Liquid ejection device and liquid ejection method

Abstract

To determine an ejection timing of liquid on the basis of a density of an image formed on a recording medium.SOLUTION: A liquid discharge device comprises: a liquid discharge part having a plurality of nozzle rows in which a plurality of nozzles for discharging liquid are arranged along a width direction which is orthogonal to a conveying direction; and a determining part that determines timings at which the plurality of nozzle rows respectively discharge the liquid, on the basis of densities of a plurality of patch images formed on a recording medium by the liquid discharged by the liquid discharge part. Each of the plurality of patch images includes reference dots formed on the recording medium by liquid discharged from a first nozzle row included in the plurality of nozzle rows, corresponding to predetermined reference pixels, and adjusted dots formed on the recording medium by liquid discharged from a second nozzle row included in the plurality of nozzle rows, corresponding to adjusted pixels which are adjacent to the reference pixels in the width direction and are deviated from the reference pixels by numbers of pixels which are different in every plurality of patch images in the conveying direction.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a liquid ejection apparatus and a liquid ejection method. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there is known a technique for determining the timing of ejecting liquid from a liquid ejecting device based on the results of reading, by a reading device, an image formed on a recording medium by liquid ejected by the liquid ejecting device.

[0003] Also disclosed is a configuration in which the timing of ejecting liquid by a liquid ejection device is determined based on the density of an image formed on a recording medium by the liquid ejected by the liquid ejection device (see, for example, Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the configuration of Patent Document 1, the overlapping area of multiple dots formed on a recording medium by the liquid ejected by the liquid ejection device is small or does not overlap, so the density of an image such as a patch image formed by these multiple dots does not change, and it may not be possible to determine the timing of ejecting the liquid.

[0005] An object of the present invention is to determine the timing of ejecting liquid based on the density of an image formed on a recording medium. [Means for solving the problem]

[0006] A liquid ejection device according to one aspect of the present invention includes: a liquid ejection device that ejects liquid onto a recording medium transported in a transport direction, the liquid ejection device comprising: a liquid ejection unit having a plurality of nozzle arrays in which a plurality of nozzles that eject the liquid are arranged along a width direction perpendicular to the transport direction; and a determination unit that determines the timing at which each of the plurality of nozzle arrays ejects the liquid based on the density of a plurality of patch images formed on the recording medium by the liquid ejected by the liquid ejection unit, wherein each of the plurality of patch images includes: a reference dot formed on the recording medium by the liquid ejected from a first nozzle array included in the plurality of nozzle arrays, corresponding to a predetermined reference pixel; and an adjustment dot formed on the recording medium by the liquid ejected from a second nozzle array included in the plurality of nozzle arrays, corresponding to an adjustment pixel that is adjacent to the reference pixel in the width direction and is shifted from the reference pixel in the transport direction by a number of pixels that differs for each of the plurality of patch images, and the plurality of patch images are formed for each combination of the nozzle arrays used to form adjacent dots in the width direction on the recording medium. [Effects of the Invention]

[0007] According to the present invention, the timing of ejecting liquid can be determined based on the density of an image formed on a recording medium. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment; [Figure 2] FIG. 2 is a diagram illustrating a configuration of an image forming unit of the image forming apparatus according to the embodiment. [Figure 3] FIG. 2 is a diagram illustrating an example of a nozzle row in a liquid ejection head. [Figure 4] 2 is a diagram illustrating an example of the arrangement of an in-line sensor in an image forming apparatus according to an embodiment. [Figure 5] FIG. 2 is a diagram illustrating a hardware configuration of a control unit of the image forming apparatus according to the embodiment. [Figure 6] 2 is a diagram illustrating an example of the functional configuration of a control unit of the image forming apparatus according to the first embodiment. FIG. [Figure 7] FIG. 10 is a diagram illustrating an example of an entire group of patch image data. [Figure 8] FIG. 10 is a diagram showing a first example of patch image data. [Figure 9] FIG. 10 is a diagram showing a second example of patch image data. [Figure 10] FIG. 10 is a diagram showing a third example of patch image data. [Figure 11] FIG. 8 is a diagram showing an entire group of patch images based on the patch image data of FIG. 7. [Figure 12] 9 is a diagram showing a patch image based on the patch image data of FIG. 8. FIG. [Figure 13] 10 is a diagram showing a patch image based on the patch image data of FIG. 9. FIG. [Figure 14] 11 is a diagram showing a patch image based on the patch image data of FIG. 10. FIG. [Figure 15] 5 is a diagram illustrating the relationship between an adjustment value and a read G value according to the first embodiment. FIG. [Figure 16] FIG. 10 is a diagram illustrating an example of the relationship between an adjustment value and an L* value according to a modified example. [Figure 17] FIG. 10 is a diagram illustrating an example of the functional configuration of a control unit of an image forming apparatus according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In each drawing, the same components are designated by the same reference numerals, and duplicated descriptions will be omitted where appropriate.

[0010] The liquid ejection device according to the embodiment ejects liquid onto a recording medium transported in the transport direction using a liquid ejection section having multiple nozzle rows in which multiple nozzles that eject liquid are arranged along a width direction perpendicular to the transport direction.

[0011] In such a liquid ejection device, if the timing of ejecting liquid from each of the multiple nozzle rows deviates from the desired timing, the position where the ejected liquid lands on the recording medium may deviate from the desired position. This positional deviation may result in, for example, a decrease in the quality of the image formed on the recording medium by the liquid ejection device.

[0012] The liquid ejection device according to the embodiment includes a determination unit that determines the timing at which each of the plurality of nozzle arrays ejects liquid based on the density of an image, such as a plurality of patch images, formed on a recording medium by the liquid ejected by the liquid ejection unit. This allows the ejection timing of the liquid from each of the plurality of nozzle arrays to be synchronized with a desired timing, thereby ensuring the quality of the image formed on the recording medium by the liquid ejection device.

[0013] In addition, the liquid ejection device according to the embodiment determines the timing of ejecting the liquid by utilizing the fact that the density of a patch image formed by multiple dots changes depending on the overlap of the multiple dots formed on the recording medium when the liquid ejected by the liquid ejection unit lands on the recording medium.

[0014] For example, if the measurement results of the dot positions on the recording medium are used to determine the timing of liquid ejection, a high-resolution measuring device that can resolve the dots on the recording medium is required. In contrast, the liquid ejection device according to the embodiment uses the density of the patch image, so the timing can be determined using a relatively inexpensive in-line sensor or the like, without using a high-resolution and expensive measuring device or the like.

