JP2007261205A - Inkjet recorder and image recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder enabling favorable image recording by avoiding color mixing fluctuation in performing image recording by reciprocating a recording head in a main scanning direction using a pigment ink and a dye ink, and an image recording method. <P>SOLUTION: In the bi-directional printing for performing image recording by reciprocating the recording head 12 in the main scanning direction, nozzles ejecting CMY inks and a K ink are so arranged that the pigment ink (K ink) is ejected after the ejection of the dye ink (CMY inks), avoiding beading caused by a difference in the infiltration rate between the dye ink and the pigment ink. Furthermore, the K ink has particles with particle diameters of their color particles of 120 nm or smaller occupying 95% or more per unit volume, and infiltration to the recording medium of the pigment ink is enhanced by increasing the infiltration rate of the dye ink, thus enabling the beading to be further avoided. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ink jet recording apparatus and an image recording method, and more particularly to an ink jet recording apparatus that forms a color image on a medium by ejecting multicolor ink from nozzles.

  A shuttle scan type head that scans the head in the main scanning direction and performs printing in this direction, and relatively moves the recording medium and the head in the sub-scanning direction (recording medium conveyance direction) to form an image on the recording medium. In the ink jet recording apparatus provided, in the method of performing image recording by reciprocating the head in the main scanning direction, band-like unevenness along the main scanning direction occurs due to the difference in the droplet ejection order of the forward and backward colors. It has a fundamental problem. In order to solve such problems, a recording method in which the forward recording head and the backward recording head are arranged symmetrically and selectively driven to improve the image quality by making the coloring order the same in both reciprocations. (Patent Document 1) Image recording employing a configuration in which a plurality of recording heads are composed of a plurality of recording head groups that handle inks of different colors, and the plurality of recording head groups are alternately shifted in the paper transport direction. An apparatus (Patent Document 2) has been proposed.

Further, in Patent Document 3, the ejection port arrays included in the first ejection port group and the second ejection port group complement each other, and the color order of the first ejection port group and the second ejection port group is arranged symmetrically. A liquid discharge recording head is disclosed.
JP 58-179653 A JP 58-215352 A JP 2001-171119 A

  However, in a system in which a dye-based ink having excellent color image colorability and a pigment-type ink having excellent water resistance and light resistance are mixed, the pigment-based ink in bidirectional printing in which the recording head is reciprocally scanned in the main scanning direction. Beading (mixed color unevenness) occurs due to the difference in permeation speed with dye-based ink. In particular, in high-speed printing in which the recording head is scanned at high speed, or in narrow-width scanning in which only the area where data exists is scanned instead of scanning the entire paper surface when the image area is narrow, the scanning time is shortened. The possibility of occurrence of beading increases.

  The present invention has been made in view of such circumstances, and avoids unevenness when image recording is performed by reciprocating the recording head in the main scanning direction using pigment-based ink and dye-based ink, and preferable image recording is performed. An object is to provide an inkjet recording apparatus and an image recording method that are realized.

  In order to achieve the above object, an ink jet recording apparatus according to the present invention includes a recording head that discharges ink onto a recording medium, and a transport unit that relatively moves the recording head and the recording medium in a predetermined movement direction. And a main scanning means for reciprocally scanning the recording head in a main scanning direction substantially orthogonal to the moving direction of the recording medium, wherein the recording head discharges a dye-based ink containing a dye as a coloring material. And a nozzle for discharging a pigment-based ink containing a pigment as a coloring material is disposed along the main scanning direction, and the pigment system is disposed behind the nozzle for discharging the dye-based ink in the reciprocating direction of the main scanning direction. A nozzle for discharging ink is disposed, and the ink color material contained in the pigment-based ink is characterized in that the color material having a particle diameter of 120 nm or less is 95% by volume or more.

  According to the present invention, the head is scanned along the main scanning direction, and an image is formed on the recording medium by the recording element while the head and the recording medium are relatively moved along the predetermined movement direction (sub-scanning direction). In the so-called shuttle scan method (serial scan method) to be formed, beading due to the difference in penetration speed of the pigment-based ink and the dye-based ink into the recording medium can be avoided. In addition, avoiding beading (uneven color mixing) is realized by increasing the penetration speed of the pigment-based ink, which has a slower penetration speed than the dye-based ink. In particular, the effect of the present invention is exhibited when performing high-speed bidirectional printing.

  “The color material having a particle size of 120 nm or less is 95% by volume or more” means that 95% by volume of the pigment particles (ink color material) contained in the pigment-based ink has a particle size of 120 nm or less. Represents. That is, the volume of the color material having a particle diameter of 120 nm or less is 95% or more of the volume of all the color materials contained in the ink.

  Discharge control means for controlling ink discharge so that ink is discharged in the order of nozzle arrangement in the main scanning direction is provided, and ink is discharged in order from the nozzles on the downstream side in the scanning direction in synchronization with scanning in the main scanning direction of the recording head. There are aspects.

  There is a mode in which the recording head includes a nozzle, a pressure chamber that stores a liquid discharged from the nozzle, and a pressurizing unit that pressurizes the liquid in the pressure chamber. Moreover, in the aspect provided with a some nozzle (pressure chamber), there exists an aspect provided with the ink supply path which distributes and supplies ink to each pressure chamber.

  In addition, a nozzle array in which a plurality of nozzles that eject dye-based ink are arranged on the recording head along a direction substantially parallel to the sub-scanning direction, and a plurality of nozzles that eject pigment-based ink are arranged in a direction substantially parallel to the sub-scanning direction. And a nozzle row.

  As a mode in which the recording head and the recording medium are relatively moved in a predetermined moving direction, the recording medium may be moved with respect to the fixed recording head, or the recording head may be moved with respect to the fixed recording medium. It may be moved. In the aspect in which the recording head is moved relative to the fixed recording medium, the recording head moves two-dimensionally in the main scanning direction and the sub-scanning direction.

  The invention according to claim 2 relates to an aspect of the ink jet recording apparatus according to claim 1, wherein the recording head includes a plurality of nozzles that eject the pigment-based ink, and the nozzle that ejects the pigment-based ink includes the nozzle It is arranged at both ends of a nozzle arranged along the main scanning direction.

  There is a mode in which nozzles for discharging a plurality of dye-based inks (for example, nozzles for discharging CMY color inks) are arranged along the main scanning direction, and nozzles for discharging pigment-based ink are arranged outside the nozzles at both ends.

  A third aspect of the present invention relates to an aspect of the ink jet recording apparatus according to the first aspect, wherein the nozzle for discharging the pigment-based ink is disposed at the center of the nozzle disposed along the main scanning direction. It is characterized by that.

  For example, there is an aspect in which a pigment-based ink discharge nozzle is disposed in the approximate center of the recording head, and a nozzle that discharges dye-based ink is disposed on both sides (both sides) in the main scanning direction.

  In order to achieve the above object, according to a fourth aspect of the present invention, there is provided a recording head for ejecting ink onto a recording medium, and the recording head and the recording medium are relatively moved in a predetermined moving direction. Conveying means, and main scanning means for reciprocally scanning the recording head in a main scanning direction substantially orthogonal to the moving direction of the recording medium, the recording head being arranged along the main scanning direction. A first nozzle group having a plurality of nozzles for ejecting ink when the head is scanned in the forward direction of the main scanning direction, and the recording head disposed along the main scanning direction is moved in the backward direction of the main scanning direction. A plurality of nozzles for ejecting ink when scanning, and a second nozzle group arranged along the main scanning direction with the first nozzle group, the first nozzle group being a color material A nozzle arrangement in which a nozzle for discharging a pigment-based ink containing a pigment in a colorant is arranged on the rear side in the forward direction of the nozzle for discharging a dye-based ink containing a colorant, and the second nozzle group includes a color It has a nozzle arrangement in which a nozzle for discharging a pigment-based ink including a pigment in a color material is disposed on the rear side in the backward direction of the nozzle that discharges a dye-based ink including a dye in the material, and is contained in the pigment-based ink The ink coloring material is characterized in that the coloring material having a particle diameter of 120 nm or less is 95% by volume or more.

