Charging roll for electrophotographic apparatus

Abstract

Provided is a charging roll for an electrophotographic apparatus that is excellent in charging property and antifouling property. 【Solution means】A charging roll 10 for an electrophotographic apparatus includes a shaft body 12, an elastic body layer 14 formed on the outer peripheral surface of the shaft body 12, and a surface layer 16 formed on the outer peripheral surface of the elastic body layer 14. The surface layer 16 contains a binder containing a urethane resin or an acrylic resin and inorganic fine particles, and the micro-roughness represented by the maximum height difference within 5 μm on the surface of the surface layer 16 is 10 nm or more and 400 nm or less.

Description

Technical Field

[0001] The present invention relates to a charging roll for electrophotographic devices, which is preferably used in electrophotographic devices such as copiers, printers, and facsimiles that employ an electrophotographic method.

Background Art

[0002] As a charging roll for electrophotographic devices, those having an elastic layer with rubber elasticity on the outer peripheral surface of a shaft body such as a core metal and having a surface layer on the outer peripheral surface of the elastic layer are known. In the charging roll, as the surface layer material, roughness-forming particles may be blended with a binder polymer. Examples of the binder polymer for the surface layer include acrylic resin, methacrylic resin, fluororesin, silicone resin, polycarbonate resin, urethane resin, polyamide resin, and the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When a urethane resin or an acrylic resin is used in the surface layer of the charging roll, the charging property becomes excellent due to high dielectric properties. However, when a urethane resin or an acrylic resin is used, the dipole moment increases due to the carbonyl group, so that it becomes easy to adsorb toner or an external additive for toner. As printing progresses, dirt on the roll surface increases, and there is a risk of image defects such as image unevenness and image streaks.

[0005] The problem to be solved by the present invention is to provide a charging roll for electrophotographic devices that is excellent in charging property and antifouling property.

Means for Solving the Problems

[0006] The charging roll for an electrophotographic apparatus according to the present invention includes a shaft body, an elastic body layer formed on the outer peripheral surface of the shaft body, and a surface layer formed on the outer peripheral surface of the elastic body layer, wherein the surface layer contains a binder containing a urethane resin or an acrylic resin and inorganic fine particles, and the micro-roughness represented by the maximum height difference within 5 μm on the surface of the surface layer is 10 nm or more and 400 nm or less.

[0007] The average particle diameter of the inorganic fine particles is preferably 10 nm or more and 450 nm or less. The content of the inorganic fine particles is preferably 30 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder. The relative dielectric constant of the inorganic fine particles is preferably 13 or less. The inorganic fine particles are preferably silica fine particles or alumina fine particles. The volume resistance of the surface layer is 3.2×10 4 Ω or more and 6.8×10 9 Ω or less.

[0008] The surface layer preferably further contains roughness-forming particles. The average particle diameter of the roughness-forming particles is preferably 5 μm or more and 30 μm or less. The content of the roughness-forming particles is preferably 15 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass of the binder.

[0009] (1) The conductive roll for an electrophotographic apparatus according to the present invention includes a shaft body, an elastic body layer formed on the outer peripheral surface of the shaft body, and a surface layer formed on the outer peripheral surface of the elastic body layer, wherein the surface layer contains a binder containing a urethane resin or an acrylic resin and inorganic fine particles, and the micro-roughness represented by the maximum height difference within 5 μm on the surface of the surface layer is 10 nm or more and 400 nm or less.

[0010] (2) In the above (1), the average particle diameter of the inorganic fine particles is preferably 10 nm or more and 450 nm or less.

[0011] (3) In the above (1) or the above (2), the content of the inorganic fine particles is preferably 30 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder.

[0012] (4) In any one of (1) to (3) above, the relative permittivity of the inorganic fine particles is preferably 13 or less.

[0013] (5) In any one of (1) to (4) above, the inorganic fine particles are preferably silica fine particles or alumina fine particles.

[0014] (6) In any one of (1) to (5) above, the volume resistivity of the surface layer is preferably 3.2×10 4 Ω or more and 6.8×10 9 Ω or less.

[0015] (7) In any one of (1) to (6) above, the surface layer preferably further contains particles for forming roughness.

[0016] (8) In (7) above, the average particle diameter of the particles for forming roughness is preferably 5 μm or more and 30 μm or less.

[0017] (9) In (7) or (8) above, the content of the particles for forming roughness is preferably 15 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass of the binder.

Advantages of the Invention

[0018] According to the charging roll for electrophotographic equipment according to the present invention, since the surface layer contains a urethane resin or an acrylic resin, the charging property is excellent. At this time, by containing inorganic fine particles together with a binder containing a urethane resin or an acrylic resin and setting the minute roughness of the surface layer within a specific range, the contact area of the toner and the external additive for toner with the roll surface can be reduced. Further, since the fine particles are composed of inorganic substances having no dipole moment, the electrostatic adsorption of the toner and the external additive for toner caused by the fine particles can be suppressed. From these, the stain on the roll surface can be prevented. As described above, the charging property and the antifouling property are excellent.

