JP2007268945A - Inkjet recording method and inkjet recording apparatus - Google Patents

Abstract

[Problem] To maintain high-quality black characters while suppressing bleeding between different colors using a black ink having a low permeability and a color ink having a high permeability.
In the vicinity of a color recording pixel determined to record color ink, the number of pixels determined to record black ink is detected, and whether or not color ink can be recorded on the color recording pixel is determined by the detected number of pixels. Judgment accordingly. Accordingly, it is possible to adjust the thinning rate of the color data stepwise according to the black density, and it is possible to thin out the color data to an appropriate amount only in a region where bleeding is likely to be a problem.
[Selection] Figure 4

Description

  The present invention relates to an ink jet recording method and an ink jet recording apparatus for recording an image on a recording medium using black ink and at least one color ink.

  Generally, a serial type ink jet recording apparatus includes a carriage on which recording means (recording head) and an ink tank are mounted, a transport means for transporting a recording medium, and a control means for controlling them. Then, a main recording scan that performs serial scanning while ejecting ink droplets from a plurality of ejection ports of the recording head, and a sub-scan that conveys the recording medium by an amount corresponding to the recording width in a direction intersecting the main recording scan. By repeating intermittently, an image is formed stepwise on the recording medium. Such an ink jet recording apparatus is widely useful as an output device for various apparatuses because it can form images on various recording media at high density and at high speed. Further, since an image is formed with ink ejected according to a recording signal while the recording head is not in contact with the recording medium, it is also known as a quiet recording method with a relatively low running cost. In recent years, many recording apparatuses that form color images using a plurality of colors of ink have been provided.

  When recording black characters or graphs in a general document, the sharpness and contrast of characters and the character density are regarded as important. In an ink jet recording apparatus, if an attempt is made to satisfy such quality requirements, the black ink to be used is often prepared so as to have low permeability to a recording medium. This is because if the ink adhering to the recording medium immediately permeates along the fibers of the recording medium, the outline becomes unclear due to bleeding (feathering) along the fibers, resulting in characters with poor sharpness. It is. Also, if the penetration speed is high, penetration in the depth direction of the recording medium proceeds more than necessary, and the amount of ink remaining on the surface is small, resulting in an image with low density and contrast. If the ink has a low permeability and a low absorption rate to the recording medium, it is fixed in a nearly circular shape near the surface of the recording medium where the ink droplets land, so sharpness, contrast, and image density can be reduced. I can expect enough. As described above, the ink prepared so as to have low permeability is disclosed in Patent Document 1 and the like.

  On the other hand, when recording a color image using a plurality of color inks, if these inks are in a low penetrability state, the different color inks come into contact with each other on the surface of the recording medium before they penetrate into the recording medium, and the inks are blurred. A matching situation arises. In such a case, an image detrimental effect such as mixed color bleeding (hereinafter referred to as bleeding) occurs on the surface of the recording medium. Therefore, in an ink jet recording apparatus that forms a color image using a plurality of color inks, the ink is often prepared so as to have high permeability to a recording medium. Such ink is disclosed in Patent Document 2 and the like.

  However, many documents that record black characters in a color image are now demanded. In such a case, bleeding between the black ink and the color cannot be avoided. Specifically, the black ink with low penetrability oozes out into a color area in contact with the black ink and degrades the image. Bleeding that occurs between black and color is easily confirmed visually, and has been regarded as one of the problems of ink jet recording apparatuses.

  Several proposals have already been made for such bleeding. For example, Patent Document 3 discloses a recording apparatus provided with fixing means such as a heat fixing device. Even when an ink having a low permeation rate is used, if the recording medium is heated during recording or immediately after recording, the ink is suitably fixed on the surface of the recording medium without causing inadvertent bleeding or penetration.

  Patent Document 4 discloses a technique of absorbing black ink bleeding in the process black region by providing a process black region formed of color ink (CMY) with high penetrability around the black ink with low penetrability. Is disclosed. According to this, since the process black recorded by the mixing of the same highly permeable color ink is in contact with the color ink, bleeding does not occur without oozing each other. On the other hand, in the black image area other than the boundary portion, the recording with the black ink having low permeability is performed, so that it is possible to maintain the high density characteristic of the black ink.

