JP2008036836A - Inkjet recorder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recorder which reduces generation of image defects. <P>SOLUTION: In the inkjet recorder, while a recording head equipped with a plurality of nozzle openings which eject ink droplets is scanned on a recording medium, the ink droplets are ejected and struck on the recording medium, thereby forming an image. The nozzle openings are arranged so that a shape of a nozzle array in which a plurality of the nozzle openings are arranged becomes a shape to form a projecting shape towards a scanning direction of the recording head when a face opposed to the recording medium of the recording head is seen from the recording medium side. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an inkjet recording apparatus that forms an image on a recording medium by ejecting ink droplets while scanning an inkjet recording head having a plurality of nozzles on the recording medium.

  In recent years, the image quality of an ink jet recording apparatus has been remarkably developed. For example, in the function of outputting photographic data, a high image quality surpassing that of a silver salt photograph has been realized. The printing speed has also improved year by year.

  Needless to say, such high speed and high image quality are realized by the development of each elemental technology that constitutes an ink jet recording apparatus such as a head, ink, medium (recording medium), etc.・ Methods for achieving high image quality include smaller droplets of ejected ink, higher resolution in the nozzle row direction by high density arrangement of multiple nozzles, and higher head scanning speed by increasing the head drive frequency. Things.

  On the other hand, in an ink jet recording apparatus, the landing position of ink droplets on a recording medium is shifted due to an air flow flowing between the head and the recording medium by scanning the recording head on the recording medium (hereinafter referred to as an inflow air flow). There is a problem that an image may be defective.

  This image defect occurs when the inflow airflow described above collides with a group of ink droplets ejected from the ink ejection ports arranged in a line on the recording head and changes the flight path of the ink droplets.

  As a result, the landing positions of the ink droplets on the recording medium are shifted, resulting in image defects and density unevenness. This becomes prominent when ink droplets are reduced, print duty, and carriage speed are increased with the aim of high speed and high image quality.

  A typical example of the landing position deviation is localized at both end portions of the nozzle row and deviated in the inner direction along the nozzle row direction from both ends of the nozzle row.

  In this case, when the recording head is scanned on the recording medium, a white streak pattern (white streak) that is a non-recorded portion appears in a portion where both end portions of the nozzle row pass.

  In order to reduce the occurrence of white stripes, several methods have already been disclosed by public relations. For example, in Japanese Patent Laid-Open No. 2003-145775, the pitch width of the nozzles at both ends is made wider than that of the inner nozzles, and the landing positions of the ink droplets ejected from the nozzles at both ends are corrected toward the outer side of the nozzle row, thereby causing white streaks. There has been proposed a method for reducing the occurrence of the above.

In Japanese Patent Laid-Open No. 2003-170595, the thermal energy applied to the ink by the heater at the nozzles at both ends is made larger than that at the inner nozzles, and the momentum of the ink droplets ejected from the nozzles at both ends is increased, thereby landing due to the influence of the airflow. A method has been proposed in which the positional deviation is reduced and the occurrence of white stripes is reduced.
JP 2003-145775 A JP 2003-170595 A

  However, if the scanning speed of the head is increased in order to achieve higher speed and higher image quality, the flow rate of the incoming airflow increases.

  For this reason, the deviation of the landing position of the ejected ink droplets becomes large, and the range where the landing position deviation occurs, which has been localized at both ends of the nozzle row so far, is expanded. To reach.

  Such an image defect is conspicuous when a small droplet having an ink discharge volume of 5 picoliters or less, a high-frequency drive with a drive frequency of 12 kHz or more, and a high-speed scan with a recording head scanning speed of 0.3 m / s or more.

(Object of invention)
An object of the present invention is to provide an ink jet recording apparatus that prevents the occurrence of image defects and stably obtains a high quality recorded image in view of the above-described problems of the prior art.

In order to solve the above problem, in the invention according to claim 1 of the present application, the recording head having a plurality of nozzle openings for discharging ink droplets is ejected while the ink droplets are ejected while scanning on the recording medium, and the recording is performed. In an inkjet recording apparatus that forms an image by landing on a medium,
The shape of the nozzle row in which a plurality of nozzle openings are arranged so as to form a convex shape in the scanning direction of the recording head when the surface of the recording head facing the recording medium is viewed from the recording medium side. The nozzle openings are arranged so as to have a simple shape.

  Usually, the air flow flowing between the recording head and the recording medium collides with the ejected ink droplet group and the air flow caused thereby, and a turbulent flow is generated, which adversely affects the landing position of the ink droplet. In the first aspect of the present invention, since the inflowing air flow moves backward without causing separation along the convex shape of the nozzle row, a turbulent flow does not occur, resulting in an adverse effect on the landing position of the ink droplets. Can be reduced.

