JP4217668B2 - Developing roller, cartridge, and image forming apparatus - Google Patents

Description

  The present invention relates to a developing roller used in an electrophotographic apparatus. Specifically, the present invention relates to a developing roller for an electrophotographic apparatus that does not cause image defects or the like even when it is operated for a long time in a low temperature / low humidity to high temperature / high humidity environment.

  In a printer using an electrophotographic system, a photosensitive member is uniformly charged by a charging roller, and an electrostatic latent image is formed by a laser or the like. Next, the developer in the developing container is uniformly applied on the developing roller with appropriate charges by the developer applying roller and the developer regulating member, and the developer is transferred (developed) at the contact portion between the photosensitive member and the developing roller. Done. Thereafter, the developer on the photoconductor is transferred onto a recording sheet by a transfer roller and fixed by heat and pressure. The developer remaining on the photoconductor is removed by a cleaning blade, and a series of processes is completed.

  In an electrophotographic apparatus, for example, in the case of a developing roller, the developing roller is always in pressure contact with the photosensitive member and the developer regulating member, and development is performed between the developing roller and the photosensitive member, and between the developing roller and the developer regulating member. It is in pressure contact with the agent. The developer that is not transferred to the photoreceptor is peeled off by the developer application roller, returned to the developing container again, stirred in the container, and conveyed again onto the developing roller by the developer application roller. As a result of repeating these steps, the developer is subjected to great stress. Accordingly, for the purpose of reducing the stress on the developer, a developing roller made of an elastic material having a low hardness has been used. In particular, the influence on the developer is large in the vicinity of the surface layer of the developing roller, and the selection of material properties plays a very important role. In order to sufficiently exhibit these material properties, the core metal outer peripheral portion is divided into an elastic body layer, an intermediate layer, an outermost layer, and the like, and each function is exhibited.

  As the polymer elastic material forming these constituent members, polymer elastomers and polymer foams having rubber elasticity are used, and these have low hardness and do not contaminate the image carrier or the transfer member. In addition, it is required to have a property of not being fused with a developer such as toner. Here, as materials constituting the polymer elastomer and polymer foam, solid rubber vulcanizates such as isoprene rubber, ethylene propylene rubber, silicone rubber, epichlorohydrin rubber, acrylonitrile butadiene rubber, and liquid raw materials such as polyol are used. Polyurethanes cured with isocyanate are used. The image forming apparatus member made of these materials may be required to have conductivity. For example, by mixing a conductive material such as carbon black or a metal oxide or adding an electrolyte, It is adjusted to the electrical resistance value. Among these, there is an advantage that conductivity can be imparted by both a conductive material and an electrolyte, and there is an advantage that the electrolyte can be used by dissolving in a liquid raw material, and a foam can be formed as necessary. Polyurethanes produced using isocyanate as the main raw material are generally used.

  As a prior art, there is a description of a low-hardness roller that has low hardness, small compression set, and does not contaminate the photoreceptor. By combining low-crystalline polyol (isoprene-based polyol) and low-crystalline isocyanate as the elastic material of the roller, it is difficult to form intermolecular hydrogen bonds, and the compression set is low with low hardness. In addition, it is possible to obtain a roller free from contamination of the photoreceptor. (For example, refer to Patent Document 1).

The surface layer material of the developing roller contains 25% by mass or more of a polyether polyol chain-extended with a raw material polyol and a diisocyanate, so that a stable image with little fogging can be obtained, and further a stable image can be maintained. (For example, refer to Patent Document 2).
JP 2001-1000048 A JP 2003-270926 A

In recent years, the required performance of an elastic member used in an electrophotographic apparatus has become higher with the increase in the speed and the quality of the image quality of the electrophotographic apparatus. More specifically, there is a strict demand for differences in fine image characteristics in the environment, image durability accompanying high-speed operation, and part durability. Various problems that cannot be realized have become apparent. Low temperature / low humidity environment (15 degrees, 10% RH: hereinafter referred to as L / L environment) that could not occur in the conventional usage period when a conventional developing roller is assembled in a developing container and used for a longer time than before. In some cases, the density of the solid image is reduced, and a ghost (a phenomenon in which the previous latent image remains in the image to which the developer is transferred) is generated. Therefore, when trying to solve these problems in the L / L environment, conversely, the high temperature / humidity environment (30 degrees, 8 degrees
% RH: hereinafter referred to as H / H), it is sometimes difficult to achieve both image characteristics in both environments, such as causing the developer to be fused and causing vertical stripes on the image.

  The present invention solves the above-mentioned problems, and an object of the present invention is to prevent solid image density reduction and ghosting in an L / L environment, which occurs when used for a longer time than in the past, and in an H / H environment. An object of the present invention is to provide a developing roller that is compatible with prevention of peeling of the surface layer.

In order to solve the above problems, the present invention is characterized by having the following configuration. That is, the present invention has at least a shaft body, a conductive elastic layer provided on the shaft body, and a conductive surface layer provided on the conductive elastic layer, and the conductive surface layer has A developing roller having polyurethane obtained by polymerizing a polyurethane polyol prepolymer and an isocyanate compound,
The polyurethane polyol prepolymer is obtained by chain-extending a bifunctional polyether polyol and a bifunctional isocyanate compound, has a weight average molecular weight of 10,000 to 50,000, a molecular weight dispersion of Mw / Mn = 3.0 or less, Mz / It is a linear polyurethane polyol prepolymer with Mw = 2.5 or less,
The polyurethane polyol prepolymer is contained in the polyurethane in the range of 70 to 95% by mass.

In the present invention, it is further preferable that the bifunctional isocyanate compound is diphenylmethane diisocyanate.
In the present invention, it is further preferable that the bifunctional polyether polyol is at least one of polypropylene polyol and polytetramethylene ether glycol. In the present invention, the polyurethane polyol prepolymer is preferably contained in the polyurethane in an amount of 75 to 95% by mass.

