JP5006136B2 - Image forming apparatus - Google Patents

Description

The present invention, for example a copying machine or a printer, an image forming equipment for printing by ejecting ink droplets or the like using a facsimile machine, a high-quality image, particularly by ejecting ink by electrostatic attraction method It relates to stable formation.

  Piezoelectric conversion and electrostatic attraction methods are used in an ink jet image forming apparatus that forms an image by flying ink. An electrostatic inkjet image forming apparatus disclosed in Patent Document 1 includes a plurality of electrodes provided on the ink discharge port side, and a counter electrode provided at a position facing the tip of the electrode, and an unintended electrode In order to eliminate the flying of ink from the ink, a high voltage, for example, a voltage of 1800 V is applied to the electrode provided in the vicinity of the electrode forming the ink discharge point for discharging the ink, and the potential of the ink discharge point is set to the position close to The ink is gathered at the ink discharge point by making it lower than the provided electrode, the ink at the tip of the adjacent electrode is reduced, the discharge meniscus is formed at the ink discharge point, and the ink droplet is ejected from the electrode at the ink discharge point. ing.

Patent Document 2 discloses an ultrafine fluid jet apparatus that ejects ink droplets by an electrostatic suction method and an electrowetting effect. The ultra-fine fluid jet apparatus disclosed in Patent Document 2 is provided with a flying electrode inside an ultra-fine diameter nozzle to which a liquid is supplied, and an electrode that covers the outside of the tip is provided outside the ultra-fine diameter nozzle. A substrate serving as a counter electrode is arranged at a distance of 0.05 mm or less at the tip of the diameter nozzle. Then, the voltage applied to the electrode provided outside the tip of the ultrafine nozzle is controlled, and the liquid in the ultrafine nozzle is moved to the counter electrode side by the electrowetting effect, and the electric field strength is locally increased to reduce the droplet. To fly.
JP-A-11-198381 Japanese Patent Laid-Open No. 2004-165588

  The inkjet image forming apparatus disclosed in Patent Document 1 requires a pulse driving device that applies a high-voltage pulse voltage in order to eject ink, and is disadvantageous in that it is expensive and has low frequency response.

  Moreover, since the ultrafine fluid jet apparatus shown by patent document 2 moves a liquid by the electrowetting effect in an ultrafine diameter nozzle, since a capillary phenomenon acts and becomes resistance, it exhibits an electrowetting effect. Therefore, it is necessary to apply a relatively high voltage of about 300V. Moreover, it is difficult to apply to high viscosity ink.

The present invention improves such disadvantages, and can stably form high-quality images by moving inks and the like at a relatively low voltage so that even high-viscosity inks can fly stably. it is an object to provide a equipment.

  The droplet flying device according to the present invention is an image forming device including an ink droplet flying device that records characters and images by ejecting ink droplets onto a recording medium that is conveyed along a conveyance path, the ink droplet flying device. Has an ink droplet ejecting means and a counter electrode arranged opposite to the ink droplet ejecting means, and the ink droplet ejecting means has a plurality of slits or one-dimensionally arranged to hold the ink to be ejected. An ink storage portion having an ink holding portion of the through hole and a flying means for flying the ink held in the ink holding portion, the flying means being arranged in a comb-teeth shape in the ink holding portion, A plurality of flying electrodes formed in a needle shape, an electric field generating means for generating an electric field between the plurality of flying electrodes and the counter electrode, and the ink holding unit corresponding to each of the flying electrodes Multiple provided A voltage is applied between the electrowetting drive electrode (EW drive electrode) and the EW drive electrode and the ink in the vicinity of each flying electrode in the ink reservoir to electrolyze the ink in the ink holder. A flying control means that moves in an electric field generated by the flying electrode of the electric field generating means due to a wetting phenomenon, and a high voltage is applied between the flying electrode and the counter electrode by the electric field generating means. In this state, the flying control means applies a pulsed low voltage between the EW drive electrode and the ink in the vicinity of each flying electrode in the ink reservoir so that the ink droplet ejection means and the counter electrode Ink droplets are caused to fly to a recording medium conveyed in between.

  A second image forming apparatus of the present invention is an image forming apparatus provided with an ink droplet flying device that records characters and images by ejecting ink droplets onto a recording medium transported along a transport path, wherein the ink droplets The flying device includes an ink droplet ejecting unit and a counter electrode disposed so as to face the ink droplet ejecting unit, and the ink droplet ejecting unit includes a plurality of slits or two-dimensionally holding ink to be ejected. An ink storage section having an ink holding section of a plurality of through holes arranged; and a flying means for flying the ink held in the ink holding section, the flying means being two-dimensionally arranged in the ink holding section A plurality of flying electrodes arranged in a needle shape; an electric field generating means for generating an electric field between the plurality of flying electrodes and the counter electrode; and the ink corresponding to each of the flying electrodes Installed in the holding part A voltage is applied between the plurality of electrowetting drive electrodes (EW drive electrodes) and the EW drive electrodes and the ink in the vicinity of the flying electrodes in the ink reservoir. Flying control means for moving the ink in an electric field generated by the flying electrode of the electric field generating means by electrowetting phenomenon, and the electric field generating means causes a high gap between the flying electrode and the counter electrode. In a state where a voltage is applied, a pulse-like low voltage is applied between the drive electrode for EW and the ink in the ink reservoir by the flight control means, and transported between the ink droplet ejection means and the counter electrode Ink droplets are caused to fly to a recording medium to be recorded.

