JP6515485B2 - Charging roll, charging device, process cartridge and image forming apparatus - Google Patents

Description

  The present invention relates to a charging roll, a charging device, a process cartridge, and an image forming apparatus.

  Methods for visualizing image information, such as electrophotography, are currently used in various fields. In electrophotography, an electrostatic charge image is formed as image information on the surface of an image carrier by charging and electrostatic charge image formation. Then, a toner image is formed on the surface of the image carrier with a developer containing toner, and after this toner image is transferred to a recording medium, the toner image is fixed to the recording medium. Through these steps, image information is visualized as an image.

  In electrophotographic imaging, for example, a charging roll is used to charge the image carrier. With respect to this charging roll, for example, a charging roll having a surface roughness Rz of the outermost layer of the roll of 2 to 15 μm (for example, Patent Document 1) is disclosed.

JP, 2010-096267, A

  The object of the present invention is to charge the member to be charged compared to the case where the skewness Rsk of the roughness curve of the surface of the charging roll satisfies 0 <Rsk or the common logarithm of the volume resistance of the charging roll is less than 7.65 Log Ω. An object of the present invention is to provide a charging roll that suppresses potential unevenness.

  The above-mentioned subject is solved by the following means.

< 1 >
A charging roll comprising: a cylindrical or cylindrical conductive base; and a conductive elastic layer provided on the outer peripheral surface of the conductive base,
The skewness Rsk of the surface roughness curve of the charging roll satisfies −0.6 <Rsk ≦ 0,
A charging roll in which a common logarithm value of a volume resistance value of the charging roll when a DC voltage of 100 V is applied is 7.65 LogΩ or more and 8.10 LogΩ or less.

< 2 >
The charging roll according to < 1 > , wherein the skewness Rsk of the roughness curve of the surface of the charging roll satisfies −0.5 <Rsk ≦ −0.1.

< 3 >
The charging device provided with the charging roll as described in < 1 > or < 2 > .

< 4 >
An image carrier,
The charging device according to < 3 > , which charges the surface of the image carrier
Equipped with
Process cartridge that is attached to and detached from the image forming apparatus.

< 5 >
An image carrier,
The charging device according to < 3 > , which charges the surface of the image carrier
An electrostatic charge image forming apparatus for forming an electrostatic charge image on the surface of the charged image carrier;
A developing device that contains an electrostatic charge image developer and develops the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer;
A transfer device for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
An image forming apparatus comprising:
< 6 >
The image formation according to < 5 > , wherein a voltage Vcln, which is a difference between the charging voltage of the surface of the image carrier after charging by the charging device and the developing voltage by the developing device, is 60 V or more and 90 V or less apparatus.

According to the invention related to < 1 > , the skewness Rsk of the roughness curve of the surface of the charging roll satisfies 0 <Rsk, or compared with the case where the common logarithm of the volume resistance of the charging roll is less than 7.65 Log Ω Provided is a charging roll that suppresses charging potential unevenness of a charging member.
According to the invention relating to < 2 > , the charging roll which suppresses the charging potential unevenness of the member to be charged is provided in comparison with the skewness Rsk of the roughness curve of the surface of the charging roll satisfying −0.1 <Rsk ≦ 0. Be done.

According to the invention concerning < 3 > , the skewness Rsk of the roughness curve of the surface of the charge roll satisfies 0 <Rsk, or the charge roll whose common logarithm value of the volume resistance value of the charge roll is less than 7.65 Log Ω is adopted A charging device is provided which suppresses the charging potential unevenness of the member to be charged, as compared with the case.

According to the invention concerning < 4 > , the skewness Rsk of the roughness curve of the surface of the charge roll satisfies 0 <Rsk, or the charge roll having a common logarithm value of the volume resistance value of the charge roll of less than 7.65 LogΩ As compared with the case, a process cartridge is provided which suppresses background fog caused by charging potential unevenness of the image carrier.

According to the invention concerning < 5 > , the skewness Rsk of the roughness curve of the surface of the charge roll satisfies 0 <Rsk, or the charge roll whose common logarithm value of the volume resistance value of the charge roll is less than 7.65 Log Ω is adopted An image forming apparatus is provided which suppresses background fogging caused by charging potential unevenness of an image carrier as compared with the case.
According to the invention concerning < 6 > , the skewness Rsk of the roughness curve of the surface of the charge roll satisfies 0 <Rsk, or the charge roll whose common logarithm value of the volume resistance value of the charge roll is less than 7.65 Log Ω is adopted As compared with the case, an image forming apparatus is provided which suppresses background fog caused by uneven charging potential of the image carrier even when the voltage Vcln is 90 V or less.

It is a schematic perspective view which shows the charging roll which concerns on this embodiment. It is a schematic sectional drawing of the charging roll which concerns on this embodiment. FIG. 2 is a schematic perspective view of the charging device according to the present embodiment. FIG. 1 is a schematic configuration view showing an image forming apparatus according to the present embodiment. It is a schematic block diagram which shows the process cartridge which concerns on this embodiment.

  Hereinafter, embodiments of the present invention will be described in detail.

