Liquid dispensing device, liquid dispensing method, and program

Abstract

To provide a liquid discharge device, a liquid discharge method, and a program that can restrict deterioration in image quality.SOLUTION: A liquid discharge device comprises: a printing part for executing multi-pass printing of alternately implementing a main scanning movement operation for moving a recording head in a main scanning direction while discharging liquid, and a sub-scanning movement operation for moving a recording head or a recording medium in a sub-scanning direction relative to the recording medium or the recording head without discharging liquid; a first quantization processing part for converting an input image to be printed by the printing part to dot data; and a second quantization processing part for converting the dot data to scan data for each main scanning movement operation according to calculation of a discriminating ejection mask in which a bit number is two bits or more. The first quantization processing part performs processing in which an input image is converted to dot data containing at least two kinds of dots, and the second quantization processing part changes a discriminating ejection method of a dot according to a kind of the dot contained in the dot data.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a liquid ejection device, a liquid ejection method, and a program.

Background Art

[0002] As a printing means in a serial inkjet printer, mask processing is known in which dot data after halftone processing is scanned with a mask pattern to form an image. In this mask processing, several threshold values are provided for the density levels of the dot data after halftone processing, and a technique has been developed to change the splitting method for each gradation by switching the mask pattern according to the threshold values (see Patent Document 1).

Summary of the Invention

Problems to be Solved by the Invention

[0003] However, in the above technique, since the splitting method is changed for each gradation by the threshold value, there is a possibility that the image quality deteriorates particularly in an image such as a gradation.

[0004] The present invention has been made in view of the above, and an object thereof is to provide a liquid ejection device, a liquid ejection method, and a program capable of suppressing deterioration of image quality.

Means for Solving the Problems

[0005] To solve the above-mentioned problems and achieve the objective, the present invention provides a printing unit that performs a multi-pass printing process that alternately performs a main scanning movement operation, which moves a recording head in a main scanning direction perpendicular to the sub-scanning direction relative to a recording medium while discharging liquid, and a sub-scanning movement operation, which moves the recording head or the recording medium in the sub-scanning direction relative to the recording medium or the recording head without discharging liquid; a first quantization processing unit that converts an input image to be printed by the printing unit into dot data; and a second quantization processing unit that converts the dot data into scan data for each main scanning movement operation by calculation of a sorting mask with 2 bits or more and the dot data, wherein the first quantization processing unit is a process that converts the input image into dot data containing at least two types of dots, and the second quantization processing unit changes the sorting method of the dots depending on the type of dots contained in the dot data. Furthermore, depending on the type of dots included in the dot data, the position in the sorting mask that is used for calculations with the dot data is changed. ru. [Effects of the Invention]

[0006] According to the present invention, the deterioration of image quality can be suppressed. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a perspective view showing an example of the overall configuration of an inkjet recording apparatus as an image forming apparatus according to the first embodiment. [Figure 2] Figure 2 is a schematic diagram showing an example of a front view of an inkjet recording device, which is an image forming apparatus (liquid ejection device) according to the first embodiment. [Figure 3] Figure 3 is a schematic diagram showing an example of a plan view of an inkjet recording apparatus according to the first embodiment. [Figure 4] Figure 4 is a plan view showing an example of the arrangement of nozzles in a recording head of an inkjet recording device according to the first embodiment. [Figure 5] Figure 5 is a block diagram showing an example of the hardware configuration of an image forming system according to the first embodiment. [Figure 6] Figure 6 is a flowchart showing an example of the flow of multi-pass printing in an inkjet recording apparatus according to the first embodiment. [Figure 7] Figure 7 is a diagram illustrating an example of the scanning data generation process by an inkjet recording device according to the first embodiment. [Figure 8] Figure 8 is a diagram illustrating an example of a method for distributing dots according to each grayscale level using an inkjet recording device according to the first embodiment. [Figure 9] Figure 9 is a diagram illustrating an example of the effect of changing the method of dotting differently for each type of droplet using an inkjet recording device according to the first embodiment. [Figure 10] Figure 10 is a diagram illustrating an example of a process for changing the dot sorting method by an inkjet recording apparatus according to the first embodiment. [Figure 11] Figure 11 is a diagram illustrating an example of a process for changing the dot patterning method by an inkjet recording apparatus according to the first embodiment. [Figure 12] Figure 12 is a diagram illustrating an example of a process for changing the dot patterning method by an inkjet recording apparatus according to the second embodiment. [Figure 13] Figure 13 is a diagram illustrating an example of a process for changing the dot sorting method by an inkjet recording apparatus according to the second embodiment. [Figure 14] Figure 14 is a diagram illustrating an example of a process for changing the dot sorting method by an inkjet recording apparatus according to the second embodiment. [Figure 15] Figure 15 is a diagram illustrating an example of a process for changing the dot patterning method by an inkjet recording apparatus according to the third embodiment. [Figure 16] Figure 16 is a diagram illustrating an example of a process for changing the dot patterning method by an inkjet recording apparatus according to the third embodiment. [Figure 17]FIG. 17 is a diagram for explaining an example of a change process of a dot splitting method by an inkjet recording apparatus according to the fourth embodiment. [Figure 18] FIG. 18 is a diagram for explaining an example of a change process of a dot splitting method by an inkjet recording apparatus according to the fourth embodiment. Embodiments for Carrying out the Invention

[0008] Hereinafter, embodiments of a liquid ejection apparatus, a liquid ejection method, and a program will be described in detail with reference to the accompanying drawings.

