JP2006088660A - Image processor and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize printing of an excellent image, in which gloss unevenness is suppressed, while using various printing sheet and ink by image processing. <P>SOLUTION: A White-Cyan line in a device color space, which shows an area where an amount to be applied of a light cyan ink most likely to cause the gloss unevenness is large and amounts to be applied of the other inks are small, is selected. Color separation is performed so that an ink ejection amount of each color at a lattice point on the line is set so as to reduce the light cyan (lc) ink and replace the light cyan (lc) ink with a cyan ink (C) by the amount equivalent to the reduced amount of the light cyan (lc) ink. Concretely, values of R, G, and B corresponding to a patch whose glossiness exceeds a prescribed value are calculated in examination of the glossiness using the patch. The replacement of the light cyan with the cyan is started at the lattice point close to the color of the calculated values of R, G, and B. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to image processing for reducing uneven glossiness and printing a good image.

  An image forming apparatus that forms image information (concepts including characters, symbols, etc.) on a printing medium includes a printer, a copier, a facsimile machine, etc., a computer, a word processor, or a workstation. It is known as what is used as an output device. In such an image forming apparatus, printing based on image information is performed on a printing medium such as paper or a plastic thin plate (OHP paper) by using a predetermined printing unit. Typical examples of these printing methods include an ink jet method, a wire dot method, a thermal method, a thermal transfer method, an electrophotographic method using a laser beam, and the like.

  Among these, the ink jet method is a method of forming an image by ejecting ink from a recording head in the form of droplets and landing on a print medium. Ink jet printers using this method have been widely used in recent years as output devices for information processing equipment such as computers. An ink jet printer can print a color image by forming ink dots of cyan, magenta, yellow, and black inks on a print medium. Furthermore, for the purpose of high-quality output such as photographic tone, light cyan ink and light magenta ink having a low colorant concentration such as a dye for cyan and magenta are widely used in addition to the above four color inks. . As a result, high-quality printing is realized, for example, by reducing the graininess caused by ink dots in the highlight portion of the printed image.

  In Patent Document 1, brightness and granularity are obtained in advance for all combinations of cyan and magenta inks, and light cyan and light magenta, which are low density inks, and based on these, colors with less granularity are obtained. A method for determining separation (combination of inks used to reproduce a certain color) is disclosed. For example, as shown in FIG. 1, color separation using the method of Patent Document 1 is performed from white (White: RGB = 0xFFFFFF) to cyan (Cyan: RGB = 0x00FFFF) to black (Back: RGB = 0x000000). The light cyan ink lc is used to reproduce the colors from white to cyan among the various colors. In this way, the light cyan ink is used in the low density portion (highlight portion) of the image to be printed, thereby making the dots less noticeable and reducing the graininess. Specifically, the amount of light cyan ink that can be applied by the printer, the amount of ink that can be received by the printing medium, the minimum lightness that can be achieved with a single color of light ink, and the maximum use within the allowable range, and regular cyan ink ( Color separation is performed so that graininess does not increase abruptly by using cyan ink of normal density.

  By the way, recently, for high-quality printing such as photographic tones, in addition to image quality factors such as color reproduction and graininess, the surface of the printed material has a strong glossiness and matte (matte) feeling. High weather resistance that does not easily fade even when exposed to gas has been demanded. In order to realize this high weather resistance, an ink using a highly weather-resistant colorant that has high cohesion and is not easily destroyed by exposure to light or gas under long-term storage has been provided.

  On the other hand, in ink jet printing, ink droplets of each color are ejected onto the printing paper to form an image. Therefore, when the density of the ejected dots increases, the ink is ejected due to factors such as ink absorbency of the printing paper. Ink droplets mix on the printing medium, or the printing paper swells and wrinkles. In order to suppress these phenomena, a limit that ink dots cannot be formed at a density higher than that of the printing paper, that is, an allowable value of the so-called ink duty is known in advance, and the ink duty is controlled accordingly. In addition, in order to realize the color reproducibility, strong gloss and matte feeling, high weather resistance, and high ink duty tolerance as described above, we offer high-performance printing paper with various surface coat layers and ink receiving layers. Has been.

  However, in particular, printing on highly functional printing paper using the above highly cohesive ink causes another problem. The so-called “bronze phenomenon”, which is a kind of uneven luster, is one of them. This “bronze phenomenon” means that the colorant of the ejected ink droplets aggregates on the surface of the printing paper or the pigment particle size differs for each ink. This is a phenomenon in which the state of reflected light changes depending on how to apply and the viewing direction, the color changes on the printed surface like “bronze”, and the glossiness becomes stronger.

  This bronze phenomenon has an effect as shown in FIG. FIG. 2 includes cyan colors in which light cyan ink and cyan ink are frequently used, such as a person, mountain, forest, and ground, as well as sky and lake. Here, a region C in FIG. 2 indicates a region in which a cyan color is used but no bronzing phenomenon occurs. A region B in the figure shows a region in which a cyan color is used and bronzing occurs due to the characteristics of the light cyan ink. As can be seen from FIG. 2, the region C and the region B may be adjacent to each other, and if the surface gloss changes in the middle of the sky or lake, which is a continuous image, it is unnatural. Recognized as uneven gloss.

  In order to solve such a “bronze phenomenon” by using the ink itself, improvement of the ink manufacturing method has been promoted (for example, Patent Document 2, Patent Document 3, Patent Document 4, Patent Document 5, Patent Reference 6 and Patent Reference 7). Further, with respect to printing paper, manufacturing methods are being improved to cope with bronzing (for example, Patent Document 7 and Patent Document 8).

  However, in an actual printer design, there is almost no case where ink that suppresses the “bronze phenomenon” as described above is exclusively used. This is because the range in which ink is used is limited by various factors such as the ejection characteristics of the recording head that ejects ink, the compatibility between the ink and the print medium, and the manufacturing cost of the ink. In particular, as described above, the printed material is required to have weather resistance, but for this reason, an ink colorant is used that has high cohesiveness and is therefore not easily destroyed by exposure to light or gas under long-term storage. In particular, in the case of a light ink having a low colorant concentration, higher cohesion is required. On the other hand, this cohesive colorant has a characteristic that easily induces a “bronze phenomenon”. Therefore, in many cases, a colorant having a relatively low glossiness and a low bronze level is used within a range permitted in terms of weather resistance. Similarly, for printing paper, printing paper that can suppress the “bronze phenomenon” is rarely used for all inks used.

  In the case of a color ink jet printing apparatus using a plurality of colors of ink, the glossiness is generally different depending on the color of the ink. This glossiness also changes depending on the amount of ink applied to the print medium, and the rate of change varies depending on the ink color. In this way, even when areas printed with inks having different glossiness are adjacent to each other, it is recognized as “gloss unevenness” due to a relative change in glossiness.

  In response to the above-mentioned measures against bronzing by improving the ink and printing paper itself, the development of a technology that suppresses the occurrence of uneven luster depending on how the ink is used in color separation performed as part of image processing has also been proposed. ing.

  Patent Document 9 discloses black (K) ink that has a relatively high glossiness and easily generates bronze, and cyan (C), magenta (M), and yellow (Y) that have relatively low gloss and hardly generate bronzes. When using both process black (composite black) obtained by mixing two inks, the presence of bronze is examined in advance to determine the conditions for bronzing, and each ink combination in the color separation table that is created produces the above bronze. When the condition is met, it is shown that the bronzing phenomenon is suppressed by replacing black ink with process black.

  3 (a) and 3 (b) are diagrams for explaining examination of bronze generation conditions in Patent Document 9. FIG.

  In Patent Document 9, first, as shown in FIG. 3A, a patch image is created for a combination of K ink and process black to be investigated, and based on this, a patch is printed using these inks. The presence or absence of bronze is determined visually for each patch image. Here, the black level on the vertical axis is an index that the lightness becomes darker as the value increases. When printing using only K ink, the value of the black level is the same as the dot recording rate of K dots. The dot recording rate is the rate at which dots are formed per pixel.

  When printing a patch of the same black level, it is possible to print using only black or using process black. A case where printing is performed using only black is called a UCR rate of 100%, and a case where printing is performed using only process black is called a UCR rate of 0%, which is shown on the horizontal axis. The UCR rate of 50% is a state in which half of the black is replaced with process black ink from the UCR rate of 100%.

  In this way, patches in which bronze is generated are visually selected from patch images printed under different conditions. In FIG. 3A, patches marked with “◯” are patches that are determined to have bronze. Generally, bronze is a phenomenon that occurs when the black level is high and the UCR rate is high.

  FIG. 3B shows a result of arranging the results of FIG. 3A. Bronze is generated under the conditions of the hatched range of FIG. 3B. For example, if an image with a black level of 70% is printed with only black, a bronzing phenomenon occurs. However, if about 20% of black is replaced with process black, the bronzing phenomenon can be avoided. Note that the number of dots formed per unit area increases by replacing 20% of black with substantially the same amount of C, M, and Y. That is, the dot recording rate is 70% before the process black is used, but as a result of using the process black for a part, the total of the K, C, M, and Y dot recording rates increases to about 98%. The ink duty shown in FIG. 3B is a value obtained by summing the dot recording rates of the respective color dots. In the example shown in this figure, in order to avoid the occurrence of bronzing, part of black is replaced with process black, but at the same time, consideration is given so that the value of ink duty does not exceed the limit value.

