JP3829430B2 - Developing roller - Google Patents

Description

【００６６】
この結果が示すように、現像ローラ全体の静電容量C₁が2.5 nF以下の値を有し、弾性層の静電容量C₂が0.8 nF以上20 nF 以下の値を有する実施例において、トナーフィルミングが確実に防止されていることがわかる。
【００６７】
【発明の効果】
上述の如く、本発明は、現像ローラ全体の静電容量C₁が2.5 nF以下の値を有し、弾性層の静電容量C₂が0.8 nF以上20 nF 以下の値を有する現像ローラであるので、現像に寄与しないトナーの静電気的付着が抑えられる程に現像ローラの時定数が十分小さくなり、現像ローラ表面のトナーフィルミングを防止することができ、もって現像ローラの耐久性を向上させることが可能となる。さらに、本発明が、1.1 ≦C₂／C₁≦11なる関係式を満たすように構成されると、現像時において、弾性層と表面層とのそれぞれの層に加わる電圧のバランスを適正に保つことができ、現像ローラを絶縁破壊などから防ぐことができる。
【００６８】
また、表面層として、ポリアミドまたはポリウレタン樹脂を主成分とするものを使用すると、弾力性が良好で、電気抵抗の環境変動の少ない表面層を得ることができ、より耐久性の高い現像ローラの作製が可能となる。一方で、表面層として、アクリル酸エステルモノマーとメタアクリル酸エステルモノマーとの一方または双方、およびカルボン酸ビニルモノマーを主原料とする共重合体を主成分とするものを使用すると、トナー帯電性を向上する点で有利な現像ローラの作製が可能となる。
【００６９】
さらに、本発明の弾性層として使用する硬化性組成物の反応物において、その主鎖を構成する主な繰り返し単位にオキシアルキレン単位からなる重合体を採用すると、少量の導電性付与剤の添加で硬化物の体積抵抗率を設定しやすく、かつ低硬度化への設定もしやすいため、現像ローラの時定数を適切な値に設定でき、現像ローラのゴム弾性を良好なものにできる。一方で、主鎖を構成する主な繰り返し単位に飽和炭化水素単位からなる重合体を採用すると、低吸水率の硬化物が得られ、その電気抵抗の環境変動が少なく、現像ローラの時定数の環境変動も少なくなり、耐久性の高い現像ローラを得ることが可能となる。
【図面の簡単な説明】
【図１】現像ローラとその周辺の構成とを示す説明図。
【符号の説明】
１ 現像ローラ
２ 導電性シャフト
３ 弾性層
４ 表面層
５ トナー
６ 供給ローラ
７ 規制ブレード
８ トナー薄層
９ 感光体
１０ トナー像[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an improvement of a developing roller incorporated in an apparatus employing an electrophotographic method, a back exposure method (so-called chargeless method), or an electrostatic recording method, such as a printer, a copying machine, or a facsimile receiving device.
[0002]
[Prior art]
In an apparatus that employs an electrophotographic system, a charging roller that uniformly supplies charges to the electrostatic latent image carrier around the electrostatic latent image carrier such as a photoconductor, and toner is supplied to the electrostatic latent image carrier. Various rollers such as a developing roller for transferring and a transfer roller for transferring the toner image onto the recording paper are arranged. Of these various rollers, the developing roller is the most important and requires various characteristics.
[0003]
FIG. 1 is a cross-sectional view schematically showing a developing device adopting a non-magnetic developing method using non-magnetic one-component toner 5,. The developing roller 1 is configured by sequentially laminating a conductive elastic layer 3 concentrically around a conductive shaft 2 made of SUS or aluminum alloy, and coating the surface layer 4 on the conductive elastic layer. . A voltage is applied between the conductive shaft 2 and the surface of the developing roller. The toners 5,... Are reliably attached to the surface of the developing roller by the supply roller 6, and are triboelectrically charged by the regulating blade 7 and the surface of the developing roller to become the toner thin layer 8, and then the photosensitive member which is an electrostatic latent image carrier. The toner image 10 is supplied to the surface 9.
[0004]
Therefore, the charging characteristics of the toner greatly depend on the material and surface structure of the surface layer of the developing roller. For the surface layer, from the viewpoint of controlling the charging characteristics of the toner, when the toner is negatively charged, a material having a frictional charge train on the positive side with respect to the toner is often selected. For example, styrene-acrylic or polyester-based and negatively chargeable toners are often used as toners, whereas the surface layer has nylon-based resins or urethanes that have a triboelectric charge train on the positive side with respect to these toners. A lot of resin is used.
