JP2012171301A - Liquid jetting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid jetting apparatus capable of collecting mist more surely and preventing the inside of the apparatus from being contaminated.SOLUTION: The liquid jetting apparatus includes: a platen loading electric voltage forming part which forms an electric field between a platen and a nozzle forming face of a recording head 2 by loading an electric voltage on the platen 5; a mist collecting part 13 which is arranged at a position being the outside of an ink jetting region on the platen where ink is jetted to recording paper 6 from the recording head; and a collecting part loading electric voltage forming part which loads an electric voltage on the mist collecting part. On the mist collecting part, an electric voltage opposite to the polarity of the loaded electric voltage on the platen is loaded.

Description

  The present invention relates to a liquid ejecting apparatus such as an ink jet recording apparatus, and more particularly to a liquid ejecting apparatus that ejects liquid in a pressure chamber from a nozzle by driving a pressure generating unit.

  The liquid ejecting apparatus includes a liquid ejecting head and ejects various liquids from the ejecting head. As this liquid ejecting apparatus, for example, there is an image recording apparatus such as an ink jet printer or an ink jet plotter, but recently, various types of manufacturing have been made by taking advantage of the ability to accurately land a very small amount of liquid on a predetermined position It is also applied to devices. For example, a display manufacturing apparatus for manufacturing a color filter such as a liquid crystal display, an electrode forming apparatus for forming an electrode such as an organic EL (Electro Luminescence) display or FED (surface emitting display), a chip for manufacturing a biochip (biochemical element) Applied to manufacturing equipment. The recording head for the image recording apparatus ejects liquid ink, and the color material ejecting head for the display manufacturing apparatus ejects solutions of R (Red), G (Green), and B (Blue) color materials. The electrode material ejecting head for the electrode forming apparatus ejects a liquid electrode material, and the bioorganic matter ejecting head for the chip manufacturing apparatus ejects a bioorganic solution.

  In recent years, recording heads used in the above printers tend to reduce the amount of ink ejected from nozzles in order to meet demands for image improvement and the like. In order to land such a small amount of droplets reliably on the recording medium, the initial velocity of the droplets is set to be relatively high. As a result, the droplets ejected from the nozzle are stretched during the flight, and separated into a leading main droplet (main droplet) and a satellite droplet (sub-droplet) after that. Some or all of the satellite droplets may suddenly decrease in speed due to the viscous resistance of air, and may become mist without reaching the recording medium. For this reason, the mist-like satellite droplets (ink mist) contaminate the inside of the apparatus and cause a malfunction due to adhesion to easily charged members such as a recording head and an electric circuit.

  In order to prevent such problems, the droplets ejected from the nozzles are charged, and the nozzle forming surface of the recording head and the support member (or platen or substrate) that supports the recording medium during recording are used. Attempts have been made to actively attract droplets to a support member and land on a recording medium by forming an electric field (see, for example, Patent Document 1 or Patent Document 2).

JP 10-278252 A JP 2004-202867 A

  However, as shown in the schematic diagram of FIG. 7A, in the process in which the ink ejected from the nozzles 64 of the recording head extends toward the recording medium P and the supporting member 65, the static electricity from the supporting member 65 charged positively. Due to the electrical induction, negative charges are induced in the leading portion (the portion that becomes the main liquid droplet Md) near the support member 65, while in the rear end portion near the nozzle 64 opposite to this, A positive charge is induced. Then, as shown in FIG. 7B, the ink ejected from the nozzle is separated into, for example, a main droplet Md, a first satellite droplet Sd1, and a second satellite droplet (mist) Sd2. In this case, the main droplet Md is negatively charged, the second satellite droplet Sd2 is positively charged, and the first satellite droplet Sd1 is uncharged. In this case, even if the main droplet Md and the first satellite droplet Sd1 land on the recording medium P, the second satellite droplet Sd2 reacts with the positively charged support member 65 and stalls, forming a nozzle. Mist drifts near the surface. Part of this mist adheres to the nozzle forming surface. When mist adheres to the nozzle forming surface, it is necessary to periodically wipe the nozzle forming surface with a wiping member. Further, the mist that has not adhered to the nozzle forming surface may adhere to and contaminate the printer component having a polarity different from that of the mist.

  The phenomenon as described above is not limited to the piezoelectric vibrator, and similarly occurs in other pressure generating means that operate by applying a driving voltage, such as a heating element.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a liquid ejecting apparatus that can collect mist more reliably and prevent contamination in the apparatus. is there.