  FIG. 4 corresponds to the bronze generation condition when the method of Patent Document 9 described above is applied to the entire printer device color space (printer color reproduction area) for the color separation table created without considering the occurrence of bronze. It is a figure which shows typically the area | region to do. Note that this printer device space is a grid point on a cubic lattice schematically showing the color separation table shown in FIG. 5, which is White, Green, Cyan, Blue, Magenta, Black (RGB = 0xFFFFFF, RGB = 0x00FF00, RGB = 0x00FFFF, RGB = 0x0000FF, RGB = 0xFF00FF, RGB = 0x000000).

  In the printer device color space shown in FIG. 4, many areas on the low brightness side indicated by diagonal lines are areas that satisfy the bronze generation condition shown in FIG. Note that the region satisfying this bronze generation condition is not only the surface layer portion of the color space indicated by hatching in FIG. 4 but also the white space (RGB = 0xFFFFFF) -Black (black line) which is a line of the color space shown in the drawing from this surface layer. (RGB = 0x000000) The internal area leading to the line is continuous as an area that satisfies the bronze generation condition.

  As described above, according to the method disclosed in Patent Document 9, replacement from black ink to process black is performed in the area indicated by the oblique lines in FIG. 4 and the area inside the area. In this case, in Patent Document 9, it is assumed that the ink that generates bronze is black ink, and this black ink, which is easily noticeable with dots, is process black with C, M, and Y inks that make dots less noticeable and less likely to cause bronzing. Therefore, it is possible to improve both the bronze and graininess at the same time for the entire area of the ink replacement target area.

  In addition to the method described in Patent Document 9 described above, Patent Document 10 describes a relatively high glossiness after completing printing with an ink group containing an ink that has a relatively high glossiness and is likely to cause bronzing. It is described that gloss unevenness is suppressed by overcoating with Y (yellow) ink which is low and hardly causes bronzing.

US Pat. No. 6,172,692 Japanese Patent Laid-Open No. 7-247452 JP-A-6-228476 JP 7-268261 A JP 2002-69340 A Japanese Patent No. 3249878 Japanese Patent Laid-Open No. 7-214892 JP-A-10-217603 JP 2001-138555 A JP 2004-181688 A JP 2002-33930 A

  However, even when the above-described conventional technique disclosed in Patent Document 9 is applied, it is difficult to avoid uneven gloss of color ink without causing deterioration in graininess or color change over a wide color gamut. There is. This problem is solved by using, for example, a combination of magenta, yellow, black, light magenta, and cyan inks that have relatively low gloss and are less likely to cause bronzing, and light cyan ink that has relatively higher gloss and are likely to cause bronzing. The system will be described.

  According to the method of Patent Document 9, gloss unevenness occurrence conditions are investigated for all combinations of cyan ink and light cyan ink, and light cyan ink is replaced with cyan ink for all portions in the color separation table that satisfy the above conditions. .

  FIG. 6 is a diagram showing the total amount of shot with two inks and the glossiness (bronze degree) obtained by a measurement method described later for all combinations of light cyan ink and cyan ink. Similar to the case shown in FIG. 3A, this is obtained by actually printing a patch on the target printing paper with the target light cyan ink and cyan ink and measuring the glossiness of the patch. is there. In Patent Document 9, a method for visually confirming the presence or absence of bronze when setting bronze generation conditions is used. However, in this specification, a glossy whose measurement method is simply established as a substitute for the bronze degree. Use degrees. Here, “gloss unevenness” is a phenomenon in which differences in glossiness between adjacent areas are recognized as unevenness due to adjacent areas having different glossiness levels. This uneven glossiness may occur depending on the pattern of the output image if inks having different glossiness levels are used simultaneously in the printing system.

  In FIG. 6, the horizontal axis indicates the amount of light cyan ink applied, and the vertical axis indicates the amount of cyan ink applied. Also, in the figure, the solid line indicates a line with the same amount of light cyan ink and a line where the total amount of ink applied by the two inks when cyan ink is printed. Similarly, the broken line indicates a line with the same glossiness. Yes. Note that the contour lines of the glossiness shown by the broken lines show only a relatively high glossiness that causes gloss unevenness. As shown in the figure, the total hit amount increases as the respective ink hit amounts increase, and increases in the direction of arrow A. Similarly, the glossiness increases as the amount of light cyan ink increases, and the total amount of light cyan ink and cyan ink increases, and increases in the direction of arrow B. This is because the light cyan ink has a relatively higher gloss than the cyan ink due to the characteristics of the ink, and the larger the total ink ejection amount, the higher the density of the colorant on the print medium and the easier it is to aggregate. This is because the degree becomes high.

  According to Patent Document 9, in the example shown in FIG. 6, the region that satisfies the uneven gloss occurrence condition for the cyan ink and the light cyan ink is a region having a relatively high glossiness indicated by a broken line in FIG. This area has a large amount of light cyan ink and a relatively large amount of ink.

  FIG. 7 is a diagram showing a region satisfying the gloss unevenness generation condition shown in FIG. 6 in the printer device color space as in FIG.

  As is apparent from FIG. 7, by applying the method of Patent Document 9, the light cyan ink in the shaded area shown in FIG. 7 and the area reaching the White-Black line inside the surface layer is replaced with cyan ink. According to this replacement, for example, light cyan ink used for color separation of gray lines is also replaced with cyan ink.

  As described above, when the method of Patent Document 9 is applied to suppress uneven gloss in printing using color ink, light cyan ink is replaced with cyan ink over almost the entire device color space of the printer, and the entire color space is The graininess deteriorates.

  FIG. 8 is a diagram schematically showing areas where gloss unevenness actually occurs in the printer device color space as in FIG. 7 in the printing system using the ink set shown in FIGS. 6 and 7.

  As shown in FIG. 8, in the actual printing result, a region having a high glossiness is distributed in an elliptical shape with the Q point as the center, and the glossiness decreases as the distance from the Q point increases. Further, the glossiness rapidly decreases as the color proceeds from the Q point on the surface layer of the printer device color space into the color space.

  This is presumed to be due to the following phenomenon. The occurrence of uneven gloss when two colors of light cyan ink and cyan ink are examined is as shown in FIG. However, when ink having a relatively low glossiness is the dominant color, the incident light is absorbed in advance by the ink having a low glossiness, so that it is estimated that uneven glossiness is unlikely to occur. Therefore, even in areas where light cyan ink is frequently used, green, which is used in combination with yellow, and blue and light cyan, which are also used with magenta ink and light magenta ink, are used as complementary colors. It is considered that uneven gloss is less likely to occur in a region that is only a region.

  As described above, even when the method disclosed in Patent Document 9 is applied to suppress uneven glossiness of color ink, the replacement of light cyan ink and cyan ink is executed even in an area where there is actually no uneven glossiness. Therefore, a significant deterioration of the graininess over a wide range in the color space cannot be avoided. Even if the method of Patent Document 10 is applied, other ink is overcoated on the light cyan region where the color is weak, and for example, other ink should be included in the region that should originally be expressed in light cyan only. There is a problem that color change is inevitable.

  The present invention has been made in order to solve the above-described problems in the prior art, and the object of the present invention is to produce a good image in which gloss unevenness is suppressed while using various existing printing papers and inks. An object is to provide an image processing apparatus and an image processing method that enable printing.

  Therefore, the present invention is an image processing apparatus that generates, as color separation amounts, data of a plurality of types of printing agents of similar colors used in a printing apparatus based on image data, and the plurality of types of printing of similar colors In generating the first and second color separation amounts in a specific region in the color space in which the first printing agent and the second printing agent having a lower gloss than the first printing agent are mainly used. As the density per unit area increases, the color separation amount of the first printing agent is gradually increased to the first color separation amount and then gradually decreased, and the color of the second printing agent Color separation generating means for generating first and second color separation amounts for expressing the specific area by gradually increasing the separation amount is provided, and the first color separation amount is a unit of a print medium. The first mark that can be driven per area The granularity when the first printing agent corresponding to the first color separation amount, which is smaller than the second color separation amount corresponding to the maximum amount of agent injection, is applied to the print medium, is the second color separation amount. It is characterized by being higher in granularity when the first printing agent corresponding to the color separation amount is driven into a printing medium.

  An image processing method for generating, as a color separation amount, data of a plurality of types of printing agents of similar colors used in a printing apparatus based on image data, wherein the plurality of types of printing agents of similar colors In generating the first and second color separation amounts in a specific region in a color space in which the first printing agent and the second printing agent having a lower gloss than the first printing agent are mainly used, a unit area As the per unit density increases, the color separation amount of the first printing agent is gradually increased to the first color separation amount and then gradually decreased, and the color separation amount of the second printing agent is decreased. By gradually increasing the color separation generation step, the first and second color separation amounts for generating the first and second color separation amounts for expressing the specific area are included, and the first color separation amount per unit area of the print medium. Maximum printing of the first printing agent that can be driven into The granularity when the first printing agent corresponding to the first color separation amount and smaller than the second color separation amount corresponding to the embedding amount is applied to the print medium is the second color separation amount. It is characterized by being higher in granularity when the first printing agent corresponding to the above is applied to a printing medium.

