JP5682100B2 - Liquid ejecting apparatus and printing method - Google Patents

Description

  The present invention relates to a liquid ejecting apparatus that ejects a liquid such as ink onto a medium, and a printing method.

  Two-dimensionally by having a head unit in which a plurality of nozzles are arranged, relatively moving the print medium in a direction different from the direction in which the nozzles are arranged, and simultaneously ejecting ink intermittently from the nozzle row There is an apparatus that forms an image by arranging dots. In the above-described apparatus, there is also an apparatus that has a plurality of the head units and arranges them in the nozzle arrangement direction to print a width equal to or larger than the width of one head unit with a small number of scans. In such an apparatus, there is a case where the joint between adjacent head units is conspicuous and the printing result is deteriorated. In order to alleviate this, there is an apparatus that makes the joints inconspicuous by overlapping the nozzles at the end of adjacent head units and distributing the output dots to each head unit in overlapping nozzles (for example, Patent Documents) 1).

JP-A-6-255175

  In such an apparatus, the dot distribution is determined so that the joints are not conspicuous under specific printing media, resolution, jet ink weight, and other conditions. However, when printing on different recording media, the output resolution and ink When the printing conditions are changed, such as changing the weight, there is a problem that the joints cannot be sufficiently reduced and the image quality is deteriorated.

  The present invention is realized as the following forms or application examples so as to solve at least a part of the problems described above.

  Application Example 1 A liquid ejecting apparatus according to this application example includes a first head having a first nozzle row in which a plurality of nozzles ejecting liquid are arranged in a predetermined direction, and the nozzles are in the same direction as the predetermined direction. A second head having a second nozzle row arranged; and a transport mechanism for relatively moving a print medium in a direction crossing the predetermined direction, the dots formed by the nozzles of the first nozzle row; The one or more dots formed by one or more nozzles of the second nozzle row overlap, whereby the first nozzle row and the second nozzle row form a composite nozzle row, A controller that controls ejection from the nozzles of the transport mechanism, the first nozzle array, and the second nozzle array, and forms a raster line by ejecting liquid from the nozzles while transporting the print medium. And in the overlapping area where the controller overlaps the dots formed by the first nozzle row and the dots formed by the second nozzle row, based on a predetermined rule, the first A printing apparatus having a function of selectively ejecting the liquid from a nozzle array and a second nozzle array, wherein the controller has a plurality of the laws and switches the laws according to ejection conditions. To do.

  Application Example 2 In the liquid ejecting apparatus according to the application example, the rule is that the number of dots formed by the first nozzle row and the dots formed by the second nozzle row in the overlapping region. It is a selection law that controls the ratio of numbers.

  Application Example 3 In the liquid ejecting apparatus according to the application example described above, the first head includes a plurality of first nozzle arrays that eject different liquids, and the second head ejects different liquids. There are a plurality of second nozzle rows to be ejected, and the ratio of the number of dots by the first nozzle row and the number of dots by the second nozzle row is different for each liquid.

  Application Example 4 In the printing method according to this application example, a first head having a first nozzle row in which a plurality of nozzles for ejecting liquid are arranged in a predetermined direction, and the nozzle is in the predetermined direction A second head having second nozzle rows arranged in the same direction; a print medium relatively moving in a direction crossing the predetermined direction; the transport mechanism; the first nozzle row; and the second nozzle row. Forming a raster line by controlling ejection from the nozzles and ejecting liquid from the nozzles while transporting the print medium, and forming by the nozzles in the first nozzle row The first nozzle row and the second nozzle row are combined by overlapping one or more dots formed by one or more of the nozzles of the second nozzle row. In a region where the dots formed by the first nozzle row and the dots formed by the second nozzle row overlap with each other, the controller forms the slip row, and based on a predetermined rule, A printing method having a function of selectively ejecting the liquid from a first nozzle row and the second nozzle row, wherein the controller switches the law according to printing conditions. And

According to this application example, a law for selectively ejecting droplets from either the first nozzle array or the second nozzle array is created as an optimal law for a plurality of liquid ejection conditions. A law for selectively ejecting liquid from any one of the nozzle array and the second nozzle array is created as an optimum law for a plurality of liquid ejection conditions. And when performing injection, the quality of the output pattern can be improved regardless of injection conditions by selecting the optimal law with respect to the set injection conditions.
In addition, when a law for selectively ejecting ink from either the first nozzle array or the second nozzle array is created as an optimum law for a plurality of liquid ejection conditions, printing is performed. By selecting an optimal rule for the printing conditions that are sometimes set, the image quality of the output image can be improved regardless of the printing conditions.
The printing condition indicates a condition including at least one of a printing medium, a printing resolution, and an output dot size when performing printing.

1 is an overall configuration block diagram of a printing system according to an embodiment. 2A is a cross-sectional view of the printer 1, and FIG. 2B is a diagram illustrating a state in which the printer 1 conveys the paper S. FIG. 4 is a schematic diagram illustrating an arrangement of nozzles on the lower surface of the head unit 30. FIG. 6 is a flowchart for explaining a printing operation. The figure which illustrates a data copy process and a masking process typically. Explanatory drawing for demonstrating the determination method about whether each dot is formed with the ink from a 1st nozzle row or a 2nd nozzle row. FIG. 10 is a schematic diagram illustrating a selectivity in the printer 1 according to a conventional example. FIG. 3 is a schematic diagram illustrating a selectivity in the printer 1 according to the present embodiment. FIG. 4 is a schematic diagram illustrating a selectivity for each ink in the printer 1 according to the present embodiment.

(Embodiment)
A configuration example of a printing system as an example of a liquid ejecting apparatus will be described with reference to FIG. 1 (functional block diagram), FIG. 2 (outline of the apparatus), and FIG. 3 (head and nozzle arrangement diagram). FIG. 1 is a block diagram of the overall configuration of a printing system according to the present embodiment. FIG. 2A is a cross-sectional view of the printer 1. FIG. 2B is a diagram illustrating a state in which the printer 1 transports the paper S (medium). FIG. 3 is a schematic diagram illustrating the arrangement of nozzles on the lower surface of the head unit 30. 2B is a diagram of the head unit 30 and the like viewed from the direction X shown in FIG.

  The printing system includes a computer 60 and a printing apparatus (line head ink jet printer, hereinafter simply referred to as printer 1). The printing system including the printer 1 and the computer 60 can also be called a “printing apparatus” in a broad sense.

  The computer 60 includes application software and a printer driver. The computer 60 converts multi-tone image data generated by application software into binarized print data. The conversion is realized by image processing by a printer driver.

  The printer 1 that has received the print data from the computer 60 controls each unit (such as the transport unit 20 and the head unit 30 as an example of a moving mechanism) by the controller 10 to form an image on a sheet S as an example of a medium. . Further, the detector group 40 monitors the situation in the printer 1, and the controller 10 controls each unit based on the detection result.

  The controller 10 is a control unit for controlling the printer 1. The interface unit 11 is for transmitting and receiving data between the computer 60 as an external device and the printer 1. The CPU 12 is an arithmetic processing unit for controlling the entire printer 1. The memory 13 is for securing an area for storing a program of the CPU 12, a work area, and the like. The CPU 12 controls each unit by a unit control circuit 14 according to a program stored in the memory 13.

  The transport unit 20 feeds the paper S to a printable position, and transports the paper S by a predetermined transport amount in the transport direction (corresponding to a predetermined direction) during printing. As illustrated in FIG. 2A, the transport unit 20 includes a paper feed roller 21, a transport roller 22, a platen 23, and a paper discharge roller 24. The paper feed roller 21 is a roller for feeding the paper S inserted into the paper insertion slot into the printer 1. The transport roller 22 is a roller that transports the paper S fed by the paper feed roller 21 to a printable area. The platen 23 supports the paper S being printed. The paper discharge roller 24 is a roller for discharging the paper S to the outside of the printer 1.