[0015] On the other hand, in the method of determining the timing based on the density of a patch image, the density of the patch image made up of multiple dots may not change if the overlapping area of multiple dots formed on the recording medium is small or does not overlap at all.If the density of the patch image does not change, the determination unit cannot determine the timing.

[0016] In an embodiment, each of the plurality of patch images includes a reference dot formed on the recording medium by liquid ejected from a first nozzle array included in the plurality of nozzle arrays, corresponding to a predetermined reference pixel, and each of the plurality of patch images also includes an adjustment dot formed on the recording medium by liquid ejected from a second nozzle array included in the plurality of nozzle arrays, corresponding to an adjustment pixel adjacent to the reference pixel in the width direction and shifted from the reference pixel in the transport direction by a number of pixels that differs for each of the plurality of patch images.

[0017] In the transport direction, the adjustment dots are shifted relative to the reference dots corresponding to different numbers of pixels for each of the multiple patch images, allowing the determination unit to determine the timing of liquid ejection by each of the multiple nozzle arrays in accordance with the number of pixels based on the density of each of the multiple patch images. Also, in the width direction, the reference pixels and the adjustment pixels are adjacent to each other, making it easy for the reference dots formed corresponding to the reference pixels and the adjustment dots formed corresponding to the adjustment pixels to overlap on the recording medium. As a result, the density of the patch image changes depending on the positional shift of the adjustment dots, allowing the determination unit to determine the timing of liquid ejection based on the density of the image formed on the recording medium.

[0018] The determination of the timing by the determination unit is mainly performed when the liquid ejection device is shipped from a factory, or when the position (height) of the liquid ejection unit relative to the recording medium is changed due to replacement of the liquid ejection unit after the liquid ejection device is installed at a customer's site, etc. However, the determination is not limited to these, and the determination of the timing by the determination unit may be performed at any time depending on the application of the liquid ejection device.

[0019] Hereinafter, an embodiment will be described in detail, taking as an example a liquid ejection type (inkjet type) image forming apparatus that forms an image on a recording medium by using liquid ejected from a liquid ejection unit. Note that the terms image formation, recording, printing, copying, and printing in the embodiments are all synonymous.

[0020] <Configuration example of image forming apparatus 1> The configuration of an image forming apparatus 1 according to an embodiment will be described with reference to Figures 1 and 2. Figure 1 is a diagram illustrating an example of the overall configuration of the image forming apparatus 1. Figure 2 is a diagram illustrating an example of the configuration of an image forming unit 200 included in the image forming apparatus 1.

[0021] As shown in FIG. 1, the image forming apparatus 1 includes a paper feed section 100, an image forming section 200, a drying section 300, a paper discharge section 400, a control section 30, and an operation section 40.

[0022] The image forming apparatus 1 forms an image on paper P, which is a recording medium as a sheet material fed from a paper feed unit 100, by ejecting ink, which is a liquid for image formation, onto the paper P using an image forming unit 200. Then, after the ink adhered to the paper P is dried by a drying unit 300, the paper P is discharged by a paper discharge unit 400.

[0023] (Paper feed section) The paper feed unit 100 includes a paper feed tray 110 on which a plurality of sheets P are stacked, a feed device 120 that separates and feeds the sheets P one by one from the paper feed tray 110, and a pair of registration rollers 130 that feeds the sheets P to the image forming unit 200. The feed device 120 can be any type of feed device, such as a device using rollers or a device using air suction. The paper P fed from the paper feed tray 110 by the feed device 120 is transported along a transport direction 20, and after the leading edge of the paper P reaches the pair of registration rollers 130, the pair of registration rollers 130 is driven at a predetermined timing to feed the paper P to the image forming unit 200. In this embodiment, the configuration of the paper feed unit 100 is not limited as long as it feeds the paper P to the image forming unit 200.

[0024] (Image forming section) 1 and 2, the image forming unit 200 includes a receiving drum 201 that receives the paper P fed from the paper feeding unit 100, and a paper carrying drum 210 that carries the paper P conveyed by the receiving drum 201 on its outer circumferential surface and conveys it. The image forming unit 200 also includes a liquid ejection unit 220 that ejects ink toward the paper P held on the paper carrying drum 210, a transfer drum 202 that delivers the paper P conveyed by the paper carrying drum 210 to the drying unit 300, and an in-line sensor 230.

[0025] The paper P transported from the paper supply unit 100 to the image forming unit 200 has its leading edge gripped by a paper gripper provided on the surface of the receiving drum 201, and is transported as the surface of the receiving drum 201 moves. The paper P transported by the receiving drum 201 is delivered to the paper carrying drum 210 at a position facing the paper carrying drum 210.

[0026] A paper gripper is provided on the surface of the paper carrying drum 210, and the leading edge of the paper P is gripped by the paper gripper. In addition, a plurality of suction holes are formed in a dispersed manner on the surface of the paper carrying drum 210, and a suction device 211 generates a suction air current inward of the paper carrying drum 210 at each suction hole. The leading edge of the paper P transferred from the receiving cylinder 201 to the paper carrying drum 210 is gripped by the paper gripper, and the paper P is adsorbed to the surface of the paper carrying drum 210 by the suction air current, and is transported as the surface of the paper carrying drum 210 moves.

[0027] The liquid ejection unit 220 forms an image by ejecting ink of four colors: C (cyan), M (magenta), Y (yellow), and K (black). The liquid ejection unit 220 is equipped with liquid ejection heads 220C, 220M, 220Y, and 220K, each for a different ink color.

[0028] Each of the liquid ejection heads 220C, 220M, 220Y, and 220K is provided with a plurality of nozzles that eject ink across the entire width of the paper P so that an image can be formed across the entire width of the paper P in the width direction 10 of the paper P, which is approximately perpendicular to the transport direction 20. This makes the image forming apparatus 1 a so-called line-type apparatus in which the liquid ejection unit 220 does not move. Note that a plurality of each of the liquid ejection heads 220C, 220M, 220Y, and 220K may be provided along the width direction 10 so that an image can be formed across the entire width of the paper P.

[0029] There are no limitations on the configuration of the liquid ejection heads 220C, 220M, 220Y, and 220K, and any configuration can be used as long as they eject liquid. If necessary, liquid ejection heads that eject special inks such as white, gold, or silver inks, or liquid ejection heads that eject liquids that do not form images, such as surface coating liquids, may be provided.

