JP6750218B2 - Printing device and printing method - Google Patents

Description

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

Conventionally, as an example of a printing apparatus, an image is printed by ejecting ink from a print head in which a plurality of nozzle rows are formed toward a print medium such as paper or film to form a plurality of dots on the print medium. An inkjet printer that performs (printing) has been known. An inkjet printer is configured to move a print head in the main scanning direction and eject ink from each nozzle to form a dot row (raster line) arranged in the main scanning direction of the print medium, and a main scan (pass). Sub-scanning for carrying (moving) in the sub-scanning direction intersecting the main scanning direction is alternately repeated. As a result, the dots are lined up in the main scanning direction and the sub scanning direction of the print medium without a gap, and an image is formed on the medium.

For example, Patent Document 1 discloses a printing apparatus that prints a band (pseudo band) in N passes (N is a natural number) by moving a print head in the main scanning direction for each pass. This printing device prints odd rows with eight nozzles in the first pass, moves the print medium in the sub-scanning direction by half the nozzle pitch, and prints even rows with the same eight nozzles in the second pass. By printing, the pseudo band is printed.

JP, 2011-235592, A

It is desirable that the density of ink (ink droplets) ejected from each of the nozzles forming the nozzle row is constant regardless of the nozzle. This is because if there is a difference in the density of the ink ejected for each nozzle, unevenness (color unevenness, light and shade unevenness) is easily visible in the printed result. The inventor has found that the density of ink ejected by the nozzles located near the ends of the nozzle row and the density of ink ejected by the nozzles located near the center of the nozzle row tend to be different. Considering the prior arts such as Patent Document 1 based on such knowledge, in the pseudo band, an area printed by only the nozzles near the ends and an area printed by only the nozzles near the center occur. However, light and shade are generated in the print result between these areas, and they are visually recognized as light and shade unevenness. As a result, there is a problem that print quality is deteriorated.

The present invention has been made to solve at least a part of the problems described above, and can be realized as the following modes or application examples.

Application Example 1 A printing apparatus according to this application example has a print head having a nozzle row in which a plurality of nozzles for conveying a print medium in a first direction and ejecting ink are formed side by side in the first direction. In a second direction that intersects the first direction, and ejects the ink from the nozzles to the print medium during the movement to perform printing, and comprises a plurality of nozzles on one end side of the nozzle row. A nozzle group composed of nozzles on one side of the nozzle group, a nozzle group composed of a plurality of nozzles on the other side of the nozzle row on the other side of the nozzle group, the one end side nozzle group and the other end side nozzle group When a nozzle group composed of a plurality of nozzles that does not correspond to any of the above is defined as a central nozzle group, nozzles that eject the ink onto the print medium during the movement are the one end side nozzle group and the central nozzle group. A first change from a nozzle included in the other end side nozzle group to a nozzle included in the central nozzle group, and a nozzle included in the other end side nozzle group and the central nozzle group to the one end side nozzle Group, and a second change for sequentially changing to the nozzles included in the central nozzle group, and an ejection control unit for changing to at least one of the second change.

According to this application example, the printing device sequentially changes the nozzles that eject ink onto the print medium from the nozzles included in the other end side and the central nozzle group to the nozzles included in the one end side and the central nozzle group. Ejection in which the print head is moved while changing to at least one of a change and a first change in which the nozzles included in the one end side and the central nozzle group are sequentially changed to the nozzles included in the other end side and the central nozzle group It has a control unit. By repeating this movement, it is possible to perform printing in which the nozzles of the central nozzle group and the nozzles of the one end side nozzle group or the nozzles of the other end side nozzle group are mixed in the second direction. It becomes difficult to visually confirm the unevenness of light and shade. Therefore, it is possible to provide a printing apparatus with improved print quality.

Application Example 2 A printing apparatus according to this application example has a print head having a nozzle row in which a plurality of nozzles for conveying a print medium in a first direction and ejecting ink are formed side by side in the first direction. In a second direction intersecting the first direction, and ejecting the ink from the nozzles to the printing medium during the movement to perform printing, wherein the nozzle row is in the first direction. Is divided into a plurality of sections along the line, the color of ink ejected from the nozzles is different for each section, and a nozzle group including a plurality of nozzles on one end side of the nozzle row for each section Group, a nozzle group composed of a plurality of nozzles on the other end side of the nozzle row for each of the sections is used for the other end side nozzle group, the one end side nozzle group for each section, and the other end side nozzle group When a nozzle group composed of a plurality of nozzles that do not correspond to the central nozzle group, a nozzle that ejects the ink onto the print medium in each of the sections during the movement is defined by the one end side nozzle group and the central nozzle. A first change in which nozzles included in a nozzle group are sequentially changed to nozzles included in the other end side nozzle group and the central nozzle group, and nozzles included in the other end side nozzle group and the central nozzle group to the one end It is characterized in that a discharge control unit for changing to at least one of a second change for sequentially changing to the nozzles included in the side nozzle group and the central nozzle group is provided.

According to this application example, the print head is divided into a plurality of sections along the first direction, and each section has a nozzle row in which the color of the ink ejected from the nozzle is different. The printing apparatus, when moving the print head in the second direction, ejects ink from the nozzles included in the other end side and the center nozzle group to the one end side and the center nozzle for each section. At least one of a second change for sequentially changing to nozzles included in the group and a first change for sequentially changing from nozzles included in the one end side and the central nozzle group to nozzles included in the other end side and the central nozzle group An ejection control unit that moves the print head while changing to one side is provided. By repeating this movement, it is possible to perform printing in which the nozzles of the central nozzle group and the nozzles of the one end side nozzle group or the other end side nozzle group are mixed for each section in the second direction. With respect to all the ink colors corresponding to the zone, it becomes difficult to visually recognize the light and shade unevenness due to the nozzle position. Therefore, it is possible to provide a printing apparatus with improved print quality.

Application Example 3 In the printing apparatus according to the above application example, the ejection control unit repeats at least one of the first change and the second change during the movement. preferable.

According to this application example, the printing apparatus moves the print head while repeating at least one of the first change and the second change. By repeating this movement, it is possible to perform printing in which the nozzles of the central nozzle group and the nozzles of the one end side nozzle group or the nozzles of the other end side nozzle group are complicatedly mixed in the second direction. It is more difficult to visually recognize the light and shade unevenness caused by the.

Application Example 4 The printing apparatus described in the above application example refers to the color conversion table for converting the color system adopted by the image data representing the image into the color system of the ink ejected by the print head. Thus, the ink amount determination unit that determines the ink amount within a predetermined upper limit value for each pixel of the image data is provided, and the ejection control unit determines ejection or non-ejection of the ink based on the ink amount. Controlling the ejection of ink by the nozzles by assigning pixels to the nozzles, and the ink amount determination unit adopts a first upper limit value for the upper limit value, and defines a first color conversion table in advance; Of the second color conversion table that is defined in advance by using a second upper limit value that is higher than the first upper limit value for the upper limit value, the ink amount is determined by referring to the second color conversion table. When determining, the ejection control unit corresponds to the nozzles that eject ink in the movement, the nozzles included in the other end side nozzle group and the central nozzle group, or the one end side nozzle group and the central nozzle. When the pixels are assigned to the nozzles included in the nozzle group and the ink amount determination unit determines the ink amount by referring to the first color conversion table, the ejection control unit, in each movement, It is preferable to allocate pixels to the nozzles included in the one end side nozzle group, the central nozzle group, and the other end side nozzle group.

According to this application example, the printing apparatus, when the condition in which the light and shade unevenness is easily visible is satisfied (refer to the second color conversion table that employs the second upper limit value that is relatively high as the upper limit value to refer to the ink amount). Is determined), the uneven density is suppressed by taking a measure to change the nozzle that ejects ink during the movement of the print head as described above. On the other hand, when the condition in which the light and shade unevenness is difficult to be visually recognized is satisfied (when the ink amount is determined by referring to the first color conversion table that adopts the relatively low first upper limit value as the upper limit value), printing is performed. By not taking measures to change the nozzles that eject ink during movement of the head, it is possible to improve the overall printing speed.

Application Example 5 In the printing apparatus according to the above application example, a ratio of the number of nozzles of the other end side nozzle group and the central nozzle group to the number of nozzles of the nozzle row, and the one end side nozzle group and the center The ratio of the number of nozzles in the nozzle group to the number of nozzles in the nozzle row is preferably 3/5 or more and 3/4 or less.

According to this application example, the ratio of the number of nozzles of the other end side and the central nozzle group to the number of nozzles of the nozzle row and the ratio of the number of nozzles of the one end side and the central nozzle group to the number of nozzles of the nozzle row are set to 3 By setting /5 or more and 3/4 or less, it is possible to accurately prevent the occurrence of a region in which the density of ejected ink is printed only by nozzles that are equally biased to either a dark state or a thin state. be able to.

Application Example 6 In the printing apparatus described in the above application, in the nozzle row, the area where the nozzle ejects cyan ink, the area where the nozzle ejects magenta ink, and the area where the nozzle ejects yellow ink. And are preferably divided into.

According to this application example, the printing apparatus includes the nozzle row that is divided into the cyan ink, the magenta ink, and the yellow ink. Therefore, by synthesizing these inks, a person recognizes by reflection of light. It can reproduce all possible colors.

Application Example 7 In the printing apparatus described in the above application example, it is preferable to use pigment ink as the ink.

According to this application example, the pigment ink is more likely to have a difference in ink density between nozzles than the dye ink. However, according to the present invention, as described above, by taking the measure of changing the nozzles that eject ink during the movement of the print head, it is possible to suppress the unevenness of light and shade due to the difference in the ink density of each nozzle, When used, the image quality can be effectively improved.

Application Example 8 In the printing apparatus according to the application example described above, it is preferable that the print head receives supply of the ink to the nozzle from an ink cartridge that holds the ink by a sponge-like absorbing member.

According to this application example, when the ink supplied to the nozzle is filled in the ink cartridge holding the ink by the sponge-like absorbing member, the pigment of the ink is likely to settle in the ink cartridge. When ink is supplied to each nozzle from the ink cartridge filled with the ink in which the pigment has settled in this way, a difference in ink density between nozzles easily occurs. However, according to the present invention, as described above, since it is possible to suppress the unevenness due to the difference in the ink density of each nozzle by taking the measure of changing the nozzle that ejects the ink during the movement of the print head, as described above. Even when an ink cartridge is used, the image quality can be effectively improved.

