Inkjet recording system and inkjet recording method

Abstract

To solve a problem that, when an image is formed by a serial printing method, streak-like density unevenness extending in a main scanning direction is generated in a boundary region between unit images for each of pass operations adjacent to each other in a sub-scanning direction on a recording material, which reduces image quality.SOLUTION: When creating ink dot data for each pass operation for forming a unit image on a medium, a computer sets positions in a sub-scanning direction of each of a plurality of boundary end portion dots arrayed in a main scanning direction to positions corresponding to a plurality of pattern waveforms having different phases. The boundary end portion dots are dots among boundary region formation dots for forming a boundary region between unit images adjacent to each other in a plurality of ink dots included in each piece of ink dot data for each pass operation. The boundary end portion dots define the boundary in the sub-scanning direction between unit images adjacent to each other in the sub-scanning direction on a medium.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording system and an inkjet recording method. [Background technology]

[0002] Inkjet printers that perform printing on recording materials using a serial printing method are known. In inkjet printers using a serial printing method, a pass operation in which an ink head is moved in the main scanning direction while ejecting ink from the ink head to form band-shaped unit images extending in the main scanning direction on the recording material is repeatedly performed in an alternating manner, and a transport operation in which the recording material is transported in a sub-scanning direction perpendicular to the main scanning direction.

[0003] When forming an image using a serial printing method, stripes of uneven density extending in the main scanning direction may occur in the boundary areas on the recording material between unit images for each pass operation adjacent in the sub-scanning direction, resulting in reduced image quality. A technique for solving this problem is disclosed, for example, in Patent Document 1. In the technique disclosed in Patent Document 1, data on a pattern of ink dots for forming unit images is created such that edge dots in the sub-scanning direction that define the boundaries between unit images form uneven portions. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5065719 Summary of the Invention

[0005] According to one aspect of the present invention, an inkjet recording system includes an ink head movable in a main scanning direction and capable of ejecting ink onto a recording material, a transport unit capable of transporting the recording material in a sub-scanning direction perpendicular to the main scanning direction, a control unit that performs an image formation process to form a plurality of unit images on the recording material in the sub-scanning direction, each unit image consisting of a plurality of ink dots corresponding to at least one pass operation, by repeatedly performing a pass operation in which the ink head moves in the main scanning direction while ejecting ink from the ink head to form a plurality of ink dots on the recording material, and a dot data creation unit that performs an ink data creation process to create, for each pass operation, ink dot data indicating data on a pattern of a plurality of ink dots for forming each of the plurality of unit images on the recording material. The control unit controls the pass operation and the transport operation in the image formation process so that adjacent unit images in the sub-scanning direction partially overlap in the sub-scanning direction, thereby forming a boundary area extending in the main scanning direction on the recording material. In the ink data creation process, the dot data creation unit sets the position in the sub-scanning direction of each of a plurality of boundary end dots that are arranged in the main scanning direction and that define the boundary in the sub-scanning direction between the unit images that are adjacent in the sub-scanning direction on the recording material, among the plurality of ink dots included in each of the ink dot data for one pass operation, to positions that correspond to a plurality of pattern waveforms that have wavelengths that correspond to the main scanning direction and amplitudes that correspond to the sub-scanning direction and that are out of phase. With this inkjet recording system according to one aspect of the present invention, it is possible to suppress degradation in the quality of images formed on the recording material.

[0006] An inkjet recording method according to another aspect of the present invention is a method for recording an image on a recording material using an ink head movable in a main scanning direction. This inkjet recording method includes an image forming step of forming a plurality of unit images on the recording material in the sub-scanning direction, each of which is composed of a plurality of ink dots corresponding to at least one pass operation, by repeatedly performing a pass operation in which the ink head moves in the main scanning direction while ejecting ink from the ink head to form a plurality of ink dots on the recording material, and a transport operation in which the recording material is transported in a sub-scanning direction perpendicular to the main scanning direction. The ink data creating step of creating, for each pass operation, ink dot data representing data on a pattern of a plurality of ink dots for forming each of the plurality of unit images on the recording material. In the image forming step, the pass operation and the transport operation are performed so that adjacent unit images in the sub-scanning direction partially overlap in the sub-scanning direction, forming a boundary area extending in the main scanning direction on the recording material. In the ink data creating step, among the plurality of ink dots included in each of the ink dot data for one pass operation, the positions in the sub-scanning direction of each of a plurality of boundary end dots arranged in the main scanning direction that define the boundary in the sub-scanning direction between the unit images adjacent in the sub-scanning direction on the recording material are set to positions corresponding to a plurality of pattern waveforms that have wavelengths corresponding to the main scanning direction and amplitudes corresponding to the sub-scanning direction and are out of phase. According to this inkjet recording method according to another aspect of the present invention, it is possible to suppress deterioration in the quality of the image formed on the recording material. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a diagram showing the overall configuration of an inkjet printing system according to an embodiment of the present invention. [Figure 2] FIG. 2 is a diagram for explaining an image forming operation in the inkjet recording system. [Figure 3]FIG. 3 is a flowchart showing the process flow of the inkjet recording method. [Figure 4] FIG. 4 is a diagram for explaining the process of creating ink dot data in an inkjet printing system. DETAILED DESCRIPTION OF THE INVENTION

[0008] The technology disclosed in the aforementioned Patent Document 1 prevents end dots in the sub-scanning direction from lining up in a straight line along the main scanning direction, which is thought to be able to suppress the occurrence of linear density unevenness along the main scanning direction. However, because the end dots in the sub-scanning direction are lined up along a single waveform with concave and convex portions, there is a risk of streak-like density unevenness along the single waveform occurring in the boundary regions between unit images.

[0009] Therefore, there is a demand for an inkjet recording system and an inkjet recording method that can suppress deterioration in the quality of images formed on recording materials.

[0010] An inkjet recording system according to an embodiment of the present invention will be described below with reference to the drawings. In the following embodiment, a specific example of an inkjet recording system will be exemplified, which is a system equipped with an inkjet printer having an ink head capable of ejecting ink for forming an image on a wide, long recording material. Inkjet printers are suitable for digital textile printing, which uses an inkjet method to print (record) images such as letters and patterns on a recording material that is a fabric material such as a woven or knitted fabric. Of course, the inkjet printer applied to the inkjet recording system according to the present invention can also be used to print various images on recording materials such as paper sheets and resin sheets.

