JP2003118150A - Ink-jet recording head and ink-jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink-jet recording head and an ink-jet recorder carrying it wherein variation in color tone between an outward passage and an inward passage is not recognized even when bi-directional printing is executed and a high speed and high quality printing can be executed, and a complex control means is not necessary. SOLUTION: There is disclosed a color ink-jet recording head wherein nozzle groups each consisting of a plurality of nozzles arranged in a sub-scanning direction are arranged in a main scanning direction and one pixel is recorded by ink drops ejected on a recording medium from one or more nozzles. The nozzles are arranged such that only a part of ink dots formed by the ink drops forming one pixel ejected from different nozzles are overlapped with each other. Namely, when the nozzle position determined such that arrival central positions of ink dots forming one pixel are approximately the same is made to be a reference position of each nozzle, at least one nozzle is positioned to be shifted from the reference position.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inkjet recording apparatus, and more particularly to a color inkjet recording apparatus for forming a color image by bidirectional printing and a recording head used for the same.

[0002]

2. Description of the Related Art In recent years, there has been an ink jet recording apparatus for forming a color image using inks of a plurality of colors. The recording head of the inkjet recording apparatus has a plurality of nozzle groups arranged in the main scanning direction. The nozzle group is composed of one or a plurality of nozzles, and each nozzle group is set to eject an ink different from the ink ejected by at least one other nozzle group. Generally, it is assigned to eject ink of different colors such as cyan and magenta.
When the recording head is mounted on a carriage and reciprocally moved in the main scanning direction, minute ink droplets are ejected from a predetermined nozzle at a predetermined timing to form pixels on a recording material to record a color image. To do.

Ink jet recording apparatuses are required to have high image quality and high-speed printability. As a method for realizing high-speed printability (high-speed recordability) of an inkjet recording device,
A bidirectional printing method has been proposed. The bidirectional printing (bidirectional printing) system is a system in which recording is performed by ejecting ink not only when the carriage is moving forward but also when it is moving backward. However, it is known that it is difficult to achieve high image quality when this method is adopted.

In the bidirectional printing method, even when pixels of the same color are formed, the ink landing order is reversed between the forward movement and the backward movement, and the pixels created during the forward movement and the backward movement The tint differs from the created pixel. Therefore, the image quality is inferior to that of the system in which pixels are formed and an image is recorded only when the carriage moves forward.

For example, an ink jet recording apparatus in which a blue pixel is formed by landing cyan and magenta ink on the same pixel is taken as an example. When the apparatus is configured such that the ink is deposited on the recording material in the order of cyan → magenta during the forward movement, the ink is deposited on the recording material in the order of magenta → cyan during the double movement. That is, the ink is landed on the recording material in a different (reverse) order between the forward movement and the backward movement. Usually, the ink droplets that land later are not sufficiently fixed at the landing positions on the recording material because the ink droplets that land first impede their penetration into the recording material. That is, the image is fixed on the inside of the recording material (behind the ink droplet landing surface (front surface)) with respect to the ink dot formed by the ink droplet that has landed first. As a result, the ink dots formed by the ink droplets that have landed on the recording material first have a larger area on the surface of the recording material than the ink dots that have been formed by the ink droplets that have landed later. Therefore, in the case of the present example, the formed pixels are blue with strong cyan during forward movement and blue with strong magenta during double movement.

As described above, the ink jet recording apparatus is
When bi-directional printing is performed and high-speed printing is performed, even pixels of the same color that have different shades appear in a predetermined cycle (every approximately the same length as the width of the nozzle group in the multiple scanning direction). Therefore, it is extremely difficult to obtain a high quality image.

As a method for solving such a problem, for example, Japanese Patent Laid-Open No. 8-295034 discloses a color ink jet recording head in which two sets of nozzles are symmetrically arranged.
Japanese Unexamined Patent Publication No. 5-155039 proposes a recording head that improves instability in color tone by rotating the recording head to perform recording. Japanese Unexamined Patent Publication No. 9-193417 proposes an inkjet recording head in which nozzle groups are arranged so as to be displaced in the sub-scanning direction by a pitch determined by the recording dot pitch and the number of color inks. Also,
Japanese Patent Application Laid-Open No. 11-207999 discloses a recording head in which, when a plurality of colors of ink are applied, the amount of ejected ink applied later is smaller than that of the ink applied first. A recording apparatus has been proposed which eliminates color unevenness by controlling the feeding in the sub-scanning direction and the dot formation in the main scanning direction.

[0008]

However, the above-mentioned prior art cannot be said to be compatible with high image quality and high-speed printability for the following reasons.

The ink jet recording head described in JP-A-8-295034 requires two groups of nozzles for each color in the main scanning direction. The recording head described in Japanese Patent Laid-Open No. 5-155039 requires a mechanism for rotating the head. Therefore, these recording heads cannot be said to have a structure suitable for miniaturization. In other words, since the recording head has to be increased in size, not only does the size of the device increase in cost, but also the variation in the ejection direction of each nozzle increases, so it is difficult to achieve high image quality. is there. When forming one pixel with a plurality of colors, the ink jet recording head described in JP-A-9-193417 forms one pixel by several operations in the main scanning and sub-scanning directions. Therefore, there is a problem that the image quality is easily affected by the control accuracy in the sub-scanning direction in addition to the above-described nozzle formation accuracy. That is, it can be said that it is extremely difficult to achieve both high-speed printability and high image quality using this technique. Also,
JP-A-9-193417, JP-A-11-2079
In the ink jet recording head or the ink jet recording apparatus described in Japanese Patent Laid-Open No. 99 and Japanese Patent Laid-Open No. 11-254712, it is necessary to newly establish control for pixel formation, and the control becomes complicated. In reality, it is extremely difficult to achieve high image quality.

The present invention has been made in view of the above problems, and in an ink jet recording apparatus for forming a color image by bidirectional printing, it eliminates the difference in tint between forward movement and backward movement, and at high speed. A first object of the present invention is to provide an inkjet recording apparatus capable of high-quality recording and a recording head used for the same. Further, another object of the present invention is to provide a color ink jet recording head having little difference in color tone between forward movement and double movement, without requiring complicated control,
This is achieved by a structure that can be downsized.

[0011]

In order to achieve the above object, an ink jet recording head according to the present invention is provided with a plurality of nozzle groups, each of which is composed of a plurality of nozzles arranged in the sub-scanning direction, arranged in the main scanning direction. A color inkjet recording head for recording one pixel with ink dots ejected from one or a plurality of nozzles onto a recording material, wherein at least one nozzle is an ink formed by an ink droplet ejected from the nozzle. The dots are arranged so as to partially overlap with the ink dots formed by the ink droplets ejected from the other nozzles forming the same pixel. That is, at least one or more nozzles are arranged such that the landing center position of the ink droplets ejected from the nozzle is displaced from the landing center position of the ink ejected from the other nozzles forming the same pixel. It As a result, ink droplets ejected from different nozzles, which form one pixel, are less likely to interfere with permeation, so the change in tint caused by the difference in ink landing order during bidirectional printing is greatly reduced. be able to. Further, since the structure is relatively simple, the recording head is not upsized and further complicated control is not required.

