JP4663360B2 - Developing roller - Google Patents

Description

  The present invention relates to a developing roller used in an electrophotographic apparatus. More specifically, the toner is uniformly and stably charged in a preferable range under both low temperature and low humidity and high temperature and high humidity, image defects such as fog due to insufficient charging or non-uniform charging, and toner overcharging ( The present invention relates to a developing roller without image unevenness due to charge-up.

  In an electrophotographic apparatus such as a copying machine or a laser printer, as a developing method for visualizing a latent image by supplying non-magnetic one-component toner to a photosensitive drum holding a latent image and attaching the toner to the latent image on the photosensitive drum, A pressure development method is conventionally known. In this developing method, a developing roller carrying toner is brought into direct contact with the photosensitive drum, and the toner is attached to the latent image on the photosensitive drum. Since no magnetic material is required, the image forming apparatus is simplified and miniaturized. In addition, the development of color toner is facilitated.

  Here, the developing roller is brought into pressure contact with the photoconductor through the toner and slides in a state where the developing roller is rotated in the opposite direction. Therefore, it is necessary to form the developing roller with a conductive elastic body. In this case, in order to prevent damage to the photoreceptor due to oozing out of the plasticizer contained in the elastic body layer and toner adhesion to the surface, a multi-layer structure in which a resin surface layer is formed on the outer periphery of the elastic body is often employed.

  Since this resin surface layer is in direct contact with the toner, a number of properties such as toner retention, toner transportability, releasability (non-adhesiveness), and flexibility are required. In addition, the toner has a charge imparting property. In the pressure development method, the toner is usually frictionally charged by pressure sliding between the regulating blade and the developing roller via the toner. If the regulating blade and the developing roller are inferior in chargeability, and if the toner is insufficiently or unevenly charged, fogging and image unevenness may occur and image quality may be significantly impaired.

Therefore, in order to impart proper charge to the toner, it has been proposed to disperse and contain a charge control agent in the resin surface layer of the developing roller (Patent Documents 1 and 2).
Japanese Patent Laid-Open No. 10-186836 Japanese Patent Application Laid-Open No. 08-179617

According to the methods of Patent Documents 1 and 2, the charge imparting ability itself of the developing roller is considerably improved, but depending on the binder resin of the resin surface layer, no effect is seen or almost good image performance is exhibited. However, the charging ability becomes excessive under low temperature and low humidity, and image unevenness due to charge-up may occur particularly in fresh toner. This is a level with no problem in document copying / printing, but it has been improved for full-color output images and graphic images having a halftone part, which have been demanded in recent years due to the development of computers. It is strongly desired.

  The object of the present invention is to provide a stable and appropriate charge to the toner without depending on the environment from low temperature and low humidity to high temperature and high humidity, and development capable of obtaining a uniform and high-quality image without uneven density. To provide a roller. More specifically, an object of the present invention is to provide a developing roller that does not cause image unevenness due to toner charge-up under low temperature and low humidity, and that exhibits good image performance in other environments.

  In order to achieve the above object, the present inventors have repeated intensive studies and have come up with the following.

That is, the present invention is a developing roller having at least two layers of a shaft core body, and a conductive elastic layer and a resin surface layer covering the outer periphery of the conductive elastic layer on the outer peripheral surface of the shaft core body. ,
A urethane resin (I) having a nitrogen concentration of 2.0 mass% or more and 4.0 mass% or less, wherein the resin surface layer is obtained by reacting the polyether polyol component (A) and the isocyanate component (B); A charge control agent (II) ,
The polyether polyol component (A) is obtained by reacting a bifunctional polyether polyol compound (a) and a bifunctional isocyanate compound (b), and has a weight average molecular weight (Mw) of 10,000 to 50,000 and a molecular weight dispersity of Mw. The developing roller is a polyurethane polyol prepolymer (A ¹ ) having / Mn of 1.0 or more and 3.0 or less and Mz / Mw of 1.0 or more and 2.5 or less .

  According to the present invention, it is possible to provide a developing roller capable of obtaining a good image without fogging and density unevenness due to charge-up regardless of the environment.

  Hereinafter, the present invention will be described in more detail.

  The present invention is a developing roller having at least two layers of a shaft core, and a conductive elastic layer and a resin surface layer covering the outer periphery of the conductive elastic layer on the outer peripheral surface of the shaft core, A urethane resin (I) having a nitrogen concentration of 2.0 mass% or more and 4.0 mass% or less, wherein the resin surface layer is obtained by reacting the polyether polyol component (A) and the isocyanate component (B); A developing roller containing a charge control agent (II). By obtaining such a developing roller, it was possible to overcome the problems that were not sufficiently solved by the prior art.

