Recording device

Abstract

To record images while suppressing the degradation of image quality due to beading, etc. [Solution] The first number, which is the number of pixels that overlap between a dot arrangement having a value lower than the median of all tones in the first dither pattern and a dot arrangement having a value lower than the median of all tones in the second dither pattern, is controlled to be greater than the second number, which is the number of pixels that overlap between a dot arrangement having a value higher than the median of all tones in the first dither pattern and a dot arrangement having a value lower than the median of all tones in the second dither pattern.

Description

Technical Field

[0001] The present invention relates to a recording apparatus that records an image on a recording medium using a reaction liquid.

Background Art

[0002] An inkjet recording apparatus that records an image on a recording medium by ejecting ink from a recording head is known. In such a recording apparatus, when recording an image on a low-permeability recording medium, since the ink hardly penetrates into the recording medium, the ink remains on the recording medium, and bleeding (hereinafter also referred to as bleed) occurs between adjacent different-colorant ink droplets due to the contact between the droplets. To reduce this bleed, a technique using a reaction liquid ink (hereinafter also referred to as a reaction liquid) that reacts with the colorant contained in the colorant ink is known. That is, by bringing the colorant ink and the reaction liquid into contact on the recording medium, aggregation of the colorant contained in the colorant ink is caused, thereby reducing bleed. However, if the reaction liquid is applied more than necessary, there is a risk that the boundary portions of adjacent dots of the reaction liquid droplets will combine and the dots will be connected (so-called beading). When beading occurs, the image quality is significantly deteriorated.

[0003] Patent Document 1 discloses a technique for applying a reaction liquid in an appropriate amount to an appropriate position according to the application amount and dot arrangement of different colorant inks on a recording medium for each recorded image data.

[0004] Further, Patent Document 2 discloses a technique for generating a mask pattern that takes into account the overlap (logical product) with the dot arrangement pattern so that the number of dot data in each recording scan is not biased toward a specific scan and is well dispersed within a certain area in order to suppress image defects such as density unevenness and texture.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

[0006] However, in so-called multi-pass recording methods, where the recording dots of a recorded image are distributed across multiple recording scans, the dot arrangement of the reaction solution differs for each recorded image data. This can lead to image defects due to biases in dot arrangement for each recording scan.

[0007] The present invention aims to record images that suppress image defects such as uneven density and texture caused by bias in dot placement for each recording scan of the reaction solution, while also suppressing image defects such as beading caused by contact between the reaction solution dots and the colorant ink dots. [Means for solving the problem]

[0008] A recording means comprising multiple discharge port rows, including a first discharge port row having multiple discharge ports arranged for dispensing a colorant ink containing a colorant, and a second discharge port row having multiple discharge ports arranged for dispensing a reaction solution that reacts with the colorant; an amount determining means for determining the amount of the colorant ink and the amount of the reaction solution to be applied to the recording medium based on input image data; and determining the dot arrangement of the colorant ink based on the amount of the colorant ink and a first dither pattern corresponding to the colorant ink, and determining the dot arrangement of the colorant ink based on the amount of the reaction solution and a second dither pattern corresponding to the reaction solution. The device comprises a dot arrangement determination means for determining the dot arrangement of the reaction solution, wherein the first number, which is the number of pixels that overlap in the dot arrangement having a value lower than the median of all tones in the first dither pattern and the dot arrangement having a value lower than the median of all tones in the second dither pattern, is greater than the second number, which is the number of pixels that overlap in the dot arrangement having a value higher than the median of all tones in the first dither pattern and the dot arrangement having a value lower than the median of all tones in the second dither pattern. [Effects of the Invention]

[0009] According to the present invention, it is possible to record images that suppress image defects such as uneven concentration and texture caused by bias in dot placement for each recording scan of the reaction solution, while also suppressing image defects such as beading. [Brief explanation of the drawing]

[0010] [Figure 1] This is a diagram showing the external appearance of the recording device. [Figure 2] This is a side view of the main body of the recording device. [Figure 3] This is a diagram showing the recording head. [Figure 4] This is a block diagram illustrating the schematic configuration of a recording system, including a host device and a control system within the recording device. [Figure 5] This is a block diagram illustrating the flow of image data conversion processing. [Figure 6] This is a schematic diagram showing the dithering patterns for each color. [Figure 7] This is a schematic diagram showing the arrangement of dots for each color in a given grayscale range. [Figure 8] This is a schematic diagram showing the overlap between the dots of each color and the dots of the reaction solution. [Figure 9] This is a schematic diagram showing the arrangement of dots of each color. [Figure 10] This is a schematic diagram showing the overlap between the dots of each color and the dots of the reaction solution. [Figure 11] This is a schematic diagram showing the mask pattern of the reaction solution. [Figure 12] This is a schematic diagram showing the dot arrangement during each recording scan of the reaction solution. [Figure 13] This is a flowchart showing the method for generating a dither pattern in a reaction solution. [Figure 14] This is a schematic diagram illustrating a method for generating a dither pattern in a reaction solution. [Figure 15] This is a schematic diagram showing the dither pattern of the reaction solution. [Figure 16]It is a flowchart showing a method for generating a dither pattern of a reaction solution. [Figure 17] It is a schematic diagram showing a dither pattern of a coloring material ink. [Figure 18] It is a schematic diagram showing a method for generating a dither pattern of a reaction solution. [Figure 19] It is a schematic diagram showing a dither pattern of a reaction solution. [Figure 20] It is a flowchart showing a method for generating a dither pattern of a reaction solution. [Figure 21] It is a schematic diagram showing the usage amount of each color ink. [Figure 22] It is a schematic diagram showing the usage amount of each color ink.

Embodiments for Carrying Out the Invention

[0011] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0012] <<First Embodiment>> The basic configuration of the inkjet recording apparatus according to this embodiment will be described.

[0013] (1) Configuration of the inkjet recording apparatus FIG. 1 is a diagram showing the appearance of an inkjet recording apparatus (hereinafter also referred to as a recording apparatus or a printer) according to this embodiment. The recording apparatus 100 in FIG. 1 is a so-called serial scanning type printer, which records an image by scanning a recording head in the X direction (scanning direction) orthogonal to the Y direction (transport direction) of the recording medium P. FIG. 2 is a side view of the main body of the recording apparatus 100.

