Charging roll for electrophotographic devices

Abstract

Provided is a charging roll for electrophotographic devices, the charging roll being capable of: realizing high chargeability and high durability; and responding to demands for high-speed printing and long service life.　A charging roll 10 for electrophotographic devices comprises: a shaft body 12; an elastic body layer 14 formed on the outer circumferential surface of the shaft body 12; and a surface layer 16 formed on the outer circumferential surface of the elastic body layer 14. The surface layer 16 contains the following (a) and (b), and the content of (b) in the surface layer 16 is 0.1-10 parts by mass with respect to 100 parts by mass of (a). (a) A binder composed of one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine (b) A fluorine-based anionic compound

Description

Charging rolls for electrophotographic equipment

[0001] The present invention relates to a charging roll for electrophotographic equipment, which is suitably used in electrophotographic equipment such as copying machines, printers, and facsimiles that employ an electrophotographic system.

[0002] Known charging rolls for electrophotographic devices include those having an elastic layer with rubber elasticity on the outer circumferential surface of a shaft such as a core metal, and a surface layer on the outer circumferential surface of the elastic layer. In charging rolls, urethane resins are sometimes used as binders for the surface layer, for example, in view of charging characteristics.

[0003] JP 2012-181224 A

[0004] Due to technological advances by manufacturers and user demands, electrophotographic equipment such as laser beam printers are required to print faster and with longer lifespans than ever before. The charging and discharging process is repeated on the surface of the charging roll. When the photoconductor or charging roll rotates at high speeds to achieve high-speed printing, this process cycle cannot keep up, resulting in areas of the photoconductor surface that are not discharged, resulting in black spots. Furthermore, ether-based urethane resins on the surface have low strength due to the influence of ether groups, making them prone to cracking during use. Furthermore, the low carbonyl group content results in low electrostatic capacitance, which is unfavorable for charging performance. Furthermore, ester-based resins are prone to hydrolysis, becoming brittle and cracking over time. Furthermore, the alkyl groups in the urethane resin on the surface are susceptible to degradation due to heat and ultraviolet light generated during discharge. This leads to cracking during use, resulting in streaky images.

[0005] The problem to be solved by the present invention is to provide a charging roll for electrophotographic equipment that realizes high charging properties and high durability and meets the demands for high-speed printing and long life.

[0006] The charging roll for an electrophotographic device according to the present invention comprises a shaft, an elastic layer formed on the outer peripheral surface of the shaft, and a surface layer formed on the outer peripheral surface of the elastic layer, wherein the surface layer contains the following (a) and (b), and the content of (b) in the surface layer is 0.1 to 10 parts by mass per 100 parts by mass of (a): (a) a binder consisting of one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine, and (b) a fluorine-based anionic compound.

[0007] The (b) may be a fluoroalkyl group-containing carboxylate or a fluoroalkyl group-containing sulfonate. The surface layer may include roughness-forming particles. The roughness-forming particles may be acrylic particles, urethane particles, or silica particles. The surface layer may include carbon black or a conductive metal oxide as a conductive agent. The elastic layer may include one or more of isoprene rubber, nitrile rubber, and hydrin rubber.

[0008] (1) The conductive roll for an electrophotographic device according to the present invention comprises a shaft, an elastic layer formed on the outer peripheral surface of the shaft, and a surface layer formed on the outer peripheral surface of the elastic layer, wherein the surface layer contains the following (a) and (b), and the content of (b) in the surface layer is 0.1 to 10 parts by mass per 100 parts by mass of (a): (a) a binder consisting of one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine, and (b) a fluorine-based anionic compound.

[0009] (2) In the above (1), (b) may be a fluoroalkyl group-containing carboxylate or a fluoroalkyl group-containing sulfonate.

[0010] (3) In the above (1) or (2), the surface layer may contain particles for providing roughness.

[0011] (4) In the above (3), the roughness-imparting particles may be acrylic particles, urethane particles, or silica particles.

[0012] (5) In any one of (1) to (4) above, the surface layer may contain carbon black or a conductive metal oxide as a conductive agent.

[0013] (6) In any one of the above (1) to (5), the elastic layer may contain at least one of isoprene rubber, nitrile rubber, and hydrin rubber.

[0014] According to the charging roll for electrophotographic devices of the present invention, the binder in the surface layer is replaced with one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine instead of a urethane resin, and a specific amount of a fluorine-based anionic compound is used together with the binder in the surface layer. This prevents black spots from appearing in durable images even under high-speed printing conditions, and enables high-speed printing with high charging properties. Furthermore, deterioration of the alkyl groups in the binder is suppressed even during durability, and high durability enables a long life. Because high charging properties and high durability can be achieved, the charging roll for electrophotographic devices meets the demands for high-speed printing and a long life.

[0015] When the toner (b) is a fluoroalkyl group-containing carboxylate or a fluoroalkyl group-containing sulfonate, high charging properties and high durability can be simultaneously achieved to a high degree.

[0016] Furthermore, when the surface layer contains roughness-forming particles, suitable surface irregularities are formed on the surface layer, which increases the discharge space between the photoreceptor and the charging roll and promotes discharge, thereby improving charging properties and suppressing image defects such as horizontal streaks and unevenness.

[0017] When the roughness-forming particles are acrylic particles, urethane particles, or silica particles, the roughness-forming particles are made of a material with a high dielectric constant, and therefore the chargeability of the roll surface is improved.

[0018] Furthermore, when the surface layer contains carbon black or a conductive metal oxide as a conductive agent, high charging properties can be maintained even during durability testing without deterioration of durability due to bleed-out of the conductive agent, and a response speed that can accommodate charging and discharging processes can be achieved even in high-speed printing.

[0019] When the elastic layer contains at least one of isoprene rubber, nitrile rubber, and hydrin rubber, the compression set is small, and the occurrence of streak images corresponding to deformed portions when the charging roll is set is suppressed.

[0020] 1A is a schematic view of the appearance of a charging roll for an electrophotographic apparatus according to one embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line AA thereof.

[0021] The charging roll for electrophotographic equipment (hereinafter, sometimes simply referred to as the charging roll) according to the present invention will be described in detail. Fig. 1 is a schematic diagram of the appearance of the charging roll for electrophotographic equipment according to one embodiment of the present invention (a) and a cross-sectional view of the same taken along line A-A (b).