In the present invention, it is preferable that the conductive surface layer further contains carbon black having a pH lower than 5.
The present invention further provides that the storage elastic modulus E ′ of the conductive surface layer is represented by the formula (1):

It is preferable to satisfy.

In the present invention, a developing roller is further mounted, a thin layer of developer is formed on the surface of the developing roller, and the developer is supplied to the surface of the image forming body by bringing the developing roller into contact with the image forming body. In an electrophotographic process cartridge that forms a visible image on the surface of the image forming body by
It is preferable that the developing roller is the developing roller.

In the present invention, a developing roller is further mounted, a thin layer of developer is formed on the surface of the developing roller, and the developer is supplied to the surface of the image forming body by bringing the developing roller into contact with the image forming body. In the image forming apparatus for forming a visible image on the surface of the image forming body by
It is preferable that the developing roller is the developing roller.

  The developing roller of the present invention has a weight average molecular weight of 10,000 to 50,000, a molecular weight dispersity of Mw / Mn = 3.0 or less, Mz / M, formed by chain extension with a bifunctional polyether polyol and a bifunctional isocyanate compound. The surface layer is composed of a polyurethane obtained by reacting a linear polyurethane polyol prepolymer having an Mw of 2.5 or less with an isocyanate compound, and the linear polyurethane polyol prepolymer is contained in the polyurethane in a range of 70 to 95% by mass. By doing so, it is possible to provide a developing roller that can prevent a decrease in the density of a solid image in an L / L environment and a problem of ghosting and can simultaneously prevent peeling of a surface layer in an H / H environment.

  The present inventors have obtained a new finding when investigating the cause of the above-mentioned occurrence problem. Regarding the decrease in density of solid images and the occurrence of ghosts in the L / L environment, the developer continues to receive great stress from the developer regulating member and the developing roller in the process of circulating in the developing container, and the circulation process is prolonged. As a result, the external additive for imparting tribo to the developer peels off from the developer surface or is embedded in the developer surface, thereby reducing the charge imparting ability of the developer and reducing the solid image density. Resulting in. Furthermore, it has been found that a developer that has lost its charge control ability cannot be developed on the photoreceptor, causing a ghost phenomenon. Further, it has been found that these problems do not occur in a normal N / N environment or an H / H environment and are specific to the L / L environment.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the above-mentioned problems can be solved when the conductive surface layer of the developing roller is made of a specific material. In the polyurethane constituting the conductive surface layer of the developing roller, by specifying the number of functional groups, molecular weight, and dispersity of the polyurethane polyol prepolymer, solid image density reduction and ghosting in an L / L environment can be prevented, and H / H It was found that the surface layer in the environment is compatible with peeling prevention.

  The present invention is a polyurethane polyol prepolymer in which the conductive surface layer of the developing roller is chain-extended with a bifunctional polyether polyol and a bifunctional isocyanate compound, and the weight average molecular weight of the polyurethane polyol prepolymer is 10,000 to 50,000. And a polyurethane polyol prepolymer as a raw material comprising a urethane obtained by polymerizing a linear polyurethane polyol prepolymer having a molecular weight dispersity of Mw / Mn = 3.0 or less and Mz / Mw = 2.5 or less with an isocyanate compound Occupies 70% by mass or more of urethane.

  According to the present invention, the polyurethane polyol prepolymer is characterized by using a bifunctional linear polyurethane polyol prepolymer chain-extended with a bifunctional polyether polyol and a bifunctional isocyanate compound. The bifunctional polyurethane polyol prepolymer produced here becomes a final form by reaction with a polyfunctional isocyanate compound (including a terminal isocyanate type prepolymer), and determines the molecular weight (crosslinking distance) between crosslinks. .

  When a polyurethane polyol prepolymer is formed, if there is something larger than bifunctional (for example, trifunctional component), a crosslinked structure is formed at that time, and an appropriate crosslinking density (flexibility) cannot be obtained. In addition, if there is something smaller than bifunctional, one end does not react, so that it cannot finally have a crosslinked structure.

  In the case of designing for softening, there is an option of increasing the molecular weight between crosslinks. However, simply increasing the molecular weight between crosslinks will decrease the material strength with softening. In the case of the surface layer material of the developing roller, when the film strength is lowered, peeling from the conductive elastic layer occurs when the film is used for a long time, and peeling of the surface layer appears.

  Polypropylene glycol, polytetramethylene glycol, or the like can be used as the bifunctional polyether polyol, but polytetramethylene glycol having strong molecular crystallinity of the polyol itself is preferable. The molecular weight (Mw) of the polyether polyol is preferably about 500 to 5000 to bring out the effects of the present invention, and more preferably about 500 to 3000. If it is 5000 or less, the proportion of the soft segment in the urethane chain is not too high, and the material strength can be maintained without extremely softening the material, so that it can be used as a material for the conductive surface layer of the developing roller. It is done.

  Examples of the bifunctional isocyanate compound include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), and phenylene diisocyanate (PPDI). ), Xylene diisocyanate (XDI), tetramethylxylene diisocyanate (TMXDI), cyclohexane diisocyanate and the like. Among these, aromatic isocyanates such as tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), naphthalene diisocyanate (NDI), phenylene diisocyanate (PPDI), xylene diisocyanate (XDI), and tetramethylxylene diisocyanate (TMXDI). A compound is preferable, and an isocyanate compound having strong crystallinity such as diphenylmethane diisocyanate is more preferable for preventing the stickiness of the material and the fusibility of the developer. By combining these bifunctional polyether polyols with a bifunctional isocyanate compound to extend the chain, the flexibility that does not give stress to the developer even during long-term use is brought out, and the fusibility of the developer is prevented. It is possible to have such crystallinity.