[0011] As shown in FIG. 1, the inkjet recording system 1 includes an inkjet printer 2 and a computer 6 connected to the inkjet printer 2 so as to be able to communicate data with it. FIG. 1 shows a schematic configuration of the inkjet printer 2 as viewed from above. In the inkjet recording system 1, the computer 6 creates ink dot data DID based on image data DG of an image to be printed on a medium W, which is a recording material, and also functions as a dot data creation unit that creates treatment liquid dot data DRD. The inkjet printer 2 prints an image on the medium W using an inkjet method based on the ink dot data DID and treatment liquid dot data DRD created by the computer 6. Note that in the inkjet recording system 1, the computer 6 may be incorporated into the inkjet printer 2. That is, the inkjet printer 2 may have the function of a dot data creation unit in addition to the function of printing an image on the medium W using an inkjet method.

[0012] The inkjet printer 2 is a printer that prints images on a wide and long medium W using an inkjet method, and is equipped with an inkjet head 20 including an ink head 3 and a treatment liquid head 4, a transport unit 21 that can transport the medium W in a transport direction F, and a carriage 22 on which the inkjet head 20 is mounted.

[0013] The inkjet printer 2 is a so-called serial printer that performs printing on the medium W using a serial printing method. In the serial printing inkjet printer 2, as shown in FIG. 2, a pass operation is repeatedly performed in which ink is ejected from the ink head 3 while the carriage 22 is moved back and forth in the main scanning direction H1 to form multiple ink dots ID on the medium W, and a transport operation is repeatedly performed in which the medium W is transported in a transport direction F parallel to a sub-scanning direction H2 that is perpendicular to the main scanning direction H1 on a horizontal plane. As a result, multiple band-shaped unit images GA extending in the main scanning direction H1 are formed on the medium W in the sub-scanning direction H2, each unit image consisting of multiple ink dots ID corresponding to at least one pass operation. During the pass operation, treatment liquid may be ejected from the treatment liquid head 4. The transport operation is performed by the transport unit 21. The pass operation and the transport operation may be repeatedly performed alternately or sequentially.

[0014] The transport unit 21 includes a feed roller 211 that pays out the medium W before printing, and a take-up roller 212 that takes up the medium W after printing. The feed roller 211 is located at the upstream end in the transport direction F, and is a shaft that supports a roll that is a wound body of the medium W before printing. The take-up roller 212 is located at the downstream end in the transport direction F, and is a shaft that supports a roll that is a wound body of the medium W after printing. The take-up roller 212 is provided with a drive source such as a motor that drives the take-up roller 212 to rotate about its axis and perform a winding operation of the medium W. The transport unit 21 transports the medium W in the transport direction F by the feed roller 211 rotating in response to the rotational drive of the take-up roller 212.

[0015] The carriage 22 is equipped with the ink head 3 and treatment liquid head 4 included in the inkjet head 20, and is capable of reciprocating in a main scanning direction H1 perpendicular to the transport direction F. The carriage 22 is fixed to a timing belt 24 that is attached to a flat carriage guide 23 extending in the main scanning direction H1 so as to be able to rotate. The timing belt 24 is an endless belt, and is driven to rotate in the main scanning direction H1 while attached to the carriage guide 23. The carriage 22 moves back and forth in the main scanning direction H1 along the carriage guide 23 as the timing belt 24 rotates in the main scanning direction H1.

[0016] Each of the ink head 3 and the treatment liquid head 4 mounted on the carriage 22 can move relative to the media W in the main scanning direction H1 and the sub-scanning direction H2 as the media W is transported in the transport direction F by the transport unit 21 and the carriage 22 moves back and forth in the main scanning direction H1.

[0017] In this embodiment, the ink head 3 includes multiple individual heads 31 capable of ejecting ink of multiple colors, and these multiple individual heads 31 are mounted on the carriage 22. Each of the multiple individual heads 31 includes multiple nozzles that eject ink droplets using an ejection method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, an ink flow path that guides the ink to the nozzles, and a wiring board for controlling the ink ejection operation. For example, a water-based pigment ink containing a water-based solvent, pigment, and binder resin can be used as the ink. The multiple individual heads 31 are mounted on the carriage 22 so as to be aligned in two rows in the main scanning direction H1. Each individual head 31 for each color has two heads. Two individual heads 31 ejecting ink of the same color are mounted on the carriage 22 so as to be offset from each other in the main scanning direction H1 and the sub-scanning direction H2. In another embodiment, a configuration in which only one ink head 3 is mounted on the carriage 22 is possible.

[0018] In this embodiment, a pre-treatment liquid head 41 and a post-treatment liquid head 42 are each mounted on the carriage 22 as the treatment liquid head 4. The pre-treatment liquid head 41 and the post-treatment liquid head 42 are mounted on the carriage 22 so as to be positioned differently from the ink heads 3 in the transport direction F parallel to the sub-scanning direction H2. The pre-treatment liquid head 41 is mounted on the carriage 22 so as to be positioned upstream of the ink heads 3 in the transport direction F. FIG. 1 shows an example in which one pre-treatment liquid head 41 is positioned near one end of the array of multiple individual heads 31 in the ink head 3 in the main scanning direction H1. The post-treatment liquid head 42 is mounted on the carriage 22 so as to be positioned downstream of the ink head 3 in the transport direction F. FIG. 1 shows an example in which one post-treatment liquid head 42 is positioned near the other end of the array of multiple individual heads 31 in the ink head 3 in the main scanning direction H1. In another embodiment, either the pre-treatment liquid head 41 or the post-treatment liquid head 42 is mounted on the carriage 22 as the treatment liquid head 4.

[0019] The pretreatment liquid head 41 includes a number of nozzles that eject pretreatment liquid droplets using an ejection method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, a pretreatment liquid flow path that guides the pretreatment liquid to the nozzles, and a wiring board for controlling the ejection operation of the pretreatment liquid. The pretreatment liquid head 41 ejects the pretreatment liquid onto a position on the medium W before the ink is ejected by the ink head 3. The pretreatment liquid is a treatment liquid that is applied to the medium W before the ink. The pretreatment liquid is a treatment liquid that comes into contact with the ink in a wet state on the medium W and is a non-coloring treatment liquid that does not develop color even when attached to the medium W. The pretreatment liquid has the function of preventing ink bleeding on the medium W. Examples of such pretreatment liquids that can be used include a treatment liquid in which a binder resin is blended into a solvent, or a treatment liquid in which a positively charged cationic resin is blended into a solvent.

