JP2010064326A - Printing apparatus and printing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the quality of an image printed in a technique for printing the image by respectively delivering inks with different properties. <P>SOLUTION: A printing apparatus creates printing data for forming dots through the first number of nozzles among a plurality of the nozzles equipped in a printing head to a single color region in the image data. Meanwhile, the second number of nozzles less than the first number of nozzles form the dots to a special gloss region in the image data. When the printing head is driven in the sub-scanning direction by a predetermined band width, on each driving of the printing head in the main scanning direction, the printing data are created by arranging the dots on a dot pattern expressing a region wherein the dots can be formed by the second number of the nozzles. In addition, the printing apparatus includes a relaxation part for relaxing a periodical shape change including the dot pattern generated in accordance with the band width. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technique for printing on a print medium.

  2. Description of the Related Art Conventionally, in the field of electrophotography, a technique has been proposed in which a solid layer is formed with a metallic toner in an area where a metallic color is designated, and then a high-definition or rough process color toner layer is formed thereon. (See Patent Document 1). In this technique, metallic colors of various tones are reproduced by printing process color toner on metallic toner.

JP 2006-50347 A

  Color printing technology using toner includes a tandem method and a four-cycle method, and any of these methods is a method in which toner of each color is superimposed and printed. Therefore, as described above, it is relatively easy to print the process color toner on the metallic toner.

  However, in the field of inkjet printers, no technology has been proposed for ejecting special glossy inks such as metallic inks and general color inks from the print head. Therefore, when printing using these inks, the point of improving the image quality has not been considered.

  In consideration of these problems, the problem to be solved by the present invention is to print an image in a technique for printing an image by ejecting inks having different properties from a print head, such as special glossy ink and color ink, respectively. It is to improve the image quality.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms or application examples.

Application Example 1 A printing apparatus including a drive mechanism that drives a print head relative to a print medium in a main scanning direction that is the width direction of the print medium and a sub-scanning direction that intersects the main scanning direction. And
A print head in which a plurality of nozzles are arranged along the sub-scanning direction;
An acquisition unit that acquires image data including a color single area to be printed with color ink, a special gloss ink and a special gloss area to be printed with the color ink;
For the color single region, print data for forming dots is generated by a first number of nozzles among the plurality of nozzles, and for the special glossy region, the print number is larger than the first number. When the print head is driven in the sub-scanning direction by a predetermined bandwidth every time the print head is driven in the main scanning direction in order to form dots with a small second number of nozzles, the second number A print data generation unit that generates print data by arranging dots on a dot pattern that represents an area in which dots can be formed by the nozzles;
A relaxation part that includes the dot pattern and relaxes a periodic shape change that occurs according to the bandwidth,
A printing apparatus comprising: a dot forming unit that controls the print head and the drive mechanism to form dots on the print medium according to the relaxed print data.

  In such a printing apparatus, dots are formed by a first number of nozzles among a plurality of nozzles provided in the print head for a color single region in image data, and for a special glossy region, Dots are formed with a second number of nozzles less than the first number. That is, in the above-described printing apparatus, printing is performed by changing the number of nozzles to be used for each of the color single area and the special gloss area. Thus, the applicant of the present application has found that when printing is performed by changing the number of nozzles according to the region in the image data, a predetermined dot pattern having periodicity is generated on the print medium. However, according to the printing apparatus, since the periodic form change can be alleviated by the mitigation unit, the image quality of the printed image can be improved.

Application Example 2 In the printing apparatus according to Application Example 1, in the special glossy region, the relaxation unit may arrange the dot arrangement belonging to a predetermined main scanning line of the dot pattern in the main scanning direction. A printing apparatus that mitigates a periodic shape change of the dot pattern by quantitatively shifting. With such a printing apparatus, it is possible to relieve the periodic form change included in the dot pattern by shifting the arrangement of the dots in the main scanning line that cause the periodic change.

[Application Example 3] In the printing apparatus according to Application Example 2, the relaxation unit may be configured to perform dots formed by the color ink and dots formed by the special gloss ink in the special gloss region, respectively. A printing apparatus that performs the shift individually. With such a printing apparatus, the dots formed by the color ink and the dots formed by the special glossy ink are moved in different directions and shift amounts, respectively, thereby relieving the periodic pattern change of the dot pattern. Can do.

Application Example 4 In the printing apparatus according to Application Example 1, the relaxation unit causes the dot formation unit to form dots in a prescribed order so as to reduce a periodic shape change of the dot pattern. Thus, a printing apparatus that alleviates a periodic shape change of the dot pattern. With such a printing apparatus, it is possible to alleviate a periodic change in the dot pattern by adjusting in advance the dot arrangement order during main scanning and the dot arrangement order during sub-scanning.

Application Example 5 In the printing apparatus according to Application Example 1, the print data generation unit generates the print data by performing a halftone process on the image data using a predetermined dither mask. The relaxation unit supplies a dither mask having a threshold value arranged along the dot pattern so as to maintain the dispersibility of dots below a predetermined threshold value to the print data generation unit, thereby A printing device that mitigates periodic morphological changes. In such a printing apparatus, by preparing a dither mask along the dot pattern and optimizing the arrangement of the threshold values in the dither mask, it is possible to suppress the occurrence of a periodic shape change in the dot pattern. Can do.

Application Example 6 The printing apparatus according to Application Example 5, wherein the size of the dither mask is determined according to the period of the dot pattern. In such a printing apparatus, since the size of the dither mask is determined according to the period of the dot pattern, halftone processing of the entire image can be easily performed. In addition, if the size of the dither mask and the size of the dot pattern are synchronized, it is easy to adjust the arrangement of the thresholds in the dither mask without special adjustment of the sub-scanning amount. It becomes possible to suppress the periodic shape change which arises.

[Application Example 7] The printing apparatus according to any one of Application Example 1 to Application Example 6, wherein the special gloss ink has a reflection angle dependency in optical characteristics after being printed on the surface of the print medium. Printing device. With such a printing apparatus, it is possible to print images having various appearances according to the angle at which the light reflected from the print medium is observed.

[Application Example 8] The printing apparatus according to any one of Application Examples 1 to 6, wherein the special glossy ink contains a pigment exhibiting a metallic feeling. With such a printing apparatus, it is possible to print an image having a metallic gloss.

  The present invention can be configured as a printing method or a computer program in addition to the configuration as the printing apparatus described above. The computer program may be recorded on a computer-readable recording medium. As the recording medium, for example, various media such as a flexible disk, a CD-ROM, a DVD-ROM, a magneto-optical disk, a memory card, and a hard disk can be used.

Hereinafter, embodiments of the present invention will be described in the following order based on examples.
A. Embodiment:
A-1. General configuration of the printing system:
A-2. Computer and printer configuration:
A-3. Nozzle placement control with dither mask:
A-4. Printing process:
B. First Example (Reduction of Periodic Change of Dot Pattern):
C. Second embodiment (another example of filling order):
D. Third embodiment (number of non-uniform nozzles):
E. Fourth embodiment (local area size is 2 × 4):
F. Fifth embodiment (local area size is 4 × 2):
G. Example 6 (unequally spaced feed):
H. Variation:

A. Embodiment:
A-1. General configuration of the printing system:
FIG. 1 is a diagram showing a schematic configuration of a printing system 10 as an embodiment of the present invention. As shown in the figure, the printing system 10 according to the present embodiment includes a computer 100 and a printer 200 that actually prints an image under the control of the computer 100. The printing system 10 functions as a printing device in a broad sense as a whole.

  The printer 200 of this embodiment includes cyan ink (C), magenta ink (M), yellow ink (Y), and black ink (K) as color inks. Thus, in this embodiment, the term “color ink” is meant to include black ink. Of course, the printer 200 may include color inks such as light cyan, light magenta, dark yellow, and red in addition to these colors.

  The printer 200 further includes a metallic ink (S) having metallic gloss as a special color ink. In this embodiment, an oil-based ink composition containing a metal pigment, an organic solvent, and a resin is used as the metallic ink. In order to effectively produce a metallic luster, the above-mentioned metal pigment is a tabular grain, and when the major axis on the plane of the tabular grain is X, the minor axis is Y, and the thickness is Z A 50% average particle diameter R50 of the equivalent circle diameter determined from the area of the XY plane of the tabular grains is 0.5 to 3 μm and satisfies the condition of R50 / Z> 5. Such a metal pigment can be formed of, for example, aluminum or an aluminum alloy, or can be formed by crushing a metal vapor-deposited film. The concentration of the metal pigment contained in the metallic ink can be 0.1 to 10.0% by weight. Of course, the metallic ink is not limited to such a composition, and any other composition can be appropriately employed as long as the metallic gloss is generated.

