JPH09290508A - Ink jet recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To diffuse the concentration unevenness generated at an interlace printing period and improve the image quality by superimposing a region to be printed at the primary scanning of specific times and a part of the region to be printed at the primary scanning at other specific times, and printing dots in the superimposed region at any of the specific times. SOLUTION: As the distance of a recording nozzle in the ancillary scanning direction of a recording nozzle is set D, by relatively moving at only (m+l/k) D or (m-1/k) D (m is an integer and m>=0, k is an integer and k>=2) in the ancillary direction and scanning at (k) times between the distance D, images are recorded through interlace printing with a recording dot concentration. At this time, the region to be printed at a primary scanning of N times (N is an integer of N>=1) and a part of the region to be printed at a primary scanning of (N+k) times are superimposed, and dots in the superimposed region are printed at any of N times and (N+k) times. As a result, concentration unevennesses generated at joint portions in a row of recording nozzles of the recording head are diffused with the result that its image quality is improved.

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, and in particular, it is possible to perform interlaced printing for recording an image with a recording dot density smaller than a recording nozzle interval of a recording head by performing main scanning a plurality of times. The present invention relates to an inkjet recording device.

[0002]

2. Description of the Related Art An ink jet recording apparatus has little vibration and noise at the time of recording and is easy to colorize. Therefore, it is used not only for a printer for outputting data of a digital processing device such as a computer but also for facsimile and copying. It is supposed to be.

As such an ink jet recording apparatus, for example, a recording head having a recording nozzle array composed of a plurality of recording nozzles arranged in a sub-scanning direction is moved in a main scanning direction and a recording medium (ink droplets are deposited). ) In a sub-scanning direction orthogonal to the main scanning direction, and ejecting ink droplets from a nozzle array of a recording head to a recording medium in accordance with a recording signal, thereby achieving high speed, high density,
Some are designed to perform high quality recording.

By the way, in such an ink jet recording apparatus, as described in, for example, Japanese Patent Publication No. 3-56186, main line feed is performed k times evenly between recording nozzle intervals D in the sub-scanning direction of the recording head. It is known that an interlaced printing method is adopted in which an image is printed at a printing dot density (resolution) D / k smaller than the printing nozzle interval by scanning.

[0005]

However, as described above, in the case of the interlaced printing system in which an image is recorded at a recording dot density smaller than the recording nozzle interval by performing main scanning of the recording head k times, For example, the moving amount (feed amount) of the recording medium in the sub-scanning direction changes depending on the movement accuracy in the sub-scanning direction, the thickness of the recording medium, the eccentricity of the platen, and the like. There is a problem that density unevenness occurs and image quality deteriorates.

The present invention has been made in view of the above points, and it is an object of the present invention to diffuse density unevenness that occurs when interlaced printing is performed and improve image quality.

[0007]

In order to solve the above-mentioned problems, an ink jet recording apparatus according to a first aspect of the present invention includes a recording head having a recording nozzle row composed of a plurality of recording nozzles arranged in the sub-scanning direction, and a recording medium. A means for moving in the sub-scanning direction, and when the recording nozzle spacing in the sub-scanning direction of the recording head is D, the recording head and the recording medium are (m + 1 / k) D in the sub-scanning direction, or ( m-1 /
k) D only (m is an integer, m ≧ 0, k is an integer, k ≧
2) In an inkjet recording apparatus capable of interlaced printing, in which an image is recorded at a recording dot density of D / k by performing relative movement and performing main scanning k times between the recording nozzle intervals D, the Nth time (N is An integer, N ≧ 1) The area to be printed at the time of main scanning and the part of the area to be printed at the time of (N + k) th main scanning are overlapped, and the dots in this overlapping area are at the Nth and (N + k) th times. It is configured to be printed on either.

An ink jet recording apparatus according to a second aspect is the ink jet recording apparatus according to the first aspect, wherein the recording nozzle rows are provided in a plurality of rows in the main scanning direction for each color, and the dots in the overlapping area are the Nth and (third) dots. (N + k) It is configured such that the print is made different for each color at any time.

According to a third aspect of the invention, there is provided an ink jet recording apparatus according to the first or second aspect, wherein:
The N-th or (N + k) -th printing of the dots in the overlapping area is determined based on a random number.

An ink jet recording apparatus according to a fourth aspect is the ink jet recording apparatus according to any one of the first to third aspects, wherein the number of recording nozzles in the overlapping area is changed according to the thickness of the recording medium.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, an outline of a mechanism of an ink jet recording apparatus to which the present invention is applied will be described with reference to FIG.

