Color processing apparatus, color processing method, and program

Abstract

To solve such a problem that there is a need to wait for a standby time in order to perform calibration that takes color variation over time into account.SOLUTION: A color processing apparatus according to the present invention includes: acquisition means that acquires color information of a color chart printed on a first recording medium; holding means that holds color information representing colors printed on the recording media after a first predetermined time has elapsed in association with correction information for correcting the color indicated by the color information to a color after a second predetermined time which is longer than the first predetermined time has elapsed for a plurality of recording media; and processing means that executes printing processing for printing the image on the first recording medium by specifying the color information to be used for the first recording medium from the held color information according to the acquired color information and using the correction information corresponding to the specified color information.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a color conversion process that takes into account color variations over time in an image. [Background technology]

[0002] In various image recording methods such as the inkjet method, electrophotographic method, and various offset methods, a color variation phenomenon over time may occur, in which a difference occurs between the color of an output immediately after printing and the color after a certain period of time has passed. Calibration is performed to address this phenomenon. In calibration, a color chart is recorded by a printing device, and the color of the chart is measured using a measuring device. Then, image processing parameters of a color conversion table are created or updated according to the difference between the measured colorimetric value and the target color or density to be output.

[0003] However, this calibration process takes a long time, not only because of the time it takes to perform the process itself, but also because it is necessary to wait until the density or color stabilizes after recording the color chart. Depending on the recording medium, it may take up to a week for the color to stabilize.

[0004] Patent Document 1 discloses that a target density value for a target printing medium is set after detecting a waiting time (color stabilization time) required for the color change of an image recorded on the printing medium to stabilize. Patent Document 2 discloses that a LUT for a predetermined printing medium is created by performing a principal component analysis on the feature amount of the recording medium to be used. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-184902 A [Patent Document 2] JP 2012-199832 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the method disclosed in Patent Document 1, although it is possible to set a standby time for color variation over time according to the printing medium and perform appropriate calibration, it is necessary to wait for the standby time. Also, in the method disclosed in Patent Document 2, although it is possible to perform optimal calibration by analyzing each recording medium, it takes a long time before printing because a color conversion table is created. [Means for solving the problem]

[0007] In consideration of the above problems, the color processing device of the present invention is characterized by having an acquisition means for acquiring color information of a color chart printed on a first recording medium, a storage means for storing, for a plurality of recording media, color information representing the color printed on the recording medium after a first predetermined time has elapsed and correction information for correcting the color indicated by the color information to the color after a second predetermined time has elapsed that is longer than the first predetermined time, in association with each other, and a processing means for identifying color information to be used for the first recording medium from the stored color information in accordance with the acquired color information, and executing a printing process to print an image on the first recording medium using the correction information corresponding to the identified color information. Effect of the Invention

[0008] It becomes possible to perform calibration that takes into account color variations over time without requiring a long period of time. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram illustrating an example of the configuration of an inkjet recording apparatus. [Diagram 2] FIG. 2 is a block diagram showing the functional configuration of the inkjet printing apparatus. [Diagram 3] FIG. 2 is a block diagram of a printer control unit in the inkjet recording apparatus. [Figure 4] 4 is a flowchart of image processing performed by a print data generating unit 201. [Diagram 5]FIG. 4 is a block diagram showing a configuration for color adjustment performed in color shift correction processing. [Figure 6] 13 is a flowchart of a reuse calibration process. [Figure 7] 1 is an example of a color chart for identifying a recording medium. [Figure 8] 5A to 5C are diagrams showing color variations over time in various recording media. [Figure 9] 1 shows examples of recording media used in each of the examples and comparative examples, and examples of recording media on a database. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present invention will be described in detail below with reference to preferred embodiments. The scope of the present invention is not limited by the following description, and all of the configurations described in the present embodiment are not essential components of the present invention and may be combined as appropriate. In addition, an inkjet recording device will be used as the recording device, but recording devices using an electrophotographic method or various offset methods may also be used.

[0011] <Inkjet recording device> An inkjet recording apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

[0012] 1 is a schematic diagram showing an example of the schematic configuration of an inkjet recording apparatus 100. This recording apparatus is a sheet-fed inkjet recording apparatus that produces a recorded matter by forming an image on a recording medium 101 using two liquids, a reaction liquid and an ink. In this embodiment, the X direction, Y direction, and Z direction respectively indicate the width direction (total length direction), depth direction, and height direction of the inkjet recording apparatus 100. The recording medium 101 is transported in the X direction.

[0013] The inkjet recording apparatus 100 also has transport units 107a, 107b, and 107c that transport the recording medium 101 in the X direction. The inkjet recording apparatus 100 also has a paper feed unit 106a that feeds the recording medium 101 to the transport unit 107a, and a paper discharge unit 106b that collects the printed recording medium 101 from the transport unit 107c. In addition, the inkjet recording apparatus 100 has a reaction liquid application unit 102 that applies a reaction liquid that reacts with the ink onto the recording medium 101, and an ink application unit 103 equipped with an inkjet head that applies ink onto the recording medium 101 to which the reaction liquid has been applied, thereby forming an image. The inkjet recording apparatus 100 also has a hot air drying unit 104 that heats and dries liquid components from the image, and a fixing unit 105 that fixes the ink.

[0014] <Recording medium and recording medium transport device> In this embodiment, the recording medium 101 is not particularly limited, and any known recording medium can be used. Examples of the recording medium include a long object wound in a roll, and a sheet cut to a predetermined size.

[0015] In the inkjet recording apparatus 100 of this embodiment, the recording medium 101 is transported in the X direction by transport units 107a, 107b, and 107c. Each of the transport units 107a, 107b, and 107c is a belt that rotates around a rotation axis in the Y direction, and may be made of a material such as resin or metal. The belts of the transport units 107a and 107b are preferably provided with a large number of holes so that the recording medium on the belt can be fixed by a suction pump installed under the belt.

