JP2018171881A - Image forming apparatus - Google Patents

Abstract

An image forming apparatus capable of shortening a printing time when printing at a density higher than a unit density is provided. A CPU 40 of a printing apparatus 30 has a high density Ph [%] higher than a unit density Pu [%] (where (j-1) × Pu <Ph <j × Pu (an integer of j ≧ 2)). When printing, based on the reference LF, the nozzle is relatively moved from the print start position a plurality of times in the sub-scanning direction, and is subjected to main scanning a number of times less than (j × R × D), and each pixel of the adjacent pixel is scanned. The ink density is set to 100% or more, and the sum of the ink densities of the adjacent pixels is set to a high density Ph [%]. R is the resolution, and D is the interval between adjacent nozzles in the sub-scanning direction. [Selection] Figure 3

Description

  The present invention relates to an image forming apparatus.

  An image forming apparatus ejects ink from a nozzle when a head provided with the nozzle is moved relative to the print medium in the main scanning direction, thereby forming a pixel row composed of a plurality of ink dots arranged in the main scanning direction. Form. The image forming apparatus forms an image on the print medium by moving the head relative to the print medium in the sub-scanning direction and arranging a plurality of pixel rows in the sub-scanning direction.

  A multi-pass method is known in which formation of one pixel column is completed by a plurality of main scans. For example, Patent Document 1 describes a multi-pass method, which is a method of printing each pixel column by causing different nozzles to scan the same pixel column among a plurality of nozzles provided in the head. By using the multi-pass method, the image forming apparatus can perform printing at a density higher than the unit density, which is the maximum density of ink that can be ejected from the nozzles once.

JP2013-154511A

  When a conventional image forming apparatus performs printing with a density higher than a unit density in a range of a predetermined number of pixel columns (hereinafter referred to as a predetermined range), the image forming apparatus performs movement of the head in the main scanning direction, By repeating the relative movement of each pixel in the sub-scanning direction, a pixel column with unit density is formed. Next, it is conceivable that the image forming apparatus performs printing with a density difference between the unit density and the desired high density within the predetermined range by returning the head to a printing start position within a predetermined range to obtain a desired high density. In this case, the head performs the movement in the main scanning direction and the relative movement of each pixel in the sub scanning direction twice within a predetermined range. It is also conceivable that the image forming apparatus performs printing at a half density of a desired high density twice for the same pixel column by the multi-pass method. Also in this case, since the head moves twice in the main scanning direction with respect to the same pixel row, a single pass in which the head moves only once in the main scanning direction with respect to the same pixel row. It takes twice as long as the method. Therefore, there is a problem that the printing time at a high density becomes long.

  An object of the present invention is to provide an image forming apparatus capable of shortening the printing time when printing at a density higher than the unit density.

  An image forming apparatus according to an aspect of the present disclosure includes a plurality of nozzles arranged in the sub-scanning direction and capable of ejecting ink, and the nozzles are relatively moved in the main scanning direction with respect to the print medium based on print data And a controller that forms an image of resolution R [dpi] by ejecting ink and moving the nozzle relative to the print medium in the sub-scanning direction. D [in], and the control unit sums the maximum density of the ink that can be ejected from the nozzle at one time for each pixel in the adjacent pixels that are adjacent in the sub-scanning direction (R × D). When printing at a high density Ph [%] higher than the unit density Pu [%] (where (j−1) × Pu <Ph <j × Pu (an integer of j ≧ 2)), the sub-scanning direction The relative movement value of the nozzle to or the average value of the movement values Based on the LF (Line Feed) value (N × Pu / Ph) (where N is the number of nozzles), the nozzle is moved a plurality of times in the sub-scanning direction from the print start position where the first pixel row is formed in the main scanning direction. , Move the nozzle relative to the main scanning direction for a number of times less than (j × R × D), eject ink, and set the ink density of each pixel of the adjacent pixel to 100% or more and each pixel of the adjacent pixel It is characterized in that the discharge control is performed to control the ink discharge and the relative movement of the nozzles so that the total density of the inks is a high density Ph [%].

  According to the above aspect, the control unit of the image forming apparatus applies (R × D) adjacent pixels to the high density Ph [%] (provided that (j−1) in the main scanning less than (j × R × D) times. ) × Pu <Ph <j × Pu (an integer of j ≧ 2)). Accordingly, when high density printing is performed by performing relative movement in the main scanning direction and relative movement in the sub-scanning direction twice for a predetermined number of pixel column ranges, or in a multi-pass method, The time for printing at a high density can be shortened as compared to the case where printing at half the density is performed on the same pixel column.

2 is a perspective view illustrating a schematic configuration of a printing device 30 and a terminal device 1. FIG. 4 is a bottom view showing a schematic configuration of a carriage 34. FIG. 3 is a block diagram showing an electrical configuration of the printing apparatus 30. FIG. It is a diagram showing a process of forming a white ink image by the ejection head 35W. It is a figure which shows the process in which a color ink image is formed with the discharge head 35C. FIG. 6 is a diagram illustrating print data 421. It is a flowchart of a main process. It is a flowchart of the main process, and is a continuation of FIG. FIG. 6 is a diagram illustrating a print buffer [1] 422. It is a figure which shows the master pointer table 423. It is a flowchart of a data acquisition process. It is a flowchart of a data acquisition process, Comprising: FIG. It is a flowchart of a high concentration determination process. It is a figure which shows LF value table 411. 3 is a conceptual diagram showing a storage area of a RAM 42. FIG.

  The present embodiment will be described with reference to the drawings. A printing apparatus 30 that is an example of an image forming apparatus will be described with reference to FIG. In FIG. 1, the lower left side, upper right side, lower right side, upper left side, upper side, and lower side are the front side, rear side, right side, left side, upper side, and lower side of the printing apparatus 30, respectively.

<Configuration of Printing Device 30>
The printing apparatus 30 is a known cloth inkjet printer. The printing apparatus 30 scans the ejection head 35 and prints an image on a cloth that is a recording medium. An example of the cloth is a T-shirt. For example, the printing apparatus 30 is connected to the terminal apparatus 1 via the cable 9. The terminal apparatus 1 creates print data 421 for causing the printing apparatus 30 to execute a printing process on the cloth. The print data 421 is transmitted from the terminal device 1 to the printing device 30. The terminal device 1 is, for example, a PC (Personal Computer), a tablet, or a high-function mobile phone.

  The printing apparatus 30 includes a pair of guide rails 37 at the lower part in the housing 31. The pair of guide rails 37 extends in the front-rear direction. The pair of guide rails 37 support the platen support base 38 so as to be movable in the front-rear direction. A platen 39 is fixed to the center of the upper surface of the platen support 38 in the left-right direction. The platen 39 is a plate. A cloth is placed on the upper surface of the platen 39. The platen support 38 is conveyed in the sub-scanning direction by the sub-scanning mechanism. The sub-scanning direction is the front-rear direction in which the cloth is conveyed by the platen 39. The sub scanning mechanism includes a sub scanning motor 47 shown in FIG. 3 and a belt (not shown).

  The printing apparatus 30 includes a pair of guide rails 33 in the housing 31 and above the platen 39. The pair of guide rails 33 extend in the left-right direction. The pair of guide rails 33 support the carriage 34 so as to be movable in the left-right direction. In the example shown in FIG. 2, the carriage 34 is mounted with a head unit 100 having four ejection heads 35W and a head unit 200 having ejection heads 35C, 35M, 35Y, and 35K. The carriage 34 is conveyed in the main scanning direction orthogonal to the sub-scanning direction by the main scanning mechanism. The main scanning direction is the left-right direction in which the four ejection heads 35W and the ejection heads 35C, 35M, 35Y, and 35K are conveyed by the carriage 34. The main scanning mechanism includes a main scanning motor 46 shown in FIG. 3 and a belt (not shown). In the following description, each of the four ejection heads 35W and the ejection heads 35C, 35M, 35Y, and 35K are also referred to as ejection heads 35. As shown in FIG. 2, a plurality of nozzles 36 are provided on the bottom surface of each ejection head 35. As an example, the number of the plurality of nozzles 36 is 420. 420 nozzles 36 are provided in each of the eight ejection heads 35 in total. In FIG. 2, 20 nozzles 36 smaller than the actual number are shown for simplification.

  Each nozzle 36 can eject ink. The nozzles 36 of the discharge heads 35 are arranged at equal intervals in the sub-scanning direction. The ink in the ink cartridge mounted on the printing apparatus 30 is supplied from the front side of the carriage 34, for example. In the present embodiment, as shown in FIGS. 4 and 5, an ink supply path 60 is connected to the front side of the ejection head 35 </ b> W, and ink is supplied to each nozzle 26. Although details are omitted, the ink supplied to each nozzle 36 is ejected downward from each nozzle 36 by driving a piezoelectric element or a heating element provided in each nozzle 36.

  As shown in FIG. 2, the four ejection heads 35 </ b> W of the head unit 100 are arranged in the main scanning direction and mounted on the carriage 34. The orientation of the nozzles 36 of the four ejection heads 35W is in a state along the sub-scanning direction. The four ejection heads 35W eject white ink from the nozzles 36. In the present embodiment, the white ink is a base ink. The ejection heads 35C, 35M, 35Y, and 35K of the head unit 200 are arranged in the main scanning direction and mounted on the carriage 34. The orientation of the nozzles 36 of the ejection heads 35C, 35M, 35Y, and 35K is in a state along the sub-scanning direction. The ejection heads 35C, 35M, 35Y, and 35K eject color ink from the nozzles 36. The ejection head 35C ejects cyan ink from the nozzles 36. The ejection head 35M ejects magenta ink from the nozzles 36. The ejection head 35Y ejects yellow ink from the nozzles 36. The ejection head 35K ejects black ink from the nozzles 36.

