JP2015178201A - Printer controller and print control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of image quality including density unevenness.SOLUTION: A printer controller controls a print head having nozzles discharging ink droplets and causes printing to be executed. In the print head, nozzle arrays being constituted of the nozzle disposed side-by-side in a first direction and discharging the ink droplets of individual predetermined colors are disposed side-by-side in a second direction intersecting with the first direction, and the nozzle arrays discharging the ink droplets of the same color are symmetrically disposed in the second direction. The print head comprises: an inclination acquisition section acquiring inclination of the print head; and a discharge control section controlling discharge of the ink droplets by the nozzles. The discharge control section causes sizes of the ink droplets discharged by the predetermined nozzle arrays including the nozzle arrays of both ends in the second direction to be different from one another in accordance with specific printing conditions correlated with the inclination and occurrence of density unevenness in printing results.

Description

  The present invention relates to a print control apparatus and a print control method.

  A print head having nozzle rows in which nozzles for ejecting ink droplets of the same color are arranged at a predetermined pitch corresponding to a plurality of ink colors is provided, and the print head is scanned with respect to the print medium so that the ink from each nozzle Ink jet printers that eject droplets are known. In an ink jet printer, each nozzle row may be arranged so that the order of ink colors to which each nozzle row corresponds is symmetrical in the scanning direction (see Patent Documents 1 and 2).

JP 2008-68501 A JP 2006-224615 A

  A print head in which a plurality of nozzle rows are arranged as described above constitutes one nozzle row for ejecting ink of one color and the other nozzle row when the mounting posture is inclined. In some cases, the gap between the nozzles and the nozzles is non-uniform. Such non-uniform nozzle spacing causes density unevenness in the printed result.

  In addition, in an ink jet printer, density unevenness called “wind pattern” or the like may occur in a print result. The wind pattern is unevenness that occurs as a result of the ink droplets ejected from the nozzles landing at a position deviated from the originally expected landing position due to the influence of the airflow, which contributes to deterioration of image quality. Each of the above-mentioned documents does not present a countermeasure against image quality deterioration due to such a wind pattern.

  The present invention has been made to solve at least one of the above-described problems, and provides a print control apparatus and a print control method that are useful for resolving image quality degradation including a wind pattern.

  One aspect of the present invention is a print control apparatus that executes printing by controlling a print head having nozzles that eject ink droplets, and the print head includes the nozzles arranged in a first direction. The nozzle rows that each eject the ink droplets of a predetermined color are arranged in a second direction intersecting the first direction, and the nozzle rows that eject the ink droplets of the same color are arranged in the second And a tilt acquisition unit that acquires the tilt of the print head, and a discharge control unit that controls the ejection of ink droplets by the nozzles, the discharge control unit including the tilt and printing The size of the ink droplets ejected to the predetermined nozzle rows including the nozzle rows at both ends in the second direction is made different according to the specific printing condition correlated with the occurrence of the wind pattern in the result.

  According to this configuration, when the print result of the predetermined nozzle row or the like is likely to cause image quality deterioration including a print pattern due to the tilt of the print head and the specific printing condition, the predetermined nozzle row or the like Such image quality deterioration can be suppressed by changing the size of the ejected ink droplets.

In one aspect of the present invention, the specific printing condition includes an ink amount defined by image data representing an image to be printed, and the ejection control unit is configured such that the inclination is a threshold value related to the inclination. When the ink amount is equal to or greater than the threshold value related to the ink amount, the size of the ink droplets ejected to the predetermined nozzle row may be increased.
According to this configuration, since the amount of ink is relatively large, in the situation where a print pattern is likely to be generated in the print result by the predetermined nozzle row or the like, the print pattern can be suppressed by increasing the size of the ink droplets to be ejected. .

In one aspect of the present invention, the specific printing condition includes a distance (hereinafter referred to as PG) between the print head and a printing medium on which the ink droplets are landed, and the ejection control unit has the inclination. The size of the ink droplets to be ejected to the predetermined nozzle row may be increased when the inclination is equal to or greater than the threshold value and PG is equal to or greater than the threshold value related to PG.
According to this configuration, in a situation where a PG is relatively long and a print pattern is likely to be generated in a print result by the predetermined nozzle row or the like, the print pattern can be suppressed by increasing the size of the ink droplets to be ejected.

According to one aspect of the present invention, the specific printing condition includes a speed of the ink droplet ejected from the nozzle, and the ejection control unit has the inclination equal to or greater than a threshold value related to the inclination. And when the said speed is more than the threshold value regarding the said speed, you may make the size of the ink droplet discharged to the said predetermined nozzle row large.
According to this configuration, in a situation where a wind pattern is likely to be generated in the printing result by the predetermined nozzle row or the like because the speed of the ink droplet is relatively high, the wind pattern is suppressed by increasing the size of the ejected ink droplet. be able to.

In one aspect of the present invention, the specific printing condition includes difficulty in bleeding of ink droplets on a printing medium on which the ink droplets are landed, and the ejection control unit is configured such that the inclination is a threshold related to the inclination. When the second print medium is used among the first print medium and the second print medium having a property that ink droplets are less likely to bleed than the first print medium, as the print medium. The size of the ink droplets ejected to the predetermined nozzle row may be increased.
According to this configuration, in a situation where the wind pattern is easily noticeable in the printing result by the predetermined nozzle row or the like because the second print medium is used, the wind pattern is made inconspicuous by increasing the size of the ejected ink droplet. be able to.

  The technical idea of the present invention is not realized only by the print control apparatus described above. For example, a printing control method including processing steps executed by each unit of the printing control apparatus can be regarded as one invention. In addition, even if the present invention is realized in various categories such as a computer program that causes a hardware (computer) to execute each step of such a print control method, and further a computer-readable print medium that records the program. Good.

