JP7314013B2 - Developing roller, developing device and image forming device - Google Patents

Description

The present invention relates to a developing roller, a developing device, and an image forming apparatus.

2. Description of the Related Art A developing roller used in image forming apparatuses such as copiers, printers, and facsimiles that employ an electrophotographic method has a function of conveying a developer to an image carrier on which an electrostatic latent image is formed. The developer transportability of the developing roller affects the quality of the image forming apparatus, especially the print density. 2. Description of the Related Art In recent years, it has been studied to form unevenness on the surface of a developing roller and to adjust the electrical properties of various materials constituting the developing roller, thereby improving the developer transportability of the developing roller.

When the developing roller is used for a long period of time, developer may adhere to its surface (also referred to as "filming"). Such filming is considered to occur, for example, because the developer is deformed or destroyed by the sliding stress of a blade or the like that is in pressure contact with the developing roller when charging or adhering the developer, and further, the developer melts due to frictional heat with the blade or the like. For this reason, there is a demand for a developing roller that suppresses the occurrence of filming as much as possible and stabilizes durable printing performance.

For example, Patent Literature 1 describes a conductive roller that contains an ionic liquid and that prevents the developer from sticking to the surface for a long period of time. Further, Patent Document 2 describes an electrophotographic member in which perfluoropolyether is contained in the outermost layer and the surface fluorine atom/carbon atom ratio is set to 0.1 or more and 0.4 or less in order to maintain toner releasability and abrasion resistance.

JP 2011-221442 A JP 2015-28613 A

However, the developing rollers described in Patent Documents 1 and 2 have a problem that the ionic liquid or the perfluoropolyether contained in the outermost layer increases the roller hardness. From this point of view, it is required to satisfactorily prevent filming without increasing the hardness.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a developing roller, a developing device, and an image forming apparatus which are excellent in durable printing performance and in which the occurrence of filming is satisfactorily suppressed.

The developing roller of the present invention comprises a shaft, an elastic layer formed on the outer periphery of the shaft, and a coating layer formed on the outer periphery of the elastic layer, the surface of the coating layer has a monomolecular film in which fluorine-containing compounds are independently bonded to the coating layer, and the MD-1 hardness of the surface of the developing roller is 45 degrees or less.

The fluorine-containing compound preferably has a perfluoroalkyl chain or a fluorinated polyether chain.

The thickness of the monomolecular film is preferably 10 nm or less.

The coating layer is preferably made of urethane resin.

The elastic layer is preferably made of silicone rubber.

A developing device of the present invention includes the developing roller of the present invention.

An image forming apparatus of the present invention includes the developing roller of the present invention.

According to the present invention, it is possible to obtain a developing roller, a developing device, and an image forming apparatus in which occurrence of filming is satisfactorily suppressed and excellent in durable printing performance.

FIG. 1 is a schematic perspective view showing one embodiment of the developing roller of the present invention. FIG. 2 is a schematic cross-sectional view showing an embodiment of the image forming apparatus of the invention.

Embodiments of the present invention will be described in detail below, but the following embodiments are presented for the purpose of illustration, and the present invention is not limited to the embodiments shown below.

[Development roller]
FIG. 1 is a schematic perspective view showing one embodiment of the developing roller of the present invention.
The developing roller 1 of the present invention, as shown in FIG. 1, comprises a shaft 2, an elastic layer 3 formed on the outer periphery of the shaft 2, and a coating layer 4 formed on the outer periphery of the elastic layer 3. The coating layer 4 has a monomolecular film of a fluorine-containing compound on its surface, and the monomolecular film is formed by independently bonding fluorine-containing compounds to the coating layer 4.
The configuration of the developing roller 1 of the present invention will be described below.

(Shaft)
As the shaft 2, preferably, a conductive shaft used for a conventionally known developing roller can be used. The shaft 2 is preferably made of, for example, at least one metal selected from the group consisting of iron, aluminum, stainless steel, and brass. The shaft body 2 made of such a metal is generally also known by the name of "metal core".

The shaft 2 may contain insulating resin. The insulating resin may be, for example, a thermoplastic resin or a thermosetting resin. The shaft 2 may include, for example, a core made of insulating resin and a plated layer provided on the core. Such a shaft 2 can be obtained, for example, by plating a core made of an insulating resin to make it conductive.
The shaft 2 is preferably a metal core in order to obtain good conductivity.

The shape of the shaft 2 is preferably, for example, rod-like or tubular. The cross-sectional shape of the shaft 2 may be, for example, circular, elliptical, or non-circular such as polygonal. The outer peripheral surface of the shaft 2 may be subjected to a cleaning treatment, a degreasing treatment, a primer treatment, or the like, in order to improve adhesion with the elastic layer 3 .

The length of the shaft 2 in the axial direction is not particularly limited, and may be appropriately adjusted according to the form of the installed image forming apparatus. For example, when the print target is A4 size, the axial length of the shaft 2 is preferably 250 mm or more and 320 mm or less, and more preferably 260 mm or more and 310 mm or less. Also, the diameter of the shaft 2 (the diameter of the circumscribed circle) is not particularly limited, and may be appropriately adjusted according to the form of the installed image forming apparatus. For example, the outer diameter (the diameter of the circumscribed circle) of the shaft 2 is preferably 4 mm or more and 14 mm or less, more preferably 6 mm or more and 10 mm or less.

(elastic layer)
The elastic layer 3 is formed by heating and curing a rubber composition on the outer peripheral surface of the shaft 2 . The rubber composition for forming the elastic layer 3 preferably contains rubber, a conductivity-imparting agent, and optionally various additives.

Examples of the rubber in the rubber composition include silicone or silicone-modified rubber, nitrile rubber, ethylene propylene rubber (including ethylene propylene diene rubber), styrene-butadiene rubber, butadiene rubber, isoprene rubber, natural rubber, acrylic rubber, chloroprene rubber, butyl rubber, epichlorohydrin rubber, urethane rubber, fluororubber, and the like. Silicone or silicone-modified rubber or urethane rubber is preferable, and silicone or silicone-modified rubber is particularly preferable because it can reduce compression set, has excellent flexibility in a low-temperature environment, and has excellent heat resistance, charging characteristics, and the like. Examples of silicone rubbers include crosslinked organopolysiloxanes such as dimethylpolysiloxane and diphenylpolysiloxane.
Examples of silicone rubber compositions include addition-curable millable conductive silicone rubber compositions and addition-curable liquid conductive silicone rubber compositions.