Application Example 9 The printing method according to this application example has a print head having a nozzle row in which a plurality of nozzles for conveying a print medium in a first direction and ejecting ink are formed side by side in the first direction. In a second direction intersecting the first direction, and ejecting the ink from the nozzles to the print medium during the movement to perform printing. A nozzle group composed of nozzles on one side of the nozzle group, a nozzle group composed of a plurality of nozzles on the other side of the nozzle row on the other side of the nozzle group, the one end side nozzle group and the other end side nozzle group When a nozzle group composed of a plurality of nozzles that does not correspond to any of the above is defined as a central nozzle group, nozzles that eject the ink onto the print medium during the movement are the one end side nozzle group and the central nozzle group. A first change from a nozzle included in the other end side nozzle group to a nozzle included in the central nozzle group, and a nozzle included in the other end side nozzle group and the central nozzle group to the one end side nozzle Group, and a second change for sequentially changing to the nozzles included in the central nozzle group, and a discharge control step for changing to at least one of the nozzles.

According to this application example, the printing method sequentially changes the nozzles that eject ink onto the print medium from the nozzles included in the other end side and the central nozzle group to the nozzles included in the one end side and the central nozzle group. Ejection in which the print head is moved while changing to at least one of a change and a first change in which the nozzles included in the one end side and the central nozzle group are sequentially changed to the nozzles included in the other end side and the central nozzle group It includes a control process. By repeating this movement, it is possible to perform printing in which the nozzles of the central nozzle group and the nozzles of the one end side nozzle group or the nozzles of the other end side nozzle group are mixed in the second direction. It becomes difficult to visually confirm the unevenness of light and shade. Therefore, it is possible to provide a printing method with improved print quality.

FIG. 3 is a block diagram showing the configuration of the printing apparatus according to the first embodiment. FIG. 3 is a perspective view schematically showing the configuration of a printer. FIG. 3 is a plan view illustrating the configuration of a print head. FIG. 3 is a diagram simply showing a configuration of an ink cartridge. The flowchart which shows a printing method. FIG. 3 is a diagram illustrating a nozzle group that forms a nozzle row and a discharge pattern. FIG. 3 is a diagram illustrating a positional relationship between a nozzle row and a print medium and a correspondence relationship between pixels assigned to nozzles. FIG. 6 is a plan view illustrating the configuration of the print head of the printing apparatus according to the second embodiment. FIG. 3 is a diagram illustrating a nozzle group that forms a nozzle row and a discharge pattern. FIG. 3 is a diagram illustrating a positional relationship between a nozzle row and a print medium and a correspondence relationship between pixels assigned to nozzles. FIG. 3 is a diagram illustrating a positional relationship between a nozzle row and a print medium and a correspondence relationship between pixels assigned to nozzles. FIG. 3 is a diagram illustrating a positional relationship between a nozzle row and a print medium and a correspondence relationship between pixels assigned to nozzles. The figure which shows the dot discharged from the 1st ward. The figure which shows the dot discharged from the 2nd ward. The figure which shows the dot discharged from the 3rd ward. FIG. 8 is a diagram illustrating a color conversion table according to Modification 1; FIG. 8 is a diagram illustrating a color conversion table according to Modification 1; FIG. 10 is a diagram showing an example of a discharge pattern according to Modification 2. FIG. 10 is a diagram showing an example of a discharge pattern according to Modification 2. FIG. 6 is a diagram illustrating a positional relationship between a nozzle array and a print medium and a formed image according to a conventional example.

Embodiments of the present invention will be described below with reference to the drawings. In each of the following drawings, the scale of each layer and each member is different from the actual scale in order to make each layer and each member recognizable.

(Embodiment 1)
<Schematic configuration of printing device>
FIG. 1 is a block diagram showing the configuration of the printing apparatus according to the first embodiment. FIG. 2 is a perspective view schematically showing the configuration of the printer. First, the schematic configuration of the printing apparatus will be described with reference to FIGS. 1 and 2.
Further, in FIG. 2, for convenience of description, an X axis, a Y axis, and a Z axis are illustrated as three axes orthogonal to each other. In the following description, a direction parallel to the X axis is referred to as “X axis direction” or “X axis direction”. The "main scanning direction" and the direction parallel to the Y-axis are called "Y-axis direction" or "sub-scanning direction".

The printing system 1 as a printing device includes a printer 20 and a control device 10 for controlling the printer 20. The control device 10 is a device in which a program for controlling the printer 20 is installed. As the control device 10, a desktop or laptop personal computer (PC), a tablet terminal, a portable terminal, or the like can be used. The control device 10 and the printer 20 that configure the printing system 1 may be separate devices that are communicatively connected, or may be devices that are integrally configured. For example, the machine body of the printer 20 may include the control device 10. In this case, the printer 20 including the control device 10 in the body corresponds to the printing system 1 or the printing device. Further, the printing system 1 and the printer 20 may be a multifunction machine that also functions as a scanner, a facsimile, or the like.

In the control device 10, the CPU 12, which is the center of the arithmetic processing, controls the entire control device 10 via the system bus. A ROM 13, a RAM 14, various interface units (I/F) 19 and the like are connected to the bus, and a hard disk drive (HDD) 16 is connected as a storage unit. However, the storage means may be a semiconductor memory or the like. The HDD 16 stores programs such as a printer driver PD, an operating system (not shown), application programs, etc., and these programs are appropriately read by the CPU 12 to the RAM 14 and executed. The CPU 12, ROM 13, and RAM 14 are collectively referred to as the control unit 11. Further, the HDD 16 may store a color conversion table (LUT: Look Up Table) 16A and the like.

The I/F 19 is connected to the printer 20 by wire or wirelessly so as to be communicable. Further, the control device 10 includes a display unit 17 including, for example, a liquid crystal display, an operation unit 18 including, for example, a keyboard, a mouse, a touch pad, a touch panel, and the like.
The items described as being executed by the control device 10 in this embodiment may be executed by the control unit 21 on the printer 20 side according to a predetermined program, in whole or in part. Further, the information held by the control device 10, such as the LUT 16A, may be held on the printer 20 side.

In the printer 20, the I/F 25 is communicably connected to the I/F 19 on the control device 10 side by wire or wirelessly, and the control unit 21 and the like are connected via a system bus. In the control unit 21, the CPU 22 appropriately reads a program (firmware or the like) stored in the ROM 23 or the like into the RAM 24 and executes predetermined arithmetic processing. The control unit 21 is connected to the print head 26, the head drive unit 27, the carriage mechanism 50, and the feed mechanism 40 to control each unit.

The carriage mechanism 50 is controlled by the control unit 21 to move the print head 26 in the second direction (the X-axis direction shown in FIG. 2, hereinafter referred to as the main scanning direction), and prints the print head 26. It moves relative to the medium G. The carriage mechanism 50 includes a carriage 51, a carriage motor 52, and the like, and the carriage 51 holds the print head 26 and the ink cartridge 32. The ink cartridge 32 stores ink and is detachably attached to the carriage 51. The carriage 51 can reciprocate in the main scanning direction, and is driven by a carriage motor 52. As a result, the print head 26 reciprocates in the main scanning direction (±X axis direction).

The print head 26 receives supply of various inks from the ink cartridges 32 for each of a plurality of types of liquids (for example, cyan (C) ink, magenta (M) ink, yellow (Y) ink, black (K) ink, etc.). .. The print head 26 can eject (eject) ink from a plurality of nozzles Nz (see FIG. 3) provided corresponding to various inks. The specific type and number of liquids used by the printer 20 are not limited to those described above, and examples thereof include light cyan, light magenta, orange, green, gray, light gray, white, metallic inks, and precoat liquids. Ink or liquid other than ink can be used.

The feeding mechanism 40 conveys (moves) the print medium G in a first direction (Y-axis direction shown in FIG. 2, hereinafter referred to as a sub-scanning direction) intersecting the main scanning direction. The feeding mechanism 40 includes a paper feed roller 41, a transportation motor 42, a transportation roller 43, a platen 44, a paper ejection roller 45, and the like. The paper feed roller 41 is a roller for supplying the print medium G inserted into the insertion port (not shown) to the inside of the printer 20. The transport roller 43 is a roller that transports the print medium G supplied by the paper feed roller 41 to a printable region, and is driven by the transport motor 42. The platen 44 is provided at a position facing the print head 26 that moves in the main scanning direction with the print medium G interposed therebetween, and supports the print medium G that is being printed. The paper discharge roller 45 is a roller for discharging the print medium G to the outside of the printer, and is provided on the downstream side in the sub scanning direction with respect to the printable area.

The head drive unit 27 is provided corresponding to each nozzle Nz of the print head 26 based on print data (print data will be described later) acquired from the control device 10 by the control unit 21 via the I/F 25. A drive voltage for driving the piezoelectric element is generated. The head drive unit 27 outputs a drive voltage to the print head 26. The piezoelectric element deforms when a drive voltage is applied, and ejects liquid from the corresponding nozzle Nz. As a result, the print head 26 moving by the carriage 51 ejects ink (ink droplet) for each ink type from the nozzles Nz to the print medium G. The ejected ink adheres to the print medium G, and dots are formed on the surface of the print medium G, so that an image based on print data is formed on the print medium G. The dot basically refers to the ink that has landed on the print medium G. However, at the stage before the ink lands on the print medium G, the expression dot may be used for convenience of explanation.

The material used as the print medium G is typically paper, but in addition to paper, various materials such as fibers, plastics, metals, and other natural and artificial materials are used.
The movement of the print head 26 from one end side to the other end side in the main scanning direction or the movement from the other end side to the one end side in the main scanning direction is referred to as "main scanning" or "pass".

Further, the printer 20 includes a display unit 30 configured by, for example, a liquid crystal display, an operation unit 31 configured by, for example, buttons, a touch panel, or the like. In the printer 20, the means for ejecting the ink from the nozzle is not limited to the piezoelectric element, and a means for heating the ink by the heating element and ejecting the ink from the nozzle may be adopted.

FIG. 3 is a plan view illustrating the configuration of the print head. In FIG. 3, the positional relationship between the print head 26 of the printer 20 and the conveyed print medium G is simply illustrated. An array of nozzles Nz on the ink ejection surface 26a of the print head 26 is illustrated on the left side of FIG. The ink ejection surface 26a is a surface on which the nozzles Nz are opened, and is a surface facing the print medium G when the print head 26 performs main scanning. The print head 26 has a nozzle row NL in which a plurality of nozzles Nz for ejecting ink are formed side by side in the first direction (sub-scanning direction). The print head 26 shown in FIG. 3 has four nozzle rows NL arranged at equal intervals along the main scanning direction for each ink color to be ejected (for example, C, M, Y, K). The density npi (nozzles per inch) of the nozzles Nz in the sub-scanning direction is half the print resolution dpi (dots per inch) recorded in the print medium G by the printer 20 in the sub-scanning direction.

