Printing method and printing system

Abstract

In low-pass printing, where the number of passes required to move the inkjet head in the scanning direction is reduced, the optical density of images printed with black ink alone was sometimes insufficient. [Solution] When m > n, the color nozzle rows, each consisting of n rows for each color, include a first color nozzle row and a second color nozzle row. When printing on medium M using all m rows of black nozzle rows, the ratio of the ejection amount for each row of black nozzle rows can be changed using a conversion table 22a that associates input data indicating the color of the input image with the ejection amount of black ink.

Description

Technical Field

[0001] The present disclosure relates to a printing method and a printing system.

Background Art

[0002] Patent Document 1 discloses an inkjet printer including an inkjet head in which a nozzle row for discharging black ink is arranged at the center in the scanning direction, and nozzle rows for discharging color inks are arranged outside in the scanning direction. In this inkjet head, the number of nozzle rows for discharging black ink is larger than the number of nozzle rows for each color of the color inks. In this inkjet printer, when performing full-color printing including black ink, printing processing is performed in which black ink is not discharged from some of the nozzle groups among the nozzle groups for discharging black ink.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the inkjet printer described in Patent Document 1, in low-pass printing in which the number of passes for moving the inkjet head in the scanning direction is reduced, the optical density of an image printed only with black ink may be insufficient.

Means for Solving the Problems

[0005] The printing method involves a print head having m rows of black nozzles (where m is a natural number of 2 or more) formed by nozzles that eject black ink arranged in the nozzle row direction, and n rows of color nozzles (where n is a natural number of 1 or more and m > n) for each color, formed by nozzles that eject a predetermined color of a different color from the black ink arranged in the nozzle row direction, and a main scanning unit that moves the print head in a main scanning direction intersecting the nozzle row direction, wherein when printing on the medium using all of the m rows of black nozzles, the ratio of the ejection amount for each row of the black nozzles can be changed using a conversion table that associates input data indicating the color of the input image with the ejection amount of the black ink.

[0006] The printing system comprises a print head having m rows of black nozzles (where m is a natural number of 2 or more) formed by nozzles for ejecting black ink arranged in the nozzle row direction, and n rows of color nozzles (where n is a natural number of 1 or more and m > n) for each color, formed by nozzles for ejecting a predetermined color of a different color from the black ink arranged in the nozzle row direction; a main scanning unit that moves the print head in a main scanning direction intersecting the nozzle row direction; a storage unit that stores a conversion table associating input data indicating the color of an input image with the amount of black ink ejected; and a control unit that determines the ejection amount using the conversion table. The control unit can change the proportion of the ejection amount for each row of the black nozzles using the conversion table when printing on a medium using all of the m rows of black nozzles. [Brief explanation of the drawing]

[0007] [Figure 1] A schematic diagram showing the general configuration of a printing system. [Figure 2] A block diagram showing the configuration of the printing system. [Figure 3] A flowchart for print control. [Figure 4] A diagram showing the arrangement of nozzle rows in the first embodiment. [Figure 5] A diagram showing an example of the correspondence between nozzle rows and ink in the first embodiment. [Figure 6] A diagram showing an example of a print mode. [Figure 7] A diagram illustrating an example of the characteristics of a conversion table. [Figure 8] A diagram showing the arrangement of nozzle rows in the second embodiment. [Figure 9] A diagram showing an example of the correspondence between nozzle rows and ink in the second embodiment. [Modes for carrying out the invention]

[0008] 1. First Embodiment The printing method and printing system 100 according to the embodiment will be described below. In the drawings shown below, the scale of each component is shown differently from the actual scale in order to make each component recognizable. In addition, the same reference numerals are used for identical components in each drawing, and redundant explanations are omitted. Furthermore, in each drawing, the X, Y, and Z axes are shown as mutually orthogonal coordinate axes as necessary. The X, Y, and Z axes are each labeled with arrows. For each of the X, Y, and Z axes, the direction of the arrow is the positive direction, and the direction opposite to the direction of the arrow is the negative direction.

[0009] For the sake of explanation, the positive direction of the Z-axis will be referred to as the upward direction or simply as "up," and the negative direction as the downward direction or simply as "down." Similarly, the positive direction of the X-axis will be referred to as the right direction or simply as "right," and the negative direction as the left direction or simply as "left." The positive direction of the Y-axis will be referred to as the forward direction or simply as "forward," and the negative direction as the backward direction or simply as "backward." In Figure 1, the X-axis direction corresponds to the main scanning direction, and the Y-axis direction corresponds to the sub-scanning direction. The direction in which the medium M is transported will also be referred to as the downstream direction, and the direction opposite to the downstream direction will be referred to as the upstream direction.

[0010] 1-1. Printing System Configuration As shown in Figure 1, the printing system 100 includes a printing device 1 and an external device 2. The printing device 1 and the external device 2 are connected to each other in a way that allows them to communicate with one another. The printing device 1 is an inkjet printer that prints by ejecting a liquid such as ink onto a medium M. The external device 2 is a computer, tablet, smartphone, etc.

[0011] The medium M may include sheets, fabrics, and three-dimensional objects. Sheets include paper, synthetic paper, and film. Fabrics include nonwoven fabrics, knits, and woven cloths. Three-dimensional objects may include clothing, shoes, daily necessities, and machine parts. Furthermore, a material to be printed can preferably be used as the medium M. A material to be printed refers to fabrics, clothing, and other fashion products that are to be printed. Fabrics include woven, knitted, and nonwoven fabrics made from natural fibers such as cotton, silk, and wool, or synthetic fibers such as nylon, or composite fibers that are mixtures of these.

[0012] The printing apparatus 1 includes a print head 16, a sub-scanning unit 17, and a main scanning unit 18. The print head 16 is mounted on a carriage 16a. The sub-scanning unit 17 includes a transport motor 17a and transport rollers 17b. The sub-scanning unit 17 rotates the transport rollers 17b using the transport motor 17a, moving the medium M in the forward and backward direction, which is the sub-scanning direction. The medium M is transported in the transport direction along a transport path formed between the print head 16 and the transport rollers 17b. The transport direction of the medium M below the print head 16 is the same as the sub-scanning direction.

[0013] The main scanning unit 18 includes a carriage 16a, a carriage shaft 16b, a carriage motor 18a, and a belt 18b. The main scanning unit 18 moves the belt 18b using the carriage motor 18a, and moves the carriage 16a mounted on the belt 18b in the left-right direction, which is the main scanning direction that intersects the sub-scanning direction along the carriage shaft 16b.

[0014] The printing head 16 has a plurality of nozzles capable of discharging ink arranged in a row in the nozzle row direction. In the present embodiment, the nozzle row direction is the direction along the Y-axis. The nozzles arranged in a row are arranged side by side in the main scanning direction as a plurality of nozzle rows. The printing head 16 is moved in the main scanning direction intersecting the nozzle row direction by the main scanning unit 18, and discharges ink downward toward the medium M while printing an image composed of dots or the like.

[0015] Thus, the sub-scanning unit 17 and the main scanning unit 18 can relatively move the printing head 16 and the medium M. After the medium M is moved by the sub-scanning unit 17, the printing head 16 discharges ink toward the stopped medium M while moving by the main scanning unit 18. By repeating this cycle, the printing apparatus 1 prints a predetermined image on the medium M.