The liquid ejecting apparatus of the present invention has been proposed in order to achieve the above-described object, and is connected to the nozzle by being driven by application of a drive signal and a nozzle forming surface on which a nozzle for ejecting liquid is formed. A liquid ejecting head having pressure generating means for causing pressure fluctuation in the liquid in the pressure chamber, and ejecting the liquid from the nozzle toward the landing target by driving the pressure generating means;
Drive signal generating means for generating a drive signal for driving the pressure generating means;
A support unit that is disposed at an interval with respect to the nozzle formation surface of the liquid jet head when performing the jetting operation, and supports the landing target;
First voltage applying means for forming an electric field between the supporting means and the nozzle forming surface by applying a voltage to the supporting means;
Droplet collecting means disposed on the outer side in the moving direction of the liquid ejecting head than the ejecting area in the support means for ejecting liquid from the liquid ejecting head to the landing target;
Second voltage applying means for applying a voltage to the droplet collecting means;
With
The front second voltage applying means applies a voltage having a polarity opposite to that applied to the supporting means to the droplet collecting means.

  According to the present invention, even when the liquid is ejected from the nozzle in a state where an electric field is formed between the nozzle forming surface of the liquid ejecting head and the support means, the mist generated due to the ejection of the liquid is more reliably generated. It is possible to collect. That is, the mist generated by separating the liquid ejected from the nozzle is charged to a polarity opposite to the charging polarity of the support means by electrostatic induction from the support means, but the mist is a voltage applied to the support means. Is attracted by the electrostatic force from the droplet collecting means charged with the opposite polarity, and landed on the droplet collecting means to be collected. Thereby, it is reduced that these mist adheres to the components (for example, a drive motor, a drive belt, a linear scale, etc.) in an apparatus. As a result, failure due to mist adhesion is suppressed, and durability and reliability of the liquid ejecting apparatus are improved.

  Further, in the above configuration, the electric field formed between the droplet collecting means and the nozzle forming surface by the second voltage applying means is generated by the first voltage applying means by the supporting means and the nozzle forming. It is desirable to employ a configuration that is set stronger than the electric field formed between the two surfaces.

  According to this configuration, the electrostatic force from the droplet collecting means acts on the mist that is relatively weakly charged and can be collected by the droplet collecting means.

  In each of the above-described configurations, it is desirable that the droplet collecting means adopts a configuration that receives the ejected liquid during a recovery process that suppresses the thickening of the liquid by ejecting the liquid from the nozzle.

  According to this configuration, there is no need to separately provide the receiving portion for recovery processing and the droplet collecting means, which can contribute to space saving of the apparatus.

  In this configuration, the second voltage applying unit adopts a configuration in which a voltage is applied to the droplet collecting unit only in a state where the nozzle forming surface of the liquid jet head and the droplet collecting unit face each other. It is desirable.

  According to this configuration, since the voltage is applied to the droplet collecting means only in a state where the nozzle forming surface of the liquid ejecting head and the droplet collecting means are opposed to each other, the liquid ejecting head is liquid to the landing target. During the jetting, the charging liquid does not affect the jetted liquid. In addition, since no voltage is applied to the absorber until the nozzle formation surface faces the droplet collecting means, the liquid ejecting head moves in the width direction of the landing target (head moving direction) on the way to the droplet collecting means. ) Is prevented from adhering to the end portion of).

  In the above configuration, it is desirable to employ an absorbing material that absorbs droplets as the droplet collecting means.

  The said structure can employ | adopt the structure which consists of a raw material which shows the reverse polarity with respect to the voltage applied to a support means.

  According to this configuration, since the absorbent material itself is charged with a polarity opposite to the voltage applied to the support means, a power source for charging the absorbent material is not required, and the mist collecting effect can be achieved with a simpler configuration. can get.

  In the above-described configuration, it is desirable to employ a configuration in which the support means is located outside the injection region and is disposed outside the end portion of the landing target having the maximum width that can be handled.

  According to this configuration, while the liquid ejecting head ejects the liquid onto the landing target, it is possible to more reliably prevent the influence of charging from the droplet collecting means on the ejected liquid.

FIG. 3 is a perspective view illustrating a configuration of a printer. FIG. 3 is a cross-sectional view of a main part of the recording head. It is sectional drawing explaining the structure of a piezoelectric vibrator. FIG. 2 is a block diagram illustrating an electrical configuration of a recording head. It is a wave form diagram explaining the structure of the ejection drive pulse of a drive signal. It is a schematic diagram explaining the collection of mist. FIG. 6 is a schematic diagram illustrating a state in which ink ejected from a nozzle is charged in a configuration in which an electric field is formed between the nozzle and a support member.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. In the embodiments described below, various limitations are made as preferred specific examples of the present invention. However, the scope of the present invention is not limited to the following description unless otherwise specified. However, the present invention is not limited to these embodiments. In the following, an ink jet recording apparatus (hereinafter referred to as a printer) will be described as an example of the liquid ejecting apparatus of the invention.