[0014] Figures 1 and 2 illustrate the configuration of the recording device 100 and its operation during recording. First, the recording medium P is transported in the Y direction from the spool 6 holding the recording medium P by transport rollers driven via gears by a transport motor (not shown). Meanwhile, at a predetermined transport position, the carriage unit 2 is reciprocated by a carriage motor (not shown) along a guide shaft 8 extending in the X direction. During this scanning process, based on the position signal obtained by the encoder 7, the recording head 9 (described later), which can be mounted on the carriage unit 2, is ejected from its ejection port, and recording is performed for a certain bandwidth corresponding to the arrangement range of the ejection ports. In this embodiment, the device is configured to scan at a scanning speed of 30 inches per second and perform the ejection operation at a recording resolution of 1200 dpi (1 / 1200 inch interval). After the recording medium P has been transported, an image is recorded for the next bandwidth.

[0015] A carriage belt can be used to transmit the driving force from the carriage motor to the carriage unit 2. Alternatively, other drive systems can be used, such as a system comprising a lead screw rotated by the carriage motor and extending in the X direction, and an engaging portion provided on the carriage unit 2 that engages with the groove of the lead screw.

[0016] The fed recording medium P is held and transported by the feed roller and pinch roller and guided to the recording position (scanning area of ​​the recording head) on the platen 4. Normally, in the idle state, the face of the recording head 9 is capped, so prior to recording, the cap is opened to make the recording head 9 (carriage unit 2) scannable. After that, once data for one scan has been accumulated in the buffer, the carriage motor causes the carriage unit 2 to scan and recording is performed as described above.

[0017] A flexible wiring board 19 is attached to the recording head 9 to supply drive pulses for ejection and signals for head temperature control. The other end of the flexible wiring board 19 is connected to a control unit (not shown) equipped with a control circuit such as a CPU that performs control of the recording device. The UI screen 50 is configured to allow the user to input or confirm information such as stopping the recording operation or information about the recording medium P.

[0018] A heater 10, supported by a frame (not shown), is positioned in the curing region, which is located downstream in the sub-scanning direction Y from the position where the recording head 9 mounted on the carriage unit 2 reciprocates in the main scanning direction X. The heater 10 dries the liquid ink on the recording medium P using heat. The heater 10 is covered by a heater cover 11. The heater cover 11 serves to efficiently irradiate the recording medium P with the heat from the heater 10 and to protect the heater 10. After recording by the recording head 9, the recording medium P is wound up by the take-up spool 12 to form a roll-shaped winding medium 13. Specifically, the heater 10 can be a sheathed heater or a halogen heater. The heating temperature of the heating section in the curing region is set considering the film-forming properties and productivity of water-soluble resin fine particles, as well as the heat resistance of the recording medium P. As a heating means for the heating section in the curing region, hot air blowing from above or contact-type heat conduction heater heating from below the recording medium can be used. In this embodiment, the heating means for the heating section in the curing region is shown as being provided in one location. However, as long as the temperature measured by the radiation thermometer (not shown) on the recording medium P does not exceed the set value of the heating temperature, two or more heating means may be provided and used in combination.

[0019] In the recording device 100 of this embodiment, so-called multi-path recording can be performed, in which an image is recorded on a predetermined area (1 / n band) on the recording medium P by scanning the recording head multiple times (n times).

[0020] (2) Recording head configuration Figure 3 shows a recording head 9 according to this embodiment. The recording head 9 is equipped with an ejection port row 22K for ejecting black ink (K), an ejection port row 22C for ejecting cyan ink (C), an ejection port row 22M for ejecting magenta ink (M), and an ejection port row 22Y for ejecting yellow ink (Y), all of which contain colorants. Since these black inks (K), cyan inks (C), magenta inks (M), and yellow inks (Y) each contain colorants, for simplicity, these inks will be referred to as colorant inks in the following description.

[0021] Furthermore, the recording head 9 is equipped with a series of 22 ejection ports for ejecting a reactive liquid ink (RCT) that does not contain colorants. This reactive liquid ink (hereinafter also referred to as the reactive liquid) does not contain colorants, but it contains reactive components that react with the colorants contained in the colorant ink, and by coming into contact with the colorant ink on the recording medium, it can reduce bleeding.

[0022] In each nozzle row, the nozzles are arranged along the sub-scanning direction. Furthermore, on the recording head 9, these nozzle rows are arranged from left to right in the order of nozzle rows 22K, 22C, 22M, 22Y, and 22RCT in the main scanning direction (X direction) intersecting the sub-scanning direction. Each of these nozzle rows 22K, 22C, 22M, 22Y, and 22RCT consists of 1280 nozzles 30, each ejecting ink, arranged in the Y direction (arrangement direction, sub-scanning direction) at a density of 1200 dpi. In this embodiment, the amount of ink ejected at one time from a single nozzle 30 is approximately 5 pl.

[0023] These ejection port rows 22K, 22C, 22M, 22Y, and 22RCT are each connected to an ink tank (not shown) that stores the corresponding ink, and ink is supplied to it. In this embodiment, the recording head 9 and the ink tank may be configured as an integrated unit, or they may be configured to be separable.

[0024] The detailed compositions of the black ink (K), cyan ink (C), magenta ink (M), yellow ink (Y), and reaction solution (RCT) will be described later. Furthermore, water-soluble resin fine particles, which form a film upon heating to improve the abrasion resistance of the recorded material, may be included in each color of the colorant ink, or they may be included in a third ink, clear emulsion ink (Em), which does not contain colorants and is different from the colorant ink or reaction solution. In this case, the recording head 9 may be equipped with a row of ejection ports 22Em for ejecting the clear emulsion ink.

