JP2009204684A - Wet type image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet type image forming apparatus capable of efficiently removing a remaining carrier liquid adhering to a fixing roller by an easy method. <P>SOLUTION: A cleaning device 85 includes a leveling member 80, a heating roller 81 and a cleaning blade 73 from an upstream side in a rotating direction of the fixing roller 71. Temperature of the heating roller 81 is set to be higher than that in a fixing nip area formed between the fixing roller 71 and a pressure roller 72. The carrier liquid shifted to a surface of the fixing roller 71 is heated by the heating roller 81 and set at higher temperature than that in the fixing nip area, whereby viscosity of the carrier liquid is made as low as possible. The carrier liquid whose viscosity is made low is easily collected by the cleaning blade 73, because its rush-in force to the cleaning blade 73 is weak. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electrophotographic image forming apparatus, and more particularly to a wet image forming apparatus that forms an image using a liquid developer in which toner is dispersed in a carrier liquid.

  In an electrophotographic image forming apparatus, an electrostatic latent image is developed on a photosensitive member with toner using a developing device. Then, for example, the electrostatic latent image developed on the photoconductor is transferred to a recording sheet to form an image. In the transfer process of such an image forming apparatus, an electrostatic transfer method is generally employed.

  When transferring a toner image to a sheet, which is a transfer target, a voltage is applied from the back side of the sheet arranged so as to face the photosensitive member by a transfer roller or the like, and an electric field is formed between the photosensitive member and the recording sheet. Thus, the toner image is electrostatically attracted to the recording paper by this electric field.

  Thereafter, the transferred toner image is fixed on the recording paper by pressure fixing with a fixing device.

  In this fixing process, in a wet type electrophotographic image forming apparatus, a liquid developer obtained by dispersing toner in a carrier liquid remains together with a transferred toner image, and the remaining liquid developer ( Hereinafter, there is a problem that the fixing property of the transferred toner image is hindered. Further, in the fixing process, when the unfixed toner is fixed, the carrier liquid trapped between the toner layers oozes out to the surface, so that the carrier liquid also becomes a factor that hinders the fixability of the toner image. .

Therefore, various methods for removing the remaining carrier liquid adhering to the recording paper have been proposed. For example, in Japanese Patent Application Laid-Open No. 2003-195543, an electric field is applied to the remaining carrier liquid transferred from the recording paper to the fixing roller. Discloses a method of further transferring to a carrier removing roller provided on the fixing roller for removal.
Japanese Patent Laid-Open No. 2003-195543

  On the other hand, when a non-volatile carrier liquid is used, the carrier liquid generally has a high viscosity, and there is a possibility of slipping through a blade or the like as a carrier liquid removing unit.

  In the above Japanese Patent Application Laid-Open No. 2003-195543, the final means for removing the remaining carrier liquid transferred to the carrier removal roller is a blade, and the carrier liquid that has passed through the blade is fixed again from the carrier removal roller. There is a possibility of transferring to the roller and eventually reaching the fixing nip region again.

For this reason, the fixing property is hindered and image noise such as oil streaks is caused.
The present invention has been made to solve the above-described problems, and is a wet image forming apparatus capable of efficiently removing the remaining carrier liquid adhering to the fixing roller by a simple method. The purpose is to provide.

  A wet image forming apparatus according to the present invention is a wet image forming apparatus that uses a liquid developer in which toner is dispersed in a carrier liquid, and includes an image carrier that carries an electrostatic latent image, and an electrostatic image on the image carrier. The latent image is developed with a liquid developer to form a toner image, a transfer device that transfers the toner image formed on the image carrier to the transfer material, and the toner image transferred to the transfer material. And a fixing device for fixing by heating. The fixing device includes a fixing member that comes into contact with the front side of the transfer material on which the toner image is transferred, a pressure member that comes into contact with the back side of the transfer material, and a cleaning device that removes the liquid developer remaining on the fixing member. Including. The fixing member includes a first heating unit that heats a region where the fixing member and the surface side to which the toner image of the transfer material is transferred are in contact with each other. The cleaning device includes a second heating unit that heats the liquid developer remaining on the fixing member. The heating temperature by the second heating means is set higher than the heating temperature by the first heating means.

  Preferably, the cleaning device further includes an agitation member that rotates so as to slidably rub the surface of the fixing member with a speed difference on the upstream side of the second heating unit in the movement direction of the surface of the fixing member.

  Preferably, the cleaning device further includes a cleaning member that removes the liquid developer remaining on the fixing member on the downstream side in the movement direction of the surface of the fixing member with respect to the second heating unit.