  The printing apparatus 30 forms a predetermined number of pixel rows in the main scanning direction by discharging ink while causing the discharge head 35 to scan in the main scanning direction. The predetermined number of pixel columns extends in the left-right direction. When the formation of the predetermined number of pixel rows by one main scanning is completed, the printing apparatus 30 moves the platen 39 in the sub-scanning direction, and again forms the predetermined number of pixel rows by the main scanning. The printing apparatus 30 repeatedly performs the above operation according to the print data 421, thereby forming a plurality of pixel columns. Therefore, the printing apparatus 30 forms an image on the cloth in which a plurality of pixel rows are arranged in the sub-scanning direction.

<Electrical configuration>
The electrical configuration of the printing apparatus 30 will be described with reference to FIG. The printing apparatus 30 includes a CPU (Central Processing Unit) 40 that controls the printing apparatus 30. The CPU 40 includes a ROM (Read Only Memory) 41, a RAM (Random Access Memory) 42, an ASIC (Application Specific Integrated Circuit) 43, a head driving unit 44, a motor driving unit 45, a display control unit 48, an operation processing unit 50, and a USB. A (Universal Serial Bus) interface 52 is connected via a bus 55.

  The ROM 41 stores a main program that controls the operation of the printing apparatus 30, an initial value, and the like. The ROM 41 stores an LF (Line Feed) value table 411 shown in FIG. 14 described later. The RAM 42 temporarily stores various data. The ASIC 43 controls the head drive unit 44 and the motor drive unit 45. The head drive unit 44 is connected to the ejection head 35 that ejects ink. The head driving unit 44 drives a piezoelectric element or a heating element provided in each nozzle 36 of the ejection head 35. The motor driving unit 45 drives the main scanning motor 46 and the sub scanning motor 47. The main scanning motor 46 moves the carriage 34 in the main scanning direction. The sub scanning motor 47 moves the platen 39 in the sub scanning direction. The display control unit 48 controls display on the display 49 according to a command from the CPU 40. The display 49 displays various screens, messages, and the like related to the operation of the printing apparatus 30. The operation processing unit 50 receives an operation input on the operation panel 51. The user can input various information and instructions from the operation panel 51. The USB interface 52 connects the printing device 30 to an external device such as the terminal device 1. Note that the printing apparatus 30 may include a serial interface of another standard instead of the USB interface 52, and may be connected to an external device such as the terminal apparatus 1 via the serial cable of the standard. Further, the printing apparatus 30 may include a wired and / or wireless communication module, and may be connected to an external device such as the terminal apparatus 1 via various networks such as the Internet and an intranet.

<Storage area of RAM 42>
The storage area of the RAM 42 will be described with reference to FIG. The storage area of the RAM 42 includes a reception buffer 420, a print buffer 422, a master pointer table storage area 423, a work area 424, a development buffer 425, an LF value table storage area 426, a white mask table storage area 427, and a color mask table storage area 428. There are a white final raster data buffer 429 and a color final raster data buffer 430. The reception buffer 420 stores print data 421 described later. The print buffer 422 and the master pointer table storage area 423 will be described later. The work area 424 temporarily stores various data. The expansion buffer 425 stores raster data expanded in S14 described later. The LF value table storage area 426 stores a high density LF value table and a normal LF value table that are set ⁱ in S153 and S154 described later. The white mask table storage area 427 stores a white mask table set in S103 described later. The color mask table storage area 428 stores a color mask table set in S109 described later. The white final raster data buffer 429 stores the white final raster data obtained in S105 described later. The color final raster data buffer 430 stores the color final raster data obtained in S111 described later.

<Outline of Operation of Printing Apparatus 30>
An outline of the operation of the printing apparatus 30 will be described with reference to FIGS. 4 and 5 show how the discharge head 35W that discharges white ink relatively moves in the sub-scanning direction as the platen 39 moves in the sub-scanning direction. Hereinafter, for ease of explanation, the movement of the platen 39 in the sub-scanning direction is referred to as “relative movement of the ejection head 35 in the sub-scanning direction”. Unless otherwise specified, “relatively moving the ejection head 35 in the sub-scanning direction” means “relatively moving the ejection head 35 backward”. In this case, the platen 39 actually moves forward with respect to the carriage 34 on which the ejection head 35 is mounted.

  In FIG. 4, for ease of explanation, the number of nozzles 36 of each ejection head 35 is 20 which is smaller than 420, which is an example. FIG. 4 illustrates an operation outline of one of the four ejection heads 35 </ b> W that eject the white ink of the head unit 100. The 20 nozzles 36 of the ejection head 35W are arranged in order from the front side, nozzles W1, W2, W3, W4, W5, W6, W7, W8, W8, W9, W10, W11, W12, W13, W14, W15, W16, W17, W18, W19, W20. The interval of each of the 20 nozzles 36 is not limited to this, but is 1/300 (in) and is expressed as “D”. The resolution of the image formed by the ejection head 35 is not limited to this, but is “1200 (dpi) (main scanning direction) × 1200 (dpi) (sub-scanning direction)”. The resolution “1200 (dpi)” in each direction is expressed as “R”. In FIG. 4, the number of ink ejection points (hereinafter referred to as “dots” or pixels) included in one pixel row in the main scanning direction is “16”. When R = 1200 (dpi) and D = 1/300 (in), 4 dots (D / (1 / R) = D × R) are formed in the interval D between the nozzles 36 adjacent in the sub-scanning direction. It is formed. Therefore, 4 dots are formed at 1 / R intervals during the interval D in the sub-scanning direction. The adjacent D × R (pixels) pixels in the sub-scanning direction are hereinafter referred to as “adjacent D × R pixels”. In this specific example, since D × R = (1/300) × 1200 = 4 dots, “adjacent D × R pixels” is hereinafter referred to as “adjacent four pixels”. The rightmost position in the movable range of the carriage 34 in the main scanning direction is referred to as an “initial position”. The ejection heads 35C, 35M, 35Y, and 35K of the head unit 200 have the same structure as the ejection head 35W.

<When a white ink image is formed>
Hereinafter, with reference to FIGS. 4 and 5, an operation when a white ink image (hereinafter referred to as “white ink image”) is formed will be described. The density of one pixel based on the maximum droplet amount that the nozzle W can eject the white ink at one time is set to 100 (%). When all the pixels constituting the adjacent four pixels are printed at a density of 100 (%), the total density of the adjacent four pixels is 400 (%). 400 (%) of the total density of the adjacent four pixels is hereinafter referred to as “unit density Pu (%)”. That is, in the case of adjacent D × R pixels, unit density Pu (%) = (D × R) × 100 (%). In some cases, the print density of adjacent four pixels specified by print data 421, which will be described later, is specified at a density higher than the unit density Pu (%). A density higher than the unit density Pu (%) is referred to as “high density Ph (%)”. Hereinafter, the high concentration Ph (%) is set to 500 (%) as an example. In the following example, the CPU 40 controls the nozzles W1 to W20 so as to discharge white ink having the maximum droplet amount that can be discharged at one time in steps P11 to P15 described later.

  As shown in FIG. 4, the CPU 40 causes white ink to be ejected from the nozzles W1 to W20 onto the cloth in order to form a white ink image with a resolution R (dpi) by one ejection head 35W (step P11). Next, the CPU 40 moves the ejection head 35W by 1 / R in the main scanning direction. The CPU 40 repeats the movement of the ejection head 35W in the main scanning direction and the ejection of white ink 15 times. Therefore, the printing apparatus 30 forms 20 pixel rows in which 16 dots are arranged in the main scanning direction at intervals of 1 / R on the cloth by one ejection head 35W. Hereinafter, the 20 pixel columns formed by the nozzles W1 to W20 in the process P11 are referred to as pixel columns V11 to V120. The pixel columns V11 to V120 are arranged on the cloth at intervals of the interval D in the sub-scanning direction.

Next, the CPU 40 moves the ejection head 35W from the position of the process P11 in the sub-scanning direction to ((N / (Ph / Pu)) + n1k) × 1 / R (where n1k is an absolute value | n1k | ≦ (D × R−1) is an integer other than “0”, k = 1, 2,... (D × R−1) and {n11, n11 + n12, n11 + n12 + n13,. (K = 1, 2,..., (D × R−1))} divided by (D × R) is {0, 1, 2,. )} Condition)) Move relative. Hereinafter, the relative movement distance ((N / (Ph / Pu)) + n1k) × 1 / R in the sub-scanning direction is expressed as “L1k”. N represents the number of nozzles 36 of the ejection head 35.
Hereinafter, as an example, n1k = −1 (k = 1, 2,..., (D × R−1)). n1k is any natural number excluding “0” in absolute value | n1k | ≦ (D × R−1), and {n11, n11 + n12, n11 + n12 + n13,... ΣΣ n1k (k = 1, 2,. , (D × R−1))} divided by D × R, the reason why the combinations {0, 1, 2,..., (D × R−1)} are satisfied. Will be described later.
In the case of this specific example, n11 = n12 = n13 = −1, N = 20, Pu = 400, Ph = 500, and R = 1200.
L11 = L12 = L13 = ((20 / (500/400)) − 1) × 1/1200
= ((20 / 1.25) -1) * 1/1200
= (16-1) x 1/1200
= 15 × 1/1200
Therefore, L11 = L12 = L13 = 15/1200 (in). In the case of this specific example, L11, L12, and L13 are the same value, and will be simply expressed as L1 below.

  Next, the CPU 40 moves the ejection head 35W in the main scanning direction. The CPU 40 discharges white ink from the nozzles W1 to W20 onto the cloth at intervals of 1 / R in the main scanning direction (process P12). Hereinafter, the 20 pixel columns formed by the nozzles W1 to W20 in the process P12 are referred to as pixel columns V21 to V220. The pixel columns V21 to V220 are respectively formed backward by L1 from each of the pixel columns V11 to V120 formed in the process P11.