  When metallic ink is printed on a print medium, light is reflected from the portion and observed. That is, it can be said that the metallic ink has a reflection angle dependency in optical characteristics after being printed on the surface of the printing medium. The metallic feeling caused by the printing of the metallic ink can be expressed by various indexes according to the reflection angle dependency. For example, a known index value In1 represented by the following formula (1) can be used as an index of metallic feeling. This index value In1 measures the lightness of reflected light at three different places defined in the equation (1) when the print medium is irradiated from an angle of −45 degrees, and the relationship between the lightness values obtained at these three places. Can be obtained from

  In addition, the index value In2 of the following equation (2), the index value In3 represented by the following equation (3), and the like can also be used as an index of metallic feeling.

  A predetermined operating system is installed in the computer 100 shown in FIG. 1, and the application program 20 operates under this operating system. A video driver 22 and a printer driver 24 are incorporated in the operating system. The application program 20 inputs image data IMG from the digital camera 120 through the peripheral device interface 108, for example. Then, the application program 20 displays an image represented by the image data IMG on the display 114 via the video driver 22. Further, the application program 20 outputs the image data IMG to the printer 200 via the printer driver 24. Image data IMG input from the digital camera 120 by the application program 20 is data composed of three color components of red (R), green (G), and blue (B).

  The application program 20 according to the present embodiment includes an area composed of three primary colors R, G, and B (hereinafter referred to as “color single area A1”), and a metallic color as a background color, and R, G, and B primary colors on it. It is possible to generate image data including a region (hereinafter referred to as “special gloss region A2”) on which a color image composed of This image data is configured by adding information indicating the range of the special glossy area A2 (hereinafter, range information) to normal RGB format image data. The range information can be expressed in a vector format or a raster format.

  FIG. 2 shows an example of the image data IMG including the color single area A1 and the special gloss area A2. In the example shown in FIG. 2, a figure representing a circle and a triangle is designated as the special glossy area A2, and the background is designated as the color single area A1.

  The printer driver 24 corresponding to the “acquisition unit” and “print data generation unit” of the present application includes an image acquisition module 40, a color conversion module 42, a halftone module 44, and a print data output module 46. The image acquisition module 40 acquires image data to be printed from the application program 20.

  The color conversion module 42 refers to the color conversion table LUT prepared in advance, and the printer 200 determines the color components R, G, and B of the color portions in the color single area A1 and the special gloss area A2 in the image data. This is converted into expressible color components (cyan (C), magenta (M), yellow (Y), and black (K)).

  The halftone module 44 performs a halftone process in which the image data after color conversion is represented by a binarized (more precisely, multivalued) dot distribution. In the present embodiment, a known systematic dither method is used as the halftone process. A dither mask used for halftone processing is supplied from the RAM 106. As the halftone process, an error diffusion method, a density pattern method, and other halftone techniques can be used in addition to the systematic dither method.

  The halftone module 44 of this embodiment includes an area determination module 45. The area determination module 45 determines the special gloss area A2 and the color single area A1 from the image data IMG acquired from the application program 20. Specifically, the area determination module 45 determines the area included in the range information added to the image data IMG as the special gloss area A2, and determines the other part as the color single area A1.

  When the area determination module 45 determines the special gloss area A2 and the color single area A1 in the image data, the halftone module 44 performs halftone processing using a different dither mask depending on the determined area. The dither mask used in the color single region A1 is a general dither mask having blue noise characteristics (hereinafter referred to as “general dither mask D1”).

  FIG. 3 shows an example of the general dither mask D1. Each element of the general dither mask D1 is provided with a threshold value so that when the image is binarized using the general dither mask D1, the image has blue noise characteristics. On the other hand, the dither mask used in the special glossy area A2 is a special dither mask generated to form metallic dots prior to the color dots (hereinafter referred to as “special dither mask D2”). A specific example of the special dither mask D2 will be described later in detail.

  The print data output module 46 rearranges the data representing the dot arrangement of each color obtained by the halftone process in accordance with the dot formation order by the print head 241 of the printer 200 and outputs the data to the printer 200 as print data.

  In the present embodiment, the printer driver 24 discriminates the special glossy area A2 and the color single area A1 from the image data, prints the former area using metallic ink and color ink, and the latter area. Is printed using only color ink. The metallic color is not generated by color conversion from each value of R, G, and B by the color conversion module 42, but for the special glossy area A2 represented by the range information added to the image data by the application program 20. Used. In other words, in this embodiment, the metallic ink is used based on specific design requirements such as the background color of the label sheet and the background color of the pattern to be conspicuous, rather than being used to reproduce a natural image.

A-2. Computer and printer configuration:
FIG. 4 is a diagram illustrating a schematic configuration of the computer 100. The computer 100 is a well-known computer configured by connecting a ROM 104, a RAM 106, and the like with a bus 116 around a CPU 102.

  The computer 100 includes a disk controller 109 for reading data such as the flexible disk 124 and the compact disk 126, a peripheral device interface 108 for exchanging data with peripheral devices, and a video interface 112 for driving the display 114. It is connected. A printer 200 and a hard disk 118 are connected to the peripheral device interface 108. Further, if the digital camera 120 or the color scanner 122 is connected to the peripheral device interface 108, it is possible to perform image processing on an image captured by the digital camera 120 or the color scanner 122. If the network interface card 110 is installed, the computer 100 can be connected to the communication line 300 to obtain data stored in the storage device 310 connected to the communication line. When the computer 100 obtains image data to be printed, the printer driver 24 controls the printer 200 to print the image data.

  Next, the configuration of the printer 200 will be described with reference to FIG. As shown in FIG. 5, the printer 200 includes a transport mechanism that transports the print medium P by the paper feed motor 235, a main scanning mechanism that reciprocates the carriage 240 in the axial direction of the platen 236 by the carriage motor 230, and the carriage 240. A mechanism for driving the mounted print head 241 to eject ink and forming dots, and a control circuit 260 that controls the exchange of signals with the paper feed motor 235, the carriage motor 230, the print head 241, and the operation panel 256. It is composed of

  The main scanning mechanism for reciprocating the carriage 240 in the axial direction of the platen 236 is an endless unit between the carriage motor 230 and a slide shaft 233 that is installed in parallel with the platen 236 axis and slidably holds the carriage 240. A pulley 232 for extending the drive belt 231 and a position detection sensor 234 for detecting the origin position of the carriage 240 are included.

  On the carriage 240, a color ink cartridge 243 that contains cyan ink (C), magenta ink (M), yellow ink (Y), and black ink (K) as color inks is mounted. The carriage 240 is mounted with a metallic ink cartridge 242 containing metallic ink (S). In the print head 241 provided at the lower part of the carriage 240, nozzle rows 244 to 248 for ejecting ink are formed for each color. When the ink cartridges 242 and 243 are mounted on the carriage 240 from above, ink can be supplied from each cartridge to the nozzle rows 244 to 248. Note that each nozzle formed on the print head 241 can eject large, medium, and small ink droplets as described later, and can form large, medium, and small dots on the print medium. Taking large dots as a reference, medium dots have about half the ink amount of large dots, and small dots have about 1/4 ink amount.

  The control circuit 260 is configured by connecting a CPU, a ROM, a RAM, a PIF (peripheral device interface), and the like with a bus. When the control circuit 260 receives the print data output from the computer 100 via the PIF, the control circuit 260 drives the carriage motor 230 to move the ink ejection heads 244 to 247 for each color in the main scanning direction with respect to the print medium P. The print medium P is moved in the sub-scanning direction by reciprocating and driving the paper feed motor 235. The control circuit 260 performs printing by driving the nozzles at an appropriate timing based on the print data in accordance with the movement of the carriage 240 reciprocally (main scanning) or the movement of paper feeding of the printing medium (sub scanning). Ink dots of appropriate colors are formed at appropriate positions on the medium P. In this way, the printer 200 can print a color image on the print medium P. In the present embodiment, the print medium is transported in the sub-scanning direction, but the position of the print medium may be fixed and the carriage 240 may be transported in the sub-scanning direction.