  The EW drive electrode is preferably formed integrally with the flying electrode along the outer peripheral surface of the flying electrode, and has an insulating water repellent film on the outer peripheral surface of the EW driving electrode.

  Further, the EW drive electrode may be provided on a wall surface parallel to the flying electrode of the ink holding portion.

  Further, the flying electrode may be provided on the wall surface of the ink holding portion, and the EW drive electrode may be provided on the wall surface facing the wall surface of the ink holding portion provided with the flying electrode.

  Further, the ink holding part may have a material that absorbs ink.

  Further, the plurality of flying electrodes are arranged at an image resolution pitch.

  In addition, the viscosity of the ink stored in the ink storage unit is at least 8 mPa · s.

  The voltage applied to the EW drive electrode by the flight control means is set to be smaller than 1/10 of the voltage applied between the flight electrode and the counter electrode by the electric field generating means. desirable.

  Furthermore, the ink droplet ejection means may be arranged in parallel in a direction orthogonal to the plurality of through holes arranged in at least two rows in the slit shape or one-dimensionally.

  Further, it is desirable that the at least two rows of ink droplet ejection means are arranged in different phases in the direction of the plurality of through holes arranged in the slit shape or one-dimensionally.

  Further, in the second image forming apparatus, the flying control means of the ink droplet flying device is configured to provide a gap between each EW drive electrode and the ink in the vicinity of each flying electrode in the ink reservoir according to image data. It is desirable to perform flash printing on a recording medium that is conveyed by applying a voltage to the recording medium.

  Furthermore, in the second image forming apparatus, it is preferable that the ink droplet flying device is arranged along the conveyance path of the recording medium for each color.

  Further, in the second image forming apparatus, the ink droplet flying device of the same color is shifted by 1/2 pixel along the recording medium conveyance path in a direction perpendicular to the conveyance direction and the conveyance direction. You may arrange 4 sets along.

  Furthermore, in the second image forming apparatus, the ink droplet flying devices may be alternately arranged along the front and back of the conveyance path of the recording medium.

  The image forming apparatus according to the present invention is opposed to a plurality of flying electrodes arranged in a comb-like manner in an ink holding portion of a plurality of through holes arranged in a slit shape or one-dimensionally arranged to hold ink to be ejected by an ink storage portion. A low voltage is applied between the drive electrode for EW and the ink in the ink reservoir by the flight control means in a state where a high voltage is applied between the electrodes and the ink in the ink holding unit is caused to fly by electrowetting phenomenon. The ink droplets can be stably ejected at a low voltage by moving within the electric field generated by the electrode for recording and flying the ink droplets onto the recording medium disposed between the ink droplet ejection means and the counter electrode. It is possible to increase the printing speed by stably ejecting ink droplets of viscosity.

  In addition, by applying a driving voltage to the flying electrode and moving the ink in the ink holding part composed of slits and through-holes to the tip of the flying electrode by electrowetting phenomenon, highly viscous ink droplets are stabilized. Can fly.

  In addition, since the flight control means only needs to generate a pulse-like low voltage, the structure is simplified to reduce the size and weight of the ink droplet flying device, and no mechanical drive unit or heating unit is required. Reliability and durability can be improved.

  In addition, since the ink reservoir is shared by a plurality of flying electrodes and the cross-sectional area of the portion other than the ink holding portion is increased to form an ink flow path to the inside of the ink holding portion, high-viscosity ink is stably held. The printing speed can be increased and the image quality can be improved.

  In addition, it has a plurality of slit-like or two-dimensionally arranged through-hole ink holding portions for holding ink to fly to the ink storage portion, and a plurality of flying needles formed in this ink holding portion in a needle shape The electrodes are arranged two-dimensionally, an EW drive electrode is provided corresponding to each flight electrode, and the EW drive electrode is set by the flight control means in a state where a high voltage is applied between the flight electrode and the counter electrode. An image is formed by applying a pulsed low voltage between the ink in the vicinity of the flying electrode in the ink reservoir and causing the ink droplet to fly to the recording medium transported between the ink droplet discharging means and the counter electrode. As a result, the printing speed can be further increased.

  Further, the flying electrode and the EW driving electrode are formed by forming the EW driving electrode integrally with the flying electrode along the outer peripheral surface of the flying electrode and providing an insulating water-repellent film on the outer peripheral surface of the EW driving electrode. In addition, the configuration can be simplified and can be stably disposed in the ink holding portion.

  Further, the EW drive electrode is provided on the wall surface parallel to the flying electrode of the ink holding unit, the flying electrode is provided on the wall surface of the ink holding unit, and the EW driving electrode is provided on the wall surface of the ink holding unit. By providing on the wall surface facing the wall surface, the ink in the ink holding portion can be efficiently moved to the tip of the flying electrode due to the electrowetting phenomenon.