  Next, the CPU 40 relatively moves the ejection head 35W from the position of the process P12 in the sub-scanning direction by L1 and moves the ejection head 35W in the main scanning direction to eject white ink from the nozzles W1 to W20 onto the cloth. (Process P13). Hereinafter, the 20 pixel columns formed by the nozzles W1 to W20 in the process P13 are referred to as pixel columns V31 to V320, respectively. The pixel columns V31 to V320 are respectively formed backward by L1 from the pixel columns V21 to V220 formed in the process P12.

  Next, the CPU 40 relatively moves the ejection head 35W by L1 from the position of the process P13 in the sub-scanning direction, and moves the ejection head 35W in the main scanning direction to eject white ink from the nozzles W1 to W20 onto the cloth ( Step P14). Hereinafter, the 20 pixel columns formed by the nozzles W1 to W20 in the process P14 are referred to as pixel columns V41 to V420. The pixel columns V41 to V420 are respectively formed behind the pixel columns V31 to V320 formed in the process P13 by L1.

  Through Steps P12 to P14, 38 pixel rows are formed in the sub-scanning direction at an interval of 1 / R in the portion between the pixel row V34 and the pixel row V217. Accordingly, in the pixel columns V34 to V217, white ink dots are arranged in a grid pattern at intervals of 1 / R in the main scanning direction and the sub-scanning direction, and the resolution is R. In this specific example, adjacent four pixels are thus formed with a resolution of 1200 (dpi). Therefore, in order to form adjacent D × R pixels at the resolution R (dpi), L1k (k = 1, 2,..., (D × R−1) in the sub-scanning direction of the ejection head 35W. Relative movement and main scanning of the ejection head 35W are repeated ((D / (1 / R)) − 1) = (D × R−1) times. Is repeated (1/300) × 1200−1 = 3 times.

Next, as shown in FIG. 5, the CPU 40 moves the ejection head 35 </ b> W from the position of the process P <b> 14 in the sub-scanning direction to ((N / (Ph / Pu)) + n2 + m) × 1 / R (where n2 is Σn1k ( k = 1, 2, 3,..., (D × R−1)), m is an integer of 0 ≦ m ≦ (D × R−1).) Relative movement Let In this specific example, the movement of the ejection head 35W by L1 in the sub-scanning direction is repeated three times, and n2 = 3 because n11 = n12 = n13 = −1. In this specific example, the following description will be made assuming that m = 0. “m” is a constant that determines which pixel column in the adjacent D × R pixels is to be increased in density. For example, when m = 0, the density of the pixel column corresponding to the foremost pixel of the adjacent D × R pixel is high and becomes 200%.
Hereinafter, the relative movement distance ((N / (Ph / Pu)) + n2 + m) × 1 / R in the sub-scanning direction is expressed as “L2”. In this specific example, N = 20, Pu = 400, Ph = 500, R = 1200, n2 = 3, and m = 0. Therefore,
L2 = ((20 / (500/400)) + 3)
× 1/1200
= ((20 / 1.25) +3) × 1/1200
= (16 + 3) × 1/1200
= 19 x 1/1200
= 19/1200
That is, L2 = 19/1200 (in).

  Next, the CPU 40 moves the ejection head 35W in the main scanning direction. The CPU 40 ejects white ink from the nozzles W1 to W20 onto the cloth at intervals of 1 / R in the main scanning direction (step P15). Hereinafter, the 20 pixel columns formed by the nozzles W1 to W20 in the process P15 are referred to as pixel columns V51 to V520. Pixel columns V51 to V520 are formed L2 backwards from the pixel columns V41 to V420 formed in step P14, respectively.

  In this specific example, the position of the nozzle W1 of the ejection head 35W in the sub-scanning direction in the process P15 coincides with the position of the nozzle W17 of the ejection head 35W in the process P11. Accordingly, the pixel column V51 is formed at the position of the pixel column V117 formed in the process P11. That is, one pixel column (hereinafter referred to as “pixel column M1”) is formed by the dots included in the pixel columns V117 and V51. Similarly, the pixel column V52 is formed at the position of the pixel column V118, the pixel column V53 is formed at the position of the pixel column V119, and the pixel column V54 is formed at the position of the pixel column V120. One pixel column (hereinafter referred to as “pixel column M2”) is formed by the dots included in the pixel columns V118 and V52, and one pixel column (hereinafter “pixel”) is formed by the dots included in the pixel columns V119 and V53. Column M3 ”), and one pixel column (hereinafter referred to as“ pixel column M4 ”) is formed by the dots included in the pixel columns V120 and V52. As described above, a method in which different nozzles 36 are scanned at the same position to form one pixel row is generally referred to as “multi-pass method” or “singling”.

<About n1k and n2>
n1k is an integer excluding any “0” with an absolute value | n1k | ≦ 3. In the specific example, n1k = −1 (k = 1, 2,..., (D × R -1)). The reason is that the ejection head 35W is moved relative to the sub scanning direction L1k (D × R−1) times to form adjacent D × R pixels in the sub scanning direction. The reason why n2 is the number obtained by converting the sign of the sum Σn1k of n1k is that white ink is ejected from the nozzle 36 so as to overlap the frontmost pixel among adjacent D × R pixels. Therefore, if m is set to a value other than “0”, white ink can be ejected from the nozzle 36 so as to overlap with the pixels other than the foremost pixel of the adjacent D × R pixels. In this specific example, when four adjacent pixels in the sub-scanning direction are printed with high density Ph (%) (for example, 500%), L1 is moved three times and L2 is moved once. In the case of high concentration Ph (%), the number of movements of L2 is round [{(R × D−1) + (Ph−Pu) / 100} / (D × R)] times. “round” is a function for truncating the decimal part. For example, round (1.23) = 1. The combination of “n11, n12, n13, n2” in the case of this specific example is “−1, −1, −1, 3” “−1, −2, 1, 2” “−2, 1, −2”. , 3 "" -2, -1, 2, 1 "" -3, 2, -1, 2 "" -3, 1, 1, 1 "and the like.

  In the pixel column M1, the pixel column V52 is printed at a printing density of 100 (%) on the pixel column V117 printed at a printing density of 100 (%). Accordingly, the print density of the pixel column M1 is 200 (%). In the pixel columns of four adjacent pixels up to the pixel columns V45, V39, V213, and M1, the print densities of the pixel columns V45, V39, and V213 are 100 (%), respectively. Accordingly, the total print density of the pixel columns V45, V39, V213, and M1 is 500 (%). Similarly, in the pixel columns of the adjacent four pixels of the pixel columns V46 to M2, the pixel columns of the adjacent four pixels of V47 to M3, and the pixel columns of the adjacent four pixels of the pixel columns V48 to M4, respectively, the total print density is , 500 (%).

  As described above, the white ink is ejected from the ejection head 35W in the process P11 to the process P15, so that a pixel row including 16 dots of white ink aligned in the main scanning direction is arranged in the sub scanning direction. In addition, the printing apparatus 30 uses the “multi-pass method” to eject the ink by scanning the ejection head 35 </ b> W in the main scanning direction five times, thereby changing the pixel row of the adjacent four pixels to a high density Ph (%) of 500 (%). ) Can be printed. As shown in FIG. 4, the printing apparatus 30 performs the printing process four times from Step P <b> 11 to Step P <b> 14 in order to print a pixel row of four adjacent pixels with a total density of 400 (%). Further, as shown in FIG. 5, the printing apparatus 30 performs the printing process five times from Steps P11 to P15 in order to print the adjacent four pixel columns at a total density of 500 (%). Therefore, the printing time of the high density Ph (%) of 500 (%) is 5/4 of the printing time of 400 (%). In the conventional printing method of high density Ph (%), for example, in order to print four pixels adjacent in the sub-scanning direction at a density of 500 (%), the printing apparatus 30 is configured so that the ejection head relative to the sub-scanning direction is relative. The movement control was performed 8 times as described above. Also, in the multi-pass method, four pixels adjacent in the sub-scanning direction are printed at a density of 500 (%), and printing at half the density of the high density Ph (%) is performed twice for the same pixel column. In the case of overlapping, since the main scanning is performed twice on the same pixel column, it takes twice as long as the single pass method in which the main scanning is performed only once on the same pixel column. Therefore, in this embodiment, the printing time for high density Ph (%) can be shortened.

  The operation of one of the four ejection heads 35W has been described above. In practice, as shown in FIG. 2, the four ejection heads 35W are mounted on the carriage 34 in a state of being aligned in the main scanning direction. Each ejection head 35W forms 20 pixel columns by ejecting white ink from the nozzles W1 to W20 while moving in the main scanning direction. The positions of the 20 pixel columns formed by the nozzles W1 to W20 of the respective ejection heads 35W coincide in the sub-scanning direction. Therefore, each pixel column formed by the nozzles W1 to W20 of each ejection head 35W forms one pixel column by overlapping the pixel columns formed by the four ejection heads.

  By using the above-described method, the high concentration Ph can be obtained simply by moving or moving the ejection head 35W {(R × D−1) + (Ph−Pu) / 100} times in the main scanning direction and the sub scanning direction. (%) Can be printed. In the specific example described above, (1200 / 300-1) + (500-400) / 100 = 4 times.

<Print data>
The print data 421 will be described with reference to FIG. The print data 421 is transmitted from the terminal device 1 illustrated in FIG. 1 to the printing device 30 via, for example, the cable 9. For example, when the print data 421 is received via the cable 9, the CPU 40 of the printing apparatus 30 stores the received print data 421 in the reception buffer 420 of the RAM 42. The CPU 40 forms a white ink image and / or a color ink image on the cloth by executing a main process shown in FIG. 7 described later based on the received print data 421. In this embodiment, a white ink image is formed on the cloth.