[0005]
Further, the surface layer is required to have toner releasability in addition to the above characteristics. This is because, when the developing roller is used for a long period of time, the surface of the developing roller is covered with a toner that does not contribute to the development and the developing characteristics deteriorate, so-called toner filming occurs. In the case of a developing roller that supplies toner in contact with the photoreceptor, if the toner filming deteriorates, the photoreceptor may be contaminated by toner that does not contribute to development. Accordingly, in order to prevent toner filming, a urethane-based resin (for example, a reaction cured product of a fluorine polyol and a polyisocyanate) having fluorine-containing particles added to the resin constituting the surface layer or a fluorine-containing component in the surface layer. The method of using is taken.
[0006]
[Problems to be solved by the invention]
For the surface layer of the developing roller, it is preferable to use a material that satisfies the above-mentioned characteristics such as toner charging characteristics and toner releasability in a well-balanced manner. However, the toner filming problem still remains unsolved.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a developing roller that has the most important characteristic for preventing toner filming among the characteristics required for the surface of the developing roller and aims to improve durability. To do.
[0008]
[Means for Solving the Problems]
As a result of diligent investigations to solve the above problems, the present inventors have found that the electrostatic capacity of the developing roller and the elastic layer is closely related to toner filming, and as a result of further investigation, The present invention has been completed.
[0009]
That is, the present invention relates to a developing roller in which a conductive shaft is disposed on a central axis, an elastic layer is formed around the conductive shaft, and a surface layer is sequentially stacked concentrically on the elastic layer. The layer is mainly composed of a polyamide or polyurethane resin, or a copolymer mainly composed of one or both of an acrylate monomer and a methacrylate monomer and a vinyl carboxylate monomer, The elastic layer comprises (A) a polymer containing at least one alkenyl group in the molecule, and a repeating unit constituting the main chain mainly consisting of an oxyalkylene unit or a saturated hydrocarbon unit; and (B) a molecule in the molecule. A curing agent comprising at least two hydrosilyl groups, (C) a hydrosilylation catalyst, and (D) a conductivity-imparting agent. Capacitance C of the entire developing roller ₁ Has a value of 0.5 nF to 2.5 nF, and the capacitance C of the elastic layer ₂ Has a value of 0.8 nF or more and 20 nF or less, and the capacitance C of the elastic layer ₂ And the electrostatic capacity C of the entire developing roller ₁ Ratio C ₂ / C ₁ Is a developing roller having a value of 1.1 or more and 11 or less.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, various typical examples according to the present invention will be described.
In the developing roller of this embodiment, an elastic layer is provided concentrically around a metal shaft made of SUS or aluminum alloy having a diameter of about 1 to 12 mm, and the outer peripheral surface of the elastic layer is covered with a surface layer. Is. Here, a resistance adjustment layer for adjusting the electric resistance of the developing roller, a primer layer for improving the adhesion between the elastic layer and the surface layer, and the like are included between the elastic layer and the surface layer. Sometimes. In the present invention, the method for forming the surface layer is not particularly limited. For example, depending on the viscosity of the resin component constituting the surface layer, dipping, spraying, roll coating, brush coating, etc. It may be applied to the outer peripheral surface of the elastic layer, which is the main base material layer of the developing roller, and dried to form a surface layer. Here, the surface layer is formed with a predetermined thickness of 10 to 150 μm.
[0014]
The greatest feature of the present invention is that it gives a certain limit to the electrostatic capacity of the developing roller before and after the surface layer coating. The electrostatic capacity of the developing roller of the present invention means that the developing roller is laid on the flat plate electrode, a load of 500 g is applied to both ends of the shaft, and the surface of the developing roller is pressed against the flat plate electrode. Obtained by measurement between the electrode and the plate electrode. In the present invention, the electrostatic capacity of the developing roller before coating the surface layer is simply referred to as the electrostatic capacity of the elastic layer.