[0019] Here, when the average particle diameter of the inorganic fine particles is 10 nm or more and 450 nm or less, it is easy to keep the surface micro-roughness within a specific range, and the effect of preventing dirt on the roll surface is excellent.

[0020] And when the content of the inorganic fine particles is 30 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder, it is easy to keep the surface micro-roughness within a specific range, and the effect of preventing dirt on the roll surface is excellent.

[0021] And when the relative dielectric constant of the inorganic fine particles is 13 or less, since the surface layer does not accumulate too much charge, the discharge property is excellent and the charging property becomes good.

[0022] And when the inorganic fine particles are silica fine particles or alumina fine particles, the wear resistance is excellent and the durability can be improved.

[0023] And when the volume resistance of the surface layer is 3.2×10 4 Ω or more and 6.8×10 9 Ω or less, the charging property is excellent.

[0024] And when the surface layer further contains roughness-forming particles, suitable surface irregularities are formed on the surface layer, so that the discharge space between the photoreceptor and the charging roll is increased and the discharge is promoted. As a result, the charging property can be improved and image defects such as horizontal streaks and unevenness can be suppressed.

[0025] And when the average particle diameter of the roughness-forming particles is 5 μm or more and 30 μm or less, the charging property is excellent.

[0026] And when the content of the roughness-forming particles is 15 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass of the binder, the balance between the charging property and the antifouling property is excellent.

Brief Description of the Drawings

[0027]

Figure 1

Best Mode for Carrying Out the Invention

[0028] The charging roll for an electrophotographic apparatus according to the present invention (hereinafter sometimes simply referred to as the charging roll) will be described in detail. FIG. 1 is an external schematic view (a) of the charging roll for an electrophotographic apparatus according to an embodiment of the present invention and a cross-sectional view taken along line A-A thereof (b).

[0029] The charging roll 10 includes a shaft body 12, an elastic body layer 14 formed on the outer peripheral surface of the shaft body 12, and a surface layer 16 formed on the outer peripheral surface of the elastic body layer 14. The elastic body layer 14 is a layer (base layer) that serves as the base of the charging roll 10. The surface layer 16 is the layer that appears on the surface of the charging roll 10. Although not particularly shown, an intermediate layer such as a resistance adjustment layer may be formed between the elastic body layer 14 and the surface layer 16 as necessary.

[0030] The shaft body 12 is not particularly limited as long as it has conductivity. Specifically, examples thereof include solid bodies and hollow cores made of metals such as iron, stainless steel, and aluminum. An adhesive, a primer, or the like may be applied to the surface of the shaft body 12 as necessary. That is, the elastic body layer 14 may be adhered to the shaft body 12 via an adhesive layer (primer layer). The adhesive, the primer, or the like may be made conductive as necessary.

[0031] The elastic body layer 14 contains crosslinked rubber. The elastic body layer 14 is formed of a conductive rubber composition containing uncrosslinked rubber. The crosslinked rubber is obtained by crosslinking the uncrosslinked rubber. The uncrosslinked rubber may be a polar rubber or a nonpolar rubber.

[0032] Polar rubbers are rubbers having polar groups. Examples of the polar groups include a chloro group, a nitrile group, a carboxyl group, an epoxy group, and the like. Specific examples of the polar rubbers include hydrin rubber, nitrile rubber (NBR), urethane rubber (U), acrylic rubber (a copolymer of an acrylate ester and 2-chloroethyl vinyl ether, ACM), chloroprene rubber (CR), epoxidized natural rubber (ENR), and the like. Among the polar rubbers, hydrin rubber and nitrile rubber (NBR) are more preferable from the viewpoint that the volume resistivity is particularly likely to be low.

[0033] Examples of the hydrin rubber include a homopolymer of epichlorohydrin (CO), a binary copolymer of epichlorohydrin and ethylene oxide (ECO), a binary copolymer of epichlorohydrin and allyl glycidyl ether (GCO), a terpolymer of epichlorohydrin, ethylene oxide, and allyl glycidyl ether (GECO), and the like.

[0034] Examples of the urethane rubber include a polyether type urethane rubber having an ether bond in the molecule. The polyether type urethane rubber can be produced by the reaction of a polyether having hydroxyl groups at both ends and a diisocyanate. The polyether is not particularly limited, and examples thereof include polyethylene glycol, polypropylene glycol, and the like. The diisocyanate is not particularly limited, and examples thereof include tolylene diisocyanate, diphenylmethane diisocyanate, and the like.

[0035] Examples of the non-polar rubbers include silicone rubber (Q), isoprene rubber (IR), natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR), and the like. Among the non-polar rubbers, isoprene rubber is more preferable from the viewpoint of excellent tensile physical properties.