[0025] (3) Recording system configuration Figure 4 is a block diagram illustrating the schematic configuration of a recording system in this embodiment, including the host device 312 and the control system within the recording device 100. The host device 312 is an information processing device connected to the recording device 100, such as a personal computer or a digital camera. The host device 312 includes a CPU 400, a memory 401, a storage unit 402, an input unit 403 such as a keyboard or mouse, and an interface 404 for communication with the recording device 100. The CPU 400 performs various processes according to programs stored in the memory 401. These programs are supplied from an external device such as a CD-ROM for storage in the storage unit 402. Programs may also be pre-stored in the storage unit 402.

[0026] The host device 312 is connected to the recording device 100 via interface 404 and transmits image processing information to the recording device 100, including image data represented by R, G, and B in the image processing process described later, and a table for subsequent image processing (recording control information). Based on the transmitted image processing information, the recording device 100 performs image processing such as color processing and binarization, as well as correction processing of recording characteristics, as described later. The host device 312 may perform at least a part of the color processing, image processing, and correction processing.

[0027] The recording device 100 has a main control unit 300. The main control unit 300 is equipped with a CPU 301 that performs processing operations such as calculation, selection, discrimination, and control, as well as recording operations. The main control unit 300 also includes a ROM 302 for storing control programs to be executed by the CPU 301, a RAM 303 used as a buffer for recording data, and input / output ports 304. Memory 313 stores mask patterns, which will be described later. The input / output ports 304 are connected to drive circuits 305, 306, 307, and 308 for the transport motor (LF motor) 309, carriage motor (CR motor) 310, recording head 9, and actuators in the heater 10. The main control unit 300 is connected to the host device 312 via an interface circuit 311.

[0028] (4) Recording media The recording device in this embodiment records on a low-permeability recording medium that is resistant to moisture penetration. A low-permeability recording medium, as used here, is a medium that has no water absorption or absorbs very little water. Therefore, with water-based inks that do not contain organic solvents, the ink is repelled and no image can be formed. On the other hand, low-permeability recording media have excellent water resistance and weather resistance, making them suitable as media for forming recordings used outdoors. Typically, a recording medium having a water contact angle of 45° or more, preferably 60° or more, at 25°C is used as a low-permeability recording medium.

[0029] Low-permeability recording media include recording media in which a plastic layer is formed on the outermost surface of the substrate, or recording media in which no ink-receiving layer is formed on the substrate. Alternatively, they may be sheets, films, or banners made of glass, Yupo, or plastic. Examples of such plastics include polyvinyl chloride, polyethylene terephthalate, polycarbonate, polystyrene, polyurethane, polyethylene, or polypropylene. Because these low-permeability recording media have excellent water resistance, light resistance, and abrasion resistance, they are generally used for recording materials for outdoor displays.

[0030] (5) Ink composition (Ink composition overview) The details of each ink that makes up the ink set used in this embodiment are described below. Unless otherwise specified, "parts" and "%" refer to mass.

[0031] (5-1) Composition of each ink The composition of each ink will be described in detail below. The colorant inks (C, M, Y, K) and reaction solution (RCT) used in this embodiment all contain a water-soluble organic solvent. For reasons of wetting and moisturizing properties of the face surface of the recording head 9, the water-soluble organic solvent is preferably one with a boiling point of 150°C to 300°C. Furthermore, from the viewpoint of its function as a film-forming aid for resin fine particles and its swelling solubility in the recording medium on which the resin layer is formed, the following are particularly preferred. Specifically, ketone compounds such as acetone and cyclohexanone, ethylene glycol derivatives such as tetraethylene glycol dimethyl ether, and heterocyclic compounds having a lactam structure represented by N-methyl-pyrrolidone and 2-pyrrolidone are particularly preferred. From the viewpoint of discharge performance, the content of the water-soluble organic solvent is preferably 3 wt% or more and 30 wt% or less. The water-soluble organic solvent can be used alone or as a mixture. Furthermore, it is desirable to use deionized water as the water. The content of the water-soluble organic solvent in the reaction solution (RCT) is not particularly limited, but in order to give the colorant inks (C, M, Y, K) the desired physical properties, surfactants, defoamers, preservatives, or fungicides may be added as appropriate in addition to the above-mentioned components.

[0032] Surfactants are used as penetrants to improve the penetration of ink into inkjet-specific recording media. The more surfactant added, the stronger its property of lowering the surface tension of the ink, thereby improving the wettability and penetration of the ink into the recording media.

[0033] Furthermore, the pH of each ink in this embodiment is stable on the alkaline side, with a value of 8.5 to 9.5. From the viewpoint of suppressing the dissolution and deterioration of components that come into contact with each ink in the recording device or recording head, and the decrease in the solubility of the dispersed resin in the ink, it is preferable that the pH of each ink be between 7.0 and 10.0. In addition, the colorant ink may include white ink (W).

[0034] (5-2) Reaction solution In this embodiment, a reaction solution is used to insolubilize some or all of the solid components of the colorant ink in order to solve image problems such as bleeding.

[0035] To insolubilize dissolved dyes, dispersed pigments, and resins, the reaction solution may include, for example, a solution containing polyvalent metal ions (e.g., magnesium nitrate, magnesium chloride, aluminum sulfate, iron chloride, etc.). As one type of cationic flocculation, a system using a low molecular weight cationic polymer flocculant can also be used for the purpose of neutralizing the charge of water-soluble resin fine particles and insolubilizing anionic soluble substances.

[0036] Another reaction system that utilizes a difference in pH can be used to insolubilize components using a reaction solution. As mentioned earlier, most colorant inks used in inkjet recording are stable on the alkaline side due to the properties of their colorants, and their pH is generally around 7 to 10. From an industrial standpoint and considering the influence of the external environment, the pH is often set to around 8.5 to 9.5. To agglomerate and solidify such colorant inks, an acidic solution can be mixed in, and by changing the pH, the stable state can be disrupted and the dispersed components can be agglomerated. An acidic solution can also be used as the reaction solution for this purpose.

[0037] (5-3) Water-soluble resin fine particles The colorant ink used in this embodiment contains water-soluble resin fine particles. In this embodiment, "water-soluble resin fine particles" means polymer fine particles that exist in a dispersed state in water. Alternatively, core-shell type resin fine particles in which the polymer composition differs between the core and shell parts constituting the resin fine particles, or resin fine particles obtained by using pre-synthesized acrylic fine particles as seed particles to control the particle size and emulsion polymerization around them, may also be used. Furthermore, hybrid type resin fine particles in which different resin fine particles, such as acrylic resin fine particles and urethane resin fine particles, are chemically bonded may also be used.

