Printing apparatus and printing method

Abstract

This invention relates to a printing apparatus and a printing method. The printing apparatus includes: a correction value setting unit for setting a correction value for the density of each grid line; a printing data generation unit for correcting image data based on the correction value of each grid line; and a printing control unit for printing a first region and a second region onto a printing medium based on the corrected image data. The first region has a plurality of first grid lines arranged in a second direction, and the second region is sandwiched between the first regions in the second direction and has second grid lines. The printing control unit causes the printing head to print one first grid line through a predetermined number of nozzles and to print one second grid line through a larger number of nozzles than the predetermined number. The correction value setting unit sets correction values ​​applied to the second grid lines and correction values ​​applied to the first grid lines, including a portion of the first grid lines adjacent to the second region, based on printing conditions that cause a change in the density difference between the second grid lines and the first grid lines.

Description

Technical Field

[0001] This invention relates to printing apparatus and printing method. Background Technology

[0002] An inkjet printer moves a printhead having multiple nozzles arranged in a predetermined nozzle orientation relative to a printing medium in a relative movement direction intersecting the nozzle orientation, and prints onto the printing medium according to printing data, where ink is ejected from each nozzle at specific points. In such printers, a known configuration includes a printhead that combines multiple head chips having multiple nozzle rows arranged in a specific nozzle orientation, with the nozzle rows overlapping at the junction of adjacent head chips. When the nozzle rows partially overlap, the printing medium produces an overlapping area consisting of a raster line formed by multiple nozzles along the relative movement direction, and a non-overlapping area consisting of a raster line formed by a single nozzle along the relative movement direction.

[0003] Furthermore, in order to suppress the concentration deviation of each grid line in the printing medium due to the deviation of the ejection characteristics of each nozzle, it is known to set a correction value for the correction concentration for each grid line and to correct the data for each grid line (see Patent Document 1).

[0004] Patent Document 1: Japanese Patent Application Publication No. 2018-149690

[0005] Here, in the non-overlapping and overlapping areas, due to the different number of nozzles used for printing the grid lines, the density of the overlapping area in the printing medium varies with the non-overlapping area, resulting in either dense or faint streaks that are visually apparent. Furthermore, even if the printhead is ideally mounted without tilt, in individual printers that are produced as products, the printhead may sometimes tilt slightly. The density difference between the overlapping and non-overlapping areas varies depending on this tilt. In the aforementioned document 1, data processing is performed based on this tilt to correct the density of the grid lines in the overlapping area. However, the main reasons for the change in the density difference between the overlapping and non-overlapping areas are not limited to the tilt of the printhead.

[0006] In this situation, further improvements are needed to suppress striped concentration unevenness when correcting the grid line concentration. Summary of the Invention

[0007] The printing apparatus includes: a print head having a plurality of nozzles that eject ink of a predetermined color; a correction value setting unit that sets a correction value for each of the grid lines representing the ink dots arranged along a first direction; a print data generation unit that corrects image data based on the correction value of each of the grid lines; and a print control unit that, based on the corrected image data, prints a first region and a second region onto a printing medium through the print head, wherein the first region has a plurality of first grid lines represented by the ink arranged in a second direction intersecting the first direction, and the second region is sandwiched by the first region in the second direction and has second grid lines represented by the ink, the print control unit causing the print head to print one first grid line through a predetermined number of the nozzles and to print one second grid line through a number greater than the predetermined number of the nozzles, and the correction value setting unit setting the correction value applied to the second grid line and the correction value applied to the first grid line including a portion of the first grid line adjacent to the second region, based on printing conditions that cause the density difference between the second grid line and the first grid line to change.

[0008] A printing method controls a print head having multiple nozzles that eject ink of a specified color to print on a printing medium. The printing method includes: a correction value setting step, which sets a correction value for each grid line representing ink dots arranged along a first direction to correct the density of each grid line; a printing data generation step, which corrects image data based on the correction value of each grid line; and a printing control step, which, based on the corrected image data, prints a first region and a second region onto the printing medium through the print head. The first region has multiple first grid lines represented by the ink arranged in a second direction intersecting the first direction. The second region is sandwiched by the first region in the second direction and has a second grid line represented by the ink. In the printing control step, the print head prints one first grid line through a predetermined number of the nozzles and prints one second grid line through a larger number of the nozzles than the predetermined number. In the correction value setting step, the correction value applied to the second grid line and the correction value applied to the first grid line including a portion of the first grid line adjacent to the second region are set according to printing conditions that cause the density difference between the second grid line and the first grid line. Attached Figure Description

[0009] Figure 1 This is a block diagram simply illustrating the device configuration of this embodiment.

[0010] Figure 2It is a diagram that simply shows the relationship between the printing media and the printhead from a top viewpoint.

[0011] Figure 3 It is a diagram that simply shows the relationship between the printing medium and the print head from a side viewpoint.

[0012] Figure 4 Through with Figure 2 The same viewpoint shows a diagram of a first nozzle array and a second nozzle array.

[0013] Figure 5 This is a flowchart illustrating the correction value preparation process of the first embodiment.

[0014] Figure 6 This is a flowchart illustrating the printing control process of the first embodiment.

[0015] Figure 7 A diagram illustrating the process of setting correction values ​​corresponding to head tilt.

[0016] Figure 8 This is a flowchart illustrating the correction value preparation process of the second embodiment.

[0017] Figure 9 This is a flowchart illustrating the printing control process of the second embodiment.

[0018] Figure 10 This diagram illustrates the process of setting the correction value corresponding to PG.

[0019] Figure 11 This is a graph used to illustrate the correction values ​​for the modified examples.

[0020] Explanation of reference numerals in the attached figures

[0021] 10… Printing apparatus, 11… Control unit, 12… Program, 13… Display unit, 14… Operation receiving unit, 15… Communication IF, 16… Storage unit, 17… Printing unit, 18… Transport unit, 19… Print head, 20… PG adjustment unit, 21… Nozzle, 22… Head chip, 23, 23C, 23M, 23Y, 23K, 23K1, 23K2… Nozzle array, 24… OL unit, 25… Nozzle surface, 26… Pressure plate, 30… Printing medium, 31… Printed image, 32, 34… First area, 33… Second area, 35, 36… Adjacent area, RL… Grid line. Detailed Implementation

[0022] Hereinafter, embodiments of the present invention will be described with reference to the figures. Please note that the figures are merely illustrative of these embodiments. Since the figures are illustrative, ratios, shapes, or parts may be inaccurate, mismatched, or omitted.

[0023] 1. Brief description of the apparatus:

[0024] Figure 1 The configuration of the printing apparatus 10 according to this embodiment is briefly shown. The printing apparatus 10 includes a control unit 11, a display unit 13, an operation receiving unit 14, a communication interface 15, a storage unit 16, and a printing unit 17. IF is short for interface. The printing method is implemented through the printing apparatus 10.

[0025] The control unit 11 is configured with one or more ICs such as a CPU 11a (serving as a processor), ROM 11b, RAM 11c, etc., as well as other non-volatile memory. In the control unit 11, the processor, i.e., the CPU 11a, uses RAM 11c, etc., as its working area and executes arithmetic processing according to the program 12 stored in ROM 11b or other memory. By following the program 12, the control unit 11 implements various functions such as the correction value setting unit 12a, the printing data generation unit 12b, and the printing control unit 12c. Furthermore, the processor is not limited to a single CPU; it can be configured to process data using multiple CPUs, ASICs, or other hardware circuits, or it can be configured to process data in cooperation with hardware circuits.

