JP2925357B2 - Ink jet recording method and apparatus - Google Patents

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 method and apparatus which form a clear image with excellent gradation by using an ink-jet recording head having a plurality of discharge ports (nozzles).

[0002]

2. Description of the Related Art An ink jet recording system is a system in which ink is ejected onto a recording medium in accordance with a recording signal to perform recording, and is widely used as a quiet recording system with a low running cost. By using a head in which a number of nozzles are formed in a straight line perpendicular to the direction of relative movement between the recording medium and the head, the width corresponding to the number of nozzles is recorded at one time in one relative scan between the head and the recording medium. And relatively high speed can be achieved.

When gradation is expressed by an ink-jet recording method, the size of a droplet to be ejected may be changed, but there is no practical method yet, and usually, a unit is obtained by pseudo halftone image processing. This is performed by controlling the number of ejected ink drops per area. In addition, the size of one ink droplet is reduced, and a plurality of ink droplets are ejected (landed) at substantially the same position to form one dot, and the number of shots (the number of impacts) is controlled to control the gradation. There is a so-called multi-droplet system for expressing. This method can perform gradation recording without lowering the resolution, and is particularly effective for ink-jet recording in which it is difficult to greatly change the size of each ink droplet.

[0004]

However, in the conventional multi-droplet method, one pixel is formed by a plurality of ink droplets ejected from one nozzle. However, there is a problem that a streak or density unevenness occurs in an image to be formed.

[0005] This problem becomes remarkable when the number of nozzles is increased to increase the width of recording by one relative scan between the head and the recording paper, as described above, in order to perform recording at high speed. As the recording width increases, the low frequency spatial frequency components of the density unevenness increase, and the unevenness becomes more conspicuous and the image quality deteriorates. When performing gradation expression, unevenness is particularly noticeable,
Density unevenness streaks can be recognized even when the discharge variation between nozzles is about several percent.

In order to avoid these problems, in the conventional multi-droplet system, the head must be manufactured very precisely in order to minimize the variation in the volume of ejected ink droplets between nozzles, resulting in a high cost. And the production yield is deteriorated. Also,
As a method of eliminating the density unevenness by software, a method of changing the number of ink droplets to be applied so as to cancel out the amount of ink droplets between nozzles by using image processing such as an error diffusion method is also effective. However, there is a problem that the cost of the system is increased by incorporating such image processing. Even if such an image processing method is used, if the variation in ink droplet volume between nozzles changes over time, it is necessary to readjust the number of ink droplets to be ejected, and there is a problem that maintenance is poor. ing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and provides an ink-jet recording method and apparatus capable of reducing the variation in ink droplet volume between nozzles and performing gradation expression in which streaking and unevenness are suppressed. Is what you do.

[0008]

SUMMARY OF THE INVENTION The present invention provides an ink jet recording method for recording a gradation image on a recording medium by ejecting substantially equal amounts of ink while main scanning a recording head having a plurality of nozzles. , The number of nozzles is n (an integer of n ≧ 2), the nozzle pitch is p (μm), the feed amount in the sub-scanning direction is s (μm), and the maximum ink ejection from one nozzle per one main scan for one pixel. The number is k (k
≧ 1) and the number of gradations of the gradation image is g (integer of g ≧ 3)
Where n / (s / p) ≧ 2 n / (s / p) × k = g−1.

According to the above configuration, m = n / (s / p)
In this case, one pixel has m different values due to m main scans.
It will be recorded by the nozzle. As a result, for example, when the variation between the nozzles of the ink droplet volume is normally distributed with the standard deviation σ, the variation between the ink volumes per pixel is reduced to σ / √m in order to form one pixel with different m nozzles. I do.