  The invention according to claim 2 of the present application is characterized in that the convex shape of the nozzle row in the invention of claim 1 is a polygonal line shape composed of two or more sides.

  The invention described in claim 3 of the present application is characterized in that the convex shape of the nozzle row in the invention of claim 1 is an arc shape.

  As described above, according to the present invention, the turbulence of the airflow when the inflow airflow collides with the airflow caused by the ejected ink droplet group is reduced, and the occurrence of image defects is also caused during small droplets, high print duty, and high-speed scanning. It can be avoided.

  The ink discharge volume is preferably 5 picoliters or less. In the case of 5 picoliters or less, since the inertial mass of the ink droplet is small, the landing position is easily affected by the air current, and the effect of the present invention can be remarkably obtained.

  The inkjet recording apparatus according to claims 1 to 3 of the present application may be configured such that the recording head scans the same portion on the recording medium a plurality of times to form an image.

  In the ink jet recording apparatus according to any one of claims 1 to 3, the liquid ejected from the recording head may be a processing liquid that acts on the ink and / or the recording medium to improve the quality of the recorded image.

  The recording head of the ink jet recording apparatus according to any one of claims 1 to 3, wherein the energy generating means for ejecting ink is an electrothermal transducer that generates heat by electrical energy and causes the ink to boil by heating. Also good.

  An embodiment of an ink jet recording apparatus according to the present invention will be described in detail with reference to FIGS. The present invention is not limited to such embodiments, and these can be further combined and applied to other techniques that are included in the concept of the present invention described in the claims of this specification. .

  The characteristics of the ink jet recording head of the ink jet recording apparatus according to this embodiment will be described with reference to FIG. FIG. 1A shows a printing operation in a conventional ink jet recording apparatus, so that an air flow generated in the vicinity of the recording head when the recording head is scanned on the recording medium is opposed to the recording medium of the recording head. It is expressed using the figure seen from the surface to do. Due to the scanning movement of the head during the printing operation, airflow flows from the head to the recording medium from the front in the scanning direction. This inflow air current collides with the ink droplet group, causes a complicated turbulent flow, and causes an image defect.

  On the other hand, (b) in FIG. 1 shows the air flow generated in the vicinity of the recording head when the recording head is scanned on the recording medium in order to perform the printing operation in the ink jet recording apparatus according to the present embodiment. It is represented using a diagram viewed from the surface facing the recording medium. Due to the scanning movement of the head during the printing operation, an airflow flows from the head to the recording medium from the front in the scanning direction, but these are confused because they fall back along the convex shape of the ink droplet group without peeling off. There is no flow. This makes it possible to avoid the occurrence of image defects.

  FIG. 2 shows the surface of the inkjet recording head of the inkjet recording apparatus according to this embodiment that faces the recording medium when viewed from the front. The head chip 001 is bonded to the alumina pedestal 002, and the alumina pedestal 002 is further fixed to the tank holder 003.

  The cyan nozzle opening row 011 has a pair of convex shapes consisting of four line segments as shown in the figure. A cyan nozzle opening array in which 128 nozzle openings are arranged in one convex shape and both are combined is composed of a total of 256 nozzle openings.

  If the xy coordinate axes are taken as shown in the figure, the nozzle openings belonging to each of the pair of convex shapes are positioned with their center y-coordinates shifted from each other by only 21 microns. A maximum resolution of 1200 dpi can be obtained in the direction.

  A total of 256 nozzle openings of black, yellow, and magenta are arranged on the same convex shape starting from positions 008, 009, and 010, respectively.

  FIG. 3 is a perspective view of the ink jet recording head of the ink jet recording apparatus according to this embodiment. As shown in FIG. 2, the cyan nozzle opening row 011 is a terminal portion of the individual flow path 013 branched from the common liquid chamber 012 to each nozzle, and ink is supplied from the common liquid chamber 012 to each nozzle. The In the middle of the individual flow path 013, an electrothermal converter 016 is provided immediately below the nozzle opening row to give thermal energy to the ink and boil the film.

  The remaining magenta, yellow, and black have the same flow path structure.

  In the ink jet recording head, a dissolvable resin layer is applied on a silicon substrate 017 on which an electrothermal transducer and a drive circuit and wiring are fabricated, and patterned into a desired pattern. Next, a clothing resin layer 018 is formed on the soluble resin layer, and a nozzle opening pattern is formed on the surface of the clothing resin layer with a material having high oxygen plasma resistance by photolithography. Here, the resin resin layer is dry-etched with oxygen plasma using the nozzle opening pattern as a mask to form nozzle openings. Subsequently, the common liquid chamber 012 is formed by dry etching from the surface opposite to the surface on which the nozzle opening row of the Si substrate is formed to the surface on which the nozzle opening row is formed. Thereafter, the dissolvable resin layer is eluted to form an ink flow path that connects the nozzle opening and the common liquid chamber 012, so that a single chip is produced.