It is a figure which shows roughly the hardware constitutions etc. concerning this embodiment. 6 is a flowchart illustrating print control processing. It is a figure which illustrates the nozzle arrangement | positioning and dot (no position shift) of a print head (no inclination). It is a figure which illustrates the nozzle arrangement | positioning and dot (with position shift) of a print head (with inclination). It is a figure which illustrates the nozzle arrangement | positioning of a print head (with an inclination) and a dot (with a positional deviation including a wind pattern). It is a figure which illustrates the 1st table and the 2nd table. It is a figure which illustrates the nozzle arrangement | positioning and dot (after size up) of a print head (with inclination). It is a figure which illustrates the partial structure of the 2nd apparatus containing a print head. It is a flowchart which shows the printing control process concerning 2nd, 3rd and 4th embodiment.

Embodiments of the present invention will be described in the following order.
1. 1. Outline of device configuration 2. Print control process Other embodiments

1. Overview of Device Configuration FIG. 1 schematically shows a hardware configuration and a software configuration according to the present embodiment. In FIG. 1, the 1st apparatus 10 and the 2nd apparatus 50 are shown. The first device 10 has a function of controlling the second device 50 to cause the second device 50 to execute printing, and corresponds to, for example, a personal computer (PC), a server, a portable terminal device, or the like. The second device 50 is a printer. A printer is an output device that makes a hard copy record of data using a sequence of discrete graphic characters belonging to one or more predetermined character sets as a main format (JIS X0012-1990). ). The second device 50 may be any device that can function as a printer, and may be a so-called multifunction device that also functions as a scanner or a copier.

  The first device 10 corresponds to an example of a print control device. Alternatively, the system 100 including the first device 10 and the second device 50 may be regarded as a print control device, or only the second device 50 may be regarded as a print control device. The print control apparatus is the execution subject of the print control method. Further, the first device 10 and the second device 50 are not based on the premise that they are separate devices. The first device 10 and the second device 50 may correspond to each part in one product (printer) configured integrally, and a part of the product functions as the first device 10, and A configuration in which other units function as the second device 50 is also included in the present embodiment.

  In the first device 10, the CPU 11 controls the second device 50 by expanding the program 21 stored in the hard disk drive (HDD) 20 or the like on the RAM 12 and performing an operation according to the program 21 under the OS. It functions as a print control unit 13 for this purpose. The program 21 can be called a print control program or a printer driver. The print control unit 13 includes functions such as an image acquisition unit 13a, an image processing unit 13b, a dot distribution unit 13c, a transfer unit 13d, and an inclination acquisition unit 13e. The image processing unit 13b, the dot distribution unit 13c, the transfer unit 13d, and the like can be collectively expressed as an ejection control unit that controls ejection of ink droplets from the nozzles. Each of these functions will be described later. When the first device 10 and the second device 50 are integrally configured as a printer, the print control unit 13 is configured as firmware FW described later, and the HDD 20 is configured as memory such as a ROM 53 described later. It is good. In addition, matters described below as being executed on the first device 10 side may be executed on the second device 50 side.

  A display 30 serving as a display unit is connected to the first device 10, and a user interface (UI) screen necessary for each process is displayed on the display 30. In addition, the first device 10 appropriately includes an operation unit 40 realized by, for example, a keyboard, a mouse, various buttons, a touch pad, a touch panel, and the like, and instructions necessary for each process are input by the user via the operation unit 40. The The display 30 and the operation unit 40 may be built in the first device 10 or may be externally connected. The first device 10 is communicably connected to the second device 50 via the transfer path 70. The transfer path 70 is a general term for a wired or wireless communication path. As described above, when the first device 10 and the second device 50 are integrated products, the transfer path 70 is a communication path in the product.

  In the second device 50, the CPU 51 controls itself by developing a program (firmware FW) stored in a memory such as the ROM 53 on the RAM 52 and performing calculations according to the firmware FW. According to the firmware FW, the CPU 51 can cause the ASIC 56 to perform printing based on the print data transmitted from the first device 10. In addition, the second device 50 can store information unique to the second device 50 (tilt information SI and the like described later) in a predetermined memory.

The ASIC 56 acquires print data, and generates a drive signal for driving, for example, the transport mechanism 57, the carriage motor 58, and the print head 62 based on the print data.
The transport mechanism 57 includes a transport motor and rollers (not shown) and is driven and controlled by the ASIC 56 to transport the print medium along a certain transport direction. The print medium is a material that holds a printed image, and is typically paper, but various materials such as plastic, fiber, metal, and other natural and artificial materials are used.

  The second device 50 includes, for example, a carriage 60, and the carriage 60 has a cartridge 61 for each of a plurality of types of ink. In the example of FIG. 1, a cartridge 61 corresponding to various liquids of cyan (C), magenta (M), yellow (Y), and black (K) is mounted. However, the specific types and number of inks used by the second device 50 are not limited to those described above. For example, various inks such as light cyan, light magenta, orange, green, gray, light gray, white, metallic, etc. Can be used. Further, the cartridge 61 may be installed at a predetermined position in the second device 50 without being mounted on the carriage 60, and the cartridge 61 may have an appearance such as an ink tank or an ink package.

  The carriage 60 includes a print head 62 that ejects (discharges) ink supplied from each cartridge 61 from a large number of ink discharge holes (hereinafter referred to as nozzles). In the print head 62, a piezoelectric element for ejecting ink (ink droplet) from the nozzle is provided corresponding to each nozzle. The piezoelectric element is deformed when the drive signal is applied, and ejects ink from the corresponding nozzle. In the present embodiment, the print head 62 can eject a plurality of ink droplets of different sizes from the nozzles according to the drive signal. Different ink droplet sizes mean different volumes per ink droplet. More specifically, the print head 62 includes the largest ink droplet (L size ink droplet), the next largest size ink droplet (M size ink droplet), and the smallest size ink droplet ( S size ink droplets) can be ejected. Here, the expression “dot” basically refers to an ink droplet that has landed on a print medium. However, even before the ink droplets land on the print medium, the expression “dot” may be used for convenience of explanation. In addition, L size ink droplets may be expressed as “large dots”, M size ink droplets as “medium dots”, and S size ink droplets as “small dots”.