In FIG. 3, an example of the ink color ejected by each nozzle row NL is shown in parentheses for reference. However, the ink of one color may be ejected not only by one nozzle row NL but also by a plurality of nozzle rows NL arranged so as to be offset from each other in the sub-scanning direction. In each nozzle row NL, a nozzle group including a plurality of nozzles Nz on one end side of the nozzle row NL is a nozzle group on one end side, and a nozzle group including a plurality of nozzles Nz on the other end side of the nozzle row NL is the other end. A nozzle group including a plurality of nozzles Nz that do not correspond to any of the side nozzle group, the one end side nozzle group, and the other end side nozzle group can be classified into three nozzle groups, a central nozzle group. Note that, in the present specification, for directions and positions of each configuration, even when expressed as orthogonal, equidistant, parallel, etc., they do not mean only strictly orthogonal, equidistant, parallel, It is meant to include an error that is allowable in product performance and an error that can occur during product manufacturing.

FIG. 4 is a diagram simply showing the configuration of the ink cartridge. FIG. 4 simply illustrates the configuration of the ink cartridge 32 included in the printer 20. The ink cartridge 32 is, for example, an ink cartridge filled with C ink. The ink cartridges respectively filled with other color inks (MYK inks) have basically the same configuration as the ink cartridge 32. The print head 26 receives the ink supply from the ink cartridge 32 holding the ink to the nozzle Nz by the sponge-like absorbing member 34. Specifically, the ink cartridge 32 is filled with a sponge-like absorbing member 34, and the ink is filled in the ink cartridge 32 while being absorbed (held) by the absorbing member 34. The absorbing member 34 is also called a foam material or the like. The ink cartridge 32 communicates with the supply port 33. The supply port 33 communicates with an ink supply flow path (not shown) formed in the print head 26, and the nozzle row NL (nozzle row) of the print head 26 from the ink cartridge 32 passes through the supply port 33 and the flow path. Ink is supplied to each of the nozzles Nz) constituting the.

In FIG. 4, a partial range in the ink cartridge 32 is illustrated as a sedimentation range SE by hatching. The sedimentation range SE means a range in which a large amount of the dye in the ink is biasedly present (is settled). Although depending on the storage state of the ink cartridge 32, the ink held by the absorbing member 34 settles in the direction in which the coloring matter in the ink is present, so that the color density of the ink in the ink cartridge 32 is not constant. For example, if the ink cartridge 32 is stored with the supply port 33 facing downward (gravity direction side), a certain range on the supply port 33 side becomes the sedimentation range SE, as illustrated in FIG. In particular, when the ink is a pigment ink, the pigment (pigment) has larger particles and is less soluble in water as compared with the dye ink, and thus the above-described sedimentation is likely to occur. In the present embodiment, the ink ejected from the print head 26 may be either pigment ink or dye ink, but in the following description, it is assumed that pigment ink is used as the ink. Further, in the mode in which the ink is held by the absorbing member 34, even if the ink cartridge 32 is vibrated, the ink is hardly stirred in the ink cartridge 32, and thus the once settled state is hardly eliminated.

Here, when the supply port 33 is roughly divided into a central region 33b and regions 33a on one end side and regions 33c on the other end side on both sides thereof, the respective regions 33a, 33b, 33c are In general, ink is supplied from the areas 32a, 32b, and 32c when the inside of the ink cartridge 32 is divided into a fan shape as illustrated in FIG. That is, ink mainly flows from the central region 32b in the ink cartridge 32 to the central region 33b of the supply port 33, and the position in the ink cartridge 32 corresponds to the region 33a on one end side of the supply port 33. Ink mainly flows from the region 32a on the one end side, and ink mainly flows from the region 32c on the other end side corresponding to the position in the ink cartridge 32 to the region 33c on the other end side of the supply port 33. Of course, the supply port 33 is not actually partitioned into the regions 33a, 33b, and 33c, and similarly, the inside of the ink cartridge 32 is not partitioned into the regions 32a, 32b, and 32c. However, since the ink is hardly stirred in the ink cartridge 32 that holds the ink by the absorbing member 34, the ink is supplied to the regions 33a, 33b, 33c of the supply port 33 and the regions 33a, 33b, 33c. The correspondence with the areas 32a, 32b, and 32c in the ink cartridge 32 is almost maintained.

As can be seen from the example of FIG. 4, the areas 32a and 32c on the one end side and the other end side in the ink cartridge 32 belong to the sedimentation range SE more than the central area 32b. Therefore, the density of the ink passing through the regions 33 a and 33 c on the one end side and the other end side of the supply port 33 tends to be higher than the concentration of the ink passing through the central region 33 b of the supply port 33. Such a difference in the density of the ink passing through the supply port 33 leads to a difference in the density of the ink finally ejected by each nozzle Nz forming the nozzle row. That is, in the nozzle row that receives the ink supply from the ink cartridge 32, the density of the ink ejected from the nozzles Nz located on one end side and the other end side of the nozzle row is ejected from the nozzle Nz located in the center of the nozzle row. The ink becomes darker than the ink density.

The flow path is interposed between the supply port 33 and the nozzle Nz as described above. Therefore, it is considered that the ink is agitated to some extent before it reaches the nozzle Nz from the supply port 33. However, in a situation where the ink is flowing at a flow velocity above a certain level in the flow channel, stirring of the ink in the flow channel is suppressed. Therefore, as a result, when the ink passes through the supply port 33, the difference in density between the central region 33b and the regions 33a and 33b on the one end side and the other end side is the nozzle row where the ink finally reaches. , There is a tendency to appear in the density difference between the ink ejected from the nozzle Nz located near the center and the ink ejected from the nozzle Nz located near the one end side and the other end side. Depending on the state of sedimentation of the ink in the ink cartridge 32, the density of the ink passing through the regions 33a and 33c on the one end side and the other end side of the supply port 33 may be the same as the concentration of the ink passing through the central region 33b of the supply port 33. It may be thinner than the concentration of. As a result, the density of the ink ejected from the nozzles Nz located near one end side and the other end side of the nozzle row that receives the ink supply from the ink cartridge 32 is the same as that of the ink ejected from the nozzle Nz located near the center. It may be thinner than the concentration.

In any case, the inventor has found that due to the above-described sedimentation, the density of the ejected ink is different depending on the position of the nozzle Nz in the nozzle row configured by the plurality of nozzles Nz that eject the ink of the same color. Obtained. In the present embodiment, on the basis of such knowledge, the device for eliminating the uneven density due to the difference in the density of the ink ejected from the nozzle Nz is devised.

FIG. 5 is a flowchart showing the printing method. The flowchart shows a method (print control process) in which the control device 10 causes the printer 20 to perform printing according to the printer driver PD.
In step S100, the control unit 11 acquires the image data arbitrarily selected by the user from a predetermined input source. The user arbitrarily selects the image data representing the image to be printed on the print medium G by operating the operation unit 18 or the like while visually checking the user interface screen (UI screen) displayed on the display unit 17 or the like. You can The input source of the image data is not particularly limited, and examples thereof include the HDD 16, a memory card (not shown) inserted into the control device 10 and the printer 20 from the outside, and any image input device communicatively connected to the control device 10. Is applicable.

The image data acquired in step S100 is, for example, in the bitmap format, and the density of the element color such as R (red), G (green), and B (blue) is gradation (for example, 0 to 255) for each pixel. It is RGB data expressed in 256 gradations. Further, when the acquired image data does not correspond to such an RGB color system, the control unit 11 converts the acquired image data into color system data. Further, the control unit 11 appropriately performs a resolution conversion process on the image data so as to match the print resolution of the printer 20 in the main scanning direction and the sub scanning direction.

In step S110, the control unit 11 executes a color conversion process on the image data after step S100. That is, the color system used by the image data is converted to the color system of ink ejected by the print head 26 (for example, CMYK). The color conversion process is executed for each pixel by referring to the LUT 16A that defines the conversion relationship of the color system in advance. As described above, when the image data represents the color of each pixel in RGB gradation, the RGB gradation value for each pixel is converted into an ink amount within a predetermined upper limit value for each CMYK. The CMYK values after such color conversion are expressed stepwise by a numerical value such as 0 to 100 (%), and it can be said that the ink amount (density) in the corresponding pixel is expressed in gradation. Hereinafter, such image data represented by CMYK values for each pixel is also referred to as “ink amount data”. The ink density indicated by the ink amount as the gradation value obtained in step S110 is the density for each pixel and for each ink color required to reproduce an image, and is described using FIG. 4 as an example. It is irrelevant to the density caused by sedimentation (actually existing density difference within the same ink). It can be said that the control unit 11 functions as an ink amount determination unit in that the process of step S110 is performed.

In step S120, the control unit 11 performs halftone processing on the image data (ink amount data) after step S110 to convert the image data into print data. The control unit 11 may perform the halftone process by dithering using a dither mask defined in advance, or may perform the halftone process by an error diffusion method, for example. By the halftone process, print data (dot data) defining ejection (with dots) or non-ejection (without dots) of the CMYK inks is generated for each pixel. In this case, the higher the value of the ink amount defined by a pixel in the ink amount data, the higher the possibility that ink ejection will be determined for the pixel as a result of the halftone process.

In step S130, the control unit 11 rearranges the pixels forming the print data (dot data) generated in step S120 in the order in which they should be transferred to the print head 26 according to a predetermined rule of allocation to the nozzles Nz. Due to the rearrangement processing, the dots defined by the pixels forming the print data can be used for any of the nozzles Nz in the print head 26, the number of passes, and the number of dots in the pass depending on the pixel position and the ink color. Whether to eject at a timing is determined. The print data after the rearrangement processing is output to the printer 20 side through the I/F 19 according to the rearranged order (output processing). As a result, the pixels forming the print data are substantially assigned to any of the nozzles Nz of the print head 26.

The control unit 21 of the printer 20 includes a carriage mechanism 50 that moves the print head 26 in the main scanning direction based on print data input through the I/F 25, and a head drive unit that causes ink to be ejected or not ejected from each nozzle Nz. 27 and the feeding mechanism 40 that conveys the print medium G in the sub-scanning direction are controlled to print the image represented by the image data acquired in step S100 on the print medium G.
In terms of executing the processes of steps S120 and S130, the control unit 11 controls the ejection of ink by the nozzle Nz by assigning the pixel determined to eject or not eject ink to the nozzle Nz. Can be said to function as. Further, the flow of steps S120 and S130 can be said to be a discharge control step of controlling discharge from the nozzle Nz. Note that “assigning pixels to nozzles” does not guarantee the actual use of nozzles (act that nozzles eject ink). Whether or not the nozzle ejects ink depends on whether or not the pixel assigned to the nozzle is the "dotted" pixel. However, it is simply understood that the pixel assigned to the nozzle is a pixel with a dot, and the pixel is assigned to the nozzle = ink for expressing the pixel is ejected from the assigned nozzle. Good.

