JP2010015033A - Carrier liquid regenerating device for liquid developer and image forming apparatus equipped with the device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a carrier liquid regenerating device for a liquid developer for improving efficiency of a reduction action and secular degradation of reduction performance by reducing an oxide of an unsaturated fatty acid component with a photocatalyst, and to provide an image forming apparatus equipped with the device. <P>SOLUTION: The carrier liquid regenerating device for a liquid developer includes: a regenerating tank 71 housing a used liquid developer L1 of a liquid developer containing an unsaturated fatty acid component as an insulating carrier liquid and toner particles dispersed therein; a photocatalyst reducing section 72 disposed in the regenerating tank 71 and reducing an oxide of the unsaturated fatty acid component included in the used liquid developer L1; a light irradiating section 73 irradiating the photocatalyst reducing section 72 with light; and a separating section separating at least the unsaturated fatty acid component in the reduced used liquid developer from water. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a carrier liquid regenerating apparatus for a liquid developer, a developing apparatus including the same, and an image forming apparatus.

In general, in an image forming apparatus using electrophotographic wet development, the surface of an electrostatic latent image carrier (for example, a photoreceptor) is charged, and the charged area is exposed based on image data to form an electrostatic latent image. And a developing method is adopted in which the electrostatic latent image is developed by bringing a liquid developer from the surface of the developing roller of the developing device into contact therewith.
This liquid developer
a) Petroleum-based aliphatic liquids (for example, “Isopa” manufactured by Exxon), silicone oils (for example, “KF-96” manufactured by Shin-Etsu Silicone), or biological oils (for example, refined oils such as castor oil and soybean oil) An insulating carrier liquid comprising:
b) a solid (for example, toner particles having a particle diameter of 1 to 2 μm) having a particle diameter of several hundred nm to several μm in which a colorant (for example, carbon black) is dispersed in a resin (for example, polyethylene); If necessary, a charge adjusting agent is added to adjust the charge of the solid content (see, for example, Patent Documents 1 and 2).

JP 2002-278306 A JP 2007-140410 A

If biological (naturally-derived) fats and oils are used in the carrier liquid in consideration of the environment and resources, the unsaturated fatty acid components contained in the fats and oils are generally easily oxidized, and there is a problem that the insulation resistance decreases due to the oxidation of the unsaturated fatty acid components. It becomes.
As a countermeasure to the oxidation of unsaturated fatty acid components, in Patent Document 2, the oxide of unsaturated fatty acid components is reduced by the catalytic action of zeolite, and the carrier liquid is maintained at a predetermined insulation resistance to stabilize the image quality. Proposals have been made. However, since zeolite has a problem that the reduction performance deteriorates with time due to adsorption of moisture in the carrier liquid, a technique for reducing oxides of unsaturated fatty acid components more efficiently is desired.

  The present invention has been made in view of the above-mentioned problems, and improves the efficiency of the reduction action and the deterioration over time of the reduction performance by reducing the oxide of the unsaturated fatty acid component contained in the carrier liquid with a photocatalyst. An object of the present invention is to provide a carrier liquid regenerating apparatus for a liquid developer that can be used and an image forming apparatus including the same.

  Thus, according to the present invention, a regeneration tank containing a liquid developer containing an unsaturated fatty acid component as an insulating carrier liquid and having toner particles dispersed therein and containing a used liquid developer, A photocatalytic reduction unit arranged to reduce the oxide of the unsaturated fatty acid component contained in the used liquid developer, a light irradiation unit for irradiating the photocatalytic reduction unit with light, and a reduction-used used There is provided a carrier liquid regenerating apparatus for a liquid developer, comprising at least an unsaturated fatty acid component in the liquid developer and a separation part for separating moisture.

  According to another aspect of the present invention, a photoconductor, a developing device that supplies a liquid developer to the photoconductor to form a toner image, and a toner image formed on the photoconductor is transferred to a transfer material. A transfer unit that fixes the toner image transferred to the transfer material, the carrier liquid reproducing device, the liquid developer that has not been transferred to the transfer material, and remains on the transfer unit. A first transfer unit capable of transferring at least one of the liquid developers to the regeneration tank of the carrier liquid regenerator, and a second transfer unit capable of transferring the carrier liquid regenerated from the carrier liquid regenerator to the developing device. An image forming apparatus is provided.

According to the carrier liquid regenerating apparatus for a liquid developer of the present invention, the unsaturated fatty acid component and moisture in the used developer after reducing the oxide of the unsaturated fatty acid component in the carrier liquid with a photocatalyst and reducing the oxide are used. Can be separated. As a result, the used carrier liquid can be regenerated into a carrier liquid whose insulation resistance has been restored to a predetermined value. Further, since the photocatalyst is used for the reduction treatment, the reduction treatment efficiency and reduction performance are deteriorated over time. Improved.
In addition, according to the image forming apparatus provided with the carrier liquid reproducing apparatus, it is possible to obtain a stable and high-quality image for a long time.

  A carrier liquid regenerator for a liquid developer according to the present invention includes a regeneration tank that contains a used liquid developer of a liquid developer containing an unsaturated fatty acid component as an insulating carrier liquid and having toner particles dispersed therein. A photocatalytic reduction unit for reducing the oxide of the unsaturated fatty acid component contained in the used liquid developer disposed in the regeneration tank, and a light irradiation unit for irradiating the photocatalytic reduction unit with light, It is characterized by comprising at least an unsaturated fatty acid component in the used liquid developer subjected to the reduction treatment and a separation unit for separating water.

  That is, this carrier liquid regenerating apparatus is applied to an electrophotographic image forming apparatus that prints a toner image on a transfer material using the liquid developer, and is transferred to the transfer material in an image forming process. By reducing the oxide of the unsaturated fatty acid component in the carrier liquid contained in the used liquid developer that was not used and removing moisture, the used carrier liquid is restored (increased) to a predetermined insulation resistance, Regenerate the carrier liquid.

Here, as the liquid developer in the present invention, a liquid developer used in this field, which contains an unsaturated fatty acid component as an insulating carrier liquid and has toner particles dispersed therein, is used. be able to. The present invention is particularly suitable as a regenerating apparatus for a carrier liquid composed mainly of biological oils (naturally derived) that are easily oxidized, such as castor oil, linseed oil, soybean oil, corn oil, sesame oil, sardine oil, mackerel oil and the like. is there.
In this liquid developer, the toner particles to which the pigment is bound by the binder resin are solid particles charged to the same polarity as the surface potential charged on the photoreceptor of the image forming apparatus, and have a predetermined concentration in the carrier liquid. Is mixed and dispersed.
The liquid developer may have a viscosity of 100 to 10,000 mPa · s (preferably 300 mPa · s) and a solid content (toner concentration) of 5 to 40% by weight (preferably 20% by weight).
Since such a liquid developer is publicly known, a detailed description of the composition, manufacturing method, and the like is omitted.

In the present invention, the photocatalytic reduction portion can be composed of a carrier that carries a photocatalyst. The photocatalyst is not particularly limited as long as it can reduce the oxide of the unsaturated fatty acid component by photocatalysis, and examples thereof include titanium oxide, zinc oxide, cadmium sulfide, and the like. The above can be used.
According to this configuration, the photocatalyst has an efficient reducing action and a self-cleaning effect on the reducing action surface, and also has excellent hydrophilicity (superhydrophilicity) on the reducing action surface, so that moisture generated by the reduction treatment and the atmosphere before the reduction treatment Since the water vapor in the tank captures and holds moisture mixed in the used liquid developer due to condensation or the like, it is possible to efficiently increase the insulation resistance of the lowered used carrier liquid.

