JP2010100018A - Inkjet recording method and inkjet recording apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrostatic attraction type inkjet recording method capable of executing highly accurate image recording by effectively destaticizing a liquid droplet after discharge and before an act on a recording medium while retaining landing accuracy by electrostatic attraction and eliminating the influence of the liquid droplet landed on an insulative recording medium on the liquid droplet during flight, and an apparatus therefor. <P>SOLUTION: The inkjet recording apparatus 1 which includes an opposite electrode 20 oppositely disposed on a nozzle face 11 of a head 10 having liquid droplet charging means 51 for charging the liquid droplet (a) discharged from a nozzle 12 attracts the charged liquid droplet (a) discharged from the nozzle 12 by the opposite electrode 20, and lands it on the insulative recording medium M disposed between the nozzle face 11 and the opposite electrode 20. In the inkjet recording apparatus 1, a destaticization member 30 capable of transmitting the liquid droplet (a) from the surface to the back face is provided between the nozzle face 11 of a head 10 and the recording medium M to cause the liquid droplet (a) discharged from the nozzle 12 to be brought into contact with the destaticization member 30, then transmitted through the destaticization member 30 and landed on the recording medium M. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ink jet recording method and an ink jet recording apparatus in which droplets discharged from nozzles are charged and landed on an insulating recording medium.

  A counter electrode is provided so as to face the nozzle surface of the ink jet head, the recording medium is disposed between the nozzle surface and the counter electrode, and the charged droplet is discharged from the nozzle, whereby the droplet is recorded by electrostatic force. In the electrostatic suction type ink jet recording apparatus that pulls toward the surface, when an insulating recording medium is used, the charge of the droplet discharged and landed does not escape. Next, the following influence is exerted on the discharged droplet.

(1) The droplet ejected next and flying is subjected to a repulsive force due to the influence of the charge (repulsive force) of the previously landed droplet, and the flight direction is bent.
(2) A small satellite associated with a droplet to be ejected next will fly in the air without landing due to the repulsive force of the droplet that has landed first.
(3) The landed droplets spread on the surface of the recording medium, but are spread unevenly due to the repulsive force of the previously landed droplets. As a result, a gap is formed between the first landed droplet and the next landed droplet, and a portion where the image is not filled with the droplet occurs.

  The above (1) and (3) affect the image quality, and (2) has a problem that the satellite flying in the air adversely affects the head and peripheral devices as well as the image quality.

  In order to solve such a problem due to the electric charge of the droplet, in Patent Document 1, the recording atmosphere of the droplet is adjusted by adjusting the discharge atmosphere of the droplet to a dew point temperature of 9 ° C. or higher and lower than the saturation temperature of water. The technology that promotes the leakage of electric charges from the droplets that have landed on the medium to the atmosphere, and the surface treatment layer that has a surface resistance of a predetermined value or less is provided in the area where the droplets of the insulating recording medium are discharged. The technology that further promotes the leakage of electric charges from the liquid droplets, the static eliminator is disposed so as to be relatively movable facing the insulating recording medium that receives the liquid droplets, and the surface potential distribution that is neutralized by the static eliminator is Techniques have been proposed in which droplets are ejected onto an insulating recording medium in a uniform state, thereby preventing ejection defects while keeping the ejection amount constant.

In Patent Document 2, a corona charger is provided so as to face the surface of the insulating recording medium, and a charge opposite to the charge charged up on the recording medium is supplied to eliminate the charge of the insulating recording medium. After performing this, a technique for stabilizing the discharged fluid by discharging the fluid has been proposed.
Japanese National Patent Publication No. 2005-014289 JP 2005-58811 A

  However, in the method of promoting leakage of electric charges from the landed droplets by adjusting the droplet discharge atmosphere, it is difficult to sufficiently and quickly discharge the droplets while maintaining a stable droplet discharge environment.

  In addition, depending on the recording medium, depending on the recording medium, a desired surface treatment may be performed by performing image recording on an insulating recording medium provided with a surface treatment layer in a range where droplets are discharged. In addition to being difficult to apply, it may be necessary to remove the surface treatment layer after image recording.

  Furthermore, in the method of neutralizing the surface of the recording medium using a static eliminator, it cannot be used in the vicinity of the droplet landing, so it is difficult to sufficiently neutralize the droplet.