  FIG. 1 is a perspective view showing the configuration of the printer 1. The printer 1 is provided with a recording head 2 as a kind of liquid ejecting head and a carriage 4 to which an ink cartridge 3 as a kind of liquid supply source is detachably attached, and below the recording head 2 during a recording operation. The arranged platen 5, the carriage 4 that moves the carriage 4 back and forth in the paper width direction of the recording paper 6 (recording medium and landing target), that is, the main scanning direction, and the sub-scanning orthogonal to the main scanning direction A transport mechanism 8 for transporting the recording paper 6 in the direction.

  The carriage 4 is attached while being supported by a guide rod 9 installed in the main scanning direction, and is configured to move in the main scanning direction along the guide rod 9 by the operation of the carriage moving mechanism 7. ing. The position of the carriage 4 in the main scanning direction is detected by the linear encoder 10, and a detection signal, that is, an encoder pulse (a kind of position information) is transmitted to the printer controller 51 (see FIG. 4). The linear encoder 10 is a kind of position information output means, and outputs an encoder pulse EP corresponding to the scanning position of the recording head 2 as position information in the main scanning direction.

  A home position serving as a base point for scanning of the carriage is set in an end area outside the recording area within the movement range of the carriage 4. A capping member 11 for sealing the nozzle forming surface (nozzle plate 24: see FIG. 2) of the recording head 2 and a wiper member 12 for wiping the nozzle forming surface are disposed at the home position in the present embodiment. Yes. The printer 1 is bi-directional between when the carriage 4 moves from the home position toward the opposite end and when the carriage 4 returns from the opposite end to the home position. So-called bidirectional recording in which characters, images, etc. are recorded on the recording paper 6 is possible.

  The platen 5 is a plate-like member that is long in the main scanning direction, and a plurality of support protrusions 5a protrude from the surface of the platen 5 at predetermined intervals along the longitudinal direction. Each support protrusion 5a protrudes above the platen surface (on the recording head 2 side during recording operation). The upper surface of each support protrusion 5a serves as an abutting surface that supports the recording paper 6, and partially supports the rear surface of the recording paper 6 (the surface opposite to the recording surface on which ink is landed). In addition, an ink absorbing material 5b is disposed on the surface of the platen 5 at a portion that is separated from each support protrusion 5a. The ink absorbing material 5b is made of a porous member having a liquid absorbing property made of, for example, felt or urethane sponge. At least a part of the platen 5 in the present embodiment is made of a conductive material. For example, the platen 5 is made conductive by including a conductive material such as carbon in the material of the platen 5 body. Alternatively, the ink absorbing material 5b may be made conductive by including a conductive material in the material of the ink absorbing material 5b. A voltage from a platen application voltage generation unit 58, which will be described later, is applied to the platen 5 (when the ink absorber 5b is conductive, the ink absorber 5b). Details of this point will be described later.

  Further, the end of the platen 5 in the main scanning direction, specifically, a region outside the region where the ink is ejected onto the recording paper 6 (ink ejection region) on the platen 5, more specifically, from the ink ejection region. Is an area outside the main scanning direction, and is the end in the width direction (maximum recording paper width) of the recording paper 6 when the maximum size recording paper 6 that can be handled by the printer 1 is arranged on the platen 5. A mist collecting section 13 that collects mist generated when ink is ejected from the recording head 2 is provided at a position on the outer side (see FIG. 6). The mist collecting unit 13 is desirably provided on both sides of the platen 5 in the main scanning direction, but may be provided on at least one side. The mist collection part 13 in this embodiment is formed in the box shape from the member which has insulation. A mist absorbing material 14 (corresponding to the absorbing material in the present invention) is disposed on the upper surface of the mist collecting portion 13. The mist absorbing material 14 is formed by including a conductive material such as carbon in a liquid-absorbing porous member made of, for example, urethane sponge. And it is comprised so that the voltage from the collection part application voltage generation part 59 mentioned later may be applied to the mist absorber 14. Details of this point will be described later. Since the mist collecting section 13 (more specifically, the mist absorbing material 14) is charged by applying a voltage, the mist collecting section 13 is disposed on the recording paper 6 by placing the mist collecting section 13 at the above-described position. On the other hand, when ink is ejected from the recording head 2, the influence of charging from the mist collecting unit 13 on the ejected ink can be prevented. In addition, the mist collecting unit 13 ejects ink from the nozzles 30 separately from the ink ejection (that is, the printing process) to the recording paper 6, thereby performing a recovery process (flushing) that suppresses the viscosity increase of the ink in the recording head 2. In the case of (processing), it also serves as a receiving portion (flushing point) for receiving the ejected ink. For this reason, it can contribute to the space-saving in a printer.