Further, the present invention uses an ink jet recording head having n (n ≧ 2) nozzles arranged at a pitch p (μm) to form one pixel as g−1 (g ≧ 3 integer). ), The ink can be formed with almost the same amount of ink,
In an ink jet recording method for expressing a gradation by changing the number of inks per pixel, a nozzle arrangement is made perpendicular to a main scanning relative speed direction between a recording medium and a recording head, and the nozzle arrangement is set for each relative scanning between the recording head and the recording medium. G-1 ink ejected from m different nozzles (n / (s / p) decimal truncated integers) by changing the relative position of the recording head and the recording medium by s (μm) in the nozzle array direction In the case where an arbitrary pixel is formed with t (t ≦ g−1 integer) inks according to the gradation information of each pixel, t
When ≧ m, ink is ejected from m different nozzles, and when t <m, ink is ejected from t different nozzles.

According to the above configuration, one pixel is composed of ink droplets ejected from a maximum of m different nozzles, the variation of the ink droplet volume among the nozzles is averaged, and the density unevenness line becomes less noticeable.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic perspective view of an ink jet recording apparatus applicable to the present invention.

In FIG. 1, reference numeral 1 denotes 128 nozzles (discharge ports) having a pitch of 63.5 μm, ie, 16 nozzles / mm (40
The recording head is provided at a density of 0 dpi), and each nozzle is provided with a heater (heating element) for generating discharge energy in a flow path communicating with the nozzle. The heater generates heat in response to an applied electric pulse, thereby causing film boiling in the ink, and causing bubbles in the ink.
The ink is ejected from the nozzles as the ink grows. In this example, the number of ejection cycles for each nozzle is 2K.
Hz, that is, the driving frequency of the heater is 2 KHz.

Reference numeral 4 denotes a carriage for mounting and moving the recording head 1, and the carriage 4 is moved while being guided by two guide shafts 5A and 5B which are slidably engaged at a part thereof. . Reference numeral 6 denotes an ink supply tube for supplying ink to the recording head 1 by an ink tank (not shown). Reference numeral 7 denotes a recording data from a control unit (not shown) to a head driving circuit provided in a part of the recording head 1. This is a flexible cable for transmitting a drive signal or a control signal based on (image information). The ink supply tube 6 and the flexible cable 7 are both formed of a flexible member so as to follow the movement of the carriage 4.

The carriage 4 includes guide shafts 5A, 5A,
B, and connected to a part of a belt (not shown) for moving the carriage 4, which is driven by a carriage motor (not shown), whereby the carriage 4 can be moved. .

3 has a guide shaft 5A, 5B
And 2 is a recording medium. The recording head 1 can perform recording by discharging ink to a portion facing the discharge port of the recording medium 2 as the carriage 4 moves.

A method for recording at 17 gradations using this apparatus will be described. That is, the number of ink droplets per pixel is 0 to
The recording is performed while being changed in the range of 16. 2 and 3 are conceptual diagrams for explaining the recording method of the present embodiment. Numeral 1 schematically shows a recording head, in which 128 nozzles are arranged in the vertical direction in the figure. For convenience, the nozzle numbers are designated as 1, 2, --- 128 from top to bottom in the figure.

When recording on a recording medium, first,
Printing is performed while moving the carriage at a speed of 31.75 mm / sec in the main scanning direction using only the nozzles 121 to 128. As a result, as shown in FIG. 3A, 1 to 8 pixels from above the recording medium are recorded with 0 or 1 ink droplets. Next, the recording medium is fed upward by 8 pixels (sub-scanning direction) (the head is relatively moved downward for convenience in the drawing). Recording is performed using nozzles 113 to 128. As a result, as shown in FIG. The nozzles of Nos. 113 to 120 were the last No. 121-
The portion of 1 to 8 pixels recorded by the nozzle of No. 128 is recorded. The nozzles 121 to 128 newly record 9 to 16 pixels. Therefore, 1 to 8 pixels are recorded with 0 to 2 ink droplets per pixel.

