JP5183086B2 - Image forming method and image forming apparatus - Google Patents

Description

  The present invention relates to an image forming method and an image forming apparatus, and more particularly, to an image forming method by an ink jet recording method using a line head type recording head.

  In a line head type recording head, the number of nozzles is enormous, and there are potentially many non-ejection nozzles. When non-ejection nozzles are generated in this way, streaky image defects occur in the recorded image.

Therefore, as disclosed in Japanese Patent Application Laid-Open No. 2004-228688, there are adjacent complementation and different color complementation as methods for correcting image defects due to the occurrence of this non-ejection nozzle. Here, the adjacent complement is to increase the ink recording amount of the adjacent nozzle adjacent to the non-ejection nozzle (increase the number of dots, increase the droplet volume), thereby making the non-ejection streak difficult to see. On the other hand, different color complementation is to make it difficult to see streaks due to non-ejection by increasing the recording amount of ink of other colors that are ejected at the same position as the ejection nozzle (increasing the number of dots and increasing the droplet volume).
JP 2003-136702 A

  However, the non-ejection correction method disclosed in Patent Document 1 has the following problems.

  In human vision, the lightness component and the chromaticity component have different spatial frequency response characteristics, and the lightness component is highly sensitive from low frequencies to relatively high frequencies, but the chromaticity component is known to be less sensitive at high frequencies. Yes.

Here, a gray image is generally reproduced by recording cyan, magenta, and yellow inks. FIGS. 13 and 14 illustrate cyan in a gray portion of an image composed of cyan, magenta, and yellow inks. An example of complementation when ink ejection failure occurs will be described. FIG. 13 shows the brightness distribution when the adjacent complement is performed, and FIG. 14 shows the chromaticity distribution when the different color complement is performed. In FIGS. 13 and 14A, the horizontal axis represents the head line direction (main scanning direction), the vertical axis represents FIG. 13 lightness distribution (L ^* ), and FIG. 14A represents chromaticity distribution (C−). R axis).

  As shown in FIG. 13, when adjacent interpolation is performed, a high frequency amplitude remains in the brightness component. As described above, the brightness component is easily visually recognized up to the high frequency region, so that it is still visually recognized as an image defect.

Further, as shown in FIG. 14A, when different color interpolation is performed, a low frequency amplitude is generated in the chromaticity distribution. For this reason, as described above, the chromaticity component is easily visually recognized in the low-frequency region, and thus is still visually recognized as an image defect. The CR axis is an axis defined as shown in FIG. 14B on the a ^* b ^* plane in CIELab.

  The present invention has been made in view of such circumstances, and an object thereof is to provide an image forming method and an image forming apparatus that are not visually recognized as image defects even when a non-ejection nozzle is present.

In order to achieve the above object, according to the first aspect of the present invention, a recording head in which a plurality of nozzles are arranged is provided for each of a plurality of liquid colors, and an image is formed by discharging and recording the liquid from the nozzles. In the image forming method, the step of identifying a non-ejection nozzle that cannot be recorded among the plurality of nozzles, and the same color adjacent to perform recording with the same color liquid at a position adjacent to the recording position where the non-ejection nozzle should be originally recorded Increase the recording amount of the nozzle, increase the recording amount of the different color corresponding nozzle that performs recording with the different color liquid at the position corresponding to the recording position where the non-ejection nozzle should be recorded, and the non-ejection nozzle should originally record by reducing the amount of recording different colors adjacent nozzles to perform recording by the liquid of different colors at a position adjacent to the recording position, images have a, a correction step of correcting, cyan color of the liquid, magenta When the color of the liquid that should be recorded by the non-ejection nozzle is any one of cyan, magenta, and yellow, the color of the liquid recorded by the different color corresponding nozzle and the different color adjacent nozzle is cyan, magenta. The non-ejection nozzles of yellow are two colors other than the color of the liquid to be originally recorded .

  According to the present invention, it is possible to prevent an image defect caused by the occurrence of a non-ejection nozzle from being visually recognized.

