JP2010214880A - Image forming apparatus and mist catching method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which reduces the number of times of maintenance of the apparatus by preventing adhesion to a nozzle surface of liquid droplets in the form of mist generated when the liquid is delivered, and enables a continuous operation for a long time, and to provide a mist catching method. <P>SOLUTION: The image forming apparatus includes: a liquid delivery head of an on-demand delivery system with a nozzle plate (60) wherein a nozzle (61) for delivering the liquid is formed; an electrode member which discharges a base material (44) to which the liquid delivered from the nozzle (61) is stuck; and an electrification control means which sticks a satellite droplet (70) separated to form from a main liquid droplet (68) of the liquid delivered by the delivery operation onto the base material (44) discharged with an opposite polarity to a charging polarity of the satellite droplet by controlling of reversing a charging polarity of the base material (44) by the electrode member matching with a timing of the delivery operation of delivering the liquid from the nozzle (61) without impression of a voltage between the liquid in a head and the electrode member. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a mist collecting method, and more particularly to a technique for preventing mist droplets (satellite droplets) from adhering to a nozzle surface when liquid is ejected from an ink jet type liquid ejection head.

  An inkjet recording apparatus that forms an image by ejecting a functional material such as ink onto a recording medium using an inkjet head is environmentally friendly and can perform high-speed recording on various recording media. Has a feature such that a high-definition image can be obtained without bleeding, and is used as a general-purpose image forming apparatus in various fields.

  When functional materials are ejected by the ink jet method, satellite droplets that are smaller than the main droplets and mist that is separated from the main droplets and stalled are generated along with the generation of the main droplets. When the evaporation of the functional material can be ignored, the size of the mist is about 0.5 μm to 10 μm, and it is particularly difficult to suppress the generation of mist around 1 μm. The mist floats in the apparatus and contaminates the inside of the apparatus. In particular, if the mist adheres to the nozzle plate (discharge surface) of the head, it may cause discharge abnormality. In addition, when mist adheres to a detector such as an encoder, an abnormality in conveyance of the recording medium can be induced, and an abnormal drawing due to the abnormality in conveyance can be caused. Such a drawing abnormality adversely affects image formation.

  To deal with these problems, Patent Document 1 discloses a method in which a conductive film formed on a nozzle plate is charged to a polarity opposite to the charged charge of satellite droplets, and the satellite droplets are adsorbed on the conductive film.

  In Patent Document 2, an electric field is applied between the nozzle plate and the base material to cause ink droplets to be adsorbed to the base material, while the edge of the paper reverses the electric field and repels the base material and the ink so that there is no border. It prevents mist from adhering to the edge during printing.

  Further, Patent Document 3 discloses a method of charging the base material and ink to opposite polarities in accordance with the discharge timing, charging the nozzle neighborhood member to opposite polarity to the base member after discharge, and collecting the mist.

JP 2007-21840 A JP 2005-349799 A Japanese Patent Laid-Open No. 5-124187

  However, in the method described in Patent Document 1, since a large amount of satellite droplets adhere to the nozzle plate, periodic wiping is indispensable. Also, it cannot be applied to ink that dries and adheres.

  In the method described in Patent Document 2, both positive and negative charged particles are generated when the ink is split. Therefore, when the ink is split, the ink droplet cannot be controlled simply by applying an electric field.

  On the other hand, in the method described in Patent Document 3, since the ink and the electrode are in contact with each other, aggregation and electrolysis occur at the electrode depending on the ink.

  In addition, in a head in which nozzles are two-dimensionally arranged, the discharge timing is different for each nozzle, so that charging cannot be controlled in accordance with the discharge timing. For this reason, there has been no effective means for preventing the attachment of mist and contaminants and capable of operating the high-nozzle density inkjet recording apparatus having a two-dimensional nozzle array for a long period of time.

  The present invention has been made in view of such circumstances, and prevents mist-like droplets generated during liquid discharge from adhering to the nozzle surface, reducing the number of maintenance times of the apparatus and enabling continuous operation over a long period of time. An object of the present invention is to provide an image forming apparatus and a mist collecting method.

  In order to achieve the above object, an image forming apparatus according to the present invention attaches a liquid discharge head of an on-demand discharge type having a nozzle plate on which nozzles for discharging a liquid are formed, and a liquid discharged from the nozzle. The electrode member is charged in accordance with the timing of the discharge operation for discharging the liquid from the nozzle without applying a voltage between the electrode member for charging the substrate and the liquid in the liquid discharge head and the electrode member. Control is performed to reverse the charging polarity of the base material, and the satellite droplets generated and separated from the main liquid droplets discharged by the discharging operation are charged on the base material charged to a polarity opposite to the charging polarity of the satellite droplets. And a charging control means for adhering.

  According to the present invention, satellite droplets generated in the ejection operation move toward the substrate away from the nozzle plate by electrostatic force, and adhere to the substrate together with the main droplets. This prevents satellite droplets (mist droplets) from adhering to the nozzle plate.

  As a result, the ejection reliability is improved and the nozzle plate is less contaminated, so that the number and frequency of head maintenance can be reduced, and continuous operation for a long time becomes possible.

Explanatory drawing which showed typically the mode at the time of the ink discharge in the conventional inkjet recording device in time series order 1 is a schematic configuration diagram showing a main configuration of an inkjet recording apparatus according to an embodiment of the present invention. Explanatory drawing which illustrated the mist collection method concerning the embodiment of the present invention typically Diagram showing the relationship between the drive pulse for ink ejection and the charging polarity of the substrate Explanatory drawing which illustrated typically the mist collection method concerning other embodiments of the present invention. Explanatory drawing which shows the characteristic of the nozzle arrangement in the inkjet head of this example Configuration of an inkjet recording apparatus according to another embodiment of the present invention Plane perspective view showing a configuration example of the inkjet head shown in FIG. Plane perspective view showing another configuration example of an inkjet head Sectional drawing which follows the AA line in FIG. FIG. 7 is a principal block diagram showing the system configuration of the ink jet recording apparatus shown in FIG.

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

  First, problems to be solved by the present invention will be briefly described with reference to the drawings.

<Mist adhesion phenomenon on the nozzle surface>
FIGS. 1A to 1E are diagrams schematically showing a state in which droplets (herein, “ink”) are ejected from a nozzle 1 in a conventional ink jet recording apparatus in time series. .

  FIG. 1A shows a discharge standby state in which a drive signal for ink discharge is not applied to an energy generating element such as a piezoelectric element. In this discharge standby state, due to the relationship between the head internal pressure and the atmospheric pressure, the meniscus 2 of the nozzle 1 has a convex curved surface toward the inside of the nozzle 1 as shown in the drawing (a concave arch as viewed from the nozzle surface 4 side). Shape). The means for generating the discharge pressure (discharge energy) for discharging the droplets from the nozzle 1 is not limited to the piezoelectric element, but may be various, such as a heater (heating element) in a thermal system and various actuators by other systems. A pressure generating element (energy generating element) can be applied.

  In FIG. 1B, when a drive signal is applied to the energy generating element, the ink 6 is pushed out from the nozzle 1, and columnar ink (hereinafter referred to as “ink liquid column”) is ejected from the nozzle 1. 6 shows a protruding state.

  Thereafter, the ink liquid column 6 further expands to become a stringed state, and eventually, as shown in FIG. In this way, the main droplet 8 immediately after separation from the nozzle 1 (spinning cutting) flies backward with tailing.

  FIG. 1D shows a state in which satellite droplets (sub-droplets) 10 generated by dividing the ink liquid column 6 are floating in the vicinity of the nozzle surface 4. When the main droplets 8 are separated by the string cutting, the satellite droplets 10 may be further separated. The minute ones of the satellite droplets 10 become mist that floats without reaching the substrate (not shown). When the main droplet 8 separated from the nozzle 1 flies toward the substrate, an air flow 12 toward the nozzle 1 is generated around the main droplet 8.

  As shown in FIG. 1E, the satellite droplet 10 is carried to the nozzle surface 4 by the air flow 12 and adheres to the nozzle surface 4. On the other hand, during the flight, the main droplet 8 is absorbed by the main droplet at the tail portion, and becomes a substantially spherical droplet that lands on the substrate. Thus, the ink mist adhering to the vicinity of the nozzle 1 causes the meniscus of the nozzle 1 to collapse and cause a discharge failure such as a flying curve.

<Configuration Example of Inkjet Recording Apparatus According to Embodiment of the Present Invention>
Next, the configuration of an ink jet recording apparatus according to an embodiment of the present invention that solves the above-described problems will be described.

  FIG. 2 is a schematic configuration diagram showing the main configuration of the inkjet recording apparatus 40 according to the present embodiment. The ink jet recording apparatus 40 supports an ink jet head 42 as means for ejecting ink which is one form of a functional material, transport rollers 46 and 48 for transporting a base material 44 to which ink is attached, and the base material 44. The conductive platen 50 includes a power supply 52 that applies a voltage to the conductive platen 50, and a control circuit 54.