  Further, Patent Document 5 and the like disclose a recording method in which a color ink that reacts with a black image is applied as a background of a black image. According to this, since the black ink is applied onto the recording medium into which the color ink has already permeated, the black ink is easily adapted to the recording medium and bleeding is suppressed. Further, since the color ink and the black ink as the base react with each other, the color material tends to remain on the surface of the recording medium, and a high-density image can be expected.

  Furthermore, Patent Document 6 discloses a method of thinning out color image data adjacent to black image data in advance. In this way, since a blank area is provided between the black ink recording position and the color ink recording position, contact between the inks on the recording medium is avoided, and bleeding can be suppressed.

Japanese Patent Laid-Open No. 9-25442 JP 55-65269 A JP-A-11-129460 Japanese Patent Laid-Open No. 6-135012 JP-A-8-281930 JP-A-6-135015

  However, even when the various methods described above are employed, the bleeding problem cannot be solved suitably. For example, the provision of a fixing unit as disclosed in Patent Document 3 increases the size of the recording apparatus and increases the size and cost of the apparatus itself. In the case of an ink jet recording apparatus for personal use characterized by being small and capable of being provided at a low price, such a configuration is not very realistic. In addition, since the recording medium is intermittently conveyed, there is a possibility that a new problem of uneven conveyance with respect to the fixing device may be raised.

  In addition, in the methods disclosed in Patent Document 4 and Patent Document 5, the bleeding of the black ink is surely reduced, but the characteristics of the color ink appear in the contour portion of the black image. The result is a lack of sharpness for certain characters.

  On the other hand, according to the method described in Patent Document 6, bleeding can be suppressed while maintaining sharpness of black characters. However, since the color image data in contact with the black data is uniformly thinned out, depending on the recording medium and the type of image, the thinned out part is noticeable in white, leading to a new image problem of white spots. There was a case.

  The degree of bleeding varies depending on the density of the black image and the state of the color image located in the vicinity thereof. That is, there is a case where it is not necessary to thin out color image data as in Patent Document 6 at a boundary where bleeding is not so noticeable. As a result of intensive studies, the present inventors have focused on the fact that the degree of bleeding and the conspicuousness can change depending on the recording rate of black data and color data, and the type of color. Then, it was determined that the recording method capable of maintaining black character quality while moderately suppressing bleeding should be changed depending on the recording rate of black data and color data.

  The present invention has been made in view of the above points, and an ink jet capable of maintaining high-quality black characters while suppressing bleeding while using a black ink with low penetrability and a color ink with high penetrability. An object is to provide a recording method.

  Therefore, in the present invention, for each pixel of the recording medium that is arranged at a predetermined recording resolution using black ink and one or more color inks that are relatively more permeable to the recording medium than the black ink. In the inkjet recording method for forming an image according to recording / non-recording of the black ink and color ink determined based on image data, in the vicinity of a color recording pixel determined to record at least one color ink, The method includes a step of detecting the number of pixels determined to record the black ink, and a step of determining whether or not the color ink can be recorded on the color recording pixels according to the number of pixels.

  Further, based on image data, each pixel of the recording medium arranged at a predetermined recording resolution using black ink and one or more color inks having a relatively higher permeability to the recording medium than the black ink is used. In the inkjet recording apparatus that forms an image according to recording / non-recording of the black ink and color ink determined in advance, the black ink is recorded in the vicinity of a color recording pixel determined to record at least one color ink. Then, there are provided means for detecting a predetermined number of pixels and means for judging whether or not the color ink can be recorded on the color recording pixels according to the number of pixels.

  According to the present invention, it is possible to adjust the thinning rate of the color data located in the vicinity in accordance with the black density, so that the color data can be thinned out to an appropriate amount only in an area where bleeding is likely to be a problem.

  Embodiments applicable to the present invention will be specifically described below with reference to the drawings.

  FIG. 1 is a perspective view for explaining a schematic configuration of a color ink jet recording apparatus applied in the present embodiment. In the figure, reference numeral 202 denotes a recording head cartridge, which is composed of a recording head 201 capable of ejecting four color inks (black, cyan, magenta, and yellow) and an ink tank that stores ink supplied to the recording head 201, respectively. Has been. In the present embodiment, the black (K) ink is prepared so that the penetrability into the recording medium is relatively low with emphasis on character quality. On the other hand, cyan (C), magenta (M), and yellow (Y) are prepared so as to have higher permeability to the recording medium than black ink so that bleeding between different colors can be avoided.