  By controlling the driving of the carriage motor 58 by the ASIC 56, the carriage 60 (and the print head 62) moves (main scanning) along the direction (main scanning direction) intersecting the transport direction, and the ASIC 56 moves in the direction. Accordingly, the print head 62 is caused to eject ink from each nozzle. Thereby, ink droplets adhere to the print medium (dots are formed on the print medium), and an image based on the print data is reproduced on the print medium. The “intersection” means orthogonal. Further, in the present specification, even if the directions and positions of each component are expressed as orthogonal, equidistant, parallel, etc., they do not mean only strictly orthogonal, equidistant, parallel, It also includes an error that is acceptable in terms of product performance and an error that may occur during product manufacture.

The second device 50 further includes an operation panel 59 and the like. The operation panel 59 includes a display unit (for example, a liquid crystal panel), a touch panel formed in the display unit, various buttons and keys, and accepts input from the user and displays a necessary UI screen on the display unit. .
The second device 50 is not limited to the piezoelectric element as means for ejecting dots from the nozzles, and may employ means for ejecting dots from the nozzles by heating ink with a heating element.

2. Print Control Processing Based on the above configuration, print control processing (method) executed in the present embodiment will be described.
FIG. 2 is a flowchart showing the print control process. Here, the description will be made assuming that the CPU 11 functions as the print control unit 13 in the first apparatus 10 to execute the flowchart.
In step S <b> 100, the print control unit 13 can accept settings of various conditions (printing conditions) related to printing from the user via the UI screen displayed on the display 30 by the user operating the operation unit 40. . As the printing conditions, for example, the type and size of the printing medium used for printing, the printing resolution (dpi), the selection of monochrome printing or color printing, the distance (PG) between the printing head 62 and the printing medium, and the like are various. There are conditions. Some of the settings received in step S100 may be referred to in the dot distribution process (step S140) described later.

  In step S110, the image acquisition unit 13a acquires image data 22 arbitrarily selected by the user as an image to be printed on the print medium. The image data 22 is, for example, bitmap data generated in advance by predetermined application software and stored in the HDD 20 or the like. Alternatively, the image acquisition unit 13a may acquire (download) the image data 22 from various image input sources such as an external server connected to a network (not shown).

  In step S120, the image processing unit 13b converts the resolution of the image data 22. That is, the resolution of the image data 22 is converted so that the resolution of the image data 22 matches the print resolution received in step S100, and the number of pixels is adjusted to the number of pixels necessary for printing with reference to the size of the print medium. To do.

  In step S130, the image processing unit 13b performs a color conversion process on the image data 22 after step S120. Specifically, the image processing unit 13b converts the color system of the image data 22 into an ink color system adopted by the printer (second device 50). For example, when the image data 22 is RGB data having red (R), green (G), and blue (B) gradation values (for example, 256 gradations from 0 to 255) for each pixel, the image processing unit 13b converts the RGB value for each pixel of the image data 22 into CMYK values that are combinations of C, M, Y, and K ink amounts (ink density, for example, 256 gradations from 0 to 255). The color conversion process can be executed by referring to a lookup table (LUT) in which the correspondence between RGB and CMYK is predetermined. The LUT is stored in a predetermined storage area (for example, HDD 20 or ROM 53). The image data 22 after the color conversion process is also called ink amount data.

  In step S140, the dot distribution unit 13c performs dot distribution processing on the ink amount data obtained by the color conversion processing. That is, a process of distributing the ink amount CMYK for each ink color of each pixel of the ink amount data to the recording rate (occurrence rate) for each of a plurality of different size ink droplets. The dot distribution process is executed by referring to a dot distribution table that defines the conversion relationship between the ink amount and the recording rate for each ink droplet of each size. In step S140, the dot allocation table to be referred to is switched according to the degree of inclination of the print head 62, the ink color, and the like, and either the first table or the second table is referred to as the dot allocation table. To do. The first table and the second table are stored in a predetermined storage area (for example, the HDD 20 or the ROM 53). As will be described in detail later, the first table is a dot allocation table in which the occurrence rate of large, medium, and small dots is set so that the granularity of image quality is good, and the second table has a relatively large size. It is a dot distribution table set so that more dots (for example, large dots) are generated.

Before describing the details of step S140 in detail, the configuration and inclination of the print head 62 will be described with reference to FIGS.
The left side of FIG. 3 illustrates the arrangement of the nozzles Nz on the ink ejection surface 62 a of the print head 62. The ink discharge surface 62a is a surface on which the nozzle Nz is opened and is a surface facing the print medium when the print head 62 performs main scanning. The print head 62 includes a plurality of nozzle rows in which the nozzles Nz are arranged at equal intervals along the first direction D1. In the example of FIG. 3, the print head 62 has eight nozzle rows (nozzle rows L1, L2, L3, L4, L5, L6, L7, L8).

  In the print head 62, nozzle rows that eject ink of the same color are arranged symmetrically in the direction in which the nozzle rows are arranged (second direction D2 orthogonal to the first direction D1). That is, the outermost nozzle rows L1 and L8 in the second direction D2 eject ink of the same color, and the nozzle rows L2 and L7 which are one inner side than the nozzle rows L1 and L8 eject ink of the same color. The nozzle rows L3 and L6 which are one inner side than the rows L2 and L7 discharge the same color ink, and the innermost nozzle rows L4 and L5 discharge the same color ink. Accordingly, in the example of FIG. 3, the print head 62 can eject ink of a maximum of four colors. Of course, the number of nozzle rows included in the print head 62 is not limited to eight. The print head 62 in which the nozzle rows for ejecting the same color of ink are arranged symmetrically in this way is called a “symmetrically arranged head” or the like.

