JP2008033273A - Polishing roller for liquid developing electrophotographic apparatus and liquid developing electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of photoreceptor performance of a liquid development electrophotographic device. <P>SOLUTION: A polishing roller for the liquid development electrophotographic device is used for surface polishing of a photoreceptor by providing the liquid development electrophotographic device and has an elastic body layer on the outer periphery of a shaft body and an abrasive material on at least an outer peripheral face. The elastic body layer is formed to use polyurethane yielded by reacting polyester polyol and two-functional isocyanate. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polishing roller for a liquid developing electrophotographic apparatus and a liquid developing electrophotographic apparatus provided with the polishing roller for a liquid developing electrophotographic apparatus.

  2. Description of the Related Art Conventionally, an electrophotographic apparatus has been widely used in which an electrostatic latent image drawn on a photosensitive member with a laser or the like is visualized with toner or the like and transferred to a surface of paper or the like for printing. In recent years, the toner particles have been refined to improve printing accuracy, and have been refined to a liquid called a carrier such as liquid paraffin, silicone oil, mineral oil, or vegetable oil, for example, to about 1 μm. A liquid developer (also referred to as a liquid toner) in which toner particles are dispersed has been used. In addition, a liquid developing electrophotographic apparatus using the liquid toner (see Patent Documents 1 and 2 below) has been used.

By the way, in a dry type electrophotographic apparatus, cleaning is performed by a cleaning blade after toner is transferred from a photosensitive member to a transfer roller, and this blade simply removes toner remaining on the surface of the photosensitive member. In addition, the surface of the photoreceptor is slightly polished to maintain the surface of the photoreceptor in a clean state.
In the liquid developing electrophotographic apparatus, the photosensitive member is usually cleaned with a blade. However, in the liquid developing electrophotographic apparatus, a liquid such as a carrier adheres to the photosensitive member. The friction force between the photosensitive member and the surface of the photosensitive member is reduced by the liquid adhering to the surface of the photosensitive member, and the surface of the photosensitive member is not sufficiently removed. There is a problem that the performance deteriorates.

  Further, in this liquid developing electrophotographic apparatus, each component is used in an environment exposed to a carrier. For example, when a metal blade coated with a resin is used as a cleaning blade, a resin is used. There is also a possibility that the layer is swollen by the carrier and the contact state between the cleaning blade and the photosensitive member is changed.

JP 2003-057913 A JP-A-2005-070181

  An object of the present invention is to suppress a decrease in the photoreceptor performance of a liquid developing electrophotographic apparatus.

The present inventors have found that a roller having a predetermined configuration is useful as a polishing roller for a liquid developing electrophotographic apparatus for polishing a photoreceptor of the liquid developing electrophotographic apparatus, and completed the present invention. It was.
That is, the present invention is provided in a liquid developing electrophotographic apparatus to be used for surface polishing of a photoreceptor, in order to solve the above problems, and an elastic body layer is provided on the outer periphery of the shaft body and at least the outer peripheral surface is polished. A polishing roller for a liquid developing electrophotographic apparatus is provided, wherein the elastic body layer is formed using polyurethane obtained by reacting a polyester polyol and a bifunctional isocyanate.

In the cleaning blade, it is difficult to set the relative speed between the cleaning blade and the surface of the photosensitive member to a speed other than the rotational speed of the photosensitive member. Is easily reflected on the surface state of the photoreceptor. Since the polishing roller for a liquid developing electrophotographic apparatus provided with an abrasive on the outer peripheral surface can be rotated and used, it can be set to a desired sliding speed with respect to the photosensitive member, and the outer peripheral surface can be applied uniformly to the photosensitive member. Can be touched.
In addition, the polishing roller for a liquid developing electrophotographic apparatus is provided with an elastic layer around the outer periphery of the shaft, and it is easy to adjust the contact width on the surface of the photosensitive member.
Further, in this polishing roller for liquid developing electrophotographic apparatus, this elastic layer is formed of polyurethane obtained by reacting polyester polyol and bifunctional isocyanate, and polyurethane obtained by reacting this polyester polyol and bifunctional isocyanate is In general, liquid paraffin, silicon oil, mineral oil, vegetable oil, etc. are not easily swollen by a substance used as a carrier of a liquid developing electrophotographic apparatus and hardly change in volume. Variation in the polishing conditions) is suppressed.
That is, according to the present invention, it is easy to adjust the polishing conditions of the photoconductor and it is easy to prevent the formation of an oxide film on the photoconductor, so that it is possible to suppress the deterioration of the photoconductor performance.