  In addition, since the ink holding portion includes a material that absorbs ink, the degree of freedom of arrangement of the ink droplet flying device can be increased and maintenance can be facilitated.

  Furthermore, by arranging the plurality of flying electrodes at an image resolution pitch, a high-quality image can be stably formed.

  In addition, the viscosity of the ink stored in the ink storage section is at least 8 mPa · s, so that a high-quality image can be stably formed and the drying of the ink droplets flying onto the recording medium can be accelerated to increase the printing speed. Can be achieved.

  Further, the voltage applied to the EW drive electrode by the flying control means is set to be smaller than 1/10 of the voltage applied between the flying electrode and the counter electrode by the electric field generating means, so that the ink droplet can be kept at a low voltage. It can fly stably.

  Furthermore, by arranging the ink droplet ejection means in parallel in a direction orthogonal to the plurality of through holes arranged in at least two rows, slit shape, or one dimension, the printing speed can be further increased.

  Further, by arranging at least two rows of ink droplet discharge means in different phases in the direction of the plurality of through holes arranged in a slit shape or one-dimensionally, it is possible to increase the print density and improve the image quality. it can.

  Further, in the image forming apparatus in which a plurality of flying electrodes are two-dimensionally arranged, the flying control means has a voltage between each EW drive electrode and ink in the vicinity of each flying electrode in the ink reservoir according to the image data. The printing speed can be further increased by applying flash to the recording medium being conveyed and performing flash printing.

  Furthermore, a color image can be printed at high speed by arranging an ink droplet flying device in which a plurality of flying electrodes are arranged two-dimensionally along the conveyance path of the recording medium for each color.

  In addition, the same color ink droplet flying device in which a plurality of flying electrodes are two-dimensionally arranged is shifted along the recording medium transport path by ½ pixel in the direction perpendicular to the transport direction. By arranging four sets along the path, the pixel density can be increased.

  Furthermore, by alternately disposing ink droplet flying devices in which a plurality of flying electrodes are arranged two-dimensionally along the front and back of the recording medium conveyance path, double-sided printing of the recording medium can be performed at high speed.

  FIG. 1 is a cross-sectional view showing a configuration of a droplet flying device according to the present invention. As shown in the figure, the droplet flying device 1 includes a droplet discharge unit 2 and a counter electrode 3 disposed to face the droplet discharge unit 2. The droplet discharge means 2 has a liquid reservoir 4 and a flying means 5. The liquid reservoir 4 has slits or through-holes (hereinafter referred to as slits) 6 and is formed of an insulating material. As shown in the cross-sectional view of FIG. 2, the flying means 5 includes a rod-like flying electrode 7, an insulating film 8 provided on the outer peripheral surface of the flying electrode 7, and an electro provided on the outer peripheral surface of the insulating film 8. Wetting drive electrode (hereinafter referred to as EW drive electrode) 9, insulating film 10 covering the outer peripheral surface of EW drive electrode 9, and water-repellent film 11 provided on the outer peripheral surface of insulating film 10, The portion protrudes slightly from the slit 6 of the liquid reservoir 4 and is provided in the slit 6. The slit 6 may be provided with a material that absorbs liquid, such as a sponge.

The flying electrode 7 is made of a material having conductivity and discharge resistance, such as copper, tungsten, or carbon, and has an outer diameter of 0.005 to 0.03 mm, for example, 0.015 mm. The EW drive electrode 9 is made of a material having good conductivity, such as copper, tungsten, or carbon, and has a thickness of 0.001 to 0.005 mm, for example, 0.001 mm. The flying electrode 7 and the EW drive electrode 9 are formed by etching, sputtering, or CVD. The insulating film 8 and the insulating film 10 are made of a material having good insulating properties and discharge resistance, such as SiO ₂ , and have a thickness of 0.001 to 0.005 mm, for example, 0.001 mm. The water repellent film 11 is made of, for example, a fluorine resin. The liquid reservoir 4 has an insulating property and stores a highly viscous ink 12, for example, an ink having a viscosity of 8 mPa · s or more, and the width of the slit 6 is determined according to the outer diameter of the flying electrode 7. When the outer diameter of the working electrode 7 is 0.015 mm, for example, it is formed to have a thickness of about 0.2 mm so as to ensure a sufficient flow path cross-sectional area for replenishing the flying ink. The counter electrode 3 is formed of a material having good conductivity, for example, copper, and is arranged to be separated from the tip of the flying electrode 7 by 0.01 to 0.5 mm, for example, 0.2 mm.

  The flying electrode 7 is connected to the counter electrode 3 via a bias power source 13, and a high bias voltage of about 2 kV, for example, is applied from the bias power source 13. The EW drive electrode 9 is connected to the ink 12 of the liquid reservoir 4 via the drive power supply 14 and the flight control means 15, and a low drive voltage of 100 V or less is applied. The bias power supply 13, the drive power supply 14, and the flight control means 15 are controlled by a control device 16 as shown in the block diagram of FIG.

