JP2019086595A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus that can suppress deterioration of a carrier liquid to be reused, and that can repeatedly use a liquid developer for longer time than a conventional case.SOLUTION: A drum cleaner 19 and a first separation and extraction apparatus 37 are connected through a drum recovered liquid transport pipe 190, a liquid developer recovered by the drum cleaner 19 is separated into a toner and a carrier liquid by the first separation and extraction apparatus 37, and the separated carrier liquid is reused. On the other hand, an intermediate transfer roller cleaner 26 and a waste liquid storage container 35 are connected through an intermediate transfer recovered liquid transport pipe 260, and the liquid developer recovered by the intermediate transfer roller cleaner 26 is transferred to the waste liquid storage container 35. In this case, since the liquid developer containing a lot of paper powder is not transferred to the first separation and extraction apparatus 37, the carrier liquid in which a component is deteriorated by containing a lot of paper powder is not reused. Thus, the liquid developer can be repeatedly used for longer time than a conventional case by suppressing the deterioration of the reused carrier liquid.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an electrophotographic image forming apparatus that forms an image using a liquid developer.

  2. Description of the Related Art Conventionally, an image forming apparatus that forms an image using a liquid developer containing toner and a carrier liquid is known. In an image forming apparatus using a liquid developer, a liquid developer not used in an image forming process is collected from a photosensitive drum, an intermediate transfer roller or the like and reused. Conventionally, the liquid developer collected from the photosensitive drum, the intermediate transfer roller, etc. after transfer of the toner image is transported to a separation device, and the toner and carrier liquid in the liquid developer are separated by the separation device, and the separated carrier liquid The process of reusing is performed (patent document 1).

JP, 2016-224132, A

  By the way, foreign matter such as paper dust is likely to be mixed in the carrier liquid recovered from an intermediate transfer roller or the like which transfers a toner image to paper in contact with paper as a recording material. In particular, when paper dust is mixed in the carrier liquid, the carrier liquid can contain components such as calcium carbonate and talc at a relatively high ratio. That is, there is a possibility that the component of the carrier liquid that has been repeatedly used has been changed and deteriorated. When a liquid developer containing a degraded carrier liquid is used, there is a possibility that an image defect may occur. For example, the color and gloss of the toner image on the recording material after fixing may be changed. In addition, in the case of an ultraviolet-curable liquid developer, the curability by the irradiation of the ultraviolet light is reduced, and the toner becomes difficult to fix on the recording material. In order to avoid this, conventionally, the container in which the collected liquid developer is temporarily stored is periodically replaced so that the liquid developer can be replaced. However, in such a case, the running cost associated with the replacement of the liquid developer is increased, and there is a problem that it takes time for the user to replace the developer.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an image forming apparatus in which a liquid developer can be repeatedly used for a longer time than before by suppressing deterioration of carrier liquid to be reused. Do.

  The image forming apparatus according to the present invention comprises a photosensitive body, a developing device for developing an electrostatic latent image formed on the photosensitive body into a toner image with a liquid developer composed of toner and carrier liquid, and toner from the photosensitive body An intermediate transfer member to which an image is primarily transferred, a transfer member to secondarily transfer a toner image primarily transferred to the intermediate transfer member to a recording material, and a liquid developer which is retained on the photosensitive member after primary transfer A cleaning unit, a second cleaning unit for recovering the liquid developer remaining on the intermediate transfer member after the secondary transfer, a separation device for separating the toner and the carrier liquid from the liquid developer, and the liquid developer are accommodated. A container, a first transport path connecting the first cleaning means and the separation device so that the liquid developer collected by the first cleaning means can be transported to the separation device, and the second cleaning means The collected liquid developer is To be transported to the container without using the releasing device, and a second transport passage for connecting the container and the second cleaning means, characterized in that.

  The image forming apparatus according to the present invention comprises a photosensitive body, a developing device for developing an electrostatic latent image formed on the photosensitive body into a toner image with a liquid developer composed of toner and carrier liquid, and toner from the photosensitive body An intermediate transfer member to which an image is primarily transferred, a transfer member to secondarily transfer a toner image primarily transferred to the intermediate transfer member to a recording material, and a photosensitive member to recover a liquid developer remaining on the photosensitive member after primary transfer A body cleaning means, a transfer member cleaning means for recovering the liquid developer remaining on the transfer member after the secondary transfer, a separation device for separating the toner and the carrier liquid from the liquid developer, and a container for containing the liquid developer A container, a separation transport path connecting the photoreceptor cleaning means and the separation device so that the liquid developer collected by the photoreceptor cleaning means can be transported to the separation device, and collected by the transfer member cleaning means Liquid The developer to be conveyed to the container without passing through the separation device, and a recovery conveyance path for connecting the storage container and the transfer member cleaning means, characterized in that.

  According to the present invention, since the deterioration of the carrier liquid to be reused is suppressed, the liquid developer can be repeatedly used for a longer time than in the past.

FIG. 1 is a schematic configuration view showing an image forming apparatus of the present embodiment. FIG. 2 is a schematic view showing a transport path of the liquid developer in the image forming apparatus of the first embodiment. The external appearance perspective view which shows a isolation | separation extraction apparatus. The perspective view which cuts and shows a part of isolation | separation extraction apparatus. Sectional drawing which shows a part of isolation | separation extraction apparatus. The enlarged view which expands and shows the A section of FIG. 6 is a graph showing the relationship between the total number of image formations and the accumulated amount of paper dust in the liquid developer in the image forming apparatus of the present embodiment. FIG. 7 is a schematic view showing a transport path of the liquid developer in the image forming apparatus of the second embodiment. 8 is a graph showing the relationship between the total number of image formations and the accumulated amount of paper dust in the liquid developer in the conventional image forming apparatus. 6 is a graph showing the relationship between the paper powder content in the liquid developer and the difference in gloss when the paper powder is mixed with the carrier liquid. The graph which shows the relationship between the paper dust content in a liquid developer of ultraviolet curing type, and the exposure energy required to harden a carrier liquid, when paper dust is mixed with a carrier liquid. 7 is a graph showing the relationship between the total number of images formed and the accumulated amount of paper dust in the liquid developer in a conventional image forming apparatus using a UV curable liquid developer.