  The support for supporting the photocatalyst is not particularly limited as long as it is made of a material that does not affect the quality of the carrier liquid and can support the photocatalyst. Specific examples of the material of the carrier include, for example, hydrophilic ceramics, hydrophilic polymer materials (for example, acrylic resin, polyethylene resin, polyamide resin, polyimide resin, etc. having resistance to carrier liquid), hydrophilic Examples thereof include glass subjected to chemical treatment, and metal subjected to hydrophilic treatment (for example, stainless steel, nickel, nickel alloy, aluminum, aluminum alloy, copper, copper alloy, etc.). In order to increase the surface area of the support supporting the photocatalyst and to easily retain the water generated by the reduction treatment, it is preferable to form the support in a porous shape, and the material forms a porous support. If it is difficult to do this, a mesh-like carrier may be formed.

The shape of the carrier is not particularly limited, and for example, a sheet shape (plate shape), a rod shape (columnar shape), a cylindrical shape, a cone or a pyramid shape (including a hollow shape), a spherical shape (including a hollow shape), a cubic shape, for example. Or a rectangular parallelepiped shape (a hollow is also included) or the shape which combined these is mentioned.
When the support is made of a heat-resistant material such as ceramic, glass, or metal, the photocatalyst can be supported on the surface of the support by applying a paste or coating solution containing photocatalyst particles to the surface of the support and firing. . Also, when the support is made of a polymer material, the paste or coating liquid containing photocatalyst particles is applied to the surface of the support, and the support is formed by forming a film by heat drying curing, UV irradiation curing, or the like according to the coating liquid A photocatalyst can be carried on the surface of the body. Alternatively, the photocatalyst may be directly supported on the surface of the support by sputtering.
In addition, the photocatalyst should just be carry | supported by the part irradiated with the light from the light irradiation part in a support body.

One or more carriers may be used, and the size is not particularly limited.
Further, if the photocatalyst is irradiated with light from the light irradiation unit, the carrier is not fixed but is settled or suspended (dispersed) in the used liquid developer even if it is fixed in the regeneration tank. May be. However, by maintaining the position of the carrier as close as possible to the light irradiating part, attenuation of light intensity when light from the light irradiating part passes through the used liquid developer is suppressed, and strong light is photocatalyst. It is preferable that the support is fixed in the regeneration tank because the photocatalyst is irradiated stably, the photocatalyst is stably irradiated, and the photocatalyst formation region having a small area can exhibit a highly efficient reduction action.

  When the carrier is fixed in the regeneration tank, the fixing position of the carrier is not particularly limited as long as the photocatalyst is irradiated by light from the light irradiation unit. It is preferable to be fixed at a position as close as possible from the irradiation unit. In this case, in consideration of the fact that it is preferable to arrange the light irradiation unit outside the inside of the regeneration tank in order to simplify the configuration of the light irradiation unit, the carrier is attached to the peripheral wall or the bottom wall of the regeneration layer. It is preferable to fix in the vicinity position.

In this case, a transparent window is provided at least on the peripheral wall portion or bottom wall portion of the regeneration tank in the vicinity of the light irradiating portion, and the strong light is transmitted through the transparent window and radiated to the photocatalyst on the support body. The end of the carrier is fixed to the bottom wall or the surrounding wall so that the light receiving surface of the body is substantially parallel to the transparent window. Furthermore, since the toner particles in the used liquid developer easily settle to the bottom wall side of the regeneration tank, the transparent window on the bottom wall is covered with the toner particles and the light from the light irradiation part is easily blocked. In consideration, it is preferable to provide a transparent window on the peripheral wall and arrange the carrier and the light irradiation part to face each other through the transparent window, and the shape of the carrier is a long sheet in a direction substantially parallel to the transparent window. A rod shape, a cylindrical shape and the like are preferable.
Further, transparent windows may be provided at a plurality of locations on the peripheral wall of the regeneration tank, and a plurality of light irradiation units may be disposed corresponding to the respective transparent windows, so that one carrier may be irradiated with light from multiple directions. A plurality of carriers and light irradiation units may be arranged corresponding to the transparent windows.

The light irradiator is not particularly limited as long as it irradiates the photocatalyst with light that excites the photocatalytic action. For example, an ultraviolet light source composed of a lamp or LED capable of irradiating ultraviolet light having a wavelength of 400 nm or less is used. be able to. The number of the ultraviolet light sources is not particularly limited, and may be one or more.
Moreover, in order to irradiate light efficiently to the support body which carry | supported the photocatalyst, a light irradiation part may be equipped with the reflecting plate in the back side of the light source which is the opposite side to a support body. The reflection plate can increase the intensity of light irradiated from one light source to the carrier and can irradiate the carrier with reflected light from a direction different from the direction of direct light irradiation to the carrier. The irradiation area is increased, and the reduction efficiency by the photocatalytic reduction unit can be further increased.

In the present invention, the separation unit has a separation membrane that is disposed so as to partition the region where the photocatalytic reduction unit is disposed in the regeneration tank and that allows the unsaturated fatty acid component to permeate and does not allow moisture to permeate. Can do. According to this configuration, it becomes easy to separate and remove the regenerated carrier liquid containing the reduced unsaturated fatty acid component and not containing moisture from the used liquid developer.
The separation membrane may be formed of a material that allows the unsaturated fatty acid component to pass therethrough and does not allow moisture to pass therethrough and does not affect the quality of the carrier liquid. For example, a porous separation membrane having an average pore diameter of several hundred nm to several tens of μm and having a lipophilic and water-repellent surface, specifically, a sintered body of high-density polyethylene resin particles having an average pore diameter of about 20 μm (See JP-A-62-142629 and JP-A-2002-113302). A foam material or an aggregate of fibers having a lipophilic and water-repellent surface can also be used as the separation membrane.
Depending on the pore size of the separation membrane and the particle size of the toner particles, it is preferable that the separation membrane does not allow the toner particles in the used liquid developer to permeate. However, a small amount of toner particles may permeate the separation membrane as long as there is no problem with the quality of the regenerated carrier liquid.

The carrier liquid regenerating apparatus of the present invention may further include a water removing unit that discharges the water in the used liquid developer that has settled to the bottom of the regenerating tank to the outside. According to this configuration, since the water settled at the bottom of the regeneration tank is not redispersed in the used liquid developer, the ability to generate a regenerated carrier liquid that does not contain moisture can be increased. In this case, the moisture removing unit is arranged in a region where the photocatalytic reduction unit is arranged in the regeneration tank partitioned by the separation membrane.
Hereinafter, the region where the photocatalytic reduction unit is arranged in the regeneration tank partitioned by the separation membrane is referred to as a first region (reduction treatment region), and the region having no photocatalytic reduction unit is the second region (regeneration carrier extraction region). ).

The moisture removing unit can be configured to have at least a support that supports the photocatalyst of the photocatalytic reduction unit, and an openable / closable drain port formed at the bottom of the regeneration tank. A water discharge pipe connected to the water discharge pipe, an on-off valve provided on the water discharge pipe for opening and closing the drain port, and a drain tank detachably connected to the downstream end of the water discharge pipe.
According to this configuration, since the surface of the photocatalyst is superhydrophilic, the water generated by reducing the oxide of the unsaturated fatty acid component by the photocatalyst is easily retained on the surface of the photocatalyst. Efficient water removal is possible because it falls by its own weight along the path. In addition, since the photocatalytic reduction unit can be used as a part of the configuration of the moisture removal unit, the carrier liquid regenerator can be reduced in size and cost.
In this case, it is preferable to provide a gradient at the bottom of the regeneration tank so that the drain port is at the lowest position, so that the water falling along the photocatalytic reduction unit and the water contained in the used liquid developer are gradients at the bottom of the bottom. Therefore, water is reliably removed.

