JP2007147977A - Developing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To surely clean a liquid developer adhered on an elastic development roller. <P>SOLUTION: A developing device for liquid development having a compression member (22) on the elastic development roller (20) developing latent images formed on an image carrier (10) keeps a cleaning roller (25) arranged at the downstream side of a rotation direction of the development roller to a development nip part and is provided with an oil application member (27) for applying oil in contact with the cleaning roller. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a developing device used in an image forming apparatus using a liquid developer having an intermediate transfer belt.

  Conventionally, an electrophotographic image forming apparatus (wet image forming apparatus) using a liquid developer is known. The developer used in the wet image forming apparatus is obtained by suspending solids (toner particles) in an electrically insulating organic solvent (carrier liquid). The particle diameter of the toner particles is 2 μm or less, usually Since it is extremely fine, about 1 μm or less, it is possible to achieve higher image quality than a dry image forming apparatus using powder toner particles of about 7 μm.

  The carrier liquid constituting the developer has a function of making the toner particles charged and further uniformly dispersed in addition to preventing the toner particles from scattering around 1 μm. It also has a role to make it easy to move by action. As described above, the carrier liquid is a component necessary for toner storage, toner conveyance, development, and transfer processes, but also adheres to non-image areas, and excessive carrier liquid after development causes transfer disturbance and the like.

In the wet image forming apparatus, an elastic developing roller is used, and the developer is supplied from the developing supply roller and developed at the developing nip portion, and then the liquid developer (carrier liquid and solid content) adhering to the roller surface is cleaned with a cleaning blade. (Patent Document 1), and the developer is compressed (film-formed) with a compression roller before the developing nip portion.
JP 2005-70184 A

  By the way, among the deposits (liquid developer) remaining after development, deposits in the non-image area are subjected to film forming action from the developer supply roller and the compression roller, and are also given electrical adhesion from the photosensitive member. The cleaning blade slips through, and it is difficult to reliably clean.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to ensure that the liquid developer adhered on the developing roller can be reliably cleaned in an apparatus using an elastic developing roller.
To this end, the present invention provides a developing device for liquid development in which a compression member is disposed with respect to an elastic developing roller that develops a latent image formed on an image carrier, and a downstream side in the rotation direction of the developing roller with respect to the developing nip portion. And an oil application member for applying oil in contact with the cleaning roller.
Further, the present invention is characterized in that the compression member is a roller, and the recovered liquid is supplied to the oil application member.
Further, the present invention is characterized in that a squeeze member is disposed on the image carrier, and a liquid recovered from the squeeze member is supplied to the oil application member.
In the invention, it is preferable that the oil application member is a crown-shaped roller having a diameter at the center portion larger than that at the end portion.

  The present invention can remove the liquid developer (solid content) by filling the voids at the surface roughness level with carrier oil against the deposit on the elastic developing roller that slips through by blade cleaning. By peeling off the solid content by applying an electric field, the deposit on the developing roller can be more reliably cleaned. Furthermore, the cleaned deposits can be recycled by using the same color.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing main components constituting the image forming apparatus according to the embodiment of the present invention. Development units 30Y, 30M, 30C, and 30K are arranged at the lower part of the image forming apparatus, and the intermediate transfer belt 40 and the secondary transfer unit 60 are arranged for the image forming unit of each color arranged in the center of the image forming apparatus. Arranged at the top of the image forming apparatus.

  The image forming unit includes image carriers 10Y, 10M, 10C, and 10K, charging rollers 11Y, 11M, 11C, and 11K, and exposure units 12Y, 12M, 12C, and 12K (not shown). The exposure units 12Y, 12M, 12C, and 12K have an optical system such as a semiconductor laser, a polygon mirror, and an F-θ lens. The image bearing members 10Y, 10M, 10C, and 10K are provided by charging rollers 11Y, 11M, 11C, and 11K. Are uniformly charged and irradiated with laser light modulated based on the input image signal by the exposure units 12Y, 12M, 12C, and 12K, and on the charged image carriers 10Y, 10M, 10C, and 10K. An electrostatic latent image is formed on the surface.

  The developing units 30Y, 30M, 30C, and 30K generally include liquid developers of respective colors including the developing rollers 20Y, 20M, 20C, and 20K, yellow (Y), magenta (M), cyan (C), and black (K). Developer containers (reservoirs) 31Y, 31M, 31C, 31K to be stored, and developer supply rollers for supplying liquid developers of these colors from the developer containers 31Y, 31M, 31C, 31K to the developing rollers 20Y, 20M, 20C, 20K 32Y, 32M, 32C, 32K and the like, and the electrostatic latent images formed on the image carriers 10Y, 10M, 10C, and 10K are developed with liquid developers of respective colors.

