JP2008107819A - Developing roller, electrophotographic process cartridge, and electrophotographic image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing roller which imparts a stable and proper frictional charge to a developer regardless of the environmental change, even if the developing roller is applied to an electrophotographic apparatus improved in speed and durability, which keeps the developer in a stable triboelectric state, and which prevents foggings under high-temperature and high-humidity and blotches under low-temperature and low-humidity to achieve excellent imaging performance; to provide an electrophotographic image forming apparatus using the same; and to provide a process cartridge for an electrophotographic apparatus. <P>SOLUTION: The developing roller 1 includes a shaft core 2, and a resin layer provided on the shaft core, wherein the resin layer 4 has a recess having a depth from 50 to 500 nm on the surface thereof. The percentage of the recess area to the surface of the resin layer is in the range from 5 to 25%, and the average current value (Ih) in the recess confirmed by measurement of the recess with an SPM (Scanning Probe Microscope) is more than 100 times the average current value (Ip) in the flat surface of the resin layer surface except the recess, that is, in the range from 0.5 to 80 nA. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a developing roller, a process cartridge for an electrophotographic apparatus using the developing roller, and an electrophotographic image forming apparatus.

  As an image formation of an electrophotographic apparatus such as a copying machine or an optical printer, a developing method using a non-magnetic one-component developer is known. Specifically, a rotatable photoreceptor is uniformly charged by a charging means such as a charging roller, and a laser beam is exposed to the uniformly charged photoreceptor surface to form an electrostatic latent image. A developing roller having a developer thin film formed on the surface thereof is opposed to the photosensitive member carrying the electrostatic latent image, and the photosensitive member and the developing roller are mutually rotated. At this time, when a developing bias is applied to the developing roller, the developer moves from the developing roller to the electrostatic latent image on the photoreceptor, and the electrostatic latent image is developed as a toner image. Thereafter, the toner image on the photosensitive member is transferred onto the recording material in the transfer portion, fixed on the fixing portion by heating or the like, and the recording material on which image formation has been completed is discharged out of the image forming apparatus.

  As a developing device for developing the electrostatic latent image carried by the photosensitive member in such image formation, an apparatus having the following configuration can be exemplified. A developing roller is provided so that the opening of the developer container for storing the developer is closed and a part of the opening is exposed to the outside of the container, and the exposed portion faces the photosensitive member. In the developer container, there are provided a developer supply roller that supplies the developer to the developing roller, and a developer regulating member that forms the developer on the developing roller in a thin film and makes the developer on the developing roller a certain amount. The developer regulating member is installed in the vicinity of the tip, for example, at a position of 0.1 to 5.0 mm from the tip so as to come into contact with the developing roller, and the developer on the developing roller supplied by the developer feeding roller is removed. It is formed into a thin film with a uniform thickness. After the development of the electrostatic latent image, the developer remaining on the developing roller is scraped off by the developer supplying roller, mixed with the developer in the developer container, and the electric charge is removed.

  In such a non-magnetic one-component developing method, in order to stabilize the image density from the initial stage of image formation, a metal developer regulating member is used, and a voltage difference is provided between the developing roller and the developer on the developing roller. Appropriate triboelectric charging is performed. The developing roller has a predetermined electric resistance value, and in combination with the developer regulating member, imparts an appropriate triboelectric charge to the developer, and further keeps the developer in an appropriate triboelectric charge state. Is required.

  As a method for maintaining the charge amount of the developer on the developing roller in response to the above requirement, a method of forming a dielectric portion and a conductor portion on the surface of the developing roller is known (Patent Documents 1 and 2). Further, as a method for preventing the developer from being reverse frictionally charged by the developing roller, a method is known in which the surface layer of the developing roller has a sea-island structure, and the elongation at break and elongation at break of each component of the sea part and the island part are defined. (Patent Document 3).

  However, in recent years, as a result of speeding up of the electrophotographic apparatus, the shearing force applied to the developer is increased more than before, and the developer is deformed and the developer is deteriorated, such as the developer external agent dropping off. The trend is high. Further, as a result of the high durability of the electrophotographic apparatus, a shearing force is continuously applied to the developer for a longer period than before. As a result, there is a problem that the developer is deteriorated due to use under high temperature and high humidity, and the frictional charging failure and the fogging accompanying it occur. Furthermore, when a potential difference is provided between the developer regulating member and the developing roller, the charged amount tends to be insufficient for the deteriorated developer, which becomes more serious.

In addition, as a result of speeding up of the electrophotographic apparatus, the rubbing applied to the developer increases, and immediately after the start of use under low temperature and low humidity, the amount of charge on the developer becomes excessive, and the developer on the developing roller is scraped off. There is a tendency for sex to decline. As a result, there is a problem in that the developer accumulates on the developing roller, normal frictional charging is not performed on the developer, and spotted fogging (so-called blotch image) occurs. Further, when a potential difference is provided between the developer regulating member and the developing roller, the triboelectric charge amount tends to increase even for a normal developer, and the above problem is more remarkable.
JP-A-9-114197 JP-A-5-332352 JP-A-9-90714

  The object of the present invention is to provide a stable and appropriate triboelectric charge to a developer regardless of environmental changes even when applied to an electrophotographic apparatus with high speed and high durability. The developing roller can be kept in a state. Another object of the present invention is to provide a developing roller that can suppress the occurrence of fogging under high temperature and high humidity and blotch under low temperature and low humidity and exhibit good image performance. Another object of the present invention is to provide a process cartridge for an electrophotographic apparatus and an electrophotographic image forming apparatus that can perform stable image formation without being affected by an environment of high temperature and high humidity to low temperature and low humidity.

