JP2005313635A - Droplet hitting control method and liquid discharge apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a droplet hitting control method which realizes both a high image quality and a high speed by conducting droplet hitting control with placement interferences of liquid droplets taken into account, and to provide a liquid discharge apparatus. <P>SOLUTION: In the case of forming a line image 140 by successively hitting ink droplets so that adjacent ink droplets overlap with each other by a short time interval in which the ink droplet hit next is placed before permeation completion of the earlier placed ink droplet, controlling is executed to increase a droplet hitting amount of the ink droplet which forms a dot 102 to be placed later. Even when the earlier placed ink droplet and the later placed ink droplet are united into one due to the placement interference, a dot formed by the earlier placed ink droplet and the dot formed by the later placed ink droplet become nearly the same size. The line image 140 of a uniform line width is formed accordingly. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a droplet ejection control method and a liquid ejection apparatus, and more particularly, to a droplet ejection control technique for forming a preferable shape such as an image or a line drawing in consideration of the influence of droplet mutual interference upon landing.

  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.

  Inkjet recording apparatuses are becoming increasingly demanded for high-speed printing and high-quality printing, and high-speed printing is realized by shortening the ink ejection cycle and conveying the recording medium at high speed.

  On the other hand, in order to print a high-quality image, the dots forming the image are miniaturized and the density is increased, thereby realizing high gradation expression and high resolution. For example, dot miniaturization is realized by ejecting a small amount of ink, and the density of dots is increased by forming nozzles for ejecting ink at high density. When the dots are densified, the formation regions overlap each other between dots formed at adjacent positions.

  In a dot row (dot group) formed so that a plurality of dots overlap each other, if the next droplet landed before completion of penetration of the previously landed ink droplet or before completion of curing of the ink droplet, it landed later The ink droplets are attracted to the ink droplets that have landed first, and landing interference in which dots of the original size are not formed at the original dot formation position may occur. Therefore, in order to suppress the mutual interference between the droplets at the time of landing (landing interference), droplet ejection control is performed such that the ink droplet that has landed next is ejected after the ink that has landed first penetrates. Done. However, it is difficult to realize high-speed printing in the droplet ejection control in which the next liquid lands after waiting for the permeation of the previously landed ink droplet.

  Here, the prior art will be described more specifically with reference to FIGS.

  FIGS. 13A and 13B are diagrams for explaining the discharge control according to the prior art.

  FIG. 13A shows a dot row 200 formed on a recording sheet using an ink jet recording apparatus. In the dot row 200, dots 202, 204, 206,... Having the same diameter D are arranged on the same line with the pitch P between the same dots.

  In FIG. 13A, the inter-dot pitch P is set smaller than the diameter D of each dot (ie, D> P), and the dot row 200 is formed so that adjacent dots overlap each other.

  On the other hand, in FIG. 13B, the ink droplets that have landed the ink droplets forming each dot of the dot row 200 shown in FIG. A line drawing 240 formed on the recording paper is shown in which ink droplets are ejected at a droplet ejection period (droplet ejection frequency). A reference numeral 202 ′ indicated by a one-dot broken line indicates a (theoretical) shape of the line drawing 240 to be originally formed. Further, the order of ink droplets forming the dot row 200 is the direction indicated by the arrow line K (the direction from left to right in FIG. 13A).

  Here, the dot generally indicates a substantially circular shape formed by fixing an ink droplet ejected onto a recording paper onto the recording paper, and represents a substantially circular shape formed after completion of the ink droplet permeation. In this specification, when the shape of the ink droplet collapses and a shape different from the substantially circular shape is formed, or when the shape of the plurality of substantially circular shapes overlaps due to a phenomenon in which the plurality of ink droplets are integrated, When formed, the shape formed at each droplet ejection point is also called a dot.

  Further, in this ink jet recording apparatus, ink droplets that are ejected at a certain droplet ejection point are ejected onto ink droplets that are adjacent in at least one of the front, rear, left, and right directions before completion of penetration into the recording paper. Has a drop frequency. For example, droplets are ejected so that the ink that forms the dots 204 adjacent to the dots 202 lands on the recording paper before the ink droplets that form the dots 202 complete penetration.

  As described above, before the ink droplet landed on the recording paper (for example, the ink droplet forming the dot 202) has completely penetrated, the dot (dot 204) adjacent to the dot (dot 202) formed by the ink droplet is changed. When the ink droplets to be formed are ejected, the ink droplets that have landed first and the ink droplets that landed later are connected to form an image together. This is a phenomenon caused by agglomeration in which ink droplets that have landed later are attracted to ink droplets that have landed first immediately after the start of droplet ejection when ink droplets are ejected continuously (the same amount).

  Originally, when ink droplets forming the dot row 200 are continuously ejected, a line drawing having a uniform line width (line width h = D) should be formed. However, due to the above-described aggregation, it is shown in FIG. Thus, immediately after writing, a line drawing 240 having a line width h = D ′ (ie, D ′> D) is formed.

  This is almost equivalent to the formation of the dot 202 ′ having the diameter D ′ by agglomeration at the droplet ejection point where the dot 202 having the diameter D is originally formed. In practice, the line width of the line drawing 240 is not uniform. Become.