When printing an image, the printer 200 according to the present embodiment performs printing by changing the positions of the nozzles that are actually used in the color single region A1 and the special glossy region A2 among a plurality of prepared nozzles.
FIG. 6 shows how the nozzle position is changed according to the print area. FIG. 6A shows the arrangement of the nozzles when printing the color single area A1, and FIG. 6B shows the arrangement of the nozzles when printing the special glossy area A2. In the figure, black circles indicate nozzles that are actually used among nozzles that can eject metallic ink, and hatched circles indicate nozzles that are actually used among nozzles that can discharge color ink. Show. White circles indicate nozzles that are not actually used. As shown in these drawings, the print head 241 includes a nozzle row having nozzles capable of ejecting metallic ink and a nozzle row having nozzles capable of ejecting color ink substantially facing each other in the sub-scanning direction. Has been placed.

  As shown in FIG. 6A, in the color single area A1, the printer 200 does not use the nozzles prepared for discharging the metallic ink, but uses all the nozzles prepared for discharging the color ink. And print. On the other hand, in the special glossy area A2, the printer 200 selects seven nozzles (hereinafter referred to as “preceding nozzle group”) that first pass through the print medium P among the 14 nozzles for discharging the metallic ink. It is used during actual printing, and the remaining seven are not used. For the color ink (C, M, Y, K) nozzle rows 244 to 247, of the 14 nozzles, the seven nozzles that pass through the print medium first are not used, and the remaining seven are used. The remaining seven nozzles are used (hereinafter referred to as “following nozzle group”). As described above, in the present embodiment, when the special glossy area A2 is printed, the preceding nozzle group and the succeeding nozzle group are shifted by a predetermined interval in the sub-scanning direction as shown in FIG. On the same area of the print medium P, the metallic ink is ejected first in time, and the color ink is ejected later in time.

  As is apparent from FIGS. 6A and 6B, in this embodiment, the metallic portion and the color portion in the special glossy area A2 are more than the number of nozzles used in the color single area A1, respectively. Printing is performed with a small number of nozzles (specifically, the number of nozzles is ½). Therefore, the number of main scans of the print head 241 for filling a predetermined local area in the color single area A1 with color ink is the same as the printing for filling the local area of the same size in the special glossy area A2 with color ink or metallic ink. This is greater than the number of main scans of the head 241 (specifically, twice as many).

A-3. Nozzle placement control with dither mask:
In the control for changing the arrangement of the nozzles actually used according to the area to be printed, a special dither mask (special dither mask D2) is applied to the special glossy area A2 during the halftone processing by the printer driver 24. It is realized with. This principle will be described in detail below.

  In this embodiment, first, as an aspect of drive control of the print head 241, the overlap number is “2”, the nozzle pitch is “2”, the paper feed amount is “7”, and the print head is moved forward and backward. It was decided to perform bidirectional printing in which ink was ejected at both times. The number of overlaps refers to the number of times of main scanning necessary to fill all the lines formed in the main scanning direction (horizontal direction) with dots. That is, when the overlap number is “2”, one line in the main scanning direction is completed in two main scans. The nozzle pitch means the number of lines (dots) existing between two nozzles. In this embodiment, since the nozzle pitch is “2”, dots are formed every other line in the main scanning of the print head 241 once. The paper feed amount refers to the amount (number of lines) by which the print head 241 is conveyed in the sub-scanning direction for each main scanning. In this embodiment, since the paper feed amount is “7”, that is, an odd number of paper feed amounts, a new dot is formed in the next main scan in the gap between dots formed in advance every other line. It will follow.

  FIG. 7 is a diagram illustrating how dots are formed by the printer 200. Here, first, it is assumed that the metallic ink can be ejected from only the first seven nozzles in the sub-scanning direction and cannot be ejected from the remaining seven nozzles of the nozzle array composed of 14 nozzles. Further, it is assumed that the color ink cannot be ejected from the first seven lines, and can be ejected only from the remaining seven lines. For convenience of illustration, it is assumed that the metallic nozzle group and the color nozzle group are included in the same nozzle row. FIG. 7A shows a state in which such a nozzle row moves in the sub-scanning direction every time main scanning is performed. In the nozzle row shown in FIG. 7 (a), the portion indicating the numerical value from 1 to 7 indicates the nozzle from which the color ink is ejected, and the portion indicating the numerical value from 8 to 14 is the metallic ink. Indicates a nozzle to be discharged. As shown in FIG. 7A, in this embodiment, since the paper feed amount is set to “7”, the print head 241 moves by 7 lines (7 nozzles) in the sub-scanning direction for each main scan. ing.

  FIG. 7B shows how many main scans each dot formed on the print medium is formed. Each grid shown in FIG. 7B represents one dot on the print medium, and the numerical value in the grid corresponds to the main scanning number shown in the upper part of FIG. 7A. That is, according to FIG. 7B, it can be seen that in the uppermost line, odd-numbered dots are formed by the first main scanning and even-numbered dots are formed by the third main scanning.

  As shown in FIG. 7B, in this embodiment, when a 2 × 2 local region (hereinafter referred to as a local region) is viewed, each dot in the local region is represented by upper left, lower left, upper right. It is filled in the order of the lower right. This order is called “filling order”. Regarding the size of the local area, the horizontal direction (main scanning direction) matches the number of overlaps (“2” in this embodiment), and the vertical direction (sub-scanning direction) corresponds to the nozzle pitch (“2” in this embodiment). Match. The filling order has a property of changing every time the print head 241 is moved in the sub-scanning direction (that is, every time main scanning is performed). In this embodiment, the filling order changes four times. Then, it returns to the original filling order. The filling order is set by the printer driver 24 giving a predetermined command to the control circuit 260 of the printer 200. When receiving the setting of the filling order from the printer driver 24, the control circuit 260 forms dots according to the order set in the filling order.

  FIG. 7C shows which nozzles form each dot formed on the print medium. The numerical value in each lattice corresponds to the nozzle number shown in FIG. When FIG. 7C and FIG. 7B are taken together, the odd-numbered dots in the uppermost line in the figure are formed by the 11th nozzle in the first main scanning, and are even-numbered. It can be seen that the second dot is formed by the fourth nozzle in the third main scan. For the second line, odd-numbered dots are formed by the eighth nozzle in the second main scan, and even-numbered dots are formed by the first nozzle in the fourth main scan. I understand that.

  FIG. 7C shows dots formed by nozzles having nozzle numbers 8 to 14, that is, nozzles for metallic ink, in a black lattice, and nozzles having nozzle numbers 1 to 7, that is, color. The dots formed by the ink nozzles are indicated by a white grid. In this way, when the dots formed by the metallic ink and the dots formed by the color ink are displayed in different colors, the color ink nozzles and the metallic ink nozzles are arranged in the head while being shifted in the sub-scanning direction. In this case, it can be seen that a specific pattern (pattern) appears on the print medium. The pattern shown in FIG. 7C changes one after another in units of 7 lines (hereinafter referred to as “band units”), which is a unit of the paper feed amount. This pattern has a property of returning to the initial pattern every time the filling order changes.

  As described above, here, the metallic ink can be ejected from only the preceding seven of the 14 nozzle nozzle rows, and the color ink can be ejected from only the following seven. Assumed. However, considering the result of FIG. 7C, conversely, as long as the pattern shown in FIG. 7C is printed, the metallic ink is ejected from only the first seven nozzles out of the 14 nozzles. In other words, the color ink is discharged only from the subsequent seven nozzles. That is, if a dither mask in which a pattern as shown in FIG. 7C appears by halftone processing is prepared in advance as a special dither mask D2, the nozzle arrangement pattern can be changed by simply switching the dither mask to be used. It can be done.