  The intermediate transfer belt 40 is an endless elastic belt member, is wound around a driving roller 41 and a tension roller 42, and is stretched between the image transfer members 10Y, 10M, and 50K at the primary transfer portions 50Y, 50M, 50C, and 50K. It is rotationally driven by the drive roller 41 while abutting 10C and 10K. The primary transfer sections 50Y, 50M, 50C, and 50K are arranged such that the primary transfer rollers 51Y, 51M, 51C, and 51K are opposed to each other with the image transfer bodies 10Y, 10M, 10C, and 10K interposed between the intermediate transfer belt 40 and the image transfer bodies 10Y, Using the contact position with 10M, 10C, and 10K as the transfer position, the developed toner images of the respective colors on the image carriers 10Y, 10M, 10C, and 10K are sequentially superimposed and transferred onto the intermediate transfer belt 40 to obtain a full color toner. Form an image.

  The toner images formed on the plurality of image carriers (photoconductors) 10 are sequentially transferred to the intermediate transfer belt 40 where the toner images are sequentially transferred onto the sheet material, and then transferred onto the sheet material. In transferring the toner image to the sheet material in the process, even if the sheet material surface is not smooth due to the fiber, etc., as a means for improving the secondary transfer characteristics following the non-smooth sheet material surface, A flexible elastic belt member is used.

The configuration of the intermediate transfer belt will be described with reference to FIG.
The intermediate transfer belt 40 has a base material layer 40a (eg, thickness) made of a polyimide material that has excellent bending durability and is less stretched by belt tension and has excellent heat resistance even when there is a heating step in the coating step of covering the elastic layer. 100 μm), urethane rubber (hardness JIS-A30 °), etc., elastic layer 40b (eg, thickness 200 μm) covering the surface of the base material layer 40a, coat layer 40C (eg, thickness 10 μm) made of fluororesin ), And an image is formed on the coat layer 40C by primary transfer. The width of the belt is 324 mm, and the volume resistance value of the belt is about log 10 Ωcm (resistance value of all layers).

  The secondary transfer unit 60 of FIG. 1 has a secondary transfer roller 61 disposed opposite to the belt drive roller 41 with the intermediate transfer belt 40 interposed therebetween, and further includes a secondary transfer roller cleaning blade 62 and a developer recovery unit 63. Is placed. In the secondary transfer unit 60, the sheet material conveyance path L is adjusted in accordance with the timing at which a full-color toner image or a single-color toner image formed by superimposing colors on the intermediate transfer belt 40 reaches the transfer position of the secondary transfer unit 60. Then, a sheet material such as paper, film or cloth is conveyed and supplied, and a single-color toner image or a full-color toner image is secondarily transferred to the sheet material. A fixing unit (not shown) is disposed in front of the sheet material conveyance path L, and a single color toner image or a full color toner image transferred onto the sheet material is fused and fixed to a recording medium (sheet material) such as paper. Image formation on the final sheet material is completed. Even if the surface of the secondary transfer roller 61 is a sheet material that is not smooth due to fiber or the like, the surface is coated with an elastic body as a means for improving the secondary transfer characteristics following the non-smooth sheet material surface. It is composed of rollers. This is an elastic belt employed in the intermediate transfer belt 40 that sequentially transfers the toner images formed on the plurality of image carriers 10 in order to be superimposed and supported on the intermediate transfer belt 40, and then collectively transferred to a sheet material. The purpose is the same as that of the member. The developer (carrier oil and solid content) remaining on the intermediate transfer belt after the secondary transfer is removed by the cleaning blade 42Y disposed opposite to the tension roller 42, and is stored in the collection container 43Y.

  Next, the image forming unit and the developing unit will be described. FIG. 3 is a cross-sectional view showing main components of the image forming unit and the developing unit. Since the configurations of the image forming unit and the developing unit for each color are the same, the following description will be made based on the yellow (Y) image forming unit and the developing unit.

  The image forming unit includes a cleaning device including a latent image eraser 16Y, an image carrier cleaning blade 17Y, and a developer recovery unit 18Y along the rotation direction of the outer periphery of the image carrier 10Y, a charging roller 11Y, an exposure unit 12Y, and a development unit. A cleaning device including a developing roller 20Y of 30Y, an image carrier squeeze roller 13Y, an image carrier squeeze roller cleaning blade 14Y, and a developer recovery unit 15Y, which are associated with the development roller 20Y, is provided. The developing unit 30Y has a cleaning roller 25Y, a cleaning blade 26Y and an oil application roller 27Y, a developer supply roller 32Y using an anilox roller, a cleaning blade 33Y, a compression roller 22Y, and a cleaning thereof on the outer periphery of the developing roller 20Y. The blade 23 is disposed, and a liquid developer stirring roller 34Y and a developer supply roller 32Y are accommodated in the liquid developer container 31Y.