- Addition Curable Millable Conductive Silicone Rubber Composition -
The addition-curable millable conductive silicone rubber composition may contain, for example, (A) an organopolysiloxane represented by the following average compositional formula (1), (B) a filler, and (C) a conductivity imparting agent.
R ¹ _n SiO _(4−n)/2 (1)
In formula (1), n represents a positive number of 1.95 or more and 2.05 or less. Also, R ¹ represents a substituted or unsubstituted monovalent hydrocarbon group which may be the same or different. The number of carbon atoms in the hydrocarbon group is preferably 1 or more and 12 or less, more preferably 1 or more and 8 or less.

Examples of R ¹ include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group and dodecyl group, cycloalkyl groups such as cyclohexyl group, alkenyl groups such as vinyl group, allyl group, butenyl group and hexenyl group, aryl groups such as phenyl group and tolyl group, and aralkyl groups such as β-phenylpropyl group. Also, R ¹ may be a group in which some or all of the hydrogen atoms of these hydrocarbon groups have been substituted with a substituent. Substituents may be, for example, halogen atoms, cyano groups, and the like. Hydrocarbon groups having a substituent include, for example, a chloromethyl group, a trifluoropropyl group, a cyanoethyl group and the like.

(A) Organopolysiloxane preferably has a molecular chain end blocked with a trialkylsilyl group such as trimethylsilyl group, a dialkylaralkylsilyl group such as dimethylvinylsilyl group, a dialkylhydroxysilyl group such as dimethylhydroxysilyl group, or a trialkylsilyl group such as trivinylsilyl group.

(A) Organopolysiloxane preferably has two or more alkenyl groups in the molecule. (A) Organopolysiloxane preferably has 0.001 mol % or more and 5 mol % or less (more preferably 0.01 mol % or more and 0.5 mol % or less) of alkenyl groups in R ¹ . (A) A vinyl group is particularly preferable as the alkenyl group possessed by the organopolysiloxane.

(A) Organopolysiloxane can be obtained, for example, by cohydrolytic condensation of one or more organohalosilanes, or by ring-opening polymerization of a cyclic polysiloxane such as a siloxane trimer or tetramer. (A) Organopolysiloxane may be basically linear diorganopolysiloxane, and may be partially branched. Also, (A) organopolysiloxane may be a mixture of two or more different molecular structures.

(A) The organopolysiloxane preferably has a kinematic viscosity at 25° C. of 100 cSt or more, more preferably 100,000 cSt or more and 1,0000,000 cSt or less. The degree of polymerization of (A) organopolysiloxane is preferably, for example, 100 cSt or more, and more preferably 3000 cSt or more and 10000 cSt or less.

(B) Fillers include, for example, silica-based fillers. Silica-based fillers include, for example, fumed silica and precipitated silica.

As the silica-based filler, a surface-treated silica-based filler surface-treated with a silane coupling agent represented by R ² Si(OR ³ ) ₃ can be preferably used. Here, R ² may be a group having a vinyl group or an amino group, such as glycidyl group, vinyl group, aminopropyl group, methacryloxy group, N-phenylaminopropyl group, mercapto group and the like. ^R3 may be an alkyl group, such as a methyl group, an ethyl group, and the like. Silane coupling agents are readily available, for example, under the trade names of "KBM1003" and "KBE402" manufactured by Shin-Etsu Chemical Co., Ltd. A surface-treated silica-based filler can be obtained by treating the surface of a silica-based filler with a silane coupling agent according to a conventional method. As the surface-treated silica-based filler, a commercially available product may be used. M. Trade name "Zeothix 95" manufactured by HUBER Corporation and the like can be mentioned.

The amount of the silica-based filler compounded is preferably 11 parts by mass or more and 39 parts by mass or less, more preferably 15 parts by mass or more and 35 parts by mass or less per 100 parts by mass of the organopolysiloxane (A). The average particle size of the silica-based filler is preferably 1 μm or more and 80 μm or less, more preferably 2 μm or more and 40 μm or less. The average particle size of the silica-based filler can be measured as a median size using a particle size distribution analyzer based on a laser beam diffraction method.

(C) Examples of conductivity-imparting agents include carbo, metals, group oxides, metal compounds, conductive polymers, and ionic liquids. The amount of the (C) conductivity-imparting agent is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the organopolysiloxane (A). The amount of the (C) conductivity-imparting agent is preferably 15 parts by mass or less, more preferably 10 parts by mass or less per 100 parts by mass of the (A) organopolysiloxane.

The addition-curable millable conductive silicone rubber composition may further contain additives other than (A) to (C). Examples of additives include auxiliary agents (chain extenders, cross-linking agents, etc.), catalysts, dispersants, foaming agents, anti-aging agents, antioxidants, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, ionic conductive agents, heat resistance improvers, flame retardancy improvers, acid acceptors, thermal conductivity improvers, release agents, solvents, and the like.

Specific examples of additives include (A) dimethylsiloxane oil having a lower degree of polymerization than organopolysiloxane, polyether-modified silicone oil, silanol, diphenylsilanediol and α,ω-dimethylsiloxanediol, both end-silanol group-capped low-molecular-weight siloxanes, and dispersants such as silanes. Specific examples of additives include heat resistance improvers such as iron octylate, iron oxide, and cerium oxide. As additives, various carbon functional silanes, various olefinic elastomers, and the like may be used for improving adhesiveness, molding processability, and the like.

-Addition Curing Liquid Conductive Silicone Rubber Composition-
The addition-curable liquid conductive silicone rubber composition may contain, for example, (D) an organopolysiloxane having two or more alkenyl groups in the molecule, (E) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms in the molecule, (F) a filler, (G) a conductivity imparting agent, and (H) an addition reaction catalyst.

(D) Organopolysiloxane is preferably a compound represented by the following average compositional formula (2).
R ⁴ _a SiO _(4-a)/2 (2)
In formula (2), a represents a positive number of 1.5 or more and 2.8 or less, preferably 1.8 or more and 2.5 or less, more preferably 1.95 or more and 2.05 or less. R ⁴ also represents a substituted or unsubstituted monovalent hydrocarbon group, which may be the same or different. However, at least two of ^R4 's in one molecule are alkenyl groups. The number of carbon atoms in the hydrocarbon group is preferably 1 or more and 12 or less, more preferably 1 or more and 8 or less.

Examples of R ⁴ include the same groups as those exemplified for R ¹ above. At least two of the ^R4 's in one molecule are alkenyl groups, and the other ^R4 's are preferably alkyl groups. The alkenyl group is preferably a vinyl group and the alkyl group is preferably a methyl group. Moreover, 90% or more of R ⁴ may be an alkyl group (preferably a methyl group), for example. The alkenyl group content in (D) organopolysiloxane is, for example, preferably 1.0×10 ⁻⁶ mol/g or more and 5.0×10 ⁻³ mol/g or less, more preferably 5.0×10 ⁻⁶ mol/g or more and 1.0×10 ⁻³ mol/g or less.

