JP2002023479A - Developing roller, electrophotographic process cartridge and electrophotographic image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing roller having excellent developing characteristic in an initial stage even in a high-speed and high-definition electrophotographic device and capable of realizing stable development even after outputting images for many sheets or even after leaving the device as it is in severe environment for a long time, and an electrophotographic process cartridge and an electrophotographic image forming device having the developing roller. SOLUTION: This developing roller is provided with a conductive shaft, a conductive elastic body base layer formed on the outer periphery of the shaft and consisting of the mixture material of a conductive agent and a high polymer elastic body and a surface layer covering the outer periphery of the conductive elastic body base layer. Conductive elastic body material constituting the conductive elastic body base layer consists of continuous phases and discontinuous phases finely separated from each other, and the content rate of the conductive agent in the continuous phase is larger than that in the discontinuous phase. Thus, the developing roller and the electrophotographic process cartridge and the electrophotographic image forming device having the roller are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a developing roller and an electrophotographic process cartridge using the developing roller.
And an electrophotographic image forming apparatus using the developing roller.

[0002]

2. Description of the Related Art As a method for developing a latent image in an electrophotographic apparatus, a contact developing method is known, and a non-magnetic one-component contact developing method using a conductive elastic roller (for example, Japanese Patent Application Laid-Open No. 52-125340). Gazettes etc.) are publicly known.

The developing roller used in the non-magnetic one-component contact developing step has not only good developing characteristics in the initial stage of using the roller, but also is left for a long time after outputting a large number of sheets or in a severe environment. After that, stable development is required.

[0004] In order to perform such stable development, Japanese Patent Application Laid-Open No. 56-89766 discloses the use of a polyamide resin for the surface layer. Thereby, the frictional charge imparting property of the developing roller to the toner is improved, and the toner can have a sufficient charge.

Japanese Patent Application Laid-Open No. 55-48767 discloses the use of silicone rubber for the developing roller. JP-A-57-181569 discloses that a roller has a two-layer structure and a soft base layer and a conductive surface layer are combined. Japanese Patent Application Laid-Open No. 5-72888 discloses that the material constituting the developing roller has a sea-island structure, thereby forming a minute closed electric field on the surface of the developing roller and conveying the developer toner by the closed electric field. Have been.

[0006]

However, in the above-mentioned conventional example, the developing characteristics of the developing roller have become insufficient for the recent high definition and high speed of the electrophotographic apparatus. That is, for example, 16 images per minute in A4 size
In an electrophotographic apparatus that outputs at 0 dpi, when a developing roller as in the conventional example is used, an image defect caused by the developing roller has become noticeable.

[0007] That is, for example, a conventional Japanese Patent Laid-Open No. 55-487.
As described in JP-A-67-67, it is becoming difficult to use a developing roller in which a conductive agent is simply dispersed in silicone rubber in a recent high-definition and high-speed electrophotographic apparatus. In other words, simply using a roller in which a conductive agent such as conductive carbon black is dispersed in silicone rubber increases the hardness of the material due to the addition of the conductive agent,
Even if a lot of soft silicone rubber is used, the toner fuses to the surface of the developing roller after outputting a large number of sheets, or the developing roller has poor compression set and is left in a severe environment for a long period of time. The problem that the contact portion between the photoconductor and the photoconductor appears in an image has appeared.

In order to obtain a medium resistance region (volume resistivity of 10 ⁴ to 10 ⁷ Ω · cm) required for a developing roller by dispersing carbon black in silicone rubber, depending on the method of adding a conductive agent, the electric resistance may be reduced. This is a region where the resistivity changes most sensitively, and it is difficult to obtain a stable medium-resistance material. The non-uniformity of the resistance may cause uneven resistance inside the roller, resulting in uneven density in the image or uneven roller quality. We need some way to get it.

Therefore, the object of the present invention is to provide a good initial performance even when incorporated and used in a high-speed and high-definition electrophotographic apparatus which outputs, for example, A4 portrait 16 images per minute at 1200 dpi. Roller having excellent developing characteristics and capable of performing stable development even after outputting a large number of sheets or being left in a severe environment for a long time, an electrophotographic process cartridge having the developing roller, and an electronic device A photographic image forming apparatus is provided.

[0010]

The above object is achieved by the present invention described below. That is, the present invention provides a conductive shaft,
A developing roller having a conductive elastic base layer formed of a mixture of a conductive agent and a polymer elastic body formed on the outer periphery of the shaft, and a surface layer covering the outer periphery of the conductive elastic base layer; The conductive elastic material constituting the base layer is composed of a continuous phase and a discontinuous phase that is finely phase-separated, and the content of the conductive agent in the continuous phase is larger than the content of the conductive agent in the discontinuous phase. Provided are a developing roller, an electrophotographic process cartridge having the developing roller, and an electrophotographic image forming apparatus.

[0011]

Next, the present invention will be described in more detail with reference to preferred embodiments. The present inventors have proposed that the conductive elastic material forming the conductive elastic base layer forming the developing roller is composed of a continuous phase and a discontinuous phase that is finely phase-separated, and the content ratio of the conductive agent in the continuous phase. Is to be larger than the content of the conductive agent in the discontinuous phase, thereby reducing the content of the conductive agent in the discontinuous phase which causes an increase in the hardness of the elastic body due to an increase in the content of the conductive agent. Thus, the present inventors have found that a very soft developing roller can be obtained.