  First, a urethane resin (I) obtained by reacting a polyether polyol component (A) and an isocyanate component (B) is used for a resin surface layer of a developing roller requiring flexibility. This is because it is flexible and the urethane resin (I) contains a specific amount of nitrogen atoms, which imparts negative charge to the toner.

  Next, the nitrogen concentration of urethane resin (I) means that the higher the value, the stronger the ability of the resin to impart negative charge to the toner. In the present invention, the nitrogen concentration of the urethane resin (I) is 2.0% by mass or more and 4.0% by mass or less with respect to the mass of the urethane resin (I), and the charge control agent (II) is added. As a result, it was possible to obtain a developing roller that provides very good image performance from low temperature and low humidity to high temperature and high humidity.

  When the concentration of nitrogen contained in the urethane resin (I) is less than 2.0% by mass, the charging ability of the urethane resin (I) is low, so that the toner is not easily charged on the resin surface layer, and the charges scattered on the resin surface layer. It will be charged only where the control agent (II) is present. The locally charged toner gradually leaks its charge at the portion of the urethane resin (I) that occupies most of the resin surface layer. In particular, in a high-temperature and high-humidity environment, the amount of charge applied to the toner becomes insufficient, so that the charged state of the toner becomes non-uniform and image defects such as fog are likely to occur. When the nitrogen concentration of the urethane resin (I) is larger than 4.0% by mass, the charge imparting ability of the urethane resin (I) becomes unnecessarily large and exceeds the ideal charging ability range. In particular, in a low-temperature and low-humidity environment, the toner may be charged up instantaneously and exhibit severe density unevenness.

  On the other hand, when the nitrogen concentration of the urethane resin (I) is in the range of 2.0 to 4.0% by mass, the toner is weakly charged at the urethane resin (I) portion, and the charge control agent. The charge amount is raised by (II). In addition, the leakage of electric charge at the urethane resin (I) portion is less likely to occur, and since the toner charge amount is uniform, fogging is less likely to occur. Further, since the toner is not charged up even in a low temperature and low humidity environment, a good image can be obtained in all environments. Preferably, it is 2.5 mass% or more and 3.5 mass% or less with respect to the mass of urethane resin (I).

Here, the nitrogen concentration of the urethane resin (I) needs to be 4.0% by mass or less. However, in a general ether-based urethane resin, the distance between cross-linking points becomes very long, and the nitrogen concentration contained May exceed 4.0% by mass. Therefore, a weight average molecular weight obtained by reacting a bifunctional polyether polyol compound (a) and a bifunctional isocyanate compound (b) as the polyether polyol component (A) used in synthesizing the urethane resin (I). A polyurethane polyol prepolymer (A ¹ ) having (Mw) of 10,000 to 50,000, a molecular weight dispersity of Mw / Mn of 1.0 to 3.0 and Mz / Mw of 1.0 to 2.5 is used. preferable. Further, it is preferably contained in a range in the raw material mixture polyurethane polyol prepolymer (A ¹⁾ 70-95% by weight of the urethane resin (I). By doing in this way, all of compression set, adhesiveness, and material strength can be made more excellent.

This is a urethane resin (I) finally obtained by reacting a bifunctional polyether polyol compound (a) and a bifunctional isocyanate compound (b) to obtain a polyurethane polyol prepolymer (A ¹ ) having a narrow molecular weight distribution. ), The distribution of the distance between the cross-linking points is narrow, that is, the part where the distance between the cross-linking points is extremely large does not occur.

  The bifunctional polyether polyol compound (a) is preferably, for example, any one of polypropylene glycol and polytetramethylene glycol or a mixture thereof, more preferably polytetramethylene glycol having strong molecular crystallinity. . The weight average molecular weight (Mw) of the bifunctional polyether polyol compound (a) is preferably 500 to 5000 to bring out the effects of the present invention, and more preferably 500 to 3000. If it is 5000 or less, the ratio of the soft segment in the urethane chain is not too high, the material can be maintained without being extremely softened, and can be suitably used as a resin surface layer of the developing roller.

  Examples of the bifunctional isocyanate compound (b) 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. As a result, an effect of preventing adhesiveness, that is, toner fusion can be obtained.