  Preferably, the cleaning device further includes a recovery mechanism for recovering the liquid developer remaining on the fixing member evaporated by the second heating unit.

  In the wet image forming apparatus according to the present invention, the fixing member includes a first heating unit, and the cleaning device includes a second heating unit that heats the liquid developer remaining on the fixing member, and the second heating unit. The heating temperature by is set higher than the heating temperature by the first heating means.

  Therefore, when the non-volatile carrier liquid is contained in the remaining liquid developer, the remaining liquid developer is heated by the second heating unit having a temperature higher than that of the first heating unit. It is possible to reduce the viscosity, and it is possible to easily remove the remaining liquid developer from the fixing member. Further, when the remaining liquid developer contains a volatile carrier liquid, the remaining liquid developer is overheated by the second heating means having a temperature higher than that of the first heating means. The remaining liquid developer can be removed by evaporation.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same.

  FIG. 1 is a schematic configuration diagram illustrating an example of a wet image forming apparatus according to an embodiment of the present invention.

  Referring to FIG. 1, a wet image forming apparatus according to an embodiment of the present invention is provided with a photoconductor 110 that is a drum-shaped image carrier, and around photoconductor 110 in the order of rotation directions indicated by arrows. A developing device 108, a squeeze roller 111, a transfer roller 114 for transferring the photosensitive member 110 to the recording paper, a cleaning blade 104 as a cleaning member for removing carrier liquid remaining on the photosensitive member 110, a charging device 116, and An exposure device 118 is provided.

  The developing device 107 includes a developing tank 105 that stores a liquid developer containing toner and a carrier liquid, a developing roller 106, and a cleaning blade that is a cleaning member for removing the liquid developer (carrier liquid) remaining on the developing roller. 107.

  Here, the liquid developer includes, as main components, an insulating liquid that is a carrier liquid, a toner that develops an electrostatic latent image, and a dispersant that disperses the toner.

  The carrier liquid can be used without particular limitation as long as it is generally used for an electrophotographic liquid developer. Among these, a non-volatile liquid is preferable. Examples of the non-volatile liquid include silicon oil, mineral oil, paraffin oil, and mineral oil.

  Any toner can be used without particular limitation as long as it is generally used for an electrophotographic liquid developer. As the toner binder resin, for example, a thermoplastic resin such as polystyrene resin, styrene acrylic resin, acrylic resin, polyester resin, epoxy resin, polyamide resin, polyimide resin, or polyurethane resin can be used. It is also possible to use a mixture of a plurality of these resins. Also, commercially available pigments and dyes used for coloring the toner can be used. For example, carbon black, bengara, titanium oxide, silica, phthalocyanine blue, phthalocyanine green, sky blue, benzidine yellow, lake red D, etc. can be used as the pigment. Solvent red 27, acid blue 9, or the like can be used as the dye.

  As a method for preparing the liquid developer, it can be prepared based on a commonly used technique. For example, the binder resin and the pigment are melt-kneaded using a pressure kneader, a roller mill or the like at a predetermined blending ratio and uniformly dispersed, and the obtained dispersion is finely pulverized by, for example, a jet mill. By classifying the obtained fine powder with, for example, an air classifier, a colored toner having a desired particle diameter can be obtained. The obtained toner is mixed with an insulating liquid as a carrier liquid at a predetermined blending ratio. This mixture can be uniformly dispersed by a dispersing means such as a ball mill to obtain a liquid developer.

  The cleaning liquid can be the same oil as the carrier liquid. For example, silicon oil, mineral oil, Isopar, etc. can be mentioned.

  A certain amount of liquid developer is supplied to the developing roller 106, and a charge is given to the toner contained in the liquid developer on the developing roller 106 by a pre-development charger (not shown). Thereafter, the charged toner conveyed to the photoconductor 110 by the developing roller 106 develops the image portion on the photoconductor 110.

  The surface of the photoconductor 110 is uniformly charged to a predetermined surface potential by the charging device 116. Thereafter, image information is exposed by the exposure device 118 to form an electrostatic latent image on the surface of the photoreceptor 110. Next, the electrostatic latent image on the photoconductor 110 is developed with the liquid developer containing toner and carrier liquid by the developing device 107 as described above, and a toner image is formed on the surface of the photoconductor 110. At this time, not only the toner but also the carrier liquid adheres to the surface of the photoreceptor 110.

