JP7439476B2 - Liquid discharge device, discharge adjustment method, and discharge adjustment program - Google Patents

Description

The present invention relates to a liquid ejection device, a ejection adjustment method, and an ejection adjustment program.

2. Description of the Related Art Inkjet recording apparatuses are known that eject ink onto a recording medium to form an image while relatively moving a recording head in which a plurality of nozzles for ejecting ink are arranged and a recording medium.

Here, in the case of an inkjet image forming apparatus having a head array in which a plurality of short recording heads are arranged in a staggered manner in the nozzle row direction (sub-scanning direction), a seam area where the plurality of recording heads overlap in the sub-scanning direction In this case, density unevenness occurs because more dots are ejected than other parts.

Therefore, Patent Document 1 discloses a configuration in which the usage rate at the end portion of the print head corresponding to the seam area between the print heads is reduced in order to eliminate density unevenness in each seam image.

Specifically, FIG. 1 is a schematic diagram showing the position where pixels are outputted by the nozzle 922 according to the thinned-out image data and the distribution of the printing rate in each of a plurality of main scanning operations in the conventional patent document 1. The left column of FIG. 1 shows the relative positional relationship in the sub-scanning direction of the head unit 920 in each of two consecutive main scanning operations, and the center shows the nozzle array from the head unit 920 shown in the left column in each of the main scanning operations. An output pattern 980 representing the positions where pixels are output by the nozzles 922 of the group 924 is shown, and the right column shows the printing rate distribution at each position in the sub-scanning direction on the recording medium in each main-scanning operation. In this technology, the printing rate at the center of each nozzle row 923 is 100%, the printing rate at the joint of the nozzle rows 923 and both ends of the nozzle row group 924 is 0%, and there is no printing between these. The distribution is such that the rate changes linearly.

However, although the technique of Patent Document 1 described above reduces density unevenness in the recorded image, when bidirectional printing is performed, due to the difference in the order of overlapping dot colors, the area on the forward path and the area on the return path are different. A boundary will occur with the previous area. Such boundaries occur in a band shape along the scanning direction of the head, resulting in banding of the recorded image, which is so-called uneven gloss.

The above-mentioned gloss banding occurs not only at the joints of nozzle rows, but also in overlapping areas in multiple scans when forming an image larger than the length of the head.

SUMMARY OF THE INVENTION In view of the above circumstances, it is an object of the present invention to provide a liquid ejecting device that can suppress banding on a recording medium.

In order to solve the above problems, in a liquid ejection device of one embodiment of the present invention,
A head having a nozzle row in which a plurality of nozzles that eject liquid onto a recording medium are arranged in a sub-scanning direction, a head array in which a plurality of nozzles are arranged in the sub-scanning direction, in a scanning direction perpendicular to the sub-scanning direction, A plurality of head units are arranged,
A scanning operation in which the head unit is moved in the scanning direction with respect to the recording medium while discharging the liquid onto the recording medium, and a scanning operation in which the head unit or the recording medium is moved in the scanning direction with respect to the recording medium without discharging the liquid. a moving unit that alternately performs an operation of moving the head unit in the sub-scanning direction relative to the head unit;
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a gradation allocation setting section that includes and sets a second pattern in which a gradation is set such that the printing rate is large and the printing rate at both ends is small;
Masking processing of image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array included in the plurality of head arrays. Department and
Equipped with a head drive unit that ejects liquid from multiple nozzles based on mask-processed image data,
In the second pattern set by the gradation allocation setting section, one gradation is set for each of a plurality of heads.
Alternatively, the second pattern set by the gradation allocation setting section includes an area in which a gradation is set with a first number of heads as one unit, and a second number of heads different from the first number. The gradation area includes an area in which a gradation is set with each head as one unit. .

According to one aspect, banding on a recording medium can be suppressed in a liquid ejection apparatus.

FIG. 2 is a schematic explanatory diagram of a gradation mask according to a conventional example. 1 is a perspective view showing the overall configuration of an example of an image forming apparatus according to a first embodiment of the present invention. FIG. 7 is a plan view of the vicinity of an image forming unit of an image forming apparatus according to a second embodiment of the present invention. FIG. 4 is a front view of the vicinity of the image forming unit of the image forming apparatus shown in FIG. 3; FIG. 1 is a block diagram of a hardware configuration in an example of an image forming apparatus according to the present invention. FIG. 3 is a functional block diagram of a control unit related to image processing of the image forming apparatus according to the first embodiment of the present invention. An explanatory diagram of a print sequence. FIG. 3 is a diagram illustrating how gloss banding occurs in multi-pass interlacing. An explanatory diagram of gloss banding. 1 is a plan view of the vicinity of an image forming unit including a head array in which a plurality of heads are arranged in a staggered manner to which a first embodiment of the present invention is applied; FIG. FIG. 3 is a diagram illustrating an example of a group of multiple gradation assignment patterns according to the first embodiment, which is applied to a head array having three heads arranged in a staggered manner. FIG. 3 is a diagram showing an example of a group of a plurality of gradation assignment patterns according to the first embodiment, which is applied to a head array having four heads arranged in a staggered manner. 1 is a control flowchart according to a first embodiment of the present invention. FIG. 6 is an explanatory diagram showing an example in which a different gradation allocation pattern according to the first embodiment is applied to each head array of a different color when an image is formed by scanning eight times for one image area. FIG. 7 is an explanatory diagram showing an example in which a different gradation assignment pattern according to the first embodiment is applied to each head array of the same color when an image is formed by scanning eight times for one image area. FIG. 7 is a diagram illustrating an example of a group of a plurality of gradation assignment patterns according to the first embodiment, which is applied to a head array in which a plurality of heads are arranged linearly according to a first modification. FIG. 7 is a diagram illustrating an example of a group of a plurality of gradation assignment patterns according to the first embodiment, which is applied to a head array in which a plurality of heads are arranged in a stepwise manner according to a second modification. FIG. 7 is a diagram showing an example of a group of a plurality of gradation assignment patterns according to the second embodiment, which is applied to a head array in which heads having a plurality of nozzle rows are arranged in a staggered manner. 7 is a control flowchart according to a second embodiment of the present invention. FIG. 7 is an explanatory diagram showing an example in which a different gradation assignment pattern according to the second embodiment is applied to each nozzle row of a different color when an image is formed by scanning eight times for one image area. FIG. 7 is a functional block diagram of a control unit related to image processing of an image forming apparatus according to a third embodiment of the present invention. FIG. 7 is a diagram showing an example of a group of gradation assignment patterns according to the third embodiment of the present invention, which is applied to one head array in which one head is arranged. 3 is a control flowchart according to a third embodiment of the present invention. FIG. 7 is an explanatory diagram showing an example in which a different gradation assignment pattern of the third embodiment is applied to each head array of a different color when an image is formed by scanning eight times for one image area. FIG. 7 is a diagram showing an example of a group of gradation assignment patterns according to a fourth embodiment of the present invention, which is applied to one head array in which one head is arranged. 5 is a control flowchart according to a fourth embodiment of the present invention. FIG. 7 is an explanatory diagram showing an example in which a different gradation allocation pattern according to the fourth embodiment is applied to each nozzle row of a different color when an image is formed by scanning eight times for one image area.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In the drawings below, the same components are denoted by the same reference numerals, and redundant explanations may be omitted.

<First embodiment>
First, the overall configuration of a plurality of embodiments of an image forming apparatus, which is an example of a liquid ejection apparatus according to the present invention, will be described.

FIG. 2 is a perspective view showing the overall configuration of an inkjet recording apparatus as an image forming apparatus according to the first embodiment of the present invention.

This inkjet recording apparatus 10 includes a carriage 200 and a stage 13 on which a recording medium is placed. The carriage 200 is provided with a head unit 300 which is an inkjet type image forming unit equipped with a plurality of liquid ejection heads each having a plurality of nozzles. An image is formed by ejecting the liquid from a liquid (see ). The nozzle is provided on a surface facing the stage 13. Note that in this embodiment, the liquid is, for example, ink that has ultraviolet curability.

Further, an irradiation unit 400, which is a light source that irradiates ultraviolet rays, is provided on the surface of the carriage 200 facing the stage 13. The irradiation unit 400 (an example of an irradiation section) irradiates light with a wavelength that hardens the liquid discharged from the nozzle N.

A guide rod 19 spans the left and right side plates 18a and 18b, and the guide rod 19 holds the carriage 200 movably in the X direction (main scanning direction).

Further, the carriage 200, the guide rod 19, and the side plates 18a and 18b are integrally movable in the Y direction (sub-scanning direction) along a guide rail 29 provided at the bottom of the stage 13. Furthermore, the carriage 200 is held movably in the Z direction (vertical direction).