[0022] The charge roll 10 includes a shaft 12, an elastic layer 14 formed on the outer peripheral surface of the shaft 12, and a surface layer 16 formed on the outer peripheral surface of the elastic layer 14. The elastic layer 14 is a layer (base layer) that forms the base of the charge roll 10. The surface layer 16 is a layer that appears on the surface of the charge roll 10. Although not specifically shown, an intermediate layer such as a resistance adjustment layer may be formed between the elastic layer 14 and the surface layer 16, if necessary.

[0023] The shaft 12 is not particularly limited as long as it is electrically conductive. Specific examples include a solid or hollow core made of metal such as iron, stainless steel, or aluminum. The surface of the shaft 12 may be coated with an adhesive, primer, or the like, as needed. That is, the elastic layer 14 may be bonded to the shaft 12 via an adhesive layer (primer layer). The adhesive, primer, or the like may be made electrically conductive as needed.

[0024] The elastic layer 14 contains a crosslinked rubber. The elastic layer 14 is formed from a conductive rubber composition containing an uncrosslinked rubber. The crosslinked rubber is obtained by crosslinking the uncrosslinked rubber. The uncrosslinked rubber may be a polar rubber or a non-polar rubber.

[0025] Polar rubber is a rubber having a polar group, and examples of the polar group include a chloro group, a nitrile group, a carboxyl group, and an epoxy group. Specific examples of polar rubber include hydrin rubber, nitrile rubber (NBR), urethane rubber (U), acrylic rubber (a copolymer of acrylic acid ester and 2-chloroethyl vinyl ether, ACM), chloroprene rubber (CR), and epoxidized natural rubber (ENR). Among the polar rubbers, hydrin rubber and nitrile rubber (NBR) are more preferred from the viewpoint that the volume resistivity tends to be particularly low.

[0026] Examples of the hydrin rubber include an epichlorohydrin homopolymer (CO), an epichlorohydrin-ethylene oxide binary copolymer (ECO), an epichlorohydrin-allyl glycidyl ether binary copolymer (GCO), and an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (GECO).

[0027] Examples of urethane rubber include polyether-type urethane rubber having an ether bond in the molecule. Polyether-type urethane rubber can be produced by reacting a polyether having hydroxyl groups at both ends with a diisocyanate. Examples of polyethers include, but are not limited to, polyethylene glycol and polypropylene glycol. Examples of diisocyanates include, but are not limited to, tolylene diisocyanate and diphenylmethane diisocyanate.

[0028] Examples of non-polar rubbers include silicone rubber (Q), isoprene rubber (IR), natural rubber (NR), styrene butadiene rubber (SBR), butadiene rubber (BR), etc. Among non-polar rubbers, isoprene rubber is more preferred from the viewpoint of excellent tensile properties.

[0029] The elastic layer 14 preferably contains one or more of isoprene rubber, nitrile rubber, and hydrin rubber. When the elastic layer 14 contains one or more of isoprene rubber, nitrile rubber, and hydrin rubber, the compression set is small, and the occurrence of streak images corresponding to deformed portions when the charging roll 10 is set is suppressed.

[0030] 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.

[0031] Examples of the sulfur crosslinking agent include conventionally known sulfur crosslinking agents such as powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur, sulfur chloride, thiuram vulcanization accelerators, and polymeric polysulfides.

[0032] Examples of the peroxide crosslinking agent include conventionally known peroxide crosslinking agents such as peroxyketals, dialkyl peroxides, peroxyesters, ketone peroxides, peroxydicarbonates, diacyl peroxides, and hydroperoxides.

[0033] Examples of the dechlorinating crosslinking agent include dithiocarbonate compounds, more specifically, quinoxaline-2,3-dithiocarbonate, 6-methylquinoxaline-2,3-dithiocarbonate, 6-isopropylquinoxaline-2,3-dithiocarbonate, and 5,8-dimethylquinoxaline-2,3-dithiocarbonate.

[0034] The amount of the crosslinking agent to be added is preferably within a range of 0.1 to 2 parts by mass, more preferably within a range of 0.3 to 1.8 parts by mass, and even more preferably within a range of 0.5 to 1.5 parts by mass, per 100 parts by mass of the uncrosslinked rubber, from the viewpoint of preventing bleeding.

[0035] 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 a weak acid salt thereof. The dechlorination crosslinking accelerator may be used in the form of DBU, but from the viewpoint of handling, it is preferable to use it in the form of a weak acid salt. Examples of weak acid salts of DBU include carbonate, stearate, 2-ethylhexyl salt, benzoate, salicylate, 3-hydroxy-2-naphthoate, phenol resin salt, 2-mercaptobenzothiazole salt, and 2-mercaptobenzimidazole salt.

[0036] The content of the dechlorination crosslinking accelerator is preferably within a range of 0.1 to 2 parts by mass, more preferably 0.3 to 1.8 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the uncrosslinked rubber, from the viewpoint of preventing bleeding.

[0037] A conductive agent can be blended into the elastic layer 14 to impart conductivity. Examples of conductive agents include electronic conductive agents and ionic conductive agents. Examples of electronic conductive agents include carbon black, graphite, and conductive metal oxides. Examples of conductive metal oxides include conductive titanium oxide, conductive zinc oxide, and conductive tin oxide. Examples of ionic conductive agents include quaternary ammonium salts, borates, and surfactants. Various additives may also be added to the elastic layer 14 as needed. Examples of additives include lubricants, vulcanization accelerators, antioxidants, light stabilizers, viscosity modifiers, processing aids, flame retardants, plasticizers, foaming agents, fillers, dispersants, antifoaming agents, pigments, and mold release agents.

[0038] The elastic layer 14 can be adjusted to a predetermined volume resistivity by adjusting the type of crosslinked rubber, the amount of ionic conductive agent, the amount of electronic conductive agent, etc. ２ ~10 １０ Ω cm, 10 ３ ~10 ９ Ω cm, 10 ４ ~10 ８The range may be appropriately set to Ω·cm.

[0039] The thickness of the elastic layer 14 is not particularly limited, and may be set appropriately within the range of 0.1 to 10 mm depending on the application.