[0009] (First Embodiment) FIG. 1 is a perspective view showing an example of the overall configuration of an inkjet recording apparatus as an image forming apparatus according to the first embodiment.

[0010] This inkjet recording apparatus 10 includes a carriage 200 and a stage 13 on which a recording medium 101 is placed. The carriage 200 is provided with a head unit 300 (see FIG. 5), which is an inkjet type image forming unit provided with a plurality of recording heads (liquid ejection heads) provided with a plurality of nozzles. The inkjet recording apparatus 10 forms an image by ejecting a liquid from the nozzles of the recording head (recording head unit). The nozzles of the recording head are provided on the surface facing the stage 13. In the present embodiment, as an example, the liquid is an ink having ultraviolet curability.

[0011] Further, an irradiation unit 400, which is a light source for irradiating ultraviolet rays, is provided on the surface of the carriage 200 facing the stage 13. The irradiation unit 400 (an example of an irradiation unit) irradiates light having a wavelength for curing the liquid ejected from the nozzles of the recording head.

[0012] Guide rods 19 are spanned between the left and right side plates 18a and 18b. The guide rods 19 hold the carriage 200 movably in the X direction (main scanning direction).

[0013] Further, the carriage 200, the guide rods 19, and the side plates 18a and 18b are integrated and movable in the Y direction (sub-scanning direction) along the guide rail 29 provided at the lower part of the stage 13. Further, the carriage 200 is held movably in the Z direction (vertical direction).

[0014] In the configuration shown in FIG. 1, the stage 13 on which the recording medium is placed is fixed. In the inkjet recording apparatus 10 as shown in FIG. 1, an image is formed by alternately repeating a main scanning operation of discharging ink from nozzles onto the recording medium 101 while moving the recording head in the main scanning direction and a sub-scanning operation of moving the recording head in the sub-scanning direction. That is, in the present embodiment, in the inkjet recording apparatus 10, the carriage 200, the guide rods 19, and the guide rail 29 function as an example of a printing unit that executes a multi-pass printing process for alternately performing the main scanning operation and the sub-scanning operation.

[0015] Here, the main scanning operation is an example of a main scanning movement operation of moving the recording head in the main scanning direction (X direction) orthogonal to the sub-scanning direction (Y direction) with respect to the recording medium 101 while discharging a liquid. Also, here, the sub-scanning operation is an example of a sub-scanning movement operation of moving the recording head or the recording medium 101 relatively in the sub-scanning direction with respect to the recording medium 101 or the recording head without discharging a liquid.

[0016] FIG. 2 is a schematic diagram showing an example of a front view of an inkjet recording apparatus which is an image forming apparatus (liquid ejection apparatus) according to the first embodiment. FIG. 3 is a schematic diagram showing an example of a plan view of the inkjet recording apparatus according to the first embodiment. In the configurations of FIGS. 2 and 3, the shape around the carriage is different from the shape in FIG. 1, but other functions are substantially the same as the configuration in FIG. 1.

[0017] In the configurations shown in FIGS. 1 to 3, in the sub-scanning operation, the recording heads 300K to 300W mounted on the carriage 200 are moved in the sub-scanning direction with respect to the recording medium 101.

[0018] As a modification of the image forming apparatus according to this embodiment, the stage 13 on which the recording medium 101 is placed may be made movable. In this case, the stage 13 becomes a moving part in the sub-scanning direction, and in the sub-scanning operation, it moves (transports) the recording medium 101 in the sub-scanning direction relative to the recording head 300K~300Y.

[0019] Note that while Figure 2 shows an example where one recording head 300K~300Y is provided in the sub-scanning direction within a single head array, multiple recording heads may be provided in the sub-scanning direction within a single head array.

[0020] Figure 4 is a plan view showing an example of the arrangement of nozzles in a recording head of an inkjet recording device according to the first embodiment.

[0021] As shown in Figure 4, the recording head of the carriage 200 may have a color ink ejection head 221 and a background ink ejection head 222. The color ink ejection head 221 and the background ink ejection head 222 are each equipped with a plurality of nozzles 221a, 222a for ejecting ink. In each ejection head, the nozzles 221a, 222a are arranged along the sub-scanning direction.

