JP2008224944A - Electrophotographic developing roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent electrophotographic developing roller having high interlayer adhesion between a conductive shaft body and a cover layer, preventing peeling of the cover layer even when a large number of sheets (for instance, 5,000 sheets) are printed and providing a high-quality print image without an image defect in a halftone image part. <P>SOLUTION: In the electrophotographic developing roller configured in such a manner that the cover layer having at least a conductive agent and a resin is directly formed on the circumference of the conductive shaft body, the base material of the conductive shaft body is free-cutting steel and the surface of the conductive shaft body is covered with a plated layer formed by an electroless plating method. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrophotographic developing roller.

  Electrophotographic image forming methods widely used at present are in contact with an electrostatic latent image formed on an electrostatic latent image carrier (usually an electrophotographic photosensitive member) with charged toner or through a narrow gap. The printed image on the latent electrostatic image bearing member formed through a development process in which the latent electrostatic image is visualized with toner is transferred onto plain paper and then fixed to form a final image. Is.

  As a development method for forming a print image, a two-component development method in which a toner is charged and developed using a two-component developer composed of a carrier and a toner, or a development in which a developer composed only of toner is conveyed There is a one-component development system in which toner is charged and developed by friction with a roller or a developer regulating member. In this one-component developing system, since no carrier is used, the developing device can be simplified, and in recent years, it has been widely used. In particular, with the trend of colorization in recent years, a non-magnetic one-component development method using a toner that does not contain a magnetic material is attracting attention because it can be colored.

  Unlike the two-component development method, the non-magnetic one-component development method is a method in which only the toner is rubbed against the charging member or charged against the developing roller surface or the like without using a carrier. There is a great merit that the mechanism is not complicated and can be made compact. As a result, there is also a feature that it can be easily applied to a color image forming apparatus that normally requires four or more developing mechanisms. In particular, in recent years, the weight reduction and downsizing of the apparatus have been actively promoted, and a developing method using a non-magnetic one-component developer has become mainstream in printers.

  As a developing roller in this non-magnetic one-component developing system, conventionally, a roller in which an elastic layer using silicone rubber is formed on the outer periphery of a conductive shaft has been used. The toner is charged by forming a thin layer of toner on the developing roller using a charging member such as a metal plate or a roller, and rubbing it against the developing roller. It becomes a vessel.

  In this developing roller, an elastic layer using a rubber-like elastic material such as silicone rubber is formed on the outer peripheral surface of a metallic or conductive resin shaft. In order to impart, a surface layer may be formed on the elastic layer. It is known to use fluororubber for the surface layer in order to prevent toner adhesion and fusion. In order to form a fluororubber layer on the elastic layer, it is necessary to improve adhesiveness, and an intermediate layer of a silane coupling agent is formed on the surface of the elastic layer, and further, fluororubber or the like as a main component is formed thereon. It is known to form a used coating layer (see, for example, Patent Document 1).

  However, due to the recent downsizing of the apparatus and shortening of the printout time, the cycle of toner transport, charging, developing, and toner replacement, which are functions of the developing roller, is accelerated and the load on the developing roller is increasing. In particular, in terms of miniaturization, when a developing roller having an elastic layer using a rubber-like elastic body such as silicone rubber is used on the outer peripheral surface of the shaft body, accumulation of residual charges due to high-speed cycles, roller layer wear, etc. There was a problem.

  Therefore, a developing roller having a configuration in which a coating layer is directly formed on a shaft body has been studied. The developing roller having a structure in which a coating layer is directly formed on the shaft body is a layer that absorbs an impact like a developing roller having a structure formed through an elastic layer when a force is applied to the coating layer from the outside by a blade or the like. Therefore, a force that peels the coating layer from the shaft is applied. Therefore, good adhesion is required between the shaft body and the coating layer.

  Studies have been made to use stainless steel as the base material of the shaft body and form a coating layer directly on the outer periphery thereof (see, for example, Patent Document 2).

Further, in order to improve the adhesion between the shaft body and the coating layer, studies have been made to provide an adhesive layer between the shaft body and the coating layer (see, for example, Patent Document 3).
JP-A-8-190263 JP 2002-14535 A JP-A-7-56434

  However, in the electrophotographic developing roller having the structure in which the coating layer is directly formed on the outer periphery of the conductive shaft described above, the interlayer adhesion between the conductive shaft and the coating layer is insufficient, and a large number of sheets are printed. The coating layer was peeled off, or an image defect occurred in the halftone image portion, so that a high-quality printed image could not be continuously obtained.

  In the present invention, the interlaminar adhesion between the conductive shaft and the coating layer is good, and even when a large number of sheets (for example, 5000 sheets) are printed, the coating layer does not peel off, and the halftone image area has image defects. An object of the present invention is to provide an excellent electrophotographic developing roller capable of continuously obtaining a high-quality print image without any problem.

  The subject of the present invention is expressed by any of the configurations described below.

1. In the electrophotographic developing roller configured by directly forming a coating layer having at least a conductive agent and a resin on the outer periphery of the conductive shaft body,
The base material of the conductive shaft is free-cutting steel,
An electrophotographic developing roller, wherein the surface of the conductive shaft is covered with a plating layer formed by an electroless plating method.

  2. 2. The electrophotographic developing roller according to 1 above, wherein the plating layer is formed using a lead-free plating solution.

  The electrophotographic developing roller of the present invention (hereinafter also simply referred to as a developing roller) has good interlayer adhesion between a conductive shaft (hereinafter also simply referred to as a shaft) and a coating layer, and has a large number (for example, 5000). Sheet) Even if printing is performed, the coating layer does not peel off, and it has an excellent effect of continuously obtaining a high-quality print image having no image defect in the halftone image portion.