  The two nozzle rows that eject ink of the same color are arranged shifted in the first direction D1 by a distance that is half the interval (nozzle pitch) of the nozzles Nz that constitute one nozzle row. Therefore, a nozzle resolution that is double the nozzle resolution of one nozzle row (number of nozzles per inch = npi) can be realized for one color. FIG. 3 also shows the nozzle pitch NP in the entire two nozzle rows that eject ink of the same color. FIG. 3 illustrates a case where the print head 62 has no inclination. The fact that the print head 62 is not inclined indicates that the first direction D1 of the print head 62 matches the transport direction (the second direction D2 of the print head 62 matches the main scanning direction).

  The right side of FIG. 3 illustrates a state where dots are formed by ink droplets ejected by the print head 62 landing on the print medium. The symbol “I18” exemplifies a dot row I18 formed by dots (for example, C ink dots) formed by the outermost nozzle rows L1 and L8, and the symbol “I45” is formed by the innermost nozzle rows L4 and L5. The dot row I45 by dots (for example, M ink dots) is illustrated. The dot rows I18 and I45 are printed over the print area AR on the print medium. However, since they are difficult to see if they are shown overlaid, they are shown separately in FIG. Each rectangle constituting the print area AR indicates an area for one pixel on the print medium derived from the print resolutions in the main scanning direction and the conveyance direction, and the distance between the center points of adjacent rectangles is the nozzle It is equal to the pitch NP. In the example of FIG. 3, the print head 62 is not inclined. Therefore, in each of the dot rows I18 and I45, the dots constituting them are arranged at the nozzle pitch NP in the transport direction. Therefore, when the dot rows I18 and I45 are printed over the print area AR, the conveyance direction is set between the C ink dots constituting the dot row I18 and the M ink dots constituting the dot row I45. There is no misalignment.

  FIG. 4 is a comparative example with respect to FIG. 3 and illustrates a case where the print head 62 has a slight inclination. Ideally, the print head 62 has an inclination of 0 when assembled in the printer (second device 50), but it is difficult to make the inclination completely zero in all mass-produced printers. Therefore, it can be said that the printer has the inclination of the print head 62 for each machine. 4 (and FIGS. 5 and 7 to be described later), the same reference numerals are used for the same components and elements as those in FIG. In the example of FIG. 4, since the print head 62 is inclined, the interval W1 between the dots by the nozzle row L1 and the dots by the nozzle row L8 constituting the dot row I18 repeats a wide interval and a narrow interval in the transport direction ( (Refer the space | interval W1 of the dashed-dotted lines in FIG. 4). Note that the wide and narrow intervals referred to here can be seen from a comparison with the intervals between the rectangles of the print area AR shown in FIG. 4 (distance between center points of adjacent rectangles = nozzle pitch NP). , An interval wider than the nozzle pitch NP and an interval narrower than the nozzle pitch NP. In addition, the distance W2 between the dots formed by the nozzle array L4 and the dots formed by the nozzle array L5 constituting the dot array I45 is repeated in the transport direction with a wide interval and a narrow interval (the interval W2 between the two-dot chain lines in FIG. 4 is repeated. reference).

  As can be seen from the comparison between the dot row I18 and the dot row I45 shown in FIG. 4, the non-uniform spacing between the dots constituting such a dot row is caused by the nozzle row used for printing the dot row. The position increases as it is more outward in the symmetrically arranged head. Therefore, when the dot rows I18 and I45 are printed over the print area AR, the conveyance direction is set between the C ink dots constituting the dot row I18 and the M ink dots constituting the dot row I45. As a result, the C ink dots and the M ink dots do not overlap each other.

  FIG. 5 is a comparative example with respect to FIGS. 3 and 4, and illustrates the case where the print head 62 has the same inclination as in FIG. 4 and the landing position of the ink droplet has shifted due to the influence of the airflow. . In the example of FIG. 5, there is a case where the position of the dots formed by the nozzle row L8 with respect to the position of the dots formed by the nozzle row L1 is further deviated from the example of FIG. Show. The “airflow” referred to here is, for example, an airflow (wind) that is generated near the surface of the print medium when a certain ink droplet lands on the print medium, and such an airflow is printed after the ink droplet. Deviations may occur in the landing positions of other ink droplets that land on the medium. Density unevenness (color unevenness) that occurs as a result of the landing position of the ink droplet being displaced by such an air flow is a “wind pattern”.

  In the example of FIG. 5, when the dot rows I18 and I45 are printed over the print area AR, between the C ink dots constituting the dot row I18 and the M ink dots constituting the dot row I45. Misalignment in the transport direction occurs, and as a result, a portion where the C ink dot and the M ink dot do not overlap occurs. Further, when the example of FIG. 5 is compared with the example of FIG. 4, the positional deviation between the C ink dots and the M ink dots is larger in some places due to the influence of the air flow. For this reason, for example, a portion that should be originally covered with C ink and M ink but is not actually covered with C ink, or a portion that is covered with a larger amount of C ink than originally expected C ink is remarkable. Such a covering state (printing result) is recognized as density unevenness. In the case of FIG. 5, density unevenness including a wind pattern is generated.

Note that the landing position shifts due to the airflow is not limited to the dots formed by the nozzle row L8, and the direction of displacement is not limited to the example shown in FIG. However, what can be generally said is that, in a situation where the print head 62 is inclined and wind ripples are likely to occur, the density unevenness is more strongly generated in the print result and the image quality tends to deteriorate. In addition, the deviation of the dot formation interval due to the inclination of the print head 62 becomes larger as the dots are formed by the nozzle rows arranged on the outer side of the symmetrically arranged head.
Based on such considerations, the present inventor has determined that the nozzle rows at both ends in the second direction D2 (FIGS. 3 and 4) according to the inclination of the print head 62 and the specific printing conditions correlated with the occurrence of the wind pattern. , 5 and 7, the sizes of the ink droplets ejected to the predetermined nozzle rows including the nozzle rows L1 and L8) are made different.

