JP2006088604A - Method and device of inkjet recording - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of inkjet recording capable of performing high speed recording of an image, reducing of a usage amount of ink when recording a high density image and recording an image at a high speed, and a device of inkjet recording. <P>SOLUTION: In this method of inkjet recording, a plurality of dots are recorded on a recording medium by using a single head having a plurality of recording channels for ejecting ink. The recording is performed by switching between a quadrate recording mode for recording the plurality of dots to arrange the most adjacent dots in a roughly orthogonal direction and a high density recording mode for recording the plurality of dots to arrange the dots such that each of the dots has an angle of 60 degrees with respect to the most adjacent dots. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention mainly relates to an ink jet recording method and apparatus for expressing density gradation of an image by image recording by area modulation, and more particularly to an ink jet recording method and apparatus for performing image recording using a plurality of dot sizes.

  Conventionally, as an aspect of an ink jet recording head, there is a multi-channel recording head having a plurality of recording channels (recording elements) for ejecting ink droplets onto a recording medium. As one of the image recording methods using such a multi-channel recording head, a recording medium such as paper is wound around and held on the side surface of the drum, and the arrangement direction of the recording channels is changed while rotating the drum (main scanning). Image recording by a so-called drum scanner is known in which a recording medium is two-dimensionally scanned by a recording head by moving (sub-scanning) a recording head that matches the axial direction of the drum in the axial direction.

As another image recording method, the recording head is moved in the width direction of the recording medium (direction perpendicular to the main scanning direction) (sub-scanning) while the recording medium is being conveyed (main scanning) by conveying means such as a conveying roller or a conveying belt. In other words, a so-called serial recording method is known in which a recording medium is scanned and recorded two-dimensionally by a recording head.
As a recording method using a multi-channel recording head, a recording method having a dot arrangement shown in FIG. 4 on a recording medium is known. In other words, the dot arrangement is a square arrangement, and two dots adjacent to a certain dot in the main scanning direction and the sub-scanning direction form an angle of 90 degrees and are adjacent to a certain dot in the main scanning direction. The distance between the centers of the dots and the distance between the centers of the dots adjacent to the dot in the sub-scanning direction are equal.

However, in the square-arranged recording method, as shown in FIG. 8, when recording a high-density image including a solid image, in order to reduce the white area (the area of the recording medium on which no dots are formed). Therefore, it is necessary to increase the dot diameter, and the overlap between adjacent dots increases. As a result, the amount of ink used increases, and problems such as wrinkles, unevenness, and image bleeding may occur depending on the type of recording medium.
In particular, in the case where the recording medium is an inkjet recording paper with a limited ink acceptance amount, if the ink absorption amount to the recording paper exceeds a certain amount, the above-described wrinkles, unevenness, image blurring, etc. There are problems that double-sided printing cannot be performed and the drying load increases.
Further, in the above-described square-arranged recording method, since the dot arrangement pattern is constant, there is a possibility that moire occurs due to interference with the pattern existing in the image, and when forming a color image, For example, moire between colors of YMCK may occur.

  An object of the present invention is to solve the problems based on the prior art, and to convert the recording resolution using a single head having a plurality of nozzles for ejecting ink and to perform high resolution recording with a plurality of dots on a recording medium. It is possible to reduce the running cost (ink cost) by reducing the amount of ink used for full-surface recording, and it is advantageous when the ink receiving amount is limited, and further, the generation of moire can be reduced. As a result, it is an object of the present invention to provide an ink jet recording method and apparatus capable of performing high-speed image recording, reduction of ink usage when performing high-density image recording, and high-quality image recording.

  In order to achieve the above object, an invention according to claim 1 is an ink jet recording method for recording a plurality of dots on a recording medium using a single head having a plurality of nozzles for ejecting ink, wherein A square recording mode for recording the plurality of dots so that the dots are arranged in a substantially orthogonal direction, and a dense recording mode for recording the plurality of dots so that the closest dot to one dot is arranged at an angle of 60 ° The present invention provides an inkjet recording method characterized by switching between and.

  According to the present invention, a recording method that takes advantage of the square recording mode and the dense recording mode is possible. For example, the square recording mode has a feature that the relative position control between the recording head and the recording medium is simple, and high-speed recording can be performed. The dense recording mode is characterized in that the amount of ink in the density region where adjacent dots overlap is smaller than that in the square arrangement, and solves problems such as wrinkles, unevenness, and image bleeding that occur depending on the type of recording medium. According to the present invention, it is possible to optimize the recording speed, the amount of ink on the recording medium, and the high image quality.

The invention according to a second aspect relates to an aspect of the ink jet recording method according to the first aspect, wherein the ink jet recording method is an area modulation type recording which is modulated by an area occupied by dots recorded in one pixel. The dense recording mode is an ink jet recording method in which the recording resolution is converted with respect to the square recording mode.
In particular, in the area modulation type inkjet recording method in which gradation representation of image density is performed by area modulation of dots covering the recording medium, the recording resolution of the dense recording mode is converted to that of the square recording mode. The present invention is more suitably applied to recording.

The invention according to claim 3 relates to an aspect of the ink jet recording method according to claim 1 or 2, and in the dense recording mode, the head is disposed at a predetermined first position with respect to the recording medium. The plurality of dots are recorded, and the head is arranged at a nozzle pitch in the arrangement direction of the plurality of nozzles (sometimes referred to as a sub-scanning direction in this specification) from the first position with respect to the recording medium. The nozzle pitch p moves relative to a second position shifted by a half pitch (p / 2) of p, and in a direction substantially perpendicular to the arrangement direction (sometimes referred to as a main scanning direction in this specification). An inkjet recording method is provided that records the plurality of dots on the recording medium moved relative to the head by a (√3 / 2) pitch (√3p / 2).
When the nozzle pitch (distance between the nozzle centers) of the nozzles adjacent to the ink ejecting nozzles is equal to p, it is assumed that this is p. By moving at least one of the head and the recording medium, (p / 2) ), Relatively moved by (√3p / 2) in the main scanning direction and recorded. Thereby, a dot pattern can be recorded in a dense arrangement.

  The invention according to a fourth aspect relates to an aspect of the ink jet recording method according to the third aspect, wherein the dense recording mode is configured such that after the head is arranged at the first position and the plurality of dots are recorded, The head is moved from the first position to the second position, and the recording medium is conveyed by the (√3 / 2) pitch (√3p / 2) in a direction substantially perpendicular to the arrangement direction. Then, the plurality of dots are recorded, and then the head is returned to the first position again, and the recording medium is moved by the (√3 / 2) pitch (√3p) in a direction substantially perpendicular to the arrangement direction. / 2) The inkjet recording method is characterized in that the plurality of dots are recorded while being conveyed, and the recording at the first position and the recording at the second position are repeated.

The invention according to claim 5 relates to an aspect of the ink jet recording method according to claim 3, and in the dense recording mode, the plurality of dots are recorded by disposing the head at the first position. Each time the recording medium is conveyed by the (√3) pitch (√3p) of the recording channel pitch p in the direction substantially orthogonal to the arrangement direction by the head arranged at the first position, After repeating the recording of the dots, the head is moved from the first position to the second position, and further, with respect to the plurality of dots recorded first or last in the first position. The head or the recording medium is moved to a position shifted by (√3 / 2) pitch (√3p / 2) of the recording channel pitch p in a direction substantially orthogonal to the arrangement direction, and the plurality of dots are moved. Each time the recording medium is conveyed by the (√3) pitch (√3p) in a direction substantially perpendicular to the arrangement direction by the head arranged at the second position, An inkjet recording method is provided that repeats recording dots.
According to the fourth and fifth aspects, an image (including characters) can be recorded in a dot arrangement by dense recording over a desired recording area of the recording medium.

A sixth aspect of the invention relates to an aspect of the ink jet recording method according to any one of the third to fifth aspects, and the dot sizes of the plurality of dots recorded at the first position in the dense recording mode. And an ink jet recording method in which the dot sizes of the plurality of dots recorded at the second position are different.
By changing the dot size between the first position and the second position, the same density can be expressed by a combination of a plurality of dot sizes, and the ink amount is reduced by selecting an appropriate combination of dot sizes. be able to. Further, it is possible to reduce moire patterns that are likely to occur when an image includes a periodic pattern.

The invention according to claim 7 relates to an aspect of the ink jet recording method according to any one of claims 3 to 6, and the dot sizes of the plurality of dots recorded at the second position are different. I will provide a.
By changing the dot size at the second position, the same density can be expressed by a combination of a plurality of dot sizes, and by selecting an appropriate combination of dot sizes, the amount of ink can be reduced. Further, it is possible to reduce moire patterns that are likely to occur when an image includes a periodic pattern.

The invention according to claim 8 relates to an aspect of the ink jet recording method according to any one of claims 2 to 7, wherein the plurality of dots in the dense recording mode have different dot sizes depending on the recording resolution. An ink jet recording method including a plurality of dots is provided.
A change in area gradation occurs in image data that has undergone recording resolution conversion with respect to image data that has not undergone resolution conversion. That is, when the recording resolution is different, the adjacent dot pitch is different, and as a result, the overlap amount (overlapping area) between adjacent dots is different and the area gradation (density gradation) changes. Furthermore, the area gradation (density gradation) with respect to the change in dot size is also different. Even when the arrangement of dots to be recorded is different as in the square recording mode and the dense recording mode, the amount of overlap between adjacent dots with respect to the change in dot size differs when comparing the two, so area gradation (density gradation) Is different. Furthermore, the area gradation (density gradation) with respect to the change in dot size is also different. As in this aspect, the area gradation (density gradation) can be appropriately controlled by a recording method including dots having different dot sizes in accordance with the recording resolution.