[0020] The post-treatment liquid head 42 includes a number of nozzles that eject post-treatment liquid droplets using an ejection method such as a piezoelectric method using a piezoelectric element or a thermal method using a heating element, a post-treatment liquid flow path that guides the post-treatment liquid to the nozzles, and a wiring board for controlling the ejection operation of the post-treatment liquid. The post-treatment liquid head 42 ejects the post-treatment liquid onto a position on the medium W after the ink has been ejected by the ink head 3. The post-treatment liquid is a treatment liquid that is applied to the medium W after the ink. The post-treatment liquid is a treatment liquid that comes into contact with the ink on the medium W in a non-dried state and is a non-color-forming treatment liquid that does not develop color even when attached to the medium W. The post-treatment liquid has the function of increasing the fixation of the ink on the medium W. A silicone-based treatment liquid or the like can be used as such a post-treatment liquid. Note that the pre-treatment liquid and the post-treatment liquid are different treatment liquids. Specifically, the components contained in the pre-treatment liquid and the post-treatment liquid are different.

[0021] Here, non-colorable treatment liquid refers to a liquid that, when printed alone on media W, is not recognized as having a color by the naked eye. Color here includes colors with a saturation of 0 (zero), such as black, white, and gray. Non-colorable treatment liquids are basically colorless and transparent, but they are not completely colorless and transparent and may appear slightly white. Such colors are very light, so when printed alone on media W, they are not recognized as having a color by the naked eye. Note that, depending on the type of treatment liquid, when printed alone on media W, changes such as glossiness may occur on the media W, but this state is not considered colored.

[0022] As shown in FIG. 1, the inkjet printer 2 further includes a printer control unit 5. The printer control unit 5 controls pass operations by an inkjet head 20, which includes an ink head 3 and a treatment liquid head 4 mounted on a carriage 22, and a transport operation of the medium W by a transport unit 21. Based on data created by a computer 6 (described below), the printer control unit 5 performs an image formation process that repeatedly performs a pass operation in which ink is ejected from the ink head 3 and treatment liquid is ejected from the treatment liquid head 4 while moving the carriage 22 in a main scanning direction H1, and a transport operation of the medium W by the transport unit 21 in a transport direction F parallel to the sub-scanning direction H2. In this way, the printer control unit 5 forms a plurality of unit images GA, each consisting of a plurality of ink dots ID corresponding to at least one pass operation, on the medium W in the sub-scanning direction H2, as shown in FIG. 2. In this image forming process, the printer control unit 5 performs pass operations and conveyance operations so that part of the unit images GA adjacent in the sub-scanning direction H2 overlap in the sub-scanning direction H2, forming a boundary area BA on the medium W that extends in the main scanning direction H1. The boundary area BA between unit images GA adjacent in the sub-scanning direction H2 is an area where the ink dots ID for forming the boundary area BA, namely, the boundary area-forming dots IDS, are mixed along the main scanning direction H1, among the ink dots ID for forming each unit image GA. By forming such a boundary area BA on the medium W, the occurrence of streaks and the like resulting from the gaps between unit images GA adjacent in the sub-scanning direction H2 is suppressed.

[0023] The printer control unit 5 sets the transport length of the medium W for each pass of the transport operation by the transport unit 21 to a length equivalent to the difference between the effective pixel width of the ink head 3 and the boundary area width of the boundary area BA divided by the number of passes used to form the unit image GA. The effective pixel width of the ink head 3 is expressed as the number of dots corresponding to the number of nozzles arranged in the sub-scanning direction H2 among the multiple nozzles provided in the ink head 3. The boundary area width of the boundary area BA indicates the width of the boundary area BA in the sub-scanning direction H2, and is expressed as the number of dots of boundary area forming dots IDS arranged in the sub-scanning direction H2 within the boundary area BA.

[0024] For example, when forming a unit image GA in one pass operation, the printer control unit 5 sets the transport length of the medium W for each pass operation in the transport operation by the transport unit 21 to a length equivalent to the difference between the effective pixel width of the ink head 3 and the boundary area width of the boundary area BA divided by the number of passes to form the unit image GA, which is 1. In this case, the combination of pass operations to form boundary areas BA between adjacent unit images GA in multiple unit images GA that are consecutive in the sub-scanning direction H2 on the medium W is the combination of the first pass operation and the second pass operation, the second pass operation and the third pass operation, and so on.

[0025] When forming a unit image GA in two passes, the printer control unit 5 sets the transport length of the medium W for each pass in the transport operation by the transport unit 21 to a length equivalent to the difference between the effective pixel width of the ink head 3 and the boundary area width of the boundary area BA divided by 2, which is the number of passes to form the unit image GA. In this case, the combinations of pass operations to form boundary areas BA between adjacent unit images GA in multiple unit images GA that are consecutive in the sub-scanning direction H2 on the medium W are the combinations of the first pass and the third pass, the second pass and the fourth pass, and so on.

[0026] When forming a unit image GA in four passes, the printer control unit 5 sets the transport length of the medium W for each pass in the transport operation by the transport unit 21 to a length equivalent to the difference between the effective pixel width of the ink head 3 and the boundary area width of the boundary area BA divided by the number of passes to form the unit image GA, which is "4." In this case, the combinations of pass operations to form boundary areas BA between adjacent unit images GA in multiple unit images GA that are consecutive in the sub-scanning direction H2 on the medium W are the combinations of the first pass and the fifth pass, the second pass and the sixth pass, the third pass and the seventh pass, the fourth pass and the eighth pass, and so on.

[0027] As described above, the combination of pass operations for forming the boundary area BA between unit images GA adjacent to each other in the sub-scanning direction H2 on the medium W is uniquely determined according to the number of pass operations for forming the unit images GA.

[0028] The computer 6 is a personal computer that has a CPU (Central Processing Unit), a storage area such as an HDD (Hard Disk Drive) or flash memory that stores processing programs, RAM (Random Access Memory) used as a working area for the CPU, etc. The computer 6 performs ink data creation processing to create ink dot data DID by the CPU executing the processing programs stored in the HDD or flash memory, and also functions as a dot data creation unit that performs treatment liquid data creation processing to create treatment liquid dot data DRD that includes pre-treatment liquid dot data DRD1 and post-treatment liquid dot data DRD2.