First Embodiment
[Image forming apparatus]
The image forming apparatus of the present embodiment will be described. First, the configuration of the image forming apparatus of the present embodiment will be described with reference to FIG. An image forming apparatus 100 illustrated in FIG. 1 is an electrophotographic digital printer that forms a toner image on a recording material S (a sheet, a sheet material such as an OHP sheet, etc.). The image forming apparatus 100 operates based on an image signal, transfers the toner image formed by the image forming unit 12 to the recording material S sequentially conveyed from the cassettes 11a and 11b, and then obtains an image by fixing. ing. The image signal is sent to the image forming apparatus 100 from an external terminal such as a scanner or a personal computer (not shown).

  The image forming unit 12 includes a photosensitive drum 13 as a photosensitive member, a charger 14, a laser exposure device 15, a developing device 16, and a drum cleaner 19. The laser light E is irradiated from the laser exposure device 15 according to the image signal onto the photosensitive drum 13 whose surface is charged by the charger 14, and an electrostatic latent image is formed on the photosensitive drum 13. The electrostatic latent image is developed by the developing device 16 as a toner image. In the case of the present embodiment, the liquid developer D in which the powder toner as the dispersoid is dispersed in the carrier liquid as the dispersion medium is contained in the developing device 16 as the developing device. Develop using.

  The liquid developer D is generated by mixing and dispersing the toner T in the carrier liquid C at a predetermined ratio in the mixer 31 as a mixer, and is supplied to the developing device 16. The carrier liquid C for replenishment is accommodated in a carrier tank 32 as a carrier container, and the toner T for replenishment is accommodated in a toner tank 33 as a toner container. Then, according to the mixed state of the carrier liquid C and the toner T in the mixer 31, the carrier liquid C or the toner T is supplied to the mixer 31 from each tank. The mixer 31 contains a stirring blade driven by a motor (not shown), and mixes the supplied carrier liquid and the toner T by stirring to disperse the toner in the carrier liquid. In the case of this embodiment, the volume of the mixer 31 is about 2000 g in terms of the weight of the developer.

  The liquid developer D supplied from the mixer 31 to the developing device 16 is coated (supplied) on the developing roller 18 by the coating roller 17 in the supply section 16 a of the developing device 16 and used for development. The developing roller 18 carries and conveys a liquid developer on the surface, and develops the electrostatic latent image formed on the photosensitive drum 13 with toner. The carrier liquid C and the toner T remaining on the developing roller 18 after development are collected in the collection section 16 b of the developing device 16. Here, the coating of the liquid developer D from the coating roller 17 to the developing roller 18 and the development from the developing roller 18 to the electrostatic latent image on the photosensitive drum 13 are performed using an electric field.

  The toner image formed on the photosensitive drum 13 is primarily transferred to the intermediate transfer roller 20 using an electric field, and conveyed to the nip portion (secondary transfer portion) formed by the intermediate transfer roller 20 and the transfer roller 21. . The liquid developer (toner T and carrier liquid C) remaining on the photosensitive drum 13 (on the photosensitive member) after the primary transfer to the intermediate transfer roller 20 is collected by the drum cleaner 19. The drum cleaner 19 as a first cleaning unit (photosensitive member cleaning unit) is made of, for example, a blade-like member made of rubber, and is in contact with the photosensitive drum 13 with a linear pressure of 30 (g / cm). At least one of the intermediate transfer roller 20 and the transfer roller 21 may be an endless belt.

  The recording material S accommodated in the cassettes 11a and 11b is conveyed toward the resist conveyance unit 23 by the feeding units 22a and 22b configured by conveyance rollers and the like. The resist conveyance unit 23 conveys the recording material S to the nip portion between the intermediate transfer roller 20 and the transfer roller 21 in accordance with the timing of the toner image transferred to the intermediate transfer roller 20.

  At the nip portion between the intermediate transfer roller 20 and the transfer roller 21, the toner image is secondarily transferred onto the passing recording material S, and the recording material S onto which the toner image has been transferred is conveyed by the conveyance belt 24 to the fixing device 25. The toner image transferred to the recording material S is fixed. The recording material S on which the toner image is fixed is discharged to the outside of the machine, and the image process is completed. In the present embodiment, the fixing device 25 employs a heat fixing method. In this system, the fixing device 25 has two rollers for sandwiching the recording material S from above and below and pressing them against each other, and the two rollers maintain their surface temperature at about 200.degree. As a result, the surface of the recording material S conveyed at a predetermined process speed (for example, 600 mm / s) is maintained at a temperature of 60 ° C. or higher, which is the glass transition point at which the toner melts. As the toner melts, the toner is fixed on the recording material S. However, when using an ultraviolet curing type liquid developer as the liquid developer D, the fixing device 25 irradiates ultraviolet light (UV light) to cure the liquid developer. The toner is fixed on the recording material S by curing of the carrier liquid.

  An intermediate transfer roller cleaner 26 as a second cleaning unit and a transfer roller cleaner 27 as a third cleaning unit (transfer member cleaning unit) for the intermediate transfer roller 20 as an intermediate transfer member and the transfer roller 21 as a transfer member. Is provided. The intermediate transfer roller cleaner 26 recovers the liquid developer (toner T and carrier liquid C) remaining on the intermediate transfer roller 20 after secondary transfer from the intermediate transfer roller 20. The transfer roller cleaner 27 recovers the liquid developer (toner T and carrier liquid C) remaining on the transfer roller 21 after the secondary transfer from the transfer roller 21. In the present embodiment, each of the intermediate transfer roller cleaner 26 and the transfer roller cleaner 27 is formed of a blade-like member made of rubber, and is applied to the intermediate transfer roller 20 and the transfer roller 21 with a linear pressure of 30 (g / cm). Be touched. However, the method of collecting the liquid developer (mainly toner T) remaining on the intermediate transfer roller 20 and the transfer roller 21 is not limited to this. For example, the toner T may be separated by an electric field by bringing a roller-like member into contact with the intermediate transfer roller 20 (on the intermediate transfer member) and the transfer roller 21 (on the transfer member).

[Liquid developer]
Next, the liquid developer D will be described. As the liquid developer D used in the image forming apparatus 100 of the present embodiment, a liquid developer conventionally used may be used, but an ultraviolet-curable liquid developer D may be used. Therefore, the ultraviolet curable liquid developer D will be described.