  In view of the above, the present invention makes it possible to land on an insulating recording medium by effectively removing electricity from the droplet after ejection and before landing on the recording medium while maintaining the landing accuracy by electrostatic suction. It is an object of the present invention to provide an electrostatic attraction type ink jet recording method and an ink jet recording apparatus which can eliminate the influence of the droplets on the droplets in flight and can perform highly accurate image recording.

  Other problems of the present invention will become apparent from the following description.

  The above problems are solved by the following inventions.

According to a first aspect of the present invention, an inkjet head having a droplet discharge means for discharging a droplet from a nozzle and a droplet charging means for charging the droplet, and a nozzle surface of the inkjet head are arranged to face each other. An inkjet recording method comprising: a counter electrode; and a charged droplet discharged from the nozzle is sucked by the counter electrode and landed on an insulating recording medium disposed between the nozzle surface and the counter electrode In
Provided between the nozzle surface of the inkjet head and the surface of the recording medium is a neutralizing member that can transmit liquid droplets from the front surface to the back surface, and after the liquid droplets discharged from the nozzle are brought into contact with the neutralizing member, An ink jet recording method, comprising: passing through a charge eliminating member and landing on the recording medium.

  A second aspect of the present invention is the ink jet recording method according to the first aspect, wherein the charge removal member is formed of a conductive material and a sheet having a large number of openings penetrating the front and back. .

  According to a third aspect of the present invention, the opening of the static elimination member has an opening diameter that is less than or equal to the diameter of the droplet, and the shortest distance between adjacent openings is less than or equal to three times the diameter of the droplet. 3. The ink jet recording method according to claim 2, wherein the ink jet recording method is arranged.

  According to a fourth aspect of the present invention, there is provided the ink jet recording method according to the first, second or third aspect, wherein the charge eliminating member is interposed at a distance from the surface of the recording medium.

According to a fifth aspect of the present invention, an inkjet head having a droplet discharge means for discharging a droplet from a nozzle and a droplet charging means for charging the droplet, and a nozzle surface of the inkjet head are arranged opposite to each other. An ink jet recording apparatus comprising: a counter electrode, wherein the charged droplets discharged from the nozzle are sucked by the counter electrode and landed on an insulating recording medium disposed between the nozzle surface and the counter electrode In
An ink jet recording apparatus comprising: a discharging member capable of transmitting the liquid droplet from the front surface to the back surface at a position where the liquid droplet discharged from the nozzle contacts the liquid droplet before landing on the recording medium. It is.

  A sixth aspect of the present invention is the ink jet recording apparatus according to the fifth aspect, wherein the charge eliminating member is formed of a sheet made of a conductive material and having a large number of openings penetrating front and back. .

  According to a seventh aspect of the present invention, the opening of the static elimination member has an opening diameter that is less than or equal to the diameter of the droplet, and the shortest distance between adjacent openings is less than or equal to three times the diameter of the droplet. The inkjet recording apparatus according to claim 6, wherein the inkjet recording apparatus is arranged.

  According to an eighth aspect of the invention, there is provided an ink jet recording apparatus according to the fifth, sixth or seventh aspect, further comprising a spacer for keeping a distance between the recording medium and the charge eliminating member.

  According to the present invention, landing on an insulating recording medium is achieved by effectively removing the charge after discharging and before landing on the recording medium while maintaining the landing accuracy by electrostatic attraction. Thus, it is possible to provide an electrostatic suction ink jet recording method and an ink jet recording apparatus capable of eliminating the influence of the droplets on the droplets in flight and performing highly accurate image recording.

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

(Overall configuration of inkjet recording apparatus)
FIG. 1 is a schematic configuration diagram showing an example of an ink jet recording apparatus according to the present invention.

  The ink jet recording apparatus 1 includes an ink jet head 10 that discharges droplets a, a recording medium M that is disposed to face the nozzle surface 11 of the ink jet head 10, and a nozzle medium 11 that is also disposed between the nozzle surface 11 of the ink jet head 10. The counter electrode 20 is disposed to be opposed to each other with the M interposed therebetween, and the neutralizing member 30 is disposed between the nozzle surface 11 of the inkjet head 10 and the surface of the recording medium M.