The carrier liquid regenerating apparatus of the present invention may further include an agitation unit for agitating the used liquid developer in the regeneration tank. According to this configuration, since the carrier liquid can be uniformly contacted with the photocatalyst by stirring the used liquid developer in the regeneration tank, the oxide of the unsaturated fatty acid component in the carrier liquid can be stabilized. It can reduce and promote moisture removal. The stirring unit is not particularly limited, but it is preferable that the used liquid developer can be sufficiently stirred without entraining air and has a simple configuration.
In this case, it is preferable to arrange the stirring unit in the first region in the regeneration tank. Further, in order to cause a turbulent flow in the used liquid developer stirred by the stirring unit so that the carrier liquid comes into contact with the photocatalyst more uniformly, protrusions (disturbances) are formed on the peripheral wall of the regeneration tank and the inner wall surface of the bottom wall. Plate), or a stepped step portion may be formed on the peripheral wall or the bottom wall.

The carrier liquid regenerating apparatus of the present invention may further include a resistance detection unit that detects the insulation resistance of the insulating carrier liquid in the regeneration tank. According to this, the unsaturated fatty acid is detected by detecting the insulation resistance of the carrier liquid. The oxidation state of the component can be detected in real time. The resistance detection unit includes an AC bridge circuit that does not have a DC component in order to avoid the electrochemical reaction of the carrier liquid and the electrodeposition of deposits such as toner on the detection electrode that accompany the resistance measurement operation. Detection of the electrical resistance of the carrier liquid can be used.
In this case, you may further provide the control part which controls the drive of a light irradiation part and a stirring part based on the detection result of the said resistance detection part. According to this configuration, it is possible to reduce the oxide of the carrier liquid (unsaturated fatty acid component) more uniformly and in a timely manner by driving the light irradiation unit and the stirring unit based on the detection result of the resistance detection unit. It becomes possible. In addition, by providing the carrier liquid regenerating apparatus in the image forming apparatus, a printed image can be stably formed with high image quality.

In addition, a pair of capture electrodes that captures toner particles by generating an electric field in the used liquid developer when a voltage is applied are provided in the region (first region) in the regeneration tank where the photocatalytic reduction unit is disposed. May be further provided. According to this configuration, since the toner particles in the used liquid developer are captured by the capture electrode, it is possible to prevent the toner particles from adhering to the separation film and causing clogging. It is possible to take out the regenerated carrier liquid whose insulating properties have been stably recovered even if it is used for a long time, and to greatly reduce the number of maintenance operations for replacing the clogged separation membrane.
In this case, two capture electrodes are arranged opposite to each other in the regeneration tank, and a voltage of, for example, about several hundred mV to several V is applied. In addition, it is preferable to maintain the capture efficiency of the toner particles by the capture electrode by periodically removing the capture electrode from the regeneration tank and washing and removing the adhered toner particles.

Moreover, the above-described resistance detection unit is disposed in at least one of the first region and the second region in the regeneration tank.
If the resistance detection unit is arranged in the first region, it is possible to quickly detect the insulation resistance of the used carrier liquid newly accommodated in this region and to control the driving of the photocatalytic reduction unit in a timely manner. In addition, if the resistance detection unit is arranged in the second region, the insulation resistance varies due to moisture contained in the used liquid developer, and an error in detecting the progress of oxidation of the unsaturated fatty acid component cannot be ignored. It is possible to confirm whether or not the insulation resistance of the regenerated carrier liquid taken out from this region has sufficiently recovered.

The carrier liquid regenerating apparatus for liquid developer thus configured can be provided in an image forming apparatus described in detail later.
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment at all.

(Embodiment 1)
FIG. 1 is a longitudinal sectional view schematically showing an overall configuration of an image forming apparatus according to a first embodiment provided with a carrier liquid regenerating apparatus for a liquid developer according to the present invention, and FIG. 2 is an image forming apparatus according to the first embodiment. FIG. 3 is a schematic cross-sectional view schematically showing the carrier liquid regenerating apparatus of the image forming apparatus according to the first embodiment and its peripheral components.

  This image forming apparatus includes a photoconductor 20, a developing device 30 that supplies a liquid developer to the photoconductor 20 to form a toner image, and a toner image formed on the photoconductor 20 as a transfer material (hereinafter referred to as paper). Transfer unit 40 for transferring to P, fixing unit 50 for fixing the toner image transferred to paper P, paper transport unit 60 for transporting paper P to transfer unit 40 and fixing unit 50, and liquid developer The carrier liquid regenerating apparatus 70, the liquid developer remaining on the photoconductor 20 without being transferred onto the paper P, and the liquid developer remaining on the transfer unit 40 can be transferred to the regenerating tank 71 of the carrier liquid regenerating apparatus 70. A transport unit 80 and a second transport unit 90 capable of transporting the carrier liquid regenerated from the carrier liquid regenerating device 70 to the developing device 30 are provided.

In the first embodiment, a tandem color image forming apparatus is illustrated, and first, second, and third colors corresponding to yellow (Ye), magenta (Ma), cyan (Cy), and black (Bl) colors are exemplified. The fourth image forming station sections 11, 12, 13, and 14 are respectively provided with a photoconductor 20 and a developing device 30 having the same configuration in this order from the upstream side of the transfer.
The image forming apparatus also includes four developer replenishing cartridges 101 for replenishing the concentrated liquid developers of the respective colors to the developing devices 30 described later of the first to fourth image forming station units 11 to 14, and unused carriers. And a carrier liquid supply cartridge 102 for supplying the liquid to each developing device 30.

<Image forming station>
Since the first to fourth image forming station units 11 to 14 shown in FIG. 1 have the same configuration, the first image forming station unit 11 will be described as a representative of them.
As shown in FIGS. 1 and 2, the first image forming station 11 includes a photoreceptor 20 that is a latent image carrier on which an electrostatic latent image is formed, and a charger 21 disposed around the photoreceptor 20. An exposure unit 22, a developing device 30, a photoreceptor cleaner 23, and the like are provided.

The photoreceptor 20 has a substantially cylindrical drum shape having a photosensitive material such as OPC (Organic Photoconductor) on the surface, is disposed above the exposure unit 22, and is driven in a predetermined direction by a drive unit and a control unit. It is controlled to rotate in the direction of the arrow in FIG.
The charger 21 is a scorotron charging unit for uniformly charging the surface of the photoconductor 20 to a predetermined potential, and is disposed in the vicinity of the outer peripheral surface of the photoconductor 20.
The charger 21 is not limited to the scorotron method, and for example, a roller charging method, a brush charging method, a corotron charging method, a sawtooth charging method, an ion emission charging method, a magnetic brush charging method, or the like can be suitably used.

The exposure unit 22 irradiates the surface of the photoconductor 20 charged by the charger 21 with laser light based on the image data output from the image processing unit (not shown), thereby exposing the exposure unit. It has a function of writing and forming an electrostatic latent image corresponding to image data on the surface of the photoreceptor by lowering the potential. The exposure device 22 receives the image data corresponding to yellow, magenta, cyan, or black, and thereby applies an electrostatic latent image corresponding to each color to each photoconductor 20 of the first to fourth image forming stations 11 to 14. Form.
As the exposure device 22, a laser scanning unit (LSU) having a laser irradiation unit and a reflection mirror, or a writing device (for example, a writing head) in which light emitting elements such as EL or LED are arranged in an array can be used.

  The photoconductor cleaner 23 removes the liquid developer remaining on the surface of the photoconductor after primary transfer of the toner image from the photoconductor 20 to the intermediate transfer belt 41. The photoconductor cleaner 23 is in contact with the surface of the photoconductor to contact the liquid developer. A cleaning blade made of urethane rubber is scraped off. The used liquid developer collected by the photoconductor cleaner 23 is sent to the carrier liquid regeneration device 70 by a first transfer unit 80 described later.