[0026] The display unit 13 is a unit for displaying visual information, and may be configured as, for example, a liquid crystal display or an organic EL display. The display unit 13 may also include a display and driving circuitry for driving the display. The operation receiving unit 14 is a unit for receiving user operations, and may be implemented using physical buttons, a touch panel, a mouse, a keyboard, etc. Of course, a touch panel may also be implemented as a function of the display unit 13. The operation panel of the printing apparatus 10, which may include the display unit 13 and the operation receiving unit 14, may also be a separate unit.

[0027] The display unit 13 and the operation receiving unit 14 may be part of the printing apparatus 10, or they may be peripheral devices external to the printing apparatus 10.

[0028] Communication IF 15 is a general term for one or more IFs used by the printing apparatus 10 to perform wired or wireless communication with external devices according to a specified communication protocol including known communication standards. The control unit 11 can communicate via communication IF 15 with, for example, a personal computer, server, smartphone, tablet terminal, etc. (not shown).

[0029] Storage unit 16 is, for example, a storage unit based on hard disk drive, solid-state drive, or other memory. A portion of the memory included in control unit 11 may also be considered storage unit 16. Storage unit 16 may also be considered part of control unit 11.

[0030] The printing unit 17 includes a transport unit 18, a print head 19, and a PG adjustment unit 20. PG is short for paper gap. The printing apparatus 10 with the printing unit 17 is equivalent to an inkjet printer that uses the print head 19 to eject liquids such as ink for printing. The ink droplets ejected by the print head 19 are also called dots.

[0031] The conveying unit 18 is a unit for conveying printing media such as paper along a specified conveying direction, and includes, for example, a roller that rotates and conveys the printing media, and an electric motor for driving the roller.

[0032] like Figure 2 As illustrated, the print head 19 has a plurality of nozzles 21 from which the printing medium 30 conveyed to the transport section 18 is ejected. It is well known that the printing apparatus 10 controls the application of drive signals to drive elements (not shown) on the nozzles 21 according to printing data, thus determining whether or not ink is ejected from the nozzles 21. The print head 19 performs printing by ejecting, for example, cyan (C), magenta (M), yellow (Y), black (K) inks, or inks of other colors.

[0033] Figure 2 The relationship between the print head 19 and the printing medium 30 is simply shown from a top viewpoint. The print head 19 may also be referred to as a recording head, a printing head, a liquid ejection head, etc. The printing medium 30 is typically paper, but it can also be a medium made of materials other than paper, as long as it is a medium that can be printed by ejecting liquid.

[0034] Direction D1 indicates the "transport direction D1" of the printing medium 30 in the transport section 18. Furthermore, direction D2, which is orthogonal or approximately orthogonal to the transport direction D1, is referred to as the "width direction D2" of the printing medium 30. The print head 19 is constructed by connecting multiple print head chips 22 along a direction intersecting the transport direction D1, and the length of the long side of the print head 19 is sufficient to cover the width of the printing medium 30. The upstream and downstream directions of the transport direction D1 are simply referred to as upstream and downstream.

[0035] The multiple printhead chips 22 all have the same configuration. The number of printhead chips 22 constituting the printhead 19 only needs to be two or more. The printhead chip 22 has multiple rows of nozzles 23 in its configuration of receiving CMYK inks from a liquid holding unit (not shown) mounted on the printing section 17, such as an ink cartridge or ink container, and ejecting them from the nozzles 21. Figure 2 In the diagram, small white circles represent individual nozzles 21. In the printhead 22, each nozzle row 23 consists of multiple nozzles 21 arranged at fixed or substantially fixed intervals (nozzle spacing) along the long side of the printhead 19. The long side of the printhead 19 is also referred to as the "nozzle arrangement direction D3". Figure 2In the example, the nozzle arrangement direction D3 is parallel to the width direction D2 and orthogonal to the conveying direction D1.

[0036] The nozzle array 23 consisting of nozzles 21 ejecting C ink is also referred to as nozzle array 23C. Similarly, the nozzle array 23 consisting of nozzles 21 ejecting M ink is referred to as nozzle array 23M, the nozzle array 23 consisting of nozzles 21 ejecting Y ink is referred to as nozzle array 23Y, and the nozzle array 23 consisting of nozzles 21 ejecting K ink is referred to as nozzle array 23K. Nozzle arrays 23C, 23M, 23Y, and 23K are aligned in the nozzle arrangement direction D3 and are arranged in a direction orthogonal to the nozzle arrangement direction D3.

[0037] Figure 2 The example illustrates a so-called linear inkjet printer, where the print head 19 performs printing by ejecting ink from the printing medium 30 conveyed along the transport direction D1. That is, in Figure 2 In the example, the transport direction D1 corresponds to the relative movement direction of the printing medium 30 and the print head 19. Alternatively, the print head 19 can be configured to move relative to the stationary printing medium 30 along the transport direction D1 while simultaneously ejecting ink. Furthermore, in Figure 2 In the example, the transport direction D1 is equivalent to the "first direction", and the width direction D2 is equivalent to the "second direction". In the printing medium 30, the line in which the display points are arranged along the transport direction D1 is called the "grid line".

[0038] like Figure 2 As shown, the interconnected head chips 22 are linked together in such a way that a portion of their nozzle arrays 23 overlap in the nozzle arrangement direction D3. The range of nozzles 21 in which a portion of the nozzle arrays 23 overlaps with each other is called the "OL section 24". OL is short for overlap. The head chips 22 are linked together in such a way that the nozzles 21 of one nozzle array 23 sharing the OL section 24 and the nozzles 21 of the other nozzle array 23 are aligned in the nozzle arrangement direction D3. It can also be considered that such a plurality of head chips 22 have a nozzle array of length covering the width of the printing medium 30 for each CMYK ink. To distinguish it from the OL section 24, the range of nozzles 21 in the nozzle array 23 that do not correspond to the OL section 24 is called the "normal section".

[0039] In this embodiment, the ink of a specified color refers to any color of ink that the printhead 19 can spray. Among the two nozzle rows 23 that spray the specified color, i.e., a certain type of ink, one of the two nozzle rows 23 that share a common OL section 24 is referred to as the "first nozzle row" and the other as the "second nozzle row". For example, the two nozzle rows 23K that share the OL section 24 form a relationship between the first nozzle row and the second nozzle row.

[0040] Figure 3 The relationship between the print head 19 and the print medium 30 is simply shown from a viewpoint facing the width direction D2. Symbol 26 is a pressure plate 26 that is part of the transport path of the print medium 30. The pressure plate 26 supports the transported print medium 30 from below.

[0041] A first roller pair consisting of rollers 18a and 18b is arranged upstream of the printhead 19. Furthermore, a second roller pair consisting of rollers 18c and 18d is arranged downstream of the printhead 19. These roller pairs are part of the transport section 18. The roller pairs rotate with the printing medium 30 sandwiched between the rollers forming the pair, thereby transporting the printing medium 30 downstream. Of course, the rollers in the transport section 18 are not limited to those shown in the figure. Furthermore, the unit of the transport section 18 for transporting the printing medium 30 can also be a belt or a worktable capable of carrying and moving the printing medium 30.

[0042] A printing head 19 is supported above the pressure plate 26. The lower surface of the printing head 19, which is opposite to the pressure plate 26, is a nozzle face 25 with nozzles 21 opening. Ink is ejected from each nozzle 21 with openings in the nozzle face 25 onto the printing medium 30 supported by the pressure plate 26. Figure 3 The figure PG is shown as the distance between the printing medium 30 and the print head 19. PG can also be referred to as the head height in terms of the height of the print head 19 from the printing medium 30.