[0036] Examples of the crosslinking agent include a sulfur crosslinking agent, a peroxide crosslinking agent, and a dechlorination crosslinking agent. These crosslinking agents may be used alone or in combination of two or more.

[0037] Examples of sulfur crosslinking agents include conventionally known sulfur crosslinking agents such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, sulfur chloride, thiuram-based vulcanization accelerators, and polymer polysulfides.

[0038] Examples of peroxide crosslinking agents include conventionally known peroxide crosslinking agents such as peroxyketals, dialkyl peroxides, peroxy esters, ketone peroxides, peroxydicarbonates, diacyl peroxides, and hydroperoxides.

[0039] Examples of dechlorination crosslinking agents include dithiocarbonate compounds. More specifically, examples include quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, 6-isopropylquinoxaline-2,3-dithiocarbonate, 5,8-dimethylquinoxaline-2,3-dithiocarbonate, and the like.

[0040] From the perspective of being difficult to bleed, the compounding amount of the crosslinking agent is preferably in the range of 0.1 to 2 parts by mass, more preferably in the range of 0.3 to 1.8 parts by mass, and even more preferably in the range of 0.5 to 1.5 parts by mass with respect to 100 parts by mass of the uncrosslinked rubber.

[0041] When a dechlorination crosslinking agent is used as the crosslinking agent, a dechlorination crosslinking accelerator may be used in combination. Examples of the dechlorination crosslinking accelerator include 1,8-diazabicyclo(5,4,0)undecene-7 (hereinafter abbreviated as DBU) or its weak acid salts. The dechlorination crosslinking accelerator may be used in the form of DBU, but from the perspective of handling, it is preferably used in the form of its weak acid salt. Examples of the weak acid salts of DBU include carbonates, stearates, 2-ethylhexanoates, benzoates, salicylates, 3-hydroxy-2-naphthoates, phenol resin salts, 2-mercaptobenzothiazole salts, 2-mercaptobenzimidazole salts, and the like.

[0042] As the content of the dechlorination crosslinking accelerator, from the viewpoint of being difficult to bleed, etc., it is preferably in the range of 0.1 to 2 parts by mass with respect to 100 parts by mass of the uncrosslinked rubber. More preferably, it is in the range of 0.3 to 1.8 parts by mass, and even more preferably, it is in the range of 0.5 to 1.5 parts by mass.

[0043] In the elastic layer 14, a conductive agent can be blended for imparting conductivity. Examples of the conductive agent include an electron conductive agent and an ion conductive agent. Examples of the electron conductive agent include carbon black, graphite, and a conductive metal oxide. Examples of the conductive metal oxide include a conductive titanium oxide, a conductive zinc oxide, and a conductive tin oxide. Examples of the ion conductive agent include a quaternary ammonium salt, a borate, and a surfactant. Further, various additives may be appropriately added to the elastic layer 14 as necessary. Examples of the additives include a lubricant, a vulcanization accelerator, an antioxidant, a light stabilizer, a viscosity modifier, a processing aid, a flame retardant, a plasticizer, a foaming agent, a filler, a dispersant, an antifoaming agent, a pigment, and a mold release agent.

[0044] The elastic layer 14 can be adjusted to a predetermined volume resistivity depending on the type of crosslinked rubber, the blending amount of the ion conductive agent, the blending of the electron conductive agent, etc. The volume resistivity of the elastic layer 14 is 10 2 ~10 10 Ω·cm, 10 3 ~10 9 Ω·cm, 10 4 ~10 8 Ω·cm, and can be appropriately set within a range such as this.

[0045] The thickness of the elastic layer 14 is not particularly limited, and can be appropriately set within a range of 0.1 to 10 mm depending on the use, etc.

[0046] The surface layer 16 contains a binder and inorganic fine particles. The surface layer 16 may further contain particles for forming roughness.

[0047] The binder is the base material that constitutes the surface layer 16. Examples of the binder include urethane resin, polyamide resin, acrylic resin, acrylic silicone resin, butyral resin (PVB), alkyd resin, polyester resin, fluororubber, fluororesin, a mixture of fluororubber and fluororesin, silicone resin, silicone graft acrylic polymer, acrylic graft silicone polymer, nitrile rubber, urethane rubber, and the like. In the present invention, the binder contains a urethane resin or an acrylic resin. Since the urethane resin and the acrylic resin have high dielectric properties due to the carbonyl group, the binder can have excellent chargeability by containing the urethane resin or the acrylic resin. The binder of the surface layer 16 may contain other materials as long as the urethane resin or the acrylic resin is the main component. The main component refers to 50% by mass or more of the binder. More preferably, the main component is 70% by mass or more, still more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0048] In the surface layer 16, by blending inorganic fine particles, fine irregularities with a nano-order fine roughness can be formed on the surface of the surface layer 16. Due to the fine irregularities with the fine roughness, the contact area of the toner and the external additive for toner with the surface of the surface layer 16 becomes small, so that the toner and the external additive for toner are less likely to adhere to the surface of the surface layer 16. Further, since the inorganic fine particles are composed of an inorganic substance having no dipole moment, the toner and the external additive for toner are less likely to be electrostatically adsorbed on the surface of the surface layer 16. By these, the contamination of the roll surface can be prevented.