In order to achieve the object, the invention according to claim 2 includes a recording head in which a plurality of nozzles are arranged for each of a plurality of liquid colors, and forms an image by discharging the liquid from the nozzles and recording. In the image forming method, the step of identifying a non-ejection nozzle that cannot be recorded among the plurality of nozzles, and the same color adjacent to perform recording with the same color liquid at a position adjacent to the recording position where the non-ejection nozzle should be originally recorded Increase the recording amount of the nozzle, increase the recording amount of the different color corresponding nozzle that performs recording with the different color liquid at the position corresponding to the recording position where the non-ejection nozzle should be recorded, and the non-ejection nozzle should originally record A correction step of correcting the image by reducing the recording amount of the different color adjacent nozzle that performs recording with the different color liquid at a position adjacent to the recording position, and changing the color of the liquid to cyan, magenta When the color of the liquid that should be recorded by the non-ejection nozzle is any one of cyan, magenta, and yellow, the color of the liquid that is recorded by the different color corresponding nozzle is black, and the different color The color of the liquid recorded by the adjacent nozzle is two colors other than the color of the liquid to be originally recorded by the non-ejection nozzle among cyan, magenta, and yellow.
In order to achieve the above object, according to a third aspect of the present invention, in the image forming method of the first or second aspect , when the recording amount to be originally recorded by the non-ejection nozzle is X, the correction step includes: The image is corrected by increasing the recording amount of the same color adjacent nozzle and the different color corresponding nozzle by approximately X / 2 and decreasing the recording amount of the different color adjacent nozzle by approximately X / 2.

  According to the present invention, the high frequency component is suppressed for the brightness component and the low frequency component is suppressed for the chromaticity component, so that an image defect due to the occurrence of a non-ejection nozzle can be prevented from being visually recognized.

In order to achieve the above object, the invention according to claim 4 includes a recording head in which a plurality of nozzles are arranged for each of a plurality of liquid colors, and forms an image by discharging the liquid from the nozzles for recording. In the image forming apparatus, the non-ejection nozzle that cannot record among the plurality of nozzles is specified, and the non-ejection nozzle performs recording with a liquid of the same color at a position adjacent to a recording position that should be recorded. Increasing the recording amount of adjacent nozzles of the same color, increasing the recording amount of different color corresponding nozzles that perform recording with different color liquids at positions corresponding to the recording positions where the non-ejection nozzles should be originally recorded, and the non-ejection nozzles originally recording by reducing the amount of recording different colors adjacent nozzles of the recording position to be to perform the recording by the liquid of different colors in adjacent positions, the image have a correcting means for correcting, cyan color of the liquid, magenta When the color of the liquid that should be recorded by the non-ejection nozzle is any of cyan, magenta, and yellow, the color of the liquid recorded by the different color corresponding nozzle and the different color adjacent nozzle is cyan, Of the magenta and yellow, the non-ejection nozzles are two colors other than the color of the liquid to be originally recorded .
According to a fifth aspect of the present invention, there is provided an image forming apparatus comprising a recording head for arranging a plurality of nozzles for each of a plurality of liquid colors, and forming an image by discharging the liquid from the nozzles for recording. A specifying means for specifying a non-ejection nozzle that cannot record among a plurality of nozzles, and a recording amount of the same color adjacent nozzle that performs recording with the same color liquid at a position adjacent to the recording position where the non-ejection nozzle should be recorded And increase the recording amount of the different color corresponding nozzle that performs recording with the different color liquid at the position corresponding to the recording position where the non-ejection nozzle should be recorded, and the non-ejection nozzle is adjacent to the recording position where the non-ejection nozzle should be originally recorded. A correction means for correcting the image by reducing the recording amount of the different color adjacent nozzles for recording with the different color liquid at the position where the liquid color is changed to cyan, magenta, yellow, black. When the liquid color to be recorded by the non-ejection nozzle is any one of cyan, magenta, and yellow, the liquid color recorded by the different color corresponding nozzle is black, and the different color adjacent nozzle is The color of the liquid to be recorded is two colors other than the color of the liquid to be originally recorded by the non-ejection nozzle among cyan, magenta, and yellow.

  According to the present invention, even when a non-ejection nozzle exists, it is not visually recognized as an image defect.

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

[Description of image correction process]
The present invention proposes an image correction process in the image forming method, in which the non-ejection correction process is performed by adding a different color adjacent complement in addition to the adjacent complement and the different color complement.

<First Embodiment>
FIG. 1 is a diagram illustrating a relationship between a non-ejection nozzle and a complement target nozzle in the first embodiment of the present invention. A gray image is generally reproduced by recording cyan, magenta, and yellow inks. FIG. 1 shows a case where cyan ink is not ejected when an input image is a gray image. In FIG. 1, one square represents a nozzle and is actually recorded by overlapping each color. For convenience of explanation, for each ink of cyan, magenta, yellow, and black, the nozzle positions correspond to each other in the main scanning direction. They are shown separately. “Dead” means no recording amount (no ejection), “Up” means an increase in recording amount, “Down” means a reduction in recording amount, and “Normal” means a normal recording amount.

  As shown in FIG. 1, when a non-ejection nozzle 11C-2 is present in a cyan ink recording head (hereinafter referred to as a head) 12C, the non-ejection nozzle 11C-2 is determined as a position to be originally recorded as an adjacent complement. For the same color adjacent nozzles 11C-1 and 11C-3 that perform recording with ink of the same color at adjacent positions, the recording amount of cyan ink is increased.