[0043] The PG adjustment unit 20 includes, for example, a motor and a support mechanism for moving the print head 19 up and down. The PG adjustment unit 20 adjusts the PG by moving the print head 19 away from or towards the pressure plate 26. Alternatively, a distance sensor capable of measuring the PG can be mounted on the print head 19, and the control unit 11 can monitor the measurement results of the distance sensor while accurately adjusting the PG of the PG adjustment unit 20. Furthermore, the distance sensor can measure the distance from the print head 19 to the pressure plate 26, and the control unit 11 can subtract the thickness of the printing medium 30 from this measurement result to determine the PG.

[0044] The configuration that includes the PG adjustment unit 20 and is capable of adjusting the PG is not a necessary configuration in this embodiment, and in particular, it may not be present in the first embodiment described later.

[0045] from Figure 2As can be seen from the positional relationship between the normal section and the OL section 24 described herein, the printing control section 12c of the control section 11 prints a "first region" and a "second region" onto the printing medium 30 via the print head 19. The "first region" has multiple "first grid lines" rendered with ink of a specified color arranged in the width direction D2. The "second region" is sandwiched between the first region in the width direction D2 and also has "second grid lines" rendered with ink of a specified color arranged in the width direction D2. The first region corresponds to the "non-OL region," and the second region corresponds to the "OL region." That is, the first grid lines are printed by the nozzles 21 of the normal section, and the second grid lines are printed by the nozzles 21 of the OL section 24. One first grid line is printed using one nozzle 21 in the normal section. On the other hand, one second grid line is printed using two nozzles 21 in the OL section 24, namely, the nozzle 21 belonging to the first nozzle column and the nozzle 21 belonging to the second nozzle column. The number of nozzles used for printing one grid line differs between the first region and the second region. Therefore, compared to the first region, the printing density of the second region on the printing medium 30 is either higher or lower, and can be visually confirmed as a striped density unevenness.

[0046] The printing in the second area is performed using nozzles 21 from the first nozzle array and nozzles 21 from the second nozzle array at approximately the same ratio, i.e., 50% to 50%. However, if viewed in terms of the second grid lines constituting the second area, the ratio of nozzles 21 from the first nozzle array to nozzles 21 from the second nozzle array is not limited to 50% to 50%. For example, one second grid line may be printed with a ratio of 10% to 90% using nozzles 21 from the first nozzle array to nozzles 21 from the second nozzle array, while other second grid lines may be printed with a ratio of 90% to 10%. Furthermore, for example, one second grid line may be printed with a ratio of 30% to 70% using nozzles 21 from the first nozzle array to nozzles 21 from the second nozzle array, while other second grid lines may be printed with a ratio of 70% to 30% using nozzles 21 from the first nozzle array to nozzles 21 from the second nozzle array. That is, within the second region as a whole, the usage ratio of nozzles 21 in the first nozzle column and nozzles 21 in the second nozzle column need to be approximately the same. The nozzle 21 usage ratio referred to here is the value when the usage ratio of nozzle 21 is set to 100% when all pixels corresponding to a grid line in the image data are sprayed using one nozzle 21.

[0047] The printing apparatus 10 can be implemented not only by a single printer, but also by multiple devices connected in a manner that allows them to communicate with each other. For example, the printing apparatus 10 can also be implemented by a system that includes an information processing unit and a printer equivalent to the printing unit 17, the information processing unit including a control unit 11 and a storage unit 16.

[0048] The following description focuses on printing using any one of the various colors of ink ejected from printhead 19, such as K ink. However, the following description also applies to printing using other colors of ink.

[0049] 2. First implementation method:

[0050] Figure 4 This is a diagram used to illustrate the tilt of the print head 19, in conjunction with... Figure 2 The same viewpoint illustrates a first nozzle array and a second nozzle array. Additionally, in Figure 4 In the image, each nozzle 21 within the nozzle array is simply represented by black dots. Figure 4 The diagram shows nozzle rows 23K1 (belonging to one head chip 22) and 23K2 (belonging to another head chip 22) in the printhead 19. Nozzle rows 23K1 and 23K2 share an OL section 24, which corresponds to a first nozzle row and a second nozzle row. In this embodiment, the tilt of the nozzle arrangement direction D3 relative to the width direction D2 is defined as the tilt of the printhead 19. Hereinafter, the tilt of the printhead 19 is also referred to as "head tilt".

[0051] exist Figure 2 In the example, the head tilt is 0°, but in Figure 4 In the example, the nozzle arrangement direction D3 is slightly tilted to the left relative to the width direction D2, and the head tilt is not 0°. The print head 19 sometimes tilts relative to the width direction D2 due to errors in the installation angle during the assembly of each printing section 17, changes over time, unexpected external forces, etc. Of course, compared to... Figure 4 Conversely, sometimes the nozzle arrangement direction D3 is tilted to the right relative to the width direction D2. For convenience, the nozzle arrangement direction D3 can also be tilted relative to... Figure 4 The leftward tilt of the width direction D2 is considered a positive tilt, and the opposite rightward tilt is considered a negative tilt.

[0052] exist Figure 4 A portion of the printed image 31 printed on the printing medium 30 via the first and second nozzle rows is illustrated. The linear region extending along the transport direction D1, indicated by the symbol RL, is a grid line RL. Figure 4In this example, the printed image 31 has: a first region 32 printed by the nozzles 21 of the normal portion of the nozzle array 23K1; a second region 33 printed by the nozzles 21 of the OL portion 24 of the nozzle arrays 23K1 and 23K2; and a first region 34 printed by the nozzles 21 of the normal portion of the nozzle array 23K2. Furthermore, a region that is part of the first region 32 and adjacent to the second region 33 is referred to as an adjacent region 35, and a region that is part of the first region 34 and adjacent to the second region 33 is referred to as an adjacent region 36.

[0053] The coverage of ink in the printing medium 30 varies in the second region 33, which uses two nozzles 21 to print each grid line, depending on the head tilt. Therefore, if the head tilt is different, the density difference between the second region 33 and the first regions 32 and 34 will also be different. For example, if... Figure 4 As the leftward tilt becomes larger, the concentration in the second region 33 sometimes becomes more concentrated relative to the first regions 32 and 34.

[0054] In this embodiment, reference to Document 1 is sufficient. For an explanation of how the concentration difference between the second region (OL region) and the first region (non-OL region) changes with head tilt, reference to Document 1 is provided. Figure 3 , Figure 4 Explanation.

[0055] In the first embodiment, the description is based on the premise that the printing condition "changes the density difference between the second grid line and the first grid line" is head tilted. Furthermore, in the first embodiment, the PG mentioned in the second embodiment is fixed, and the influence of PG is ignored in the description.

[0056] Figure 5 The flowchart illustrates the preparation process of the correction value implemented by the control unit 11 according to program 12. The correction value refers to information used to correct the concentration of each grid line. This is achieved through... (as described later). Figure 6 As explained, the amount of ink in each grid line is adjusted to suppress the density deviation of each grid line in the printed result.