[0016] 1, the dotted arrow on the inside of each component diagram indicates the rotation direction of that component, and the dotted arrow on the outside indicates the transport path of the recording medium 101. The recording medium 101 is transported from a paper feed unit 106a to a transport unit 107a. An image is formed on the recording medium 101 on the transport unit 107a by a reaction liquid deposition unit 102 and an ink deposition unit 103. To prevent the recording medium 101 from shifting on the transport unit 107a when the image is formed, a fixing device 108 installed under the belt of the transport unit 107a fixes the recording medium 101 on the belt by sucking it with negative pressure using a suction pump or the like.

[0017] The recording medium 101 on which the image has been formed is transported from the transport unit 107a to the transport unit 107b. In the transport unit 107b, the recording medium 101 is dried by the hot air drying section 104 while the recording medium 101 is fixed on the belt.

[0018] Thereafter, the recording medium 101 is transported from the transport unit 107b to the transport unit 107c. The recording medium 101 on the transport unit 107c is heated by the fixing unit 105, so that the ink is fixed.

[0019] The recording medium 101 is transported from the transport unit 107c to the paper discharge unit 106b, and is stacked in the paper discharge unit 106b.

[0020] <Hot air drying section> The hot air drying unit 104 can heat and dry the surface to which the reaction liquid and ink are applied by applying hot air to the surface to which the reaction liquid and ink are applied, as shown in Fig. 1. Alternatively, the surface to which the reaction liquid and ink are applied may be heated from the rear side to heat and dry the surface from both sides.

[0021] The hot air temperature and the back surface heating temperature are preferably from 40° C. to 100° C., and more preferably from 60° C. to 80° C. The moisture content of the reaction liquid and ink after drying with hot air is preferably 10% by mass or less to suppress cockling of the recording medium 101, and is preferably 2% by mass or more to maintain the fastness of the ink film after fixing.

[0022] <Fixing section> The fixing unit 105 heats and solidifies the ink applied to the recording medium 101. By heating and drying the recording medium 101 on which an image has been formed, a film is formed by the resin particles contained in the ink. In this way, the ink is turned into a film on the recording medium 101, and a high-quality image with excellent abrasion resistance can be obtained.

[0023] <Reaction solution application section> The inkjet recording apparatus 100 of this embodiment has a reaction liquid application unit 102 that applies a reaction liquid to a recording medium 101. The reaction liquid reduces the fluidity of the ink and / or part of the ink composition on the recording medium 101 by contacting with the ink, and can suppress bleeding and beading during image formation by the ink. Specifically, a reactant (also called an ink viscosity increasing component) contained in the reaction liquid chemically reacts or physically adsorbs with a coloring material, a resin, or the like that is a part of the composition that constitutes the ink by contacting with the coloring material, or the like. This causes an increase in the viscosity of the entire ink, or a local increase in viscosity due to aggregation of a part of the components that constitute the ink, such as the coloring material, and can reduce the fluidity of the ink and / or part of the ink composition. The application of the reaction liquid may be performed before or after the application of the ink, as long as it can be mixed (reacted) with the ink on the recording medium 101.

[0024] The amount of the reaction liquid applied is determined by optimizing it for each recording device, recording medium, and ink set. In particular, since the purpose is to aggregate the coloring material as described above, a method of adjusting the amount applied based on the permeability of the ink into the recording medium (ease of ink sinking) is preferably used. For example, in the case of offset uncoated paper with high permeability, the applied ink sinks into the paper surface quickly, so that a printed matter of good image quality tends to be obtained by applying a large amount of reaction liquid. On the other hand, in the case of offset coated paper with low permeability, the coloring material sinks slowly, so that a small amount of reaction liquid can be applied, and from the viewpoint of drying efficiency and image quality improvement, a small amount of reaction liquid tends to produce a good printed matter. In addition, in paper with a receiving layer such as inkjet coated paper, the porous surface is processed so that the coloring material remains on the surface layer, so that a printed matter of good image quality tends to be obtained with a small amount of reaction liquid or no reaction liquid. The permeability of the recording medium will be described later in <Recording medium>.

[0025] <Ink application section> In this embodiment, an inkjet head is used as the ink applying unit 103 that applies ink. Examples of inkjet heads include a type that ejects ink by generating film boiling in the ink using an electrothermal converter to form bubbles, a type that ejects ink using an electromechanical converter, and a type that ejects ink using static electricity.

[0026] In this embodiment, the inkjet head is a line head extending in the Y direction, and the nozzles are arranged in a range covering the width of the image recording area of ​​the largest usable size of recording medium. The inkjet head has an ink ejection surface with nozzles opening on its lower surface (the recording medium 101 side), and the ink ejection surface faces the surface of the recording medium 101 with a minute gap (about a few millimeters) therebetween.

[0027] The amount of ink applied can be expressed by the density value of the image data, the ink thickness, etc., but in this embodiment, the ink application amount (g / m) is calculated by multiplying the mass of each ink dot by the number of ink dots applied and dividing the result by the printing area to obtain the average value. 2The maximum amount of ink applied in the image area is set to at least 5 mm within the area used as information on the ejection medium from the viewpoint of removing the liquid components in the ink. 2 The amount of ink applied to the above area is shown. The amount of ink applied is optimized and determined for each recording device, recording medium, and ink set. As with the amount of reaction liquid applied described above, a method of adjusting the amount applied based on the permeability of the ink into the recording medium (ease of ink sinking) is preferably used. For example, in the case of offset uncoated paper, the ink is likely to sink easily, so applying a larger amount, and in the case of offset coated paper, the ink is less likely to sink, so applying a smaller amount tends to produce a good printed product.