  Further, as different color complementation, the recording amounts of magenta ink and yellow ink in the different color corresponding nozzles 11M-2 and 11Y-2 that perform recording with different color inks at positions corresponding to positions where the non-ejection nozzle 11C-2 should originally record. Increase.

  In the present invention, as a feature point that does not exist in the prior art, different color adjacent complement is further performed. The different color adjacent complement is for the different color adjacent nozzles 11M-1, 11M-3, 11Y-1, and 11Y-3 that perform recording with different color inks at positions adjacent to the positions where the non-ejection nozzle 11C-2 should originally record. The recording amount of magenta ink and yellow ink is reduced. By this different color adjacent complement, the chromaticity is changed in the opposite direction to the non-ejection position while the brightness change does not occur in the portion of the recorded image corresponding to the position of the same color adjacent nozzles 11C-1 and 11C-3. Low frequency components of the chromaticity distribution can be reduced.

As described above, the lightness distribution and the chromaticity distribution as shown in FIG. 2 can be obtained by combining the adjacent complement, the different color complement, and the different color adjacent complement. In FIG. 2, the horizontal axis represents the head line direction (main scanning direction), and the vertical axis represents lightness distribution (L ^* ) and (b) chromaticity distribution (CR axis). . As shown in FIG. 2 (a), a brightness component having a high sensitivity up to a high frequency can be spatially flat and is not visually recognized as a defect. Further, as shown in FIG. 2B, the low frequency component is suppressed while the high frequency component remains, but since the high frequency sensitivity of the chromaticity component is low, it is not visually recognized as a defect. For this reason, the image defect that has been visually recognized in the conventional method can be completely invisible.

  Here, the applicant examined the amount of increase / decrease of the recording amount for obtaining a good correction result by experiment. A normal recording amount of cyan ink from each nozzle 11C is assumed to be Xc. Each maximum recording amount is Xc = 1. According to the experiment, when the nozzle 11C-2 of the cyan ink head 12C does not eject, the increase amount of the cyan ink recording amount of both the adjacent nozzles 11C-1 and 11C-3 required for the adjacent complement is represented by a · (Xc). ), The increase amounts of the recording amounts of the magenta ink and the yellow ink of the corresponding nozzles 11M-2 and 11Y-2 required for different color complementation are respectively b · (Xc), and the corresponding adjacent nozzles 11M-1 and 11M-3 required for different color adjacent complementation , 11Y-1 and 11Y-3, and when the amount of decrease in the recording amount of magenta ink and yellow ink is c · (Xc), 0.4 <(a, b, c) < It was found that a good correction result can be obtained when 0.6.

Second Embodiment
FIG. 3 is a diagram illustrating a relationship between a non-ejection nozzle and a complement target nozzle in the second embodiment of the present invention. FIG. 3 shows a non-ejection correction processing method when cyan ink is non-ejection when the input image is a gray image as in the first embodiment.

  As shown in FIG. 3, in the second embodiment, when the non-ejection nozzle 11C-2 is present in the cyan ink head 12C, the non-ejection nozzle 11C-2 corresponds to a position where the non-ejection nozzle 11C-2 should be originally recorded as a different color complement. The recording amount of black ink is increased for the different color corresponding nozzle 11Bk-2 that performs recording with different color ink at the position. On the other hand, the magenta ink and the yellow ink are not discharged to the different color corresponding nozzles 11M-2 and 11Y-2 which perform recording with different color inks at positions corresponding to positions where the non-discharge nozzle 11C-2 should originally record.

  In this way, unlike the first embodiment, the non-ejection nozzle 11C-2 does not eject magenta ink and yellow ink at a position corresponding to the position where printing should be performed, but increases the recording amount of black ink, thereby It is possible to suppress the fluctuation of the degree smaller. Others are common to the first embodiment.

As described above, the brightness distribution and chromaticity distribution as shown in FIG. 4 can be obtained. In FIG. 4, the horizontal axis represents the head line direction (main scanning direction), and the vertical axis represents the lightness distribution (L ^* ) and (b) the chromaticity distribution (CR axis). .

  As shown in FIG. 4A, the brightness component having high sensitivity up to a high frequency can be spatially flat and is not visually recognized as a defect. Further, as shown in FIG. 4B, since the variation in chromaticity can be suppressed smaller than in the first embodiment, and the high frequency component of the chromaticity component can be suppressed smaller, it is visually recognized as a defect. Not. For this reason, the image defect that has been visually recognized by the conventional method can be completely prevented from being visually recognized, as compared with the first embodiment.

  In the above embodiment, the case where cyan ink does not eject has been described, but the same applies to cases where magenta ink or yellow ink does not eject.