  The inkjet head 10, the recording medium M, the counter electrode 20, and the charge removal member 30 are configured to be relatively movable. For example, the position of the inkjet head 10 may be fixed, and the recording medium M, the counter electrode 20 and the charge removal member 30 may be integrated to be horizontally movable in the X and Y directions with respect to the inkjet head 10. The position of the member 30 may be fixed, and the inkjet head 10 may be horizontally movable in the XY direction. Further, the inkjet head 10 is horizontally moved in the X direction, for example, and the recording medium M, the counter electrode 20 and the charge removal member 30 are moved in the Y direction, for example. It is also possible to move both of them horizontally.

(Inkjet head)
In the inkjet head 10, a nozzle 12 is formed on a nozzle surface 11 facing downward in the drawing, and a liquid stored in an internal liquid chamber 13 is discharged from the nozzle 12 as a droplet a. Although only one set of the nozzles 12 and the liquid chambers 13 is illustrated here, the inkjet head 10 may include a plurality of sets of the nozzles 12 and the liquid chambers 13 arranged. The liquid is supplied from the liquid storage tank 40 to the liquid chamber 13.

  The inkjet head 10 is a recording in which a liquid droplet discharge means (none of which is not shown) is driven and controlled by the discharge control means to discharge the liquid in the liquid chamber 13 from the nozzle 12 as a liquid droplet a, and is opposed to the recording. Fly toward the medium M.

  The specific mode of the droplet discharge means for discharging the droplet a is not particularly limited in the present invention. For example, a piezoelectric element, which is an electromechanical conversion element, is used on the side wall constituting the liquid chamber 13, and a predetermined voltage is applied to the piezoelectric element to deform the side wall so that the discharge pressure is applied to the liquid in the liquid chamber 13. A mode of applying, a mode of applying a discharge pressure to the liquid in the liquid chamber 13 by expanding and contracting the diaphragm facing the liquid chamber 13 using a piezo element, and a diaphragm facing the liquid chamber 13 using electrostatic force A mode in which discharge pressure is applied to the liquid in the liquid chamber 13 by operating, and a discharge pressure is applied to the liquid by utilizing the bursting action of bubbles generated in the liquid by energizing the heater provided in the liquid chamber 13 And the like.

  In the present invention, the outlet side diameter of the nozzle 12 is preferably 5 to 50 μm.

  Examples of the liquid that can be used in the present invention include aqueous dye ink and pigment solvent ink.

  In the present invention, the droplet a is preferably 0.1 to 50 pl.

  In the liquid chamber 13 of the inkjet head 10, a charging electrode 51 is provided as a droplet charging means for charging the stored liquid. A predetermined voltage is applied to the charging electrode 51 by the charging controller 50.

(Recording medium M)
In the present invention, the recording medium M has an insulating property. Here, the insulating property means that the resistivity is 10 ¹⁰ (Ω · m) or more. The insulation may be on the surface of the recording medium M.

  Examples of such an insulating recording medium M include paper and glass.

  The distance between the nozzle surface 11 of the inkjet head 10 and the surface of the recording medium M is preferably 0.5 to 3.0 mm.

(Counter electrode)
The counter electrode 20 is provided at a position facing the nozzle surface 11 with the recording medium M and the charge removal member 30 sandwiched between the nozzle surface 11 of the inkjet head 10 and the surface of the counter electrode 20 mounts the entire recording medium M. It has a size that can be placed and supported. The recording medium M is supported in direct contact with the surface of the counter electrode 20.

  A predetermined potential is applied to the counter electrode 20, and an electrostatic force is applied to the charged droplet a discharged from the nozzle 12 of the inkjet head 10 by forming an electric field with the inkjet head 10. Then, accelerated suction is performed toward the counter electrode 20.

(Charging member)
The charge removal member 30 is a member for discharging the charged droplet a by contacting the droplet a discharged from the nozzle 12 of the inkjet head 10, and discharged from the nozzle 12 of the inkjet head 10. Before the droplet a flying is landed on the surface of the recording medium M, the droplet a is arranged on the surface of the recording medium M so as to be opposed to the nozzle surface 11 of the inkjet head 10 so that the droplet a can come into contact with the droplet a. Has been.

  The static eliminating member 30 is formed using a conductive material and has a size that can cover at least the recording area of the surface of the recording medium M, and is landed on the surface by being grounded. Accordingly, the static electricity is removed from the droplet a that has come into contact.