  Hereinafter, preferred embodiments of the present invention will be described (based on the accompanying drawings).

  First, a liquid developing electrophotographic apparatus using a polishing roller for a liquid developing electrophotographic apparatus according to this embodiment will be described with reference to FIG.

In the liquid developing electrophotographic apparatus of this embodiment, a photoreceptor and various rollers are used. That is, the photosensitive member 1 is formed in a cylindrical shape, rotates around the central axis of the cylindrical shape, and a visible image is continuously formed on the outer peripheral surface by liquid toner, and the peripheral surface is brought into contact with the photosensitive member 1. An intermediate transfer roller 2 that primarily transfers a visible image formed on the photosensitive member 1 and secondarily transfers it to a printing material A such as paper, and the intermediate transfer roller 2 and the intermediate transfer roller 2 that are arranged with their peripheral surfaces in contact with each other. By rotating, the printed material A such as paper is pressed against the intermediate transfer roller 2 while the printed material A is moved in the rotation direction of the intermediate transfer roller 2, and the visible image primarily transferred to the intermediate transfer roller 2 is transferred to the printed material. A pressure roller 3 or the like for secondary transfer to A is provided.
Further, in the liquid developing electrophotographic apparatus, the liquid toner Y accommodated in the liquid toner storing portion X is brought into contact with the outer peripheral surface, and the liquid toner is attached to the outer peripheral surface by rotating to form a liquid film. A toner pumping roller 4 (also referred to as an anilox roller) for pumping toner and a liquid toner adhering to the outer peripheral surface of the toner pumping roller 4 disposed in contact with the peripheral surface of the toner pumping roller 4 are smoothed. A leveling roller 5 for transferring to the outer peripheral surface and a developing roller 6 for transferring the liquid toner from the leveling roller 5 to be supplied to the photoreceptor 1 are arranged. It is provided.
Further, in the liquid developing electrophotographic apparatus, a bias voltage is applied to the developing roller 6 and an electric charge is applied, and the liquid toner supplied from the leveling roller 5 is separated into a carrier layer and a toner aggregation layer in the developing roller 6. A squeeze roller 8 for squeezing the carrier of the liquid toner supplied from the roller 7 and the developing roller 6 to the photoconductor 1, a cleaning blade 10 for cleaning the surface of the developing roller 6, and the surface of the photoconductor For example, a cleaning blade 10 ′ for cleaning is provided.
Further, in the liquid developing electrophotographic apparatus of the present embodiment, the polishing roller 9 (liquid) that contacts the photoconductor 1 and keeps the surface of the photoconductor 1 clean on the downstream side of the cleaning blade 10 ′ in the photoconductor rotation direction. A developing roller for a developing electrophotographic apparatus).

This polishing roller is composed of a cored bar serving as a shaft body and an elastic layer formed of an elastic body on the outer periphery of the cored bar, and the elastic layer is in a state of being provided around the outermost surface side. Yes.
This elastic body layer is formed of polyurethane obtained by reacting polyester polyol and difunctional isocyanate. In this polyurethane, an abrasive is blended, and the elastic layer is formed so that the JIS-A hardness is 40 to 70 degrees, and the blended abrasive is bare on the outer peripheral surface. Provided on the roller surface.
This elastic layer has a JIS-A hardness of 40 to 70 degrees. If it is less than 40 degrees, it is too soft to provide sufficient polishing performance for the photoreceptor, and 70 degrees In the case of exceeding, not only is it difficult to make contact with the photoreceptor with an appropriate contact width, but also the polishing performance becomes too high and the surface of the photoreceptor may be scraped too much.
Therefore, by forming an elastic body layer having a JIS-A hardness of 40 to 70 degrees on this polishing roller, polishing performance suitable for the polishing roller for a liquid developing electrophotographic apparatus can be imparted.
In addition, this JIS-A hardness intends the type A durometer hardness (instantaneous value) prescribed | regulated to JISK6253 measured in the standard state.

