Printing apparatus and printing method

Abstract

To suppress generation of streaks and color unevenness in a conveyance direction in a medium after printing.SOLUTION: A printer 1 includes a printing head 10 and a control part 30. The printing head 10 has a nozzle area NA1 in which a distance between a nozzle array 23Y and a nozzle array 23C in a relative moving direction is defined as a distance D1, and a nozzle area NA2 in which a distance between a nozzle array 23Y and a nozzle array 23C in the relative moving direction is defined as a distance D2 longer than the distance D1. When a ratio of the size of a plurality of ink droplets discharged from nozzles of the nozzle area NA1 is defined as a first ratio, and a ratio of the size of a plurality of ink droplets discharged from nozzles of the nozzle area NA2 is defined as a second ratio, the control part 30 performs first printing in which a ratio of ink droplets having a size other than a maximum size in the second ratio is smaller than a ratio of ink droplets other than a maximum size in the first ratio.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a printing apparatus and a printing method.

Background Art

[0002] An inkjet printer, which is one type of printing apparatus, forms an image on a medium such as paper by discharging ink droplets from a plurality of nozzles provided in a print head onto the medium. Specifically, the print head includes a plurality of nozzles arranged in the nozzle row direction, and forms an image on the medium by discharging ink droplets from the nozzles of the print head toward the medium while conveying the medium in a relative movement direction different from the nozzle row direction.

[0003] Patent Document 1 discloses a technique related to a line head type inkjet printer in which nozzles are arranged over the entire width direction intersecting the conveyance direction of the medium. Hereinafter, the line head type inkjet printer is also referred to as a line printer.

[0004] In the line printer disclosed in Patent Document 1, nozzle rows of cyan (C), magenta (M), yellow (Y), and black (K) are arranged in a 2-row and 2-column pattern on one head chip. Specifically, the C nozzle row and the Y nozzle row are arranged side by side in the nozzle arrangement direction, and the M nozzle row and the K nozzle row are arranged side by side in the nozzle arrangement direction. Then, a plurality of such head chips are arranged in the width direction of the medium to constitute a print head.

[0005] Also, when a plurality of head chips are arranged in the width direction of the medium in this way, a region where no nozzles exist is formed between each head chip. Therefore, while arranging a plurality of head chips in the width direction of the medium, a plurality of head chips are also arranged in the conveyance direction, and the print head is configured such that the head chips overlap in the conveyance direction.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-40215 [Overview of the project] [Problems that the invention aims to solve]

[0007] However, if the print head is configured so that the head tips overlap in the transport direction, streaks or uneven coloring may occur along the transport direction when secondary colors are formed by ink droplets ejected from the two nozzle rows.

[0008] In other words, when forming secondary colors, ink droplets of different colors are ejected from different nozzle rows on the same line along the transport direction. In this case, there are combinations where the distance between nozzle rows is constant and combinations where the distance between nozzle rows is different on the same line along the transport direction.

[0009] For example, if the distance between nozzle rows is long in the transport direction, there is time for the first ink droplet to dry after impact, so subsequent ink droplets will exhibit good color development. On the other hand, if the distance between nozzle rows is short in the transport direction, the next ink droplet will hit before the first one has dried, causing the droplets to interfere with each other and bleed, resulting in poor color development. Thus, there is a difference in color development depending on the distance between nozzle rows in the transport direction, and this difference in color development can be seen as streaks or uneven coloring.

[0010] In the technology disclosed in Patent Document 1, when the combination of head rows used to form secondary colors results in different distances between nozzle rows, the first and subsequent ink droplets are prevented from interfering with each other on the medium. In other words, by reducing the amount of overlap between ink droplets on the medium, differences in color development are suppressed. However, this configuration, which suppresses color unevenness by preventing interference between ink droplets, has the problem of not being able to cope when the printing duty cycle increases, that is, when the amount of ink ejected increases. For this reason, other technologies are needed to suppress streaks and color unevenness. [Means for solving the problem]

[0011] A printing apparatus according to one aspect of the present invention comprises a print head having a plurality of nozzles capable of ejecting ink droplets onto a medium, and a plurality of nozzle rows in which the nozzles are arranged in the direction of the nozzle row, and a control unit for controlling the ejection of the ink droplets from the nozzles, wherein the print head and the medium move relative to each other in a relative movement direction different from the direction of the nozzle row, the print head has a first nozzle row and a second nozzle row, each ejecting different ink droplets, the number of the first nozzle row and the second nozzle row is 2 or more, and the plurality of nozzle rows that eject ink droplets on the same line along the relative movement direction have a first distance between the first nozzle row and the second nozzle row in the relative movement direction. The device has a first nozzle region and a second nozzle region where the distance between the first nozzle row and the second nozzle row in the relative movement direction is a second distance which is longer than the first distance, and the nozzles are capable of forming dots of multiple sizes on the medium by ejecting ink droplets of multiple sizes, and when the ratio of the sizes of the multiple ink droplets ejected from the nozzles in the first nozzle region is defined as the first ratio and the ratio of the sizes of the multiple ink droplets ejected from the nozzles in the second nozzle region is defined as the second ratio, the control unit is characterized in that it performs a first print in which the proportion of ink droplets other than the maximum size in the second ratio is smaller than the proportion of ink droplets other than the maximum size in the first ratio.