  The liquid developer D is a UV curable liquid developer containing a cationically polymerizable liquid monomer, a photopolymerization initiator, and toner particles insoluble in the cationically polymerizable liquid monomer. The cationically polymerizable liquid monomer is a vinyl ether compound, and the photopolymerization initiator is a compound represented by the following general formula (1).

  It will be described more specifically. The toner particles include a coloring material that emits a color in a toner resin. In addition to the toner resin and the colorant, other materials such as a charge control agent may be contained. As a method for producing toner particles, known techniques such as core shelving in which a coloring material is dispersed, polymerizing and encapsulating resin gradually, melting of resin and the like, and incorporating coloring material in resin may be used. Good. As the toner resin, epoxy, styrene acrylic, etc. are used. The colorant that emits a color may be a general organic-inorganic pigment. In addition, although a dispersant is used to improve toner dispersibility in production, a synergist is also possible.

  On the other hand, the curable liquid, which is a carrier liquid, is composed of a charge control agent that gives the charge on the toner surface, a photopolymerization agent that generates an acid upon irradiation with ultraviolet light (UV), and a monomer that bonds with the acid. . The monomer is a vinyl ether compound that polymerizes by a cationic polymerization reaction. In addition to the photopolymerization agent, a sensitizer may be contained. Since the preservability is lowered by photopolymerization, 10 to 5000 ppm of a cationic polymerization inhibitor may be added. In addition, charge control aids, other additives, etc. may be used.

  The UV curing agent (monomer) of this developer comprises about 90% (by weight) of a monofunctional monomer (formula 2) having one vinyl ether group and a bifunctional monomer (formula 3) having two vinyl ether groups. % Mixed.

  As a photoinitiator, 0.1% of what is represented by following (Formula 4) is mixed. By using this photopolymerization initiator, a high resistance liquid developer can be obtained unlike the case where an ionic photoacid generator is used, while achieving good fixation.

  The cationically polymerizable liquid monomer is dicyclopentadiene vinyl ether, cyclohexane dimethanol divinyl ether, tricyclodecane vinyl ether, trimethylolpropane trivinyl ether, 2-ethyl-1,3-hexanediol divinyl ether, 2,4-diethyl- 1,5-Pentanediol divinyl ether, 2-butyl-2-ethyl-1,3-propanediol divinyl ether, neopentyl glycol divinyl ether, pentaerythritol tetravinyl ether and 1,2-decanediol divinyl ether It is desirable that the compound be

  Further, as the charge control agent, known ones can be used. Specific compounds include oils and fats such as linseed oil and soybean oil; alkyd resins, halogen polymers, aromatic polycarboxylic acids, acid group-containing water-soluble dyes, oxidation condensates of aromatic polyamines, cobalt naphthenate, naphthenic acid Metallic soaps such as nickel, iron naphthenate, zinc naphthenate, cobalt octylate, nickel octylate, zinc octylate, cobalt dodecylate, nickel dodecylate, zinc dodecylate, aluminum stearate, cobalt 2-ethylhexanoate; Metal salts of petroleum based sulfonic acid metal salt, metal salt of sulfosuccinic acid ester; phospholipids such as lecithin; salicylic acid metal salts such as t-butylsalicylic acid metal complex; polyvinyl pyrrolidone resin, polyamide resin, sulfonic acid-containing resin, Hydroxybenzoic acid derivatives etc. .

[Conveying of liquid developer]
Next, conveyance of the liquid developer D in the present embodiment will be described with reference to FIG. First, the liquid developer collected by the drum cleaner 19 as described above is sent to the first separation and extraction device 37 and the second separation and extraction device 34. The liquid developer remaining on the developing roller 18 after development and collected in the collection section 16b of the developing device 16 is returned to the mixer 31, but is transported to the first separation and extraction device 37 and the second separation and extraction device 34. You may do so.

  On the other hand, the liquid developer collected by the intermediate transfer roller cleaner 26 is stored as a waste liquid W in a waste liquid storage container 35 as a storage container. Further, in the present embodiment, the liquid developer collected by the transfer roller cleaner 27 is held as it is by the transfer roller cleaner 27 because the amount thereof is small. However, as in the second embodiment described later (see FIG. 8), the liquid developer collected by the transfer roller cleaner 27 may be stored in the waste liquid storage container 35 as the waste liquid W. The waste liquid storage container 35 may be provided exchangeably with respect to the apparatus main body 100 a (see FIG. 1) of the image forming apparatus 100. In that case, it is preferable that the user can be notified of the replacement of the waste liquid storage container 35 when the waste liquid W stored in the waste liquid storage container 35 exceeds a predetermined amount.

  The first separation and extraction device 37 as a separation device, which will be described in detail later, separates the carrier liquid and the waste liquid W that may contain foreign substances such as toner and paper powder when the carrier liquid and the toner are separated. The separated waste liquid W is collected in the waste liquid storage container 35.

  The second separation and extraction device 34 separates unnecessary components in the carrier liquid other than toner from the carrier liquid separated and extracted by the first separation and extraction device 37, which will be described in detail later. Specifically, a substance with a low volume resistivity (low resistance carrier) contained in the carrier liquid can be mentioned. As described above, the substance forming the carrier liquid contains the charge control agent, and the component of the low resistance carrier is mainly the charge control agent. Here, the volume resistivity of the charge control agent is, by way of example, 1.0E + 9 Ωcm. In addition, the volume resistivity of the carrier liquid which does not contain a charge control agent is 1.0E + 12 ohm-cm.

  The transportation of the liquid developer D will be described more specifically. The transport pipes from the carrier tank 32 and the toner tank 33 to the mixer 31 are provided with solenoid valves 41 and 42, respectively. The solenoid valves 41 and 42 adjust the supply amounts of the carrier liquid C and the toner T to the mixer 31. From the mixer 31, a liquid developer D necessary for development is supplied to the developing device 16 using a pump 44 as a liquid developer supply means.

  The liquid developer collected in the collection section 16 b of the developing device 16 is returned to the mixer 31 by the pump 43. This is because the liquid developer collected in the collection section 16b is not used for development or the like and is hardly deteriorated.