  FIG. 2 is a cross-sectional view of a main part for explaining the configuration of the recording head 2. The recording head 2 includes a case 15, a vibrator unit 16 accommodated in the case 15, a flow path unit 17 joined to the bottom surface (tip surface) of the case 15, a cover member 45, and the like. . The case 15 is made of, for example, an epoxy-based resin, and a storage space 18 for storing the vibrator unit 16 is formed in the case 15. The vibrator unit 16 includes a piezoelectric vibrator 20 that functions as a kind of pressure generating means, a fixed plate 21 to which the piezoelectric vibrator 20 is joined, and a flexible cable 22 that supplies a drive signal to the piezoelectric vibrator 20. ing.

  FIG. 3 is a cross-sectional view in the element longitudinal direction illustrating the configuration of the vibrator unit 16. As shown in the figure, the piezoelectric vibrator 20 is a laminated piezoelectric vibrator formed by alternately laminating a piezoelectric body 41 with a common internal electrode 39 and individual internal electrodes 40. Here, the common internal electrode 39 is an electrode common to all the piezoelectric vibrators 20 and is set to the ground potential. The individual internal electrode 40 is an electrode whose potential varies according to the ejection drive pulse DP (see FIG. 5) of the applied drive signal. In this embodiment, the free end portion 20a is a portion of the piezoelectric vibrator 20 from the vibrator tip to about half or about two thirds of the vibrator longitudinal direction (direction orthogonal to the stacking direction). Yes. The remaining part of the piezoelectric vibrator 20, that is, the part from the base end of the free end 20a to the vibrator base end is a base end 20b.

  An active region (overlap portion) A in which the common internal electrode 39 and the individual internal electrode 40 overlap each other is formed at the free end 20a. When a potential difference is applied to these internal electrodes 39, 40, the piezoelectric body 41 in the active region A is activated and deformed, and the free end 20a is displaced in the longitudinal direction of the vibrator to expand and contract. The base end of the common internal electrode 39 is electrically connected to the common external electrode 42 at the base end face portion of the piezoelectric vibrator 20. On the other hand, the tip of the individual internal electrode 40 is electrically connected to the individual external electrode 43 at the tip surface portion of the piezoelectric vibrator 20. Note that the distal end of the common internal electrode 39 is positioned slightly in front of the distal end surface portion of the piezoelectric vibrator 20 (base end surface side), and the proximal end of the individual internal electrode 40 is the boundary between the free end portion 20a and the proximal end portion 20b. Is located.

  The individual external electrodes 43 (corresponding to the drive electrodes in the present invention) are arranged in series on the tip surface portion of the piezoelectric vibrator 20 and a wiring connection surface (upper surface in FIG. 3) which is one side surface of the piezoelectric vibrator 20 in the stacking direction. The wiring pattern of the flexible cable 22 as a wiring member and each individual internal electrode 40 are electrically connected. And the part by the side of the wiring connection surface of this separate external electrode 43 is continuously formed toward the front end side from the base end part 20b. The common external electrode 42 is formed on the base end face portion of the piezoelectric vibrator 20, the above-described wiring connection face, and a fixing plate mounting face (lower face in FIG. 3) which is the other side face of the piezoelectric vibrator 20 in the stacking direction. These are electrodes formed in series, and conduct between the wiring pattern of the flexible cable 22 and each common internal electrode 39. The portion on the wiring connection surface side of the common external electrode 42 is continuously formed from a little before the end portion of the individual external electrode 43 toward the base end surface portion side, and the portion on the fixed portion mounting surface side is It is continuously formed from a position slightly ahead of the distal end surface portion of the vibrator toward the proximal end side.

  The base end portion 20b is a non-operation portion that does not expand and contract even when the piezoelectric body 41 in the active region A is operated. The flexible cable 18 is disposed on the wiring connection surface side of the base end portion 20b, and the individual external electrode 43 and the common external electrode 42 and the flexible cable 22 are electrically connected on the base end portion 20b. A drive signal is applied to each individual external electrode 43 through the flexible cable 22.

  The flow path unit 17 is configured by joining a nozzle plate 24 to one surface of the flow path forming substrate 23 and a diaphragm 25 to the other surface of the flow path forming substrate 23. The flow path unit 17 is provided with a reservoir 26 (common liquid chamber), an ink supply port 27, a pressure chamber 28, a nozzle communication port 29, and a nozzle 30. A series of ink flow paths from the ink supply port 27 to the nozzle 30 through the pressure chamber 28 and the nozzle communication port 29 are formed corresponding to each nozzle 30.

  The nozzle plate 24 is a thin plate made of metal such as stainless steel in which a plurality of nozzles 30 are formed in a row at a pitch (for example, 180 dpi) corresponding to the dot formation density. The nozzle plate 24 is provided with a plurality of nozzle rows (nozzle groups) by arranging nozzles 30, and one nozzle row is composed of, for example, 180 nozzles 30. The surface of the nozzle plate 24 on the side where ink is ejected corresponds to the nozzle formation surface in the present invention.