[0012] A printing method according to one aspect of the present invention is a printing method using a printing apparatus that comprises a print head having a plurality of nozzles capable of ejecting ink droplets onto a medium, and a plurality of nozzle rows in which the nozzles are arranged in the direction of the nozzle row, wherein the print head and the medium move relative to each other in a relative movement direction different from the direction of the nozzle row, wherein the print head has a first nozzle row and a second nozzle row, each ejecting different ink droplets, the number of the first nozzle row and the second nozzle row is 2 or more, and the plurality of nozzle rows that eject ink droplets on the same line along the relative movement direction are a first nozzle region where the distance between the first nozzle row and the second nozzle row in the relative movement direction is a first distance The invention provides a first printing process characterized by having a second nozzle region in which the distance between the first nozzle row and the second nozzle row in the relative movement direction is a second distance which is longer than the first distance, and the nozzles are capable of forming dots of multiple sizes on the medium by ejecting ink droplets of multiple sizes, wherein the ratio of the sizes of the multiple ink droplets ejected from the nozzles in the first nozzle region is defined as the first ratio, and the ratio of the sizes of the multiple ink droplets ejected from the nozzles in the second nozzle region is defined as the second ratio, and the proportion of ink droplets other than the largest size in the second ratio is smaller than the proportion of ink droplets other than the largest size in the first ratio. [Brief explanation of the drawing]

[0013] [Figure 1] This is a block diagram showing an example of a printing apparatus according to an embodiment. [Figure 2] This is a schematic diagram showing an example of a print head included in a printing apparatus according to an embodiment. [Figure 3] This is a schematic diagram showing an example of a head chip found in a print head. [Figure 4] This diagram illustrates the operation when printing a secondary color in a nozzle region NA1 where the distance between nozzle rows is distance D1. [Figure 5] This diagram illustrates the operation when printing a secondary color in a nozzle region NA2 where the distance between nozzle rows is distance D2. [Figure 6] This table shows the upper limits on the utilization rate of each dot size according to the nozzle row distance and print mode. [Figure 7] This table shows the relationship between input image color, ink color combination, and nozzle row distance. [Figure 8] This graph shows the amount of dots inserted and the dot generation rate for each size. [Figure 9] This flowchart shows an example of the operation of a printing apparatus according to an embodiment. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described below with reference to the drawings. Figure 1 is a block diagram showing an example of a printing apparatus 1 according to an embodiment. Figure 2 is a schematic diagram showing an example of a print head 10 included in the printing apparatus 1 according to an embodiment. Figure 3 is a schematic diagram showing an example of a head chip 21 included in the print head 10. Figures 2 and 3 are schematic diagrams of the print head 10 and head chip 21 viewed from the rear, and ink droplets are ejected in the positive Z-axis direction.

[0015] The printing apparatus 1 according to this embodiment is typically an inkjet printer, and this specification shows an example configuration of a line printer. The invention according to this embodiment can be broadly applied to devices using inkjet technology, such as photocopiers, facsimile machines, and multifunction devices with these functions.

[0016] As shown in Figure 1, the printing apparatus 1 according to this embodiment comprises a print head 10, a control unit 30, and a transport mechanism 40. The printing apparatus 1 according to this embodiment ejects ink droplets 60 from nozzles 22 provided on the print head 10 onto a medium 50 to form an image on the medium 50. The medium 50 is transported by the transport mechanism 40. Ink is supplied to each nozzle 22 of the print head 10 from an ink supply unit 13.

[0017] Specifically, as shown in FIG. 2, the print head 10 includes a plurality of head chips 21a to 21f. The plurality of head chips 21a to 21f are arranged side by side in the X-axis direction, that is, the width direction of the medium 50. Each of the head chips 21a to 21f includes a plurality of nozzle rows 23C, 23M, 23Y, and 23K arranged in the nozzle row direction ND. A plurality of nozzles 22C, 22M, 22Y, and 22K (see FIG. 3) are formed in each of the nozzle rows 23C, 23M, 23Y, and 23K, respectively. The plurality of head chips 21a to 21f are provided so as to extend in the nozzle row direction ND. In other words, the plurality of head chips 21a to 21f are provided so as to be inclined with respect to the X-axis direction.

[0018] In the printing apparatus 1 according to the present embodiment, an image is formed on the medium 50 by the relative movement of the print head 10 and the medium 50 in a relative movement direction (Y-axis direction) different from the nozzle row direction ND. That is, while the medium 50 is conveyed in the relative movement direction, ink droplets 60 are ejected from the nozzle rows 23C, 23M, 23Y, and 23K of the print head 10 toward the medium 50, thereby forming an image on the medium. In this specification, the "relative movement direction" is synonymous with the "conveying direction". Also, in FIG. 2, only a part of the medium 50 is illustrated.

[0019] As shown in FIG. 3, the head chip 21 includes four nozzle rows 23C, 23M, 23Y, and 23K. The four nozzle rows 23C, 23M, 23Y, and 23K are arranged in two rows and two columns. Specifically, the nozzle row 23C and the nozzle row 23Y are arranged side by side in the nozzle row direction ND, and the nozzle row 23M and the nozzle row 23K are arranged side by side in the nozzle row direction ND. In this specification, the head chips 21a to 21f are also collectively referred to as the head chip 21. The same applies to other components.