  As a more specific example, in FIGS. 14 (a) to (d) and FIGS. 15 (a) to (c), a single droplet is formed by an ink droplet amount of 2 pl, and this ink droplet. In this case, the diameter D of each dot D = 30 μm, the pitch P between dots = 10 μm, and a line drawing 242 formed when two or more ink droplets are ejected under a droplet ejection condition where the droplet ejection cycle is 10% of the ink droplet permeation time. ~ 246.

  In FIGS. 14 (a) to (d) and FIGS. 15 (a) to (d), the same or similar parts as those in FIGS. 13 (a) and (b) are denoted by the same reference numerals. Omitted.

  FIG. 14A shows a case where one dot 202 is formed by ejecting only one ink droplet. When only one ink droplet is ejected, only one dot having a diameter of 30 μm is formed.

  FIG. 14 (b) shows a line drawing 242 formed when five ink droplets are continuously ejected under the above conditions. The traveling direction of the droplet ejection is the direction indicated by the arrow K from left to right in FIG.

  As shown in FIG. 14 (b), when a droplet is ejected so that the next ink droplet lands before completion of the penetration of the previously landed ink droplet, it is usually landed on the first landed ink droplet next. Ink drops are attracted.

  This is substantially the same as the amount of ink larger than the predetermined amount 2 pl landed on the landing position of the previous ink droplet and the amount of ink droplet smaller than the predetermined amount 2 pl landed on the landing position of the subsequent ink droplet. The shape formed by these ink droplets is different from the shape of two dots having the same dot diameter to be originally formed, and is originally formed at the landing position of the ink droplet that has landed first. Dots with a larger dot diameter are formed, and dots having a smaller dot diameter than the originally formed dots are formed at the landing positions of the ink droplets that have landed later. Are the same.

  Similarly, there is a phenomenon in which the third ink droplet is attracted to the ink droplet in which the first ink droplet and the second ink droplet are integrated, and the ink droplet that has landed later is attracted to the ink droplet landed first. It happens sequentially. Note that the ratio of ink droplets that have landed later to the ink droplet side that landed first (amount of ink change) decreases with the progress of droplet ejection.

  The final shape of the line drawing 242 after completion of ink penetration formed in this way is such that the width h1 (= 40 μm) on the first droplet side (the writing side, the left end in FIG. 14B) is the final droplet side (writing). The end side width hn (h5 = 20 .mu.m in FIG. 14B) becomes wider. The density on the writing side is higher than the density on the writing end side. This is because the second and subsequent droplets are attracted to the liquid on the writing side that landed first, so that the writing side (left side in FIG. 14 (b)) is on the writing end side (right side in FIG. 14 (b)). This is because the amount of droplet ejection liquid is increased.

  Note that the line width h1 at the writing side end is 40 μm, which is larger than the original line width 30 μm, and the line width h5 at the writing end side end is 20 μm, which is smaller than the original line width 30 μm. The line width of the line drawing 242 gradually decreases from the writing side toward the writing end side.

  FIG. 14 (c) shows a line drawing 244 formed when 10 ink droplets are continuously ejected under the above conditions, and FIG. 14 (d) shows 60 ink droplets continuously ejected under the above conditions. A line drawing 246 formed in the case is shown.

  As shown in FIG. 14 (c), in the line drawing 244 formed from 10 ink droplets, the width h1 on the writing side is 45 .mu.m and the width hn on the writing end side (h10 in FIG. 14 (c)) is 20 .mu.m. In addition, since the width of the line drawing 244 gradually changes, the gradient (the rate at which the width changes) is substantially constant.

  On the other hand, as shown in FIG. 14D, in the line drawing 246 formed from 60 ink droplets, the width h1 on the writing side is 50 μm and the width hn on the writing end side (h60 in FIG. 14D) is 15 μm. However, the gradient of the width of the line drawing 246 shown in FIG. 14D differs depending on the writing area 260, the intermediate area 262, and the writing end area 264.

  That is, in the writing area 260, the width of the line drawing 246 gradually decreases from h1 (50 .mu.m in FIG. 14 (d)) to hi (hi = 30 .mu.m in FIG. 14 (d)), and in the intermediate area 262, the line drawing 246. In the writing end region 264, the width of the line drawing 246 gradually decreases from hi to hn (h60 = 15 .mu.m in FIG. 14 (c)).

  15A to 15D show the three-dimensional shapes (cross-sectional shapes) of the inks forming the line drawings 242 244 and 246 shown in FIGS. 14B to 14D.

  As shown in FIGS. 15B and 15C, in the line drawings 242 and 244 formed from about 5 to 10 ink droplets, the height of the ink droplet gradually increases from the writing side toward the writing end side. To change.

  On the other hand, in the line drawing 246 shown in FIG. 15 (d), the ink drop height gradually changes from the writing side to the writing end side in the writing area 260 and the writing end area 264, while the ink drop height increases in the intermediate area 262. There is a tendency not to change.

  Therefore, as shown in FIGS. 14A to 14D and FIGS. 15A to 15D, the first ink droplet landed first before the completion of the penetration has landed first. When landing so as to overlap with ink droplets, a phenomenon occurs in which the width of the formed line image becomes non-uniform due to landing interference occurring on the recording paper, resulting in a reduction in image quality. This phenomenon is difficult to be visually recognized as a difference in thickness, but is easily recognized as a difference in density. In particular, when a plurality of line drawings are formed side by side, the phenomenon is easily observed.

  The numerical values shown in FIGS. 13 and 14 are merely examples, and differ depending on the type of ink, the type of recording paper (recording medium), and a combination thereof.