Note that in the configuration of FIG. 2, the stage 13 on which the recording medium is placed is fixed. The inkjet recording apparatus shown in FIG. 2 has a main scanning operation in which ink is ejected onto the recording medium from the nozzles N while moving the recording head in the main scanning direction, and a sub-scanning operation in which the recording head is moved in the sub-scanning direction. This is repeated alternately to form an image.

Therefore, in this embodiment, the carriage 200 and the guide rod 19 are moving parts in the main scanning direction (X direction, second direction), and the carriage 200 and guide rail 29 are moving parts in the sub scanning direction (Y direction, first direction). ) functions as a moving part.

<Second embodiment>
FIG. 3 is a schematic diagram showing an example of a front view of an inkjet recording apparatus 1, which is an image forming apparatus (liquid ejection apparatus) according to a second embodiment of the present invention, and FIG. FIG. 2 is a schematic diagram showing an example of a plan view of FIG.

In the configurations of FIGS. 2 and 3, the stage 230 on which the recording medium 101 is placed is movable. In the inkjet recording apparatus 1 as shown in FIGS. 2 and 3, the recording medium is moved in the sub-scanning direction with respect to the recording head in the sub-scanning operation.

Although FIG. 3 shows an example in which one head is provided in one head array, a plurality of heads may be provided in one head array in the sub-scanning direction (see FIG. 10).

Next, an example of a hardware configuration in an image forming system including an image forming apparatus (inkjet recording apparatuses 10 and 1) will be described.

FIG. 5 is a block diagram showing an example of the hardware configuration of the image forming system of this embodiment. In the system shown in FIG. 5, in the image forming system, as shown in FIGS. 2 to 4, a PC 2 which is an external device is An example is shown in which the PC 2 is connected and the PC 2 executes image processing. Note that functions related to image processing executed by the PC 2 may be provided inside the image forming apparatus.

As shown in FIG. 5, the image forming apparatus 30 (inkjet recording apparatuses 1, 10) of this embodiment includes a controller unit 3, a detection group 4, a transport unit 100 as a transport section, a carriage 200, and a head unit. 300 (an example of a liquid ejection head), an irradiation unit 400 (an example of an irradiation section), and a maintenance unit 500.

Further, the controller unit 3 includes a unit control circuit 31, a memory 32, a CPU (Central Processing Unit) 33, and an I/F 34. Note that the curing device may be any device as long as it includes at least the controller unit 3 and the irradiation unit 400, as shown by the broken line in FIG.

The I/F 34 is an interface for connecting the image forming apparatus 30 (1, 10) to an external PC (Personal Computer) 2. The image forming apparatus 30 (1, 10) and the PC 2 may be connected in any manner, such as a connection via a network or a direct connection between the two using a communication cable.

Examples of the detection group 4 include various sensors included in the inkjet recording apparatus 1, such as the height sensor 41 shown in FIGS. 3 and 4.

The CPU 33 uses the memory 32 as a work area to control the operation of each unit of the inkjet recording apparatus 1 via the unit control circuit 31. Specifically, the CPU 33 controls the operation of each unit based on the recording data received from the PC 2 and the data detected by the detection group 4, and coats the liquid application surface on the recording medium 101 (also referred to as a base material etc.). 102 is formed.

Note that a printer driver is installed in the PC 2, and this printer driver generates recording data to be sent to the inkjet recording apparatus 1 from the image data. The print data includes command data for operating the transport unit 100 of the inkjet printing apparatus 1, and pixel data regarding the image (liquid application surface 102). Pixel data consists of 2-bit data for each pixel, and is expressed in four gradations.

Next, members in the mechanical mechanism of the image forming apparatus will be explained using FIGS. 2 to 5. The transport unit 100 includes a stage 130 and a suction mechanism 120. The suction mechanism 120 has a fan 110 and a plurality of suction holes 100a provided in the stage 130. The suction mechanism 120 temporarily fixes the recording medium 101 to the transport unit 100 by driving the fan 110 and sucking the recording medium 101 through the suction hole 100a. The suction mechanism 120 may use electrostatic suction to suction the paper. The movement of the transport unit 100 in the Y-axis direction (sub-scanning direction) is controlled based on a drive signal from the CPU 33 (unit control circuit 31).

In the configuration shown in FIGS. 3 and 4, the conveyance unit 100 includes a conveyance control section 210, a roller 105, and a motor 104. The conveyance control unit 210 moves the recording medium 101 in the Y-axis direction (sub-scanning direction) by driving the motor 104 and rotating the roller 105.

The transport unit 100 may move the carriage 200 in the Y-axis direction (sub-scanning direction) instead of the recording medium 101 as shown in FIG. That is, the transport unit 100 relatively moves the recording medium 101 and the carriage 200 in the Y-axis direction (sub-scanning direction).

For example, as shown on the right side of FIG. 4, the transport unit 100 includes a side plate 407b that supports two guides 201 that guide the carriage 200 in the X-axis direction (main scanning direction), and a stand 406 that supports the side plate 407b. , a belt 404 fixed to a stand 406, a drive pulley 403 and a driven pulley 402 around which the belt 404 is wound, a motor 405 that rotationally drives the drive pulley 403, and a conveyance control section 210.

Further, as shown on the left side of FIG. 4, the transport unit 100 includes a side plate 407a that supports two guides 201 that guide the carriage 200 in the X-axis direction (main scanning direction), and a side plate 407a that supports the side plate 407a in a slidable manner. and a groove 409 formed on the stand 408 to guide the side plate 407a in the sub-scanning direction.

In the transport unit 100, the transport control unit 210 drives the motor 405 to rotate the drive pulley 403 and move the belt 404 in the Y-axis direction (sub-scanning direction). The carriage 200 can be moved in the Y-axis direction (sub-scanning direction) by moving the table 406 on which the carriage 200 is supported in the Y-axis direction (sub-scanning direction) as the belt 404 moves. As the table 406 moves in the Y-axis direction (sub-scanning direction), the side plate 407a moves along the groove 409 of the table 408 in the Y-axis direction (sub-scanning direction).

In the embodiment shown in FIGS. 2 and 3, the carriage 200, the table 406x, the belt 404, the drive pulley 403, the driven pulley 402, the rotationally driven motor 405, etc. direction). Furthermore, the transport unit 100 including the stage 130, rollers 105, motor 104, etc. functions as a moving unit in the sub-scanning direction (Y direction, first direction).

As shown in FIGS. 3 and 4, the head unit 300 includes head arrays 300K, 300C, 300M, 300Y, which eject K, C, M, Y, CL, and W UV curable inks (an example of liquid), respectively. 300CL and 300W, and is provided on the lower surface of the carriage 200.

Each head array 300K to 300W is provided with one or more heads. When the head is composed of a plurality of heads, the plurality of heads may be staggered or arranged in a line.

Each head is equipped with a piezo that is a driving element, and when a drive signal is applied to the piezo by the CPU 33 (unit control circuit 31), the piezo causes a contraction movement, and the pressure change caused by the contraction movement causes UV Curable ink is ejected onto the recording medium 101. As a result, a liquid application surface 102 (an example of a liquid application surface) is formed on the recording medium 101.

Examples of UV-curable inks suitable for this embodiment include inks containing methacrylate monomers. Methacrylate monomers have the advantage of relatively low skin sensitivity, but they also have a characteristic of having a greater degree of curing shrinkage than general inks.

The irradiation unit 400 is provided on the side surface (the surface in the X-axis direction) of the carriage 200, and irradiates UV light based on a drive signal from the CPU 33 (unit control circuit 31). The irradiation unit 400 mainly includes a UV irradiation lamp that irradiates UV light.

The movement of the carriage 200 in the Z-axis direction (height direction) and the X-axis direction (main scanning direction) is controlled based on drive signals from the CPU 33 (unit control circuit 31).

The carriage 200 scans and moves along the guide 201 in the main scanning direction (X-axis direction). The scanning unit 206 includes a drive pulley 203, a driven pulley 204, a drive belt 202, and a motor 205. The carriage 200 is fixed to a drive belt 202 that is stretched between a drive pulley 203 and a driven pulley 204. By driving the drive belt 202 with the motor 205, the carriage 200 scans left and right in the main scanning direction. The guide 201 is supported by side plates 211A and 211B of the device main body.

The height adjustment section 207 has a motor 209 and a slider 208. The height adjustment unit 207 moves the guide 201 up and down by driving the motor 209 and moving the slider 208 up and down. As the guide 201 moves up and down, the carriage 200 moves up and down, and the height of the carriage 200 relative to the recording medium 101 can be adjusted.

