JP2003225994A - Printing for suppressing graininess - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the graininess of a printing image due to dots formed by the bonding of a plurality of ink drops. <P>SOLUTION: A printing apparatus is constituted so as to perform printing by forming dots on a printing medium while performing the main scanning of a printing head having a plurality of nozzles arranged at a constant nozzle pitch PN along a sub-scanning direction in order to discharge at least the same ink of one color. The main scanning lines arranged parallelly at a constant main interscanning pitch in the sub-scanning direction are printed by recording a plurality of main scanning lines using this printing apparatus. In this printing, one or more pixels arranged at mutually adjacent positions are contained and the maximum number of pixels, contained in a pixel group wherein ink drops are discharged at pixel positions adjacent in continuous main scanning, is restricted and, therefore, the size of dots formed by the flocculation of a plurality of ink drops on the pixel group can be reduced. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for ejecting ink to print an image on a print medium.

[0002]

2. Description of the Related Art Ink jet printers that form ink dots on a print medium by ejecting ink droplets to print an image are widely used as an output device for an image created by a computer or the like.

[0003]

Ink jet printers generally perform printing by ejecting ink droplets onto a print medium while performing main scanning of a print head. In such a printing method, when ink droplets are ejected to adjacent pixels in continuous main scanning, both ink droplets may be combined with each other to form a large dot. When the dots formed in this way become large, there is a problem in that the print quality is deteriorated due to graininess.

The present invention has been made in order to solve the above-mentioned problems in the prior art, and an object thereof is to suppress the graininess of a printed image due to dots formed by combining a plurality of ink droplets. .

[0005]

Means for Solving the Problems and Their Actions / Effects In order to solve at least some of the above problems, the present invention provides
A printing apparatus that performs printing by ejecting ink droplets onto a print medium while performing main scanning of the print head, wherein the print head is configured to eject at least one color of the same ink in a sub-scanning direction. Having a plurality of nozzles arranged at a constant nozzle pitch along the line, the printing device, main scanning lines arranged in parallel at a constant main scanning pitch in the sub-scanning direction,
There is a specific print mode in which printing is performed by recording with a plurality of main scans, and the specific print mode includes one or more pixels arranged at positions adjacent to each other, and pixels adjacent to each other in continuous main scans. The ink droplets are ejected such that the maximum number of pixels included in the pixel group in which the ink droplets are ejected at a position is smaller than a value obtained by dividing the nozzle pitch by the pitch between main scans.

According to the present invention, the maximum number of pixels included in a pixel group that includes one or more pixels arranged at positions adjacent to each other and in which ink droplets are ejected at adjacent pixel positions in continuous main scanning is limited. Therefore, it is possible to reduce the size of a dot formed by agglomeration of a plurality of ink droplets on such a pixel group. As a result,
It is possible to suppress the graininess of the printed image due to large dots that can be perceived by human eyes.

In the above printing apparatus, in the specific printing mode, the maximum number of pixels included in the pixel group is
2 which is a value obtained by dividing the nozzle pitch by the main scanning pitch.
The ink droplets may be ejected so as to be one-half or less.

In this way, the present invention can be applied by simply changing the dot arrangement.

In the above printing apparatus, in the specific printing mode, the minimum number of pixels included in the pixel group is
It is preferable that the ink droplets are ejected so that the number is two or more.

When the lower limit value is set for the number of pixels included in each pixel group in this way, the variation in the number of pixels included in each pixel group can be reduced, which may improve the image quality. is there.

In the above printing apparatus, the pixel group may be a group of pixels arranged linearly continuously in an oblique direction between the main scanning direction and the sub scanning direction.

In the above printing apparatus, the print head discharges ink of one kind of density for each color of black, cyan, magenta and yellow.
The effect of the present invention is remarkably obtained when one nozzle row is provided or when pigment ink is ejected. This is because the graininess of the printed image is likely to stand out in such printing.

The present invention can be implemented in various modes. For example, a printing method and a printing apparatus,
A computer program for realizing the functions of those methods or apparatuses, a recording medium recording the computer program, a data signal embodied in a carrier wave including the computer program, and the like can be realized.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Next, embodiments of the present invention will be described in the following order based on examples. A. Device Configuration: B. Dot Recording Method in Comparative Example and Example: C.I. Modification:

A. Device Configuration: FIG. 1 is a block diagram showing the configuration of a printing system as an embodiment of the present invention. This printing system includes a computer 90 as a print control device, a color printer 20 as a printing unit,
Is equipped with. The combination of the color printer 20 and the computer 90 can be called a “printing device” in a broad sense.