[0020] Nozzle row 23C has a plurality of nozzles 22C arranged in the nozzle row direction ND. Each of the plurality of nozzles 22C is configured to independently eject cyan (C) ink droplets. Nozzle row 23M has a plurality of nozzles 22M arranged in the nozzle row direction ND. Each of the plurality of nozzles 22M is configured to independently eject magenta (M) ink droplets. Nozzle row 23Y has a plurality of nozzles 22Y arranged in the nozzle row direction ND. Each of the plurality of nozzles 22Y is configured to independently eject yellow (Y) ink droplets. Nozzle row 23K has a plurality of nozzles 22K arranged in the nozzle row direction ND. Each of the plurality of nozzles 22K is configured to independently eject black (K) ink droplets. Each of the nozzles 22C, 22M, 22Y, and 22K is supplied with ink of the respective color from the ink supply unit 13 (see Figure 1).

[0021] Furthermore, as shown in Figure 3, the head tip 21 has gaps 25 between nozzle row 23Y and nozzle row 23C, and between nozzle row 23K and nozzle row 23M. The gaps 25 extend a predetermined distance in the X-axis direction and are regions where nozzle row 23 is not formed.

[0022] In Figure 3, a configuration is shown in which one head chip 21 has four nozzle rows 23C, 23M, 23Y, and 23K. However, in this embodiment, one head chip may have five or more nozzle rows. For example, the head chip 21 may further have nozzle rows that eject light cyan (Lc), light magenta (Lm), dark yellow (Dy), light black (Lk), red (R), orange (Or), green (G), and uncolored ink for improving image quality. Also, the number of nozzles in one nozzle row 23 can be any number.

[0023] In this embodiment, the print head 10 shown in Figure 2 can be constructed by arranging multiple head chips 21 shown in Figure 3 in the X-axis direction. Furthermore, by providing multiple print heads 10 each equipped with multiple head chips 21a to 21f in the X-axis direction, a line head can be constructed in which nozzle rows are arranged across the entire width direction of the medium 50. In the configuration example shown in Figure 2, a configuration example is shown in which six head chips 21a to 21f are provided on one print head 10, but the number of head chips 21 provided on one print head 10 may be less than six or more than six.

[0024] Next, the system configuration of the printing apparatus 1 according to this embodiment will be described using Figure 1. As shown in Figure 1, the printing apparatus 1 according to this embodiment comprises a print head 10, a control unit 30, and a transport mechanism 40. The print head 10 comprises a drive circuit 11, a drive element 12, and a nozzle 22. The control unit 30 comprises a resolution conversion unit 31, a color conversion unit 32, a halftone processing unit 33, an ejection control unit 34, a print switching unit 35, a transport control unit 36, and an environmental information acquisition unit 37. The control unit 30 can be configured using, for example, a SoC (System on a Chip).

[0025] The resolution conversion unit 31 in the control unit 30 generates input color data by converting the resolution of the supplied image data to the print resolution for printing on the medium 50. For example, the print resolution may be 720 x 720 dpi or 360 x 360 dpi. The supplied image data is represented, for example, as RGB data, where each pixel has an integer value of 256 gradations of RGB. If the acquired image data is not RGB data, the image data may be converted to RGB data.

[0026] The color conversion unit 32 performs color conversion processing on the input color data generated by the resolution conversion unit 31 to generate output color data, which is CMYK data. Specifically, the color conversion unit 32 converts the RGB data, which is set as the print resolution, into CMYK data, which has integer values ​​of 256 gradations for each pixel.

[0027] The halftone processing unit 33 performs halftone processing based on the output color data, which is color-converted image data. The halftone processing unit 33 reduces the number of gradations in the gradation values ​​(ink amount data) of each pixel constituting the output color data by performing a predetermined halftone processing method, such as dithering, error diffusion, or density pattern method, and generates print data.

[0028] The ejection control unit 34 generates a control signal to control the drive element 12 based on the print data generated by the halftone processing unit 33. For example, the ejection control unit 34 generates a drive signal as a control signal that corresponds to the voltage signal applied to the drive element 12 of the print head 10, based on the print data. The control signal generated by the ejection control unit 34 is supplied to the drive circuit 11 of the print head 10.

[0029] The print switching unit 35 switches the printing of the printing device 1 to either the first print or the second print, which will be described later. In this embodiment, the ejection control unit 34 may generate a control signal for controlling the nozzle 22 in response to the print signal supplied from the print switching unit 35.

[0030] The transport control unit 36 ​​controls the transport mechanism 40 for transporting the medium 50 in the relative movement direction. For example, the transport mechanism 40 can be constructed using rollers or the like.

[0031] Furthermore, in this embodiment, the control unit 30 may also include an environmental information acquisition unit 37. The environmental information acquisition unit 37 acquires environmental information of the location where the printing device 1 is installed. For example, the environmental information may include the temperature and humidity near the print head 10.