  In the dot distribution process (step S140), the inclination acquisition unit 13e first acquires the inclination of the print head 62 (step S141). The method for acquiring the inclination of the print head 62 is not particularly limited as long as information indicating the inclination of the print head 62 directly or indirectly can be acquired as a result. For example, in the printer (second device 50), the inclination of the print head 62 (for example, the main scanning direction and the second direction D2) is made for each machine after the print head 62 is attached and before being shipped to the market. (The absolute value of the angle) may be measured, and the measurement result may be stored in a predetermined memory as tilt information SI (see FIG. 1). As described above, when the second device 50 has the inherent inclination information SI, the inclination acquisition unit 13 e can acquire the inclination information SI by communicating with the second device 50. Alternatively, in step S141, the inclination acquisition unit 13e causes the second device 50 to print a predetermined test pattern, and acquires the inclination of the print head 62 based on automatic measurement or human evaluation of the test pattern print result. (Input) may be used.

  Next, the dot distribution unit 13c determines whether or not the inclination (for example, the value indicated by the inclination information SI) of the print head 62 acquired in step S141 is equal to or greater than a predetermined threshold value TH1. Determination is made (step S142). If the inclination of the print head 62 is greater than or equal to the threshold value TH1, the process proceeds to step S143. If the inclination of the print head 62 is less than the threshold value TH1, the process proceeds to step S145.

  In step S143, the dot distribution unit 13c performs dot distribution processing by referring to the first table according to the ink amount CMYK for each ink color included in each pixel constituting the ink amount data (step S145). Or the dot allocation process (step S144) referring to the second table. Here, the dot allocating portion 13c has nozzle rows at both ends in the second direction D2 (nozzle rows L1 and L8 in the examples of FIGS. 3, 4, 5, and 7; hereinafter referred to as “end nozzle rows”). The amount of ink applied to the color of ink to be ejected is allocated to the dot distribution process (step S144) referring to the second table, and the amount of ink applied to the color of ink ejected by the other nozzle rows is referred to the first table. To the dot distribution process (step S145) to be performed. The end nozzle row is an example of the predetermined nozzle row. The color of the end nozzle row is determined in advance, and is assumed to be C in CMYK, for example. When the process proceeds directly from step S142 to step S145 (when the inclination of the print head 62 is less than the threshold value TH1), the ink amounts of all the ink colors of all the pixels constituting the ink amount data are It becomes a target of dot distribution processing referring to the first table.

  FIG. 6A is an example of the first table (T1), and FIG. 6B is an example of the second table (T2). These dot allocation tables are tables (or functions) in which the input (horizontal axis) is the ink amount gradation value (0 to 255) and the output (vertical axis) is the dot recording rate (0 to 100%). is there. As the dot recording rate, for example, the coverage of dots in a unit area on a print medium is assumed. Both the first table T1 and the second table T2 are a table LT (solid line) that defines the recording rate of large dots, a table MT (two-dot chain line) that defines the recording rate of medium dots, and a recording rate of small dots. And a table ST (one-dot chain line) that defines

  As the input increases from the minimum value (0) to the maximum value (255), the first table T1 first generates only a small dot recording rate (ST), and then generates a medium dot recording rate (MT). Next, a large dot recording rate (LT) is also generated at a certain gradation value J1 or higher. According to the first table T1, an image having a relatively low ink density (low gradation) is reproduced using many relatively small dots, and an image having a relatively high ink density (high gradation) An image is reproduced using many relatively large dots. Even on the high gradation side, since there are some small dot and medium dot recording rates, the entire image has good graininess. In step S145, the first table T1 is input with the amount of ink to be subjected to dot distribution processing, and converted to a recording rate of small dots, medium dots, and large dots (or part of them).

  On the other hand, the second table T2 differs from the first table T1 in that only a large dot recording rate (LT) is generated at a predetermined gradation value J2 higher than the gradation value J1. In step S144, the amount of ink to be subjected to dot distribution processing is input to the second table T2 and converted to a recording rate of small dots, medium dots, and large dots (or a part thereof). The gradation value J2 shown in the second table T2 corresponds to an example of “threshold value related to ink amount” in the claims. In other words, when the amount of ink targeted for dot distribution processing is equal to or greater than the gradation value J2, by performing dot distribution processing with reference to the second table T2, large ink droplets are ejected to the end nozzle rows. Can be a dot.

  It should be noted that the ink amount for each ink color defined by each pixel of the image data 22 (ink amount data) subjected to the dot distribution process in step S140 is one of the specific printing conditions correlated with the occurrence of a wind pattern. Applicable. If the image is a high-density image that requires a relatively large amount of ink, it can be said that a wind pattern is more likely to occur than a low-density image that is reproduced with relatively little ink. This is because a higher density image ejects more dots into a certain area of the printing medium within a certain time, and when each dot is formed, the ink droplets that have landed first in the vicinity It is because it is easy to be influenced by the air current (wind) caused by the wind. When viewed in pixel units, if the amount of ink that the pixel has is relatively high, there is a high tendency to use a relatively large amount of ink (a large number of ink droplets are ejected) in the neighborhood including the pixel. It can be said. Therefore, in the present embodiment, after the determinations in steps S142 and S143, in step S144, if the ink amount of the pixel is equal to or greater than the threshold value (tone value J2), it is one of the conditions that a wind pattern is likely to occur. Therefore, a large dot recording rate is generated.

  In step S150, the image processing unit 13b performs halftone processing on the image data 22 after the dot distribution processing in step S140. The halftone process can be performed by, for example, a dither method, an error diffusion method, or the like. Here, as an example, a dither method using a dither mask (dither matrix) (not shown) is employed. The dither mask is stored in a predetermined storage area (for example, the HDD 20 or the ROM 53). In the image data 22 after step S140, for each ink color of each pixel, a recording rate is defined for a plurality of size dots (or a part of the plurality of sizes). Therefore, the image processing unit 13b sets the threshold value (for example, 0 to 255) stored in the dither mask and dots of each size for each pixel and ink color that overlap when the dither mask and the image data 22 are superimposed. Halftone data that has been compared with other recording rates and determined whether one of large, medium, and small dots is formed (large dot on, medium dot on, or small dot on) or dot non-formation (dot off). (4-value data) is generated. Halftone data is also called print data.