In the present embodiment, the above-mentioned predetermined rule of allocation is that nozzles that eject ink onto the print medium during a pass are nozzles Nz included in the one end side nozzle group and the center nozzle group to the other end side nozzle group and the center nozzle. A first change to sequentially change to the nozzles Nz included in the group, and a second change to sequentially change from the nozzles Nz included in the other end side nozzle group and the central nozzle group to the nozzles Nz included in the one end side nozzle group and the central nozzle group And a change to at least one of the following. In the following description, the above-mentioned change of the nozzle Nz that ejects ink is also simply referred to as “first change” and “second change”.

Next, the process of assigning pixels to nozzles in step S130 will be described in detail. FIG. 6 is a diagram illustrating a nozzle group and a discharge pattern that form a nozzle row. FIG. 7 is a diagram illustrating a positional relationship between a nozzle array and a print medium and a correspondence relationship between pixels assigned to nozzles. In the following description, for simplification of the description, the print head 26 is provided with one nozzle row NL formed of 11 nozzles Nz (nozzle numbers #1 to #11), and one color It shall be printed with ink.

As shown in FIG. 6, eleven nozzles Nz are formed in the nozzle row NL, and the eleven nozzles Nz are three nozzles, one end side nozzle group A, a central nozzle group B, and the other end side nozzle group C. It is classified into a nozzle group. More specifically, the nozzles Nz having nozzle numbers #1 to #3 belong to the one-end side nozzle row group A, the nozzles Nz having nozzle numbers #4 to #8 belong to the central nozzle group B, and the other end side. Nozzles Nz having nozzle numbers #9 to #11 belong to the nozzle group C. The ratio of the total number of nozzles of the other end side nozzle group C and the central nozzle group B to the number of nozzles of the nozzle row NL, and the total number of nozzles of the one end side nozzle group A and the central nozzle group B are the nozzle row NL. The ratio of the number of nozzles to the number of nozzles is set within the range of 3/5 or more and 3/4 or less. As a result, it is possible to accurately prevent the generation of a region printed by only the nozzles in which the density of the ejected ink is similarly biased to either the dark state or the thin state.

In FIG. 6, the table shown on the right side of the nozzle row NL shows the ejection pattern and the position of the ink ejected from each nozzle Nz. The nozzle row NL of this embodiment moves in a range of 4 pixels in the X direction (corresponding to the main scanning direction)×21 pixels in the Y direction (corresponding to the sub scanning direction) in one movement (pass) in the main scanning direction. To do. The nozzle density (npi) of the nozzle row NL is half the print resolution (dpi). The hatched portion in the table shows an example of the ejection pattern JP in which the area where the ink is ejected in one pass is patterned, and the black circles indicate the pixels from which the ink is ejected based on the ejection pattern JP. In the following description, for example, the pixel located at the intersection of the first in the X direction and the first in the Y direction is “X1Y1 pixel”, and the nozzle of nozzle number #n (n=1 to 11) is “#n”. Nozzle".

For example, the control unit 11 allocates the X4Y3 pixels, which are determined to eject ink based on the ejection pattern JP, to the #2 nozzle, so that the ink is ejected from the #2 nozzle toward the X4Y3 pixel in the pass in the main scanning direction. , X4Y3 pixels form dots. Similarly, X3Y5 and X4Y5 pixels are assigned to the #3 nozzle. The X2Y7, X3Y7 and X4Y7 pixels are assigned to the #4 nozzle. The X1Y9, X2Y9, X3Y9 and X4Y9 pixels are assigned to the #5 nozzle. The X1Y11, X2Y11, X3Y11 and X4Y11 pixels are assigned to the #6 nozzle. The X1Y13, X2Y13, X3Y13 and X4Y13 pixels are assigned to the #7 nozzle. The X1Y15, X2Y15, and X3Y15 pixels are assigned to the #8 nozzle. The X1Y17 and X2Y17 pixels are assigned to the #9 nozzle. The X1Y19 pixels are assigned to the #10 nozzle.

When the nozzle row NL (print head 26) performs main scanning (pass) from one end side to the other end side (right direction in FIG. 6) of the main scanning direction based on the ejection pattern JP, ink is printed on the print medium G. The nozzles to be ejected are sequentially changed from the nozzles Nz included in the other end side nozzle group C and the central nozzle group B to the nozzles Nz included in the one end side nozzle group A and the central nozzle group B (second change).
When the nozzle row NL (print head 26) performs the main scan (pass) from the other end side to the one end side (to the left in FIG. 6) in the main scan direction based on the ejection pattern JP, ink is printed on the print medium G. The nozzles to be ejected are sequentially changed from the nozzles Nz included in the one end side nozzle group A and the central nozzle group B to the nozzles Nz included in the other end side nozzle group C and the central nozzle group B (first change).
By sequentially changing the nozzles Nz that eject ink during the pass, it is possible to stir the ink having a density difference due to the ink settling in the ink flow path from the ink cartridge to the nozzle Nz. As a result, it is possible to reduce the difference in density of the inks ejected from the nozzle groups A, B, and C.

The left side of FIG. 7 shows a path for moving the print head 26 in the main scanning direction while ejecting ink from the nozzle Nz from the upper end of the print medium G, and a conveyance for feeding the print medium G in the sub-scanning direction by a predetermined feed amount. 4 shows the relative position between the print medium G and the nozzle row NL in the sub-scanning direction when 4 times are repeated. That is, in FIG. 7, the nozzle row NL is depicted as moving with respect to the print medium G, but the positional relationship between the nozzle row NL and the print medium G may be relatively changed. It may move, the print medium G may move, or both the nozzle array NL and the print medium G may move. In this embodiment, a case where the print medium G is moved (conveyed) in the sub-scanning direction will be described as an example. Since the nozzle row NL in each pass is shown obliquely in the main scanning direction so as not to overlap, the positional relationship between the print medium G and the nozzle row NL in the main scanning direction does not make sense.

In the upper left part of FIG. 7, the feed amount (conveyance amount) in each pass and the moving direction of the nozzle row NL (print head 26) are indicated by arrows. The feeding amount is the amount of feeding the print medium G in the sub-scanning direction each time one pass is completed, and its unit is the printing resolution in the sub-scanning direction (pixel interval (raster line interval described later)) and nozzle array. This corresponds to ½ of the nozzle density (nozzle interval) of NL. In the following description, the first pass will be referred to as "pass 1", for example. In the even-numbered passes (for example, pass 2), the print medium G is fed by one raster line (one pixel) in the sub-scanning direction, and in the odd-numbered passes other than pass 1 (for example, pass 3), the print medium G corresponds to 11 raster lines ( (11 pixels) is sent in the sub-scanning direction. Further, because of space limitations, the nozzle numbers (#1 to #11) and the nozzle groups A, B, and C are shown only for the nozzle row NL in pass 1, but the same applies to the nozzle rows in other passes. .. Further, a region in which odd-numbered passes and even-numbered passes are printed in adjacent passes (for example, pass 1 and pass 2) with a feed amount of one raster line is referred to as a “band”.

In the right diagram of FIG. 7, pixels in which ink is ejected from each nozzle Nz in each pass of pass 1 to pass 4 and pixel positions of all dots formed in pass 1 to pass 4 are defined as pixels X1 to X4 in the X direction. And the raster (raster line) numbers L1 to L34 in the Y direction. The interval between the pixels X1 to X4 in the X direction is the print resolution of the printer 20 in the main scanning direction. The raster line is formed by dots (pixels) of X1 to X4 arranged in the X direction. The raster line interval is the printing resolution of the printer 20 in the sub-scanning direction.

In each of the "Pass 1" to "Pass 4" columns in the table, the pixels to which ink is ejected from the nozzle Nz to which the pixel is assigned are indicated by dots in each pass. In each pass, a pixel assigned to the nozzle Nz of the one end side nozzle group A is a “black square”, a pixel assigned to the nozzle Nz of the central nozzle group B is a “black circle”, and a nozzle Nz of the other end side nozzle group C is a nozzle Nz. Pixels to be assigned are indicated by "black triangles". Further, in each pass, a region where the nozzle row NL (print head 26) moves is indicated by hatching.
The “pass 1-4 total” column represents dots formed in the main scanning of pass 1 to pass 4, and the image formed by the dots corresponds to image data. The image data shown here indicates the above-mentioned print data (dot data), but even if it is interpreted as the image data before the color conversion processing (RGB data) or the image data after the color conversion processing (ink amount data). Good.

In step S130, the control unit 11 allocates each pixel forming the image data IM to one of the nozzles Nz based on the printing method already set for the printer 20. The printing method referred to here is the printing resolution in each of the main scanning direction and the sub-scanning direction, the feed amount of the printing medium G described above, the number of passes required to form one raster line, and the ejection pattern JP described above. The behavior of the printer 20 is determined by a predetermined allocation rule including the above.

The "pass 1" to "pass 4" columns are also the result of assigning each pixel to each nozzle Nz in step S130.
In pass 1, the Y1 to Y21 pixels in the Y direction shown in FIG. 6 are replaced with the pixels with raster numbers L1 to L21, and the pixels for which ink ejection has been determined based on the ejection pattern JP are assigned to each nozzle Nz.
Specifically, X4L3 pixels are assigned to the #2 nozzle. The X3L5 and X4L5 pixels are assigned to the #3 nozzle. The X2L7, X3L7 and X4L7 pixels are assigned to the #4 nozzle. The X1L9, X2L9, X3L9 and X4L9 pixels are assigned to the #5 nozzle. The X1L11, X2L11, X3L11, and X4L11 pixels are assigned to the #6 nozzle. The X1L13, X2L13, X3L13 and X4L13 pixels are assigned to the #7 nozzle. The X1L15, X2L15, and X3L15 pixels are assigned to the #8 nozzle. The X1L17 and X2L17 pixels are assigned to the #9 nozzle. X1L19 pixels are assigned to the #10 nozzle.