  If there is a non-uniform portion of the composition in the base material used as the shaft of the developing roller, burrs, cracks, etc. occur during cutting. If a shaft body with burrs, cracks, etc. is used, when a coating layer is formed by applying a coating solution for the coating layer, the burrs, cracks, etc. will be the starting point and uneven coating will occur, forming a uniform coating film. I can't.

  When an image is formed with a developing roller made using a shaft body with burrs or cracks, the coating layer peels off or an image defect occurs in the halftone image area. Can not be obtained.

  When the present inventors formed an image using a developing roller having a coating layer directly formed on the outer periphery of the conductive shaft body, the interlayer adhesion between the conductive shaft body and the coating layer was good, and a large number of sheets were printed. The shaft used for the production of a developing roller that can continuously obtain a good image without image defects even after performing the above was investigated.

  As a result of study, when free-cutting steel is used for the base material of the conductive shaft body, machinability, that is, chip removal property, cutting tool life is greatly improved, cutting without defective parts such as burrs and cracks It has been found that it can be processed, has good machinability, and has excellent productivity.

  When image formation is performed with a developing roller made by directly providing a coating layer on the outer periphery of the shaft body plated on the surface of this machined product, film peeling and image defects do not occur even when a large number of sheets are printed. As a result, they found that high-quality print image quality was obtained.

  The reason for the lack of cutting defects such as burrs and cracks is that the additive metal heated above the melting point is eluted by the temperature rise during the cutting process, and the eluted additive metal becomes a lubricant between the tool and the chip. The reason is that the frictional resistance of the cutting tool has decreased.

  Further, due to the molten metal embrittlement of the additive metal heated to the melting point or higher due to the temperature rise during the cutting process, the deformation region in front of the cutting tool blade is made brittle, and the shear strength of the work material is lowered. Furthermore, in order to make it easy to generate | occur | produce a crack in a chip, it is guessed that it is because the chip | tip parting property improved.

  In the present invention, for the purpose of preventing the occurrence of rust and the like, a conductive shaft body in which a plated layer is applied to the surface of a machined free-cutting steel by an electroless plating method is provided.

  The shaft body with the plated layer on the surface of the machined free-cutting steel is rusted even if the developing roller is left in an environment of high temperature and high humidity (for example, 30 ° C, 80% RH for 7 days) for a long time. Does not occur, and has the effect of preventing film peeling and image defects due to rust.

  The plating layer is formed by electroless plating. When a lead-free plating solution is used as the electroless plating solution, lead is not contained in the plating layer, which is preferable in terms of the environment.

  Hereinafter, the present invention will be described in detail.

<Configuration of developing roller>
The developing roller of the present invention is configured by directly forming a coating layer having at least a conductive agent and a resin on the outer periphery of a conductive shaft.

  FIG. 1 is a schematic sectional view showing an example of the developing roller of the present invention.

  The developing roller 25 shown in FIG. 1 has a coating layer 254 provided on the outer periphery of a conductive shaft body 253 obtained by applying a plating layer 252 to the surface of a cylindrical substrate 251.

<Interlayer adhesion>
The developing roller of the present invention preferably has a strong interlayer adhesion between the conductive shaft and the coating layer.

  The interlayer adhesion between the conductive shaft and the coating layer is evaluated by the value obtained by measurement by the following method.

  FIG. 2 is a schematic diagram for explaining a method for measuring an interlayer adhesive force between a conductive shaft and a coating layer.

  As shown in FIG. 2A, the developing roller 25 is cut along the outer periphery of the coating layer 254 at the center of the roller with a width of 2.5 cm as indicated by a broken line X. 12 is cut in the direction of the developing roller 25 (broken line Y), and the covering layer 254 provided on the outer periphery of the cram pair 253 is slightly peeled from the cut, and as shown in FIG. The end of 254 is pinched with the grip 5 of “Autograph AGS (manufactured by Shimadzu Corporation)”, pulled up vertically (in the direction of arrow Z), and with what force, the coating layer is pulled from the conductive shaft body 253. Measure the adhesion between layers by measuring whether it begins to peel off.

  Specifically, in the process of raising the coating layer at a speed of 100 mm / min and increasing the load capacity to 20 N, a load value that can raise the coating layer without increasing the load is obtained, and the value is indirectly obtained from the layer. It is assumed to be strong.

  Next, the conductive shaft and the coating layer according to the present invention will be described.

<Conductive shaft>
The present invention is characterized in that free-cutting steel is used as the base material of the shaft body.

  The free-cutting steel as used in the present invention refers to a steel material to which a specific amount of manganese element, phosphorus element, sulfur element, lead element, selenium element, tellurium element or the like is added alone or in combination, with low cutting resistance, It has the advantages of being easy, excellent in finishing accuracy, and easy to dimension the workpiece. Moreover, it has the merit that it has a favorable mechanical precision characteristic, and since it is the tendency for a chip not to continue at the time of a process, it is easy to process a chip.

  The amount of elements contained in free-cutting steel has a range suitable for each element. Recently, in consideration of response to the environment, free-cutting steel called “Pb-free free-cutting steel” does not contain lead elements. There is also cut steel, and the amount of elements contained in this “Pb-free free-cutting steel” is specifically 0.30 to 1.35% by mass of manganese element and phosphorus element with respect to the total mass of free-cutting steel Of 0.02 to 0.12% by mass and 0.08 to 0.37% by mass of sulfur element.

  Specifically, as general free-cutting steel, 0.30 to 1.35% by mass of manganese element, 0.02 to 0.09% by mass of phosphorus element, and sulfur element to the total mass of free-cutting steel Examples include 0.28 to 0.36 mass% and lead element containing 0.08 to 0.40 mass%.