  The print data 421 includes header information, raster information, and footer information. The header information includes resolution, density information, platen information, and hitting designation information. The resolution indicates the resolution R (dpi) of the image to be printed. In the following, it is assumed that the resolution R (dpi) is “1200 (dpi)”. An example of the interval D between the nozzles 36 is “1/300 (in)”, satisfies the relationship of R = 4 / D, and will be described as m = 0. The density information indicates the density at which the white ink image is printed. The platen information indicates the area of the platen 39 supported by the platen support base 38 by coordinate information. The hitting designation information includes: (1) a white ink image only, (2) only a color ink image, (3) a white ink image, and a color ink image. Including either. In the present embodiment, the hitting designation information indicates (1) that only the white ink image is included, and the white ink image is formed on the cloth.

  The raster information includes a pixel column number, color information, a left margin, a right margin, and raster data. The pixel column number indicates a number assigned to each of a plurality of pixel columns arranged at intervals of 1 / R in the sub-scanning direction in order from the front side, such as “1”, “2”, “3”,. That is, each pixel column number indicates a position where a corresponding pixel column is formed on the print medium.

  The color information is information indicating the color of the ink used to form the pixel row having the corresponding pixel row number. As the color information, in this specific example, white 1-4, cyan, magenta, yellow, and black are associated with the pixel column numbers. In one pixel column, ink is ejected from a total of eight ejection heads 35 including four ejection heads 35W (white 1 to 4), ejection heads 35C (cyan), 35M (magenta), 35Y (yellow), and 35K (black). Is formed. Accordingly, as shown in FIG. 6, in this specific example, eight different color information (white 1 to 4, cyan, magenta, yellow, and black) are associated with each pixel column number.

  The left margin and the right margin are information for specifying the position of the platen 39 based on an encoder (not shown) provided on the guide rail 33, which is associated with the raster data. The left margin indicates the position of the left end of the pixel column corresponding to the pixel column number by the distance from the left end of the platen 39. The write margin indicates the position of the right end of the pixel column corresponding to the pixel column number by the distance from the right end of the platen 39.

  The raster data indicates whether or not ink is ejected from the nozzles 36 in order to form a pixel row by main scanning. Raster data is bit information in which “1” or “0” is arranged. Bit “1” of the raster data indicates that ink dots are ejected from the nozzle 36. Bit “0” of the raster data indicates that ink dots are not ejected from the nozzle 36.

<Print buffer>
The print buffer 422 will be described with reference to FIG. In the present embodiment, there are X (X = (R × D) + (Ph−Pu) / 100) print buffers 422 in the RAM 42. In the following description, the print buffer 422 of number X is displayed as print buffer [X] 422. FIG. 9 shows a print buffer [1] 422, which is an example of the print buffer [X] 422. The print buffer [1] 422 stores a pre-scan LF value, a post-scan LF value, a final left margin, a final right margin, and a read pointer table [8] [420]. The pre-scan LF value, post-scan LF value, final left margin, and final right margin will be described later. In the read pointer table [8] [420], 8 × 420 pointers included in a master pointer table 423 shown in FIG. 10 described later are set. The CPU 40 sets “0” to the pre-scan LF value, the post-scan LF value, the final left margin, and the final right margin by the initialization process S1 of the main process described later. Hereinafter, the white mask table and the color mask table suffix are referred to as “index”.

<Main processing>
The main process executed by the CPU 40 will be described with reference to FIGS. For example, when a power switch (not shown) of the operation panel 51 shown in FIG. 2 is turned on, the CPU 40 reads the main program from the ROM 41 and executes the main process.

  As shown in FIG. 7, the CPU 40 first performs an initialization process (S1). An example of the initialization process will be specifically described. The CPU 40 is in a state where all the ejection heads 35 are covered with caps. The CPU 40 places the carriage 34 at the initial position. The CPU 40 moves the platen 39 to the rearmost position. The CPU 40 initializes variables stored in the RAM 42. For example, the CPU 40 sets “1” to a counter value “Cnt” indicating the number of times of main scanning (including the number of times raster data is all “0” and not main-scanned). The counter value Cnt corresponds to X in the print buffer [X] 422. The CPU 40 blanks the fields for storing the mask values of the white mask table [420] and the color mask table [420], which are 420 mask value arrays. The CPU 40 initializes X print buffers [X] 422 (X = 1, 2,...). That is, the CPU 40 sets “0” for the pre-scan LF value, the post-scan LF value, the final left margin, and the final right margin, and also sets “0” in each field storing the pointers of the lead point table [8] [420]. "Set.

  As shown in FIG. 7, the CPU 40 determines whether a print instruction has been received (S11). More specifically, for example, the CPU 40 determines that a print instruction has been received when a print button (not shown) of the operation panel 51 illustrated in FIG. 3 is pressed and a print instruction signal is received from the terminal device 1. If the CPU 40 determines that it has not received a print instruction (S11: NO), it returns to S11. The CPU 40 continuously monitors the print instruction. When it is determined that the print instruction has been received (S11: YES), the CPU 40 proceeds to S12. The CPU 40 determines whether the print data 421 shown in FIG. 6 is stored in the reception buffer 420 (S12). When the CPU 40 determines that the print data 421 is not stored in the reception buffer 420 (S12: NO), the CPU 40 displays an error notification screen indicating that the print data 421 is not stored in the reception buffer 420 as shown in FIG. 49 is displayed (S39). The CPU 40 returns to S11.

  When it is determined that the print data 421 is stored in the reception buffer 420 (S12: YES), the CPU 40 starts a process of developing raster information in the print data 421 shown in FIG. 6 (S14). The process of expanding the raster information is executed simultaneously with the main process by another process executed in parallel with the main process. The expanded raster information is stored in the expansion buffer 425 of the RAM 42.

  Next, the CPU 40 performs a high density determination process (S15). The high density determination process will be described with reference to FIG. The CPU 40 acquires density information from the header information of the print data 421 (S151). Next, the CPU 40 determines whether there is high density information indicating that printing is performed with high density Ph (%) in the density information (S152). An example of the high density information is information indicating that printing is performed at 500 (%) or 600 (%). If the CPU 40 determines that the high density information is present (S152: YES), the CPU 40 sets (Cnt-1) (where Cnt ≧ 2) according to the density information from the LF value table 411 shown in FIG. The combination of LF values corresponding to the remainder when dividing by (D × R) is stored in the LF value table storage area 426 of the RAM 42 as a high density LF value table (S153). For example, when high density information is information indicating that printing is performed at 500%, and D × R = 4, the CPU 40 divides (Cnt−1) (where Cnt ≧ 2) by “4”. The LF value combination “335, 335, 335, 339” corresponding to the remainder value “1, 2, 3, 0” is stored in the LF value table storage area 426 as a high density LF value table.

  If the CPU 40 does not determine that there is high density information (S152: NO), the CPU 40 uses (Cnt-1) (however, for printing at a normal density (400% in the specific example) from the LF value table 411. A combination of LF values corresponding to the remainder when (Cnt ≧ 2) is divided by (D × R) is stored in the LF value table storage area 426 of the RAM 42 as a normal LF value table (S154). After the end of S153 or S154, the CPU 40 proceeds to S16 of the main process shown in FIG.

<LF value table 411>
The LF value table 411 stored in the ROM 41 will be described with reference to FIG. The LF value table 411 illustrated in FIG. 14 is an example in the case where the adjacent D × R pixels are the adjacent four pixels and n11 = n12 = n13 = −1. In the LF value table 411, resolution, density information, and LF values are associated with each other. The information indicating that printing is performed at 500 (%) of the high density information indicates that the pixel columns of the adjacent four pixels are printed at the high density Ph (%) = 500 (%). The information indicating that printing is performed at 600 (%) of the high density information indicates that the pixel columns of the adjacent four pixels are printed at the high density Ph (%) = 600 (%). Normally, the density information indicates that the adjacent four pixels are printed with the unit density Pu (%) = 400 (%). In this specific example, the LF value is a remainder value “1”, “2”, “3”, “0” when (Cnt−1) (where Cnt ≧ 2) is divided by “4”. Is associated with.

  The LF value of the LF value table 411 will be described. In this specific example, an image having a resolution R (dpi) = 1200 (dpi) is formed. As described above, 3 dots ({(D / (1 / R)) − 1} = D × R−1) are formed between the nozzles 36. Therefore, in order to form four adjacent pixels with the resolution R (dpi) = 1200 (dpi), the LF value is set in advance as follows. First, a reference LF value is calculated. The reference LF value is a value obtained by dividing “420”, which is the number N of nozzles 36, by the ratio (Ph / Pu) of the high concentration Ph (%) to the unit concentration Pu (%). The reference LF value is an average value of the LF amount when high density Ph (%) is printed by the multi-pass method. For example, when the high concentration Ph (%) is 500 (%), the reference LF value is “420 / (500/400) = 336”. In this specific example, since n11 = n12 = n13 = −1, “335” obtained by subtracting “1” from the reference LF value is obtained by dividing (Cnt−1) (where Cnt ≧ 2) by “4”. The remainder values “1”, “2”, and “3” are respectively associated with the cases. In this specific example, since n2 = 3, “339” obtained by adding “3” to the reference LF value is associated with the remainder “0”. When the high concentration Ph (%) is 600 (%), the reference LF value is “420 / (600/400) = 280”. In this specific example, since n11 = n12 = n13 = −1, “279” obtained by subtracting “1” from the reference LF value becomes the remaining values “1”, “2”, and “3”, respectively. It is associated. In this specific example, since n2 = 3, “283” obtained by adding “3” to the reference LF value is associated with the remainder “0”. When the density information is normal, the reference LF value is “420”. In this specific example, since n11 = n12 = n13 = −1, “419” obtained by subtracting “1” from the reference LF value is associated with the remaining values “1”, “2”, and “3”, respectively. Yes. In this specific example, since n2 = 3, “423” obtained by adding “3” to the reference LF value is associated with the remainder “0”.