This ink jet recording apparatus is equipped with a carriage 3 slidably supported in the main scanning direction by a guide rod 1 and a guide plate 2 arranged in the main scanning direction. The carriage 3 has four heads HY, HM, HC, HB
Are mounted in the main scanning direction, and the carriage 3 (recording head 4) is moved in the main scanning direction by a main scanning motor (not shown) via a timing belt.
On the other hand, a platen 6 for transporting the sheet 5 as a recording medium in the sub-scanning direction is provided.
Is transported.

As shown in FIG. 2, the recording head 4 has a head HY having a recording nozzle array 11Y composed of a plurality of recording nozzles 11 for ejecting yellow (Y) ink, and a nozzle for ejecting magenta (M) ink. Each of four recording heads, a head HM having a row 11M, a head HC having a recording nozzle row 11C for ejecting cyan (C) ink, and a head HB having a nozzle row 11B for ejecting black (Bk) ink, are used for recording. Nozzle rows 11Y, 11M, 1
The carriage 3 is arranged in the main scanning direction so that the recording nozzles 1C and 11B are arranged in the sub-scanning direction.

Here, the heads HY, HM, HC, HB
As shown in FIG. 3, a nozzle plate 14 in which a plurality of recording nozzles 11 are formed is provided on the front surface of a liquid chamber forming member 13 that forms a liquid chamber 12, and energy such as a piezoelectric element (not shown) and a heater for generating bubbles is provided. By applying pressure to the ink in the liquid chamber 12 by an actuator as a generating means, the ink in the liquid chamber 12 flies as ink droplets 15 from the recording nozzles 11 of the nozzle plate 14 and adheres to the paper 5 as dots. . At this time, a desired image can be printed by selectively driving an actuator that applies pressure to each liquid chamber 12.

Next, an outline of the control unit of this ink jet recording apparatus will be described with reference to FIG. The control unit includes a microcomputer (hereinafter, referred to as a “CPU”) 21 that controls the entire recording apparatus, and four frames each corresponding to each of the heads HY, HM, HC, and HB of the recording head 4. Memory 22Y, 22M, 22C, 2
2B, line buffers 23Y, 23M, 23C, 23B
And head drivers 24Y, 24M, 24C, 24B
A reception buffer 25 for receiving print data transferred from the host, a color processing circuit 26 for performing processing such as decomposing the print data into necessary color data, and motor drivers 27 and 28. I have.

Then, the recording data received by the reception buffer 25 is processed by the color processing circuit 26 to generate print data of a desired color as the frame memories 22Y, 22M, 22C, 2 and 2.
2B. The frame memories 22Y, 22M,
One of the printing data of each color stored in the print data 22C and 22B.
The data to be printed in the main scan is transferred to the line buffer 23Y,
23M, 23C, and 23B, and the recording heads H from the line buffers 23Y, 23M, 23C, and 23B.
The data corresponding to the number of recording nozzles of Y, HM, HC, and HB are sequentially read, and the head drivers 24Y, 24M, 24
C, 24B. Thereby, the head driver 24
Y, 24M, 24C, and 24B drive the actuator elements of each of the heads HY, HM, HC, and HB according to the printing data, and eject the ink droplets of the assigned color from the nozzles of each of the heads.

In this case, since the arrangement direction of each head of the recording head 4 is the main scanning direction as described above, in order to make the ink droplets of each color land at the same printing dot position, the distance between the heads is Only the delay time obtained from the main scanning speed, for example, if the head HK is used as a reference, the head H
The drive timings of C, HM, and HY are sequentially delayed by the delay time. When printing black, only the head HB is used, so that such delay control is not performed.

On the other hand, the main scanning motor 29 is rotationally driven via the motor driver 27 to reciprocate the carriage 3 in the main scanning direction, and the motor driver 2
8, the sub-scanning motor 8 is driven to rotate and the platen 6 is rotated to feed the paper 5 in the sub-scanning direction.
A color image (including a black image) corresponding to the recording data can be printed thereon.

Next, the first embodiment of the present invention in the ink jet recording apparatus thus constructed will be described with reference to FIGS. In the above-described inkjet recording apparatus, the recording head 4 is configured by four heads, and each head has two nozzle rows.
In the first embodiment, for ease of understanding, 1
The description will be given with respect to one recording head having a row of nozzle rows.

