JP5564771B2 - Printing apparatus, printing method, computer program, recording medium, printing medium, and printer - Google Patents

Description

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

  Conventionally, in a serial type printing apparatus, since paper is fed for each predetermined band, a phenomenon called banding in which a joint between bands is recognized as a horizontal stripe may occur. In order to suppress the occurrence of such banding, various techniques such as interlace scanning and overlap scanning have been developed (see Patent Document 1 below).

JP 11-34398 A

  When interlaced scanning or overlapping scanning is performed, a new dot is formed in the gap between the already formed dots each time the print head is scanned in the main and sub-scans. Therefore, there is an effect that the horizontal stripes are less noticeable. However, these techniques are mainly used for the purpose of improving the image quality, and have not been assumed to be used for other purposes.

  Therefore, the problem to be solved by the present invention is to provide a technique for giving a printing effect different from the conventional one in a serial type printing apparatus capable of interlace scanning and overlap scanning.

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.
A first aspect of the present invention is a printing apparatus including a printing mechanism that moves a print head in a main scanning direction and moves a print medium in a sub scanning direction that intersects the main scanning direction.
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The printing head and the printing mechanism are controlled, the printing head is moved in the main scanning direction, the printing medium is moved in the sub scanning direction by a predetermined conveyance amount, and dots are formed by the first ink. A printing control unit that forms an image along the dot pattern whose form periodically changes according to the conveyance amount on the printing medium;
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
The printing control unit forms the image by overlapping at least a part of the dots formed by the first ink and the second ink in the vicinity of the boundary of the shape change of the dot pattern. a printing apparatus for.
According to a second aspect of the present invention, there is provided a printer including a printing mechanism that moves a print head in a main scanning direction and moves a print medium in a sub scanning direction that intersects the main scanning direction.
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The printing head and the printing mechanism are controlled, the printing head is moved in the main scanning direction, the printing medium is moved in the sub scanning direction by a predetermined conveyance amount, and dots are formed by the first ink. A control circuit for forming an image along the dot pattern whose form periodically changes according to the transport amount on the print medium;
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
The control circuit forms the image by overlapping at least a part of dots formed by the first ink and dots formed by the second ink in the vicinity of the boundary of the shape change of the dot pattern. It is a printer.
According to the applicant of the present application, when serial printing is performed by the first nozzle row from which the first ink is ejected and the second nozzle row from which the second ink is ejected, the gradation value is constant. It has been found that even with image data, an image along a predetermined dot pattern having periodicity is generated on a print medium. Therefore, according to the printing apparatus and the printer, it is possible to easily form a predetermined pattern on the print medium without performing special control. Further, according to the printing apparatus and the printer, it is possible to make the change in the form of the dot pattern look smooth.

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
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. The first nozzle row and the second nozzle row are arranged at a predetermined interval in the sub-scanning direction,
By controlling the print head and the drive mechanism and driving the print head in the sub-scanning direction by a predetermined conveyance amount every time the print head is driven in the main scanning direction, A printing apparatus comprising: a printing control unit that forms an image along a dot pattern whose form periodically changes for each band corresponding to the amount on the printing medium with at least one of the first ink and the second ink.

  According to the applicant of the present application, the first nozzle row from which the first ink is ejected and the second nozzle row from which the second ink is ejected are shifted by a predetermined interval in the sub-scanning direction, and printing is performed in a serial manner. It was found that even with image data having a constant gradation value, an image along a predetermined dot pattern having periodicity is generated on the print medium. Therefore, according to the printing apparatus, it is possible to easily form a predetermined pattern (dot pattern) on the print medium without performing special control.

Application Example 2 In the printing apparatus according to Application Example 1, image data including a first color corresponding to the first ink and a second color corresponding to the second ink is acquired. The print control unit performs a halftone process on the acquired image data using a dither mask in which a threshold value is arranged at a position corresponding to each dot on the dot pattern. A printing apparatus for forming the image. According to such a printing apparatus, a predetermined dot pattern can be easily formed by using a dither mask.

Application Example 3 In the printing apparatus according to Application Example 2, in the print control unit, the dither mask has different threshold arrangements for the first color and the second color, respectively. Printing device using a dither mask. With such a printing apparatus, it is possible to apply a dither mask suitable for each of the first color and the second color in the image data.

Application Example 4 In the printing apparatus according to Application Example 3, in the first color dither mask and the second color dither mask, threshold values are arranged at exclusive positions, respectively. Printing device. With such a printing apparatus, it is possible to form a dot pattern in which dots of the first ink and dots of the second ink are formed at exclusive positions.

[Application Example 5] The printing apparatus according to Application Example 4, wherein one of the first color dither mask and the second color dither mask is the dot pattern of the dot pattern. A printing apparatus that is generated by shifting the arrangement of the threshold value of the other dither mask by a predetermined amount corresponding to the period. With such a printing apparatus, it is possible to easily generate the other dither mask only by preparing one dither mask.