  The inventors of the present invention have a developing roller having a resin layer having a specific shape and physical properties on the surface, so that a stable and appropriate triboelectric charge is imparted to and held by the developer. We obtained the knowledge that the blotch under low humidity was suppressed and good image performance was exhibited. Based on this knowledge, the present invention has been completed.

  That is, the present invention provides a developing roller having a shaft core and a resin layer provided on the shaft core, the resin layer having a recess having a depth of 50 nm or more and 500 nm or less on the surface. The area occupied by the resin layer surface is in the range of 5% to 25% with respect to the area of the resin layer surface, and the average current value (Ih) of the recesses measured using a scanning probe microscope is the surface of the resin layer excluding the recesses The developing roller is characterized in that it is larger than 100 times the average current value (Ip) of the flat surface and in the range of 0.5 nA to 80 nA.

  The present invention also provides a process cartridge for an electrophotographic apparatus, which has a developing roller for supplying a developer so that the electrostatic latent image of the electrostatic latent image carrier is a toner image, and is detachably provided on the main body of the electrophotographic apparatus. The process roller according to claim 1, wherein the developing roller is the developing roller.

  The present invention also includes a developing roller for supplying a developer for making the electrostatic latent image on the electrostatic latent image carrier a toner image, and a developer regulating member for making the amount of developer on the developing roller constant. In the electrophotographic image forming apparatus provided, the developing roller is the developing roller, and a voltage applied to the developer regulating member has a difference of −400 V or more and −50 V or less with respect to a voltage applied to the developing roller. The present invention relates to an electrophotographic image forming apparatus.

  The developing roller of the present invention imparts a stable and appropriate triboelectric charge to the developer regardless of environmental changes even when applied to a high speed and high durability electrophotographic apparatus. It can be kept charged. Therefore, it is possible to suppress the occurrence of fogging under high temperature and high humidity and blotch under low temperature and low humidity, and to exhibit good image performance. The process cartridge for an electrophotographic apparatus and the electrophotographic image forming apparatus of the present invention can perform stable image formation without being affected by an environment of high temperature and high humidity to low temperature and low humidity.

  The developing roller of the present invention has a shaft core and a resin layer provided on the shaft core.

  The shaft core used in the developing roller of the present invention has a strength capable of supporting the upper resin layer, and has conductivity that acts as an electrode for the resin layer. Examples of the material of the shaft core include a metal or an alloy such as aluminum, copper alloy, and stainless steel; iron plated with chromium or nickel; a synthetic resin having conductivity. Furthermore, the metal shaft core may be subjected to rust prevention treatment such as plating and oxidation treatment.

  The shape of the shaft core may be any of a columnar shape, a cylindrical shape, etc., and the surface may be subjected to primer treatment as necessary. Examples of the outer diameter of the shaft core include a range of 4 mm to 10 mm.

  It is preferable that the resin layer provided on the shaft core has a recess having a depth of 50 nm or more and 500 nm or less on the surface, and many recesses are uniformly formed over the entire surface of the resin layer. By having a large number of recesses of 50 nm or more and 500 nm or less uniformly, the surface of the resin layer has a function capable of appropriately performing frictional charging and holding of the toner.

  The said recessed part can confirm the resin layer surface using a scanning probe microscope (Scanning Probe Microscope: SPM). Specifically, by Q-Scope 250 (manufactured by Quesant Instrument Corporation), it is possible to observe an image obtained at a scanning range of 10 μm × 10 μm and a scanning rate of 4 Hz in a contact mode. It can be said that the concave portion is a discontinuous portion observed at a depth of 50 nm to 500 nm from the flat surface of the resin layer surface. Here, the flat surface of the resin layer surface is located at a position higher than the average height of 160000 observation points in the enlarged image obtained by SPM, and has a flat surface roughness Ra of 0.5 to 10 nm by SPM observation. It is assumed that it is an area. The surface roughness Ra is a value measured by SPM at a measurement length of 0.5 μm.

  If the depth of the recess is 50 nm or more, the toner that has deteriorated after long-term use can be sufficiently frictionally charged, and the occurrence of fogging can be suppressed even under high temperature and high humidity. This is because if the depth of the recess is shallower than 50 nm, it is impossible to suppress the flow of charge from the flat surface to the bottom of the recess, but the difference in height of 50 nm suppresses the flow of charge from the flat surface to the bottom of the recess. This is thought to be one of the reasons. If the depth of the recess is 500 nm or less, the charge-up of the resin layer can be suppressed even under low temperature and low humidity, and the occurrence of a blotch image can be suppressed. This is because if the depth of the concave portion is deeper than 500 nm, excessively charged toner and the charge on the flat surface are prevented from flowing to the bottom portion of the concave portion. Part of it is thought to be part of it.

  The area occupied by such recesses on the surface of the resin layer is in the range of 5% to 25% with respect to the resin layer surface area. When the area occupied by the recesses on the surface of the resin layer is 5% or more with respect to the surface area of the resin layer, the resin layer can suppress the charge-up under low temperature and low humidity, and the occurrence of blotch images can be suppressed. It is considered that when the concave portion occupies 5% or more of the resin layer surface area, the excessively charged toner and the charge on the flat surface of the resin layer surface can be released. If the area occupied by the recesses is 25% or less of the surface area of the resin layer, sufficient frictional charging can be imparted to toner that has deteriorated after long-term use, and the occurrence of fogging under high temperature and high humidity is suppressed. can do. If the area occupied by the recesses on the surface of the resin layer is 25% or less, it is considered that a flat surface capable of imparting sufficient charge to the toner can be secured.