  The cleaning blade 107 removes carrier liquid remaining on the developing roller 106 after development on the photoconductor 110. In this example, a configuration in which the cleaning blade 107 is counter-contacted with the rotation direction of the developing roller 106 is illustrated as an example as a configuration for scraping the remaining carrier liquid, but the remaining carrier liquid is scraped off. As long as the structure can be used, the direction of contact is not particularly limited. The same applies to other cleaning blades. Further, in this example, the configuration for removing the remaining carrier liquid using a cleaning blade is described. However, the carrier remaining while the web roll paper, cloth, etc. are pressed against the photoconductor and taken up and moved. It is also possible to employ so-called web cleaning that removes the liquid.

  Next, excess liquid developer is removed from the toner image on the photoconductor 110 by the squeeze roller 111. The squeeze roller 111 is provided with a cleaning blade 112 for scraping off the removed liquid developer. In the squeeze roller 111, the carrier liquid between the toner layers is not removed.

  Next, the toner image formed on the photoconductor 110 moves to a position (transfer position) facing the transfer roller 114 or the like to which a predetermined voltage is applied, and the transfer image is transferred via the conveyance belt 119 at the transfer position. A toner image is formed on the conveyed recording paper. Specifically, a predetermined voltage is applied to the transfer roller 114, and an electric field is formed between the photoconductor 110 and the recording paper, and the toner image is electrostatically attracted to the recording paper by this electric field. As a result, a toner image is formed on the recording paper 300.

  Then, the recording paper 300 onto which the toner image has been transferred is conveyed to the fixing device 109 via the conveyance belt 119.

  The fixing device 109 includes a fixing roller 71, a pressure roller 72, and a cleaning device 85 for removing the carrier liquid remaining on the fixing roller.

  In the fixing device 109, a fixing process for fixing the toner image transferred to the recording paper 300 by heat and pressure is performed by the fixing roller 71 and the pressure roller 72 each having a heater (heat source) therein, and the fixing process is completed. To do. In this example, a case where a heater (heat source) is provided for each of the fixing roller 71 and the pressure roller 72 will be described. However, any one of them may be used.

  Here, the conveyance path of the recording paper will be described. The recording paper taken out from the paper feed cassette 51 is transported onto the transport belt 119 by the transport roller 64. The conveyor belt 119 is driven by drive rollers 113 and 115. The recording paper 300 conveyed on the conveying belt 119 is sent to a transfer position between the transfer roller 114 and the photoconductor 110, and a toner image is transferred onto the surface of the recording paper. Then, the toner image is fixed in the fixing device 109. Then, the paper is discharged out of the apparatus by a paper discharge mechanism (not shown).

  Hereinafter, cleaning device 85 in fixing device 109 according to the embodiment of the present invention will be described.

First, the case where the carrier liquid is nonvolatile will be described.
As described above, in the fixing process, there is residual carrier liquid together with the toner image transferred to the recording paper. Further, when the unfixed toner is fixed, the carrier liquid trapped between the toner layers oozes out, so that the carrier liquid oozes from the toner layer in the fixing nip region to the fixing roller 71 in contact with the toner image. Adheres.

  Accordingly, the carrier liquid remaining on the recording sheet is attached to the fixing roller 71 and the carrier liquid remaining on the fixing roller 71 needs to be removed.

  Here, since there is no liquid retained in the toner layer in the white background portion where the toner image of the recording paper is not formed, the carrier liquid is usually less present than in the portion corresponding to the toner layer.

  Therefore, the amount of carrier liquid adhering to the recording paper on which the toner image is formed varies depending on the toner image forming region, and as a result, the carrier liquid adhering to the surface of the fixing roller is also fixed to the fixing roller 71. The carrier liquid does not adhere uniformly in the longitudinal direction of the film, and the amount of the carrier liquid to be attached varies depending on the location.

FIG. 2 is a diagram illustrating a cleaning device 85 according to the embodiment of the present invention.
Referring to FIG. 2, cleaning device 85 according to the embodiment of the present invention has a configuration in which leveling member 80, heating roller 81, and cleaning blade 73 are provided from the upstream side in the rotation direction of fixing roller 71. is there.

  The heating roller 81 is set to a temperature higher than the fixing nip region formed between the fixing roller 71 and the pressure roller 72.

  The carrier liquid transferred to the surface of the fixing roller 71 is heated by the heating roller 81 and set to a temperature higher than the fixing nip region, so that the viscosity of the carrier liquid can be reduced as much as possible. As a result, it is possible to enter the cleaning blade 73 provided on the downstream side in the rotation direction of the fixing roller 71. The carrier liquid having a reduced viscosity has a weak impact input to the cleaning blade 73 and can be easily collected by the cleaning blade 73.

  The leveling member 80 is composed of a roller, a brush, or the like, and slidably rubs the surface of the fixing roller with a speed difference while swinging in the longitudinal direction of the fixing roller 71 on the upstream side in the rotation direction of the fixing roller 71. The carrier liquid adhering by rotating is leveled.