[0032] The drive circuit 11 of the print head 10 applies a voltage signal to the drive element 12 based on a control signal supplied from the ejection control unit 34. The drive element 12 can be a piezoelectric element that applies pressure to the ink in the pressure chamber communicating with the nozzle 22, or a bubble generating element that generates bubbles in the pressure chamber using heat to eject ink droplets 60 from the nozzle 22. Ink is supplied to the pressure chamber of the print head 10 from the ink supply unit 13.

[0033] The ink in the pressure chamber is ejected as ink droplets 60 from the nozzle 22 toward the medium 50 by the drive element 12, forming dots of ink droplets 60 on the medium 50. In this way, the control unit 30 can form an image on the medium 50 by transporting the medium 50 in the relative movement direction and ejecting ink droplets 60 toward the medium 50 from the nozzle 22 of the print head 10.

[0034] In the printing apparatus 1 according to this embodiment, as shown in Figure 2, a print head 10 is constructed by arranging a plurality of head chips 21a to 21f in line along the X-axis. At this time, each head chip 21a to 21f is arranged to overlap each other in the relative movement direction (Y-axis direction). In addition, each head chip 21a to 21f has a gap 25 between nozzle row 23Y and nozzle row 23C, and between nozzle row 23K and nozzle row 23M.

[0035] Therefore, along the same line in the relative movement direction (Y-axis direction), there exist combinations in which each nozzle row has a different distance between them. For example, the combination of yellow (Y) and cyan (C) results in different distances between nozzle rows. That is, in the case of the yellow (Y) and cyan (C) combination, there exists a nozzle region NA1 where the distance between the yellow (Y) nozzle row 23Y (first nozzle row) and the cyan (C) nozzle row 23C (second nozzle row) in the relative movement direction is distance D1, and a nozzle region NA2 where the distance between the yellow (Y) nozzle row 23Y and the cyan (C) nozzle row 23C in the relative movement direction is distance D2. In this case, the distance between nozzle rows D2 (second distance) in nozzle region NA2 (second nozzle region) is longer than the distance between nozzle rows D1 (first distance) in nozzle region NA1 (first nozzle region).

[0036] Therefore, when printing green (G), a secondary color of yellow (Y) and cyan (C), onto the medium 50, two areas are formed on the medium 50: area M1 printed by nozzle area NA1 with a nozzle row distance of distance D1, and area M2 printed by nozzle area NA2 with a nozzle row distance of distance D2. Since the nozzle row distances D1 and D2 are different in nozzle area NA1 and nozzle area NA2, the time between the first ink droplet 60 landing on the medium 50 and the next ink droplet 60 landing on the medium 50 is different.

[0037] Figure 4 illustrates the operation when printing a secondary color in a nozzle region NA1 where the distance between nozzle rows is distance D1. As shown in the upper part of Figure 4, when printing the secondary color green (G) onto the medium 50, first a yellow ink droplet 60Y is ejected from nozzle 22Y, forming a dot of ink droplet 60Y on the medium 50. Then, after the medium 50 moves a distance D1 in the relative movement direction (Y-axis direction), as shown in the lower part of Figure 4, a cyan ink droplet 60C is ejected from nozzle 22C, forming a dot of cyan ink droplet 60C on the medium 50. At this time, the time between the first ink droplet 60Y landing on the medium 50 and the next ink droplet 60C landing on the medium 50 corresponds to the time between nozzle rows D1.

[0038] Figure 5 illustrates the operation when printing a secondary color in a nozzle region NA2 where the distance between nozzle rows is distance D2. As shown in the upper part of Figure 5, when printing the secondary color green (G) onto the medium 50, first a yellow ink droplet 60Y is ejected from nozzle 22Y, forming a dot of ink droplet 60Y on the medium 50. Then, after the medium 50 moves a distance D2 in the relative movement direction (Y-axis direction), as shown in the lower part of Figure 5, a cyan ink droplet 60C is ejected from nozzle 22C, forming a dot of cyan ink droplet 60C on the medium 50. At this time, the time between the first ink droplet 60Y landing on the medium 50 and the next ink droplet 60C landing on the medium 50 corresponds to the distance D2 between nozzle rows.

[0039] Thus, since the nozzle row distances D1 and D2 are different in nozzle region NA1 and nozzle region NA2, the time between the first ink droplet 60Y landing on the medium 50 and the next ink droplet 60C landing on the medium 50 is different. In other words, since the nozzle row distance D2 is longer than the nozzle row distance D1, the time between the first ink droplet 60Y landing on the medium 50 and the next ink droplet 60C landing on the medium 50 is longer in nozzle region NA2 than in nozzle region NA1. For this reason, conventionally, streaks and color unevenness along the relative movement direction sometimes occurred on the medium 50.

[0040] In other words, in nozzle region NA2, the distance D2 between nozzle rows is long, so after the first ink droplet 60Y lands, there is time for it to dry, and even when the next ink droplet 60C lands, it exhibits good color development. On the other hand, in nozzle region NA1, the distance D1 between nozzle rows is short, so after the first ink droplet lands, the next ink droplet lands before the first ink droplet has dried, causing the ink droplets to interfere with each other and bleed, thus suppressing color development. Thus, there is a difference in color development depending on the distances D1 and D2 between nozzle rows in the relative direction of movement, and this difference in color development could be seen as streaks or uneven color. In short, because the color development is good in nozzle region NA1, the color appears darker than in nozzle region NA2, and dark streaks may appear.