[0030] The ejection operation of each of the liquid ejection heads 220C, 220M, 220Y, and 220K is controlled by a drive signal corresponding to image data. When the paper P carried on the paper carrying drum 210 passes through an area facing the liquid ejection unit 220, ink of each color is ejected from the liquid ejection heads 220C, 220M, 220Y, and 220K, and an image corresponding to the image data is formed on the paper P. In this embodiment, the configuration of the image forming unit 200 is not limited as long as it forms an image by depositing liquid on the paper P.

[0031] An in-line sensor 230 is provided downstream of the liquid ejection unit 220 in the transport direction 20. The in-line sensor 230 is an example of a reading unit that reads a plurality of patch images formed on the paper P with ink ejected by the liquid ejection unit 220. Note that the transport direction 20 corresponds to the rotation direction of the paper carrying drum 210 in the image forming unit 200.

[0032] The inline sensor 230 includes a plurality of reading pixels arranged across the entire width of the paper P in the width direction 10. For example, the inline sensor 230 includes an imaging element such as a CCD (Charge Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor), and the reading pixels are pixels of the imaging element that output an electrical signal according to the intensity of the received light.

[0033] In this embodiment, the inline sensor 230 has reading pixels that output electrical signals according to the light intensity of each of the received colors R (red), G (green), and B (blue), and outputs a color read image obtained by reading multiple patch images.

[0034] (Drying section) 1, the drying unit 300 includes a heating mechanism 301 for drying the ink deposited on the paper P in the image forming unit 200, and a transport mechanism 302 for transporting the paper P transported from the image forming unit 200. The paper P transported from the image forming unit 200 is received by the transport mechanism 302, then transported to pass through the heating mechanism 301 and delivered to the paper discharge unit 400. As the paper P passes through the heating mechanism 301, the ink on the paper P is subjected to a heat treatment, which evaporates the liquid content in the ink, such as water, and fixes the ink on the paper P, while suppressing curling of the paper P.

[0035] (Paper ejection section) The paper discharge section 400 is provided with a paper discharge tray 410 on which a plurality of sheets of paper P are stacked. The sheets of paper P conveyed from the drying section 300 are sequentially stacked and held on the paper discharge tray 410. In this embodiment, the paper discharge section 400 is not limited in its configuration as long as it can discharge the sheets of paper P.

[0036] (Control unit) The control unit 30 controls the overall operation of the image forming apparatus 1. In particular, in this embodiment, the control unit 30 generates patch image data for forming a plurality of patch images on the paper P with ink ejected by the liquid ejection unit 220. The control unit 30 then determines the timing at which each of the plurality of nozzle rows ejects ink, based on the density of the plurality of patch images formed on the paper P based on the patch image data. In FIG. 1 , the control unit 30 is provided in the image forming unit 200, but the control unit 30 may be installed anywhere inside or outside the image forming apparatus 1.

[0037] (Operation unit) The operation unit 40 includes a touch panel, a keyboard, and the like, and accepts operation inputs to the image forming apparatus 1 from an operator who operates the image forming apparatus 1. In FIG. 1, the operation unit 40 is provided in the paper feed unit 100, but the operation unit 40 may be installed anywhere inside or outside the image forming apparatus 1.

[0038] (Other functional parts) The image forming apparatus 1 of this embodiment includes a paper feed unit 100, an image forming unit 200, a drying unit 300, and a paper discharge unit 400, but other functional units may be added as appropriate. For example, a pre-processing unit that performs pre-processing for image formation may be added between the paper feed unit 100 and the image forming unit 200, or a post-processing unit that performs post-processing for image formation may be added between the drying unit 300 and the paper discharge unit 400.

[0039] An example of a pre-treatment unit is one that performs a treatment liquid application process in which a treatment liquid that reacts with ink to suppress bleeding is applied to the paper P, but there are no particular restrictions on the content of the pre-treatment.

[0040] Examples of post-processing sections include a paper inversion and transport processing section, a binding processing section, a correction mechanism, and a cooling mechanism. The paper inversion and transport processing section inverts the paper P on which an image has been formed in the image forming section 200 and sends it back to the image forming section 200 to form images on both sides of the paper P. The binding processing section performs a process of binding multiple sheets of paper P on which images have been formed. The forcing mechanism corrects deformation of the paper P, and the cooling mechanism cools the paper P. However, there are no particular restrictions on the content of the post-processing.

[0041] (Example of the configuration of nozzle rows in a liquid ejection head) 3 is a diagram illustrating an example of nozzle rows in the liquid ejection head 220K provided in the image forming apparatus 1. The liquid ejection head 220K has four nozzle rows L1, L2, L3, and L4. Each of the four nozzle rows L1, L2, L3, and L4 has a plurality of nozzles N arranged along the width direction 10.

[0042] In the liquid ejection head 220K, the multiple nozzles N are arranged in a staggered pattern. Here, staggered pattern means that, for example, a nozzle N included in a nozzle row L3 adjacent to the nozzle row L1 in the transport direction 20 is arranged between two nozzles N adjacent to each other in the width direction 10 in the nozzle row L1.

[0043] Ink is ejected from each of the multiple nozzles N. When the ejected ink lands on the paper P, dots are formed on the paper P. In this embodiment, the dots formed on the paper P by the ink ejected from the nozzles N of the nozzle rows L2 and L4 are formed at positions on the paper P adjacent in the width direction 10 to the dots formed on the paper P by the ink ejected from the nozzles N of the nozzle row L1.

[0044] If the distance between two adjacent nozzles in the nozzle row is distance d, then by displacing the two liquid ejection heads 220K by d / 2 along the transport direction 20, it is possible to double the image formation resolution of the image forming apparatus 1 compared to when a single liquid ejection head 220K is provided. Note that, although the nozzle row of the liquid ejection head 220K is illustrated in Fig. 3, the nozzle rows of the liquid ejection heads 220C, 220M, and 220Y are also configured in the same manner as the liquid ejection head 220K.

[0045] (Configuration example of inline sensor 230) 4 is a diagram illustrating the arrangement of inline sensor 230 provided in image forming apparatus 1. Inline sensor 230 has first inline sensor 231 and second inline sensor 232. First inline sensor 231 is provided upstream of second inline sensor 232 in conveyance direction 20. First inline sensor 231 and second inline sensor 232 are provided at positions offset from each other along width direction 10 so as to be able to read the entire width of paper P in width direction 10. Overlapping region 233 represents the region in width direction 10 where the reading ranges of first inline sensor 231 and second inline sensor 232 overlap.