<Image forming operation>
The image forming operation of the inkjet recording apparatus 1 shown in FIG. 2 will be described below.
First, the transport unit 100 moves in the Y-axis direction (sub-scanning direction) based on a drive signal from the CPU 33 (unit control circuit 31), and moves the recording medium 101 to form an image (liquid application surface 102). position at the initial position.

Next, based on the drive signal from the CPU 33 (unit control circuit 31), the carriage 200 is moved to a height suitable for ejecting the UV curable ink by the head unit 300 (for example, in the head arrays 300K to 300W of the head unit 300). , to a height such that the inter-head gap between the lower surface of each head and the recording medium 101 is 1 mm). Note that the height of the head unit 300 is detected by the height sensor 41 so that the CPU 33 can understand it.

Next, the carriage 200 reciprocates in the X-axis direction (main scanning direction) based on a drive signal from the CPU 33 (unit control circuit 31), and during this reciprocating movement, the head unit 300 UV curable ink is ejected based on a drive signal from a control circuit 31). As a result, an image (liquid application surface 102) for one scan is formed on the recording medium 101.

Subsequently, when an image for one scan (liquid application surface 102) is formed on the recording medium 101, the transport unit 100 moves in the Y-axis direction (sub-direction) based on a drive signal from the CPU 33 (unit control circuit 31). (scanning direction) by one scan.

Thereafter, the operation of forming an image (liquid application surface 102) for one scan and the operation of moving the transport unit 100 for one scan in the Y-axis direction are alternately performed until the formation of the image (liquid application surface 102) is completed. It will be done.

When the formation of the image (liquid application surface 102) on the recording medium 101 is completed, the UV curable ink is kept on standby until it is smoothed (hereinafter sometimes referred to as "leveling time"). , UV light irradiation is performed by the irradiation unit 400.

<Functional blocks of the first embodiment>
Next, functional blocks of the present invention will be explained. FIG. 6 is a functional block diagram related to image processing in the image forming system according to the first embodiment of the present invention.

Image processing device 11 includes a main control section 12 . The main control unit 12 is a computer including a CPU, etc., and controls the entire image processing device 11. Note that the main control section 12 may be composed of something other than a general-purpose CPU, and for example, the main control section 12 may be composed of a circuit or the like.

Further, the image processing device 11 may be realized by a PC 2 connected to the image forming device 30, as shown in FIG. 6, or may be provided inside the image forming device 30.

The main control section 12 includes a data reception section 12A, a data creation section 12B, and a data output section 12C. A part or all of the data receiving section 12A, data creating section 12B, and data outputting section 12C may be realized by having a processing device such as a CPU execute a program, that is, by software, or may be realized by using an IC (Integrated It may be realized by hardware such as a circuit), or it may be realized by using a combination of software and hardware.

The data receiving unit 12A receives image data. The image data is information such as the shape and color of the image to be formed. The data receiving section 12A may obtain image data from an external device via the communication section, or may obtain image data from a storage means provided in the image processing device 11.

The data creation unit 12B performs predetermined data processing such as mask processing on the image data received by the data reception unit 12A. In this embodiment, color ink image data and clear ink image data are created based on image data (for example, JPEG image data) and desired glossiness.

The data output unit 12C outputs the image data created by the data creation unit 12B to the image forming apparatus 30.

The image forming apparatus 30 (1, 10) includes a recording section 14, a print mode receiving section 21, an irradiation section 22, a driving section 25 (23, 24), and a recording control section 28.

The recording unit 14 is a head driving unit that drives droplet ejection from each head of the head arrays 300K to 300W based on image data controlled by the recording control unit 26.

The drive section 25 drives the moving section, the first drive section 23 drives the movement of the carriage 200 in the X direction during scanning, and the second drive section 24 drives the movement of the carriage 200 in the X direction during sub-scanning. The carriage 200 or the recording medium 101 is driven to move in the sub-scanning direction.

The recording control unit 28 receives print data from the image processing device 11. The recording control unit 28 controls the recording unit 14, the drive unit 25, and the irradiation unit 22 so that droplets corresponding to each pixel are ejected from the head 18 according to the received print data.

For example, the recording control unit 28 calculates the time from ink ejection to light irradiation, calculates the glossiness of an image formed on the recording medium 101 from the amount of ink ejection and the time from light irradiation, and calculates the glossiness of the image formed on the recording medium 101. Calculations are performed to determine the amount of clear ink to be ejected to make the density uniform.

The recording control section 28 also includes a print sequence setting section 28A, an allocation pattern storage section 28B, a gradation allocation setting section 28C, and an image drive waveform generation section 28D.

The print sequence setting unit 28A sets a print sequence based on image data and print mode. By setting the print sequence (see FIG. 7), it is possible to determine how many times the carriage 200 on which the recording unit 14 is mounted is scanned in the forward or backward direction in the main scanning direction to form an image for each image area. Specify whether or not to do so. It also controls image formation of a color ink image based on color ink image data. In other words, the formation order for each ink color, the amount of each ink to be applied, and the position to print (dot arrangement position) are controlled.

In this embodiment, the assignment pattern storage unit 28B stores a plurality of types of gradation assignment patterns associated with a head array having a plurality of heads.

The gradation allocation setting unit 28C of this embodiment sets different gradation allocation patterns for the entire head array area in the sub-scanning direction, using the head as the minimum division unit.

In this embodiment, the gradation assignment pattern for each head associated with the head array includes at least a pattern ((1) in FIG. 11(b)) in which the gradation is assigned using the entire head array as one gradation assignment area. The allocation pattern may include an allocation pattern ((2) in FIG. 11(b)) in which the heads in the head array are the minimum division unit.

Specifically, the gradation is a pattern in which the center is dark in the sub-scanning direction and the edges are thin (the number of dots (printing rate) ejected from the nozzle decreases toward the edges). A specific setting example of the gradation allocation pattern will be described in detail from FIG. 11 onwards. Note that the gradation is not limited to one that monotonically increases or decreases, but may include noise partially, and only needs to increase or decrease when a moving average is taken.

Here, the printing rate refers to the ratio of pixels that are output by ejecting ink according to the value of the pixel data, among the pixels related to the pixel data corresponding to the nozzles in each head of the head unit. It is a value. For example, when the head unit 300 is scanned at a predetermined speed, if a specific nozzle is capable of ejecting X droplets (X is an integer), and if the nozzle performs the ejection operation at all positions, It becomes 100%. However, since the ejection operation may not be performed at all positions, the printing rate (%) is the number of times the output data (drive data) to actually perform the ejection operation is applied, using X droplets as a parameter. do.

The image drive waveform generation unit 28D is an example of a mask processing unit, and generates drive data based on image data that has been subjected to mask processing by applying a plurality of gradation masks included in a gradation allocation pattern. .

The recording unit 14 (head driving unit) drives the heads H1 to H4 to eject liquid from the plurality of nozzles N based on the drive data generated by the image drive waveform generation unit 28D.

Note that in this block diagram, an example in which the image forming apparatus side has a function to adjust the gradation allocation pattern has been described, but the function to adjust the gradation allocation pattern may be provided in the data creation unit 12B on the PC 2 side. .

Furthermore, in another information processing device (for example, a host device) connected to the PC 2, a program is set in advance and stored in a calculation file (for example, a CSV (Comma Separated Value) file or an Excel file). The ejection adjustment program for the gradation assignment pattern may be executed by reading the program at the step.

<Print sequence>
The gradation allocation adjustment of the present invention is applicable to multi-pass interlacing such as bidirectional printing.

Here, a printing sequence in image conversion when generating image data for each scan from a document (original data) including multi-pass interlacing will be described. FIG. 7 is a diagram showing patterns of a plurality of print sequences, and is an explanatory diagram of image conversion processing.

As image conversion processing, the data creation unit 12B (see FIG. 6) performs one scan of the head unit 300 in the main scanning direction ) to convert the image data for each output image.

One of the squares included in the grid shown in FIGS. 7(a) to (h) represents one dot of the recorded image. Further, the numbers inside the squares represent the scanning order of the head. Image data is formed in the order in which the pattern shown in FIG. 7 is repeated in the main scanning direction X and the sub-scanning direction Y.

Note that the number of times of printing in the main scanning direction X may be referred to as a pass. That is, if the number of times of printing in the main scanning direction X is one, it is called one pass, and if it is two, it is called two passes.

Further, the number of times of printing in the sub-scanning direction Y is sometimes referred to as interlacing. That is, if the number of times of printing in the sub-scanning direction Y is one, it is called 1/1 interlace, and if it is twice, it is called 1/2 interlace.

