JP5495768B2 - Developing roller and manufacturing method thereof, process cartridge, and electrophotographic image forming apparatus - Google Patents

Description

  The present invention relates to a developing roller, a manufacturing method thereof, a process cartridge, and an electrophotographic image forming apparatus.

  The object of the invention described in Patent Document 1 is to suppress the discharge phenomenon at the end in the charging roll axial direction without providing an extra coating layer, to reduce the etching action on the surface of the photosensitive drum, and to extend the life of the photosensitive drum. It is to provide a charging roll capable of achieving the above. And in Patent Document 1, a conductive layer containing an ionic conductive agent is formed around the shaft body, and the ionic conductive agent is deposited on the outer side or the inner side in the roll radial direction of the end portion in the roll axial direction. It is described that the above-mentioned object is achieved by a charging roll having an increased electrical resistance at the end portion in the roll axial direction.

JP-A-11-272040

  The inventors of the present invention have examined the configuration described in Patent Document 1 and have confirmed the effect of suppressing current leakage in the roll axis direction. There is a problem that the electrical resistance easily changes with use.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a developing roller that can further suppress the discharge at the end portion with another member that abuts, and that exhibits stable charging performance over a long period of time, and a method for manufacturing the developing roller. Another object of the present invention is to provide an electrophotographic image forming apparatus and a process cartridge capable of providing high-quality electrophotographic images over a long period of time.

The developing roller according to the present invention is a developing roller comprising a shaft core, a conductive elastic layer containing silicone rubber and conductive particles, and a resin layer in this order,
Silicon dioxide is unevenly distributed at the axial end portion of the elastic layer, and the electric resistance of the end surface of the elastic layer is increased.

  Further, in the method for producing the developing roller according to the present invention, the resin layer is formed on the peripheral surface of the conductive elastic layer containing silicone rubber and conductive particles, and then the axial end portion of the elastic layer is formed. And a step of selectively applying a direct current to the substrate to burn siloxane contained in the elastic layer to form silicon dioxide at the end of the elastic layer.

  Furthermore, a process cartridge according to the present invention includes a photoconductor and a developing roller disposed in contact with the photoconductor, and is configured to be detachable from the main body of the electrophotographic image forming apparatus. The developing roller is the above-described developing roller.

  Furthermore, the electrophotographic image forming apparatus according to the present invention includes a photoconductor and a developing roller disposed in contact with the photoconductor, wherein the developing roller is the above-described developing roller. It is characterized by being.

  According to the present invention, it is possible to suppress the occurrence of current leakage between the developing roller and the contact member to the developing roller at the end portion in the axial direction of the developing roller. Further, the process cartridge and the electrophotographic image forming apparatus of the present invention are capable of stable image formation over a long period of time.

It is sectional drawing of the direction orthogonal to the axial direction of the developing roller concerning this invention, and an axis | shaft. Is an illustration of SiO ₂ unevenly distributed processing apparatus developing roller according to the present invention. It is a schematic block diagram of a resistance measuring apparatus. 1 is a cross-sectional view of an electrophotographic image forming apparatus according to the present invention. It is sectional drawing of the process cartridge which concerns on this invention.

As described above, the present inventors suppress current leakage by making SiO ₂ unevenly distributed on both end faces of the conductive elastic layer containing the silicone rubber and conductive particles of the developing roller to increase resistance. The inventors have found that a developing roller capable of being realized can be realized, and have completed the present invention. In the following, for the sake of simplicity, the elastic layer containing silicone rubber of the developing roller may be referred to as “silicone rubber elastic layer”.

  The current leakage of the developing roller is caused by the current flowing into the developing roller due to the potential difference provided between the developing roller and another member used, and the developing bias applied to the developing roller fluctuates. This is a phenomenon in which horizontal streaks are formed. The current flowing into the developing roller is larger at the end compared to the central portion of the developing roller. This is because the current flows more easily on the end face of the developing roller than in the elastic layer and the resin layer constituting the developing roller. Therefore, controlling the resistance of the end face of the developing roller is effective in suppressing current leakage.

  However, when a high resistance material layer different from the elastic layer is formed at the end of the elastic layer to increase the resistance, current flows easily at the interface between the elastic layer and the high resistance material layer, resulting in current leakage. Cannot be sufficiently suppressed.

Therefore, as a result of intensive studies on a method for suppressing current leakage from the end face of the elastic layer, the elastic layer is formed of a material containing silicone rubber, SiO ₂ is unevenly distributed at the axial end of the elastic layer, and the axis of the elastic layer is It has been found that current leakage can be effectively suppressed by increasing the resistance of the direction end face. That is, when a direct current is selectively applied to the end portion of the silicone rubber elastic layer, the low molecular weight siloxane unavoidably present in the silicone rubber is burned by electric energy, and is oxidized at the axial end portion of the elastic layer. Silicon (SiO ₂ ) is produced. As a result, the elastic layer is in a state where SiO ₂ is unevenly distributed at the axial end portion, and the electric resistance of the end surface of the elastic layer is increased. As the direct current applied to the axial end of the elastic layer, it is preferable to apply a current of 0.1 mA to 10 mA. That is, by setting the applied direct current within the above range, low molecular siloxane can be efficiently burned, and a mixed state of silicone rubber and SiO ₂ can be more preferably formed at the axial end of the elastic layer.