  A specific method of the halftone process is not particularly limited, and for example, a method disclosed in Japanese Patent Application Laid-Open No. 2011-223520 may be employed. Alternatively, the recording rate of large dots, the recording rate of medium dots, and the recording rate of small dots after dot distribution processing (step S140) for a certain ink color of a certain pixel are respectively large dot recording rate = LR, medium dot When the recording rate is MR and the small dot recording rate is SR, the dither mask threshold value THD may be compared as follows. Here, it is assumed that the threshold value THD is standardized in the same numerical range (0 to 100%) as LR, MR, and SR.

First, the image processing unit 13b calculates numerical values of LR, LR + MR, and LR + MR + SR. next,
If THD ≦ LR, determine large dot on,
If LR <THD ≦ LR + MR, determine medium dot on,
If LR + MR <THD ≦ LR + MR + SR, determine small dot on,
If LR + MR + SR <THD, dot off is determined.
If LR = 0%, MR = 10%, SR = 40% and THD = 35%, according to the above example, it is determined that small dots are on.

  In step S160, the transfer unit 13d rearranges the print data obtained by the process in step S150 in the order to be transferred to the print head 62, and sequentially transfers the print data to the second device 50 side via the transfer path 70. . According to such rearrangement processing, dots of each size defined in the print data (more precisely, information indicating the formation of dots of each size) are detected by the print head 62 according to the pixel position and ink color. Which nozzle is used to determine at which timing the ejection is performed. As a result, on the second device 50 side, the image represented by the image data 22 is printed on the print medium based on the print data.

  According to this embodiment, the print control apparatus that controls the print head 62 that is a symmetrically arranged head to execute printing has the inclination when the inclination of the print head 62 is equal to or greater than the threshold TH1 related to the inclination. For the ink of the color ejected by the end nozzle row that causes the largest landing position deviation due to the influence of the ink, the ink droplet size is increased when the ink amount is equal to or greater than the threshold value related to the ink amount (to make the dot large) ). Accordingly, it is possible to accurately suppress uneven color and uneven density caused by landing position deviation and wind ripples due to the influence of the inclination of the print head 62.

  FIG. 7 is a comparative example with respect to FIG. 5 and illustrates the effect of the present embodiment. FIG. 7 illustrates a case where the print head 62 has the same inclination as that in FIG. 5 and the landing positions of the ink droplets are shifted due to the influence of the air flow as in FIG. However, in the example of FIG. 7, the dot row I18 formed by the nozzle rows L1 and L8 at both ends is a large dot (the dot rows I18 and I45 illustrated in FIGS. 3, 4 and 5 are all small dots). Or it is a medium dot). In this way, by increasing the dot size constituting the dot row I18, the actual landing position deviation (landing position deviation and wind pattern due to the inclination of the print head 62) is alleviated (made difficult to see). Can do. In the example of FIG. 7, when the dot rows I18 and I45 are printed over the print area AR, the C ink dots constituting the dot row I18 and the M ink dots constituting the dot row I45 are formed. The non-overlapping range is reduced as compared with the example of FIG. 5, and as a result, uneven density in the print area AR is alleviated.

  Further, by increasing the dot size as described above, it is possible to suppress the occurrence of the wind pattern itself. That is, by increasing the weight per ink droplet, the flying ink droplet is less likely to be flowed by the air current, and the landing position deviation is reduced. In addition, using many large dots reduces the number of dots to be ejected due to the characteristics of halftone processing (step S150). In FIG. 7, for the sake of convenience, the dot row I18 has continuous large dots, but the dot row I18 as the same “image” is expressed using small dots and medium dots, and only the large dots as shown in FIG. The number of dots is reduced in the latter case. When the number of dots is reduced, the turbulence of the air current on the print medium that induces a wind pattern is also reduced, so that image quality deterioration called a wind pattern can be further suppressed.

3. Other Embodiments The present invention is not limited to the above-described embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the embodiments described below are also possible. A configuration in which the above-described embodiment and each embodiment described below are appropriately combined is also included in the disclosure of the present invention. Further, the above embodiment may be referred to as “first embodiment” for convenience.

Second embodiment:
The specific print condition correlated with the occurrence of the wind pattern may include the distance (PG) between the print head 62 and the print medium. Then, the discharge control unit discharges to the end nozzle row when the inclination of the print head 62 is equal to or greater than the threshold value TH1 relating to the inclination and PG is equal to or greater than the predetermined threshold value TH2 relating to PG. The size of the ink droplets to be made may be increased.

  FIG. 8 is a diagram illustrating a partial configuration of the second device 50 including the print head 62 from a viewpoint from the transport direction. A platen 63 is disposed at a position facing the ink ejection surface 62a of the print head 62 that performs main scanning. The print medium P is intermittently conveyed on the platen 63. The second device 50 can mechanically adjust the height of the print head 62 in accordance with the setting of PG, and by this adjustment, PG, which is the distance between the ink ejection surface 62a of the print head 62 and the print medium P, is adjusted. Match the setting. For example, PG is enlarged when double-sided printing is executed. Specifically, when double-sided printing is set as one of the printing conditions by the user's operation in step S100, the second device 50 performs the PG for single-sided printing at a timing before starting ink ejection. The operation of changing to PG for longer duplex printing is performed. Alternatively, the second device 50 may change the PG according to the type of print medium set for use in printing (for example, the thickness of the print medium or the presence or absence of unevenness).