  According to the present invention, the color separation amount of a printing agent with high glossiness can be reduced with respect to the color for which the printing agent is mainly used, and can be replaced with a printing agent with lower glossiness. This makes it possible to replace the above within a limited range, and this minimizes the deterioration of granularity due to the printing agent even if the printing agent with lower glossiness deteriorates the granularity. However, uneven gloss or bronzing can be suppressed.

  First, terms used in the description of the embodiment of the present invention will be defined.

(Driving amount)
In the present specification, “imposition amount” represents an ink application amount that is applied per unit area by monochromatic ink as a printing agent. The total shot amount represents the total amount of ink shots of all ink sets used in accordance with the color separation table. Note that (ink) duty, (ink) application amount, (ink) application amount, and the like are also used synonymously.

(Multiple types (multiple colors) of ink with different glossiness)
In the present specification, “a plurality of types (multiple colors) of inks having different glossiness” refers to different glossiness for each ink when the same amount of ink is applied to a unit area of a specific printing paper. Means something. In the following, an ink that exhibits a relatively high gloss when the same amount is applied to a unit area is referred to as “a relatively (relatively) highly glossy ink”, and a relatively low glossiness. Is expressed as “ink with relatively low gloss (relatively relative)”. For example, when focusing on light cyan and magenta, as is apparent from FIG. 9, when compared with the same shot amount, the light cyan gloss is higher than the magenta gloss. The ink corresponds to “relatively high ink”, and the magenta ink corresponds to “ink with relatively low gloss”. Furthermore, when comparing light cyan ink and cyan ink, it can be seen that light cyan ink is relatively high in gloss.

  Further, in this specification, “the amount of change in the gloss level due to the change in the ink placement amount per unit area is different” means that the glossiness is changed when the placement amount is changed within a predetermined range (for example, 0 to 200%). This means that the degree of change is different. Specifically, referring to FIG. 9, the glossiness changes according to the ink placement amount, and the glossiness increases as the ink placement amount increases, but the degree of increase in the glossiness varies depending on the ink type. For example, while yellow (Y) has a glossiness that quickly reaches its peak as the ink ejection amount increases, light cyan (lc) increases rapidly when the ink ejection amount exceeds a certain amount. It can be seen that the amount of change in gloss differs depending on the species.

(Bronze phenomenon)
“Bronze phenomenon” means that colorants such as dyes in the ejected ink aggregate on the surface of the printing paper, or the particle size of the pigment differs for each ink. This is a phenomenon in which the state of light reflected on the surface of the printing paper changes depending on the viewing direction, the color changes on the printing surface like “bronze”, and the glossiness increases.

  However, although this “bronze phenomenon” is a phenomenon known to those skilled in the art, its general quantification has not yet been made. Therefore, in this specification, the “bronze phenomenon” is regarded as “gloss unevenness caused by the change in the glossiness depending on the amount of ink applied”, and for convenience, is defined as the one that can be substituted with the glossiness for which the measurement method has already been established. The following explanation will be given. Therefore, in the present specification, the degree of bronze is described as synonymous with the glossiness.

(Bronze degree measuring method (glossiness measuring method))
FIG. 9 shows the results when the glossiness is taken as a physical quantity recognized as glossiness and the glossiness of a plurality of colors of ink is measured for each ink placement amount. In FIG. 9, the horizontal axis indicates the amount of ink applied to the print medium, and the vertical axis indicates the glossiness of the print medium corresponding to each ink amount, for each ink color. In the measurement, a gloss checker (IG-320) manufactured by HORIBA, Ltd. was used. In addition, when this is disposed in a state inclined by 60 ° with respect to the perpendicular along with the light source part, and the glossiness of the glass plate surface having a refractive index of 1.567 as defined in JIS is set to “100”, the glossiness of “90” Calibration was performed by measuring a standard plate.

  From this measurement result, it can be seen that the glossiness varies depending on the ink color. In any ink, the glossiness basically increases according to the amount of ink applied, but it can also be confirmed that the rate of increase or change varies depending on the color of the ink.

  Thus, one of the reasons for the difference in glossiness depending on the color is that the glossiness depends on the aggregation of colorants such as dyes and pigments, and the degree depends on the molecular structure of the colorant. Can be mentioned. Further, such agglomeration is also promoted by contact between adjacent dots before the ejected ink is absorbed by the print medium. Therefore, it can be said that an ink having a relatively low permeation rate is likely to have a higher gloss feeling than an ink having a high permeation rate.

  From FIG. 9, it can be seen that light cyan, in particular, has much higher gloss than any other ink, followed by cyan ink and other inks.

  The method for reducing gloss unevenness described in the present specification is not limited by the method for measuring glossiness (bronze degree) as described above, but is measured and quantified by other methods. Needless to say, this is also effective for the phenomenon.

(Granularity)
In this specification, the “granularity” represents the roughness of ink dots that can be felt by human vision.
“The granularity is deteriorated” and “the granularity is high” represent that the roughness is felt more coarsely than the roughness of the comparison target. In the description of the present specification, regarding this granularity, simply based on the general phenomenon that dot formation with regular ink (normal density ink that is not light ink) has higher granularity than dot formation with light ink. However, it is of course possible to compare the granularity based on the quantitative results obtained by a known granularity measuring method. As this known granularity measuring method, RMS granularity, Wiener spectrum (spectrum), etc. that are common in the field of silver salt photography can be used.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Configuration of Apparatus FIG. 10 is an explanatory diagram showing the configuration of a printing system including an image processing apparatus according to an embodiment of the present invention.

  As shown in the figure, this printing system includes a computer 80 as an image processing apparatus and a print control apparatus, and a color printer 20 as a printing apparatus, and a predetermined program is loaded to the computer 80 and executed. As a result, the functions of the printing system are executed as a whole.

  A color document to be printed is captured using the color scanner 21 connected to the computer 80, or an image created by various application programs on the computer 80 is used. The image data ORG is converted into image data that can be printed by the color printer 20 by the CPU 81 in the computer 80 and output to the color printer 20 as image data FNL. The color printer 20 prints a color image on printing paper by forming ink dots of each color on the printing medium according to the image data FNL.

  The computer 80 includes a CPU 81 that executes various arithmetic processes, a RAM 83 that temporarily stores data, a ROM 82 that stores various programs, a hard disk 26, and the like. Further, by connecting to the public telephone line PNT via the SIO 88 and the modem 24, it becomes possible to download necessary data and programs from the server SV on the external network to the hard disk 26.

  The color printer 20 is a printer capable of printing a color image. In this embodiment, a total of six colors of cyan, magenta, yellow, black, light cyan, and light magenta are used on the printing paper, and these inks are used. A color image is printed by applying and forming dots. Of course, a printer that uses other inks such as red ink, green ink, and blue ink in addition to these six colors of ink may be used.

  The ink ejection method of the recording head used in the ink jet printer of the present embodiment employs a method using a piezo element PE as will be described later, but uses a printer having a nozzle unit that ejects ink by other methods. It is good. For example, the present invention may be applied to a printer of a system that energizes a heater disposed in an ink passage and ejects ink by bubbles generated in the ink passage.

  FIG. 11 is a block diagram conceptually showing the configuration of software operating on the computer 80 shown in FIG.

  In the computer 80, all application programs 91 operate under an operating system. A video driver 90 and a printer driver 92 are incorporated in the operating system, and image data output from each application program 91 is output to the color printer 20 via these drivers. When the application program 91 issues a print command, the printer driver 92 of the computer 80 receives image data from the application program 91, performs predetermined image processing, and converts the image data into printable image data.

  As shown in FIG. 11, the image processing performed by the printer driver 92 is a resolution conversion module 93, a color conversion module 94, a halftone module 95, and an interlace module 96, as will be described later with reference to FIGS. It consists of four modules.

  Although details of image processing performed by each module will be described later, the image data received by the printer driver 92 is converted by these modules and then output to the color printer 20 as final image data FNL. Note that the color printer 20 of this embodiment only serves to form dots according to the image data FNL, and does not perform image processing. Of course, the color printer 20 performs part of image conversion. There may be.

  FIG. 12 is a diagram showing a schematic configuration of the color printer 20 described above.

  As shown in the figure, the color printer 20 generally includes a mechanism for driving a recording head 41 mounted on a carriage 40 to eject ink and forming dots, and the carriage 40 is moved by a carriage motor 30 to the axis of a platen 36. It comprises a mechanism for reciprocating in the direction, a mechanism for transporting the printing paper P by the paper feed motor 35, and a control circuit 60.

  The mechanism for reciprocating the carriage 40 in the axial direction of the platen 36 is an endless drive between the carriage motor 30 and the slide shaft 33 slidably holding the carriage 40 laid in parallel to the axis of the platen 36. A pulley 32 that stretches the belt 31 and a position detection sensor 34 that detects the origin position of the carriage 40 are provided. The mechanism for transporting the printing paper P includes a platen 36, a paper feed motor 35 that rotates the platen 36, a paper feed auxiliary roller (not shown), and a gear train that transmits the rotation of the paper feed motor 35 to the platen 36 and the paper feed auxiliary roller. (Not shown). The printing paper P is set so as to be sandwiched between the platen 36 and the paper feed auxiliary roller, and is fed by a predetermined amount according to the rotation angle of the platen 36.

