Image processing apparatus, image processing method and program

Abstract

To provide an image processing apparatus capable of performing calibration taking temporal color variation into consideration without requiring a long processing time unlike in conventional art that needs to wait for stand-by time.SOLUTION: An image processing apparatus includes: input means configured to input image data; and color conversion means configured to perform, on the image data, on the basis of temporal color variation characteristics of a print image on a first recording medium, color conversion corresponding to temporal color variation of a second recording medium.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 inkjet, electrophotographic, and various offset methods, a color variation phenomenon may occur over time, 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 such as 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, in calibration, it may take a long time for the density or color of a chart to stabilize after it is printed. Therefore, if color measurement is performed immediately after printing a patch, the color measurement result may not represent the actual printing characteristics of the printing device at that time, and as a result, the image processing parameters updated by calibration may not be appropriate. It is also known that the time until the density or color stabilizes varies greatly depending on the type of printing medium and ink set.

[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 color fluctuations of a limited portion of the entire color gamut reproduced by an image forming device are monitored to predict color fluctuations of the entire color gamut. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-184902 A [Patent Document 2] JP 2013-56468 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, in the case of a printing medium that takes a relatively long time for the density or color to stabilize, for example, a printing medium that takes several days to a week for the color to stabilize, it is difficult to continue monitoring within the device, and there are cases where it is necessary to wait for a long time. [Means for solving the problem]

[0007] In consideration of the above problems, the image processing device of the present invention is characterized by having an input means for inputting image data, and a color conversion means for performing color conversion on the image data corresponding to the color variation over time of a second recording medium based on the color variation characteristics over time of a printed image on a first recording medium. Effect of the Invention

[0008] According to the present invention, it is possible to perform calibration that takes into account color variation 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 recording data generating unit. [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 calibration process for color variation over time. 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 unit 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 unit> 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. It is also possible to heat and dry the surface from both sides by heating the reverse side of the surface to which the reaction liquid and ink are applied.

[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] <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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] <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.

[0029] [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.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] [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.

[0036] 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.

[0037] [Resin Composition] Examples of the resin include acrylic resin, urethane resin, and olefin resin.

[0038] [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.

[0039] [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.

[0040] 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.

[0041] 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.

[0042] [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.

[0043] [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.

[0044] <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 printing.

[0045] 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.

[0046] [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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] In S404, in this embodiment, the output gamma correction of the color shift correction process is performed on the 10-bit data of 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, color shift correction processing is performed using the one-dimensional color conversion table for color shift correction of each of the colors C, M, Y, and K. This one-dimensional color conversion table for color shift correction is an image processing parameter that is created or updated by the time-dependent color change calibration described in each embodiment described later.

[0051] 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).

[0052] <Recording Media> The recording medium is not particularly limited, and may be uncoated paper such as fine paper or plain paper, offset coated paper having a coating layer made of calcium carbonate or kaolin, PET film, inkjet paper having a liquid receiving layer for inkjet printing, etc. Among them, the present invention is preferably applicable to recording media having low absorbency for water-based inks (low absorbency recording media).

[0053] 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.

[0054] <Calibration for color variation over time> [Printing and measuring color charts] 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.

[0055] In this calibration, first, a color chart for creating a color conversion table is recorded on a recording medium on which a new color conversion table for temporal color fluctuation is to be created. The color chart for creating a color conversion table can be set appropriately according to the target correction accuracy and the number of colors to be used, and the more colors in the chart, the higher the accuracy of reproducing the target colors.

[0056] The color chart recorded on the recording medium is measured at a predetermined first time. The first time refers to the time that has elapsed since printing on the recording medium. There is no limitation on the setting of the first time, and it may be within a few seconds immediately after drying and fixing or several days later. However, from the viewpoint of utilizing the effects of the above-mentioned invention, it is desirable to set the first time to one minute or less after drying and fixing, so that the waiting time until calibration can be shortened. Moreover, the color measurement may be performed inside or outside the recording device.

[0057] The color space information obtained by color measurement may be 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.