  According to the fourth aspect of the present invention, in bidirectional printing in which the recording head is reciprocated in the main scanning direction to perform image recording, the pigment-based ink is discharged after the dye-based ink is discharged in both the forward direction and the backward direction. Thus, beading does not occur due to a difference in permeation speed between the dye-based ink and the pigment-based ink. Further, since the penetration of the pigment-based ink is accelerated, no beading occurs even when high-speed image recording of bidirectional printing is performed.

  A fifth aspect of the present invention relates to an aspect of the ink jet recording apparatus according to any one of the first to fourth aspects, wherein the nozzles that discharge the dye-based ink are cyan, magenta, and yellow color inks. The nozzle that discharges the pigment-based ink includes a nozzle that discharges black ink.

  According to the invention described in claim 5, for example, in an image in which a color image formed with CMK color ink (dye-based ink) and a text formed with black ink (pigment-based ink) are mixed, It is possible to obtain a preferable image in which mixed color unevenness of an image and a black image and band-like unevenness in a color image are avoided.

  You may add the nozzle which discharges light system inks, such as light yellow and light cyan, to dye system ink.

  A sixth aspect of the invention relates to an aspect of the ink jet recording apparatus according to the fifth aspect of the invention, wherein the first nozzle group and the second nozzle group have a symmetrical nozzle arrangement with respect to ink color. And

  According to the sixth aspect of the invention, since the nozzles of the first nozzle group and the second nozzle group are arranged so as to be targeted with respect to color, the band due to the difference in the discharge order between the forward direction and the backward direction A preferable image in which unevenness of the shape is avoided can be obtained.

  A seventh aspect of the present invention relates to an aspect of the ink jet recording apparatus according to any one of the first to sixth aspects, wherein the nozzle for discharging the pigment-based ink of the first nozzle group is the first one. The second nozzle group is arranged at a position adjacent to a nozzle for discharging pigment-based ink.

  According to the seventh aspect of the present invention, when the nozzles for ejecting the pigment-based inks of the first nozzle group and the second nozzle group are arranged so as to be adjacent to each other, an image is formed using only the pigment-based ink. In addition, the scanning amount (scanning width) of the recording head in the main scanning direction can be shortened, which contributes to speeding up image recording.

  According to an eighth aspect of the present invention, there is provided the ink jet recording apparatus according to the seventh aspect, wherein an ink supply path corresponding to a nozzle for ejecting pigment-based ink of the first nozzle group and the second nozzle group. The ink supply path corresponding to the nozzle for discharging the pigment-based ink is made common.

  According to the eighth aspect of the present invention, the pigment-based ink is disposed by disposing the nozzle that discharges the pigment-based ink at a substantially central portion of the recording head that is a boundary position between the first nozzle group and the second nozzle group. The ink supply path can be made common, and the width (size) of the ink supply path of the pigment-based ink can be increased. Therefore, clogging of the pigment-based ink is prevented in the ink supply path, contributing to stabilization of the pigment-based ink discharge.

  A nozzle that discharges black ink, which is pigment-based ink, is arranged at a substantially central portion in the main scanning direction of the recording head, and the dye-based ink is disposed on both sides of the nozzle that discharges black ink. It is more preferable that the nozzles for ejecting cyan, magenta, and yellow inks are arranged so as to be symmetrical with respect to the color, and the ink supply paths corresponding to the nozzles for ejecting black ink are made common.

  A ninth aspect of the present invention relates to an aspect of the ink jet recording apparatus according to any one of the first to eighth aspects, wherein the first nozzle group and the second nozzle group are the same type of ink. A plurality of nozzles that discharge nozzles are arranged at predetermined intervals along the sub-scanning direction, and the first nozzle group and the second nozzle group are sub-scanning in the sub-scanning direction. It is characterized by being arranged with a shift of approximately ½ of the nozzle pitch in the direction.

  According to the ninth aspect of the present invention, the substantial nozzle density in the sub-scanning direction is increased, the dots constituting the recorded image can be arranged at a high density, and the first nozzle group and the first nozzle group are provided in the forward pass. By recording an image with both nozzles of the two nozzle groups, high-speed image recording is possible, and band-like (band width) color unevenness is also suppressed in bidirectional printing.

  The invention according to claim 10 relates to an aspect of the ink jet recording apparatus according to claim 9, wherein the first nozzle group and the second nozzle group include a plurality of nozzles that discharge the pigment-based ink. There are two nozzle rows arranged along the sub-scanning direction, and the two nozzle rows for discharging the pigment-based ink are arranged with a shift of about ½ of the inter-nozzle pitch in the sub-scanning direction. And

  According to the invention described in claim 10, since the first nozzle group and the second nozzle group can be used in both the forward direction and the backward direction in reciprocating printing, it contributes to the efficiency of image recording and is the same. It is possible to eject pigment-based ink after always ejecting dye-based ink at the same resolution during scanning. Both image recording in which dye-based ink and pigment-based ink coexist with both beading suppressed. High-speed image recording by bidirectional printing becomes possible.

  An eleventh aspect of the present invention relates to an aspect of the ink jet recording apparatus according to any one of the first to tenth aspects of the present invention, a recording medium type detecting means for detecting the type of the recording medium 3, and a recorded image A discharge amount determining means for determining the discharge amount of the dye-based ink and the pigment-based ink based on the image data; and a scan width determining for determining the scan width of the recording head in the main scanning direction based on the image data Means, a beading judgment means for judging the occurrence of beading of the recorded image based on the ejection amount of the dye-based ink, the ejection amount of the pigment-based ink, and the scanning width, and the recorded image by the beading determining means If it is determined that beading will occur, the image recording mode is changed or the image recording is controlled so that the image is temporarily suspended and kept in a standby state for a predetermined period. Characterized by comprising an image recording control means.

  According to the eleventh aspect of the present invention, when beading is determined by the beading determining means, the image recording mode is changed or the image recording standby is executed. Is avoided.

  A twelfth aspect of the invention relates to an aspect of the ink jet recording apparatus according to the eleventh aspect, wherein the image recording mode includes changing the scanning speed of the recording head in the main scanning direction and the main scanning of the recording head. It includes at least one of switching from reciprocating scanning to unidirectional scanning in the direction.

  According to the twelfth aspect of the present invention, the time (interval) from the discharge of the dye-based ink to the discharge of the pigment-based ink from the subsequent nozzle is increased by slowing the scanning speed in the main scanning direction. For example, it is possible to avoid beading even for a recording medium that penetrates very slowly using not only pigment-based ink but also dye-based ink. In addition, by making the reciprocating scanning in the main scanning direction one-way scanning, the time (interval) from the discharge of pigment-based ink to the discharge of dye-based ink in the next scan becomes longer, and the penetration of pigment-based ink However, it is possible to avoid beading even when a very slow recording medium is used.

  Moreover, the method invention for achieving the said objective is provided. That is, in the image recording method according to the thirteenth aspect, the recording head for ejecting ink onto the recording medium is reciprocated in the main scanning direction substantially parallel to the width direction of the recording medium, and substantially orthogonal to the main scanning direction. The recording medium and the recording head are relatively moved in the sub-scanning direction, and after the reciprocating scanning, the dye-based ink including the dye is included in the color material, and then the pigment-based ink including the pigment is discharged in the color material. Features.

  According to the present invention, in image recording using a pigment-based ink and a dye-based ink, the pigment-based ink is ejected after the dye-based ink is ejected. Beading (mixed color unevenness) is avoided, and preferable image recording is realized.

