JP5262603B2 - Liquid ejection control device, liquid ejection control method, and liquid ejection control program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively prevent gloss irregularities and density irregularities without lowering a printing speed. <P>SOLUTION: A duty D<SB>1</SB>(N) is predetermined by a quadratic function of monotonous increase in which the slope becomes gradually steep at nozzle groups of the leading side, and a duty D<SB>3</SB>(N) is predetermined by a quadratic function of monotonous decrease in which the slope becomes gradually steep at nozzle groups of the rear side. These are formed symmetric with respect to a straight line representative of 50%. By contrast, the duty D<SB>1</SB>(N) and the duty D<SB>3</SB>(N) are made asymmetric with respect to a line in a direction orthogonal to the straight line. A duty D<SB>2</SB>(N)=100 is held for middle nozzle groups. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  In the present invention, the ejection target medium and the ejection nozzle row are relatively scanned in the main scanning direction, which is a direction intersecting the ejection nozzle row, with the ejection medium and the ejection nozzle row that ejects the liquid. The present invention relates to a liquid ejection control apparatus, a liquid ejection control method, and a liquid ejection control program that perform sub-scanning relatively in a sub-scanning direction substantially orthogonal to the main scanning direction.

By performing main scanning a plurality of times with respect to the same raster line on the ejection target medium, overlap type droplet ejection for forming the raster line is performed (see Patent Document 1). By performing such overlapping-type droplet ejection, it is possible to suppress the influence of variations in individual main scans, and to obtain a printing result with a good final image quality.
JP 2002-11859 A

By performing the main scan a plurality of times, the droplets land on the same raster line over a plurality of times. The injection nozzle row tends to have a larger error at the end due to the inclination at the time of manufacture. At this time, by increasing the amount of ink linearly toward the center of the ejection nozzle row in accordance with the number of main scans, the use of end portions where errors are likely to increase is reduced, thereby reducing uneven gloss and uneven density. It has also been proposed. However, when the ink amount is linearly increased, the increase (slope) of the ink amount corresponding to the number of main scans becomes uniform, so that a constant density is reproduced if the amount of ink landed at the initial stage is extremely small. For this reason, the number of main scans required for the increase does not increase, and the printing speed decreases.
The present invention has been made in view of the above problems, and provides a printing apparatus that effectively prevents uneven gloss and uneven density without reducing the printing speed. Furthermore, the problem is not limited to a printing apparatus that ejects ink droplets, but a general liquid ejection control device that ejects liquid droplets, a liquid ejection control method, and a liquid ejection control program also have the same problem. Provided is an application to the general liquid ejection control device, the liquid ejection control method, and the liquid ejection control program.

  In order to solve the above-mentioned problem, in the present invention, the ejection target medium and the ejection nozzle array that ejects liquid are relatively main-scanned in a main scanning direction that intersects the ejection nozzle array, and the ejection target When the medium and the ejection nozzle row are relatively sub-scanned in the sub-scanning direction orthogonal to the main scanning direction, the main scanning is performed a plurality of times for main scanning lines at the same position in the sub-scanning direction on the ejection target medium. It is assumed that That is, the present invention is premised on performing overlap printing. In performing overlap printing, the ejection rate for each main scan that the ejection nozzle row ejects with respect to the main scan line includes an increase and a decrease between the main scans. The injection is controlled to be asymmetric. In other words, since the ejection rate for each main scan varies asymmetrically, adjustment of the variation in the ejection rate according to the characteristics of the liquid and the ejection medium can be realized. Note that the main scanning direction and the sub-scanning direction do not have to be strictly orthogonal, and may intersect at an angle within a range of some variation with respect to 90 degrees.

  Further, liquid is ejected from a plurality of ejection nozzles to the main scanning line at the same position in the sub-scanning direction, and the ejection rate for each main scanning ejected by each ejection nozzle is asymmetric with respect to the position of the ejection nozzle. The injection is controlled so that Even in this case, the ejection rate for each main scan ejected to a certain main scan line can be varied asymmetrically. Note that the main scanning line at the same position in the sub-scanning direction is intentionally performed at the same position. For example, even if an offset amount or a mechanical accuracy error amount in interlace is included, it corresponds to the same position of the present invention.

Further, in the head-side injection nozzle group that first reaches the target medium to be sub-scanned, the injection rate for each main scan becomes nonlinear as it reaches the rear side that finally reaches the target medium. As a result, the amount of liquid that first lands on the ejected medium can be suppressed. On the other hand, in the rear side injection nozzle group, the injection rate for each main scan decreases nonlinearly toward the rear side. By doing in this way, the said injection rate decreased in the said head side injection nozzle group can be supplemented by the said back side injection nozzle group, and it can prevent that the said injection rate becomes non-uniform | heterogenous.
As one aspect of the present invention, the medium to be ejected and the ejection nozzle array that ejects the liquid are relatively main-scanned in a main scanning direction that intersects the ejection nozzle array, A liquid ejecting control apparatus that relatively sub-scans an ejection nozzle row in a sub-scanning direction orthogonal to the main scanning direction, wherein a predetermined ejection nozzle ejects a main scanning line at the same position in the sub-scanning direction. An injection control means for controlling the injection so that the injection rate of each injection nozzle is asymmetric with respect to the position of the injection nozzle when the ratio responsible for the injection rate is the injection rate and the maximum value of the injection rate is 100% In the first injection nozzle group that first reaches the target medium to be sub-scanned, the injection rate increases nonlinearly as it becomes the rear side that finally reaches the target medium, Rear side In the injection nozzle group, the injection rate decreases nonlinearly toward the rear side, and the injection rate is constant in the injection nozzle group between the front injection nozzle group and the rear injection nozzle group. In addition, the increase and the amount of decrease may be in a complementary relationship.