  Referring to FIG. 7, in S16 of the main process, CPU 40 initializes master pointer table 423 shown in FIG. 10 stored in RAM 42 (S16). More specifically, as shown in FIG. 10, the master pointer table 423 associates head types, nozzles, and pointers. The head types are a total of eight ejection heads 35 (four ejection heads 35W (white 1 to 4), ejection heads 35C (cyan), 35M (magenta), 35Y (yellow), 35K (black)) mounted on the carriage 34. ). The nozzles indicate 420 nozzles 36 (hereinafter referred to as nozzle [1], nozzle [2]... Nozzle [420]) of each of the eight ejection heads 35. The pointer associated with each nozzle 36 is a pointer indicating raster data for the corresponding nozzle 36 to form one pixel row in the main scanning direction among the raster information stored in the development buffer 425. is there.

  As an example, the CPU 40 uses the pixel column number “1” of the raster information stored in the development buffer 425 as the pointer corresponding to the nozzle [1] of the head type “white 1” in the master pointer table 423, and the color information. A pointer indicating raster data corresponding to “white 1” is associated. The CPU 40 sets the pixel column number “5” of the raster information stored in the development buffer 425 as the pointer corresponding to the head type nozzle [2] of “white 1” in the master pointer table 423 and the color information “white”. A pointer indicating raster data corresponding to 1 "is associated. This is because the interval between the nozzles 36 of the ejection head 35W is D, which is four times the interval 1 / R in the sub-scanning direction of the pixel column. Therefore, the pixel column number corresponding to the nozzle [2] is 5 (= 4 + 1).

  Thereafter, the CPU 40 uses the same method to set the pixel row of the raster information as a pointer corresponding to the nozzle [n] (n = 1, 2,... 420) of the head type “white 1” in the master pointer table 423. A pointer indicating raster data corresponding to the number “4 (n−1) +1” and the color information “white 1” is associated. The CPU 40 associates pointers corresponding to the nozzle types [1] to [420] of the head types “white 2 to white 4” in the master pointer table 423 in the same manner as described above. In this embodiment, since only a white ink image is formed, description of pointers corresponding to colors is omitted, but the pointer association method is basically the same.

  As shown in FIG. 7, after initializing the master pointer table 423 in S16, the CPU 40 executes the data acquisition process shown in FIGS. 11 and 12 (S17). The data acquisition process will be described with reference to FIGS. 11 and 12. In the data acquisition process, the CPU 40 stores a pointer indicating raster data used when moving the carriage 34 in the main scanning direction for the Cnt time in the read pointer table [8] [420] of the print buffer [Cnt] 422 as follows. Store like so.

  A specific processing flow will be described. The CPU 40 determines whether the raster information stored in the expansion buffer 425 includes all the raster data indicated by the 8 × 420 pointers in the master pointer table 423 shown in FIG. 10 (S81). If the CPU 40 determines that all are not included (S81: NO), the data acquisition process is terminated. However, it is determined whether there is print data in S12 of the main process. Only when it is determined that there is print data, the processes after S14 of the main process are executed. Therefore, in S81 of the data acquisition process, it is not usually determined as NO, but if there is a special abnormality, it is determined as NO.

  If the CPU 40 determines that all are included (S81: YES), it proceeds to S83. The CPU 40 sets the 8 × 420 pointers in the master pointer table 423 as the read pointer table [8] [420] of the print buffer [Cnt] 422 (S83).

  Next, the CPU 40 updates the 8 × 420 pointers in the master pointer table 423 as follows. The CPU 40 adds the LF value to 8 × 420 pointers in the master pointer table 423 (S85). More specifically, the CPU 40 sets (Cnt−1) to (D × R) (in this specific example, “D × R) based on the LF value table 411 stored in the ROM 41 in the high density determination process of FIG. The LF value corresponding to the remainder when dividing by 4 ″) is specified. The CPU 40 adds the specified LF value to 8 × 420 pointers in the master pointer table 423 shown in FIG. If the remainder of dividing (Cnt−1) by (D × R) is “0”, the specified LF value is set to a constant m (m = 0, 1, 2,..., (D The value obtained by adding × N−1)) is added to 8 × 420 pointers in the master pointer table 423 shown in FIG. For example, when the density information is 500 (%), the LF value table 411 in FIG. 14 stores the remainder values “1”, “2”, “3” when (Cnt−1) is divided by “4”. The LF values “335”, “335”, “335”, and “339” corresponding to “0” are set. Therefore, when the remainder value obtained by dividing (Cnt−1) by “4” is “1” to “3”, the CPU 40 sets the LF value “335” to 8 × 420 in the master pointer table 423. Is added to the pointer. Further, when the remainder value when (Cnt−1) is divided by “4” is “0”, the CPU 40 sets the value obtained by adding the LF value “339” and the constant m to 8 in the master pointer table 423. Add to × 420 pointers.

  The CPU 40 specifies 8 × 420 raster data indicated by the 8 × 420 pointers set in the read pointer table [8] [420] of the print buffer [Cnt] 422 in S83. The CPU 40 determines whether all the bits of the specified 8 × 420 raster data are “0” (S87). If the CPU 40 determines that all of the 8 × 420 raster data bits are “0” (S87: YES), the CPU 40 proceeds to S89. The CPU 40 adds the value added to the pointer in S85 to the pre-scan LF value of the print buffer [Cnt] 422 (S89). When the printing process is executed based on raster data in which all 8 × 420 bits are “0”, ink is not ejected from the ejection head 35. The CPU 40 adds “1” to the counter value Cnt to update the counter value Cnt (S91). The CPU 40 returns to S83.

  On the other hand, if the CPU 40 determines that all of the 8 × 420 raster data bits are not “0” (S87: NO), the CPU 40 adds the LF value after scanning of the print buffer [Cnt] 422 to the pointer in S85. The set value is set (S93). CPU40 advances a process to S101 shown in FIG. The pre-scan LF value and the post-scan LF value calculated in S83 to S93 are obtained after the movement when the row where the pixel row is not formed is skipped and the carriage 34 is relatively moved in the sub-scanning direction to the row where the pixel row is formed. Used to identify the location.

  As shown in FIG. 12, the CPU 40 determines whether the white ink image is included in the hitting designation information in the header information of the print data 421 stored in the reception buffer 420 (S101). When it is determined that a white ink image is included, the header information includes (1) only a white ink image or (3) information indicating that a white ink image and a color ink image are included. is there. If the CPU 40 determines that no white ink image is included (S101: NO), the CPU 40 proceeds to S107.

  When it is determined that the white sync image is included (S101: YES), the CPU 40 performs white mask table setting (S103). More specifically, when discharging the white ink from all the nozzles [1] to [420], the CPU 40 stores the white mask tables “1” to “420” stored in the white mask table storage area 427 of the RAM 42. ] Is set to “0xffff” (“1111111111111111”) as a mask value.

  The CPU 40 performs an AND operation on the bits of the white raster data using the white mask table (S105). More specifically, the CPU 40 specifies 8 × 420 raster data indicated by 8 × 420 pointers set in the read pointer table [8] [420] of the print buffer [Cnt] 422. The CPU 40 selects 4 × 420 raster data corresponding to the four ejection heads 35W that eject white ink from the identified raster data. The CPU 40 sets each bit of the raster data corresponding to the nozzles [1] to [420] among the selected 4 × 420 raster data and the mask set in each of the white mask tables [1] to [420]. An AND operation with the value “0xffff” is executed. When the number of bits of the raster data is larger than “16”, the CPU 40 repeatedly applies the value set in the white mask table from the previous value to the 17th and subsequent bits of the raster data, and executes an AND operation. . The CPU 40 stores the result of the AND operation as white final raster data in the white final raster data buffer [4] [420] 429 in the RAM. Next, the CPU 40 proceeds to S107.

  In the header information of the print data 421 stored in the reception buffer 420, the CPU 40 uses (2) information indicating that a color ink image is included as the hitting designation information, or (3) a white ink image and a color ink image. It is determined whether information indicating inclusion is included (S107). If the CPU 40 determines that (1) information indicating that only a white ink image is included is included (S107: NO), the CPU 40 proceeds to S113.

  The CPU 40 sets “final left margin” and “final right margin” of the print buffer [Cnt] 422 (S113). More specifically, the CUP 40 specifies 8 × 420 raster data indicated by 8 × 420 pointers set in the read pointer table [8] [420] of the print buffer [Cnt] 422. The CPU 40 extracts all the left margin and right margin associated with the specified raster data from the raster information stored in the expansion buffer 425. The CPU 40 sets the smallest left margin among all the left margins as the “final left margin” of the print buffer [Cnt] 422. Further, the CPU 40 sets the smallest write margin among all the write margins as the “final write margin” of the print buffer [Cnt] 422. The CPU 40 ends the data acquisition process and proceeds to S19 of the main process shown in FIG.

  When it is determined that the information indicating (2) or (3) is included in the hitting designation information (S107: YES), the CPU 40 sets a color mask table (S109). Next, the CPU 40 performs an AND operation on the mask value of the color mask table and each bit of the raster data (S111). The CPU 40 stores the result of the AND operation in the color final raster data buffer [4] [420] 430 in the RAM 42 as color final raster data.