In the computer 90, the application program 9 is executed under a predetermined operating system.
5 is working. A video driver 91 and a printer driver 96 are incorporated in the operating system, and the application program 95 outputs print data PD to be transferred to the color printer 20 via these drivers. The application program 95 performs desired processing on the image to be processed, and also displays the image on the CRT 21 via the video driver 91.

When the application program 95 issues a print command, the printer driver 9 of the computer 90
6 receives the image data from the application program 95 and converts it into print data PD to be supplied to the color printer 20. In the example shown in FIG. 1, the printer driver 96 includes a resolution conversion module 97, a color conversion module 98, a halftone module 99, a print data generation module 100, and a color conversion table LUT. ing.

The resolution conversion module 97 plays a role of converting the resolution (that is, the number of pixels per unit length) of the color image data handled by the application program 95 into a resolution that can be handled by the printer driver 96. The image data whose resolution has been converted in this way is still image information consisting of three colors of RGB. The color conversion module 98 converts the RGB image data into multi-tone data of a plurality of ink colors usable by the color printer 20 for each pixel while referring to the color conversion table LUT.

The color-converted multi-tone data is, for example, 25
It has 6 gradation values. The halftone module 99 disperses and forms ink dots,
The color printer 20 executes halftone processing for expressing the gradation value. The halftone-processed image data is sorted by the print data generation module 100 in the order of data to be transferred to the color printer 20,
The final print data PD is output. The print data PD includes raster data indicating a dot recording state at each main scan and data indicating a sub-scan feed amount.

The printer driver 96 corresponds to a program for realizing the function of generating the print data PD. The program for realizing the functions of the printer driver 96 is supplied in the form recorded in a computer-readable recording medium. Examples of such a recording medium include a flexible disk, a CD-ROM, a magneto-optical disk, an IC card, a ROM cartridge, a punch card, a printed matter on which codes such as a bar code are printed, and an internal storage device (RAM, ROM, etc.) of a computer. memory)
Also, various computer-readable media such as an external storage device can be used.

FIG. 2 is a schematic configuration diagram of the color printer 20. The color printer 20 includes a sub-scan feed mechanism that conveys the print paper P in the sub-scan direction by the paper feed motor 22, and a main scan feed that reciprocates the carriage 30 in the axial direction (main scan direction) of the platen 26 by the carriage motor 24. Mechanism, a head drive mechanism that drives a print head unit 60 (also referred to as a “print head assembly”) mounted on the carriage 30 to control ink ejection and dot formation, the paper feed motor 22, and the carriage motor. 24, print head unit 60 and operation panel 32
And a control circuit 40 that controls the exchange of signals with the. The control circuit 40 is connected to the computer 90 via the connector 56.

The sub-scan feed mechanism for conveying the printing paper P is
A gear train (not shown) that transmits the rotation of the paper feed motor 22 to a platen 26 and a paper transport roller (not shown) is provided. Further, the main scanning feed mechanism for reciprocating the carriage 30 is provided in parallel with the axis of the platen 26, and a drive shaft 36 which is endless between the slide shaft 34 which slidably holds the carriage 30 and the carriage motor 24. And a position sensor 39 for detecting the origin position of the carriage 30.

FIG. 3 is a block diagram showing the configuration of the color printer 20 centering on the control circuit 40. The control circuit 40 includes a CPU 41 and a programmable ROM (PRO
M) 43, a RAM 44, and a character generator (CG) 45 that stores a dot matrix of characters, and is configured as an arithmetic logic operation circuit. The control circuit 40 further has an I / F dedicated circuit 50 dedicated to interface with an external motor and the like, and a head connected to the I / F dedicated circuit 50 for driving the print head unit 60 to eject ink. A drive circuit 52 and a motor drive circuit 54 that drives the paper feed motor 22 and the carriage motor 24 are provided. The I / F dedicated circuit 50 has a built-in parallel interface circuit and has a connector 5
The print data PD supplied from the computer 90 via 6 can be received. The color printer 20
Printing is executed according to this print data PD. In addition, R
The AM 44 functions as a buffer memory for temporarily storing raster data.