In the recording method and apparatus described in Patent Document 1, in order to prevent mutual interference between adjacent dots, original recording data and interpolation data are output during separate head scans to perform the recording. Thus, ink bleeding and ink mixing can be prevented.
JP-A-9-272226

  However, in the control in which the next ink lands after the permeation of the previously landed ink droplet, the droplet ejection cycle cannot be shortened. In addition, since the ink penetration time (penetration speed) varies depending on the combination of the ink and the recording medium, it is necessary to control the droplet ejection period to change according to the type of ink used and the type of recording medium. The control burden on the device increases.

  In the recording method and apparatus described in Patent Document 1, when dots are formed at high density, it is necessary to separately scan original recording data and scan correction data, and a reduction in productivity is inevitable. It was difficult to achieve both high image quality and high speed.

  The present invention has been made in view of such circumstances, and provides a droplet ejection control method and a liquid ejection device that achieve both high image quality and high speed by performing droplet ejection control in consideration of droplet landing interference. The purpose is to do.

  In order to achieve the above object, the invention according to claim 1 is a droplet ejection control method for a liquid ejection apparatus that ejects droplets from a ejection head onto a medium to be ejected, and the adjacent ejection on the surface of the medium to be ejected. When droplets are continuously ejected from the ejection head so that at least some of the droplets ejected at the droplet point overlap, at least a part of the plurality of droplets ejected continuously Control for changing the droplet ejection volume so that the volume of the droplet ejection liquid sequentially becomes relatively large, and the flight speed of at least some of the plurality of droplets that are continuously ejected It is characterized in that at least one of the controls for changing the flying speed of the droplets so as to become relatively large sequentially is executed.

  That is, when droplets are continuously ejected so that the droplets ejected at adjacent droplet ejection points on the ejection target medium overlap, at least some of the droplets that are continuously ejected , At least one of the control for changing the droplet ejection volume so that the volume of the droplet ejection liquid sequentially increases and the control for changing the flight speed of the droplets so that the flight speed becomes relatively faster Therefore, it is possible to eliminate the case where the droplets ejected at the adjacent droplet ejection points on the ejection target medium interfere with each other and the dot diameter after the droplet fixing becomes nonuniform. . In addition, the dot after fixing includes a shape different from the original substantially circular shape formed at each droplet ejection point (dot formation point on the image data), or a shape formed by integrating a plurality of droplets. The shape corresponding to the originally formed dots formed at each droplet ejection point may be included.

  Adjacent droplet ejection points may be droplet ejection points adjacent to each other in the width direction of the medium to be ejected and droplet ejection points adjacent to each other in a direction substantially perpendicular to the width direction of the medium to be ejected. It may be a droplet ejection point adjacent in an oblique direction having a component in a direction substantially perpendicular to the width direction of the medium.

  The continuous droplet ejection may include a mode in which a plurality of droplets are ejected at a droplet ejection cycle such that the next droplet lands before completion of penetration of the previously landed droplet, A mode in which a plurality of droplets are ejected at a droplet ejection period set based on the ratio of the droplet permeation time (for example, a time until 10% of the appropriate amount of all ejected liquids permeates) may be included.

  In an aspect in which the droplet ejection volume is relatively increased sequentially, the droplet ejection volume may be increased continuously, or the droplet ejection volume may be increased in stages every few drops. .

  By increasing the amount of droplets to be ejected and increasing the flying speed of the droplets, it is possible to increase the area where the droplets cover the discharged medium when the discharged medium lands.

  For the ejection head, a full line type ejection head in which ejection holes for ejecting droplets are arranged over a length corresponding to the entire width of the medium to be ejected, and a nozzle row corresponding to each color of KMCY corresponds to the entire width of the medium to be ejected. Serial type discharge that discharges liquid droplets while scanning the head in the width direction of the medium to be discharged, with the head width in the direction between the nozzle rows arranged in a direction orthogonal to the direction of the recording medium shorter than the length corresponding to the entire width of the recording medium There is a head (shuttle scan type discharge head).

  In addition, in a full-line type ejection head, short heads having short ejection hole arrays that are less than the length corresponding to the full width of the medium to be ejected are arranged in a staggered manner and connected to form the full width of the medium to be ejected. It may be a corresponding length.

  Examples of the medium to be ejected include various media, such as continuous paper, cut paper, seal paper, and the like, resin sheets such as papers and OHP sheets, film, cloth, metal, and other materials. The ejection medium includes a medium called a recording medium, a recording medium, a recording medium, a liquid receiving medium, and an image forming medium.

  In order to achieve the above object, the invention according to claim 2 is a liquid ejection apparatus including an ejection head for ejecting liquid droplets onto a medium to be ejected, and adjacent droplet ejection on the surface of the medium to be ejected. In the case where droplets are continuously ejected from the discharge head so that at least some of the droplets ejected at a point overlap, at least a part of the plurality of droplets ejected continuously Control for changing the droplet ejection volume so that the volume of droplet ejection is sequentially relatively increased, and the flight speeds of at least some of the plurality of droplets that are continuously ejected are sequentially Control means for executing at least one of the controls for changing the flying speed of the droplet so as to be relatively large is provided.

  At least one of a droplet ejection volume changing means for changing the droplet ejection volume and a flying speed changing means for changing the flying speed of the droplet is provided.

