JP2011175209A - Electrophotographic printer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic printer for improving printing quality in printing information on a second surface of a printed matter. <P>SOLUTION: The electrophotographic printer has: developing units 31-34 for transferring a liquid toner on a photoreceptor formed with an electrostatic latent image; an intermediate transfer body 35 for transferring the liquid toner developed by the developing unit; a backup roller (pressure body) 36 for forming a nip part N1 by being in contact with the intermediate transfer body 35 and applying a bias voltage for sucking the liquid toner; and a flash light emitting device (toner fixing means) 38 for fixing the liquid toner by heating the liquid toner transferred on a printing sheet S (printed matter). The electrophotographic printer 10 for printing information on the second surface which is opposite to a first surface after printing the information on the first surface of the printing sheet S has a moisture adding means 60A(60B) for adding moisture on the second surface of the printing sheet S with the information printed on the first surface. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an electrophotographic printing apparatus that performs printing on both sides of an object to be printed by a liquid developing electrophotographic system that performs printing using toner dispersed in a liquid carrier.

  Conventionally, an electrostatic latent image formed on a photoreceptor is developed using a liquid toner in which a toner composed of a thermoplastic resin and a pigment is dispersed in a carrier, and the liquid toner is transferred to the surface of a printing material. There has been proposed an electrophotographic printing apparatus that performs printing by fixing toner in a transferred liquid toner onto a substrate.

  As such an electrophotographic printing apparatus, for example, a double-sided printing apparatus as shown in Patent Document 1 is known. The double-sided printing apparatus includes a paper feeding unit that feeds printed materials, which are sheets, to the printing unit one by one, a printing unit that performs printing on both sides of the printed material fed from the paper feeding unit, and printing. A paper discharge unit that discharges a printed material that has been printed on both sides by the unit.

  The printing unit includes a developing unit that performs development by transferring a liquid toner in which charged particulate toner is dispersed in a liquid carrier onto a photoreceptor on which an electrostatic latent image is formed, and the developing unit develops the toner. A roller-like intermediate transfer member for transferring the liquid toner, and a backup roller to which a bias voltage is applied so as to form a nip portion in contact with the intermediate transfer member and suck the liquid toner. In the substrate to be printed fed from the sheet feeding unit, the liquid toner on the intermediate transfer member is first transferred to one surface (first surface) at the nip portion. The printed material having the liquid toner transferred to the first surface is conveyed to the toner fixing unit, and the printed material is heated by the toner fixing unit, whereby the toner in the liquid toner transferred to the first surface is melted. Liquid toner is fixed on the first surface. The substrate on which the liquid toner is fixed on the first surface is guided to the sheet reversing mechanism and reversed, and then conveyed again to the nip portion. In the nip portion, on the surface opposite to the first surface. The liquid toner on the intermediate transfer member is transferred to a certain second surface. The printed material having the liquid toner transferred to the first surface is conveyed again to the toner fixing means, and the printed material is heated by the toner fixing device, so that the liquid toner transferred to the second surface is transferred to the second surface. It is fixed. The substrate to be printed on both sides by the printing unit according to the above procedure is discharged to the paper discharge unit, thereby completing the double-sided printing.

JP 2009-163064 A

  However, in the double-sided printing apparatus disclosed in Patent Document 1, after the liquid toner is transferred to the first surface, which is one side of the printed material, the printed material is heated by the toner fixing unit to fix the liquid toner on the first surface. The moisture in the printing material evaporates and the water content decreases. For this reason, when transferring the liquid toner to the second surface at the nip portion, there is a problem that the transfer efficiency of the liquid toner to the second surface is reduced and the print quality is lowered. This is because the surface resistivity of the printing material increases as the water content in the printing material decreases, and electrostatic transfer of the liquid toner due to the bias voltage of the backup roller is hindered.

  SUMMARY An advantage of some aspects of the invention is that it provides an electrophotographic printing apparatus capable of improving print quality when printing on a second surface of a substrate.

  In order to achieve the above object, an electrophotographic printing apparatus according to the present invention includes a developing unit that transfers a liquid toner onto a photoreceptor on which an electrostatic latent image is formed and performs development, and the developing unit that is developed by the developing unit. An intermediate transfer member for transferring liquid toner; a pressure member to which a bias voltage for sucking the liquid toner is applied while being in contact with the intermediate transfer member; and a liquid transferred to the substrate And a toner fixing unit that fixes the liquid toner by heating the toner, and prints the second surface, which is the surface opposite to the first surface, after printing the first surface of the substrate. In the photographic printing apparatus, a moisture applying means for applying moisture to the second surface of the substrate on which the first surface is printed is provided.

  According to the present invention, since the moisture applying means for applying moisture is provided on the second surface of the printed material on which the first surface is printed, the toner is fixed on the first surface by the toner fixing device, The second surface can be printed in a state where the water content (water content) is returned to an appropriate range. As a result, the transfer efficiency of the liquid toner onto the second surface can be improved as compared with the conventional case, and the print quality can be improved.

  Further, the electrophotographic printing apparatus of the present invention is provided in a conveyance path on the downstream side of the toner fixing unit, and a reversing unit for reversing the front and back of the printing material on which the liquid toner is fixed on the first surface, A reversing path for transporting the printed material reversed by the reversing means to the nip portion, and the moisture applying means is provided in the conveying path from the exit of the toner fixing means to the reversing means or in the middle of the reversing path. It is characterized by being able to.

  According to the present invention, the reversing unit is provided in the conveyance path on the downstream side of the toner fixing unit and reverses the front and back of the printed material on which the liquid toner is fixed on the first surface, and is reversed by the reversing unit. And a reversing path for transporting the printed material to the nip portion, and the moisture applying means is provided in the transport path from the exit of the toner fixing means to the reversing means or in the middle of the reversing path. In the electroprinting photographic apparatus of the type in which the printing on the first surface and the second surface is performed using the same intermediate transfer member, backup roller, and toner fixing means, the transfer efficiency of the liquid toner to the second surface can be improved, Print quality can be improved.

  In the electrophotographic printing apparatus of the present invention, the moisture applying unit includes a mist generating device, and the mist is sprayed from the mist generating device onto the second surface of the substrate.

  According to the present invention, since the mist generating device is applied as the moisture applying means, the mist generating device can be easily installed in the electrophotographic printing apparatus, the mist supply amount can be easily controlled, and the printed material can be efficiently processed. Moisture can be added.

  In the electrophotographic printing apparatus of the present invention, the moisture applying unit includes a discharge electrode disposed on the second surface side of the substrate, and a collecting electrode disposed in contact with the first surface of the substrate. Mist is sprayed on the discharge electrode, and a voltage is applied between the collection electrode and the discharge electrode to charge the mist on the discharge electrode, and the mist is discharged from the discharge electrode by electrostatic force. The mist is attached to the second surface by being moved to the second surface of the printed matter.

