JP2009145481A - Wet type image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wet type image forming device capable of maintaining favorably cleanability for a long period, with simple constitution. <P>SOLUTION: This wet type image forming device is arranged with a secondary transfer roller 102, a cleaning liquid supply part 204 for supplying a cleaning liquid, a cleaning roller 201 (stirring member) of an intermediate transfer body 103, and a cleaning blade 202 for the intermediate transfer body 103 that is a cleaning member for removing toner remained in the intermediate transfer body 103 respectively in the periphery of the intermediate transfer body 103. The wet type image forming device is provided further with a potential setting part 209 for setting potentials of the intermediate transfer body 103 and the cleaning roller 201. The cleaning roller 201 is impressed with a bias voltage of the potential equal to a prescribed bias voltage impressed to the intermediate transfer body 103, by the potential setting part 209. <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 using an intermediate transfer member, an electrostatic latent image formed on a photosensitive member is developed with toner, and the toner image is primarily transferred to the intermediate transfer member. Further, the image is formed by secondary transfer from the intermediate transfer member to the recording paper. In the transfer process of such an image forming apparatus, an electrostatic transfer method is generally employed.

  When transferring the toner image of the intermediate transfer member to the sheet to be transferred, a voltage is applied by a transfer roller or the like from the back surface of the sheet arranged to face the intermediate transfer member, and the intermediate transfer member and the sheet An electric field is formed between the toner image and the toner image is electrostatically attracted to the sheet by the electric field.

  In such a transfer process, if the electric field is disturbed or the adhesion force of the toner to the intermediate transfer member is too strong, a part of the toner remains on the intermediate transfer member without being transferred, resulting in a decrease in transfer efficiency. It will be.

  Therefore, it is necessary to sufficiently clean the toner remaining on the intermediate transfer member every time it is transferred.

Various cleaning means for this purpose have been proposed in the past. In JP-A-2002-82537, the cleaning roller made of polyurethane foam is pressed against the intermediate transfer belt while the intermediate transfer belt is pressed against the intermediate transfer belt. A configuration is disclosed in which the cleaning blade is arranged in the direction opposite to the surface movement direction, and the cleaning blade is disposed downstream of the cleaning roller in the surface movement direction of the intermediate transfer belt.
JP 2002-82537 A

  However, in the configuration of Patent Document 1 described above, there is a problem in that the toner can adhere to the cleaning roller so that the cleaning roller has a short period during which the original function can be performed, and good cleaning performance cannot be maintained over a long period of time. To do. This problem is considered to be caused by the fact that the charged toner is only collected by the cleaning roller and is not discharged.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wet image forming apparatus capable of maintaining good cleaning properties for a long period of time with a simple configuration. .

  The wet image forming apparatus of the present invention is a wet image forming apparatus using 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 latent image on the image carrier. Developing the image with a liquid developer to form a toner image, an intermediate transfer member to which the toner image formed on the image carrier is transferred, and transferring the toner image on the intermediate transfer member to the transfer material And a cleaning device for cleaning the toner remaining on the intermediate transfer body after the transfer of the toner image onto the transfer material. The cleaning device includes a stirring member that rotates so as to rub the surface of the intermediate transfer member with a speed difference, a potential setting unit that sets the stirring member to the same potential as the intermediate transfer member, and the surface of the intermediate transfer member rather than the stirring member. And a cleaning member for removing toner remaining on the intermediate transfer member on the downstream side in the moving direction.

Preferably, the stirring member is configured by a foam roller that is a foam.
In particular, the foaming roller has foam cells that are gaps surrounded by the skeleton of the foam, and the average cell diameter of the foam cells is 30 μm to 200 μm.

  Preferably, the cleaning device includes a liquid supply mechanism that supplies a cleaning liquid onto the intermediate transfer member on the upstream side in the movement direction of the surface of the intermediate transfer member with respect to the stirring member.