  The control circuit 60 includes a PC interface 64 for exchanging data with the computer 80, a peripheral input / output unit (PIO) 65 for exchanging data with the paper feed motor 35, the carriage motor 30, and the like, and an ink ejection head 44. A drive buffer 67 for supplying dot on / off signals to 47, a CPU 61 for controlling these, a RAM 63 for temporarily storing data, and the like are provided. The control circuit 60 is also provided with an oscillator 70 for outputting a drive waveform and a distribution output device 69 for distributing the output of the oscillator 70 to the recording heads 44 to 47 at a predetermined timing. In addition to the four colors of cyan, magenta, yellow, and black shown in the drawing, a recording head that discharges a total of six colors of ink including light cyan and light magenta (not shown) is used.

  The CPU 61 outputs a trigger signal to the oscillator 70 while outputting a drive signal to the carriage motor 30, and reads an on / off signal of dots stored in the RAM 63 while synchronizing with the trigger signal, thereby driving the drive buffer 67. Output to. In this way, ink droplets are ejected from each nozzle of the recording head while performing main scanning of the carriage 40 under the control of the CPU 61. The CPU 61 controls the movement of the paper feed motor 35 in synchronization with the movement of the carriage. In this way, ink dots are formed at appropriate positions on the printing paper.

  The carriage 40 stores an ink cartridge 42 that stores black (K) ink, and inks of five colors, cyan (C), magenta (M), yellow (Y), light cyan (lc), and light magenta (lm). An ink cartridge 43 is mounted. Of course, K ink and other color inks may be stored in the same ink cartridge. Alternatively, each ink may be stored in a separate cartridge. If a plurality of inks can be stored in one cartridge, the ink cartridge can be configured compactly.

  FIG. 13 is a perspective view showing the external shape of the ink cartridge 42. As shown in the figure, an identification label 56 is affixed to the ink cartridge, and a number representing the type of ink stored in the ink cartridge is entered. As will be described later, in the printing apparatus according to the present embodiment, it is possible to print a good image that is less likely to cause uneven glossiness based on information on the type of ink and printing paper. Among these, the type of ink is specified by the number written on the identification label 56.

  Below, an example of the ink composition accommodated in the ink cartridges 42 and 43 is shown. As an example of the ink to which the present invention can be applied, for example, the following colorants are used.

(Light cyan colorant)
C. I. Phthalocyanine dyes such as Direct Blue 86, 199, and 307 are used. However, the applicable condition of the present invention is not limited to these, as long as it is easier to bronz the cyan colorant.

(Cyan colorant)
C. I. A triphenylmethane dye such as Acid Blue 9 is used. However, the applicable conditions of the present invention are not limited to these, as long as they are more difficult to bronz than light cyan colorants.

(Yellow colorant)
C. I. Direct yellow: 8, 11, 12, 27, 28, 33, 39, 44, 50, 58, 85,
86, 87, 88, 89, 98, 100, 110, 132, 173; C.I. I. Acid Yellow: 1, 3,
7, 11, 17, 23, 25, 29, 36, 38, 40, 42, 44, 76, 98, 99;
C. I. Pigment Yellow: 1, 2, 3, 12, 13, 14, 15, 16, 17, 73,
74, 75, 83, 93, 95, 97, 98, 114, 128, 138, 180

(Magenta colorant)
C. I. Direct red: 2, 4, 9, 11, 20, 23, 24, 31, 39, 46, 62, 75,
79, 80, 83, 89, 95, 197, 201, 218, 220, 224, 225, 226, 227,
228, 229, 230; C.I. I. Acid Red: 6, 8, 9, 13, 14, 18, 26, 27, 32,
35, 42, 51, 52, 80, 83, 87, 89, 92, 106, 114, 115, 133, 134,
145, 158, 198, 249, 265, 289, C.I. I. Food Red: 87, 92, 94;
C. I. Direct violet 107; I. Pigment Red: 2, 5, 7, 12, 48: 2,
48: 4, 57: 1, 112, 122, 123, 168, 184, 202

(Black colorant)
C. I. Direct black: 17, 19, 22, 31, 32, 51, 62, 71, 74, 112,
113, 154, 168, 195; I. Acid Black: 2, 48, 51, 52, 110, 115,
156; I. Food Black 1, 2; Carbon Black The solvent or additive can be used in the same manner as described above.

(Solvent or additive)
As the aqueous medium, water and a water-soluble organic solvent are used. Here, as a preferable water-soluble organic solvent,
Ethanol, isopropanol, n-butanol, isobutanol, sec-butanol,
C1-C4 alkanols such as tertiary butanol, carboxylic acid amides such as N, N-dimethylformamide or N, N-dimethylacetamide, ketones such as acetone, methyl ethyl ketone, 2-methyl-2-hydroxypentan-4-one, or , Cyclic ethers such as keto alcohol, tetrahydrofuran and dioxane, glycerin,
Ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol,
1,2- or 1,3-propylene glycol, 1,2- or 1,4-butylene glycol, polyethylene glycol,
1,3-butanediol, 1,5-pentanediol, 1,2-hexanediol, 1,6-hexanediol,
Dithioglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol,
Polyhydric alcohols such as acetylene glycol derivatives and trimethylolpropane,
Ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether,
Alkyl ethers of polyhydric alcohols such as triethylene glycol monoethyl (or butyl) ether,
Heterocycles such as 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylmorpholine, sulfur-containing compounds such as dimethyl sulfoxide, urea, urea derivatives, etc. A suitable example is given.

  In addition to this, the ink composition of the present embodiment includes a surfactant, a pH adjuster, a chelating agent, a rust inhibitor, an antiseptic, an antifungal agent, an ultraviolet absorber, a viscosity modifier, an antifoaming agent, In addition, various additives such as a water-soluble polymer may be contained.

  In the present embodiment, the above-described colorant is shown as an example of a suitable colorant, but the combination of colorants in which the present invention is effective is not limited to the above, and other colorants may be used. In the present embodiment, as an example, magenta ink, yellow ink, black ink, light magenta ink, and cyan ink, which have relatively low gloss and are less likely to generate bronze, and light cyan, which has relatively high gloss and easily generates bronze. Since the case where the ink is used is given, the above composition is described as an example. However, the method of the present invention can be applied to light magenta ink having relatively high gloss and relatively low gloss. Needless to say, the present invention can be similarly applied to ink made of magenta ink, and in such a case, it goes without saying that the composition is completely different from the above-described composition.

Needless to say, the present invention is not limited to the compositions described above, and inks of various compositions can be applied. Here, it is apparent that the inks having various compositions include not only the dyes as described above but also pigments.
When the ink cartridges 42 and 43 containing such ink are mounted on the carriage 40, each ink in the cartridge is supplied to the ink ejection heads 44 to 47 for each color through an introduction pipe (not shown). The ink supplied to each recording head is ejected by the method described below to form dots on the printing paper.

  FIG. 14A shows the internal structure of each color recording head. The recording heads 44 to 47 for each color are provided with 48 nozzles Nz for each color, and each nozzle is provided with an ink passage 50 and a piezoelectric element PE on the passage. As is well known, the piezo element PE is an element that transforms electro-mechanical energy at a very high speed because the crystal structure is distorted by application of a voltage. In the present embodiment, by applying a voltage having a predetermined time width between the electrodes provided at both ends of the piezo element PE, the piezo element PE is expanded by the voltage application time, as shown in FIG. One side wall of the ink passage 50 is deformed. As a result, the volume of the ink passage 50 expands and contracts according to the expansion of the piezo element PE, and the ink corresponding to the contraction is ejected from the nozzle Nz as particles Ip. The ink Ip lands on the printing paper P on the platen 36 and then penetrates, whereby dots are formed on the printing paper P. Note that the size of the ink droplets to be ejected can be controlled by controlling the voltage waveform applied to the piezo element PE. The size of the ink dots formed on the printing paper can be controlled by controlling the size of the ejected ink droplets.

  FIG. 15 is a diagram illustrating the arrangement of the ink jet nozzles Nz in the recording heads 44 to 47. As shown in the figure, four sets of nozzle arrays for ejecting ink of each color are formed on the bottom surface of the recording head, and 48 nozzles Nz per set of nozzle arrays are staggered at a constant nozzle pitch k. Are arranged in a shape. Note that the 48 nozzles Nz included in each nozzle array are not necessarily arranged in a staggered manner, and may be arranged in a straight line. However, there is an advantage that the value of the nozzle pitch k can be reduced by arranging them in a zigzag pattern.

  As shown in FIG. 15, the recording heads 44 to 47 are displaced in the transport direction of the carriage 40. Further, the nozzles for each color head are also arranged in a zigzag pattern, so the positions are shifted in the conveyance direction of the carriage 40. The control circuit 60 of the color printer 20 discharges ink droplets by driving each PE element at an appropriate timing in consideration of the difference in nozzle positions while conveying the carriage 40.

  The color printer 20 having the hardware configuration as described above drives the carriage motor 30 to move the ink ejection heads 44 to 47 of the respective colors in the main scanning direction with respect to the printing paper P, and the paper feed motor. By driving 35, the printing paper P is moved in the sub-scanning direction. Under the control of the control circuit 60, while repeating main scanning and sub-scanning of the carriage 40, a nozzle is driven at an appropriate timing to eject ink droplets, whereby a color image can be printed on printing paper.

Overview of Printing Process As described above, the color printer 20 has a function of printing a color image by receiving the supply of the image data FNL from the computer 80. The image data FNL supplied to the color printer 20 is a color image by the computer 80. Are generated by performing predetermined image processing.