  The weight average molecular weight of the polyurethane polyol prepolymer needs to be in the range of 10,000 to 50,000. If it exceeds 50,000, the crosslink density becomes too low and the amount of residual deformation with respect to the stress becomes too large, causing image defects such as set marks. If it is less than 10,000, sufficient flexibility that does not give stress to the developer cannot be obtained. The weight average molecular weight is preferably 10,000 to 40,000, and more preferably 10,000 to 30,000.

  As the molecular weight dispersion of the polyurethane polyol prepolymer, Mn: number average molecular weight, Mw: weight average molecular weight, and Mz: Z average molecular weight are used. The Z average molecular weight is most important for the contribution of the high molecular weight compound to the average molecular weight, and is defined as follows.

  When there are Ni molecules having a molecular weight Mi in the polymer, it is expressed by the following formula (2).

  Mw / Mn needs to be 3.0 or less. Preferably, it is Mw / Mn = 2.7 or less.

  When Mw / Mn is greater than 3.0, the molecular weight between crosslinks varies, causing a problem that the change in mechanical properties in the environment increases. Further, it is necessary to set Mz / Mw = 2.5 or less. Preferably, Mz / Mw = 2.0 or less. By setting Mz / Mw = 2.5 or less, it is possible to obtain an effect of further suppressing changes in mechanical properties in the environment.

  Moreover, the content of the polyurethane polyol prepolymer in the polyurethane needs to be 70 to 95% by mass. The content of the polyurethane polyol prepolymer is preferably 75 to 95% by mass, and more preferably 75 to 90% by mass. When the content is within these ranges, a developing roller having low hardness and excellent toner transportability can be obtained.

  As an isocyanate compound for reacting with a polyurethane polyol prepolymer to obtain a polyurethane, an isocyanate compound having an average functional group number larger than 2 and smaller than 6 or a terminal isocyanate type prepolymer can be used. Isocyanate compounds with an average functional group number greater than 2 and less than 6 include polyfunctional isocyanates such as triphenylmethane triisocyanate and dimethyltriphenylmethane tetraisocyanate, crude type compounds containing polynuclear components, and modified diisocyanates (urethane-modified). Body, allophanate modified body, biuret modified body, isocyanurate modified body) and the like. When the average number of functional groups is larger than 2, a crosslinked structure is obtained and the material strength is increased, so that characteristics as a developing roller can be obtained. When the average number of functional groups is less than 6, the crosslinking density does not become too high, and a developing roller having good flexibility and permanent distortion characteristics can be obtained.

  In modified compounds such as urethane modified products, the mechanical properties may vary somewhat depending on the molecular weight of the polyol prior to the formation of the modified product, but the polyurethane polyol prepolymer is used to form a conductive surface layer polyurethane. If it accounts for 70% by mass or more in the urethane raw material, the effect of the present invention can be exhibited. More preferably, it is 75 mass% or more.

  For the formation of the polyurethane constituting the conductive surface layer, the polyurethane polyol prepolymer and the isocyanate compound can be used so that the isocyanate index (NCO / OH) is in the range of 0.9 to 1.5. The isocyanate index is preferably in the range of 1.0 to 1.2. These are also parameters in which the mechanical property value fluctuates. However, the effect of the present invention can be exhibited if the polyurethane polyol prepolymer accounts for 70% by mass or more of the raw material as described above.

  Examples of the conductivity-imparting substance added to the conductive elastic layer and the conductive surface layer include electron conductive substances such as carbon black, graphite, metal filler, and metal oxide whisker, and ion conductive substances such as metal salts.

  Among these, carbon black, which is inexpensive in cost, is widely used. In the present invention, the pH of carbon black added to the conductive surface layer is preferably less than 5.

The carbon black content in the conductive surface layer is preferably in the range of 10 to 40% by mass, and more preferably in the range of 15 to 35% by mass. When a material having a pH of 5 or less is used, when dispersed in the paint, the carbon black does not agglomerate, the dispersion stability is good, and the life of the paint is prolonged. In the formulation of the present invention, the effect of making the pH of the carbon black lower than 5 is particularly great. The volume resistance value of the conductive surface layer is preferably 1 × 10 ³ to 1 × 10 ¹⁰ Ωcm, and more preferably 1 × 10 ⁴ to 1 × 10 ⁸ cm.

  When the material in the present invention is used, the rate of change of the storage elastic modulus in the vicinity of the use environment temperature can be reduced.

  The storage elastic modulus E ′ is expressed by the formula (1)

It is preferable to satisfy the condition, and the effects of the present invention can be sufficiently obtained. When it is 0.3 or less, since the change in storage elastic modulus at 10 ° C. and storage elastic modulus at 40 ° C. is small, it is possible to achieve both image characteristics in an L / L environment and an H / H environment. Further, the adverse effect on the developer is eliminated, and the developer can be stably supplied until the end of its service life while maintaining the charging ability of the developer. When the storage elastic modulus at 40 ° C. is set to an appropriate value when it is 0.3 or less, the storage elastic modulus at 10 ° C. does not become too high, and the developer is given tribo when used for a long time. This is because problems such as a decrease in the charging ability of the developer due to the external additive being peeled off from the surface of the developer or embedded in the surface of the developer do not occur. On the other hand, even if the storage elastic modulus at 10 ° C. is set to a low value, the storage elastic modulus at 40 ° C. is not less than a predetermined value, so that there is no problem in terms of surface material strength.

Hereinafter, the present invention will be described in detail.
FIG. 1 is a schematic diagram showing an example of the structure of the developing roller in the present invention. The developing roller 1 of the present invention has a shaft core 11 made of a conductive material such as metal as a shaft core at the center, and a conductive elastic layer (base layer) on the outer peripheral surface of the shaft core 11. 12 is fixed, and a conductive surface layer (surface layer) 13 is laminated on the outer peripheral surface of the conductive elastic layer 12.