[Outline of non-ejection correction processing]
FIG. 5 is a flowchart of the non-ejection correction process according to the present invention. First, in step S1, a pixel to be subjected to non-ejection correction processing is specified. As a specifying method, a method of detecting a non-ejection pixel from a recorded image in advance and identifying a pixel targeted for non-ejection correction processing from the detected non-ejection pixel can be considered. This recognizes a non-ejection head and nozzles.

  Next, in step S2, the input image is determined based on the recording amount of each color ink. Subsequently, in step S3, in order to select a non-ejection correction processing method in the image correction process, it is determined whether or not the input image is within a predetermined color region in which a predetermined amount or more of each color ink of cyan, magenta, and yellow is ejected. judge.

  If it is not within the range of the predetermined color region (in the case of No), only non-ejection correction processing by the above-described adjacent interpolation method is performed in the image correction process (step S4-2). Note that the case where the input image is not within the predetermined color region (in the case of No) includes, for example, a case where the input image is a single color image.

  On the other hand, if it is within the range of the predetermined color region (in the case of Yes), non-ejection correction processing is performed by the method of “adjacent interpolation + different color complementation + different color adjacent complement” proposed in the present invention in the image correction step (step S4-1).

  Thereafter, when the non-ejection correction process is completed, in step S5, the next pixel to be subjected to the non-ejection correction process is specified, and the same process is performed.

  Here, the range of the predetermined color region in step S3 is considered as follows from the above experiment. Assume that the recording amounts of cyan ink, magenta ink, and yellow ink are Xc, Xm, and Xy. In view of the fact that 0 ≦ (Xc, Xm, Xy) ≦ 1, in order to realize the increase or decrease of the above approximate Xc / 2, 0 <Xc <0 as the cyan ink recording amount. .67, the magenta ink recording amount must be within the range of the color region that satisfies Xc / 2 <Xm <0.67, and the yellow ink recording amount Xc / 2 <Xy <0.67. This color area range is the predetermined color area range in step S3. The same applies to a case where a nozzle having a magenta ink or yellow ink head does not discharge.

[Outline of image forming method]
FIG. 6 is a flowchart of the image forming method including the non-ejection correction process. As shown in FIG. 6, non-ejection correction processing is performed on cyan, magenta, yellow, and black input images based on non-ejection nozzle information. Thus, cyan, magenta, yellow, and black corrected images are generated, and after halftoning processing, cyan, magenta, yellow, and black print data are generated.

[Configuration of inkjet recording apparatus]
Next, an ink jet recording apparatus as a specific application example of the image forming apparatus that realizes the image forming method will be described.

  FIG. 7 is an overall configuration diagram of an ink jet recording apparatus showing an embodiment of an image forming apparatus according to the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a plurality of heads 12Bk, 12C, and 12C provided corresponding to black (Bk), cyan (C), magenta (M), and yellow (Y) inks. A printing unit 12 having 12M, 12Y, an ink storage / loading unit 14 for storing ink to be supplied to each head 12Bk, 12C, 12M, 12Y, and a paper feeding unit 18 for supplying recording paper 16 as a recording medium. And a decurling unit 20 for removing the curl of the recording paper 16 and a nozzle surface (ink ejection surface) of the printing unit 12 and conveying the recording paper 16 while maintaining the flatness of the recording paper 16 A belt conveyance unit 22 that performs printing, a print detection unit 24 that reads a printing result of the printing unit 12, and a paper discharge unit 26 that discharges recorded recording paper (printed material) to the outside.

  The ink storage / loading unit 14 has an ink tank that stores ink of a color corresponding to each of the heads 12Bk, 12C, 12M, and 12Y, and each tank has a head 12Bk, 12C, 12M, and 12Y via a required pipe line. Communicated with. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  In FIG. 7, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20.

  In the case of an apparatus configuration using roll paper, a cutter (first cutter) 28 is provided as shown in FIG. 7, and the roll paper is cut into a desired size by the cutter 28. Note that the cutter 28 is not necessary when cut paper is used.

  After the decurling process, the cut recording paper 16 is sent to the belt conveyance unit 22. The belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least a portion facing the nozzle surface of the printing unit 12 and the sensor surface of the printing detection unit 24 is a horizontal plane (flat). Surface).

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 7, an adsorption chamber 34 is provided at a position facing the nozzle surface of the print unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. The recording paper 16 is sucked and held on the belt 33 by sucking the suction chamber 34 with a fan 35 to a negative pressure. In place of the suction adsorption method, an electrostatic adsorption method may be adopted.

  When the power of the motor (reference numeral 88 in FIG. 12) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, the belt 33 is driven in the clockwise direction in FIG. The held recording paper 16 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area).