First, referring to FIG. 5, when the recording nozzle interval of the recording head in the sub-scanning direction is D, the recording head 4
And the paper (recording medium) 5 in the sub-scanning direction (m + 1 /
k) D or (m-1 / k) D only (m is an integer, m ≧
0 and k are integers, and k ≧ 2) are relatively moved, and the interlace printing method for recording an image at a recording dot density of D / k by performing main scanning k between recording nozzle intervals D explain.

Here, as shown in FIG. 3A, the number of recording nozzles of the recording head 4 is set to 1 of the recording nozzles n1 to n10.
Letting 0 be a constant m = 3, k = 3, and the recording nozzle interval (interval of each recording nozzle) be D, the movement amount in the sub-scanning direction is (m
+ 1 / k) D. Then, during the first main scan, printing is performed using the print nozzles n7 to n10, and the print head 4 and the paper 5 are relatively moved by (m + 1 / k) D, that is, the paper 5 is moved in the sub-scanning direction in this example. After moving by (m + 1 / k) D, printing is performed using the recording nozzles n4 to n10 in the second main scanning, and the paper 5 is also moved in the sub scanning direction by (m + 1 / k).
/ K) After moving by D, printing is performed by using all the recording nozzles n1 to n10 at the time of the third main scanning, and thereafter all the recording nozzles n1 to n10 are similarly used to perform the fourth and subsequent main scanning. To print.

By doing so, the recording nozzle interval D
It is possible to perform recording with a recording dot density of D / k using the recording head of No. 1. In this case, if all the conditions such as the movement accuracy in the sub-scanning direction, the thickness management of the recording medium, the eccentricity of the platen, etc. are satisfied, FIG.
As shown in (1), an ideal printed dot pattern without density unevenness can be obtained.

However, in practice, it is difficult to adjust all the conditions such as the moving accuracy in the sub-scanning direction, the thickness control of the recording medium, the eccentricity of the platen, etc.
An error occurs in the amount of movement in the sub-scanning direction. That is, FIG.
As shown in FIG. 5A, when the movement amount in the sub-scanning direction (paper feed amount) becomes larger than the design value by an error ΔL with the same setting as shown in FIG. The pattern is as shown in FIG. 7B, and density unevenness occurs in the entire pattern.

Among the density unevenness, what is visually noticeable is a streak-shaped low density area (so-called "white area" generated at the joint between the end portions of the recording nozzle rows during the Nth and (N + k) th main scans. Streaks "). The reason why the white stripes occur is that the recording nozzle n1 is displaced from the normal position by (ΔL × k) in the (N + k) th main scan in FIG.

Therefore, in the ink jet recording apparatus according to the present invention, there are an area to be printed at the Nth (N is an integer, N ≧ 1) main scanning and an area to be printed at the (N + k) th main scanning. Overlapping a part of this, the dots in this overlapping area are N
It prints either the first time or the (N + k) th time.

For example, as shown in FIG. 7A, the number of recording nozzles of the recording head 4 is the same as that described above.
By setting the moving amount in the sub-scanning direction to (m + 1 / k) D with 10 as n10, constants m = 2, k = 3, and the recording nozzle interval D, printing is performed at the Nth time, for example, the first main scan. Area to be copied and (N + k) th time, eg (1 + 3) =
A part of the area to be printed at the time of the fourth main scanning is overlapped.
That is, the area printed by the recording nozzles n7 to n10 in the first main scan and the recording nozzles n1 to n in the fourth main scan.
Part of the area to be printed in 3 is overlapped. In this case, the number of recording nozzles in the overlapping area is three.

As a result, the dots printed by the recording nozzles n7 to n10 during the first (Nth) main scanning and the recording nozzles n1 to n3 during the fourth {(N + k) th main scanning.
As shown in FIG. 7B, since the dots printed in step 1 partially overlap with each other in the sub-scanning direction, the dots in this overlapping area are printed either during the first main scanning or during the fourth main scanning. Make a copy. As a result, the white stripes in the overlapping portion are diffused, and the density unevenness is reduced. It should be noted that the dots shown by broken lines in FIG. 7B are only shown by broken lines for the sake of explanation in order to clarify the dots in the overlapping area.

Therefore, when there is no error in the movement amount in the sub-scanning direction shown in FIG. 5B, the printing dot pattern printed by using all the recording nozzles, the superposition shown in FIG. 6B. A similar printing dot pattern when an error occurs in the movement amount in the sub-scanning direction without giving an area, the movement in the sub-scanning direction with an overlapping area as in the present invention shown in FIG. 7B. The density was measured with a microdensitometer for a similar printed dot pattern when an error occurred in the amount.
The measurement results are shown in FIGS.