[0029] The computer 6 performs ink data creation processing to create ink dot data DID as data used by the printer control unit 5 to control the ejection of ink from the ink head 3 for each pass operation, and performs treatment liquid data creation processing to create treatment liquid dot data DRD as data used by the printer control unit 5 to control the ejection of treatment liquid from the treatment liquid head 4 for each pass operation.

[0030] In the inkjet recording system 1 according to this embodiment, the printer control unit 5 and the computer 6 execute the processes of each step of the inkjet recording method. The processes of each step of the inkjet recording method executed by the printer control unit 5 and the computer 6 will be described in detail with reference to FIGS.

[0031] 2 under the control of the printer control unit 5, image quality may be reduced due to the occurrence of streak-like density unevenness extending in the main scanning direction H1 in the boundary area BA between unit images GA adjacent in the sub-scanning direction H2 on the medium W. In the inkjet recording system 1 according to this embodiment, the computer 6 creates ink dot data DID that can suppress the occurrence of streak-like density unevenness in the boundary area BA between unit images GA.

[0032] Specifically, the computer 6 acquires image data DG of an image to be printed on the medium W (image data acquisition step s1). Upon acquiring the image data DG, the computer 6 performs an ink data creation process to create, for each pass operation, ink dot data DID indicating data on a pattern of multiple ink dots ID for forming each of multiple unit images GA on the medium W in accordance with the ejection of ink by the ink head 3, based on the image data DG (ink data creation step s2). The computer 6 performs halftone processing such as dithering on the image data DG to convert the image data DG into halftone image data that can be printed on the medium W by the inkjet printer 2. In this way, the computer 6 creates ink dot data DID with a resolution that can be printed by the inkjet printer 2.

[0033] 4, when creating ink dot data DID for each pass operation, the computer 6 sets the position in the sub-scanning direction H2 of each of the plurality of boundary end dots IDS1 lined up in the main scanning direction H1 among the plurality of ink dots ID included in each ink dot data DID for each pass operation to positions corresponding to the plurality of out-of-phase pattern waveforms SW1, SW2, SW3, SW4 among the plurality of boundary area forming dots IDS lined up in the main scanning direction H1 to form the boundary area BA, which defines the boundary B in the sub-scanning direction H2 between the unit images GA adjacent in the sub-scanning direction H2 on the medium W.

[0034] FIG. 4 shows boundary area forming dots IDS for forming a boundary area BA between unit images GA adjacent in the sub-scanning direction H2 for the multiple ink dots ID included in each ink dot data DID for each pass. Specifically, FIG. 4 shows boundary area forming dots IDS for forming a boundary area BA between a first unit image GA and a second unit image GA adjacent to the first unit image GA on the upstream side of the transport direction F. The boundary area BA is an area where boundary area forming dots IDS corresponding to the first unit image GA and boundary area forming dots IDS corresponding to the second unit image GA coexist along the main scanning direction H1. As described above, the combination of pass operations for forming the boundary area BA between the first unit image GA and the second unit image GA is uniquely determined by the number of pass operations for forming the unit images GA. The boundary area forming dots IDS for the first unit image GA are shown as dots shaded with multiple diagonal lines, and the boundary area forming dots IDS for the second unit image GA are shown as dots shaded with multiple dots. Furthermore, among the boundary area forming dots IDS of the first unit image GA, of the multiple boundary end dots IDS1 aligned in the main scanning direction H1 that define the boundary B in the sub-scanning direction H2 between the first unit image GA and the second unit image GA, the boundary end dots IDS1 located within the boundary area BA are indicated by dots shaded with multiple diagonal lines and surrounded by thick solid frames, while the boundary end dots IDS1 located outside the boundary area BA are indicated by dots shaded with multiple diagonal lines and surrounded by thick dashed frames. Similarly, among the boundary area forming dots IDS of the second unit image GA, of the multiple boundary end dots IDS1 aligned in the main scanning direction H1 that define the boundary B in the sub-scanning direction H2 between the first unit image GA and the second unit image GA, the boundary end dots IDS1 located within the boundary area BA are indicated by dots shaded with multiple dots and surrounded by thick solid frames, while the boundary end dots IDS1 located outside the boundary area BA are indicated by dots shaded with multiple dots and surrounded by thick dashed frames.

[0035] The boundary B in the sub-scanning direction H2 between a first unit image GA and a second unit image GA adjacent in the sub-scanning direction H2 on the medium W is defined by a boundary end dot IDS1 located at the most upstream position in the transport direction F at each position in the main scanning direction H1 in the boundary area forming dot IDS corresponding to the first unit image GA, and a boundary end dot IDS1 located at the most downstream position in the transport direction F at each position in the main scanning direction H1 in the boundary area forming dot IDS corresponding to the second unit image GA.

[0036] The position in the main scanning direction H1 of each of the multiple boundary end dots IDS1 lined up in the main scanning direction H1 is defined by a main scanning coordinate J that indicates the coordinate on a coordinate axis parallel to the main scanning direction H1. In the example of Fig. 4, the main scanning coordinate J is shown to be composed of a total of 32 coordinate groups: "0, 1, 2,..., 29, 30, 31." Similarly, the position in the sub-scanning direction H2 of each of the multiple boundary end dots IDS1 is defined by a sub-scanning coordinate I that indicates the coordinate on a coordinate axis parallel to the sub-scanning direction H2. In the example of Fig. 4, the sub-scanning coordinate I is shown to be composed of a total of 10 coordinate groups: "0, 1, 2,..., 7, 8, 9" within the range of the boundary area width BAW that indicates the width in the sub-scanning direction H2 of the boundary area BA between the unit images GA on the medium W.

[0037] The multiple pattern waveforms SW1, SW2, SW3, and SW4 with different phases used by the computer 6 when setting the positions in the sub-scanning direction H2 of the multiple boundary end dots IDS1 arranged in the main scanning direction H1 are waveforms represented by a periodically changing wave pattern having a wavelength λ corresponding to the main scanning direction H1 and an amplitude A corresponding to the sub-scanning direction H2. Examples of the waves represented by the multiple pattern waveforms SW1, SW2, SW3, and SW4 include a sine wave, a rectangular wave, a triangular wave, and a sawtooth wave. The waves represented by each of the multiple pattern waveforms SW1, SW2, SW3, and SW4 may be a mixture of multiple waves or may be the same wave. Furthermore, the number of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is not particularly limited as long as it is two or more. In the example of Figure 4, the computer 6 sets the position in the sub-scanning direction H2 of each of the multiple boundary end dots IDS1 that are lined up in the main scanning direction H1 among the multiple ink dots ID included in each ink dot data DID for each pass operation to positions corresponding to four pattern waveforms SW1, SW2, SW3, and SW4 with different phases α, which are represented by sine waves in the following equation (1).