  The head unit 30 is for ejecting ink as an example of liquid onto the paper S. The head unit 30 prints an image on the paper S by forming dots on the paper S by ejecting ink onto the paper S being conveyed. The head unit 30 according to the present embodiment can form dots for the paper width at a time. In addition, the liquid is not limited to ink, but may be any fluid (liquid material) including solid matter and capable of being ejected from the nozzle.

  Here, the configuration of the head unit 30 according to the present embodiment will be described in detail with reference to FIG. The head unit 30 includes a plurality of heads 31. On the lower surface of each head 31, a plurality of nozzles that are ink ejecting portions are provided. A plurality of (four in this embodiment) nozzles that eject inks of different colors in the transport direction are in a predetermined color order (in this embodiment, black K → cyan C → magenta M → yellow Y). Are lined up. The four nozzles arranged in the transport direction form a nozzle row, and a plurality of nozzle rows are arranged at a constant interval (360 dpi) in the (paper) width direction (corresponding to the cross direction) intersecting the transport direction. (In this embodiment, 360) are arranged. Each nozzle is provided with a pressure chamber (not shown) containing ink and a drive element (piezo element) for changing the volume of the pressure chamber to eject ink.

  The plurality of heads 31 are arranged in a staggered manner in the width direction. In other words, the plurality of heads 31 includes an upstream head 32 (also referred to as a preceding head 32) positioned upstream in the transport direction and a downstream head 33 (also referred to as a trailing head 33) positioned downstream in the transport direction. In the width direction, the upstream head 32 and the downstream head 33 are alternately arranged (that is,... → the upstream head 32 → the downstream head 33 → the upstream head 32 →... ). Further, the upstream head 32 and the upstream head 32 adjacent to each other such that the end of one head of the upstream head 32 and the downstream head 33 adjacent to each other in the width direction and the end of the other head overlap in the width direction. A downstream head 33 is arranged.

  For example, when the upstream head 32 indicated by reference numeral 320 in FIG. 3 is the first head 320 and the downstream head 33 indicated by reference numeral 330 is the second head 330, the first head 320 that is the upstream head 32 A front side end in the width direction (corresponding to an end on one end side) and a back side end in the width direction of the second head 330 which is the downstream head 33 positioned downstream in the transport direction from the first head 320 ( Corresponding to the end on the other end side) in the width direction. Then, there are Q (eight in the present embodiment) nozzle rows (hereinafter, the nozzle row of the first head 320 is referred to as a first nozzle row) located at the front end of the first head 320. In addition, it overlaps in the width direction with Q nozzle rows (the nozzle row of the second head 330 will be referred to as a second nozzle row hereinafter) located at the back end of the second head 330. As a result, Q composite nozzle rows (see FIG. 3) in which the first nozzle row and the second nozzle row are arranged in the transport direction are formed.

<Print processing example>
Here, a color printing process will be described as an example and a printing process example will be described. When receiving a print command and print data from the computer 60, the controller 10 analyzes the contents of various commands included in the print data and performs the following processing using each unit.

  First, the controller 10 rotates the paper feed roller 21 to feed the paper S to be printed into the printer 1. Then, the controller 10 rotates the transport roller 22 to position the fed paper S at the print start position. At this time, the paper S is opposed to at least some of the nozzles of the head 31 (the above is referred to as a first print processing step for convenience).

  Next, the sheet S is conveyed by the conveying roller 22 without stopping at a constant speed, and passes under the head 31 (on the platen 23). While the paper S passes under the head 31, ink is intermittently ejected from each nozzle. As a result, a dot row (raster line) composed of a plurality of dots along the transport direction is formed on the paper S (the above is referred to as a second print processing step for convenience).

  Finally, the controller 10 discharges the paper S on which image printing has been completed by the paper discharge roller 24 (the above is called a third print processing step for convenience).

  Here, the second printing process step will be further described. In the color printing process, the controller 10 ejects ink of different colors from each of the nozzles belonging to the above-described nozzle row (or composite nozzle row) to the conveyed paper S, and creates the color-superposed dots. A plurality of raster lines are arranged along the transport direction to form a raster line for each nozzle row (or composite nozzle row). In this embodiment, the colors to be overlaid are cyan C, magenta M, and yellow Y, and the three color inks are landed on the same position on the paper S to form the color-superimposed dots.

<Specific examples of printing operations>
Next, a specific example of the printing operation will be described based on the flowchart of FIG.
When printing is instructed on the application program, the controller 10 performs resolution conversion processing (step S11). The resolution conversion process is a process of converting image data (text data, image data) to be printed into a resolution (print resolution) when printing on the paper S. The printing resolution in the printer 1 is 360 dpi × 360 dpi, and the image data after the resolution conversion process is data of 256 gradations represented by the RGB color space. And this image data is comprised by the pixel data group which shows a gradation value for every pixel. Therefore, the controller 10 converts the image data to be printed received from the application program into a print resolution of 360 dpi × 360 dpi, and converts the gradation of each pixel data into 256 gradations.

  If the resolution conversion process is performed, the controller 10 performs a color conversion process (step S12). The color conversion process is a process of converting the color space of the image data subjected to the resolution conversion process into an ink color space. In this printing system, image data of 256 gradations expressed in the RGB color space is converted into image data of 256 gradations expressed in the CMYK color space.

  Next, the controller 10 performs density unevenness correction processing (step S13). The density unevenness correction process corrects the gradation value of each pixel data included in the image data after color conversion (CMYK color space, 256 gradations) based on the correction value for the purpose of suppressing the density unevenness of the print image. It is processing to do. This correction value is acquired for each raster line based on the density of the printed test pattern. Briefly, a test pattern having a predetermined density is printed on the paper S, and the density (color density) of the test pattern is acquired for each raster line. An average density is calculated from the density for each raster line, and a correction value is acquired based on the difference from the calculated average density. For example, for a plurality of different types of tone values, the command tone value is plotted on the horizontal axis, and the average density for each command tone value is plotted on the vertical axis, and a correction value is obtained based on the obtained linear expression. That is, the density for each raster line is applied to a linear expression, and a correction value is calculated by linear interpolation. The calculated correction value is stored in the memory 13. The correction value is read from the memory 13 when the controller 10 executes the printer driver.

  If the density unevenness correction processing is performed, the controller 10 performs halftone processing (step S14). The halftone process is a process of converting image data (pixel data group) having a high gradation number into image data having a low gradation number. By performing this halftone process, print image data having the number of gradations that can be handled by the printer 1 is obtained. For example, 256 gradation image data is converted into two gradation image data (hereinafter also referred to as binary image data) that can be expressed by the printer 1. This binary image data is constituted by a pixel data group indicating two types of pixel formation and non-formation. For this reason, two types of control including ejection and non-ejection can be performed as ink droplet ejection control. Depending on the printer 1, this halftone process converts the image data into four-gradation image data composed of large dots, medium dots, small dots, and non-formed dots.

  If the halftone process is performed, the controller 10 performs a data copy process (step S15). In the data copy process, two binary image data (pixel data group) obtained by the halftone process correspond to each of a part of nozzles of the preceding head 32 and a part of nozzles of the succeeding head 33. In this process, the value image data is included in the binary image data for the preceding head 32 and also included in the binary image data for the succeeding head 33. The data copy process will be described later.