  The shaft core itself has a columnar or hollow cylindrical shape and often uses a shaft core 11 formed of a conductive material such as metal. However, the developing roller is electrically insulated. When used in a state in which the shaft core is used, it may be made of a non-conductive material as long as the shape of the shaft core itself can be firmly held against an external force applied to the developing roller.

  Even if such a developing roller is used with an electrical bias applied or grounded, the main body is made of a non-conductive material instead of being composed of a conductive material. It is also possible to use a material which is formed of a material and has a structure in which the surface is subjected to a conductive treatment satisfying desired conductivity, for example, a coating with a highly conductive conductive surface layer.

  Since a developing roller used in an electrophotographic apparatus is generally used with an electric bias applied or grounded, the shaft core body is a conductive base, so-called shaft core metal. 11 forms. The shaft core 11 is, of course, a support member. For example, a metal or alloy such as aluminum, copper alloy, or stainless steel, or iron or synthetic resin that has been plated with chromium, nickel, or the like, At least the outer peripheral surface is made of a conductive material sufficient to apply a predetermined voltage to the roller layer formed thereon. In the developing roller used in the electrophotographic apparatus, the outer diameter of the conductive substrate that is the shaft core is usually in the range of 4 to 10 mm.

  The conductive elastic layer 12 serving as a base layer is formed as a molded body using rubber as a main ingredient. Various rubbers conventionally used for elastic rollers can be used as the raw material rubber for the conductive elastic layer 12. Specifically, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR). ), Rubber material such as fluoro rubber, silicone rubber, epichlorohydrin rubber, NBR hydride, polysulfide rubber, urethane rubber, etc., when other components are added to form an elastic layer, the desired elastic body hardness These rubber materials can be used alone or in admixture of two or more.

  The hardness of the conductive elastic layer, which is a molded body mainly composed of rubber, is prepared separately according to the rubber material hardness measurement method, specifically according to the standard standard Asker C-type SRIS (Japan Rubber Association Standard) 0101. It is defined by the hardness measured by an Asker rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.). Similarly, the compression set is defined by a value measured according to the JIS K-6262 vulcanized rubber test method (10. compression set test) using a separately prepared test piece.

  The hardness (Asker-C) of the rubber molded body forming the conductive elastic layer as the base layer is selected in the range of 15 to 70 °. More preferably, it selects in the range of 20-60 degrees.

  At the same time, the compression set of the rubber molded body forming the conductive elastic layer is selected within a range of 10% or less. More preferably, it is selected within the range of 7.0% or less.

  In particular, when silicone rubber is used as the main component rubber of the rubber molded body forming the conductive elastic layer, the low hardness and the low compression set as described above are easily obtained. Examples of silicone rubber that can be used include polydimethylsiloxane, polymethyltrifluoropropylsiloxane, polymethylvinylsiloxane, polytrifluoropropylvinylsiloxane, polymethylphenylsiloxane, polyphenylvinylsiloxane, and copolymers of these polysiloxanes. It is done. When the compression molding is set to the above range when the rubber molded body is formed, the degree of polymerization of the various silicone rubbers described above is preferably in the range of 3000 to 15000. If necessary, natural rubber, isoprene rubber, chloroprene rubber, other than silicone rubber used as the main component, as long as both hardness and compression set remain within the above ranges in the rubber molded body forming the conductive elastic layer. Further, an elastomer such as EPDM, SBR, NBR or the like can be contained in a proportion of 20% by mass or less of the rubber molded body to be formed.

  Furthermore, in the developing roller of the present invention, when forming a rubber molded body for forming the conductive elastic layer, components necessary for the functions required for the conductive elastic layer itself, such as a conductive agent, a non-conductive filler, etc. Various additives such as a crosslinking agent, a catalyst, and a dispersion accelerator, which are used when forming a rubber molded body, can be appropriately mixed with the main rubber material.

  The conductive agent added for the purpose of imparting conductivity to the conductive elastic layer includes various conductive metals or alloys such as carbon black, graphite, aluminum, copper, tin, and stainless steel, tin oxide, zinc oxide, and indium oxide. Further, various conductive metal oxides such as titanium oxide, tin oxide-antimony oxide solid solution, tin oxide-indium oxide solid solution, and fine powders such as insulating substances coated with these conductive materials can be used. Among these, carbon black can be suitably used because it can be obtained relatively easily and good chargeability can be obtained regardless of the type of the main rubber material. As a means for dispersing the finely powdered conductive agent in the main rubber material, conventionally used means such as a roll kneader, a Banbury mixer, a ball mill, a sand grinder, a paint shaker, etc. may be used. What is necessary is just to use suitably according to material.

In addition, as a means for imparting conductivity to the conductive elastic layer, a technique of adding a conductive polymer compound instead of the conductive agent or together with the conductive agent can be used. For example, as a conductive polymer compound, as a host polymer, polyacetylene, poly (p-phenylene), polypyrrole, polythiophenine, poly (p-phenylene oxide), poly (p-phenylene sulfide), poly (p-ferene vinylene) ), Poly (2,6-dimethylphenylene oxide), poly (bisphenol A carbonate), polyvinylcarbazole, polydiacetylene, poly (N-methyl-4-vinylpyridine), polyaniline, polyquinoline, poly (phenylene ether sulfone) and the like. These are used as dopants, such as AsF ₅ , I ₂ , Br ₂ , SO ₃ , Na, K, ClO ₄ , FeCl ₃ , F, Cl, Br, I, Kr, and other ions, Li, TCNQ (7 , 7,8,8-tetracyanoquinodimethane) What it is conventionally employed.

  Examples of the non-conductive filler that can be added to the rubber molded body include diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, and the like.