[0038] Furthermore, the water-soluble resin fine particles do not necessarily need to be included in the colorant ink; they may also be included in a third ink, clear emulsion ink (Em), which is different from the colorant ink and reaction solution and does not contain colorants.

[0039] (6) Image processing Figure 5 is a block diagram illustrating the flow of the image data conversion process in this embodiment. Figure 5 shows the image processing procedure for converting input image data, represented by 8 bits (256 gradations) for each RGB color, input to the recording device 100, into 1 bit data for each ink color and outputting it. This recording system consists of a host device 312 and a recording device 100.

[0040] The host device 312 is, for example, a personal computer (PC) and has an application J1 and a printer driver (not shown) for the recording device 100 in this embodiment. The application J0001 performs the process of creating image data to be passed to the printer driver based on information specified by the user on the UI screen of the host device 312, and the process of setting recording control information that controls recording.

[0041] Image data and recording control information processed by application J0001 are passed to the printer driver during recording. The main control unit 300 of the recording device performs image processing on the image data transferred from the host device 312 on which the printer driver is installed, via the interface circuit 311.

[0042] The main control unit 300 has an image processing configuration that includes a pre-processing unit J0002, a post-processing unit J0003, a gamma correction unit J0004, and a half-toning unit J0005. Each of these units is realized by the CPU 301 of the main control unit 300 executing a program stored in the ROM 302 or memory 313, etc. Some or all of the functions of each of these units may be realized by hardware such as an ASIC or electronic circuit. Each process is briefly described below.

[0043] The pre-processing unit J0002 performs color gamut mapping. This process involves data conversion to map the color gamut reproduced by sRGB standard image data (R, G, B) into the color gamut reproduced by the recording device 100. Specifically, 256-level data, each represented by 8 bits for R, G, and B, is converted into 8-bit R, G, and B data (RGB values) with different color gamuts using a 3D LUT (Lookup Table).

[0044] The subsequent processing unit J0003 converts the R, G, and B data, whose color gamut mapping was performed by the preceding processing unit J0002, into 8-bit color separation data, which is a combination of inks that reproduces the color represented by this data, based on a 3D LUT for subsequent processing. In this embodiment, four inks, C, M, Y, and K, are used as colorant inks, so the subsequent processing unit J0003 converts the R, G, and B data into color separation data, which is a combination of these ink colors. Here, as with the preceding processing unit J0002, interpolation is used in conjunction with the 3D LUT for the conversion. Furthermore, the subsequent processing unit J0003 also generates 8-bit color separation data for the reaction solution (RCT) in the ink combination. That is, the subsequent processing unit J0003 converts the R, G, and B data into color separation data for C, M, Y, K, and RCT.

[0045] The gamma correction unit J0004 performs a conversion of the density values ​​(gradation values) for each color in the color separation data for each color obtained by the subsequent processing unit J0003. Specifically, it uses a one-dimensional LUT to perform a conversion that linearly maps the color separation data to the gradation characteristics of the recording device 100.

[0046] The half-toning unit J0005 performs quantization processing to convert each of the 8-bit color separation data for each color, which has undergone gamma correction, into 1-bit data. In this embodiment, the dithering method is used to convert the 256-level 8-bit data into 1-bit data of "1" or "0" (binarization). This makes it possible to obtain binary data indicating whether or not the recording device ejects ink. The quantization processing will be explained in detail later.

[0047] The mask processing unit J0006 performs masking on the dot arrangement of each color determined by the half-toning unit J0005 using multiple mask patterns that complement each other. This generates recording data for each color C, M, Y, K, and RCT for each recording scan in multi-pass recording. Figures 11(a) and (b) show the mask patterns of the reaction solution, which are mask patterns for completing the image in four recording scans. In Figures 11(a) and (b), the pixels filled in black represent the pixels that can be recorded, and the regions indicated as 1P, 2P, 3P, and 4P are mask patterns corresponding to each scan, and these are complementary.

[0048] The mask pattern for the reaction solution in this embodiment, shown in Figure 11(a), reduces interference with the dither pattern for the reaction solution shown in Figure 6(e). The method for generating a mask pattern that reduces interference between the dither pattern and the mask pattern follows the method disclosed in Japanese Patent Application Publication No. 2007-306551, and the arrangement of recordable pixels is generated considering the overlap (logical AND) with the dot arrangement determined by the dither pattern. That is, the distribution of recordable pixels in the mask pattern when superimposed with the dot arrangement has few low-frequency components and is well dispersed. The interference reduction effect is compared with a comparative mask pattern, Figure 11(b), generated without interference reduction processing with the dither pattern. Figure 12(c) shows the dot arrangement when a uniform solid image with 20 / 255 grayscale is input as the input image for the reaction solution in this embodiment. Figures 12(a) and (b) show the dot arrangement in each scan when unfolded using the mask patterns of Figures 11(a) and (b) relative to Figure 12(c). In Figures 12(a) and (b), the regions labeled 1P, 2P, 3P, and 4P represent the dot arrangement corresponding to each scan. The dot arrangement diagram 12(b) for each scan, unfolded using the comparison mask pattern Figure 11(b) generated without interference reduction processing with the dither pattern, shows a large bias in the number of reaction solution dots assigned in each scan. On the other hand, the dot arrangement diagram 12(a) for each scan, unfolded using the mask pattern Figure 11(a) generated with interference reduction processing with the dither pattern in this embodiment, shows a small bias in the number of reaction solution dots assigned in each scan. Thus, by using the masking process with the mask pattern generated with interference reduction processing with the dither pattern, the dot data for each scan is not biased towards a particular scan, and is well distributed within a certain range. This good dispersion suppresses image defects such as density unevenness and texture.

[0049] The generated recording data is supplied to the head drive circuit J0007 at the appropriate timing during the multiple recording scans performed in multi-pass recording. The recording data input to the head drive circuit J0007 is then converted into drive pulses for the recording head J0008, and ink is ejected from the ejection ports 30 of each color at predetermined timings. As a result, ink is ejected according to the recording data, and an image is recorded on the recording medium.