[0022] Furthermore, the color ink ejection head 221 and the background ink ejection head 222 are positioned such that the positions of the nozzles 221a and 222a of their respective ejection heads coincide in the sub-scanning direction within the overlapping region Ro. Here, the overlapping region Ro is the region where the color ink ejection head 221 and the background ink ejection head 222 overlap. That is, within the overlapping region Ro, the nozzles 221a and 222a of the color ink ejection head 221 and the background ink ejection head 222 are positioned to overlap in the main scanning direction.

[0023] The ejection pattern of ink droplets ejected from the color ink ejection head 221 and the background ink ejection head 222 is controlled by drive pulses applied to drive elements provided corresponding to each nozzle 221a, 222a of each ejection head. Piezoelectric elements such as PZTs are used as drive elements.

[0024] Next, an example of a hardware configuration in an image forming system, including an image forming apparatus (inkjet recording apparatus 10), will be described using Figures 1 to 3 and 5.

[0025] Figure 5 is a block diagram showing an example of the hardware configuration of an image forming system according to the first embodiment. In the image forming system shown in Figure 5, as shown in Figures 1 to 3, an external device, the PC2, is connected to the image forming apparatus (inkjet recording apparatus 10) which forms images using a mechanical structure, and the PC2 performs image processing. Note that the image processing functions performed by the PC2 may also be provided inside the image forming apparatus.

[0026] As shown in Figure 5, the image forming apparatus (inkjet recording apparatus 10) of this embodiment includes a controller unit 3, a detection group 414, a transport unit 100 which is a transport section, a carriage 200, a head unit 300, an irradiation unit 400, and a maintenance unit 500.

[0027] Furthermore, the controller unit 3 includes a unit control circuit 31, a memory 32, a CPU (Central Processing Unit) 33, and an I / F 34.

[0028] I / F34 is an interface for connecting the image forming apparatus (inkjet recording device 10) to an external PC (Personal Computer) 2. The connection method between the image forming apparatus (inkjet recording device 10) and the PC 2 can be anything, for example, a connection via a network or a direct connection between the two using a communication cable.

[0029] The detection group 414 includes, for example, various sensors provided in the inkjet recording device 10.

[0030] The CPU 33 uses the memory 32 as a working area to control the operation of each unit of the inkjet recording device 10 via the unit control circuit 31. Specifically, the CPU 33 controls the operation of each unit based on the recording data received from the PC 2 and the data detected by the detection group 414 to form an image, which is a liquid-coated surface 102, on the recording medium 101 (also referred to as a substrate, etc.). In this embodiment, the CPU 33 has a color plate division data generation unit 511, a first quantization processing unit 512, and a second quantization processing unit 513. The operation of the color plate division data generation unit 511, the first quantization processing unit 512, and the second quantization processing unit 513 will be described later.

[0031] Furthermore, a printer driver is installed on PC2, and this printer driver generates recording data from image data to be sent to the inkjet recording device 10. The recording data includes command data to operate the transport unit 100, etc., of the inkjet recording device 10, and pixel data related to the image (liquid-coated surface 102). The pixel data consists of 2 bits of data for each pixel and is represented in 4 grayscale levels.

[0032] Next, the components of the mechanical mechanism of the image forming apparatus will be described using Figures 2, 3, and 5. The transport unit 100 has a stage 13 and a suction mechanism 120. The suction mechanism 120 has a fan 110 and a plurality of suction holes 100a provided in the stage 13. The suction mechanism 120 temporarily fixes the recording medium 101 to the transport unit 100 by driving the fan 110 to pick up the recording medium 101 from the suction holes 100a. The suction mechanism 120 may also pick up paper using electrostatic suction. The transport unit 100's movement in the Y-axis direction (sub-scanning direction) is controlled based on a drive signal from the CPU 33 (unit control circuit 31).

[0033] In the configuration shown in Figures 2, 3, and 5, the transport unit 100 includes a transport control unit 210, a roller 105, and a motor 104. The transport control unit 210 drives the motor 104 to rotate the roller 105, thereby moving the recording medium 101 in the Y-axis direction (sub-scanning direction).

[0034] The transport unit 100 may move the carriage 200 in the Y-axis direction (sub-scanning direction) instead of the recording medium 101, as shown in Figure 1. In other words, the transport unit 100 moves the recording medium 101 and the carriage 200 relative to each other in the Y-axis direction (sub-scanning direction).

[0035] For example, as shown on the right side of Figure 2, the transport unit 100 includes a side plate 407b that supports two guides 201 that guide the carriage 200 in the X-axis direction (main scanning direction), a base 406 that supports the side plate 407b, a belt 404 fixed to the base 406, a drive pulley 403 and a driven pulley 402 around which the belt 404 is wrapped, a motor 405 that rotates the drive pulley 403, and a transport control unit 210.

