JP2003089199A - Ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an ink jet recorder in which excessive adhesive of ink to a recording body can be prevented, print speed is increased by increasing the drying rate of ink, image quality is prevented from lowering, image length is equalized in the main scanning direction and the sub-scanning direction, and jaggy is reduced at the outline part. SOLUTION: Recording dot pitch p in the main scanning direction is equalized to the recording dot pitch q in the sub-scanning direction, a shift dot pattern where the position of dots 35 is shifted by p/2 in the main scanning direction is generated between adjacent lines 31 in the sub-scanning direction, and print out is effected by arranging droplet dots 35s additionally at the outline part of the shift dot pattern. Consequently, excessive adhesion of ink to a recording body can be prevented by reducing the overlap rate of dots, high speed printing is realized by increasing the drying rate of ink, and the image length is equalized in the main scanning direction and the sub-scanning direction thus reducing jaggy at the outline part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording apparatus for outputting an image in a printer, copier, facsimile or the like.

[0002]

2. Description of the Related Art An ink jet recording apparatus is capable of recording at high speed, recording on so-called plain paper without requiring a special fixing process, and noise generation during recording is so small that it can be ignored. Has been done. Conventionally, various systems have been proposed or already commercialized and put into practical use. Such an ink jet recording apparatus has an ink liquid chamber and an ink jet head in which a nozzle communicating with the ink liquid chamber is formed, and ink droplets in the ink liquid chamber are ejected from the nozzles in accordance with image information, so that a paper, a film, or the like is ejected. An image is formed by adhering it to a recording medium. Further, there are a serial type inkjet printer and a line type inkjet printer due to the difference in the configuration of the inkjet head. A serial-type inkjet printer forms an image while scanning the inkjet head in the width direction of the paper (main scanning direction), and after one or more scans is completed, conveys the paper and prints the image on the next recording line. It will be recorded.
On the other hand, in the line type ink jet printer, the nozzles are formed almost all over the width direction of the paper, and the paper is recorded while being conveyed without scanning in the width direction of the paper. The latter has the advantage that the recording speed is fast because one line in the width direction is formed at one time, but the size of the printer as a whole becomes large due to the large head itself, and high resolution recording is required. In order to do so, it is necessary to arrange the nozzles themselves in a high density, which raises the problem of increasing the manufacturing cost of the head. In comparison,
The former uses a relatively small head to form images, so
Since the cost of the device is low, most of the current inkjet printers are basically serial inkjet printers.

A recorded image of this serial type ink jet printer is, as shown in FIG. 21, a straight line group 52 parallel to the main scanning direction of the ink jet head, and this straight line group 52.
As a basic recording position, a grid point formed by a group of straight lines 51 parallel to the sub-scanning direction is used as a basic recording position, and ink droplets are ejected so as to land at this basic recording position to record an image of a set of dots 50. .

In the conventional recording method in which dots are formed using the grid points of the parallel lines as basic recording positions, the image to be printed has characters of a specific size, simple vertical lines and horizontal lines such as ruled lines and tables. There was an advantage when Therefore, when printing the characters recorded in such a recording dot pattern on the paper surface, it was rational to record the ink based on the square grid position.

However, in order to completely fill the recording surface of the paper with ink containing a color material at the conventional basic recording position, theoretically, as shown in FIG. The diameter D is about 1. The recording dot pitch p in the main scanning direction or the recording dot pitch q in the sub scanning direction is about 1.
It is necessary to make it four times or more. Therefore, when the surface is painted over, the overlapping portion of the dots 50 becomes very large, and the overlapping ratio is about 57% in terms of area ratio. Therefore, when there are many characters, graphics, images, etc. on one page, the ink on the paper becomes excessive, and as a result,
Ink, which is called cockling, excessively penetrates into the paper, causing waviness in the paper, causing the paper to come into contact with the inkjet head and other members, causing the print surface to become dirty and changing the distance between the inkjet head and the paper. As a result, there is a problem that the landing position of the jet dot is displaced. Further, there is a problem in that bleeding occurs due to the overlapping of the inks and the image quality is deteriorated, and that it takes time to dry the inks and the recording speed is substantially decreased. Such problems are becoming more serious as the recent increase in recording speed, increase in the number of filled image patterns, and the widespread use of color recording in which two or more colors of ink are overprinted.

[0006] As a method for solving this problem, Japanese Patent Laid-Open No. Hei 8
There is a technique described in Japanese Patent Publication No. 2003-2003. This is a group of three parallel lines 53, 5 forming an angle of 120 degrees with each other.
In the printing apparatus, the basic recording position is a grid point at which the intervals of the parallel lines are equal to each other and the three parallel lines forming the parallel line groups 53, 54, and 55 intersect at one position. (See Figure 23). By recording with such dot arrangement, the dot overlap rate can be reduced and dots can be arranged on the paper without gaps.

[0007]

However, when such a dot arrangement is used, unevenness is generated in the contour portion of the image, and so-called jaggies occur, which deteriorates the image quality.

In general, the density of the recorded image is 300 dpi × 300 dpi in length × width, 360 dpi × 360 dpi, 60
Many of the basic recording positions are grid points (herein referred to as orthogonal grids), which are conventionally composed of two parallel line groups that are orthogonal to each other, such as 0 dpi x 600 dpi and 720 dpi x 720 dpi, and various application software ( Photoshop, word processing software, etc.) is also usually used as a pixel unit orthogonal grid. Also, when expressing letters, ruled lines, tables, etc. with dots, it is better to draw a straight line based on the orthogonal grid. As for the image density, there are other images having different vertical and horizontal resolutions, such as 720 dpi × 1440 dpi, but the image recording position also uses the orthogonal grid as the basic recording position. Therefore, when the image data sent from the PC (personal computer) to the printer is based on the orthogonal grid, it is not necessary to perform special processing on the host computer side, and when rasterized into data corresponding to the recording dot pattern. Processing speed does not slow down.

However, in the technique disclosed in Japanese Unexamined Patent Publication No. 8-2003, a grid point intersecting with three parallel line groups forming an angle of 120 degrees with each other is used as a basic recording position. In other words, each vertex of a triangle (that is, an equilateral triangle) having all angles of 60 degrees is a recording position. Therefore, when one parallel line is aligned with the main scanning direction,
When recording is performed at the recording dot pitch p in the main scanning direction, the recording dot pitch q in the sub-scanning direction is q = p√3 / 2, as described in the specification, which is approximately q = 0.8.
It becomes 7p. That is, when an image with an orthogonal grid arrangement is sent from a host computer such as a PC, printing with this basic grid reduces the sub-scanning relative to the main-scanning.
The problem is that the image becomes a flat image.