[0058] [Calculation of color space signal values ​​after aging] Each color L after the color of the unregistered recording medium has stabilized * a * b * The value of the first time L* a * b * The color conversion table is created using a standard recording medium, and the color change over time is predicted and calculated from the L value and the amount of color change over time of a standard recording medium of the same type. In the following, the time required from printing until the color becomes stable is defined as the second time, and specific examples of numerical value changes are described in Tables 1-1 to 1-3. Table 1-1 shows the color chart for creating the color conversion table created using the standard recording medium, and the L value of the first time. * a * b * value and second time L * a * b * value and its difference (ΔL * , Δa * , Δb * ) The second time required for color variation over time differs depending on the type of recording medium and color material such as ink, and therefore must be calculated for each device. As an example, in the calculation of the second time in this embodiment, the second time is determined as the time at which the last point is measured when the color difference ΔE of the color space signal values ​​measured every four hours is within 0.05 for three consecutive points.

[0059] [Table 1-1]

[0060] The color difference ΔE can be calculated using any of the general color difference formulas. For example, the CIE 1976 color difference formula (ΔE76), the CIE 1994 formula (ΔE94), and the CIE 2000 formula (ΔE00) can be used. In this embodiment, ΔE00 (hereinafter referred to as ΔE) is used, which is preferable from the viewpoint of perceptual uniformity.

[0061] [Color space signal value fluctuation and prediction after aging for unregistered recording media] Table 1-2 shows the L of each color when a color chart for creating a color conversion table recorded on a recording medium with no registered color conversion table (hereinafter referred to as an unregistered recording medium) was measured at the first time. * , a * , b *A part of the above is shown. In this example, a commercially available general coated paper was used as an unregistered recording medium. The color fluctuation information of the reference recording medium calculated in advance in Table 1-1 was applied to the color space signal value of this first time, and the L of the unregistered recording medium at the second time was calculated. * a * b * The value is predicted as predicted color information. * a * b * The value was calculated in advance using a standard recording medium. * , Δa * , Δb * The second time prediction L is calculated by simply adding the values * a * b * The L value for this second time was calculated. * a * b * The method of predicting the value is not limited to simple addition, and can be changed as appropriate according to the characteristics of the recording device and ink used. The important point is that the classification of the unregistered recording medium matches the classification of the reference recording medium. The classification is roughly divided into two types: absorbent recording media such as uncoated paper and inkjet coated paper with a porous surface treatment, and low absorbent recording media such as offset coated paper. If the classification of the unregistered recording medium can be specified, it is possible to further subdivide it. As an example of such a case, the classification exemplified in [Recording media] above can be used.

[0062] [Table 1-2]

[0063] [Creating a color conversion table that takes into account color fluctuations over time 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 to be output by the image forming unit 502 in response to the YMCK data. In this embodiment, this conversion is performed by converting the L obtained by color measurement into * a * b* This is done using a color conversion table that converts color space information into output Y'M'C'K' data.

[0064] The color conversion table is for device-independent color spaces (L * a * b * ) to device-dependent color space (CMYK) to correct color mixing.

[0065] The color conversion table is created by color processing unit 503. In color processing unit 503, image information acquisition unit 504 acquires color information on the above-mentioned color conversion table creation chart, and color prediction unit 505 adds the amount of color variation over time of each color to the color information at the first time to calculate color information at the second time. By calculating this color information, a color conversion table that takes into account the color variation characteristics over time can be created. Color conversion unit 506 creates a color conversion table based on the color information at the second time. Specifically, the color space signal value (L * (t) , a * (t) , b * (t) ) to the input values ​​Y´M´C´K´ for each color.

[0066] [Calibration flow for color variation over time] FIG. 6 is a flowchart showing the procedure of the calibration process.

[0067] In S601, when printing, a UI screen for setting printing conditions is displayed on the display. The UI screen displays a list of names of recording media held by the printing device in order to specify the recording medium, which is one of the printing conditions.

[0068] In S602, a selection instruction from the user is accepted from the displayed list of recording media. Note that a list of recording media categories may be displayed first and a selection instruction from the user may be accepted, and then a list of recording media belonging to the selected category may be displayed and a selection instruction from the user may be accepted from the list. Also, the list may not be the names of recording media, but may be, for example, serial numbers, or any other identifier that can identify the recording media.