  Reference numeral 103 denotes a paper feed roller which, together with the auxiliary roller 104, rotates in the direction of the arrow while holding down the recording medium 107 and conveys the recording medium 107 in the Y direction. A paper feed roller 105 feeds the recording medium into the apparatus. The pair of conveyance rollers 103 and the pair of paper feed rollers 105 also play a role of maintaining the smoothness of the recording surface by stretching the recording medium 107 in an area where recording is performed by the recording head 201 from both sides. A carriage 106 is capable of reciprocating in the X direction in the figure with the recording head cartridge 202 mounted. During the non-recording operation of the recording apparatus or when the recovery operation of the recording head is performed, the carriage 106 is disposed at a home position H indicated by a dotted line in the drawing.

  When the recording start command is received, the recording medium 107 is fed by the paper feed roller 105 and positioned in a recordable area by the recording head 201. The carriage 106 located at the home position H moves in the X direction at a predetermined speed, and during this movement, ejection corresponding to image signals is executed from a plurality of recording elements provided in the recording head 201. When recording in an area corresponding to the recording width of the recording head is performed by such recording scanning, the pair of transport rollers 103 and the pair of paper feed rollers 105 are rotated, and the recording medium is rotated by Y corresponding to the recording width. Transport in the direction. Images are sequentially formed on the recording medium by alternately repeating such recording scanning and conveying operation.

  Although not shown in the drawing, at the home position H, a capping unit for capping the ejection port surface of the recording head 102, a suction unit for removing thickened ink and bubbles from the capped recording head, etc. Is provided. A cleaning blade supported so as to protrude toward the recording head 201 is provided on the side of the capping unit. When the recording head 201 after the recovery operation moves in the X direction, an unnecessary ink droplet or dirt on the ejection port surface can be wiped off by projecting the cleaning blade into the moving path of the recording head.

  FIG. 2 is a schematic diagram for explaining the ejection mechanism of the recording head 201. Reference numeral 308 denotes a silicon plate. A plurality of electrothermal transducers 303, a circuit configuration for transmitting signals to the electrothermal conversion elements 303, a temperature sensor for detecting the temperature of the recording head, a sub heater, and the like are collectively formed by a semiconductor manufacturing process. Yes. The back surface of the silicon plate 308 is bonded to an aluminum base plate 307 for heat dissipation, while the surface on which various electrical wirings are applied is covered with a plastic cover 306 in which a liquid path 302 and a common liquid chamber 301 are formed by injection molding. ing.

  By covering the silicon plate 308 on which the electrothermal conversion elements 303 are arranged at a pitch corresponding to the recording resolution of the recording head with a plastic cover on which the liquid paths 302 are arranged at the same pitch, it is possible to discharge at the above resolution. A plurality of recording elements are formed. The joint pipe 304 is connected to the ink tank via the ink filter 305 and guides ink from the ink tank to the common liquid chamber 301. The ink stored in the common liquid chamber 301 enters the individual liquid paths 302 by capillary action and forms a meniscus at the discharge port 300.

  On the other hand, a signal circuit 312 for supplying a signal from the recording apparatus main body to the recording head is formed on the printed board 309, and the circuit connection portion 311 of the silicon plate 308 is connected to the signal circuit 312 by the ultrafine wire 310. Has been.

  When a voltage pulse is applied to the electrothermal conversion elements 303 arranged in the individual recording elements based on the recording signal, the ink in the vicinity of the electrothermal conversion elements 303 is rapidly heated to generate bubbles in the liquid path 302. The ink droplets 313 are ejected from the ejection port 300 due to the expansion of the bubbles.

  FIG. 3 is a block diagram for explaining a control configuration of the ink jet recording apparatus applied in the present embodiment. In the figure, 401 is an MPU that controls the entire apparatus. The MPU 401 controls various mechanisms according to a program stored in the ROM 402. Reference numeral 404 denotes a gate array that controls supply of print data to the print head 201, and also performs data transfer control between the interface 400, MPU 401, and DRAM 403.

  The image data input from the interface 400 is sent to the MPU 401 via the gate array 404 and subjected to various image processing. At this time, the DRAM 403 is used as a work area when performing the image processing. In addition, the DRAM 403 can also store the number of ejections of the recording head 201, the number of replacements of the recording head cartridge, and the like.