  When the droplet flying device 1 causes the droplet of the ink 12 in the liquid storage section 4 to fly to the medium 17 conveyed between the droplet discharge means 2 and the counter electrode 3, the control device 16 is supplied from the bias power source 13. A high voltage is applied to the flying electrode 7 to generate an electric field 18 between the flying electrode 7 and the counter electrode 3 as shown in FIG. At this time, the surface on the slit 6 side of the ink 12 in the slit 6 of the liquid reservoir 4 is inside the slit 6 outside the electric field 18 of the flying electrode 7 due to the meniscus generated by the water repellent effect of the water repellent film 11 of the flying means 5. Is located. In this state, the control device 16 applies on / off control to the flight control means 15 to apply a low drive voltage from the drive power supply 14 to the EW drive electrode 9. When a drive voltage is applied to the EW drive electrode 9, the ink 12 in the slit 6 moves to the tip of the flying electrode 7 as shown in FIG. 4 due to the electrowetting phenomenon. That is, when a drive voltage is applied between the EW drive electrode 9 and the ink 12 in the liquid reservoir 4 to charge the ink 12 and charge it, the surface tension of the ink 12 is reduced and the water repellent film 11 and The surface of the ink 12 in the slit 6 moves to the tip of the flying electrode 7. Since a high electric field is generated between the tip of the flying electrode 7 on which the surface of the ink 12 has moved and the counter electrode 3, the ink 12 that has moved to the tip of the flying electrode 7 faces along the electric field. The ink droplets 12a are landed on the medium 17 by flying toward the electrode 3.

  In this way, the ink droplets 12a of the ink 12 in the liquid reservoir 4 can be made to fly by simply turning on / off the low voltage applied to the EW drive electrode 9, for example, a drive voltage of 100V or less, and the flight control means. The structure of 15 can be simplified and the droplet flying apparatus 1 can be made low-cost.

  Further, by applying a driving voltage to the flying electrode 7 and moving the ink 12 in the slit 6 to the tip of the flying electrode 7 by electrowetting phenomenon, the highly viscous ink 12 can be stably ejected. Can do.

  An image forming apparatus using the droplet flying apparatus 1 will be described. As shown in the perspective view of FIG. 5A and the cross-sectional view of FIG. 5B, the image recording apparatus has a plurality of flying means 5a to 5n in the liquid storage section 4 having the slits 6 of the droplet flying apparatus 1. It has the one-dimensional discharge unit 20 arranged in the shape of a comb at a pitch. A counter electrode 3 is provided opposite to the tip of the needle-like flying electrode 7 of the flying means 5a to 5n, and the recording paper conveyed by the conveying belt 68 between each flying electrode 7 and the opposed electrode 3. 17 is supplied. The flying electrodes 7 of the flying means 5a to 5n are connected to the bias power supply 13, the EW drive electrodes 9 are connected to the drive power supply 14 via the flight control sections 15a to 15n, and the corresponding flying electrodes 7 are provided. The adjacent ink 12 is charged. The flying electrodes 7 of the plurality of flying means 5 a to 5 n are integrally connected at the rear ends not arranged in the liquid reservoir 4. The connected flying electrodes 7 are preferably formed at a constant minute interval by etching.

  As shown in the perspective view of FIG. 6, the image forming apparatus 51 having the one-dimensional discharge unit 20 has a paper feed tray 52 that is mounted on the apparatus main body and accommodates recording paper, and is mounted on the apparatus main body to record an image. A paper discharge tray 53 for stocking recording paper. An upper cover 54 is provided on the upper side of the apparatus main body so as to be opened and closed. Further, one end portion of the front surface 55 of the apparatus main body has a cartridge loading portion 56 that protrudes forward and is positioned lower than the upper surface cover 54. On the upper surface of the cartridge loading portion 56, operation keys, indicators, and the like are operated. A portion 57 is provided. The cartridge loading unit 56 has a front cover 58 that can be opened and closed on the front surface thereof. By opening the front cover 58, an ink cartridge 59 that is a main tank for replenishing ink can be attached and detached.

  The mechanism of the image recording apparatus 51 may use either a carriage movement method or a line head method. As shown in the side configuration diagram of FIG. 7A and the plan configuration diagram of FIG. 7B, the carriage movement type mechanism unit includes a guide rod 61 and a stay 62 that are guide members horizontally mounted on the side plate of the apparatus main body 51. Thus, the carriage 63 is slidably held in the main scanning direction, and moved and scanned in the carriage main scanning direction by the main scanning motor. The carriage 63 has four one-dimensional ink ejection units that use the droplet flying device 1 to fly yellow (Y), cyan (C), magenta (M), and black (Bk) ink droplets. 20 is attached. Further, the carriage 63 is equipped with a sub tank 64 that is a liquid container of each color for supplying ink of each color to the one-dimensional ejection unit 20. Ink is supplied to the sub tank 64 from each ink cartridge 59. As shown in the side configuration diagram of FIG. 8A and the plan configuration diagram of FIG. 8B, the line head type mechanism unit has a one-dimensional ejection unit 20 having a width corresponding to the paper width of the recording paper 17 in the head holder 631. Are printed while moving the recording paper 17 at a constant speed.