  On the ejection surface (nozzle surface 42A) of the inkjet head 42, a plurality of nozzles (not shown) serving as ink ejection ports are formed. The inkjet head 42 is an on-demand ejection method that ejects a required amount of liquid droplets from each nozzle at a necessary timing. By applying a pressure to the liquid in the inkjet head 42, a piezo method, a thermal method, a static method, or the like. There are aspects such as electric systems.

  In the on-demand ejection method, the liquid in the inkjet head is pressurized by applying a driving pulse (driving signal) corresponding to the image data to be drawn to the pressurizing element (energy generating element) corresponding to the nozzle, and a desired pressure is applied. A droplet is discharged at the timing.

  By ejecting ink from the inkjet head 42 toward the base material 44 while transporting the base material 44 by the transport rollers 46 and 48, a two-dimensional image is drawn with dots formed by ink droplets that have landed on the base material 44. The In this example, the conveying rollers 46 and 48 are used as the conveying means for the base material 44, but various forms such as a nip conveying method, a drum conveying method, and a belt conveying method are adopted as the substrate conveying means. obtain.

  The conductive platen 50 is disposed to face the ejection surface (nozzle surface 42A) of the inkjet head 42, and supports the substrate 44 conveyed by the conveyance rollers 46 and 48 from the back surface thereof. As a result, the position of the surface of the substrate 44 relative to the nozzle surface 42A of the ink jet head 42 (the distance between the two ink droplets flying) is defined, and the substrate 44 is conveyed while maintaining a stable clearance (slow distance). .

  A power source 52 connected to the conductive platen 50 is a power source provided with polarity reversing means capable of switching between positive and negative polarities and outputting a predetermined voltage. For example, the power supply 52 includes a positive voltage output power supply unit that outputs a positive direct current (DC) voltage, a negative voltage output power supply unit that outputs a negative direct current (DC) voltage, and a circuit that selectively switches these outputs ( Switch).

  By controlling the output (polarity) of the power source 52 by the control circuit 54, the charging polarity of the base material 44 on the conductive platen 50 can be reversed. When a positive voltage is applied to the conductive platen 50, the substrate 44 is charged positively with respect to the ground potential, and when a negative voltage is applied to the conductive platen 50, the substrate 44 is charged negatively with respect to the ground potential. To do.

  The control circuit 54 is means for comprehensively controlling the ejection drive of the inkjet head 42, the conveyance of the base material 44 by the conveyance rollers 46 and 48, and the output of the power supply 52. In this example, the polarity of the voltage applied to the conductive platen 50 in accordance with the discharge timing from the inkjet head 42 in order to prevent the mist generated when the droplets are discharged from the inkjet head 42 from adhering to the nozzle surface 42A. (That is, the charging polarity of the base material 44 is controlled), and the mist is collected by the base material 44 by the electrostatic force. The ink in the inkjet head 42 may be in an electrically floating state, or a configuration in which the ink in the head and the conductive platen 50 are electrically connected is adopted. The ink in the head and the substrate 44 may be charged with the same polarity by the applied voltage.

<Explanation of mist collection method>
Next, a method for collecting ink mist in the present embodiment will be described.

  FIGS. 3A to 3E are explanatory views schematically showing the operation at the time of ink ejection in the ink jet recording apparatus 40 according to the present embodiment in order of time series. Here, it demonstrates centering on the difference compared with FIG.

  FIG. 3A shows an ejection standby state (non-ejection state) in which a drive signal for ink ejection is not applied to the piezoelectric element and other energy generating elements. The nozzle plate 60 is made of, for example, silicon, and the shape of the nozzle 61 is processed with high accuracy by a semiconductor process. In the discharge standby state (non-discharge state), as shown in FIG. 3A, the substrate 44 is charged to a positive polarity. On the nozzle surface 64 side of the nozzle plate 60 facing the positively charged base material 44, a negative charge is generated by electrostatic polarization.

  The ink jet head 42 of the ink jet recording apparatus 40 according to the present embodiment is not provided with an electrode that contacts the ink in the head, and the ink in the head is in an electrically floating state. Since the ink and the electrode are not in contact with each other in the head, problems such as ink aggregation and electrolysis do not occur. In addition, the problem of a short (electrical short circuit) between the ink and the substrate 44 does not occur.

  FIG. 3B shows a state in which the ink liquid column 66 protrudes from the nozzle 61 toward the outside when a drive signal is applied to the energy generating element. As shown in FIG. 5B, the polarity of the base material 44 is switched from positive polarity to negative polarity in response to the start of the discharge operation. As a result, positive charges are generated on the nozzle surface 64 side of the nozzle plate 60 facing the substrate 44 due to electrostatic polarization.

  FIG. 3C shows a state in which the ink liquid column 66 protruding to the outside of the nozzle 61 is cut into a string to form a droplet (main droplet 68). In FIG. 3B, “+” represents a positive charged ion molecule, and “−” represents a negative charged ion molecule. When the main droplets 68 are separated by the splitting of the ink liquid column 66, the base material 44 is negatively charged and the nozzle surface 64 is positively charged. Therefore, charged ions in the split main droplets 68 are charged. The movement of the molecules occurs, the positively charged ion molecules (+) are attracted to the part close to the base material 44, and the negative charge is applied to the part close to the nozzle surface 64 (the tailing part far from the base material 44). Ion molecules (-) gather.

  FIG. 3D shows a state in which the satellite droplet 70 is split from the tail portion of the main droplet 68. Since the satellite droplet 70 is split from a portion near the nozzle surface 64 of ink ejected from the nozzle 61 (portion where negatively charged charged ion molecules are gathered), it is charged negatively. In response to the generation of the satellite droplet 70 (mist) charged to the negative polarity, as shown in FIG. 3D, the charging polarity of the base material 44 is switched to the positive polarity. That is, the polarity of the conductive platen 50 described in FIG. 2 is reversed.

  By doing so, negative charges are generated by electrostatic polarization on the nozzle surface 64, and a repulsive force due to electrostatic force acts between the nozzle surface 64 and the satellite droplets 70, and the base material 44 and the satellite droplets 70. The attractive force due to the electrostatic force acts between the satellite droplets 70 in a direction away from the nozzle surface 64 (that is, in the direction of the base material 44) (see FIG. 3E).

  On the other hand, since the satellite droplet 70 charged to the negative polarity is split, the main droplet 68 is equivalent to the state charged to the positive polarity (FIG. 3D). Since the main droplets 68 have a sufficient mass and speed, even if the base material 44 is charged to a positive polarity, it is not easily affected and is not attracted to the nozzle surface 64.

  As shown in FIG. 3 (e), a suction force due to electrostatic force acts between the satellite droplet 70 charged to the negative polarity and the main droplet 68 charged to the positive polarity, and the main droplet of the satellite droplet 70. Unification to 68 is promoted. During the flight of the main droplet 68 or after landing on the substrate 44, the satellite droplet 70 coalesces with the main droplet 68 and adheres to the substrate 44.

  Thereby, adhesion of the satellite droplet 70 (mist) to the nozzle surface 64 can be prevented.

  The material of the nozzle plate 60 is not limited to silicon. Instead of the nozzle plate 60 made of silicon, a nozzle plate made of a non-conductive material can be employed. By using a non-conductive nozzle plate, a mist repulsion effect by electrostatic polarization can be obtained as in the case of silicon.

  FIG. 4 is a diagram showing the relationship between a drive pulse (drive signal) 80 for ink ejection and the charging polarity 82 of the base material 44 (that is, the polarity of the voltage applied to the conductive platen 50). The drive pulse 80 shown in the figure is a positive logic pulse signal, and an energy generating element such as a piezoelectric element operates during the H level period.

At timing t ₁ when the drive pulse 80 is applied to the energy generating element (at the rising edge at which the drive pulse 80 changes from L level to H level), the charging polarity 82 of the substrate 44 is switched from positive polarity to negative polarity. Then, after the application end timing t ₂ of the drive pulse 80 (the drive pulse 80 after the falling edge changes from H level to L level), the charge polarity of the substrate 44 is switched to the positive from the negative polarity.

Thereafter, the charge polarity 82 of the substrate 44 at the start timing t ₁₁ of the next drive pulse 80 is switched from the positive polarity to the negative polarity. In this way, switching of the charging polarity 82 of the substrate 44 is repeated in response to the drive pulse 80.

That is, during the discharge operation period, the base material 44 is charged to a negative polarity, and the polarity of the base material 44 is reversed corresponding to the end timing of the discharge operation, so that the satellite droplets 70 generated by the discharge of the ink droplets are generated. On the other hand, a repulsive force due to static electricity is applied to the nozzle surface 64. The timing t _f for switching the charging polarity 82 of the base material 44 from the negative polarity to the negative polarity is not limited to the application start timing t ₁ of the drive pulse 80 but may be slightly before or after the ejection operation start timing. Since a time difference occurs between the drive pulse and the actual ink behavior depending on the physical properties of the ink, the timing for switching the charging polarity 82 of the base material 44 from the positive polarity to the negative polarity is the application start timing t ₁ of the drive pulse 80A. it is also possible to set between the application end timing t ₂ of the drive pulse 80A from.