The weight average molecular weight of the polyurethane polyol prepolymer (A ¹ ) obtained by reacting the bifunctional polyether polyol compound (a) and the bifunctional isocyanate compound (b) is preferably in the range of 10,000 to 50,000. By setting it to 50000 or less, an appropriate crosslinking density is obtained, and the amount of residual deformation with respect to stress is reduced. Moreover, by setting it to 10,000 or more, it becomes possible to bring out sufficient flexibility so as not to give stress to the developer. The weight average molecular weight is more preferably 10,000 to 40,000, and further preferably 10,000 to 30,000.

Mn: number average molecular weight, Mw: weight average molecular weight, Mz: Z average molecular weight are used for the definition of the molecular weight dispersion of the polyurethane polyol prepolymer (A ¹ ). 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 Ni molecules having a molecular weight Mi exist in the polymer, it is represented by the following formula (1).
Mz = (ΣMi ³ Ni) / (ΣMi ² Ni) (1)

  Mw / Mn is preferably 1.0 or more and 3.0 or less. More preferably, Mw / Mn is 1.0 or more and 2.7 or less. By making Mw / Mn 1.0 or more and 3.0 or less, variation in molecular weight between crosslinks is reduced, and an effect of further suppressing changes in mechanical properties in the environment can be obtained. Moreover, it is preferable that Mz / Mw shall be 1.0 or more and 2.5 or less. More preferably, Mz / Mw is 1.0 or more and 2.0 or less. By setting Mz / Mw to 1.0 or more and 2.5 or less, the molecular weight distribution on the high molecular weight side can also be sharpened, and the molecular weight between crosslinks of the produced coating film is made more uniform. Therefore, the effect which further suppresses the change of the mechanical characteristic in the environment of the produced | generated coating film can be taken out.

The content of the polyurethane polyol prepolymer in the raw material mixture of the urethane resin (I) (A ¹⁾ is preferably 75 to 95 wt%, more preferably 75 to 90 wt%. When the content is within these ranges, a developing roller having low hardness and excellent toner transportability can be obtained.

  As the isocyanate component (B) which is a raw material of the urethane resin (I), it is preferable to use an isocyanate compound having an average functional group number larger than 2 and smaller than 6, or a terminal isocyanate type prepolymer. 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, a suitable crosslinking density can be obtained, 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 slightly depending on the molecular weight of the polyol before forming the modified product, but the polyether polyol component (A) forms the urethane resin (I) of the resin surface layer. If it occupies 70 mass% or more in the raw material mixture used when doing, it will become possible to exhibit the effect of this invention. More preferably, it is 75 mass% or more.

  In forming the urethane resin (I) constituting the resin surface layer, the polyether polyol component (A) and the isocyanate component (B) have an isocyanate index (NCO / OH) in the range of 0.9 to 1.5. Can be used as 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, but if the polyether polyol component (A) accounts for 70% by mass or more in the raw material mixture as described above, the effect of the present invention can be exhibited.

  A well-known thing is used as charge control agent (II) contained in the resin surface layer of this invention. From the viewpoint of imparting negative charge, an electron donating compound is usually used. Specifically, aminosilane surface-treated inorganic fine particles, imidazole, imidazoline, imidazolone, pyrazoline, pyrazole, pyrazolone, oxazoline, oxazole, oxazolone, thiazoline, thiazole, thiazolone, selenazoline, selenazole, selenazolone, oxadiazole, thiadiazole, tetrazole, Benzimidazole, benzotriazole, benzoxazole, benzothiazole, benzoselenazole, pyrazine, pyrimidine, pyridazine, triazine, oxazine, thiazine, tetrazine, polyazaine, indole, isoindole, indazole, carbazole, quinoline, pyridine, isoquinoline, cinnoline, quinazoline , Quinoxaline, phthalazine, purine, pyrrole, triazole, phenazine Compounds having a nitrogen-containing heterocyclic group, cationic dyes such as triphenylmethane dyes, quaternary ammonium salts, nigrosine dyes and fatty acid metal salt derivatives, diorganotin oxides such as dibutyltin oxide, dioctyltin oxide, dicyclohexyltin oxide, Examples include diorganotin borate such as dibutyltin borate, dioctyltin borate, and dicyclohexyltin borate. Further, an imidazole compound represented by the following formula (II-1), a polymer or copolymer having a monomer unit represented by the following formula (II-2) as a structural unit, and the like are also included. These can be used alone or in combination of two or more. Of the charge control agents described above, triphenylmethane dyes and nigrosine dyes are particularly suitable. The amount of the charge control agent used is preferably 0.05 to 20 parts by mass and more preferably 0.1 to 10 parts by mass with respect to 100 parts by mass of the urethane resin in the resin surface layer.