[0049] The surface roughness is represented by the maximum height difference within 5 μm on the surface of the surface layer 16. The surface roughness of the surface layer 16 shall be 10 nm or more and 400 nm or less. If the surface roughness of the surface layer 16 is less than 10 nm, the surface roughness is too small, the effect of reducing the contact area with the toner or the external additive of the toner is low, and the effect of reducing the stain during durability is low. Also, from this perspective, the surface roughness of the surface layer 16 is preferably 15 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. On the other hand, if the surface roughness of the surface layer 16 exceeds 400 nm, the surface roughness is too large, and the toner or the external additive of the toner easily enters the concave portions of the unevenness caused by the inorganic fine particles, and local stains are likely to occur during durability. Also, from this perspective, the surface roughness of the surface layer 16 is preferably 350 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less.

[0050] The surface roughness in the surface layer 16 can be obtained from the captured image using a scanning probe microscope. For example, in a measurement image with a measurement range of 20 μm × 20 μm, the maximum height difference within an arbitrary 5 μm is measured at 100 points, and it can be obtained from the average value. The surface roughness in the surface layer 16 can be adjusted by the particle diameter, blending amount, type (material), etc. of the inorganic fine particles.

[0051] The average particle diameter of the inorganic fine particles is preferably 10 nm or more and 450 nm or less. When the average particle diameter of the inorganic fine particles is within the above range, it is easy to make the surface roughness of the surface layer 16 within a specific range, and the effect of preventing the stain on the roll surface is excellent. And from the perspective of increasing the surface roughness of the surface layer 16 to reduce the contact area between the toner or the external additive of the toner and the roll surface, the average particle diameter of the inorganic fine particles is more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 30 nm or more. Also, from the perspective of reducing the contact area between the toner or the external additive of the toner and the roll surface, the average particle diameter of the inorganic fine particles is more preferably 400 nm or less, even more preferably 350 nm or less, and particularly preferably 300 nm or less. The average particle diameter of the inorganic fine particles is measured by the laser diffraction method and represented by the average of any 20 points.

[0052] The content of the inorganic fine particles is preferably 30 to 60 parts by mass with respect to 100 parts by mass of the binder. When the content is 30 parts by mass or more, the inorganic fine particles are sufficiently filled in the surface layer 16, so that the generation of local stains can be suppressed. From this viewpoint, the content is more preferably 35 parts by mass or more. Further, when the content is 60 parts by mass or less, aggregation of the inorganic fine particles is suppressed, and the uniformity of discharge is easily ensured. From this viewpoint, the content is more preferably 55 parts by mass or less, and even more preferably 50 parts by mass or less.

[0053] The relative permittivity of the inorganic fine particles is preferably 13 or less. When the relative permittivity of the inorganic fine particles is 13 or less, the surface layer 16 does not accumulate too much charge due to the influence of the inorganic fine particles, so that the discharge property is excellent and the charging property becomes good. From this viewpoint, the relative permittivity of the inorganic fine particles is more preferably 10 or less, even more preferably 7 or less, and particularly preferably 5 or less. On the other hand, the lower limit value of the relative permittivity of the inorganic fine particles is not particularly limited, but is preferably 2 or more.

[0054] The material of the inorganic fine particles is not particularly limited. Since the inorganic fine particles are not used as a conductive agent, those with low conductivity may be used. As the inorganic fine particles, silica fine particles, alumina fine particles, etc. are preferable from the viewpoints of low conductivity, excellent wear resistance, and the ability to improve durability.

[0055] The particles for forming roughness are particles for imparting micro-order roughness to the surface of the surface layer 16. That is, they are particles for imparting micro-order unevenness to the surface of the surface layer 16. The micro-order surface unevenness of the surface layer 16 by the particles for forming roughness increases the discharge space between the photoreceptor and the charging roll 10 and promotes discharge. Thereby, the charging property can be improved, and image defects such as horizontal streaks and unevenness can be suppressed.

[0056] Particles for forming roughness are made of resin particles, inorganic particles, etc. The material of the particles for forming roughness is not particularly limited. The particles for forming roughness are preferably composed of a polymer having a carbonyl group. This is because a polymer having a carbonyl group is a material with a relatively high relative permittivity, and it is easy to ensure excellent chargeability of the charging roll 10. Examples of the polymer having a carbonyl group include urethane resin, polyamide resin, acrylic resin, acrylic silicone resin, silicone graft acrylic polymer, acrylic graft silicone polymer, urethane rubber, etc. Among these, from the viewpoints of relative permittivity and chargeability, urethane resin, urethane rubber, and acrylic resin are preferable.