[Charging roll]
FIG. 1 is a schematic perspective view showing the charging roll according to the present embodiment. FIG. 2 is a schematic cross-sectional view of the charging roll according to the present embodiment. 2 is a cross-sectional view taken along the line A-A of FIG.

As shown in FIGS. 1 and 2, the charging roll 121 according to the present embodiment includes, for example, a cylindrical or cylindrical conductive base material 30 (hereinafter referred to as “base material 30”), and a conductive base material 30. Conductive elastic layer 31 (hereinafter referred to as "elastic layer 31") provided on the outer peripheral surface of the conductive layer, and conductive surface layer 32 provided on the outer peripheral surface of the elastic layer 31 (hereinafter referred to as "surface layer 32" And the like. In addition, between the base material 30 and the elastic layer 31, for example, an adhesive layer (not shown) is provided.
The charging roll 121 is such that the skewness Rsk of the surface roughness curve of the charging roll satisfies −0.6 <Rsk ≦ 0, and the common logarithm value of the volume resistance of the charging roll when a DC voltage of 100 V is applied , 7.65 LogΩ or more and 8.10 LogΩ or less.

  However, in the charging roll 121 according to the present embodiment, the surface layer 32 may be a layer provided as needed, and the charging roll 121 may not have the surface layer 32. Further, the charging roll 121 is not limited to the above layer configuration, and for example, a configuration in which an intermediate layer is provided between the base 30 and the elastic layer 31, or a resistance adjusting layer or an elastic layer between the elastic layer 31 and the surface layer. The structure which provided the migration prevention layer may be sufficient.

In the present specification, conductivity means that the volume resistivity at 20 ° C. is less than 1 × 10 ¹³ Ωcm.

  The charging roll 121 according to the present embodiment suppresses the unevenness in the charging potential of the member to be charged by setting the skewness Rsk of the surface roughness curve in the above relationship and the common logarithm of the volume resistance value in the above range. Although the reason is not clear, it is considered as the following reason.

  First, it is known to take control of the arithmetic mean roughness Ra or the ten-point mean roughness Rz of the surface of the charging roll 121 as a means for suppressing the charging potential unevenness of the member to be charged by the charging roll 121. However, it has been found that the control of the arithmetic mean roughness Ra or the ten-point mean roughness Rz alone is insufficient to further suppress the charging potential unevenness of the member to be charged.

  Here, the skewness Rsk of the roughness curve is defined in JIS B 0601 (1982), and is an index (skewness) representing the symmetry of the peak and valley with respect to the average line of the roughness curve. When this Rsk is positive (Rsk> 0), it shows that the peak and the valley are unevenly distributed below the average line of the roughness curve. On the other hand, when this Rsk is negative (Rsk <0), the peaks and valleys are unevenly distributed above the mean line of the roughness curve.

  That is, in the case where Rsk is positive (Rsk> 0), on the surface of the charging roll, there are few peaks projecting to the roll outer peripheral surface side. As a result, charge is concentrated in a small peak area, which may cause abnormal discharge. Then, it is considered that this abnormal discharge causes discharge unevenness of the charging roll, resulting in uneven charging potential of the member to be charged.

  On the other hand, when Rsk is negative (Rsk <0), on the surface of the charging roll, there are many peaks projecting to the roll outer peripheral surface side. For this reason, it is considered that the concentration of charge on the peak portion is alleviated, and the occurrence of abnormal discharge is suppressed.

  In addition to this, it is considered that the occurrence of abnormal discharge itself is suppressed by controlling the common logarithm value of the volume resistance value of the charging roll 121 in the above-mentioned high range.

  From the above, in the charging roll 121 according to the present embodiment, since the discharge unevenness caused by the abnormal discharge can be suppressed, it is considered that the charging potential unevenness of the member to be charged is suppressed.

In particular, in the manufacturing process of the charging roll 121, the formation of the elastic layer 31 (that is, for example, the formation of the elastic layer through the polishing process after the rubber forming process) is often performed through the polishing process. When this polishing step is carried out, a polishing pattern (hereinafter also referred to as "grind") enters the surface of the elastic layer 31, and the surface texture becomes uneven due to the grind. Then, it has been found that the skewness Rsk of the roughness curve of the outer peripheral surface of the charging roll 121 is likely to be positive (Rsk> 0) when the surface property unevenness due to the polishing eye occurs. Therefore, the charging roll 121 that has undergone the polishing process when forming the elastic layer 31 is likely to generate abnormal discharge. As a result, charging potential unevenness of the member to be charged is also likely to occur.
However, even with the charging roll 121 that has undergone the polishing process when forming the elastic layer 31, the skewness Rsk of the surface roughness curve is in the above relationship, and the common logarithm of the volume resistance is in the above range. Uneven charging potential of the member is suppressed.