  It is provided with a recording means for recording in advance a data table of the droplet ejection volume and droplet flying speed in each droplet when performing continuous droplet ejection, and from the data table when continuous droplet ejection is performed You may comprise so that the amount of droplet ejection liquid and the flying speed of a droplet may be read.

  As shown in claim 3, in the invention described in claim 2, in the writing unit having a predetermined number of droplets from the first droplet among the plurality of droplets continuously ejected, At least one of the control for changing the droplet ejection volume so that the volume of the droplet ejection is sequentially increased and the control for changing the flight speed of the droplet so that the flight speed of the droplet is sequentially increased relatively In addition to executing the control, the droplet ejection volume and the flight speed are controlled so that the droplet ejection volume after the writing section and the droplet ejection volume are the same and the same flight speed are obtained by the continuous droplet ejection. It is characterized in that the diameter of a line drawing drawn by a group of dots is made uniform.

  That is, in consideration of the behavior of landing interference (aggregation) that occurs when the droplets land on the medium to be ejected so that the droplets overlap each other, a predetermined number of droplets from the first droplet are continuously ejected. In the interim writing unit, at least one of the control to sequentially increase the droplet ejection volume and the control to sequentially increase the flying speed is executed. On the other hand, in the droplet ejection after the writing unit, the same droplet ejection volume and the same amount are performed. By performing droplet ejection control so as to achieve the flying speed, it is possible to obtain a line drawing having a uniform width over the entire length.

  At the end of writing from the final droplet ejection to a predetermined number of droplet ejection, at least one of the control for sequentially increasing the droplet ejection volume and the control for sequentially increasing the flying speed may be executed.

  According to a fourth aspect of the present invention, the invention described in the third aspect is characterized in that the writing unit includes from the first droplet ejection to the tenth droplet ejection.

  This droplet ejection control is particularly effective in the writing area. In addition, it is preferable to apply this droplet ejection control between the last droplet ejection and before 10 droplet ejections.

  Further, according to a fifth aspect of the present invention, in the invention described in the second, third, or fourth aspect, the control unit is configured to cause the remaining droplet amount of the droplet to be previously ejected to land on the ejection target medium. It is characterized in that droplet ejection control is performed in which droplets that are subsequently ejected are landed on the recording medium at a timing that is 0.9 or more of the ratio to the time droplet amount.

  A mode in which the next droplet is ejected at a timing at which the remaining droplet amount of the previously ejected liquid on the medium to be ejected is substantially the same as the droplet amount upon landing is preferable.

  Further, according to a sixth aspect of the present invention, in the invention described in any one of the second to fifth aspects, the control unit may first drop a droplet ejection amount of a droplet to be ejected later. At least one of the ratio of making the droplet relatively larger than the formed droplet and the proportion of making the flying speed of the droplet to be ejected later relatively larger than that of the previously ejected droplet, The amount of overlap between the droplets to be ejected and the droplets to be ejected later on the ejection medium, and the surface tension acting between the droplets that are ejected earlier and the droplets that are ejected later It is characterized by changing according to at least one of them.

  That is, the larger the surface tension with which the two liquids in contact with each other are pulled, the larger the amount of droplets that will be ejected later, and the higher the flying speed of the droplets that are subsequently ejected. By controlling either one of them, the dot diameter of dots formed after fixing can be more reliably realized.

  According to a seventh aspect of the present invention, in the invention described in any one of the second to sixth aspects, the control means may reduce the amount of the first droplet ejection liquid from the original droplet ejection volume. It is characterized by performing less control.

  In other words, the droplet that was first ejected interferes with the droplet that was ejected next, and the amount of liquid increased from the amount that was actually ejected. A dot larger than the originally formed dot is formed in. Accordingly, in anticipation of this, since the initial droplet ejection volume is reduced in advance, dots of the size originally formed are formed at the landing positions by the first droplet ejection.

  During the period from the first droplet ejection to a predetermined number of droplet ejection, the actual droplet ejection amount may be smaller than the original droplet ejection amount.

  According to the present invention, when continuous droplet ejection is performed so that the droplets that have landed on the medium to be ejected overlap, the droplet ejected after the droplet ejection amount of the droplet ejected first At least one of the control to increase the amount of liquid droplets ejected and the control to increase the flight speed of droplets ejected after the droplets ejected earlier. By doing so, non-uniformity of the dot diameter after fixing can be eliminated.

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

[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 printed recording paper (printed matter) 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 greater 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 a mode 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 print area, the image easily spreads because the roller contacts the printing surface of the sheet immediately after printing. There is a problem. 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 paper conveyance path formed by the suction belt conveyance unit 22. The heating fan 40 heats the recording paper 16 by blowing heated air onto the recording paper 16 before printing. 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 paper feed 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 head. The ejection determination includes the presence / absence of ejection, measurement of dot size, measurement of dot landing position, and the like. Details of discharge detection will be described later.

  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 substances 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.

  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, and FIG. 4 is a cross-sectional view showing the three-dimensional configuration of the ink chamber unit (along line 4-4 in FIG. 3A). 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 inks including nozzles 51 from which ink droplets are ejected and pressure chambers 52 corresponding to the nozzles 51. The chamber units 53 have a structure in which the chamber units 53 are arranged in a staggered matrix, thereby achieving an increase in the apparent nozzle pitch density.

  That is, in the print head 50 according to the present embodiment, as shown in FIGS. 3A and 3B, the plurality of nozzles 51 that eject ink correspond to the entire width of the print medium in a direction substantially orthogonal to the print medium feed direction. This is a full line head having one or more nozzle rows arranged over a length of the same.