[0050] In the example shown in Figure 5, the preceding processing unit J0002 and subsequent units are implemented in the recording device 100, but some of the processing units may be executed in the printer driver of the host device 312, for example.

[0051] (7) Quantization process Next, the quantization process will be explained. Figure 6 shows the dither patterns for each color used in the dithering process, which is the quantization process in this embodiment. Figure 6(a) shows the dither pattern for cyan, (b) for magenta, (c) for yellow, (d) for black, and (e) for the reaction solution. As shown in Figure 6, the dither pattern in this embodiment consists of a pattern with threshold values ​​from 0 to 255 set in a 16x16 pixel grid, and the quantization process is performed by unfolding this dither pattern in a tile-like manner vertically and horizontally. Data from 0 to 255 is input to each pixel of each color, and as a result of comparing it with the threshold value of the dither pattern of the corresponding pixel, if the input data is greater than the threshold value, it is represented as "1" (dot data generation), and if it is less than the threshold value, it is represented as "0" (no dot data), and a pseudo-halftone image is expressed.

[0052] In this embodiment, in order to improve the contact establishment between the colorant ink dots and the reaction solution dots, the reaction solution dither pattern is generated by filling in the reaction solution dither pattern thresholds in ascending order, starting from the pixel positions where the colorant ink has a small dither threshold. The specific generation method is shown below in accordance with the flowchart in Figure 13.

[0053] In S1000, the generation of the reaction solution dither pattern is started, and in S1001, the natural numbers N and M are set to "1". In S1002, the Nth (=1)th smallest pixel in the cyan ink dither pattern is identified, and a threshold M (=0) is set for the pixel at the same position in the reaction solution dither pattern. Based on the fact that the pixel with the smallest threshold "0" in the cyan ink dither pattern Figure 6(a) is at position (horizontal 5, vertical 16), the smallest threshold "0" in the reaction solution dither pattern Figure 6(e) is set at position (horizontal 5, vertical 16). Next, in S1003, the value of the natural number M is increased by 1. Subsequently, in S1004, the Nth (=1)th smallest pixel in the magenta ink dither pattern is identified, and a threshold M (=1) is set for the pixel at the same position in the reaction solution dither pattern. Based on the fact that the pixel with the smallest threshold "0" in the magenta ink dither pattern Figure 6(b) is located at (horizontal 9, vertical 12), the second smallest threshold "1" in the reaction solution dither pattern Figure 6(e) is set to the position (horizontal 9, vertical 12). Next, in S1005, the value of the natural number M is increased by 1. Subsequently, in S1006, the pixel with the N (=1) smallest value in the yellow ink dither pattern is identified, and the threshold M (=2) is set for the pixel at the same position in the reaction solution dither pattern. Based on the fact that the pixel with the smallest threshold "0" in the yellow ink dither pattern Figure 6(c) is located at (horizontal 5, vertical 3), the third smallest threshold "2" in the reaction solution dither pattern Figure 6(e) is set to the position (horizontal 5, vertical 3). Next, in S1007, the value of the natural number M is increased by 1. Next, in S1008, the pixel with the N (=1) smallest threshold in the black ink dither pattern is identified, and a threshold M (=3) is set for the pixel at the same position in the reaction solution dither pattern. Based on the fact that the pixel with the smallest threshold "0" in the black ink dither pattern Figure 6(d) is at position (2 horizontally, 12 vertically), the fourth smallest threshold "3" in the reaction solution dither pattern Figure 6(e) is set at position (2 horizontally, 12 vertically). Next, in S1009, the value of the natural number M is increased by one. After this, the process proceeds to S10100, and if the reaction solution dither pattern is complete, the process proceeds to S1012 and terminates; otherwise, it returns to S1002.In other words, the second smallest threshold for cyan is "1", the second smallest threshold for magenta is "1", the second smallest threshold for yellow is "1", the second smallest threshold for black is "1", and so on, identifying the threshold locations for each color ink in ascending order, and setting the thresholds in ascending order at the same positions in the reaction solution dither pattern in Figure 6(e).

[0054] For comparison with the reaction solution dither pattern in this embodiment shown in Figure 6(e), Figure 6(f) shows the reaction solution dither pattern generated without using the method of this embodiment. Figures 7(a) to (f) show, as an example, the dot arrangement when a uniform solid image with 10 / 256 gradations is input as the input image for each dither pattern in Figures 6(a) to (f). Based on these, Figure 8 shows the dot overlap positions of each colorant ink and the reaction solution in the 10 / 256 solid image of each colorant ink and the 10 / 256 solid image of the reaction solution. Figures 8(a) to (d) show the dot overlap between cyan, magenta, yellow, and black and the reaction solution when using the reaction solution dither pattern in this embodiment, and it can be seen that the number of overlapping dots for each color is 3 dots, 3 dots, 2 dots, and 3 dots. Figures 8(e) to (h) show the dot overlap between cyan, magenta, yellow, and black and the reaction solution when a dither pattern generated without using the method of this embodiment is used for the reaction solution. It can be seen that the number of overlapping dots for each color is 1 dot, 0 dots, 1 dot, and 0 dots. Thus, it can be seen that the dot overlap when using the reaction solution dither pattern of this embodiment shown in Figures 8(a) to (d) is greater than when using a dither pattern generated without using the method of this embodiment shown in Figures 8(e) to (h) for the reaction solution. According to this embodiment, as a result of increasing the dot overlap between the low-gradation side of the colorant ink and the low-gradation side of the reaction solution, the following dot overlap characteristics occur depending on the gradation. Specifically, there is more dot overlap between the dots on the side of the colorant ink below the median of all gradations and the dots on the side of the reaction solution below the median of all gradations than there is dot overlap between the dots on the side of the colorant ink below the median of all gradations and the dots on the side of the reaction solution below the median of all gradations. Figures 9(a),(b),(c),(d), and(e) show the dot arrangement on the lower gradation side of the median value for each colorant ink and reaction solution. In this embodiment, a total of 256 gradations can be expressed, so these figures represent the dot arrangement at the 128th gradation, which is the median gradation. Figures 9(f),(g),(h), and(i) show the dot arrangement on the higher gradation side of the median gradation for each colorant ink. In other words, Figures 9(f),(g),(h), and(i) are the inverted dot arrangements of Figures 9(a),(b),(c),(d), and(e).When the overlapping dots between the low-gradation dot arrangement diagrams 9(a)(b)(c)(d) of each colorant ink in this embodiment and the low-gradation dot arrangement diagram 9(e) of the reaction solution are extracted, the result is as shown in Figure 10(a)(b)(c)(d). On the other hand, when the overlapping dots between the high-gradation dot arrangement diagrams 9(f)(g)(h)(i) of each colorant ink in this embodiment and the low-gradation dot arrangement diagram 9(e) of the reaction solution are extracted, the result is as shown in Figure 10(e)(f)(g)(h). Counting the number of overlapping dots on the low-gradation side of the reaction solution against the dot arrangement diagrams 9(a)(b)(c)(d) for each colorant ink yields 81, 84, 72, and 73, respectively. In contrast, counting the number of overlapping dots on the low-gradation side of the reaction solution against the dot arrangement diagrams 9(f)(g)(h)(i) for each colorant ink yields 48, 45, 57, and 56, respectively. This indicates that there is more overlapping dots on the low-gradation side of the colorant ink and the reaction solution than there is overlapping dots on the high-gradation side of the colorant ink and the reaction solution. Thus, according to this embodiment, the contact probability of the colorant ink can be increased with less reaction solution, and image defects caused by reaction solution beading can be suppressed.

