JP2014156046A - Liquid discharge method and liquid discharge device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress density unevenness in a conveying direction of a medium due to difference of a pass number.SOLUTION: A first correction value corresponding to a first nozzle row and a pass number that is the number of passes in which dot formation operation is performed and a second correction value corresponding to a second nozzle row and the pass number are set. When forming a dot row with the first nozzle row and the second nozzle row, the first correction value corresponding to the pass number and the second correction value corresponding to the pass number in the dot row are weighted on the basis of a duty cycle of the first nozzle row and a duty cycle of the second nozzle row in the dot row to correct an amount of liquid discharged for forming the dot row.

Description

  The present invention relates to a liquid ejection method and a liquid ejection apparatus.

  Conventionally, for example, as described in Patent Document 1, when ejecting liquid using a plurality of nozzle arrays, liquid ejection that suppresses the noticeable difference in the characteristics of the nozzle arrays using the nozzle array usage ratio Methods and liquid ejection devices have been known.

JP 2009-143135 A

  However, in the liquid ejection method and the liquid ejection apparatus described in Patent Document 1, since there is one correction value corresponding to the nozzle row, there is a problem that the density difference between the areas is noticeable when the number of passes is different from area to area. was there.

  An object of the present invention is to suppress a conspicuous density difference for each area when the number of passes differs for each area.

  [Application Example 1] A main invention for achieving the above object includes a transport operation for transporting a medium in a transport direction, a first nozzle row in which a plurality of first nozzles are arranged in the transport direction, and a plurality of second ones. Dot forming operation for forming dots on the medium by discharging liquid from the first nozzle and the second nozzle while moving the second nozzle row in which the nozzles are arranged in the transport direction in the moving direction, alternately. By repeating, the liquid ejection method for forming a plurality of dot rows composed of dots arranged in the moving direction in the transport direction, the number of passes corresponding to the first nozzle row and performing the dot forming operation A first correction value corresponding to the number of passes and a second correction value corresponding to the second nozzle row and corresponding to the number of passes are set, and the first nozzle row and the second nozzle Dot row by row When forming, the first correction value corresponding to the number of passes in the dot row and the second correction value corresponding to the number of passes are used as the usage rate of the first nozzle row and the second nozzle in the dot row. Weighting is performed based on the usage rate of the row, and the amount of the liquid ejected to form the dot row is corrected.

  Application Example 2 A main invention for achieving the above object is that a transport unit that transports a medium in the transport direction, a first nozzle row in which a plurality of nozzles are arranged in the transport direction, and a plurality of nozzles that are in the transport direction. A second nozzle array arranged in a line, a transport operation for transporting the medium in the transport direction by the transport section, and discharging the liquid from the nozzle while moving the first nozzle array and the second nozzle array in the travel direction. A liquid ejecting apparatus comprising: a dot forming operation that forms dots on the medium alternately; and a controller that forms a plurality of dot rows composed of dots arranged in the moving direction in the transport direction by alternately repeating the dot forming operation. A first correction value corresponding to the first nozzle row and corresponding to the number of passes which is the number of passes for performing the dot forming operation, and corresponding to the second nozzle row and the pass. When the dot row is formed by the first nozzle row and the second nozzle row, the first correction value corresponding to the number of passes in the dot row and The second correction value corresponding to the number of passes is weighted based on the usage rate of the first nozzle row and the usage rate of the second nozzle row in the dot row, and is ejected to form the dot row. The amount of the liquid is corrected.

  According to the application example described above, the first correction value and the second correction value corresponding to the number of passes are also provided when the printing speed is improved and the image quality is realized by changing the number of passes at the position in the medium conveyance direction. As a result, density unevenness in the transport direction can be suppressed. Therefore, it is possible to provide a liquid ejection method and a liquid ejection apparatus capable of suppressing the density difference between areas from being noticeable when the number of passes differs from area to area.

The block diagram of the whole structure of a printer. FIG. 2A is a schematic diagram of the overall configuration of the printer. FIG. 2B is a cross-sectional view of the overall configuration of the printer. Explanatory drawing which shows the arrangement | sequence of a nozzle. Explanatory drawing of a virtual nozzle row. Explanatory drawing of a normal process. 6A is an explanatory diagram of dot formation in the region A and the region B in FIG. FIG. 6B is a representation of FIG. 6A in another notation. Explanatory drawing of a dot formation method. The graph of the usage rate of the 1st nozzle row when performing the dot formation method using the nozzle row with 180 nozzles. Explanatory drawing of the acquisition process of an uneven color correction value. Explanatory drawing of an uneven color correction value. The block diagram at the time of the printing process under a user. FIG. 5 is a flowchart of processing performed by a printer driver. The flowchart of a color nonuniformity correction process. FIG. 14A is a dot generation rate table used for halftone processing. FIG. 14B is a graph showing the relationship between the gradation value and the ink amount when ink is ejected at the reference amount. FIG. 14C is a graph showing the relationship between the gradation value and the ink amount when an amount of ink different from the reference amount is ejected. Explanatory drawing of an ink amount table. Explanatory drawing of a correction amount table. FIG. 17A is an explanatory diagram of a comparative example when color unevenness cannot be completely corrected. FIG. 17B is an explanatory diagram of this embodiment when color unevenness cannot be completely corrected. The graph of the density | concentration of each raster line of the transition area vicinity when printing using an actual nozzle row | line | column. Explanatory drawing of another dot formation method.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
=== Printer configuration ===
<Inkjet printer configuration>
FIG. 1 is a block diagram of the overall configuration of the printer 1. FIG. 2A is a schematic diagram of the overall configuration of the printer 1. FIG. 2B is a cross-sectional view of the overall configuration of the printer 1. Hereinafter, a basic configuration of the printer will be described.

  The printer 1 includes a transport unit 20, a carriage unit 30, a head unit 40, a detector group 50, and a controller 60. The printer 1 that has received print data from the computer 110 that is an external device controls each unit (the conveyance unit 20, the carriage unit 30, and the head unit 40) by the controller 60. The controller 60 controls each unit based on the print data received from the computer 110 and prints an image on paper. The situation in the printer 1 is monitored by the detector group 50, and the detector group 50 outputs the detection result to the controller 60. The controller 60 controls each unit based on the detection result output from the detector group 50.

  The transport unit 20 is for transporting a medium (for example, paper S) in a predetermined direction (hereinafter referred to as a transport direction). The transport unit 20 includes a paper feed roller 21, a transport motor 22 (also referred to as a PF motor), a transport roller 23, a platen 24, and a paper discharge roller 25. The paper feed roller 21 is a roller for feeding the paper inserted into the paper insertion slot into the printer. The transport roller 23 is a roller that transports the paper S fed by the paper feed roller 21 to a printable region, and is driven by the transport motor 22. The platen 24 supports the paper S being printed. The paper discharge roller 25 is a roller for discharging the paper S to the outside of the printer, and is provided on the downstream side in the transport direction with respect to the printable area.