  The diaphragm 25 has a double structure in which an elastic film 32 is laminated on the surface of the support plate 31. In the present embodiment, the vibration plate 25 is manufactured using a composite plate material in which a stainless steel plate, which is a kind of metal plate, is used as the support plate 31 and a resin film is laminated on the surface of the support plate 31 as an elastic film 32. The diaphragm 25 is provided with a diaphragm 33 that changes the volume of the pressure chamber 28. The diaphragm 25 is provided with a compliance portion 34 that seals a part of the reservoir 26.

  The diaphragm 33 is produced by partially removing the support plate 31 by etching or the like. That is, the diaphragm portion 33 includes an island portion 35 to which the tip end surface of the free end portion 20 a of the piezoelectric vibrator 20 is joined, and a thin elastic portion 36 surrounding the island portion 35. The compliance part 34 is produced by removing the support plate 31 in the region facing the opening surface of the reservoir 26 by etching processing or the like in the same manner as the diaphragm part 33, and the pressure fluctuation of the liquid stored in the reservoir 26 is reduced. Functions as a damper to absorb.

  Since the tip surface of the piezoelectric vibrator 20 is joined to the island portion 35, the volume of the pressure chamber 28 can be changed by expanding and contracting the free end portion 20a of the piezoelectric vibrator 20. As the volume changes, pressure fluctuations occur in the ink in the pressure chamber 28. The recording head 2 ejects ink from the nozzles 30 using this pressure fluctuation.

  The cover member 45 is a member that protects the side surface of the flow path unit 17 and the side surface of the head case 41, and is made of a conductive plate material such as stainless steel. A part of the cover member 45 in this embodiment is in contact with the peripheral portion of the nozzle forming surface in a state where the nozzle 30 of the nozzle plate 24 is exposed, and is electrically connected to the nozzle plate 24. . The cover member 45 is grounded, and is brought into contact with the nozzle plate 24 so as to be conductive. For example, static electricity generated from the recording paper 6 or the like is transmitted through the nozzle plate 24, damage to the driving IC, or the like. It is designed to prevent charging.

Next, the electrical configuration of the printer 1 will be described.
FIG. 4 is a block diagram illustrating the electrical configuration of the printer 1. The external device 50 is an electronic device that handles images, such as a computer or a digital camera. The external device 50 is communicably connected to the printer 1 and transmits print data corresponding to the image or the like to the printer 1 so that the printer 1 prints an image or text on a recording medium such as the recording paper 6. .

  The printer 1 in the present embodiment includes a transport mechanism 8, a carriage moving mechanism 7, a linear encoder 10, a recording head 2, a platen 5, a mist collecting unit 13, and a printer controller 51.

  The printer controller 51 is a control unit for controlling each part of the printer. The printer controller 51 includes an interface (I / F) unit 54, a CPU 55, a storage unit 56, a drive signal generation unit 57, and a collection unit applied voltage generation unit 59. The interface unit 54 transmits and receives printer status data such as sending print data and a print command from the external device 50 to the printer 1 and receiving the status information of the printer 1 from the external device 50. The CPU 55 is an arithmetic processing unit for controlling the entire printer. The memory | storage part 56 is an element which memorize | stores the data used for the program and various control of CPU55, and contains ROM, RAM, and NVRAM (nonvolatile memory element). The CPU 55 controls each unit according to a program stored in the storage unit 56.

  The CPU 55 functions as a timing pulse generator that generates a timing pulse PTS from the encoder pulse EP output from the linear encoder 10. Then, the CPU 55 controls the transfer of print data, the generation of the drive signal COM by the drive signal generation unit 57, and the like in synchronization with the timing pulse PTS. Further, the CPU 55 generates a timing signal such as a latch signal LAT based on the timing pulse PTS and outputs the timing signal to the head controller 53 of the recording head 2. The head controller 53 controls the application of the ejection drive pulse DP (see FIG. 5) of the drive signal COM to the piezoelectric vibrator 20 of the recording head 2 based on the head control signal (print data and timing signal) from the printer controller 51. I do.

  The platen application voltage generator 58 (corresponding to the first voltage application means in the present invention) functions as a power source that generates a voltage to be applied to the platen 5. In this embodiment, by applying a voltage having the same polarity as the polarity of the drive signal to the platen 5, the platen 5 is added, that is, the individual external electrode 43 when driving the piezoelectric vibrator 20. Charge to the same polarity as the polarity. Since the nozzle plate 24 is grounded as described above, an electric field corresponding to the voltage applied to the platen 5 and the distance between the platen 5 and the nozzle plate 24 is formed between the platen 5 and the nozzle plate 24. Is done.