  Reference numeral 408 denotes a motor driver for driving the paper feed motor 405, 407 a motor driver for driving the carriage motor 406, and 409 a head driver for driving the recording head 201. The MPU 401 controls these motor drivers based on the image data stored in the print buffer 403, thereby executing a recording operation.

  The characteristic configuration of the present embodiment will be specifically described below. In the present embodiment, when a color image is formed on a recording medium using a black ink having a relatively low permeability and a color ink having a relatively high permeability, recording of color data in contact with black data is performed. The rate is modulated according to the ratio of black data located in the vicinity.

  FIG. 4 is a block diagram for explaining a recording data generation process for each color executed by the recording apparatus of the present embodiment. In the present embodiment, recording data D1033, D1030, D1031, and D1032 that each color is actually recorded are generated from various binary original data D1000, D1002, D1003, and D1004 through various determination processes. .

  FIG. 5 is a flowchart for explaining step by step the steps executed by the MPU 401 in the recording data generation process. Hereinafter, each processing step will be described along the flowchart with reference to the block diagram of FIG.

  In FIG. 5, the MPU 401 first performs a “black dot neighboring pixel data detection process” E1000 on the binary original black data D1000 (step S401). As a result, “black 1-dot neighborhood thinning target pixel data” D1001 is generated.

  FIG. 6 is a flowchart for explaining a process of “detection process of pixel data of black dots” E1000.

  When this processing is started, the MPU 401 counts the number of black recording dots in the neighboring 3 × 3 pixels for the target pixel. Then, it is determined whether the number of dots is 1 or more (step S101). If one or more, that is, if there is even one recorded data in the 3 × 3 pixel area, the process proceeds to step S102, and the bit of the target pixel is turned ON. On the other hand, if it is less than 1, that is, no recording data exists in the 3 × 3 pixel area, the process proceeds to step S103, and the bit of the target pixel is turned OFF.

  FIG. 7 is a schematic diagram for explaining bit data obtained in each step of this process. FIG. 7A is a diagram illustrating a 3 × 3 pixel region with respect to the target pixel (center). FIG. 5B shows an example of original black data D1000. Here, for the sake of simplicity, bit data of an 8 pixel × 8 pixel area is shown, but in actuality, it has the number of pixels corresponding to the entire recording area of the recording medium. In the figure, black pixels indicate ON and white pixels indicate OFF. Through the steps S101 to S103, bit data with ON / OFF determined as shown in FIG. 7C is obtained from the original black data D1000 as shown in FIG. 7B.

  Referring again to FIG. 6, in the subsequent step S105, a logical product is obtained between the bit data of FIG. 7C and the inverted version of the original black data D1000.

  The above steps are executed for all the recording pixels while shifting the target pixel one by one (step S106). If it is determined in step S107 that the above processing has been completed for all pixels, this processing is terminated.

  As a result, from the original black data shown in FIG. 7B, “black 1-dot neighborhood pixel data” D1001 as shown in FIG. 7D is obtained. In D1001, a pixel obtained by subtracting the position of the black recording data itself is extracted as an ON area, although the area is an extension of the original black recording data. This area is an area to be thinned out for color data.

  Refer to FIG. 5 again. When the “black dot neighboring pixel data detection process” E1000 in step S401 ends, the process proceeds to step S402, and the “decimation target color selection process” E1001 is executed. In this processing, “decimation target color data” D1005 is generated from the three original color data D1002 to D1004.

  FIG. 8 is a logic circuit diagram used when generating “thinning target color data” D1005. The three-color original data D1002 to D1004 have different original or inverted states in order to generate respective single-color data, secondary color data by a combination of two colors, and tertiary color data by a combination of three colors. Connected to 7 types of AND circuits.

  In the present embodiment, it is possible to select which of the color data or any combination is to be thinned out when adjacent to the black data. For example, if bleeding between black and yellow deteriorates the image, but bleeding between other colors is not so noticeable, only yellow data can be targeted for thinning. In addition, bleeding between secondary colors to which more ink is applied is conspicuous, but it is difficult to notice in the primary color, and conversely, the white spots in the thinned-out portions are conspicuous in the primary color. Pixels of secondary color or higher can be targeted for thinning. The degree of bleeding and the degree of whiteout vary depending on the type of recording medium and the form of the image. Therefore, in the present embodiment, the setting of the selector shown in FIG. 8 is switched automatically when the type of the recording medium and the recording mode are set or according to a user instruction, and the ink color to be thinned is changed. It is possible to do this.