Next, the paper is again moved upward by 8 pixels, and 1
Recording is performed using nozzles 05 to 128. FIG.
As shown in (c) and (d), when such recording is sequentially repeated, when the 16th recording is completed, pixels 1 to 8 have been recorded with 0 to 16 drops of ink.
Gradation recording is obtained. If the recording is repeated in the same manner as above from the 17th time, an image of 17 gradations is obtained over the entire screen. At the lowermost end of the image, recording is sequentially stopped from the lower side by 8 nozzles for each scan to form an image end.

In the image obtained in this manner, for example, Focusing on pixel 1, this pixel is nozzle N
o. 1, 9, 17, 25, 33, 41, 49, 57, 6
5, 73, 81, 89, 97, 105, 113, 121
Since the ink droplets are formed from 0 to 1 ink droplets respectively ejected from a total of 16 nozzles (the order of recording is the reverse), variations in the ink droplet volume of each nozzle are averaged, and an image with no noticeable streaks or unevenness is obtained. Will be.

When various images were recorded using the above-described recording method, an extremely clear image without stripes and unevenness was obtained as compared with a conventional one in which one pixel was recorded with a plurality of ink droplets ejected from the same nozzle. Was done.

(Embodiment 2) Next, Embodiment 2 of the present invention will be described. FIG. 4 is a schematic perspective view of the ink jet recording apparatus applied to the second embodiment. 11 is the number of nozzles 51
2. An ink jet recording head using thermal energy having a density of 16 nozzles / mm. The nozzles are arranged in the horizontal direction in the figure and move on rails 14. A recording medium 12 is wound around a drum 13. The drum 13 is rotated by a motor (not shown).

A method of printing nine gradations using this apparatus will be described with reference to a pixel forming process diagram shown in FIG. First, the recording head 11 is positioned at the leftmost end in FIG. Using only the 64 nozzles 449 to 512, the recording is performed by rotating the drum 13 once (main scanning) (FIG. 5).
(A)). Next, the recording head 11 is moved to the right by 64 pixels (sub-scan), and the nozzle No. is moved. 385-512 of 12
Recording is performed by rotating the drum 13 once using eight nozzles (FIG. 5B). Thus, the recording head 11 is moved rightward by 6
Recording was performed by sequentially moving the drum 13 four times and then rotating the drum 13 once to record the entire surface.

As a result, for example, the first pixel is the nozzle N
o. 1, 65, 129, 193, 257, 321, 38
5, 449 will be formed using 8 nozzles,
Nine gradations can be recorded with 0 to 8 ink droplets.

When various images were recorded using the above-described recording method, extremely clear images were obtained without streaks or unevenness.

(Embodiment 3) Next, Embodiment 3 of the present invention will be described. In the present embodiment, recording of 17 gradations is performed, and the device configuration is the same as that of the second embodiment except for the head portion. The recording head 11 has 256 nozzles, and is configured to discharge smaller ink droplets than those in the second embodiment.

FIG. 6 shows a conceptual diagram of the recording method. FIG. 2 shows the recording medium 12 removed from the drum 13 and expanded in the vertical direction. Reference numeral 11a indicates a position where the recording head 11 is first located. In this embodiment, the drum 13
Rotates (main scanning), and at the same time, the recording head 11 also moves rightward (sub scanning). The moving speed is such that the recording head 11 moves 16 pixels to the right per one rotation of the drum. That is, the recording head 11 is continuously moved so as to be located at 1b at the beginning of the second rotation of the drum 13 and at 1c at the beginning of the third rotation. As a result, the image is spirally recorded on the drum. At this time, the same pixels are recorded by ink droplets ejected from different nozzles as in the first and second embodiments. FIG. 7 shows this pixel forming process.

When various images were recorded in this manner, clear images without streaks and unevenness were obtained.

In this embodiment, the image is slightly tilted.
The inclination is 16 pixels / image size. For example, when the image size is 200 mm, the inclination is 0.3 degrees, and there is no problem since it is completely invisible to human eyes. If the recording medium 12 is shifted in the opposite direction when the recording medium 12 is mounted on the drum 13, it is possible to obtain an image in which both sides cancel each other and have no inclination.