The print head unit 60 includes the print head 2
8 and an ink cartridge can be mounted. The print head unit 60 is attached to and detached from the color printer 20 as one component. That is, when the print head 28 is replaced, the print head unit 60 is replaced.

FIG. 4 is a block diagram showing the main structure of the head drive circuit 52 (FIG. 3). Head drive circuit 52
Is an original drive signal generator 220 and a plurality of mask circuits 22.
2 and the piezo element PE of each nozzle. The mask circuit 222 is provided corresponding to each nozzle of the print head described later.

FIG. 5A is a timing chart showing the operation of the head drive circuit 52. Original drive signal generator 2
Reference numeral 20 denotes an original drive signal COM commonly used for each nozzle.
DRV is generated and supplied to the plurality of mask circuits 222.
The original drive signal COMDRV is a signal including one pulse within the main scanning period Td for one pixel. Each mask circuit 222 has an original drive signal COMDR according to the level of the serial print signal PRT (i) of each nozzle connected to it.
Mask V.

Specifically, the mask circuit 222 outputs the original drive signal COM when the print signal PRT (i) is at the 1 level.
Since the DRV is passed as it is, the original drive signal is supplied to the piezo element PE as the drive signal DRV. On the other hand, when the print signal PRT (i) is at 0 level, the original drive signal C
OMDRV is shut off. This serial print signal PRT
(I) is a signal indicating the printing state of each pixel printed by each nozzle in one main scan, and is the print data PD (FIG. 1) given from the computer 90 decomposed for each nozzle. Note that FIG. 5A is an example in which dots are recorded every other pixel, and when dots are recorded in all pixels, the original drive signal COMDRV is directly applied to the piezo element PE as the drive signal DRV. Supplied.

FIGS. 5B and 5C are timing charts showing the operation of the head drive circuit 52 in the overlap system. The overlap method is a method of recording dots on the same main scanning line using a plurality of different nozzles, and is characterized by having an effect of suppressing banding. The examples shown in FIGS. 5B and 5C are timing charts in a method of recording each main scanning line using two different nozzles, that is, a recording method when the overlap number s is 2. is there.

FIG. 5B is a timing chart when dots are formed at odd pixel positions, and FIG. 5C is a timing chart.
7 is a timing chart when dots are formed at even pixel positions. In this example, the waveform of the original drive signal COMDRV is generated at a rate of 1 pixel per 2 pixels. Therefore, when the original drive signal waveform of FIG. 5B is used, even if the serial print signals PRT (i) are all at "1" level, dots can only be formed at odd pixel positions. Similarly, when the original drive signal waveform of FIG. 5C is used, dots can only be formed at even pixel positions even when the serial print signals PRT (i) are all at "1" level.

In such a recording method, a plurality of dots on the same main scanning line can be recorded by a plurality of different "main scanning". On the other hand, since sub-scan feed is performed during each main scan, different nozzles are arranged on the same main scan line. As a result, it can be seen that a plurality of dots on the same main scanning line can be printed by using a plurality of different “nozzles”. As a result, the deviation of the dot formation position caused by the error of the nozzle formation position or the like is dispersed, so that the effect of suppressing banding is produced.

FIG. 6 is an explanatory view showing the nozzle arrangement on the lower surface of the print head 28. On the lower surface of the print head 28, a black ink nozzle group KD for ejecting black ink, a dark cyan ink nozzle group CD for ejecting dark cyan ink, and a light cyan ink nozzle for ejecting light cyan ink. A group CL, a dark magenta ink nozzle group MD for ejecting dark magenta ink, a light magenta ink nozzle group ML for ejecting light magenta ink, and a yellow ink nozzle group YD for ejecting yellow ink. Has been formed.

The capital letter of the first alphabet in the code indicating each nozzle group means the ink color,
The subscript "D" means that the ink has a relatively high density, and the subscript "L" means that the ink has a relatively low density.

The plurality of nozzles of each nozzle group are aligned at a constant nozzle pitch k · D along the sub-scanning direction SS. Here, k is an integer, and D is a pitch (“dot pitch”) corresponding to the printing resolution in the sub-scanning direction.
Is called). In the present specification, it is also referred to as "the nozzle pitch is k dots". The unit [dot] at this time is
It means the dot pitch of the print resolution. Similarly, for the sub-scan feed amount, the unit of [dot] is used. In each embodiment described below, the nozzle pitch k · D
Is 1/180 inch. Also, the dot pitch is
It corresponds to the "pitch between main scans" in the claims.