[0046] The number of inline sensors included in inline sensor 230 is not limited to two and may be any number as long as it is possible to read the entire width of paper P in width direction 10. In this embodiment, first inline sensor 231 and second inline sensor 232 have the same configuration and function, but as long as they can read paper P with equivalent quality, the configuration and function of first inline sensor 231 and second inline sensor 232 do not necessarily have to be the same.

[0047] <Configuration example of control unit 30> (Hardware configuration) 5 is a block diagram showing an example of the hardware configuration of the control unit 30. The control unit 30 includes a CPU (Central Processing Unit) 301, a ROM (Read Only Memory) 302, a RAM (Random Access Memory) 303, a HDD (Hard Disk Drive) / SSD (Solid State Drive) 304, and an I / F (Interface) 305. These components are electrically connected to each other via a system bus B, and are also connected to the liquid ejection unit 220, the in-line sensor 230, and the operation unit 40 via the system bus B so as to be able to send and receive data and signals.

[0048] The CPU 301 uses the RAM 303 as a work area and executes the programs stored in the ROM 302. The HDD / SSD 304 is used as a storage unit and stores preset setting values. The information stored in the HDD / SSD 204 may be read by the CPU 201 and used when executing the programs. The I / F 305 is an interface that enables communication between the image forming apparatus 1 and an external PC (Personal Computer) 50.

[0049] [First embodiment] (Functional configuration) 6 is a block diagram showing an example of the functional configuration of the control unit 30 according to the first embodiment. The control unit 30 includes a patch image data generation unit 31, a discharge control unit 32, and a determination unit 33. These functions are realized by the CPU 301 in FIG. 5 executing a predetermined program stored in the ROM 302 or the like.

[0050] The patch image data generating unit 31 generates patch image data for forming a plurality of patch images with different densities on the paper P using ink ejected from the liquid ejecting unit 220.

[0051] The ejection control unit 32 controls the ink ejection operation by the liquid ejection unit 220. In particular, in this embodiment, the ejection control unit 32 controls the ink ejection operation by the liquid ejection unit 220 based on the patch image data generated by the patch image data generation unit 31. The ejection control unit 32 also controls the ink ejection operation by the liquid ejection unit 220 so that each of the multiple nozzle rows L1, L2, L3, and L4 ejects ink at the timing determined by the determination unit 33.

[0052] The determination unit 33 determines the timing at which each of the multiple nozzle arrays L1, L2, L3, and L4 ejects ink based on the density of multiple patch images formed on the paper P with ink ejected by the liquid ejection unit 220 under the control of the ejection control unit 32. In this embodiment, the determination unit 33 determines the timing at which each of the multiple nozzle arrays L1, L2, L3, and L4 ejects ink based on read images obtained by reading the multiple patch images formed on the paper P with the inline sensor 230.

[0053] <Patch image example> The patch image formed on the paper P will be described with reference to Fig. 7 to Fig. 14. Fig. 7 to Fig. 10 are diagrams illustrating patch image data generated by the patch image data generating unit 31 to form the patch image. Fig. 11 to Fig. 14 are diagrams illustrating the patch image formed on the paper P based on the patch image data.

[0054] (patch image data) Fig. 7 is a diagram illustrating an example of an entire patch image data group made up of multiple patch image data. In Fig. 7, each of multiple rectangles represents patch image data 700 for one patch image. The patch image data group 70 includes a total of 28 patch image data 700 arranged in a matrix of four columns along the width direction 10 and seven rows along the conveyance direction 20. Note that patch image data 700 is a collective term for the 28 patch image data.

[0055] In the patch image data group 70 , each of the patch image data strings 701 to 704 includes seven patch image data arrayed along the transport direction 20 .

[0056] The patch image data included in the patch image data array 701 is for forming a patch image on paper P by ejecting ink from the nozzles N of the nozzle array L1 and the nozzle array L2.

[0057] The patch image data included in the patch image data array 702 is for forming a patch image on the paper P by ejecting ink from the nozzles N of the nozzle array L2 and the nozzle array L3.

[0058] The patch image data included in the patch image data array 703 is for forming a patch image on the paper P by ejecting ink from the nozzles N of the nozzle array L3 and the nozzle array L4.

[0059] The patch image data included in the patch image data array 704 is for forming a patch image on the paper P by ejecting ink from the nozzles N of the nozzle array L4 and the nozzle array L1.

[0060] The patch image data generation unit 31 generates these patch image data strings for each combination of nozzle arrays used to form adjacent dots in the width direction 10 on the paper P. In this embodiment, the image forming apparatus 1 forms adjacent dots in the width direction 10 on the paper P using each combination of nozzle array L1 and nozzle array L2, nozzle array L2 and nozzle array L3, nozzle array L3 and nozzle array L4, and nozzle array L4 and nozzle array L1. Therefore, in the example of FIG. 7, the patch image data generation unit 31 generates patch image data strings 701 to 704 in accordance with these combinations.

[0061] In the patch image data group 70, each of the patch image data rows 705 to 711 is for forming patch images with different densities on the paper P, and each includes four patch image data.

[0062] FIG. 8 is a diagram showing a first example of patch image data, and is an enlarged view of patch image data 700a from the patch image data group 70. In FIG.

[0063] In FIG. 8, pixels 720 shown as small grids represent individual pixels constituting patch image data 700a. Patch image data 700a includes a total of 336 pixels 720 arranged in a matrix of 16 columns along the width direction 10 and 21 rows along the transport direction 20. Note that pixel 720 is a collective notation for the 336 pixels. Of the 336 pixels 720, solid black pixels represent pixels from which ink is to be ejected, and unfilled white pixels represent pixels from which ink is not to be ejected. Image forming apparatus 1 forms dots constituting a patch image on paper P using ink ejected from nozzles N corresponding to the pixels from which ink is to be ejected.

[0064] Pixel row L1a is a pixel row that forms dots on paper P by ejecting ink from nozzles N included in nozzle row L1, pixel row L2a is a pixel row that forms dots on paper P, pixel row L3a is a pixel row that forms dots on nozzle row L2, pixel row L3a is a pixel row that forms dots on nozzle row L4, and pixel row L4a is a pixel row that forms dots on paper P. Similarly, from the downstream side to the upstream side in the width direction 10, a pixel row for nozzle row L1, a pixel row for nozzle row L2, a pixel row for nozzle row L3, and a pixel row for nozzle row L4 are repeatedly arranged in this order.

[0065] The patch image data 700a is used by the determination unit 33 to determine the ink ejection timing of the nozzle row L2 relative to the nozzle row L1. In this case, the nozzle row L1 corresponds to the first nozzle row, and the nozzle row L2 corresponds to the second nozzle row. The patch image data 700a does not include pixels (black pixels) that eject ink in the pixel rows L3a and L4a.