An object of the present invention is to significantly reduce the area of the dot-to-dot overlapping portion to prevent stains and bleeding caused by excessive ink adhering to the paper, and to prevent image distortion, and An object of the present invention is to provide an ink jet recording apparatus that can shorten the drying time and speed up printing.

An object of the present invention is to generate a shift dot pattern by using a recording dot pattern developed on a conventional basic grid so that a general application for image formation can be used. An inkjet recording apparatus that can be used as

An object of the present invention is to provide an ink jet recording apparatus which can reduce jaggies.

An object of the present invention is to provide an ink jet recording apparatus which can more effectively reduce jaggies by means of droplet dots whose dot diameter is appropriately set to a small diameter.

An object of the present invention is to provide an ink jet recording apparatus which can reduce jaggies by simple means.

[0015]

The invention according to claim 1 is
It has an inkjet head in which a nozzle for ejecting ink is formed, and by the inkjet head,
In an inkjet recording apparatus for recording an image composed of a plurality of dots on a recording medium, when one of the conveyance direction of the recording medium and a direction orthogonal to the conveyance direction is a main scanning direction and the other is a sub-scanning direction Between adjacent lines in the sub-scanning direction, the dot position is set to p in the main scanning direction.
Shift dot pattern generating means for generating a shift dot pattern shifted by 1/2, and a droplet shape having a dot diameter smaller than the dots around the outline of the shift dot pattern is additionally arranged in the outline of the outline of the outline of the outline of the shift dot pattern. And an image developed as the shift dot pattern corrected by the image contour correction unit is output from the inkjet head.

Therefore, the dot overlap rate can be reduced to half or less in area as compared with the conventional method. This makes it possible to prevent unnecessary excess ink from adhering to the recording medium. Therefore, the drying speed of the ink is improved and the recording speed can be increased, and at the same time, the deterioration of the image quality due to the ink bleeding and the flow can be prevented. Further, even in an image based on the conventional dot configuration (orthogonal lattice arrangement), the image is not flat and the image lengths in the main scanning direction and the sub scanning direction can be made equal. Further, it is possible to reduce the jaggies that are likely to occur in the image contour portion by the droplet dots.

According to a second aspect of the present invention, in the first aspect of the present invention, the diameter of the dot developed in the shift dot pattern is D1, and the diameter of the droplet dot additionally arranged by the image contour correction means. Is defined as (1/2) × D1 ≧ D2.

Therefore, the jaggies can be more effectively reduced by the droplet dots whose dot diameter is properly set to a small diameter.

According to a third aspect of the present invention, in the first or second aspect of the invention, the image type recognition means for recognizing the image to be printed out by distinguishing it between an image and an image other than the image is provided. The image contour portion correcting means corrects the contour portion of the shift dot pattern only when it is recognized as an image other than the image image.

Therefore, since small dots are not added to the image image, the image image is faithfully output, and characters, ruled lines, which are mainly straight lines other than the image image,
For an image such as a front set, it is possible to improve the image quality by smoothing the straight line of the contour portion.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the inkjet recording apparatus according to any one of items 1 to 5, the image contour correction unit may include a dot after a non-printing portion for an odd-numbered line in the sub-scanning direction, and an even number in the sub-scanning direction. When there is a non-printing portion after the dot for the line of the row, a droplet dot is arranged in the area of the non-printing portion adjacent to the dot, or in the line of the even-numbered row in the sub-scanning direction. On the other hand, when there is a dot after the non-printing portion, and when there is a non-printing portion after the dot for the lines of odd rows, the droplet dot is in the area of the non-printing portion adjacent to the dot. Is added.

Here, the conditions for additionally arranging the small dot in the non-printing portion adjacent to the dot as the print data are: (1) For the odd-numbered lines in the sub-scanning direction, the dots are placed after the non-printing portion. And if there is a non-printing part after the dot for the line of the even-numbered column in the sub-scanning direction (2) After the non-printing part for the line of the even-numbered column in the sub-scanning direction There are two cases where there are dots and when there are non-printing areas after the dots for odd-numbered lines. And the line that exists after
Assuming that the dots are alternately arranged in the sub-scanning direction, the condition (1) is applied when the first line has dots after the non-printing portion, and the lines in the first row are non-printing after the dots. When the print portion is present, the condition (2) is applied.

Therefore, it is possible to reduce the jaggies that are likely to occur in the image contour portion by the additional arrangement of the droplet dots. In this case, the shift dot pattern forming the print output image can be recognized in the process of rasterizing the image data, and the arrangement of the droplet dots can be regularized according to the recognized pattern, so that a special mechanism is provided. You can reduce jaggies without any problems.

The invention according to claim 5 is the invention according to claims 1 to 3.
In any one of the inventions described above, the image contour portion correction means, when there is a concave portion due to the unevenness of the dots in the contour portion of the shift dot pattern, a droplet dot in the area of the concave portion. Is added.

Therefore, the jaggies can be reduced by filling the concave portions between the dots which are likely to occur in the image contour portion with the small droplet dots. In this case, the shift dot pattern forming the print output image can be recognized in the process of rasterizing the image data, and the arrangement of the droplet dots can be regularized according to the recognized pattern, so that a special mechanism is provided. You can reduce jaggies without any problems.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the image contour portion correcting means performs the additional placement processing of the droplet dots under the condition that dots adjacent in the sub-scanning direction exist. I do.

Therefore, when there are no adjacent dots in the sub-scanning direction, it is possible to omit the additional placement processing of the droplet dots on the line.

The invention according to claim 7 is the invention according to claims 1 to 3.
In any one of the above-mentioned inventions, the image contour correction means adds a droplet dot when there is a straight line portion inclining with respect to the sub-scanning direction and the main scanning direction in the contour portion of the shift dot pattern. Deploy.

Therefore, jaggies due to the tendency of dots to become uneven in the straight line portion of the image contour portion can be reduced by the droplet dots. In this case, the shift dot pattern forming the print output image can be recognized in the process of rasterizing the image data, and the arrangement of the droplet dots can be regularized according to the recognized pattern, so that a special mechanism is provided. You can reduce jaggies without any problems.