  Here, the surface area of the resin layer is the surface area of the resin layer when the surface of the resin layer is assumed to be flat, and is the area obtained by adding the area obtained by projecting the recess to the surface of the resin layer and the above-described flat surface. It is not an addition of area.

  As the area occupied by the recess with respect to the area of the resin layer surface, a value measured under the above conditions using SPM can be adopted.

  The average current value (Ih) by SPM measurement of the recess is greater than 100 times the average current value (Ip) of the flat surface, and is in the range of 0.5 nA to 80 nA.

Ih ≧ Ip × 100
0.5nA ≦ Ih ≦ 80nA
If the average current value (Ih) measured by SPM measurement of the concave portion is 0.5 nA or more, it is possible to suppress the resin layer from being charged up under low temperature and low humidity, thereby suppressing the occurrence of blotch images. When the average current value (Ih) is 80 nA or less, sufficient charge can be imparted to the deteriorated toner after long-term use, and the occurrence of fogging under high temperature and high humidity can be suppressed. In addition, if the average current value (Ih) by SPM measurement of the recess is larger than 100 times the average current value (Ip) of the flat surface, the outflow of charge from the flat surface is suppressed, and the deteriorated toner after long-term use In contrast, sufficient charge can be imparted. Moreover, generation | occurrence | production of the fog under high temperature and high humidity can be suppressed.

  Here, as the average current values (Ih) and (Ip), values obtained as average values of the measured values of the recesses and the flat surface using SPM can be adopted. Specifically, an average value obtained from measured values under the following conditions using Q-Scope 250 (manufactured by Quesant Instrument Corporation) can be adopted. The measurement conditions are a measurement in which the shaft core is grounded, a voltage of 50 V is applied to the cantilever, the scanning i range is 10 μm × 10 μm, and the number of measurement data is 400 × 400.

  Further, the concave portion preferably has a surface roughness Ra by SPM measurement of 15.0 nm or more and 75.0 nm or less. If the surface roughness Ra of the recess is 15.0 nm or more, the charge-up of the resin layer under low temperature and low humidity can be suppressed, and the occurrence of blotch images can be suppressed. If it is 75.0 nm or less, the outflow of charge in the deteriorated toner after long-term use can be suppressed, and the occurrence of fogging under high temperature and high humidity can be suppressed.

  Moreover, it is preferable that a recessed part is provided in the resin layer surface in the range whose opening diameter is 0.1 to 5.0 micrometer, More preferably, it is 1.0 to 3.0 micrometer. By having such an opening diameter, the toner can be charged to an appropriate charge amount. Here, the opening diameter can be an average value of the measured values of the minimum opening width in each recess. The measured value of the opening diameter of the recess can be a value measured using SPM.

  Specific examples of the material of the base material of the resin layer include polyamide, urethane resin, urea resin, polyimide, melamine resin, fluororesin, phenol resin, alkyd resin, silicone resin, polyester, and the like. . These resins can be used alone or in combination of two or more as required. Among these resins, urethane resins are preferable because they are excellent in charging of toner and have abrasion resistance.

  The urethane resin as the base material of the resin layer is preferably a resin obtained by polymerizing a polyurethane prepolymer and an isocyanate. The polyurethane prepolymer is a mixture of two types of polyurethane polyol prepolymers (A) and (B) that are very similar in structure, so that a large number of micro level recesses can be formed uniformly on the surface of the resin layer. This is preferable.

  Specifically, the polyurethane polyol prepolymer (B) is a chain polymer obtained by polymerizing a bifunctional polyether polyol having a number average molecular weight Mn (b) of 650 or more and 2000 or less and diphenylmethane diisocyanate. The number average molecular weight Mn (B) of the polyurethane polyol prepolymer (B) is preferably 3000 or more and 30000 or less, more preferably 17000 or more and 30000 or less. When the number average molecular weight Mn (B) of the polyurethane polyol prepolymer (B) is within this range, the uncured composition having an optimum viscosity capable of easily achieving the shape and electrical properties of the resin layer in the formation of the resin layer. It becomes a thing.

  The polyurethane polyol prepolymer (A) is a chain polymer obtained by polymerizing a bifunctional polyether polyol satisfying the relationship of the formula (1) as a number average molecular weight Mn (a) and diphenylmethane diisocyanate.

1.4 <Mn (a) / Mn (b) <5 (1)
The number average molecular weight Mn (A) of the polyurethane polyol prepolymer (A) preferably satisfies the relationship of the formula (2).

0.25 ≦ Mn (A) / Mn (B) ≦ 4 (2)
The bifunctional polyether polyols constituting the polyurethane polyol prepolymers (A) and (B) may be different but are preferably the same. Examples of the bifunctional polyether polyol include polytetramethylene glycol (PTMG), polypropylene glycol (PPG), and polyethylene glycol (PEG). Among these, polytetramethylene glycol is preferable because it has high crystallinity and can easily achieve the concave shape and electrical properties of the resin layer surface. Polytetramethylene glycol can be synthesized using tetrahydrofuran as a raw material, but commercially available products can also be applied. The following can be mentioned as a commercial item. Poly THF650 (Mn = 650), PolyTHF 1000 (Mn = 1000), PolyTHF 1800 (Mn = 1800), PolyTHF 2000 (Mn = 2000), PolyTHF 2900 (Mn = 2900) manufactured by BASF. PTG850 (Mn = 850) manufactured by Hodogaya Chemical Co., Ltd.