  According to the present invention, a so-called shuttle scan system that scans the head along the main scanning direction and forms an image on the recording medium by the recording element while relatively moving the head and the recording medium along the sub-scanning direction. In this case, it is possible to avoid beading due to the difference in the penetration speed of the pigment-based ink and the dye-based ink into the recording medium. In addition, avoiding beading (uneven color mixing) is realized by increasing the penetration speed of the pigment-based ink, which has a slower penetration speed than the dye-based ink. In particular, the effect of the present invention is exhibited when performing high-speed bidirectional printing.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an overall configuration diagram of an inkjet recording apparatus 10 according to the present invention. In the ink jet recording apparatus 10 shown in FIG. 1, a recording head 12 corresponding to color inks of K (black), C (cyan), M (magenta), and Y (yellow) is positioned on the carriage 14 and detachably mounted. Has been. The carriage 14 is provided with an electrical connection for transmitting a drive signal and the like to each ejection element (see FIG. 6) via an external signal input terminal on the recording head 12.

  The carriage 14 is supported so as to be capable of reciprocating along a guide shaft 16 provided with an axial direction parallel to the main scanning direction. The carriage 14 is driven by a main scanning motor 18 through driving mechanisms such as a motor pulley 20, a driven pulley 22, and a timing belt 24, and the position and movement of the carriage 14 are controlled. The carriage 14 is provided with a home position sensor 28 for detecting the position of the shielding plate 26. With this home position sensor 28, when the carriage 14 passes the position of the shielding plate 26, the home position sensor 28 on the carriage 14 detects the shielding plate 26, so that the position of the carriage 14 can be detected. Has been.

  Recording media 30 such as recording paper and plastic film are separated and fed one by one from an auto sheet feeder (ASF) 36 by rotating a pickup roller 34 from a paper feed motor 32 via a gear. Subsequently, the separated and fed recording medium 30 is conveyed in the sub-scanning direction through the recording position facing the discharge port surface of the recording head 12 by the rotation of the conveying roller 38. The conveying roller 38 is moved through a gear by the rotation of a line feed (LF) motor 40. At this time, the determination of whether or not the paper has been fed and the determination of the cueing position at the time of paper feeding are performed by the paper edge sensor 42 when the recording medium 30 passes the paper edge sensor 42. Further, the paper edge sensor 42 is also used to finally determine the current recording position from the actual rear end where the rear end of the recording medium 30 is located.

  Note that the back surface of the recording medium 30 is supported by a platen (not shown) so that the recording medium 30 forms a flat recording surface at the recording position. In this case, the recording head 12 mounted on the carriage 14 is held so that the discharge port surfaces thereof protrude downward from the carriage 14 and are parallel to the recording medium 30 between the two pairs of transport rollers described above. Has been.

  The recording head 12 is mounted on the carriage 14 such that the arrangement direction of a plurality of nozzles that eject ink is in a direction that intersects the scanning direction (main scanning direction) of the carriage 14 described above. Characters, images, and the like are recorded on the recording medium 30 by ejecting.

  A recording medium type detection sensor 44 that detects the type of the recording medium 30 is provided on the conveyance path of the recording medium 30. Based on the detection result of the recording medium type detection sensor 44, the type of the recording medium 30 is determined in the system control system (see FIG. 7) of the inkjet recording apparatus 10.

  An imaging element such as a CCD is applied to the recording medium type detection sensor 44 of this example. The type of the recording medium 30 is determined based on the imaging result obtained by imaging the surface of the recording medium 30 by the recording medium type detection sensor 44. In addition, a reading element that reads information (recording medium type information) stored in an information storage body such as an IC tag is applied to the recording medium detection sensor 44, and the recording medium type information is read from the information storage body attached to the recording medium 30. May be configured to read.

  Further, although not shown in FIG. 1, the nozzle is protected in close contact with the nozzle surface of the recording head 12 at the home position, and is used as a waste ink receiver during maintenance (recovery processing) such as purge (preliminary ejection) and suction. A cap and blade are provided. That is, when the recording head 12 is positioned at the home position, such as when printing is finished or when printing is waiting, the cap is brought into close contact with the nozzle surface of the recording head 12 to prevent the ink in the nozzle from drying and thickening. Further, at the time of initialization (initialization, reset) or recovery processing of the recording head 12, the recording head 12 moves to the home position, and recovery processing such as purge or suction of the recording head 12 is performed with the cap closely attached to the nozzle surface. And the deteriorated ink in the nozzles is discharged to the outside of the recording head 12.

  The blade described above is means for wiping and removing deposits such as ink adhered to the nozzle surface of the recording head 12, and an elastic member such as rubber, a porous member, and a liquid absorbing member such as a nonwoven fabric are used. That is, the adhering matter adhering to the nozzle surface is removed by relatively moving the recording head 12 and the blade while the blade is in contact with the nozzle surface. In addition, when removing the deposit on the nozzle surface with the blade, the deposit may be mixed into the nozzle. Therefore, it is preferable to perform preliminary discharge after removing the deposit with the blade.

  Although not shown in FIG. 1, an ink supply unit that supplies KCMY color inks to the recording head 12 is provided. The ink supply unit includes an ink tank (ink storage unit) containing each color ink, a tube serving as an ink flow path from the ink tank to the recording head 12, and an open / close valve that opens and closes the ink flow path. And a pump (pressure varying means) for varying the pressure in the ink flow path.

  The ink tank includes notifying means (display means, warning sound generating means, etc.) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. A cartridge system may be used for the ink tank. That is, an ink cartridge as an ink tank is configured to be detachable from the recording head 12. When the ink in the ink cartridge becomes empty, the ink cartridge is replaced and the ink supplied to the recording head 12 is replenished.

[Description of structure of recording head]
Next, the structure of the recording head 12 will be described in detail with reference to FIGS. 2 to 5 are schematic views as seen from the nozzle surface of the recording head 12 (surface on which the nozzles 50 (50K, 50C, 50M, 50Y) are formed). 3 to 5, the same reference numerals are given to the same or similar parts as in FIG. 2, and the description thereof is omitted.

  In the recording head 12, the nozzles 50K, 50C, 50M, and 50Y corresponding to the respective colors of KCMY are arranged at equal intervals along the sub-scanning direction substantially orthogonal to the main scanning direction (directions indicated by F and R in FIG. 2). A first nozzle group 52 having nozzle rows 52K, 52C, 52M, and 52Y and a second nozzle having nozzle rows 54Y, 54M, 54C, and 54K in which nozzles 50K, 50C, 50M, and 50Y are similarly arranged in the sub-scanning direction. Nozzle group 54.

  The first nozzle group 52 is equally spaced in the order of the nozzle row 52K, the nozzle row 52C, the nozzle row 52M, and the nozzle row 52Y from the left in the figure along the main scanning direction (upstream in the forward direction indicated by F in FIG. 2). The second nozzle group 54 is arranged at equal intervals in the order of the nozzle row 54Y, the nozzle row 54M, the nozzle row 54C, and the nozzle row 54K from the upstream side in the forward direction along the main scanning direction. It has a nozzle arrangement.

  In other words, the recording head 12 has two or more nozzle rows corresponding to each color, and the nozzle rows corresponding to other colors are symmetric with respect to the colors with the nozzle rows 52Y and 54Y corresponding to Y ink as the center. Has an array. In such a nozzle arrangement, the color order from the upstream side in the forward direction is the same as the color order from the upstream side in the return direction indicated by R in FIG.

  In the ink jet recording apparatus 10 shown in this example, a pigment-based ink with less bleeding and excellent light resistance is used for the K ink, and a dye-based ink having a good coloring property is used for the C ink, the M ink, and the Y ink. In such an inkjet system in which pigment-based ink and dye-based ink are mixed, dye-based ink is used for color image printing (recording) and pigment-based ink is used for text printing, taking advantage of the characteristics of each ink. Further preferable image recording is performed.

  Note that the term “image” in this specification indicates not only so-called images such as photographs and pictures but also broad images including text such as characters and symbols, line drawings, and the like.