  The CPU 40 sets the final left margin and the final right margin (S113). The CPU 40 ends the data acquisition process and proceeds to S19 of the main process shown in FIG. The CPU 40 starts moving the platen 39 to the print start position (S19). More specifically, the CPU 40 starts moving the platen 39 by the LF value before scanning of the print buffer [Cnt = 1]. The CPU 40 opens the caps that cover the 420 ejection nozzles 35 of the four ejection heads 35W and the ejection heads 35C, 35M, 35Y, and 35K (S21). The CPU 40 moves the carriage 34 to the flushing position (S23). The flushing position is a position where a flushing receiver (not shown) is provided.

  The CPU 40 determines whether or not the movement of the pre-scan LF value of the platen 39 started in S19 is completed (S25). When the CPU 40 determines that the movement of the platen 39 by the LF value before scanning is not completed (S25: NO), the CPU 40 returns to S25. The CPU 40 continuously monitors whether the movement of the platen 39 by the LF value before scanning is completed. When it is determined that the movement of the platen 39 by the LF value before scanning is completed (S25: YES), the CPU 40 performs a flushing process (S27).

  After completing the flushing process (S27), the CPU 40 adds “1” to the counter value Cnt to update the counter value Cnt (S29). The CPU 40 executes data acquisition processing based on the updated counter value Cnt added with “1” (S31). The data acquisition process is the same as the data acquisition process executed in S17 shown in FIG. The CPU 40 advances the process to S41 shown in FIG.

  As shown in FIG. 8, the CPU 40 calculates the coordinates of the positions indicated by the final left margin and the final right margin as the movement source and movement destination coordinates of the carriage 34 (S41). More specifically, the CPU 40 acquires the final left margin and the final right margin of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422, respectively. The CPU 40 selects the smaller final left margin among the final left margins of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422. Similarly, the CPU 40 selects the smaller final write margin among the final write margins of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422. Thereby, the movement of the carriage 34 can be made efficient. The CPU 40 calculates the coordinates of the positions indicated by the selected final left margin and final right margin as the movement source and movement destination coordinates of the carriage 34. Next, the CPU 40 sets the calculated coordinates, the read pointer table [8] [20] of the print buffer [Cnt] 422, and the main scanning direction as the printing direction in the storage unit of the ASIC 43 (S43).

  The CPU 40 starts the movement of the carriage 34 in the main scanning direction by outputting a signal to the ASIC 43 (S45). More specifically, the ASIC 43 controls the head driving unit 44 and the motor driving unit 45 shown in FIG. The motor driving unit 45 starts the movement of the carriage 34 in the main scanning direction under the control of the ASIC 43. The head drive unit 44 causes white ink to be ejected from the nozzles 36 at intervals of 1 / R in the main scanning direction under the control of the ASIC 43. The ASIC 43 controls the head driving unit 44 based on the white final raster data, and discharges white ink from the discharge head 35 at a timing when the bit of the raster data is “1”. On the other hand, the ASIC 43 controls the head driving unit 44 based on the final white raster data, and prevents the white ink from being ejected from the ejection head 35 at the timing when the bit of the raster data is “0”. Similarly, the ASIC 43 controls the head driving unit 44 based on the color final raster data, and causes the ejection head 35 to eject the color ink at the timing when the bit of the raster data is “1”. On the other hand, the ASIC 43 controls the head driving unit 44 based on the color final raster data so that the color ink is not ejected from the ejection head 35 at the timing when the bit of the raster data is “0”.

  The CPU 40 determines whether the movement of the carriage 34 in the main scanning direction is completed (S47). If the CPU 40 determines that the movement of the carriage 34 in the main scanning direction has not been completed (S47: NO), the CPU 40 returns to S47. If the CPU 40 determines that the movement of the carriage 34 in the main scanning direction has been completed (S47: YES), the CPU 40 proceeds to S49.

  The CPU 40 starts moving the platen 39 (S [satokj1] [I2] 49). More specifically, the CPU 40 acquires the pre-scan LF value and the post-scan LF value of the print buffer [Cnt] 422. The CPU 40 adds the acquired pre-scan LF value and post-scan LF value, and specifies the position of the platen 39 after the movement. The CPU 40 starts the movement of the platen 39 to the position after the movement. Next, the CPU 40 determines whether or not the movement of the platen 39 has been completed (S50). If the CPU 40 determines that the movement of the platen 39 has not been completed (S50: NO), the CPU 40 returns to S50. When the CPU 40 determines that the movement of the platen 39 has been completed (S50: YES), the CPU 40 proceeds to S51.

  The CPU 40 determines whether there is an unprocessed print buffer 422 (S51). If the CPU 40 determines that there is no unprocessed print buffer 422 (S51: NO), it proceeds to S69. On the other hand, if it is determined that there is an unprocessed print buffer 422 (S51: YES), the CPU 40 adds "1" to the counter value Cnt and updates the counter value Cnt (S53). The CPU 40 executes the data acquisition process shown in FIGS. 12 and 13 based on the updated counter value Cnt obtained by adding “1” to the counter value Cnt (S55). The data acquisition process is the same as the data acquisition process executed in S17 shown in FIG. The CPU 40 proceeds to S59.

  The CPU 40 calculates the coordinates of the positions indicated by the final left margin and the final right margin as the movement source and movement destination coordinates of the carriage 34 (S59). More specifically, the CPU 40 acquires the final left margin and the final right margin of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422, respectively. The CPU 40 selects the smaller final left margin among the final left margins of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422. Similarly, the CPU 40 selects the smaller final write margin among the final write margins of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422. Thereby, the movement of the carriage 34 can be made efficient. The CPU 40 calculates the coordinates of the respective positions indicated by the selected final left margin and final right margin as the movement source and destination coordinates of the carriage. Next, the CPU 40 sets the calculated coordinates, the read pointer table [8] [420] of the print buffer [Cnt] 422, and the main scanning direction as the printing direction in the storage unit of the ASIC 43 (S61).

  The CPU 40 determines whether or not a predetermined time has elapsed since it was determined in S47 that the movement of the carriage 34 in the main scanning direction was completed (S63). When it is determined that the predetermined time has not elapsed (S63: NO), the CPU 40 returns to S63. When it is determined that the predetermined time has elapsed (S63: YES), the CPU 40 proceeds to S65. The CPU 40 starts the movement of the carriage 34 in the main scanning direction by outputting a signal to the ASIC 43 (S65). The CPU 40 returns to S47.

  In S69, the CPU 40 starts moving the platen 39 to the frontmost position (S69). The CPU 40 moves the carriage 34 to the maintenance position (S71). The maintenance position is a position where a wiper (not shown) is provided. The CPU 40 executes wiping (S73). Wiping is a process of scraping ink adhering to the nozzles 36 with a wiper. The CPU 40 keeps all the ejection heads 35 covered with caps (S75). The CPU 40 determines whether the movement of the platen 39 is completed (S77). If the CPU 40 determines that the movement of the platen 39 has not been completed (S77: NO), the CPU 40 returns to S77. When the CPU 40 determines that the movement of the platen 39 has been completed (S77: YES), the main process is terminated.

<Main action and effect>
As described above, the CPU 40 relatively moves the ejection head 35 to the print start position in the sub-scanning direction based on the print buffer [1] 422 (S19 of the main process). Next, the CPU 40 moves the ejection head 35 in the main scanning direction based on the print buffer [1] 422, and ejects white ink from the nozzle 36 at intervals of 1 / R in the main scanning direction (main). Processing S45). Next, the CPU 40 relatively moves the ejection head 35 in the sub-scanning direction (main treatment S49). For example, when the total print density of the pixel columns of the adjacent four pixels is printed at a high density of 500 (%), the CPU 40 reads the read pointer table “8” [420] of the print buffers [2] 422 to [4] 422. ] Is added to the LF value “335” in the LF value table 411 shown in FIG. 14 (S85 of the data acquisition process). The LF value corresponds to the number of pixels. Accordingly, the CPU 40 relatively moves the ejection head 35 in the sub-scanning direction by (335 / R). Next, the CPU 40 moves the ejection head 35 in the main scanning direction based on the print buffers [2] 422 to [4] 422 to eject white ink from the nozzles 36 (S65 of the main process). The pixel rows of white ink formed in this way are arranged at 1 / R intervals in the sub-scanning direction.

  Next, the CPU 40 adds the LF value “339” of the LF value table 411 and the constant m to each pointer of the read pointer table “8” [420] of the print buffer [5] 422 (S85 of the data acquisition process). . The CPU 40 adds the position after moving the ejection head 35 relative to the sub-scanning direction to each pointer of the read pointer table “8” [420] of the print buffer [5] 422 (LF value “339”). "And a value obtained by adding a constant m) (S49 of the main process). The CPU 40 relatively moves the ejection head 35 in the sub-scanning direction by ((339 + m) / R) from the position of the ejection head 35 when ink is ejected based on the print buffer [4] 422 (in the main process). S49). Next, based on the print buffer [5] 422, the CPU 40 moves the ejection head 35 in the main scanning direction to eject white ink from the nozzles 36 (main process S65). Therefore, the CPU 40 ejects ink based on the print buffer [5] 422 to the same pixel column as the pixel where ink was ejected based on the print buffer [m] 422. Therefore, the print density of the pixel column is 200 (%). Based on the print buffers [2] 422 to [4] 422, the print density of the formed pixel columns is 100 (%), so the CPU 40 sets the print density of the pixel columns of the adjacent four pixels to 500 (%). it can.