  A primary transfer roller 51Y of the primary transfer portion is disposed along the intermediate transfer belt 40 at a position facing the image carrier 10Y, and an intermediate transfer belt squeeze roller 53Y, a backup roller 54Y, an intermediate transfer belt are disposed downstream of the moving direction. An intermediate transfer belt squeeze device 52Y including a belt squeeze roller cleaning blade 55Y and a developer recovery unit 56Y is disposed.

FIG. 4 is a diagram illustrating the squeeze device 52Y.
The squeeze device 52Y is provided between the colors of the intermediate transfer belt, and the squeeze roller 53Y is for removing the carrier liquid contained in the liquid developer on the intermediate transfer belt 40, and rotates at the same speed as the intermediate transfer belt. is doing. The squeeze roller 53Y is configured by winding a PFA tube 20 μm around a surface layer of urethane rubber (hardness JIS-A 30 °) having a thickness of 2 mm (outside diameter φ14 mm) on a φ10 mm metal shaft, and has a roller width of 307 mm. A squeeze backup roller 54Y (φ10 mm metal shaft) is disposed opposite to the intermediate transfer belt 40 and is in contact with the intermediate transfer belt at a linear pressure of about 50 gf / cm. The actual resistance value of the roller is about Log4Ω, and a bias voltage of +150 V is applied between the squeeze roller 53Y and the squeeze backup roller 54Y so that the solid content in the developer is not removed. The squeeze roller 54Y is cleaned by contact with a cleaning blade 55Y made of urethane rubber (hardness JIS-A 70 °). With these configurations, the carrier liquid of the liquid developer is squeezed out on the intermediate transfer belt 40 and stored in the developer recovery unit 56Y.

  The image carrier 10Y is a photosensitive drum made of a cylindrical member having a width wider than about 320 mm of the developing roller 20Y and having a photosensitive layer formed on the outer peripheral surface thereof. For example, the image carrier 10Y rotates in a clockwise direction as shown in FIG. To do. The photosensitive layer of the image carrier 10Y is composed of an organic image carrier or an amorphous silicon image carrier. The charging roller 11Y is disposed upstream of the nip portion between the image carrier 10Y and the developing roller 20Y in the rotation direction of the image carrier 10Y, and a bias having the same polarity as the charging polarity of the developing toner particles is applied from a power supply device (not shown). Then, the image carrier 10Y is charged. The exposure unit 12Y irradiates laser light onto the image carrier 10Y charged by the charging roller 11Y on the downstream side in the rotation direction of the image carrier 10Y with respect to the charging roller 11Y, thereby forming a latent image on the image carrier 10Y. To do.

  The developing unit 30Y includes a compression roller 22Y, a developer container 31Y that stores a liquid developer in which toner is dispersed in a carrier liquid in an approximate weight ratio of about 25%, a developing roller 20Y that carries the liquid developer, and a liquid developer. The developer supply roller 32Y, the regulating blade 33Y, the stirring roller 34Y, and the liquid developer carried on the developing roller 20Y for compressing (forming a film) are maintained in a uniform dispersed state by stirring the developer and supplying the developer to the developing roller 20Y. ) Having a compression roller 22Y to be in a state, a cleaning roller 25Y for cleaning the developing roller 20Y, a cleaning blade 26Y, and an oil application roller 27Y for applying cleaning oil.

  The liquid developer accommodated in the developer container 31Y is a low concentration (about 1 to 2 wt%) and low viscosity, which is conventionally used, using Isopar (trademark: Exxon) as a carrier liquid. It is not a volatile liquid developer having volatility, but a non-volatile liquid developer having a high concentration and high viscosity and having non-volatility at room temperature. That is, in the liquid developer in the present invention, a solid having an average particle diameter of 1 μm in which a colorant such as a pigment is dispersed in a thermoplastic resin is introduced into a liquid solvent such as an organic solvent, silicon oil, mineral oil, or edible oil. It is a liquid developer having a high viscosity (about 30 to 10,000 mPa · s) which is added together with a dispersant and has a toner solid content concentration of about 25%.