［式中、Ｒ₁及びＲ₂は、水素原子、アルキル基、アラルキル基またはアリール基を表し、Ｒ₁及びＲ₂は同一であっても異なっていても良い。Ｒ₃及びＲ₄は炭素数が３〜３０の直鎖状アルキル基を表し、Ｒ₃及びＲ₄は同一であっても異なっていても良い。］

[Wherein, R ₁ and R ₂ represent a hydrogen atom, an alkyl group, an aralkyl group or an aryl group, and R ₁ and R ₂ may be the same or different. R ₃ and R ₄ represent a linear alkyl group having 3 to 30 carbon atoms, and R ₃ and R ₄ may be the same or different. ]

〔式中、Ｒ₁，Ｒ₂，Ｒ₃及びＲ₄は、水素原子あるいは炭素数１〜４の飽和炭化水素基を示し、ｎは１〜４の整数を示す。〕

[Wherein R ₁ , R ₂ , R ₃ and R ₄ represent a hydrogen atom or a saturated hydrocarbon group having 1 to 4 carbon atoms, and n represents an integer of 1 to 4. ]

  A conductivity imparting substance may be added to the resin surface layer as necessary to impart conductivity. Examples of the conductivity imparting material include electron conductive materials such as carbon black, graphite, metal filler, and metal oxide whisker, and ion conductive materials such as metal salts. Among them, inexpensive carbon black is widely used.

  Further, various metal particles, inorganic particles, and resin particles may be added to the resin surface layer as needed for the purpose of providing an appropriate uneven shape on the roller surface. As the inorganic particles, diatomaceous earth, quartz powder, dry silica, wet silica, titanium oxide, zinc oxide, aluminosilicate, calcium carbonate, and the like can be used. As the resin particles, various rubber particles, nylon particles, urethane particles, polymethyl methacrylate (PMMA) particles, and any other particles can be used as long as they do not dissolve or melt in the molding process.

  FIG. 1 shows an example of the structure of the developing roller in the present invention. The developing roller 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 12 is fixed on the outer peripheral surface of the shaft core 11. The resin elastic layer 12 has a structure in which the resin 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 made of a conductive material such as metal, but the developing roller is electrically insulated. When used, the shaft core may be formed 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 thereof is subjected to a conductive treatment satisfying desired conductivity, for example, a coating with a highly conductive resin 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 is a molded body using rubber as a raw material main component. As the rubber as the main ingredient of the conductive elastic layer 12, various rubbers conventionally used for developing rollers can be used. Specifically, ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), natural rubber (NR), isoprene rubber (IR), styrene-butadiene rubber (SBR). ), Fluoro rubber, silicone rubber, epichlorohydrin rubber, hydride of NBR, polysulfide rubber, urethane rubber and the like. 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 preferably in the range of 15 to 70 °. More preferably, it is in the range of 20 to 60 °.

  At the same time, it is preferable to set the compression set of the rubber molding forming the conductive elastic layer to a range of 10% or less. More preferably, the range is 7.0% or less.

  In particular, it is preferable to use silicone rubber as the main component rubber of the rubber molded body forming the conductive elastic layer because 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. In addition, 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 is relatively inexpensive and easily available, and good chargeability is 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.

  Examples of the crosslinking agent used in producing the rubber molded body include di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, dicumyl peroxide, t -Butyl peroxybenzoate, p-chlorobenzoyl peroxide, etc. can be mentioned. 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.

  The thickness of the conductive elastic layer is preferably 0.5 mm or more in order to ensure a uniform nip width when contacting the developing roller and in addition to satisfy a suitable setting property. More preferably, the thickness is 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 thickness of the resin surface layer is preferably selected from the range of 3 to 50 μm from the viewpoint of wear resistance and flexibility.

  The concentration of nitrogen contained in the resin surface layer may be measured by an organic element analysis method if a sample of the resin alone can be produced. On the other hand, if it is a composition containing a conductive agent, a charge control agent, etc., and separation of the resin by extraction or the like is difficult, measure the amount of resin in the composition using a thermobalance, and then perform solid NMR. The nitrogen atom derived from the urethane group may be quantified.