When these bifunctional polyether polyols satisfy the following three requirements, the polyurethane polyol prepolymers (A) and (B) can be adjusted to a polar balance suitable for forming recesses on the surface of the resin layer.
(1) The urethane polyol prepolymers (A) and (B) have different number average molecular weights, respectively.
(2) Satisfying the relationship of formula (1),
(3) Number average molecular weight Mn (b) has the said range.

  Here, as the number average molecular weight (Mn), a measurement value obtained by a GPC method using Gel Permeation Chromatography can be adopted. Specifically, a high-performance liquid chromatograph analyzer “HLC-8120GPC” (manufactured by Tosoh Corporation) in which two GPC columns “TSKgel SuperHM-m” (manufactured by Tosoh Corporation) are connected in series is used. The measurement conditions are a temperature of 40 ° C., a flow rate of 0.6 ml / min, and an RI (refractive index), and the measurement sample is measured as a 0.1 mass% tetrahydrofuran (THF) solution. As a standard sample, monodisperse standard polystyrene “TSK standard polystyrene F-128, F-80, F-40, F-20, F-10, F-4, F-2, F-1, A-5000, A-2500 , A-1000, A-500 "(manufactured by Tosoh Corporation) to create a calibration curve. The molecular weight distribution is obtained from the retention time of the measurement sample or the count number from the calibration curve. The number average molecular weight Mn can be obtained from this distribution.

  As the isocyanate that polymerizes with such a bifunctional polyether polyol to form a chain polyurethane polyol prepolymer (A) or (B), it is preferable to use diphenylmethane diisocyanate. Use of diphenylmethane diisocyanate is preferable because the polyurethane polyol prepolymers (A) and (B) are in a compatible state suitable for forming a recess on the surface of the resin layer. The reaction between the bifunctional polyether polyol and diphenylmethane diisocyanate can be performed in a nitrogen atmosphere by mixing these with a solvent such as methyl ethyl ketone (MEK). By selecting the reaction temperature and time, the molecular weight of the resulting polyurethane polyol prepolymer can be adjusted.

When these polyurethane polyol prepolymers (A) and (B) satisfy the following requirements, the polyurethane prepolymer can be adjusted to a viscosity balance suitable for forming a recess on the surface of the resin layer.
(1) The number average molecular weights Mn (A) and Mn (B) of the polyurethane polyol prepolymers (A) and (B) have the relationship of the above formula (2).
(2) Number average molecular weight Mn (b) has the said range.

  The polyurethane polyol prepolymers (A) and (B) are preferably used in a mass ratio A / B in the range of 5/95 to 25/75. By using the polyurethane polyol prepolymers (A) and (B) at this ratio, the area ratio occupied by the concave portion and the flat surface on the surface of the resin layer can be within the above range.

  The isocyanate that forms a urethane resin by polymerizing with the polyurethane prepolymer containing the polyurethane polyol prepolymers (A) and (B) is not particularly limited, and examples thereof include the following. Aliphatic polyisocyanates such as ethylene diisocyanate and 1,6-hexamethylene diisocyanate (HDI). Cycloaliphatic polyisocyanates such as isophorone diisocyanate (IPDI), cyclohexane-1,3-diisocyanate, cyclohexane-1,4-diisocyanate. Aromatic isocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, diphenylmethane diisocyanate (MDI). These copolymers and their block bodies. The amount of isocyanate used can be such that the amount of isocyanate groups in the isocyanate is 1.0 to 2.0 times the amount of hydroxyl groups in the polyurethane prepolymer.

  It is preferable that the resin layer contains a conductive agent because the conductivity having the current value can be imparted to a concave portion or a flat surface of the surface. As a conductive agent, carbon black imparts the above conductivity to the concave or flat surface of the resin layer surface, and can control the triboelectric charging performance and triboelectric charge retention performance of the toner to an optimum balance, and charge under low temperature and low humidity. It is preferable because it is excellent in suppressing the increase.

  Specific examples of the carbon black include conductive carbon black such as ketjen black and acetylene black; carbon black for rubber such as SAF, ISAF, HAF, FEF, GPF, SRF, FT, and MT. In addition, oxidation-treated carbon black for color ink, pyrolytic carbon black, and the like can be used.

  The carbon black content is preferably 10% by mass or more and 30% by mass or less in the resin.

  In addition to the above carbon black, usable conductive agents include the following. Graphite such as natural graphite and artificial graphite; metal powder such as copper, nickel, iron and aluminum; metal oxide powder such as titanium oxide, zinc oxide and tin oxide; conductive polymer such as polyaniline, polypyrrole and polyacetylene. These may be used alone or in combination of two or more as required.

  For the resin layer, other than the above resin such as urethane resin and the function of the conductive agent, the crosslinking agent, plasticizer, filler, extender, vulcanizing agent, vulcanization aid, crosslinking aid, oxidation agent An inhibitor, an anti-aging agent, a processing aid and the like can be contained.

  Examples of the thickness of the resin layer include a range of 1 μm to 100 μm.