  The developer supply roller 32Y is a cylindrical member that rotates in a clockwise direction as shown in FIG. 3, for example, and is unevenly formed by a spiral groove that is finely and uniformly so as to easily carry the developer on the surface. An anilox roller having a surface formed on the surface. The groove dimensions are such that the groove pitch is about 130 μm and the groove depth is about 30 μm. The developer supply roller 32Y supplies the liquid developer from the developer container 31Y to the developing roller 20Y. The stirring roller 34Y and the developer supply roller 32Y may be in sliding contact with each other, but may be arranged in a distant relationship.

  The regulating blade 33Y is composed of an elastic blade whose surface is covered with an elastic body, a rubber portion made of urethane rubber or the like that contacts the surface of the developer supply roller 32Y, and a metal plate or the like that supports the rubber portion. The Then, the film thickness and amount of the liquid developer carried and conveyed by the developer supply roller 32Y composed of an anilox roller are regulated and adjusted, and the amount of liquid developer supplied to the developing roller 20Y is adjusted. The rotation direction of the developer supply roller 32Y may be the opposite direction instead of the arrow direction shown in FIG. 3, and the regulating blade 33Y at that time requires an arrangement corresponding to the rotation direction.

  The developing roller 20Y is formed of a cylindrical member having a diameter of 24 mm, a core metal diameter of 15 mm, and a width of about 320 mm, and rotates counterclockwise around the rotation axis as shown in FIG. The developing roller 20Y is configured by providing JIS-A 30 ° urethane on the outer peripheral portion of an inner core made of metal such as iron and JIS-A 85 ° high-hardness urethane, fluororesin, or acrylic resin on the surface layer.

  Returning to FIG. 1, carrier oil is supplied from the carrier cartridges 1Y, 1M, 1C, and 1K to the developer containers 31Y, 31M, 31C, and 31K, and the developer is supplied from the developer cartridges 2Y, 2M, 2C, and 2K, respectively. Is done. On the other hand, the developer (mainly carrier liquid) squeezed by the squeeze rollers 13Y, 13M, 13C and 13K of each color image carrier, and the developer (mainly squeezed by the intermediate transfer belt squeeze devices 52Y, 52M, 52C and 52K). The carrier liquid) and the developer scraped off by the intermediate transfer belt cleaning blade 42Y are transported to the filter 5 through the developer transport path 3 by the pump action, and are collected by the secondary transfer roller cleaning blade 62 to collect the developer. The developer (mainly carrier liquid) and paper dust accumulated in the section 63 are also transported to the filter 5 through the developer transport path by a pump action. The carrier liquid from which solid content and paper dust are removed by the filter 5 so as not to cause the color mixing phenomenon is pooled in the carrier buffer tank 6 and supplied to the developer containers 31Y, 31M, 31C, and 31K through the carrier conveyance path 4. Yes. Of course, it may be supplied to each carrier cartridge.

  In the present invention, the cleaning roller 25 is disposed on the downstream side in the rotation direction from the developing nip portion of the developing roller 20, and the sponge roller 27Y as an oil application member is disposed in contact with the cleaning roller 25 to provide oil for cleaning. The developer (carrier liquid and solid content) adhering to the surface of the developing roller after passing through the developing nip is easily removed, and this embodiment will be described below.

FIG. 5 is a diagram illustrating a first embodiment in which a sponge roller is used as the oil application member.
Of the deposits (liquid developer) remaining on the developing roller 20 after passing through the developing nip, the deposits in the non-image area are given film adhesion from the compression roller 22 and then give an electric adhesion force from the photosensitive member. Therefore, if a conventional cleaning blade is used, it will slip through it. Accordingly, the sponge roller 26 applies oil to the cleaning roller 25, and the cleaning roller 25 cleans the developing roller surface while applying oil to the developing roller surface.

FIG. 6 is a diagram for explaining a cleaning mechanism by oil application.
FIG. 6A shows a state in which the oil applied from the sponge roller 26 is applied to the surface of the developing roller by the cleaning roller 25. The gap at the developing roller surface roughness level is filled with oil, and the remaining solid content of the development is It shows a state immersed in oil. FIG. 6B shows a state in which the solid content is lowered by the applied oil. In such a state, a developer concentration gradient is generated. As shown in FIG. The dispersion (relaxation) of the minute occurs, the solid content separated from the developing roller increases, and the adhering matter can be easily cleaned. Although not shown in the drawing, it is possible to perform more reliable cleaning by applying an appropriate bias voltage between the cleaning roller and the developing roller and peeling off the solid content from the developing roller surface by applying an electric force. Become.