The nozzles to be displaced may be a nozzle unit or a nozzle group composed of a plurality of nozzles. The nozzle groups corresponding to one ink may be displaced, or the nozzle groups corresponding to a plurality of inks may be displaced. The displacement direction may be either the main scanning direction or the sub scanning direction, may be displaced simultaneously in the main scanning direction and the sub scanning direction, or may be different for each nozzle. The amount of shifting may be such that the maximum distance between the landing center positions of ink droplets ejected from different nozzles that form the same pixel is 1/5 or more and 4/5 or less of the length corresponding to the printing resolution. It is preferable that the length is 1/3 or more and 2/3 or less of the length corresponding to the resolution. Furthermore, it is more preferable that the length is approximately 1/2 of the length corresponding to the print resolution. The amount of shift may be the same for the nozzle groups, or may be different for each nozzle. The color and combination of the displaced nozzles are not particularly limited, and can be appropriately selected according to the number and properties of the ink used. However, it is preferable that the center positions of the cyan and magenta inks are arranged so as not to be substantially the same. More preferably, the nozzles are preferably arranged such that the center position of the magenta ink landing is offset from the center position of the other ink landing.

When the arrangement position is shifted in units of nozzles, the sub-scanning of the product of the number of nozzles that are not displaced and the nozzle interval, that is, an image formed by ink dots formed by landing ink droplets at the landing center position at substantially the same position The nozzles are arranged so that the length in the direction is within a period in which no change in color appears visually, generally within 300 μm.

The arrangement of the nozzles of the recording head is not particularly limited, and a nozzle group is formed by arranging a plurality of nozzle rows in which a plurality of nozzles corresponding to one ink color are arranged in the sub-scanning direction. Alternatively, a structure in which a plurality of the nozzle groups are arranged in the main scanning direction may be used. For example, a structure may be adopted in which a plurality of nozzle groups in which nozzles corresponding to one ink color are arranged in a matrix of a plurality of rows × a plurality of columns are arranged in the main scanning direction. Moreover, different ink colors may be mixed in such a nozzle group.

By mounting the recording head on an ink jet recording apparatus, a desired ink jet recording apparatus is realized.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an ink jet recording apparatus and an ink jet recording head according to the present invention will be described in detail below with reference to the drawings.

In the ink jet recording head according to the present embodiment, a plurality of nozzle groups including one or a plurality of nozzles arranged in the sub scanning direction are arranged in the main scanning direction, and at least one of the one or a plurality of nozzle groups is arranged. It is applied to an inkjet recording head that records one pixel by ejecting ink droplets from one nozzle to a predetermined position on a recording material. As such a recording head, for example, cyan, magenta, yellow, and black inks can be ejected, and one or a plurality of these ink droplets are ejected to form an ink dot on a recording material and eject the ink. There are some which form pixels of mixed colors. The nozzles forming at least one nozzle group have at least one of the other nozzle groups when at least one nozzle group ejects ink droplets from at least one nozzle to a predetermined position on the recording material to form a pixel. It is arranged at a position where the ink droplets land at a position different from the landing position of the ink droplets ejected from the one nozzle. Ink drops
It is landed at a position different from the landing position of the other at least one ink droplet. Therefore, the ink dots formed by the ink droplets on the recording material are formed so as not to at least partially overlap the ink dots formed by the at least one other ink droplet. As a result, the difference in color between the forward movement and the backward movement during bidirectional printing can be extremely reduced. In the specification of the present application, a pixel is a “pixel” on a recording material formed of one or a plurality of ink dots corresponding to one pixel of input image data. That is, the head according to the present invention, by one or a plurality of ink dots,
A recording pixel corresponding to one pixel of input image data is recorded on the recording material.

In the above recording head, when all the nozzle groups discharge ink droplets from at least one nozzle to a predetermined position on the recording material to form a pixel, the landing center position of each ink droplet is substantially the same. With respect to the reference position of each nozzle, which is the same position as each nozzle, the at least one nozzle group has a configuration in which one or a plurality of nozzles are arranged so as to be displaced from the reference position. It can also be realized. When the ink droplet ejection directions of all the nozzles are the same, the reference position of each nozzle for forming the same pixel is the position (height) in the sub-scanning direction on the surface of the print head on which the nozzle (nozzle group) is provided. Are the same. By arranging nozzles at the reference position, moving the recording head in the main scanning direction, and ejecting ink from each nozzle at a predetermined timing, each nozzle can form an ink dot at the same location on the recording material. . Therefore, if one or a plurality of nozzles for forming the same pixel are arranged so as to be displaced from the reference position, the ink dots can be formed as described above. In other words, the reference position is the same among the nozzles for forming the same pixel.
It can also be said to be the position of a nozzle for forming an ink dot at the same position as this reference nozzle when one nozzle is used as a reference. It should be noted that the nozzles arranged so as to be displaced from the reference position may be arranged so as to be displaced from the reference position in the main scanning direction and / or the sub scanning direction. Further, the nozzles forming at least one nozzle group may be arranged so as to be displaced in the same direction and the same length with respect to the reference position. Alternatively, the nozzles arranged substantially at the same position as the reference position and the nozzles arranged offset may be provided alternately in the sub-scanning direction. The reference position may be set to eject a single color ink from a nozzle group having nozzles that are displaced from the reference position.

The inventor of the present invention composes one pixel.
Of the distances between the landing center positions of the ink droplets ejected from different nozzles, the maximum distance is 4/5 or less, preferably 2/3 or less, preferably 1/2 of the length corresponding to the printing resolution.
It has been found that it is preferable to arrange the nozzles as follows.

Further, it is preferable that the nozzles are arranged so that the landing center positions of at least the cyan and magenta ink droplets are not substantially the same. The mixed colors of cyan ink dots and magenta ink dots have extremely different tints when the ink droplet landing order (ink dot formation order) is different. This tendency is stronger than in the case of a mixed color between other ink dots (cyan ink dots and non-magenta ink dots, magenta ink dots and non-cyan ink dots). Therefore, by making both ink dots partially overlap, it is possible to reduce the difference in tint between pixels having different ink droplet landing orders. Further, the nozzles may be arranged so that at least the landing center position of the magenta ink droplet does not become substantially the same as the landing center position of the other ink droplets. Compared to the mixed color of ink dots other than magenta, the mixed color of magenta ink dots and other ink dots is the tint of the pixels created during the forward and backward movements of bidirectional printing. There is a strong difference.
Therefore, if the magenta ink dots and other ink dots are prevented from overlapping, the difference in tint between the pixels created during the forward movement and the pixels created during the backward movement, which is a problem during bidirectional printing, will be extremely small. Can be made smaller.

Further, the maximum distance between the landing center positions of the ink droplets forming adjacent pixels ejected from the nozzles corresponding to the same color is the maximum of the ink dots formed by the ink droplets ejected from one nozzle. It is preferably smaller than the diameter.

Further, the center distance of the pixels formed in the same ink droplet landing order in the sub-scanning direction is a distance within a range in which the user using the obtained image cannot confirm the difference in tint, preferably 300 μm. The nozzles may be arranged as follows. If a predetermined number (predetermined distance) of pixels formed in the same ink droplet landing order successively appear in the sub-scanning direction,
This is because human beings can confirm the difference in tint due to the difference in the ink droplet landing order between the pixel created during the forward movement of bidirectional printing and the pixel during the backward movement.

If nozzle groups having ink ejection nozzles corresponding to colors other than black are arranged at both ends of the recording head in the main scanning direction, a high quality color image can be obtained. In particular, the nozzle groups arranged at both ends of the recording head in the main scanning direction are arranged so that the center positions of the ink droplets ejected from the nozzles forming each nozzle group are substantially the same. If provided, a very high quality color image can be obtained.

The nozzles in the nozzle group may be arranged in a matrix. The matrix-shaped nozzle group means, for example, a nozzle group as shown in FIG. This nozzle group has 8 in the main scanning direction and 8 in the sub scanning direction.
If the position in the main scanning direction is ignored (projecting in the main scanning direction), 64 nozzles are provided in the sub scanning direction. That is, when the recording head moved in the main scanning direction is controlled to eject ink from a predetermined nozzle at a predetermined timing, the ink is actually ejected from 64 nozzles.