  The collector application voltage generator 59 (corresponding to the second voltage application means in the present invention) is a power source that generates a voltage to be applied to the mist absorbent 14 of the mist collector 13. The mist absorbing material 14 is negatively charged by applying a voltage having a polarity opposite to the voltage applied to the platen 5, that is, a negative voltage in this embodiment. It is configured to let you. The collection unit applied voltage generation unit 59 is controlled to be turned on / off by the CPU 55. Specifically, the recording head 2 is moved above the mist collecting portion 13 so that the nozzle forming surface and the mist absorbing material 14 face each other (the state where both overlap in a plane parallel to the nozzle forming surface). When this occurs, the collector application voltage generator 59 is switched on. As a result, a voltage is applied to the mist absorber 14 and an electric field is formed between the mist absorber 14 and the nozzle formation surface of the recording head. The strength of the electric field is set to be higher than the strength of the electric field formed between the platen 5 and the nozzle formation surface of the recording head 2 by applying a voltage to the platen 5 by the platen applied voltage generator 58. . Thereby, the electrostatic force from the mist absorbent 14 can act on the mist that is relatively weakly charged, and can be collected in the mist absorbent 14. When the recording head 2 moves to the ink ejection region side of the platen 5 and the nozzle forming surface does not face the mist collecting unit 13 (does not overlap in a plan view), the collecting unit applied voltage generation unit 59 Is switched off. As a result, no voltage is applied to the mist absorber 14.

  The drive signal generator 57 generates an analog voltage signal based on waveform data relating to the waveform of the drive signal. The drive signal generator 57 amplifies the voltage signal to generate the drive signal COM. This drive signal COM is applied to the piezoelectric vibrator 20 which is a pressure generating means of the recording head 2 at the time of printing processing (recording processing or jetting processing) on the recording medium. 6 is a series of signals including at least one injection driving pulse DP shown in FIG. Here, the ejection drive pulse DP is for causing the piezoelectric vibrator 20 to perform a predetermined operation in order to eject ink droplets from the nozzles 30 of the recording head 2.

  FIG. 5 is a waveform diagram showing an example of the configuration of the ejection drive pulse DP included in the drive signal COM. In FIG. 5, the vertical axis represents potential and the horizontal axis represents time. In addition, the ejection drive pulse DP has an expansion element p1 that expands the pressure chamber 28 by changing the potential from the reference potential (intermediate potential) Vb to the maximum potential (maximum voltage) Vmax, and maintains the maximum potential Vmax for a certain period of time. The expansion maintaining element p2, the contraction element p3 for rapidly contracting the pressure chamber 28 by changing the potential from the maximum potential Vmax to the minimum potential (minimum voltage) Vmin, and the contraction maintaining for maintaining the minimum potential Vmin for a certain time. (Vibration hold) element p4 and a return element p5 for returning the potential from the minimum potential Vmin to the reference potential Vb are included. The ejection drive pulse DP in the present embodiment has a positive voltage waveform as a whole because the minimum potential (minimum voltage) Vmin is 0 or more, but for example, in relation to the bias voltage applied to the common external electrode 42, The structure which shows a negative value partially may be sufficient. In this case, the voltage of the ejection drive pulse DP is assumed to be positive on average.

  When the ejection drive pulse DP is applied to the piezoelectric vibrator 20, it operates as follows. First, the piezoelectric vibrator 20 is contracted by the expansion element p1, and the pressure chamber 28 is expanded from the reference volume corresponding to the reference potential Vb to the maximum volume corresponding to the maximum potential Vmax. Thereby, the meniscus exposed to the nozzle 30 is drawn into the pressure chamber side. The expansion state of the pressure chamber 28 is maintained constant throughout the application period of the expansion maintaining element p2. When the contraction element p3 is applied to the piezoelectric vibrator 20 subsequent to the expansion maintaining element p2, the piezoelectric vibrator 20 expands, whereby the pressure chamber 28 has a minimum volume corresponding to the minimum potential Vmin from the maximum volume. Shrinks rapidly until The ink in the pressure chamber 28 is pressurized by the rapid contraction of the pressure chamber 28, and thereby, several pl to several tens pl of ink is ejected from the nozzle 30. The contraction state of the pressure chamber 28 is maintained for a short time over the application period of the contraction maintaining element p4, and then the damping element p5 is applied to the piezoelectric vibrator 20 so that the pressure chamber 28 corresponds to the minimum potential Vmin. The volume returns to the reference volume corresponding to the reference potential Vb.

  In the printer 1 according to the present invention, for example, when a small ink droplet of several pl (several ng) is ejected, or a recording method for recording an image or the like without a margin on the recording surface of the recording paper 6 (so-called edge). Even in the case of performing (non-printing), the ink droplets (mainly main droplets) ejected from the nozzles 30 are configured to land more reliably on the recording paper 6 on the platen 5. Specifically, by applying a voltage to the platen 5 and ejecting ink from the nozzles 30 in a state where an electric field is formed between the platen 5 and the nozzle formation surface of the recording head 2, the ejected ink droplets are ejected. The main liquid droplets are mainly attracted to the recording paper 6 by the electrostatic force and landed more reliably.