  When bi-directional (reciprocating) printing is performed in the main scanning direction using the recording head 12 having the nozzle arrangement shown in FIG. 2, image recording is executed using the first nozzle group 52 in the forward direction indicated by F in FIG. Then, image recording is performed using the second nozzle group 54 in the backward direction indicated by R in FIG. That is, the first nozzle group 52 functions as a nozzle group for forward direction printing, and the second nozzle row 54 functions as a nozzle group for backward direction printing. In bi-directional printing using the recording head 12, since the CMY ink of the dye-based ink is ejected after the CMY ink of the dye-based ink is ejected in both the forward direction printing and the backward direction printing, the dye-based ink and the pigment ink are ejected. In an image in which system ink is mixed, occurrence of mixed color unevenness (beading) due to a difference in permeation speed between dye-based ink and pigment-based ink is suppressed, and a preferable image can be obtained.

  For example, when printing an image in which a color image and text using K ink are mixed, in the forward direction printing, nozzle row 52Y, nozzle row 52M, and nozzle row 52C to CMY ink (at least one of CMY inks) After the ink droplets are ejected, the subsequent nozzle row 52K is driven, and in the backward direction ink, after the nozzle row 54Y, the nozzle row 54M, and the nozzle row 54C are driven, the K ink is ejected from the subsequent nozzle row 54K. Accordingly, the K ink is ejected after the CMY ink is ejected in both the forward direction printing and the backward direction printing.

  Note that, depending on the image data, there is a region of only K ink, but in this region of only K ink, CMY ink is not ejected from the nozzle rows 52Y, 52M, 52C, 54Y, 54M, 54C, and the nozzle row 52K and the nozzles Only K ink is ejected from the row 54K (at least one of the nozzle row 52K and the nozzle row 54K).

  The K ink (pigment-based ink) used in the inkjet recording apparatus 10 shown in this example is characterized in that the pigment particles having a particle diameter exceeding 120 nm are 5% by volume or less. In the pigment-based ink, the volume average particle diameter is often used as an index representing the mode of pigment particle distribution, and the value is about 50 nm to 150 nm in a general pigment-based ink.

Since how much particles having a size larger than the average particle size are included affects the penetration, in this example, the existence ratio of particles having a large size is considered as a problem. It is an index representing a D ₉₅ size of the particle diameter of 95% cumulative fraction) from the side.

In a typical pigment-based inks, although D ₉₅ described above is about 130Nm～200nm, pigmented inks used in the inkjet recording apparatus 10 is generally small pigment particles less large pigment particles than pigment-based ink the are contained in large quantities, by the D ₉₅ and 120nm or less, penetration speed is faster than the typical pigment-based ink.

  The particle diameter of the pigment particles means the diameter when the planar shape of the pigment particles is a substantially circular shape. When the pigment particles have a planar shape other than a substantially circular shape, the average value of the maximum width and the minimum width is set. The particle diameter in the present invention can be measured by a known measuring method. As an example, it can be measured using a particle size analyzer UPA-EX150 manufactured by Nikkiso Co., Ltd.

  In addition, when forming a color image, the ink droplet ejection order is the same between the forward direction printing and the backward direction printing. Unevenness is also suppressed.

  In the nozzle row arrangement shown in FIG. 2, a mode in which the nozzle rows 52Y and 54Y corresponding to the Y ink are made common is also possible. That is, by sharing the nozzle row 52Y and the nozzle row 54Y corresponding to the same color ink adjacent in the substantially central portion of the recording head 12 in the main scanning direction, the number of nozzle rows and the common liquid that supplies ink to the nozzle rows are shared. The number of chambers (reference numeral 65 in FIG. 3) is reduced, the recording head 12 is downsized, and the manufacturing ease is expected to be improved.

  The nozzle arrangement shown in FIG. 2 is merely an example, and the number of nozzles included in each nozzle row (FIG. 2 shows an aspect in which each nozzle row has six nozzles) is the size of the recording head 12, the resolution of the recording image, It is determined appropriately depending on the printing speed. The inter-nozzle pitch (inter-nozzle pitch) in each nozzle row and the inter-nozzle row pitch (inter-nozzle pitch) are also determined appropriately according to the size of the print head 12, the resolution of the print image, and the print speed. It is done.

  FIG. 3A shows another nozzle arrangement example. In the nozzle row arrangement shown in FIG. 3A, the nozzle row 54C, nozzle row 54M, nozzle row 54Y, nozzle row 54K, nozzle row 52K, nozzle row 52Y, nozzle row 52M, nozzle row 52C are arranged in this order from the left in the drawing. Nozzle rows are arranged.

  In other words, with respect to the nozzle arrangement shown in FIG. 2, the first nozzle group 52 and the second nozzle group 54 are interchanged, and further, the nozzle arrays 52K and 54K corresponding to K ink correspond to other colors. It has a nozzle arrangement in which nozzle rows are arranged symmetrically with respect to color.

  Further, a common liquid chamber (ink supply path) 65K for supplying ink to the nozzle row 52K of the first nozzle group 52 and the nozzle row 54K of the second nozzle group 54 (shown by a broken line in FIG. 3A). Is common. Unlike the dye-based ink, the pigment-based ink used for the K ink is not dissolved in the color material, and therefore is more likely to be clogged in the common liquid chamber 65K than the dye-based ink. By commonizing the common liquid chamber 65K corresponding to the two nozzle rows for ejecting K ink and increasing the flow path width, it is possible to prevent clogging of the ink in the common liquid chamber 65. Discharge stabilization is expected.

  As described above, when the ejection stability of K ink is ensured, the ejection frequency of K ink can be further increased, and the ejection frequency can be increased in a system in which the ejection frequency of K ink is rate-limiting. is there.

  In the mode shown in FIG. 3A, the nozzle rows 52K and 54K corresponding to the K ink are arranged in the approximate center of the recording head 12 in the main scanning direction, so that scanning in the main scanning direction during monochrome printing such as text printing is performed. The amount (scanning width) can be reduced, and the speed of monochrome printing can be increased. A particularly large effect can be obtained in narrow-width scanning in which only a region where data exists is reciprocally scanned to shorten the scanning time.

  Note that in image recording in which a color image and an image with black ink are mixed, a region where image printing is performed with only black ink may be determined from image data, and the narrow scan described above may be applied to the region.

  As shown in FIG. 3B, the number of nozzles in the nozzle rows 52K and 54K corresponding to K ink is set to be larger than that in the other nozzle rows (the nozzle row lengths of the nozzle rows 52K and 54K corresponding to K ink are increased). If the length of the nozzle row corresponding to the other ink is set to be longer than the nozzle row length), an area that can be printed using K ink in one main scan is increased, which further contributes to speeding up monochrome printing. Further, a mode in which the nozzle row 52K and the nozzle row 54K corresponding to the K ink are made common is also possible.

  For example, when printing an image in which a color image and text using K ink are mixed, in forward direction printing, CMY ink is ejected from nozzle row 52C, nozzle row 52M, and nozzle row 52Y, and then K ink from subsequent nozzle row 52K is printed. In the backward printing, the CMY ink is ejected from the nozzle row 54C, the nozzle row 54M, and the nozzle row 54Y, and then the K ink is ejected from the subsequent nozzle row 54K. Therefore, since the K ink is ejected after the CMY ink is ejected in both the forward direction printing and the backward direction printing, color mixing unevenness due to the difference in the permeation speed of the dye-based ink and the pigment-based ink can be suppressed.

  When forming dots of the secondary color G, C ink and Y ink are ejected in the order of the nozzle row 52C and the nozzle row 52Y in the forward direction printing, and C in the order of the nozzle row 54C and the nozzle row 54Y in the backward direction printing. Since ink and Y ink are ejected, band-like color unevenness due to the difference in the droplet ejection order between forward direction printing and backward direction printing is also suppressed.