[0057] In step S100, the correction value setting unit 12a sets the "reference correction value ai". The reference correction value ai refers to the correction value that should be used when the head tilt is at the design reference value. Here, the head tilt = 0° is set as the reference value. The reference correction value ai can be set, for example, in the following manner. First, in the stage before the product of the printing apparatus 10 is shipped, etc., with the head tilted at 0° as accurately as possible and installed on the printing unit 17, the correction value setting unit 12a causes the print head 19 to print a test image based on K ink onto the printing medium 30 based on test image data representing a specified concentration such as 50%. Furthermore, for all grid lines on both sides of the first and second regions that are the printing results of the test image, the concentration is measured using a concentration meter, and the average concentration Ak0 of the measured concentration is calculated.

[0058] Next, the correction value setting unit 12a sets a reference correction value ai for the grid lines of interest to make the measured concentration k0i of the grid lines of interest consistent with the average concentration Ak0. Variable i is a variable used to identify each of all grid lines including the first and second regions, and its value ranges from 1 to the total number of grid lines. In the sense of grid line numbering, variable i is also called grid number. For example, the reference correction value ai can be the ratio of the difference Ak0-k0i to the average concentration Ak0 (Ak0-k0i) / Ak0. Furthermore, the correction value setting unit 12a stores the reference correction value ai set for each grid line in the storage unit 16. The reference correction value ai is positive or negative depending on the relationship between the average concentration Ak0 and the measured concentration k0i. When the correction value for a certain grid line is positive, the concentration of that grid line in the printed result is relatively light, thus meaning that a correction value has been obtained to make it darker. Conversely, if the correction value for a grid line is negative, the density of that grid line in the printed result will be relatively high, thus indicating that a correction value was obtained to make it lighter.

[0059] In step S110, the correction value setting unit 12a sets a "prescribed tilt correction value bi". The prescribed tilt correction value bi refers to the correction value to be used when the head tilt is a prescribed tilt α that is different from the reference value. As an example, α = +1°. The prescribed tilt correction value bi can be set in the same way as the reference correction value ai. In the stage before the product leaves the printing device 10, etc., with the head tilt = α, the correction value setting unit 12a causes the print head 19 to print the test image based on K ink onto the printing medium 30, and calculates the average concentration Akα of the measured concentration related to all grid lines of both the first and second regions, which are the printing results of the test image. Next, the correction value setting unit 12a sets a prescribed tilt correction value bi for the grid lines of interest to make the measured concentration kαi of the grid lines of interest consistent with the average concentration Akα. For example, the prescribed tilt correction value bi can be the ratio of the difference Akα-kαi to the average concentration Akα (Akα-kαi) / Akα. Furthermore, the correction value setting unit 12a stores the predetermined tilt correction value bi set for each grid line in the storage unit 16. Of course, the tilt correction value bi is also predetermined to be positive or negative based on the relationship between the average concentration Akα and the measured concentration kαi.

[0060] In step S120, the correction value setting unit 12a sets the "correction value offset ci" for the second grid line constituting the second region and the first grid line including a portion of the adjacent grid line. The "adjacent grid line" is a grid line that is the first grid line and is adjacent to the second region. Hereinafter, the first grid line including a portion of the adjacent grid line will be simply referred to as the "partial first grid line".

[0061] The correction offset ci can be obtained by the following formula (1).

[0062] ci=bi-ai…(1)

[0063] That is, the difference between the specified tilt correction value bi and the reference correction value ai for the same grid number (variable i) is set as the correction value offset ci. For the second region, the correction value setting unit 12a sets its own correction value offset ci for all second grid lines. On the other hand, for the first region, the correction value setting unit 12a sets its own correction value offset ci for a portion of the first grid lines. Furthermore, the correction value setting unit 12a stores the set correction value offset ci in the storage unit 16.

[0064] Reference Figure 4A specific example of step S120 will be explained. As an example, nozzle arrays 23K1 and 23K2 each have 100 nozzles 21, with the five nozzles 21 at their ends overlapping. In this case, the five second grid lines printed by the 10 nozzles 21 of the OL section 24 constitute the second region 33. Therefore, in step S120, the correction value setting unit 12a sets a correction value offset ci for each of these five second grid lines. The correction value offset ci of the second grid lines can be considered as a correction value used to correct the density change of the second grid lines generated in the printing result based on the change from the reference value tilted from the beginning to the specified tilt α.

[0065] Furthermore, in step S120, the correction value setting unit 12a sets a correction value offset ci for each of the first grid lines constituting adjacent regions 35 and 36. That is, the adjacent regions 35 and 36 are a portion of the first grid lines. Figure 4 The diagram shows an example where adjacent regions 35 and 36 are each composed of two or more specific numbers of first grid lines. However, adjacent regions 35 and 36 could also be simply adjacent grid lines.

[0066] Here, the density of the second region in the printed result varies due to different head tilts. Therefore, the tilt correction value *bi* is defined as a different value from the reference correction value *ai*, and the correction value offset *ci* is essentially not zero. That is, the correction value offset *ci* of the second grid line is not zero. On the other hand, it is also anticipated that the density of the first region in the printed result is almost unaffected by head tilt. Therefore, the tilt correction value *bi* is defined as the same value as the reference correction value *ai*, and the correction value offset *ci* is zero. That is, the correction value offset *ci* of the first grid line is more likely to be zero compared to the correction value offset *ci* of the second grid line.

[0067] When calculating the correction value offset ci of the first grid line constituting adjacent regions 35 and 36, even if the calculation result is assumed to be 0, the correction value setting unit 12a sets a non-zero correction value offset ci. For example, the correction value setting unit 12a may set the first grid line constituting adjacent region 35 to the same value as the correction value offset ci of the second grid line constituting the second region 33 that is adjacent to the adjacent region 35, or a value to which a predetermined correction has been applied. Similarly, the correction value setting unit 12a may set the first grid line constituting adjacent region 36 to the same value as the correction value offset ci of the second grid line constituting the second region 33 that is adjacent to the adjacent region 36, or a value to which a predetermined correction has been applied.

[0068] The above is a flowchart of the calibration value setting unit 12a completing the calibration value preparation process.

[0069] Furthermore, in step S120, the specified tilt correction value bi required for setting the correction value offset ci is the specified tilt correction value bi of the second grid line and the specified tilt correction value bi of a portion of the first grid line. Therefore, for the first grid line that is not the object of setting the correction value offset ci in step S120, the correction value setting unit 12a may not set the specified tilt correction value bi in step S110.

[0070] Figure 6 The flowchart illustrates the printing control process implemented by the control unit 11 according to program 12. The printing control process is performed after the correction value preparation process has been completed. The printing control process involves the correction of image data using the correction values.

[0071] In step S200, the print data generation unit 12b acquires image data representing an image of the printing object. For example, the user visually confirms the UI screen displayed on the display unit 13 and operates the operation receiving unit 14 to arbitrarily select an image as the printing object. UI is short for User Interface. The print data generation unit 12b acquires image data related to the image selected by the user from a predetermined storage source.

[0072] In this embodiment, the printing data generation unit 12b performs correction on the image data of the ink color system used by the print head 19 in printing based on correction values. Therefore, the printing data generation unit 12b performs color conversion on the color system of the acquired image data as needed for correction. Color conversion can be performed, for example, by referring to a color conversion lookup table for converting the color system. In this step S200, as a result, the printing data generation unit 12b acquires CMYK image data in bitmap form, where each pixel has a grayscale value for each CMYK. The grayscale value is, for example, a value represented by 256 gray levels from 0 to 255, and is also referred to as ink amount. Furthermore, ink amount represents the density of each pixel.