  Further, in the head side injection nozzle group, as the injection rate for each main scan increases non-linearly toward the rear side, the increase amount may increase as it goes to the rear side. . By doing in this way, the said injection rate in the said injection | spray nozzle group can be effectively suppressed. For example, in the head side injection nozzle group, the injection rate in the head side injection nozzle group is effectively increased by increasing the injection rate like a rising portion from a quadratic function inflection point. Can be suppressed. Further, the ejection rate may be controlled differently depending on the type of liquid ejected from the ejection nozzle. Since the ejection characteristics vary depending on the type of liquid, it is desirable to control the ejection rate suitable for each type of liquid.

  Further, the ejection rate may be controlled differently depending on the type of liquid ejected from the ejection nozzle. Since the ejection characteristics vary depending on the type of liquid, it is desirable to control the ejection rate suitable for each type of liquid. Specifically, when a liquid having a longer fixing time in the ejection medium than other liquids is ejected from the ejection nozzle row, of the main scans with respect to the main scan line at the same position in the sub-scanning direction. It is desirable that the ejection rate in the initial main scan is higher than that of other liquids. Since a large amount of liquid with a long fixing time in the ejection medium can be ejected and fixed at an initial stage, problems such as bleeding and unevenness can be suppressed. In general, since the liquid having a lower density tends to have a longer fixing time, the ejection rate in the initial main scan among the main scans may be adjusted according to the density.

  In particular, when a pair of liquids having the same mixed material and having different concentrations of the mixed material are ejected from the ejection nozzle row, the sub-scanning direction is selected for one of the pair of liquids having a low concentration. Among the main scans for the main scan line at the same position, the ejection rate in the initial main scan may be higher than the other. By doing so, it is possible to eject and fix a large amount of the liquid having a long fixing time in the ejection target in the initial stage. Further, when the ejection control unit ejects the first and second liquids having a larger ejection amount than the other liquids from the ejection nozzle row, the first liquid has the same position in the sub-scanning direction. It is desirable that the ejection rate in the initial main scan among the main scans for the main scan line is higher than that of the second liquid. Further, since the fluctuations in the ejection rates of the first and second liquids are made symmetrical to each other, it is possible to prevent the ejection rates of both the liquids from becoming high in the initial main scanning and the final stage of each main scanning. By doing so, the total amount of the ejection amount of each main scan with respect to the main scan line can be reduced, and bleeding and unevenness can be prevented.

  Furthermore, the technical idea of the present invention can be embodied not only by a specific liquid ejection control device but also by a method thereof. That is, the present invention can also be specified as a method having steps corresponding to each means performed by the liquid ejection control apparatus described above. Of course, when the above-described liquid ejection control apparatus reads the program to realize each of the above-described means, the technique of the present invention is applied to a program for executing a function corresponding to each of the means and various recording media on which the program is recorded. Needless to say, the idea can be embodied. Needless to say, the liquid ejection control device of the present invention can be distributed not only by a single device but also by a plurality of devices. For example, each unit included in the liquid ejection control device can be distributed in both the printer driver executed on the personal computer and the printer. In addition, each unit of the liquid ejection control apparatus of the present invention can be included in a printing apparatus such as a printer.

Hereinafter, embodiments of the present invention will be described in the following order.
A. Device configuration B. Print control process Print result D.E. About combinations of multiple inks Modified example

A. Apparatus Configuration FIG. 1 schematically shows a hardware configuration of a liquid ejection control apparatus according to an embodiment of the present embodiment. In the figure, the liquid ejection control device is mainly constituted by a computer 10, which has a CPU 11, a RAM 12, a ROM 13, a hard disk drive (HDD) 14, a general purpose interface (GIF) 15, and a video interface (VIF) 16. An interface (IIF) 17 and a bus 18 are included. The bus 18 implements data communication between the elements 11 to 17 constituting the computer 10, and communication is controlled by a chip set (not shown). The HDD 14 stores program data 14a for executing various programs including an operating system (OS), and the CPU 11 executes calculations according to the program data 14a while expanding the program data 14a in the RAM 12. . The GIF 15 provides an interface conforming to the USB standard, for example, and connects an external printer 20 to the computer 10. The VIF 16 connects the computer 10 to an external display 40 and provides an interface for displaying an image on the display 40. The IIF 17 connects the computer 10 to an external keyboard 50a and a mouse 50b, and provides an interface for the computer 10 to acquire input signals from the keyboard 50a and the mouse 50b.