The timing t _r to switch the charging polarity 82 of the base 44 from the negative polarity to the positive polarity, timing satellite droplet 70 is generated by severance during ink ejection (Fig. 3 (c) ~ (d) refer) and Good. Thus, “during the ejection operation period” includes a period from the drive pulse application start timing (for example, t ₁ ) in _one ejection operation to the thread cutting timing (not shown) at the time of ejection. .

Here, the timing of severance during ink ejection is included in the period from the application end timing t ₂ of the drive pulse 80A until the application start timing t ₁₁ of the next drive pulse 80B. Since differences occur depending on the ink physical properties, drive pulse waveform, amplitude (voltage), and structure of the inkjet head, it is preferable to grasp the timing of thread cutting at the time of ink ejection through experiments or simulations and set the timing appropriately.

In general, when the pulse width of the drive pulse and T / 2 (although, T is the resonance period of the ink channels of the head), 0 or more from the application end timing t ₂ of the drive pulse 80A to the timing of severance during ink ejection It is good to set it as (3xT) / 2 or less, More preferably, it is T / 2 or more and T or less.

  In the above description, it has been described that satellite droplets are generated when droplets are discharged. However, it is not always necessary to discharge with the generation of satellite droplets. For example, the present invention can also be applied to a case where satellite droplets are not generated during normal ejection, and the droplets are divided into a plurality of parts in the period from ejection start to landing at least during ejection abnormality.

  In FIG. 4, for the sake of simplicity, a rectangular wave drive signal is illustrated, but the waveform of the drive signal is not particularly limited when the present invention is implemented. For example, in a form in which a piezoelectric element is used as the energy generating element, a first pulling operation for increasing the volume of the pressure chamber is first performed, and then a pushing operation for decreasing the volume of the pressure chamber is performed. Pull-push-pull (pull-push-pull), which pulls out the liquid from the liquid and performs a second pulling operation to increase the volume of the pressure chamber again and tears (cuts) the liquid column to form a microdroplet. ) A driving waveform such as a driving method or a push-pull driving method may be applied.

<Other charge control methods>
In FIG. 3, the ink in the head is in an electrically floating state, but instead of this mode, an electrode that contacts the ink is provided in the head, and the electrode and the conductive platen 50 are electrically connected. It is also possible to adopt a mode in which both are set to substantially equipotential and the ink in the head and the substrate 44 are charged with the same polarity.

  FIG. 5 is an explanatory diagram schematically showing the operation at the time of ink ejection in a mode in which the ink in the head and the substrate 44 are charged to the same polarity in order of time series.

  (A) to (e) in FIG. 5 correspond to the states described in (a) to (e) of FIG. 3, respectively. The difference from FIG. The ink is charged with the same polarity as the base material 44. In FIG. 5, elements that are the same as or similar to those in FIG. 3 are given the same reference numerals, and descriptions thereof are omitted.

  In FIG. 5, since the ink in the nozzle 61 is charged with the same polarity as that of the base material 44, the charge distribution of the ink liquid column 66 ((b) and (c) in FIG. 5) and satellite droplets during the ejection operation. The charging polarity 70 (FIG. 5D) is as shown in the figure, and the satellite droplet 70 split from the main droplet 68 is easily charged to the positive polarity.

  In response to the generation of the satellite droplet 70 (mist) charged to the positive polarity, as shown in FIG. 5D, the charging polarity of the base material 44 is switched to the positive polarity. That is, the polarity of the conductive platen 50 described in FIG. 2 is reversed.

  By doing so, the ink in the nozzle 61 is positively charged, and a repulsive force due to electrostatic force acts between the ink in the nozzle 61 and the satellite droplet 70. According to such an aspect, the repulsive force of the droplet with respect to the nozzle is improved, and a short circuit between the ink and the substrate 44 is prevented.

<Consideration of nozzle arrangement in inkjet head 42>
In order to obtain the effect of preventing mist adhesion as shown in FIGS. 3 and 5 for all the nozzles of the inkjet head 42 facing the conductive platen 50, it is desirable to synchronize the dischargeable timing of all the nozzles.

  For example, as shown in FIG. 6, nozzles 91 are two-dimensionally arranged in the head module 90 constituting the inkjet head 42, and the substrate conveyance direction (in the case of a so-called full-line type head) indicated by a white arrow in the figure. The nozzle interval in the base material transport direction is n × D (where n is a natural number) with respect to the nozzle interval D (substantial nozzle interval D in the main scanning direction) for drawing adjacent dots aligned in the vertical direction with ).

  In the illustrated example, the distance in the substrate conveyance direction between the nozzles 91a and 91b arranged at different positions in the substrate conveyance direction is m × D (m is a natural number, for example, m = 2), and between the nozzles 91c and 91d. The distance in the substrate conveyance direction is l × D (l is a natural number, for example, l = 1). As described above, for all the nozzles 91 in the head module 90, the distance in the substrate conveyance direction between the nozzles arranged at different positions in the substrate conveyance direction is n × D.

  Thereby, when the base material 44 is conveyed at a constant speed, the discharge possible timings of all the nozzles of the head module 90 can be matched (synchronized).

  According to the above-described embodiment, it is possible to prevent the mist from adhering to the nozzle surface, improve the ejection reliability, and reduce the frequency of head maintenance.

<Another configuration example of the ink jet recording apparatus>
FIG. 7 is a configuration diagram of the ink jet recording apparatus according to the embodiment of the present invention. The ink jet recording apparatus 110 uses an ink jet head 172M on a recording medium 124 (corresponding to “base material”, hereinafter sometimes referred to as “paper” for convenience) held on an impression cylinder (drawing drum 170) of the drawing unit 116. , 172K, 172C, and 172Y, an ink jet recording apparatus of an impression cylinder direct drawing method that forms a desired color image by ejecting ink of a plurality of colors by an on-demand ejection method, on the recording medium 124 before ink ejection Is an image forming apparatus to which a two-liquid reaction (aggregation) method is applied in which a processing liquid (here, an aggregating processing liquid) is applied, and the processing liquid and an ink liquid are reacted to form an image on the recording medium 124.

  As shown in the figure, the ink jet recording apparatus 110 mainly includes a paper feeding unit 112, a treatment liquid application unit 114, a drawing unit 116, a drying unit 118, a fixing unit 120, and a discharge unit 122.

(Paper Feeder)
The paper feeding unit 112 is a mechanism that supplies the recording medium 124 to the processing liquid application unit 114, and the recording media 124 that are sheets are stacked on the paper feeding unit 112. The paper feed unit 112 is provided with a paper feed tray 150, and the recording medium 124 is fed from the paper feed tray 150 to the processing liquid application unit 114 one by one.

  In the inkjet recording apparatus 110 of this example, a plurality of types of recording media 124 having different paper types and sizes (paper sizes) can be used as the recording medium 124. A mode is also possible in which a plurality of paper trays (not shown) for separately collecting various recording media are provided in the paper feeding unit 112 and the paper to be sent to the paper feeding tray 150 is automatically switched from among the plurality of paper trays. In addition, a mode is also possible in which the operator selects or replaces the paper tray as necessary. In this example, a sheet (cut paper) is used as the recording medium 124, but a configuration in which continuous paper (roll paper) is cut to a required size and fed is also possible.

(Processing liquid application part)
The processing liquid application unit 114 is a mechanism that applies the processing liquid to the recording surface of the recording medium 124. The treatment liquid contains a color material aggregating agent that agglomerates the color material (pigment in this example) in the ink applied by the drawing unit 116, and the ink comes into contact with the treatment liquid and the ink. And the solvent are promoted.

  As shown in FIG. 7, the treatment liquid application unit 114 includes a paper feed cylinder 152, a treatment liquid drum 154, and a treatment liquid application device 156. The treatment liquid drum 154 is a drum that holds and rotates the recording medium 124. The processing liquid drum 154 includes a claw-shaped holding means (gripper) 155 on the outer peripheral surface thereof, and the recording medium 124 is sandwiched between the claw of the holding means 155 and the peripheral surface of the processing liquid drum 154. The tip can be held. The treatment liquid drum 154 may be provided with a suction hole on the outer peripheral surface thereof and connected to a suction unit that performs suction from the suction hole. As a result, the recording medium 124 can be held in close contact with the peripheral surface of the treatment liquid drum 154.