According to an eighth aspect of the present invention, in the first aspect of the invention, when the image contour correction means sets the dot pitch of the dots of the shift dot pattern to p, the center of the nearest dot is set. The distance separated by p
The droplet dots are added to the following positions.

Therefore, it is possible to reduce the occurrence of blanks between the dots and the droplet dots in the image contour portion.

The present invention as defined in claim 9 is any one of claims 1 to 8.
In the invention described above, the image contour portion correcting means additionally arranges the droplet dots by hardware.

Therefore, the additional placement process of the droplet dots can be performed at high speed.

According to a tenth aspect of the present invention, in the invention according to the fourth to seventh aspects, the image contour portion correcting means additionally arranges the droplet dots by executing a program.

Therefore, the additional placement processing of the small dot can be realized by software at a low cost.

According to an eleventh aspect of the present invention, in addition to the tenth aspect of the present invention, a storage medium in which the program is stored is provided.

Therefore, the additional placement processing of the droplet dots can be realized by software at a low cost.

[0038]

BEST MODE FOR CARRYING OUT THE INVENTION A schematic structure of an ink jet recording apparatus according to an embodiment of the present invention will be described. FIG. 1 is a perspective view showing a mechanical structure of a serial type ink jet recording apparatus applied to the present invention, FIG. 2 is a sectional view showing a tip portion of an ink jet head of an ink jet recording apparatus, and FIG. 3 is a nozzle plate of the ink jet head. 4 is a front view showing another nozzle plate, FIG. 5 is a block diagram showing an outline of an electrical configuration in the host computer, and FIG. 6 is a block diagram showing an outline of an electrical configuration in the inkjet recording apparatus. .

As shown in FIG. 1, in an ink jet recording apparatus (ink jet printer) P, a carriage 4 is movably mounted on guide rails 2 and 3 extending horizontally on a frame 1, and an ink jet head 5 is mounted on the carriage 4. Then, in order to scan the carriage 4 in the arrow A direction by the carriage motor described later and convey the paper 7 as the recording medium set on the guide plate 6 in the arrow B direction, a platen motor The rotational force is transmitted to the platen 10 having the feed knob 10a via the gears 8 and 9. A pressure roller 11 is pressed against the peripheral surface of the platen 10.

In the ink jet recording apparatus P, the paper 7 is moved while the carriage 4 is moved and scanned together with the ink jet head 5 in the main scanning direction (direction of arrow A).
Is conveyed in the sub-scanning direction (arrow B direction), and ink droplets are ejected from the inkjet head 5 to print an image on the paper 7.

Here, the ink jet head 5 is shown in FIG.
Further, as shown in FIG. 3, the liquid chamber forming member 13 forming the liquid chamber 12 has a nozzle plate 15 having a plurality of nozzles 14 formed on the front surface thereof. To fly. In this case, the driving principle of the inkjet head 5 is a bubble jet (registered trademark) method in which a voltage is applied to a heater to boil the ink in the liquid chamber 12, a piezo method in which the distortion effect of a piezoelectric element is used,
Any of electrostatic methods using electrostatic attraction generated by applying voltage between electrodes may be used. In any case, ink can be ejected from a desired nozzle 14 by selectively applying energy to each liquid chamber 12.

The nozzle plate 15 may have a plurality of nozzles 14 arranged in a line in a direction orthogonal to the main scanning direction A (see FIG. 1) as shown in FIG. 3, and as shown in FIG. The nozzles 14 may be arranged in two rows. The nozzle rows in the example of FIG. 4 are arranged in the main scanning direction A. In any case, the array pitch (nozzle pitch) Pn between the nozzles 14 arranged in the sub-scanning direction is formed to be twice the recording pitch (recording pitch M) for image formation (Pn = 2M). The present embodiment shows an example in which 64 nozzles are arranged.

Inkjet recording apparatus P of this embodiment
Then, an example in which the apparatus does not have a function of generating a dot pattern to be actually printed in response to an image drawing or character print command is shown. That is, a print command from application software or the like executed by the host computer is processed by a print driver incorporated as software in the host computer and rasterized into dot pattern data.
Will be transferred to and printed.

As shown in FIG. 5, the host computer H
Under the control of the control unit 17 having a CPU, C is a command for drawing an image or recording a character from the application software 18 or the operating system (for example, a description of the position, thickness and shape of a line to be recorded, a recording The font type, size, position, etc. of the character to be written are temporarily stored in the drawing data memory 19. These commands are written in a specific print language. The command stored in the drawing data memory 19 is the rasterizer 2
If it is a line recording command, it is converted into a dot pattern according to the specified position, thickness, etc., and if it is a character recording command, the font outline stored in the host computer HC. The contour information of the corresponding character is called from the data 21 and converted into a recording dot pattern according to the designated position and size. The recording dot pattern rasterized in this way is stored in the raster data memory 22. At this time, the host computer HC sets the conventional orthogonal grid as the basic recording position,
Rasterize to data of recording dot pattern. The recording dot pattern (see FIG. 7) stored in the raster data memory 22 is transferred to the inkjet recording apparatus P via the interface 23.

As shown in FIG. 6, the ink jet recording apparatus P connects the data processing unit 24 and the print processing unit 25 which receive the print dot pattern transferred from the host computer HC, and the print processing unit 25 is connected to the print processing unit 25. Carriage 4
A carriage drive control unit 27 that controls the drive of a carriage motor 26 for moving the head, a head drive control unit 28 that controls the drive of the inkjet head 5, and a platen 1.
It is formed by connecting to a line feed drive control unit 30 that controls the drive of a platen motor 29 for rotating 0.

The print data (recording dot pattern) transferred from the host computer HC to the ink jet recording apparatus P is stored in a raster data memory (not shown),
After receiving the predetermined data, it is sent to the head drive control unit 28 via the data processing unit 24, and the output of the head drive control unit 28 causes an ink droplet to be ejected (ejected) from a desired nozzle 14 of the inkjet head 5. The carriage drive control unit 27 controls the carriage motor 26 to scan the carriage 4, and the line feed drive control unit 30 drives the platen motor 29 to rotate the platen 10 for sub-scanning. The conveyance of the paper 7 in the direction is controlled.

The data processing section 24 in the present embodiment
On the basis of the recording dot pattern transferred from the host computer HC, functions as a shift dot pattern generating means for generating a shift dot pattern for generating a shift dot pattern for printing output from the inkjet head 5, and shifts the shift dot pattern. It functions as an image contour correction means for correcting the shape of the contour by additionally arranging droplet dots having a smaller dot diameter than the dots around the contour in the contour of the dot pattern.