Furthermore, it is preferable to control the amount of SiO ₂ formed on the end face of the silicone rubber elastic layer. Specifically, SiO ₂ is mixed with silicone rubber on the end face of the elastic layer. At this time, the average atomic ratio A of Si atoms belonging to SiO ₂ with respect to all Si atoms detected on the surface of the elastic layer end face by X-ray photoelectron spectroscopy satisfies the following formula (1): It is preferable in order to achieve both suppression of current leakage and durability over a long period of use.
0.50 ≦ A <1.00 Formula (1)

Furthermore, it is possible to form a mixed state of SiO ₂ and silicone rubber at the end of the silicone rubber elastic layer by applying a direct current to the end of the silicone rubber elastic layer, and control the amount of applied current. Thus, the mixed state can be set within a desired range.

Furthermore, before applying a direct current to the end portion of the elastic layer, if the end portion is previously heated at a temperature of 50 ° C. or higher and 120 ° C. or lower, SiO ₂ at the end portion of the elastic layer is more efficiently performed. . This is presumably because unreacted siloxane in the silicone rubber elastic layer is extracted on the surface of the silicone rubber, and the uneven distribution of SiO ₂ is more easily promoted. That is, by setting the end portion of the silicone rubber elastic layer to 50 ° C. or higher, siloxane in the elastic layer can be easily extracted on the surface, and SiO ₂ can be efficiently formed. Moreover, by setting it as 120 degrees C or less, the hardness of the silicone rubber elastic layer by heat | fever does not fall, but durability can fully be acquired.

  By mounting the developing roller of the present invention as a developing roller on a process cartridge including a photosensitive member and a developing roller disposed in contact with the photosensitive member, current leakage is suppressed and stable over a long period of time. Image formation is possible. The process cartridge is configured to be detachable from the electrophotographic image forming apparatus.

  Further, the developing roller of the present invention suppresses current leakage by being mounted as a developing roller on an electrophotographic image forming apparatus provided with a developing roller disposed in contact with a photosensitive member, without using a process cartridge. In addition, stable image formation is possible over a long period of time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

<Developing roller>
A sectional view of an example of the developing roller according to the present invention is shown in FIG. (A) is sectional drawing of an axial direction, (b) is sectional drawing of the direction orthogonal to an axis | shaft.

The developing roller 10 is provided on a cylindrical shaft core 11, a conductive elastic layer 12 formed of a material including silicone rubber and conductive particles provided around the shaft core 11, and the periphery thereof. Further, at least one resin layer 13 is provided in this order. Moreover, the resin layer may be formed of two or more layers. Then, the end surface of the silicone rubber elastic layer 12 layer SiO ₂ is unevenly distributed silicone rubber and SiO ₂ are mixed (SiO ₂ enriched region) 14 is formed.

  The material of the shaft core 11 is not particularly limited as long as it is conductive, and can be appropriately selected from carbon steel, alloy steel, cast iron, and conductive resin. Examples of the alloy steel include stainless steel, nickel chromium steel, nickel chromium molybdenum steel, chromium steel, chromium molybdenum steel, nitriding steel to which Al, Cr, Mo and V are added. Furthermore, as a rust prevention measure, the shaft core body can be plated and oxidized. As the type of plating, either electroplating or electroless plating may be used, but electroless plating is preferable from the viewpoint of dimensional stability. Examples of the electroless plating used here include nickel plating, copper plating, gold plating, Kanigen plating, and other various alloy plating. Examples of the nickel plating include Ni-P, Ni-B, Ni-WP, and Ni-P-PTFE composite plating. The thickness of the plating is preferably 0.05 μm or more, more preferably 0.10 μm to 30.00 μm. In the above description, a columnar shape is shown, but a cylindrical shape may be used as long as it has sufficient strength. Further, the diameter is suitably 3 mm to 10 mm, and preferably 4 mm to 8 mm.

  The elastic layer 12 is formed from a material containing silicone rubber. The silicone rubber may be used alone or in combination with one or more selected from natural rubber, isoprene rubber, styrene rubber, butyl rubber, butadiene rubber, fluorine rubber, and urethane rubber.

  Any silicone rubber can be used as long as it can be used for forming the elastic layer of the developing roller, and specific examples thereof include the following. Polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polytrifluoropropylvinylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, and a copolymer comprising a plurality of structural units of these polysiloxanes.

  The thickness of the elastic layer 12 is preferably 0.5 mm to 10.0 mm in order to give the developing roller 10 sufficient elasticity. If the thickness of the elastic layer 12 is 0.5 mm, the developing roller 10 has sufficient elasticity and wear of the photoreceptor is suppressed. The thickness of the elastic layer 12 is not particularly limited as long as it does not hinder the developer conveyance, but is preferably 10.0 mm in view of cost and the like.

  The elastic layer 12 preferably has an Asker-C hardness of 10 degrees to 80 degrees. When the hardness of the elastic layer 12 is 10 degrees or more, the occurrence of image defects due to deformation of the elastic layer is suppressed, and when the hardness is 80 degrees or less, the wear of the photoreceptor is suppressed. In addition, when MD-1 hardness measured with the developing roller after providing the resin layer described below is in a predetermined range, it is not necessary to confirm the hardness of the elastic layer 12 itself.