  As shown in FIG. 2, the drum cleaner 19 and the first separation and extraction device 37 are connected to each other by a drum recovery liquid transport pipe 190 as a first transport path (transport path for separation). The drum cleaner 19 and the first separation and extraction device 37 are connected by the drum collection liquid transfer pipe 190, so that the liquid developer collected by the drum cleaner 19 can be transported to the first separation and extraction device 37. The liquid developer collected by the drum cleaner 19 is conveyed to the first separation and extraction device 37 by a pump 48 provided in the middle of the drum collected liquid transport pipe 190. The carrier liquid (liquid developer) separated and extracted by the first separation and extraction device 37 is conveyed to the second separation and extraction device 34 by the solenoid valve 51.

  On the other hand, in the present embodiment, the intermediate transfer roller cleaner 26 and the waste liquid storage container 35 are connected to each other by a middle recovery liquid transport pipe 260 as a second transport path. Since the intermediate transfer roller cleaner 26 and the waste liquid storage container 35 are connected by the medium recovery liquid transport pipe 260, the liquid developer collected by the intermediate transfer roller cleaner 26 can be transported to the waste liquid storage container 35. . The liquid developer collected by the intermediate transfer roller cleaner 26 is a small amount compared to the liquid developer collected by the drum cleaner 19, and the toner concentration (the ratio of the weight of the toner to the total weight of the toner and the carrier liquid: TD) Also called ratio) and viscosity are relatively high. Therefore, the liquid developer collected by the intermediate transfer roller cleaner 26 is transported to the waste liquid storage container 35 by a screw (not shown) or the like provided in the middle recovery liquid transport pipe 260. Of course, the present invention is not limited to this, and a pump (not shown) may be provided in the middle of the middle recovery liquid transport pipe 260 to be able to be transported by this pump.

  The carrier liquid separated by the first separation and extraction device 37 and the second separation and extraction device 34 is reusable, and is transported to the carrier tank 32 by the solenoid valve 45 as a carrier supply means for reuse. On the other hand, since it is difficult to reuse the waste liquid W (mainly toner) separated by the first separation and extraction device 37, the waste liquid W is transported to the waste liquid storage container 35 by the solenoid valve 47 provided in the waste liquid transport pipe 370 as a discharge conveyance path. Be done. In addition, since it is difficult to reuse the waste liquid W (mainly low resistance carrier) separated by the second separation and extraction device 34, it is provided in a transport pipe connecting the second separation and extraction device 34 and the waste liquid storage container 35. It is transported to the waste liquid storage container 35 by the solenoid valve 52.

  Next, separation of the toner and the carrier in the first separation and extraction device 37 described above and component separation of the carrier liquid in the second separation and extraction device 34 will be described with reference to FIGS. In the present embodiment, the first separation and extraction device 37 is a device that separates the liquid developer into toner and carrier liquid using an electric field, and separately extracts the carrier liquid and the toner. The second separation and extraction apparatus 34 is an apparatus for separating and extracting a low resistance carrier (mainly a charge control agent) from the carrier liquid separated and extracted by the first separation and extraction apparatus 37 using an electric field. The first separation and extraction device 37 and the second separation and extraction device 34 may have the same configuration. Therefore, in the following, the second separation and extraction device 34 will be described with reference to FIGS. 3 to 6, and the same configuration of the first separation and extraction device 37 is attached with reference numerals in parentheses for the same configuration. Explain to.

  First, the reason for providing the second separation and extraction device 34 will be described. As the carrier liquid is repeatedly recycled, a substance with a low volume resistivity (low resistance carrier) is accumulated in the carrier liquid. As a result, the resistance of the entire liquid developer decreases, which may cause image defects. In particular, when a high density image such as a solid image (a toner image formed on the entire surface of an image formable area of the photosensitive drum and having an image ratio (printing rate) of 100%) is formed, the output image In particular, the resistance is apt to decrease because the ratio of the carrier liquid to the In the present embodiment, the second separation and extraction device 34 is provided to suppress such a decrease in the volume resistivity of the carrier liquid.

  The carrier liquid (liquid developer) separated by the first separation and extraction device 37 is transported into the liquid storage container 346 from the inlet 34 b of the second separation and extraction device 34 as shown by the arrows in FIGS. 3 and 4. . Then, it is supplied to the buffer container 348 (see FIG. 4) in the liquid storage container 346. In the present embodiment, the buffer container 348 is provided in the second separation and extraction device 34, but may be provided alone. The carrier liquid supplied to the buffer container 348 is transported by the pump 34c and passes through the filter 34d.

  The carrier liquid having passed through the filter 34d is introduced into the supply tray 346a as shown in FIG. In the second separation and extraction device 34, the filter 34d may be omitted, and the carrier liquid separated and extracted by the first separation and extraction device 37 may be directly introduced into the supply tray 346a. The carrier liquid introduced into the supply tray 346 a is divided into a low resistance carrier (mainly a charge control agent) and a high resistance carrier in the second separation and extraction device 34. Then, the extracted low resistance carrier is sent to the waste liquid storage container 35, and the extracted high resistance carrier (carrier liquid) is transported to the carrier tank 32.

  As shown in FIG. 4 and FIG. 5, in the liquid storage container 346, a coat electrode member 341, a conductive electrode roller 342, a recovery device 350 and the like are arranged. The coat electrode member 341 and the electrode roller 342 constitute a pair of second electrodes between which the liquid developer can pass, the electrode roller 342 being one side of the second electrode 342a, and the coat electrode member 341 being the other side. Each has a second electrode 341a. The liquid storage container 346 is a container capable of containing a carrier liquid, and includes the above-described supply tray 346a, a discharge portion 346b from which the carrier liquid which can be reused as will be described later is discharged, and a liquid that becomes waste liquid. And a developer collection portion 354.

  The electrode roller 342 is, for example, a conductive roller in which a urethane rubber elastic layer is formed by integral molding on a core metal surface layer formed of solid stainless steel and having an outer diameter of 40 mm. The electrode roller 342 receives a drive from the outside by a drive motor (not shown), and rotates in a predetermined direction (the arrow direction in FIGS. 4 and 5). In the present embodiment, the rotational speed of the drive motor is 2000 rpm. Then, the electrode roller 342 decelerates the rotation of the drive motor and rotates, for example, at a rotational speed of 400 rpm.