Here, the generation of the shift dot pattern will be described. FIG. 7 is an explanatory diagram showing an example of the recording dot pattern as it is output from the host computer HP,
FIG. 8 is an explanatory diagram showing the dot arrangement of the shift dot pattern, FIG. 9 is an explanatory view showing a part of the dot arrangement extracted, and FIG. 10 is an explanatory view showing an example of the shift dot pattern.

First, the shift dot pattern will be described with reference to FIG. 8 as an example of outputting solid print data. The parallel line group indicated by reference numeral 31 in the drawing is a parallel line group which is arranged at equal intervals at a dot pitch q in the sub-scanning direction (paper transport direction). On the other hand, the parallel line group indicated by 32 has a dot pitch p / 2 in the main scanning direction (paper width direction).
It is a group of parallel lines arranged at equal intervals. These 31,
The group of 32 parallel lines orthogonally forms a lattice, and the lattice point is the position of the dot 35 indicated by a circle. Odd-numbered lines 31 of the parallel line group 31 arranged in the sub-scanning direction
-For odd, a group of parallel lines 3 arranged in the main scanning direction
2 every other line 32, that is, the intersection 33 with the parallel line group 32 having the dot pitch p as the recording position, and the even-numbered lines 31- of the parallel line group 31 arranged in the sub-scanning direction For even, in the parallel line group 32 in the main scanning direction, the odd-numbered lines 31 in the sub-scanning direction
An intersection 34 between the parallel line group 32 arranged at the dot pitch p and located between the line 32 forming the intersection of −odd and the recording position is the recording position. Therefore, when viewed from the lines 31 of the odd-numbered columns and the even-numbered columns of the horizontal parallel line group 31 arranged in the sub-scanning direction, the intersections 33 and 34, which are the recording positions, are
The positions are shifted by p / 2 in the main scanning direction, and are arranged at the dot pitch p. At this time, by setting p = q, the dot formation pitches in the main scanning direction and the sub-scanning direction become equal, so even if the recording dot pattern created at the recording position of the conventional orthogonal grid is transferred, the image is The flatness does not occur in the sub-scanning direction.

This will be described with reference to FIG. The line connecting the intersections 33 and 34 has the angles θ ₁ , θ ₂ ,
Form an isosceles triangle with θ ₃ . θ ₁ , θ ₂ , θ ₃
Are tan θ ₁ = 2, tan θ ₂ = 2, and tan (θ ₃ /
2) = 1/2, which is approximately θ ₁ = 6
It is 3.4 degrees, θ ₂ = 63.4 degrees, and θ ₃ = 54.2 degrees. In other words, the vertex of the isosceles triangle formed by θ ₁ , θ ₂ , and θ ₃ is the recording position. The circle shown centering on this intersection is the basic recording position of the dot 35 according to the present invention.

Next, the optimum dot diameter D of the present invention will be described. When a certain area is completely filled with print dots like a solid image, in order to avoid blank spaces between the surrounding dots, the circles that intersect at points equidistant from the three vertices of the above-mentioned isosceles triangle are used. The dot diameter D may be equal to or larger than the diameter, and the dot pitch of the dots 35 may be p (=
q), the dot diameter D = 5p / 4 = 1.25p. With this setting, it is possible to fill a solid image without blank areas.

As shown in FIG. 3, when printing is performed by the inkjet head 5 having one nozzle row, the dots 35 of the odd-numbered lines 31-odd in FIG. 8 are formed in the process of scanning the inkjet head 5. The dots 35 of the even-numbered lines 31-even are printed during the process of printing, carrying the paper 7 by the dot pitch q (Pn / 2), and then scanning the inkjet head 5.

Here, an example of printing a specific image will be described as a printing example using the shift dot pattern generated as described above. Dot 3 in the main and sub scanning directions
The array density of 5 is 300 dpi. The dot pitch at this time is p = q = 84.7 μm. Further, the positions of the dots 35 on the adjacent main scanning loci are shifted by p / 2, and the ink is ejected so that the average diameter D1 of the dots 35 on the paper 7 is 1.25 times p, 106 μm. The amount and discharge speed are set. By defining the parameters in this way, it is possible to reduce the overlap between the dots 35 and to arrange the dots 35 without a gap.

FIG. 7 is an image of a recording dot pattern of a certain image transferred from the host computer HC. In the figure, 31-1, 31-3, ... Are lines 31-odd of odd columns in the sub-scanning direction, 31-2, 32-4, ... Are lines 31-even of even columns. Looking at this recording dot pattern, when outputting from the inkjet recording device P as it is, all the adjacent dots 35
Since the center of the dot exists on the square lattice point, the dot diameter D1
It can be seen that a space is produced between the adjacent dots 35 unless .alpha. Is increased. In this conventional method, that is, in the case of outputting the recording dot pattern transferred from the host computer HP as it is at a density of 300 dpi × 300 dpi,
It is necessary to set the dot diameter D1 on the paper 7 of 1 dot to about 120 μm, and a large amount of ink adheres to the paper 7.

On the other hand, based on the recording dot pattern shown in FIG. 7, the position of the dot 35 is shifted by p / 2 in the main scanning direction between adjacent lines 31 in the sub scanning direction to generate a shift dot pattern. In this case, the space between the adjacent dots 35 can be suppressed as shown in FIG. By the way, for example, in the method of the present invention, the dot diameter D1 of one dot on the paper 7 can be reduced to about 106 μm, which is about 13% smaller. Further, in the conventional method, when the dots are filled with circular dots, 57% of the overlapping portions between the dots 35 are geometrically generated, and the ink becomes excessive. However, in the present invention, the overlapping portions of the dots 35 overlap each other. Could be significantly reduced to about 37%. This means that less ink is needed to obtain the same image with the same resolution. As a result, the ink dries faster, high-speed recording is possible, and wrinkles due to the wetting of the paper 7 can be prevented. Further, since the ink consumption amount is small, the running cost can be reduced. 10, 31-1, 31-3, ... Show odd-numbered lines 31-odd, 31-2, 3 in the sub-scanning direction.
2-4 ... are lines 31-even in even columns.