[Application Example 6] The printing apparatus according to any one of Application Examples 2 to 5, wherein a size of the dither mask is determined according to a period of the dot pattern. With such a printing apparatus, since the size of the dither mask and the size of the dot pattern can be synchronized, it is possible to easily form the dot pattern using the dither mask. If the size of the dither mask and the size of the dot pattern are synchronized, the periodic arrangement that occurs on the print medium can be achieved simply by adjusting the arrangement of the thresholds in the dither mask without performing special adjustment of the sub-scanning amount. It is also possible to make some of the morphological changes look smooth.

Application Example 7 In the printing apparatus according to any one of Application Example 1 to Application Example 6, the print control unit is formed by the first ink in the vicinity of the boundary of the form change of the dot pattern. A printing apparatus that forms at least a part of dots formed by dots and the second ink to form the image. With such a printing apparatus, it becomes possible to make the change in the form of the dot pattern look smooth.

[Application Example 8] The printing apparatus according to any one of Application Example 1 to Application Example 7, wherein the first ink or the second ink is an optical characteristic after being printed on the surface of the print medium. Is a special glossy ink having a reflection angle dependency. 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 9] The printing apparatus according to any one of Application Examples 1 to 7, wherein the first ink or the second ink is an ink containing a pigment that develops a metallic feeling. apparatus. With such a printing apparatus, it is possible to print an image having a metallic gloss.

  In addition to the configuration as the above-described printing apparatus, the present invention can also be configured as a print medium printed by the above-described printing apparatus, a printing method, and a computer program. 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. First 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. Second embodiment (another example of filling order):
C. Third embodiment (number of non-uniform nozzles):
D. Fourth embodiment (local area size is 2 × 4):
E. Fifth embodiment (local area size is 4 × 2):
F. Example 6 (unequally spaced feed):
G. Variations:

A. First Example 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 of this 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 a cyan ink (C), a magenta ink (M), a yellow ink (Y), and a black ink (K), which are dye-based 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) containing a pigment exhibiting a metallic feeling as a special glossy 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 the background. 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 “printing control 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 this embodiment, a known systematic dither method is used as the halftone process. 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 this 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. That is, 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 for reproducing natural images.

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 this 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 actually used nozzles in the color single region A1 and the special glossy region A2 among the 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”). In this way, in this embodiment, when the special glossy area A2 is printed, the preceding nozzle group and the succeeding nozzle group are arranged at 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 single color 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”, and the paper feed amount is “7”. 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 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 a 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 1 times “28”). 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 for 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.

  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. Note that the special dither mask D2b (or D2a) is dynamically generated by shifting the special dither mask D2a (or D2b) by ½ period when the printer driver 24 is activated by the computer 100. Also good.

A-4. Printing process:
FIG. 12 is a flowchart of print processing executed by the computer 100 according to 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 that the printer 200 forms on the print medium P, and it indicates whether or not to form small dots, medium dots, or large dots. 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 this 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” with respect to 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 to eject ink both during forward movement and during backward movement. 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.

  Further, according to the present embodiment, the nozzle row is divided into the preceding nozzle group and the succeeding nozzle group, so that an image along the dot pattern having periodicity can be printed on the printing medium according to the density of the metallic ink or the color ink. It is formed. For example, if both densities are 100%, a dot pattern as shown in FIG. 7C is formed on the print medium. This dot pattern (pattern) changes variously only by changing the arrangement or filling order of the preceding nozzle group and the succeeding nozzle group, as shown in other embodiments and modifications described later. Therefore, various patterns can be formed on the print medium without performing special control. In the present embodiment, the dot pattern is formed of the metallic ink and the color ink, but may be formed of only one of the inks. Further, for example, it may be formed by only one arbitrary color ink such as one red color.

  In the present embodiment, the color single area A1 is printed using more nozzles than the special gloss area A2 (in other words, the special gloss area 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 significantly higher than when all the printing areas are printed by dividing the nozzle from the beginning into the preceding and following groups. Become.

  Furthermore, in this embodiment, the arrangement of nozzles that are actually used can be controlled simply by switching the dither mask used during halftone processing 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.

  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 this embodiment, the halftone process is performed on the color portion of the special glossy area A2 using the dot recording rate table T1 similar to that of 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. Second embodiment (another example of filling order):
In the first 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, number of color nozzles, number of overlaps, nozzle pitch, paper feed amount, and bidirectional printing conditions are the same as in the first embodiment.