Then, when the charging roll 121 according to the present embodiment is applied to an electrophotographic image forming apparatus (charging device thereof), background fog caused due to uneven charging potential of the image carrier can be suppressed.
When the abnormal discharge of the charging roll occurs, for example, a region where the charging potential is lower than the target charging potential (hereinafter, “charging potential reduction region”) is partially formed on the surface of the image carrier. This causes the charging potential unevenness of the image carrier. In the area where the charging potential is reduced on the surface of the image carrier, the difference between the absolute value of the charging voltage Vh (charging potential) of the surface of the image carrier after charging by the charging device and the developing voltage Vh (development potential) by the developing device A certain voltage Vcln (potential difference: hereinafter also referred to as "background voltage Vcln") decreases. And in the area | region where this background voltage Vcln fell, the tendency for a toner to be developed increases and a background fog arises.
On the other hand, in the charging roll 121 according to the present embodiment, the occurrence of abnormal discharge is suppressed and the charging potential unevenness of the image carrier is suppressed, so the occurrence of the background fog is suppressed.

  In particular, in an image forming apparatus in which the background voltage Vcln is set to a small value of 60 V or more and 90 V or less, abnormal discharge of the charging roll occurs, and when charging potential unevenness of the image carrier occurs, background fog easily occurs. However, when the charging roll 121 according to the present embodiment is employed, the occurrence of background fogging is suppressed even if the background voltage Vcln is set to a small value between 60 V and 90 V.

  Hereinafter, the details of the charging roll 121 according to the present embodiment will be described. In addition, the code | symbol is abbreviate | omitted and demonstrated.

The skewness Rsk of the roughness curve of the surface of the charging roll satisfies −0.6 <Rsk ≦ 0, and from the point of suppressing the charging potential unevenness of the member to be charged, −0.5 <Rsk ≦ −0.1. Is more preferable, and it is more preferable to satisfy −0.4 <Rsk ≦ −0.2.
The skewness Rsk of the roughness curve is controlled, for example, by the outer circumferential surface of the charging roll itself or the polishing conditions of the elastic layer.
The skewness Rsk of the roughness curve is a value obtained by measuring the profile of the surface roughness of one end to the other end of the charging roll in the axial direction according to JIS B 0601 (1982). As a measuring device, Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd. is used. Measurement conditions are cut-off: 0.8 mm, measurement length: 2.4 mm, traverse speed: 0.3 mm / sec.

The ten-point average roughness Rz of the surface of the charging roll is preferably 6 μm or more and 13 μm or less, and more preferably 8 μm or more and 11 μm or less, from the viewpoint of suppressing the charging potential unevenness of the member to be charged.
The ten-point average roughness Rz is controlled, for example, by the peripheral surface itself of the elastic layer of the charging roll or the polishing conditions of the elastic layer.
According to JIS B 0601 (1982), the ten-point average roughness Rz is measured at three positions at both ends in the axial direction of the charging roll at 20 mm and at the central portion, and is the average value. As a measuring device, Surfcom 1400 manufactured by Tokyo Seimitsu Co., Ltd. is used. Measurement conditions are cut-off: 0.8 mm, measurement length: 2.4 mm, traverse speed: 0.3 mm / sec.

The common logarithm value of the volume resistance value of the charging roll (the common logarithm value of volume resistance value when a DC voltage of 100 V is applied) is 7.65 LogΩ or more and 8.10 LogΩ or less.
The volume resistivity is controlled, for example, by the type and amount of the conductive agent in the elastic layer.
The volume resistance value is a value measured by the following method. First, the charge roll is placed on the metal plate so that the outer peripheral surface of the charge roll is in contact with the surface of the metal plate. Next, a load of 500 g is applied in the metal plate direction from both axial ends of the base material of the charging roll. In this state, an applied voltage of 100 V is applied between the base of the charging roll and the metal plate under an environment of a temperature of 22 ° C. and a humidity of 55% RH, and a current value I (A) after 10 seconds is measured. The volume resistance (R) is calculated according to the equation "volume resistance R = applied voltage V / current I". The measurement and calculation are carried out by rotating the charge roll in the circumferential direction by 90 ° at four points, and the average value is taken as the volume resistance value of the charge roll.

(Base material)
The base material functions as an electrode and a supporting member of the charging roll, and as its material, for example, iron (such as free-cutting steel), copper, brass, stainless steel, aluminum, nickel or other metal or alloy; chromium, nickel Iron that has been plated by As a conductive base material, a member (for example, resin, ceramic member) which performed plating processing to a peripheral face, a member (for example, resin, ceramic member) etc. where a conductive agent was distributed are mentioned. The substrate may be a hollow member (cylindrical member) or a non-hollow member.

(Adhesive layer)
Examples of the material of the adhesive layer include a known adhesive which is a composition that adheres the base material and the elastic layer and has conductivity. Examples of the adhesive include a resin composition containing an electron conductive agent, and a resin composition containing a conductive resin.

(Elastic layer)
The elastic layer contains an elastic material and a conductive agent. The elastic layer may optionally contain other additives. The elastic layer may also serve as a resistance adjustment layer.

As an elastic material, for example, isoprene rubber, chloroprene rubber, epichlorohydrin rubber, butyl rubber, urethane rubber, silicone rubber, fluororubber, styrene-butadiene rubber, butadiene rubber, nitrile rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide Copolymer rubbers, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubbers, ethylene-propylene-diene copolymer rubbers, acrylonitrile-butadiene copolymer rubbers, natural rubber, rubbers obtained by mixing these, etc. may be mentioned.
Among these elastic materials, silicone rubber, ethylene propylene rubber, epichlorohydrin-ethylene oxide copolymer rubber, epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber, and a mixture of these are preferable.
The rubber material may be foamed or non-foamed.