  According to the present invention, since the mist is charged and the mist is adhered to the second surface of the printing material by electrostatic force, the adhesion of the mist to the printing material can be further improved.

  In the electrophotographic printing apparatus of the present invention, the moisture applying unit includes a pair of rollers disposed on the wake side of the mist generating device so as to face each other with the conveyance path interposed therebetween. After the mist is sprayed on the second surface of the printing material, the printing material is pressurized by the pair of rollers.

  According to the present invention, since the mist is sprayed on the second surface of the printing material from the mist generating device and then the printing material is pressed by the pair of rollers, the adhesion of the mist to the printing material is further increased. Can be improved.

  The electrophotographic printing apparatus of the present invention is installed between a mist generation amount control means for controlling a mist generation amount generated by the mist generation apparatus, the toner fixing means, and the moisture applying means, and the substrate to be printed. A moisture detection sensor for detecting the amount of moisture in the mist, and the mist generation amount control means controls the mist generation amount based on the amount of moisture in the printed material detected by the moisture detection sensor. To do.

  According to the present invention, since the amount of mist generated by the mist generating device is controlled based on the amount of moisture in the printing material detected by the moisture detection sensor, the amount of moisture in the printing material is adjusted with high accuracy. be able to.

  The electrophotographic printing apparatus of the present invention further comprises mist generation amount control means for controlling a mist generation amount generated by the mist generation apparatus, and the mist generation amount control means has a pattern area on the first surface of the printed material. The mist generation amount is controlled based on a rate.

  According to the present invention, since the amount of mist generated by the mist generator is controlled based on the pattern area ratio on the first surface of the substrate, the amount of moisture in the substrate can be adjusted with high accuracy. it can.

  The electrophotographic printing apparatus of the present invention further comprises mist generation amount control means for controlling a mist generation amount generated by the mist generation apparatus, and the mist generation amount control means is based on a preset type of substrate to be printed. And controlling the amount of mist generated.

  According to the present invention, since the amount of mist generated by the mist generating device is controlled based on the preset type of printed material or the appropriate amount of moisture, the amount of moisture in the printed material is adjusted with high accuracy. be able to.

  According to the electrophotographic printing apparatus of the present invention, since the moisture imparting means for imparting moisture is provided on the second surface of the printed material on which the first surface is printed, the toner is fixed on the first surface by the toner fixing means. Thereafter, the second surface can be printed in a state in which the moisture content in the substrate is returned to an appropriate range. As a result, the transfer efficiency of the liquid toner onto the second surface can be improved as compared with the conventional case, and the print quality can be improved.

FIG. 1 is a schematic configuration diagram of an electrophotographic printing apparatus according to the first embodiment. FIG. 2 is a conceptual diagram of moisture applying means applied in the first embodiment. FIG. 3 is a conceptual diagram of moisture applying means applied in the second embodiment. FIG. 4 is a conceptual diagram showing a control example of the mist generating device of the moisture applying means. FIG. 5 is a conceptual diagram showing a control example of the mist generating device of the moisture applying means. FIG. 6 is a conceptual diagram showing a control example of the mist generating device of the moisture applying means.

  Exemplary embodiments of an electrophotographic printing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. In addition, this invention is not limited by this Example.

  FIG. 1 is a schematic configuration diagram of an electrophotographic printing apparatus 10 according to the first embodiment. An electrophotographic printing apparatus 10 illustrated in FIG. 1 is a liquid developing electrophotographic double-sided printing machine, and includes a paper feeding unit 11, a printing unit 12, and a paper discharging unit 13. The paper feeding unit 11 can supply a sheet (printed material) S, which is a sheet, from the paper feeding tray 21 to the printing unit 12 one by one. The printing unit 12 performs printing on one side (hereinafter referred to as “first side”) of the supplied print sheet S, and then reverses the front and back sides of the print sheet S so as to be opposite to the first side. By printing on this side (hereinafter referred to as “second side”), printing is performed on both sides (first side and second side) of the print sheet S. The paper discharge unit 13 can discharge the print sheet S printed on both sides by the printing unit 12 to a paper discharge tray 22.

  Although illustration is omitted, the electrophotographic printing apparatus 10 is connected to a main control device including a calculation unit, a display unit, and an input unit, and each unit of the electrophotographic printing device 10 receives a control signal from the main control device. It is comprised so that it may be controlled by.

  The electrophotographic printing apparatus 10 is configured to be able to perform process color printing, and the printing unit 12 includes K (black), C (indigo), M (red), and Y (yellow) process color colors. Four developing units 31, 32, 33, and 34 corresponding to are provided. The printing unit 12 includes developing units 31 to 34, an intermediate transfer member 35, a backup roller (pressure member) 36, a chain gripper 37, a flash irradiation device (toner fixing unit) 38, a switch mechanism 39, a reciprocating guide roller (reversing unit). ) 40, a switchback roller (reversing means) 41, a sheet storage portion (reversing means) 42, a reversing path 43, a pair of heating rollers 44, and a moisture applying device (moisture providing means) 60A. Is.

  The appropriate moisture content in the printing sheet S (optimum moisture content for printing: hereinafter referred to as “appropriate moisture content”) is generally about 5%, but the liquid transferred to the first surface of the printing sheet S. When the toner is fixed by the flash irradiation device (toner fixing means) 38, the moisture in the print sheet S evaporates due to the heat of the flash irradiation device 38, so the water content (hereinafter referred to as “moisture content”) is about 3%. To decrease. If the liquid toner is transferred to the second surface in a state where the moisture content of the print sheet S is lower than the appropriate moisture content, the transfer efficiency of the liquid toner to the second surface is lowered, and the print quality is lowered. In the electrophotographic printing apparatus 10 of the present embodiment, the liquid toner transferred to the first surface of the printing sheet S is fixed by the flash irradiation device 38, and then moisture is supplied to the printing sheet S by the moisture applying means 60A. As a result, the moisture content in the print sheet S is returned to an appropriate range, and the print quality of the second surface is improved as compared with the conventional case. Hereinafter, each unit of the printing unit 12 will be described with reference to FIG.

  The developing units 31 to 34 are arranged around the intermediate transfer body 35 along the rotation direction thereof, and are respectively formed on the photosensitive drum (photosensitive body) 51 based on image data transmitted from the main control device. An electrostatic latent image is formed, and liquid toner (not shown) is transferred from the photosensitive drum 51 to the intermediate transfer member 35 at a position corresponding to the electrostatic latent image and transferred to the peripheral surface of the intermediate transfer member 35. It is configured. The liquid toner is obtained by dispersing and blending a particulate toner formed of a thermoplastic material and a coloring matter (pigment or dye) in a liquid carrier. In this embodiment, a petroleum-based toner is used as the carrier. A liquid toner containing 10 to 40 percent by weight of a particulate toner having an average particle diameter of about 1 to 2 μm in a non-polar solvent (for example, mineral oil as a non-polar paraffinic solvent). Yes.