  Next, the controller 10 performs data distribution processing (step S16). The data distribution process is a process for obtaining binary image data for each head 31 from the binary image data after the data copy process. In this printing system, when data distribution processing is performed, binary image data output by each head 31 is obtained.

  If the data distribution process is performed, the controller 10 performs a masking process (S17). The masking process is related to binary pixel data included in binary image data for the upstream head (leading head) 32 and binary image data included in the binary image data for the downstream head (following head) 33. This is a process for determining whether to enable. By this masking process, the pixel data of one head 31 is validated and the pixel data of the other head 31 is invalidated. As a result, when dots can be formed with nozzles belonging to the upstream head (leading head) 32 group and dots can be formed with nozzles belonging to the downstream head (following head) 33 group, Whether to form dots using a nozzle is determined. As the masking data used in the masking process, a plurality of masking data is stored in the memory 13, and the optimum masking data is selected according to the printing conditions such as the printing medium, resolution, and dot size when printing. To execute the masking process. The masking process and the mask data to be used will be described later.

  If the masking process is performed, the controller 10 performs a data transfer process (S18). The data transfer process is a process of transferring binary image data for each head subjected to the masking process to the unit control circuit 14. When the binary image data is transferred to the unit control circuit 14, a dot formation process is performed (S19). In the dot formation process, ink droplet ejection control is performed based on the transferred binary image data. For example, when the pixel data constituting the binary image data indicates dot formation (ink droplet ejection), the unit control circuit 14 applies the drive signal COM to the drive element corresponding to the nozzle. As a result, the drive element operates and ink droplets are ejected from the corresponding nozzle. On the other hand, when the pixel data indicates no dot formation (ink non-ejection), the unit control circuit 14 does not apply the drive signal COM to the drive element corresponding to the nozzle. In this case, since the driving element does not operate, no ink droplet is ejected from the corresponding nozzle.

  A series of processing from resolution conversion processing (S11) to dot formation processing (S19) is repeatedly performed until there is no image data to be printed (S20). This series of processing is performed in synchronization with the conveyance of the paper S. That is, the controller 10 controls the transport unit 20 to transport the paper S. As a result, an image defined by the image data is printed on the paper S.

<About data copy processing>
Next, the data copy process (S15) will be described. As described above, the data copy process is performed by using predetermined binary image data (binary pixel data group) for each of the binary image data group for the preceding head 32 and the binary image data group for the following head 33. It is processing to be included in.

  As shown in the uppermost part of FIG. 5, the binary image data (input image) before the data copy process is data for each raster line. For this reason, with respect to the raster lines indicated by reference numerals L1 to L8 in the figure, dots can be formed by the first nozzle # 1 to the eighth nozzle # 8 of each head 31 serving as the preceding head 32. It is also possible to form dots from the 353rd nozzle # 353 to the 360th nozzle # 360 of each head 31 that becomes the row head 33.

  Here, as in the prior art, when the head in charge is switched according to the position in the paper width direction (that is, the raster line) and randomization is performed, the processing efficiency is deteriorated. This is because it is necessary to collectively process the binary image data in the entire paper width direction. In this regard, in the printer 1 of the present embodiment, binary image data is divided for each head HD. As a result, the unit of data to be handled is reduced, and subsequent data processing can be performed for each head HD. As a result, the processing efficiency can be improved.

  At this time, binary image data corresponding to each of a part of the nozzles located on the end side of the preceding nozzle group and a part of the nozzles located on the end side of the succeeding nozzle group is used for the preceding head 32. In addition to being included in the binary image data group, it is also included in the binary image data group for the trailing head 33. Thereby, the size and arrangement order of the data are aligned, and the binary image data group for the preceding head 32 and the binary image data group for the succeeding head 33 can be handled equally. Also in this respect, the processing efficiency can be improved.

  Here, the binary pixel data group constituting the binary image data corresponds to an ejection command because it represents ejection and non-ejection of ink droplets. Therefore, in the data copy process, the discharge command group corresponding to each of some of the nozzles included in the preceding nozzle group and some of the nozzles included in the succeeding nozzle group is used as the discharge command group for the preceding head 32. This corresponds to the process of being included in the discharge command group for the trailing head 33 as well as in the discharge head 33.

  In the above, the case of the first to eighth nozzles # 1 to # 8 of the preceding head and the 353 to 360th nozzles # 353 to # 360 of the following head has been described. The same relationship holds true for the 360th to # 360 nozzles # 353 to # 360 and the 1st to 8th nozzles # 1 to # 8 of the trailing head 33. For this reason, in the data copy process, binary image data in a range corresponding to these nozzles is similarly processed. That is, the binary image data in this range is included in each of the binary image data group for the leading head 32 and the binary image data group for the trailing head 33.

<About masking processing>
Next, the masking process (S17) will be described. As described above, the masking process determines which nozzle is used to form dots in a range where some nozzles of the preceding head 32 and some nozzles of the following head 33 overlap in the paper width direction. This is a process to be determined. This masking process is performed using the mask data MD.

  The mask data MD is conceptually shown in the middle part of FIG. 5 and the central part of FIG. In this mask data MD, one square corresponds to one unit region. Here, the unit area means a virtual small area where one dot can be formed. In the printer 1, formation or non-formation of dots for one unit region is determined by ejection control based on binary pixel data. In other words, ejection or non-ejection of ink droplets by one nozzle is determined. For this reason, the mask data MD corresponds to a mask that indicates validity and invalidity of binary pixel data for each nozzle.

  In the mask data MD of FIG. 6, eight unit areas composed of L1 to L8 are arranged in the paper width direction, and eight unit areas composed of n1 to n8 are arranged in the transport direction. Note that the codes L1 to L8 are used as codes indicating raster lines, but are also used as codes for specifying a unit area. This is because the size of the unit area in the paper width direction and the width of each raster line are considered to be the same. In this mask data MD, a black portion means data for validating the pixel data, and a white portion means data for invalidating the pixel data. Therefore, when this mask data MD is applied to a certain head 31, as shown in the right part of FIG. 6, dots are formed by the nozzles of the head HD in the unit area marked with [1]. On the other hand, in the unit area marked with [2], dots are formed by nozzles of other heads HD.

  For example, it is assumed that the mask data MD is applied to the first to eighth nozzles # 1 to # 8 in the heads 31 and 320 (see FIG. 3). In this case, in the unit area of [1] shown in the right part of FIG. 6, dots are formed by the first to eighth nozzles # 1 to # 8 in the heads 31 and 320. For the 353rd to 360th nozzles # 353 to # 360 in the heads 31 and 330, the mask data MD (inverted black and white in the figure) is obtained by inverting the valid / invalid relationship in the mask data MD in the center of FIG. Applied mask data) is applied. Thereby, in the unit area [2] shown in the right part of FIG. 6, dots are formed by the 353rd to 360th nozzles # 353 to # 360 in the heads 31 and 320. FIG. 5 shows two types of binary image data (input images) that are divided for the preceding head 32 and the succeeding head 33 in the data copying process by inverting the data validity / invalidity relationship. A process for obtaining binary image data for each head 31 by applying the mask data MD is described. A method for creating the mask data MD will be described later.

<About ink stacking order>
Here, considering the order in which the colors (inks) are overlaid for the three colors (inks), the three colors are ejected from each of the nozzles belonging to the composite nozzle row. When forming overlapped dots and nozzle rows that are not composite nozzle rows (for example, the first nozzle row located on the far side in the width direction than the composite nozzle row or the front side in the width direction relative to the composite nozzle row) In this case, the three nozzles are ejected from each of the nozzles belonging to the second nozzle row (refer to FIG. 3 for each case), and also referred to as a non-composite nozzle row, to form dots in which the three colors are superimposed. Is different.