The invention according to a ninth aspect relates to an aspect of the ink jet recording method according to any one of the second to eighth aspects, wherein in the dense recording mode, the recording is performed in consideration of a density change in an overlapping portion of the plurality of dots. An inkjet recording method is provided that performs gradation calibration that compensates for changes in area modulation accompanying resolution conversion.
As described above, the area gradation (density gradation) changes before and after the conversion of the recording resolution. Therefore, the gradation calibration is performed by compensating for this in consideration of the density change of the overlapping portions of the plurality of dots. Can be controlled appropriately.
A tenth aspect of the invention relates to an aspect of the ink jet recording method according to any one of the first to ninth aspects, wherein the head is an electrostatic ink jet head.
The electrostatic ink jet head can continuously change the dot size by controlling the voltage value applied to the discharge electrode for generating the ink discharge force, and functions suitably by changing the dot size. It is suitable for application to the inventions according to claims 1-9.

To achieve the above object, an invention according to claim 11 is an ink jet recording apparatus that records a plurality of dots on a recording medium, wherein a plurality of nozzles that eject ink are arranged in a predetermined arrangement direction. Two heads, position switching means for switching a relative position of the head position and the recording medium in the arrangement direction, and the recording medium is moved relative to the head in a direction substantially orthogonal to the arrangement direction. A square recording mode for recording the plurality of dots so that the closest dots are arranged in a substantially orthogonal direction, and the plurality of dots so that the closest dots for one dot are arranged at an angle of 60 °. Mode switching means for switching between dense recording modes for recording, and the position switching means and the moving hand according to the square recording mode and the dense recording mode. And controls the, there is provided an ink jet recording apparatus characterized by a control means for controlling recording of said plurality of dots by the head onto the recording medium.
According to the present invention, it is possible to optimize the recording speed, the amount of ink on the recording medium, and the high image quality.

A twelfth aspect of the invention relates to an aspect of the ink jet recording apparatus according to the eleventh aspect, wherein the ink jet recording apparatus is an area capable of resolution conversion modulated by an area occupied by dots recorded in one pixel. The inkjet recording apparatus according to claim 1, wherein the modulation type inkjet recording method is performed, and the dense recording mode performs recording in which a recording resolution is converted with respect to the square recording mode.
In particular, gradation representation of image density is more preferably applied to area-modulation type ink jet recording apparatuses in which the dense recording mode performs recording with a recording resolution converted to the square recording mode. The

A thirteenth aspect of the invention relates to an aspect of the ink jet recording apparatus according to the eleventh or twelfth aspect of the invention, wherein the position switching unit sets the position of the head to a predetermined first position with respect to the recording medium. And a second position relatively shifted from the first position by a half pitch (p / 2) of the nozzle pitch p in the arrangement direction. In the recording mode, the position switching unit arranges the head at the first position with respect to the recording medium, records the plurality of dots by the head, and the position switching unit records the head. Switching from the first position to the second position with respect to the medium, the moving means shifts the (√3 / 2) pitch of the nozzle pitch p in a direction substantially perpendicular to the arrangement direction. Inkjet recording apparatus for controlling the head, the position switching means, and the moving means so as to record the plurality of dots on the recording medium moved relative to the head by (√3p / 2) I will provide a.
When the nozzle pitch (distance between the nozzle centers) of the nozzles adjacent to the ink ejecting nozzles is equal to p, it is assumed that this is p. By moving at least one of the head and the recording medium, (p / 2) ), Relatively moved by (√3p / 2) in the main scanning direction and recorded. Thereby, a dot pattern can be recorded in a dense arrangement.

  A fourteenth aspect of the invention relates to an aspect of the ink jet recording apparatus according to the thirteenth aspect of the invention, wherein, in the dense recording mode, the control unit moves the head relative to the recording medium by the position switching unit. After the plurality of dots are recorded by the head, the head is switched from the first position to the second position with respect to the recording medium by the position switching unit. The recording medium is conveyed by the (√3 / 2) pitch (√3p / 2) in a direction substantially orthogonal to the arrangement direction by moving means, and the plurality of dots are recorded by the head, and thereafter The head is again returned to the first position with respect to the recording medium by the position switching means, and the recording medium is arranged by the moving means. The plurality of dots are recorded by being conveyed by the (√3 / 2) pitch (√3p / 2) in a direction substantially orthogonal to the first position, and recording at the first position and recording at the second position are performed. An inkjet recording apparatus that is controlled to repeat is provided.

According to a fifteenth aspect of the present invention, in the ink jet recording apparatus according to the thirteenth aspect, in the dense recording mode, the control unit moves the head relative to the recording medium by the position switching unit. The plurality of dots are recorded at the position of the recording channel pitch p, and the recording channel pitch p (√) in the direction substantially perpendicular to the arrangement direction is moved by the moving means by the head arranged at the first position. 3) Each time the recording medium is conveyed by a pitch (√3p), the head repeatedly records the plurality of dots by the head, and then the position switching means moves the head to the recording medium. Switching from the first position to the second position, and for the plurality of dots recorded first or last at the first position, The recording medium is moved by the moving means to a position shifted by (√3 / 2) pitch (√3p / 2) of the recording channel pitch p in a direction substantially orthogonal to the head, or the head is moved by the position switching means. The plurality of dots are recorded, and the recording medium is moved in the direction substantially perpendicular to the arrangement direction by the moving means by the head arranged at the second position. Provided is an ink jet recording apparatus that controls to repeat the recording of the plurality of dots by the dots each time the sheet is conveyed by the minute (√3p).
According to the aspects of the fourteenth and fifteenth aspects, it is possible to record dots over a desired recording area of the recording medium and form an image (including characters).

A sixteenth aspect of the invention relates to an aspect of the ink jet recording apparatus according to any one of the thirteenth to fifteenth aspects, wherein the control unit records the plurality of information recorded at the first position in the dense recording mode. There is provided an ink jet recording apparatus for controlling the head so that the dot size of each of the dots differs from the dot size of the plurality of dots recorded at the second position.
By changing the dot size between the first position and the second position, the same density can be expressed by a combination of a plurality of dot sizes, and the ink amount is reduced by selecting an appropriate combination of dot sizes. be able to. Further, it is possible to reduce moire patterns that are likely to occur when an image includes a periodic pattern.

The invention according to claim 17 relates to an aspect of the ink jet recording apparatus according to any one of claims 13 to 16, wherein the control means has a dot size of the plurality of dots recorded at the second position. Differently, an ink jet recording apparatus for controlling the head is provided.
By changing the dot size at the second position, the same density can be expressed by a combination of a plurality of dot sizes, and by selecting an appropriate combination of dot sizes, the amount of ink can be reduced. Further, it is possible to reduce moire patterns that are likely to occur when an image includes a periodic pattern.
The invention according to claim 18 relates to an aspect of the ink jet recording apparatus according to any one of claims 12 to 17, wherein the control unit is configured such that the plurality of dots in the dense recording mode differ according to the recording resolution. An ink jet recording apparatus for controlling the head so as to include dots of dot size is provided.
As in this aspect, the area gradation can be appropriately controlled by a recording apparatus including dots having different dot sizes in accordance with the recording resolution.

The invention according to claim 19 relates to an aspect of the ink jet recording apparatus according to any one of claims 12 to 18, wherein the control means takes into account density changes in the overlapping portions of the plurality of dots in the dense recording mode. An inkjet recording apparatus having a gradation calibration unit that performs gradation calibration that compensates for a change in area modulation accompanying the conversion of the recording resolution is provided.
Since the area modulation changes before and after the conversion of the recording resolution, the gradation calibration can be appropriately controlled by compensating for this in consideration of the density change of the overlapping portion of the plurality of dots.
A twentieth aspect of the invention relates to an aspect of the ink jet recording apparatus according to the eleventh aspect of the invention, wherein the head is an electrostatic ink jet head.
The electrostatic inkjet head can change the dot size continuously by controlling the voltage value applied to the ejection electrode for generating the ink ejection force, and functions suitably by changing the dot size. It is suitable for application to the inventions according to claims 11 to 19.

According to the inkjet recording method and apparatus of the present invention, recording is performed by switching between the square recording mode and the dense recording mode, so that recording using the advantages of both the square recording mode and the dense recording mode is possible, and the image quality is high. There are effects such as image recording, high-speed recording, and ink amount reduction due to a decrease in the overlap amount between adjacent dots.
That is, according to the present invention, high-resolution recording is possible, and full-surface recording can be performed with a small amount of ink, so that the ink cost can be kept low, and the use of a recording medium with a limited ink receiving amount can be achieved. It is advantageous, is also advantageous for double-sided printing, can reduce the drying load, can perform high-definition recording at high resolution, and can reduce or reduce moire by selecting resolution.

  Hereinafter, an ink jet recording method and apparatus of the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.

[Description of overall configuration, head, and ejection principle of electrostatic ink jet recording apparatus]
FIG. 1 shows a conceptual diagram of an embodiment of an ink jet recording apparatus for carrying out the ink jet recording method of the present invention. In the present embodiment, an electrostatic ink jet recording apparatus using an electrostatic ink jet head is used, and in the following description, for the sake of simplification of explanation, the recording head is assumed to eject one color ink.
The recording head used in the present invention may be a recording head that discharges a single color ink. However, the three colors of cyan (C), magenta (M), and yellow (Y), or C, M, Y And black (K) ink, or red (R), green (G) and blue (B) inks, respectively, can be used for full-color recording. it can. As the ink used in the present invention, each of C, M, and Y may further include two types of ink, dark ink and light ink. In addition to the CMYK ink, one or more inks such as R, G, and B may be further provided.

  The electrostatic ink jet recording apparatus shown in FIG. 1 has a head unit 14 provided with an electrostatic ink jet head (hereinafter also referred to as an ink jet head) 10 for discharging ink, and a recording medium W on which an image is recorded on an outer peripheral surface. A rotating drum 16 that is wound and held, a main scanning rotation driving unit 8 that rotates the rotating drum 16, and a sub-scanning driving unit 18 that moves the head unit 14 in a sub-scanning direction parallel to the rotation shaft 16 a of the rotating drum 16. The recording control means 20 for driving the ink-jet head 10 in accordance with the image data, the ink supply means 22 for supplying ink to the ink-jet head 10, and the switching of the recording mode, which is the most characteristic feature of the present invention, that is, the square recording mode and the dense recording mode Recording mode control that controls recording in each recording mode by switching between recording modes A stage 24, and a general control unit (not shown) or the like for controlling the entire of each section of the recording apparatus.