  The carriage unit 30 is for moving (also referred to as “scanning”) the head in a predetermined direction (hereinafter referred to as a moving direction). The carriage unit 30 includes a carriage 31 and a carriage motor 32 (also referred to as a CR motor). The carriage 31 can reciprocate in the moving direction and is driven by a carriage motor 32. Further, the carriage 31 detachably holds an ink cartridge that stores ink.

  The head unit 40 is for ejecting ink onto paper. The head unit 40 includes a head 41 having a plurality of nozzles. Since the head 41 is provided on the carriage 31, when the carriage 31 moves in the movement direction, the head 41 also moves in the movement direction. Then, by intermittently ejecting ink while the head 41 is moving in the moving direction, dot lines (raster lines) along the moving direction are formed on the paper.

  The head 41 is provided with a first nozzle group 41A and a second nozzle group 41B. The configuration of these two nozzle groups will be described later.

  The detector group 50 includes a linear encoder 51, a rotary encoder 52, a paper detection sensor 53, an optical sensor 54, and the like. The linear encoder 51 detects the position of the carriage 31 in the moving direction. The rotary encoder 52 detects the rotation amount of the transport roller 23. The paper detection sensor 53 detects the position of the leading edge of the paper being fed. The optical sensor 54 detects the presence or absence of paper by a light emitting unit and a light receiving unit attached to the carriage 31. The optical sensor 54 can detect the position of the edge of the paper while being moved by the carriage 31, and can detect the width of the paper. The optical sensor 54 also detects the leading end (the end on the downstream side in the transport direction, also referred to as the upper end) and the rear end (the end on the upstream side in the transport direction, also referred to as the lower end) depending on the situation. it can.

  The controller 60 is a control unit (control unit) for controlling the printer. The controller 60 includes an interface unit 61, a CPU 62, a memory 63, and a unit control circuit 64. The interface unit 61 transmits and receives data between the computer 110 that is an external device and the printer 1. The CPU 62 is an arithmetic processing unit for controlling the entire printer. The memory 63 is for securing an area for storing a program of the CPU 62, a work area, and the like, and includes storage elements such as a RAM and an EEPROM. The CPU 62 controls each unit via the unit control circuit 64 in accordance with a program stored in the memory 63.

  Further, the controller 60 is provided with a drive signal generation circuit 65. The drive signal generation circuit 65 includes a first drive signal generation unit 65A and a second drive signal generation unit 65B. The first drive signal generator 65A generates a first drive signal for driving the piezo elements of the first nozzle group 41A. The second drive signal generator 65B generates a second drive signal for driving the piezo elements of the second nozzle group 41B. Each drive signal generator generates a drive signal for odd pixels when dots are formed in odd pixels (described later), and generates a drive signal for even pixels when dots are formed in even pixels (described later). Generate. The drive signal generators are independent of each other. For example, when the first drive signal generator 65A generates a drive signal for odd pixels, the second drive signal generator 65B Can be generated, and a drive signal for even-numbered pixels can be generated.

  When performing printing, the controller 60 alternately repeats a dot forming operation for ejecting ink from the head 41 moving in the movement direction and a conveyance operation for conveying paper in the conveyance direction, and an image composed of innumerable dots. On the paper. The dot forming operation may be referred to as “pass”, and the nth pass may be referred to as “pass n”.

=== Configuration of Head 41 ===
<About configuration>
FIG. 3 is an explanatory diagram showing the arrangement of nozzles. Two nozzle groups (a first nozzle group 41A and a second nozzle group 41B) are provided on the lower surface of the head 41. Each nozzle group is provided with eight nozzle rows. The eight nozzle rows are dark cyan (C), dark magenta (M), yellow (Y), dark black (K), light cyan (LC), light magenta (LM), light black (LK), and pole, respectively. Light black (LLK) ink is ejected.

  Each nozzle row is provided with 180 nozzles arranged in the transport direction at a nozzle pitch of 180 dpi. In addition, the nozzles in each nozzle row are assigned a lower number toward the downstream side in the transport direction. Each nozzle is provided with a piezo element (not shown) as a drive element for ejecting ink droplets from each nozzle.

  The first nozzle group 41A is provided downstream of the second nozzle group 41B in the transport direction. Also, the first nozzle group 41A and the second nozzle group 41B are provided so that the positions of the four nozzles in the transport direction overlap. For example, the position in the transport direction of the nozzle # 177A of the first nozzle group 41A is the same as the position in the transport direction of the nozzle # 1B of the second nozzle group 41B. Thus, in a certain dot forming operation, when the nozzle # 177A of the first nozzle group 41A can form a dot for a certain pixel, the dot can also be formed for the pixel by the nozzle # 1B of the second nozzle group 41B. It is.

=== Method of forming dots ===
<About the notation method of the nozzle row>
First, before describing the dot formation method, the nozzle row and nozzle notation method will be described.

FIG. 4 is an explanatory diagram of the virtual nozzle row 42X.
On the left side of the drawing, the dark black nozzle row of the first nozzle group 41A and the dark black nozzle row of the second nozzle group 41B are shown. In the following description, the dark black nozzle row of the first nozzle group 41A is referred to as “first nozzle row 42A”, and the dark black nozzle row of the second nozzle group 41B is referred to as “second nozzle row 42B”. For simplification of explanation, the number of nozzles in each nozzle row is 15.
Four nozzles (nozzle # 12A to nozzle # 15A) on the upstream side in the transport direction of the first nozzle row 42A, and four nozzles (nozzle # 1B to nozzle # 4B) on the downstream side in the transport direction of the second nozzle row 42B. Are overlapped in the transport direction. In the following description, these four nozzles in each nozzle row are referred to as “overlapping nozzles”.

Each nozzle of the first nozzle row 42A is indicated by a circle, and each nozzle of the second nozzle row 42B is indicated by a triangle. In addition, a cross mark is shown for nozzles that do not eject ink (that is, nozzles that do not form dots).
Here, of the overlapping nozzles in the first nozzle row 42A, ink is ejected from nozzle # 12A and nozzle # 13A, and ink is not ejected from nozzle # 14A and nozzle # 15A. Here, among the overlapping nozzles in the second nozzle row 42B, the nozzle # 1B and the nozzle # 2B do not eject ink, and the nozzle # 3B and the nozzle # 4B eject ink.
In such a case, the two nozzle rows can be described as one virtual nozzle row 42X as described in the center portion in the figure. In the following description, the state of dot formation will be described using one virtual nozzle row 42X instead of drawing two nozzle rows separately.