  FIG. 16 is a flowchart showing an outline of processing in which the computer 80 outputs the image data FNL to the color printer 20 to print the image. This process is realized by a process executed by the CPU 81 in accordance with the printer driver 92 operating on the computer 80. The outline of the printing process will be described below with reference to FIG.

  As shown in FIG. 16, when the print processing routine is started, the CPU 81 first inputs image data (step S100). This image data is data supplied from the application program 91 as described with reference to FIG. 11, and 256 gradations having a value of 0 to 255 for each color of R, G, and B for each pixel constituting the image. It is data which has. The resolution of the image data varies depending on the resolution of the original image data ORG. When the input of the image data is completed, the CPU 81 converts the resolution of the image data into a resolution for printing by the color printer 20 (step S102). If the image data is lower than the printing resolution, resolution conversion is performed by generating new data between adjacent original image data by linear interpolation. Conversely, when the image data is higher than the print resolution, resolution conversion is performed by thinning out the data at a constant rate.

  Next, the CPU 81 performs color conversion processing (step S104). In this color conversion process, image data composed of R, G, and B gradation values is converted into gradation value data of each color of ink C, M, Y, K, lc, and lm used in the color printer 20. It is processing. This process is performed using a color conversion table (look-up table: LUT) (see FIG. 11). In the LUT, a color composed of a combination of R, G, and B is expressed by the color printer 20. The above combinations of gradation values are stored for C, M, Y, K, lc, and lm.

  The color conversion process according to an embodiment of the present invention reduces uneven gloss generation by using a color separation table corresponding to a combination of printing paper and ink. Details of this color conversion processing will be described later.

  When the color conversion process ends, a binarization process is performed (step S106). In the present embodiment, the image data after color conversion is a 256 gradation image of 6 colors of C, M, Y, K, lc, and lm. On the other hand, the color printer 20 forms an image in two states, whether or not dots are formed. Therefore, an image having 256 gradations is converted into an image expressed in 2 gradations that can be expressed by the color printer 20 using a technique such as dithering.

  When completing the binarization process, the CPU 81 performs an interlace process (step S108). This process is a process of rearranging the image data converted into a format representing the presence or absence of dot formation by the binarization process in the order to be transferred to the color printer 20. That is, as described above, the color printer 20 drives the recording head 41 while repeating main scanning and sub-scanning of the carriage 40 to form dot rows (raster) on the printing paper P. As described with reference to FIG. 15, since the recording heads 44 to 47 for each color are provided with a plurality of nozzles Nz, a plurality of rasters can be formed by one main scanning. The rasters are separated from each other by a nozzle pitch k. Therefore, in one main scan, first, a plurality of rasters separated by the nozzle pitch k is formed, and then the head position is slightly shifted, and a new raster is formed between the rasters. When such control is performed, the order in which the color printer 20 actually forms the dots is different from the order of the pixels on the image data. Therefore, the image data is rearranged in the interlace processing. When the interlace processing is completed, the image data is output to the color printer 20 as image data FNL that can be printed by the printer (step S110). The color printer 20 forms dots according to the image data FNL, thereby printing an image on the printing paper.

  In the present embodiment, as described above, in the color conversion processing in the image processing for printing, the color conversion table LUT is referred to and the image data of each color of R, G, B is converted into C, M, Y, K, lc, 1m is converted into gradation data of each color (step S104).

  FIG. 17 is a diagram conceptually showing the color conversion LUT. The gradation values of the R, G, and B colors are taken as three axes orthogonal to each other, and the space formed by the three axes is subdivided into a lattice shape. By making the R, G, and B coordinate values of each grid point configured in this way correspond to the gradation values of each color of R, G, and B, each grid point can represent each color. . A set of gradation values of C, M, Y, K, lc, and lm that reproduces the color of each lattice point is stored in each lattice point. Thus, the color conversion table can be configured as a three-dimensional number table.

  The CPU 81 performs color conversion as follows while referring to the color conversion table. For example, when the gradation values of the image data R, G, and B are RA, GA, and BA, a point A represented by these coordinates (RA, GA, and BA) is determined, and the smallest cube dV that includes the point A is determined. Is determined. Then, C, M, Y, K, lc, and lm gradation values stored in the cube corresponding to the lattice points of the respective vertices are read out, and an interpolation operation is performed based on a set of these read out gradation values. To calculate the gradation values of C, M, Y, K, lc, and lm corresponding to the point A, and use them as variable outputs.

Color Conversion Processing The color conversion processing using the LUT described above is, in detail, a color correction portion that performs color adjustment such as color matching and memory color correction, and the printer devices R, G, and B are ink colors. It includes two processes of the color separation part that separates into C, M, Y, K, lc, and lm. In the description of this embodiment, for convenience of explanation, explanation of color correction such as color adjustment such as color matching and memory color correction is omitted, and only color separation is explained as described above. Note that when the color conversion process is described including color correction in addition to color separation, the difference is the description of the LUT. That is, after obtaining R, G, and B obtained by performing color correction on the R, G, and B values on the lattice points of the LUT using a known interpolation technique, as described above, C, M, Y, K, lc, and lm values may be obtained by interpolation.

  FIG. 18 is a flowchart illustrating details of processing performed in the color conversion processing (step S104 in FIG. 16) during image processing.

  When the color conversion process is started, the CPU 81 first acquires printing conditions (ink type and printing paper) (step S400). That is, as described above, gloss unevenness does not occur at all or the generated range differs depending on the combination of the type of ink and the printing paper. Therefore, information on the ink type and the printing paper type is acquired in advance, and an appropriate color conversion table is selected based on this information. In this embodiment, the print condition is acquired based on information set by the user of the color printer 20 with respect to the printer driver 92. Specifically, when the user inputs the product number of ink to the printer driver 92 from the CRT screen, the printer driver 92 specifies the ink type from the product number. The product number of the ink is described on a label attached to the ink cartridge as shown in FIG. Of course, instead of such a method for specifying the type of ink, a specifying method using chip information attached to the ink cartridge can also be used. In such a case, it is possible to save the user the trouble of inputting the product number of the ink and to prevent human error such as an input error. As for the type of printing paper, various types of printing paper are displayed on the CRT screen, and the user selects them. In response to this, the printer driver 92 specifies the type of printing paper from the selection result. Information regarding the ink type and the printing paper type specified in this way is stored in the printer driver 92 and held until the user changes the setting through the CRT screen.

  Next, a corresponding color conversion table is selected according to the acquired printing conditions (step S402). The color conversion table database referred to by the color conversion module 94 stores color conversion tables A, B, and C for each printing condition in the format shown in FIG. Select a table. For example, when ink type 2 and printing paper 3 are selected, the color conversion table C is selected by referring to the table of FIG. In this embodiment, the printer driver has been described as automatically selecting the corresponding color conversion table according to the printing conditions. However, an appropriate color conversion table is designated from the outside according to the printing conditions. It doesn't matter. That is, the degree of aggregation or the degree of glossiness is determined depending on the relationship between the printing medium and ink used, but the amount of color separation or color separation should be reduced as much as possible depending on the degree of glossiness for each printing medium. Select a table.

  With reference to the color conversion table thus selected, the RGB image data is converted into CMYKlclm image data (step S404). When the color conversion processing is completed for all pixels (step S406), the color conversion processing is exited. Return to the print processing routine. As described above, in the color conversion process of the present embodiment, a color conversion table corrected for each printing condition is used so that gloss unevenness does not occur. Details of the color conversion table for reducing the uneven gloss will be described below.

Color separation table used in color conversion (color separation) processing In this embodiment, first, lines indicated by solid lines, broken lines, and alternate long and short dash lines for the entire RGB input color space (printer device color space) shown in FIG. A color separation table is defined for each of the grid points, and the other grid points are complemented using, for example, a known table interpolation technique as disclosed in Patent Document 11, and the color at each grid point is determined. Find the decomposition value. In this way, the corresponding color separation values for the entire printer device color space are obtained and stored as a three-dimensional color separation table.

  In this embodiment, when setting the color separation table, the occurrence condition and glossiness of gloss unevenness are confirmed, and the color separation table is set so as to avoid color separation with high glossiness. As a result, color separation with less gloss unevenness is performed. Specifically, first, the uneven gloss generation condition and the gloss level are investigated.

(1) Gloss unevenness generation conditions for light cyan ink and cyan ink As shown above, FIG. 6 shows the total shot amount and glossiness (of bronze) for all combinations of light cyan ink and cyan ink. Degree), the horizontal axis indicates the amount of light cyan ink applied, the vertical axis indicates the amount of cyan ink applied, and the solid lines indicate the two light cyan inks and cyan inks when the corresponding ink amounts are printed. Contour lines of the total amount of ink deposited, and similarly, broken lines indicate gloss contour lines. The total ejection amount increases as the respective ink ejection amount increases, and increases in the direction of arrow A. Similarly, the glossiness increases as the amount of light cyan ink increases, and the total amount of light cyan ink and cyan ink increases, and increases in the direction of arrow B. This is because the light cyan ink has relatively higher gloss than the cyan ink due to the characteristics of the ink, and the higher the total ink ejection amount, the higher the density of the colorant on the print medium and the more likely it is to aggregate. This is because the glossiness is increased.