When the developing roller is soft, a stable developing nip can be formed, an initial good image can be obtained, and the toner is fused to the surface of the developing roller even after outputting a large number of sheets. Therefore, there is an effect that a good image can be obtained. In addition, due to the above characteristics, since the content of the conductive agent in the discontinuous phase is small, the compression set of the discontinuous phase is good, and the compression set of the entire conductive elastic base layer is also good. Because it has an action, it has sufficient conductivity as a developing roller to supply charge to toner, has good compression set, and outputs high-definition images at high speed after being left in a harsh environment for a long time. Even in such a case, there is an effect that a developing roller having good developing characteristics can be obtained.

Further, according to the above feature, the content ratio of the conductive agent in the continuous phase is a region where the resistance is slightly smaller (large amount of addition) than in a region where the electric resistance of the continuous phase is remarkably changed depending on the content. There is an effect that the resistance of the conductive elastic base layer changes slowly with respect to the content of the conductive agent, and even if there is some unevenness in the concentration of the conductive agent, the electrical resistance does not change so much, and the unevenness of the electrical resistance is stably small. There is also an effect that a developing roller can be manufactured. It is considered that the reason why these functions and effects are exhibited is that the conductive elastic body base layer separates into a continuous phase and a discontinuous phase, and that the continuous phase contains more conductive agent.

Regarding the uniformity of conductivity, when a conductive agent is dispersed as it is in a single kind of elastic material which is not phase-separated as in a conventional developing roller, the resistance unevenness is small if the conductive agent is large. However, the resistance is small, and if the amount of the conductive agent is small, the resistance unevenness is small but the resistance is large. In either case, the desired material in the medium resistance region of about 10 ⁴ to 10 ⁷ Ω · cm of the developing roller can be obtained. Absent.

Further, in the case where the conductive agent is dispersed in a medium amount, the resistance value may enter the medium resistance region on average, but the resistance unevenness increases, and in any case, a single type of the phase resistance is used. If the conductive agent is dispersed in the unseparated elastic biomaterial as it is, a uniform, medium-resistance conductive elastic biomaterial cannot be obtained.

In the present invention, since the continuous phase having small resistance and small resistance unevenness is uniformly present in the base layer material,
When a low-resistance material with a small apparent cross-sectional area is uniformly dispersed in the material, when viewed as a whole conductive elastic material,
It is considered to be a uniform material with medium resistance.

Regarding softness and low compression set,
Since the content of the conductive agent in the discontinuous phase is low, the discontinuous phase retains the original softness of the rubber, is flexible as a whole material, and has no orientation along the conductive agent, so that the compression set is small. It is considered to be.

Japanese Unexamined Patent Publication No. 5-48767 discloses a developing roller having "sea-island structure". This developing roller exposes the sea-island structure to the surface and removes toner by a minute electric field generated on the surface. This is a technique of transporting, which is a completely different technical idea from the method of the present invention in which a surface layer having a triboelectric property is provided on a phase-separated base layer to sufficiently charge and transport the toner.

Next, the structure of the developing roller which mainly characterizes the present invention will be described. As shown in FIG. 1 schematically showing the cross-sectional structure and FIG. 2 showing the entire perspective view, the developing roller of the present invention has a conductive shaft 3 and a conductive agent formed on the outer periphery of the shaft 3. A developing roller having a conductive elastic base layer 2 made of a mixture material with a molecular elastic body and a surface layer 3 covering the outer periphery of the conductive elastic base layer 2, and a conductive roller constituting the conductive elastic base layer 2. The elastic elastic material comprises a continuous phase and a minutely phase-separated discontinuous phase, and the content of the conductive agent in the continuous phase is larger than the content of the conductive agent in the discontinuous phase.

The conductive shaft 3 used in the present invention is a column in which the surface of a carbon steel alloy is plated with industrial nickel having a thickness of 5 μm. Other examples of the material constituting the conductive core include, for example, metals such as iron, aluminum, titanium, copper, and nickel, and alloys such as stainless steel, duralumin, brass, and bronze containing these metals, and carbon black and the like. A well-known rigid and conductive material such as a composite material obtained by solidifying carbon fibers with plastic can also be used. Further, the shape may be a cylindrical shape having a hollow center portion, in addition to a cylindrical shape.

In the present invention, first, a conductive elastic base layer is formed on the outer periphery of the conductive shaft. A preferred polymer material for forming the conductive elastic base layer is a mixture of acrylic rubber and silicone rubber. The base layer is formed by kneading an unvulcanized (uncrosslinked) acrylic rubber described below and an unvulcanized (uncrosslinked) silicone rubber (polyorganohydrogensiloxane) described below at a desired ratio, and the two are compatible with each other. The resulting mixture is prepared, and a polyorganohydrogensiloxane cross-linking catalyst is added to the mixture and further kneaded, whereby the polyorganohydrogensiloxane is cross-linked to form a uniform silicone rubber in the unvulcanized acrylic rubber. A fine phase separation occurs, with the acrylic rubber becoming the continuous phase and the silicone rubber becoming the fine discontinuous phase. By adding an appropriate amount of conductive agent to the phase separation mixture thus formed and kneading the same, the conductive agent is uniformly dispersed in the phase separation mixture, but the finely separated silicone rubber is already crosslinked. In this state, the dispersion of the conductive agent in the silicone rubber fine dispersion is more difficult than in the uncrosslinked acrylic rubber, and therefore, the concentration of the conductive agent in the continuous phase is discontinuous. It is higher than the concentration of the conductive agent in the phase. In the present invention, if necessary, a vulcanizing agent (crosslinking agent) may be added to the phase-separated mixture containing the above-described conductive agent, using a vulcanizing mold having the same internal shape as the outer shape of the base layer. A desired base layer can be formed by holding the rubber composition in the center of a cylindrical mold having the rubber composition, placing the rubber composition in the mold, performing a heat crosslinking treatment, and removing the mold. The method for forming the base layer may be a known method.