  The inkjet head 10 is provided with a plurality of recording channels (ink ejection units) arranged in the sub-scanning direction parallel to the rotation shaft 16 a of the rotary drum 16. Here, the ink supply means 22 includes an ink tank 6 that stores ink, a pump 5 that supplies ink from the ink tank 6 to the inkjet head 10, and a supply path 7 that connects the inkjet head 10 and the ink tank 6. . The ink-jet head unit 14 is provided with a multi-channel ink-jet head 10 for each color ink, and each ink-jet head 10 has an ink tank 6, a pump 5 and a supply path 7 for each ink color. And are provided. Although not shown, the ink supply means 22 includes an ink circulation mechanism that collects and circulates ink from the inkjet head 10 to the ink tank 6 for each ink, a concentrate replenishment tank, a diluting liquid replenishing tank, and a replenishing liquid tank. Etc. may be provided.

The main scanning rotation driving means 8 is for rotating the rotating drum 16. For example, although not shown, the rotation driving force of a driving motor serving as a driving source is supplied to the rotating shaft 16 a of the rotating drum 16 via a pulley. It is possible to adopt a configuration in which the rotary drum 16 is rotated.
The sub-scanning driving means 18 is for moving in the sub-scanning direction parallel to the rotation shaft 16a of the rotary drum 16. For example, the sub-scanning driving means 18 is screwed along the guide bar 18a extending in the rotation axis direction of the rotary drum 16. For example, means such as transmission, belt transmission using a pulley, a gear such as a rack and pinion, or the like can be used.
Various means can be used as long as the main scanning rotation driving means 8 and the sub-scanning driving means 18 can achieve the desired movement accuracy.

  The recording mode control unit 24 also functions as a mode switching unit that switches between the square recording mode and the dense recording mode and a control unit that controls recording of a plurality of dots in each recording mode. At the time of switching, the main scanning rotation driving means 8, the sub scanning driving means 18 and the recording control means 20 are controlled according to each recording mode to perform image recording in each recording mode. Here, the sub-scanning driving unit 18 also functions as a position switching unit of the present invention that switches the relative position in the sub-scanning direction between the position of the inkjet head 10 and the position of the recording medium W on the rotary drum 16. The drive unit 8 also functions as a position switching unit of the present invention that moves the recording medium W on the rotary drum 16 relative to the inkjet head 10.

Next, the electrostatic ink jet head and the ink ejection principle will be described in more detail with reference to FIG.
FIG. 2 is a schematic cross-sectional view showing a schematic configuration of an embodiment of the electrostatic inkjet head. The electrostatic ink jet recording method uses an electrostatic force by applying a predetermined voltage to the ejection electrode of the electrostatic ink jet head 10 according to image data using ink containing a charged fine particle component. In this method, ink ejection is controlled and an image corresponding to the image data is recorded on a recording medium.

The electrostatic ink jet head 10 shown in the figure discharges an ink Q containing a fine particle component such as a charged pigment (for example, toner) by an electrostatic force, and an image is recorded on a recording medium W according to image data. For recording, the head substrate 32, the ink guide 34, the insulating substrate 36, the ejection electrode 38, the counter electrode 40 on the outer peripheral surface of the rotary drum 16 that supports the recording medium W, and the recording medium W are charged. A charging unit 42, a signal voltage source 44, and a floating conductive plate 46.
In addition, the example shown in FIG. 2 conceptually represents only the individual electrodes that are one ejection unit constituting the inkjet head 10. There are a plurality of individual electrodes, and they are arranged one-dimensionally to constitute a line head.

  In the ink jet head 10 shown in the drawing, the ink guide 34 is made of an insulating resin flat plate having a projecting tip portion 34a and having a predetermined thickness, and is disposed on the head substrate 32 for each individual electrode. The insulating substrate 36 has a through hole 48 at a position corresponding to the arrangement of the ink guide 34. The ink guide 34 passes through a through hole 48 opened in the insulating substrate 36, and a tip end portion 34a thereof protrudes above the upper surface of the insulating substrate 36 in the drawing, that is, the surface on the recording medium W side. Yes. Note that a cutout (not shown) serving as an ink guide groove for collecting the ink Q in the tip end portion 34a by capillary action may be formed in the central portion of the ink guide 34 in the vertical direction in the drawing.

  The leading end portion 34a of the ink guide 34 is formed into a substantially triangular shape (or a trapezoidal shape) that gradually becomes thinner toward the counter electrode 40 side. In addition, it is preferable that a metal is vapor-deposited on the tip portion (the most advanced portion) 34a of the ink guide 34 from which the ink Q is discharged. Although the metal vapor deposition of the tip portion 34a of the ink guide 34 may not be performed, the metal vapor deposition makes the dielectric constant of the tip portion 34a of the ink guide 34 substantially infinite, and can easily generate a strong electric field. Since there is an effect, it is preferable to perform metal vapor deposition. The shape of the ink guide 34 is not particularly limited as long as the ink Q, in particular, the charged fine particle component in the ink Q can be concentrated to the tip portion 34a through the through hole 48 of the insulating substrate 36. For example, the tip portion 34a may be changed as appropriate, for example, not necessarily protruding.

  The head substrate 32 and the insulating substrate 36 are disposed with a predetermined distance therebetween, and an ink flow path that functions as an ink reservoir (ink chamber) for supplying the ink Q to the ink guide 34 therebetween. 50 is formed. The ink Q in the ink flow path 50 includes a fine particle component charged with the same polarity as the voltage applied to the ejection electrode 38. During recording, an ink circulation mechanism (not shown) (see ink supply means 22 in FIG. 1) is used. ) Is circulated at a predetermined speed (for example, an ink flow of 200 mm / s) from the right side to the left side in the ink flow path 50 in the illustrated example. Hereinafter, the case where the colored particles in the ink are positively charged will be described as an example.

Further, as shown in FIG. 3A, the discharge electrode 38 surrounds the periphery of the through-hole 48 opened in the insulating substrate 36 in the drawing, that is, on the recording medium W side. Are arranged in a ring shape for each individual electrode, that is, as a circular electrode 38a. The ejection electrode 38 is supplied with a pulse signal corresponding to ejection data (ejection signal) such as image data and print data supplied from the recording control means 20 (a predetermined pulse voltage, for example, 0V at a low voltage level, a high voltage level). Of 400 to 600V) is connected to a signal voltage source 44.
The discharge electrode 38 is not limited to the ring-shaped circular electrode 38 a shown in FIG. 3A, but is a surrounding electrode arranged so as to surround the outer periphery of the ink guide 34, or on both sides of the ink guide 34. Any parallel electrodes may be used as long as they are spaced apart and opposed to each other. For example, in the case of a surrounding electrode, the discharge electrode 38 is preferably a substantially circular electrode, but more preferably a circular electrode.
Hereinafter, a ring-shaped circular electrode 18a shown in FIG. 3A will be described as a representative example of the surrounding electrode.

  The counter electrode 40 includes a cylindrical electrode substrate 40a that covers the outer peripheral surface of the cylindrical main body 16b of the rotary drum 16, and a cylindrical insulating sheet 40b that covers the outer peripheral surface of the electrode substrate 40a. An outer peripheral portion of the rotary drum 16 is formed. The insulating sheet 40b is disposed on the outer surface (outer peripheral surface) of the cylindrical electrode substrate 40a, that is, the surface on the ink guide 34 side. In addition, the main body 16a itself of the rotating drum 16 may be made of an electrode material and used as the electrode substrate 40a. Here, the electrode substrate 40a is grounded. As a result, even when the drum 16 rotates, the electrode substrate 40a is always arranged and grounded at a position facing the tip portion 34a of the ink guide 34. The recording medium W is electrostatically adsorbed, for example, on the outer surface (outer peripheral surface) of the cylindrical counter electrode 40, that is, the surface on the ink guide 34 side, that is, the outer surface (outer peripheral surface) of the insulating sheet 40b. The counter electrode 40 (insulating sheet 40b) functions as a platen of the recording medium W.

  Here, at least at the time of recording, the charging unit 42 causes the recording medium W on the outer peripheral surface of the insulating sheet 40b of the counter electrode 40 to have a predetermined negative polarity opposite to the high voltage (pulse voltage) applied to the ejection electrode 38. It is maintained in a charged state at a high voltage, for example, -1.5 kV. As a result, the recording medium W is negatively charged by the charging unit 42, is always biased to a negative high voltage with respect to the ejection voltage 38, and is electrostatically attracted to the insulating sheet 40 b of the counter electrode 40. The charging unit 42 includes a scorotron charger 42a for charging the recording medium W to a negative high voltage, and a bias voltage source 42b for supplying a negative high voltage to the scorotron charger 42a. The charging means of the charging unit 42 used in the present invention is not limited to the scorotron charger 42a, and various discharge means such as a corotron charger, a solid charger, and a discharge needle can be used.

In the illustrated example, the counter electrode 40 is composed of an electrode substrate 40a and an insulating sheet 240b, and the recording medium W is electrostatically attracted to the surface of the insulating sheet 40b by charging the recording medium W to a negative high voltage. However, the present invention is not limited to this, and the counter electrode 40 is composed only of the electrode substrate 40a, and the counter electrode 40 (the electrode substrate 40a itself) is connected to a negative high voltage bias voltage source. Alternatively, the recording medium W may be electrostatically attracted to the surface of the counter electrode 40 by constantly biasing to the high voltage.
Further, the electrostatic adsorption of the recording medium W to the counter electrode 40 and the charging of the recording medium W to a negative high voltage or the application of a negative bias high voltage to the counter electrode 40 are separate negative high voltage sources. You may go by. A method and means for supporting the recording medium W by the counter electrode 40, that is, supporting or fixing the recording medium W to the outer peripheral surface of the cylindrical counter electrode 40 (insulating sheet 40 b), such as electrostatic adsorption of the recording medium W, etc. The method is not limited to the electrical support or fixing method or means, but may be a mechanical or physical method or means, or may be another magnetic support method or means such as a magnetic method or means.