  FIG. 8 shows an example of the special dither mask D2 for color ink used in this embodiment. As shown in FIG. 8, the special dither mask D2 of this embodiment is generated based on the pattern shown in FIG. The size of the special dither mask D2 in the horizontal direction is an integral multiple of the number of overlaps (in this embodiment, “16” which is 8 times), and the vertical size is an integral multiple of the pattern shown in FIG. (In the present embodiment, it is “28” which is 1 time). If this special dither mask D2 is a normal dither mask, threshold values from 1 to 488 (= 16 * 28) are arranged for each element. Therefore, the data in the range from 0 to 488 can be binarized by turning off the dots when the data to be compared is less than the threshold and turning on the dots when the data to be compared is greater than or equal to the threshold. However, the special dither mask D2 for color ink shown in FIG. 8 has substantially threshold values only at positions corresponding to the white grid shown in FIG. 7C (that is, positions where color dots are formed). Is arranged. At a position corresponding to the black grid shown in FIG. 7C (that is, a position where a metallic dot is formed), a value exceeding the maximum value of the dot recording rate compared with the threshold value of the special dither mask D2 is present. Is set. Thus, if a value exceeding the maximum value of the dot recording rate is set for the position where the metallic dot is formed, no dot is formed at that portion. Therefore, if the special dither mask D2 shown in FIG. 8 is used, only color dots can be formed. Even if a special code is arranged in the hatched portion in FIG. 8 and the processing for comparing the threshold value is skipped for the portion where the code is recorded during the halftone processing, dot formation for the portion is performed. Can be suppressed. In FIG. 8, only threshold values of 112 or less are displayed, and illustration of all threshold values is omitted.

  FIG. 9 shows a halftone result when the dot recording rate is 10% using the special dither mask D2 shown in FIG. FIG. 10 shows a halftone result when the dot recording rate is 25%. As shown in these drawings, if the arrangement of the thresholds on the special dither mask D2 is optimized, even if the special dither mask D2 generates a pattern as shown in FIG. Up to this, it becomes possible to ensure good dot dispersibility. That is, by optimizing the arrangement of the threshold values, it is possible to mitigate the appearance of a periodic shape change in the dot pattern below a predetermined threshold value (approximately 30% or less in this embodiment).

  FIG. 8 shows a special dither mask D2 for color ink (hereinafter referred to as “special dither mask D2a”). In this embodiment, the special dither mask D2a is ½ cycle in the vertical direction. The shifted dither mask is used as a special dither mask for metallic ink (hereinafter referred to as “special dither mask D2b”). In the pattern shown in FIG. 7 (c), the metallic portion and the color portion are completely interchanged with each other in half in the vertical direction. Therefore, by shifting the special dither mask D2a by 1/2 period in the vertical direction, this threshold value arrangement can be used as it is for metallic ink. FIG. 11 shows an example of the special dither mask D2b obtained by shifting the special dither mask D2a in the vertical direction by ½ period in this way. Comparing FIG. 8 with FIG. 11, the special dither mask D2a for color ink and the special dither mask D2b for metallic ink are in exclusive positions except for the hatched portion that does not substantially function as a threshold value. A threshold is arranged. Therefore, in the special glossy area A2 to which these dither masks are applied, the dots made of metallic ink and the dots made of color ink are formed at exclusive positions.

  The computer 100 individually stores these two types of special dither masks D2a and D2b in advance. That is, the computer 100 performs halftone processing by properly using three types of dither masks: a general dither mask D1, a special dither mask for color ink D2a, and a special dither mask for metallic ink D2b. Hereinafter, a printing process for performing printing using these dither masks will be described in detail.

A-4. Printing process:
FIG. 12 is a flowchart of print processing executed by the computer 100 of this embodiment. This printing process is performed by the CPU 102 as hardware executing a program prepared as the printer driver 24. When this printing process is started, the computer 100 first inputs RGB format image data including the color single area A1 and the special glossy area A2 from the application program 20 (step S100). As described above, the range of the special glossy area A2 is added to the image data as range information.

  When the image data is input, the computer 100 uses the color conversion module 42 to convert the RGB format image data input in step S100 into CMYK format image data (step S200). By this color conversion processing, the color single area A1 and the color portion of the special glossy area A2 are converted from the RGB format to the CMYK format.

  When the CMYK format image data is obtained, the computer 100 uses the halftone module 44 to perform halftone processing for each color of cyan (C), magenta (M), yellow (Y), black (K), and metallic (S). Tone processing is performed to generate data that can be transferred to the printer 200 (step S300). The data that can be transferred to the printer 200 is data (referred to as dot data) indicating the size of ink droplets formed on the print medium P by the printer 200, and it means that small dots, medium dots, or large dots are not formed. It is data.

  In the present embodiment, it is assumed that the metallic color printed in the special glossy area A2 is uniformly subjected to halftone processing at a density of 25% in the processing of step S300 described above. This concentration can be appropriately selected by the user. For example, a user interface capable of specifying the density of the metallic color printed in the special glossy area A2 is provided on the setting screen of the printer driver 24, and the user can appropriately set the user interface. Alternatively, the user may set the density according to the function of the application program 20, and the application program 20 may record the value as additional information in the image data. The printer driver 24 can determine the density of the metallic ink to be printed in the special glossy area A2 by referring to this additional information.

  When the halftone process ends, the computer 100 outputs the dot data for C, M, Y, K, and S generated by the halftone process to the printer 200 as print data using the print data output module 46. (Step S400).

  The printer 200 receives print data output from the computer 100, and prints an image by ejecting ink onto a print medium according to the received print data. In the present embodiment, the printer 200 sets the number of overlaps to “2”, the nozzle pitch to “2”, the paper feed amount to “7”, and performs bidirectional printing, so that the print head 241, the carriage motor 230, and the paper A printing mechanism such as a feed motor 235 is controlled.

Of the print processing described above, details of the halftone processing executed in step S300 will be described in detail below.
FIG. 13 is a flowchart showing a halftone processing routine. This halftone process is performed for each color of C, M, Y, K, and S. As shown in the figure, when this process is started, first, the computer 100 performs a process of reading gradation data of the pixel of interest (step S302). The initial position of the pixel of interest is the upper left corner of the image data. As described above, it is assumed that the gradation data of the metallic color is uniformly 25% during the halftone processing of the metallic color.

  When the gradation data of the pixel of interest is read (step S302), the computer 100 refers to the range information attached to the image data to determine whether the position of the pixel of interest is included in the special glossy area A2. Judgment is made (step S304). If it is determined that it is not included in the special glossy area A2 (in other words, if it is determined that it is included in the color single area A1), the computer 100 performs processing for selecting the dot recording rate table T1 (step S306). ), A process of selecting the general dither mask D1 is performed (step S408). The “dot recording rate table” is a table in which the occurrence rates of small, medium, and large dots that are generated in the pixel in accordance with the gradation data of the pixel of interest are defined. A specific example of this table will be described later.

  If it is determined in step S304 that the position of the pixel of interest is included in the special glossy area A2, the computer 100 performs processing for selecting the dot recording rate table T2 (step S310), and further, the color currently being processed. Is determined to be metallic (step S312). If the color being processed is metallic, the computer 100 selects the special dither mask D2b for metallic (step S314), and if it is another color (C, M, Y, K), the special dither for color is selected. The mask D2a is selected (step S316).

  14 and 15 show examples of the dot recording rate tables T1 and T2 selected in the above-described processing in step S306 or S310. As shown in FIG. 14, the dot recording rate table T1 defines the formation ratios of large, medium, and small dots for C, M, Y, and K. In this dot recording rate table T1, the recording rate S of small dots gradually increases until the recording rate reaches the maximum in the range of gradation data from 0 to 15, and then the range of gradation data reaches 40. The recording rate is set to gradually decrease until it reaches zero. Similarly, the recording rate M of medium dots gradually increases until the recording rate reaches a maximum in the range of gradation data from 15 to 40, and then becomes 0 in the range of the gradation data up to 80. It is set to decrease gradually. Further, the recording rate L for large dots is set so as to gradually increase until the recording rate reaches the maximum in the range of image data from 40 to 100 (exactly, when the gradation data is in the range of 80 or more, it increases gradually. Is lower than a range of less than 80).

  On the other hand, in the dot recording rate table T2, as shown in FIG. 15, the recording rate S for small dots is not set, and only the recording rates for medium dots and large dots are set. Specifically, when the gradation data is in the range of 0 to 20, the medium dot recording rate M is gradually increased to about 30% of the maximum value, and then the gradation data is in the range of up to 40, and the recording rate is Decrease until zero. Similarly, the recording rate L of large dots gradually increases until the recording rate reaches the maximum in the range of gradation data from 20 to 100 (exactly, in the range of gradation data of 40 or more, the rate of increase gradually increases). , Lower than the range of 40 or less).