Further, the number of types of division is referred to as the number of divisions N. Specifically, in the case of one-pass 1/1 interlace shown in FIG. 7(b), N=1. Further, in the case of a 2-pass 1/1 interlace shown in FIG. 7(c) or a 1-pass 1/2 interlace shown in FIG. 7(d), N=2.

Further, in the case of 2-pass 1/2 interlace shown in FIG. 7(e), N=4. In the case of 4-pass 1/2 interlace shown in FIG. 7(f) or 2-pass 1/4 interlace shown in FIG. 7(g), N=8. In the case of 4-pass 1/4 interlacing shown in FIG. 7(h), N=16.

Note that the one-pass sequence shown in FIGS. 7(b) and 7(d) is performed in normal mode, FIG. 7(c), FIG. 7(e), FIG. 7(f), FIG. 7(g), and FIG. The sequence of multiple passes shown in h) may also be referred to as a multi-pass printing mode.

In the control of the present invention, the head array included in the head unit is divided in the sub-scanning direction, and each head array (first embodiment, third embodiment) or nozzle row (second embodiment) is lined up in the main scanning direction. , Fourth Embodiment), since the gradation allocation pattern is set, it is applicable to multi-pass interlacing, which is bidirectional printing in which images are printed in a superimposed manner.

Note that in the inkjet recording apparatuses 1 and 10, the multi-pass printing mode and the number of multi-passes at that time are specified, and the interlaced printing mode and the number of interlaces are specified in advance, such as by setting the initial printing method. The printing mode (multipass printing mode), the number of multipasses, and the number of interlaces are stored as printing methods in a storage medium such as a memory (not shown).

The setting of the gradation allocation pattern according to the present invention will be described below for the case where the print sequence is multi-pass interlaced.

<Example of gloss banding caused by multi-pass interlace printing>
Here, gloss banding that occurs when an image is formed in the multi-pass interlaced printing mode will be explained with reference to FIGS. 8 and 9.

FIG. 8 is a diagram illustrating how gloss banding occurs, and FIG. 9 is a diagram illustrating gloss banding. Specifically, in FIG. 8, an image is formed on the recording medium 101 by setting the printing sequence of N=8 in FIGS. 7(f) and 7(g) and scanning an arbitrary image area 8 times. It shows the gloss banding that occurs when In FIG. 9, (a) is a schematic diagram of a black filled-in diagram, and (b) is a photograph in which the recording medium is filled with a plurality of colors.

As shown in FIG. 8, when bidirectional printing is performed using a plurality of head arrays, the color of the uppermost layer differs due to the difference in the order of overlapping dots.

When bidirectional printing is performed in this way, when the ink undergoes a chemical reaction when exposed to UV light, the time from ink ejection until light is irradiated varies depending on the order in which the colors of the dots overlap. Therefore, due to the difference in the time during which the ink hardens and contracts after landing, a boundary occurs between a cured portion and an uncured portion. Such a boundary between cured and uncured occurs in a band shape along the scanning direction (main scanning direction) of the head, resulting in gloss banding of the recorded image, which is so-called gloss unevenness.

As shown in FIGS. 8 and 9, such a boundary occurs in a band shape along the main scanning direction of the head, and is caused by uneven gloss, which is caused by the height of the ink in the recorded image during curing. Banding occurs.

Further, as shown in the photograph of FIG. 9(b), gloss banding is particularly likely to occur in black.

Furthermore, in the conventional example shown in FIG. 1, the printing rate of the recording elements in the joint area of the recording element group is set to be smaller than the printing rate of the recording elements other than the joint area. Although density unevenness (density banding) can be suppressed, since the density is adjusted for each head, the gradation is steep and gloss banding may become noticeable.

In order to suppress such gloss banding, in the first embodiment of the present invention, a plurality of heads are arranged in the sub-scanning direction in the head array in order to allocate a gradation pattern to each head as the minimum unit in the head array. It is assumed that.

Here, FIG. 10 shows an example in which each head array is provided with a plurality of heads. FIG. 10 is a plan view of the vicinity of an image forming unit to which a plurality of heads are mounted in a staggered head array to which the first embodiment of the present invention is applied.

As shown in FIG. 10, the image forming unit 300a according to this embodiment includes a serial type head array. From the left side of Figure 5, six head arrays 300Ka, 300Ca, 300Ma, 300Ya, and 300CLa correspond to black (K), cyan (C), magenta (M), yellow (Y), clear (CL), and white (W). and 300W are installed.

The black (K) head array 300Ka according to this embodiment has four heads H1, H2, H3, and H4 arranged in a staggered manner in a nozzle row direction Y that is parallel to the conveyance direction T of the recording medium 101. Each of the heads H1, H2, H3, and H4 has a plurality of nozzle rows NA in the X direction.

In each of the heads H1, H2, H3, and H4, a plurality of nozzles that eject droplets onto the recording medium 101 are arranged in a row in the nozzle row direction (sub-scanning direction). In each of the heads H1, H2, H3, and H4, the number of nozzle rows may be one, or two or more rows may be arranged in parallel in the X direction.

In the head array 300Ka, the ends of the nozzle rows of adjacent heads are arranged so that they overlap in the nozzle row direction Y and are at different positions in the transport direction T. The nozzle row direction Y is the same direction as the conveyance direction.

In FIG. 10, regions where the ends of nozzle rows of adjacent heads overlap in the nozzle row direction Y are indicated by thick dotted line portions Oa, Ob, and Oc. These regions are referred to as overlap portions Oa, Ob, and Oc.

By overlapping the ends of the nozzle rows of adjacent heads in the nozzle row direction Y, the image forming unit 300a can form an image seamlessly between the heads in the nozzle row direction Y of the recording medium 101. . Note that the configurations of the other head arrays 300Ca, 300Ma, 300Ya, 300CLa, and 300Wa are similar to the configuration of the black (K) head array 300Ka, and therefore the description thereof will be omitted.

Although FIG. 10 shows an example in which four heads H1 to H4 are provided in the head array 300Ka, the number and arrangement of heads provided in the head array are not limited to this, and may be changed as appropriate. can. In the first embodiment described below, in order to perform dot adjustment, it is assumed that two or more heads are provided in the sub-scanning direction (Y) in each head array.

<Control of the first embodiment>
(Example of gradation assignment pattern for 3 heads)
Next, a specific example of an allocation pattern for a head array having a plurality of heads in the sub-scanning direction will be described using FIG. 11.

FIG. 11 is a diagram showing an example of a group of allocation patterns according to the first embodiment, which is applied to a head array having three heads. Note that, in FIG. 10, an example in which four heads H1 to H4 are provided in the head array is described, but in FIG. 11, an example in which three heads H1 to H3 are provided in each head array is described.

Specifically, in FIG. 11, (a) is a conceptual diagram showing the configuration of a plurality of head arrays 300Kb, 300Cb, and (b) is a conceptual diagram showing the assignment of a plurality of gradations that can be applied to each head array 300Kb, 300Cb. FIG. 3 is a diagram showing a group of patterns. Head arrays 300Kb and 300Cb correspond to examples of a first head array and a second head array, respectively.

In FIG. 11B, (1) shows an example in which gradation is assigned to the entire head array as one gradation assignment area. Note that the allocation pattern (1) corresponds to the first pattern.

In (2), the head arrays 300Kb and 300Cb are divided into the same number (=3) of heads H1, H2, and H3, and one gradation allocation area is assigned to each head. An example of assigning gradations to each is shown. Note that allocation patterns (2), (3), and (4) correspond to the second pattern.

In (3) and (4), the head array is divided into fewer than the number of heads (=2), and gradation allocation areas are assigned to each head unit of a different number. shows an example of assigning gradients of different lengths. That is, in (3) and (4), there is an area where the gradation is set with a first number of heads as one unit, and a region where the gradation is set with a second number of heads different from the first number as one unit. This is an example that includes a region.

Specifically, (3) shows an example in which the two heads H1 and H2 are set as one unit and set as an allocation area to which one gradation is applied, and the head H3 is set as one unit and set as one gradation allocation area. .

(4) shows an example in which one gradation allocation area is set with one head H1 as one unit, and one gradation allocation area is set with heads H2 and H3 as one unit.

Here, as a gradation assignment pattern, if one gradation is applied over a wide range as in (1), the gradation is gentle, so the gloss banding is less noticeable, but the density banding due to the joint of the head is noticeable. There is.

On the other hand, if a gradation is applied to each head as in (2), density banding due to head joints can be prevented, but since the gradation is steep, gloss banding is noticeable.