[0036] Furthermore, as shown on the left side of Figure 2, the transport unit 100 includes a side plate 407a that supports two guides 201 that guide the carriage 200 in the X-axis direction (main scanning direction), a base 408 that supports the side plate 407a so that it can slide, and a groove 409 formed in the base 408 that guides the side plate 407a in the sub-scanning direction.

[0037] The transport unit 100 rotates the drive pulley 403 by driving the motor 405 with the transport control unit 210, moving the belt 404 in the Y-axis direction (sub-scanning direction). The base 406 on which the carriage 200 is supported moves in the Y-axis direction (sub-scanning direction) along with the movement of the belt 404, thereby allowing the carriage 200 to move in the Y-axis direction (sub-scanning direction). As the base 406 moves in the Y-axis direction (sub-scanning direction), the side plate 407a moves along the groove 409 of the base 408 in the Y-axis direction (sub-scanning direction).

[0038] As shown in Figure 2, the head unit 300 consists of head arrays (recording heads) 300K, 300C, 300M, 300Y, 300CL, and 300W, which eject UV-curable inks (examples of liquids) of types K, C, M, Y, CL, and W, respectively, and is located on the underside of the carriage 200.

[0039] Each head array 300K~300W is equipped with one or more recording heads. If the heads consist of multiple recording heads, they may be arranged in a staggered pattern or in a single row.

[0040] Each recording head is equipped with a piezo element, which is a drive element. When a drive signal is applied to the piezo by the CPU 33 (unit control circuit 31), the piezo undergoes a contraction motion, and the pressure change caused by this contraction motion ejects UV-curable ink onto the recording medium 101. As a result, a liquid-coated surface 102 (an example of a liquid-coated surface) is formed on the recording medium 101.

[0041] Suitable UV-curable inks for this embodiment include, for example, inks containing methacrylate monomers. Methacrylate monomers have the advantage of being relatively less sensitizing to the skin, but they have the characteristic of having a greater degree of curing shrinkage compared to general inks.

[0042] The irradiation unit 400 is located on the side (X-axis direction) of the carriage 200 and irradiates UV light based on a drive signal from the CPU 33 (unit control circuit 31). The irradiation unit 400 mainly consists of a UV irradiation lamp that emits UV light.

[0043] The carriage 200's movement in the Z-axis direction (height direction) and the X-axis direction (main scanning direction) is controlled based on drive signals from the CPU 33 (unit control circuit 31).

[0044] The carriage 200 scans along the guide 201 in the main scanning direction (X-axis direction). The scanning unit 206 has a drive pulley 203, a driven pulley 204, a drive belt 202, and a motor 205. The carriage 200 is fixed to the drive belt 202 which is routed between the drive pulley 203 and the driven pulley 204. By driving the drive belt 202 with the motor 205, the carriage 200 scans left and right in the main scanning direction. The guide 201 is supported by the side plates 211A and 211B of the device body.

[0045] The height adjustment unit 207 includes a motor 209 and a slider 208. The height adjustment unit 207 moves the guide 201 up and down by driving the motor 209 to move the slider 208 up and down. As the guide 201 moves up and down, the carriage 200 moves up and down, and the height of the carriage 200 relative to the recording medium 101 can be adjusted.

[0046] Next, the image formation operation of the inkjet recording device 10 shown in Figure 1 will be described. First, the transport unit 100 moves in the Y-axis direction (sub-scanning direction) based on a drive signal from the CPU 33 (unit control circuit 31) to position the recording medium 101 at the initial position for forming an image (liquid coated surface 102).

[0047] Next, the carriage 200 moves to a height suitable for ejecting UV-curable ink by the head unit 300 based on a drive signal from the CPU 33 (unit control circuit 31) (for example, a height where the head gap between the bottom surface of each head and the recording medium 101 in the head array 300K~W of the head unit 300 is 1 mm). The height of the head unit 300 is detected by the height sensor 41 and known to the CPU 33.

[0048] Next, the carriage 200 moves back and forth in the X-axis direction (main scanning direction) based on a drive signal from the CPU 33 (unit control circuit 31). During this back and forth movement, the head unit 300 ejects UV-curable ink based on the drive signal from the CPU 33 (unit control circuit 31). As a result, an image (liquid-coated surface 102) for one scan is formed on the recording medium 101.

[0049] Next, once one scan's worth of image (liquid-coated surface 102) is formed on the recording medium 101, the transport unit 100 moves one scan's worth in the Y-axis direction (sub-scanning direction) based on a drive signal from the CPU 33 (unit control circuit 31).

[0050] From here on, until the formation of the image (liquid-coated surface 102) is complete, the operation of forming one scan portion of the image (liquid-coated surface 102) and the operation of moving the transport unit 100 one scan portion in the Y-axis direction are performed alternately.

[0051] Then, once the formation of the image (liquid-coated surface 102) on the recording medium 101 is complete, the system waits until the UV-curable ink is smoothed out (hereinafter sometimes referred to as the "leveling time"), after which UV light is irradiated by the irradiation unit 400.