  First, the non-composite nozzle row will be described. Since the paper S is transported in the transport direction, the ink ejected from the nozzle on the upstream side in the transport direction is landed on the paper S at an earlier timing. In the non-composite nozzle row according to the present embodiment, the nozzles of the respective colors are arranged in the transport direction in the order of black K → cyan C → magenta M → yellow Y. → Magenta M → Yellow Y

  On the other hand, in the composite nozzle row, the nozzles for each color are black K (for the first nozzle row) → cyan C (for the first nozzle row) → magenta M (for the first nozzle row) → (for the first nozzle row). Lined up in the transport direction in the order of yellow Y → black K (second nozzle row) → cyan C (second nozzle row) → magenta M (second nozzle row) → yellow Y (second nozzle row) For each color of cyan C, magenta M, and yellow Y to be overlaid, there are two nozzles that can eject ink (that is, nozzles in the first nozzle row and nozzles in the second nozzle row). Therefore, the controller 10 ejects ink from one of the nozzles of the first nozzle row and the second nozzle row for each color (that is, for each of the three colors of cyan C, magenta M, and yellow), and A raster line is formed by arranging a plurality of dots in which three colors are superimposed in the transport direction. For example, for a certain dot (dot a) belonging to a raster line, cyan C ink, magenta M ink, and yellow Y ink from the first nozzle row may be superimposed. For other dots (referred to as dots b), cyan C ink from the second nozzle row, magenta M ink from the first nozzle row, and yellow Y ink may be overlaid. For the dot (referred to as dot c), cyan C ink from the second nozzle row, magenta M ink, and yellow Y ink from the first nozzle row may be superimposed.

  The same applies to the composite nozzle row in that the ink ejected from the nozzle on the upstream side in the transport direction is landed on the paper S at an earlier timing. Unlike the case, it is indefinite. For example, for the dot a, the order of the three colors is cyan C → magenta M → yellow Y as in the case of the non-composite nozzle row, but for the dot b, magenta M → yellow Y → cyan. C, the dot c is yellow Y → cyan C → magenta M.

= Selectivity =
As described above, in the printer 1 according to the present embodiment, the end of one head 31 and the end of the other head 31 of the upstream head 32 and the downstream head 33 adjacent to each other in the width direction are wide. By arranging the heads 31 so as to overlap in the direction, a composite nozzle row is formed, and the controller 10 makes the first nozzle row and the second nozzle row of the composite nozzle row for each color with respect to the paper S being conveyed. A raster line is formed by ejecting ink from either one of the nozzles and arranging a plurality of overlapping dots in the transport direction.

  Here, the merits resulting from the above will be described. When the above is not performed (for example, there is no overlapping portion between adjacent heads, and a plurality of heads are simply arranged in a straight line in the width direction). In such a case, white streaks (portions where dots are not present) are conspicuous in the image when, for example, the distance between adjacent heads becomes too large due to head mounting errors. Generation of white stripes can be suppressed. Even if there is no error in the mounting of the heads, if the head characteristic difference between adjacent heads is large, the characteristic difference appears in the image, and the image portion formed by one head and the other Although a phenomenon may occur in which the image characteristics change abruptly at the boundary with the image portion formed by the head, the occurrence of such a phenomenon can be suppressed by the above.

  In the conventional printer 1, the above has been performed in order to enjoy the merits.

  Further, as described above, in both the printer 1 according to this embodiment and the conventional example, the controller 10 determines which of the first nozzle row and the second nozzle row of the composite nozzle row for each color with respect to the sheet S to be conveyed. Ink is ejected from one of the nozzles, and the ratio of the first nozzle row and the second nozzle row to be selected is determined in advance. That is, when viewed in dot units, it is determined at random whether the dots are formed by ink ejected from the first nozzle row or ink ejected from the second nozzle row, but in raster line units. In the case of the above, the ratio of the ink ejected from the first nozzle array and the ink ejected from the second nozzle array is set to a predetermined value (for measures for realizing such matters, Will be described in detail later).

  That is, in both the present embodiment and the printer 1 according to the conventional example, the controller 10 determines the number of dots formed by the ink ejected from the first nozzle row (second nozzle row) and all the dots belonging to the raster line. A raster line is formed by ejecting ink so that the ratio to the number of the dots becomes a predetermined value and arranging a plurality of dots with overlapping colors. In other words, the controller 10 determines the amount of ink ejected from the first nozzle row (second nozzle row) on the raster line and the ink ejected from the first nozzle row and the ink ejected from the second nozzle row. A raster line is formed by ejecting ink so that the ratio to the sum of the amounts on the raster line (that is, the total ink amount on the raster line) becomes a predetermined value, and arranging a plurality of overlapping dots. .

In the following, first, how the ratio (hereinafter also referred to as a selection rate for convenience) is set in the printer 1 according to the conventional example will be described, and problems in such a case will be described.
Subsequently, how the selection rate is set in this embodiment will be described, and in this case, the conventional problem will be solved. Following this, the above measures will be described.

<Setting of Selectivity and Problems in Conventional Printer 1>
First, setting of the selection rate in the printer 1 according to the conventional example will be described with reference to FIG. FIG. 7 is a schematic diagram showing the selectivity in the printer 1 according to the conventional example.

  On the upper side of FIG. 7, Q (eight) composite nozzle rows are shown. For convenience of explanation, a composite nozzle row on the front side (one end side) to a composite nozzle row on the far side (the other end side) is shown. L1 to L8 are set in this order. In addition, a first nozzle row that is a non-composite nozzle row located on the back side of the composite nozzle row is S1, and a second nozzle row that is a non-composite nozzle row located on the near side of the composite nozzle row is S2.

  Moreover, the selectivity of the 1st nozzle row with respect to each of the composite nozzle rows L1-L8 is shown on the lower side of FIG. For reference, the selectivity of the first nozzle row with respect to the non-composite nozzle rows S1 and S2 is also shown. (Naturally, since the non-composite nozzle row S1 is the first nozzle row, the non-composite nozzle row The selectivity of the first nozzle row for S1 is 100%, and the non-composite nozzle row S2 is the second nozzle row, so the selectivity of the first nozzle row for the non-composite nozzle row S2 is 0%).

  FIG. 7 shows only the selectivity of the first nozzle row and does not show the selectivity of the second nozzle row. This is because the relational expression of the selection ratio of the second nozzle array = 100−selectivity of the first nozzle array is established, and therefore the selection ratio of the second nozzle array is automatically determined when the selection ratio of the first nozzle array is determined. Because. Therefore, in the following, only the setting of the selectivity of the first nozzle will be referred to, and the setting of the selectivity of the second nozzle will not be mentioned. In addition, the term “selectivity” means the selectivity of the first nozzle row.

  As is clear from FIG. 7, in the printer according to the conventional example, the selection rate for the composite nozzle row is set to 50% uniformly, and the selection rate does not vary depending on the print medium, the dot size, and the print resolution.

<Problems when the selectivity is set as above>
The setting of a uniform selection rate of 50% in the conventional example is simple and convenient. However, when the selection rate is set in this way, there has been a problem that the image characteristics in the region ejected by the composite nozzle array differ depending on the printing conditions.
Specifically, the following phenomenon occurred. In the printer 1 according to the conventional example, a predetermined time has elapsed from the time when 50% is ejected by the first nozzle row until the rest is ejected by the second nozzle row, and the second nozzle row is ejected. In some cases, the ink ejected from the first nozzle row spread on the medium. When the ink is ejected from the second nozzle array onto the spread medium, the dots ejected from the second nozzle array tend to be greatly spread on the print medium as compared with the case where the ink is ejected from only the first nozzle array. is there. When such a phenomenon occurs, the area ejected by the composite nozzle array differs from the area ejected by only a single nozzle array in image characteristics such as density, and the image quality may deteriorate.