  The floating conductive plate 46 is disposed below the ink flow path 50 and is in an electrically insulated state (high impedance state). In the illustrated example, it is arranged inside the head substrate 32. In the present invention, the floating conductive plate 46 may be disposed anywhere below the ink flow path 50. For example, the floating conductive plate 46 may be disposed below the head substrate 32 or more than the position of the individual electrode. It may be arranged upstream of the ink flow path 50 and inside the head substrate 32.

The floating conductive plate 46 generates an induced voltage in accordance with the voltage value applied to the individual electrode during image recording, and the fine particle component is separated from the insulating substrate in the ink Q in the ink flow path 50. It is intended to migrate to the 36 side and concentrate. Therefore, it is preferable that the floating conductive plate 46 be disposed closer to the head substrate 32 than the ink flow path 50. The floating conductive plate 46 is preferably arranged on the upstream side of the ink flow path 50 from the position of the individual electrode. In order to increase the concentration of the charged fine particle component in the upper layer in the ink flow path 50 by the floating conductive plate 46, the concentration of the charged fine particle component in the ink Q passing through the through hole 48 of the insulating substrate 36 is increased to a predetermined concentration. It is possible to stabilize the concentration of the charged fine particle component in the ink Q that is condensed as the ink droplet R and ejected as the ink droplet R at a predetermined concentration.
Moreover, since the induced voltage changes according to the number of operating channels by arranging the floating conductive plate, the charged particles necessary for ejection can be supplied without controlling the voltage to the floating conductive plate. Can be prevented. A predetermined voltage may be applied by connecting a power source to the floating conductive plate.

In the inkjet head 10 configured as described above, at the time of recording, an ink containing a fine particle component charged to the same polarity as the voltage applied to the ejection electrode 38 is transferred in a predetermined direction, in the illustrated example, by an ink circulation mechanism (not shown). While being circulated in the ink flow path 50 from the right side to the left side, a part of the ink flow path 50 passes through the through hole 48 of the insulating substrate 36 due to a capillary phenomenon or the like and passes through the front end portion 34a of the ink guide 34. To be supplied.
Here, when a pulse voltage, for example, DC 500 V (Note; for example) (ON) (0 V: OFF) is applied to the ejection electrode 38 from the signal voltage source 44, the result is ink Q, particularly ink. The charged fine particle component in Q rises along the ink guide 34 and aggregates at the tip end portion 34a. In this way, the ink Q containing the charged fine particle component aggregated at the tip portion 34a of the ink guide 34 jumps out of the tip portion 34a by electrostatic force, is pulled by the grounded counter electrode 40a, and adheres to the recording medium W. A dod is formed by the charged fine particle component.

Thus, an image corresponding to the image data is recorded on the recording medium W by performing recording with the ink Q dot while relatively moving the inkjet head 10 and the recording medium W supported by the counter electrode 40a. .
The dot size on the recording medium can be changed by changing the amount of ink ejected onto the recording medium in order to record an image. For example, by changing the drive signal supplied to the inkjet head 10 by the recording control means 20 according to the dot diameter modulation characteristics, specifically, the pulse width of the voltage applied from the signal voltage source 44 to the ejection electrode 38 is changed. By doing so, the amount of ink ejected can be changed, and the dot size can be changed. For the dot diameter modulation characteristic, the dot diameter for a plurality of drive signals (voltage and pulse width) is measured in advance, a drive signal having a required dot diameter is obtained, and the relationship between the two is obtained. For example, when the recording resolution is 600 dpi, the normal recording dot diameter 2R (R = radius) is 42.3 μm, and in all recordings in the square recording mode and the dense recording mode described later, the recording dot diameter is Since (√2) · 2R (= (√2) p) and (√14) · 2R / 3 (= (√14) p / 3), the dot diameter is 2R, (√2) · 2R and What is necessary is just to obtain | require each the drive signal used as ((root) 14) * 2R / 3.

[Description of dot arrangement in recording channel arrangement, square recording mode, and dense recording mode]
Next, the dot arrangement in the recording channel arrangement, the square recording mode, and the dense recording mode will be described.
For convenience of explanation, it is assumed that the number of recording channels of the inkjet head 10 shown in FIG. 1 is 6, and an image is recorded at a resolution of 600 dpi. Of course, the recording resolution in the present invention is not limited to 600 dpi, and the number of recording channels (number of nozzles) is not limited to six. The six recording channels are arranged at equal distances on a straight line in the sub-scanning direction, and the distance (recording channel pitch) between the centers of adjacent recording channels is p. As shown in FIG. 2, in the electrostatic ink jet head 10, the recording channel corresponds to a portion for ejecting ink Q, which includes an ink guide 34, a discharge electrode 38, a through hole (nozzle) 48, and the like.

In the electrostatic ink jet recording apparatus of the present invention, a square recording mode is provided as the first recording mode among the recording modes switched and controlled by the recording mode control means 24. As shown in FIG. 4, the arrangement of dots recorded in the square recording mode is such that the center-to-center distance Pm between a certain dot Da1 and a dot Db1 adjacent in the main scanning direction, and a dot adjacent to a certain dot Da1 in the sub-scanning direction. The distance Ps between the centers with Dc1 is equal, and the straight line connecting the centers of the dots Da1 and Db1 and the straight line connecting the centers of the dots Da1 and Dc1 form an angle of 90 degrees. The center distances Ps and Pm are also equal to the recording channel pitch p.
That is, each line shown in FIG. 4 is rotated in the main scanning direction without switching the relative position of the inkjet head 10 and the recording medium W in the sub scanning direction (horizontal direction in the figure) by the sub scanning sub scanning driving means 18. It is recorded by the ink jet head 10 controlled by the recording control means 20 every time the driving means 8 moves in the main scanning direction (vertical direction in the figure) by the pitch p.

A new dense recording mode is provided as a second recording mode that is switched and controlled by the recording mode control means 24. As shown in FIG. 5, the arrangement of dots recorded in the dense recording mode is such that the center distance between a certain dot Da2 and a dot Db2 adjacent in the main scanning direction is p, and the dot Dc2 adjacent in the sub-scanning direction. The distance between the centers is also p, and the straight line connecting the centers of the dots Da2 and Db2 and the straight line connecting the centers of the dots Da2 and Dc2 form an angle of 60 degrees. That is, all the six dots adjacent to the dot Da2 have a center-to-center distance p of the dot Da2, and the straight lines connecting the centers of the six dots with the center of the dot Da2 are at an angle of 60 degrees. I am doing.
That is, the odd-numbered lines shown in FIG. 5 are generated by the main scanning rotation driving unit 8 without switching the relative positions of the inkjet head 10 and the recording medium W in the sub scanning direction by the sub scanning sub scanning driving unit 18. It is recorded by the inkjet head 10 controlled by the recording control means 20 every time it moves by √3 pitch (√3p) in the main scanning direction. As compared with the odd-numbered lines, the even-numbered lines shown in FIG. 5 have the ink jet head 10 moved by the sub-scanning sub-scanning driving unit 18 so that the relative position in the sub-scanning direction with respect to the recording medium W is half pitch (p / 2) The image is recorded by the ink-jet head 10 controlled by the recording control means 20 every time it moves differently by the main scanning rotation driving means 8 and moves by a pitch √3p in the main scanning direction.

Next, the unit cell (pixel) in the two recording modes and the occupancy rate of the dot in the unit cell are considered by the area ratio of the unit cell and the dot. When droplets are ejected with a dot diameter of p in the dot arrangement recorded in the square recording mode, considering a lattice as a unit, it becomes a square like K and K ′ in FIG. At this time, the occupancy rate of dots in the unit cell is π / 4.
On the other hand, when dots are ejected at a dot diameter of p in the dot arrangement recorded in the dense recording mode, considering a unit lattice, a regular hexagon is formed as indicated by “K” in FIG. The dot occupancy is (√3) π / 6.
It can be seen that the dot arrangement recorded in the dense recording mode has a higher occupation ratio than the dot arrangement recorded in the square recording mode.

Next, let us consider the dot diameter required when the dots completely cover the recording medium in the two recording modes.
As shown in FIG. 8, in the dot arrangement recorded in the square recording mode, when the dot diameter is (√2) p, the entire recording medium can be covered. As shown in FIG. 9, in the dot arrangement recorded in the dense recording mode, the entire recording medium can be covered when the dot diameter is (√14) p / 3.

  Accordingly, the dot arrangement recorded in the dense recording mode can cover the entire surface of the recording medium and record a full image even if the dot diameter is small, that is, the amount of ink is small. Since not only the solid image but also the amount of ink is less than that in the square recording mode at the time of high density recording of the image, the ink can be used efficiently and the ink cost (running cost) can be reduced. In addition, even when the recording medium is a recording medium with a limited ink receiving amount, such as when the recording medium is a penetrating system, wrinkles, unevenness (cockling), which occurs when the ink absorption amount exceeds a certain amount, There is an advantage that problems such as image bleeding are less likely to occur. Furthermore, it is possible to reduce the drying load for reliably fixing the ink on the recording medium. In particular, the effect becomes more remarkable in the case of double-sided printing.

[Description of Image Recording Method in Electrostatic Inkjet Recording Apparatus of the Present Invention]
Next, an image recording method in the electrostatic ink jet recording apparatus of the present invention will be described. The electrostatic ink jet recording apparatus of the present invention has both the square recording mode and the dense recording mode described above, and has a function of recording by switching between these modes.

