one nozzle other than the abnormal nozzle with respect to a discharge position other than the partial discharge position in the normal discharge target position. the printing apparatus according to claim 1, wherein the ejecting 8. When any one of the nozzles is the abnormal nozzle, the control unit applies ink droplets to a plurality of nozzles other than the abnormal nozzle with respect to ejection positions other than the partial ejection position in the normal ejection target position. the printing apparatus according to claim 1, wherein the ejecting 8. When the ejection characteristics of the abnormal nozzle are outside a preset allowable range with respect to the normal range,
Wherein the control unit does not eject ink droplets to the abnormal nozzle, for all of the normal time discharge target position from claim 1, characterized in that eject ink droplets to the nozzle other than the malfunctioning nozzle 10 The printing apparatus in any one. A printing method for printing on a medium by an inkjet method,
Using an inkjet head having a nozzle row in which a plurality of nozzles each ejecting ink droplets in an inkjet system are arranged in a predetermined direction,
Control the ejection of ink droplets from each nozzle in the inkjet head,
A main scanning operation for ejecting ink droplets while moving relative to the medium in a preset main scanning direction, and a movement relative to the medium in a sub-scanning direction orthogonal to the main scanning direction Causing the inkjet head to perform sub-scanning operation, and causing the inkjet head to perform multi-pass printing in which the main scanning operation is performed a plurality of times for each position on the medium,
Regarding the ejection characteristics of the individual nozzles, the nozzles whose ejection characteristics fall within a preset normal range are defined as normal nozzles, and the nozzles whose ejection characteristics fall outside the normal range are defined as abnormal nozzles, and the nozzles For each of the nozzles in the row, when the discharge position for discharging ink droplets when the nozzle is the normal nozzle is further defined as a normal discharge target position,
Ri Ah in the abnormal nozzle is one of the nozzles in the nozzle array, and, if the discharge characteristics of the abnormal nozzle is out in the preset allowable range with respect to the normal range, the abnormality nozzle For some ejection positions of the normal ejection target positions set when the nozzles are normal nozzles, the abnormal nozzles are caused to eject ink droplets, and the abnormal nozzles are brought to the partial ejection positions. In contrast, in the main scanning operation that is different from the main scanning operation for discharging ink droplets, ink is discharged to nozzles other than the abnormal nozzle with respect to ejection positions other than the partial ejection positions at the normal ejection target position. A printing method characterized by discharging droplets .

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