[0041] To solve these problems, the printing apparatus 1 according to this embodiment has the following configuration. In other words, in the printing apparatus 1 according to this embodiment, each nozzle 22 is configured to eject ink droplets of multiple sizes. In other words, the printing apparatus 1 is configured to form dots of multiple sizes on the medium 50.

[0042] Furthermore, the ratio of the sizes of multiple ink droplets ejected from the nozzle 22 in nozzle region NA1 is defined as the first ratio, and the ratio of the sizes of multiple ink droplets ejected from the nozzle 22 in nozzle region NA2 is defined as the second ratio. In this embodiment, the control unit 30 is configured to perform printing (first printing) such that the proportion of ink droplets other than the largest size in the second ratio is smaller than the proportion of ink droplets other than the largest size in the first ratio. In other words, in the second ratio, the utilization rate of the smallest ink droplet among the multiple sizes of ink droplets is reduced compared to the first ratio.

[0043] For example, if there are two types of ink droplets ejected from nozzle 22—large and small—then "the proportion of ink droplets other than the largest size in the first ratio" means "the proportion of small ink droplets." Similarly, if there are three types of ink droplets ejected from nozzle 22—large, medium, and small—then "the proportion of ink droplets other than the largest size in the first ratio" means "the proportion of small and medium ink droplets." The same applies to the second ratio.

[0044] Figure 6 is a table showing the nozzle row distance and the upper limits of the usage rate of each dot size according to the first or second printing. For example, if each nozzle 22 is capable of ejecting two types of ink droplets, small and large, then small and large dots will be formed on the medium 50. In this specification, the ink ejected from the nozzle 22 is referred to as "small ink droplets" and "large ink droplets," and the dots formed by these ink droplets on the medium 50 are referred to as "small dots" and "large dots," but these terms have substantially the same meaning.

[0045] As shown in the first print in Figure 6, the ratio of the sizes of multiple ink droplets ejected from nozzle 22 at a nozzle row distance D1, i.e., from nozzle 22 in nozzle region NA1 (first ratio), is set to 50% small dots and 100% large dots. Here, "50% small dots" represents the maximum usage rate of small dots, and "100% large dots" represents the maximum usage rate of large dots. In this case, the "percentage of ink droplets of sizes other than the maximum size in the first ratio" is equal to "the maximum usage rate of small ink droplets = 50%".

[0046] Similarly, the ratio of the sizes of multiple ink droplets ejected from nozzle 22 at a nozzle row distance D2, i.e., nozzle 22 in nozzle region NA2 (second ratio), is set to small dots = 20% and large dots = 100%. In this case, the "percentage of ink droplets other than the largest size in the second ratio" is "the maximum usage rate of small ink droplets = 20%".

[0047] Thus, in this embodiment, the nozzle region NA2, where the distance between nozzle rows is distance D2, is set to have a low utilization rate for small dots. In other words, in the nozzle region NA2, where the distance between nozzle rows D2 is long, the maximum value of the utilization rate for small dots is set lower compared to the nozzle region NA1, where the distance between nozzle rows D1 is short. To put it another way, in the second ratio, which is the ratio of ink droplet sizes in the nozzle region NA2, the utilization rate of the smallest ink droplet among multiple sizes of ink droplets is set to be lower compared to the first ratio, which is the ratio of ink droplet sizes in the nozzle region NA1.

[0048] Here, because small ink droplets are small, after landing on the medium 50, they do not penetrate deeply into the medium 50, and they do not bleed together easily. As a result, they fix and dry near the surface of the medium 50, exhibiting good color development. On the other hand, because large ink droplets are large, after landing on the medium 50, they penetrate deeply into the medium 50, and they may bleed together easily. Therefore, the color development of large ink droplets that is visible from the surface tends to be suppressed. Thus, since small ink droplets produce better color development than large ink droplets, reducing the usage rate of small ink droplets can suppress the color development.

[0049] In this embodiment, the color development in nozzle region NA2, which has good color development, is suppressed by reducing the usage rate of small ink droplets in nozzle region NA2, that is, in nozzle region NA2 where the distance between nozzle rows D2 is long. As a result, the difference in color development between the area M1 printed by nozzle region NA1 and the area M2 printed by nozzle region NA2 on the medium 50 can be reduced, and the formation of streaks and color unevenness on the medium 50 can be suppressed.

[0050] Furthermore, the technology disclosed in Patent Document 1 suppressed differences in color development by reducing the amount of overlap between ink droplets on the medium. However, a configuration that suppresses color unevenness by preventing interference between ink droplets had the problem of not being able to cope when the printing duty cycle increased.

[0051] In contrast, in this embodiment, the usage rate of small ink droplets is reduced in the nozzle region NA2 where color development is good, and color development in the nozzle region NA2 is suppressed, thereby preventing the formation of streaks and color unevenness on the medium 50. Therefore, even when the printing duty cycle increases, the formation of streaks and color unevenness on the medium 50 can be effectively suppressed.