[0016] The printing apparatus 1 can be equipped with, for example, an ink cartridge or an ink tank storing ink or a liquid having a predetermined functionality. Examples of the ink include ink containing coloring materials such as CMYK. Examples of the liquid having a predetermined functionality include a reaction liquid containing a flocculant for aggregating the ink, a treatment liquid containing a softening agent, and a post-treatment liquid. The ink cartridge or the like supplies liquids such as inks of each color to the nozzle rows of the corresponding printing heads 16.

[0017] As shown in FIG. 2, in addition to the above-described configuration, the printing apparatus 1 includes a control unit 10, a storage unit 15, and a communication unit 19. The control unit 10 includes a CPU (Central Processing Unit) that comprehensively controls each part of the printing apparatus 1, a UART (Universal Asynchronous Receiver Transmitter) that manages input / output, and an FPGA (Field Programmable Gate Array) or a PLD (Programmable Logic Device) which is a logic circuit.

[0018] The storage unit 15 includes a flash ROM (Read Only Memory), which is a rewritable non-volatile memory, a RAM (Random Access Memory), which is a volatile memory, and the like. The CPU of the control unit 10 reads programs such as firmware stored in the flash ROM of the storage unit 15 and executes them using the RAM of the storage unit 15 as a working area. The communication unit 19 includes a communication circuit capable of wired or wireless communication with the external device 2.

[0019] As shown in FIG. 2, the external device 2 includes an external control unit 20 including a CPU, an external storage unit 22, and an external communication unit 23. The external storage unit 22 includes a RAM, a flash ROM, which is a non-volatile memory, a HDD (Hard Disk Drive), and the like. A conversion table 22a, which will be described later, is stored in the external storage unit 22. The external communication unit 23 includes a communication circuit capable of communicating with the printing device 1.

[0020] The CPU included in the external control unit 20 reads and executes programs such as a graphic creation application, a graphic creation application, and a text creation application stored in the external storage unit 22. The external control unit 20 generates image data by executing the program.

[0021] Further, the external control unit 20 generates pixel data for ejecting ink from the nozzles of the print head 16 based on the image data, and has a driver 21 capable of controlling the printing device 1. The driver 21 includes an ejection amount conversion processing unit 21a, a halftone processing unit 21b, a rasterization processing unit 21c, and the like, which will be described later. The external communication unit 23 transmits the pixel data, which is output data, to the communication unit 19 of the printing device 1.

[0022] The control unit 10 applies a drive signal to the drive elements of the nozzles of the print head 16 based on the pixel data output from the external device 2 and received via the communication unit 19, causing ink to be ejected from the nozzles onto the medium M. In this way, the printing system 100 can print an image consisting of dots onto the medium M by transferring image data generated by the external device 2 to the printing device 1, causing ink to be ejected from the nozzles of the printing device 1.

[0023] Furthermore, the control unit 10 can change the amount of ink ejected per unit area from the nozzle by changing the pattern of the applied drive signal. This allows the print head 16 to form dots of different sizes on the medium M. Depending on the characteristics of the nozzle, the control unit 10 can also change the amount of ink ejected onto the medium M and form dots of different sizes by changing the number of times the drive signal is applied to the drive element without changing the pattern of the applied drive signal.

[0024] 1-2. Printing control method The printing method using the printing system 100 will be explained with reference to Figures 2 and 3. First, the process by which the external control unit 20 of the external device 2 processes image data will be explained. The external control unit 20 generates image data from a program (step S1). The image data consists of bitmap data expressed in the CMYK color space, for example. Specifically, the bitmap data is represented by 256 gradation values ​​from 0 to 255, which are represented by 8 bits as input data indicating each CMYK color of the input image data. The 256 gradation values, which are input data indicating each CMYK color, correspond to values ​​indicating the density of each CMYK color from 0% to 100%.

[0025] Next, the driver 21 selects one print mode from among several print modes for the image data to be printed, based on the user's specification (step S2). In this embodiment, the print modes include the first mode, second mode, third mode, and fourth mode, which will be described later. By selecting a print mode, it is possible to control the ink ejected from the nozzle row and to perform printing with relatively different movement amounts of the print head 16 and the media M.

[0026] When a print mode is selected, the ejection amount conversion processing unit 21a refers to the conversion table 22a stored in the external storage unit 22. The conversion table 22a contains multiple LUTs (lookup tables) stored in the external storage unit 22. The conversion table 22a contains multiple LUTs that associate the values ​​of each input data representing the color of the input image expressed in the CMYK color space with the ejection amount of each ink color, such as CMYK. In this way, the ejection amount conversion processing unit 21a uses the conversion table 22a to determine the ejection amount of CMYK and other inks to be injected per unit area. The conversion table 22a also includes multiple LUTs that correspond to printing conditions such as the type of medium M and the resolution of the image data.

[0027] Then, the ejection volume conversion processing unit 21a performs an ejection volume conversion process to convert the bitmap data, which is input data expressed in the CMYK color space, into ejection volume data for CMYK and other inks corresponding to each nozzle (step S3). In other words, by referring to the conversion table 22a, the ejection volume conversion processing unit 21a can convert the image data of the input image into ink ejection volume data according to conditions such as the print mode, the type of medium M, and the resolution of the image data. The ink ejection volume data is represented, for example, by 256 gradation values ​​from 0 to 255, which are represented by 8 bits as values ​​indicating each CMYK color.

[0028] Next, the halftone processing unit 21b of the driver 21 performs halftone processing to convert the ink ejection amount data converted by the ejection amount conversion processing unit 21a into data with a number of gradations that can be realized by the print head 16 (step S4).

[0029] The halftone processing unit 21b can, for example, convert ink ejection amount data expressed in 256 gradations into 2-bit data with 4 gradations, including "no dot," "small dot," "medium dot," and "large dot," which are capable of forming dots of various sizes. As the ink ejection amount data increases, it is converted to larger dot sizes. In the following explanation, the data corresponding to "no dot," "small dot," "medium dot," and "large dot" will be referred to as dot data.

[0030] The halftone processing unit 21b can produce a lighter print result by generating dot data including "small dots" when the ink ejection amount data value is small. On the other hand, the halftone processing unit 21b can produce a darker print result by generating dot data including "large dots" when the ink ejection amount data value is large.

[0031] The external storage unit 22 stores a dot generation rate table (not shown) that indicates the rate at which dot data representing "no dot," "small dot," "medium dot," and "large dot" is generated. The halftone processing unit 21b refers to the dot generation rate table in the external storage unit 22 and generates dot data corresponding to the ink ejection amount data. The halftone processing unit 21b also uses methods such as dithering and error diffusion to create dot data so that each dot is formed in a dispersed manner, based on the dot data obtained from the dot generation rate table.

[0032] Furthermore, the halftone processing unit 21b can also convert the dot data to correspond to, for example, the amount of ink ejected from the nozzle. In addition, the ink ejection amount data can also be converted to correspond to, for example, the number of times ink is ejected from the nozzle. The dot data that has undergone these processes is temporarily stored in the external storage unit 22 in a matrix arrangement.