  The coat electrode member 341 is disposed, as shown in FIGS. 5 and 6, through a part of the electrode roller 342 and a gap 347 as a second gap. A supply tray 346a is connected to the rotational direction upstream end 347a of the electrode roller 342 in the gap 347. Then, the carrier liquid introduced into the supply tray 346a as described above is supplied into the gap 347 from the upstream end 347a. Both ends of the gap 347 in the rotational axis direction of the electrode roller 342 are sealed, and the carrier liquid supplied to the gap 347 is transported downstream in the rotational direction in the gap 347 as the electrode roller 342 rotates. A discharge portion 346b is connected to the downstream end 347b of the gap 347 in the rotational direction of the electrode roller 342 (see FIG. 6). Then, the carrier liquid having passed through the gap 347 is sent from the discharge unit 346b to the carrier tank 32 via the transport pipe 346c (see FIG. 2).

  As described above, in the coated electrode member 341 disposed via the electrode roller 342 and the gap 347, at least the surface of the portion 341x through which the liquid passes is formed of a conductive material. The coat electrode member 341 is formed of, for example, solid stainless steel to a width of 400 mm. The portion 341x through which the liquid passes has a shape for accommodating a part of the electrode roller 342, and the surface of the portion 341x facing the electrode roller 342 is a predetermined distance from the surface of the electrode roller 342 (that is, the gap 347). It has a curved shape so as to keep The predetermined distance is, for example, 0.2 mm. In the case of this embodiment, the carrier liquid collected by the drum cleaner 19 as described above and supplied from the supply tray 346a to the gap 347 is separated into the low resistance carrier and the high resistance carrier by passing through the gap 347. Be done.

  The recovery device 350 is located downstream of the coat electrode member 341 with respect to the rotation direction of the electrode roller 342, and recovers the low resistance carrier carried by the electrode roller 342. The recovery device 350 has a recovery roller 351, a blade member 352, and a voltage application device (not shown).

  The recovery roller 351 is, for example, a conductive roller formed of solid stainless steel and having an outer diameter of φ20, and is disposed to abut on the electrode roller 342. Then, the collection roller 351 contacts the electrode roller 342, and is driven to rotate in the arrow direction in FIGS. The rotation speed of the collection roller 351 is, for example, 800 rpm.

[Supplementary Description of First Separation and Extraction Device]
As described above, the liquid developer collected by the drum cleaner 19 is transported from the inlet 37 b of the first separation and extraction device 37 into the liquid storage container 376 as shown by the arrows in FIGS. 4 and 5. Then, it is supplied to the buffer container 378 in the liquid storage container 376. The liquid developer supplied to the buffer container 378 is transported by the pump 37c and passes through the filter 37d.

  The liquid developer that has passed through the filter 37d is supplied to the supply tray 376a, as shown in FIG. As described in detail later, the liquid developer introduced into the supply tray 376a is divided into the toner and the carrier liquid in the first separation and extraction device 37. Then, the extracted toner is sent to the waste liquid storage container 35, and the extracted carrier liquid is transported to the second separation and extraction device 34 as described above.

  As shown in FIGS. 4 and 5, in the liquid storage container 376, a coat electrode member 371, a conductive electrode roller 372, a toner collection device 380, and the like are disposed. The coat electrode member 371 and the electrode roller 372 constitute a pair of first electrodes between which the liquid developer can pass, the electrode roller 372 being one side of the first electrode 372a, and the coat electrode member 371 being the other side. Each has a first electrode 371a. The liquid storage container 376 is a container capable of containing the liquid developer, and includes the above-described supply tray 376a, the discharge portion 376b from which the carrier liquid is discharged, and a recovery portion 384 of the liquid developer that has become waste liquid. doing.

  The electrode roller 372 receives drive from the outside by a drive motor (not shown), and rotates in a predetermined direction (arrow direction in FIGS. 4 and 5). In the present embodiment, the rotational speed of the drive motor is 2000 rpm. The driving motor for driving the electrode roller 342 of the second separation and extraction device 34 and the electrode roller 372 of the first separation and extraction device 37 may be the same or different.

  As shown in FIGS. 5 and 6, the coat electrode member 371 is disposed via a part of the electrode roller 372 and a gap 377 as a first gap. A supply tray 376a is connected to the rotational direction upstream end 377a of the electrode roller 342 in the gap 377. Then, the liquid developer introduced into the supply tray 376a as described above is supplied from the upstream end 377a into the gap 377. The liquid developer supplied to the gap 377 is transported downstream in the rotational direction in the gap 377 as the electrode roller 372 rotates. A discharge portion 376b is connected to the downstream end 377b of the gap 377 in the rotational direction of the electrode roller 372 (see FIG. 4). Then, the liquid developer that has passed through the gap 377 is sent from the discharge unit 376b to the second separation and extraction device 34 via the transport pipe 376c (see FIGS. 2 and 4).

  As described above, in the coat electrode member 371 disposed via the electrode roller 372 and the gap 377, at least the surface of the portion 371x through which the liquid passes is formed of a conductive material. A voltage is applied between the coat electrode member 371 and the electrode roller 372 so that an electric field for moving the toner toward the electrode roller 342 is generated by a high voltage power supply (not shown). That is, a voltage is applied to the gap 377 such that an electric field is generated such that the toner is attracted to the electrode roller 372.

  In this embodiment, since the toner is negatively charged by the charge control agent, for example, minus 300 V is applied to the electrode roller 372 and minus 1000 V is applied to the coat electrode member 371. As a result, while the liquid developer passes through the gap 377, the toner is carried by the electrode roller 372, and the toner and the carrier liquid are separated. The separated carrier liquid is discharged to the discharge portion 376b connected to the downstream end 377b of the gap 377.

  The toner recovery device 380 is located on the downstream side of the coat electrode member 371 with respect to the rotation direction of the electrode roller 372, and recovers the toner carried on the electrode roller 372. The toner recovery device 380 has a recovery roller 381 and a blade member 382.