  A processing liquid coating device 156 is provided outside the processing liquid drum 154 so as to face the peripheral surface thereof. The processing liquid coating device 156 includes a processing liquid container in which the processing liquid is stored, an anix roller partially immersed in the processing liquid in the processing liquid container, and the recording medium 124 on the anix roller and the processing liquid drum 154. And a rubber roller that transfers the measured processing liquid to the recording medium 124. According to the processing liquid coating apparatus 156, the processing liquid can be applied to the recording medium 124 while being measured.

  In the present embodiment, the configuration in which the application method using the roller is exemplified, but the present invention is not limited to this. For example, various methods such as a spray method and an ink jet method can be applied.

  The recording medium 124 to which the processing liquid is applied by the processing liquid applying unit 114 is transferred from the processing liquid drum 154 to the drawing drum 170 of the drawing unit 116 via the intermediate transport unit 126.

(Drawing part)
The drawing unit 116 includes a drawing drum 170, a paper holding roller 174, and ink jet heads 172M, 172K, 172C, and 172Y. Similar to the treatment liquid drum 154, the drawing drum 170 includes a claw-shaped holding means (gripper) 171 on the outer peripheral surface thereof. The recording medium 124 fixed to the drawing drum 170 is conveyed with the recording surface facing outward, and ink is applied to the recording surface from the inkjet heads 172M, 172K, 172C, 172Y.

  The inkjet heads 172M, 172K, 172C, and 172Y are full-line inkjet recording heads (inkjet heads) each having a length corresponding to the maximum width of the image forming area on the recording medium 124. Is formed with a nozzle row in which a plurality of nozzles for ink ejection are arranged over the entire width of the image forming area. Each inkjet head 172M, 172K, 172C, 172Y is installed so as to extend in a direction orthogonal to the conveyance direction of the recording medium 124 (the rotation direction of the drawing drum 170).

  The droplets of the corresponding color ink are ejected from the inkjet heads 172M, 172K, 172C, and 172Y toward the recording surface of the recording medium 124 held in close contact with the drawing drum 170, whereby the processing liquid application unit 114 performs the processing. The ink comes into contact with the treatment liquid previously applied to the recording surface, and the color material (pigment) dispersed in the ink is aggregated to form a color material aggregate. Thereby, the color material flow on the recording medium 124 is prevented, and an image is formed on the recording surface of the recording medium 124.

  In this example, the configuration of CMYK standard colors (four colors) is illustrated, but the combination of ink colors and the number of colors is not limited to this embodiment, and light ink, dark ink, and special colors are used as necessary. Ink may be added. For example, it is possible to add an inkjet head that discharges light-colored ink such as light cyan and light magenta, and the arrangement order of the color heads is not particularly limited.

  The drawing drum 170 of this example uses a conductive member on the surface that supports the recording medium 124, and a power source (not shown) (corresponding to reference numeral 52 described in FIG. 2) is connected to the conductive member. That is, the drawing drum 170 (conductive member) plays the same role as the conductive platen 50 described in FIG. With this configuration, the entire recording medium 124 held on the drawing drum 170 can be uniformly charged. By switching the polarity of the voltage applied to the drawing drum 170 (conductive member), the drawing drum The charging polarity of the recording medium 124 on 170 can be switched.

  As described above, the drawing drum 170 functions as a common (single) platen for the plurality of ink-jet heads 172M, 172K, 172C, and 172Y for each color, and thus is arranged around the drawing drum 170. In the inkjet heads 172M, 172K, 172C, and 172Y for each color, the nozzle arrangement in each head and the arrangement relationship between the heads are designed from the same viewpoint as in FIG. 6 so that the dischargeable timing of all the nozzles is synchronized. ing.

  The recording medium 124 on which an image is formed by the drawing unit 116 is transferred from the drawing drum 170 to the drying drum 176 of the drying unit 118 via the intermediate conveyance unit 128.

(Drying part)
The drying unit 118 is a mechanism for drying moisture contained in the solvent separated by the color material aggregating action, and includes a drying drum 176 and a solvent drying device 178.

  Similar to the processing liquid drum 154, the drying drum 176 includes a claw-shaped holding unit (gripper) 177 on the outer peripheral surface thereof, and the holding unit 177 can hold the leading end of the recording medium 124.

  The solvent drying device 178 is disposed at a position facing the outer peripheral surface of the drying drum 176, and includes a plurality of halogen heaters 180 and hot air ejection nozzles 182 disposed between the halogen heaters 180.

  Various drying conditions can be realized by appropriately adjusting the temperature and air volume of the hot air blown toward the recording medium 124 from each hot air ejection nozzle 182 and the temperature of each halogen heater 180.

  The surface temperature of the drying drum 176 is set to 50 ° C. or higher. Drying is accelerated by heating from the back surface of the recording medium 124, and image destruction during fixing can be prevented. The upper limit of the surface temperature of the drying drum 176 is not particularly limited, but from the viewpoint of safety of maintenance work such as cleaning ink adhering to the surface of the drying drum 176 (preventing burns due to high temperatures). It is preferably set to 75 degrees or less (more preferably 60 degrees C or less).

  It is held on the outer peripheral surface of the drying drum 176 so that the recording surface of the recording medium 124 faces outward (that is, in a state where the recording surface of the recording medium 124 is convex), and is dried while being rotated and conveyed. By doing so, it is possible to prevent the recording medium 124 from being wrinkled or lifted, and to reliably prevent unevenness in drying due to these.

  The recording medium 124 that has been dried by the drying unit 118 is transferred from the drying drum 176 to the fixing drum 184 of the fixing unit 120 via the intermediate conveyance unit 130.

(Fixing part)
The fixing unit 120 includes a fixing drum 184, a halogen heater 186, a fixing roller 188, and an inline sensor 190. Like the processing liquid drum 154, the fixing drum 184 includes a claw-shaped holding unit (gripper) 185 on the outer peripheral surface, and the leading end of the recording medium 124 can be held by the holding unit 185.

  With the rotation of the fixing drum 184, the recording medium 124 is conveyed with the recording surface facing outward. The recording surface is preheated by the halogen heater 186, fixing processing by the fixing roller 188, and by the inline sensor 190. Inspection is performed.

  The halogen heater 186 is controlled to a predetermined temperature (for example, 180 ° C.). Thereby, preheating of the recording medium 124 is performed.

  The fixing roller 188 is a roller member that heats and pressurizes the dried ink to weld the self-dispersing polymer fine particles in the ink to form a film of the ink, and is configured to heat and press the recording medium 124. The Specifically, the fixing roller 188 is disposed so as to be in pressure contact with the fixing drum 184 and constitutes a nip roller with the fixing drum 184. As a result, the recording medium 124 is sandwiched between the fixing roller 188 and the fixing drum 184 and nipped at a predetermined nip pressure (for example, 0.15 MPa), and the fixing process is performed.

  The fixing roller 188 is configured by a heating roller in which a halogen lamp is incorporated in a metal pipe such as aluminum having good thermal conductivity, and is controlled to a predetermined temperature (for example, 60 to 80 ° C.). By heating the recording medium 124 with this heating roller, thermal energy equal to or higher than the Tg temperature (glass transition temperature) of the latex contained in the ink is applied, and the latex particles are melted. As a result, pressing and fixing are performed on the unevenness of the recording medium 124, and the unevenness of the image surface is leveled to obtain glossiness.

  In the embodiment shown in FIG. 7, only one fixing roller 188 is provided. However, a structure in which a plurality of fixing rollers 188 are provided may be used depending on the thickness of the image layer and the Tg characteristics of latex particles.

  On the other hand, the in-line sensor 190 is a measuring means for measuring a check pattern, a moisture content, a surface temperature, a glossiness, and the like for an image fixed on the recording medium 124, and a CCD line sensor or the like is applied.

  According to the fixing unit 120 configured as described above, the latex particles in the thin image layer formed by the drying unit 118 are heated and pressurized by the fixing roller 188 and are melted. Can be made. The surface temperature of the fixing drum 184 is set to 50 ° C. or higher. The recording medium 124 held on the outer peripheral surface of the fixing drum 184 is heated from the back surface to accelerate drying, thereby preventing image destruction at the time of fixing and increasing the image strength by the effect of increasing the image temperature. Can do.

(Discharge part)
As shown in FIG. 7, a discharge unit 122 is provided following the fixing unit 120. The discharge unit 122 includes a discharge tray 192, and a transfer drum 194, a conveyance belt 196, and a stretching roller 198 are provided between the discharge tray 192 and the fixing drum 184 of the fixing unit 20 so as to be in contact therewith. It has been. The recording medium 124 is sent to the conveyor belt 196 by the transfer drum 194 and discharged to the discharge tray 192.

  Although not shown in the drawing, the ink jet recording apparatus 110 of the present example has an ink storage / loading unit for supplying ink to each of the ink jet heads 172M, 172K, 172C, and 172Y, and a treatment liquid application, in addition to the above configuration. A means for supplying a processing liquid to the unit 114, and a head maintenance unit for cleaning each ink jet head 172M, 172K, 172C, 172Y (wiping, purging, nozzle suction, etc. of the nozzle surface), A position detection sensor for detecting the position of the recording medium 124, a temperature sensor for detecting the temperature of each part of the apparatus, and the like are provided.