  Each of the developing units 31 to 34 includes a photosensitive drum (photosensitive member) 51, a cleaning unit 52, a static eliminator 53, a photosensitive member charging device 54, an exposure device 55, and a developing device 56 disposed around the photosensitive drum 51. It is configured.

  The photosensitive drum 51 includes a photosensitive layer formed on the peripheral surface by containing a photosensitive agent such as amorphous silicon (a-Si) or a photosensitive polymer. The photosensitive drum 51 is in contact with the intermediate transfer member 35 at the nip portion N3, and is on the photosensitive drum 51. The liquid toner can be transferred to the intermediate transfer member 35 side. The cleaning unit 52 removes the liquid toner remaining on the peripheral surface of the photosensitive drum 51 and discharges it to a toner collection path (not shown). The static eliminator 53 has a function of erasing charges remaining on the photosensitive layer of the photosensitive drum 51. The photoreceptor charging device 54 includes a plurality of non-contact discharge chargers such as a corotron type or a scorotron type along the circumferential direction of the photosensitive drum 51, and the photosensitive layer of the photosensitive drum 51 is formed. For example, it has a function of charging to about 500 V, for example. The exposure device 55 is composed of a light emitting device (LED array) in which light emitters (LEDs in this embodiment) are arranged in a rod shape along the axial direction of the photosensitive drum 51, and image data sent from the main control device. Based on the above, each LED is caused to emit light. That is, the light from the exposure device 55 is irradiated onto the surface of the photosensitive layer of the photosensitive drum 51 that is uniformly charged by the photosensitive member charging device 54, so that the photosensitive layer is uncharged in the light irradiation portion. An electrostatic latent image based on image data can be formed on the photosensitive layer. The developing device 56 includes an anilox roller, a leveling roller, a developing roller, a toner charger, a blade, a toner supply port, and a liquid toner storage portion, and a portion where an electrostatic latent image of the photosensitive drum 51 is formed. The liquid toner is transferred to the surface.

  The roller-shaped intermediate transfer member 35 and the backup roller 36 are in contact with each other, and a nip portion (transfer position) N1 is formed at the contact portion. The peripheral surface of the intermediate transfer member 35 is made of, for example, urethane conductive rubber or conductive resin, and the intermediate transfer member 35 has a bias voltage difference from the photosensitive drum.

  On the other hand, the backup roller 36 is disposed to apply a pressure to the intermediate transfer member 35 at a predetermined pressure, for example, about 1 to 13 kg / cm, and forms the nip portion N1 described above. For this reason, the print sheet S is conveyed between the intermediate transfer member 35 and the backup roller 36, whereby a predetermined nip pressure is applied. Further, for example, a transfer bias of about −800 V is applied to the backup roller 36. Therefore, the bias voltage difference between the intermediate transfer member 35 and the backup roller 36 gives a force for sucking the liquid toner of the developing units 31 to 34 toward the backup roller 36, and the liquid toner from the intermediate transfer member 35 to the print sheet S It is designed to promote electrotransfer.

  At the nip portion N1, an image of liquid toner is transferred from the intermediate transfer body 35 to the print sheet S. Note that a gripper (not shown) that holds the print sheet S that has passed through the nip portion N1 is provided on the peripheral surface of the backup roller 36.

  The chain gripper 37 includes two endless chains arranged in parallel in parallel, and a plurality of grippers (not shown) are attached to each chain at equal intervals. The interval between the grippers is set to be shorter than the length of the print sheet S in the sheet conveyance direction. The gripper is configured to grip a side end portion of the print sheet S. The gripper grips the print sheet S at a predetermined transport position by a gripping release mechanism, and releases the grip of the print sheet S at another predetermined position. It is like that.

  The flash irradiation device (toner fixing means) 38 is constituted by a xenon flash lamp, a metal halide lamp, a krypton lamp, a xenon-mercury lamp or the like, and performs heating by flash according to a signal from the main controller. The flash irradiation device 38 is disposed above the conveyance path of the print sheet S by the chain gripper 37, and the print sheet S is synchronized with the timing when the print sheet S passes the lower part of the flash irradiation device 38 by the chain gripper 37. By instantaneously irradiating the print surface with flash light, the print sheet S is heated without contacting the print sheet S, and the liquid toner transferred to the print sheet S is fixed to the print sheet S.

The main control device performs printing so that the heating amount of the liquid toner becomes the first heating amount Q1 when the printing sheet S fed from the paper feeding unit 11 passes the lower part of the flash irradiation device 38 for the first time. The output of the flash irradiation device 38 is adjusted to the first surface of the sheet S. The first heating amount Q1 is irradiated with flash light so that the surface resistivity R [Ω / m ² ] of the opposite surface (second surface) of the printing sheet S does not become excessively large due to drying of the printing sheet S by heating. This is a value obtained by a predetermined experiment or the like determined in advance by an experiment or the like based on the assumed dryness of the printing sheet S assumed after fixing by heating by the device 38. More specifically, the first heating amount Q1 is set so that the surface resistivity of the second surface of the printed sheet S is in the range of about 10 ⁷ to 10 ⁸ [Ω / m ² ].

  In addition, when the print sheet S passes through the lower part of the flash irradiation device 38 for the second time, the main control device sets the second heating amount in which the heating amount of the liquid toner is larger than the first heating amount Q1. The output of the flash irradiation device 38 is adjusted to the second surface of the print sheet S so that Q2 (Q1 <Q2). The second heating amount Q2 sufficiently melts the liquid toner on the second surface of the print sheet S and fixes it on the second surface of the print sheet S and also fixes the liquid toner on the first surface of the print sheet S. It is a value obtained in advance by experiments or the like so as to promote.

  The switch mechanism 39 has a guide part 39a for guiding the conveyance direction of the print sheet S, and is supported so as to be rotatable about a rotation shaft 39b. The position of the guide part 39a is switched by the main controller. It is possible. The reciprocating guide roller 40 has three rollers, and the printing sheet S conveyed from the switch mechanism 39 to the reciprocating guide roller 40 side is conveyed to the switchback roller 41 side by the rotational drive of the upper two rollers. Is done. On the other hand, the printing sheet S conveyed from the switch mechanism 39 to the reciprocating guide roller 40 side is conveyed to the reversing path 43 side by rotational driving of the two lower rollers.

  The switchback roller 41 is configured so that the print sheet S can be gripped and conveyed by a pair of drive rollers, and the print sheet S is set in advance while holding the print sheet S carried in from the reciprocating guide roller 40 side. The sheet is temporarily stored in the sheet storage unit 42 for the required length. Thereafter, the switchback roller 41 is rotationally driven in the opposite direction while the print sheet S is held, and the held print sheet S is conveyed in the opposite direction from the sheet storage unit 42 to the reciprocating guide roller 40 side. ing.