[0040] The surface layer 16 contains the following (a) and (b): The binder is a base material that constitutes the surface layer 16. (a) A binder made of one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine; and (b) a fluorine-based anionic compound.

[0041] Isocyanurates are composed of isocyanate trimers and have a six-membered isocyanurate ring. Examples of isocyanates that constitute isocyanurates include 4,4'-diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), trimethylhexamethylene diisocyanate (TMHDI), tolylene diisocyanate (TDI), polymethylene phenyl isocyanate (PAPI), orthotoluidine diisocyanate (TODI), naphthylene diisocyanate (NDI), xylene diisocyanate (XDI), hexamethylene diisocyanate (HMDI), paraphenylene diisocyanate (PDI), lysine diisocyanate methyl ester (LDI), and dimethyl diisocyanate (DDI). Among these, from the viewpoint of uniform reactivity and the like, 4,4'-diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), trimethylhexamethylene diisocyanate (TMHDI), and tolylene diisocyanate (TDI) are more preferred as the isocyanate constituting the isocyanurate.

[0042] Isocyanurates can be represented by the following general formula (1):

[0043] In formula (1), R １is a divalent hydrocarbon group. Examples of the divalent hydrocarbon group include alkylene groups having 1 to 20 carbon atoms, such as methylene, 1,1-ethylene, 1,2-ethylene, 1,1-propylene, 1,2-propylene, 1,3-propylene, 1,1-butylene, 1,2-butylene, 1,3-butylene, 1,4-butylene, 1,2-pentylene, 1,2-hexylene, 1,2-nonylene, and 1,2-dodecylene; 1,2-cyclopropylene, 1,2-cyclobutylene, 1,3-cyclobutylene, 1,2-cyclopentylene, 1,2-cyclohexylene, and 1,2- Cycloalkylene groups having 3 to 20 carbon atoms such as cyclononylene and 1,2-cyclododecylene; 1,1-ethenylene, 1,2-ethenylene, 1,2-ethenylenemethylene, 1-methyl-1,2-ethenylene, 1,2-ethenylene-1,1-ethylene, 1,2-ethenylene-1,2-ethylene, 1,2-ethenylene-1,2-propylene, 1,2-ethenylene-1,3-propylene, 1,2-ethenylene-1,4-butylene, 1,2-ethenylene-1,2-butylene, 1,2-ethenylene-1,2-heptylene, 1,2- alkenylene groups having 2 to 20 carbon atoms such as ethenylene-1,2-decylene; alkynylene groups having 2 to 20 carbon atoms such as ethynylene, ethynylenemethylene, ethynylene-1,1-ethylene, ethynylene-1,2-ethylene, ethynylene-1,2-propylene, ethynylene-1,3-propylene, ethynylene-1,4-butylene, ethynylene-1,2-butylene, ethynylene-1,2-heptylene, and ethynylene-1,2-dodecylene; 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, and 1,2-naphthylene; arylene groups having 6 to 20 carbon atoms such as a 1,4-naphthylene group, a 1,5-naphthylene group, a 2,3-naphthylene group, a 2,6-naphthylene group, a 3-phenyl-1,2-phenylene group, and a 2,2'-diphenylene group; a 1,2-phenylenemethylene group, a 1,3-phenylenemethylene group, a 1,4-phenylenemethylene group, a 1,2-phenylene-1,1-ethylene group, a 1,2-phenylene-1,2-ethylene group, a 1,2-phenylene-1,2-propylene group, a 1,2-phenylene-1,3-propylene group, a 1,2-phenylene-1,4-butylene group, a 1,Examples include bifunctional hydrocarbon groups consisting of an arylene group and an alkylene group having 7 to 20 carbon atoms, such as a 2-phenylene-1,2-butylene group, a 1,2-phenylene-1,2-hexylene group, a methylene-1,2-phenylenemethylene group, a methylene-1,3-phenylenemethylene group, and a methylene-1,4-phenylenemethylene group.

[0044] In the formula (1), the divalent hydrocarbon group is particularly preferably an alkylene group having 1 to 20 carbon atoms or a cycloalkylene group having 3 to 20 carbon atoms, from the viewpoint of stability in the solvent.

[0045] Uretdiones are composed of isocyanate dimers and have a four-membered uretdione ring. Examples of isocyanates constituting uretdiones include the same isocyanates as those constituting the isocyanurates. Among these, from the viewpoint of uniform reactivity, 4,4'-diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), trimethylhexamethylene diisocyanate (TMHDI), and tolylene diisocyanate (TDI) are more preferred as isocyanates constituting uretdiones.

[0046] Uretdiones can be represented by the following general formula (2):

[0047] In formula (2), R ２ is R of the isocyanurate １ As with the isocyanurates, the divalent hydrocarbon group in formula (2) is a divalent hydrocarbon group. Examples of the divalent hydrocarbon group in uretdione include the same as the divalent hydrocarbon groups in the isocyanurates. As with the isocyanurates, the divalent hydrocarbon group in formula (2) is particularly preferably an alkylene group having 1 to 20 carbon atoms or a cycloalkylene group having 3 to 20 carbon atoms.

[0048] Carbodiimide diisocyanate can be represented by the following general formula (3).

[0049] In formula (3), R ３ is R of the isocyanurate １As with the isocyanurates, the divalent hydrocarbon group in formula (3) is a divalent hydrocarbon group. Examples of the divalent hydrocarbon group in carbodiimide diisocyanates include the same as the divalent hydrocarbon groups in the isocyanurates. As with the isocyanurates, the divalent hydrocarbon group in formula (3) is particularly preferably an alkylene group having 1 to 20 carbon atoms or a cycloalkylene group having 3 to 20 carbon atoms.

[0050] Polyurea is a polymer produced by the chemical reaction of an isocyanate and an amine. Examples of isocyanates that constitute polyurea include the same isocyanates that constitute the isocyanurate. Among these, from the viewpoint of uniform reactivity, 4,4'-diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), 4,4'-dicyclohexylmethane diisocyanate (hydrogenated MDI), trimethylhexamethylene diisocyanate (TMHDI), and tolylene diisocyanate (TDI) are more preferred as isocyanates that constitute uretdione. Examples of amines that constitute polyurea include primary amines. Examples of primary amines include amines having 1 to 20 carbon atoms. Examples of primary amines include methylamine, ethylamine, propylamine, and butylamine.