The conductive agent includes an electron conductive substance and an ion conductive substance.
Examples of the electron conductive substance include carbon blacks such as ketjen black and acetylene black, pyrolytic carbon, graphite, zinc, aluminum, copper, iron, metals such as iron, nickel, chromium and titanium, ZnO-Al ₂ O ₃ , SnO ₂ -Sb ₂ O ₃ , In ₂ O ₃ -SnO ₂ , ZnO-TiO ₂ , MgO-Al ₂ O ₃ , FeO-TiO ₂ , TiO ₂ , SnO ₂ , Sb ₂ O ₃ , In ₂ O ₃ , ZnO And known metal oxides such as MgO.
Examples of the ion conductive material include known salts such as quaternary ammonium salts, perchlorates of alkali metals, and perchlorates of alkaline earth metals.

  These conductive agents may be used alone or in combination of two or more.

The content of the conductive agent is not particularly limited as long as the target characteristics of the elastic layer can be obtained.
Specifically, in the case of the electron conductive material, the content of the conductive agent is preferably 1 part by mass or more and 90 parts by mass or less with respect to 100 parts by mass of the elastic material.
On the other hand, in the case of the ion conductive material, the content of the conductive agent is preferably 0.01 parts by mass or more and 10 parts by mass or less with respect to 100 parts by mass of the elastic material.

  Other additives in the elastic layer include well-known additives such as a softener, a plasticizer, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a surfactant, and a coupling agent.

  The thickness of the elastic layer varies depending on the device to which the charging roll is applied, but for example, it is preferably 1 mm to 10 mm, preferably 2 mm to 5 mm.

  The thickness of the elastic layer is a value measured by the following method. The thickness of the film is observed at an appropriate magnification according to the thickness of 5 to 50 times of the cross section of the sample cut by cutting with a single-edged knife the three axial positions of both ends 20 mm in the axial direction and the central part of the elastic layer (charging roll) Was measured and taken as the average value. As a measurement apparatus, Keyence Corporation digital microscope VHX-200 is used. "

(Surface layer)
The charging roll may be provided with a surface layer constituting an outer peripheral surface on the elastic layer, if necessary. This surface layer may be an embodiment in which a resin layer or the like is provided independently on the elastic layer, or an embodiment in which the cells in the surface layer portion of the foamed elastic layer are impregnated with a resin or the like (that is, in the cells). The surface layer portion of the elastic layer impregnated with a resin or the like may be a surface layer).

As a material for forming a surface layer, resin is mentioned, for example.
As the resin, for example, acrylic resin, fluorine modified acrylic resin, silicone modified acrylic resin, cellulose resin, polyamide resin, copolymer nylon, polyurethane resin, polycarbonate resin, polyester resin, polyimide resin, epoxy resin, silicone resin, polyvinyl alcohol resin Polyvinyl butyral resin, cellulose resin, polyvinyl acetal resin, ethylene tetrafluoroethylene resin, melamine resin, polyethylene resin, polyvinyl resin, polyarylate resin, polythiophene resin. Polyethylene terephthalate resin (PET), fluorocarbon resin (polyvinylidene fluoride resin, tetrafluoroethylene resin, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), etc. Can be mentioned. The resin is preferably one obtained by curing or crosslinking a curable resin with a curing agent or a catalyst.
Here, the copolymerized nylon is a copolymer including any one or more of 610 nylon, 11 nylon, and 12 nylon as a polymerization unit. The copolymerized nylon may contain other polymerized units such as 6 nylon and 66 nylon.

  Among these, polyvinylidene fluoride resin, tetrafluoroethylene resin, and polyamide resin are preferable as the resin from the viewpoint of fouling prevention, and from the viewpoint of the abrasion resistance of the surface layer and the separation suppression of porous resin particles, the polyamide resin Is more preferred.

  In particular, as the polyamide resin, an alkoxymethylated polyamide (alkoxymethylated nylon) is preferable from the viewpoint of the abrasion resistance of the surface layer, and more preferably a methoxymethylated polyamide (N-methoxymethylated nylon).

  The resin may have a crosslinked structure from the viewpoint of improving the mechanical strength of the surface layer and suppressing the occurrence of cracks in the surface layer.

  Other materials for forming the surface layer include, for example, a surface layer such as a conductive agent, a filler, a curing agent, a vulcanizing agent, a vulcanization accelerator, an antioxidant, a surfactant, a coupling agent, etc. There are known additives which can be added.

  The thickness of the surface layer is, for example, 2 μm to 25 μm, preferably 3 μm to 20 μm, more preferably 3 μm to 15 μm, and still more preferably 5 μm to 15 μm.

  The thickness of the surface layer is a value measured by the following method. The thickness of both ends of the surface layer (charging roll) at 20 mm and three parts at the center were cut out with a single-edged knife, and the cross section of the cut sample was observed at a magnification of 1000 times to measure the film thickness and determine the average value. . As a measurement apparatus, Keyence Corporation digital microscope VHX-200 is used.

[Charging device]
Hereinafter, the charging device according to the present embodiment will be described.
FIG. 3 is a schematic perspective view of the charging device according to the present embodiment.