[0015]
Therefore, the developing roller of this example has a capacitance C after the surface layer coating. ₁ Has a value of 2.5 nF or less, and the capacitance C of the elastic layer ₂ Is configured to have a value between 0.8 nF and 20 nF. As a result, toner filming on the surface of the developing roller is prevented. Furthermore, this developing roller has a capacitance C of the elastic layer. ₂ And electrostatic capacity C of the entire developing roller ₁ Ratio C to ₂ / C ₁ Is configured to have a value between 1.1 and 11 inclusive.
[0016]
Capacitance C after surface layer coating ₁ Has a value of 2.5 nF or less, and the capacitance C of the elastic layer ₂ The reason why toner filming is suppressed on the surface of the developing roller having a value of 0.8 nF to 20 nF is considered as follows. That is, in terms of electric circuit, the developing roller can be regarded as an elastic layer and a surface layer connected in series. Immediately after the toner adhering to the surface of the developing roller moves to the photosensitive member, electric charges that are equal to the absolute value of the total charge amount of the moved toner and have the opposite polarity remain on the surface of the developing roller. Capacitance C of developing roller after surface layer coating ₁ By setting the value to 2.5 nF or less, the time constant of the developing roller (product of electrostatic capacity and electrical resistance) becomes sufficiently small, and the charge injected from the shaft side can quickly move to the surface layer, and the remaining charge Neutralize immediately. Since this neutralization is performed quickly, electrostatic adhesion of toner that does not contribute to development on the surface of the developing roller can be suppressed, and toner filming can be prevented. Therefore, a uniform toner thin layer can be formed on the surface of the developing roller using only the toner that contributes to the development. Here, the capacitance C of the elastic layer ₂ Has a value of 0.8 nF or more and 20 nF or less, the balance between the electric resistance and the electrostatic capacity of the developing roller becomes good, and the developing roller adheres non-magnetic one-component toner to the surface of the photoconductor. It is possible to function effectively to supply to.
[0017]
In this embodiment, the capacitance C ₁ Has a value less than or equal to 2.5 nF and 1.1 ≦ C ₂ / C ₁ A developing roller satisfying the relational expression ≦ 11 is employed. This is because an excessive voltage is applied to either one of the elastic layer and the surface layer during development, so that dielectric breakdown or the like does not occur.
[0018]
Specifically, the elastic layer of such a developing roller is
(A) a polymer comprising at least one alkenyl group in the molecule, wherein the repeating unit constituting the main chain is mainly an oxyalkylene unit or a saturated hydrocarbon-based unit;
(B) a curing agent containing at least two hydrosilyl groups in the molecule;
(C) a hydrosilylation catalyst;
(D) a conductivity imparting agent;
It is comprised from the reaction material of the curable composition which has as a main component.
[0019]
The polymer of the component (A) in this curable composition is a component that is cured by a hydrosilylation reaction with the component (B) and contains at least one alkenyl group in the molecule, so that the hydrosilylation reaction occurs. It becomes polymer and hardens. The number of alkenyl groups contained in component (A) is at least one from the viewpoint of hydrosilylation reaction with component (B), but from the viewpoint of obtaining sufficient rubber elasticity, In this case, it is preferred that two alkenyl groups exist at both ends of the molecule, and in the case of a branched molecule, two or more alkenyl groups exist at the molecule end. (A) The main repeating unit which comprises the principal chain of a component is an oxyalkylene unit or a saturated hydrocarbon unit.
[0020]
First, the case where the main repeating unit constituting the main chain of the component (A) is a polymer composed of oxyalkylene units will be described. At this time, if a small amount of the conductivity imparting agent as component (D) is added to the cured product, the volume resistivity of the cured product is 10 ⁸ Ωcm ~ 10 ⁹ Since it becomes Ωcm, it is preferable. From the viewpoint of reducing the hardness of the cured product, an oxyalkylene polymer in which the repeating unit is an oxyalkylene unit, and an oxypropylene polymer in which the repeating unit is an oxypropylene unit are desirable.
[0021]
Here, the oxyalkylene polymer refers to a polymer comprising 30% or more, preferably 50% or more of oxyalkylene units among the units constituting the main chain. The unit contained in addition to the oxyalkylene unit is a compound containing two or more active hydrogens used as a starting material in polymer production, such as ethylene glycol, bisphenol compounds, glycerin, trimethylolpropane, pentaerythritol, etc. Units. When the repeating unit is oxypropylene-based, it may be a copolymer (including a graft copolymer) with a unit composed of ethylene oxide, butylene oxide, or the like.