  Either the recording data or the null data is selected in each selector, and the “thinning-target color data” D1005 is determined by calculating the logical sum of the selected seven data.

  FIG. 9 is a schematic diagram for explaining bit data when “decimation target color data” D1005 is obtained from original data of three colors by “decimation target color selection processing” E1001. As in FIG. 7, in the 8 × 8 pixel area, black pixels indicate ON and white pixels indicate OFF. Here, it is assumed that the selector shown in FIG. 8 is set so that yellow data is to be thinned out. Thereby, bit data with ON / OFF determined as indicated by D1005 is obtained from the original data as indicated by D1002 to D1004.

  Refer to FIGS. 5 and 4 again. When the “decimation target color selection process” E1001 in step S402 is completed, the process proceeds to step S403, and “black dot vicinity density-specific data classification process” E1002 is executed.

  FIG. 10 is a flowchart for explaining a process of performing “data classification processing by density near black dots” E1002 for “thinning target color data” D1005 obtained by “thinning target color selection processing” E1001. This “black dot vicinity density-specific data separation process” E1002 divides the “thinning-target color data” D1005 into three in accordance with the recording rate of black data located in the vicinity.

  When the processing is started, first, in step S201, the target pixel of the “thinning target color data” D1005 is turned ON, and the original black data is turned ON in the 3 × 3 pixel region centered on the target pixel. It is determined whether or not there are four or more areas. If it is determined that the above condition is satisfied, the process proceeds to step S202, and the target pixel of the black high density vicinity color data is set to ON. On the other hand, if it is determined that the above condition is not satisfied, the process proceeds to step S203.

  In step S203, the target pixel of the “thinning target color data” D1005 is ON, and there are two or more pixels in the 3 × 3 pixel area centered on the target pixel where the original black data is ON. Determine whether or not to do. Here, if it is determined that the above condition is satisfied, the process proceeds to step S204, and the target pixel of the color data in the vicinity of black density is set to ON. On the other hand, if it is determined that the above condition is not satisfied, the process proceeds to step S205.

  Further, in step S205, it is determined whether or not the target pixel of the “thinning target color data” D1005 is ON. If it is determined that the above condition is satisfied, the process proceeds to step S206, and the target pixel of the black low density neighborhood color data is set to ON. On the other hand, if it is determined that the above condition is not satisfied, the process proceeds to step S207.

  In step S207, the black high density vicinity color data, the black medium density vicinity color data, the black low density vicinity color data, and all the target pixels are set to OFF.

  In the subsequent step S208, the target pixel is shifted by one pixel, and in step S209, it is determined whether or not the above determination process has been completed for all the pixels of the “thinning target color data” D1005. If there are still pixels to be determined, the process returns to step S201. When it is determined that the determination process has been completed for all the pixels, this process ends.

  FIG. 11 is a diagram showing bit data of black high density vicinity color data D1006, black medium density vicinity color data D1007, and black low density vicinity color data D1008 obtained as a result of “black dot vicinity density data separation processing” E1002. is there. By performing the processing described with reference to FIG. 10, the ON data of the thinning target color data D1005 is assigned to any one of black high density vicinity color data D1006, black medium density vicinity color data D1007, and black low density vicinity color data D1008. . Specifically, among the ON data of the thinning target color data D1005, the data having four or more black data in the neighboring eight pixels is allocated to the black high density neighboring color data D1006. On the other hand, in the case of 2 pixels or more and less than 4 pixels, the black low density neighborhood color data D1007 is assigned to the black low density neighborhood color data D1007, and the data having only 1 pixel or less is assigned to the black low density neighborhood color data D1008.

  Since the “thinning target color data” D1005 included in the “black one-dot vicinity thinning target data” D1001 is color data recorded adjacent to the black dots, the thinning pixels can be determined from the logical product of the two. . However, the present invention is characterized in that not all pixels obtained as a result of the logical product are thinned out, but the color data thinning-out rate is changed in accordance with the recording rate of neighboring black data. Therefore, referring to FIG. 5 again, next, in step S404, the MPU 401 performs a logical product of each of the color data D1006, D1007, and D1008 for each density with “black 1-dot vicinity thinning target data” D1001. .