(Embodiment 4) A description will be given of an embodiment 4 in which the same apparatus (FIG. 1) and the same recording head 1 as those in the first embodiment are used, and 17 gradations are recorded by using a different recording method.

FIG. 8 shows an image forming process of this embodiment.

When recording on the recording medium 2, first, N
o. Carriage 4 using 16 nozzles 113 to 128
Is recorded while moving (main scanning). At this time, printing is performed using 0, 1, or 2 ink droplets per pixel according to the image density (FIG. 8A). Next, the recording medium 2 is moved upward by 16 pixels (sub-scan), 97-128
The recording is performed by using the nozzles. As a result, no. 97 ~
The nozzle of No. 112 is the last nozzle. No. 1 to 16 pixels recorded by nozzles 113 to 128 are recorded. 11
The nozzles 3 to 128 record 17 to 32 new pixels (FIG. 8B). Therefore, pixels 1 to 16 are recorded with 0 to 4 ink droplets per pixel.

Next, the recording medium 2 is sent upward by 16 pixels again. Recording is performed using nozzles 81 to 128 (FIG. 8C). When such recording is repeated sequentially, 8
When the first recording is completed, pixels 1 to 16 are 0 to 16
This means that recording was performed with ink droplets, and recording of 17 gradations was obtained. When the recording is repeated in the same manner as above from the ninth time onward,
An image of 17 gradations can be obtained over the entire screen.

When various images were recorded by using the above recording method, extremely clear images were obtained without stripes and unevenness.

In this embodiment, the number of ink droplets recorded per pixel per scan is 0, 1, or 2.
This may be 3 or more.

(Embodiment 5) A description will be given of an embodiment 5 in which four gradations are printed by using an apparatus different from the embodiment 3 only in the recording head 11. The recording head 11 is configured to discharge larger ink droplets than those of the second embodiment with 129 nozzles.

FIG. 9 shows an image forming process of this embodiment.

In this embodiment, the movement of the drum 13 (main scanning)
The speed is such that the recording head 11 moves to the right by 43 pixels (sub-scan) per rotation of the drum. As a result, the image is spirally recorded on the drum 13 as in the third embodiment. At this time, the same pixel is recorded by ink droplets ejected from three different nozzles.

When various images were recorded in this manner, clear images without streaks and unevenness were obtained.

In this embodiment, the image is tilted in the same manner as in the third embodiment. The tilt is 43 pixels / image size, which is almost invisible to the human eye, and may be used as it is. It is also possible to obtain an image having no inclination by displacing it in the opposite direction when attaching it to the camera.

Here, the recording method of each embodiment described above is shown in FIG. At this time, the number of nozzles is n, the value obtained by converting the feed amount in the sub-scanning direction into the number of nozzles is s, the maximum number of ink droplets (droplets) per one pixel per scan is k, and the number of gradations is g. If m = n / s, each embodiment satisfies m ≧ 3, and one pixel is recorded by m different nozzles by m main scans. As a result, for example, when the variation between the nozzles of the ink droplet volume is normally distributed with the standard deviation σ, the variation between the ink volumes per pixel is reduced to σ / √m in order to form one pixel with different m nozzles. I do. Ink capacity variations between pixels are recognized as variations in pixel density, but pixel density variations do not need to be zero in order for an image to be clearly visible. It becomes easy to obtain a clear image with a simple system configuration as compared with the example. The value of m is desirably as large as possible in order to reduce the variation between pixels. When m is 3 or more as in each of the above embodiments, extremely clear pixels can be obtained. According to the study by the present inventors, a sufficiently clear image can be obtained even when m = 2 as compared with the conventional recording method.

(Embodiment 6) Next, Embodiment 6 of the present invention will be described. In this embodiment, the same apparatus (FIG. 1) as in the first embodiment is used, and recording of 17 gradations is performed using a different recording method. Here, the maximum number of ink droplets (k) per one pixel per scan is 4, and the number of scans (m) for forming one pixel is 4 (see FIG. 10).