  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.

  As shown in FIG. 5, a large number of ink chamber units 53 having such a structure are arranged in 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 lattice 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 nozzles are divided into blocks, and each block is sequentially driven from one side to the other. A line or a plurality of rows of dots in the width direction of the paper (direction perpendicular to the paper conveyance direction) The driving of the nozzle that prints a line composed of dots 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, the sub-scan is defined as the above-described full-line head and the paper are moved relative to each other to repeatedly print a line composed of one row of dots or a plurality of rows of dots formed by the above-described main scan. To do.

  In this embodiment, the full-line type print head is exemplified, but the scope of application of the present invention is not limited to this, and the shuttle type that forms one line in the main scanning direction while scanning the print head in the main scanning direction. A print head may be applied.

  Furthermore, the nozzle arrangement structure is not limited to the illustrated example in the implementation of the present invention. A print head having one nozzle row in the main scanning direction may be applied.

  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 ink remaining amount 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. As the communication interface 70, a serial interface such as USB, IEEE 1394, Ethernet, and wireless network, or a parallel interface such as Centronics can be applied. 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 of the ink droplets of the print head 50 and the flying speed of the ink droplets 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 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.

  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 instructions 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.

[First Embodiment]
Next, the droplet ejection control of the inkjet recording apparatus 10 according to the first embodiment of the present invention will be described in detail.

  In the ink jet recording apparatus 10, ink droplets are continuously ejected at short time intervals (for example, when a subsequent ink droplet lands within the time when 10% of the ink droplets landed first penetrate the recording paper 16). When a line image is formed by using ink droplets, droplet ejection control is performed so that the line width h is substantially uniform over the entire length of the line image even if landing interference (aggregation) described in the prior art occurs.

  Aggregation depends on the magnitude relationship between the ink droplets that land on the surface of the recording paper 16 that landed earlier and the ink droplets that landed later on the moment of landing. Even if the amount (discharge volume) of the ink droplet that landed first and the ink droplet that landed later are equal, the ink droplet that landed first and the ink droplet that landed later overlap on the surface of the recording paper 16 and strike. In the case of droplets, the ink droplets that are landed later are attracted to the ink droplets that have landed first at the moment the ink droplets landed later, and the diameter of the ink droplets that landed first increases, and the ink liquid that landes later The droplet diameter of the droplet is smaller than the droplet diameter when originally landing alone.

  In addition, the gradients of the line drawings 240 to 246 shown in FIGS. 13 and 14 tend to increase as the inter-dot pitch P (droplet ejection interval) approaches, and when the ink droplet penetration amount is small (that is, recording). There is a tendency for the ink remaining on the surface of the paper 16 to increase).

  In this droplet ejection control, when ink droplets that have landed first and ink droplets that land later are overlapped on the recording paper 16, droplet diameters that land first and ink droplet sizes that land after Are controlled so that the amount of ink droplets to be ejected later is larger than the amount of ink droplets previously ejected. The ratio of increasing the amount of the next droplet to be ejected is determined according to the dot pitch, the ink non-penetration amount, the surface tension of the ink, and the like.

  Since the ink permeation speed depends on the type of ink and the type of recording paper 16 (recording medium), the ink type information and the recording paper are used when determining the ratio of increasing the droplet ejection amount according to the ink non-penetration amount. Ink penetration time information may be recorded in advance for each of the 16 types.

  Here, the ink droplet diameter refers to a substantially circular diameter obtained by projecting a non-penetrating ink droplet that does not penetrate the recording paper 16 and remains on the surface onto the surface of the recording paper 16 (recording medium). This corresponds to the size of the area occupied by the non-penetrating ink droplets on the recording paper 16.

  That is, when ink droplets land on the recording medium (here, recording paper 16), the ink droplets continue to spread gradually on the recording medium for a certain period immediately after the landing, and ink on the recording medium after a predetermined time has elapsed since landing. As the infiltration of ink drops progresses, the infiltration amount of the ink drops decreases, the diameter of the ink droplets on the surface of the recording medium gradually decreases, and when the infiltration of the ink drops is completed, the infiltration amount of the ink drops becomes zero. The droplet diameter becomes zero.

  8A shows a dot row 120 including dots 100, 102, 104, 106,... Arranged at equal intervals with an inter-dot pitch P. FIG. 8B shows a dot row 120 shown in FIG. The ink droplets forming the dot row 120 shown are continuously applied in the direction indicated by the arrow line K (from the left to the right in FIG. 8) at the droplet ejection interval until the amount of 10% of the ink droplet permeates. A line drawing 140 of line width h = D formed when droplets are ejected is shown. A dot row 120 shows a case where dots are formed without landing interference between the dots (that is, a dot row including ideally formed dots).

  That is, in this droplet ejection control, droplet ejection is performed at time intervals until the remaining droplet amount in the non-penetrating state becomes 90% (0.9) of the droplet amount at the time of landing, and the first ink droplet When the second droplet (ink droplet forming the dot 102 in FIG. 8 (a)) lands after the droplet (ink droplet forming the dot 100 in FIG. 8 (a)) has landed, the second droplet At least one of the first droplet ejection amount and the second droplet ejection amount is changed so that the ink droplet diameter at the moment of landing is substantially the same as the first ink droplet diameter. The droplet ejection control is executed.