As can be seen from the figure, when there is no error in the amount of movement in the sub-scanning direction, a substantially ideal image without density unevenness is formed as shown in FIG. On the other hand, when an error occurs in the amount of movement in the sub-scanning direction without providing the overlapping area, a white stripe occurs at the joint of the recording nozzle rows as shown in FIG. descend. On the other hand, when the overlapping area is provided as in the present invention, even when an error occurs in the moving amount in the sub-scanning direction, an image having no white stripes and almost ideal density unevenness is obtained. It is formed.

Thus, when the recording nozzle interval of the recording head in the sub-scanning direction is D, in the sub-scanning direction (m + 1 /
k) D or (m-1 / k) D only (m is an integer, m ≧
0 and k are integers, and k ≧ 2) are relatively moved, and the image is recorded at the recording dot density of D / k by performing main scanning k times between recording nozzle row intervals D, and the Nth time (N is an integer, N ≧ 1) The area to be printed during main scanning and a part of the area to be printed during (N + k) th main scanning are overlapped, and the dots in this overlapping area are set at Nth and (N + k) )
By performing the printing at any one of the times, it is possible to diffuse the density unevenness generated at the joint portion of the print nozzle row of the print head and improve the image quality.

Here, the case where the movement amount in the sub-scanning direction has an error ΔL larger than the specified value (design value) is described as an example, but the movement amount in the sub-scanning direction is the specified value. There may be a case where an error ΔL that is smaller than that of In this case, a streak-like high-density area will be generated,
As described above, the area to be printed during the N-th (N is an integer, N ≧ 1) main scan and a part of the area to be printed during the (N + k) -th main scan are overlapped to form a dot in the overlap area. Is printed in either the N-th or (N + k) -th printing, density unevenness is diffused, and an almost ideal image with less density unevenness can be formed.

Next, a second embodiment of the present invention will be described with reference to FIGS. 9 and 10. This embodiment relates to the case of printing a color image by superimposing a plurality of colors, and in this case, as described above, the movement accuracy in the sub-scanning direction,
If all the conditions such as the thickness control of the recording medium, the eccentricity of the platen, etc. are not met, not only density unevenness will occur, but also the density will be emphasized as the number of colors increases, and image deterioration will become remarkable. .

Therefore, for each color, N times (N is an integer,
The area to be printed in the main scanning of (N ≧ 1) and a part of the area to be printed in the (N + k) -th main scanning are overlapped, and this overlapped area is either the N-th or the (N + k) -th main scanning. Sometimes imprinted. FIG. 9 shows a print dot pattern in the overlapping area. In the figure (a), when the Nth printing and the (N + k) th printing are performed alternately for each dot, the (b) printing is performed in the reverse order of the (a) printing. In the case shown in FIG. 9C, the Nth printing and the (N + k) th printing are performed alternately every 2 dots. This is the case.

FIG. 10 shows the same density measurement result as described above. When printing is performed by using all the recording nozzles of the heads of each color without providing an overlapping region, the sub-scanning direction is shown. When there is an error in the movement amount of, the white line is generated at the joint portion of the recording nozzle row as shown in FIG. Also, Y, M, C,
When all of K are printed alternately dot by dot at the N-th time and the (N + k) -th time shown in FIG.
Although the image quality is improved as compared with the case (a), white stripes are slightly generated.

On the other hand, for K, the pattern of FIG. 14A, for Y the pattern of FIG. 14B, for M the pattern of FIG. 14C, and for C the pattern of FIG. When each is used, white stripes are eliminated as shown in FIG. 10 (c), and it is possible to record an image having substantially no density unevenness.

As described above, in the case of color printing, an area to be printed at the Nth (N is an integer, N ≧ 1) main scanning,
A part of the area to be printed in the (N + k) -th main scan is overlapped, and dots in this overlap area are printed differently for each color in either the N-th or (N + k) -th printing. When the number of colors increases, the stripe-shaped density unevenness generated at the seam at the end of the recording nozzle row, which is emphasized, is diffused, and a high-quality image without density unevenness can be printed.

Next, FIG. 11 shows the third embodiment of the present invention.
This will be described with reference to FIG. In the above-described first and second embodiments, the main scan for printing the dots in the overlapping area is regularly determined to be either the Nth time or the (N + k) th time, whereas in the third embodiment, the Nth time is determined. And (N + k) -th printing is decided based on a random number. An example of the printing dot pattern of the overlapping area in the case of irregularly deciding on the basis of random numbers in this manner (a)
~ (D).