The molecular weight distribution of the polyurethane polyol prepolymer may be measured by the following procedure using gel permeation chromatography (GPC). 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 a 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 (trade names) manufactured by Showa Denko KK and Waters A combination of μ-styrel 500, 103, 104, 105 (trade name) manufactured by the company can be mentioned.

  The nitrogen concentration in the resin surface layer is measured by an organic elemental analysis method.

  The surface roughness of the roller surface is defined by a value measured according to JIS B-0601 10-point average roughness (Rzjis). The range of Rzjis is preferably 3.0 to 15.0 μm mainly from the viewpoint of image density and fogging. More preferably, it is the range of 5.0-10.0 micrometers.

  FIG. 2 shows an example of an electrophotographic image forming apparatus using the developing roller of the present invention. The developing roller 25 is provided in contact with the photoreceptor 21 and the developer supply roller 26. The developer 28 put in the developing container 34 of the developing device 24 is supplied to the developing roller 25 by the developer supply roller 26. At this time, the amount is adjusted by the developer regulating member 27. On the other hand, an image is formed by the laser beam 23 on the photosensitive member 21 charged by the charging roller 22, and the developer adheres from the developing roller 25. Thereafter, the paper 33 passes between the photosensitive member 21 and the transfer roller 29, whereby the developer is transferred to the paper, and the developer is fixed on the paper by the fixing roller 32. The developer remaining on the photoreceptor 21 is scraped off by the cleaning blade 30 and dropped into the waste toner container 31.

  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 another roller used in the 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.

  The nitrogen content of the resin was based on the organic element analysis method, and FLASH 1112SERIES EA (trade name) manufactured by ThermoQuest was used. A plurality of measurement samples were cut out from the roller surface, organic elemental analysis of the roller surface layer resin portion was performed, three samples were measured for each sample, and the average value was used as a representative value.

  The weight average molecular weight Mw, number average molecular weight Mn, Z average molecular weight Mz, molecular weight dispersity Mw / Mn, and Mz / Mw of the polyurethane polyol prepolymer were measured using HLC-8120GPC (trade name, manufactured by Shimadzu Corporation). ), Shodex GPC KF-801, 802, 803, 804, 805, 806, 807 (above trade names) manufactured by Showa Denko Co., Ltd. for the column, and those manufactured by Tosoh Corporation for the standard polystyrene sample, and the above procedure It was measured.

  The surface roughness (Rzjis) of the developing roller is according to JIS B-0601, using a surf coder SE-3500 (trade name) manufactured by Kosaka Laboratory, cut-off value: 0.8 mm, measurement length: 2. Rzjis was determined by measuring 10 points on the developing roller at 5 mm (longitudinal direction) and a measurement speed of 0.2 mm / sec.

<Production of developing roller>
Example 1
The shaft core was made of a metal shaft core, and conductivity was imparted to both the conductive elastic layer and the resin surface layer constituting the roller layer. A specific method for imparting conductivity to these layers was to appropriately add carbon black as a conductive agent to both the conductive elastic layer and the coating layer of the resin surface layer, and to produce a developing roller according to the following procedure. . The amount of conductive agent carbon black added was adjusted so that the electrical resistance of the roller layer was 1 × 10 ⁶ Ω or less when the developing roller was brought into contact.

  As the shaft core, a SUM core bar having a diameter of 8 mm was subjected to nickel plating, and an outer peripheral surface thereof was coated with an adhesive and baked. This shaft core was placed in a mold, and liquid conductive silicone rubber (manufactured 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 heat treatment at 150 ° C. for 30 minutes. After cooling, the mold was removed, and a heat treatment was performed at 200 ° C. for 4 hours to provide a conductive elastic layer having a thickness of 4 mm on the outer peripheral surface of the shaft core.

Next, 100 parts by mass of polytetramethylene glycol (bifunctional polyether polyol compound (a), trade name: PTG1000SN; molecular weight Mn = 1000, f = 2 (f represents the number of functional groups); manufactured by Hodogaya Chemical Co., Ltd.) In addition, 21.5 parts by mass of a bifunctional isocyanate compound (b) (trade name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) is mixed stepwise in a MEK solvent, and 80 under a nitrogen atmosphere. A bifunctional polyurethane polyol prepolymer having a weight average molecular weight Mw = 50000, hydroxyl value 5.4, molecular weight dispersity Mw / Mn = 3.0, and Mz / Mw = 2.5 (A ¹ ) got.