[0073] In step S210, the control unit 11 acquires the head tilt. The head tilt acquired in step S210 is recorded as "head tilt β". The control unit 11 only needs to be able to acquire the current head tilt β, and the acquisition method is not particularly limited. For example, the control unit 11 can cause the print head 19 to perform printing of a pattern image such as grid lines for detecting head tilt β, and the user who has visually confirmed the tilt of the grid lines, etc., as a result of the printing of the pattern image inputs the head tilt β through the operation receiving unit 14. Alternatively, the reading device can automatically read the printing result of the pattern image, and the control unit 11 can calculate the head tilt β by analyzing the read image data acquired from the reading device. Alternatively, the printing unit 17 can have a sensor for detecting head tilt β, and the control unit 11 can input the detection result of the sensor to acquire the head tilt β. Of course, the description related to the tilt angle acquisition unit in the aforementioned document 1 can also be used to acquire the head tilt β. In addition, the timing of executing step S210 can also be before step S200.

[0074] In step S220, the correction value setting unit 12a uses information stored in the storage unit 16 during the correction value preparation process to set a "correction value di" corresponding to the head tilt β for the second grid lines constituting the second region and a portion of the first grid lines. For the first grid lines other than a portion of the first grid lines, it is not necessary to set a correction value di. Step S220 is equivalent to at least a part of the "correction value setting process". If the reference correction value ai, the correction value offset ci, and the head tilt β are known, then, for example, the correction value di for correcting the concentration of the second grid lines under the head tilt β condition can be calculated using the following formula (2).

[0075] di=ai+(β / α)ci…(2)

[0076] For example, if α = +1° and β = +2°, then according to equation (2), di = ai + 2ci. According to ci = bi - ai, equation (2) can be written as equation (3).

[0077] di=ai+(β / α)(bi-ai)…(3)

[0078] Assuming β = α, then di = bi. Furthermore, if β = 0°, then di = ai.

[0079] If the baseline correction value ai and the specified tilt correction value bi are known, then the offset of the correction value ci can be calculated. Figure 5 Step S120 may also be performed during the timing of step S220, instead of during the correction value preparation process.

[0080] Furthermore, the coefficient multiplied by the correction value offset ci may not be the ratio of head tilt β to specified tilt α itself, but as shown in equation (4), which is a function f(β / α) corresponding to the ratio β / α.

[0081] di=ai+f(β / α)×ci…(4)

[0082] Any of equations (2), (3), and (4) can be used, but equation (2) is used here. See again... Figure 4 For a specific example, in step S220, the correction value setting unit 12a sets a correction value di for each of the second grid lines constituting the second region 33. Furthermore, the correction value setting unit 12a sets a correction value di for each of the first grid lines constituting adjacent regions 35 and 36.

[0083] Figure 7 This diagram illustrates the process of setting the correction value di for each grid line RL corresponding to the head tilt β in step S220. Figure 7 In this context, specific raster numbers (variable i) are used to identify raster lines RL, correction values ​​ai, bi, and correction offset ci. Figure 7 In the example, the five grid lines RL96 to RL100 correspond to the second grid lines, i.e., the second region 33. Furthermore, in... Figure 7 In the example, grid lines RL94, RL95, RL101, and RL102 form the first grid line of a portion. Grid lines RL94 and RL95 correspond to adjacent region 35, and grid lines RL101 and RL102 correspond to adjacent region 36. Grid lines RL95 and RL101 are adjacent grid lines. Figure 7 For example, the correction value setting unit 12a sets correction values ​​di for these grid lines RL94 to RL102 respectively. For example, the correction value di for grid line RL96 with i = 96 is a96 + (β / α) × c96.

[0084] In step S230, the printing data generation unit 12b corrects the image data according to the correction value of each grid line. The image data has grid lines composed of multiple pixels arranged corresponding to the transport direction D1 as data. The grid lines in the image data can also be referred to as grid line data. The printing data generation unit 12b corrects the ink amount of each pixel K constituting a certain grid line in the image data according to the correction value K for that grid line.

[0085] The printing data generation unit 12b can correct the first grid line in the image data that is not a part of the first grid line by using the reference correction value ai set for each grid line in the correction value preparation process. Of course, the first grid line and the second grid line in the image data can be corrected by using the correction value di set for each grid line in step S220. For example, when the gray value of the ink amount of K ink representing a certain pixel is set to P, and the correction value of K for the grid line to which the pixel belongs is set to Hi, the printing data generation unit 12b can calculate the corrected gray value Q of the gray value P according to the following formula (5).

[0086] Q = P + Hi × P…(5)

[0087] The correction value di or ai is substituted into the correction value Hi based on the grid line to which the pixel to be corrected belongs. Of course, in equation (5), coefficients or constants can be further used to make the correction more reasonable. This correction is performed on all pixels of the image data. As a result, grid lines that are relatively lighter in density in the printed result without correction are corrected to have increased ink amount, and conversely, grid lines that are relatively darker in density in the printed result without correction are corrected to have decreased ink amount.

[0088] In step S240, the printing data generation unit 12b converts the corrected image data from step S230 to generate printing data. Specifically, the printing data generation unit 12b performs halftone processing on the corrected image data, converting each pixel into binary image data specifying whether ink is ejected (dot on) or not ejected (dot off) for each CMYK. Of course, the printing data is not limited to binary image data; it can also be multi-valued image data specifying whether any point in multiple sizes such as large, medium, and small is dot on or dot off. These steps S230 and S240 are equivalent to a "printing data generation process." In addition, "printing data" is only the name of the data processed in step S240, so it can also continue to be referred to as image data.

[0089] In step S250, the printing control unit 12c performs output processing, which causes the printing unit 17 to execute printing based on the printing data generated in step S240. Specifically, the printing control unit 12c arranges the pixel data of each grid line of the printing data according to the order in which each nozzle 21 of the print head 19 is used, distributes it to each nozzle 21, and transfers it to the print head 19. Furthermore, the printing control unit 12c causes the transport unit 18 to begin transporting the printing medium 30. As a result, in the printing unit 17, by driving the print head 19 and the transport unit 18, the image represented by the printing data is printed onto the printing medium 30. Of course, at this time, as referred to... Figure 2As explained, on the printing medium 30, the first grid lines are printed through the nozzles 21 of the normal section, and the second grid lines are printed through the nozzles 21 of the OL section 24. Step S250 corresponds to a "printing control process," which, based on the corrected image data, causes the print head 19 to print a first region and a second region onto the printing medium 30. The first region has multiple first grid lines arranged in a second direction intersecting the first direction, and the second region is sandwiched between the first region in the second direction and has second grid lines. The above is the flowchart for ending the printing control process.

[0090] 3. Second implementation method:

[0091] Next, the second embodiment will be described. As described above, the PG adjustment unit 20 can adjust the PG. If the PG is different, the flight time of the dots ejected from the printhead 19 to the printing medium 30 will be different, and the degree to which the dots are affected by the airflow during flight will also be different. Therefore, in the second region 33 where each grid line is printed using two nozzles 21, the ink coverage in the printing medium 30 is easily affected by the PG. Therefore, if the PG is different, the concentration difference between the second region 33 and the first regions 32 and 34 will also be different.

[0092] For example, even if there is a tendency for the second region 33 to be printed with a higher concentration than the first regions 32 and 34, there are cases where the larger the PG, the lighter the second region 33 becomes, and the concentration difference between the second region 33 and the first regions 32 and 34 decreases. Therefore, in the second embodiment, the description is based on the premise that the "printing conditions that cause the concentration difference between the second grid lines and the first grid lines to change" are PG. In the second embodiment, the effect of head tilt is ignored as the head tilt is fixed. Furthermore, in the second embodiment, descriptions common to the first embodiment are appropriately omitted.