  FIG. 2 schematically shows a software configuration of a program executed by the computer 10. In the figure, the computer 10 mainly executes an OS P1, an application P2, a printer driver P3 (liquid ejection control program), and a display driver P4. The OS P1 provides an API that can be commonly used by each program. The application P2 is an application program for generating the print data PD, and generates the print data PD according to an input operation from the keyboard 50a or the mouse 50b. The printer driver P3 includes a renderer P3a, a color conversion unit P3b, a halftone unit P3c, a rasterizer P3d (ejection control means), and a print control data output unit P3e. The renderer P3a performs processing for drawing print image data based on the print data PD. The color conversion unit P3b acquires the print image data, and converts the print image data into data in the ink amount space used by the printer 20. The halftone portion P3c acquires the color-converted print image data, performs halftone processing on the print image data, and generates halftone data HTD. The rasterizer P3d acquires the halftone data HTD, decomposes the halftone data HTD, and generates nozzle discharge data ND in each main scan. The print control data output unit P3e generates print control data PCD based on the nozzle discharge data ND and outputs it to the printer 20. Details of the print control process executed by the printer driver P3 will be described later.

  FIG. 3 shows a schematic configuration of the printer 20 according to the present embodiment. In the figure, a printer 20 includes a main controller 21, a paper feed controller 22, a paper feed motor 22a, a carriage controller 23, a carriage motor 23a, a head controller 24, a driver 24a, a communication interface (IF) 25, a bus 26, and a print head HD. And each unit communicates data with each other via the bus 26. The communication IF 25 receives the print control data PCD transmitted from the computer 10 and sends it to the main controller 21. The main controller 21 acquires the print control data PCD, and controls the paper feed controller 22, the carriage controller 23, and the head controller 24 based on the print control data PCD.

  The paper feed controller 22 controls the drive amount and drive timing of the paper feed motor 22a based on the print control data PCD. The paper feed motor 22a drives a paper feed roller that transports the print paper P as an ejected medium, and the print paper P is fed (sub-scanned) by driving the paper feed motor 22a. The carriage controller 23 controls the drive amount and drive timing of the carriage motor 23a based on the print control data PCD. The carriage motor 23a reciprocates (main scans) the carriage having the print head HD in a direction orthogonal to the direction in which the printing paper P is sub-scanned.

  In the ejection head HD of the present embodiment, a nozzle row in which ejection nozzles NZ for each color of CMYK are arranged in the sub-scanning direction is provided, and the row of each ejection nozzle NZ is arranged in the main scanning direction. The ejection head HD has a length of 1 inch in the main scanning direction. In each nozzle row, 360 ejection nozzles NZ are arranged at a uniform pitch in the sub-scanning direction. That is, the density of the discharge nozzles NZ in the sub-scanning direction of the discharge head HD is 360 dpi. Each discharge nozzle NZ communicates with an ink chamber to which ink is supplied, and a piezoelectric element (not shown) that applies mechanical pressure to the ink chamber is provided for each discharge nozzle NZ.

  The head controller 24 causes the driver 24a to generate a drive pulse to be applied to each piezo element of the print head HD based on the print control data PCD. Thereby, a plurality of ink droplets are ejected from each ejection nozzle NZ, and the ink droplets land on the printing paper P and dry, whereby a plurality of ink dots are recorded on the printing paper P. When the print head HD performs one main scan, a raster line can be formed on the print paper P in the main scan direction by outputting a drive pulse a plurality of times to each piezo element. The density of ink dots in the main scanning direction on the printing paper P can be adjusted by adjusting the output period of the drive pulse, and the ink dots in the main scanning direction on the printing paper P can be adjusted by adjusting the output timing. The formation position of can be adjusted. The output period and output timing of the drive pulse are controlled mainly based on the nozzle discharge data ND generated by the rasterizer P3d. In the present embodiment, a bidirectional printing method is employed in which drive pulses are output when the print head HD performs main scanning in each of the forward direction and the backward direction.

  FIG. 4 shows the main scanning of the ejection head HD and the sub-scanning of the printing paper P. In this embodiment, bidirectional printing is performed, and the ejection head HD alternately performs main scanning while ejecting (jetting) ink from each ejection nozzle NZ. Further, the paper feed controller 22 sub-scans the printing paper P by 1/6 inch each time the ejection head HD completes one main scanning. By performing main scanning and sub-scanning in this way, a two-dimensional plane image can be formed on the printing paper P. Further, it is assumed that one pass cycle is constituted by one sub-scan and one main scan. In the odd-numbered pass cycle, the ejection head HD performs main scanning in the right direction on the paper surface, and in the even-numbered pass cycle, the ejection head HD performs main scanning in the right direction on the paper surface. The pass cycle number is represented as C.