[0033] Next, the rasterization processing unit 21c of the driver 21 performs rasterization processing to rearrange the matrix-like dot data stored in the external storage unit 22 (step S5). Rasterization processing is the process of rearranging the dot data in an order that allows dots to be formed by ejecting ink from the nozzles in each pass, after the medium M is moved by the sub-scanning unit 17 and the print head 16 is moved by the main scanning unit 18. A pass refers to a printing operation performed while the print head 16 moves in the +X direction or the -X direction.

[0034] The rasterization processing unit 21c generates pixel data based on the dot data generated by the halftone processing unit 21b, which allows each nozzle of the print head 16 to be driven to form dots. The pixel data is stored in the external storage unit 22 by the rasterization processing unit 21c so that each nozzle of the print head 16 can form dots. The pixel data can be the same as the dot data, or it can be the same as the ink ejection amount data.

[0035] Next, the external communication unit 23 transmits print data, including pixel data generated by the rasterization processing unit 21c, to the printing device 1 (step S6). Then, the communication unit 19 of the printing device 1 receives the print data transmitted from the external device 2 (step S7). The print data received by the printing device 1 is stored in the storage unit 15.

[0036] Next, the control unit 10 of the printing device 1 reads the program stored in the storage unit 15 and sequentially reads print data including pixel data from the storage unit 15. Based on the print data, it controls the print head 16, sub-scanning unit 17, and main scanning unit 18 to perform printing processing to print an image on the medium M (step S8).

[0037] Using the printing method described above, the printing system 100 can print an image onto the medium M.

[0038] 1-3. Printhead Configuration The configuration of the print head 16 will be described with reference to Figures 4 and 5. As shown in Figure 4, the print head 16 has heads H1 to H10. The configuration of heads H1 to H10 is the same for each. Heads H1 to H10 each have four head chips Hc1 to Hc4. Head chips Hc1 to Hc4 each have a first nozzle row La and a second nozzle row Lb. The first nozzle row La and the second nozzle row Lb each have a plurality of nozzles N capable of ejecting ink. The plurality of nozzles N are arranged at a predetermined pitch interval in the direction of the nozzle row in which the plurality of nozzles N are arranged in series.

[0039] The first nozzle row La and the second nozzle row Lb are arranged adjacent to each other along the X-axis direction, which is the main scanning direction. Furthermore, the nozzles N forming the first nozzle row La and the nozzles N forming the second nozzle row Lb are offset from each other by half a pitch, or so-called half-pitch, along the Y-axis direction. In other words, each nozzle N in the first nozzle row La and each nozzle N in the second nozzle row Lb are arranged in a staggered pattern. A staggered arrangement means that each nozzle N, which is arranged in parallel along the X-axis direction, is alternately offset by half a pitch in the Y-axis direction. The predetermined pitch in the Y-axis direction between each nozzle N is set appropriately according to the dpi (dots per inch) of the printing resolution.

[0040] Head chips Hc1 and Hc3 are arranged in series with a predetermined distance between them along the Y-axis direction, which is the sub-scanning direction. Head chip Hc1 is positioned upstream of head chip Hc3 in the -Y direction, which is the direction in which the medium M is transported. Head chips Hc2 and Hc4 are also arranged in series with a predetermined distance between them along the Y-axis direction, which is the sub-scanning direction. Head chip Hc2 is positioned upstream of head chip Hc4 in the -Y direction. In this embodiment, the predetermined distance refers to a distance determined in correlation with the pitch of each nozzle N.

[0041] The first nozzle row La of head tip Hc1 and the first nozzle row La of head tip Hc3 are arranged in series along the nozzle row direction. The second nozzle row Lb of head tip Hc1 and the second nozzle row Lb of head tip Hc3 are arranged in series along the nozzle row direction. The first nozzle row La of head tip Hc2 and the first nozzle row La of head tip Hc4 are arranged in series along the nozzle row direction. The second nozzle row Lb of head tip Hc2 and the second nozzle row Lb of head tip Hc4 are arranged in series along the nozzle row direction.

[0042] Furthermore, head chips Hc1 and Hc2 are positioned at a predetermined distance from each other along the X-axis. Head chips Hc1 and Hc2 are also positioned at a predetermined distance from each other along the Y-axis. Head chips Hc3 and Hc4 are positioned at a predetermined distance from each other along the X-axis. Head chips Hc3 and Hc4 are also positioned at a predetermined distance from each other along the Y-axis. In other words, head chips Hc1 to Hc4 are arranged in a staggered pattern.

[0043] Furthermore, when the downstream side of head tip Hc1 and the upstream side of head tip Hc2 are projected onto a plane perpendicular to the X-axis, head tips Hc1 and Hc2 are positioned so that parts of them overlap each other. Also, when the downstream side of head tip Hc2 and the upstream side of head tip Hc3 are projected onto a plane perpendicular to the X-axis, head tips Hc3 and Hc2 are positioned so that parts of them overlap each other. Furthermore, when the downstream side of head tip Hc3 and the upstream side of head tip Hc4 are projected onto a plane perpendicular to the X-axis, head tips Hc3 and Hc4 are positioned so that parts of them overlap each other.

[0044] By arranging the head tips Hc1 to Hc4 in this way, adjacent first nozzle rows La among the head tips Hc1 to Hc4 can be partially overlapped in the X-axis direction, thereby forming a continuous row of nozzles N across the nozzle row direction. Furthermore, adjacent second nozzle rows Lb among the head tips Hc1 to Hc4 can be partially overlapped in the X-axis direction, thereby forming a continuous row of nozzles N across the nozzle row direction.

[0045] Of the heads H1 to H10, heads H1, H3, H5, H7, and H9 are arranged in this order at equal intervals along the X-axis direction, which is the main scanning direction. Of the heads H1 to H10, heads H2, H4, H6, H8, and H10 are located downstream of heads H1, H3, H5, H7, and H9. Also, heads H2, H4, H6, H8, and H10 are arranged in this order at equal intervals along the X-axis direction, which is the main scanning direction.

[0046] The first nozzle row La of head H1 and the first nozzle row La of head H2 are arranged in series with a predetermined gap between them along the nozzle row direction. The second nozzle row Lb of head H1 and the second nozzle row Lb of head H2 are arranged in series with a predetermined gap between them along the nozzle row direction.

[0047] When the downstream side of the head tip Hc4 of head H1 and the upstream side of the head tip Hc1 of head H2 are projected onto a plane perpendicular to the X-axis, the head tip Hc4 of head H1 and the head tip Hc1 of head H2 are positioned so that parts of them overlap. By positioning head H1 and head H2 in this way, the first nozzle row La of the head tip Hc4 of head H1 and the first nozzle row La of the head tip Hc1 of head H2 can be partially overlapped in the X-axis direction, thereby forming a continuous row of nozzles N across the nozzle row direction.

[0048] Since the print head 16 is configured as described above, the printing device 1 can print an image on the medium M by moving the print head 16, which includes a plurality of first nozzle rows La and a plurality of second nozzle rows Lb along the main scanning direction, and the medium M relatively. The printing device 1 can print an image using single-color or multi-color inks, for example, with a resolution of 300 dpi or 600 dpi in the main scanning direction and a resolution of 600 dpi in the sub-scanning direction.