  The printing sheet S conveyed from the switchback roller 41 to the reciprocating guide roller 40 is guided to the reverse path 43 side and is conveyed to the nip portion N1 by a plurality of conveying rollers.

  At this time, since the printed sheet S has already been reversed from the front and back when it first passes through the nip portion N1, the intermediate transfer member 35 is the surface opposite to the first surface of the printed sheet S in the nip portion N1. The second surface is in contact. That is, the intermediate transfer member 35 and the backup roller 36 that transfer the liquid toner of the developing units 31 to 34 to the first surface of the print sheet S, and the liquid toner of the developing units 31 to 34 are transferred to the second surface of the print sheet S. The intermediate transfer member 35 and the backup roller 36 are configured to be shared. The flash irradiation device 38 that irradiates the first surface of the printing sheet S with the flash irradiation device 38 and the flash irradiation device 38 that irradiates the second surface of the printing sheet S with the flash light are shared.

  The pair of heating rollers 44 are disposed on the paper discharge unit 13 side with respect to the switch mechanism 39, and the surface temperatures of the pair of heating rollers 44 are set at appropriate temperatures. When the print sheet S passes, the pair of heating rollers 44 A nip portion N2 that pressurizes the print sheet S is formed.

  The moisture applying device 60 </ b> A applies moisture to the printing sheet S heated by the flash irradiation device 38. As described above, when the flash toner irradiation device 38 fixes the liquid toner on the first surface, the heating amount is adjusted so that the surface resistivity of the second surface does not become excessively large due to the drying of the print sheet S. However, since it is necessary to fix the liquid toner securely on the first surface, the heating amount of the flash irradiation device 38 cannot be reduced more than necessary. For this reason, when the fixing process in the flash irradiation device 38 is performed, the moisture content in the printing sheet S decreases from 5%, which is an appropriate moisture content, to about 3%. Therefore, after the liquid toner transferred to the first surface of the printing sheet S is fixed by the flash irradiation device 38, moisture is applied to the second surface by the moisture applying means 60A, and the moisture content in the printing sheet S is increased. After recovering to an appropriate moisture content, the printing sheet S is sent again to the nip portion N1 to perform printing on the second surface.

  As shown in FIG. 1, the moisture applying device 60 </ b> A has a conveyance path from the exit of the flash irradiation device 38 to the nip portion N <b> 1 via the switch mechanism 39, the reciprocating guide roller 40, the switchback roller 41, and the reverse path 43. It is provided in the middle. In the installation example shown in FIG. 1, the moisture applying device 60 </ b> A is disposed in the middle of the transport path P between the flash irradiation device 38 and the switch mechanism 39. However, the installation position of the moisture applying device 60A is not limited to this. In short, after the toner is fixed on the first surface by the flash irradiation device 38, the transfer of the second surface is performed at the nip portion N1. What is necessary is just to give a water | moisture content to the printing sheet S before. For example, the moisture applying device 60 </ b> A may be installed in the middle of the inversion path 43.

  The main control device drives the moisture applying device 60A when the print sheet S passes the moisture applying device 60A for the first time (that is, after the liquid toner on the first surface is fixed by the flash irradiation device 38), while printing is performed. When the sheet S passes the moisture application device 60A for the second time (that is, after the liquid toner on the second surface is fixed by the flash irradiation device 38), the drive control of the moisture application device 60A is performed so that the moisture application device 60A is not driven. Do.

  FIG. 2 is a conceptual diagram of the moisture applying device 60A shown in FIG. Hereinafter, the specific configuration of the moisture applying device 60A applied in the present embodiment will be described in detail with reference to FIG. The moisture applying device 60 </ b> A includes a mist generating device 61, a discharge electrode 62, and a collecting electrode 63.

  The mist generating device 61 is a device that generates a mist 64 by making a liquid into a mist, and includes a tank that stores a liquid such as water and a mist supply port that discharges the mist 64 to the outside (both not shown). Have. As the mist generator 61, for example, a vaporization type that generates mist by evaporating normal temperature water, such as a vapor permeable film vaporization type that generates nano mist or a drop permeation vaporization type, and water is heated by a heater to generate water vapor. A vapor type to be generated, a water spray type such as an ultrasonic type and a high pressure spray type can be appropriately selected and used.

  As shown in FIG. 2, the mist generating device 61 is disposed below the transport path P, and the mist generator 61 is disposed toward the surface on which the printing sheet S transported along the transport path P is not printed, that is, toward the second surface. Supply. This is because the liquid toner is transferred to the first surface of the print sheet S, so that even if the mist 64 is supplied from the first surface side, moisture is hardly absorbed inside the sheet. In particular, when the liquid toner is oily, water is repelled by the liquid toner, so that it is difficult for water to be absorbed inside the sheet. The amount of mist applied per printed sheet (a mistake and the amount of mist generated from the generator 61) varies depending on the moisture content and thickness of the printed sheet S.

  The discharge electrode 62 is a flat plate member made of a metal such as steel or aluminum alloy, and is disposed between the mist generator 61 and the transport path P as shown in FIG. The distance between the discharge electrode 62 and the printing sheet S is about 5 mm to 50 mm. The width dimension of the discharge electrode 62 (the length dimension in the direction perpendicular to the conveyance direction of the conveyance path P) is substantially the same as the width dimension of the print sheet S (the length dimension in the direction orthogonal to the conveyance direction of the conveyance path P). It has become. The length of the discharge electrode 62 in the sheet conveyance direction is determined according to the conveyance speed of the printing sheet S, the spraying speed of the mist 64, and the like.

  The collection electrode 63 is a roller-shaped member made of a metal such as steel or an aluminum alloy, and is in a mode of being in contact with the first surface of the printing sheet S and above the conveyance path P as shown in FIG. Be placed. The width dimension of the collecting electrode 63 (the length dimension in the direction orthogonal to the transport direction of the transport path P) is substantially the same as the width dimension of the print sheet S (the length dimension in the direction orthogonal to the transport direction of the transport path P). Have The diameter of the collecting electrode 63 is determined according to the conveyance speed of the printing sheet S, the spraying speed of the mist 64, and the like. In the example shown in FIG. 2, the shape of the collecting electrode 63 is a roller shape, but may be a flat plate shape similar to the discharge electrode 62.

  The moisture applying device 60A configured as described above mainly supplies the mist 64 to the second surface of the printing sheet S in accordance with the timing when the printing sheet S passes between the discharge electrode 62 and the collecting electrode 63. It is controlled by the control device. More specifically, the mist 64 is supplied from the mist generator 61 toward the discharge electrode 62 in accordance with the timing at which the print sheet S passes between the discharge electrode 62 and the collection electrode 63. By applying a voltage to the collecting electrode 63, the mist 64 on the discharge electrode 62 is charged, and the mist 64 is moved from the discharge electrode 62 to the second surface of the printed sheet S by electrostatic force, and absorbed inside the sheet. Let Here, the applied voltage is about 5 to 15 kV. 2 shows a state in which the positively charged mist 64 is attracted to the negatively charged collecting electrode, the mist 64 may be negatively charged and the collecting electrode may be positively charged. By comprising as mentioned above, compared with the case where mist is directly supplied to the 2nd surface of the printing sheet S from the mist generating apparatus 61, the mist 64 can be efficiently adhered to the 2nd surface, and printing The moisture content in the sheet S can be increased to an appropriate moisture content.