  As a crosslinking agent used when producing a rubber molded body, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, Examples thereof include t-butyl peroxybenzoate and p-chlorobenzoyl peroxide. For example, when a liquid silicone rubber is used, the rubber components are cross-linked by using a platinum-based catalyst with polyorganohydrogensiloxane as a cross-linking component.

  Note that the thickness of the conductive elastic layer is preferably 0.5 mm or more, more preferably, in order to ensure a uniform nip width when abutting, and to satisfy a suitable setting property. Is preferably 1.0 mm or more. In addition, as long as the outer diameter accuracy of the produced elastic roller is not impaired, there is no particular upper limit to the thickness of the conductive elastic layer, but generally, when the thickness of the conductive elastic layer is excessively increased, the produced rubber molding It is difficult to keep the production cost of the body within an appropriate range, and considering this practical limitation, the thickness of the conductive elastic layer is preferably 6.0 mm or less, and more preferably 5.0 mm or less. Further, the thickness of the conductive elastic layer is appropriately selected according to the hardness in order to achieve the target nip width.

  In the developing roller of the present invention, the resistance value of the roller was measured by pressing the developing roller against a cylindrical metal roller (φ30) with a constant pressure load of 500 g on one side and applying a DC voltage of 100V. It is.

The thickness of the conductive surface layer of the developing roller in the present invention is measured as follows.
The roller on which the conductive elastic layer and the conductive surface layer were formed was cut out, and the cross section of the conductive surface layer was measured with a video micro (magnification 1000 to 2000 times) at nine points to obtain an average value.

  In the developing roller of the present invention, the thickness of the conductive surface layer is preferably selected to be 3 μm or more in order to ensure sufficient wear resistance. On the other hand, the developing roller is an elastic roller having conductivity, and in this case, in order to achieve uniform conductivity, the thickness of the conductive surface layer is preferably limited to 50 μm or less. Further, when the thickness of the conductive surface layer is 3 μm or more, it is easy to uniformly apply and form a desired thin film thickness on the surface of the conductive elastic layer. On the other hand, since the hardness of the conductive surface layer is higher than the hardness of the conductive elastic layer, if the film thickness is 50 μm or less, the influence on the deformability of the entire developing roller is not large. In addition, the thickness of the conductive surface layer may be appropriately selected in the above range in consideration of the hardness and the like.

The roughness (Rz) of the conductive surface layer is defined by a value measured according to Rzjis of JIS B-0601. The roughness (Rz) of the conductive surface layer is preferably in the range of 3 to 15 μm. More preferably, it is the range of 5-10 micrometers.
A method for evaluating the storage elastic modulus of the conductive surface layer is described below.

  The conductive surface layer coating solution was cast into a flat mold and dried until the solvent was sufficiently volatilized, and then heated and cured at 140 ° C. for 1 hour to prepare a sheet having a thickness of 0.2 mm. This sheet was punched out to a width of 5 mm to prepare a measurement sample.

  This is set in a dynamic viscoelastic device DVA-220 (IT Measurement Control Co., Ltd.) with a chuck distance of 20 mm, and in an expansion / contraction mode, a frequency of 10 Hz, a strain of 1%, a heating rate of 10 ° C./min, and a measurement temperature range of 0 To 80 ° C. Here, E ′ (10 ° C.) represents the storage elastic modulus (MPa) at 10 ° C., and E ′ (40 ° C.) represents the storage elastic modulus (MPa) at 40 ° C.

A method for measuring the molecular weight distribution of the polyurethane polyol prepolymer by GPC is described below.
The molecular weight (Mn, Mw, Mz) of the chromatogram by gel permeation chromatography (GPC) is measured under the following conditions. The column was stabilized in a heat chamber at 40 ° C., and tetrahydrofuran (THF) as a solvent was passed through the column at this temperature at a flow rate of 1 ml / min, and the sample concentration was adjusted to 0.05 to 0.6% by mass. About 50 to 200 μl of THF sample solution is injected and measured. In measuring the molecular weight of a sample, the molecular weight distribution of the sample is calculated from the relationship between the logarithmic value of a calibration curve prepared from several types of monodisperse polystyrene standard samples and the number of counts (retention time). Examples of standard polystyrene samples for preparing a calibration curve include those manufactured by Tosoh Corporation or Pressure Chemical Co. The molecular weights manufactured are 6 × 10 ² , 2.1 × 10 ³ , 4 × 10 ³ , 1.75 × 10 ⁴ , 5.1 × 10 ⁴ , 1.1 × 10 ⁵ , 3.9 × 10 ⁵ , 8 ^{.6 × 10 5, 2 × 10} 6, used as a 4.48 × 10 ^6, it is appropriate to use at least about 10 standard polystyrene samples. An RI (refractive index) detector is used as the detector.

  As the column, it is preferable to combine a plurality of commercially available polystyrene gel columns. For example, combinations of shodex GPC KF-801, 802, 803, 804, 805, 806, 807 manufactured by Showa Denko KK, and μ- manufactured by Waters A combination of stylels 500, 103, 104, and 105 can be given.

  For forming the conductive elastic layer, a method can be used in which the raw material of the conductive surface layer film body is applied in the form of a liquid and applied to the surface of the conductive elastic layer, and then a coating body is formed. The method for applying the conductive elastic layer raw material is not particularly limited, but the application raw material is uniformly applied to the surface of the conductive elastic layer at a desired thickness by a method such as air spray, roll coating, curtain coating, or dipping. . Thereafter, in order to obtain a coating body, heat treatment may be performed as necessary.

  Hereinafter, the present invention will be described more specifically with reference to examples. These examples are examples of the best mode of the present invention, but the present invention is not limited to the examples. The developing roller produced by the method shown in the embodiment can be suitably used as a roller used in an electrophotographic apparatus.