[0049] As shown in Table Ta1 of Figure 5, the first nozzle rows La located on the head tips Hc1 to Hc4 of head H1 and the head tips Hc1 to Hc4 of head H2 are capable of ejecting yellow Y ink.

[0050] Similarly, the second nozzle row Lb of heads H1 and H2 is capable of ejecting magenta ink (M).

[0051] Similarly, the first nozzle row La of heads H3 and H4 is capable of ejecting cyan ink.

[0052] Similarly, the second nozzle row Lb of heads H3 and H4 is capable of ejecting black ink (K). In the following description, the second nozzle row Lb of heads H3 and H4 will also be simply referred to as "nozzle row K1".

[0053] Similarly, the first nozzle row La of heads H5 and H6 is capable of ejecting black ink (K). In the following description, the first nozzle row La of heads H5 and H6 will also be simply referred to as "nozzle row K2".

[0054] Similarly, the second nozzle row Lb of heads H5 and H6 is capable of ejecting black ink (K). In the following description, the second nozzle row Lb of heads H5 and H6 will also be simply referred to as "nozzle row K3".

[0055] Similarly, the first nozzle row La of heads H7 and H8 is capable of ejecting black ink (K). In the following description, the first nozzle row La of heads H7 and H8 will also be simply referred to as "nozzle row K4".

[0056] Similarly, the second nozzle row Lb of heads H7 and H8 is capable of ejecting cyan ink.

[0057] Similarly, the first nozzle row La of heads H9 and H10 is capable of ejecting magenta ink (M).

[0058] Similarly, the second nozzle row Lb of heads H9 and H10 is capable of ejecting yellow Y ink.

[0059] In the following explanation, ink with the color black (K) will simply be referred to as "black ink." Ink with a different color from "black ink," such as cyan (C), magenta (M), and yellow (Y), will simply be referred to as "color ink." Furthermore, when the first nozzle row La and the second nozzle row Lb are not distinguished, they will simply be referred to as "nozzle row L." Also, nozzle rows K1 to K4 that eject "black ink" will simply be referred to as the "black nozzle row," and nozzle row L that ejects "color ink" will simply be referred to as the "color nozzle row."

[0060] As described above, the print head 16 has multiple nozzles N that eject "black ink" arranged in the nozzle row direction. The nozzle row L, in which the multiple nozzles N that eject "black ink" are arranged, is formed as four "black nozzle rows" in the main scanning direction. The four "black nozzle rows" are arranged in the order of "nozzle row K1", "nozzle row K2", "nozzle row K3", and "nozzle row K4" from the -X direction to the +X direction. In addition, the print head 16 has multiple nozzles N that eject "color ink" of a predetermined color different from the color of "black ink" arranged in the nozzle row direction. The nozzle row L, in which the multiple nozzles N that eject "color ink" of a predetermined color are arranged, is formed as two "color nozzle rows" in the main scanning direction.

[0061] The two rows of "color nozzles" consist of a first color nozzle row and a second color nozzle row. The four rows of "black nozzles" are positioned between the first color nozzle row and the second color nozzle row in the main scanning direction. In other words, in addition to the two rows of "black nozzles" between the first and second color nozzle rows of the two rows of "color nozzles" that emit a predetermined color, there are two more rows of "black nozzles" positioned between them.

[0062] This configuration allows for the ejection of equal amounts of ink from two rows of color nozzles and two rows of black nozzles, each within the range from the minimum to the maximum ejection volume. This ensures stable print quality. Furthermore, the addition of two rows of black nozzles allows for printing on medium M using all four rows of black nozzles. This means that printing can be done using only two rows of black nozzles, or the optical density of the image printed with black ink can be increased by using all four rows of black nozzles.

[0063] In this embodiment, the case where there are 4 rows of "black nozzles" and 2 rows of "color nozzles" for each color is described, but the invention is not limited to this. The number of "black nozzles" and "color nozzles" can be increased or decreased as appropriate by changing the configuration of the print head 16. The number of "black nozzles" and "color nozzles" can be increased or decreased as appropriate by satisfying the relationship m > n, where m is the number of "black nozzles" (m is a natural number of 2 or more) and n is the number of "color nozzles" for each color (n is a natural number of 1 or more).

[0064] Furthermore, as shown in Figures 4 and 5, the ink colors that can be ejected from the "nozzle row L" are arranged in the following order from head H1 in the +X direction: yellow Y, magenta M, cyan C, black K, black K, black K, black K, cyan C, magenta M, and yellow Y. In addition, each "nozzle row L" is arranged at equal intervals along the X axis.

[0065] Therefore, when printing by moving the print head 16 back and forth in the X-axis direction, the order in which ink colors are ejected when moving in the +X direction and the order in which ink colors are ejected when moving in the -X direction can be made the same. Furthermore, since each "nozzle row L" is arranged at equal intervals, the order in which the inks are layered on the medium M can be made the same, and the time difference in when different types of inks or other liquids land can also be made the same. Thus, it is possible to suppress color differences due to differences in printing position in the main scanning direction and differences in the degree of ink aggregation due to differences in the main scanning direction, thereby improving print quality.

[0066] 1-4. Configuration of the Conversion Table The configuration of the conversion table 22a will be described with reference to Figures 6 and 7. Figure 6 shows an example of a print mode corresponding to the print head 16 shown in Figures 4 and 5.

[0067] The conversion table 22a is configured to include LUTs corresponding to multiple printing modes shown in Table Ta2 of Figure 6. The multiple printing modes include the first mode, second mode, third mode, and fourth mode. The external control unit 20 uses the conversion table 22a when printing on the medium M using all of the "black nozzle rows". In this embodiment, the conversion table 22a is configured to include LUTs corresponding to the first mode, second mode, third mode, and fourth mode, but is not limited to this configuration. It does not have to include any of the first mode, second mode, third mode, and fourth mode, or it may be configured to include LUTs corresponding to other modes.

[0068] In modes 1 through 4, the "color nozzle rows" corresponding to each "color ink" consist of a total of six rows: two rows for cyan (C), two rows for magenta (M), and two rows for yellow (Y). Each color is configured with two "color nozzle rows," resulting in a resolution (dpi) of 300 x 600 corresponding to the "color ink." Furthermore, the ejection volume ratio and ejection rate (%) values ​​corresponding to the "color ink" are appropriately configured according to each print mode, media type (M), and image data resolution.

[0069] Note that the ejection volume ratio and ejection volume rate shown in Figure 6 represent an example where the input data value for K in the CMYK color space is 100%, and also correspond to the case where the input data is 100% in Figure 7. Furthermore, when the input data value for K in the CMYK color space is other than 100%, the ejection volume ratio and ejection volume rate shown in Figure 6 change relative to the input data value, as shown in Figure 7.

[0070] Furthermore, modes 1 through 4 each correspond to "black ink." The "black nozzle row" consists of four rows, each capable of ejecting black K ink. The four rows of "black nozzle row" result in a resolution (dpi) of 600 x 600 corresponding to "black ink."

[0071] The first mode is set so that the proportion of discharged volume from each of the four rows of "black nozzles" is equal to one another. Furthermore, the first mode has the characteristic of making the discharged volume from all four rows of "black nozzles" equal to the maximum discharged volume that can be discharged from two rows of "black nozzles".