[0022]
The molecular weight of such an oxyalkylene polymer is 500 to 50,000, more preferably 1,000 to 40,000 in terms of number average molecular weight (Mn) from the viewpoint of improving the balance between reactivity and low hardness. It is preferable. In particular, those having a number average molecular weight of 5,000 or more, more preferably 5,000 to 40,000 are preferred. When the number average molecular weight is less than 500, it becomes difficult to obtain sufficient mechanical properties (rubber hardness, elongation) and the like when the curable composition is cured. On the other hand, if the number average molecular weight is too large, the molecular weight per alkenyl group contained in the molecule increases, or the reactivity decreases due to steric hindrance, often resulting in insufficient curing, The viscosity tends to be too high and the processability tends to deteriorate.
[0023]
In addition, although there is no restriction | limiting in particular in the alkenyl group which the said oxyalkylene type polymer has, the alkenyl group shown by following General formula (1) is especially preferable at the point which is excellent in sclerosis | hardenability.
[0024]
H ₂ C = C (R ¹ -(1)
(Wherein R ¹ Is a hydrogen atom or a methyl group)
[0025]
One of the characteristics of this curable composition is that it is easy to reduce the hardness. In order to exhibit this characteristic, it is preferable that the number of alkenyl groups be 2 or more at the molecular end. However, if the number of alkenyl groups is too large compared to the molecular weight of the component (A), it becomes rigid and it becomes difficult to obtain good rubber elasticity.
[0026]
Next, the case where the component (A) is a polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon unit will be described. This polymer is preferable in that a cured product having a low water absorption rate and a small environmental fluctuation of electrical resistance can be obtained. Similarly to the case of the oxyalkylene polymer, the component (B) is a component that is cured by a hydrosilylation reaction and has at least one alkenyl group in the molecule. It becomes molecular and hardens. Further, the number of alkenyl groups contained in the component (A) is at least one from the viewpoint of hydrosilylation reaction with the component (B), but from the viewpoint of obtaining good rubber elasticity, In some cases, two molecules are preferably present at both ends of the molecule, and in the case of a branched molecule, two or more molecules are preferably present at the molecule end.
[0027]
Typical examples of the polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon unit include an isobutylene polymer, a hydrogenated isoprene polymer, and a hydrogenated butadiene polymer. These polymers may contain repeating units of other components such as a copolymer, but contain at least saturated hydrocarbon units of 50% or more, preferably 70% or more, more preferably 90% or more. This is important in order not to impair the feature of the saturated hydrocarbon system having a low water absorption rate.
[0028]
As the molecular weight of the polymer of the component (A) in which the main repeating unit constituting this main chain is a saturated hydrocarbon unit, the number average molecular weight (Mn) is about 500 to 50,000, and further 1,000 to 15 It is about 1,000, and is preferably a liquid and fluid at room temperature in terms of ease of handling and workability.
[0029]
The alkenyl group introduced into such a saturated hydrocarbon polymer is the same as in the case of the oxyalkylene polymer.
[0030]
Therefore, as a preferred specific example of the polymer containing at least one alkenyl group in the molecule as the component (A) and the main repeating unit constituting the main chain being a saturated hydrocarbon unit, Polyisobutylene, hydrogenated polybutadiene, hydrogenated, having two groups, linear number average molecular weight (Mn) of 2,000 to 15,000 and Mw / Mn of 1.1 to 1.2 Examples include polyisoprene polymers.
[0031]
Further, the component (B) in the curable composition is not particularly limited as long as it is a compound having at least two hydrosilyl groups in the molecule, but if the number of hydrosilyl groups contained in the molecule is too large, Since a large amount of hydrosilyl groups are likely to remain in the cured product later and cause voids and cracks, the number of hydrosilyl groups contained in the molecule is preferably 50 or less. Furthermore, this number is preferably 2 to 30, more preferably 2 to 20, from the viewpoint of control of rubber elasticity of the cured product and storage stability, and further, it easily prevents foaming during curing. In terms of 20 or less, and 3 in that it is difficult to cause poor curing even when the hydrosilyl group is deactivated, the most preferable range is 3 to 20.
[0032]
By the way, in the present invention, having one hydrosilyl group means having one H bonded to Si. ₂ In this case, it means that it has two hydrosilyl groups. However, it is preferable from the viewpoint of curability and rubber elasticity that H bonded to Si is bonded to different Si.