  The elements contained in the free-cutting steel and the mass thereof can be measured by high frequency inductively coupled plasma optical emission spectrometry.

  High frequency inductively coupled plasma emission spectroscopy (Inductively Coupled Plasma) is a method in which a solution sample in which a metal is dissolved in acid, alkali, or the like is sprayed into Ar plasma, and excited light is split into each wavelength and the light is dispersed. This is a method for quantifying the type and content of an element from its strength. This method has a linear relationship between light intensity and content from a minute range to a high concentration, and each element can be analyzed simultaneously.

  “ULTIMA2000 (manufactured by Horiba, Ltd.)” can be used as a measuring device for high-frequency inductively coupled plasma optical emission spectrometry.

Since the conductive shaft also serves as a member that leaks charges accumulated on the surface of the developing roller, it is preferable to use a conductive shaft having a specific resistance of 1 × 10 ⁴ Ω · cm or less. The specific resistance can be measured by a known method.

  As the conductive shaft, one having a plating layer whose surface is formed by an electroless plating method is used. Here, the electroless plating method is the action of electrons released by oxidation of the reducing agent contained in the plating solution, and deposits a metal film on the surface of the conductive shaft that is the object to be plated impregnated in the plating solution. And forming a plating layer.

  On the other hand, the electrolytic plating method forms a metal film on the surface of the conductive shaft body by the action of electrons by energization.

  The thickness of the plating layer is preferably 1 to 20 μm, and more preferably 3 to 6 μm.

  The reason why electroless plating is preferable is not clear, but in the case of electrolytic plating, if there are slight defects such as burrs and cracks in the shaft base material, the electric field concentrates on the defective part and the electric field strength distribution is disturbed. It is assumed that the plating film thickness is not uniform because defects such as burrs and cracks are exaggerated.

  In addition, although electroless plating takes longer processing time, it is possible to obtain a high-precision film thickness because of excellent uniformity of the plating layer thickness, and excellent corrosion resistance because there are few defects such as pinholes. thinking.

  Examples of the electroless plating include nickel plating, copper plating, and gold plating. Among the electroless platings, electroless nickel plating is more preferably used from the viewpoint of the stability of the plating solution and cost.

  In electroless nickel plating, heavy metal compounds, particularly lead compounds, are generally used as plating solution stabilizers and gloss imparting agents, and about 100 to 1000 ppm of lead co-deposits in the plating film. Depending on the type and usage conditions of the plating solution, the amount of lead co-deposited in the plating film may exceed 1000 ppm, so a lead-free plating solution that uses metals, inorganic compounds, and organic compounds instead of lead can be used. It is preferable for the environment to be used for plating.

<Coating layer>
The coating layer is applied to the outer peripheral surface of the conductive shaft body by applying a coating liquid prepared by appropriately blending at least a conductive agent (for example, an electronic conductive agent or an ionic conductive agent) and a resin, and if necessary, a non-conductive filler, This can be dried and, if desired, cured to form.

<Resin for coating layer>
The resin of the coating layer is not particularly limited, but specifically, siloxane-modified polyurethane resin, acrylic resin, urea resin, melamine resin, alkyd resin, phenol-modified / silicone-modified, etc. modified alkyd resin, oil A free alkyd resin, a silicone resin, a fluorine resin, a phenol resin, a polyamide resin, an epoxy resin, a polyester resin, a maleic acid resin, a urethane resin, and the like can be given. Of these, siloxane-modified polyurethane resin, acrylic resin, polyamide resin, and the like are preferably used from the viewpoint of self-film reinforcing property, toner charging property, and the like. Among these, it is particularly preferable to use a siloxane-modified polyurethane resin from the viewpoint of obtaining good abrasion resistance.

  The urethane resin is obtained by reacting a urethane raw material containing a polyhydroxy compound and an isocyanate compound. For example, the urethane resin is obtained by a method of cross-linking a prepolymer, or a polyol is obtained by a one-shot method. The thing obtained by the method of making it react with a polyisocyanate cake etc. are mentioned.

  In this case, as a polyhydroxyl compound used when obtaining a urethane resin, a polyol used for production of a general flexible polyurethane foam or a urethane elastomer, for example, a polyether polyol having a polyhydroxyl group at a terminal, a polyester polyol, or a polyether In addition to polyester polyols, general polyols such as polyolefin polyols such as polybutadiene polyol and polyisoprene polyol, and so-called polymer polyols obtained by polymerizing ethylenically unsaturated monomers in polyols can be used. As the isocyanate compound, polyisocyanate used in the production of general flexible polyurethane foam and urethane elastomer, that is, tolylene diisocyanate (sometimes referred to as TDI), crude TDI, 4,4'-diphenylmethane. Diisocyanate (sometimes referred to as MDI), crude MDI, aliphatic polyisocyanate having 2 to 18 carbon atoms, alicyclic polyisocyanate having 4 to 15 carbon atoms, and mixtures and modified products of these polyisocyanates, such as partially polyol A prepolymer obtained by reacting with a polymer can be used. In particular, the mixing ratio of the polyisocyanate may be lowered for the purpose of reducing the universal hardness of the coating layer.

  Moreover, the urethane resin may be prepared using a one-pack type or two-pack type urethane raw material containing a polyhydroxyl compound and a polyisocyanate, and an epoxy resin or a melamine resin is used as a crosslinking agent as necessary. Also good.