  As a paper feed unit for feeding the recording paper 17 loaded on the paper stacking unit (pressure plate) 65 of the paper feed tray 52, the half-moon roller (feeding) the recording paper 17 from the paper stacking unit 65 separately one by one. Paper separation roller 67, and a separation pad 67 that is made of a material having a large friction coefficient and is biased toward the paper supply roller 66 side. As a transport unit for transporting the recording paper 17 fed from the paper feed tray 52 from the guide 68 to the lower side of the one-dimensional ejection unit 20, a transport belt 69 for transporting the recording paper 17 and a paper feed unit Counter roller 70 for transporting the recording paper 17 fed from the guide 67 through the conveying belt 69 and the recording paper 17 fed substantially vertically upward by turning the recording paper 17 by approximately 90 degrees. A conveyance guide 71 for following the image and a tip pressure roller 73 urged toward the conveyance belt 69 by a pressing member 72 are provided. A counter electrode 3 is provided on the back side of the transport belt 69 so as to face each flying means 5 of the one-dimensional ink discharge unit 20. The conveyance belt 69 is an endless belt, and is configured so as to be looped around the conveyance roller 74 and the tension roller 75. The conveyor belt 69 may have a two-layer structure, and the inside may be a conductive member such as a metal such as nickel. Further, when a high voltage is applied to the conductive member of the transport belt 69 from the transport roller 74, it can be used instead of the counter electrode 3.

  As a paper discharge unit for discharging the recording paper 17 recorded by the one-dimensional discharge unit 20, a separation claw 76 for separating the recording paper 17 from the conveyance belt 69, a paper discharge roller 77, and a paper discharge roller 78 are provided. A paper discharge tray 53 is provided below the paper discharge roller 77. A double-sided paper feeding unit 79 is detachably attached to the back surface of the apparatus main body 51. This double-sided paper feeding unit 79 takes in the recording paper 17 returned by the reverse rotation of the conveying belt 69, reverses it, and sends it to the conveying belt 69 again. A manual paper feed unit 80 is provided on the upper surface of the duplex paper feed unit 79.

  When printing on the recording paper 17 by this image forming apparatus, the driving control units 15a to 15a apply driving voltages to be applied to the EW driving electrodes 9 of the flying means 5a to 5n of the one-dimensional ejection unit 20 according to the image data to be printed. On / off at 15n, the ink 12 in the vicinity of each flying electrode 7 is charged and moved to the tip of the predetermined flying electrode 7 by the electrowetting phenomenon and generated at the predetermined flying electrode 7. The ink droplets 12a are caused to fly by an electric field, and land on the recording paper 17 for recording as shown in FIG. The operation speed when the ink droplet 12 a is caused to fly depends on the speed at which the ink 12 moves to the tip of the flying electrode 7 due to the electrowetting phenomenon when a drive voltage is applied to the EW drive electrode 9. The moving speed of the ink 12 varies depending on the viscosity of the ink 12. For example, if it takes 0.1 msec to move 100 μm, the printing speed corresponds to 120 ppm, and the speed can be increased.

  Thus, since the one-dimensional discharge unit 20 is constituted by the liquid reservoir 4 having the slit 6 and the plurality of flying means 5a to 5n, it is possible to reduce the size and weight with a simple structure and to move the mechanical unit. Reliability and durability can be improved because no drive unit or heating unit is required.

  In addition, since the liquid reservoir 4 is shared by the plurality of flying means 5a to 5n and the cross-sectional area including the slit 6 of the liquid reservoir 4 is increased to form the ink flow path, the ink with high viscosity can be stabilized. The ink can be supplied into the slit 6 and the printing speed can be increased and the image quality can be improved.

  Moreover, since it is not necessary to provide an individual liquid chamber for each of the plurality of flying means 5a to 5n, it can be easily manufactured and the yield at the time of manufacturing can be improved.

  Further, by arranging the one-dimensional ejection units 20 in parallel in at least two rows in a direction orthogonal to the slits 6, it is possible to cope with an increase in the size of dots and an increase in speed.

  Furthermore, by arranging the one-dimensional ejection units 20 in at least two rows and with a phase shifted by 1/2 pixel in the direction of the slit 6, high density can be achieved.

  In the above description, the case where the one-dimensional discharge unit 20 is used in the image forming apparatus has been described. However, as shown in the perspective view of FIG. 9, a plurality of flying means 5ij (i = a to n, j = a to m) are provided. You may use the two-dimensional discharge unit 21 arrange | positioned two-dimensionally.

  The image forming apparatus using the two-dimensional discharge unit 21 applies a driving voltage to the EW driving electrodes 9 of the plurality of flying units 5ij according to the image data while conveying the recording paper 17, and flashes them. By printing, the printing speed can be further increased. For example, when the conveyance speed of the recording paper 17 is 1 m / sec, the printing speed corresponds to 286 ppm, and printing can be performed at high speed.