[0072] Specifically, in the first mode shown in Figure 6, the proportion of black ink ejected from each of the four rows of black nozzles is set to 25%, which is equal to each other. Furthermore, in the first mode, the ejection rate from all four rows of black nozzles is set to 100%. This 100% ejection rate is equal to the maximum ejection rate of 100% that can be ejected from the black nozzles when printing using only two rows of black nozzles.

[0073] In other words, the first mode maintains the same optical density as when printing with two rows of black nozzles, even when printing with four rows of black nozzles, and uniformly reduces the drive load across the entire black nozzle array.

[0074] In this embodiment, the discharge rate is the value representing the total discharge amount from each of the four rows of black nozzles, expressed as a percentage, when the maximum discharge amount of black ink discharged from all two rows of black nozzles is set to 100%. The proportion of discharge amount is a value that shows the breakdown of the discharge rate. For example, if the discharge rate is 100% and the proportion of discharge amount from each of the four rows of black nozzles is equal to each other, then the proportion of discharge amount from each of the four rows of black nozzles will be 25%.

[0075] In the first mode, the proportion of discharge volume discharged from each "black nozzle row" is not limited to 25%. For example, if the "black nozzle row" consists of 5 rows, the proportion of discharge volume discharged from each of the 5 rows may be set equally to 20%.

[0076] In the second mode, the proportion of discharge volume from each of the four rows of "black nozzles" is set to be equal to one another. Furthermore, the second mode has the characteristic that the discharge volume from all four rows of "black nozzles" is greater than the maximum discharge volume that can be discharged from two rows of "black nozzles".

[0077] Specifically, in the second mode shown in Figure 6, the proportion of black ink ejected from each of the four rows of black nozzles is set to 30%. Furthermore, in the second mode, the ejection rate from all four rows of black nozzles is set to 120%. This ejection rate of 120% is greater than the maximum ejection rate of 100% that can be ejected from the black nozzles when printing using only two rows of black nozzles.

[0078] In other words, the second mode uses four rows of "black nozzles" to achieve high optical density printing and uniformly reduces the drive load across the entire "black nozzle array." That is, even with low-pass printing, the second mode ensures that the optical density of the image printed with "black ink" is not insufficient, allowing for faster printing speeds and uniformly reducing the drive load across the entire "black nozzle array."

[0079] In the second mode, the proportion of discharge volume discharged from each "black nozzle row" is not limited to 30%. For example, if the "black nozzle row" consists of three rows, the proportion of discharge volume discharged from each of the three "black nozzle rows" may be set equally to 40%.

[0080] In the third mode, in the main scanning direction, the proportion of the discharge amount from the "black nozzle rows" located at both ends of the four "black nozzle rows" is set higher than the proportion of the discharge amount from the "black nozzle rows" located in between the ends. Furthermore, the third mode has the characteristic of being able to discharge more than the maximum discharge amount that can be discharged from two "black nozzle rows" when discharging from all four "black nozzle rows".

[0081] Specifically, in the third mode shown in Figure 6, the proportion of black ink ejected from the four rows of black nozzles is set to 45% for nozzle rows K1 and K4, which are located at both ends. Also, in the third mode shown in Figure 6, the proportion of black ink ejected from the four rows of black nozzles is set to 15% for nozzle rows K2 and K3, which are located between the ends. In other words, the proportion of black ink ejected is set higher for the black nozzle rows at both ends than for the black nozzle rows located between the ends. Furthermore, in the third mode, the ejection rate from all four rows of black nozzles is set to 120%. This ejection rate of 120% is higher than the maximum ejection rate of 100% that can be ejected from the black nozzle rows when printing using only two rows of black nozzles.

[0082] Generally, the relationship between the spacing of the "nozzle rows L" that eject ink and the print misalignment is such that the wider the spacing between the "nozzle rows L", the less the printer is affected by the airflow generated by each ejection, resulting in less print misalignment. In the third mode, the proportion of ink ejected from the "black nozzle rows" at both ends, which are spaced far apart and not adjacent to each other, is increased, so the print misalignment caused by the airflow generated by each ejection is particularly reduced. As a result, even when performing solid printing with high optical density of images printed using "black ink", uneven printing due to the effects of airflow can be reduced.

[0083] In other words, the third mode uses four rows of "black nozzles" to achieve high optical density printing and uniformly reduces the drive load on the entire "black nozzle row." Furthermore, the third mode can reduce printing unevenness caused by airflow even when performing solid color printing with high optical density.

[0084] In the third mode, the proportion of discharge volume discharged from each "black nozzle row" is not limited to 45% or 15%. For example, if the "black nozzle row" consists of three rows, the proportion of discharge volume discharged from the "black nozzle rows" arranged at both ends may be set to 45%, and the proportion of discharge volume discharged from the "black nozzle row" arranged in between the ends may be set to 30%. Also, since the "black nozzle rows" only need to be arranged at both ends and in between the ends, the number of "black nozzle rows" only needs to satisfy the relationship m≧3.

[0085] In the fourth mode, in the main scanning direction, the proportion of the discharge amount from the "black nozzle row" located between the two ends of the four "black nozzle rows" is set higher than the proportion of the discharge amount from the "black nozzle rows" located at the ends. Furthermore, the fourth mode has the characteristic of being able to discharge more from all four "black nozzle rows" than the maximum discharge amount that can be discharged from two "black nozzle rows".

[0086] Specifically, in the fourth mode shown in Figure 6, the proportion of black ink ejected from the four rows of black nozzles is set to 45% for nozzle rows K2 and K3, which are located between the two ends. Also, in the fourth mode shown in Figure 6, the proportion of black ink ejected from the four rows of black nozzles is set to 15% for nozzle rows K1 and K4, which are located at the two ends. In other words, the proportion of black ink ejected is set higher for the black nozzle rows located between the two ends than for the black nozzle rows located at the two ends. Furthermore, in the fourth mode, the ejection rate from all four rows of black nozzles is set to 120%. This ejection rate of 120% is higher than the maximum ejection rate of 100% that can be ejected from the black nozzle rows when printing using only two rows of black nozzles.

[0087] Generally, if the print head 16 is tilted unintentionally, the greater the distance between the nozzle rows L that eject ink, the greater the print misalignment due to the tilt of the print head 16, and the closer the distance between the nozzle rows L, the smaller the print misalignment. In the fourth mode, the proportion of the ejection amount of the black nozzle rows, which are arranged between both ends and where the distance between the nozzle rows L is not wide, is set high, thereby reducing print misalignment due to the tilt of the print head 16. As a result, even when printing with high optical density, print misalignment is reduced, enabling high-resolution printing of lines and other details.

[0088] In other words, the fourth mode uses four rows of "black nozzles" to achieve high optical density printing and uniformly reduces the drive load on the entire "black nozzle row." Furthermore, the fourth mode is capable of achieving high optical density in high-resolution printing such as ruled lines.