[Development equipment]
As shown in FIG. 2, the developing device 30 includes a developing tank 31 as a toner reservoir for storing the liquid developer, and the liquid developer L inside the developing tank 31 is maintained at a predetermined liquid level. It has been adjusted to lean. The developing tank 31 includes a developing roller 32, a coating roller 33, a supply roller 34, a stirring screw 35, and a concentration detector 38 as rotating members parallel to the liquid level.

The stirring screw 35 is a pair of parallel screws that rotate in the liquid developer L. The stirring of the liquid developer L prevents the toner particles that are solids from being precipitated, and the toner particles in the liquid developer L Keep the dispersion uniform. The two agitating screws 35 are configured such that the agitating flow direction of the liquid developer L by these is reversed.
The supply roller 34 has a rotation shaft disposed above the liquid level of the liquid developer L in the developing tank 31, and the barrel rotates while being immersed in the liquid developer L. The liquid developer L is carried and supplied to the application roller 33.

  The application roller 33 is a stainless gravure roller having a groove-shaped dent with a predetermined density on the surface. The application roller 33 is lightly pressed by the development roller 32, and the opposing surfaces of the application roller 33 and the development roller 32 are constant in the same direction. It is driven to rotate. Further, in the vicinity of the application roller 33, a regulation blade 36 made of a thin stainless steel plate for regulating the amount of the liquid developer L adhering to the surface of the application roller 33 is disposed in contact with the surface of the application roller 33. .

  The facing portion between the supply roller 34 and the application roller 33 is arranged at a position above the liquid developer L with a gap therebetween, and this gap is the liquid developer L carried on the surface of the supply roller 34. Is set to about 0.3 mm, which is smaller than the thickness of the layer (hereinafter referred to as a liquid developer layer). The peripheral speeds of the supply roller 34 and the application roller 33 are constant, and both rollers rotate in opposite directions so that their opposing surfaces move in the same direction.

  The developing roller 32 is formed by laminating a conductive urethane rubber on a stainless steel core, and the opposing surfaces of the developing roller 32 and the photoconductor 20 are set in the same direction and the like by a control unit and a driving unit (not shown). It is configured to rotate at a high speed. A urethane rubber scraping blade 37 for removing the liquid developer L remaining on the surface of the developing roller 32 after development is disposed in contact with the surface of the developing roller 32 in the vicinity of the developing roller 32. Yes.

  The developing tank 31 has a developing opening formed at a position facing the photoconductor 20, and a part of the developing roller 32 is disposed in the developing tank 2 in a state of being exposed from the opening. Further, the entire developing tank 31 is urged toward the photoconductor 20 to such an extent that the developing roller 32 comes into light contact with the photoconductor 20.

The density detector 38 detects the toner density by detecting the transmittance of the liquid developer in the developing tank 31 by a combination of a light emitting element and a light receiving element, and the height of the stirring screw 35 in the developing tank 31 is detected. Located in the vicinity. As the density detector 38, for example, a general density detector such as density detection based on a reflection optical system, density detection based on a transmission optical system, density detection based on the viscosity of a developer, and the like can be used. The resistance of the carrier liquid in the regeneration tank 71 is detected. For example, the resistance of the carrier liquid in the regeneration tank 71 is attached to the inner surface of the peripheral wall of the regeneration tank 71 in the vicinity of the photocatalytic reduction unit 72.
The detected density signal from the density detector 38 is transmitted to a control unit (not shown), and the control unit determines whether the detected density is within a predetermined value. When the detected density becomes lower than the lower limit value, a predetermined amount of concentrated liquid developer is supplied into the developing tank 31. When the detected concentration becomes higher than the upper limit value, the carrier liquid is replenished into the developing tank 31 in an amount that the detected concentration is within a predetermined value. The replenishment of the concentrated liquid developer and carrier liquid will be described later in detail.

[Description of Operation of Image Forming Apparatus]
Next, the operation at the time of image formation of the image forming apparatus configured as described above and the operation of the carrier liquid regenerating apparatus will be described with reference to FIGS.
At the time of image formation, the liquid developer L in the developing device 30 is adsorbed on the surface of the supply roller 34 by surface tension, and is conveyed to a portion facing the application roller 33 by the rotation of the supply roller 34. Since the gap between the supply roller 34 and the application roller 33 is smaller than the thickness of the liquid developer layer on the supply roller 34, there is a liquid developer pool at a position in front of the facing portion between the supply roller 34 and the application roller 33. It is formed. Then, when the application roller 33 rotates, the liquid developer layer is carried on the surface of the application roller 33.
The amount of the liquid developer L on the application roller 33 is regulated to a predetermined amount determined by the distance between the regulation blade 36 and the application roller 33, the groove depth on the surface of the application roller 33, and the groove density. The liquid developer layer L regulated to a predetermined amount on the application roller 33 is conveyed to a portion where the application roller 33 and the development roller 32 face each other, and the liquid developer layer having a uniform desired film thickness is formed on the development roller 32. It is formed.

  Further, the liquid developer on the developing roller 32 is supplied to the surface of the photoconductor 20, and toner particles are attracted by the electrostatic force of the electrostatic latent image formed on the surface of the photoconductor 20, thereby forming an electrostatic latent image. Development is performed to form a toner image on the surface of the photoreceptor 20. Of the liquid developer on the developing roller 32, the carrier liquid and the toner particles that have not been used for development are returned to the developing tank 31 again by the rotation of the developing roller 32 and scraped off by the scraping blade 37. It falls to the lower part of the developing tank 31.

<Transfer section>
As shown in FIG. 1, the transfer unit 40 includes a primary transfer station having an intermediate transfer belt 41 on which a toner image is formed by an arbitrary image forming station unit, and a toner image formed on the intermediate transfer belt 41 on a sheet P. And a secondary transfer station having a function of causing the image to be transferred. The intermediate transfer belt 41 is made of, for example, semiconductive polyimide.
In the primary transfer station, the intermediate transfer belt 41 is stretched between a pair of stretching rollers 42 disposed in the vicinity of the upper positions of the first and fourth image forming station portions 11 and 14, and the inner space of the intermediate transfer belt 41. Are arranged with four primary transfer rollers 43 that press the outer peripheral surface of the belt 41 against the photoreceptor 20 of the first to fourth image forming station portions 11 to 14. In the second transfer station, a secondary transfer roller 44 is disposed so as to face the stretching roller 42 on the downstream side of the primary transfer (the fourth image forming station unit 14 side).

  In the transfer unit 40, the intermediate transfer belt 41 is aligned and overlapped with the toner images formed on the photoreceptors 20 of the first to fourth image forming stations 11 to 14 of each color, so that four colors are formed on the surface. A toner image composed of the toner is carried. As the intermediate transfer belt 41 rotates, the four color toner images are conveyed to the secondary transfer station. At the secondary transfer station, the secondary transfer roller 44 comes into pressure contact with the intermediate transfer belt 41 via the paper P that is conveyed in synchronization with the conveyance of the toner image. At this time, a negative potential that attracts toner is applied to the secondary transfer roller 44, and the toner image on the intermediate transfer belt 41 is transferred to the paper P.

  Further, the transfer unit 40 is provided with an intermediate transfer cleaner 45 facing the stretching roller 42 on the primary transfer upstream side (first image forming station unit 11 side) of the intermediate transfer belt 41. The intermediate transfer cleaner 45 removes and collects the liquid developer remaining on the outer peripheral surface of the intermediate transfer belt 41 after the toner image is transferred to the paper P, and is a photoconductor that contacts the intermediate transfer belt 41. It has a cleaning blade made of urethane rubber similar to the cleaner 23. Note that the used liquid developer recovered by the intermediate transfer cleaner 45 is also sent to the carrier liquid regenerating apparatus 70 by the first transfer unit 80 described later.