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the paper conveyance path formed by the belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  Each of the heads 12Bk, 12C, 12M, and 12Y of the printing unit 12 has a length corresponding to the maximum paper width of the recording paper 16 targeted by the ink jet recording apparatus 10, and a recording medium having the maximum size on the nozzle surface. This is a full-line head in which a plurality of nozzles for ink ejection are arranged over a length exceeding at least one side (full width of the drawable range) (see FIG. 8).

  The heads 12Bk, 12C, 12M, and 12Y are arranged in the order of black (Bk), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 16, and the respective heads. 12Bk, 12C, 12M, and 12Y are fixedly installed so as to extend along a direction substantially orthogonal to the conveyance direction of the recording paper 16.

  A color image can be formed on the recording paper 16 by ejecting different color inks from the heads 12Bk, 12C, 12M, and 12Y while the recording paper 16 is conveyed by the belt conveyance unit 22.

  As described above, according to the configuration in which the full-line heads 12Bk, 12C, 12M, and 12Y having the nozzle rows covering the entire width of the paper are provided for each color, the recording paper 16 and the printing unit in the paper feeding direction (sub-scanning direction). The image can be recorded on the entire surface of the recording paper 16 by performing the operation of moving the 12 relatively once (that is, by one sub-scan). Thereby, it is possible to perform high-speed printing as compared with a shuttle type head in which the head reciprocates in a direction orthogonal to the paper conveyance direction, and productivity can be improved.

  In this example, the configuration of the BkCMY standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special color ink are used as necessary. May be added. For example, it is possible to add an ink jet head that discharges light ink such as light cyan and light magenta. Also, the arrangement order of the color heads is not particularly limited.

  The print detection unit 24 shown in FIG. 7 includes an image sensor (line sensor or area sensor) for imaging the droplet ejection result of the printing unit 12, and clogging of nozzles is detected from the droplet ejection image read by the image sensor. It functions as a means for checking ejection characteristics such as landing position errors.

  As the print detection unit 24 of this example, a CCD area sensor in which a plurality of light receiving elements (photoelectric conversion elements) are two-dimensionally arranged on the light receiving surface can be suitably used. The area sensor is assumed to have an imaging range in which the entire area of the ink ejection width (image recording width) by at least the heads 12Bk, 12C, 12M, and 12Y can be imaged.

  Also, a line sensor can be used instead of the area sensor. In this case, it is preferable that the line sensor has a light receiving element array (photoelectric conversion element array) that is wider than at least the ink ejection width (image recording width) by each of the heads 12Bk, 12C, 12M, and 12Y. A test pattern or practical image printed by the heads 12Bk, 12C, 12M, and 12Y of each color is read by the print detection unit 24, and ejection determination of each head is performed. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined surface uneven shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a sorting means (not shown) for switching the paper discharge path in order to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. Yes. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48.

[Head structure]
Next, the structure of the head will be described. Since the structures of the heads 12Bk, 12C, 12M, and 12Y for each color are common, the heads are represented by the reference numeral 50 in the following.

  FIG. 9A is a plan perspective view showing an example of the structure of the head 50, and FIG. 9B is an enlarged view of a part thereof. FIG. 9C is a plan perspective view showing another structural example of the head 50, and FIG. 10 is a cross-sectional view showing a three-dimensional configuration of one droplet discharge element (an ink chamber unit corresponding to one nozzle 11). It is sectional drawing which follows the 10-10 line in Fig.9 (a).

  In order to increase the dot pitch printed on the recording paper 16, it is necessary to increase the nozzle pitch in the head 50. As shown in FIGS. 9A and 9B, the head 50 in this example includes a plurality of ink chamber units (liquids) including nozzles 11 serving as ink discharge ports and pressure chambers 52 corresponding to the nozzles 11. The droplet discharge elements 53 are arranged in a staggered matrix (two-dimensionally), and are thereby projected substantially in a line along the head longitudinal direction (direction perpendicular to the paper feed direction). High density of nozzle spacing (projection nozzle pitch) is achieved.

  The configuration in which one or more nozzle rows are configured over a length corresponding to the entire width of the recording paper 16 in a direction substantially orthogonal to the feeding direction of the recording paper 16 is not limited to this example. For example, instead of the configuration of FIG. 9A, as shown in FIG. 9C, short head modules 50 ′ in which a plurality of nozzles 11 are two-dimensionally arranged are arranged in a staggered manner and connected. A line head having a nozzle row having a length corresponding to the entire width of the recording paper 16 may be configured.

  The pressure chamber 52 provided corresponding to each nozzle 11 has a substantially square planar shape (see FIGS. 9A and 9B), and the nozzle 11 is located at one of the diagonal corners. An outlet for supplying ink (supply port) 54 is provided on the other side. The shape of the pressure chamber 52 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon and other polygons, a circle, and an ellipse.