The ink jet recording apparatus according to the present embodiment is characterized by including any one of the ink jet recording heads described above. The details will be described below.

FIGS. 1 and 2 are diagrams showing an example of the construction of an ink jet recording apparatus and an ink jet recording head according to the present invention. In FIG. 1, the inkjet recording apparatus has at least a recording head 11, an ink tank 12, a carriage 13, a belt 14, a carriage guide shaft 15, and a feed roller 17. Carriage 13
Is mounted with a recording head 11 and an ink tank 12, and moves along a carriage guide shaft 14. The belt 14 is arranged on the carriage guide shaft 14 in a substantially parallel direction.
The belt 14 is connected to the carriage 13 and a drive motor (not shown). The drive motor uses the belt 14 to control the position of the carriage 13 on the carriage guide shaft 14. The feed roller 17 conveys the recording material 16 in a direction orthogonal to the carriage guide shaft 15 (moving direction of the carriage 13). In the present specification, the direction in which the carriage 13 moves (carriage guide shaft 15
The longitudinal direction) of the recording medium 16 is called the main scanning direction, and the direction in which the recording material 16 is conveyed (the recording material conveying direction at the position of the carriage guide shaft 15) is called the sub-scanning direction.

FIG. 2 shows a mechanism for ejecting minute ink droplets from the recording head. As shown in FIG. 2, the recording head 11 includes at least a nozzle 23, a piezoelectric actuator 21, and a pressure generating chamber 22. Pressure generation chamber 22
Is filled with ink from the ink supply path 26 via the supply port 25 and stores the ink. Piezoelectric actuator 21
Are arranged on the opposite side of the diaphragm 27. When a predetermined voltage is applied, the piezoelectric actuator 21 generates a pressure wave in the pressure generating chamber 22 via the vibration plate 27. The nozzle 23 ejects the (minute) ink droplet 24 toward the recording material by the pressure wave.

The ink jet recording apparatus according to the present invention is
In order to speed up printing, printing is performed for a length corresponding to the width of the nozzle group in the sub-scanning direction with one main scan (1-pass printing), and the recording material is sequentially conveyed with each operation of the carriage. Then, an image is formed on the entire surface of the recording material.

The recording head 11 can be formed by laminating stainless steel thin plates, and the nozzle 23, the pressure generating chamber 22 and the like can be formed by etching or laser processing. However, the manufacturing method and material are not limited to this, and other known materials and manufacturing methods may be used. Note that, in the example of FIG. 2, an example in which a piezoelectric actuator that is an electromechanical conversion element is used as a pressure generation method is shown, but a method that uses thermal energy or electrostatic force can naturally be adopted. Hereinafter, the structure of the recording head according to the present invention will be described in detail with reference to the drawings.

(First Recording Head) The first recording head according to the present invention will be described in detail in comparison with a recording head according to the prior art (hereinafter referred to as a conventional recording head).
FIG. 3 is a schematic diagram showing the nozzle arrangement of the conventional recording head, and FIG. 4 is a schematic diagram showing the nozzle arrangement of the first recording head. In both figures,
The nozzle 31 is indicated by a circle. In addition, the color of the ink ejected from each nozzle 31 is changed to the letters K (black), C (cyan),
It is marked with M (magenta) and Y (yellow).

(Common items between the first recording head and the conventional recording head) Both the first recording head and the conventional recording head have a structure in which six nozzles 31 are arranged at equal intervals in the sub-scanning direction. These six nozzles 31 are for ejecting ink of the same color, and form a nozzle group 32. Four nozzle groups 32 are provided for each color (kind) of ink, and the nozzle groups 32 are arranged at equal intervals in the main scanning direction. That is, the recording heads of FIGS.
The nozzle group 32 constituted by 1 has a nozzle arrangement structure in which four rows are arranged in the main scanning direction. The color (or type) of the ink ejected by the nozzle group 32 is different from the color (or type) of the ink ejected by at least one other nozzle group 32. In the specification of the present application, an array of the nozzles 31 in the main scanning direction is appropriately referred to as a nozzle line 33.

Each nozzle in the recording head is arranged at a reference position. The reference position is the position of the nozzle for causing the ink droplets of each color to land at substantially the same landing position in each pixel. If the ink ejection direction of each nozzle is the same,
As shown in FIG. 3, the heights (positions) of the nozzles arranged in the nozzle line in the sub-scanning direction are the same. In FIG. 3, the nozzles KCMY forming each nozzle line are set to the same height in the sub-scanning direction. However, when the ink droplet ejection directions of the nozzles are different from each other, the reference position may be appropriately set in accordance with the ejection direction. In this embodiment, the ink droplet ejection directions of the nozzles are all substantially the same. An interval (nozzle interval) between the reference positions in the sub-scanning direction is determined according to the recording density set in the print image. In general, a length corresponding to the printing resolution in the sub-scanning direction or a length that is an integral fraction of the length is adopted. The interval between the reference positions in the main scanning direction (nozzle interval) is determined by the structure of the pressure generating chamber 22 and the ink supply path 26 shown in FIG. 2, but is generally a length corresponding to the printing resolution in the main scanning direction. The length is an integral multiple of the length. The length corresponding to the print resolution may be calculated using a known method. In the present embodiment, the printing resolution in the sub-scanning direction is set to the printing resolution of 300 dpi, and the interval between the reference positions in the sub-scanning direction is the length “84.7” corresponding to the printing resolution.
μm ”is adopted. Also, the printing resolution in the main scanning direction is 6
The length is "42.3 .mu.m" corresponding to the printing resolution. That is, the recording head according to the present embodiment is moved by 42.3 μm in the main scanning direction after performing one ejection operation, and performs the next ejection operation.
Pixels are formed by sequentially repeating this operation (for KCMY).

(Conventional recording head) In FIG. 3, broken lines are added in the main scanning direction and the sub-scanning direction so that the positional relationship of each nozzle is clear. The intersection of the broken lines is the position at which the nozzles at which the center positions of the ink droplets forming the same pixel land are substantially the same, and is called the reference position 30 for each nozzle. That is, since each nozzle 31 in the conventional print head is provided with the same height in the sub-scanning direction as the other nozzles 31 for the same pixel configuration, it is substantially the same as the landing position of the ink droplet from this other nozzle 31. Place the ink at the position. Note that FIG.
In the drawings including the arrangement of the nozzles in the recording head including FIG. 4, a broken line similar to that in FIG. 3 is appropriately added. In addition, the displacement of the nozzle placement position from the reference position 30
The description will be made assuming that the direction shown in FIG. 3 is positive.

(First Recording Head) On the other hand, in the first recording head, as shown in FIG. 4, each nozzle of the nozzle group 32 for ejecting M ink is sub-scanned from each reference position 30 of the nozzle. They are arranged with +42.3 μm offset in the direction. Therefore, the ink droplet of M lands on the recording medium with the landing center position displaced by about 42.3 μm from the other ink droplets forming the same pixel.

(Comparison between First Recording Head and Conventional Recording Head) With reference to FIGS. 5 and 6, the manner of ink dots formed on a recording material by the conventional recording head and the recording head of the present invention will be described. . FIG. 5 shows a state of a pixel formed by a conventional recording head. FIG. 6 shows a state of pixels formed by the first recording head. FIGS. 5A and 6B show one pixel formed on the recording material on the upper surface of the recording material (on the side where the ink droplet has landed, on the side where the pixel on the recording material is formed). The plan views viewed from above, (c) and (d) are cross-sectional views of the recording material including the portion where the above-mentioned pixel is formed. The pixels shown in FIGS. 5 and 6 are blue (B) pixels formed by using C and M.