  In the embodiment shown in FIG. 8A, the dot 100 is formed by the first ink droplet, the dot 102 is formed by the second ink droplet, the dot 104 is formed by the third ink droplet, and the fourth droplet is formed. Dots 106 are formed by the ink droplets. Thereafter, ink droplets are sequentially ejected at a predetermined droplet ejection period, and a line image 140 shown in FIG. 8B is formed.

  If the first droplet ejection volume is v1, the second droplet ejection volume is v2, the third droplet ejection volume is v3, the fourth droplet ejection volume is vc, ... , V1 <v2 <v3 <vc, the ink ejection amount is controlled.

  In the embodiment shown in FIG. 8 (a), the droplet ejection amounts after the fourth droplet are substantially the same, and the droplet ejection amount is vc. Of course, the amount of droplet ejection after the fourth droplet may be gradually changed.

  Here, the dot 100 is a dot that can be formed by a droplet ejection amount v1 at a predetermined droplet ejection point, and its diameter is D1. Similarly, the dot diameter of the dot 102 is D2, the dot diameter of the dot 104 is D3, the dot diameter of the dot 106, and the ink ejected after the dot 106 is Dc.

  However, the dots 102 to 106 here are virtual dots, and indicate dots that can be formed at a predetermined droplet deposition point (landing point) when each ink droplet is ejected alone. The respective ink droplets are integrated by agglomeration occurring at the time of landing, and a shape corresponding to the shape of the integrated ink droplet is formed.

  Further, in order to realize the line width h = D of the line drawing 140, the droplet ejection amounts v1 to v3 and vc of each dot are adjusted. Considering an increase in the amount of droplets after the second droplet, at least h> D1.

  In FIG. 8 (c), the droplet ejection volume v1 to v10 from the first to the 10th droplet is gradually changed, and the droplet ejection volume after the 11th droplet is expressed as the droplet ejection volume v10 (= vc) of the 10th droplet. The mode to do is shown. As shown in FIG. 8C, the dot diameters of the dots 100 to 110 are D1 to D10, and D1 <D2 <D3 <... <D9 <D10 = D11 = Dc. The embodiment shown in FIG. 8 (c) is suitable for forming a relatively long line drawing.

  Further, in order to increase the droplet diameter of the ink droplet upon landing, the flying speed of the ink droplet may be increased in addition to the method of increasing the droplet ejection amount.

  For the third and subsequent ink droplets, the droplet ejection amount or the flying speed may be changed as compared to the first ink droplet (the droplet ejection amount or the flying speed may be changed stepwise) or immediately before. The droplet ejection amount or flight speed may be changed as compared with the ejected ink droplets (the droplet ejection amount or flight speed may be changed continuously).

  Thus, by changing the flying speed, the contact area with the recording paper 16 when the ink droplets land is changed, and the same effect as the droplet ejection amount control described above can be obtained.

  FIG. 9 (a) shows a line drawing 142 having a length of 70 μm formed by 5 ink droplets capable of forming a dot having a diameter of 2 μl and a diameter of 30 μm. FIG. 9 (b) and FIG. 9 (c) Shows a line drawing 144 having a length of 120 μm formed by 10 ink droplets and a line drawing 146 having a length of 620 μm formed by 60 ink droplets. Note that the length of the line drawing may be smaller than the above value.

  When a line drawing 146 having a long overall length as shown in FIG. 9 is formed, the line width is changed in the writing area 260 and the writing end area 264 as shown in FIG. Alternatively, the flying speed change control may be applied to the writing area 260 and the writing end area 264, and droplet ejection may be performed in the intermediate area 262 without performing the droplet ejection amount changing control or the flying speed changing control. Further, the droplet ejection amount change control or the flight speed change control may be applied only to the writing area 260.

  In this embodiment, the writing area 260 and the writing end area 264 are each 10 drops (in FIG. 14D, 60 μm from the writing side end is the writing area 260 and 60 μm from the writing end side is the writing end area 264). Of course, the writing area 260 and the writing end area 264 are not limited to 10 drops (10 drops), and it is preferable that the writing area 260 and the writing end area 264 can be appropriately changed according to the type of recording paper and the type of ink. More preferably, the type of recording paper and the type of ink are determined, and the writing area 260 and the writing end area 264 are automatically switched.

  Line drawings 142 to 146 shown in FIGS. 9 (a) to 9 (c) are abbreviated as the dot diameter (30 μm in FIGS. 9 (a) to 9 (c)) when each ink droplet forms a dot independently. Have the same width h (30 μm). The numerical values shown in FIGS. 9 (a) to 9 (c) are merely examples, and do not indicate the scope of application of the present invention.

  Further, in the case of continuous printing in which the number of ink droplets exceeds five droplets, a line image having a uniform width can be formed by adjusting the droplet ejection amount so as to gradually increase the droplet ejection amount.

  In the droplet ejection control in the ink jet recording apparatus 10 configured as described above, when an adjacent (adjacent) droplet lands before an infiltration of a certain droplet and forms an image integrally, the original image is Even in the case of a line with the same density, the droplet ejection control is performed so that the droplet ejection amount (discharge amount) of a certain droplet and the surrounding droplets is different, so that the printing density of one line can be made constant. One-line printing results can be formed in a fixed shape, and higher-definition printing is possible.

[Second Embodiment]
Next, droplet ejection control according to the second embodiment of the present invention will be described with reference to FIGS. 10 (a), 10 (b) and FIG.