In the specific examples described below, commercially available high-purity products were used as reagents used in the respective examples unless otherwise specified.
<Example>
Example 1
The shaft core body of the developing roller was a metal shaft core, and conductivity was imparted to both the conductive elastic layer and the conductive surface layer constituting the roller layer. A specific method for imparting conductivity to these layers is to add carbon black as a conductive agent to the conductive elastic layer and the coating layer of the conductive surface layer, respectively, and produce an elastic roller according to the following procedure. did. The amount of the conductive agent carbon black added was adjusted so that the electrical resistance of the roller when the elastic roller was brought into contact was 1 × 10 ⁶ Ω or less.

  As the shaft core body, a SUM core metal having a surface plated with nickel and further coated with an adhesive on its outer peripheral surface and baked was used. This shaft core was placed in a mold, and liquid silicone rubber 1 (made by Toray Dow Corning Silicone) was injected into a cavity formed in the mold. Subsequently, the mold was heated, and the injected silicone rubber was cured by heating at 150 ° C. for 30 minutes. After cooling and demolding, a heat treatment was further performed at 200 ° C. for 4 hours to provide a conductive elastic layer having a thickness of 4 mm as a main component of silicone rubber on the outer peripheral surface of the shaft core. .

  As a material of the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2 (f represents the number of functional groups); manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (commodity). Name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 21.2 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 6 hours under a nitrogen atmosphere to obtain a molecular weight Mw = 48000, hydroxyl value 5.6, molecular weight dispersity Mw / Mn = 2.9, and bifunctional polyurethane polyol prepolymer of Mz / Mw = 2.5 were obtained.

  [NCO] 100 parts by mass of the above polyurethane polyol prepolymer and 7.2 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, equivalent to f (average functional group) = 3; manufactured by Mitsui Takeda Chemical Co., Ltd.) The value of / [OH] was set to 1.2. Further, an appropriate amount of carbon black (# 1000; pH 3.0; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Acrylic resin particles (MBX-12; φ12 μm; Sekisui Plastics Co., Ltd.) prepared by adding an organic solvent to the raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm). Made in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  The shaft core after the formation of the conductive elastic layer was immersed in the raw material liquid for the conductive surface layer to coat the outer surface of the conductive elastic layer, and then pulled up and dried naturally. Next, the raw material of the coated conductive surface layer is cured by heat treatment at 140 ° C. for 60 minutes, and the conductive surface layer is laminated on the outer peripheral surface of the conductive elastic layer. A conductive surface layer having a surface roughness (Rz) of 7.2 μm was formed.

(Example 2)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 18.7 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere. Molecular weight Mw = 10000, hydroxyl value 18.2 A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.2 and Mz / Mw = 1.6 was obtained.

  100 parts by mass of the above polyurethane polyol prepolymer and isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3 equivalent; made by Mitsui Takeda Chemical Co., Ltd.) 23.4 parts by mass were added, and [NCO] The value of / [OH] was set to 1.2. Further, an appropriate amount of carbon black (# 1000; pH 3.0; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Acrylic resin particles (MBX-12; φ12 μm; Sekisui Plastics Co., Ltd.) prepared by adding an organic solvent to the raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm). Made in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.4 μm.

(Example 3)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 19.9 parts by mass in a MEK solvent was mixed stepwise and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere, molecular weight Mw = 30000, hydroxyl value 8.4. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.4 and Mz / Mw = 1.9 was obtained.

  100 parts by mass of the polyurethane polyol prepolymer and 10.8 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3 equivalent; manufactured by Mitsui Takeda Chemical Co., Ltd.) The value of / [OH] was set to 1.2. Further, an appropriate amount of carbon black (# 1000; pH 3.0; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Acrylic resin particles (MBX-12; φ12 μm; Sekisui Plastics Co., Ltd.) prepared by adding an organic solvent to the raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm). Made in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Example 4)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI, f = 2: Nippon Polyurethane Industry Co., Ltd.) 19.9 parts by mass in MEK solvent was mixed stepwise and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere, molecular weight Mw = 30000, hydroxyl value 8.4. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.4 and Mz / Mw = 1.9 was obtained.

  Add 100 parts by mass of the above polyurethane polyol prepolymer and isocyanate (trade name: Coronate 2516; Crude MDI, f (average functional group number) = 2.6 equivalent: manufactured by Nippon Polyurethane Industry Co., Ltd.), and add [NCO ] / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (Art Pearl C400; φ14 μm; manufactured by Negami Kogyo Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) Was added in the range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Example 5)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000; f = 2; manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 19.9 parts by mass in a MEK solvent was mixed stepwise and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere, molecular weight Mw = 30000, hydroxyl value 8.4. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.4 and Mz / Mw = 1.9 was obtained.

  100 parts by mass of the above polyurethane polyol prepolymer and 41.8 parts by mass of isocyanate (trade name: Coronate 2521; urethane-modified MDI, f (average functional group number) = 3.8 equivalent; manufactured by Nippon Polyurethane Co., Ltd.) are added, and [NCO ] / [OH] was set to 1.5. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (Art Pearl C400; φ14 μm; manufactured by Negami Kogyo Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) Was added in the range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Example 6)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000; f = 2; manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 18.7 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere. Molecular weight Mw = 10000, hydroxyl value 18.2 A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.2 and Mz / Mw = 1.6 was obtained.

  100 parts by mass of the above polyurethane polyol prepolymer and isocyanate (trade name: Coronate 2521; urethane-modified MDI, f (average functional group number) = 3.8 equivalent; manufactured by Nippon Polyurethane Co., Ltd.) are added, and [NCO ] / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (Art Pearl C400; φ14 μm; manufactured by Negami Kogyo Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) Was added in the range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.4 μm.

(Example 7)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG3000SN; molecular weight Mn = 3000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 5.9 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere to obtain a molecular weight Mw = 30000 and a hydroxyl value of 9.1. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.4 and Mz / Mw = 1.9 was obtained.