<Inkjet head structure>
Next, the structure of the inkjet head will be described. Since the inkjet heads 172M, 172K, 172C, and 172Y corresponding to the respective colors have the same structure, the heads are represented by the reference numeral 250 in the following.

  FIG. 8A is a plan perspective view showing an example of the structure of the head 250, and FIG. 8B is an enlarged view of a part thereof. 9 is a perspective plan view showing another structural example of the head 250, and FIG. 10 is a three-dimensional configuration of one-channel droplet discharge elements (ink chamber units corresponding to one nozzle 251) serving as recording element units. FIG. 9 is a cross-sectional view (a cross-sectional view taken along line AA in FIG. 8).

  As shown in FIG. 8, the head 250 of this example has a matrix of a plurality of ink chamber units (droplet discharge elements) 253 including nozzles 251 serving as ink discharge ports and pressure chambers 252 corresponding to the nozzles 251. The nozzle spacing (projection nozzle pitch) is projected (orthogonally projected) so as to be aligned along the longitudinal direction of the head (direction perpendicular to the paper feed direction). High density is achieved.

  The form in which the nozzle row having a length corresponding to the full width of the recording medium 124 in the direction (main scanning direction) substantially orthogonal to the feeding direction (sub-scanning direction) of the recording medium 124 is not limited to this example. For example, instead of the configuration of FIG. 8A, as shown in FIG. 9A, short head modules 250 ′ in which a plurality of nozzles 251 are two-dimensionally arranged are arranged in a staggered manner and connected. Then, there is an aspect in which a line head having a nozzle row having a length corresponding to the entire width of the recording medium 124 is configured, or an aspect in which the head modules 250 ″ are arranged in a line and connected as shown in FIG. This head configuration is also configured such that the dischargeable timing is synchronized for all nozzles 251 from the same viewpoint as in FIG.

  The pressure chamber 252 provided corresponding to each nozzle 251 has a substantially square planar shape (see FIGS. 8A and 8B), and the nozzle 251 is provided at one of the diagonal corners. An outlet for supplying ink (supply port) 254 is provided on the other side. Note that the shape of the pressure chamber 252 is not limited to this example, and the planar shape may have various forms such as a quadrangle (rhombus, rectangle, etc.), a pentagon, a hexagon, other polygons, a circle, and an ellipse. As shown in FIG. 10, the head 250 has a structure in which a nozzle plate 251A in which nozzles 251 are formed and a flow path plate 252P in which flow paths such as a pressure chamber 252 and a common flow path 255 are formed are laminated and joined. The nozzle plate 251A constitutes a nozzle surface (ink ejection surface) 250A of the head 250, and a plurality of nozzles 251 communicating with the pressure chambers 252 are two-dimensionally formed.

  The flow path plate 252P forms a side wall of the pressure chamber 252 and a flow path that forms a supply port 254 as a narrowed portion (most narrowed portion) of an individual supply path that guides ink from the common flow path 255 to the pressure chamber 252. It is a forming member. For convenience of explanation, although shown in FIG. 10 in a simplified manner, the flow path plate 252P has a structure in which one or a plurality of substrates are stacked.

  The nozzle plate 251A and the flow path plate 252P can be processed into a required shape by a semiconductor manufacturing process using silicon as a material.

  The common flow channel 255 communicates with an ink tank (not shown) as an ink supply source, and ink supplied from the ink tank is supplied to each pressure chamber 252 via the common flow channel 255.

  A piezoelectric element 258 having an individual electrode 257 is joined to a diaphragm 256 constituting a part of the pressure chamber 252 (the top surface in FIG. 10). The diaphragm 256 of this example is made of silicon (Si) with a nickel (Ni) conductive layer functioning as a common electrode 259 corresponding to the lower electrode of the piezoelectric element 258, and is an actuator arranged corresponding to each pressure chamber 252. Also serves as a common electrode of the piezoelectric element 258 here. It is also possible to form the diaphragm with a non-conductive material such as resin. In this case, a common electrode layer made of a conductive material such as metal is formed on the surface of the diaphragm member. Moreover, you may comprise the diaphragm which serves as a common electrode with metals (conductive material), such as stainless steel (SUS).

  By applying a driving voltage to the individual electrode 257, the piezoelectric element 258 is deformed and the volume of the pressure chamber 252 is changed, and ink is ejected from the nozzle 251 due to the pressure change accompanying this. When the piezoelectric element 258 returns to its original state after ink ejection, new ink is refilled into the pressure chamber 252 from the common flow channel 255 through the supply port 254.

  As shown in FIG. 8B, the ink chamber units 253 having such a structure are arranged in a fixed manner along a row direction along the main scanning direction and an oblique column direction having a constant angle θ that is not orthogonal to the main scanning direction. By arranging a large number of patterns in a lattice pattern, the high-density nozzle head of this example is realized. In this matrix arrangement, when the interval between adjacent nozzles in the sub-scanning direction is Ls, in the main scanning direction, each nozzle 251 is substantially equivalent to a linear arrangement with a constant pitch P = Ls / tan θ. It can be handled.

  In the case of this example, as described with reference to FIG. 6, in order to synchronize the dischargeable timing of all the nozzles in the head, Ls is set to a value that is a natural number multiple of the nozzle interval P for drawing adjacent dots in the scanning direction. Thereby, it is possible to make the ejection timing of each nozzle 251 coincide with the recording medium 124 conveyed at a constant speed.

  In this example, the piezoelectric element 258 is applied as a means for generating ink ejection force to be ejected from the nozzles 251 provided in the head 250. However, a heater (heating element) is provided in the pressure chamber 252, and a film formed by heating the heater is used. It is also possible to apply a thermal method in which ink is ejected using boiling pressure, an electrostatic actuator method, or the like.

  In the implementation of the present invention, the arrangement form of the nozzles 251 in the head 250 is not limited to the illustrated example, and various nozzle arrangement structures can be applied. For example, instead of the matrix array described in FIG. 8, a linear array of lines, a V-shaped nozzle array, and a zigzag (W-shaped) nozzle array having a V-shaped array as a repeating unit. Etc. are also possible.

  As described above, according to the configuration in which the full line head having the nozzle row covering the entire width of the image forming area of the recording medium 124 is provided for each ink color, the recording medium 124 is conveyed at a constant speed by the drawing drum 170. In this transport direction (sub-scanning direction), the recording medium 124 and each of the inkjet heads 172M, 172K, 172C, and 172Y are moved only once (that is, in one sub-scanning operation). Images can be recorded in 124 image forming areas. Single-pass image formation with such a full-line (page wide) head is a multi-pass with a serial (shuttle) type head that reciprocates in the direction (main scanning direction) orthogonal to the recording medium conveyance direction (sub-scanning direction). High-speed printing is possible as compared with the case where the method is applied, and print productivity can be improved.

  Note that the application range of the present invention is not limited to the printing method using a line type head, and a short head that is less than the length in the width direction (main scanning direction) of the recording medium 124 is scanned in the width direction of the recording medium 124. Printing in the width direction is performed, and when printing in one width direction is completed, the recording medium 124 is moved by a predetermined amount in the direction perpendicular to the width direction of the recording medium 124 (sub-scanning direction). A serial method in which printing is performed in the width direction and printing is performed over the entire printing area of the recording medium 124 by repeating this operation may be applied.

<Description of control system>
FIG. 11 is a principal block diagram showing the system configuration of the inkjet recording apparatus 110. The inkjet recording apparatus 110 includes a communication interface 270, a system controller 272, a memory 274, a motor driver 276, a heater driver 278, a print control unit 280, an image buffer memory 282, a head driver 284, and the like.

  The communication interface 270 is an interface unit as an image input unit that receives image data transmitted from the host computer 286. As the communication interface 270, a serial interface such as USB (Universal Serial Bus), IEEE 1394, Ethernet (registered trademark), a wireless network, or a parallel interface such as Centronics can be applied. In this part, a buffer memory (not shown) for speeding up communication may be mounted. Image data sent from the host computer 286 is taken into the inkjet recording apparatus 110 via the communication interface 270 and temporarily stored in the memory 274.

  The memory 274 is a storage unit that temporarily stores an image input via the communication interface 270, and data is read and written through the system controller 272. The memory 274 is not limited to a memory made of a semiconductor element, and a magnetic medium such as a hard disk may be used.

  The system controller 272 includes a central processing unit (CPU) and its peripheral circuits, and functions as a control device that controls the entire inkjet recording apparatus 110 according to a predetermined program, and also functions as an arithmetic device that performs various calculations. . That is, the system controller 272 controls the communication interface 270, the memory 274, the motor driver 276, the heater driver 278, the processing liquid application control unit 296, the drying control unit 297, the fixing control unit 298, the charging control unit 300, and the like. Control of communication with the host computer 286, read / write control of the memory 274, and the like, and control signals for controlling the above-described units are generated.