[0028] The ink application unit 103 may have a plurality of inkjet heads for applying each color ink onto the recording medium 101. For example, when forming each color image using yellow ink, magenta ink, cyan ink, and black ink, the ink application unit 103 has four inkjet heads that respectively eject the above four types of ink onto the recording medium 101. These inkjet heads are arranged in a line in the X direction.

[0029] <Ink> The components of the ink used in this embodiment will be described in detail below. In this embodiment, a water-based pigment ink is used as a suitable example, but the present invention is not limited to water-based pigment ink.

[0030] [Colorant] The ink preferably contains a coloring material. Pigments or dyes can be used as the coloring material. The content (mass %) of the coloring material in the ink is preferably 0.5% by mass or more and 15.0% by mass or less, and more preferably 1.0% by mass or more and 10.0% by mass or less, based on the total mass of the ink.

[0031] Specific examples of pigments include inorganic pigments such as carbon black and titanium oxide; and organic pigments such as azo, phthalocyanine, quinacridone, isoindolinone, imidazolone, diketopyrrolopyrrole, and dioxazine.

[0032] As a pigment dispersion method, resin-dispersed pigments using a resin as a dispersant, self-dispersed pigments in which hydrophilic groups are bonded to the pigment particle surface, etc. can be used. In addition, resin-bonded pigments in which organic groups containing a resin are chemically bonded to the pigment particle surface, and microcapsule pigments in which the pigment particle surface is coated with a resin or the like can be used.

[0033] As the resin dispersant for dispersing the pigment in the aqueous medium, it is preferable to use one that can disperse the pigment in the aqueous medium by the action of anionic groups. As the resin dispersant, a resin as described below, particularly a water-soluble resin, can be used. The content (mass%) of the pigment in the ink is preferably 0.3 times or more and 10.0 times or less in mass ratio to the content of the resin dispersant.

[0034] As the self-dispersing pigment, an anionic group such as a carboxylic acid group, a sulfonic acid group, or a phosphonic acid group can be used, which is bonded to the particle surface of the pigment directly or via another atomic group (-R-). The anionic group may be either an acid type or a salt type, and when it is a salt type, it may be either a partially dissociated state or a completely dissociated state. When the anionic group is a salt type, examples of the cation that serves as the counter ion include an alkali metal cation, ammonium, and organic ammonium. Specific examples of the other atomic group (-R-) include a linear or branched alkylene group having 1 to 12 carbon atoms; an arylene group such as a phenylene group or a naphthylene group; a carbonyl group; an imino group; an amide group; a sulfonyl group; an ester group; and an ether group. In addition, it may be a group that is a combination of these groups.

[0035] The dye preferably has an anionic group. Specific examples of the dye include azo, triphenylmethane, (aza)phthalocyanine, xanthene, and anthrapyridone dyes. The coloring material is preferably a pigment, and more preferably a resin-dispersed pigment.

[0036] [resin] The ink preferably contains resin particles. By using an ink containing resin particles, it is possible to suppress image peeling and record an image with improved fixability and abrasion resistance. The ink may further contain a water-soluble resin that can be dissolved in an aqueous medium. The water-soluble resin can be added to the ink (i) to stabilize the dispersion state of the pigment, that is, as a resin dispersant or its auxiliary. In addition, it can be added to the ink (ii) to improve various properties of the image to be recorded.

[0037] The content (mass %) of the resin in the ink is preferably from 0.1 to 20.0% by mass, more preferably from 0.5 to 15.0% by mass, based on the total mass of the ink. The form of the resin may be a block copolymer, a random copolymer, a graft copolymer, or a combination thereof.

[0038] [Resin Composition] Examples of the resin include acrylic resin, urethane resin, and olefin resin.

[0039] [Wax particles] The ink can contain particles formed from wax (wax particles). By containing wax in the ink, it is possible to improve the slipperiness of the surface of the printed matter, reduce scratches on the printed matter, and prevent blocking between printed matters.

[0040] [Aqueous medium] The ink used in the recording method of the present embodiment is an aqueous ink containing at least water as an aqueous medium. The ink may contain water or an aqueous medium that is a mixed solvent of water and a water-soluble organic solvent.

[0041] The water-soluble organic solvent contained in the ink is preferably one having a boiling point of 250° C. or higher, as this contributes to suppression of adhesion to the inkjet head due to drying of moisture, and for example, glycerin can be used. Furthermore, from the viewpoint of suppressing deformation of the paper of the printed matter, it is preferable that the ink contains the following specific water-soluble hydrocarbon compound. This water-soluble hydrocarbon compound is a compound having a hydrocarbon chain having three or more carbon atoms substituted with two or more hydrophilic groups selected from the group consisting of hydroxyl groups, amino groups, and anionic groups. However, the hydrocarbon chain may be interrupted by a sulfonyl group or an ether group.

[0042] The content (mass %) of the water-soluble hydrocarbon compound in the ink is preferably 1.0 mass % or more and 20.0 mass % or less based on the total mass of the ink.

[0043] [Other ingredients] The ink may contain various other components as necessary, such as defoamers, surfactants, pH adjusters, viscosity adjusters, rust inhibitors, preservatives, antifungal agents, antioxidants, and antireducing agents.

[0044] [Ink properties] The ink of this embodiment is a water-based ink applied to the inkjet method. Therefore, from the viewpoint of reliability, it is preferable to appropriately control the physical property values. Specifically, the surface tension of the ink at 25°C is preferably 20 mN / m or more and 60 mN / m or less. In addition, the viscosity of the ink at 25°C is preferably 1.0 mPa·s or more and 10.0 mPa·s or less. The pH of the ink at 25°C is preferably 7.0 or more and 9.5 or less, and more preferably 8.0 or more and 9.5 or less.