Further, according to the conventional method, the ink may become excessive and flow out in the image recording portion of the fill or the line, or an ink pool may be formed to largely deteriorate the image quality, but in the present invention, the excessive ink is small. It is possible to prevent deterioration of image quality. In particular, in color recording in which color expression is performed by overlapping inks of yellow, magenta, cyan, black, etc., the ink tends to be excessive, and the present invention is very effective in color recording.

Further, when the gradation expression is performed by the conventional method, the density does not increase so much even if the number of dots per area is increased especially in the high density area because the overlapping ratio between the dots 35 is large. However, in the present invention, the relationship between the number of dots and the density can be made substantially proportional, and the gradation expression capability is improved. When expressing a light gradation close to the color of the paper 7 in gradation expression, a method of recording the dots 35 sparsely is used, but in this case, the dot diameter D1 of 1 dot is used.
Is smaller, the dots 35 are less conspicuous, and a fine and fine impression can be obtained. From this point as well, the present invention enables recording of a high-quality image.

On the other hand, as compared with the method described in Japanese Patent Application Laid-Open No. 8-2003, the overlap rate is slightly higher, but FIG.
As shown in, the shape of the image itself does not become flat, and an image that is the same as that of a normal orthogonal lattice arrangement can be obtained. That is, according to the present invention, various problems caused by the conventional dot diameter D and the large overlapping ratio of the dots 35 can be solved without causing problems such as image flatness. In addition, the fact that the overlapping rate is slightly increased means that even if the deviation rate is larger than the flying speed of the ink droplets 16 and variations in dot position accuracy caused by ejection bending, the dots 35 are connected to the adjacent dots 35, resulting in white spots. Since it does not occur, it can be said that the present invention is more advantageous.

Further, as a printing method according to the present invention, 1
An image having a nozzle width of a desired resolution (a width of 64 nozzles in the case of the present embodiment) can be created by performing main scanning once.
This can be realized because the overlapping rate of the dots 35 decreases and the problems such as cockling and bleeding described above are less likely to occur. By using such a printing method, the number of times the paper 7 is conveyed in the sub-scanning direction is reduced, the time for outputting an image for one sheet, that is, the throughput may be short, and high-speed printing is possible.

Further, as a mode selection means, a mode selection key (not shown) is provided so that the mode for generating the shift dot pattern shown in FIG. 10 and the mode for directly printing out the recording dot pattern shown in FIG. 7 can be selected. You may comprise. When the mode of printing out the recorded dot pattern as it is is selected, the process of generating the shift dot pattern is not required, so that the process can be speeded up. When a shift dot pattern is generated and printed out, as shown in FIG. 10, the print result is formed in a zigzag pattern as compared with the original data (recording dot pattern in FIG. 7), and unevenness occurs in the contour portion. However, the deviation is p / 2, which is a very slight unevenness of 0.1 mm or less for a recent high-density image. In general, when printing is performed on the paper 7, the ink slightly bleeds on the paper, so slight unevenness is reduced by the bleeding and becomes almost inconspicuous.

As described above, by generating the shift dot pattern shown in FIG. 10 from the recording dot pattern shown in FIG. 7, various effects described above can be obtained. However, in the shift dot pattern, as can be seen by enlarging the dots 35, the arrangement of the dots 35 in the image contour portion is not uniform,
It is undeniable that the contour portion, which should be a straight line, becomes uneven. Since the actual dot 35 is extremely small, the deterioration of the image quality is not so problematic, but it is possible to obtain a higher quality image by preferably correcting this unevenness. Therefore, the present invention seeks to add droplet dots to the contour portion of an image.

A first embodiment of the droplet dot addition placement processing by the image contour correction means will be described below with reference to FIGS. 11 to 13. FIG. 11A shows an odd-numbered column odd-n in the sub-scanning direction (for example, 31-3 in FIG. 10A).
FIG. 12B is an explanatory view showing the arrangement of dots on a line, FIG. 12B is an explanatory view showing a state in which droplet dots are additionally arranged on the lines of odd-numbered columns odd-n, and FIG. An even-numbered column even-n (for example, 31- in FIG. 10A)
4) is an explanatory view showing an array of dots on the line, FIG. 6B is an explanatory view showing a state in which the droplet dots are additionally arranged on the even-numbered line even-n line, and FIG. It is explanatory drawing which shows an example of a shift dot pattern.

In FIGS. 11 and 12, the solid line circle indicates the dot 35, and the dotted line circle indicates the non-printing area (NULL).
The presence or absence of this non-printing portion in the area bordered by the hatched dot 35a is judged in the 1-dot area of the data). The circle marked with a small diameter solid line is the droplet dot 3 that is additionally arranged.
It is 5s. This also applies to other embodiments described later.

As shown in FIG. 11A, in the case of the odd-numbered line odd-n, when the area after the dot (print data) 35a with the oblique line is a non-print portion, b)
As shown in, the small dot 35s is additionally arranged in the area of the non-printing portion. Further, as shown in FIG. 12A, for the even-numbered line even-n, if the area in front of the dot (print data) 35a hatched is a non-print portion,
As shown in FIG. 7B, the droplet dot 35s is additionally arranged in the area of the non-printing portion. Note that the additional placement of the droplet dot 35s in the area of the non-printing portion means conversion of the NULL data into the data of the droplet dot 35s. This also applies to the subsequent embodiments.

By performing such additional placement of the droplet dots for all the lines, as shown in FIG. 13, the linearity of the outline portion of the shift dot pattern is reduced to the droplet dot 35s.
Can be modified by

Further, the second embodiment of the droplet dot addition placement processing by the image contour correction means is shown in FIGS.
It will be described based on. 14 to 17 are explanatory diagrams showing an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally arranged.

As shown in FIG. 14, for the odd-numbered lines in the sub-scanning direction, when a dot (print data) 35 of a certain line odd-n is followed by a non-printing portion indicated by a dotted circle, The dot 35 shown by a solid line is present on both the even-numbered lines even-n-1 and even-n in the front and rear rows at the position shifted by p / 2 after the dot (dotted line) 35a before the non-printed portion. If present, hatched dot 35
Since a concave portion is formed in the non-printing portion after a, the small dot 35s is additionally arranged in the non-printing portion after the dot (dotted line) 35a of the odd-numbered line odd-n. As a result, the droplet dot 35s is added to the concave portion of the contour which is the linear portion of the image, and a contour close to a straight line is obtained. However, in this case, the small dot 35s is not added to the corner portion where the straight line in the sub-scanning direction and the straight line in the main scanning direction intersect.