  A filler may be added to the elastic layer 12 as long as the low hardness and low compression set characteristics of the silicone rubber are not impaired. Specific examples of the filler include the following. Quartz fine powder, fumed silica, wet silica, diatomaceous earth, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate, barium sulfate Glass fiber, organic reinforcing agent, organic filler and so on. These fillers may be treated with an organosilicon compound such as polydiorganosiloxane to make the surface hydrophobic.

  As a means for making the elastic layer 12 conductive, there is a technique of making it conductive by adding a conductive agent by an ionic conduction mechanism or an electronic conduction mechanism to the material.

The following are mentioned as a electrically conductive agent by an ionic conduction mechanism. Periodic table group 1 metal salts such as LiCF ₃ SO ₃ , NaClO ₄ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , NaSCN, KSCN, NaCl, NH ₄ Cl, (NH ₄ ) ₂ SO ₄ , NH ₄ NO ₃ Ammonium salts such as Ca (ClO ₄ ) ₂ , Ba (ClO ₄ ) ₂ and other group 2 metal salts, salts thereof and 1,4-butanediol, ethylene glycol, polyethylene glycol, propylene glycol, Complexes of poly (propylene glycol) with polyhydric alcohols and derivatives thereof, complexes of these salts with ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, polyethylene glycol monomethyl ether, polyethylene glycol monoethyl ether monool, quaternary ammonium Salt cationic surfactant , Aliphatic sulfonate, alkyl sulfate ester salt, alkyl phosphate ester anionic surfactant, betaine amphoteric surfactant and the like.

  Moreover, the following are mentioned as a electrically conductive agent by an electronic conduction mechanism. Carbon materials such as carbon black and graphite, metals or alloys such as aluminum, silver, gold, tin-lead alloy, copper-nickel alloy, zinc oxide, titanium oxide, aluminum oxide, tin oxide, antimony oxide, indium oxide, oxidation Metal oxides such as silver and various fillers plated with conductive metal such as copper, nickel and silver.

  These conductive agents based on the ion conductive mechanism and the electronic conductive mechanism can be used alone or in admixture of two or more in the form of powder or fiber. Among these, carbon black is preferably used as the conductive agent from the viewpoint that the conductivity can be easily controlled and is economical.

  The resin layer 13 is formed on, for example, a roller having an elastic layer manufactured by injecting the material for the elastic layer on the outer periphery of the shaft core body 11 into a cylindrical mold containing the shaft core body and curing it. It is manufactured by applying and curing a raw material coating solution for a layer. For example, the resin layer can be obtained by applying a raw material coating solution for the resin layer on the elastic layer using a general method such as a dipping method, a spray coating method, or a roll coating method, followed by heat curing. .

  Examples of the material used for the resin layer 13 include the following. Epoxy resin, diallyl phthalate resin, polycarbonate resin, fluororesin, polypropylene resin, urea resin, melamine resin, silicon resin, polyester resin, styrene resin, vinyl acetate resin, phenol resin, polyamide resin, fiber resin, urethane resin, Silicone resin, acrylic urethane resin, water-based resin. It is also possible to use a combination of two or more of these. Among these, it is particularly preferable to use a urethane resin or an acrylic urethane resin, which are nitrogen-containing compounds, because the toner can be stably charged, and more preferably, a urethane resin obtained by reacting an isocyanate compound and a polyol.

  The following are mentioned as an isocyanate compound. Diphenylmethane-4,4′-diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethylbiphenyl-4,4′-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, Carbodiimide-modified MDI, xylylene diisocyanate, trimethylhexamethylene diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, paraphenylene diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl polyisocyanate. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  Moreover, the following are mentioned as a polyol used here. As a divalent polyol (diol), ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, hexanediol, neopentyl glycol, 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, Xylene glycol, triethylene glycol; 1,1,1-trimethylolpropane, glycerin, pentaerythritol, sorbitol as trivalent or higher polyols. Furthermore, polyols such as high molecular weight polyethylene glycol, polypropylene glycol, and ethylene oxide-propylene oxide block glycol obtained by adding ethylene oxide and propylene oxide to diol and triol can also be used. Moreover, these mixtures can also be used and the mixing ratio may be any ratio.

  Furthermore, the resin layer 13 can be used after imparting conductivity. As a method for imparting conductivity, it is possible to use a method similar to the method for making the elastic layer 12 conductive.

  The thickness of the resin layer 13 is preferably 1.0 μm to 500.0 μm, and more preferably 1.0 μm to 50.0 μm. By making the resin layer 13 1.0 μm or more, durability can be given. Further, by setting the resin layer 13 to 500.0 μm or less, more preferably 50.0 μm or less, the MD-1 hardness (described later) of the developing roller 10 can be prevented from becoming too high, and toner adhesion can be suppressed. . When a plurality of resin layers are formed, it is desirable that the thickness of the entire plurality of layers be in the above range.

  The thickness of the resin layer 13 is measured by, for example, observing a cross section in the thickness direction of the resin layer using a digital microscope VHX-600 (trade name) manufactured by Keyence Corporation, and from the flat portion of the resin layer surface to the elastic layer. It is the average distance to the interface.