The charging device according to the present embodiment is an embodiment in which the charging roll according to the present embodiment is applied as the charging roll.
Specifically, in the charging device 12 according to the present embodiment, as shown in FIG. 3, for example, the charging roll 121 and the cleaning member 122 are disposed in contact with each other at a specific bite amount. The axial direction ends of the base 30 of the charging roll 121 and the base 122A of the cleaning member 122 are held by conductive bearings 123 (conductive bearings) so that each member can rotate. A power source 124 (an example of a voltage application device) is connected to one of the conductive bearings 123.
Note that the charging device according to the present embodiment is not limited to the above configuration, and may have a configuration without the cleaning member 122, for example.

  The cleaning member 122 is a cleaning member for cleaning the surface of the charging roll 121, and is, for example, in a roll shape. The cleaning member 122 includes, for example, a cylindrical or cylindrical base material 122A, and an elastic layer 122B on the outer peripheral surface of the base material 122A.

  The base material 122A is a conductive rod-like member, and the material thereof is, for example, a metal such as iron (such as free-cutting steel), copper, brass, stainless steel, aluminum, nickel or the like. Further, as the base material 122A, a member (for example, a resin or a ceramic member) whose outer peripheral surface is subjected to a plating treatment, a member (for example, a resin or a ceramic member) in which a conductive agent is dispersed may be mentioned. The substrate 122A may be a hollow member (cylindrical member) or a non-hollow member.

  The elastic layer 122B is made of a foam having a porous three-dimensional structure, and it is preferable that a cavity or a concavo-convex portion (hereinafter referred to as a cell) be present inside or on the surface, and have elasticity. The elastic layer 122 B is a foamable resin material such as polyurethane, polyethylene, polyamide, olefin, melamine, polypropylene, or NBR (acrylonitrile-butadiene copolymer rubber), EPDM (ethylene-propylene-diene copolymer rubber), natural rubber And foamable rubber materials such as styrene-butadiene rubber, chloroprene rubber, silicone rubber and nitrile rubber.

  Among these foamable resin materials or rubber materials, foreign matter such as toner and external additive is efficiently cleaned by driven rubbing with the charging roll 121, and at the same time, the surface of the charging roll 121 is rubbed with the cleaning member 122. In order to make it difficult to be scratched by the above, and also to make it difficult to cause breakage and breakage over a long period of time, polyurethane which is resistant to tearing and tensile strength is particularly preferably applied.

  The polyurethane is not particularly limited, and, for example, polyols (for example, polyester polyols, polyether polyols, acrylic polyols etc.), isocyanates (2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4 Reaction products of diphenylmethane diisocyanate, tolidine diisocyanate, 1,6-hexamethylene diisocyanate, etc., and reaction products by these chain extenders (eg, 1,4-butanediol, trimethylolpropane etc.) . The polyurethane is generally foamed using a foaming agent (water or an azo compound (azodicarbonamide, azobisisobutyronitrile, etc.)).

  The number of cells of the elastic layer 122B is preferably 20/25 mm or more and 80/25 mm or less, more preferably 30/25 mm or more and 80/25 mm or less, and preferably 30/25 mm or more and 50/25 mm or less Particularly preferred.

  The hardness of the elastic layer 122B is preferably 100N to 500N, more preferably 100N to 400N, and particularly preferably 150N to 400N.

  The conductive bearing 123 is a member that holds the charging roll 121 and the cleaning member 122 integrally and rotatably and holds the distance between the members. The conductive bearing 123 may be of any material and form as long as it is made of a conductive material, for example, a conductive bearing or a conductive sliding bearing may be applied.

  The power source 124 is a device for charging the charging roll 121 and the cleaning member 122 to the same polarity by applying a voltage to the conductive bearing 123, and a known high voltage power source device is used.

  In the charging device 12 according to the present embodiment, for example, when a voltage is applied from the power supply 124 to the conductive bearing 123, the charging roll 121 and the cleaning member 122 are charged to the same polarity.

[Image forming apparatus, process cartridge]
The image forming apparatus according to the present embodiment includes an image carrier, a charging device for charging the surface of the image carrier, an electrostatic charge image forming device for forming an electrostatic charge image on the surface of the charged image carrier, and an electrostatic charge. A developing device for containing an image developer and developing an electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer, a toner image formed on the surface of the image carrier as a recording medium And a transfer device for transferring the image to the surface of the image forming apparatus. Then, the charging device according to the present embodiment is applied as the charging device.

The image forming apparatus according to the present embodiment is an apparatus provided with a fixing device for fixing a toner image transferred to the surface of a recording medium; direct transfer for directly transferring a toner image formed on the surface of an image carrier to a recording medium An intermediate transfer system in which the toner image formed on the surface of the image carrier is primarily transferred onto the surface of the intermediate transfer body, and the toner image transferred onto the surface of the intermediate transfer body is secondarily transferred onto the surface of the recording medium A device comprising a cleaning device for cleaning the surface of the image carrier prior to charging after transfer of the toner image; discharging the surface of the image carrier before charging after the transfer of the toner image; A known image forming apparatus such as an apparatus provided with a static eliminator is applied.
In the case of an intermediate transfer type apparatus, for example, an intermediate transfer member to which a toner image is transferred on the surface, and a primary transfer on which the toner image formed on the surface of the image carrier is primarily transferred to the surface of the intermediate transfer member. A configuration is applied that includes a device and a secondary transfer device that secondarily transfers the toner image transferred to the surface of the intermediate transfer member to the surface of the recording medium.