  FIG. 9 is a flowchart showing the print control process. FIG. 9 is different from FIG. 2 in that step S1401 is added in the dot distribution processing in step S140. In step S1401, the dot distribution unit 13c determines whether or not a specific printing condition (specific condition) is satisfied. In the second embodiment, the establishment of the specific condition indicates that PG is greater than or equal to the threshold value TH2. The dot distribution unit 13c determines whether PG is greater than or equal to the threshold value TH2 according to the contents of the direct or indirect setting for the PG received in step S100, and if PG is greater than or equal to the threshold value TH2. The process proceeds to step S141, and if PG is less than the threshold value TH2, the process proceeds to step S145. When the process directly proceeds from step S1401 to step S145, the ink amounts of all the ink colors of all the pixels constituting the ink amount data are the targets of the dot distribution process referring to the first table.

Note that, as shown in FIG. 6B, the second table T2 referred to in step S144 in FIG. 9 is a dot having a characteristic of converting an input having a certain gradation value J2 or more into only a large dot recording rate (LT). Although it may be an allocation table, it may be a dot allocation table having a characteristic of converting only to a large dot recording rate over the entire input range (0 to 255).
When the PG is long, it can be said that the ink droplets are likely to be caused to flow by the air current until the ink droplets land on the print medium, as compared with the case where the PG is short. However, according to the second embodiment, when the inclination of the print head 62 is equal to or greater than the threshold value TH1 relating to the inclination and PG is equal to or greater than the threshold value TH2 relating to PG, a large dot is formed by the end nozzle row. Formed (large dots are likely to be formed). Accordingly, it is possible to accurately suppress uneven color and uneven density caused by landing position deviation and wind ripples due to the influence of the inclination of the print head 62.

Third embodiment:
The specific printing conditions correlated with the occurrence of the wind pattern may include the speed of ink droplets ejected from the nozzles of the print head 62 (ejection speed). Then, the ejection control unit, when the inclination of the print head 62 is equal to or greater than the threshold value TH1 relating to the inclination and the ejection speed is equal to or greater than the predetermined threshold value TH3 regarding the ejection speed, The size of the ink droplets to be discharged may be increased.

  A third embodiment will also be described with reference to FIG. In step S1401, the dot distribution unit 13c determines whether the specific condition is satisfied. In the third embodiment, the establishment of the specific condition indicates that the discharge speed is equal to or higher than the threshold value TH3. Ideally, the discharge speed should be the same among mass-produced printers. However, due to variations in the characteristics of the piezoelectric elements mounted on the print head 62, variations in the waveform of the drive voltage applied to the piezoelectric elements, and the like, the ejection speed actually varies between mass-produced printers. Therefore, for example, similarly to the tilt information SI, the printer (second device 50) stores an average discharge speed for each machine as information in a predetermined memory. The dot distribution unit 13c can acquire information on the ejection speed by communicating with the second device 50. The dot allocating unit 13c determines whether the discharge speed is equal to or higher than the threshold value TH3. If the discharge speed is equal to or higher than the threshold value TH3, the process proceeds to step S141. If the discharge speed is lower than the threshold value TH3, step S145 is performed. Proceed to

It can be said that when the discharge speed is high, the air current turbulence that occurs near the surface of the print medium when ink droplets land on the print medium is larger than when the discharge speed is low, and a wind ripple is likely to occur. However, according to the third embodiment, when the inclination of the print head 62 is equal to or greater than the threshold value TH1 related to the inclination and the discharge speed is equal to or higher than the threshold value TH3 related to the discharge speed, the end nozzle row is larger. Dots are formed (large dots are easily formed). Accordingly, it is possible to accurately suppress uneven color and uneven density caused by landing position deviation and wind ripples due to the influence of the inclination of the print head 62.

Fourth embodiment:
The specific printing condition correlated with the occurrence of the wind pattern may include difficulty in bleeding of the ink droplet on the printing medium on which the ink droplet is landed. The ejection control unit has a characteristic in which the inclination of the print head 62 is equal to or greater than a threshold TH1 relating to the inclination, and the ink droplets are less likely to bleed as the print medium than the first print medium and the first print medium. When the second print medium is used among the two print media, the size of the ink droplets ejected to the end nozzle row may be increased.

  The fourth embodiment will also be described with reference to FIG. In step S1401, the dot distribution unit 13c determines whether the specific condition is satisfied. In the fourth embodiment, the establishment of the specific condition indicates that the print medium set in step S100 is the second print medium. The second print medium may uniquely indicate a specific type of paper that is relatively difficult to bleed ink, and various types of print media that can be used by the printer (second device 50) are bleeded by ink. It may be considered as a generic term for a medium in which ink is difficult to bleed when it is roughly classified into an easy medium and a medium that does not easily bleed. The first print medium is a medium that can be used by the second device 50 that is not the second print medium. The dot distribution unit 13c determines whether the print medium set in step S100 is the second print medium. If the print medium is the second print medium, the process proceeds to step S141. If the print medium is the first print medium, the process proceeds to step S145.

  If the ink is less likely to bleed on the print medium, it can be said that the wind pattern is more conspicuous because the deviation is more conspicuous even when there is a deviation in the landing position of the ink droplet as compared with the case where the ink is likely to bleed. However, according to the fourth embodiment, when the inclination of the print head 62 is equal to or greater than the threshold TH1 relating to the inclination and the print medium is the second print medium in which ink does not easily bleed, the end nozzle row is larger. Dots are formed (large dots are easily formed). Accordingly, uneven color and uneven density caused by landing position deviation and wind ripples due to the tilt of the print head 62 can be made inconspicuous.