  In addition, before performing the printing of the first surface, it is conceivable that moisture (for example, 7%) is given to the printing sheet S in advance so as to exceed the appropriate moisture content. Since the first surface is printed in an excessive state, there is a possibility that the liquid toner is excessively transferred to the first surface. Therefore, after fixing the liquid toner on the first surface, before the liquid toner is transferred to the second surface, moisture is applied to the print sheet S so that the print quality of both the first surface and the second surface is desired. It is possible to ensure the state.

  Next, the operation of the electrophotographic printing apparatus 10 according to the first embodiment configured as described above will be described. As shown in FIG. 1, when only one print sheet S is fed from the paper feed tray 21 to the printing unit 12, in the printing unit 12, the first of the print sheets S is formed by the developing units 31 to 34. Corresponding K (black), C (blue), M (red), and Y (yellow) liquid toners are transferred to the peripheral surface of the photosensitive drum 51 on which an electrostatic image to be transferred is formed. Then, the image is developed on the photosensitive drum 51. Then, the liquid toner transferred to the peripheral surface of the photosensitive drum 51 is transferred to the intermediate transfer body 35, and the surface (from the peripheral surface of the intermediate transfer body 35 in contact with the intermediate transfer body 35 of the printing sheet S at the nip portion N1 ( Liquid toner is transferred to the first surface. At this time, the temperature of the printing sheet S is about 25 ° C., and the printing sheet S maintains an appropriate moisture content (for example, about 5%).

  The printing sheet S on which the liquid toner is transferred to the first surface is conveyed in a state where both ends are gripped by the chain gripper 37, and the first surface of the printing sheet S is irradiated with the flash light from the flash irradiation device 38. Heated. As a result, the toner in the liquid toner transferred to the first surface of the print sheet S is melted and the carrier is evaporated to fix the liquid toner to the first surface of the print sheet S. Here, the temperature of the print sheet S heated by the flash irradiation device 38 becomes 100 ° C. or higher, and the water content decreases to, for example, about 3%.

  The print sheet S having the liquid toner fixed on the first surface is conveyed on the conveyance path P at a predetermined conveyance speed and guided to the moisture applying device 60A. At this time, the mist 64 is sprayed from the mist generating device 61 toward the discharge electrode 62 and a voltage is applied between the discharge electrode 62 and the collection electrode 63, whereby the mist 64 on the discharge electrode 62 is charged. Then, the mist 64 adheres to the second surface of the printing sheet S due to electrostatic force. The mist 64 adhering to the second surface is attracted to the collecting electrode 63 and penetrates into the printed sheet S. Thereby, the moisture content in the printing sheet S can be recovered from about 3% to about 5%.

  The printing sheet S to which moisture has been applied by the moisture applying device 60A is guided to the switch mechanism 39 and stored in the temporary sheet storage unit 42 while being held by the switchback roller 41. After the print sheet S is stored in the sheet storage portion 42 by the switchback roller 41, the print sheet S is conveyed again to the reciprocating guide roller 40 side and guided to the reversing path 43 by the reciprocating guide roller 40.

  The print sheet S conveyed through the reverse path 43 is sent to the printing unit 12 again. K (black), C (blue), and M (red) corresponding to the peripheral surface of the photosensitive drum 51 on which the electrostatic image to be transferred to the second surface of the print sheet S is formed by the developing units 31 to 34. , Y (yellow) liquid toners are transferred, and an image is developed on the photosensitive drum 51.

  Then, the liquid toner transferred to the peripheral surface of the photosensitive drum 51 is transferred to the intermediate transfer body 35, and the surface (from the peripheral surface of the intermediate transfer body 35 in contact with the intermediate transfer body 35 of the printing sheet S at the nip portion N1 ( Liquid toner is transferred to the second surface. At this time, since the moisture content of the printing sheet S is in an appropriate range, the printing quality is not deteriorated, and the same quality as the first surface is maintained. Thereafter, the flash light is irradiated on the print sheet S by the flash irradiation device 38, and the second surface of the print sheet S is heated. Thereby, the toner of the liquid toner on the second surface of the print sheet S is sufficiently melted, and the liquid toner on the second surface of the print sheet S is applied to the second surface of the print sheet S by evaporating the carrier. It is fixed.

  Although the printing sheet S having the liquid toner fixed on the second surface passes through the moisture applying device 60A, the moisture applying device 60A is not driven, so that moisture is not applied to the printing sheet S. Thereafter, the print sheet S is conveyed through the switch mechanism 39 to the nip portion N2 of the pair of heating rollers 44, and both surfaces of the print sheet S are pressurized. Thereafter, the print sheet S on which both the first surface and the second surface are heated is cooled while being transported through the paper discharge unit 13 and discharged to the paper discharge tray 22, thereby completing the printing.

  In this embodiment, the mist 64 is charged on the discharge electrode 62 and the mist 64 is adhered to the second surface of the print sheet S by electrostatic force. However, the mist 64 is directly applied to the print sheet S from the mist generator 61. If it is possible to sufficiently recover the moisture content of the printing sheet S to the appropriate moisture content by spraying on the second surface, the discharge electrode 62 and the collecting electrode 63 are omitted, and moisture is given only by the mist generator 61. You may go.

  As described above, according to the electrophotographic printing apparatus 10 of the present embodiment, the toner fixing means (flash irradiation device 38) passes through the reversing means (reciprocating guide roller 40, switchback roller 41, sheet storage portion 42). Since the moisture applying device 60A is provided in the conveyance path leading to the nip portion N1, and configured to apply moisture to the printing sheet S from the second surface side of the printing sheet S before printing the second surface, After the toner is fixed on the first surface by the toner fixing unit, the second surface can be printed in a state where the amount of water contained in the print sheet S is returned to an appropriate range. As a result, the transfer efficiency of the liquid toner onto the second surface can be improved as compared with the conventional case, and the print quality can be improved.

  In the electrophotographic printing apparatus 10 of the present embodiment, since the mist generating device 61 is applied as the moisture applying device 60A, the mist generating device 61 can be easily installed in the electrophotographic printing device 10, and the supply amount (spraying speed) of the mist 64 can be reduced. Control can be easily performed and moisture can be efficiently applied to the printing sheet S.