  In FIG. 5, the relative positional relationship between the ejection head HD and the printing paper P is schematically shown. For simplification of illustration, only a single nozzle row (one row of C ink) is shown. The ejection head HD moves only in the main scanning direction and does not actually move in the sub-scanning direction, but moves relative to the printing paper P by the sub-scanning of the printing paper P. It is illustrated that the ejection head HD is moved in the sub-scanning direction over the pass cycle of C = 1 to 6 while being fixed. Since the printing paper P is sub-scanned from the lower side of the paper surface to the upper side with respect to the ejection head HD, the lower side of the paper surface of the ejection head HD first reaches the printing paper P. For this reason, the lower side of the paper surface of the ejection head HD is referred to as the leading side, and the upper side of the paper surface is referred to as the rear side. Each discharge nozzle NZ has a nozzle number N, the discharge nozzle NZ at the front end is number 1 (N = 1), and the discharge nozzle NZ at the rear end is number 360 (N = 360). ). Furthermore, 60 discharge nozzles NZ are grouped in groups, the most front group being the first (M = 1) nozzle group, and the most rear group being the sixth (M = 6) nozzle group. To do.

  In the present embodiment, the paper feed controller 22 sub-scans the printing paper P by 1/6 inch each time the ejection head HD completes one main scanning. Accordingly, in the drawing, the discharge head HD advances with respect to the printing paper P downward by 1/6 inch. Therefore, when a discharge nozzle NZ belonging to the (M = m) number nozzle group is in charge of forming an ink dot at a certain position in the sub-scanning direction on the printing paper P in a certain pass cycle, in the next pass cycle, The discharge nozzles NZ belonging to the (M = m + 1) th nozzle group are in charge of forming ink dots at the positions. More specifically, when the n-th ejection nozzle NZ is in charge of forming an ink dot of a main scanning line L in the sub-scanning direction on the printing paper P in a certain pass cycle, in the next pass cycle, The (N = n + 60) th discharge nozzle NZ is in charge of forming the ink dots of the main scanning line L. Further, in the first pass cycle (C = 1), the C (C ≦ 6) th arbitrary C (C ≦ 6) th with respect to the main scanning line L in which the n (n <60) th discharge nozzle NZ was in charge of ink dot formation. It can be said that the discharge nozzle NZ in which the ink dots are formed in the pass cycle is the (N = n + 60 × (C−1)) th discharge nozzle NZ.

  FIG. 6 shows an arrangement rule of ink dots (recording pixels) in the present embodiment. In the drawing, a detailed position where the (N = n + 60 × (C−1)) th nozzle forms an ink dot on the main scanning line L of the printing paper P in each pass cycle is schematically shown. Here, the number of each pass cycle and an arrow indicating the direction of reciprocation of each pass cycle are shown in association with the ink dot formation position. Basically, the position on the printing paper P where the (N = n + 60 × (C−1)) th nozzle forms the ink dot is substantially the same, but in this embodiment, the position is slightly shifted. Ink dots are formed at a recording density of 720 × 720 dpi. Here, the positions of the ink dots formed in the (C = 1, 4, 5) th pass cycle and the (C = 2, 3, 6) th pass cycle are the pitches of the discharge nozzles NZ in the sub-scanning direction. The paper feed controller 22 adjusts the paper feed amount so as to shift by half the distance.

  Thereby, an ink dot density of 720 dpi can be realized in the sub-scanning direction. The positions of the ink dots formed in the (C = 1, 2) pass cycle, the (C = 3, 4) pass cycle, and the (C = 5, 6) pass cycle are the main scans. The head controller 24 adjusts the ejection timing so as to shift by 1/720 inch in the direction. It should be noted that by repeating ejection at each periodic ejection timing in a single main scan, the recording density of the ink dots alone formed in each pass cycle becomes 360 dpi in the main scan direction, and as a result, in all pass cycles The recording density in the main scanning direction is 720 dpi. The above arrangement rule is uniformly determined for all areas where ink dots can be formed. By designating an arbitrary position on the printing paper P, a pass cycle for forming ink dots at that position and the discharge nozzles NZ. It is possible to specify the discharge timing. In the present embodiment, the following print control process is executed on the premise of the ink dot arrangement rule as described above.

B. Print Control Processing FIG. 7 shows the flow of print control processing executed by the printer driver P3. The renderer P3a acquires the print data PD generated by the application P2 in step S100. For example, text data, a drawing command, etc. are acquired as the print data PD. In step S110, the renderer P3a generates print image data including a plurality of pixels having color information in the RGB color space by performing drawing based on the print data PD. In step S120, the color conversion unit P3b acquires the drawn print image data, and converts it into print image data in which the color of each pixel is expressed in the CMYK ink amount color space used by the printer 20. At that time, a color conversion profile that defines the correspondence between the RGB color space and the ink amount color space is used. In step S130, the halftone unit P3c acquires print image data in the ink amount color space, and performs halftone processing by the dither method, the error diffusion method, or the like on the print image data. As a result, halftone data HTD instructing whether or not to eject ink for each pixel is generated for each ink. In step S140, the rasterizer P3d executes the rasterization process based on the halftone data HTD, thereby generating the nozzle discharge data ND.