(D) Organopolysiloxane is preferably liquid at 25°C, and preferably has a viscosity at 25°C of 100 mPa·s to 1,000,000 mPa·s, more preferably 200 mPa·s to 100,000 mPa·s. The average degree of polymerization of (D) organopolysiloxane is preferably 100 or more and 800 or less, more preferably 150 or more and 600 or less.

(E) Organohydrogenpolysiloxane is preferably a compound represented by the following average compositional formula (3).
R ⁵ _b H _c SiO _(4-bc)/2 (3)
In formula (3), b represents a positive number of 0.7 or more and 2.1 or less, c represents a positive number of 0.001 or more and 1.0 or less, and bc is 0.8 or more and 3.0 or less. R ⁵ also represents a substituted or unsubstituted monovalent hydrocarbon group which may be the same or different. The number of carbon atoms in the hydrocarbon group is preferably 1 or more and 10 or less. Examples of R ⁵ include the same groups as those exemplified for R ¹ above.

(E) Organohydrogenpolysiloxane has two or more silicon-bonded hydrogen atoms (Si—H) in one molecule, preferably three or more. The number of silicon-bonded hydrogen atoms in one molecule of (E) organohydrogenpolysiloxane is preferably 200 or less, more preferably 100 or less.

In (E) organohydrogenpolysiloxane, the content of silicon-bonded hydrogen atoms is preferably 0.001 mol/g or more and 0.017 mol/g or less, more preferably 0.002 mol/g or more and 0.015 mol/g or less.

Examples of (E) organohydrogenpolysiloxane include methylhydrogenpolysiloxane with both ends trimethylsiloxy group-blocked, dimethylsiloxane-methylhydrogensiloxane copolymer with both ends trimethylsiloxy group-blocked, dimethylpolysiloxane with both ends dimethylhydrogensiloxy group-blocked, dimethylsiloxane-methylhydrogensiloxane copolymer with both ends dimethylhydrogensiloxy group-blocked, methylhydrogensiloxane-diphenylsiloxane copolymer with both ends trimethylsiloxy group-blocked, and methylhydrogensiloxane-diphenyl with both ends trimethylsiloxy group-blocked. siloxane-dimethylsiloxane copolymer, (CH₃)₂HSiO_1/2units and SiO_4/2units, (CH₃)₂HSiO_1/2units and SiO_4/2unit and (C₆H.₅) SiO_3/2units, and the like.

The amount of (E) organohydrogenpolysiloxane to be blended is preferably 0.1 to 30 parts by mass, more preferably 0.3 to 20 parts by mass, per 100 parts by mass of (D) organopolysiloxane. The molar ratio of Si—H in (E) organohydrogenpolysiloxane to alkenyl groups in (D) organopolysiloxane is preferably 0.3 to 5.0, more preferably 0.5 to 2.5.

(F) The filler may be, for example, an inorganic filler. By adding (F) the filler to the addition-curable liquid conductive silicone rubber composition, the compression set is lowered, the volume resistivity is stabilized over time, and sufficient roller durability is obtained.

(F) The average particle size of the filler is preferably 1 μm or more and 30 μm or less, more preferably 2 μm or more and 20 μm or less. (F) When the average particle size of the filler is 1 μm or more, the change in volume resistivity over time is further suppressed. Further, when the average particle size of the (F) filler is 30 μm or less, the elastic layer 3 having even better durability can be obtained. The average particle size of the filler (F) can be measured as a median size using a particle size distribution analyzer based on a laser beam diffraction method.

(F) The bulk density of the filler is preferably 0.1 g/cm ³ or more and 0.5 g/cm ³ or less, more preferably 0.15 g/cm ³ or more and 0.45 g/cm ³ or less. (F) By adjusting the bulk density of the filler to the above range, the compression set can be further reduced, the change in volume resistivity with time is further suppressed, and the elastic layer 3 with further excellent durability can be obtained. (F) The bulk density of the filler can be obtained based on the method of measuring apparent specific gravity according to JIS K 6223.

(F) Fillers include, for example, diatomaceous earth, perlite, mica, calcium carbonate, glass flakes, and hollow fillers. Among these, diatomaceous earth, perlite, and pulverized perlite foam can be suitably used as the filler (F).

The amount of filler (F) to be blended is preferably 5 parts by mass or more and 100 parts by mass or less, more preferably 10 parts by mass or more and 80 parts by mass or less per 100 parts by mass of organopolysiloxane (D).

(G) Examples of conductivity-imparting agents include carbon, metals, metal oxides, metal compounds, conductive polymers, and ionic liquids. The amount of the (G) conductivity-imparting agent is preferably 0.5 parts by mass or more and 15 parts by mass or less, more preferably 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the organopolysiloxane (D).

(H) The addition reaction catalyst may be a catalyst capable of activating the addition reaction between (D) organopolysiloxane and (E) organohydrogenpolysiloxane. (H) Addition reaction catalysts include, for example, catalysts containing a platinum group element. Examples of the catalyst having a platinum group element include platinum-based catalysts (e.g., platinum black, platinic chloride, chloroplatinic acid, reactants of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, platinum bisacetoacetate, etc.), palladium-based catalysts, rhodium-based catalysts, and the like.

(H) The addition reaction catalyst may be added in a catalytic amount. For example, the amount of addition reaction catalyst (H) to be added is preferably such that the amount of platinum group element is 0.5 ppm by mass or more and 1000 ppm by mass or less with respect to the total mass of (D) organopolysiloxane and (E) organohydrogenpolysiloxane, and more preferably 1 mass ppm or more and 500 mass ppm or less.

The addition-curable liquid conductive silicone rubber composition may further contain additives other than (D) to (H). Examples of additives include auxiliary agents (chain extenders, cross-linking agents, etc.), foaming agents, dispersants, antioxidants, antioxidants, ion conductive agents, pigments, colorants, processing aids, softeners, plasticizers, emulsifiers, heat resistance improvers, flame retardant improvers, acid acceptors, thermal conductivity improvers, release agents, diluents, reactive diluents, solvents, and the like.

Specific examples of additives include dispersants such as low-molecular-weight siloxane esters, polyether-modified silicone oils, silanol, and phenylsilanediol. Heat resistance improvers such as iron octylate, iron oxide and cerium oxide are also included. Also, various carbon functional silanes, various olefinic elastomers, and the like may be used for improving adhesiveness, molding processability, and the like. A halogen compound or the like that imparts flame retardancy may also be used.

The viscosity of the addition-curable liquid conductive silicone rubber composition at 25° C. is preferably 5 Pa·s or more and 500 Pa·s or less, more preferably 5 Pa·s or more and 200 Pa·s or less.

The thickness of the elastic layer 3 is not particularly limited, and is preferably 0.1 mm or more and 6 mm or less, more preferably 1 mm or more and 4 mm or less. The thickness in this specification indicates the thickness in the direction perpendicular to the axial direction of the developing roller 1 .

