JP2002132104A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the cleaning fault by the toner solidifying and remaining on the surface of a photoreceptor of a cleaning device for the untransferred developing materials of an image forming device of a liquid development system and to prevent the defective main electrostatic charge in an image region by bleeding of a cleaning liquid and a developer out of the front and rear ends of the cleaning device and the inaccuracy of the clearance size between a photoreceptor drum and a developing roller in a non-image region. SOLUTION: The untransferred residual toners are sufficiently diluted by uniform coating application of the cleaning liquid to the photoreceptor side by the cleaning liquid coating application roller on the upstream side of the rotation of the photoreceptor to make the photoreceptor easily cleanable and thereafter both of the cleaning liquid and the untransferred residual toners on the downstream side are wiped away by a cleaning roller, by which the photoreceptor surface is made clean. Since the cleaning roller is under rotation, the developer, etc., are rapidly removed without remaining in the cleaning nip and therefore the remaining and solidifying of only the toner particles are averted and the spreading of the cleaning liquid to the non-image region is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus using a liquid developing system, and more particularly to a cleaning coating roller and a cleaning coating roller in which toner remaining on the surface of a photosensitive drum after transfer of a developer is disposed around the photosensitive drum. The present invention relates to an image forming apparatus provided with a cleaning device for removing with a roller.

[0002]

2. Description of the Related Art In an image forming apparatus using electrophotography, a liquid developing method using a liquid developer in which toner particles are dispersed in a carrier liquid is increasingly used. Examples of the liquid developer include those described in JP-A-62-289971. In this method, a toner particle containing a binder, a colorant, an additive, and the like is dispersed in an electrically insulating carrier liquid having a high electric resistance such as an aliphatic hydrocarbon solvent and a low dielectric constant. Things. A natural or synthetic resin as a binder, a pigment or dye as a colorant, and a dispersant such as metal soap as an additive are each mixed with a carrier liquid and uniformly kneaded to form a concentrated toner having a nonvolatile content of about 1 to 20% by weight. And then the concentrated toner is adjusted to have a nonvolatile content of about 0.1 to 5 wt%. The toner particle size is around 0.5 to 2 μm.

The liquid developing system has the following advantages. (1) The toner particle size is fine. That is, the powder toner in the dry development method has a particle diameter of 6 to 7 μm for improving the image quality.
m, but the toner particles in the liquid developer can be further reduced to about 1/10 compared to the powder toner, and an extremely high-definition image can be obtained compared to dry development. (2) High toner transparency. That is, since the transparency is higher than that of the powder toner, an image with rich saturation can be obtained in full-color development. (3) No toner scattering.

In the liquid developing method, only the toner particles in the developer are completely separated from the carrier liquid and transferred to the surface of the photoreceptor through development, transfer and cleaning of the toner. Carrier liquids are also working together. For this reason, in a cleaning device of a liquid developed image forming apparatus, a cleaning blade used for removing a normal powder toner completely drops and removes residual toner on a blade edge surface due to an adhesive force of a carrier liquid. It is difficult. If the carrier liquid dries in this state, there is a problem that the toner solidifies on the blade edge surface, resulting in poor cleaning.

Conventionally, various measures have been taken to completely remove the untransferred residual toner including the carrier liquid. For example, in JP-A-6-230704, a means for supplying a developer to the surface of a photoreceptor, a cleaning foam roller (corresponding to a cleaning liquid applying means of the present application),
In a wet electrostatic copying apparatus equipped with a cleaning blade, a scraping blade is provided downstream of the cleaning foam roller and between the cleaning foam roller and the cleaning blade to scrape a developing solution of a photoconductor thinner than the cleaning blade. A cleaning device characterized by the following has been proposed. However, in the cleaning device having the above configuration, although the toner and the cleaning liquid can be completely removed once, the liquid is not sufficiently cut off from the blade edge surface and moves to both side edge portions of the blade during repeated use. In this state, the blade leaks from the side of the blade during further use and contaminates the non-image area of the photoconductor. The leaked toner and cleaning liquid are moved in a short time to the developing roller provided on the other side of the photoconductor by rotation of the photoconductor, and the accuracy of the positioning roller that determines the gap size between the developing roller and the photoconductor Worsen.
Also, if the developing solution continuously spreads to the non-image area of the photoreceptor, it also leaches out to the image area of the photoreceptor, so that uniform main charging of the photoreceptor surface is impaired, and normal image formation is hindered. become.