Each of the recording heads ejects ink droplets onto the recording material in the order of C → M when moving forward and in the order of M → C when returning. Ink droplets are landed on the recording material in the order described above.

In the conventional recording head, as shown in FIGS. 5C and 5D, the landing center position of the M ink droplet and the landing center position of the C ink droplet are substantially the same position. Therefore, the ink droplets that have landed on the recording material later are prevented from penetrating into the recording material by the ink droplets that have landed first, and penetrate further into the recording material 35 than the ink droplets that landed first. as a result,
The amount fixed on the surface of the recording material 35 is reduced. That is,
The ink dots formed by the ink droplets that have landed first on the recording material have a larger area (dominant) on the surface of the recording material than the ink dots that have formed by the ink droplets that have landed later. Therefore, even for the same B pixel,
C is predominant in the forward movement and M is predominant in the backward movement, so that the tint changes due to bidirectional printing.

On the other hand, in the recording head of the first embodiment, since the M nozzles 31 are arranged so as to be displaced from the reference position 30, as shown in FIG. 34 is displaced. As a result, the ratio (range, area) of the ink droplets that have landed first on the recording material 35 to hinder the penetration of the ink droplets that have landed later on the recording material decreases. Compared to the ink droplets (ink dots) formed by the conventional recording head shown in FIG. 5, ink dots formed by the ink droplets that have landed on the recording material later remain on the surface of the recording material. The change in color is alleviated. In other words, the difference in the area on the surface of the recording material between the ink dots formed by the ink droplets that have landed on the recording material first and the ink dots formed by the ink droplets that have landed later is the same as in the case of the conventional recording head. It will be extremely small compared to. As a result, the change in color between the forward movement and the backward movement is reduced.

Pixels in the case where the conventional print head and the first print head are mounted on the ink jet printer shown in FIGS. 1 and 2, and the pixels of the secondary colors B of C and M in the forward movement and the double movement are created. The result of measuring the color of B is shown in FIG. ΔE indicating the distance in the Lab space was applied as the evaluation index. Generally, it is ΔE of 1.0 or more that a person with normal eyesight can distinguish the difference in color when viewed from a position 300 mm away. In addition, ΔE of single color ink such as M, C and Y
Is about 0.1 to 0.2. The printing conditions are: average diameter of ink droplets 36μm, carriage movement speed 0.762m
/ S, the recording material was plain paper of virgin pulp. The colorimetric conditions were a light source D65, a viewing angle of 2 degrees, and no filter insertion.

ΔE was 1.80 in the conventional recording head, whereas it was 0.16 in the first recording head (a plot of the shift rate of 0.5 in FIG. 7), which is almost the same as ΔE of a single color ink. It became a value of the degree. From this result, it was found that the first recording head can suppress the difference in hue between the forward movement and the backward movement to the same extent as in the case of a single color even when an image is formed by color mixing.

In FIG. 7, the length in which the position of the M nozzle 31 of the first recording head is displaced from the reference position 30 to the positive side, and the ΔE of the B pixel created by the inks of M and C are shown.
I also noted the relationship with. The “shift rate” in FIG. 7 means the length between the nozzles 31 in the sub-scanning direction (84.
7 μm) is set to 1, the amount of displacement of the M nozzle 31 from the reference position 30 in the positive direction (42.3 μm in the example of FIG. 4)
It is a ratio of m). That is, it is the ratio of the distance between the landing center positions of the M and C ink droplets to the length corresponding to the printing resolution. Also, for the secondary colors (mixed color) red of M and Y (hereinafter referred to as R), ΔE is measured by changing the shift amount of the nozzle 31 of M from the reference position from 0 to 1.00. The results are also shown. The results of measuring the color of green (hereinafter referred to as G), which is a secondary color of C and Y, only when the offset rate is 0 are shown.

In both cases of B and R, ΔE has a shift rate of 0.
When the value exceeds 1 and is smaller than 1, the value is smaller than that of the conventional recording head (when the shift amount is 0). Further, when the shift ratio is in the range of 0.20 to 0.80, ΔE is 1.
It became 0 or less, and the change in color could not be visually recognized.
In the range where the shift ratio is 0.33 or more and 0.67 or less, ΔE is 0.3 or less, which is almost the same as ΔE of the pixel formed by one ink, and it is extremely difficult to visually determine the hue difference. It was When the shift rate is 0.5, ΔE
Was the least.

From this result, it was found that when the shift ratio is smaller than 0.20, the effect that ΔE becomes smaller than that of the conventional recording head is recognized, but there is still a large possibility that the inks are inhibited from each other. . It was also found that when the shift ratio exceeds 0.80, the dot overlap of adjacent pixels becomes large, and thus a hue difference appears. Therefore, the rate of shifting the nozzle 31 from the reference position 30 which has an effect of not making a change in the tint between the forward movement and the backward movement is 0.80 or less (preferably 0.20 or more and 0.8
It was found to be 0 or less). That is, the distance between the landing center positions of ink droplets of different colors ejected from different nozzles forming one pixel is 4/5 or less (preferably 1/5 or more and 4/5 or less) of the length corresponding to the printing resolution. ), It was found that bidirectional printing with little change in color tone can be performed. Further, it was found that the preferable shift ratio is 0.67 or less (preferably 0.33 or more and 0.67 or less). That is, the distance between the landing center positions of ink droplets of different colors ejected from different nozzles forming one pixel is ⅔ or less (preferably ⅓ or more and ⅔ or less) of the length corresponding to the printing resolution. It was found that bidirectional printing with extremely little change in color tone can be performed within the range of (). Further, it has been found that when the shift rate is 0.5 or less (preferably about 0.5), extremely preferable bidirectional printing can be performed. That is, if the distance between the landing center positions of the ink droplets ejected from the nozzles of different color inks forming one pixel is set to 1/2 (preferably about 1/2) of the length corresponding to the printing resolution. It was found that it was almost impossible to visually confirm the difference in color between the forward movement and the backward movement.

The relative positional relationship of the nozzles is changed to
The above-described remarkable effect can be obtained by shifting the landing center positions of the ink droplets forming the same pixel ejected from different nozzles, and the shifting nozzle group is not limited to the one for ejecting M ink. . For example, when C is shifted as shown in FIG. 8, it goes without saying that the hue difference of the B pixel is reduced as in the case where M is shifted as shown in FIG. The hue difference of the color G can be reduced. When Y is shifted as shown in FIG. 9, the effect described above becomes remarkable with R, which is a secondary color of Y and M, and G, which is a secondary color of Y and C.

Also, paying attention to the magnitude of ΔE at the shift rate of 0 in FIG. 7, it was found that the magnitude of the secondary color ΔE was in the order of B>R> G. This means that the inks have a strong tendency to interfere with each other in the combination order of C and M, M and Y, and C and Y. That is, it was found that the color difference between the forward movement and the backward movement in the conventional print head was extremely large in the pixel of the mixed color of M and the ink of other colors. Therefore,
In order to reduce the hue difference due to bidirectional printing, it is effective to shift the M nozzle among the three color nozzles, and at least the C and M inks are arranged so that the landing positions of the inks are displaced. Is good. In other words, the relative positions of the M ink ejection nozzles 31 and the other color ink ejection nozzles 31 in the sub-scanning direction are changed to set the M ink droplet landing position and the other ink droplet landing position. By shifting the position, high image quality can be ensured even when bidirectional printing is performed.