[0066] The reference pixel M1a in the patch image data 700a is a pixel to which ink is ejected from the nozzle row L1 and is an example of a predetermined reference pixel. The adjustment pixel M2a in the patch image data 700a is an example of an adjustment pixel that is adjacent to the reference pixel M1a in the width direction 10 and is shifted from the reference pixel M1a in the transport direction 20 by a number of pixels that differs for each of the multiple patch images.

[0067] Here, adjacent pixels in the width direction 10 means that two pixels from which ink is ejected are adjacent in the width direction 10. However, this is not limited to the case where the two pixels are offset by one pixel in the width direction 10. Even if two pixels are separated by two or more pixels in the width direction 10, the two pixels can be said to be adjacent in the width direction 10 as long as there is no pixel from which ink is ejected between them. Note that the two pixels do not necessarily have to be adjacent in the transport direction 20.

[0068] The adjustment pixel M2a is adjacent to the reference pixel M1a, from which ink is ejected, in the width direction 10, and is positioned 0 pixels away from the reference pixel M1a in the transport direction 20. In the patch image data 700a, pixels from which ink is ejected other than the reference pixel M1a and adjustment pixel M2a are also positioned in the same positional relationship as the reference pixel M1a and adjustment pixel M2a.

[0069] The patch image data generating unit 31 generates other patch image data included in the patch image data row 708 in the patch image data group 70 of FIG. 7 using the same pixel arrangement as the patch image data 700a.

[0070] 9 is a diagram showing a second example of patch image data, and is an enlarged view of patch image data 700b from the patch image data group 70. Since FIG. 9 can be viewed in the same way as FIG. 8, redundant explanations will be omitted where appropriate.

[0071] The patch image data 700b is used by the determination unit 33 to determine the ink ejection timing of the nozzle row L2 relative to the nozzle row L1. In this case, the nozzle row L1 corresponds to the first nozzle row, and the nozzle row L2 corresponds to the second nozzle row. Furthermore, the patch image data 700a does not include pixels (black pixels) that eject ink in the pixel rows L3a and L4a.

[0072] The reference pixel M1b is an example of a reference pixel, and the adjustment pixel M2b is an example of an adjustment pixel. The adjustment pixel M2b is adjacent to the reference pixel M1b, from which ink is ejected, in the width direction 10, and is positioned three pixels downstream of the reference pixel M1b in the transport direction 20.

[0073] In patch image data 700b, pixels for ejecting ink other than reference pixel M1b and adjustment pixel M2b are also arranged in the same positional relationship as reference pixel M1b and adjustment pixel M2b.

[0074] The patch image data generating unit 31 generates other patch image data included in the patch image data row 705 in the patch image data group 70 of FIG. 7 using the same pixel arrangement as the patch image data 700b.

[0075] 10 is a diagram showing a third example of patch image data, and is an enlarged view of patch image data 700c in the patch image data group 70. Since FIG. 10 can be viewed in the same way as FIG. 8, redundant explanations will be omitted where appropriate.

[0076] The patch image data 700c is used by the determination unit 33 to determine the ink ejection timing of nozzle row L1 relative to nozzle row L4. In this case, nozzle row L4 corresponds to the first nozzle row, and nozzle row L1 corresponds to the second nozzle row. Furthermore, the patch image data 700c does not include pixels (black pixels) that eject ink in pixel rows L2a and L3a.

[0077] The reference pixel M4c is an example of a reference pixel, and the adjustment pixel M1c is an example of an adjustment pixel. The adjustment pixel M1c is adjacent to the reference pixel M4c, from which ink is ejected, in the width direction 10, and is positioned two pixels downstream of the reference pixel M4c in the transport direction 20.

[0078] In patch image data 700c, pixels for ejecting ink other than reference pixel M4c and adjustment pixel M1c are also arranged in the same positional relationship as reference pixel M4c and adjustment pixel M1c.

[0079] The patch image data generating unit 31 generates other patch image data included in the patch image data row 706 in the patch image data group 70 of FIG. 7 using the same pixel arrangement as the patch image data 700c.

[0080] As described above, the patch image data generating unit 31 generates the patch image data included in each of the patch image data rows 705 to 711 with the same pixel arrangement for each patch image data row.

[0081] In each of patch image data rows 705 to 711, the adjustment pixel is adjacent to the reference pixel in the width direction 10. However, in the transport direction 20, the adjustment pixel is shifted by a different number of pixels from the reference pixel. If a pixel shift toward the downstream side in the transport direction is represented by "-" and a pixel shift toward the upstream side is represented by "+", the adjustment pixel is shifted from the reference pixel in the transport direction by 0 pixels in patch image data row 708, -1 pixel in patch image data row 707, -2 pixels in patch image data row 706, and -3 pixels in patch image data row 705. Furthermore, the adjustment pixel is shifted from the reference pixel in the transport direction by +1 pixel in patch image data row 709, +2 pixels in patch image data row 710, and +3 pixels in patch image data row 711.

[0082] The density of the patch image formed on the paper P based on the patch image data varies depending on the number of pixels by which the adjustment pixel is shifted from the reference pixel in the transport direction 20. The determination unit 33 determines the ink ejection timing for each of the nozzle rows L1 to L4 by utilizing such differences in the density of the patch images.

[0083] (Patch image) 11 is a diagram illustrating an example of an entire patch image group 80 consisting of a plurality of patch images formed on a sheet P based on the patch image data group 70 of FIG. The image forming apparatus 1 forms the patch image group 80 in at least a partial area of the sheet P.

[0084] 11, each of the multiple rectangles represents one patch image 800. The patch image group 80 corresponds to the patch image data group 70 and includes a total of 28 patch images 800 arranged in a matrix of four columns along the width direction 10 and seven rows along the transport direction 20. Note that patch image 800 is a collective term for the 28 patch images.

[0085] In the patch image group 80, each of the patch image sequences 801 to 804 includes seven patch images.

[0086] The patch images included in patch image column 801 include dots formed on paper P by ink ejected from the nozzles N of nozzle column L1 and nozzle column L2. The patch images included in patch image column 802 include dots formed on paper P by ink ejected from the nozzles N of nozzle column L2 and nozzle column L3. The patch images included in patch image column 803 include dots formed on paper P by ink ejected from the nozzles N of nozzle column L3 and nozzle column L4. The patch images included in patch image column 804 include dots formed on paper P by ink ejected from the nozzles N of nozzle column L4 and nozzle column L1.