  The developing roller of the present invention may have an elastic layer between the shaft core and the resin layer. As such an elastic layer, the hardness and elasticity that can be pressed against the photoconductor with an appropriate nip width and nip pressure are developed so that the toner can be supplied to the electrostatic latent image formed on the photoconductor surface without excess or deficiency. Provided to apply to the roller. Such an elastic layer is preferably formed of a rubber material, and specific examples include the following. Ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR). Fluoro rubber, silicone rubber, epichlorohydrin rubber, NBR hydride, urethane rubber. These can be used alone or in combination of two or more. Among these, it is preferable to use silicone rubber from the viewpoint of setting performance. Examples of the silicone rubber include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polyphenylvinylsiloxane, and copolymers of these polysiloxanes.

  The elastic layer preferably contains a conductive agent and has semiconductivity. As the conductive agent, either an ionic conductive agent or an electronic conductive agent may be used. Specifically, carbon-based materials such as carbon black and graphite; metal powders such as copper, nickel, iron and aluminum; metal oxide powders such as titanium oxide, zinc oxide and tin oxide; and conductive materials such as polyaniline, polypyrrole and polyacetylene Can be mentioned. These can be used alone or in combination of two or more. These conductive agents can be used as powdered or fibrous fine particles. Among these, carbon black is preferable because it is easy to control the conductivity, can impart good chargeability to the developing roller, and is economical.

The volume resistivity of the elastic layer is preferably in the range of 1 × 10 ³ Ω · cm to 1 × 10 ¹⁰ Ω · cm when a DC voltage of 100 V is applied. If the volume resistivity of the conductive elastic layer is within the above range, the toner can be uniformly triboelectrically charged. In the case of carbon black, the amount of the conductivity-imparting agent used to make the elastic layer have such a volume resistivity may be 15 to 80 parts by mass with respect to 100 parts by mass of the rubber component. preferable.

  Here, when measuring the volume resistivity of the elastic layer, the elastic layer material is cured under the same conditions as those for forming the elastic layer to produce a 2.0 mm thick elastic layer test piece. To make measurements. Specifically, the elastic layer material is formed into a sheet and placed in an oven at a temperature of 130 ° C. and heated for 20 minutes to form two sheets having a thickness of 2.0 mm, and then heated in an oven at a temperature of 200 ° C. for 4 hours to obtain a secondary material. Vulcanize. After that, the sheet is left in an environment of temperature 25 ° C. and humidity 45% for 24 hours or more, and measured by applying a voltage of 100 V using Hiresta IP (manufactured by Mitsubishi Oil Chemical Co., Ltd.). The volume resistivity can be obtained as an average value.

  For the elastic layer, other than the above, the crosslinking agent, plasticizer, filler, extender, vulcanizing agent, vulcanization aid, crosslinking aid, antioxidant, as long as the function of the composition is not impaired. Various additives such as anti-aging agent and processing aid can be contained. Non-conductive fillers can include silica, quartz powder, titanium oxide, zinc oxide, and calcium carbonate. Examples of the crosslinking agent include di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, and dicumyl peroxide.

  The thickness of the elastic layer can be appropriately selected so as to have a desired elasticity in relation to the developer regulating member and the photosensitive member. For example, the thickness may be in the range of 2.0 mm to 6.0 mm. It is more preferable that it is 3.0-5.0 mm.

  As a manufacturing method of the developing roller of this invention, a resin layer is shape | molded on the elastic layer shape | molded by the method mentioned later on a shaft core body or a shaft core body. The resin layer is molded by mixing the polyurethane polyol prepolymers (A) and (B) with a conductive agent such as isocyanate and carbon black, a solvent, and other additives as necessary to prepare a resin layer molding composition. To do. This can be used for molding and curing using extrusion molding, molding or injection molding, but the coating molding method is preferred. As the coating molding method, spraying, dipping, or roll coating can be used. After a coating film is formed on the shaft core or the elastic layer, this is dried to remove the solvent and cure by heating. The method can be used. Specifically, the curing may be performed by either heating or electron beam irradiation. In the case of heating, for example, the temperature can be 120 to 180 ° C. and the curing time can be 60 to 300 minutes.

  When dip coating is used to form the coating film, it is simple and excellent in production stability to use a coating apparatus as described in JP-A-57-5047 that overflows the paint from the upper end of the dip tank. Therefore, it is preferable.

  As shown in the schematic configuration diagram of FIG. 1, the coating apparatus includes a cylindrical immersion tank 27 having an inner diameter slightly larger than the outer diameter of the roller and having a depth capable of immersing the roller in the axial direction. . An annular liquid receiving portion is provided on the outer periphery of the upper edge of the immersion tank 27 and connected to the stirring tank 29. The bottom of the immersion tank 27 is connected to the stirring tank 29.

  The paint in the stirring tank 29 is sent to the bottom of the immersion tank 27 by the liquid feed pump 28. From the upper end of the immersion tank, the paint overflows and returns to the agitation tank 29 via the liquid receiving part on the outer periphery of the upper edge of the immersion tank 27. The shaft core body 2 provided with the elastic layer 3 is fixed vertically to the lifting device 30, immersed in the immersion tank 27, and pulled up to form a resin layer.

  After forming the coating film, the roller is removed from the lifting device 30, the coating film is dried and cured, and the surface layer is formed to obtain a developing roller.

  In addition, as a method of creating an elastic layer on the shaft core, a composition containing an uncured rubber component constituting the elastic layer, a conductivity imparting agent, and other components as necessary (referred to as an uncured rubber composition) .) Is prepared. Using this uncured rubber composition, an uncured product is formed on the shaft core by a method such as an extrusion molding method, a mold molding method, an injection molding method, or a coating molding method, and cured by heating or electron beam irradiation. Then, the elastic layer is formed. In order to improve adhesion with the upper resin layer and suppress peeling, the surface can be polished or modified by a surface modification method such as corona treatment, flame treatment, or excimer treatment.