  FIG. 16 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. 16B, in this embodiment, the period in which dots are formed in even rows is the first implementation. Compared to the example, it is shifted by one dot in the horizontal direction. Therefore, finally, as shown in FIG. 16C, 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. 16C, each nozzle of the print head 241 is moved to the preceding nozzle group and the succeeding nozzle as in the first embodiment. It is possible to perform printing separately from nozzle groups.

C. Third embodiment (number of non-uniform nozzles):
In the first and second embodiments 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 first embodiment.

  FIG. 17 shows a printing result according to this embodiment. FIG. 17A shows a state in which the nozzles in which the preceding nozzle group and the succeeding nozzle group are divided non-uniformly move in the sub-scanning direction. FIG. 17B 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 FIGS. 17B and 17C, the preceding nozzle group and the succeeding nozzle group are made non-uniform in number. This makes it possible to perform printing. As can be seen from FIG. 17, 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.

D. 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. 18 shows a part of the printing result according to this embodiment. FIG. 18A and FIG. 18B 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. 18, 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 based on the patterns shown in FIG. 18A and FIG. 18B, 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.

E. 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. 19 shows a printing result according to this embodiment. FIG. 19A, FIG. 19B, and FIG. 19C 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. 19, even if the filling order is set to a size of 4 × 2, 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 FIGS. 19A, 19B, and 19C, 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, when the three types of patterns shown in FIG. 19 are viewed, FIG. 19B shows a large pattern change, and FIG. 19C shows vertical stripes caused by two consecutive dots. Therefore, it can be considered that the pattern shown in FIG. 19A is the most advantageous pattern in terms of image quality.

F. 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. 20 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. 20A 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. 20B and FIG. 20C show the printing results by such nozzle control. In these drawings, printing results in different filling orders are shown. As shown in FIG. 20, 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. 20B and FIG. 20C, 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.

G. Variations:
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.

(G1) 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 gradation data after error addition.
(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.

(G2) 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.

(G3) 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.

(G4) 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.

(G5) 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. 21, the positions of the preceding nozzle group and the succeeding nozzle group in the sub-scanning direction may partially overlap. Further, as shown in FIG. 22, unused nozzles 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. 23, 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. 21 to 23, by generating a special dither mask according to the principle described in the first embodiment, the nozzles used for printing the special glossy area A2 can be obtained. It is possible to print separately for the preceding nozzle group and the succeeding nozzle group.

(G6) Modification 6:
In the embodiment described above, for example, as shown in FIG. 7C, the metallic dots and the color dots are all formed at exclusive positions. On the other hand, in the present modification, printing is performed while allowing metallic dots and color dots to be formed in the vicinity of the boundary of the dot pattern.

  FIG. 24 is a diagram illustrating a state in which a part of the metallic dots and the color dots are formed overlappingly. In this modification, the nozzle row includes 18 nozzles, and the number of nozzles included in the preceding nozzle group and the subsequent nozzle group is nine. In addition, the paper feed amount is 7, the overlap number is 2, the nozzle pitch is 2, and bidirectional printing is performed. In other words, in this modification, printing was performed with the number of nozzles being 18 more than in the first embodiment while maintaining the same paper feed amount and nozzle pitch as in the first embodiment (first embodiment). Then 14).

  For the convenience of illustration, FIG. 24A shows only the dot pattern printed by the preceding nozzle group under the above conditions, and FIG. 24B shows the dots printed by the succeeding nozzle group. Only the pattern is shown. Of course, on the actual print medium, the dot patterns shown in FIGS. 24A and 24B are superimposed and printed. Numerical values in the figure indicate nozzle numbers. In this modification, Nos. 1-9 are metallic nozzles and Nos. 10-18 are color nozzles. When comparing FIG. 24A and FIG. 24B, there is a portion where dots are formed at the same position in the preceding nozzle group and the succeeding nozzle group. FIG. 24 (c) shows an extracted portion where dots are overlapped at the same position. In this modification, since the paper feed amount is set to 7, the dot pattern changes every 7 lines as shown in FIG. 24A. However, when FIG. 24C is viewed, the dot pattern changes. It can be seen that there is a portion where metallic dots and color dots are formed in the vicinity of the boundary. Note that the black grid in FIG. 24C indicates a portion where more metallic dots are formed than the printing result of the first embodiment shown in FIG. 7C, and the hatched grid is A portion where more color dots are formed than the printing result of one embodiment is shown.

  According to this modification, a special dither mask for metallic and a dither mask for color are generated in advance based on the dot patterns shown in FIGS. In the vicinity of the boundary, a portion where the metallic dot and the color dot can be overlapped is formed. If a portion where the metallic dots and the color dots can be formed in an overlapping manner is generated in this way, the degree of freedom of dot arrangement is increased for the overlapping portion as compared with the first embodiment. Can be made smoother.

  In this modification, printing is performed with the same number of metallic nozzles and color nozzles, but the number of either one (for example, color nozzles) may be increased. By doing so, it is possible to increase the degree of freedom of dot arrangement for the color on the side where the number of nozzles is increased.