[0052] Figure 6 is a flowchart showing an example of the multi-pass printing process in an inkjet recording device according to the first embodiment. Next, an example of the multi-pass printing process in the inkjet recording device 10 according to this embodiment will be described using Figures 5 and 6.

[0053] When image data to be printed is input, the color plate division data generation unit 511 generates color plate division data for each ink color implemented in the inkjet recording device 10 from the input image data (an example of an input image) (step S801). For example, if the inkjet recording device 10 prints using CMYK inks, the color plate division data generation unit 511 generates color plate division data for each CMYK color from the input image data.

[0054] Next, the first quantization processing unit 512 applies a dot data generation mask to the color plate division data for each color generated by the color plate division data generation unit 511 to generate dot data (step S802). Here, the dot data generation mask is, for example, a dither mask with a set threshold used for halftone processing. That is, the first quantization processing unit 512 functions as a first quantization processing unit that converts image data into dot data. At that time, the CPU 33 converts the image data into dot data that includes at least two types of dots. The dot data includes at least two types of dots, namely small droplet dots and large droplet dots with a larger droplet volume than the small droplet dots. The dot data may also include medium droplet dots, which have a larger droplet volume than the small droplet dots but a smaller droplet volume than the large droplet dots.

[0055] Next, the second quantization processing unit 513 applies a sorting mask to the dot data generated by the first quantization processing unit 512 to generate scan data (step S803). That is, for each dot in the dot data, the second quantization processing unit 513 determines which nozzles 221a, 222a will form the dot for each scan in the main scanning direction of the recording head. Here, the sorting mask is an example of a mask with 2 or more bits.

[0056] In this embodiment, the second quantization processing unit 514 functions as an example of a second quantization processing unit that converts the dot data into scan data for each scan (main scanning movement operation) by performing calculations on the dot mask and the dot data. At that time, the second quantization processing unit 514 changes the dot sorting method depending on the type of dots contained in the dot data. This makes it possible to continuously change the dot sorting method without switching the dot sorting method at specific gradations. As a result, it is possible to suppress deterioration of image quality, especially in images such as gradients.

[0057] The unit control circuit 31 then transfers the generated scan data to the drive circuit inside the recording head and performs image printing on the recording medium 101 according to the scan data.

[0058] Figure 7 is a diagram illustrating an example of the scan data generation process by the inkjet recording device according to the first embodiment. Next, using Figure 7, an example of the scan data generation process by the inkjet recording device 10 according to this embodiment will be described. In the following description, the scan data generation process for the 1st and 3rd scans of the recording head in the case of multi-scanning with 2-pass 1 / 2 interlacing will be described, but the scan data for the 2nd and 4th scans will be generated in the same manner.

[0059] First, as shown in Figure 7, the second quantization processing unit 513 extracts from the dot data the pixels located at the positions where nozzles 221a and 222a scan during the 1st and 3rd scans of the recording head (1st and 3rd scan nozzle position dot data). Specifically, the dashed lines in Figure 7 represent the scanning positions where nozzles 221a and 222a scan during the 1st and 3rd scans, and the second quantization processing unit 513 extracts the pixels located at these scanning positions (1st and 3rd scan nozzle position dot data).

[0060] Next, the second quantization processing unit 513 generates scan data for the first and third scans (scan data for the first and third scans) by performing a masking process on the extracted pixels using a sorting mask (scan mask for the first and third scans). For example, as shown in Figure 7, the second quantization processing unit 513 generates scan data for the dot data of the first and third scans using the sorting masks for the first and third scans, respectively.

[0061] At that time, the second quantization processing unit 513 generates scan data indicating that liquid should be discharged to pixels corresponding to "1" in the sorting mask, and that liquid should not be discharged to pixels corresponding to "0" in the sorting mask. Here, the sorting mask is provided for each scan of the recording head and indicates the dot placement position, which is the position of the pixels from which liquid will be discharged from nozzles 221a and 222a in that scan. For example, as shown in Figure 7, the sorting mask is binary data for each dot, indicating whether or not liquid will be discharged from nozzles 221a and 222a.

[0062] When performing multi-scanning with 2-pass 1 / 2 interlacing, the sorting mask used to generate scan data where the positions of nozzles 221a and 222a in the sub-scanning direction overlap is complementary. Therefore, the second quantization processing unit 513 can decompose the dot data into scan data equal to the number of scans performed by the recording head by performing mask processing on the dot data using the sorting mask which is complementary.

[0063] Next, an example of a method for differentiating dot placement for each gradation level using the inkjet recording device 10 according to this embodiment will be explained with reference to Figure 8. Figure 8 is a diagram illustrating an example of a method for differentiating dot placement for each gradation level using the inkjet recording device according to the first embodiment. In Figure 8, lighter colored areas have less dot placement than darker colored areas. The dot placement amount corresponds to the proportion of dots included in the original dot data that are placed on the recording medium 101 in each scan. First, a dot placement method suitable for low-gradation areas and high-gradation areas will be explained.