[0093] Figure 8 The flowchart illustrates the correction value preparation process in the second embodiment.

[0094] Figure 9 The printing control process in the second embodiment is illustrated by a flowchart.

[0095] The second embodiment rereads the head tilt in the first embodiment as "PG", the reference correction value ai in the first embodiment as "reference correction value ei", the specified tilt correction value bi as "specified PG correction value fi", the correction value offset ci as "correction value offset gi", the correction value di as "correction value hi", the tilt α as "pg1", and the tilt β as "pg2", which can be roughly understood.

[0096] exist Figure 8 In step S300, the correction value setting unit 12a sets a "reference correction value ei". The reference correction value ei refers to the correction value to be used when PG is the reference value. The reference value of PG can be set to any value, but as an example, the minimum value that PG can be used is set as the reference value. Hereinafter, the reference value of PG will be referred to as "pg0". The reference correction value ei can be set in accordance with the first embodiment. That is, in the stage before the product leaves the printing apparatus 10, when PG = pg0, the correction value setting unit 12a causes the print head 19 to print the test image based on K ink onto the printing medium 30, and calculates the average concentration of the measured concentration related to all grid lines in both the first and second regions, which are the printing results of the test image. Next, the correction value setting unit 12a sets a reference correction value ei for the grid lines of interest to make the measured concentration of the grid lines of interest consistent with the average concentration. That is, the reference correction value ei for the grid lines of interest can be the ratio of the difference between the average concentration and the measured concentration of the grid lines of interest to the average concentration. The correction value setting unit 12a stores the reference correction value ei set for each grid line in the storage unit 16 in the manner described above.

[0097] In step S310, the correction value setting unit 12a sets a "prescribed PG correction value fi". The prescribed PG correction value fi refers to the correction value to be used when PG is a prescribed PG that is different from the reference value pg0. Hereinafter, the prescribed PG will be referred to as "pg1". Here, pg1 > pg0. The prescribed PG correction value fi can also be set in accordance with the description up to this point. That is, in the stage before the product of the printing apparatus 10 leaves the factory, when PG = pg1, the correction value setting unit 12a causes the print head 19 to print the test image based on K ink onto the printing medium 30, and calculates the average concentration of the measured concentration related to all grid lines of both the first and second regions, which are the printing results of the test image. Next, the correction value setting unit 12a sets a prescribed PG correction value fi for the grid lines of interest to make the measured concentration of the grid lines of interest consistent with the average concentration. The prescribed PG correction value fi for the grid lines of interest can be the ratio of the difference between the average concentration and the measured concentration of the grid lines of interest to the average concentration. The correction value setting unit 12a stores the specified PG correction value fi set for each grid line in the storage unit 16 in the manner described above.

[0098] In step S320, the correction value setting unit 12a sets a "correction value offset gi" for the second grid line and a portion of the first grid line constituting the second region. The correction value offset gi can be calculated as gi = fi - ei. The correction value setting unit 12a stores the set correction value offset gi in the storage unit 16. As can be seen from the description so far, the correction value offset gi of the second grid line can be considered as a correction value used to change the density of the second grid line generated in the printing result according to the change of PG from the reference value pg0 to the predetermined value pg1.

[0099] If the PG values ​​are different, the density of the second region in the printed result will be different. Therefore, the PG correction value fi and the reference correction value ei are specified to be different values, and the correction value offset gi is essentially not 0. That is, the correction value offset ci of the second grid line is not 0. On the other hand, it is also anticipated that the density of the first region in the printed result will not be affected by the PG to the extent of the second region. Therefore, the PG correction value fi and the reference correction value ei are specified to be the same value, and the correction value offset gi is 0. When calculating the correction value offset gi of a portion of the first grid line, the correction value setting unit 12a sets a non-zero correction value offset gi in the same way as in the first embodiment, even if the calculation result is 0. The above is a flowchart of the correction value setting unit 12a completing the correction value preparation process.

[0100] Figure 9 Step S400 and Figure 6 The steps are the same as in step S200.

[0101] In step S410, the control unit 11 acquires the PG. The PG acquired in step S410 is recorded as "PG at use". The control unit 11 only needs to acquire the PG at use, and the acquisition method is not particularly limited. If the user sets the PG to be used during printing from multiple PGs through the operation receiving unit 14, causing the PG adjustment unit 20 to adjust the configuration of the PG, then the control unit 11 only needs to acquire the currently set PG as the PG at use. Furthermore, as described above, if the printing unit 17 has a distance sensor capable of measuring the PG, the control unit 11 can also acquire the PG at use based on the measurement result of the sensor. Hereinafter, the PG at use acquired in step S410 will be recorded as "pg2".

[0102] In step S420, the correction value setting unit 12a uses information stored in the storage unit 16 during the correction value preparation process to set a "correction value hi" corresponding to the usage PG for the second grid line and a portion of the first grid line constituting the second region. If the reference correction value ei, the correction value offset gi, and the usage PG are known, the correction value hi for correcting the concentration of the second grid line under the usage PG condition can be calculated. Following the first embodiment, the correction value setting unit 12a only needs to calculate the correction value hi, for example, as hi = ei + (pg2 / pg1)gi. Assuming pg2 = pg1, hi = fi. In addition, if pg2 = pg0, the correction value setting unit 12a considers pg2 / pg1 as 0, and hi = ei.

[0103] Figure 10 This diagram illustrates the process of setting the correction value hi for each grid line RL corresponding to pg2 in step S420. Figure 10 Observation methods and Figure 7 The observation method is the same. That is, grid lines RL96 to RL100 correspond to the second grid lines, and grid lines RL94, RL95, RL101, and RL102 correspond to a portion of the first grid lines. According to... Figure 10 For example, the correction value setting unit 12a sets correction values ​​hi for these grid lines RL94 to RL102 respectively. For example, the correction value hi for grid line RL96 with i = 96 is e96 + (pg2 / pg1) × g96.

[0104] In step S430, similar to step S230, the printing data generation unit 12b corrects the image data based on the correction value of each grid line. The printing data generation unit 12b only needs to use the reference correction value ei for each grid line set in the correction value preparation process to correct the first grid line in the image data that is not a part of the first grid line. Of course, the correction values ​​hi for each grid line set in step S420 are used to correct a portion of the first grid line and the second grid line in the image data.

[0105] Steps S440 and S450 are the same as steps S240 and S250.

[0106] 4. Summary:

[0107] Therefore, according to this embodiment, the printing apparatus 10 includes: a print head 19 having a plurality of nozzles 21 for ejecting ink of a predetermined color; a correction value setting unit 12a for setting a correction value for each grid line for correcting the density of each grid line representing the ink dots arranged along a first direction; a print data generation unit 12b for correcting image data based on the correction value of each grid line; and a print control unit 12c for causing the print head 19 to print a first region and a second region onto a print medium 30 based on the corrected image data. The first region has a plurality of first grid lines represented by the ink arranged in a second direction intersecting the first direction, and the second region is sandwiched between the first region in the second direction and has second grid lines represented by the ink. The print control unit 12c causes the print head 19 to print one first grid line through a predetermined number of nozzles 21 and to print one second grid line through a greater number of nozzles 21 than the predetermined number. The correction value setting unit 12a sets a correction value applied to the second grid line and a correction value applied to the first grid line, which includes a portion of the first grid line adjacent to the second region, based on printing conditions that cause the density difference between the second grid line and the first grid line to change.