In addition, in (3) and (4), the part where the gradation is applied to the same size as the head prevents density banding, makes gloss banding stand out, and In the area where the gradation is applied using two heads as one unit, gloss banding is prevented and density banding is noticeable, as in the case where the gradation is applied over the entire area.

By selecting a gradation assignment pattern mask that includes different division units for each head array from among gradation assignment patterns with different characteristics, countermeasures against density banding and countermeasures against gloss banding can be implemented for each color. , both can be combined. Therefore, both density banding and gloss banding can be suppressed in the formed image.

Here, when selecting a gradation assignment mask for the plurality of head arrays 300Kb and 300Cb, it is preferable to include at least one gradation assignment pattern (1) shown in FIG. 11(b) in order to prevent gloss banding. be.

<Example of gradation assignment pattern for 4 heads>
FIG. 12 is a diagram showing an example of a group of allocation patterns according to the first embodiment in a head array having four heads.

Specifically, in FIG. 12, (a) is a conceptual diagram showing the configuration of a plurality of head arrays 300Ka, 300Ca, and (b) is a conceptual diagram showing the assignment of a plurality of gradations that can be applied to each head array 300Ka, 300Ca. It is a figure showing a pattern. Head arrays 300Ka and 300Ca correspond to examples of a first head array and a second head array, respectively.

In FIG. 12B, (1) shows an example in which gradation is assigned to the entire head array as one gradation assignment area. Note that the allocation pattern (1) corresponds to the first pattern.

(2) shows an example in which the head array is divided into the same number of heads (=4), and each head is assigned one gradation allocation area, and each head is assigned a gradation of equal length. There is. Note that allocation patterns (2), (3), (4), and (5) correspond to the second pattern.

(3) shows an example in which the three heads H1, H2, and H3 are set as one unit to be assigned to one gradation, and the head H4 is set as one unit to be assigned to one gradation assignment area.

(4) shows an example in which one gradation allocation area is set with one head H1 as one unit, and one gradation allocation area is set with three heads H2, H3, and H4 as one unit.

(5) shows an example in which one gradation allocation area is set with two heads H1 and H2 as one unit, and one gradation allocation area is set with two heads H3 and H4 as one unit. That is, in (5), a gradation assignment pattern is set in which one gradation is evenly assigned to each of a plurality of heads (every two heads).

Although not shown, as another example, in a head array having four heads, the gradation area is divided into three. It is also possible to set three gradation allocation patterns including one gradation in which two heads constitute one allocation area.

Therefore, in a configuration in which the head array includes four heads, the number of gradation assignment patterns that can be set is eight.

Comparing FIG. 11 and FIG. 12, as the number of heads provided in one head array in the sub-scanning direction increases, the number of selectable gradation assignments also increases. When setting a gradation for each head, if the number of types of gradation allocation patterns that can be set is P, it is expressed as "P=2n", where n corresponds to the "number of heads".

Therefore, when the number of heads in the head array is two, there are two ways, when there are three, there are four ways as shown in Figure 11, when there are four, there are eight ways in total (the pattern shown in Figure 12 + three ways), and when there are five, there are eight ways. In the case of 6, there are 16 ways, and in the case of 6, there are 32 ways, etc.

It is preferable that the types of these applicable gradation assignment patterns are stored in advance in the assignment pattern storage unit 28B as a group of gradation assignment patterns for each number of heads.

From the group of assignment patterns, a gradation assignment pattern is selected and set for at least one head to be different from the other heads from among the P numbers, depending on the number of head arrays to be used.

(Flow of the first embodiment)
FIG. 13 is a flowchart showing a gradation mask setting procedure according to the first embodiment of the present invention.

In step S11, image data and print mode are input.

In step S12, a group of a plurality of preset gradation assignment patterns is read out according to the number of heads in the head array.

Step S13 selects and sets a different gradation assignment pattern for each head array from the group of gradation assignment patterns read out in S12. The gradation assignment pattern includes a first pattern in which one gradation is set so that the printing rate is large in the center and small in both ends for the entire head array in the sub-scanning direction, and an arbitrary number of gradation patterns. Each head includes a second pattern in which a gradation is set such that the printing rate is high in the center and the printing rate is small at both ends.

Then, in step S14, a print sequence is determined and the number of scans for the print is set. Note that the print sequence setting in S14 may be performed in parallel with steps S12 and S13.

In step S15, gradation mask processing corresponding to the selected gradation assignment pattern is performed on the image data, and the data is output as drive data (drive waveform) and sent to the recording section (head drive section) 14.

In this way, by setting different gradation allocation patterns for head arrays, gradation masks with different range lengths with the head as the minimum unit can be applied to each head array or each nozzle row of the head array. It is possible to suppress both density banding and gloss banding in an image. A specific example of allocation will be explained below.

<Assignment example 1: Unique head array>
FIG. 14 is an explanation showing an example in which a different pattern is applied to each head array of a different color in the gradation allocation pattern according to the first embodiment when one image area is scanned eight times to form an image. It is a diagram.

In Figure 14, in multi-pass interlacing, each image area is scanned with line breaks in each pass, so the image data is divided into blocks in the sub-scanning direction of the head scanning area according to the number of passes, and is scanned multiple times. The paths overlap and complement each other to form an image.

Here, in a portion where passes for forming one image overlap, a plurality of image data for forming one image are combined so that images formed by other scans complement each other. It is allocated (distributed) for each scan.

For example, image area 1 corresponding to one head array is allocated and formed in the 1st to 8th scans, image area 2 is allocated and formed in the 5th to 16th scans, and image area 3 is allocated and formed in the 13th to 24th scans. It is formed by That is, one image area is formed by eight scans.

Therefore, if you want to assign a gradation assignment pattern to an image formed by multi-pass interlace like this, set the gradation assignment pattern immediately after the image data is input, and apply each gradation mask included in that pattern. After application, it is preferable to allocate image data for each scan to each image area.

When forming an image using multi-pass interlacing in which the image is scanned with line breaks in this way, by setting different gradation allocation patterns for each head array, gradations with different ranges of change can be included. Therefore, the image data contains a mixture of steep gradations and gentle gradations, and both density banding and gloss banding can be suppressed.

<Assignment example 2: Same color head array>
FIG. 15 shows an example in which a different pattern is applied to each head array of the same color in the gradation allocation pattern according to the first embodiment when an image is formed by scanning eight times for one image area. It is a diagram.

In FIG. 14 described above, an example was explained in which different gradation assignment patterns are set for head arrays of different colors. However, when two or more head arrays 300K1 and 300K2 of the same color are provided in a head unit, the entire head array area is For each head array of the same color, a different gradation allocation pattern may be set with the head as the minimum division unit.

Even in a configuration where two head arrays 300K1 and 300K2 of the same color are provided, gloss banding may occur because the time required for curing by irradiation differs depending on whether scanning is performed in an odd number of times or an even number of times. However, by setting different gradation allocation patterns for each head array as shown in FIG. 15, both density banding and gloss banding can be suppressed.

In the above description, the plurality of heads are arranged in a staggered row as the head array, but the plurality of heads provided in the head array to which the first embodiment of the present invention is applied may have different shapes. .

(First modification)
FIG. 16 is a diagram illustrating an example of a group of a plurality of gradation assignment patterns of the first embodiment, which is applied to a head array in which a plurality of heads are arranged linearly, according to a first modification.

Specifically, in FIG. 16, (a) is a conceptual diagram showing the configuration of a plurality of head arrays 300Kd, 300Cd, and (b) is a conceptual diagram showing a plurality of gradation assignment patterns that can be applied to each head array 300Kd, 300Cd. It is a figure which shows the example of the group of. Head arrays 300Kd and 300Cd correspond to examples of a first head array and a second head array, respectively.

In the head arrays 300Kd and 300Cd shown in FIG. 16A, three or more heads Ha, Hb, and Hc are arranged in contact with or close to each other so as to be lined up in the same straight line in the sub-scanning direction. In this configuration, the areas around the boundaries of adjacent heads that do not overlap are defined as joint areas J1 and J2.

Further, the gradation assignment pattern shown in FIG. 16(b) is the same as that in FIG. 11(b).

In this modification as well, in order to apply a gradation mask with a different range length to each head array, with the head as the smallest unit, countermeasures against density banding and countermeasures against gloss banding are combined and handled for each color. Different. Therefore, both density banding and gloss banding can be suppressed in the formed image.

Although FIG. 16 shows an example in which gradation masks with different range lengths according to the first embodiment are applied to head arrays of different colors in the first modification, in this configuration also, the gradation masks as shown in FIG. Furthermore, the gradation masks with different range lengths according to the first embodiment may be applied to a plurality of head arrays of the same color.