[0051] Polyurea can be represented by the following general formula (4).

[0052] In formula (4), R ４ , R ５ are the same or different monovalent hydrocarbon groups. Examples of the monovalent hydrocarbon group include an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, and an aryl group having 6 to 20 carbon atoms. In formula (4), an alkyl group having 1 to 20 carbon atoms is particularly preferred as the monovalent hydrocarbon group.

[0053] Examples of alkyl groups include methyl, ethyl, n-propyl, i-propyl, n-butyl, i-butyl, sec-butyl, t-butyl, pentyl, isopentyl, neopentyl, hexyl, heptyl, octyl, and 2-ethylhexyl groups. Examples of cycloalkyl groups include cyclopentyl, cyclohexyl, cycloheptyl, and 2-methylcyclohexyl groups. Examples of aryl groups include phenyl, tolyl, xylyl, naphthyl, and biphenyl groups.

[0054] Uretone imine can be represented by the following general formula (5).

[0055] In formula (5), R ６ is the R of the above polyurea ４ As in the case of the polyurea, the monovalent hydrocarbon group in formula (5) is a monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group in the uretonimine include the same monovalent hydrocarbon groups as those in the polyurea. In formula (5), as in the case of the polyurea, an alkyl group having 1 to 20 carbon atoms is particularly preferred as the monovalent hydrocarbon group.

[0056] As the binder (a), isocyanurate and uretdione are more preferred from the viewpoints of stain resistance and compression set.

[0057] The binder (a) is the main component of the binder of the surface layer 16. The binder (a) preferably accounts for 50% by mass or more of the total binder components of the surface layer 16. More preferably, it is 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more. In addition to the binder (a), the binder components of the surface layer 16 are polymer components such as polyurethane.

[0058] The binder (a) is not polyurethane and does not contain ester or ether groups, so there is no risk of hydrolysis due to ester groups. Furthermore, there is no risk of strength reduction or low dielectric constant due to ether groups. Furthermore, by eliminating ester or ether groups and containing carbonyl groups, strength reduction due to decomposition or the like is suppressed, and when used in combination with the fluorine-based anionic compound (b), the following advantageous effects are achieved:

[0059] When used in combination with the binder (a), the fluorine-based anionic compound (b) electrostatically repels the carbonyl groups of the binder (a) while being arranged around the hydrocarbon groups of the binder (a), thereby preventing decomposition of the hydrocarbon groups of the binder (a) due to heat, ultraviolet rays, ozone, etc. This suppresses decomposition of the binder (a), thereby improving durability. Furthermore, because the fluorine-based anionic compound (b) is anionic, it electrostatically repels the carbonyl groups of the binder (a), maintaining the dipole moment of the carbonyl groups of the binder (a), allowing it to exhibit high dielectric and high charging properties. This allows it to exhibit a response speed that can handle charging and discharging processes even in high-speed printing.

[0060] The fluorine-based anionic compound (b) has an anionic group. The anionic group is a carboxylate group (—COO － ), sulfonate group (—SO ４ ２－ Among these, carboxylate groups and sulfonate groups are particularly preferred from the viewpoints of being excellent in the effect of suppressing decomposition of the hydrocarbon groups of the binder (a) through interaction with the binder (a) and achieving both high chargeability and high durability at a high level.

[0061] The fluorine-based anionic compound (b) is a compound having an organic group containing fluorine (a compound having a fluorine-containing group). Examples of the fluorine-containing group include fluoroalkyl groups having 1 to 20 carbon atoms. The fluoroalkyl group may be a perfluoroalkyl group in which all hydrogen atoms of the alkyl group have been substituted with fluorine atoms, or a fluoroalkyl group in which some hydrogen atoms of the alkyl group have been substituted with fluorine atoms. Of these, perfluoroalkyl groups are more preferred from the viewpoint of their excellent effect of suppressing decomposition of the hydrocarbon group of the binder (a) through interaction with the binder (a). Furthermore, the fluorine-containing group preferably has 6 or less carbon atoms. It is more preferred to have 1 to 6 carbon atoms, and more preferably 2 to 6 carbon atoms. Since fluorine-containing groups having 8 or more carbon atoms raise concerns about environmental regulations, it is preferred that the fluorine-containing group have 6 or less carbon atoms. Furthermore, fluorine-containing groups having 2 or more carbon atoms are preferred from the viewpoint of their excellent function of protecting the hydrocarbon group of the binder (a).

[0062] The fluorine-based anionic compound (b) may have one or more fluorine-containing groups in the molecule, but is particularly preferably one having one fluorine-containing group in the molecule from the viewpoints of small steric hindrance with the binder (a) and excellent function of protecting the hydrocarbon group of the binder (a).Furthermore, the fluorine-based anionic compound (b) may have one or more anionic groups in the molecule, but is particularly preferably one having one anionic group in the molecule from the viewpoints of excellent interaction with the binder (a).

[0063] The fluorine-based anionic compound (b) may be a monomer or a polymer. The fluorine-based anionic compound (b) is preferably a monomer rather than a polymer, from the viewpoint of reducing steric hindrance between the fluorine-based anionic compound (b) and the binder (a). The molecular weight (number average molecular weight) of the fluorine-based anionic compound (b) is preferably 400 or more, from the viewpoint of the stability of the interaction state. It is more preferably 500 or more, and even more preferably 1000 or more. Furthermore, the molecular weight (number average molecular weight) of the fluorine-based anionic compound (b) is preferably less than 3000, from the viewpoint of the number of reactive groups. It is more preferably 2500 or less, and even more preferably 2000 or less.

[0064] The content of the fluorine-based anionic compound (b) in the surface layer 16 is 0.1 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the binder (a). If the content of the fluorine-based anionic compound (b) is low, the effect of suppressing decomposition of the hydrocarbon group of the binder (a) is low. This results in cracks and streak images during durability testing. On the other hand, if the content of the fluorine-based anionic compound (b) is high, the effect of maintaining the dipole moment of the carbonyl group of the binder (a) is reduced, preventing high charging performance. This results in black spot images during high-speed printing. For the above reasons, the content is more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more. For the above reasons, the content is more preferably 8 parts by mass or less, and even more preferably 5 parts by mass or less.