  The memory 274 stores programs executed by the CPU of the system controller 272 and various data necessary for control. The memory 274 is used as a temporary storage area for image data, and is also used as a program development area and a calculation work area for the CPU.

  Various control programs are stored in the program storage unit 290, and the control programs are read and executed in accordance with instructions from the system controller 272. The program storage unit 290 may use a semiconductor memory such as a ROM or EEPROM, or may use a magnetic disk or the like. An external interface may be provided and a memory card or PC card may be used. Note that the program storage unit 290 may also be used as a means for storing operation parameters and other information.

  The motor driver 276 is a driver that drives the motor 288 in accordance with an instruction from the system controller 272. In FIG. 11, the motors arranged in the respective units in the apparatus are represented by reference numeral 288. For example, the motor 288 shown in FIG. 11 includes a motor for driving rotation of the paper feed drum 152, the processing liquid drum 154, the drawing drum 170, the drying drum 176, the fixing drum 184, the transfer drum 194, etc. shown in FIG. Motors for driving the units 126, 128, and 130 are included.

  The heater driver 278 is a driver that drives the heater 289 in accordance with an instruction from the system controller 272. In FIG. 11, the heaters arranged in the respective units in the apparatus are represented by reference numeral 289. For example, the heater 289 shown in FIG. 11 includes heaters for heating the surfaces of the halogen heater 180, the drying drum 176, and the fixing drum 184 of the solvent drying device 178 provided in the drying unit 118 shown in FIG.

  Further, the ink jet recording apparatus 110 includes a processing liquid application control unit 296, a drying control unit 297, a fixing control unit 298, and a charging control unit 300, and in accordance with instructions from the system controller 272, the processing liquid coating apparatus, respectively. 156, the operation of each unit of the solvent drying device 178, the fixing roller 188, and the power source 302 is controlled.

  The power source 302 plays a role similar to that of the power source described with reference numeral 52 in FIG. 2, applies a voltage to the drawing drum 170 in FIG. 7, and makes the recording medium 124 on the drawing drum 170 a positive electrode or a negative electrode. To charge. The output voltage of the power supply 302 and its polarity are controlled via the charging control unit 300 in accordance with the ejection timing of the head 250.

  The print control unit 280 has a signal processing function for performing various processes and corrections for generating a print control signal from the image data in the memory 274 according to the control of the system controller 272. The generated print data This is a control unit that supplies (dot data) to the head driver 284. Necessary signal processing is performed in the print control unit 280, and the ejection droplet amount (droplet ejection amount) and ejection timing of the head 250 are controlled via the head driver 284 based on the image data. Thereby, a desired dot size and dot arrangement are realized.

  The print control unit 280 is provided with an image buffer memory 282, and image data, parameters, and other data are temporarily stored in the image buffer memory 282 when image data is processed in the print control unit 280. Also possible is an aspect in which the print control unit 280 and the system controller 272 are integrated to form a single processor.

  In the ink jet recording apparatus 110, a pseudo continuous tone image is formed by changing the droplet ejection density and dot size of fine dots with ink (coloring material) to the human eye. It is necessary to convert to a dot pattern that reproduces the gradation (shading of the image) as faithfully as possible. Therefore, the original image data (image data to be printed, for example, RGB image data) stored in the memory 274 via the communication interface 270 is sent to the print control unit 280 via the system controller 272, The print control unit 280 converts the data into dot data for each ink color by a halftoning process using a threshold matrix or an error diffusion method. Thus, the dot data generated by the print control unit 280 is stored in the image buffer memory 282.

  The head driver 284 generates a drive signal to be applied to the piezoelectric element 258 of the head 250 based on the image data given from the print control unit 280, and applies the drive signal to the piezoelectric element 258 to drive the piezoelectric element 258. Including a driving circuit. Note that the head driver 284 shown in FIG. 11 may include a feedback control system for keeping the driving condition of the head 250 constant.

  The sensor 285 is a variety of sensors provided in each part of the apparatus, and includes a temperature sensor, a position detection sensor, a pressure sensor, a linear encoder provided in the transport system, etc. in addition to the inline sensor 190 shown in FIG. Yes. The output signal of the sensor 285 is sent to the system controller 272, and the system controller 272 sends a control signal to each part of the apparatus based on the output signal, and each part of the apparatus is controlled.

<About ink>
The ink used in the present embodiment is an aqueous pigment ink containing a pigment that is a coloring material (colorant), polymer fine particles, or the like as a solvent-insoluble material.

  The concentration of the solvent-insoluble material is preferably 1 wt% or more and 20 wt% or less considering a viscosity of 20 mPa · s or less suitable for ejection. More preferably, the pigment concentration is 4 wt% or more in order to obtain the optical density of the image.

  The surface tension of the ink is preferably 20 mN / m or more and 40 mN / m or less in consideration of ejection stability.

  The color material used in the ink can be a pigment or a mixture of a dye and a pigment. From the viewpoint of aggregability at the time of contact with the treatment liquid, a pigment in a dispersed state in the ink is preferable because it aggregates more effectively. Among the pigments, a pigment dispersed by a dispersant, a self-dispersing pigment, a pigment whose surface is coated with a resin (microcapsule pigment), and a polymer graft pigment are particularly preferable. From the viewpoint of pigment aggregation, a form modified with a carboxyl group having a low dissociation degree is more preferable.

  In the colored ink liquid used in the present invention, polymer fine particles not containing a colorant are preferably added as a component that reacts with the treatment liquid. The polymer fine particles can enhance the thickening action and aggregation action of the ink by reaction with the treatment liquid, and can improve the image quality. In particular, a highly safe ink can be obtained by incorporating anionic polymer fine particles into the ink.

  By using polymer fine particles that react with the treatment liquid and cause thickening and aggregating action in the ink, the quality of the image can be improved. At the same time, depending on the type of polymer fine particles, the polymer fine particles form a film on the recording medium. It also has the effect of improving the scratch resistance and water resistance of the image.

  The dispersion method in the polymer ink is not limited to emulsion, and it may be dissolved or exist in a colloidal dispersion state.

  The polymer fine particles may be obtained by dispersing the polymer fine particles using an emulsifier, or may be dispersed without using an emulsifier. As the emulsifier, a low molecular weight surfactant is usually used, but a high molecular weight surfactant can also be used as an emulsifier. It is also preferable to use capsule type polymer fine particles (core / shell type polymer fine particles having different compositions at the center and outer edge of the particle) whose outer shell is made of acrylic acid, methacrylic acid or the like.

  Examples of the resin component added to the ink as polymer fine particles include acrylic resins, vinyl acetate resins, styrene-butadiene resins, vinyl chloride resins, acrylic-styrene resins, butadiene resins, styrene resins, and the like.

  From the viewpoint of imparting high-speed cohesiveness to the polymer fine particles, those having a carboxylic acid group having a low dissociation degree are more preferable. Since the carboxylic acid group is easily affected by pH change, the dispersion state is easily changed and the cohesiveness is high.

  The change of the dispersion state with respect to the pH change of the polymer fine particles can be adjusted by the content ratio of the constituent component in the polymer fine particles having a carboxylic acid group such as an acrylate ester, and the like depending on the anionic surfactant used as the dispersant. Can also be adjusted.

  The resin component of the polymer fine particles is preferably a polymer having both a hydrophilic portion and a hydrophobic portion. By having the hydrophobic portion, the hydrophobic portion is oriented inside the polymer fine particle, the hydrophilic portion is efficiently oriented outside, and the effect of increasing the dispersion state with respect to the pH change of the liquid is greater, and aggregation is caused. Done more efficiently.

  Further, two or more kinds of polymer fine particles may be mixed and used in the ink.

  As the pH adjuster added to the ink of the present embodiment, an organic base or an inorganic alkali base can be used as a neutralizing agent. The pH adjusting agent is preferably added so that the inkjet ink has a pH of 6 to 10 for the purpose of improving the storage stability of the inkjet ink.

  The ink used in this embodiment preferably contains a water-soluble organic solvent for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water-soluble organic solvents include wetting agents and penetrants.

  Examples of the water-soluble organic solvent include polyhydric alcohols, polyhydric alcohol derivatives, nitrogen-containing solvents, alcohols, sulfur-containing solvents and the like, as in the case of the treatment liquid.

  In addition, surfactants, pH buffers, antioxidants, fungicides, viscosity modifiers, conductive agents, ultraviolet absorbers, and the like can be added as necessary.

<About treatment liquid>
The treatment liquid (aggregation treatment liquid) used in the practice of the present invention is preferably a treatment liquid that causes aggregation of pigments and polymer fine particles contained in the ink by changing the pH of the ink.