[0038]

number

[0039] In equation (1) relating to the sine wave representing the wave motion of the plurality of pattern waveforms SW1, SW2, SW3, and SW4, "A" represents the amplitude, "ω" represents the angular frequency, and "α" represents the phase.

[0040] The wavelength λ of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is set to a value corresponding to the movement distance MD of the carriage 22 per unit time along the main scanning direction H1. The movement distance MD of the carriage 22 per unit time is expressed as the number of dots of the boundary area forming dots IDS aligned in the main scanning direction H1. In the example of FIG. 4, the movement distance MD of the carriage 22 per unit time is expressed as "32," which is the number of dots of the boundary area forming dots IDS aligned in the main scanning direction H1. Therefore, the wavelength λ of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is expressed as "32," which is the number of dots of the boundary area forming dots IDS aligned in the main scanning direction H1. Furthermore, the wavelength λ of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is set to a multiple of the number of the multiple pattern waveforms SW1, SW2, SW3, and SW4. For example, if the number of pattern waveforms SW1, SW2, SW3, and SW4 is "4," the wavelength λ of the pattern waveforms SW1, SW2, SW3, and SW4 is set to "32," which is a multiple of "4."

[0041] The amplitude A of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is set to, for example, a value equivalent to half the boundary area width BAW, which indicates the width in the sub-scanning direction H2 of the boundary area BA between the unit images GA on the medium W. The boundary area width BAW is expressed as the number of dots of the boundary area dots IDS aligned in the sub-scanning direction H2 within the boundary area BA. In the example of FIG. 4, the boundary area width BAW is expressed as "10," which is the number of dots of the boundary area dots IDS aligned in the sub-scanning direction H2 within the boundary area BA. Therefore, the amplitude A of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is expressed as "5," which is half the number of dots of the boundary area dots IDS aligned in the sub-scanning direction H2 within the boundary area BA, which is "10."

[0042] The phase difference of the phase α among the plurality of pattern waveforms SW1, SW2, SW3, and SW4 is set to a value obtained by dividing 2π by the number of the plurality of pattern waveforms SW1, SW2, SW3, and SW4. For example, if the number of the plurality of pattern waveforms SW1, SW2, SW3, and SW4 is "4," the phase difference of the phase α among the plurality of pattern waveforms SW1, SW2, SW3, and SW4 is "2π / 4."

[0043] As described above, the computer 6 sets the positions in the sub-scanning direction H2 of the multiple boundary edge dots IDS1 aligned in the main scanning direction H1 among the multiple ink dots ID included in each ink dot data DID for each pass operation to positions corresponding to the multiple pattern waveforms SW1, SW2, SW3, and SW4 with different phases α among the multiple ink dots ID included in each ink dot data DID for each pass operation. As a result, the multiple boundary edge dots IDS1 that define the boundary B in the sub-scanning direction H2 between adjacent unit images GA on the medium W are restricted from aligning in a straight line along the main scanning direction H1 and from aligning along a single waveform. This allows the multiple boundary edge dots IDS1 to be irregularly distributed in the sub-scanning direction H2. As a result, the occurrence of streaky density unevenness due to the multiple boundary edge dots IDS1 in the boundary area BA between unit images GA on the medium W can be prevented, thereby reducing degradation in the quality of the image formed on the medium W.

[0044] The multiple pattern waveforms SW1, SW2, SW3, and SW4 with different phases α may be set to have the same wavelength λ and the same amplitude A. If the multiple pattern waveforms SW1, SW2, SW3, and SW4 have the same wavelength λ, the periods will also be the same. By setting the positions of the multiple boundary end dots IDS1 in the sub-scanning direction H2 to positions corresponding to the multiple pattern waveforms SW1, SW2, SW3, and SW4 with the same wavelength λ, amplitude A, and period but different phases α, it is possible to prevent interference fringes from occurring in the boundary areas BA between the unit images GA on the medium W.

[0045] The processing of the computer 6 when setting the position of each of the boundary end dots IDS1 in the sub-scanning direction H2 to a position corresponding to the plurality of pattern waveforms SW1, SW2, SW3, and SW4 will be described in more detail with reference to Fig. 4. In the following description, when distinguishing between the plurality of pattern waveforms SW1, SW2, SW3, and SW4, they will be referred to as the first pattern waveform SW1, the second pattern waveform SW2, the third pattern waveform SW3, and the fourth pattern waveform SW4.

[0046] The computer 6 sets the position of each of the boundary end dots IDS1 in the sub-scanning direction H2 to a position corresponding to a plurality of pattern waveforms SW1, SW2, SW3, and SW4 having different phases α so that the boundary end dots IDS1 that define the boundary B in the sub-scanning direction H2 between unit images GA adjacent to each other in the sub-scanning direction H2 on the medium W are not aligned along a single waveform. In this case, for all combinations of boundary end dots IDS1 adjacent to each other in the main scanning direction H1, the positions in the sub-scanning direction H2 of the boundary end dots IDS1 adjacent to each other in the main scanning direction H1 do not necessarily have to be positions corresponding to different pattern waveforms SW1, SW2, SW3, and SW4. In other words, when setting the position of each of the boundary end dots IDS1 in the sub-scanning direction H2 to a position corresponding to a plurality of pattern waveforms SW1, SW2, SW3, and SW4, the computer 6 may allow the positions in the sub-scanning direction H2 of the boundary end dots IDS1 adjacent to each other in the main scanning direction H1 to be positions corresponding to the same pattern waveform in a partial region of the main scanning direction H1.