  FIG. 4A shows a mode in which the first nozzle group 52 and the second nozzle group 54 are shifted in the sub-scanning direction by a half of the inter-nozzle pitch in the sub-scanning direction. In the recording head 12 to which such a nozzle arrangement is applied, the substantial nozzle pitch in the sub-scanning direction is halved, and the substantial nozzle density of the recording head 12 is increased. Therefore, as compared with the modes of FIGS. 2 and 3, high-speed image recording of a color image is performed by recording an image with both nozzles of the first nozzle group 52 and the second nozzle group 54 in both forward and backward passes in one scan. Is possible. Further, the discharge order of each color is the same in both the forward and backward passes, and band-like color unevenness in bidirectional printing is suppressed.

  Further, as shown in FIG. 4B, each of the first nozzle group 52 and the second nozzle group 54 may include two nozzle rows corresponding to K ink. That is, each of the first nozzle group 52 and the second nozzle group 54 has two nozzle rows 52K1, 52K2, 54K1, and 54K2 corresponding to K ink, and the nozzle row 52K1 and the nozzles belonging to the first nozzle group. The row 52K2 is arranged so as to be shifted in the sub-scanning direction by 1/2 of the nozzle pitch in the sub-scanning direction. Similarly, the nozzle row 54K1 and the nozzle row 54K2 belonging to the second nozzle group are arranged so as to be shifted in the sub-scanning direction by 1/2 of the inter-nozzle pitch in the sub-scanning direction.

  In bidirectional printing using the recording head 12 having the nozzle arrangement shown in FIG. 4B, both the first nozzle group 52 and the second nozzle group 54 are used for both the forward direction printing and the backward direction printing. In image recording in which a dye-based ink and a pigment-based ink are mixed, the pigment-based ink can be ejected after the dye-based ink with the same resolution.

  That is, in the forward direction printing, the first nozzle group 52 is used, and after performing CMY ink ejection from the nozzle arrays 52Y, 52M, and 52C, ink ejection is performed from the nozzle array 52K1, and the nozzle arrays 54C, 54M, and 54Y are performed. The ink droplet ejection is controlled so that the ink droplet ejection is performed from the nozzle row 52K2 after the CMY ink droplet ejection is performed.

  In the backward direction printing, the second nozzle group 54 is used. After ink droplets are ejected from the nozzle rows 54Y, 54M, 54C, ink droplets are ejected from the nozzle row 54K1, and from the nozzle rows 52C, 52M, 52Y. Ink droplet ejection is controlled so that ink droplet ejection is performed from the nozzle row 54K2 after ink droplet ejection.

  When forming a secondary color G dot in forward direction printing and further forming a K dot in the vicinity thereof, in the first nozzle group 52, the ink is in the order of Y ink and C ink from the nozzle row 52Y and the nozzle row 52C. After the ink is ejected, K ink is ejected from the nozzle row 52K1. In the second nozzle group 54, the C ink and the Y ink are ejected in this order from the nozzle array 54C and the nozzle array 54Y, and then the K ink is ejected from the nozzle array 52K2.

  In the backward direction printing, after the droplets are ejected in the order of C ink and Y ink from the nozzle row 52C and nozzle row 52Y belonging to the first nozzle group 52, K ink is ejected from the nozzle row 54K2 belonging to the second nozzle group 54. Dropped. Further, after the Y ink and the C ink are ejected in this order from the nozzle array 54Y and the nozzle array 54C belonging to the second nozzle group 54, the K ink is ejected from the nozzle array 54K1 belonging to the first nozzle group 52. .

  In the recording head 12 having the nozzle arrangement shown in FIG. 4B, both the dye-based ink and the pigment-based ink can be ejected at the same resolution by the same scanning, and the first nozzle group 52 and the second nozzle group. 54 can be used for both the forward direction printing and the backward direction printing, so that the printing efficiency can be improved.

  Further, a mode in which the nozzle arrangement shown in FIGS. 5A and 5B is applied is also possible. In the nozzle arrangement shown in FIG. 5 (a), the first nozzle group 52K corresponding to the K ink of the first nozzle group 52 and the nozzle row 54K corresponding to the K ink of the second nozzle group 54 are the first nozzles. The nozzle arrays 52C, 52M, and 52Y of the group 52 and the second nozzle groups 54C, 54M, and 54Y have nozzle arrangements that are symmetrical with respect to color, and are shown in FIGS. 3 (a) and 3 (b). Similar to the embodiment, a common liquid chamber 65 that supplies ink to the nozzle rows 52K and 54K corresponding to K ink is shared.

  That is, the second nozzle group 54 and the first nozzle group 52 are arranged in this order from the upstream side in the forward direction, and from the same direction, the nozzle row 54C, the nozzle row 54M, the nozzle row 54Y, the nozzle row 54K, the nozzle row 52K, and the nozzle The nozzle rows are arranged in the order of the row 52Y, the nozzle row 52M, and the nozzle row 52C.

  Furthermore, the nozzle rows 52C, 52M, 52Y, and 52K belonging to the first nozzle group 52 and the nozzle rows 54C, 54M, 54Y, and 54K belonging to the second nozzle group are between the nozzles in the sub-scanning direction in the sub-scanning direction. They are shifted by a half of the pitch.

  In the nozzle arrangement shown in FIG. 5B, the nozzle arrays 52K and 54K corresponding to K ink have a larger number of nozzles than the nozzle arrays corresponding to other colors.

  Here, an example of droplet ejection control in the recording head 12 having the nozzle arrangement shown in FIGS. 5A and 5B will be described.

  When printing an image in which a color image and text using K ink are mixed, the first nozzle group 52 is used in forward direction printing, and after CMY ink is ejected from the nozzle row 52C, the nozzle row 52M, and the nozzle row 52Y. K ink is ejected from the succeeding nozzle row 52K, and the second nozzle group 54 is used in the backward printing, and the subsequent nozzle is ejected after CMY ink is ejected from the nozzle row 54C, the nozzle row 54M, and the nozzle row 54Y. K ink is ejected from the row 54K. Therefore, since the K ink is ejected after the CMY ink is ejected in both the forward direction printing and the backward direction printing, color mixing unevenness due to the difference in the permeation speed of the dye-based ink and the pigment-based ink can be suppressed.

  In monochrome printing in which text or the like is printed using only K ink, printing efficiency can be improved by printing using the nozzle row 52K and the nozzle row 54K. When printing with only K ink using the nozzle arrangement shown in FIG. 5 (b), printing can be performed using K ink in one main scan as in the nozzle arrangement of FIG. 3 (b). The area becomes large, and monochrome printing using only K ink is accelerated.

  In the case of recording a color image with only CMY inks with the nozzle arrangement shown in FIGS. 5A and 5B, the second color G dot is formed by scanning the recording head 12 in the forward direction. In the nozzle group 54, Y ink is ejected from the nozzle 54Y and then C ink is ejected from the nozzle 54C. In the first nozzle group 52, C ink is ejected from the nozzle 52C and then Y ink is ejected from the nozzle 52Y.

  To form the secondary color G dots by scanning the recording head 12 in the backward direction, the second nozzle group 54 ejects Y ink from the nozzle 54Y after ejecting C ink from the nozzle 54C, In the first nozzle group 52, the Y ink is ejected from the nozzle 52Y, and then the C ink is ejected from the nozzle 52C. In this way, the printing efficiency is expected to be improved by ejecting ink from the first nozzle group 52 and the second group 54 in both reciprocations.

  Next, the structure of the ink ejection system of the recording head 12 will be described with reference to FIGS. 6 (a) and 6 (b). 6A is a cross-sectional view showing a three-dimensional structure of the recording head 12, and FIG. 6B is an enlarged view of a part thereof.

  The recording head 12 includes a plurality of nozzles 50 (see FIGS. 2 to 5, and the nozzles 50K, 50C, 50M, and 50Y are collectively referred to as the nozzle 50), and the nozzle 50 includes a pressure chamber 62 that stores ink. The electrothermal conversion element 64 is provided inside the pressure chamber 62.