[0045] <Control system> The inkjet recording apparatus in this embodiment has a control system for controlling each device. Fig. 2 is a block diagram showing the control system for the entire inkjet recording apparatus shown in Fig. 1. The control system has a recording data generating unit 201 such as an external print server, an operation control unit 202 such as an operation panel, a printer control unit 203 for performing the recording process, and a recording medium transport control unit 204 for transporting the recording medium. It also has an inkjet device 205 for performing print processing.

[0046] Fig. 3 is a block diagram of the printer control unit 203 in the inkjet recording apparatus of Fig. 1. The printer control unit 203 has a CPU 301 that controls the entire printer, a ROM 302 for storing a control program for the CPU, and a RAM 303 for executing the program. An application specific integrated circuit (ASIC) 304 has the following built-in: a network controller, a serial IF controller, a head data generation controller, a motor controller, etc. A head control unit 305 generates final ejection data for the inkjet device 205, generates drive voltages, etc.

[0047] [Record data generation] Fig. 4 is a flowchart of image processing performed by the print data generation unit 201 to generate print data in the printing system of this embodiment described above with reference to Figs. 1 to 3. The image processing of this embodiment receives image data (brightness data) of 8 bits (256 gradations each) for each of red (R), green (G), and blue (B). Then, processing is performed to finally output 1-bit image data (print data) ejected by the print heads of C, M, Y, and K. Note that the types of colors and color gradations are not limited to these values.

[0048] In S401, a three-dimensional color conversion table is used to convert image data represented by 8-bit luminance signals for each of the R, G, and B colors into 8-bit or 10-bit R', G', and B' data for each color. This color space conversion preprocessing (also called pre-color processing) is performed to correct the difference between the color space represented by the R, G, and B image data of the recording object and the color space reproducible by the recording device.

[0049] In S402, the R', G', and B' color data that has been subjected to pre-stage color processing is converted using a three-dimensional color conversion table into 10-bit data for each of C, M, Y, and K. This color conversion processing (also called post-stage processing) converts the input RGB system image data expressed as a luminance signal into C, M, Y, and K image data used by the inkjet device 205.

[0050] In S403, output gamma correction is performed on the 10-bit data for each of the colors C, M, Y, and K that has been subjected to post-stage color processing, using a one-dimensional color conversion table for each color. Normally, the number of dots recorded per unit area of ​​the recording medium and the recording characteristics such as reflection density obtained by measuring the recorded image do not have a linear relationship. Therefore, output gamma correction is performed to correct the input gradation levels of each of the 10 bits of C, M, Y, and K so that the input gradation levels of each of the 10 bits of C, M, Y, and K and the density levels of the image recorded based on them have a linear relationship.

[0051] In S404, in this embodiment, the output gamma correction of the color shift correction process is performed on the 10-bit data for each of the colors C, M, Y, and K that has been subjected to the output gamma correction, using a one-dimensional color conversion table for color shift correction of each color. For example, there are individual differences in the amount of ink ejected from each nozzle in a print head that ejects ink used in a printing device, that is, the size of the printed dots. Therefore, even if the number of dots printed is adjusted by output gamma correction using the one-dimensional color conversion table, color shift may occur due to differences in the obtained optical density. For this reason, in this embodiment, the color shift correction process is performed using the one-dimensional color conversion table for color shift correction of each of the colors C, M, Y, and K.

[0052] In S405, the 10-bit data for each of the C, M, Y, and K colors is converted into 1-bit binary data for each of the C, M, Y, and K colors by binarization (quantization).

[0053] <Recording Media> The recording medium is not particularly limited, and may be uncoated paper such as fine paper or plain paper, coated paper for offset printing having a coating layer made of calcium carbonate or kaolin, non-permeable PET film, inkjet paper having a liquid receiving layer for inkjet printing, etc. Among them, the present invention is preferably applicable to recording media with low absorbency for water-based inks (low absorbency recording media).

[0054] A low-absorbency recording medium is a recording medium having a water absorption of 4 mL / m2 or more and 10 mL / m2 or less from the start of contact to 30 msec1 / 2 in the Bristow method. Examples of low-absorbency recording media include recording media that do not have an ink-receiving layer and recording media with a thin ink-receiving layer. Examples include printing papers such as art paper, fine coated paper, medium coated paper, fine lightweight coated paper, medium lightweight coated paper, light-coated paper, and cast coated paper.

[0055] <Reusing color conversion tables> [Printing and measuring a color chart for identifying recording media] Next, the calibration for color variation over time in this embodiment will be described. Calibration is executed by inputting a calibration start command as a part of the processing by the CPU 301 or as a user input via the operation control unit 202 in the printer control unit in FIG.

[0056] First, a color chart for determining the classification of the recording medium (first recording medium) to be printed is printed on the first recording medium. The color chart varies depending on the recording method and color material set, so there is no limitation on the number of colors, but from the viewpoint of improving the accuracy of recording medium determination, the number of colors is better, and from the viewpoint of performing the determination process quickly, the number of colors is better. Therefore, it is desirable to determine the optimal number of colors of the color chart in consideration of this trade-off relationship. In particular, from the viewpoint of improving the accuracy of correction, it is more preferable to include the gradation patterns of each monochromatic color to be used and multi-order colors that are appropriately combined with each monochromatic color. In this embodiment, a 100-patch color chart conforming to ISO12647 is used as the evaluation chart. The 100 patches are composed of 8 gradations of each of the monochromatic gradation patterns described above and the remaining combination patterns of multi-order colors.