Similarly, in pass 2, in the form of replacing the Y1 to Y21 pixels in the Y direction shown in FIG. 6 with L2 to L22 pixels, the pixels for which ink ejection has been determined based on the ejection pattern JP are assigned to each nozzle. In pass 3, the Y1 to Y21 pixels in the Y direction shown in FIG. 6 are replaced with L13 to L33 pixels, and the pixels for which ink ejection has been determined based on the ejection pattern JP are assigned to each nozzle Nz. In pass 4, the pixels for which ink ejection has been determined based on the ejection pattern JP are assigned to each nozzle Nz by replacing the Y1-Y21 pixels in the Y direction shown in FIG. 6 with L14-L34 pixels. For example, it means that the X1 to X3 pixels forming the raster line L15 are assigned to the #8 nozzle of pass 1 and the pixels of X4 forming the raster line L15 are assigned to the #2 nozzle of pass 3.

“Pass 1-4 total” is an image formed by ejecting ink toward the pixels assigned to each nozzle Nz in pass 1 to pass 4. By the pass 1 to pass 4, the normal printing portion in which dots are formed in all the pixels of the raster lines L9 to L26 is completed. The raster lines L1 to L8 are upper end portions, and the raster lines L27 to L34 are lower end portions. The upper end portion and the lower end portion are separately subjected to upper end processing and lower end processing by minute feeding of the print medium G.

Here, a conventional printing method will be described.
FIG. 12 is a diagram illustrating the positional relationship between the nozzle array and the print medium, and the image formed.
The left side of FIG. 12 shows a path for moving the print head 26 in the main scanning direction from the upper end of the print medium G while ejecting ink from the nozzle Nz, and a conveyance for feeding the print medium G in the sub-scanning direction by a predetermined feed amount. 4 shows the relative position between the print medium G and the nozzle row NL in the sub-scanning direction when 4 times are repeated. The number of nozzles and the configuration of the nozzle group are the same as those of the nozzle row NL of this embodiment shown in FIG. In the conventional example, ink is ejected from each nozzle Nz forming the nozzle row NL in all passes. In the even-numbered passes (for example, pass 2), the print medium G is fed by one raster line (one pixel) in the sub-scanning direction, and in the odd-numbered passes other than pass 1 (for example, pass 3), the print medium G is 21 raster lines. Minute (21 pixels) is sent in the sub-scanning direction.

In the right diagram of FIG. 12, the pixel positions of all the dots formed in pass 1 to pass 4 are indicated by raster (raster line) numbers L1 to L44 and pixels X1 to X4 in the X direction. The dots ejected from the one end side nozzle group A are indicated by "black squares", the dots ejected from the central nozzle group B are indicated by "black circles", and the dots ejected from the other end side nozzle group C are indicated by "black triangles". ing. As shown in the right diagram of FIG. 12, in the printing method of the conventional example, the joints of the bands, the area where only the dots (ink) ejected from the nozzles Nz of the one end side nozzle group A are concentrated, and the nozzles of the central nozzle group B are arranged. A region where only the ink discharged from Nz is concentrated and a region where only the ink discharged from the nozzle Nz of the other end side nozzle group C is concentrated are generated along the raster line. When a difference in ink density occurs between the nozzle groups A, B, and C due to ink settling, uneven density is visually recognized between these areas.

Returning to FIG. 7, the image formed in this embodiment will be described. According to the present embodiment, as shown in the diagram of the “Pass 1-4 total” column of FIG. 7, the area of the ink ejected from the joints of the bands and the nozzles Nz of the nozzle groups A, B, and C is It is distributed diagonally to the raster line.
Specifically, for example, the X1 to X4 pixels in the raster lines L9 to L14 are formed only by the dots ejected from the nozzles Nz of the central nozzle group B.
X1 to X3 pixels in the raster lines L15 and L16 are formed by dots ejected from the nozzles Nz of the central nozzle group B, and X4 pixels are formed by dots ejected from the one end side nozzle group A.
The X1 and X2 pixels in the raster lines L17 and L18 are formed by dots ejected from the nozzle Nz of the other end side nozzle group C, and the X3 and X4 pixels are formed by dots ejected from the one end side nozzle group A.
X1 pixels in the raster lines L19 and L20 are formed by dots ejected from the nozzle Nz of the other end side nozzle group C, and X2 to X4 pixels are formed by dots ejected from the central nozzle group B.
Then, the X1 to X4 pixels in the raster lines L21 to L26 are formed only by the dots ejected from the nozzles Nz of the central nozzle group B again.

By forming dots in this way, the joints of the bands are inclined with respect to the raster lines, and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups. As a result, even when a difference in ink concentration occurs between the nozzle groups A, B, and C by using an ink cartridge or a pigment ink that holds the ink with a sponge-like absorbing member in which the ink is likely to settle. , It becomes difficult to visually confirm the unevenness of light and shade.

As described above, according to the printing apparatus of this embodiment, the following effects can be obtained.
The printing system 1 as a printing device includes an ejection control unit that assigns the pixels for which ejection of ink has been determined based on the ejection pattern JP, to the nozzles Nz of the nozzle row NL. Based on the ejection pattern JP, the ejection control unit controls the nozzles Nz that eject ink onto the print medium G from the nozzles Nz included in the other end side nozzle group C and the central nozzle group B to the one end side nozzle group during the odd pass. A and the nozzles Nz included in the central nozzle group B are sequentially changed. Alternatively, in the even-numbered passes, the nozzles Nz included in the one end side nozzle group A and the central nozzle group B are sequentially changed to the nozzles Nz included in the other end side nozzle group C and the central nozzle group B. The image formed by this is such that the joints of the bands are inclined with respect to the raster lines and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups, so that each nozzle group is caused by ink settling. Even if there is a difference in the ink density for each of A, B, and C, it is difficult to visually recognize the uneven density. Therefore, it is possible to provide a printing apparatus with improved print quality.

The ratio of the total number of nozzles of the other end side nozzle group C and the central nozzle group B to the number of nozzles of the nozzle row NL, and the total number of nozzles of the one end side nozzle group A and the central nozzle group B are nozzles of the nozzle row NL The ratio to the number is set within the range of 3/5 or more and 3/4 or less. As a result, it is possible to accurately prevent the generation of a region in which the density of the ejected ink is printed only by the nozzles Nz that are similarly biased to either the dark state or the thin state.
In the present embodiment, a pigment ink is used, which tends to cause a density difference due to ink settling. However, by taking measures to change the nozzle Nz that ejects ink during a pass, uneven density due to the difference in ink density for each nozzle is suppressed, so that the image quality is effectively improved when a pigment ink is used. be able to.
In the present embodiment, the ink cartridge 32 that holds the ink by the sponge-like absorbing member 34 that tends to cause a density difference due to the ink settling is used. However, by taking measures to change the nozzle Nz that ejects ink during the pass, unevenness in light and shade due to the difference in ink density for each nozzle is suppressed, and thus the ink cartridge 32 that holds the ink by the sponge-like absorbing member 34. When the is used, the image quality can be effectively improved.

The printing method of the printing system 1 as the printing device includes an ejection control step of allocating the pixels for which the ejection of ink has been determined based on the ejection pattern JP to each nozzle Nz of the nozzle row NL. In the ejection control step, pixels are assigned to the nozzles Nz based on the ejection pattern JP. As a result, the nozzles Nz that eject ink onto the print medium G are included in the one end side nozzle group A and the center nozzle group B from the nozzles Nz included in the other end side nozzle group C and the center nozzle group B in the odd pass. The nozzles Nz are changed sequentially. Further, the nozzles Nz for ejecting ink onto the print medium G are included in the nozzles Nz included in the one end side nozzle group A and the central nozzle group B to the other end side nozzle group C and the central nozzle group B in the even-numbered pass. The nozzle Nz is sequentially changed. The image formed by this is such that the joints of the bands are inclined with respect to the raster line and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups, so that each nozzle group is caused by ink settling. Even if there is a difference in the ink density for each of A, B, and C, it is difficult to visually recognize the uneven density. Therefore, it is possible to provide a printing method with improved print quality.

(Embodiment 2)
FIG. 8 is a plan view illustrating the configuration of the print head of the printing apparatus according to the second embodiment.
First, the configuration of the print head of the printing apparatus will be described with reference to FIG. The printing apparatus of the present embodiment differs from that of the first embodiment in the nozzle row formed in the print head. Further, the same numbers are used for the same components as those of the first embodiment, and duplicate explanations are omitted.

FIG. 8 simply exemplifies the positional relationship between the print head 126 of the printer 20 and the conveyed print medium G. The arrangement of the nozzles Nz on the ink ejection surface 126a of the print head 126 is illustrated on the left side of FIG. The ink ejection surface 126a is a surface on which the nozzles Nz are opened and is a surface facing the print medium G when the print head 126 performs main scanning. The print head 126 has nozzle rows NL1 and NL2 in which a plurality of nozzles Nz for ejecting ink are formed side by side in the first direction (sub-scanning direction/feeding direction). In the nozzle row NL1, a plurality of nozzles Nz for ejecting K ink are formed side by side in the sub-scanning direction. In the nozzle NL2, a plurality of nozzles Nz for ejecting CMY ink as color (chromatic color) ink are arranged in the sub-scanning direction.

As shown in FIG. 8, the nozzle row NL2 is divided into a plurality of sections along the first direction, and the colors of ink ejected from the nozzles Nz are different for each section. Further, the nozzle row NL2 is divided into a section where the nozzle Nz ejects cyan (C) ink, a section where the nozzle Nz ejects magenta (M) ink, and a section where the nozzle Nz ejects yellow (Y) ink. It is divided. For example, the nozzle row NL2 includes a first section CR in which a plurality of nozzles Nz for ejecting C ink are arranged in the feed direction, and a second section MR, Y ink in which a plurality of nozzles Nz for ejecting M ink are arranged in the feed direction. The third zone YR includes a plurality of ejection nozzles Nz arranged in the feed direction. In other words, the first to third zones CR, MR, YR of the nozzle groups that respectively eject the specific color inks are formed so as to be displaced from each other in the tangential direction of those rows, and constitute the nozzle row NL2 as a whole. There is.

The nozzle row NL1 shown in FIG. 8 is divided into ranges that form pairs with the first section CR, the second section MR, and the third section YR. Here, the term “make a pair” means a relationship within the same range in the sub-scanning direction. For example, a range that is a part of the nozzle row NL1 and forms a pair with the first section CR is a first section KR1, and a range that is a part of the nozzle row NL1 and forms a pair with the second section MR is a second section KR2. A range that is a part of the nozzle row NL1 and forms a pair with the third section YR is called a third section KR3. The first section CR, the second section MR, the third section YR, the first section KR1, the second section KR2, and the third section KR3 each have the same number of nozzles Nz. The density npi of the nozzles Nz in the sub-scanning direction shown in FIG. 8 is half the print resolution dpi in the sub-scanning direction recorded on the print medium G by the printer 20.