[0087] The image forming apparatus 1 forms a patch image string for each combination of nozzle strings used to form adjacent dots in the width direction 10 on the paper P. In this embodiment, the image forming apparatus 1 forms patch image strings 801 to 804.

[0088] 11, the patch images 800 included in the patch image group 80 have different densities. The closer (lighter) the color of the patch image 800 is to the color of the paper P, the lower the density of the patch image 800. For example, if the color of the paper P is white, the closer the color of the patch image 800 is to white, the lower the density of the patch image 800.

[0089] The difference in density of patch image 800 is caused by the coalescence of two dots formed by ink ejected from nozzle N and landing on paper P. Here, coalescence refers to two dots joining together on paper P. The closer the distance between two dots is, the more they coalesce, which results in a decrease in the amount of ink covering paper P, making the color of paper P more visible and lowering the density of patch image 800.

[0090] The closer the adjustment dot that is ejected from nozzle N and formed on paper P in response to the adjustment pixel is to the reference dot that is ejected from nozzle N and formed on paper P in response to the reference pixel, the lower the density of patch image 800 becomes due to the dot merging effect.

[0091] 12 is a diagram showing a patch image 800a formed on paper P based on the patch image data 700a of FIG. 8. The reference dot Q1a formed corresponding to the reference pixel M1a and the adjustment dot Q2a formed corresponding to the adjustment pixel M2a are formed in close positions and therefore merge together. As a result, as shown in FIG. 11, of the seven patch images included in the patch image array 801, the density of the patch image 800a is the lowest. This indicates that the ink ejection timing deviation of nozzle array L2 relative to nozzle array L1 is a deviation of 0 pixels in the transport direction 20, i.e., there is no deviation.

[0092] Fig. 13 shows patch image 800b formed on paper P based on patch image data 700b in Fig. 9. Reference dot Q1b formed corresponding to reference pixel M1b and adjustment dot Q2b formed corresponding to adjustment pixel M2b are formed at separate positions and therefore do not merge. As a result, of the seven patches included in patch image series 801, patch image 800b has the highest density, as shown in Fig. 11.

[0093] FIG. 14 is a diagram showing patch image 800c formed on paper P based on patch image data 700c in FIG. 10. Reference dot Q4c formed corresponding to reference pixel M4c and adjustment dot Q1c formed corresponding to adjustment pixel M1c are formed in close proximity to each other and therefore merge. As a result, as shown in FIG. 11, patch image 800c has the lowest density of the seven patch images included in patch image array 804. This indicates that the ink ejection timing deviation of nozzle array L1 relative to nozzle array L4 is a deviation of two pixels downstream in the transport direction 20.

[0094] 15 is a diagram illustrating the relationship between the adjustment value and the read G value according to this embodiment. Fig. 15 shows the results of inline sensor 230 reading each patch image included in patch image sequence 804 in patch image group 80 in Fig. 11.

[0095] The adjustment value, which is the horizontal axis in FIG. 15, indicates the number of pixels by which the adjustment pixel is shifted relative to the reference pixel along the transport direction 20. The unit is [number of pixels]. In the adjustment value, "-" indicates the downstream side in the transport direction 20, and "+" indicates the upstream side.

[0096] 11. Similarly, the plot corresponding to adjustment value -2 corresponds to the patch image included in patch image row 806, the plot corresponding to adjustment value -1 corresponds to the patch image included in patch image row 807, and the plot corresponding to adjustment value 0 corresponds to the patch image included in patch image row 808. Furthermore, the plot corresponding to adjustment value +1 corresponds to the patch image included in patch image row 809, the plot corresponding to adjustment value +2 corresponds to the patch image included in patch image row 810, and the plot corresponding to adjustment value +3 corresponds to the patch image included in patch image row 811.

[0097] 15 indicates the read G value, which is the read value of the G color among the read values of the R, G, and B colors output by the in-line sensor 230. The unit is [gradation].

[0098] 15, the read G value is largest at adjustment value -2, and therefore the result in Fig. 15 indicates that patch image 800c has the lowest density among the patch images included in patch image row 805. From the result in Fig. 15, the determination unit 33 detects that the ink ejection timing of nozzle row L1 is shifted by two pixels downstream in the transport direction 20 with respect to nozzle row L4, that is, that it is delayed by two pixels, and determines that the ink ejection timing of nozzle row L1 should be advanced by two pixels.

[0099] <Operation and effect of image forming apparatus 1> As described above, the image forming apparatus 1 (liquid ejection apparatus) according to this embodiment ejects ink (liquid) onto paper P (recording medium) transported in the transport direction 20. The image forming apparatus 1 includes a liquid ejection unit 220 having a plurality of nozzle rows L1 to L4 in which a plurality of nozzles N that eject ink are arranged along the width direction 10, and a determination unit 33 that determines the timing at which each of the plurality of nozzle rows L1 to L4 ejects ink based on the density of a plurality of patch images 800 formed on paper P by the ink ejected by the liquid ejection unit 220. Each of the multiple patch images 800 includes a reference dot Q1a formed on the paper P by ink ejected from nozzle row L1 (first nozzle row) corresponding to a reference pixel M1a, and an adjustment dot Q2a formed on the paper P by ink ejected from nozzle row L2 (second nozzle row) corresponding to an adjustment pixel M2a that is adjacent to the reference pixel M1a in the width direction 10 and is shifted from the reference pixel M1a in the transport direction 20 by a number of pixels that differs for each of the multiple patch images 800.

[0100] In the transport direction 20, each of the multiple patch images 800 corresponds to a different number of pixels, and the adjustment dots such as the adjustment dot Q2a are shifted relative to the reference dots such as the reference dot Q1a. This allows the determination unit 33 to determine the timing at which each of the multiple nozzle arrays L1 to L4 ejects ink in accordance with the number of pixels based on the density of each of the multiple patch images 800. For example, the determination unit 33 can determine the timing at which each of the multiple nozzle arrays L1 to L4 ejects ink based on the number of pixels by which the adjustment pixels are shifted relative to the reference pixels in the patch image 800 with the lowest density among the multiple patch images 800 formed on the paper P.

[0101] Furthermore, in this embodiment, because a reference pixel such as reference pixel M1a and an adjustment pixel such as adjustment pixel M2a are adjacent to each other in the width direction 10, the reference dots formed corresponding to the reference pixels and the adjustment dots formed corresponding to the adjustment pixels tend to overlap on the paper P. As a result, the density of the patch image 800 changes depending on the positional deviation of the adjustment dots, and the determination unit 33 can determine the timing at which each of the multiple nozzle arrays L1 to L4 ejects ink based on the density of the patch image 800 formed on the paper P. As a result, the timing at which each of the multiple nozzle arrays L1 to L4 ejects ink can be adjusted to the desired timing, ensuring the quality of the image formed on the paper P by the image forming apparatus 1.