[0055] As described above, following this embodiment, the threshold locations of the dither patterns of each colorant ink are identified in ascending order, and thresholds are set in ascending order at the same positions in the reaction solution dither pattern. By performing image formation using the dither patterns generated in this way, it is possible to suppress image defects such as density unevenness and texture caused by bias in dot placement for each recording scan of the reaction solution, while also suppressing image defects caused by beading of the reaction solution.

[0056] <<Second Embodiment>> In this embodiment, while based on the example described in the first embodiment, a different example of a method for generating a reaction solution dither pattern will be explained along the flowcharts in Figures 16(a) and (b).

[0057] In Figure 16(a), reference table 1 is generated based on the dither patterns of each colorant ink. The generation of reference table 1 is started in S2000, and in S2001, the natural number N is set to "1". In S2002, pixel N (=1) is set as the pixel of interest. In this embodiment, pixel 1 is set as a pixel with dimensions (vertical 1, horizontal 1), and the process will be described as moving to adjacent pixels from here on. In S2003, the color with the smallest and second smallest threshold values ​​at the pixel of interest in the dither pattern of each colorant ink is identified, and these values ​​are set to A1 and A2, respectively. Subsequently, in S2004, the value of A1 + A2 is set for the pixel of interest in reference table 1. Figure 14 shows reference table 1 for generating the dither pattern of the reaction solution in this embodiment, and the results of performing the following arithmetic on the threshold values ​​of each pixel in the dither patterns of the four colorant inks shown in Figures 6(a) to (d) are described. At position (vertical 1, horizontal 1) in Figure 14, the value obtained by adding the smallest value and the second smallest value from the thresholds at position (vertical 1, horizontal 1) in Figures 6(a) to (d) is written. The smallest threshold is "49" in Figure 6(a), and the second smallest threshold is "53" in Figure 6(d), so their sum, "102," is written at position (vertical 1, horizontal 1) in Figure 14. Figure 14 is the result of performing the same arithmetic for all pixel positions. From the reference data in Figure 14, it can be seen that pixels with smaller values ​​tend to be more likely to form colorant ink dots. After this, proceed to S2005, and if reference table 1 is completed, proceed to S2007 and finish, otherwise return to S2002.

[0058] Figure 16(b) shows the generation of a dither pattern for the reaction solution based on reference table 1. The generation of the dither pattern for the reaction solution is started in S2100, and in S2101, the natural number N is set to "1". In S2102, the pixel corresponding to the Nth (=1)th smallest numerical value in reference table 1 is identified, and the Nth (=1)th smallest threshold value "0" is set for the pixel at the same position in the reaction solution dither pattern. After this, the process proceeds to S2103, and if the reaction solution dither pattern is complete, it proceeds to S2105 to finish; otherwise, it returns to S2102. Figure 15 shows the reaction solution dither pattern in this embodiment, created based on reference table 1 in Figure 14. The locations of the numerical values ​​in reference table 1 in Figure 14 are identified in ascending order, and thresholds are set in ascending order for the same positions in the reaction solution dither pattern. In the reference data figure 14, the smallest value is "7" at position (vertical 9, horizontal 13). Therefore, the smallest value, "0", is set at position (vertical 9, horizontal 13) in the reaction solution dither pattern figure 15. In figure 14, the next smallest value is "12" at position (vertical 7, horizontal 3). Therefore, the next smallest value, "1", is set at position (vertical 7, horizontal 3) in the reaction solution dither pattern figure 15. Similarly, locations are identified in ascending order from the smallest values ​​in the reference data figure 14, and thresholds are set in ascending order at the same positions in the reaction solution dither pattern figure 15.

[0059] As described above, reference data is created from the dithering pattern threshold of the colorant ink to identify positions where colorant ink dots are likely to form, and the dithering pattern threshold of the reaction solution is set sequentially from the positions where colorant ink dots are likely to form. By performing image formation using the dithering pattern generated in this way, it is possible to suppress image defects caused by beading of the reaction solution.

[0060] <<Third Embodiment>> In this embodiment, a different method for generating the reaction solution dither pattern will be described, based on the example described in the second embodiment. In this embodiment, when the dot size is larger than the pixel size of the dither pattern, and the dot size is approximately 3 pixels vertically and 3 pixels horizontally, the reaction solution dither pattern is generated by determining the degree of dot overlap considering the dot size. The method for generating the reaction solution dither pattern will be described below in accordance with the flowcharts in Figures 20(a), (b), (c), and (d).