  By applying an electrical pulse, which is a recording signal, to the electrothermal transducer 64, thermal energy is applied to the ink inside the pressure chamber 62, and the bubble pressure generated at the time of film boiling in the ink is used for ink ejection. When ink droplets are ejected from the nozzle 50, ink is filled from the common liquid chamber 65 into the pressure chamber 62 via the supply port (supply throttle) 66.

  FIG. 6A shows an aspect in which the common liquid chamber 65 common to the two adjacent nozzles 50 is equivalent to the aspect in which the common liquid chamber 65 of the nozzle 52K and the nozzle 54K shown in FIGS. Indicated.

[Explanation of control system]
Next, the control system of the inkjet recording apparatus 10 will be described. FIG. 7 is a principal block diagram showing the system configuration of the inkjet recording apparatus 10. The inkjet recording apparatus 10 includes a communication interface 70, a system controller 72, an image memory 74, a ROM 75, a motor control unit 76, a recovery control unit 78, a print control unit 80, an image processing unit 81, an image buffer memory 82, a head driver 84, a temperature. A detection unit 85 and the like are provided.

  The communication interface 70 is an interface unit that receives image data sent from the host computer 86. A serial interface or a parallel interface can be applied to the communication interface 70. In this part, a buffer memory (not shown) for speeding up communication may be mounted.

  Image data sent from the host computer 86 is taken into the inkjet recording apparatus 10 via the communication interface 70 and temporarily stored in the image memory 74. The image memory 74 is a storage unit that temporarily stores an image input via the communication interface 70, and data is read and written through the system controller 72. The image memory 74 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The ROM 75 stores system parameters and various control programs. A rewritable storage medium such as an EEPROM may be applied to the ROM 75.

  The system controller 72 is a control unit that controls the communication interface 70, the image memory 74, the motor control unit 76, the recovery control unit 78, and the like. The system controller 72 includes a central processing unit (CPU) and its peripheral circuits, and performs communication control with the host computer 86, read / write control of the image memory 74, etc. A control signal for controlling the temperature adjusting heater is generated.

  The motor control unit 76 is a driver (drive circuit) that drives a motor 88 such as the main scanning motor 18 and the conveyance motor 40 shown in FIG. 1 in accordance with an instruction from the system controller 72.

  The recovery control unit 78 is a control block that controls the recovery operation of the recording head 12. Under the control of the system controller 72, a cap drive unit 90 that operates a cap (cap drive system), a blade drive unit 92 that operates a blade (blade drive system), and a suction device 94 that sucks ink from the nozzles 50 are provided. Control.

  The print controller 80 sends the image data in the image memory 74 to the image processor 81 under the control of the system controller 72. The image processing unit 81 has a signal processing function for performing various processing and correction processes for generating a print control signal on the image data, and the generated print control signal (dot data) is sent to the print control unit 80. To the head driver 84.

  Necessary signal processing is performed in the image processing unit 81, and the ejection amount and ejection timing of the ink droplets of the recording head 12 are controlled via the head driver 84 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 80 includes an image buffer memory 82, and image data, parameters, and other data are temporarily stored in the image buffer memory 82 when image data is processed in the image processing unit 81. In FIG. 7, the image buffer memory 82 is shown in a mode associated with the print control unit 80, but it can also be used as the image memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with one processor.

  The head driver 84 generates electric pulses for driving the electrothermal conversion elements 64 (see FIG. 6) of the recording heads 12 of the respective colors based on the dot data (print data) given from the print control unit 80, and the electrothermal conversion elements The generated electric pulse is supplied to 64. The head driver 84 may include a feedback control system for keeping the driving conditions of the recording head 12 constant.

  The recording medium type information obtained from the recording medium type detection sensor 44 also shown in FIG. 1 is sent to the system controller 72. The system controller 72 stores the recording medium type information in a predetermined memory (storage element) and sends it to the print control unit 80.

  The temperature detection unit 85 includes a temperature sensor provided in the ink jet recording apparatus 10, and the system controller 72 that sends temperature information of each unit obtained from the temperature sensor to the system controller 72 is based on the obtained temperature information. A temperature control device (a heater, a cooling fan, etc.) in the ink jet recording apparatus 10 is controlled.

[Specific examples of image recording control]
Next, a specific example of image recording control according to the present invention will be described. FIG. 8 is a flowchart showing the flow of image recording control according to the present invention. In the image recording control shown in FIG. 8, a beading threshold value is set according to the recording medium type M, and the beading threshold is set from the applied amount (droplet ejection amount) of CMY ink (dye-based ink) and K ink (pigment-based ink). It is determined whether or not bedding has occurred, and if there is a possibility of beading, control is performed to change the print mode.

  That is, when image recording is started (step S10), the system controller 72 determines the recording medium type M based on the recording medium type information obtained from the recording medium type detection sensor 44 shown in FIG. 7 (FIG. 1). (Step S12 in FIG. 8), the process proceeds to Step S14. In step S14, a beading threshold B corresponding to the recording medium type M is set.

  The setting of the beading threshold value B in step S14 has a mode in which the beading threshold value corresponding to the recording medium type is read out from the beading threshold value table stored in advance as a data table for each recording medium type. .

  Thereafter, image data is acquired (step S16), and the main scanning width W in the main scanning direction of the recording head 12 in the image data is set (step S18), and the ink application amount is set (step S20). . Of the ink application amounts set in step S20, the pigment-based ink (K ink) application amount is V1, and the dye-based ink (CMY ink) application amount is V2.

  In step S22, the beading determination value A is obtained based on the main scanning width W and the ink application amounts V1 and V2 obtained in step S18 and step S20. This beading determination value A is expressed by A = α × W × β × V1 × γ × V2.

  α, β, and γ are coefficients appropriately set from experiments on various recording media 30, stored in a table stored in a storage element such as the ROM 75 of FIG. 7, and recorded when the beading determination value A is calculated. The information is appropriately read from the table according to the type of the medium 30.

  The beading determination value A obtained in step S22 is compared with the beading threshold value B corresponding to the recording medium M set in step S14 (step S24), and the beading determination value A <beading. If it is the threshold value B (YES determination), it is determined that beading does not occur (or the possibility that beading will occur) is low, and normal image recording (bidirectional printing) is performed (step S26).

  In this way, image recording is executed, and when image recording based on predetermined image data ends, the process proceeds to step S30, and the presence or absence of the next image data is determined. If there is next image data in step S30, the process proceeds to step S32 to determine whether or not the type of the recording medium 30 is changed.

  In step S32, when the type of the recording medium 30 is changed (YES determination), the process proceeds to step S12, and after the recording medium type is detected, the beading threshold B is reset in step S14. . On the other hand, when the type of the recording medium 30 is not changed (NO determination), the process proceeds to step S16, and the image data is acquired without changing the beading threshold B.

  In step S30, if there is no next image data (NO determination), the image recording control is ended (step S34).

  On the other hand, in the case of a medium with very slow penetration in step S24, beading determination value A> beading threshold value B (NO determination), and beading occurs (or the possibility of occurrence of beading). And any one of the following processes is executed.

  If it is determined in step S24 that beading occurs, whether the scanning speed of the recording head 12 in the main scanning direction is reduced, the print head is shifted to a print standby state, or bidirectional printing is switched to one-way printing. , One of the processes is performed.

  Which of the “decelerating scanning speed” processing, “standby state” processing, and “switching from bidirectional printing to unidirectional printing” processing is selected depends on the type of the recording medium 30 and the beading determination value. It may be determined from the size, or may be determined uniformly according to the type of the recording medium 30 or the like.

  An example of the “decelerate scanning speed” process (control for changing the scanning speed in the main scanning direction) is to send a speed change command from the system controller 72 shown in FIG. There is a mode in which the rotational speed of the main scanning motor 18 in FIG. 1 is changed in response to this speed change command. Further, the conveyance speed of the recording medium 30 is also changed corresponding to the change in speed in the main scanning direction. This is also effective when using the recording medium 30 in which not only pigment-based ink but also dye-based ink penetrates slowly.