[0108] According to the aforementioned configuration, a correction value applied to the second grid line is set based on printing conditions that cause a change in the density difference between the second grid line and the first grid line. Therefore, when printing under these conditions, the density of the second grid line can be appropriately corrected, suppressing striped density unevenness in the printed result. Furthermore, in this configuration, a correction value applied to a "part of the first grid line" is also set according to the printing conditions. As a result, by supplementing the density correction of the second grid line with the density correction of adjacent first grid lines, it is possible to more appropriately suppress the second grid line from appearing as striped density unevenness in the printed result.

[0109] According to the first embodiment and the second embodiment, the printing conditions refer to at least one of the tilt of the print head 19 relative to the second direction (head tilt) or the distance (PG) between the print medium 30 and the print head 19.

[0110] The effects of this implementation method will be explained in more detail.

[0111] For example, when the head tilt is at a certain tilt β, the second region tends to be printed lighter than the first region. In this case, the second grid lines constituting the second region are printed based on a correction performed by increasing the density according to the degree of tilt β. Therefore, in the printing result, the white stripes in the second region that are visually perceived as faint are suppressed to some extent. However, the second region is smaller than the first region, so sometimes the effect of suppressing stripe-like density unevenness is insufficient by adjusting the density of the second grid lines themselves alone. In contrast, in this embodiment, a portion of the first grid lines are also printed based on a correction performed by increasing the density according to the degree of tilt β. Therefore, in the printing result, the density of the second grid lines is supplemented nearby based on the density of a portion of the first grid lines, and the white stripes that are visually perceived as faint in the second region are suppressed more appropriately. The same effect is achieved when the PG is at a certain pg2, and the second region tends to be printed lighter than the first region. Of course, in the case of correcting for the dark stripes in the second region that are visually identified as being darker than the first region due to head tilt and PG, the concentration correction of the first grid line based on this part also has a supplementary effect on the second grid line.

[0112] The combination of the first embodiment and the second embodiment is also within the scope of this embodiment.

[0113] That is, the correction value setting unit 12a can also set correction values ​​applied to the second grid line and correction values ​​applied to a portion of the first grid line based on the head tilt and PG. For example, the correction value setting unit 12a can simply set the correction value of the grid line with grid number i to (di+hi) / 2 for the second grid line and the portion of the first grid line. Alternatively, the correction value can be the value obtained by weighting di and hi according to the rules related to the head tilt and PG.

[0114] This embodiment is not limited to printing apparatus or system, but discloses inventions of various categories such as methods executed by apparatus or system and programs 12 for causing processors to execute methods.

[0115] For example, a printing method controls a print head 19 having multiple nozzles 21 that eject ink of a specified color to print on a printing medium 30. The printing method includes: a correction value setting step, which sets a correction value for each grid line used to correct the density of each grid line representing the ink dots arranged along a first direction; a print data generation step, which corrects image data based on the correction value of each grid line; and a print control step, which, based on the corrected image data, causes the print head 19 to print a first region and a second region onto the printing medium 30. The first region has multiple first grid lines represented by the ink arranged in a second direction intersecting the first direction, and the second region is sandwiched between the first region in the second direction and has second grid lines represented by the ink. In the print control step, the print head 19 prints one first grid line through a specified number of nozzles 21 and prints one second grid line through a number greater than the specified number of nozzles 21. In the calibration value setting process, calibration values ​​applied to the second grid line and calibration values ​​applied to the first grid line, including a portion of the first grid line adjacent to the second region, are set according to the printing conditions that cause the density difference between the second grid line and the first grid line to change.

[0116] 5. Variation example:

[0117] Some variations included in this embodiment will be described. Combinations of these variations are also within the scope of this embodiment.

[0118] Variation Example 1:

[0119] Alternatively, the correction value setting unit 12a may change the range in the second direction of the first grid line for which the correction value is set according to the printing conditions. "The range in the second direction of the first grid line for which the correction value is determined according to the printing conditions" refers to the width in direction D2 of adjacent regions 35 and 36, and is also the number of first grid lines constituting these regions. Adjacent regions 35 and 36 must each include adjacent grid lines; therefore, the minimum width of each of adjacent regions 35 and 36 is only the width of the adjacent grid line, i.e., the width of one first grid line.

[0120] The more the head tilt β deviates from the reference value of head tilt, the greater the concentration difference between the first region and the second region will be. Therefore, in the first embodiment, for example, the greater the difference between the reference value of head tilt and the head tilt β obtained in step S210, the more the correction value setting unit 12a increases the width in the direction D2 of the adjacent regions 35, 36 that are the objects of setting the correction value di in step S220.

[0121] Furthermore, as an example, it is conceivable that a larger PG tends to result in a smaller concentration difference between the first and second regions. In this case, in the second embodiment, the larger the pg2 obtained in step S410 as the PG during use, the smaller the width of the correction value setting unit 12a in the direction D2 of the adjacent regions 35 and 36 that are the setting objects as the correction value hi in step S420. However, if it is observed that a larger PG tends to result in a larger concentration difference between the first and second regions, then the larger the pg2 obtained in step S410 as the PG during use, the larger the width of the correction value setting unit 12a in the direction D2 of the adjacent regions 35 and 36 that are the setting objects as the correction value hi in step S420.

[0122] Based on this variation, the range of the first grid line of the object for which the correction values ​​di and hi are set is determined by matching the degree of printing conditions such as head tilt β and usage PG. Therefore, the effect of supplementing the density of the second grid line through the density correction of the first grid line can be made more reasonable, avoiding over-supplementation or under-supplementation.

[0123] Variation Example 2:

[0124] Alternatively, when setting a correction value based on printing conditions, the correction value setting unit 12a sets a correction value so that the value applied to each grid line changes linearly from the first grid line to the center of the second region in the second direction.

[0125] Figure 11 This is a graph used to illustrate this correction value. In Figure 11 In the diagram, the usage ratio and correction value of nozzle 21 are shown according to grid number (variable i). As explained so far, i = 94 and 95 refer to the first grid line constituting adjacent region 35, i = 96 to 100 refer to the second grid line constituting second region 33, and i = 101 and 102 refer to the first grid line constituting adjacent region 36.

[0126] exist Figure 11 In the diagram, the usage ratio represented by solid lines is the usage ratio of each nozzle 21 constituting nozzle row 23K1, which is the first nozzle row, and the usage ratio represented by dashed lines is the usage ratio of each nozzle 21 constituting nozzle row 23K2, which is the second nozzle row. The grid lines up to i = 95 are the first grid lines. To print these first grid lines, the usage ratio of each nozzle 21 in the normal portion of nozzle row 23K1 is 100%, and the usage ratio of each nozzle 21 in nozzle row 23K2 is 0%. Furthermore, the grid lines from i = 101 onwards are the first grid lines. To print these first grid lines, the usage ratio of each nozzle 21 in the normal portion of nozzle row 23K2 is 100%, and the usage ratio of each nozzle 21 in nozzle row 23K1 is 0%.

[0127] according to Figure 11 The usage ratio of each nozzle 21 in the OL section 24 of the nozzle column 23K1 used for printing the second grid lines i = 96 to 100 decreases as the grid number increases. Conversely, the usage ratio of each nozzle 21 in the OL section 24 of the nozzle column 23K2 used for printing the second grid lines i = 96 to 100 increases as the grid number increases. The sum of the usage ratios of the nozzles 21 in the nozzle column 23K1 and the nozzles 21 in the nozzle column 23K2 used for printing the second grid lines i = 96 to 100 is 100% in each second grid line. Therefore, the second grid line located in the center of the second region 33 in the second direction... Figure 11 In the example of the second grid line i=98, the usage ratio of nozzle 21 of nozzle column 23K1 used for printing is approximately 50% to 50% of the usage ratio of nozzle 21 of nozzle column 23K2.