[0102] Furthermore, the image forming apparatus 1 determines the timing of ink ejection by utilizing the fact that the density of a patch image 800 formed by a plurality of dots changes depending on the overlap of the dots formed on the paper P when the ink ejected by the liquid ejection unit 220 lands on the paper P. This makes it possible to determine the timing of ink ejection from each of the plurality of nozzle rows L1 to L4 using a relatively inexpensive in-line sensor 230 (reading unit) without using a high-resolution and expensive measuring instrument. As a result, the cost of the image forming apparatus 1 can be reduced.

[0103] Furthermore, in this embodiment, the multiple patch images 800 are formed for each combination of nozzle arrays used to form adjacent dots in the width direction 10 on the paper P. For example, patch image arrays 801 to 804 correspond to patch images formed for each combination of nozzle arrays. This makes it possible to determine the timing of ink ejection for each combination of nozzle arrays in the multiple nozzle arrays L1 to L4.

[0104] Furthermore, in this embodiment, the liquid ejection unit 220 has a plurality of nozzles N provided across the entire width of the paper P in the width direction 10. This allows the image forming apparatus 1, which is a line-type liquid ejection device, to determine the timing at which each of the plurality of nozzle rows L1 to L4 ejects ink.

[0105] Furthermore, this embodiment includes an in-line sensor 230 (reading unit) that reads a plurality of patch images 800 formed on paper P by ink ejected by the liquid ejection unit 220, and the determination unit 33 determines the timing at which each of the plurality of nozzle rows L1 to L4 ejects ink based on the reading results from the in-line sensor 230. This makes it possible to quantitatively detect the density of the patch image 800 and automatically determine the timing.

[0106] Furthermore, the image forming apparatus 1 can also use an inline sensor, which is used for inspecting printed materials and correcting images by the image forming apparatus 1, as a reading unit. This eliminates the need to provide a new reading unit such as the inline sensor 230 for determination by the determination unit 33, thereby simplifying the configuration of the image forming apparatus 1 and reducing costs.

[0107] Furthermore, in this embodiment, inline sensor 230 includes a plurality of reading pixels provided across the entire width of paper P in width direction 10. This makes it possible to read patch image 800 formed at any position on paper P in width direction 10. As a result, even when the position on paper P at which patch image 800 can be formed is restricted depending on the application of image forming apparatus 1, determination unit 33 can make a determination.

[0108] In the present embodiment, the image forming apparatus 1 is illustrated as having the in-line sensor 230 as a reading unit, but the present invention is not limited to this. For example, the image forming apparatus 1 can be equipped with a spectrophotometer instead of the in-line sensor 230, and the determination unit 33 can determine the timing at which each of the multiple nozzle rows L1 to L4 ejects ink based on the measurement results of the spectrophotometer.

[0109] Fig. 16 is a diagram illustrating the relationship between the adjustment value and the L* value (lightness) in the measurement results by a spectrophotometer. Like Fig. 15, Fig. 16 shows the results of measuring the colors of each patch image included in the patch image sequence 804 in the patch image group 80 of Fig. 11 by the spectrophotometer. Fig. 16 can be read in the same way as Fig. 15, so a duplicated explanation will be omitted here.

[0110] 16, the L* value at adjustment value -2 is the highest, and therefore the result in Fig. 16 indicates that patch image 800c has the lowest density among the patch images included in patch image row 805. From the result in Fig. 16, the determination unit 33 detects that the ink ejection timing by nozzle row L1 is shifted by two pixels downstream in the transport direction 20 with respect to nozzle row L4, that is, that it is delayed by two pixels, and can determine to advance the ink ejection timing by nozzle row L1 by two pixels.

[0111] [Second embodiment] An image forming apparatus 1a according to the second embodiment will be described below. Note that the same components as those in the first embodiment are given the same reference numerals, and redundant description will be omitted as appropriate.

[0112] 17 is a block diagram showing an example of the functional configuration of a control unit 30a included in the image forming apparatus 1a. As shown in FIG. 17, the control unit 30a includes a determination unit 33a.

[0113] The determination unit 33a receives information indicating the patch image with the lowest density, which is recognized, for example, by an operator of the image forming apparatus 1a by visually checking the plurality of patch images 800 formed on the paper P and input via the operation unit 40. Based on the received information, the determination unit 33a determines the timing at which each of the plurality of nozzle rows L1 to L4 ejects ink.

[0114] With this configuration, the image forming apparatus 1a can determine the timing at which each of the nozzle rows L1 to L4 ejects ink with a simple configuration, without including a reading unit such as an in-line sensor. Note that other effects are the same as those shown in the first embodiment.

[0115] Although examples of embodiments of the present invention have been described above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

[0116] The liquid ejection device according to the embodiment is not limited to an image forming device that includes a liquid ejection unit that ejects liquid toward a surface of a recording medium to be dried and that visualizes meaningful images such as letters, figures, etc. For example, the liquid ejection device according to the embodiment also includes a device that forms a pattern that does not have any meaning in itself.

[0117] The recording medium is not limited to any particular material, and may be any material to which a liquid can be attached, even temporarily, such as paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, or ceramics. For example, the recording medium may be used for film products, fabric products such as clothing, building materials such as wallpaper and flooring, or leather products.

[0118] The "liquid" is not particularly limited as long as it has a viscosity and surface tension that allows it to be ejected from a head, but it is preferable that the viscosity be 30 mPa·s or less at room temperature and normal pressure, or upon heating or cooling. More specifically, it is a solution, suspension, emulsion, etc. containing solvents such as water or organic solvents, colorants such as dyes or pigments, functionalizing materials such as polymerizable compounds, resins, and surfactants, biocompatible materials such as DNA, amino acids, proteins, and calcium, edible materials such as natural pigments, etc., and these can be used for applications such as inkjet inks and surface treatment solutions.

[0119] The term "image forming apparatus" includes serial type apparatuses in which the liquid ejection unit is moved, line type apparatuses in which the liquid ejection unit is not moved, and the like.

[0120] The liquid ejection unit is a functional component that ejects and sprays liquid from an ejection hole (nozzle). As an energy generation source for ejecting liquid, ejection energy generation means such as a piezoelectric actuator (a laminated piezoelectric element or a thin-film piezoelectric element), a thermal actuator using an electrothermal conversion element such as a heating resistor, or an electrostatic actuator consisting of a vibration plate and an opposing electrode can be used, but the ejection energy generation means to be used is not limited.