  By providing the leveling member 80, it is possible to evenly level areas where the amount of carrier liquid transferred to the fixing roller 71 is different, and a heating roller provided on the downstream side in the rotation direction of the fixing roller 71. It is possible to heat evenly at 81, and it is possible to further improve the efficiency of removing the carrier liquid by making the amount of the carrier liquid adhering to the cleaning blade 73 uniform.

  Therefore, the configuration of the cleaning device according to the present embodiment, that is, when the remaining carrier liquid is non-volatile, the heating roller that is set to a temperature higher than the fixing nip region is provided on the fixing roller 71, so that it adheres to the fixing roller. The viscosity of the remaining carrier liquid can be reduced and efficiently removed by the cleaning blade 73.

Next, the case where the carrier liquid is volatile will be described.
FIG. 3 is a diagram illustrating a cleaning device 85 # replaceable with the cleaning device 85 according to the embodiment of the present invention.

  Referring to FIG. 3, cleaning device 85 # according to the embodiment of the present invention collects leveling member 80, heating roller 81, and volatilized carrier liquid from the upstream side in the rotation direction of fixing roller 71. A duct (mist collecting mechanism) 90 is provided.

  In the fixing device 109, the carrier liquid can be volatilized by heating each of the fixing roller 71 and the pressure roller 72 with a built-in heater (heat source).

  However, if the energy required to volatilize is applied at once, for example, when coated paper is used, the moisture inside the paper may vaporize, expand, and explode, creating a paper blister that is a blistering phenomenon. There is. Even in high-quality paper that does not generate paper blisters, excessive application of heat will damage the paper.

  Therefore, in reality, it is difficult to remove the carrier liquid remaining on all the recording sheets in the fixing nip region where the fixing roller 71 and the pressure roller 72 are in contact with each other via the recording sheet. The remaining carrier liquid adheres to the surface of the fixing roller.

  Further, as described above, the amount of the carrier liquid adhering to the recording paper on which the toner image is formed varies depending on the toner image forming region, and as a result, the carrier liquid adhering to the surface of the fixing roller However, the carrier liquid does not uniformly adhere in the longitudinal direction of the fixing roller 71, and the amount of the carrier liquid to be attached varies depending on the location.

  The leveling member 80 is constituted by a roller, a brush, or the like, and levels the carrier liquid adhering to the upstream side in the rotation direction of the fixing roller 71 while being swung in the longitudinal direction of the fixing roller 71.

  By providing the leveling member 80, it is possible to evenly level areas where the amount of carrier liquid transferred to the fixing roller 71 is different, and a heating roller provided on the downstream side in the rotation direction of the fixing roller 71. Volatilization at 81 can be promoted.

  The heating roller 81 is set to a temperature higher than the temperature of the fixing nip region formed by the fixing roller 71 and the pressure roller 72 so that the carrier liquid adhering to the fixing roller 71 can be sufficiently removed.

  Thereby, volatilization of the remaining carrier liquid adhering to the fixing roller 71 can be promoted. Further, since the heat given by the heating roller 81 is not directly transmitted to the recording paper, it is possible to suppress damage to paper such as paper blisters.

  Therefore, the configuration of the cleaning device according to the present embodiment, that is, when the remaining carrier liquid is volatile, by providing the fixing roller 71 with the heating roller 81 set to a temperature higher than the fixing nip region, damage to the paper is caused. In addition, the remaining carrier liquid adhering to the fixing roller is volatilized and the remaining carrier liquid can be efficiently removed.

(Example)
The wet image forming apparatus shown in FIG. 1 was used.

  Photoreceptor 110, which is an image bearing member, is obtained by forming an organic photoreceptor film (film thickness: 35 μm) on an aluminum drum having a diameter of 210 mm, and the rotational peripheral speed was set to 350 mm / sec.

  The charging device 116 is a scorotron charger and is set so that the surface potential of the photoconductor 110 becomes −450V.

  The exposure device 118 was set so that the surface potential of the image carrier was −100 V when the image portion was exposed with a semiconductor laser.

  As the liquid developer, non-volatile liquid paraffin was used as the carrier liquid. As the toner, black toner in a color copier C350 manufactured by Konica Minolta Business Technologies, Ltd. was pulverized to an average particle diameter of 3 μm. As for the added dispersant, Solsperse 13940 manufactured by Avicia Co. was set to a concentration of 25 weight percent with respect to the toner amount.