  In the printer 1 according to the present invention, a problem caused by ejecting ink in a state where an electric field is formed between the platen 5 and the nozzle formation surface of the recording head 2, that is, an ink droplet ejected from the nozzle 30 is generated. The mist generated during the flight is charged to a polarity opposite to that of the main liquid droplet by electrostatic induction (same polarity as the charging polarity of the platen 5), and thus repels the platen 5 and drifts in the atmosphere. In order to solve the problem, the mist is positively adsorbed to the mist absorbent 14 by applying a voltage having a polarity opposite to the voltage applied to the platen 5 to the mist absorbent 14 of the mist collector 13. It is configured as follows.

FIG. 6 is a schematic diagram for explaining mist collection. In FIG. 6A, the recording head 2 is shown as a partial sectional view.
As described above, the nozzle plate 24 is grounded through the cover member 45, while the platen 5 is positively charged by the application of the voltage from the platen application voltage generator 58. Thereby, a potential difference is generated between the platen 5 and the nozzle plate 24 to form an electric field. In this state, the ink droplets ejected from the nozzles 30 are electrostatically induced from the positively charged platen 5 until landing on the recording paper 6, so that the leading portion on the side close to the platen 5 (the main droplet Md and the main droplet Md). On the other hand, a negative charge is induced, while a positive charge is induced in the rear end portion on the side close to the nozzle 30 opposite to this. When the ink ejected from the nozzle 30 is separated into, for example, the main liquid droplet Md, the satellite liquid droplet Sd, and the mist Ms, the main liquid droplet Md at the head portion is negatively charged and the satellite liquid at the central portion is charged. The droplet Sd is almost uncharged, and the mist Ms corresponding to the rear end portion is positively charged. Since the inertia force at the time of jetting and the electrostatic force from the platen 5 act on the main droplet Md, the main droplet Md is attracted to the recording paper 6 and landed by these combined forces. Further, although the electrostatic force from the platen 5 hardly acts on the satellite droplet Sd, it reaches the recording paper 6 by the inertial force at the time of ejection. However, since the mist Ms is charged to the opposite polarity to the platen 5 and has a very small mass compared to the main droplet Md and the satellite droplet Sd, the mist Ms repels the platen 5 and moves toward the recording paper 6. Stall and drift near the nozzle formation surface.

  The mist Ms moves with the recording head 2 due to the negative pressure generated by the movement of the recording head 2. Then, as shown in FIG. 6B, the recording head 2 moves over the ink ejecting area of the platen 5 and the maximum recording paper width to above the mist collecting section 13, and the nozzle forming surface becomes the mist absorbing material 14. When facing each other, a negative voltage is applied to the mist absorbent 14 from the collector application voltage generator 59, and the mist absorbent 14 is negatively charged. As a result, the mist having a positive charge floating in the vicinity of the recording head 2 is adsorbed and collected by the mist absorber 14 by electrostatic force. As described above, when the recording head 2 moves to the ink ejection region side of the platen 5 and the nozzle forming surface does not face the mist absorbing material 14, a voltage is applied to the mist absorbing material 14. It becomes a state that is not. For this reason, while the recording head 2 ejects ink onto the recording paper 6, the ejected ink is not affected by the charging of the mist absorbing material 14. Further, since no voltage is applied to the mist absorbing material 14 until the nozzle forming surface faces the mist absorbing material 14, the recording head 2 is moved toward the mist collecting portion 13 in the width direction end of the recording paper 6. It is prevented that mist adheres to the part.

  By adopting the above configuration, even in a configuration in which ink is ejected from the nozzles 30 of the recording head 2 with an electric field formed between the nozzle formation surface of the recording head 2 and the platen 5, the ejection of the ink is performed. It is possible to more reliably collect the mist generated along with this, and the mist is less likely to adhere to components in the printer (for example, components that are easily charged such as a drive motor, a drive belt, and a linear scale). . As a result, failure due to mist adhesion is suppressed, and durability and reliability of the printer 1 are improved.

  By the way, the present invention is not limited to the above-described embodiment, and various modifications can be made based on the description of the scope of claims.

  For example, in each of the above embodiments, the configuration in which the main droplet Md is negatively charged and the mist Ms is positively charged among the ink ejected from the nozzle 30 by charging the platen 5 positively is exemplified. However, it is not limited to this. For example, by applying a negative voltage to the platen 5 to charge the platen 5 negatively, the main droplet Md of the ink ejected from the nozzle 30 is positively charged and the mist Ms is negatively charged. Even in this case, the present invention can be applied. In this case, the ink absorbing material 14 is charged to a polarity opposite to the polarity of the voltage applied to the platen 5 (that is, in this case, plus), so that mist is applied to the ink absorbing material 14 in the same manner as in the above embodiment. Can be collected.