[0121] The embodiments also include a liquid ejection method. For example, the liquid ejection method is a liquid ejection method using a liquid ejection device that ejects liquid onto a recording medium transported in a transport direction. The liquid ejection device ejects the liquid using a liquid ejection unit having multiple nozzle arrays, each of which has multiple nozzles that eject the liquid arranged along a width direction perpendicular to the transport direction. A determination unit determines the timing at which each of the multiple nozzle arrays ejects the liquid based on the density of multiple patch images formed on the recording medium with the liquid ejected by the liquid ejection unit. Each of the multiple patch images includes: a reference dot formed on the recording medium by the liquid ejected from a first nozzle array included in the multiple nozzle arrays, corresponding to a predetermined reference pixel; and an adjustment dot formed on the recording medium by the liquid ejected from a second nozzle array included in the multiple nozzle arrays, corresponding to an adjustment pixel that is adjacent to the reference pixel in the width direction and shifted from the reference pixel in the transport direction by a number of pixels that varies for each of the multiple patch images. Such a liquid ejection method can achieve the same effects as the image forming apparatus 1 described above.

[0122] The ordinal numbers, quantities, and other figures used in the description of the embodiments are all provided as examples to specifically explain the technology of the present invention, and the present invention is not limited to the illustrated figures. Furthermore, the connection relationships between the components are provided as examples to specifically explain the technology of the present invention, and do not limit the connection relationships that realize the functions of the present invention.

[0123] For example, the number of patch image data, the number of patch images, the number of pixels included in the patch image data, and the number of dots included in the patch image shown in the embodiment can be changed as appropriate depending on the intended use of the image forming apparatus 1, etc.

[0124] Each function of the embodiments can be realized by one or more processing circuits. Here, the term "processing circuit" in this specification includes a processor programmed to perform each function by software, such as a processor implemented by an electronic circuit, as well as devices such as an ASIC (Application Specific Integrated Circuit), a DSP (Digital Signal Processor), an FPGA (Field Programmable Gate Array), and conventional circuit modules designed to perform each function described above. [Explanation of symbols]

[0125] 1. Image forming apparatus (an example of a liquid ejection apparatus) 10 Width direction 20 Conveying direction 30 Control Unit 31 Patch image data generation unit 32 Discharge control section 33 Decision Section 40 Control section 50 External PC 70 patch image data sets 700, 700a, 700b, 700c Patch image data 701 to 704 Patch image data string 705 to 711 Patch image data lines 80 patch images 800, 800a, 800b, 800c patch images 801 to 804 Patch image sequence 805 to 811 Patch image rows 100 Paper feed section 200 Image forming unit 220 Liquid discharge part 220K, 220C, 220M, 220Y liquid ejection head 230 Inline sensor (example of reading unit) 231 First inline sensor 232 Second inline sensor 300 Drying section 400 Paper output section L1, L2, L3, L4 nozzle rows P Paper (an example of a recording medium) N nozzle M1a, M1b, M4c reference pixels M2a, M2b, M1c adjustment pixels Q1a, Q1b, Q4c reference dots Q2a, Q2b, Q1c adjustment dots [Prior art documents] [Patent documents]

[0126] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-201094

Claims

1. A liquid ejection device that ejects liquid onto a recording medium transported in a transport direction, a liquid ejection unit having a plurality of nozzle rows in which a plurality of nozzles for ejecting the liquid are arranged along a width direction perpendicular to the transport direction; a determination unit that determines timing at which each of the plurality of nozzle arrays ejects the liquid based on densities of a plurality of patch images formed on the recording medium by the liquid ejected by the liquid ejection unit, Each of the plurality of patch images is a reference dot formed on the recording medium by the liquid ejected from a first nozzle row included in the plurality of nozzle rows, in correspondence with a predetermined reference pixel; adjustment dots formed on the recording medium by the liquid ejected from a second nozzle row included in the plurality of nozzle rows, the adjustment dots being adjacent to the reference pixel in the width direction and corresponding to adjustment pixels that are shifted from the reference pixel in the transport direction by a number of pixels that differs for each of the plurality of patch images; a liquid ejection device in which the plurality of patch images are formed for each combination of the nozzle arrays used to form dots adjacent to each other in the width direction on the recording medium;

2. A liquid ejection device as described in Claim 1, characterized in that the multiple nozzle rows include, in addition to the first nozzle row and the second nozzle row, a nozzle row that is not used when forming each of the multiple patch images.

3. 3. The liquid ejection device according to claim 1, wherein the liquid ejection section has the plurality of nozzles provided across the entire width of the recording medium in the width direction.

4. a reading unit that reads the plurality of patch images formed on the recording medium by the liquid ejected by the liquid ejection unit, The liquid ejection apparatus according to claim 1 , wherein the determination unit determines the timing based on a reading result obtained by the reading unit.

5. The liquid ejection device according to claim 4 , wherein the reading unit includes a plurality of reading pixels provided across the entire width of the recording medium in the width direction.

6. A liquid ejection device as described in any one of claims 1 to 5, wherein the determination unit determines the timing based on the number of pixels in which the adjustment pixel is misaligned with the reference pixel in the patch image with the lowest density among the plurality of patch images formed on the recording medium.

7. A liquid ejection method using a liquid ejection device that ejects liquid onto a recording medium that is transported in a transport direction, the liquid ejection device comprising: ejecting the liquid using a liquid ejection unit having a plurality of nozzle rows in which a plurality of nozzles for ejecting the liquid are arranged along a width direction perpendicular to the transport direction; a determination unit determining timings at which each of the plurality of nozzle arrays ejects the liquid based on densities of a plurality of patch images formed on the recording medium by the liquid ejected by the liquid ejection unit; Each of the plurality of patch images is a reference dot formed on the recording medium by the liquid ejected from a first nozzle row included in the plurality of nozzle rows, in correspondence with a predetermined reference pixel; adjustment dots formed on the recording medium by the liquid ejected from a second nozzle row included in the plurality of nozzle rows, the adjustment dots being adjacent to the reference pixel in the width direction and corresponding to adjustment pixels that are shifted from the reference pixel in the transport direction by a number of pixels that differs for each of the plurality of patch images; a liquid ejection method, wherein the plurality of patch images are formed for each combination of the nozzle arrays used to form dots adjacent to each other in the width direction on the recording medium;

Images