  The recovery roller 381 is biased toward the electrode roller 372 and abuts on the electrode roller 372. Then, the collection roller 381 abuts on the electrode roller 372 and is driven to rotate in the arrow direction of FIGS. 4 and 5. The electrode roller 372 and the recovery roller 381 are disposed substantially in parallel with each other, and both end portions in the rotational axis direction are rotatably supported by the liquid storage container 376. A voltage is applied between the collection roller 381 and the electrode roller 372 by a high voltage power supply (not shown) so that an electric field to move the toner to the collection roller is generated. In the present embodiment, for example, minus 300 V is applied to the electrode roller 372 and minus 200 V is applied to the collection roller 381. Thus, the toner carried on the electrode roller 372 and transported to the collection roller 381 moves from the electrode roller 372 to the collection roller 381.

  The blade member 382 contacts the collection roller 381 and scrapes the toner on the collection roller. The blade member 382 is disposed on the downstream side of the collecting roller 381 in the rotational direction with respect to the position where the electrode roller 372 and the collecting roller 381 are in contact with each other so as to contact the collecting roller 381 in the counter direction. The toner moved from the electrode roller 372 to the collection roller 381 as described above is scraped off by the blade member 382 and sent to the collection unit 384. The toner collected by the collection unit 384 is sent to the waste liquid storage container 35 as described above.

  The first separation and extraction device 37 may have a configuration different from that of the second separation and extraction device 34 as long as toner and carrier liquid are separated and extracted.

  By the way, as described above, the first separation and extraction device 37 and the second separation and extraction device 34 separate the toner having the positive / negative polarity electrically or the component (mainly charge control agent) in the carrier liquid by electrophoresis. doing. However, when the liquid developer contains components such as calcium carbonate and talc, it is difficult for the first separation and extraction device 37 and the second separation and extraction device 34 to separate calcium carbonate and talc.

  That is, when the recording material S for forming a toner image is paper, calcium carbonate or talc (a metal compound such as magnesium) is contained as a filler for forming a white area on the paper. The content ratio of calcium carbonate and talc varies depending on the type of paper. When the recording material S is not a roll sheet but a cut sheet having a cut shape, paper dust is particularly likely to be generated at the end of the paper, and the intermediate transfer roller cleaner 26 directly in contact with the cut sheet Foreign substances are easily attached. Therefore, relatively large amounts of paper dust can be mixed in the liquid developer collected by the intermediate transfer roller cleaner 26. Since calcium carbonate and talc in the liquid developer which has passed through the strong electric field associated with the secondary transfer can have either positive or negative polarity electrically, the first separation and extraction device 37 and the second separation and extraction device 34 It is difficult to separate calcium carbonate and talc.

  In the conventional image forming apparatus, the carrier liquid recovered by the intermediate transfer roller cleaner 26, that is, the carrier liquid which contains components such as calcium carbonate and talc at a relatively high ratio and may be deteriorated is the first separation It has been transported to the extractor 37. However, as described above, in the first separation and extraction apparatus 37 (and the second separation and extraction apparatus 34), it is difficult to separate calcium carbonate and talc from the carrier liquid, and the altered carrier liquid may be reused. . When the altered carrier liquid is reused, the color tone and gloss of the toner image on the recording material after fixing are changed, and the curing property due to the irradiation of the ultraviolet light is reduced, so that the toner becomes difficult to fix on the recording material And other inconveniences may occur.

The degree of deterioration of the carrier liquid described above varies depending on the amount of accumulated paper dust (the amount of accumulated paper dust) contained in the carrier liquid. Therefore, the amount of accumulated paper dust in the carrier liquid will be described. In the mixer 31, the accumulated amount of paper dust in the carrier liquid at the Nth sheet passing is X (N), the carrier consumption amount per recording material provided for development by the developing roller 18 is “a”, recording material I The amount of paper dust generated per sheet is "p". These units are grams (g), and the recording material S is A4 cut paper. Then, it is assumed that the generated paper dust is all collected by the intermediate transfer roller cleaner 26. Further, it is assumed that the total amount of the carrier liquid in the mixer 31 is "A", and the carrier liquid consumed for one sheet of the recording material by the developing roller 18 is always replenished with the new carrier liquid. Further, paper dust collected by the intermediate transfer roller cleaner 26 is uniformly dispersed in the mixer 31, and the carrier liquid is used when forming a toner image on the next recording material S. In this case, the accumulated amount of paper dust X (N) in the carrier liquid at the Nth sheet passing can be expressed by the following equation (1).
X (N) = X (N-1)-(a / A) x X (N-1) + p (Equation 1)

  In the formula (1), the first term “X (N−1)” on the right side represents the amount of accumulated paper dust in the carrier liquid on the (N−1) th sheet of the recording material S. The second term “(a / A) × X (N−1)” on the right side is the toner image of the Nth sheet of the paper dust accumulated in the carrier liquid up to the (N−1) th sheet. This represents the amount of paper dust discharged out of the mixer 31. The third term "p" on the right side represents the amount of paper dust generated per recording material, as described above.

Here, the carrier amount per recording material provided for development by the developing roller 18 is “0.05 g”, and the carrier liquid in the drum cleaner 19 and the mixer 31 per recording material is “2000 g”, The amount of paper dust generated per recording material is “2.0 × 10 ⁻⁴ g”. In FIG. 9, the cumulative number of sheets for image formation (the number of durable sheets) and paper powder accumulation in the carrier liquid in the conventional image forming apparatus in which the carrier liquid collected by the intermediate transfer roller cleaner 26 is conveyed to the first separation and extraction device 37 The relationship with the quantity X (n) is shown.

  In FIG. 10, when paper dust (specifically, talc is contained in the component) is mixed with the carrier liquid, the paper dust content in the liquid and the image quality change (specifically, gloss) of the toner image after fixing Show the relationship between In FIG. 10, the horizontal axis indicates the paper powder content (w%) relative to the carrier liquid, and the vertical axis indicates the image quality change by the gloss difference (Δ gloss). A gloss meter "PG-II" manufactured by Nippon Denshoku Kogyo Co., Ltd. was used as a gloss meter for measuring the gloss. Generally, when the gloss is "2 °" or more, the user can recognize image degradation. Therefore, here, the gloss difference "2 °" is used as the boundary value of the image quality deterioration (indicated by a dotted line in FIG. 10). As can be understood from FIG. 10, when the paper powder content is “0.2 w%”, in this case, the weight of the paper powder contained in the carrier liquid exceeds “4 g”, the gloss difference exceeds “2 °”. Therefore, the image quality drops significantly.