Here, in the image forming apparatus according to the present embodiment, the background voltage Vcln, which is the difference between the charging voltage of the surface of the image carrier after charging by the charging device and the developing voltage by the developing device, is 60V to 90V. The device may be Specifically, for example, the image forming apparatus controls each voltage application device that applies a voltage to the charging device (its charging roll) and the developing device (the developing roll) so that the background voltage Vcln falls within the above range. Preferably, a controller is provided.
Even in the image forming apparatus in which the background voltage Vcln is 60 V or more and 90 V or less, as described above, the background fog caused due to the charging potential unevenness of the image carrier is suppressed.

  On the other hand, the process cartridge according to the present embodiment includes, for example, an image carrier, which is detachably attached to the image forming apparatus having the above-described configuration, and a charging device that charges the image carrier. Then, the charging device according to the present embodiment is applied as the charging device. The process cartridge according to the present embodiment may be, for example, a charging device for charging the surface of the image carrier; an electrostatic charge image forming device for forming an electrostatic charge image on the surface of the charged image carrier; A developing device for developing an electrostatic charge image formed on the surface of an image carrier as a toner image by a developer; and a transfer device for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium At least one selected from the group may be provided.

  Next, an image forming apparatus and a process cartridge according to the present embodiment will be described with reference to the drawings. FIG. 4 is a schematic configuration view showing the image forming apparatus according to the present embodiment. FIG. 5 is a schematic configuration view showing a process cartridge according to the present embodiment.

  The image forming apparatus 101 according to the present embodiment, as shown in FIG. 4, includes an image carrier 10, and around the periphery thereof a charging device 12 for charging the image carrier and an image carrier charged by the charging device 12. An exposure device 14 that exposes 10 to form an electrostatic charge image, a development device 16 that develops the electrostatic charge image formed by the exposure device 14 with toner to form a toner image, and a toner image formed by the development device 16 A transfer device 18 for transferring to a recording medium P and a cleaning device 20 for removing residual toner on the surface of the image carrier 10 after transfer are provided. The image forming apparatus further includes a fixing device 22 that fixes the toner image transferred to the recording medium P by the transfer device 18. Furthermore, a control device 26 connected to each device and each member in the image forming device 101 is provided to control the operation of each device and each member.

  The image forming apparatus 101 according to the present embodiment includes, for example, the charging roll 121, the cleaning member 122 disposed in contact with the charging roll 121, and both axial ends of the charging roll 121 and the cleaning member 122 as the charging device 12. A charging device according to the present embodiment in which a conductive bearing 123 (conductive bearing) for holding each member so as to be rotatable and a power source 124 connected to one of the conductive bearings 123 are disposed. Has been applied.

  On the other hand, in the image forming apparatus 101 according to the present embodiment, as for the configuration other than the charging device 12 (charging roller 121), conventionally known configurations as each configuration of an electrophotographic image forming apparatus are applied. Hereinafter, an example of each configuration will be described.

  The image carrier 10 is not particularly limited, and a known photoreceptor is applied, but an organic photoreceptor having a so-called function separation type in which the photosensitive layer is separated into a charge generation layer and a charge transport layer is suitably applied. Be done. Further, as the image carrier 10, one having a surface layer coated with a protective layer having charge transportability and a crosslinked structure is also suitably applied. A photosensitive member composed of a siloxane-based resin, a phenol-based resin, a melamine resin, a guanamine resin, and an acrylic resin as a crosslinking component of this protective layer is also suitably applied.

  For example, a laser optical system, a light emitting diode (LED) array, or the like is applied as the exposure device 14.

  For example, the developing device 16 brings the electrostatic charge image of the surface of the image carrier 10 by bringing the developing roller 161 (an example of a developer carrier) having a developer layer formed on the surface into contact with or in proximity to the image carrier 10. It is a developing device that deposits toner to form a toner image. The developing device 16 includes a power supply 162 (an example of a voltage application device) for applying a voltage to the developing roller 161. As a developing method of the developing device 16, a developing method using a two-component developer is suitably applied as a known method. Examples of the developing method using this two-component developer include a cascade method and a magnetic brush method.

  The transfer device 18 may be, for example, a non-contact transfer method such as corotron, or a contact transfer method of transferring a toner image onto the recording medium P by bringing a conductive transfer roll into contact with the image carrier 10 via the recording medium P. You may adapt.

  The cleaning device 20 is, for example, a member that brings a cleaning blade into direct contact with the surface of the image carrier 10 to remove toner, paper powder, dust and the like adhering to the surface. As the cleaning device 20, in addition to the cleaning blade, a cleaning brush, a cleaning roll or the like may be applied.