  The MD-1 hardness of the developing roller 10 is preferably 25.0 ° to 40.0 °. Within this range, toner adhesion and deformation due to the contact member can be effectively suppressed. Here, the MD-1 hardness is a hardness (micro rubber) measured in an environment of a temperature of 23 ° C. and a humidity of 50% RH using a micro rubber hardness meter MD-1 type (trade name) manufactured by Kobunshi Keiki Co., Ltd. Hardness).

  Since the surface roughness of the developing roller 10 greatly affects the toner conveying force, the arithmetic average roughness Ra in JIS B 0601: 2001 is preferably 0.05 μm to 3.00 μm. By setting Ra to 0.05 μm or more, it is possible to obtain a toner conveying force, and it is possible to suppress a decrease in image quality such as a decrease in image density and a ghost. Further, by setting Ra to 3.00 μm or less, it is possible to suppress deterioration in image quality such as fogging and roughness.

  As a means for controlling the surface roughness, it is effective to make the resin layer 13 contain particles having a desired particle diameter. Moreover, it is also possible to form a desired surface roughness by appropriately performing a polishing treatment before and after the formation of the resin layer. In that case, when only the elastic layer is formed, polishing treatment may be performed after the elastic layer is formed. In the case of forming a plurality of elastic layers, polishing treatment may be performed after the formation of all elastic layers. When the elastic layer and the resin layer are formed, the resin layer may be formed after the elastic layer is formed and then the polishing process may be performed, or the polishing process may be performed after the resin layer is formed.

  As the particles to be contained in the resin layer 13, metal particles and resin particles having a particle diameter of 0.1 μm to 30.0 μm can be used. Among these, resin particles that are highly flexible, have a relatively small specific gravity, and easily obtain the stability of the paint are more preferable. Examples of such resin particles include urethane particles, nylon particles, acrylic particles, and silicone particles. These resin particles can be used alone or in combination of two or more. In the case of forming a plurality of resin layers, all of the plurality of layers may contain particles, or at least one of the plurality of layers may contain particles.

The SiO ₂ unevenly distributed portions 14 are formed on both end surfaces of the elastic layer 12 as shown in FIG.

The thickness of the SiO ₂ uneven distribution portion 14 is preferably 0.05 μm or more and 10 μm or less. By setting the thickness to 0.05 μm or more, a leak suppressing effect can be sufficiently obtained. Further, by setting the thickness to 10 μm or less, it is possible to suppress the occurrence of toner sticking to the developer regulating blade due to local charge-up at the end.

The thickness of the SiO ₂ unevenly distributed portion 14 is measured using a method such as TEM (Transmission Electron Microscope).
After cutting off both end faces of the elastic layer 12, a microtome is used to produce a flake including a cross section of the SiO ₂ unevenly distributed portion 14 having a 100 μm square and a thickness of 100 nm. This sample is observed at a magnification of 10,000 times using a transmission electron microscope (trade name: H-7500, manufactured by Hitachi High-Technologies Corporation), and the thickness of the SiO ₂ unevenly distributed portion 14 is confirmed.

In the SiO ₂ unevenly distributed portion 14, it is preferable that the average atomic ratio A of Si atoms belonging to SiO ₂ with respect to all Si atoms detected by X-ray photoelectron spectroscopy satisfies 0.50 ≦ A <1.00. . Si atoms other than those belonging to SiO ₂ mainly include Si atoms belonging to the silicone rubber constituting the elastic layer 12, but other than that, it is attributed to the cyclic polysiloxane contained in the silicone rubber. Si atoms are mentioned.

The SiO ₂ unevenly distributed portion 14 is formed by changing the silicone rubber contained in the elastic layer to SiO ₂ by applying a direct current to the end portion of the elastic layer by a method described later after forming the elastic layer and the resin layer. It is possible. However, there is no particular limitation as long as a mixed state of silicone rubber and SiO ₂ can be formed.

<Method of unevenly distributing SiO ₂ on the end face of the silicone rubber elastic layer>
FIG. 2 shows an explanatory diagram of an example of a device (SiO ₂ uneven distribution processing device) used for forming SiO ₂ unevenly distributed portions by distributing SiO ₂ on the end surface of the silicone rubber elastic layer. In addition, (a) is sectional drawing parallel to a longitudinal direction, (b) is a side view.

  The apparatus 20 includes a DC power source 21 and an ammeter 22 connected to the shaft core 11 of the developing roller 10 and an Al ground electrode 23 connected to the ground. The ground electrode 23 is configured to contact the end of the developing roller 10. The shape of the ground electrode 23 is not particularly limited as long as a desired direct current can be applied to the end portion of the elastic layer.

  For example, the ground electrode 23 is provided at one end of a cylinder having an inner diameter of 12 mm, a thickness of 1 mm, and a length of 5 mm, with respect to the developing roller 10 having an outer diameter of 12 mm, in which an elastic layer and a resin layer are formed on the shaft core body 11 having an outer diameter of 6 mm. Further, it is possible to join a disc obtained by hollowing out a circle having a diameter of 10 mm. The ground electrode 23 only needs to be in contact with at least the outermost peripheral portion of the end surface of the developing roller 10 and apply a current to the end portion of the elastic layer. As the DC power source 21, for example, a small power source PL-650-0.1 (trade name, manufactured by Matsusada Precision Co., Ltd.) can be used.