<Fixing part>
The fixing unit 50 has a heating roller 51 and a pressure roller 52 facing each other, and passes the sheet P from the secondary transfer station unit through a nip portion between the heating roller 51 and the pressure roller 52 to form a toner image. Is fixed to the paper P by thermocompression bonding.

<Paper transport section>
The paper transport unit 60 contains a plurality of paper sheets P and can be pulled out and attached to the main body casing of the image forming apparatus in the front-rear direction (direction orthogonal to the paper transport direction), and the paper feed cassette A sheet guide 62 serving as a conveyance path for conveying the sheet P from the sheet 61 to the sheet discharge section (not shown) via the secondary transfer station section of the transfer section 40 and the fixing section 50, and the sheet P at the uppermost position of the sheet feeding cassette 61. A pickup roller 63 that feeds the sheet one by one to the entrance of the conveyance path 62 and a plurality of pairs of registration rollers 64 that are arranged in the conveyance path 62 at a predetermined interval and control the conveyance timing of the paper P are provided.

<Developer supply cartridge>
The developer supply cartridge 101 includes four cartridges corresponding to yellow (Ye), magenta (Ma), cyan (Cy), and black (Bl). Each developer supply cartridge 101 includes toner particles of each color. A liquid developer is contained. Each developer supply cartridge 101 is connected to the developing tank 31 of each developing device 30 of the first to fourth image forming station units 11 to 14 by a pipe 101a, and is concentrated by a pump P1 provided on the pipe 101a. The liquid developer can be sent to the developing tank 31.

<Carrier fluid supply cartridge>
The carrier liquid supply cartridge 102 is connected to the developing tanks 31 of the developing devices 30 of the first to fourth image forming station portions 11 to 14 by pipes 102a and branch pipes 102b, and branches into four branch pipes 102b. The concentrated liquid developer can be sent to each developing tank 31 by the pump P2 provided in each pipe. The downstream end of the pipe 102a and the upstream end of the branch pipe 102b are connected by a switching valve (electromagnetic valve) 103. The switching valve 103 is also connected to a buffer tank 91 of the second transfer unit 90 described later by a pipe 93. It is connected.

<Carrier liquid regeneration device>
As shown in FIG. 3, the carrier liquid regenerator 70 includes a regeneration tank 71 for storing a used liquid developer L1, and an unsaturated fatty acid disposed in the used liquid developer L1 in the regeneration tank 71 by photocatalysis. A photocatalytic reduction unit 72 for reducing the component oxides, a light irradiation unit 73 for irradiating light to a contact portion of the photocatalytic reduction unit 72 with the used liquid developer L1 to excite the photocatalytic action, and a used liquid developer A moisture removing unit 74 that discharges moisture in the L1 from the regeneration tank 71 to the outside and a separation unit 75 that separates unsaturated fatty acid components from the used liquid developer L1 are provided.

  The regeneration tank 71 has a substantially rectangular parallelepiped shape having an upper wall, a bottom wall, and a peripheral wall. The bottom wall is inclined along the longitudinal direction, the upper wall is partially formed with an opening, and the regeneration tank 71 is open to the atmosphere. In addition, the peripheral wall has a transparent window at least on the lower position side of the bottom wall. The upper wall may be configured with a detachable lid.

The photocatalytic reduction unit 72 includes titanium oxide as a photocatalyst and a support made of a porous member that supports the titanium oxide. The support is close to the transparent window on the peripheral wall of the regeneration tank 71. Has been placed. In the case of Embodiment 1, the shape of the carrier is a sheet shape (plate shape), a prismatic shape, or a cylindrical shape, and is arranged along the transparent window so that the length direction thereof is the vertical direction. In this case, for example, the support body can be detachably installed in the regeneration tank 71 by providing fixing pieces for positioning and fixing the upper and lower ends of the support body on the upper wall and the bottom wall of the regeneration tank 71.
The material of the carrier is a hydrophilic porous ceramic, a hydrophilized polymer film (for example, GE Water Technologies made M series long hydrophilic using PAN <polyacrylic resin> subjected to superhydrophilic treatment) UF module membrane) can be used.

The light irradiation unit 73 is an ultraviolet lamp disposed in the vicinity of the transparent window outside the regeneration tank 71, and irradiates light (ultraviolet light) onto the photocatalyst on the support through the transparent window and the used liquid developer L1. Since the carrier is disposed in the vicinity of the transparent window, the attenuation of light of the ultraviolet lamp 73 irradiated toward the catalyst is suppressed to a small level.
Further, when the carrier is in the shape of a prism or cylinder, for example, the transparent window of the regeneration tank 71 is formed in an arc shape, and an arc concave reflector is provided on the back side of the ultraviolet lamp (opposite the transparent window). It may be provided. In this way, as the light from the ultraviolet lamp, not only the direct light to the carrier but also the reflected light that is reflected by the reflector and incident on the carrier can be used. It can be expanded to increase the reduction efficiency of the photocatalyst.

The separation unit 75 permeates the unsaturated fatty acid component disposed on the high position side of the bottom wall of the regeneration tank 71 so as to partition the region where the carrier of the photocatalytic reduction unit 72 is disposed in the regeneration tank 71. The separation membrane does not allow moisture to permeate. When the separation membrane 75 has flexibility, for example, a frame is attached around the separation membrane 75, and both side edges and lower edges of the frame are attached to the peripheral wall and the bottom wall of the regeneration tank 71. Furthermore, by providing a pair of vertical guide pieces for holding both side edges of the frame on the opposing surface of the peripheral wall of the regeneration tank 71, the separation membrane 75 is detachably inserted into the guide piece pair in the vertical direction so that the regeneration tank 71 You may make it attach to.
A used liquid developer is supplied to the first region having the photocatalytic reduction unit 72 partitioned by the separation membrane 75 by a first transfer unit described later, and the regenerated carrier liquid is described later from a second region adjacent to the first region. It is supplied to the developing device 30 by the second transfer unit.

The moisture removing unit 74 includes a carrier carrying the photocatalyst of the photocatalytic reduction unit 72 disposed in the first region, a drain port 74a formed at a low position on the bottom wall of the regeneration tank 71 in the first region, and a drain port. An openable / closable moisture discharge pipe 74b connected to 74a, a drain tank 74c connected to the moisture discharge pipe 74b, and a drain valve 74d disposed between the drain port 74a and the drain tank 74c in the moisture discharge pipe 74b. It is configured. That is, the photocatalytic reduction unit 72 is also used as a part of the configuration of the water removal unit 74.
For example, an electromagnetic valve is used as the drain valve 74d. The drain tank 74c includes, for example, a case portion having a connection port connected to the moisture discharge pipe 74b, and a container portion that is detachably attached to the case portion and receives water droplets falling from the connection port. . For example, the regeneration tank 71 may be mounted on the case portion of the drain tank 74 so that the drain tank 74 is disposed below the regeneration tank 71.

The carrier liquid regenerator 70 further includes a stirrer 76, a pair of capture electrodes 77, and a resistance detector 78 in the first region in the regenerator 71.
The stirring unit 76 includes a shaft that passes through the upper wall of the regeneration tank 71, a motor (not shown) that rotates the shaft, and a stirring blade attached to the tip of the shaft in the used liquid developer L1 in the regeneration tank 71. The used liquid developer in the regeneration tank 71 is agitated by being disposed at a substantially central position of the regeneration tank 71. For example, the motor is fixed to the upper wall of the regeneration tank 71, so that the shaft is rotatably held vertically.