  FIG. 8 shows a detailed flow of the rasterizing process. In the figure, halftone data HTD for C ink is input to the rasterizer P3d (step S141). In the halftone data HTD, each position on the printing paper P is designated by each pixel having a pixel density of 360 × 360 dpi, and it is instructed whether or not C ink is ejected for each pixel. By comparing the arrangement rule of the ink dots (recording pixels) shown in FIG. 6 with the position of each pixel of the halftone data HTD, it is determined whether or not each ink dot should be formed (step S142). As described above, when it can be determined whether or not each 720 × 720 dpi ink dot shown in FIG. 6 should be formed, the data is discharged from each discharge nozzle NZ in each main scan based on the arrangement rule of FIG. Is disassembled into nozzle discharge data ND for specifying (step S143).

  FIG. 9 schematically illustrates how nozzle discharge data ND for a certain discharge nozzle NZ is generated in a certain main scan. This figure shows a state in which dot formation data indicating that ink dots should be formed at all positions that can be ejected in a certain main scan is input based on halftone data HTD. In FIG. 9, a mask is conceptually illustrated. By applying a mask to each dot formation data, ink is actually ejected by a ratio corresponding to the duty in the formation of ink dots originally designated by the dot formation data. Restrictions will be added. Thereby, nozzle discharge data ND for instructing whether or not discharge is possible for a certain discharge nozzle NZ in a certain main scan is generated. Note that if the discharge restriction is biased in the main scanning direction, it appears as a bias in ink density in the main scanning direction, so it is desirable to use a uniform mask in the main scanning direction. Further, as schematically shown in FIG. 9, it can be considered that the printer 20 generates a drive pulse to be output to each piezo element based on the nozzle discharge data ND after the mask processing. The duty described above is defined for each discharge nozzle NZ, that is, according to the position of each discharge nozzle NZ in the sub-scanning direction.

FIG. 10 illustrates a change in duty defined according to the position of the discharge nozzle NZ in the sub-scanning direction. In this duty, the first to 120th discharge nozzles NZ (corresponding to M = 1 and 2 in the nozzle group) and the 121st to 240th discharge nozzles NZ in the middle (corresponding to M = 3 and 4 in the nozzle group) are discharged. For the nozzle NZ and the rear side 240-360th discharge nozzles NZ (corresponding to M = 5 and 6 in the nozzle group), different duty shapes are defined. This duty is expressed by the following equation (1).

In the above equation (1), D ₁ (N), D ₂ (N), D ₃ (N) indicate the duty [%] for each discharge nozzle NZ, and D ₁ (N), D ₂ (N ), D ₃ (N) is expressed as a function of nozzle number N. In the first to 120th discharge nozzles NZ on the front side, the duty D ₁ (N) is represented by a monotonically increasing quadratic function whose slope gradually increases, and in the 240th to 360th discharge nozzles NZ on the rear side. The duty D ₃ (N) is represented by a monotonically decreasing quadratic function whose slope gradually increases. D ₁ (N) and D ₃ (N) are symmetrical with respect to a straight line indicating a certain density when expressed in a graph. That is, the top side of the duty D ₁ N in any n of (N) duty D ₁ of the when (0 <n ≦ 120) was substituted for (n), and the N of the duty D ₃ of the rear side (N) ( A mutually complementary relationship is established in which the sum of duty D ₃ (n + 240) to which n + 240) is substituted is always 100%. On the other hand, the duty D ₁ (N) and the duty D ₃ (N) are asymmetric with respect to the line in the direction orthogonal to the straight line. That is, the duty for each nozzle is asymmetric with respect to the nozzle position. Since the 121-240 th discharge nozzle NZ intermediate is duty D ₂ (N) = 100, mask processing with respect to the nozzle discharge data ND of Figure 9 is not performed substantially.

The discharge nozzle NZ at the leading end has a duty D ₁ (n) immediately after rising from the inflection point of the quadratic curve, so that the discharge rate is greatly suppressed. In the present embodiment, the above-described duty restriction is performed on the nozzle discharge data ND of each main scan, thereby generating the nozzle discharge data ND considering the duty. Although only C ink has been described here, the same rasterization process is performed for other MYK inks. When the nozzle discharge data ND for each discharge nozzle NZ in each main scan can be generated as described above, the rasterizing process is terminated. In step S150 in FIG. 7, the print control data output unit P3e generates print control data PCD by attaching data for controlling the paper feed controller 22 and the carriage controller 23 to each nozzle discharge data ND. Further, the print control data PCD is output to the printer 20 and the printer 20 actually executes printing. As a result, main scanning and sub-scanning as shown in FIGS. 4 to 6 are sequentially performed.

C. Printing Result FIG. 11 schematically shows how ink dots are formed on the printing paper P. In the figure, on the printing paper P when printing an image in which the halftone result of the C ink is uniform over the entire area (for example, an image showing ejection of all pixels of the halftone data HTD) on the printing paper P. The ink dot density change is shown for each pass cycle. By performing mask processing on such an image in step S144, a density distribution corresponding to the duties D ₁ (N), D ₂ (N), and D ₃ (N) is formed in each pass cycle. It will be. In addition, since it can be considered that the amount of ink ejected to form each ink dot is uniform, it is considered that the density distribution corresponds to the distribution of the ink amount ejected at each sub-scanning position. be able to. During each pass cycle, the discharge head HD advances relative to the printing paper P by 1/6 inch, and is responsible for forming ink dots on the main scanning line L at a predetermined position in the sub-scanning direction. One nozzle group will shift to the rear side one by one. More specifically, the nozzle number N of the discharge nozzles NZ formed by the ink dots of the main scanning line L increases by 60. In each pass cycle, the main scanning direction is alternated.