Next, an operation procedure for making SiO ₂ unevenly distributed on the end face of the elastic layer will be described. The developing roller 10 is installed in the apparatus 20 installed in an environment of a temperature of 23 ° C. and a humidity of 50% RH so that the end surface of the elastic layer is in contact with the ground electrode 23. Next, a DC power source 21 and an ammeter 22 are connected to the shaft core 11 of the developing roller 10. Then, after applying a voltage to the shaft core 11 and adjusting the voltage so that the necessary DC current is applied to the end of the elastic layer, the DC power supply 21 is stopped when the SiO ₂ uneven distribution process of the silicone rubber proceeds sufficiently. To do. The voltage, the amount of direct current, the application time, etc. are adjusted as appropriate according to the amount of SiO ₂ formed.

  In the present invention, the end face of the elastic layer may be heated in advance prior to application of the direct current. In that case, it is more preferable to apply a direct current to the end portion of the elastic layer after heating to a temperature of 50 ° C. or higher and 120 ° C. or lower. The heat source is not particularly limited, but an infrared halogen lamp is preferable from the viewpoint of cost and temperature increase rate.

By changing the silicone rubber to SiO ₂ at the end of the elastic layer by the method as described above, a state in which SiO ₂ and silicone rubber are mixed (SiO ₂ unevenly distributed portion 14) is formed on the end surface of the elastic layer. The end face is increased in resistance.

<Measurement method for increasing resistance at end of developing roller>
Whether or not the end face of the elastic layer has a high resistance can be confirmed using, for example, a resistance measuring device 30 as shown in FIG.

  The resistance measuring device 30 includes an electrode roller 32 having three metal electrodes 31, a DC power source 33 that can be connected to the shaft core 11 of the developing roller 10, an internal resistance 34 and a voltmeter 35 connected to each of the metal electrodes 31. Consists of. The metal electrode 31 has a cylindrical shape with a width of 5 mm made of Al, and is provided at a position facing a total of three locations on both ends and the center of the developing roller 10. The electrode roller 32 is composed of an insulating member other than the metal electrode 31, and can be rotated by a drive motor (not shown). As the DC power supply 33, for example, a small power supply PL-650-0.1 (trade name, manufactured by Matsusada Precision Co., Ltd.) can be used. For example, a digital multimeter Fluke 83 (trade name, manufactured by Fluke) can be used as the voltmeter 35.

Next, a measurement procedure for increasing the resistance of the end portion of the developing roller will be described. The developing roller 10 is placed in pressure contact with a load applied to the electrode roller 32 in a resistance measuring device 30 installed in an environment of a temperature of 23 ° C. and a humidity of 50% RH. A load of 500 g (4.9 N) was applied to each end of the shaft core 11 to obtain a total load of 1 kg (9.8 N). Next, the electrode roller 32 is rotationally driven to adjust the rotational speed, and the rotational speed of the developing roller 10 that is driven and rotated is adjusted to 32 rpm. A voltage of 50 V is applied from the DC power source 33 to the shaft core body 11. At this time, the resistance values at both ends and the center of the developing roller 10 are measured by the following method. A voltage Vr across the internal resistor 34 connected to each of the metal electrodes 31 is measured by a voltmeter 35. The resistance value R [Ω] of the internal resistor 34 is appropriately selected so that the voltage measured by the voltmeter 35 is 0.1 to 1V. The measurement voltage Vr [V] is an average value for 3 seconds from 3 seconds after voltage application. The resistance value Rr [Ω] having a width of 5 mm at both ends and the center of the developing roller 10 is obtained by the following equation (3).
Rr = R × (50 / Vr−1) Formula (3)

  The average value of the two end portions of the developing roller 10 is defined as the resistance value of the both end portions, and the resistance value at the both end portions is higher than that at the central portion compared to the resistance value at the central portion. Judging that the end face has increased resistance.

<Analysis of SiO ₂ by X-ray photoelectron spectroscopy at the end face of elastic layer>
The degree to which SiO _{2 is} unevenly distributed on the end surface of the elastic layer is determined by quantitative analysis of SiO _{2 on} the end surface of the elastic layer by X-ray photoelectron spectroscopy. The sample is prepared by cutting the elastic layer at a 2 mm square and a depth of 3 mm from the end surface of the elastic layer of the developing roller to be measured. As the measuring device, for example, an X-ray photoelectron spectrometer (trade name: Quantum 2000, manufactured by ULVAC-PHI Co., Ltd.) can be used. The sample is placed on the X-ray photoelectron spectrometer and composition analysis is performed. Here, the analysis region is in the range of φ100 μm on the end face of the elastic layer, and Al Kα (15 kV, 25 W) is used as the X-ray source. Specifically, the peak due to the binding energy of the 2p orbit of Si is measured, the Si peak attributed to SiO ₂ is 103.5 eV, and the Si peak attributed to Si—O is 102.5 eV. Perform peak separation. From the area ratio of each waveform separated from the peak, the ratio of Si atoms attributed to SiO ₂ and Si atoms attributed to Si—O was determined. The sum total of Si atoms attributed to SiO ₂ and Si atoms attributed to Si—O was taken as the total Si atoms detected, and the average atomic ratio A of Si atoms attributed to SiO ₂ with respect to all Si atoms was calculated. In the present invention, the average atomic ratio A is obtained by measuring a total of six locations on the end surface of the developing roller, for a total of six locations.