[0057] The size of the particles for forming roughness is not particularly limited, but from the viewpoints such as being easy to ensure uniform chargeability, those having an average particle diameter of 3.0 μm or more and 50 μm or less are preferable. More preferably, those having an average particle diameter of 5.0 μm or more and 30 μm or less are preferable. The average particle diameter of the particles for forming roughness is observed by a laser microscope on the surface of the surface layer 16, and the diameter of the particles for forming roughness visible during surface observation is taken as the particle diameter and represented by the average of any 20 points.

[0058] The content of the particles for forming roughness in the surface layer 16 is not particularly limited, but from the viewpoints such as excellent balance between chargeability and antifouling property and being easy to ensure uniform chargeability, it is preferably 15 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass of the binder in the surface layer 16. More preferably, it is 20 parts by mass or more and 50 parts by mass or less.

[0059] Various additives may be appropriately added to the surface layer 16 as needed. Examples of the additives include plasticizers, leveling agents, fillers, vulcanization accelerators, processing aids, mold release agents, etc.

[0060] The volume resistance of the surface layer 16 is preferably set in the semiconductive region from the viewpoint of chargeability, etc. Specifically, for example, 3.2×10 4 Ω or more and 6.8×10 9It may be set within the range of Ω or less. The thickness of the surface layer 16 is not particularly limited and may be set in the range of 0.1 to 30 μm, for example. The thickness of the surface layer 16 can be measured by observing a cross section using a laser microscope (such as "VK-9510" manufactured by Keyence). For example, at five locations at arbitrary positions, the distance from the surface of the elastic body layer 14 to the surface of the surface layer 16 can be measured respectively and represented by the average value.

[0061] The elastic body layer 14 can be formed, for example, as follows. First, the shaft body 12 is coaxially installed in the hollow part of a roll forming die, an uncured conductive rubber composition is injected, heated and cured (cross-linked), and then demolded, or the elastic body layer 14 is formed on the outer periphery of the shaft body 12 by extruding the uncured conductive rubber composition onto the surface of the shaft body 12.

[0062] The surface layer 16 can be formed by using the forming material of the surface layer 16, applying this to the outer peripheral surface of the elastic body layer 14, and appropriately performing drying treatment and the like. The forming material of the surface layer 16 may contain a diluting solvent. Examples of the diluting solvent include ketone solvents such as methyl ethyl ketone (MEK) and methyl isobutyl ketone, alcohol solvents such as isopropyl alcohol (IPA), methanol, and ethanol, hydrocarbon solvents such as hexane and toluene, acetic acid solvents such as ethyl acetate and butyl acetate, ether solvents such as diethyl ether and tetrahydrofuran, and water.

[0063] According to the charging roll 10 having the above configuration, since the surface layer 16 contains a urethane resin or an acrylic resin, it has excellent chargeability. At this time, by containing inorganic fine particles together with a binder containing a urethane resin or an acrylic resin and setting the micro roughness of the surface layer 16 within a specific range, the area where the toner or the external additive for toner contacts the roll surface can be reduced. In addition, since the fine particles are composed of inorganic substances having no dipole moment, the electrostatic adsorption of the toner or the external additive for toner caused by the fine particles can be suppressed. From these, the contamination of the roll surface can be prevented. From the above, it is excellent in chargeability and antifouling property.

Example

[0064] Hereinafter, the present invention will be described in detail using examples and comparative examples.

[0065] (Example 1) ><Preparation of Conductive Rubber Composition> To 100 parts by mass of isoprene rubber, 30 parts by mass of carbon black, 6 parts by mass of zinc oxide, 2 parts by mass of stearic acid, 1 part by mass of sulfur, 0.5 part by mass of a thiazole-based vulcanization accelerator, 0.5 part by mass of a thiuram-based vulcanization accelerator, and 50 parts by mass of heavy calcium carbonate were blended, and kneaded for 10 minutes using a sealed mixer adjusted to a temperature of 50°C to prepare a conductive rubber composition.

[0066] As materials for the conductive rubber composition, the following materials were prepared. · Isoprene rubber (IR): "JSR IR2200" manufactured by JSR · Carbon black: "Show Black N762" manufactured by Cabot Japan · Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry · Stearic acid: "Cherry Stearic Acid" manufactured by NOF Corporation · Sulfur: "Powder Sulfur" manufactured by Tsurumi Chemical Industry · Thiazole-based vulcanization accelerator: "Nocceler DM" manufactured by Ouchi Shinko Chemical Industry · Thiuram-based vulcanization accelerator: "Nocceler TRA" manufactured by Ouchi Shinko Chemical Industry · Heavy calcium carbonate: "Whiteon B" manufactured by Shiraishi Calcium, average particle diameter 3.6 μm

[0067] ><Production of Elastic Body Layer> A mandrel (diameter 8 mm) was set in a molding die (pipe shape), the above composition was injected, heated at 180°C for 30 minutes, then cooled and demolded to form an elastic body layer made of a conductive rubber elastomer with a thickness of 1.9 mm on the outer periphery of the mandrel.