  In addition, regarding the mist collecting unit 13, in the above embodiment, the configuration in which the mist absorbing material 14 is charged by applying a voltage to the conductive mist absorbing material 14 is exemplified, but the invention is not limited thereto. As the mist absorbing material 14, a material having a polarity opposite to the polarity of the voltage applied to the platen 5 in the charging train can be used. For example, as the material exhibiting negative polarity in the charge train, a sponge made of silicone, polypropylene, or polyvinyl chloride can be used. In addition, as a material exhibiting positive polarity in the charge train, a nylon sponge, a wool absorbent material, or the like can be employed. According to this configuration, since the mist absorbing material 14 itself is charged to a polarity opposite to the polarity of the applied voltage to the platen 5, a power source such as the collecting unit applied voltage generating unit 59 is not required, and the mist can be configured with a simpler configuration. The collection effect is obtained.

  Furthermore, in each of the above-described embodiments, the so-called longitudinal vibration type piezoelectric vibrator 20 is exemplified as the pressure generating means. However, the present invention is not limited to this, and for example, a so-called flexural vibration type piezoelectric vibrator 20 may be employed. is there. In this case, the waveform of the drive signal (ejection drive pulse DP) illustrated in FIG. 5 is a waveform in which the direction of potential change, that is, the top and bottom are inverted. In addition, the pressure generation means includes a heating element that causes pressure fluctuations by causing ink to boil by heat generation, an electrostatic actuator that causes pressure fluctuations by displacing the partition walls of the pressure chamber by electrostatic force, etc. The present invention can also be applied to a configuration employing pressure generating means driven by application.

  Furthermore, the present invention is not limited to a printer as long as it is a liquid ejecting apparatus capable of controlling the ejection of liquid using a pressure generating means, and various ink jet recording apparatuses and recording apparatuses such as a plotter, a facsimile machine, and a copying machine. The present invention can also be applied to other liquid ejecting apparatuses such as a display manufacturing apparatus, an electrode manufacturing apparatus, and a chip manufacturing apparatus. In the display manufacturing apparatus, a solution of each color material of R (Red), G (Green), and B (Blue) is ejected from the color material ejecting head. Moreover, in an electrode manufacturing apparatus, a liquid electrode material is ejected from an electrode material ejection head. In the chip manufacturing apparatus, a bioorganic solution is ejected from a bioorganic ejecting head.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 2 ... Recording head, 5 ... Platen, 6 ... Recording paper, 13 ... Mist collection part, 14 ... Mist absorber, 20 ... Piezoelectric vibrator, 24 ... Nozzle plate, 28 ... Pressure chamber, 30 ... Nozzle , 42 ... common external electrode, 43 ... individual external electrode, 57 ... drive signal generator, 58 ... platen application voltage generator, 59 ... collector application voltage generator

Claims (7)

A nozzle forming surface on which nozzles for ejecting liquid are formed, and pressure generating means that is driven by application of a drive signal to cause pressure fluctuations in the liquid in the pressure chamber that communicates with the nozzles. A liquid ejecting head that ejects liquid from the nozzle toward the landing target by driving;
Drive signal generating means for generating a drive signal for driving the pressure generating means;
A support unit that is disposed at an interval with respect to the nozzle formation surface of the liquid jet head when performing the jetting operation, and supports the landing target;
First voltage applying means for forming an electric field between the supporting means and the nozzle forming surface by applying a voltage to the supporting means;
Droplet collecting means disposed at a position outside the ejection region in the support means for ejecting liquid from the liquid ejecting head to the landing target;
Second voltage applying means for applying a voltage to the droplet collecting means;
With
The liquid ejecting apparatus according to claim 2, wherein the second voltage applying unit applies a voltage having a polarity opposite to a voltage applied to the supporting unit to the droplet collecting unit.   The electric field formed between the droplet collecting means and the nozzle formation surface by the second voltage application means is formed between the support means and the nozzle formation surface by the first voltage application means. The liquid ejecting apparatus according to claim 1, wherein the liquid ejecting apparatus is set to be stronger than the applied electric field.   The liquid droplet collecting means receives the ejected liquid during a recovery process for suppressing the increase in the viscosity of the liquid by ejecting the liquid from the nozzle. The liquid ejecting apparatus described.   2. The second voltage applying unit applies a voltage to the droplet collecting unit only in a state where a nozzle forming surface of the liquid jet head and the droplet collecting unit face each other. The liquid ejecting apparatus according to claim 3.   5. The liquid ejecting apparatus according to claim 1, wherein the droplet collecting unit includes an absorbing material that absorbs the droplet.   The liquid ejecting apparatus according to claim 5, wherein the absorbent material is made of a material having a polarity opposite to a voltage applied to the support means.   2. The droplet collecting means is disposed at a position outside a jet region in the support means and outside an end portion of a landing target having a maximum width that can be handled. The liquid ejecting apparatus according to claim 6.

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