Here, when the average atomic ratio A of Si atoms belonging to SiO ₂ with respect to all Si atoms is 1, it means that the end face of the elastic layer is entirely covered with SiO ₂ . Similarly, when the average atomic ratio A is 0, it means that SiO ₂ is not formed.

In the present invention, it is preferable that the average atomic ratio A satisfies 0.00 <A <1.00, that is, SiO ₂ is mixed and formed in the silicone rubber. ) Is more preferable.
0.50 ≦ A <1.00 Formula (1)

<Electrophotographic image forming apparatus>
FIG. 4 is a sectional view schematically showing an example of an electrophotographic image forming apparatus equipped with the developing roller of the present invention. The electrophotographic image forming apparatus 400 is a tandem color image forming apparatus in which image forming units a, b, c, and d are provided for each of yellow toner, magenta toner, cyan toner, and black toner. The image forming unit is provided with a photoreceptor 401 as an electrostatic latent image carrier that rotates in the direction of the arrow. Around the photosensitive member, a charging device 407 for the photosensitive member, exposure means for irradiating the charged photosensitive member with laser light 406 to form an electrostatic latent image, and toner on the photosensitive member on which the electrostatic latent image is formed. A developing device 405 for supplying and developing is provided. Further, a transfer conveyance belt 416 that conveys a recording material 418 such as paper supplied by a paper supply roller 419 is provided to be suspended from a drive roller 412, a driven roller 417, and a tension roller 415. A charge is applied to the transfer / conveying belt 416 from the attraction bias power source 421 via the attraction roller 420, and the recording material 418 is electrostatically attached to the surface and conveyed. A transfer roller 413 disposed on the back surface of the transfer conveyance belt 416 applies a charge for transferring the toner image on the photosensitive member of each image forming unit to the recording material 418 conveyed by the transfer conveyance belt 416. A bias power supply 414 is connected. The toner images of the respective colors formed in the image forming units are sequentially superimposed and transferred onto a recording material 418 conveyed by a transfer conveying belt 416 that is moved in synchronization with the image forming unit. . Further, a fixing device 411 for fixing the toner image superimposed and transferred on the recording material 418 by heating or the like, and a conveying device (not shown) for discharging the recording material 418 on which the image has been formed out of the device are provided.

  The image forming unit includes a cleaning device 408 having a cleaning blade that removes transfer residual toner on the photoreceptor. A developing device 405 provided in the image forming unit is provided with a non-magnetic toner as a one-component developer, a toner container 403 containing the non-magnetic toner, and an opening of the toner container, and is exposed from the toner container. A developing roller 10 is provided so as to face the photoconductor at a portion. The image forming apparatus unit according to the present invention includes the developing roller described above as the developing roller.

  In the toner container 403, a toner supply roller 402 is directed to scrape off toner remaining on the developing roller after development, while supplying toner to the developing roller 10. Further, the toner container 403 is provided with a developer regulating blade 404 made of SUS304 that forms the toner on the developing roller 10 in a thin layer and is frictionally charged. These are disposed in contact with the developing roller 10, respectively. A developer regulating blade bias power source 409 is connected to the developer regulating blade 404, a developing roller bias power source 410 is connected to the developing roller 10, and voltages are respectively applied to the developer regulating blade 404 and the developing roller 10 during image formation. Is applied. The developer regulating blade bias power source 409 outputs a voltage that is 50V to 400V lower than the voltage output from the developing roller bias power source 410. This voltage difference is appropriately set in consideration of the supply amount of the developer supplied onto the developing roller 10 and the triboelectric charge amount.

  In the present invention, an electrophotographic process cartridge can be formed by combining any of the charging member 407, the developing device 405, and the cleaning device 408 with the photosensitive member 401. FIG. 5 shows a schematic cross-sectional view of an example of an electrophotographic process cartridge equipped with the developing roller of the present invention. The process cartridge 500 includes a photosensitive member 401, a charging member 407, a developing device 405, and a cleaning device 408, which are integrated and detachable from the main body of the electrophotographic image forming apparatus. As the developing device 405, the same one as described in the electrophotographic image forming apparatus can be used. That is, as described above, the developing roller provided in the developing device 405 is used.

  Hereinafter, the present invention will be described in detail based on examples.

[Example 1]
<Production of developing roller>
According to the following procedure, a developing roller having an elastic layer and a resin layer provided as a coating layer around a cylindrical shaft core (made of SUS304 having a diameter of 6 mm and a length of 279 mm) and a SiO ₂ unevenly distributed portion is provided. Produced.

First, the following materials were mixed to obtain a liquid silicone rubber base material.
-100 parts by mass of dimethylpolysiloxane having vinyl groups at both ends and a viscosity of 100 Pa · s at 25 ° C.
-7 parts by mass of quartz powder (manufactured by Pennsylvania Glass Sand, trade name: Min-USil) as a filler.
Carbon black (manufactured by Denki Kagaku Kogyo Co., Ltd., trade name: Denka Black, powdered product) 8 parts by mass.