  Further, when the viscosity of the ink 12 is high, the speed at which the ink 12 moves to the tip of the flying electrode 7 becomes slow due to the electrowetting phenomenon when the driving voltage is applied to the EW driving electrode 9. Even when the moving speed of the ink 12 is slow, as shown in the waveform diagram of FIG. 10, the pixel signal is input and the drive voltage is applied to the EW drive electrode 9 to cause the ink 12 to fly due to the electrowetting phenomenon. When the ink droplet 12a is moved by the electric field generated at the flying electrode 7 when it moves to the tip of the electrode 7, the printing speed is low even if the speed at which the ink 12 moves to the tip of the flying electrode 7 is as slow as 210 msec, for example. Can be about 286 ppm, and printing can be performed at high speed even when the high viscosity ink 12 is used.

  Further, the two-dimensional discharge unit 21 is recorded by a conveying roller pair 741 and a tension roller pair 751 provided before and after the recording area, as shown in a side configuration diagram of a mechanism portion of the image forming apparatus 51 in FIG. An image can be printed on the recording paper 17 at a high speed by providing it on the conveyance path for conveying the paper 17 and using the counter electrode 3 facing the two-dimensional ejection unit 21 as a conveyance guide for the recording paper 17. In addition, as shown in FIG. 11B, a two-dimensional discharge unit 21 is arranged in the conveyance path of the roll-shaped recording paper 17, or in the conveyance path of the roll-shaped recording paper 17, as shown in FIG. By disposing the two-dimensional discharge units 21Y, 21C, 21M, and 21Bk of yellow (Y), cyan (C), magenta (M), and black (Bk), a single color image or a full color image can be printed at high speed. In addition, the image forming apparatus can be reduced in size.

  Further, as shown in FIG. 12, for example, four two-dimensional ejection units 21A to 21D are provided in the conveyance path of the roll recording paper 17, and the first two-dimensional ejection is performed with respect to the reference position (x1, y1), for example. The unit 21A is shifted by -1/2 pixel in the X direction and the Y direction, the second two-dimensional discharge unit 21B is shifted by -1/2 pixel in the X direction and +1/2 pixel in the Y direction, and the third two-dimensional discharge unit 21C is shifted by +1/2 pixel in the X direction and −1/2 pixel in the Y direction, and the fourth two-dimensional ejection unit 21D is shifted by +1/2 pixel in the X direction and +1/2 pixel in the Y direction, By applying a drive voltage with the same pixel signal to the four two-dimensional ejection units 21A to 21D, for example, a pixel density of 600 dpi can be increased to 1200 dpi.

  In addition, as shown in FIG. 13, the two-dimensional discharge units 21 are alternately arranged on the front side and the back side along the conveyance direction of the conveyance path of the recording paper 17, so that printing can be continuously performed on both surfaces of the recording paper 17. Printing efficiency can be improved. Further, yellow (Y), cyan (C), magenta (M), and black (Bk) two-dimensional ejection units 21Y, 21C, 21M, and 21Bk are alternately arranged on the front side and the back side of the conveyance path of the recording paper 17. As a result, the drying time of the ink flying on the recording paper 17 can be secured.

  In the above description, the flying means 5 of the droplet discharge means 2 has been described as being provided independently of the liquid reservoir 4, but the flying means 5 is shown in the cross-sectional views of FIGS. May be disposed along the wall surface 4 a that forms the slit 6 of the liquid reservoir 4, and the flying means 5 may be integrated with one wall surface 4 a of the liquid reservoir 4. In this case, an EW drive electrode 9 is provided in a region on a half of the outer peripheral surface of the insulating film 8 covering the outer peripheral surface of the flying electrode 7, and the outer peripheral surface of the EW drive electrode 9 is formed on the insulating film 10 and the water repellent film 11. The region where the EW drive electrode 9 of the insulating film 8 that covers the outer peripheral surface of the flying electrode 7 is not provided is fixed along one wall surface 4 a that forms the slit 6 of the liquid reservoir 4.

  Thus, by providing the flying means 5 along one wall surface 4a forming the slit 6 of the liquid reservoir 4, the flying means 5 can be stably held and the flying means 5 can be easily held. Can do.

  14A shows a case where the entire flying electrode 7 is placed along the wall surface 4a forming the slit 6 of the liquid storage section 4, and FIG. 14B shows the tip of the flying electrode 7 that generates an electric field. The case where it leaves | separated only the fixed space from the wall surface 4a which forms the slit 6 of the liquid storage part 4 is shown. As shown in FIG. 14B, the generated electric field can be further stabilized by separating the tip of the flying electrode 7 that generates the electric field from the wall surface 4a.

  In each of the above explanations, the flying means 5 of the droplet discharge means 2 has been described in the case where the flying electrode 7 and the EW drive electrode 9 are integrally formed. However, as shown in the sectional view of FIG. A flying electrode 7 whose outer peripheral surface is covered with a water-repellent film 11 is arranged in the slit 6, and an EW drive is provided in a portion corresponding to the flying electrode 7 on both wall surfaces 4 a and 4 b forming the slit 6 of the liquid reservoir 4. An electrode 9 may be provided. In this case, the outer peripheral surface of the EW drive electrode 9 may be covered with the insulating film 10, and the water repellent film 11 may be covered except for the attachment surface of the insulating film 10 to the wall surfaces 4 a and 4 b.