  The wet image forming apparatus of the present invention includes a stirring member that rotates to rub the surface of the intermediate transfer member with a speed difference in the cleaning device, a potential setting unit that sets the stirring member to the same potential as the intermediate transfer member, And a cleaning member that removes toner remaining on the intermediate transfer member on the downstream side in the movement direction of the surface of the intermediate transfer member with respect to the stirring member. This method eliminates the potential difference between the intermediate transfer member and the stirring member, and prevents the charged toner remaining on the intermediate transfer member from being collected by being attracted to the stirring member and being discharged without being discharged. At the same time, it is possible to prevent the phenomenon that the intermediate transfer member 103 is attracted. Therefore, it is possible to maintain a good cleaning property for a long time with a simple configuration by suppressing a decrease in the life of the stirring member and a decrease in the collecting power of the remaining toner.

  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, in a wet image forming apparatus according to an embodiment of the present invention, a developing device 107 and a photoconductor 110 are arranged around a photoconductor 110, which is a drum-shaped image carrier, in the rotation direction indicated by arrows. Remaining on the intermediate transfer member 103, which is an image carrier that is primarily transferred from the toner, a cleaning liquid supply unit (liquid supply mechanism) 112 that supplies a cleaning liquid, a cleaning roller (stirring member) 108 of the photosensitive member 110, and the photosensitive member 110. A cleaning blade 104, a charging device 116, and an exposure device 118, which are cleaning members for removing toner, are provided.

  Further, around the intermediate transfer member 103, a secondary transfer roller 102, a cleaning liquid supply unit 204 for supplying a cleaning liquid, a cleaning roller 201 (stirring member) for the intermediate transfer member 103, and an intermediate transfer in the order of rotation indicated by arrows. A cleaning blade 202 for the intermediate transfer member 103, which is a cleaning member for removing toner remaining on the member 103, is provided. Further, a potential setting unit 209 for setting the potentials of the intermediate transfer member 103 and the cleaning roller 201 is provided. In this example, a configuration in which the cleaning liquid is supplied from the cleaning liquid supply unit (liquid supply mechanism) 112 to improve the cleaning property will be described. However, the cleaning liquid supply unit (liquid supply mechanism) 112 is provided. It is also possible to adopt a configuration without this.

  The developing device 107 includes a developing tank 105 that stores a liquid developer (also referred to as developer) containing toner and carrier liquid, and a developing roller 106.

  Here, the developer mainly includes an insulating liquid as a carrier liquid, a toner for developing an electrostatic latent image, and a dispersant for dispersing the toner.

  The carrier liquid can be used without particular limitation as long as it is generally used for an electrophotographic developer, but a non-volatile liquid is particularly 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 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.

  The developer 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 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 developer is supplied to the developing roller 106, and a charge is given to the toner contained in the 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 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.

  Next, the toner image formed on the photoconductor 110 is primarily transferred to the intermediate transfer body 103 to which a predetermined voltage is applied. Then, the toner image is formed on the recording sheet 300 by being secondarily transferred from the intermediate transfer member 103 to the recording sheet 300 by the secondary transfer roller 102.

  The secondary transfer roller 102 can also be a roller for simultaneous transfer and fixing with a built-in heater. It is also possible to fix the recording sheet 300 after transfer with a fixing roller (not shown).

  On the other hand, the toner remaining on the intermediate transfer member 103 after the secondary transfer is cleaned by a cleaning device. The cleaning device for the intermediate transfer member 103 includes a cleaning roller (stirring member) 201 and a cleaning blade 202 that is a cleaning member for removing the toner remaining on the intermediate transfer member 103. In this example, the cleaning liquid supply unit 204 is further provided as a cleaning device for the intermediate transfer member 103 to supply the cleaning liquid. However, the cleaning liquid supply unit 204 is not provided. It is also possible to do. The supply liquid of the cleaning liquid can be directly applied to the cleaning roller 201, or can be directly applied to the intermediate transfer body 103 upstream of the cleaning roller 201.