[0128] Therefore, in order to print the second area 33, the following method was adopted. Figure 11 With that usage ratio, in the second region 33, it was also observed that the density difference between the second grid line located closer to the center and the first grid line tended to be greater. Conversely, in the second region 33, the second grid lines closer to the first region 32 and the second grid lines closer to the first region 34 were mainly printed using nozzles 21 from either the first or second nozzle array, and therefore a tendency was observed for the density difference with the first grid line to decrease. Therefore, it can be considered that the required degree of correction is different for each second grid line constituting the second region 33.

[0129] Therefore, the correction value setting unit 12a sets the correction value di or correction value hi, which are set for a portion of the first grid lines and the second grid lines respectively in steps S220 and S420, as follows: Figure 11 As shown, it linearly changes in the second direction from a portion of each of the first regions sandwiching the second region towards the center of the second region. Figure 11 In the example, the correction value di or hi represents a positive correction value, that is, a correction value used to increase the concentration of a portion of the first and second grid lines, and the closer the grid line is to the center of the second region 33, the greater the increase in concentration. Of course, sometimes a negative correction value is set, that is, a correction value used to decrease the concentration of a portion of the first and second grid lines, and the closer the grid line is to the center of the second region 33, the greater the decrease in concentration. In other... Figure 11In this context, the correction values ​​ai or ei applied to each of the first grid lines, except for a portion of them, are simply represented as fixed values. According to this variation, the correction value di or hi can be an appropriate value that roughly corresponds to the difference in concentration of each grid line corresponding to the usage ratio of nozzle 21.

[0130] In steps S220 and S420, the correction value setting unit 12a, by executing the processes described up to the first and second embodiments, can sometimes set a correction value di or hi that linearly changes from the adjacent regions 35 and 36 towards the center of the second region 33 in the second direction. Alternatively, if executing the processes described up to the first and second embodiments alone cannot set a correction value di or hi that linearly changes towards the center of the second region in the second direction, the correction value setting unit 12a further adjusts the correction value and sets it to a correction value di or hi that linearly changes towards the center of the second region in the second direction.

[0131] Variation Example 3:

[0132] In steps S110 and S120, the correction value setting unit 12a may also set a predetermined tilt correction value bi for each of the multiple tilts α, and set a correction value offset ci based on the difference between the predetermined tilt correction value bi for each of the multiple tilts α and the reference correction value ai. Furthermore, in step S220, the correction value setting unit 12a may also set a correction value di using a correction value offset ci set based on the difference between the predetermined tilt correction value bi of the tilt α closest to tilt β and the reference correction value ai. Similarly, in steps S310 and S320, the correction value setting unit 12a may also set a predetermined PG correction value fi for each of the multiple pg1, and set a correction value offset gi based on the difference between the predetermined PG correction value fi of each of the multiple pg1 and the reference correction value ei. Furthermore, in step S420, the correction value setting unit 12a may also set a correction value hi using a correction value offset gi set based on the difference between the predetermined PG correction value fi of the pg1 closest to pg2 and the reference correction value ei.

[0133] Variation Example 4:

[0134] This implementation method may also be excluded. Figure 2 The illustrated linear inkjet printer is used in a so-called serial inkjet printer where the print head 19 scans via a movable carriage. That is, [the printer is described in the original text]. Figure 2The printhead 19 shown is mounted on a carriage (not shown) and scans along direction D1 via the carriage. In this case, the transport direction of the printing medium 30 of the transport unit 18 is not direction D1 but direction D2. That is, printing is performed on the printing medium 30 by combining the transport of the printing medium 30 over a fixed distance in direction D2 with the scanning of the printhead 19. Furthermore, in the case of a serial inkjet printer, the printhead chip 22 of the printhead 19 can be a single chip. That is, by making the transport distance of the printing medium 30 performed by the transport unit 18 between the carriage-based scan and the next scan a predetermined distance shorter than the length of the nozzle array 23 in direction D2, a printed image on the printing medium 30 can be formed by a first area and a second area that has undergone OL printing.

[0135] Variation Example 5:

[0136] Up to this point, the following configuration has been described: a first grid line constituting a first region is printed using one (predetermined number) of nozzles 21 that spray ink of a predetermined color, and a second grid line constituting a second region is printed using two more nozzles 21 that spray ink of the predetermined color than the predetermined number. However, the first region and the second region can simply be different in the number of nozzles 21 of the same color used for printing each grid line. Therefore, for example, this embodiment can also be applied to a configuration where, for the first region, each grid line is printed using two (predetermined number) of nozzles 21 that spray ink of the predetermined color, and for the second region, each grid line is printed using four more nozzles 21 that spray ink of the predetermined color than the predetermined number.

Claims

1. A printing apparatus, characterized in that, have: A printhead has multiple nozzles that eject ink of a specified color; The correction value setting unit sets a correction value for each grid line used to correct the density of each grid line representing the ink dots arranged along the first direction; The printing data generation unit corrects the image data according to the correction value for each of the grid lines; as well as The printing control unit, based on the corrected image data, prints a first region and a second region onto the printing medium via the print head. The first region has multiple first grid lines represented by the ink arranged in a second direction intersecting the first direction. The second region is sandwiched between the first region in the second direction and has second grid lines represented by the ink. The printing control unit causes the print head to print one first grid line through a predetermined number of nozzles, and to print one second grid line through a greater number of nozzles than the predetermined number. The correction value setting unit sets a second correction value applied to the second grid line based on printing conditions that cause the density difference between the second grid line and the first grid line to change, and sets a first correction value applied to the first grid line including a portion of the first grid line adjacent to the second region based on the printing conditions and the second correction value.

2. The printing apparatus according to claim 1, characterized in that, The printing conditions are at least one of the following: the tilt of the print head relative to the second direction or the distance between the printing medium and the print head.

3. The printing apparatus according to claim 1 or 2, characterized in that, The correction value setting unit changes the range in the second direction of the first grid line that has been set with the first correction value according to the printing conditions.

4. The printing apparatus according to claim 1 or 2, characterized in that, When the correction value is set according to the printing conditions, the correction value setting unit sets the correction value so that the value applied to each grid line changes linearly from the first grid line to the center of the second region in the second direction.

5. A printing method, characterized in that, The printing method comprises controlling a print head having multiple nozzles that eject ink of a specified color to print on a printing medium, wherein the printing head controls the printing head to print on a printing medium. The correction value setting process sets a correction value for each grid line used to correct the concentration of each grid line representing the ink dots arranged along the first direction. The printing data generation process corrects the image data according to the correction value for each of the grid lines; as well as In the printing control process, based on the corrected image data, a first region and a second region are printed onto the printing medium via the print head. The first region has multiple first grid lines represented by the ink arranged in a second direction intersecting the first direction. The second region is sandwiched between the first region in the second direction and has second grid lines represented by the ink. In the printing control process, the print head prints one first grid line through a predetermined number of nozzles, and prints one second grid line through a greater number of nozzles than the predetermined number. In the correction value setting process, a second correction value is set for the second grid line based on the printing conditions that cause the concentration difference between the second grid line and the first grid line to change, and a first correction value is set for the first grid line including a portion of the first grid line adjacent to the second region based on the printing conditions and the second correction value.

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