Each nozzle is provided with a piezo element (not shown) as a drive element for driving each nozzle to eject ink droplets. When printing, print head 2
Ink droplets are ejected from each nozzle while 8 moves in the main scanning direction MS.

The plurality of nozzles in each nozzle group need not be arranged in a straight line along the sub-scanning direction.
For example, they may be arranged in a staggered pattern. Even when the nozzles are arranged in a staggered pattern, the nozzle pitch k · D measured in the sub-scanning direction can be defined as in the case of FIG. In this specification, the term "a plurality of nozzles arranged in the sub-scanning direction" has a broad meaning including nozzles arranged in a straight line and staggered nozzles. There is.

The color printer 20 having the above-described hardware configuration conveys the paper P by the paper feed motor 22, reciprocates the carriage 30 by the carriage motor 24, and simultaneously drives the piezo element of the print head 28. , Ink droplets of each color are ejected to form ink dots, and a multi-color multi-tone image is formed on the paper P.

B. Dot Recording Method in Comparative Example and Example: FIGS. 7 and 8 are explanatory views showing the dot recording method of the first comparative example. The parameters of this recording method are
The number of nozzles N = 64, the nozzle pitch k · D = 8 dots, the sub-scan feed amount L = 15 dots, and the overlap number s = 4. The print resolution is 144 in both the main scanning direction and the sub scanning direction.
It is 0 dpi.

The pixel position numbers shown at the right end of FIG. 7 indicate the order of arrangement of pixels on each main scanning line, and the numbers in the circles are the main scans (passes) responsible for forming dots at the pixel positions. Shows the number. As can be seen from FIG. 7, in pass 1, (4 × n + 1) is obtained on the (8 × n + 8 (n is a non-negative integer; the same applies hereinafter) th main scanning line.
A dot is formed at the th pixel position. Next, the print medium is fed in the sub-scanning direction by 15 dots which is the sub-scan feed amount L, and then (4 × n + 7) th main scan line
A dot is formed at the (n + 2) th pixel position. For example, in pass 1, dots are formed at the 1st, 5th, and 9th pixel positions on the 8th and 16th main scanning lines, respectively. Next, in pass 2, dots are formed at the 2nd, 6th and 10th pixel positions on the 7th and 15th main scanning lines, respectively.

When dots are formed by shifting the pixel position to the right one by one in each pass in this manner, dots are continuously formed linearly in an oblique direction between the main scanning direction and the sub-scanning direction. It can be seen that the ink droplets are continuously ejected to the arranged continuous pixel groups. Further, pass 9 shown in FIG.
It can be seen that through the pass 16 as well, the ink droplets are similarly ejected to the consecutive pixel groups. In this example, the number of pixels included in each of these pixel groups is eight.

In this way, when ink drops are ejected to adjacent pixels in successive main scans such as pass 1 and pass 2, the ink drops ejected in the previous main scan are sufficiently absorbed by the print medium. In some cases, an ink droplet may be ejected to an adjacent pixel before the operation. For this reason, ink droplets ejected on eight pixels that are adjacent to each other may be combined with each other to form a large dot. The large dots contribute to the graininess and deteriorate the printed image.

9 and 10 are explanatory views showing the dot recording method of the first embodiment. The parameters of this recording method are the same as those of the first comparative example shown in FIGS. 7 and 8.
However, the pixel positions of the dots formed in each pass are different from those in the first comparative example. For example, in pass 5, dots are formed at the (4 × n + 1) th pixel position in the first comparative example as shown in FIG. 7, but as shown in FIG. A dot is formed at the (xn + 2) th pixel position. As a result, the above-mentioned pixel group is divided in half, and the maximum number of pixels included in this is reduced from eight to four. Further, as shown in FIG. 10, it can be seen that the other pixel groups are also divided in half.