  The cleaning liquid supplied from the cleaning liquid supply unit 204 is mixed with the toner remaining on the intermediate transfer member 103, and the toner is redispersed in the cleaning liquid. As a result, it is possible to improve the cleaning power for scraping off the toner remaining on the cleaning blade 202 pressed against the intermediate transfer member 103 from the intermediate transfer member 103.

  The cleaning roller 201 rotates so that the surface of the intermediate transfer member 103 is rubbed against the intermediate transfer member 103 with a speed difference, and disturbs the toner image remaining on the intermediate transfer member 103 in the liquid developer. Agitate the particles and the carrier.

  The cleaning blade 202 is in counter contact with the rotational direction of the intermediate transfer body 103 on the downstream side of the surface of the intermediate transfer body 103 in the moving direction, and the intermediate transfer is performed by the tip (edge) of the cleaning blade 202. The toner remaining on the surface of the body 103 is scraped off.

  With this configuration, the cleaning liquid containing the residual toner is removed from the surface of the intermediate transfer member 103, and the cleaning process ends.

  In this example, a configuration in which the cleaning blade 202 is counter-contacted with the rotation direction of the intermediate transfer member 103 is illustrated as an example of a configuration for scraping off residual toner, but the residual toner is scraped off. If it is the structure which can do, it will not be specifically limited to the direction of the contact. Further, in this example, a configuration for removing residual toner using the cleaning blade 202 is described. However, a web roll-like paper, cloth, or the like is pressed against the photoconductor to be wound up and moved on the photoconductor. It is also possible to employ so-called web cleaning that removes residual toner.

  Although the cleaning process of the intermediate transfer member 103 has been described here, the same applies to the cleaning process of the photosensitive member 110 using the cleaning roller 108 and the cleaning blade 104 provided on the photosensitive member 110.

  In this embodiment, the cleaning roller 201 applies a bias voltage having the same potential as the predetermined bias voltage applied to the intermediate transfer member 103 by the potential setting unit 209 in order to maintain good cleaning performance. Applied to 201.

  By this method, the potential difference between the intermediate transfer member 103 and the cleaning roller 201 can be eliminated.

  As a result, the intermediate transfer member 103 is pressed in contact with the intermediate transfer member 103 by the cleaning roller 201 and the toner image and the carrier are stirred by disturbing the toner image remaining on the intermediate transfer member 103 in the liquid developer. Since there is no potential difference between the cleaning roller 201 and the cleaning roller 201, it is possible to prevent a phenomenon that the charged toner is attracted to the cleaning roller 201 and collected, and the cleaning roller 201 becomes dirty without being discharged.

  Further, since there is no potential difference between the intermediate transfer member 103 and the cleaning roller 201, it is possible to prevent the phenomenon that the intermediate transfer member 103 is attracted to the intermediate transfer member 103, and it is possible to suppress a reduction in the collecting power of the remaining toner. Is possible.

  Note that the value of the bias voltage applied to the cleaning roller 201 is switched between when it is recovered and when it is discharged, whereby the charged toner is recovered by drawing it, and the recovered toner is now removed from the cleaning roller 201. In this case, a method of discharging by separating them can be considered, but the configuration becomes complicated because of a complicated sequence such as adjustment of bias voltage and adjustment of switching timing.

  Therefore, as in the present invention, by setting the potential of the cleaning roller 201 to the same potential as the potential of the intermediate transfer member 103, the toner remaining on the intermediate transfer member 103 stirred by the cleaning roller 201 is removed from the cleaning roller 201 and the intermediate transfer member. It can be collected and discharged without being drawn to either side of the body 103, and it is possible to perform a good cleaning for a long time with a simple configuration by suppressing a reduction in the life of the cleaning roller and a reduction in the collecting power of the remaining toner. It is possible to maintain sex.