  As shown on the right side of the figure, the virtual nozzle row 42X can form dots on even pixels even when the round nozzles form dots on odd pixels. Is possible. Of course, when the round nozzles form dots on odd pixels, the triangular nozzles can also form dots on odd pixels.

<Reference: Normal processing>
FIG. 5 is an explanatory diagram of normal processing. The normal process is a process (dot forming operation and transport operation) performed when printing the central portion of the paper. The controller 60 implements normal processing described below by controlling each unit.

  In the drawing, the relative positional relationship of the virtual nozzle row 42X with respect to the paper during each dot forming operation is shown. In the drawing, the virtual nozzle row 42X is depicted as moving with respect to the paper, but actually the paper moves in the transport direction. As shown in the drawing, in normal processing, paper is transported with a transport amount 9D for nine dots in a transport operation performed between passes.

  In area A (area on the paper) in the figure, dots are formed by pass 1 to pass 6. In a region B in the figure, dots are formed by pass 2 to pass 7.

  In the odd-numbered pass, each nozzle is positioned at an even-numbered (or odd-numbered) raster line. After the odd-numbered pass, the even-numbered pass is performed after the paper is transported by the transport amount 9D for nine dots. Therefore, in the even-numbered pass, each nozzle is even-numbered (or odd-numbered). It becomes the position of the raster line. In this way, the positions of the nozzles are alternately odd-numbered or even-numbered raster line positions for each pass.

FIG. 6A is an explanatory diagram of dot formation in the area A and the area B of FIG.
On the left side in the figure, the relative positions of the nozzles in each pass are shown. The black-filled nozzle forms dots at a rate of one pixel per two pixels in the pass. For example, nozzle # 8B in pass 2 forms dots at a rate of one pixel per two pixels. The nozzles hatched with diagonal lines form dots at a rate of one pixel per four pixels. For example, nozzle # 10A in pass 4 forms dots at a rate of one pixel per four pixels.
A nozzle hatched with diagonal lines forms only half of the dots compared to a black-filled nozzle. The nozzles hatched by the oblique lines are referred to as “POL nozzles”.

Four nozzles (nozzles # 10A to 13A) on the upstream side in the transport direction of the first nozzle row 42A in a pass, and downstream in the transport direction of the first nozzle row 42A after two transport operations have been performed from that pass The four nozzles (nozzles # 1A to 4A) on the side overlap in the transport direction. Such a nozzle becomes a POL nozzle. For example, nozzle # 10A to nozzle # 13A in pass 4 and nozzle # 1A to nozzle # 4A in pass 6 are POL nozzles because the positions in the transport direction overlap.
Similarly, four nozzles (nozzle # 12B to nozzle # 15B) on the upstream side in the transport direction of the second nozzle array 42B of a certain pass, and the second nozzle array after two transport operations have been performed from that pass The four nozzles (nozzle # 3B to nozzle # 6B) on the downstream side in the transport direction of 42B have overlapping positions in the transport direction. Such a nozzle becomes a POL nozzle. For example, nozzle # 12B to nozzle # 15B in pass 2 and nozzle # 3B to nozzle # 6B in pass 4 are POL nozzles because the positions in the transport direction overlap.

  On the right side of the figure, nozzles for forming dots in each pixel are shown. For example, the first raster line (raster line with raster number 1) is composed of dots formed on odd pixels by nozzle # 8B and dots formed on even pixels by nozzle # 10A and nozzle # 1A. The Here, for simplification of explanation, each raster line is composed of only eight dots.

  In the upper left in the figure, the positions of dots formed by the nozzle rows are shown. For example, in pass 1, the nozzles in the first nozzle row 42A (nozzles # 1A to # 13A) form dots at odd pixels, and the nozzles in the second nozzle row 42B (nozzles # 3B to nozzle # 15B) are even pixels. To form dots.

  Each raster line is composed of dots formed by two or three nozzles. In other words, two or three nozzles are associated with each raster line. For example, the first raster line is associated with nozzle # 8B for pass 2, nozzle # 10A for pass 4, and nozzle # 1A for pass 6. Each raster line is composed of dots formed by at least one nozzle of the first nozzle row 42A and dots formed by at least one nozzle of the second nozzle row 42B. In other words, at least one nozzle of the first nozzle row 42A and at least one nozzle of the second nozzle row 42B are associated with each raster line.

  When only one nozzle is associated with an odd pixel or even pixel of a raster line, the nozzle forms dots at a rate of one pixel per two pixels. For example, only one nozzle # 8B is associated with the odd pixels of the first raster line (other nozzles are not associated). Therefore, nozzle # 8B forms dots at a rate of 1 pixel per 2 pixels.

  On the other hand, when two nozzles are associated with an odd pixel or an even pixel of a raster line, each of the two nozzles forms a dot at a ratio of one pixel to four pixels (a POL nozzle). Become). For example, nozzle # 10A and nozzle # 1A are associated with the even pixels of the first raster line. For this reason, the nozzle # 10A and the nozzle # 1A each form dots at a rate of one pixel per four pixels (becomes a POL nozzle).

  In the normal processing, the position (position in the movement direction) where the first nozzle row 42A forms dots differs from the position where the second nozzle row 42B forms dots in a certain pass. Specifically, when the first nozzle row 42A forms dots at odd pixels, the second nozzle row 42B forms dots at even pixels. Conversely, when the first nozzle row 42A forms dots at even pixels, the second nozzle row 42B forms dots at odd pixels. Since the first drive signal generator 65A and the second drive signal generator 65B described above can generate drive signals independently of each other, such dot formation becomes possible.

  Further, in the normal process, when a certain pass is compared with the next pass, the positions where the nozzle rows form dots are different. For example, when the first nozzle row 42A forms dots in odd pixels and the second nozzle row 42B forms dots in even pixels in a certain pass, the first nozzle row 42A forms dots in even pixels in the next pass. The second nozzle row 42B forms dots at odd pixels.

  By forming dots in this way, dots are formed in a staggered pattern by one nozzle array, and dots are formed in a staggered pattern by the other nozzle array so as to fill the space between the dots. Is formed. If attention is paid to the right side of FIG. 6A, the round dots formed by the first nozzle row 42A have a staggered pattern, and the triangular dots formed by the second nozzle row 42B also have a staggered pattern. It has become. In terms of the dot formation order, after the dots are formed in a staggered pattern by the second nozzle row 42B, the dots are formed by the first nozzle row 42A so as to fill the space therebetween.

  When a raster line is formed by normal processing, half dots are formed by the first nozzle row 42A and the remaining half dots are formed by the second nozzle row 42B in the raster line. In other words, the usage rate of each nozzle row when forming these raster lines is 50% for the first nozzle row 42A and 50% for the second nozzle row 42B.