[0069] In S603, the recording medium specified by the received selection instruction from the user is set as the printing condition. Note that the printing conditions are not limited to the recording medium, but also include print quality and the like.

[0070] In S604, it is confirmed whether or not the color conversion table of the recording medium set above exists in the database (DB) of the recording device. Specifically, the name of the recording medium and the color conversion table corresponding to this name are linked and stored in the DB. Therefore, by comparing the stored name with the name set above, it is confirmed whether or not the color conversion table is stored.

[0071] If the check shows that a color conversion table exists in the DB, then in S608, the existing color conversion table is applied to the recording device, thereby making it possible to perform calibration for color changes over time.

[0072] On the other hand, if the check result indicates that the color conversion table does not exist in the DB, the following process is performed in S605: A message indicating that the set color conversion table does not exist in the DB and the classification (e.g., coated paper, uncoated paper) of the unregistered recording medium (second recording medium) to be printed on are displayed on the UI screen.

[0073] In S606, a selection instruction for the displayed classification is accepted from the user. When the classification is specified, the above-mentioned color variation information previously stored for a reference recording medium (first recording medium), which is a recording medium that is a predetermined representative of each classification, is also specified.

[0074] The selection instruction is an instruction manually input by the user via the operation control unit, but is not limited to this. For example, an instruction to read the recording medium to be printed on can be accepted from the UI screen, and the characteristics of the recording medium are read by this instruction. On the other hand, the characteristics of the recording medium representative of each of the above-mentioned classifications or the recording media held may be held in the above-mentioned DB, and the recording medium with the highest degree of match may be identified by comparing the held characteristics with the obtained characteristics. In this case, once the reference recording medium is identified, the color variation information associated with it is also identified.

[0075] In S607, an instruction to print a color chart for creating a color conversion table on the recording medium to be printed is sent to the image forming unit. The color chart printed in the image forming unit is colorimetrically measured by a scanner at a first time and obtained as colorimetric information. In this case, the colorimetric information of the printed image is obtained in L*a*b* values.

[0076] In S608, the color variation information of the reference recording medium specified in S606 is added to the acquired color measurement information, and predicted color information after the second time has elapsed, which is longer than the first time and is the time at which the color development becomes stable over time, is generated. Note that the method for generating the predicted color information is the same as that described above.

[0077] In S609, a second color conversion table for the unregistered recording medium is created by correcting the colorimetric information measured at the first time for the unregistered recording medium on which printing is to be performed based on the generated predicted color information. That is, this correction allows the color variation characteristics of the unregistered medium to be obtained. As a specific process of the correction, the L*a*b* values, which are the colorimetric information constituting the first color conversion table, may be replaced with the predicted color information, or the predicted color information may be added to the first color conversion table.

[0078] In S610, the newly created second color conversion table is stored in the memory of the recording medium. Note that the table may be registered in the DB described above in association with the second recording medium in S603.

[0079] In S611, the created color conversion table is applied to the printing process of the image data.

[0080] Table 1-3 specifically shows the effect of predictive correction. Table 1-3 lists the color space signal values ​​when predictive color correction is applied to the unregistered recording medium and the color space signal values ​​when no correction is applied, using Table 1-1 and Table 1-2 as examples of a reference recording medium and an unregistered recording medium. Detailed printing conditions, etc., are the same as those of the examples described below. A 100-patch color chart is used as the evaluation chart. This chart complies with ISO12647 (Process Control For The Production of Halftone Colour Separations, Proof and Production Prints). When comparing the ΔE values ​​of the color space signal values ​​without correction and with correction with the target value for each CMYK printing amount ratio patch, for example, ΔE=1.82 without correction for patch 99, while ΔE=0.75 with correction. It is possible to correct color differences that are barely noticeable when comparing color distances.

[0081] [Table 1-3] EXAMPLES

[0082] 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.

[0083] (Common conditions) In this example, an inkjet recording apparatus 100 shown in FIG. 1 was used. The conveying speed was 0.5 m / s, and various recording media described below were used as the recording medium 101. The reaction liquid applied by the reaction liquid application unit 102 was prepared as follows, and the application amount was 2 g / m 2 It was decided.