  This base material is prepared with a mixture of a trace amount of a platinum compound as a curing catalyst and a mixture of 3 parts by weight of an organohydrogenpolysiloxane and mixed at a mass ratio of 1: 1 to obtain a liquid silicone rubber material. It was.

A shaft core is placed in the center of a cylindrical mold having an inner diameter of 12 mm, and this liquid silicone rubber is injected into the cylindrical mold from the injection port, and is cured by heating at a temperature of 120 ° C. for 5 minutes, and then cooled to room temperature. Thereafter, the elastic layer integrated with the shaft core was removed. Further, the curing reaction was completed by heating at a temperature of 150 ° C. for 4 hours, and an elastic layer mainly composed of silicone rubber having a thickness of 3 mm was provided on the outer peripheral surface of the shaft core body. Then, the surface of the elastic layer is irradiated with a capillary excimer lamp (manufactured by Harrison Toshiba Lighting Co., Ltd.) capable of irradiating ultraviolet rays with a wavelength of 172 nm while rotating at 30 rpm with the shaft core as the rotation axis so that the integrated light quantity becomes 120 mJ / cm ² Processed. The distance between the elastic layer surface and the excimer lamp at the time of irradiation was 2 mm.

  First, 100 parts by mass of polytetramethylene glycol and 21.2 parts by mass of an isocyanate component are mixed stepwise in methyl ethyl ketone (MEK) and reacted at 80 ° C. for 6 hours in a nitrogen atmosphere to form a bifunctional polyurethane prepolymer. Obtained. Polytetramethylene glycol is manufactured by Hodogaya Chemical Co., Ltd. under the trade name: PTG650SN, number average molecular weight Mn = 1000, f = 2 (f represents the number of functional groups, the same shall apply hereinafter). Moreover, an isocyanate component is a brand name: Millionate MT, (MDI), f = 2, the product made from Nippon Polyurethane Industry Co., Ltd. The obtained polyurethane prepolymer had a weight average molecular weight Mw = 10000, a hydroxyl value of 20.0 (mg · KOH / g), a molecular weight dispersity Mw / Mn = 2.9, and Mz / Mw = 2.5. It was.

  30.0 parts by mass of polyisocyanate (trade name: Coronate 2521, manufactured by Nippon Polyurethane Industry Co., Ltd.) was added to 100.0 parts by mass of this polyurethane prepolymer so that the NCO equivalent was 1.4. The NCO equivalent represents a ratio ([NCO] / [OH]) between the number of moles of isocyanate groups in the isocyanate compound and the number of moles of hydroxyl groups in the polyol component.

  Furthermore, 22.0 parts by mass of carbon black (trade name: # 1000, pH 3.0, manufactured by Mitsubishi Chemical Corporation) was added, then MEK was added, and the solid content was 20% by mass so that a film thickness of about 20 μm was obtained. It adjusted suitably in the range thru | or 30 mass%. Thereafter, 21.0 parts by mass of urethane resin particles (trade name: C400 transparent, diameter 14 μm, manufactured by Negami Kogyo Co., Ltd.) were added, uniformly dispersed, and mixed to obtain a resin layer raw material liquid.

In the resin layer raw material liquid, the roller on which the surface of the elastic layer was irradiated was immersed, and then pulled up and dried naturally. Next, a heat treatment was performed at a temperature of 140 ° C. for 60 minutes to cure the resin layer raw material liquid to form a resin layer having an average thickness of 20.0 μm. Thereafter, both end portions were cut perpendicularly to the shaft core body so that the length of the coating layer was 235 mm to obtain a developing roller for SiO ₂ uneven distribution processing.

Then, by installing the SiO ₂ unevenly distributed processing developing roller to SiO ₂ unevenly distributed processing apparatus described above, after heating the elastic layer end surface to a temperature of 80 ° C. using an infrared halogen lamp, a direct current 1mA in the elastic layer end The voltage was adjusted to be applied, and a direct current was applied for 30 seconds.

  In this manner, a developing roller having an outer diameter of about 12 mm, a coating layer length of 235 mm, and an arithmetic average roughness Ra of 1.5 μm was produced.

<Evaluation of developing roller>
As a result of measuring the resistance by the above-described measuring method for increasing the resistance of the end portion of the developing roller, the resistance value at both ends of the developing roller is 1.0 × 10 ⁷ Ω, and the resistance value at the center portion is 2.0 × 10 6. ⁶ Ω. Therefore, it was confirmed that the resistance value of the both end portions of the developing roller was higher than that of the central portion, and the end surface of the developing roller was increased in resistance.

According to the analysis of SiO ₂ by X-ray photoelectron spectroscopy on the end face of the elastic layer, quantitative analysis of SiO _{2 on} the end face of the elastic layer was performed. As a result, the average atomic ratio A of Si atoms belonging to SiO ₂ with respect to all Si atoms was 0.75, and it was confirmed that SiO ₂ was formed in the silicone rubber.

The thickness of the SiO ₂ uneven portion 14 was confirmed by the method for evaluating the thickness of the SiO ₂ uneven portion 14 on the end face of the elastic layer. As a result, the thickness of the SiO ₂ unevenly distributed portion 14 on the elastic layer end face was 0.8 μm.