  From FIG. 6, the uneven gloss generation condition for cyan ink and light cyan ink is a region with a relatively high glossiness indicated by a broken line in FIG. 6, in a region with a large amount of light cyan ink and a relatively large amount of shot. is there. Further, it is possible not to perform printing or measurement for a region where the total driving amount exceeds the upper limit value (ink duty limit value) of the ink acceptance amount of the printing medium. Thus, by omitting the unusable area in advance, the labor of printing and measurement can be saved.

(2) Confirmation of Gloss Unevenness Generation Conditions for the Entire Printer Device Color Space The gloss unevenness generation conditions for the light cyan ink and cyan ink in the above (1) are small in the entire printer device color space, and In addition, color separation with attention to graininess and color reproduction cannot be performed. Therefore, in the embodiment of the present invention, for the conventional color separation table that does not consider uneven gloss, conditions for generating uneven gloss are confirmed over the entire color space.

  FIG. 8 schematically shows an actual bronze generation region for the entire printer device color space as described above.

  As shown in FIG. 8, regions with high glossiness are distributed in an elliptical shape around the Q point, and the glossiness decreases as the distance from the Q point increases. In addition to the surface layer of the printer device color space in which an elliptical shape is shown, the glossiness decreases as the color proceeds from this surface layer into the color space. In the present embodiment, when the glossiness is confirmed for the entire area of the printer device color space shown in FIG. 8, the patch that obtains the result shown in FIG. 6 is expanded, and the entire area of the printer device color space is expanded at an appropriate sampling interval. Glossiness can be determined by printing and measuring a sampled patch. Alternatively, instead of this, it is also possible to use a method of printing a chart created so as to cover the entire color space of the printer device and measuring or visually confirming the chart.

  When printing, measuring, and visually confirming such patches and charts, for example, if it is clear that gloss unevenness does not occur in an area below a specific total driving amount in advance, such areas are Printing, measurement, and visual confirmation of patches can be omitted, and labor of printing, measurement, and visual confirmation can be omitted. For example, in this specification, a state where the paper surface within a unit area is completely filled with ink dots and is not overprinted is defined as a state where the driving amount is 100%. Therefore, the paper surface is completely filled with ink having a relatively high glossiness in an area where the amount of driving exceeds 100%. In such a case, it is only necessary to print, measure, and visually check the patch image only for the region where the total ink ejection amount exceeds 100%.

  Further, when measuring the glossiness and granularity of patches corresponding to the entire printer device color space corresponding to FIG. 8, for example, an upper limit value of ink reception amount (limit value of ink duty) of the target print medium is set. It is also possible not to perform printing or measurement for a region that exceeds the total driving amount. By omitting such unusable areas in advance, printing and measurement can be saved.

  From the results shown in FIG. 8, it can be confirmed that the region where uneven gloss is likely to occur is centered on the region where the amount of light cyan ink applied is large and the amount of other ink applied is small.

  Therefore, in the embodiment of the present invention, the White-Cyan in the device color space shown in FIG. 5 or FIG. 8 is used as a central area representing such an area where the light cyan ink application amount is large and the other ink application amount is small. A line is selected, and the amount of ink applied to each color of the lattice points on this line is set to color separation in which light cyan (lc) ink is reduced and the corresponding amount is replaced with cyan ink (C).

  FIG. 20 is a diagram showing the amount of ink applied for each color as a result of the color separation of the White-Cyan line. Here, the light cyan ink is increased as the density per unit area increases from the White point, and the cyan ink is reached before the light cyan ink amount reaches the region where the uneven glossiness is relatively noticeable (the region including the point Q) in FIG. Reduce gloss unevenness by starting to use. Specifically, for example, in the examination of the glossiness using the patch described in FIG. 8, R, G, and B values corresponding to patches whose glossiness is equal to or higher than a predetermined value are obtained, and a grid close to the color Start replacing light cyan with cyan at the point. Further, the replacement with cyan ink is further determined so as not to deteriorate the graininess and not to exceed the maximum ink receiving amount of the printing medium in consideration of the gradation of the White-Cyan line.

  The amount of light ink used is less than the amount of light ink used (see FIG. 1) in a conventional system that does not consider uneven glossiness due to replacement with cyan. In a typical light and light ink system, the maximum amount of light ink that can be applied by the printer, the amount of ink that can be received by the printer, and the minimum lightness that can be achieved with a single color of light ink in order to maximize the effect of reducing the graininess of light ink In the range of a plurality of permissible values, color separation is performed so that graininess does not increase rapidly by using regular ink (cyan). Therefore, the light cyan ink according to the conventional White-Cyan line color separation (FIG. 1) that performs color separation without considering uneven glossiness uses the maximum amount of ink applied by the printer.

  As a region where light cyan ink is frequently used, a White (RGB = 0xFFFFFF) -Green (RGB = 0x00FF00) line and a White (RGB = 0xFFFFFF) -Blue (RGB = 0x00FF00) line can be cited. However, in the present embodiment, the light cyan ink is frequently used due to the uneven gloss generation conditions for the entire color space of the printer device shown in FIG. Therefore, the same color separation as the conventional color separation is performed. In the color separation on the White (RGB = 0xFFFFFF) -Magenta (RGB = 0xFF00FF) line, which is a line other than the White-Cyan line, as shown in FIG. The same color separation as the conventional color separation is performed.

  That is, the color separation of the light ink in a conventional system that does not take into account uneven gloss is the color separation of the light cyan ink between white and cyan shown in FIG. 1, and the color separation of the light magenta ink between white and magenta shown in FIG. It is like that. All of these use the maximum amount of color separation that can be provided by the system at the lattice point having the maximum amount of color separation.

  On the other hand, in the color separation of the light cyan ink in which gloss unevenness easily occurs in the present embodiment, as shown in FIG. 20, the maximum color separation amount that can be provided by the system is reached even at the lattice point that is the maximum color separation amount. There is nothing. Therefore, in the light cyan color separation that easily causes uneven gloss as shown in FIG. 20, the color separation amount at the lattice point that is the maximum color separation amount is the color separation of the light magenta ink that is less likely to cause uneven gloss as shown in FIG. It is less than The color separation in consideration of uneven glossiness of the present invention is different from the conventional one in that different color separations are performed depending on the difference in glossiness even between light inks.

  In this embodiment, when color separation of predetermined lines (solid line, broken line, and alternate long and short dash line in FIG. 5) is set in the printer device color space described above, next, for areas other than these lines, for example, Patent Literature 11 is complemented using a known table interpolation technique as disclosed in FIG. In this way, the corresponding color separation can be set for the entire printer device color space, and a three-dimensional color separation table can be created.

  As described above, in the present embodiment, in a region where gloss unevenness is likely to occur, the light cyan ink which is likely to cause uneven gloss is replaced with a cyan ink which is less likely to cause uneven gloss. In comparison, it is possible to suppress uneven gloss while reducing the deterioration of the graininess.

  FIG. 22 is a diagram illustrating the ink replacement amount of light cyan ink replaced with cyan ink in the color separation table of the present embodiment created as described above for the entire printer device color space. Using this, a comparison with the amount of light cyan ink used in a conventional color separation table that does not take into account uneven gloss is as follows.

  In FIG. 22, the high density area indicates that the amount of light ink used in the color separation table in the present embodiment is greatly reduced compared to the conventional one, and the low density area has little difference from the conventional one. It is shown that. The region shown in FIG. 22 also corresponds to a region where the granularity is deteriorated as compared with the color separation considering the conventional granularity. That is, the high density portion in the region shown in FIG. 22 has a high degree of granularity deterioration because light cyan ink has been replaced with cyan ink to prevent uneven glossiness in this embodiment, and the low density region. Similarly, it shows that the granularity is only slightly worse than in the past. Although not shown in FIG. 22, the light cyan ink replacement amount rapidly decreases as the color proceeds from the surface layer of the printer device color space to the inside of the color space. Therefore, the deterioration of the graininess remains on the surface layer of the color space. The inside is the same as before.

  However, when the area shown in FIG. 22 is compared with the area where the glossiness is high when assuming the color separation not considering the uneven glossiness shown in FIG. Since only the color separation is corrected, the region where the granularity deteriorates can be minimized as compared with the method described in Patent Document 9.

  Further, in the method described in Patent Document 9, bronze generation conditions are set visually. Since it is difficult to visually quantify the bronze degree, it can be said that the bronze generation condition described in Patent Document 9 is set based on binary information, that is, the presence or absence of bronze. In the method, the degree of bronze is quantified by glossiness, and color separation is adaptively set according to the degree of gloss unevenness by this quantification. In addition, this causes the color separation method to be suddenly switched between a region where gloss unevenness occurs (a region which matches gloss unevenness generation conditions) and a region where gloss unevenness does not occur (region which does not match gloss unevenness generation conditions). Therefore, there is no occurrence of gradation skip due to abrupt changes in the amount of ink applied or glossiness gradation skip due to sudden changes in glossiness.

  Furthermore, unlike the method of Patent Document 10, the method of the present embodiment does not apply inks of different colors, and therefore does not cause deterioration in color reproduction as a price for reducing uneven gloss.

(Modification 1)
Color separation when the selection state of the printing paper changes will be described as a first modification of the embodiment of the present invention. In the following, only points different from the above-described embodiment will be described, and the description of the other will be omitted.

  In the present embodiment described above, the case where the color conversion table C is selected by selecting the ink type 2 and the printing paper 3 that are the most likely combination of gloss unevenness and referring to the table of FIG. 19 has been described.