  In this way, by providing the EW drive electrodes 9 on the both wall surfaces 4a and 4b forming the slit 6 of the liquid reservoir 4, the ink 12 can be efficiently moved to the tip of the flying electrode 7 by the electrowetting phenomenon. And the printing speed can be further increased.

  When forming the one-dimensional discharge unit 20 or the two-dimensional discharge unit 21, a plurality of flying electrodes 7 are integrally formed in a comb-teeth shape by etching or the like as shown in FIG. By forming the insulating film 8 on the outer peripheral surface, the flying electrode pair 22 can be easily manufactured.

  Further, as shown in FIG. 17, by sharpening the tip of each flying electrode 7, the electric field generated in each flying electrode 7 is made more stable, and the ink 12 that moves due to the electrowetting phenomenon is used for flying. It can be easily moved to the tip of the electrode 7 and the printing speed can be further increased.

  Further, as shown in FIG. 18, the EW drive electrode 9 is formed integrally with the flying electrode 7, and the water repellent film 11 is provided on both wall surfaces 4 a and 4 b forming the slit 6 of the liquid reservoir 4. Also good.

  In the above description, the case where the ink 12 in the slit 6 of the liquid reservoir 4 is moved to the tip of the flying electrode 7 by the electrowetting phenomenon has been described, but the side view of FIG. 19A and the bottom view of FIG. As shown in FIG. 4, the flying means 5 having the flying electrodes 7 instead of the slits 6 is provided with one or a plurality of U-shaped, V-shaped or spiral ink conduits 23 to store the ink stored in the liquid storage section 4. 12 may be guided to the ink guide path 23, and the ink 12 may be moved to the tip of the flying electrode 7 by an electrowetting phenomenon.

  In the above description, the rod-like flying electrode 7 is provided on the flying means 5 of the droplet flying device 1 for flying the ink droplet 12a by the one-dimensional ejection unit 20 or the two-dimensional ejection unit 21 for flying the ink droplet 12a of the image forming apparatus. Although the case where it provided was demonstrated, as shown to Fig.20 (a), the front-end | tip part arrange | positioned in the slit 6 of the liquid storage part 4 of the electrode 7 for a flight is made into a flat shape, or it shows to FIG.20 (b). As shown in FIG. 20C, the tip of the flying electrode 7 disposed in the slit 6 of the liquid reservoir 4 of the liquid reservoir 4 is cylindrical, or the slit 6 of the liquid reservoir 4 of the flying electrode 7 as shown in FIG. The tip portion arranged in the inside has a spherical shape, or the tip portion placed in the slit 6 of the liquid storage portion 4 of the flying electrode 7 has a truncated cone shape as shown in FIG. As shown in FIG. The flight electrode 7 disposed in the slit 6 of the reservoir 4 can be adopted various shapes such as a ballpoint pen shape.

It is sectional drawing which shows the structure of the droplet flying apparatus of this invention. It is sectional drawing which shows the structure of an electrode part. It is a block diagram which shows the connection of the control apparatus with respect to each power supply and flight control means. It is sectional drawing which shows the state which is making the droplet fly by a droplet flying apparatus. It is a block diagram of a one-dimensional discharge unit. 1 is a perspective view illustrating a configuration of an image forming apparatus. 2 is a configuration diagram of a mechanism unit of the image forming apparatus. FIG. It is a block diagram of the other mechanism part of an image forming apparatus. It is a perspective view which shows the structure of a two-dimensional discharge unit. It is a wave form diagram which shows operation | movement when an ink droplet is made to fly. It is a block diagram of another image forming apparatus. FIG. 10 is another layout diagram of a two-dimensional discharge unit for a roll-shaped recording sheet. FIG. 3 is a layout diagram of two-dimensional ejection units provided on the front and back of a recording paper conveyance path. It is sectional drawing which shows the structure of a 2nd droplet flight apparatus. It is sectional drawing which shows the structure of a 3rd droplet flight apparatus. It is a front view which shows the comb-shaped flight electrode. It is sectional drawing which shows the structure of a 4th droplet flight apparatus. It is sectional drawing which shows the structure of a 5th droplet flight apparatus. It is a perspective view which shows the structure of the electrode part which has the electrode for a flight provided with the ink conducting path. It is sectional drawing which shows the shape which the electrode for flight hides.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1; Droplet flight apparatus, 2; Droplet discharge means, 3; Counter electrode, 4; Liquid storage part,
5; flying means, 6; slit, 7; flying electrode, 8; insulating film, 9; driving electrode for EW,
10; insulating film, 11; water repellent film, 12; ink, 13;
14; drive power supply; 15; flight control means; 16; control device; 17; medium (recording paper);
20; one-dimensional discharge unit, 21; two-dimensional discharge unit,
22; comb-like flying electrodes; 23; ink guide; 51; image forming apparatus.