According to the duty D ₁ (N) that prescribes the ink dot density of the nozzle group (M = 1, 2) that reaches the printing paper P first, the rising edge immediately after the inflection point of the quadratic curve causes the printing paper P to The amount of ink ejected first can be suppressed as much as possible. Thereby, it is possible to suppress ink bleeding and aggregation in the initial stage of ink dot formation. By holding the ink droplets at an appropriate position at the initial stage of ink dot formation, it is possible to prevent bleeding and aggregation of ink droplets that land after that. Accordingly, it is possible to prevent uneven glossiness and uneven density in the final print finish. In this way, by defining the duty by a non-linear function, it is possible to finely control the density of ink dots. In the forward pass cycle (C = 1, 3, 5), it is the odd-numbered (M = 1, 3, 5) nozzle group that is responsible for forming the ink dots of the main scanning line L, and the sub-pass pass cycle. In (C = 2, 4, 6), it is the even-numbered (M = 2, 4, 6) nozzle group that takes charge of the ink dot formation of the main scanning line L.

Here, the duty D ₁ N in any n of (N) duty (0 <n ≦ 120) when substituting D ₁ corresponding to the nozzle group of the head-side (n), and corresponding to the nozzle group of the rear side The mutual complementarity relationship is established so that the sum of duty D ₃ (n + 240) obtained by substituting (n + 240) for N of duty D ₃ (N) to be performed is always 100%. Therefore, the discharge amount (ink dot density) of the nozzle group (M = 1) in the forward pass cycle (C = 1) is set to the discharge amount of the nozzle group (M = 5) in the forward pass cycle (C = 5). It can be complemented by the amount (ink dot density). That is, even if the ink dot density by the head nozzle group is reduced by the duty D ₁ (N), the decrease can be compensated by the ink dot density increase by the rear nozzle group. The initial ink dot density can be suppressed without increasing the cycle. Similarly, the ejection amount (ink dot density) of the nozzle group (M = 2) in the backward pass cycle (C = 2) is equal to that of the nozzle group (M = 6) in the backward pass cycle (C = 6). It can be complemented by the discharge amount (ink dot density). Accordingly, the ink dot density is constant at the time when all the pass cycles are completed at any position in the sub-scanning direction. In addition, since the ink dot density formed by all pass cycles in the forward direction and the ink dot density formed by all pass cycles in the backward direction are the same, there is a difference between the ejection characteristics in the reciprocating direction. Even in this case, a uniform ink dot density can be maintained.

D. Combination of Multiple Inks FIG. 12 shows an example of the duty. In the figure, the duty for the discharge nozzle NZ that discharges C ink and the duty for the discharge nozzle NZ that discharges M ink are shown in comparison. In the above-described embodiment, only the discharge nozzle NZ that discharges C ink has been described as an example. However, since the discharge nozzle NZ that discharges MYK ink is also provided in reality, these discharge nozzles NZ are also masked. It is necessary to define a duty for performing processing. By specifying the duty as described above, it is possible to prevent ink bleeding and unevenness. However, since ink bleeding and unevenness occur not only in a single ink but also in a plurality of inks, it is possible to use various types of ink. It is desirable to set the duty in consideration of the usage situation.

  As shown in FIG. 12, the duty of the CM ink to be paired is symmetrical with respect to the duty axis. Specifically, the duty of C ink is increased from the initial stage of raster line formation, while the duty of M ink is decreased. On the contrary, at the end of raster line formation, the duty of M ink is lowered and the duty of C ink is raised. In the present embodiment, when average image data is color-converted, the amount of CM ink tends to be larger than that of other YK inks, so the duty of CM ink is as shown in FIG. I have control. The CM ink tends to have a higher density of ink dots than other YK inks, and when the ink dots of the CM ink land on the printing paper P at the same time, ink bleeding and unevenness are likely to occur. That is, in order to prevent ink bleeding and unevenness, it is desirable not to land ink dots of CM ink as much as possible. As shown in FIG. 12, while the duty of the C ink is increased from the beginning, while the duty of the M ink is decreased, the interference between the CM inks in the initial stage can be prevented.