First, a recording method using the square recording mode according to the present invention will be described with reference to FIGS. FIG. 10 is a flowchart illustrating an example of a recording method in the square recording mode, and FIG. 11 is a schematic diagram illustrating an example of the arrangement and recording order of dots recorded in the square recording mode.
For convenience of description, the position coordinates on the recording medium in FIG. 11 are represented by (x, y) where the upper left corner of the recording medium is the origin, the main scanning direction is x, and the sub-scanning direction is y. In addition, the coordinates on the recording medium of the leftmost recording channel in the drawing are represented by (xs, ys). The positive direction in the x direction is the downward direction on the recording medium, and the positive direction in the y direction is the right direction of the recording medium.

First, as shown in FIG. 1, the recording channel (the inkjet head 10 of the head unit 14) comes to a predetermined recording position of the recording medium W that is wound and held around the outer peripheral surface of the rotary drum 16. Set. That is, as shown in FIG. 10, the rotary drum 16 is rotated by the main scanning rotation driving means 8 to adjust the initial recording start position in the main scanning direction (step S11), and the head unit 14 is sub-scanned by the sub-scanning driving means 18. In the sub-scanning direction to perform initial registration (step S12).
In the example shown in FIG. 11, the leftmost recording channel is set to a position facing the recording start initial position (x0, y0) on the recording medium. That is, (xs, ys) = (x0, y0). At this time, the other five recording channels are set to (x0, y0 + p), (x0, y0 + 2p),..., (X0, y0 + 5p) when the recording channel pitch is p. This completes the setting of the recording channel at the image recording start position.

Next, in step S13 shown in FIG. 10, ink is ejected according to the image data to be recorded from the six recording channels, thereby forming dots on the recording medium. Subsequently, after rotating the rotary drum 16 by 1 pitch p in the main scanning direction on the recording medium by the main scanning rotation driving means 8 in step S14, the position is within the recording area in the main scanning direction in step S15. Or if it is within the recording area instead of the end position (N), return to step S13 to eject ink from the six recording channels and To form dots. Subsequently, a rotation movement in the main scanning direction (step S14) and a determination of whether the recording area is finished (step S15) are performed.
Thereafter, as long as the recording channel of the inkjet head 10 is in the recording area (N), dot formation by ink ejection from the recording channel (step S13), rotational movement in the main scanning direction (step S14), and the end of the recording area. The determination (step S15) is repeated and image recording for the width in the sub-scanning direction corresponding to the six recording channels is performed over the entire image recording area in the main scanning direction.

Next, when it is determined in step S15 that the movement position by the rotational movement in the main scanning direction (step S14) has reached the recording area end position (Y), in step S16, the main scanning rotation driving means 8 causes the main scanning rotation driving means 8 to move. The rotary drum 16 is rotated and aligned to the recording start initial position (xs = x0), and the head unit 14 is moved in the sub-scanning direction by the sub-scanning driving unit 18 so that the next sub-scanning recording start position (2 At the second time, ys = y0 + 6p; at the nth time, alignment is made to ys = y0 + (n−1) · 6p (n = 1, 2, 3,...)) (See FIG. 11).
Next, in step S17, it is determined whether the recording start position in the sub-scanning direction is in the recording area in the sub-scanning direction or the end position outside the recording area, and if it is in the recording area instead of the end position. (N), it returns to step S13.
Thereafter, dot formation by ink ejection (step S13), rotational rotation of the rotary drum 16 by p in the main scanning direction on the recording medium (step S14), and determination of whether it is within the main scanning recording area (step S15). ) By repeating the image recording of the width (6p) in the sub-scanning direction over the entire area of the image recording in the main scanning direction, rotating the drum to the initial recording start position in the main scanning direction, and moving to the sub-scanning direction recording start position The alignment (step S16) and the determination of whether or not it is in the sub-scanning recording area (step S17) are repeated, and the movement position by the movement to the sub-scanning direction recording start position (step S16) becomes the sub-scanning recording area end position. When it is determined (Y) (step S17), the recording in the square recording mode is terminated.
By repeatedly performing image recording as described above, image formation can be performed over the entire image recording area in both the main and sub scanning directions.

  At this time, dot formation by ink ejection (step S13) and rotational movement in the main scanning direction (step S14) are performed while continuously rotating the rotary drum 16 in the main scanning direction, that is, the recording medium W. The recording may be performed while continuously moving in the main scanning direction, and the initial recording start position in the main scanning direction (step S11) and the drum rotation to the main scanning direction recording start position (step S16) are recorded control means. Alternatively, the recording timing may be controlled by 20. Further, the determination of whether or not it is in the main scanning recording area (step S15) and the determination of whether or not it is in the sub scanning recording area (step S17) is performed in advance with respect to the lengths of the main scanning recording area and the sub scanning recording area, From the relationship between the pitch and the sub main scanning movement pitch, the number of main scanning movements and the number of sub main scanning movements necessary for recording in the entire recording area are obtained, and the number of main scanning movements and the number of sub main scanning movements are counted. May be.

  Next, a recording method in the dense recording mode according to the present invention will be described with reference to FIGS. 1, 12, 13, and 14. FIG. FIG. 12 is a flowchart showing an example (first mode) of the recording method in the dense recording mode, and FIG. 13 is a flowchart showing another example (first mode) of the recording method in the dense recording mode. FIG. 14 is a schematic diagram illustrating an example of the arrangement and recording order of dots recorded in the dense recording mode. 14 are the same as those in the description of the square recording mode shown in FIG.

First, the first mode of the dense recording mode will be described with reference to FIG. 1, FIG. 12, and FIG.
First, as shown in FIG. 1, a recording channel (the inkjet head 10 of the head unit 14) is located at a predetermined recording position of a recording medium W on which an image is recorded, which is wound and held around the outer peripheral surface of the rotary drum 16. Set to come. That is, as shown in FIG. 12, the rotary drum 16 is rotated by the main scanning rotation driving means 8 to adjust the initial recording start position in the main scanning direction (step S21), and the head unit 14 is sub-scanned by the sub-scanning driving means 18. In the sub-scanning direction to perform initial position registration (step S22). In this example, the leftmost recording channel in FIG. 14 is set at a position facing the recording start position (x0, y0) on the recording medium. That is, (xs, ys) = (x0, y0). As a result, the recording channel is set at the image recording start position.

Next, in step S23 shown in FIG. 12, ink is ejected from the six recording channels according to the recording image data to form dots on the recording medium.
Next, in step S24, the head unit 14 is shifted by the half pitch (p / 2) of the recording channel in the sub-scanning direction by the sub-scanning driving unit 18, and ys = y0 + (p / 2) (y + (p / 2) Y is moved to the position of the previous sub-scanning recording start position), and the recording position in the sub-scanning direction is adjusted. Further, the main scanning rotation driving means 8 rotates the rotary drum 16 by (√3p / 2) on the recording medium to adjust the recording position in the main scanning direction (see FIG. 14).
Next, in step S25, (xs, ys) = (x0 + (√3p / 2), y0 + (p / 2)) (= (x + (√3p / 2), y + (p / 2))); x, Ink is ejected from the six recording channels at a position y (the previous sub-scan recording start position) to form dots on the recording medium (see FIG. 14).

Next, in step S26, the head unit 14 is returned to the negative direction of the sub-scanning direction by (p / 2) by the sub-scanning driving unit 18, and the recording position in the sub-scanning direction is adjusted by setting ys = y0 (y). The drum is rotated by (√3p / 2) on the recording medium by the scanning rotation driving means 8 to adjust the recording position in the main scanning direction (see FIG. 14).
Subsequently, in step S27, it is determined whether or not the main scanning direction recording position is in the main scanning direction recording area or the end position outside the recording area. N), returning to step S23.
Thereafter, as long as the recording channel of the inkjet head 10 is in the recording region (N), dot formation on the recording medium by ejecting ink from the six recording channels (step S23) and the sub-scanning direction (forward direction) ) Movement and rotation movement in the main scanning direction (step S24), dot formation on the recording medium by ink ejection (step S25), movement in the sub-scanning direction (negative direction), and movement in the main scanning direction The recording position alignment by rotational movement (step S26) and the determination of whether the recording area ends (step S27) are repeated. Thus, image recording for the width in the sub-scanning direction corresponding to the six recording channels is performed over the entire image recording area in the main scanning direction.

Next, when it is determined in step S27 that the recording position by the rotational movement in the main scanning direction (step S26) has reached the recording region end position (Y), the main scanning rotation driving means 8 causes the initial start of recording in the main scanning direction. The rotary drum 16 is rotated to the position (xs = x0) for alignment, and the head unit 14 is moved by 6 pitches (6p) in the sub-scanning direction by the sub-scanning driving means 18, and the next sub-scanning direction recording start position (In the second time, ys = y0 + 6p; in the nth time, ys = y0 + (n−1) · 6p (n = 1, 2, 3,...)). That is, the head unit 14 is set to the recording start position (xs, ys) = (x0, y0 + 6p) at the second recording time, and (x0, y0 + (n−1) · 6p) at the nth recording time. (See FIG. 14).
Next, in step S29, it is determined whether the recording start position in the sub-scanning direction is within the recording area in the sub-scanning direction or the end position outside the recording area. If (N), the process returns to step S23.

Subsequently, the sub-scanning width of the entire image recording area in the main scanning direction is obtained by repeating the steps from dot formation on the recording medium (step S23) to determination of whether the recording area is ended (step S27). (6p) image recording, alignment in the recording start position by rotation movement in the main scanning direction and movement in the sub-scanning direction (6p) (step S28), and determination as to whether it is in the sub-scanning recording area (step) S29) is repeated, and when it is determined that the movement position by the movement to the recording start position in the sub scanning direction (step S28) has become the sub scanning recording area end position (Y) (step S29), the dense recording mode is set. The recording in the first mode is finished.
By repeatedly performing image recording as described above, image formation can be performed over the entire image recording area in both the main and sub scanning directions.

  The dot formation recorded by the recording method in the first mode of the above-described dense recording mode is shown in FIG. 14, where B61 to B66 and D61 to D66 are the end of the image in the main scanning direction, and the dot formation is A11 to A16. , B11 to B16, A21 to A26, B21 to B26,..., A61 to A66, B61 to B66, followed by C11 to C16, D11 to D16, C21 to C26, D21 to D26,. C66, D61 to D66 are performed in this order.