  The “standby” process is more effective for the recording medium 30 that penetrates more slowly. As an example of control in the standby state, there is a mode in which image recording is interrupted and the remaining image recording is continued after a predetermined time has elapsed. This aspect is effective for the recording medium 30 in which both the dye-based ink and the pigment-based ink penetrate slower. In addition, when image recording is interrupted, a recovery operation is performed on the recording head 12 such as performing preliminary ejection outside the image recording area, so that the standby time can be effectively utilized together with ejection stabilization control. An embodiment in which is performed is preferable.

  Further, as a control example of the process of “switching from bidirectional printing to unidirectional printing”, droplet ejection control in the main scanning direction is performed only in the forward path, and only the movement is performed in the backward path without performing droplet ejection. At that time, the conveyance of the recording medium 30 is switched to the conveyance control that is performed only after the forward scanning. This aspect is effective for the recording medium 30 in which the penetration of the pigment-based ink is slow.

  In normal image recording in which beading is determined not to occur in step S26, image recording by bidirectional printing in which the recording head 12 is reciprocally scanned in the main scanning direction is executed, and color images are mixed in color image and black image recording. In a region where a black image (dot) is present in the vicinity of (dot), K ink is ejected after CMY ink is ejected.

[Description of ink]
Next, the pigment-based ink (K ink in this example) used in the inkjet recording apparatus 10 will be described in detail. A pigment-based ink in which pigment particles having a particle diameter exceeding 120 nm are 5% by volume or less is applied to the inkjet recording apparatus 10. Since how much large size particles are contained in the ink affects the permeation, in this example, the existence ratio of particles having a size larger than the average particle size is a problem, and 5% by volume from the larger particle distribution. the size of the particle diameter of the minute (5% by volume fraction from the smallest) is an index representing the D _95. In a typical pigment-based _{ink, D 95} is of the order of 130Nm～200nm, the pigment-based ink used in the inkjet recording apparatus 10, the general less _{D 95} large pigment particles compared to pigment based inks 120nm It is as follows. Accordingly, the permeation speed is higher than that of a general pigment-based ink.

  The applicant of the present application experimentally obtained the relationship between the particle diameter contained in the pigment-based ink and the beading and band-like color unevenness. The result is shown in FIG.

  In this experiment, a recording head capable of ejecting dye-based ink and pigment-based ink is used, and the recording head is reciprocated in the main scanning direction to print an image in which the dye-based ink and the pigment-based ink are mixed. The image was recorded on the medium 30, and the recorded image was enlarged and visually checked to confirm the print quality (whether or not beading occurred and whether or not band-like color unevenness occurred).

  In the “head structure” column of FIG. 9, a recording head having a structure in which the KCMY ink droplet ejection order is the same in both directions in bidirectional printing is set as “with a return nozzle”, and the KCMY ink droplet ejection order is in the forward path and the backward path. A recording head having a different structure is described as “no return nozzle”.

In the “first ink type” column of FIG. 9, “dye” and pigment-based ink are used when ink is ejected in the order of dye-based ink (CMY ink) and pigment-based ink (K ink) in one main scan. , a case where ejected in order of the dye-based inks described as "pigment", in the column "D ₉₅ of the pigment-based ink", as measured by a particle size distribution measuring apparatus UPA-EX150 (Nikkiso Co., Ltd.), particle size The particle size value at which the cumulative volume distribution is 95% from the small particle size side is described.

In the experiment, a dye-based ink prepared using 5% by weight of a dye, 10% by weight of diethylene glycol, 10% by weight of glycerin, 1% by weight of a surfactant, and the remaining amount of water was used. Those having different _D95 measured were prepared by using 5% by weight of pigment, 10% by weight of diethylene glycol, 10% by weight of glycerin, 1% by weight of surfactant and water as the remaining amount.

  By changing the conditions of “head structure”, “leading ink type” and “particle size of pigment-based ink” described above, the recorded image is evaluated in four stages from the viewpoint of “beading” and “band-like color unevenness” did. Regarding the evaluation of “band-like unevenness”, a solid image in which the density level of medium density gray was changed in three stages on inkjet photographic paper was printed by bidirectional printing, and the printing quality was evaluated. X indicates a state where band-like unevenness occurs at any density, and ◯ indicates a state where band-like unevenness does not occur at any density level.

  With regard to the evaluation of “beading”, an image obtained by changing the print width of a black frame line pattern to a medium density gray on five levels on an inkjet photographic paper was printed by bidirectional printing, and the print quality was evaluated. X indicates a state in which clear beading is visually recognized in 3 to 5 stages, and Δ indicates a state in which beading that can be visually confirmed is present in 1 to 2 stages. In addition, ◯ indicates a state in which beading that cannot be visually confirmed (mild) is occurring, and ◎ indicates a state in which beading is not visually recognized at all stages.

  Based on the evaluation results of “beading” and “band-like color unevenness”, “unevenness comprehensive determination” was described in three stages. In “unevenness comprehensive determination”, “◎” indicates a case where “beading” and “band-like color unevenness” are “◎” or “◯”. In addition, ◯ indicates a case where at least one of “beading” and “band-like color unevenness” is ◎ or ◯, and the other is Δ. X is a case where at least one of “beading” and “band-like color unevenness” is x.

In FIG. 9, Examples 1 to 3 are “with reciprocating nozzles”, “advanced ink type of the same scanning is dye-based ink”, “size corresponding to 95% of cumulative pigment particle size distribution from the smallest (D ₉₅ ) ”is a condition of“ 100 nm to 120 nm ”, no beading occurs, and no band-like color unevenness occurs.

  That is, the smaller the pigment particle size of the pigment-based ink, the better the permeability of the pigment-based ink into the recording medium 30, and if the pigment particle having a particle diameter of 120 nm or less contains 95% by volume or more, the pigment-based ink It was found that beading did not occur due to the penetration rate of.

On the other hand, in FIG. 9, “D ₉₅ is 130 nm” in Comparative Example 1, and “D ₉₅ is 150 nm” in Comparative Example 2, and beading occurs under these conditions. In addition, under the condition of “no forward nozzle” as in Comparative Example 3, beading does not occur, but band-like color unevenness occurs.

Comparative Example 4 is “pigment ink for the same scanning is pigment-based ink”, and under these conditions, beading occurs even if “D ₉₅ is 110 nm”. Comparative Example 5 is “no return nozzle” and “pigment-based ink for the same scan”. Under these conditions, even when “D ₉₅ is 110 nm”, beading and band-like color unevenness occur. . Therefore, in this evaluation experiment, “there is a return nozzle”, “the pre-scanned ink in the same scan is a dye-based ink”, “the size corresponding to 95% (D ₉₅ ) accumulated from the smaller pigment particle size distribution is 120 nm or less” When this condition is satisfied, beading does not occur and band-like color unevenness does not occur.

  In the inkjet recording apparatus 10 configured as described above, a color image (CMY) is obtained by using dye-based ink (CMY ink) and pigment-based ink (K ink) by bidirectional printing in which the recording head 12 is reciprocated in the main scanning direction. In the case of performing an image in which both an ink image) and a monochrome image (K ink image) are mixed, since the pigment ink is ejected after the dye ink is ejected, the permeation of the dye ink and the pigment ink is permeated. The occurrence of beading due to the difference in speed can be prevented. Further, by making the pigment particles of 120 nm or more contained in the pigment-based ink 5% or less per unit volume, the permeability of the pigment-based ink can be improved and the occurrence of beading can be suppressed.

  Further, by making the CMY ink droplet ejection order the same in the forward direction printing and the backward direction printing, band-like color unevenness due to the difference in the CMY ink droplet ejection order is also eliminated.