(Second modification)
FIG. 17 is a diagram illustrating an example of a group of a plurality of gradation assignment patterns according to the first embodiment, which is applied to a head array in which a plurality of heads are arranged in a stepwise manner, according to a second modification.

Specifically, in FIG. 17, (a) is a conceptual diagram showing the configuration of a plurality of head arrays 300Ke, 300Ce, and (b) is a conceptual diagram showing a plurality of gradation assignment patterns that can be applied to each head array 300Ke, 300Ce. It is a figure which shows the example of the group of. Head arrays 300Ke and 300Ce correspond to examples of a first head array and a second head array, respectively.

In the head arrays 300Ke and 300Ce shown in FIG. 17(a), three or more heads Hd, He, and Hf are arranged in a stepwise manner, that is, the heads Hd, He, and Hf are arranged in positions in the scanning direction. The heads, which are all different and adjacent in the scanning direction, are arranged while being shifted in stages in the sub-scanning direction so that they overlap at the ends of the nozzle rows in the sub-scanning direction. In this configuration, the joint regions where the boundaries of adjacent heads overlap are Od and Oe.

Further, the gradation assignment pattern shown in FIG. 17(b) is the same as that in FIG. 11(b).

In this modification as well, in order to apply gradation masks with different range lengths with the head as the minimum unit to each head array or each nozzle row of the head array, countermeasures against density banding and countermeasures against gloss banding are applied for each color. , can be combined to support both. Therefore, both density banding and gloss banding can be suppressed in the formed image.

Although FIG. 17 shows an example in which gradation masks with different range lengths according to the first embodiment are applied to head arrays of different colors in the second modified example, in this configuration as well, Furthermore, the gradation masks with different range lengths according to the first embodiment may be applied to a plurality of head arrays of the same color.

Note that in FIGS. 11, 12, 14, and 15, each head is provided with one nozzle row in the scanning direction (main scanning direction), but each head has multiple nozzle rows. Even in a configuration in which a plurality of head arrays of the same color are provided, the gradation masks having different range lengths according to the first embodiment may be applied to a plurality of head arrays of the same color.

Alternatively, in a configuration in which each head is provided with a plurality of nozzle rows, different gradation patterns can be assigned to each nozzle row within the head. This example will be described below as a second embodiment.

≪Second Example≫
Next, the ejection adjustment in the second embodiment of the present invention will be explained using FIGS. 18 to 20.

In the second embodiment, assignment of a gradation pattern to a head array including a head in which a plurality of nozzle rows are arranged in the sub-scanning direction will be described. Note that in this control, since a pattern is assigned to each nozzle row, there may be one head array in the sub-scanning direction in the head unit, or a plurality of head arrays may be provided as in the first embodiment. It's okay.

FIG. 18 is a diagram showing an example of a group of a plurality of gradation assignment patterns according to the second embodiment, which is applied to a head array in which heads having a plurality of nozzle rows are arranged in a staggered manner.

Specifically, in FIG. 19, (a) is a conceptual diagram showing the configuration of a plurality of nozzle rows NK, NC in the head array 300KC, and (b) is a conceptual diagram showing the configuration of each nozzle row NK, NC in the head array 300KC. FIG. 3 illustrates an example of a group of gradation assignment patterns that may be applied. The nozzle rows NK and NC correspond to examples of a first nozzle row and a second nozzle row, respectively.

In the second embodiment, a first pattern is used for a first nozzle row (nozzle row NK) included in a head array, and a second pattern is used for a second nozzle row (nozzle row NC). The difference from the first embodiment is that the image data is masked using the mask processing method.

In addition, in the sub-scanning direction, a first pattern in which one gradation is set for the entire head array so that the printing rate in the center is large and the printing rate in both ends is small, and for each arbitrary number of heads, This embodiment is similar to the first embodiment in that it includes a second pattern in which a gradation is set such that the printing rate is high in the center and the printing rate is low at both ends.

Similar to the first embodiment, the gradation pattern of the entire head array (1) has a high effect of suppressing gloss banding and a low effect of suppressing density banding. On the other hand, each head in (2) has a high effect of suppressing density banding due to gradation patterns and seams, and a low effect of suppressing gloss banding.

Therefore, in this control, a first pattern (gradation) is set for one nozzle row NK, and a second pattern (gradation pattern) different from the first pattern is set for the other nozzle row CN. Select from (1) to (4) in FIG. 18, assign, and set.

Here, when selecting a gradation assignment pattern (mask) for a plurality of nozzle rows, it is preferable to include at least one gradation assignment pattern (1) shown in FIG. 18(b) in order to prevent gloss banding. be.

Therefore, for example, the gradation pattern (1) in FIG. 18(b) is selected as the first pattern, and the gradation pattern (2), (3), (4) in FIG. 18(b) is selected as the second pattern. It is preferable to select one of these and set it for each nozzle row.

The configuration for executing the second embodiment is the same as the functional block diagram of FIG. 6 for executing the first embodiment.

FIG. 19 is a control flowchart according to the second embodiment of the present invention.

In this embodiment, in S23, a different gradation assignment pattern is assigned to each nozzle row of the head array. Other points are common to the first embodiment.

FIG. 20 is an explanatory diagram showing an example in which a different pattern is applied to each nozzle row of a different color in the gradation assignment pattern of the second embodiment when one image area is scanned eight times to form an image. It is.

In this embodiment as well, in multi-pass interlacing, each image area is scanned with a new line in each pass, so the image data is divided into blocks in the sub-scanning direction of the scanning area of the head according to the number of passes. The two passes overlap and complement each other to form an image.

Then, in areas where passes for forming one image overlap, image data for forming one image is shared between multiple scans so that the images formed by other scans complement each other. It is allocated (separately fired) for each nozzle row.

Therefore, by setting the gradation area to be different in the sub-scanning direction as shown in Figure 20, the gradation range differs for each nozzle row, resulting in a mixture of steep gradation and gentle gradation in the image data. Therefore, both density banding and gloss banding can be eliminated.

Although FIG. 20 describes an example in which a different gradation allocation pattern is set for each nozzle row of a different color, if a plurality of nozzle rows ejecting the same color are formed in each head array, the example shown in FIG. The gradation mask having a different range length according to the second embodiment may be applied to each nozzle row of the same color in the head array.

Furthermore, in the configurations shown in FIGS. 18 and 20, a plurality of nozzle rows are arranged in the scanning direction in each head, unlike the staggered configuration shown in FIG. 11 of the first embodiment. Although the second embodiment is applicable to a configuration in which a plurality of nozzle rows are arranged in a head, even if the heads are arranged in the same straight line in the sub-scanning direction as shown in FIG. Alternatively, as shown in FIG. 17, the nozzle row ends of adjacent heads may be arranged in a stepped manner so as to overlap in the sub-scanning direction.

Furthermore, in FIGS. 18 and 20, the configuration in which the head array has one head in the scanning direction except for the overlapped portion has been described, but the head having multiple nozzle rows also has a single head in the scanning direction except for the overlapped portion. Control for assigning a gradation pattern to each nozzle row may also be applied to a head array arranged in a plurality of directions. For example, if a head with two nozzle rows is provided in two rows in the scanning direction even in areas other than the overlapped part, a maximum of four types of Gradation patterns can be set separately. Note that if a different gradation pattern is applied to at least one nozzle row among four nozzle rows in a head unit including a head array having a plurality of heads in the sub-scanning direction, the second embodiment of the present invention is applied. Assume that the example applies.

In the first and second embodiments described above, for a configuration in which a plurality of heads are provided in the sub-scanning direction in one head array, gradation assignment patterns are applied to different head arrays or different nozzle rows. Although the control for each assignment has been described, the gradation assignment control of the present invention can be applied even to a configuration in which one head is provided in the sub-scanning direction in one head array. An example of this will be described below as a third embodiment.

≪Third Example≫
FIG. 21 is a functional block diagram of a control unit related to image processing of an image forming apparatus according to a third embodiment of the present invention.

In the head array to which this embodiment is applied, one head is provided in one head array in the sub-scanning direction, as shown in FIG. In this embodiment, in order to allocate gradation to a configuration of a plurality of head arrays in which a single head is provided, it is necessary to divide regions within one head.

Therefore, the recording control unit 28α of the image forming apparatus 30α that implements this embodiment includes a head division number setting unit 28E and an allocation pattern storage unit 28F for each division number.

Specifically, the allocation pattern storage unit 28F for each division number stores an allocation pattern for each division number. For example, as shown in FIG. 22, when the head is divided into three, there are 4 types of allocation patterns, when the number of divisions is 4, there are 8 types, when the number of divisions is 5, there are 16 types, and when the number of divisions is 6, there are 32 types. The street becomes...