[0089] In the fourth mode, the proportion of discharge volume discharged from each "black nozzle row" is not limited to 45% or 15%. For example, if the "black nozzle row" consists of three rows, the proportion of discharge volume discharged from the "black nozzle row" located between the two ends may be 46%, and the proportion of discharge volume discharged from the "black nozzle rows" located at both ends may be set to 37% each. Also, since the "black nozzle rows" only need to be located at both ends and in between, the number of "black nozzle rows" only needs to satisfy the relationship m≧3.

[0090] The second through fourth modes also include the characteristic of enabling the ejection of "black ink" by the four rows of "black nozzles" at an amount greater than the maximum amount that can be ejected from two of the four rows of "black nozzles".

[0091] In this way, the external control unit 20 can change the ejection ratio and ejection rate for each column of the "black nozzle row" by selecting one of the multiple printing modes. In other words, the external control unit 20 can print an image on the medium M by changing the ejection ratio and ejection rate for each column of the "black nozzle row" using the conversion table 22a. Note that when printing on the medium M using all four columns of "black nozzle row", the ejection ratio for each "black nozzle row" is a value greater than 0%.

[0092] The multiple LUTs included in conversion table 22a are composed of multiple characteristics, as shown in Figure 7, corresponding to the first to fourth modes, etc. Figure 7 shows the relationship between the input data value (%) of K in the CMYK color space and the ejection rate of "black ink" in the image data of the input image. Figure 7 indicates that a lower input data value indicates a lower density in the K color space, and a higher input data value indicates a higher density in the K color space. Furthermore, a lower ejection rate indicates a smaller amount of "black ink" ejected, and a higher ejection rate indicates a larger amount of "black ink" ejected. In addition, Figure 7 illustrates the first characteristic C1, second characteristic C2, third characteristic C3, and fourth characteristic C4 among the multiple characteristics.

[0093] The amount of "black ink" dispensed is determined by the first characteristic C1, second characteristic C2, third characteristic C3, and fourth characteristic C4 included in the conversion table 22a. The amount of "black ink" dispensed, determined by the first characteristic C1, changes linearly from a minimum value of 0% to a first maximum value of 100% as the input data of K, which indicates the color of the input image, changes from a minimum value of 0% to a maximum value of 100%. The amount of "black ink" dispensed, determined by the second characteristic C2, changes linearly from a minimum value of 0% to a second maximum value of 120%, which exceeds the first maximum value of 100%, as the input data of K, which indicates the color of the input image, changes from a minimum value of 0% to a maximum value of 100%. The third characteristic C3 is an intermediate characteristic between the first characteristic C1 and the second characteristic C2. In other words, the amount of "black ink" dispensed, determined by the third characteristic C3, is greater than or equal to the amount of "black ink" dispensed, determined by the first characteristic C1, and less than or equal to the amount of "black ink" dispensed, determined by the second characteristic C2.

[0094] The fourth characteristic C4 is the characteristic when the second maximum value in the second characteristic C2 is 200%. The third characteristic C3 may be a characteristic in which the discharge rate changes within a range that is greater than or equal to the discharge rate determined by the first characteristic C1 and less than or equal to the discharge rate determined by the fourth characteristic C4.

[0095] Furthermore, the discharge amount determined by the third characteristic C3 is closer to the first characteristic C1 than to the second characteristic C2 in the first region where the input data K representing the color of the input image is lower than a predetermined value. Moreover, the discharge amount determined by the third characteristic C3 is closer to the second characteristic C2 than to the first characteristic C1 in the second region where the input data is higher than to the first region. In addition, the discharge amount determined by the third characteristic C3 may be closer to the fourth characteristic C4 than to the first characteristic C1 in the second region where the input data K representing the color of the input image is higher than to the first region.

[0096] As a result, in the third characteristic C3, the amount of "black ink" ejected in the first region can be suppressed, making it possible to print images with reduced graininess. In addition, in the second region, the third characteristic C3 makes it possible to print images with higher optical density using "black ink".

[0097] Thus, the first characteristic C1, in which the amount of "black ink" ejected changes linearly, is suitable for the first mode. Furthermore, the third characteristic C3, which suppresses the granularity of the image printed in the first region and increases the optical density of the image printed in the second region, is suitable for the second to fourth modes. Additionally, the second characteristic C2 and the fourth characteristic C4, in which the ejection amount changes linearly to a value exceeding the first maximum value of 100%, are suitable for other printing modes where it is particularly desirable to increase the optical density of the image printed using "black ink".

[0098] As described above, the printing method and printing system 100 of the first embodiment can be used to obtain the following effects. According to this printing method, when printing on medium M using all m rows of "black nozzle rows," the ratio of the ejection amount for each row of "black nozzle rows" can be changed using a conversion table 22a that associates input data indicating the color of the input image with the ejection amount of "black ink." This allows the optical density of the image printed with "black ink" to be increased according to the user's requirements. Furthermore, since the proportion of the drive load of the drive element that ejects "black ink" is appropriately distributed for each nozzle row, the drive load for the entire nozzle row can be reduced.

[0099] According to this printing method, the m rows of black nozzles can eject black ink at a rate greater than the maximum ejection rate from the n rows of black nozzles (which are equal to the number of color nozzle rows for each color). This allows for a higher optical density of images printed using black ink.

[0100] According to this printing method, the ejection amount determined by the conversion table 22a is greater than or equal to the ejection amount determined by the first characteristic C1, which changes linearly from the minimum value to a first maximum value as the input data changes from the minimum value to the maximum value. Furthermore, it is less than or equal to the ejection amount determined by the second characteristic C2, which changes linearly from the minimum value to a second maximum value that exceeds the first maximum value as the input data changes from the minimum value to the maximum value. This makes it possible to print images using "black ink" while changing the optical density within a predetermined range.

[0101] According to this printing method, the ejection amount determined by the conversion table 22a is closer to the first characteristic C1 than to the second characteristic C2 in the first region where the input data is lower than a predetermined value. Also, in the second region where the input data is higher than in the first region, the ejection amount is closer to the second characteristic C2 than to the first characteristic C1. As a result, the ejection amount of "black ink" can be suppressed in the first region, making it possible to print with reduced granularity in the printed image. Furthermore, in the second region, it is possible to print with a higher optical density of the image using "black ink". In other words, it is possible to perform printing that is suitable for both the first and second regions.

[0102] This printing method includes the characteristic that the proportion of the amount ejected from each of the m rows of black nozzles is equal to each other, and the total amount ejected from all of the m rows of black nozzles is equal to the maximum amount that can be ejected from the n rows of black nozzles, which is the same as the number of color nozzle rows for each color. As a result, the proportion of the drive load of the drive element that ejects black ink is appropriately distributed for each black nozzle row, so that the drive load for each black nozzle row is uniformly reduced. Furthermore, since the amount ejected from each black nozzle row can be reduced relatively, the printing misalignment caused by the airflow generated by each ejection can be uniformly reduced.

[0103] This printing method ensures that the proportion of ink ejected from each of the m rows of black nozzles is equal, and that the total amount ejected from all of the m rows of black nozzles is greater than the maximum amount that can be ejected from the n rows of black nozzles, which is equal to the number of color nozzle rows for each color. This uniformly reduces the drive load on the drive element that ejects black ink from each black nozzle row. In particular, it is possible to increase the overall ejection amount of the black nozzle row while relatively suppressing the ejection amount of each individual black nozzle row. This allows for printing with a higher optical density of the image printed using black ink, while uniformly reducing print misalignment caused by the airflow generated by each ejection.