  In the table of FIG. 19, ink type 1 is relatively light with uneven gloss, ink type 2 is relatively heavy with uneven gloss, and printing paper 1 is semi-gloss and relatively glossy. Uneven noticeable unevenness, printing paper 3 is strong glossy and easily causes uneven glossiness, printing paper 2 has color development and ink acceptance similar to printing paper 3, and is easy to generate uneven glossiness. 1 and an intermediate property between the printing paper 3.

  By the way, in the method of the embodiment of the present invention, the light cyan ink that easily generates uneven gloss is replaced with the cyan ink that does not easily generate uneven gloss, thereby performing color separation that does not easily generate uneven gloss. Therefore, granularity is sacrificed in order to further suppress uneven glossiness in a region where the glossiness is high in the color space. Further, if the difference in glossiness between the uneven glossiness is small, the degree of sacrifice of the granularity becomes light.

  From the table of FIG. 19, when ink type 2 and printing paper 3 that are prominently uneven in gloss are selected, color separation table C that minimizes gloss unevenness and sacrifices granularity is used. In this color separation table C, the color separation of the White-Cyan line is as shown in FIG. 20, and the light cyan ink is greatly reduced and the cyan ink is used frequently.

  Here, consider re-selecting the print paper setting from the print paper 3 to the print paper 1. From Table 19, ink type 2 that easily shows uneven gloss is selected, but uneven gloss does not occur by selecting printing paper 1 that does not easily generate uneven gloss. Therefore, in this case, the color separation table A is selected, which is the same color separation as that of the conventional method of Patent Document 1, taking into consideration the granularity to the maximum and not taking any measures against uneven glossiness.

  The color separation of this color separation table A is shown in FIG. 1, and light cyan ink is used to the maximum between White and Cyan in consideration of the reduction in granularity to the maximum, and the use of cyan ink is used. Is suppressed.

  Further, consider re-selecting the printing paper setting to printing paper 2. From Table 19, the ink type 2 that is easily noticeable in gloss unevenness is selected, and further, by selecting the printing paper 2 that generates moderate gloss unevenness, it is not as much as the combination of (ink type 2 and printing paper 3). A color separation table B that is provided with a measure against uneven glossiness of a medium level is selected.

  As shown in FIG. 23, the color separation of this color separation table B is a measure for moderate gloss unevenness by slightly reducing the use of light cyan ink while considering granularity between White and Cyan. Is what you do.

(Modification 2)
This modification relates to color separation when the ink type selection state changes.

  In the embodiment described above, the color conversion table C is selected by using the ink type 2 and the printing paper 3 which are the most likely combination of gloss unevenness and referring to the table of FIG.

  Here, a case is considered in which the selected ink type is changed from the ink type 2 that easily causes uneven gloss to the ink type 3 that is relatively less likely to cause uneven gloss. From the table of FIG. 19, in this case, the color separation table is changed from the color separation table C to the color separation table B for the highly glossy printing paper 3 on which gloss unevenness easily occurs.

  This is because, in the case of ink type 2 where the ink type is likely to cause uneven gloss, a color separation table is set according to the degree of uneven gloss for print paper 2 and print paper 3 which are similar to each other but slightly different in appearance of gloss unevenness. On the other hand, when ink type 1 that is relatively difficult to cause uneven gloss is used, the difference in the appearance of uneven gloss between the printing paper 2 and the printing paper 3 is small. This is because a sufficient effect can be obtained by taking a countermeasure against moderate gloss unevenness on both sheets.

  Here, the color separation of the color separation table B is as shown in FIG. 23, and moderate gloss unevenness is obtained by slightly reducing the use of light cyan ink while considering granularity between White and Cyan. Measures are being taken.

(Modification 3)
In the present modification, for example, when the ink type 2 and the printing paper 3 on which gloss unevenness is conspicuous are selected, the color separation table B on which measures against moderate gloss unevenness are selected.

  The color separation of this color separation table B is shown in FIG. 23, and as described above, it is moderate by slightly reducing the use of light cyan ink while taking into consideration the granularity between White and Cyan. If this is applied when (ink type 2, printing paper 3) is combined, an output with little granularity can be obtained although gloss unevenness remains slightly.

(Modification 4)
For example, as in the color separation of the color separation table B, gloss unevenness can be reduced by reducing the light cyan ink and replacing it with cyan ink. In the color separation table B shown in FIG. 23, the light cyan ink is increased from the White point, the light cyan ink is decreased before reaching the maximum printable light cyan ink amount, and the use amount of the light cyan ink is set to zero at the Cyan point. .

  In the fourth modification, the color separation as shown in FIG.

  In FIG. 24, the middle-level gloss unevenness countermeasure similar to that of the color separation table B is taken by slightly reducing the use of light cyan ink while considering granularity between White and Cyan. Further, in the fourth modification, by using the light cyan ink also at the Cyan point, the change in the total shot amount represented by the broken line and the change in the light cyan ink between the White-Cyan-Black are moderate between the Cyan point. Thus, the gradation can be improved.

(Other embodiments)
The color separation is performed by the method of the conventional patent document 1 without considering the occurrence of uneven glossiness, and for the obtained color separation, the area having a high glossiness is weighted by the glossiness so that the replacement rate is high, and the relative separation is performed. In particular, by replacing light cyan ink having a high glossiness with cyan ink having a relatively low glossiness, color separation that reduces the occurrence of uneven glossiness may be obtained.

  In the above-described embodiment, the ink system using ink as a printing agent has been described. However, the printing agent applicable in the present invention is not limited to ink, and for example, an electrophotographic system using toner as a printing agent. It is also applicable to.

  Furthermore, in the above-described embodiment, the configuration using one light cyan color that easily causes gloss unevenness has been described, but the present invention is not limited to this. As long as at least one color is used as an ink that easily causes gloss unevenness, the method of the present invention can be easily applied to a configuration that uses, for example, light cyan that easily causes gloss unevenness and light magenta that easily causes gloss unevenness. Applicable.

  Furthermore, in the above-described embodiment, a method of using a three-dimensional color separation table as the color separation method has been described. However, it may be processed by calculation by appropriately replacing this with a function. In such a case, since the area of the color conversion table to be stored is reduced, it is possible to save necessary storage capacity, which is preferable. A specific table may be appropriately converted by the method of the present invention.

  In the above embodiment, for the sake of simplicity, an example using six colors of C, M, Y, K, lc, and lm has been described. However, the present invention is not limited to using these six colors. Absent. Inks (secondary color inks such as red, green, and blue) that take into account graininess (for example, dark, medium, light, and multiple density inks), color stability (gray ink and skin color ink), and color reproducibility Some use multiple, and print with more ink, such as 6 colors, 7 colors, and 8 colors. In any case, the characteristics of the glossiness with respect to the ink placement amount of each ink color are examined, and the ink color having a large change amount in the glossiness depending on the ink placement amount is replaced with an alternative ink group according to the glossiness. If the color separation table is set, the present invention becomes effective.

  In the above description, the ink using a dye as a colorant has been described as an example. However, the present invention is not necessarily limited to this. For example, when using a relatively slow penetrating ink using a pigment as a colorant, uneven glossiness is more likely to occur. This is because the ink having poor permeability remains in the vicinity of the coat layer of the printing paper and easily aggregates. Therefore, in such a case, the method of the present invention can be used more effectively.

  In the above embodiment, color separation that reduces gloss unevenness is set for any combination as a color separation method that is set according to the ink type and the printing paper type. However, as described above, the uneven gloss caused by the cohesiveness of the ink is contrary to the weather resistance. Therefore, color separation that does not reduce gloss unevenness can be exceptionally set for a specific printing mode (combination of ink type and printing paper type) that places importance on weather resistance.

  Further, for example, an image processing apparatus and its program when a software program (application program) that realizes the above-described function is supplied to a main memory or an external storage device of a computer system via a communication line and executed. It is in category.

  In addition, the ink jet printing apparatus can take any form such as an image output terminal of an information processing device such as a computer, a copying apparatus combined with a reader, and a facsimile apparatus having a transmission / reception function. There may be.