The liquid developer of “2000 g (2 liters)” is circulated between the mixer 31 and the developing device 16, and “1.0 × 10 ⁻⁴ g” of paper powder is an intermediate transfer roller for each sheet of recording material. It shall be collected by the cleaner 26. In the case of the conventional image forming apparatus, as shown in FIG. 9, the paper powder having a weight (4 g) having a gloss difference exceeding “2 °” is contained in the total number of images formed (durable sheet) After about 27,000 copies. As described above, in the conventional image forming apparatus, when the paper powder exceeding 4 g is contained in the carrier liquid, the difference in glossiness becomes “2 °” or more, and the image quality may be deteriorated. On the other hand, in the image forming apparatus, for example, about 1,000,000 sheets are assumed as the number of recording materials S capable of appropriately forming an image (referred to as the number of sheets usable). Therefore, in the case of the conventional image forming apparatus, it is necessary to replace the liquid developer every time when an image is formed on the recording material S of about 27,000 sheets, and the running cost associated with the replacement of the liquid developer increases. Also, it takes time for the user.

  In view of the above point, in the present embodiment, as described above, the intermediate transfer roller cleaner 26 and the waste liquid storage container 35 and the waste liquid storage container 35 can transport the liquid developer collected by the intermediate transfer roller cleaner 26 to the waste storage container 35. Are connected by an add-on recovery liquid transfer pipe 260. That is, the liquid developer collected by the intermediate transfer roller cleaner 26 is transported not to the first separation and extraction device 37 but to the waste liquid storage container 35. This makes it possible to increase the number of durable sheets taken until the paper powder having a weight difference exceeding 2 ° is included in the carrier liquid, as compared with the conventional case. Hereinafter, this point will be described.

  FIG. 7 shows the relationship between the total number of image formations (the number of durable sheets) and the accumulated amount of paper dust in the carrier liquid in the image forming apparatus 100 of the present embodiment. In the case of this embodiment, most of the paper dust is collected together with the liquid developer by the intermediate transfer roller cleaner 26 and is transported to the waste liquid storage container 35 together with the liquid developer, so it does not reach the first separation and extraction device 37 . However, a very small amount of paper dust may be mixed in the liquid developer collected by the drum cleaner 19. Since the liquid developer collected by the drum cleaner 19 is conveyed to the first separation and extraction device 37, as shown in FIG. 7, the amount of accumulated paper dust contained in the carrier liquid is constant (here Increase to 0.08g). In this case, the accumulated amount of paper dust is suppressed to "about 0.08 g" even when the durable sheet number of 1,000,000 sheets has passed. That is, the accumulated amount of paper dust does not reach up to "4 g" where the gloss difference becomes "2 °" or more and the image quality may be deteriorated. As described above, in the image forming apparatus 100 according to the present embodiment, the paper powder having a weight difference exceeding “2 °” is not included in the carrier liquid even after the number of sheets has passed. Therefore, it is not necessary to replace the liquid developer.

  Further, in the case of the present embodiment, the fixing device 25 (see FIG. 1) emits ultraviolet light (UV light of, for example, 10 to 20 mJ) to the toner image secondarily transferred to the recording material S conveyed by the conveyance belt 24. To harden the carrier liquid, and fix the toner image on the recording material S. In the case of the present embodiment, the output upper limit of the ultraviolet light by the fixing device 25 is “20 mJ”. Also, the exposure energy required to cure the carrier liquid by the irradiation of ultraviolet light is "8 mJ" or more.

  The exposure energy required to cure the carrier liquid varies with the change in the state of the carrier liquid. FIG. 11 shows the relationship between the paper powder content in the UV-curable liquid developer and the exposure energy required to cure the carrier liquid when paper dust (specifically, talc) is mixed with the carrier liquid. . As shown in FIG. 11, as the paper dust content (w%) in the liquid increases, the exposure energy required to cure the carrier liquid increases. In the case of the present embodiment, when the exposure energy required to cure the carrier liquid is 20 mJ or more, the output upper limit is exceeded and the carrier liquid can not be cured, and the toner image is fixed to the recording material S. It will be difficult to Therefore, here, the exposure energy "20 mJ" is used as the boundary value of fixing possibility (indicated by a dotted line in FIG. 11).

  As can be understood from FIG. 11, in the case of the present embodiment, when the paper powder content is “0.3 w%”, here, the weight of the paper powder contained in the carrier liquid exceeds “6 g”, the carrier liquid is The exposure energy required for curing exceeds 20 mJ, making fixing difficult. This is because talc (a metal ion such as magnesium) contained in the carrier liquid inhibits the curing reaction of the monomer contained in the carrier liquid.

  In the case of the conventional image forming apparatus, the paper powder having a weight (6 g) whose exposure energy exceeds “20 mJ” is contained in the carrier liquid, as shown in FIG. It is after about 520,000 copies. As described above, in the conventional image forming apparatus, when the paper powder exceeding 6 g is contained in the carrier liquid, the exposure energy exceeds “20 mJ”, and the fixing by the ultraviolet light irradiation becomes difficult.

  On the other hand, in the image forming apparatus 100 of the present embodiment, as shown in FIG. 7, the accumulated amount of paper dust contained in the carrier liquid increases to a fixed amount (here, 0.08 g) according to the number of durable sheets. However, even when one million sheets have passed, the accumulated amount of paper dust is suppressed to "about 0.08 g". That is, the accumulated amount of paper dust does not reach to "6 g" where exposure energy exceeds "20 mJ" and fixation by ultraviolet light irradiation becomes difficult. As described above, in the image forming apparatus 100 according to the present embodiment, the amount of paper dust which is difficult to be fixed by the irradiation of the ultraviolet light is not included in the carrier liquid even after the number of sheets has passed. Therefore, it is not necessary to replace the liquid developer.