[0068] ><Preparation of Surface Layer Material> To 100 parts by mass of the urethane resin, 50 parts by mass of carbon black, 30 parts by mass of roughness-forming particles (urethane particles 5 μm), and 35 parts by mass of inorganic fine particles (silica 300 nm) were added, and 200 parts by mass of methyl ethyl ketone (MEK) was added and mixed and stirred at a predetermined stirring speed to prepare a surface layer-forming composition.

[0069] <Fabrication of the surface layer> The surface layer-forming composition was roll-coated on the outer peripheral surface of the elastomer layer and heat-treated to form a surface layer with a thickness of 1.0 μm on the outer periphery of the elastomer layer. Thereby, the charged roll of Example 1 was fabricated.

[0070] (Examples 2, 4 - 5, 10 - 12) In the preparation of the surface layer material, a charged roll was fabricated in the same manner as in Example 1 except that the formulation described in the table was changed.

[0071] (Example 3) <Preparation of the conductive rubber composition> To 100 parts by mass of Hydrin rubber, 5 parts by mass of vulcanization aid, 10 parts by mass of carbon, 0.5 parts by mass of vulcanization accelerator, 2 parts by mass of sulfur, and 50 parts by mass of filler were added, and these were stirred and mixed by a stirrer to prepare a conductive rubber composition.

[0072] The following materials were prepared as materials for the conductive rubber composition. · Hydrin rubber (ECO, "Hydrin H1100" manufactured by Nippon Zeon Co., Ltd.) · Vulcanization aid (zinc oxide, "Zinc Oxide No. 2" manufactured by Mitsui Mining & Smelting Co., Ltd.) · Carbon ("Ketjen Black EC300J" manufactured by Ketjen Black International) · Vulcanization accelerator (2-mercaptobenzothiazole, "Nocceler M-P" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) · Sulfur ("Sulfax PTC" manufactured by Tsurumi Chemical Industry Co., Ltd.) · Filler (calcium carbonate, "White Swan CC" manufactured by Shiraishi Kogyo Co., Ltd.)

[0073] <Fabrication of the elastomer layer> In the same manner as in Example 1, an elastic body layer made of a conductive rubber elastic body was formed.

[0074] <Production of the surface layer> In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 1, except that the formulation described in the table was changed.

[0075] (Examples 6 - 9, 13) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 3, except that the formulation described in the table was changed.

[0076] (Example 14) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 1, except that the formulation described in the table was changed. In Example 14, particles for roughness formation were not blended.

[0077] (Comparative Example 1) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 1, except that the formulation described in the table was changed. In Comparative Example 1, the binder of the surface layer was changed to a silicone resin.

[0078] (Comparative Example 2) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 3, except that the formulation described in the table was changed. In Comparative Example 2, the inorganic fine particles of the surface layer were changed to organic fine particles.

[0079] (Comparative Example 3) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 3, except that the formulation described in the table was changed. In Comparative Example 3, the inorganic fine particles of the surface layer were changed to silica 9 nm.

[0080] (Comparative Example 4) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 3, except that the formulation described in the table was changed. In Comparative Example 4, the inorganic fine particles of the surface layer were changed to silica 500 nm.

[0081] (Comparative Example 5) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 1 except that the formulation described in the table was changed. In Comparative Example 5, the blending amount of the inorganic fine particles in the surface layer was decreased.

[0082] (Comparative Example 6) In the preparation of the surface layer material, a charging roll was produced in the same manner as in Example 1 except that the formulation described in the table was changed. In Comparative Example 6, the blending amount of the inorganic fine particles in the surface layer was increased.