  Since the dots are formed in the area A by the passes 1 to 6 and the dots are formed in the area B by the passes 2 to 7, the path is shifted by one time between the areas A and B. Since the pass is shifted once, the nozzles associated with each raster line are common in each region, but the position of the dots formed by each nozzle (position in the movement direction) differs depending on whether it is an odd pixel or an even pixel. ing. For example, for the first raster line, nozzle # 8B in pass 2 forms dots in odd pixels, but for nozzle 10 in the tenth raster line, nozzle # 8B in pass 3 forms dots in even pixels.

  Although not shown here, dots are formed in the 19th to 27th raster lines positioned upstream of the region B in the transport direction in substantially the same manner as the region A by pass 3 to pass 8. For example, the 19th raster line is associated with nozzle # 8B, nozzle # 10A, and nozzle # 1A, and nozzle # 8B forms dots at odd-numbered pixels on the 19th raster line. In the 28th to 36th raster lines located on the upstream side in the transport direction from the 19th to 27th raster lines, dots are formed in substantially the same manner as in the region B by pass 4 to pass 9. As described above, when the normal processing is continuously performed, the dot formation similar to the region A and the region B is repeatedly performed.

FIG. 6B expresses FIG. 6A by another notation method.
In the upper left notation in the figure, odd numbers are indicated by “1” and even numbers are indicated by “2”. For example, in pass 1, the nozzles in the first nozzle row 42A (nozzles # 1A to # 13A) form dots in odd pixels, and the nozzles in the second nozzle row 42B (nozzles # 3B to nozzle # 15B) are even pixels. Are shown to form dots.

  Also in the notation on the right side in the figure, odd-numbered pixels are indicated by “1” and even-numbered pixels are indicated by “2”. When there is one nozzle associated with the odd pixel, a symbol representing the nozzle is shown under “1” indicating the odd pixel. For example, it is indicated that the nozzle # 8B is associated with the odd pixel of the first raster line. When there is one nozzle associated with an even pixel, a symbol indicating that nozzle is shown under “2” indicating an even pixel. For example, it is shown that nozzle # 7B is associated with the even pixels of the eighth raster line. In other words, if a symbol representing a nozzle is shown under “1” indicating an odd pixel, the nozzle forms dots at a rate of one pixel per two pixels. Similarly, if a symbol representing a nozzle is shown under “2” indicating an even-numbered pixel, the nozzle forms dots at a rate of one pixel per two pixels.

  In addition, when there are two nozzles associated with an odd pixel or an even pixel, the nozzle becomes a POL nozzle. Therefore, the symbol of the two nozzles is below the word “POL” in the figure. It is shown. For example, nozzle # 10A and nozzle # 1A are associated with the even pixels of the first raster line, and these nozzles are POL nozzles. Therefore, below the word “POL” on the right side of the figure, Symbols indicating nozzle # 10A and nozzle # 1A are described. In other words, if a symbol representing two nozzles is shown under the word “POL”, each nozzle forms dots at a rate of one pixel per four pixels.

  When a symbol representing two nozzles is shown under the word “POL”, a symbol representing a nozzle is below “1” indicating an odd pixel or “2” indicating an even pixel. Not shown. If there is no symbol representing a nozzle under “1” indicating an odd pixel, the POL nozzle forms a dot on the odd pixel. For example, in the ninth raster line, the nozzles # 12B and # 3B, which are POL nozzles, form dots at odd-numbered pixels. If there is no symbol representing a nozzle under “2” indicating an even pixel, the POL nozzle forms a dot at the even pixel. For example, in the first raster line, the nozzle # 10A and the nozzle # 1A, which are POL nozzles, form dots in even pixels.

  From the description so far, it can be understood from the description on the right side of FIG. 6B that dots are formed as shown on the right side of FIG. 6A. Therefore, in the following description, the state of dot formation will be described using the notation method of FIG. 6B. Further, for convenience of drawing space, the numbers in the circles and triangles on the right side of FIG. 6B are also omitted.

<Dot formation method>
Next, a dot forming method will be described.

FIG. 7 is an explanatory diagram of a dot forming method. The overlapping nozzles in the virtual nozzle row shown on the right side in the figure are indicated by bold lines.
In the upper end processing, overlapping nozzles are indicated by square marks in the virtual nozzle rows of pass 1 to pass 4 in the figure, and when dots are formed on pixels associated with the nozzles of the square marks, the first ratio is half. The nozzles of the nozzle row 42A are used, and the nozzles of the second nozzle row 42B are used at the rate of the remaining half.

  For example, in the 30th raster line, a square mark nozzle (pass 6) is associated with an even pixel. Therefore, the nozzle # 12A of the first nozzle row 42A forms dots for half of the even pixels, and the nozzle # 1B of the second nozzle row 42B forms dots for the remaining half of the even pixels. Form. As a result, in the 30th raster line, the nozzles of the first nozzle row 42A form dots at a rate of 3 pixels per 4 pixels, and the nozzles of the second nozzle row 42B form dots at a rate of 1 pixel per 4 pixels. To do. That is, the nozzle usage rate is 75% for the first nozzle row 42A and 25% for the second nozzle row 42B.

  For example, in the 24th raster line, square nozzles (pass 4) and round nozzles (pass 8) are associated as POL nozzles for odd pixels. For this reason, the square-shaped nozzles are associated with half of the odd-numbered pixels. That is, the nozzles of square marks are associated with the ratio of one pixel to four pixels. As a result, in the 24th raster line, the nozzles of the first nozzle row 42A form dots at a rate of 7 pixels in 8 pixels, and the nozzles of the second nozzle row 42B form dots at a rate of 1 pixel in 8 pixels. To do. That is, the nozzle usage rate is 87.5% for the first nozzle row 42A and 12.5% for the second nozzle row 42B.

  In this dot forming method, the transition area is composed of 23 raster lines (24th to 46th raster lines).

<Actual usage rate>
FIG. 8 is a graph of the usage rate of the first nozzle row 42A when this dot forming method is performed using a nozzle row having 180 nozzles. The horizontal axis of the graph is the distance from the front end (upper end) of the paper. The vertical axis of the graph represents the usage rate of the first nozzle row 42A. As shown in FIG. 8, the usage rate of the first nozzle row 42A is 100% in the upper end region, and the usage rate of the first nozzle row 42A is 50% in the normal region.

  Note that the printer driver is provided with the usage rate data shown in the drawing as a usage rate table in advance. Also, since the usage rate differs even if the raster number is the same if the dot formation method is different, the printer driver has a usage rate table for each dot formation method. This usage rate table is used in correcting color unevenness.