  As described above, the CPU 40 uses the “multi-pass method” for five main prints when printing is performed at a high density Ph (%) with respect to the unit density Pu (%) of a pixel row of four adjacent pixels. By ejecting ink by scanning the ejection head 35 </ b> W in the scanning direction, it is possible to print the pixel rows of the adjacent four pixels at a high density Ph (%) of 500 (%). As shown in FIG. 4, the printing apparatus 30 performs the printing process four times from Step P <b> 11 to Step P <b> 14 in order to print a pixel row of four adjacent pixels with a total density of 400 (%). Further, as shown in FIG. 5, the printing apparatus 30 performs the printing process five times from Steps P11 to P15 in order to print the adjacent four pixel columns at a total density of 500 (%). Therefore, the printing time of the high density Ph (%) of 500 (%) is 5/4 of the printing time of 400 (%). On the other hand, the conventional 500 (%) high density Ph (%) printing method took twice as long as the time required to print adjacent four pixels at 400 (%) as described above. . That is, when printing four adjacent pixels at a high density Ph (%) of 500%, it has conventionally been necessary to perform main scanning eight times. Therefore, in the present embodiment, the printing time for high density Ph (%) can be shortened compared to the conventional case.

<Modification 1>
Clogging may occur in some of the plurality of nozzles 36 of the ejection head 35W from which white ink is ejected. The plurality of nozzles 36 of the ejection head 35W from which the white ink is ejected is more likely to be clogged than the plurality of nozzles 36 of the color ink ejection heads 35C, 35M, 35Y, and 35K. As described above, the ink of the ink cartridge attached to the printing apparatus 30 is supplied from the front side to the carriage 34 in this specific example. For this reason, among the plurality of nozzles 36 of the white ink ejection head 35 </ b> W, the possibility of clogging increases as the nozzle 36 disposed on the rear side of the carriage 34. For example, among the 420 nozzles 36, the white ink is appropriately discharged from the first to 360th nozzles 36 in order from the front side, whereas the white ink is appropriate due to clogging at the 361 to 420th nozzles 36. May not be discharged.

Specifically, the CPU 40 sets “0xEEEE” as a mask value in the white mask tables “1” to “360”, and sets “0x1111” as a mask value in the white mask tables [361] to [420] ( Data acquisition processing S103). The CPU 40 performs an AND operation on the set mask value of the white mask table and each bit of the raster data (S105 of the data acquisition process). In this case, the LF value shown in FIG. 14 corresponds to the remainder value “1, 2, 3, 0” when (Cnt−1) is divided by “4”, and the density information is 500 ( %), The LF values are “287, 287, 287, 291”, and when the density information is 600 (%), the LF values are “239, 239, 239, 243”. In this case, the reference LF value is (NM) / (Ph / Pu), where M is the number of nozzles 36 before and after the density is changed. Accordingly, the reference LF value when the unit density Pu (%) is 400%, the high density Ph (%) is 500 (%), the number of nozzles N = 420, and M = 60 is calculated as follows.
420−60 = 360
360 / (500/400) = 288
The LF values “287”, “287”, “287”, and “291” are obtained by setting the calculated value “288” as a reference LF value, n11 = n12 = n13-1, and n2 = 3. Similarly, the reference LF value when the density information is 600 (%) is calculated as follows.
420−60 = 360
360 / (600/400) = 240
The LF values “239”, “239”, “239”, and “243” are obtained by setting the calculated value “240” as the reference LF value, n11 = n12 = n13 = −1, and n2 = 3. . By doing so, clogging can be suppressed. Similarly to the above-described embodiment, the four adjacent pixels can be set to a high density Ph (%) of 500% by five main scans. That is, in order to make adjacent D × R pixels high density Ph (%) (where (j−1) × Pu <Ph <j × Pu) (an integer of j ≧ 2)), “j × (D × R) "main scans were required. In the first modification, printing with high density Ph (%) is possible in less than “j × (D × R)” times.

  In addition, the CPU 40 performs control based on the raster data, whereby the ratio of the number of times white ink is ejected from the first to 360th nozzles 36 and the ratio of the number of times white ink is ejected from the 361 to 420th nozzles 36. Can be different. In this case, when it is difficult to eject ink at 100 (%) by a nozzle, the ratio of the number of ink ejections from the nozzle can be reduced. Therefore, the influence of defective ejection of ink from the nozzle can be reduced. Specifically, the ratio of the number of times white ink is ejected from the first to 360th nozzles 36 is 75% of the total, and the ratio of the number of times white ink is ejected from the 361 to 420th nozzles 36 is 25% of the total. To do. In this way, the ratio of the number of times of ejection from the 1st to 360th nozzles 36 is made higher than the ratio of the number of times of ejection from the 361 to 420th nozzles 36. Thus, even when the discharge amount of the white ink is reduced due to clogging of the 361 to 420th nozzles 36, the pixel row of the white ink can be appropriately formed. The ratio of the number of times white ink is ejected from each of the first to 60th nozzles 36 is constant at 75% of the total, and the ratio of the number of times white ink is ejected from each of the 361 to 420th nozzles 36 is the entire ratio. 25% is constant. That is, the sum of the ratio of the number of times white ink is ejected from the 1st to 60th nozzles 36 and the ratio of the number of times white ink is ejected from the 361 to 420th nozzles 36 is 100%. The number of times white ink is ejected from each of the 61st to 360th nozzles 36 is constant at 100% of the total. As described above, the CPU 40 can easily control the discharge of the white ink from the nozzle 36. In this case as well, high-density Ph (%) printing can be performed with less than the number “j × (D × R)” of the conventional main scanning by relatively moving the nozzles in the sub-scanning direction based on the reference LF value. It becomes possible.

<Modification 2>
In the first modification, the CPU 40 sets the ratio of the number of times white ink is ejected from the 1st to 60th nozzles 36 to 75% of the total, and the ratio of the number of times white ink is ejected from the 61st to 360th nozzles 36 as a whole. The ratio of the number of times white ink is ejected from the 361 to 420th nozzles 36 is 25% of the total. On the other hand, CPU40 is good also considering the ratio of the frequency | count of each discharge as a ratio different from the above. For example, the CPU 40 sets the ratio of the number of times white ink is ejected from the 1st to 60th nozzles 36 to 50% of the total, and sets the ratio of the number of times white ink is ejected from the 361st to 420th nozzles 36 to 50% of the total. , You may match. In this case, the ratio of the number of ink ejections is 50% in the portion other than the ratio of the number of ink ejections ejected from the nozzles of 100%. Therefore, even if ejection failure occurs in the nozzle, the influence on the formed pixel row is 50% or less. Therefore, the possibility of banding is reduced. In this case as well, high-density Ph (%) printing can be performed with less than the number “j × (D × R)” of the conventional main scanning by relatively moving the nozzles in the sub-scanning direction based on the reference LF value. It becomes possible.

<Modification 3>
The CPU 40 varies the ratio of the number of times white ink is ejected according to the nozzle 36 between the 100% portion and the portion other than 100%, and the ratio of the number of times white ink is ejected in portions other than 100% is as follows. Depending on the nozzle 36, it may be different. The drying speed of the ink is different between the pixel row outside the portion where the image is formed and the pixel row inside. Therefore, the ink drying speed can be made uniform by making the ratio of the portion other than the ratio of the number of times of ejecting the white ink different depending on the nozzle 36. Therefore, the color development of the ink is made uniform. In this case as well, high-density Ph (%) printing can be performed with less than the number “j × (D × R)” of the conventional main scanning by relatively moving the nozzles in the sub-scanning direction based on the reference LF value. It becomes possible.

<Modification 4>
White ink is supplied to 420 nozzles 36 provided in the ejection head 35W through an ink supply path 60 shown in FIGS. Since the white ink is a sedimentary ink containing a pigment, ejection failure may occur in some nozzles far from the ink supply path. Accordingly, the ratio of the number of times white ink is ejected from the 1st to 60th nozzles 36 close to the ink supply path 60 is 75% of the total, and the number of times white ink is ejected from the 361 to 420th nozzles 36 far from the ink supply path 60. The ratio is 25% of the total, and ink is ejected with different ratios according to the distance of the nozzle 36 from the ink supply path 60. In this case, since the discharge amount of the 361st to 420th inks far from the ink supply path 60 is reduced, the ejection failure of the nozzles far from the ink supply path is reduced. In this case as well, high-density Ph (%) printing can be performed with less than the number “j × (D × R)” of the conventional main scanning by relatively moving the nozzles in the sub-scanning direction based on the reference LF value. It becomes possible.

  The present disclosure is not limited to the above-described embodiments and modifications, and various modifications can be made. In the above, the printing apparatus 30 ejected white ink from the nozzles 36 of the four ejection heads 35W. The printing apparatus 30 ejected cyan ink, magenta ink, yellow ink, and black ink from the nozzles 36 of the ejection heads 35C, 35M, 35Y, and 35K. On the other hand, the color of the ink ejected from the nozzles 36 of the four ejection heads 35W and the ejection heads 35C, 35M, 35Y, and 35K may be different from the color in the above embodiment.

  In the embodiment and the specific example, the printing apparatus 30 performs the relative movement of L1 in the sub-scanning direction of the carriage 34 three times in succession, and then performs the relative movement of L2 in the sub-scanning direction. For example, the relative movement of L2 in the sub-scanning direction of the carriage 34 may be performed first, and then the relative movement of L1 in the sub-scanning direction may be performed thereafter. Further, the relative movement of L1 in the sub-scanning direction may be performed before and after the relative movement of L2 in the sub-scanning direction of the carriage 34.

  In the embodiment and each modification, the white ink is used as the base ink. However, the present invention is not limited to this. For example, the base ink may be a discharge agent that removes the color of the print medium. In addition, the base ink may be a pretreatment agent that vividly develops color ink. An example of the pretreatment agent is a metal salt such as CaCl2.

    The number of ejection heads 35 (8), the number of nozzles 36 (420), and the interval (1/300 (in)) between adjacent nozzles 36 in the sub-scanning direction are examples, and other It may be a value.