  Here, when the dot recording rate table T1 and the dot recording rate table T2 are compared, all the recording rates of small dots, medium dots, and large dots are set in the dot recording rate table T1, and the dot recording rate table In T2, a recording rate of only medium dots and large dots is set. Therefore, for the same gradation data, a larger dot is formed by using the dot recording rate table T2 than the dot recording rate table T1.

  When the process of selecting a dither mask is performed in any one of steps S308, S314, and S316, the computer 100 corresponds to the gradation data read in step S302 from the dot recording rate table selected in step S306 or step S310. Processing for reading the dot recording rate is performed (step S318). Subsequently, the computer 100 reads the threshold value corresponding to the position of the pixel of interest from the dither mask selected in any of steps S308, S314, and S316 (step S320), and the dot recording rate read in step S318 and step S320. The binarization is performed by the systematic dither method using the threshold value read in (step S322). Since the systematic dither method is a well-known technique, a detailed description is omitted, but in short, the recording rate corresponding to the gradation data of the target pixel is compared with the threshold value in the dither mask corresponding to the position of the target pixel. If the recording rate is higher, a dot is formed on the pixel, and if the recording rate is lower, it is determined that no dot is formed.

  With reference to the dot recording rate table T1 or the dot recording rate table T2, the recording rates of two or more types of dots may be read. For example, in the dot recording rate table T1 of FIG. 14, two types of recording are performed such that the recording rate S for small dots is “48” and the recording rate M for medium dots is “16” for the gradation data CS1. The rate is read. In such a case, the computer 100 determines the size of the dot formed for the pixel of interest by the following procedure.

(1) First, the large dot recording rate L is compared with a threshold value. If the large dot recording rate L is larger than the threshold value, it is determined that a large dot is to be formed at the target pixel.
(2) If the recording rate L for large dots is smaller than the threshold value, the sum (L + M) of the recording rate L for large dots and the recording rate M for medium dots is compared with the threshold value. As a result, if this sum (L + M) is larger than the threshold value, it is determined that a medium dot is to be formed in the target pixel.
(3) If the sum (L + M) is smaller than the threshold, the sum (L + M + S) of the recording rate of large dots, the recording rate of medium dots, and the recording rate of small dots is compared with the threshold. As a result, if this sum (L + M + S) is larger than the threshold value, it is determined that a small dot is to be formed on the pixel of interest. On the other hand, if this sum (L + M + S) is smaller than the threshold value, it is determined that no dot is formed on the target pixel.

  Here, it is assumed that the recording rate L for large dots is “0”, the recording rate M for medium dots is “16”, the recording rate S for small dots is “48”, and the threshold is “30”. Then, in the step (1), since the recording rate of large dots is smaller than the threshold value, it is not determined that large dots are formed, and the process proceeds to step (2). In step (2), the sum (L + M) of the large dot recording rate L and the medium dot recording rate M is 16 (= 0 + 16), but the value is still smaller than the threshold (= 30). Go to 3). In step (3), the sum (L + M + S) of the large dot recording rate, the medium dot recording rate, and the small dot recording rate is 64 (= 0 + 16 + 48), which is larger than the threshold (= 30). It is determined to form a dot. In this way, if the recording rate of each dot size is added one after another and compared with the threshold value, it is possible to determine which size of dot is formed with only one threshold value.

  When the halftone process for the target pixel is completed by the process described above, the computer 100 designates the next pixel (step S324), and determines whether the process for all the pixels is completed (step S326). ). If the processing for all the pixels has not been completed, the computer 100 returns the processing to step S302 and repeats the above processing. On the other hand, if the processing has been completed for all the pixels, the halftone process is terminated.

  When the above-described halftone process is completed, the print data generated by the halftone process is transmitted to the printer 200. Upon receiving this print data, the printer 200 drives the print head 241 with the overlap number being “2”, the nozzle pitch being “2”, and the paper feed amount being “7” as described above. Bidirectional printing is performed in which ink is ejected both when the head 241 moves forward and when it moves backward. Then, as shown in FIGS. 7A and 7B, in the color single region A1, all the nozzles for color ink are used for printing. In the special glossy area A2, metallic ink is printed by the preceding nozzle group, and color ink is printed by the succeeding nozzle group. Therefore, since the metallic ink can be printed prior to the color ink in the special glossy area A2, the drying of the metallic ink can be promoted. As a result, mixing of the metallic ink and the color ink is suppressed, so that it is possible to improve the color developability of both the metallic ink and the color ink.

  In the present embodiment, the color single region A1 is printed using more nozzles than the special glossy region A2 (in other words, the special glossy region A2 is filled with dots of color ink or metallic ink. The number of scans in which the color single area A1 is filled with dots of color ink is larger than the number of scans). As a result, since the printing speed for the color single area A1 is improved, the printing speed of the entire image is markedly increased compared to printing all the printing areas by dividing the nozzles from the beginning into the preceding and following groups. .

  Furthermore, in the present embodiment, the arrangement of the used nozzles can be controlled simply by switching the dither mask used in the halftone process according to the printing area. This eliminates the need for a circuit that gives special control signals to each nozzle to instruct whether or not to use it, and allows the arrangement of the nozzles to be varied without significantly changing the configuration of a conventional printer. become.

  Further, in this embodiment, when printing metallic ink in the special glossy area A2, larger dots are formed by using the dot recording rate table T2. Considering the use of metallic ink, the gradation expression or image reproducibility by the metallic ink in the special glossy area A2 is not so important, so it is not necessary to consider much countermeasures against image quality degradation such as dot graininess and banding. It is. As a result, the amount of metallic ink ejected per unit area increases, so that the range in which metallic dots are formed can be increased even with a small number of scans.

  In the present embodiment, halftone processing is performed in the color portion of the special glossy area A2 using the dot recording rate table T1 similar to that in the color single area A1. In contrast, the color portion of the special glossy area A2 is subjected to halftone processing using a dot recording rate table (for example, dot recording rate table T2) in which the size of the used dots is larger than the dot recording rate table T1. It may be done. This is because in the special glossy area A2, since the background is a metallic color, the presence of color ink is not conspicuous in the first place, and it is not necessary to take much measures against image quality deterioration such as graininess and banding. From another viewpoint, for example, the metallic ink in the special glossy area A2 can be printed with small dots, and the color ink can be printed with large dots. By doing so, it becomes possible to make the color ink in the special glossy area A2 more conspicuous than the metallic ink. Of course, the halftone process can also be performed on the special glossy area A2 by using a table similar to the dot recording rate table used in the color single area A1.

B. First Example (Reduction of Periodic Change of Dot Pattern):
Based on the above-described embodiment, in the first example described below, a process for mitigating the periodic shape change of the dot pattern shown in FIG. 7C is performed.
FIG. 16 shows a schematic configuration of the printing system 10 as the first embodiment, and FIG. 17 shows a flowchart of a printing process executed in this embodiment. As shown in FIG. 16, in this embodiment, a pattern mitigation module 47 is added to the printer driver 24 with respect to the printing system 10 of the embodiment shown in FIG. The pattern relaxation module 47 is a module that performs a process of relaxing the periodic shape change as shown in FIG. 7C for the dots formed in the special glossy area A2. As shown in FIG. 17, in this embodiment, a pattern relaxation process (by a function of the pattern relaxation module 47) between the halftone process (step S 300) and the print data output process (step S 400). Step S350) is added. In step S400, the print data that has been subjected to the pattern relaxation processing is output. Hereinafter, details of the pattern relaxation processing performed on the special glossy area A2 will be described.

  FIG. 18 is a diagram illustrating the concept of pattern relaxation processing. In this example, as in the above embodiment, the filling order is set so that the 2 × 2 local region is filled in the order of upper left, lower left, upper right, and lower right. Further, the number of metallic nozzles, the number of color nozzles, the number of overlaps, the nozzle pitch, the paper feed amount, and the printing conditions for bidirectional printing are the same as in the above embodiment.

  FIG. 18A shows how the nozzles move in the sub-scanning direction, and FIG. 18B shows the result of printing under the above-described printing conditions. The pattern shown in FIG. 18B is the same as the pattern shown in FIG. That is, this pattern is a pattern immediately after the halftone process is performed in step S300 of the printing process shown in FIG.