[0033]
The molecular weight of the component (B) is 30,000 or less in terms of number average molecular weight (Mn) from the viewpoint of dispersibility and roller processability when the conductivity imparting agent as the component (D) is added. More preferably 20,000 or less, and particularly preferably 15,000 or less. Considering the reactivity and compatibility with the component (A), the number average molecular weight is preferably 300 to 10,000.
[0034]
Regarding the component (B), the cohesive force of the component (A) is larger than the cohesive force of the component (B), so that phenyl group-containing modification is important in terms of compatibility. A styrene modified product is preferable in terms of compatibility and availability, and an α-methylstyrene modified product is preferable in terms of storage stability.
[0035]
In addition, the hydrosilylation catalyst as component (C) is not particularly limited as long as it can be used as a hydrosilylation catalyst. Platinum alone, solid platinum supported on a simple substance such as alumina, chloroplatinic acid (Including complexes such as alcohols), platinum complexes, and chlorides of metals such as rhodium, ruthenium, iron, aluminum, and titanium. Among these, chloroplatinic acid, platinum-olefin complexes, and platinum-vinylsiloxane complexes are desirable from the viewpoint of catalytic activity. These catalysts may be used alone or in combination of two or more.
[0036]
As a use ratio of the component (B) to the component (A) in the curable composition as described above, the hydrosilyl group in the component (B) is 0.2 to 5 per mole of the alkenyl group in the component (A). It is preferable from the point of obtaining good rubber elasticity that it is set to be present in an amount of 0.0 mol, and further 0.4 to 2.5 mol.
[0037]
The amount of component (C) used is 10 with respect to 1 mole of alkenyl group in component (A). ^-1 -10 ^-8 Mole, especially 10 ^-3 -10 ^-6 It is preferably used in a molar range. The amount of component (C) used is 10 ^-8 The reaction does not proceed if the molarity is not reached. On the other hand, the hydrosilylation catalyst is generally expensive and corrosive, and has a property that a large amount of hydrogen gas is generated and the cured product is foamed. ^-1 It is preferable not to use more than a mole.
[0038]
Furthermore, if the electroconductivity imparting agent which is (D) component is added to the above-mentioned curable composition and it is set as an electroconductive composition, it is suitable as a developing roller. Examples of the conductivity imparting agent of the component (D) include carbon black, metal fine powder, and organic compounds having a quaternary ammonium base, a carboxylic acid group, a sulfonic acid group, a sulfate ester group, a phosphate ester group, and the like. Alternatively, an antistatic agent such as a polymer, an ether ester amide, an ether imide polymer, an ethylene oxide-epihalohydrin copolymer, a compound having a conductive unit represented by methoxypolyethylene glycol acrylate, or a polymer compound, The compound etc. which can provide electroconductivity can be mentioned. These conductivity-imparting agents may be used alone or in combination of two or more.
[0039]
In addition, it is preferable from the point which does not raise rubber hardness that the addition amount of the electroconductivity imparting agent which is (D) component shall be 30 weight% or less with respect to the total amount of (A)-(C) component. On the other hand, in order to obtain a uniform volume resistance, the addition amount is preferably 10% by weight or more, and the volume resistance of the cured product is 10%. ^Three -10 ^Ten The addition amount is preferably determined so as to be Ωcm.
[0040]
Furthermore, the curable composition contains, in addition to the components (A) to (D), a storage stability improver, for example, a compound having an aliphatic unsaturated bond, an organic phosphorus compound, an organic sulfur compound, and a nitrogen content. A compound, a tin compound, an organic peroxide, or the like may be added. Specific examples thereof include, but are not limited to, benzothiazole, thiazole, dimethyl malate, dimethyl acetylene carboxylate, 2-pentenenitrile, 2,3-dichloropropene, quinoline, and the like. Among these, thiazole and dimethyl malate are particularly preferable from the viewpoint of achieving both pot life and fast curability. In addition, the said storage stability improving agent may be used independently and may be used together with 2 or more types.
[0041]
Further, from the viewpoint of improving processability and cost, a filler, a storage stabilizer, a plasticizer, an ultraviolet absorber, a lubricant, a pigment and the like may be added to the curable composition.