  The arrangement of the four ejection heads 35W and the ejection heads 35C, 35M, 35Y, and 35K is not limited to the above example, and other arrangements may be used. The number of ejection heads 35W is not limited to four, but may be 1 to 3, and 5 or more. The ejection head 35K may not be provided on the carriage 34. The number of nozzles 36 included in the four discharge heads 35W may be smaller than the number of nozzles 36 included in each of the discharge heads 35C, 35M, 35Y, and 35K. Of the 420 nozzles 36 of the ejection head 35W, the number of nozzles 36 that are likely to be clogged is not limited to 60 (361 to 420th nozzles 36), and may be any other number.

  The above-described embodiment and each modification can be applied to the case where printing is performed by moving the platen 39 without moving the ejection head 35. That is, the printing apparatus 30 only needs to move the platen 39 and relatively move the ejection head 35 in the main scanning direction and the sub-scanning direction. Further, the above-described embodiment and modification can be applied to the case where printing is executed by moving the ejection head 35 in the main scanning direction and the sub-scanning direction.

  In each modification example of the above embodiment, in S113 of the data acquisition process, the CPU 40 performs 8 × indicated by 8 × 420 pointers set in the read pointer table [8] [420] of the print buffer [Cnt] 422. 420 pieces of raster data are specified. Next, the CPU 40 extracts all the left margin and right margin associated with the specified raster data from the raster information stored in the expansion buffer 425. Next, the CPU 40 sets the smallest left margin among all the left margins as the “final left margin” of the print buffer [Cnt] 422. Further, the CPU 40 sets the smallest write margin among all the write margins as the “final write margin” of the print buffer [Cnt] 422. Next, in S41 of the main process, the CPU 40 acquires the final left margin and the final right margin of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422, respectively. Next, the CPU 40 selects the smaller final left margin among the final left margins of the print buffer [Cnt−1] 422 and the print buffer [Cnt] 422. Similarly, the CPU 40 selects the smaller final write margin among the final write margins of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422. As described above, the CPU 40 selects the final left margin and the final right margin. However, the CPU 40 may select (acquire) by the following method.

  In S113 of the data acquisition process, the CPU 40 indicates 8 × 420 pointers set in the read pointer table [8] [420] of the print buffer [Cnt-1] 422 and the print buffer [Cnt] 422, respectively. Each of the 420 pieces of raster data is specified. Next, the CPU 40 extracts all the left margin and right margin associated with the specified raster data from the raster information stored in the expansion buffer 425. Next, the CPU 40 sets the smallest left margin among all the left margins as the “final left margin” of the print buffer [Cnt] 422. Further, the CPU 40 sets the smallest write margin among all the write margins as the “final write margin” of the print buffer [Cnt] 422. Next, in S41 of the main process, the CPU 40 acquires the final left margin and the final right margin of the print buffer [Cnt] 422, respectively.

  The CPU 40 shown in FIG. 3 loads various programs stored in a nonvolatile storage device (not shown) (for example, a flash memory) into the RAM 42, and executes various processes while using the RAM 42 as a working memory.

  Note that various programs for executing the above operation may be stored in a disk device or the like of a server device on the Internet, and the various programs may be downloaded to the computer of the printing apparatus 30.

  Depending on the embodiment, other types of storage devices other than the ROM 41 and the RAM 42 may be used. For example, the printing apparatus 30 may include a storage device such as a CAM (Content Addressable Memory), an SRAM (Static Random Access Memory), or an SDRAM (Synchronous Dynamic Random Access Memory).

  Depending on the embodiment, the electrical configuration of the printing apparatus 30 may be different from that in FIG. 3, and other hardware other than the standards and types illustrated in FIG. 3 may be applied to the printing apparatus 30. .

  For example, the control unit of the printing apparatus 30 illustrated in FIG. 3 may be realized by a hardware circuit. Specifically, the control unit may be realized by a reconfigurable circuit such as an FPGA (Field Programmable Gate Array), an ASIC, or the like instead of the CPU 40. Of course, the control unit may be realized by both the CPU 40 and the hardware circuit.

<Others>
The printing apparatus 30 is an example of an “image forming apparatus”. The CPU 40 is an example of a “control unit”. White ink is an example of “ink”. The nozzles [1] to [420] are an example of “a plurality of nozzles”. The main processes S17, S19, S29, S31, S41, S43, S45, S49, S53, S55, S59, S61, and S65 are examples of “ejection control”. The process of S152 of the high density determination process is an example of “determination control”. The ejection head 35W is an example of a “head”.

30 Printing device 35, 35W, 35C, 35M, 35Y, 35K Discharge head 36 Nozzle 39 Platen 40 CPU
60 Ink supply path

Claims (10)

A plurality of nozzles arranged in the sub-scanning direction and capable of discharging ink;
Based on the print data, the nozzle is moved relative to the print medium in the main scanning direction, the ink is ejected, and the nozzle is moved relative to the print medium in the sub-scanning direction, A control unit for forming an image of resolution R [dpi];
With
The nozzles are arranged at an interval D [in] in the sub-scanning direction,
The controller is
A unit density Pu [%] which is a total density of the maximum density of the ink that can be ejected from the nozzle at one time for each pixel in an adjacent pixel which is an adjacent pixel in the sub-scanning direction (R × D). The relative movement value of the nozzle in the sub-scanning direction when printing at a higher density Ph [%] (where (j−1) × Pu <Ph <j × Pu (an integer of j ≧ 2)). Alternatively, based on a reference LF (Line Feed) value (N × Pu / Ph) (where N is the number of the nozzles), which is an average value of movement values, printing is started to form the first pixel row in the main scanning direction. From the position, the nozzle is relatively moved a plurality of times in the sub-scanning direction, the nozzle is relatively moved in the main scanning direction a number of times less than (j × R × D), and the ink is ejected to eject the adjacent pixels. The density of the ink of each pixel is 100% or more and the adjacent An image forming apparatus that performs ejection control for controlling ejection of the ink and relative movement of the nozzle, wherein the total density of the ink of each pixel of the contact pixel is set to the high density Ph [%]. . The controller is
In the discharge control,
When printing at the high density Ph [%] for the adjacent pixels, the nozzle is moved in the sub-scanning direction {(R × D−1) + (Ph−Pu) / 100} times from the printing start position. Relatively moving (R × D) times, the nozzle is relatively moved in the main scanning direction (S17, S31, S45, S55, S65), and the ink is ejected from the nozzle to cause each pixel in the adjacent pixel The ink density is set to 100%, the unit density Pu (%) is set, and (Ph-Pu) / 100 times, one of the pixel rows in the adjacent pixels is overlapped to set the nozzle to the main density. Relative movement in the scanning direction (S31, S55, S65), the ink is ejected from the nozzle, and the total density of the ink of each pixel of the adjacent pixels is set to the high density Ph [%]. Request The image forming apparatus according to 1. The controller is
In the discharge control,
The nozzle is relatively moved in the main scanning direction, and the first ejection control is performed to eject the ink having the maximum density that can be ejected from the nozzle at a time,
The controller is
In the discharge control,
Further, the position of each nozzle is ((N / (Ph / Pu)) + n1k) × 1 / R (where n1k is an integer excluding “0” in absolute value | n1k | ≦ (R × D−1)). , {N11, n11 + n12, n11 + n12 + n13,..., .SIGMA.n1k (k = 1, 2,..., (D.times.R-1)} each divided by the number of adjacent pixels D.times.R is { 1, 2, 3,... (D × R−1)}), and a first movement control for relative movement in the sub-scanning direction;
After the execution of the first movement control, the second ejection control for relatively moving the nozzle in the main scanning direction and ejecting the ink with the maximum density that can be ejected from the nozzle in one time;
<{(D × R−1) + (Ph−Pu) / 100} −round [{(R × D−1) + (Ph−Pu) / 100} / (D × R)]> times. ,
The round is a function for truncating the decimal part.
The controller is
In the discharge control,
The position of each nozzle is further set to ((N / (Ph / Pu)) + n2 + m) × 1 / R (where n2 is the sum of n1k at the time of (D × R−1) repetitions of the first movement control). Sigma n1k converted number, m is an integer of 0 ≦ m ≦ (D × R−1)), the second movement control for relative movement in the sub-scanning direction;
After the execution of the second movement control, the third ejection control for relatively moving the nozzle in the main scanning direction and ejecting the ink having the maximum density that can be ejected from the nozzle at one time;
Are executed round [{(R × D−1) + (Ph−Pu) / 100} / (D × R)] times.
The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus. The controller is
2. The image forming apparatus according to claim 1, wherein the ejection control causes the ink to be ejected by changing a ratio of the number of times the ink is ejected from each of the plurality of nozzles according to the nozzle. 3. . The controller is
The ink is ejected by changing the ratio of the number of times the ink is ejected from each of the plurality of nozzles to 100% and 50% according to the nozzle in the ejection control. The image forming apparatus according to 1. The controller is
In the ejection control, the ratio of the number of times the ink is ejected from each of the plurality of nozzles is varied between 100% and other than 100% according to the nozzle, and the ink other than the 100% is ejected. The image forming apparatus according to claim 1, wherein the number of times is varied depending on the nozzle to cause the ink to be ejected. The nozzle includes an ink supply path through which the ink is supplied,
The controller is
The ejection control causes the ink to be ejected by changing a ratio of the number of times the ink is ejected from each of the plurality of nozzles according to a distance of the nozzle from the ink supply path. Item 2. The image forming apparatus according to Item 1. The controller is
Based on the print data, further executes determination control for determining whether to print at the high density Ph [%] higher than the unit density Pu [%] in the adjacent pixels,
8. The printing according to claim 1, wherein when it is determined that printing is performed with the high density Ph (%), the printing with the high density Ph [%] is performed on the adjacent pixels in the ejection control. An image forming apparatus according to claim 1.   The image forming apparatus according to claim 1, further comprising a head provided with the nozzle.     The image forming apparatus according to claim 1, wherein the ink is a white ink.

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