[Head cartridge]
As shown in FIG. 4, cyan (C), magenta (M), yellow (Y), and black (K) color heads 111 to 114 are prepared, and each color head shown in FIG. Bonding is performed along the main scanning direction so that the positive direction of the x-axis coincides with the main scanning direction. In the alumina pedestal, ink flow paths 115 to 118 communicating with the common liquid chamber of each head are formed.

  5 and 6, the alumina pedestal 002 is bonded to a tank holder 003, and the ink flow paths 115 to 118 in the alumina pedestal shown in FIG. It communicates with 131-134.

  As shown in FIG. 5, the wiring formed on each chip is electrically connected to the contact substrate 121 through the flexible wiring 122. The contact substrate is bonded and fixed to the tank holder 120.

  As shown in FIG. 6, ink tanks 141 to 144 are detachably attached to the tank holder 120, and the openings on the lower surface of the ink tank are connected to the ink tank connection ports 131 to 134, respectively. Supplied.

  Hereinafter, each of the color heads 111 to 114, the alumina pedestal 002, and the entire structure 146 including the ink tanks 141 to 144 in the tank holder 120 will be referred to as a head cartridge.

[Inkjet recording device body]
FIG. 7 is a cutaway perspective view showing an example of an ink jet recording apparatus using the ink jet recording head according to the present invention. The chassis 200 of the ink jet recording apparatus is composed of a plurality of plate-like metal members having a predetermined rigidity, and forms the skeleton of the ink jet printer.

[Recording medium transport system]
The chassis 200 includes a recording medium holding unit 201 that holds a recording medium (not shown), and sends the recording medium to the conveyance unit. Further, the conveyance unit moves in a direction A in FIG. A transport roller 204 that can feed the recording medium to the rear, a discharge roller 205 that discharges the recording medium after predetermined recording is performed, and a tray 206 that holds the discharged recording medium. The transport roller is driven by a transport motor 207 via a gear 208.

[Recovery Department]
In addition, the chassis 200 is provided with a recovery unit 209, which prevents the evaporation of the solvent by capping the ejection surface of the recording head during non-recording, and sucks the ejection surface of the recording head in a capped state. It is possible to remove ink in the discharge nozzles thickened by evaporation and to discharge bubbles accumulated in the flow path of the recording head.

[carriage]
In the drawing, the carriage 203 can perform a reciprocating motion (B direction in the drawing) for scanning the recording head along the guide shaft 211 by a carriage drive motor 210 via a pulley and a belt. A head cartridge 146 is detachably mounted on the carriage. At this time, the head cartridge is electrically connected via a metal terminal assembled to the carriage.

[Linear encoder]
In the movement range of the carriage 203, a linear scale 212 is provided in which 1200 scales are engraved at equal intervals in one inch. The carriage is provided with a linear encoder 213, and light emitted from the light emitting part of the previous linear encoder is repeatedly reflected and transmitted by the scale on the linear scale, and this optical signal is detected by the light receiving part of the linear encoder. Then, the signal is converted into an electric signal representing the movement position or movement speed of the carriage by a signal processing circuit (not shown), and the movement of the carriage and the ejection timing of the recording head are controlled based on this information. For example, in the control of ink ejection timing, a predetermined ejection timing signal is output to the driver of the recording head as the recording head is scanned by moving the carriage, and ink is ejected from the recording head in accordance with this, thereby recording. Dots corresponding to predetermined image data can be formed at predetermined positions on the medium. At this time, for example, when dots are formed by discharging each time a scale is detected, printing can be performed with a resolution of 1200 dpi in the main scanning direction.

[Image signal processing]
The recorded image data is color-separated into cyan, magenta, yellow, and black by the printer driver. Subsequently, it is decomposed so that the gradation in the pixel can be expressed by the number of ink droplets that are shot into the pixel. In addition, when an image is formed by scanning the same part a plurality of times, the data of the corresponding part is further decomposed for each scanning time. Further, the nozzle opening columns that are paired with a shift of 21 microns in the y-axis direction for each color are divided into groups each corresponding to a resolution of 600 dpi, and the data also corresponds to 2 companies corresponding to 600 dpi. Disassemble into groups. The data after separation corresponds to each color, each nozzle row, and each nozzle on a one-to-one basis, and this is called raster data.