[0042]
Next, the surface layer coated on the elastic layer will be described. This surface layer is preferably composed of a resin composition mainly composed of polyamide or polyurethane having —NHCO— bond in consideration of the charging property of the toner, and considering the elasticity and electric resistance of the surface layer, Among polyurethanes, those having a polyether skeleton are preferred. From the viewpoint of environmental stability, -ROCO such as a polycarbonate skeleton among polyurethanes. ₂ A resin composition containing as a main component a resin having a repeating unit of-or an acrylic-modified polyurethane such as polymethyl methacrylate can be used, and a blend resin obtained by blending these can also be used.
[0043]
Specific examples of the polyamide include nylon obtained by modifying a part of hydrogen of —NHCO— bond and methoxymethylating, but the present invention is not limited thereto.
[0044]
Specific examples of the polycarbonate urethane include -ROCO ₂ In general, -R is a bisphenol A type, but the present invention is not limited to this, and may be a modified form of bisphenol A, an alicyclic group, an alkyl group, or the like. Absent. Considering the balance between low hardness and low absorption rate, this is preferably an alkyl group.
[0045]
An example of the blend resin is a blend resin of polyamide or polyurethane resin diluted in tetrahydrofuran, dimethylformamide, or the like.
[0046]
Moreover, as the surface layer, a resin composition containing an acrylic-vinyl carboxylate copolymer as a main component can be used. The acrylic-vinyl carboxylate copolymer is a total amount of acrylic ester monomer component, methacrylic ester monomer component and vinyl carboxylate monomer component in the resin component of 50% by weight or more, preferably 80% by weight or more. And a copolymer containing a vinyl carboxylate monomer component in the resin component in an amount of 3% by weight or more, preferably 5% by weight or more, and more preferably 10% by weight or more.
[0047]
Examples of the vinyl carboxylate monomer component include vinyl acetate, vinyl propionate, vinyl valerate, and vinyl isovalerate from the viewpoint that the polymerization proceeds well. Among these, vinyl acetate is particularly preferably used because it is easily available and the toner is negatively charged.
[0048]
Examples of the acrylate monomer component include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate and the like from the viewpoint that polymerization proceeds well. Examples of the methacrylic acid ester monomer component include methyl methacrylate, ethyl methacrylate, and butyl methacrylate from the viewpoint that the polymerization proceeds well. Among these, methyl methacrylate is preferable because it is easily available.
[0049]
【Example】
Now, specific examples of the developing roller according to the present invention will be described below. 1-4 and 6 After explaining in detail, the comparative example which is these developing roller and the conventional developing roller 1-3 Compare with.
[0050]
First, the elastic layer uses the following three types. These elastic layers 1 to 3 are all formed with a thickness of 7.5 mm on a SUS shaft having a diameter of 10 mm.
[0051]
The elastic layer 1 is produced as follows. That is,
(A-1) For 100 parts by weight of the terminal allylated polyoxypropylene polymer having a number average molecular weight (Mn) of 8,000 and a molecular weight distribution of 2,
(B-1) 6.6 parts by weight of a polysiloxane curing agent (SiH value 0.36 mol / 100 g),
(C-1) 0.06 parts by weight of a 10% isopropyl alcohol solution of chloroplatinic acid,
(D-1) 8 parts by weight of carbon black 3030B (manufactured by Mitsubishi Chemical Corporation),
And a composition obtained by degassing under a reduced pressure of 10 mmHg or less for 120 minutes is coated on a shaft and allowed to stand for 30 minutes in an environment of 120 ° C. in a mold to be cured. An elastic layer 1 made of a 5 mm rubber elastic body was produced. Capacitance C of this elastic layer 1 ₂ Was 18.5 nF.
[0052]
The elastic layer 2 is produced as follows. That is,
(A-2) The number average molecular weight (Mn) is 10,000, and 100 parts by weight of the polyisobutylene polymer having two vinyl groups at the terminals,
(B-2) 2.7 parts by weight of a polysiloxane curing agent (SiH value 0.36 mol / 100 g),
(C-2) 0.06 part by weight of a 10% isopropyl alcohol solution of chloroplatinic acid,
(D-2) 10 parts by weight of carbon black 3030B (Mitsubishi Chemical Corporation),
(E) 75 parts by weight of a plasticizer PS-32 (made by Idemitsu Kosan Co., Ltd.)