In this embodiment, when the maximum number of ink droplets (k) per one pixel scan is 2 or more, the ink droplets ejected from the nozzles are evenly distributed to each nozzle. This is to prevent the discharge from being concentrated.

When recording on the recording medium 2, first, the first
In the second scan, N out of all n (n = 128) nozzles
o. Recording is performed while moving (main scanning) the carriage 4 at a speed of 31.75 mm / sec using s (s = 32) nozzles of 97 to 128. At this time, according to the value of the gradation information Kx, y (0 to 16) for each pixel, A1 (Kx, y / n /
s (decimal point of s). Then, the gradation information Kx, y is represented by K1x, y (K1x, y = Kx,
y-A1). Assuming that the gradation information Kx, y is 13, A1 becomes 4 and K1x, y becomes 9.

Next, in the second scan, the recording paper 2 is
The paper is transported (sub-scanning) upward by the amount of the nozzle, 65-128
Carriage 4.31.75 using 2 * s nozzles
Recording is performed while moving at a speed of mm / sec. At that time, N
o. Nozzles 97 to 128 perform the above-described processing according to the new gradation information Kx, y. The s nozzles of 65 to 96 are the gradation information K processed in the previous scan of the print head 1.
In accordance with 1x and y, A2 (K1x, y / (n / s-1) rounded-up integer) ink droplets are ejected at the corresponding pixel position (x, y) on the recording medium 2. Then, the gradation information K1x, y is converted into K2x, y (K2x, y = K1x, y
-A2). In the previous example, A1 is 4, K2
x and y are 5.

Next, in the third scan, the recording medium 2 is conveyed in advance upward by s nozzles. 3 * of 33-128
The carriage 4 is moved to 31.75 mm /
Recording is performed while moving at a speed of seconds. At that time, No. 9
The nozzles No. 7 to 128 perform the above-described processing according to the new gradation information Kx, y. The s nozzles of 65 to 96 perform the above-described processing according to the gradation information K1x, y processed in the previous main scan. No. According to the gradation information K2x, y processed in the previous main scan, the s nozzles 33 to 64 are A3 nozzles (K2) at the corresponding pixel positions (x, y) on the recording medium 2.
Ink droplets of x, y / (n / s-2) are rounded up. Then, the gradation information K2x, y is represented by K3x,
Replace with y (K3x, y = K2x, y-A3). In the above example, A3 is 4 and K3x, y is 1.

Next, in the fourth scan, the recording medium 2 is conveyed in advance upward by s nozzles. Printing is performed while moving the carriage 4 at a speed of 31.75 mm / sec using all the nozzles 1 to 128. At that time, No. 97-128
Nozzles perform the above-described processing according to the new gradation information Kx, y, The s nozzles Nos. 65 to 96 perform the above-described processing according to the gradation information K1x and y processed in the previous main scan. The s nozzles 33 to 64 perform the above-described processing according to the gradation information K2x, y processed in the previous main scan. No. According to the gradation information K3x, y processed in the previous main scan, the s nozzles 1 to 32 have A4 (K3x, y / (n / s) at the corresponding pixel position (x, y) on the recording paper.
-3) = Ink droplets of K3x, y) are ejected. Here, A4 is 1.

Thereafter, the processing performed in the fourth scan is sequentially repeated to achieve the entire recording on the recording medium 2. As a result, the gradation information K is stored at the pixel position (x, y) on the recording medium 2.
Kx, y ink drops equal to x, y are ejected.
The image obtained in this manner has gradation information Kx,
When y is 2 or more, 2 or more, and at most n / s (here,
Since the ink droplets are formed by the different nozzles in 4), variations in the ink droplet volume of each nozzle are averaged, and an image with less noticeable unevenness can be obtained. In the above, 0-1
FIG. 11 shows the numbers A1 to A4 of ink droplets ejected in each scan for six pieces of gradation information K.