  The degree to which the above-described image quality degradation occurs depends on printing conditions such as the ink absorbability of the printing medium, the size of the ejected ink droplets, and the printing resolution. When printing with small ink droplets on a print medium that has an absorbent layer that easily absorbs ink on the surface, the dots ejected by the second nozzle array tend not to spread even after ejection by the first nozzle array. Even when the conventional method is used, the image quality is hardly deteriorated. In such a case, it was optimal to reduce the occurrence of the white streaks described above by setting the selection probability of the first nozzle row to 50% as in the conventional example. However, when the same processing is performed under the printing conditions for printing with a large dot size on a medium that does not have the above-described absorbing layer and has a high ink absorbability, the selection probability of the first nozzle row is 50%. In this way, the dots ejected by the second nozzle row spread, and image quality deterioration occurs. Therefore, for such media, the selection probability of the first nozzle row is less than 50%, and the state in which the ink does not spread on the print medium when ejected from the second nozzle row is maintained. Therefore, it is necessary to use different selection probabilities such as improving the image quality rather than setting the selection probability to 50%.

<<< Selection Rate Setting in Printer 1 According to the Present Embodiment >>>
Next, setting of the selection rate in the printer 1 according to the present embodiment will be described with reference to FIG. FIG. 8 is a schematic diagram illustrating the selectivity in the printer 1 according to the present embodiment. Note that FIG. 8 is a diagram corresponding to FIG. 7 already shown, and the way of viewing is the same as FIG.

  As is apparent from FIG. 8, in the printer 1 according to this embodiment, the selectivity for the composite nozzle row differs depending on the printing conditions, unlike the printer 1 according to the conventional example. Printing conditions 1 to 3 are different in any of the printing medium, dot size, resolution, and the like. In FIG. 8, the selection rate is 50% in the printing condition 1 as in the conventional example, but the selection rate is set low in the printing condition 2 and is set lower in the printing condition 3. As the selection rates for the printing conditions 1 to 3 in FIG. 8, a selection rate is selected such that the image quality is high for each printing condition. In the printing system shown in FIG. 1, the memory 13 selects which ink is formed from the first nozzle row or the second nozzle row so that the selection ratio of the printing conditions 1 to 3 shown in FIG. A mask pattern (details will be described later) is stored, a mask pattern suitable for the printing condition instructed at the time of printing is selected, and printing is executed in accordance with this mask pattern.

  By storing a plurality of mask patterns corresponding to the printing conditions in this way and selecting and printing either the first nozzle row or the second nozzle row at an appropriate selection rate according to the printing conditions, a plurality of mask patterns can be obtained. Even in this printing condition, the difference in printing characteristics between the non-composite area and the composite area can be reduced, and the image quality can be improved.

  In FIG. 8, the selection rate is constant regardless of the color, but a different selection rate can be set for each color. Similarly, with respect to the nozzle rows L1 to L8, it is also possible to set different selection rates for each nozzle row. Details of this point will be described later.

<<< Setting of Selectivity by Color in Printer 1 >>>
So far, the method for setting the same selection rate for all colors has been described. However, it is possible to further improve the image quality by setting the selection rate for each color. The reason is described below.

  The order of color overlap in the dots formed by the ink ejected from the non-composite nozzle row is always cyan C → magenta M → yellow Y. In other words, the color overlapping order always matches the color order of the nozzles arranged in the transport direction in the nozzle row. On the other hand, the color superposition order of dots formed by the ink ejected from the composite nozzle row is indefinite.

Here, when considering the color overlapping order in the composite nozzle row in more detail, the following five cases may occur as the color overlapping order.
The first case is cyan C → magenta M → yellow Y, which is the same color overlapping order as the color overlapping order in the non-composite nozzle array, and this case has four combinations (cyan C from the first nozzle array). Ink, magenta M ink, yellow Y ink are overlaid, cyan C ink from the second nozzle row, magenta M ink, yellow Y ink are overlaid, cyan C from the first nozzle row are overlaid. Ink, magenta M ink, and yellow Y ink from the second nozzle row are overlaid with cyan C ink from the first nozzle row, magenta M ink and yellow Y ink from the second nozzle row. Occurs when they are overlapped).

  The second case is cyan C → yellow Y → magenta M, and this case has one combination (cyan C ink from the first nozzle row, magenta M ink from the second nozzle row, This occurs when yellow Y ink from the first nozzle row is overlaid.

  The third case is magenta M → cyan C → yellow Y. This case has one combination (cyan C ink from the second nozzle row, magenta M ink from the first nozzle row, This occurs when yellow Y ink from the second nozzle row is overlaid.

  The fourth case is magenta M → yellow Y → cyan C. This case has one combination (cyan C ink from the second nozzle row, magenta M ink from the first nozzle row, Occurs when yellow Y ink is overlaid.

  The fifth case is yellow Y → cyan C → magenta M, and this case has one combination (cyan C ink from the second nozzle row, magenta M ink, magenta M ink from the first nozzle row). Occurs when yellow Y ink is overlaid.

  As described above, in the four combinations out of the eight combinations, the color overlapping order in the composite nozzle array is different from the color overlapping order in the non-composite nozzle array. In addition to this, since the selectivity is uniformly 50% regardless of the difference in color, dots with a color superposition order different from the color superposition order in the non-composite nozzle row are generated with a half probability. Become.

Next, problems caused by the difference in the color overlapping order in the composite nozzle array and the color overlapping order in the non-composite nozzle array will be described.
By the way, when a plurality of inks are overlaid, the degree of bleeding of each ink differs depending on the order in which the inks are overlaid. For example, the first superimposed ink has less ink bleeding because the ink does not exist at the landing destination when the ink lands on the paper S (that is, the landing destination on the paper S is dry). On the other hand, the third superimposed ink has two inks at the landing destination when the ink lands on the paper S (that is, the landing destination on the paper S is remarkably moistened). There is a significant increase in bleeding.

  Accordingly, the image characteristics of an image (pixel) realized by dots in which the three colors of cyan C, magenta M, and yellow Y are overlaid differ depending on the order in which the three colors are overlaid. For example, a dot that is overlaid in the order of cyan C → magenta M → yellow Y becomes a dot in which the ink of yellow C is noticeably blurred without much ink of cyan C, and in the order of magenta M → yellow Y → cyan C. The color-superimposed dots are dots in which magenta M ink is not so blurred and cyan C ink is significantly blotted. Therefore, the image characteristics of the image (pixel) realized by both dots are different from each other even though the same three colors are superimposed.

  As described above, the order of color overlap in the dots formed by the ink ejected from the non-composite nozzle row is always cyan C → magenta M → yellow Y, while it is formed by the ink ejected from the composite nozzle row. For dots that are different from the color superposition order in the non-composite nozzle row, a dot of a color superposition order is generated with a probability of half, so that the dots are formed by ink ejected from the non-composite nozzle row (raster line The image characteristics of the image portion (which is an aggregate) and the image portion formed by the ink ejected from the composite nozzle array are different (the difference in the image characteristics may appear as a streak on the image), and the image The image quality of the (entire image) will deteriorate.