[0052] The first printing described above, that is, printing in which the proportion of ink droplets other than the maximum size in the second ratio is smaller than the proportion of ink droplets other than the maximum size in the first ratio, may be performed when printing on a medium 50 in which ink droplets 60 are prone to bleeding. A medium 50 in which ink droplets 60 are prone to bleeding is, for example, plain paper. In addition, photographic paper, glossy paper, matte paper, etc. may also be used as the medium 50, but if bleeding may occur on these media 50 depending on the usage conditions, the first printing described above may be performed.

[0053] Furthermore, in this embodiment, there are combinations in which each nozzle row 23 has the same distance between nozzle rows on the same line along the relative movement direction (Y-axis direction). Specifically, as shown in Figure 2, on the same line along the relative movement direction, the distance between the magenta nozzle row 23M (third nozzle row) and the cyan nozzle row 23C (second nozzle row) is constant at distance D3. When the magenta nozzle row 23M and the cyan nozzle row 23C are used, the secondary color blue (B) can be printed. In this case, the area printed by nozzle row 23M and nozzle row 23C may have a higher upper limit set for the ejection ratio of ink droplets of sizes other than the maximum size compared to the area printed by the nozzle area NA2 described above.

[0054] Specifically, as shown in the first print in Figure 6, when the nozzle row distance is distance D3, the settings may be set to small dots = 50% and large dots = 100%. In this case, the nozzle row distance D3 results in small dots = 50%, and the nozzle row distance D2 results in small dots = 20%, so the upper limit setting for the ejection ratio of ink droplets of sizes other than the maximum size is set higher at the nozzle row distance D3.

[0055] The printing apparatus 1 according to this embodiment may be configured to perform printing (second printing) in which there is no difference between a first ratio, which is the ratio of the sizes of multiple ink droplets ejected from the nozzle 22 in nozzle region NA1, and a second ratio, which is the ratio of the sizes of multiple ink droplets ejected from the nozzle 22 in nozzle region NA2. When performing second printing, for example, as shown in the second printing in Figure 6, the settings may be set such that small dots = 50% and large dots = 100% for all nozzle row distances D1 to D3. Note that the setting values ​​for small dots and large dots in the first and second printing shown in Figure 6 are just examples, and other setting values ​​may be used in this embodiment.

[0056] Figure 7 is a table showing the relationship between input image color, ink color combination, and nozzle row distance. Figure 7 summarizes the relationship between ink color combinations and nozzle row distance when printing the secondary colors red (R), green (G), and blue (B) using a print head 10 with the configuration shown in Figure 2.

[0057] When the input image color is red (R), the ink color combination is yellow (Y) and magenta (M), and different combinations of nozzle row distances D1 and D2 exist. When the input image color is green (G), the ink color combination is yellow (Y) and cyan (C), and different combinations of nozzle row distances D1 and D2 exist. When the input image color is blue (B), the ink color combination is yellow (Y) and cyan (C). In this case, the nozzle row distance D3 is constant. Note that if the arrangement of the nozzle rows 23 for each color of the print head 10 shown in Figure 2 is different, the nozzle row distance will differ according to the arrangement of the nozzle rows 23 for each color.

[0058] The printing device 1 according to this embodiment may include an interface that allows the user to specify whether to perform a first print or a second print. In this case, the printing device 1 can perform either the first print or the second print by the user setting either the first print or the second print using the interface. The interface may be, for example, a settings screen displayed on a PC screen or a settings screen displayed on a display unit (not shown) provided by the printing device 1.

[0059] Furthermore, the control unit 30 may decide whether to perform the first print or the second print depending on the type of medium 50 used for printing. For example, if the user specifies a medium 50 in which ink easily bleeds using the interface, the control unit 30 may control the print head 10 to perform the first print. Also, since a difference in color between area M1 and area M2 is clearly visible in a medium 50 in which ink easily penetrates, the control unit 30 may perform the first print when such a medium 50 is used.

[0060] Furthermore, the control unit 30 may decide whether to perform the first print or the second print depending on the specified print mode. For example, if the user sets a high-quality print mode, the control unit 30 may control the print head 10 to perform the first print. Alternatively, if the user specifies a print mode that prioritizes print speed, the control unit 30 may control the print head 10 to perform the second print.

[0061] This switching between the first and second printing is performed by the print switching unit 35 provided in the control unit 30 shown in Figure 1. For example, the print switching unit 35 supplies a print signal to the ejection control unit 34 for switching between the first and second printing. The ejection control unit 34 generates a control signal for controlling the nozzle 22 based on the print signal supplied from the print switching unit 35 and the print data supplied from the halftone processing unit 33.

[0062] Furthermore, as shown in Figure 1, the control unit 30 in this embodiment may also include an environmental information acquisition unit 37. In this case, the control unit 30 may perform a first print or a second print according to the environmental information acquired by the environmental information acquisition unit 37. The environmental information is the temperature and humidity near the print head 10 of the printing device 1. For example, the environmental information acquisition unit 37 may be configured to acquire at least one of temperature and humidity as environmental information. In this case, the control unit 30 may perform a first print or a second print according to at least one of the temperature and humidity acquired by the environmental information acquisition unit 37.