The density of each single color, the secondary color and the tertiary color is measured by measuring the optical density (hereinafter referred to as OD value), which is an index thereof, and the OD value when the nozzle is displaced and when it is not displaced. Was confirmed to be about the same. Therefore, it can be said that there is practically no problem in arranging the nozzles so as to be displaced from the reference position 30.

In this example, the printing resolution is 300 dpi in the sub-scanning direction and 600 dpi in the main scanning direction, but the same effect as described above can be obtained even if the printing resolutions in the main scanning direction and the sub-scanning direction are the same. Also, 360 dpi, 600
Even when recording is performed at another printing resolution such as dpi or 720 dpi, the same effect as described above can be obtained. Therefore, it was found that regardless of the print resolution, if the shift ratio is within the above range, the change in tint during bidirectional printing can be significantly reduced by one-pass printing.

(Second recording head) The arrangement order of the respective color nozzle groups in the main scanning direction is not limited to the arrangement order in the first recording head (KCMY order in the main scanning direction), and the ink used It can be appropriately selected depending on the property and the type of the nozzle to be displaced. FIG. 10 shows the nozzle arrangement of the recording heads of the second recording head according to this embodiment. In this recording head, the nozzle group 32 has Y, M, K, and C in the main scanning operation direction.
No. M nozzles are arranged so as to be displaced from the reference position 30 in the sub-scanning direction. Even if such a nozzle arrangement is adopted, the landing position of the ink droplet on the recording material is at least the landing position of the ink droplet of at least one other color on the recording material, as in the first recording head. Since it is out of alignment, high image quality can be obtained even in bidirectional printing. That is, since the nozzle group 32 for ejecting any one of CMYK colors is arranged so as to be displaced from the reference position 30, the difference in tint between the forward movement and the backward movement becomes small.

Further, in this example, the nozzle group 32 for ejecting ink of M and the nozzle group 32 for ejecting ink of C are passed through the nozzle group 32 for ejecting K ink (in the order of M → K → C). At) a group of nozzles is provided. When such an arrangement example is adopted, the interference between the ink droplets ejected from the nozzle groups arranged apart from each other is further reduced, and the difference in tint between the forward movement and the backward movement can be made extremely small. In the second recording head, after ejecting ink droplets from the nozzle group 32 for ejecting M ink, ink droplets are ejected from the nozzle group 32 for ejecting K ink droplet, and then the nozzle group 32 for ejecting C ink droplet. Ink droplets are ejected from the. Therefore, the time from the landing of the M ink droplet on the recording material to the landing of the C ink droplet is longer than that of the first recording head. The ink droplets have a weaker force of blocking other inks as time elapses after landing, so that it is possible to alleviate the mutual interference of the inks.

(Third Recording Head) FIG. 11 shows an arrangement example of the nozzles 31 of the third recording head. In the third recording head, two nozzle groups are arranged so as to be offset from the reference position 30 in the sub scanning direction. The two nozzle groups arranged so as to be displaced from the reference position 30 have different displacement amounts (rates). In FIG. 11, the M and Y nozzles 31 are respectively +28.2 μm (shift rate 0.3 from the reference position in the sub-scanning direction).
3) and +56.4 μm (shift rate: 0.67). In this recording head, the maximum distance of the landing center position of the ink droplets ejected from the different color ejection nozzles forming the same pixel is about 56.4 μm.

R at the time of forward movement and double movement of the third recording head,
ΔE of G and B is 0.25, 0.23 and 0.2, respectively.
It was 7. 1.47 with the conventional recording head,
Since it was 0.54 and 1.80, it was found that the hue difference due to bidirectional printing was significantly improved.

In the above-mentioned first to third recording heads, the case where the nozzle group is shifted to the plus side in the sub-scanning direction has been exemplified, but it goes without saying that the same effect can be obtained even if the nozzle group is shifted to the minus side. Yes. Further, even when the nozzle group is displaced in the main scanning direction, the same effect as described above can be obtained if the amount of displacement is within the above range. That is, the first
The third recording head is merely an example, and the present invention is not limited to this. Therefore, the one nozzle group may be arranged on the recording head so that the center position of the ink droplet landing on the same pixel is different from at least the one nozzle group for ejecting the other color. More specifically, at least one nozzle group is provided with a nozzle on a reference position, and the other one or a plurality of nozzle groups are arranged so as to be displaced from a position other than the reference position in the sub-scanning direction and / or the main scanning direction. The nozzle group arranged so as to be displaced from the reference position is located in the sub-scanning direction and / or the main scanning direction from the reference position 30 in a range less than a distance (nozzle interval) corresponding to the resolution, and preferably in a position within the above range. Nozzles are provided. Further, the nozzle groups in which the nozzles are arranged so that the landing center positions of the nozzle droplets are substantially the same are separated (with other nozzle groups in between).
It is preferable to provide it. For example, when arranging the C and Y ink ejection nozzle groups at the reference position, rather than arranging the C and Y nozzle groups adjacent to each other like “CYMK”, “C
It is preferable to provide M between them (separated) like “MYK”. This is because, as described above, the force (ratio or influence) of the ink droplets that have landed on the recording material first to impede the penetration of the ink droplets that land on the recording material to the recording material decreases. Less than,
Other nozzle arrangement examples are also shown.

(Fourth Recording Head) In the fourth recording head, nozzles of three colors of C, M and Y are arranged so as to be displaced in different directions. FIG. 12 shows an example of nozzle arrangement of the fourth recording head. The recording head shown in FIG.
The nozzle groups 32 are arranged in different directions from the reference position 30 so that the landing center positions of the ink droplets ejected from the C, M, and Y nozzles do not become substantially the same position. C is +28.2 μm in the sub-scanning direction, −14.1 μm in the main scanning direction, and M is −28.2 μm in the sub-scanning direction.
Y is +14.1 μm in the sub scanning direction and +2 in the main scanning direction.
They are arranged with a shift of 8.2 μm. Therefore, the maximum distance between the landing center positions of ink droplets forming the same pixel is
Sub scanning direction is 56.4 μm, main scanning direction is 28.2 μm
Becomes That is, the shift rate is 0.67 in both the main scanning direction and the sub scanning direction.

FIG. 13 is a plan view (viewed from the upper side of the ink droplet landing surface) showing the state of ink dots formed on the recording material by the recording head of FIG. The recording head causes ink droplets to land in the order of K → C → M → Y during forward movement to form pixels as shown in FIG. 13A on the recording material. At the time of double action, ink droplets are landed on the recording material in the order of Y → M → C → K to form pixels as shown in FIG. 13B. The nozzle groups of the recording head are arranged such that the positions from the reference position are relatively different from each other. Therefore, as shown in FIG. 13, the ink droplets ejected from the respective nozzles land on the recording material with their landing center positions displaced, forming ink dots. Therefore, the overlapping area (ratio) of each ink dot
Is smaller than the ink dots formed by the conventional recording head, and the influence of the ink droplets that have landed first on the permeation of the ink into the recording material is small, so that the change in tint due to bidirectional printing is alleviated.

FIG. 14 shows the maximum shift rate of the landing center position (nozzle disposition position) of the fourth recording head from 0 to 1.
The results of measuring ΔE of process black (hereinafter referred to as PK), which is a tertiary color of C, M, and Y, by changing the value up to 00 are shown. As shown in FIG. 14, ΔE has a shift rate of 0.2.
As described above, it is significantly reduced as compared with the case of the conventional recording head (when the shift rate is 0), and it becomes 1.0 or less, which makes it difficult to visually confirm the change in tint during forward movement and backward movement. I found out. Further, it was found that the shift ratio was about 0.5 between 0.53 and 0.67, and the minimum value was obtained at the shift ratio of 0.5.