Next, the second mode of the dense recording mode will be described with reference to FIG. 1, FIG. 13, and FIG.
First, as shown in FIG. 1, a recording channel (the inkjet head 10 of the head unit 14) is located at a predetermined recording position of a recording medium W on which an image is recorded, which is wound and held around the outer peripheral surface of the rotary drum 16. Set to come. That is, as shown in FIG. 13, the rotating drum 16 is rotated by the main scanning rotation driving means 8 to align the recording start initial position in the main scanning direction (step S31), and the head unit 14 is moved by the sub scanning driving means 18. The position is moved in the sub-scanning direction to align the initial position of recording start in the sub-scanning direction (step S32). This sets the recording start position (xs, ys) = (x0, y0).

Next, in step S33 shown in FIG. 13, the routine switch SW = 0 is set, and in step S34, ink is ejected from the six recording channels according to the recording image data to form dots on the recording medium.
Next, in step S35, the drum is rotated by (√3p) on the recording medium by the main scanning rotation driving means 8, and (xs, ys) = (x0 + (√3p), y0) (first movement) ), (X0 + (n × √3p), y0) (the nth movement), the head unit 14 is moved. In step S36, it is determined whether this position is within the recording area in the main scanning direction or the end position outside the recording area. If it is not the end position but within the recording area (N), the process returns to step S34. .

  Thereafter, as long as the recording channel is in the recording area (N), the dot formation on the recording medium by ink ejection from the recording channel (step S34), the rotational movement in the main scanning direction (step S35), and the end of the recording area. The determination (step S36) is repeated, and printing is performed up to the last scanning line of the image recording area in the main scanning direction or the line immediately before the last scanning line. This corresponds to recording dots A11 to A16, A21 to A26,..., A61 to A66 in FIG. Thus, image recording for the width in the sub-scanning direction corresponding to the six recording channels is performed every other line (only the dot A line) over the entire image recording area in the main scanning direction.

  Next, when it is determined in step S36 that the movement position by the rotational movement in the main scanning direction (step S35) has reached the recording area end position (Y), it is determined in step S37 whether or not the routine switch SW = 0. If the routine switch SW = 0 (Y), in step S38, the rotary drum 16 is rotated by the main scanning rotation driving means 8, the head unit 14 is moved by the sub scanning driving means 18, and the recording start position (xs , Ys) = (x0 + (√3p / 2), y0 + p / 2) (= (x + (√3p / 2), y + p / 2)), and in step S39, the routine switch SW = 1 is set. Returning to S34, ink is ejected from the six recording channels to form dots on the recording medium.

Next, in step S35, the rotary drum 16 is rotated by (√3p) on the recording medium by the main scanning rotation driving means 8, and the recording start position (xs, ys) = (x0 + (3√3p) / 2. , Y0 + p / 2) (= (x + (√3p), y + p / 2)), and in step S36, it is determined whether or not the position is within the recording area in the main scanning direction. As long as the recording channel is in the recording area (N), the process returns to step S34, and dot formation on the recording medium (step S34), rotational movement in the main scanning direction (step S35), and determination of whether the recording area ends (step S36). Are repeated until the end scanning line of the image recording area in the main scanning direction or the line immediately before the end scanning line is recorded. This corresponds to recording the dots B11 to B16, B21 to B26,..., B61 to B66 in FIG.
Thus, image recording for the width in the sub-scanning direction corresponding to the six recording channels is performed every other line (dot B line only) over the entire image recording area in the main scanning direction. Fills the space between the dots A, and image recording for the width (approximately 6p) in the sub-scanning direction corresponding to approximately six recording channels is performed over the entire image recording region in the main scanning direction.

Next, when it is determined in step S36 that the movement position by the rotational movement in the main scanning direction (step S35) has reached the recording area end position (Y), it is determined in step S37 whether or not the routine switch SW = 0. However, in this case, since SW = 1 (N), the process moves to step 40, and in step S40, the main scanning rotation driving means 8 sets the main scanning direction recording start initial position (xs = x0). The rotary drum 16 is rotated, and the head unit 14 is moved by the sub-scanning driving means 18 so that the next sub-scanning direction recording start position (ys = y0 + 6p at the second time; ys = y0 + (n− at the second time). 1) Align to 6p (n = 1, 2, 3,...)). That is, the head unit 14 is set to the recording start position (xs, ys) = (x0, y0 + 6p) at the second recording time, and (x0, y0 + (n−1) · 6p) at the nth recording time. (See FIG. 14).
Next, in step S41, it is determined whether or not the recording start position in the sub-scanning direction is in the recording area in the sub-scanning direction or the end position outside the recording area. If (N), the process returns to step S33 to set the routine switch SW = 0.

Thereafter, in step S34, ink is ejected from the six recording channels to form dots on the recording medium.
Next, at step S35, the main scanning rotation driving means 8 rotates the rotary drum 16 by (√3p) on the recording medium, and at the time of the second recording, the recording start position (xs, ys) = (x0 + The head unit 14 is moved to (√3p, y0 + 6p) (= (x + √3p, y)).
Thereafter, in step S36, it is determined whether or not the position is in the recording area in the main scanning direction, and as long as the recording channel is in the recording area (N), the process returns to step S34 to form dots on the recording medium. (Step S34), rotational movement in the main scanning direction (Step S35), and determination of whether or not to end the recording area (Step S36) are repeated, and one of the end scanning line or the end scanning line of the image recording area in the main scanning direction is repeated. Record up to the previous line. This corresponds to sequentially recording each line of dots C11 to C16, C21 to C26,..., C61 to C66 corresponding to each line of the dot A in FIG.

  Next, when it is determined in step S36 that the movement position by the rotational movement in the main scanning direction (step S35) has reached the recording area end position (Y), it is determined in step S37 whether or not the routine switch SW = 0. If the routine switch SW = 0 (Y), in step S38, the rotary drum 16 is rotated by the main scanning rotation driving means 8, the head unit 14 is moved by the sub scanning driving means 18, and the recording start position (xs , Ys) = (x0 + (√3p / 2), y0 + 13p / 2) (= (x + √3p / 2, y + p / 2)). In step S39, the routine switch SW = 1 is set and step S34 is entered. Returning, ink is ejected from the six recording channels to form dots on the recording medium.

  Next, in step S35, the rotary drum 16 is rotated by (√3p) on the recording medium by the main scanning rotation driving means 8, and the recording start position (xs, ys) = (x0 + (3√3p) / 2. , Y0 + 13p / 2) (= (x + √3p, y)), and in step S36, it is determined whether or not the position is within the recording area in the main scanning direction. As long as it is within the area (N), the process returns to step S34, and dot formation on the recording medium (step S34), rotational movement in the main scanning direction (step S35), and determination of whether the recording area ends (step S36). Repeatedly, recording is performed up to the last scanning line of the image recording area in the main scanning direction or the line before the last scanning line. This corresponds to sequentially recording each line of dots D11 to D16, D21 to D26,..., D61 to D66 corresponding to each line of the dot B in FIG.

In this way, image recording for the next width in the sub-scanning direction (approximately 6p) corresponding to approximately six recording channels is performed over the entire image recording area in the main scanning direction.
Subsequently, the above steps S33 to S41 are performed in the predetermined order described above, and image recording for the next width in the sub-scanning direction (approximately 6p) is sequentially performed over the entire image recording area in the main scanning direction. When it is determined that the movement position by the movement to the recording start position in the sub-scanning direction (step S40) has become the sub-scanning recording area end position (Y) (step S41), the second dense recording mode is performed. End recording by mode.
By repeatedly performing image recording as described above, image formation can be performed over the entire image recording area in both the main and sub scanning directions.

In the recording method according to the second mode of the dense recording mode described above, dot formation is performed in A11 to A16, A21 to A26,..., A61 to A66, B11 to B16, B21 to B26, B61 to B66 in FIG. Subsequently, C11 to C16, C21 to C26, ..., C61 to C66, D11 to D16, D21 to D26, ..., D61 to D66 are performed in this order.
As described above, recording in the dense recording mode can be performed.

  In the dense recording mode as well as in the square recording mode, dot formation by ink ejection (steps S23, S25, S34) and rotational movement in the main scanning direction (steps S24, S26, 35) are performed using the rotating drum 16 as the main. The recording medium W may be continuously rotated in the scanning direction, that is, the recording medium W may be continuously moved in the main scanning direction, and the initial recording start position in the main scanning direction is adjusted (steps S21 and S31). The drum rotation (steps S28, S38, S40) to the recording start position in the scanning direction may be performed by controlling the recording timing by the recording control means 20. In addition, the determination of whether or not it is in the main scanning recording area (steps S27 and S36) and whether or not it is in the sub scanning recording area (steps S29 and S41) are the lengths of the main scanning recording area and the sub scanning recording area in advance. The number of main scanning movements and the number of sub main scanning movements necessary for recording in the entire recording area are obtained from the relationship between the main scanning movement pitch and the sub main scanning movement pitch, and the number of main scanning movements and the number of sub main scanning movements are counted. It may be done by doing.

The relative alignment between the recording channel and the recording medium can be changed as appropriate, for example, by changing the order of the alignment in the main scanning direction and the alignment in the sub-scanning direction. That is, for the alignment of the coordinates (xs, ys) of the leftmost recording channel on the recording medium, the description has been given of the alignment in the order of the main scanning direction x and the sub-scanning direction y. You may change the order.
In the ink jet recording apparatus of the present invention, switching between the square recording mode and the dense recording mode may be performed in different images. The dense recording mode functions more suitably in an image having a high proportion of high density areas.
Further, during one image recording, switching between the square recording mode and the dense recording mode may be performed. In this case, it is preferable to perform dense recording in the dense recording mode in a portion where the ratio of the high density region is high.