In this way, by determining which of the Nth scanning and the (N + k) th main scanning the dots in the overlapping area are printed based on a random number, there is no regularity or bias, and the recording nozzle rows are connected. The streak-like density unevenness generated by the eyes is further diffused, and a high-quality image with less density unevenness can be obtained.

Also in the case of printing a color image, whether to print the dots in the overlapping area at the Nth time or at the (N + k) th time is determined for each color based on a random number. The streak-shaped density unevenness generated at the joints of the recording nozzle arrays is further diffused, and a high-quality image with less density unevenness can be obtained.

Next, a fourth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. This embodiment is shown in FIG.
As shown in FIG. 6, the number of dots in the overlapping area is set to 6 so that the printing is performed regularly at either the Nth time or the (N + k) th time, as in the first and second embodiments. FIG. 13 shows the same density measurement result as described above for the printed dot pattern using all the recording nozzles in this case.

Thus, the Nth time (N is an integer, N ≧
When the area to be printed during the main scanning in 1) and a part of the area to be printed during the (N + k) -th main scanning are overlapped, the number of dots in the overlapping area can be increased or decreased as appropriate, and the type of recording medium and recording An optimum number may be selected according to the number of recording nozzles, intervals, and the like of the apparatus.

Next, a fifth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. This embodiment is shown in FIG.
As shown in, the number of dots in the overlapping area is set to 6 and the Nth printing or the (N + k) th printing is determined based on a random number as in the third embodiment. FIG. 1 shows the same density measurement result as described above for the printed dot pattern using all the recording nozzles in this case.
It is shown in FIG.

Here, in the case of the density measurement result shown in FIG. 15 according to the regular pattern example shown in FIG. 13 described above, although the image has no density unevenness, a specific pattern is visually recognized in detail. can do. On the other hand, in the case of the density measurement result shown in FIG. 15 according to the irregular pattern example using random numbers shown in FIG. 14, there is no specific pattern, and a higher quality image can be obtained.

Thus, by using random numbers,
Even if the number of dots in the overlapping area is increased, an image with a desired image quality can be obtained. In the case of color printing, the density is emphasized, but a high-quality image can be formed in the same manner.

Next, a sixth embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG. In this embodiment, since the amount of movement in the sub-scanning direction changes according to the thickness of the recording medium, the number of dots in the overlapping area is varied according to the thickness of the recording medium. That is, as shown in FIG. 16, the recording head 4 is conveyed while the sheet 5 is in close contact with the platen 6.
When printing on the surface of the paper 5, the amount of movement on the surface of the paper 5 changes depending on the thickness of the paper 5. In particular, when thick paper or an OHP film is used, the diameter of the platen is increased by the thickness. And the amount of movement in the sub-scanning direction is larger than that of plain paper.

Therefore, for example, as shown in Table 1, when using special paper or plain paper having a thickness of less than 0.5 mm, the number of dots in the overlapping area is set to 3 and the thickness of the thick paper or OHP film is 0.5 mm or more. If the number of dots in the overlapping area is set to 4 when using, the number of dots in the overlapping area is changed according to the thickness of the recording medium, so that white stripes are diffused and high-quality images with no density unevenness are obtained. An image can be formed.

[0047]

[Table 1]

[0048]

As described above, according to the ink jet recording apparatus of the first aspect, when the recording nozzle interval in the sub scanning direction of the recording head is D, (m + 1) in the sub scanning direction.
/ K) D, or (m-1 / k) D only (m is an integer, m
≧ 0 and k are integers, and k ≧ 2) An image is recorded at a recording dot density of D / k by relatively moving the recording head and the recording medium and performing main scanning k times between recording nozzle row intervals D. Nth time (N is an integer, N ≧ 1) in case of interless printing
Area to be printed at the time of the main scanning and part of the area to be printed at the time of the (N + k) th main scanning are overlapped, and the dots in this overlapping area are printed at either the Nth time or the (N + k) th time. Therefore, it is possible to improve the image quality by diffusing streak-shaped density unevenness that occurs at the joints of the ends of the print recording nozzle rows.