The polishing agent used for this polishing roller is not particularly limited, but it is elastic by mixing powders such as alumina, silica, chromium oxide, zirconium oxide, cerium oxide, iron oxide, and diamond alone or by mixing a plurality of these powders. It can mix | blend and use so that content in a body layer may be 0.5-30 weight%, for example.
The blending amount of the abrasive is 0.5 to 30% by weight. When the blending amount of the abrasive is less than 0.5% by weight, it is difficult to impart sufficient polishing performance to the photoreceptor. In the case where it exceeds 30% by weight, the polishing performance becomes too high and the surface of the photoreceptor may be scraped too much. Moreover, even if it is attempted to add abrasives in an amount exceeding 30% by weight, the viscosity of the mixture of polyurethane and abrasive becomes too high to form a uniform dispersed state, and handling in the manufacturing process is reduced. For example, cast molding becomes difficult.
Accordingly, by adding 0.5 to 30% by weight of an abrasive to the elastic layer of the polishing roller, it is possible to provide a polishing performance suitable for a polishing roller for a liquid developing electrophotographic apparatus and to make the polishing roller easy to manufacture. Can do.
Moreover, as an average particle diameter of this abrasive | polishing agent, a 0.5-2.5 micrometer thing can be used normally. The average particle diameter can be measured by obtaining a 50% value of a cumulative particle size distribution curve obtained by a laser diffraction method or the like.
Among the above abrasives, cerium oxide is preferable in that it exhibits superior polishing efficiency as compared with iron oxide, zirconium oxide, and the like.

  Polyester polyol is used for the polyurethane, and when other polyol is used, it is easily swelled with a substance generally used as a carrier such as liquid paraffin, silicone oil, mineral oil, or vegetable oil. This is because the volume change of the layer (polishing roller) exceeds 10%, for example, and the polishing state of the surface of the photoreceptor is changed by the volume change of the polishing roller.

The polyester polyol is not particularly limited, but a polyester polyol obtained by reacting adipic acid, bifunctional glycol and trimethylolpropane is preferably used.
As a raw material component of this polyester polyol, adipic acid is used when the adipic acid is used compared to the case where other dicarboxylic acids such as sebacic acid are used. Volume change can be further reduced.
Moreover, as bifunctional glycol, a C2-C6 thing is preferable and it is preferable that they are either diethylene glycol, 1, 4- butanediol, or 3-methylpentanediol.
When the bifunctional glycol has 2 to 6 carbon atoms, particularly diethylene glycol, 1,4-butanediol, or 3-methylpentanediol, the volume of the elastic layer is further changed by the carrier. It can be made smaller.

The difunctional isocyanate is not particularly limited, but any of tolylene diisocyanate (TDI), xylene diisocyanate (XDI) or diphenylmethane diisocyanate (MDI) is preferably used, and in particular tolylene diisocyanate or xylene diisocyanate. It is preferable that it is either.
By using tolylene diisocyanate or xylene diisocyanate as the difunctional isocyanate, the volume change of the elastic layer due to the carrier can be further reduced.
Moreover, by using tolylene diisocyanate or xylene diisocyanate, the curing reaction with the polyester polyol can be carried out at a higher reaction rate than when diphenylmethane diisocyanate is used. Therefore, it can be set as the grinding | polishing roller which can be manufactured efficiently by using tolylene diisocyanate or xylene diisocyanate.

  The compounding quantity of these polyester polyols and bifunctional glycol can be adjusted suitably, and can be mix | blended in the quantity which can be made into the hardening state which can be substantially used as a grinding | polishing roller. For example, a polyester polyol obtained by reacting adipic acid, a bifunctional glycol, and trimethylolpropane, tolylene diisocyanate or xylene diisocyanate, and an abrasive so that the hardness after curing is JIS-A hardness 40 to 70 degrees. It can mix | blend and an elastic body layer can be formed.

Further, as the shaft body of the polishing roller, a conductive bar-like body, specifically, a metal core having a circular cross section and a hollow or solid metal bar-like body can be used.
For this core metal, for example, a metal made of a metal such as copper, iron, aluminum, nickel or an alloy thereof, or a metal plated by means such as hot dipping, electrolytic plating or electroless plating is used. More specifically, it is possible to use a stainless steel that is excellent in strength and durability and subjected to electroless nickel plating in order to further improve the adhesion.