  The square recording mode and the dense recording mode have the relationship shown in FIGS. 15, 16, and 17 in the recording length in the main scanning direction. FIG. 15 shows the repetitive unit length Ls in the main scanning direction in the square recording mode. In the square recording mode, Ls = p. FIG. 16 shows the repetitive unit length Lt in the main scanning direction in the dense recording mode. In the dense recording mode, Lt = (√3p). From the relationship between the repeating units of both types, the integer multiples of the repeating units almost coincide as shown in FIG. 17 when the recording length in the main scanning direction is 7p in the square recording mode and 4√3p in the dense recording mode. ≈6.928p. In the dense recording mode, approximately 8 dots are included in the length in which 7 dots are included in the square recording mode. When switching between these modes, the length in the main scanning direction may be adjusted using this relationship. The sub-scanning direction can be similarly adjusted.

[Density calibration in square recording mode and dense recording mode]
Next, density calibration in the square recording mode and the dense recording mode will be described. FIG. 18 is a graph showing the relationship between the change in the dot diameter and the area ratio of the dots covering the recording medium at that time when recording on the recording medium with the same dot diameter in both the square recording mode and the dense recording mode. Show. In the square recording mode, when the dot diameter exceeds p, overlap between adjacent dots begins to occur, and when the dot diameter becomes √2p, the area ratio becomes 100%. An area ratio of 100% means a state in which dots completely cover the recording medium.
Even in the dense recording mode, when the dot diameter exceeds p, overlap between adjacent dots begins to occur, and when (p√14) / 3, the area ratio becomes 100%.
Such density gradation calibration can be performed by the recording control means 20.

  In the recording method that expresses the image density gradation by the dot area modulation that covers the recording medium, the image density that the person actually sees is determined mainly by the dot area, but the overlapping of the dots overlaps each other The ink film thickness of the portion is larger than that of the non-overlapping ink portion, and the density may actually be higher depending on the type of ink. In the square recording mode and the dense recording mode, the overlap amount with respect to the dot diameter is different, and even with the same area ratio, different image densities may be obtained. Therefore, in order to reproduce a higher quality image, even if the area ratio is the same in the square recording mode and the dense recording mode, the difference in density between the two modes should be calibrated in consideration of the overlap amount. Is desirable. This ink jet recording apparatus has a correction table for calibrating the difference in density between the two modes. Using this correction table, when the square recording mode and the dense recording mode are switched, the correction value from the correction table is read for the image density to be recorded, and the ink discharge amount is controlled.

[Description of image recording using dots with different dot diameters]
Next, an example in which image recording is performed using dots having different dot diameters will be described.
Even when the same image density is expressed, there are a plurality of combinations by changing the dot diameter. In particular, in the electrostatic ink jet recording method, the dot diameter can be continuously changed, and the same image density can be recorded by a combination of various dot diameters.

FIGS. 19A and 19B are examples in which the same image density is recorded with different dot diameters. 19A, the dots A11 to A24 have a dot diameter of T1, the dots B11 to B13 have a dot diameter of T2, and the dots shown in FIG. 19B are dots of dots A′11 to A′24. When the diameter is T3 and the dot diameter of the dots B′11 to B′13 is T4, the same image density is expressed by a combination of different dot diameters by adjusting the dot diameter in the relationship of T1>T3>T4> T2. Can do.
In FIGS. 19A and 19B, recording with two types of dot diameters has been described, but the number of dot diameters may be three or more.

The ability to express the same image density with a combination of different dot diameters works advantageously when an image having a specific frequency pattern of density change is recorded on the image. When there is a specific frequency pattern of density change in the image, the ink jet recording method records with a certain periodic dot arrangement, so the specific frequency pattern of density change and the specific dot pattern cause interference and generate moire. As a result, the image quality may deteriorate. Recording with a plurality of dot diameters has the effect of dispersing and averaging the intensity of a specific frequency (amplitude of density change) in the nearby frequency. As a result, the intensity of moire (the density change) (Amplitude) can be reduced. Therefore, there is an effect of suppressing a decrease in image quality.
When recording a color image, each of C, M, Y, and K may be recorded with a plurality of dot diameters so as to reduce moire.

  The inkjet recording apparatus and the recording method of the present invention are not limited to electrostatic inkjet, and various inkjet recording heads can be used. The electrostatic type is particularly desirable in that the dot size can be continuously changed. In addition, a piezoelectric element type ink jet using a piezoelectric element such as a piezo as an ink discharge actuator is preferable in that the dot size can be varied discretely in a short period.

Also, a thermal method using a heater provided near the nozzle as an ink discharge actuator can be used in a discharge cycle in which the dot size can be varied. Note that the recording channel corresponds to a nozzle portion for ejecting ink in the piezoelectric element method and the thermal method.
The arrangement of the head unit and the drum is not limited to the outer drum system as shown in FIG. 1, and may be an inner drum system.
Further, although the ink jet apparatus of the present invention has been described in the drum system shown in FIG. 1 in which main scanning is performed by rotating the drum and movement in the sub scanning direction is performed by parallel movement of the head unit, the present invention is not limited to this. Alternatively, as shown in FIG. 20, a drum system in which main scanning is rotational movement of the drum and movement in the sub-scanning direction is parallel movement of the drum may be used, or movement in the main scanning direction is parallel movement of the head unit by a carriage or the like. Alternatively, the recording medium may be sub-scanned and transported using a transport belt, transport rollers (two transport roller pairs), a flat bed, or the like.

[Overall configuration of electrostatic ink jet recording apparatus]
FIG. 20 shows a schematic configuration of another embodiment of the electrostatic ink jet recording apparatus of the present invention. The electrostatic ink jet recording apparatus 60 shown in the figure embodies a drum system in which main scanning is performed by rotational movement of the drum and movement in the sub-scanning direction is performed by parallel movement of the drum, and a fixed dot diameter variable ink jet head. A unit 62, a recording medium W mounted on the outer peripheral surface, a rotating drum 64 that can rotate in the main scanning direction and can move in parallel in the sub scanning direction, and a main scanning rotation drive that rotates the rotating drum 64 in the main scanning direction Means 66, sub-scanning driving means 68 for moving the rotary drum 64 in the sub-scanning direction parallel to the rotation axis, main scanning rotation driving means 66 and scanning control means 70 for controlling the sub-scanning driving means 68, and head unit A head control means 72 for controlling the 62 ink jet heads, an overall control means 74 for controlling the scanning control means 70 and the head control means 72, and this The body control unit 74, and a data supply source 76 supplies the character-image data to be recorded on the recording medium W.

Here, except that the head unit 62 is fixed, the head unit 14 shown in FIG. 1 and the rotary drum 64 are parallel to the sub-scanning direction, and the rotary drum 16 shown in FIG. The sub-scanning drive unit 68 is substantially the same as the main-scanning rotation driving unit 8 except that the rotary drum 64 is moved in parallel in the sub-scanning direction. be able to.
The scanning control means 70 rotates in the main scanning direction of the rotating drum 64 by the main scanning rotation driving means 66 and rotates by the sub scanning driving means 68 in the recording modes characterized by the present invention, that is, the square recording mode and the dense recording mode. This is for controlling the parallel movement of the drum 64 in the sub-scanning direction.
The head control means 72 includes a head drive driver 78 for ejecting ink by driving the ink-jet head of the head unit 62 according to character / image data or the like, or a recording mode such as a square recording mode or a dense recording mode. Converts the recording resolution according to the recording mode such as the square recording mode and the dense recording mode, changes the ink dot size, recording density, recording position, etc. depending on the amount of ink to be ejected, and generates the head drive signal accordingly A resolution converting unit 80 for performing density gradation calibration in accordance with recording modes such as a square recording mode and a dense recording mode.

Here, the overall control means 74 not only performs various controls of the entire apparatus, but also has the function of the recording mode switching means of the present invention, and the characters to be recorded on the recording medium W supplied from the data supply source 76. Depending on the image data, the recording mode is switched between the square recording mode and the dense recording mode, and a control signal for controlling the main scanning rotation movement and the sub-scanning parallel movement according to each recording mode is generated. In order to send to the scanning control means 70 and to perform image recording according to each mode, an image recording signal is generated according to the recording mode such as character / image data or the square recording mode and the dense recording mode, and the head This is sent to the control means 72.
In the inkjet recording apparatus 60 shown in FIG. 20, the above-described square recording mode and dense recording mode can be similarly performed.

The ink jet head used in the present invention may be a top shooter type that ejects ink in a direction perpendicular to the head surface, or a side shooter type that ejects ink in a direction parallel to the head surface. May be.
Further, although the mode of moving in the sub-scanning direction by six printing elements has been described, a full-line head having a printing channel corresponding to all printing areas in the width direction of the printing medium is used, and movement in the sub-scanning direction is p / A mode in which only 2 is performed is also possible. The full line head may be a recording head in which short recording heads are arranged in a linear shape, a staggered lattice shape, or the like to increase the length.

  In the above-described example, the dot size is changed by changing the drive signal (voltage and pulse width) supplied to the inkjet head 10, but the present invention is not limited to this. For example, FIG. Head unit moving means (not shown) is provided for moving the head unit 14 shown along a straight line passing through the center of the rotary drum 16, and is wound around the tip 34 a of the ink guide 34 of the inkjet head 10 and the outer peripheral surface of the rotary drum 16. By changing the distance between the recording medium W and the recording medium W, the intensity of the electric field formed at the tip 34a of the ink guide 34 is changed to change the amount of ink Q (particulate component) that aggregates, and recording on the recording medium W is performed. You can change the dot size of the dots. At this time, the head unit moving unit may be controlled by the recording mode control unit 24 together with the main scanning rotation driving unit 8, the sub scanning driving unit 18, and the recording control unit 20.

  The inkjet recording method and apparatus according to the present invention have been described in detail with reference to various embodiments. However, the present invention is not limited to the above-described various embodiments, and various modifications can be made without departing from the spirit of the present invention. Of course, improvements and changes may be made.