  In this example, a method for setting the potential of the cleaning roller 201 to the same potential as the potential of the intermediate transfer member 103 will be described. However, the same applies to the case where the potentials of the photosensitive member 110 and the cleaning roller 108 are set to the same potential. It is possible to obtain the same effect.

  Further, in order to maintain good cleaning properties, the cleaning roller 201 of the intermediate transfer member 103 in this example uses a foaming roller that is a foam. Hereinafter, the cleaning roller 201 is also referred to as a foam roller.

  The foam roller has foam cells that are gaps surrounded by the skeleton of the foam. The toner is collected at the skeleton of the foam cells, mixed with the cleaning liquid held in the foam cells, and discharged.

  Therefore, the physical properties of the foam roller are the key to achieving both good recovery and discharge of toner remaining in the foam roller and maintaining good cleaning properties.

  In this respect, the foaming roller needs to be molded from a material that does not swell or deform with a cleaning liquid or a carrier liquid, and it is desirable to use an ester-based urethane foam.

  In addition, the smaller the average cell diameter of the foaming cells of the foaming roller, the larger the ratio of the skeleton portion and the easier it is to collect the toner. The average cell diameter of the foam cells can be adjusted based on the mixing ratio of the foaming agent when the foam roller is molded, and the technology is general, so the details will be described. Omitted.

  This is because the toner diameter is about 1 to 3 μm, and the average cell diameter of the foamed cells only needs to be about 5 μm to 500 μm larger than the toner diameter.

  Preferably, it has an average cell diameter of 10 μm to 300 μm, more desirably 20 to 200 μm.

  Moreover, not only the average cell diameter of the foam cells but also how many cells are in a certain length, the number of cells in a certain length is also a factor that determines the scraping force, and generally the more cells the more desirable.

  According to the experiments by the present inventors, it was found that if the number of cells is 50 or more in 25 mm, it has a good scraping power.

  Further, the developer discharged from the cleaning roller 201 is mixed with the cleaning liquid held in the foamed cell, and the cleaning roller 201 maintains an appropriate pressure contact force with the intermediate transfer member 103, whereby the surface of the intermediate transfer member 103 is moved in the downstream direction. Will be discharged to the side.

The pressure contact force required to be discharged is preferably 20 N / m or more.
However, if the pressure contact force is too high, the life of the cleaning roller 201 is shortened.

  As a result of experiments by the present inventors, the life of the cleaning roller 201 was measured while changing the pressure contact conditions. In order to achieve both the life of the cleaning roller 201 and the discharge of the cleaning roller, a pressure contact force of 20 to 250 N / m is desirable. It turned out that.

  Moreover, even if the average cell diameter of the foamed cells is too large for discharging, the cleaning liquid cannot be retained and good cleaning properties cannot be maintained.

  Therefore, the average cell diameter is desirably 10 μm or more and 500 μm or less. Preferably, it is 20 μm or more and 300 μm or less. Furthermore, it is preferably 30 μm or more and 200 μm or less.

  Therefore, it is desirable that the average cell diameter of the foamed cell that is most preferable for achieving both recovery and discharge of the foamed roller is 30 μm or more and 200 μm or less.

  Further, in order to improve the cleaning property, the surface of the intermediate transfer body 103 can be made of fluorine, silicon, urethane, PI (polyimide), PG (polycarbonate) or the like. Furthermore, the base material may be resin or rubber.

  In order to maintain good cleaning properties, it is desirable that the surface roughness of the intermediate transfer member 103 is within the maximum height Rz = 10 μm, which is a JIS standard.

The example which implemented this invention based on said embodiment is demonstrated below.
(Example)
The cleaning property was evaluated with the configuration shown in FIG.

  The bias voltage of the intermediate transfer member 103 and the cleaning roller 201 was set to + 300V. Further, as a developer to be used, a toner for Bizhub C352 manufactured by Konica Minolta was further pulverized, and a toner having an average particle size of 2.2 μm was used. A pulverized toner dispersed in silicone oil was used as a liquid developer.