[0047] In this embodiment, the computer 6 may set the position of each of the boundary end dots IDS1 in the sub-scanning direction H2 so that the positions of adjacent boundary end dots IDS1 in the sub-scanning direction H2 in the main scanning direction H1 correspond to different pattern waveforms SW1, SW2, SW3, and SW4. For example, for the boundary end dots IDS1 corresponding to the first unit image GA, the computer 6 sets the sub-scanning coordinate I that defines the position in the sub-scanning direction H2 of the boundary end dot IDS1 whose main scanning coordinate J is "0" to "5" corresponding to the first pattern waveform SW1. The computer 6 sets the sub-scanning coordinate I of the boundary end dot IDS1 whose main scanning coordinate J is "1" adjacent to "0" to "9" or a value subsequent to "10" corresponding to the second pattern waveform SW2, which has a phase α different from that of the first pattern waveform SW1. Similarly, for the multiple boundary end dots IDS1 corresponding to the second unit image GA, the computer 6 sets the sub-scanning coordinate I, which defines the position in the sub-scanning direction H2 of the boundary end dot IDS1 whose main scanning coordinate J is "0," to "4" according to the first pattern waveform SW1. For the boundary end dot IDS1 whose main scanning coordinate J is "1" adjacent to "0," the computer 6 sets the sub-scanning coordinate I to "9" according to the second pattern waveform SW2, which has a phase α different from that of the first pattern waveform SW1. The computer 6 repeatedly performs the above process to set the positions in the sub-scanning direction H2 of each of the multiple boundary end dots IDS1 corresponding to each of the first and second unit images GA so that the positions in the sub-scanning direction H2 of boundary end dots IDS1 adjacent to each other in the main scanning direction H1 correspond to the different pattern waveforms SW1, SW2, SW3, and SW4. This more reliably distributes the multiple boundary end dots IDS1 irregularly in the sub-scanning direction H2. Therefore, it is possible to more reliably prevent stripe-like density unevenness resulting from the plurality of boundary end dots IDS1 from occurring in the boundary area BA between the unit images GA on the medium W.

[0048] Alternatively, the computer 6 may divide the coordinate group of the main scanning coordinate J, which defines the position of each of the boundary end dots IDS1 in the main scanning direction H1, into multiple regions including coordinates equal to the number of the pattern waveforms SW1, SW2, SW3, and SW4. In the example of FIG. 4, the computer 6 divides a total of 32 coordinate groups of "0, 1, 2, . . . , 29, 30, 31" in the main scanning coordinate J into "8" regions. Each of the "8" regions includes "4" coordinates, corresponding to the number of the pattern waveforms SW1, SW2, SW3, and SW4. In this case, the computer 6 sets region coordinates K, which indicate "4" coordinates for each of the "8" regions, corresponding to the main scanning coordinate J. In the region coordinate K, each of the "8" regions includes a total of four coordinates: "0, 1, 2, 3." That is, the area coordinate K corresponding to the main scanning coordinate J is "0,1,2,3,...,0,1,2,3", and the coordinate "0,1,2,3" is repeated for the number of divided areas.

[0049] When the computer 6 sets the area coordinates K by dividing the coordinate group of the main scanning coordinate J into multiple areas, it sets the position in the sub-scanning direction H2 of each of the multiple boundary end dots IDS1 belonging to each of the multiple areas so that the position in the sub-scanning direction H2 of each boundary end dot IDS1 belongs to a position corresponding to a different pattern waveform SW1, SW2, SW3, SW4.

[0050] Specifically, the computer 6 sets the sub-scanning coordinate I, which defines the position in the sub-scanning direction H2 of the boundary end dot IDS1 whose area coordinate K corresponding to the main scanning coordinate J is "0," in accordance with the first pattern waveform SW1. The computer 6 sets the sub-scanning coordinate I, which defines the position in the sub-scanning direction H2 of the boundary end dot IDS1 whose area coordinate K corresponding to the main scanning coordinate J is "1" adjacent to "0," in accordance with the second pattern waveform SW2, which has a phase α different from that of the first pattern waveform SW1. The computer 6 sets the sub-scanning coordinate I, which defines the position in the sub-scanning direction H2 of the boundary end dot IDS1 whose area coordinate K corresponding to the main scanning coordinate J is "2" adjacent to "1," in accordance with the third pattern waveform SW3, which has a phase α different from that of the first pattern waveform SW1 and the second pattern waveform SW2. The computer 6 sets the sub-scanning coordinate I, which specifies the position in the sub-scanning direction H2 of the boundary end dot IDS1 of "3" adjacent to "2" whose area coordinate K corresponding to the main scanning coordinate J, according to a fourth pattern waveform SW4 which has a phase α different from that of the first pattern waveform SW1, the second pattern waveform SW2, and the third pattern waveform SW3.

[0051] When the plurality of pattern waveforms SW1, SW2, SW3, and SW4 are sinusoidal waveforms, the computer 6 sets the position of each of the plurality of boundary end dots IDS1 in the sub-scanning direction H2 according to the following equation (2).

[0052]

number

[0053] In equation (2), "I" indicates sub-scanning coordinate I, "J" indicates main-scanning coordinate J, "K" indicates area coordinate K, "SWN" indicates the number of pattern waveforms SW1, SW2, SW3, and SW4, "λ" indicates wavelength λ of the pattern waveforms SW1, SW2, SW3, and SW4, and "A" indicates amplitude A of the pattern waveforms SW1, SW2, SW3, and SW4. Also, in equation (2), "round" indicates rounding to the nearest integer.

[0054] Assume that the number SWN of the multiple pattern waveforms SW1, SW2, SW3, and SW4 is "4," the wavelength λ is "32," and the amplitude A is "5." In this case, for the sub-scanning coordinate I that defines the position in the sub-scanning direction H2 of the boundary end dot IDS1 whose main scanning coordinate J is "0" and whose area coordinate K is "0," the computer 6 sets the boundary end dot IDS1 corresponding to the first unit image GA to "5" according to the first pattern waveform SW1 in accordance with the above formula (2), and sets the boundary end dot IDS1 corresponding to the second unit image GA to "4," which is adjacent to the "5" in the sub-scanning direction H2. Similarly, for the sub-scanning coordinate I of the boundary end dot IDS1 whose main scanning coordinate J is "1" adjacent to "0" and whose area coordinate K is "1" adjacent to "0", the computer 6 sets the boundary end dot IDS1 corresponding to the first unit image GA to "10" in accordance with the second pattern waveform SW2 in accordance with the above formula (2), and sets the boundary end dot IDS1 corresponding to the second unit image GA to "9" adjacent to "10" in the sub-scanning direction H2. Furthermore, for the sub-scanning coordinate I of the boundary end dot IDS1 whose main scanning coordinate J is "2" adjacent to "1" and whose area coordinate K is "2" adjacent to "1", the computer 6 sets the boundary end dot IDS1 corresponding to the first unit image GA to "3" in accordance with the third pattern waveform SW3 in accordance with the above formula (2), and sets the boundary end dot IDS1 corresponding to the second unit image GA to "2" adjacent to "3" in the sub-scanning direction H2. Furthermore, for the sub-scanning coordinate I of the boundary end dot IDS1 whose main scanning coordinate J is "3" adjacent to "2" and whose area coordinate K is "3" adjacent to "2", the computer 6 sets the boundary end dot IDS1 corresponding to the first unit image GA to "1" corresponding to the fourth pattern waveform SW4 in accordance with the above equation (2), and sets the boundary end dot IDS1 corresponding to the second unit image GA to "0" adjacent to "1" in the sub-scanning direction H2.