  As shown in FIG. 10, each pressure chamber 52 communicates with a common flow channel 55 via a supply port 54. The common channel 55 communicates with an ink tank (not shown) as an ink supply source, and the ink supplied from the ink tank is distributed and supplied to each pressure chamber 52 via the common channel 55.

  An actuator 58 having an individual electrode 57 is joined to a pressure plate (vibrating plate that also serves as a common electrode) 56 constituting a part of the pressure chamber 52 (the top surface in FIG. 10). By applying a drive voltage between the individual electrode 57 and the common electrode, the actuator 58 is deformed and the volume of the pressure chamber 52 is changed, and ink is ejected from the nozzle 11 due to the pressure change accompanying this. The actuator 58 is preferably a piezoelectric element using a piezoelectric material such as lead zirconate titanate or barium titanate. After the ink is ejected, when the displacement of the actuator 58 returns to its original state, new ink is refilled into the pressure chamber 52 from the common channel 55 through the supply port 54.

  As shown in FIG. 10, the ink chamber units 53 having the above-described structure are arranged in a constant arrangement pattern along the row direction along the main scanning direction and the oblique column direction having a constant angle θ not orthogonal to the main scanning direction. The high-density nozzle head of this example is realized by arranging a large number in a lattice pattern.

  That is, with a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along a certain angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to be aligned in the main scanning direction is d × cos θ. Thus, in the main scanning direction, each nozzle 11 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction.

  When driving a nozzle with a full line head having a nozzle row having a length corresponding to the entire printable width, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially moved from one side to the other. (3) The nozzles are divided into blocks, and the nozzles are sequentially driven from one side to the other for each block, etc., and one line (1 in the width direction of the paper (direction perpendicular to the paper conveyance direction)) Driving a nozzle that prints a line of dots in a row or a line consisting of dots in a plurality of rows is defined as main scanning.

  In particular, when the nozzles 11 arranged in a matrix as shown in FIG. 11 are driven, the main scanning as described in the above (3) is preferable. That is, the nozzles 11-11, 11-12, 11-13, 11-14, 11-15, 11-16 are made into one block (other nozzles 11-21,..., 11-26 are made into one block, Nozzles 11-31,..., 11-36 as one block,..., And the recording paper 16 by sequentially driving the nozzles 11-11, 11-12,. One line is printed in 16 width directions.

  On the other hand, by relatively moving the above-mentioned full line head and the paper, printing of one line (a line formed by one line of dots or a line composed of a plurality of lines) formed by the above-described main scanning is repeatedly performed. This is defined as sub-scanning.

  The direction indicated by one line (or the longitudinal direction of the belt-like region) recorded by the main scanning is referred to as a main scanning direction, and the direction in which the sub scanning is performed is referred to as a sub scanning direction. In other words, in the present embodiment, the conveyance direction of the recording paper 16 is the sub-scanning direction, and the direction orthogonal to it is the main scanning direction.

  In implementing the present invention, the nozzle arrangement structure is not limited to the illustrated example. In the present embodiment, a method of ejecting ink droplets by deformation of an actuator 58 typified by a piezo element (piezoelectric element) is adopted. However, in the practice of the present invention, the method of ejecting ink is not particularly limited. Instead of the piezo jet method, various methods such as a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure can be applied.

[Explanation of control system]
FIG. 12 is a block diagram showing a system configuration of the inkjet recording apparatus 10. As shown in the figure, the inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a ROM 75, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like. It has.

  The communication interface 70 is an interface unit (image input unit) that functions as an image input unit that receives image data sent from the host computer 86. As the communication interface 70, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 10 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 72 controls the communication interface 70, the image memory 74, the motor driver 76, the heater driver 78, and the like, and performs communication control with the host computer 86, read / write control of the image memory 74 and the ROM 75, and the like. At the same time, a control signal for controlling the motor 88 and the heater 89 of the transport system is generated.

  The ROM 75 stores programs executed by the CPU of the system controller 72 and various data necessary for control. The ROM 75 may be a non-rewritable storage means, or may be a rewritable storage means such as an EEPROM.

  The image memory 74 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  The motor driver 76 is a driver (driving circuit) that drives the conveyance motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heater 89 such as the post-drying unit 42 in accordance with an instruction from the system controller 72.

  Under the control of the system controller 72, the print control unit 80 performs various processes such as processing and correction for generating a droplet ejection control signal from image data (multi-value input image data) in the image memory 74. In addition to functioning as signal processing means, it also functions as drive control means for controlling the ejection drive of the head 50 by supplying the generated ink ejection data to the head driver 84.