  In this embodiment, a pair of CM inks has been described as an example in which the ink amount is larger than that of other inks. However, the present invention is not limited to CM inks. In the present embodiment, the color conversion unit P3b refers to the color conversion profile and performs color conversion to the image data of the ink amount of CMYK ink. Therefore, which ink amount increases depends on the color conversion profile. . Even if the average amount of CM ink tends to be larger than other YK inks in average image data, for example, if the image data is monochrome, the amount of K ink is higher than that of other inks. Become more. Accordingly, an ink pair having a larger amount of ink than other inks may be selected according to the print mode (color conversion profile) or the like. In this embodiment, the duty of the C ink, which has a lower fixability than that of the M ink, is increased from the beginning of the raster line formation. However, if there is no significant difference in the fixability of the CM ink, the duty of the M ink is changed to the raster. You may make it high from the beginning of line formation. The fixability can be grasped by the fixing time required from when the ink dots land on the printing paper P until the ink is fixed. Generally, the ink having a lower density should be vaporized in order to fix the color material (mixed material). It can be considered that the fixing time becomes longer because the amount of water increases. Note that once the color material is fixed on the printing paper P, interference with other ink dots hardly occurs. For this reason, it is desirable to fix the low density ink before reaching the middle of the raster line formation where a large amount of ink dots land.

  FIG. 13 shows another example of the duty. In this example, it is assumed that the ejection head HD also includes ejection nozzles NZ for ejecting lc (light cyan) lm (light magenta) ink in addition to CMYK ink. Note that the lclm ink is prepared by preparing the same color material as the CM ink at a low density. As shown in FIG. 13, C ink and lc ink are paired, and M ink and lm ink are paired. And the duty of the ink which becomes a pair mutually becomes a shape symmetrical with respect to the duty axis. Specifically, the duty of lclm ink is increased from the initial stage of raster line formation, while the duty of CM ink is decreased. On the other hand, at the end of raster line formation, the duty of lclm ink is lowered and the duty of CM ink is raised. In this way, for the lclm ink whose fixing time is longer than that of the CM ink, ink dots can be landed on the printing paper P at the initial stage of raster line formation, and a large number of ink dots land on the middle stage. Before, it is possible to fix lclm ink to some extent. Therefore, it is possible to prevent ink bleeding and unevenness from occurring in the middle of the raster line formation.

E. Modified Example FIG. 14 shows the duty according to a modified example. In the figure, the curve is changed to a cubic curve so that the duty D ₁ (N) corresponding to the nozzle group on the head side becomes smaller than that in the above embodiment. Thereby, the density of ink dots formed by the nozzle group on the head side can be further suppressed. For example, when it is known that the ink droplet speed discharged from the discharge nozzle NZ belonging to the head nozzle group and the natural frequency of the piezoelectric element that generates the mechanical energy required for discharge from the discharge nozzle NZ are large. In this case, it is desirable to switch so that the duty D ₁ (N) based on the cubic curve as in the present modification is applied instead of the duty D ₁ (N) based on the above-described quadratic curve. Of course, a Bezier curve, an exponential function, or the like can be used as a nonlinear function that defines the duty. Moreover, it is not restricted to a strict curve, It is good also as the staircase shape which becomes a curve if it approximates. Further, in the above-described embodiment, it is assumed that the size of the ink droplets ejected from the ejection nozzle NZ is constant for the sake of simplification. The present invention can be applied. For example, when three types of ink dots, large dots, medium dots, and small dots, can be formed, ejection is performed with equal probability for ejection of large dots, medium dots, and small dots in the nozzle ejection data ND. Mask processing for restricting ejection may be performed, or mask processing for restricting ejection may be performed with different probabilities according to dot sizes.

  In the above-described embodiment, an example in which paper is fed by 1/6 inch with respect to a 1-inch ejection head HD is illustrated, but the size and the paper feed amount of the ejection head HD are not limited to these. Of course, the resolution is not limited to the case where the printing of the same portion is completed by six pass cycles, but also when the printing is completed by more pass cycles or when the paper feed width in the sub-scanning direction is different for each pass. The present invention can also be applied to printing with the printer. In the above-described embodiment, the printer driver P3 executed on the computer performs the rasterization. However, the printer 20 itself may perform the rasterization. Of course, the processing is not limited to the one in which rasterization is executed by software, and equivalent processing may be executed by hardware. Furthermore, although the above-described embodiment exemplifies what forms a print image by ejecting liquid, the present invention only needs to be able to control liquid ejection, for example, surface treatment, circuit formation, etc. The present invention can also be applied to industrial applications.

It is a block diagram which shows the hardware constitutions of a liquid ejection control apparatus. 3 is a block diagram illustrating a software configuration of the liquid ejection control apparatus. FIG. FIG. 2 is a block diagram illustrating a schematic configuration of a printer. It is explanatory drawing which shows the relationship between main scanning and subscanning. It is explanatory drawing which shows the relative positional relationship of an ejection head and printing paper. It is a figure which shows the arrangement | sequence rule of an ink dot. 6 is a flowchart illustrating a flow of print control processing. It is a flowchart of a rasterization process. It is a schematic diagram of nozzle discharge data. It is a figure which shows a duty. It is a schematic diagram which shows a mode that an ink dot is formed. It is a figure which shows a duty. It is a figure which shows a duty. It is a figure which shows the duty concerning a modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Computer, 11 ... CPU, 12 ... RAM, 13 ... ROM, 14 ... HDD, 15 ... GIF, 16 ... VIF, 17 ... IIF, 18 ... Bus, P1 ... OS, P3 ... Printer driver, P3a ... Renderer, P3b ... color converter, P3c ... halftone part, P3d ... rasterizer, P3e ... print control data output part.