[0006]

[Problems to be solved by the invention] Therefore, an object of the present invention is to solve the above-described problem of the cleaning device in the image forming apparatus of the liquid developing system, and to prevent the developer and the cleaning liquid from leaking from the front and rear ends in the longitudinal direction of the cleaning blade and to downstream of the cleaning device. It is an object of the present invention to provide an image forming apparatus capable of maintaining a clean state in which the untransferred toner and the cleaning liquid are completely removed from the surface of the photosensitive member on the side.

[0007]

According to a first aspect of the present invention, there is provided a cleaning apparatus having a liquid developing apparatus and a cleaning liquid applying means for applying a cleaning liquid to a surface of a photoreceptor after toner transfer. The cleaning device includes a cleaning roller disposed downstream of the photoconductor in the rotation direction of the photoconductor with respect to the cleaning liquid application unit, and a toner removing member in contact with the surface of the cleaning roller. It is characterized by being. According to the first aspect of the present invention, the untransferred toner and the cleaning liquid on the photoconductor are wiped off on the entire peripheral surface of the cleaning roller, so that the solidification is prevented from stagnating in a contact line with the photoconductor. In addition, since the developer and the cleaning liquid on the cleaning roller are quickly scraped off by the developer removing member on the roller surface, the effect of the cleaning roller can be maintained for a long time.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the cleaning liquid has the same composition as a carrier liquid constituting a liquid developer. According to the second aspect of the present invention, the cleaning liquid having the best effect of dispersing the toner particles is selected, so that the cleaning effect of the residual developer can be enhanced.

According to a third aspect of the present invention, in the image forming apparatus according to the first or second aspect, the cleaning roller is housed in an inner housing except for an opening on the photosensitive drum side. At least one discharge port is provided at a position above the contact position between the cleaning roller and the toner removing member on the opposite wall surface. According to the third aspect of the present invention, of the mixed liquid of the cleaned toner and the cleaning liquid, the toner having a high specific gravity is stored at the bottom of the inner housing, and the cleaning liquid having a low specific gravity flows out of an outlet provided on the wall surface of the inner housing. Since the cleaning liquid falls into the main housing, the cleaning liquid can be circulated and reused.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. The following embodiment is an example embodying the present invention and does not limit the technical scope of the present invention. FIG. 1 is a schematic diagram showing a main part of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus includes a main charging unit 21, an image exposing unit 22, a developing unit 23, and a roller transfer unit 25 disposed around the photosensitive drum 2. The registration roller pair 24 temporarily stops the sheet P sent from a sheet feeding / conveying device (not shown), and performs secondary feeding so that the image forming area reaches the roller transfer unit 25 by rotation of the photosensitive drum. Do the paper. The paper P to which the toner has been transferred in the roller transfer unit 25 passes through the fixing unit 26 on the downstream side, and the toner image is fixed.

The photosensitive drum 2 is moved by +
After being uniformly charged to 800 V, the image area is lightly attenuated to +150 V by laser light irradiation from the exposure unit 22, and an electrostatic latent image is formed on the photosensitive drum.