[0064] In low-gradation areas, density unevenness is more likely to occur compared to high-gradation areas. One of the main causes of this density unevenness is that the dot diameter at the edge of the recording head (hereinafter referred to as the head edge area) is different from the rest of the image. Therefore, a mask A that reduces the amount of dots in the head edge area of ​​the recording head is desirable.

[0065] On the other hand, in the high-gradation region, density saturates and density unevenness becomes less visible. However, as the amount of ink applied increases, surface unevenness becomes more apparent, and gloss unevenness begins to stand out (especially with UV ink). When there is a rapid change in the amount of ink applied, as in mask A, differences in surface condition occur in the region where the amount of ink applied changes, resulting in gloss unevenness. Therefore, in the high-gradation region, mask B, which has less change in the amount of ink applied, is preferable.

[0066] Therefore, there is a trade-off in the optimal mask shape between the high-gradation and low-gradation regions. Accordingly, the second quantization processing unit 513 changes the rendering method depending on the gradation. This makes it possible to improve image quality.

[0067] Next, using Figure 9, an example of the effect of changing the method of dotting for each type of dot (hereinafter referred to as "droplet type") using the inkjet recording device according to this embodiment will be explained. Figure 9 is a diagram illustrating an example of the effect of changing the method of dotting for each droplet type using the inkjet recording device according to the first embodiment. In Figure 9, the horizontal axis represents Input (input gradation), and the vertical axis represents Output (amount of dotting for each droplet type).

[0068] In this embodiment, the second quantization processing unit 513 changes the dot placement method for each droplet type. Normally, the droplet types used for printing are controlled and replaced as shown in Figure 9. For example, if the input gradation, which is the gradation of the input image, is 50%, the second quantization processing unit 513 converts the dot data to contain 50% large droplets and 50% small droplets. As shown in Figure 9, the first quantization processing unit 512 converts the input image into dot data such that in the low-gradation areas, the proportion of small droplets to the total dots is larger, and the proportion of large droplets to the total dots is smaller, compared to the high-gradation areas. The second quantization processing unit 513 then converts the small droplets in the dot data into scan data using a mask (mask A) in which the amount of dotting at the edges of the recording head is lower than that at the center of the recording head. The second quantization processing unit 513 also converts the large droplets in the dot data into scan data using a mask B in which the rate of change of the amount of dotting is smaller than that of mask A for small droplets.

[0069] Here, for example, when mask B is applied to the large droplets and mask A is applied to the small droplets as shown in Figure 9, it is clear that the amount of mask B used increases continuously as the input grayscale level increases. Also, for example, when the input grayscale level is 50%, the second quantization processing unit 513 uses mask A 50% and mask B 50%. As a result, the second quantization processing unit 513 can change the dotting method for each droplet type, and can continuously change the dotting method depending on the density, so it is possible to suppress deterioration of image quality, especially when printing images such as gradients.

[0070] Figures 10 and 11 illustrate an example of a process for changing the dot pattern using an inkjet recording apparatus according to the first embodiment. In the dot data (RIP data) shown in Figure 10, 00 represents a void, 01 represents a small droplet, 10 represents a medium droplet, and 11 represents a large droplet.

[0071] In this embodiment, the second quantization processing unit 513 performs a second quantization process to convert dot data into scan data for each scan using a pre-prepared sorting mask and an arithmetic table. Here, the arithmetic table is a table that associates dot data with the sorting mask to be applied to that dot data. The sorting mask shown in Figure 10 has three types of dots and three bits, and may be, for example, a sorting mask with 1px horizontally, 8px vertically, and 3 bits. The dot data may also be, for example, 8px horizontally, 8px vertically, and 2 bits. As shown in Figure 10, the second quantization processing unit 513 may also generate scan data by performing calculations between the sorting mask and RIP data using the arithmetic table (see Figure 11).

[0072] Thus, according to the inkjet recording apparatus 10 of the first embodiment, the dot sorting method can be continuously changed according to density without switching the dot sorting method at specific gradations. As a result, deterioration of image quality, especially in images such as gradients, can be suppressed.

[0073] (Second Embodiment) This embodiment is an example in which the dot data and the position in the sorting mask that is used for calculations are different depending on the type of dots contained in the dot data. In the following description, the same configuration as in the first embodiment will be omitted.

[0074] Figures 12-14 illustrate an example of a process for changing the dot sorting method by an inkjet recording apparatus according to the second embodiment. In this embodiment, the second quantization processing unit 513 may perform calculations on different bits in the sorting mask depending on the type of dot data (droplet type). Here, the number of bits in the sorting mask is equal to or greater than the number of types of dot data. In this case, the second quantization processing unit 513 may perform different sorting methods for all droplet types of dots contained in the dot data.