[0055] When the computer 6 sets the region coordinates K by dividing the coordinate group of the main scanning coordinate J into multiple regions, it repeatedly performs the process according to equation (2) for each of the multiple boundary end dots IDS1 corresponding to the first and second unit images GA so that the position in the sub-scanning direction H2 of each boundary end dot IDS1 belonging to each of the multiple regions corresponds to a different pattern waveform SW1, SW2, SW3, SW4. This sets the position of each boundary end dot IDS1 in the sub-scanning direction H2. This more reliably distributes the multiple boundary end dots IDS1 irregularly in the sub-scanning direction H2. This more reliably prevents streaky density unevenness caused by the multiple boundary end dots IDS1 in the boundary region BA between the unit images GA on the medium W.

[0056] If the ink head 3 of the inkjet printer 2 includes multiple individual heads 31 capable of ejecting multiple colors of ink, the computer 6 generates ink dot data DID for each color corresponding to each of the multiple individual heads 31 for each pass operation. The computer 6 sets the positions in the sub-scanning direction H2 of the multiple boundary end dots IDS1 in the ink dot data DID for each color to positions corresponding to the multiple pattern waveforms SW1, SW2, SW3, and SW4. In this case, the computer 6 changes at least one of the phase α and wavelength λ in the multiple pattern waveforms SW1, SW2, SW3, and SW4 for each color of ink dot data DID. This makes it possible to prevent streaky density unevenness, such as those caused by the multiple boundary end dots IDS1, from occurring in the boundary areas BA between unit images GA on the medium W when forming a multiple-color image on the medium W.

[0057] When setting the positions of the multiple boundary edge dots IDS1 in the ink dot data DID for each color in the sub-scanning direction H2 according to the multiple pattern waveforms SW1, SW2, SW3, and SW4, the computer 6 changes at least one of the phase α and wavelength λ in the multiple pattern waveforms SW1, SW2, SW3, and SW4 for each ink dot data DID for each color so that adjacent hues differ when the colors are arranged on a color wheel. Black, white, and the neutral gray are achromatic colors that lack hue and saturation, among the three color attributes of lightness, hue, and saturation. For this reason, achromatic colors are not typically included in a color wheel. Therefore, when the computer 6 uses a color wheel, the colors it targets are chromatic colors other than achromatic colors.

[0058] 3, after creating the ink dot data DID for each pass operation in the ink data creating step s2, the computer 6 performs a treatment liquid data creating process for creating, for each pass operation, treatment liquid dot data DRD indicating data on a pattern of treatment liquid dots to be formed on the medium W in response to the ejection of treatment liquid by the treatment liquid head 4, based on the ink dot data DID (treatment liquid data creating step s3). The computer 6 creates, as the treatment liquid dot data DRD, pretreatment liquid dot data DRD1 indicating data on a pattern of pretreatment liquid dots to be formed on the medium W in response to the ejection of pretreatment liquid by the pretreatment liquid head 41. Similarly, the computer 6 creates, as the treatment liquid dot data DRD, posttreatment liquid dot data DRD2 indicating data on a pattern of posttreatment liquid dots to be formed on the medium W in response to the ejection of posttreatment liquid by the posttreatment liquid head 42. In this embodiment, the computer 6 creates treatment liquid dot data DRD common to the pretreatment liquid dot data DRD1 and the posttreatment liquid dot data DRD2.

[0059] The computer 6 creates the treatment liquid dot data DRD so that each treatment liquid dot in the treatment liquid dot data DRD includes at least a dot at the same position as each ink dot ID in the ink dot data DID. If the ink head 3 in the inkjet printer 2 is equipped with a plurality of individual heads 31 capable of ejecting a plurality of colors of ink, the computer 6 creates the treatment liquid dot data DRD based on logical sum data obtained by taking the logical sum of the ink dot data DID for each color. In this case, the computer 6 creates the treatment liquid dot data DRD so that each treatment liquid dot in the treatment liquid dot data DRD includes at least a dot at the same position as each ink dot ID in the logical sum data. It should be noted that the computer 6 may also create the treatment liquid dot data DRD based on image data DG.

[0060] The computer 6 creates treatment liquid dot data DRD in which treatment liquid dots are arranged at the same positions as each ink dot ID in the ink dot data DID, and in which treatment liquid dots are also arranged in the area surrounding each ink dot ID. In this case, as in the case of the ink dot data DID, the computer 6 may set the position in the sub-scanning direction H2 of each treatment liquid dot that corresponds to the plurality of boundary end dots IDS1 in the ink dot data DID, out of the plurality of treatment liquid dots included in the treatment liquid dot data DRD, to a position that corresponds to the plurality of pattern waveforms SW1, SW2, SW3, SW4.

[0061] After creating the ink dot data DID and treatment liquid dot data DRD for each pass operation, the computer 6 transmits the created ink dot data DID and treatment liquid dot data DRD to the inkjet printer 2 (data transmission step s4).

[0062] When the ink dot data DID and treatment liquid dot data DRD are received in the inkjet printer 2 (data receiving step s5), the printer control unit 5 repeatedly performs a pass operation step s6 in which the inkjet head 20, which includes the ink head 3 and treatment liquid head 4 mounted on the carriage 22, executes a pass operation, and a transport step s7 in which the transport unit 21 executes a transport operation for the medium W. In this way, the printer control unit 5 performs image formation processing in the image forming step in which a plurality of unit images GA, each consisting of a plurality of ink dots ID corresponding to at least one pass operation, are formed on the medium W in the sub-scanning direction H2. The printer control unit 5 determines whether image formation on the medium W has been completed (determining step s8), and repeatedly performs the pass operation step s6 and transport step s7 until image formation is completed.