  Polyamide resin is nylon 6,6,6,6,10,6,12,11,12,12,12 and polyamides obtained from polycondensation between different types of polyamide monomers, and from the viewpoint of workability Alcohol-soluble ones are preferred. For example, those obtained by adjusting the molecular weight of a polyamide terpolymer or quaternary copolymer, or those obtained by methoxymethylating nylon 6 or nylon 12 to be soluble in alcohol or water.

  The acrylic resin includes polyacrylate, polymethyl methacrylate, polymethyl ethacrylate, those obtained by substituting these side chain ends with a hydroxyalkyl group, and copolymers thereof.

  Monomers constituting the acrylic resin include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, methacrylic acid. Examples include hexyl, 2-ethylhexyl methacrylate, ethyl β-hydroxyacrylate, propyl γ-aminoacrylate, stearyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, and the like.

  As the resin used in the present invention, a silicone copolymer polyurethane resin is more preferable. The silicone copolymer polyurethane resin can be synthesized from a compound having in its molecule a silicone skeleton having a polyfunctional isocyanate having two or more functional groups and a hydroxyl group having two or more functional groups.

  The silicone copolymer polyurethane resin is not particularly limited, but those disclosed in Japanese Patent Publication No. 7-33427 can be used.

  Examples of the siloxane-modified polyurethane resin include a polyurethane resin (1) obtained from a polyol, an isocyanate and a chain extender and having a functional group reactive with an epoxy group, and an epoxy compound having one hydroxyl group in one molecule ( A) (hereinafter simply referred to as an epoxy compound (A)) and an alkoxy obtained by reacting an alkoxy group-containing alkoxysilane partial condensate (2) obtained by a dealcoholization reaction between the alkoxysilane partial condensate (B). A group-containing siloxane-modified polyurethane resin can be used, but is not limited thereto.

  The functional group having reactivity with the epoxy group in the polyurethane resin (1) may be present at either the terminal or the main chain of the polyurethane resin (1). Examples of such functional groups include acidic groups such as carboxyl groups, sulfonic acid groups, and phosphoric acid groups, amino groups, hydroxyl groups, and mercapto groups. An acidic group and an amino group are preferable from the viewpoint of reactivity with an epoxy group and ease of imparting a functional group. The method for imparting an acidic group to the polyurethane resin (1) is not particularly limited. For example, the functional group can be imparted by using a compound having the aforementioned functional group as the chain extender or the polymerization terminator. .

  As a method for producing the polyurethane resin (1) used in the present invention, a one-stage method in which a polymer polyol, a diisocyanate compound and, if necessary, a chain extender and / or a polymerization terminator are reacted at once in a suitable solvent, A polymer polyol and a diisocyanate compound are reacted under an excess of isocyanate groups to prepare a prepolymer having an isocyanate group at the terminal of the polymer polyol, and then this is added to a chain extender in an appropriate solvent and, if necessary, And a two-stage method of reacting with a polymerization terminator. The two-stage method is preferred for the purpose of obtaining a uniform polymer solution. In these production methods, the solvent used is usually an aromatic solvent such as benzene, toluene or xylene; an ester solvent such as ethyl acetate or butyl acetate; methanol, ethanol, isopropanol, n-butanol, diacetone alcohol or the like. Alcohol solvents; ketone solvents such as acetone, methyl ethyl ketone, and methyl isobutyl ketone; other solvents such as dimethylformamide, dimethylacetamide, ethylene glycol dimethyl ether, tetrahydrofuran, and cyclohexanone can be used alone or in combination.

  The method for imparting amino groups to the polyurethane resin (1) is not limited. For example, polyamines may be reacted with the terminal isocyanate groups of the prepolymer so that the amino groups are excessive. The amount of the epoxy group-reactive functional group in the polyurethane resin (1) is not particularly limited, but it is usually preferably 0.1 to 20 KOHmg / g. When it is less than 0.1 KOHmg / g, the flexibility and heat resistance of the obtained polyurethane resin-silica hybrid are lowered, and when it exceeds 20 KOHmg / g, the water resistance of the polyurethane resin-silica hybrid tends to be lowered. In the polyurethane resin, those containing a urea bond are more preferable for interlayer adhesion.

  As described above, the epoxy group-containing alkoxysilane partial condensate (2) of the present invention is obtained by a dealcoholization reaction between the epoxy compound (A) and the alkoxysilane partial condensate (B).

  As the epoxy compound (A), the number of epoxy groups is not particularly limited as long as it is an epoxy compound having one hydroxyl group in one molecule. In addition, as the epoxy compound (A), the smaller the molecular weight, the better the compatibility with the alkoxysilane partial condensate (B), and the higher the heat resistance and adhesion imparting effect. Is preferred. Specific examples include monoglycidyl ethers having one hydroxyl group at the molecular end obtained by reacting epichlorohydrin with water, dihydric alcohol or phenol; epichlorohydrin and glycerin, pentaerythritol, etc. Polyglycidyl ethers having one hydroxyl group at the molecular end obtained by reacting with a trihydric or higher polyhydric alcohol of the above; one hydroxyl group at the molecular end obtained by reacting epichlorohydrin and amino monoalcohol Examples thereof include alicyclic hydrocarbon monoepoxides having one hydroxyl group in the molecule (for example, epoxidized tetrahydrobenzyl alcohol). Among these epoxy compounds, glycidol is most suitable in terms of heat resistance imparting effect, and is also optimal because of its high reactivity with the alkoxysilane partial condensate (2).

  Further, the alkoxysilane partial condensate (B) is obtained by hydrolyzing a hydrolyzable alkoxysilane monomer represented by the following general formula (a) in the presence of acid or alkaline water and partially condensing it. Is used.