=== Uneven color correction ===
The amount of ink ejected from each nozzle row is not uniform due to the effects of nozzle row manufacturing errors and the like. For this reason, the nozzle row that ejects a larger amount of ink than the reference amount prints darkly, and the nozzle row that ejects a smaller amount of ink than the reference amount prints lightly, resulting in uneven color in the printed image. May occur.

  Therefore, color unevenness of a printed image is suppressed by the following color unevenness correction processing. Hereinafter, the procedure of color unevenness correction processing will be described.

<Color unevenness correction value acquisition processing>
FIG. 9 is an explanatory diagram of an uneven color correction value acquisition process performed in a printer manufacturing factory. The printer manufacturing factory has a computer and a colorimeter for obtaining correction values. The colorimeter is connected to a computer in advance. When a printer is manufactured at the factory, the printer is connected to a computer for obtaining correction values. Each module drawn in the computer in the figure is realized by software and hardware.

  First, the printing module of the computer generates print data based on the test pattern printing data and transmits it to the printer. This printing module is equivalent to a so-called printer driver. Data for test pattern printing is stored in advance in a computer memory.

Next, the printer that has received the print data prints a test pattern, and the measurer measures the printed test pattern using a colorimeter. A large number of patch patterns are formed in the test pattern, and the control module acquires the color measurement result of each patch pattern from the colorimeter.
Next, the correction value calculation module compares the color measurement result with reference color data stored in advance, and calculates a color unevenness correction value.
Finally, the writing module writes the color unevenness correction value in the memory of the printer. The printer is shipped from the factory with color unevenness correction values stored in memory.

  FIG. 10 is an explanatory diagram of the uneven color correction value. Color unevenness correction values for each number of passes are prepared for each of the first nozzle row group and the second nozzle row group. In addition, three types of color unevenness correction values (small dots, medium dots, large dots) are prepared for each nozzle row of each nozzle row group (for each ink color).

  When the correction value is “100”, it means that the same ink amount as the reference amount is ejected from the nozzle. For example, the cyan nozzle row of the second nozzle row group ejects the same ink amount as the reference amount when ejecting small dots.

  When the correction value is 100 or more, it means that a larger amount of ink than the reference amount is ejected from the nozzle. For example, a 4-pass cyan nozzle row in the first nozzle row group ejects an ink amount larger than the reference amount when ejecting small dots. For this reason, when this nozzle row forms dots, a dark image is obtained.

  When the correction value is 100 or less, it means that an ink amount smaller than the reference amount is ejected from the nozzle. For example, a 4-pass cyan nozzle row in the first nozzle row group ejects an ink amount smaller than the reference amount when ejecting large dots. For this reason, when this nozzle row forms dots, a light image is obtained.

  In the above description, the color unevenness correction value is obtained by measuring the test pattern, but the present invention is not limited to this. For example, the color unevenness correction value similar to that in FIG. 10 may be acquired by directly measuring the ink amount of the ejected ink droplets.

<Processing during printing>
FIG. 11 is a block diagram at the time of print processing under the user. FIG. 12 is a flowchart of processing performed by the printer driver. A printer driver as a program implements each module in FIG. 11 and each process in FIG. 12 in cooperation with computer hardware (CPU, memory, etc.).

  First, the printer driver obtains an uneven color correction value (see FIG. 10) from the printer memory (S101). The printer driver stores the obtained color unevenness correction value in the memory on the computer side.

  Next, the printer driver performs resolution conversion processing (S102). The resolution conversion process is a process of converting image data (text data, image data, etc.) output from an application into image data having a resolution (print resolution) to be printed on paper. For example, when the print resolution is specified as 1440 × 720 dpi, the image data in the vector format received from the application is converted into image data having a resolution of 1440 × 720 dpi. Each pixel data of the image data after the resolution conversion process is data indicating a gradation value of 256 gradations in the RGB color space.

  Note that the image indicated by the image data after resolution conversion is composed of pixels arranged in a matrix. Each pixel has a gradation value of 256 gradations in the RGB color space. The pixel data after the resolution conversion indicates the gradation value of the corresponding pixel. Pixel data corresponding to one column of pixels arranged in the horizontal direction among pixels arranged in a matrix may be referred to as “raster data” in the following description. The direction in which the corresponding pixels of the raster data are arranged corresponds to the moving direction of the nozzle row when printing an image.

  Next, the printer driver performs color conversion processing (S103). The color conversion process is a process of converting RGB color space data into color space data corresponding to the ink color of the printer. The pixel data after the color conversion processing is data indicating 256 gradation levels represented by an 8-dimensional color space of C, M, Y, K, LC, LM, LK, and LLK.

  Next, the printer driver extracts raster data (S104). More specifically, pixel data corresponding to one column of pixels arranged in the horizontal direction is extracted from image data of a certain color (for example, cyan).

  Next, the printer driver performs color unevenness correction processing on the extracted raster data (S105). This uneven color correction process will be described later.

  Next, the printer driver performs halftone processing (S106). The halftone process is a process of converting 256-gradation pixel data into 4-gradation pixel data, which is the number of gradations that can be formed by the printer. The four-tone pixel data after the halftone process is data indicating the size of the dot formed in the corresponding pixel. Specifically, the data indicates any one of large dots, medium dots, small dots, and no dots.

  Note that the printer driver uses a dot generation rate table for halftone processing. This dot generation rate table is a data table indicating the probability of dot generation (dot generation rate) for each gradation value of 256 gradations. For example, there is a case where a small dot generation rate of 40% and a medium dot / large dot generation rate of 0% are associated with the gradation value 20 as shown in a dot generation rate table described later (FIG. 14A). If the gradation value of 256 gradations of the pixel data is 20, as a result of the halftone process, the pixel data is converted into pixel data (4 gradations) indicating a small dot with a probability of 40%, and 60% It is converted into pixel data (4 gradations) indicating no dot with probability.

  Next, the printer driver determines whether or not halftone processing of all pixel data has been completed (S107). For example, if there is another raster data of cyan, NO is determined, and NO is also determined if there is raster data of another color.

  Next, the printer driver performs rasterization processing (S108). The rasterization process is a process of extracting pixel data of pixels that are the dot formation targets of each pass from the image data and rearranging the pixel data for each pass. For example, in the case of the dot formation method of FIG. 7, pixel data of odd-numbered pixels of the first, third, fifth, and seventh raster lines are extracted as the pixel data of the pixel that is the target of dot formation in pass 1. become.

  Finally, the printer driver adds command data to the rasterized pixel data to generate print data, and transmits the print data to the printer (S109). The printer controls each unit according to the command data in the print data, and ejects ink from each nozzle according to the pixel data in the print data, thereby forming dots on the pixels on the paper and printing an image.