  The ink discharge data is generated from the image data (multi-value input image data) in the image memory 74 in the ink discharge data generation unit 80A. If there is a non-ejection nozzle, first, a non-ejection nozzle that cannot be recorded is identified from among a plurality of nozzles in the non-ejection identification section 80C in the print control unit 80 as a specifying unit. Next, the non-ejection correction is performed on the initial ink ejection data generated from the image data (multi-valued input image data) in the image memory 74 by the correction processing unit 80B in the print control unit 80 as a correction unit. After performing the processing, the ink discharge data generation unit 80A generates ink discharge data.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the print control unit 80. In FIG. 12, the image buffer memory 82 is shown in a mode associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  An overview of the flow of processing from image input to print output is as follows. Image data to be printed is input from the outside via the communication interface 70 and stored in the image memory 74. At this stage, for example, RGB multivalued image data is stored in the image memory 74.

  The print control unit 80 performs processing for converting the input RGB image data into dot data of four colors Bk, C, M, and Y. Thus, the dot data generated by the print control unit 80 is stored in the image buffer memory 82. The dot data for each color is converted into CMYBk droplet ejection data for ejecting ink from the nozzles of the head 50, and the ink ejection data to be printed is determined.

  The head driver 84 outputs a drive signal for driving the actuator 58 corresponding to each nozzle 11 of the head 50 in accordance with the print content based on the ink ejection data and the drive waveform signal given from the print control unit 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  In this way, when the drive signal output from the head driver 84 is applied to the head 50, ink is ejected from the corresponding nozzle 11. An image is formed on the recording paper 16 by controlling the ink ejection from the head 50 in synchronization with the conveyance speed of the recording paper 16.

  As described above, the recording amount and ejection timing of ink droplets from each nozzle are controlled via the head driver 84 based on the ink ejection data and the drive signal waveform generated through the required signal processing in the print controller 80. Is done. Thereby, a desired dot size and dot arrangement are realized.

  As described with reference to FIG. 7, the print detection unit 24 is a block including an image sensor, reads an image printed on the recording paper 16, performs necessary signal processing, and the like to perform a print status (whether ejection is performed, droplet ejection And the detection result is provided to the print controller 80 and the system controller 72.

  The print control unit 80 performs various corrections on the head 50 based on information obtained from the print detection unit 24 as necessary, and performs cleaning operations (nozzle recovery operation) such as preliminary ejection, suction, and wiping as necessary. Perform the controls to be implemented.

  The image forming method and the image forming apparatus of the present invention have been described in detail above. However, the present invention is not limited to the above examples, and various improvements and modifications are made without departing from the gist of the present invention. Of course it is also good.

It is a figure which shows the relationship between the non-ejection nozzle in the non-ejection correction process of 1st Embodiment, and a complementation target nozzle. It is a figure showing the brightness distribution and chromaticity distribution after the non-ejection correction process of 1st Embodiment. It is a figure which shows the relationship between the non-ejection nozzle in the non-ejection correction process of 2nd Embodiment, and a complementation target nozzle. It is a figure showing the brightness distribution and chromaticity distribution after the non-ejection correction process of 2nd Embodiment. It is a figure which shows the flowchart of the non-ejection correction process in which the non-ejection correction processing method of this invention is used. It is a figure which shows the flowchart of an image forming method. 1 is an overall configuration diagram of an inkjet recording apparatus showing an embodiment of an image recording apparatus. It is a principal part top view of the printing part periphery of the inkjet recording device shown in FIG. It is a plane perspective view which shows the structural example of a head. It is a principal part enlarged view of Fig.9 (a). It is a plane perspective view which shows the other structural example of a full line type head. It is sectional drawing which follows the 10-10 line in Fig.9 (a). FIG. 10 is an enlarged view showing a nozzle arrangement of the head shown in FIG. It is a principal part block diagram which shows the structure of the image recording system which concerns on this embodiment. It is a figure which shows the mode of the lightness distribution and chromaticity distribution in the vicinity of the non-ejection nozzle at the time of performing adjacent complement. It is a figure which shows the mode of the brightness distribution and chromaticity distribution in the vicinity of the non-ejection nozzle at the time of performing different color complementation.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 11 ... Nozzle, 11C-2 ... Non-ejection nozzle, 11C-1, 11C-3 ... Same color adjacent nozzle, 11M-2, 11Y-2 ... Different color corresponding nozzle, 11M-1, 11Y-1, 11M-3, 11Y-3 ... adjacent nozzles of different colors, 12 ... recording head, 12C ... recording head (cyan ink), 12M ... recording head (magenta ink), 12Y ... recording head (yellow ink), 12Bk ... recording head (black) ink)

Claims (5)