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. 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. It is a figure which shows a mode that a part of metallic dot and color dot were formed overlappingly.

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 (13)

A printing apparatus having a printing mechanism that moves a print head in a main scanning direction and moves a print medium in a sub scanning direction that intersects the main scanning direction,
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The printing head and the printing mechanism are controlled, the printing head is moved in the main scanning direction, the printing medium is moved in the sub scanning direction by a predetermined conveyance amount, and dots are formed by the first ink. A printing control unit that forms an image along the dot pattern whose form periodically changes according to the conveyance amount on the printing medium;
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
The printing control unit forms the image by overlapping at least a part of the dots formed by the first ink and the second ink in the vicinity of the boundary of the shape change of the dot pattern. printing apparatus for. The printing apparatus according to claim 1,
An acquisition unit that acquires image data including a first color corresponding to the first ink and a second color corresponding to the second ink;
The printing control unit forms the image by performing a halftone process on the acquired image data using a dither mask in which a threshold is arranged at a position corresponding to each dot on the dot pattern. Printing device. The printing apparatus according to claim 2,
The printing apparatus, wherein the printing control unit uses a dither mask having different threshold arrangements for the first color and the second color as the dither mask. The printing apparatus according to claim 3,
The printing apparatus, wherein a threshold value is arranged at an exclusive position in each of the first color dither mask and the second color dither mask. The printing apparatus according to claim 4,
Of the first color dither mask and the second color dither mask, one dither mask shifts the arrangement of threshold values of the other dither mask by a predetermined amount corresponding to the period of the dot pattern. A printing device that is generated by A printing apparatus according to any one of claims 2 to 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 printing apparatus, wherein the first ink or the second ink is a special glossy ink whose optical characteristics after being printed 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 printing apparatus, wherein the first ink or the second ink is an ink containing a pigment that develops a metallic feeling. A printing method by a printing apparatus having a printing mechanism that moves a print head in a main scanning direction and moves a print medium in a sub-scanning direction that intersects the main scanning direction,
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The printing head and the printing mechanism are controlled, the printing head is moved in the main scanning direction, the printing medium is moved in the sub scanning direction by a predetermined conveyance amount, and dots are formed by the first ink. By forming an image along the dot pattern whose form periodically changes according to the transport amount on the print medium,
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
A printing method for forming the image by overlapping at least a part of dots formed by the first ink and dots formed by the second ink in the vicinity of the boundary of the shape change of the dot pattern . A computer program for controlling a printing apparatus having a printing mechanism for moving a print head in a main scanning direction and moving a print medium in a sub-scanning direction intersecting the main scanning direction,
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The printing head and the printing mechanism are controlled, the printing head is moved in the main scanning direction, the printing medium is moved in the sub scanning direction by a predetermined conveyance amount, and dots are formed by the first ink. doing, to realize the function of forming an image along the periodic dot pattern form is changed according to the transport distance to the print medium into the computer,
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
The function of forming the image on the print medium is that at least a part of the dots formed by the first ink and the second ink are formed in the vicinity of the boundary of the shape change of the dot pattern. A computer program for superimposing the image . The computer-readable recording medium which recorded the computer program of Claim 10 . A printing medium printed by a printing apparatus having a printing mechanism that moves a print head in a main scanning direction and moves a printing medium in a sub-scanning direction that intersects the main scanning direction,
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The print head is moved in the main scanning direction, the printing medium is moved in the sub-scanning direction by a predetermined conveyance amount, and dots are formed by the first ink, thereby periodically depending on the conveyance amount. An image is formed along a dot pattern that changes in shape.
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
A printing medium on which the image is formed by overlapping at least part of the dots formed by the first ink and the dots formed by the second ink in the vicinity of the boundary of the shape change of the dot pattern . A printer having a printing mechanism for moving a print head in a main scanning direction and moving a print medium in a sub-scanning direction intersecting the main scanning direction,
The print head includes a first nozzle row having a plurality of nozzles ejecting the first ink along the sub-scanning direction, and a second nozzle having a plurality of nozzles ejecting the second ink along the sub-scanning direction. Nozzle rows, and
The printing head and the printing mechanism are controlled, the printing head is moved in the main scanning direction, the printing medium is moved in the sub scanning direction by a predetermined conveyance amount, and dots are formed by the first ink. A control circuit for forming an image along the dot pattern whose form periodically changes according to the transport amount on the print medium;
The dot pattern includes a position to be determined or not formed or forming the dot, Ri pattern der indicating the position of not forming the dots,
The control circuit forms the image by overlapping at least a part of dots formed by the first ink and dots formed by the second ink in the vicinity of the boundary of the shape change of the dot pattern. Printer.

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