  Treatment liquid components include polyacrylic acid, acetic acid, glycolic acid, malonic acid, malic acid, maleic acid, ascorbic acid, succinic acid, glutaric acid, fumaric acid, citric acid, tartaric acid, lactic acid, sulfonic acid, orthophosphoric acid, pyrrolidone It is preferably selected from carboxylic acid, pyrone carboxylic acid, pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof.

  Moreover, as a preferable example of the treatment liquid, a treatment liquid to which a polyvalent metal salt or polyallylamine is added can be exemplified. These compounds may be used alone or in combination of two or more.

  From the viewpoint of pH aggregation performance with the ink, the treatment liquid preferably has a pH of 1 to 6, more preferably 2 to 5, and particularly preferably 3 to 5.

  In addition, the treatment liquid preferably contains water and other additive-soluble organic solvents for the purpose of preventing clogging of the nozzles of the inkjet head due to drying. Such water and other additive-soluble organic solvents include wetting agents and penetrants. These solvents can be used alone or in combination with water and other additives.

  The treatment liquid may further contain a resin component in order to improve fixability and abrasion resistance. The resin component may be any resin component that does not impair the ejection properties from the head when the treatment liquid is ejected by the ink jet method and has storage stability, and water-soluble resins and resin emulsions can be used freely.

  In addition, surfactants, pH buffers, antioxidants, fungicides, viscosity modifiers, conductive agents, ultraviolet rays, absorbents, and the like can be added as necessary.

<Application examples to other device configurations>
The ink jet recording apparatus 110 described with reference to FIG. 7 employs a drum transport method in which the recording medium 124 is wound around a drum and transported. However, as a transport method for the recording medium (base material), a belt transport method is used instead of the drum transport method. It is also possible to adopt a belt conveyance system in which the recording medium is conveyed together with the belt by adsorbing the recording medium on the top.

  In the above embodiment, the application to an inkjet recording apparatus for printing has been described as an example. However, the scope of application of the present invention is not limited to this example. For example, a wiring drawing apparatus for drawing a wiring pattern of an electronic circuit, a manufacturing apparatus for various devices, a resist printing apparatus that uses a resin liquid as a functional liquid for ejection, a color filter manufacturing apparatus, and a material deposition material. The present invention can be widely applied to an image forming apparatus that obtains various shapes and patterns using a liquid functional material, such as a fine structure forming apparatus that forms a structure.

<Appendix>
As will be understood from the description of the embodiments of the invention described in detail above, the present specification includes disclosure of various technical ideas including at least the invention described below.

  (Invention 1): On-demand discharge type liquid discharge head having a nozzle plate on which nozzles for discharging liquid are formed, an electrode member for charging a base material to which the liquid discharged from the nozzle is attached, and the liquid discharge Control is performed to reverse the charging polarity of the substrate by the electrode member in accordance with the timing of the discharge operation of discharging the liquid from the nozzle without applying a voltage between the liquid in the head and the electrode member. Charge control means for attaching satellite droplets separated and generated from the main droplets of the liquid ejected by the ejection operation onto the base material charged to the opposite polarity to the charged polarity of the satellite droplets. An image forming apparatus.

  According to the present invention, by reversing the charging polarity of the substrate in accordance with the timing of ejection from the nozzle, the minute satellite droplets (mist-like droplets) separated from the main droplets are caused by the action of electrostatic force. It can be moved toward the substrate away from the nozzle plate, and the satellite droplets are prevented from adhering to the nozzle plate.

  As an example of the configuration of the liquid discharge head, an aspect including a liquid chamber (pressure chamber) communicating with the nozzle and a pressurizing unit (an energy generating element such as a piezoelectric element or a heating element) that pressurizes the liquid in the liquid chamber can be given. It is done. In addition, the liquid ejected from the liquid ejection head includes various functional liquids such as a resin liquid that forms a predetermined pattern on the base material in addition to the color ink that forms (records) an image on the base material made of various materials. Is included.

  “Discharge operation” means that after pressurizing the liquid in the nozzle, the liquid in the nozzle protrudes to the outside of the nozzle, and after the droplets are separated from the liquid protruding to the outside of the nozzle, the liquid is discharged to the outside of the nozzle. It is a concept that includes the process until the protruding liquid returns to the inside of the nozzle.

  For example, as an example of charging the base material with a positive polarity or a negative polarity in response to the start of the discharge operation, the drive member is applied to the electrode member at the timing of applying a drive signal to the pressurizing unit that pressurizes the liquid in the nozzle A mode in which the substrate is charged by switching the voltage can be mentioned. Further, there is a mode in which the polarity of the voltage applied to the electrode member is reversed at the timing when satellite droplets are generated by the ejection operation, and the charging polarity of the substrate is reversed.

  The “satellite droplet” is a concept including a minute droplet having a smaller volume than the main droplet separated from the main droplet discharged from the nozzle. There are various ways of calling such satellite droplets, and they are sometimes called satellites, sub-droplets, sub-drops, mist-like droplets, mist, and contamination.

  (Invention 2): The image forming apparatus according to Invention 1, wherein the liquid discharge head does not have an electrode in contact with the liquid in the head.

  Since the liquid and the electrode are not in contact with each other in the head, problems such as aggregation and electrolysis of the liquid composition do not occur. Further, there is no problem of a short circuit between the ink in the head and the substrate.

  (Invention 3): In the image forming apparatus according to Invention 1, the liquid in the liquid discharge head and the electrode member are electrically connected, and a voltage applied to the electrode member causes a change in the liquid discharge head. An image forming apparatus, wherein the liquid and the substrate are charged with the same polarity.

  According to this aspect, the adsorptive power of droplets to the substrate is improved. Further, a short circuit between the ink in the head and the substrate is also prevented.

  (Invention 4): In the image forming apparatus according to any one of Inventions 1 to 3, the electrode member is disposed to face the nozzle surface of the liquid discharge head and supports the back surface of the substrate. An image forming apparatus.

  According to this aspect, it is possible to switch the charging polarity of the base material by switching the polarity of the voltage applied to the electrode member, and reverse the charging polarity of the base material on the nozzle surface side of the nozzle plate by electrostatic polarization. It is also possible to generate polar charges.

  (Invention 5): In the image forming apparatus according to any one of Inventions 1 to 4, the charging control unit is configured such that the charging polarity of the base material is adjusted in accordance with the timing of cutting the string of the liquid discharged from the nozzle. Is switched to the opposite polarity.

  According to this aspect, immediately after the satellite droplet (mist-like droplet) is generated, the mist floating in the vicinity of the nozzle is switched by switching the charging polarity of the substrate to the opposite polarity to the charging polarity of the mist-like droplet. Can be effectively prevented from approaching the nozzle plate. As a result, the occurrence of ejection defects such as flying bends hardly occurs and the reliability is improved.

  “Liquid string cutting” is a state in which the tip of the liquid column protruding outside the nozzle is separated from the liquid column and formed into droplets.

  (Invention 6): In the image forming apparatus according to any one of Inventions 1 to 5, a plurality of nozzles are two-dimensionally arranged on the nozzle plate, and ejection timings of all the nozzles are synchronized. An image forming apparatus.

  According to this aspect, in the two-dimensional array nozzle, it is possible to collect mist (satellite droplets) on the base material by the electrode member, and it is easy to control the configuration of the electrode member and the applied voltage.

  (Invention 7): In the image forming apparatus according to any one of Inventions 1 to 6, a plurality of nozzles are two-dimensionally arranged on the nozzle plate, and adjacent dots are perpendicular to a conveyance direction of the substrate. The image forming apparatus is characterized in that the nozzle interval in the transport direction is n × D (n is a natural number) with respect to the nozzle interval D for drawing the image.

  According to this aspect, it is possible to synchronize the discharge possible timing (discharge period) of all the nozzles with respect to the substrate conveyed at a constant speed, and in the two-dimensional array nozzle, Mist collection is possible.

  (Invention 8): The image forming apparatus according to any one of Inventions 1 to 7, wherein the nozzle plate is formed of a non-conductive material.

  According to this aspect, with the charging of the base material, it is possible to generate a charge having a polarity opposite to the charging polarity of the base material on the nozzle surface side of the nozzle plate by electrostatic polarization. This electrostatic polarization makes the nozzle surface the same polarity as the polarity of the satellite droplets, so that a repulsive force due to electrostatic force can be applied, and the adhesion of satellite droplets to the nozzle surface can be effectively prevented. It is.

  (Invention 9): The image forming apparatus according to any one of Inventions 1 to 8, wherein the nozzle plate is formed of silicon.

  According to this aspect, as in the case of Invention 8, with the charging of the base material, it is possible to generate a charge having a polarity opposite to the charging polarity of the base material on the nozzle surface side of the nozzle plate by electrostatic polarization. The repulsive force can effectively prevent the satellite droplets from adhering to the nozzle surface. In addition, the nozzle plate can be processed with high accuracy by applying a semiconductor process.