  Furthermore, in the electrophotographic printing apparatus 10 of the present embodiment, the moisture applying device 60A is provided on the mist generating device 61, the discharge electrode 62 disposed on the second surface side of the print sheet S, and the first surface of the print sheet S. The mist 64 on the discharge electrode 62 is charged by spraying the mist 64 on the discharge electrode 62 and applying a voltage between the collection electrode 63 and the discharge electrode 62. The mist 64 is caused to adhere to the second surface by moving the mist 64 from the discharge electrode 62 to the second surface of the print sheet S by electrostatic force, so that the adhesion of the mist 64 to the print sheet S is improved. Further improvement can be achieved.

  Next, an electrophotographic printing apparatus according to Embodiment 2 of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the said Example 1, and the overlapping description is abbreviate | omitted. In addition, the configurations of the electrophotographic printing apparatuses of Examples 2 to 5 described later have the same configuration as the electrophotographic printing apparatus 10 of Example 1 except for the configuration of the moisture applying apparatus. Therefore, in Examples 2 to 5 described later, description will be made with reference to FIG.

  FIG. 3 is a conceptual diagram of a moisture applying device 60B applied to the electrophotographic printing apparatus 10 of the second embodiment. The moisture applying device 60B illustrated in FIG. 3 is disposed so as to face the mist generating device 61 and the downstream side of the mist generating device 61 (between the mist generating device 61 and the switch mechanism 39) with the conveyance path P interposed therebetween. A pair of rollers 65a and 65b is provided. Similar to the moisture applying device 60A of the first embodiment, the moisture applying device 60B is connected to the nip portion via the switch mechanism 39, the reciprocating guide roller 40, the switchback roller 41, and the reverse path 43 from the exit of the flash irradiation device 38. It is provided in the middle of the transport path up to N1. In the example shown in FIG. 3, the moisture applying device 60 </ b> B is disposed in the middle of the conveyance path P between the flash irradiation device 38 and the switch mechanism 39, but after the print sheet S is reversed by the switchback roller 41. You may install in the middle of the inversion path | route 43 to the nip part N1.

  The mist generating device 61 has the same configuration as that used in the first embodiment, and is disposed below the transport path P as shown in FIG.

  The pair of rollers 65a and 65b is made of a material such as rubber, and is arranged in a manner adjacent to the supply area of the mist 64 on the wake side of the mist generator 61 as shown in FIG. Yes. The pair of rollers 65a and 65b form a nip portion N4 by making contact with each other in the conveyance path P, and are rotationally driven so as to convey the print sheet S to the downstream side while being pressed by the nip portion N4. The width dimension of the pair of rollers 65a and 65b (the length dimension in the direction perpendicular to the conveyance direction of the conveyance path P) is the width dimension of the print sheet S (the length dimension in the direction orthogonal to the conveyance direction of the conveyance path P). Have approximately the same length.

  The moisture applying device 60B configured as described above sprays the mist 64 from the mist generating device 61 toward the second surface of the printing sheet S in accordance with the timing when the printing sheet S passes over the mist generating device 61. At the same time, the main controller controls the pair of rollers 65a and 65b. In this way, after the mist 64 is applied from the mist generating device 61 toward the second surface of the print sheet S, the print sheet S is pressurized by the nip portion N4 of the pair of rollers 65a and 65b. The mist 64 adhering to the second surface can be efficiently absorbed into the print sheet S. As a result, the amount of water in the printing sheet S can be reliably recovered to an appropriate range.

  As described above, according to the electrophotographic printing apparatus 10 of the second embodiment, similarly to the first embodiment, the toner fixing means (flash irradiation device 38) to the reversing means (reciprocating guide roller 40, switchback roller 41, A moisture applying device 60B is provided in the conveyance path from the sheet storage unit 42) to the nip portion N1, and moisture is applied to the printing sheet S from the second surface side of the printing sheet S before printing on the second surface. Since the toner is applied, the toner fixing unit fixes the toner on the first surface, and then the second surface can be printed in a state where the amount of water contained in the print sheet S is returned to the appropriate range. As a result, the transfer efficiency of the liquid toner onto the second surface can be improved as compared with the conventional case, and the print quality can be improved.

  Also, in the electrophotographic printing apparatus 10 of the second embodiment, since the mist generating device 61 is applied as the moisture applying apparatus 60B, the mist generating apparatus 61 can be easily installed in the electrophotographic printing apparatus 10 and the supply amount (spraying speed) of the mist 64 Can be easily controlled, and moisture can be efficiently applied to the printing sheet S.

  Furthermore, in the electrophotographic printing apparatus 10 according to the second embodiment, the moisture applying device 60B is configured such that the mist generating device 61 and a pair of rollers 65a disposed opposite to each other on the downstream side of the mist generating device 61 with the conveyance path P interposed therebetween. , 65b, and after the mist 64 is sprayed from the mist generating device 61 toward the second surface of the print sheet S, the print sheet S is pressurized by the pair of rollers 65a, 65b. The adhesion of the mist 64 to the can be further improved.

  Next, an electrophotographic printing apparatus according to Embodiment 3 of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the said Examples 1, 2, and the overlapping description is abbreviate | omitted.

  FIG. 4 is a conceptual diagram illustrating a first control example of the mist generating device 61 in the moisture applying device 60B described in the second embodiment. In addition to the configuration of the second embodiment, the moisture applying device 60B shown in FIG. 4 includes a moisture detection sensor 66 that detects the amount of moisture contained in the printed sheet S, and a mist based on the moisture amount detected by the moisture detection sensor 66. The configuration further includes a mist generation amount control device 70 </ b> A that controls the amount of mist generated from the generation device 61. The mist generation amount control device 70 is incorporated in the main control device described above.

  The moisture detection sensor 66 is a sensor that detects the amount of moisture (moisture content) contained in the measurement object (printed sheet S). As shown in FIG. 4, the moisture detection sensor 66 is disposed at a predetermined position on the downstream side of the flash irradiation device 38 and on the upstream side of the supply region of the mist 64. It is configured to detect the amount of water (water content) after the liquid toner is fixed. The moisture detection sensor 66 may be a non-contact type moisture detection sensor that detects the amount of moisture in a non-contact manner with respect to the print sheet S, or a contact-type moisture detection sensor that detects the amount of moisture in contact with the print sheet S. Either can be applied. In the present embodiment, a non-contact moisture detection sensor 66 is used and is disposed at a predetermined distance from the print sheet S as shown in FIG. As the non-contact moisture detection sensor 66, for example, an infrared reflection type two-wavelength sensor that determines the amount of moisture in the measurement object from the ratio of the reflectance of the wavelength that moisture absorbs to the wavelength that does not absorb moisture is used. it can.