[0057] Next, the color chart recorded on the recording medium is measured. This color measurement is performed immediately after printing the color chart. Here, "immediately after printing" refers to after a first predetermined time has elapsed, that is, after the color material has been applied to the recording medium and then the drying and fixing and cooling processes have been performed. The color measurement may be performed inside or outside the recording device, but from the viewpoint of performing calibration quickly, it is preferable to perform the color measurement inside the recording device. Note that, when the color measurement is performed outside the recording device, the color measurement may be performed in advance, and during calibration, the measured colorimetric value data may simply be obtained as color information.

[0058] The color space information obtained by color measurement is various color system signal values. For example, the CIE color system, the RGB color system, the XYZ color system, etc. can be used as appropriate. In this embodiment, the L * a * b * Color space signal value (hereafter referred to as L * a * b * The color measurement can be performed using various commercially available color measuring devices.

[0059] Based on the example of a part of the 100 patches in Figure 7, the color chart and L * a * b *As shown in Figure 7, for each patch of CMYK, the target color L * a * b * There is a difference between the corrected value and the uncorrected color space signal value, and the comparison of these values ​​is the color difference ΔE. This difference occurs due to color variation over time. For example, in the case of patch 1, which is a single color of cyan, ΔE is 0.56, and the color variation over time is small, whereas in the case of patch 99, which is a multi-color, ΔE=1.82, and the color variation over time is large. According to the standards published by the Color Science Association of Japan, ΔE=0.4 to 0.8 is the AAA-class tolerance range, which is the limit range where strict allowable color difference standards can be set, that is, the level where color changes are almost invisible. On the other hand, ΔE=1.6 to 3.2 is the A-class tolerance range, which is the color difference that is almost unnoticeable in a distant color comparison, that is, the level where the color difference can be seen in a close-up comparison, and the visibility of the color difference can be evaluated by the value of ΔE.

[0060] [Calculating ΔE for recording medium discrimination] L immediately after printing on the recording medium to be printed * a * b * The value and the color conversion table are stored in a recording medium, i.e., in a database in the device. * a * b * L of the recording medium on which the value is stored * a * b * The color difference ΔE is calculated by comparing the color information immediately after printing with the color information representing the color reproduced after the second predetermined time, which is longer than the first predetermined time, has elapsed, for a plurality of recording media that can be printed by the recording device used. The recording media in the database hold a correspondence relationship between the color information immediately after printing and the color information representing the color reproduced after the second predetermined time, which is longer than the first predetermined time, has elapsed. In other words, conversion table information to be used when correcting the color information immediately after printing based on this correspondence relationship is prepared in advance.

[0061] The present invention will be described in detail with reference to Fig. 8. Fig. 8(a) shows the L immediately after printing and after color stabilization, using two types of recording media each of which is an example of one of three different classifications of recording media (absorbent recording media, low absorbent recording media, and porous surface-processed recording media). * a * b * value and Δ(L * a * b * ) are shown. As shown in Fig. 8(a), each of the three recording media has its own characteristics. For example, the low absorbency recording medium has a higher L than the other recording media. * is low, a * and b * shows a relatively high value. This shows a similar tendency regardless of the type of coated paper. On the other hand, absorbent recording media has a high L * shows a high value. * and b * The characteristics of the porous surface recording medium are dependent on the individual recording medium. * is higher than that of the absorbent recording medium, and a * Furthermore, the L * The amount of change (ΔL * ) from the ΔL of the low absorbency recording medium * It can be seen that the variation range is wider than for other recording media. Since these variation trends do not vary significantly within each recording medium type, it is possible to distinguish the recording medium type and reuse the color conversion information.

[0062] Due to the above trends in recording media, it is necessary to prepare at least one type of recording media belonging to the three recording media classifications (absorbent recording media, low absorbent recording media, and recording media with porous processed surfaces) in advance in the database. It is preferable to prepare at least one type of recording media belonging to each classification described in <Recording Media>, so that a recording medium with properties similar to the recording medium to be printed can be selected and color correction can be performed with high accuracy. Note that, although the recording media are classified here, they may be specified directly without classification.

[0063] Now, as mentioned above, the L * a* b * The value and the color conversion table prepared in advance in the database of the device. * a * b * The values ​​are compared to calculate the color difference ΔE, and a general color difference formula can be used as appropriate for the color difference ΔE. For example, the CIE 1976 color difference formula (ΔE76), the CIE 1994 calculation formula (ΔE94), and the CIE 2000 calculation formula (ΔE00) can be used. In this embodiment, ΔE00 (hereinafter referred to as ΔE), which is preferable from the viewpoint of perceptual uniformity, is used. Specific examples of recording media on the database and examples of reusing printing conditions by comparing ΔE will be described later in the examples.

[0064] [Reusing color conversion tables and image processing] The color adjustment will be described in detail with reference to FIG. 5. The color adjustment is performed by an image processing unit 501 in the print data generating unit 201. The image processing unit 501 performs color adjustment of this YMCK data so that it matches the target color that should be originally output by the image forming unit 502 in response to the YMCK data. In this embodiment, this conversion is performed by converting the L * a * b * The color space information is converted to the output Y´M´C´K´ data using a color conversion table. The color conversion table is a device-independent color space (L * a * b * ) to device-dependent color space (CMYK) to correct color mixing.

[0065] The color conversion table to be used is determined by the color processing unit 503. In the color processing unit 503, the image information acquisition unit 504 acquires the L immediately after printing of the recording medium identification color chart printed on the recording medium to be printed. * a * b * The color comparison processing unit 505 obtains the L value data immediately after printing of various recording media recorded in the database of the ROM 302. * a * b *The color conversion unit 506 uses the color conversion table and printing conditions of the selected recording medium to convert to the final input values ​​Y'M'C'K' of each color in the image forming unit 502.