  (Invention 10): In the image forming apparatus according to any one of Inventions 1 to 9, the charging control unit charges the base material positively before the start of the discharge operation, and performs the discharge operation. An image forming apparatus, wherein the base material is charged to a negative polarity corresponding to a start time, and the base material is charged to a positive polarity in accordance with a timing at which the satellite droplet is generated by the discharge operation.

  According to this aspect, since the satellite droplets split from the discharged droplets are negatively charged, the satellite droplets can be collected by the positively charged base material having the opposite polarity.

  (Invention 11): In the image forming apparatus according to any one of Inventions 1 to 10, the substrate conveying means for conveying the substrate is made of a conductor, and the substrate conveying means is the electrode member. An image forming apparatus, wherein

  According to this aspect, it is possible to uniformly charge the entire base material held and transported by the base material transport unit.

  (Invention 12): In the image forming apparatus according to any one of Inventions 1 to 11, a plurality of modules of the liquid ejection head are arranged in the width direction of the base material, and ejection is performed on nozzles of all the modules. An image forming apparatus, wherein possible timings are synchronized.

  According to this aspect, it is possible to form an image on a wide substrate at high speed.

  (Invention 13): In the image forming apparatus according to any one of Inventions 1 to 12, in order to eject a plurality of types of liquids, at least one liquid ejection head is provided for each type of liquid, An image forming apparatus characterized in that ejection timings of all nozzles of a plurality of liquid ejection heads corresponding to the plurality of types of liquids are synchronized.

  There is an embodiment in which multiple colors of ink are used as the multiple types of liquid. According to this aspect, it is possible to use a common electrode member for a plurality of liquid ejection heads corresponding to the plurality of types of liquids, and it becomes easy to control the charging polarity.

  (Invention 14): In the image forming apparatus according to any one of Inventions 1 to 13, a transport unit that transports the substrate to the liquid discharge head, and a discharge that controls liquid discharge of the liquid discharge head. Control means, and the liquid discharge head has a structure in which a plurality of nozzles are arranged corresponding to the length in the width direction of the base material substantially orthogonal to the transport direction of the base material by the transport means. The discharge control means controls the liquid discharge of the liquid discharge head so as to form the desired image on the substrate by transporting the substrate only once relative to the liquid discharge head. An image forming apparatus.

  When a so-called single-pass image formation is performed, if a discharge abnormality occurs in any of the nozzles in the head, streaky unevenness (image defect) along the substrate conveyance direction occurs. The present invention can effectively prevent nozzle ejection abnormalities that cause such image quality degradation.

  (Invention 15): Using an electrode member that charges a substrate facing a liquid discharge head of an on-demand discharge type having a nozzle plate on which nozzles for discharging liquid are formed, to positive polarity or negative polarity, and in the liquid discharge head The charging polarity of the base material by the electrode member in accordance with the timing of the discharge operation when the liquid is discharged from the nozzle toward the base material without applying a voltage between the liquid and the electrode member The mist collecting method in which the satellite droplets separated from the main liquid droplets ejected by the ejection operation are attached onto the base material charged to the opposite polarity to the charged polarity of the satellite droplets.

  According to the present invention, it is possible to prevent the satellite droplets generated when the liquid is discharged from adhering to the nozzle plate. In the present invention, a mode in which the charging polarity of the base material is switched in response to the thread cutting of the liquid discharged from the nozzle is preferable.

  Further, in the present invention, there is an aspect in which a head that does not have an electrode that contacts the liquid in the head is used as the liquid discharge head.

  Alternatively, the liquid in the liquid discharge head is electrically connected to the electrode member, and the liquid in the liquid discharge head and the substrate are charged to the same polarity by applying a voltage to the electrode member. There is a mode to make it.

  DESCRIPTION OF SYMBOLS 40 ... Inkjet recording device, 42 ... Inkjet head, 44 ... Base material, 50 ... Conductive platen, 52 ... Power supply, 54 ... Control circuit, 60 ... Nozzle plate, 61 ... Nozzle, 64 ... Nozzle surface, 66 ... Ink liquid column , 68 ... Main droplet, 70 ... Satellite droplet, 90 ... Head module, 91 ... Nozzle, 110 ... Inkjet recording apparatus, 124 ... Recording medium, 170 ... Drawing drum, 172M, 172K, 172C, 172Y ... Inkjet head, 250 ... Head, 250A ... nozzle surface, 251 ... nozzle, 251A ... nozzle plate, 252 ... pressure chamber, 258 ... piezoelectric element, 250 ', 250 "... head module, 272 ... system controller, 300 ... charging controller, 302 ... power supply

Claims (15)

An on-demand discharge type liquid discharge head having a nozzle plate on which nozzles for discharging liquid are formed;
An electrode member for charging a base material to which the liquid discharged from the nozzle is attached;
The charging polarity of the substrate by the electrode member is reversed in accordance with the timing of the discharge operation for discharging the liquid from the nozzle without applying a voltage between the liquid in the liquid discharge head and the electrode member. Charging control means for performing control and attaching satellite droplets generated and separated from the main droplets of the liquid ejected by the ejection operation onto the base material charged to a polarity opposite to the charging polarity of the satellite droplets;
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The image forming apparatus, wherein the liquid discharge head does not have an electrode that contacts the liquid in the head. The image forming apparatus according to claim 1,
The liquid in the liquid discharge head and the electrode member are electrically connected,
An image forming apparatus, wherein the liquid in the liquid discharge head and the base material are charged to the same polarity by a voltage applied to the electrode member. The image forming apparatus according to any one of claims 1 to 3,
The image forming apparatus according to claim 1, wherein the electrode member is a member that is disposed to face a nozzle surface of the liquid discharge head and supports the back surface of the base material. The image forming apparatus according to any one of claims 1 to 4, wherein:
The image forming apparatus according to claim 1, wherein the charging control unit switches the charging polarity of the base material to an opposite polarity in accordance with a timing of cutting the string discharged from the nozzle. The image forming apparatus according to any one of claims 1 to 5,
2. An image forming apparatus according to claim 1, wherein a plurality of nozzles are two-dimensionally arranged on the nozzle plate, and ejection timings of all the nozzles are synchronized. The image forming apparatus according to any one of claims 1 to 6,
A plurality of nozzles are two-dimensionally arranged on the nozzle plate, and the nozzle interval in the transport direction is n × D (n is the nozzle interval D for drawing adjacent dots in the direction perpendicular to the transport direction of the substrate. An image forming apparatus characterized by a natural number). The image forming apparatus according to any one of claims 1 to 7,
The image forming apparatus, wherein the nozzle plate is formed of a non-conductive material. The image forming apparatus according to any one of claims 1 to 8,
The image forming apparatus, wherein the nozzle plate is made of silicon. The image forming apparatus according to any one of claims 1 to 9,
The charging control means charges the base material to a positive polarity before the start of the discharge operation,
Corresponding to the start of the discharge operation, the substrate is charged to a negative polarity, and the substrate is charged to a positive polarity in accordance with the timing at which the satellite droplets are generated by the discharge operation. apparatus. The image forming apparatus according to any one of claims 1 to 10,
An image forming apparatus, wherein the substrate conveying means for conveying the substrate is made of a conductor, and the substrate conveying means serves as the electrode member. The image forming apparatus according to any one of claims 1 to 11,
An image forming apparatus, wherein a plurality of modules of the liquid discharge head are arranged in the width direction of the base material, and the dischargeable timing is synchronized with respect to the nozzles of all the modules. The image forming apparatus according to any one of claims 1 to 12,
In order to discharge a plurality of types of liquid, at least one liquid discharge head is provided for each type of liquid, and the discharge possible timings of all nozzles of the plurality of liquid discharge heads corresponding to the plurality of types of liquid are synchronized. An image forming apparatus. The image forming apparatus according to claim 1,
Conveying means for conveying the substrate to the liquid ejection head;
A discharge control means for controlling the liquid discharge of the liquid discharge head,
The liquid discharge head has a structure in which a plurality of nozzles are arranged corresponding to the length in the width direction of the base material substantially orthogonal to the transport direction of the base material by the transport means,
The discharge control means controls the liquid discharge of the liquid discharge head so as to form the desired image on the substrate by transporting the substrate only once relative to the liquid discharge head. An image forming apparatus. Using an electrode member that charges the substrate facing the liquid discharge head of the on-demand discharge method having a nozzle plate on which nozzles for discharging liquid are formed, to positive polarity or negative polarity,
Without applying a voltage between the liquid in the liquid discharge head and the electrode member, in accordance with the timing of the discharge operation when discharging the liquid from the nozzle toward the substrate, the electrode member performs the operation. Invert the charging polarity of the substrate,
A mist collecting method in which satellite droplets separated and generated from main liquid droplets ejected by the ejection operation are attached to the base material charged to a polarity opposite to the charged polarity of the satellite droplets.

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