Next, FIG. 1 shows a control configuration applied to the present invention.
This will be described with reference to FIG. In the figure, image information from a host computer 101 is transmitted to a main controller 10.
2 is temporarily stored in the frame memory 103. The main controller 102 processes the image information and converts it into a gradation signal according to the system (printing apparatus) to be adopted. For example, in the first embodiment, image information having a value of 0 to 255 is converted into a 17-gradation signal of 0 to 16.

The gray scale signal is given to the driver controller 104, and the driver controller 104 distributes the gray scale signal to a plurality of scans and supplies it to the head driver 105 as a recording signal. The head driver 105 drives the recording head 106 according to the supplied recording signal, and ejects ink droplets. The motor drivers 107, 10
Reference numeral 8 drives the carriage feed motor 109 and the paper feed motor 110, respectively.

The present invention can be applied to color printing, and can be realized by having a plurality of printing heads in each of the above embodiments.

In the above-described embodiment, the present invention has been described in connection with the recording method in which ink droplets are ejected by heating the ink by a film heating element in the recording head. The present invention is also effective in a so-called piezo jet recording method.

The present invention provides an excellent effect particularly in a recording head and a recording apparatus of a type in which ink is ejected by utilizing thermal energy among ink jet recording methods.

The typical configuration and principle are described in, for example, US Pat. Nos. 4,723,129 and 4,740.
It is preferable to use the basic principle disclosed in the specification of Japanese Patent No. 796. This method can be applied to both the so-called on-demand type and the continuous type. However, recording is performed on a sheet holding a liquid (ink) or an electrothermal converter arranged corresponding to a liquid path. Applying at least one drive signal corresponding to the information and providing a rapid temperature rise above nucleate boiling causes the electrothermal transducer to generate thermal energy, causing the heat-acting surface of the recording head to film boil, As a result, air bubbles in the liquid (ink) can be formed in one-to-one correspondence with the drive signal, which is effective. By discharging the liquid (ink) through the discharge opening by the growth and contraction of the bubble, at least one droplet is formed. When the drive signal is formed into a pulse shape, the growth and shrinkage of the bubble are performed immediately and appropriately, so that the ejection of a liquid (ink) having particularly excellent responsiveness can be achieved, which is more preferable. As the pulse-shaped drive signal, US Pat.
Nos. 59 and 4,345,262 are suitable. If the conditions described in U.S. Pat. No. 4,313,124 relating to the temperature rise rate of the heat acting surface are adopted, more excellent recording can be performed.

[0056]

As described above, according to the present invention, pixels having two or more pieces of gradation information are recorded by a plurality of different nozzles. Therefore, variations in ink droplet volume between nozzles are averaged, and sharpness with less density unevenness is observed. It is possible to obtain a perfect image.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing an inkjet recording apparatus to which the present invention can be applied.

FIG. 2 is a diagram for explaining a recording operation according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a pixel forming process according to the first embodiment.

FIG. 4 is a schematic perspective view showing an ink jet recording apparatus used in a second embodiment.

FIG. 5 is a diagram illustrating a pixel forming process according to a second embodiment.

FIG. 6 is a diagram for explaining a recording operation according to a third embodiment.

FIG. 7 is a diagram illustrating a pixel forming process according to a third embodiment.

FIG. 8 is a diagram illustrating a pixel forming process according to a fourth embodiment.

FIG. 9 is a diagram illustrating a pixel forming process according to a fifth embodiment.

FIG. 10 is a diagram illustrating a recording method according to each embodiment of the present invention.

FIG. 11 is a table showing the number of ink droplets ejected in each scan according to the sixth embodiment.

FIG. 12 is a block diagram showing a control configuration to which the present invention can be applied.