  A bias voltage of −300 V was applied to the developing roller 106. The transfer bias applied to the transfer roller 114 was adjusted so that the transfer efficiency was 90% or more. In this embodiment, a constant current of −250 μA was supplied to the transfer roller 114.

The squeeze roller 111 applied a bias having the same polarity as the toner.
In this embodiment, the toner adhesion amount as a solid image is 3 g / m ² as the toner image (sample image) to be fixed on the recording paper by adjusting the bias voltage and the like, and the carrier liquid amount at that time is 2 g / m. ^It was set to be ² .

The recording paper used was 127 g / m ² of US tsubo in OK Top Coat +, a coated paper made by Oji Paper Co., Ltd.

  As for the fixing device 109, the fixing roller 71 and the pressure roller 72 are both made of silicon rubber, and the roller surface layer is covered with a PFA tube (30 μm) in consideration of releasability. As for the PFA tube, a SUPER PFA TEFRON (registered trademark) 451HP-J manufactured by Mitsui DuPont Fluorochemical Co., Ltd. was used to cover the silicon rubber roller by 30 μm.

The roller configuration was such that the roller diameter was 50 mm and the wall thickness was 5 mm.
As the configuration of the fixing device 109, the surface pressure of the fixing roller 71 and the pressure roller 72 was set to 150 KPa, and the surface temperatures were set to be held at 150 degrees.

  Further, the time (nip time) for the toner image of the conveyed recording paper to pass through the fixing nip region formed between the fixing roller 71 and the pressure roller 72 was set to 60 ms.

  The leveling member 80 is swung in the longitudinal direction of the fixing roller while rotating in the same direction as the fixing roller 71.

  Here, a silicon rubber foam sponge is used as the leveling member 80. The leveling member 80 is not particularly limited as long as it is composed of a brush, a roller or the like and the material has heat resistance.

  The heating roller 81 was formed of a SUS metal roller, and a surface layer coated with fluoro rubber was used. And it managed so that the surface temperature of the metal roller of SUS could be controlled. In this example, the surface temperature was set to 170 ° C.

  The cleaning blade 73 is not particularly limited as long as it can contact the surface of the fixing roller with heat-resistant fluoro rubber, urethane rubber, SUS, or the like. In this example, a urethane rubber blade is used.

Then, 30 sample images were continuously passed.
As a result, image noise such as oil streaks and poor fixing did not occur.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 is a schematic configuration diagram illustrating an example of a wet image forming apparatus according to an embodiment of the present invention. It is a figure explaining the cleaning apparatus 85 according to embodiment of this invention. It is a diagram illustrating a cleaning device 85 # replaceable with the cleaning device 85 according to the embodiment of the present invention.

Explanation of symbols

  71 Fixing roller, 72 Pressure roller, 73, 104, 107, 112 Cleaning blade, 80 Leveling member, 81 Heating roller, 85, 85 # Cleaning device, 90 Duct, 105 Developing layer, 106 Developing roller, 108 Developing device 109 developing device 110 photoconductor 111 squeeze roller 114 transfer roller 116 charging device 118 exposure device 119 transport belt 300 recording paper.

Claims (4)

A wet image forming apparatus using a liquid developer in which toner is dispersed in a carrier liquid,
An image carrier for carrying an electrostatic latent image;
A developing device for developing an electrostatic latent image on the image carrier with the liquid developer to form a toner image;
A transfer device for transferring a toner image formed on the image carrier to a transfer material;
A fixing device that heat-fixes the toner image transferred to the transfer material,
The fixing device includes:
A fixing member in contact with the surface side to which the toner image of the transfer material is transferred;
A pressure member in contact with the back side of the transfer material;
A cleaning device for removing the liquid developer remaining on the fixing member,
The fixing member includes a first heating unit that heats a region where the fixing member and a surface side on which a toner image of the transfer material is transferred are in contact with each other;
The cleaning device includes a second heating unit that heats the liquid developer remaining on the fixing member,
The wet image forming apparatus, wherein a heating temperature by the second heating unit is set higher than a heating temperature by the first heating unit.   The cleaning device further includes an agitation member that rotates so as to slidably rub the surface of the fixing member with a speed difference on the upstream side in the movement direction of the surface of the fixing member with respect to the second heating unit. Wet image forming apparatus.   3. The wet method according to claim 1, wherein the cleaning device further includes a cleaning member that removes the liquid developer remaining on the fixing member on the downstream side in the movement direction of the surface of the fixing member with respect to the second heating unit. Image forming apparatus.   The wet image forming apparatus according to claim 1, wherein the cleaning device further includes a recovery mechanism that recovers the liquid developer remaining on the fixing member evaporated by the second heating unit.

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