  In the pattern relaxation processing in step S350 of FIG. 17, the metallic dots to be formed by the preceding nozzle group are shifted to the left by one dot in the main scan when the filling order is “3” and “4” in the special glossy area A2. Further, the color dots to be formed by the succeeding nozzle group are shifted to the right by one dot at the time of main scanning in which the filling order is “1” and “2”. When such processing is performed, as shown in FIG. 18C, the metallic dots and the color dots are arranged in the special glossy area A2 without overlapping each other vertically.

  In the above-described embodiment, the special glossy area A2 is printed by reducing the number of nozzles to be used while applying the printing timing (filling order) in the color single area A1 as it is. Therefore, a predetermined dot pattern (see FIG. 7C) is generated on the print medium due to the reduced number of nozzles. However, in this embodiment, when the special glossy area A2 is printed, the dot formation position is shifted by a predetermined amount in the main scanning direction with respect to the dot formation position in the color single area A1. As a result, the dot pattern form change that has occurred in band units is eliminated, and the image quality of the image formed in the special glossy area A2 can be improved.

  In the above embodiment, the special dither masks D2a and D2b are generated assuming the dot pattern shown in FIG. 7C. In this embodiment, the dot pattern shown in FIG. 18C is used. As a result, special dither masks D2a and D2b are generated. Since the dot pattern shown in FIG. 18C has no form change in band units, for example, the vertical threshold of the general dither mask D1 shown in FIG. 3 is subtracted exclusively one by one. These dither masks can be applied as a special dither mask D2a and a special dither mask D2b, respectively. This makes it possible to use a dither mask having general blue noise characteristics as a special dither mask.

  In the present embodiment, as described above, the metallic dots to be formed by the preceding nozzle group are shifted to the left by one dot during the main scanning with the filling order of “3” and “4”, and the filling order is “1”. In addition, by shifting the color dots to be formed by the succeeding nozzle group by one dot to the right during the main scanning of “2”, the change in the dot pattern form was alleviated. However, the method of relieving the change in the form of the dot pattern is not limited to such a method. Hereinafter, some modifications of the first embodiment will be described.

(Modification 1 of the first embodiment):
In the first embodiment described above, both metallic dots and color dots are shifted, but only one of them may be shifted. For example, if processing is performed to shift the metallic dots to be formed by the preceding nozzle group by one dot to the left during the main scanning with the filling order “3” and “4”, the dot pattern of only the metallic dots is changed. It becomes possible to eliminate the shape change. On the other hand, if only the process of shifting the color dots to be formed by the succeeding nozzle group by one dot to the right during the main scanning with the filling order “1” and “2” is performed only for the color dots. It becomes possible to eliminate the change in the form of the dot pattern. In addition, when the process which shifts only any one dot like these is performed, the part which a metallic dot and a color dot overlap partially will arise. However, in this embodiment as well, since the preceding nozzle group and the succeeding nozzle group are arranged with a predetermined amount shifted in the sub-scanning direction on the print head 241, metallic dots are formed prior to the formation of color dots. It will be. Therefore, since the drying of the metallic dots can be promoted, the influence on the image quality is extremely small.

(Modification 2 of the first embodiment):
In the first embodiment described above, the metallic dots to be formed by the preceding nozzle group are shifted to the left by one dot at the time of main scanning when the filling order is “3” and “4”, and the filling orders are “1” and “ By shifting the color dots to be formed by the succeeding nozzle group by one dot to the right during the main scanning of “2”, the change in the form of the dot pattern was alleviated. However, more simply, it is possible to perform a process of shifting all the dots to be formed at the time of main scanning with the filling order “3” and “4” to the left by one dot.

  FIG. 19 shows an example in which the dot pattern shape change is alleviated by such processing. FIG. 19A shows how the nozzles move in the sub-scanning direction, and FIG. 19B shows a dot pattern before the pattern relaxation processing. When all the dots to be formed in the main scanning with the filling order “3” and “4” are shifted to the left by one dot with respect to this dot pattern, the metallic dots are as shown in FIG. In this way, dots are arranged in every other column in the vertical direction. On the other hand, with respect to the color dots, as shown in FIG. 19D, the dots are arranged in a single vertical line at a position matching the metallic dots. As described above, according to this modification, it is possible to alleviate the change in the form of the dot pattern by an extremely simple process.

(Modification 3 of the first embodiment):
In the first embodiment described above, the dot pattern is corrected so that the metallic dots and the color dots are arranged in a vertical row. On the other hand, in this modification, correction is performed so that the dot patterns are arranged in a zigzag pattern.

  FIG. 20 is a diagram illustrating an example in which dot patterns are arranged in a zigzag pattern. FIG. 20A shows a state where the nozzle moves in the sub-scanning direction, and FIG. 20B shows a dot pattern before the pattern relaxation processing. In the present modification, a process is performed in which all the dots to be formed during the main scanning with the filling order of “1” and “4” are shifted to the right by one dot. If such pattern relaxation processing is performed, as shown in FIG. 20C, the dots are arranged in a zigzag pattern for the metallic dots, and the dots are arranged in a zigzag pattern at the same positions as the metallic dots as well. Will be. In this way, if dots are arranged in a staggered manner, it is possible to suppress the occurrence of unevenness in the printed image due to dot gain.

(Modification 4 of the first embodiment):
In the first embodiment described above, the dot pattern form change is alleviated by the action of the pattern relaxation module 47 of the printer driver 24. On the other hand, the printer 200 may analyze the print data input from the computer 100 and shift the position of the corresponding dot. It is also possible to shift the position of the corresponding dot by delaying an electric signal for driving the print head 241 by a buffer circuit or the like.

  In the first embodiment and the modification described above, the metallic dots and the color dots are shifted rightward or leftward by one dot, but the shift amount is not limited to one dot. If it is possible to alleviate the periodic shape change of the dot pattern, the dot pattern may be shifted by 2 dots or more.

C. Second embodiment (another example of filling order):
In the embodiment described above, as shown in FIG. 7, the filling order is set so that the 2 × 2 local region is filled in the order of upper left, lower left, upper right, and lower right. On the other hand, in the second embodiment, the filling order is set so that the 2 × 2 local region is filled in the order of upper left, lower right, upper right, and lower left. The number of metallic nozzles, the number of color nozzles, the number of overlaps, the nozzle pitch, the paper feed amount, and the printing conditions for bidirectional printing are the same as in the above embodiment.

  FIG. 21 shows a printing result according to this example. If the filling order is set as described above, as can be seen by comparing FIG. 7B and FIG. 21B, in this embodiment, the period in which dots are formed in even rows is the above embodiment. As compared with the case, it is shifted by one dot in the horizontal direction. Therefore, finally, as shown in FIG. 21C, a pattern different from the pattern shown in FIG. 7C is formed on the print medium. Also in this embodiment, by forming the special dither mask D2 based on the pattern shown in FIG. 21C, each nozzle of the print head 241 is changed to the preceding nozzle group and the succeeding nozzle as in the above embodiment. Printing can be performed separately for each group.

D. Third embodiment (number of non-uniform nozzles):
In the embodiment and the second example described above, printing was performed by equally dividing the preceding nozzle group and the succeeding nozzle group by 7 each. On the other hand, in the third embodiment, printing is performed by dividing the number of the preceding nozzle group and the succeeding nozzle group in an uneven manner. Specifically, four nozzles are included in the preceding nozzle group, and ten nozzles are included in the subsequent nozzle group. The printing conditions for the number of overlaps, nozzle pitch, paper feed amount, and bidirectional printing are the same as in the above embodiment.

  FIG. 22 shows a printing result according to this embodiment. FIG. 22A shows a state in which the nozzles in which the preceding nozzle group and the succeeding nozzle group are divided unevenly move in the sub-scanning direction. FIG. 22B and FIG. The dot generation patterns with different filling orders are shown. Also in this embodiment, by forming the special dither mask D2 based on the patterns shown in FIG. 22B and FIG. 22C, the number of leading nozzle groups and the number of succeeding nozzle groups is not equal. This makes it possible to perform printing. As is apparent from FIG. 22, in this embodiment, the number of main scans of the print head 241 for filling a predetermined local area in the special glossy area A1 with metallic ink is because the same local area is filled with color ink. This is less than the number of main scans of the print head 241.