[0084] <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 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.

[0085] The ink used was prepared as follows.

[0086] <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%.

[0087] [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%.

[0088] [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%.

[0089] [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%.

[0090] <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. Also, 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%.

[0091] <Printing conditions> A hot air dryer was used as the hot air drying unit 104 for heating and drying the ink, and it was set so that the surface temperature of the recording medium 101 was a predetermined temperature. The surface temperature of the recording medium was measured using a radiation thermometer.

[0092] The fixing unit 105 used a fixing belt that can be heated from inside the belt by a halogen heater. A PTFE material was used for the fixing member that comes 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.

[0093] Under the above printing conditions, color charts for creating a color conversion table were printed on various recording media 101 of A3 size.

[0094] <Creating a color conversion table> The printed color chart is measured after the first time has elapsed to obtain the color space signal value L * a * b * The color was measured using a fluorescence spectrodensitometer under the following conditions.

[0095] [Colorimetric 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 Color chart of each color first time * a * b * The value is added to the ΔL from the first time to the second time of the previously confirmed reference recording medium. * Δa * Δb * The amount of variation is added to the color space signal value (L * +ΔL * , a * +Δa * , b * +Δb * A color conversion table was created to convert the calculated color space signal values ​​and the color fluctuation values ​​until color stabilization into CMYK for output by the device.

[0096] <Printing the evaluation chart> In this embodiment, the above-mentioned color conversion table was applied to the image file to print the evaluation chart. A 100-patch color chart was used as the evaluation chart. This chart complies with ISO12647 (Process Control For The Production of Halftone Colour Separations, Proof and Production Prints). The printing conditions were the same as those in the above-mentioned <Printing Conditions>.

[0097] 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.

[0098] 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.

[0099] In Example 1, uncoated paper product 1 was used as the unregistered recording medium, and uncoated paper product 7 was used as the reference recording medium. The first time was 10 minutes after printing, and the second time was 144 hours after printing in order to measure the color after the color had sufficiently stabilized.

[0100] Example 2 In Example 2, uncoated paper product 2 was used as the unregistered recording medium, and printing and evaluation were performed under the same conditions as in Example 1 except for that.

[0101] Example 3 In Example 3, coated paper product 3 was used as the unregistered recording medium, and coated paper product 8 was used as the reference recording medium. Printing and evaluation were performed under the same conditions as in Example 1 except for the above.

[0102] Example 4 In Example 4, coated paper product 4 was used as the unregistered recording medium, and printing and evaluation were performed under the same conditions as in Example 3 except for that.

[0103] Example 5 In Example 5, label paper product 5 was used as the unregistered recording medium, and product 9 was used as the reference recording medium. Printing and evaluation were performed under the same conditions as in Example 1 except for the above.

[0104] Example 6 In Example 6, the inks prepared as follows (ink set b) were used. Printing and evaluation were performed under the same conditions as in Example 1 except for the above.

[0105] <Preparation of ink set b> The components shown below (unit: %) were mixed to prepare cyan, magenta, yellow and black inks.

[0106] 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.

[0107] 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.

[0108] Example 7 In Example 7, ink set b was used, and printing and evaluation were performed under the same conditions as in Example 3 except for that.

[0109] Example 8 In Example 8, ink set b was used, and printing and evaluation were performed under the same conditions as in Example 4 except for that.

[0110] Example 9 In Example 9, printing and evaluation were performed under the same conditions as in Example 8, except that the first time period was set to 15 seconds.

[0111] Example 10 In Example 10, the reference recording medium was changed from Product 8 to the average of five types of recording media. Specifically, the average color variation amounts of Products 8, 10, 11, 12, and 13, which are all low-absorbency recording media, were used. Printing and evaluation were performed under the same conditions as in Example 9.

[0112] Comparative Example 1 In Comparative Example 1, Product 7 was used as the reference paper, and printing and evaluation were performed under the same conditions as in Example 9, except for that.

[0113] Comparative Example 2 In Comparative Example 2, Product 6 was used as the unregistered recording medium, and printing and evaluation were performed under the same conditions as in Example 10 except for that.