A pair of capture electrodes 77 are arranged along the opposing inner wall surfaces of the peripheral wall of the regeneration tank 71 and at a position between the photocatalytic reduction unit 72 and the separation unit 75. For example, an opposing inner wall surface of the peripheral wall is provided with an L-shaped receiving piece that holds the lower edge and both side edges of the capture electrode, and the capture electrode is detachably mounted in the vertical direction by the receiving piece.
Of the pair of capture electrodes 77, the first capture electrode 77 is electrically connected to a power supply unit (not shown), and the second capture electrode is grounded. When a voltage having a polarity opposite to the charge of the toner particles (for example, about several hundred mV to several V) is applied to the first capture electrode 77, an electric field is generated in the used liquid developer, and the toner particles are It moves to the capture electrode 77 side, deposits and is captured.

  The resistance detection unit 78 detects the resistance of the carrier liquid in the regeneration tank 71 and is attached, for example, at a position in the vicinity of the photocatalytic reduction unit 72 on the inner surface of the peripheral wall of the regeneration tank 71.

  The carrier liquid regenerator 70 further includes a control unit (not shown) that controls the light irradiation unit 73 and the agitation unit 76 based on the detection result of the resistance detection unit 78. The control unit controls the light irradiation unit 73 and the agitation unit 76 to be driven if they are below the predetermined insulation resistance, and stops the light irradiation unit 73 and the agitation unit 76 if the carrier liquid satisfies the predetermined insulation resistance.

The carrier liquid regenerating apparatus 70 configured as described above is preferably provided integrally in the image forming apparatus, but is externally attached to the image forming apparatus and appropriately connected to the first and second transfer units 80 and 90. May be.
When the carrier liquid regenerating apparatus 70 is provided in the image forming apparatus, for example, the carrier liquid regenerating apparatus 70 is disposed on the lower side of the main body casing portion of the image forming apparatus and on the rear side of the paper feed cassette 61. . Further, when the carrier liquid reproducing device 70 is externally attached to the image forming apparatus, the carrier liquid reproducing device 70 is disposed on the back surface, left side surface or right side surface of the main body casing portion so as not to obstruct the drawing and mounting of the paper feed cassette 61.

<First transfer section>
As shown in FIGS. 1 to 3, the first transfer unit 80 includes the photosensitive region cleaners 23 of the first to fourth image forming station units 11 to 14 and the first region of the regeneration tank 71 of the carrier liquid regeneration device 70. And a secondary pipe 82 that connects the intermediate transfer cleaner 45 and the first region of the regeneration tank 71, the secondary pipe 82 includes paper contained in the used liquid developer L1. A mesh filter 82a for removing powder, dust and the like is provided.
Since the positions of the photoconductor cleaners 23 and the intermediate transfer cleaner 45 are higher than the position of the regeneration tank 71, the used liquid developer collected by the photoconductor cleaners 23 and the intermediate transfer cleaner 45 is primarily piped by its own weight. 81 and the secondary pipe 82 are dropped to the first region of the regeneration tank 71.

<Second transfer section>
The second transfer unit 90 includes the buffer tank 91 that stores the regenerated carrier liquid regenerated by the carrier liquid regenerating apparatus 70, a pipe 92 that connects the second region of the regenerating tank 71 and the buffer tank 91, and a pump P3. And the pipe 93 that connects the buffer tank 91 and the switching valve 103, the branch pipe 102b, and the pump P2.

<Other configurations>
The image forming apparatus includes image data transmitted from various terminal devices (for example, personal computers), digital cameras, digital video cameras, and the like connected via a network (not shown), and images read by a document reading device such as a scanner. Based on the data, the printer P has a printer function for forming a color image or a monochrome image on the paper P as a recording medium.

The image data can be transmitted to the image forming apparatus using wireless or wired.
In wireless, for example, wireless LAN (IEEE802.11), WirelessUSB (UWB), Bluetooth, mobile communication network ((WiMAX (IEEE 802.16-2004, IEEE 802.16e, IEEE 802.16a, IEEE 802.16h, etc.)), satellite communication A network, optical wireless (including LED lighting wireless), infrared rays such as IrDA and remote control can be used.
For wired communication, for example, IEEE1394, USB, power line carrier, cable TV line, telephone line, ADSL line, Internet, intranet, extranet, LAN, ISDN, VAN, CATV communication network, etc. can be used.

<Description of Image Forming Operation and Carrier Liquid Regenerating Operation>
At the time of image formation, the developing device 30 is configured so that the liquid developer on the developing roller 32 comes into contact with the electrostatic latent image on the photoconductor 20, and the electrostatic latent image is generated by the developing electric field generated by the developing bias applied to the developing roller 32. Is developed with a liquid developer on the developing roller 32 to form a toner image (visible image).

  In the primary transfer station, a bias voltage having a polarity opposite to the charging polarity of the toner is applied to the primary transfer roller 43, so that the toner on the photoreceptor 20 rotating in the first to fourth image forming station units 11 to 14. The images are sequentially transferred onto the rotating intermediate transfer belt 41 and overlapped to form one toner image (primary transfer), and the toner image on the intermediate transfer belt 41 is conveyed to the secondary transfer station. The liquid developer L1 remaining on the photoconductor 20 after the primary transfer is collected by the photoconductor cleaner 23 and sent to the first region of the regeneration tank 71 through the primary pipe 81 of the first transfer unit. .

  On the other hand, the paper transport unit 60 transports the paper P to the secondary transfer station so that the toner image on the intermediate transfer belt 41 is transported, and the secondary transfer roller 44 passes the paper P through the intermediate transfer belt 41. Press contact. At this time, a negative potential that attracts toner is applied to the secondary transfer roller 44, and the toner image on the intermediate transfer belt 41 is transferred to the paper P (secondary transfer). The paper P onto which the toner image has been transferred in this manner is sent to a paper discharge tray (not shown) after the fixing process of the toner image is performed by the fixing unit 50. The liquid developer L1 remaining on the intermediate transfer belt 41 after the secondary transfer is collected by the intermediate transfer cleaner 45 and sent to the first region of the regeneration tank 71 through the secondary pipe 82 of the first transfer unit. It is done.

FIG. 4 is a flowchart showing the regeneration operation control of the carrier liquid regeneration device. As shown in FIG. 4, while the developing device 30 is being driven, in the carrier liquid regenerating device 70, the resistance detector 78 has the insulation resistance Rc of the carrier liquid in the used liquid developer L <b> 1 in the regenerating tank 71. Is being monitored. Since the insulation resistance Rc of the carrier liquid (unsaturated fatty acid component) decreases with oxidation, if the insulation resistance Rc is smaller than the lower limit (for example, 1 × 10 ¹⁰ Ωcm), the control unit emits light (UV lamp). ) 73 is turned ON, and the titanium oxide as the catalyst on the support of the photocatalytic reduction unit 72 is irradiated with ultraviolet rays, thereby exciting the photocatalytic action of the titanium oxide. At the same time, the stirring unit 76 is turned on and the liquid developer L1 is stirred. Note that while the main power supply of the image forming apparatus is ON, a predetermined voltage is applied to the first capture electrode 77, and the toner particles in the used liquid developer L 1 are captured by the first capture electrode 77. Has been.

  The oxide of the unsaturated fatty acid component is reduced by the photocatalytic action (reduction action) of titanium oxide, and the water generated during the reduction descends along the surface of the titanium oxide due to the super hydrophilicity of the titanium oxide, and the drain port 74a Gather around. At this time, since the liquid developer L1 is uniformly stirred by the stirring unit 76, the carrier liquid in the developing tank 71 is uniformly in contact with the titanium oxide, and the reduction efficiency is improved.