  Subsequently, the raster data is shifted by the printer driver in the main scanning direction by the offset amount. FIGS. 8A to 8C show offset amounts for 32 nozzles in one nozzle row in a pair of cyan nozzle openings as an example of the offset amount. In the figure, nozzle numbers 1 to 32 are assigned to the nozzles for the sake of explanation. Here, as shown in FIG. 8A, the offset amount is a distance from a straight line passing through the center of the reference nozzle opening in the previous recording head and orthogonal to the main scanning direction to the center of each nozzle opening. As shown in FIG. 8B, this offset amount is defined in advance by rounding off the fraction and using the nearest integer value in dpi units. The printer driver refers to this value and shifts the data in the raster data by the corresponding nozzle offset amount in the main scanning direction. Note that, as shown in FIG. 8C, a blank portion formed when the raster data is shifted is handled as data for which ejection is not performed. Therefore, this process increases the size of the raster data in the main scanning direction by the maximum offset amount.

  When the above processing is completed, the raster data is sent to the ASIC by serial transfer, converted into data for turning on / off the electrothermal transducer at a predetermined timing, and printing is started.

  Note that all of the embodiments described above are an ink jet recording head of a type in which bubbles are generated in ink by heat energy generated by an electrothermal element and ink is ejected by the generation pressure of the bubbles, and an ink jet recording apparatus using the ink jet recording head. is there. However, the application of the present invention is not limited to the case of using this method, and can be applied to, for example, an ink jet recording head that discharges ink by displacement of a piezoelectric element and an ink jet recording apparatus using the ink jet recording head. This is because even in an ink jet recording head using a piezoelectric element, an image defect due to the landing position of an ink droplet being displaced by the air flow becomes a problem.

1 is a plan view of an ink jet recording head that forms part of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a cutaway perspective view of an ink jet recording head forming a part of an ink jet recording apparatus according to an embodiment of the present invention. 1 is an exploded perspective view of the vicinity of an ink jet recording head and an alumina pedestal forming a part of an ink jet recording apparatus according to an embodiment of the present invention. 1 is a perspective view of a head cartridge forming a part of an ink jet recording apparatus according to an embodiment of the present invention, as viewed from a contact substrate side. 1 is a perspective view of a head cartridge that forms part of an ink jet recording apparatus according to an embodiment of the present invention, as viewed from an ink tank side. 1 is a cutaway perspective view showing a main part of an ink jet recording apparatus which is an embodiment of the present invention. FIG. 1 is a top view of an inkjet recording head that represents the definition of an offset amount in an inkjet recording apparatus that is an embodiment of the present invention, a list of offset amounts (part), and a schematic diagram that represents image signal processing of raster data (part) It is. It is a figure which shows an example of the offset amount in the inkjet recording device which is one Example of this invention.

Explanation of symbols

001 Head chip 002 Alumina pedestal 003 Tank holder 008 Black nozzle opening row starting position 009 Yellow nozzle opening row starting position 010 Magenta nozzle opening row starting position 011 Cyan nozzle opening row 012 Common liquid chamber 013 Individual flow channel 016 Electric heat Conversion body 017 Silicon substrate 018 Resin layer 111 Cyan (C) head 112 Magenta (M) head 113 Yellow (Y) head 114 Black (K) head 115 Cyan (C) ink flow path 116 Magenta (M) ink flow path 117 Yellow (Y) ink flow path 118 Black (K) ink flow path 120 Tank holder 121 Contact substrate 122 Flexible wiring 131 Cyan (C) ink tank connection port 132 Magenta (M) ink tank connection port 133 Yellow (Y) Ink tank connection port 134 Black (K) ink tank connection port 141 Cyan (C) ink tank 142 Magenta (M) ink tank 143 Yellow (Y) ink tank 144 Black (K) ink tank 146 Head cartridge 200 Chassis 201 Recording medium holding unit 203 Carriage 204 Conveyor Roller 205 Discharge Roller 206 Tray 207 Conveyor Motor 208 Gear 209 Recovery Unit 210 Carriage Drive Motor 211 Guide Shaft 212 Linear Scale 213 Linear Encoder

Claims (3)

In an ink jet recording apparatus for forming an image by ejecting the ink droplets while causing a recording head having a plurality of nozzle openings for ejecting ink droplets to scan on the recording medium and landing on the recording medium.
The shape of the nozzle row in which a plurality of nozzle openings are arranged so as to form a convex shape in the scanning direction of the recording head when the surface of the recording head facing the recording medium is viewed from the recording medium side. An ink jet recording apparatus, wherein the nozzle openings are arranged so as to have a simple shape.   2. The ink jet recording apparatus according to claim 1, wherein the shape of the nozzle row is a polygonal line shape including two or more sides.   The inkjet recording apparatus according to claim 1, wherein a shape formed by the nozzle rows is an arc shape.

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