FIG. 11 is an explanatory diagram showing the dot arrangements of the first comparative example and the first embodiment of the present invention. As can be seen from FIG. 11A, the dot array of the first comparative example is composed of pixel groups including eight pixels. In particular,
This dot arrangement is used for pixel groups in which dots are formed in pass 1 to pass 8, pass 9 to pass 16, pass 17 to pass 2
4. Each of the passes 25 to 32 includes a pixel group in which dots are formed. On the other hand, as can be seen from FIG. 11B, the dot array of the first embodiment is composed of pixel groups including four pixels. Specifically, this dot array is composed of pixel groups in which dots are formed in pass 1 to pass 4, pass 5 to pass 8, pass 9 to pass 12, pass 13 to pass 16, pass 17 to pass 20, pass 21. .. pass 24, pass 25 to pass 28, and pass 29 to pass 32 each include a pixel group in which dots are formed.

In the first comparative example, since each pixel group includes eight pixels, the length of the pixel group is about 0.2 mm (= 25.4 mm / 1440 × 8 × 1.4).
It becomes 1). On the other hand, in the first embodiment, since each pixel group includes four pixels, the length of the pixel group is half that of the first comparative example, which is 0.1 mm. When these lengths are converted into spatial frequencies, the spatial frequency of the pixel group of the first comparative example is 5 cycles / mm, and the spatial frequency of the pixel group of the first comparative example is 10 cycles / mm.
Becomes

FIG. 12 is a graph showing the relationship between the spatial frequency and the number of distinguishable gradations in human visual characteristics. This graph shows that as the spatial frequency increases, the number of gray levels that can be recognized by humans decreases. For example, since the dots formed by combining the ink droplets on the pixel group of the first comparative example have a spatial frequency of 5 cycles / mm, it is possible to identify more than 10 gradation levels. On the other hand, it can be seen from the graph that the dots formed on the pixel group of the first embodiment have a spatial frequency of 10 cycles / mm, and thus are almost indistinguishable by human eyes.

As described above, in this embodiment, the maximum number of a plurality of pixels included in a specific pixel group is limited, so that a plurality of ink droplets are formed on such a pixel group. The size of the dot can be reduced. As a result, it is possible to suppress the graininess of the printed image due to the large dots that can be perceived by human eyes.

FIG. 13 is an explanatory diagram showing dot arrays of the second comparative example and the second embodiment of the present invention. The parameters of these recording methods are the same as those in the above-described embodiment except that the overlap number s is 2. As can be seen from the second comparative example shown in FIG. 13A, even when the number of overlaps s is 2, the dot array includes a pixel group including eight pixels, and thus the first comparison It can be seen that large dots similar to the example can be formed.

As can be seen from FIG. 13B, also in the present embodiment, the pixel positions of the dots formed in each pass are adjusted in the same manner as in the first embodiment, so that the number of pixels included in the pixel group is adjusted. Can be reduced. In this embodiment, the number of pixels included in the pixel group is reduced from eight in the second comparative example to two.

As described above, in printing in which a main scanning line is recorded by a plurality of main scans, the pixel position formed in each pass can be adjusted. Therefore, the overlap number s is 4 in the present invention.
It is understood that the present invention is not limited to the case of the number of times and is generally applicable to printing in which main scanning lines are recorded by a plurality of main scannings.

C. Modifications: The present invention is not limited to the above-described embodiments and embodiments, and can be implemented in various modes without departing from the gist thereof. For example, the following modifications are also possible. is there.

C-1. In the above embodiment, the pixel group includes a plurality of pixels, but it may include only a single pixel as shown in the modification of FIG. In general, the pixel group in the present invention may be any pixel group that includes one or more pixels arranged at positions adjacent to each other and that ejects ink droplets at adjacent pixel positions in successive main scans. However, if a lower limit value (for example, two) is set for the number of pixels included in the pixel group, the variation in the number of pixels included in each pixel group can be reduced, and the image quality may be improved depending on the print mode. There is an advantage.

The effect of the present invention can be obtained if the maximum number of pixels included in the pixel group is smaller than the value obtained by dividing the nozzle pitch by the pitch between main scans. There is no simple relationship that the printed image is beautiful. For example, it has been confirmed by experiments that the print image printed by the recording method of the first embodiment of the present invention has less graininess than that printed by the recording method of the modified example.

As described above, it is sufficient that the maximum number of pixels included in the pixel group is smaller than the value obtained by dividing the nozzle pitch by the pitch between main scans. Further, it is preferable to actually perform printing in each print mode within this range and set an optimum dot array for each print mode.