In addition, in the above, the case where the polishing roller is formed only of the elastic body layer in which the core metal and the abrasive are dispersed is illustrated, but a surface layer in which the abrasive is further dispersed may be provided on the outer peripheral side of the elastic body layer. Is possible.
In the case of providing a surface layer in which this abrasive is dispersed, it is also possible to adopt a configuration in which no abrasive is contained in the elastic layer.
Further, the polishing roller can be formed with another layer between the elastic layer and the shaft (core metal).

  The above surface layer can be formed, for example, by dissolving a thermoplastic polyurethane in a solvent and using a polyurethane solution in which an abrasive is dispersed.

  As a method for producing a polishing roller having such a material and configuration, a generally used method for producing a roller made of polyurethane can be used. After the body is provided around, the surface of the elastic layer may be polished and adjusted to a predetermined surface smoothness. Further, when the surface layer as described above is provided, a method of directly applying and heat-treating the surface of the elastic layer by dip-coating the polyurethane solution for forming the surface layer as described above is used. be able to.

  When the above-described polishing roller is used in a liquid developing electrophotographic apparatus, the surface of the photoconductor is polished by contacting the photoconductor while rotating the photoconductor at a peripheral speed difference of 1% or more. However, it is preferable in that the surface of the photoconductor can be surely cleaned, and in particular, by rotating the photoconductor and the polishing roller in the same direction and bringing them into contact with each other, the surfaces are moved in the opposite directions to perform polishing. Is preferred.

  In the present embodiment, the polishing roller configured as described above and used as described above has been described as an example. However, the polishing roller for a liquid developing electrophotographic apparatus of the present invention is limited to those exemplified above. It is not what is done.

EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.
(Consideration of polyurethane elastic body)
(Formulation Examples 1-39)
Polyurethane elastic body samples were prepared by blending the polyols and isocyanates listed in Table 1 so as to have the hardness shown in Table 1 after curing.
The hardness shown in Table 1 is a type A durometer hardness (JIS-A hardness) defined in JIS K 6253 measured in a standard state.
The prepared polyurethane elastic body was cut into a width 30 mm × length 30 mm × thickness 2 mm to prepare a cuboid sample, and the prepared cuboid sample was a hydrocarbon carrier mainly composed of isoparaffin (manufactured by Exxonmobile, A product name “IsoparM”) was immersed for a total of 7 days, and how the volume of each sample changed with the number of days of immersion was measured.
In addition, the temperature of “IsoparM” to be dipped is tested at 23 ° C. and 40 ° C., and the volume change rate is measured with a caliper, and the thickness is measured according to JIS K 6253. The increase relative to the initial volume was expressed as a percentage, measured according to the method described.
Table 1 shows the results of the volume change rate of the immersion test (after 7 days of immersion) at 23 ° C. and 40 ° C. for each formulation example.
Table 2 shows the measurement results of the volume change rate after 0.5, 1, 2, 3, 5, and 7 days after immersion for the polyurethane elastic body samples of Formulation Examples 1, 28, 34, 38, and 39.

From Tables 1 and 2 above, it can be seen that polyurethanes obtained by reacting polyester polyols and difunctional isocyanates are less likely to swell and hardly undergo volume change with respect to substances generally used as carriers such as liquid paraffin.
In addition, as the polyester polyol, adipic acid is used because the volume change is small compared to the case where other dicarboxylic acids such as sebacic acid are used, and the bifunctional glycol has 2 to 6 carbon atoms. In particular, when diethylene glycol, 1,4-butanediol, or 3-methylpentanediol is used, volume change is less likely to occur than when other bifunctional glycols are used. I understand that.
Furthermore, by using tolylene diisocyanate (TDI) or xylene diisocyanate (XDI) as the bifunctional isocyanate to be reacted with this polyester polyol, the volume change of the elastic layer due to the carrier can be made as compared with the case of using diphenylmethane diisocyanate (MDI) or the like. It can also be seen that it can be made smaller.