  Incidentally, in this embodiment, the number of preceding nozzle groups that eject metallic ink is smaller than the number of succeeding nozzle groups, but it is of course possible to increase the number of preceding nozzle groups.

E. Fourth embodiment (local area size is 2 × 4):
In each of the above-described embodiments, the filling order is set in a local area having a size of 2 × 2. On the other hand, in the fourth embodiment, the filling order is set in the local area of 2 × 4 size.

  FIG. 23 shows a part of the printing result according to this embodiment. FIG. 23 (a) and FIG. 23 (b) show printing results with different filling orders. In this embodiment, bi-directional printing is performed with seven nozzles included in the preceding nozzle group and the succeeding nozzle group, two overlap numbers, four nozzle pitches, and seven paper feed amounts. As shown in FIG. 23, even if the filling order is set to a size of 2 × 4, a predetermined pattern is generated on the print medium. Also in this embodiment, the special dither mask D2 is formed on the basis of the patterns shown in FIGS. 23A and 23B, so that each nozzle of the print head 241 is replaced with the preceding nozzle group and the succeeding nozzle group. It is possible to print separately.

F. Fifth embodiment (local area size is 4 × 2):
In the fourth embodiment, the filling order is set in a local area of 2 × 4 size. On the other hand, in the fifth embodiment, the filling order is set for the local region having a size of 4 × 2.

  FIG. 24 shows a printing result according to this embodiment. FIG. 24A, FIG. 24B, and FIG. 24C show printing results in different filling orders. In this embodiment, 28 nozzles are included in the nozzle row, and 14 nozzles are included in both the preceding nozzle group and the succeeding nozzle group. In addition, the number of overlaps is 4, the nozzle pitch is 2, the paper feed amount is 7, and bidirectional printing is performed. As shown in FIG. 24, even if the filling order is set to a 4 × 2 size, a predetermined pattern is generated on each print medium. Also in this embodiment, the special dither mask D2 is formed based on the patterns shown in FIG. 24A, FIG. 24B, and FIG. 24C, so that each nozzle of the print head 241 is replaced with the preceding nozzle. It is possible to perform printing separately in groups and subsequent nozzle groups.

In order to increase the dispersibility of dots formed on the print medium, the pattern formed on the print medium is
・ As little as possible changes in the form of bands,
・ Metallic dots and color dots are evenly distributed.
A pattern in which dots are not formed as continuously as possible at adjacent pixel positions is preferable. From this point of view, looking at the three types of patterns shown in FIG. 24, FIG. 24B shows a large pattern change, and FIG. 24C shows vertical stripes caused by two consecutive dots. Therefore, the pattern shown in FIG. 24A can be considered to be the most advantageous pattern in terms of image quality. Accordingly, the computer 100 performs halftone processing using the special dither mask generated based on the pattern shown in FIG. 24A, and causes the printer 200 to form dots in the filling order in which the pattern is generated. Thus, it becomes possible to easily relieve the periodic shape change of the dot pattern.

G. Example 6 (unequally spaced feed):
In each of the above-described embodiments, an example in which the nozzles move in the sub-scanning direction with an equally spaced paper feed amount is shown. In contrast, the sixth embodiment shows an example in which the paper feed amount is changed for each main scan.

  FIG. 25 shows a printing result according to this embodiment. In the present embodiment, 14 nozzles are included in the nozzle row, and the number of nozzles included in the preceding nozzle group and the succeeding nozzle group is seven. In addition, the number of overlaps is 2, the nozzle pitch is 2, and bidirectional printing is performed. FIG. 25A shows how the nozzles move at unequal intervals in the sub-scanning direction. As shown in the drawing, in this embodiment, the paper feed amount changes in order of “7”, “6”, “7”, “8” for each main scan. FIG. 25B and FIG. 25C show a printing result by such nozzle control. In these drawings, printing results in different filling orders are shown. As shown in FIG. 25, even if the paper feed amount changes at unequal intervals, a predetermined pattern is generated on each print medium. Also in this embodiment, the special dither mask D2 is formed based on the patterns shown in FIG. 25B and FIG. 25C, so that each nozzle of the print head 241 is replaced with the preceding nozzle group and the succeeding nozzle group. It is possible to print separately.

  In the second to sixth embodiments described above, the filling order of the main scanning lines that cause a periodic shape change in the dot pattern is grasped in advance, and the dots formed in this filling order are determined as dot patterns. If a process of shifting a predetermined amount so as to cancel the morphological change is performed, it is possible to alleviate the periodic morphological change of the dot pattern in these embodiments as in the first embodiment. It is also possible to shift the dots in the sub-scanning direction.

H. Variation:
As mentioned above, although the various Example of this invention was described, it cannot be overemphasized that this invention is not limited to these Examples, and can take a various structure in the range which does not deviate from the meaning. For example, the following modifications are possible.

(H1) Modification 1:
In each of the above-described embodiments, a special dither mask (special dither mask D2) is used during halftone processing by a systematic dither method, so that the nozzle row of the print head 241 is separated into a preceding nozzle group and a subsequent nozzle group. And printing. On the other hand, the nozzle row can be separated into the preceding nozzle group and the succeeding nozzle group also by the halftone process using the error diffusion method.

Specifically, assuming that the gradation data of each pixel takes a value from 0 to 255, in the normal error diffusion method,
(1) The error distributed from the processed pixel is added to the gradation data of the target pixel.
(2) The gradation data after the error addition is compared with a predetermined threshold value (= 127) and binarized.
(3) Error calculation between the binarized value (0 or 255) and the original gradation data.
(4) Distribute errors to surrounding unprocessed pixels at a predetermined ratio.
(5) Move the processing target to the next pixel.
Halftone processing is performed by the procedure. In the present modification, halftone processing is performed for the color single region A1 in such a procedure.

  On the other hand, in the special glossy area A2, prior to the procedure (2), it is determined whether the number of the nozzle that forms dots for the pixel of interest is 7 or less (that is, the subsequent nozzle group). In the case of No. 7 or less, processing for changing the threshold value to an extremely high value (for example, 1000) is added. Then, the probability of forming dots with the 1st to 7th nozzles becomes extremely small. As a result, the metallic ink can be preferentially printed by the preceding nozzle groups Nos. 8-14.

(H2) Modification 2:
In each embodiment described above, printing is performed in the printing system 10 including the computer 100 and the printer 200. On the other hand, the printer 200 itself may perform printing by inputting image data from a digital camera or various memory cards. That is, the CPU in the control circuit 260 of the printer 200 may perform printing by executing processing equivalent to the above-described printing processing and halftone processing.

(H3) Modification 3:
In each of the above-described embodiments, it is assumed that white printing paper is used as the printing medium. Therefore, the color ink is printed after the metallic ink is printed first. On the other hand, assuming that a transparent film is used as a printing medium and the film is viewed from the opposite side of the printing surface, it is preferable to print the color ink prior to printing the metallic ink. In this case, the special dither mask D2a for color ink shown in FIG. 8 may be used for metallic, and the special dither mask D2b for metallic ink shown in FIG. 11 may be used for color. In this case, the preceding nozzle group is configured by nozzles that eject color ink, and the subsequent nozzle group is configured by nozzles that eject metallic ink.

(H4) Modification 4:
In each embodiment described above, printing is performed using metallic ink and color ink. On the other hand, instead of metallic ink, white ink or transparent ink may be used. When the transparent ink is used for the purpose of protecting the printing surface or polishing, the transparent ink needs to be printed after the color ink is printed first. In this case, the threshold is arranged in the special dither mask D2 so that the preceding nozzle group is configured by nozzles that discharge color ink and the subsequent nozzle group is configured by nozzles that discharge transparent ink. Specifically, the special dither mask D2a for color ink shown in FIG. 8 may be diverted for transparent ink, and the special dither mask D2b for metallic ink shown in FIG. 11 may be diverted for color ink.