[0075] For example, as shown in Figures 12 and 13, the second quantization processing unit 513 determines whether a large droplet is 0 (no discharge) or 1 (discharge) based on the value in the tens place, the medium droplet is 2s place, and the small droplet is 1s place. Based on this, the second quantization processing unit 513 generates scan data as shown in Figure 14.

[0076] Thus, the inkjet recording apparatus 10 according to the second embodiment can obtain the same effects and advantages as the first embodiment.

[0077] (Third embodiment) This embodiment is an example in which the number of bits in the sorting mask is smaller than the number of dot types contained in the dot data. In the following description, the same configuration as in the first embodiment will be omitted.

[0078] Figures 15 and 16 illustrate an example of the process for changing the dot sorting method by an inkjet recording apparatus according to the third embodiment. In this embodiment, the sorting mask has fewer bits than the number of dot types. This reduces the number of droplet types that require different sorting methods, thereby speeding up the processing of the conversion from dot data to scan data. The second quantization processing unit 513 then performs calculations between the sorting mask and the RIP data using an arithmetic table, as shown in Figure 15. As a result, the second quantization processing unit 513 generates scan data as shown in Figure 16.

[0079] Thus, according to the inkjet recording apparatus 10 of the third embodiment, the number of droplet types that are differentiated in the printing method can be reduced, and the processing speed of the conversion process from dot data to scan data can be increased.

[0080] (Fourth embodiment) In this embodiment, the dot-blocking mask is such that the dot dots constituting the low-gradation portion of the dot data have a lower dot dot density at the edges of the recording head compared to the center, while the rate of change in dot density for dots constituting the high-gradation portion of the dot data is smaller than that for the low-gradation portion. In the following description, configurations similar to those in the above-described embodiment will be omitted.

[0081] Figures 17 and 18 illustrate an example of a modification process for the dot differentiation method using an inkjet recording apparatus according to the fourth embodiment. In this embodiment, the differentiation mask is a mask that reduces the amount of dots at the edges of the recording head compared to the center for dots that constitute the low-gradation portion of the dot data. As a result, density unevenness can be suppressed in the low-gradation region by reducing the amount of dots at the edges of the recording head.

[0082] Furthermore, in this embodiment, the dosing mask is a mask in which the rate of change in dosing amount is smaller for dots constituting the high-gradation areas compared to the low-gradation areas. As a result, rapid changes in dosing amount can be suppressed in the high-gradation areas, thereby suppressing the occurrence of gloss unevenness. For example, in the case of the droplet configuration shown in Figure 17, the second quantization processing unit 513 uses density unevenness suppression mask A for small droplets and gloss unevenness suppression mask B for large droplets, as shown in Figure 18.

[0083] Thus, according to the fourth embodiment of the inkjet recording apparatus 10, by changing the printing method according to the gradation, density unevenness can be suppressed in the low gradation region by reducing the amount of printing at the edge of the recording head, and the occurrence of gloss unevenness can be suppressed in the high gradation region by suppressing abrupt changes in the amount of printing.

[0084] The program executed by the inkjet recording device 10 of this embodiment is provided pre-installed in a ROM or the like. The program executed by the inkjet recording device 10 of this embodiment may also be provided as an installable or executable file recorded on a computer-readable recording medium such as a CD-ROM, flexible disk (FD), CD-R, or DVD (Digital Versatile Disk).

[0085] Furthermore, the program executed by the inkjet recording device 10 of this embodiment may be stored on a computer connected to a network such as the Internet and provided by downloading it via the network. Alternatively, the program executed by the inkjet recording device 10 of this embodiment may be provided or distributed via a network such as the Internet.

[0086] The program executed in the inkjet recording device 10 of this embodiment has a modular configuration that includes the above-described parts (color plate division data generation unit 511, first quantization processing unit 512, and second quantization processing unit 513). In actual hardware, the CPU 33 (an example of a processor) reads the program from the memory 32 such as the ROM and executes it, thereby loading the above-described parts onto the main memory, and generating the color plate division data generation unit 511, the first quantization processing unit 512, and the second quantization processing unit 513 on the main memory. [Explanation of symbols]

[0087] 3. Controller Unit 31 Unit Control Circuit 32 memory 33 CPU 34 I / F 10. Inkjet recording device 19 Guide Rods 29 Guide rails 200 Carriage 300 Head Unit 300K, 300C, 300M, 300Y, 300CL, 300W recording head 511 Color Plate Splitting Data Generation Unit 512 First Quantization Processing Unit 513 Second Quantization Processing Unit [Prior art documents] [Patent Documents]