[0066] [Overall flow of reusing printing conditions] FIG. 6 is a flowchart showing the procedure of the calibration process.

[0067] In S101, first, for the recording medium to be printed, it is confirmed whether or not printing conditions including a color conversion table for that recording medium exist in the database (DB) of the printing device. As an example of the comparison, if the user sets the name of the recording medium to be printed as a printing condition, a comparison is made to see whether or not that name exists in the DB. If the comparison shows that the printing conditions exist, the printing can be performed by applying the printing conditions to print, thereby performing printing that also calibrates color variations.

[0068] In S102, if the result of the check in S101 is that no printing conditions exist, color measurement data of a color chart for specifying a recording medium to be printed is acquired.

[0069] In S103, the color measurement value immediately after printing the acquired color chart and the L * a * b * The recording medium type is classified by comparing the value.

[0070] In S104, the closest recording medium is identified from among the classified types of recording media.

[0071] In S105, the printing conditions of the identified registered recording medium are set.

[0072] In S106, printing is performed using the correction information included in the set printing conditions. The correction information used here is correction information for correcting the colorimetric values ​​acquired in S103 to colors after a second predetermined time has elapsed that is longer than the colorimetric values ​​immediately after printing, and is information stored in the DB in association with the colorimetric values ​​immediately after printing for each recording medium.

[0073] In S107, the printing conditions identified in S105 are registered in the DB as a new record. EXAMPLES

[0074] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples as long as it does not exceed the gist of the invention. The amounts of components are expressed as "parts" and "%" by weight unless otherwise specified. The recording media shown here are merely examples and do not limit the scope of application.

[0075] (Common conditions) In this embodiment, an inkjet recording apparatus 100 shown in Fig. 1 was used. The conveying speed was 0.5 m / s, and various recording media, which will be described later, were used as the recording medium 101.

[0076] <Preparation of reaction solution> The components shown below were mixed and thoroughly stirred, and then pressure filtered through a cellulose acetate filter with a pore size of 3.0 μm to prepare a reaction liquid. Magnesium nitrate hexahydrate 15.0% by mass Ethylene glycol 8.0% by mass Acetylenol E100 1.0% by mass Ion-exchanged water 76.0% by mass The ink used was prepared as follows.

[0077] <Preparation of pigment dispersion> [Pigment dispersion 1] A styrene-ethyl acrylate-acrylic acid copolymer (resin 1) with an acid value of 150 mgKOH / g and a weight average molecular weight of 8,000 was prepared. 20.0 parts of resin 1 were neutralized with potassium hydroxide in an amount equimolar to the acid value, and then an appropriate amount of pure water was added to prepare an aqueous solution of resin 1 with a resin (solid content) content of 20.0%. 10.0 parts of pigment (CI Pigment Blue 15:3), 15.0 parts of the aqueous solution of resin 1, and 75.0 parts of pure water were mixed to obtain a mixture. The obtained mixture and 200 parts of zirconia beads with a diameter of 0.3 mm were placed in a batch-type vertical sand mill and dispersed for 5 hours while cooling with water. After centrifuging to remove coarse particles, the mixture was pressure-filtered with a cellulose acetate filter with a pore size of 3.0 μm to prepare pigment dispersion 1 with a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0%.

[0078] [Pigment dispersion 2] Pigment dispersion 2 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Red 122. The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0079] [Pigment dispersion 3] Pigment dispersion 3 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to CI Pigment Yellow 74. The pigment content was 10.0% and the resin dispersant (resin 1) content was 3.0%.

[0080] [Pigment dispersion 4] Pigment dispersion 4 was prepared using the same procedure as for pigment dispersion 1 described above, except that the pigment was changed to carbon black. The pigment dispersion 4 had a pigment content of 10.0% and a resin dispersant (resin 1) content of 3.0%.

[0081] <Preparation of resin particles> (Resin particle dispersion 1) In a four-neck flask equipped with a stirrer, a reflux condenser, and a nitrogen gas inlet tube, 74.0 parts of ion-exchanged water and 0.2 parts of potassium persulfate were mixed. In addition, 24.0 parts of ethyl methacrylate, 1.5 parts of methacrylic acid, and 0.3 parts of a reactive surfactant were mixed to prepare an emulsion. Under a nitrogen atmosphere, the prepared emulsion was dropped into the four-neck flask over 1 hour, and a polymerization reaction was carried out for 2 hours while stirring at 80°C. After cooling to 25°C, ion-exchanged water and an aqueous solution containing potassium hydroxide in an amount equimolar to the acid value of the resin particles were added to prepare an aqueous dispersion 1 of resin particles having a resin particle (solid content) content of 25.0%.

[0082] <Printing condition a> The hot air drying unit 104 that heats and dries the ink uses a hot air dryer, and the ink ejection amount and drying conditions were set so that the surface temperature of the recording medium 101 would be a predetermined temperature. The reaction liquid applied by the reaction liquid application device 102 was prepared as described above, and the application amount was 2 g / m 2 The ink application device 103 uses an inkjet head that uses an electrothermal conversion element to eject ink on demand, and the amount of ink applied is 24 g / m 2 It was decided.

[0083] The surface temperature of the recording medium was measured using a radiation thermometer. The fixing unit 105 used a fixing belt that could be heated from inside the belt with a halogen heater. The surface temperature of the fixing device 105 immediately before contacting the recording medium 101 was set to a predetermined temperature. A PTFE material was used for the fixing member that came into contact with the recording medium, and fixing was performed at a temperature of 90° C. and a fixing pressure of 200 Pa. The surface temperature of the fixing member was measured using a radiation thermometer.