In a developing solution reservoir 23a of the developing unit 23, 1.5 parts by weight of toner particles having a particle diameter of about 1 μm are dispersed in 100 parts by weight of Isopar G (manufactured by Exxon Chemical Co., Ltd., the main component is isoparaffin) as a carrier liquid. Liquid developer is stored. The liquid developer transfers to the surface of the pumping roller 23b rotating in the illustrated direction, and
The amount of coating is regulated by c, and the surface moves to the surface of the developing roller 23d made of elastic rubber. A regulating blade 23e is also provided on the surface of the developing roller 23d, and forms a thin layer of the developer. The developing roller 23 d has a gap of 70 μm from the photosensitive drum 2, and a thin layer of developer formed on the surface of the developing roller 23 d is in contact with the photosensitive drum 2. A bias voltage of +400 V is applied to the developing roller 23d, and when the electrostatic latent image formed on the surface of the photosensitive drum 2 passes through the developing area, the toner particles in the developing solution are electrostatically charged on the photosensitive member surface. Visualize the latent image. When the toner development area on the photoconductor surface passes through the roller transfer section simultaneously with the sheet P, most of the toner particles are transferred onto the sheet P by the action of the transfer voltage of -1 KV applied to the transfer roller. The toner particles of the portion remain on the photosensitive drum without being transferred, and head toward the cleaning device 1. At this time, as a feature of the liquid developer, since a small amount of carrier liquid around the toner particles cooperates with the toner particles,
Hereinafter, the toner in the text includes a small amount of the surrounding carrier liquid. The surface of the photoreceptor that has returned to a clean surface by the cleaning device 1 is irradiated with light by the charge removing lamp 10 to remove the memory of the electrostatic latent image, and then proceeds to the main charging unit 21 for the next image formation.

Next, the details of the cleaning device will be described with reference to FIG. The cleaning device 1 is disposed parallel to the photosensitive drum 2 in the axial direction, and is provided with an application roller 3 as cleaning liquid application means that is in contact with the surface of the photosensitive drum 2, a cleaning roller 4, a coating roller 3, and a cleaning roller 4. And an inner housing 6 that accommodates only the cleaning roller 4 and has an opening on the photoconductor side and is disposed in the main body housing 5. The application roller 3 is located on the upstream side in the rotation direction of the photosensitive drum 2, and the cleaning roller 4 is located on the downstream side in the rotation direction of the photosensitive drum 2.

The application roller 3 is composed of a sponge roller and is configured to rotate following the photosensitive drum.
A coating liquid amount regulating blade 11 that comes into contact with the liquid coating roller 3 is provided in the main body housing 5. The coating liquid regulating blade 11 uses a SUS plate having a thickness of 1 mm. The application liquid regulating blade 11 is provided so that the mounting direction is tangential to the application roller 3 and the liquid application roller 3 comes out of the application liquid and abuts at an intermediate position toward the photosensitive drum. At the bottom of the main body housing 5, a sufficient amount of cleaning liquid 3a for immersing at least the lower part of the liquid application roller 3 is stored. The cleaning liquid 3a is applied to the surface of the photoconductor in order to facilitate the cleaning by diluting and dispersing the untransferred toner particles. In the present embodiment, in particular, in order to enhance the dispersing effect of the toner particles, a liquid developer is used. Isopar G itself, which is a carrier liquid to be formed, is used. The cleaning liquid 3a is applied to the photosensitive drum 2
After being adhered to the surface of the application roller 3 that is driven to rotate and pumped up, the application liquid regulating blade 11 forms an appropriate thin film state. The cleaning liquid 3a is uniformly applied to the surface of the photosensitive drum 2 at the contact position between the liquid applying roller 3 and the surface of the photosensitive drum 2.

The surface of the cleaning roller 4 is formed of a urethane foam rubber layer, and is rotated in a reverse direction at a nip portion with the photosensitive drum 2 by driving means (not shown). 2 and approximately the same. In the inner housing 6, a scraping blade 7 that contacts the cleaning roller 4 is provided as a toner removing member. The scraping blade 7 uses a SUS plate with a thickness of 0.5 mm. The mounting direction of the scraping blade 7 is tangential to the cleaning roller 4, and the fixed end 7 a is mounted on the inner housing such that the free end 7 b is located on the line of contact with the photosensitive drum 10.