C-2. The print resolution is not limited to 1440 dpi which is the resolution of each of the above embodiments, and the present invention can be applied to other resolutions. However, a remarkable effect is obtained when the resolution in the sub-scanning direction is large. This is because the combination of the ink droplets ejected to the adjacent pixels is caused by an error in the ink ejection position with respect to the pixel position, but this error with respect to the pixel size increases as the printing resolution increases. is there. It should be noted that the cause of the error in the ink ejection position is the vibration of the carriage and the feeding error of the main scanning and the sub scanning.

The nozzle pitch is not limited to 1/180 inch which is the pitch of the embodiment, and the present invention can be applied to other pitches. However, a remarkable effect is obtained when the nozzle pitch is large. This is because, as can be seen from the above embodiments, the larger the nozzle pitch, the larger the size of the pixel group tends to be.

C-3. Although the type of ink is not taken into consideration in each of the above embodiments, the present invention exerts a remarkable effect in printing using a pigment ink. Pigment ink is ink that uses a pigment as a coloring material. This is because when printing is performed with an ink that uses a pigment as a color material, the graininess is particularly noticeable.

Further, the present invention has a remarkable effect in printing using the slow penetration ink. This is because the slow-penetration ink hardly penetrates into the print medium, and thus ink droplets are likely to be bonded on the print medium.

Here, the terms "super-penetration ink" and "slow-penetration ink" refer to the relative characteristics of these inks. That is, when the same amount is dropped on a standard print medium (for example, plain paper), the super-penetration ink penetrates the print medium faster than the slow-penetration ink. For example, an ink having a surface tension at about 20 ° C. of less than about 40 × 10 −3 N / m can be used as the super-penetration ink. Also, as the slow penetration ink,
Inks with surface tensions above about 40 x 10-3 N / m at about 20 ° C can be used. It is possible to use either a dye or a pigment as the coloring material for the super-penetration ink or the slow-penetration ink.

C-4. In the above embodiment, printing is performed using six inks of black, cyan, magenta, yellow, light cyan, and light magenta, but the light cyan ink nozzle row and the light magenta ink nozzle row are not used. It can also be applied to printing with one ink. It should be noted that since the graininess tends to be conspicuous in printing without using the light ink, the effect of the present invention can be remarkably obtained.

Further, for example, in order to suppress a color change due to metamerism, black ink may be positively used in a region having relatively high lightness for printing. Even in such printing, since the graininess tends to be conspicuous, the effect of the present invention is similarly remarkable.

C-5. The present invention can be applied to monochrome printing as well as color printing. It can also be applied to printing in which multiple gradations are expressed by expressing one pixel with a plurality of ink dots. It can also be applied to a drum printer. In the drum printer, the drum rotation direction is the main scanning direction and the carriage traveling direction is the sub scanning direction. Also,
The present invention can be applied not only to an ink jet printer but also to an ink dot recording apparatus that generally records on the surface of a print medium using a recording head having a plurality of nozzle rows.

C-6. In the above embodiment, part of the configuration realized by hardware may be replaced with software, or conversely, part of the structure realized by software may be replaced with hardware. For example, some or all of the functions of the printer driver 96 shown in FIG.
Alternatively, the control circuit 40 therein may be executed.
In this case, the control circuit 40 of the printer 20 realizes some or all of the functions of the computer 90 as a print control device that creates print data.

When some or all of the functions of the present invention are realized by software, the software (computer program) can be provided in a form stored in a computer-readable recording medium. In the present invention, "computer-readable recording medium"
The term is not limited to a portable recording medium such as a flexible disk or a CD-ROM, but includes an internal storage device in a computer such as various RAMs and ROMs, and an external storage device fixed to the computer such as a hard disk. I'm out.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a printing system as an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of a printer.

FIG. 3 is a block diagram showing a configuration of a control circuit 40 in the color printer 20.

FIG. 4 is a block diagram showing a main configuration of a head drive circuit 52.

FIG. 5 is a diagram showing a timing chart showing the operation of the print head drive unit 214.

FIG. 6 is an explanatory diagram showing a nozzle array on the lower surface of the print head.

FIG. 7 is an explanatory diagram showing a dot recording method of a first comparative example.

FIG. 8 is an explanatory diagram showing a dot recording method of a first comparative example.

FIG. 9 is an explanatory diagram showing a dot recording method in the first embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a dot recording method according to the first embodiment of the present invention.

FIG. 11 is an explanatory diagram showing dot arrays of a first comparative example and a first example of the present invention.