<Color unevenness correction processing>
FIG. 13 is a flowchart of color unevenness correction processing.
First, the printer driver acquires a color unevenness correction value of the corresponding color (S105-1). For example, when color unevenness correction processing is performed on raster data of cyan image data, a cyan color unevenness correction value is acquired. At this time, the printer driver acquires both the color unevenness correction value corresponding to the first nozzle row 42A and the color unevenness correction value corresponding to the second nozzle row 42B.
Next, a correction amount table corresponding to the number of passes in the region is created for each nozzle row (S105-2).

Here, before describing the correction amount table, the amount of ink ejected will be described with reference to FIGS. 14A to 14C.
FIG. 14A is a dot generation rate table used for halftone processing. The horizontal axis in the figure indicates 256 gradation values. The vertical axis represents the dot generation rate. As shown in the figure, for example, the gradation value 20 is associated with a small dot generation rate of 40% and a medium dot / large dot generation rate of 0%.

  FIG. 14B is a graph of the relationship between the gradation value and the ink amount when ink is ejected at the reference amount. The horizontal axis in the figure indicates 256 gradation values. The vertical axis indicates the ink amount when the ink amount ejected when the gradation value is 256 is 1. As shown in the figure, when ink is ejected at a reference amount, an ink amount proportional to the gradation value is ejected.

  FIG. 14C is a graph of the relationship between the gradation value and the ink amount when an amount of ink different from the reference amount is ejected. The thin line in the graph is the same as the graph of FIG. 14B, and the thick line is a graph of the relationship between the gradation value and the ink amount when an amount of ink different from the reference amount is ejected. Here, a graph is shown when ink is ejected from a nozzle row in which the color unevenness correction value for small dots is 110, the color unevenness correction value for medium dots is 108, and the color unevenness correction value for large dots is 96. As shown in the figure, at a low gradation value in which small dots and medium dots are mainly ejected, the ejected ink amount is larger than the reference amount. On the other hand, at high gradation values where large dots are mainly ejected, the amount of ink ejected is smaller than the reference amount.

  The relationship between the gradation value and the ink amount as shown in FIG. 14C can be calculated based on the dot generation rate table and the color unevenness correction value. Therefore, the printer driver first performs the gradation value and the ink amount as shown in FIG. 14C based on the dot generation rate table and the color unevenness correction value acquired in S105-1 during the process of S105-2. An ink amount table showing the relationship is calculated.

  FIG. 15 is an explanatory diagram of the meaning indicated by the ink amount table. The dotted line graph in the drawing is a graph of the ink amount in FIG. 14B, that is, a graph of the ink amount table when ink is ejected at the reference amount. A solid line graph in the figure is a graph of an ink amount table when an amount of ink different from the reference amount is ejected. Of the solid line graph, the thin line graph is a graph of the ink amount table of the first nozzle array 42A, and the thick line graph is a graph of the ink amount table of the second nozzle array 42B.

  When the gradation value indicated by the pixel data is 120, if ink is to be ejected without correcting the gradation value, a larger amount of ink than the reference amount is ejected from the first nozzle array 42A, and the second nozzle array 42B. Therefore, an ink amount smaller than the reference amount is ejected. On the other hand, if the gradation value corresponding to the reference amount of the gradation value 120 is 100 in the ink amount table of the first nozzle array 42A, if ink is to be ejected from the first nozzle array 42A according to the gradation value 100, It is considered that ink can be ejected from the first nozzle row 42A with the reference amount of the gradation value 120. Further, assuming that the gradation value corresponding to the reference amount of the gradation value 120 in the ink amount table of the second nozzle array 42B is 150, if ink is to be ejected from the second nozzle array 42B according to the gradation value 150, It is considered that ink can be ejected from the second nozzle row 42B with a reference amount of gradation value 120.

  Therefore, the printer driver associates the gradation value 100 with the gradation value 120 in the correction amount table of the first nozzle row 42A. In other words, a correction amount table is created so that when the input gradation value (input gradation value) is 120, the gradation value 100 is output. The printer driver creates a correction amount table for the first nozzle row 42A by associating output gradation values based on the ink amount table with other input gradation values.

  The printer driver creates such a correction amount table for each nozzle row and each pass number. In the present embodiment, a correction amount table for the first nozzle row 42A and a correction amount table for the second nozzle row 42B are created. As is clear from the above description, the correction amount table of the first nozzle row 42A is created based on the color unevenness correction value of the first nozzle row 42A and the dot generation rate table, and the second nozzle row 42B. The correction amount table is created based on the color unevenness correction value of the second nozzle row 42B and the dot generation rate table.

  FIG. 16 is an explanatory diagram of a correction amount table. In this way, a correction amount table in which the input gradation value and the output gradation value are associated with each other is created for each nozzle row and each pass number.

  Note that the created correction amount table is stored in the memory when performing color unevenness correction processing for raster data of a certain color, and the correction amount table is stored again during color unevenness correction processing for another raster data of the same color. May be used. That is, when the correction amount table has already been created, the printer driver may omit the process of creating the correction amount table (S105-2).

  After creating the correction amount table, the printer driver obtains the usage rate data of the raster number corresponding to the raster data extracted in S104 based on the usage rate table (see FIG. 8) (S105-3). If the raster line corresponding to the raster data belongs to the upper end region, the usage rate of the first nozzle row 42A becomes 1 (100%) and the usage rate of the second nozzle row 42B becomes 0 ( 0%). Further, if the raster line corresponding to the raster data belongs to the normal region, the usage rate of the first nozzle row 42A is 0.5 (50%), and the usage rate of the second nozzle row 42B is also 0. 5 (50%). The relationship between the raster number and the usage rate is uniquely determined once the dot formation method is determined.

  According to the present embodiment, there is a transition region between the upper end region and the normal region, and a raster line in which the usage rate of the first nozzle row 42A is between 0.5 and 1 is present in this transition region. Exists. For example, a raster line in which the usage rate of the first nozzle row 42A is 0.75 (75%) exists in the transition region.

  Next, the printer driver corrects the gradation value of each pixel data of the raster data based on the correction amount table and the usage rate data (S105-4). For example, in the case of 4 passes, when the gradation value of the pixel data is 120 and the usage rate of the first nozzle row 42A is 1, the corrected gradation value is 100. When the gradation value of the pixel data is 120 and the usage rate of the first nozzle row 42A is 0.5, the corrected gradation value is 125 (= 100 × 0.5 + 150 × 0.5). Become. When the gradation value of the pixel data is 120 and the usage rate of the first nozzle row 42A is 0.75, the corrected gradation value is 112.5 (= 100 × 0.75 + 150 × 0.25). )become. As described above, the printer driver uses the gradation value (for example, 120) of the pixel data as the input gradation value, and outputs each gradation value (for example, 100 and 150) based on the correction amount table for each number of passes in each nozzle row. ) And adding the output gradation values weighted with the respective usage rates (for example, 0.75 and 0.25), the corrected gradation value (for example, 112.5) is calculated.