The unvulcanized acrylic rubber used above is a monomer (1) comprising an alkyl (meth) acrylate and / or an alkoxyalkyl (meth) acrylate, and a carbon-carbon double bond which is a crosslinking point. It can be prepared by copolymerizing a monomer (2) for introducing a bond into a side chain in the presence of a radical polymerization initiator. In the present invention, “(meth) acryl” means both “acryl” and “methacryl”.

The alkyl acrylate which is the monomer (1) of the acrylic rubber includes, for example, (meth)
Methyl acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, pentyl (meth) acrylate,
Hexyl (meth) acrylate, heptyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (meth) acrylate, nonyl (meth) acrylate,
Decyl (meth) acrylate and the like can be mentioned. These can be used alone or in combination of two or more.

The alkoxyalkyl (meth) acrylate as the monomer (1) includes, for example, methoxymethyl (meth) acrylate, methoxyethyl (meth) acrylate, methoxypropyl (meth) acrylate,
Examples thereof include ethoxymethyl (meth) acrylate, ethoxyethyl (meth) acrylate, ethoxypropyl (meth) acrylate, and butoxyethyl (meth) acrylate. These can be used alone or in combination of two or more. Among them, preferably ethyl (meth) acrylate, butyl (meth) acrylate and (meth) acrylate
It is methoxyethyl acrylate.

The polymerization ratio of the monomer (1) in the acrylic rubber is from 80 to 99.99% by weight, preferably from 90 to 9% by weight.
9.98% by weight. If this proportion is less than 80% by weight, the crosslinked product of the acrylic rubber composition obtained will not have a suitable elastic state due to excessive hardness. On the other hand, if the proportion exceeds 99.99% by weight, the crosslinked product of the acrylic rubber composition obtained will have too low a tensile strength and will not have a suitable mechanical strength.

The monomer (2) for having a carbon-carbon double bond in the side chain of the acrylic rubber includes, for example, (meth)
Dihydrodicyclopentenyl acrylate, dihydrodicyclopentenyl itaconate, dihydrodicyclopentenyl maleate, dihydrodicyclopentenyl fumarate,
Dihydrodicyclopentenyloxyethyl (meth) acrylate, dihydrodicyclopentenyloxyethyl itaconate, dihydrodicyclopentenyloxyethyl maleate, dihydrodicyclopentenyloxyethyl fumarate, 2- (meth) acryloyloxyethyl, vinyl ( Meth) acrylate, allyl (meth) acrylate,
Allyl (meth) acrylate dicyclopentadiene, methyldicyclopentadiene, ethylidene norbornene,
1,1-dimethylpropenyl (meth) acrylate,
3,3-dimethylbutenyl (meth) acrylate, vinyl 1,1-dimethylpropenyl ether, vinyl 3,3
-Dimethylbutenyl ether, 1- (meth) acryloyloxy-1-phenylethene, 1- (meth) acryloyloxy-2-phenylethene and the like can be used. These can be used alone or in combination of two or more. The polymerization ratio of the monomer (2) in the acrylic rubber is 0.01 to 20% by weight, preferably 0.02 to 5% by weight.
It is. If it exceeds 20% by weight, the resulting acrylic rubber will have low elongation. On the other hand, when the content is less than 0.01% by weight, the tensile strength of the obtained acrylic rubber is inferior.

Further, as a monomer constituting the acrylic rubber, a copolymerizable monomer (3) other than the monomers (1) and (2) can be contained. Monomer (3)
Styrene, vinyltoluene, vinylpyridine, α-methylstyrene, vinylnaphthalene, halogenated styrene, (meth) acrylonitrile, (meth) acrylamide, N-methylol (meth) acrylamide,
(Meth) acrylates of aromatic and alicyclic alcohols such as vinyl acetate, vinyl chloride, vinylidene chloride, and cyclohexyl (meth) acrylate, benzyl (meth) acrylate, and ethylene glycol di (meth) acrylate; ) Esters of unsaturated carboxylic acids such as acrylic acid, itaconic acid, fumaric acid and maleic acid with lower alcohols.
In addition, these are used as needed and can be used individually or in mixture of 2 or more types. The proportion of the monomer (3) in the acrylic rubber is from 0 to 10% by weight. If it exceeds 10% by weight, the obtained acrylic rubber becomes hard, which is not preferable.

Further, as the monomer (3) other than the above-mentioned monomers, a divinyl compound may be included in order to enhance crosslinking. Specifically, if necessary, divinylbenzene, divinyltoluene, divinylxylene, divinylnaphthalene, divinylsulfone, divinylketone,
Divinyl ether, ethylene glycol di (meth) acrylate, bicyclo (2,2,1) -5-heptene-2
-Dimethylol di (meth) acrylate and the like. These divinyl compounds can be used alone or in combination of two or more, and a good acrylic rubber can be produced.

As the radical polymerization initiator used in the synthesis of the acrylic rubber of the present invention, any one capable of generating a radical can be used. Specific examples include potassium persulfate, p-chlorobenzoyl peroxide, methyl Examples include peroxides such as isopropyl ketone peroxide and azo compounds such as azobisisobutyronitrile. These radical polymerization initiators are used at a ratio of 0.001 to 1.0% by weight based on the monomer mixture.

In the present invention, the polymerization reaction of the acrylic monomer mixture can be carried out by usual suspension polymerization, emulsion polymerization, solution polymerization or the like. The acrylic rubber (unvulcanized state) used in the present invention has an average molecular weight (average molecular weight in terms of polystyrene, the same applies hereinafter) of 1,000 or more, preferably 10,000 or more. If it is less than 1,000, the processability of the rubber is inferior, and the desired tensile strength and compression set cannot be obtained.

The structure of the polyorganohydrogensiloxane forming the silicone rubber used in the present invention is as follows:
For example, it is represented by the following formula (I).

[0032]

Embedded image

The above-mentioned polyorganohydrogensiloxane must have at least two or more silicon-hydrogen bonds in the molecule in order to cause a crosslinking reaction. The molecular weight of the polyorganohydrogensiloxane is not particularly limited, and may be from low molecular weight (oligomer) to high molecular weight. Such a polyorganohydrogensiloxane can be used in the present invention, for example, under the trade name of TSF483 or the like from a manufacturer such as Toshiba Silicone Co., Ltd. In the present invention, the proportion of the polyorganohydrogensiloxane used in preparing the material for forming the base layer is usually 10 to 200 parts by weight, preferably 3 to 100 parts by weight of the acrylic rubber.
0 to 100 parts by weight.

In the present invention, instead of chloroplatinic acid hexahydrate used as a catalyst for crosslinking polyorganohydrogensiloxane, a transition metal compound having a catalytic action in a hydrosilylation reaction can be used. Although there is no particular limitation, for example, Fe (CO) ₅ , Co (CO) ₈ , RuCl
_3, IrCl _3, [(olefin) PtCl _{2] 2,} a vinyl group-containing polysiloxane -Pt complex, H ₂ PtCl ₆ · 6H
₂ O, L ₃ RhCl ₃ , L ₂ Ni (olefin), L ₄ P
d, L ₄ Pt and L ₂ NiCl ₂ (where L = PPh ₃ or PR ′ ₃ , where Ph represents a phenyl group and R ′ represents an alkyl group). Among them, preferred are platinum, palladium and rhodium-based transition metal compound catalysts.

The amount of the catalyst depends on the content of carbon-carbon double bonds in the acrylic rubber and the amount of hydrogen-silicon bonds present in the polyorganohydrogensiloxane. On the other hand, 0.
00001-1 part by weight, preferably 0.0001-0.
About 5 parts by weight, and in the case of a platinum compound, preferably about 5 to 1000 ppm in terms of platinum element,
If it is less than 1 part by weight, the hydrosilylation reaction is insufficient.
On the other hand, if it exceeds 1 part by weight, the reaction proceeds rapidly and the obtained rubber becomes brittle, which is not preferable.

Organic peroxides which can be used in place of dicumyl peroxide include, for example, 2,5-dimethyl-2,
5-di (t-butylperoxy) hexyne-3,2,5
-Dimethyl-2,5-di (t-butylperoxy) hexane, 2,2'-bis (t-butylperoxy) -p-
Diisopropylbenzene, dicumyl peroxide, di-t-butyl peroxide, t-butyl perbenzoate, 1,1-bis (t-butylperoxy) -3,
3,5-trimethylcyclohexane, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, azobisisobutyronitrile and the like, preferably 2,5-dimethyl-2,5-di (t-butylperoxy) ) Hexin-3,2,5-dimethyl-2,5-di (t
-Butylperoxy) hexane, 2,2′-bis (t-
(Butylperoxy) -p-diisopropylbenzene.

The amount of the organic peroxide used in the present invention is usually 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, based on 100 parts by weight of the rubber used in the present invention. If the amount used is too small, the crosslink density of the obtained rubber is low, and the mechanical strength and the low compression set are inferior.On the other hand, if the amount is too large, the crosslink density of the obtained rubber is too high, and the hardness is undesirably high. .

Incidentally, at the time of crosslinking, a bifunctional vinyl monomer or the like may be used as a crosslinking aid. Examples of such a crosslinking aid include the following compounds. Ethylene glycol di (meth) acrylate, 1,
3-butanediol di (meth) acrylate, 1,4-
Butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, polyethylene glycol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 2,2'-bis- (4- (meth) acryloyldiethoxyphenyl) propane, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, divinylbenzene, N, N'-methylenebis (meth) acrylamide , P-quinone dioxime, p, p'-dibenzoylquinone dioxime, triazine dithiol, triallyl cyanurate, triallyl isocyanurate, bismaleimide and the like.

The amount of the crosslinking aid used is usually 0.01 to 20 parts by weight, preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, based on 100 parts by weight of rubber. is there. If the amount of the crosslinking aid is too small, the crosslinking density is low, and the mechanical strength of the obtained rubber is inferior to the low compression set.On the other hand, if the amount is too large, the crosslinking density of the obtained rubber is too high, and the hardness is too high. It is undesirably high.

Various additives commonly used in rubbers can be added as long as the characteristics of low hardness and low compression set are not impaired. These compounds may be added as needed in the process of producing the base material of the present invention. For example, as rubber, natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, (meth) acrylonitrile butadiene rubber, ethylene propylene rubber, ethylene propylene diene rubber, butyl rubber, halogenated butyl rubber, silicone rubber, fluorine rubber, urethane rubber, Ethylene-vinyl acetate copolymer, ethylene- (meth) acrylate rubber, epichlorohydrin rubber and the like.

As the reinforcing filler and extender, for example,
Conductive carbon black, conductive filler, conductive plasticizer, KSCN, LiClO ₄ , NaClO ₄ , ion conductive substances such as quaternary ammonium salts, fumed silica,
Wet silica, quartz fine powder, diatomaceous earth, carbon black, zinc oxide, basic magnesium carbonate, activated calcium carbonate, magnesium silicate, aluminum silicate, titanium dioxide, talc, mica powder, aluminum sulfate, calcium sulfate, barium sulfate, Glass fibers, organic reinforcing agents and organic fillers can be mentioned. The surface of these fillers may be treated with an organic silicon compound, for example, polydiorganosiloxane or the like to make them hydrophobic.

As the plasticizer, for example, polydimethylsiloxane oil, diphenylsilanediol, trimethylsilanol, phthalic acid derivative, adipic acid derivative, and as the softener, for example, lubricating oil, process oil, coal tar, castor oil, aging Examples of the inhibitor include phenylenediamines, phosphates, quinolines,
Cresols, phenols, dithiocarbamate metal salts, and heat-resistant agents include, for example, iron oxide, cerium oxide, potassium hydroxide, iron naphthenate, potassium naphthenate, and other processing aids, coloring agents, ultraviolet absorbers, flame retardants , An oil resistance improver, a foaming agent, an anti-scorch agent, a tackifier, a lubricant and the like.

As the conductive agent, for example, aluminum,
Metal powders and fibers such as palladium, iron, copper and silver, carbon black, metal powders and metal oxides such as titanium oxide, tin oxide and zinc oxide, metal compound powders such as copper sulfide and zinc sulfide, or suitable Electrolytic treatment, spray coating, mixing and shaking the surfaces of various particles with tin oxide, antimony oxide, indium oxide, molybdenum oxide, zinc, aluminum, gold, silver, copper, chromium, cobalt, iron, lead, platinum and rhodium And carbon powder such as acetylene black, Ketjen black, PAN-based carbon black, and pitch-based carbon black. As a conductive agent, the addition of a small amount can reduce the electrical resistivity,
Carbon black is particularly preferred because conductivity can be imparted without increasing the hardness of the rubber composition. As brands of carbon black, for example, Ketjen Black EC, Ketjen Black EC600JD
(Both Ketchen Black International)
Is preferred.

The concentration of the conductive agent in the continuous layer is 2
~ 50% by weight is good. More preferably, it is 5 to 30% by weight. If the amount of the conductive material is too small, the electrical resistivity of the rubber composition changes abruptly with respect to the insertion of the conductive agent, so it becomes difficult to control the conductivity, and if the amount is too large, the rubber becomes hard, Not preferred.

In the present invention, the Asker C hardness of the base layer formed as described above is preferably 50 ° or less. If the Asker C hardness exceeds 50 °, friction between the developing roller and the photosensitive drum undesirably fuses the toner to the surface of the developing roller and the photosensitive drum. The “Asker C hardness” is the hardness of a roller measured using an Asker C type spring-type rubber hardness meter (manufactured by Kobunshi Keiki Co., Ltd.) based on the Japan Rubber Association Standard SRIS0101, and Wet (23 ° C, 55% R
H) For the roller left in the environment for 12 hours or more,
The measured value is 30 seconds after the above hardness tester is brought into contact with a force of 10 N.

In the present invention, a surface layer is further formed on the surface of the conductive elastic base layer formed as described above. As the material for forming the surface layer, various polyamides, fluorine resins,
Examples include hydrogenated styrene-butylene resin, urethane resin, silicone resin, polyester resin, phenol resin, imide resin, and olefin resin. When the surface layer is formed from a polyamide resin, the polyamide resin has a high ability to charge the toner by friction, and the base layer has a sufficient conductivity, so that the triboelectric charging property is also good. That is, by using the polyamide resin for the surface layer, a sufficient development density can be obtained.

The polyamide as a material for forming the surface layer of the developing roller includes, in addition to methoxymethylated polyamide, for example, 6-nylon, 6,6-nylon, 6,10-nylon, 12-nylon, Are used. The preferred number average molecular weight of this polyamide is between 5,000 and 50,000. More preferably, it is 10,000-25,000. The reason is that if the number average molecular weight is too small, the temporal stability of the surface layer (particularly, moisture resistance) is poor, and if the number average molecular weight is too large, there is a problem in solubility in a solvent. By using such a solvent-soluble polyamide as the surface layer forming material, the solubility of the polyamide resin is improved, the outermost layer of the developing roller is easily coated with the polyamide solution, and a sufficient triboelectric charge is imparted to the toner. can do.

The material constituting these surface layers is dispersed by using a conventionally known dispersing device using beads such as a sand mill, a paint shaker, a dyno mill, and a pearl mill. The obtained paint for forming the surface layer is spray-coated,
It is applied to the surface of the conductive substrate by a dipping method or the like. In the present invention, since the surface of the developing roller is preferably uniformly roughened, spray coating is particularly preferably used. The thickness of the surface layer is 5 to 500 μm,
Particularly, 10 to 30 μm is preferable. If the thickness is too small, low molecular weight components in the base layer may seep out and contaminate the photoreceptor. If the thickness is too large, the developing roller becomes too hard to cause fusing, which is not preferable.

In the present invention, by dispersing fine particles having a mass average particle diameter of 1 to 10 μm in the surface layer formed as described above, it is possible to easily transport the toner on the developing roller surface, and An appropriate amount of toner can be conveyed to the development area. Examples of the fine particles used for such purposes include, for example, plastic pigments such as polymethyl methacrylate fine particles, silicone rubber fine particles, polyurethane fine particles, polystyrene fine particles, amino resin fine particles, and phenol resin fine particles. Methyl acid fine particles and silicone rubber fine particles are preferred.
It is preferable to add in the range of 0 to 200% by weight.

Next, an electrophotographic process cartridge having the developing roller of the present invention will be described. The electrophotographic process cartridge includes a photosensitive drum 12, a developing roller 22, a primary charging roller 11, and a developer supply roller 23.
, The toner layer thickness regulating member 26, the stirring blade 31, and the toner 25 are combined into one cartridge, and can be replaced in the electrophotographic apparatus. The toner sent to the developer supply roller by the stirring blade is uniformly coated on the surface of the developing roller by the toner layer thickness regulating member, and the photosensitive drum 12
Transported to the surface and developed. After the toner is transferred to a recording medium (not shown), the surface of the photoreceptor is uniformly charged again by the primary charging roller.

Next, an example of a schematic diagram of a contact developing type electrophotographic image forming apparatus having the developing roller of the present invention is shown in FIG.
Shown in Looking at the contact developing type electrophotographic image forming apparatus according to FIG. 4, the developing roller 22 of the present invention holds the toner 25 on the surface thereof and rotates the laser beam 29 on the photoreceptor 12 while rotating in the direction of the arrow. Is developed, and the toner remaining on the surface of the developing roller without being used for the development is returned to the developing container 24 while being carried on the surface.

Inside the developing container, a developer supply roller 23 is provided.
Removes toner remaining on the surface of the developing roller from the surface of the developing roller and supplies new toner to the surface of the developing roller. The new toner supplied to the surface of the developing roller is adjusted to a uniform coating thickness by the toner layer thickness regulating member 26, and is conveyed to the developing area. By this repetition, the developing roller always coats new toner uniformly to develop the electrostatic latent image.

The developed toner image is conveyed to the transfer area by the rotation of the photosensitive member, and is transferred by the transfer roller 19 to the recording medium 2.
Transferred to 0. Thereafter, the unfixed toner image passes between the fixing roller 15 and the pressure roller 17 and is fixed on the recording medium by pressure and heat to form a fixed image 16. The toner remaining on the photoconductor without being transferred in the transfer process is removed from the photoconductor by the cleaning elastic blade 13 as the photoconductor rotates.
The photoreceptor surface whose surface has been cleaned is charged by the primary charging roller 11, and the process of exposing and developing again is repeated.

[0054]

Next, the present invention will be described more specifically with reference to examples and comparative examples. In Examples and Comparative Examples,
Image development evaluation of the developing roller was performed as follows. The electrophotographic laser printer used in this evaluation was A4
With a machine for vertical output, the output speed of the recording media is
45 mm / sec, and the image resolution is 1200 dpi. The photoreceptor is a reversal developing type photosensitive drum in which an OPC layer is coated on an aluminum cylinder, and the outermost layer is a charge transport layer using modified polycarbonate as a binder resin.

The toner has a glass transition obtained by polymerizing a random copolymer of styrene and butyl (meth) acrylate containing a CA agent and a dye, mainly a wax, further polymerizing a polyester thin film on the surface and externally adding silica fine particles and the like. This is a polymerized toner having a temperature of 63 ° C. and an average particle diameter of 6 μm. 900μ at 900Hz for DC voltage -670V for primary charging
A charging roller on which the current of A was superimposed was used.

The toner image developed on the photoreceptor is transferred to a recording medium by a transfer roller, and is thermally fixed by a fixing unit. The toner not transferred by the transfer roller is scraped off from the photoreceptor by a cleaning blade. The contact force between the photosensitive drum and the developing roller is 5N for both bearings. At least the developing portion is formed as a cartridge, and a developing blade abuts on the developing roller in the counter direction to regulate the toner layer thickness.

The contact pressure and the amount of intrusion were adjusted so that the toner coverage on the developing roller was 0.35 mg / cm ² . Further, a toner supply roller made of a soft urethane sponge for scraping old toner from the developing roller and supplying new toner to the developing roller is provided.

Image development of the developing roller was performed immediately after the developing roller was incorporated in the electrophotographic apparatus, immediately after the continuous durability after 10,000 sheets of continuous durability, and further, the roller having the same configuration was incorporated into the electrophotographic apparatus having the same configuration. Temperature 40 ° C x Humidity 9
After being left in an environment of 5% RH for 30 days, 23 ° C. × 55
The test was carried out after standing for 12 hours in an environment of% RH.

In the image formation at the initial stage and immediately after the endurance, an image was drawn in which a horizontal line having a width of 1 dot and an interval of 2 dots was drawn in the rotation direction and the vertical direction of the photosensitive member. During endurance, an image was drawn in which a horizontal line having a width of 2 dots and an interval of 50 dots was drawn. Images with sufficiently high image density and no image defect of the developing roller pitch due to fusion of toner on the surface of the developing roller, etc. are observed. ◎, image density is faintly low or image defect of the developing roller pitch is slightly recognized. However, an image having no problem in practical use was evaluated as ○, an image having a low image density or an image defect of the developing roller pitch was recognized. X.

When the base layer is formed on the conductive shaft,
As shown in FIG. 2, an aluminum sheet 5 having a width of 1 cm and a thickness of 50 μm is wrapped around the base layer, and the DC electric resistance between the surface of the base layer roller 4 and the core metal (conductive shaft) 3 is measured at an applied voltage of 250 V. did. The value 5 seconds after the start of voltage application was defined as the resistance value. Further, a sample for measuring hardness having a thickness of 12.9 mm was formed from the material for forming the base layer under the same forming conditions, and the hardness was measured with an Asker C type hardness meter. After drawing,
A slice was cut from the base rubber and observed with a TEM. A sea-island structure was taken, and the case where the conductive agent was unevenly distributed in the sea portion (continuous phase) was evaluated as ○, and the case where the sea-island structure was not recognized was evaluated as ×. In addition, all the evaluations were performed in an environment of normal temperature and normal humidity (23 ° C., 55% RH).

[Example 1] (Formation of base layer) 100 parts by weight of acrylic rubber, 50 parts by weight of polymethylhydrogensiloxane (trade name: TSF483, manufactured by Toshiba Silicone Co., Ltd.), isopropyl alcohol of chloroplatinic acid hexahydrate 1 part by weight of a 1% by weight solution and 1 part by weight of zinc stearate are mixed with a pressure kneader for 65 parts.
At 10 ° C. for 10 minutes, and then carbon black (trade name “Ketjen Black 600JD”,
6 parts by weight (Ketjen Black International), 2 parts by weight of dicumyl peroxide, and 1 part by weight of N, N-metaphenylenebismaleimide were added and kneaded with two rolls at 50 ° C.

The acrylic rubber is a copolymer of 47 parts by weight of ethyl acrylate, 50 parts by weight of butyl acrylate and 3 parts by weight of dihydropentenyloxyethyl acrylate. The obtained composition was used for a sample having a diameter of 8 mm and a length of 300 mm.
mm SUS nickel-plated cored bar was poured into a pipe mold and heated and vulcanized at 170 ° C for 25 minutes.
A conductive roller base layer having a length of 6.0 mm and a rubber portion length of 240 mm was obtained.

When the resistance of the obtained base layer was measured, the resistance value was 0.8 MΩ, indicating a moderate resistance, and the resistance unevenness depending on the location was extremely small. When the hardness was measured, it was very low at 40 °.

(Coating of Surface Layer) Next, a solution prepared by dissolving 1% by weight of γ- (2-aminoethyl) aminopropyltrimethoxysilane in toluene was applied to the base layer by dipping and dried at 130 ° C. for 10 minutes. And a primer layer.

10 parts by weight of methoxymethylated polyamide was dissolved in 150 parts by weight of methanol, and then 50 parts by weight of spherical poly (methyl methacrylate) particles having a diameter of 7 μm were stirred and dispersed in this solution. This particle-dispersed polyamide solution was used as a surface coating. The base layer was dipped with the surface paint and dried at 100 ° C. for 20 minutes to provide a surface layer having a thickness of 10 μm.

When the obtained developing roller was incorporated into an electrophotographic apparatus and an image was output, an image having a very uniform and appropriate density was obtained. An image was output even after the end of 10,000 sheets while the developing roller was directly incorporated in the electrophotographic apparatus, but an image having a very uniform and appropriate density was obtained. Furthermore, an image having a very uniform and appropriate density was obtained even after the image was left after the severe storage. In addition, a clear sea-island structure was observed by TEM observation of the base layer.

Example 2 A developing roller was manufactured in the same manner as in Example 1, except that the polymethylhydrogensiloxane was used in an amount of 100 parts by weight. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 3 A developing roller was manufactured in the same manner as in Example 1 except that the polymethylhydrogensiloxane was used in an amount of 30 parts by weight. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 4 A developing roller was manufactured in the same manner as in Example 1 except that the polymethylhydrogensiloxane was used in an amount of 200 parts by weight. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 5 A developing roller was produced in the same manner as in Example 1, except that the polymethylhydrogensiloxane was used in an amount of 10 parts by weight. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 1 A developing roller was produced in the same manner as in Example 1 except that only the base layer of Example 1 was used and the surface layer was not used and used as a developing roller. Example 1
The measurement was performed in the same manner as described above, and the results are summarized in Table 1.

Comparative Example 2 Same as Example 1 except that the acrylic rubber was increased to 150 parts by weight, and a 1% by weight solution of polymethylhydrogensiloxane and chloroplatinic acid hexahydrate in isopropyl alcohol was not used. To produce a developing roller. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 3 A developing roller was produced in the same manner as in Example 1 except that a 1% by weight solution of polymethylhydrogensiloxane and chloroplatinic acid hexahydrate in isopropyl alcohol was not used. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 4 A developing roller was produced in the same manner as in Example 1 except that no acrylic rubber was used.
The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Comparative Example 5 A developing roller was manufactured in the same manner as in Example 1 except that the acrylic rubber was not used and the amount of carbon black was increased to 9 parts. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 6 A developing roller was prepared in the same manner as in Example 1 except that polymethyl methacrylate spherical particles having a diameter of 7 μm were replaced with silicone rubber particles having the same diameter.
The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 7 A developing roller was manufactured in the same manner as in Example 1 except that polymethyl methacrylate spherical particles having a diameter of 7 μm were not used. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 8 A silicone resin was used as the surface resin.
A developing roller was prepared in the same manner as in Example 1 except that toluene was used as the solvent, and polymethyl methacrylate spherical particles having a diameter of 7 μm were replaced with silicone rubber particles having the same diameter. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

Example 9 A developing roller was prepared in the same manner as in Example 1 except that the surface resin was a fluororesin, the solvent was toluene, and the polymethyl methacrylate spherical particles of 7 μm in diameter were silicone rubber particles of the same diameter. did. Example 1
The measurement was performed in the same manner as described above, and the results are summarized in Table 1.

Example 10 The surface resin was hydrogenated styrene-
A developing roller was prepared in the same manner as in Example 1, except that the butylene resin and the solvent were toluene and polymethyl methacrylate spherical particles having a diameter of 7 μm were changed to silicone rubber particles having the same diameter. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

[Example 11] The surface resin was a urethane resin,
A developing roller was prepared in the same manner as in Example 1 except that toluene was used as the solvent, and polymethyl methacrylate spherical particles having a diameter of 7 μm were replaced with silicone rubber particles having the same diameter. The measurement was performed in the same manner as in Example 1, and the results are summarized in Table 1.

[0082]

[Table 1]

[0083]

As described above, according to the present invention,
For example, even when used in a high-speed and high-definition electrophotographic apparatus that outputs 16 images per minute at 1200 dpi in A4 portrait mode, it has good development characteristics at the initial stage and has a large number of sheets. It is possible to provide a developing roller capable of performing stable development even after output or after being left for a long time in a severe environment, an electrophotographic process cartridge having the developing roller, and an electrophotographic image forming apparatus. it can.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram of a cross section of a developing roller of the present invention.

FIG. 2 is a conceptual diagram of a method for measuring the resistance of a base layer of a developing roller according to the present invention.

FIG. 3 is a conceptual diagram illustrating an example of the electrophotographic process cartridge of the present invention.

FIG. 4 is a conceptual diagram illustrating an example of the electrophotographic image forming apparatus of the present invention.

[Explanation of symbols]

 1: Surface layer 2: Base layer 3: Core metal 4: Developing roller 5: Aluminum sheet 6: Voltmeter 7: Ammeter 8: High voltage power supply 11: Primary charging roller 12: Photoconductor 13: Elastic blade 15: Fixing roller 16: Fixing Image 17: Pressure roller 19: Transfer roller 20: Recording medium 22: Developing roller 23: Developer supply roller 24: Developing container 25: Toner 26: Toner layer thickness regulating member 29: Laser beam

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) F16C 13/00 F16C 13/00 BD EF term (reference) 2H077 AD06 FA12 FA22 FA27 3J103 AA02 AA14 AA33 AA51 BA31 BA41 FA02 FA06 FA07 FA12 FA14 FA18 GA02 GA52 HA03 HA04 HA05 HA11 HA12 HA15 HA20 HA31 HA32 HA33 HA36 HA37 HA41 HA46 HA52 HA53 HA55 4J002 BG04W BG05W BG06W BG07W CP04X DA036 DA076 DA096 DE096 DE106 DE136 DE186 DF006 FD006 DG006 FD006 DG006

Claims (11)

[Claims] 1. A conductive shaft, a conductive elastic base layer formed of a mixture of a conductive agent and a polymer elastic material formed on the outer periphery of the shaft, and a surface layer covering the outer periphery of the conductive elastic base layer. In the developing roller having, the conductive elastic material constituting the conductive elastic base layer,
A developing roller comprising a continuous phase and a discontinuous phase slightly separated into phases, wherein the content of the conductive agent in the continuous phase is larger than the content of the conductive agent in the discontinuous phase. 2. A conductive elastic material constituting a conductive elastic base layer, wherein a discontinuous phase of silicone rubber is present in the acrylic rubber continuous phase with a slight phase separation, and a content ratio of the conductive agent in the acrylic rubber. 2. The developing roller according to claim 1, wherein is a conductive elastic material having a content greater than the content of the conductive agent in the silicone rubber. 3. The developing roller according to claim 1, wherein the surface layer is made of a polyamide resin. 4. The developing roller according to claim 3, wherein the polyamide resin is a solvent-soluble polyamide resin. 5. The developing roller according to claim 1, wherein fine particles having a mass average particle diameter of 1 to 10 μm are dispersed in the surface layer. 6. The developing roller according to claim 5, wherein the fine particles are fine particles of polymethyl methacrylate. 7. The developing roller according to claim 5, wherein the fine particles are fine particles of silicone rubber. 8. The developing roller according to claim 1, wherein the conductive agent is carbon black. 9. The developing roller according to claim 1, wherein the Asker C hardness of the conductive elastic material constituting the conductive elastic base layer is 50 ° or less. 10. An electrophotographic process cartridge detachably mounted on a main body of an image forming apparatus, wherein the cartridge has the developing roller according to claim 1. Photo process cartridge. 11. An electrophotographic image forming apparatus having an electrostatic holding member for holding an electrostatic latent image and a developing roller disposed in contact with the electrostatic holding member, wherein the developing roller is An electrophotographic image forming apparatus, comprising the developing roller according to any one of claims 9 to 13.