In an image forming method in which a recording head for arranging a plurality of nozzles is provided for each of a plurality of liquid colors, and an image is formed by discharging and recording the liquid from the nozzles.
Identifying a non-ejection nozzle that cannot be recorded among the plurality of nozzles;
The recording amount of the same color adjacent nozzle that performs recording with the same color liquid at the position adjacent to the recording position where the non-ejection nozzle should be originally recorded is increased, and the non-ejection nozzle is different in color to the position corresponding to the recording position that should be originally recorded. Increasing the recording amount of the different color corresponding nozzle that performs recording with the liquid, and reducing the recording amount of the different color adjacent nozzle that performs recording with the different color liquid at a position adjacent to the recording position where the non-ejection nozzle should be recorded, possess a correction step of correcting the image, and
When the liquid color is cyan, magenta, or yellow, and the liquid color that should be recorded by the non-ejection nozzle is either cyan, magenta, or yellow, the different color corresponding nozzle and the different color adjacent nozzle perform recording. The color of the liquid to be performed is two colors other than the color of the liquid that should be recorded by the non-ejection nozzle among cyan, magenta, and yellow.
An image forming method. In an image forming method in which a recording head for arranging a plurality of nozzles is provided for each of a plurality of liquid colors, and an image is formed by discharging and recording the liquid from the nozzles.
Identifying a non-ejection nozzle that cannot be recorded among the plurality of nozzles;
The recording amount of the same color adjacent nozzle that performs recording with the same color liquid at the position adjacent to the recording position where the non-ejection nozzle should be originally recorded is increased, and the non-ejection nozzle is different in color to the position corresponding to the recording position that should be originally recorded. Increasing the recording amount of the different color corresponding nozzle that performs recording with the liquid, and reducing the recording amount of the different color adjacent nozzle that performs recording with the different color liquid at a position adjacent to the recording position where the non-ejection nozzle should be recorded, A correction step of correcting the image,
When the liquid color is cyan, magenta, yellow, or black, and the liquid color that should be recorded by the non-ejection nozzle is either cyan, magenta, or yellow, The color is black, and the color of the liquid recorded by the different color adjacent nozzles is two colors other than the color of the liquid that the non-ejection nozzle should originally record among cyan, magenta, and yellow.
An image forming method. The image forming method according to claim 1 or 2 ,
When the recording amount that should be recorded by the non-ejection nozzle is X,
And correcting the image by increasing the recording amount of the adjacent nozzle of the same color and the nozzle corresponding to the different color by approximately X / 2 and decreasing the recording amount of the adjacent nozzle of the different color by approximately X / 2 in the correction step.
An image forming method. In an image forming apparatus that includes a recording head that arranges a plurality of nozzles for each of a plurality of liquid colors, and forms an image by discharging and recording the liquid from the nozzles.
A specifying means for specifying a non-ejection nozzle that cannot record among the plurality of nozzles;
The recording amount of the same color adjacent nozzle that performs recording with the same color liquid at the position adjacent to the recording position where the non-ejection nozzle should be originally recorded is increased, and the non-ejection nozzle is different in color to the position corresponding to the recording position that should be originally recorded. Increasing the recording amount of the different color corresponding nozzle that performs recording with the liquid, and reducing the recording amount of the different color adjacent nozzle that performs recording with the different color liquid at a position adjacent to the recording position where the non-ejection nozzle should be recorded, We have a correction means for correcting the image,
When the liquid color is cyan, magenta, or yellow, and the liquid color that should be recorded by the non-ejection nozzle is either cyan, magenta, or yellow, the different color corresponding nozzle and the different color adjacent nozzle perform recording. The color of the liquid to be performed is two colors other than the color of the liquid that should be recorded by the non-ejection nozzle among cyan, magenta, and yellow.
An image forming apparatus. In an image forming apparatus that includes a recording head that arranges a plurality of nozzles for each of a plurality of liquid colors, and forms an image by discharging and recording the liquid from the nozzles.
A specifying means for specifying a non-ejection nozzle that cannot record among the plurality of nozzles;
The recording amount of the same color adjacent nozzle that performs recording with the same color liquid at the position adjacent to the recording position where the non-ejection nozzle should be originally recorded is increased, and the non-ejection nozzle is different in color to the position corresponding to the recording position that should be originally recorded. Increasing the recording amount of the different color corresponding nozzle that performs recording with the liquid, and reducing the recording amount of the different color adjacent nozzle that performs recording with the different color liquid at a position adjacent to the recording position where the non-ejection nozzle should be recorded, Having correction means for correcting the image;
When the liquid color is cyan, magenta, yellow, or black, and the liquid color that should be recorded by the non-ejection nozzle is either cyan, magenta, or yellow, The color is black, and the color of the liquid recorded by the different color adjacent nozzles is two colors other than the color of the liquid that the non-ejection nozzle should originally record among cyan, magenta, and yellow.
An image forming apparatus.

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