[0065] The surface layer 16 may contain roughness-forming particles. The roughness-forming particles are particles for imparting roughness to the surface of the surface layer 16. In other words, they are particles for imparting irregularities to the surface of the surface layer 16. The surface irregularities of the surface layer 16 increase the discharge space between the photoreceptor and the charging roll 10, promoting discharge. This improves charging properties and can suppress image defects such as horizontal streaks and unevenness.

[0066] The roughness-forming particles may be resin particles or inorganic particles. Examples of inorganic particles include silica particles. The material of the roughness-forming particles is not particularly limited. The roughness-forming particles are preferably composed of a polymer having a carbonyl group. This is because polymers having a relatively high dielectric constant tend to ensure excellent charging performance of the charging roll 10. Furthermore, like the binder (a) of the surface layer 16, the polymers share the polar carbonyl group, which strengthens the adhesion between the binder (a) and the roughness-forming particles in the surface layer 16, improving strength. Examples of polymers having a carbonyl group include urethane resin, polyamide resin, acrylic resin, acrylic silicone resin, silicone-grafted acrylic polymer, acrylic-grafted silicone polymer, and urethane rubber. Among these, urethane resin and acrylic resin are particularly preferred due to their excellent dielectric constant and excellent adhesion between the binder (a) and the roughness-forming particles.

[0067] The size of the roughness-forming particles is not particularly limited, but from the viewpoint of easily ensuring uniform charging properties, an average particle diameter of 3.0 μm to 50 μm is preferred. More preferably, an average particle diameter of 5.0 μm to 30 μm is preferred. The average particle diameter of the roughness-forming particles is expressed as the average of 20 arbitrary points, where the surface of the surface layer 16 is observed with a laser microscope, and the diameter of the roughness-forming particles 16 visible during surface observation is taken as the particle diameter.

[0068] The content of the roughness-forming particles in the surface layer 16 is not particularly limited, but from the viewpoint of easily ensuring uniform charging properties, it is preferably 3 parts by mass or more and 50 parts by mass or less, more preferably 5 parts by mass or more and 40 parts by mass or less, relative to 100 parts by mass of the binder polymer in the surface layer 16.

[0069] The surface layer 16 may contain a conductive agent. Examples of the conductive agent include an electronic conductive agent and an ionic conductive agent. Examples of the electronic conductive agent include carbon black, graphite, and conductive metal oxides. Examples of the conductive metal oxide include conductive titanium oxide, conductive zinc oxide, and conductive tin oxide. Examples of the ionic conductive agent include a quaternary ammonium salt, a quaternary phosphonium salt, an imidazolium salt, a borate, and a surfactant.

[0070] The surface layer 16 preferably does not contain an ionic conductive agent, from the viewpoints of deterioration of durability due to bleed-out and reaction delays in high-speed machines. Furthermore, even if the surface layer 16 contains an ionic conductive agent, the amount is preferably 5 parts by mass or less per 100 parts by mass of the binder (a). Furthermore, an electronic conductive agent is preferred as the conductive agent. Carbon black and conductive metal oxides are particularly preferred. When the surface layer 16 contains carbon black or conductive metal oxide as the conductive agent, high charging performance can be maintained even during durability without deterioration of durability due to bleed-out of the conductive agent, and a response speed that can accommodate charging and discharging processes can be achieved even in high-speed printing.

[0071] The content of the electronic conductive agent in the surface layer 16 is not particularly limited, but is preferably 10 parts by mass or more and 90 parts by mass or less, more preferably 15 parts by mass or more and 70 parts by mass or less, and even more preferably 20 parts by mass or more and 50 parts by mass or less, relative to 100 parts by mass of the binder polymer in the surface layer 16.

[0072] If necessary, various additives may be added appropriately to the surface layer 16. Examples of the additives include a plasticizer, a leveling agent, a filler, a vulcanization accelerator, a processing aid, and a mold release agent.

[0073] The volume resistivity of the surface layer 16 is preferably set to a semi-conductive region from the viewpoint of electrostatic chargeability, etc. Specifically, for example, 1.0×10 ７ ~1.0 x 10 １０The volume resistivity can be set in the range of Ω·cm. The volume resistivity can be measured in accordance with JIS K6911. The thickness of the surface layer 16 is not particularly limited, and can be set in the range of 0.1 to 30 μm. The thickness of the surface layer 16 can be measured by observing the cross section using a laser microscope (such as Keyence's "VK-9510"). For example, the distance from the surface of the elastic layer 14 to the surface of the surface layer 16 can be measured at five arbitrary positions, and the thickness can be expressed as the average of the measured distances.

[0074] The elastic layer 14 can be formed, for example, as follows: First, the shaft 12 is placed coaxially in the hollow portion of a roll molding die, and an uncrosslinked conductive rubber composition is injected and heated and cured (crosslinked), and then the composition is demolded, or the uncrosslinked conductive rubber composition is extruded onto the surface of the shaft 12, thereby forming the elastic layer 14 on the outer periphery of the shaft 12.

[0075] The surface layer 16 can be formed by using a material for forming the surface layer 16, applying the material to the outer peripheral surface of the elastic layer 14, and then appropriately performing a drying process, etc. The material for forming the surface layer 16 may contain a diluent solvent. Examples of the diluent 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.

[0076] The material for forming the surface layer 16 includes (a) a binder and (b) a fluorine-based anionic compound. The material for forming the surface layer 16 may further include roughness-imparting particles as needed. It may also include carbon black or a conductive metal oxide as a conductive agent. It may also include additives that are blended as needed.

[0077] According to the charge roll 10 configured as described above, the binder in the surface layer 16 is replaced with one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine instead of a urethane resin, and a specific amount of a fluorine-based anionic compound is used together with the binder in the surface layer 16. This prevents black spots from appearing in durable images even under high-speed printing conditions, and enables high-speed printing with high chargeability. Furthermore, deterioration of the alkyl groups in the binder is suppressed even during durability, enabling a long life due to high durability. Because it is possible to achieve high chargeability and high durability, the charge roll 10 meets the demands for high-speed printing and a long life.