Formula (a): R _1p Si (OR ₂ ) _4-p
(In the formula, p represents 0 or 1. R ₁ represents a lower alkyl group, aryl group or unsaturated aliphatic residue which may have a functional group directly connected to a carbon atom. R ₂ represents a methyl group. Or an ethyl group, and R ₂ may be the same or different.
Specific examples of such hydrolyzable alkoxysilane monomers include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyl Trialkoxysilanes such as tripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane It is done. In addition, as these alkoxysilane partial condensates (B), those exemplified above can be used without particular limitation, but when two or more of these examples are used in combination, tetramethoxysilane is replaced with alkoxysilane. What was synthesized using 70 mol% or more of all alkoxysilane monomers constituting the partial condensate (B) is preferable. In addition, when the ratio of the silane skeleton contained in the polyurethane resin-silica hybrid is 1.0% by mass or more and 30.0% by mass or less, very stable adhesiveness is exhibited.

  The alkoxysilane partial condensate (B) is represented by, for example, the following general formula (b) or (c).

(In the general formula (b), R ₁ represents a lower alkyl group, an aryl group or an unsaturated aliphatic residue which may have a functional group directly connected to a carbon atom. R ₂ represents a methyl group or an ethyl group. R ₂ may be the same or different, and n is an integer.)

(In the general formula (c), the same .n as R _1, R ₂ of R _1, R ₂ is In formula (b) is an integer.)
<Electronic conductive agent>
Examples of the electronic conductive agent include various conductive metals or alloys such as carbon black, graphite, aluminum, copper, tin, and stainless steel, tin oxide, zinc oxide, indium oxide, titanium oxide, tin oxide antimony monoxide solid solution, tin oxide Various conductive metal oxides such as indium oxide solid solution, and fine powders such as insulating substances coated with these conductive materials can be used. Among these, carbon black is preferably used because it can be obtained relatively easily and good chargeability can be obtained.

  The type of carbon black is not particularly limited, and various conventionally known carbon blacks such as ketjen black, channel black, and furnace black can be used. The blending amount of carbon black is not particularly limited because it varies depending on the type of carbon black to be used, but it is usually preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass with respect to 100 parts by mass of the resin component. preferable. This blending amount is appropriately set according to the conductivity and universal hardness required for the coating layer.

<Ionic conductive agent>
As the ionic conductive agent, conventionally known inorganic ionic salts and organic ionic salts can be appropriately selected and used. Specifically, alkali metal halides such as Li, LiCl, NaI, NaBr, and KI, perchlorates such as LiClO ₄ , KCl1O ₄ , CuCl ₂ Mg (ClO ₄ ) ₂ , and thiocyanic acids such as LiSCN, NaSCN, and CsSCN Inorganic ion salts such as salts, aliphatic sulfonates, higher alcohol sulfates, higher alcohol phosphates, higher alcohol ethylene oxide addition sulfates, higher alcohol ethylene oxide addition phosphates, quaternary ammonium Examples thereof include organic ion salts such as salts and betaines. Among these, quaternary ammonium salts such as trimethyloctadecyl ammonium perchlorate, tetramethylammonium chloride, and benzyltrimethylammonium chloride are particularly preferable. These ionic conductive agents may be used alone or in combination of two or more.

  The compounding amount of the ionic conductive agent is not particularly limited and is appropriately selected according to various situations, but is preferably 0.001 to 5 parts by mass with respect to 100 parts by mass of the resin component forming the coating layer, and 0.05 to 2 Part by mass is more preferable.

As a result, in the resistance region of 1 × 10 ⁴ to 1 × 10 ¹⁰ Ω · cm, there is little variation in the position of the electrical resistance, and the voltage dependence of the electrical resistance is small. A coating layer having low conductivity can be obtained.

  Next, production of the developing roller will be described.

<Production of conductive shaft>
The shape of the conductive shaft is a hollow cylindrical shape having a small diameter (for example, an outer diameter of 5 to 30 mm) and a thin wall thickness (for example, 0.5 to 2.0 mm) in order to reduce the size, weight, and cost of the image forming apparatus. The thing of the shape which attached the flange to the both ends of a pipe | tube is preferable.

  The shaft body is manufactured by using a cutting tool to machine a free-cutting steel containing the above elements with a cutting tool into a hollow tube having the desired dimensions and surface roughness, and providing the plating layer on the surface. Can do. It does not specifically limit as a cutting machine, A well-known cutting machine can be used.

<< Production of coating layer >>
As a method of forming a coating layer on the outer periphery of the conductive shaft body, a coating liquid in which the above-described components (resin and conductive agent, and if necessary, nonconductive filler) are dissolved and dispersed in an organic solvent is applied to the shaft body. A coating method is preferred. The resin component concentration of the coating solution is not particularly limited and may be appropriately adjusted according to the required layer thickness. However, the resin component concentration is 10% by mass or more from the dispersibility and stability of the solid matter in the coating solution. Preferably there is.

  The solvent used for preparing the resin component concentration of the coating solution is not particularly limited as long as it can dissolve the resin component, and examples thereof include lower alcohols such as methanol, ethanol and isopropanol, and ketones such as methyl ethyl ketone. , Cyclohexane, toluene, xylene and the like are preferably used.

  Examples of the method for applying the coating layer include dipping, spraying, roll coating, or brush coating method depending on the viscosity of the coating solution. Among these, dipping and spraying methods that can easily form the coating layer uniformly. Is preferred.

  1-30 micrometers is preferable and, as for the thickness of a coating layer, 5-20 micrometers is more preferable. The thickness of the coating layer is measured from a micrograph of the cross-sectional sample obtained by taking a cross-sectional sample including the coating layer from the developing roller.

  Next, the developing device and the full-color image forming apparatus according to the present invention will be described.