(Fifth to Tenth Recording Heads) FIGS. 15 to 20 show recording heads having a nozzle arrangement structure other than the first to fourth recording heads. In the fifth recording head shown in FIG. 15, M nozzle groups are arranged with a displacement of 21.2 μm on the plus side in the main scanning direction. The sixth recording head shown in FIG. 16 is
C nozzle group is 28.2μ on the minus side in the sub-scanning direction
The m and Y nozzle groups are 28.2μ on the plus side in the sub-scanning direction.
m are offset from each other. Seventh shown in FIG.
In the recording head of No. 2, the C nozzle group is displaced 14.1 .mu.m on the negative side in the main scanning direction, and the M nozzle group is displaced 14.1 .mu.m on the positive side in the main scanning direction. In the eighth recording head shown in FIG. 18, the C nozzle group is displaced by 21.2 μm on the plus side in the main scanning direction, and the M nozzle group is displaced by 42.3 μm on the plus side in the sub scanning direction. . In the ninth recording head shown in FIG. 19, the C nozzle group is 21.2 μm on the plus side in the main scanning direction, the M nozzle group is 42.3 μm on the plus side in the sub scanning direction, and the Y nozzle group is main scanning. 42.3 μm on the plus side in the direction and 21.2 μm on the plus side in the sub-scanning direction. In the tenth recording head shown in FIG. 20, the C nozzle group is 28.2 μm on the minus side in the sub-scanning direction, the M nozzle group is 21.2 μm on the plus side in the main scanning direction, and the Y nozzle group is sub-scanning. The positions are shifted by 28.2 μm on the plus side in the direction.

In any of the fifth to tenth recording heads, ink droplets ejected from one or a plurality of different nozzles forming one pixel are displaced from the center position of impact and land on the recording material. It was confirmed that high-quality images can be obtained by alleviating the change in color due to bidirectional printing.

(First to Twelfth Recording Heads) The first to tenth recording heads have been shown to form pixels using KCMY ink, but the present invention is not limited to this. A pixel (image) may be formed by using a plurality of inks of arbitrary colors. Further, the ink to be adopted is not limited to four colors (four) and may be any number. For example, light cyan (hereinafter referred to as LC), light magenta (hereinafter referred to as LM), R, G, and B inks may be used. The ink combinations are K, C, M,
Six colors of Y, LC and LM and seven colors of K, C, M, Y, R, G and B may be used.

The eleventh recording head shown in FIG. 21 has K,
It has a nozzle arrangement of a recording head using six color inks in which LC and LM are added to C, M and Y. The M and LM nozzles are arranged +28.2 μm in the sub-scanning direction, and the Y nozzles are arranged +56.4 μm in the sub-scanning direction.
The twelfth recording head shown in FIG. 22 has nozzle arrangements of recording heads using seven color inks in which B, G, and R are added to K, C, M, and Y. M and G nozzles + in the sub-scanning direction
28.2 μm, Y and G nozzles are +56.
4 μm, which are offset from each other.

The eleventh and twelfth recording heads are arranged at positions where nozzles ejecting a small number of times on the same pixel are not relatively displaced from each other, that is, the ink droplet landing center positions are substantially the same. ing. In the recording head of FIG. 21, C and LC, M and LM, and C of the recording head of FIG.
And R, M and G, and Y and B are arranged so as not to shift relative to each other. As described above, the number of nozzles to be displaced and the total displacement amount can be reduced by appropriately selecting the nozzle displacement method in consideration of the properties of the ink to be used.

(Thirteenth to Fourteenth Recording Heads) The recording head according to the present invention is applicable as long as it forms one pixel with ink ejected from a plurality of nozzles.
It is not affected by the overall nozzle arrangement of the nozzle group. That is, although the nozzle groups of the first to twelfth recording heads are composed of a plurality of nozzles arranged in one row in the sub-scanning direction, a matrix of a plurality of rows × a plurality of rows is formed by the rows of nozzles arranged in a plurality of rows. Naturally, it is also possible to adopt a nozzle group configured in a shape.

The thirteenth recording head of FIG. 23 and FIG.
In the nozzle group 40 of the fourteenth recording head, the nozzles 31 are arranged in a plurality of rows in the sub-scanning direction. In the nozzle group 40 of the 13th recording head, the nozzles 31 are arranged in a staggered pattern (2 × 3 matrix). In the nozzle group 40 of the fourteenth recording head, the nozzles 31 are arranged in an 8 × 8 matrix. That is, the nozzle group of the thirteenth recording head has two nozzle rows 42, and the nozzle group of the fourteenth recording head has eight nozzle rows 42.

The nozzle arrangement when the arrangement of one nozzle group 40 is projected in the sub-scanning direction will be described with reference to FIGS. 23 and 24. As shown in the figure, in the projected nozzle group 41, the nozzles 31 are arranged in the sub-scanning direction at intervals of a length corresponding to the printing resolution, and the nozzle groups corresponding to each ink color are arranged in one row. You can think of it as you would. That is, only one or a plurality of nozzles 31 arranged in a line in the sub-scanning direction as shown in the projected nozzle group is moved in the main scanning direction, and essentially the above first to twelfth
No different from the nozzle group. Therefore, even in a recording head in which the nozzle group is composed of a plurality of nozzle rows in the main scanning direction, that is, the nozzles are arranged in a matrix of a plurality of rows × a plurality of columns, the nozzle group is formed in the same manner as described above. If they are arranged in a staggered manner, high-quality images can be obtained even when bidirectional printing is performed.

FIG. 25 shows an example of nozzle arrangement in the thirteenth recording head. As shown in FIG. 25, in the thirteenth recording head, four nozzle groups 40 in each of which one ink ejecting nozzle 31 is arranged in a staggered manner are arranged in the main scanning direction. FIG. 26 shows an example of nozzle arrangement in the fourteenth recording head. As shown in FIG. 26, the fourteenth recording head has eight nozzles 40 in the sub-scanning direction and four nozzle groups 40 in the main scanning direction having an 8 × 8 matrix structure in which eight nozzles are arranged in the main scanning direction. Recording head. Note that FIG.
In FIG. 6, some nozzles of the nozzle group 40 are omitted in order to make the drawing easy to see.

In the thirteenth and fourteenth recording heads, M nozzle groups 40 are arranged at a shift rate of 0.50 from the reference position 30 in the sub-scanning direction. The nozzle arrangement of these recording heads is similar to that of the first recording head when projected in the sub-scanning direction. Therefore, the ink droplet of M forms an ink dot with the landing center position displaced from the ink droplets ejected from the other nozzles forming the same pixel, so that the change in tint during bidirectional printing can be mitigated. .

(Fifteenth to seventeenth recording heads) First to first
In the recording head of No. 4, the nozzles of the nozzle group arranged so as to be displaced from the reference position are arranged so as to be displaced from the reference position in the same direction by the same amount. In contrast, the 15th
-17 recording heads, one or more (including all)
Each nozzle of the nozzle group is arranged so as to be displaced from at least one other nozzle of the nozzle group in a different direction and / or different amount from the reference position. In this case, the nozzles are arranged so that the length in the sub-scanning direction of the image formed by the continuous nozzle group arranged without shifting is within a period in which the difference in tint cannot be visually recognized, generally within 300 μm. If it is installed, the change in color due to bidirectional printing is not recognized. That is, the center distance between the pixels formed in the same ink droplet landing order in the sub-scanning direction may be set to 300 μm or more.