The above composition was coated on the shaft and allowed to stand for 30 minutes in a mold at 120 ° C. for curing to prepare an elastic layer 2 made of a rubber elastic body having a thickness of 7.5 mm. Capacitance C of this elastic layer 2 ₂ Was 10.3 nF.
[0053]
The elastic layer 3 is produced as follows. That is, the components (A-1), (B-1) and (C-1) of the elastic layer 1 and 5 parts by weight of (D-3) carbon black 3030B (manufactured by Mitsubishi Chemical Corporation) are mixed. A composition obtained by vacuum degassing for 120 minutes at 10 mmHg or less is coated on a shaft, allowed to stand for 30 minutes in a mold at 120 ° C. for 30 minutes, and cured with a rubber elasticity of 7.5 mm. An elastic layer 3 made of a body was produced. Capacitance C of this elastic layer 3 ₂ Was 1.2 nF.
[0054]
Next, the developing roller which coat | covered the outer surface of these elastic layers with the surface layers 1-5 shown below was produced, and it was set as Examples 1-6. These examples satisfy the relational expression of capacitance according to the present invention.
[0055]
In Example 1, the outer peripheral surface of the elastic layer 1 was dipped with a solution obtained by diluting an ether-based urethane solution (Himlen Y-237: manufactured by Dainichi Seika Co., Ltd.) with a mixed solution of cyclohexanone and dimethylformamide, and the oven was heated at 80 ° C. The surface layer 1 having a thickness of 20 μm obtained by drying for 1 hour is formed.
[0056]
In Example 2, a solution obtained by diluting an ether-based urethane solution (Himlen Y-258: manufactured by Dainichi Seika Co., Ltd.) with a mixed solution of methyl ethyl ketone and dimethylformamide was dipped on the outer peripheral surface of the elastic layer 2, and an oven at 80 ° C. The surface layer 2 having a thickness of 20 μm obtained by drying for 1 hour is formed.
[0057]
In Example 3, a solution obtained by diluting a carbonate urethane solution (Rezamin ME8220LP: manufactured by Dainichi Seika Co., Ltd.) with methyl ethyl ketone to a solid content of 5% by weight was dipped on the outer peripheral surface of the elastic layer 2, and an oven at 80 ° C. The surface layer 3 having a thickness of 10 μm obtained by drying for 1 hour is formed.
[0058]
In Example 4, the surface layer 3 used in Example 3 is formed on the outer peripheral surface of the elastic layer 3.
[0059]
Comparative Example 3 Is a thickness obtained by dipping a solution obtained by diluting methoxymethylated nylon (EM-20: manufactured by Lead City Corporation) with methanol on the outer peripheral surface of the elastic layer 1 and drying it in an oven at 80 ° C. for 1 hour. A surface layer 4 having a thickness of 15 μm is formed.
[0060]
And Example 6 dipped on the outer peripheral surface of the elastic layer 1 a solution obtained by diluting an acrylic-vinyl acetate copolymer (Kanevirak L-DBF: Kaneka Chemical Co., Ltd.) with ethyl acetate, The surface layer 5 having a thickness of 10 μm obtained by drying for 1 hour in an oven is formed.
[0061]
On the other hand, developing rollers in which the outer peripheral surface of the elastic layer was coated with the following two types of surface layers were designated as Comparative Examples 1 and 2. These comparative examples do not satisfy the relational expression of capacitance according to the present invention.
[0062]
In Comparative Example 1, on the outer peripheral surface of the elastic layer 1, copolymer nylon (CM-8000: manufactured by Toray Industries, Inc.) was diluted with methanol, and then Elecut S512 (quaternary ammonium salt: manufactured by Takemoto Yushi Co., Ltd.) A surface layer 6 having a thickness of 20 μm obtained by dipping a solution obtained by adding 10 parts by weight to 100 parts by weight of 8000 and drying it in an oven at 80 ° C. for 1 hour is formed.
[0063]
In Comparative Example 2, methoxymethylated nylon (EM-20: manufactured by Lead City) was diluted with methanol on the outer peripheral surface of the elastic layer 1, and then KKS-001 (acrylic polymer: manufactured by Takemoto Yushi Co., Ltd.) The surface layer 7 having a thickness of 15 μm obtained by dipping a solution added with 20 parts by weight with respect to 100 parts by weight of −20 and drying in an oven at 80 ° C. for 1 hour is formed.