As a method of improving this, as shown in FIG. 15, in the odd-numbered line odd-n, there is a non-printing portion indicated by a dotted circle after the dot (printing data) 35. , The dot 35 exists only on one of the even-numbered lines even-n-1 and even-n before and after the dot (hatched dot) 35a before the non-printed portion at a position shifted by p / 2. If you want to, for example, the line in the front row
Area C of even-n-1 is the non-printing area, and the line in the rear row
The dot (print data) 35 exists in the even-n area I, and the area M on the same line one pitch after the dot 35 in the area I is a non-printing portion, and the dot 3 in the area I
Rear row line odd-n at a position shifted by p / 2 after 5
When the +1 area L is a non-printing portion, the hatched dot 35a is considered to be at a certain corner in the shift dot pattern. In this case, the droplet dot 35s is additionally arranged in the non-printing portion after the dot (dotted dot) 35a of the odd-numbered line odd-n.

As shown in FIG. 16, for an even-numbered line in the sub-scanning direction, a dot 35 of a certain line even-n
There is a non-printed portion indicated by a dotted circle in front of, and p / in front of the dot (dotted line) 35a after the non-printed portion.
Two odd lines before and after odd-n, o
Dots 35 shown by solid lines in both areas D and J of dd-n + 1
When there is a small dot 35 s, the small dot 35 s is additionally arranged in the non-printing part before the dot (dotted line) 35 a of the even-numbered line even-n. As a result, the droplet dot 35s is added to the concave portion of the contour that is a straight line portion, and a contour that is close to a straight line is obtained. However, in this case, the small dot 35s is not added to the corner portion where the straight line in the sub-scanning direction and the straight line in the main scanning direction intersect.

As a method for improving this, as shown in FIG. 17, in the above-described even-numbered line even-n, there is a non-printing portion indicated by a dotted circle before the dot (printing data) 35. Thus, the dot 35 exists only on one of the odd-numbered lines odd-n and odd-n + 1 before and after the position (p / 2) shifted before the dot (dotted line) 35a after the non-printed portion. If, for example, line od in the back row
The area J of d−n + 1 is the non-printing part, and the line odd in the front row
The dot (print data) 35 exists in the area D of -n, the area N on the same line one pitch before the dot 35 in the area D is a non-print portion, and the dot 35 in the area D is If the area A of the front row line even-n-1 at the position shifted by p / 2 from the previous position is a non-printing portion, the dot 35a hatched is drawn.
Is considered to be at some corner in the shift dot pattern. In this case, the dots of even-line line even-n
Droplet dots 35s are additionally arranged in the non-printed portion after (dots with diagonal lines) 35a.

By doing so, the linearity of the outline portion of the shift dot pattern can be corrected by the droplet dot 35s, and further, the dot 35 is omitted between the dots 35 in the outline portion of the shift dot pattern. Since the droplet dot 35s is added only when the concave portion is present,
The linearity is obtained, and the droplet dot 35s is not accidentally added when the concave portion does not exist,
Higher image quality can be achieved.

Further, FIG. 18 to FIG. 20 show the third embodiment of the droplet dot addition placement processing by the image contour correction means.
It will be described based on. 18 and 19 are explanatory diagrams showing an arrangement of dots on a certain line in the sub-scanning direction and a state in which small droplet dots are additionally arranged, and an explanatory diagram showing an example of a shift dot pattern with a modified contour portion.

As shown in FIG. 18, for the odd-numbered lines in the sub-scanning direction, when a dot (print data) 35 of a certain line odd-n is followed by a non-print portion indicated by a dotted circle. Is odd− on the line even−n−1 in the front row.
p / 2 in the front-back direction in the main scanning direction with respect to the non-printing part on n.
When the dots 35 are present in the displaced areas C and O, or in the rear line line even-n, the areas I and M are displaced by p / 2 in the front-back direction in the main scanning direction with respect to the non-printed portion on odd-n. If there is a dot 35 in the line, the line odd-n
The small dot 35s is additionally arranged in the non-printing portion after the dot (dotted line) 35a.

As shown in FIG. 19, a non-printing portion indicated by a dotted circle is present in front of a dot (printing data) 35 of a certain line even-n for the lines of even columns in the sub-scanning direction. In the case where the dots 35 are present in the areas N and D which are shifted by p / 2 in the front-back direction of the main scanning direction with respect to the non-printed portion on the even-n in the line odd-n in the front row, or the line in the back row In odd-n + 1, an area P shifted by p / 2 in the front-back direction in the main scanning direction with respect to the non-printed portion on even-n,
When the dot 35 is present in J, the droplet dot 35s is additionally arranged in the non-printing part before the dot (dotted line) 35a of the line even-n.

By doing so, even if the contour portion of the shift dot pattern has an oblique straight portion as shown in FIG. 20, the contour portion can be made into a smooth straight line. The method described with reference to FIGS. 18 to 20 may be implemented in combination with the method for improving the above-described linear unevenness described with reference to FIGS. 11 to 17. As a result, for straight lines, their corners, and diagonal lines,
Can improve jaggies.

By the method as described above, the outline portion of the print data developed in the shift dot pattern is set to the droplet dot 35s.
Corrected by the additional layout of, and actually 300dpi × 300d
When outputting an image of pi, the diameter D1 of the dot 35 as print data is 106 μm, and the diameter D2 of the droplet dot 35s for correcting the contour portion is 10 μm, 25 μm, 55 μm,
80 μm and 106 μm were set, and the jaggy state due to the difference in these parameters was evaluated.

As a result, when the small dot 35s is 55 μm or less (that is, about 1/2 or less of the diameter of the dot 35 as print data), jaggies are hardly noticeable,
Good character quality was obtained. Droplet dot 35s is 80μ
m or more (approx. 3 / diameter of dot 35 as print data)
In 4) and above, jaggies remained noticeable.

The above-described small dot addition processing is as follows.
It can be implemented by software using a microcomputer, or ASIC (Aplication Replication Spec).
The integrated circuit may be incorporated into hardware as represented by ific integrated circuit). When implemented by software, there is a drawback that the processing speed becomes slower than when implemented by hardware, but there is an advantage that it can be implemented at low cost. When implemented by software, the above-described additional placement processing method of the droplet dot 35s is converted into a humogram and stored in a storage medium such as a ROM, and the program can be easily executed by executing the program by a microcomputer.