  As the fixing device 22, a heating fixing device using a heat roll is suitably applied. The heat-fixing device includes, for example, a fixing roller provided with a heater lamp for heating inside a cylindrical core metal, and a so-called release layer formed by a heat-resistant resin film layer or a heat-resistant rubber film layer on its outer peripheral surface; A pressure roller or a pressure belt which is disposed in contact with the fixing roller under a specific contact pressure and has a heat-resistant elastic layer formed on the outer peripheral surface of a cylindrical core metal or the surface of a belt-like substrate. . In the fixing process of the unfixed toner image, for example, the recording medium P to which the unfixed toner image is transferred is inserted between the fixing roller and the pressure roller or the pressure belt, and the binder resin in the toner Fix by heat melting such as additives.

  The image forming apparatus 101 according to the present embodiment is not limited to the above configuration. For example, an image forming apparatus of an intermediate transfer type using an intermediate transfer member, and an image forming unit forming toner images of respective colors are arranged in parallel. It may be a so-called tandem type image forming apparatus.

  On the other hand, as shown in FIG. 5, in the image forming apparatus shown in FIG. 4, the process cartridge according to the present embodiment is an image formed by the case 24 provided with the opening 24A for exposure and the mounting rail 24C. A carrier 10, a charging device 12 for charging the image carrier, a developing device 16 for developing an electrostatic charge image formed by the exposure device 14 with toner to form a toner image, and a surface of the image carrier 10 after transfer. The process cartridge 102 is configured by integrally holding a cleaning device 20 for removing residual toner. The process cartridge 102 is detachably mounted to the image forming apparatus 101 shown in FIG. In FIG. 5, the power supply 124 and the power supply 162 are not shown.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited by the following examples. In addition, "part" means a "mass part" unless there is particular notice.

Example 1
A mixture of the following components was kneaded with an open roll, and cylindrically coated on the surface of a 6 mm diameter conductive substrate made of SUS416 so as to have a thickness of 1.5 mm. The resultant was put in a cylindrical mold having an inner diameter of 18.0 mm, vulcanized at 170 ° C. for 30 minutes, taken out from the mold, and then polished to obtain a cylindrical foamed elastic layer.
Here, the polishing was carried out using LEO-600FS manufactured by Mizuguchi Mfg. Co., Ltd. under the conditions of a rotation speed of 200 rpm and a grinding wheel rotation speed of 2,300 rpm.

-Component of the foamed elastic layer-
Rubber material: 100 parts by mass (epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer rubber) Gechron 3106: manufactured by Nippon Zeon Co., Ltd.
Conducting agent (carbon black Asahi Thermal: manufactured by Asahi Carbon Co., Ltd.): 25 parts by mass Conducting agent (Ketjen black EC: manufactured by Lion): 8 parts by mass Ion conductive agent (lithium perchlorate): 1 part by mass Vulcanizing agent (sulfur) 200 mesh: manufactured by Tsurumi Chemical Industry Co., Ltd .: 1 part by mass. Vulcanization accelerator (Noxcella DM: manufactured by Ouchi Emerging Chemical Industry Co., Ltd.): 2.0 parts by mass vulcanization accelerator (Noxceler TT: Ouchi New Chemical Industry Co., Ltd.): 0.5 parts by mass

  Next, a mixture of the following components was dispersed by a bead mill, and dispersion liquid A obtained was diluted with methanol to prepare a coating liquid having a viscosity of 0.04 Pa · s. Using this coating liquid, it was dip-coated on the surface of the foamed elastic layer, and after impregnating the coating liquid in the air bubbles of the surface layer portion of the foamed elastic layer, it was dried by heating at 140 ° C. for 15 minutes to form a surface layer. The obtained conductive roll was used as a charging roll.

-Component of surface layer-
Polymer material: 100 parts by mass (copolymerized nylon) Alamine CM 8000: manufactured by Toray Co., Ltd. Conductive agent: 30 parts by mass (antimony-doped tin oxide) SN-100P: manufactured by Ishihara Sangyo Co., Ltd. Solvent (methanol): 500 parts by mass Solvent (butanol): 240 parts by mass

Example 2
A charging roll was obtained in the same manner as in Example 1 except that in the formation of the foamed elastic layer, the polishing conditions were changed to 300 rpm for the object to be polished and 3,450 rpm for the grinding wheel.

Example 3
In the formation of the surface layer, a charge roll was obtained in the same manner as Example 1, except that the amount of solvent was adjusted to prepare a coating solution having a viscosity of 0.06 Pa · s.

Example 4
A charging roll was obtained in the same manner as Example 1, except that in the formation of the foamed elastic layer, the polishing conditions were changed to the rotation speed of an object to be polished of 600 rpm and the grinding wheel rotation speed of 6,900 rpm.

Example 5
In the formation of the foamed elastic layer, the polishing conditions are changed to the rotation speed of the object to be polished at 600 rpm and the grinding wheel rotation speed to 6,900 rpm, and in the formation of the surface layer, the amount of solvent is adjusted to adjust the coating solution with a viscosity of 0.06 Pa · s A charging roll was obtained in the same manner as in Example 1 except that it was prepared.

Example 6
A charging roll was obtained in the same manner as in Example 1 except that in the formation of the foamed elastic layer, the polishing conditions were changed to the rotation speed of the object to be polished of 240 rpm and the grinding wheel rotation speed of 2,760 rpm.