Claims (15)

An image forming apparatus including an ink droplet flying device that ejects ink droplets onto a recording medium transported along a transport path to record characters and images,
The ink droplet flying device includes an ink droplet ejection unit, and a counter electrode disposed to face the ink droplet ejection unit,
The ink droplet ejecting means includes an ink reservoir having a plurality of through holes arranged in a slit or one-dimensionally holding ink to be ejected, and a flight for ejecting the ink retained in the ink holder. Means,
The flying means is arranged in a comb-like shape in the ink holding portion and generates a plurality of flying electrodes formed in a needle shape, and an electric field is generated between the plurality of flying electrodes and the counter electrode. Means, a plurality of electrowetting drive electrodes (EW drive electrodes) provided in the ink holding unit corresponding to the flying electrodes, and the flying in the EW drive electrode and the ink reservoir. A flying control means for applying a voltage between the ink in the vicinity of the electrode and moving the ink in the ink holding portion into an electric field generated by the flying electrode of the electric field generating means by an electrowetting phenomenon;
In the state where a high voltage is applied between the flying electrode and the counter electrode by the electric field generating means, the EW drive electrode and the ink in the vicinity of each flying electrode in the ink reservoir by the flying control means An image forming apparatus, wherein a pulsed low voltage is applied between the ink droplet ejecting means and the recording medium transported between the ink droplet ejecting means and the counter electrode. An image forming apparatus including an ink droplet flying device that ejects ink droplets onto a recording medium transported along a transport path to record characters and images,
The ink droplet flying device includes an ink droplet ejection unit, and a counter electrode disposed to face the ink droplet ejection unit,
The ink droplet discharge means has an ink reservoir having a plurality of slit-like or two-dimensionally arranged through-hole ink holders for holding the ink to be ejected, and the ink retained in the ink holder And flying means
The flying means includes a plurality of flying electrodes that are two-dimensionally arranged in the ink holding portion and formed in a needle shape, and an electric field generating means that generates an electric field between the plurality of flying electrodes and the counter electrode. A plurality of electrowetting drive electrodes (EW drive electrodes) provided in the ink holding portion corresponding to the flying electrodes, and the flying electrodes in the EW drive electrode and the ink reservoir. A flying control means for applying a voltage between the ink in the vicinity of the electrode and moving the ink in the ink holding portion into an electric field generated by the flying electrode of the electric field generating means by an electrowetting phenomenon;
In the state where a high voltage is applied between the flying electrode and the counter electrode by the electric field generating means, the EW drive electrode and the ink in the vicinity of each flying electrode in the ink reservoir by the flying control means An image forming apparatus, wherein a pulsed low voltage is applied between the ink droplet ejecting means and the recording medium transported between the ink droplet ejecting means and the counter electrode.   3. The image formation according to claim 1, wherein the EW drive electrode is formed integrally with the flying electrode along an outer peripheral surface of the flying electrode, and has an insulating water-repellent film on the outer peripheral surface of the EW driving electrode. apparatus.   The image forming apparatus according to claim 1, wherein the EW drive electrode is provided on a wall surface parallel to the flying electrode of the ink holding unit.   3. The image formation according to claim 1, wherein the flying electrode is provided on a wall surface of the ink holding portion, and the EW drive electrode is provided on a wall surface facing the wall surface of the ink holding portion provided with the flying electrode. apparatus.   The image forming apparatus according to claim 1, wherein the ink holding portion includes a material that absorbs ink.   The image forming apparatus according to claim 1, wherein the plurality of flying electrodes are arranged at an image resolution pitch.   The image forming apparatus according to claim 1, wherein the viscosity of the ink stored in the ink storage unit is at least 8 mPa · s.   The voltage applied to the EW drive electrode by the flight control means is set smaller than 1/10 of the voltage applied between the flight electrode and the counter electrode by the electric field generating means. The image forming apparatus according to claim 8.   The image forming apparatus according to claim 1, wherein the ink droplet discharge units are arranged in parallel in a direction orthogonal to the plurality of through holes arranged in at least two rows in the slit shape or one dimension.   The image forming apparatus according to claim 10, wherein the at least two rows of ink droplet ejection units are arranged in different phases in the direction of the plurality of through-holes arranged in the slit shape or one-dimensionally.   The flying control means of the ink droplet flying device is a recording in which a voltage is applied between each of the EW drive electrodes and the ink in the vicinity of each of the flying electrodes in the ink reservoir according to image data. The image forming apparatus according to claim 2, which performs flash printing on a medium.   The image forming apparatus according to claim 12, wherein the ink droplet flying device is arranged for each color along a conveyance path of the recording medium.   13. The four sets of ink droplet flying devices of the same color are arranged along the recording medium transport path along the recording medium transport path, shifted by 1/2 pixel in the transport direction and in a direction orthogonal to the transport direction. Image forming apparatus. The image forming apparatus according to claim 12, wherein the ink droplet flying devices are alternately arranged along the front and back of the conveyance path of the recording medium .

Images