[0088] [Patent Document 1] Japanese Patent Publication No. 2004-209943

Claims

1. A printing unit that performs multi-pass printing processing by alternately performing a main scanning movement operation, which moves the recording head in a main scanning direction perpendicular to the sub-scanning direction relative to the recording medium while discharging liquid, and a sub-scanning movement operation, which moves the recording head or the recording medium in the sub-scanning direction relative to the recording medium or the recording head without discharging liquid, A first quantization processing unit that converts the input image to be printed by the printing unit into dot data, The system comprises a sorting mask with two or more bits, and a second quantization processing unit that converts the dot data into scan data for each main scanning movement operation through calculations with the dot data, The first quantization processing unit is a process that converts the input image into dot data containing at least two types of dots, The second quantization processing unit changes the method of dispensing the dots according to the type of dots contained in the dot data, and the liquid dispensing device differs the position in the dispensing mask from the dot data in the dispensing mask according to the type of dots contained in the dot data.

2. The number of bits in the sorting mask is equal to or greater than the number of types of dots included in the dot data. The liquid dispensing apparatus according to claim 1, wherein the second quantization processing unit causes the method of dispensing the dots to differ for all types of dots included in the dot data.

3. The liquid dispensing apparatus according to claim 1, wherein the sorting mask has a number of bits smaller than the number of dot types included in the dot data.

4. The liquid dispensing apparatus according to claim 1, wherein the dotting mask is such that the amount of dotting at the edges of the recording head is lower for dots constituting the low-gradation portion of the dots included in the dot data compared to the central portion, and the rate of change in the amount of dotting at the edges of the recording head is smaller for dots constituting the high-gradation portion of the dots included in the dot data compared to the low-gradation portion.

5. The aforementioned dot data includes two or more types of dots, such as small droplet dots and large droplet dots with a larger volume than the small droplet dots. The liquid dispensing apparatus according to claim 1, wherein the second quantization processing unit converts small droplets in the dot data into scan data using a first mask in which the amount of data inserted at the edge of the recording head is lower than that at the center of the recording head, and converts large droplets in the dot data into scan data using a second mask which is smaller than the first mask.

6. A printing unit that performs a multi-pass printing process by alternately performing a main scanning movement operation, which moves the recording head in a main scanning direction perpendicular to the sub-scanning direction relative to the recording medium while discharging liquid, and a sub-scanning movement operation, which moves the recording head or the recording medium in the sub-scanning direction relative to the recording medium or the recording head without discharging liquid, A first quantization processing unit that converts the input image to be printed by the printing unit into dot data, The system comprises a sorting mask with two or more bits, and a second quantization processing unit that converts the dot data into scan data for each main scanning movement operation through calculations with the dot data, The first quantization processing unit is a process that converts the input image into dot data containing at least two types of dots, The second quantization processing unit changes the method of sorting the dots according to the type of dots contained in the dot data, and converts the dot data into scan data using the sorting mask and calculation table of the dot data that have been prepared in advance. Liquid dispensing device, wherein the dispensing mask is such that the amount of docking at the edges of the recording head is lower for dots constituting the low-gradation portion of the dot data compared to the central portion, and the rate of change in the amount of docking for dots constituting the high-gradation portion of the dot data is smaller for those dots compared to the low-gradation portion.

7. A liquid discharge method performed by a liquid discharge device, A printing unit that performs a multi-pass printing process, which alternately performs a main scanning movement operation in which a recording head is moved in a main scanning direction perpendicular to the sub-scanning direction relative to the recording medium while discharging liquid, and a sub-scanning movement operation in which the recording head or the recording medium is moved in the sub-scanning direction relative to the recording medium or the recording head without discharging liquid, converts an input image to be printed by the printing unit into dot data; The process includes a second quantization step which converts the dot data into scan data for each main scanning movement operation by performing calculations with a sorting mask having two or more bits and the dot data, The first quantization step is a process of converting the input image into dot data that includes at least two types of dots, The second quantization step is a liquid dispensing method which changes the method of dispensing dots according to the type of dots contained in the dot data, and makes the position in the dispensing mask that is used for calculations with the dot data different according to the type of dots contained in the dot data.

8. Computers, A printing unit that performs a multi-pass printing process that alternately performs a main scanning movement operation, which moves the recording head in a main scanning direction perpendicular to the sub-scanning direction relative to the recording medium while discharging liquid, and a sub-scanning movement operation, which moves the recording head or the recording medium in the sub-scanning direction relative to the recording medium or the recording head, without discharging liquid, converts the input image to be printed by the printing unit into dot data, and A second quantization processing unit is configured to convert the dot data into scan data for each main scanning movement operation by performing calculations with a sorting mask having two or more bits and the dot data. The first quantization processing unit is a process that converts the input image into dot data containing at least two types of dots, The second quantization processing unit is a program that changes the method of sorting the dots according to the type of dots contained in the dot data, and makes the position in the sorting mask that is used for calculations with the dot data different according to the type of dots contained in the dot data.

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