  Examples of the conductive material include silicon, SUS (stainless steel), aluminum, nickel, and carbon fibers (such as carbon nanotubes and carbon fibers). Among these, it is preferable to use SUS from the viewpoint of conductivity and strength.

  Since the charge removal member 30 is interposed between the nozzle surface 11 of the inkjet head 10 and the recording medium M, the flying of the droplets a from the nozzle 12 toward the recording medium M does not hinder the surface of the charge removal member 30. It is necessary to set the thickness so that the droplet a landed on the recording medium M can reach the recording medium M on the back surface side and reach the recording medium M. From this viewpoint, the thickness of the static elimination member 30 is preferably set to 1 to 1000 μm.

  The static elimination member 30 has a large number of openings 31 penetrating the front and back so that the droplets a contacting the surface can reach the recording medium M on the back side. It is configured to be transmissive to the back surface. For this reason, the droplet a discharged from the nozzle 12 is discharged by first contacting the charge removing member 30 before landing on the surface of the recording medium M, and passes through the opening 31 by gravity, capillary force, and adhesive force. Then, the discharged droplet a that has passed through the charge removal member 30 reaches the surface of the recording medium M.

  The size of each opening 31 varies depending on the size of the droplet a ejected from the nozzle 12, but in order to ensure that the ejected droplet a can come into contact with the charge removal member 30, the aperture diameter is The diameter is equal to or smaller than the diameter of the droplet a.

  The shape of the opening 31 is not particularly limited, such as a circular shape or a square shape, but the opening diameter is the shortest distance of the inner diameter of the opening 31.

  Further, if the interval between the adjacent openings 31 is too large, the droplet a may land between the adjacent openings 31 and may not be transmitted through the opening 31 to the recording medium M on the back surface side. The openings 31 are arranged so that the shortest distance between the openings 31 is three times or less the diameter of the droplet a. The reason why the diameter of the droplet a is three times or less is that the landed droplet a spreads in the horizontal direction and has a diameter several times the diameter. If it is 3 times or less the diameter of the droplet a, even if it lands between the openings 31 of the static elimination member 31, it can reach any one of the adjacent openings 31 by spreading in the lateral direction.

  Below, some aspects of the static elimination member 30 are given.

  FIG. 2 is a plan view of a static elimination member 30A formed in a mesh shape using a linear body 301 made of a large number of conductive materials. The broken line in the figure represents the droplet a that has contacted the surface of the charge removal member 30A.

  Each linear body 301 has a width (diameter) of 1 to 50 μm, and is arranged in a sheet shape as a whole by being arranged so that the number is 20 to 200 per 1000 μm vertically and horizontally. Thereby, a large number of openings 31 penetrating the front and back are formed in the vertical and horizontal directions of the static elimination member 30A.

  Such a charge removal member 30A is woven or knitted using the linear body 301 formed in a thin thread shape, or presses the linear body 301 arranged at predetermined intervals to form the openings 31 in the vertical and horizontal directions. Can be created by doing.

  FIG. 3 is a plan view of a charge removal member 30 </ b> B in which a sheet 302 made of a conductive material is used and a large number of openings 31 are opened in the sheet 302. The broken line in the figure represents the droplet a that has contacted the surface of the charge removal member 30A.

  The sheet 302 has a thickness of 100 to 1000 μm and is formed so that a large number of openings 31 penetrate the front and back. The arrangement of the openings 31 is not particularly limited, but it is preferable that the openings 31 be arranged so that the intervals between all the openings 31 around the opening 31 are equal as shown in the figure. Also, the shape of the opening 31 is arbitrary such as a circular shape or a square shape.

  Such a charge removal member 30B can be formed by using a plate-like conductive material and laser processing or pressing the opening 31 therein.

  The neutralizing member 30 may be disposed so as to be in direct contact with the surface of the recording medium M, but it is preferable to form a gap of 10 to 100 μm with the surface of the recording medium M. By providing the gap, it is possible to easily remove the charge eliminating member 30 from the surface of the recording medium M after image recording, and it is also easy for the droplets a that have landed on the surface of the charge eliminating member 30 to flow from the front side to the back side through the opening 31. In addition, it is possible to prevent the occurrence of white spots by reliably landing on the surface of the recording medium M.