[0084] Under the above printing conditions, the above-mentioned color chart for discriminating the type of recording medium was printed on various recording media 101 of A3 size.

[0085] <Identifying the recording medium type> The printed color chart was measured one minute after printing to obtain the color space signal value L * a * b* The color was measured using a fluorescence spectrodensitometer under the following conditions.

[0086] [Color measurement conditions] Measurement environment: 25℃, 50% Measurement method: Reflection measurement Lighting conditions: M1 (D50) Observation field of view: 2° Observation light source: D50 Change filter: Not installed L of each color of the measured color chart * a * b * The L value of each color after 1 minute of printing on the reference recording medium in the database confirmed in advance * a * b * The values ​​were compared and the recording medium in the database with the closest ΔE was selected. The recording media in the database were prepared in advance from 18 types of recording media with different surface properties, including absorbent and non-absorbent recording media.

[0087] FIG. 9(a) shows the L of each embodiment and the recording medium on the database. * a * b * The results of comparing values ​​are shown below. Note that when ΔE exceeds 10, it is left blank (shown as a horizontal bar) since it is not worth comparing.

[0088] <Printing the evaluation chart> In this embodiment, the above-mentioned recording medium type discrimination color chart was printed under the same printing conditions as those in the above-mentioned <Printing Conditions>.

[0089] Example 1 <Preparation of ink set a> The components shown below (unit: %) were mixed to prepare cyan, magenta, yellow, and black inks. The resin particle dispersion 1 and pigment dispersions 1 to 4 obtained above were mixed with the components shown below. Note that the cyan ink was prepared using only pigment dispersion 1, the magenta ink 2, the yellow ink using only pigment dispersion 3, and the black ink using only pigment dispersion 4 to prepare the cyan, magenta, yellow, and black inks. The remaining amount of ion-exchanged water is the amount that makes the total of all components constituting the ink 100.0% by mass. Pigment dispersion 20.0% by mass ·Resin particle dispersion 1 24.0% by mass Ethylene glycol 7.0% by mass Surfactant 0.5% by weight Ion-exchanged water Remainder This was thoroughly stirred to disperse, and then pressure filtered through a microfilter having a pore size of 3.0 μm to prepare an ink.

[0090] Ink set a can volatilize almost all of the water and water-soluble organic solvent in the ink layer by heating and fixing after printing with the recording device of the present invention. Ink set a can be used to print on paper-based paper and non-absorbent films, but when used on paper-based paper, the effect of suppressing curling and cockling tends to be inferior to when ink set b described below is used.

[0091] In Example 1, offset uncoated paper was used as the unregistered recording medium. In Fig. 9(a), a comparison was made with the recording media in the database, and Product 1 (ΔE = 0.64) was selected as the recording medium with the closest average ΔE, and the color conversion table of OK Prince wood-free paper was applied to print the evaluation chart.

[0092] Example 2 In Example 2, offset coated paper was used as the unregistered recording medium. The evaluation chart was printed using the product 10 from Figure 9(a) as the color conversion table to be used. Printing and evaluation were performed under the same conditions as in Example 1.

[0093] Example 3 In Example 3, the ink (ink set b) prepared as follows was used. The color conversion table used was the product 12 shown in FIG. 9(a) and used to print the evaluation chart. Other than that, printing and evaluation were performed under the same conditions as in Example 2.

[0094] <Preparation of ink set b> The components shown below (unit: %) were mixed to prepare cyan, magenta, yellow and black inks.

[0095] The above-mentioned resin particle dispersion 1 and pigment dispersions 1 to 4 were mixed with the following components. Note that cyan ink was prepared using only pigment dispersion 1, magenta ink 2, yellow ink using only pigment dispersion 3, and black ink using only pigment dispersion 4 to prepare cyan, magenta, yellow, and black inks. The remainder of the ion-exchanged water is the amount that makes the total of all the components constituting the ink 100.0% by mass. Pigment dispersion 20.0% by mass ·Resin particle dispersion 1 24.0% by mass Ethylene urea 7.0% by mass Polyethylene glycol (number average molecular weight (Mn): 1,000) 1.0% by mass Surfactant 0.5% by weight Ion-exchanged water Remainder This was thoroughly stirred to disperse, and then pressure filtered through a microfilter having a pore size of 3.0 μm to prepare an ink.

[0096] In addition, when ink set B is printed and then heated and fixed by a recording device, the water content is almost entirely evaporated, allowing the water-soluble organic solvent to penetrate into the paper. The water-soluble organic solvent contained in ink set B penetrates into the paper, effectively preventing curling and cockling of the paper after printing.

[0097] Example 4 In Example 4, the following conditions (printing conditions b) were used as printing conditions. Printing and evaluation were performed under the same conditions as in Example 3 except for the above.

[0098] <Printing conditions b> The hot air drying device 104 for heating and drying the ink was a hot air dryer, and was set so that the surface temperature of the recording medium 101 was a predetermined temperature. The reaction liquid applied by the reaction liquid application unit 102 was prepared as described above, and the application amount was 1 g / m 2 The ink application unit 103 uses an inkjet head that uses an electrothermal conversion element to eject ink on demand, and the amount of ink applied is 18 g / m 2 It was decided.

[0099] The surface temperature of the recording medium was measured using a radiation thermometer. The fixing device 105 used a fixing belt that could be heated from inside the belt with a halogen heater. The surface temperature of the fixing device 105 immediately before contacting the recording medium 101 was set to a predetermined temperature. A PTFE material was used for the fixing member that came into contact with the recording medium, and fixing was performed at a temperature of 90° C. and a fixing pressure of 200 Pa. The surface temperature of the fixing member was measured using a radiation thermometer.