Further, the processing for expanding the print data into a shift dot pattern and the processing for correcting the contour portion of the shift dot pattern by additionally arranging the droplet dots 35s are as follows.
In the present embodiment, as shown in FIG. 6, the data processing unit 24 on the ink jet recording apparatus P side performs the processing, but these processes are performed on the host computer HP side and sent to the ink jet recording apparatus P. May be.

On the other hand, when the droplet dots 35s are additionally arranged by hardware, there is an advantage that high speed processing is possible.

As a means for forming small droplets, a method of changing the dot size by changing the amount of ink ejected from the nozzle 14 can be used. Alternatively, by optimizing the particle formation conditions at the time of ejecting ink, the dot 35 as the print data and the small dot 35s for countermeasures against jaggies can be obtained by ejecting the ink once.
It is also possible to use a method of simultaneously correcting and.

Further, the small droplet dots 35s are formed on the image at the same pitch as the pitch at which the dots 35 as the print data are formed, but if formed at a position closer to the dots 35 as the print data than that. , A large blank does not occur between the dot 35 and the droplet dot 35s, so that they are integrated as an image and the image quality is improved.

Further, although it may be possible to select whether or not to add the small dot 35s to the dots 35 of all kinds of images, the kind of the image is judged by the image kind recognition means (not shown), and the straight line is drawn. More preferably, it is performed only for so-called graphics images such as characters, ruled lines, and tables that are formed mainly of curved lines, and not for so-called image images such as photographs. This is because characters and graphics images are composed of straight lines and curved lines as a group of dots, whereas image images make sense for each dot. This is because the image is rather deteriorated.

[0084]

According to the first aspect of the present invention, the dot position between adjacent lines in the sub-scanning direction is set to p / 2 in the main scanning direction.
Shift dot pattern generation means for generating a shifted shift dot pattern, and small dots having a dot diameter smaller than the dots around the contour part are additionally arranged in the contour part of the shift dot pattern to correct the shape of the contour part. Since the image contour portion correcting means is provided and the image developed as the shift dot pattern corrected by the image contour portion correcting means is output from the inkjet head,
The dot overlap rate can be reduced to half or less in area as compared with the conventional method. This can prevent unnecessary excess ink from adhering to the recording medium.
Therefore, the drying speed of the ink is improved and the recording speed can be increased, and at the same time, the deterioration of the image quality due to the ink bleeding and the flow can be prevented. Further, even in an image based on the conventional dot configuration (orthogonal lattice arrangement), the image is not flat and the image lengths in the main scanning direction and the sub scanning direction can be made equal. Further, the jaggies that are likely to occur in the image contour portion can be reduced by the droplet dots. Furthermore, in color recording, even when multiple colors of ink are overlaid and recorded, problems such as excessive ink do not cause problems and image quality does not deteriorate as in the conventional method. It is possible to reduce the diameter, and it is possible to realize an image having fine texture and less unevenness particularly when recording an image including gradation expression.

According to a second aspect of the present invention, in the first aspect of the present invention, the diameter of the dot developed in the shift dot pattern is D1, and the diameter of the droplet dot additionally arranged by the image contour correction means. Since D2 is defined as (1/2) × D1 ≧ D2, the jaggies can be more effectively reduced by the droplet dots whose dot diameter is appropriately set to a small diameter.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the image type recognition means for recognizing the image to be printed out by distinguishing it between an image image and other images is provided. Since the image contour correction means corrects the contour of the shift dot pattern only when the image is recognized as an image other than the image, the image is faithfully output because it does not add droplet dots. For images such as characters, ruled lines, and tables, which are mainly straight lines other than the image image, the straight line of the contour portion can be smoothed to improve the image quality.

The invention according to claim 4 is the same as claims 1 to 3.
In the inkjet recording apparatus according to any one of items 1 to 5, the image contour correction unit may include a dot after a non-printing portion for an odd-numbered line in the sub-scanning direction, and an even number in the sub-scanning direction. When there is a non-printing portion after the dot for the line of the row, a droplet dot is arranged in the area of the non-printing portion adjacent to the dot, or in the line of the even-numbered row in the sub-scanning direction. On the other hand, when there is a dot after the non-printing portion, and when there is a non-printing portion after the dot for the lines of odd rows, the droplet dot is in the area of the non-printing portion adjacent to the dot. Is additionally arranged, it is possible to reduce jaggies that are likely to occur in the image contour portion due to the additional arrangement of the droplet dots.
In this case, the shift dot pattern forming the print output image can be recognized in the process of rasterizing the image data, and the arrangement of the droplet dots can be regularized according to the recognized pattern, so that a special mechanism is provided. You can reduce jaggies without any problems.

The invention according to claim 5 is the same as claims 1 to 3.
In any one of the above-described inventions, the image contour correction unit additionally arranges the droplet dots in the region of the recess when there is a recess due to uneven dots in the contour of the shift dot pattern. Therefore, the jaggies can be reduced by filling the concave portions between the dots that are likely to occur in the image contour portion with the droplet dots. In this case, the shift dot pattern forming the print output image can be recognized in the process of rasterizing the image data, and the arrangement of the droplet dots can be regularized according to the recognized pattern.
Jaggies can be reduced without having a special mechanism.

According to a sixth aspect of the invention, in the fifth aspect of the invention, the image contour correcting means performs the additional placement processing of the small dot under the condition that the adjacent dots exist in the sub-scanning direction. If there is no adjacent dot in the sub-scanning direction, it is possible to omit the additional placement process of the droplet dots on the line.

The invention according to claim 7 is the same as claims 1 to 3.
In any one of the above-described inventions, the image contour portion correcting means additionally arranges the droplet dots when there is a straight line portion inclining with respect to the sub-scanning direction and the main scanning direction in the contour portion of the shift dot pattern. Therefore, jaggies due to the tendency of dots to become uneven in the straight line portion of the image contour portion can be reduced by the droplet dots. In this case, the shift dot pattern forming the print output image can be recognized in the process of rasterizing the image data, and the arrangement of the droplet dots can be regularized according to the recognized pattern, so that a special mechanism is provided. You can reduce jaggies without any problems.

According to an eighth aspect of the invention, in the first aspect of the invention, the image contour correction means separates from the center of the nearest dot when the dot pitch of the dots of the shift dot pattern is p. Since the small droplet dots are added to the position where the distance is equal to or smaller than p, it is possible to reduce the occurrence of blanks between the dots and the small droplet dots in the image contour portion.