The untransferred toner particles remaining on the surface of the photoreceptor that has passed through the roller transfer section 25 are diluted and dispersed by the action of the cleaning liquid applied from the application roller 3, and are in a state of being easily cleaned. When the photosensitive drum reaches the position of the cleaning roller 4 in this state, it can be sufficiently transferred to the cleaning roller side at the nip position with the photosensitive member surface, and the photosensitive member surface becomes a clean state in which the developer is completely removed. . The cleaning effect is exerted over the entire peripheral surface of the rotating cleaning roller, and the cleaning effect is maintained because the surface of the cleaning roller 4 is always clean by the scraping blade 7 since the toner and the cleaning liquid are dropped.

The back plate 8 of the inner housing 6 opposite to the opening on the photoreceptor side has a discharge port 12 at a position above the contact position between the cleaning roller 4 and the scraping blade 7.
Is provided. Although a large amount of untransferred toner particles and cleaning liquid have been transferred to the cleaning roller 4, the toner particles are quickly removed by the scraping effect of the scraping blade 7 and accumulated on the bottom 6 a of the inner housing 6. In the mixed liquid of the untransferred toner particles and the cleaning liquid accumulated in the inner housing bottom 6a, the toner layer 15 having a large specific gravity sinks below the staying liquid, and the cleaning liquid layer 16 having a small specific gravity exists above. The cleaning liquid is repeatedly used in this state, and when the amount of the staying liquid increases and the liquid level reaches the discharge port 12, the upper cleaning liquid containing no toner particles is discharged from the discharge port 12.
Through the body housing bottom. As described above, since the cleaning liquid is recycled, there is an advantage that a new replenishment of the cleaning liquid is not required or a small amount of the cleaning liquid is required.

In this embodiment, a SUS plate having a thickness of 0.5 mm is used for the scraping blade 7 as a toner removing member. However, the thickness is not limited to this, and is 0.1 to 1.
A 0 mm one can be used. The material is not limited to this, and an appropriate material can be appropriately selected from various resin plates, metal plates, and the like. Further, the contact state of the scraping blade with the cleaning roller 4 is such that the free end thereof is tangential at the contact point, but the present invention is not limited to this. It may have an angle to the tangent. Further, in the configuration as the toner removing member, various rollers may be brought into contact with the cleaning roller 4 in addition to the scraping blade.

In this embodiment, a SUS plate having a thickness of 1 mm is used for the coating liquid regulating blade 11, but the thickness is not limited to this, and a blade having a thickness of 0.5 to 2.0 mm can be used. In addition, the contact state of the coating liquid regulating blade 11 with the coating roller 3 is such that the free end is tangential at the contact point, but is not limited to this, and the free end may exceed the contact point. The contact may have an angle with respect to the tangent. The material is not limited to this, and various resin and metal blade plates, rubber blade plates and the like can be used. Further, the shape is not limited to the blade shape, and a thick stay shape or the like can be used.

The cleaning liquid supplied to the coating roller is usually the same as the carrier liquid used for the developer, but any liquid can be used as long as it can sufficiently disperse and remove the toner. Therefore Isopar G as the cleaning liquid and the carrier liquid in the present embodiment (Exxon Chemical Co., main component isoparaffins) but was used, electric resistance dielectric constant 10 ⁷ Ω · cm or more are not limited thereto 3 The following are aliphatic hydrocarbon solvents, aromatic hydrocarbons and mixtures thereof having a boiling point of 140 to 250 ° C. Specifically, Isopar H, L (manufactured by Exxon Chemical Co., Ltd., main component is isoparaffin), and Shellsol A , B (manufactured by Shell),
Naphthesol L, M, H (manufactured by Nippon Oil Co., Ltd.) and the like can be used.

In this embodiment, the cleaning roller 4
The surface is made of foamed polyurethane rubber. However, the present invention is not limited to this, and a roller wrapped with a nonwoven fabric such as cotton fiber or a brush roller made of acrylic, nylon, rayon or the like can be used. In the present embodiment, an elastic sponge roller is used as an application roller as a cleaning liquid application unit, but the invention is not limited to this, and is lipophilic.
A foam type with impregnating properties can be suitably used,
A web type may be used.

In this embodiment, the application roller 3 is driven by the photosensitive member. However, the present invention is not limited to this. The application roller 2 may be driven by external driving means. In this case, the application roller 2 is brought into contact with the photosensitive drum. Both the same direction and the opposite direction are possible. Further, in the present embodiment, the cleaning roller 4 is rotated in the reverse direction in the nip with the photosensitive drum 2, but either the driving in the same direction or the following movement to the photosensitive drum 2 is sufficient, so that the cleaning effect is most exhibited. Good.

FIG. 3 shows an outline of a conventional image forming apparatus. Instead of the cleaning roller of the present invention, the cleaning blade 30 is directly in contact with the surface of the photosensitive drum 2. Since a part of the aggregated toner 31 adhered and dried on the blade edge surface slips through the edge surface, cleaning failure occurs. FIG. 4 schematically illustrates the cleaning blade 30, the developing roller 23d, and the positioning rollers 32 and 33 with the photosensitive drum 2 interposed therebetween from above.
The dotted line in FIG. 4 depicts the above-described cleaning failure. As shown by the solid line with arrows in FIG. 4, the toner and the cleaning liquid staying on the blade edge surface leak from both ends in the longitudinal direction of the cleaning blade. The leaked toner and cleaning liquid migrate to the photoconductor side and contaminate the positioning rollers 32 and 33 which determine the gap between the developing roller and the photoconductor. The toner that contaminates the surface of the positioning roller is dried and solidified, and remarkably deteriorates the positioning accuracy. Normal main charging is hindered in the next image formation due to the toner and the cleaning liquid spread on the photoconductor surface.

[0024]

According to the cleaning device of the present invention,
The cleaning liquid application roller on the upstream side of the rotation of the photoreceptor uniformly dilutes the untransferred residual toner by uniformly applying the cleaning liquid to the photoreceptor side so that the cleaning liquid can be easily cleaned. Both untransferred residual toner is wiped off to provide a clean photoreceptor surface. Since the cleaning roller is rotating, the developer and the like are quickly removed without staying in the cleaning nip, so that only the toner particles do not remain and solidify, and the cleaning liquid or the like spreads to the non-image area. Can be prevented.

[Brief description of the drawings]

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

FIG. 2 is a schematic diagram showing a cleaning device according to an embodiment of the present invention.

FIG. 3 is a schematic diagram of a conventional technique.

FIG. 4 is an explanatory diagram for explaining occurrence of a defect in a conventional technique.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 cleaning device 2 photoreceptor drum 3 application roller 3a cleaning liquid 4 cleaning roller 5 main housing 6 inner housing 6a inner housing bottom 7 scraping blade 7a fixed end portion 7b free support portion 8 back plate 9 lowest point 10 discharging lamp 11 coating Liquid regulating blade 12 Discharge port 15 Toner layer 16 Cleaning liquid layer 21 Main charging section 22 Exposure section 23 Developing section 23a Developing solution storage section 23b Pumping roller 23c Regulation blade 23d Development roller 23e Regulation blade 24 Registration roller pair 25 Roller transfer section 26 Fixing Unit P Paper 30 Cleaning blade 31 Aggregated toner 32, 33 Positioning roller

Claims (3)

[Claims] An image forming apparatus comprising: a liquid developing device; and a cleaning device having a cleaning liquid applying means for applying a cleaning liquid to the surface of a photoreceptor after toner transfer. An image forming apparatus comprising: a cleaning roller disposed downstream of a photoconductor in a rotation direction; and a toner removing member in contact with a surface of the cleaning roller. 2. An image forming apparatus according to claim 1, wherein said cleaning liquid has the same composition as a carrier liquid constituting a liquid developer. 3. The cleaning roller is housed in an inner housing except for the opening on the photosensitive drum side, and the inner housing has a wall facing the opening, which is located closer to a contact position between the cleaning roller and the toner removing member. 3. The image forming apparatus according to claim 1, wherein at least one discharge port is provided at an upper position.