[Explanation of symbols]

 1,11 recording head 2,12 recording medium 3,13 drum

Claims (9)

(57) [Claims] 1. A method of ejecting substantially equal amounts of ink while main scanning a recording head having a plurality of nozzles,
In the ink jet recording method for recording a gradation image on a recording medium, the number of nozzles is n (n is an integer of 2 or more), and the nozzle pitch is p (μ).
m), the feed amount in the sub-scanning direction is s (μm), the maximum number of ink ejections from one nozzle per one main scan per pixel is k (an integer of k ≧ 1), and the number of gradations of the gradation image is g (g ≧ 3
Where n / (s / p) ≧ 2 n / (s / p) × k = g−1. 2. An n number (n) arrayed at a pitch p (μm)
By using an ink jet recording head having nozzles of ≧ 2), one pixel can be formed with g−1 (g ≧ 3 integers) of substantially equal amounts of ink by changing the number of inks per pixel. In the ink jet recording method for expressing gradation, a nozzle arrangement is made perpendicular to a main scanning relative speed direction between a recording medium and a recording head, and s (μm) is set in a nozzle arrangement direction for each relative scanning between the recording head and the recording medium. By changing the relative position between the recording head and the recording medium, m (n / (s /
p) It can be formed with g-1 inks ejected from different nozzles with different decimal points, and t pixels (t ≦ g−) according to the gradation information of each pixel.
In the case of forming with ink of (integer of 1), when t ≧ m, m
An ink jet recording method, wherein the ink is ejected from different nozzles, and when t <m, the ink is ejected from t different nozzles. 3. An ink jet recording method for recording a gradation image on a recording medium by discharging a substantially equal amount of ink while relatively scanning a recording head having a plurality of discharge ports in a main scanning direction with respect to the recording medium. In the case where one pixel is formed by a plurality of inks corresponding to gradation information, the one pixel is formed by a plurality of inks ejected from different ejection ports in a plurality of main scans. 4. A gradation image is formed on a recording medium by discharging a substantially equal amount of ink while relatively performing main scanning on a recording medium having a plurality of discharge ports arranged in a predetermined width. In the ink jet recording method for recording, a main scanning step of ejecting a number of inks according to gradation information from a certain ejection port to land on one pixel area while main scanning the recording head; A sub-scanning step of relatively sub-scanning the recording medium by an amount less than the predetermined width of the recording head; and performing main scanning of the recording head while discharging a number of inks according to gradation information from another ejection port. A main scanning step of discharging and landing on the one pixel area. 5. The ink jet recording method according to claim 4, further comprising a repeating step of repeating the sub-scanning step and the main scanning step of discharging ink from the other discharge port. 6. A print head having n (an integer of n ≧ 2) ejection ports arranged at a pitch p (μm) and having a predetermined width is substantially equal in amount while being main-scanned relative to a print medium. By discharging the ink, the gradation number g (g ≧ g) is printed on the recording medium.
3) In the ink jet recording method for recording a gradation image, the main scanning of the recording head is performed, and an ink of k (an integer of k ≧ 1) or less corresponding to the gradation information is ejected from a certain ejection port. A main scanning step of landing on a pixel area; a sub-scanning step of sub-scanning the recording head relative to a recording medium by an amount s (μm) less than the predetermined width of the recording head; A main scanning step of ejecting ink of k or less according to the gradation information from another ejection port to land on the one pixel area while scanning, and a sub-scanning step and ejecting ink from the other ejection port. A repetition step of repeating the main scanning step at least (g−1) / k−1 times. 7. The ink-jet recording apparatus according to claim 1, wherein the recording head causes a state change in the ink by thermal energy, and discharges the ink from the nozzle based on the state change. Recording method. 8. An ink jet recording apparatus for recording a gradation image on a recording medium by ejecting substantially equal amounts of ink while main scanning a recording head having a plurality of nozzles arranged in a predetermined width. Scanning control means for causing the recording head to perform main scanning on the recording medium a plurality of times through a relative sub-scanning of the recording head with respect to the recording medium by an amount less than the width; An ink jet recording apparatus comprising: a drive control unit that drives the recording head to land ink of a number corresponding to gradation information ejected from different nozzles to one pixel area during the main scanning period. . 9. The ink jet recording apparatus according to claim 8, wherein the recording head causes a state change in the ink by thermal energy, and discharges the ink from the nozzle based on the state change.