(H5) Modification 5:
In the embodiment described above, as shown in FIG. 6B, the positions of the preceding nozzle group and the succeeding nozzle group are completely separated from each other in the sub-scanning direction. On the other hand, as shown in FIG. 26, the positions of the preceding nozzle group and the succeeding nozzle group in the sub-scanning direction may partially overlap. Moreover, as shown in FIG. 27, an unused nozzle may be interposed between the preceding nozzle group and the succeeding nozzle group. In the above-described embodiment, the position in the sub-scanning direction of each nozzle that ejects metallic ink and the position in the sub-scanning direction of each nozzle that ejects color ink all coincide. On the other hand, as shown in FIG. 28, the positions in the sub-scanning direction may be shifted between the nozzles that discharge the metallic ink and the nozzles that discharge the color ink. Even when the nozzles are arranged as shown in FIGS. 26 to 23, the special dither mask is generated according to the principle shown in the above-described embodiment, so that the nozzle used when printing the special glossy area A2 can be preceded. Printing can be performed separately for the nozzle group and the succeeding nozzle group.

1 is a diagram illustrating a schematic configuration of a printing system 10 as an embodiment of the present invention. It is a figure which shows the image data IMG containing color single area | region A1 and special glossy area | region A2. It is a figure which shows the general dither mask D1. 1 is a diagram illustrating a schematic configuration of a computer 100. FIG. 2 is a diagram illustrating a configuration of a printer 200. FIG. It is a figure which shows a mode that a nozzle position is changed according to a printing area | region. FIG. 3 is a diagram illustrating how dots are formed by a printer. It is a figure which shows the special dither mask D2 for color inks. It is a figure which shows the halftone result when the dot generation rate is 10% using the special dither mask D2. It is a figure which shows the halftone result when the dot generation rate is 25% using the special dither mask D2. It is a figure which shows special dither mask D2b which shifted special dither mask D2 by 1/2 period to the vertical direction. 3 is a flowchart of print processing executed by a computer 100. It is a flowchart which shows a halftone process routine. It is a figure which shows the dot recording rate table T1. It is a figure which shows the dot recording rate table T2. 1 is a diagram illustrating a schematic configuration of a printing system 10 as a first embodiment. It is a flowchart of the printing process performed in 1st Example. It is a figure showing the concept of pattern relaxation processing. It is a figure which shows the modification of a pattern relaxation process. It is a figure which shows the modification of a pattern relaxation process. It is a figure which shows the printing result by 2nd Example. It is a figure which shows the printing result by 3rd Example. It is a figure which shows the printing result by 4th Example. It is a figure which shows the printing result by 5th Example. It is a figure which shows the printing result by 6th Example. It is a figure which shows the example in which the preceding nozzle group and the succeeding nozzle group partially overlapped. It is a figure which shows the example which the unused nozzle intervened between the preceding nozzle group and the succeeding nozzle group. It is a figure which shows the example which the position in the sub scanning direction of each nozzle which discharges metallic ink and each nozzle which discharges color ink has shifted | deviated.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printing system 20 ... Application program 22 ... Video driver 24 ... Printer driver 40 ... Image acquisition module 42 ... Color conversion module 44 ... Halftone module 45 ... Area discrimination module 46 ... Print data output module 100 ... Computer 102 ... CPU
104 ... ROM
106 ... RAM
DESCRIPTION OF SYMBOLS 108 ... Peripheral device interface 109 ... Disk controller 110 ... Network interface card 112 ... Video interface 114 ... Display 116 ... Bus 118 ... Hard disk 120 ... Digital camera 122 ... Color scanner 200 ... Printer 230 ... Carriage motor 231 ... Drive belt 232 ... Pulley 233 ... Sliding shaft 234 ... Position detection sensor 235 ... Paper feed motor 236 ... Platen 240 ... Carriage 241 ... Print head 242 ... Metal ink cartridge 243 ... Color ink cartridge 256 ... Operation panel 260 ... Control circuit 300 ... Communication line 310 ... Storage device

Claims (11)

A printing apparatus comprising a drive mechanism for driving a print head relative to a print medium in a main scanning direction that is the width direction of the printing medium and a sub-scanning direction that intersects the main scanning direction,
A print head in which a plurality of nozzles are arranged along the sub-scanning direction;
An acquisition unit that acquires image data including a color single area to be printed with color ink, a special gloss ink and a special gloss area to be printed with the color ink;
For the color single region, print data for forming dots is generated by a first number of nozzles among the plurality of nozzles, and for the special glossy region, the print number is larger than the first number. When the print head is driven in the sub-scanning direction by a predetermined bandwidth every time the print head is driven in the main scanning direction in order to form dots with a small second number of nozzles, the second number A print data generation unit that generates print data by arranging dots on a dot pattern that represents an area in which dots can be formed by the nozzles;
A relaxation part that includes the dot pattern and relaxes a periodic shape change that occurs according to the bandwidth,
A printing apparatus comprising: a dot forming unit that controls the print head and the drive mechanism to form dots on the print medium according to the relaxed print data. The printing apparatus according to claim 1,
The mitigation unit mitigates a periodic shape change of the dot pattern by shifting the arrangement of dots belonging to a predetermined main scanning line of the dot pattern by a predetermined amount in the main scanning direction for the special glossy area. Printing device. The printing apparatus according to claim 2,
The mitigation unit is a printing apparatus that individually shifts the dots formed by the color ink and the dots formed by the special gloss ink in the special gloss region. The printing apparatus according to claim 1,
The relaxation unit relaxes the periodic shape change of the dot pattern by causing the dot forming portion to form dots in a prescribed order so as to reduce the periodic shape change of the dot pattern. . The printing apparatus according to claim 1,
The print data generation unit generates the print data by performing a halftone process on the image data using a predetermined dither mask,
The relaxation unit supplies a dither mask in which thresholds are arranged along the dot pattern so as to maintain the dispersibility of dots below a predetermined threshold, to the print data generation unit, whereby the cycle of the dot pattern Printing device that alleviates typical form changes. The printing apparatus according to claim 5,
A printing apparatus, wherein a size of the dither mask is determined according to a period of the dot pattern. The printing apparatus according to any one of claims 1 to 6,
The special glossy ink is a printing apparatus in which optical characteristics after printing on the surface of the printing medium have a reflection angle dependency. The printing apparatus according to any one of claims 1 to 6,
The special glossy ink is a printing apparatus containing a pigment that develops a metallic feeling. A printing method for performing printing while driving a print head relative to a print medium in a main scanning direction that is the width direction of the printing medium and a sub-scanning direction that intersects the main scanning direction,
In the print head, a plurality of nozzles are arranged along the sub-scanning direction,
An acquisition step of acquiring image data having a color single area to be printed with color ink, a special gloss ink and a special gloss area to be printed with the color ink, and
For the color single region, print data for forming dots is generated by a first number of nozzles among the plurality of nozzles, and for the special glossy region, the print number is larger than the first number. When the print head is driven in the sub-scanning direction by a predetermined bandwidth every time the print head is driven in the main scanning direction in order to form dots with a small second number of nozzles, the second number A print data generation step of generating print data by arranging dots on a dot pattern that represents an area where dots can be formed by the nozzles;
A relaxation process that includes the dot pattern and relaxes a periodic shape change that occurs according to the bandwidth,
A dot forming step of forming dots on the print medium according to the relaxed print data while driving the print head in the main scanning direction and the sub-scanning direction. Computer for controlling a printing apparatus comprising a drive mechanism for driving a print head relative to a print medium in a main scanning direction that is the width direction of the printing medium and a sub-scanning direction that intersects the main scanning direction A program,
In the print head, a plurality of nozzles are arranged along the sub-scanning direction,
An acquisition function for acquiring image data having a color single area to be printed with color ink, a special gloss ink and a special gloss area to be printed with the color ink, and
For the color single region, print data for forming dots is generated by a first number of nozzles among the plurality of nozzles, and for the special glossy region, the print number is larger than the first number. When the print head is driven in the sub-scanning direction by a predetermined bandwidth every time the print head is driven in the main scanning direction in order to form dots with a small second number of nozzles, the second number A print data generation function for generating print data by arranging dots on a dot pattern representing an area where dots can be formed by the nozzles of
A relaxation function that includes the dot pattern and relaxes a periodic shape change that occurs according to the bandwidth;
A computer program for controlling a print head and the drive mechanism to cause a computer to realize a dot forming function for forming dots on the print medium according to the relaxed print data.   The computer-readable recording medium which recorded the computer program of Claim 10.

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