FIG. 27 shows a fifteenth recording head. The fifteenth recording head has nozzles 3 in the M nozzle group.
Every other number 1 in the sub-scanning direction is displaced by +28.2 μm (shift rate 0.33) from the reference position in the sub-scanning direction. FIG. 28 shows the 16th recording head. First
The recording head of No. 6 has nozzles 31 in the nozzle group of M.
Shows the nozzle arrangement of the recording head arranged in units of three units in the sub-scanning direction with a shift of +28.2 μm (shifting rate 0.33) from the reference position in the sub-scanning direction. Even if a nozzle arrangement such as that of the fifteenth or sixteenth recording head is adopted, the length in the sub-scanning direction in which the ink dots landed at the same location continues is 300 μm or less, so that the difference in tint is not recognized. Live.

The amount of displacement and / or the direction of displacement from the reference position need not be the same for all nozzles arranged to be displaced from the reference position. FIG. 29 shows a seventeenth recording head. The seventeenth recording head is to be shifted for each nozzle in the M nozzle group (shift amount, shift direction)
Are different. The displacement rate of each nozzle is 0.5, 0, -0.5, 0.33, 0, 0.2 in the main scanning direction.
5, in the sub-scanning direction, -0.1, 0.2, 0, -0.5,
Either 0 or 0.5 is adopted. ΔE for the B pixel by the 17th recording head was 0.33, and it was confirmed that the change in tint was sufficiently improved. As described above, the present invention has the same effect even if the nozzles are shifted in units of nozzles, and the way of shifting the nozzles can be set for each nozzle. However, when shifting in units of nozzles, it is necessary to prevent white lines from appearing in one-pass printing. In order to prevent this phenomenon, for example, the maximum distance between the landing center positions of ink droplets ejected from adjacent nozzles is determined by the difference between the nozzle interval length in the sub-scanning direction of the nozzles and the diameter of the ink dot formed by the nozzles. Should be small. That is, if the nozzles are arranged so as to be displaced within the range in which the ink dots formed by the ink droplets ejected from different nozzles at least overlap, a white line will not appear during printing. In other words, the maximum distance between the landing center positions of the ink droplets forming the adjacent pixels ejected from the nozzles corresponding to the same color is the maximum diameter of the ink dot formed by the ink droplets ejected from one nozzle. If it is smaller than this, an extremely high quality image can be obtained.

(Eighteenth Recording Head) In the eighteenth recording head, a plurality of nozzles for ejecting ink are mixedly arranged in one nozzle group. FIG. 30 shows a nozzle arrangement example of the eighteenth recording head. This recording head is arranged so that the C and M nozzles 31 in the nozzle groups 39 and 39 ′ are alternately arranged in the adjacent nozzle lines 33. Further, these nozzles 31 are arranged so as to be displaced from the reference position 30 in the sub scanning direction. That is, in the nozzle shown in FIG. 30, each nozzle of the nozzle group configured by the K ink ejection nozzles and the nozzle group configured by the Y ink ejection nozzles is arranged at the reference position 30.
The respective nozzles of the two nozzle groups, which are composed of the C ink ejection nozzles and the M ink ejection nozzles, are arranged so as to be displaced from the reference position in the sub-scanning direction. Further, if the nozzle of one nozzle group of the two nozzle groups is the C ink ejection nozzle, the nozzles of the other nozzle group that ejects ink to the same pixel as the nozzle are for the M ink ejection nozzle. And By adopting the nozzle arrangement in this way, ink dots having different ink landing orders can alternately appear during forward movement / double movement during bidirectional printing. In this recording head, the secondary color G of C and Y and the secondary color B of M and Y, which are arranged relatively offset, are displaced from each other by ΔE when the offset rate is 0.5.
Were 0.25 and 0.18, respectively.

The eighteenth recording head can also be realized by adopting the structure shown in FIG. 31 or 32. Figure 31
4 shows the nozzle arrangement of the recording head in which the nozzles 31 are arranged in a staggered manner with respect to the ink supply path. M nozzles and C nozzles are alternately arranged in the nozzle group 44 and the nozzle group 44 ′, and the M and C nozzles are arranged in the sub-scanning direction with a shift ratio of 0.5. When the recording head shown in FIG. 31 is projected in the sub-scanning direction, it is understood that it is equivalent to the nozzle of FIG. A recording head in which nozzles corresponding to different ink colors are mixed in the nozzle group can be realized by arranging an ink supply path 51 corresponding to each ink and changing the ink in each supply path 51. At this time,
When the adjacent supply paths 51 correspond to the same ink, the supply paths 51 may be common as shown in FIG.

FIG. 32 shows the nozzle arrangement of a recording head having a nozzle group 45 composed of nozzles arranged in an 8 × 8 matrix. Although the nozzle is not shown,
It is assumed that it is formed on the pressure generating chamber 52. At this time, in the nozzle groups 45 and 45 ′ in which the C and M nozzles are arranged, the M and C nozzles are alternately arranged in the main scanning direction, and further shifted in the sub scanning direction by a shift ratio of 0.5. It is arranged. This recording head is also considered to have the same arrangement as the nozzle arrangement shown in FIG. 30 when the nozzle arrangement is projected in the sub-scanning direction (however, the number of nozzles in the sub-scanning direction is 64).
Individual). As described above, in order to mix nozzles corresponding to a plurality of colors in one nozzle group, the ink supply path main streams 53 of different colors are arranged at both ends of the nozzle group 45, and the ink supply path tributary 54 is provided from there. The ink supply path tributaries 54 of different colors may be alternately arranged in a comb shape. At this time, when the ink supply path main streams 53 corresponding to the same color are adjacent to each other, they can be shared.

Although the preferred embodiments of the present invention have been described above, the above-described embodiments are merely examples for explaining the present invention, and are intended to limit the scope of the present invention to only these embodiments. Absent. A person skilled in the art can implement the present invention in various other modes in which various variations, improvements, modifications, simplifications, etc. are added to the above embodiments without departing from the gist of the present invention. For example, although an example in which a piezoelectric actuator that is an electromechanical conversion element is used as the pressure generating means is shown, the present invention is not limited to this, and various pressure generating means such as bubble jet (registered trademark) and electrostatic force can be used. Applicable.

Further, although an example in which one nozzle is provided in one pressure chamber has been shown, the present invention is not limited to this, and it has a multi-nozzle structure in which a plurality of nozzles are provided in one pressure chamber. Also, the same can be applied to any recording head that forms the same pixel with ink droplets ejected from a plurality of nozzles.

Although a color ink jet printer is shown as an example of the color ink jet recording apparatus using the present invention, the present invention is not limited to this, and can be applied to a color ink jet recording apparatus using an ink jet recording head, such as a copying machine or a fax machine. Obviously, can also be applied.

[0075]

As is apparent from the above description, according to the present invention, by changing the relative positional relationship of the nozzles and shifting the landing center position of ink droplets ejected from different nozzles forming one pixel, It is possible to significantly reduce the change in color tone due to the difference in the ink landing order in orientation printing. Therefore, high image quality can be realized by the bidirectional printing method. Since such an effect can be achieved by a relatively simple structure in which the nozzle position is shifted, the recording head of the present invention can be formed in a small size without increasing in size. Also,
There is no need for special control such as changing the ejection timing for ejecting ink, or changing the feeding of the recording material in accordance with the carriage operation, so the apparatus does not become complicated. Therefore, according to the present invention,
An ink jet recording head having high image quality and high-speed printability can be realized in a small size, at low cost, and without requiring complicated control.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an inkjet recording apparatus.

FIG. 2 is a cross-sectional view showing the structure of a recording head of the inkjet recording apparatus.

FIG. 3 is a diagram showing a nozzle arrangement of a conventional inkjet recording head.