  The developing roller of the present invention has a resin layer on the shaft core, but preferably has one or more elastic layers between the shaft core and the resin layer, and further between the elastic layer and the resin layer. It may have a functional layer having a function such as easy charging or friction resistance. As an example of the present invention, there can be mentioned a developing roller 1 having an elastic layer 3 and a resin layer 4 on a conductive shaft core 2 as shown in FIG.

  The electrophotographic image forming apparatus according to the present invention includes a developing roller for supplying a developer for making an electrostatic latent image on a latent image carrier a toner image, and a developer regulation that makes the amount of developer on the developing roller constant. And a developing roller is the developing roller. As an example, a tandem color electrophotographic apparatus shown in the schematic configuration diagram of FIG. 3 can be cited. The color electrophotographic apparatus shown in FIG. 3 includes image forming units a to d that are provided for each color toner of yellow toner, magenta toner, cyan toner, and black toner. Each image forming unit is provided with a photoreceptor 5 as an electrostatic latent image carrier that rotates in the direction of the arrow. Around each photoconductor, a charging device 12 for uniformly charging the photoconductor, exposure means for irradiating the uniformly charged photoconductor with laser light 11 to form an electrostatic latent image, electrostatic A developing device 10 is provided that supplies toner to the photoreceptor on which the latent image is formed to develop the electrostatic latent image. On the other hand, a transfer conveyance belt 21 that conveys a recording material 23 such as paper supplied by a paper feed roller 24 is provided suspended from a drive roller 17, a driven roller 22, and a tension roller 20. A charge of the suction bias power supply 26 is applied to the transfer and transport belt 21 via the suction roller 25, and the recording material 23 is electrostatically attached to the surface and transported.

  Each image forming unit is provided with a transfer bias power source 19 for applying a charge for transferring the visualized toner image on the photosensitive member to the recording material 23 conveyed by the transfer conveyance belt 21. The transfer bias power is applied to the back surface of the transfer conveyance belt 21 via the transfer roller 18. The toner images of the respective colors formed in the respective image forming units are sequentially transferred onto the recording material 23 conveyed by the transfer conveying belt 21 that is moved in synchronization with the image forming unit by the transfer bias charge applied from the back surface thereof. The images are superimposed and transferred.

  Further, the color electrophotographic image forming apparatus includes a fixing device 16 for fixing the toner image superimposed and transferred onto the recording material by heating, and a conveying device (not shown) for discharging the image-formed recording material 23 to the outside. Provided.

  On the other hand, each image forming unit is provided with a cleaning device 13 having a cleaning blade for removing residual toner remaining without being transferred onto each photoconductor and cleaning the surface. Further, a waste toner container for storing toner scraped off from the photoreceptor is provided. The cleaned photoconductor is set in an image-formable state and stands by.

  The developing device 10 provided in each of the image forming units is provided with a toner container 8 containing a non-magnetic toner as a one-component toner and a toner container that closes an opening of the toner container, and a photosensitive member is exposed at a portion exposed from the toner container. A developing roller 6 is provided so as to oppose to. In the toner container, the toner is supplied to the developing roller, and at the same time, the developer supplying roller 7 for scraping off the toner remaining on the developing roller after development, and the toner on the developing roller are formed in a thin film shape. In addition, a developer regulating member 9 that is frictionally charged is provided. A blade bias power source 14 is connected to the developer regulating member 9, and a developing roller bias power source 15 is connected to the developing roller 6, and charges are applied to the developer regulating member and the developing roller at the time of image formation. The blade bias power supply 14 applies the voltage of the developer regulating member so as to provide a difference of −400 to −50 V based on the voltage of the developing roller applied by the developing roller bias power supply 15.

  The developer supply roller includes a foamed sponge body, polyurethane foam on the shaft core, and a fur brush structure in which fibers such as rayon and polyamide are implanted, and residual toner on the developing roller after development. It is preferable because it can be easily removed.

  In such an electrophotographic image forming apparatus, even when the developer regulating member is applied with a voltage difference of −400 V or more and −50 V or less with respect to the voltage applied to the developing roller, the occurrence of fog or blotch image is suppressed. can do. By using the above developing roller, the toner that has deteriorated after long-term use is sufficiently charged, the toner is prevented from being overcharged at low temperature and low humidity, and the toner on the developing roller is imparted with an appropriate frictional charge. It is considered that the friction charge can be retained.

  The process cartridge for an electrophotographic apparatus of the present invention has a developing roller for supplying a developer for using the electrostatic latent image of the latent image carrier as a toner image, and is detachably provided on the main body of the electrophotographic apparatus. The developing roller is the above-mentioned developing roller. As an example, a process cartridge for an electrophotographic apparatus shown in the schematic configuration diagram of FIG. 4 can be cited. The process cartridge for an electrophotographic apparatus shown in FIG. 4 includes a developing device 10, a photoreceptor 5, and a cleaning device 13, which are integrated and detachably provided on the main body of the electrophotographic apparatus. Examples of the developing device 10 include the same ones as described above. In addition to the above, the process cartridge for an electrophotographic apparatus of the present invention replaces a transfer member for transferring a toner image on a photosensitive member to a recording material together with the above member or one or more of the above members. May be provided integrally.