Other:
The evaluation of the inclination of the print head 62 is not limited to a simple evaluation such as whether the threshold value TH1 is greater than or less than the threshold value TH1, and may be evaluated in stages. Similarly, the amount of ink specified by the image data, the PG, the discharge speed, the difficulty of ink bleeding on the print medium, and the like as conditions under which wind ripples are likely to occur are greater than or equal to a threshold value (second print medium? ) Not only a simple evaluation of whether it is less than the threshold value (whether it is the first print medium), but may be evaluated in a stepwise manner. That is, depending on the combination of the stepwise evaluation of the inclination of the print head 62 and the stepwise evaluation of the degree of specific printing conditions that correlate with the occurrence of wind ripples, for example, a large number of medium dots may be generated, The degree of increasing the ink size, such as generating a large number of large dots, can be changed stepwise.

  The color of ink that can refer to the second table T2 in the dot distribution process (step S140) is not limited to the color of ink ejected by the end nozzle row. For example, the nozzle row inside one of the end nozzle rows (the nozzle rows L2 and L7 in the examples of FIGS. 3, 4, 5, and 7) is also the predetermined nozzle row, and the ink amount of the ink color ejected by the predetermined nozzle row The dot distribution process (step S144) referring to the second table T2 may be performed. In addition, as the inclination of the print head 62 increases, the nozzle array whose ink color is the target of the dot distribution process with reference to the second table T2 from the outer nozzle array to the inner nozzle array in the symmetric array head. It may be increased gradually.

  However, with regard to a specific color, image quality degradation such as wind ripples is difficult to see in the first place, and even if the dot size is increased, the effect of making the image quality degradation inconspicuous is low. The specific color referred to here is, for example, a relatively dense ink such as Y. Therefore, even if the ink amount is the target of step S144 in the processing flow described so far, the normal dot distribution processing (step S145) may be performed for the ink amount related to the specific color.

  Until now, when the inclination of the print head 62 is equal to or greater than the threshold value TH1 relating to the inclination, the ink amount defined by the image data is the threshold value relating to the ink amount (the gradation value J2) as a condition that the wind pattern is likely to occur. ), PG is greater than or equal to the threshold TH2 relating to PG, the ejection speed is greater than or equal to the threshold TH3 relating to the ejection speed, or the second printing medium in which ink droplets do not easily spread is used. If one or more holds, the dot size is increased. However, the dot size may be increased when all of the conditions that are likely to cause a wind pattern are satisfied, or the dot size may be increased when not all of the conditions that are likely to cause a wind pattern are satisfied. You may make it bigger.

  ・ The expressions “large dot”, “medium dot”, and “small dot” are merely names for distinguishing three types of dots with different ink drop sizes, and such names give the unique size and weight of ink drops. It doesn't mean. Further, the dot size that the print head 62 can eject from each nozzle is not limited to three types, and may be two types or four or more types.

DESCRIPTION OF SYMBOLS 10 ... 1st apparatus, 13 ... Print control part, 13a ... Image acquisition part, 13b ... Image processing part, 13c ... Dot distribution part, 13d ... Transfer part, 13e ... Inclination acquisition part, 22 ... Image data, 50 ... 1st 2 devices, 62 ... print head, SI ... tilt information, T1 ... first table (dot allocation table), T2 ... second table (dot allocation table)

Claims (6)

A print control device that controls a print head having a nozzle that ejects ink droplets to execute printing,
The print head is a nozzle row composed of the nozzles arranged in a first direction, and the nozzle rows that discharge the ink droplets of a predetermined color are arranged in a second direction intersecting the first direction, and The nozzle rows for ejecting the ink droplets of the same color are arranged symmetrically in the second direction;
An inclination acquisition unit for acquiring the inclination of the print head;
An ejection control unit that controls ejection of ink droplets by the nozzle,
The ejection control unit ejects ink to a predetermined nozzle row including the nozzle rows at both ends in the second direction according to the inclination and a specific printing condition correlated with the occurrence of a wind pattern in a printing result. A printing control apparatus characterized in that droplet sizes are made different.   The specific printing condition includes an ink amount defined by image data representing an image to be printed, and the ejection control unit has the inclination equal to or greater than a threshold value related to the inclination, and the ink amount. 2. The print control apparatus according to claim 1, wherein the size of the ink droplets ejected to the predetermined nozzle row is increased when the value is equal to or greater than a threshold value related to the ink amount.   The specific printing condition includes a distance between the print head and a printing medium on which the ink droplet is landed, and the ejection control unit is configured such that the inclination is equal to or greater than a threshold value related to the inclination, and the distance 3. The print control apparatus according to claim 1, wherein the size of the ink droplets ejected to the predetermined nozzle row is increased when is equal to or greater than a threshold value related to the distance.   The specific printing condition includes a speed of the ink droplet ejected from the nozzle, and the ejection control unit is configured such that the inclination is equal to or greater than a threshold value related to the inclination, and the speed relates to the speed. 4. The print control apparatus according to claim 1, wherein a size of an ink droplet ejected to the predetermined nozzle row is increased when the value is equal to or greater than a threshold value. 5. The specific printing conditions include difficulty in bleeding ink droplets on a printing medium on which the ink droplets are landed,
The ejection control unit includes a second print medium having a characteristic that the inclination is equal to or greater than a threshold value related to the inclination, and the ink is less likely to bleed than the first print medium and the first print medium as the print medium. 5. The print control apparatus according to claim 1, wherein when the second print medium is used, a size of an ink droplet ejected to the predetermined nozzle row is increased. . A printing control method for executing printing by controlling a print head having a nozzle for ejecting ink droplets,
A nozzle row composed of the nozzles arranged in a first direction, wherein the nozzle rows that discharge the ink droplets of a predetermined color are arranged in a second direction intersecting the first direction, and the inks of the same color Using the print head in which the nozzle rows for ejecting droplets are arranged symmetrically in the second direction;
An inclination acquisition step of acquiring the inclination of the print head;
An ejection control step for controlling ejection of ink droplets by the nozzles,
In the ejection control step, ink is ejected to a predetermined nozzle row including the nozzle rows at both ends in the second direction according to the inclination and a specific printing condition correlated with the occurrence of a wind pattern in a printing result. A printing control method, wherein the droplet sizes are made different.

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