By the way, when the liquid developer L1 is stirred, water generated on the titanium oxide surface may be dispersed in the liquid developer L1. Further, in the course of the image forming process, there is a risk that water vapor in the atmosphere is mixed into the liquid developer, or condensed moisture is mixed into the liquid developer.
The water mixed in the used liquid developer L1 collected in the developing tank 71 cannot enter the second region by the separation part (separation membrane) 75 that separates the oil and the water, and is separated. Captured by the membrane 75. As moisture capture by the separation membrane 75 proceeds, moisture accumulates on the separation membrane 75 and water droplets become larger, and the water droplets settle by their own weight, so that the separation membrane 75 is self-cleaned.

Water droplets that have fallen from the separation membrane 75 to the bottom surface of the regeneration tank 71 are collected toward the drain port 74a due to the gradient of the bottom surface. The water collected at the drain port 74 is collected and discarded by the drain tank 74c when the drain valve 74d is periodically opened and closed.
Further, the toner particles contained in the liquid developer L1 collected in the first region in the regeneration tank 71 cannot enter the second region by the separation film 75, and the first capture electrode to which a voltage is applied. Since the deposit is captured at 77, clogging of the separation membrane 75 with time is prevented.

When the reduction of the oxide of the unsaturated fatty acid component proceeds in this way and the insulation resistance Rc of the carrier liquid recovers until it exceeds the upper limit (for example, 5 × 10 ¹⁰ Ωcm), the detection signal from the resistance detector 78 is used. Then, the ultraviolet lamp 73 is stopped by the control unit, and the unsaturated fatty acid component is prevented from being decomposed by excessive irradiation. At the same time, the stirring unit 76 is also stopped. Then, when the developing device 30 is stopped, the resistance detection unit 78 is turned off.
Since the carrier liquid whose insulation resistance Rc has increased to the upper limit value has been regenerated, the regenerated carrier liquid that does not contain moisture and toner particles that have penetrated the separation membrane 75 from the first area and moved to the second area has been transferred to the second area. It is sent to the buffer tank 91 and stored by the pump P3 of the section 90.

  On the other hand, as shown in FIG. 5, in the developing device 30, the concentration of the liquid developer L in the developing tank 31 is monitored by the concentration detector 38, and the detected concentration is the lower limit (for example, 17.5% by weight). When the temperature is lower than the lower limit, the controller 101 drives the pump 101a to supply a predetermined amount of concentrated liquid developer (for example, toner concentration 30% by weight) in the developer supply cartridge 101a into the developing tank 31. When the detected concentration exceeds an upper limit (for example, 22.5% by weight), the buffer valve 91 is preferentially switched by switching the switching valve 103 in consideration of the remaining amount of unused carrier liquid in the carrier liquid supply cartridge 102. The regenerated carrier liquid is replenished into the developing tank 31 so as to be within a predetermined concentration range. Then, when the developing device 30 is stopped, the density detector 38 is turned off. At this time, switching of the switching valve 103 is controlled so that the control unit preferentially selects the buffer tank 91.

In the first embodiment, the control unit for monitoring and controlling the toner concentration of the liquid developer L in the developing tank 31 of the developing device 30 and the insulation resistance of the carrier liquid in the regenerating tank 71 of the carrier liquid regenerating device 70 are described. The control unit related to monitoring and control may be the same or different. Further, the control unit may control to open and close the drain valve 74d periodically (for example, once a day).
Further, it is preferable that the capture electrode 77 of the carrier liquid regenerating apparatus 70 is taken out from the regenerating tank 71 and the adhering toner particles are periodically removed and washed. When the photocatalyst carrier and the separation membrane 75 are somewhat clogged, it is preferable. It is preferable to remove from the regeneration tank 71 and clean it periodically.

(Embodiment 2)
FIG. 6 is a schematic diagram showing a carrier liquid regenerating apparatus and its peripheral components of the image forming apparatus according to the second embodiment of the present invention.
The configuration of the carrier liquid regenerating apparatus of the second embodiment is different from that of the first embodiment in the shape of the photocatalytic reduction unit 172, the arrangement of the pair of capture electrodes 77, and the arrangement of the resistance detection unit 78. Other configurations in the second embodiment The drive control is the same as that of the first embodiment. In FIG. 6, the same components as those in FIG. 3 are denoted by the same reference numerals.
Hereinafter, differences of the second embodiment from the first embodiment will be mainly described.

  In the second embodiment, the photocatalytic reduction unit 172 is a hydrophilic porous member similar to the carrier of the first embodiment in order to enhance the water removal function of the carrier that supports titanium oxide as a photocatalyst. It is formed in a cylindrical shape. Further, the lower end of the center hole of the carrier communicates with the drain port 74a, and the upper end of the carrier is covered with a cap.

When the titanium oxide on the support is irradiated by the ultraviolet lamp 73, the oxide of the unsaturated fatty acid component is reduced by the titanium oxide. In addition, the water generated by the reduction reaction, the water mixed in the carrier liquid, and the water falling by its own weight on the gradient of the bottom surface of the regeneration tank 71 are captured and held by the superhydrophilic property of titanium oxide, and the hydrophilic porous carrier is formed. It penetrates toward the hollow hole of the carrier by the capillary phenomenon of the fine pores, and the water that reaches the hollow hole is discharged through the drain port 74a.
The average pore diameter of the porous member constituting the carrier is preferably 5 times or more of the toner particle diameter to prevent clogging with the toner particles, and 100 μm or less in consideration of separation performance.

  In the pair of capture electrodes 77, the first capture electrode 77 connected to the power supply unit is disposed with a gap along the inclined bottom surface of the regeneration tank 71, and the second capture electrode 77 that is grounded is the first capture electrode 77. It is arranged at an upper position in the used liquid developer L1 so as to face the electrode 77. When arranging a pair of capture electrodes 77 in this manner, for example, the outer peripheral edges of the capture electrodes 77 are held in a holding frame oppositely, and the pair of capture electrodes 77 are submerged in the used liquid developer together with the holding frame. It can be installed in the regeneration tank 71. Furthermore, a locking portion for positioning and fixing the lower end of the holding frame may be provided on the bottom surface of the regeneration tank 77.

  The resistance detector 78 is disposed in the second region on the regeneration carrier liquid extraction side of the regeneration tank 71 partitioned by the separation membrane 75, and detects the insulation resistance of the carrier liquid in the second region. In the arrangement of the resistance detection unit 78 in the second region, the insulation resistance fluctuates due to moisture contained in the used liquid developer, and an error in detecting the progress of oxidation of the unsaturated fatty acid component is ignored. The case where it becomes impossible is dealt with, and the insulation resistance of the carrier liquid that has passed through the separation membrane 75 is detected to control the irradiation of the ultraviolet lamp 73.

(Other embodiments)
In the above-described embodiment, the case of a color image forming apparatus using four color toners of yellow, magenta, cyan, and black is illustrated, but the toner color is not limited to four colors, and for example, has the same hue as cyan and magenta. In addition, the present invention can also be applied to a color image forming apparatus using six color toners to which light cyan and light magenta having a lighter density characteristic are added.
Moreover, although the case where titanium oxide was used as a photocatalyst was illustrated in the above-mentioned embodiment, zinc oxide, cadmium sulfide, or the like may be used alone, or two or more of these may be used in appropriate combination. .

Using the image forming apparatus described in the first embodiment (see FIGS. 1 to 3) as Example 1 and using the image forming apparatus described in the embodiment (see FIG. 6) as Example 2, monochrome toner images are formed on paper. Is printed, and the carrier liquid in the used liquid developer is reduced, and the reduced regenerated carrier liquid is replenished into the developing device 30 while continuously circulating 10,000 sheets, and the insulation resistance and image density of the carrier liquid are printed. The image quality was examined, and the results are shown in Table 1.
Further, as Comparative Example 1, the carrier reproducing device is removed from the image forming apparatus of Embodiment 1, and the used liquid developer collected by the photoreceptor cleaner 23 and the intermediate transfer cleaner 45 is circulated to the developing tank 31. The same test as in Examples 1 and 2 was performed using the image forming apparatus, and the results are also shown in Table 1.