(Example 1)
Using the polyurethane shown in Table 3, an elastic body layer having a thickness of about 3 mm is provided on a core metal having a diameter of 10 mm, and surface polishing is performed so that the outer diameter is about 16 mm. did.
More specifically, a polyester polyol mixed with cerium oxide is dehydrated, heated to 100 ° C., added with TDI (tolylene diisocyanate), and stirred to obtain a uniform mixed state. The elastic body layer was provided around the outer periphery of the cored bar by injecting it into a 150 ° C. mold set with and reacting for 1 hour. After the reaction at 150 ° C. × 1 hour, the mold was removed and post-crosslinking was performed at 140 ° C. × 2 hours to prepare a preform.
The surface of this preform was polished with a cylindrical grinder to a predetermined size, and the polishing roller of Example 1 was produced.

(Example 2, Comparative Examples 1 and 2, Reference Example 1)
A polishing roller was produced in the same manner as in Example 1 except that the blending of polyurethane was changed.
As a reference example, a roller provided with an elastic body layer made of only polyurethane without blending cerium oxide was prepared.

(Carrier resistance evaluation 1)
(Polyurethane elastic sample carrier immersion test)
Using the same formulation as each example and comparative example, reacting at the same temperature as each example and comparative example to prepare a sample for evaluating carrier resistance, as in the above-mentioned “examination of blending polyurethane elastomer” The volume change rate was measured.
That is, a polyurethane elastic body sample having a width of 30 mm, a length of 30 mm, and a thickness of 2 mm was prepared according to the formulation shown in Table 3.
The produced polyurethane elastic body is immersed in a hydrocarbon carrier mainly composed of isoparaffin (product name “IsoparM” manufactured by ExxonMobil Corporation) for a total of 7 days, and how the volume of each sample changes with the number of immersion days. It was measured.
The temperature of “IsoparM” to be dipped is tested at 23 ° C. and 40 ° C., and the volume change rate is measured with a caliper, and the thickness is described in JIS K 6253. The increase relative to the initial volume was expressed as a percentage.
The results are shown in Table 4.

(Carrier resistance evaluation 2)
(Roller rotation test by carrier immersion)
Formed on the surface of the polishing roller with rotation in a state where the polishing roller of each example, comparative example and reference example is horizontally supported and the lower half is immersed in a liquid toner (about 30 ° C.) using isoparaffin as a carrier. A carrier resistance test was performed in which the liquid film of the liquid toner was rotated at a rotational speed of about 40 rpm while being scraped off with a blade.
At this time, the hardness of the polishing roller (JIS-A hardness) and the change in the outer diameter of the roller were measured.
Specifically, for the polishing rollers of Examples 1 and 2 and Reference Example 1, the values in the initial state and the values after 7 days of the carrier resistance test were measured.
About the grinding | polishing roller of the comparative examples 1 and 2, swelling (volume change) was large and the outer diameter change was not able to be measured. Regarding the hardness of the polishing roller of Comparative Example 1, the value of the carrier resistance test 4 days was measured, and for the polishing roller of Comparative Example 2, the value of the carrier resistance test 2 days was measured.
The results are shown in Table 5.

(Photoconductor polishing performance evaluation)
As shown in FIG. 2, the photoconductor (φ30 mm) was polished by a polishing roller (φ16 mm).
In this photoconductor polishing, after a liquid developer carrier is dropped on the surface of the photoconductor, it is removed by a cleaning blade, a polishing roller is brought into contact with the photoconductor after being cleaned by this cleaning blade, By rotating the polishing roller in the same direction as the photosensitive member, the photosensitive member and the polishing roller were rotated so that the outer peripheral surfaces thereof moved in opposite directions to polish the photosensitive member.
Further, the surface of the photoreceptor polished by the polishing roller was charged with a Colontron charger.
The photosensitive member and the polishing roller were driven using a motor and a gear. The photosensitive member was rotated at 60 rpm and the polishing roller was rotated at 40 rpm.
Further, a load of 750 gf was applied to each end of the shaft body toward the polishing roller toward the polishing roller so that the nip width of the polishing roller was about 1.2 mm.
Further, charging was performed by applying a voltage of 3 kV to the Colontron charger.