[0104] This printing method includes a characteristic that makes the proportion of the ejected ink from the "black nozzle rows" arranged at both ends of the main scanning direction higher than the proportion of the ejected ink from the "black nozzle rows" arranged between the ends. Furthermore, it includes a characteristic that makes the ejected amount from all m rows of "black nozzle rows" greater than the maximum ejected amount that can be ejected from n rows of "black nozzle rows," which is the same as the number of "color nozzle rows" for each color. And, because the proportion of the ejected ink from the "black nozzle rows" at both ends, which are spaced far apart and not adjacent to each other, is increased, printing misalignment caused by the airflow generated by each ejection is particularly reduced. As a result, even when performing solid printing with high optical density of images printed using "black ink," printing unevenness due to the influence of airflow can be reduced.

[0105] This printing method includes a characteristic that makes the proportion of the ejection amount from the "black nozzle rows" arranged between the ends of the main scanning direction higher than the proportion of the ejection amount from the "black nozzle rows" arranged at both ends. Furthermore, it includes a characteristic that makes it possible to eject more than the maximum ejection amount that can be ejected from n rows of "black nozzle rows," which is the same as the number of "color nozzle rows" for each color. In this printing method, the proportion of the ejection amount from the "black nozzle rows" arranged between the ends, where the "nozzle rows L" are not spaced far apart, is set to be high. If the print head 16 is tilted unintentionally, the print ejected from the "black nozzle rows" where the "nozzle rows L" are not spaced far apart will have less print misalignment. As a result, even if the print head 16 is tilted unintentionally, the print misalignment due to the tilt of the print head 16 is reduced, so high-definition printing such as lines with high optical density can be performed.

[0106] According to this printing system 100, when printing on medium M using all m rows of "black nozzle rows", the external control unit 20 can change the ratio of the ejection amount for each row of "black nozzle rows" using a conversion table 22a that associates input data indicating the color of the input image with the ejection amount of "black ink". This makes it possible to increase the optical density of the image printed with "black ink" to suit the user's requirements. Furthermore, since the proportion of the drive load of the drive element that ejects "black ink" is appropriately distributed for each nozzle row, the drive load of the nozzle row as a whole can be reduced.

[0107] 2. Second Embodiment In the second embodiment, the printing device 1 has a print head 16h as shown in Figure 8, unlike the print head 16 shown in the first embodiment. Also, the printing device 1 has a conversion table 22b (not shown) as shown in Figure 8, unlike the conversion table 22a shown in the first embodiment. In Figures 8 and 9, components identical to those shown in previous figures are denoted by the same reference numerals and detailed descriptions are omitted.

[0108] 2-1. Printhead Configuration Referring to Figures 8 and 9, the configuration of the print head 16h in the second embodiment will be described. The print head 16h has heads H1 to H18. The configuration of heads H1 to H18, including head chips Hc1 to Hc4, is the same as in the first embodiment.

[0109] As shown in Figure 8, among the heads H1 to H18, heads H1, H3, H5, H7, H9, H11, H13, H15, and H17 are arranged in this order at equal intervals along the X-axis direction, which is the main scanning direction. Heads H2, H4, H6, H8, H10, H12, H14, H16, and H18 are located downstream of heads H1, H3, H5, H7, H9, H11, H13, H15, and H17. Also, heads H2, H4, H6, H8, H10, H12, H14, H16, and H18 are arranged in this order at equal intervals along the X-axis direction, which is the main scanning direction.

[0110] Since the print head 16h is configured as described above, the printing device 1 can print an image on the medium M by relatively moving the print head 16h, which includes a plurality of first nozzle rows La and a plurality of second nozzle rows Lb along the main scanning direction, and the medium M. The printing device 1 can print an image using single-color or multi-color inks, for example, with a resolution of 300 dpi or 600 dpi in the main scanning direction and a resolution of 600 dpi in the sub-scanning direction.

[0111] As shown in Table Ta3 of Figure 9, the first nozzle rows La located on the head tips Hc1 to Hc4 of head H1 and the head tips Hc1 to Hc4 of head H2 are capable of ejecting yellow Y ink.

[0112] Similarly, the second nozzle row Lb of heads H1 and H2 is capable of ejecting ink with an orange color (O).

[0113] Similarly, the first nozzle row La of heads H3 and H4 is capable of ejecting red ink (R).

[0114] Similarly, the second nozzle row Lb of heads H3 and H4 is capable of ejecting blue B ink.

[0115] Similarly, the first nozzle row La of heads H5 and H6 is capable of ejecting ink with the color gray G.

[0116] Similarly, the second nozzle row Lb of heads H5 and H6 is capable of ejecting magenta (M) ink.

[0117] Similarly, the first nozzle row La of heads H7 and H8 is capable of ejecting cyan ink.

[0118] Similarly, the second nozzle row Lb of heads H7 and H8 is capable of ejecting black ink (K). In the following description, the second nozzle row Lb of heads H7 and H8 will also be simply referred to as "nozzle row K1".

[0119] Similarly, the first nozzle row La of heads H9 and H10 is capable of ejecting black ink (K). In the following description, the first nozzle row La of heads H9 and H10 will also be simply referred to as "nozzle row K2".

[0120] Similarly, the second nozzle row Lb of heads H9 and H10 is capable of ejecting black ink (K). In the following description, the second nozzle row Lb of heads H9 and H10 will also be simply referred to as "nozzle row K3".

[0121] Similarly, the first nozzle row La of heads H11 and H12 is capable of ejecting black ink (K). In the following description, the first nozzle row La of heads H11 and H12 will also be simply referred to as "nozzle row K4".

[0122] Similarly, the second nozzle row Lb of heads H11 and H12 is capable of ejecting cyan (C) ink.

[0123] Similarly, the first nozzle row La of heads H13 and H14 is capable of ejecting magenta ink (M).

[0124] Similarly, the second nozzle row Lb of heads H13 and H14 is capable of ejecting ink with the color gray G.

[0125] Similarly, the first nozzle row La of heads H15 and H16 is capable of ejecting ink of color blue B.

[0126] Similarly, the second nozzle row Lb of heads H15 and H16 is capable of ejecting red ink (R).

[0127] Similarly, the first nozzle row La of heads H17 and H18 is capable of ejecting ink with an orange color (O).

[0128] Similarly, the second nozzle row Lb of heads H17 and H18 is capable of ejecting yellow Y ink.

[0129] 2-2. Configuration of the Conversion Table In the second embodiment, the conversion table 22b (not shown) has multiple modes of LUTs, similar to the first embodiment. In each LUT, the input data is associated with the ejection amount of each color ink described above.

[0130] As described above, the second embodiment can obtain the same effects as the first embodiment.

[0131] Although each embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to each embodiment and may be modified, substituted, or deleted as long as it does not depart from the gist of this invention. Furthermore, other embodiments described below may also be used.