[0063] For example, ink is more likely to bleed when humidity is high and temperature is low because it dries more slowly. Therefore, the control unit 30 may perform the first print when the humidity acquired by the environmental information acquisition unit 37 is higher than a predetermined humidity. The control unit 30 may also perform the first print when the temperature acquired by the environmental information acquisition unit 37 is lower than a predetermined temperature. The control unit 30 may also perform the first print when the humidity acquired by the environmental information acquisition unit 37 is higher than a predetermined humidity and the temperature acquired by the environmental information acquisition unit 37 is lower than a predetermined temperature.

[0064] Figure 8 is a graph showing the ink density and the dot generation rate for each size. Figure 8 shows the case where there are three types of ink droplets 60 ejected from the nozzle 22: large, medium, and small. In the graph in Figure 8, the horizontal axis represents the ink density per unit area on the printing medium, and the vertical axis represents the dot generation rate. Here, the dot generation rate corresponds to the ink droplet usage rate.

[0065] The control unit 30 changes the type of ink droplet 60 used according to the ink density. In other words, when the ink density is small, small ink droplets are used preferentially, as the ink density increases, the use of medium ink droplets increases, and when the ink density increases even further, the use of large ink droplets increases. Note that the "maximum ink density" in Figure 8 is the amount of ink that can be ejected per predetermined unit area, and is basically a value determined by the type of printing medium.

[0066] As described above, in this embodiment, the control unit 30 performs printing (first printing) such that the proportion of ink droplets of sizes other than the maximum size in the second ratio is smaller than the proportion of ink droplets of sizes other than the maximum size in the first ratio. In the example shown in Figure 8, the ink droplets of sizes other than the maximum size are small and medium ink droplets, and in the first printing, the proportion of small and medium ink droplets in the second ratio is made smaller than the proportion of small and medium ink droplets in the first ratio. In other words, as shown by the white arrows in Figure 8, the proportion of small and medium ink droplets in the second ratio (shown by dashed lines in Figure 8) is made smaller than the proportion of small and medium ink droplets in the first ratio (shown by solid lines in Figure 8). By performing such first printing, the formation of streaks and color unevenness on the medium 50 can be suppressed. Note that Figure 8 shows the case where the proportion of small and medium ink droplets in the second ratio is reduced, but in this embodiment, only the proportion of small ink droplets in the second ratio may be reduced.

[0067] Furthermore, in this embodiment, a test pattern printing step may be performed in advance to print a test pattern that can acquire unevenness information regarding printing unevenness between nozzle region NA1 and nozzle region NA2. Then, depending on the unevenness information obtained in the test pattern printing step, either the first printing or the second printing may be performed.

[0068] Figure 9 is a flowchart showing the operation of the printing apparatus 1 according to this embodiment, and is a flowchart for explaining the operation including the test pattern printing process. First, the printing apparatus 1 prints a test pattern on the medium 50 set by the user (step S1). The test pattern uses a combination of patterns in which each nozzle row 23 has different nozzle row distances D1 and D2 on the same line along the relative movement direction. For example, the combination of yellow (Y) and cyan (C) results in different nozzle row distances D1 and D2, so a solid pattern of green (G), which is the secondary color of yellow (Y) and cyan (C), is printed on the medium 50. At this time, the printing apparatus 1 performs test pattern printing in a second print in which there is no difference between the first ratio of nozzle area NA1 and the second ratio of nozzle area NA2.

[0069] Subsequently, unevenness information is obtained from the test pattern printed in step S1. If the printing unevenness is greater than or equal to a predetermined standard (step S2: Yes), the first print is performed (step S3). On the other hand, if the printing unevenness is less than the predetermined standard (step S2: No), the second print is performed (step S4).

[0070] For example, if the printing device 1 is equipped with a scanner, unevenness information may be obtained by scanning a test pattern with the scanner. The printing device 1 performs a first print if the printing unevenness exceeds a predetermined standard, that is, if the unevenness between area M1 of the medium 50 printed by nozzle area NA1 and area M2 of the medium 50 printed by nozzle area NA2 exceeds a predetermined standard. The unevenness between areas M1 and M2 of the medium 50 may be automatically determined using image information read by the scanner. Alternatively, if the user visually inspects the test pattern and determines that the printing unevenness exceeds a predetermined standard, the user may use an interface to set the print settings to the first print.

[0071] It should be noted that the present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention. Figure 2 shows a print head 10 in which a plurality of head chips 21a to 21f are arranged at an angle with respect to the X-axis direction. However, the present invention can be similarly applied to a print head configured such that the longitudinal direction of the plurality of head chips 21 extends in the X-axis direction, and a plurality of head chips 21 are arranged in the Y-axis direction.

[0072] Furthermore, the print head 10 shown in Figure 2 has a configuration in which the nozzle rows 23 of the same color do not overlap in the Y-axis direction. However, in the present invention, the nozzle rows 23 of the same color may be arranged to overlap in the Y-axis direction. That is, the cyan nozzle row 23C may be configured to overlap on the same line in the Y-axis direction between each head chip. Also, the magenta nozzle row 23M may be configured to overlap on the same line in the Y-axis direction between each head chip. Also, the yellow nozzle row 23Y may be configured to overlap on the same line in the Y-axis direction between each head chip. Also, the black nozzle row 23K may be configured to overlap on the same line in the Y-axis direction between each head chip.