100 parts by mass of the above polyurethane polyol prepolymer and 11.7 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3 equivalent; manufactured by Mitsui Takeda Chemical Co., Ltd.) are added, and [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (Printex L6; pH 9.0; manufactured by Degussa, Germany) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.
A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer with an average surface roughness (Rz) of 7.1 μm of 9 points.

(Example 8)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polyoxypropylene glycol (trade name: PP-1000: molecular weight Mn = 1000, f = 2; manufactured by Sanyo Chemical Industries, Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI) F = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 18.7 parts by mass in a MEK solvent stepwise and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere to obtain a molecular weight Mw = 30000 and a hydroxyl value of 9 A bifunctional polyurethane polyol prepolymer having a molecular weight dispersity Mw / Mn = 2.4 and Mz / Mw = 1.9 was obtained.

  Add 100 parts by mass of the above polyurethane polyol prepolymer and 12.0 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3; manufactured by Mitsui Takeda Chemical Co., Ltd.), [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (Printex L6; pH 9.0; manufactured by Degussa, Germany) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

Example 9
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000; f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Coronate T-80; TDI) F = 2: Nippon Polyurethane Industry Co., Ltd.) 13.0 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours in a nitrogen atmosphere, molecular weight Mw = 30000, hydroxyl value 8 A bifunctional polyurethane polyol prepolymer having a molecular weight dispersity Mw / Mn = 2.3 and Mz / Mw = 1.9 was obtained.

  100 parts by mass of the polyurethane polyol prepolymer and isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3 equivalent; manufactured by Mitsui Takeda Chemical Co., Ltd.) 10.4 parts by mass are added, and [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (Printex L6; pH 9.0; manufactured by Degussa, Germany) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Example 10)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material of the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2 (f represents the number of functional groups); manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (commodity). Name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 21.5 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 6 hours under a nitrogen atmosphere to obtain a molecular weight Mw A bifunctional polyurethane polyol prepolymer having 50000, a hydroxyl value of 5.4, a molecular weight dispersity of Mw / Mn = 3.0, and Mz / Mw = 2.5 was obtained.

  Add 100 parts by mass of the above polyurethane polyol prepolymer and 6.9 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3; made by Mitsui Takeda Chemical Co., Ltd.) [NCO] The value of / [OH] was set to 1.2. Further, an appropriate amount of carbon black (# 1000; pH 3.0; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Acrylic resin particles (MBX-12; φ12 μm; Sekisui Plastics Co., Ltd.) prepared by adding an organic solvent to the raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm). Made in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Comparative Example 1)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000; f = 2; manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 27 parts by mass and 2 parts by mass of trimethylolpropane (f = 3) were mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere. A polyurethane polyol prepolymer having a branch of molecular weight Mw = 23000, hydroxyl value 36, molecular weight dispersity Mw / Mn = 3.8, Mz / Mw = 3.2 was obtained.

  100 parts by mass of the polyurethane polyol prepolymer and isocyanate (trade name: Takenate B830; TMP-modified TDI, equivalent to f (average functional group) = 3; made by Mitsui Takeda Chemical Co., Ltd.) 46.3 parts by mass are added, and [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.2 μm.

(Comparative Example 2)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000; f = 2; manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 19.9 parts by mass in a MEK solvent was mixed stepwise and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere, molecular weight Mw = 30000, hydroxyl value 8.4. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.4 and Mz / Mw = 1.9 was obtained.

  100 parts by mass of the above polyurethane polyol prepolymer and isocyanate (trade name: Coronate 2521; urethane-modified MDI, equivalent to f (average functional group) = 3.8; made by Nippon Polyurethane Co., Ltd.) 55.7 parts by mass are added, and [NCO ] / [OH] was set to 2.0. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Comparative Example 3)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 18.3 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere to obtain a molecular weight Mw = 7000 and a hydroxyl value of 22.6. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 1.8 and Mz / Mw = 1.4 was obtained.

  100 parts by mass of the polyurethane polyol prepolymer and isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3 equivalent; made by Mitsui Takeda Chemical Co., Ltd.) 29.0 parts by mass were added, and [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.2 μm.

(Comparative Example 4)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000; f = 2; manufactured by Hodogaya Chemical Co., Ltd.) is added to isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 22.4 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere to obtain a molecular weight Mw = 60000 and a hydroxyl value of 5.3. A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 2.8 and Mz / Mw = 2.4 was obtained.

  Add 100 parts by mass of the above polyurethane polyol prepolymer and 6.8 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average number of functional groups) = 3; made by Mitsui Takeda Chemical Co., Ltd.) [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

(Comparative Example 5)
The developing roller was coated with a conductive surface layer in the following procedure using a conductive elastic layer having the same composition and thickness as the developing roller produced in Example 1 on the shaft core. Produced.

  As a material for the conductive surface layer, polytetramethylene glycol (trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.) 100 parts by mass, isocyanate (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 19.9 parts by mass in a MEK solvent was mixed stepwise and reacted at 80 ° C. for 3 hours under a nitrogen atmosphere, molecular weight Mw = 30000, hydroxyl value 12.5 A bifunctional polyurethane polyol prepolymer having molecular weight dispersities Mw / Mn = 3.1 and Mz / Mw = 2.6 was obtained.

  Add 100 parts by mass of the above polyurethane polyol prepolymer and 16.1 parts by mass of isocyanate (trade name: Takenate B830; TMP-modified TDI, f (average functional group number) = 3 equivalent; manufactured by Mitsui Takeda Chemical Co., Ltd.) [NCO] The value of / [OH] was set to 1.2. Furthermore, an appropriate amount of carbon black (MA100; pH 3.5; manufactured by Mitsubishi Chemical Corporation) was added to adjust the resistance value. Urethane resin particles (CFB-101-40; φ16 μm; Dainippon Ink Co., Ltd.) prepared by adding an organic solvent to the above raw material mixture and adjusting the solid content in the range of 20% to 30% (so that the film thickness is 15 to 20 μm) (Chemical Industry Co., Ltd.) was added in a range of 5 to 25 parts by mass, and uniformly dispersed and mixed to obtain a raw material liquid for the conductive surface layer.