[0061] In Figure 20(a), a reference table 2 is generated for each color based on the dither pattern of each colorant ink. The generation of reference table 2 is started in S3000, and in S3001, the natural number N is set to "1". In S3002, the pixel with the Nth (=1st) largest threshold in the dither pattern of each colorant ink is identified and designated as the pixel of interest. In S3003, the threshold of the pixel of interest is compared with the thresholds of adjacent pixels. In S3004, for adjacent pixels whose threshold value is greater than that of the pixel of interest, the threshold value of the pixel of interest is used, and this value is set in reference table 2. After this, the process proceeds to S3005, and if reference table 2 is complete, it proceeds to S3007; otherwise, it returns to S3002. The reference tables 2 for each colorant ink generated according to the flowchart in Figure 20(a) are shown in Figures 17(a) to (d). Figures 17(a) to 17(d) are reference data showing the threshold values ​​of each pixel in the dither patterns of the four color inks shown in Figures 6(a) to 17(d), enlarged to a 3x3 size. As the threshold values ​​are enlarged, Figure 17 expands the area to include adjacent pixels from 16x16 to 17x17.

[0062] Next, in Figure 20(b), a reference table 3 is generated based on the reference table 2 for each color ink. The generation of the reference table 3 is started in S3100, and the natural number N is set to "1" in S3101. In S3102, pixel N (=1) is set as the pixel of interest. In this embodiment, pixel 1 is set as a pixel with dimensions (vertical 1, horizontal 1), and the process will be described as moving to adjacent pixels from here on. In S3003, the color with the smallest value and the second smallest value in the reference table 2 for each color ink are identified, and these values ​​are set to B1 and B2, respectively. Subsequently, in S3004, the value of B1 + B2 is set for the pixel of interest in the reference table 3.

[0063] Figures 18(a) to (c) show reference table 3 for generating the dither pattern of the reaction solution in this embodiment.

[0064] Figures 17(a) to (d) show the sum of the smallest and second smallest threshold values ​​for the same pixel position. The smallest threshold is "3" in Figure 17(d), and the second smallest threshold is "12" in Figure 17(b), so their sum, "15," is shown at the same pixel position in Figure 18(a). The process then proceeds to S3205, and if reference table 3 is complete, proceeds to S3207 to finish; otherwise, returns to S3202. Figure 18(a) shows reference table 4, which is the result of performing the same arithmetic for all pixel positions.

[0065] Next, in Figure 20(c), reference table 4 is generated based on reference table 3. Generation of reference table 4 is started in S3200, and in S3201, the natural number N is set to "1". In S3202, pixel N (=1) is set as the pixel of interest. In S3203, the value obtained by adding the value of the pixel of interest and the values ​​of adjacent pixels in reference table 3 is calculated and set as C. In S3204, C is set as the pixel of interest in reference table 4. Figure 18(b) shows reference table 4, and for a 3x3 region centered on the pixel of interest, the sum of the threshold values ​​from Figure 18(a) showing reference table 3 is written in each image. The "382" written at position (vertical 1, horizontal 1) in Figure 18(b) showing reference table 4 is the sum of the threshold values ​​of the 3x3 pixels enclosed by the dotted line in Figure 17(a) showing reference table 3. Similarly, the sum of the values ​​of the 3x3 regions centered on the pixel of interest in Figure 18(a) is set as the pixel of interest in Figure 18(b) showing reference table 4.

[0066] Next, in Figure 20(d), a dither pattern for the reaction solution is generated based on reference table 4. In S3300, the generation of the reaction solution dither pattern is started, and in S3301, the natural number N is set to "1". In S3302, the pixel with the smallest numerical value in reference table 4 is identified, and the Nth (=1)th smallest threshold is set for the pixel at the same position in the reaction solution dither pattern. Looking at Figure 18(b) which shows reference table 4, the pixel with the smallest numerical value is found to be "47" at position (vertical 6, horizontal 4). Based on this, the smallest threshold "0" in the reaction solution dither pattern Figure 19 in this embodiment is set at position (vertical 6, horizontal 4). Then, in S3303, the numerical value of the pixel at the same position in reference table 3 is replaced with the numerical value D, and in S3304, reference table 4 is updated based on the flow in Figure 20(c). In this embodiment, for convenience, the numerical values ​​in the 3x3 region centered on (vertical 6, horizontal 4) in Figure 18(a) showing reference table 3 are replaced with the largest numerical value in the table, "219", as numerical value D, and Figure 18(c) showing the updated reference table 3 is obtained based on the flow in Figure 20(c). After this, the process proceeds to S3305, and if the dither pattern of the reaction solution is complete, the process proceeds to S3307 and ends; otherwise, it returns to S3302. The same arithmetic is repeated thereafter, and the thresholds are summed for the 3x3 region centered on the pixel of interest in Figure 18(c) showing the updated reference table 3 to identify the pixel with the smallest numerical value, and the second smallest threshold "1" in the reaction solution dither pattern Figure 19 is set, and this arithmetic is repeated.

[0067] As described above, the threshold range for the dither pattern of the colorant ink is expanded, reference data is created based on this to identify positions where colorant ink dots are likely to form, and the threshold for the dither pattern of the reaction solution is set sequentially, starting from positions where reaction solution dots are likely to overlap with colorant ink dots. By performing image formation using the dither pattern generated in this way, it becomes possible to suppress image defects caused by reaction solution beading.

[0068] In Embodiments 1 to 3, the case where all cyan, magenta, yellow, and black dither patterns are referenced to generate the reaction solution dither pattern was described, but it is not necessary to reference the dither patterns of all colors. Figure 21 is a graph showing how the amount of ink used for each color changes from white to black in the print data. The left end of the horizontal axis of the graph represents the case where the print data is white, and the right end represents the case where the print data is black. As can be seen from the graph, the amount of reaction solution used increases in proportion to the amount of color ink, so in the region where the print data is close to white, the amount of cyan, magenta, and yellow ink used is small, and the amount of reaction solution used is also small. On the other hand, black ink is only used when cyan, magenta, and yellow inks are used in large quantities, so the amount of reaction solution used is large. Therefore, the probability of contact between the colorant ink and the reaction solution dots can also be increased by referencing only the dither patterns of cyan, magenta, and yellow inks, which are the colors for which you want to increase the probability of contact with the reaction solution.