  FIG. 12 is a diagram for explaining the result of the logical product for each color data for each density. The result of the logical product of “black high density vicinity color data” D1006 and “black 1 dot vicinity thinning target data” D1001 is “black high density vicinity thinning target color data” D1034. The result of the logical product of “black medium density vicinity color data” D1007 and “black 1 dot vicinity thinning target data” D1001 is “black medium density vicinity thinning target color data” D1035. Further, the result of the logical product of “black low density vicinity color data” D1008 and “black 1 dot vicinity thinning target data” D1001 is “black low density vicinity thinning target color data” D1036.

  When such logical product processing is completed, final thinned data is created by applying mask patterns having different thinning rates to the respective thinning target color data obtained here. Specifically, the thinning rate for the “black high density near thinning target color data” D1034 is set high, and the thinning rate for the “black low density near thinning target color data” D1036 is set low.

  Therefore, referring to FIG. 5 again, the MPU 401 proceeds to step S405, and first generates color thinning data 1 D1018 to D1020 in the black high density region.

  FIG. 13 shows the color thinning data D1018 to D1020 in the black high density region obtained by performing a logical product with the color masks C1, M1 and Y1 on the “black high density vicinity thinning target color data” D1034. It is a figure for demonstrating. In the mask data D1009 to D1011 in the figure, black areas indicate pixels from which data is thinned, and white areas indicate pixels from which data is not thinned. In this example, an example in which the color to be thinned is yellow is described, and therefore a mask with a thinning rate of 0% is selected for the cyan mask 1 and the magenta mask 1. Since it is a color to be thinned and there are many black data in the vicinity, the thinning rate of the yellow mask 1 is set to 100%. As a result of the logical product of each of the mask patterns D1009 to D1011 and the “black high density vicinity thinning target color data” D1034, thinning data 1 for each color, that is, D1018 to D1020 is obtained.

  Next, the process proceeds to step S406 (see FIG. 5) to generate color thinning data 2 D1021 to D1023 in the black medium density region.

  FIG. 14 shows the color thinning data D1021 to D1023 in the black medium density region obtained by performing a logical product with the color masks C2, M2, and Y2 on the “black medium density vicinity thinning target color data” D1035. It is a figure for demonstrating. Also in the mask data D1012 to D1014 in the figure, black areas indicate pixels from which data is thinned, and white areas indicate pixels from which data is not thinned. In this example, since the example in which the color to be thinned is yellow is described, a mask with a thinning rate of 0% is also selected for the cyan mask 2 and the magenta mask 2. The yellow mask 2 has a thinning rate of 50% because it is a color to be thinned and black data is present in the vicinity. As a result of the logical product of each of the mask patterns D1012 to D1014 and “black density darkening target color data” D1035, thinning data 2 for each color, that is, D1021 to D1023 is obtained.

  Further, the process proceeds to step S407 (see FIG. 5), and color thinning data 3 D1024 to D1026 in the black low density region are generated.

  FIG. 15 shows color thinning data D1024 to D1026 in the black low density region obtained by performing a logical product with the color masks C3, M3, and Y3 on the “black low density vicinity thinning target color data” D1036. It is a figure for demonstrating. Also in the mask data D1015 to D1017 in the figure, black areas indicate pixels from which data is thinned, and white areas indicate pixels from which data is not thinned. In this example, since the example in which the color to be thinned is yellow is described, a mask with a thinning rate of 0% is also selected for the cyan mask 3 and the magenta mask 3. Since it is a color to be thinned and there is not much black data in the vicinity, the thinning rate of the yellow mask 3 is set to 25%. As a result of the logical product of each of the mask patterns D1015 to D1017 and the “black low density vicinity thinning target color data” D1036, thinning data 3 for each color, that is, D1024 to D1026 is obtained.

  Next, the MPU 401 proceeds to step S408 (see FIG. 5), takes the logical sum of the thinned data of each black density for each color, and further inverts this. As a result, reversal masks D1027 to D1029 for each color are obtained.