According to the ink jet recording apparatus of the second aspect, in the ink jet recording apparatus of the first aspect,
Since there are a plurality of recording nozzle rows for each color in the main scanning direction, and the dots in the overlapping area are printed differently for each color at either the Nth or (N + k) th time, it is possible to enhance the density of multiple colors. It is possible to improve the image quality by diffusing the stripe-shaped density unevenness that occurs at the joints of the ends of the recording nozzle rows.

According to the ink jet recording apparatus of the third aspect, in the ink jet recording apparatus according to the first or second aspect, it is determined whether the dot in the overlapping area is printed N times or (N + k) times based on a random number. Since the determination is made, it is possible to further diffuse the stripe-shaped density unevenness that occurs at the joint between the end portions of the recording nozzle rows, and it is possible to further improve the image quality.

According to the ink jet recording apparatus of the fourth aspect, in the ink jet recording apparatus according to any one of the first to third aspects, the number of recording nozzles (the number of dots) in the overlapping area is set.
Was changed according to the thickness of the recording medium,
Regardless of the type of recording medium, it is possible to further diffuse the stripe-shaped density unevenness that occurs at the joints of the end portions of the recording nozzle rows, and it is possible to further improve the image quality.

[Brief description of drawings]

FIG. 1 is a perspective view of a main part showing an outline of a mechanism of an ink jet recording apparatus to which the present invention is applied.

FIG. 2 is a schematic perspective explanatory view showing an example of a recording head of the ink jet recording apparatus.

FIG. 3 is an enlarged sectional view of a main part of the recording head.

FIG. 4 is a block diagram of a control unit of the inkjet recording apparatus.

FIG. 5 is an explanatory diagram for explaining an interlaced printing method.

6 is an explanatory diagram illustrating a state where an error occurs in the interlaced printing of FIG.

FIG. 7 is an explanatory diagram for explaining the first embodiment of the present invention.

FIG. 8 is an explanatory diagram showing the density measurement result of the printed dot pattern used in the description of FIGS. 5 to 7;

FIG. 9 is an explanatory diagram of a dot pattern in an overlapping area used for explaining a second embodiment of the present invention.

FIG. 10 is an explanatory diagram showing a density measurement result of a printed dot pattern used in the description of the embodiment.

FIG. 11 is an explanatory diagram of a dot pattern in an overlapping area used for explaining a third embodiment of the present invention.

FIG. 12 is an explanatory diagram of a dot pattern in an overlapping area used for explaining a fourth embodiment of the present invention.

FIG. 13 is an explanatory diagram showing a density measurement result of a printed dot pattern used in the description of the embodiment.

FIG. 14 is an explanatory diagram of a dot pattern in an overlapping area used for explaining a fifth embodiment of the present invention.

FIG. 15 is an explanatory diagram showing a density measurement result of a printed dot pattern used for explaining the embodiment.

FIG. 16 is an enlarged explanatory view of a mechanism portion for explaining a sixth embodiment of the present invention.

[Explanation of Codes] 3 ... Carriage, 4 ... Recording head, 5 ... Paper (recording medium), 6 ... Platen, 7 ... Sub-scanning motor, 29 ... Main scanning motor.

Claims (4)

[Claims] 1. A recording nozzle in a sub-scanning direction of the recording head, comprising: a recording head having a recording nozzle array composed of a plurality of recording nozzles arranged in the sub-scanning direction; and a means for moving a recording medium in the sub-scanning direction. When the distance is D, the recording head and the recording medium are moved in the sub-scanning direction by (m + 1 /
k) D or (m-1 / k) D only (m is an integer, m ≧
0 and k are integers, and k ≧ 2) are relatively moved, and an interless printing capable of recording an image at a recording dot density of D / k by performing main scanning k times between the recording nozzle intervals D is performed. In the recording device, N times (N is an integer, N
.Gtoreq.1), the area to be printed at the time of main scanning and a part of the area to be printed at the time of (N + k) -th main scanning are overlapped, and the dots of this overlapping area are changed by either the N-th or (N + k) -th printing. An ink jet recording apparatus for printing. 2. The ink jet recording apparatus according to claim 1, wherein the recording nozzle row is provided in a plurality of rows for each color in the main scanning direction, and the dot in the overlapping area is either the Nth time or the (N + k) th time. An ink jet recording apparatus characterized by differently printing for each color. 3. The ink jet recording apparatus according to claim 1 or 2, wherein it is determined based on a random number whether to print the dots in the overlapping area at the Nth time or the (N + k) th time. Inkjet recording device. 4. The inkjet recording apparatus according to claim 1, wherein the number of recording nozzles in the overlapping area is changed according to the thickness of the recording medium.