  FIG. 10A shows a dot row 120 ′ that is a line drawing 140 ′ formed by applying the droplet ejection control, and FIG. 10B shows a line drawing 140 ′. 10 (a) and 10 (b), the same or similar parts as those in FIG.

  In this droplet ejection control, when the line image 140 having the width h = D is formed by continuous droplet ejection, the droplet ejection amount of the ink droplet immediately after the writing is reduced in advance in anticipation of an increase in the line width of the writing region. Thereafter, control is performed to gradually increase the droplet ejection amount so as to approach the original droplet ejection amount.

That is, the ink amount v1 ′ of the first ink droplet (dot diameter D1 ′ when the ink droplet alone forms the dot 100 ′, where D> D1 ′), the ink amount v2 of the second ink droplet '(Dot diameter D2' when ink droplet forms dot 102 'alone), ink amount v3' of the third ink droplet (dot diameter D3 when ink droplet forms dot 104 'alone) ) If the droplet ejection amount after the fourth ink droplet is vc ′ (dot diameter Dc ′ when the ink droplet alone forms the dot 106 ′), v1 ′ <v2 ′ <v3 ′ <vc ′ ( The droplet ejection control is performed so that D1 ′ <D2 ′ <D3 ′ <Dc ′). As a result, the line width of the line drawing 140 can be made substantially uniform over the entire length.

  Also in this example, as shown in the first embodiment, when forming a line drawing having a long overall length, the main droplet ejection control may be applied to at least the writing area and the writing end area.

  Next, a mode in which the ratio (correction amount) for changing the droplet ejection amount of each ink droplet is determined by the graph shown in FIG.

  In the writing area (for example, reference numeral 260 in FIG. 14 (d)), the droplet ejection amount of the first ink droplet ejected is v1, the droplet ejection amount of the second ink droplet ejected is v2, and the third droplet ejection amount. The droplet ejection amount of the ink droplet to be ejected on the ink is v3,... The droplet ejection amount of the i-th ink droplet is vi, and the ink droplet ejection in the intermediate region (for example, reference numeral 262 in FIG. 14D). The droplet volume is set to vc (fixed volume), and the droplet ejection volumes v1, v2, v3,..., Vi are controlled so that v1 / vc <v2 / vc <v3 / vc <... <vi / vc.

  If G1 = v1 / vc, G2 = v2 / vc, G3 = v3 / vc,..., Gi = vi / vc, the change pattern of G1, G2, G3,. Set as 180.

  That is, as the degree of pulling of the surface droplets (ink droplets on the surface of the recording paper 16) due to aggregation is larger, the degree of correction of the droplet ejection amount to be corrected is controlled to be stronger.

  For example, the patterns A, B, C, and D of the graph 180 are changed according to the amount of overlap between the surface droplets of the ink droplets that have landed first and the surface droplets of the ink droplets that have landed later and the surface tension of the surface droplets. select.

  When the overlap amount and the surface tension are small, the pattern D of the graph 180 is used, and as these increase, control for switching the ratio of the correction amount such as the pattern C, the pattern B, and the pattern A is performed.

  That is, the graph 180 shown in FIG. 11 plots the ratio of the droplet ejection amount as the surface droplet overlap or the surface tension of the surface droplet decreases according to the patterns A, B, C, and D. ing.

  It should be noted that the ink droplet ejection amount in each pattern is made into a data table and recorded in advance in recording means such as the memory 74 shown in FIG. 7, and droplet ejection is performed while referring to the data table when performing continuous droplet ejection. Control may be performed.

In addition, although the correction pattern shown in the graph 180 of FIG. 11 showed the example of correction | amendment with a straight line, you may use a curve like x1 ^{/ 2} , for example.

  It is also possible to correct not only the droplet ejection amount but also the flight speed using the same method as in this example.

  12 (a) to 12 (c) show the ink hitting so that the next ink drop lands at the timing when the appropriate amount of the remaining liquid on the recording paper 16 reaches 90% of the volume upon landing. An example of controlling droplets is shown.

  FIG. 12 (a) shows a first drop (first landing) ink drop 100 '. At the timing when the ink droplet 100 'penetrates into the recording paper 16 and is indicated by reference numeral 100 "in FIG. The droplet ejection control is performed so that the ink droplets that are to be landed on the recording paper 16 are landed on the recording paper 16. At this time, in such droplet ejection control, the line width is reduced over the entire region without lowering the droplet ejection frequency. Can form a substantially uniform line drawing.

  When an ink droplet that lands later is landed, the diameter of the ink droplet that lands later is preferably substantially the same as the diameter of the ink droplet that landed earlier.

  In the droplet ejection control in the inkjet recording apparatus 10 configured as described above, the droplet ejection amount in the writing area is controlled to be smaller than a predetermined amount in advance in anticipation of the line width immediately after writing being increased. The line width can be made uniform over the entire length of the line drawing 140 ′, and a desired line width (original line width) can be obtained. Further, since the ratio of changing the droplet ejection amount can be changed according to the overlapping amount of the droplets and the surface tension between the droplets, the dot diameter can be made more uniform.

  In the above-described embodiment, an example in which a substantially linear line drawing 140 or the like is formed in a certain direction (for example, the main scanning direction) is illustrated. However, the present invention forms a curved line drawing or a line drawing that combines straight lines and curves. It can also be applied.

  The line drawing formation direction is not limited to the sub-scanning direction, and may be the main scanning direction, or may be an oblique direction having a main scanning direction component and a sub-scanning direction component.