[0069] Furthermore, while embodiments 1 to 3 described a recording device using four colorant inks—cyan, magenta, yellow, and black—the colorant ink configuration may be other. For example, a recording device using six color inks, including light cyan (LC) and light magenta (LM) with different colorant concentrations in addition to the four colors mentioned above, may be used. To generate the dither pattern of the reaction solution, the dither patterns of all six colors may be referenced, or only the dither patterns of some of the colors may be referenced. Figure 22 is a graph showing how the amount of ink used for each color changes from white to black in print data when six colorant inks are used. As can be seen from the graph, the amount of reaction solution used increases in proportion to the amount of colorant ink, so in areas where the print data is close to white, the amount of light cyan, light magenta, and yellow inks with low colorant concentrations is used, and the amount of reaction solution used is also small. On the other hand, the use of cyan and magenta inks with high colorant concentrations begins when light cyan, light magenta, and yellow inks with low colorant concentrations are used in large quantities, so the amount of reaction solution used is large. Furthermore, since black ink is only used when cyan, magenta, and yellow inks are being used in large quantities, a large amount of reaction solution is used. Therefore, the probability of contact between the colorant ink and the reaction solution dots can be increased by generating the reaction solution dither pattern by referencing only the dither patterns of the low-colorant concentration light cyan, light magenta, and yellow inks, which are preferred to have a higher probability of contact with the reaction solution.

Claims

1. A recording means comprising multiple rows of discharge ports, including a first row of discharge ports arranged with multiple discharge ports for dispensing a colorant ink containing a colorant, and a second row of discharge ports arranged with multiple discharge ports for dispensing a reaction solution that reacts with the colorant, A quantity determination means for determining the amount of the colorant ink and the amount of the reaction solution to be applied to the recording medium based on input image data, A dot arrangement determination means that determines the dot arrangement of the colorant ink based on the amount of the colorant ink and a first dither pattern corresponding to the colorant ink, and determines the dot arrangement of the reaction solution based on the amount of the reaction solution and a second dither pattern corresponding to the reaction solution, Equipped with, A recording device characterized in that the first number, which is the number of pixels that overlap in the dot arrangement having a value lower than the median of all tones in the first dither pattern and the dot arrangement having a value lower than the median of all tones in the second dither pattern, is greater than the second number, which is the number of pixels that overlap in the dot arrangement having a value higher than the median of all tones in the first dither pattern and the dot arrangement having a value lower than the median of all tones in the second dither pattern.

2. The recording device according to claim 1, characterized in that the recording means comprises a series of ejection ports for dispensing cyan ink containing a cyan colorant, a series of ejection ports for dispensing magenta ink containing a magenta colorant, a series of ejection ports for dispensing yellow ink containing a yellow colorant, and a series of ejection ports for dispensing black ink containing a black colorant.

3. The recording apparatus according to claim 2, characterized in that the dot arrangement determination means determines the dot arrangement of the cyan ink based on a dither pattern corresponding to the cyan ink, determines the dot arrangement of the magenta ink based on a dither pattern corresponding to the magenta ink, determines the dot arrangement of the yellow ink based on a dither pattern corresponding to the yellow ink, and determines the dot arrangement of the black ink based on a dither pattern corresponding to the black ink.

4. In the dither pattern corresponding to the black ink, the number of overlapping pixels in the dot arrangement having a value lower than the median of all tones and the dot arrangement in the second dither pattern having a value lower than the median of all tones is: The recording device according to claim 3, characterized in that the number of overlapping pixels in a dot arrangement having a value lower than the median value of the entire dither pattern corresponding to the cyan ink and a dot arrangement having a value lower than the median value of the entire dither pattern is 1.

5. The recording device according to claim 1, characterized in that the threshold values ​​for each pixel of the second dither pattern are set in order from the pixel position where the threshold value of the first dither pattern is smallest.

6. The first reference table is obtained by performing an arithmetic operation on each pixel, where the threshold values ​​of two or more colors are added together in ascending order from the threshold values ​​of the pixels at the same position in each dither pattern of multiple color inks, and the sum of these values ​​is set for the pixels at the same position. The recording device according to claim 3, characterized in that the threshold values ​​for each pixel in the dither pattern of the reaction solution are set to decrease sequentially from the pixel at the same position as the pixel with the smallest value in the first reference table.

7. For each dither pattern of multiple color inks, the pixel with the largest threshold value is identified and designated as the pixel of interest. The first arithmetic procedure involves comparing the threshold values ​​of adjacent pixels with the threshold value of the pixel of interest, and replacing any pixels where the value of the adjacent pixel is larger with the threshold value of the pixel of interest. The tables for each color obtained by repeatedly performing the first arithmetic operation on each dither pattern of the multiple color inks, starting from the pixel with the largest threshold, are used as the second reference tables for each color. A new table is obtained as the third reference table by performing an arithmetic operation on each pixel to set the sum of the threshold values ​​for two or more colors in ascending order from the threshold value of the pixel at the same position in the second reference table for multiple color inks, and setting the sum of the values ​​for the pixel at the same position. Focusing on each pixel in the third reference table, and setting the numerical value obtained by adding the numerical values ​​of the pixel of interest and its adjacent pixels to the corresponding pixel at the same position, a new table is obtained, which is designated as the fourth reference table. The threshold in the dither pattern of the reaction solution is determined by setting the smallest threshold for the pixel at the same position as the pixel with the smallest value in the fourth reference table, and updating the third reference table by replacing the value at the same pixel position in the third reference table with a different value that is larger than the original value. The fourth reference table is updated by focusing on each pixel in the updated third reference table and setting the value obtained by adding the values ​​of the pixel of interest and its adjacent pixels to the corresponding pixel at the same position. The next smallest threshold in the dither pattern of the reaction solution is set at the pixel position with the smallest value in the fourth reference table, The recording device according to claim 3, characterized in that a threshold value is set for each pixel of the dither pattern of the reaction solution by repeatedly updating the third reference table and all of the fourth reference tables.

Images