The invention according to claim 9 is the invention according to claims 1 to 8.
In the invention described above, the image contour correction unit additionally arranges the droplet dots by hardware, so that the addition arrangement processing of the droplet dots can be performed at high speed.

According to a tenth aspect of the present invention, in the inventions according to the fourth to seventh aspects, the image contour portion correcting means additionally arranges the droplet dots by executing the program. Can be realized by software at low cost.

According to the eleventh aspect of the present invention, in the tenth aspect of the present invention, the storage medium in which the program is stored is provided, so that the droplet dot additional placement processing can be realized by software at low cost.

[Brief description of drawings]

FIG. 1 is a perspective view showing a mechanical configuration of a serial type ink jet recording apparatus according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a front end portion of an inkjet head of an ink jet recording apparatus.

FIG. 3 is a front view showing a nozzle plate of an inkjet head.

FIG. 4 is a front view showing another nozzle plate.

FIG. 5 is a block diagram showing an outline of an electrical configuration in a host computer.

FIG. 6 is a block diagram showing an outline of an electrical configuration of the inkjet recording apparatus.

FIG. 7 is an explanatory diagram showing an example of a recording dot pattern.

FIG. 8 is an explanatory diagram showing a dot array of a shift dot pattern.

FIG. 9 is an explanatory diagram in which a part of the dot array is extracted.

FIG. 10 is an explanatory diagram showing an example of a shift dot pattern.

11A and 11B show a first embodiment of the droplet dot adding and arranging process, wherein FIG. 11A is an explanatory diagram showing an array of dots on a line of an odd-numbered column in the sub-scanning direction, and FIG. It is explanatory drawing which shows the state which added and arranges the droplet dot to the line of a row.

12A is an explanatory diagram showing an array of dots on a line of an even-numbered column in the sub-scanning direction, and FIG. 12B is an explanatory diagram showing a state in which droplet dots are additionally arranged on the line of the even-numbered column. .

FIG. 13 is an explanatory diagram showing an example of a shift dot pattern with a modified contour portion.

FIG. 14 is a diagram illustrating a second embodiment of the droplet dot additional placement processing, and is an explanatory diagram illustrating an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally placed.

FIG. 15 is an explanatory diagram showing an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally arranged.

FIG. 16 is an explanatory diagram showing an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally arranged.

FIG. 17 is an explanatory diagram showing an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally arranged.

FIG. 18 is a diagram illustrating a third embodiment of the droplet dot additional placement processing, and is an explanatory diagram illustrating an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally placed.

FIG. 19 is an explanatory diagram showing an arrangement of dots on a certain line in the sub-scanning direction and a state in which droplet dots are additionally arranged.

FIG. 20 is an explanatory diagram showing an example of a shift dot pattern with a modified contour portion.

FIG. 21 is an explanatory diagram showing a conventional recording dot pattern.

FIG. 22 is an explanatory diagram showing an example of a conventional recording dot pattern.

FIG. 23 is an explanatory diagram showing an example of another conventional recording dot pattern.

[Explanation of symbols]

P Inkjet recording device 5 Inkjet head 7 Recording medium 14 Nozzle 24 Shift dot pattern generation means, image contour correction means 35, 35a Dots 35s Small droplet dots p Recording dot pitch q in the main scanning direction q Recording dot pitch in the sub scanning direction

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Claims (11)

[Claims] 1. An inkjet recording apparatus, comprising an inkjet head having nozzles for ejecting ink, wherein the inkjet head records an image composed of a plurality of dots on a recording medium. When one of the conveyance direction of the body and the direction orthogonal to the conveyance direction is the main scanning direction and the other is the sub scanning direction, the dot position between the lines adjacent in the sub scanning direction is p / 2 in the main scanning direction. Shift dot pattern generation means for generating a shifted shift dot pattern, and the outline of the shift dot pattern is corrected by additionally arranging small droplet dots having a dot diameter smaller than the dots around the outline. An image contour portion correcting means for performing the shift dot pattern corrected by the image contour portion correcting means. An ink jet recording apparatus characterized by an open image was to output from said ink jet head. 2. When the diameter of the dots developed in the shift dot pattern is D1 and the diameter of the droplet dots additionally arranged by the image contour correction unit is D2, (1/2) × D1 ≧ The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is defined by D2. 3. An image type recognizing means for recognizing the image to be printed out by distinguishing it between an image image and an image other than the image, and the image contour correction means is recognized as an image other than the image image. The contour portion of the shift dot pattern is corrected only in the case.
Or the ink jet recording apparatus according to 2. 4. The image contour correction means, when a dot is present after a non-printing portion for an odd-numbered line in the sub-scanning direction, and for an even-numbered line in the sub-scanning direction. When a non-printing portion exists after a dot, a droplet dot is arranged in the area of the non-printing portion adjacent to the dot, or the non-printing portion is arranged for an even-numbered line in the sub-scanning direction. If there is a dot after the dot and if there is a non-printing part after the dot for the lines in the odd columns, it is possible to additionally arrange the droplet dots in the region of the non-printing part adjacent to the dot. The ink jet recording apparatus according to any one of claims 1 to 3, which is characterized in that. 5. The image contour portion correcting means additionally arranges a droplet dot in the region of the concave portion when there is a concave portion due to the irregularity of the dots in the contour portion of the shift dot pattern. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is an inkjet recording apparatus. 6. The ink jet recording according to claim 5, wherein the image contour correction unit performs the additional placement processing of the droplet dots under a condition that adjacent dots exist in the sub-scanning direction. apparatus. 7. The image contour portion modifying means is configured to additionally arrange the droplet dots when there is a straight line portion inclining to the sub-scanning direction and the main scanning direction in the contour portion of the shift dot pattern. Claim 1 to 3 characterized by the above-mentioned.
2. The inkjet recording device according to any one of 1. 8. The image contour portion correcting means, when the dot pitch of the dots of the shift dot pattern is p, the small distance is set to a position where a distance separated from the center of the nearest dot is p or less. The ink jet recording apparatus according to claim 1, wherein a droplet dot is added. 9. The ink jet recording apparatus according to claim 1, wherein the image contour portion correcting means additionally arranges small droplet dots by hardware. 10. The ink jet recording apparatus according to claim 4, wherein the image contour portion correcting means additionally arranges the droplet dots by executing a program. 11. The inkjet storage device according to claim 10, further comprising a storage medium in which the program is stored.