  In the present embodiment, an aspect in which a nozzle row corresponding to each color of KCMY is provided in one recording head is shown, but an aspect in which recording heads corresponding to each color of KCMY are provided and the recording heads of each color are arranged in a predetermined arrangement is shown. Is also possible. That is, the head arrangement corresponding to the nozzle arrangement shown in FIG. 2 is the first K head, first C head, first M head, first Y head, second Y head The head arrangement is such that the second M head, the second C head, and the second K head are arranged in this order.

  An example of the nozzle arrangement in the monochromatic recording head is shown in FIGS. The recording head 100 shown in FIG. 10A includes nozzles 102 and 104 that discharge two pigment-based inks, and a nozzle 106 that discharges one dye-based ink. A nozzle arrangement that is arranged along the main scanning direction and sandwiches a nozzle 106 that ejects dye-based ink by nozzles 102 and 104 that eject two pigment-based inks is applied.

  When the recording head 100 scans in the right direction in FIG. 10A, ink is ejected from the nozzles 102 and 106, and when the recording head 100 scans in the left direction in FIG. Ink is discharged from the nozzles 104 and 106.

  The recording head 110 shown in FIG. 10B has a nozzle 112 that ejects one pigment-based ink and nozzles 114 and 116 that eject two dye-based inks. A nozzle arrangement that is arranged along the main scanning direction and sandwiches a nozzle 112 that discharges pigment-based ink by nozzles 114 and 116 that discharge two dye-based inks is applied.

  When the recording head 110 scans in the right direction in FIG. 10B, ink is ejected from the nozzles 112 and 116, and when the recording head 110 scans in the left direction in FIG. Ink is discharged from the nozzles 112 and 114.

  In the recording heads 100 and 110 shown in FIGS. 10A and 10B, the effect of eliminating beading can be obtained even in the case of monochromatic ink.

1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 1 is a schematic plan view of the recording head of FIG. The figure which shows the one aspect | mode of the nozzle arrangement | positioning shown in FIG. The figure which shows the other aspect of nozzle arrangement | positioning shown in FIG. The figure which shows the further another aspect of the nozzle arrangement | positioning shown in FIG. Configuration diagram showing the internal structure of the recording head Main block diagram showing the system configuration of the inkjet recording apparatus 7 is a flowchart showing the flow of control of the image recording method according to the present invention. The figure which shows the result of the evaluation experiment with the abundance ratio of the particle size which is larger than the average particle size of the pigment ink The figure explaining the nozzle arrangement of the recording head corresponding to monochromatic ink

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Inkjet recording apparatus 12,100,110 ... Recording head, recording medium, 44 ... Recording medium kind detection sensor, 50 ... Nozzle, 52 ... 1st nozzle group, 54 ... 2nd nozzle group, 62 ... Pressure chamber 65 ... Common liquid chamber, 80 ... Print control unit, 102 ... Density unevenness correction processing unit,

Claims (13)

A recording head for ejecting ink onto the recording medium;
Conveying means for relatively moving the recording head and the recording medium in a predetermined moving direction;
Main scanning means for reciprocally scanning the recording head in a main scanning direction substantially orthogonal to the moving direction of the recording medium;
With
In the recording head, a nozzle for discharging a dye-based ink containing a dye as a coloring material and a nozzle for discharging a pigment-based ink containing a pigment as a coloring material are arranged along the main scanning direction. A nozzle that discharges the pigment-based ink is disposed behind the nozzle that discharges the dye-based ink in both the reciprocating direction,
The ink coloring material contained in the pigment-based ink is an ink jet recording apparatus characterized in that a coloring material having a particle diameter of 120 nm or less is 95% by volume or more. The recording head includes a plurality of nozzles that discharge the pigment-based ink,
2. The ink jet recording apparatus according to claim 1, wherein the nozzles for discharging the pigment-based ink are disposed at both ends of the nozzles disposed along the main scanning direction.   2. The ink jet recording apparatus according to claim 1, wherein the nozzle for discharging the pigment-based ink is disposed at the center of the nozzle disposed along the main scanning direction. A recording head for ejecting ink onto the recording medium;
Conveying means for relatively moving the recording head and the recording medium in a predetermined moving direction;
Main scanning means for reciprocally scanning the recording head in a main scanning direction substantially orthogonal to the moving direction of the recording medium;
With
The recording head is disposed along the main scanning direction and has a first nozzle group having a plurality of nozzles that eject ink when the recording head is scanned in the forward direction of the main scanning direction; and the main scanning direction And a second nozzle that is arranged along the main scanning direction and has a plurality of nozzles that eject ink when the recording head scans in the backward direction of the main scanning direction. With a group of nozzles,
The first nozzle group has a nozzle arrangement in which a nozzle for discharging a pigment-based ink including a pigment in a color material is disposed on the rear side in the forward direction of the nozzle for discharging a dye-based ink including a dye in a color material. And
The second nozzle group has a nozzle arrangement in which a nozzle for discharging a pigment-based ink containing a pigment in a color material is disposed on the rear side in the return path direction of a nozzle for discharging a dye-based ink containing a dye in a color material. And
The ink coloring material contained in the pigment-based ink is an ink jet recording apparatus characterized in that a coloring material having a particle diameter of 120 nm or less is 95% by volume or more. The nozzles that discharge the dye-based ink include nozzles that discharge each color ink of cyan, magenta, and yellow,
The inkjet recording apparatus according to claim 1, wherein the nozzle that discharges the pigment-based ink includes a nozzle that discharges black ink.   6. The ink jet recording apparatus according to claim 5, wherein the first nozzle group and the second nozzle group have a symmetrical nozzle arrangement with respect to ink color.   The nozzle for discharging the pigment-based ink of the first nozzle group is disposed at a position adjacent to the nozzle for discharging the pigment-based ink of the second nozzle group. The inkjet recording apparatus of any one.   The ink supply path corresponding to the nozzle for discharging the pigment-based ink of the first nozzle group and the ink supply path corresponding to the nozzle for discharging the pigment-based ink of the second nozzle group are made common. An ink jet recording apparatus according to claim 7. The first nozzle group and the second nozzle group have a nozzle row in which a plurality of nozzles that discharge the same type of ink are arranged at predetermined intervals along the sub-scanning direction,
9. The first nozzle group and the second nozzle group are arranged so as to be shifted in the sub-scanning direction by approximately ½ of the inter-nozzle pitch in the sub-scanning direction. The inkjet recording device of any one of them. The first nozzle group and the second nozzle group have two nozzle rows in which a plurality of nozzles that eject the pigment-based ink are arranged along the sub-scanning direction,
10. The ink jet recording apparatus according to claim 9, wherein the two nozzle arrays that discharge the pigment-based ink are arranged with a shift of approximately ½ of the inter-nozzle pitch in the sub-scanning direction. Recording medium type detecting means for detecting the type of the recording medium;
A discharge amount determining means for determining a discharge amount of the dye-based ink and the pigment-based ink based on image data of a recorded image;
Scanning width determining means for determining a scanning width of the recording head in the main scanning direction based on the image data;
Beading determining means for determining whether or not beading occurs in a recorded image based on the discharge amount of the dye-based ink, the discharge amount of the pigment-based ink, and the scan width;
Image recording control means for controlling image recording so that the image recording mode is changed or the image is temporarily suspended and kept in a standby state for a predetermined period when it is determined by the beading determination means that the beading occurs in the recorded image. When,
The ink jet recording apparatus according to claim 1, wherein the ink jet recording apparatus is provided.   The image recording mode includes at least one of changing a scanning speed of the recording head in the main scanning direction and switching the reciprocating scanning to one-way scanning in the main scanning direction of the recording head. The inkjet recording apparatus according to claim 11. A recording head that discharges ink to the recording medium is reciprocated in a main scanning direction substantially parallel to the width direction of the recording medium, and the recording medium and the recording head are moved in a sub-scanning direction substantially orthogonal to the main scanning direction. An image recording method characterized by relatively moving and ejecting a pigment-based ink containing a pigment in a color material after ejecting a dye-based ink containing a dye in the color material in both the reciprocating scanning.

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