The gradation allocation setting unit 28Cα of this embodiment sets different gradation allocation patterns for the entire head array area in the sub-scanning direction, using divided regions as the minimum division unit.

In this embodiment, the gradation assignment pattern for each head associated with the head array includes at least a pattern ((1) in FIG. 22(b)) in which the gradation is assigned using the entire head array as one gradation assignment area. and may include an allocation pattern ((2) in FIG. 22(b)) in which one divided region in the head array is the minimum division unit.

The image drive waveform generation unit 28Dα generates drive data for each head based on image data that has been subjected to mask processing by applying a plurality of gradation masks included in the gradation assignment pattern.

The recording unit 14 (head driving unit) drives the head Hg to eject liquid from the plurality of nozzles N based on the drive data generated by the image drive waveform generation unit 28Dα.

FIG. 22 is a diagram showing an example of a group of gradation assignment patterns according to the third embodiment of the present invention, which is applied to one head array in which one head is arranged.

Specifically, in FIG. 22, (a) is a conceptual diagram showing the configuration of a plurality of head arrays 300K, 300C, and (b) is a conceptual diagram showing a plurality of gradation assignment patterns that can be applied to each head array 300K, 300C. It is a figure which shows the example of the group of. Head arrays 300Kf and 300C correspond to examples of a first head array and a second head array, respectively.

In the third embodiment, the gradation allocation setting unit 28Cα sets one gradation for the entire head array in the sub-scanning direction so that the printing rate at the center is large and the printing rate at both ends is small. The point of setting is to include a pattern and a second pattern in which a gradation is set for each arbitrary number of divisions into which the head array is divided so that the printing rate is large in the center and the printing rate is small at both ends. This is different from the first embodiment.

In addition, the first pattern is used for the first head array (for example, 300K) included in the plurality of head arrays, and the second pattern is used for the second head array (for example, 300C), so that the image This embodiment is similar to the first embodiment in that data is masked.

In FIG. 22(b), the gradation pattern of the entire head array (1) has a high effect of suppressing gloss banding and a low effect of suppressing density banding. On the other hand, the gradation pattern for each small division unit (2) has a high effect of suppressing density banding due to seams, but a low effect of suppressing gloss banding.

Therefore, in this control, one head (head array) is set with a first pattern (gradation pattern), and the other head (head array) is set with a second pattern (different from the first pattern). gradation pattern) is selected from (1) to (4) in FIG. 22(b) and assigned.

Here, in order to prevent gloss banding, it is preferable that at least one of the masks includes the gradation assignment pattern (1) shown in FIG. 22(b). Therefore, for example, the gradation pattern (1) in FIG. 22(b) is selected as the first pattern, and the gradation patterns (2), (3), and (4) in FIG. 22(b) are selected as the second pattern. It is preferable to select one of these and set it for each nozzle row.

FIG. 23 is a control flowchart according to the third embodiment of the present invention.

In this control, areas are set by dividing the head, so after inputting the print mode, the sub-scanning direction of the head is divided into a plurality of divided areas in S32.

Then, in S33, a group of gradation assignment patterns preset according to the number of divisions is read out. In the first embodiment, the group of allocation patterns to be used was determined by the number of heads in the sub-scanning direction in the head array as shown in FIGS. ) is divided in the sub-scanning direction to determine the group of allocation patterns to be used.

Thereafter, in the same steps as in the first embodiment, a different gradation pattern is assigned to each head array in S34, a print sequence is set in S35, and the gradation mask processing of the gradation assignment pattern is reflected in S36, and the drive data is Create.

In this way, when assigning a gradation assignment pattern to an image formed by multi-pass interlacing, set the gradation assignment pattern immediately after the image data is input, and apply each gradation mask included in that pattern. After this, it is preferable to allocate image data for each scan to each divided area.

FIG. 24 is an explanatory diagram showing an example in which a different pattern is applied to each head array of a different color in the gradation assignment pattern of the third embodiment when one image area is scanned eight times to form an image. It is.

In this embodiment as well, in multi-pass interlacing, each image area is scanned with a new line in each pass, so the image data is divided into blocks in the sub-scanning direction of the scanning area of the head according to the number of passes. The two passes overlap and complement each other to form an image.

Therefore, in areas where passes for forming one image overlap, image data for forming one image is transferred to the head array so that images formed by other scans complement each other. Allocated (separated) to each category.

Therefore, by setting the gradation area to be different in the sub-scanning direction as shown in Figure 24, the gradation range differs for each head array, resulting in a mixture of steep gradation and gentle gradation in the image data. This makes it possible to eliminate both density banding and gloss banding, which tend to occur with solid paint, especially black.

Although FIG. 24 describes an example in which different gradation allocation patterns are set for head arrays 300K and 300C of different colors, each head array is provided with a plurality of head arrays that eject the same color. In the configuration as well, gradation masks with different range lengths according to the third embodiment in which heads are divided and set may be applied to head arrays of the same color.

≪Fourth Example≫
FIG. 25 is a diagram showing an example of a group of gradation assignment patterns according to the fourth embodiment of the present invention, which is applied to one head array in which one head is arranged.

Specifically, in FIG. 25, (a) is a conceptual diagram showing the configuration of the plurality of nozzle rows NK1, NC1 of the head Hh provided in the head array 300KC1, and (b) is a conceptual diagram showing the configuration of the plurality of nozzle rows NK1, NC1 of the head Hh provided in the head array 300KC1. 7 is a diagram illustrating an example of a group of multiple gradation assignment patterns that can be applied to nozzle rows NK1 and NC1, respectively. FIG. The nozzle rows NK1 and NC1 correspond to an example of a first nozzle row and a second nozzle row, respectively.

In FIG. 25(b), the gradation pattern of the entire head array (1) has a high effect of suppressing gloss banding and a low effect of suppressing density banding. On the other hand, the gradation pattern for each small division unit (2) has a high effect of suppressing density banding due to seams, but a low effect of suppressing gloss banding.

Therefore, in this control, a first pattern (gradation) is set for one nozzle row, and a second pattern (gradation pattern) different from the first pattern is set for the other nozzle row. Select from (1) to (4) in Section 25(b), assign, and set.

Here, in order to prevent gloss banding, it is preferable that at least one gradation assignment pattern (1) shown in FIG. 25(b) is included. Therefore, for example, the gradation pattern (1) in FIG. 25(b) is selected as the first pattern, and the gradation patterns (2), (3), and (4) in FIG. 25(b) are selected as the second pattern. It is preferable to select one of these and set it for each nozzle row.

The configuration for executing the fourth embodiment is the same as the functional block diagram of FIG. 21 for executing the third embodiment.

FIG. 26 is a control flowchart according to the fourth embodiment of the present invention. This control is almost the same as the third embodiment, except that in S44, a gradation pattern is assigned to each nozzle row.

FIG. 27 is an explanatory diagram showing an example in which a different pattern is applied to each nozzle row of a different color in the gradation assignment pattern of the fourth embodiment when one image area is scanned eight times to form an image. It is.

In this embodiment as well, in multi-pass interlacing, each image area is scanned with a new line in each pass, so the image data is divided into blocks in the sub-scanning direction of the scanning area of the head according to the number of passes. The two passes overlap and complement each other to form an image.

Therefore, in areas where the passes for forming one image overlap, the image data for forming one image is transferred to the nozzle array so that the images formed by the other scans complement each other. Allocated (separated) to each category.

Therefore, by setting the gradation area to be different in the sub-scanning direction as shown in Fig. 27, the gradation range differs for each nozzle row, so that the image data contains a mixture of steep gradation and gentle gradation. This makes it possible to eliminate both density banding and gloss banding, which tend to occur with solid paint, especially black.

Note that in FIG. 27, an example was explained in which different gradation assignment patterns are set for each nozzle row of a different color. However, if each head array has a plurality of nozzle rows that eject the same color, the head array A different gradation allocation pattern may be set for each head array of the same color in which the minimum division unit is a division area for the entire head array.

In addition, although FIGS. 25 and 27 describe a configuration in which the head array has one head in the scanning direction, a head array in which a plurality of heads each having a plurality of nozzle rows is arranged in the scanning direction is also applicable. , control for assigning gradation patterns to nozzle rows may be applied. For example, if two rows of heads with two nozzle rows are provided in the scanning direction, up to four types of gradation patterns can be set separately for the four nozzle rows in the two rows and two head groups. can do. Note that if a different gradation pattern is applied to at least one nozzle row among four nozzle rows in a head unit including a head array having one head in the sub-scanning direction, the fourth embodiment of the present invention is applied. Assume that the example applies.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and within the scope of the embodiments of the present invention described in the claims. Various modifications and changes are possible.