1 is a schematic configuration diagram of an embodiment of an electrostatic ink jet recording apparatus of the present invention. FIG. 2 is a schematic cross-sectional view illustrating a schematic configuration of an embodiment of an electrostatic ink jet head of the electrostatic ink jet recording apparatus illustrated in FIG. 1. FIG. 3 is a schematic configuration diagram of an embodiment of a discharge electrode structure of the electrostatic inkjet head shown in FIG. 2. It is the schematic showing arrangement | positioning of the dot recorded by the square recording mode of this invention method. It is the schematic showing arrangement | positioning of the dot recorded by the dense recording mode of this invention method. FIG. 5 is a diagram illustrating a unit lattice and an occupation ratio of dot arrangement recorded in the square recording mode illustrated in FIG. 4. FIG. 6 is a diagram showing a unit lattice and an occupation ratio of dot arrangement recorded in the dense recording mode shown in FIG. 5. FIG. 5 is a schematic diagram showing a dot size necessary for recording with an area ratio of 100% by arrangement of dots recorded in the square recording mode shown in FIG. 4. FIG. 6 is a schematic diagram showing a dot size necessary for recording with an area ratio of 100% by arrangement of dots recorded in the dense recording mode shown in FIG. 5. It is a flowchart which shows an example of the recording method by square recording mode. It is the schematic showing the arrangement | positioning and recording order of the dot recorded by square recording mode. It is a flowchart which shows an example of the recording method by dense recording mode. It is a flowchart which shows another example of the recording method by dense recording mode. It is the schematic showing the arrangement | positioning and recording order of the dot recorded by dense recording mode. It is a figure which shows the repetition unit length in the main scanning direction in a square recording mode. It is a figure which shows the repetition unit length in the main scanning direction in dense recording mode. FIG. 6 is a diagram illustrating a relationship between dot positions in a main scanning direction in a square recording mode and a dense recording mode. FIG. 6 is a diagram showing the relationship between the change in dot diameter and the area ratio at which the dot covers the recording medium when recording is performed on the recording medium with the same dot diameter in both the square recording mode and the dense recording mode. FIG. 6 is a diagram illustrating an example in which the same image density is recorded with different dot diameters. It is the structure schematic of other embodiment of the electrostatic inkjet recording device of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 5 ... Pump 6 ... Ink tank 7 ... Supply path 8 ... Main scanning rotation drive means 10 ... Inkjet head 14 ... Head unit 16 ... Rotary drum 18 ... Sub-scanning drive means 20 ... Recording control means 22 ... Ink supply means 24 ... Recording mode Control means 42 ... Charging unit

Claims (20)

An inkjet recording method for recording a plurality of dots on a recording medium using a single head having a plurality of recording channels for ejecting ink,
A square recording mode in which the plurality of dots are recorded so that the closest dots are arranged in a substantially orthogonal direction, and the plurality of dots are recorded so that the closest dots to one dot are arranged at an angle of 60 °. An inkjet recording method, wherein the recording mode is switched. The inkjet recording method is an area modulation type recording method that is modulated by the area occupied by dots recorded in one pixel,
The inkjet recording method according to claim 1, wherein the dense recording mode performs recording in which a recording resolution is converted with respect to the square recording mode.   In the dense recording mode, the head is arranged at a predetermined first position with respect to the recording medium to record the plurality of dots, and the head is moved to the first position with respect to the recording medium. To a second position shifted by a half pitch (p / 2) of the recording channel pitch p in the arrangement direction of the plurality of recording channels, and the recording channel pitch p in a direction substantially orthogonal to the arrangement direction. 3. The inkjet according to claim 1, wherein the plurality of dots are recorded on the recording medium moved relative to the head by (√3 / 2) pitch (√3p / 2). Recording method. In the dense recording mode, after the plurality of dots are recorded by arranging the head at the first position,
The head is moved from the first position to the second position, and the recording medium is conveyed by the (√3 / 2) pitch (√3p / 2) in a direction substantially perpendicular to the arrangement direction. To record the plurality of dots,
Thereafter, the head is returned to the first position, and the recording medium is conveyed by the (√3 / 2) pitch (√3p / 2) in a direction substantially orthogonal to the arrangement direction. Record the dots,
The inkjet recording method according to claim 3, wherein the recording at the first position and the recording at the second position are repeated. In the dense recording mode, the plurality of dots are recorded by disposing the head at the first position,
Each time the recording medium is conveyed by the (√3) pitch (√3p) of the recording channel pitch p in the direction substantially perpendicular to the arrangement direction by the head arranged at the first position, After repeating the dot recording,
The head is moved from the first position to the second position, and recording is performed in a direction substantially orthogonal to the arrangement direction with respect to the plurality of dots recorded first or last at the first position. The plurality of dots are recorded by moving the head or the recording medium to a position shifted by (√3 / 2) pitch (√3p / 2) of the channel pitch p,
The plurality of dots are recorded each time the recording medium is conveyed by the (√3) pitch (√3p) in a direction substantially orthogonal to the arrangement direction by the head arranged at the second position. The inkjet recording method according to claim 3, wherein the method is repeated.   The dot size of the plurality of dots recorded at the first position in the dense recording mode is different from the dot size of the plurality of dots recorded at the second position. The inkjet recording method according to any one of the above.   The inkjet recording method according to claim 3, wherein dot sizes of the plurality of dots recorded at the second position are different.   The inkjet recording method according to claim 2, wherein the plurality of dots in the dense recording mode includes dots having different dot sizes according to the recording resolution.   The gradation calibration for compensating for the change in area modulation accompanying the conversion of the recording resolution in consideration of the density change of the overlapping portion of the plurality of dots in the dense recording mode. Inkjet recording method.   The inkjet recording method according to claim 1, wherein the head is an electrostatic inkjet head. An inkjet recording apparatus that records a plurality of dots on a recording medium,
One head in which a plurality of recording channels for ejecting ink are arranged in a predetermined arrangement direction;
Position switching means for switching a relative position in the arrangement direction between the position of the head and the recording medium;
Moving means for moving the recording medium relative to the head in a direction substantially perpendicular to the arrangement direction;
A square recording mode in which the plurality of dots are recorded so that the closest dots are arranged in a substantially orthogonal direction, and the plurality of dots are recorded so that the closest dots to one dot are arranged at an angle of 60 °. Mode switching means for switching between recording modes;
Control means for controlling the position switching means and the moving means in accordance with the square recording mode and the dense recording mode to control the recording of the plurality of dots by the head onto the recording medium. An ink jet recording apparatus. The inkjet recording apparatus performs an area-modulated inkjet recording method capable of resolution conversion that is modulated by an area occupied by dots recorded in one pixel,
The inkjet recording apparatus according to claim 11, wherein the dense recording mode performs recording with a recording resolution converted with respect to the square recording mode. The position switching means sets the position of the head to a predetermined first position with respect to the recording medium and a half pitch (p / 2) of a recording channel pitch p from the first position to the arrangement direction. And switching between the relatively shifted second positions,
In the dense recording mode, the control unit arranges the head at the first position with respect to the recording medium by the position switching unit, records the plurality of dots by the head, and switches the position. The head is switched from the first position to the second position with respect to the recording medium by means, and the recording channel pitch p is (√3 / 2) in the direction substantially perpendicular to the arrangement direction by the moving means. The head, the position switching unit, and the moving unit are controlled so as to record the plurality of dots on the recording medium moved relative to the head by a pitch (√3p / 2). Item 13. The ink jet recording apparatus according to Item 11 or 12. The control means, in the dense recording mode,
After the head is arranged at the first position with respect to the recording medium by the position switching means and the plurality of dots are recorded by the head,
The position switching means switches the head from the first position to the second position with respect to the recording medium, and the moving means moves the recording medium in the direction substantially orthogonal to the arrangement direction (√3 / 2) Convey by the pitch (√3p / 2), and record the plurality of dots by the head,
Thereafter, the position switching means returns the head again to the first position with respect to the recording medium, and the moving means causes the recording medium to move in the direction substantially perpendicular to the arrangement direction (√3). / 2) Convey the pitch (√3p / 2) and record the plurality of dots,
The ink jet recording apparatus according to claim 13, wherein control is performed so as to repeat recording at the first position and recording at the second position. The control means, in the dense recording mode,
The plurality of dots are recorded by disposing the head at the first position with respect to the recording medium by the position switching means,
Each time the recording medium is conveyed by the moving means by the (√3) pitch (√3p) of the recording channel pitch p in the direction substantially orthogonal to the arrangement direction by the head arranged at the first position. And after repeating the recording of the plurality of dots by the head,
The head is switched from the first position to the second position with respect to the recording medium by the position switching means, and for the plurality of dots recorded first or last at the first position, The recording medium is moved by the moving means to a position shifted by (√3 / 2) pitch (√3 / 2) of the recording channel pitch p in a direction substantially orthogonal to the arrangement direction, or the position switching means To move the head to record the plurality of dots,
Each time the recording medium is transported by the moving means by the (√3) pitch (√3p) in the direction substantially perpendicular to the arrangement direction, the dots arranged by the head are arranged at the second position. The inkjet recording apparatus according to claim 13, wherein the recording is controlled so as to repeat the recording of the plurality of dots.   The control means is configured such that the dot size of the plurality of dots recorded at the first position in the dense recording mode is different from the dot size of the plurality of dots recorded at the second position. The ink jet recording apparatus according to claim 13, wherein the head is controlled.   The ink jet recording apparatus according to claim 13, wherein the control unit controls the head so that dot sizes of the plurality of dots recorded at the second position are different.   18. The head according to claim 12, wherein the control unit controls the head such that the plurality of dots in the dense recording mode include dots having different dot sizes according to the recording resolution. Inkjet recording device.   In the dense recording mode, the control means considers a density change in an overlapping portion of the plurality of dots, and performs a gray scale calibration unit that performs a gray scale calibration that compensates for a change in area modulation accompanying the conversion of the print resolution The ink jet recording apparatus according to claim 12, comprising:   The ink jet recording apparatus according to claim 11, wherein the head is an electrostatic ink jet head.

Images