The first section CR, the second section MR, the third section YR, the first section KR1, the second section KR2, and the third section KR3 in which the nozzle row is sectioned into sections are a plurality of nozzles Nz on one end side of each section. Of the nozzle group composed of the one end side nozzle group, the nozzle group composed of a plurality of nozzles Nz on the other end side for each section, the other end side nozzle group, the one end side nozzle group for each section and the other end side nozzle group A nozzle group composed of a plurality of nozzles Nz that does not correspond to any of the above can be classified into three nozzle groups, which is a central nozzle group.

Next, a predetermined rule for assigning to the nozzle Nz of the present embodiment (see step S130 of the first embodiment) will be described.
The predetermined rule of allocation according to the present embodiment is that nozzles that eject ink onto a print medium for each section during a pass are changed from the nozzle Nz included in the one end side nozzle group and the nozzle Nz included in the central nozzle group to the other end side nozzle group. A first change in which the nozzles Nz included in the central nozzle group are sequentially changed, and a nozzle Nz included in the other end side nozzle group and the central nozzle group is sequentially changed to a nozzle Nz included in the one end side nozzle group and the central nozzle group. The discharge pattern JP (see FIG. 9) of changing to at least one of the second change is included.

Next, the process of assigning pixels to nozzles in step S130 will be described in detail. FIG. 9 is a diagram illustrating a nozzle group and a discharge pattern that form a nozzle row. 10 to 12 are diagrams illustrating the positional relationship between the nozzle array and the print medium, and the correspondence relationship between the pixels assigned to the nozzles. In the following description, for simplification of the description, the print head 126 has one row of 11 nozzles Nz formed in each of the first section CR, the second section MR, and the third section YR. It is assumed that the nozzle row NL2 is provided and printing is performed with the three color inks of C ink, M ink, and Y ink. The K ink is printed by the method shown in the first embodiment using the first section KR1 of the nozzle row NL1.

As shown in FIG. 9, the nozzle row NL2 has the nozzles Nz with nozzle numbers #1 to #33, the nozzle numbers #1 to #11 belong to the third section YR, and the nozzle numbers #12 to #22 are the nozzle numbers #12 to #22. The nozzles #23 to #33 belong to the second zone MR, and the nozzle numbers #23 to #33 belong to the first zone CR. The 11 nozzles Nz belonging to each of the first section CR, the second section MR, and the third section YR are divided into three nozzle groups, one end side nozzle group A, a central nozzle group B, and the other end side nozzle group C. being classified. For example, the nozzles Nz of nozzle numbers #23 to #25 belong to the one-end side nozzle row group A of the first section CR, and the nozzles of nozzle numbers #26 to #30 belong to the central nozzle group B of the first section CR. Nozzles Nz of nozzle numbers #31 to #33 belong to the other end side nozzle group C of the first section CR. In FIG. 9 and subsequent figures, the regions of the nozzles Nz belonging to the first zone CR, the second zone MR, and the third zone YR are indicated by different hatching.

In FIG. 9, the table shown on the right side of the nozzle row NL shows the ejection patterns and the positions where ink is ejected from the nozzles Nz for each of the first section CR, the second section MR, and the third section YR. .. The nozzle row NL2 of this embodiment moves in a range of 4 pixels in the X direction (corresponding to the main scanning direction)×65 pixels in the Y direction (corresponding to the sub scanning direction) in one movement (pass) in the main scanning direction. To do. The nozzle density (npi) of the nozzle row NL2 is half the print resolution (dpi). The hatched portion in the table shows an example of the ejection pattern JP in which the area where the ink is ejected from the nozzle Nz for each section in one pass is patterned, and the black circles indicate the pixels from which ink is ejected based on the ejection pattern JP. Showing.

For example, the first section CR will be described in detail. The control unit 11 allocates the X4Y47 pixels for which ink ejection has been determined based on the ejection pattern JP to the #24 nozzles, so that the #24 nozzles pass in the main scanning direction. Ink is ejected toward the X4Y3 pixels, and dots are formed at the X4Y47 pixels. Similarly, the X3Y49 and X4Y49 pixels are assigned to the #25 nozzle. The X2Y51, X3Y51, and X4Y51 pixels are assigned to the #26 nozzle. The X1Y53, X2Y53, X3Y53 and X4Y53 pixels are assigned to the #27 nozzle. The X1Y55, X2Y55, X3Y55 and X4Y55 pixels are assigned to the #28 nozzle. The X1Y57, X2Y57, X3Y57 and X4Y57 pixels are assigned to the #29 nozzle. The X1Y59, X2Y59 and X3Y59 pixels are assigned to the #30 nozzle. The X1Y61 and X2Y61 pixels are assigned to the #31 nozzle. The X1Y62 pixel is assigned to the #62 nozzle.

When the nozzle row NL2 (print head 126) performs main scanning (pass) from one end side to the other end side (right direction in FIG. 9) in the main scanning direction based on the ejection pattern JP, the first section CR and the second section In each of the section MR and the third section YR, the nozzles that eject ink onto the print medium G are from the nozzle Nz included in the other end side nozzle group C and the central nozzle group B to the one end side nozzle group A and the central nozzle group. The nozzles Nz included in B are sequentially changed (first change).
When the nozzle row NL2 (print head 126) performs the main scan (pass) from the other end side to the one end side (to the left in FIG. 9) in the main scan direction based on the ejection pattern JP, the first section CR and the second section In each of the section MR and the third section YR, the nozzles that eject ink onto the print medium G are from the nozzle Nz included in the one end side nozzle group A and the central nozzle group B to the other end side nozzle group C and the central nozzle group. The nozzles Nz included in B are sequentially changed (second change).
By sequentially changing the nozzles Nz that eject the ink during the pass, the ink having a density difference due to the settling of the ink is generated in the ink flow path from each of the C ink cartridge, the M ink cartridge, and the Y ink cartridge to the nozzle Nz. It has the effect of stirring. As a result, it is possible to reduce the density difference of the ink ejected from each of the nozzle groups A, B, and C for each of the first section CR, the second section MR, and the third section YR.

The left side of FIGS. 10 to 12 is a path for moving the print head 126 in the main scanning direction from the upper end of the print medium G while ejecting ink from the nozzles Nz, and a predetermined feed amount of the print medium G in the sub scanning direction. The relative positions of the print medium G and the nozzle row NL2 in the sub-scanning direction when the feeding and transporting are repeated 12 times are shown. Further, in the upper left part of FIGS. 10 to 12, the feed amount (conveyance amount) in each pass and the moving direction of the nozzle row NL2 (print head 126) are indicated by arrows. For the sake of space, paths 1 to 4 are shown in FIG. 10, paths 5 to 8 are shown in FIG. 11, and paths 9 to 12 are shown in FIG. In the second embodiment, the odd-numbered passes and the even-numbered passes are adjacent passes with a feed amount of one raster line (for example, pass 1 and pass 2), and the area to be printed for each section is referred to as “band”. ".

The right tables of FIGS. 10 to 12 show pixels X1 to X4 from which ink is ejected from each nozzle Nz in each pass, and raster (raster line) numbers L1 to L34 in the Y direction.
Further, in the columns of "pass 1" to "pass 12" in the table, the pixels to which ink is ejected from the nozzles Nz to which the pixels are assigned are indicated by dots in each pass. In each section of each pass, the pixel assigned to the nozzle Nz of the one end side nozzle group A is “black square”, the pixel assigned to the nozzle Nz of the central nozzle group B is “black circle”, and the nozzle of the other end side nozzle group C is Pixels assigned to Nz are indicated by "black triangles". Further, in each pass, regions in which the nozzles Nz belonging to the first zone CR, the second zone MR, and the third zone YR move are represented by different hatching.

FIG. 13 is a diagram showing dots ejected from the first section. FIG. 14 is a diagram showing dots ejected from the second section. FIG. 15 is a diagram showing dots ejected from the third section.
FIG. 13 shows dots that are ejected from the first section CR and are formed on the print medium G in the main scanning from pass 1 to pass 6, and the image formed by the dots corresponds to the image data of C ink.
FIG. 14 shows dots that are ejected from the second zone MR and are formed on the print medium G in the main scanning from pass 3 to pass 8, and the image formed by the dots corresponds to the image data of M ink.
FIG. 15 shows dots that are ejected from the third section YR and are formed on the print medium G in the main scanning from pass 7 to pass 12, and the image formed by the dots corresponds to image data of Y ink.

In pass 1, Y45 to Y65 pixels in the Y direction shown in FIG. 9 are replaced with pixels of raster numbers L1 to L21, and the pixels for which ink ejection is determined based on the ejection pattern JP of the first section CR are nozzles. Assigned to Nz.
In pass 2, the Y45 to Y65 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of the raster numbers L2 to L22, and the pixels for which ink ejection has been determined based on the ejection pattern JP of the first section CR are nozzles. Assigned to Nz.
In pass 3, the Y33 to Y65 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of the raster numbers L1 to L33, and ink is ejected based on each ejection pattern JP of the first zone CR and the second zone MR. The determined pixel is assigned to each nozzle Nz.
In pass 4, the Y33 to Y65 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of the raster numbers L2 to L34, and ink is ejected based on each ejection pattern JP of the first zone CR and the second zone MR. The determined pixel is assigned to each nozzle Nz.

In pass 5, the Y21 to Y53 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of the raster numbers L1 to L33, based on the ejection patterns JP of the first section CR, the second section MR, and the third section YR. Pixels for which ejection of ink has been determined are assigned to each nozzle Nz.
In pass 6, the Y21 to Y53 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of the raster numbers L2 to L34, and based on the ejection patterns JP of the first section CR, the second section MR, and the third section YR. Pixels for which ejection of ink has been determined are assigned to each nozzle Nz.
In pass 7, the Y9 to Y41 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of the raster numbers L1 to L33, and ink is ejected based on each ejection pattern JP of the second zone MR and the third zone YR. The determined pixel is assigned to each nozzle Nz.
In pass 8, the Y9 to Y41 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of raster numbers L2 to L34, and ink is ejected based on each ejection pattern JP of the second zone MR and the third zone YR. The determined pixel is assigned to each nozzle Nz.