  FIG. 3 is a schematic sectional view showing an example of the developing device according to the present invention.

  The developing device 20 shown in FIG. 3 has a buffer chamber 26 adjacent to the developing roller 25, and a hopper 27 and the like adjacent to the buffer chamber 26.

  In the buffer chamber 26, a blade 28 as a toner regulating member is disposed in pressure contact with the developing roller 25. The blade 28 regulates the charge amount and adhesion amount of the toner on the developing roller 25. It is also possible to further provide an auxiliary blade 29 for assisting regulation of the toner charge amount and adhesion amount on the developing roller 25 on the downstream side of the blade 28 with respect to the rotation direction of the developing roller 25.

  A supply roller 30 is pressed against the developing roller 25. The supply roller 30 is driven to rotate in the same direction as the developing roller 25 (counterclockwise direction in the drawing) by a motor (not shown). The supply roller 30 has a conductive cylindrical base and a foam layer formed of urethane foam or the like on the outer periphery of the base.

  The hopper 27 contains toner T which is a non-magnetic one-component developer. The hopper 27 is provided with a rotating body 31 for stirring the toner T. A film-like conveying blade is attached to the rotating body 31, and the toner T is conveyed by the rotation of the rotating body 31 in the direction of the arrow. The toner T conveyed by the conveying blades is supplied to the buffer chamber 26 via a passage 28 provided in a partition wall that separates the hopper 27 and the buffer chamber 26. The shape of the conveying blade is bent while conveying the toner T in front of the rotating direction of the blade as the rotating body 31 rotates, and returns to a straight state when the left end of the passage 32 is reached. Thus, the toner T is supplied to the passage 32 by returning the shape of the blade straightly through the curved state.

  The passage 32 is provided with a valve 321 for closing the passage 32. This valve is a film-like member, and one end is fixed to the upper side of the right side of the passage 32 of the partition wall. When the toner T is supplied from the hopper 27 to the passage 28, the valve 32 is pushed rightward by the pressing force from the toner T. Can be opened. As a result, the toner T is supplied into the buffer chamber 26.

  Further, a regulating member 322 is attached to the other end of the valve 321. The regulating member 322 and the supply roller 30 are arranged so as to form a slight gap even when the valve 321 closes the passage 32. The regulating member 322 adjusts so that the amount of toner accumulated at the bottom of the buffer chamber 26 does not become excessive, so that a large amount of toner T collected from the developing roller 25 to the supply roller 30 does not fall to the bottom of the buffer chamber 26. Adjusted to

  In the developing device 20, the developing roller 25 is rotationally driven in the arrow direction during image formation, and the toner in the buffer chamber 26 is supplied onto the developing roller 25 by the rotation of the supply roller 30. The toner T supplied onto the developing roller 25 is charged and thinned by the blade 28 and the auxiliary blade 29 and then conveyed to a region facing the image carrier to develop the electrostatic latent image on the image carrier. To be served. The toner that has not been used for development returns to the buffer chamber 26 as the developing roller 25 rotates, and is scraped and collected from the developing roller 25 by the supply roller 30.

  FIG. 4 is a schematic sectional view showing an example of a full-color image forming apparatus.

  In the full-color image forming apparatus shown in FIG. 4, a charging brush 111 and the like for uniformly charging the surface of the photosensitive drum 10 to a predetermined potential are provided around the photosensitive drum 10 that is rotationally driven.

  Further, a laser scanning optical system 20 for scanning and exposing the photosensitive drum 10 charged by the charging brush 111 with a laser beam is provided. The laser scanning optical system 20 includes a laser diode, a polygon mirror, and an fθ optical element. As is well known, print data for each of yellow, magenta, cyan, and black is transferred from the host computer to the control unit. The laser scanning optical system 20 sequentially outputs the laser beam as a laser beam based on the print data for each color, scans and exposes the photosensitive drum 10, and thereby the static image for each color is formed on the photosensitive drum 10. Electro latent images are sequentially formed.

In addition, the full-color developing device 30 that supplies full-color development to the photosensitive drum 10 on which the electrostatic latent image is formed in this manner, performs yellow, magenta, cyan, and black around the support shaft 33. Four color-developing units 31Y, 31M, 31C, and 31Bk each containing a non-magnetic one-component toner are provided. The developing units 31Y, 31M, 31C, and 31Bk rotate around the support shaft 33. It is guided to a position facing the photosensitive drum 10.

  Further, in each of the developing devices 31Y, 31M, 31C, and 31Bk in the full-color developing device 30, as shown in FIG. 4, the toner is formed on the outer peripheral surface of the developer carrying member (developing roller) 25 that rotates and conveys the toner. A regulating member is in pressure contact, and the toner regulating member regulates the amount of toner conveyed by the developing roller 25 and charges the conveyed toner. In the full-color developing device 30, two toner regulating members may be provided in order to appropriately regulate and charge the toner conveyed by the developing roller.

  Then, whenever the electrostatic latent image of each color is formed on the photosensitive drum 10 by the laser scanning optical system 20 as described above, the full-color developing device 30 is rotated around the support shaft 33 as described above. Then, the developing devices 31Y, 31M, 31C, and 31Bk containing toner of the corresponding colors are sequentially guided to positions facing the photosensitive drum 10, and the developing rollers 25 in the developing devices 31Y, 31M, 31C, and 31Bk are moved. As described above, development is performed by sequentially supplying charged toner of each color toward the photosensitive drum 10 on which the electrostatic latent images of each color are sequentially formed.