[0114] <Evaluation> The image samples obtained above were evaluated by the following evaluation methods. The evaluation results are shown in Table 2. * 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 using the color conversion table. The calculation of ΔE was performed according to the color difference formula CIE2000 mentioned above.

[0115] [Table 2]

[0116] [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.

[0117] (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 Examples 1 and 2, product 7 was used as the reference paper for color correction on absorbent recording media. In Example 1, the average ΔE after correction was 0.19, demonstrating a high correction effect. In Example 2, when correction was performed with product 2, the correction was sufficient, although it was inferior to the thin paper of Example 1. In Examples 3 and 4, color correction was performed on low-absorbent recording media, and in Example 5, color correction was performed on non-absorbent recording media, but the correction value was evaluated as A in both cases. Examples 6 to 10 are examples in which the ink set was changed to non-volatile solvent-based ink set b for correction. From the results of Examples 6 to 8, color correction was possible for both absorbent and low-absorbent recording media. In particular, in the low-absorbent recording media of Examples 7 and 8, the maximum ΔE was 2.55 → 1.02 and 2.26 → 0.67, and correction was possible with a high correction effect compared to the volatile solvent-based ink a. In Example 9, when the first time was changed to 15 seconds, the maximum ΔE was 2.91 → 0.58, and the correction effect was higher than that of Example 8, in which the first time was 10 minutes. In Example 10, the reference recording medium was changed to an average of five types. As a result, the correction value was better than the single reference recording medium of Example 9. On the other hand, in Comparative Example 1, correction was attempted using reference paper of a different recording medium type, but the color change tendency was different, resulting in a worsening of ΔE than before correction. When the classification of the unregistered recording medium and the reference recording medium did not match, the amount of color change was different, and therefore no correction effect was obtained. In Comparative Example 2, a recording medium with a surface layer modified for electrophotography was used, but in that case, the correction effect was also not obtained because the color change tendency was different from that of the reference recording medium.

[0118] As a result, it is now possible to create a color conversion table for various recording media without having to wait for a long time, and to perform color correction that takes into account color fluctuations over time.

[0119] 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]

[0120] 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 input means for inputting image data; a color conversion means for performing color conversion on the image data in accordance with the color variation characteristics of the printed image on the first recording medium, the color conversion corresponding to the color variation on the second recording medium over time; 13. An image processing device comprising:

2. 2. The image processing device according to claim 1, wherein the color variation characteristics over time are color variation characteristics from a first time before the color printed on the first recording medium stabilizes to a second time after the color stabilizes.

3. a storage means for storing a color conversion table used for the color conversion for each of the recording media; 3. The image processing device according to claim 2, characterized in that the color conversion is performed when the color conversion table corresponding to the printing conditions when the image data is printed using the second recording medium according to the color variation characteristics up to the second time is not held.

4. an acquisition unit for acquiring colorimetric information obtained by measuring the color chart printed on the second recording medium at the first time; 4. The image processing device according to claim 3, wherein the color conversion means creates the color conversion table corresponding to the printing conditions by adding the temporal color variation characteristics to the color measurement information, and performs the color conversion using the created color conversion table.

5. 5. The image processing apparatus according to claim 4, wherein the color chart is formed by using ink, the ink containing a water-soluble organic solvent having a boiling point of 250[deg.] C. or higher.

6. 3. The image processing apparatus according to claim 2, wherein the first time period is one minute or less after printing.

7. 2. An image processing apparatus according to claim 1, wherein the second recording medium is a low absorbency recording medium.

8. The low absorbency recording medium has a water absorption of 4 mL / m2 from the start of contact to 30 msec1 / 2 in the Bristow method. ２ 10mL / m or more ２ 8. The image processing apparatus according to claim 7, wherein:

9. 2. The image processing apparatus according to claim 1, wherein the first recording medium is classified as a recording medium in the same manner as the second recording medium.

10. A program for causing a computer to function as each of the means of the image processing apparatus according to claim 1.

11. an input step of inputting image data; a color conversion step of performing color conversion on the image data corresponding to the color variation over time of the second recording medium based on the color variation over time characteristic of the printed image on the first recording medium; 13. An image processing method comprising:

Images