[0073] Although the present invention has been described above in accordance with the above embodiments, the present invention is not limited to the configuration of the above embodiments, and of course includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the claims of the present patent application. [Explanation of symbols]

[0074] 1…Printing device, 10…Print head, 11…Drive circuit, 12…Drive element, 21, 21a~21f…Head chip, 22, 22C, 22M, 22Y, 22K…Nozzle, 23, 23C, 23M, 23Y, 23K…Nozzle row, 30…Control unit, 31…Resolution conversion unit, 32…Color conversion unit, 33…Halftone processing unit, 34…Ejection control unit, 35…Print switching unit, 36…Transport control unit, 37…Environmental information acquisition unit, 40…Transport mechanism, 50…Media, 60, 60Y, 60C…Ink droplet

Claims

1. A print head having multiple nozzles capable of ejecting ink droplets onto a medium, and having multiple nozzle rows in which multiple nozzles are arranged in the direction of the nozzle row, The system comprises a control unit that controls the ejection of ink droplets from the nozzle, A printing apparatus in which the print head and the medium move relative to each other in a relative movement direction different from the nozzle row direction, The print head has a first nozzle row and a second nozzle row, each ejecting different ink droplets. The number of the first nozzle row and the second nozzle row are each two or more. The plurality of nozzle rows that eject ink droplets on the same line along the relative movement direction have a first nozzle region where the distance between the first nozzle row and the second nozzle row in the relative movement direction is a first distance, and a second nozzle region where the distance between the first nozzle row and the second nozzle row in the relative movement direction is a second distance which is longer than the first distance. The nozzle is capable of forming dots of multiple sizes on the medium by ejecting ink droplets of multiple sizes. A printing apparatus characterized in that, when the ratio of the sizes of a plurality of ink droplets ejected from the nozzles of the first nozzle region is defined as the first ratio, and the ratio of the sizes of a plurality of ink droplets ejected from the nozzles of the second nozzle region is defined as the second ratio, the control unit performs a first print in which the proportion of ink droplets other than the maximum size in the second ratio is smaller than the proportion of ink droplets other than the maximum size in the first ratio.

2. The printing apparatus according to claim 1, characterized in that the second ratio, compared to the first ratio, has a lower utilization rate for the smallest ink droplet among the plurality of ink droplet sizes.

3. The printing apparatus according to claim 1, characterized in that the control unit performs the first printing when printing on a medium in which the ink droplets are prone to bleeding.

4. It features multiple different printing modes, The control unit is capable of performing a second print in which there is no difference between the first ratio of the first nozzle region and the second ratio of the second nozzle region. The printing apparatus according to claim 1, characterized in that it performs the first printing or the second printing according to the printing mode.

5. The printing apparatus according to claim 4, wherein the control unit performs the first printing when the printing mode is a high-quality printing mode.

6. The printing apparatus is further equipped with an environmental information acquisition unit capable of acquiring environmental information about the surrounding environment, The control unit is capable of performing a second print in which there is no difference between the first ratio of the first nozzle region and the second ratio of the second nozzle region. The printing apparatus according to claim 1, characterized in that it performs the first printing or the second printing in accordance with the environmental information.

7. The environmental information acquisition unit is configured to acquire at least one of temperature and humidity as environmental information. The printing apparatus according to claim 6, characterized in that the control unit performs the first printing or the second printing according to at least one of the temperature and humidity obtained by the environmental information acquisition unit.

8. The control unit is capable of performing a second print in which there is no difference between the first ratio of the first nozzle region and the second ratio of the second nozzle region. The print head has a third nozzle row that ejects ink droplets different from the first nozzle row and the second nozzle row, The distance between the second nozzle row and the third nozzle row in the relative movement direction is constant. The printing apparatus according to claim 1, characterized in that the area where printing is performed by the second nozzle row and the third nozzle row has a higher upper limit on the ejection ratio of ink droplets of sizes other than the maximum size compared to the area where printing is performed by the second nozzle area.

9. The print head has multiple nozzles capable of ejecting ink droplets onto a medium, and multiple nozzle rows in which these nozzles are arranged in the direction of the nozzle row. A printing method using a printing apparatus in which the print head and the medium move relative to each other in a relative movement direction different from the nozzle row direction, The print head has a first nozzle row and a second nozzle row, each ejecting different ink droplets. The number of the first nozzle row and the second nozzle row are each two or more. The plurality of nozzle rows that eject ink droplets on the same line along the relative movement direction have a first nozzle region where the distance between the first nozzle row and the second nozzle row in the relative movement direction is a first distance, and a second nozzle region where the distance between the first nozzle row and the second nozzle row in the relative movement direction is a second distance which is longer than the first distance. The nozzle is capable of forming dots of multiple sizes on the medium by ejecting ink droplets of multiple sizes. A printing method characterized in that, when the ratio of the sizes of a plurality of ink droplets ejected from the nozzles of the first nozzle region is defined as a first ratio, and the ratio of the sizes of a plurality of ink droplets ejected from the nozzles of the second nozzle region is defined as a second ratio, the printing is performed in a first printing step in which the proportion of ink droplets other than the largest size in the second ratio is smaller than the proportion of ink droplets other than the largest size in the first ratio.

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