To 100 parts by mass of the polyurethane polyol prepolymer (A ¹ ), an isocyanate component (B) (trade name: Takenate B830; TMP-modified TDI, equivalent to f (average functional group number) = 3; manufactured by Mitsui Takeda Chemical Co., Ltd.) 6.9 A part by mass was added so that the value of [NCO] / [OH] was 1.2. Furthermore, 28 parts by mass of carbon black (# 1000; pH 3.0; manufactured by Mitsubishi Chemical Corporation), a triphenylmethane dye (trade name: Copy Blue PR) represented by the following formula (II-3) as a charge control agent (II) 5 parts by mass of Clariant) and 22 parts by mass of PMMA resin particles (trade name: MBX-12; average particle size 12 μm; Sekisui Plastics Co., Ltd.).

  Methyl ethyl ketone was added to this raw material mixture, the solid content was adjusted to 40% by mass, and circulation dispersion was performed using an IMEX ready mill (trade name) until no grind gauge could be confirmed. The obtained paint stock solution was diluted with MEK so that the viscosity was 20 mPa · s to obtain a resin surface layer paint.

  This paint is put into an overflow type dip coater, circulated so as to be always overflowed, the shaft core body on which the conductive elastic layer is formed is immersed at 50 mm / sec, and then from 200 mm / min to 50 mm. The outer surface of the conductive elastic layer was dip-coated by pulling up while gradually raising the pulling speed to / min. After naturally drying this for 30 minutes, the resin surface layer was cured by heat treatment at 140 ° C. for 60 minutes to form a resin surface layer. Thereafter, both ends of the roller layer were cut off at predetermined positions to obtain a developing roller. The concentration of nitrogen contained in the resin surface layer of the obtained developing roller was 2.0% by mass, the film thickness of the resin surface layer was 21 μm, and the average value of the surface roughness measured at 10 points on the roller surface (10-point average roughness: Rzjis ) Was 7.2 μm.

(Example 2)
A developing roller was produced under the same composition and conditions as in Example 1 except that the charge control agent (II) added to the resin surface layer was 5 parts by mass of nigrosine dye (trade name: N-9; manufactured by Orient Chemical Co., Ltd.). The concentration of nitrogen contained in the resin surface layer of the obtained developing roller was 2.0 mass%, the film thickness of the resin surface layer was 20 μm, and the average value of the surface roughness measured at 10 points on the roller surface (10-point average roughness: Rzjis ) Was 7.4 μm.

(Example 3)
The developing roller was subjected to the same composition and conditions as in Example 1 except that the charge control agent (II) added to the resin surface layer was an imidazole compound (made by Shikoku Kasei Kogyo Co., Ltd.) represented by the following formula (II-4). Produced. The resulting urethane resin has a nitrogen concentration of 2.0 mass%, a roller resin surface layer film thickness of 19 μm, and an average surface roughness (10-point average roughness: Rzjis) measured at 10 points on the roller surface of 7. .8 μm.

Example 4
Except that the charge control agent (II) added to the resin surface layer was a nitrogen-containing vinyl monomer copolymer (manufactured by Sanyo Chemical Industries) represented by the following formula (II-5), the same composition and conditions as in Example 1 were used. A developing roller was produced. The resulting urethane resin has a nitrogen concentration of 2.0% by mass, a roller resin surface layer thickness of 22 μm, and an average surface roughness (10-point average roughness: Rzjis) measured at 10 points on the roller surface is 7. .1 μm.

(Example 5)
A developing roller was produced under exactly the same composition and conditions as in Example 1 except that the charge control agent (II) added to the resin surface layer was aminosilane-treated silica (manufactured by Nippon Aerosil Co., Ltd., trade name: RY200). The obtained urethane resin has a nitrogen concentration of 2.0% by mass, a roller resin surface layer thickness of 20 μm, and an average surface roughness (10-point average roughness: Rzjis) measured at 10 points on the roller surface is 7. It was 5 μm.

(Example 6)
To 100 parts by mass of polytetramethylene glycol (bifunctional polyether polyol compound (a), trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.), bifunctional isocyanate compound (b) (product 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 in a nitrogen atmosphere. A bifunctional polyurethane polyol prepolymer (A ¹ ) having a molecular weight Mw = 10000, a hydroxyl value of 18.2, a molecular weight dispersity Mw / Mn = 2.2, and Mz / Mw = 1.6 was obtained.