  FIG. 16 is a diagram for explaining the result of the logical sum of the black density thinning data and the result of inverting the result for each color. For example, in the case of yellow, three logical sums of yellow thinning data 1 D1020, yellow thinning data 2 D1023, and yellow thinning data 3 D1026 are obtained, and the result is D1039. Further, the inverted yellow mask D1029 is obtained by inverting this. In this example, with respect to cyan and magenta, since the thinning data of any black density is null, the logical sum is also null data for both D1037 and D1038. Is turned on. In the figure, for the inversion masks D1027 to D1029, pixels that allow printing are indicated as ON (black), and pixels that do not allow printing are indicated as OFF (white). That is, in this example, for cyan and magenta, pixels are permitted to be recorded for all data regardless of the presence of black data, and for yellow, pixels that are permitted to be recorded are determined according to the recording density of black data. ing.

  By taking the logical product of the inversion masks D1027 to D1029 thus obtained and the original data D1002 to D1004 for each color, the recording data D1030 to D1032 for each color to be actually recorded are obtained. For black data, the original black data D1000 becomes the black recording data D1033 as it is.

  FIG. 17 is a diagram for explaining the state of recording data obtained by performing the above-described series of processing on input original data. FIG. 17A is a diagram showing the original data D1000 to D1004 of the four colors together, and FIG. 17B is a diagram showing the recording data D1030 to D1033 of the four colors together. In the figure, K, C, M, and Y indicate pixels in which black data (K), cyan data (C), magenta data (M), and yellow data (Y) are ON. When the two figures are compared, the cyan data and the magenta data are not changed. However, with respect to the yellow data, the data indicated by gray in the figure is changed to OFF in the recording data. Such a portion increases as the area where more black data exists.

  The series of processes shown in the block diagram of FIG. 4 and the flowchart of FIG. The MPU 401 drives the head driver 409 in accordance with the recording data obtained in this way, and ejects ink from the recording head 201 of each color.

  The processing of the present embodiment as described above is effective when the bleeding problem between black and yellow is particularly regarded as a problem. Further, since the color data thinning rate is adjusted step by step in accordance with the black density, the color data can be thinned out to an appropriate amount only in an area where bleeding is likely to be a problem. Therefore, it is possible to avoid white spots caused by thinning out the color data more than necessary, and to smoothly represent a change in gradation even when a black gradation image exists on the color image. High-quality black characters with high density and excellent sharpness can also be reproduced in a color image without bleeding.

  In the above-described embodiment, various parameters and threshold values are used in various determination processes, but these can be changed as appropriate.

  For example, in the “black dot vicinity pixel data detection process” E1000 and the “black dot vicinity density data classification process” E1002, a detection process is performed on a 3 × 3 pixel area centered on the target pixel. Can be changed according to the situation. When the degree of bleeding is further increased or there is a tendency in the direction of bleeding, the above processing may be performed for a wider area or a different shape area other than a square. At this time, the threshold for turning on the bit of the target pixel is set to 1 in the above example (step S101 in FIG. 5), but this value can of course be changed.

  In addition, in the “black dot neighborhood density data classification process” E1002, in this embodiment, the threshold value when allocating to each density data is divided into three levels, 4 or more, 2 or more, and 0 or more. The direction can also be changed. Of course, the threshold value may be set to another value, and more threshold values may be set to adjust the thinning rate more finely with respect to the black density.

  In addition, the present invention is not limited to the form described above for the mask patterns of each color prepared for each density. In the above description, the color data to be thinned near black high density is 100%, the medium density is 50%, and the low density is 25%. However, the thinning rate may be changed as appropriate. Further, in this embodiment, as shown in FIGS. 13 and 14, a mask pattern that is relatively periodically dispersed is used. However, this may have various features. For example, a mask pattern having no regularity and randomness may be used.

  Also, in the above embodiment, various block diagrams and flowcharts are illustrated to explain the mechanism for achieving the object of the present invention. However, in the present invention, the structure or process described in the drawings is used. It is not an essential requirement to step on. In an ink jet recording method using black ink with low penetrability and color ink with high penetrability, color data located in the vicinity of black data is recorded according to a thinning rate adjusted according to the black data recording rate. If included, it is included in the category of the present invention.