  Further, an endless intermediate transfer belt 40 that is rotationally driven is provided as an intermediate transfer body 40 at a position downstream of the full-color developing device 30 in the rotation direction of the photosensitive drum 10. Is driven to rotate in synchronization with the photosensitive drum 10. The intermediate transfer belt 40 is pressed by a rotatable primary transfer roller 41 so as to come into contact with the photosensitive drum 10, and a portion of a support roller 42 that supports the intermediate transfer belt 40 includes: A secondary transfer roller 43 is rotatably provided, and the recording material S such as recording paper is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43.

  Further, a cleaner 50 that scrapes off the toner remaining on the intermediate transfer belt 40 is provided in a space between the full-color developing device 30 and the intermediate transfer belt 40 so as to be able to contact with and separate from the intermediate transfer belt 40. ing.

  Further, the paper feeding means 60 that guides the recording material S such as plain paper to the intermediate transfer belt 40 includes a paper feeding tray 61 that accommodates the recording material S and the recording material S that is accommodated in the paper feeding tray 61 one by one. The recording material S fed in synchronization with the paper feed roller 62 for feeding paper and the image formed on the intermediate transfer belt 40 is sent between the intermediate transfer belt 40 and the secondary transfer roller 43. The recording material S sent between the intermediate transfer belt 40 and the secondary transfer roller 43 in this way is pressed against the intermediate transfer belt 40 by the secondary transfer roller 43. The toner image is pressed and transferred from the intermediate transfer belt 40 to the recording material S.

  On the other hand, the recording material S on which the toner image is pressed and transferred as described above is guided to the fixing device 70 by the conveying means 66 constituted by an air suction belt or the like, and is transferred by the fixing device 70. The toner image is fixed on the recording material S, and then the recording material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.

  Next, the operation of forming a full color image using this full color image forming apparatus will be specifically described.

  First, the photosensitive drum 10 and the intermediate transfer belt 40 are rotationally driven in the respective directions at the same peripheral speed, and the photosensitive drum 10 is charged to a predetermined potential by the charging brush 11.

  The photosensitive drum 10 thus charged is exposed to a yellow image by the laser scanning optical system 20 to form an electrostatic latent image of the yellow image on the photosensitive drum 10. The yellow image is developed by supplying the yellow toner charged by the toner regulating member as described above from the developing device 31Y in which the yellow toner is accommodated in the photosensitive drum 10, and the yellow toner image is thus formed. The intermediate transfer belt 40 is pressed against the body drum 10 by the primary transfer roller 41, and the yellow toner image formed on the photosensitive drum 10 is primarily transferred to the intermediate transfer belt 40.

  After the yellow toner image is transferred to the intermediate transfer belt 40 in this way, the full-color developing device 30 is rotated around the support shaft 33 as described above, and the developing device 31M containing magenta toner is exposed to light. As in the case of the yellow image described above, the magenta image is exposed to the photosensitive drum 10 charged by the laser scanning optical system 20 to form an electrostatic latent image. The electrostatic latent image is developed by a developing device 31M containing magenta toner, and the developed magenta toner image is primarily transferred from the photosensitive drum 10 to the intermediate transfer belt 40. Black image exposure, development, and primary transfer are sequentially performed, and yellow, magenta, cyan, and black print images are sequentially superimposed on the intermediate transfer belt 40. To form a full color toner image.

  When the final black toner image is primarily transferred onto the intermediate transfer belt 40, the recording material S is fed between the secondary transfer roller 43 and the intermediate transfer belt 40 by the timing roller 63, and the secondary transfer roller. The recording material S is pressed against the intermediate transfer belt 40 by 43, and the full color toner image formed on the intermediate transfer belt 40 is secondarily transferred onto the recording material S.

  When the full-color toner image is secondarily transferred onto the recording material S in this way, the recording material S is guided to the fixing device 70 by the conveying means 66, and the full-color toner transferred by the fixing device 70 is transferred. The image is fixed on the recording material S, and then the recording material S is discharged onto the upper surface of the apparatus main body 100 through the vertical conveyance path 80.

  The present invention will be specifically described below with reference to examples, but the embodiments of the present invention are not limited to these examples.

<Production of developing roller>
A developing roller was prepared according to the following procedure.

<Preparation of shaft body 1>
(Cutting)
“Free-cutting steel 1” containing the metal elements listed in Table 1 was cut to produce a hollow cylindrical tube having a diameter of 16 mm.

(Formation of plating layer)
The hollow cylindrical tube produced above was plated using an electroless nickel plating solution “Top Nicolon PAL” (Okuno Pharmaceutical Co., Ltd.) to form a plating layer having a thickness of 5 μm.

<Production of shafts 2 to 7>
Plating conditions (plating time) so that the “free cutting steel 1” used in the production of the shaft body 1 becomes the “free cutting steel 2 to 5” shown in Table 1 and the plating layer thickness shown in Table 1 is obtained. “Shafts 2 to 7” were produced in the same manner except that was changed.

<Production of shaft bodies 8 and 9>
The electroless nickel plating solution “Top Nicolon PAL” (manufactured by Okuno Pharmaceutical Co., Ltd.) used in the production of the shaft body 1 was replaced with the lead-free (lead-free) electroless nickel plating solution “Top Nicolon BL” (Okuno Pharmaceutical Industry Co., Ltd.). “Shafts 8 and 9” were produced in the same manner except that the plating conditions were changed so that the thickness of the plating layer described in Table 1 was obtained.

<Preparation of shaft body 10>
A hollow cylindrical tube prepared for the production of the shaft body 1 without a plating layer was designated as “shaft body 10”.

<Preparation of shaft 11>
In the production of the shaft body 1, the “shaft body 11” was produced in the same manner except that the base material was changed from the free-cutting steel 1 to “stainless steel” and no plating layer was formed.