[0078] In this case, when the elastic layer 14 contains nitrile rubber or hydrin rubber, the nitrile rubber or hydrin rubber has polar groups that easily attract the polar groups of the binder (a) of the surface layer 16, improving the adhesion between the elastic layer 14 and the surface layer 16. This increases the resistance to shear forces applied to the elastic layer 14 and the surface layer 16 during endurance testing, improving durability. Isoprene rubber is sensitive to heat, and there is a risk that a portion of the main chain may undergo oxidative decomposition during vulcanization. In this case, it is believed that carbonyl groups (polar groups) are present at the sites of oxidative decomposition. The generated carbonyl groups are then easily attracted to the polar groups of the binder (a) of the surface layer 16, improving the adhesion between the elastic layer 14 and the surface layer 16, even when the elastic layer 14 contains isoprene rubber.

[0079] The present invention will be described in detail below using examples and comparative examples.

[0080] (Example 1) <Preparation of conductive rubber composition> 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 parts by mass of a thiazole-based vulcanization accelerator, 0.5 parts by mass of a thiuram-based vulcanization accelerator, and 50 parts by mass of heavy calcium carbonate were blended with 100 parts by mass of isoprene rubber, and the mixture was kneaded for 10 minutes using an internal mixer whose temperature was adjusted to 50°C to prepare a conductive rubber composition.

[0081] The following materials were prepared as materials for the conductive rubber composition. Isoprene rubber (IR): "JSR IR2200" manufactured by JSR Carbon black: "Showblack N762" manufactured by Cabot Japan Zinc oxide: "Zinc oxide type 2" manufactured by Sakai Chemical Industry Co., Ltd. Stearic acid: "Sakura stearate" manufactured by Nippon Oil & Fats Co., Ltd. Sulfur: "Powdered sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd. Thiazole vulcanization accelerator: "Noccela DM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Thiram vulcanization accelerator: "Noccela TRA" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Heavy calcium carbonate: "Whiten B" manufactured by Shiraishi Calcium Co., Ltd., average particle size 3.6 μm

[0082] <Preparation of Elastic Layer> A core metal (diameter 8 mm) was set in a molding die (pipe-shaped), the above composition was injected, and the mixture was heated at 180°C for 30 minutes, cooled, and demolded to form an elastic layer made of a conductive rubber elastic body having a thickness of 1.9 mm around the outer periphery of the core metal.

[0083] <Preparation of Surface Layer Material> A composition for forming a surface layer was prepared by blending 1 part by mass of a fluorine-based anionic compound <1>, 30 parts by mass of carbon black, and 30 parts by mass of particles for forming roughness (acrylic particles) with 100 parts by mass of isocyanurate, adding 200 parts by mass of methyl ethyl ketone (MEK), and mixing and stirring at a predetermined stirring speed.

[0084] The surface layer-forming composition was roll-coated onto the outer peripheral surface of the elastic layer, and the resulting mixture was heat-treated to form a surface layer having a thickness of 1.0 μm on the outer periphery of the elastic layer. This produced the charging roll of Example 1.

[0085] (Example 2) <Preparation of conductive rubber composition> 5 parts by mass of a vulcanization aid, 10 parts by mass of carbon, 0.5 parts by mass of a vulcanization accelerator, 2 parts by mass of sulfur, and 50 parts by mass of a filler were added to 100 parts by mass of hydrin rubber, and these were stirred and mixed using a stirrer to prepare a conductive rubber composition.

[0086] 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 Type 2" manufactured by Mitsui Metals Co., Ltd.) Carbon ("Ketjenblack EC300J" manufactured by Ketjenblack International Co., Ltd.) Vulcanization accelerator (2-mercaptobenzothiazole, "Noccela MP" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) Sulfur ("Sulfax PTC" manufactured by Tsurumi Chemical Industry Co., Ltd.) Filler (calcium carbonate, "Shiraenka CC" manufactured by Shiraishi Kogyo Co., Ltd.)

[0087] <Preparation of Elastic Layer> In the same manner as in Example 1, an elastic layer made of a conductive rubber elastic material was molded.

[0088] <Preparation of Surface Layer Material> A composition for forming a surface layer was prepared by blending 1 part by mass of a fluorine-based anionic compound <2>, 30 parts by mass of a conductive metal oxide, and 30 parts by mass of particles for forming roughness (urethane particles) with 100 parts by mass of uretdione, adding 200 parts by mass of methyl ethyl ketone (MEK), and mixing and stirring at a predetermined stirring speed.

[0089] <Preparation of Surface Layer> A surface layer having a thickness of 1.0 μm was formed on the outer periphery of the elastic layer in the same manner as in Example 1. In this way, a charging roll of Example 2 was prepared.

[0090] (Example 3) <Preparation of conductive rubber composition> 0.7 parts by mass of stearic acid, 5 parts by mass of zinc oxide, 2 parts by mass of hydrotalcite, 3 parts by mass of a peroxide crosslinking agent, and 20 parts by mass of carbon were blended with 100 parts by mass of NBR, and the mixture was stirred and mixed using a stirrer to prepare a conductive rubber composition.

[0091] The following materials were prepared as materials for the conductive rubber composition: NBR: "Nipol 1041" manufactured by Nippon Zeon Co., Ltd. Stearic acid: "Sakura Stearate" manufactured by NOF Corp. Zinc oxide: "Zinc oxide type 2" manufactured by Sakai Chemical Industry Co., Ltd. Hydrotalcite: "DHT4A" manufactured by Kyowa Chemical Industry Co., Ltd. Peroxide crosslinking agent: "Perkmyl D40" manufactured by NOF Corp. Carbon: "Ketjenblack EC300J" manufactured by Ketjenblack International Co., Ltd.

[0092] <Preparation of Elastic Layer> An elastic layer made of a conductive rubber elastic material was molded in the same manner as in Example 1, except that the heating temperature was changed to 170°C.

[0093] <Preparation of Surface Layer Material> 0.1 parts by mass of a fluorine-based anionic compound <1>, 30 parts by mass of carbon black, and 30 parts by mass of particles for forming roughness (silica particles) were blended with 100 parts by mass of carbodiimide diisocyanate, and 200 parts by mass of methyl ethyl ketone (MEK) was added. The mixture was mixed and stirred at a predetermined stirring speed to prepare a composition for forming a surface layer.

[0094] <Preparation of Surface Layer> A surface layer having a thickness of 1.0 μm was formed on the outer periphery of the elastic layer in the same manner as in Example 1. In this way, a charging roll of Example 3 was prepared.