  In order to eliminate such a problem (that is, to improve the image quality), for the dots formed by the ink ejected from the composite nozzle array, a color different from the color overlapping order in the non-composite nozzle array It is necessary to prevent the overlapping dots from being generated as much as possible.

  Next, a method for setting the selection rate in the printer 1 for each color will be described with reference to FIG. Note that FIG. 9 is a diagram corresponding to FIG. 7 already shown, and the way of viewing is the same as FIG. However, in FIG. 9, the selectivity for the composite nozzle row differs depending on the color difference and which nozzle row of the composite nozzle rows L1 to L8.

  First, a description will be given of the difference in the selectivity depending on the color difference. As shown in FIG. 9, the selectivity of the ink of the first color (for example, cyan C) is later than the first color in the transport direction. It is larger than the ink selection rate of the second color (for example, magenta M) which is the color order. That is, the controller 10 of the printer 1 according to the present embodiment belongs to the raster line of the number of dots formed by the first color (for example, cyan C) ink ejected from the first nozzle row. The ratio of the number of dots formed by the ink of the color (for example, cyan C) is the number of dots formed by the ink of the second color (for example, magenta M) ejected from the first nozzle row. The ink is ejected so as to be larger than the ratio to the total number of dots formed by the ink of the second color (for example, magenta M) belonging to the raster line, thereby forming the raster line. In other words, the controller 10 sets the amount of the first color (for example, cyan C) ejected from the first nozzle row on the raster line to A1, and the first color ejected from the second nozzle row ( For example, the amount of cyan C) ink on the raster line is A2, the amount of the second color (for example, magenta M) ink ejected from the first nozzle row on the raster line is B1, and from the second nozzle row When the amount of the ejected ink of the second color (for example, magenta M) on the raster line is B2, the ratio of A1 to A1 + A2 (hereinafter also referred to as the first ratio) is the ratio of B1 to B1 + B2 ( Hereinafter, the ink is ejected so as to be larger than the second ratio) to form a raster line.

  By doing so, the above-described problems can be solved. That is, when compared with a method using the same selectivity for all colors, the above-described eight combinations may occur, and color superposition in the composite nozzle row is performed using four of the eight combinations. Although the order is the same as the order of color overlap in the non-composite nozzle row, the selectivity is not uniform regardless of the color difference, but the above is performed according to the color difference. The probability of occurrence of dots in the color superposition order different from the color superposition order in the composite nozzle row (the probability of occurrence of the four combinations) is reduced from half.

  That is, for dots formed by the ink ejected from the composite nozzle row, it is difficult for the dots in the color superposition order different from the color superposition order in the non-composite nozzle row to occur, and the dots are formed by the ink ejected from the non-composite nozzle row. Difference between the image characteristics of the image portion and the image portion formed by the ink ejected from the composite nozzle row is suppressed, and the image quality of the image (entire image) is improved.

  In the present embodiment, the above-described relationship relating to the selectivity is established for the three colors to be overlaid. That is, not only when the first color is cyan C and the second color is magenta M, but when the first color is cyan C and the second color is yellow Y, the first color is magenta M and the second color. The relationship is also established when the color is yellow Y. That is, the selection ratio of cyan C ink is larger than the selection ratio of magenta M and yellow Y inks in the color order after cyan C in the transport direction, and the selection ratio of magenta M ink. However, it is larger than the selectivity of yellow Y ink in the color order after the magenta M in the transport direction.

  That is, the controller 10 of the printer 1 according to the present embodiment has the number of dots formed by the cyan C ink ejected from the first nozzle row, and all the dots formed by the cyan C ink belonging to the raster line. The ratio to the number is larger than the ratio of the number of dots formed by the magenta M ink ejected from the first nozzle row to the total number of dots formed by the magenta M ink belonging to the raster line. Ink is ejected to form raster lines. Further, the ratio of the number of dots formed by the magenta M ink ejected from the first nozzle row to the total number of dots formed by the magenta M ink belonging to the raster line is ejected from the first nozzle row. Raster lines are formed by ejecting ink such that the number of dots formed by yellow Y ink is greater than the ratio of the number of dots formed by yellow Y ink to the total number of dots formed by yellow Y ink.

  In other words, the controller 10 determines the amount of cyan C ink ejected from the first nozzle row on the raster line C1, the amount of cyan C ink ejected from the second nozzle row on the raster line C2, The amount of magenta M ink ejected from the first nozzle row on the raster line is M1, the amount of magenta M ink ejected from the second nozzle row on the raster line is M2, and the amount is ejected from the first nozzle row. The ratio of C1 to C1 + C2> M1 to M1 + M2 where Y1 is the amount of yellow Y ink on the raster line and Y2 is the amount of yellow Y ink ejected from the second nozzle row Raster lines are formed by ejecting ink so as to satisfy the relational expression of the ratio of> Y1 to Y1 + Y2.

  For this reason, dots formed by the ink ejected from the composite nozzle array are more unlikely to generate dots having a color overlap order different from the color overlap order in the non-composite nozzle array. Differences in image characteristics between the formed image portion and the image portion formed by the ink ejected from the composite nozzle array are further suppressed, and the image quality of the image (the entire image) is further improved. .

<Setting of the selection rate for each nozzle row in the printer 1>
In the printer 1 according to the present embodiment, as illustrated in FIG. 9, the selectivity for the composite nozzle row differs depending on which nozzle row of the composite nozzle rows L1 to L8. That is, in the present embodiment, the controller 10 has the first nozzle row belonging to the composite nozzle row for each color and each of the Q (eight) composite nozzle rows and the paper S to be transported. Q (eight) raster lines are formed by ejecting ink from one of the nozzles of the second nozzle array and arranging a plurality of dots that are overlaid in color along the transport direction. The raster line located on the far side (the other end side) of the Q (eight) raster lines has a higher selection rate (as apparent from FIG. 9, for each color, L1 → The selection rate increases in the order of L2->L3->L4->L5->L6->L7-> L8).

  That is, the controller 10 causes the ink to be ejected so that the first ratio and the second ratio described above increase in the raster lines located on the far side (the other end side) of the Q (8) raster lines. Forming a raster line.

  And by doing in this way, the following merits arise. That is, in such a case, for Q (eight) raster lines, the raster line located on the back side (the other end side) has more dots formed by the ink from the first nozzle row of the first head 320. The raster line located on the near side (one end side) tends to have more dots formed by the ink from the second nozzle row of the second head 330. As described above, when a characteristic difference occurs between the first head 320 and the second head 330, the characteristic difference appears in the image. In this case, the characteristic difference is formed by ink ejected from the composite nozzle row. In the image portion to be displayed, the characteristic of the first head 320 appears more noticeably on the back side (the other end side), and the characteristic of the second head 330 appears more noticeably on the front side (one end side). Then, on the far side (the other end side) in the width direction with respect to the image portion formed by the ink ejected from the composite nozzle array, it is ejected only from the first nozzle array of the first head 320 which is a non-composite nozzle array. The image portion formed by the ink (only the characteristic of the first head 320 appears in the image portion) is closer to the front side in the width direction than the image portion formed by the ink ejected from the composite nozzle row On the one end side, an image portion formed by ink ejected only from the second nozzle row of the second head 330 that is a non-composite nozzle row (only the characteristics of the second head 330 appear in the image portion). However, it is possible to obtain an image whose image characteristics change gently (non-abruptly) in the width direction. Therefore, the image quality of the image can be improved.