[0064]
Examples thus obtained 1-4, 6 And comparative examples 1-3 Table 1 shows the results obtained by measuring the electrostatic capacity. As for toner filming, a developing roller is installed in a commercially available printer (6 ppm), a durability image output test is performed for 5 hours using a polyester-based toner, and the surface of the developing roller after the test is visually observed. evaluated. In this evaluation, good samples in which toner adhesion was not observed on the surface layer were indicated by ◯, those in which toner adhesion was slightly observed were indicated by Δ, and those in which toner adhesion was clearly observed were indicated by ×.
[0065]
[Table 1]

[0066]
As this result shows, the electrostatic capacity C of the entire developing roller ₁ Has a value of 2.5 nF or less, and the capacitance C of the elastic layer ₂ It can be seen that toner filming is reliably prevented in the example in which the value of 0.8 nF to 20 nF.
[0067]
【The invention's effect】
As described above, the present invention provides the electrostatic capacity C of the entire developing roller. ₁ Has a value of 2.5 nF or less, and the capacitance C of the elastic layer ₂ Is a developing roller with a value of 0.8 nF to 20 nF, the time constant of the developing roller is sufficiently small to prevent electrostatic adhesion of toner that does not contribute to development, preventing toner filming on the surface of the developing roller Therefore, it is possible to improve the durability of the developing roller. Furthermore, the present invention provides 1.1 ≦ C ₂ / C ₁ When configured so as to satisfy the relational expression ≦ 11, the balance of the voltage applied to each of the elastic layer and the surface layer can be properly maintained during development, and the development roller can be prevented from dielectric breakdown. Can do.
[0068]
In addition, when a surface layer mainly composed of polyamide or polyurethane resin is used, a surface layer having good elasticity and less electrical fluctuation in electrical resistance can be obtained, and a more durable developing roller can be produced. Is possible. On the other hand, if the surface layer uses one or both of an acrylate monomer and a methacrylic acid ester monomer, and a copolymer mainly composed of a vinyl carboxylate monomer as a main component, toner chargeability is improved. It is possible to produce a developing roller that is advantageous in terms of improvement.
[0069]
Furthermore, in the reaction product of the curable composition used as the elastic layer of the present invention, when a polymer composed of oxyalkylene units is adopted as the main repeating unit constituting the main chain, a small amount of a conductivity-imparting agent can be added. Since the volume resistivity of the cured product can be easily set and the hardness can be easily reduced, the time constant of the developing roller can be set to an appropriate value, and the rubber elasticity of the developing roller can be improved. On the other hand, when a polymer composed of saturated hydrocarbon units is adopted as the main repeating unit constituting the main chain, a cured product having a low water absorption rate is obtained, the environmental resistance fluctuation is small, and the time constant of the developing roller is reduced. Environmental fluctuation is also reduced, and a highly durable developing roller can be obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory view showing a developing roller and its peripheral configuration.
[Explanation of symbols]
1 Development roller
2 Conductive shaft
3 Elastic layer
4 Surface layer
5 Toner
6 Supply roller
7 Regulatory blade
8 Toner thin layer
9 Photoconductor
10 Toner image

Claims (1)

In the developing roller, in which a conductive shaft is arranged on the central axis, an elastic layer is formed around the conductive shaft, and a surface layer is sequentially stacked concentrically on the elastic layer.
The surface layer is composed mainly of a polyamide or polyurethane resin, or a copolymer mainly composed of one or both of an acrylate monomer and a methacrylate monomer and a vinyl carboxylate monomer,
The elastic layer comprises (A) a polymer containing at least one alkenyl group in the molecule, and a repeating unit constituting the main chain mainly consisting of an oxyalkylene unit or a saturated hydrocarbon unit; and (B) a molecule in the molecule. A curing agent comprising at least two hydrosilyl groups, (C) a hydrosilylation catalyst, and (D) a conductivity-imparting agent.
The electrostatic capacity C _{1 of the} entire developing roller has a value of 0.5 nF to 2.5 nF, the electrostatic capacity C ₂ of the elastic layer has a value of 0.8 nF to 20 nF, and the elastic layer A developing roller characterized in that the ratio C ₂ / C ₁ between the electrostatic capacity C ₂ and the electrostatic capacity C ₁ of the entire developing roller has a value of 1.1 or more and 11 or less.

Images