  Such a gap can be formed by interposing a spacer 60 between the charge removal member 30 and the recording medium M, as shown in FIG.

  The spacer 60 can be formed of SUS or a resin material. In addition to supporting both ends of the static elimination member 30, it is preferable to support the static elimination member 30 at a plurality of points so that the static elimination member 30 can be supported as a whole without bending. For example, a spherical spacer having a diameter of 10 to 100 μm Are preferably scattered at a plurality of locations between the static elimination member 30 and the recording medium M.

  It is preferable that the static elimination member 30 is heated so that it may become a temperature of 40-80 degreeC. This has the effect of facilitating the permeation of the droplet a to the back side of the charge removal member 30 by lowering the viscosity and surface tension of the landed droplet a. When the static elimination member 30 is heated, the static elimination member 30 separately heated using a heater or the like so as to reach the above temperature is disposed on the surface of the recording medium M immediately before recording, or prior to recording. Then, it can be performed by blowing warm air to the neutralizing member 30 arranged on the surface of the recording medium M so as to reach the above temperature.

  In addition, when the liquid is aqueous, it is preferable that the charge removal member 30 is subjected to a hydrophilic treatment. This has the effect of facilitating the permeation of the droplets a made of an aqueous liquid landed on the charge removal member 30 to the back surface. Examples of the hydrophilic treatment in this case include mechanical polishing of the surface of the static elimination member 30, chemical cleaning such as acid cleaning, plasma processing, and the like.

  According to such an ink jet recording apparatus 1, the charged droplet a discharged from the nozzle 12 of the ink jet head 10 is accelerated and sucked by the action of an electric field formed between the counter electrode 20 and the bending direction thereof. The component flies toward the recording medium M in a relatively small state, and comes into contact with the charge removal member 30 before landing on the recording medium M. Due to the contact with the charge removal member 30, the electric charge of the droplet a is removed and the charge is removed.

  The droplet a ejected from the nozzle 12 is affected by the electric field formed between the counter electrode 20 until it comes into contact with the charge eliminating member 30, and is recorded while maintaining high positional accuracy by the electrostatic suction method. Although it flies toward the medium M, the droplet a after contacting the static elimination member 30 no longer flies, and passes through the static elimination member 30 from the front surface to the back surface, and reaches a predetermined position on the recording medium M. Therefore, even if the droplet a is discharged before the recording medium M is landed, the landing accuracy by electrostatic attraction can be maintained. Therefore, it is possible to effectively remove the charge from the droplet a after ejection and before landing on the recording medium M, and the droplet a landed on the insulating recording medium M is ejected next. The influence on the inside droplet a can be eliminated, and high-precision image recording can be realized.

(Configuration of inkjet recording apparatus)
Two inkjet heads (head 1 and head 2) having the same structure each having droplet charging means are prepared, and as shown in FIG. 4, the head 1 and the head 2 are arranged so that the nozzle row direction is orthogonal to the recording direction. A gap of 30 mm is provided between the head 1 and the head 2, and the nozzle pitch is arranged in parallel so that the nozzle pitch is deviated by 150 μm, so that printing can be performed on the recording medium by a one-pass method along the recording direction. An ink jet recording apparatus was constructed.

The specifications of the inkjet head are as follows.
Droplet: 14 pl (droplet diameter ≈ φ30 μm, when glass reaches φ200 to 250 μm)
Nozzle diameter: 30 μm
Nozzle material: Polyimide Head moving speed: 300 m / sec
Ink used: Water-based dye ink Charging voltage: 5 kV

(Printing method)
Using the inkjet head shown in FIG. 4, each nozzle is ejected, such as the first nozzle of the head 1, the first nozzle of the head 2, the second nozzle of the head 1, the second nozzle of the head 2, and so on. As a result, a straight line was printed in one line for each dot.

  Using this ink jet recording apparatus, printing was performed on a conductive recording medium (1 mm thick SUS plate) as described above, and the center-of-gravity distance between two adjacent landing dots was measured to be 151 μm.

  Similarly, printing was performed on an insulating recording medium (1 mm thick glass plate) (without a neutralizing member), and the center-of-gravity distance between two adjacent landing dots was measured and found to be 183 μm.