FIG. 4 is a diagram showing a nozzle arrangement of a first recording head.

FIG. 5 is a diagram illustrating the shape of an ink dot formed by the recording head of FIG.

FIG. 6 is a diagram illustrating a shape of an ink dot formed by a first inkjet recording head.

FIG. 7 shows a result of color measurement by the first inkjet recording head.

FIG. 8 is a diagram showing another nozzle arrangement example of the first recording head.

FIG. 9 is a diagram showing another arrangement example of nozzles of the first recording head.

FIG. 10 is a diagram showing a nozzle arrangement example of a second inkjet recording head.

FIG. 11 is a diagram showing a nozzle arrangement example of a third inkjet recording head.

FIG. 12 is a diagram showing an example of nozzle arrangement of a fourth inkjet recording head.

FIG. 13 is a schematic diagram for explaining the shape of an ink dot formed by a fourth inkjet recording head.

FIG. 14 shows a result of color measurement by a fourth inkjet recording head.

FIG. 15 is a diagram showing an arrangement example of nozzles of a fifth recording head.

FIG. 16 is a diagram showing an example of nozzle arrangement of a sixth recording head.

FIG. 17 is a diagram showing an arrangement example of nozzles of a seventh recording head.

FIG. 18 is a diagram showing an arrangement example of nozzles of an eighth recording head.

FIG. 19 is a diagram showing an example of nozzle arrangement of a ninth recording head.

FIG. 20 is a diagram showing an example of nozzle arrangement of a tenth recording head.

FIG. 21 is a diagram showing an arrangement example of nozzles of an eleventh recording head.

FIG. 22 is a diagram showing an example of nozzle arrangement of a twelfth recording head.

FIG. 23 shows an example of nozzle arrangement in the case where a nozzle group is projected in the sub-scanning direction by an inkjet recording head having nozzles arranged in a staggered manner (thirteenth recording head example).

FIG. 24 shows an example of nozzle arrangement in a case where a nozzle group is projected in the sub-scanning direction by an inkjet recording head in which nozzles are arranged in a matrix (example of fourteenth recording head).

FIG. 25 shows an example of nozzle arrangement in a thirteenth recording head.

FIG. 26 shows an example of nozzle arrangement in a fourteenth recording head.

FIG. 27 shows an arrangement example of nozzles of a fifteenth recording head.

FIG. 28 shows an example of nozzle arrangement in a sixteenth recording head.

FIG. 29 shows an example of nozzle arrangement in a seventeenth recording head.

FIG. 30 shows an arrangement example of nozzles of an eighteenth recording head.

FIG. 31 shows a modification of the eighteenth recording head.

FIG. 32 shows a second modification of the eighteenth recording head.

[Explanation of symbols]

11 recording head 12 ink tank 13 carriage 14 belt 15 Carriage guide shaft 16, 35 Recording material 17 Feed roller 21 Piezoelectric actuator 22, 52 Pressure generation chamber 23 nozzles 24 ink drops 25 supply port 26, 51 Ink supply path 27 diaphragm 30 reference position 31 nozzles 32, 37, 38, 38 ', 39, 39' Nozzle group 33 nozzle lines 34 Center position of impact 40, 44, 44 ', 45, 45' nozzle group 41 Projected nozzle group 42 nozzle row 53 Ink supply main stream 54 Ink supply channel tributary

Claims (16)

[Claims] 1. A plurality of nozzle groups each including one or a plurality of nozzles arranged in the sub-scanning direction are arranged in the main scanning direction,
An ink jet recording head in which one or a plurality of nozzle groups ejects ink droplets from at least one nozzle to a predetermined position on a recording material to record one pixel, and the nozzles forming at least one nozzle group include: In the case where all nozzle groups each eject an ink droplet from at least one nozzle to a predetermined position on the recording material to form a pixel, the landing position of the ink droplet ejected from at least one other nozzle is different. An ink jet recording head, characterized in that the ink jet recording head is arranged at a position where ink droplets land on the position. 2. A plurality of nozzle groups each including one or a plurality of nozzles arranged in the sub-scanning direction are arranged in the main scanning direction,
An ink jet recording head for ejecting ink droplets from at least one nozzle of one or a plurality of nozzle groups to a predetermined position on a recording material to record a recording pixel for one input image data pixel with one or a plurality of pixels. When all the nozzle groups eject ink droplets from at least one nozzle to a predetermined position on the recording material to form a pixel, the landing center position of each ink droplet becomes substantially the same position. An ink jet recording head, characterized in that at least one nozzle group is arranged such that one or a plurality of nozzles that are arranged are displaced from the reference position with respect to the reference position of each nozzle that is the arrangement position of the nozzle. 3. The recording head according to claim 2, wherein the nozzles arranged to be displaced from the reference position are arranged to be displaced from the reference position in the main scanning direction and / or the sub scanning direction. 4. The nozzles constituting at least one nozzle group are arranged so as to be offset from each other in the same direction and with the same length with respect to the reference position. Inkjet recording head. 5. The nozzles forming at least one nozzle group are alternately provided with nozzles arranged substantially at the same position as the reference position and nozzles arranged offset in the sub-scanning direction. The ink jet recording head according to claim 2 or 3, wherein 6. The nozzle group having nozzles arranged to be displaced from the reference position is set to eject only one color ink.
7. The inkjet recording head according to any one of items 1. 7. The nozzle so that the maximum distance of the distances between the landing center positions of the ink droplets ejected from different nozzles that form one pixel is 4/5 or less of the length corresponding to the printing resolution. 7. The inkjet recording head according to claim 1, wherein the inkjet recording head is provided. 8. The nozzle so that the maximum distance of the distances between the landing center positions of the ink droplets ejected from different nozzles that form one pixel is not more than ⅔ of the length corresponding to the printing resolution. 7. The inkjet recording head according to claim 1, wherein the inkjet recording head is provided. 9. A nozzle so that the maximum distance of the distances between the landing center positions of ink droplets ejected from different nozzles, which constitutes one pixel, is 1/2 or less of the length corresponding to the printing resolution. 7. The inkjet recording head according to claim 1, wherein the inkjet recording head is provided. 10. The inkjet according to claim 1, wherein the nozzles are arranged so that the landing center positions of at least cyan and magenta ink droplets do not become substantially the same position. Recording head. 11. A nozzle is arranged so that at least a landing center position of a magenta ink drop does not become substantially the same as a landing center position of another ink drop. The inkjet recording head according to any one of claims 1. 12. The maximum distance between the landing center positions of ink droplets forming adjacent pixels ejected from nozzles corresponding to the same color is the maximum of ink dots formed by ink droplets ejected from one nozzle. The inkjet recording head according to any one of claims 1 to 11, which has a diameter smaller than a diameter. 13. A center distance between pixels formed in the same ink droplet landing order in the sub-scanning direction is within a range in which a user who uses the obtained image cannot confirm a difference in tint. The inkjet recording head according to any one of claims 1 to 12, wherein a nozzle is provided. 14. A nozzle group having nozzles for ejecting ink corresponding to colors other than black is arranged at both ends of the recording head in the main scanning direction, and each nozzle group is arranged at both ends of the recording head in the main scanning direction. 14. The nozzles are arranged such that the landing center positions of the ink droplets ejected from the nozzles forming the respective nozzle groups are substantially the same position. The inkjet recording head according to 1. 15. The ink jet recording head according to claim 1, wherein the nozzle group is composed of nozzles arranged in a matrix of a plurality of rows and a plurality of columns. 16. An inkjet recording apparatus comprising the inkjet recording head according to claim 1. Description: