JP2000010403A - Developing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller by which the developing characteristic of the developing roller used in a non-magnetic developing system is stabilized and whose the environmental characteristic is excellent even through the peripheral environment is fluctuated. SOLUTION: As to a developing roller for an electrophotographic system by which toner adheres to an electrostatic latent image on the surface of an electrostatic latent image carrier, the developing roller is made by concentrically forming an elastic layer around a conductive shaft and single or plural resin layers on the elastic layer. At the same time, the ratio CL/CH of the capacitance CL of the developing roller measured under the environment of 10 deg.C and relative humidity 15% and the capacitance CH of the developing roller measured under the environment of 40 deg.C and the relative humidity 90% is within the range of >=0.2 and <=0.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a developing roller incorporated in an electrophotographic image forming apparatus such as a printer, a copying machine or a facsimile receiving apparatus.

[0002]

2. Description of the Related Art In an image forming apparatus adopting an electrophotographic system, a charging roller for uniformly charging the surface of an electrostatic latent image carrier and toner carrying an electrostatic latent image are provided around the electrostatic latent image carrier. Various rollers such as a developing roller for supplying to the body and a transfer roller for transferring the toner image to the recording paper are arranged. The method of carrying the toner on the surface of the developing roller and moving the toner to the electrostatic latent image is largely divided into a non-magnetic developing method and a magnetic developing method. The magnetic developing method is a method in which a magnetic toner is adhered to the surface of a developing roller by magnetic force, and the non-magnetic developing method is a method in which non-magnetic toner is adhered to the surface of a developing roller by electrostatic force without using magnetic force. is there. The non-magnetic developing method has attracted attention in recent years because it has the advantages that the toner can be easily colored and a good halftone image can be obtained in monochrome image formation, as compared with the magnetic developing method.

FIG. 1 is a schematic diagram showing an example of a developing device 1 disposed in an image forming apparatus employing a non-magnetic developing system and a photosensitive member 2 serving as an electrostatic latent image carrier. As the photoconductor 2, a negatively chargeable organic photosensitive drum or the like is used. The developing device 1 includes a toner container 4 for storing the non-magnetic toner 3, a regulating blade 5 provided in the toner container 4, a developing roller 6, a supply roller 7, and the like. The developing roller 6 is provided around a conductive support 8 such as a metal shaft.
An elastic layer 9 having rubber elasticity is formed, and a resin layer 10 for improving the chargeability of the toner and preventing toner filming is coated around the elastic layer 9. The toner 3 in the toner container is supplied to the surface of the developing roller 6 by the supply roller 7 and then pressed by the regulating blade 5 to form a thin toner layer. When the toner becomes a thin toner layer, the toner is charged electrically and frictionally. The thin toner layer is electrostatically attracted to the electrostatic latent image on the surface of the photoreceptor 2 and becomes a toner image on the surface of the photoreceptor 2, thereby performing development.

[0004]

Although the developing roller greatly affects the charging characteristics of the toner, the operating environment of the developing roller varies from a low-temperature and low-humidity environment in winter to a high-humidity environment in the rainy season and a high-temperature environment in summer. Therefore, it is required that the charging characteristics of the toner be kept stable even when the surrounding temperature and humidity change. Generally, in a low-humidity environment, the toner tends to be excessively charged, and the image force (Coulomb force) acting between the toner and the surface of the developing roller increases. The amount of toner that moves to becomes smaller. As a result, the image density is reduced. Also, under high humidity environment, the toner becomes insufficiently charged,
It can cause image defects called fog. The present invention has been made in view of such a problem, even if the surrounding environment fluctuates.
An object of the present invention is to provide a developing roller having excellent environmental characteristics by stabilizing the developing characteristics of a developing roller used in a non-magnetic developing system.

[0005]

Means for Solving the Problems The present inventors have solved the above problems.
As a result of intensive research to solve the problem,
The present inventors have found that capacity is closely related to development characteristics, and
Was completed. That is, the present invention relates to an electrophotographic system.
Wherein the developing roller is a conductive shuffling roller.
Layer around the elastic layer, and one or more resin layers on the elastic layer
Are formed concentrically, and the relative humidity is 10 ° C.
The capacitance C of the developing roller measured under an environment of 15%
_LAnd development measured at 40 ° C. and 90% relative humidity
Roller capacitance C_HRatio C_L / C_HIs 0.2 or more and 5.0
A developing roller (Claim 1) comprising: a main component of an outermost layer (hereinafter referred to as a surface layer) of the resin layer;
And characterized by using polycarbonate urethane
The developing roller according to claim 1, wherein the main component of the outermost layer (surface layer) of the resin layer is acrylic.
Luster ester monomer and methacrylate ester monomer
And / or vinyl carboxylate monomer
-Acrylic-vinyl carboxylate copolymer
2. The developing roller according to claim 1, wherein a developing member is used.
(Claim 3) The elastic layer (A) has at least one alkene in a molecule.
And the repeating unit constituting the main chain is oxyal
A polymer which is a kylene unit or a saturated hydrocarbon unit,
(B) having at least two hydrosilyl groups in the molecule
Curing agent, (C) hydrosilylation catalyst, and (D) conductive
From the reaction product of the curable composition containing the
The method according to any one of claims 1 to 3, wherein
The developing roller according to claim 4.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various embodiments according to the present invention will be described. The developing roller according to the present invention is provided with an elastic layer concentrically around a conductive shaft made of SUS, aluminum or a conductive resin having a diameter of about 1 to 12 mm, and has a predetermined thickness of 10 μm to 150 μm on the outer peripheral surface thereof. It is constituted by covering the surface layer. A single layer or a plurality of primer layers may be formed between the elastic layer and the surface layer, and a primer layer for improving adhesion between the layers may be formed.

As shown in FIG. 2, the capacitance according to the present invention is obtained by applying a load of 500 g to both ends of the shaft in the direction of the plate electrode while pressing a roller in parallel to the plate electrode. This is to measure the capacitance between the plate electrode. The developing roller according to the present invention has a capacitance C _L measured in an environment (hereinafter referred to as an LL environment) of 10 ° C. and a relative humidity of 15% (hereinafter abbreviated as RH) with respect to the capacitance obtained by the measuring method. And a configuration in which the ratio C _L / C _{H of the} capacitance C _H measured in an environment of 40 ° C. and 90% RH (hereinafter referred to as an HH environment) is 0.2 or more and 5.0 or less. It is.

Considering the state in which toner adheres to the surface of the developing roller in terms of an electric circuit, the developing roller and the toner layer are each regarded as a capacitor. When both are connected in series, the amount of charge stored in the toner layer And the amount of charge stored in the developing roller becomes equal. The amount of charge stored in the toner layer is the amount of charge of the toner, and therefore, the amount of charge of the toner has a relationship with the amount of charge stored in the developing roller. Here, the amount of electric charge stored in the developing roller is proportional to the capacitance of the developing roller. Therefore, if the capacitance of the developing roller changes due to fluctuations in the surrounding environment, the charging characteristics of the toner on the surface of the developing roller are adversely affected, and Leads to defects.

The developing roller according to the present invention has a temperature of 10.degree.
And the electrostatic capacitance C _L, measured in an environment of RH%, 40 ℃, 9
Ratio C _L / C _{H of} capacitance C _H measured in an environment of 0% RH
Is 0.2 or more and 5.0 or less, preferably 0.2 or more and 3.0 or less.
The variation of the capacitance of the developing roller is small even if the surrounding environment changes, and the charging characteristics of the toner can be kept stable.

When the capacitance ratio C _L / C _H is out of the above range, as described above, a decrease in image density and image defects such as fog occur. That is, if it is smaller than 0.2, the toner becomes excessively charged in the LL environment, and the image force with the surface of the developing roller becomes too large, so that the toner does not move to the photoreceptor side, leading to a decrease in image density. If it is larger, the absolute value of the toner charge amount is small in both the LL and HH environments, and fog is likely to occur.

The main component of the surface layer of the developing roller contains an -NHCO- bond from the viewpoint of improving the charging characteristics of the negatively charged toner, and contains a polycarbonate skeleton from the viewpoint of environmental stability. Na-ROCO _2-
What is necessary is just to consist of the resin composition which has the resin which has a repeating unit of a main component as a main component.
Polycarbonate urethane or the like having both a —NHCO— bond and a —ROCO ₂ — repeating unit in the molecule may be used.

The polycarbonate urethane includes:
It is preferable that the —R group of the —ROCO ₂ — skeleton is an alicyclic group or an alkyl group. Among these, it is preferable that the -R group be an alkyl group from the viewpoint that a low hardness and a low water absorption of the surface layer can be obtained in a well-balanced manner. Further, the polycarbonate urethane is a compound obtained by reacting a polycarbonate polyol with a polyisocyanate. The polycarbonate polyol is obtained by condensation of a polyhydric alcohol with phosgene, chloroformate, dialkyl carbonate or diallyl carbonate. As the polyhydric alcohol, it is desirable to use 1,6-hexanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, or the like, and the number average molecular weight (Mn) of the polycarbonate polyol is preferably , About 300-1
It is desirably in the range of 5,000. The polycarbonate polyol is preferably used alone, but may be used in combination with a polyester polyol, a polyether polyol or a polyester-polyether polyol.

The polyisocyanates which react with the above-mentioned polycarbonate polyols include tolylene diisocyanate (TDI), 4,4'-diphenylmethane diisocyanate (MDI), xylene diisocyanate (XDI), and hexamethylene diisocyanate (HD).
I), hydrogenated MDI, hydrogenated TDI or isophorone diisocyanate (IPDI) is used. Among these, hydrogenated MDI is considered in consideration of the balance between availability, cost, and various characteristics required for the developing roller.
Alternatively, it is preferable to use IPDI.

On the other hand, as a main component of the surface layer, a resin composition containing an acrylic-vinyl carboxylate-based copolymer as a main component may be used from the viewpoint of reducing environmental fluctuation of capacitance due to moisture absorption or the like. it can. This acrylic
The vinyl carboxylate copolymer is a copolymer in which the total amount of the acrylate ester monomer component, the methacrylate ester monomer component, and the vinyl carboxylate monomer component is 50% by weight or more, preferably 80% by weight or more in the resin component. It is a copolymer in which the vinyl carboxylate monomer component is contained in the resin component in an amount of 3% by weight or more, preferably 5% by weight or more, more preferably 10% by weight or more.

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 favorably. Examples of the methacrylate ester monomer component include methyl methacrylate, ethyl methacrylate, and butyl methacrylate from the viewpoint that polymerization proceeds favorably. Among these, methyl methacrylate is preferred from the viewpoint of availability.

The vinyl carboxylate monomer component includes vinyl acetate, vinyl propionate, vinyl valerate, vinyl isovalerate and the like from the viewpoint that polymerization proceeds favorably. Among these, it is preferable to use vinyl acetate from the viewpoint of availability and favorable negative charging of the toner. Next, as the elastic layer, (A) a polymer having at least one alkenyl group in a molecule and a repeating unit constituting a main chain being an oxyalkylene unit or a saturated hydrocarbon-based unit; A) a curing agent having at least two hydrosilyl groups in the molecule, (C) a hydrosilylation catalyst, and (D)
It is preferable to use a reaction product of a curable composition containing a conductivity imparting agent as a main component.

The polymer of the component (A) in the curable composition is a component which is cured by a hydrosilylation reaction with the component (B) and has at least one alkenyl group in the molecule. Occurs to become a polymer and harden. The number of alkenyl groups contained in the component (A) must be at least one in view of hydrosilylation reaction with the component (B), but from the viewpoint of obtaining sufficient rubber elasticity, the number of In the case of a molecule having two alkenyl groups at both ends of the molecule and having a branch,
It is desirable that two or more alkenyl groups be present at the molecular terminals. The main repeating unit constituting the main chain of the component (A) is an oxyalkylene unit or a saturated hydrocarbon unit.

First, the case where the main repeating unit constituting the main chain of the component (A) is a polymer comprising an oxyalkylene unit will be described. At this time, when a small amount of the conductivity-imparting agent as the component (D) is added to the cured product, the volume resistivity of the cured product becomes 10 ⁸ Ωcm to 10 ⁹ Ωcm, which is preferable when used as a developing roller. . From the viewpoint of lowering 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 preferable.

Here, the oxyalkylene polymer refers to a polymer in which 30% or more, preferably 50% or more, of the units constituting the main chain are composed of oxyalkylene units. The unit contained other than the oxyalkylene unit contains 2 units of active hydrogen used as a starting material in the production of the polymer.
Compounds having at least one such as ethylene glycol,
Units composed of bisphenol compounds, glycerin, trimethylolpropane, pentaerythritol and the like. When the repeating unit is an oxypropylene-based unit, it may be a copolymer (including a graft copolymer) with a unit composed of ethylene oxide, butylene oxide, or the like.

The molecular weight of such an oxyalkylene polymer is from 500 to 50,000 in terms of number average molecular weight (Mn) from the viewpoint of improving the balance between reactivity and low hardness.
0, more preferably 1,000 to 40,000. In particular, those having a number average molecular weight of 5,000 or more,
Further, those having a molecular weight of 5,000 to 40,000 are preferable. 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 alkenyl group 1
Because the molecular weight per unit increases or the reactivity decreases due to steric hindrance, curing often becomes insufficient,
Further, the viscosity tends to be too high and the processability tends to be poor.

The alkenyl group contained in the oxyalkylene polymer is not particularly limited, but an alkenyl group represented by the following general formula (1) is particularly preferable in terms of excellent curability. ^{_{H 2 C = C (R 1}} ) - (1) ( wherein, R ¹ represents a hydrogen atom or a methyl group) In addition, one of the features of this curable composition is that to be set to a low hardness In order to exhibit this characteristic, the number of alkenyl groups is preferably two or more at the molecular terminal. However, if the number of alkenyl groups is too large as compared with the molecular weight of the component (A), the composition becomes rigid and it is difficult to obtain good rubber elasticity.

Next, the case where the component (A) is a polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon-based unit will be described. This polymer is preferable in that it has a low water absorption and a cured product having a small environmental change in electric resistance is easily obtained. Further, similarly to the case of the oxyalkylene-based polymer, the component is a component which is cured by a hydrosilylation reaction with the component (B), 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 required to be at least one from the viewpoint of performing a hydrosilylation reaction with the component (B). However, from the viewpoint of obtaining good rubber elasticity, in the case of a linear molecule, Preferably, two molecules are present at both ends of the molecule, and in the case of a molecule having a branch, two or more molecules are preferably present at the molecular terminals.

Typical examples of the polymer in which the main repeating unit constituting the main chain is a saturated hydrocarbon-based unit include an isobutylene-based polymer, a hydrogenated isoprene-based polymer, and a hydrogenated butadiene-based polymer. . These polymers may contain a repeating unit of another component such as a copolymer, but at least 50% or more of a saturated hydrocarbon-based unit,
It is important that the content is preferably 70% or more, more preferably 90% or more, so as not to impair the characteristic of the saturated hydrocarbon based on low water absorption.

The molecular weight of the component (A) polymer in which the repeating unit constituting the main chain is a saturated hydrocarbon-based unit is about 500 to 50,000 in number average molecular weight (Mn), and more preferably 1,000. ~ 15,000
A liquid material having fluidity at room temperature is preferable in terms of ease of handling and workability. The alkenyl group introduced into such a saturated hydrocarbon polymer is the same as in the case of the oxyalkylene polymer.

Therefore, preferred specific examples of the polymer as component (A), which contains at least one alkenyl group in the molecule and in which the main repeating unit constituting the main chain is a saturated hydrocarbon unit, include: Two alkenyl groups at both ends
And a linear number average molecular weight (Mn) of 2,000 to
Examples thereof include polyisobutylene-based, hydrogenated polybutadiene-based, and hydrogenated polyisoprene-based polymers having 15,000 and Mw / Mn of 1.1 to 1.2.

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 the number of hydrosilyl groups in the molecule is too large. Then, even after curing, a large amount of hydrosilyl groups easily remain in the cured product, causing voids and cracks. Therefore, the number of hydrosilyl groups contained in the molecule is preferably 50 or less. Further, this number is from 2 to 30 in view of control of rubber elasticity of the cured product and storage stability.
, More preferably 2 to 20,
Furthermore, in terms of easily preventing foaming during curing, there are 20
The number is preferably 3 or more, and the most preferable range is 3 to 20 from the viewpoint that hardening failure hardly occurs even when the hydrosilyl group is deactivated.

In the present invention, the above-mentioned hydrosilyl group is
To have one means to have one H bonded to Si. In the case of SiH ₂ , it means to have two hydrosilyl groups, but H bonded to Si is preferably bonded to different Si. It is preferable in terms of curability and rubber elasticity.
The molecular weight of the component (B) is determined from the viewpoints of dispersibility and roller workability when the conductivity imparting agent as the component (D) is added.
The number average molecular weight (Mn) is preferably 30,000 or less, more preferably 20,000 or less, particularly 15.0 or less.
00 or less is preferable. In consideration of the reactivity and compatibility with the component (A), the number average molecular weight is preferably in the range of 300 to 10,000.

Regarding the component (B), since the cohesive force of the component (A) is greater than the cohesive force of the component (B), the phenyl group-containing modification is important in terms of compatibility. Styrene-modified products are preferred in terms of compatibility with the components and availability, and α-methylstyrene-modified products are preferred in terms of storage stability. The hydrosilylation catalyst as the component (C) is not particularly limited as long as it can be used as a hydrosilylation catalyst, and is a simple substance such as simple platinum or alumina on which solid platinum is supported, and chloroplatinic acid ( Complexes such as alcohols), various complexes of platinum, and chlorides of metals such as rhodium, ruthenium, iron, aluminum, and titanium. Among these, chloroplatinic acid, a platinum-olefin complex, and a platinum-vinylsiloxane complex are preferable from the viewpoint of catalytic activity. These catalysts may be used alone or in combination of two or more.

The proportion of the component (B) to the component (A) in the curable composition as described above is such that the hydrosilyl group in the component (B) is 0.2 per mole of the alkenyl group in the component (A). When it is set so as to be present in an amount of from about 5.0 to about 5.0 moles, and more preferably from about 0.4 to about 2.5 moles, it is preferable to obtain good rubber elasticity. The amount of the component (C) used is as follows:
(A) 10 ^-1 to 1 mol of the alkenyl group in the component.
It is preferably used in the range of 10 ^-8 mol, particularly 10 ^-3 to 10 ^-6 mol. If the amount of the component (C) is less than 10 ^-8 mol, the reaction does not proceed. On the other hand, hydrosilylation catalysts
In general, it is expensive, corrosive, and has a property that a large amount of hydrogen gas is generated to cause foaming of the cured product. Therefore, it is preferable not to use more than 10 ^-1 mol.

Further, by adding a conductivity-imparting agent as a component (D) to the curable composition to form a conductive 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 group, a phosphate group, and the like. Or a polymer, an ether ester amide, or an ether imide polymer, an ethylene oxide-epihalohydrin copolymer, a compound having a conductive unit represented by methoxypolyethylene glycol acrylate, or an antistatic agent such as a polymer compound, Examples thereof include compounds capable of imparting conductivity. These conductivity imparting agents may be used alone or in combination of two or more.

The addition amount of the conductivity-imparting agent as the component (D) is preferably not more than 30% by weight based on the total amount of the components (A) to (C). preferable. On the other hand, in order to obtain a uniform volume resistivity, the addition amount is preferably 10% by weight or more, and the addition amount is determined so that the volume resistivity of the cured product is 10 ³ to 10 ¹⁰ Ωcm. Is preferred.

The above curable composition includes the above (A) to
In addition to the component (D), a storage stability improver, for example, a compound having an aliphatic unsaturated bond, an organic phosphorus compound, an organic sulfur compound, a nitrogen-containing compound, a tin compound, or an organic peroxide may be added. good. Specific examples thereof include, but are not limited to, benzothiazole, thiazole, dimethylmalate, dimethylacetylenecarboxylate, 2-pentenenitrile, 2,3-dichloropropene, quinoline and the like. Among these, thiazole and dimethyl malate are particularly preferred from the viewpoint of achieving both pot life and rapid curing properties. The storage stability improvers may be used alone or in combination of two or more.

Further, a filler, a storage stabilizer, a plasticizer, an ultraviolet absorber, a lubricant, a pigment, and the like may be added to the curable composition from the viewpoint of improving processability and cost. The elastic layer, the curable composition, urethane rubber,
An elastic material such as silicone rubber, for example,
Casting, injection molding, extrusion molding, etc. into a mold with a conductive shaft made of US or aluminum alloy etc., and heat-curing at an appropriate temperature and time to form a conductive elastic layer around the shaft Form. In this case, after semi-curing,
It may be post-cured.

In the developing roller according to the present invention, a resin constituting a surface layer is applied to a predetermined thickness around the elastic layer by dipping, spraying, roll coating or brush coating, and dried at a predetermined temperature. And cured.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the first to fifth embodiments according to the present invention will be described below in detail, and then the comparison between these embodiments and comparative examples 1 to 3 will be made. The developing rollers of these examples and comparative examples are configured such that a 7.5 mm thick elastic layer is provided concentrically around a SUS shaft having a diameter of 10 mm, and a surface layer is coated on the elastic layer.

The elastic layer includes elastic layers 1 to 3 shown below.
Is used. (Elastic Layer 1) (B-1) Polysiloxane based on 100 parts by weight of terminally allylated polyoxypropylene polymer having a number average molecular weight (Mn) of 8,000 and a molecular weight distribution of 2.0. System curing agent (SiH value 0.36 mol / 100 g): 6.6 parts by weight, (C-1) 10% isopropyl alcohol solution of chloroplatinic acid: 0.06 parts by weight, (D-1) carbon black 3030B ( (Mitsubishi Chemical Co., Ltd.): 8 parts by weight, and a composition obtained by degassing under reduced pressure at 10 mmHg or less for 120 minutes is coated on a shaft, and left standing in a mold at 120 ° C. for 30 minutes. This was placed and cured to form an elastic layer 1 made of a rubber elastic body having a thickness of 7.5 mm. (Elastic Layer 2) (A-2) Number average molecular weight (Mn): 10,000, 10 of polyisobutylene polymer having two vinyl groups at terminals
With respect to 0 parts by weight, (B-2) a polysiloxane-based curing agent (SiH value 0.97 mol / 100 g): 2.7 parts by weight,
(C-2) 10% isopropyl alcohol solution of chloroplatinic acid: 0.06 parts by weight, (D-2) carbon black 3
030B (manufactured by Mitsubishi Chemical Corporation): 10 parts by weight, and (other) plasticizer PS-32 (manufactured by Idemitsu Kosan Co., Ltd.): 75 parts by weight, and a composition obtained by defoaming under 10 mmHg or less for 120 minutes under reduced pressure. Was coated on a shaft and allowed to stand for 30 minutes in a mold at 120 ° C. for 30 minutes to cure, thereby forming an elastic layer 2 made of a rubber elastic body having a thickness of 7.5 mm. (Elastic layer 3) (A-1), (B-1) and (C-1) described above, and (D-3) carbon black 3030B
(Manufactured by Mitsubishi Chemical Corporation): 4 parts by weight and 10 mmH
g or less, and the composition obtained by defoaming under reduced pressure for 120 minutes is coated on a shaft, allowed to stand for 30 minutes in a mold at an environment of 120 ° C. and cured, and a rubber elastic body having a thickness of 7.5 mm is formed. Was produced.

As the surface layer of Examples 1 to 5, any one of the following surface layers 1 to 5 obtained by dip coating the outer periphery of the elastic layer is used. (Surface layer 1) A solution obtained by diluting a carbonate urethane solution (Rezamine ME8220LP: manufactured by Dainichi Seika Co., Ltd.) with methyl ethyl ketone to a solid content of 5% by weight is dipped on the outer peripheral surface of the elastic layer, and the solution is placed in an oven at 80 ° C. After drying for 1 hour, a surface layer 1 having a thickness of 15 μm was obtained. (Surface layer 2) A solution obtained by diluting carbonate urethane (E980: manufactured by Nippon Miractran Co., Ltd.) with dimethylformamide to a solid content of 5% by weight is dipped on the outer peripheral surface of the elastic layer, and is then placed in an oven at 80 ° C. for 1 hour. It was dried to form a surface layer 2 having a thickness of 15 μm. (Surface layer 3) Polycarbonate (Teflon A2500: manufactured by Idemitsu Petrochemical Co., Ltd.) and ether-based urethane solution (Heimlen Y-258: manufactured by Dainichi Seika Co., Ltd.) having a total solid content of 5% by weight ( The solution diluted with dimethylformamide was dipped so as to have a solid content ratio of 1: 1), and dried in an oven at 80 ° C. for 1 hour.
The surface layer 3 was 20 μm thick. (Surface layer 4) A solution obtained by diluting an acryl-vinyl acetate copolymer (Kanevirac L-DBF: manufactured by Kaneka Corporation) with ethyl acetate to a solid content of 5% by weight is dipped on the outer peripheral surface of the elastic layer. Then, it was dried in an oven at 80 ° C. for 1 hour to obtain a surface layer 4 having a thickness of 10 μm.

(Surface layer 5) A solution obtained by diluting a polycarbonate urethane (T-9290: manufactured by Dainippon Ink) with a mixture of methyl ethyl ketone and dimethylformamide until the solid content becomes 5% is dipped on the outer peripheral surface of the elastic layer. It was dried in an oven at 100 ° C. for 1 hour to obtain a surface layer 5 having a thickness of 20 μm.

As the surface layers of Comparative Examples 1 to 3, the following surface layers 6 and 7 are used. (Surface layer 6) Copolymer nylon (CM)
A solution obtained by diluting -8000: manufactured by Toray Co., Ltd. with methanol to a solid content of 10% was dipped and dried in an oven at 80 ° C. for 1 hour to form a surface layer 6 having a thickness of 15 μm. (Surface layer 7) A solution obtained by diluting methoxymethylated nylon (EM-120: manufactured by Lead City Co., Ltd.) with methanol to a solid content of 10% was dipped on the outer peripheral surface of the elastic layer.
It was dried in an oven at 0 ° C. for 1 hour to form a surface layer 7 having a thickness of 20 μm.

Table 1 shows the structures of the developing rollers of Examples 1 to 5 and Comparative Examples 1 to 3. Table 1 shows the combination of the elastic layer and the surface layer described above as the configuration of the developing roller, and 10
The ratio C _L / C _{H of the} capacitance C _L of the development roller measured under an environment of 15 ° C. and 15% RH and the capacitance C _H of the development roller measured under an environment of 40 ° C. and 90% RH are shown. ing.

[0041]

[Table 1]

As described above, the capacitance (C _L , C _H ) is measured by pressing a roller in parallel with a flat plate electrode and applying a load of 500 g to both ends of the shaft in the direction of the flat plate electrode. The capacitance between the conductive shaft and the plate electrode is measured. Examples 1 to 5 and Comparative Example 1
Table 1 also shows the image evaluation results of the developing rollers Nos. 1 to 3. The evaluation of the developing roller was performed by using the developing roller incorporated in the laser printer at 10 ° C., 15% RH, 40 ° C., 90%
Under each environment of RH, a black solid image having a width of 1 cm and a length of 15 cm was printed, and the image density was measured using a Macbeth densitometer. The image evaluation was performed according to the criteria shown in Table 2.

[0043]

[Table 2]

According to Table 1 above, the capacitance C _L of the developing roller measured in an environment of 10 ° C. and 15% RH is 40
In the embodiment where the ratio C _L / C _H of the electrostatic capacity C _H of the developing roller measured in an environment of 90 ° C. and 90% RH is in the range of 0.2 or more and 5.0 or less, the image is compared with the comparative example. It turns out that the result of evaluation is good.

[0045]

As described above, the developing roller of the present invention is formed by forming one or a plurality of resin layers around a conductive shaft, and forming a surface layer concentrically on the resin layer.
The capacitance C of the developing roller measured in an environment of 15% RH
And _L, 40 ° C., the ratio C _L / C _H of the capacitance C _H of the developing roller was measured in an environment of 90% RH is adjusted to be within a range of 0.2 to 5.0 Even if the surrounding environment changes, the developing characteristics are stabilized, and a developing roller having excellent environmental characteristics can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a developing device and a photoconductor.

FIG. 2 is a diagram illustrating a method of measuring the capacitance of a developing roller.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 developing device 2 photoreceptor 3 non-magnetic toner 4 toner container 5 regulating blade 6 developing roller 7 supply roller 8 conductive support 9 elastic layer 10 resin layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Hiroshi Ogoshi 2-1-1 Hieitsuji, Otsu City, Shiga Prefecture Kaneka Chemical Industry Co., Ltd. F-term (reference) 2H077 AC04 AD06 AD13 AD36 FA12 FA22 FA25 GA25

Claims (5)

[Claims] 1. A developing roller for an electrophotographic system,
The developing roller is formed by forming an elastic layer around a conductive shaft, and forming one or more resin layers concentrically on the elastic layer, and measuring the developing roller under an environment of 10 ° C. and 15% relative humidity. Capacitance C _L , 40 ° C., relative humidity 90
% Of the ratio C _L of the capacitance C _H of the developing roller was measured in an environment
/ _CH is 0.2 or more and 5.0 or less. 2. The developing roller according to claim 1, wherein the capacitance ratio C _L / C _H is 0.2 or more and 3.0 or less. 3. The developing roller according to claim 1, wherein polycarbonate urethane is used as a main component of the outermost layer (surface layer) of the resin layer. 4. An acrylic-carboxylic acid containing, as main components, one or both of an acrylate monomer and a methacrylate monomer and a vinyl carboxylate monomer as main components of an outermost layer (surface layer) of the resin layer. 3. The developing roller according to claim 1, wherein a vinyl copolymer is used. 5. The polymer according to claim 1, wherein the elastic layer comprises (A) a polymer having at least one alkenyl group in a molecule and a repeating unit constituting a main chain being an oxyalkylene unit or a saturated hydrocarbon unit. (B) a curing agent having at least two hydrosilyl groups in a molecule, (C) a hydrosilylation catalyst, and (D) a conductivity-imparting agent. The developing roller according to any one of claims 1 to 4, wherein: