JP3969429B2 - Liquid ejection device and droplet ejection control method - Google Patents

Description

  The present invention relates to a liquid ejection apparatus and a droplet ejection control method, and more particularly to a droplet ejection control technique in a liquid ejection apparatus that forms a shape such as an image or a predetermined pattern on a medium to be ejected by ejecting droplets from ejection holes. .

  In recent years, inkjet printers have become widespread as data output devices for images and documents. An ink jet printer can drive recording elements such as nozzles provided in a recording head in accordance with data, and can form data on a recording medium (recording medium) such as recording paper by ink ejected from the nozzles. .

  In an ink jet printer, a desired image is formed on a recording medium by relatively moving a recording head having a large number of nozzles and a recording medium and ejecting ink droplets from the nozzles.

  Up to now, ink jet printers have been used mainly as document output devices in homes and offices, but recently, they have come to be used as output devices for images taken using a digital camera or the like. There are also devices that support A3 and poster-size recording media, and can be used as output devices for advertisements and posters.

  In image printing, there is a high demand for image quality, and high-quality image printing is realized by increasing the number of colors (full color), multi-level tone, finer dots, and higher density. For example, by using multi-color ink such as light ink, multi-color and multi-step tone are realized, and by increasing nozzle density and droplet size, dot density and dot size are reduced. Realized. In addition, when droplet ejection control is performed so that ink is deposited so that adjacent dots overlap, dots can be formed on the recording medium with high density.

  However, when adjacent dots are formed to overlap, if the next ink lands before the previously ejected ink is fixed on the recording medium, the shape of each dot collapses or the ink that lands later In some cases, the droplets may approach the ink droplets that have landed first, resulting in streaking or unevenness in the resulting image. Furthermore, when inks of different colors are deposited and ejected, mixed colors occur, and a preferable color and gradation may not be realized.

  In general, in order to prevent such landing interference, a method of performing droplet ejection control that waits until a previously landed ink droplet penetrates to some extent and then deposits the next ink droplet, or a recording medium on which the ink has landed And a temperature adjusting means for warming the ink landed on the recording medium, a method for promoting the fixing of the ink using the temperature adjusting means, and an ultraviolet curable ink as the ink for forming the image, and the discharged ink. A method of accelerating the fixing of ink landed on a recording medium by irradiating with ultraviolet rays is used.

  The ink jet recording method described in Patent Document 1 and the ink jet recording apparatus using the method differ in the ink jet recording method in which recording is performed by moving a plurality of recording heads arranged in parallel relative to the recording medium. The recording time of any one of the ink dots in contact with the boundary between the ink dots and the other ink dots is shifted.

  Further, the ink jet recording apparatus described in Patent Document 2 includes a drum for fixing paper and a plurality of ink jet heads arranged at predetermined intervals in the circumferential direction with respect to the drum. In the ink jet recording apparatus that drives the ink jet head and performs color printing on the paper, the time T until the dots of different colors contact or overlap each other at the landing position is T ≧ 10 msec. ing.

  In addition, in the printing method described in Patent Document 3 and the print head device used in this method, a charged ink is used, and a channel for ejecting ink is provided between electrodes that generate an electric field, and the ink is ejected from the channel. The ink is deflected by applying an electric field to the ink.

In addition, in the inkjet nozzle, inkjet recording head, inkjet cartridge, and inkjet recording apparatus described in Patent Document 4, each nozzle is provided with a plurality of heaters that generate bubbles in the ink, and the heaters are controlled to generate different bubbles in the ink. And configured to deflect the flying direction of the ink.
JP-A-6-183129 JP 2002-120361 A JP 2000-177115 A JP 2000-185403 A

  However, when the next ink droplet is ejected after waiting for the ink droplet that has landed first to penetrate to some extent, a difference in landing time between adjacent dots is required, so there is a limit to high-speed printing. Further, in the method of promoting the fixing of ink by temperature and ultraviolet rays, a temperature adjusting means and an ultraviolet light source are required, and the types of ink and media that can be used may be limited.

  In the ink jet recording method described in Patent Document 1, the ink jet recording apparatus in which the method is used, and the ink jet recording apparatus described in Patent Document 2, the landing timing between different colors is regulated to prevent bleeding and density reduction. In this way, high image quality is realized, but the landing interference of the same color ink is unsolved, and the problem for high-speed printing has not been solved.

  Further, in the printing method described in Patent Document 3, the print head apparatus used in this method, and the inkjet nozzle, inkjet recording head, inkjet cartridge, and inkjet recording apparatus described in Patent Document 4, the flying direction of the ejected ink droplets Although a method for preventing image deterioration such as unevenness by deflecting is disclosed, a control method for preventing landing interference and its problem are not disclosed.

  The present invention has been made in view of such circumstances, and a liquid ejection apparatus and a droplet ejection control method capable of obtaining a preferable dot by preventing landing interference of dots formed to overlap each other and realizing high-speed droplet ejection The purpose is to provide.

In order to achieve the above object, according to the first aspect of the present invention, there is provided a relative relationship between an ejection head having an ejection hole for ejecting droplets onto an ejection medium and at least one of the ejection head and the ejection medium. Conveying means for moving the ink droplets in one direction, a flying direction deflecting means for deflecting the flying direction of the droplets ejected from the ejection head in a direction parallel to the relative transport direction at the time of droplet ejection of the ejection target medium, and the ejection During the relative conveyance of the discharge medium to the head at a constant conveyance speed, droplets are ejected at a constant droplet ejection period, and a dot row in which at least some of the adjacent dots overlap in the relative conveyance direction is formed. During the formation, the flying direction deflecting unit is controlled so that the inter-dot pitch Pts of the dot row in the relative transport direction of the ejection target medium, and the landing position of the landing positions of the droplets successively ejected from the ejection holes. Relative transport of discharge medium The relationship between the shift amount I consisting of two or more kinds of integers satisfying Δy ≧ 2 × Pts in the direction center-to-center distance Δy and the droplet landing position change amount y in the relative transport direction of the ejection target medium is expressed by the following equation: While satisfying y = Pts × I , the shift amount I is equal to the droplet landing position change amount y alternately in the positive direction and the negative direction so as to include one or more natural numbers k satisfying the following formula I = ± k. And a deflection control section for changing the droplet landing position to land the droplet while avoiding continuous landing of adjacent dots in the relative transport direction of the recording medium.

That is, when forming a dot row along the relative transport direction of the ejection target medium, the flight direction of the liquid droplets ejected from the ejection head is deflected in a direction parallel to the relative transport direction at the time of ejection of the ejection medium. Then, the landing position of the droplet is shifted by a predetermined landing position change amount y (= Pts × I) in the relative conveyance direction of the medium to be ejected, and the droplet is landed at a dispersed position. Accordingly, the continuously ejected droplets land at a distance Δy (≧ 2 × Pts) in the relative transport direction of the medium to be ejected, so that landing interference does not occur and waiting for penetration of the landed droplets does not occur. The droplets can be ejected sequentially. Further , since the shift amount I includes one or more kinds of k satisfying I = ± k, the droplet ejection sequence (deflection sequence and droplet ejection arrangement setting sequence) can be simplified.

  When a full-line type ejection head in which a plurality of ejection holes are arranged over the entire width of the ejection medium is applied to the ejection head, a dot row formed in the relative conveyance direction of the ejection medium is a liquid ejected from one nozzle. Formed by drops. Further, an aspect in which two dots adjacent to each other in the discharge medium relative conveyance direction overlap each other may include an aspect in which the two dots are in contact with each other.

  When a full-line type ejection head is used, droplets can be ejected over the entire area where the ejection medium can be ejected by single-pass control in which the ejection medium is scanned only once.

The deflected droplet flight direction includes a component of the original droplet flight direction (a direction in which the ejection head is substantially orthogonal to the surface facing the ejection medium and perpendicular to the ejection surface of the ejection medium). Yes. Also, among the flying direction of the deflected droplets, when the flat row direction relative conveyance direction at the time of droplet ejection of the ejection receiving medium moving relative to the forward direction (e.g., discharge head ejection receiving medium is fixed Direction of travel of the medium to be ejected) and a negative direction (a direction opposite to the positive direction) may be included.

  The positive direction and the negative direction may be alternately switched, or may be switched every several cycles.

  The shift amount I composed of two or more arbitrary integers may include a positive integer and a negative integer. The shift amount I indicates that the deflected liquid droplet is landed to a position shifted by I dots along the relative transport direction of the discharged medium from the original liquid droplet landing position where the flight direction is not deflected. . Note that the shift amount I may include zero.

  The angle (deflection angle) between the original droplet flying direction (substantially perpendicular to the ejection surface of the medium to be ejected) and the deflected droplet flying direction is θ, the droplet landing position change amount is y, and ejection When the clearance between the head and the medium to be ejected is z, the deflection angle θ is expressed by θ = arctan (y / z).

  The medium to be ejected is a medium (medium) from which ink droplets are ejected from the ejection head. Specifically, paper such as continuous paper, cut paper, and seal paper, resin sheets such as OHP sheets, film, cloth, etc. Regardless of material and shape, various media are included. Note that there are some mediums to be ejected called image forming media, print media, image receiving media, and the like.

By setting the shift amount I, the relationship between the distance between the diameter D of the dot-dot (inter dot center distance), the recording of the dot overlap degree becomes D / 2 ≦ Pts, is jetting continuously It is possible to control so that the dots do not overlap.

In order to achieve the above object, the invention described in claim 2 is characterized in that at least one of the ejection head having ejection holes for ejecting droplets onto the ejection target medium and the ejection head or the ejection target medium. Conveying means for moving either one relatively in one direction, and a flying direction for deflecting the flying direction of droplets ejected from the ejection head in a direction parallel to the relative conveying direction when ejecting the ejected medium During the relative conveyance of the medium to be ejected with respect to the deflection unit and the ejection head, droplet ejection is performed at a constant droplet ejection period, and at least one of the adjacent dots in the relative conveyance direction is ejected. When forming a dot row with overlapping portions, the flying direction deflecting unit is controlled, and the dot pitch Pts between the dot rows in the relative transport direction of the ejection target medium, droplets ejected successively from the ejection holes Of the landing position of A shift amount I consisting of two or more kinds of integers satisfying Δy ≧ 2 × Pts so that the center-to-center distance Δy in the relative conveyance direction of the ejection medium, and a droplet landing position change amount y in the relative conveyance direction of the ejection medium By changing the droplet landing position by the droplet landing position change amount y so that the relationship satisfies the following expression y = Pts × I and the shift amount I includes an integer of 5 or more, the recording target And deflection control means for landing droplets while avoiding continuous landing of adjacent dots in the relative conveyance direction of the medium .

  The three or more types of integers preferably include positive and negative integers.

Further, according to a third aspect of the present invention, in the invention described in the first aspect , the flight direction control means is configured such that the droplet ejection period Tf of the ejection head and the penetration time T0 of the droplet into the ejection medium are as follows. It includes a shift amount setting means for setting the natural number k that satisfies the expression Tf × (2k−1) ≧ T0.

  That is, it is possible to set a flight direction deflection pattern that prevents landing interference with respect to various parameter conditions such as dot density, relative transport speed of the medium to be ejected, and time for penetration of droplets into the medium to be ejected. Specifically, it is possible to set the deflection amount parameter k such that the landing time difference between adjacent dots in the relative conveyance direction of the recording medium on the recording medium is larger than the penetration time of the previously landed dots.

According to a fourth aspect of the present invention, in the first , second, or third aspect , the relative conveyance of the medium to be ejected is included in a dot row formed along the relative conveyance direction of the medium to be ejected. The diameters D1 and D2 of the dots so that the diameter D1 and the diameter D2 of the two dots sharing the adjacent dots in the direction and the inter-dot pitch Pts in the relative conveyance direction of the discharged medium satisfy the following formula D1 + D2 ≦ 2 × Pts. It is characterized in that it includes droplet ejection control means for setting at least one of the diameter D2 or the dot pitch Pts in the relative conveyance direction of the medium to be ejected.

  That is, if the total dot diameter of two consecutively ejected dots is less than or equal to twice the inter-dot pitch Pt in the recording medium relative transport direction, there is no overlap between adjacent dots. Can be ejected continuously. By performing droplet ejection control in this manner, a degree of freedom in dot size (dot diameter) can be obtained between adjacent dots, and gradation can be improved.

According to a fifth aspect of the present invention, in the invention described in any one of the first to fourth aspects, the ejection head is a full line in which a plurality of ejection holes are arranged over the entire width of the ejection target medium. It includes a discharge head of a mold.

  A full-line type ejection head has a length corresponding to the entire width of the recording medium by connecting short heads having short ejection hole arrays that are less than the length corresponding to the entire width of the recording medium in a staggered manner. It may be good.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the ejection head includes a matrix head in which the ejection holes are two-dimensionally arranged, and is substantially orthogonal to a relative conveyance direction of the ejection target medium. The ejection holes for ejecting droplets that form dots adjacent to each other in the direction to be moved are shifted by a predetermined distance in the relative transport direction of the medium to be ejected.

  That is, it is possible to effectively utilize the two-dimensionally arranged nozzle arrangement pattern suitable for high density droplet ejection.

  The two-dimensionally arranged ejection holes include a plurality of ejection hole arrays arranged in a direction that forms an angle with the relative conveyance direction of the medium to be ejected.

In order to achieve the above object, the invention described in claim 7 is characterized in that at least one of the ejection head having ejection holes for ejecting droplets onto the ejection target medium and the ejection head or the ejection target medium. A transport unit that transports one side in a direction substantially orthogonal to the width direction of the ejection medium and relatively moves the ejection head and the ejection medium in one direction; and droplets ejected from the ejection head A droplet ejection control method for a liquid ejection apparatus comprising: a flight direction deflecting unit that deflects a flight direction during droplet ejection, wherein the ejection target medium is being transported relative to the ejection head at a constant transportation speed. When the droplets are ejected at a constant droplet ejection period to form a dot row in which at least some of the adjacent dots overlap in the relative transport direction, the ejection direction deflecting means is used to eject the ejection. Strike from the discharge hole of the head. The flying direction of the liquid droplets is deflected in a direction parallel to at least the relative transport direction when the ejected medium is ejected, and the inter-dot pitch Pts of the dot rows in the relative transport direction of the ejected medium is determined from the ejection holes. Shift amount I consisting of two or more arbitrary integers satisfying Δy ≧ 2 × Pts where the center-to-center distance Δy in the relative transport direction of the medium to be ejected is the landing position of the continuously ejected liquid droplets, The relationship with the droplet landing position change amount y in the relative transport direction of the medium satisfies the following expression y = Pts × I, and the shift amount I is one or more natural numbers of two or more satisfying the following expression I = ± k. By changing the droplet landing position by the droplet landing position change amount y alternately in the positive direction and the negative direction so as to include k, the liquid can be avoided while avoiding continuous landing of adjacent dots in the relative transport direction of the recording medium. It is characterized by landing a drop.

  That is, preferable droplet ejection that does not cause landing interference while performing high-speed droplet ejection is performed without changing the relative relationship between the ejection target medium and the ejection head. On the other hand, when the relative transport speed of the medium to be ejected or the droplet ejection cycle changes, the condition of the droplet landing position change amount is changed accordingly.

According to the present invention, in droplet ejection performed continuously in the relative conveyance direction of the ejection target medium, the droplet flying direction is deflected in a direction parallel to the relative conveyance direction at the time of ejection of the ejection target medium. Since the droplet landing position is shifted from the original landing position by an integral multiple of the dot-to-dot pitch of the dot row formed along the relative transport direction of the medium to be ejected, dots are not formed adjacent to each other even in continuous ejection. , Landing interference can be prevented. Further, since the shift amount I includes one or more kinds of k satisfying I = ± k, the droplet ejection sequence (deflection sequence and droplet ejection arrangement setting sequence) can be simplified.

[Overall configuration of inkjet recording apparatus]
FIG. 1 is an overall configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. As shown in the figure, the inkjet recording apparatus 10 includes a print unit 12 having a plurality of print heads 12K, 12C, 12M, and 12Y provided for each ink color, and each print head 12K, 12C, 12M, An ink storage / loading unit 14 for storing ink to be supplied to 12Y, a paper feeding unit 18 for supplying recording paper 16, a decurling unit 20 for removing curling of the recording paper 16, and a nozzle of the printing unit 12 A suction belt transport unit 22 that is disposed to face a surface (ink ejection surface) and transports the recording paper 16 while maintaining the flatness of the recording paper 16, and a print detection unit 24 that reads a printing result by the printing unit 12, A paper discharge unit 26 that discharges the printed recording paper 16 (printed material) to the outside.

  In FIG. 1, a magazine for rolled paper (continuous paper) is shown as an example of the paper supply unit 18, but a plurality of magazines having different paper widths, paper quality, and the like may be provided side by side. Further, instead of the roll paper magazine or in combination therewith, the paper may be supplied by a cassette in which cut papers are stacked and loaded.

  When multiple types of recording paper are used, an information recording body such as a barcode or wireless tag that records paper type information is attached to the magazine, and the information on the information recording body is read by a predetermined reader. Therefore, it is preferable to automatically determine the type of paper to be used and perform ink ejection control so as to realize appropriate ink ejection according to the type of paper.

  The recording paper 16 delivered from the paper supply unit 18 retains curl due to having been loaded in the magazine. In order to remove this curl, heat is applied to the recording paper 16 by the heating drum 30 in the direction opposite to the curl direction of the magazine in the decurling unit 20. At this time, it is more preferable to control the heating temperature so that the printed surface is slightly curled outward.

  In the case of an apparatus configuration that uses roll paper, a cutter (first cutter) 28 is provided as shown in FIG. 1, and the roll paper is cut into a desired size by the cutter 28. The cutter 28 includes a fixed blade 28A having a length equal to or greater than the conveyance path width of the recording paper 16, and a round blade 28B that moves along the fixed blade 28A. The fixed blade 28A is provided on the back side of the print. The round blade 28B is disposed on the printing surface side with the conveyance path interposed therebetween. Note that the cutter 28 is not necessary when cut paper is used.

  After the decurling process, the cut recording paper 16 is sent to the suction belt conveyance unit 22. The suction belt conveyance unit 22 has a structure in which an endless belt 33 is wound between rollers 31 and 32, and at least portions facing the nozzle surface of the printing unit 12 and the sensor surface of the printing detection unit 24 are horizontal ( Flat surface).

  The belt 33 has a width that is wider than the width of the recording paper 16, and a plurality of suction holes (not shown) are formed on the belt surface. As shown in FIG. 1, a suction chamber 34 is provided at a position facing the nozzle surface of the print unit 12 and the sensor surface of the print detection unit 24 inside the belt 33 spanned between the rollers 31 and 32. Then, the suction chamber 34 is sucked by the fan 35 to be a negative pressure, whereby the recording paper 16 on the belt 33 is sucked and held.

  When the power of a motor (not shown in FIG. 1, described as reference numeral 88 in FIG. 7) is transmitted to at least one of the rollers 31 and 32 around which the belt 33 is wound, the belt 33 rotates in the clockwise direction in FIG. , And the recording paper 16 held on the belt 33 is conveyed from left to right in FIG.

  Since ink adheres to the belt 33 when a borderless print or the like is printed, the belt cleaning unit 36 is provided at a predetermined position outside the belt 33 (an appropriate position other than the print area). Although details of the configuration of the belt cleaning unit 36 are not shown, for example, there are a method of niping a brush roll, a water absorbing roll, etc., an air blow method of blowing clean air, or a combination thereof. In the case where the cleaning roll is nipped, the cleaning effect is great if the belt linear velocity and the roller linear velocity are changed.

  Although an embodiment using a roller / nip conveyance mechanism instead of the suction belt conveyance unit 22 is also conceivable, if the roller / nip conveyance is performed in the printing area, the roller contacts the printing surface of the recording paper 16 immediately after printing, so that the image is displayed. There is a problem of easy bleeding. Therefore, as in this example, suction belt conveyance that does not bring the image surface into contact with each other in the print region is preferable.

  A heating fan 40 is provided on the upstream side of the printing unit 12 on the recording paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 blows heated air on the recording paper 16 before printing to heat the recording paper 16. Heating the recording paper 16 immediately before printing makes it easier for the ink to dry after landing.

  The printing unit 12 is a so-called full line type head in which line type heads having a length corresponding to the maximum paper width are arranged in a direction (main scanning direction) orthogonal to the recording paper conveyance direction (see FIG. 2). Although a detailed structural example will be described later (FIGS. 3 to 5), each of the print heads 12K, 12C, 12M, and 12Y is a recording paper of the maximum size targeted by the inkjet recording apparatus 10 as shown in FIG. The line head includes a plurality of ink discharge ports (nozzles) arranged over a length exceeding at least one side of 16.

  A print head corresponding to each color ink in the order of black (K), cyan (C), magenta (M), and yellow (Y) from the upstream side along the feeding direction of the recording paper 16 (hereinafter referred to as the recording paper transport direction). 12K, 12C, 12M, and 12Y are arranged. A color image can be formed on the recording paper 16 by discharging the color inks from the print heads 12K, 12C, 12M, and 12Y while the recording paper 16 is conveyed.

  Thus, according to the printing unit 12 in which the full line head that covers the entire area of the paper width is provided for each ink color, the operation of relatively moving the recording paper 16 and the printing unit 12 in the sub-scanning direction is performed once. An image can be recorded on the entire surface of the recording paper 16 only by performing it (that is, by one sub-scan). Thereby, it is possible to perform high-speed printing as compared with a shuttle type head in which the print head reciprocates in the main scanning direction, and productivity can be improved.

  In this example, the configuration of KCMY standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink and dark ink are added as necessary. May be. For example, it is possible to add a print head that discharges light ink such as light cyan and light magenta.

  As shown in FIG. 1, the ink storage / loading unit 14 has tanks that store inks of colors corresponding to the print heads 12K, 12C, 12M, and 12Y, and each tank is connected via a conduit (not shown). The print heads 12K, 12C, 12M, and 12Y communicate with each other. Further, the ink storage / loading unit 14 includes notifying means (display means, warning sound generating means) for notifying when the ink remaining amount is low, and has a mechanism for preventing erroneous loading between colors. ing.

  The print detection unit 24 includes an image sensor for imaging the droplet ejection result of the print unit 12, and functions as a means for checking nozzle clogging and other ejection defects from the droplet ejection image read by the image sensor.

  The print detection unit 24 of this example is composed of a line sensor having a light receiving element array that is wider than at least the ink ejection width (image recording width) by the print heads 12K, 12C, 12M, and 12Y. The line sensor includes an R sensor row in which photoelectric conversion elements (pixels) provided with red (R) color filters are arranged in a line, a G sensor row provided with green (G) color filters, The color separation line CCD sensor is composed of a B sensor array provided with a blue (B) color filter. Instead of the line sensor, an area sensor in which the light receiving elements are two-dimensionally arranged can be used.

  The print detection unit 24 reads the test pattern printed by the print heads 12K, 12C, 12M, and 12Y for each color, and detects the ejection of each print head. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like.

  A post-drying unit 42 is provided following the print detection unit 24. The post-drying unit 42 is means for drying the printed image surface, and for example, a heating fan is used. Since it is preferable to avoid contact with the printing surface until the ink after printing is dried, a method of blowing hot air is preferred.

  When printing on porous paper with dye-based ink, the weather resistance of the image is improved by preventing contact with ozone or other things that cause dye molecules to break by pressurizing the paper holes with pressure. There is an effect to.

  A heating / pressurizing unit 44 is provided following the post-drying unit 42. The heating / pressurizing unit 44 is a means for controlling the glossiness of the image surface, and pressurizes with a pressure roller 45 having a predetermined surface uneven shape while heating the image surface to transfer the uneven shape to the image surface. To do.

  The printed matter generated in this manner is outputted from the paper output unit 26. It is preferable that the original image to be printed (printed target image) and the test print are discharged separately. The ink jet recording apparatus 10 is provided with a sorting means (not shown) that switches the paper discharge path so as to select the print product of the main image and the print product of the test print and send them to the discharge units 26A and 26B. Yes. Note that when the main image and the test print are simultaneously formed in parallel on a large sheet, the test print portion is separated by a cutter (second cutter) 48. The cutter 48 is provided immediately before the paper discharge unit 26, and cuts the main image and the test print unit when the test print is performed on the image margin. The structure of the cutter 48 is the same as that of the first cutter 28 described above, and includes a fixed blade 48A and a round blade 48B.

  Although not shown in FIG. 1, the paper output unit 26A for the target prints is provided with a sorter for collecting prints according to print orders.

  Next, the structure of the print head will be described. Since the structures of the print heads 12K, 12C, 12M, and 12Y provided for the respective ink colors are common, the print heads are represented by reference numeral 50 in the following.

  In this example, paper is exemplified as the medium to be ejected by the ink jet recording apparatus 10, but the medium to be ejected is not limited to paper, but a metal plate, a resin plate, wood, cloth, leather, etc. Various media that can fix the ink, can be conveyed relative to the print head 50, and can secure a clearance from the print head 50 can be applied.

  FIG. 3 (a) is a plan perspective view showing an example of the structure of the print head 50, and FIG. 3 (b) is an enlarged view of a part thereof. 3C is a perspective plan view showing another example of the structure of the print head 50, FIG. 4 is a sectional view showing a three-dimensional configuration of the ink chamber unit, and FIG. 4A is a cross-sectional view of FIG. 4B is a cross-sectional view taken along line 4a-4a in FIG. 4B, and FIG. 4B is a cross-sectional view taken along line 4b-4b in FIG.

  In order to increase the dot pitch printed on the recording paper surface, it is necessary to increase the nozzle pitch in the print head 50. As shown in FIGS. 3A to 3C and FIG. 4, the print head 50 of this example includes a plurality of nozzles 51 from which ink droplets are ejected and pressure chambers 52 corresponding to the nozzles 51. The ink chamber unit 53 has a structure that is arranged in a matrix so as to include nozzle rows arranged on a line having a predetermined angle with respect to the main scanning direction, thereby achieving an increase in apparent nozzle pitch density. is doing.

  That is, as shown in FIGS. 3A and 3B, the print head 50 according to the present embodiment has a plurality of nozzles 51 for ejecting ink in the full width of the recording paper 16 in a direction substantially orthogonal to the recording paper transport direction. A full line head having one or more nozzle rows arranged over corresponding lengths.

  Each nozzle is provided with flying direction deflecting means 1 for deflecting the flying direction of the ink droplets ejected from the nozzle 51 in a direction substantially parallel to the recording paper transport direction. The flight direction deflecting means 1 includes a pair of electrodes 2 and 3 arranged along a direction substantially parallel to the recording paper conveyance direction so as to face each other with the nozzle 51 interposed therebetween.

  Further, as shown in FIG. 3 (c), short two-dimensionally arranged heads 50 'may be arranged in a staggered manner and connected to form a length corresponding to the entire width of the print medium.

  The pressure chamber 52 provided corresponding to each nozzle 51 has a substantially square planar shape, and the nozzle 51 and the supply port 54 are provided at both corners on the diagonal line. Each pressure chamber 52 communicates with a common flow channel 55 through a supply port 54.

  An actuator 58 having an individual electrode 57 is joined to the pressure plate 56 constituting the top surface of the pressure chamber 52, and the actuator 58 is deformed by applying a driving voltage to the individual electrode 57, and the nozzle 51 Ink is ejected. When ink is ejected, new ink is supplied from the common channel 55 to the pressure chamber 52 through the supply port 54.

  When an electric field E (shown by a broken line) is generated between the electrodes 2 and 3 shown in FIGS. 4A and 4B, the electric field acts on the ink droplets ejected from the nozzle 51, and the ink The flight direction of the droplet is deflected in a direction deviated from the original flight direction by an angle θ. As shown in FIG. 4B, the direction of the electric field E is a direction from the electrode 2 to the electrode 3 (that is, a direction substantially parallel to the recording paper conveyance direction).

  When the electric field E is applied to the ink droplets ejected from the nozzle 51, the flying direction is deflected by an angle θ from the original flying direction of the ink droplet to the recording paper transport direction, and the landing position of the ink droplet whose flying direction is deflected is The landing position is deflected to a position s ′ that is shifted from the original landing position s by y in a direction substantially parallel to the recording sheet conveyance direction.

  That is, the relationship between the distance Z from the nozzle forming surface of the print head 50 to the recording paper 16, the angle (flying deflection angle) θ between the original ink flying direction and the deflected ink flying direction, and the landing position change amount y. Is represented by the following equation [Equation 1].

[Equation 1]
y = z × tan θ
As shown in FIG. 5, a large number of ink chamber units 53 having such a structure are arranged along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. The structure is arranged in a grid pattern. With a structure in which a plurality of ink chamber units 53 are arranged at a constant pitch d along a certain angle θ with respect to the main scanning direction, the pitch P of the nozzles projected so as to be aligned in the main scanning direction is d × cos θ. .

  That is, in the main scanning direction, each nozzle 51 can be handled equivalently as a linear arrangement with a constant pitch P. With such a configuration, it is possible to realize a high-density nozzle configuration in which 2400 nozzle rows are projected per inch (2400 nozzles / inch) so as to be aligned in the main scanning direction. Hereinafter, for convenience of explanation, it is assumed that the nozzles 51 are linearly arranged at a constant interval (pitch P) along the longitudinal direction (main scanning direction) of the head.

  When the nozzles are driven by a full line head having a nozzle row corresponding to the full width of the paper, (1) all the nozzles are driven simultaneously, (2) the nozzles are sequentially driven from one side to the other (3) ) The nozzle is divided into blocks, and drive control such as sequentially driving from one side to the other for each block is performed, and one line or one in the width direction of the recording paper 16 (direction perpendicular to the recording paper transport direction) Nozzle driving for printing individual strips is defined as main scanning.

  In particular, when the nozzles 51 arranged in the matrix as shown in FIG. 5 are driven, the main scanning as described in the above (3) is preferable. That is, the nozzles 51-11, 51-12, 51-13, 51-14, 51-15, 51-16 are made into one block (other nozzles 51-21,..., 51-26 are made into one block, The nozzles 51-31,..., 51-36 are set as one block,..., And the recording paper 16 is driven by sequentially driving the nozzles 51-11, 51-12,. One line is printed in the width direction.

  On the other hand, repetitively moving the above-described full line head and the paper to repeatedly perform one line or one band-like printing formed by the above-described main scanning is defined as sub-scanning.

  In the implementation of the present invention, the nozzle arrangement structure is not limited to the illustrated example. In the present embodiment, a method of ejecting ink droplets by deformation of an actuator 58 typified by a piezo element (piezoelectric element) is adopted. However, in the practice of the present invention, the method of ejecting ink is not particularly limited. Instead of the piezo jet method, various methods such as a thermal jet method in which ink is heated by a heating element such as a heater to generate bubbles and ink droplets are ejected by the pressure can be applied.

  FIG. 6 is a schematic diagram showing the configuration of the ink supply system in the inkjet recording apparatus 10.

  The ink supply tank 60 is a base tank for supplying ink, and is installed in the ink storage / loading unit 14 described with reference to FIG. There are two types of ink supply tank 60: a system that replenishes ink from a replenishment port (not shown) and a cartridge system that replaces the entire tank when the remaining amount of ink is low. A cartridge system is suitable for changing the ink type according to the intended use. In this case, it is preferable that the ink type information is identified by a barcode or the like, and ejection control is performed according to the ink type. The ink supply tank 60 in FIG. 6 is equivalent to the ink storage / loading unit 14 in FIG. 1 described above.

  As shown in FIG. 6, a filter 62 is provided between the ink supply tank 60 and the print head 50 in order to remove foreign substances and bubbles. The filter mesh size is preferably equal to or smaller than the nozzle diameter (generally about 20 μm).

  Although not shown in FIG. 6, a configuration in which a sub tank is provided in the vicinity of the print head 50 or integrally with the print head 50 is also preferable. The sub-tank has a function of improving a damper effect and refill that prevents fluctuations in the internal pressure of the head.

  Further, the inkjet recording apparatus 10 is provided with a cap 64 as a means for preventing the nozzle 51 from drying or preventing an increase in ink viscosity near the nozzle, and a cleaning blade 66 as a nozzle surface cleaning means.

  The maintenance unit including the cap 64 and the cleaning blade 66 can be moved relative to the print head 50 by a moving mechanism (not shown), and is moved from a predetermined retracted position to a maintenance position below the print head 50 as necessary. The

  The cap 64 is displaced up and down relatively with respect to the print head 50 by an elevator mechanism (not shown). The cap 64 is raised to a predetermined raised position when the power is turned off or during printing standby, and is brought into close contact with the print head 50, thereby covering the nozzle surface with the cap 64.

  During printing or standby, if the frequency of use of a specific nozzle 51 is reduced and ink is not ejected for a certain period of time, the ink solvent near the nozzle evaporates and the ink viscosity increases. In such a state, ink cannot be ejected from the nozzle 51 even if the actuator 58 operates.

  Before such a state is reached (within the range of the viscosity that can be discharged by the operation of the actuator 58), the actuator 58 is operated, and the cap 64 (ink near the nozzle whose viscosity has increased) is discharged. Preliminary ejection (purging, idle ejection, collar ejection, dummy ejection) is performed toward the ink receiver.

  Further, when air bubbles are mixed into the ink in the print head 50 (in the pressure chamber 52), the ink cannot be ejected from the nozzle even if the actuator 58 is operated. In such a case, the cap 64 is applied to the print head 50, the ink in the pressure chamber 52 (ink mixed with bubbles) is removed by suction with the suction pump 67, and the suctioned and removed ink is sent to the collection tank 68. .

  In this suction operation, the deteriorated ink with increased viscosity (solidified) is sucked out when the ink is initially loaded into the head or when the ink is used after being stopped for a long time. Since the suction operation is performed on the entire ink in the pressure chamber 52, the amount of ink consumption increases. Therefore, it is preferable to perform preliminary ejection when the increase in ink viscosity is small.

  The cleaning blade 66 is made of an elastic member such as rubber, and can slide on the ink discharge surface (surface of the nozzle plate) of the print head 50 by a blade moving mechanism (wiper) (not shown). When ink droplets or foreign substances adhere to the nozzle plate, the nozzle plate surface is wiped by sliding the cleaning blade 66 on the nozzle plate to clean the nozzle plate surface. It should be noted that when the ink ejection surface is cleaned by the blade mechanism, preliminary ejection is performed in order to prevent foreign matter from being mixed into the nozzle 51 by the blade.

  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, a memory 74, a motor driver 76, a heater driver 78, a print control unit 80, an image buffer memory 82, a head driver 84, and the like.

The communication interface 70 is an interface unit that receives image data sent from the host computer 86. A serial interface such as USB (Universal Serial Bus) , IEEE 1394, Ethernet (registered trademark) , a wireless network, or a parallel interface such as Centronics can be applied to the communication interface 70. In this part, a buffer memory (not shown) for speeding up communication may be mounted. The 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 memory 74. The 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 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 system controller 72 is a control unit that controls the communication interface 70, the memory 74, the motor driver 76, the heater driver 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 memory 74, and the like, and controls the motor 88 and heater 89 of the transport system. A control signal to be controlled is generated.

  The motor driver 76 is a driver (drive circuit) that drives the motor 88 in accordance with an instruction from the system controller 72. The heater driver 78 is a driver that drives the heater 89 such as the post-drying unit 42 in accordance with an instruction from the system controller 72.

  The print control unit 80 has a signal processing function for performing various processing and correction processing for generating a print control signal from image data in the memory 74 in accordance with the control of the system controller 72, and the generated print control. A control unit that supplies a signal (print data) to the head driver 84. Necessary signal processing is performed in the print controller 80, and the ejection amount and ejection timing (droplet ejection control) of the ink droplets of the print head 50 are performed 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 print control unit 80. 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 memory 74. Also possible is an aspect in which the print controller 80 and the system controller 72 are integrated and configured with a single processor.

  Further, the deflection control unit 85 in the print control unit 80 controls the driving of the electrodes 2 and 3 provided in each nozzle via the electrode driving unit 4. That is, when deflecting the flying direction of the ink droplet ejected from each nozzle based on the print data, a command signal is given to the electrode driving unit 4 to generate an electric field between the electrode 2 and the electrode 3.

  The head driver 84 drives the actuators of the print heads 12K, 12C, 12M, and 12Y for each color based on the print data given from the print control unit 80. The head driver 84 may include a feedback control system for keeping the head driving conditions constant.

  Various control programs are stored in a program storage unit (not shown), and the control programs are read and executed in accordance with commands from the system controller 72. The program storage unit may be a semiconductor memory such as a ROM or EEPROM, or a magnetic disk. An external interface may be provided and a memory card or PC card may be used. Of course, you may provide several recording media among these recording media.

  The program storage unit may also be used as a recording unit (not shown) for operating parameters.

  As described with reference to FIG. 1, the print detection unit 24 is a block including a line sensor, reads an image printed on the recording paper 16, performs necessary signal processing, and the like to perform a print status (whether ejection is performed, droplet ejection And the detection result is provided to the print control unit 80.

  The print control unit 80 performs various corrections on the print head 50 based on information obtained from the print detection unit 24 as necessary.

  In the example shown in FIG. 1, the print detection unit 24 is provided on the print surface side, and the print surface is illuminated by a light source (not shown) such as a cold cathode tube disposed in the vicinity of the line sensor. Although the configuration is such that the reflected light is read by the line sensor, other configurations may be used in the implementation of the present invention.

(Drip ejection control)
Next, the droplet ejection control of the inkjet recording apparatus 10 will be described in detail.

  In the ink jet recording apparatus 10, even when adjacent dots are formed by ink that is continuously ejected from the same ejection hole (nozzle 51), it is possible to prevent the occurrence of dot shape abnormality due to landing interference. Drop control is performed.

  First, the dots formed on the recording paper 16 by the ink droplets ejected from the print head 50 will be described.

  FIG. 8 shows dots 100, 102, 104, 106 formed by ink droplets ejected from the print head 50. The dots 100 are formed so as to partially overlap with the dots 102 adjacent in the main scanning direction, and are formed so as to partially overlap with the dots 104 adjacent in the sub-scanning direction. Further, the dots 106 that are adjacent to each other in the oblique direction are formed so as not to overlap with each other, and the dots 100 and the dots 106 do not overlap each other.

  In other words, assuming that the dot pitch in the main scanning direction is Ptm, the dot pitch in the sub-scanning direction is Pts (where Ptm = Pts = Pt), and the diameter of the dots to be formed (hereinafter referred to as dot diameter) is D. The dots 100, 102, 104, and 106 shown in FIG. 8 have the relationship shown in the following equation [Formula 2].

[Equation 2]
D = Pt × 2 ^1/2
In the example shown in FIG. 9, the dots 100 are formed so as to partially overlap with the adjacent dots 106 in the oblique direction, and the dots 100, 102, 104, and 106 are expressed by the following equation (Equation 3). Have a relationship.

[Equation 3]
D = Pt × 2
In the inkjet recording apparatus 10, when a dot row in the sub-scanning direction (dot row formed by ink droplets ejected from the same nozzle) is formed, Droplet that deflects the flying direction of ink droplets in at least one of the following droplets or subsequent droplets along the sub-scanning direction and shifts the dot landing position by a predetermined amount in the sub-scanning direction Control is performed. The shift amount is determined to be an integral multiple of the dot pitch Pts in the sub-scanning direction. The landing position change amount y (displacement from the original landing position) in the sub-scanning direction is expressed by the following equation [Equation 4] using two or more arbitrary integers I.

[Equation 4]
y = I × Pt
A unit of length (mm, μm, etc.) is applied to the landing position change amount y in the sub-scanning direction.

  In other words, when ink droplets are continuously executed using the same nozzle, ink droplets forming adjacent dots are not continuously ejected, and when ink droplets are continuously ejected in the sub-scanning direction, ink droplets fly. The droplet ejection control is performed so that the direction is deflected along the sub-scanning direction and shifted from the original landing position just below the nozzle by I dots in the sub-scanning direction.

  In other words, the integer I represents the shift amount in the sub-scanning direction indicating how many dots are shifted in the sub-scanning direction.

  FIG. 10 is a diagram in which the dot rows in the sub-scanning direction formed by the inkjet recording apparatus 10 are arranged in chronological order. In FIG. 10, the vertical series indicates the sub-scanning direction, and the horizontal series shows the droplet ejection timing (time) from the left to the right in the order of time (time).

  The dots indicated by solid lines are dots that have already been formed, and the dots indicated by broken lines are dots that are formed after the next droplet ejection timing (dots that are not formed at that timing). Further, the dots indicated by the two-dot broken line are dots formed by performing droplet ejection at the timing.

  The numbers shown in the dots indicate the order of droplet ejection, and the subscripts of the numbers indicate the shift amount I in the sub-scanning direction and the sign in the shift direction. The shift direction + indicates that the ink droplet flight direction is deflected upstream in the recording paper transport direction (sub-scanning direction), and the-indicates that the ink droplet flight direction is deflected downstream in the recording paper transport direction. Show. A number indicating the shift amount I in the sub-scanning direction is represented by the number of dots.

For example, 1 ⁺⁰ is displayed on the dot 110 ejected at the timing t1. This indicates a dot that is ejected at timing t1 and has a shift amount of zero (that is, no shift). Similarly, 2 ⁺² is displayed on the dot 112 ejected at the timing t2, and this is a position where the droplet is ejected at the timing t2 and the shift direction is shifted by 2 dots in the upstream direction of the recording paper conveyance direction. The flying direction is deflected and droplets are ejected.

  Here, as for the flying direction of the ink droplet, “upstream side in the recording paper conveyance direction” may be simply referred to as “positive direction”, and “downstream side” may be simply referred to as “negative direction”.

  According to FIG. 10, at time t1, droplet ejection for forming dots 110 whose flight direction is not deflected is performed. At the next ejection timing t2, dots 112 are formed at positions shifted by 2 dots in the forward direction. Further, at timing t3, a dot 114 is formed at a position shifted by one dot in the negative direction, at timing t4, a dot 116 is formed at a position shifted by one dot in the positive direction, and at timing t5, two dots are formed in the negative direction. A dot 118 is formed at the dot position shifted by the minute. At timing t6, a dot 120 with a shift amount of zero is formed as in timing t1.

In the example shown in FIG. 10, five types of integers of 0, ± 1, and ± 2 are applied as the shift amount I in the sub-scanning direction. However, the shift amount I in the sub-scanning direction includes three or more types of integers. Just do it. Note that, as in the case of applying the two integers in the sub-scanning direction of the shift amount I is the distance between the dots formed by droplets that are droplet continuously becomes over two dots or more ejected Control is performed.

  When ink droplet ejection is controlled in this way, ink droplets that form adjacent dots are first ejected at timing t3. That is, at timing t3, which is two cycles after the ejection cycle of timing t1, ink that forms the dots 114 adjacent to the dots 110 formed by the ink deposited at timing t1 is ejected. Further, the penetration or fixing of the ink droplets of the dots 110 proceeds, and landing interference does not occur even when the ink droplets forming the dots 114 are ejected.

  Similarly, at timing t4, ink droplets that form dots 116 adjacent to the dots 112 formed by the ink droplets ejected at timing t2 are ejected, but ink droplets that form dots 112 in two cycles. The penetration or fixing of the ink advances, and landing interference does not occur even when ink droplets that form adjacent dots 116 in the sub-scanning direction at timing t4 are applied.

  In this way, even if single pass printing is performed while maintaining a constant droplet ejection cycle and a constant transport speed without changing the relative relationship between the print head 50 and the recording paper 16, landing interference does not occur and predetermined printing is performed. Speed can be secured. When the droplet ejection control such as the droplet ejection cycle (ejection cycle) and the conveyance speed of the recording paper 16 changes, the deflection condition in the droplet flight direction is changed accordingly.

  FIG. 11 shows a flight deflection control pattern. In FIG. 11, the vertical axis indicates the shift amount I in the sub-scanning direction, and the horizontal axis indicates the transport amount in the sub-scanning direction (unit: μm). In the flying deflection control pattern shown in FIG. 11, the ink jet recording apparatus 10 indicates that droplet ejection is performed with a predetermined shift amount at each droplet ejection timing every 1 μm in the sub-scanning direction. A desired image is formed on the recording paper 16 while repeating such a flight deflection control pattern. Here, Ptm = Pts = Pt = 1 μm is described for convenience. However, when the resolution is 1200 dpi, Pt≈10 μm.

  Here, as a method of deflecting the flying direction of the ink droplet in the sub-scanning direction, as described in Japanese Patent Application Laid-Open No. 2000-177115, the ink is charged (charged ink may be used). A method of deflecting the flying direction of the ink droplet by applying an electric field to the space may be used, or the bubble generating heater described in Patent Document 4 (Japanese Patent Laid-Open No. 2000-185403) is used in the sub-scanning direction with respect to one nozzle. A method of deflecting the ink flying direction by selectively turning on and off these heaters may be used. Of course, a method other than the above may be applied to the method of deflecting the flying direction of the ink.

  Next, a modified example of the droplet ejection control described with reference to FIG.

  FIG. 12 shows a modified example of the droplet ejection control shown in FIG. 12, parts that are the same as or similar to those in FIG. 10 are given the same reference numerals, and descriptions thereof are omitted.

  In FIG. 12, −2 and 2 are applied to the integer I. In other words, when one type of integer is k, the relationship between the shift amount I in the sub-scanning direction and the integer k is expressed by the following equation [Equation 5].

[Equation 5]
I = ± k
However, k is a positive integer of 2 or more (that is, a natural number of 2 or more).

  In the modification shown in FIG. 12, a dot 110 'ejected at timing t1 is formed at a position shifted by two dots in the positive direction, and at timing t2, a dot is formed at a position shifted by two dots in the negative direction. 112 'is formed. Furthermore, dots 114 'and 116' are formed at positions shifted by two dots in the positive direction at timing t3 and by two dots in the negative direction at timing t4. After timing t5, ink droplets are formed so that dots 118 ', 120', 122 ', 124', 126 ', and 128' are alternately formed at positions shifted by two dots in the positive direction and two dots in the negative direction. The flight direction is controlled.

  In the modification shown in FIG. 12, droplet ejection for forming dots adjacent in the sub-scanning direction is performed for the first time at timing t4. That is, the ink that forms the dot 116 ′ adjacent to the dot 110 ′ formed by the ink droplet ejected at the timing t1 is ejected at the timing t4, and the ink droplet that forms the dot 110 ′ is 3 Since penetration or fixing proceeds during the cycle, landing interference does not occur even when an ink droplet forming the dot 116 'is ejected at timing t4.

  In the example shown in FIG. 12, ink droplets that form adjacent dots are ejected after a period of three cycles, so there is a margin of one cycle compared to the example shown in FIG. The interval can be shortened.

  FIG. 13 shows a flight deflection control pattern for dot formation shown in FIG. A desired image is formed on the recording paper 16 while repeating the flight deflection control pattern shown in FIG.

  10 and 12 are not shown so that adjacent dots overlap to describe numbers and subscripts in the dots, but actually formed dots are adjacent to each other as shown in FIGS. They overlap each other.

  FIG. 14 shows an example in which dots having different dot diameters are continuously formed in the sub-scanning direction. The dot diameter of the dot 200 is D1, the dot diameter of the dot 202 is D2, and the dot diameter of the dot 204 is D3. In order to form such a dot, the dot 204 is continuously formed after the droplets forming the dot 200 are formed. When droplet formation is performed, the condition that the dot 200 and the dot 204 do not overlap is as shown in the following equation [Formula 6].

[Equation 6]
D1 + D3 <2 x Pts
The dot diameters D1 and D3 and the dot pitch Pts in the sub-scanning direction may be set so as to satisfy the above [Equation 5].

  That is, if the condition that every other dot does not overlap is ensured, even if the dots 200 and 204 are successively ejected, there is no overlapping portion of both dots, so in the case of FIG. Can be continuously ejected.

  In this example, the droplet ejection control for preventing landing interference in the sub-scanning direction has been described. However, as shown in FIGS. 8 and 9, the adjacent dots in the main scanning direction are formed so as to overlap with each other. It is preferable to control droplet ejection so that ink droplets that form adjacent dots do not land on the recording paper 16 at the same time.

  As shown in FIG. 5, in the print head 50 having the nozzle rows arranged in a matrix, the nozzles that form dots adjacent in the main scanning direction include, for example, nozzles 51-11 and 51-12.

  The nozzles 51-11 and 51-12 are arranged at a distance d × sin θ apart from each other in the sub-scanning direction. The ink droplets ejected from the nozzle 51-11 and the ink droplets ejected from the 51-12 are Since the discharge timing is deviated, a difference occurs in the landing time.

  That is, in order to prevent ink droplets that form adjacent dots in the main scanning direction from landing simultaneously, the nozzles that eject ink droplets that form adjacent dots in the main scanning direction are shifted by a predetermined distance in the sub-scanning direction. A difference is provided in the landing time of ink droplets that are arranged and form dots adjacent in the main scanning direction.

  The difference in landing time is obtained from the conveyance speed of the recording paper 16, the flying speed of the ink droplets, the distance (shift amount) between the nozzles, the ink penetration time or the fixing time determined from the type of the recording paper 16 and the type of ink. That is, by controlling the conveyance speed of the recording paper 16 in accordance with the ink penetration time, a preferable difference in landing time of ink droplets forming dots adjacent in the main scanning direction is realized. For each type of recording paper 16 and ink type, the permeation time, the transport speed of the recording paper 16, and the flying speed of ink droplets are converted into a data table and stored in a memory means (for example, an MPU such as the image memory 74 or system controller in FIG. 7). It may be recorded in a built-in memory or the like.

  FIG. 15 shows dots formed on the recording paper 16 under the condition that dots adjacent in the main scanning direction and sub-scanning direction shown in FIG. 8 overlap and dots adjacent in the oblique direction do not overlap. FIG. 16 shows dots formed on the recording paper 16 under the condition that dots that are adjacent to each other in the main scanning direction, the sub-scanning direction, and the oblique direction shown in FIG. 9 are formed (arranged). .

  15 and 16, the same or similar parts as those in FIGS. 10 and 12 are denoted by the same reference numerals, and the description thereof is omitted.

  In FIG. 15, the vertical direction series represents the sub-scanning direction, and the horizontal direction series represents the main scanning direction. In the sub-scanning direction, the upper side in FIG. 15 indicates the upstream side, and the lower side indicates the downstream side.

  In the dot row shown in FIG. 15, the droplet ejection control shown in FIG. 10 is applied in the sub-scanning direction. On the other hand, the nozzles that form dots adjacent in the main scanning direction are arranged so as to be shifted in the sub-scanning direction by the dot pitch Pts in the sub-scanning direction. Dropping is performed with a delay. In FIG. 15, the dots 300, 302, and 304 are not adjacent to each other in the main scanning direction, but actually these dots are formed to be adjacent to each other in the main scanning direction.

  In FIG. 15, dots having the same number shown in the dots are adjacent to each other in the main scanning direction.

  In FIG. 16, the nozzles that form dots adjacent in the main scanning direction are arranged in the sub scanning direction so as to be shifted by twice the dot pitch in the sub scanning direction (2 × Pts).

  In the present embodiment, the mode in which the landing positions of the ink droplets are alternately shifted in the positive direction and the negative direction is illustrated, but a mode in which the positive direction and the negative direction are switched every several cycles may be applied.

(Print speed)
Next, the relationship between the printing speed and the droplet ejection control according to the present invention will be described.

  FIG. 16 shows dot rows formed when 35 postcard-sized recording papers 16 are printed per minute.

  In the example shown in FIG. 16, the conveyance speed of the recording paper 16 is 1.67 mm / sec. When the dot density is 600 dpi, the dot pitch Pt is 42.2 μm, and the droplet ejection cycle is 25.3 msec.

  If the penetration time of the medium (recording paper 16) to be used can be applied to the above-described general ink penetration time of 20 msec, even if the droplet ejection control according to the present invention is not applied, landing is possible even at this conveyance speed of 1.67 mm / sec. Printing is possible without interference.

  However, if the conveying speed is increased to approximately 10 mm / sec (approximately 6 times the above example) in order to increase the production capacity, the droplet ejection cycle is approximately 4.2 msec. Therefore, the droplet ejection control according to the present invention is performed. If not applied, ink penetration will not be in time, landing interference will occur, and the dot shape will collapse, making it impossible to form a desired image.

  Therefore, by applying the droplet ejection control according to the present invention, as shown in FIG. 17, the flying deflection is shifted from the dots formed immediately below the nozzles to the four adjacent dot positions, and the upstream side in the recording paper transport direction and When the flying deflection is alternately performed on the downstream side, the landing time difference between the ink droplets forming the adjacent dots is approximately 25.3 msec for seven cycles, and the infiltration time is longer than 20 msec, so that landing interference can be prevented.

  FIG. 17 shows dots formed by applying ± 4 to the shift amount (deflection shift amount) I in the sub-scanning direction. In FIG. 17, as in FIGS. 10 and 12, the horizontal series indicates time, and the latest series indicates the sub-scanning direction (downstream on the upstream side and upward on the downstream side). Further, the numbers described in the dots represent the droplet ejection timing.

  According to FIG. 17, at time t9, ink droplets are ejected to form dots 402 that are adjacent to the dots 400 formed by the ink ejected at timing t2, in the sub-scanning direction. Therefore, there is a difference in landing time for 7 cycles (approximately 25.3 msec), which is longer than a typical ink penetration time of 20 msec, so that the dot 402 is ejected after the ink droplet forming the dot 400 has penetrated. Will be.

  Further, in droplet ejection after timing t11, ink droplets that form adjacent dots other than the dots 400 and 402 are landed, but in any case, there is a landing time difference of 7 cycles or more. Therefore, landing interference does not occur and a desired image can be obtained.

  In general, the time T until the adjacent dots land is expressed by the following equation [Formula 7] using the shift amount I (± k) in the sub-scanning direction and the droplet ejection period Tf.

[Equation 7]
T = Tf × (2k−1)
The k shown in [Equation 7] may be set so that the time T becomes larger than the permeation time To (that is, T ≧ To).

  In other words, the shift amount I in the sub-scanning direction may be set so as to satisfy the above [Equation 7]. This is shown in the following equation [Equation 8].

[Equation 8]
k ≧ {(To / Tf) +1} / 2
This is an equation obtained by modifying the following equation [Equation 9] with respect to I.

[Equation 9]
Tf × (2k−1) ≧ To
[Flight deflection]
Next, the flight deflection amount (flying angle) will be described.

  As shown in FIGS. 3 and 4, the inkjet recording apparatus 10 includes a flying direction deflecting unit that deflects the flying direction of the ink.

  As shown in FIG. 4B, the distance z (clearance) between the nozzle forming surface of the print head 50 and the recording paper 16 is approximately 2 mm. From the shift amount y in the sub-scanning direction and the clearance z between the print head 50 and the recording paper 16, the flying deflection angle θ of the ink droplet can be obtained by the following equation [Equation 10].

[Equation 10]
θ = arctan (y / z)
However, [Equation 10] is an equation obtained by transforming [Equation 1] with respect to θ.

  That is, when the dot density is 600 dpi, the dot pitch is 42.2 μm, and when the shift amount in the sub-scanning direction shown in FIG. 17 is 4 dots, the shift amount y in the sub-scanning direction is 0.08, and the flying The deflection angle θ is 4.82 ° (deg).

  If the shift amount in the sub-scanning direction is 11 dots, the flight deflection angle θ is 13.1 °.

  In the ink jet recording apparatus 10 configured as described above, when forming a dot row along the sub-scanning direction so that at least dots adjacent in the sub-scanning direction overlap, The flying direction of at least one of the ink droplets caused by the following ink droplets and the ink droplets caused by the subsequent ink droplets is deflected along the sub-scanning direction. Does not occur.

  The deflection amount when deflecting the ink droplet flying direction in the sub-scanning direction is set to an integral multiple (I times) of the dot pitch in the sub-scanning direction. The deflection direction may include a positive direction and a negative direction. Further, in order to simplify the droplet ejection control sequence, the deflection amount may be ± k times the dot pitch in the sub-scanning direction (k is a natural number of 2 or more, ie, I = ± k).

  The time at which adjacent dots land is expressed by Tf × (2k−1) from the shift amount I in the sub-scanning direction and the droplet ejection period Tf in the sub-scanning direction. Assuming that the ink permeation time is To, since I is configured to satisfy Tf × (2k−1) ≧ To, various parameters such as the dot density, the conveyance speed of the recording paper 16, and the ink permeation time are set. It is possible to set a flight direction deflection pattern that can prevent landing interference with respect to conditions.

  When dots that overlap in the main scanning direction as well as in the sub-scanning direction are formed using a matrix head in which nozzles are two-dimensionally arranged, ink droplets that form dots adjacent in the main scanning direction are ejected. If the nozzles to be moved are arranged so as to be shifted by a predetermined distance in the sub-scanning direction, it is possible to provide a difference in the landing time of ink droplets that form adjacent dots in the main scanning direction, which is suitable for high-density droplet ejection. In addition, the array pattern of the two-dimensional array nozzle can be used effectively.

  In the present embodiment, a full-line type print head provided with a nozzle row having a length corresponding to the recording width of the recording paper is exemplified, but the scope of the present invention is not limited to the above-described full-line type print head. The present invention can also be applied to a shuttle type print head having a nozzle row having a length shorter than the recording width of the recording paper and reciprocating in the width direction of the recording paper. In particular, the one-pass shuttle type (single-pass shuttle type) that completes the formation of the image of the area scanned by the print head in one shuttle scan is particularly effective.

  On the other hand, the effect of the present invention can also be obtained by a system in which the intermittent feed amount of the recording paper is made smaller than the print length of the print head in the sub-scanning direction and the same image area is printed by a plurality of scans.

  A method for printing on the recording paper 16 using the single pass shuttle method will be described with reference to FIG.

  FIG. 18 shows a print area of the recording paper 16 printed using the shuttle type print head. As shown in FIG. 18, the shuttle scanning width (scanning width in the main scanning direction) of the print head is set larger than the printable width in the main scanning direction.

  In the first shuttle scan, the print area 501 is printed. The length of the print area 501 in the sub-scanning direction is substantially the same as the print effective length of the print head.

  In the second shuttle scan, the print area 502 is printed, and then the print area 503 is printed. When the print head is scanned once in the main scanning direction in this way, the print head and the recording paper 16 are relatively moved in the sub-scanning direction, and printing is sequentially performed.

  When the print area 504 is printed in the (i-1) th shuttle scan, and the print area 505 is printed in the i-th shuttle scan, printing is performed on the entire surface of the recording paper 16, and the recording paper 16 has a desired printout. An image is formed.

  In one main scanning movement, the print head may be moved in one direction to perform printing in the main scanning direction of the printing area, or the printing head may be moved back and forth to move the main area of the printing area. Printing in the scanning direction may be performed.

  That is, when printing the print area 501, the print head is moved in one of the main scanning directions (for example, from the left to the right in FIG. 18), and when printing the printing area 502, the main scanning direction. It may be controlled to move in the other direction (for example, the direction from right to left in FIG. 18).

  The shuttle type print head is provided with a main scanning direction moving means for relatively moving the head and the recording paper 16 in the main scanning direction. The main scanning direction moving means may move the print head relative to the fixed recording paper 16, or may move the recording paper 16 relative to the fixed print head. Further, both the print head and the recording paper 16 may be moved.

  Further, control is performed so that the print areas do not overlap at the boundary between adjacent print areas (for example, print area 501 and print area 502).

  In this embodiment, an inkjet head used in an inkjet recording apparatus is exemplified as a droplet ejection head. However, the present invention is not limited to liquids (water, chemicals) on an ejection medium such as a wafer, a glass substrate, or an epoxy substrate. In addition, the present invention can be applied to a discharge head used in a liquid discharge apparatus that discharges a resist, a processing liquid) to form a three-dimensional shape such as an image, circuit wiring, or a processing pattern.

1 is a basic configuration diagram of an ink jet recording apparatus according to an embodiment of the present invention. FIG. 1 is a plan view of the main part around the printing of the ink jet recording apparatus shown in FIG. Plane perspective view showing structural example of print head Sectional drawing which shows the three-dimensional structure of the print head shown in FIG. Enlarged view showing the nozzle arrangement of the print head shown in FIG. Schematic diagram showing the configuration of the ink supply unit in the inkjet recording apparatus according to the present embodiment Main part block diagram which shows the system configuration | structure of the inkjet recording device which concerns on this embodiment. The figure explaining the dot formed with the inkjet recording device which concerns on this embodiment The figure explaining the other aspect of the dot shown in FIG. The figure explaining the droplet ejection control of the inkjet recording device which concerns on this embodiment The figure which shows the pattern of the flight direction deflection | deviation control in the droplet ejection control shown in FIG. The figure which shows the other aspect of droplet ejection control shown in FIG. The figure which shows the pattern of the flight direction deflection | deviation control in the droplet ejection control shown in FIG. The figure explaining the relationship between the dot pitch and the dot diameter in the droplet ejection control of the ink jet recording apparatus according to the embodiment of the present invention. The figure explaining the droplet ejection control of the main scanning direction of the inkjet recording device which concerns on this embodiment. The figure explaining the other aspect of droplet ejection control of the main scanning direction shown in FIG. The figure which shows the dot formed by applying the droplet ejection control of the inkjet recording device which concerns on this embodiment Diagram explaining single-pass printing of shuttle head

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording device, 16 ... Recording paper, 22 ... Adsorption belt conveyance part, 50 ... Print head, 72 ... System controller, 80 ... Print control part, 100, 102, 104, 106, 110, 112, 114, 116, 118, 120, 200, 202, 204, 300, 302, 304, 400, 402 ... dots

Claims (7)

An ejection head having an ejection hole for ejecting droplets onto an ejection medium;
Conveying means for relatively moving at least one of the ejection head or the ejection target medium in one direction;
A flying direction deflecting means for deflecting a flying direction of a droplet ejected from the ejection head in a direction parallel to a relative transport direction when the ejected medium is ejected;
A dot in which droplets are ejected at a constant droplet ejection period during relative conveyance of the ejection medium to the ejection head at a constant conveyance speed, and at least a part of dots adjacent in the relative conveyance direction overlap. When forming the row, the flight direction deflecting means is controlled,
The inter-dot pitch Pts of the dot rows in the relative transport direction of the ejected medium, and the center-to-center distance Δy in the relative transport direction of the ejected medium at the landing positions of droplets successively ejected from the ejection holes are Δy ≧ The relationship between the shift amount I consisting of two or more arbitrary integers satisfying 2 × Pts and the droplet landing position change amount y in the relative transport direction of the ejection target medium is expressed by the following equation: y = Pts × I
And the shift amount I is given by
I = ± k
By changing the droplet landing position by the droplet landing position change amount y alternately in the positive direction and the negative direction so as to include one or more types of natural numbers k satisfying two or more, the adjacent in the relative transport direction of the recording medium Deflection control means for landing droplets while avoiding continuous landing of dots,
A liquid ejection apparatus comprising: An ejection head having an ejection hole for ejecting droplets onto an ejection medium;
Conveying means for relatively moving at least one of the ejection head or the ejection target medium in one direction;
A flying direction deflecting means for deflecting a flying direction of a droplet ejected from the ejection head in a direction parallel to a relative transport direction when the ejected medium is ejected;
A dot in which droplets are ejected at a constant droplet ejection period during relative conveyance of the ejection medium to the ejection head at a constant conveyance speed, and at least a part of dots adjacent in the relative conveyance direction overlap. When forming the row, the flight direction deflecting means is controlled,
The inter-dot pitch Pts of the dot rows in the relative transport direction of the ejected medium, and the center-to-center distance Δy in the relative transport direction of the ejected medium at the landing positions of droplets successively ejected from the ejection holes are Δy ≧ The relationship between the shift amount I composed of two or more arbitrary integers satisfying 2 × Pts and the droplet landing position change amount y in the relative transport direction of the medium to be ejected is expressed by the following equation:
y = Pts × I
In addition, by changing the droplet landing position by the droplet landing position change amount y so that the shift amount I includes an integer of 5 or more, the adjacent dots in the relative transport direction of the recording medium are consecutive. Deflection control means for landing droplets while avoiding landing, and
Liquid discharge device you comprising the. In the flight direction control means, the droplet ejection period Tf of the ejection head and the penetration time T0 of the droplet into the ejection medium are expressed by the following equation: Tf × (2k−1) ≧ T0
Liquid discharge apparatus according to claim 1, characterized in that it comprises a shift amount setting means for the setting the natural number k satisfying. Among the dot rows formed along the relative transport direction of the discharged medium, the diameters D1 and D2 of two dots sharing the adjacent dots in the relative transport direction of the discharged medium, the relative transport of the discharged medium The inter-dot pitch Pts is expressed by the following formula: D1 + D2 ≦ 2 × Pts
Claim 1, characterized in that it comprises a droplet ejection control means for setting at least one of the dot pitch Pts in the dot diameter D1, the diameter D2 or the dot ejection receiving medium relative conveyance direction so as to satisfy, 2. The liquid ejection device according to 2 or 3 . The discharge head, a liquid ejecting apparatus according to any one of claims 1 to 4, characterized in that it comprises the full line type ejection head having a plurality of discharge holes over the entire width of the ejection receiving medium are arranged . The ejection head includes a matrix head in which the ejection holes are two-dimensionally arranged,
The ejection holes for ejecting droplets that form adjacent dots in a direction substantially orthogonal to the relative conveyance direction of the ejection target medium are arranged by being shifted by a predetermined distance in the relative conveyance direction of the ejection target medium. The liquid discharge apparatus according to claim 5 . An ejection head having ejection holes for ejecting droplets onto the ejection medium; and at least one of the ejection head or the ejection medium is conveyed in a direction substantially perpendicular to the width direction of the ejection medium, and A transport unit that relatively moves the ejection head and the medium to be ejected in one direction, and a flying direction deflecting unit that deflects the flying direction of droplets ejected from the ejection head. A droplet ejection control method for a liquid ejection device,
A dot in which droplets are ejected at a constant droplet ejection period during relative conveyance of the ejection medium to the ejection head at a constant conveyance speed, and at least a part of dots adjacent in the relative conveyance direction overlap. When forming the rows, the droplet flying direction deflecting means is used to make the flying direction of the droplets ejected from the ejection holes of the ejection head parallel to at least the relative transport direction when ejecting the ejected medium. Direction, the center P in the relative conveyance direction of the medium to be ejected, the inter-dot pitch Pts of the dot rows in the relative conveyance direction of the medium to be ejected, and the landing position of droplets successively ejected from the ejection holes The relationship between the shift amount I consisting of two or more arbitrary integers satisfying Δy ≧ 2 × Pts between the distances Δy and the droplet landing position change amount y in the relative transport direction of the discharged medium is expressed by the following equation: y = Pts × I
And the shift amount I is given by
I = ± k
By changing the droplet landing position by the droplet landing position change amount y alternately in the positive direction and the negative direction so as to include one or more types of natural numbers k satisfying two or more, the adjacent in the relative transport direction of the recording medium A droplet ejection control method characterized by causing droplets to land while avoiding continuous landing of dots.

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