  The mist generation amount control device 70A includes a calculation unit 71 and a mist generation amount database 72A. When the calculation unit 71 receives the moisture content detected by the moisture detection sensor 66, the calculation unit 71 calculates a difference from the optimum moisture content. For example, when the optimal moisture content is 5% and the moisture content detected by the moisture detection sensor 66 is 3%, the calculation unit 71 calculates the difference 2% between the two. The mist generation amount database 72A stores data of mist generation amounts (mist amounts supplied per printed sheet) corresponding to the above differences. For example, when the difference from the optimum moisture content is 1%, 0.1 g of mist is supplied per printing sheet, and when the difference from the optimum moisture content is 2%, 0 per printing sheet. Data such as .2g mist is stored. The relationship between the difference between the optimum water content and the amount of mist generated is obtained in advance by experiments or the like. The mist generation amount is a value converted to a printing sheet equivalent to A3 size.

  When the calculation unit 71 calculates the difference (2%) between the optimum moisture content (5%) and the detected value (3%), the mist generation amount corresponding to the difference (2%) from the mist generation amount database 72A. (0.2 g) of data is received and this value is transmitted to the mist generator 61. The mist generator 61 generates a mist 64 (0.2 g) of mist received from the calculation unit 71 and applies the mist 64 to the print sheet S.

  In the present embodiment, the case where the mist generating device 61 in the moisture applying apparatus 60B according to the second embodiment is controlled has been described. However, the same operation is performed when the mist generating apparatus 61 in the moisture applying apparatus 60A according to the first embodiment is controlled. Therefore, the description is omitted.

  As described above, in the electrophotographic printing apparatus 10 according to the third embodiment, the mist generation amount control device 70A for controlling the mist generation amount from the mist generation device 61, the flash irradiation device (toner fixing means) 38, and the moisture applying device. And a moisture detection sensor 66 that detects the moisture content in the print sheet S. The mist generation amount control device 70A is based on the moisture content in the print sheet S detected by the moisture detection sensor 66. The mist generation amount is controlled. By setting it as the said structure, in addition to the effect of Example 1, 2, it becomes possible to return the moisture content in the printing sheet S to an appropriate range accurately.

  Next, an electrophotographic printing apparatus according to Embodiment 4 of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the said Examples 1-3, and the overlapping description is abbreviate | omitted.

  FIG. 5 is a conceptual diagram illustrating a second control example of the mist generating device 61 in the moisture applying device 60B described in the second embodiment. In the third embodiment described above, the mist generation amount is controlled based on the moisture amount in the print sheet S detected by the moisture detection sensor 66. However, in the fourth embodiment, the pattern area on the first surface of the print sheet S is controlled. The difference from the third embodiment is that the mist generation amount is controlled based on the rate. In addition to the configuration of the second embodiment, the moisture applying device 60B shown in FIG. 5 controls the amount of mist generated from the mist generating device 61 based on the pattern area ratio on the first surface of the printing sheet S. The apparatus 70B is further provided.

  Here, the pattern area ratio means the ratio of the area occupied by the transfer portion of the liquid toner on the paper surface of the printing sheet S. The amount of water evaporated from the print sheet S by the fixing process in the flash irradiation device 38 varies depending on the pattern area ratio. When the pattern area ratio on the first surface is relatively large, that is, when the ratio of the liquid toner transfer portion on the first surface is relatively large, the liquid toner prevents the moisture in the print sheet S from diffusing to the outside. The amount of evaporation is relatively small. On the other hand, when the pattern area ratio on the first surface is relatively small, that is, when the ratio of the liquid toner transfer portion on the first surface is relatively small, the water inside the print sheet S easily evaporates from the first surface. Therefore, the amount of evaporation increases. Therefore, it is necessary to increase the amount of mist supplied to the printing sheet S as the pattern area ratio of the first surface of the printing sheet S is smaller. Therefore, by adjusting the amount of mist generated from the mist generating device 61 (the amount of mist supplied per printed sheet) based on the pattern area ratio of the first surface, the amount of moisture in the printed sheet S can be increased with high accuracy. Can be adjusted.

  The pattern area ratio of the first surface of the print sheet S is calculated by the pattern area ratio calculation unit 73 of the main controller when the liquid toner is transferred to the first surface in the nip portion N1.

  The mist generation amount control device 70B includes a calculation unit 71 and a mist generation amount database 72B. The mist generation amount database 72B stores data on the mist generation amount (mist amount supplied per printed sheet) corresponding to the pattern area ratio of the first surface. For example, when the pattern area ratio on the first surface is 10%, 0.1 g of mist is supplied per printed sheet, and when the pattern area ratio on the first surface is 20%, one print sheet. Data such as supplying 0.2 g of mist per unit is accumulated. The relationship between the pattern area ratio on the first surface and the amount of mist generated is obtained in advance by experiments or the like.

  When the calculation unit 71 receives the pattern area rate of the first surface from the pattern area rate calculation unit 73, the calculation unit 71 receives data on the amount of mist generation corresponding to the pattern area rate from the mist generation amount database 72B, and generates this value as mist generation. Transmit to device 61. The mist generating device 61 generates a mist 64 having a mist generation amount received from the calculation unit 71 and applies the generated mist 64 to the print sheet S.

  In addition, although the case where the mist generator 61 in the moisture applying apparatus 60B of the second embodiment is controlled has been described above, the case where the mist generator 61 in the moisture applying apparatus 60A of the first embodiment is controlled is performed in the same manner. The description is omitted.

  As described above, the electrophotographic printing apparatus 10 according to the fourth embodiment includes the mist generation amount control device 70B that controls the mist generation amount from the mist generation device 61. The mist generation amount control device 70B is provided on the print sheet S. The mist generation amount is controlled based on the pattern area ratio of the first surface. By setting it as the said structure, in addition to the effect of Example 1, 2, it becomes possible to return the moisture content in the printing sheet S to an appropriate range accurately.

  Next, an electrophotographic printing apparatus according to Embodiment 5 of the present invention will be described. In addition, the same code | symbol is attached | subjected to the member which has the same function as what was demonstrated in the said Examples 1-4, and the overlapping description is abbreviate | omitted.

  FIG. 6 is a conceptual diagram illustrating a third control example of the mist generating device 61 in the moisture applying device 60B described in the second embodiment. In the fourth embodiment described above, the mist generation amount is controlled based on the pattern area ratio of the first surface of the print sheet S. However, in the fifth embodiment, the mist generation amount is determined based on the paper type of the print sheet S. The difference from the fourth embodiment is that the configuration is controlled. In addition to the configuration of the second embodiment, the moisture applying device 60B shown in FIG. 6 controls the amount of mist generated from the mist generating device 61 based on the paper type or the appropriate moisture content of the printing sheet S. 70C is further provided.

  The range of the appropriate moisture content in the printed sheet S varies depending on the sheet type (sheet thickness, coating, etc.). For example, the range of the appropriate moisture content of the paper type A is 4 to 5%, the range of the appropriate moisture content of the paper type B is 7 to 8%, and the range of the appropriate moisture content of the paper type C is 3 to 4%. Therefore, by adjusting the amount of mist generated from the mist generator 61 based on the paper type of the print sheet S, the amount of moisture in the print sheet S can be adjusted with high accuracy.