  A conductive surface layer was laminated on the conductive elastic layer in the same manner as in Example 1 to form a conductive surface layer having a 9-point average surface roughness (Rz) of 7.3 μm.

<Evaluation of characteristics>
Regarding the developing rollers produced in Examples 1 to 9 and Comparative Examples 1 to 5, the image performance was initially incorporated into the developing cartridge as a developing roller with respect to the item after printing 30000 sheets (30 k), and evaluated as follows. Table 1 shows the evaluation results.

<Evaluation of L / L environment>
A developing roller was incorporated in the cartridge, and continuous image formation with a printing rate of 2% was performed in a low-temperature / low-humidity environment (15 degrees, 10% RH), and a solid image and a ghost determination pattern were formed initially and after 30k. About the obtained solid image, 9 points | pieces were measured per image using the Macbeth densitometer, and the average value was computed. Next, the difference (average density decrease) between the solid density average values at the initial stage and after 30 k was calculated and judged based on the following levels. Further, with respect to a ghost determination pattern after 30k (a pattern in which a 15 mm square solid image and a halftone image are continuously formed in one image), by visually evaluating the presence or absence of density unevenness in the halftone portion, The ghost level was judged.
A: Solid density difference is 0.1 or less, and no ghost is generated. O: Solid density difference is 0.2 or less, and a slight ghost is generated. Some x: A solid density difference exceeds 0.2 and a ghost is generated.

<Evaluation of H / H environment>
The developing roller was incorporated in the cartridge, and continuous image formation was performed in a high temperature / high humidity environment (30 degrees, 80% RH). After 30 k, the developing roller was taken out from the cartridge, and the peeled state of the conductive surface layer was observed. Based on the judgment, evaluation was made according to the following criteria.
◎: Good with no peeling of the conductive surface layer ○: Peeling of the conductive surface layer is confirmed slightly, but is not a problem on the image ×: Peeling of the conductive surface layer is confirmed, image Things that cause problems.

<Coating fluid stability evaluation>
The coating liquid was circulated in the coating apparatus and left for 7 days, and the solid content of the coating liquid after the first day and 6 days later was measured. Based on the judgment, evaluation was made according to the following criteria.
○: The fluctuation range of solid content is smaller than 1%. Δ: The fluctuation range of solid content is in the range of 1 to 5%. X: The fluctuation range of solid content is larger than 5%.

  As is apparent from the results of characteristic evaluation in Table 1, the developing rolls of Examples 1 to 9 coated with the conductive surface layer according to the present invention did not decrease in concentration even when used for a long time in an L / L environment. The image ghost was also suppressed. Further, even when used in a H / H environment for a long time, peeling of the conductive surface layer was prevented, and a good image was obtained in both environments.

In addition, this invention is not limited to the conditions shown in the specific example mentioned above, It can implement after changing embodiment according to various uses within the technical scope of this invention. .

It is a figure which represents typically the two-layer structure of the developing roller in this invention. It is a conceptual diagram which shows an example of the electrophotographic image forming apparatus of this invention.

Explanation of symbols

1 Developing roller 11 Shaft core (shaft core pair)
12 Conductive elastic layer (base layer)
13 Conductive surface layer 21 Photoconductor 22 Charging roller 23 Laser beam 24 Developing device 25 Developing roller 26 Developing material supply roller 27 Developing material regulating member 28 Developing material 29 Transfer roller 30 Cleaning blade 31 Waste toner container 32 Fixing roller 33 Paper 34 Development container

Claims (9)

A mandrel having a provided on the mandrel conductive elastic layer, and provided on the conductive elastic layer electrically conductive surface layer at least, the conductive surface layer Gapo polyurethane A developing roller having
The polyurethane comprises (a) a chain extension of a bifunctional polyether polyol and a bifunctional isocyanate compound, and has a weight average molecular weight of 10,000 to 50,000 and a molecular weight dispersity of Mw / Mn = 3.0 or less, Mz / It is obtained from a urethane raw material consisting of a linear polyurethane polyol prepolymer of Mw = 2.5 or less and (b) isocyanate,
The urethane raw material, the straight-chain polyurethane polyol prepolymer, a developing roller for a free Ndei Rukoto characterized in the range of 70 to 95% by weight of the urethane materials. Developing roller of the isocyanate compound of the difunctional stated 請 Motomeko 1 Ru diphenylmethane diisocyanate der. The bifunctional polyether polyol is polypropylene glycol and Poritetoramechire ring recall at least one Der Ru請 Motomeko 1 or 2 to the developing roller according. The linear polyurethane polyol prepolymer, the developing roller according to any one of the previous Kiu urethane in the raw material Ru contained in the range of 75 to 95 wt% 請 Motomeko 1-3. The conductive surface layer further developing roller according to any one of 請 Motomeko 1 to 4 pH is that contained less than 5 carbon black. The storage elastic modulus E ′ of the conductive surface layer is expressed by the formula (1)

The developing roller according to any one of 請 Motomeko 1-5 that meet the. The linear polyurethane polyol prepolymer has a weight average molecular weight of 10,000 to 50,000, Mw / Mn of 2.2 to 3.0, and Mz / Mw of 1.6 to 2.5. The developing roller according to claim 1, which has a molecular weight dispersity . Cartridge it characterized in that the developing roller is incorporated according to any one of claims 1 to 7. An image forming apparatus comprising the developing roller according to claim 1.

Images