The outer diameter of the elastic layer 3 is not particularly limited, and is preferably 6 mm or more and 25 mm or less, more preferably 7 mm or more and 21 mm or less.

The outer peripheral surface of the elastic layer 3 may be subjected to surface treatment such as primer treatment, corona treatment, plasma treatment, excimer treatment, UV treatment, Itro treatment, flame treatment, etc. for the purpose of improving adhesion with the coating layer 4.

The elastic layer 3 is formed on the outer peripheral surface of the shaft 2 by performing heat curing and molding simultaneously or continuously by a known molding method. The method of curing the rubber composition may be any method as long as the heat necessary for curing the rubber composition can be applied, and the method of molding the elastic layer 3 is not particularly limited, such as continuous vulcanization by extrusion molding, press molding, molding by injection, and the like. For example, when the rubber composition is an addition-curable millable conductive silicone rubber composition, for example, extrusion molding can be selected, and when the rubber composition is an addition-curable liquid conductive silicone rubber composition, for example, a molding method using a mold can be selected. Alternatively, the elastic body (cured product of the silicone rubber composition) formed on the shaft 2 may be ground or polished.

The heating temperature for curing the rubber composition is preferably 100° C. or higher and 500° C. or lower, more preferably 120° C. or higher and 300° C. or lower, in the case of an addition-curable millable conductive silicone rubber composition. The heating time is preferably several seconds to 1 hour, more preferably 10 seconds to 35 minutes. In the case of an addition-curable liquid conductive silicone rubber composition, the heating temperature is preferably 100° C. or higher and 300° C. or lower, more preferably 110° C. or higher and 200° C. or lower. The heating time is preferably 5 minutes or more and 5 hours or less, more preferably 1 hour or more and 3 hours or less. In addition, secondary vulcanization may be performed as necessary. In the case of the addition-curable millable conductive silicone rubber composition, for example, the curing conditions are selected at 100° C. or higher and 200° C. or lower for about 1 hour or longer and 20 hours or shorter. In addition, in the case of an addition-curable liquid conductive silicone rubber composition, for example, the curing conditions are selected at 120° C. or higher and 250° C. or lower for about 2 hours or more and 70 hours or less. Further, the rubber composition can be foamed and cured by a known method to easily form a sponge-like elastic layer having cells.

(coating layer)
The coating layer 4 is provided on the outer periphery of the elastic layer 3 and on the outermost surface of the developing roller 1 . The coating layer 4 is formed by applying a coating layer resin composition to the outer peripheral surface of the elastic layer 3 or an optionally formed primer layer, and then heating and curing the coated coating layer resin composition.
The coating layer 4 may be a layer made of urethane resin. Examples of the coating layer resin composition include those containing (a) a polyol, (b) an isocyanate, (c) a surface roughening agent, and (d) a conductivity imparting agent.
The components (a) to (d) of the coating layer resin composition are described below.

(a) Polyol The polyol may be any of various polyols commonly used in the preparation of polyurethanes, and is preferably at least one polyol selected from polyether polyols, polyester polyols, polyacrylate polyols, and polycarbonate polyols.

Examples of polyether polyols include polyalkylene glycols such as polyethylene glycol, polypropylene glycol, polypropylene glycol-ethylene glycol, polytetramethylene ether glycol, copolymer polyols of tetrahydrofuran and alkylene oxide, various modified products thereof, and mixtures thereof.

A polyester polyol has two or more ester bonds and two or more hydroxyl groups in the molecule. Polyester polyols include, for example, condensation reaction products of dicarboxylic acids and polyols. Examples of dicarboxylic acids include aromatic dicarboxylic acids such as phthalic acid, terephthalic acid and isophthalic acid, and aliphatic dicarboxylic acids such as adipic acid and sebacic acid.

Polyacrylate polyols are copolymers of hydroxyl group-containing monomers with other olefinically unsaturated monomers, such as esters of (meth)acrylic acid, styrene, α-methylstyrene, vinyl toluenes, vinyl esters, mono- and dialkyl maleates, mono- and dialkyl fumarates, α-olefins and other unsaturated oligomers and polymers.

Polycarbonate polyols have two or more carbonate bonds and two or more hydroxyl groups in the molecule. Polycarbonate polyols include, for example, condensation reaction products of polyols and carbonate compounds. Moreover, examples of the carbonate compound include dialkyl carbonate, diaryl carbonate, alkylene carbonate, and the like. Polyols used as raw materials for polycarbonate polyols include, for example, diols such as hexanediol and butanediol, and triols such as 2,4-butanetriol.
The polyol preferably has a number average molecular weight of 1,000 to 8,000, more preferably 1,000 to 5,000, from the viewpoint of excellent compatibility with isocyanate and the like, which will be described later. A number average molecular weight is a molecular weight when converted into standard polystyrene by gel permeation chromatography (GPC).

(b) Isocyanate The isocyanate may be any of various isocyanates that are commonly used in preparing polyurethanes, such as aliphatic isocyanates, aromatic isocyanates, derivatives thereof, and the like. The isocyanate is preferably an aliphatic isocyanate because of its excellent storage stability and easy control of the reaction rate.
Examples of aliphatic isocyanates include hexamethylene diisocyanate (HDI), 4,4′-dicyclohexylmethane diisocyanate (hydrogenated MDI), orthotoluidine diisocyanate, lysine diisocyanate methyl ester, isophorone diisocyanate (IPDI), norbornane diisocyanate methyl, transcyclohexane-1,4-diisocyanate, triphenylmethane-4,4′,4″-triisocyanate, and the like.
Examples of aromatic isocyanates include xylylene diisocyanate (XDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (also referred to as tolylene diisocyanate, TDI), 3,3'-bitrylene-4,4'-diisocyanate, 3,3'-dimethyldiphenylmethane-4,4'-diisocyanate, 2,4-tolylene diisocyanate uretidinedione (dimer of 2,4-TDI), xylylene diisocyanate, and naphthalene diisocyanate. (NDI), paraphenylene diisocyanate (PDI), tolidine diisocyanate (TODI), metaphenylene diisocyanate, and the like.
Examples of derivatives include polyisocyanate polynuclears, urethane-modified products modified with polyols (including urethane prepolymers), uretidione-formed dimers, isocyanurate-modified products, carbodiimide-modified products, uretonimine-modified products, allohanate-modified products, urea-modified products, burette-modified products, and the like. Polyisocyanate can be used alone or in combination of two or more. The polyisocyanate preferably has a molecular weight of 500-2000, more preferably 700-1500.

The (b) isocyanate used in the coating layer resin composition is preferably a polyisocyanate. (b) The number of isocyanate groups in one isocyanate molecule is preferably more than 2, more preferably 2.5 or more, and even more preferably 3 or more.
The mixing ratio in the mixture of polyol and polyisocyanate is not particularly limited, but usually the molar ratio (NCO/OH) between the hydroxyl group (OH) contained in the polyol and the isocyanate group (NCO) contained in the polyisocyanate is preferably 0.7 or more and 1.15 or less. This molar ratio (NCO/OH) is more preferably 0.85 or more and 1.10 or less in terms of preventing hydrolysis of the polyurethane. In practice, it may be blended in an amount equivalent to 3 to 4 times the proper molar ratio, taking into consideration work environment and work errors.

The resin composition for the coating layer may be used in combination with an auxiliary agent, such as a chain extender or a cross-linking agent, which is usually used for the reaction between (a) the polyol and (b) the isocyanate. Examples of chain extenders and cross-linking agents include glycols, hexanetriol, trimethylolpropane, and amines.

(c) Surface roughness material The coating layer 4 contains a surface roughness material. The surface roughness material is particles that adjust the surface roughness of the coating layer 4 . The average particle size of the surface roughening agent blended in the coating layer 4 is preferably 0.1 μm or more and 20 μm or less, more preferably 1 μm or more and 15 μm or less. By blending such a surface roughness material in the coating layer 4, the surface roughness of the outer peripheral surface can be easily adjusted to an appropriate range. By adjusting the surface roughness of the outer peripheral surface of the developing roller 1, the toner transportability is improved, and even better printing characteristics can be obtained. The average particle size of the surface roughness material can be measured as a median size using a particle size distribution analyzer based on laser light diffraction.

The surface roughness (Rz) of the coating layer 4 is, for example, preferably 1-20 μm, more preferably 1-15 μm. In this specification, the surface roughness (Rz) of the coating layer 4 indicates ten-point average roughness measured by the method specified in JIS-1994. The surface roughness of the coating layer 4 can be easily adjusted by, for example, the type and amount of filler to be blended.

The type of the surface roughening material blended in the coating layer 4 is not particularly limited, and can be appropriately selected from known fillers (fillers) and used. For example, it may be silica, spherical resin particles, metal oxides, or the like.

The content of the surface roughness material in the coating layer resin composition is preferably 0.1 to 50 parts by mass, more preferably 1 to 40 parts by mass, per 100 parts by mass of the coating layer resin composition.

(d) Conductivity imparting agent The coating layer 4 may further contain a conductivity imparting agent. The conductivity imparting agent is not particularly limited as long as it is a component that can impart conductivity to the coating layer 4 . Examples of conductivity-imparting agents include carbon black (eg, acetylene black, Ketjenblack), ionic conductive agents, metals, metal oxides, conductive polymers, antistatic agents, ionic conductive resins, surfactants, and the like. The amount of the conductivity-imparting agent to be blended is not particularly limited, and may be appropriately adjusted according to the type of the conductivity-imparting agent, the desired conductivity performance, and the like. Moreover, one type of conductivity-imparting agent may be used alone, or two or more types may be used in combination.

The coating layer 4 may further contain additives other than those described above. For example, the coating layer 4 may further contain additives such as silane coupling agents, lubricants, charge control agents, polymerization catalysts, dispersants and fillers.

The coating layer 4 is formed by applying a coating layer resin composition onto the elastic layer 3, and by heating or the like, (a) the polyol component and (b) the isocyanate component are polymerized and cured. The solvent used for the coating liquid is preferably a solvent capable of dissolving the polyol component and the isocyanate component, and may be, for example, ethyl acetate, butyl acetate, or the like.

The coating of the coating layer resin composition is carried out by known coating methods such as a coating method of applying a coating liquid of the coating layer resin composition, a dipping method of immersing the elastic layer or the like in the coating liquid, or a spray coating method of spraying the coating liquid onto the elastic layer or the like. The resin composition for the coating layer may be applied as it is, or a volatile solvent such as an alcohol such as methanol and ethanol, an aromatic solvent such as xylene and toluene, an ester solvent such as ethyl acetate and butyl acetate, or a coating liquid obtained by adding water may be applied to the resin composition for the coating layer. The method for curing the coating layer resin composition coated in this way may be any method as long as the heat necessary for curing the coating layer resin composition can be applied. Examples thereof include a method of heating the elastic layer coated with the coating layer resin composition with a heater, and a method of leaving the elastic layer coated with the resin composition at a high temperature. The heating temperature for heat curing the coating layer resin composition is, for example, preferably 100° C. or higher and 200° C. or lower, particularly preferably 120° C. or higher and 160° C. or lower, and the heating time is preferably 10 minutes or longer and 120 minutes or shorter, and more preferably 30 minutes or longer and 60 minutes or shorter.
In the coating layer formed in this manner, when an ionic conductive material is used as the conductivity-imparting agent, the precursor forming the resin and the ionic conductive material may be reacted to be integrated, or may form a composite. Also, the ion conductive material may be dispersed in the resin without reacting with the precursor forming the resin.

Specifically, the thickness of the coating layer 4 is preferably 1 μm or more and 15 μm or less, more preferably 3 μm or more and 10 μm or less, from the viewpoint of satisfactorily suppressing filming and improving durable printing performance.

(Other configurations)
The developing roller 1 of the present invention may have an intermediate layer such as an adhesive layer or a primer layer between the shaft 2 and the elastic layer 3 and between the elastic layer 3 and the coating layer 4 .
Among these intermediate layers, the adhesive layer and the primer layer provided between the elastic layer 3 and the coating layer 4 can adjust the electrical characteristics of the developing roller 1 by adjusting the electrical characteristics thereof. As a result, the developing performance of the developing roller 1 can be adjusted satisfactorily.

As the primer layer, one commonly used as a primer layer of the developing roller can be used. For example, by forming a primer layer made of a urethane resin having an ester group, the developing performance of the developing roller 1 can be maintained well.

(Monolayer of fluorine-containing compound)
The developing roller 1 of this embodiment has a monomolecular film of a fluorine-containing compound on the surface of the coating layer 4 .
The monomolecular film of the fluorine-containing compound preferably has perfluoroalkyl chains or fluorinated polyether chains. As such a fluorine-containing compound, the following are preferred.

-Fluorine-containing compound having a perfluoroalkyl chain-
In the present invention, the fluorine-containing compound having a perfluoroalkyl chain is represented by the following formula (4).

CF ₃ (CF ₂ ) _r -X ¹ -Z (4)
In formula (4), the symbols represent the following.
X ¹ : a single bond or an alkylene having 1 to 3 carbon atoms Z: a group represented by the following formula (4-1), a group represented by the following formula (4-2), a group represented by the following formula (4-3) or a group represented by the following formula (4-4) —CH ₂ CH ₂ CH ₂ SiL _m R _n (4-1)
—CH ₂ CH(SiL _m R _n )CH ₃ (4-2)
—CH ₂ CH=CH ₂ (4-3)
-CH=CHCH ₃ (4-4)
r is an integer of 10 or less, more preferably 6 or less.
Symbols in formulas (4-1) to (4-4) are as follows.
L: hydrolyzable group R: monovalent hydrocarbon group m is an integer of 1 to 3, n is an integer of 0 to 2, and m+n=3.

L is a hydrolyzable group such as an alkoxy group, a halogen atom, an acyl group, and an isocyanate group. As the alkoxy group, an alkoxy group having 1 to 4 carbon atoms is preferable. L becomes a hydroxyl group bonded to a silicon atom by a hydrolysis reaction. Si--L becomes a silanol group (--Si--OH) by a hydrolysis reaction. A silanol group can react with a hydroxyl group on the urethane surface of the coating layer to form a chemical bond, and this reaction chemically bonds the compound (1) to the substrate surface.

R is a monovalent hydrocarbon group. Monovalent hydrocarbon groups include alkyl groups, cycloalkyl groups, alkenyl groups and allyl groups. R is particularly preferably a monovalent saturated hydrocarbon group. The monovalent saturated hydrocarbon group preferably has 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms, and particularly preferably 1 to 2 carbon atoms. R is preferably an alkyl group having 1 to 6 carbon atoms, more preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably an alkyl group having 1 to 2 carbon atoms, from the viewpoint of simplicity of synthesis.

n is an integer from 0 to 2, m+n=3. n is preferably 0 or 1, particularly preferably 0. That n is 0 or 1 means that m is 3 or 2.

-SiL _m R _n includes -Si(OCH ₃ ) ₃ , -SiCH ₃ (OCH ₃ ) ₂ , -Si(OCH ₂ CH ₃ ) ₃ , -SiCl ₃ , -Si(OCOCH ₃ ) ₃ and -Si(NCO) ₃ . —Si(OCH ₃ ) ₃ is preferred for ease of handling in industrial production.

Fluorine-containing compounds having a perfluoroalkyl chain include commercially available SF-coat (AGC Seimi Chemical Co., Ltd.).

- Fluorine-containing compound having a fluorinated polyether chain -
In the present invention, the fluorine-containing compound having a perfluoroalkyl chain is represented by the following formula (5).

A ² -OQ-(C _b F _2b O) _d -X ² -OZ (5)
The symbols in formula (5) represent the following.
A ² : a perfluoroalkyl group having 1 to 20 carbon atoms, or Z below
Q: single bond, -CH ₂ -, -CHF-, -Q ¹ -CH ₂ -, -Q ¹ -CHF-, -Q ¹ -O-CH ₂ -, -Q ¹ -O-CHF-, -Q ¹ -CH ₂ -O- or Q ¹ -CHFO-
Q ¹ : a fluoroalkylene group having 1 to 10 carbon atoms, a fluoroalkylene group having 2 to 10 carbon atoms having an etheric oxygen atom between carbon-carbon atoms, an alkylene group having 1 to 10 carbon atoms, or an alkylene group having 2 to 10 carbon atoms having an etheric oxygen atom between carbon-carbon atoms b, d: b is an integer of 1 to 10, d is an integer of 1 to 200, and when d is 2 or more, ( _{C b} F _2b O)d is different from b It may consist of two or more kinds of _CbF2bO .
X ² : divalent organic group not having CF ₂ O Z: Same as Z in formula (4) above.

X ² is a divalent organic group without CF ₂ O. As the divalent organic group, a fluoroalkylene group having 1 to 6 carbon atoms and an alkylene group having 1 to 6 carbon atoms are preferred. From the viewpoint of ease of production, a fluoroalkylene group having 1 to 6 carbon atoms and containing at least one hydrogen atom is more preferred, and a group represented by the following formula (6) is particularly preferred.

—(CF ₂ ) _a CFX ³ —CH ₂ — (6)
However, in formula (6), a is 0 to 2, and ^X3 is F or _CF3 .

Group (6) includes, for example, -CF ₂ CH ₂ -, -CF ₂ CF ₂ CH ₂ -, -CF ₂ CF ₂ CF ₂ CH ₂ -, -CF(CF ₃ )CH ₂ - and the like.

Examples of the fluorine-containing compound having a fluorinated polyether chain include commercially available SURECO (AGC Co., Ltd.).

A monomolecular film can be formed by the following method. First, the composition containing the fluorine-containing compound is applied onto the coating layer by spray coating, dip coating, brush coating, dry cloth coating, or the like to form a coating film. After the coating film is dried, it is heated at 80° C. to 150° C. for about 10 to 30 minutes to form a monomolecular film. Finally, a step of rinsing with a fluorine-based solvent may be included.

The thickness of the monomolecular film is preferably 10 nm or less. The monolayer coating may be a stack of monolayers.

The MD-1 hardness of the surface of the developing roller 1 of the present invention is 45 or less from the viewpoint of preventing damage to the developer. The MD-1 hardness of the surface of the developing roller 1 is preferably 43 or less.
MD-1 hardness tester (manufactured by Kobunshi Keiki Co., Ltd., "Micro rubber hardness tester MD-1)" is used to measure the MD-1 hardness. The indenter of the MD-1 hardness tester is pressed against the roll surface, and the value read in the peak hold mode with a hold time of 3 seconds is taken as the MD-1 hardness. In principle, the MD-1 hardness tester conforms to the type A durometer described in JIS K6253.

By having a monomolecular film composed of a fluorine-containing compound such as that of the present invention, water- and oil-repellency is imparted to the coating layer, and the externally added silica of the developer does not adhere, so filming can be satisfactorily prevented. Moreover, since there is no need to introduce a fluorine-containing group into the resin constituting the coating layer as in the prior art, filming can be prevented without increasing the hardness of the coating layer.

[Developing device and image forming device]
The developing roller 1 of the present invention can be suitably used as a developer carrier in a developing device and an image forming device. In this embodiment, the configuration of the image forming apparatus other than the developing roller 1 is not particularly limited. An example of a developing device and an image forming apparatus equipped with the developing roller 1 of the present invention will be described with reference to FIG.

The image forming apparatus 10 is a tandem type color image forming apparatus in which a plurality of image carriers 11B, 11C, 11M, and 11Y equipped with developing units B, C, M, and Y of respective colors (black, cyan, magenta, and yellow) are arranged in series on the transfer/conveyor belt 6, and the developing units B, C, M, and Y are arranged in series on the transfer/conveyor belt 6. The developing unit B includes an image carrier 11B such as a photosensitive member (also referred to as a photosensitive drum), a charging means 12B such as a charging roller, an exposure means 13B, a developing device 20B, a transfer means 14B such as a transfer roller that contacts the image carrier 11B via the transfer/conveyor belt 6, and a cleaning means 15B.

The developing device 20B is an example of the developing device of the present invention, and as shown in FIG. 2, includes the developing roller 1 of the present invention and developer 22B. Therefore, in this image forming apparatus 10, the developing roller 1 is mounted as developer carriers 23B, 23C, 23M and 23Y. Specifically, the developing device 20B includes a housing 21B containing a one-component non-magnetic developer 22B, a developer carrier 23B for supplying the developer 22B to the image carrier 11B, a toner supply roller 25B for supplying the developer 22B to the developer carrier 23B, and a developer amount adjusting means 24B such as a blade for adjusting the thickness of the developer 22B. In the developing device 20B, as shown in FIG. 2, the developer amount adjusting means 24B is in contact or pressure contact with the outer peripheral surface of the developer carrier 23B. That is, the developing device 20B is a "contact developing device". Developing units C, M and Y are basically configured in the same manner as developing unit B, and the same elements are denoted by the same reference numerals and symbols C, M or Y indicating each unit, and description thereof is omitted.

In the image forming apparatus 10, the developer carrier 23B of the developing device 20B is arranged so that its surface contacts or presses against the surface of the image carrier 11B. Similarly to the developing device 20B, the developing devices 20C, 20M and 20Y are also arranged such that the surfaces of the developer carriers 23C, 23M and 23Y contact or press against the surfaces of the image carriers 11C, 11M and 11Y. That is, the image forming apparatus 10 is a "contact image forming apparatus".

The fixing means 30 is arranged downstream of the developing unit Y. As shown in FIG. The fixing means 30 includes a fixing roller 31, an endless belt supporting roller 33 arranged near the fixing roller 31, an endless belt 36 wound around the fixing roller 31 and the endless belt supporting roller 33, and a pressure roller 32 arranged opposite to the fixing roller 31 in a housing 34 having an opening 35 through which the recording medium 16 passes. A supported pressure heat fixing device. At the bottom of the image forming apparatus 10, a cassette 41 that accommodates the recording medium 16 is installed. The transfer/conveyor belt 6 is wound around a plurality of support rollers 42 .

The developers 22B, 22C, 22M, and 22Y used in the image forming apparatus 10 may be dry developers or wet developers, non-magnetic developers, or magnetic developers, as long as they can be charged by friction. The housings 21B, 21C, 21M and 21Y of the developing units B, C, M and Y contain one-component non-magnetic black developer 22B, cyan developer 22C, magenta developer 22M and yellow developer 22Y, respectively.

The image forming apparatus 10 forms a color image on the recording medium 16 as follows. First, in the developing unit B, an electrostatic latent image is formed by the exposing means 13B on the surface of the image carrier 11B charged by the charging means 12B, and a black electrostatic latent image is developed with the developer 22B supplied by the developer carrier 23B. A black electrostatic latent image is transferred to the surface of the recording medium 16 when the recording medium 16 passes between the transfer means 14B and the image carrier 11B. Next, in the same manner as the developing unit B, the developing units C, M and Y superimpose a cyan image, a magenta image and a yellow image on the recording medium 16 on which the electrostatic latent image has been visualized as a black image, respectively, thereby visualizing a color image. Next, the color image is fixed on the recording medium 16 as a permanent image by the fixing means 30 on the recording medium 16 on which the color image has been visualized. A color image can be formed on the recording medium 16 in this way.

The developing device 20B is provided with the developing roller 1, is excellent in developer transportability, suppresses the occurrence of toner filming, and contributes to long-term formation of high-density, high-quality images. Further, an image forming apparatus equipped with this developing device 20B can form high-density, high-quality images over a long period of time.

The developing device and image forming apparatus of the present invention are not limited to those described above, and various modifications are possible as long as the object of the present invention can be achieved.

The image forming apparatus is an electrophotographic image forming apparatus, but in the present invention, the image forming apparatus is not limited to an electrophotographic image forming apparatus, and may be, for example, an electrostatic image forming apparatus. Further, the image forming apparatus provided with the developing roller of the present invention is not limited to a tandem type color image forming apparatus in which a plurality of image carriers having respective color developing units are arranged in series on a transfer conveyor belt. Further, the developer used in the image forming apparatus is a one-component non-magnetic developer, but in the present invention, it may be a one-component magnetic developer, a two-component non-magnetic developer, or a two-component magnetic developer.

The image forming apparatus is a contact type image forming apparatus in which the surface of the developer image carrier is arranged in contact or pressure contact with the surface of the image carrier. The image forming apparatus of the present invention may be a non-contact image forming apparatus arranged with a gap so that the surface of the developer bearing member does not come into contact with the surface of the image bearing member.

Although the present invention has been described using the embodiments, it goes without saying that the technical scope of the present invention is not limited to the scope of the invention described in the above embodiments. In addition, it is clear from the description of the scope of claims that inventions with such modifications or improvements can also be included in the technical scope of the present invention.

Hereinafter, the present invention will be described in detail with reference to examples. It should be noted that the present invention is by no means limited to the examples shown below.

[Example 1]
(Formation of primer layer)
A shaft (made of SUM22, diameter 10 mm, length 275 mm) subjected to electroless nickel plating was washed with ethanol, and a silicone primer (trade name “Primer No. 16”, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied to the surface. The primer-treated shaft was baked at a temperature of 150° C. for 10 minutes using a gear oven, and then cooled at room temperature for 30 minutes or more to form a primer layer on the outer peripheral surface of the shaft.

(Formation of elastic layer)
Next, a silicone rubber composition for forming an elastic layer was prepared as follows.すなわち、両末端がジメチルビニルシロキシ基で封鎖されたジメチルポリシロキサン（重合度３００）１００質量部、ＢＥＴ比表面積が１１０ｍ ^２ ／ｇである疎水化処理されたヒュームドシリカ（商品名「Ｒ－９７２」、日本アエロジル株式会社製）１質量部、平均粒子径６μｍ、嵩密度が０．２５ｇ／ｃｍ ^３である珪藻土（商品名「オプライトＷ－３００５Ｓ」、中央シリカ株式会社製）４０質量部、及び、アセチレンブラック（商品名「デンカブラックＨＳ－１００」、デンカ株式会社製）５質量部、をプラネタリーミキサーに入れ、３０分撹拌した後、３本ロールに１回通した。 This was returned to the planetary mixer again, and 2.1 parts by mass of methylhydrogenpolysiloxane having Si—H groups at both ends and side chains (degree of polymerization: 17, Si—H content: 0.0060 mol/g), 0.1 part by mass of ethynylcyclohexanol, and 0.1 part by mass of a platinum-based catalyst (Pt concentration: 1% by mass) were added, followed by stirring and defoaming for 30 minutes to prepare an addition-curable liquid conductive silicone rubber composition.

The prepared addition-curable liquid conductive silicone rubber composition was injection molded using a mold to form an elastic body made of a rubber material on the outer peripheral surface of the shaft. In injection molding, the addition-curable liquid conductive silicone rubber composition was cured by heating at 120° C. for 10 minutes, followed by secondary vulcanization at 200° C. for 4 hours to form an elastic layer with an outer diameter of 16 mm.

(Formation of coating layer)
Next, a resin composition for forming a coating layer was prepared as follows.
Table 1 shows the total content of (a) polyol and (b) isocyanate, the content (parts by mass) of (c) surface roughness agent, and (d) ion conductive agent in the resin composition for coating layer.

-Resin composition for coating layer-
(a) Polyester polyol 28 parts by mass (b) Hexamethylene diisocyanate (trade name "Duranate TPA-100", manufactured by Asahi Kasei Corporation) 14 parts by mass (c) Surface roughness material (silica) (trade name "ACEMATT412", manufactured by Evonik Japan Co., Ltd.) 3 parts by mass (d) Carbon black (trade name "Toka Black #5500", manufactured by Tokai Carbon Co., Ltd.)
5 parts by mass

The coating layer resin composition was applied to the outer peripheral surface of the elastic layer by a spray coating method and heated at 160° C. for 30 minutes to form a coating layer having a layer thickness of 15 μm.

(Monolayer of fluorine-containing compound)
The compositions shown below were used as compositions containing fluorine-containing compounds.
SURECO AF (manufactured by AGC Co., Ltd.) Appropriate amount SURECO was applied by dipping and then heated at 120°C for 30 minutes to form a monomolecular film.
As described above, a developing roller having a shaft, an elastic layer and a coating layer was produced.

[Example 2]
A developing roller was produced in the same manner as in Example 1, except that the composition containing a fluorine-containing compound was replaced with SF-coat (manufactured by AGC Co., Ltd.).

[Comparative Example 1]
A developing roller was obtained in the same manner as in Example 1, except that (a) polyol was 20 parts by mass of polyester polyol and 6 parts by mass of fluorine polyol in the coating layer resin composition, and no monomolecular film was formed.

[Comparative Example 2]
A developing roller was obtained in the same manner as in Comparative Example 1, except that (a) polyol in the coating layer resin composition was changed to 20 parts by mass of fluorine polyol.

[evaluation]
An image forming apparatus C610dn2 (model number, manufactured by Oki Data Co., Ltd.) was prepared, and the developing roller of this image forming apparatus was replaced with the developing roller of each example and each comparative example to obtain an image forming apparatus. The resulting image forming apparatus was evaluated for filming, print density, and image uniformity by the following methods, and the results are shown in Table 1.

(Method for measuring MD-1 hardness)
Using an MD-1 hardness meter (manufactured by Kobunshi Keiki Co., Ltd., "Micro rubber hardness meter MD-1), press the indenter of the MD-1 hardness meter against the roll surface, peak hold mode, hold time is 3 seconds. The value read was taken as MD-1 hardness.

(Evaluation of filming)
Using an image forming apparatus equipped with the developed developing roller, after printing 10,000 sheets under the conditions of a temperature of 23° C. and a humidity of 55% RH, after sucking the developer adhering to the surface of the developing roller, the mass transferred to the filming weight measuring jig was measured. The evaluation of filming was based on the following criteria based on the mass of the transferred developer. In this test, an evaluation of B for the amount of filming is acceptable.
-Evaluation criteria-
A: The mass of the transferred developer is 0 mg or more and less than 0.02 mg B: The mass of the transferred developer is 0.02 mg or more and less than 0.05 mg C: The mass of the transferred developer is 0.05 mg or more

(Evaluation of print density)
A solid image was printed under conditions of a temperature of 23° C. and a humidity of 55% RH, a temperature of 30° C. and a humidity of 80% RH, and a temperature of 10° C. and a humidity of 20% RH.
-Evaluation criteria-
A: 1.4 or more B: 1.2 or more and less than 1.4 C: 1.0 or more and less than 1.2

(Evaluation of image uniformity)
Conditions of temperature 23 ° C., humidity 55% RH, temperature 30 ° C., humidity 80% RH, temperature 10 ° C., humidity 20% RH are changed in cycles to perform a predetermined printing pattern on 10,000 sheets.
-Evaluation criteria-
A: Density step ratio is 1.4 or more B: Density step ratio is 1.2 or more and less than 1.4 C: Density step ratio is 1.0 or more and less than 1.2

Table 1 shows the evaluation results.

As shown in Table 1, the developing roller having the coating layer of the present invention is excellent in filming, print density, and image uniformity.
On the other hand, as in Comparative Examples 1 and 2, the developing roller having no monomolecular film and using fluorine polyol as the polyol of the coating layer has high hardness and is inferior in evaluation of filming, print density, and image uniformity.

Reference Signs List 1 developing roller 2 shaft 3 elastic layer 4 coating layer 6 transfer/conveyor belt 10 image forming apparatus 11B, 11C, 11M, 11Y image carrier 12B, 12C, 12M, 12Y charging means 13B, 13C, 13M, 13Y exposure means 14B, 14C, 14M, 14Y transfer means 15B, 15C, 15M , 15Y Cleaning means 16 Recording medium 20B, 20C, 20M, 20Y Developing device 21B, 21C, 21M, 21Y, 34 Housing 22B, 22C, 22M, 22Y Developer 23B, 23C, 23M, 23Y Developer carrier 24B, 24C, 24M, 24Y Developer amount adjusting means 25B, 25C , 25M, 25Y toner supply roller 30 fixing means 31 fixing roller 32 pressure roller 33 endless belt support roller 35 opening 36 endless belt 41 cassette 42 support roller B, C, M, Y development unit

Claims (6)

A developing roller comprising a shaft, an elastic layer formed on the outer periphery of the shaft, and a coating layer formed on the outer periphery of the elastic layer,
A developing roller having, on the surface of the coating layer, a monomolecular film in which a fluorine-containing compound having a perfluoroalkyl chain or a fluorinated polyether chain is independently bonded to the coating layer by a silanol group , and the MD-1 hardness of the surface of the developing roller is 45 or less. 2. The developing roller according to claim 1 , wherein the monomolecular film has a thickness of 10 nm or less. 3. The developing roller according to claim 1 , wherein the coating layer is made of urethane resin. 4. The developing roller according to any one of claims 1 to 3 , wherein said elastic layer is made of silicone rubber. A developing device comprising the developing roller according to any one of claims 1 to 4 . An image forming apparatus comprising the developing roller according to any one of claims 1 to 4 .

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