In pass 9, the Y1 to Y29 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of raster numbers L5 to L33, and ink is ejected based on each ejection pattern JP of the second zone MR and the third zone YR. The determined pixel is assigned to each nozzle Nz.
In pass 10, the Y1 to Y29 pixels in the Y direction shown in FIG. 9 are replaced with the pixels of raster numbers L6 to L34, and ink is ejected based on each ejection pattern JP of the second zone MR and the third zone YR. The determined pixel is assigned to each nozzle Nz.
In the pass 11, in the form of replacing the Y1 to Y17 pixels in the Y direction shown in FIG. 9 with the pixels of the raster numbers L17 to L33, the pixels determined to eject ink based on the ejection pattern JP of the third section YR are the nozzles. Assigned to Nz.
In pass 12, in the form of replacing the Y1 to Y17 pixels in the Y direction shown in FIG. 9 with the pixels of raster numbers L18 to L34, the pixels determined to eject ink based on the ejection pattern JP of the third section YR are the nozzles. Assigned to Nz.

For example, it means that the X1 pixel of the raster line L20 formed by the C ink is assigned to the #33 nozzle belonging to the first section CR of the pass 2, and the X2 to X4 pixels are assigned to the #26 nozzle of the pass 4. ..
For example, the X1 and X2 pixels of the raster line L20 formed by M ink are assigned to the #20 nozzle belonging to the second section MR of the pass 6, and the X3 and X4 pixels are #14 nozzle belonging to the second section MR of the pass 8. Means assigned to.
For example, it means that X1 to X3 pixels of the raster line L20 formed by Y ink are assigned to the #8 nozzle belonging to the first section CR of the pass 10, and X4 pixel is assigned to the #2 nozzle of the pass 12. ..

FIG. 13 is an image formed by ejecting C ink toward the pixels assigned to the nozzles Nz (#23 to #33 nozzles) belonging to the first section CR in passes 1 to 6. By the pass 1 to pass 6, the normal printing portion in which the dots of the C ink are formed on all the pixels of the raster lines L9 to L34 is completed. The raster lines L1 to L8 are the upper end portions, and the upper end portions are separately subjected to the upper end processing by the minute feeding of the print medium G.

According to the present embodiment, the image formed by the C ink has the seams of the bands of the first section CR and the area of the ink ejected from the nozzles Nz of the nozzle groups A, B, and C of the first section CR. It is distributed diagonally to the raster line.
Specifically, for example, the X1 to X4 pixels in the raster lines L9 to L14 are formed only by the dots ejected from the nozzles Nz of the central nozzle group B of the first section CR (see FIG. 10).
X1 to X3 pixels in the raster lines L15 and L16 are formed by dots ejected from the nozzles Nz of the central nozzle group B of the first section CR, and X4 pixels are dots ejected from the one end side nozzle group A of the first section CR. (See FIG. 10).
The X1 and X2 pixels in the raster lines L17 and L18 are formed by dots ejected from the nozzles Nz of the other end side nozzle group C of the first section CR, and the X3 and X4 pixels are formed from the one end side nozzle group A of the first section CR. It is formed of ejected dots (see FIG. 10).
The X1 pixels in the raster lines L19 and L20 are formed by dots ejected from the nozzles Nz of the other end side nozzle group C of the first section CR, and the X2 to X4 pixels are ejected from the central nozzle group B of the first section CR. It is formed of dots (see FIG. 10).
Then, the X1 to X4 pixels in the raster lines L21 to L26 are formed again only by the dots ejected from the nozzles Nz of the central nozzle group B of the first section CR (see FIG. 10).
As a result, in the image formed in the first section CR, the joints of the bands are inclined with respect to the raster lines, and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups, so that C Even if there is a difference in ink density between the nozzle groups A, B, and C of the first section CR that ejects ink, it is difficult to visually recognize the uneven density.

FIG. 14 is an image formed by ejecting M ink toward the pixels assigned to the nozzles Nz (#12 to #22 nozzles) belonging to the second zone MR in passes 3 to 8. By the pass 3 to the pass 8, the normal printing portion in which the dots of the M ink are formed in all the pixels of the raster lines L9 to L34 is completed.

According to the present embodiment, in the image formed by the M ink, the joints of the bands of the second zone MR and the area of the ink ejected from the nozzles Nz of each nozzle group A, B, C of the second zone MR are , Distributed diagonally to the raster line.
Specifically, for example, the X1 to X4 pixels in the raster lines L11 to L16 are formed only by the dots ejected from the nozzles Nz of the central nozzle group B of the second zone MR (see FIG. 11).
X1 to X3 pixels in the raster lines L17 and L18 are formed by dots ejected from the nozzles Nz of the central nozzle group B of the second zone MR, and X4 pixels are dots ejected from the one end side nozzle group A of the second zone MR. (See FIG. 11).
The X1 and X2 pixels in the raster lines L19 and L20 are formed by dots ejected from the nozzles Nz of the other end side nozzle group C of the second section MR, and the X3 and X4 pixels are formed from the one end side nozzle group A of the second section MR. It is formed of ejected dots (see FIG. 11).
The X1 pixels in the raster lines L21 and L22 are formed by dots ejected from the nozzles Nz of the other end side nozzle group C of the second section MR, and the X2 to X4 pixels are ejected from the central nozzle group B of the second section MR. It is formed of dots (see FIG. 11).
Then, the X1 to X4 pixels in the raster lines L23 to L28 are formed again only by the dots ejected from the nozzles Nz of the central nozzle group B of the second zone MR (see FIG. 11).
As a result, the image formed in the second zone MR has the joints of the bands oblique to the raster lines, and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups, so that M Even if there is a difference in the ink density between the nozzle groups A, B, and C of the second section MR that ejects ink, it is difficult to visually recognize the uneven density.

FIG. 15 is an image formed by ejecting Y ink toward the pixels assigned to the nozzles Nz (#1 to #11 nozzles) belonging to the third section YR in passes 7 to 12. By the pass 7 to pass 12, the normal printing unit in which the dots of the Y ink are formed on all the pixels of the raster lines L1 to L30 is completed. The raster lines L31 to L34 are the lower end portions, and the lower end portions are separately subjected to the lower end processing by minutely feeding the print medium G.

According to the present embodiment, in the image formed with the Y ink, the joints of the bands of the third section YR and the areas of the ink ejected from the nozzles Nz of the nozzle groups A, B, and C of the third section YR are , Distributed diagonally to the raster line.
Specifically, for example, the X1 to X4 pixels in the raster lines L13 to L18 are formed only by the dots ejected from the nozzles Nz of the central nozzle group B in the third section YR (see FIG. 12).
The X1 to X3 pixels in the raster lines L19 and L20 are formed by the dots ejected from the nozzles Nz of the central nozzle group B of the third section YR, and the X4 pixels are the dots ejected from the one end side nozzle group A of the third section YR. (See FIG. 12).
The X1 and X2 pixels in the raster lines L21 and L22 are formed by dots ejected from the nozzles Nz of the other end side nozzle group C of the third section YR, and the X3 and X4 pixels are formed from the one end side nozzle group A of the third section YR. It is formed of ejected dots (see FIG. 12).
The X1 pixels in the raster lines L23 and L24 are formed by dots ejected from the nozzles Nz of the other end side nozzle group C of the third section YR, and the X2 to X4 pixels are ejected from the central nozzle group B of the third section YR. It is formed of dots (see FIG. 12).
Then, the X1 to X4 pixels in the raster lines L25 to L30 are formed again only by the dots ejected from the nozzles Nz of the central nozzle group B in the third section YR (see FIG. 12).
As a result, in the image formed in the third section YR, the joints of the bands are inclined with respect to the raster lines, and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups. Even if there is a difference in the ink density for each of the nozzle groups A, B, and C of the third section YR that ejects ink, it is difficult to visually recognize the uneven density.

As described above, according to the printing apparatus of this embodiment, the following effects can be obtained.
The printing system 1 as a printing device has a print head 126 including a nozzle row NL2 including a first section CR, a second section MR, and a third section YR for each color of ink. The ejection control unit includes nozzles Nz that eject ink on the print medium G in the other end side nozzle group C and the central nozzle group B for each of the first to third sections CR, MR, and YR in the odd-numbered pass. The nozzles Nz included in the one end side nozzle group A and the nozzles Nz included in the central nozzle group B are sequentially changed. Alternatively, in the even-numbered passes, the nozzles Nz included in the one end side nozzle group A and the central nozzle group B are included in the other end side nozzle group C and the central nozzle group B for each of the first to third sections CR, MR, YR. The nozzles Nz are changed sequentially. As a result, the image formed by each ink of CMY has the joints of the bands oblique to the raster lines, and the raster lines at the joints of the bands are formed by dots ejected from different nozzle groups. Even if there is a difference in the ink density for each nozzle group A, B, C in the third section CR, MR, YR, it is difficult to visually recognize the unevenness of light and shade for all the ink colors corresponding to each section.

The present invention is not limited to the above-described embodiments, and various changes and improvements can be added to the above-described embodiments. A modified example will be described below.

(Modification 1)
16 and 17 are diagrams showing an example of a color conversion table (LUT). In this modification, in the print control process of the printing system 1, the control unit 11 can switch the LUT 16A used in the color conversion process (step S110) according to the mode designated by the user.
Hereinafter, the print control process according to the modification will be described with reference to FIGS. 16 and 17.

16 illustrates the LUT 16A1 and FIG. 17 illustrates the LUT 16A2. Each of the LUTs 16A1 and 16A2 is a kind of the LUT 16A, and defines the conversion relationship between the RGB value and the ink amount for each CMYK. The LUT 16A1 and the LUT 16A2 have different upper limit values (MAX) to be observed when setting CMYK values corresponding to certain RGB values. The upper limit value here is meant to include the upper limit value of the sum of the C, M, Y, and K ink amounts and the upper limit value of each of the C, M, Y, and K ink amounts for each color. As an example, in the LUT 16A1, the upper limit value of the total CMYK ink amount is set to “120”, and the ink amount of each ink color is defined so as to be within this upper limit value. On the other hand, in the LUT 16A2, for example, the upper limit value of the sum of the CMYK ink amounts is set to "150", which is higher than that of the LUT 16A1, and the ink amount of each ink color is defined so as to be within this upper limit value. ..

As can be seen from FIG. 16 and FIG. 17, the CMYK values corresponding to the same RGB values tend to be set higher in the LUT 16A2 in which the upper limit of the total is set higher than in the LUT 16A1. To be 16 and 17, the upper limit value for each color of C, M, Y, and K inks is set to 100 (%) for both LUT 16A1 and LUT 16A2. For example, LUT 16A1 may be set to 80 (%) or the like. It may be. In any case, the LUT 16A1 is an example of a "first color conversion table" that is defined in advance by adopting an upper limit value (first upper limit value) for the upper limit value, and the LUT 16A2 is the first color conversion table for the upper limit value. It is an example of a “second color conversion table” that is defined in advance by using a second upper limit value that is higher than the upper limit value of 1.