  Hereinafter, the developing roller, the process cartridge for an electrophotographic apparatus, and the electrophotographic image forming apparatus of the present invention will be described in detail, but the technical scope of the present invention is not limited to these. Hereinafter, “part” means “part by mass”.

[Example 1]
[Preparation of elastic layer]
An axial core body having a diameter of 8 mm and a length of 280 mm was placed concentrically in a cylindrical mold having an inner diameter of 16 mm, and the pieces at both ends were fixed at a pressure of 0.3 MPa. A liquid conductive silicone rubber (Asker C hardness 50 degree, volume resistivity 10 ⁶ Ωcm product manufactured by Toray Dow Silicone Co., Ltd.) was cast as an elastic layer, placed in an oven at a temperature of 130 ° C., and heat-molded for 20 minutes. After demolding, secondary vulcanization was performed in an oven at a temperature of 200 ° C. for 2 hours to prepare an elastic layer having a thickness of 4 mm.

[Preparation of polyurethane prepolymer]
Polytetramethylene glycol PolyTHF 2900 (BASF) 100 parts, chain extension isocyanate compound Cosmonate MDI (Mitsui Chemicals Polyurethane Co., Ltd.) 22 parts are mixed stepwise in MEK solvent, and the temperature is increased to 80 ° C. in a nitrogen atmosphere. For 2 hours. A polyurethane polyol prepolymer (A) having a number average molecular weight Mn = 7500 was obtained.

  To 100 parts of polytetramethylene glycol PolyTHF 1000 (manufactured by BASF), 22 parts of chain extension isocyanate compound Cosmonate MDI (manufactured by Mitsui Chemicals Polyurethane) were mixed stepwise in a MEK solvent, and the mixture was added at 80 ° C. under nitrogen atmosphere. Reacted for hours. A polyurethane polyol prepolymer (B) having a number average molecular weight Mn = 4000 was obtained.

  Next, 25 parts of polyurethane polyol prepolymer (A) and 75 parts of polyurethane polyol prepolymer (B) were mixed to obtain a polyurethane prepolymer. Table 1 shows the values of Mn (a) / Mn (b) and Mn (A) / Mn (B). Table 1 shows the following. Type and number average molecular weight (Mn (a), Mn (b)), reaction time of the polyol (original raw material polyol) constituting the polyether polyol of the raw material of the polyurethane polyol prepolymer (A) and polyurethane polyol prepolymer (B) . Number average molecular weights (Mn (A), Mn (B)) and mixing ratio of the obtained polyurethane polyol prepolymer (A) and polyurethane polyol prepolymer (B).

[Preparation of surface layer]
30 parts of coronate 2521 (manufactured by Nippon Polyurethane Industry Co., Ltd.) and 30 parts of carbon black MA11 (manufactured by Mitsubishi Chemical Corporation) were mixed with 100 parts of the obtained polyurethane prepolymer. It melt | dissolved and mixed in methyl ethyl ketone (MEK) so that it might become 30 mass% of total solid content, and it disperse | distributed uniformly with the sand mill, and obtained the dispersion liquid. This dispersion was diluted with MEK to a viscosity of 10 to 13 cps to prepare a coating solution.

  After dip-coating the obtained coating solution on the elastic layer, it is dried at room temperature for 5 hours, and heat-treated at a temperature of 150 ° C. for 2 hours to produce a resin layer having a thickness of about 15 μm on the outer periphery of the elastic layer, A developing roller was obtained.

[Development roller property evaluation]
According to the method described above, the depth of the recess on the surface of the resin layer, the area occupied by the recess on the surface of the resin layer, the average current value of the recess (Ih), and the average current value of the flat surface of the resin layer excluding the recess (Ip ), The surface roughness Ra of the recesses was evaluated. The results are shown in Table 2.

[Image evaluation]
The produced developing roller was mounted on a laser printer (trade name: LBP5500; manufactured by Canon) having the configuration of the electrophotographic image forming apparatus shown in FIG. . The laser printer was remodeled from 17 sheets / minute to 40 sheets / minute (hereinafter referred to as a modified machine). The results are shown in Table 2.

[Blotch image evaluation]
The modified machine was left in a low temperature and low humidity environment (L / L) at a temperature of 15 ° C. and a humidity of 10% RH for 24 hours. Thereafter, under the same environment, a bias of −350 V was applied to the developing roller and a bias of −600 V was applied to the stainless steel developer regulating member, and 10 halftone images were output at a speed of 40 sheets / minute. Blotch images were evaluated on the 1st to 10th images according to the following criteria.

A: Blotch is not observed at all B: Blotch is observed up to the 1st to 3rd sheets, but not observed in the 3rd to 10th sheets C: Blotch is recognized up to the 1st to 7th sheets, but 8 to 10 Not recognized on the first sheet D: Blotch is observed even on the tenth sheet. Moreover, the blotch image evaluation at room temperature and normal humidity (N / N) at a temperature of 23.5 ° C. and a humidity of 50% RH was also performed.

[Durability cover evaluation]
After the developing roller was loaded into the modified machine, it was left for 24 hours in a high temperature and high humidity environment (H / H) at a temperature of 30 ° C and a humidity of 80% RH. Thereafter, under the same environment, a bias of −350 V was applied to the developing roller, a bias of −600 V was applied to the stainless steel developer regulating member, and 35000 sheets were continuously output at a printing rate of 1% at a speed of 40 sheets / min. The printer was stopped during image output. The toner adhering to the photosensitive member is peeled off with a tape and attached to white paper (Business Multipurpose 4200: manufactured by XEROX), and the reflection density is measured with a reflection densitometer (TC-6DS / A, manufactured by Tokyo Denshoku). Was measured. Only the tape was affixed to white paper as a standard, and the amount of decrease in reflectance (%) relative to the standard was defined as a fog value (%), and evaluation was performed according to the following standards.