  The micro rubber hardness measured using a micro rubber hardness meter MD-1 type (trade name) manufactured by Kobunshi Keiki Co., Ltd. installed in an environment of a temperature of 23 ° C. and a humidity of 50% RH is measured at the center position of the developing roller and both ends. A total of 3 points 30 mm from the part were measured. As a result of obtaining the average value and obtaining the MD-1 hardness of the developing roller, the MD-1 hardness was 36.1.

  Further, image evaluation (leakage evaluation) was performed with an electrophotographic image forming apparatus using a developing roller manufactured under the same conditions. For the electrophotographic image forming apparatus, Color Laser Jet 3600 (trade name) manufactured by Hewlett-Packard Company was used. The process cartridge used was a dedicated black one, and the developing roller of this process cartridge was manufactured as described above, and the developer regulating blade 408 was replaced with a 100 μm thick SUS304. Further, the developer regulating blade bias power supply 413 supplies a voltage 300V lower than the voltage output from the developing roller bias power supply 414 to the developer regulating blade 408 to output an evaluation image.

(Leak evaluation)
The modified process cartridge was mounted in the black position of the image forming apparatus main body and left in an environment of a temperature of 15 ° C. and a humidity of 10% RH for 24 hours. In this environment, the initial halftone image was output first. Thereafter, 20000 sheets of images having a printing rate of 2% were output continuously, and then a halftone image after durability was output. Leak evaluation was performed from each halftone image by the following method. Leakage was determined visually by checking the presence or absence of horizontal stripes on the halftone image, and then using a reflection densitometer (trade name: GretagMacbeth RD918, manufactured by Macbeth), the density difference between the horizontal stripes and the normal part was measured. Evaluation was made according to the following criteria.
A: No horizontal streak is confirmed.
B: Although very slight horizontal streaks are confirmed, the density difference is less than 0.03.
C: Horizontal streaks are confirmed, and the density difference is 0.05 or more and less than 0.1.
D: Horizontal stripes are confirmed, and the density difference is 0.1 or more.

  The above evaluation results are shown in Table 1.

[Comparative Example 1]
The same evaluation as in Example 1 was performed using the developing roller for uneven distribution of SiO ₂ produced in Example 1 as it was as the developing roller. The resistance value at both ends of the developing roller was 1.0 × 10 ⁶ Ω, and the resistance value at the center was 2.0 × 10 ⁶ Ω. The average atomic ratio A of Si atoms belonging to SiO ₂ with respect to all Si atoms was 0.00. The evaluation results are shown in Table 1.

[Comparative Example 2]
A developing roller was prepared in the same manner as in Example 1 except that the SiO ₂ layer was directly formed on the end face of the elastic layer by a sputtering device instead of the treatment by the SiO ₂ uneven distribution processing device. went.

To form the SiO ₂ layer, a sputtering apparatus (trade name: E-200S, manufactured by Canon Anelva Engineering Co., Ltd.) was used, and the SiO ₂ layer was uniformly formed to a thickness of 1 μm using a SiO ₂ target. Further, the resistance value at both ends of the developing roller was 3.0 × 10 ⁷ Ω, the resistance value at the center portion was 2.0 × 10 ⁶ Ω, and the end face of the elastic layer was increased in resistance. The average atomic ratio A of Si atoms belonging to SiO ₂ with respect to all Si atoms was 1.00. The evaluation results are shown in Table 1.

[Examples 2 to 9]
In the uneven distribution treatment of SiO ₂ , a developing roller was prepared in the same manner as in Example 1 except that the applied DC current and the heating temperature of the end face of the elastic layer before the DC current were changed as shown in Table 1, respectively. The same evaluation as in Example 1 was performed. The evaluation results are shown in Table 1.

10 the developing roller 11 the mandrel 12 elastic layer 13 resin layer 14 SiO ₂ enriched region

Claims (5)

A developing roller comprising a shaft core, a conductive elastic layer containing silicone rubber and conductive particles, and a resin layer in this order,
A developing roller, wherein silicon dioxide is unevenly distributed at an axial end portion of the elastic layer, and an electric resistance of an end surface of the elastic layer is increased. It is a manufacturing method of the developing roller according to claim 1,
After forming a resin layer on the peripheral surface of the conductive elastic layer containing silicone rubber and conductive particles, a direct current is selectively applied to the axial end of the elastic layer to A method for producing a developing roller, comprising a step of burning siloxane contained therein to form silicon dioxide at an end of the elastic layer.   The method for producing a developing roller according to claim 2, wherein the axial end of the elastic layer is heated to 50 ° C. or higher and 120 ° C. or lower in advance prior to application of a direct current to the axial end of the elastic layer. In a process cartridge configured to be detachable from a main body of an electrophotographic image forming apparatus, comprising a photosensitive member and a developing roller disposed in contact with the photosensitive member.
An electrophotographic process cartridge, wherein the developing roller is the developing roller according to claim 1.   An electrophotographic image forming apparatus comprising a photoconductor and a developing roller disposed in contact with the photoconductor, wherein the developing roller is the developing roller according to claim 1. Forming equipment.

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