A developing roller was produced under the same composition and conditions as in Example 2 except that this polyurethane polyol prepolymer (A ¹ ) was used. The nitrogen concentration in the resin surface layer of the obtained developing roller is 4.
0% by mass, the resin surface layer film thickness is 20 μm, the roller resin surface layer film thickness is 20 μm, and the average surface roughness (10-point average roughness: Rzjis) measured at 10 points on the roller surface is 7.5 μm. there were.

(Example 7)
To 100 parts by mass of polytetramethylene glycol (bifunctional polyether polyol compound (a), trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.), bifunctional isocyanate compound (b) (product Name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 19.9 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours in a nitrogen atmosphere. A bifunctional polyurethane polyol prepolymer (A ¹ ) having a molecular weight Mw = 30000, a hydroxyl value 8.4, a molecular weight dispersity Mw / Mn = 2.4, and Mz / Mw = 1.9 was obtained.

A developing roller was produced under the same composition and conditions as in Example 2 except that this polyurethane polyol prepolymer (A ¹ ) was used. The concentration of nitrogen contained in the resin surface layer of the developing roller thus obtained was 2.9% by mass, the film thickness of the resin surface layer was 20 μm, the film thickness of the resin surface layer of the roller was 20 μm, and the surface roughness measured at 10 points on the roller surface. The average value (10-point average roughness: Rzjis) was 7.5 μm.

(Comparative Example 1)
To 100 parts by mass of polytetramethylene glycol (bifunctional polyether polyol compound (a), trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.), bifunctional isocyanate compound (b) (product Name: Millionate MT; MDI, f = 2; manufactured by Nippon Polyurethane Industry Co., Ltd.) 18.4 parts by mass are mixed stepwise in a MEK solvent and reacted at 80 ° C. for 3 hours in a nitrogen atmosphere to obtain a molecular weight Mw = 8000, hydroxyl value 19.0, molecular weight dispersity Mw / Mn = 2.1, Mz / Mw = 1.6, a bifunctional polyurethane polyol prepolymer (A ¹ ) was obtained.

A developing roller was produced under the same composition and conditions as in Example 2 except that this polyurethane polyol prepolymer (A ¹ ) was used. The concentration of nitrogen contained in the resin surface layer of the obtained developing roller was 4.2% by mass, the film thickness of the resin surface layer was 20 μm, the film thickness of the resin surface layer of the roller was 20 μm, and the surface roughness measured at 10 points on the roller surface. The average value (ten-point average roughness: Rzjis) was 7.4 μm.

(Comparative Example 2)
To 100 parts by mass of polytetramethylene glycol (bifunctional polyether polyol compound (a), trade name: PTG1000SN; molecular weight Mn = 1000, f = 2; manufactured by Hodogaya Chemical Co., Ltd.), bifunctional isocyanate compound (b) (product 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 6 hours in a nitrogen atmosphere to obtain a molecular weight Mw = 60000, a hydroxyl value of 5.3, a molecular weight dispersity Mw / Mn = 2.8, and a bifunctional polyurethane polyol prepolymer (A ¹ ) of Mz / Mw = 2.4 were obtained.

A developing roller was produced under the same composition and conditions as in Example 2 except that this polyurethane polyol prepolymer (A ¹ ) was used. The concentration of nitrogen contained in the resin surface layer of the developing roller obtained was 1.8% by mass, the film thickness of the resin surface layer was 23 μm, the film thickness of the resin surface layer of the roller was 20 μm, and the surface roughness was measured at 10 points on the roller surface. The average value (ten-point average roughness: Rzjis) was 7.0 μm.

(Comparative Example 3)
A developing roller was produced under the same composition and conditions as in Comparative Example 2 except that the charge control agent (II) added to the resin surface layer was changed to 5 parts by mass of the triphenylmethane dye used in Example 1. The nitrogen concentration in the resin surface layer of the developing roller obtained was 1.8% by mass, the resin surface layer film thickness was 21 μm, the roller resin surface layer film thickness was 20 μm, and the surface roughness measured at 10 points on the roller surface ( The average value of Rzjis) was 7.1 μm.

(Comparative Example 4)
A developing roller was produced under the same composition and conditions as in Example 6 except that the charge control agent (II) was not added to the resin surface layer. The nitrogen concentration in the resin surface layer of the obtained developing roller was 4.0% by mass, the film thickness of the resin surface layer was 23 μm, and the average value of the surface roughness measured at 10 points on the roller surface (10-point average roughness: Rzjis ) Was 6.9 μm.