  The sponge roller 27 as an oil application member is configured by winding a urethane sponge (Asker A hardness 40 °) having a thickness of 5 mm (outer diameter φ20 m) around a metal shaft φ10 mm. The sponge roller has the same rotational speed as the developing roller 20, and the rotational direction is rotating. However, it is not limited to this. The sponge roller and developing roller are brought into contact with a total load of 1 kgf (linear pressure is 333 gf / cm).

  The cleaning roller 25 has a diameter of 25 mm, a core metal of 20 mm, a 2.5 mm hardness urethane rubber with a hardness of JIS-A 30 ° is wound around the core metal, and a urethane coating of about 100 μm and 85 degrees is applied. The cleaning roller 25 is driven in the follower direction at the same speed as the developing roller 20. By setting the resistance value of the cleaning roller to, for example, Log 4Ω and applying a bias voltage between the cleaning roller and the developing roller, the belt can be satisfactorily cleaned by attracting the charged solid content in the applied liquid.

  The blade 26 for cleaning the cleaning roller 25 is made by bringing a blade having a hardness of JIS-A 90 ° (thickness 2 mm, free length 6.5 mm) into contact with the roller rotation direction in the counter direction. Since the counter has a high hardness, the cleaning roller can be subjected to blade cleaning. The contact angle is not particularly limited, but good cleaning can be obtained when contact is made at 30 ° with a total load of 1 kgf.

FIG. 7 is a view showing a second embodiment in which oil collected by supplying the recovered liquid from the compression roller to the sponge roller is applied.
In this embodiment, the developer (mainly carrier oil) collected from the compression roller 22 by the cleaning blade 23 and stored in the collection container 24 is supplied to the sponge roller 27 by the pump through the conveyance path 28 and applied to the developing roller 20. Except for this, it is the same as the first embodiment. The main component of the liquid recovered from the compression roller 22 is carrier oil, and since it has a low viscosity, it is easy to remove deposits on the developing roller. Further, since the recovered liquid of the compression roller 22 is reused for the developing roller of the same color, it can be used effectively without causing color mixing.

FIG. 8 is a view showing a third embodiment in which the liquid recovered from the photoreceptor is supplied to the sponge roller and applied with oil.
In this embodiment, the developer (mainly carrier oil) squeezed by the squeeze roller 13 and collected in the collection container 16 by the cleaning blade 15 is supplied to the sponge roller 27 through the conveyance path 29, and is supplied through the conveyance path 29. May be performed using a pump or using gravity. Also in this embodiment, since the liquid collected by the squeeze roller 13 is reused for the developing roller of the same color, it can be used effectively without causing color mixing.

FIG. 9 is a diagram illustrating the configuration of an oil application roller as an oil application member.
The oil application roller 27 has a crown shape in which the diameter Dc at the center is larger than the diameter Ds at the end, and the width of the roller is smaller than the width of the belt (for example, the roller width is 310 mm, the belt width is 324 mm). By adopting such a configuration, the roller and the belt can be bent easily and can be contacted even in the central part that is difficult to contact, the application at the central part is good, and the applied liquid is prevented from dripping from the end part. be able to.

  According to the present invention, the liquid developer adhered on the elastic developing roller can be reliably cleaned, and thus the industrial utility value is great.

1 is a diagram illustrating an overall configuration of an image forming apparatus of the present invention. FIG. 4 is a diagram illustrating a configuration of an intermediate transfer belt. FIG. 3 is a diagram illustrating main components of an image forming unit and a developing unit. FIG. 6 is a diagram illustrating an intermediate transfer belt squeeze device. It is a figure explaining 1st Embodiment. It is a figure explaining a cleaning mechanism. It is a figure explaining 2nd Embodiment. It is a figure explaining 3rd Embodiment. It is a figure explaining an oil application roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Photoconductor, 20 ... Developing roller, 22 ... Compression roller, 25 ... Cleaning roller, 27 ... Sponge roller.

Claims (4)

In a developing device for liquid development in which a compression member is disposed with respect to an elastic developing roller that develops a latent image formed on an image carrier, a cleaning roller is disposed downstream of the developing nip portion in the rotation direction of the developing roller. And a developing device provided with an oil applying member that contacts the cleaning roller and applies oil. The developing device according to claim 1, wherein the compression member includes a roller, and the recovered liquid is supplied to the oil application member. 2. The developing device according to claim 1, wherein a squeeze member is disposed on the image carrier, and a liquid recovered from the squeeze member is supplied to the oil application member. The developing device according to claim 1, wherein the oil application member includes a crown-shaped roller having a diameter at a center portion larger than a diameter at an end portion.

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