[0095] Example 4 Preparation of Conductive Rubber Composition 50 parts by mass of NBR and 30 parts by mass of carbon black were blended and stirred and mixed using a mixer. Next, 50 parts by mass of isoprene rubber (IR), 5 parts by mass of a peroxide crosslinking agent, 3 parts by mass of a vulcanization aid, and 3 parts by mass of a catalyst were blended and stirred and mixed using a mixer to prepare a conductive rubber composition.

[0096] The following materials were prepared as materials for the conductive rubber composition: NBR: "Nipol 1041" manufactured by Nippon Zeon Co., Ltd. IR: "Nipol IR2200" manufactured by Nippon Zeon Co., Ltd. Carbon black: "Showblack N762" manufactured by Cabot Japan Co., Ltd. Peroxide crosslinking agent: "Perkmyl D40" manufactured by NOF Corp. Vulcanization aid (zinc oxide, "zinc oxide type 2" manufactured by Mitsui Metals Co., Ltd.)

[0097] <Preparation of Elastic Layer> An elastic layer made of a conductive rubber elastic material was molded in the same manner as in Example 1, except that the heating temperature was changed to 180°C.

[0098] <Preparation of Surface Layer Material> 10 parts by mass of a fluorine-based anionic compound <1>, 30 parts by mass of carbon black, and 30 parts by mass of particles for forming roughness (acrylic particles) were blended with 100 parts by mass of polyurea, and 200 parts by mass of methyl ethyl ketone (MEK) was added. The mixture was mixed and stirred at a predetermined stirring speed to prepare a composition for forming a surface layer.

[0099] <Preparation of Surface Layer> A surface layer having a thickness of 1.0 μm was formed on the outer periphery of the elastic layer in the same manner as in Example 1. In this way, a charging roll of Example 4 was prepared.

[0100] Example 5 Preparation of Conductive Rubber Composition 50 parts by mass of NBR and 30 parts by mass of carbon black were blended and stirred and mixed using a stirrer. Next, 50 parts by mass of hydrin rubber, 5 parts by mass of peroxide crosslinking agent, 3 parts by mass of vulcanization aid, and 3 parts by mass of catalyst were blended and stirred and mixed using a stirrer to prepare a conductive rubber composition.

[0101] The following materials were prepared as materials for the conductive rubber composition: NBR: "Nipol 1041" manufactured by Nippon Zeon Co., Ltd. Hydrin rubber (ECO, "Hydrin H1100" manufactured by Nippon Zeon Co., Ltd.) Carbon black: "Showblack N762" manufactured by Cabot Japan Co., Ltd. Peroxide crosslinking agent: "Perkmyl D40" manufactured by NOF Corp. Vulcanization aid (zinc oxide, "zinc oxide type 2" manufactured by Mitsui Metals Co., Ltd.)

[0102] <Preparation of Elastic Layer> An elastic layer made of a conductive rubber elastic material was molded in the same manner as in Example 1, except that the heating temperature was changed to 180°C.

[0103] <Preparation of Surface Layer Material> 5 parts by mass of a fluorine-based anionic compound <2>, 90 parts by mass of carbon black, and 30 parts by mass of particles for forming roughness (urethane particles) were blended with 100 parts by mass of uretonimine, and 200 parts by mass of methyl ethyl ketone (MEK) was added. The mixture was mixed and stirred at a predetermined stirring speed to prepare a composition for forming a surface layer.

[0104] <Preparation of Surface Layer> A surface layer having a thickness of 1.0 μm was formed on the outer periphery of the elastic layer in the same manner as in Example 1. In this way, a charging roll of Example 5 was prepared.

[0105] Examples 6, 9, and 10 Charging rolls were produced in the same manner as in Example 3, except that the surface layer material was prepared by changing the materials as shown in the table.

[0106] Examples 7 and 11 Charging rolls were produced in the same manner as in Example 1, except that the surface layer material was prepared by changing the materials as shown in the table.

[0107] Example 8 A charging roll was produced in the same manner as in Example 2, except that the surface layer material was prepared by changing the materials as shown in the table.

[0108] Comparative Example 1 A charging roll was produced in the same manner as in Example 2, except that in the preparation of the surface layer material, the binder was changed to polyurethane (ether type) and the ingredients were blended as shown in the table.

[0109] Comparative Example 2 A charging roll was produced in the same manner as in Example 1, except that in the preparation of the surface layer material, the binder was changed to polyurethane (ester type) and the ingredients were blended as shown in the table.

[0110] Comparative Example 3 A charging roll was produced in the same manner as in Example 1, except that in the preparation of the surface layer material, the main binder was changed to polyurethane (ether type) and the ingredients were blended as shown in the table.

[0111] Comparative Example 4 A charging roll was produced in the same manner as in Example 2, except that in preparing the surface layer material, a fluorine-based cationic compound was used instead of the fluorine-based anionic compound and was blended as shown in the table.

[0112] The materials used for the surface layer are as follows. (Binder) Isocyanurate: MDI trimer (produced by stirring MDI (Kanto Chemical Co., Ltd.'s "10449-30") in an oven at 180°C for 10 hours in the presence of a quaternary ammonium salt catalyst). Uretdione: MDI dimer (produced by stirring MDI (Kanto Chemical Co., Ltd.'s "10449-30") in a warm bath at 70°C for 10 hours in the presence of a phosphine catalyst). Carbodiimide diisocyanate: produced by stirring MDI (Kanto Chemical Co., Ltd.'s "10449-30") in a warm bath at 60°C for 3 hours in the presence of a phospholene catalyst. Polyurea: produced by adding purified water to MDI (Kanto Chemical Co., Ltd.'s "10449-30") and stirring in a warm bath at 40°C for 3 hours. Uretonimine: MDI (manufactured by Kanto Chemical Co., Ltd., "10449-30") was stirred in a hot bath at 60°C for 3 hours in the presence of a phosphorene catalyst to produce carbodiimide diisocyanate, to which MDI was again added, and the mixture was stirred in a hot bath at 50°C for 3 hours to produce uretonimine.・Polyurethane (ester type): "ADEKA New Ace NS-2400" manufactured by ADEKA ・Polyurethane (ether type): "ADEKA Polyether BPX-11" manufactured by ADEKA (additive) ・Fluorine-based anionic compound <1>: carbon number 6, carboxylate, AGC Seimi Chemical "Surflon S-211" manufactured by AGC Seimi Chemical ・Fluorine-based anionic compound <2>: carbon number 4, sulfonate, Kanto Chemical "24041-35" manufactured by Kanto Chemical ・Fluorine-based anionic compound <3>: carbon number 6, sulfonate (sulfonate containing hexafluoropropene group): NEOS "Ftergent 110" ・Fluorine-based cationic compound: perfluoroalkyltrialkylammonium halide, carbon number 6, ammonium salt, AGC Seimi Chemical "Surflon S-221" (conductive agent) ・Carbon black: Cabot Japan "Showblack N762" Conductive metal oxide: conductive tin oxide ("SN-100P" manufactured by Ishihara Sangyo Kaisha), average particle size 0.01-0.03 μm (particles for forming roughness) Acrylic particles: "MBX-5" manufactured by Sekisui Chemical Co., Ltd., average particle size 5 μm Urethane particles: "Art Pearl C800 Transparent" manufactured by Negami Chemical Industries, Ltd., average particle size 5 μm Silica particles: "Sicastar 43-00-503" manufactured by micromod, average particle size 5 μm