It is a perspective view for demonstrating schematic structure of the color inkjet recording device applied with embodiment of this invention. FIG. 2 is a schematic diagram for explaining a discharge mechanism of a recording head. It is a block diagram for demonstrating the structure of control of the inkjet recording device applied with embodiment of this invention. It is a block diagram for demonstrating the production | generation process of the recording data of each color which the recording device of embodiment of this invention performs. 6 is a flowchart for step-by-step explaining steps executed by an MPU in a recording data generation process. 10 is a flowchart for explaining a process of “detection processing of pixel data near black dots”. (A)-(d) is a schematic diagram for demonstrating the bit data obtained in each process of "detection process of pixel data of the black dot vicinity". It is a logic circuit diagram used when generating “thinning-target color data”. FIG. 10 is a schematic diagram for explaining bit data when “decimation target color data” is obtained from original data of three colors by “thinning target color selection processing”. 12 is a flowchart for explaining a process of performing “data classification processing by density near black dots” for “thinning target color data”. It is a figure which shows the bit data of black high density vicinity color data, black medium density vicinity color data, and black low density vicinity color data. It is a figure for demonstrating the result of a logical product for every color data according to density. “FIG. 7 is a diagram for explaining color thinning data in a black high density region obtained by performing a logical product with color masks C1, M1 and Y1 on black high density vicinity thinning target color data. It is a figure for demonstrating the color thinning data in a black medium density area | region obtained by taking a logical product between the color masks C2, M2, and Y2 with respect to "black medium density vicinity thinning object color data". It is a figure for demonstrating the color thinning data in a black low density area | region obtained by taking a logical product between color masks C3, M3, and Y3 with respect to "black low density vicinity thinning object color data". It is a figure for demonstrating the result of the logical sum of the thinning data of black density, and the result of inverting this for every color. (A) And (b) is a figure for demonstrating the mode of the recording data obtained by performing a series of processes with respect to the input original data.

Explanation of symbols

103 Conveying roller 104 Auxiliary roller
DESCRIPTION OF SYMBOLS 105 Paper feed roller 106 Carriage 107 Recording medium 201 Recording head 202 Recording head cartridge 300 Discharge port 301 Common liquid chamber 302 Liquid path 303 Electrothermal conversion element 304 Joint pipe 305 Ink filter 306 Plastic cover 307 Aluminum base plate 308 Silicon plate 309 Print board
310 extra fine wire 311 circuit connection 312 signal circuit
400 interface
401 MPU
402 ROM
403 DRAM
404 Gate array 405 Paper feed motor
406 Carriage motor 407 Motor driver
408 Motor driver 409 Head driver

Claims (8)

Using black ink and one or more color inks having a relatively higher permeability to the recording medium than the black ink, each pixel of the recording medium arranged at a predetermined recording resolution is determined based on image data. In the inkjet recording method of forming an image according to the recording / non-recording of the black ink and the color ink,
Detecting the number of pixels determined to record the black ink in the vicinity of a color recording pixel determined to record at least one color ink;
And a step of determining whether or not the color ink can be recorded on the color recording pixels according to the number of pixels.   The determining step selects one of a plurality of mask patterns prepared in advance so that recording is possible for a plurality of pixels and the ratio of the availability is different from each other according to the number of pixels, 2. The ink jet recording method according to claim 1, wherein whether or not the color ink can be recorded is determined using the selected mask pattern.   The ink jet recording method according to claim 1, wherein the mask pattern is prepared independently for each of the one or more color inks.   4. The ink jet recording method according to claim 1, wherein the vicinity is an area including eight pixels adjacent to the color recording pixel.   5. The ink jet recording method according to claim 1, further comprising a step of selecting the at least one color ink from the one or more color inks.   6. The ink jet recording method according to claim 1, wherein the one or more color inks include cyan, magenta, and yellow. Using black ink and one or more color inks having a relatively higher permeability to the recording medium than the black ink, each pixel of the recording medium arranged at a predetermined recording resolution is determined based on image data. In an inkjet recording apparatus for forming an image in accordance with recording / non-recording of the black ink and color ink,
Means for detecting the number of pixels determined to record the black ink in the vicinity of the color recording pixels determined to record at least one color ink;
An ink jet recording apparatus comprising: means for determining whether or not the color ink can be recorded on the color recording pixels according to the number of pixels. The determination means selects one of a plurality of mask patterns prepared in advance so as to determine whether or not recording is possible for a plurality of pixels and the ratio of the availability is different from each other according to the number of pixels, 8. The ink jet recording apparatus according to claim 7, wherein whether or not the color ink can be recorded is determined using the selected mask pattern.

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