The photoconductor was polished for 12 hours, and the change in the thickness of the charge transport layer of the photoconductor before and after the polishing was measured with a film thickness measuring system “MPCD-3000” manufactured by Otsuka Electronics Co., Ltd.
Further, a toner cartridge (“HP Laser Jet 3500” manufactured by Hewlett-Packard) was attached to the photoconductor after polishing, and image evaluation was performed.
In the image evaluation, an image printed with an English character random pattern of 5% density / sheet was visually observed.
As a result, in the roller of Reference Example 1, the photoconductor is not polished, and so-called “image blur” (a phenomenon in which the outline of characters is blurred due to a decrease in resolution) is observed, which is considered to be due to the formation of an oxide film by a colontron charger. It was done.
On the other hand, in the polishing roller of Example 1, the photoreceptor was polished by 1.3 μm, and no deterioration of the image was observed.
In the polishing roller of Example 2, the photosensitive member is not polished, and unless the number of rotations of the polishing roller is increased or the load is increased to increase the nip width, the polishing roller of Example 1 is used. It has been found that it is difficult to suppress a decrease in the performance of the photoreceptor.
This also indicates that the blending amount of the abrasive is preferably 0.5% by weight or more.

1 is a schematic diagram showing the configuration of a liquid developing electrophotographic apparatus. Schematic which shows a photoconductor grinding | polishing performance evaluation test method.

Explanation of symbols

  1: photoconductor, 2: intermediate transfer roller, 3: pressure roller, 4: toner pumping roller (anilox roller), 5: leveling roller, 6: developing roller, 7: aggregating roller, 8: squeeze roller, 9 : Polishing roller, 10, 10 ': cleaning blade, A: substrate, X: liquid toner reservoir, Y: liquid toner

Claims (10)

  Provided in a liquid developing electrophotographic apparatus and used for surface polishing of a photoreceptor, an elastic body layer is provided on the outer periphery of a shaft body, and at least an outer peripheral surface is provided with an abrasive. A polishing roller for a liquid developing electrophotographic apparatus, wherein the polishing roller is formed using polyurethane obtained by reacting a polyol and a bifunctional isocyanate.   The polishing roller for a liquid developing electrophotographic apparatus according to claim 1, wherein either tolylene diisocyanate or xylene diisocyanate is used as the bifunctional isocyanate.   3. The polishing roller for a liquid developing electrophotographic apparatus according to claim 1, wherein the polyester polyol is obtained by reacting adipic acid, a bifunctional glycol, and trimethylolpropane.   The polishing roller for a liquid developing electrophotographic apparatus according to claim 3, wherein the bifunctional glycol has 2 to 6 carbon atoms.   The polishing roller for a liquid developing electrophotographic apparatus according to claim 4, wherein any one of diethylene glycol, 1,4-butanediol, or 3-methylpentanediol is used as the bifunctional glycol.   The liquid developing electron according to claim 1, wherein the abrasive is dispersed in an elastic body layer, and the elastic body layer is disposed on the outermost peripheral side, whereby the surface is provided with the abrasive. Polishing roller for photographic equipment.   The polishing roller for a liquid developing electrophotographic apparatus according to claim 1, wherein the abrasive is cerium oxide powder.   The abrasive is dispersed so that the proportion of the abrasive in the elastic layer is 0.5 to 30% by weight, and an elastic layer having a JIS-A hardness of 40 to 70 degrees is formed. 8. A polishing roller for a liquid developing electrophotographic apparatus according to 7.   A polishing roller for a liquid developing electrophotographic apparatus according to claim 1 is provided, and the polishing roller for liquid developing electrophotographic apparatus and a photosensitive member are brought into contact with each other while rotating at a peripheral speed difference of 1% or more. A liquid developing electrophotographic apparatus, wherein the polishing roller for liquid developing electrophotographic apparatus and the photosensitive member are arranged so that a surface of the photosensitive member can be polished by the polishing roller for liquid developing electrophotographic apparatus.   By bringing the photoconductor and the polishing roller for the liquid developing electrophotographic apparatus into contact with each other while rotating in the same direction, the photoconductor and the liquid developing are performed so that the surfaces are moved in the opposite directions and the polishing is performed. The liquid developing electrophotographic apparatus according to claim 9, wherein an electrophotographic polishing roller is disposed.

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