A: Less than 2% B: 2% or more and less than 10% C: 10% or more and less than 15% D: 15% or more In addition, durability fogging evaluation under normal temperature and normal humidity was also performed.

[Examples 2 to 10]
A developing roller was prepared in the same manner as in Example 1 except that the polyurethane polyol prepolymer (A) and the polyurethane polyol prepolymer (B) were synthesized and adjusted as shown in Table 1. went. The results are shown in Table 2.

[Comparative Examples 1-6]
A developing roller was prepared in the same manner as in Example 1 except that the polyurethane polyol prepolymer (A) and the polyurethane polyol prepolymer (B) were synthesized and adjusted as shown in Table 3, and the development roller physical property evaluation and image evaluation were performed. went. The results are shown in Table 4.

Table 5 shows materials indicated by the abbreviations of the original raw material polyols in Tables 1 and 3.

  From the results, by using the developing roller of the present invention, it is possible to give a stable and appropriate charge to the toner without depending on the environment and hold it, and a fogged image under high temperature and high humidity and a blotch image under low temperature and low humidity can be obtained. It can be seen that good images can be formed while being suppressed.

It is a schematic block diagram which shows an example of the manufacturing apparatus of the developing roller of this invention. It is a schematic side view which shows an example of the developing roller of this invention. 1 is a schematic configuration diagram illustrating an example of an electrophotographic image forming apparatus of the present invention. 1 is a schematic configuration diagram illustrating an example of a process cartridge for an electrophotographic apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 6 Developing roller 2 Shaft core body 3 Elastic layer 4 Resin layer 5 Photoconductor 7 Developer supply roller 8 Toner container 9 Developer control member 10 Developing device 11 Laser beam 12 Charging device 13 Cleaning device 14 Blade bias power supply 15 Developing roller Bias power supply 16 Fixing device 17 Drive roller 18 Transfer roller 19 Transfer bias power supply 20 Tension roller 21 Transfer conveyance belt 22 Driven roller 23 Recording material 24 Paper feed roller 25 Adsorption roller 26 Adsorption bias power supply 27 Immersion tank 28 Liquid feed pump 29 Stirring tank 30 lift device

Claims (8)

  In a developing roller having a shaft core and a resin layer provided on the shaft core, the resin layer has a recess having a depth of 50 nm or more and 500 nm or less on the surface, and the area occupied by the recess on the surface of the resin layer Is in the range of 5% or more and 25% or less with respect to the surface area of the resin layer, and the average current value (Ih) of the recesses as measured using a scanning probe microscope is the average current of the flat surface of the resin layer surface excluding the recesses A developing roller having a value greater than 100 times the value (Ip) and in the range of 0.5 nA to 80 nA.   2. The developing roller according to claim 1, wherein the surface roughness Ra of the concave portion of the resin layer is 15.0 nm or more and 75.0 nm or less. The resin layer is formed using a resin obtained by polymerizing a polyurethane prepolymer and an isocyanate, and the polyurethane prepolymer has a mass of the following polyurethane polyol prepolymer (A) and the following polyurethane polyol prepolymer (B). The developing roller according to claim 1 or 2, wherein the ratio A / B is in the range of 5/95 to 25/75 and contains carbon black.
(However, the polyurethane polyol prepolymer (B) is obtained by chain-extending a bifunctional polyether polyol having a number average molecular weight Mn (b) of 650 to 2,000 with diphenylmethane diisocyanate, and having a number average molecular weight Mn (B) of 3,000 or more. 30000 or less.
The polyurethane polyol prepolymer (A) is obtained by chain-extending a bifunctional polyether polyol having a number average molecular weight Mn (a) satisfying the following formula (1) with diphenylmethane diisocyanate, and the number average molecular weight Mn (A) is represented by the following formula: Satisfy (2).
1.4 <Mn (a) / Mn (b) <5 (1)
0.25 ≦ Mn (A) / Mn (B) ≦ 4 (2))   The polyurethane polyol prepolymer (A) or the polyurethane polyol prepolymer (B), or the bifunctional polyether polyol constituting the polyurethane polyol prepolymer (A) and the polyurethane polyol prepolymer (B) is polytetramethylene glycol. The developing roller according to claim 3.   5. The developing roller according to claim 3, wherein the polyurethane polyol prepolymer (B) has a number average molecular weight Mn (B) of 17,000 or more and 30000 or less.   6. The developing roller according to claim 1, further comprising an elastic layer between the shaft core and the resin layer.   In a process cartridge for an electrophotographic apparatus, which has a developing roller for supplying a developer for making the electrostatic latent image of the electrostatic latent image carrier a toner image, and is detachably provided in the electrophotographic apparatus main body, the developing roller includes 7. A process cartridge for an electrophotographic apparatus, which is the developing roller according to claim 1.   Electrophotographic image forming comprising: a developing roller for supplying a developer for forming an electrostatic latent image on an electrostatic latent image carrier into a toner image; and a developer regulating member for making the amount of developer on the developing roller constant In the apparatus, the developing roller is the developing roller according to any one of claims 1 to 6, and a voltage applied to the developer regulating member has a difference of −400 V or more and −50 V or less with respect to a voltage applied to the developing roller. An electrophotographic image forming apparatus comprising:

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