It is a figure which shows the color separation in the White-Cyan-Black line by the conventional color separation method. It is a figure explaining the gloss nonuniformity phenomenon in the printed image. (A) And (b) is a figure which shows one example of a conventional color separation method, and explains the result of having investigated the generation | occurrence | production condition of bronze from the printing result of a patch. FIG. 4 is a diagram illustrating an area where black ink is replaced with process black by the color separation method illustrated in FIG. 3 for the entire printer device color space. It is a figure which shows a color separation table as the space of the cubic lattice prescribed | regulated by R, G, B. It is a figure which shows the relationship between the printing amount of these two inks, total printing amount, and glossiness about all the combinations of the light cyan ink and cyan ink printing amount. When the conventional color separation method shown in FIG. 3 is expanded and applied to a system using a light cyan ink having a relatively high glossiness and another ink including a cyan ink having a relatively low glossiness, FIG. 6 is a diagram illustrating an area replaced with cyan ink for the entire printer device color space. When color separation is performed without considering uneven glossiness in a system that uses light cyan ink with relatively high glossiness and other inks including cyan ink with relatively low glossiness, the glossiness in the actual print results It is a figure which shows the area | region which becomes high about the printer device color space whole region. It is a figure which shows the result at the time of measuring the glossiness of the ink of several colors for every ink placement amount. 1 is a diagram illustrating a schematic configuration of a printing system according to an embodiment of the present invention. It is a figure which shows the structure of the software used with the system shown in FIG. It is a figure which shows schematic structure of the printer used with the system shown in FIG. It is a figure which shows the external appearance shape of the ink cartridge used with the printer shown in FIG. It is a figure explaining the ink discharge principle of the recording head used with the printer shown in FIG. It is a figure which shows the nozzle arrangement of the said recording head. 6 is a flowchart illustrating print processing according to an embodiment of the present invention. It is a figure explaining the color conversion table used by a color conversion process. It is a flowchart which shows the detail of the color conversion process concerning one Embodiment of this invention. It is a figure which shows a mode that the color conversion table used by embodiment of this invention is memorize | stored for every printing condition. It is a figure which shows the color separation in the White-Cyan-Black line by the color separation method which concerns on one Embodiment of this invention. It is a figure which shows the color separation in the White-Magenta-Black line which concerns on one Embodiment of this invention. When the color separation according to the embodiment of the present invention is applied to a system using a light cyan ink having a relatively high glossiness and another ink including a cyan ink having a relatively low glossiness, the amount of light cyan ink is reduced. It is a figure which shows the area | region reduced rather than the conventional color separation about the printer device color space whole region. It is a figure which shows the color separation in the White-Cyan-Black line calculated | required by the method of the modification 3 of embodiment of this invention. It is a figure which shows the color separation in the White-Cyan-Black line calculated | required by the method of the modification 4 of embodiment of this invention.

Explanation of symbols

20 Color Printer 21 Color Scanner 24 Modem 26 Hard Disk 41 Recording Head 42, 43 Ink Cartridge 44-47 Recording Head 60 Control Circuit 61 CPU
63 RAM
64 PC interface 67 Drive buffer 69 Distribution output device 70 Oscillator 80 Computer 81 CPU
82 ROM
83 RAM
88 SIO
90 Video Driver 91 Application Program 92 Printer Driver 93 Resolution Conversion Module 94 Color Conversion Module 95 Halftone Module 96 Interlace Module

Claims (14)

An image processing apparatus that generates data of a plurality of types of printing agents of similar colors used in a printing apparatus as color separation amounts based on image data,
The first and second in a specific region in a color space in which the first printing agent and the second printing agent having a lower gloss than the first printing agent among the plurality of types of printing agents of the same color are mainly used. The color separation amount of the first printing agent is gradually increased to the first color separation amount and gradually decreased as the density per unit area increases. Color separation generating means for generating first and second color separation amounts for expressing the specific area by gradually increasing the color separation amount of the second printing agent;
The first color separation amount is smaller than a second color separation amount corresponding to the maximum placement amount of the first printing agent that can be placed per unit area of the print medium,
The granularity when the first printing agent corresponding to the first color separation amount is applied to the print medium is the granularity when the first printing agent corresponding to the second color separation amount is applied to the printing medium. An image processing apparatus characterized by being higher than the granularity of time.   The image processing apparatus according to claim 1, wherein the plurality of types of printing agents include a cyan ink and a light cyan ink that exhibits a higher glossiness in a print medium than the cyan ink. An image processing apparatus that generates printing agent data used in a printing apparatus as a color separation amount based on image data,
A first printing agent that exhibits a predetermined gloss when applied to a printing medium among a plurality of types of printing agents used in a printing apparatus, and a second printing agent that exhibits a lower gloss than the first printing agent, respectively. Color separation means for generating a color separation amount of the first printing agent in a specific area in a color space in which the first printing agent is mainly used. The color separation amount of each of the first printing agent and the second printing agent is generated so as to be smaller than the maximum color separation amount of the second printing agent in a specific region in the color space in which the agent is mainly used. ,
An image processing apparatus. An image processing apparatus that generates printing agent data used in a printing apparatus as a color separation amount based on image data,
A first printing agent that exhibits a predetermined gloss when applied to a printing medium among a plurality of types of printing agents used in a printing apparatus, and a second printing agent that exhibits a lower gloss than the first printing agent, respectively. Color separation processing means for generating a color separation amount of
The color separation processing means includes
A first color separation process in which the maximum color separation amount of the first printing agent is different from the maximum color separation amount of the second printing agent;
A second color separation process in which the maximum color separation amount of the first printing agent and the maximum color separation amount of the second printing agent are substantially the same;
An image processing apparatus, wherein the first color separation process and the second color separation process are switched according to a type of printing agent used in the printing apparatus. An image processing apparatus that generates printing agent data used in a printing apparatus as a color separation amount based on image data,
A first printing agent that exhibits a predetermined gloss when applied to a printing medium among a plurality of types of printing agents used in a printing apparatus, and a second printing agent that exhibits a lower gloss than the first printing agent, respectively. Color separation processing means for generating a color separation amount of
The color separation processing means includes
A first color separation process in which a color separation amount of the first printing agent is different from a color separation amount of the second printing agent;
A second color separation process in which a color separation amount of the first printing agent and a color separation amount of the second printing agent are substantially the same;
An image processing apparatus, wherein the first color separation process and the second color separation process are switched in accordance with a type of print medium used in the printing apparatus. An image processing apparatus that generates printing agent data used in a printing apparatus as a color separation amount based on image data,
A first printing agent that exhibits a predetermined gloss when applied to a printing medium among a plurality of types of printing agents used in a printing apparatus, and a second printing agent that exhibits a lower gloss than the first printing agent, respectively. Color separation processing means for generating a color separation amount of
The color separation processing means includes
A first color separation process in which a color separation amount of the first printing agent is different from a color separation amount of the second printing agent;
A second color separation process in which a color separation amount of the first printing agent and a color separation amount of the second printing agent are substantially the same;
An image processing apparatus that switches between the first color separation process and the second color separation process in accordance with both the type of printing agent used in the printing apparatus and the type of print medium.   The image processing apparatus according to claim 3, wherein the first printing agent is light cyan ink, and the second printing agent is light magenta ink. An image processing method for generating data of a plurality of types of printing agents of similar colors used in a printing apparatus as color separation amounts based on image data,
The first and second in a specific region in a color space in which the first printing agent and the second printing agent having a lower gloss than the first printing agent among the plurality of types of printing agents of the same color are mainly used. The color separation amount of the first printing agent is gradually increased to the first color separation amount and gradually decreased as the density per unit area increases. A color separation generating step of generating first and second color separation amounts for expressing the specific region by gradually increasing the color separation amount of the second printing agent;
The first color separation amount is smaller than a second color separation amount corresponding to the maximum placement amount of the first printing agent that can be placed per unit area of the print medium,
The granularity when the first printing agent corresponding to the first color separation amount is applied to the print medium is the granularity when the first printing agent corresponding to the second color separation amount is applied to the printing medium. An image processing method characterized by being higher than the granularity of time.   The image processing method according to claim 8, wherein the plurality of types of printing agents include a cyan ink and a light cyan ink exhibiting a higher glossiness in a print medium than the cyan ink. An image processing method for generating printing agent data used in a printing apparatus as a color separation amount based on image data,
A first printing agent that exhibits a predetermined gloss when applied to a printing medium among a plurality of types of printing agents used in a printing apparatus, and a second printing agent that exhibits a lower gloss than the first printing agent, respectively. A color separation process for generating a color separation amount of
In the color separation step, the maximum color separation amount of the first printing agent in the specific region in the color space where the first printing agent is mainly used is the specific region in the color space in which the second printing agent is mainly used. Generating a color separation amount of the first and second printing agents to be less than a maximum color separation amount of the second printing agent in
An image processing method.   The image processing method according to claim 10, wherein the first printing agent is light cyan ink, and the second printing agent is light magenta ink. An image processing method for generating printing agent data used in a printing apparatus as a color separation amount based on image data,
The color separation amount of the first printing agent exhibiting a predetermined glossiness when applied to the printing medium among a plurality of types of printing agents used in the printing apparatus is determined in a color space in which the first printing agent is mainly used. By replacing the color separation amount of the second printing agent having a lower gloss than the first printing agent and having the same hue as the first printing agent and a higher colorant concentration in the specific region. A step of generating color separation amounts of the first and second printing agents, wherein the position where replacement is started in the specific area is the second print in the specific area when the granularity of the print image is taken into consideration; A color separation step that is a position where the granularity deteriorates more than the replacement start position of the agent,
An image processing method characterized by comprising:   The image processing method according to claim 12, wherein the first printing agent is light cyan ink, and the second printing agent is cyan ink. A program for causing a computer to execute image processing for generating printing agent data used in a printing apparatus as a color separation amount based on image data, the image processing comprising:
The color separation amount of the first printing agent exhibiting a predetermined glossiness when applied to a printing medium among a plurality of types of printing agents used in the printing apparatus is represented by a line in a color space in which the first printing agent is mainly used. In the first and second printing agents, the first and second printing agents are replaced with the color separation amount of the second printing agent that exhibits a lower gloss than the first printing agent and has the same hue as the first printing agent and a higher colorant concentration. The step of generating the color separation amount of the second printing agent, where the replacement start position on the line is the replacement start of the second printing agent on the line when the granularity of the print image is taken into consideration A color separation process where the granularity is worse than the position,
The program characterized by having.

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