In Example 1, Example 2, and Comparative Example 1, unused carrier liquid was not replenished into the developing tank 31 from the carrier liquid replenishment cartridge 102 (see FIGS. 3 and 6).
The liquid developers used in Examples 1, 2 and Comparative Example 1 were the same and were prepared as follows.
93 parts by weight of a polyester resin and 7 parts by weight of a pigment (carbon black) are melt-kneaded with an open roll kneader and the kneaded product is dry-sparsely pulverized, then wet granulated to an average particle size of 1.5 μm, washed and dried. Thus, toner particles were prepared. Thereafter, 20 parts by weight of toner particles were mixed with 80 parts by weight of linseed oil to obtain a liquid developer having an insulation resistance of 5 × 10 ¹¹ Ωcm.

(Evaluation methods)
<Insulation resistance>
Insulation resistance of liquid developer before use (initial value) Insulation resistance of liquid developer between detection electrodes provided in the developing devices of Example 1, Example 2 and Comparative Example 1 after continuous printing of 10,000 sheets Measured with an AC bridge.
The criterion for determining the insulation resistance was 1 × 10 ⁹ Ωcm as the allowable lower limit.

<Image density>
Image density of toner image after printing one sheet (initial value) Image density of toner image of Example 1 after continuous printing of 10,000 sheets, and toner image of solid image portion of Comparative Example 1 after continuous printing of 10,000 sheets The image density was measured with a Macbeth densitometer.
The image density was judged to be good if the density was 1.2 or more, and insufficient if it was less than 1.2.

<Image quality>
The image quality (initial value) of the toner image after printing one sheet was visually checked for the image quality of the toner image of Example 1 after continuous printing of 10,000 sheets and the image quality of the test chart image of Comparative Example 1 after continuous printing of 10,000 sheets. Judged.

From the results of Table 1, in Examples 1 and 2, the insulation resistance of the liquid developer in the developing tank after continuous printing of 10,000 sheets was slightly lower than the initial value, but the image density was hardly changed, and the image quality was Good condition could be maintained. On the other hand, in Comparative Example 1 in which the used carrier liquid was circulated without being reduced, the insulation resistance of the liquid developer in the developing tank after continuous printing of 10,000 sheets was greatly reduced, which caused image density and It is thought that the image quality has dropped significantly.
From these facts, the carrier liquid regenerating apparatus used in Examples 1 and 2 can generate a regenerated carrier liquid that is reduced to a sufficient insulation resistance by reducing the used carrier liquid and is deteriorated over time. It turns out that there are few.

FIG. 2 is a longitudinal sectional view schematically showing the entire configuration of the image forming apparatus according to the first exemplary embodiment provided with a carrier liquid reproducing device for a liquid developer according to the present invention as viewed from the front. 2 is a longitudinal sectional view schematically showing an image forming station unit in the image forming apparatus of Embodiment 1. FIG. FIG. 2 is a schematic diagram illustrating a carrier liquid reproducing device of the image forming apparatus according to the first exemplary embodiment and its peripheral components. FIG. 3 is a flowchart showing regeneration operation control of the carrier liquid regeneration device of the first embodiment. FIG. 6 is a flowchart illustrating liquid developer concentration adjustment control in the developing device according to the first exemplary embodiment. FIG. 6 is a schematic diagram illustrating a carrier liquid reproducing device of an image forming apparatus according to a second embodiment and its peripheral components.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 1st image forming station part 12 2nd image forming station part 13 3rd image forming station part 14 4th image forming station part 20 Photoconductor 23 Photoconductor cleaner 30 Developing device 38 Density detector 40 Transfer part 45 Intermediate transfer cleaner 50 Fixing unit 70, 170 Carrier liquid regeneration device 71 Regeneration tank 72, 172 Photocatalytic reduction unit 73 Light irradiation unit 74 Moisture removal unit 75 Separation unit (separation membrane)
76 Stirrer 77 Capture electrode 78 Resistance detector 80 First transfer unit 90 Second transfer unit L Liquid developer L1 Used liquid developer P Transfer material (paper)

Claims (10)

  A regeneration tank that contains a used liquid developer of a liquid developer containing an unsaturated fatty acid component as an insulating carrier liquid and having toner particles dispersed therein, and the used liquid development disposed in the regeneration tank A photocatalytic reduction part for reducing oxides of unsaturated fatty acid components contained in the agent, a light irradiation part for irradiating the photocatalytic reduction part with light, and at least an unsaturation in the used spent liquid developer subjected to the reduction treatment A carrier liquid recycling apparatus for a liquid developer, comprising a separation unit for separating a fatty acid component and moisture.   The said separation part has the separation membrane which permeate | transmits an unsaturated fatty-acid component and permeate | transmits a water | moisture content arrange | positioned so that the area | region where the photocatalytic reduction part in the said reproduction | regeneration tank may be arrange | positioned is divided. The carrier liquid reproduction | regeneration apparatus for liquid developers of description. The moisture includes moisture generated by the reduction treatment of the unsaturated fatty acid component oxide by the photocatalytic reduction unit, and moisture mixed in the used liquid developer before the reduction treatment,
The carrier liquid regenerating apparatus for liquid developer according to claim 1, further comprising a water removing unit that discharges water in the used liquid developer settled on the bottom surface in the regeneration tank to the outside. The photocatalytic reduction part is composed of a carrier carrying a photocatalyst, and this carrier is formed in a sheet shape, a rod shape or a cylindrical shape and is arranged at the bottom of the regeneration tank,
The moisture removing unit has a carrier carrying the photocatalyst of the photocatalytic reduction unit, and an openable / closable drain port disposed at the bottom of the regeneration tank,
The carrier liquid regeneration device for a liquid developer according to claim 3, wherein the regeneration tank has a gradient at the bottom so that the position of the drain port is the lowest.   The carrier liquid regeneration device for a liquid developer according to any one of claims 1 to 4, further comprising an agitation unit for agitating the used liquid developer in the regeneration tank.   The carrier liquid regenerating apparatus for a liquid developer according to claim 1, further comprising a resistance detection unit that detects an insulation resistance of the carrier liquid in the regeneration tank.   7. The carrier liquid regenerating apparatus for liquid developer according to claim 6, further comprising a control unit that controls driving of the light irradiation unit and the stirring unit based on a detection result of the resistance detection unit.   A pair of capture electrodes that captures toner particles by generating an electric field in the used liquid developer when a voltage is applied are further provided in a region where the photocatalytic reduction unit in the regeneration tank is disposed. Item 8. A carrier liquid recycling apparatus for a liquid developer according to any one of Items 2 to 7.   The carrier liquid regenerating apparatus for a liquid developer according to any one of claims 4 to 8, wherein the photocatalyst is composed of one kind or two or more kinds selected from titanium oxide, zinc oxide, and cadmium sulfide.   A photosensitive member, a developing device that supplies a liquid developer to the photosensitive member to form a toner image, a transfer unit that transfers the toner image formed on the photosensitive member to a transfer material, and the transfer material transferred to the transfer material A fixing unit that fixes a toner image, the carrier liquid reproducing device according to any one of claims 1 to 9, a liquid developer that remains on the photosensitive member without being transferred to the transfer material, and a residual that remains on the transfer unit A first transfer unit capable of transferring at least one of the liquid developers to the regeneration tank of the carrier liquid regenerator, and a second transfer unit capable of transferring the carrier liquid regenerated from the carrier liquid regenerator to the developing device. An image forming apparatus.

Images