[0132] In each embodiment, the external control unit 20 is assumed to have the driver 21, but the control unit 10 may also have the driver 21. Also, the external storage unit 22 is assumed to have the conversion tables 22a and 22b, but the storage unit 15 may also have the conversion tables 22a and 22b. Note that the control unit 10 and the external control unit 20 are just examples of "control units". Even in this case, the printing system 100 can obtain the same effects as in each embodiment.

[0133] In each embodiment, the driver 21 selects one print mode from among several print modes for the image data to be printed, as specified by the user. However, the driver 21 may have an algorithm that dynamically selects a print mode according to the characteristics of the input data of the input image. This eliminates the need for the user to select a print mode.

[0134] In each embodiment, the nozzle row direction is defined as being along the Y-axis, but this is not limited to this. For example, the nozzle row direction may be inclined with respect to the Y-axis. This also allows for the same effects as in each embodiment to be obtained.

[0135] In each embodiment, the correspondence between each "nozzle row L" and the ink color is illustrated in Tables Ta1 and Ta3, but the invention is not limited thereto. Without departing from the spirit of the invention, each "nozzle row L" may be associated with ink of another color or a liquid having a predetermined function.

[0136] In each embodiment, the "black nozzle row" is assumed to be positioned between the "color nozzle rows" in the main scanning direction, but this is not limited to this configuration. The "black nozzle row" may not be positioned between the "color nozzle rows". For example, in the direction from -X to +X, the nozzle rows may be arranged in the order of "first color nozzle row", "second color nozzle row", "black nozzle row" (nozzle row K1), "nozzle row K2", "nozzle row K3", and "nozzle row K4".

[0137] In each embodiment, the conversion tables 22a and 22b are tables that associate the values ​​of each CMYK input data with the ejection amounts of ink colors such as CMYK, but the invention is not limited to this. The conversion tables 22a and 22b may also be tables that associate the values ​​of each RGB input data with the ejection amounts of ink colors such as CMYK. The same effects as in each embodiment can be obtained with this as well.

[0138] In each embodiment, when printing in different passes among the passes through which the print head 16 is moved by the main scanning unit 18, different LUTs may be used for printing. This allows for a finer image formation effect to be obtained by printing in multiple passes. [Explanation of symbols]

[0139] 1...Printing device, 2...External device, 10...Control unit, 15...Storage unit, 16,16h...Print head, 16a...Carriage, 16b...Carriage shaft, 17...Sub-scanning unit, 17a...Transport motor, 17b...Transport roller, 18...Main scanning unit, 18a...Carriage motor, 18b...Belt, 19...Communication unit, 20...External control unit, 21...Driver, 21a...Ejection amount conversion processing unit, 21b...Halftone processing unit, 21c...Rasterization processing unit, 22...External storage unit, 22a,22b...Conversion table, 23...External communication unit, H1~H18...Head, Hc1~Hc4...Head chip, La...First nozzle row, Lb...Second nozzle row, L,K1~K4...Nozzle row, M...Media, N...Nozzle.

Claims

1. A print head having m rows of black nozzles (where m is a natural number of 2 or more) formed by arranging nozzles for ejecting black ink in the direction of the nozzle row, and n rows of color nozzles (where n is a natural number of 1 or more and m > n) for each color, formed by arranging nozzles for ejecting a predetermined color of color different from the color of the black ink in the direction of the nozzle row, A printing method for printing on a medium using a main scanning unit that moves the print head in a main scanning direction intersecting the nozzle row direction, A printing method characterized in that, when printing on the medium using all of the m rows of black nozzles, the ratio of the ejection amount can be changed for each row of the black nozzles using a conversion table that associates input data indicating the color of the input image with the ejection amount of the black ink.

2. Among the m rows of black nozzles, the black ink can be ejected by the m rows of black nozzles at a discharge amount greater than the maximum discharge amount that can be discharged from the n rows of black nozzles, which are equal to the number of color nozzles for each color. The printing method according to claim 1.

3. The discharge amount determined by the conversion table is greater than or equal to the discharge amount determined by the first characteristic, in which the discharge amount changes linearly from the minimum value to a first maximum value as the input data changes from the minimum value to the maximum value, and less than or equal to the discharge amount determined by the second characteristic, in which the discharge amount changes linearly from the minimum value to a second maximum value that exceeds the first maximum value as the input data changes from the minimum value to the maximum value. The printing method according to claim 1 or claim 2.

4. The discharge amount determined by the conversion table is closer to the first characteristic than the second characteristic in the first region where the input data is lower than a predetermined value, and closer to the second characteristic than the first characteristic in the second region where the input data is higher than the first region. The printing method according to claim 3.

5. The aforementioned conversion table includes tables corresponding to multiple print modes, The plurality of printing modes include a first mode characterized in that the proportion of the ejection amount ejected from each of the m black nozzle rows is equal to one another, and the total ejection amount ejected from all of the m black nozzle rows is equal to the maximum ejection amount that can be ejected from n black nozzle rows, which is the same as the number of color nozzle rows for each color. The printing method according to claim 1.

6. The aforementioned conversion table includes tables corresponding to multiple print modes, The plurality of printing modes include a second mode characterized in that the proportion of the ejection amount ejected from each of the m rows of black nozzles is equal to one another, and the total ejection amount ejected from all of the m rows of black nozzles is greater than the maximum ejection amount that can be ejected from n rows of black nozzles, which is equal to the number of color nozzle rows for each color. The printing method according to claim 2.

7. m is a natural number greater than or equal to 3, The aforementioned conversion table includes tables corresponding to multiple print modes, The plurality of printing modes include a third mode characterized in that, in the main scanning direction, the proportion of the ejection amount ejected from the black nozzle rows arranged at both ends of the m rows of black nozzle rows is higher than the proportion of the ejection amount ejected from the black nozzle rows arranged between the ends, and the total ejection amount ejected from all of the m rows of black nozzle rows is greater than the maximum ejection amount that can be ejected from n rows of black nozzle rows, which is equal to the number of color nozzle rows for each color. The printing method according to claim 2.

8. m is a natural number greater than or equal to 3, The aforementioned conversion table includes tables corresponding to multiple print modes, The plurality of printing modes include a fourth mode characterized in that, in the main scanning direction, the proportion of the ejection amount ejected from the black nozzle rows arranged between the ends of the m rows of black nozzle rows is higher than the proportion of the ejection amount ejected from the black nozzle rows arranged at both ends, and the total ejection amount ejected from all of the m rows of black nozzle rows is greater than the maximum ejection amount that can be ejected from n rows of black nozzle rows, which is equal to the number of color nozzle rows for each color. The printing method according to claim 2.

9. A print head having m rows of black nozzles (where m is a natural number of 2 or more) formed by arranging nozzles for ejecting black ink in the direction of the nozzle row, and n rows of color nozzles (where n is a natural number of 1 or more and m > n) for each color, formed by arranging nozzles for ejecting a predetermined color of color different from the color of the black ink in the direction of the nozzle row, A main scanning unit moves the print head in a main scanning direction intersecting the nozzle row direction, A storage unit that stores a conversion table which associates input data indicating the color of the input image with the amount of black ink ejected. The system comprises a control unit that determines the discharge amount using the conversion table, The printing system is characterized in that the control unit can change the ratio of the discharge amount for each row of the black nozzles using the conversion table when printing on a medium using all of the m rows of black nozzles.

Images