  When the printer driver corrects the gradation values of all the pixel data of the raster data, the color unevenness correction process is terminated.

<Effect of uneven color correction processing>
Here, as shown in FIG. 15, it is assumed that an ink amount larger than the reference amount is ejected from the first nozzle row 42A, and an ink amount smaller than the reference amount is ejected from the second nozzle row 42B. An example of the effect of the correction process will be described.

  In the upper end region, as already described, a raster line is formed only by the first nozzle row 42A. For this reason, if color unevenness correction processing is not performed, the upper end region has an image quality that directly reflects the characteristics of the first nozzle row 42A, and thus becomes a dark image. On the other hand, when color unevenness correction processing is performed (S105), the gradation value (256 gradations) of the pixel data belonging to the upper end region is corrected to a low gradation value. When the pixel data corrected to a low gradation value (256 gradations) is subjected to halftone processing (S106), the expected value of the amount of ink ejected to the pixel corresponding to the pixel data decreases. However, since the first nozzle row 42A ejects a larger amount of ink than the reference amount, if dots are formed according to pixel data (4 gradations) obtained by performing halftone processing on the corrected pixel data (256 gradations), An image can be printed in the upper end area with the density of the gradation value indicated by the original pixel data (256 gradations).

  In the normal region, as already described, the first nozzle row 42A is 50%, and the second nozzle row 42B is also 50%. When the uneven color correction process is performed, if the gradation value of the pixel data (256 gradations) is 120, the corrected gradation value is 125 (= 100 × 0.5 + 150 × 0.5). become. That is, although the amount of ink larger than the reference amount is ejected from the first nozzle row 42A, as a result of the color unevenness correction process, the amount of ink ejected to the pixels in which the first nozzle row 42A forms dots. Expected value becomes high. For example, in the 48th raster line in FIG. 11 (the raster line in the normal region), the first nozzle row 42A forms dots on even pixels, and the even pixels on this raster line have a color correction that is not corrected. A larger amount of ink will be ejected. On the other hand, although the amount of ink smaller than the reference amount is ejected from the second nozzle row 42B, as a result of the color unevenness correction process, the amount of ink ejected to the pixels in which the second nozzle row 42B forms dots is determined. Expected value is lower. For example, in the 48th raster line in FIG. 7 (the raster line in the normal area), the second nozzle row 42B forms dots in odd pixels, and the odd pixels in this raster line have a color correction that is not corrected. Further, a smaller amount of ink is ejected.

  As described above, when each pixel in the normal region is viewed microscopically, the amount of ejected ink is biased as a result of the uneven color correction process. However, when the user views the printed image, the user cannot visually recognize the individual dots but can only visually recognize the image density (macroscopic density) according to the dot density. For this reason, whether or not the macroscopic density is corrected is more important than whether or not the amount of ink ejected to each pixel is corrected.

  If the entire raster line composed of a plurality of pixels is viewed macroscopically, the amount of ink ejected as a result of color unevenness correction processing corresponds to the gradation value indicated by the original pixel data (256 gradations). The ink amount is reached. In other words, as a result of the uneven color correction process, even if there is a bias in the amount of ink ejected to individual pixels, the amount of ink ejected to the entire raster line is corrected, so the level indicated by the original pixel data is An image can be printed with the density of the tone value.

  In the pixel data belonging to the transition area, the gradation value is corrected in consideration of the usage rate of the nozzle row, as in the case of the normal area. As a result, even in the transition region, as a result of the uneven color correction process, the amount of ink ejected becomes an ink amount corresponding to the gradation value indicated by the original pixel data (256 gradations).

  By the way, when the above color unevenness correction process is performed, the color unevenness is improved, but the color unevenness cannot be completely corrected (theoretically, even though the color unevenness can be corrected, an actual apparatus was used). Experiments cannot completely correct color irregularities). That is, the density of the gradation value indicated by the pixel data before correction (256 gradations) and the density of the actually printed image do not completely match.

FIG. 17A is an explanatory diagram of a comparative example when color unevenness cannot be completely corrected. FIG. 17B is an explanatory diagram of this embodiment when color unevenness cannot be completely corrected. The horizontal axis in the figure is the raster number, and the vertical axis in the figure is the density. In the comparative example, a dot formation method different from that of the present embodiment is performed, and there is no transition area. Also, the density correction value corresponding to the number of passes is not applied.
In both FIG. 17A and FIG. 17B, as a result of performing the uneven color correction process, the difference between the density of the upper end area and the density of the normal area is small. For this reason, the uneven color correction process makes the difference between the image quality of the upper end region and the image quality of the normal region less noticeable.

However, since there is no transition area in the comparative example, the density difference is improved, but the density changes rapidly at the joint between the upper end area and the normal area. If the density changes abruptly in this way, the difference between the image quality of the upper end area and the image quality of the normal area is likely to be visually recognized.
Further, in the comparative example, since the density correction value corresponding to the number of passes is not applied, the density difference between the numbers of passes in the upper end region is likely to be visually recognized.

On the other hand, in the present embodiment, a transition region is formed, and the transition region has a raster line having an intermediate property between the upper end region and the normal region (for example, a raster line in which the usage rate of the first nozzle row 42A is 75%). Exists. Furthermore, the usage rate in the transition region can be gradually changed by making the usage of the overlapping nozzles in the upper end processing and the transition processing different from the usage of the overlapping nozzles in the normal processing. As a result, among the raster lines in the transition area, the usage rate of the first nozzle row 42A in the raster line close to the upper end region becomes a value closer to 100%, and the usage rate of the first nozzle row 42A in the raster line close to the normal region. The value is closer to 50%.
In the present embodiment, since the density correction value corresponding to the number of passes is applied, the density difference between the numbers of passes is reduced.
When the color unevenness correction process described above is performed at the time of printing to form such an upper end area and a transition area, a density distribution as shown in FIG. 17B is obtained.

  As shown in FIG. 17B, the density in the transition area is an intermediate density between the density in the upper end area and the density in the normal area. In the transition area, the closer to the upper end area, the closer to the density of the upper end area, and the closer to the normal area, the closer to the density of the normal area, the density gradually changes.

  As described above, according to the present embodiment, even when the color unevenness cannot be completely corrected by the color unevenness correction process, there is no portion where the density changes suddenly, so that it is difficult to visually recognize the change in density. As a result, the quality of the printed image is improved.

  FIG. 18 is a graph of the density of each raster line in the vicinity of the transition area when printing is performed using an actual nozzle row (nozzle row having 180 nozzles).