(Comparative Example 5)
A developing roller was produced under the same composition and conditions as in Comparative Example 2, except that the charge control agent (II) was not added to the resin surface layer. The concentration of nitrogen contained in the resin surface layer of the developing roller obtained was 1.8% by mass, the film thickness of the resin surface layer was 19 μm, and the average value of the surface roughness measured at 10 points on the roller surface (10-point average roughness: Rzjis ) Was 6.9 μm.

<Evaluation of developing roller characteristics>
The developing rollers prepared in Examples 1 to 7 and Comparative Examples 1 to 5 were incorporated in a developing cartridge and evaluated as follows. Table 1 shows the evaluation results.

<Development roller evaluation method>
A developing roller is incorporated in the cartridge, and printing is performed with Canon Color LBP in a low-temperature, low-humidity (LL) environment (15 ° C, 10% RH) and a high-temperature, high-humidity (HH) environment (30 ° C, 80% RH) A continuous image of 2% was formed, and a solid image and a halftone image were formed after printing 30000 sheets (30 k).

The solid image and the halftone image were determined based on the following criteria by focusing on density unevenness due to toner charge-up.
A: The concentration is uniform over the entire area, and no unevenness is observed.
○: Density unevenness due to charge-up is slightly occurring, but there is no problem.
X: Density unevenness due to charge-up can be clearly confirmed, and there is a quality problem.

For fogging, the apparatus was stopped halfway when printing a white solid image, the toner adhering to the photosensitive drum was collected with a tape and affixed to a white paper, and the reflectance was measured.
A: The reflectance is 1% or less.
○: Reflectance of 5% or less.
X: Reflectance greater than 5%.

※荷電制御剤（ＩＩ）・・・Ａ：トリフェニルメタン系、Ｂ：ニグロシン系、Ｃ：イミダゾール系、Ｄ：含窒素ビニルモノマ共重合体、Ｅ：アミノシラン処理シリカ

* Charge control agent (II): A: Triphenylmethane, B: Nigrosine, C: Imidazole, D: Nitrogen-containing vinyl monomer copolymer, E: Aminosilane-treated silica

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

FIG. 2 is a schematic cross-sectional view of a developing roller in the present invention, a left cross-sectional view cut in a direction parallel to the axial direction, and a right cross-sectional view cut in a direction perpendicular to the axial direction. It is a schematic diagram showing an example of an electrophotographic image forming apparatus using the developing roller of the present invention.

Explanation of symbols

11 Shaft core (shaft core)
12 Conductive elastic layer (base layer)
DESCRIPTION OF SYMBOLS 13 Resin surface layer 21 Photoconductor 22 Charging roller 23 Laser beam 24 Developing apparatus 25 Developing roller 26 Developer supply roller 27 Developer control member 28 Developer 29 Transfer roller 30 Cleaning blade 31 Waste toner container 32 Fixing roller 33 Paper 34 Developer container

Claims (7)

A developing roller having at least two layers of a shaft core, and a conductive elastic layer and a resin surface layer covering the outer periphery of the conductive elastic layer on an outer peripheral surface of the shaft core,
A urethane resin (I) having a nitrogen concentration of 2.0 mass% or more and 4.0 mass% or less, wherein the resin surface layer is obtained by reacting the polyether polyol component (A) and the isocyanate component (B); A charge control agent (II) ,
The polyether polyol component (A) is obtained by reacting a bifunctional polyether polyol compound (a) and a bifunctional isocyanate compound (b), and has a weight average molecular weight (Mw) of 10,000 to 50,000 and a molecular weight dispersity of Mw. A developing roller, which is a polyurethane polyol prepolymer (A ¹ ) having a / Mn of 1.0 to 3.0 and Mz / Mw of 1.0 to 2.5 . The developing roller according to claim 1 , wherein the bifunctional isocyanate compound (b) is diphenylmethane diisocyanate. The bifunctional polyether polyol (a) is, the developing roller according to claim 1 or 2, characterized in that any one or a mixture of polypropylene glycol and polytetramethylene glycol. The developing roller according to any one of claims 1 to 3, wherein the content of nitrogen concentration is 3.5 or less wt% 2.5 wt% or more. The charge control agent (II) is, the developing roller according to any one of claims 1 to 4, characterized in that an electron-donating compound. 6. The developing roller according to claim 5 , wherein the electron donating compound is a triphenylmethane dye or a nigrosine dye. The polyurethane polyol prepolymer (A ¹ 7) Mw / Mn is 2.2 or more and 3.0 or less, and Mz / Mw is 1.6 or more and 2.5 or less. Development roller.

Images