[0100] Comparative Example 1 In Comparative Example 1, offset coated paper was used as the unregistered recording medium. The evaluation chart was printed using the product 14 from Figure 9(a) as the color conversion table to be used. Printing and evaluation were performed under the same conditions as in Example 3 otherwise.

[0101] <Evaluation> The image samples obtained in the above examples were evaluated by the following evaluation method. The evaluation results are shown in FIG. 9(b). * a * b * The color space signal values ​​were confirmed, and the average ΔE of 100 patches and the maximum ΔE of 100 patches were calculated for each of the target color and the color after color stabilization without correction, and the target color and the color after color stabilization with correction. The calculation of ΔE was performed according to the color difference formula CIE2000 mentioned above.

[0102] [Evaluation Criteria] In this embodiment, the evaluation was determined as described above when both the average ΔE range and the maximum ΔE range below were satisfied. The evaluation criteria were S to B as preferable levels, and C as an unacceptable level.

[0103] (Correction value) S: Average ΔE<0.3, maximum ΔE<0.6 A: Average ΔE<0.5, maximum ΔE<1.0 B: Average ΔE<0.8, maximum ΔE<1.5 C: Average ΔE>0.8, maximum ΔE>1.5 (Correction effect) *Correction rate = (Maximum ΔE with correction / Maximum ΔE without correction) S: Correction factor <0.3 A: Correction factor <0.6 B: Correction factor <1.0 C: Correction factor>1.0 In Example 1, the printing conditions for offset uncoated paper were used as an example of an absorbent recording medium. In the case of an absorbent recording medium, the effect of color correction is small because the color change over time is originally small, but the correction value can be corrected with an average ΔE of 0.47 to 0.26 and a maximum ΔE of 1.12 to 0.73. In Example 2, the printing conditions for offset coated paper were used as an example of a low absorbent recording medium. Although the ΔE after correction is slightly higher than that of an absorbent recording medium, it can be corrected with a good correction effect. In Example 3, the ink (ink set b) was changed to one containing a water-soluble organic solvent with a boiling point of 250°C or more. As mentioned above, water-soluble organic solvents with high boiling points are kept on the paper surface, so color fluctuation over time is large. In particular, it changes over time on low absorbent recording media, but as shown in this example, it can be corrected by reusing the printing conditions of the recording medium on the database that has the closest color change tendency. The correction values ​​are 0.88 to 0.38 for the average ΔE, and 2.64 to 0.63 for the maximum ΔE, resulting in a higher correction effect than the ink sets used in Examples 1 and 2. Example 4 is an example in which printing conditions were changed to b, which is optimized for non-absorbent recording media. As a result, both the correction value and the correction effect are better than those of printing condition a. In all of the examples, the average ΔE after correction tends to be a value close to the ΔE of the recording medium selected for reuse when comparing immediately after printing in paper type discrimination.

[0104] On the other hand, Comparative Example 1 is an example of a special offset coated paper whose surface has been modified for electrophotography. * a * b * If there is no offset coated paper with similar values ​​in the database, the printing conditions cannot be reused because color correction cannot be performed accurately. In such cases, the solution is to increase the variety of recording media types in the database.

[0105] As a result, it is possible to perform color correction for various recording media without creating new color conversion tables.

[0106] The present invention can also be realized by a process in which a program for implementing one or more of the functions of the above-described embodiments is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program. The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions. [Explanation of symbols]

[0107] 201 Recording data generation unit 202 Operation control section 203 Printer control unit 204 Recording medium transport control unit 205 Inkjet Devices 301 CPU 302 ROM 303 RAM 304 ASIC

Claims

1. An acquisition means for acquiring color information of a color chart printed on a first recording medium; a storage means for storing color information representing a color printed on a plurality of recording media after a first predetermined time has elapsed and correction information for correcting the color represented by the color information to a color after a second predetermined time has elapsed that is longer than the first predetermined time, in association with each other; a processing means for specifying color information to be used for the first recording medium from the stored color information according to the acquired color information, and executing a print process for printing an image on the first recording medium using the correction information corresponding to the specified color information; A color processing device comprising:

2. 2. The color processing device according to claim 1, wherein the processing means classifies the type of the first recording medium according to the color information after the first predetermined time has elapsed, and specifies the color information to be used for the first recording medium according to the classified type.

3. 2. The color processing apparatus according to claim 1, wherein the processing means executes a print process for printing an image on the first recording medium by using the correction information corresponding to the specified color information.

4. 2. The color processing apparatus according to claim 1, wherein the printing process is performed using ink deposition amounts and drying conditions that are preset according to the classified types.

5. 2. The color processing device according to claim 1, wherein the correction information is information that represents a correspondence relationship between a color indicated by the color information after the first predetermined time has elapsed and a color indicated by the color information after the second predetermined time has elapsed.

6. 2. The color processing apparatus according to claim 1, wherein the color chart is an image formed by using ink, and the ink contains a water-soluble organic solvent having a boiling point of 250[deg.] C. or higher.

7. 2. The color processing apparatus according to claim 1, wherein the first recording medium is a low-absorbency recording medium.

8. A program for causing a computer to function as each of the means of the color processing device according to claim 1. an acquisition step of acquiring color information of a color chart printed on a first recording medium; a storage step of storing color information representing a color printed on a plurality of recording media after a first predetermined time has elapsed and correction information for correcting the color represented by the color information to a color after a second predetermined time has elapsed that is longer than the first predetermined time, in association with each other; a processing step of specifying color information to be used for the first recording medium from the stored color information according to the acquired color information, and executing a printing process for printing an image on the first recording medium using the correction information corresponding to the specified color information; A color processing method comprising the steps of:

Images