[0083] The materials used for the surface layer are as follows. The particle diameters of the roughness-forming particles and the fine particles are average particle diameters. (Binder) ·Urethane resin: "Adekabontaiter HUX380" manufactured by ADEKA ·Acrylic resin: "Aron A-104" manufactured by Toagosei Co., Ltd. ·Silicone resin: "KW-255" manufactured by Shin-Etsu Silicone (Roughness-forming particles) ·Urethane resin 5μm: "Art Pearl C-800 transparent" manufactured by Negami Kogyo ·Urethane resin 30μm: "Art Pearl C-200 transparent" manufactured by Negami Kogyo ·Acrylic resin 5μm: "Tech Polymer MBX-5" manufactured by Sekisui Chemical Co., Ltd. ·Acrylic resin 30μm: "Tech Polymer MBX-30" manufactured by Sekisui Chemical Co., Ltd. (Inorganic fine particles) ·Silica 9nm: "Snowtex ST-S" manufactured by Nissan Chemical Industries, Ltd. ·Silica 12nm: "Snowtex ST-30" manufactured by Nissan Chemical Industries, Ltd. ·Silica 300nm: "Seehoster KE-S30" manufactured by Nippon Shokubai Co., Ltd. ·Silica 450nm: "Snowtex MP-4540M" manufactured by Nissan Chemical Industries, Ltd. ·Silica 500nm: "Seehoster KE-S50" manufactured by Nippon Shokubai Co., Ltd. ·Silica 300nm: "43-02-302" manufactured by micromod, high dielectric silica (relative dielectric constant 12.9), carboxyl group modified ·Alumina 170nm: "AKP-53" manufactured by Sumitomo Chemical Co., Ltd. ·Alumina 200nm: "AKP-50" manufactured by Sumitomo Chemical Co., Ltd. · Alumina 420 nm: Sumitomo Chemical "AKP-20" · Calcium carbonate 40 nm: "1957RH" manufactured by SkySpring Nanomaterials (Organic microparticles) · PMMA 150 nm: "Epostar MX100W" manufactured by Nippon Shokubai (Conductive agent) Carbon black: "8653BLACK" manufactured by Tokushi Kiki

[0084] Image evaluation was performed using the manufactured charging roll. Also, measurements of micro-roughness, relative permittivity, and volume resistance were taken.

[0085] (Micro-roughness) Using a scanning probe microscope (Hitachi "AFM5000II"), an image of a 20 μm × 20 μm area on the surface layer was taken. After performing three-dimensional tilt correction processing on the taken image, the maximum height difference (Rp-v) within an arbitrary 5 μm was measured at 100 points in the image, and the average value was calculated as the micro-roughness.

[0086] (Relative permittivity) A fine particle solution dispersed in pure water or acetone was dropped onto a PET sheet with an aluminum electrode previously vapor-deposited, dried, an aluminum electrode was vapor-deposited on the surface of the produced sheet, and measurement was performed using an LCR meter ZM2353 manufactured by NF Circuit Design Block Co., Ltd. Measurement conditions: Voltage 1 V / Frequency 1 MHz Measurement environment: 25°C × 50% RH

[0087] (Measurement method of volume resistance) The volume resistance was measured by contacting an electrode probe (Nissin Electric "Surface Resistance Measurement Electrode SME-8302") with the charging roll and using a Nissin Electric "Ultra Insulation Meter SM7110".

[0088] (Non-uniform image: Endurance stain) The fabricated charging roll was attached to the unit (black) of an actual machine (Konica Minolta's "bizhub C650 i"), and printing was performed at a 25% density halftone in an environment of 10°C × 10% RH. Evaluation was carried out after 1.5 million prints. Those with no non-uniformity in the image due to toner or external additives were rated as very good "◎", those with slight non-uniformity within the allowable range were rated as good "○", and those with non-uniformity outside the allowable range were rated as bad "×".

[0089] (Striped image: Endurance stain) The fabricated charging roll was attached to the unit (black) of an actual machine (Konica Minolta's "bizhub C650 i"), and printing was performed at a 25% density halftone in an environment of 10°C × 10% RH. Evaluation was carried out after 1.5 million prints. Those with no stripes in the image due to toner or external additives were rated as very good "◎", those with slight stripes within the allowable range were rated as good "○", and those with stripes outside the allowable range were rated as bad "×".

[0090] (Black dot image: Chargeability) The fabricated charging roll was attached to the unit (black) of an actual machine (Konica Minolta's "bizhub C650 i"), and printing was performed at a 25% density halftone in an environment of 10°C × 10% RH. Evaluation was carried out after 1.5 million prints. Those with no black dots in the image were rated as good "◎", those with slight black dots within the allowable range were rated as good "○", and those with black dots outside the allowable range were rated as bad "×".

[0091]

Table 1

[0092]

Table 2

[0093]

Table 3

[0094] Since the surface layer of the example contains a urethane resin or an acrylic resin in the binder, it has excellent chargeability and the black dot image is suppressed. And since it contains inorganic fine particles together with the binder containing the urethane resin or the acrylic resin and the micro-roughness of the surface layer is within a specific range, the area where the toner or the external additive for toner contacts the roll surface becomes small. Also, since the fine particles are composed of inorganic substances having no dipole moment, the electrostatic adsorption of the toner or the external additive for toner due to the fine particles is suppressed. From these, the contamination of the roll surface can be prevented, and the uneven image and streak image during durability are suppressed.

[0095] The surface layer of Comparative Example 1 is composed of a silicone resin as the binder. For this reason, the chargeability is inferior and a black dot image is generated. The surface layer of Comparative Example 2 contains organic fine particles together with a urethane resin instead of inorganic fine particles. The organic fine particles are composed of PMMA. Since PMMA has a carbonyl group, it has a large dipole moment and electrostatic adsorption of the toner or the external additive for toner is likely to occur. And in Comparative Example 2, the contamination of the roll surface during durability is not suppressed and the uneven image during durability is not suppressed.