(Evaluation methods)
An SUS (thickness 0.1 mm, pickled) neutralizing member was placed on an insulating recording medium (1 mm thick glass plate), and printing was performed as described above.

  The evaluation is based on the center-of-gravity distance 151 μm between the landing dots on the conductive recording medium and the center-of-gravity distance 183 μm between the landing dots on the insulating recording medium, and the landing on the recording medium when the charge eliminating member is used. The center-of-gravity distance X between the dots was determined, and it was evaluated as ◯ if it satisfied the following expression, and x otherwise.

  | X-151 μm | <| 183 μm-151 μm |

Example 1
FIG. 5 shows the results of evaluation according to the evaluation method described above using each static elimination member arranged as shown in FIG. 3 with the center interval A (see FIG. 5) between adjacent openings common to 50 μm and the aperture diameters varied as follows. It is shown in 1.

Example 2
Evaluation was carried out according to the above evaluation method using the respective static eliminating members arranged as shown in FIG. 3 with the same aperture diameter of 20 μm and with the interval B (see FIG. 5), which is the shortest distance between adjacent openings, varied as follows. The results are shown in Table 2.

  When the distance B between the openings was 120 μm, the shortest distance between the openings exceeded three times the droplet diameter (≈30 μm), and some of the dots on the recording medium were missing.

1 is a schematic configuration diagram showing an example of an ink jet recording apparatus according to the present invention. The top view which shows an example of a static elimination member The top view which shows another example of a static elimination member Configuration diagram of inkjet head used in Examples Explanatory drawing of center distance A and shortest distance B between openings

Explanation of symbols

1: Inkjet recording apparatus 10: Inkjet head 11: Nozzle surface 12: Nozzle 13: Liquid chamber 20: Counter electrode 30, 30A, 30B: Static elimination member 31: Opening 301: Linear body 302: Sheet 40: Storage tank 50: Charging Control part 51: Electrode for charging M: Recording medium a: Droplet

Claims (8)

An inkjet head having droplet ejection means for ejecting droplets from the nozzle and droplet charging means for charging the droplets; and a counter electrode disposed to face the nozzle surface of the inkjet head, the nozzle In the ink jet recording method, the charged droplets discharged from the liquid are sucked by the counter electrode and landed on an insulating recording medium disposed between the nozzle surface and the counter electrode.
Provided between the nozzle surface of the inkjet head and the surface of the recording medium is a neutralizing member that can transmit liquid droplets from the front surface to the back surface, and after the liquid droplets discharged from the nozzle are brought into contact with the neutralizing member, An ink jet recording method, comprising: passing through a charge eliminating member and landing on the recording medium.   2. The ink jet recording method according to claim 1, wherein the charge eliminating member is formed of a sheet made of a conductive material and having a large number of openings penetrating the front and back.   The openings of the static elimination member are arranged such that the opening diameter is equal to or smaller than the diameter of the droplet, and the shortest distance between adjacent openings is equal to or smaller than three times the diameter of the droplet. The inkjet recording method according to claim 2.   4. The ink jet recording method according to claim 1, wherein the static eliminating member is interposed at a distance from the surface of the recording medium. An inkjet head having droplet ejection means for ejecting droplets from the nozzle and droplet charging means for charging the droplets; and a counter electrode disposed to face the nozzle surface of the inkjet head, the nozzle In the ink jet recording apparatus, the charged droplets discharged from the suction electrode are sucked by the counter electrode and landed on an insulating recording medium disposed between the nozzle surface and the counter electrode.
An ink jet recording apparatus comprising: a discharging member capable of transmitting the liquid droplet from the front surface to the back surface at a position where the liquid droplet discharged from the nozzle contacts the liquid droplet before landing on the recording medium. .   6. The ink jet recording apparatus according to claim 5, wherein the charge eliminating member is formed of a conductive material and a sheet having a large number of openings penetrating the front and back surfaces.   The openings of the static elimination member are arranged such that the opening diameter is equal to or smaller than the diameter of the droplet, and the shortest distance between adjacent openings is equal to or smaller than three times the diameter of the droplet. An ink jet recording apparatus according to claim 6.   8. The ink jet recording apparatus according to claim 5, further comprising a spacer for keeping a distance between the recording medium and the charge eliminating member.

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