  There are the following modes as application examples of the present embodiment.

  With a print head that combines a print head that deposits droplets at odd-numbered droplet ejection points and a print head that deposits droplets at even-numbered droplet ejection points, droplets are ejected simultaneously at odd-numbered droplet ejection points, and the time is short. Drops are ejected to odd-numbered droplet ejection points at a droplet ejection period of an interval (for example, as shown in FIG. 12, the time until the remaining ink droplet amount reaches 90% of the ink droplet amount upon landing). When a liquid equal to or larger than the liquid droplet is ejected, the spread of the liquid droplets subsequently ejected may be evenly drawn to the liquid droplets on both sides without being biased toward only one liquid droplet. Of course, a print head for ejecting droplets at odd-numbered droplet ejection points and a print head for ejecting droplets at even-numbered droplet ejection points may be provided separately.

  In the above-described embodiment, the print head used in the ink jet recording apparatus is exemplified as the droplet discharge head. However, the present invention is not limited to liquids (water, water, The present invention can also be applied to a discharge head used in a liquid discharge apparatus that discharges a chemical solution, a resist, or a processing solution) to form a three-dimensional shape such as an image, circuit wiring, or processing pattern.

1 is a basic configuration diagram of an ink jet recording apparatus equipped with a print head 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 follows the 4-4 line in FIG. FIG. 3 is an enlarged view showing the nozzle arrangement of the print head shown in FIG. 1 is a conceptual diagram showing the configuration of an ink supply system in an ink jet recording apparatus equipped with a print head according to the present embodiment. Main part block diagram which shows the system configuration | structure of the inkjet recording device carrying the print head concerning this embodiment. The figure explaining the droplet ejection control which concerns on 1st Embodiment of this invention. The figure which shows the line drawing formed by applying the droplet ejection control shown in FIG. The figure explaining the droplet ejection control which concerns on 2nd Embodiment of this invention. Graph showing an example of droplet ejection amount correction pattern The figure explaining the one aspect | mode of droplet ejection amount correction | amendment The figure explaining the droplet ejection control concerning a prior art The figure which shows the line drawing formed by applying the droplet ejection control shown in FIG. Sectional drawing which shows the three-dimensional shape of the line drawing shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Inkjet recording apparatus, 50 ... Print head, 72 ... System controller, 74 ... Memory, 80 ... Print control part, 100, 102, 104, 106, 202, 204, 206 ... Dot

Claims (7)

A droplet ejection control method for a liquid ejection apparatus that ejects droplets from a ejection head onto a medium to be ejected,
When droplets are continuously ejected from the ejection head so that at least some of the droplets ejected at adjacent droplet ejection points on the surface of the ejection medium overlap, the droplets are continuously ejected. Control for changing the droplet ejection volume so that the volume of the droplet ejection of at least some of the plurality of droplets sequentially increases, and among the plurality of droplets that are continuously ejected A droplet ejection control method characterized by executing at least one of control for changing the flying speed of droplets so that the flying velocity of at least some of the droplets sequentially increases. A liquid discharge apparatus including a discharge head that discharges liquid droplets onto a discharge medium,
When droplets are continuously ejected from the ejection head so that at least some of the droplets ejected at adjacent droplet ejection points on the surface of the ejection medium overlap, the droplets are continuously ejected. Control for changing the droplet ejection volume so that the volume of the droplet ejection of at least some of the plurality of droplets becomes relatively larger sequentially, and among the plurality of droplets that are continuously ejected Liquid ejection comprising a control means for executing at least one of control for changing the flying speed of the droplets so that the flying speed of at least some of the droplets is sequentially relatively increased apparatus.   In the writing unit having a predetermined number of droplets from the first droplet ejection among the plurality of droplets continuously ejected, the control means adjusts the droplet ejection volume so that the droplet ejection volume is sequentially relatively increased. At least one of the control for changing and the control for changing the flying speed of the droplets so that the flying speed of the droplets becomes relatively larger sequentially is executed, and the same is applied to the droplets after the writing unit. The droplet ejection volume and the flight speed are controlled so that the droplet ejection volume and the flying speed are the same, and the diameter of the line drawing drawn by the dot group obtained by the continuous droplet ejection is made uniform. The liquid ejection device according to claim 2.   The liquid ejecting apparatus according to claim 3, wherein the writing unit includes a first droplet ejection to a tenth droplet ejection.   The control means is configured to drop a droplet to be ejected later at a timing at which the remaining droplet amount on the ejection medium of the previously ejected droplet becomes 0.9 or more of the ratio to the droplet amount at the time of landing. 5. The liquid ejection apparatus according to claim 2, 3 or 4, wherein droplet ejection control for landing on a recording medium is performed.   The control means applies a rate at which the amount of droplets to be ejected later is relatively larger than that of the previously ejected droplet and the flying speed of the subsequently ejected droplet. At least one of the proportions of the droplets that are relatively larger than the formed droplets is the amount of overlap between the droplets that are ejected first and the droplets that are ejected later, 6. The method according to claim 2, wherein a surface tension acting between a droplet to be ejected on the surface and a droplet to be subsequently ejected is changed according to at least one of the surface tensions. Liquid discharge device. The liquid ejecting apparatus according to any one of claims 2 to 6, wherein the control unit performs control to reduce a droplet ejection amount of the first droplet ejection from an original droplet ejection amount.

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