14 Recording section (head drive section)
28A Print sequence setting section 28B Assignment pattern storage section 28C, 28Cα Gradation assignment setting section 28D Image drive waveform generation section (mask processing section)
28E Head division number setting section 28F Assignment pattern storage section for each division number 101 Recording medium 200 Carriage 300, 300a Image forming unit (head unit)
300K, 300C, 300M, 300Y, 300CL, 300W Head (head part, first head part, second head part)
300Ka, 300Ca, 300Ma, 300Ya, 300CLa, 300Wa Head array (first head array, second head array)
300Kb, 300Cb, 300Mb, 300Yb, 300CLb, 300Wb head array (first head array, second head array)
400 Irradiation unit H1, H2, H3, H4 Multiple heads (heads)
Ha, Hb, Hc Multiple heads (heads)
X Second direction (scanning direction)
Y First direction (sub-scanning direction, nozzle row direction)
N nozzle row

International Publication No. 2016/8152208

Claims (11)

A head having a nozzle row in which a plurality of nozzles that eject liquid onto a recording medium are arranged in a sub-scanning direction, a head array in which a plurality of nozzles are arranged in the sub-scanning direction, in a scanning direction perpendicular to the sub-scanning direction, A plurality of head units are arranged,
A scanning operation in which the head unit is moved in the scanning direction with respect to the recording medium while discharging the liquid onto the recording medium, and a scanning operation in which the head unit or the recording medium is moved in the scanning direction with respect to the recording medium without discharging the liquid. a moving unit that alternately performs an operation of moving the head unit in the sub-scanning direction relative to the head unit;
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a gradation allocation setting section that includes and sets a second pattern in which a gradation is set such that the printing rate is large and the printing rate at both ends is small;
Masking processing of image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array included in the plurality of head arrays. Department and
Equipped with a head drive unit that ejects liquid from multiple nozzles based on mask-processed image data ,
In the second pattern set by the gradation allocation setting section, one gradation is set for each of the plurality of heads.
Liquid discharge device. A head having a nozzle row in which a plurality of nozzles that eject liquid onto a recording medium are arranged in a sub-scanning direction, a head array in which a plurality of nozzles are arranged in the sub-scanning direction, in a scanning direction perpendicular to the sub-scanning direction, A plurality of head units are arranged,
A scanning operation in which the head unit is moved in the scanning direction with respect to the recording medium while discharging the liquid onto the recording medium, and a scanning operation in which the head unit or the recording medium is moved in the scanning direction with respect to the recording medium without discharging the liquid. a moving unit that alternately performs an operation of moving the head unit in the sub-scanning direction relative to the head unit;
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a gradation allocation setting section that includes and sets a second pattern in which a gradation is set such that the printing rate is large and the printing rate at both ends is small;
Masking processing of image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array included in the plurality of head arrays. Department and
Equipped with a head drive unit that ejects liquid from multiple nozzles based on mask-processed image data ,
The second pattern set by the gradation allocation setting section includes an area in which a gradation is set using a first number of heads as one unit, and a second number of heads different from the first number. Contains an area where the gradation is set as one unit.
Liquid discharge device. The liquid ejecting device according to claim 1 , wherein the first head array and the second head array eject liquids of different colors. The liquid ejection device according to claim 1 , wherein the first head array and the second head array eject liquid of the same color. Each head of the plurality of heads has a plurality of nozzle rows arranged in a sub-scanning direction in which a plurality of nozzles that eject liquid onto the recording medium are arranged in a scanning direction perpendicular to the sub-scanning direction.
The liquid ejection device according to any one of claims 1 to 4 . The head array is provided with three or more heads,
The heads adjacent in the sub-scanning direction are located at different positions in the scanning direction, and the ends of the nozzle rows of the heads adjacent in the sub-scanning direction are arranged so as to overlap in the sub-scanning direction. The liquid ejection device according to any one of Items 1 to 5 . The liquid ejecting device according to any one of claims 1 to 5 , wherein in the head array, the plurality of heads are arranged so as to be aligned in the same straight line in the sub-scanning direction. A discharge adjustment method for a liquid discharge device, the method comprising:
The liquid ejecting device includes a head having a nozzle row in which a plurality of nozzles for ejecting liquid onto a recording medium are arranged in a sub-scanning direction, and a head array in which a plurality of nozzles are arranged in the sub-scanning direction is perpendicular to the sub-scanning direction. a scanning operation in which a plurality of head units are arranged in a scanning direction, and the head units are moved relative to the recording medium in a scanning direction perpendicular to the sub-scanning direction while discharging the liquid onto the recording medium; and a moving unit that alternately moves the head unit or the recording medium in the sub-scanning direction relative to the recording medium or the head unit without ejecting liquid. and
The discharge adjustment method is
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a second pattern in which the gradation is set such that the printing rate is large and the printing rate at both ends is small;
masking image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array;
a head driving step of ejecting the liquid from the plurality of nozzles based on mask-processed image data ;
In the second pattern set in the gradation allocation setting step, one gradation is set for each of a plurality of heads.
Discharge adjustment method. A discharge adjustment method for a liquid discharge device, the method comprising:
The liquid ejecting device includes a head having a nozzle row in which a plurality of nozzles for ejecting liquid onto a recording medium are arranged in a sub-scanning direction, and a head array in which a plurality of nozzles are arranged in the sub-scanning direction is perpendicular to the sub-scanning direction. a scanning operation in which a plurality of head units are arranged in a scanning direction, and the head units are moved relative to the recording medium in a scanning direction perpendicular to the sub-scanning direction while discharging the liquid onto the recording medium; and a moving unit that alternately moves the head unit or the recording medium in the sub-scanning direction relative to the recording medium or the head unit without ejecting liquid. and
The discharge adjustment method is
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a second pattern in which the gradation is set such that the printing rate is large and the printing rate at both ends is small;
masking image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array;
a head driving step of ejecting the liquid from the plurality of nozzles based on mask-processed image data ;
The second pattern set in the gradation allocation setting step includes an area in which a gradation is set using a first number of heads as one unit, and a second number of heads different from the first number. Contains an area where the gradation is set as one unit.
Discharge adjustment method. A discharge adjustment program for a liquid discharge device, the program comprising:
The liquid ejecting device includes a head having a nozzle row in which a plurality of nozzles for ejecting liquid onto a recording medium are arranged in a sub-scanning direction, and a head array in which a plurality of nozzles are arranged in the sub-scanning direction is perpendicular to the sub-scanning direction. a scanning operation in which a plurality of head units are arranged in a scanning direction, and the head units are moved relative to the recording medium in a scanning direction perpendicular to the sub-scanning direction while discharging the liquid onto the recording medium; and a moving unit that alternately moves the head unit or the recording medium in the sub-scanning direction relative to the recording medium or the head unit without ejecting liquid. and
The discharge adjustment program is
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a second pattern in which the gradation is set such that the printing rate is large and the printing rate at both ends is small;
masking the image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array;
causing a computer to execute head driving processing for ejecting the liquid from the plurality of nozzles based on the mask-processed image data ;
In the second pattern set in the gradation allocation setting process, one gradation is set for each of the plurality of heads.
Discharge adjustment program. A discharge adjustment program for a liquid discharge device, the program comprising:
The liquid ejecting device includes a head having a nozzle row in which a plurality of nozzles for ejecting liquid onto a recording medium are arranged in a sub-scanning direction, and a head array in which a plurality of nozzles are arranged in the sub-scanning direction is perpendicular to the sub-scanning direction. a scanning operation in which a plurality of head units are arranged in a scanning direction, and the head units are moved relative to the recording medium in a scanning direction perpendicular to the sub-scanning direction while discharging the liquid onto the recording medium; and a moving unit that alternately moves the head unit or the recording medium in the sub-scanning direction relative to the recording medium or the head unit without ejecting liquid. and
The discharge adjustment program is
In the sub-scanning direction, one gradation is set for the entire area of the head array so that the printing rate at the center is large and the printing rate at both ends is small; a second pattern in which the gradation is set such that the printing rate is large and the printing rate at both ends is small;
masking the image data using the first pattern for a first head array included in the plurality of head arrays and using the second pattern for a second head array;
causing a computer to execute head driving processing for ejecting the liquid from the plurality of nozzles based on the mask-processed image data ;
The second pattern set in the gradation allocation setting process includes an area in which a gradation is set with a first number of heads as one unit, and a second number of heads different from the first number. Contains an area where the gradation is set as one unit.
Discharge adjustment program.

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