[0096] The surface layer of Comparative Example 3 contains a urethane resin in the binder and contains inorganic fine particles together with the urethane resin, but the average particle diameter of the inorganic fine particles is too small and the micro-roughness of the surface layer is too small. And in Comparative Example 3, the effect of reducing the area where the toner or the external additive for toner contacts the roll surface is small, the contamination of the roll surface during durability is not suppressed, and the uneven image during durability is not suppressed. The surface layer of Comparative Example 4 contains a urethane resin in the binder and contains inorganic fine particles together with the urethane resin, but the average particle diameter of the inorganic fine particles is too large and the micro-roughness of the surface layer is too large. And in Comparative Example 4, the toner or the external additive for toner enters the concave portion of the unevenness due to the inorganic fine particles, and the local contamination during durability is not suppressed and the streak image during durability is not suppressed.

[0097] The surface layer of Comparative Example 5 contains an acrylic resin in the binder and contains inorganic fine particles together with the acrylic resin. However, the blending amount of the inorganic fine particles is too small, and the micro-roughness of the surface layer is too small. In Comparative Example 5, the effect of reducing the area of contact between the toner and the external toner additive with the roll surface is small, the stain on the roll surface cannot be suppressed during durability, and the uneven image during durability is not suppressed. The surface layer of Comparative Example 6 contains an acrylic resin in the binder and contains inorganic fine particles together with the acrylic resin. However, the blending amount of the inorganic fine particles is too large, and the micro-roughness of the surface layer is too large. In Comparative Example 6, the toner and the external toner additive enter the concave portions of the unevenness caused by the inorganic fine particles, and the local stain cannot be suppressed during durability, and the streak image during durability is not suppressed.

[0098] From the above Examples and Comparative Examples, it can be seen that the surface layer contains a binder containing a urethane resin or an acrylic resin and inorganic fine particles, and the micro-roughness represented by the maximum height difference within 5 μm on the surface of the surface layer is 10 nm or more and 400 nm or less, whereby the chargeability and antifouling property are excellent.

[0099] Although the embodiments and examples of the present invention have been described above, the present invention is not limited to the above embodiments and examples at all, and various modifications can be made without departing from the spirit of the present invention.

Explanation of Signs

[0100] 10 Charging roll 12 Shaft body 14 Elastic body layer 16 Surface layer

Claims

1. A charging roll for electrophotographic equipment, comprising: a shaft body, an elastic body layer formed on the outer peripheral surface of the shaft body, and a surface layer formed on the outer peripheral surface of the elastic body layer, wherein the surface layer contains a binder containing a urethane resin or an acrylic resin, and inorganic fine particles, and the surface roughness represented by the maximum height difference within 5 μm of the surface of the surface layer is 10 nm or more and 400 nm or less.

2. The charging roll for electrophotographic equipment according to claim 1, wherein the average particle diameter of the inorganic fine particles is 10 nm or more and 450 nm or less.

3. The charging roll for electrophotographic equipment according to claim 1 or claim 2, wherein the content of the inorganic fine particles is 30 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder.

4. The charging roll for electrophotographic equipment according to claim 1 or claim 2, wherein the relative dielectric constant of the inorganic fine particles is 13 or less.

5. The charging roll for electrophotographic equipment according to claim 1 or claim 2, wherein the inorganic fine particles are silica fine particles or alumina fine particles.

6. The volume resistance of the surface layer is 3.2×10 ４ Ω or more and 6.8×10 ９ Ω or less. The charging roll for an electrophotographic apparatus according to claim 1 or claim 2.

7. The charging roll for electrophotographic equipment according to claim 1, wherein the surface layer further contains roughness-forming particles.

8. The charging roll for electrophotographic equipment according to claim 7, wherein the average particle diameter of the roughness-forming particles is 5 μm or more and 30 μm or less.

9. The charging roll for electrophotographic equipment according to claim 7 or claim 8, wherein the content of the roughness-forming particles is 15 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass of the binder.

10. The average particle diameter of the inorganic fine particles is 10 nm or more and 450 nm or less, the content of the inorganic fine particles is 30 parts by mass or more and 60 parts by mass or less with respect to 100 parts by mass of the binder, the relative dielectric constant of the inorganic fine particles is 13 or less, the inorganic fine particles are silica fine particles or alumina fine particles, The volume resistance of the surface layer is 3.2×10 ４ Ω or more and 6.8×10 ９ Ω or less, and the surface layer further contains roughness-forming particles, the average particle diameter of the roughness-forming particles is 5 μm or more and 30 μm or less, and the content of the roughness-forming particles is 15 parts by mass or more and 65 parts by mass or less with respect to 100 parts by mass of the binder. The charging roll for electrophotographic equipment according to claim 1.

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