  In this embodiment, an open-cell urethane roller is used as the cleaning roller 201. The hardness of the cleaning roller 210 was 13 degrees as measured using the Asker C type used in the Japan Rubber Association Standard (SRIS).

The average cell diameter of the cleaning roller 201 was 85 μm.
The pressing force of the cleaning roller 201 against the intermediate transfer member 103 was 50 N / m.

  The toner in the produced liquid developer is negatively charged in the developing unit, and after transferring to the recording paper, the potential of the cleaning roller 201 is set to the same potential as that of the intermediate transfer member 103, so that the intermediate transfer member 103 described above is transferred. When the remaining toner was cleaned, good cleaning properties could be maintained. Even after 1000 sheets were passed, good cleaning performance could be maintained without any problem in the image quality of the recording paper.

(Comparative Example 1)
The bias voltage of the intermediate transfer member 103 was set to + 300V, and the bias voltage of the cleaning roller 201 was set to + 500V. Specifically, a potential difference is generated between the cleaning roller 201 and the intermediate transfer member 103 so as to attract the charged toner to the cleaning roller 201. Other than that, the cleaning property was evaluated under the same conditions as in the example with the configuration shown in FIG.

  There was no problem with the cleanability of the first recording sheet, but the image quality of the recording sheet after passing 1,000 sheets was confirmed as so-called background fogging, which is image noise such as vertical streaks due to residual toner on the intermediate transfer member 103. That is, a cleaning failure was confirmed.

(Comparative Example 2)
The bias voltage of the intermediate transfer member 103 was set to +300 volts, the bias voltage of the cleaning roller 201 was not applied, and the float state was set. Therefore, the charged toner is prevented from being attracted to the cleaning roller 201. Other than that, the cleaning property was evaluated under the same conditions as in the example with the configuration shown in FIG.

  Although there was no problem with the cleaning performance of the first recording sheet, the above-described background fogging occurred in the recording sheet after 300 sheets were passed, and a cleaning failure was confirmed.

  Therefore, as shown in the examples, it was confirmed that good cleaning performance can be maintained for a long time with a simple configuration by setting the bias voltages of the intermediate transfer member 103 and the cleaning roller 201 to the same potential. .

  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.

Explanation of symbols

  102 Secondary transfer roller, 103 Intermediate transfer member, 104, 202 Cleaning blade, 105 Developing layer, 106 Developing roller, 107 Developing device, 108, 201 Cleaning roller, 110 Photoconductor, 112, 204 Cleaning liquid supply unit, 116 Charging Apparatus, 118 exposure apparatus, 209 potential setting unit.

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;
An intermediate transfer member to which a toner image formed on the image carrier is transferred;
A transfer device for transferring the toner image on the intermediate transfer member to a transfer material;
A cleaning device for cleaning toner remaining on the intermediate transfer body after transfer of the toner image to the transfer material,
The cleaning device includes:
A stirring member that rotates to rub the surface of the intermediate transfer member with a speed difference;
A potential setting section for setting the stirring member to the same potential as the intermediate transfer member;
And a cleaning member that removes toner remaining on the intermediate transfer member on the downstream side in the moving direction of the surface of the intermediate transfer member with respect to the stirring member.   The wet image forming apparatus according to claim 1, wherein the stirring member is configured by a foam roller that is a foam. The foam roller has a foam cell which is a gap surrounded by a foam skeleton,
The wet image forming apparatus according to claim 2, wherein the foamed cells have an average cell diameter of 30 μm to 200 μm.   4. The liquid cleaning mechanism according to claim 1, wherein the cleaning device includes a liquid supply mechanism that supplies a cleaning liquid onto the intermediate transfer body upstream of the stirring member in the movement direction of the surface of the intermediate transfer body. The wet image forming apparatus described.

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