[0113] The produced charging roll was used to perform image evaluation.

[0114] (Image evaluation: black spots (fogging)) The produced charging roll was attached to a unit of an actual machine ("bizhum 750i" manufactured by Konica Minolta), and images were output at 25% density halftone in an environment of 10°C x 10% RH, and evaluation was performed after 1 million sheets were printed. Images with no black spots were rated as very good "◎", images with several spots found but within an acceptable range were rated as good "◯", and images with unacceptable spots were rated as poor "×".

[0115] (Image evaluation: cracks) The produced charging roll was attached to the unit of an actual machine ("bizhum 750i" manufactured by Konica Minolta), and images were output at 25% density halftone in an environment of 10°C x 10% RH, and evaluation was performed after 1 million sheets were printed. Those that did not produce streaky images due to cracks in the surface layer were rated as very good "◎", those that showed several cracks but were within the acceptable range were rated as good "◯", those that were equivalent to current technology were rated as equivalent "△", and those that were unacceptable were rated as poor "×".

[0116]

[0117]

[0118] In Examples 1 to 11, the binder for the surface layer is one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine, and a fluorine-based anionic compound is used in combination with these binders. According to Examples 1 to 11, no black spots appear on the durable image even under high-speed printing conditions, and high-speed printing is possible with high electrostatic chargeability. Furthermore, it is clear that degradation of the alkyl group in the binder is suppressed even during durability, and high durability allows for a long life.

[0119] In contrast, Comparative Example 1 uses an ether-type polyurethane as the binder for the surface layer, rather than the isocyanurate, and uses a fluorine-based anionic compound together with the polyurethane. According to Comparative Example 1, charging performance is insufficient under high-speed printing conditions, and the charging / discharging process cannot keep up with the high-speed rotation of the charging roll, resulting in areas on the photoreceptor surface where discharge does not occur, resulting in black spot images. This makes it unsuitable for high-speed printing. Furthermore, since the polyurethane binder contains ether groups, it has low strength and is prone to cracking. As a result, streak images caused by cracking occur during endurance testing. This makes it unsuitable for durability. Meanwhile, Comparative Example 2 uses an ester-type polyurethane as the binder for the surface layer, rather than the isocyanurate, and uses a fluorine-based anionic compound together with the polyurethane. In Comparative Example 2, since the polyurethane binder contains ether groups, the binder is prone to hydrolysis, resulting in streak images caused by cracking during endurance testing. This makes it unsuitable for durability.

[0120] In Comparative Example 3, the main material of the binder in the surface layer is an ether-type polyurethane, and a fluorine-based anionic compound is used together with this binder. In Comparative Example 3, since the polyurethane binder has an ether group, the strength is low and cracks tend to occur. As a result, streaky images caused by cracks occur during durability testing. Therefore, durability is not achieved.

[0121] Comparative Example 4 uses one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine as the binder for the surface layer, but uses a fluorine-based cationic compound instead of a fluorine-based anionic compound in addition to these binders. Comparative Example 4 fails to maintain the dipole moment of the binder's carbonyl group, and thus fails to exhibit high chargeability. Therefore, chargeability is insufficient under high-speed printing conditions, and the charging / discharging process cannot keep up with the high-speed rotation of the charging roll, resulting in areas on the photoreceptor surface that are not discharged, resulting in black spot images. This makes it unsuitable for high-speed printing. Furthermore, because it is difficult to arrange the binder around the alkyl group, the effect of suppressing deterioration of the binder's alkyl group is small. This causes binder deterioration during durability testing, resulting in streaky images due to cracks. This makes it unsuitable for durability.

[0122] 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, and various modifications are possible within the scope of the invention.

[0123] 10 charging roll 12 shaft body 14 elastic layer 16 surface layer

Claims

1. A charging roll for an electrophotographic device, comprising a shaft, an elastic layer formed on the outer peripheral surface of the shaft, and a surface layer formed on the outer peripheral surface of the elastic layer, wherein the surface layer contains the following (a) and (b), and the content of (b) in the surface layer is 0.1 to 10 parts by mass per 100 parts by mass of (a): (a) a binder consisting of one or more of isocyanurate, uretdione, carbodiimide diisocyanate, polyurea, and uretonimine, and (b) a fluorine-based anionic compound.

2. The charging roll for electrophotographic equipment according to claim 1, wherein said (b) is a fluoroalkyl group-containing carboxylate or a fluoroalkyl group-containing sulfonate.

3. A charging roll for an electrophotographic device according to claim 1 or 2, wherein the surface layer contains particles for providing roughness.

4. The charging roll for an electrophotographic device according to claim 3, wherein the roughness-forming particles are acrylic particles, urethane particles, or silica particles.

5. The charging roll for an electrophotographic device according to any one of claims 1 to 4, wherein the surface layer contains carbon black or a conductive metal oxide as a conductive agent.

6. The charging roll for electrophotographic equipment according to any one of claims 1 to 5, wherein the elastic layer contains at least one of isoprene rubber, nitrile rubber, and hydrin rubber.

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