Example 7
In the formation of the foamed elastic layer, the polishing conditions are changed to the rotation speed of the object to be polished at 240 rpm and the grinding wheel rotation speed to 2,760 rpm, and in the formation of the surface layer, the amount of solvent is adjusted to adjust the coating solution with a viscosity of 0.06 Pa · s A charging roll was obtained in the same manner as in Example 1 except that it was prepared.

Comparative Example 1
A charging roll was obtained in the same manner as in Example 1 except that in the formation of the foamed elastic layer, the polishing conditions were changed to 100 rpm for the object to be polished and 1,150 rpm for the grinding wheel.

Comparative Example 2
In the formation of the surface layer, a charge roll was obtained in the same manner as Example 1, except that the amount of solvent was adjusted to prepare a coating solution having a viscosity of 0.02 Pa · s.

<Measurement / Evaluation>
(Various measurements)
For the charging roll of each example, the skewness Rsk of the roughness curve of the roll surface (indicated as "Rsk" in the table), the ten-point average roughness Rz of the roll surface (indicated as "Rz" in the table), and a DC voltage of 100 V The commonly used logarithmic value (represented as "R" in the table) of the volume resistance value when measured was measured according to the method described above. The results are shown in Table 1.

(Evaluation)
The charging roll of each example was attached to "DocuPrint CP200w" manufactured by Fuji Xerox Co., Ltd., and used as an evaluation apparatus. The device for this evaluation makes it possible to vary the voltage applied to the charging roll and the developing roll, and adjusts the charging voltage (charging potential) of the surface of the photosensitive member after charging by the charging device and the developing voltage (development voltage) by the developing device. The equipment was remodeled as possible. Thus, the device for evaluation can set the background voltage (background potential) which is the difference between the absolute values of the charging voltage (charging potential) and the developing voltage (development voltage).

A4 paper in a high temperature and high humidity environment (temperature 30 ° C., 80% RH environment) in a state where the background voltage Vcln shown in Table 1 (indicated as “Vcln” in the table) is set using an evaluation device. 10 sheets of white paper printing (output not forming an image) were carried out. Then, the output sheet was visually observed on the tenth sheet to evaluate the background fog. The evaluation of the background fog was performed for each background voltage Vcln set as shown in Table 1. The results are shown in Table 1. The evaluation criteria are as follows.
A: There is no occurrence of background fog B: If you look closely, it is confirmed that background fog occurs.
C: Some occurrence of background fog was confirmed, but there was no problem in practice. D: Occurrence of background fog was confirmed to the extent that it can be seen at a glance.
E: The occurrence of background fog with a certain density was confirmed.

From the above results, it can be seen that the occurrence of background fogging is suppressed in the present example as compared to the comparative example.
Further, in the present embodiment, even when the background voltage Vcln is 90 V or less, it is understood that the occurrence of background fog is suppressed as compared with the comparative example.

DESCRIPTION OF SYMBOLS 10 image carrier, 12 charging device, 14 exposure device, 16 developing device, 18 transfer device, 20 cleaning device, 22 fixing device, 24 case, 24A opening, 24C attachment rail, 30 base materials, 31 conductive elastic layer , 32 conductive surface layer, 101 image forming apparatus, 102 process cartridge, 121 charging roll, 122 cleaning member, 123 conductive bearing, 122A base material, 122B elastic layer, 124 power source

Claims (7)

A charging roll comprising: a cylindrical or cylindrical conductive base; and a conductive elastic layer provided on the outer peripheral surface of the conductive base,
The skewness Rsk of the surface roughness curve of the charging roll satisfies −0.6 <Rsk ≦ 0,
A charging roll in which a common logarithm value of a volume resistance value of the charging roll when a DC voltage of 100 V is applied is 7.65 LogΩ or more and 8.10 LogΩ or less.   The charging roll according to claim 1, wherein the skewness Rsk of the roughness curve of the surface of the charging roll satisfies −0.5 <Rsk ≦ −0.1. The conductive elastic layer is a conductive foam elastic layer,
And wherein the bubble of the surface layer portion of the conductive foamed elastic layer, charging roll according to claim 1 or claim 2 and the surface portion of the conductive foamed elastic layer the resin is impregnated with the surface layer even without low.   The charging device provided with the charging roll of any one of Claims 1-3. An image carrier,
The charging device according to claim 4, wherein the surface of the image carrier is charged.
Equipped with
Process cartridge that is attached to and detached from the image forming apparatus. An image carrier,
The charging device according to claim 4, wherein the surface of the image carrier is charged.
An electrostatic charge image forming apparatus for forming an electrostatic charge image on the surface of the charged image carrier;
A developing device that contains an electrostatic charge image developer and develops the electrostatic charge image formed on the surface of the image carrier as a toner image by the electrostatic charge image developer;
A transfer device for transferring a toner image formed on the surface of the image carrier to the surface of a recording medium;
An image forming apparatus comprising:   7. The image formation according to claim 6, wherein a voltage Vcln which is a difference between an absolute value of a charging voltage of the surface of the image carrier after charging by the charging device and a developing voltage by the developing device is 60V to 90V. apparatus.