  As described above, in the present embodiment, the drum cleaner 19 and the first separation and extraction device 37 are connected to each other by the drum recovery liquid transport pipe 190, while the intermediate transfer roller cleaner 26 and the waste liquid storage container 35 are connected. They are connected to one another by an add-on recovery liquid transport pipe 260. In this case, the liquid developer collected by the drum cleaner 19 is separated into the toner and the carrier liquid by the first separation and extraction device 37, and the separated carrier liquid is reused. On the other hand, since the liquid developer collected by the intermediate transfer roller cleaner 26 is conveyed to the waste liquid storage container 35, it is not separated into the toner and the carrier liquid by the first separation and extraction device 37. That is, since the liquid developer containing a large amount of paper dust is not separated by the first separation and extraction device 37, the carrier liquid in which the components are degraded is not reused by containing a large amount of paper dust. Thus, in the present embodiment, since deterioration of the carrier liquid to be reused can be suppressed, it is possible to obtain an effect that the liquid developer can be repeatedly used longer than in the past. Then, if the liquid developer can be repeatedly used for a longer time than in the past, the running cost associated with the replacement of the liquid developer can be suppressed, and the time and effort of the user can be reduced.

Second Embodiment
In the first embodiment described above, the liquid developer collected by the transfer roller cleaner 27 is held as it is by the transfer roller cleaner 27. However, the present invention is not limited to this. The liquid developer collected by the transfer roller cleaner 27 It may be configured to be transported to 35. Such a second embodiment will be described with reference to FIG. Below, the case where an ultraviolet curing type liquid developer is used will be described as an example. In addition, about the structure similar to 1st embodiment mentioned above, the same code | symbol is attached | subjected and description is simplified or abbreviate | omitted.

  As shown in FIG. 8, in the present embodiment, the transfer roller cleaner 27 and the waste liquid storage container 35 are connected to each other by a double recovery liquid transport pipe 270 as a third transport path (transport path for recovery). The transfer roller cleaner 27 and the waste liquid storage container 35 are connected by the second recovery liquid transport pipe 270 so that the liquid developer collected by the transfer roller cleaner 27 can be transported to the waste storage container 35. The liquid developer collected by the transfer roller cleaner 27 is transported to the waste liquid storage container 35 by a screw (not shown) or the like provided in the double recovery liquid transport pipe 270. Alternatively, a pump (not shown) may be provided in the middle of the second recovery liquid transport pipe 270 so that it can be transported by this pump.

Other Embodiments
In addition to the use of a pump, for example, the liquid developer may be transported using its own weight without being provided with a pump if it can be transported by its own weight drop.

13: photosensitive body (photosensitive drum), 16: developing device (developing device), 19: first cleaning means (photosensitive body cleaning means, drum cleaner), 20: intermediate transfer body (intermediate transfer roller), 21: transfer member ( Transfer roller) 25 Fixing device 26 Second cleaning means (intermediate transfer roller cleaner) 27 Third cleaning means (transfer member cleaning means, transfer roller cleaner) 31 Mixer (mixer) 32 Carrier Container (carrier tank) 33: toner container (toner tank) 35: storage container (waste liquid storage container) 37: separation device (first separation and extraction device) 45: carrier supply means (electromagnetic valve) 100: image Forming device, 100a ... main body of the device, 190 ... first transport path (transport path for separation, drum recovery liquid transport pipe), 260 ... second transport path (middle recovery liquid transport pipe), 270 ... third transport path (recovery Transport path, Rolling recovered liquid transport pipe), 370 ... discharge transport path (waste transport pipe)

Claims (8)

A photoconductor,
A developing device for developing an electrostatic latent image formed on the photosensitive member into a toner image with a liquid developer comprising toner and carrier liquid;
An intermediate transfer member to which a toner image is primarily transferred from the photosensitive member;
A transfer member for secondarily transferring the toner image primarily transferred to the intermediate transfer member to a recording material;
First cleaning means for collecting liquid developer remaining on the photosensitive member after primary transfer;
A second cleaning unit for recovering the liquid developer remaining on the intermediate transfer member after the secondary transfer;
A separation device for separating the toner and the carrier liquid from the liquid developer;
A container for containing the liquid developer;
A first transport path connecting the first cleaning unit and the separation device so that the liquid developer collected by the first cleaning unit can be transported to the separation device;
And a second transport path connecting the second cleaning unit and the storage container so that the liquid developer collected by the second cleaning unit can be transported to the storage container without the separation device.
An image forming apparatus characterized by Third cleaning means for collecting the liquid developer remaining on the transfer member after the secondary transfer;
And a third transport path connecting the third cleaning unit and the storage container so that the liquid developer collected by the third cleaning unit can be transported to the storage container without the separation device.
The image forming apparatus according to claim 1, A photoconductor,
A developing device for developing an electrostatic latent image formed on the photosensitive member into a toner image with a liquid developer comprising toner and carrier liquid;
An intermediate transfer member to which a toner image is primarily transferred from the photosensitive member;
A transfer member for secondarily transferring the toner image primarily transferred to the intermediate transfer member to a recording material;
Photoreceptor cleaning means for collecting liquid developer remaining on the photoreceptor after primary transfer;
A transfer member cleaning unit that recovers a liquid developer remaining on the transfer member after secondary transfer;
A separation device for separating the toner and the carrier liquid from the liquid developer;
A container for containing the liquid developer;
A separation transport path connecting the photoreceptor cleaning means and the separation device so that the liquid developer collected by the photoreceptor cleaning means can be transported to the separation device;
And a recovery transport path connecting the transfer member cleaning unit and the storage container so that the liquid developer collected by the transfer member cleaning unit can be transported to the storage container without the separation device.
An image forming apparatus characterized by A discharge conveyance path connecting the separation device and the storage container so that the toner separated from the liquid developer by the separation device can be transported to the storage container;
The image forming apparatus according to any one of claims 1 to 3, wherein The liquid developer is a UV curable liquid developer.
The image forming apparatus according to any one of claims 1 to 4, characterized in that: The toner image secondarily transferred onto the recording material is irradiated with ultraviolet light to cure the carrier liquid, and a fixing device for fixing the toner image on the recording material is provided.
The image forming apparatus according to claim 5, A toner container for containing toner,
A carrier container containing a carrier liquid;
A mixer which contains a liquid developer, and mixes and disperses the toner supplied from the toner container and the carrier liquid supplied from the carrier container;
The carrier container is provided with carrier supply means for supplying a carrier liquid obtained by separating the toner from the liquid developer by the separation device;
The image forming apparatus according to any one of claims 1 to 6, wherein The container is provided exchangeably with respect to the device body.
The image forming apparatus according to any one of claims 1 to 7, wherein

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