  The mist generation amount control device 70C includes a calculation unit 71 and a mist generation amount database 72C. The mist generation amount database 72C stores data of mist generation amounts (mist amounts supplied per print sheet) corresponding to each paper type of a plurality of types of print sheets S that are normally used. For example, in the case of paper type A, 0.1 g of mist is supplied per printed sheet, and in the case of paper type B, 0.2 g of mist is supplied per printed sheet. Yes. The relationship between the above paper type and the amount of mist generated is obtained in advance by experiments or the like.

  The paper type of the print sheet S is input by the user from the paper type input unit 74 when printing is performed. The paper type input unit 74 is configured to be able to input the paper type of the print sheet S stored in the mist generation amount database 72C. For example, paper type selection buttons (not shown) corresponding to a plurality of paper types are provided on the input screen.

  When the user inputs the paper type of the print sheet S from the paper type input unit 74, the calculation unit 71 receives the paper type from the input unit 74, and generates the mist corresponding to the paper type from the mist generation amount database 72C. A quantity of data is received and this value is sent to the mist generator 61. The mist generating device 61 generates a mist 64 having a mist generation amount received from the calculation unit 71 and applies the generated mist 64 to the print sheet S.

  It should be noted that a paper type other than the paper type displayed on the paper type selection button of the paper type input unit 74 (that is, a paper type not stored in the mist generation amount database 72C) is used. When the corresponding mist generation amount is known in advance, the user can input the paper type to be used and the numerical value of the mist generation amount corresponding to the paper type from the paper type input unit 74. . When the user inputs the paper type of the printing sheet S and the numerical value of the mist generation amount corresponding to the paper type from the paper type input unit 74, the calculation unit 71 transmits the mist generation amount value to the mist generation device 61. The mist generating device 66 generates a mist of the mist generation amount received from the calculation unit 71 and applies it to the print sheet S. At the same time, the calculation unit 71 stores data in which the paper type input by the user is associated with the mist generation amount in the mist generation amount database 72C.

  In addition, although the case where the mist generator 61 in the moisture applying apparatus 60B of the second embodiment is controlled has been described above, the case where the mist generator 61 in the moisture applying apparatus 60A of the first embodiment is controlled is performed in the same manner. The description is omitted.

  As described above, the electrophotographic printing apparatus 10 according to the fifth embodiment includes the mist generation amount control device 70C that controls the mist generation amount from the mist generation device 61. The mist generation amount control device 70C The mist generation amount is controlled based on the paper type. By setting it as the said structure, in addition to the effect of Example 1, 2, it becomes possible to return the moisture content in the printing sheet S to an appropriate range accurately.

  The electrophotographic printing apparatus according to the present invention is particularly useful for an electrophotographic printing apparatus that performs printing on both sides of an object to be printed by a liquid development electrophotographic system that performs printing using liquid toner.

DESCRIPTION OF SYMBOLS 10 Electrophotographic printing apparatus 11 Paper feed part 12 Printing part 13 Paper discharge part 31, 32, 33, 34 Development unit 35 Intermediate transfer body (intermediate transfer body for electrophotographic printing)
36 Backup roller (pressurized body)
38 Flash irradiation device (toner fixing means)
39 Switch mechanism 40 Reciprocating guide roller (reversing means)
41 Switchback roller (reversing means)
42 Sheet storage (reversing means)
43 inversion path 60A, 60B moisture applying device (moisture providing means)
61 Mist Generator 62 Discharge Electrode 63 Collecting Electrode 64 Mist 65a, 65b Rollers 70A, 70B, 70C Mist Generation Control Device (Mist Generation Control Unit)
71 Calculation Units 72A, 72B, 72C Mist Generation Database 73 Picture Area Ratio Calculation Unit 74 Paper Type Input Unit

Claims (8)

A developing unit that performs development by transferring liquid toner onto a photoreceptor on which an electrostatic latent image is formed; and
An intermediate transfer member for transferring the liquid toner developed by the developing unit;
A pressure member to which a bias voltage is applied to form a nip portion by contacting the intermediate transfer member and suck the liquid toner;
Toner fixing means for fixing the liquid toner by heating the liquid toner transferred to the substrate;
In the electrophotographic printing apparatus that performs printing on the second surface that is the surface opposite to the first surface after printing the first surface of the substrate,
An electrophotographic printing apparatus comprising: a moisture applying unit that applies moisture to the second surface of the substrate on which the first surface is printed. A reversing unit that is provided in a conveyance path on the downstream side of the toner fixing unit and that reverses the front and back of the printed material on which the liquid toner is fixed on the first surface;
A reversing path for conveying the printed material reversed by the reversing means to the nip portion,
The moisture applying means is
The electrophotographic printing apparatus according to claim 1, wherein the electrophotographic printing apparatus is provided in a conveyance path from the exit of the toner fixing unit to the reversing unit or in the middle of the reversing path. The moisture applying means includes a mist generating device,
The electrophotographic printing apparatus according to claim 1, wherein the mist is sprayed from the mist generating apparatus onto the second surface of the printing material. The moisture applying means is
A discharge electrode disposed on the second surface side of the substrate, and a collecting electrode disposed in contact with the first surface of the substrate,
The mist is sprayed on the discharge electrode, and a voltage is applied between the collection electrode and the discharge electrode to charge the mist on the discharge electrode, and the mist is discharged from the discharge electrode by electrostatic force. The electrophotographic printing apparatus according to claim 3, wherein the mist is attached to the second surface by being moved to two surfaces. The moisture applying means is
A pair of rollers disposed on the downstream side of the mist generating device so as to face each other with the conveyance path interposed therebetween, and after spraying mist from the mist generating device onto the second surface of the substrate, the pair of rollers The electrophotographic printing apparatus according to claim 3, wherein the printed material is pressed by a roller. Mist generation amount control means for controlling the mist generation amount generated by the mist generation device;
A moisture detection sensor that is installed between the toner fixing unit and the moisture applying unit and detects the amount of moisture in the substrate;
The mist generation amount control means includes:
The electrophotographic printing apparatus according to claim 3, wherein the mist generation amount is controlled based on a moisture amount in the printing material detected by the moisture detection sensor.   Mist generation amount control means for controlling a mist generation amount generated by the mist generation device is provided, and the mist generation amount control means controls the mist generation amount based on a pattern area ratio on the first surface of the substrate. The electrophotographic printing apparatus according to any one of claims 3 to 5, wherein the electrophotographic printing apparatus is characterized in that:   A mist generation amount control unit that controls a mist generation amount generated by the mist generation device is provided, and the mist generation amount control unit controls the mist generation amount based on a preset type of a substrate to be printed. An electrophotographic printing apparatus according to any one of claims 3 to 5.

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