Claims (10)

While subjecting the ejection medium and the ejection nozzle array for ejecting the liquid to main scanning in the main scanning direction which is a direction intersecting the ejection nozzle array, the ejection medium and the ejection nozzle array are moved in the main scanning direction. A liquid ejection control device that performs sub-scanning relatively in a sub-scanning direction orthogonal to
When the ratio at which the predetermined injection nozzle is responsible for the injection is the injection rate with respect to the main scanning line at the same position in the sub-scanning direction, and the maximum value of the injection rate is 100% ,
Comprising injection control means for controlling the injection so that the injection rate of each injection nozzle is asymmetric with respect to the position of the injection nozzle ;
In the first-side jet nozzle group that first reaches the target medium to be sub-scanned, the injection rate increases nonlinearly as it becomes the rear side that finally reaches the target medium,
In the rear side injection nozzle group, the injection rate decreases nonlinearly toward the rear side,
In the injection nozzle group between the front injection nozzle group and the rear injection nozzle group, the injection rate is constant,
The liquid ejection control apparatus according to claim 1, wherein the increase and the decrease are in a complementary relationship . 2. The liquid according to claim 1 , wherein, in the head-side injection nozzle group, an injection rate increases nonlinearly toward the rear side, and an increase amount increases toward the rear side. Injection control device. 3. The liquid ejection control apparatus according to claim 1, wherein the ejection rate for each main scan varies in a quadratic function according to the position of each ejection nozzle in the sub-scanning direction. 4. The liquid ejection control apparatus according to claim 1 , wherein the ejection control unit controls the ejection rate that varies depending on a type of liquid ejected from the ejection nozzle. 5. . The ejection control unit ejects a liquid from the ejection nozzle row having a longer fixing time in the ejection target medium than other liquids.
The liquid ejection control apparatus according to claim 4 , wherein the ejection rate in the initial main scanning is higher than that of other liquids. When the ejection control unit ejects a liquid having a lower concentration than other liquids from the ejection nozzle row,
The liquid ejection control apparatus according to claim 4 , wherein the ejection rate in the initial main scanning is higher than that of other liquids. In the case where the ejection control means ejects a pair of liquids having the same mixed material and different concentrations of the mixed material from the ejection nozzle row,
In each main scan with respect to the main scan line at substantially the same position,
Variations in the ejection rate of the pair of liquids are symmetrical to each other,
The liquid ejection control apparatus according to claim 6 , wherein, for one of the pair of liquids having a low concentration, the ejection rate in the initial main scanning is set higher than the other one. In the case where the ejection control unit ejects the first and second liquids having a larger ejection amount than other liquids from each of the first and second ejection nozzle rows,
The liquid ejection control apparatus according to claim 4 , wherein the ejection rate in the initial main scanning is higher than that of the second liquid for the first liquid. While subjecting the ejection medium and the ejection nozzle array for ejecting the liquid to main scanning in the main scanning direction which is a direction intersecting the ejection nozzle array, the ejection medium and the ejection nozzle array are moved in the main scanning direction. A liquid ejection control method for performing sub-scanning relatively in a sub-scanning direction orthogonal to
When the ratio at which the predetermined injection nozzle is responsible for the injection is the injection rate with respect to the main scanning line at the same position in the sub-scanning direction, and the maximum value of the injection rate is 100% ,
Controlling the injection so that the injection rate of each injection nozzle is asymmetric with respect to the position of the injection nozzle ;
In the head side injection nozzle group that first reaches the target medium to be sub-scanned, the injection rate is increased nonlinearly as it becomes the rear side that finally reaches the target medium,
In the rear-side injection nozzle group, the injection rate is reduced nonlinearly toward the rear side,
In the injection nozzle group between the front injection nozzle group and the rear injection nozzle group, the injection rate is constant,
A liquid ejection control method, wherein the increase and the amount of decrease are in a complementary relationship . While subjecting the ejection medium and the ejection nozzle array for ejecting the liquid to main scanning in the main scanning direction which is a direction intersecting the ejection nozzle array, the ejection medium and the ejection nozzle array are moved in the main scanning direction. A liquid ejection control program for causing a computer to execute a function for performing sub-scanning relatively in a sub-scanning direction substantially orthogonal to
When the ratio at which the predetermined injection nozzle is responsible for the injection is the injection rate with respect to the main scanning line at the same position in the sub-scanning direction, and the maximum value of the injection rate is 100% ,
Controlling the injection so that the injection rate of each injection nozzle is asymmetric with respect to the position of the injection nozzle ;
In the head side injection nozzle group that first reaches the target medium to be sub-scanned, the injection rate is increased nonlinearly as it becomes the rear side that finally reaches the target medium,
In the rear-side injection nozzle group, the injection rate is reduced nonlinearly toward the rear side,
In the injection nozzle group between the front injection nozzle group and the rear injection nozzle group, the injection rate is constant,
A liquid ejection control program that causes a computer to execute an ejection control function that complements the amount of increase and decrease .

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