  Table 1 shows the base material of the shaft body, the contained metal element and its mass%, the plating solution, and the thickness of the plating layer.

  In addition, the measurement of the film thickness of the plating layer was performed by the fluorescent X-ray method. Specifically, the plating thickness is measured by irradiating the plating surface with X-rays and measuring the amount of fluorescent X-rays generated from the plating layer and the substrate. Free-cutting steel was used as a reference sample, plating was performed under the same conditions, and the plating thickness was measured to determine the thickness of the plating layer formed on the surface of the shaft.

<Preparation of coating solution for coating layer formation>
100 parts by mass of an alkoxy group-containing siloxane-modified polyurethane resin (referred to as urethane resin) having a Si content of 6.0% by mass in terms of silica mass obtained by the method described in JP-A No. 2002-220431 is methyl ethyl ketone 400. It was dissolved in a mixed solvent of 300 parts by mass of isopropyl alcohol. Carbon black (volume resistivity 1 × 10 ⁻¹ Ωcm, number average primary particle size 50 nm) 30 parts by mass, tetramethylammonium chloride 1.0 part by mass, median diameter (D ₅₀ ) on the number basis is 20 μm. 20 parts by mass of crosslinked urethane resin particles were mixed and dispersed to prepare a “coating layer forming coating solution”.

<Preparation of developing roller 1>
“Coating layer forming coating solution” is spray coated on the outer peripheral surface of “shaft body 1”, dried, and then heat treated at 120 ° C. for 1 hour to form a coating layer having a film thickness of 15 μm. Produced.

<Preparation of developing rollers 2-11>
“Developing rollers 2-11” were produced in the same manner except that “shaft body 1” used in the production of developing roller 1 was changed to “shaft bodies 2-11” shown in Table 1.

<Evaluation>
<Interlayer adhesion evaluation>
The interlayer adhesion between the conductive shaft body and the coating layer of the developing roller produced above was measured and evaluated using the measuring apparatus shown in FIG. In addition, an interlayer adhesive strength of 8.0 N or more is regarded as acceptable.

  The developing roller produced above was previously left in an environment of 30 ° C. and 80% RH for 7 days before being used for evaluation of interlayer adhesion.

<Live-action evaluation>
The actual image evaluation was performed by preparing a color laser printer “Magicor 2430DL (manufactured by Konica Minolta Business Technologies)” as an image forming apparatus, sequentially mounting the developing roller prepared above on the developing device, and printing.

  The developing roller produced above was previously left in an environment of 30 ° C. and 80% RH for 7 days before being used for evaluation of actual images.

  In the initial performance evaluation of the developing roller, 10 originals (A4 size) having a pixel rate of 20% (full color mode of 5% each color of yellow, magenta, cyan, and black) were printed, and the print image quality was evaluated.

  Thereafter, 5,000 originals (A4 size) having an image rate of 2% (full color mode of 0.5% for each color of yellow, magenta, cyan, and black) were printed.

  For performance evaluation after printing 5000 sheets, 10 originals (A4 size) with a pixel rate of 20% (full color mode of 5% for each color of yellow, magenta, cyan, and black) are printed, and the covering layer is peeled off. The state and the image defect of the halftone image part were evaluated. In addition, the evaluation is ◯ or higher.

<Peeling of coating layer>
The peeling of the coating layer was carried out by taking out the developing roller after completion of printing 5000 sheets and visually evaluating the peeling state of the coating layer.

Evaluation criteria A: No peeling of the coating layer was observed. O: A little peeling of the coating layer was observed at the edge of the coating layer, but there was no practical problem. X: Peeling of the coating layer was seen at the edge of the coating layer. There is a problem.

<Image defects in the halftone image area (including black and white spots)>
The image defect in the halftone image area was evaluated by visually observing the obtained print image after printing the 5000 sheets and printing a black halftone image area having an image density of 0.5.

Evaluation criteria A: Uniform image with no image defects in the halftone image portion ○: Stripe-like thin density unevenness, black spots, and white spots exist in the halftone image portion, but there is no practical problem ×: Halftone image There are several streaky density irregularities, black spots, and white spots in the area, which is a practical problem.

  Table 2 shows the evaluation results of the developing roller used in the evaluation, interlayer adhesion, peeling of the coating layer, and image defects in the halftone image area.

  As shown in Table 2, “Developing rollers 1 to 9” of Examples 1 to 9 corresponding to the present invention obtained good results in all evaluation items, whereas Comparative Example 1 outside the present invention. No. 2 “developing rollers 10 and 11” had a problem in any of these evaluation items, and it was confirmed that the effects of the present invention were not exhibited.

It is a cross-sectional schematic diagram showing an example of the developing roller of the present invention. It is a schematic diagram for demonstrating the measuring method of the interlayer adhesive force of a conductive shaft and a coating layer. It is a cross-sectional schematic diagram showing an example of the developing roller of the present invention. It is a schematic sectional drawing which shows an example of a full-color image forming apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 25 Developing roller 251 Base material 252 Plated layer 253 Shaft body 254 Covering layer 10 Photosensitive drum 20 Developing device 26 Buffer chamber 27 Hopper 28 Restricting blade 29 Auxiliary blade 30 Supply roller T Toner 31 Rotating body 32 Path 321 Valve 322 Restricting member

Claims (2)

In the electrophotographic developing roller configured by directly forming a coating layer having at least a conductive agent and a resin on the outer periphery of the conductive shaft body,
The base material of the conductive shaft is free-cutting steel,
An electrophotographic developing roller, wherein the surface of the conductive shaft is covered with a plating layer formed by an electroless plating method. 2. The electrophotographic developing roller according to claim 1, wherein the plating layer is formed using a lead-free plating solution.

Images