The LUT 16A1 and LUT 16A2 are, for example, color conversion tables prepared in advance for each print mode that the user can arbitrarily select. The print mode is, for example, a mode according to the type of print medium used, the type of image to be printed (photograph, CG, text, etc.), or the color effect desired by the user. In this modification, an environment in which a plurality of color conversion tables are prepared in this way is used, and for example, the color conversion table to be referred to in accordance with the selection of the mode is the LUT 16A1 or the LUT 16A2. The printing method may be switched depending on the type.

Specifically, when the control unit 11 (ejection control unit) refers to the LUT 16A2 and determines the ink amount in step S110, in step S130, the nozzle Nz that ejects ink onto the print medium during the pass. Of allocating pixels to each nozzle Nz based on the discharge pattern JP in which at least one of the first and second changes is sequentially performed (that is, the process of step S130 described in the first embodiment). To execute.
On the other hand, when the control unit 11 (ejection control unit) refers to the LUT 16A1 and determines the ink amount in step S110, in step S130, the one end side nozzle group and the central nozzle group are associated with each pass. And a process of assigning a pixel to each nozzle Nz included in the other end side nozzle group (for example, the assigning process described in the conventional example (FIG. 20)).

When the ink amount is determined with reference to the LUT 16A2 that employs the second upper limit value that is relatively high as the upper limit value, more ink is used than when the ink amount is determined with reference to the LUT 16A1. Are likely to be ejected, and as a result, uneven density is likely to be visually recognized on the print medium. Therefore, according to the present modified example, when the ink amount is determined by referring to the LUT 16A2, the nozzle Nz for ejecting ink is changed during the pass as described in the embodiment. It is possible to make the light and shade unevenness less visible.
When the ink amount is determined with reference to the LUT 16A1 that employs a first upper limit value that is relatively low as the upper limit value, since unevenness in light and shade is not likely to occur originally, a measure for changing the nozzle Nz that ejects ink during a pass However, the printing speed can be improved by using all the nozzles Nz for ejecting ink in each pass as described in the conventional example.

The printing system (printing apparatus) to which this modification is applied is not limited to the printer 20 that uses the ink cartridge 32 having the absorbing member 34 as illustrated in FIG. 4. That is, even if the ink cartridge does not have the absorbing member, the ink may settle, so that this modification is applicable to a printer that uses an ink cartridge (ink tank) of a type that does not have the absorbing member. is there.

(Modification 2)
The ejection pattern JP as the predetermined rule in the process of assigning pixels to the nozzles Nz described in the embodiment is not limited to the pattern shape shown in the embodiment. The ejection pattern JP may have a pattern shape in which at least one of the first change and the second change is repeated during the pass.

18 and 19 are diagrams showing an example of the ejection pattern. As shown in FIGS. 18 and 19, n (for example, n=180) nozzles Nz are formed in the nozzle row NL, and the nozzle row NL has m pixels in the X direction×2n in the Y direction in one pass. -Moving a range of 1 pixel.

When the control unit 11 (ejection control unit) of the printing system 1 executes the process of assigning pixels to each nozzle Nz based on the ejection pattern JP1 shown in FIG. 18, the nozzles that eject ink onto the print medium during the pass. The first change of sequentially changing Nz is repeated three times.
When the control unit 11 (ejection control unit) of the printing system 1 executes the process of assigning pixels to each nozzle Nz based on the ejection pattern JP2 shown in FIG. 19, the nozzles that eject ink onto the print medium during the pass. A first change and a second change that sequentially change Nz are performed.
As a result, the joints of the obliquely inclined bands are divided or the direction of inclination is changed, so that it is possible to form an image in which uneven density is less likely to be visually recognized. The shapes of the ejection patterns JP, JP1, JP2 are examples, and the control unit 11 (ejection control unit) may be caused to execute the process of allocating pixels to the nozzles Nz based on ejection patterns of other shapes.

1... Printing system as a printing device, 10... Control device, 11, 21... Control part, 12, 22... CPU, 13, 23... ROM, 14, 24... RAM, 16... HDD, 16A, 16A1, 16A2... Color Conversion table, 19, 25... Interface unit (I/F), 20... Printer, 26, 126... Print head, 27... Head drive unit, 32... Ink cartridge, 40... Feed mechanism, 50... Carriage mechanism, 51... Carriage , A... One end side nozzle group, B... Central nozzle group, C... Other end side nozzle group, G... Print medium, NL, NL1, NL2... Nozzle row, Nz... Nozzle, JP, JP1, JP2... Ejection pattern.

Claims (8)

A print head that conveys a print medium in a first direction and has a nozzle row in which a plurality of nozzles for ejecting ink are formed side by side in the first direction is moved in a second direction that intersects the first direction. A printing apparatus that performs printing by ejecting the ink from the nozzle to the print medium during the movement,
A nozzle group including a plurality of nozzles on one end side of the nozzle row is a one-end side nozzle group, a nozzle group including a plurality of nozzles on the other end side of the nozzle row is a other-end side nozzle group, the one-end side nozzle When the nozzle group composed of a plurality of nozzles that do not correspond to any of the group and the other end side nozzle group is the central nozzle group,
During the one movement in the second direction, the nozzles for ejecting the ink on the print medium are changed from nozzles included in the one end side nozzle group and the central nozzle group to the other end side nozzle group and the nozzle. A first change to a nozzle included in the central nozzle group, and a change from a nozzle included in the other end side nozzle group and the central nozzle group to a nozzle included in the one end side nozzle group and the central nozzle group And a discharge control unit for changing to at least one of
In the first change and the second change, the nozzle that ejects the ink onto the print medium is positioned at the position in the second direction of the print head during the one-time movement in the second direction. Change accordingly,
The printing apparatus, wherein the ejection control unit repeats at least one of the first change and the second change during the movement. A print head that conveys a print medium in a first direction and has a nozzle row in which a plurality of nozzles for ejecting ink are formed side by side in the first direction is moved in a second direction that intersects the first direction. A printing apparatus that performs printing by ejecting the ink from the nozzle to the print medium during the movement,
The nozzle row is divided into a plurality of sections along the first direction, and the color of ink ejected from the nozzles is different for each section.
A nozzle group composed of a plurality of nozzles on one end side for each section, a nozzle group composed of a plurality of nozzles on the other end side for each section, a nozzle group on the other end side, for each section When the central nozzle group is a nozzle group composed of a plurality of nozzles that do not correspond to any of the one end side nozzle group and the other end side nozzle group,
Nozzles for ejecting the ink onto the print medium for each of the sections are moved from the nozzles included in the one end side nozzle group and the central nozzle group to the other end during the movement in the second direction once. A first change to a nozzle included in the side nozzle group and the nozzle included in the central nozzle group; and a nozzle included in the other end side nozzle group and the central nozzle group included in the one end side nozzle group and the central nozzle group A second control for changing to a nozzle and a discharge control section for changing to at least one of:
In the first change and the second change, the nozzle that ejects the ink onto the print medium is positioned at the position in the second direction of the print head during the one-time movement in the second direction. Change accordingly,
The printing apparatus, wherein the ejection control unit repeats at least one of the first change and the second change during the movement. Within a predetermined upper limit value for each pixel of the image data, by referring to a color conversion table for converting the color system adopted by the image data representing the image into the color system of the ink ejected by the print head. Equipped with an ink amount determination unit that determines the ink amount with
The ejection control unit controls the ejection of ink by the nozzles by assigning to the nozzles pixels that have been determined to eject or not eject the ink based on the ink amount.
The ink amount determination unit employs a first upper limit value for the upper limit value and defines a first color conversion table in advance, and a second upper limit value for the upper limit value that is higher than the first upper limit value. When the ink amount is determined by referring to the second color conversion table of the second color conversion table defined in advance, the ejection control unit ejects ink during the movement. Corresponding to the nozzles, the pixels included in the nozzles included in the other end side nozzle group and the central nozzle group, or the nozzles included in the one end side nozzle group and the central nozzle group,
When the ink amount determination unit determines the ink amount with reference to the first color conversion table, the ejection control unit, in each movement, the one end side nozzle group, the central nozzle group, The printing device according to claim 1, wherein pixels are assigned to the nozzles included in the nozzle group on the other end side. The ratio of the number of nozzles of the other end side nozzle group and the central nozzle group to the number of nozzles of the nozzle row, and the ratio of the number of nozzles of the one end side nozzle group and the central nozzle group to the number of nozzles of the nozzle row Is 3/5 or more and 3/4 or less, The printing apparatus as described in any one of Claim 1 to 3 characterized by the above-mentioned. The nozzle row is divided into a section where the nozzle ejects cyan ink, a section where the nozzle ejects magenta ink, and a section where the nozzle ejects yellow ink. The printing device according to 2. The printing apparatus according to any one of claims 1 to 5, wherein a pigment ink is used as the ink. The printing head according to any one of claims 1 to 6, wherein the print head receives supply of the ink to the nozzle from an ink cartridge that holds the ink by a sponge-like absorbing member. apparatus. A print head that conveys a print medium in a first direction and has a nozzle row in which a plurality of nozzles for ejecting ink are formed side by side in the first direction is moved in a second direction that intersects the first direction. A printing method for performing printing by ejecting the ink from the nozzle to the print medium during the movement,
A nozzle group including a plurality of nozzles on one end side of the nozzle row is a one-end side nozzle group, a nozzle group including a plurality of nozzles on the other end side of the nozzle row is a other-end side nozzle group, the one-end side nozzle When the nozzle group composed of a plurality of nozzles that do not correspond to any of the group and the other end side nozzle group is the central nozzle group,
During the one movement in the second direction, the nozzles for ejecting the ink on the print medium are changed from nozzles included in the one end side nozzle group and the central nozzle group to the other end side nozzle group and the nozzle. A first change to a nozzle included in the central nozzle group, and a change from a nozzle included in the other end side nozzle group and the central nozzle group to a nozzle included in the one end side nozzle group and the central nozzle group 2 and a discharge control step of changing to at least one of
In the first change and the second change, the nozzle that ejects the ink onto the print medium is positioned at the position in the second direction of the print head during the one-time movement in the second direction. Change accordingly,
The printing method, wherein the discharge control unit repeats at least one of the first change and the second change during the movement.

Images