[0063] In the pass operation step s6, the printer control unit 5 ejects pretreatment liquid from the pretreatment liquid head 41 (step s61), ejects ink from the ink head 3 (step s62), and ejects posttreatment liquid from the posttreatment liquid head 42 (step s63) while moving the carriage 22 in the main scanning direction H1 based on the ink dot data DID and the treatment liquid dot data DRD.

[0064] As described above, among the ink dots ID included in each ink dot data DID for one pass, the boundary area forming dots IDS for forming the boundary area BA, the boundary edge dots IDS1 that define the boundary B in the sub-scanning direction H2 between unit images GA adjacent in the sub-scanning direction H2 on the medium W, are restricted from lining up in a straight line along the main scanning direction H1, and are restricted from lining up in a single waveform. This allows the boundary edge dots IDS1 to be dispersed irregularly in the sub-scanning direction H2. As a result, it is possible to prevent streaky density unevenness resulting from the boundary edge dots IDS1 from occurring in the boundary area BA between unit images GA on the medium W. This prevents degradation of the quality of the image formed on the medium W. [Explanation of symbols]

[0065] 1 Inkjet recording system 2. Inkjet printer 3 ink head 31 individual heads 5 Printer control unit (control unit) 6 Computer (dot data creation section) DID Ink Dot Data GA unit image H1 Main scanning direction H2 Sub-scanning direction ID Ink Dot IDS boundary area forming dots IDS1 Boundary Edge Dot W Media (recording material)

Claims

1. an ink head that is movable in the main scanning direction and is capable of ejecting ink onto a recording material; a conveying section capable of conveying the recording material in a sub-scanning direction perpendicular to the main scanning direction; a control unit that performs an image forming process in which a pass operation in which the ink head is moved in the main scanning direction while ejecting the ink from the ink head to form a plurality of ink dots on the recording material, and an operation in which the conveying unit conveys the recording material in the sub-scanning direction are repeatedly performed, thereby forming a plurality of unit images, each of which is made up of a plurality of the ink dots corresponding to at least one pass operation, on the recording material in the sub-scanning direction; a dot data creating unit that performs an ink data creating process to create ink dot data indicating data of a pattern of a plurality of ink dots for forming each of a plurality of unit images on the recording material for each pass operation, the control unit causes the passing operation and the conveying operation to be performed in the image forming process so that a boundary area extending in the main scanning direction is formed on the recording material by overlapping portions of the unit images adjacent to each other in the sub-scanning direction in the sub-scanning direction, and In the ink data creation process, the dot data creation unit sets the sub-scanning direction position of each of a plurality of boundary end dots that are lined up in the main scanning direction and that define the boundary in the sub-scanning direction between the unit images that are adjacent in the sub-scanning direction on the recording material, among the plurality of ink dots included in each of the ink dot data for each pass operation, to positions that correspond to a plurality of pattern waveforms that have wavelengths corresponding to the main scanning direction and amplitudes corresponding to the sub-scanning direction and are different in phase.

2. 2. The inkjet printing system according to claim 1, wherein the dot data creation unit sets the sub-scanning direction positions of each of the plurality of boundary end dots so that the sub-scanning direction positions of adjacent boundary end dots in the main scanning direction correspond to different pattern waveforms.

3. The dot data creation unit Dividing a group of main scanning coordinates that define the positions of each of the plurality of boundary end dots in the main scanning direction into a plurality of regions including coordinates equal in number to the number of the plurality of pattern waveforms; 2. The inkjet printing system according to claim 1, wherein the sub-scanning direction position of each of the plurality of boundary end dots belonging to each of the plurality of regions is set so that the sub-scanning direction position of each of the plurality of boundary end dots is a position corresponding to a different pattern waveform.

4. 2. The inkjet recording system according to claim 1, wherein the plurality of pattern waveforms have the same wavelength and the same amplitude.

5. the ink head includes a plurality of individual heads capable of ejecting each of the inks of a plurality of colors, In the ink data creation process, the dot data creation unit: creating the ink dot data for each color corresponding to each of the plurality of individual heads for each pass operation; 2. The inkjet printing system according to claim 1, wherein when the positions in the sub-scanning direction of the plurality of boundary end dots in the ink dot data of each color are set to positions corresponding to the plurality of pattern waveforms, at least one of the phase and the wavelength in the plurality of pattern waveforms is changed for each of the ink dot data of each color.

6. 6. The inkjet recording system of claim 5, wherein, in the ink data creation process, when the dot data creation unit sets the positions in the sub-scanning direction of the multiple boundary end dots in the ink dot data of each color to positions corresponding to the multiple pattern waveforms, the dot data creation unit changes at least one of the phase and the wavelength in the multiple pattern waveforms for each of the ink dot data of each color so that adjacent hues differ when the colors are arranged on a hue wheel.

7. 7. The inkjet recording system according to claim 1, wherein the recording material is a fabric member made of fabric.

8. An inkjet recording method for recording an image on a recording material using an ink head that is movable in a main scanning direction, comprising: an image forming process in which a pass operation in which ink is ejected from the ink head while moving the ink head in the main scanning direction to form a plurality of ink dots on the recording material, and a conveying operation in which the recording material is conveyed in a sub-scanning direction perpendicular to the main scanning direction, are repeatedly performed, thereby forming a plurality of unit images, each consisting of a plurality of ink dots corresponding to at least one pass operation, on the recording material in the sub-scanning direction; an ink data creating step of creating ink dot data representing data of a plurality of ink dot patterns for forming each of the plurality of unit images on the recording material for each pass operation, In the image forming step, the passing operation and the conveying operation are performed so that a boundary area extending in the main scanning direction is formed on the recording material by overlapping portions of the unit images adjacent to each other in the sub-scanning direction in the sub-scanning direction, and In the ink data creation process, among the plurality of ink dots included in each of the ink dot data for each pass operation, the ink jet recording method sets the sub-scanning direction position of each of a plurality of boundary end dots that are lined up in the main scanning direction and define the boundary in the sub-scanning direction between the unit images that are adjacent in the sub-scanning direction on the recording material, to positions that correspond to a plurality of pattern waveforms that have wavelengths corresponding to the main scanning direction and amplitudes corresponding to the sub-scanning direction and are different in phase.

Images