FIG. 12 is a graph showing the relationship between the spatial frequency and the number of distinguishable gradations in human visual characteristics.

FIG. 13 is an explanatory diagram showing dot arrays of a second comparative example and a second example of the present invention.

FIG. 14 is an explanatory diagram showing a dot array of a modified example of the present invention.

[Explanation of symbols]

20 ... Color printer 21 ... CRT 22 ... Paper feed motor 24 ... Carriage motor 26 ... Platen 28 ... Print head 30 ... Carriage 32 ... Operation panel 34 ... Sliding shaft 36 ... Drive belt 38 ... pulley 39 ... Position sensor 40 ... Control circuit 41 ... CPU 44 ... RAM 50 ... I / F dedicated circuit 52 ... Head drive circuit 54 ... Motor drive circuit 56 ... Connector 60 ... Print head unit 90 ... Computer 91 ... Video driver 95 ... Application program 96 ... Printer driver 97 ... Resolution conversion module 98 ... Color conversion module 99 ... Halftone module 100 ... Print data generation module 214 ... Print head drive unit 220 ... Original drive signal generator 222 ... Mask circuit

Claims (9)

[Claims] 1. A printing apparatus for printing by ejecting ink droplets onto a print medium while performing main scanning of the print head, wherein the print head ejects at least one color of the same ink. A plurality of nozzles arranged at a constant nozzle pitch along the sub-scanning direction, wherein the printing device has a plurality of main scanning lines arranged in parallel at a constant main-scan pitch in the sub-scanning direction. Has a specific print mode in which printing is performed by recording with, and the specific print mode includes one or more pixels arranged at positions adjacent to each other, and ink drops are formed at adjacent pixel positions in continuous main scanning. The ink droplet is ejected such that the maximum number of pixels included in the pixel group in which is ejected is smaller than a value obtained by dividing the nozzle pitch by the pitch between main scans. 2. The printing apparatus according to claim 1, wherein, in the specific print mode, the maximum number of pixels included in the pixel group is 2 which is a value obtained by dividing the nozzle pitch by the main scanning pitch. A printing device that ejects ink droplets so that the amount of the ink droplets is less than or equal to one-half. 3. The printing apparatus according to claim 1, wherein the specific print mode ejects ink droplets such that the minimum number of pixels included in the pixel group is 2 or more. Printing device. 4. The printing device according to claim 1, wherein the pixel groups are arranged linearly continuously in an oblique direction between a main scanning direction and a sub scanning direction. A printing device, which is a group of pixels. 5. The printing apparatus according to claim 1, wherein the print head discharges ink of one type having a density for each color of black, cyan, magenta, and yellow. A printing device having four nozzle rows. 6. The printing apparatus according to claim 1, wherein the print head ejects pigment ink. 7. A printing method for performing printing by ejecting ink droplets onto a print medium while performing main scanning of a print head, wherein at least one color of the same ink is ejected in the sub-scanning direction. A step of preparing a print head having a plurality of nozzles arranged at a constant nozzle pitch along the main scanning line and a plurality of main scanning lines arranged in parallel at a constant main scanning pitch in the sub-scanning direction And a step of performing printing by the method, wherein the step of performing printing includes one or more pixels arranged at positions adjacent to each other, and ink droplets are ejected to adjacent pixel positions in continuous main scanning. A printing method, comprising the step of ejecting ink droplets such that the maximum number of pixels included in is smaller than a value obtained by dividing the nozzle pitch by the pitch between main scans. 8. A dot is printed on a print medium while main scanning is performed by a print head having a plurality of nozzles arranged at a constant nozzle pitch along the sub-scanning direction to eject at least one color of the same ink. A computer program for controlling a printing apparatus that performs printing by forming a plurality of main scanning lines recorded in a plurality of main scans at a constant main scanning pitch in the sub-scanning direction. A program for causing the computer to realize a function of printing by arranging in parallel is provided, wherein the function includes one or more pixels arranged at positions adjacent to each other, and ink drops are formed at adjacent pixel positions in continuous main scanning. So that the maximum number of pixels included in the pixel group in which is ejected is smaller than a value obtained by dividing the nozzle pitch by the main scanning pitch. Characterized in that it comprises a function for ejecting ink droplets, the computer program. 9. A computer-readable recording medium in which the computer program according to claim 8 is recorded.