  Next, in the present embodiment, specific values for the selection ratio for the composite nozzle row for each color and for each of the composite nozzle rows L1 to L8 will be described with reference to FIG. To do. In the x-axis of FIG. 9, S2, L1 to L8, and S1 are arranged on the coordinate at equal intervals (that is, the value on the x-axis of S2 is 0, and the value on the x-axis of S1 is 9). Sometimes the values of L1 to L8 on the x-axis are 1 to 8). FIG. 9 shows a quadratic curve for each color, and every quadratic curve passes through the point (0, 0) and the point (9, 100). For the black K and cyan C quadratic curves, further points (4.5, 65), for the magenta M quadratic curve, further points (4.5, 35), and for yellow Y, Furthermore, the point (4.5, 19) is passed.

  The selectivity for each color and each of the composite nozzle rows L1 to L8 is set based on these quadratic curves. That is, the selectivity for black K and cyan C with respect to the composite nozzle row Li (i = 1 to 8) passes through the point (0, 0), the point (9, 100), and the point (4.5, 65). In the next curve, the value on the y-axis when the value on the x-axis is i. Further, the selection rate for magenta M with respect to the composite nozzle row Li is a value on the x-axis in a quadratic curve passing through the point (0, 0), the point (9, 100), and the point (4.5, 35). The value is on the y-axis when i. Similarly, the selectivity for yellow Y with respect to the composite nozzle row Li is a value on the x axis in a quadratic curve passing through the point (0, 0), the point (9, 100), and the point (4.5, 19). Is the value on the y-axis when i is i.

  Note that, as described above, in this embodiment, the black K ink is not a target color for color overlap. In the present embodiment, that the selection rate for the black K ink is the above value means that the selection rate is obtained when monochrome printing is performed.

  As described above, even when the masking process is performed using different selection rates for the respective colors, the optimum selection rates differ depending on the printing conditions. Therefore, by storing the mask data MD for each color optimum for each printing condition in the memory and selecting and printing the mask data MD suitable for the printing conditions at the time of printing, even when the printing conditions are different. High image quality can be realized.

<Determination method for determining whether each dot is formed by ink from the first nozzle row or the second nozzle row>
As described above, in the printer 1 according to the present embodiment, when viewed in dot units, dots are formed by either the ink ejected from the first nozzle row or the ink ejected from the second nozzle row. Although it is determined at random, when viewed in raster line units, the ratio of the ink ejected from the first nozzle array to the ink ejected from the second nozzle array is a predetermined value. .

  More specifically, when viewed in dot units, it is determined whether a dot is formed by cyan C ink ejected from the first nozzle row or cyan C ink ejected from the second nozzle row. Although determined randomly, when viewed in raster line units, the amount of cyan C ink ejected from the first nozzle row on the raster line is C1, and the cyan C ink ejected from the second nozzle row When the amount on the raster line of C1 is C2, the ratio of C1 to C1 + C2 is set to the predetermined value shown in FIG. 9 for each of the composite nozzle rows L1 to L8 (also this The same applies to inks of other colors as well as cyan C ink).

  Here, with reference to FIG. 6, a method for determining whether each dot is formed by ink from the first nozzle row or the second nozzle row will be described, and a policy for realizing the above will be clarified. FIG. 6 is an explanatory diagram for explaining a determination method as to whether each dot is formed by ink from the first nozzle row or the second nozzle row.

  This determination method uses a technique similar to the halftone processing (processing for converting multi-gradation data into binarized data) that is generally performed in the above-described image processing.

  First, image data corresponding to an image as shown in the left diagram of FIG. 6 is created. This image is composed of Q pixels (that is, the number of composite nozzle rows; 8 in this embodiment) × N pixels (the number of dots arranged on a raster line). ) The data is multi-gradation data (for example, 0 to 255).

  The image is composed of strip patterns having M (8) types of densities. That is, the tone values of the image (pixel) data of the N pixels belonging to the same strip pattern are all the same value, while the tone values of the image (pixel) data of each of the Q strip patterns are the same. Are different from each other.

  The gradation values of the image (pixel) data of each of the Q strip-shaped patterns correspond to the selection rates (shown in FIG. 5) for each of the composite nozzle rows L1 to L8 for cyan C. . That is, the selectivity for cyan C with respect to the composite nozzle rows L1, L2, L3, L4, L5, L6, L7, and L8 shown in FIG. 9 is a1%, a2%, a3%, a4%, a5%, respectively. Assuming that a6%, a7%, and a8%, the gradation values of the image (pixel) data of each of the Q strip-shaped patterns are 255 × (a1 / 100), 255 × (a2 / 100) from the left in FIG. ) 255 × (a3 / 100), 255 × (a4 / 100), 255 × (a5 / 100), 255 × (a6 / 100), 255 × (a7 / 100), 255 × (a8 / 100) It has become.

  Next, halftone processing by a generally known dither method, error diffusion method, or the like is performed on the multi-gradation image data to create binarized image data. The image shown in the center part of FIG. 6 represents an example of an image realized by the binarized image data (pixels painted in black are “1” in the image (pixel) data). That is, a white pixel that is not filled means that the image (pixel) data is “0”).

  Then, each of the Q × N image (pixel) data is associated with each dot (Q × N dots) belonging to Q (8) raster lines, and each dot is defined as It is determined which of the first nozzle row and the second nozzle row is formed by cyan C ink. That is, as understood by comparing the center diagram and the right diagram in FIG. 6, with respect to dots corresponding to image (pixel) data of “1”, the cyan C ink from the first nozzle row is used. The dots corresponding to the image (pixel) data of “0” are formed by cyan C ink from the second nozzle row (the numbers 1 and 2 in the dots in the right diagram are , Meaning that the ink is formed with cyan C ink from the first nozzle row and that formed with cyan C ink from the second nozzle row, respectively). In other words, when the center diagram is superimposed on the right diagram (when the center diagram is used as a mask), for the dots masked by the black-painted portion (pixel), cyan C from the first nozzle row The dots that are not masked are formed with cyan C ink from the second nozzle row.

  The above-described processing is processing for cyan C, and the same processing is performed for other colors. For example, for magenta M, the selection rates for magenta M with respect to the composite nozzle rows L1, L2, L3, L4, L5, L6, L7, and L8 shown in FIG. 9 are b1%, b2%, b3%, and b4%, respectively. , B5%, b6%, b7%, b8%, the gradation values of the image (pixel) data of each of the Q strip-shaped patterns are 255 × (b1 / 100), 255 × (b2 / 100 ) 255 × (b3 / 100), 255 × (b4 / 100), 255 × (b5 / 100), 255 × (b6 / 100), 255 × (b7 / 100), 255 × (b8 / 100) First, an image (more precisely, image data) corresponding to the image shown in the left diagram of FIG. 6 is created. Then, the masking process is performed after the halftone process is performed on the image data. The same applies to yellow Y and black K.

= Other embodiments =
The above-described embodiment is mainly described with respect to a printing system having a printer, but also includes disclosure of a fluid (ink) ejection method and the like. The above-described embodiments are for facilitating understanding of the present invention, and are not intended to limit the present invention. The present invention can be changed and improved without departing from the gist thereof, and it is needless to say that the present invention includes equivalents thereof. In particular, the embodiments described below are also included in the present invention.

  In the above-described embodiment, the ink jet printer for the print medium mainly composed of paper is exemplified as the printing apparatus. However, the present invention is not limited to this and can be applied to various industrial apparatuses. For example, a textile printing device for patterning a fabric, a display manufacturing device such as a color filter manufacturing device or an organic EL display, a DNA chip manufacturing device for manufacturing a DNA chip by applying a solution in which DNA is dissolved in a chip, a circuit board manufacturing The present invention can be applied to an apparatus or the like.