  The thin line in the drawing is a graph of density when color unevenness correction processing is not performed. As can be seen from this figure, it is considered that an ink amount smaller than the reference amount is ejected from the first nozzle row 42A, and an ink amount larger than the reference amount is ejected from the second nozzle row 42B. As a result, the density difference between the upper end region and the normal region is large. In the transition region, the density of each raster line also changes gradually as the nozzle row usage rate changes gradually.

  A thick line in the figure is a graph of density when color unevenness correction processing is performed. The uneven color correction process corrects the amount of ink ejected to each raster line, increasing the density of the upper end area, reducing the density of the normal area, and reducing the difference between the density of the upper end area and the density of the normal area. ing.

  Although the difference between the density in the upper end area and the density in the normal area is reduced, it does not completely match. However, since the density in the transition region is an intermediate density, there are no places where the density suddenly changes, and the density change is difficult to visually recognize.

=== Another Embodiment ===
FIG. 19 is an explanatory diagram of another dot forming method. Here, a state of dot formation when performing the lower end processing for printing the lower end of the paper after performing the normal processing is shown. Since the dot forming method performed on the lower end side can be understood from this figure, detailed description is omitted.

  As described above, a dot forming method substantially similar to the dot forming method performed on the upper end side may be performed on the lower end side. Thereby, the effect similar to the effect acquired by the upper end side can be acquired also by the lower end side.

=== Other Embodiments ===
The above-described embodiment is mainly described for a printer. Among them, a printing apparatus, a recording apparatus, a liquid ejection apparatus, a printing method, a recording method, a liquid ejection method, a printing system, a recording system, and a computer system are included. Needless to say, the disclosure includes a program, a storage medium storing the program, a display screen, a screen display method, a printed material manufacturing method, and the like.

  Moreover, although the printer etc. as one embodiment were demonstrated, said embodiment is for making an understanding of this invention easy, and is not for limiting and interpreting this 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.

<About the printer>
In the above-described embodiment, the printer has been described. However, the present invention is not limited to this. For example, color filter manufacturing apparatus, dyeing apparatus, fine processing apparatus, semiconductor manufacturing apparatus, surface processing apparatus, three-dimensional modeling machine, liquid vaporization apparatus, organic EL manufacturing apparatus (especially polymer EL manufacturing apparatus), display manufacturing apparatus, film formation The same technology as that of the present embodiment may be applied to various liquid ejection devices to which inkjet technology such as a device and a DNA chip manufacturing device is applied. These methods and manufacturing methods are also within the scope of application. Even if this technology is applied to such a field, the liquid can be directly ejected (directly drawn) toward the object. You can go down.

<About ink>
Since the above-described embodiment was an embodiment of a printer, dye ink or pigment ink was ejected from the nozzle. However, the liquid ejected from the nozzle is not limited to such ink. For example, liquids (including water) including metal materials, organic materials (especially polymer materials), magnetic materials, conductive materials, wiring materials, film-forming materials, electronic inks, processing liquids, gene solutions, etc. are ejected from nozzles. May be. If such a liquid is directly discharged toward the object, material saving, process saving, and cost reduction can be achieved.

<About nozzle>
In the above-described embodiment, ink is ejected using a piezoelectric element. However, the method for discharging the liquid is not limited to this. For example, other methods such as a method of generating bubbles in the nozzle by heat may be used.

<Number of nozzle rows>
In the above embodiment, the number of nozzle groups (nozzle rows) is two, but may be three or more. Even if the number of nozzle groups is three or more, if upper end processing or normal processing is performed, the upper end region where dots are formed by only one nozzle group or dots are formed by a plurality of nozzle groups. There is a normal area. Even when the number of nozzle groups is three or more, if the same processing as in the above embodiment is performed, the difference in image quality between the upper end region and the normal region is less noticeable.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 20 ... Conveyance unit, 21 ... Feed roller, 22 ... Conveyance motor (PF motor), 23 ... Conveyance roller, 24 ... Platen, 25 ... Discharge roller, 30 ... Carriage unit, 31 ... Carriage, 32 ... Carriage motor (CR motor) 40 ... head unit 41 ... head 41A ... first nozzle group 41B ... second nozzle group 42A ... first nozzle row 42B ... second nozzle row 42X ... virtual nozzle row 50 ... Detector group, 51 ... Linear encoder, 52 ... Rotary encoder, 53 ... Paper detection sensor, 54 ... Optical sensor, 60 ... Controller, 61 ... Interface unit, 62 ... CPU, 63 ... Memory, 64 ... Unit control Circuit 65 ... Drive signal generation circuit 65A ... First drive signal generation unit 65B ... Second drive Signal generation unit.

Claims (2)

A transport operation for transporting the medium in the transport direction;
A first nozzle row in which a plurality of first nozzles are arranged in the carrying direction and a second nozzle row in which a plurality of second nozzles are arranged in the carrying direction are moved in the moving direction while moving the first nozzle and the first nozzle. A dot forming operation in which liquid is discharged from two nozzles to form dots on the medium;
By alternately repeating the above, a liquid ejection method for forming a plurality of dot rows composed of dots arranged in the moving direction in the transport direction,
A first correction value corresponding to the number of passes corresponding to the first nozzle row and performing the dot forming operation, and a second correction value corresponding to the second nozzle row and corresponding to the number of passes. Correction value is set,
When a dot row is formed by the first nozzle row and the second nozzle row, a first correction value corresponding to the number of passes in the dot row and a second correction value corresponding to the number of passes are the dots. Weighting is performed based on the usage rate of the first nozzle row and the usage rate of the second nozzle row in a row, and the amount of the liquid ejected to form the dot row is corrected. Liquid ejection method. A transport unit for transporting the medium in the transport direction;
A first nozzle row in which a plurality of nozzles are arranged in the transport direction;
A second nozzle row in which a plurality of nozzles are arranged in the transport direction;
A transport operation that transports the medium in the transport direction by the transport unit, and a dot that forms a dot on the medium by ejecting liquid from the nozzle while moving the first nozzle row and the second nozzle row in the movement direction. A controller for forming a plurality of dot rows composed of dots arranged in the moving direction in the transport direction by alternately repeating the forming operation, and
A liquid ejection device comprising:
A first correction value corresponding to the number of passes corresponding to the first nozzle row and performing the dot forming operation, and a second correction value corresponding to the second nozzle row and corresponding to the number of passes. Correction value is set,
When a dot row is formed by the first nozzle row and the second nozzle row, a first correction value corresponding to the number of passes in the dot row and a second correction value corresponding to the number of passes are the dots. Weighting is performed based on the usage rate of the first nozzle row and the usage rate of the second nozzle row in a row, and the amount of the liquid ejected to form the dot row is corrected. Liquid ejection device.

Images