  The ink ejection method may be a piezo method in which fluid is ejected by applying a voltage to the drive element (piezo element) to expand and contract the ink chamber, or bubbles are generated in the nozzle using a heating element. And a thermal method in which fluid is ejected by the bubbles may be used.

  Further, in the above-described embodiment, the line head ink jet printer having a head unit that does not move has been described as an example of the ink jet printer. However, the present invention is not limited to this, for example, so-called serial in which the head unit moves. The present invention can also be applied to a printer.

  Further, in the above-described embodiment, the controller is configured so that the first ratio and the second ratio are increased as the raster line is located on the other end side (the back side) of the Q (eight) raster lines. The raster lines are formed by ejecting ink. However, the present invention is not limited to this. For example, as shown in FIG. Raster lines may be formed by ejecting ink so that the second ratio is the same.

  In addition, the printer according to the above-described embodiment has four colors of ink of black K, cyan C, magenta M, and yellow Y, and the three colors of cyan C, magenta M, and yellow Y are overlaid. It was decided to be done. Then, the first ratio is set to be larger than the second ratio for the three colors.

  However, the present invention is not limited to this. For example, black K may be overlaid, and the first ratio may be larger than the second ratio for four colors including black K. In addition, the printer has an ink of a color different from the four colors (for example, light cyan, light magenta, dark yellow, etc.), and the first ratio is the second ratio for multiple colors including these colors. It is good also as making it become larger than a ratio.

  In the above-described embodiment, the order in which the black K, cyan C, magenta M, and yellow Y in the first nozzle row of the first head 320 are arranged in the transport direction is the four in the second nozzle row of the second head 330. Although it is the same as the arrangement order of the colors in the transport direction, the present invention is not limited to this, and the first color (for example, cyan C) and the second color (for example, magenta M) described above are the first. The arrangement order in the nozzle row and the arrangement order in the second nozzle row need only be the same. For example, when the order of the four colors in the first nozzle row is black K → cyan C → magenta M → yellow Y, and the order of the four colors in the second nozzle row is cyan C → magenta M → yellow Y → black K. It may be.

Moreover, in the said embodiment, although the composite nozzle row was formed with the single 1st nozzle row and the single 2nd nozzle row, it is not limited to this. For example, even when a composite nozzle row is formed by a single first nozzle row (second nozzle row) and two second nozzle rows (first nozzle row) adjacent to each other in the width direction. Good. Due to head mounting errors and the like, the first nozzle row and the second nozzle row do not line up in a straight line, and in this case, two second nozzle rows (first nozzle row adjacent to each other in the width direction). ) And a single first nozzle row (second nozzle row) positioned between the two second nozzle rows in the width direction, and the above-described processing (raster line formation) In such a case (in such a case, the fluid is ejected from the nozzles of the single first nozzle row and the two second nozzle rows belonging to the composite nozzle row, and the raster line corresponding to the composite nozzle row) Is also an embodiment of the present invention.
In the above-described embodiment, as shown in FIG. 9, the selection rate for each of the composite nozzle rows L1 to L8 is set based on a quadratic curve defined by the coordinates of three points. It is not limited to. For example, it may be set based on a straight line (polygonal line) connecting the coordinates of three points. Moreover, it is good also as setting irrespective of a quadratic curve or a straight line.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 10 ... Controller, 11 ... Interface part, 12 ... CPU, 13 ... Memory, 14 ... Unit control circuit, 20 ... Conveyance unit, 21 ... Paper feed roller, 22 ... Conveyance roller, 23 ... Platen, 24 ... Exhaust Paper roller, 30 ... head unit, 31 ... head, 32 ... upstream head (leading head), 33 ... downstream head (following head), 40 ... detector group, 60 ... computer, 320 ... first head, 330 ... second head.

Claims (2)

A transport mechanism for relatively moving the print medium in a predetermined direction;
A first nozzle that ejects a first color liquid, and a second nozzle that is disposed side by side with the first nozzle in the predetermined direction and ejects a second color liquid that is different from the first color. A first head comprising a plurality of first nozzle rows including nozzles in a direction intersecting the predetermined direction;
A second nozzle array including: a third nozzle that ejects the first color liquid; and a fourth nozzle that is arranged alongside the third nozzle in the predetermined direction and ejects the second color liquid. A plurality of second heads provided in a direction intersecting the predetermined direction;
A controller for controlling injection from the first, second, third and fourth nozzles and the relative movement by the transport mechanism;
With
The first head and the second head are arranged such that a part of the plurality of first nozzle rows and a part of the plurality of second nozzle rows overlap in the predetermined direction,
In the overlapping region where the dots formed by the first nozzle row and the dots formed by the second nozzle row overlap, the controller is configured to use one first nozzle row based on a plurality of predetermined rules. The first color liquid and the second color liquid are selectively ejected from the first, second, third, and fourth nozzles included in one second nozzle row, and the printing is performed. A function to form one raster line on the medium;
The law is formed by the first nozzles included in the first nozzle row in the one first nozzle row and the one second nozzle row used to form the one raster line. Sum of the number of dots formed by the first nozzle included in the first nozzle row and the number of dots formed by the third nozzle included in the second nozzle row And the number of dots formed by the second nozzles included in the first nozzle row and the number of dots formed by the second nozzles included in the first nozzle row. a second ratio which is the ratio of the total number of dots and which is formed by the fourth nozzle in the second nozzle array of the several one, with different, multiple rasters formed in the overlapping region In-in, as the raster line located on the other end side of the raster line located at one end of a distal side of the first head in the direction crossing the predetermined direction, wherein the raster line first A selection rule that increases the ratio ,
The liquid ejecting apparatus according to claim 1, wherein the controller switches the plurality of laws in accordance with ejection conditions. A transport mechanism that relatively moves the print medium in a predetermined direction, a first nozzle that ejects a liquid of a first color, and a color different from the first color that is arranged alongside the first nozzle in the predetermined direction A first head that includes a plurality of first nozzle rows in the direction intersecting the predetermined direction, and a first nozzle that ejects the first color liquid. A plurality of second nozzle arrays including three nozzles and a fourth nozzle that is arranged alongside the third nozzle in the predetermined direction and that ejects the liquid of the second color are provided in a direction intersecting the predetermined direction. A second head; and a controller that controls ejection from the first, second, third, and fourth nozzles and the relative movement by the transport mechanism, the first head and the second head And the plurality of first nozzle rows A part of the part the plurality of second nozzle array, a said printing method using an arrangement has been that the liquid ejecting apparatus so as to overlap in a given direction,
In the overlapping region where the dots formed by the first nozzle row and the dots formed by the second nozzle row overlap, one of the first nozzle rows and one of the ones is based on a plurality of predetermined rules. The liquid of the first color and the liquid of the second color are selectively ejected from the first, second, third, and fourth nozzles included in the second nozzle row, and one is applied onto the print medium. Forming a raster line of
The law is formed by the first nozzles included in the first nozzle row in the one first nozzle row and the one second nozzle row used to form the one raster line. Sum of the number of dots formed by the first nozzle included in the first nozzle row and the number of dots formed by the third nozzle included in the second nozzle row And the number of dots formed by the second nozzles included in the first nozzle row and the number of dots formed by the second nozzles included in the first nozzle row. a second ratio which is the ratio of the total number of dots and which is formed by the fourth nozzle in the second nozzle array of the several one, with different, multiple rasters formed in the overlapping region In-in, as the raster line located on the other end side of the raster line located at one end of a distal side of the first head in the direction crossing the predetermined direction, wherein the raster line first A selection rule that increases the ratio ,
A printing method, wherein the plurality of laws are switched according to an ejection condition.

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